Publications by authors named "Philip I Aaronson"

51 Publications

Pulmonary hypertension associated with chronic hypoxia: just ASIC-ness?

J Physiol 2021 Nov 30;599(21):4731-4732. Epub 2021 Sep 30.

Department of Inflammation Biology, School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.

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http://dx.doi.org/10.1113/JP282325DOI Listing
November 2021

Redox Regulation, Oxidative Stress, and Inflammation in Group 3 Pulmonary Hypertension.

Adv Exp Med Biol 2021 ;1303:209-241

School of Immunology and Microbial Sciences, King's College London, London, UK.

Group 3 pulmonary hypertension (PH), which occurs secondary to hypoxia lung diseases, is one of the most common causes of PH worldwide and has a high unmet clinical need. A deeper understanding of the integrative pathological and adaptive molecular mechanisms within this group is required to inform the development of novel drug targets and effective treatments. The production of oxidants is increased in PH Group 3, and their pleiotropic roles include contributing to disease progression by promoting prolonged hypoxic pulmonary vasoconstriction and pathological pulmonary vascular remodeling, but also stimulating adaptation to pathological stress that limits the severity of this disease. Inflammation, which is increasingly being viewed as a key pathological feature of Group 3 PH, is subject to complex regulation by redox mechanisms and is exacerbated by, but also augments oxidative stress. In this review, we investigate aspects of this complex crosstalk between inflammation and oxidative stress in Group 3 PH, focusing on the redox-regulated transcription factor NF-κB and its upstream regulators toll-like receptor 4 and high mobility group box protein 1. Ultimately, we propose that the development of specific therapeutic interventions targeting redox-regulated signaling pathways related to inflammation could be explored as novel treatments for Group 3 PH.
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http://dx.doi.org/10.1007/978-3-030-63046-1_13DOI Listing
April 2021

Hydroxycobalamin Reveals the Involvement of Hydrogen Sulfide in the Hypoxic Responses of Rat Carotid Body Chemoreceptor Cells.

Antioxidants (Basel) 2019 Mar 13;8(3). Epub 2019 Mar 13.

Departamento de Bioquímica y Biología Molecular y Fisiología. Facultad de Medicina. Universidad de Valladolid. Instituto de Biología y Genética Molecular-CSIC, 47005 Valladolid, Spain.

Carotid body (CB) chemoreceptor cells sense arterial blood PO₂, generating a neurosecretory response proportional to the intensity of hypoxia. Hydrogen sulfide (H₂S) is a physiological gaseous messenger that is proposed to act as an oxygen sensor in CBs, although this concept remains controversial. In the present study we have used the H₂S scavenger and vitamin B analog hydroxycobalamin (Cbl) as a new tool to investigate the involvement of endogenous H₂S in CB oxygen sensing. We observed that the slow-release sulfide donor GYY4137 elicited catecholamine release from isolated whole carotid bodies, and that Cbl prevented this response. Cbl also abolished the rise in [Ca] evoked by 50 µM NaHS in enzymatically dispersed CB glomus cells. Moreover, Cbl markedly inhibited the catecholamine release and [Ca] rise caused by hypoxia in isolated CBs and dispersed glomus cells, respectively, whereas it did not alter these responses when they were evoked by high [K⁺]. The L-type Ca channel blocker nifedipine slightly inhibited the rise in CB chemoreceptor cells [Ca] elicited by sulfide, whilst causing a somewhat larger attenuation of the hypoxia-induced Ca signal. We conclude that Cbl is a useful and specific tool for studying the function of H₂S in cells. Based on its effects on the CB chemoreceptor cells we propose that endogenous H₂S is an amplifier of the hypoxic transduction cascade which acts mainly by stimulating non-L-type Ca channels.
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http://dx.doi.org/10.3390/antiox8030062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466535PMC
March 2019

K 1.5 channel down-regulation in pulmonary hypertension is nothing short of MiR-1-aculous!

J Physiol 2019 02 21;597(4):989-990. Epub 2018 Jun 21.

Department of Inflammation Biology, School of Immunology and Microbial Sciences, King's College London, London, UK.

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http://dx.doi.org/10.1113/JP276390DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6376071PMC
February 2019

Actin polymerization contributes to ROS- and Rho-dependent Ca sensitization in pulmonary arteries from chronic hypoxic rats.

Am J Physiol Heart Circ Physiol 2018 08 6;315(2):H314-H317. Epub 2018 Apr 6.

School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine, King's College London , London , United Kingdom.

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http://dx.doi.org/10.1152/ajpheart.00135.2018DOI Listing
August 2018

Role of reactive oxygen species and sulfide-quinone oxoreductase in hydrogen sulfide-induced contraction of rat pulmonary arteries.

Am J Physiol Lung Cell Mol Physiol 2018 04 28;314(4):L670-L685. Epub 2017 Dec 28.

Division of Asthma, Allergy and Lung Biology, King's College London , London , United Kingdom.

Application of HS ("sulfide") elicits a complex contraction in rat pulmonary arteries (PAs) comprising a small transient contraction (phase 1; Ph1) followed by relaxation and then a second, larger, and more sustained contraction (phase 2; Ph2). We investigated the mechanisms causing this response using isometric myography in rat second-order PAs, with NaS as a sulfide donor. Both phases of contraction to 1,000 μM NaS were attenuated by the pan-PKC inhibitor Gö6983 (3 μM) and by 50 μM ryanodine; the Ca channel blocker nifedipine (1 μM) was without effect. Ph2 was attenuated by the mitochondrial complex III blocker myxothiazol (1 μM), the NADPH oxidase (NOX) blocker VAS2870 (10 μM), and the antioxidant TEMPOL (3 mM) but was unaffected by the complex I blocker rotenone (1 μM). The bath sulfide concentration, measured using an amperometric sensor, decreased rapidly following NaS application, and the peak of Ph2 occurred when this had fallen to ~50 μM. Sulfide caused a transient increase in NAD(P)H autofluorescence, the offset of which coincided with development of the Ph2 contraction. Sulfide also caused a brief mitochondrial hyperpolarization (assessed using tetramethylrhodamine ethyl ester), followed immediately by depolarization and then a second more prolonged hyperpolarization, the onset of which was temporally correlated with the Ph2 contraction. Sulfide application to cultured PA smooth muscle cells increased reactive oxygen species (ROS) production (recorded using L012); this was absent when the mitochondrial flavoprotein sulfide-quinone oxoreductase (SQR) was knocked down using small interfering RNA. We propose that the Ph2 contraction is largely caused by SQR-mediated sulfide metabolism, which, by donating electrons to ubiquinone, increases electron production by complex III and thereby ROS production.
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http://dx.doi.org/10.1152/ajplung.00283.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5966778PMC
April 2018

Hydrogen Sulfide as an O Sensor: A Critical Analysis.

