3-4-dihydro-5-(4-(1-piperidinyl)butoxy)-1(2h)-isoquinolinone and Myocardial-Infarction

Myocardial infarction (MI) is defined as the deprivation of the myocardial tissue of oxygen and nutrients, resulting in the induction of inflammation and apoptosis of the cardiomyocytes. Poly (ADP‑ribose) polymerase 1 (PARP1) is a nuclear enzyme closely associated with MI, that can be activated by DNA damage. Inducible nitric oxide synthase (iNOS) is a critical enzyme among the inflammatory cytokines. The present study aimed to investigate the underlying mechanism of the protective effects of PARP1 and iNOS inhibitor against MI, in rats. A total of 40 male Wistar rats were divided into four groups. The rats were anesthetized with sodium pentobarbital (50 mg/kg), and the left anterior descending coronary artery was occluded by ligation, using a 6‑0 polypropylene monofilament suture, at the left atrial apex, in order to induce MI. The rats from each group received an abdominal injection of either dimethylsulfoxide (100 µl, for MI group); PARP‑1 inhibitor, 3,4‑dihydro‑5‑[4‑(1‑piperidinyl)butoxy]‑1(2H)‑ isoquinolinone (DPQ; 10 mg/kg); or iNOS inhibitor, N‑(1‑naphthyl)ethylenediamine dihydrochloride (1400W; 10 mg/kg). The hearts were harvested from the rats after four weeks. Inhibition of PARP and iNOS activity improved heart function, as determined by serial echocardiography. The rate of apoptosis, as determined by a terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling assay, was reduced by 39.71 and 39.00% in the DPQ and 1400W groups, respectively, and this was accompanied by the downregulated expression of cleaved caspase‑3 and PARP1. Effective inhibition of PARP and iNOS, by DPQ and 1400W, was detected by western blotting and immunofluorescence, and was shown to repress O2‑ and nitrotyrosine levels, following MI. The present study confirmed that inhibition of PARP1 and iNOS was able to protect against ischemic myocardial damage, by reducing the levels of apoptosis.

Topics: Amidines; Animals; Apoptosis; Benzylamines; Cardiotonic Agents; Caspase 3; Disease Models, Animal; Enzyme Inhibitors; Isoquinolines; Male; Myocardial Infarction; Myocardium; Nitric Oxide Synthase Type II; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Rats; Ventricular Function

We have identified three novel structures for inhibitors of the poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA and implicated in DNA repair, apoptosis, organ dysfunction or necrosis. 2-[4-(5-Methyl-1H-imidazol-4-yl)-piperidin-1-yl]-4,5-dihydro-imidazo[4,5,1-i,j]quinolin-6-one (BYK49187), 2-(4-pyridin-2-yl-phenyl)-4,5-dihydro-imidazo[4,5,1-i,j]quinolin-6-one (BYK236864), 6-chloro-8-hydroxy-2,3-dimethyl-imidazo-[1,2-alpha]-pyridine (BYK20370), and 4-(1-methyl-1H-pyrrol-2-ylmethylene)-4H-isoquinolin-1,3-dione (BYK204165) inhibited cell-free recombinant human PARP-1 with pIC(50) values of 8.36, 7.81, 6.40, and 7.35 (pK(i) 7.97, 7.43, 5.90, and 7.05), and murine PARP-2 with pIC(50) values of 7.50, 7.55, 5.71, and 5.38, respectively. BYK49187, BYK236864, and BYK20370 displayed no selectivity for PARP-1/2, whereas BYK204165 displayed 100-fold selectivity for PARP-1. The IC(50) values for inhibition of poly(ADP-ribose) synthesis in human lung epithelial A549 and cervical carcinoma C4I cells as well in rat cardiac myoblast H9c2 cells after PARP activation by H(2)O(2) were highly significantly correlated with those at cell-free PARP-1 (r(2) = 0.89-0.96, P < 0.001) but less with those at PARP-2 (r(2) = 0.78-0.84, P < 0.01). The infarct size caused by coronary artery occlusion and reperfusion in the anesthetized rat was reduced by 22% (P < 0.05) by treatment with BYK49187 (3 mg/kg i.v. bolus and 3 mg/kg/h i.v. during 2-h reperfusion), whereas the weaker PARP inhibitors, BYK236864 and BYK20370, were not cardioprotective. In conclusion, the imidazoquinolinone BYK49187 is a potent inhibitor of human PARP-1 activity in cell-free and cellular assays in vitro and reduces myocardial infarct size in vivo. The isoquinolindione BYK204165 was found to be 100-fold more selective for PARP-1. Thus, both compounds might be novel and valuable tools for investigating PARP-1-mediated effects.

Topics: Animals; Cell Line; Cell Line, Tumor; Fibroblasts; Humans; Imidazoles; Isoquinolines; Kinetics; Male; Mice; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Pyridines; Quinolones; Rats; Rats, Wistar; Recombinant Proteins; Solubility; Structure-Activity Relationship