Nephrotoxic Nephritis Model Research Articles

Cardiotrophin-1 therapy reduces disease severity in a murine model of glomerular disease.

Cardiotrophin-1 (CT-1), a member of the interleukin (IL)-6 cytokine family, has renoprotective effects in mouse models of acute kidney disease and tubulointerstitial fibrosis, but its role in glomerular disease is unknown. To address this, we used the mouse model of nephrotoxic nephritis to test the hypothesis that CT-1 also has a protective role in immune-mediated glomerular disease. Using immunohistochemistry and analysis of single-cell RNA-sequencing data of isolated glomeruli, we demonstrate that CT-1 is expressed in the glomerulus in male mice, predominantly in parietal epithelial cells and is downregulated in mice with nephrotoxic nephritis. Furthermore, analysis of data from patients revealed that human glomerular disease is also associated with reduced glomerular CT-1 transcript levels. In male mice with nephrotoxic nephritis and established proteinuria, administration of CT-1 resulted in reduced albuminuria, prevented podocyte loss, and sustained plasma creatinine, compared with mice administered saline. CT-1 treatment also reduced fibrosis in the kidney cortex, peri-glomerular macrophage accumulation and the kidney levels of the pro-inflammatory mediator complement component 5a. In conclusion, CT-1 intervention therapy delays the progression of glomerular disease in mice by preserving kidney function and inhibiting renal inflammation and fibrosis.

#3636 INHIBITION OF THE STING PATHWAY AMELIORATES EXPERIMENTAL CRESCENTIC GLOMERULONEPHRITIS

Abstract Background and Aims Rapidly progressive glomerulonephritis/crescentic glomerulonephritis (RPGN/cGN) may compromise renal function in the short or medium term thus evolving into acute kidney injury (AKI) or chronic kidney disease. Innate and adaptive immune responses are placed at the epicentre of cGN. However, molecular pathways involved in the activation of these responses are by far less known. Sting is an innate immune DNA-sensing involved in promoting kidney injury and fibrosis with unknown participation in RPGN/cGN. Method We investigated whether Sting pathway activation contributes to the development and progression of RPGN/cGN in a preclinical model of nephrotoxic nephritis (NTN) induced by an anti-glomerular basal membrane serum. Sting expression as well as humoral and cellular innate immune responses, histological injury and functional responses in the kidney were studied in wild-type and Sting-/- mice. Results Sting was found expressed at higher gene and protein levels and located in tubulointerstitial and intraglomerular and periglomerular areas and tubules in kidneys from NTN wild-type mice compared to non-diseased control animals. Sting deficiency significantly decreased NTN-induced cytokine/chemokine synthesis and hence the intrarenal transit of both mononuclear phagocytes and overall or specific T-cell subsets. Sting-deficient mice also displayed less extensive histological affection, namely a fewer number of glomerular crescents and associated lesions (sclerosis, endocapillary hypercellularity/sinaquiae), and tubular injury. The presence of TUNEL-positive dead cells was also significantly reduced in Sting-/- mice. Consistent with these findings, Sting absence significantly diminished NTN-increased urea and creatinine plasma levels. Conclusion Sting inhibition positively impacted several well-characterized cGN-associated pathogenic events thus ameliorating the outcomes of the disease. These results identified Sting antagonism as a potential therapy to help combat cGN.