Adv Exp Med Biol 2017 ;967:261-276

Division of Asthma, Allergy and Lung Biology, Faculty of Life Sciences and Medicine, King's College London, London, UK.

There is increasing interest in the physiological actions and therapeutic potential of the gasotransmitter hydrogen sulfide (HS). In addition to exerting antihypertensive, anti-inflammatory, antioxidant, and pro-angiogenic effects, HS has been suggested to play a central and ubiquitous role in O sensing. According to this concept, because HS is metabolized by oxidation, its cellular concentration varies inversely with the ambient pO such that hypoxia causes a rise in intracellular [HS]; this then acts to induce appropriate cellular responses. In particular, it has been proposed that HS underpins O sensing in the carotid body, which triggers increases in ventilation in response to hypoxemia, and also in pulmonary arteries, which constrict in response to local alveolar hypoxia. This process, termed hypoxic pulmonary vasoconstriction (HPV), acts to divert blood to better-oxygenated regions of the lung, thereby maintaining the ventilation-perfusion ratio and minimizing hypoxia-induced falls in blood O saturation. In this chapter, we present a critical review of the evidence supporting and questioning this model in both HPV and the carotid body.
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http://dx.doi.org/10.1007/978-3-319-63245-2_15DOI Listing
April 2018

Glabridin-induced vasorelaxation: Evidence for a role of BK channels and cyclic GMP.

Life Sci 2016 Nov 26;165:26-34. Epub 2016 Sep 26.

Division of Asthma, Allergy & Lung Biology, School of Medicine, King's College London, London WC2R 2LS, United Kingdom. Electronic address:

Background And Purpose: Glabridin is a major flavonoid in Glycyrrhiza glabra (licorice) root, a traditional Asian medicine. Glabridin is reported to have anti-atherogenic, anti-inflammatory and anti-nephritic properties; however its effects on vascular tone remain unexplored.

Experimental Approach: We examined the effect of glabridin on rat main mesenteric artery using isometric myography and also ELISA to measure cGMP levels.

Key Results: Glabridin (30μM) relaxed arteries pre-constricted with the thromboxane A analog U46619 (0.2μM) by ~60% in an endothelium-independent manner. Relaxation to 30μM glabridin was abolished by the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (1μM) and by the BK channel blocker tetraethyammonium (1mM) but was unaffected by the estrogen receptor antagonist ICI182780. The concentration-response curve to glabridin (0.1 to 30μM) was downshifted by the K channel blocker glibenclamide (10μM), the K channel blocker 4-aminopyridine (300μM), and the K blocker BaCl (30μM). In U46619-contracted arteries partially relaxed by 0.1μM sodium nitroprusside, application of 10 and 30nM glabridin caused additional vasorelaxation. Glabridin (30μM) approximately doubled tissue [cyclic GMP]. Application of the phosphodiesterase inhibitor isobutylmethylxanthine caused a much larger rise in [cyclic GMP], and glabridin failed to cause vasorelaxation or a further rise in [cGMP] when co-applied with IBMX.

Conclusions And Implications: Vasorelaxation to glabridin is dependent on the opening of K channels, particularly BK, probably caused by a rise in cellular [cyclic GMP] owing to phosphodiesterase inhibition. In the presence of sodium nitroprusside an effect of glabridin is observed at nM concentrations, similar those measured in plasma following human ingestion of licorice flavonoid oil.
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http://dx.doi.org/10.1016/j.lfs.2016.09.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5101995PMC
November 2016

Reactive oxygen species facilitate the EDH response in arterioles by potentiating intracellular endothelial Ca(2+) release.

Free Radic Biol Med 2016 08 16;97:274-284. Epub 2016 Jun 16.

King's College London, Faculty of Life Sciences and Medicine, Division of Asthma, Allergy & Lung Biology, London, United Kingdom. Electronic address:

There is abundant evidence that H2O2 can act as an endothelium-derived hyperpolarizing factor in the resistance vasculature. However, whilst scavenging H2O2 can abolish endothelial dependent hyperpolarization (EDH) and the associated vascular relaxation in some arteries, EDH-dependent vasorelaxation can often be mimicked only by using relatively high concentrations of H2O2. We have examined the role of H2O2 in EDH-dependent vasodilatation by simultaneously measuring vascular diameter and changes in endothelial cell (EC) [Ca(2+)]i during the application of H2O2 or carbachol, which triggers EDH. Carbachol (10µM) induced dilatation of phenylephrine-preconstricted rat cremaster arterioles was largely (73%) preserved in the presence of indomethacin (3µM) and l-NAME (300µM). This residual NO- and prostacyclin-independent dilatation was reduced by 89% upon addition of apamin (0.5µM) and TRAM-34 (10µM), and by 74% when an extracellular ROS scavenging mixture of SOD and catalase (S&C; 100Uml(-1) each) was present. S&C also reduced the carbachol-induced EC [Ca(2+)]i increase by 74%. When applied in Ca(2+)-free external medium, carbachol caused a transient increase in EC [Ca(2+)]i. This was reduced by catalase, and was enhanced when 1µM H2O2 was present in the bath. H2O2 -induced dilatation, which occurred only at concentrations ≥100µM, was reduced by a blocking antibody to TRPM2, which had no effect on carbachol-induced responses. Similarly, iberotoxin and Rp-8bromo cGMP reduced the vasodilatation induced by H2O2, but not by carbachol. Inhibiting PLC, PLA2 or CYP450 2C9 each greatly reduced the carbachol-induced increase in EC [Ca(2+)]i and vasodilatation, but adding 10µM H2O2 during PLA2 or CYP450 2C9 inhibition completely restored both responses. The nature of the effective ROS species was investigated by using Fe(2+) chelators to block the formation of ∙OH. A cell permeant chelator was able to inhibit EC Ca(2+) store release, but cell impermeant chelators reduced both the vasodilatation and EC Ca(2+) influx, implying that ∙OH is required for these responses. The results indicate that rather than mediating EDH by acting directly on smooth muscle, H2O2 promotes EDH by acting within EC to enhance Ca(2+) release.
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http://dx.doi.org/10.1016/j.freeradbiomed.2016.06.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5005039PMC
August 2016

Role of Hydrogen Sulfide in Systemic and Pulmonary Hypertension: Cellular Mechanisms and Therapeutic Implications.

