Chemoprevention against arsenic-induced mutagenic DNA breakage and apoptotic liver damage in rat via antioxidant and SOD1 upregulation by green tea (Camellia sinensis) which recovers broken DNA resulted from arsenic-H2O2 related in vitro oxidant stress.
J Environ Sci Health C Environ Carcinog Ecotoxicol Rev. 2014 ;32(4):338-61. PMID: 25436473
Green tea (Camellia sinensis; CS) strongly reverses/prevents arsenic-induced apoptotic hepatic degeneration/micronecrosis and mutagenic DNA damage in in vitro oxidant stress model and in rat as shown by comet assay and histoarchitecture (HE and PAS staining) results. Earlier, we demonstrated a link between carcinogenesis and impaired antioxidant system-associated mutagenic DNA damage in arsenic-exposed human. In this study, arsenic-induced (0.6 ppm/100 g body weight/day for 28 days) impairment of cytosolic superoxide-dismutase (SOD1), catalase, xanthine-oxidase, thiol, and urate activities/levels led to increase in tissue levels of damaging malondialdehyde, conjugated dienes, serum necrotic-marker lactate-dehydrogenase, and metabolic inflammatory-marker c-reactive protein suggesting dysregulation at the transcriptional/signal-transduction level. These are decisively restrained by CS-extract (≥10 mg/ml aqueous) with a restoration of DNA/tissue structure. The structural/functional impairment of dialyzed and centrifugally concentrated (6-8 kd cutoff) hepatic SOD1 via its important Cys modifications by H2O2/arsenite redox-stress and that protection by CS/2-mercaptoethanol are shown in in vitro/in situ studies paralleling the present Swiss-Model-generated rSOD1 structural data. Here, arsenite(3+) incubation (≥10(-8) μM + 10 mM H2O2, 2 hr) is shown for the first time with this low-concentration to initiate breakage in rat hepatic-DNA in vitro whereas, arsenite/H2O2/UV-radiation does not affect DNA separately. Arsenic initiates Fe and Cu ion-associated free-radical reaction cascade in vivo. Here, 10 μM of Cu(2+)/Fe(3+)/As(3+) +H2O2-induced in vitro DNA fragmentation is prevented by CS (≥1 mg/ml), greater than the prevention of ascorbate or tocopherol or DMSO or their combination. Moreover, CS incubation for various time with differentially and already degraded DNA resulted from pre-incubation in 10 μM As(3+)-H2O2 system markedly recovers broken DNA. Present results decisively suggest for the first time that CS and its mixed polyphenols have potent SOD1 protecting, diverse radical-scavenging and antimutagenic activities furthering to DNA protection/therapy in arsenic-induced tissue necrosis/apoptosis.