Numerous reports have indicated that patients suffering from inflammatory diseases(e.g., arthritis)who take anti-inflammatory medication have a reduced risk of developing Alzheimer’s disease(AD).Thus, the first generation of anti-inflammatory cyclooxygenase(COX)inhibitors, such as aspirin and indomethacin, have been tested as potential therapeutics in AD.Because the inhibition of COX-1 is also known to cause tissue damage in the gastrointestinal system from the resultant reduced cytoprotection, selective COX-2 inhibitors are being investigated and tested clinically as potentially better therapeutics for AD patients.However, such drugs may also trigger unwanted effects;for example, the COX-2 inhibitors, which reduce the production of one type of eicosanoids, the prostaglandins, may increase the production of other eicosanoids;i.e., the leukotriene B₄(LTB₄), which is one of the most potent endogenous chemotactic/inflammatory factors.LTB₄ production is initiated by the enzyme 5-lipoxygenase(5-LOX).The expression of the 5-LOX gene is upregulated during neurodegeneration and with aging.In spite of the fact that 5-LOX and leukotrienes are major players in the inflammation cascade, their role in AD pathobiology/therapy has not been extensively investigated.We propose that the 5-LOX inflammatory cascade may take part in the process of aging-associated neurodegenerative diseases, and we point to the role of 5-LOX in neurodegeneration and discuss its relevance for anti-inflammatory therapy of AD.

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Nitric oxide(NO)is recognized as an endogenous mediator of vascular tone, a neurotransmitter and an immune effector molecule.Furthermore, it has been implicated in the development of various diseases.Because NO is extremely labile in the biological milieu, its activities can be effected not only by NO itself but also by relatively stable physiologic NO carriers or NO donors.Dinitrosyl iron complexes have been recognized as endogenous NO carrier molecules as well as S-nitrosothiols.The complex has been found in cells and the tissues of mammals and bacteria via its readily detectable, characteristic electron paramagnetic resonance(EPR)signals.Endogenously produced dinitrosyl iron complex with thiolate ligands(DNIC)has a critical biological potential;and it can function as a physiologic regulatory factor in a biological system, especially the immune and cardiovascular systems.We have been studying the in vivo behavior and distribution of DNIC to elucidate its physiological roles and pharmacokinetics.In this article, an attempt is made to provide an overview of the history, physiology and in vivo behavior of DNIC.

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We investigated the effects of troglitazone, a new orally active hypoglycemic agent, on the voltage-dependent L-type Ca²⁺ current in single cardiac ventricular myocytes of guinea pigs by the whole-cell voltage clamp technique.Troglitazone blocked the Ca²⁺ currents in a concentration-dependent manner.The inhibitory effect was more potent at the holding potential(HP)of −50mV than at −80mV.The half-maximum inhibiting concentration(IC₅₀)of troglitazone was 0.8μM with the Hill coefficient of 0.84 at −50mV HP.In contrast, the IC₅₀ value was higher than 10μM at −80mV HP.These results suggest that troglitazone at therapeutic concentrations inhibit the Ca²⁺ channels and may exert cardioprotective effects in diabetic conditions.

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Pharmacological characterization of peripheral type benzodiazepine receptors in rat, rabbit, mouse and human salivary glands was determined by receptor binding and photoaffinity labeling analysis using [³H]PK14105(1-(2-fluoro-5-nitrophenyl)-3-isoquinolinecarboxylic acid).[³H]PK14105 bound to the membranes of salivary glands in rats, rabbits, mice and humans with high affinity at the nanomolar level.The rank order of receptor density in submandibular glands among several species was as follows:human≥rat≥mouse>rabbit.Competitive potency of receptor ligands against[³H]PK14105 was as follows:PK11195≥Ro5-4864>deazepam>clonazepam>Ro15-1788.The rank order of potency against calcium channel ligands and co-transport inhibitors was as follows:nitrendipine>BAY K 8644>bumetanide>furosemide.Pretreatment with nitrendipine or BAY K 8644 decreased the affinity of[³H]PK14105 binding to rat parotid gland membranes, without changing the density.The photoaffinity labeling with[³H]PK14105 indicated the presence of the 18-kDa protein in all salivary glands of our experiment.The inhibition of photolabeling by some receptor ligands was the same results as the receptor binding assay.In conclusion, the peripheral type benzodiazepine receptors include the 18-kDa protein photolabeled with[³H]PK14105 in salivary glands of rat, mouse, rabbit and human.

