Age-dependent changes in the proteolytic-antiproteolytic balance after alcohol and black tea consumption

Aging is accompanied by changes in the redox balance that is additionally modified by alcohol. Ethanol metabolism is connected with generation of free radicals which can damage cell components especially when antioxidant mechanisms are not able to neutralize them. In connection with the necessity of prevention against oxidative consequences, natural antioxidants are looked for. A natural and commonly used component of the diets with antioxidant properties are teas, especially the black tea. This study provides evidence of the role of black tea in the protection of rat plasma proteins and lipids against oxidative stress caused by aging and ethanol intoxication. For 5 weeks, the rats (2-, 12-, and 24-months old) used for the experiment received a black tea beverage (3 g/l) without or with alcohol (given for 4 weeks). The decrease in antioxidant abilities determined as total antioxidant status during aging and ethanol intoxication resulted in enhanced lipid and protein oxidation (determined as malondialdehyde, carbonyl groups, dityrosine, tryptophan and sulfhydryl groups level). In consequence the decrease in anti-proteases (alpha-1-antitrypsin, alpha-2-macroglobulin) activity and the increase in proteases (elastase and cathepsin G) activity were observed. Black tea protected the plasma antioxidants and prevented oxidative modifications of lipid and protein observed during aging as well as ethanol intoxication. The results indicate that a shift into plasma proteolytic activity results from a decrease in antioxidant abilities, so the use of black tea appears to be beneficial in reducing oxidative stress caused by ethanol and/or aging.