The ratio of prematurely aging to non-prematurely aging mice cohabiting, conditions their behavior, immunity and lifespan

Adult prematurely aging mice (PAM) show behavioral deterioration, premature immunosenescence and increased oxidative stress, impairments that are associated with their shorter lifespan, compared to the corresponding exceptional non-prematurely aging mice (ENPAM). When PAM live in a predominantly ENPAM environment (2/5, respectively) they exhibit an improvement of immunity and redox state in their spleen and thymus leukocytes, and an increased lifespan. Nevertheless, it is unknown if other PAM/ENPAM ratios could affect behavioral and peritoneal leukocyte functions of PAM and change their lifespan. ENPAM and PAM were divided into the following groups: C-ENPAM (8 ENPAM in the cage); C-PAM (8 PAM in the cage); ENPAM>50% and PAM<50% (5 ENPAM/2 PAM in each cage); ENPAM = 50% and PAM = 50% (4 ENPAM/4 PAM in each cage), and PAM>50% and ENPAM<50% (5 PAM/2 ENPAM in each cage). After two months, mice were submitted to a battery of behavioral tests. Several functions and oxidative stress parameters were then assessed in their peritoneal leukocytes. Animals were maintained in these conditions to analyze their lifespan. The results showed that PAM>50%, PAM = 50% and PAM<50% exhibited better behavioral responses, immunity and redox states in their peritoneal leukocytes than C-PAM. This improvement was higher when the number of ENPAM in the cage was increased, with most of the parameters in PAM<50% reaching similar values to those in C-ENPAM, and an increased lifespan. However, ENPAM that cohabited with PAM showed, in general, an impairment of parameters studied. In conclusion, the PAM/ENPAM cohabitation ratio is relevant to behavior and immunity.

Social Environment Ameliorates Behavioral and Immune Impairments in Tyrosine Hydroxylase Haploinsufficient Female Mice

The social environment can influence the functional capacity of nervous and immune systems, and consequently the state of health, especially in aged individuals. Adult female tyrosine hydroxylase haploinsufficient (TH-HZ) mice exhibit behavioral impairments, premature immunosenescence and oxidative- inflammatory stress. All these deteriorations are associated with a lower lifespan than wild type (WT) counterparts. The aim was to analyze whether the cohabitation with WT animals could revert or at least ameliorate the deterioration in the nervous and immune systems that female TH-HZ mice show at adult age. Female TH-HZ and WT mice at age of 3-4 weeks were divided into following groups: control TH-HZ (5 TH-HZ mice in the cage; TH-HZ100%), control WT (5 WT mice in the cage; WT100%), TH-HZ > 50% and WT < 50% (5 TH-HZ with 2 WT mice in each cage) as well as TH-HZ < 50% and WT > 50% (2 TH-HZ and 5 WT mice in each cage). At the age of 37-38 weeks, all mice were submitted to a battery of behavioral tests, evaluating sensorimotor abilities, exploratory capacities and anxiety-like behaviors. Subsequently, peritoneal leukocytes were extracted and several immune functions as well as oxidative and inflammatory stress parameters were analyzed. The results showed that the TH-HZ < 50% group had improved behavioral responses, especially anxiety-like behaviors, and the immunosenescence and oxidative stress of their peritoneal leukocytes were ameliorated. However, WT mice that cohabited with TH-HZ mice presented higher anxiety-like behaviors and deterioration in immune functions and in their inflammatory stress parameters. Thus, this social environment is capable of ameliorating the impairments associated with a haploinsufficiency of the th gene. Graphical Abstract.