Adenoviral gene transfer of SERCA2a improves left-ventricular function in aortic-banded rats in transition to heart failure

Abstract

In human and experimental models of heart failure, sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) activity is decreased, resulting in abnormal calcium handling. The disturbances in calcium metabolism have been shown to contribute significantly to the contractile dysfunction observed in heart failure. We investigated whether increasing SERCA2a expression can improve ventricular function in an animal model of heart failure obtained by creating ascending aortic constriction in rats. After 19-23 wk of banding during the transition from compensated hypertrophy to heart failure (documented by >25% decrease in fractional shortening), rats were randomized to receive either an adenovirus carrying the SERCA2a gene (Ad.SERCA2a, n = 13) or beta-galactosidase (Ad.betagal, n = 14) by using a catheter-based technique. The failing hearts infected with Ad. betagal were characterized by a significant decrease in SERCA2a expression and a decrease in SERCA2a activity compared with nonfailing sham-operated rats (n = 11). In addition, these failing hearts had reduced left-ventricular systolic pressure, maximal rate of left-ventricular pressure rise and decline (+dP/dt, -dP/dt), and rate of isovolumic relaxation (tau). Overexpression of SERCA2a restored both SERCA2a expression and ATPase activity to nonfailing levels. Furthermore, rats infected with Ad.SERCA2a had significant improvement in left-ventricular systolic pressure, +dP/dt, -dP/dt, and rate of isovolumic relaxation (tau) normalizing them back to levels comparable to sham-operated rats. In this study, we show that in an animal model of heart failure where SERCA2a protein levels and activity are decreased and severe contractile dysfunction is present, overexpression of SERCA2a in vivo restores both systolic and diastolic function to normal levels.

Figure 1

Cardiomyocytes isolated from hearts from Sham + Ad.βgal, and Failing + Ad.βgal, which were also stained with X-Gal.

Figure 2

(A) Immunoblots of SERCA2a and phospholamban at days 0, 2, 7, 14, and 28 after infection with Ad.SERCA2a in control rats. (B) Immunoblots of SERCA2a, phospholamban, and calsequestrin from crude membranes of left ventricles from control, sham rats infected with Ad.βgal, sham rat hearts infected with Ad.SERCA2a, failing rat hearts infected with Ad.βgal, and failing hearts infected with Ad.SERCA2a at day 2–3. (C) Protein levels of SERCA2a in preparations from sham rats infected with Ad.βgal (n = 7), sham rat hearts infected with Ad.SERCA2a (n = 8), preparations from failing rat hearts infected with Ad.βgal (n = 8), and preparations of failing hearts infected with Ad.SERCA2a at day 2–3 (n = 9). *, P < 0.05 compared with Sham + Ad.βgal; †, P < 0.05 compared with Failing + Ad.βgal; ‡, P < 0.05 compared with Sham + Ad.SERCA2a.

Figure 3

ATPase activity measured vs. [Ca²⁺] in membrane preparations from control uninfected sham rats (n = 6, ♦), sham rats infected with Ad.βgal (n = 7, ●), sham rat hearts infected with Ad.SERCA2a (n = 8, ○), preparations from failing rat hearts infected with Ad.βgal (n = 8, ▴), and preparations of failing hearts infected with Ad.SERCA2a at day 2–3 (n = 9, ▵).

Figure 4

(A) Dependence of LV +dP/dt on heart rate in the different groups of animals: control uninfected sham rats (n = 6, ■), sham rats infected with Ad.βgal (n = 5, ●), sham rat hearts infected with Ad.SERCA2a (n = 4, ○), preparations from failing rat hearts infected with Ad.βgal (n = 5, ▴), and preparations of failing hearts infected with Ad.SERCA2a (n = 5, ▵ ). *, P < 0.001 compared with sham + Ad.βgal; †, P < 0.005 compared with Failing + Ad.βgal; ‡, P < 0.05 compared with Sham + Ad.SERCA2a. (B) LV pressure +dP/dt measurements at baseline and during infusion of 0.1 μg/kg/min of isoproterenol in the different groups of animals: control rats (n = 4), sham rats infected with Ad.βgal (n = 5), sham rat hearts infected with Ad.SERCA2a (n = 4), failing rat hearts infected with Ad.βgal (n = 4), and failing hearts infected with Ad.SERCA2a (n = 4). *, P < 0.001 compared with Sham + Ad.βgal; †, P < 0.005 compared with Failing + Ad.βgal.