Cardiovasc Hematol Agents Med Chem 2016 ;14(1):4-22

Division of Asthma, Allergy and Lung Biology, King's College London, London, UK.

There is increasing interest in the possible therapeutic benefits of the gasotransmitter hydrogen sulfide (H2S sulfide), and drugs which release sulfide are currently being evaluated in both preclinical and clinical studies as treatments for conditions ranging from cancer to cardiovascular disease to inflammation. Sulfide is generally considered to act as a vasodilator, and it is therefore not surprising that the effects of sulfide donors on both systemic and pulmonary hypertension are being examined. In this review, we provide a critical evaluation of both the evidence that H2S may be of benefit in treating systemic and pulmonary hypertension, and of current hypotheses regarding the cellular mechanisms underlying sulfide's effects on the systemic and pulmonary vascular systems.
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http://dx.doi.org/10.2174/1871525714999160201121220DOI Listing
January 2017

Potentiation of Hypoxic Pulmonary Vasoconstriction by Hydrogen Sulfide Precursors 3-Mercaptopyruvate and D-Cysteine Is Blocked by the Cystathionine γ Lyase Inhibitor Propargylglycine.

Adv Exp Med Biol 2015 ;860:81-7

Division of Asthma, Allergy & Lung Biology, Faculty of Life Sciences and Medicine, King's College London, London, WC2R 2LS, UK.

Although the gasotransmitter hydrogen sulfide (H(2)S) generally dilates systemic arteries in mammals, it causes constriction of pulmonary arteries. In isolated rat pulmonary arteries, we have shown that the H(2)S precursor cysteine enhances both hypoxic pulmonary vasoconstriction and tension development caused by the agonist prostaglandin F(2α) under normoxic conditions. These effects were blocked by propargylglycine (PAG), a blocker of the enzyme cystathionine γ lyase which metabolises cysteine to sulfide. In the present study, we evaluated whether 3-mercaptopyruvate (3-MP), a sulfide precursor which is thought to give rise to sulfide when it is metabolised by the enzyme mercaptopyruvate sulfurtransferase, also enhanced contraction. Application of 3-MP prior to hypoxic challenge caused a marked enhancement of HPV which was completely blocked by both L- and D,L-PAG (both 1 mM). Cumulative application of 3-1,000 μM 3-MP during an ongoing contraction to PGF(2α) under normoxic conditions also caused a marked increase in tension. Application of D-cysteine (1 mM) also enhanced HPV, and this effect was prevented by both the D-amino acid oxidase inhibitor sodium benzoate (500 μM) and 1 mM L-PAG.
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http://dx.doi.org/10.1007/978-3-319-18440-1_10DOI Listing
January 2016

Sphingosylphosphorylcholine potentiates vasoreactivity and voltage-gated Ca2+ entry via NOX1 and reactive oxygen species.

Cardiovasc Res 2015 Apr 6;106(1):121-30. Epub 2015 Feb 6.

Division of Asthma, Allergy, and Lung Biology, King's College London, 5th Floor Tower Wing, Guy's Campus, London SE1 9RT, UK

Aims: Sphingosylphosphorylcholine (SPC) elicits vasoconstriction at micromolar concentrations. At lower concentrations (≤1 µmol/L), however, it does not constrict intrapulmonary arteries (IPAs), but strongly potentiates vasoreactivity. Our aim was to determine whether this also occurs in a systemic artery and to delineate the signalling pathway.

Methods And Results: Rat mesenteric arteries and IPAs mounted on a myograph were challenged with ∼25 mmol/L [K+] to induce a small vasoconstriction. SPC (1 µmol/L) dramatically potentiated this constriction in all arteries by ∼400%. The potentiation was greatly suppressed or abolished by inhibition of phospholipase C (PLC; U73122), PKCε (inhibitory peptide), Src (PP2), and NADPH oxidase (VAS2870), and also by Tempol (superoxide scavenger), but not by inhibition of Rho kinase (Y27632). Potentiation was lost in mesenteric arteries from p47(phox-/-), but not NOX2(-/-), mice. The intracellular superoxide generator LY83583 mimicked the effect of SPC. SPC elevated reactive oxygen species (ROS) in vascular smooth muscle cells, and this was blocked by PP2, VAS2870, and siRNA knockdown of PKCε. SPC (1 µmol/L) significantly reduced the EC50 for U46619-induced vasoconstriction, an action ablated by Tempol. In patch-clamped mesenteric artery cells, SPC (200 nmol/L) enhanced Ba2+ current through L-type Ca2+ channels, an action abolished by Tempol but mimicked by LY83583.

Conclusion: Our results suggest that low concentrations of SPC activate a PLC-coupled and NOX1-mediated increase in ROS, with consequent enhancement of voltage-gated Ca2+ entry and thus vasoreactivity. We speculate that this pathway is not specific for SPC, but may also contribute to vasoconstriction elicited by other G-protein coupled receptor and PLC-coupled agonists.
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http://dx.doi.org/10.1093/cvr/cvv029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4362402PMC
April 2015

Hypoxic pulmonary vasoconstriction in isolated rat pulmonary arteries is not inhibited by antagonists of H2 S-synthesizing pathways.

J Physiol 2015 Jan;593(2):385-401

Division of Asthma, Allergy & Lung Biology, School of Medicine, King's College London, London, WC2R 2LS, UK.

