Characterization of intracellular signaling cascades in 4-hydroxynonenal-induced apoptosis:

Official URL: http://risc01.sabanciuniv.edu/record=b1164865 (Table of Contents)

In this thesis we have studied the signaling pathways involved in HNE-induced apoptotis and the effect of resveratrol in signal transduction mechanisms leading to apoptosis in 3T3 fibroblasts when exposed to 4-hydroxynonenal (HNE). The results demonstrate the ability of HNE to induce apoptosis and ROS formation in a dose-dependent manner. In order to get insight into the mechanisms of apoptotic response by HNE, we followed MAP kinase and caspase activation pathways; HNE induced early activation of JNK and p38 proteins but downregulated the basal activity of ERK 1/2. We were also able to demonstrate HNE-induced release of cytochrome c from mitochondria, caspase-9 and caspase-3 activation. Resveratrol effectively prevented HNE-induced JNK and caspase activation hence apoptosis, as well as the formation of ROS. Activation of AP-1 along with increased c-Jun and phospho-c-Jun levels could be inhibited by pretreatment of cells with resveratrol. Additionally, overexpression of dominant negative c-Jun and JNK1 in 3T3 fibroblasts prevented HNE-induced apoptosis, which indicates a role for JNK-c-Jun/AP-1 pathway. Moreover, HNE induced decreased Bcl-2 and increased Bax, Bak and Bim protein levels, which could be prevented by resveratrol. In light of the JNK-dependent induction of c-Jun/AP-1 activation and the protective role of resveratrol, these data indicate a critical potential role for JNK in the cellular response against toxic products of lipid peroxidation. Resveratrol also prevents modulation of Bcl-2 proteins and formation of ROS by HNE. In this respect, resveratrol acting through MAP kinase and Bcl-2 protein pathways in addition to act as antioxidant-quenching reactive oxygen intermediates is a potential small molecule against apoptosis-related human pathologies.