Nitric oxide induces hydroxyl radical generation in rat hearts via depolarization-induced nitric oxide synthase activation

We examined the effect of NG-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, on extracellular potassium ion concentration ([K+]o) and induced hydroxyl free radical (.OH) generation by an in vivo microdialysis technique. A flexibly mounted microdialysis technique was used to detect the generation of .OH in in-vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and tissue was perfused with Ringer's solution through the microdialysis probe at a rate of 1.0 microl/min. To measure the level of .OH, sodium salicylate in Ringer's solution (0.5 nmol/microl per min) was infused directly through a microdialysis probe to detect the generation of .OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (2,3-DHBA). Induction of high-concentration [K+]o (20, 70 and 140 mM) significantly increased formation of .OH trapped as 2,3-DHBA in a concentration-dependent manner. However, the application of L-NAME (50 mg/kg, i.v.) and allopurinol, a xanthine oxidase inhibitor, abolished the [K+]o depolarization-induced .OH generation. Tyramine (1.0 mM) increased the level of 2,3-DHBA. However, the application of L-NAME did not change the level of 2,3-DHBA. On the other hand, pretreatment with allopurinol (10 mg/kg, i.v.) abolished the KCl- or tyramine-induced .OH generation. Moreover, when iron (II) was administered to [K+]o (70 mM)-pretreated animals, there was a marked increased in the level of 2,3-DHBA. However, the application of L-NAME was not related to a Fenton-type reaction via [K+]o depolarization-induced .OH generation. To examine the effect of L-NAME on ischemic/reperfused rat myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion by left anterior descending coronary artery branch (LAD). When the heart was reperfused, a marked elevation of the level of 2,3-DHBA was observed. However, L-NAME attenuated .OH generation by ischemic/reperfused rat heart. These results suggest that NOS inhibition is associated with a cardioprotective effect due to the suppression of [K+]o depolarization-induced .OH generation.

Histamine increases interstitial adenosine concentration via activation of ecto-5'-nucleotidase in rat hearts in vivo

We examined whether histamine enhances the production of interstitial adenosine via stimulation of ecto-5'-nucleotidase (a key enzyme responsible for adenosine production) using microdialysis techniques in in situ rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused in the presence of adenosine 5'-monophosphate (AMP). Histamine (10-500 microM) administered into the perfusate had a tendency to increase the adenosine concentration. In the presence of prazosin (50 microM), an antagonist of alpha1-adrenoceptors, or of chelerythrine (10 microM), a protein kinase C (PKC) inhibitor, and in reserpinized rats, histamine failed to increase the AMP-primed dialysate adenosine concentration. Accumulation of norepinephrine in the extracellular fluid elicited by pargyline (100 microM), a monoamine oxidase inhibitor, significantly increased histamine-induced adenosine production. Okadaic acid (50 microM), an inhibitor of protein phosphatase, enhanced the histamine-induced increase in adenosine concentration. Norepinephrine is known to activate alpha1-adrenoceptors and PKC. Taken together, the results demonstrate that histamine-released norepinephrine activates both alpha1-adrenoceptors and PKC, which increased ecto-5'-nucleotidase activity and augmented release of adenosine in rat hearts.

Allopurinol suppresses para-nonylphenol and 1-methyl-4-phenylpyridinium ion (MPP(+))-induced hydroxyl radical generation in rat striatum

We recently demonstrated that para-nonylphenol, an environmental estrogen-like chemical, enhances hydroxyl radical (*OH) generation in the rat striatum. In the present study we have examined whether para-nonylphenol enhanced 1-methyl-4-phenylpyridinium ion (MPP(+))-induced *OH generation in the rat striatum using a microdialysis technique. Para-nonylphenol significantly enhanced MPP(+)-induced *OH generation. Further, we studied the effect of allopurinol, a xanthine oxidase inhibitor, on para-nonylphenol and MPP(+)-induced *OH generation. Allopurinol significantly suppressed para-nonylphenol and MPP(+)-induced *OH generation. The results indicate that para-nonylphenol enhanced *OH generation based on superoxide anion production, and allopurinol may have preventive effect on para-nonylphenol and MPP(+)-induced *OH generation.

