Background: Phosphodiesterase type 5 (PDE5) inhibition has been shown to exert profound beneficial effects in the failing heart, suggesting a significant role for PDE5 in the development of congestive heart failure (CHF). The purpose of this study is to test the hypothesis that oxidative stress causes increased PDE5 expression in cardiac myocytes and that increased PDE5 contributes to the development of CHF.
Methods and results: Myocardial PDE5 expression and cellular distribution were determined in left ventricular samples from patients with end-stage CHF and normal donors and from mice after transverse aortic constriction (TAC)-induced CHF. Compared with donor human hearts, myocardial PDE5 protein was increased approximately equal 4.5-fold in CHF samples, and the increase of myocardial PDE5 expression was significantly correlated with myocardial oxidative stress markers 3'-nitrotyrosine or 4-hydroxynonenal expression (P<0.05). Histological examination demonstrated that PDE5 was mainly expressed in vascular smooth muscle in normal donor hearts, but its expression was increased in both cardiac myocytes and vascular smooth muscle of CHF hearts. Myocardial PDE5 protein content and activity also increased in mice after TAC-induced CHF (P<0.05). When the superoxide dismutase (SOD) mimetic M40401 was administered to attenuate oxidative stress, the increased PDE5 protein and activity caused by TAC was blunted, and the hearts were protected against left ventricular hypertrophy and CHF. Conversely, increased myocardial oxidative stress in superoxide dismutase 3 knockout mice caused a greater increase of PDE5 expression and CHF after TAC. In addition, administration of sildenafil to inhibit PDE5 attenuated TAC-induced myocardial oxidative stress, PDE5 expression, and CHF.
Conclusions: Myocardial oxidative stress increases PDE5 expression in the failing heart. Reducing oxidative stress by treatment with M40401 attenuated cardiomyocyte PDE5 expression. This and selective inhibition of PDE5 protected the heart against pressure overload-induced left ventricular hypertrophy and CHF.