Koji Tominaga

Fukuoka University, Hukuoka, Fukuoka, Japan

Are you Koji Tominaga?

Claim your profile

Publications (10)24.11 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Chronic obstructive pulmonary disease (COPD) shows progressive, irreversible airflow limitation induced by emphysema and lung inflammation. The aim of the present study was to determine if COPD conditions induce blood-brain barrier (BBB) dysfunction. We found that the intratracheal administration of porcine pancreatic elastase (PPE; 3 U) induced alveolar enlargement, increased neutrophil number in bronchoalveolar lavage fluid, and decreased blood oxygen saturation in mice at 21 days after inhalation. In parallel with these lung damages, BBB permeability to sodium fluorescein and Evans blue albumin was markedly increased. Our findings demonstrate that COPD conditions are associated with risk for BBB impairment.
    Journal of Pharmacological Sciences 09/2015; 129(1). DOI:10.1016/j.jphs.2015.08.008 · 2.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The metabolic syndrome, characterized by conditions such as obesity and insulin resistance, is more prevalent in postmenopausal women than in premenopausal women, and increases the risk of cardiovascular disease and type 2 diabetes. The main objective of the present study was to investigate the combined effects of ovariectomy (OVX) and high-fat diet (HFD) on metabolic parameters, vascular function and glucose homeostasis in mice. After OVX or sham operation (Sham), mice were fed with either a normal diet (ND) or a HFD. Mice were divided into ND+Sham, ND+OVX, HFD+Sham, and HFD+OVX groups. After 4weeks, HFD+OVX mice developed marked increases in body weight and plasma insulin levels, but not blood glucose levels. The area under the glucose tolerance curve (Δ AUC(glucose)) following an oral glucose tolerance test and the homeostasis model assessment of insulin resistance (HOMA-IR) revealed that HFD+OVX mice had higher values than any other group. Concomitantly with these metabolic disturbances, decreased tail skin blood flow and augmented tail skin flushing, a marker of hot flashes, were observed in HFD+OVX mice. These vascular modulations likely result from vasomotor dysfunction. Furthermore, we investigated whether OVX and HFD affect the insulin signaling pathway in mice. Insulin-induced Akt phosphorylation in the livers of HFD+OVX mice was significantly downregulated compared with ND+Sham and HFD+Sham mice. Thus, the HFD+OVX mice used in the present study constitute an experimental animal model of postmenopausal metabolic syndrome. Herein, we provide experimental evidence that vascular dysfunction and impaired insulin signaling may contribute to the pathogenesis of postmenopausal metabolic syndrome.
    Microvascular Research 06/2011; 82(2):171-6. DOI:10.1016/j.mvr.2011.06.004 · 2.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Statins have pleiotropic vascular protective effects that are independent of their cholesterol-lowering effects. The aim of the present study was to determine if statins have anti-flushing actions in an animal model of forced exercise-induced temperature dysregulation in menopausal hot flushes, and to clarify the critical role of statins in regulating vascular reactivity in the tail arteries of ovariectomized rats. Administration of fluvastatin or pravastatin (3mg/kg/day for 7days, p.o.) significantly ameliorated the flushing of tail skin in ovariectomized mice, and the effect of each statin was comparable with that of estrogen replacement (1mg/kg/week for 3weeks, i.m.). In phenylephrine-pre-contracted rat-tail arteries, ovariectomy inhibited acetylcholine-induced relaxation, but augmented sodium nitroprusside-induced relaxation. These ovariectomy-altered vasodilator responses were restored by fluvastatin treatment as well as by estrogen replacement. Nitrite/nitrate levels in the plasma of ovariectomized animals showed significantly lower values than those in sham-operated animals; this ovariectomy-reduced production of nitric oxide was improved by fluvastatin treatment. These data provide the first experimental evidence that statins such as fluvastatin and pravastatin exert anti-flushing effects by improving vasomotor dysfunction through nitric oxide-mediated mechanisms in ovariectomized animals. Thus, therapeutic methods that target improvement of vasomotor dysfunction could be novel strategies for reducing menopausal hot flushes.
    European journal of pharmacology 01/2011; 651(1-3):234-9. DOI:10.1016/j.ejphar.2010.10.084 · 2.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Flushing is one of the most common vasodilation-related adverse effects associated with both nitrates and phosphodiesterase type 5 (PDE5) inhibitors. The present study aimed to investigate the effects of orchidectomy and ovariectomy on isosorbide dinitrate-, sildenafil-, vardenafil- and tadalafil-induced flushing of tail-skin in mice. Both orchidectomy and ovariectomy markedly increased the tail-skin temperature, a good parameter of flushing, induced by isosorbide dinitrate (500 microg/kg, i.p.). These observations suggest that both testosterone withdrawal and estrogen withdrawal are risk factors for isosorbide dinitrate-induced flushing. In contrast, sildenafil (100 mg/kg, p.o.)-, vardenafil (10 mg/kg, p.o.)- and tadalafil (40 mg/kg, p.o.)-induced flushing of tail-skin in mice was aggravated by ovariectomy but not by orchidectomy. Orchidectomized male mice, but not ovariectomized female mice, showed significantly lower levels of PDE5 mRNA expression in tail artery compared with those of sham-operated mice. The present findings suggest that estrogen withdrawal, but not testosterone withdrawal, is a risk factor for PDE5 inhibitor-induced flushing. These gender differences in the vascular adverse reactions of PDE5 inhibitors may be interpreted as occurring due to differences in the levels of PDE5 mRNA expression in peripheral arteries.
    European journal of pharmacology 10/2009; 624(1-3):66-70. DOI:10.1016/j.ejphar.2009.09.051 · 2.53 Impact Factor