Nitric oxide enhances MPP(+)-induced hydroxyl radical generation via depolarization activated nitric oxide synthase in rat striatum

We examined the effect of N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, on extracellular potassium ion concentration ([K(+)](o))-enhanced hydroxyl radical (.OH) generation due to 1-methyl-4-phenylpyridinium ion (MPP(+)) was examined in the rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/microl per min) was infused through a microdialysis probe to detect the generation of.OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Induction of KCl (20, 70 and 140 mM) increased MPP(+)-induced.OH formation trapped as 2,3-dihydroxybenzoic acid (DHBA) in a concentration dependent manner. However, the application of L-NAME (5 mg/kg i.v.) abolished the [K(+)](o) depolarization-induced.OH formation with MPP(+). Dopamine (DA; 10 microM) also increased the levels of DHBA due to MPP(+). However, the effect of DA after application of L-NAME did not change the levels of DHBA. On the other hand, the application of allopurinol (20 mg/kg i.v., 30 min prior to study), a xanthine oxidase (XO) inhibitor was abolished the both [K(+)](o)- and DA-induced.OH generation. Moreover, when iron(II) was administered to MPP(+) then [K(+)](o) (70 mM)-pretreated animals, a marked increase in the level of DHBA. However, when corresponding experiments were performed with L-NAME-pretreated animals, the same results were obtained. Therefore, NOS activation may be no relation to Fenton-type reaction via [K(+)](o) depolarization-induced.OH generation. The present results suggest that [K(+)](o)-induced depolarization augmented MPP(+)-induced.OH formation by enhancing NO synthesis.

Nicorandil increases adenosine 5'-monophosphate-primed interstitial adenosine via activation of ecto-5'-nucleotidase in rat hearts

With the use of microdialysis techniques, we examined the effects of nicorandil, a hybrid of an ATP-sensitive K+ (K ATP) channel opener and a nitrate compound, on the production of interstitial adenosine in rat hearts in situ. The level of dialysate adenosine measured under a constant supply of adenosine 5'-monophosphate (AMP) reflected the activity of endogenous ecto-5'-nucleotidase. Nicorandil (0.3-3mM) increased the level of AMP (100 microM)-primed dialysate adenosine in a concentration-dependent manner, and this effect was completely abolished by the guanylate cyclase inhibitor, methylene blue (100 microM), but not by the K ATP channel blocker, glibenclamide (10 microM). Another K ATP channel opener, cromakalim (0.1-1mM), did not increase the production of AMP-primed dialysate adenosine. These results suggest that nicorandil increases the level of interstitial adenosine via cyclic guanosine monophosphate-mediated activation of ecto-5'-nucleotidase.

Effect of fluvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on nitric oxide-induced hydroxyl radical generation in the rat heart

We examined the effect of fluvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on the production of hydroxyl radical (*OH) generation via nitric oxide synthase (NOS) activation by an in vivo microdialysis technique. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and tissue was perfused with Ringer's solution through the microdialysis probe at a rate of 1 microl/min. Sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused directly through a microdialysis probe to detect the generation of *OH. Induction of [K(+)](o) (70 mM) or tyramine (1 mM), significantly increased the formation of *OH trapped as 2,3-dihydroxybenzoic acid (DHBA). The application of N(G)-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, significantly decreased the K(+) depolarization-induced *OH formation, but the effect of tyramine significantly increased the level of 2,3-DHBA. When fluvastatin (100 microM), an inhibitor of low-density lipoprotein (LDL) oxidation, was administered to L-NAME-pretreated animals, both KCl and tyramine failed to increase the level of 2,3-DHBA formation. The effect of fluvastatin may be unrelated to K(+) depolarization-induced *OH generation. To examine the effect of fluvastatin on ischemic/reperfused rat myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, a marked elevation of the level of 2,3-DHBA was observed. However, in the presence of fluvastatin (100 microM), the elevation of 2,3-DHBA was not observed in ischemia/reperfused rat heart. Fluvastatin, orally at a dose of 3 mg/kg/day for 4 weeks, significantly blunted the rise of serum creatine phosphokinase and improved the electrocardiogram 2 h after coronary occlusion. These results suggest that fluvastatin is associated with a cardioprotective effect due to the suppression of noradrenaline-induced *OH generation by inhibiting LDL oxidation in the heart.

