Project Summary Cisplatin is one of the most widely used and most potent chemotherapy drugs for cancer treatment, but it is also notorious for side effects in normal tissues and organs, especially kidneys. Cisplatin induces acute kidney injury (AKI) within days of exposure, which may progress into chronic kidney disease (CKD). Persistent inflammation is a key feature of, and contributes critically to, AKI-CKD transition, but its molecular basis remains largely unknown. The goal of this application is to delineate the mechanism of persistent renal inflammation during CKD development after cisplatin exposure. NF-kB is a central player in inflammation by transactivating pro-inflammatory genes. In preliminary studies, we demonstrated a continuous NF-kB activation in post-cisplatin kidneys, which was associated with persistent renal inflammation, fibrosis and decline of renal function. JSH-23, an inhibitor of NF-kB, suppressed inflammation and CKD development, supporting a pathogenic role of NF-kB. Interestingly, similar protective effects were shown by 5-aza, an inhibitor of DNA methyltransferases (DNMT) and DNA methylation. Remarkably, inhibition of NF-kB with JSH-23 attenuated DNMT expression in post- cisplatin kidneys, while inhibition of DNMT with 5-aza decreased NF-kB activation, suggesting a novel, reciprocal regulation between NF-kB and DNMT. Mechanistically, our preliminary results suggest that NF-kB may transactivate DNMT by binding to its gene promotor and, conversely, DNMT may up- regulate NF-kB by methylating and repressing PDLIM2, an E3 ligase for ubiquitination and degradation of the key NF-kB protein p65. We therefore hypothesize that cisplatin treatment leads to the activation of NF-kB in renal tubular cells, which transcriptionally induces DNMT. Upon induction, DNMT provide a positive feedback mechanism for NF-kB signaling by methylating and repressing PDLIM2. The reciprocal regulation between NF-kB and DNMT promotes persistent inflammation in post-cisplatin kidneys for the development of CKD. Therapeutically, inhibitors of NF-kB or DNMT may protect kidneys, while enhancing the chemotherapy effects of cisplatin in tumors. To test this hypothesis, we will verify the roles of NF-kB and DNMT in persistent inflammation and CKD development in post-cisplatin kidneys, elucidate the reciprocal regulation between NF-kB and DNMT after cisplatin exposure, and test the hypothesis that inhibitors of NF-kB or DNMT may attenuate renal inflammation and CKD while enhancing the chemotherapy effect of cisplatin in tumor-bearing animals. Completion of the research will gain significant new insights into the mechanisms of chronic renal inflammation and CKD following cisplatin chemotherapy. Moreover, by targeting NF-kB and DNMT, we may identify novel strategies that not only protect kidneys in cisplatin treatment but also enhance chemotherapy in tumors.