Abstract: TH-PO300

Inhibition of Bromodomain Protein BRD4 Suppresses Cisplatin Induced p53 Activation and Apoptosis in Renal Tubular Cells

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Zhou, Xia, University of Kansas Medical Center, Kansas City, Kansas, United States
  • Li, Xiaogang, University of Kansas Medical Center, Kansas City, Kansas, United States
Background

Bromodomain protein BRD4 recognizes and binds acetylated histones to regulate gene transcription. Inhibitor of bromodomain protein, JQ1, has been reported to be effective in treating a variety of cancers. Cisplatin has been used for the chemotherapy of cancers for decades with the side effect of nephrotoxicity and acute kidney injury. One of the mechanisms of nephrotoxicity is p53 mediated apoptosis. However, whether JQ1 has a cytoprotective effect during cisplatin treatment of renal tubular cells is unknown.

Methods

To understand the effect of JQ1 on cisplatin induced acute kidney injury, we treated rat renal proximal tubule cells (RPTC) and mice with cisplatin with or without the presence of JQ1, and analyzed the cells and kidneys by flow cytometry, western blot, TUNEL and immunohistochemistry staining.

Results

We found that BRD4 positively regulated the mRNA and protein expression of p53, and BRD4 bound with p53 promoter in renal epithelial cells as examined by ChIP-PCR analysis. Cisplatin treatment induced 16.5% of cell apoptosis in RPTC cells at the concentration of 20 µM. JQ1 at the concentration of 60 nM did not induced apoptosis. However, co-treatment with cisplatin (20 µM) and JQ1 (60 nM) decreased the percentage of apoptotic cells to 4.1% as analyzed by FACS. JQ1 treatment decreased cisplatin induced RPTC cell apoptosis was further confirmed by TUNEL assay. We further found that cisplatin treatment increased the expression of p53 and its downstream pro-apoptotic protein Bax, as well as the apoptotic cell markers, cleaved PARP and active caspase 3. Cisplatin induced upregulation of p53 and apoptotic associated proteins could be down-regulated by the co-treatment with JQ1. In consistent with the results in vitro, JQ1 treatment attenuated cisplatin induced nephrotoxicity in vivo. We found that JQ1 treatment preserved renal function as seen by decreased the serum BUN level in cisplatin treated mice, the cortical and medullary tubular necrosis, and the TUNEL positive tubular cells.

Conclusion

This is the first report that BRD4 regulated p53 transcription in renal tubule cells. Inhibition of BRD4 with JQ1 attenuates cisplatin induced acute kidney injury by suppressing cisplatin induced p53 activation and apoptosis in renal tubular cells.

Funding

  • NIDDK Support