FC016: Nephrotoxicity of Antiangiogenic Therapies: Direct Impact of Sorafenib on the Podocyte via GSK3Β

BACKGROUND AND AIMS

Tumor angiogenesis is one of the therapeutic targets used in oncology, to limit cancer growth and spreading. The main angiogenesis signalling pathway is mediated by the vascular endothelial growth factor (VEGF) that binds to its tyrosine kinase receptor (VEGFR), mainly expressed on endothelial cells. The antiangiogenic therapy could target the VEGF ligand (anti-VEGF), or its receptors by inhibition of kinase activity (tyrosine kinase inhibitor, TKI) such as sorafenib. The toxicity of antiangiogenic therapies is a growing concern in clinical use. Indeed, nephrotoxicity is a critical side-effect that leads to discontinuation of therapy. Renal histological illustration of this toxicity is minimal change nephropathy/focal segmental glomerulosclerosis (MCNS/FSGS) and thrombotic micro-angiopathy (TMA), involving two distinct cell types, podocytes and endothelial cells respectively. Podocytes are the main source of VEGF and express VEGFR in the glomerulus. Mechanisms linking TKI therapy to podocyte dysfunction and nephrotic level proteinuria are still poorly understood. The working hypothesis is that nephrotoxicity of sorafenib is primarily through its effect on glomerular podocytes.

METHOD

Based on LC-MS/MS proteomic analysis, we have identified dysregulated cellular pathways on sorafenib-exposed podocytes. We validated these results by western blotting and immunofluorescence staining, on a cultured podocyte line exposed to sorafenib (2.5 µmol/L, 24-h).

RESULTS

Our results showed that sorafenib inhibits the downstream signalling pathways of VEGFR on podocytes, which induce injury by decreasing the expression of podocyte-specific markers (WT1, podocin). This is associated with podocyte morphology changes with podocyte cytoskeleton damages (actin and microtubules) and focal adhesions loss. We identified a novel podocyte target of sorafenib: the GSK3β. Indeed, sorafenib reduces significantly GSK3β inhibitory phosphorylation. Moreover, GSK3β regulates Tau, microtubule-associated proteins (MAP) and key regulator of microtubules remodelling. We show that tau phosphorylation increases significantly in sorafenib-treated cells. Furthermore, we found that sorafenib impairs the autophagic flux in podocytes, as indicated by an increase in LC3-II/LC3-I ratio in western blot, reflect of autophagosomes accumulation in podocytes. These results indicate that GSK3β overactivity induced by sorafenib participates in the disruption of the microtubules through tau phosphorylation, which interferes with cellular vesicle trafficking and blocks autophagic flux in podocytes. In addition, sorafenib leads to podocyte apoptosis through induction of endoplasmic reticulum (ER) stress (GADD153 protein induction and its nuclear translocation) and mitochondrial dysfunction. ER stress induced a decrease in podocyte protein synthesis with increased eIF2α phosphorylation. Sorafenib also causes mitochondrial membrane potential loss and mitochondrial depolarization.

CONCLUSION

Thus, in the current study, we show that sorafenib has a direct effect on podocytes, modulating specific signalling pathways to induce podocyte damage and ultimately glomerular lesions. However, we have to confirm the clinical relevance of our results on kidney biopsies from patients diagnosed with nephrotic syndrome following sorafenib treatment.

FC019: Parietal Epithelial Cells Activation During Gemcitabine-Induced Nephrotoxicity: Communication With Endothelial Cells?

