Neuropilin-1 regulates renin synthesis in juxtaglomerular cells.

Renin is the key enzyme of the systemic renin-angiotensin-aldosterone system, which plays an essential role in regulating blood pressure and maintaining electrolyte and extracellular volume homeostasis. Renin is mainly produced and secreted by specialized juxtaglomerular (JG) cells in the kidney. In the present study, we report for the first time that the conserved transmembrane receptor neuropilin-1 (NRP1) participates in the development of JG cells and plays a key role in renin production. We used the myelin protein zero-Cre (P0-Cre) to abrogate Nrp1 constitutively in P0-Cre lineage-labelled cells of the kidney. We found that the P0-Cre precursor cells differentiate into renin-producing JG cells. We employed a lineage-tracing strategy combined with RNAscope quantification and metabolic studies to reveal a cell-autonomous role for NRP1 in JG cell function. Nrp1-deficient animals displayed abnormal levels of tissue renin expression and failed to adapt properly to a homeostatic challenge to sodium balance. These findings provide new insights into cell fate decisions and cellular plasticity operating in P0-Cre-expressing precursors and identify NRP1 as a novel key regulator of JG cell maturation. KEY POINTS: Renin is a centrepiece of the renin-angiotensin-aldosterone system and is produced by specialized juxtaglomerular cells (JG) of the kidney. Neuropilin-1 (NRP1) is a conserved membrane-bound receptor that regulates vascular and neuronal development, cancer aggressiveness and fibrosis progression. We used conditional mutagenesis and lineage tracing to show that NRP1 is expressed in JG cells where it regulates their function. Cell-specific Nrp1 knockout mice present with renin paucity in JG cells and struggle to adapt to a homeostatic challenge to sodium balance. The results support the versatility of renin-producing cells in the kidney and may open new avenues for therapeutic approaches.

Tumor Lysis Syndrome and AKI: Beyond Crystal Mechanisms.

BACKGROUND: The pathophysiology of AKI during tumor lysis syndrome (TLS) is not well understood due to the paucity of data. We aimed to decipher crystal-dependent and crystal-independent mechanisms of TLS-induced AKI. METHODS: Crystalluria, plasma cytokine levels, and extracellular histones levels were measured in two cohorts of patients with TLS. We developed a model of TLS in syngeneic mice with acute myeloid leukemia, and analyzed ultrastructural changes in kidneys and endothelial permeability using intravital confocal microscopy. In parallel, we studied the endothelial toxicity of extracellular histones in vitro. RESULTS: The study provides the first evidence that previously described crystal-dependent mechanisms are insufficient to explain TLS-induced AKI. Extracellular histones that are released in huge amounts during TLS caused profound endothelial alterations in the mouse model. The mechanisms of histone-mediated damage implicates endothelial cell activation mediated by Toll-like receptor 4. Heparin inhibits extracellular histones and mitigates endothelial dysfunction during TLS. CONCLUSION: This study sheds new light on the pathophysiology of TLS-induced AKI and suggests that extracellular histones may constitute a novel target for therapeutic intervention in TLS when endothelial dysfunction occurs.

The Angiogenesis Inhibitor Isthmin-1 (ISM1) Is Overexpressed in Experimental Models of Glomerulopathy and Impairs the Viability of Podocytes.

Focal segmental glomerulosclerosis (FSGS) is a major cause of end-stage renal disease and remains without specific treatment. To identify new events during FSGS progression, we used an experimental model of FSGS associated with nephroangiosclerosis in rats injected with L-NAME (Nω-nitro-L-arginine methyl ester). After transcriptomic analysis we focused our study on the role of Isthmin-1 (ISM1, an anti-angiogenic protein involved in endothelial cell apoptosis. We studied the renal expression of ISM1 in L-NAME rats and other models of proteinuria, particularly at the glomerular level. In the L-NAME model, withdrawal of the stimulus partially restored basal ISM1 levels, along with an improvement in renal function. In other four animal models of proteinuria, ISM1 was overexpressed and localized in podocytes while the renal function was degraded. Together these facts suggest that the glomerular expression of ISM1 correlates directly with the progression-recovery of the disease. Further in vitro experiments demonstrated that ISM1 co-localized with its receptors GRP78 and integrin αvß5 on podocytes. Treatment of human podocytes with low doses of recombinant ISM1 decreased cell viability and induced caspase activation. Stronger ISM1 stimuli in podocytes dropped mitochondrial membrane potential and induced nuclear translocation of apoptosis-inducing factor (AIF). Our results suggest that ISM1 participates in the progression of glomerular diseases and promotes podocyte apoptosis in two different complementary ways: one caspase-dependent and one caspase-independent associated with mitochondrial destabilization.

