Ryoichi Nagata

Extracellular high mobility group box chromosomal protein 1 is a coupling factor for hypoxia and inflammation in arthritis

OBJECTIVE Tissue hypoxia is closely associated with arthritis pathogenesis, and extracellular high mobility group box chromosomal protein 1 (HMGB-1) released from injured cells also has a role in arthritis development. This study was thus undertaken to investigate the hypothesis that extracellular HMGB-1 may be a coupling factor between hypoxia and inflammation in arthritis. METHODS Concentrations of tumor necrosis factor alpha, interleukin-6, vascular endothelial growth factor, lactic acid, lactate dehydrogenase, and HMGB-1 were measured in synovial fluid (SF) samples from patients with inflammatory arthropathy (rheumatoid arthritis and pseudogout) and patients with noninflammatory arthropathy (osteoarthritis). The localization of tissue hypoxia and HMGB-1 was also examined in animal models of collagen-induced arthritis (CIA). In cell-based experiments, the effects of hypoxia on HMGB-1 release and its associated cellular events (i.e., protein distribution and cell viability) were studied. RESULTS In SF samples from patients with HMGB-1-associated inflammatory arthropathy (i.e., samples with HMGB-1 levels >2 SD above the mean level in samples from patients with noninflammatory arthropathy), concentrations of HMGB-1 were significantly correlated with those of lactic acid, a marker of tissue hypoxia. In CIA models in which the pathologic phenotype could be attenuated by HMGB-1 neutralization, colocalization of HMGB-1 with tissue hypoxia in arthritis lesions was also observed. In cell-based experiments, hypoxia induced significantly increased levels of extracellular HMGB-1 by the cellular processes of secretion and/or apoptosis-associated release, which was much more prominent than the protein release in necrotic cell injury potentiated by oxidative stress. CONCLUSION These findings indicate that tissue hypoxia and its resultant extracellular HMGB-1 might play an important role in the development of arthritis.

CYP2C76, a Novel Cytochrome P450 in Cynomolgus Monkey, Is a Major CYP2C in Liver, Metabolizing Tolbutamide and Testosterone

Monkeys are widely used as a primate model to study drug metabolism because they generally show a metabolic pattern similar to humans. However, the paucity of information on cytochrome P450 (P450) genes has hampered a deep understanding of drug metabolism in the monkey. In this study, we report identification of the CYP2C76 cDNA newly identified in cynomolgus monkey and characterization of this CYP2C along with cynomolgus CYP2C20, CYP2C43, and CYP2C75. The CYP2C76 cDNA contains the open reading frame encoding a protein of 489 amino acids that are only approximately 80% identical to any human or monkey P450 cDNAs. Gene and protein expression of CYP2C76 was confirmed in the liver of cynomolgus and rhesus monkeys but not in humans or the great apes. Moreover, CYP2C76 is located at the end of the CYP2C gene cluster in the monkey genome, the region of which corresponds to the intergenic region adjacent to the CYP2C cluster in the human genome, strongly indicating that this gene does not have the ortholog in humans. Among the four CYP2C genes expressing predominantly in the liver, the expression level of CYP2C76 was the greatest, suggesting that CYP2C76 is a major CYP2C in the monkey liver. Assays for the capacity of CYP2C76 to metabolize drugs using several substrates typical for human CYP2Cs revealed that CYP2C76 showed unique metabolic activity. These results suggest that CYP2C76 contributes to overall drug-metabolizing activity in the monkey liver and might account for species difference occasionally seen in drug metabolism between monkeys and humans.

Experimental thromboembolic stroke in cynomolgus monkey

To develop an experimental model of thromboembolic stroke without intracranial surgery, an autologous blood clot was delivered to the middle cerebral artery (MCA) via the internal carotid artery in cynomolgus monkeys. Male cynomolgus monkeys, in which a chronic catheter had been earlier implanted in the left internal carotid artery, were used. The clot was flushed into the internal carotid artery under sevofluorane anesthesia. A neurologic deficit score was assigned after MCA embolization. After 24 h, cerebral infarct size and location were determined by the TTC staining method. Cerebral blood flow (CBF) was measured prior to and after MCA embolization, using positron emission tomography (PET). After embolization, long-lasting and profound extensor hypotonia of the contralateral upper and lower limbs, and mild to severe incoordination were observed. Contralateral hemiplegia was observed over the following 24 h. In gross morphologic observation of the brain, the lesions involved mostly the caudate nucleus, putamen, globus pallidus and insular cortex. CBF was maximally reduced in the left MCA territory, but not in the right MCA territory. This model is relevant to thromboembolic stroke in human in neurologic dysfunction and histopathologic brain damage.

Genetic variants of CYP3A4 and CYP3A5 in cynomolgus and rhesus macaques.

