Publications by authors named "Valentin Schatz"

18 Publications

  • Page 1 of 1

Mechanical Stress Induce PG-E2 in Murine Synovial Fibroblasts Originating from the Temporomandibular Joint.

Cells 2021 Feb 1;10(2). Epub 2021 Feb 1.

Department of Orthodontics, University Medical Centre of Regensburg, D-93053 Regensburg, Germany.

Genetic predisposition, traumatic events, or excessive mechanical exposure provoke arthritic changes in the temporomandibular joint (TMJ). We analysed the impact of mechanical stress that might be involved in the development and progression of TMJ osteoarthritis (OA) on murine synovial fibroblasts (SFs) of temporomandibular origin. SFs were subjected to different protocols of mechanical stress, either to a high-frequency tensile strain for 4 h or to a tensile strain of varying magnitude for 48 h. The TMJ OA induction was evaluated based on the gene and protein secretion of inflammatory factors (, , , , , , , PG-E2), subchondral bone remodelling (, ), and extracellular matrix components (, , collagen and hyaluronic acid deposition) using RT-qPCR, ELISA, and HPLC. A short high-frequency tensile strain had only minor effects on inflammatory factors and no effects on the subchondral bone remodelling induction or matrix constituent production. A prolonged tensile strain of moderate and advanced magnitude increased the expression of inflammatory factors. An advanced tensile strain enhanced the and PG-E2 expression, while the expression of further inflammatory factors were decreased. The tensile strain protocols had no effects on the expression, while the advanced tensile strain significantly reduced the deposition of matrix constituent contents of collagen and hyaluronic acid. The data indicates that the application of prolonged advanced mechanical stress on SFs promote PG-E2 protein secretion, while the deposition of extracellular matrix components is decreased.
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http://dx.doi.org/10.3390/cells10020298DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7912861PMC
February 2021

Mechanisms controlling bacterial infection in myeloid cells under hypoxic conditions.

Cell Mol Life Sci 2021 Mar 30;78(5):1887-1907. Epub 2020 Oct 30.

Mikrobiologisches Institut, Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, 91054, Erlangen, Germany.

Various factors of the tissue microenvironment such as the oxygen concentration influence the host-pathogen interaction. During the past decade, hypoxia-driven signaling via hypoxia-inducible factors (HIF) has emerged as an important factor that affects both the pathogen and the host. In this chapter, we will review the current knowledge of this complex interplay, with a particular emphasis given to the impact of hypoxia and HIF on the inflammatory and antimicrobial activity of myeloid cells, the bacterial responses to hypoxia and the containment of bacterial infections under oxygen-limited conditions. We will also summarize how low oxygen concentrations influence the metabolism of neutrophils, macrophages and dendritic cells. Finally, we will discuss the consequences of hypoxia and HIFα activation for the invading pathogen, with a focus on Pseudomonas aeruginosa, Mycobacterium tuberculosis, Coxiella burnetii, Salmonella enterica and Staphylococcus aureus. This includes a description of the mechanisms and microbial factors, which the pathogens use to sense and react to hypoxic conditions.
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http://dx.doi.org/10.1007/s00018-020-03684-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7966188PMC
March 2021

NCX1 represents an ionic Na+ sensing mechanism in macrophages.

PLoS Biol 2020 06 22;18(6):e3000722. Epub 2020 Jun 22.

Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg, Regensburg, Germany.

Inflammation and infection can trigger local tissue Na+ accumulation. This Na+-rich environment boosts proinflammatory activation of monocyte/macrophage-like cells (MΦs) and their antimicrobial activity. Enhanced Na+-driven MΦ function requires the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5), which augments nitric oxide (NO) production and contributes to increased autophagy. However, the mechanism of Na+ sensing in MΦs remained unclear. High extracellular Na+ levels (high salt [HS]) trigger a substantial Na+ influx and Ca2+ loss. Here, we show that the Na+/Ca2+ exchanger 1 (NCX1, also known as solute carrier family 8 member A1 [SLC8A1]) plays a critical role in HS-triggered Na+ influx, concomitant Ca2+ efflux, and subsequent augmented NFAT5 accumulation. Moreover, interfering with NCX1 activity impairs HS-boosted inflammatory signaling, infection-triggered autolysosome formation, and subsequent antibacterial activity. Taken together, this demonstrates that NCX1 is able to sense Na+ and is required for amplifying inflammatory and antimicrobial MΦ responses upon HS exposure. Manipulating NCX1 offers a new strategy to regulate MΦ function.
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http://dx.doi.org/10.1371/journal.pbio.3000722DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307728PMC
June 2020

Mononuclear phagocytes orchestrate prolyl hydroxylase inhibition-mediated renoprotection in chronic tubulointerstitial nephritis.

