Background: Elevated serum concentration of interleukin (IL)-6 is a predictor for poor prognosis in congestive heart failure. It was shown previously in rats, that IL-6 expression in the left ventricle (LV) was followed by LV hypertrophy. Methods: Using IL-6 deficient mice (IL-6^-/-), we studied the role of IL-6 in a model of norepinephrine (NE)-induced LV hypertrophy. Results: In wild type (WT) mice, IL-6 mRNA expression and its concentration in the serum were elevated after 4 h of NE-treatment (s.c. 0.25 mg/kg·h). Further, NE-induced LV hypertrophy was detected: LV weight/body weight (LVW/BW) ratio (+12.3±3%, p < 0.05) and mRNA expression of atrial natriuretic peptide (ANP) in WT mice (+120±25%, p < 0.05) after 3 days were increased. In contrast, NE did not induce elevation of LVW/BW ratio and ANP expression in IL-6^-/- mice. Replacement with recombinant IL-6 restored the hypertrophy-inducing effect of NE in IL-6^-/- mice. As to the extracellular matrix (ECM) proteins, NE increased collagen type I and III expression only in WT mice and not in IL-6^-/- mice. The addition of recombinant IL-6 elevated the expression of the ECM proteins to the WT level. Conclusion: IL-6 is a major player in the development of NE-induced LV hypertrophy in mice.

Background: Matrix metalloproteinases (MMPs) play an important role in myocardial remodeling. Their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). The present study analyzed the contribution of changes in functional and molecular parameters to early cardiac remodeling in mice hearts. The role that TIMPs might play in this process was specially acknowledged. Methods: The remodeling was induced by norepinephrine (NE) given sc in balb/c mice. Varying concentrations, time and the addition of a neutralizing TIMP-1 antibody were evaluated. Results: High dose NE led to insufficiency of the left ventricle (LV) as evidenced by reduced NE-induced elevation of LV systolic pressure, contractility and relaxation. Further, signs of lung congestion were seen. NE induced a concentration-dependent increase of LV weight/body weight (LVW/BW) ratio and elevated mRNA expression of atrial natriuretic peptide (ANP). This was accompanied by induction of collagen type I and III, as well as TIMP-1 expression. Conclusions: The NE-induced increase of TIMP-1 expression may induce the elevation of the antihypertrophic cardiac factor ANP since NE-induced increase of ANP expression was abolished by neutralizing TIMP-1 antibody. Thus, TIMP-1 may mediate ANP-induced attenuation of NE-induced hypertrophy in the mouse heart.