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Biomedical subjects

Akinori Iwashita

Publications and source records attributed to Akinori Iwashita.

At least 19 recordsLinked to original sources
PubMed2006

Neuroprotective efficacy of the peroxisome proliferator-activated receptor delta-selective agonists in vitro and in vivo.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily and function as ligand-modulated transcription factors that regulate gene expression in many important biological processes. The PPARdelta subtype has the highest expression in the brain and is postulated to play a major role in neuronal cell function; however, the precise physiological roles of this receptor remain to be elucidated. Herein, we show that the high-affinity PPARdelta agonists L-165041 [4-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-propoxyl]phenoxy]-acetic acid] and GW501516 [2-methyl4-((4-methyl-2-(4-trifluoromethylphenyl)-1,3-triazol-5-yl)-methylsulfanyl)phenoxy acetic acid] protect against cytotoxin-induced SH-SY5Y cell injury in vitro and both ischemic brain injury and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in vivo. In the SH-SY5Y studies, treatment with L-165041 or GW501516 significantly and concentration-dependently attenuated cell death following thapsigargin, 1-methyl-4-phenylpyridinium, or staurosporine exposure, with the extent of damage correlated with the level of caspase-3 inhibition. In the transient (90 min) middle cerebral artery occlusion model of ischemic brain injury in rats, i.c.v. infusion of L-165041 or GW501516 significantly attenuated the ischemic brain damage measured 24 h after reperfusion. Moreover, the PPARdelta agonists also significantly attenuated MPTP-induced depletion of striatal dopamine and related metabolite contents in mouse brain. These results demonstrate that subtype-selective PPARdelta agonists possess antiapoptotic properties in vitro, which may underlie their potential neuroprotective potential in in vivo experimental models of cerebral ischemia and Parkinson's disease (PD). These findings suggest that PPARdelta agonists could be useful tools for understanding the role of PPARdelta in other neurodegenerative disorders, as well as attractive therapeutic candidates for stroke and neurodegenerative diseases such as PD.

Acetates↗
PubMed2006

Jumbo biopsy is useful for the diagnosis of colonic prolapsing mucosal polyps with diverticulosis.

We report here a case of multiple prolapsing mucosal polyps with diverticulosis in the sigmoid colon. A 52-year-old man was admitted to our hospital because of bloody diarrhea. Colonoscopy and barium enema showed multiple diverticula, markedly thickened mucosal folds and polypoid lesions with mucus on the top of them in the sigmoid colon. Endoscopic ultrasonography showed thickening of the mucosal and submucosal layers. Several endoscopic biopsy specimens were taken from the polypoid lesions. Histological examination revealed only chronic inflammatory cell infiltration. In order to obtain a definite diagnosis, we performed endoscopic jumbo biopsy for the polypoid lesions after obtaining informed consent. Histological examination revealed marked lymphocyte infiltration, hemosiderin deposits and fibromuscular obliteration in the lamina propria, features similar to those of mucosal prolapsing syndrome. After anti-diarrhetic treatment, clinical findings were improved. Thus, jumbo biopsy is useful for diagnosis and treatment of prolapsing mucosal polyps.

Biopsy↗
PubMed2005

Discovery of potent and selective PARP-1 and PARP-2 inhibitors: SBDD analysis via a combination of X-ray structural study and homology modeling.

We disclose herein our efforts aimed at discovery of selective PARP-1 and PARP-2 inhibitors. We have recently discovered several novel classes of quinazolinones, quinazolidinones, and quinoxalines as potent PARP-1 inhibitors, which may represent attractive therapeutic candidates. In PARP enzyme assays using recombinant PARP-1 and PARP-2, the quinazolinone derivatives displayed relatively high selectivity for PARP-1 and quinoxaline derivatives showed superior selectivity for PARP-2, and the quinazolidinone derivatives did not have selectivity for PARP-1/2. Structure-based drug design analysis via a combination of X-ray structural study utilizing the complexes of inhibitors and human PARP-1 catalytic domain, and homology modeling using murine PARP-2 suggested distinct interactions of inhibitors with PARP-1 and PARP-2. These findings provide a new structural framework for the design of selective inhibitors for PARP-1 and PARP-2.