Kidney Int 2019 08 5;96(2):378-396. Epub 2019 Mar 5.

Department of Internal Medicine 4-Nephrology and Hypertension, Friedrich-Alexander-University Erlangen-Nürnberg (FAU) and University Hospital Erlangen, Erlangen, Germany. Electronic address:

Prolyl hydroxylase domain enzyme inhibitors (PHDIs) stabilize hypoxia-inducible factors (HIFs), and are protective in models of acute ischemic and inflammatory kidney disease. Whether PHDIs also confer protection in chronic inflammatory kidney disease models remains unknown. Here we investigated long-term effects of PHDI treatment in adenine-induced nephropathy as a model for chronic tubulointerstitial nephritis. After three weeks, renal dysfunction and tubulointerstitial damage, including proximal and distal tubular injury, tubular dilation and renal crystal deposition were significantly attenuated in PHDI-treated (the isoquinoline derivative ICA and Roxadustat) compared to vehicle-treated mice with adenine-induced nephropathy. Crystal-induced renal fibrosis was only partially diminished by treatment with ICA. Renoprotective effects of ICA treatment could not be attributed to changes in adenine metabolism or urinary excretion of the metabolite 2,8-dihydroxyadenine. ICA treatment reduced inflammatory infiltrates of F4/80+ mononuclear phagocytes in the kidneys and supported a regulatory, anti-inflammatory immune response. Furthermore, interstitial deposition of complement C1q was decreased in ICA-treated mice fed an adenine-enriched diet. Tubular cell-specific HIF-1α and myeloid cell-specific HIF-1α and HIF-2α expression were not required for the renoprotective effects of ICA. In contrast, depletion of mononuclear phagocytes with clodronate largely abolished the nephroprotective effects of PHD inhibition. Thus, our findings indicate novel and potent systemic anti-inflammatory properties of PHDIs that confer preservation of kidney function and structure in chronic tubulointerstitial inflammation and might counteract kidney disease progression.
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http://dx.doi.org/10.1016/j.kint.2019.02.016DOI Listing
August 2019

HIF1A and NFAT5 coordinate Na-boosted antibacterial defense via enhanced autophagy and autolysosomal targeting.

Autophagy 2019 11 14;15(11):1899-1916. Epub 2019 Apr 14.

Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg , Regensburg , Germany.

