Die Rolle von Dendritischen Zellen und der von ihnen exprimierten Chemokinrezeptoren in Homöostase und Nephritis

Als zentrale Regulatoren von Immunantworten sind Dendritische Zellen (DCs) in allen lymphatischen und nicht-lymphatischen Organen zu finden. Auch die Nieren sind von einem dichten Netzwerk von DCs durchzogen. Diese spielen sowohl bei der Aufrechterhaltung der Organhomöostase als auch beim Einleiten von Immunantworten gegen einwandernde Mikroorganismen eine wichtige Rolle und können kontextabhängig sowohl protektive als auch destruktive Funktionen ausüben. Ob sie in den häufigsten immunvermittelten Nierenerkrankungen, den Glomerulonephritiden (GNs), protektiv oder pro-inflammatorisch wirken, wird kontrovers diskutiert. Ziel dieser Arbeit war es, die Rolle renaler DCs in der Nephrotoxischen Nephritis (NTN), einem murinen Modell der rapid-progressiven crescentischen GN zu klären. Diese stellt die aggressivste Form der GN dar, die unbehandelt meist zum terminalen Nierenversagen mit Dialysepflicht führt. Ich konnte zeigen, dass renale DCs , die unter homöostatischen Bedingungen nicht-immunogen und im frühen Stadium der NTN protektiv sind, während der NTN-Progression eine funktionelle Wandlung zu pro-inflammatorischen Zellen durchlaufen. Sie reifen, beginnen pro-inflammatorische Zytokine zu produzieren und nehmen unter proteinurischen Bedingungen vermehrt filtriertes Antigen auf. Dies befähigt vor allem die DCs in der Nierenrinde, in der sich die bei der GN primär betroffenen Glomeruli befinden, dazu, T-Zellen zu aktivieren und die Produktion pro-inflammatorischer Zytokine zu induzieren. Während meiner Arbeit beobachtete ich, dass sich in den Nieren von Mäusen, denen der Chemokinrezeptor CX3CR1 fehlt, sehr viel weniger DCs befanden als bei Kontrollmäusen. In keinem anderen Organ war eine solche CX3CR1-Abhängigkeit der DCs zu beobachten. Als mögliche Erklärung konnte ich eine vergleichsweise hohe Expression des Liganden CX3CR1 in der Niere feststellen. Meine Befunde identifizieren CX3CR1 als ersten nierenspezifischen „Homing-Rezeptor“ für DCs. Dies ist im Zusammenhang mit der NTN interessant, vor allem, weil über die Funktion dieses Chemokinrezeptors, der von einem Großteil aller DCs in nicht-lymphatischen Organen exprimiert wird, wenig bekannt ist. Durch die CX3CR1-abhängige Reduktion der DCs, insbesondere in der Nierenrinde, war die NTN in CX3CR1-defizienten Mäusen abgemildert. Im Gegensatz dazu war die Immunabwehr gegen die häufigste Niereninfektion, die bakterielle Pyelonephritis (PN), durch CX3CR1-Defizienz nicht beeinträchtigt, was durch die geringere CX3CR1-Abhängigkeit der DCs im Nierenmark, die bei der PN antibakterielle Effektorzellen in die Nieren rekrutieren, erklärt werden kann. Zudem übernehmen CX3CR1-unabhängig eingewanderte neutrophile Granulozyten teilweise Funktionen der DCs. Zusammenfassend schlage ich CX3CR1 als Therapie-Angriffspunkt bei der GN vor, da die Abwesenheit von CX3CR1 selektiv DCs in der Niere beeinflusst, ohne die Neigung zu bakteriellen Niereninfektionen zu verstärken

Exclusive CX3CR1 dependence of kidney DCs impacts glomerulonephritis progression.

DCs and macrophages both express the chemokine receptor CX3CR1. Here we demonstrate that its ligand, CX3CL1, is highly expressed in the murine kidney and intestine. CX3CR1 deficiency markedly reduced DC numbers in the healthy and inflamed kidney cortex, and to a lesser degree in the kidney medulla and intestine, but not in other organs. CX3CR1 also promoted influx of DC precursors in crescentic glomerulonephritis, a DC-dependent aggressive type of nephritis. Disease severity was strongly attenuated in CX3CR1-deficient mice. Primarily CX3CR1-dependent DCs in the kidney cortex processed antigen for the intrarenal stimulation of T helper cells, a function important for glomerulonephritis progression. In contrast, medullary DCs played a specialized role in inducing innate immunity against bacterial pyelonephritis by recruiting neutrophils through rapid chemokine production. CX3CR1 deficiency had little effect on the immune defense against pyelonephritis, as medullary DCs were less CX3CR1 dependent than cortical DCs and because recruited neutrophils produced chemokines to compensate for the DC paucity. These findings demonstrate that cortical and medullary DCs play specialized roles in their respective kidney compartments. We identify CX3CR1 as a potential therapeutic target in glomerulonephritis that may involve fewer adverse side effects, such as impaired anti-infectious defense or compromised DC functions in other organs

Kidney Dendritic Cells Become Pathogenic during Crescentic Glomerulonephritis with Proteinuria

