Hsp70 basal levels, a tissue marker of the rate of aging and longevity in mice.

Under stressful conditions, the expression of the chaperone Hsp70 is induced, which acts as a cellular defense mechanism. The impairment in this induction has been related to aging, whereas an increased expression has been related to longevity. Nevertheless, it is still not known if the basal levels of Hsp70 can be indicative of the aging rate of different tissues. The aim of this study was to quantify the basal levels of Hsp70 in tissues from female mice throughout their aging process including long-lived mice, as well as from prematurely aging mice (PAM). Adult, old and long-lived (6, 18 and 30months of age, respectively) female ICR-CD1 and Balb/C mice were used. Tissues with mainly mitotic (liver and renal medulla) or post-mitotic (heart, renal cortex, cerebral cortex, spleen) cells and peritoneal leukocytes from these animals as well as from adult PAM and non-prematurely aging mice (NPAM), were studied. Basal levels of Hsp70 were assessed using an ELISA method. The results showed that the aging-associated variation of the levels of Hsp70 followed a different pattern in post-mitotic and mitotic tissues, being lower or higher in old mice comparing to adults, respectively. In all the tissues analyzed the Hsp70 levels from long-lived mice were similar to those from adult animals. In addition, in adult PAM these Hsp70 levels were similar to those in chronologically old animals. In conclusion, Hsp70 basal levels show tissue-specific age-associated variations and are preserved in long-lived animals, demonstrating their role as markers of the rate of aging and longevity.