Effects of social stress on pain behavior, immune cells and serum concentrations of TNF-α, Interleukin-1 and Interleukin-6 in female mice

Introduction: Based on human studies, inequality and social injustice have adverse effects on the individual and community health. In this study, the effects of food intake inequality and social status changes on pain perception and immunological factors were investigated in Balb/C mice. Methods: The present study was conducted by implementing different social stresses including food deprivation, food intake inequality and unstable social status (cage-mate change every 3 days) in 48 female mice. Formalin test was performed and thereafter the viability of peritoneal macrophages and spleen lymphocytes was evaluated by MTT assay. Concentrations of proinflammatory cytokines including IL-6, IL- 1 and TNF-α were also measured. Results: Our results showed that the implementation of food deprivation and inequality induced significant changes in chronic phase of formalin test compared to the control group (P<0.05). Pain perception was considerably decreased and this decline in inequality exposed subjects was well above the isolated ones. However, unstable social situation did not affect pain perception. Moreover, cell viability of peritoneal macrophages decreased, while cell viability of spleen lymphocytes and proinflammatory cytokines concentrations were increased in the serum of all stressed animals in comparison with controls (P<0.05). Conclusion: These results revealed that although food deprivation and social inequality can induce analgesia, some socioeconomic situations like social instability does not affect pain perception. All of these situations decrease cell viability in macrophages but enhance cell viability in lymphocytes. It seems that a proinflammatory stress condition is involved in these situations.