  • 01/2007; 33(6):534-539. DOI:10.5649/jjphcs.33.534
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hot flushes are one of the most frequent symptoms in menopausal women. We investigated effect of soybean isoflavones (Soyaflavone HG) on nifedipine-induced flushing in ovariectomized mice. Ovariectomy markedly aggravated nifedipine-induced increase in tail skin temperature. Soyaflavone HG (10 mg/kg, p.o., once a day for 5 days) inhibited nifedipine-induced flushing in ovariectomized mice. The inhibitory effect of Soyaflavone HG was significantly reversed by an estrogen-receptor antagonist, ICI 182,780, suggesting that Soyaflavone HG prevents nifedipine-induced flushing partially through estrogen receptors. We presented the experimental evidence suggesting that soybean isoflavones including Soyaflavone HG have the benefits for menopausal hot flushes.
    Journal of Pharmacological Sciences 09/2004; 95(4):476-8. DOI:10.1254/jphs.SCJ04005X · 2.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Flushing is one of the most common vasodilation-related adverse effects associated with Ca(2+) channel antagonist treatment. This symptom is known to occur more frequently in women than men. The present study aimed at investigating the effect of ovariectomy on nifedipine-induced flushing in mice. Ovariectomy markedly increased the tail skin temperature, a parameter of skin flushing, induced by nifedipine at a dose showing no influence on blood pressure. This event was blocked by estradiol replacement. Estrogen withdrawal is, therefore, included in the risk factors for nifedipine-induced flushing and this risk is lessened by estrogen replacement.
    European Journal of Pharmacology 12/2003; 481(1):79-82. DOI:10.1016/j.ejphar.2003.08.085 · 2.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we investigated the effect of cyclosporin A on the binding properties of the GABAA receptor in the hippocampus, known to be responsible for the induction of seizures, to clarify the mechanism of cyclosporin A-inhibited GABA neurotransmission in ovariectomized rats, as a climacterium model. The effects of single and subchronic treatments with cyclosporin A were examined on [3H]muscimol binding to hippocampal synaptosomal membranes in sham, ovariectomized, and estradiol/ovariectomized rats. A single treatment with cyclosporin A (40 mg/kg, i.p.) failed to change [3H]muscimol binding in the 3 groups, when compared with each corresponding vehicle-treated group. Subchronic treatment with cyclosporin A (40 mg/kg, i.p., once a day for 5 days) significantly decreased the amount of [3H]muscimol binding in ovariectomized rats. However, this inhibitory effect was not observed in sham or estradiol/ovariectomized rats. These results demonstrated that the binding activity of the GABAA receptor was decreased in ovariectomized rats after subchronic cyclosporin A treatment. This study supports the hypothesis that ovariectomy elevates the susceptibility to cyclosporin A-induced convulsions by accelerating the inhibitory actions of cyclosporin A on GABA neurotransmission in the hippocampus.
    Life Sciences 01/2003; 72(4-5):425-30. DOI:10.1016/S0024-3205(02)02272-5 · 2.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The possible cyclosporin A application for rheumatoid arthritis that develops preferentially in middle-aged women raises concerns about adverse effects of cyclosporin A, including neurotoxicity in patients with climacterium. The present study was aimed at elucidating the effect of cyclosporin A on the convulsive activity and gamma-aminobutyric acid (GABA) neural activity of the hippocampus in ovariectomized rats, as a menopause/climacterium model. Ovariectomy markedly aggravated the effect of repeated administration of cyclosporin A (40 mg/kg, once a day for 5 or 6 days), convulsions and reduction of the basal GABA levels and aminooxyacetic acid-evoked GABA accumulation. These aggravations were blocked by estradiol replacement. The present findings demonstrated that ovariectomy increased the susceptibility to cyclosporin A-induced convulsions by accelerating an inhibitory action of cyclosporin A on GABA neural activity in the hippocampus, this being blocked by estrogen replacement. Menopause/climacterium is, therefore, included in the risk factors for cyclosporin A-induced neurotoxicity and this risk is lowered by estrogen replacement therapy.
    European Journal of Pharmacology 12/2001; 430(2-3):243-9. DOI:10.1016/S0014-2999(01)01377-2 · 2.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tominaga K, Kataoka Y, Sendo T, et al. Contrast medium-induced pulmonary vascular hyperpermeability is aggravated in a rat climacterium model. Invest Radiol 2001;36:131-135. To test whether climacterium influences adverse pulmonary reactions to contrast media, the authors investigated the effect of ioxaglate on pulmonary vascular permeability in ovariectomized rats as a climacterium model. From 7 days after surgery, ovariectomized rats were treated with estradiol valerate or vehicle once per week for 3 weeks. At 28 days after surgery, ioxaglate, an ionic contrast medium, was intravenously injected at 1.5 mL/min in rats. Pulmonary vascular permeability was evaluated by measuring the amount of Evans blue dye in the lung tissue. Ioxaglate dose-dependently increased pulmonary vascular permeability in sham-operated and ovariectomized rats. Ovariectomized rats showed a 2.6-fold increased aggravation of vascular permeability by ioxaglate 4 g I/kg compared with sham-operated rats. Estradiol valerate (0.2-5.0 mg/kg) dose-dependently blocked ioxaglate-increased vascular permeability in ovariectomized rats. These findings suggest that climacterium is included, at least in part, in the risk factors for contrast-induced adverse pulmonary reactions, and this risk is lowered by estrogen replacement therapy.
    Investigative Radiology 04/2001; 36(3):131-5. DOI:10.1097/00004424-200103000-00001 · 4.44 Impact Factor