The CCR6/CCL20 axis expands RORγt+ Tregs to protect from glomerulonephritis

Previous studies have identified a unique Treg population, which expresses the Th17 characteristic transcription factor RORγt. These RORγt+ Tregs possess enhanced immunosuppressive capacity, which endows them with great therapeutic potential. However, as a caveat, they are also capable of secreting pro-inflammatory IL-17A. Since the sum function of RORγt+ Tregs in glomerulonephritis (GN) remains unknown, we studied the effects of their absence. Purified CD4+ T cell populations, containing or lacking RORγt+ Tregs, were transferred into immunocompromised RAG1 knockout mice and the nephrotoxic nephritis model of GN was induced. Absence of RORγt+ Tregs significantly aggravated kidney injury, demonstrating overall kidney-protective properties. Analyses of immune responses showed that RORγt+ Tregs were broadly immunosuppressive with no preference for a particular type of T cell response. Further characterization revealed a distinct functional and transcriptional profile, including enhanced production of IL-10. Expression of the chemokine receptor CCR6 marked a particularly potent subset, whose absence significantly worsened GN. As an underlying mechanism, we found that chemokine CCL20 acting through receptor CCR6 signaling mediated expansion and activation of RORγt+ Tregs. Finally, we also detected an increase of CCR6+ Tregs in kidney biopsies, as well as enhanced secretion of chemokine CCL20 in 21 patients with anti-neutrophil cytoplasmic antibody associated GN compared to that of 31 healthy living donors, indicating clinical relevance. Thus, our data characterize RORγt+ Tregs as anti-inflammatory mediators of GN and identify them as promising target for Treg directed therapies.

Characterization of a Novel Anti-inflammatory Biogenic Amine

Abstract Tryptophan (Trp) is an essential amino acid whose catabolism generates a cascade of over fifty molecules in a cell-specific manner. Three major Trp metabolic pathways have been described: synthesis of serotonin, synthesis of melatonin and generation of kynurenines. In mammalian cells, 90% of Trp is processed through the kynurenine pathway and kynurenine metabolites are regarded as one of the most powerful mechanism for immune regulation. We recently reported a novel biogenic amine, 3HKA, generated through a still uncharacterized lateral pathway of Trp catabolism. This novel biogenic amine is generated by both professional (Dendritic Cells) and non-professional (Lymphatic Endothelial Cells) antigen presenting cells and, differently from all others Trp metabolites, display unique “in vivo” immunosuppressive capabilities. In vitro, 3-HKA exhibited an anti-inflammatory profile by inhibiting the IFN-g-mediated STAT1/NF-kB pathway in both mouse and human dendritic cells (DCs) with a consequent decrease in the release of pro-inflammatory chemokines and cytokines; most notably, TNFa, IL-6, and IL12p70. In vivo, 3-HKA exerted protective effects in an experimental mouse model of Psoriasis by decreasing skin thickness, erythema, scaling and fissuring, reducing TNFa, IL-1b, IFN-g, and IL-17 production, and inhibiting generation of effector CD8+ T cells. Similarly, in a mouse model of nephrotoxic nephritis, besides reducing inflammatory cytokines, 3-HKA improved proteinuria and serum urea nitrogen, overall ameliorating the immune-mediated glomerulonephritis and renal dysfunction. Overall we propose that this novel biological amine is a crucial component of Trp-mediated immune tolerance.

CSF2-dependent monocyte education in the pathogenesis of ANCA-induced glomerulonephritis

ObjectivesMyeloid cell activation by antineutrophil cytoplasmic antibody (ANCA) is pivotal for necrotising vasculitis, including necrotising crescentic glomerulonephritis (NCGN). In contrast to neutrophils, the contribution of classical monocyte (CM) and non-classical...

Experimentally Induced Anti-Myeloperoxidase Vasculitis Is Not Attenuated in Factor B or VISTA Deficient Mice

Background: Anti-neutrophil cytoplasmic antibody vasculitis is characterized by antibodies to myeloperoxidase or proteinase 3. Previous work in murine anti-myeloperoxidase vasculitis has shown a role for the alternative pathway complement component factor B and the anaphylatoxin C5a. However, mice deficient in properdin, which stabilizes the alternative pathway convertase, were not protected. V-Type immunoglobulin domain-containing suppressor of T-cell activation (VISTA)-deficient mice were protected in the nephrotoxic nephritis model but the role of VISTA in anti-myeloperoxidase vasculitis is unknown. Objectives: This study had 2 aims. First, we attempted to reproduce previous findings on the role of factor B in anti-myeloperoxidase vasculitis. Second, we examined the role of VISTA in this model, in order to see if the protection in the nephrotoxic nephritis model extended to anti-myeloperoxidase vasculitis. Methods: Anti-myeloperoxidase vasculitis was induced in wild type, factor B, or VISTA deficient mice. Disease was assessed by quantifying glomerular crescents and macrophages, in addition to albuminuria and serum creatinine. Results: When wild type and factor B deficient mice were compared, there were no differences in any of the histological or biochemical parameters of disease assessed. Similarly, when wild type or VISTA deficient mice were compared, there were no differences. Conclusions: Factor B deficient mice were not protected which is in contrast to previous studies. Therefore alternative pathway activation is not essential in this model, under the conditions used in this study. VISTA deficient mice were not protected, suggesting that therapies targeting VISTA may not be effective in vasculitis.

