Antiplatelet therapy attenuates subcellular remodelling in congestive heart failure

Abstract

Antiplatelet agents, sarpogrelate (SAR), a 5-HT(2A) receptor antagonist, and cilostazol (CIL), a phosphodiesterase III (PDE-III) inhibitor, are used for the treatment of peripheral vascular disease. We tested whether these agents affect cardiac function and subcellular remodelling in congestive heart failure (CHF) induced by myocardial infarction (MI). Three weeks after MI, rats were treated daily with 5 mg/kg SAR or CIL as well as vehicle for 5 weeks. Sham-operated animals served as controls. At end of the treatment period, haemodynamic measurements were performed and the left ventricle was processed for the determination of sarcoplasmic reticulum (SR) Ca(2+)-uptake and -release activities, and expression of SR Ca(2+)-pump, phospholamban and ryanodine receptors, as well as myofibrillar ATPase activities, expression of alpha- and beta-myosin heavy chain (MHC) isoforms, and phosphorylation of phospholamban and cardiac troponin-I (c Tn-I). Marked haemodynamic changes in the MI-induced CHF were associated with depressions in SR Ca (+)-uptake and -release activities as well as in protein content and gene expression for SR proteins. Furthermore, myofibrillar Ca(2+)-stimulated ATPase activity, as well as protein content and gene expression for alpha-MHC were decreased whereas those for beta-MHC were increased in the failing heart. Also, phosphorylation levels of phospholamban and cTn-I were reduced in failing hearts. The MI-associated changes in cardiac function, SR and myofibillar activities, as well as SR and myofibrillar protein and gene expression were attenuated by treatment with SAR or CIL. The results suggest that SAR and CIL improve cardiac function by ameliorating subcellular remodelling in the failing heart and indicate the potential therapy of CHF with antiplatelet agents.

1

Sarcoplasmic reticulum (SR) Ca²⁺-uptake (A) and Ca²⁺-release (B) activities in sham, vehicle-treated (MI), sarpogrelate-treated (MI+SAR) and cilostazol-treated (MI+CIL) rats at 8 weeks after surgery. MI, myocardial infarction. Values are means ± S.E.M. of 6–9 animals for each group. *P < 0.05 versus sham; #P < 0.05 versus MI.

2

Representative western blots and densitometric analysis of protein content for sarcoplasmic reticulum SERCA2a (A), RyR (B) and PLB (C) proteins in sham, vehicle-treated (MI), sarpogrelate-treated (MI+SAR) and cilostazol-treated (MI+CIL) rats at 8 weeks after surgery. SERCA2a: sarcoplasmic reticulum Ca²⁺-ATPase; RyR: ryanodine receptor. Values are means ± S.E.M. of 6–9 animals for each group. *P < 0.05 versus sham; #P < 0.05 versus MI.

3

Representative western blots and densitometric analysis of protein contents for sarcoplasmic reticulum phosphorylated PLB (A) and phosphorylated cTnI (B) in sham, vehicle-treated (MI), sarpogrelate-treated (MI+SAR) and cilostazol-treated (MI+CIL) rats at 8 weeks after surgery. PLB: phospholamban; cTnI: cardiac troponin I. Values are means ± SEM of 6–9 animals for each group. *P < 0.05 versus sham; # P < 0.05 versus MI.

4

Representative northern blots and densitometric quantification of mRNA abundance for sarcoplasmic reticulum SERCA2 (A), RyR (B) and PLB (C) in sham, vehicle-treated (MI), sarpogrelate-treated (MI+SAR) and cilostazol-treated (MI+CIL) rats at 8 weeks after surgery. SERCA2a: sarcoplasmic reticulum Ca²⁺-ATPase; RyR: ryanodine receptor; PLB: phospholamban. Values are means ± S.E.M. of 6–10 animals for each group. *P < 0.05 versussham; #P < 0.05 versus MI.

5

Myofibrillar Ca²⁺-stimulated and Mg²⁺-ATPase activities in sham, vehicle-treated (MI), sarpogrelate-treated (MI+SAR) and cilostazol-treated (MI+CIL) rats at 8 weeks after surgery. MI: myocardial infarction; Values are means ± S.E.M. of 6–9 animals for each group. *P < 0.05 versus sham; #P < 0.05 versus MI.

6

Coomassie blue-stained gels showing α- and β-MHC protein expression and their corresponding densitometric analysis (A) and representative northern blots and densitometric quantification of mRNA abundance for α-MHC (B) and β-MHC (C) in sham, vehicle-treated (MI), sarpogre-late-treated (MI+SAR) and cilostazol-treated (MI+CIL) rats at 8 weeks after surgery. MI: myocardial infarction; MHC: myosin heavy chain. Values are means ± S.E.M. of 6–9 animals for each group. *P < 0.05 versus sham; #P < 0.05 versus MI.