Expression of leukocyte chemotactic cytokines in myocardial tissue

Cytotoxic action of leukocytes may be involved in the pathogenesis of inflammatory heart muscle disorders. We investigated the expression of rat leukocyte chemotactic cytokines--cytokine induced neutrophil chemoattractant (CINC) and JE--in cultured neonatal rat cardiac myocytes; CINC belongs to the interleukin 8 (IL-8) family and JE is a homologue of human monocyte chemoattractant protein 1 (MCP-1). In Northern blot analysis, CINC and JE transcripts were not clearly observed in unstimulated rat cardiac myocytes. However, their expression was clearly observed after exposure to tumour necrosis factor-alpha (TNF-alpha; 100 U/ml) for 2-6 h. We then evaluated IL-8 and MCP-1 mRNA expression in human endomyocardial biopsy specimens from seven patients with idiopathic dilated cardiomyopathy by polymerase chain reaction analysis. Both IL-8 and MCP-1 mRNA transcripts were recognized in all patients studied. These results show for the first time that leukocyte chemotactic cytokines, IL-8 and MCP-1, are expressed in myocardial tissue, which might contribute to the pathogenesis of inflammatory heart muscle disorders.