Circulating neuregulin-1ß levels vary according to the angiographic severity of coronary artery disease and ischemia.

BACKGROUND: Coronary artery disease (CAD) is the leading killer in the United States. Patients with severe CAD and ischemia have worse prognosis. Therefore expansion of biomarker research, to identify at-risk individuals and explain the complex biology between cardiovascular growth factors and atherosclerosis is needed. Neuregulin-1ß (NRG-1ß) is a myocardial stress activated growth and survival factor released from endocardial and endothelial cells. NRG-1ß is essential for cardiovascular development and a regulator of angiogenesis. We postulated that plasma and serum levels of NRG-1ß would vary in relation to CAD severity and the presence of stress-induced ischemia. METHODS: We measured serum and plasma levels of NRG-1ß and vascular endothelial growth factor (VEGF) in 60 patients undergoing cardiac catheterization. CAD severity was calculated from angiographic results using a modified Duke jeopardy score. RESULTS: Serum NRG-1ß (sNRG-1ß), plasma NRG-1ß (pNRG-1ß), serum VEGF, and plasma VEGF were detectable in the majority of patients. The pNRG-1ß levels were approximately two-fold higher than sNRG-1ß. Both sNRG-1ß and pNRG-1ß correlated inversely with CAD severity. pNRG-1ß levels were statistically higher in patients with stress-induced ischemia denoted by a positive myocardial perfusion imaging study that correlated with angiographic findings (P=0.02). CONCLUSION: Both sNRG-1ß and pNRG-1ß correlated inversely with angiographic severity of CAD. pNRG-1ß levels were two-fold higher than serum and were higher in patients with stress-induced ischemia. Therefore we conclude that plasma is the optimal source for the further exploration of the biological significance of NRG-1ß as a biomarker of CAD severity and ischemia.

Neuregulin-1ß regulation of embryonic endothelial progenitor cell survival.

Endothelial progenitor cells (EPCs) are mobilized into the vascular space and home to damaged tissues, where they promote repair in part through a process of angiogenesis. Neuregulins (NRGs) are ligands in the epidermal growth factor family that signal through type I receptor tyrosine kinases in the erbB family (erbB2, erbB3, and erbB4) and regulate endothelial cell biology, promoting angiogenesis. Stimuli such as ischemia and exercise that promote EPC mobilization also induce cleavage and release of transmembrane NRG from cardiac microvascular endothelial cells (CMECs). We hypothesized that NRG/erbB signaling may regulate EPC biology. Using an embryonic (e)EPC cell line that homes to and repairs injured myocardium, we were able to detect erbB2 and erbB3 transcripts. Identical receptor expression was found in EPCs isolated from rat bone marrow and human whole blood. NRG treatment of eEPCs induces phosphorylation of kinases including Akt, GSK-3ß, and Erk1/2 and the nuclear accumulation and transcriptional activation of ß-catenin. NRG does not induce eEPC proliferation or migration but does protect eEPCs against serum deprivation-induced apoptosis. These results suggest a role for tissue-derived NRG in the regulation of EPC survival.

Neuregulin-1 beta is associated with disease severity and adverse outcomes in chronic heart failure.

BACKGROUND: Neuregulin-1 (NRG-1) is a paracrine factor released by microvascular endothelial cells that has cardioprotective effects in animal models of heart failure. However, circulating NRG-1 has not been studied in human heart disease. We used a novel immunoassay to test whether circulating NRG-1beta is associated with disease severity and clinical outcomes in chronic heart failure. METHODS AND RESULTS: Serum NRG-1beta was quantified in 899 outpatients in the Penn Heart Failure Study, a referral cohort representing a broad spectrum of systolic heart failure. Circulating NRG-1beta was significantly elevated in patients with worse disease severity (median, 6.2 ng/mL for New York Heart Association class IV versus 4.4 ng/mL for class I; P=0.002). In adjusted models, NRG-1beta was independently associated with an increased risk of death or cardiac transplantation over a median follow-up of 2.4 years (adjusted hazard ratio, 1.58; 95% confidence interval, 1.04 to 2.39; P=0.03 comparing fourth versus first NRG-1beta quartile). Associations with outcome differed by heart failure cause and symptom severity, with the strongest associations observed in patients with ischemic cardiomyopathy (interaction P=0.008) and New York Heart Association class III/IV symptoms (interaction P=0.01). These findings were all independent of brain natriuretic peptide, and assessment of NRG-1beta and brain natriuretic peptide jointly provided better risk stratification than each biomarker individually in patients with ischemic or New York Heart Association class III/IV heart failure. CONCLUSIONS: Circulating NRG-1beta is independently associated with heart failure severity and risk of death or cardiac transplantation. These findings support a role for NRG-1/ErbB signaling in human heart failure and identify serum NRG-1beta as a novel biomarker that may have clinical applications.