BACKGROUND AND AIMS

Gemcitabine (GEM) is an anticancer drug, indicated in the treatment of several types of solid cancers such as pancreatic, breast, bladder cancer, etc. This molecule is effective in tumor processes but causes adverse effects on other organs, including the haematopoietic system and the kidney. The renal toxicity of gemcitabine is illustrated by thrombotic microangiopathy (TMA), whose onset is dramatic and associated in more than 97% of cases with acute renal failure. This adverse effect induces discontinuation of treatment with negative consequences on tumor control. It is, therefore, essential to understand the pathophysiological mechanisms of gemcitabine nephrotoxicity. TMA at the glomerular level reflects damage to the endothelial cell (ECs). However, previously, data of our team show that other glomerular cells, parietal epithelial cells (PECs), could be involved in these lesions. Thus, in this project, we want: i) to describe the modifications of the PEC and EC proteome exposed to gemcitabine and ii) to analyse PEC and EC secretome exposed to gemcitabine and to study the cell communication between PECs and ECs.

METHOD

In our in vitro experiments, we used a murine PEC cell line and a murine EC cell line. The PECs are exposed to 100 μM GEM for 24-h and the culture supernatants are recovered. These PEC supernatants are used in conditioned media experiments to expose ECs for 24-h. On the other hand, ECs were directly exposed to 1 μM GEM for 24-h and culture supernatants were also recovered. Analyses of protein expression are carried out by western blot and immunofluorescence staining.

RESULTS

When PECs are exposed to GEM (100 µM, 24-h), we observe an increase in apoptosis (caspase 3 cleavage) as well as DNA damage (γH2AX). However, PECs specific markers, such as PAX2 and Claudin-1, do not appear to be affected. Our results also show an increase in the expression of the transcription factor CHOP and the chaperone protein BIP, suggesting the presence of endoplasmic reticulum (ER) stress in PECs exposed to gemcitabine.

In order to study cell communication between PECs and ECs, we set up conditioned media experiments. We first studied the expression of different endothelial markers on ECs exposed to PEC supernatants. The expression of the endothelial markers such as E-cadherin, CD31 and PDGFRβ decreases compared with control cells when ECs are exposed to PEC supernatants. Actin cytoskeleton reorganization is also observed with an increase in cortical actin. Moreover, the microtubule network seems to be also affected with a tendency to decrease tubulin expression. Finally, there is an increase in γH2AX suggesting the presence of DNA damage in ECs exposed to PEC supernatant. The next experiments aim at identifying the factors responsible for this cell communication (proteins, lipid mediators, non-coding RNA, extracellular vesicles).

CONCLUSION

Our results show GEM has a direct effect on PECs (apoptosis, DNA damage, ER stress). In addition, we show the effect of PEC supernatants exposed to GEM on ECs (decrease in endothelial markers, cytoskeleton modifications, DNA damage).

FC074: Mineralocorticoid Receptor Drives Parietal Epithelial Cell Activation and Glomerular Injury During Crescentic Glomerulonephritis

BACKGROUND AND AIMS

We have recently demonstrated that targeting specific pathways in parietal epithelial cells (PEC) can markedly alleviate experimental extracapillary glomerular injury (1). Accumulating evidence has indicated the potential contributions of aldosterone and mineralocorticoid receptor (MR) to the pathophysiology of chronic kidney disease. MR is strongly expressed in endothelial cells, glomerular mesangial cells, podocytes and distal tubular cells. Previous studies have shown that administration of mineralocorticoid receptor antagonists, including spironolactone and eplerenone, has beneficial effects in various renal injury animal models, such as unilateral ureteral obstruction, ischemia-reperfusion, cyclosporine-induced nephrotoxicity and hypertensive renal injury. The role of the MR in extra capillary glomerulopathies is still elusive and mechanistically unclear.

METHOD

To investigate the cell-specific role of the MR in PEC in the course of crescentic glomerulonephritis, we generated chimeric mice specifically lacking MR (Pec Cre Nr3c2lox/lox) in PECs using an inducible Cre recombinase system. Crescentic glomerulonephritis (GN) was induced using the antiglomerular basement membrane nephrotoxic serum (NTS) model. In vivo, biological parameters (albuminuria, blood urea nitrogen—BUN), glomerular injury, as well as PEC activation (CD44, CD9 and fibronectin staining) were assessed.