The lectin pathway does not contribute to glomerular injury in the nephrotoxic nephritis model

Rapidly progressive crescentic glomerulonephritis occurs in number systemic and primary glomerular diseases, including anti-glomerular basement membrane disease, anti-neutrophil cytoplasmic antibody vasculitis and lupus nephritis. Our understanding of pathogenic mechanisms comes from animal models of disease such as the nephrotoxic nephritis model. The lectin pathway of complement activation has been shown to play a key role in several models of inflammation including renal ischaemia reperfusion. However, the lectin pathway is not required for crescentic glomerulonephritis in the anti-myeloperoxidase model of anti-neutrophil cytoplasmic antibody vasculitis. The aim of the current study was to explore the role of the lectin pathway in the nephrotoxic nephritis model, which is another model of crescentic glomerulonephritis. Nephrotoxic nephritis was induced in wild type and mannan-binding lectin-associated serine protease-2 deficient mice. Diseases were assessed by quantifying glomerular crescents and macrophages, in addition to albuminuria and serum creatinine. There was no difference between wild type and MASP-2 deficient mice in any of the histological or biochemical parameters of disease assessed. In addition, there was no difference in the humoral immune response to sheep IgG. These data show that the lectin pathway of complement activation is not required for the development of crescentic glomerulonephritis in the nephrotoxic nephritis model, reinforcing previous findings in the anti-myeloperoxidase model.

The Atypical Cyclin-Dependent Kinase 5 (Cdk5) Guards Podocytes from Apoptosis in Glomerular Disease While Being Dispensable for Podocyte Development.

Cyclin-dependent kinase 5 (Cdk5) is expressed in terminally differentiated cells, where it drives development, morphogenesis, and survival. Temporal and spatial kinase activity is regulated by specific activators of Cdk5, dependent on the cell type and environmental factors. In the kidney, Cdk5 is exclusively expressed in terminally differentiated glomerular epithelial cells called podocytes. In glomerular disease, signaling mechanisms via Cdk5 have been addressed by single or combined conventional knockout of known specific activators of Cdk5. A protective, anti-apoptotic role has been ascribed to Cdk5 but not a developmental phenotype, as in terminally differentiated neurons. The effector kinase itself has never been addressed in animal models of glomerular disease. In the present study, conditional and inducible knockout models of Cdk5 were analyzed to investigate the role of Cdk5 in podocyte development and glomerular disease. While mice with podocyte-specific knockout of Cdk5 had no developmental defects and regular lifespan, loss of Cdk5 in podocytes increased susceptibility to glomerular damage in the nephrotoxic nephritis model. Glomerular damage was associated with reduced anti-apoptotic signals in Cdk5-deficient mice. In summary, Cdk5 acts primarily as master regulator of podocyte survival during glomerular disease and—in contrast to neurons—does not impact on glomerular development or maintenance.

3-hydroxy-L-kynurenamine is an immunomodulatory biogenic amine

Tryptophan catabolism is a major metabolic pathway utilized by several professional and non-professional antigen presenting cells to maintain immunological tolerance. Here we report that 3-hydroxy-l-kynurenamine (3-HKA) is a biogenic amine produced via an alternative pathway of tryptophan metabolism. In vitro, 3-HKA has an anti-inflammatory profile by inhibiting the IFN-γ mediated STAT1/NF-κΒ pathway in both mouse and human dendritic cells (DCs) with a consequent decrease in the release of pro-inflammatory chemokines and cytokines, most notably TNF, IL-6, and IL12p70. 3-HKA has protective effects in an experimental mouse model of psoriasis by decreasing skin thickness, erythema, scaling and fissuring, reducing TNF, IL-1β, IFN-γ, and IL-17 production, and inhibiting generation of effector CD8+ T cells. Similarly, in a mouse model of nephrotoxic nephritis, besides reducing inflammatory cytokines, 3-HKA improves proteinuria and serum urea nitrogen, overall ameliorating immune-mediated glomerulonephritis and renal dysfunction. Overall, we propose that this biogenic amine is a crucial component of tryptophan-mediated immune tolerance.