Binding Sites↗
PubMed2005

4-Phenyl-1,2,3,6-tetrahydropyridine, an excellent fragment to improve the potency of PARP-1 inhibitors.

We have shown that a 4-phenyl-1,2,3,6-tetrahydropyridine fragment plays an important role in improving inhibitory potency against poly(ADP-ribose) polymerase-1 (PARP-1). Various benzamide analogues linked with this fragment via alkyl spacers have been prepared and evaluated. As a result, some of them have been found to be highly potent PARP-1 inhibitors.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2005

Identification of a ring chromosome with spectral karyotyping in a pleural synovial sarcoma.

The origin of a ring chromosome in a monophasic synovial sarcoma of the diaphragmatic pleura of an 18-year-old man was investigated using spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). Conventional cytogenetic analysis revealed the following clonal karyotypic abnormalities: 47,Y,t(X;18)(p11.2;q11.2),t(11;19)(q12;q13.4),+12,-13,+r[6]. The SYT-SSX1 fusion transcript was detected with reverse transcriptase-polymerase chain reaction analysis. SKY analysis suggested that the ring chromosome was composed of material from chromosome 8. Subsequent FISH analysis with a whole-chromosome 8 paint probe confirmed the SKY results. This study demonstrates the usefulness of SKY as an adjunct for determining the chromosomal composition of ring chromosomes.

Adolescent↗
PubMed2005

Discovery of quinazolinone and quinoxaline derivatives as potent and selective poly(ADP-ribose) polymerase-1/2 inhibitors.

Two classes of quinazolinone derivatives and quinoxaline derivatives were identified as potent and selective poly(ADP-ribose) polymerase-1 and 2 (PARP-1) and (PARP-2) inhibitors, respectively. In PARP enzyme assays using recombinant PARP-1 and PARP-2, quinazolinone derivatives displayed relatively high selectivity for PARP-1 and quinoxaline derivatives showed superior selectivity for PARP-2. SBDD analysis via a combination of X-ray structural study and homology modeling suggested distinct interactions of inhibitors with PARP-1 and PARP-2. These findings provide a new structural framework for the design of selective inhibitors for PARP-1 and PARP-2.

Crystallography, X-Ray↗
PubMed2005

Deep infiltrative low-grade MALT (mucosal-associated lymphoid tissue) colonic lymphomas that regressed as a result of antibiotic administration: endoscopic ultrasound evaluation.

Since 1997 we have experienced three cases of low-grade colonic mucosal-associated lymphoid tissue (MALT) lymphomas. The depth of tumor invasion was evaluated by endoscopic ultrasonography (EUS) and the mass lesions were all diagnosed as having extended beyond the deep region of the submucosal layer. Although all of these patients tested negative for gastric Helicobacter pylori, their tumor lesions regressed after antibiotic treatment in accordance with H. pylori eradication therapy. In general, consensus has been reached regarding antibiotic therapy for gastric MALT lymphomas. However, as a prerequisite for antibiotic therapy, the therapy has been deemed effective against these gastric tumors if the extent of infiltration, as evaluated by EUS, is limited to the mucosal layer or the superficial region of the submucosal layer. Based on the therapeutic outcomes seen in the three patients studied here, it is suggested that antibiotic therapy might be useful in treating MALT lymphomas of the colon, even in patients with advanced invasive tumors, in contrast to the extent of the lesions in the stomach suitable for antibiotic treatment. The success of the antibiotic treatment also suggests that MALT lymphomas may be caused by unknown luminal microorganisms, other than H. pylori.

Aged↗
PubMed2005

A clinicopathological investigation of "tumor nodules" in colorectal cancer.