Significance of integrin alpha2/beta1 in peritoneal dissemination of a human gastric cancer xenograft model

In the present study, the role of integrin alpha2/beta1 in peritoneal dissemination of gastric cancer was investigated using an in vivo xenograft model for the highly metastatic MKN-45-P gastric cancer cells. Metastatic ability of MKN-45-P cells was significantly associated with the simultaneous expression of integrin alpha2 and alpha3 subunits. In an in vitro adhesion assay, neutralizing antibody for integrin alpha2 or beta1 subunit inhibited the adhesion of MKN-45-P cells to collagen type I and type IV. Moreover, the injection of anti-beta1 monoclonal antibody reduced the number of cancer cells on the peritoneum in nude mice that had been inoculated with MKN-45-P cells. These results suggest that integrin alpha2/beta1 represents a candidate target molecule available for the prevention of gastric cancer peritoneal dissemination.

A motif-based profile scanning approach for genome-wide prediction of signaling pathways

The rapid increase in genomic information requires new techniques to infer protein function and predict protein-protein interactions. Bioinformatics identifies modular signaling domains within protein sequences with a high degree of accuracy. In contrast, little success has been achieved in predicting short linear sequence motifs within proteins targeted by these domains to form complex signaling networks. Here we describe a peptide library-based searching algorithm, accessible over the World Wide Web, that identifies sequence motifs likely to bind to specific protein domains such as 14-3-3, SH2, and SH3 domains, or likely to be phosphorylated by specific protein kinases such as Src and AKT. Predictions from database searches for proteins containing motifs matching two different domains in a common signaling pathway provides a much higher success rate. This technology facilitates prediction of cell signaling networks within proteomes, and could aid in the identification of drug targets for the treatment of human diseases.

[Parkinsonism induced by MPTP and free radical generation]

Oxygen free radical formation has been implicated in dopaminergic toxicity caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and iron. Although MPTP produces a parkinsonian syndrome after its conversion to 1-methyl-4-phenylpyridine (MPP+) by type B monoamine oxidase (MAO-B) in the brain, the etiology of this disease remains obscure. MPP+ is one of the most potent dopamine (DA)-releasing agents. Iron-catalyzed DA autoxidation and oxidative stress may be involved in the pathogenesis of Parkinson's disease. If indeed the effect of MPP+ on hydroxyl radical (.OH) formation is due to DA release, reserpine-induced DA depletion may reduce MPP(+)-induced .OH formation. Imidapril, an angiotensin converting enzyme (ACE) inhibitor, can resist MPP(+)-induced .OH formation via suppression of release of DA by angiotensin. Histidine, a singlet oxygen (1O2) scavenger, protects MPP(+)-induced .OH formation. Fluvastatin, an inhibitor of low-density lipoprotein (LDL) oxidation, can resist MPP(+)-induced .OH formation. The inhibitory effect on the susceptibility of LDL oxidation can reduce .OH generation. These drugs may be applied as antiparkinsonian agents. Further clinical investigation is necessary in the future.

Postrest contraction in the ventricular papillary muscle of spontaneously diabetic WBN/Kob rat

In the present study, we investigated the characteristics of the postrest contraction (PRC) in chronic diabetic ventricular muscle. We used WBN/Kob rats of 7-8 weeks as the spontaneously diabetic animal and Wistar rats of 7-8 weeks as the control. We found: (1) No significant differences were seen in the amplitude, the contracting speed, and the relaxing speed of electrically stimulated twitch tension between control and WBN/Kob rats. In addition, the relationship between amplitude of twitch tension and stimulus cycle lengths (0.2-5 sec) was very similar in both animals. (2) The ratios of the first twitch tension (T1) of PRC with various rest intervals (5-600 sec) to the steady-state tension (Tss) were significantly smaller in the diabetic rats than in the controls. (3) When the preparation was stimulated at shorter cycle lengths, the recovery process of PRC was separated into at least two components (fast and slow components). In the diabetic rats, the time constant (tau) of both components was significantly longer than in controls. (4) After caffeine (10(-3) M) treatment, tau of the fast component in the control rats became longer, whereas it remained unchanged in diabetic rats. These findings suggest a dysfunction of the intracellular calcium handling system in spontaneously diabetic heart that is likely to include impaired calcium sequestration and/or extrusion.