It is unclear why kidney dendritic cells attenuate some models of kidney disease but aggravate others. Kidney dendritic cells ameliorate the early phase of nonaccelerated nephrotoxic nephritis, a murine model of crescentic glomerulonephritis, but their effect on the later phase is unknown. Here, we report that kidney dendritic cells at later stages of nephrotoxic nephritis expressed higher levels of costimulatory molecules but lower levels of the cosuppressor molecule ICOS-L and started production of IL-12/23p40 and TNF-α. Furthermore, we noted that kidney dendritic cells captured more filterable antigen in proteinuric mice at late time points of nephrotoxic nephritis and started to capture molecules that were too large for filtration by a healthy kidney. They presented filtered antigen to Th cells, which responded by producing the proinflammatory cytokines IL-2, IFN-γ, TNF-α, IL-6, and IL-17. Notably, production of the suppressive cytokine IL-10 further increased in late nephrotoxic nephritis. Depletion of kidney dendritic cells at a late stage attenuated nephrotoxic nephritis, in contrast to the exacerbation observed with depletion at an early stage, indicating that their acquired proinflammatory phenotype adversely affected disease. These findings indicate that the intrarenal inflammatory microenvironment determines how kidney dendritic cells affect nephritis. In addition, proteinuria may harm the kidney by providing dendritic cells with more antigens to stimulate potentially pathogenic Th cells

Advanced Skin Antisepsis: Application of UVA-Cleavable Hydroxyethyl Starch Nanocapsules for Improved Eradication of Hair Follicle-Associated Microorganisms

Hair follicles constitute important drug delivery targets for skin antisepsis since they contain ≈25% of the skin microbiome. Nanoparticles are known to penetrate deeply into hair follicles. By massaging the skin, the follicular penetration process is enhanced based on a ratchet effect. Subsequently, an intrafollicular drug release can be initiated by various trigger mechanisms. Here, we present novel ultraviolet A (UVA)-responsive nanocapsules (NCs) with a size between 400 and 600 nm containing hydroxyethyl starch (HES) functionalized by an o-nitrobenzyl linker. A phase transfer into phosphate-buffered saline (PBS) and ethanol was carried out, during which an aggregation of the particles was observed by means of dynamic light scattering (DLS). The highest stabilization for the target medium ethanol as well as UVA-dependent release of ethanol from the HES-NCs was achieved by adding 0.1% betaine monohydrate. Furthermore, sufficient cytocompatibility of the HES-NCs was demonstrated. On ex vivo porcine ear skin, a strong UVA-induced release of the model drug sulforhodamine 101 (SR101) could be demonstrated after application of the NCs in cyclohexane using laser scanning microscopy. In a final experiment, a microbial reduction comparable to that of an ethanol control was demonstrated on ex vivo porcine ear skin using a novel UVA-LED lamp for triggering the release of ethanol from HES-NCs. Our study provides first indications that an advanced skin antisepsis based on the eradication of intrafollicular microorganisms could be achieved by the topical application of UVA-responsive NCs

A high-salt diet compromises antibacterial neutrophil responses through hormonal perturbation

The Western diet is rich in salt, which poses various health risks. A high-salt diet (HSD) can stimulate immunity through the nuclear factor of activated T cells 5 (Nfat5)-signaling pathway, especially in the skin, where sodium is stored. The kidney medulla also accumulates sodium to build an osmotic gradient for water conservation. Here, we studied the effect of an HSD on the immune defense against uropathogenic E. coli-induced pyelonephritis, the most common kidney infection. Unexpectedly, pyelonephritis was aggravated in mice on an HSD by two mechanisms. First, on an HSD, sodium must be excreted; therefore, the kidney used urea instead to build the osmotic gradient. However, in contrast to sodium, urea suppressed the antibacterial functionality of neutrophils, the principal immune effectors against pyelonephritis. Second, the body excretes sodium by lowering mineralocorticoid production via suppressing aldosterone synthase. This caused an accumulation of aldosterone precursors with glucocorticoid functionality, which abolished the diurnal adrenocorticotropic hormone-driven glucocorticoid rhythm and compromised neutrophil development and antibacterial functionality systemically. Consistently, under an HSD, systemic Listeria monocytogenes infection was also aggravated in a glucocorticoid-dependent manner. Glucocorticoids directly induced Nfat5 expression, but pharmacological normalization of renal Nfat5 expression failed to restore the antibacterial defense. Last, healthy humans consuming an HSD for 1 week showed hyperglucocorticoidism and impaired antibacterial neutrophil function. In summary, an HSD suppresses intrarenal neutrophils Nfat5-independently by altering the local microenvironment and systemically by glucocorticoid-mediated immunosuppression. These findings argue against high-salt consumption during bacterial infections

PTPN

Although adoptive T-cell therapy has shown remarkable clinical efficacy in haematological malignancies, its success in combating solid tumours has been limited. Here, we report that PTPN2 deletion in T cells enhances cancer immunosurveillance and the efficacy of adoptively transferred tumour-specific T cells. T-cell-specific PTPN2 deficiency prevented tumours forming in aged mice heterozygous for the tumour suppressor p53. Adoptive transfer of PTPN2-deficient CD8+ T cells markedly repressed tumour formation in mice bearing mammary tumours. Moreover, PTPN2 deletion in T cells expressing a chimeric antigen receptor (CAR) specific for the oncoprotein HER-2 increased the activation of the Src family kinase LCK and cytokine-induced STAT-5 signalling, thereby enhancing both CAR T-cell activation and homing to CXCL9/10-expressing tumours to eradicate HER-2+ mammary tumours in vivo. Our findings define PTPN2 as a target for bolstering T-cell-mediated anti-tumour immunity and CAR T-cell therapy against solid tumours