PURPOSE: Tumor nodules (tn) have been histologically identified within the fatty tissue or the detached fatty tissue around dissected lymph nodes, or else picked up as lymph nodes from resected specimens with no lymph node components. The TNM classification of malignant tumors provides a description of how to deal with tn, but there has so far been no description within the Japanese classification of colorectal carcinoma. The aim of this study was to determine whether we should regard tn as metastatic lymph nodes from the viewpoint of prognosis. METHODS: A total of 544 patients who underwent a resection of colorectal adenocarcinoma between 1985 and 1995 were reviewed. RESULTS: Tumor nodules were found in 54 (17.6%) of 307 colon cancer patients, and in 41 (17.3%) of 237 rectal cancer patients. We classified the curability A patients into four groups for both colon and rectal cancer; positive lymph nodes with tn (Group A), negative lymph nodes with tn (Group B), positive lymph nodes without tn (Group C), and negative lymph nodes without tn (Group D). The prognosis was not significantly different between Groups A, B, and C, but it was significantly different between Group D and Groups A, B, and C (P < 0.01) in both the colon and the rectum. CONCLUSION: From the viewpoint of prognosis, it thus appears justifiable to regard tn as lymph node metastasis.

Adenocarcinoma↗
PubMed2005

Novel zoom endoscopy technique for visualizing the microvascular architecture in gastric mucosa.

We have developed and established a zoom endoscopy technique based on visualization of the mucosal microvascular architecture in units as small as the capillary in the normal stomach and early gastric cancer. With regard to the microvascular architecture of the normal stomach, the findings differed according to the section of the stomach. The gastric body showed a honeycomb-like subepithelial capillary network pattern with collecting venule, whereas the gastric antrum showed a coil-shaped subepithelial capillary network pattern. Regarding early gastric cancer, the following findings seemed to be specific for differentiated carcinoma: (1) a demarcation line between the cancerous and the noncancerous mucosa, (2) the disappearance of the regular subepithelial capillary network pattern, and (3) the presence of an irregular microvascular pattern. These findings, which were visualized by magnified observation, could be useful in clinical practice when we attempt to make a correct endoscopic diagnosis of flat reddened lesions (gastritis vs cancer) and when we attempt to determine the precise horizontal margin of early gastric cancer. This could help us to perform successful endoscopic resection based on endoscopic findings alone. In conclusion, our zoom endoscopy for visualizing the microvascular architecture in gastric mucosa could be a new system for diagnosing early gastric cancer.

Diagnosis, Differential↗
PubMed2005

[Histopathology of ulcerative colitis in biopsy].

For histologic diagnosis on biopsy specimens, we gave an outline of macroscopic and microscopic features of ulcerative colitis (UC), including differential diagnosis. The most important histologic features on biopsy are dense mixed inflammatory infiltrate in the lamina propria mucosae, mucosal architectural abnormality, and vascular change. Evidence of colorectal adenocarcinoma, dysplasia, and cytomegalovirus infection should also be taken into account. Although diagnostic criteria for UC are well understood, the biopsy diagnosis of UC is comparatively difficult. Thus the diagnosis of UC should be made mainly by clinical pictures, course of the illness, and radiological and endoscopic pictures.

Biopsy↗
PubMed2004

Pharmacological characterization of FR194921, a new potent, selective, and orally active antagonist for central adenosine A1 receptors.