An increase in the H2 S (hydrogen sulphide, hereafter sulphide) concentration in pulmonary artery smooth muscle cells (PASMCs) has been proposed to mediate hypoxic pulmonary vasoconstriction (HPV). We evaluated this hypothesis in isolated rat intrapulmonary arteries (IPAs) by examining the effects of the sulphide precursor cysteine and sulphide-synthesis blockers on HPV and also on normoxic pulmonary vasoconstriction (NPV) stimulated by prostaglandin F2α (PGF2α ) and by the drug LY83583, which causes contraction in IPAs by increasing cellular reactive oxygen species levels. Experiments with several blockers of cystathionine γ-lyase (CSE), the enzyme responsible for sulphide synthesis in the vasculature, demonstrated that propargylglycine (PAG, 1 mm) had little or no effect on the NPV caused by PGF2α or LY83583. Conversely, other CSE antagonists tested, aminooxyacetic acid (AOAA, 100 μm), β-cyanoalanine (BCA, 500 μm) and hydroxylamine (HA, 100 μm), altered the NPV to PGF2α (BCA increased, HA inhibited) and/or LY83583 (BCA increased, AOAA and HA inhibited). Preincubating IPAs in physiological saline solution (PSS) containing 1 mm cysteine increased the amplitude of the NPV to PGF2(α) by ∼50%, and had a similar effect on HPV elicited by hypoxic challenge with 0% O2 . The enhancement of both responses by cysteine was abolished by pretreatment with 1 mm PAG. Measurements carried out with an amperometric electrode demonstrated that incubation with 1 mm cysteine under anoxic conditions (to minimize sulphide oxidation) greatly potentiated the release of sulphide from pieces of rat liver and that this release was strongly antagonized by PAG, indicating that at this concentration PAG could enter cells intact and antagonize CSE. PAG at 1 mm had no effect on HPV recorded in control PSS, or in PSS supplemented with physiological concentrations of cysteine (10 μm), cystine (50 μm) and glutamate (100 μm) in order to prevent the possible depletion of intracellular cysteine during experiments. Application of a combination of 1 mm cysteine and 1 mm α-ketoglutarate to promote sulphide synthesis via the cysteine aminotransferase/mercaptopyruvate sulphurtransferase (CAT/MST) pathway caused an increase in HPV similar to that observed for cysteine. This was partially blocked by the CAT antagonist aspartate (1 mm) and also by PAG. However, HPV was not increased by 1 mm α-ketoglutarate alone, and HPV in the absence of α-ketoglutarate and cysteine was not attenuated by aspartate. Pretreatment of IPAs with dithiothreitol (DTT, 1 mm), proposed to promote the conversion of mitochondrial thiosulphate to sulphide, did not increase the release of sulphide from pieces of rat liver in either the presence or the absence of 1 mm cysteine, and virtually abolished HPV. The results provide evidence that the sulphide precursor cysteine can promote both NPV and HPV in rat IPA by generating sulphide via a PAG-sensitive pathway, presumably CSE. However, HPV evoked under control conditions was unaffected by the blockade of CSE. Moreover, HPV was not affected by the CAT antagonist aspartate and was blocked rather than enhanced by DTT. The data therefore indicate that sulphide generated by CSE or CAT/MST or from thiosulphate is unlikely to contribute to O2 sensing during HPV in these arteries.
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http://dx.doi.org/10.1113/jphysiol.2014.277046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4303384PMC
January 2015

Investigating the potential role of TRPA1 in locomotion and cardiovascular control during hypertension.

Pharmacol Res Perspect 2014 Aug 23;2(4):e00052. Epub 2014 Jun 23.

Cardiovascular Division, BHF Centre of Excellence and Centre of Integrative Biomedicine, School of Medicine, King's College London London, SE1 9NH, U.K.

Radiotelemetry was used to investigate the in vivo cardiovascular and activity phenotype of both TRPA1 (transient receptor potential ankyrin 1) wild-type (WT) and TRPA1 knockout (KO) mice. After baseline recording, experimental hypertension was induced using angiotensin II infusion (1.1 mg(-1) kg(-1) a day, for 14 days). TRPA1 WT and KO mice showed similar morphological and functional cardiovascular parameters, including similar basal blood pressure (BP), heart rate, size, and function. Similar hypertension was also displayed in response to angiotensin II (156 ± 7 and 165 ± 11 mmHg, systolic BP ± SEM, n = 5-6). TRPA1 KO mice showed increased hypertensive hypertrophy (heart weight:tibia length: 7.3 ± 1.6 mg mm(-1) vs. 8.8 ± 1.7 mg mm(-1)) and presented with blunted interleukin 6 (IL-6) production compared with hypertensive WT mice (151 ± 24 vs. 89 ± 16 pg mL(-1)). TRPA1 expression in dorsal root ganglion (DRG) neurones was upregulated during hypertension (163% of baseline expression). Investigations utilizing the TRPA1 agonist cinnamaldehyde (CA) on mesenteric arterioles isolated from näive mice suggested a lack of TRPA1-dependent vasoreactivity in this vascular bed; a site with notable ability to alter total peripheral resistance. However, mesenteric arterioles isolated from TRPA1 KO hypertensive mice displayed significantly reduced ability to relax in response to nitric oxide (NO) (P < 0.05). Unexpectedly, naïve TRPA1 KO mice also displayed physical hyperactivity traits at baseline, which was exacerbated during hypertension. In conclusion, our study provides a novel cardiovascular characterization of TRPA1 KO mice in a model of hypertension. Results suggest that TRPA1 has a limited role in global cardiovascular control, but we demonstrate an unexpected capacity for TRPA1 to regulate physical activity.
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http://dx.doi.org/10.1002/prp2.52DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4186440PMC
August 2014

Intracellular remodelling of Ca2+ stores in pulmonary hypertension.

Cardiovasc Res 2014 Jul 15;103(2):189-91. Epub 2014 Jun 15.

School of Medicine, Division of Asthma, Allergy and Lung Biology, King's College London, Strand, London WC2R 2LS, UK

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http://dx.doi.org/10.1093/cvr/cvu149DOI Listing
July 2014

Hypoxic pulmonary vasoconstriction in the absence of pretone: essential role for intracellular Ca2+ release.

