Abstract
Bardoxolone methyl [methyl-2-cyano-3, 12-dioxooleana-1, 9(11)dien-28-oate (CDDO-Me)], an activator of the nuclear factor erythroid-derived 2-related factor2 pathway, is a potential therapeutic candidate for the treatment of kidney diseases. However, its effect against cellular senescence remains unclear. This study aimed to investigate whether CDDO-Me protects cells against cisplatin-induced cellular senescence using an in vitro model. The human renal proximal tubular epithelial cell line HK-2 was treated with cisplatin for 6 h, followed by treatment with or without CDDO-Me (0.1 or 0.2 μmol/L). Senescence markers were analyzed using western blotting and real-time PCR. Apoptosis was evaluated through TUNEL staining. Cisplatin induced changes in the levels of markers specific for proliferation, cell cycle, and senescence in a time- and dose-dependent manner. Furthermore, IL-6 and IL-8 levels in the culture medium increased markedly. These data suggested that cellular senescence-like alterations occurred in HK-2 cells exposed to cisplatin. CDDO-Me treatment reversed the cisplatin-mediated alterations in the levels of cellular senescence markers. The antioxidant enzymes, HO1, NQO1, GPX1, and CAT were upregulated by CDDO-Me treatment. Furthermore, CDDO-Me treatment induced apoptosis in cisplatin-exposed HK-2 cells. Pretreatment with Ac-DEVD-CHO, the caspase inhibitor, suppressed the reversal effect of CDDO-Me against cisplatin-induced cellular senescence-like alterations. This study showed that CDDO-Me attenuated cisplatin-induced premature senescence of HK-2 cells. This beneficial effect may be related to Nrf2 activation. Our findings also showed that CDDO-Me induced apoptosis in cisplatin-treated HK-2 cells, potentially protecting the kidneys from cellular senescence. CDDO-Me appears to be a candidate treatment for acute kidney injury.
Highlights
Acute kidney injury (AKI) is a complex syndrome characterized by renal dysfunction and is associated with high morbidity and mortality worldwide
We examined whether cisplatin exposure induces cellular senescence in HK-2 cells
The expression of the cell cycle markers pRb, Rb, cyclin D, and cyclin A increased in cisplatin-exposed HK-2 cells
Summary
Acute kidney injury (AKI) is a complex syndrome characterized by renal dysfunction and is associated with high morbidity and mortality worldwide. Patients with post-AKI are at an increased risk for chronic kidney disease, CKD [1,2,3]. Proximal tubule injury caused by AKI triggers several features of CKD by inducing inflammation and interstitial fibrosis [4]. It is important to protect the proximal tubules for preventing the progression of AKI to CKD; the definitive evidence for this effect is lacking. There is an association between cellular senescence in proximal tubular epithelial cells (PTCs) and CKD in the animal models of hypertension [5] or diabetes [6]. Senescence induces cell cycle arrest in cells exposed to various stresses
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