Antioxidative and Antiinflammatory Activities of Asiatic Acid, Glycyrrhizic Acid, and Oleanolic Acid in Human Bronchial Epithelial Cells

Protective effects of triterpenic acids, asiatic acid (AA), glycyrrhizic acid (GA), or oleanolic acid (OA), for two human bronchial epithelial cells, 16HBE and BEAS-2B cells, against hydrogen peroxide (H2O2) induced injury were examined. Cells were pretreated by triterpenic acid at 4 or 8 μmol/L and followed by H2O2 treatment. Results showed that H2O2 significantly upregulated both Bax and cleaved caspase-3 expression, and also downregulated Bcl-2 expression in test cells. AA at these doses retained Bcl-2 expression, but GA and OA only at 8 μmol/L reserved Bcl-2 expression. Test triterpenic acids lowered cleaved caspase-3 expression dose-dependently. H2O2 treatment lowered Na(+)-K(+)-ATPase activity and mitochondrial membrane potential in cells. Triterpenic acid pretreatments significantly maintained mitochondrial membrane potential and Na(+)-K(+)-ATPase activity. H2O2 enhanced reactive oxygen species, interleukin-6, tumor necrosis factor-α, and prostaglandin E2 levels in test cells. Three triterpenic acid treatments dose-dependently reversed these changes. H2O2 promoted the protein expression of p47(phox), gp91(phox), cyclooxygenase-2 (COX-2), mitogen-activated protein kinase, and nuclear factor-κB (NF-κB). AA, GA, or OA pretreatments dose-dependently downregulated the expression of p47(phox), COX-2, NF-κB p65, and p-p38 but only at 8 μmol/L decreased gp91(phox) expression. These results support that these triterpenic acids could protect bronchial epithelial cells to attenuate apoptotic, oxidative, and inflammatory stress.