J Physiol 2013 Sep 17;591(18):4473-98. Epub 2013 Jun 17.

P. I. Aaronson: Room 1.19, Henriette Raphael House, Guy's Campus, King's College London, London SE1 9HN, UK.

  Hypoxic pulmonary vasoconstriction (HPV) maintains blood oxygenation during acute hypoxia but contributes to pulmonary hypertension during chronic hypoxia. The mechanisms of HPV remain controversial, in part because HPV is usually studied in the presence of agonist-induced preconstriction ('pretone'). This potentiates HPV but may obscure and distort its underlying mechanisms. We therefore carried out an extensive assessment of proposed mechanisms contributing to HPV in isolated intrapulmonary arteries (IPAs) in the absence of pretone by using a conventional small vessel myograph. Hypoxia elicited a biphasic constriction consisting of a small transient (phase 1) superimposed upon a sustained (phase 2) component. Neither phase was affected by the L-type Ca2+ channel antagonists diltiazem (10 and 30 μm) or nifedipine (3 μm). Application of the store-operated Ca2+ entry (SOCE) blockers BTP2 (10 μm) or SKF96365 (50 μm) attenuated phase 2 but not phase 1, whereas a lengthy (30 min) incubation in Ca2+-free physiological saline solution similarly reduced phase 2 but abolished phase 1. No further effect of inhibition of HPV was observed if the sarco/endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (30 μm) was also applied during the 30 min incubation in Ca2+-free physiological saline solution. Pretreatment with 10 μm ryanodine and 15 mm caffeine abolished both phases, whereas treatment with 100 μm ryanodine attenuated both phases. The two-pore channel blocker NED-19 (1 μm) and the nicotinic acid adenine dinucleotide phosphate (NAADP) antagonist BZ194 (200 μm) had no effect on either phase of HPV. The lysosomal Ca2+-depleting agent concanamycin (1 μm) enhanced HPV if applied during hypoxia, but had no effect on HPV during a subsequent hypoxic challenge. The cyclic ADP ribose antagonist 8-bromo-cyclic ADP ribose (30 μm) had no effect on either phase of HPV. Neither the Ca2+-sensing receptor (CaSR) blocker NPS2390 (0.1 and 10 μm) nor FK506 (10 μm), a drug which displaces FKBP12.6 from ryanodine receptor 2 (RyR2), had any effect on HPV. HPV was virtually abolished by the rho kinase blocker Y-27632 (1 μm) and attenuated by the protein kinase C inhibitor Gö6983 (3 μm). Hypoxia for 45 min caused a significant increase in the ratio of oxidised to reduced glutathione (GSSG/GSH). HPV was unaffected by the NADPH oxidase inhibitor VAS2870 (10 μm), whereas phase 2 was inhibited but phase 1 was unaffected by the antioxidants ebselen (100 μm) and TEMPOL (3 mm). We conclude that both phases of HPV in this model are mainly dependent on [Ca2+]i release from the sarcoplasmic reticulum. Neither phase of HPV requires voltage-gated Ca2+ entry, but SOCE contributes to phase 2. We can detect no requirement for cyclic ADP ribose, NAADP-dependent lysosomal Ca2+ release, activation of the CaSR, or displacement of FKBP12.6 from RyR2 for either phase of HPV. Sustained HPV is associated with an oxidising shift in the GSSG/GSH redox potential and is inhibited by the antioxidants ebselen and TEMPOL, consistent with the concept that it requires an oxidising shift in the cell redox state or the generation of reactive oxygen species.
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http://dx.doi.org/10.1113/jphysiol.2013.253682DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3784194PMC
September 2013

Gap junctions support the sustained phase of hypoxic pulmonary vasoconstriction by facilitating calcium sensitization.

Cardiovasc Res 2013 Aug 25;99(3):404-11. Epub 2013 May 25.

Department of Experimental Therapeutics, Institute of Pharmacology and Toxicology of National Academy of Medical Sciences of Ukraine, Kiev, Ukraine.

Aims: To determine the role of gap junctions (GJs) in hypoxic pulmonary vasoconstriction (HPV).

Methods And Results: Studies were performed in rat isolated intrapulmonary arteries (IPAs) mounted on a myograph and in anaesthetized rats. Hypoxia induced a biphasic HPV response in IPAs preconstricted with prostaglandin F2α (PGF2α, 3 µM) or 20 mM K⁺. The GJ inhibitors 18β-glycyrrhetinic acid (18β-GA, 30 µM), heptanol (3.5 mM), or 2-aminoethoxydiphenyl borate (2-APB) (75 µM) had little effect on the transient Phase 1 of HPV, but abolished the sustained Phase 2 which is associated with Ca²⁺ sensitization. The voltage-dependent Ca²⁺ channel blocker diltiazem (10 µM) had no effect on HPV, and did not alter the inhibitory action of 18β-GA. Sustained HPV is enhanced by high glucose (15 mM) via potentiation of Ca²⁺ sensitization, in the presence of high glucose 18β-GA still abolished sustained HPV. Simultaneous measurement of tension and intracellular Ca²⁺ using Fura PE-3 demonstrated that whilst 18β-GA abolished tension development during sustained HPV, it did not affect the elevation of intracellular Ca²⁺. Consistent with this, 18β-GA abolished hypoxia-induced phosphorylation of the Rho kinase target MYPT-1. In anaesthetized rats hypoxia caused a biphasic increase in systolic right ventricular pressure. Treatment with oral 18β-GA (25 mg/kg) abolished the sustained component of the hypoxic pressor response.

Conclusion: These results imply that GJs are critically involved in the signalling pathways leading to Rho kinase-dependent Ca²⁺ sensitization during sustained HPV, but not elevation of intracellular Ca²⁺, and may explain the dependence of the former on an intact endothelium.
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http://dx.doi.org/10.1093/cvr/cvt129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3718323PMC
August 2013

Does TRPC3 macrodominate the myoendothelial gap junction microdomain?

Cardiovasc Res 2012 Sep 20;95(4):399-400. Epub 2012 Jul 20.

