Experimentally induced anti-myeloperoxidase vasculitis is not attenuated in factor B or VISTA deficient mice

Background: Anti-neutrophil cytoplasmic antibody vasculitis is characterised 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 anaphylotoxin C5a. However, mice deficient in properdin, which stabilizes the alternative pathway convertase, were not protected. 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 two aims. Firstly, we attempted to reproduce previous findings on the role of factor B in anti-myeloperoxidase vasculitis. Secondly, 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 wildtype, factor B, or VISTA deficient mice. Disease was assessed by quanitfying 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 defiicent 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 targetting VISTA may not be effective in vasculitis.

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.

Decreased expression of the GLP-1 receptor after segmental artery injury in mice.

The glucagon-like peptide-1 receptor (GLP-1R) is expressed in the renal vasculature and known to be decreased under hypertensive conditions in rats and humans. However, little is known about the regulation in other types of renal pathology involving vascular changes. This study investigates the expression of the GLP-1R in renal vasculature after glomerular injury in the nephrotoxic nephritis mouse model, high cholesterol, and atherosclerosis in the Ldlr-/- mouse on western diet, and ex vivo injury in an organ culture model. The immunohistochemical signal of the GLP-1R was significantly decreased in arteries from mice with nephrotoxic nephritis after 42 days compared to 7 days and saline control (p<0.05). Histological evaluation of kidneys from Ldlr-/- mice on western diet showed a decreased GLP-1R specific immunohistochemical signal (p<0.05). The dilatory response to liraglutide was decreased in western diet fed Ldlr-/- mice compared to C57Bl/6J controls (p<0.05). Organ culture significantly decreased the immunohistochemical signal of the GLP-1R (p<0.05) and the expression of Glp-1r mRNA (p<0.005) compared to fresh. Organ cultured vessels showed vascular smooth muscle cell remodelling as Acta2 expression was decreased (p<0.005) and Ednrb was increased (p<0.05). In conclusion, nephrotoxic nephritis and hypercholesterolemia led to decreased GLP-1R specific immunohistochemical signal. Ex vivo vascular injury in the organ culture model lead to a decrease in expression of GLP-R expression and contractile VSMC specific markers and increase in expression of dedifferentiation markers suggestive of an inverse relationship between phenotypic swich of the VSMC and the expression of the GLP-1R however, the causal relationship remains elusive.

IL-17C/IL-17 Receptor E Signaling in CD4+ T Cells Promotes TH17 Cell-Driven Glomerular Inflammation

The IL-17 cytokine family and the cognate receptors thereof have a unique role in organ-specific autoimmunity. Most studies have focused on the founding member of the IL-17 family, IL-17A, as the central mediator of diseases. Indeed, although pathogenic functions have been ascribed to IL-17A and IL-17F in the context of immune-mediated glomerular diseases, the specific functions of the other IL-17 family members in immunity and inflammatory kidney diseases is largely unknown. Here, we report that compared with healthy controls, patients with acute Anti-neutrophil cytoplasmatic antibody (ANCA)-associated crescentic glomerulonephritis (GN) had significantly elevated serum levels of IL-17C (but not IL-17A, F, or E). In mouse models of crescentic GN (nephrotoxic nephritis) and pristane-induced lupus nephritis, deficiency in IL-17C significantly ameliorated the course of GN in terms of renal tissue injury and kidney function. Deficiency of the unique IL-17C receptor IL-17 receptor E (IL-17RE) provided similar protection against crescentic GN. These protective effects associated with a reduced TH17 response. Bone marrow transplantation experiments revealed that IL-17C is produced by tissue-resident cells, but not by lymphocytes. Finally, IL-17RE was highly expressed by CD4+ TH17 cells, and loss of this expression prevented the TH17 responses and subsequent tissue injury in crescentic GN. Our findings indicate that IL-17C promotes TH17 cell responses and immune-mediated kidney disease via IL-17RE expressed on CD4+ TH17 cells. Targeting the IL-17C/IL-17RE pathway may present an intriguing therapeutic strategy for TH17-induced autoimmune disorders.

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.