CCDC92 promotes podocyte injury by regulating PA28α/ABCA1/cholesterol efflux axis in type 2 diabetic mice.

Podocyte lipotoxicity mediated by impaired cellular cholesterol efflux plays a crucial role in the development of diabetic kidney disease (DKD), and the identification of potential therapeutic targets that regulate podocyte cholesterol homeostasis has clinical significance. Coiled-coil domain containing 92 (CCDC92) is a novel molecule related to metabolic disorders and insulin resistance. However, whether the expression level of CCDC92 is changed in kidney parenchymal cells and the role of CCDC92 in podocytes remain unclear. In this study, we found that Ccdc92 was significantly induced in glomeruli from type 2 diabetic mice, especially in podocytes. Importantly, upregulation of Ccdc92 in glomeruli was positively correlated with an increased urine albumin-to-creatinine ratio (UACR) and podocyte loss. Functionally, podocyte-specific deletion of Ccdc92 attenuated proteinuria, glomerular expansion and podocyte injury in mice with DKD. We further demonstrated that Ccdc92 contributed to lipid accumulation by inhibiting cholesterol efflux, finally promoting podocyte injury. Mechanistically, Ccdc92 promoted the degradation of ABCA1 by regulating PA28α-mediated proteasome activity and then reduced cholesterol efflux. Thus, our studies indicate that Ccdc92 contributes to podocyte injury by regulating the PA28α/ABCA1/cholesterol efflux axis in DKD.

GPR97 deficiency ameliorates renal interstitial fibrosis in mouse hypertensive nephropathy.

Hypertensive nephropathy (HTN) ranks as the second-leading cause of end-stage renal disease (ESRD). Accumulating evidence suggests that persistent hypertension injures tubular cells, leading to tubulointerstitial fibrosis (TIF), which is involved in the pathogenesis of HTN. G protein-coupled receptors (GPCRs) are implicated in many important pathological and physiological processes and act as important drug targets. In this study, we explored the intrarenal mechanisms underlying hypertension-associated TIF, and particularly, the potential role of GPR97, a member of the adhesion GPCR subfamily, in TIF. A deoxycorticosterone acetate (DOCA)/salt-induced hypertensive mouse model was used. We revealed a significantly upregulated expression of GPR97 in the kidneys, especially in renal tubules, of the hypertensive mice and 10 patients with biopsy-proven hypertensive kidney injury. GPR97-/- mice showed markedly elevated blood pressure, which was comparable to that of wild-type mice following DOCA/salt treatment, but dramatically ameliorated renal injury and TIF. In NRK-52E cells, we demonstrated that knockdown of GPR97 suppressed the activation of TGF-ß signaling by disturbing small GTPase RhoA-mediated cytoskeletal reorganization, thus inhibiting clathrin-mediated endocytosis of TGF-ß receptors and subsequent Smad activation. Collectively, this study demonstrates that GPR97 contributes to hypertension-associated TIF at least in part by facilitating TGF-ß signaling, suggesting that GPR97 is a pivotal intrarenal factor for TIF progression under hypertensive conditions, and therapeutic strategies targeting GPR97 may improve the outcomes of patients with HTN.

JAML promotes acute kidney injury mainly through a macrophage-dependent mechanism.

Although macrophages are undoubtedly attractive therapeutic targets for acute kidney injury (AKI) because of their critical roles in renal inflammation and repair, the underlying mechanisms of macrophage phenotype switching and efferocytosis in the regulation of inflammatory responses during AKI are still largely unclear. The present study elucidated the role of junctional adhesion molecule-like protein (JAML) in the pathogenesis of AKI. We found that JAML was significantly upregulated in kidneys from 2 different murine AKI models including renal ischemia/reperfusion injury (IRI) and cisplatin-induced AKI. By generation of bone marrow chimeric mice, macrophage-specific and tubular cell-specific Jaml conditional knockout mice, we demonstrated JAML promoted AKI mainly via a macrophage-dependent mechanism and found that JAML-mediated macrophage phenotype polarization and efferocytosis is one of the critical signal transduction pathways linking inflammatory responses to AKI. Mechanistically, the effects of JAML on the regulation of macrophages were, at least in part, associated with a macrophage-inducible C-type lectin-dependent mechanism. Collectively, our studies explore for the first time to our knowledge new biological functions of JAML in macrophages and conclude that JAML is an important mediator and biomarker of AKI. Pharmacological targeting of JAML-mediated signaling pathways at multiple levels may provide a novel therapeutic strategy for patients with AKI.

Vitexin protects against cardiac hypertrophy via inhibiting calcineurin and CaMKII signaling pathways.