Amphiregulin Aggravates Glomerulonephritis via Recruitment and Activation of Myeloid Cells.

Recent studies have identified the EGF receptor (EGFR) ligand amphiregulin (AREG) as an important mediator of inflammatory diseases. Both pro- and anti-inflammatory functions have been described, but the role of AREG in GN remains unknown. The nephrotoxic nephritis model of GN was studied in AREG-/- mice after bone marrow transplantation, and in mice with myeloid cell-specific EGFR deficiency. Therapeutic utility of AREG neutralization was assessed. Furthermore, AREG's effects on renal cells and monocytes/macrophages (M/M) were analyzed. Finally, we evaluated AREG expression in human renal biopsies. Renal AREG mRNA was strongly upregulated in murine GN. Renal resident cells were the most functionally relevant source of AREG. Importantly, the observation that knockout mice showed significant amelioration of disease indicates that AREG is pathogenic in GN. AREG enhanced myeloid cell responses via inducing chemokine and colony stimulating factor 2 (CSF2) expression in kidney resident cells. Furthermore, AREG directly skewed M/M to a proinflammatory M1 phenotype and protected them from apoptosis. Consequently, anti-AREG antibody treatment dose-dependently ameliorated GN. Notably, selective abrogation of EGFR signaling in myeloid cells was sufficient to protect against nephritis. Finally, strong upregulation of AREG expression was also detected in kidneys of patients with two forms of crescentic GN. AREG is a proinflammatory mediator of GN via (1) enhancing renal pathogenic myeloid cell infiltration and (2) direct effects on M/M polarization, proliferation, and cytokine secretion. The AREG/EGFR axis is a potential therapeutic target for acute GN.

P0652THYMOSIN BETA 4 AND KIDNEY FUNCTION: AN INVERSE RELATIONSHIP?

Abstract Background and Aims Thymosin β4 (Tβ4) is an abundant peptide in urine and plasma, involved in multiple processes including cell morphology, wound healing, and inflammation. A major, yet not well defined role of Tβ4 was described in the context of kidney and cardiovascular disease. Knock out of Tβ4 resulted, among others, in increased albuminuria in a nephrotoxic nephritis model. In animal models it has been shown that Tβ4 can modify renal and cardiovascular disease, fibrosis and inflammation. However, most of the data are derived from animal models and the relevance of Tβ4 in human is less clear. As a first step towards investigating the potential relevance of Tβ4 in chronic kidney disease (CKD) in human, we investigated the abundance of Tβ4 in human urine. Method We investigated human urine in 2240 subjects with a wide spread of kidney function for the presence of Tβ4 using capillary-electrophoresis coupled mass spectrometry (CE-MS) and tandem mass spectrometry. In addition, we evaluated the presence of Tβ4 abundance in hemodialysis fluid of 10 subjects. Results The full length acetylated Tβ4 peptide could be identified in human urine in high abundance (molecular mass 4960.485 Da). In addition, an oxidized isoform could also be observed at high abundance. When investigating the distribution of both isoforms in control subjects and patients at different stages of CKD, a highly significant inverse association of the abundance of Tβ4 with eGFR could be observed for both, with rho -0.388 for the non-oxidized and -0.387 for the oxidized isoform, p<0.0001 in each case. In hemodialysate, Tβ4 is found as the most abundant peptide in 2 of the 10 analyzed subjects, on average the second most abundant peptide, with β2 microglobuline being the most abundant one. Conclusion Tβ4 is highly significantly inversely associated with kidney function, suggesting a role of Tβ4 in kidney disease and/or its complications. Based on the experimental data published from animal models, the increase in Tβ4 may reflect a potential physiological mechanism to counteract CKD and its complications. Investigation of association of Tβ4 levels with progression in CKD, cardiovascular complications and death may inform on a potentially beneficial effect of Tβ4, is currently ongoing in longitudinal datasets and will be presented.