Infection and inflammation are able to induce diet-independent Na-accumulation without commensurate water retention in afflicted tissues, which favors the pro-inflammatory activation of mouse macrophages and augments their antibacterial and antiparasitic activity. While Na-boosted host defense against the protozoan parasite is mediated by increased expression of the leishmanicidal NOS2 (nitric oxide synthase 2, inducible), the molecular mechanisms underpinning this enhanced antibacterial defense of mouse macrophages with high Na (HS) exposure are unknown. Here, we provide evidence that HS-increased antibacterial activity against was neither dependent on NOS2 nor on the phagocyte oxidase. In contrast, HS-augmented antibacterial defense hinged on HIF1A (hypoxia inducible factor 1, alpha subunit)-dependent increased autophagy, and NFAT5 (nuclear factor of activated T cells 5)-dependent targeting of intracellular to acidic autolysosomal compartments. Overall, these findings suggest that the autolysosomal compartment is a novel target of Na-modulated cell autonomous innate immunity. : ACT: actins; AKT: AKT serine/threonine kinase 1; ATG2A: autophagy related 2A; ATG4C: autophagy related 4C, cysteine peptidase; ATG7: autophagy related 7; ATG12: autophagy related 12; BECN1: beclin 1; BMDM: bone marrow-derived macrophages; BNIP3: BCL2/adenovirus E1B interacting protein 3; CFU: colony forming units; CM-HDCFDA: 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester; CTSB: cathepsin B; CYBB: cytochrome b-245 beta chain; DAPI: 4,6-diamidino-2-phenylindole; DMOG: dimethyloxallyl glycine; DPI: diphenyleneiodonium chloride; ; FDR: false discovery rate; GFP: green fluorescent protein; GSEA: gene set enrichment analysis; GO: gene ontology; HIF1A: hypoxia inducible factor 1, alpha subunit; HUGO: human genome organization; HS: high salt (+ 40 mM of NaCl to standard cell culture conditions); HSP90: heat shock 90 kDa proteins; LDH: lactate dehydrogenase; LPS: lipopolysaccharide; Lyz2/LysM: lysozyme 2; NFAT5/TonEBP: nuclear factor of activated T cells 5; MΦ: macrophages; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFI: mean fluorescence intensity; MIC: minimum inhibitory concentration; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; NaCl: sodium chloride; NES: normalized enrichment score; n.s.: not significant; NO: nitric oxide; NOS2/iNOS: nitric oxide synthase 2, inducible; NS: normal salt; PCR: polymerase chain reaction; PGK1: phosphoglycerate kinase 1; PHOX: phagocyte oxidase; RFP: red fluorescent protein; RNA: ribonucleic acid; ROS: reactive oxygen species; sCFP3A: super cyan fluorescent protein 3A; SBFI: sodium-binding benzofuran isophthalate; SLC2A1/GLUT1: solute carrier family 2 (facilitated glucose transporter), member 1; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like kinase 1; v-ATPase: vacuolar-type H-ATPase; WT: wild type.
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http://dx.doi.org/10.1080/15548627.2019.1596483DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6844503PMC
November 2019

Limitation of TCA Cycle Intermediates Represents an Oxygen-Independent Nutritional Antibacterial Effector Mechanism of Macrophages.

Cell Rep 2019 03;26(13):3502-3510.e6

Mikrobiologisches Institut, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, 91054 Erlangen, Germany. Electronic address:

In hypoxic and inflamed tissues, oxygen (O)-dependent antimicrobial defenses are impaired due to a shortage of O. To gain insight into the mechanisms that control bacterial infection under hypoxic conditions, we infected macrophages with the obligate intracellular pathogen Coxiella burnetii, the causative agent of Q fever. Our experiments revealed that hypoxia impeded C. burnetii replication in a hypoxia-inducible factor (HIF) 1α-dependent manner. Mechanistically, under hypoxia, HIF1α impaired the activity of STAT3, which in turn reduced the intracellular level of TCA cycle intermediates, including citrate, and impeded C. burnetii replication in macrophages. However, bacterial viability was maintained, allowing the persistence of C. burnetii, which is a prerequisite for the development of chronic Q fever. This knowledge will open future research avenues on the pathogenesis of chronic Q fever. In addition, the regulation of TCA cycle metabolites by HIF1α represents a previously unappreciated mechanism of host defense against intracellular pathogens.
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http://dx.doi.org/10.1016/j.celrep.2019.02.103DOI Listing
March 2019

Dectin-1 Positive Dendritic Cells Expand after Infection with Parasites and Represent Promising Targets for Vaccine Development.

Front Immunol 2018 26;9:263. Epub 2018 Feb 26.

Regensburg Center for Interventional Immunology (RCI), Institute of Immunology, University Medical Center Regensburg, University of Regensburg, Regensburg, Germany.