Vitexin is a flavone glycoside isolated from the leaf of Crataeguspinnatifida Bunge, the utility of which has been demonstrated in several cardiovascular diseases. However, its role in cardiac hypertrophy remains unclear. In the present study, we aimed to determine whether vitexin prevents cardiac hypertrophy induced by isoproterenol (ISO) in cultured neonatal rat ventricular myocytes in vitro and pressure overload-induced cardiac hypertrophy in mice in vivo. The results revealed that vitexin (10, 30, and 100 µM) dose-dependently attenuated cardiac hypertrophy induced by ISO in vitro. Furthermore, vitexin (3, 10, and 30 mg kg(-1)) prevented cardiac hypertrophy induced by transverse aortic constriction as assessed by heart weight/body weight, left ventricular weight/body weight and lung weight/body weight ratios, cardiomyocyte cross-sectional area, echocardiographic parameters, and gene expression of hypertrophic markers. Further investigation demonstrated that vitexin inhibited the increment of the resting intracellular free calcium induced by ISO. Vitexin also inhibited the expression of calcium downstream effectors calcineurin-NFATc3 and phosphorylated calmodulin kinase II (CaMKII) both in vitro and in vivo. Taken together, our results indicate that vitexin has the potential to protect against cardiac hypertrophy through Ca2+-mediated calcineurin-NFATc3 and CaMKII signaling pathways.

Tetraethylammonium enhances the rectal and colonic motility in rats and human in vitro.

Hirschsprung's disease is the congenital absence of generating the peristaltic contractions transmitting from the proximal colon to rectum. We previously have found that tetraethylammonium (TEA), the nonselective Ca(2+)-activated K(+) channel blocker, increases the maximal contractile force and the amplitude of the contraction in rat duodenum. The present study is to test the effect of TEA on motility of colon and rectum from rats and Hirschsprung's disease patients in vitro, in order to find an alternative method to improve the syndrome of Hirschsprung's disease. The rectal and colonic motility was recorded by a tension transducer connected to a biology function experiment system. Histology was analyzed with standard hematoxylin and eosin staining. TEA (1, 3, and 5 mM) significantly increased the amplitude and frequency of contractility of colon and rectum from rats in longitudinal and circular direction. TEA at 5 and 15 mM concentrations showed no effect on histology of colon and rectum from rats that were administered locally with TEA into colon lumen from anus for 10 days. TEA at 15 mM increased the amplitude and frequency of contractions of the colon and rectum from Hirschsprung's disease patients. Our data showed that TEA increased the contractility of colon and rectum from rats and Hirschsprung's disease patients in vitro, suggesting that local administration of TEA in colon or rectum lumen might be an alternative method to ameliorate the syndrome of Hirschsprung's disease patients who are not cured completely by surgery or not suitable for surgery.

Heme oxygenase-1 transgenic overexpression did not prevent artery injury induced by electric stimulation and pressure overload in mice.

Heme oxygenase-1 (HO-1) shows multiple beneficial effects on cardiovascular diseases. However, the effect of HO-1 on the injury of artery has never been identified. In the present study, we established systemic HO-1 overexpression transgenic mice and investigated the effect of HO-1 on the injury of artery induced by electric stimulation and pressure-overload in transgenic mice. Artery injury was induced by electric stimulation and pressure overload. The contractive function, endothelium-dependent and -independent relaxation of arteries were measured through an isometric force transducer connected to a multichannel acquisition and analysis system. Western blot results showed that HO-1 protein level in transgenic mice arteries was significantly higher than that in wild type mice arteries, while no difference of HO-2 protein level in the arteries of transgenic and wild type mice. Arterial reendothelialization after electric injury was accelerated in transgenic mice. No significant difference in contractive function, endothelium-dependent and -independent relaxation of arteries was observed between wild type and transgenic mice at day 7 after electric injury and 4 weeks after pressure overload. We concluded that HO-1 overexpression accelerated the reendothelialization, but did not prevent the functional impairment of injured artery in mice.

Effects of isosorbide mononitrate on the restoration of injured artery in mice in vivo.

The pharmacological basis of isosorbide mononitrate (ISMN), a widely used drug for cardiovascular diseases, is that it is metabolized to nitric oxide (NO). However, NO is a double-edged sword that results in either beneficial or detrimental effect. Vascular injury is the common consequence of many cardiovascular diseases, but it is not determined whether ISMN influences the restoration of injured artery in vivo. Carotid artery injury was induced by electric stimulation in mice. Vasoconstriction and endothelium-dependent and -independent relaxation were recorded by a multichannel acquisition and analysis system. ISMN (10 mg/kg, p.o.) treatment for 1 week and 1 month had no effect on reendothelialization, histology and function of carotid artery injured by electric stimulation. L-arginine (500 mg/kg, p.o.) and Nomega-nitro-L-arginine methyl ester (L-NAME) (50 mg/kg, p.o.) treatment for 1 week did not affect the reendothelialization process, but L-NAME treatment induced neointimal hyperplasia and inhibited endothelium-dependent relaxation in electrically injured artery. These results suggest that supplement of exogenous or endogenous NO has no effect on the restoration of injured artery, but inhibition of endogenous NO induces neointimal hyperplasia in injured artery. ISMN treatment does not affect the restoration of injured artery.