Publications by authors named "Peter Ruth"

132 Publications

cGMP and mitochondrial K channels-Compartmentalized but closely connected in cardioprotection.

Br J Pharmacol 2021 May 15. Epub 2021 May 15.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany.

The 3',5'-cGMP pathway triggers cytoprotective responses and improves cardiomyocyte survival during myocardial ischaemia and reperfusion (I/R) injury. These beneficial effects were attributed to NO-sensitive GC induced cGMP production leading to activation of cGMP-dependent protein kinase I (cGKI). cGKI in turn phosphorylates many substrates, which eventually facilitate opening of mitochondrial ATP-sensitive potassium channels (mitoK ) and Ca -activated potassium channels of the BK type (mitoBK). Accordingly, agents activating mitoK or mitoBK provide protection against I/R-induced damages. Here, we provide an up-to-date summary of the infarct-limiting actions exhibited by the GC/cGMP axis and discuss how mitoK and mitoBK, which are present at the inner mitochondrial membrane, confer mito- and cytoprotective effects on cardiomyocytes exposed to I/R injury. In view of this, we believe that the functional connection between the cGMP cascade and mitoK channels should be exploited further as adjunct to reperfusion therapy in myocardial infarction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/bph.15536DOI Listing
May 2021

Slack K channels attenuate NMDA-induced excitotoxic brain damage and neuronal cell death.

FASEB J 2021 05;35(5):e21568

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany.

The neuronal Na -activated K channel Slack (aka Slo2.2, K 1.1, or Kcnt1) has been implicated in setting and maintaining the resting membrane potential and defining excitability and firing patterns, as well as in the generation of the slow afterhyperpolarization following bursts of action potentials. Slack activity increases significantly under conditions of high intracellular Na levels, suggesting this channel may exert important pathophysiological functions. To address these putative roles, we studied whether Slack K channels contribute to pathological changes and excitotoxic cell death caused by glutamatergic overstimulation of Ca - and Na -permeable N-methyl-D-aspartic acid receptors (NMDAR). Slack-deficient (Slack KO) and wild-type (WT) mice were subjected to intrastriatal microinjections of the NMDAR agonist NMDA. NMDA-induced brain lesions were significantly increased in Slack KO vs WT mice, suggesting that the lack of Slack renders neurons particularly susceptible to excitotoxicity. Accordingly, excessive neuronal cell death was seen in Slack-deficient primary cerebellar granule cell (CGC) cultures exposed to glutamate and NMDA. Differences in neuronal survival between WT and Slack KO CGCs were largely abolished by the NMDAR antagonist MK-801, but not by NBQX, a potent and highly selective competitive antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type ionotropic glutamate receptors. Interestingly, NMDAR-evoked Ca signals did not differ with regard to Slack genotype in CGCs. However, real-time monitoring of K following NMDAR activation revealed a significant contribution of this channel to the intracellular drop in K . Finally, TrkB and TrkC neurotrophin receptor transcript levels were elevated in NMDA-exposed Slack-proficient CGCs, suggesting a mechanism by which this K channel contributes to the activation of the extracellular-signal-regulated kinase (Erk) pathway and thereby to neuroprotection. Combined, our findings suggest that Slack-dependent K signals oppose the NMDAR-mediated excitotoxic neuronal injury by promoting pro-survival signaling via the BDNF/TrkB and Erk axis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1096/fj.202002308RRDOI Listing
May 2021

Comparison of antimicrobial prescription patterns in calves in Switzerland before and after the launch of online guidelines for prudent antimicrobial use.

BMC Vet Res 2021 Jan 5;17(1). Epub 2021 Jan 5.

Clinic for Ruminants, Department for Farm Animals, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, CH-8057, Zurich, Switzerland.

Background: The increasing threat of bacterial resistance promotes the need for antibiotic stewardship programs to foster responsible antimicrobial use. Therefore, guidelines for prudent use supported by an online stewardship tool (AntibioticScout.ch) were introduced in Switzerland in December 2016. They recommend (with decreasing preference) a first, second or third line antimicrobial for treatment. The objective of this study was to evaluate antimicrobial prescriptions for Swiss calves before (2016) and after (2018) the launch of these guidelines. Cases of calves with pneumonia, diarrhea and otitis from a university hospital and eight private practices in Switzerland were included. Data on anamnesis, clinical findings, diagnostic work-up and treatment were collected. Type and percentages [95% confidence interval] of antimicrobial prescriptions were compared between 2016 and 2018.

Results: Of the total number of calves, 88.2% [85.4-90.6] in 2016 (n = 625) and 88.4% [85.7-90.7] in 2018 (n = 655) were treated with antibiotics. The use of highest priority critically important antimicrobials (HPCIAs) decreased from 52.7% [48.6-56.9] in 2016 to 38.0% [34.2-41.9] in 2018; this decrease was found at the university hospital and in private practice and in cases with pneumonia and diarrhea. Particularly the use of fluoroquinolones decreased (2016: 43.1% [39.2-47.2]; 2018: 31.1% [27.6-34.8]). Overall, the number of first line treatments increased from 12.8% [10.4-15.6] in 2016 to 20.2% [17.3-23.4] in 2018. In cases of pneumonia, first line treatments increased (2016: 15.3% [11.6-19.9]; 2018: 26.5% [21.8-31.9]) and third line treatments decreased (2016: 43.5% [38.0-49.3]; 2018: 27.9% [23.1-33.3]); this was seen at the university hospital, whereas in private practice only a decrease of third line treatments was observed. In cases of diarrhea, more second line at the expense of unlisted antimicrobials were prescribed at the university hospital in 2018. Antimicrobial treatment of calves with otitis did not change from 2016 to 2018.

Conclusions: After the introduction of AntibioticScout.ch, more prudent use was observed in the treatment of calves with pneumonia and diarrhea as less HPCIAs, particularly fluoroquinolones, and more first line antimicrobials were prescribed. However, the overall frequency of antimicrobial treatment did not change and the use of HPCIAs was still common in 2018, especially in private practices. Therefore, further antimicrobial stewardship activities are necessary.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12917-020-02704-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7786965PMC
January 2021

Functional Coupling of Slack Channels and P2X3 Receptors Contributes to Neuropathic Pain Processing.

Int J Mol Sci 2021 Jan 2;22(1). Epub 2021 Jan 2.

Institut für Pharmakologie und Klinische Pharmazie, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main, Hessen, Germany.

