Effect of propranolol on cardiac cytokine expression after myocardial infarction in rats

The pro-inflammatory cytokines interleukin (IL)-1beta and IL-6 have been shown to be upregulated in the myocardium after injury and after adrenergic receptor stimulation. Together with other cytokines, such as the transforming growth factor (TGF)-beta, the pro-inflammatory cytokines have been implicated in the initiation of tissue repair and wound healing after myocardial infarction (MI). In the present study, the effect of beta-adrenergic receptor blockade with propranolol (2 mg/kg.h s.c. by miniosmotic pumps) on cardiac cytokine expression and on wound healing was analyzed in rats from 6-72 h after MI. IL-1beta and IL-6 gene expression strongly increased in the infarcted myocardium 6 h after MI and peaked after 12 h, while TGF-beta, progressively increased from 12 h onwards. Also, TGF-beta(2) increased after 12 h, peaked after 24 h and declined thereafter, while TGF-beta, was only elevated after 72 h. Treatment with propranolol had a negative chronotropic effect throughout the observation period of 72 h. It attenuated the initial elevation in LVEDP and increased cardiac output ultimately. Furthermore, propranolol attenuated IL-1beta mRNA expression, but had not effect on the other cytokines. Moreover, MMP-9 gelatinolytic activity was markedly attenuated by propranolol indicating a delayed resorption of the necrotic tissue and, possibly, collagen turnover. Replacement by scar tissue, however, was not affected as indicated by normal collagen expression.