SO^sub 4^ ^sup =^ uptake and catalase role in preconditioning after H2O2-induced oxidative stress in human erythrocytes

Preconditioning (PC) is an adaptive response to a mild and transient oxidative stress, shown for the first time in myocardial cells and not described in erythrocytes so far. The possible adaptation of human erythrocytes to hydrogen peroxide (H2O2)-induced oxidative stress has been here verified by monitoring one of band 3 protein functions, i.e., Cl-/HCO3 - exchange, through rate constant for SO4 = uptake measurement. With this aim, erythrocytes were exposed to a mild and transient oxidative stress (30 min to either 10 or 100 [mu]M H2O2), followed by a stronger oxidant condition (300- or, alternatively, 600-[mu]M H2O2 treatment). SO4 = uptake was measured by a turbidimetric method, and the possible role of catalase (CAT, significantly contributing to the anti-oxidant system in erythrocytes) in PC response has been verified by measuring the rate of H2O2 degradation. The preventive exposure of erythrocytes to 10 [mu]M H2O2, and then to 300 [mu]M H2O2, significantly ameliorated the rate constant for SO4 = uptake with respect to 300 [mu]M H2O2 alone, showing thus an adaptive response to oxidative stress. Our results show that (i) SO4 = uptake measurement is a suitable model to monitor the effects of a mild and transient oxidative stress in human erythrocytes, (ii) band 3 protein anion exchange capability is retained after 10 [mu]M H2O2 treatment, (iii) PC response induced by the 10 [mu]M H2O2 pretreatment is clearly detected, and (iv) PC response, elicited by low-concentrated H2O2, is mediated by CAT enzyme and does not involve band 3 protein tyrosine phosphorylation pathways. Erythrocyte adaptation to a short-term oxidative stress may serve as a basis for future studies about the impact of more prolonged oxidative events, often associated to aging, drug consumption, chronic alcoholism, hyperglycemia, or neurodegenerative diseases.