RESULTS

At baseline, Pec Cre Nr3c2wt/wt and Pec Cre Nr3c2lox/lox mice displayed no kidney morphology and function differences. When challenged using the NTS model, Pec Cre Nr3c2lox/lox mice showed less albuminuria and preserved renal function as compared to Pec Cre Nr3c2 wt/wt counterparts. Crescents were also more numerous and organized in Pec Cre Nr3c2wt/wt mice.

Next, we examined whether pharmacological MR inhibition could alleviate the severity of crescentic GN. When Pec Cre Nr3c2wt/wt mice were orally given eplerenone for 14 days after the onset of the crescentic GN, they were significantly protected from renal injury and failure (decreased proteinuria, normal BUN and reduced number of crescent). Such global action was associated with less activation molecule CD44 on PECs. Thus, genetic disruption of MR in PEC as well as pharmacological inhibition using eplerenone reduced glomerular expression of CD44 and crescent formation.

Furthermore, kidney biopsies of individuals diagnosed with crescentic glomerulonephritis displayed increased expression of MR in PEC and crescents.

CONCLUSION

Altogether, these results indicate the critical role of MR in PEC activation during crescentic glomerulonephritis along with the recently discovered CD9/EGFR/PDGFR pathway. This further supports the idea that the PEC phenotype switch is not a bystander event but plays a targetable critical active pathogenic role in crescentic GN. MR modulation using eplerenone may be a new therapeutic option for the management of such severe disease.

Circulating plasmablasts and high level of BAFF are hallmarks of minimal change nephrotic syndrome in adults

BACKGROUND

The recent success achieved with the use of B cell-depleting agents in some patients with minimal change nephrotic syndrome (MCNS) suggests an unexpected role for B lymphocytes in the pathogenesis of this immune-mediated glomerular disease. Nevertheless, no extensive B-cell phenotyping analysis has ever been performed in untreated adult patients soon after MCNS diagnosis.

METHODS

We investigated the distribution of the different B-cell subpopulations in 22 untreated adult patients with biopsy-proven MCNS [MCNS relapse (MCNS-Rel)]. We compared these data with those for 24 healthy controls, 13 MCNS patients in remission (with no specific treatment) and 19 patients with idiopathic membranous nephropathy (IMN).

RESULTS

Patients with MCNS-Rel or IMN had higher proteinuria and lower serum albumin and gammaglobulin levels (P < 0.0001 for all comparisons) than MCNS patients in remission. Plasmablasts were the only B-cell subsets present at significantly higher levels in MCNS-Rel patients than in the patients of the other three groups (P < 0.05 for all comparisons). The lower albumin levels and higher proteinuria levels were positively correlated with the percentage of circulating plasmablasts (Spearman test's ρ = -0.54, P = 0.01 and ρ = 0.65, P = 0.002, respectively). Similarly, the increase of immunoglobulin M (IgM) and the decrease of IgG levels were significantly associated with the percentage of plasmablasts in MCNS-Rel patients (Spearman's ρ = 0.36, P = 0.01 and Spearman's ρ = -0.60, P = 0.01, respectively). Increased production of interleukin (IL)-21, IL-6 and B-cell activating factor (BAFF) in the serum of MCNS-Rel patients was found significantly correlated with the percentage of plasmablasts (ρ = 0.72, P = 0.0002, ρ = 0.49, P = 0.04 and ρ = 0.62, P = 0.009, respectively).

CONCLUSIONS

An increase in the proportion of circulating plasmablasts seems to be a hallmark of untreated MCNS in adult patients. Further studies are required to more precisely determine the phenotype and functions of these cells.

