Divergent effects of ischemia/reperfusion and nitric oxide donor on TNFα mRNA accumulation in rat organs

We previously showed that serum TNFα bioactivity in rats is proportional to the extent of graded tissue injury caused by laparotomy, intestinal ischemia, and reperfusion and that the spleen is an important source of TNFα secretion in this condition. TNFα production varies, depending on the type and duration of tissue injury. It is also affected by other mediators, such as nitric oxide (NO). TNFα is known to increase NO production, but the effect of NO on the production of TNFα has not yet been fully elucidated. In this study we determined the levels of TNFα mRNA in rat organs after graded injury caused by anesthesia, laparotomy, intestinal ischemia, and reperfusion and evaluated the effects of the NO donor S-nitroso-N-acetylpenicillamine (SNAP) on it. Samples from different organs were removed, and TNFα gene expression was evaluated by semiquantitative RT-PCR. TNFα mRNA was not detected in the intestine (the ischemic organ) and in the kidney, brain, heart, or liver after all 4 experimental protocols. In the mesenteric lymph node (draining the ischemic organ) a basal level of expression of TNFα mRNA was detected in the control (anesthesia alone) group, which was increased significantly after ischemia. In the spleen (a remote immune organ not directly involved in the ischemia), a significant gradual increase in TNFα mRNA, which correlated to the severity of the experimental protocol, was observed. In the lung (a central participant in post-injury multiple organ failure), all interventions increased TNFα mRNA. Infusion of SNAP exerted a differential effect on TNFα mRNA: diminished its accumulation in the lymph node, enhanced it in the lung, and had no effect in the spleen. The divergent organ pattern of TNFα transcription emphasizes the importance of its localized expression, which is critical to the understanding of its autocrine and paracrine actions in ischemia and reperfusion.