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IL-1 and TNF Down-Regulate CRH Receptor-2 mRNA Expression in the Mouse Heart

Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland, Oregon 97201

Address all correspondence and requests for reprints to: Mary P. Stenzel-Poore, Ph.D., Department of Molecular Microbiology and Immunology, L220, Oregon Health Sciences University, 3181 Southwest Sam Jackson Park Road, Portland, Oregon 97201. E-mail: poorem{at}ohsu.edu

Two receptors (CRH receptor type 1 and CRH receptor type 2) have been identified for the stress-induced neuropeptide, CRH and related peptides, urocortin, and urocortin II. We previously found marked down-regulation of cardiac CRH receptor type 2 expression following administration of bacterial endotoxin, lipopolysaccharide, a model of systemic immune activation, and inflammation. We postulated that inflammatory cytokines may regulate CRH receptor type 2. We show that systemic IL-1 administration significantly down-regulates CRH receptor type 2 mRNA in mouse heart. In addition, TNF treatment also reduces CRH receptor type 2 mRNA expression, although the effect was not as marked as with IL-1. However, CRH receptor type 2 mRNA expression is not altered in adult mouse ventricular cardiomyocytes stimulated in vitro with TNF or IL-1. Thus, cytokine regulation may be indirect. Exogenous administration of corticosterone in vivo or acute restraint stress also reduces cardiac CRH receptor type 2 mRNA expression, but like cytokines, in vitro corticosterone treatment does not modulate expression in cardiomyocytes. Interestingly, treatment with urocortin significantly decreases CRH receptor type 2 mRNA in cultured cardiomyocytes. We speculate that in vivo, inflammatory mediators such as lipopolysaccharide and/or cytokines may increase urocortin, which in turn down-regulates CRH receptor type 2 expression in the heart. Because CRH and urocortin increase cardiac contractility and coronary blood flow, impaired CRH receptor type 2 function during systemic inflammation may ultimately diminish the adaptive cardiac response to adverse conditions.