Calpastatin prevents Angiotensin II-mediated podocyte injury through maintenance of autophagy

The strong predictive value of proteinuria in chronic glomerulopathies is firmly established as well as the pathogenic role of angiotensin II promoting progression of glomerular disease with an altered glomerular filtration barrier, podocyte injury and scarring of glomeruli. Here we found that chronic angiotensin II-induced hypertension inhibited autophagy flux in mouse glomeruli. Deletion of Atg5 (a gene encoding a protein involved autophagy) specifically in the podocyte resulted in accelerated angiotensin II-induced podocytopathy, accentuated albuminuria and glomerulosclerosis. This indicates that autophagy is a key protective mechanism in the podocyte in this condition. Angiotensin-II induced calpain activity in podocytes inhibits autophagy flux. Podocytes from mice with transgenic expression of the endogenous calpain inhibitor calpastatin displayed higher podocyte autophagy at baseline that was resistant to angiotensin II-dependent inhibition. Also, sustained autophagy with calpastatin limited podocyte damage and albuminuria. These findings suggest that hypertension has pathogenic effects on the glomerular structure and function, in part through activation of calpains leading to blockade of podocyte autophagy. These findings uncover an original mechanism whereby angiotensin II-mediated hypertension inhibits autophagy via calcium-induced recruitment of calpain with pathogenic consequences in case of imbalance by calpastatin activity. Thus, preventing a calpain-mediated decrease in autophagy may be a promising new therapeutic strategy for nephropathies associated with high renin-angiotensin system activity.

[Renal failure and renal symptoms associated with molecular targeted therapies in oncology]

"Targeted therapies and pathophysiological mechanisms of proteinuria Targeted therapy represents a promising therapeutic approach for patients with diverse cancers and has enabled significant development in medical oncology. This new class of anticancer drugs includes antibodies, fusion-proteins and receptor tyrosine kinase inhibitors among others. Depending on their molecular targeting, side effects can affect multiple organs, especially the kidney. Antiangiogenic agents inhibit the VEGF/VEGFR pathway resulting in reduction of nitric oxide production and alteration of podocytes function, which causes hypertension and proteinuria. EGFR inhibitors are responsible of electrolytic disorders. Hereby, we synthetized the current knowledge on renal toxicities on main molecular targeted therapies. Toxicities management is mainly based on clinical and biological monitoring, which can lead to drug withdrawing or dose adaptation."

Podocyte Injury in Lupus Nephritis

Systemic lupus erythematosus (SLE) is characterized by a broad spectrum of renal lesions. In lupus glomerulonephritis, histological classifications are based on immune-complex (IC) deposits and hypercellularity lesions (mesangial and/or endocapillary) in the glomeruli. However, there is compelling evidence to suggest that glomerular epithelial cells, and podocytes in particular, are also involved in glomerular injury in patients with SLE. Podocytes now appear to be not only subject to collateral damage due to glomerular capillary lesions secondary to IC and inflammatory processes, but they are also a potential direct target in lupus nephritis. Improvements in our understanding of podocyte injury could improve the classification of lupus glomerulonephritis. Indeed, podocyte injury may be prominent in two major presentations: lupus podocytopathy and glomerular crescent formation, in which glomerular parietal epithelial cells play also a key role. We review here the contribution of podocyte impairment to different presentations of lupus nephritis, focusing on the podocyte signaling pathways involved in these lesions.

Local miscommunications between glomerular cells as potential therapeutic targets for crescentic glomerulonephritides

Necrotizing and crescentic rapidly progressive glomerulonephritis or crescentic glomerulonephritis is one of the severest forms of acquired glomerular diseases with significant mortality. Risk of end-stage renal failure at 5 years is near 30%, with a number of patients developing chronic kidney disease. Currently, autoimmune crescentic glomerulonephritides are treated with broad-spectrum immunosuppression inducing remission of the injury in the majority of patients. However, treatment is associated with significant side effects and by the time remission is achieved the majority of patients have developed renal tissue damage and significant impairment of their kidney function with a steep slope of deterioration within the first weeks following initiation of immunosuppression. It is therefore important to develop complementary strategies that would be immediately active on the common process of destructive epithelial processes. We have worked to identify the major cellular pathways contributing to glomerular destruction in this context by a systematic comparison of patient tissues and experimental models. Our studies demonstrate the pivotal role of local intra- and intercellular communications in orchestrating the global glomerular tolerance to a severe rapidly progressive glomerulonephritis model with excellent anatomoclinical correlative expressions in kidney biopsies of individuals diagnosed with crescentic glomerulonephritis, irrespectively of the causal immune disorder. We hope that such approaches deciphering mechanisms of cellular adaptation that underlie kidney damage control in response to vasculitides, integrating both stress and damage responses, will delineate novel complementary therapies.