Canonical BMP signaling in tubular cells mediates recovery after acute kidney injury

Bone morphogenetic protein (BMP) signaling has been shown to modulate the development of renal fibrosis in animal models of kidney injury, but the downstream mediators are incompletely understood. In wild-type mice, canonical BMP signaling mediated by SMAD1/5/8 transcription factors was constitutively active in healthy renal tubules, transiently down-regulated after ischemia reperfusion injury (IRI), and reactivated during successful tubular regeneration. We then induced IRI in mice with a tubular-specific BMP receptor 1A (BMPR1A) deletion. These mice failed to reactivate SMAD1/5/8 signaling in the post-ischemic phase and developed renal fibrosis after injury. Using unbiased genomic analyses, we identified three genes encoding inhibitor of DNA-binding (ID) proteins (Id1, Id2, and Id4) as key targets of BMPR1A-SMAD1/5/8 signaling. BMPR1A-deficient mice failed to re-induce these targets following IRI. Instead, BMPR1A-deficiency resulted in activation of pro-fibrotic signaling proteins that are normally repressed by ID proteins, namely, p38 mitogen-activated protein kinase and cell cycle inhibitor p27. These data indicate that the post-ischemic activation of canonical BMP signaling acts endogenously to repress pro-fibrotic signaling in tubular cells and may help to prevent the progression of acute kidney injury to chronic kidney disease.

Inhibitors of the renin-angiotensin system ameliorates clinical and pathological aspects of experimentally induced nephrotoxic serum nephritis

Introduction: Chronic kidney disease (CKD) is a global health concern, but the current treatments only slow down the progression. Thus an improved understanding of the pathogenesis and novel treatments of CKD are needed. The nephrotoxic nephritis (NTN) model has the potential to study the pathogenesis of CKD as it resembles human CKD. The classical treatments with angiotensin II receptor blocker (ARB) or the angiotensin-converting enzyme inhibitor (ACE I) have shown a clinical effect in CKD.Methods: We characterized the disease development in the NTN model over 11 weeks by investigating functional and histopathological changes. We tested doses of 15 and 30 mg/kg/day enalapril and losartan in the NTN model in order to investigate the effect of inhibiting the renin-angiotensin-system (RAS).Results: The NTN model displayed albuminuria peaking on days 6–7, mesangial expansion (ME), renal fibrosis, inflammation and iron accumulation peaking on day 42. However, albuminuria, ME, renal fibrosis and inflammation were still significantly present on day 77, suggesting that the NTN model is useful for studying both the acute and chronic disease phases. Enalapril and losartan significantly enhanced the glomerular filtration rate (GFR) and decreased albuminuria, ME, renal fibrosis and inflammation of NTN-induced kidney disease in mice.Conclusions: This is the first study showing a comprehensive pathological description of the chronic features of the murine NTN model and that inhibiting the RAS pathway show a significant effect on functional and morphological parameters.

Temporal Regulation of Glomerular and Cortical Tubulointerstitial Genes Involved in the Development of Nephrotoxic Serum Nephritis

Background/Aims: Murine nephrotoxic nephritis (NTN) is a well-established model resembling chronic kidney disease. Investigating gene expression patterns separately in the glomerular and cortical tubulointerstitial structure could provide new knowledge about structure-specific changes in expression of genes in the NTN model. Methods: Glomerular, cortical tubulointerstitial and whole kidney tissues from mice subjected to nephrotoxic serum (NTS) or phosphate buffered saline (PBS) were collected on day 7, 21 and 42 using laser microdissection (LMD). Total RNA was extracted and subjected to nCounter NanoString. Histology, immunohistochemistry, in situ hybridization and/or quantitative real time PCR (qRT PCR) were performed to confirm regulation of selected genes. Results: LMD provided detailed information about genes that were regulated differently between structures over time. Some of the fibrotic and inflammatory genes (Col1a1, Col3a1 and Ccl2) were upregulated in both structures, whereas other genes such as Spp1 and Grem1 were differentially regulated suggesting spatial pathogenic mechanisms in the kidney. Downregulation of cortical tubulointerstitium genes involved in iron metabolism was detected along with iron accumulation. Conclusion: This study demonstrates several regulated genes in pathways important for the pathogenesis of the NTN model and that LMD identifies structure-specific changes in gene expression during disease development. Furthermore, this study shows the benefits of isolating glomeruli and cortical tubulointerstitium in order to identify gene regulation.

