The cytotoxic action of leukocytes may be a most probable cause of cardiac myocyte damage seen in chronic myocarditis and dilated cardiomyopathy (DCM). The migration and tissue infiltration of leukocytes is regulated by chemotactic cytokines. Recently, the presence of monocyte chemoattractant protein 1 (MCP-1) messenger RNA has been demonstrated in endomyocardial biopsy tissue obtained from patients with DCM. This chemokine could contribute to enhanced leukocyte recruitment and activation resulting in chronic damage of cardiomyocytes. Accordingly, we sought to determine whether the severity of left ventricular dysfunction in DCM is associated with quantitative alterations of MCP-1 messenger RNA and MCP-1 protein in endomyocardial biopsy tissue. A group of DCM patients with low to moderate impairment of left ventricular function (ejection fraction 45.3+/-2.3%, n=7) was compared to patients with severe left ventricular dysfunction (ejection fraction 25.5+/-3.1%, n=7). MCP-1 messenger RNA expression was determined by quantitative polymerase chain reaction. MCP-1 protein and the presence of infiltrating inflammatory cells were detected by immunohistochemistry. DCM patients with severe left ventricular dysfunction showed a 2.35 fold higher MCP-1 messenger RNA expression when compared to DCM patients with less severe dysfunction (P=0.0229). Positive immunohistochemical staining for MCP-1 was found in all seven patients with severe left ventricular dysfunction and was particularly distinct within the cardiac interstitum. In five of seven patients with less severe systolic dysfunction, MCP-1 protein was found, but was less pronounced and distributed in patchy interstitial areas, close to intramyocardial vessels. Furthermore, there was a consistent trend toward a higher infiltration of inflammatory cells in DCM patients with lower ejection fraction. In conclusion, MCP-1 is dynamically regulated in DCM related deterioration of left ventricular function. This mechanism might contribute to myocyte damage via infiltrated and activated monocytes.
Copyright 1998 Academic Press.