Afinidades imunológicas entre o envelhecimento e o estresse crônico

Abstract

The aging and stress processes have been associated with alterations in the activities of the immune system. These modifications can be observed in lymphoid organs as well as in cellular components of the immune system. Stress is defined as any alteration in the functional and homeostatic stimulation of the organism. Usually, aging is considered as a process that starts in long periods of life, but the biological, and most important, immunological alterations are gradual and constant phenomena during all periods of development since birth. On the other hand, senescense is a final step in the gradual process of aging when biological changes are accumulated and accentuated. Both processes result in a variety of biological alterations among which hormones, neurological mediators and immunological elements play an important role. Herein, we compare the changes brought about by senescence and by chronic restraint stress. Eightweek-old BALB/c male mice were submitted to stress by physical contention for 2 hours for 5 consecutive days. Twenty-four hours after the last stress session, mice were sacrificed. We also analysed 52-week-old BALB/c male mice as compared to control 8week-old mice. Stressed animals had diarrhea, hair loss, increase in the neutrophil numbers but reduction in lymphocytes in periférico blood and an augment of cortisol and dehidroepiandrosterona (DHEA) in plasma levels. In 52-week-old senescent BALB/c mice, production of serum immunoglobulins (total Ig, IgM, IgG, IgA and IgE) and IL-4 from splenocytes increases. Interestingly, both stressed and old animals showed drastic reduction of thymic weight and thymic celularity (approximately 82% and 50% in the cortical region), alterations of some serum immunoglobulin isotypes (such as increase of serum IgE) and high levels of secretory IgA (sIgA) in gut. Production of IL-2, IL-6 and IFN-gamma by spleen cells stimulated in vitro with Concanavalina A (Con A) or with monoclonal antibodies anti-CD3/anti-CD28, and plasmatic IL-6 were also increased in both. However, in stressed mice, the phenotypic profile of T and B cells in blood, spleen and mesenteric lymph node were naïve while in aging there were a prevalence of memory/activated cells profile. Our results suggest that chronic stress result in immunological and morphological alterations that are similar to the ones observed in aged animals.