Control of Humoral Response in Renal Transplantation by Belatacept Depends on a Direct Effect on B Cells and Impaired T Follicular Helper-B Cell Crosstalk

Generation of de novo donor-specific antibodies (dnDSAs) after renal transplant is recognized as the leading cause of late transplant failure. Hence, the optimal immunosuppressive strategies to limit dnDSA development need to be defined. Recent clinical trials using the novel costimulatory blockade agent CTLA4-Ig (Belatacept) have shown that kidney transplant recipients (KTRs) treated with Belatacept have better graft survival and function and a lower proportion of dnDSAs than control-treated KTRs. Mechanisms involved in the control of humoral responses by Belatacept remain to be investigated. Here, we analyzed the effect of Belatacept on different steps of the B cell-mediated response in humans. In vitro, Belatacept reduced plasmablast differentiation, Ig production, and the expression of the major transcription factor involved in plasma cell function, Blimp-1, in a T cell-independent manner. Moreover, Belatacept induced activation of the STAT3 transcription factor in stimulated B cells and reduced the expression of CD86. Additionally, Belatacept blocked CD28-mediated activation of T follicular helper cells (Tfhs) in an autologous Tfh-memory B cells model. We then validated these observations in KTRs treated with Belatacept, who had a reduced proportion of blood effector B cells and activated Tfh (PD1⁺ICOS⁺) compared with control-treated KTRs. Our in vitro and in vivo results suggest that Belatacept modulates B cell function directly and at the level of B cell-Tfh interaction. These mechanisms likely account for the optimal control of humoral responses observed in KTRs treated with Belatacept.

Genetic and Pharmacological Inhibition of TREM-1 Limits the Development of Experimental Atherosclerosis

BACKGROUND

Innate immune responses activated through myeloid cells contribute to the initiation, progression, and complications of atherosclerosis in experimental models. However, the critical upstream pathways that link innate immune activation to foam cell formation are still poorly identified.

OBJECTIVES

This study sought to investigate the hypothesis that activation of the triggering receptor expressed on myeloid cells (TREM-1) plays a determinant role in macrophage atherogenic responses.

METHODS

After genetically invalidating Trem-1 in chimeric Ldlr^-/-Trem-1^-/- mice and double knockout ApoE^-/-Trem-1^-/- mice, we pharmacologically inhibited Trem-1 using LR12 peptide.

RESULTS

Ldlr^-/- mice reconstituted with bone marrow deficient for Trem-1 (Trem-1^-/-) showed a strong reduction of atherosclerotic plaque size in both the aortic sinus and the thoracoabdominal aorta, and were less inflammatory compared to plaques of Trem-1^+/+ chimeric mice. Genetic invalidation of Trem-1 led to alteration of monocyte recruitment into atherosclerotic lesions and inhibited toll-like receptor 4 (TLR 4)-initiated proinflammatory macrophage responses. We identified a critical role for Trem-1 in the upregulation of cluster of differentiation 36 (CD36), thereby promoting the formation of inflammatory foam cells. Genetic invalidation of Trem-1 in ApoE^-/-/Trem-1^-/- mice or pharmacological blockade of Trem-1 in ApoE^-/- mice using LR-12 peptide also significantly reduced the development of atherosclerosis throughout the vascular tree, and lessened plaque inflammation. TREM-1 was expressed in human atherosclerotic lesions, mainly in lipid-rich areas with significantly higher levels of expression in atheromatous than in fibrous plaques.