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http://dx.doi.org/10.1093/cvr/cvs243DOI Listing
September 2012

Hypoxic pulmonary vasoconstriction.

Physiol Rev 2012 Jan;92(1):367-520

Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School ofMedicine, Baltimore, Maryland, USA.

It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
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http://dx.doi.org/10.1152/physrev.00041.2010DOI Listing
January 2012

S-nitrosophytochelatins: investigation of the bioactivity of an oligopeptide nitric oxide delivery system.

Biomacromolecules 2011 Jun 29;12(6):2103-13. Epub 2011 Apr 29.

Institute of Pharmaceutical Science, King's College London, London, SE1 9NH, UK.

This study investigates the in vitro bioactivity of S-nitrosophytochelatins (SNOPCs), oligopeptide analogues of S-nitrosoglutathione (GSNO), and their mechanisms of nitric oxide (NO) delivery. SNOPCs were more potent than GSNO in inhibiting platelet aggregation and stimulating vasorelaxation. Their potency was related to the number of S-nitrosated moieties per mole compound. Transnitrosation reactions with cell membrane surface components were shown to be the primary mode of NO delivery to intracellular targets for SNOPCs, while delivery via γ-glutamyl transpeptidase was unique to GSNO. Due to rapid NO release, larger SNOPCs elicited a more transitory effect compared to smaller compounds. The duration of effect was influenced by compound molecular weight, NO release kinetics, ability to undergo transnitrosation, and incubation time with tissues. In summary, a new oligopeptide NO delivery system based on SNOPCs was shown to be biologically active and can be used to investigate the mechanisms of NO delivery to intracellular targets.
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http://dx.doi.org/10.1021/bm200159hDOI Listing
June 2011

Key role of the RhoA/Rho kinase system in pulmonary hypertension.

Pulm Pharmacol Ther 2011 Feb 15;24(1):1-14. Epub 2010 Sep 15.

Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College London, United Kingdom.

Pulmonary hypertension (PH) is a general term comprising a spectrum of pulmonary hypertensive disorders which have in common an elevation of mean pulmonary arterial pressure (mPAP). The prototypical form of the disease, termed pulmonary arterial hypertension (PAH), is a rare but lethal syndrome with a complex aetiology characterised by increased pulmonary vascular resistance (PVR) and progressive elevation of mPAP; patients generally die from heart failure. Current therapies are inadequate and median survival is less than three years. PH due to chronic hypoxia (CH) is a condition separate from PAH and is strongly associated with chronic obstructive pulmonary disease (COPD). An early event in the pathogenesis of this form of PH is hypoxic pulmonary vasoconstriction (HPV), an acute homeostatic process that maintains the ventilation-perfusion ratio during alveolar hypoxia. The mechanisms underlying HPV remain controversial, but RhoA/Rho kinase (ROK)-mediated Ca²+-sensitisation is considered important. Increasing evidence also implicates RhoA/ROK in PASMC proliferation, inflammatory cell recruitment and the regulation of cell motility, all of which are involved in the pulmonary vascular remodelling occurring in all forms of PH. ROK is therefore a potential therapeutic target in treating PH of various aetiologies. Here, we examine current concepts regarding the aetiology of PAH and also PH due to CH, focusing on the contribution that RhoA/ROK-mediated processes may make to their development and on ROK inhibitors as potential therapies.
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http://dx.doi.org/10.1016/j.pupt.2010.09.001DOI Listing
February 2011

Superoxide differentially controls pulmonary and systemic vascular tone through multiple signalling pathways.

Cardiovasc Res 2011 Jan 30;89(1):214-24. Epub 2010 Aug 30.

Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College London, Room 3.20, Franklin Wilkins Building, Stamford Street, London SE1 9NH, UK.

Aims: the aim of this study was to determine the relative importance of Ca(2+) sensitization, ion channels, and intracellular Ca(2+) ([Ca(2+)](i)) in the mixed constrictor/relaxation actions of superoxide anion on systemic and pulmonary arteries.

Methods And Results: pulmonary and mesenteric arteries were obtained from rat. Superoxide was generated in arteries and cells with 6-anilino-5,8-quinolinequinone (LY83583). Following pre-constriction with U46619, 10 μmol/L LY83583 caused constriction in pulmonary and relaxation in mesenteric arteries. Both constrictor and relaxant actions of LY83583 were inhibited by superoxide dismutase and catalase. LY83583 caused Rho-kinase-dependent constriction in α-toxin-permeabilized pulmonary but not mesenteric arteries. Phosphorylation of myosin phosphatase-targeting subunit-1 (MYPT-1; as determined by western blot), was enhanced by LY83583 in pulmonary artery only. However, in both artery types, changes in tension were closely correlated with changes in phosphorylation of the 20 kDa myosin light chain as well as changes in [Ca(2+)](i) (as measured with Fura PE-3), with LY83583 causing increases in pulmonary and decreases in mesenteric arteries. When U46619 was replaced by 30 mmol/L K(+), all changes in [Ca(2+)](i) were abolished and LY83583 constricted both artery types. The K(V) channel inhibitor 4-aminopyridine abolished the LY83583-induced relaxation in mesenteric artery without affecting constriction in pulmonary artery. However, LY83583 caused a similar hyperpolarizing shift in the steady-state activation of K(V) current in isolated smooth muscle cells of both artery types.

Conclusions: superoxide only causes Rho-kinase-dependent Ca(2+) sensitization in pulmonary artery, resulting in constriction, and whilst it opens K(V) channels in both artery types, this only results in relaxation in mesenteric.
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http://dx.doi.org/10.1093/cvr/cvq275DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3002873PMC
January 2011

Cell redox state and hypoxic pulmonary vasoconstriction: recent evidence and possible mechanisms.

Respir Physiol Neurobiol 2010 Dec 27;174(3):165-74. Epub 2010 Aug 27.

Division of Asthma, Allergy and Lung Biology, King's College London, United Kingdom.