Protective effect of histidine on potassium chloride depolarization enhances 1-methyl-4-phenylpyridinium ion-induced hydroxyl radical generation in the rat striatum

The present study examined the antioxidant effect of histidine on extracellular potassium ion concentration, [K+]o-induced depolarization enhances 1-methyl-4-phenylpyridinium ion (MPP+)-induced hydroxyl radical (*OH) generation in the rat striatum. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol/M microl/min) was infused through a microdialysis probe to detect the generation of *OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Induction of [K+]o (20, 70 and 140 mM) significantly increased the level of 2,3-DHBA by the action of MPP+ (5 mM) in a concentration-dependent manner. However, histidine (25 mM) reduced the [K+]o-induced *OH formation. Although the level of MPP+-induced dopamine (DA) and 2,3-DHBA formation after [K+]o (70 mM) treatment increased, [K+]o failed to increase either the level of MPP+-induced DA and 2,3-DHBA in the reserpinized group. When iron (II) was administered to [K+]o (70 mM)-pretreated rats, iron (II) clearly produced a dose-dependent increase in the level of 2,3-DHBA, as compared with MPP+-only treated rats. However, in the presence of histidine (25 mM), the effect of [K+]o was abolished. These results indicated that histidine may reduce the [K+]o-induced depolarization enhanced *OH formation by the action of MPP+ in the rat striatum.

Formation of hydroxy radicals by environmental estrogen-like chemicals in rat striatum

We investigated effects of environmental estrogen-like chemicals, para-nonylphenol and bisphenol A, on hydroxy radical formation in the striatum of adult rats, using an in vivo microdialysis system. Para-nonylphenol significantly stimulated hydroxy radical formation in the striatum. Bisphenol A also increased hydroxy radical formation, albeit effect being slight. The formation of hydroxy radicals induced by para-nonylphenol was dose-dependently inhibited by tamoxifen, which suggests that the effect of this chemical was an estrogenic action via estrogen receptors. The results of the present study are the first demonstration on hydroxy radical formation induced by environmental estrogen-like chemicals and suggest that the in vivo microdialysis may be useful for evaluating toxic effects of environmental chemicals on nervous tissues.

Evidence for existence of immobilization stress-inducible semicarbazide-sensitive amine oxidase inhibitor in rat brain cytosol

An endogenous inhibitor of semicarbazide-sensitive amine oxidase (SSAO) was separated by gel filtration from 105000xg supernate in rat brain cytosol following immobilization stress (IMMO). The molecular weight of this inhibitor was estimated to be 500-700 by gel filtration. This inhibitor was proved to be heat-stable resistant to protease treatment. These results suggest that this inhibitor is induced by IMMO. SSAO activity in rat brain might be regulated by the level of this inhibitor.

[Polyarthralgia as the initial manifestation of isolated ACTH deficiency]

A 57-year-old man, employed as a taxi driver, noticed arthralgia of his fingers beginning in May 1999. He was unable to work due to the arthralgia and the accompanying general malaise and anorexia, and was thus admitted to a local hospital in July 1999. Since a diagnosis of rheumatic disease was suspected due to elevated inflammatory reactions and joint symptoms, he was referred to our hospital in September 1999. Although no joint swelling was observed, severe tenderness was present in both the fingers and wrists. His grasping power had decreased markedly and fever was intermittently observed. All autoantibodies aside from antinuclear antibody were negative. Given that hyponatremia (126 mEq/l) and fasting hypoglycemia were demonstrated, an endocrinological examination, in particular for hypopituitary-adrenal function, was performed. Both plasma and urinary cortisol concentrations were very low, and an associated low concentration of plasma ACTH (6.0 pg/ml) was noted. The ACTH circadian rhythm was absent and there was no response to the administration of corticotropin releasing hormone. All other pituitary hormones were secreted at normal levels and brain MRI revealed a normal appearance of a pituitary gland. Based on these findings, the patient was diagnosed as having isolated ACTH deficiency. Arthralgia and general malaise both improved soon after replacement of glucocorticoid, and CRP levels were normalized. Isolated ACTH deficiency should be considered in the differential diagnosis of patients suffering from polyarthralgia, given that fever and increased inflammatory reactions occasionally develop and that rheumatic symptoms are also present, as in the present case.

