Oxidants, antioxidants and carcinogenesis.

摘要: Reactive oxygen metabolites (ROMs), such as superoxide anions (O 2 . hydrogen peroxide (H O ), and hydroxl radical (.OH), malondialdehyde (MDA) nitric oxide (NO) are directly or indirectly involved in multistage process of carcinogenesis. They mainly DNA damage leading sometimes to mutations tumour suppressor genes. also act initiator and/or promotor Some them mutagenic mammalian systems. , H .OH reported be higher frequencies sister chromatid exchanges (SCEs) chromosome breaks gaps (CBGs). MDA, a bi-product lipid peroxidation (LPO), is said adduct formations, which believed responsible for NO, on the other hand, plays duel role cancer. At high concentration it kills cells, but at low promotes growth metastasis. It causes single double strand breaks. The NO peroxynitrite (OONO - ) potent mutagen that can induce transversion mutations. stimulate /H /.OH-induced LPO. These deleterious actions oxidants countered by antioxidant defence system humans. There first line defense antioxidants dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT). SOD converts further converted with help GPx CAT. inhibits OH production. antipoliferative agent, anticarcinogens, inhibitor initiation promotion/transformation stage another antioxidative enzyme catalyses convert O. most CAT important inactivation many environmental mutagens. found reduce SCE levels chromosomal aberrations. Antioxidative vitamins vitamin A, E, C have number biological activities immune stimulation, inhibition nitrosamine formation an alteration metabolic activations carcinogens. prevent genetic changes inhibiting induced ROMs. Therefore, these may helpful treatment human However, detailed studies required draw definite conclusion.