Resistant mouse strains mount a protective T cell-mediated immune response upon infection with (L.) parasites. Healing correlates with a T helper (Th) cell-type 1 response characterized by a pronounced IFN-γ production, while susceptibility is associated with an IL-4-dependent Th2-type response. It has been shown that dermal dendritic cells are crucial for inducing protective Th1-mediated immunity. Additionally, there is growing evidence that C-type lectin receptor (CLR)-mediated signaling is involved in directing adaptive immunity against pathogens. However, little is known about the function of the CLR Dectin-1 in modulating Th1- or Th2-type immune responses by DC subsets in leishmaniasis. We characterized the expression of Dectin-1 on CD11c DCs in peripheral blood, at the site of infection, and skin-draining lymph nodes of -infected C57BL/6 and BALB/c mice and in peripheral blood of patients suffering from cutaneous leishmaniasis (CL). Both mouse strains responded with an expansion of Dectin-1 DCs within the analyzed tissues. In accordance with the experimental model, Dectin-1 DCs expanded as well in the peripheral blood of CL patients. To study the role of Dectin-1 DCs in adaptive immunity against , we analyzed the T cell stimulating potential of bone marrow-derived dendritic cells (BMDCs) in the presence of the Dectin-1 agonist Curdlan. These experiments revealed that Curdlan induces the maturation of BMDCs and the expansion of -specific CD4 T cells. Based on these findings, we evaluated the impact of Curdlan/Dectin-1 interactions in experimental leishmaniasis and were able to demonstrate that the presence of Curdlan at the site of infection modulates the course of disease in BALB/c mice: wild-type BALB/c mice treated intradermally with Curdlan developed a protective immune response against whereas Dectin-1 BALB/c mice still developed the fatal course of disease after Curdlan treatment. Furthermore, the vaccination of BALB/c mice with a combination of soluble antigens and Curdlan was able to provide a partial protection from severe leishmaniasis. These findings indicate that the ligation of Dectin-1 on DCs acts as an important checkpoint in adaptive immunity against and should therefore be considered in future whole-organism vaccination strategies.
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http://dx.doi.org/10.3389/fimmu.2018.00263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5834765PMC
March 2019

Hypoxia, Hypoxia-Inducible Factor-1α, and Innate Antileishmanial Immune Responses.

Front Immunol 2018 22;9:216. Epub 2018 Feb 22.

Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg, University of Regensburg, Regensburg, Germany.

Low oxygen environments and accumulation of hypoxia-inducible factors (HIFs) are features of infected and inflamed tissues. Here, we summarize our current knowledge on oxygen levels found in -infected tissues and discuss which mechanisms potentially contribute to local tissue oxygenation in leishmanial lesions. Moreover, we review the role of hypoxia and HIF-1 on innate antileishmanial immune responses.
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http://dx.doi.org/10.3389/fimmu.2018.00216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5827161PMC
April 2019

Salt-responsive gut commensal modulates T17 axis and disease.

Nature 2017 11 15;551(7682):585-589. Epub 2017 Nov 15.

Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.

A Western lifestyle with high salt consumption can lead to hypertension and cardiovascular disease. High salt may additionally drive autoimmunity by inducing T helper 17 (T17) cells, which can also contribute to hypertension. Induction of T17 cells depends on gut microbiota; however, the effect of salt on the gut microbiome is unknown. Here we show that high salt intake affects the gut microbiome in mice, particularly by depleting Lactobacillus murinus. Consequently, treatment of mice with L. murinus prevented salt-induced aggravation of actively induced experimental autoimmune encephalomyelitis and salt-sensitive hypertension by modulating T17 cells. In line with these findings, a moderate high-salt challenge in a pilot study in humans reduced intestinal survival of Lactobacillus spp., increased T17 cells and increased blood pressure. Our results connect high salt intake to the gut-immune axis and highlight the gut microbiome as a potential therapeutic target to counteract salt-sensitive conditions.
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http://dx.doi.org/10.1038/nature24628DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6070150PMC
November 2017

Myeloid Cell-Derived HIF-1α Promotes Control of Leishmania major.

J Immunol 2016 11 17;197(10):4034-4041. Epub 2016 Oct 17.

Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg, University of Regensburg, 93053 Regensburg, Germany;

Hypoxia-inducible factor-1α (HIF-1α), which accumulates in mammalian host organisms during infection, supports the defense against microbial pathogens. However, whether and to what extent HIF-1α expressed by myeloid cells contributes to the innate immune response against Leishmania major parasites is unknown. We observed that Leishmania-infected humans and L. major-infected C57BL/6 mice exhibited substantial amounts of HIF-1α in acute cutaneous lesions. In vitro, HIF-1α was required for leishmanicidal activity and high-level NO production by IFN-γ/LPS-activated macrophages. Mice deficient for HIF-1α in their myeloid cell compartment had a more severe clinical course of infection and increased parasite burden in the skin lesions compared with wild-type controls. These findings were paralleled by reduced expression of type 2 NO synthase by lesional CD11b cells. Together, these data illustrate that HIF-1α is required for optimal innate leishmanicidal immune responses and, thereby, contributes to the cure of cutaneous leishmaniasis.
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http://dx.doi.org/10.4049/jimmunol.1601080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7249608PMC
November 2016

Elementary immunology: Na as a regulator of immunity.