Cynomolgus and rhesus macaques are frequently used in preclinical trials due to their close evolutionary relationships to humans. We conducted an initial screening for genetic variants in cynomolgus and rhesus macaque genes orthologous to human CYP3A4 and CYP3A5. Genetic screening of 78 Indochinese and Indonesian cynomolgus macaques and 34 Chinese rhesus macaques revealed a combined total of 42 CYP3A4 genetic variants, including 12 nonsynonymous variants, and 34 CYP3A5 genetic variants, including nine nonsynonymous variants. Four of these nonsynonymous variants were located at substrate recognition sites or the heme-binding region, domains essential for protein function, including c.886G>A (V296M) and c.1310G>A (S437N) in CYP3A4 and c.1437C>G (N479K) and c.1310G>C (T437S) in CYP3A5. The mutant proteins of these genetic variants were expressed in Escherichia coli and purified. Metabolic activity of these proteins measured using midazolam and nifedipine as substrates showed that none of these protein variants substantially influences the drug-metabolizing capacity of CYP3A4 or CYP3A5 protein. In Indonesian cynomolgus macaques, we also found IVS3+1delG in CYP3A4 and c.625A>T in CYP3A5, with which an intact protein cannot be produced due to a frameshift generated. Screening additional genomes revealed that two of 239 animals and three of 258 animals were heterozygous for IVS3+1delG of CYP3A4 and c.625A>T of CYP3A5, respectively. Some genetic variants were unevenly distributed between Indochinese and Indonesian cynomolgus macaques and between cynomolgus and rhesus macaques. Information on genetic diversity of macaque CYP3A4 and CYP3A5 presented here could be useful for successful drug metabolism studies conducted in macaques.

Microminipig, a Non-rodent Experimental Animal Optimized for Life Science Research: Novel Atherosclerosis Model Induced by High Fat and Cholesterol Diet

Atherosclerotic lesions were observed in male and ovariectomized female Microminipig (MMP) fed a high fat and cholesterol diet with sodium cholate (HFCD/SC) for 3 months. HFCD/SC induced hypercholesterolemia accompanied by an increase in serum total cholesterol (T-Cho), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and cholesterol ester (CE). Unlike the mouse or rabbit, a dominant LDL-C fraction in the intact MMP, similar to that in humans, was observed by serum lipoprotein analysis. HFCD/SC increased body weight gain. At the end of the experiment, computed tomography scans of conscious animals showed that HFCD/SC had decreased liver attenuation values (Hounsfield unit) and increased subcutaneous and abdominal fat, suggesting the induction of fatty liver and obesity. HFCD/SC induced atherosclerotic lesions in systemic arteries, including the external and internal iliac arteries, abdominal aorta, coronary artery, and cerebral arterial circle. Atherosclerosis and pathological findings induced by HFCD/SC in MMP were similar to those in humans. The MMP is a potentially suitable tool for investigating human atherosclerosis.

Effects of ropinirole on various parkinsonian models in mice, rats, and cynomolgus monkeys.

Ropinirole (4-[2-(dipropylamino)ethyl]-2-indolinone monohydrochloride) a nonergoline dopamine receptor agonist with high affinity for native dopamine D(2)-like receptors in human caudate tissue, was tested with respect to the stimulation of postsynaptic brain dopamine receptors in standard preclinical models of Parkinsons disease. Additionally, in these animal models the antiparkinsonian activity of ropinirole was compared to that of bromocriptine. The ED(50)s (95% confidence limits) of ropinirole and bromocriptine on the turning behavior in 6-OHDA-lesioned rats were 20.17 mg/kg (14.27-26.88 mg/kg) and 11.99 mg/kg (9.37-14.17 mg/kg), respectively. The ED(50)s (95% confidence limits) of ropinirole and bromocriptine on the catalepsy induced by reserpine were 18.55 mg/kg (15.29-22.99 mg/kg) and 12.56 mg/kg (10.25-14.64 mg/kg), respectively. Ropinirole and bromocriptine had no effect on the tremors induced by oxotremorine in mice, whereas atropine markedly suppressed the tremors. The ED(50)s (95% confidence limits) of ropinirole and bromocriptine on the tremors in VMT-lesioned monkeys were 0.18 mg/kg (0.12-0.29 mg/kg) and 2.63 mg/kg (1.06-6.45 mg/kg), respectively. In rodent parkinsonian models, bromocriptine was more potent than ropinirole; however, in the nonhuman primate parkinsonian model, ropinirole was a more potent inhibitor of parkinsonian activity than bromocriptine. This study suggests that ropinirole is a dopamine D(2)-like receptor agonistic drug of potential use in the treatment of Parkinsons disease.

