Endogenous reverse transcriptase as a mediator of ursolic acid's anti-proliferative and differentiating effects in human cancer cell lines.

Ursolic acid (UA) is a pentacyclic triterpenoid compound that is widely distributed in the plant kingdom and has a broad range of biological effects. Here, we examined the effects of UA on the proliferation and differentiation of human tumor cell lines from melanoma (A375), glioblastoma (U87) and thyroid anaplastic carcinoma (ARO), and on the proliferation of a non-transformed human fibroblast cell line (WI-38). The results show that UA inhibits tumor cell proliferation in a dose- and time-dependent manner. Consistent with this finding, UA treatment promotes differentiation of all of the analyzed tumor cell lines. Interestingly, we found that UA inhibits the endogenous reverse transcriptase (RT) activity in tumor cells, which has recently been shown to be involved in the control of proliferation and differentiation of neoplastic cells. Considering these findings, we suggest that the observed anti-proliferative and differentiating effects of UA may be related to this target.

Anti-inflammatory effect of lemon mucilage: in vivo and in vitro studies.

The mucilage extracted from a lemon juice centrifugation pulp was studied for its anti-inflammatory effect in rat. In vivo the lemon mucilage significantly inhibited carrageenan-induced edema in rat paw from 59% to 73.5% showing the highest effect at the third hour. In vitro, at the doses of 10(-8), 10(-6), 10(-4) or 10(-2) mg/mL the lemon mucilage stimulated the superoxide anion production in rat testing neutrophils in whole blood but inhibited it in FMLP stimulated cells at the dose of 10(-2) mg/mL. The neutrophils of rats receiving p.o. the lemon mucilage for 21 days showed a significant decrease of 45.5% in O2- generation after FMLP stimulation, and a not-significant increase after phorbol-12-myristate-13-acetate (PMA) or zymosan stimulation. Since the activity on zymosan- and PMA-induced O2- production was not significant, the inhibition exerted by FMLP in rat neutrophils occurred mainly through the blockade of phospholipase D.