TNFa mRNA and protein biosynthesis were examined in the adult feline heart after stimulation with endotoxin. When freshly isolated hearts were stimulated with endotoxin in vitro, de novo TNFa mRNA expression occurred within 30 min, and TNFa protein production was detected within 60-75 min; however, TNFa mRNA and protein production were not detected in diluent-treated hearts. Immunohistochemical studies localized TNFa to endothelial cells, smooth muscle cells, and cardiac myocytes in the endotoxin-treated hearts, whereas TNFa immunostaining was absent in the diluent-treated hearts. To determine whether the cardiac myocyte was a source for TNFa production, two studies were performed. First, in situ hybridization studies, using highly specific biotinylated probes, demonstrated TNFa mRNA in cardiac myocytes from endotoxin-stimulated hearts; in contrast, TNFa mRNA was not expressed in myocytes from diluent-treated hearts. Second, TNFa protein production was observed when cultured cardiac myocytes were stimulated with endotoxin, whereas TNFa protein production was not detected in the diluent-treated cells. The functional significance of the intramyocardial production of TNFa was determined by examining cell motion in isolated cardiac myocytes treated with superfusates from endotoxinand diluent-stimulated hearts. These studies showed that cell motion was depressed in myocytes treated with superfusates from the endotoxin-treated hearts, but was normal with the superfusates from the diluent-treated hearts; moreover, the negative inotropic effects of the superfusates from the endotoxin-treated hearts could be abrogated completely by pretreatment with an anti-TNFa antibody. Finally, endotoxin stimulation was also shown to result in the intramyocardial production of TNFa mRNA and protein in vivo.Thus, this study shows for the first time that the adult mammalian myocardium synthesizes biologically active TNFa. (J. Clin. Invest. 1995. 96:1042-1052

Beginning in the first 60 minutes after reperfusion, C5a, TGF-beta 1, and MCP-1, acting sequentially, promote infiltration of monocytes into formerly ischemic myocardium. These events may promote the healing of myocardial injury facilitated by reperfusion.

MCP-1 mRNA is induced in the endothelium of a specific class of small veins immediately after reperfusion. MCP-1 induction is confined to the previously ischemic area that has been reperfused. We suggest a significant role for MCP-1 in monocyte trafficking in the reperfused myocardium.