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As a potent chemotherapy drug, cisplatin is also notorious for its side-effects including nephrotoxicity in kidneys, presenting a pressing need to identify renoprotective agents. Cisplatin nephrotoxicity involves epigenetic regulations, including changes in histone acetylation. Bromodomain and extraterminal (BET) proteins are "readers" of the epigenetic code of histone acetylation. Here, we investigated the potential renoprotective effects of JQ1, a small molecule inhibitor of BET proteins. We show that JQ1 significantly ameliorated cisplatin-induced nephrotoxicity in mice as indicated by the measurements of kidney function, histopathology, and renal tubular apoptosis. JQ1 also partially prevented the body weight loss during cisplatin treatment in mice. Consistently, JQ1 inhibited cisplatin-induced apoptosis in renal proximal tubular cells. Mechanistically, JQ1 suppressed cisplatin-induced phosphorylation or activation of p53 and Chk2, key events in DNA damage response. JQ1 also attenuated cisplatin-induced MAP kinase (p38, ERK1/2, and JNK) activation. In addition, JQ1 enhanced the expression of antioxidant genes including nuclear factor erythroid 2-related factor 2 and heme oxygenase-1, while diminishing the expression of the nitrosative protein inducible nitric oxide synthase. JQ1 did not suppress cisplatin-induced apoptosis in A549 nonsmall cell lung cancer cells and AGS gastric cancer cells. These results suggest that JQ1 may protect against cisplatin nephrotoxicity by suppressing DNA damage response, p53, MAP kinases, and oxidative/nitrosative stress pathways.

Mutations in PKHD1 (polycystic kidney and hepatic disease gene 1) gene cause the autosomal recessive polycystic kidney disease (ARPKD). Fibrocystin/polyductin (FPC), encoded by PKHD1, is a membrane-associated receptor-like protein. Although it is widely accepted that cystogenesis is mostly due to aberrant cell proliferation and apoptosis, it is still unclear how apoptosis is regulated. The aim of this study is to analyze the relationship among apoptosis, phosphatidylinositol 3-kinase (PI3K)/Akt and nuclear factor κB (NF-κB) in FPC knockdown kidney cells. We show that PKHD1-silenced HEK293 cells demonstrate a higher PI3K/Akt activity. Selective inhibition of PI3K/Akt using LY294002 or wortmannin in these cells increases serum starvation-induced HEK293 cell apoptosis with a concomitant decrease in cell proliferation and higher caspase-3 activity. PI3K/Akt inhibition also leads to increased NF-κB activity in these cells. We conclude that the PI3K/Akt pathway is involved in apoptotic function in PKHD1-silenced cells, and PI3K/Akt inhibition correlates with upregulation of NF-κB activity. These observations provide a potential platform for determining FPC function and therapeutic investigation of ARPKD., (Copyright © 2011 Elsevier Inc. All rights reserved.)

This study aims to investigate the effects of TNF receptors associated factor 3 (TRAF3) on the signaling pathway and expression of downstream products of nuclear factor kappa B (NF-κB) in the epithelial cells of renal ducts in individuals with polycystic kidney disease (PKD). We observe the TRAF3 genic overexpression of the epithelial cells, which form a tubular branch structure, in polycystic kidneys and to explore the protective effect of TRAF3 on the cystogenesis and progression of PKD. Western blotting analysis was conducted to examine the signaling changes of NF-κB in PKD the epithelial cells and TRAF3 transgenic PKD epithelial cells. Changes in the downstream apoptosis factor and cell proliferation in PKD epithelial cells and TRAF3 transgenic PKD epithelial cells were detected. A three-dimensional matrigel culture experiment was performed to examine abnormal tubulomorphogenesis in vitro. The overexpression of TRAF3 significantly inhibited the signaling pathway of NF-κB in the PKD epithelial cells, downregulated the expression of downstream factors Bcl-2 and Bcl-xl, and significantly decreased cystic epithelial cell proliferation. Additional branch structures were observed in the PKD epithelial cells with a three-dimensional culture compared to wildtype cells. TRAF3 may likely induce apoptosis and resistance to proliferation and may be a new target to inhibit the cyst formation in PKD by regulating the NF-κB signaling pathway Bcl-2 and Bcl-xl activity. © 2017 IUBMB Life, 69(3):170-178, 2017 [ABSTRACT FROM AUTHOR]

Abstract: Mutations in PKHD1 (polycystic kidney and hepatic disease gene 1) gene cause the autosomal recessive polycystic kidney disease (ARPKD). It is widely accepted that cystogenesis is owing to aberrant cell proliferation and apoptosis, increased fluid secretion, and extracellular matrix abnormality. Fibrocystin/polyductin (FPC), the encoded protein product by PKHD1, is a single transmembrane protein and believed to be a novel receptor-like molecule. FPC has been located mainly on the plasma membrane and cilium/basal body. However, its biological functions remain poorly understood. To investigate the roles of FPC in the pathogenesis of ARPKD, we searched for FPC-interacting proteins by yeast two-hybrid assay, and found a novel partner, prosaposin. Prosaposin is a glycoprotein with multiple functions. With GST pull-down assay and co-immunoprecipitation, we confirmed the interaction between FPC and prosaposin. In order to study the effects of FPC–prosaposin interaction on cell proliferation and apoptosis, we have made stable cell lines in which FPC was overexpressed or knocked down alone or in combination with prosaposin overexpression. By MTT assay, we found that FPC knockdown and prosaposin overexpression increased cell proliferation, respectively, while overexpression of FPC C-tail did the opposite. With apoptosis assay, we found that overexpression of FPC C-tail promoted cell apoptosis. However, overexpression of prosaposin significantly enhanced cell survival in FPC knockdown cells. All these findings indicated that FPC and prosaposin may play significant roles in regulation of cell proliferation and apoptosis. Taken together, we have disclosed a novel signaling pathway of FPC, which may be important for the pathogenesis of ARPKD. [ABSTRACT FROM AUTHOR]