Gallic acid induces vascular smooth muscle cell death via hydroxyl radicalproduction

In the present study, we investigated whether gallic acid (GA) can induce d eath in cultured vascular smooth muscle cells (VSMCs), and whether producti on of the hydroxyl radical (. OH) is involved in the process of GA action. GA killed cultured VSMCs from rat aorta, in a dose- and time-dependent mann er. Cytoplasmic shrinkage and nuclear condensation were observed light micr oscopically in GA-treated VSMCs, which appeared apoptotic. However, the ult rastructure of the VSMC was not typical of apoptosis: nuclear condensation was not glossy, and the plasma membrane and subcellular organelles were dis rupted. Although the VSMC were positive for in situ nick end-labeling (TUNE L), they did not show a DNA ladder pattern on gel electrophoresis and were negative for Taq polymerase-based in situ ligation, which is more specific for apoptosis than TUNEL. Moreover, GA-induced cell death was not prevented by Boc-Asp-fmk (a pan-caspase inhibitor). Production of . OH was detected in GA-treated VSMCs using high-performance liquid chromatography with salic ylic acid as a trapping agent. Lipid peroxidation was also observed. The pr oduction of . OH was inhibited by catalase (CAT) and deferoxamine (DFX), an d these treatments completely rescued VSMCs from cell death. In a cell-free system, GA produced OH in the presence of Fe2+-EDTA, which was quenched by CAT and DFX, suggesting involvement of the Haber-Weiss reaction. Oxidative stress by reactive oxygen species. . OH in particular, is one of the mecha nisms of GA-induced death of VSMCs, the mode of which was different from ty pical apoptosis.