The sodium-activated potassium channel Slack (K1.1, Slo2.2, or Kcnt1) is highly expressed in populations of sensory neurons, where it mediates the sodium-activated potassium current (I) and modulates neuronal activity. Previous studies suggest that Slack is involved in the processing of neuropathic pain. However, mechanisms underlying the regulation of Slack activity in this context are poorly understood. Using whole-cell patch-clamp recordings we found that Slack-mediated I in sensory neurons of mice is reduced after peripheral nerve injury, thereby contributing to neuropathic pain hypersensitivity. Interestingly, Slack is closely associated with ATP-sensitive P2X3 receptors in a population of sensory neurons. In vitro experiments revealed that Slack-mediated I may be bidirectionally modulated in response to P2X3 activation. Moreover, mice lacking Slack show altered nocifensive responses to P2X3 stimulation. Our study identifies P2X3/Slack signaling as a mechanism contributing to hypersensitivity after peripheral nerve injury and proposes a potential novel strategy for treatment of neuropathic pain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms22010405DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7795269PMC
January 2021

Paxilline Prevents the Onset of Myotonic Stiffness in Pharmacologically Induced Myotonia: A Preclinical Investigation.

Front Physiol 2020 23;11:533946. Epub 2020 Nov 23.

Division of Neurophysiology in the Center of Rare Diseases, Ulm University, Ulm, Germany.

Reduced Cl conductance causes inhibited muscle relaxation after forceful voluntary contraction due to muscle membrane hyperexcitability. This represents the pathomechanism of myotonia congenita. Due to the prevailing data suggesting that an increased potassium level is a main contributor, we studied the effect of a modulator of a big conductance Ca- and voltage-activated K channels (BK) modulator on contraction and relaxation of slow- and high-twitch muscle specimen before and after the pharmacological induction of myotonia. Human and murine muscle specimens (wild-type and BK) were exposed to anthracene-9-carboxylic acid (9-AC) to inhibit CLC-1 chloride channels and to induce myotonia . Functional effects of BK-channel activation and blockade were investigated by exposing slow-twitch (soleus) and fast-twitch (extensor digitorum longus) murine muscle specimens or human musculus vastus lateralis to an activator (NS1608) and a blocker (Paxilline), respectively. Muscle-twitch force and relaxation times (T) were monitored. Compared to wild type, fast-twitch muscle specimen of BK mice resulted in a significantly decreased T in presence of 9-AC. Paxilline significantly shortened T of murine slow- and fast-twitch muscles as well as human vastus lateralis muscle. Moreover, twitch force was significantly reduced after application of Paxilline in myotonic muscle. NS1608 had opposite effects to Paxilline and aggravated the onset of myotonic activity by prolongation of T. The currently used standard therapy for myotonia is, in some individuals, not very effective. This study demonstrated that a BK channel blocker lowers myotonic stiffness and thus highlights its potential therapeutic option in myotonia congenital (MC).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fphys.2020.533946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7719791PMC
November 2020

Effect of antimicrobial stewardship on antimicrobial prescriptions for selected diseases of dogs in Switzerland.

J Vet Intern Med 2020 Nov 28;34(6):2418-2431. Epub 2020 Oct 28.

Division of Small Animal Internal Medicine, Department of Clinical Veterinary Science, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

Background: Antimicrobial stewardship programs (ASPs) are important tools to foster prudent antimicrobial use.

Objective: To evaluate antimicrobial prescriptions by Swiss veterinarians before and after introduction of the online ASP AntibioticScout.ch in December 2016.

Animals: Dogs presented to 2 university hospitals and 14 private practices in 2016 or 2018 for acute diarrhea (AD; n = 779), urinary tract infection (UTI; n = 505), respiratory tract infection (RTI; n = 580), or wound infection (WI; n = 341).

Methods: Retrospective study. Prescriptions of antimicrobials in 2016 and 2018 were compared and their appropriateness assessed by a justification score.

Results: The proportion of dogs prescribed antimicrobials decreased significantly between 2016 and 2018 (74% vs 59%; P < .001). The proportion of prescriptions in complete agreement with guidelines increased significantly (48% vs 60%; P < .001) and those in complete disagreement significantly decreased (38% vs 24%; P < .001) during this time. Antimicrobial prescriptions for dogs with AD were significantly correlated with the presence of hemorrhagic diarrhea in both years, but a significantly lower proportion of dogs with hemorrhagic diarrhea were unnecessarily prescribed antimicrobials in 2018 (65% vs 36%; P < .001). In private practices, in 2018 a bacterial etiology of UTI was confirmed in 16% of dogs. Prescriptions for fluoroquinolones significantly decreased (29% vs 14%; P = .002). Prescriptions for antimicrobials decreased significantly in private practices for RTI (54% vs 31%; P < .001).

Conclusion: Antimicrobials were used more prudently for the examined indications in 2018 compared to 2016. The study highlights the continued need for ASPs in veterinary medicine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/jvim.15906DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694852PMC
November 2020

Antimicrobial prescriptions in cats in Switzerland before and after the introduction of an online antimicrobial stewardship tool.

BMC Vet Res 2020 Jul 3;16(1):229. Epub 2020 Jul 3.

Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, CH-8057, Zurich, Switzerland.

Background: Antimicrobial stewardship activities are essential to improve prudent antimicrobial use. The aim of the present study was to evaluate changes in antimicrobial prescriptions in cats after the introduction of prudent use guidelines promoted by an online antimicrobial stewardship tool (AntibioticScout.ch) in Switzerland. Data from 792 cats presented to two university hospitals and 14 private practices in 2018 were included and compared to 776 cases from 2016. Cats were diagnosed with acute upper respiratory tract disease (aURTD), feline lower urinary tract disease (FLUTD) and abscesses. Clinical history, diagnostic work-up and antimicrobial prescriptions (class, dosage, duration) were assessed. Type and proportions [95% confidence intervals] of antimicrobial prescriptions were compared between the two evaluation periods and a mixed effects logistic regression model was applied to evaluate compliance with Swiss prudent use guidelines.

Results: From 2016 to 2018, the proportion of antimicrobial prescription in all included cases decreased from 75.0% [71.8-78.0] to 66.7% [63.3-69.9]; this decrease was most pronounced for treatments at university hospitals (67.1% [59.5-74.0] to 49.3% [40.9-57.8]) and for cats with FLUTD (60.1% [54.6-65.4] to 48.8% [43.2-54.4]). Use of 3rd generation cephalosporins in private practices declined from 30.7% [26.5-35.1] to 22.1% [18.4-26.2], while overall use of non-potentiated aminopenicillins increased from 19.6% [16.4-23.0] to 27.8% [24.1-31.9]. In cases where antimicrobial therapy was indicated, compliance with guidelines did not increase (33.3% [26.6-40.6] to 33.5% [27.2-40.2]), neither at universities nor in private practices. On the other hand, antimicrobial treatment was more often withheld in cases with no indication for antimicrobial therapy (35.6% [30.1-41.4] to 54.0% [47.6-60.4]); this was found for private practices (26.7% [20.8-33.4] to 46.0% [38.4-53.7]) and for aURTD cases (35.0% [26.5-44.2] to 55.4% [44.7-65.8]).

