Hélène François

Prevention of renal vascular and glomerular fibrosis by epidermal growth factor receptor inhibition

Hypertension is frequently associated with the development of renal vascular and glomerular fibrosis. The purpose of the present study was to investigate whether epidermal growth factor receptor (EGFR) activation participates in the development of renal fibrosis and to test if blockade of EGFR activation would have therapeutic effects. Experiments were performed during nitric oxide (NO) deficiency‐induced hypertension in rats (L‐NAME model). After 4 weeks of L‐NAME treatment, animals developed hypertension associated to deterioration of renal structure and function. Over the same period, EGFR was activated twofold within glomeruli. This activation was accompanied by increased activity of the mitogen‐activated protein kinase (MAPK) p42/p44 pathway and exaggerated collagen I expression. Gefitinib, an EGFR‐tyrosine kinase inhibitor, given concomitantly with L‐NAME, normalized MAPK activation and collagen I expression and prevented the decline of renal function and the development of fibrosis. Since endothelin mediates the L‐NAME‐induced fibrogenesis, the endothelin‐EGFR interaction was tested in transgenic mice expressing luciferase under the control of collagen I‐α2 promoter: In renal cortex of these animals, the endothelin‐induced collagen I gene activity was inhibited by an EGFR‐phosphorylation inhibitor. These results provide the first evidence that EGFR activation plays an important role in the progression of renal vascular and glomerular fibrosis.

Advances in immunosuppression for renal transplantation.

The development of immunosuppressants with minimal adverse and nephrotoxic effects is important to improve outcomes, such as acute and chronic antibody-mediated rejection, after organ transplantation. In addition, the application of expanded criteria for donors and transplantation in immunized patients necessitates the development of new therapies. Drug development over the past 10 years has generally been disappointing, but several new promising compounds have been or are being developed to prevent acute and chronic transplant rejection. In this Review, we report on several compounds that have been developed to remove allogenic T cells and/or to inhibit T-cell activation. We also discuss compounds that interfere with antibody-mediated rejection.

Cannabinoid receptor 1 is a major mediator of renal fibrosis

Chronic kidney disease, secondary to renal fibrogenesis, is a burden on public health. There is a need to explore new therapeutic pathways to reduce renal fibrogenesis. To study this, we used unilateral ureteral obstruction (UUO) in mice as an experimental model of renal fibrosis and microarray analysis to compare gene expression in fibrotic and normal kidneys. The cannabinoid receptor 1 (CB1) was among the most upregulated genes in mice, and the main endogenous CB1 ligand (2-arachidonoylglycerol) was significantly increased in the fibrotic kidney. Interestingly, CB1 expression was highly increased in kidney biopsies of patients with IgA nephropathy, diabetes, and acute interstitial nephritis. Both genetic and pharmacological knockout of CB1 induced a profound reduction in renal fibrosis during UUO. While CB2 is also involved in renal fibrogenesis, it did not potentiate the role of CB1. CB1 expression was significantly increased in myofibroblasts, the main effector cells in renal fibrogenesis, upon TGF-β1 stimulation. The decrease in renal fibrosis during CB1 blockade could be explained by a direct action on myofibroblasts. CB1 blockade reduced collagen expression in vitro. Rimonabant, a selective CB1 endocannabinoid receptor antagonist, modulated the macrophage infiltrate responsible for renal fibrosis in UUO through a decrease in monocyte chemoattractant protein-1 synthesis. Thus, CB1 has a major role in the activation of myofibroblasts and may be a new target for treating chronic kidney disease.

Rituximab in anti-GBM disease: A retrospective study of 8 patients

OBJECTIVES Anti-glomerular basement membrane (GBM) disease is a rare autoantibody-mediated disorder presenting as rapidly progressive glomerulonephritis, and often with pulmonary hemorrhage. Antibody removal with plasmapheresis and immunosuppressive drugs are the cornerstones of the treatment. Data regarding the use of specific B-cell depleting therapy such as rituximab are lacking. METHODS We conducted a retrospective observational study of 8 patients with severe and/or refractory GBM disease that received rituximab therapy. RESULTS Eight patients (2 men, 6 women) with a mean age of 26 ± 13.1 years old were included. Seven had severe renal involvement [median creatinin level was 282 μmol/l, range (65-423)] requiring high immunosuppressive or plasmapheresis dependent, and two had relapse of pulmonary hemorrhage including one with renal failure. Patients received an initial immunosuppressive treatment including steroid and cyclosphosphamide (n = 8) and plasmapheresis (n = 5). Except one late relapse, rituximab therapy was started within two months after diagnosis. All patients except one received 4 weekly dose of rituximab (375 mg(2)). Anti-GBM antibodies were still present in 6/8 patients, at rituximab initiation. Complete remission was observed in 7 out of 8 patients, mostly 3 months after rituximab therapy. After a mean follow-up of 25.6 months (range 4-93), patient and renal survival were 100% and 75% respectively, but rituximab use did not improve GFR. Anti-GBM antibodies remained negative for all patients during follow-up. Only one patient developed a severe bacterial infection but no opportunistic or viral infections were reported. CONCLUSION Rituximab may represent an additional and/or alternative therapy in the induction treatment of anti-GBM disease.