Genetic inactivation of Semaphorin 3C protects mice from acute kidney injury.

To guide the development of therapeutic interventions for acute kidney injury, elucidating the deleterious pathways of this global health problem is highly warranted. Emerging evidence has indicated a pivotal role of endothelial dysfunction in the etiology of this disease. We found that the class III semaphorin SEMA3C was ectopically upregulated with full length protein excreted into the blood and truncated protein secreted into the urine upon kidney injury and hypothesized a role for SEAM3C in acute kidney injury. Sema3c was genetically abrogated during acute kidney injury and subsequent kidney morphological and functional defects in two well-characterized models of acute kidney injury; warm ischemia/reperfusion and folic acid injection were analyzed. Employing a beta actin-dependent, inducible knockout of Sema3c, we demonstrate that in acute kidney injury SEMA3C promotes interstitial edema, leucocyte infiltration and tubular injury. Additionally, intravital microscopy combined with Evans Blue dye extravasation and primary culture of magnetically sorted peritubular endothelial cells identified a novel role for SEMA3C in promoting vascular permeability. Thus, our study points to microvascular permeability as an important driver of injury in acute kidney injury, and to SEMA3C as a novel permeability factor and potential target for therapeutic intervention.

Activation of Notch3 in Renal Tubular Cells Leads to Progressive Cystic Kidney Disease.

BACKGROUND: Polycystic kidney disease (PKD) is a genetic disorder affecting millions of people worldwide that is characterized by fluid-filled cysts and leads to end-stage renal disease (ESRD). The hallmarks of PKD are proliferation and dedifferentiation of tubular epithelial cells, cellular processes known to be regulated by Notch signaling. METHODS: We found increased Notch3 expression in human PKD and renal cell carcinoma biopsies. To obtain insight into the underlying mechanisms and the functional consequences of this abnormal expression, we developed a transgenic mouse model with conditional overexpression of the intracellular Notch3 (ICN3) domain specifically in renal tubules. We evaluated the alterations in renal function (creatininemia, BUN) and structure (cysts, fibrosis, inflammation) and measured the expression of several genes involved in Notch signaling and the mechanisms of inflammation, proliferation, dedifferentiation, fibrosis, injury, apoptosis and regeneration. RESULTS: After one month of ICN3 overexpression, kidneys were larger with tubules grossly enlarged in diameter, with cell hypertrophy and hyperplasia, exclusively in the outer stripe of the outer medulla. After three months, mice developed numerous cysts in proximal and distal tubules. The cysts had variable sizes and were lined with a single- or multilayered, flattened, cuboid or columnar epithelium. This resulted in epithelial hyperplasia, which was observed as protrusions into the cystic lumen in some of the renal cysts. The pre-cystic and cystic epithelium showed increased expression of cytoskeletal filaments and markers of epithelial injury and dedifferentiation. Additionally, the epithelium showed increased proliferation with an aberrant orientation of the mitotic spindle. These phenotypic tubular alterations led to progressive interstitial inflammation and fibrosis. CONCLUSIONS: In summary, Notch3 signaling promoted tubular cell proliferation, the alignment of cell division, dedifferentiation and hyperplasia, leading to cystic kidney diseases and pre-neoplastic lesions.

Periostin Promotes Cell Proliferation and Macrophage Polarization to Drive Repair after AKI.