A triglyceride-rich lipoprotein environment exacerbates renal injury in the accelerated nephrotoxic nephritis model.

SummaryHyperlipidaemia accompanies chronic renal disease either as a consequence of the renal dysfunction or as part of generalized metabolic derangements. Under both situations, the lipid profile is characterized by accumulation of triglyceride‐rich lipoproteins (TGRLs). This lipid profile is recognized as a risk factor for cardiovascular complications. Whether it may pose a risk for renal injury as well remains unclear. A hyper‐TGRL state was generated in C57BL/6 mice using poloxamer‐407 (P‐407) and immune complex‐mediated renal injury was triggered using the accelerated nephrotoxic nephritis (ANTN) model. The hyper‐TGRL animals were hypersensitive to ANTN demonstrated by greater haematuria and glomerular cellularity. These changes were accompanied by increased glomerular accumulation of CD68+ macrophages. The hypersensitive response to ANTN was not seen in low‐density lipoprotein receptor knock‐out mice fed with a high fat diet, where triglyceride levels were lower but cholesterol levels comparable to those obtained using P‐407. These data indicate that a hyper‐TGRL state might be more detrimental to the kidneys than low‐density lipoprotein‐driven hypercholesterolaemia during immune complex‐mediated nephritis. We speculate that the hyper‐TGRL environment primes the kidney to exacerbated renal damage following an inflammatory insult with increased accumulation of macrophages that may play a key role in mediating the injurious effects.

Murine Nephrotoxic Nephritis as a Model of Chronic Kidney Disease.

Using the nonaccelerated murine nephrotoxic nephritis (NTN) as a model of chronic kidney disease (CKD) could provide an easily inducible model that enables a rapid test of treatments. Originally, the NTN model was developed as an acute model of glomerulonephritis, but in this study we evaluate the model as a CKD model and compare CD1 and C57BL/6 female and male mice. CD1 mice have previously showed an increased susceptibility to CKD in other CKD models. NTN was induced by injecting nephrotoxic serum (NTS) and evaluated by CKD parameters including albuminuria, glomerular filtration rate (GFR), mesangial expansion, and renal fibrosis. Both strains showed significant albuminuria on days 2-3 which remained significant until the last time point on days 36-37 supporting dysfunctional filtration also observed by a significantly declined GFR on days 5-6, 15–17, and 34–37. Both strains showed early progressive mesangial expansion and significant renal fibrosis within three weeks suggesting CKD development. CD1 and C57BL/6 females showed a similar disease progression, but female mice seemed more susceptible to NTS compared to male mice. The presence of albuminuria, GFR decline, mesangial expansion, and fibrosis showed that the NTN model is a relevant CKD model both in C57BL/6 and in CD1 mice.

Conditional Deletion of Smad1 Ameliorates Glomerular Injury in Progressive Glomerulonephritis.