During alveolar hypoxia, hypoxic pulmonary vasoconstriction (HPV) maintains blood oxygenation near optimum via incompletely defined mechanisms. It is proposed that a hypoxia-induced rise in the intracellular concentration of reactive oxygen species (ROS) or an oxidising shift in the cytoplasmic redox state provides the signal which initiates the constriction of pulmonary arteries (PA), although this is controversial. Here, we review recent investigations demonstrating that hypoxia causes a rise in [ROS] in PA smooth muscle, and that ROS and antioxidants have effects on PA which would be predicted if cell oxidation causes contraction. We argue that intracellular Ca2+ release and Ca2+-sensitisation are the key effector mechanisms causing HPV, and discuss evidence that both processes are promoted by ROS or oxidative protein modifications. We conclude that while it is plausible that an increase in cytoplasmic [ROS] activates HPV effector mechanisms, proving this link will require the determination of whether hypoxia causes oxidative modifications of proteins involved in Ca2+ homeostasis and sensitisation.
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http://dx.doi.org/10.1016/j.resp.2010.08.016DOI Listing
December 2010

Ca(2+) homeostasis and structural and functional remodelling of airway smooth muscle in asthma.

Thorax 2010 Jun;65(6):547-52

King's College London, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK.

Asthma is characterised by airway hyper-responsiveness and remodelling, and there is mounting evidence that alterations in the phenotype of airway smooth muscle (ASM) play a central role in these processes. Although the concept that dysregulation of ASM Ca(2+) homeostasis may underlie at least part of these alterations has been around for many years, it is only relatively recently that the availability of ASM biopsies from subjects with mild and moderate asthma has allowed it to be properly investigated. In this article, critical components of the pathobiology of asthmatic ASM, including contractile function, proliferation, cell migration and secretion of proinflammatory cytokines and chemokines, are reviewed and related to associated changes in ASM Ca(2+) homeostasis. Based on this evidence, it is proposed that a unifying mechanism for the abnormal asthmatic phenotype is dysregulation of Ca(2+) homeostasis caused at least in part by a downregulation in expression and function of sarcoendoplasmic Ca(2+) ATPases (SERCAs).
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http://dx.doi.org/10.1136/thx.2009.129296DOI Listing
June 2010

Superoxide constricts rat pulmonary arteries via Rho-kinase-mediated Ca(2+) sensitization.

Free Radic Biol Med 2009 Mar 6;46(5):633-42. Epub 2008 Dec 6.

King's College London, UK.

Reactive oxygen species play a key role in vascular disease, pulmonary hypertension, and hypoxic pulmonary vasoconstriction. We investigated contractile responses, intracellular Ca(2+) ([Ca(2+)](i)), Rho-kinase translocation, and phosphorylation of the regulatory subunit of myosin phosphatase (MYPT-1) and of myosin light chain (MLC(20)) in response to LY83583, a generator of superoxide anion, in small intrapulmonary arteries (IPA) of rat. LY83583 caused concentration-dependent constrictions in IPA and greatly enhanced submaximal PGF(2alpha)-mediated preconstriction. In small femoral or mesenteric arteries of rat, LY83583 alone was without effect, but it relaxed a PGF(2)alpha-mediated preconstriction. Constrictions in IPA were inhibited by superoxide dismutase and tempol, but not catalase, and were endothelium and guanylate cyclase independent. Constrictions were also inhibited by the Rho-kinase inhibitor Y27632 and the Src-family kinase inhibitor SU6656. LY83583 did not raise [Ca(2+)](i), but caused a Y27632-sensitive constriction in alpha-toxin-permeabilized IPA. LY83583 triggered translocation of Rho-kinase from the nucleus to the cytosol in pulmonary artery smooth muscle cells and enhanced phosphorylation of MYPT-1 at Thr-855 and of MLC(20) at Ser-19 in IPA. This enhancement was inhibited by superoxide dismutase and abolished by Y27632. Hydrogen peroxide did not activate Rho-kinase. We conclude that in rat small pulmonary artery, superoxide triggers Rho-kinase-mediated Ca(2+) sensitization and vasoconstriction independent of hydrogen peroxide.
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http://dx.doi.org/10.1016/j.freeradbiomed.2008.11.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6016743PMC
March 2009

Constriction of pulmonary artery by peroxide: role of Ca2+ release and PKC.

Free Radic Biol Med 2008 Nov 5;45(10):1468-76. Epub 2008 Sep 5.

Division of Asthma, Allergy and Lung Biology, King's College London, London SE1 9RT, UK.

Reactive oxygen species are implicated in pulmonary hypertension and hypoxic pulmonary vasoconstriction. We examined the effects of low concentrations of peroxide on intrapulmonary arteries (IPA). IPAs from Wistar rats were mounted on a myograph for recording tension and estimating intracellular Ca2+ using Fura-PE3. Ca2+ sensitization was examined in alpha-toxin-permeabilized IPAs, and phosphorylation of MYPT-1 and MLC(20) was assayed by Western blot. Peroxide (30 microM) induced a vasoconstriction with transient and sustained components and equivalent elevations of intracellular Ca2+. The transient constriction was strongly suppressed by indomethacin, the TP-receptor antagonist SQ-29584, and the Rho kinase inhibitor Y-27632, whereas sustained constriction was unaffected. Neither vasoconstriction nor elevation of intracellular Ca2+ was affected by removal of extracellular Ca2+, whereas dantrolene suppressed the former and ryanodine abolished the latter. Peroxide-induced constriction of permeabilized IPAs was unaffected by Y-27632 but abolished by PKC inhibitors; these also suppressed constriction in intact IPAs. Peroxide caused translocation of PKCalpha, but had no significant effect on MYPT-1 or MLC(20) phosphorylation. We conclude that in IPAs peroxide causes transient release of vasoconstrictor prostanoids, but sustained constriction is associated with release of Ca2+ from ryanodine-sensitive stores and a PKC-dependent but Rho kinase- and MLC(20)-independent constrictor mechanism.
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http://dx.doi.org/10.1016/j.freeradbiomed.2008.08.020DOI Listing
November 2008

Role of src-family kinases in hypoxic vasoconstriction of rat pulmonary artery.

Cardiovasc Res 2008 Dec 5;80(3):453-62. Epub 2008 Aug 5.