Peptide and protein library screening defines optimal substrate motifs for AKT/PKB

AKT was originally identified as a proto-oncogene with a pleckstrin homology and Ser/Thr protein kinase domains. Recent studies revealed that AKT regulates a variety of cellular functions including cell survival, cell growth, cell differentiation, cell cycle progression, transcription, translation, and cellular metabolism. To clarify the substrate specificity of AKT, we have used an oriented peptide library approach to determine optimal amino acids at positions N-terminal and C-terminal to the site of phosphorylation. The predicted optimal peptide substrate (Arg-Lys-Arg-Xaa-Arg-Thr-Tyr-Ser*-Phe-Gly where Ser* is the phosphorylation site) has similarities to but is distinct from optimal substrates that we previously defined for related basophilic protein kinases such as protein kinase A, Ser/Arg-rich kinases, and protein kinase C family members. The positions most important for high V(max)/K(m) ratio were Arg-3>Arg-5>Arg-7. The substrate specificity of AKT was further investigated by screening a lambdaGEX phage HeLa cell cDNA expression library. All of the substrates identified by this procedure contained Arg-Xaa-Arg-Xaa-Xaa-(Ser/Thr) motifs and were in close agreement with the motif identified by peptide library screening. The results of this study should help in prediction of likely AKT substrates from primary sequences.

Methamphetamine enhances 1-methyl-4-phenylpyridinium ion-induced hydroxyl radical generation in the rat striatum

We determined the methamphetamine (MA), a potent dopamine (DA) releaser, enhances 1-methyl-4-phenylpyridinium ion (MPP(+))-induced hydroxyl radical (&z.rad;OH) generation in the rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused through a microdialysis probe to detect the generation of .OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. After administration of MA (5 mg/kg i.v., every 2 h, four times), MA drastically increased DA release and the &z.rad;OH formation. When iron (II) was administered to the MA-treated animals, a marked elevation of DHBA was observed, compared with MPP(+)-only treated animals, that showed a positive linear correlation between DA and .OH formation trapped as DHBA (R(2)=0.985) in the dialysate. These results suggest that MA enhances the &z.rad;OH products of efflux/oxidation due to MPP(+).

Smoking and oxidant stress: assay of isoprostane in human urine by gas chromatography-mass spectrometry

Isoprostane (8-epi-prostaglandin F2alpha) is synthesized non-enzymatically from arachidonate and active oxygen. We examined the relationship of smoking and excretion of isoprostane in urine with gas chromatography-mass spectrometry selected ion monitoring assay and the stable isotope dilution method. Urine isoprostane concentrations were significantly higher in smokers (n=81, 605.24+/-59.01 ng/mg creatinine) than in non-smokers (n=39, 424.07+/-70.37 ng/mg creatinine), but concentrations in ex-smokers (n=21, 487.27+/-98.48 ng/mg creatinine) did not differ significantly from those in the other groups. In smokers, age, the duration of smoking, and the number of cigarettes per day were not correlated with urine isoprostane concentrations. However, urine isoprostane concentrations were negatively correlated with time since quitting in ex-smokers and with age in non-smokers. These results indicate that smoking increases isoprostane concentration in urine and suggest that smoking causes lipid peroxidation by oxidant stress.

The protooncogene TCL1 is an Akt kinase coactivator

Human T cell prolymphocytic leukemia can result from chromosomal translocations involving 14q32.1 or Xq28 regions. The regions encode a family of protooncogenes (TCL1, MTCP1, and TCL1b) of unknown function. In yeast two-hybrid screening, we found that TCL1 interacts with Akt. All TCL1 isoforms bind to the Akt pleckstrin homology domain. Both in vitro and in vivo TCL1 increases Akt kinase activity and as a consequence enhances substrate phosphorylation. In vivo, TCL1 stabilizes the mitochondrial transmembrane potential and enhances cell proliferation and survival. In vivo, TCL1 forms trimers, which associate with Akt. TCL1 facilitates the oligomerization and activation of Akt. Our data show that TCL1 is a novel Akt kinase coactivator, which promotes Akt-induced cell survival and proliferation.

Block of cardiac ATP-sensitive K(+) channels reduces hydroxyl radicals in the rat myocardium