BACKGROUND: The matricellular protein periostin has been associated with CKD progression in animal models and human biopsy specimens. Periostin functions by interacting with extracellular matrix components to drive collagen fibrillogenesis and remodeling or by signaling through cell-surface integrin receptors to promote cell adhesion, migration, and proliferation. However, its role in AKI is unknown. METHODS: We used mice with conditional tubule-specific overexpression of periostin or knockout mice lacking periostin expression in the renal ischemia-reperfusion injury model, and primary cultures of isolated tubular cells in a hypoxia-reoxygenation model. RESULTS: Tubular epithelial cells showed strong production of periostin during the repair phase of ischemia reperfusion. Periostin overexpression protected mice from renal injury compared with controls, whereas knockout mice showed increased tubular injury and deteriorated renal function. Periostin interacted with its receptor, integrin-ß1, to inhibit tubular cell cycle arrest and apoptosis in in vivo and in vitro models. After ischemia-reperfusion injury, periostin-overexpressing mice exhibited diminished expression of proinflammatory molecules and had more F4/80+ macrophages compared with knockout mice. Macrophages from periostin-overexpressing mice showed increased proliferation and expression of proregenerative factors after ischemia-reperfusion injury, whereas knockout mice exhibited the opposite. Coculturing a macrophage cell line with hypoxia-treated primary tubules overexpressing periostin, or treating such macrophages with recombinant periostin, directly induced macrophage proliferation and expression of proregenerative molecules. CONCLUSIONS: In contrast to the detrimental role of periostin in CKD, we discovered a protective role of periostin in AKI. Our findings suggest periostin may be a novel and important mediator of mechanisms controlling renal repair after AKI.

Anaesthesia-Induced Transcriptomic Changes in the Context of Renal Ischemia Uncovered by the Use of a Novel Clamping Device.

Ischemia is a common cause of acute kidney injury worldwide, frequently occurring in patients undergoing cardiac surgery or admitted to the intensive care unit (ICU). Thus, ischemia-reperfusion injury (IRI) remains one of the main experimental models for the study of kidney diseases. However, the classical technique, based on non-traumatic surgical clamps, suffers from several limitations. It does not allow the induction of multiple episodes of acute kidney injury (AKI) in the same animal, which would be relevant from a human perspective. It also requires a deep and long sedation, raising the question of potential anaesthesia-related biases. We designed a vascular occluding device that can be activated remotely in conscious mice. We first assessed the intensity and the reproducibility of the acute kidney injury induced by this new device. We finally investigated the role played by the anaesthesia in the IRI models at the histological, functional and transcriptomic levels. We showed that this technique allows the rapid induction of renal ischemia in a repeatable and reproducible manner, breaking several classical limitations. In addition, we used its unique specificities to highlight the renal protective effect conferred by the anaesthesia, related to the mitigation of the IRI transcriptomic program.

Microvasculature partial endothelial mesenchymal transition in early posttransplant biopsy with acute tubular necrosis identifies poor recovery renal allografts.

Acute tubular necrosis (ATN), a frequent histopathological feature in the early post-renal transplant biopsy, affects long-term graft function. Appropriate markers to identify patients at risk of no or incomplete recovery after delayed graft function are lacking. In this study, we first included 41 renal transplant patients whose biopsy for cause during the first month after transplantation showed ATN lesions. Using partial microvasculature endothelial (fascin, vimentin) and tubular epithelial (vimentin) to mesenchymal transition markers, detected by immunohistochemistry, we found a significant association between partial endothelial to mesenchymal transition and poor graft function recovery (Spearman's rho = -0.55, P = .0005). Transforming growth factor-ß1 was strongly expressed in these phenotypic changed endothelial cells. Extent of ATN was also correlated with short- and long-term graft dysfunction. However, the association of extensive ATN with long-term graft dysfunction (24 months posttransplant) was observed only in patients with partial endothelial to mesenchymal transition marker expression in their grafts (Spearman's rho = -0.64, P = .003), but not in those without. The association of partial endothelial to mesenchymal transition with worse renal graft outcome was confirmed on 34 other early biopsies with ATN from a second transplant center. Our results suggest that endothelial cell activation at the early phase of renal transplantation plays a detrimental role.

Notch3 orchestrates epithelial and inflammatory responses to promote acute kidney injury.

Acute kidney injury is a major risk factor for subsequent chronic renal and/or cardiovascular complications. Previous studies have shown that Notch3 was de novo expressed in the injured renal epithelium in the early phases of chronic kidney disease. Here we examined whether Notch3 is involved in the inflammatory response and the epithelial cell damage that typifies ischemic kidneys using Notch3 knockout mice and mice with short-term activated Notch3 signaling (N3ICD) in renal epithelial cells. After ischemia/reperfusion, N3ICD mice showed exacerbated infiltration of inflammatory cells and severe tubular damage compared to control mice. Inversely, Notch3 knockout mice were protected against ischemia/reperfusion injury. Renal macrophages derived from Notch3 knockout mice failed to activate proinflammatory cytokines. Chromatin immunoprecipitation analysis of the Notch3 promoter identified NF-κB as the principal inducer of Notch3 in ischemia/reperfusion. Thus, Notch3 induced by NF-κB in the injured epithelium sustains a proinflammatory environment attracting activated macrophages to the site of injury leading to a rapid deterioration of renal function and structure. Hence, targeting Notch3 may provide a novel therapeutic strategy against ischemia/reperfusion and acute kidney injury by preservation of epithelial structure and disruption of proinflammatory signaling.

