A model of premature aging in mice based on altered stress-related behavioral response and immunosenescence

Abstract

The intensity of behavioral and neuroendocrine responses to stressful stimuli in rodent strains seems to be inversely related to their life span. We have previously shown that interindividual differences in members of outbred Swiss and inbred BALB/c mouse populations, both male and female, may be related to their behavior in a simple T-maze test. The animals that explore the maze slowly show impaired neuromuscular vigor and coordination, decreased locomotor activity, increased level of emotionality/anxiety, decreased levels of brain biogenic amines as well as immunosenescence and decreased life span, when compared to their control counterparts, which quickly explore the maze. These traits are similar to some of the alterations previously observed in aging animals and therefore we proposed that those 'slow mice' are biologically older than the fast animals and may be a model of prematurely aging mice (PAM). Although most of our work on this model has been performed on chronologically adult-mature animals, we have also shown that certain characteristics of PAM, such as increased anxiety and deficient immune response, are already present in chronologically young animals. Thus, it is tempting to hypothesize that chronic hyperreactivity to stress (trait anxiety) leading to immune dysfunction may have a causal relationship with impaired health and premature aging. In view of the link between oxidative stress and the aging process, the redox state of peritoneal leukocytes from PAM has been studied, showing an oxidative stress situation. In the present work we have determined the levels of a key antioxidant, reduced glutathione (GSH), and the oxidant malondialdehyde (MDA), a marker of lipid peroxidation, both in the spleen and brain of male and female PAM and non-PAM (NPAM). We found that GSH and MDA are decreased and increased, respectively, in PAM with respect to NPAM. Moreover, diet supplementation with antioxidants showed to be an effective strategy for protection against early immune and behavioral decline, altered redox state of leukocytes and premature mortality in PAM, which supports the validity of this model of premature aging as well as its link with oxidative stress.