The present study examined whether opening of an ATP-sensitive K(+) (K(ATP)) channel can induce hydroxyl free radical ((*)OH) generation in the rat myocardium. Sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused directly through a microdialysis probe to detect the generation of (*)OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Induction of cromakalim (100 microM), a K(ATP) channel opener, through the microdialysis probe significantly increased the level of 2,3-DHBA. Another K(ATP) channel opener, nicorandil, also increased the level of 2,3-DHBA. When iron(II) was administered to cromakalim-pretreated animals, a marked elevation of DHBA was observed, compared with iron(II) only-treated animals. A positive linear correlation between iron(II) and formation of (*)OH, trapped as DHBA in the dialysate, was shown (r(2) = 0.988). When corresponding experiments were performed with nicorandil-treated animals, a positive linear correlation between iron(II) and DHBA in the dialysate was shown (r(2) = 0.988). However, the presence of glibenclamide (1-50 microM) decreased the cromakalim-induced 2,3-DHBA formation in a concentration-dependent manner (IC(50) = 9.1 microM). 5-Hydroxydecanoate (5-HD; 100 microM), another K(ATP) channel antagonist, also decreased cromakalim-induced (*)OH formation. The IC(50) value for 5-HD against cromakalim-evoked increase in 2,3-DHBA was 107.2 microM. In the presence of glibenclamide (10 microM), the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, the normal elevation of 2,3-DHBA in the heart dialysate was not observed in animals pretreated with glibenclamide (10 microM). When corresponding experiments were performed with 5-HD (100 microM) pretreated animals, the same results were obtained. These results suggest that opening of cardiac K(ATP) channels may cause (*)OH generation.

Inhibition of monkey brain semicarbazide-sensitive amine oxidase by various antidepressants

We examined whether the antidepressant drugs, such as the dicyclic drug zimeldine, the tricyclic drug imipramine, tetracyclic drug maprotiline, and the non-cyclic drug nomifensine, inhibit in vitro semicarbazide-sensitive amine oxidase (SSAO) activity in monkey brain. The deamination of 1 microM benzylamine was not inhibited at high concentrations of clorgyline or deprenyl, while it was highly sensitive for semicarbazide. When corresponding experiments were performed with 100 microM benzylamine, the opposite results were obtained. The most potent of inhibition of SSAO was observed by imipramine, followed by maprotiline, zimeldine and nomifensine. Inhibition of SSAO was not enhanced by varying the time of preincubation of the enzyme and various antidepressant drugs, indicating direct action on and reversible inhibition of SSAO. We found the tricyclic antidepressant drug to be the most selective inhibitors of SSAO activity in monkey brain, as compared with other type of antidepressant drugs.

Seizure frequency and bilateral temporal abnormalities: a proton magnetic resonance spectroscopy of temporal lobe epilepsy

Proton magnetic resonance spectroscopy ((1)H-MRS) was performed in seven healthy volunteers and 17 patients with temporal lobe epilepsy (TLE) to clarify the correlation of the severity of epilepsy with bilateral temporal changes in N-acetylaspartate (NAA), choline-containing compounds (Cho) and creatine + phosphocreatine (Cr). Despite unilateral EEG focus, bilateral temporal reduction in NAA /(Cho + Cr) was revealed in patients with intractable seizures. The potential for seizure generation correlated with the NAA /(Cho + Cr) reduction not only on the ipsilateral side but also on the contralateral side. Proton MRS proved to be a useful measurement for obtaining important information about the neuronal changes as well as the lateralization of the epileptogenic focus in TLE patients.

An increase of the native interstitial adenosine concentration during histidine application

We examined whether histidine can increase the production of interstitial adenosine via noradrenaline (NA) release-mediated activation of ecto-5'-nucleotidase in the ventricular myocardium, with use of microdialysis techniques in in situ rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts and the tissue was perfused with Tyrode's solution containing adenosine 5'-monophosphate (AMP) through the dialysis probe at a rate of 1.0 microl/min. Adenosine in the dialysate collected during perfusion with Tyrode's solution containing 100 microM AMP (through the probe) originated from the hydrolysis of AMP catalyzed by endogenous ecto-5'-nucleotidase, so that the level of adenosine reflected the activity of ecto-5'-nucleotidase in this tissue. In the presence of NA (10 microM), histidine, a scavenger of highly active singlet oxygen (1O2), significantly increased concentration of adenosine. Histidine (5-50 mM) increased the level of AMP-primed dialysate adenosine in a concentration-dependent manner. When histidine (25 mM) was infused to rat myocardium, small increase in the levels of adenosine were observed. However, when corresponding experiments were performed with NA (10 microM)-pretreated animals, a marked elevation of the level of adenosine in rat heart dialysate was obtained. To confirm the possible mechanism of interaction between 1O2 and NA, we examined the effect of histidine in ischemic-reperfused rat hearts. In the presence of histidine (25 mM), a marked elevation of NA and adenosine was observed. However, when corresponding experiments were performed with reserpinized rat hearts, the elevation of both NA and adenosine was not observed in ischemia-reperfused rat hearts. These results indicate that histidine increases interstitial adenosine concentration via NA release-mediated activation of ecto-5'-nucleotidase.