Genetically increased angiotensin I-converting enzyme alters peripheral and renal vascular reactivity to angiotensin II and bradykinin in mice.

Angiotensin I-converting enzyme (ACE) levels in humans are under strong genetic influence. Genetic variation in ACE has been linked to risk for and progression of cardiovascular and renal diseases. Causality has been documented in genetically modified mice, but the mechanisms underlying causality are not completely elucidated. To further document the vascular and renal consequences of a moderate genetic increase in ACE synthesis, we studied genetically modified mice carrying three copies of the ACE gene (three-copy mice) and littermate wild-type animals (two-copy mice). We investigated peripheral and renal vascular reactivity to angiotensin II and bradykinin in vivo by measuring blood pressure and renal blood flow after intravenous administration and also reactivity of isolated glomerular arterioles by following intracellular Ca2+ mobilization. Carrying three copies of the ACE gene potentiated the systemic and renal vascular responses to angiotensin II over the whole range of peptide concentration tested. Consistently, the response of isolated glomerular afferent arterioles to angiotensin II was enhanced in three-copy mice. In these mice, signaling pathways triggered by endothelial activation by bradykinin or carbachol in glomerular arterioles were also altered. Although the nitric oxide (NO) synthase (NOS)/NO pathway was not functional in arterioles of two-copy mice, in muscular efferent arterioles of three-copy mice NOS3 gene expression was induced and NO mediated the effect of bradykinin or carbachol. These data document new and unexpected vascular consequences of a genetic increase in ACE synthesis. Enhanced vasoconstrictor effect of angiotensin II may contribute to the risk for cardiovascular and renal diseases linked to genetically high ACE levels. NEW & NOTEWORTHY A moderate genetic increase in angiotensin I-converting enzyme (ACE) in mice similar to the effect of the ACE gene D allele in humans unexpectedly potentiates the systemic and renal vasoconstrictor responses to angiotensin II. It also alters the endothelial signaling pathways triggered by bradykinin or carbachol in glomerular efferent arterioles.

Endothelial Epas1 Deficiency Is Sufficient To Promote Parietal Epithelial Cell Activation and FSGS in Experimental Hypertension.

FSGS, the most common primary glomerular disorder causing ESRD, is a complex disease that is only partially understood. Progressive sclerosis is a hallmark of FSGS, and genetic tracing studies have shown that parietal epithelial cells participate in the formation of sclerotic lesions. The loss of podocytes triggers a focal activation of parietal epithelial cells, which subsequently form cellular adhesions with the capillary tuft. However, in the absence of intrinsic podocyte alterations, the origin of the pathogenic signal that triggers parietal epithelial cell recruitment remains elusive. In this study, investigation of the role of the endothelial PAS domain-containing protein 1 (EPAS1), a regulatory α subunit of the hypoxia-inducible factor complex, during angiotensin II-induced hypertensive nephropathy provided novel insights into FSGS pathogenesis in the absence of a primary podocyte abnormality. We infused angiotensin II into endothelial-selective Epas1 knockout mice and their littermate controls. Although the groups presented with identical high BP, endothelial-specific Epas1 gene deletion accentuated albuminuria with severe podocyte lesions and recruitment of pathogenic parietal glomerular epithelial cells. These lesions and dysfunction of the glomerular filtration barrier were associated with FSGS in endothelial Epas1-deficient mice only. These results indicate that endothelial EPAS1 has a global protective role during glomerular hypertensive injuries without influencing the hypertensive effect of angiotensin II. Furthermore, these findings provide proof of principle that endothelial-derived signaling can trigger FSGS and illustrate the potential importance of the EPAS1 endothelial transcription factor in secondary FSGS.

Vancomycin-Associated Cast Nephropathy.