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The effects of capsaicin cream on neurogenic inflammation and thermal nociceptive threshold were investigated in rats.Firstly, for topical application of capsaicin cream to hind paw, we shaped boots from dental cement to prevent the animals from licking off the drug.Capsaicin cream(1%) led to significant increases in the amounts of Evans blue and substance P(SP) released into the perfusate, and the former response was significantly suppressed by pretreatment with RP67580, an NK₁-receptor antagonist, but not by treatment with an NK₂-receptor antagonist.Subsequent electrical stimulation of the sciatic nerve resulted in a significant reduction in Evans blue and SP extravasation 24h after topical application of capsaicin cream.On the other hand, when capsaicin cream was repeatadly applied to both hind paws once a day, withdrawal latency for noxious heat stimulation decreased after 24h, and this thermal hyperalgesia was reversed 3 days later.These results suggest that capsaicin cream initially affects neurogenic inflammation mechanisms and then blocks the pain transmission mechanism.

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To investigate the possible drug interaction with herbal medicine, furanocoumarin derivatives isolated from several Umbelliferous crude drugs were examined for their inhibitory effects on a typical human drug metabolizing enzyme, cytochrome P450 3A(CYP3A).Most furanocoumarins tested at 0.1mM reduced microsomal testosterone 6β-hydroxylation as an index of CYP3A activity to less than 50% of the control.In particular, the dimer and trimer derivatives of furanocoumarins showed striking inhibition, whose potencies were similar to that of a typical CYP3A inhibitor, ketoconazole.Preincubation of dimer types of furanocoumarins increased suppression but not most of the monomer derivatives, suggesting that the inhibition on CYP3A activity was caused by at least plural mechanisms.These results raised the possibility that the furanocoumarin containing herbal medicines may alter pharmacokinetics of co-ingested drugs similar to the case with grapefruit juice.

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The involvement of α₂-adrenoceptors in the antinociception induced by the tricyclic antidepressants amitriptyline and imipramine was investigated in mice by using the hot-plate and abdominal constriction tests.The antinociception produced by amitriptyline(15mg/kg, i.p.) and imipramine(15mg/kg, i.p.) was prevented by reserpine(2mg/kg, i.p.) and yohimbine(3-10mg/kg, i.p.) but not by naloxone(1mg/kg, i.p.), atropine(5mg/kg, i.p.), CGP 35348(100mg/kg, i.p.) and prazosin(1mg/kg, i.p.).On the basis of the above data, it can be postulated that amitriptyline and imipramine exerted their antinociceptive effect by activation of α₂-adrenoceptors.Administration of the α_2A-adrenoceptor antagonist BRL 44408(1mg/kg, i.p.) prevented amitriptyline and imipramine antinociception, whereas the α_2B/C-adrenoceptor antagonist ARC 239(10mg/kg, i.p.) was ineffective.These data indicate that the enhancement of the pain threshold produced by amitriptyline and imipramine is mediated by activation of α_2A-adrenoceptors.Neither tricyclic antidepressants nor the antagonists used impaired mouse performance evaluated by the rota-rod and hole-board tests.

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Facilitation of acetylcholine(ACh) release by SK-951((−)4-amino-N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-5-chloro-2, 3-dihydro-2-methylbenzo[b]furan-7-carboxamine hemifumarate), a benzofuran derivative, via the 5-hydroxytryptamine(5-HT)₄ receptor in guinea pig stomach was examined by in vitro receptor autoradiography and functional studies.[¹²⁵I]SB207710 binding was detected in the myenteric plexus of the gastric corpus.High densities of binding sites were observed in the myenteric plexus and a moderate density in the muscle layer.SK-951 inhibited the binding of [¹²⁵I]SB207710, a specific 5-HT₄-receptor ligand, as in the case of SB204070, a specific 5-HT₄-receptor antagonist, thus indicating the presence of 5-HT₄ receptors in guinea pig stomach.SK-951 as well as 5-HT enhanced the electrically stimulated twitch contractions of gastric corpus strips, which were sensitive to tetrodotoxin and atropine, and enhanced electrically stimulated release of ACh from corporal strips, which was tetrodotoxin-sensitive and Ca²⁺-dependent.The enhancements of twitch contractions and ACh release by SK-951 were antagonized by GR113808, a selective 5-HT₄-receptor antagonist.Thus, SK-951 binds to 5-HT₄ receptors of the guinea pig gastric corpus and may accelerate gastric motility due to facilitation of ACh release.