Pediatr Nephrol 2017 02 26;32(2):201-210. Epub 2016 Feb 26.

Institute of Clinical Microbiology and Hygiene, Universitätsklinikum Regensburg-Universität Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany.

The skin can serve as an interstitial Na reservoir. Local tissue Na accumulation increases with age, inflammation and infection. This increased local Na availability favors pro-inflammatory immune cell function and dampens their anti-inflammatory capacity. In this review, we summarize available data on how NaCl affects various immune cells. We particularly focus on how salt promotes pro-inflammatory macrophage and T cell function and simultaneously curtails their regulatory and anti-inflammatory potential. Overall, these findings demonstrate that local Na availability is a promising novel regulator of immunity. Hence, the modulation of tissue Na levels bears broad therapeutic potential: increasing local Na availability may help in treating infections, while lowering tissue Na levels may be used to treat, for example, autoimmune and cardiovascular diseases.
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http://dx.doi.org/10.1007/s00467-016-3349-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5203836PMC
February 2017

Ferritin-Mediated Iron Sequestration Stabilizes Hypoxia-Inducible Factor-1α upon LPS Activation in the Presence of Ample Oxygen.

Cell Rep 2015 Dec 25;13(10):2048-55. Epub 2015 Nov 25.

Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen and Friedrich-Alexander Universität (FAU) Erlangen-Nürnberg, 91054 Erlangen, Germany; Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg, 93053 Regensburg, Germany. Electronic address:

Both hypoxic and inflammatory conditions activate transcription factors such as hypoxia-inducible factor (HIF)-1α and nuclear factor (NF)-κB, which play a crucial role in adaptive responses to these challenges. In dendritic cells (DC), lipopolysaccharide (LPS)-induced HIF1α accumulation requires NF-κB signaling and promotes inflammatory DC function. The mechanisms that drive LPS-induced HIF1α accumulation under normoxia are unclear. Here, we demonstrate that LPS inhibits prolyl hydroxylase domain enzyme (PHD) activity and thereby blocks HIF1α degradation. Of note, LPS-induced PHD inhibition was neither due to cosubstrate depletion (oxygen or α-ketoglutarate) nor due to increased levels of reactive oxygen species, fumarate, and succinate. Instead, LPS inhibited PHD activity through NF-κB-mediated induction of the iron storage protein ferritin and subsequent decrease of intracellular available iron, a critical cofactor of PHD. Thus, hypoxia and LPS both induce HIF1α accumulation via PHD inhibition but deploy distinct molecular mechanisms (lack of cosubstrate oxygen versus deprivation of co-factor iron).
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http://dx.doi.org/10.1016/j.celrep.2015.11.005DOI Listing
December 2015

High salt reduces the activation of IL-4- and IL-13-stimulated macrophages.

J Clin Invest 2015 Nov 20;125(11):4223-38. Epub 2015 Oct 20.

A high intake of dietary salt (NaCl) has been implicated in the development of hypertension, chronic inflammation, and autoimmune diseases. We have recently shown that salt has a proinflammatory effect and boosts the activation of Th17 cells and the activation of classical, LPS-induced macrophages (M1). Here, we examined how the activation of alternative (M2) macrophages is affected by salt. In stark contrast to Th17 cells and M1 macrophages, high salt blunted the alternative activation of BM-derived mouse macrophages stimulated with IL-4 and IL-13, M(IL-4+IL-13) macrophages. Salt-induced reduction of M(IL-4+IL-13) activation was not associated with increased polarization toward a proinflammatory M1 phenotype. In vitro, high salt decreased the ability of M(IL-4+IL-13) macrophages to suppress effector T cell proliferation. Moreover, mice fed a high salt diet exhibited reduced M2 activation following chitin injection and delayed wound healing compared with control animals. We further identified a high salt-induced reduction in glycolysis and mitochondrial metabolic output, coupled with blunted AKT and mTOR signaling, which indicates a mechanism by which NaCl inhibits full M2 macrophage activation. Collectively, this study provides evidence that high salt reduces noninflammatory innate immune cell activation and may thus lead to an overall imbalance in immune homeostasis.
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http://dx.doi.org/10.1172/JCI80919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4639967PMC
November 2015

