Summary

Background:

Systemic CD11b+ cells have been associated with several cardiac diseases, such as chronic heart failure.

Objectives:

To assess the levels of circulating CD11b+ cells and pro-inflammatory cytokines in cardiomyopathy induced by chronic adrenergic stimulation.

Methods:

Male Lewis rats were injected with low doses of isoproterenol (isoprel) for 3 months. Cardiac parameters were tested by echocardiography. The percentage of CD11b+ cells was tested by flow cytometry. The levels of inflammatory cytokines in the sera were determined by an inflammation array, and the expression levels of cardiac interleukin-1 (IL-1) receptors were analyzed by real-time polymerase chain reactions. Cardiac fibrosis and inflammation were determined by histological analysis.

Results:

Chronic isoprel administration resulted in increased heart rate, cardiac hypertrophy, elevated cardiac peri-vascular fibrosis, reduced fractional shortening, and increased heart weight per body weight ratio compared to control animals. This clinical presentation was associated with accumulation of CD11b+ cells in the spleen with no concomitant cardiac inflammation. Cardiac dysfunction was also associated with elevated sera levels of IL-1 alpha and over expression of cardiac IL-1 receptor type 2.

Conclusions:

CD11b+ systemic levels and IL-1 signaling are associated with cardiomyopathy induced by chronic adrenergic stimulation. Further studies are needed to define the role of systemic immunomodulation in this cardiomyopathy.