Vancomycin is a widely prescribed antibiotic, but the exact nature of vancomycin-associated nephrotoxicity is unclear, in particular when considering the frequent coadministration of aminoglycosides. We describe here the initial case of a 56-year-old woman with normal renal function developing unexplained ARF without hypovolemia after administration of vancomycin without coadministration of aminoglycosides. Studying the patient's renal biopsy specimen, we ascertained that obstructive tubular casts composed of noncrystal nanospheric vancomycin aggregates entangled with uromodulin explained the vancomycin-associated ARF. We developed in parallel a new immunohistologic staining technique to detect vancomycin in renal tissue and confirmed retrospectively that deleterious vancomycin-associated casts existed in eight additional patients with acute tubular necrosis in the absence of hypovolemia. Concomitant high vancomycin trough plasma levels had been observed in each patient. We also reproduced experimentally the toxic and obstructive nature of vancomycin-associated cast nephropathy in mice, which we detected using different in vivo imaging techniques. In conclusion, the interaction of uromodulin with nanospheric vancomycin aggregates represents a new mode of tubular cast formation, revealing the hitherto unsuspected mechanism of vancomycin-associated renal injury.

Stress Response Gene Nupr1 Alleviates Cyclosporin A Nephrotoxicity In Vivo.

Acute tubular damage is a major cause of renal failure, especially at the early phase of kidney transplant when ischemia-reperfusion injury and cyclosporin A toxicity may coexist. The mechanisms of the latter are largely unknown. Using an mRNA microarray on microdissected tubules from a rat model of cyclosporin A toxicity to describe the related epithelial-specific transcriptional signature in vivo, we found that cyclosporin A induces pathways dependent on the transcription factor ATF4 and identified nuclear protein transcriptional regulator 1 (Nupr1), a stress response gene induced by ATF4, as the gene most strongly upregulated. Upon cyclosporin A treatment, Nupr1-deficient mice exhibited worse renal tubular lesions than wild-type mice. In primary cultures treated with cyclosporin A, renal tubular cells isolated from Nupr1-deficient mice exhibited more apoptosis and ATP depletion than cells from wild-type mice. Furthermore, cyclosporin A decreased protein synthesis and abolished proliferation in wild-type tubular cells, but only reduced proliferation in Nupr1-deficient cells. Compared with controls, mouse models of ischemia-reperfusion injury, urinary obstruction, and hypertension exhibited upregulated expression of renal NUPR1, and cyclosporin A induced Nupr1 expression in cultured human tubular epithelial cells. Finally, immunohistochemical analysis revealed strong expression of NUPR1 in the nuclei of renal proximal tubules of injured human kidney allografts, but not in those of stable allografts. Taken together, these results suggest that epithelial expression of NUPR1 has a protective role in response to injury after renal transplant and, presumably, in other forms of acute tubular damage.

Glomerular common gamma chain confers B- and T-cell-independent protection against glomerulonephritis.

Crescentic glomerulonephritis is a life-threatening renal disease that has been extensively studied by the experimental anti-glomerular basement membrane glomerulonephritis (anti-GBM-GN) model. Although T cells have a significant role in this model, athymic/nude mice and rats still develop severe renal disease. Here we further explored the contribution of intrinsic renal cells in the development of T-cell-independent GN lesions. Anti-GBM-GN was induced in three strains of immune-deficient mice (Rag2-/-, Rag2-/-Il2rg-/-, and Rag2-/-Il2rb-/-) that are devoid of either T/B cells or T/B/NK cells. The Rag2-/-Il2rg-/- or Rag2-/-Il2rb-/- mice harbor an additional deletion of either the common gamma chain (γC) or the interleukin-2 receptor ß subunit (IL-2Rß), respectively, impairing IL-15 signaling in particular. As expected, all these strains developed severe anti-GBM-GN. Additionally, bone marrow replenishment experiments allowed us to deduce a protective role for the glomerular-expressed γC during anti-GBM-GN. Given that IL-15 has been found highly expressed in nephritic kidneys despite the absence of lymphocytes, we then studied this cytokine in vitro on primary cultured podocytes from immune-deficient mice (Rag2-/-Il2rg-/- and Rag2-/-Il2rb-/-) compared to controls. IL-15 induced downstream activation of JAK1/3 and SYK in primary cultured podocytes. IL-15-dependent JAK/SYK induction was impaired in the absence of γC or IL-2Rß. We found γC largely induced on podocytes during human glomerulonephritis. Thus, renal lesions are indeed modulated by intrinsic glomerular cells through the γC/IL-2Rß receptor response, to date classically described only in immune cells.