Conclusions: Overall proportions of antimicrobial prescription, unjustified antimicrobial therapy and, in private practices, use of 3rd generation cephalosporins decreased from 2016 to 2018 for the investigated feline diseases. However, overall compliance with Swiss prudent use guidelines was still low, implying that further efforts are required to foster prudent antimicrobial use in cats.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12917-020-02447-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7333330PMC
July 2020

Subunits of BK channels promote breast cancer development and modulate responses to endocrine treatment in preclinical models.

Br J Pharmacol 2020 May 28. Epub 2020 May 28.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany.

Background And Purpose: Pore-forming α subunits of the voltage- and Ca -activated K channel with large conductance (BKα) promote malignant phenotypes of breast tumour cells. Auxiliary subunits such as the leucine-rich repeat containing 26 (LRRC26) protein, also termed BKγ1, may be required to permit activation of BK currents at a depolarized resting membrane potential that frequently occur in non-excitable tumour cells.

Experimental Approach: Anti-tumour effects of BKα loss were investigated in breast tumour-bearing MMTV-PyMT transgenic BKα knockout (KO) mice, primary MMTV-PyMT cell cultures, and in a syngeneic transplantation model of breast cancer derived from these cells. The therapeutic relevance of BK channels in the context of endocrine treatment was assessed in human breast cancer cell lines expressing either low (MCF-7) or high (MDA-MB-453) levels of BKα and BKγ1, as well as in BKα-negative MDA-MB-157.

Key Results: BKα promoted breast cancer onset and overall survival in preclinical models. Conversely, lack of BKα and/or knockdown of BKγ1 attenuated proliferation of murine and human breast cancer cells in vitro. At low concentrations, tamoxifen and its major active metabolites stimulated proliferation of BKα/γ1-positive breast cancer cells, independent of the genomic signalling controlled by the oestrogen receptor. Finally, tamoxifen increased the relative survival time of BKα KO but not of wild-type tumour cell recipient mice.

Conclusion And Implications: Breast cancer initiation, progression, and tamoxifen sensitivity depend on functional BK channels thereby providing a rationale for the future exploration of the oncogenic actions of BK channels in clinical outcomes with anti-oestrogen therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/bph.15147DOI Listing
May 2020

Antimicrobial prescriptions and adherence to prudent use guidelines for selected canine diseases in Switzerland in 2016.

Vet Rec Open 2020 9;7(1):e000370. Epub 2020 Mar 9.

Department Clinical Veterinary Medicine, Division Small Animal Internal Medicine, Vetsuisse Faculty University of Bern, Bern, Switzerland.

Background: Antimicrobial resistance is an increasing problem in human and veterinary medicine and is closely linked to the use of antimicrobials. The objective of this study was to describe antimicrobial prescriptions for selected canine diseases in Switzerland during 2016.

Methods: Dogs presented to two university hospitals and 14 private practices for acute diarrhoea (AD; n=371), suspected or confirmed urinary tract infections (UTIs; n=245), respiratory tract infections (RTIs; n=274) or wound infections (WIs; n=175) were included. Clinical history, diagnostic work-up and antimicrobial prescription (class, dosage and duration) were retrospectively assessed. A justification score was applied to evaluate appropriateness of antimicrobial therapy based on available national and international consensus guidelines.

Results: Antimicrobials were prescribed in 65 per cent of dogs with AD, 88 per cent with UTI, 62 per cent with RTI and 90 per cent with WI. The most prescribed antimicrobial classes (monotherapy and combination therapy) were potentiated aminopenicillins (59 per cent), nitroimidazoles (22 per cent), non-potentiated aminopenicillins (16 per cent) and fluoroquinolones (13 per cent). Overall, 38 per cent (95 per cent CI 0.35 to 0.41) of the prescriptions were in accordance with consensus guidelines. In dogs with AD, antimicrobial therapy was associated with the presence of haemorrhagic diarrhoea (P<0.05) and complied in 32 per cent with consensus guidelines, which recommend antimicrobial treatment only when sepsis is suspected. A bacterial aetiology was confirmed via culture and/or sediment examination in 36 per cent of dogs with suspected UTI.

Conclusions: Overall, adherence to consensus guidelines was poor both, at university hospitals and private practices. Antimicrobial stewardship measures are therefore needed to improve prudent use.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/vetreco-2019-000370DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064144PMC
March 2020

Impaired motor skill learning and altered seizure susceptibility in mice with loss or gain of function of the Kcnt1 gene encoding Slack (K1.1) Na-activated K channels.

Sci Rep 2020 02 21;10(1):3213. Epub 2020 Feb 21.

Departments of Pharmacology and Cellular and Molecular Physiology, Yale University, New Haven, CT, USA.

Gain-of-function mutations in KCNT1, the gene encoding Slack (K1.1) channels, result in epilepsy of infancy with migrating focal seizures (EIMFS) and several other forms of epilepsy associated with severe intellectual disability. We have generated a mouse model of this condition by replacing the wild type gene with one encoding Kcnt1, a cytoplasmic C-terminal mutation homologous to a human R474H variant that results in EIMFS. We compared behavior patterns and seizure activity in these mice with those of wild type mice and Kcnt1 mice. Complete loss of Kcnt1 produced deficits in open field behavior and motor skill learning. Although their thresholds for electrically and chemically induced seizures were similar to those of wild type animals, Kcnt1 mice were significantly protected from death after maximum electroshock-induced seizures. In contrast, homozygous Kcnt1 mice were embryonic lethal. Video-EEG monitoring of heterozygous Kcnt1 animals revealed persistent interictal spikes, spontaneous seizures and a substantially decreased threshold for pentylenetetrazole-induced seizures. Surprisingly, Kcnt1 mice were not impaired in tasks of exploratory behavior or procedural motor learning. These findings provide an animal model for EIMFS and suggest that Slack channels are required for the development of procedural learning and of pathways that link cortical seizures to other regions required for animal survival.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-60028-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7035262PMC
February 2020

K3.1 Channels Confer Radioresistance to Breast Cancer Cells.

Cancers (Basel) 2019 Sep 1;11(9). Epub 2019 Sep 1.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, 72076 Tuebingen, Germany.