A Null Allele Impairs Function of CYP2C76 Gene in Cynomolgus Monkeys: A Possible Genetic Tool for Generation of a Better Animal Model in Drug Metabolism

The monkey CYP2C76 gene does not correspond to any of the human CYP2C genes, and its enzyme is at least partly responsible for the species difference occasionally seen in drug metabolism between monkeys and humans. To establish a line and/or lines of monkeys that are expected to show metabolic patterns highly similar to humans, we set out to find monkeys that lacked CYP2C76 activity. By genetic screening of 73 monkeys and a database search of expressed sequence tags, we found a total of 10 nonsynonymous genetic variants in the coding region of CYP2C76, including a null genotype (c.449TG>A). Some of the variants were differently distributed between two animal groups originating from different geographical regions (Indochina and Indonesia). After screening 170 additional genomic samples, we identified a total of eight animals (six males and two females) that were heterozygous for c.449TG>A, which could be used for establishing a homozygous line. If the homozygotes show drug-metabolizing properties more similar to humans than wild-type monkeys, the homozygotes may serve as a better animal model for drug metabolism. The data presented in this article provide the essential genetic information to perform a successful study by using cynomolgus monkeys and present a possible tool to generate a better animal model for drug metabolism.

CYP2C76-mediated species difference in drug metabolism: A comparison of pitavastatin metabolism between monkeys and humans

The monkey is often used to predict metabolism of drugs in humans since it generally shows a metabolic pattern similar to humans. However, metabolic profiles different from humans are occasionally seen in monkeys for some drugs including pitavastatin. Recently, we have successfully identified a monkey-specific cytochrome P450 (CYP) 2C76, which possibly accounts for a species difference between monkeys and humans because of its sequence and functional uniqueness. The present study on the role of CYP2C76 and other monkey CYP2Cs in pitavastatin metabolism, as an example, has revealed that CYP2C76 is important for the metabolism of the lactone form, indicating a major role of CYP2C76 for the difference in the metabolism of pitavastatin and possibly other drugs between monkeys and humans. The current investigation on the involvement of CYP2C76 in the metabolism of other drugs is expected to reveal further the further importance of this monkey-specific drug-metabolizing enzyme.

Molecular Cloning and Functional Analysis of Cynomolgus Monkey CYP1A2

Complementary DNA fragments encoding cynomolgus monkey CYP1A2 were amplified by the reverse transcriptase-polymerase chain reaction (RT-PCR) method from the liver total RNA of a 3-methylcholanthrene (3-MC)-treated cynomolgus monkey. The nucleotide sequence determined was 1630 bp long and contained an open reading frame for a polypeptide of 516 residues. The nucleotide and the deduced amino acid sequences of cynomolgus monkey CYP1A2 showed 95.1 and 92.8% identities to those of human CYP1A2, respectively. The level of CYP1A2 mRNA in the liver of untreated cynomolgus monkey was very low. Treatment with 3-MC increased it. Still, it was one-fortieth that of CYP1A1. Cynomolgus monkey CYP1A2 expressed in recombinant yeasts activated 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,8dimethylimidazo[4,5-flquinoxaline (MeIQx) at efficient rates in the umu mutagenicity test. This cytochrome P450 (CYP) also activated 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), but less efficiently. These results indicate that cynomolgus monkeys have a functionally active CYPIA2 gene, but its expression level is very low in the liver of untreated cynomolgus monkeys.

Effect of low-dose 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on influenza A virus-induced mortality in mice

Dioxins, including the most toxic congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), exert diverse biological effects in humans and animals. Host resistance, especially to virus infections, is considered one of the most sensitive targets of TCDD-toxicity, while a recent study showed that the vulnerability to TCDD of host resistance to viruses varied form experiment to experiment. Burleson et al. [Fundam. Appl. Toxicol. 29 (1996) 40] reported that a single oral dose as low as 10 ng TCDD/kg increased the mortality of mice infected with influenza A virus. If this value had been adopted as the basis for the tolerable daily intake (TDI) of dioxins, the TDI of 1-4 pg toxic equivalent (TEQ)/kg per day recommended by WHO would have to be lower. In the present study, we used the same experimental protocol described by Burleson et al. to determine whether low-dose TCDD consistently compromises the host resistance of mice infected with influenza A virus. To do so, we investigated the effect of TCDD in the dose range of 0-500 ng/kg on the mortality of virus-infected female B6C3F1 mice. We also investigated the sex- and strain-dependency of host resistance in male B6C3F1 mice and in female C57Bl/6, Balb/c, and DBA/2 mice by administering the same dose range of TCDD. The results showed that TCDD doses up to 500 ng/kg did not increase the mortality of virus-infected mice in any of the strains. Further studies on the mechanism underlying the toxicity of TCDD are needed to assess the risk of exposure to this compound in influenza A virus infection.