CONCLUSIONS

We identified TREM-1 as a major upstream proatherogenic receptor. We propose that TREM-1 activation orchestrates monocyte/macrophage proinflammatory responses and foam cell formation through coordinated and combined activation of CD36 and TLR4. Blockade of TREM-1 signaling may constitute an attractive novel and double-hit approach for the treatment of atherosclerosis.

Liver microRNA-21 is overexpressed in non-alcoholic steatohepatitis and contributes to the disease in experimental models by inhibiting PPARα expression

OBJECTIVE

Previous studies suggested that microRNA-21 may be upregulated in the liver in non-alcoholic steatohepatitis (NASH), but its role in the development of this disease remains unknown. This study aimed to determine the role of microRNA-21 in NASH.

DESIGN

We inhibited or suppressed microRNA-21 in different mouse models of NASH: (a) low-density lipoprotein receptor-deficient (Ldlr^-/-) mice fed a high-fat diet and treated with antagomir-21 or antagomir control; (b) microRNA-21-deficient and wild-type mice fed a methionine-choline-deficient (MCD) diet; (c) peroxisome proliferation-activator receptor α (PPARα)-deficient mice fed an MCD diet and treated with antagomir-21 or antagomir control. We assessed features of NASH and determined liver microRNA-21 levels and cell localisation. MicroRNA-21 levels were also quantified in the liver of patients with NASH, bland steatosis or normal liver and localisation was determined.

RESULTS

Inhibiting or suppressing liver microRNA-21 expression reduced liver cell injury, inflammation and fibrogenesis without affecting liver lipid accumulation in Ldlr^-/- fed a high-fat diet and in wild-type mice fed an MCD diet. Liver microRNA-21 was overexpressed, primarily in biliary and inflammatory cells, in mouse models as well as in patients with NASH, but not in patients with bland steatosis. PPARα, a known microRNA-21 target, implicated in NASH, was decreased in the liver of mice with NASH and restored following microRNA-21 inhibition or suppression. The effect of antagomir-21 was lost in PPARα-deficient mice.

CONCLUSIONS

MicroRNA-21 inhibition or suppression decreases liver injury, inflammation and fibrosis, by restoring PPARα expression. Antagomir-21 might be a future therapeutic strategy for NASH.

Oleate dose-dependently regulates palmitate metabolism and insulin signaling in C2C12 myotubes

Because the protective effect of oleate against palmitate-induced insulin resistance may be lessened in skeletal muscle once cell metabolism is overloaded by fatty acids (FAs), we examined the impact of varying amounts of oleate on palmitate metabolic channeling and insulin signaling in C2C12 myotubes. Cells were exposed to 0.5mM of palmitate and to increasing doses of oleate (0.05, 0.25 and 0.5mM). Impacts of FA treatments on radio-labelled FA fluxes, on cellular content in diacylglycerols (DAG), triacylglycerols (TAG), ceramides, acylcarnitines, on PKCθ, MAPKs (ERK1/2, p38) and NF-ΚB activation, and on insulin-dependent Akt phosphorylation were examined. Low dose of oleate (0.05mM) was sufficient to improve palmitate complete oxidation to CO₂ (+29%, P<0.05) and to alter the cellular acylcarnitine profile. Insulin-induced Akt phosphorylation was 48% higher in that condition vs. palmitate alone (p<0.01). Although DAG and ceramide contents were significantly decreased with 0.05mM of oleate vs. palmitate alone (-47 and -28%, respectively, p<0.01), 0.25mM of oleate was required to decrease p38 MAPK and PKCθ phosphorylation, thus further improving the insulin signaling (+32%, p<0.05). By contrast, increasing oleate concentration from 0.25 to 0.5mM, thus increasing total amount of FA from 0.75 to 1mM, deteriorated the insulin signaling pathway (-30%, p<0.01). This was observed despite low contents in DAG and ceramides, and enhanced palmitate incorporation into TAG (+27%, p<0.05). This was associated with increased incomplete FA β-oxidation and impairment of acylcarnitine profile. In conclusion, these combined data place mitochondrial β-oxidation at the center of the regulation of muscle insulin sensitivity, besides p38 MAPK and PKCθ.