K3.1 K channels reportedly contribute to the proliferation of breast tumor cells and may serve pro-tumor functions in the microenvironment. The putative interaction of K3.1 with major anti-cancer treatment strategies, which are based on cytotoxic drugs or radiotherapy, remains largely unexplored. We employed K3.1-proficient and -deficient breast cancer cells derived from breast cancer-prone MMTV-PyMT mice, pharmacological K3.1 inhibition, and a syngeneic orthotopic mouse model to study the relevance of functional K3.1 for therapy response. The K3.1 status of MMTV-PyMT cells did not determine tumor cell proliferation after treatment with different concentrations of docetaxel, doxorubicin, 5-fluorouracil, or cyclophosphamide. K3.1 activation by ionizing radiation (IR) in breast tumor cells in vitro, however, enhanced radioresistance, probably via an involvement of the channel in IR-stimulated Ca signals and DNA repair pathways. Consistently, K3.1 knockout increased survival time of wildtype mice upon syngeneic orthotopic transplantation of MMTV-PyMT tumors followed by fractionated radiotherapy. Combined, our results imply that K3.1 confers resistance to radio- but not to chemotherapy in the MMTV-PyMT breast cancer model. Since K3.1 is druggable, K3.1 targeting concomitant to radiotherapy seems to be a promising strategy to radiosensitize breast tumors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/cancers11091285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770875PMC
September 2019

Dynamic- and Frequency-Specific Regulation of Sleep Oscillations by Cortical Potassium Channels.

Curr Biol 2019 09 29;29(18):2983-2992.e3. Epub 2019 Aug 29.

Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, University of Zürich, Winterthurerstrasse 190, Zürich 8057, Switzerland. Electronic address:

Primary electroencephalographic (EEG) features of sleep arise in part from thalamocortical neural assemblies, and cortical potassium channels have long been thought to play a critical role. We have exploited the regionally dynamic nature of sleep EEG to develop a novel screening strategy and used it to conduct an adeno-associated virus (AAV)-mediated RNAi screen for cellular roles of 31 different voltage-gated potassium channels in modulating cortical EEG features across the circadian sleep-wake cycle. Surprisingly, a majority of channels modified only electroencephalographic frequency bands characteristic of sleep, sometimes diurnally or even in specific vigilance states. Confirming our screen for one channel, we show that depletion of the KCa1.1 (or "BK") channel reduces EEG power in slow-wave sleep by slowing neuronal repolarization. Strikingly, this reduction completely abolishes transcriptomic changes between sleep and wake. Thus, our data establish an unexpected connection between transcription and EEG power controlled by specific potassium channels. We postulate that additive dynamic roles of individual potassium channels could integrate different influences upon sleep and wake within single neurons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cub.2019.07.056DOI Listing
September 2019

Expression of the LRRC52 γ subunit (γ2) may provide Ca-independent activation of BK currents in mouse inner hair cells.

FASEB J 2019 11 26;33(11):11721-11734. Epub 2019 Jul 26.

Hearing Research, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany.

Mammalian inner hair cells (IHCs) transduce sound into depolarization and transmitter release. Big conductance and voltage- and Ca-activated K (BK) channels are responsible for fast membrane repolarization and small time constants of mature IHCs. For unknown reasons, they activate at around -75 mV with a voltage of half-maximum activation () of -50 mV although being largely insensitive to Ca influx. Ca-independent activation of BK channels was observed by others in heterologous expression systems if γ subunits leucine-rich repeat-containing protein (LRRC)26 (γ1) and LRRC52 (γ2) were coexpressed with the pore-forming BKα subunit, which shifted by -140 and -100 mV, respectively. Using nested PCR, we consistently detected transcripts for LRRC52 but not for LRRC26 in IHCs of 3-wk-old mice. Confocal immunohistochemistry showed synchronous up-regulation of LRRC52 protein with BKα at the onset of hearing. Colocalization of LRRC52 protein and BKα at the IHC neck within ≤40 nm was specified using an proximity ligation assay. Mice deficient for the voltage-gated Ca1.3 Ca channel encoded by do not express BKα protein. LRRC52 protein was neither expressed in IHCs of BKα nor in IHCs of Ca1.3 knockout mice. Together, LRRC52 is a γ2 subunit of BK channel complexes and is a strong candidate for causing the Ca-independent activation of BK currents at negative membrane potentials in mouse IHCs.-Lang, I., Jung, M., Niemeyer, B. A., Ruth, P., Engel, J. Expression of the LRRC52 γ subunit (γ2) may provide Ca-independent activation of BK currents in mouse inner hair cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1096/fj.201900701RRDOI Listing
November 2019

A new host cell internalisation pathway for SadA-expressing staphylococci triggered by excreted neurochemicals.

Cell Microbiol 2019 09 7;21(9):e13044. Epub 2019 Jun 7.

Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.

Staphylococcus aureus is a facultative intracellular pathogen that invades a wide range of professional and nonprofessional phagocytes by triggering internalisation by interaction of surface-bound adhesins with corresponding host cell receptors. Here, we identified a new concept of host cell internalisation in animal-pathogenic staphylococcal species. This new mechanism exemplified by Staphylococcus pseudintermedius ED99 is not based on surface-bound adhesins but is due to excreted small neurochemical compounds, such as trace amines (TAs), dopamine (DOP), and serotonin (SER), that render host cells competent for bacterial internalisation. The neurochemicals are produced by only one enzyme, the staphylococcal aromatic amino acid decarboxylase (SadA). Here, we unravelled the mechanism of how neurochemicals trigger internalisation into the human colon cell line HT-29. We found that TAs and DOP are agonists of the α2-adrenergic receptor, which, when activated, induces a cascade of reactions involving a decrease in the cytoplasmic cAMP level and an increase in F-actin formation. The signalling cascade of SER follows a different pathway. SER interacts with 5HT receptors that trigger F-actin formation without decreasing the cytoplasmic cAMP level. The neurochemical-induced internalisation in host cells is independent of the fibronectin-binding protein pathway and has an additive effect. In a sadA deletion mutant, ED99ΔsadA, internalisation was decreased approximately threefold compared with that of the parent strain, and treating S. aureus USA300 with TAs increased internalisation by approximately threefold.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cmi.13044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6771854PMC
September 2019

Cancer-Associated Intermediate Conductance Ca-Activated K⁺ Channel K3.1.

Cancers (Basel) 2019 Jan 17;11(1). Epub 2019 Jan 17.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, 72076 Tuebingen, Germany.

