Plasma cardiotrophin-1 is elevated in human hypertension and stimulated by ventricular stretch

Abstract

Cardiotrophin-1 (CT-1) is an interleukin-6-related cytokine with known hypertrophic and protective actions upon cardiac myocytes. We provide here the first report of cardiac tissue and plasma levels of CT-1 in human and experimental hypertension, demonstrate cardiac CT-1 secretion stimulated by ventricular stretch, and characterise molecular forms of CT-1 in tissue and plasma. CT-1 levels in human and rat plasma and in rat cardiac tissue extracts were determined by specific radioimmunoassay (RIA). Cardiac CT-1 secretion during ventricular stretch was studied in isolated, perfused hearts. Molecular forms of CT-1 were identified using RIA coupled with high performance liquid chromatography (HPLC). Results are given as mean+/-SEM. Plasma levels of CT-1 in patients with untreated hypertension (UTH, 606+/-18 pmol/L, n=24) were significantly higher than those in age-and BMI-matched normotensive volunteers (NT, 546+/-12 pmol/L, n=31, P<0.01 vs. UTH). CT-1 levels in matched patients with treated hypertension (THT, 618+/-10 pmol/L, n=35) were similar to those in UTH patients, but higher than in NT controls (P<0.01). Plasma CT-1 demonstrated a weak but significant correlation with systolic blood pressure in all patients (r=0.241, P<0.05, n=90). In contrast, CT-1 levels in male, 40-week-old, NT-WKY rats (1295+/-98 pmol/L) were significantly higher than those in matched UTH-SHR (937+/-31 pmol/L, P<0.01). In both WKY and SHR rats, atrial tissue concentrations of CT-1 were 8-fold higher than ventricular levels. Left ventricular tissue CT-1 protein concentrations were significantly higher in 40-week-old SHR compared with age-matched WKY (SHR 12.6+/-0.5 fmol/g vs. WKY 9.5+/-0.8 fmol/g, P<0.01). Ventricular stretch of Langendorff perfused, isolated WKY/SHR hearts resulted in significant, acute release of CT-1 and BNP. HPLC coupled with specific RIA revealed CT-1 in human/rat plasma, isolated rat heart perfusate, and rat heart tissue extracts to consist of complex, high molecular weight forms. This is the first report to show increased levels of plasma CT-1 in hypertensive disease. CT-1 is a unique cardiac cytokine whose release is stimulated by ventricular stretch. The atrium contains the highest levels of the protein. The stored and circulating molecular form of CT-1 is complex, which may modulate its in vivo role in cardiovascular disease.