Sexual dimorphism in the effect of sound stress on neutrophil function

It has been hypothesized that stress contributes to the severity of inflammatory diseases. However, the mechanisms underlying this effect are incompletely understood. In this study we investigated the effects of sound stress on function of the polymorphonuclear neutrophil-immune cells that play key roles in both the acute and chronic inflammatory response. Specifically, we examined the effect of stress on the production of reactive oxygen species (ROS) and phagocytosis by rat neutrophils, and the role of sympathoadrenal stress axis in these effects. Since many inflammatory diseases exhibit sexual dimorphism, we also investigated the contribution of sex and gonadal hormones to the effects of stress on neutrophil function. Peripheral blood neutrophils were harvested from male and female rats exposed to intermittent sound stress (over 4 days). Stress suppressed ROS production in males (but not females) an effect that was eliminated in adrenal medullectomized males. Stress also suppressed neutrophil phagocytosis in males and females. Again, this effect was absent following adrenal medullectomy. To investigate the role of sex hormones in these sexual dimorphic responses to stress, rats were gonadectomized prepubertally and exposed to stress as adults. In gonadectomized males, stress produced an even larger decrease in ROS production, but had no effect on the stress-induced inhibition of phagocytosis. Gonadectomy prevented the stress-induced inhibition of neutrophil phagocytosis in females. These data indicate that the adrenal medulla, perhaps via release of epinephrine, suppresses neutrophil ROS production in males and phagocytosis in males and females.