Several tumor entities have been reported to overexpress K3.1 potassium channels due to epigenetic, transcriptional, or post-translational modifications. By modulating membrane potential, cell volume, or Ca signaling, K3.1 has been proposed to exert pivotal oncogenic functions in tumorigenesis, malignant progression, metastasis, and therapy resistance. Moreover, K3.1 is expressed by tumor-promoting stroma cells such as fibroblasts and the tumor vasculature suggesting a role of K3.1 in the adaptation of the tumor microenvironment. Combined, this features K3.1 as a candidate target for innovative anti-cancer therapy. However, immune cells also express K3.1 thereby contributing to T cell activation. Thus, any strategy targeting K3.1 in anti-cancer therapy may also modulate anti-tumor immune activity and/or immunosuppression. The present review article highlights the potential of K3.1 as an anti-tumor target providing an overview of the current knowledge on its function in tumor pathogenesis with emphasis on vasculo- and angiogenesis as well as anti-cancer immune responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/cancers11010109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357066PMC
January 2019

Accessory heterozygous mutations in cone photoreceptor CNGA3 exacerbate CNG channel-associated retinopathy.

J Clin Invest 2018 12 12;128(12):5663-5675. Epub 2018 Nov 12.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy.

Mutations in CNGA3 and CNGB3, the genes encoding the subunits of the tetrameric cone photoreceptor cyclic nucleotide-gated ion channel, cause achromatopsia, a congenital retinal disorder characterized by loss of cone function. However, a small number of patients carrying the CNGB3/c.1208G>A;p.R403Q mutation present with a variable retinal phenotype ranging from complete and incomplete achromatopsia to moderate cone dysfunction or progressive cone dystrophy. By exploring a large patient cohort and published cases, we identified 16 unrelated individuals who were homozygous or (compound-)heterozygous for the CNGB3/c.1208G>A;p.R403Q mutation. In-depth genetic and clinical analysis revealed a co-occurrence of a mutant CNGA3 allele in a high proportion of these patients (10 of 16), likely contributing to the disease phenotype. To verify these findings, we generated a Cngb3R403Q/R403Q mouse model, which was crossbred with Cnga3-deficient (Cnga3-/-) mice to obtain triallelic Cnga3+/- Cngb3R403Q/R403Q mutants. As in human subjects, there was a striking genotype-phenotype correlation, since the presence of 1 Cnga3-null allele exacerbated the cone dystrophy phenotype in Cngb3R403Q/R403Q mice. These findings strongly suggest a digenic and triallelic inheritance pattern in a subset of patients with achromatopsia/severe cone dystrophy linked to the CNGB3/p.R403Q mutation, with important implications for diagnosis, prognosis, and genetic counseling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/JCI96098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264655PMC
December 2018

BDNF-Live-Exon-Visualization (BLEV) Allows Differential Detection of BDNF Transcripts and .

Front Mol Neurosci 2018 27;11:325. Epub 2018 Sep 27.

Department of Otolaryngology, Tübingen Hearing Research Centre (THRC), Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany.

exon-IV and exon-VI transcripts are driven by neuronal activity and are involved in pathologies related to sleep, fear or memory disorders. However, how their differential transcription translates activity changes into long-lasting network changes is elusive. Aiming to trace specifically the network controlled by exon-IV and -VI derived BDNF during activity-dependent plasticity changes, we generated a transgenic reporter mouse for - - ), in which expression of exon-IV and -VI can be visualized by co-expression of CFP and YFP. CFP and YFP expression was differentially activated and targeted in cell lines, primary cultures and BLEV reporter mice without interfering with BDNF protein synthesis. CFP and YFP expression, moreover, overlapped with BDNF protein expression in defined hippocampal neuronal, glial and vascular locations . So far, activity-dependent BDNF cannot be explicitly monitored independent of basal BDNF levels. The BLEV reporter mouse therefore provides a new model, which can be used to test whether stimulus-induced activity-dependent changes in BDNF expression are instrumental for long-lasting plasticity modifications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnmol.2018.00325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170895PMC
September 2018

Visualizing BDNF Transcript Usage During Sound-Induced Memory Linked Plasticity.

Front Mol Neurosci 2018 31;11:260. Epub 2018 Jul 31.

Department of Otolaryngology, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany.

Activity-dependent BDNF (brain-derived neurotrophic factor) expression is hypothesized to be a cue for the context-specificity of memory formation. So far, activity-dependent BDNF cannot be explicitly monitored independently of basal BDNF levels. We used the BLEV ( DNF- - ) reporter mouse to specifically detect activity-dependent usage of exon-IV and -VI promoters through bi-cistronic co-expression of CFP and YFP, respectively. Enriching acoustic stimuli led to improved peripheral and central auditory brainstem responses, increased Schaffer collateral LTP, and enhanced performance in the Morris water maze. Within the brainstem, neuronal activity was increased and accompanied by a trend for higher expression levels of exon-IV-CFP and exon-VI-YFP transcripts. In the hippocampus BDNF transcripts were clearly increased parallel to changes in parvalbumin expression and were localized to specific neurons and capillaries. Severe acoustic trauma, in contrast, elevated neither transcript levels, nor auditory responses, parvalbumin or LTP. Together, this suggests that critical sensory input is essential for recruitment of activity-dependent auditory-specific BDNF expression that may shape network adaptation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnmol.2018.00260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6089339PMC
July 2018

Purkinje cell BKchannel ablation induces abnormal rhythm in deep cerebellar nuclei and prevents LTD.

Sci Rep 2018 03 9;8(1):4220. Epub 2018 Mar 9.

Laboratory of Neurophysiology and Movement Biomechanics, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium.

Purkinje cells (PC) control deep cerebellar nuclei (DCN), which in turn inhibit inferior olive nucleus, closing a positive feedback loop via climbing fibers. PC highly express potassium BK channels but their contribution to the olivo-cerebellar loop is not clear. Using multiple-unit recordings in alert mice we found in that selective deletion of BK channels in PC induces a decrease in their simple spike firing with a beta-range bursting pattern and fast intraburst frequency (~200 Hz). To determine the impact of this abnormal rhythm on the olivo-cerebellar loop we analyzed simultaneous rhythmicity in different cerebellar structures. We found that this abnormal PC rhythmicity is transmitted to DCN neurons with no effect on their mean firing frequency. Long term depression at the parallel-PC synapses was altered and the intra-burst complex spike spikelets frequency was increased without modification of the mean complex spike frequency in BK-PC mice. We argue that the ataxia present in these conditional knockout mice could be explained by rhythmic disruptions transmitted from mutant PC to DCN but not by rate code modification only. This suggests a neuronal mechanism for ataxia with possible implications for human disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-018-22654-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5845018PMC
March 2018

Cardioprotection by ischemic postconditioning and cyclic guanosine monophosphate-elevating agents involves cardiomyocyte nitric oxide-sensitive guanylyl cyclase.

Cardiovasc Res 2018 05;114(6):822-829

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, 72076 Tübingen, Germany.

