Acute psychological stress: effects on hippocampal neurogenesis and the role of microglia

Abstract

Among all the factors that can contribute to the onset of psychopathological disorders, stress is the main environmental factor. The hippocampus is one of the most sensitive regions to the harmful effects of stress, in which the neurogenic process is impaired. On the other hand, under stress situations, microglia are also affected and can trigger a proinflammatory response, acting as anti-neurogenic cells and releasing cytokines and other proinflammatory molecules. Knowing what happens in the early stages of stress may be relevant to investigate the temporal aspects of the development of stressassociated psychopathological disorders, and even their possible treatment. Therefore, after subjecting C57BL/6J mice for 2 hours to an acute and intense stress procedure called WIRS (water immersion restraint stress), data were analyzed to study microglia, cell proliferation and neuronal maturation. In addition, a mediation analysis study was conducted for data integration. The results revealed that the applied acute stress is sufficiently intense to induce an increase in the number of microglia, accompanied by morphometric changes, as well as negatively affecting the neuronal maturational process. Furthermore, these data suggest that effects on the neurogenic process mediate the microglial response to an intense acute stressor. This leads to the conclusion that this may be the initial mechanism for any intense stress response, or may even be the first steps in the development of the response to a chronic stressor.