P4-173: Cytoplasmic gelsolin, a beta-amyloid binding protein, is induced by oxidative stress in Pc-12 cells

Abstract

Gelsolin binds to actin and amyloid beta-protein (Aβ), and exists in all cell types including neurons. It plays important roles in cytoskeletal remodeling, apoptosis, and carcinogenesis. Recent evidence from our and other laboratories also suggests a role of gelsolin in regulation of beta-amyloidosis in Alzheimer's disease (AD). Our previous results showed that both cytoplasmic and plasma gelsolin form a complex with Aβ, irrespective of their differences in amino acid sequences and cysteine thiol groups. Plasma gelsolin inhibited Aβ fibrillization and defibrillized preformed Aβ fibrils. It is known that hydrogen peroxide (H2O2) induces apoptosis in rat pheochromocytoma cell line (PC-12) cells by triggering oxidative stress, and gelsolin has anti-apoptotic property. Oxidative damage and neuronal cell loss are characteristics of AD. Therefore, a relationship between oxidative stress, apoptosis and intracellular gelsolin was envisioned. Gelsolin, actin, caspase-9 and poly ADP-ribose polymerase (PARP) were probed by western blot. Malonyldialdehyde (MDA), an end product of lipid peroxidation, was measured by thiobarbituric acid. We report that expression of cytoplasmic gelsolin is induced in PC-12 cells by oxidative stress. When PC-12 cells were subjected to oxidative stress, i.e., H2O2, the expression of gelsolin significantly increased in a time- and dose-dependent manner. Meanwhile, cleaved products of procaspase-9 and PARP were observed in the H2O2-treated PC-12 cells. We also found increased MDA, a marker of oxidative stress, in the brains of patients with Alzheimer's disease as compared to control subjects. These results suggest that oxidative stressor induces expression of gelsolin, which may delay the development of AD by its anti-apoptotic property and interaction with amyloid-beta protein.