Matrix expansion and cell proliferation are concomitantly observed in various glomerular injuries. However, the molecular mechanisms responsible for these changes have not been fully elucidated. We have reported that Smad1 is a key signalling molecule that regulates the transcription of type IV collagen (Col4) in mesangial matrix expansion and is thereby involved in glomerular injury in an acute model of glomerulonephritis. In this study, we addressed the role of Smad1 signalling in accelerated nephrotoxic nephritis (NTN), a model of progressive glomerulonephritis, using conditional deletion of Smad1 in Rosa26CreERT2 mice (Smad1-CKO). Mesangial matrix expansion in the Smad1-CKO mice with NTN was significantly inhibited compared with that in wild type mice with NTN, which was consistent with the decrease in Col4 expression level. On the other hand, STAT3 activation and cell proliferation were not influenced by Smad1 deletion in the NTN model. Therefore, we investigated another factor that activates cell proliferation in the absence of Smad1. Id2 induced VEGF secretion and subsequent STAT3 activation, independently of Smad1 expression in mouse mesangial cells. Here we show that Smad1 plays an important role in the development of glomerular injury without affecting cell proliferation, in progressive glomerulonephritis.

S100A8/A9 (Calprotectin) Is Critical for Development of Glomerulonephritis and Promotes Inflammatory Leukocyte–Renal Cell Interactions

Glomerulonephritis is a common cause of end-stage renal disease. Infiltrating leukocytes interacting with renal cells play a critical role during the initiation and progression of glomerulonephritis, but the exact mechanisms are not clearly defined. By using the murine model of nephrotoxic nephritis, we investigated the role of S100A8/A9 [myeloid-related protein (MRP) 8/14, calprotectin] in promoting glomerulonephritis. In nephrotoxic nephritis, wild-type (WT) mice with glomerulonephritis have elevated serum levels of S100A8/A9, whereas mice deficient in MRP14 (S100a9(-/-)), and hence S100A8/A9, are significantly protected from disease. By using bone marrow transplants, we showed that MRP14 deficiency is required in both the hemopoietic and intrinsic cells for the protective effect. In vitro, both the WT bone marrow-derived macrophages and renal mesangial cells stimulated with S100A8/A9 secrete IL-6, CXCL1, and tumor necrosis factor α; however, Mrp14(-/-) cells exhibit significantly blunted proinflammatory responses. The interaction of WT bone marrow-derived macrophages with renal microvascular endothelial cells results in increased levels of monocyte chemotactic protein 1, IL-8, and IL-6 cytokines, which is attenuated in Mrp14(-/-) bone marrow-derived macrophages. Data shows that S100A8/A9 plays a critical role during glomerulonephritis, exerting and amplifying autocrine and paracrine proinflammatory effects on bone marrow-derived macrophages, renal endothelial cells, and mesangial cells. Therefore, complete S100A8/A9 blockade may be a new therapeutic target in glomerulonephritis.

Podocyte biology: Differentiation of parietal epithelial cells into podocytes.

A new study demonstrates that knockdown of miR-193a in human parietal epithelial cells induces their differentiation into podocytes. Inhibition of miR-193a in a model of nephrotoxic nephritis resulted in reduced proteinuria and crescent formation. These data suggest that promoting differentiation of parietal progenitors into podocytes has potential therapeutic relevance.

B‐cell‐derived IL‐10 does not vitally contribute to the clinical course of glomerulonephritis

IL-10-secreting regulatory B cells have been postulated as negative mediators of inflammation. However, their impact on immune-mediated diseases requires further investigation. We recently found that IL-10-secreting B cells infiltrate the kidney during crescentic glomerulonephritis (GN). We therefore studied the function of B-cell-derived IL-10 in light of the potential risks associated with increasingly used B-cell depleting therapies. Lack of IL-10 production by B cells, however, did not influence acute or adaptively mediated progressive renal injury in terms of renal function and histological damage in the nephrotoxic nephritis model of GN. Renal leukocyte infiltration and cytokine expression were similar apart from increased macrophages in mice lacking B-cell-derived IL-10. Systemic immune responses as assessed by cytokine production, leukocyte composition, proliferation, and activation were indistinguishable, while production and renal deposition of Ag-specific IgG were mildly impaired in the absence of B-cell-produced IL-10. Importantly, detailed analysis of systemic and renal regulatory T cells did not show any differences between nephritic mice bearing IL-10-deficient B cells and WT controls. Finally, studies in reporter mice revealed that B cells are only a minor source of systemic IL-10. In summary, our data reveal that endogenous B-cell-derived IL-10 does not play a major role in the nephrotoxic nephritis model of crescentic GN.