Poly(ADP-ribose) polymerase-1 (PARP-1 1 ; EC 2.4.2.30) is an abundant nuclear protein that is activated by DNA strand breakage and that catalyzes the covalent attachment of poly-(ADP-ribose) (PAR) from NAD ϩ to numerous nuclear proteins and transcription factors, including histones; DNA polymerase ␣ and ␤; p53; and PARP-1, itself being the major target, via its automodification domain (1, 2). Besides PARP-1, another six PARPs have been identified: short PARP, PARP-2, PARP-3, tankylase-1/2, and vault PARP (2, 3). However, the physiological roles of poly(ADP-ribosyl)ation of nuclear proteins and transcription factors induced by PARPs are not completely understood. The initially identified subtype of the enzyme, PARP-1, has been thought to play a central role in the process of poly(ADP-ribosyl)ation because poly(ADP-ribosyl)ation is markedly reduced in most tissues of PARP-1 null mice (4). Transient poly(ADP-ribosyl)ation by PARP-1 can be induced by a wide variety of environmental stimuli, including reactive oxygen, ionizing radiation, and genotoxic stress (1, 2). Thus, PARP-1 has been suggested to regulate DNA repair (5). On the other hand, overactivation of PARP-1 by massively damaged DNA consumes NAD ϩ and consequently ATP, resulting in necrotic cell death by energy failure (3, 6).There are many reports suggesting that PARP-1 is also involved in regulation of gene expression at the transcriptional step (2, 3). PARP-1 seems to play dual roles in transcription. Poly(ADP-ribosyl)ation of transcription factors such as YinYang 1 (7), RNA polymerase II-associated factors (8), and p53 (9) results in reversible silencing of transcription by impairing the DNA binding of these proteins. In other instances, PARP-1 was found to have only one function, stimulating the DNA binding activity of transcription factors such as Oct-1 (10) and B-Myb (11). Recent reports have also shown that PARP-1 is required for specific nuclear factor-B (NF-B)-dependent gene expression and acts as a coactivator for 14). Indeed, the NF-B-dependent transcription of some inflammatory mediators in response to endotoxin (13) or pro-inflammatory cytokines such as tumor necrosis factor-␣ (TNF-␣) and interleukin-1␤ (IL-1␤) (12-14) is almost completely abrogated in PARP-1 null mice. Thus, anti-inflammatory effects of PARP-1 inhibitors have been extensively discussed in relation to various inflammation-related diseases (15, 16). However, the exact biochemical mechanism by which PARP-1 regulates NF-B-dependent transcription is obscure. To date, some groups have reported that the enzyme activity of PARP-1 might directly influence NF-B-dependent transcription. Kameoka et al. (17) showed that poly(ADP-ribosyl)ation markedly suppresses the DNA binding activity of NF-B via direct modification in vitro. demonstrated that the DNA binding activity of NF-B p50 is NAD ϩ -dependent and reversibly regulated by the automodification of PARP-1 under cell-free conditions. In contrast, Hassa et al. (14) concluded that neither the enzyme activity nor the DNA binding

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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

These data suggest that the H3 agonists may have anxiolytic-like effects similar to those of selective serotonin reuptake inhibitors but not benzodiazepine anxiolytics and represent a novel strategy for the treatment of some anxiety disorders in which selective serotonin reuptake inhibitors are prescribed.

As a part of our search for novel histamine H3 receptor agonists, we designed and synthesized hybrid compounds in which the lipophilic (4'-alkylphenylthio)ethyl moiety of a novel H3 receptor agonist, 4-(2-(4'-tert-butylphenylthio)ethyl)-1H-imidazole (1), was incorporated into N(alpha)-methylhistamine, immepip, and immethridine derivatives. These hybrid compounds were expected to interact concurrently with the histamine-binding site and a putative hydrophobic region in the H3 receptor. Among them, piperidine- and pyridine-type derivatives displayed partial agonist activity, and (S)-4-(1-(1H-imidazol-4-yl)-2-(4-(trifluoromethyl)phenylthio)ethyl)piperidine (36) was identified as a potent H3 agonist. We performed computational docking studies to examine the binding mode of the agonists. The results indicated that immepip interacts with the key residues, Asp114 and Glu206, in a different manner from histamine. The binding mode of 36 to these residues is similar to that of immepip, and the lipophilic tail of 36 has an additional interaction with a hydrophobic region in transmembrane helix 6 of the receptor. These results indicated that 36 served as a useful tool for studies on receptor-agonist interactions and drug design.