Neuregulin-1β Partially Improves Cardiac Function in Volume-Overload Heart Failure Through Regulation of Abnormal Calcium Handling

Abstract

Background: Neuregulin (NRG-1), an essential stress-mediated paracrine growth factor, has a cardioprotective effect in failing heart. However, the underlying mechanism remains unclear. The role of NRG-1β in heart failure (HF) rats was examined. Methods and Results: Volume-overload HF rat model was created by aortocaval fistula surgery. The sham-operated (SO) rats received the same surgical intervention without the fistula. Thirty-five HF rats were injected with NRG-1β (NRG, 10 μg/kg·d) via the tail vein for 7 days, whereas 35 HF rats and 20 SO rats were injected with the same dose of saline. The echocardiographic findings showed left ventricular dilatation, systolic and diastolic dysfunction, and QTc interval prolongation in HF rats. The NRG-1β treatment attenuated the ventricular remodeling and shortened the QTc interval. Patch clamp recordings showed I_Ca-L was significantly decreased in the HF group, and NRG-1β treatment attenuated the decreased I_Ca-L. No significant differences in the kinetic properties of I_Ca-L were observed. The expressions of Cav1.2 and SERCA2a were significantly reduced, but the expression level of NCX1 was increased dramatically in the HF group. NRG-1β treatment could partially prevent the decrease of Cav1.2 and SERCA2a, and the increase of NCX1 in HF rats. Conclusions: NRG-1β could partly attenuate the heart function deterioration in the volume-overload model. Reduced function and expression of calcium transportation-related proteins might be the underlying mechanism.

Keywords: L-type calcium channel; SERCA2a; calcium handling; heart failure; neuregulin-1β.

Figure 1

Schematic depiction of the animal study. Volume-overload heart failure (HF) was established in rats by aorta-caval fistula surgery. Sham-operated rats (SO group) received the same operation without the fistula. HF rats were confirmed at 8 weeks after surgery by echocardiographic measurement. HF rats were injected with NRG-1β (10 μg/kg·d) by intravenous injection via the tail vein for 7 days as previously reported. The rats in the HF group and the SO group were administered with the same dose of saline. All of the rats were maintained for 12 weeks. Echocardiographic and hemodynamic measurements measured cardiac function. Rats were sacrificed after the last measurement

Figure 2

Effects of NRG-1β on I_Ca-L in rat ventricular myocytes. (A) Stimulated protocol and original current recording. (B) I–V relationship of I_Ca-L. For obtaining the current-voltage (I–V) curves and steady-state activation curves, the holding potential was set at −40 mV, and I_Ca-L was elicited by a single pulse of 300 ms to +70 mV from the holding potential in 5-mV increments at 0.1 Hz. The current amplitude was normalized to the cell capacitance (current density, pA/pF).

Figure 3

Kinetics of I_Ca-L. (A) Steady-state activation curve of I_Ca-L. (B) Steady-state inactivation curve. (C) Biexponential recovery from inactivation of I_Ca-L. The cells were depolarized from −40 to 0 mV over 150 ms, and various interpulse (10–12,800 ms) were applied. NRG-1β did not affect the time dependence of I_Ca-L recovery from inactivation.

Figure 4

Expressions of calcium handling proteins. The confocal image showed fluorescein isothiocyanate (green)-labeled Cav1.2, SERCA2a, and NCX1 expressed in isolated rat cardiac ventricular myocytes in SO (left panel), HF (middle panel), and NRG group (right panel). Nuclei were stained with DAPI (blue). The scale bar represents 20 μm (n = 5 for each set of staining).

Figure 5

Quantitative analysis of calcium handling proteins expressions. (A) Representative expression of Cav1.2, SERCA2a, and NCX1, β-actin as loading controls. (B) Comparison of Cav1.2 protein expression (n = 3 rats). (C) Comparison of SERCA2a protein expression (n = 4 rats). (D) Comparison of NCX1 protein expression (n = 4 rats). *P < 0.05, **P < 0.01 vs. SO; ^# P < 0.05, ^## P < 0.01 vs. HF.