Aims: It has been suggested that the nitric oxide-sensitive guanylyl cyclase (NO-GC)/cyclic guanosine monophosphate (cGMP)-dependent signalling pathway affords protection against cardiac damage during acute myocardial infarction (AMI). It is, however, not clear whether the NO-GC/cGMP system confers its favourable effects through a mechanism located in cardiomyocytes (CMs). The aim of this study was to evaluate the infarct-limiting effects of the endogenous NO-GC in CMs in vivo.

Methods And Results: Ischemia/reperfusion (I/R) injury was evaluated in mice with a CM-specific deletion of NO-GC (CM NO-GC KO) and in control siblings (CM NO-GC CTR) subjected to an in vivo model of AMI. Lack of CM NO-GC resulted in a mild increase in blood pressure but did not affect basal infarct sizes after I/R. Ischemic postconditioning (iPost), administration of the phosphodiesterase-5 inhibitors sildenafil and tadalafil as well as the NO-GC activator cinaciguat significantly reduced the amount of infarction in control mice but not in CM NO-GC KO littermates. Interestingly, NS11021, an opener of the large-conductance and Ca2+-activated potassium channel (BK), an important downstream effector of cGMP/cGKI in the cardiovascular system, protects I/R-exposed hearts of CM NO-GC proficient and deficient mice.

Conclusions: These findings demonstrate an important role of CM NO-GC for the cardioprotective signalling following AMI in vivo. CM NO-GC function is essential for the beneficial effects on infarct size elicited by iPost and pharmacological elevation of cGMP; however, lack of CM NO-GC does not seem to disrupt the cardioprotection mediated by the BK opener NS11021.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/cvr/cvy039DOI Listing
May 2018

TRPM8 is required for survival and radioresistance of glioblastoma cells.

Oncotarget 2017 Nov 30;8(56):95896-95913. Epub 2017 Sep 30.

Department of Radiation Oncology, University of Tübingen, Tübingen, Germany.

TRPM8 is a Ca-permeable nonselective cation channel belonging to the melastatin sub-group of the transient receptor potential (TRP) family. TRPM8 is aberrantly overexpressed in a variety of tumor entities including glioblastoma multiforme where it reportedly contributes to tumor invasion. The present study aimed to disclose further functions of TRPM8 in glioma biology in particular upon cell injury by ionizing radiation. To this end, TCGA data base was queried to expose the TRPM8 mRNA abundance in human glioblastoma specimens and immunoblotting was performed to analyze the TRPM8 protein abundance in primary cultures of human glioblastoma. Moreover, human glioblastoma cell lines were irradiated with 6 MV photons and TRPM8 channels were targeted pharmacologically or by RNA interference. TRPM8 abundance, Ca signaling and resulting K channel activity, chemotaxis, cell migration, clonogenic survival, DNA repair, apoptotic cell death, and cell cycle control were determined by qRT-PCR, fura-2 Ca imaging, patch-clamp recording, transfilter migration assay, wound healing assay, colony formation assay, immunohistology, flow cytometry, and immunoblotting. As a result, human glioblastoma upregulates TRPM8 channels to variable extent. TRPM8 inhibition or knockdown slowed down cell migration and chemotaxis, attenuated DNA repair and clonogenic survival, triggered apoptotic cell death, impaired cell cycle and radiosensitized glioblastoma cells. Mechanistically, ionizing radiation activated and upregulated TRPM8-mediated Ca signaling that interfered with cell cycle control probably via CaMKII, cdc25C and cdc2. Combined, our data suggest that TRPM8 channels contribute to spreading, survival and radioresistance of human glioblastoma and, therefore, might represent a promising target in future anti-glioblastoma therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.18632/oncotarget.21436DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707069PMC
November 2017

cGMP-Elevating Compounds and Ischemic Conditioning Provide Cardioprotection Against Ischemia and Reperfusion Injury via Cardiomyocyte-Specific BK Channels.

Circulation 2017 Dec 19;136(24):2337-2355. Epub 2017 Oct 19.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Germany (S.F., A.K., J.S., E.M., P.R., R.L.)

Background: The nitric oxide-sensitive guanylyl cyclase/cGMP-dependent protein kinase type I signaling pathway can afford protection against the ischemia/reperfusion injury that occurs during myocardial infarction. Reportedly, voltage and Ca-activated K channels of the BK type are stimulated by cGMP/cGMP-dependent protein kinase type I, and recent ex vivo studies implicated that increased BK activity favors the survival of the myocardium at ischemia/reperfusion. It remains unclear, however, whether the molecular events downstream of cGMP involve BK channels present in cardiomyocytes or in other cardiac cell types.

Methods: Gene-targeted mice with a cardiomyocyte- or smooth muscle cell-specific deletion of the BK (CMBK or SMBK knockouts) were subjected to the open-chest model of myocardial infarction. Infarct sizes of the conditional mutants were compared with litter-matched controls, global BK knockout, and wild-type mice. Cardiac damage was assessed after mechanical conditioning or pharmacological stimulation of the cGMP pathway and by using direct modulators of BK. Long-term outcome was studied with respect to heart functions and cardiac fibrosis in a chronic myocardial infarction model.

Results: Global BK knockouts and CMBK knockouts, in contrast with SMBK knockouts, exhibited significantly larger infarct sizes compared with their respective controls. Ablation of CMBK resulted in higher serum levels of cardiac troponin I and elevated amounts of reactive oxygen species, lower phosphorylated extracellular receptor kinase and phosphorylated AKT levels and an increase in myocardial apoptosis. Moreover, CMBK was required to allow beneficial effects of both nitric oxide-sensitive guanylyl cyclase activation and inhibition of the cGMP-degrading phosphodiesterase-5, ischemic preconditioning, and postconditioning regimens. To this end, after 4 weeks of reperfusion, fibrotic tissue increased and myocardial strain echocardiography was significantly compromised in CMBK-deficient mice.

Conclusions: Lack of CMBK channels renders the heart more susceptible to ischemia/reperfusion injury, whereas the pathological events elicited by ischemia/reperfusion do not involve BK in vascular smooth muscle cells. BK seems to permit the protective effects triggered by cinaciguat, riociguat, and different phosphodiesterase-5 inhibitors and beneficial actions of ischemic preconditioning and ischemic postconditioning by a mechanism stemming primarily from cardiomyocytes. This study establishes mitochondrial CMBK channels as a promising target for limiting acute cardiac damage and adverse long-term events that occur after myocardial infarction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCULATIONAHA.117.028723DOI Listing
December 2017

NO-Sensitive Guanylate Cyclase Isoforms NO-GC1 and NO-GC2 Contribute to Noise-Induced Inner Hair Cell Synaptopathy.