Interleukin-15 Plays a Central Role in Human Kidney Physiology and Cancer through the γc Signaling Pathway

The ability of Interleukin-15 (IL-15) to activate many immune antitumor mechanisms renders the cytokine a good candidate for the therapy of solid tumors, particularly renal cell carcinoma. Although IL-15 is being currently used in clinical trials, the function of the cytokine on kidneys components has not been extensively studied; we thus investigated the role of IL-15 on normal and tumor renal epithelial cells. Herein, we analyzed the expression and the biological functions of IL-15 in normal renal proximal tubuli (RPTEC) and in their neoplastic counterparts, the renal clear cell carcinomas (RCC). This study shows that RPTEC express a functional heterotrimeric IL-15Rαβγc complex whose stimulation with physiologic concentrations of rhIL-15 is sufficient to inhibit epithelial mesenchymal transition (EMT) commitment preserving E-cadherin expression. Indeed, IL-15 is not only a survival factor for epithelial cells, but it can also preserve the renal epithelial phenotype through the γc-signaling pathway, demonstrating that the cytokine possess a wide range of action in epithelial homeostasis. In contrast, in RCC in vitro and in vivo studies reveal a defect in the expression of γc-receptor and JAK3 associated kinase, which strongly impacts IL-15 signaling. Indeed, in the absence of the γc/JAK3 couple we demonstrate the assembly of an unprecedented functional high affinity IL-15Rαβ heterodimer, that in response to physiologic concentrations of IL-15, triggers an unbalanced signal causing the down-regulation of the tumor suppressor gene E-cadherin, favoring RCC EMT process. Remarkably, the rescue of IL-15/γc-dependent signaling (STAT5), by co-transfecting γc and JAK3 in RCC, inhibits EMT reversion. In conclusion, these data highlight the central role of IL-15 and γc-receptor signaling in renal homeostasis through the control of E-cadherin expression and preservation of epithelial phenotype both in RPTEC (up-regulation) and RCC (down-regulation).

Complement modulation in solid-organ transplantation

The complement system is a major constituent of the innate immune system. It has a critical role in defense against pathogens but dysregulation of complement activation may lead to tissue injury and modulate the adaptive immune response. In organ transplantation, local complement activation is involved in hyper-acute rejection and antibody-mediated rejection. This last decade, interest in complement activation has increased due to new insights into the pathophysiology of antibody-mediated rejection, but also since the availability of news drugs that target terminal complement activation. In this review, we discuss our current understanding of how local complement activation induces acute and chronic graft injury, and review recent advances in clinical trials that block complement activation using the anti-C5 monoclonal antibody, eculizumab. Finally, we discuss how complement-targeted therapy may be integrated into our current immunosuppressive regimen and what type of patient will benefit most from this therapy.

Protein A immunoadsorption cannot significantly remove the soluble receptor of urokinase from sera of patients with recurrent focal segmental glomerulosclerosis

BACKGROUND Focal segmental glomerulosclerosis (FSGS) is a serious disease, the pathogenesis of which is unknown. Its recurrence after transplantation (Tx) and its partial remission after treatment with immunoadsorption (IA) on a protein A column indicate the existence of a circulating factor responsible for the disease that is able to bind to a protein A column. Recently, the soluble receptor of urokinase (suPAR) was described as the factor responsible for FSGS. We tested the capacity of suPAR to bind to protein A and to be eliminated by IA. METHODS We measured suPAR in eluates of protein A columns from seven patients with recurrent FSGS after Tx (rFSGS) treated with IA, and in the serum of 13 patients with rFSGS and 11 healthy donors (HDs). Additionally, the plasma of these patients was immunoadsorbed in vitro on a protein A Sepharose column, and we quantified suPAR in the eluates and in pre- and post-column samples. RESULTS The concentration of suPAR was higher in the plasma of patients with rFSGS than that of HD patients. However, the concentration of suPAR was similar before and after IA on protein A for the rFSGS and HD samples. The suPAR concentration was very low in the eluates from protein A columns incubated with plasma from HD or rFSGS patients. However, 85% of rFSGS patients showed a decrease in immunoglobulin G and proteinuria. CONCLUSIONS Thus, suPAR does not significantly bind to protein A in vitro or in vivo.

