Glycyrrhizin exhibits potential chemopreventive activity on 12-O-tetradecanoyl phorbol-13-acetate-induced cutaneous oxidative stress and tumor promotion in swiss albino mice

Glycyrrhizin and its aglycone, glycyrrhetic acid has been found useful for various therapeutic purposes. Glycyrrhizin has been shown to possess many physiological functions like anti-inflammatory activity, detoxification and inhibition of carcinogenic promoters. 12-O-Tetradecanoyl phorbol-13-acetate (TPA), a well-known phorbal ester is known for its tumor promotion activity. The induction of inflammation in skin mediated by TPA is believed to be governed by cyclooxygenase (COX), lipoxygenase and ornithine decarboxylase (ODC). These markers of inflammatory responses are important for skin tumor promotion. In our present study, we studied the chemopreventive effect of glycyrrhizin on TPA (20nmol/0.2mL acetone/animal, topically) -induced oxidative stress and hyperproliferation markers in skin. TPA enhanced lipid peroxidation with reduction in the level of catalase, glutathione, glutathione peroxidase, glutathione reductase and glutathione-stransferase. TPA treatment also enhanced ODC activity and [H-3] thymidine incorporation into cutaneous DNA. Prophylactic treatment of mice with glycyrrhizin (2.0 & 4.0 mg/0.2 mL acetone/animal, topically) resulted in a significant decrease in cutaneous microsomal lipid peroxidation (P < 0.001) and recovery of cutaneous glutathione content (P < 0.001) and its dependent enzymes. A significant inhibition in ODC activity and DNA synthesis (P < 0.001) was also observed. Thus, the results demonstrate that pretreatment with glycyrrhizin is protective against TPA-induced oxidative stress and tumor promotion in Swiss albino mice.