Synergistic Effect of Rapamycin and Metformin Against Age-Dependent Oxidative Stress in Rat Erythrocytes

Erythrocytes are particularly vulnerable toward age-dependent oxidative stress-mediated damage. Caloric restriction mimetics (CRMs) may provide a novel strategy for the maintenance of redox balance as well as effective treatment of age-associated diseases. Herein, we have investigated the beneficial effect of cotreatment with CRM-candidate drugs, rapamycin (an immunosuppressant drug and inhibitor of mammalian target of rapamycin) and metformin (an antidiabetic biguanide and activator of adenosine monophosphate kinase), against aging-induced oxidative stress in erythrocytes and plasma of aging rats. Male Wistar rats of age 4 (young) and 24 months (old) were coexposed to rapamycin (0.5 mg/kg body weight [b.w.]) and metformin (300 mg/kg b.w.), and data were compared with the response of rats receiving an independent exposure to these chemicals at similar doses. The exposure of individual candidate drugs significantly reversed the age-dependent alterations in the endpoints associated with oxidative stress such as reactive oxygen species, ferric reducing ability of plasma, malondialdehyde, reduced glutathione, plasma membrane redox system, plasma protein carbonyl, and acetyl cholinesterase in erythrocytes and plasma of aging rats. However, the cotreatment with rapamycin and metformin showed a significant augmented effect compared with individual drug interventions on reversal of these age-dependent biomarkers of oxidative stress, suggesting a synergistic response. Thus, the findings open up further possibilities for the design of new combinatorial therapies to prevent oxidative stress- and age-associated health problems.