| Summary: | 博士 === 國防醫學院 === 生命科學研究所 === 104 === Cisplatin is the most widely used as a chemotherapeutic agent for several solid tumor types. Despite its effectiveness for cancer therapy, the clinical use of cisplatin is frequently limited by its toxicity against normal tissues, particular kidney toxicity. Accumulating evidence supports that tubular cell apoptosis significantly contributes to the pathogenesis of cisplatin-induced acute kidney injury (AKI). KCa3.1, a calcium-activated potassium channel, is widely expressed in both excitable and non-excitable cells. It is activated by the increase of intracellular calcium to regulate intracellular potassium efflux, membrane potential, and calcium signaling in various cellular processes. It has also been reported to contribute to various pathological events. Recently, KCa3.1 has been reported to participate in the regulation of apoptosis. However, its involvement in cisplatin-induced AKI is unknown. The aim of this thesis is that to determine the involvement of KCa3.1 in the pathogenesis of cisplatin-induced AKI. First, we determined the causal relationship between KCa3.1 expression and cisplatin-induced AKI in vitro and in vivo. We found that cisplatin treatment triggered an early induction of KCa3.1 expression associated with apoptosis in HK-2 cells. We also found that the induction of KCa3.1 expression was associated with the development of renal tubular damage and apoptosis in cisplatin-treated mice. We then used the highly selective KCa3.1 blocker TRAM-34 treatment to evaluate whether KCa3.1 induction was involved in cisplatin-induced apoptosis in vitro. We found that treatment with TRAM-34 suppressed cisplatin-induced apoptosis in HK-2 cells. We further assessed whether KCa3.1 mediated cisplatin-induced AKI in genetic knockout and pharmacological blockade mouse models. We found that KCa3.1 deficiency reduced renal function loss, renal tubular damage, and the induction of the apoptotic marker caspase-3 in the kidneys of cisplatin-treated KCa3.1-/- mice. Pharmacological blockade of KCa3.1 by TRAM-34 similarly attenuated cisplatin-induced AKI in mice. Furthermore, we dissected the mechanisms underlying cisplatin-induced apoptosis reduction via KCa3.1 blockade. We found that KCa3.1 blockade attenuated cytochrome c release and the increase in the intrinsic apoptotic mediators Bax, Bak, and caspase-9 after cisplatin treatment. KCa3.1 blocking inhibited the cisplatin-induced activation of the endoplasmic reticulum (ER) stress mediator caspase-12, which is independent of calcium-dependent protease m-calpain activation. In conclusion, KCa3.1 blockade protects against cisplatin-induced AKI through the attenuation of apoptosis by interference with intrinsic apoptotic and ER stress-related mediators, providing a potential target for the prevention of cisplatin-induced AKI.
|
|---|
