Resilience to social stress: is it in the blood?

In social mammalian species, such as human and mouse, social stress can arise from different social interactions; for example, from encounters with aggressive strangers (whether they be mice or men). Repeated exposure to such stress can lead to various conditions, including depression and anxiety, but different individuals show varying degrees of resilience to such stress. To explore the mechanisms underlying such differential response to stress, Sakamoto et al. from Johns Hopkins University and University of Alabama at Birmingham used a mouse model of chronic 'social defeat' stress (CSDS) to examine molecular changes in the blood following stress. In an article published in this issue of FEBS Open Bio, the authors report how molecular alterations in circulating extracellular vesicles (EVs) influence social behaviours and resilience to chronic social stress. Test mice were classified as resilient or susceptible to social stress and their blood samples were analysed. Their data demonstrated that mice susceptible to CSDS have alterations in the miRNA content of circulating EVs, and these EVs in turn influence the expression of pro-inflammatory cytokines in microglia cells, thereby resulting in social avoidance phenotypes. Since low resilience to social stress may be linked to the progression of several psychiatric disorders, it may ultimately be possible to determine prognosis or likely response to therapy for individuals susceptible to or suffering from such conditions by profiling pro-inflammatory cytokines and EV-associated miRNAs in blood samples.