Chronic Stress Causes Sex-Specific and Structure-Specific Alterations in Mitochondrial Respiratory Chain Activity in Rat Brain.

Chronic restraint stress (CRS) induces a variety of changes in brain function, some of which are mediated by glucocorticoids. The response to stress occurs in a sex-specific way, and may include mitochondrial and synaptic alterations. The synapse is highly dependent on mitochondrial energy supply, and when mitochondria become dysfunctional, they orchestrate cell death. This study aimed to investigate the CRS effects on mitochondrial respiratory chain activity, as well as mitochondrial potential and mass in cell body and synapses using hippocampus, cortex and striatum of male and female rats. Rats were divided into non-stressed (control) and stressed group (CRS during 40 days). Results showed that CRS increased complex I-III activity in hippocampus. We also observed an interaction between CRS and sex in the striatal complex II activity, since CRS induced a reduction in complex II activity in males, while in females this activity was increased. Also an interaction was observed between stress and sex in cortical complex IV activity, since CRS induced increased activity in females, while it was reduced in males. Glucocorticoid receptor (GR) content in cortex and hippocampus was sexually dimorphic, with female rats presenting higher levels compared to males. No changes were observed in GR content, mitochondrial potential or mass of animals submitted to CRS. It was concluded that CRS induced changes in respiratory chain complex activities, and some of these changes are sex-dependent: these activities are increased in the striatal mitochondria by CRS protocol mainly in females, while in males it is decreased.

Hyperhomocysteinemia selectively alters expression and stoichiometry of intermediate filament and induces glutamate- and calcium-mediated mechanisms in rat brain during development.

The aim of the present work was to investigate the actions of a chemically induced chronic hyperhomocysteinemia model on intermediate filaments (IFs) of cortical and hippocampal neural cells and explore signaling mechanisms underlying such effects. Results showed that in hyperhomocysteinemic rats the expression of neural IF subunits was affected. In cerebral cortex, glial fibrillary acidic protein (GFAP) expression was donwregulated while in hippocampus high and middle molecular weight neurofilament subunits (NF-H and NF-M, respectively) were up-regulated. Otherwise, the immunocontent of IF proteins was unaltered in cerebral cortex while in hippocampus the immunocontent of cytoskeletal-associated low molecular weight neurofilament (NF-L) and NF-H subunits suggested a stoichiometric ratio consistent with a decreased amount of core filaments enriched in lateral projections. These effects were not accompanied by an alteration in IF phosphorylation. In vitro results showed that 500muM Hcy-induced protein phosphatases 1-, 2A- and 2B-mediated hypophosphorylation of NF subunits and GFAP in hippocampal slices of 17-day-old rats without affecting the cerebral cortex, showing a window of vulnerability of cytoskeleton in developing hippocampus. Ionotropic and metabotropic glutamate receptors were involved in this action, as well as Ca(2+) release from intracellular stores through ryanodine receptors. We propose that the mechanisms observed in the hippocampus of 17-day-old rats could support the neural damage observed in these animals.