Deletion of mineralocorticoid receptors in smooth muscle cells blunts renal vascular resistance following acute cyclosporine administration.

Calcineurin inhibitors such as cyclosporine A (CsA) are still commonly used after renal transplantation, despite CsA--induced nephrotoxicity (CIN), which is partly related to vasoactive mechanisms. The mineralocorticoid receptor (MR) is now recognized as a key player in the control of vascular tone, and both endothelial cell- and vascular smooth muscle cell (SMC)-MR modulate the vasoactive responses to vasodilators and vasoconstrictors. Here we tested whether vascular MR is involved in renal hemodynamic changes induced by CsA. The relative contribution of vascular MR in acute CsA treatment was evaluated using mouse models with targeted deletion of MR in endothelial cell or SMC. Results indicate that MR expressed in SMC, but not in endothelium, contributes to the increase of plasma urea and creatinine, the appearance of isometric tubular vacuolization, and overexpression of a kidney injury biomarker (neutrophil gelatinase--associated lipocalin) after CsA treatment. Inactivation of MR in SMC blunted CsA--induced phosphorylation of contractile proteins. Finally, the in vivo increase of renal vascular resistance induced by CsA was blunted when MR was deleted from SMC cells, and this was associated with decreased L-type Ca2D channel activity. Thus, our study provides new insights into the role of vascular MR in renal hemodynamics during acute CIN, and provides rationale for clinical studies of MR antagonism to manage the side effects of calcineurin inhibitors.

Administration of recombinant soluble urokinase receptor per se is not sufficient to induce podocyte alterations and proteinuria in mice.

Circulating levels of soluble forms of urokinase-type plasminogen activator receptor (suPAR) are generally elevated in sera from children and adults with FSGS compared with levels in healthy persons or those with other types of kidney disease. In mice lacking the gene encoding uPAR, forced increases in suPAR concentration result in FSGS-like glomerular lesions and proteinuria. However, whether overexpression of suPAR, per se, contributes to the pathogenesis of FSGS in humans remains controversial. We conducted an independent set of animal experiments in which two different and well characterized forms of recombinant suPAR produced by eukaryotic cells were administered over the short or long term to wild-type (WT) mice. In accordance with the previous study, the delivered suPARs are deposited in the glomeruli. However, such deposition of either form of suPAR in the kidney did not result in increased glomerular proteinuria or altered podocyte architecture. Our findings suggest that glomerular deposits of suPAR caused by elevated plasma levels are not sufficient to engender albuminuria.

Circulating Dipeptidyl Peptidase 3 Modulates Systemic and Renal Hemodynamics Through Cleavage of Angiotensin Peptides.

BACKGROUND: High circulating DPP3 (dipeptidyl peptidase 3) has been associated with poor prognosis in critically ill patients with circulatory failure. In such situation, DPP3 could play a pathological role, putatively via an excessive angiotensin peptides cleavage. Our objective was to investigate the hemodynamics changes induced by DPP3 in mice and the relation between the observed effects and renin-angiotensin system modulation. METHODS: Ten-week-old male C57Bl/6J mice were subjected to intravenous injection of purified human DPP3 or an anti-DPP3 antibody (procizumab). Invasive blood pressure and renal blood flow were monitored throughout the experiments. Circulating angiotensin peptides and catecholamines were measured and receptor blocking experiment performed to investigate the underlying mechanisms. RESULTS: DPP3 administration significantly increased renal blood flow, while blood pressure was minimally affected. Conversely, procizumab led to significantly decreased renal blood flow. Angiotensin peptides measurement and an AT1R (angiotensin II receptor type 1) blockade experiment using valsartan demonstrated that the renovascular effect induced by DPP3 is due to reduced AT1R activation via decreased concentrations of circulating angiotensin II, III, and IV. Measurements of circulating catecholamines and an adrenergic receptor blockade by labetalol demonstrated a concomitant catecholamines release that explains blood pressure maintenance upon DPP3 administration. CONCLUSIONS: High circulating DPP3 increases renal blood flow due to reduced AT1R activation via decreased concentrations of circulating angiotensin peptides while blood pressure is maintained by concomitant endogenous catecholamines release.

Protective Role of the Podocyte IL-15 / STAT5 Pathway in Focal Segmental Glomerulosclerosis.