Renal fibrosis: Recent translational aspects

Renal fibrogenesis is the common final pathway to all renal injuries that consequently leads to Chronic Kidney Disease (CKD). Renal fibrogenesis corresponds to the replacement of renal functional tissue by extra-cellular matrix proteins, mainly collagens, that ultimately impairs kidney function. Blockade of the renin angiotensin system by Angiotensin Converting Enzyme inhibitors (ACEi) or Angiotensin Receptor Blockers (ARBs) was the first strategy that proved efficient to blunt the development of renal fibrogenesis independently of its systemic action on blood pressure. Although this strategy has been published 20years ago, there is to date no novel therapeutic targets that are both safe and efficient in hindering renal fibrogenesis and CKD in humans, nor there is any new biomarker to precisely quantify this process. In our review, we will focus on the most recent pathways leading to fibrogenesis which have a high therapeutic potential in humans and on the most promising biomarkers of renal fibrosis.

Intracellular lactate flux: a new regulator of the allogenic immune response

During the past decade, long-term graftand patient-survival rates have not improved significantly, despite the reduced incidence of acute rejections. This is partly because of the toxicities of immunosuppressive drugs and patients’ deaths from cardiovascular events, which can be associated with the cardiovascular risk factors related to immunosuppressive drugs [1]. Among these drugs, calcineurin inhibitors (CNIs) are strongly associated with renal toxicity and the development of cardiovascular risk factors, including hypertension, diabetes, and dyslipidemia; thus, there is a need for a toxicity-free CNIfree regimen [2]. However, very few molecules have emerged that can totally or partially replace CNIs. Most evaluated molecules have targeted or regulate T-cell activation, especially signal 1 or 2 activation of T cells, as well as the third signal involved in the expansion of activated T cells. It has recently been shown that other mechanisms are implicated in the development or differentiation of T lymphocytes. These modify nutrients or precursors that are not only involved in the expansion phase of activated lymphocytes, such as inositol monophosphate dehydrogenase, but are also able to modulate T-cell activation or to switch their phenotype from activated T cells to regulatory cells. For example, tryptophan metabolism induced by IDO-expressing dendritic cells is associated with inducing regulator T cells [3]. Adenosine metabolism, induced by the CD73 ecto-enzyme, also participates in the development of regulatory cells [4]. However, the mechanisms that make thesemetabolites effective are still not completely understood, although they do affect the phenotype of T cells, which leads to the development of regulatory T cells. For adenosine, the binding of the small molecule induces some signaling in the cell through the A2A adenosine receptor [5]. Their role in organ transplantation has yet to be demonstrated, but this finding opens up a new area of transplantation research. Other compounds may also be of interest. Påhlman et al. [6] demonstrated that inhibition of lactate transport in lymphocytes favored tolerance in rats. The lactate transporters are a group of proton-linked monocarboxylate transporters of at least eight members but only four have been functionally characterized (MCT-1, MCT-2, MCT-3, MCT-4) that have been cloned independently by two research groups [7]. MCT-1 is wildly expressed in vivo in several tissues such as kidney, gut, hematopoietic cells, brain, gut, muscles, and lymphocytes [8,9]. MCT-1 can favor the release of lactate accumulated in cells following glycolysis. Without MCT-1, lactates and pyruvates will be accumulated in the cytoplasm of cells and the normal aerobic glycolysis can’t be processed because of the intracellular accumulation of lactate and protons. Overexpression of MCT-1 in Chinese hamster ovary cells or in chronically stimulated skeletal muscles increases

Plasma cell neoplasia after kidney transplantation: French cohort series and review of the literature

Although post-transplant lymphoproliferative disorder (PTLD) is the second most common type of cancer in kidney transplantation (KT), plasma cell neoplasia (PCN) occurs only rarely after KT, and little is known about its characteristics and evolution. We included twenty-two cases of post-transplant PCN occurring between 1991 and 2013. These included 12 symptomatic multiple myeloma, eight indolent myeloma and two plasmacytomas. The median age at diagnosis was 56.5 years and the median onset after transplantation was 66.7 months (2–252). Four of the eight indolent myelomas evolved into symptomatic myeloma after a median time of 33 months (6–72). PCN-related kidney graft dysfunction was observed in nine patients, including six cast nephropathies, two light chain deposition disease and one amyloidosis. Serum creatinine was higher at the time of PCN diagnosis than before, increasing from 135.7 (±71.6) to 195.9 (±123.7) μmol/l (p = 0.008). Following transplantation, the annual rate of bacterial infections was significantly higher after the diagnosis of PCN, increasing from 0.16 (±0.37) to 1.09 (±1.30) (p = 0.0005). No difference was found regarding viral infections before and after PCN. Acute rejection risk was decreased after the diagnosis of PCN (36% before versus 0% after, p = 0.004), suggesting a decreased allogeneic response. Thirteen patients (59%) died, including twelve directly related to the hematologic disease. Median graft and patient survival was 31.7 and 49.4 months, respectively. PCN after KT occurs in younger patients compared to the general population, shares the same clinical characteristics, but is associated with frequent bacterial infections and relapses of the hematologic disease that severely impact the survival of grafts and patients.