A Newly Synthesized Poly(ADP-Ribose) Polymerase Inhibitor, DR2313 [2-Methyl-3,5,7,8-tetrahydrothiopyrano[4,3-d]-pyrimidine-4-one]: Pharmacological Profiles, Neuroprotective Effects, and Therapeutic Time Window in Cerebral Ischemia in Rats

Abstract

We investigated the pharmacological profiles of DR2313 [2-methyl-3,5,7,8-tetrahydrothiopyrano[4,3-d]pyrimidine-4-one], a newly synthesized poly(ADP-ribose) polymerase (PARP) inhibitor, and its neuroprotective effects on ischemic injuries in vitro and in vivo. DR2313 competitively inhibited poly(ADPribosyl)ation in nuclear extracts of rat brain in vitro (K i ϭ 0.23 M). Among several NAD ϩ -utilizing enzymes, DR2313 was specific for PARP but not selective between PARP-1 and PARP-2. DR2313 also showed excellent profiles in water solubility and rat brain penetrability. In in vitro models of cerebral ischemia, exposure to hydrogen peroxide or glutamate induced cell death with overactivation of PARP, and treatment with DR2313 reduced excessive formation of poly(ADP-ribose) and cell death. In both permanent and transient focal ischemia models in rats, pretreatment with DR2313 (10 mg/kg i.v. bolus and 10 mg/kg/h i.v. infusion for 6 h) significantly reduced the cortical infarct volume. To determine the therapeutic time window of neuroprotection by DR2313, the effect of posttreatment was examined in transient focal ischemia model and compared with that of a free radical scavenger, MCI-186 (3-methyl-1-phenyl-2-pyrazolone-5-one). Pretreatment with MCI-186 (3 mg/kg i.v. bolus and 3 mg/kg/h i.v. infusion for 6 h) significantly reduced the infarct volume, whereas the posttreatment failed to show any effects. In contrast, posttreatment with DR2313 (same regimen) delaying for 2 h after ischemia still prevented the progression of infarction. These results indicate that DR2313 exerts neuroprotective effects via its potent PARP inhibition, even when the treatment is initiated after ischemia. Thus, a PARP inhibitor like DR2313 may be more useful in treating acute stroke than a free radical scavenger.The excessive release of the excitotoxic amino acid glutamate plays a critical role in the pathogenesis of neuronal cell death following cerebral ischemia. NO produced by nNOS has been implicated in N-methyl-D-asparate (NMDA) receptor-mediated neurotoxicity of glutamate in cerebral ischemia . NMDA receptor activation causes an increase in intracellular calcium concentration leading to activation of nNOS. A part of the neurotoxicity evoked by NO is a result of the reaction of NO with superoxide anion to form a highly toxic radical, peroxynitrite Pieper et al., 1999). Postischemic injury is also exacerbated by the increased formation of hydroxyl radical, the most reactive molecule of all oxygen radicals (Chan, 2001). These reactive oxygen species (ROS) can contribute to the DNA strand breakage, which is followed by overactivation of poly(ADP-ribose) polymerase-1 (PARP-1; EC 2.4.2.30) (Szabo and Dawson, 1998;Pieper et al., 1999).PARP-1 is an abundant nuclear protein which is activated Article, publication date, and citation information can be found at

Neuroprotection for ischemic stroke: Past, present and future

“…Early pre-clinical reports described salutary effects in both global and focal cerebral ischemia (Watanabe et al, 1994). In a rat modelf of transient (1-h) MCA occlusion, edaravone reduced infarct volume when administered prior to the insult but failed to protect when started at 1-2 hours after onset of ischemia (Nakajima et al, 2005). Another study reported ~30% reduction of total infarct volume in rats with 2-h MCA occlusion treated at the onset of reperfusion (Amemiya et al, 2005).…”

Endonuclease G does not play an obligatory role in poly(ADP-ribose) polymerase-dependent cell death after transient focal cerebral ischemia

“…Several studies have shown that administration of various PARP inhibitors decreases infarct volume at 1 day after MCAO (1,15,16,21). However, continued inflammatory processes beyond 1 day could negate the short-term benefit.…”

“…DR2313 (Alexis, Lausen, Switzerland) was dissolved in sterile saline at a final concentration of 10 mg/ml. The dosing regimen was based on that used by others (16) to achieve a pharmacologically active brain concentration: bolus injection of 1 ml/kg body wt 5 min before the onset of MCAO and again 5 min before reperfusion (85 min of MCAO); continuous infusion of 1 ml·kg Ϫ1 ·h Ϫ1 throughout the 90 min of MCAO and the first 4.5 h of reperfusion. Control cohorts received the same volume of saline as the drug-treated cohorts.…”

“…Intravenous infusion of the PARP inhibitor DR2313 (2-methyl-3,5,7,8-tetrahydrothiopyrano [4,3-d]pyrimidine-4-one) has been reported to decrease infarct volume after MCAO (16). In subsets of male WT and EndoG Ϫ/Ϫ mice, a catheter was placed into the right jugular vein and exited through a small incision in the back.…”

Neuroprotective effects of NU1025, a PARP inhibitor in cerebral ischemia are mediated through reduction in NAD depletion and DNA fragmentation

“…Recent evidence also suggest the role of PARP in regulation of matrix metalloproteinase Life Sciences 79 (2006) 2293 -2302 www.elsevier.com/locate/lifescie activity and nuclear translocation of apoptosis inducing factor (AIF) in cerebral ischemia (Koh et al, 2005;Komjati et al, 2005;Komjati et al, 2004). Accumulating evidence implicate the role of PARP overactivation in cerebral IR injury (Chiarugi, 2005;Ikeda et al, 2005;Kamanaka et al, 2004;Koh et al, 2004;Nakajima et al, 2004). Neuroprotective potential of PARP inhibitors such as nicotinamide; 3-aminobenzamide; 4-amino-1, 8-napthalimide; 1, 5 isoquinolinediol have been demonstrated in cerebral IR injury (Gupta et al, 2004;Kabra et al, 2004;Koh et al, 2005;Sharma et al, 2004).…”