Adenosine A1 receptors in the brain are believed to play an important role in brain functioning. We have discovered a novel adenosine A1 receptor antagonist, FR194921 (2-(1-methyl-4-piperidinyl)-6-(2-phenylpyrazolo[1,5-a]pyridin-3-yl)-3(2H)-pyridazinone), and characterized the pharmacological activity in the present study. FR194921 showed potent and selective affinity for the adenosine A1 receptor without affinity for A2A and A3 receptors and did not show any species differences in binding affinity profile among human, rat, and mouse. Pharmacokinetic study in rats revealed that FR194921 was orally active and highly brain penetrable. Oral administration of FR194921 dose-dependently ameliorated the hypolocomotion induced by the A1 receptor agonist N6-cyclopentyladenosine in rats, indicating this compound exerts A1-antagonistic action in vivo. In the passive avoidance test, scopolamine (1 mg/kg)-induced memory deficits were significantly ameliorated by FR194921 (0.32, 1 mg/kg). In two animal models of anxiety, the social interaction test and elevated plus maze, FR194921 showed specific anxiolytic activity without significantly influencing general behavior. In contrast, FR194921 did not show antidepressant activity even at a dose of 32 mg/kg in the rat forced swimming test. These results indicate that the novel, potent, and selective adenosine A1 receptor antagonist FR194921 exerts both cognitive-enhancing and anxiolytic activity, suggesting the therapeutic potential of this compound for dementia and anxiety disorders.

Adenosine↗
PubMed2004

Rational approaches to discovery of orally active and brain-penetrable quinazolinone inhibitors of poly(ADP-ribose)polymerase.

A novel class of quinazolinone derivatives as potent poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors has been discovered. Key to success was application of a rational discovery strategy involving structure-based design, combinatorial chemistry, and classical SAR for improvement of potency and bioavailability. The new inhibitors were shown to bind to the nicotinamide-ribose binding site (NI site) and the adenosine-ribose binding site (AD site) of NAD+.

Administration, Oral↗
PubMed2004

A new poly(ADP-ribose) polymerase inhibitor, FR261529 [2-(4-chlorophenyl)-5-quinoxalinecarboxamide], ameliorates methamphetamine-induced dopaminergic neurotoxicity in mice.

Methamphetamine (METH) administration in mice, results in a chronic dopamine (DA) depletion associated with nerve terminal damage, with DA oxidation and generation of reactive oxygen species (ROS) primarily mediating this neurotoxicity. The oxidative stress induced by METH putatively activates nuclear enzyme poly(ADP-ribose) polymerase (PARP), with excessive PARP activation eventually leading to cell death. In this study, we show that prevention of PARP activation by treatment with FR261529 [2-(4-chlorophenyl)-5-quinoxalinecarboxamide], the compound that was recently identified as a novel PARP inhibitor (IC50 for PARP-1 = 33 nM, IC50 for PARP-2 = 7 nM), protects against both ROS-induced cells injury in vitro and METH-induced dopaminergic neuronal damage in an in vivo Parkinson's disease (PD) model. In PC12 cells, exposure of hydrogen peroxide or METH markedly induced PARP activation, and treatment with FR261529 (1 microM) significantly reduced PARP activation and attenuated cell death. In the mouse METH model, METH (15 mg/kg x 2 i.p., 2 h apart) intoxication accelerated DA metabolism and oxidation in the striatum, with subsequent cell damage in nigrostriatal dopaminergic neurons after 4 days. Oral administration of FR261529 (10 or 32 mg/kg) attenuated the damage of dopaminergic neurons via marked reduction of PARP activity and not via changes in dopamine metabolism or body temperature. These findings indicate that the neuroprotective effects of a novel PARP inhibitor, FR261529, were accompanied by inhibition of METH-induced PARP activation, suggesting that METH induces nigrostriatal dopaminergic neurodegeneration involving PARP activation and also orally active and brain-penetrable PARP inhibitor FR261529 could be a novel attractive therapeutic candidate for neurodegenerative disorders such as PD.

Animals↗
PubMed2004

A novel and potent poly(ADP-ribose) polymerase-1 inhibitor, FR247304 (5-chloro-2-[3-(4-phenyl-3,6-dihydro-1(2H)-pyridinyl)propyl]-4(3H)-quinazolinone), attenuates neuronal damage in in vitro and in vivo models of cerebral ischemia.

