ABSTRACT
Recent studies from our laboratory have suggested that acute alcohol ingestion prior to burn injury enhances gut bacterial translocation by suppressing T cell-mediated intestinal immune defense. To determine the mechanism responsible for suppressed T cell function, we examined the activation of mitogen-activated protein kinases (MAPK) members p-38 and ERK-1/2. Both p-38 and ERK-1/2 are known to play a significant role in the T cell proliferation and their cytokine production. Rats were gavaged with ethanol to achieve a blood alcohol level of approximately 100 mg/dl, before they were subjected to a 25% total body surface area burn injury. Two days after injury, rats were sacrificed and mesenteric lymph node (MLN) T cells were isolated and their ability to proliferate in response to anti-CD3 was determined. For p-38 and ERK-1/2 determination, T cells were divided into two groups. Cells in one group were stimulated with anti-CD3 for 3 min and lysed. The cells in the second group were cultured for approximately 18 h in the presence of anti-CD3 and lysed. MAPK status in 18-h cultured cells allowed us to determine whether or not the changes in p-38 and ERK-1/2 are transient or persist in the proliferating cells. Two days after injury, anti-CD3-mediated MLN T cell proliferation was more suppressed in rats gavaged with alcohol prior to burn injury compared to rats receiving either burn injury alone or sham-injured rats regardless of their exposure. Western blot analyses showed significant inhibition of ERK-1/2 phosphorylation in both freshly isolated and 18-h cultured T cells from alcohol and burn-injured rats compared to the sham rat T cells. The inhibition of p-38 phosphorylation in T cells derived from alcohol and burn-injured rats was found to be transient as no significant difference in p-38 phosphorylation was noted between the 18 h incubated MLN T cells of sham and alcohol and burn-injured rats. Taken together, our findings suggest that low levels of ERK-1/2 activation is likely to play a significant role in MLN T cell proliferative suppression in alcohol and burn-injured rats.
