Abstract
1568 Stress is a state of altered homeostasis resulting from either an external or an internal stressor. Various forms of stressors can affect liver function and physical behavior. Water immersion stress and Propionibacterium acnes (P.acnes) stress has been used as a physiological stress and biological stress model, respectively. Whereas most of the evidence has been provided by these stressors, the role of immune function is poorly characterized. PURPOSE: The purpose of this study was to clarify recovery patterns of spontaneous activity and liver disease after Water immersion stress and P.acnes stress. METHODS: Female Fischer 344 rats were treated with 10mg/kg heatkilled P.acnes killed or water immersion (for 24h at 23°C) stress and then voluntary wheelrunning activity was examined for six days. Seven days after these stressors, the rats were injected with 0.2mg/kg lipopolysaccharide (LPS), and then we examined serum corticosterone, alanine aminotransferase (ALT) activity, histological appearance of the liver, tumor necrosis factor alpha (TNF-α), and mRNA expression of TNF-α, CD14, and toll-like receptor (TLR)4 in liver and lung. We also examined the cell surface markers CD14 and TLR4 on RAW264.7 cells after P.acnes challenge. RESULT: The recovery of physical activity in P. acnes treated rats was faster than that in water immersion treated rats (p<0.01). However, seven day after the stress treatments, ALT activity in P. acnes treated rats was higher than the water immersion treated group 24h after LPS injection (p<0.01). We also observed increased plasma TNF-α (p<0.01), constant expression of TNF-α, CD14, and TLR4 mRNA, massive necrosis in the liver, and a reduction of survival rate in P.acnes treated rats after LPS injection, but not in water immersion treated rats. Furthermore, we observed that induction of TLR4 occurred in RAW264.7 cells by P.acnes but not LPS treatment. CONCLUSION: These results suggest that P.acnes, but not immersion, stress induces TLR4 expression of macrophages, which causes serious inflammation when stimulated by LPS, although rapid recovery of physical activity was shown during the priming stage.
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