High stress hormone levels accelerate the onset of memory deficits in male Huntington's disease mice

Abstract

Huntington's disease (HD) is a neurodegenerative disorder caused by a tandem repeat mutation in the huntingtin gene. Lifestyle factors, such as lack of activity may contribute to the variability in the age of disease onset. Therefore, better understanding of environmental modifiers may uncover potential therapeutic approaches to delay disease onset and progression.Recent data suggest that HD patients and transgenic mouse models show a dysregulated stress response. In this present study, we elevated stress hormone levels through oral corticosterone (CORT) treatment and assessed its impact on the development of motor impairment and cognitive deficits using the R6/1 transgenic mouse model of HD. We found that CORT consumption did not alter rotarod performance of R6/1 HD or wild-type (WT) littermates. However, the onset of hippocampal-dependent Y-maze deficits was accelerated in male R6/1 mice by 5days of CORT treatment, whereas short term memory of WT and female R6/1 mice was unaffected.We then further investigated the male HD susceptibility to CORT by measuring TrkB activation, BDNF and glucocorticoid receptor expression as well as the level of cell proliferation in the hippocampus. CORT treatment increased the levels of phosphorylated TrkB in male R6/1 mice only. There were no effects of CORT on hippocampal BDNF protein or mRNA levels; nor on expression of the glucocorticoid receptors in any group. Hippocampal cell proliferation was decreased in male R6/1 mice and this was further reduced in CORT-drinking male R6/1 mice. Female mice (WT and R6/1) appeared to be protected from the impacts of CORT treatment in all our hippocampal measures. Overall, our data demonstrate that treatment with corticosterone is able to modulate the onset of HD symptomatology.We present the first evidence of a male-specific vulnerability to stress impacting on the development of short-term memory deficits in HD. More generally, we found that female mice were protected from the detrimental effects of CORT treatment on a variety of hippocampus-based measures. Hippocampal plasticity and memory in HD may be more susceptible to the impacts of stress in a sex-dependent manner. We propose clinical investigations of stress as a key environmental modifier of HD symptom onset.