Low-oxygen tensions found in Salmonella-infected gut tissue boost Salmonella replication in macrophages by impairing antimicrobial activity and augmenting Salmonella virulence.

Cell Microbiol 2015 Dec 16;17(12):1833-47. Epub 2015 Jul 16.

Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Institut für Klinische Mikrobiologie und Hygiene, Universitätsklinikum Erlangen und Friedrich-Alexander Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany.

In Salmonella infection, the Salmonella pathogenicity island-2 (SPI-2)-encoded type three secretion system (T3SS2) is of key importance for systemic disease and survival in host cells. For instance, in the streptomycin-pretreated mouse model SPI-2-dependent Salmonella replication in lamina propria CD11c(-)CXCR1(-) monocytic phagocytes/macrophages (MΦ) is required for the development of colitis. In addition, containment of intracellular Salmonella in the gut critically depends on the antimicrobial effects of the phagocyte NADPH oxidase (PHOX), and possibly type 2 nitric oxide synthase (NOS2). For both antimicrobial enzyme complexes, oxygen is an essential substrate. However, the amount of available oxygen upon enteroinvasive Salmonella infection in the gut tissue and its impact on Salmonella-MΦ interactions was unknown. Therefore, we measured the gut tissue oxygen levels in a model of Salmonella enterocolitis using luminescence two-dimensional in vivo oxygen imaging. We found that gut tissue oxygen levels dropped from ∼78 Torr (∼11% O2) to values of ∼16 Torr (∼2% O2) during infection. Because in vivo virulence of Salmonella depends on the Salmonella survival in MΦ, Salmonella-MΦ interaction was analysed under such low oxygen values. These experiments revealed an increased intracellular replication and survival of wild-type and t3ss2 non-expressing Salmonella. These findings were paralleled by blunted nitric oxide and reactive oxygen species (ROS) production and reduced Salmonella ROS perception. In addition, hypoxia enhanced SPI-2 transcription and translocation of SPI-2-encoded virulence protein. Neither pharmacological blockade of PHOX and NOS2 nor impairment of T3SS2 virulence function alone mimicked the effect of hypoxia on Salmonella replication under normoxic conditions. However, if t3ss2 non-expressing Salmonella were used, hypoxia did not further enhance Salmonella recovery in a PHOX and NOS2-deficient situation. Hence, these data suggest that hypoxia-induced impairment of antimicrobial activity and Salmonella virulence cooperate to allow for enhanced Salmonella replication in MΦ.
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http://dx.doi.org/10.1111/cmi.12476DOI Listing
December 2015

Cutaneous Na+ storage strengthens the antimicrobial barrier function of the skin and boosts macrophage-driven host defense.

Cell Metab 2015 Mar;21(3):493-501

Interdisciplinary Center for Clinical Research and Department of Nephrology and Hypertension, Universitätsklinikum Erlangen and Friedrich-Alexander Universität (FAU) Erlangen-Nürnberg, Germany; Divison of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.

Immune cells regulate a hypertonic microenvironment in the skin; however, the biological advantage of increased skin Na(+) concentrations is unknown. We found that Na(+) accumulated at the site of bacterial skin infections in humans and in mice. We used the protozoan parasite Leishmania major as a model of skin-prone macrophage infection to test the hypothesis that skin-Na(+) storage facilitates antimicrobial host defense. Activation of macrophages in the presence of high NaCl concentrations modified epigenetic markers and enhanced p38 mitogen-activated protein kinase (p38/MAPK)-dependent nuclear factor of activated T cells 5 (NFAT5) activation. This high-salt response resulted in elevated type-2 nitric oxide synthase (Nos2)-dependent NO production and improved Leishmania major control. Finally, we found that increasing Na(+) content in the skin by a high-salt diet boosted activation of macrophages in a Nfat5-dependent manner and promoted cutaneous antimicrobial defense. We suggest that the hypertonic microenvironment could serve as a barrier to infection.
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http://dx.doi.org/10.1016/j.cmet.2015.02.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4350016PMC
March 2015

Hypoxia in Leishmania major skin lesions impairs the NO-dependent leishmanicidal activity of macrophages.

