Sex-specific hippocampal trajectories induced by peripubertal and adult acute stress: proteomic profile, microglial alterations, neurogenic dysregulation, and depression-like behaviors

Abstract Depression is highly prevalent, and early-life adversity is an important risk factor for adult psychopathology. Although females show greater vulnerability to stress-related affective disorders, the mechanisms underlying sex-dependent stress responses remain unclear. Using a two-hit framework, we examined whether juvenile stress (JS) modifies responses to acute adult stress (AS) and assessed long-term behavioral, cellular, and molecular outcomes in the hippocampus. We evaluated saccharin preference, social exploratory behavior, microglial morphology, cell proliferation, immature neurons, cytokines, and proteomic profiles. Effects were selective and depended on sex, stress condition, endpoint, and hippocampal subregion. In males, stress did not clearly alter saccharin preference or the social measures examined. AS increased hippocampal IFN-γ and was associated with selective microglial findings, whereas proliferative and neurogenic effects were limited and region-specific. Combined stress was associated with proteomic differences involving synaptic and metabolic processes. In females, JS was associated with sex-dependent alterations in saccharin preference, while JS and combined stress affected specific components of social exploratory behavior. Cellular effects were subtle and region-specific, whereas proteomic changes were broader and more connected, particularly after combined stress. Overall, most cytokines were unchanged, microglial morphology was mainly characterized by sex-related differences, and neurogenic effects were restricted to specific cell populations and subregions. These findings indicate distinct sex- and timing-dependent patterns of behavioral and hippocampal response, involving neuroimmune, neurogenic, and proteomic changes that were not always accompanied by overt behavioral alterations.