The activation of poly(ADP-ribose) polymerase-1 (PARP-1) after exposure to nitric oxide or oxygen-free radicals can lead to cell injury via severe, irreversible depletion of NAD. Genetic deletion or pharmacological inhibition of PARP-1 attenuates brain injury after focal ischemia and neurotoxicity in several neurodegenerative models in animals. FR247304 (5-chloro-2-[3-(4-phenyl-3,6-dihydro-1(2H)-pyridinyl)propyl]-4(3H)-quinazolinone) is a novel PARP-1 inhibitor that has recently been identified through structure-based drug design. In an enzyme kinetic analysis, FR247304 exhibits potent and competitive inhibition of PARP-1 activity, with a K(i) value of 35 nM. Here, we show that prevention of PARP activation by FR247304 treatment protects against both reactive oxygen species-induced PC12 cell injury in vitro and ischemic brain injury in vivo. In cell death model, treatment with FR247304 (10(-8)-10(-5) M) significantly reduced NAD depletion by PARP-1 inhibition and attenuated cell death after hydrogen peroxide (100 microM) exposure. After 90 min of middle cerebral artery occlusion in rats, poly(ADP-ribosy)lation and NAD depletion were markedly increased in the cortex and striatum from 1 h after reperfusion. The increased poly(ADP-ribose) immunoreactivity and NAD depletion were attenuated by FR247304 (32 mg/kg i.p.) treatment, and FR247304 significantly decreased ischemic brain damage measured at 24 h after reperfusion. Whereas other PARP inhibitors such as 3-aminobenzamide and PJ34 [N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylactamide] showed similar neuroprotective actions, they were less potent in in vitro assays and less efficacious in an in vivo model compared with FR247304. These results indicate that the novel PARP-1 inhibitor FR247304 exerts its neuroprotective efficacy in in vitro and in vivo experimental models of cerebral ischemia via potent PARP-1 inhibition and also suggest that FR247304 or its derivatives could be attractive therapeutic candidates for stroke and neurodegenerative disease.

Animals↗
PubMed2004

Neuroprotective effects of a novel poly(ADP-ribose) polymerase-1 inhibitor, 2-[3-[4-(4-chlorophenyl)-1-piperazinyl] propyl]-4(3H)-quinazolinone (FR255595), in an in vitro model of cell death and in mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease.

The massive activation of poly(ADP-ribose) polymerase-1 (PARP-1) by DNA-damaging stimuli, such as exposure to reactive oxygen species (ROS), can lead to cell injury via severe, irreversible depletion of the NAD and ATP pool, and PARP-1 inhibitors have been expected to rescue neurons from degeneration in a number of disease models. We have recently identified 2-[3-[4-(4-chlorophenyl)-1-piperazinyl] propyl]-4(3H)-quinazolinone (FR255595) as a novel and potent PARP-1 inhibitor through structure-based drug design and high-throughput screening. This compound potently inhibited PARP activity with an IC(50) value of 11 nM and was orally active and highly brain penetrable. Here, we show that prevention of PARP activation by FR255595 protects against both ROS-induced cells injury in vitro and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigrostriatal dopaminergic damage in an in vivo Parkinson's disease (PD) model. In cell death models in vitro, exposure of hydrogen peroxide induced cell death with PARP overactivation in PC12 cells and SH-SY5Y cells, and pre- and post-treatment with FR255595 (10(-9)-10(-5) M) significantly reduced PARP activation and cell death. In mouse MPTP model, MPTP (20 mg/kg i.p.) intoxication lead to PARP activation and cell damage in the nigrostriatal dopaminergic pathway, which was significantly ameliorated by oral administration of FR255595 (10-32 mg/kg), both in the substantia nigra and in the striatum via marked reduction of PARP activation, even with delayed treatment. These findings clearly indicate that the novel PARP-1 inhibitor FR255595 exerts neuroprotective effect through its potent PARP-1 inhibitory actions in PD model, suggesting that the drug could be an attractive candidate for several neurodegenerative disorders, including PD.

Animals↗