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In previous studies hepatocytes undergoing cell death by apoptosis but not normal hepatocytes in rat liver showed immunostaining for transforming growth factor ,1 (TGF-13). Staining was much stronger with antibodies recognizing the pro-region of TGF-I31 than the mature peptide itself. Therefore we investigated the ability of both forms of TGF-31 to induce apoptosis in primary cultures of rat hepatocytes.Mature TGF-fi1 induced rounding up of the cells and fragmentation into multiple vesicles. As revealed by the DNAspecific stain H33258, the chromatin of these cells condensed and segregated into masses at the nuclear membrane; this was obviously followed by fragmentation of the nucleus. Ultrastructurally the cytoplasm was well preserved, as demonstrated by the presence of intact cell organelles. These features strongly suggest the occurrence of apoptosis. Quantification of nuclei with condensed chromatin revealed that mature TGF-131 was 30-fold more effective than the TGF-P1 latency-associated protein complex. Finally, we administered TGF-131 in vivo using an experimental model in which regression of rat liver was initiated by a short preceding treatment with the hepatomitogen cyproterone acetate. Two doses of TGF-P1, each 1 nM/kg, augmented the incidence of apoptotic hepatocytes 5-fold. Equimolar doses of TGF-fi1 latency-associated protein complex were ineffective. These studies suggest that TGF-P1 is involved in the initiation of apoptosis in the liver and that the mature form of TGF-fi1 is the active principle.

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Green tea is the most widely consumed beverage. It has attained high reputation as a health-promoting dietary component ascribed to the antioxidant activity of (-)-epigallocatechin-3-gallate (EGCG), its main polyphenolic constituent. Evidence is increasing that tea constituents can be cell damaging and pro-oxidant themselves. These effects were suggested to be due to spontaneous H2O2 generation by polyphenols in solution. In the present study, we investigated the oxidant and antioxidant properties of green tea extracts (GTE) and of EGCG by means of the rodent macrophage-like RAW 264.7 and human promyelocytic leukemic HL60 cell lines. The results obtained show that both under cell-free conditions and in the presence of cells the oxidant activities of GTE and EGCG exceeded those of spontaneously generated H2O2 (FOX assay). Increase of intracellular oxidative stress was indicated by 2',7'-dichlorofluorescin probing, and the enhanced genotoxicity was demonstrated by the alkaline comet assay and by the micronucleus assay (cytokinesis block). Time- and dose-dependent induction of cell death was monitored by trypan blue exclusion, MTT assay, and Hoechst staining. Furthermore, in our systems in vitro, EGCG neither directly scavenges H2O2 nor mediates other antioxidant activities but rather increased H2O2-induced oxidative stress and DNA damage. In conclusion, our data suggest that detailed mechanistic studies on the effects of GTE and EGCG should be performed in vivo before excessive intake and/or topical application of green tea products can be recommended to healthy and/or diseased persons.