Mol Pharmacol 2017 10;92(4):375-388

Department of Otolaryngology, Head and Neck Surgery, Hearing Research Centre Tübingen, Molecular Physiology of Hearing, University of Tübingen, Tübingen (D.M., K.R., S.W., K.V., N.E., H.-S.G., U.Z., M.K., L.R.), Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen (M.W., R.F.), Department of Pharmacology and Toxicology, University of Bochum, Bochum (E.M., D.K.), Bayer AG, Drug Discovery Pharma Research Centre Wuppertal, Wuppertal (P.S.), Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen (P.R.), and Department of Physiology, University of Würzburg, Würzburg (A.F.), Germany

Nitric oxide (NO) activates the NO-sensitive soluble guanylate cyclase (NO-GC, sGC) and triggers intracellular signaling pathways involving cGMP. For survival of cochlear hair cells and preservation of hearing, NO-mediated cascades have both protective and detrimental potential. Here we examine the cochlear function of mice lacking one of the two NO-sensitive guanylate cyclase isoforms [NO-GC1 knockout (KO) or NO-GC2 KO]. The deletion of NO-GC1 or NO-GC2 did not influence electromechanical outer hair cell (OHC) properties, as measured by distortion product otoacoustic emissions, neither before nor after noise exposure, nor were click- or noise-burst-evoked auditory brainstem response thresholds different from controls. Yet inner hair cell (IHC) ribbons and auditory nerve responses showed significantly less deterioration in NO-GC1 KO and NO-GC2 KO mice after noise exposure. Consistent with a selective role of NO-GC in IHCs, NO-GC 1 mRNA was found in isolated IHCs but not in OHCs. Using transgenic mice expressing the fluorescence resonance energy transfer-based cGMP biosensor cGi500, NO-induced elevation of cGMP was detected in real-time in IHCs but not in OHCs. Pharmacologic long-term treatment with a NO-GC stimulator altered auditory nerve responses but did not affect OHC function and hearing thresholds. Interestingly, NO-GC stimulation exacerbated the loss of auditory nerve response in aged animals but attenuated the loss in younger animals. We propose NO-GC2 and, to some degree, NO-GC1 as targets for early pharmacologic prevention of auditory fiber loss (synaptopathy). Both isoforms provide selective benefits for hearing function by maintaining the functional integrity of auditory nerve fibers in early life rather than at old age.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/mol.117.108548DOI Listing
October 2017

K3.1 channels modulate the processing of noxious chemical stimuli in mice.

Neuropharmacology 2017 Oct 18;125:386-395. Epub 2017 Aug 18.

Pharmakologisches Institut für Naturwissenschaftler, Goethe-Universität, Fachbereich Biochemie, Chemie und Pharmazie, 60438 Frankfurt am Main, Germany; Institut für Pharmakologie und Toxikologie, Universität Witten/Herdecke, ZBAF, 58453 Witten, Germany.

Intermediate conductance calcium-activated potassium channels (K3.1) have been recently implicated in pain processing. However, the functional role and localization of K3.1 in the nociceptive system are largely unknown. We here characterized the behavior of mice lacking K3.1 (K3.1) in various pain models and analyzed the expression pattern of K3.1 in dorsal root ganglia (DRG) and the spinal cord. K3.1 mice demonstrated normal behavioral responses in models of acute nociceptive, persistent inflammatory, and persistent neuropathic pain. However, their behavioral responses to noxious chemical stimuli such as formalin and capsaicin were increased. Accordingly, formalin-induced nociceptive behavior was increased in wild-type mice after administration of the K3.1 inhibitor TRAM-34. In situ hybridization experiments detected K3.1 in most DRG satellite glial cells, in a minority of DRG neurons, and in ependymal cells lining the central canal of the spinal cord. Together, our data point to a specific inhibitory role of K3.1 for the processing of noxious chemical stimuli.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuropharm.2017.08.021DOI Listing
October 2017

Slack K Channels Influence Dorsal Horn Synapses and Nociceptive Behavior.

Mol Pain 2017 Jan-Dec;13:1744806917714342

Program in Neuroscience, University at Buffalo, The State University of New York, NY, USA.

Abstract: The sodium-activated potassium channel Slack (Kcnt1, Slo2.2) is highly expressed in dorsal root ganglion neurons where it regulates neuronal firing. Several studies have implicated the Slack channel in pain processing, but the precise mechanism or the levels within the sensory pathway where channels are involved remain unclear. Here, we furthered the behavioral characterization of Slack channel knockout mice and for the first time examined the role of Slack channels in the superficial, pain-processing lamina of the dorsal horn. We performed whole-cell recordings from spinal cord slices to examine the intrinsic and synaptic properties of putative inhibitory and excitatory lamina II interneurons. Slack channel deletion altered intrinsic properties and synaptic drive to favor an overall enhanced excitatory tone. We measured the amplitudes and paired pulse ratio of paired excitatory post-synaptic currents at primary afferent synapses evoked by electrical stimulation of the dorsal root entry zone. We found a substantial decrease in the paired pulse ratio at synapses in Slack deleted neurons compared to wildtype, indicating increased presynaptic release from primary afferents. Corroborating these data, plantar test showed Slack knockout mice have an enhanced nociceptive responsiveness to localized thermal stimuli compared to wildtype mice. Our findings suggest that Slack channels regulate synaptic transmission within the spinal cord dorsal horn and by doing so establishes the threshold for thermal nociception.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1744806917714342DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5486487PMC
September 2018

SK4 channels modulate Ca signalling and cell cycle progression in murine breast cancer.

Mol Oncol 2017 09 26;11(9):1172-1188. Epub 2017 Jun 26.

Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Germany.

Oncogenic signalling via Ca -activated K channels of intermediate conductance (SK4, also known as K 3.1 or IK) has been implicated in different cancer entities including breast cancer. Yet, the role of endogenous SK4 channels for tumorigenesis is unclear. Herein, we generated SK4-negative tumours by crossing SK4-deficient (SK4 KO) mice to the polyoma middle T-antigen (PyMT) and epidermal growth factor receptor 2 (cNeu) breast cancer models in which oncogene expression is driven by the retroviral promoter MMTV. Survival parameters and tumour progression were studied in cancer-prone SK4 KO in comparison with wild-type (WT) mice and in a syngeneic orthotopic mouse model following transplantation of SK4-negative or WT tumour cells. SK4 activity was modulated by genetic or pharmacological means using the SK4 inhibitor TRAM-34 in order to establish the role of breast tumour SK4 for cell growth, electrophysiological signalling, and [Ca ] oscillations. Ablation of SK4 and TRAM-34 treatment reduced the SK4-generated current fraction, growth factor-dependent Ca entry, cell cycle progression and the proliferation rate of MMTV-PyMT tumour cells. In vivo, PyMT oncogene-driven tumorigenesis was only marginally affected by the global lack of SK4, whereas tumour progression was significantly delayed after orthotopic implantation of MMTV-PyMT SK4 KO breast tumour cells. However, overall survival and progression-free survival time in the MMTV-cNeu mouse model were significantly extended in the absence of SK4. Collectively, our data from murine breast cancer models indicate that SK4 activity is crucial for cell cycle control. Thus, the modulation of this channel should be further investigated towards a potential improvement of existing antitumour strategies in human breast cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/1878-0261.12087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579333PMC
September 2017

Amplified pathogenic actions of angiotensin II in cysteine-rich LIM-only protein 4-negative mouse hearts.

