Lupeol, a triterpene, prevents free radical mediated macromolecular damage and alleviates benzoyl peroxide induced biochemical alterations in murine skin.

In our earlier communication we have shown that Lupeol inhibits early responses of tumour induction in murine skin. The free radical mediated damage to the cellular macromolecules such as DNA, proteins, lipids and alteration in the activities of quinone reductase and xanthine oxidase are important biochemical parameters of tumor development. The suppression of free radical mediated damage to cellular macromolecules and induction of quinone reductase along with depletion of xanthine oxidase are prominent characteristics of chemopreventive agents. In the present investigation, we have elucidated the mechanism of action of lupeol (Lup-20 (29)-en-3beta-ol), a triterpene found in moderate amount in many vegetables, fruits and anti-tumor herbs. In the present investigation, lupeol significantly reduced the free radical mediated DNA-sugar damage and microsomal lipid peroxidation in an iron/ascorbate free radical generating system in vitro. Benzoyl peroxide, a known free radical generating tumor promoter mediated oxidation of proteins and modulation in the activities of quinone reductase as well as xanthine oxidase was significantly prevented by lupeol when tested on murine skin in vivo. It was concluded from this study that lupeol acts as an effective chemopreventive agent against cutaneous toxicity.

Insights into the mechanism of action of benzoyl peroxide as a tumor promoter.

A comparison of the mechanism of action of benzoyl peroxide, a tumor promoter was studied in three different cell lines i.e. NIH 3T3, HDCS and A431. Benzoyl peroxide was found to mediate its effect by inducing poly ADP-ribosylation in all the three cell types studied but to different extents, with histone H1 serving as a common acceptor for poly ADP-ribose. It also stimulated the activities of the antioxidant enzymes CuZn superoxide dismutase and catalase in NIH 3T3 and HDCS cells, but not in A431. Alterations in the expression of c-jun and c-fos were observed in NIH 3T3 and A431 cells. Benzoyl Peroxide appeared to mediate its effect via genetic and epigenetic mechanisms.