Thesis (Ph.D.)--Chulalongkorn University, 2011

Massive apoptosis of hair follicle cells has been implicated in the pathogenesis of chemotherapy-induced alopecia (CIA), but the underlying mechanisms of regulation are not well understood. The present study investigated the apoptotic effect of cisplatin and doxorubicin on human hair follicle dermal papilla cells and HaCaT keratinocytes, and determined the identity and role of specific reactive oxygen species (ROS) involved in the process. Treatment of the cells with cisplatin and doxorubicin induced ROS generation and a parallel increase in caspase activation and apoptotic cell death. Inhibition of ROS generation by antioxidants inhibited the apoptotic effect of cisplatin and doxorubicin, indicating the role of ROS in the process. ROS inhibition studies showed the essential role of different ROS in apoptotic effects of cisplatin and doxorubicin. Hydroxyl radical is the primary oxidative species responsible for the apoptotic effect of cisplatin, while superoxide anion is responsible for apoptosis by doxorubicin. Electron spin resonance studies confirmed the formation of hydroxyl radical and superoxide induced by cisplatin and doxorubicin, respectively. The mechanisms by which these specific ROS mediate the apoptotic effect of cisplatin and doxorubicin were shown to involve down-regulation of Bcl-2 via ubiquitin-proteasomal degradation. Ubiquitination and degradation of Bcl-2 was further shown to be mediated by dephosphorylation of Bcl-2. Together, our results indicate the essential role of ROS in cisplatin- and doxorubicin-induced cell death of hair follicle cells through Bcl-2 regulation. Since CIA is a major side effect of cisplatin, doxorubicin and many other chemotherapeutic agents with no known effective treatments, the knowledge gained from this study could be useful in the design of preventive treatment strategies for CIA through localized therapy without compromising the chemotherapy efficacy