Endothelial cell and podocyte autophagy synergistically protect from diabetes-induced glomerulosclerosis

The glomerulus is a highly specialized capillary tuft, which under pressure filters large amounts of water and small solutes into the urinary space, while retaining albumin and large proteins. The glomerular filtration barrier (GFB) is a highly specialized filtration interface between blood and urine that is highly permeable to small and midsized solutes in plasma but relatively impermeable to macromolecules such as albumin. The integrity of the GFB is maintained by molecular interplay between its 3 layers: the glomerular endothelium, the glomerular basement membrane and podocytes, which are highly specialized postmitotic pericytes forming the outer part of the GFB. Abnormalities of glomerular ultrafiltration lead to the loss of proteins in urine and progressive renal insufficiency, underlining the importance of the GFB. Indeed, albuminuria is strongly predictive of the course of chronic nephropathies especially that of diabetic nephropathy (DN), a leading cause of renal insufficiency. We found that high glucose concentrations promote autophagy flux in podocyte cultures and that the abundance of LC3B II in podocytes is high in diabetic mice. Deletion of Atg5 specifically in podocytes resulted in accelerated diabetes-induced podocytopathy with a leaky GFB and glomerulosclerosis. Strikingly, genetic alteration of autophagy on the other side of the GFB involving the endothelial-specific deletion of Atg5 also resulted in capillary rarefaction and accelerated DN. Thus autophagy is a key protective mechanism on both cellular layers of the GFB suggesting autophagy as a promising new therapeutic strategy for DN.

Direct action of endothelin-1 on podocytes promotes diabetic glomerulosclerosis

The endothelin system has emerged as a novel target for the treatment of diabetic nephropathy. Endothelin-1 promotes mesangial cell proliferation and sclerosis. However, no direct pathogenic effect of endothelin-1 on podocytes has been shown in vivo and endothelin-1 signaling in podocytes has not been investigated. This study investigated endothelin effects in podocytes during experimental diabetic nephropathy. Stimulation of primary mouse podocytes with endothelin-1 elicited rapid calcium transients mediated by endothelin type A receptors (ETARs) and endothelin type B receptors (ETBRs). We then generated mice with a podocyte-specific double deletion of ETAR and ETBR (NPHS2-Cre×Ednra(lox/lox)×Ednrb(lox/lox) [Pod-ETRKO]). In vitro, treatment with endothelin-1 increased total β-catenin and phospho-NF-κB expression in wild-type glomeruli, but this effect was attenuated in Pod-ETRKO glomeruli. After streptozotocin injection to induce diabetes, wild-type mice developed mild diabetic nephropathy with microalbuminuria, mesangial matrix expansion, glomerular basement membrane thickening, and podocyte loss, whereas Pod-ETRKO mice presented less albuminuria and were completely protected from glomerulosclerosis and podocyte loss, even when uninephrectomized. Moreover, glomeruli from normal and diabetic Pod-ETRKO mice expressed substantially less total β-catenin and phospho-NF-κB compared with glomeruli from counterpart wild-type mice. This evidence suggests that endothelin-1 drives development of glomerulosclerosis and podocyte loss through direct activation of endothelin receptors and NF-κB and β-catenin pathways in podocytes. Notably, both the expression and function of the ETBR subtype were found to be important. Furthermore, these results indicate that activation of the endothelin-1 pathways selectively in podocytes mediates pathophysiologic crosstalk that influences mesangial architecture and sclerosis.