Augmented expression of cardiotrophin-1 in failing human hearts is accompanied by diminished glycoprotein 130 receptor protein abundance.

BACKGROUND Cardiotrophin-1 (CT-1), a member of the interleukin-6 superfamily, is a potent inducer of cardiomyocyte hypertrophy that prolongs myocyte survival. Although cardiac CT-1 gene expression is known to be upregulated in some animal models of congestive heart failure, the activation state of the CT-1 system in patients with congestive heart failure is unknown. METHODS AND RESULTS This study was designed to determine left ventricular expression of CT-1 and its glycoprotein 130 (gp130)/leukemia inhibitory factor receptor complex in human end-stage heart failure due to ischemic and dilated cardiomyopathy. In addition, we investigated the activation state of signal transducer and activator of transcription 3 (STAT3), the downstream effector of gp130 signaling. In the failing left ventricular myocardium, expression levels of CT-1 mRNA and protein were significantly increased by 142% and 68%, respectively, compared with non-failing donor hearts. Immunohistochemistry confirmed the increased expression of CT-1 in cardiac myocytes. Although gp130 gene expression was increased by 91% (P<0.001), gp130 protein abundance was significantly diminished by 34% in the failing myocardium. In contrast, leukemia inhibitory factor receptor and suppressor of cytokine signaling-3 protein concentrations were not changed. In addition, the ratio of activated tyrosine phosphorylated STAT3 to total STAT3 was not significantly altered in failing hearts compared with non-failing controls. CONCLUSIONS Our data suggest that gp130 receptor downregulation balances enhanced CT-1 expression in human heart failure and thereby inhibits excessive activation of the gp130 signaling pathway.