Adult nephron-specific MR-deficient mice develop a severe renal PHA-1 phenotype

Aldosterone is the main mineralocorticoid hormone controlling sodium balance, fluid homeostasis, and blood pressure by regulating sodium reabsorption in the aldosterone-sensitive distal nephron (ASDN). Germline loss-of-function mutations of the mineralocorticoid receptor (MR) in humans and in mice lead to the "renal" form of type 1 pseudohypoaldosteronism (PHA-1), a case of aldosterone resistance characterized by salt wasting, dehydration, failure to thrive, hyperkalemia, and metabolic acidosis. To investigate the importance of MR in adult epithelial cells, we generated nephron-specific MR knockout mice (MR$^{Pax8/LC1}$) using a doxycycline-inducible system. Under standard diet, MR$^{Pax8/LC1}$ mice exhibit inability to gain weight and significant weight loss compared to control mice. Interestingly, despite failure to thrive, MR$^{Pax8/LC1}$ mice survive but develop a severe PHA-1 phenotype with higher urinary Na^+ levels, decreased plasma Na(+), hyperkalemia, and higher levels of plasma aldosterone. This phenotype further worsens and becomes lethal under a sodium-deficient diet. Na^+/Cl^- co-transporter (NCC) protein expression and its phosphorylated form are downregulated in the MR$^{Pax8/LC1}$ knockouts, as well as the αENaC protein expression level, whereas the expression of glucocorticoid receptor (GR) is increased. A diet rich in Na^+ and low in K^+ does not restore plasma aldosterone to control levels but is sufficient to restore body weight, plasma, and urinary electrolytes. In conclusion, MR deletion along the nephron fully recapitulates the features of severe human PHA-1. ENaC protein expression is dependent on MR activity. Suppression of NCC under hyperkalemia predominates in a hypovolemic state

Pathogenic Effects of Mineralocorticoid Pathway Activation in Retinal Pigment Epithelium

International audienceGlucocorticoids are amongst the most used drugs to treat retinal diseases of various origins. Yet, the transcriptional regulations induced by glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) activation in retinal pigment epithelium cells (RPE) that form the outer blood–retina barrier are unknown. Levels of endogenous corticoids, ligands for MR and GR, were measured in human ocular media. Human RPE cells derived from induced pluripotent stem cells (iRPE) were used to analyze the pan-transcriptional regulations induced by aldosterone—an MR-specific agonist, or cortisol or cortisol + RU486—a GR antagonist. The retinal phenotype of transgenic mice that overexpress the human MR (P1.hMR) was analyzed. In the human eye, the main ligand for GR and MR is cortisol. The iRPE cells express functional GR and MR. The subset of genes regulated by aldosterone and by cortisol + RU-486, and not by cortisol alone, mimics an imbalance toward MR activation. They are involved in extracellular matrix remodeling (CNN1, MGP, AMTN), epithelial–mesenchymal transition, RPE cell proliferation and migration (ITGB3, PLAUR and FOSL1) and immune balance (TNFSF18 and PTX3). The P1.hMR mice showed choroidal vasodilation, focal alteration of the RPE/choroid interface and migration of RPE cells together with RPE barrier function alteration, similar to human retinal diseases within the pachychoroid spectrum. RPE is a corticosteroid-sensitive epithelium. MR pathway activation in the RPE regulates genes involved in barrier function, extracellular matrix, neural regulation and epithelial differentiation, which could contribute to retinal pathology

Mutual recognition of parental and F1 lymphocytes. Selective abrogation of eytotoxic potential of FI lymphoeytes by parental lymphocytes.J. Exp. Med

The injection of F1 hybrid animals with parental spleen or lymph node cells leads to the activation of specific parental lymphocytes which recognize major histocompatibility complex (MHC) 1-coded antigens of the other parental haplotype expressed by the F1 host (1). Such recognition can result in graft-vs.-host (GVH) reactions which are frequently associated with depressed in vivo cell-mediated immune functions, such as resistance to bacterial infection (2), skin graft rejection (2, 3), T-helper cell dysfunction (4), as well as antibody responses to thymic-dependent and-independent antigens (5-8). The depression of T-cell-mediated lympholysis (CML) responses by cells from F1 hybrid mice injected with parental lymphocytes has not been reported but could provide a useful approach for investigating T-cell receptors because self MHC-restricted as well as allogeneic CML responses can be analyzed. This report describes an experimental system in which intravenous injection of F1 hybrid mice with parental T-splenic lymphocytes can result in the abrogation or severe depression of CML potential. This loss of CML activity did not appear to be specific for self determinants because responses to alloantigens, trinitrophenyl (TNP)modified F1 cells (TNP-self), and TNP-modified parental cells were all affected. However, an unexpected finding was the observation that the parental-induced CML depression was dependent upon the H-2 type of the injected parental lymphocytes. Thus, the injection of H-2 a, H-2 k, or H-2 a, but not H-2 6, parental lymphocytes resulted in depressed CML potential. These findings are discussed with respect to (a) the selective resistance of F1 mice to H-2 b parental lymphocytes, and (b) the possibility that Fa lymphocytes recognize idiotypic determinants specific for non-H-2 b antigens on H-2 b lymphocytes, but not those for H-2 b antigens on non-H-2 b lymphocytes