Department of Asthma, Allergy and Respiratory Science, School of Medicine, King's College London, Room 3.20, Franklin Wilkins Building, Stamford Street, London SE1 9NH, UK.

Aims: We investigated the role of src-family kinases (srcFKs) in hypoxic pulmonary vasoconstriction (HPV) and how this relates to Rho-kinase-mediated Ca(2+) sensitization and changes in intracellular Ca(2+) concentration ([Ca(2+)](i)).

Methods And Results: Intra-pulmonary arteries (IPAs) were obtained from male Wistar rats. HPV was induced in myograph-mounted IPAs. Auto-phosphorylation of srcFKs and phosphorylation of the regulatory subunit of myosin phosphatase (MYPT-1) and myosin light-chain (MLC(20)) in response to hypoxia were determined by western blotting. Translocation of Rho-kinase and effects of siRNA knockdown of src and fyn were examined in cultured pulmonary artery smooth muscle cells (PASMCs). [Ca(2+)](i) was estimated in Fura-PE3-loaded IPA. HPV was inhibited by two blockers of srcFKs, SU6656 and PP2. Hypoxia enhanced phosphorylation of three srcFK proteins at Tyr-416 (60, 59, and 54 kDa, corresponding to src, fyn, and yes, respectively) and enhanced srcFK-dependent tyrosine phosphorylation of multiple target proteins. Hypoxia caused a complex, time-dependent enhancement of MYPT-1 and MLC(20) phosphorylation, both in the absence and presence of pre-constriction. The sustained component of this enhancement was blocked by SU6656 and the Rho-kinase inhibitor Y27632. In PASMCs, hypoxia caused translocation of Rho-kinase from the nucleus to the cytoplasm, and this was prevented by anti-src siRNA and to a lesser extent by anti-fyn siRNA. The biphasic increases in [Ca(2+)](i) that accompany HPV were also inhibited by PP2.

Conclusion: Hypoxia activates srcFKs and triggers protein tyrosine phosphorylation in IPA. Hypoxia-mediated Rho-kinase activation, Ca(2+) sensitization, and [Ca(2+)](i) responses are depressed by srcFK inhibitors and/or siRNA knockdown, suggesting a central role of srcFKs in HPV.
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http://dx.doi.org/10.1093/cvr/cvn209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2583063PMC
December 2008

Effects of amiloride, benzamil, and alterations in extracellular Na+ on the rat afferent arteriole and its myogenic response.

Am J Physiol Renal Physiol 2008 Jul 21;295(1):F272-82. Epub 2008 May 21.

Smooth Muscle Research Group, Faculty of Medicine, Department of Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta, Canada.

Recent studies have implicated epithelial Na+ channels (ENaC) in myogenic signaling. The present study was undertaken to determine if ENaC and/or Na+ entry are involved in the myogenic response of the rat afferent arteriole. Myogenic responses were assessed in the in vitro hydronephrotic kidney model. ENaC expression and membrane potential responses were evaluated with afferent arterioles isolated from normal rat kidneys. Our findings do not support a role of ENaC, in that ENaC channel blockers did not reduce myogenic responses and ENaC expression could not be demonstrated in this vessel. Reducing extracellular Na+ concentration ([Na+]o; 100 mmol/l) did not attenuate myogenic responses, and amiloride had no effect on membrane potential. Benzamil, an inhibitor of ENaC that also blocks Na+/Ca2+ exchange (NCX), potentiated myogenic vasoconstriction. Benzamil and low [Na+]o elicited vasoconstriction; however, these responses were attenuated by diltiazem and were associated with significant membrane depolarization, suggesting a contribution of mechanisms other than a reduction in NCX. Na+ repletion induced a vasodilation in pressurized afferent arterioles preequilibrated in low [Na+]o, a hallmark of NCX, and this response was reduced by 10 micromol/l benzamil. The dilation was eliminated, however, by a combination of benzamil plus ouabain, suggesting an involvement of the electrogenic Na+-K+-ATPase. In concert, these findings refute the premise that ENaC plays a significant role in the rat afferent arteriole and instead suggest that reducing [Na+](o) and/or Na+ entry is coupled to membrane depolarization. The mechanisms underlying these unexpected and paradoxical effects of Na+ are not resolved at the present time.
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http://dx.doi.org/10.1152/ajprenal.00200.2007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2494521PMC
July 2008

Low concentrations of sphingosylphosphorylcholine enhance pulmonary artery vasoreactivity: the role of protein kinase C delta and Ca2+ entry.

Hypertension 2008 Feb 24;51(2):239-45. Epub 2007 Dec 24.

Department of Physiology, Henriette Raphael House, King's College London, Guy's Hospital Campus, London SE1 1UL, United Kingdom.

Sphingosylphosphorylcholine (SPC) is a powerful vasoconstrictor, but in vitro its EC(50) is approximately 100-fold more than plasma concentrations. We examined whether subcontractile concentrations of SPC (100 nmol/L of SPC, and independent of the endothelium, 2-aminoethoxydiphenylborane-sensitive Ca(2+) entry, and Rho kinase. It was abolished by the phospholipase C inhibitor U73122, the broad spectrum protein kinase C (PKC) inhibitor Ro31-8220, and the PKC delta inhibitor rottlerin, but not by Gö6976, which is ineffective against PKC delta. The potentiation could be attributed to enhancement of Ca(2+) entry. SPC also potentiated the responses to prostaglandin F(2 alpha) and U436619, which activate a 2-aminoethoxydiphenylborane sensitive nonselective cation channel in intrapulmonary arteries. In this case, potentiation was partially inhibited by diltiazem but abolished by 2-aminoethoxydiphenylborane, Ro31-8220, and rottlerin. SPC (1 micromol/L) caused translocation of PKC delta to the perinuclear region and cytoskeleton of cultured intrapulmonary artery smooth muscle cells. We present the novel finding that low, subcontractile concentrations of SPC potentiate Ca(2+) entry in intrapulmonary arteries through both voltage-dependent and independent pathways via a receptor-dependent mechanism involving PKC delta. This has implications for the physiological role of SPC, especially in cardiovascular disease, where SPC is reported to be elevated.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.107.104802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2231840PMC
February 2008
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