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We compared recombinant human chymase expressed in Escherichia coli with human chymase purified from vascular tissues.The recombinant chymase, the structure of which was NH₂-enterokinase cleavage site-chymase-COOH, was expressed in Escherichia coli and then was solubilized and renatured.The protein did not have a chymase activity, but gained this activity after the cleavage of the N-terminal site by enterokinase.The enzyme was purified by heparin affinity and gel filtration columns.The N-terminal sequence of the protein was identical to the sequence for human chymase.The molecular weights of the recombinant chymase and chymase purified from human vascular tissues were 26 and 30kDa, respectively, and the 4kDa difference was thought to be due to the presence or absence of glycan.The optimum pH of the recombinant enzyme activity was between 7.5 and 9.0.The activity of the recombinant enzyme was inhibited by chymostatin, soybean trypsin inhibitor and phenylmethylsulfonyl fluoride, but not by ethylenediaminetetraacetic acid and aprotinin.This enzyme cleaved specifically the Phe⁸-His⁹ bond of angiotensin(Ang)I to form Ang II and that of big endothelin(ET)-1 to form ET-1-(1-31).These findings demonstrated that the enzymatic characteristics of the recombinant enzyme were identical to that of native human chymase.

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m-(Iodobenzyl)trozamicol(MIBT)is a recently discovered vesamicol analgoue.It has been shown that radiolabelled [¹²⁵I]MIBT can be used as a marker of cholinergic innervation in the heart as well as in the brain.The purpose of this study was to analyze the direct effects of MIBT on the atrioventricular and intraventricular conduction in addition to the coronary blood flow using the canine isolated, blood-perfused atrioventricular node preparation.Intracoronary administration of MIBT suppressed the atrioventricular and intraventricular conduction, while it increased the coronary blood flow.The effect and duration of action on the intraventricular conduction was less pronounced compared with other effects.Moreover, the doses of MIBT needed to cause negative dromotropic and coronary vasodilator effects in this study was much greater than those needed for imaging the cardiac cholinergic innervation.Pretreatment of the preparations with a muscarinic receptor antagonist, atropine, did not block these effects of MIBT, suggesting that MIBT may possess muscarinic receptor-independent ion channel activity in the cardiac conduction system and coronary arteries.

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Effects of a Na⁺/Ca²⁺ exchanger inhibitor, KB-R7943(2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulfonate), on the sinoatrial nodal pacemaker activity, atrial contractility and ventricular contractility were investigated in the isolated and blood-perfused right atrium and left ventricle of the dog.KB-R7943(0.03-3μmol)induced negative inotropic effects and negative followed by positive chronotropic effects in the right atrium and negative inotropic effects in the left ventricle.Neither atropine nor hexamethonium affected the cardiac responses to KB-R7943.Propranolol attenuated the positive chronotropic response to KB-R7943 but imipramine did not.Tetrodotoxin potentiated the positive chronotropic response to KB-R7943 in 6 of 11 isolated atria.When NaCl infusion increased atrial contractile force and atrial rate, KB-R7943-induced negative inotropic and chronotropic responses were attenuated in a dose-dependent manner.CaCl₂ infusion potentiated the negative chronotropic response to KB-R7943 but did not affect the inotropic response significantly.On the other hand, ouabain(17nmol)attenuated the negative inotropic response, but not chronotropic response, to KB-R7943.These results suggest that KB-R7943-induced cardiac effects relate to the Na⁺ activity, probably mediated through the Na⁺/Ca²⁺ exchanger, and the Na⁺/Ca²⁺ exchanger modifies the pacemaker activity and myocardial contractility in the dog heart.

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Participation of the nitric oxide-cyclic GMP pathway in nonadrenergic, noncholinergic(NANC)relaxation induced by electrical field stimulation of longitudinal muscle of the rectum of Wistar-ST rats was studied by using a selective inhibitor of soluble guanylyl cyclase, 1H-[1, 2, 4]oxadiazolo[4, 3-a]quinoxalin-1-one(ODQ).ODQ concentration dependently inhibited the relaxation and at 10μM, maximally inhibited it by 83%.However, results obtained with N^G-nitro-L-arginine, L-arginine and exogenously added nitric oxide excluded the participation of nitric oxide in the relaxation.An inhibitor of cyclic GMP-dependent protein kinase(PKG)partially(39%)inhibited the relaxation.ODQ also significantly inhibited the relaxation, which persisted after the PKG inhibitor-treatment, by 85%.The results strongly suggest that ODQ inhibits the NANC relaxation in a cyclic GMP-PKG pathway-independent manner.

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Nitric oxide(NO)is involved in the mechanism of castor oil-induced diarrhea.This study was performed to elucidate the source of NO.Diarrhea was induced by oral administration of castor oil in rats.Diarrhea was significantly inhibited by the pre-treatment with a relatively selective nerve NO synthase inhibitor, 7-nitroindazole.This effect was attenuated by the treatment with L-arginine.Capsaicin-sensitive afferent nerve degeneration did not affect the diarrhea.N^G-Nitro-L-arginine methylester significantly inhibited diarrhea even in capsaicin-pretreated rats.These data suggest, a least in part, the involvement of NO from nerves on the diarrhea induced by castor oil in rats.

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