Deletion of the serine protease CAP2/Tmprss4 leads to dysregulated renal water handling upon dietary potassium depletion

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CFH exerts anti-oxidant effects on retinal pigment epithelial cells independently from protecting against membrane attack complex

International audienceAge Related Macular Degeneration (AMD) is the first cause of social blindness in people aged over 65 leading to atrophy of retinal pigment epithelial cells (RPE), photoreceptors and choroids, eventually associated with choroidal neovascularization. Accumulation of undigested cellular debris within RPE cells or under the RPE (Drusen), oxidative stress and inflammatory mediators contribute to the RPE cell death. The major risk to develop AMD is the Y402H polymorphism of complement factor H (CFH). CFH interacting with oxidized phospholipids on the RPE membrane modulates the functions of these cells, but the exact role of CFH in RPE cell death and survival remain poorly understood. The aim of this study was to analyze the potential protective mechanism of CFH on RPE cells submitted to oxidative stress. Upon exposure to oxidized lipids 4-HNE (4-hydroxy-2-nonenal) derived from photoreceptors, both the human RPE cell line ARPE-19 and RPE cells derived from human induced pluripotent stem cells were protected from death only in the presence of the full length human recombinant CFH in the culture medium. This protective effect was independent from the membrane attack complex (MAC) formation. CFH maintained RPE cells tight junctions’ structure and regulated the caspase dependent apoptosis process. These results demonstrated the CFH anti-oxidative stress functions independently of its capacity to inhibit MAC formation

Lack of Renal Tubular Glucocorticoid Receptor Decreases the Thiazide-Sensitive Na+/Cl– Cotransporter NCC and Transiently Affects Sodium Handling

International audienceChronic glucocorticoid infusion impairs NCC activity and induces a non-dipping profile in mice, suggesting that glucocorticoids are essential for daily blood pressure variations. In this paper, we studied mice lacking the renal tubular glucocorticoid receptor (GR) in adulthood (GR knockouts, Nr3c1Pax8/LC1). Upon standard salt diet, Nr3c1Pax8/LC1 mice grow normally, but show reduced NCC activity despite normal plasma aldosterone levels. Following diet switch to low sodium, Nr3c1Pax8/LC1 mice exhibit a transient but significant reduction in the activity of NCC and expression of NHE3 and NKCC2 accompanied by significant increased Spak activity. This is followed by transiently increased urinary sodium excretion and higher plasma aldosterone concentrations. Plasma corticosterone levels and 11βHSD2 mRNA expression and activity in the whole kidney remain unchanged. High salt diet does not affect whole body Na+ and/or K+ balance and NCC activity is not reduced, but leads to a significant increase in diastolic blood pressure dipping in Nr3c1Pax8/LC1 mice. When high sodium treatment is followed by 48 h of darkness, NCC abundance is reduced in knockout mice although activity is not different. Our data show that upon Na+ restriction renal tubular GR-deficiency transiently affects Na+ handling and transport pathways. Overall, upon standard, low Na+ and high Na+ diet exposure Na+ and K+ balance is maintained as evidenced by normal plasma and urinary Na+ and K+ and aldosterone concentrations

CFH exerts anti-oxidant effects on retinal pigment epithelial cells independently from protecting against membrane attack complex

Age Related Macular Degeneration (AMD) is the first cause of social blindness in people aged over 65 leading to atrophy of retinal pigment epithelial cells (RPE), photoreceptors and choroids, eventually associated with choroidal neovascularization. Accumulation of undigested cellular debris within RPE cells or under the RPE (Drusen), oxidative stress and inflammatory mediators contribute to the RPE cell death. The major risk to develop AMD is the Y402H polymorphism of complement factor H (CFH). CFH interacting with oxidized phospholipids on the RPE membrane modulates the functions of these cells, but the exact role of CFH in RPE cell death and survival remain poorly understood. The aim of this study was to analyze the potential protective mechanism of CFH on RPE cells submitted to oxidative stress. Upon exposure to oxidized lipids 4-HNE (4-hydroxy-2-nonenal) derived from photoreceptors, both the human RPE cell line ARPE-19 and RPE cells derived from human induced pluripotent stem cells were protected from death only in the presence of the full length human recombinant CFH in the culture medium. This protective effect was independent from the membrane attack complex (MAC) formation. CFH maintained RPE cells tight junctions’ structure and regulated the caspase dependent apoptosis process. These results demonstrated the CFH anti-oxidative stress functions independently of its capacity to inhibit MAC formation