Introduction: During glomerular diseases, podocyte-specific pathways can modulate the intensity of histological disease and prognosis. The therapeutic targeting of these pathways could thus improve the management and prognosis of kidney diseases. The Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) pathway, classically described in immune cells, has been recently described in detail in intrinsic kidney cells. Methods: We describe STAT5 expression in human kidney biopsies from patients with focal segmental glomerulosclerosis (FSGS) and studied mice with a podocyte-specific Stat5 deletion in experimental glomerular diseases. Results: Here, we show, for the first time, that STAT5 is activated in human podocytes in FSGS. In addition, podocyte-specific Stat5 inactivation aggravates the structural and functional alterations in a mouse model of FSGS. This could be due, at least in part, to an inhibition of autophagic flux. Finally, interleukin 15 (IL-15), a classical activator of STAT5 in immune cells, increases STAT5 phosphorylation in human podocytes, and its administration alleviates glomerular injury in vivo by maintaining autophagic flux in podocytes. Conclusion: Activating podocyte STAT5 with commercially available IL-15 represents a potential new therapeutic avenue for FSGS.

Genetic inhibition of discoidin domain receptor 1 protects mice against crescentic glomerulonephritis.

This study investigated the role of discoidin domain receptor 1 (DDR1), a collagen receptor that displays tyrosine-kinase activity, in the development of glomerulonephritis. Crescentic glomerulonephritis was induced in DDR1-deficient mice and their wild-type (WT) littermates as controls, by injection of alloimmune sheep nephrotoxic serum (NTS). Histological, functional and transcriptomic studies were performed. Glomerulonephritis produced a 17-fold increase of DDR1 expression, predominantly in glomeruli. DDR1 deletion protected NTS-treated mice against glomerular disease (proteinuria/creatininuria 5.5±1.1 vs. 13.2±0.8 g/mmol in WT, crescents 12±2 vs. 24±2% of glomeruli, urea 16±2 vs. 28±5 mM), hypertension (123±11 vs. 157±8 mmHg), and premature death (70 vs. 10% survival) (all P<0.05). Reciprocal stimulation between DDR1 and interleukin-1b expression in vivo and in cultured podocytes suggested a positive feed-back loop between DDR1 and inflammation. In NTS-treated WT mice, administration of DDR1-specific antisense oligodeoxynucleotides decreased DDR1 expression (-56%) and protected renal function and structure, including nephrin expression (4.2±1.4 vs. 0.9±0.4 arbitrary units, P<0.05), compared to control mice receiving scrambled oligodeoxynucleotides. The therapeutic potential of this approach was reinforced by the observation of increased DDR1 expression in glomeruli of patients with lupus nephritis and Goodpasture's syndrome. These results prompt further interest in DDR1 blockade strategies, especially in the treatment of glomerulonephritis.

Calpastatin controls polymicrobial sepsis by limiting procoagulant microparticle release.

RATIONALE: Sepsis, a leading cause of death worldwide, involves widespread activation of inflammation, massive activation of coagulation, and lymphocyte apoptosis. Calpains, calcium-activated cysteine proteases, have been shown to increase inflammatory reactions and lymphocyte apoptosis. Moreover, calpain plays an essential role in microparticle release. OBJECTIVES: We investigated the contribution of calpain in eliciting tissue damage during sepsis. METHODS: To test our hypothesis, we induced polymicrobial sepsis by cecal ligation and puncture in wild-type (WT) mice and transgenic mice expressing high levels of calpastatin, a calpain-specific inhibitor. MEASUREMENTS AND MAIN RESULTS: In WT mice, calpain activity increased transiently peaking at 6 hours after cecal ligation and puncture surgery. Calpastatin overexpression improved survival, organ dysfunction (including lung, kidney, and liver damage), and lymphocyte apoptosis. It decreased the sepsis-induced systemic proinflammatory response and disseminated intravascular coagulation, by reducing the number of procoagulant circulating microparticles and therefore delaying thrombin generation. The deleterious effect of microparticles in this model was confirmed by transferring microparticles from septic WT to septic transgenic mice, worsening their survival and coagulopathy. CONCLUSIONS: These results demonstrate an important role of the calpain/calpastatin system in coagulation/inflammation pathways during sepsis, because calpain inhibition is associated with less severe disseminated intravascular coagulation and better overall outcomes in sepsis.