Metcalf Pate, K. A., Freeman, Z. T., Shirk, E. et al. 2012. Platelet activation in the context of stress in self-injurious rhesus macaques. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 640 (Abstract #PS49).

Stress has been associated with adverse hematologic and physiologic consequences, including immunosuppression and an increased risk of cardiac disease. Aberrant platelet activation has been documented in humans exposed to mental stress, and activated platelets, as participants in both immunity and hemostasis, have the potential to significantly contribute to sequelae of stress. We hypothesized that stressed macaques would have more activated platelets than unstressed macaques. Chronic mental stress in macaques can manifest as abnormal behavior, including self-injurious behaviors ranging from hair pulling to wounding. We, therefore, queried platelet activation in the whole blood of 19 adult male rhesus macaques (Macaca mulatta) with documented selfinjurious behavior at 2 time points 2 wk apart using a mutiplexed flow cytometry assay that measures the activation markers p-selectin and PAC1 on the platelet surface. These self-injurious macaques showed classic hematologic evidence of stress, demonstrating significantly lower lymphocyte counts on CBC when compared with five behaviorally normal age and gender matched controls (unpaired t test, P = 0.01). In accordance with our hypothesis, a higher percentage of platelets from self-injurious macaques expressed p-selectin (unpaired t test, P = 0.04) and PAC1 (unpaired t test, P = 0.01) when compared to controls, indicating increased platelet activation in stressed self-injurious macaques; the presence of wounding (n = 14) compared with nonwounding (n = 5) self-injurious behavior had no effect on platelet activation (unpaired t tests, P = 0.6 for p-selectin, P = 0.7 for PAC1). Platelet activation, therefore, occurs in the context of stress in self-injurious rhesus macaques, and may contribute to additional sequelae of stress that warrant further investigation in this model.