J Invest Dermatol 2014 Sep 28;134(9):2339-2346. Epub 2014 Feb 28.

Mikrobiologisches Institut-Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen und Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany. Electronic address:

Cure of infections with Leishmania major is critically dependent on the ability of macrophages to induce the type 2 nitic oxide (NO) synthase (NOS2) that produces high levels of NO in the presence of ample oxygen. Therefore, we analyzed the oxygen levels found in leishmanial skin lesions and their effect on the NOS2-dependent leishmanicidal activity of macrophages (MΦ). When L. major skin lesions of self-healing C57BL/6 mice reached their maximum size, the infected tissue displayed low oxygen levels (pO2∼21 Torr). MΦ activated under these oxygen tensions failed to produce sufficient amounts of NO to clear L. major. Nos2-deficient and hypoxic wild-type macrophages displayed a similar phenotype. Killing was restored when MΦ were reoxygenated or exposed to a NO donor. The resolution of the lesion in C57BL/6 mice was paralleled by an increase of lesional pO2. When mice were kept under normobaric hypoxia, this caused a persistent suppression of the lesional pO2 and a concurrent increase of the parasite load. In Nos2-deficient mice, there was no effect of atmospheric hypoxia. Low oxygen levels found at leishmanial skin lesions impaired the NOS2-dependent leishmanicidal activity of MΦ. Hence, tissue oxygenation represents an underestimated local milieu factor that participates in the persistence of Leishmania.
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http://dx.doi.org/10.1038/jid.2014.121DOI Listing
September 2014

Electroporation of siRNA into mouse bone marrow-derived macrophages and dendritic cells.

Methods Mol Biol 2014 ;1121:111-9

Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.

Dendritic cells (DC) and macrophages (MΦ) play a pivotal role in antimicrobial defense, in the regulation of immune responses, and in maintaining tissue homeostasis. The analysis of DC and MΦ function relies on primary cells albeit these cells are known to be difficult to transfect. This makes the use of small interfering RNA (siRNA) for targeted manipulation of gene expression by RNA interference difficult. In the following chapter, we provide a detailed protocol for the successful transfer of siRNA via electroporation into a defined population of mouse bone marrow-derived MΦ or DC that does not cause toxicity to the myeloid cells or nonspecific alterations of their biological functions. Factors that influence the transfection and knockdown rate will be highlighted.
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http://dx.doi.org/10.1007/978-1-4614-9632-8_9DOI Listing
September 2014

Ratiometric luminescence 2D in vivo imaging and monitoring of mouse skin oxygenation.

Methods Appl Fluoresc 2013 Aug 12;1(4):045002. Epub 2013 Aug 12.

Mikrobiologisches Institut-Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Wasserturmstraße 3-5, D-91054 Erlangen, Germany.

Tissue oxygenation plays a critical role in the pathogenesis of various diseases, but non-invasive, robust and user-friendly methods for its measurement in vivo still need to be established. Here, we are presenting an in vivo oxygen-detection system that uses ratiometric luminescence imaging (RLI) as a readout scheme to determine the skin oxygen tension of mouse hind footpads via side-by-side comparison with more established techniques including luminescence-lifetime imaging using planar sensor films and the polarographic electrode as the gold standard. We also demonstrate that this technology allows the detection of changes in mouse skin tissue oxygenation induced by subjecting mice to systemic hypoxia. The data demonstrate oxygen imaging based on RLI to be a most useful tool for reliably and easily analyzing and monitoring skin tissue oxygenation in vivo. This technology will advance our understanding of local regulation of skin tissue oxygenation in various disease conditions.
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http://dx.doi.org/10.1088/2050-6120/1/4/045002DOI Listing
August 2013