Akt/protein kinase B prevents injury-induced motoneuron death and accelerates axonal regeneration

Motoneurons require neurotrophic factors for their survival and axonal projection during development, as well as nerve regeneration. By using the axotomy-induced neuronal death paradigm and adenovirus-mediated gene transfer, we attempted to gain insight into the functional significances of major growth factor receptor downstream cascades, Ras-extracellular signal-regulated kinase (Ras-ERK) pathway and phosphatidylinositol-3 kinase-Akt (PI3K-Akt) pathway. After neonatal hypoglossal nerve transection, the constitutively active Akt-overexpressing neurons could survive as well as those overexpressing Bcl-2, whereas the constitutively active ERK kinase (MEK)-overexpressing ones failed to survive. A dominant negative Akt experiment demonstrated that inhibition of Akt pathway hastened axotomy-induced neuronal death in the neonate. In addition, the dominant active Akt-overexpressing adult hypoglossal neurons showed accelerated axonal regeneration after axotomy. These results suggest that Akt plays dual roles in motoneuronal survival and nerve regeneration in vivo and that PI3K-Akt pathway is probably more vital in neuronal survival after injury than Ras-ERK pathway.

MAP kinase pathways activated by stress: the p38 MAPK pathway

A stress-activated serine/threonine protein kinase, p38 mitogen-activated protein kinase (p38 MAPK), belongs to the MAP kinase superfamily. Diverse extracellular stimuli, including ultraviolet light, irradiation, heat shock, high osmotic stress, proinflammatory cytokines and certain mitogens, trigger a stress-regulated protein kinase cascade culminating in activation of p38 MAPK through phosphorylation on a TGY motif within the kinase activation loop. p38 MAPK appears to play a major role in apoptosis, cytokine production, transcriptional regulation, and cytoskeletal reorganization, and has been causally implicated in sepsis, ischemic heart disease, arthritis, human immunodeficiency virus infection, and Alzheimer's disease. The availability of specific inhibitors helps to clarify the role that p38 MAPK plays in these processes, and may ultimately offer therapeutic benefit for certain critically ill patients.

MR in vivo imaging of oxygen suppression effect of soft contact lens on the human cornea

The O(2) suppression effect of a soft contact lens on the human cornea was measured using dynamic magnetic resonance imaging (MRI) of the anterior chamber transcorneally exposed to O(2). Dynamic T(1)-weighted fast spin echo imaging of anterior chambers (TR = 2 s, TE = 15 ms, 5-mm slice) was performed both before and during oxygen supply to a full goggle placed on the face of volunteers wearing a soft contact lens on one eye and nothing on the other eye as a control. Within 15 min after O(2) administration, significantly lower intensity changes were obtained in the anterior chambers of the eyes with the contact lens than in those of the eyes without one, suggesting that dynamic MRI of the anterior chamber transcorneally exposed to O(2) can be used to evaluate the O(2) suppression effect of a soft contact lens on the cornea.

Fluvastatin, a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, resists hydroxyl radical generation in the rat myocardium

The aim of this study was to determine whether fluvastatin, an inhibitor of low-density lipoprotein (LDL) oxidation, can resist Cu (II)-induced hydroxyl radical generation (*OH) in the extracellular fluid of rat myocardium. Rats were anaesthetized and sodium salicylate in Ringer's solution (0.5 nmol microL(-1) min(-1)) was infused through a microdialysis probe to detect the generation of *OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (2,3-DHBA) in the myocardium. When Cu (II) (0, 10, 25 or 50 microM) was administered to 1 mM tyramine-pretreated rats, a marked elevation in the levels of 2,3-DHBA was found, indicating a positive linear correlation between Cu (II) and the increase in *OH formation trapped as 2,3-DHBA in the dialysate (r2 = 0.977). In the presence of fluvastatin (100 microM), a marked decrease in the levels of 2,3-DHBA was found. Corresponding experiments performed with iron (II) (0, 10, 25 or 50 microM), showed a marked elevation in the levels of 2,3-DHBA, indicating a positive linear correlation between iron (II) and the increase in *OH formation trapped as 2,3-DHBA in the dialysate (r2 = 0.986). However, in the presence of fluvastatin (100 microM) a small decrease in the level of 2,3-DHBA was found. The results show that iron (II) against LDL oxidation may be insensitive compared with Cu (II). Cu (II)-induced *OH formation may be reduced by inhibiting LDL with fluvastatin.