FASEB J 2017 04 30;31(4):1620-1638. Epub 2017 Jan 30.

Department of Pharmacology, Toxicology, and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany;

LIM domain proteins have been identified as essential modulators of cardiac biology and pathology; however, it is unclear which role the cysteine-rich LIM-only protein (CRP)4 plays in these processes. In studying CRP4 mutant mice, we found that their hearts developed normally, but lack of CRP4 exaggerated multiple parameters of the cardiac stress response to the neurohormone angiotensin II (Ang II). Aiming to dissect the molecular details, we found a link between CRP4 and the cardioprotective cGMP pathway, as well as a multiprotein complex comprising well-known hypertrophy-associated factors. ignificant enrichment of the cysteine-rich intestinal protein (CRIP)1 in murine hearts lacking CRP4, as well as severe cardiac defects and premature death of CRIP1 and CRP4 morphant zebrafish embryos, further support the notion that depleting CRP4 is incompatible with a proper cardiac development and function. Together, amplified Ang II signaling identified CRP4 as a novel antiremodeling factor regulated, at least to some extent, by cardiac cGMP.-Straubinger, J., Boldt, K., Kuret, A., Deng, L., Krattenmacher, D., Bork, N., Desch, M., Feil, R., Feil, S., Nemer, M., Ueffing, M., Ruth, P., Just, S., Lukowski, R. Amplified pathogenic actions of angiotensin II in cysteine-rich LIM-only protein 4 negative mouse hearts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1096/fj.201601186DOI Listing
April 2017

In vitro Evaluation of the Cleansing Effect of a Monofilament Fiber Debridement Pad Compared to Gauze Swabs.

Skin Pharmacol Physiol 2016 18;29(6):318-323. Epub 2017 Jan 18.

Department of Dermatology, University Hospital Jena, Jena, Germany.

Background: Removal of nonvital tissue is an accepted method to eradicate biofilms and to stimulate wound healing. Debridement using a monofilament polyester fiber pad has clinically been shown to be effective as well as pain and trauma free.

Methods: For in vitro determination of the cleansing capacity of this product compared to gauze swabs, a wound debridement model was used with glass plates coated with a bovine serum albumin solution, stained with hematoxylin. Both products were moistened and fixed to a weight connected to a regulated motor and were then pulled over the holding device with the coated glass plate under standardized conditions (power = 0.067 N/cm2, velocity = 1.6 cm/s).

Results: At a low coating concentration (0.5%) both products were equally effective, but at a high concentration (1.5%) cleansing did not occur after 5 wipes. When wiping the plates 15 times, the debridement pad cleansed significantly (p < 0.001) better than gauze. When consecutively wiping 4 coated plates with a single debridement pad or swab, the pad exhibited and maintained a significantly higher cleansing capacity while gauze quickly lost its effect.

Conclusion: Our in vitro test results indicated a higher cleansing capacity of the debridement pad compared to gauze swabs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1159/000454720DOI Listing
March 2017

Obesogenic and Diabetogenic Effects of High-Calorie Nutrition Require Adipocyte BK Channels.

Diabetes 2016 Dec 7;65(12):3621-3635. Epub 2016 Sep 7.

Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, Tübingen, Germany

Elevated adipose tissue expression of the Ca- and voltage-activated K (BK) channel was identified in morbidly obese men carrying a BK gene variant, supporting the hypothesis that K channels affect the metabolic responses of fat cells to nutrients. To establish the role of endogenous BKs in fat cell maturation, storage of excess dietary fat, and body weight (BW) gain, we studied a gene-targeted mouse model with global ablation of the BK channel (BK) and adipocyte-specific BK-deficient (adipoqBK) mice. Global BK deficiency afforded protection from BW gain and excessive fat accumulation induced by a high-fat diet (HFD). Expansion of white adipose tissue-derived epididymal BK preadipocytes and their differentiation to lipid-filled mature adipocytes in vitro, however, were improved. Moreover, BW gain and total fat masses of usually superobese ob/ob mice were significantly attenuated in the absence of BK, together supporting a central or peripheral role for BKs in the regulatory system that controls adipose tissue and weight. Accordingly, HFD-fed adipoqBK mutant mice presented with a reduced total BW and overall body fat mass, smaller adipocytes, and reduced leptin levels. Protection from pathological weight gain in the absence of adipocyte BKs was beneficial for glucose handling and related to an increase in body core temperature as a result of higher levels of uncoupling protein 1 and a low abundance of the proinflammatory interleukin-6, a common risk factor for diabetes and metabolic abnormalities. This suggests that adipocyte BK activity is at least partially responsible for excessive BW gain under high-calorie conditions, suggesting that BK channels are promising drug targets for pharmacotherapy of metabolic disorders and obesity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2337/db16-0245DOI Listing
December 2016

Stimulation of Slack K(+) Channels Alters Mass at the Plasma Membrane by Triggering Dissociation of a Phosphatase-Regulatory Complex.

Cell Rep 2016 08 18;16(9):2281-8. Epub 2016 Aug 18.

Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA; Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA. Electronic address:

Human mutations in the cytoplasmic C-terminal domain of Slack sodium-activated potassium (KNa) channels result in childhood epilepsy with severe intellectual disability. Slack currents can be increased by pharmacological activators or by phosphorylation of a Slack C-terminal residue by protein kinase C. Using an optical biosensor assay, we find that Slack channel stimulation in neurons or transfected cells produces loss of mass near the plasma membrane. Slack mutants associated with intellectual disability fail to trigger any change in mass. The loss of mass results from the dissociation of the protein phosphatase 1 (PP1) targeting protein, Phactr-1, from the channel. Phactr1 dissociation is specific to wild-type Slack channels and is not observed when related potassium channels are stimulated. Our findings suggest that Slack channels are coupled to cytoplasmic signaling pathways and that dysregulation of this coupling may trigger the aberrant intellectual development associated with specific childhood epilepsies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2016.07.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123741PMC
August 2016
-->