Protective effect of fluvastatin, a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on MPP(+)-induced hydroxyl radical in the rat striatum

We examined whether fluvastatin, an inhibitor of low-density lipoprotein (LDL) oxidation, can resist 1-methyl-4-phenylpyridine (MPP(+))-induced hydroxyl radical generation (.OH) in the extracellular fluid of rat striatum. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol/microliter/min) was infused through a microdialysis probe to detect the generation of.OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. MPP(+) (5 mM; total dose 75 nmol) clearly produced an increase in.OH formation. However, fluvastatin (100 microM) reduced the.OH formation by the action of MPP(+). These results indicated that fluvastatin, a potent inhibitor of LDL oxidation, may resist the formation of.OH products of MPP(+).

Reserpine attenuates interstitial adenosine-mediated activation of ecto-5'-nucleotidase in rat hearts in vivo

We examined whether reserpine-induced norepinephrine (NE) depletion attenuated the products of adenosine in rat heart. A flexibly mounted microdialysis technique was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in rat hearts in situ. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at rate of 1.0 microliter/min. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM. The introduction of AMP (100 microM) through the probe increased markedly the dialysate adenosine to 8.95 +/- 0.86 microM, and this increase was inhibited by ecto-5'-nucleotidase inhibitor, alpha, beta-methyleneadenosine 5'-diphosphate (AOPCP, 100 microM), to 0.66 +/- 0.38 microM. Thus, the level of dialysate adenosine is a measure of the ecto-5'-nucleotidase activity in the tissue in situ. AMP concentration for the half-maximal effect of adenosine release (EC(50)) was 107.3 microM. The maximum attainable concentration of dialysate adenosine (E(max)) by AMP was 21.1 microM. However, the EC(50) and E(max) values with reserpinized animals were 106.9 and 7.1 microM, respectively. Electrical stimulation of the left stellate ganglion increased significantly dialysate adenosine concentration, from the control level of 8.66 +/- 0.96 microM to 12.38 +/- 1.11 microM. After stimulation, dialysate adenosine returned to near the prestimulation level. When corresponding experiments were performed with reserpinized animals, the effect of electrical stimulation was abolished. Tyramine (endogenous catecholamine trigger) increased the adenosine concentration in a concentration-dependent manner. However, the elevation of adenosine concentration with reserpinized animals was not observed. These results suggest that reserpine attenuates NE-induced adenosine via stimulation of alpha(1)-adrenoceptor and protein kinase C mediated activation of ecto-5'-nucleotidase in rat heart.

Potassium chloride depolarization enhances MPP+-induced hydroxyl radical generation in the rat striatum

We determined that extracellular potassium ion concentration, [K+]o-induced depolarization, enhances 1-methyl-4-phenylpyridinium ion (MPP+)-induced hydroxyl radical (*OH) generation in the rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused through a microdialysis probe to detect the generation of *OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Induction of high concentration KCl (70 mM) drastically increased formation of *OH trapped as DHBA by the action of MPP+. When dopamine (DA) was administered to the high KCl-treated animals, a marked elevation of DHBA was observed, compared with MPP+-only-treated animals, that showed a positive linear correlation between DA and *OH formation trapped as DHBA (R2 = 0.979) in the dialysate. When corresponding experiments were performed with iron (II), the same results were obtained: a positive linear correlation between the release of iron (II) and DHBA (R2 = 0.988) in the dialysate. These results suggest that [K+]o-induced depolarization enhances the formation of *OH products of efflux/oxidation due to MPP+.

Protective effect of imidaprilat, an angiotensin-converting enzyme inhibitor on *OH generation in rat myocardium

We used a flexibly mounted microdialysis technique to the hearts of rats and examined the protective effect of imidaprilat, an angiotensin-converting enzyme (ACE) inhibitor, on the production of hydroxyl free radical (*OH) generation. A microdialysis probe was implanted into the left ventricular myocardium, and dialysate norepinephrine (NE) concentrations were measured as an index of myocardial interstitial NE levels. Sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was directly infused through a microdialysis probe to detect the generation of *OH reflected by the formation of dihydroxybenzoic acid (DHBA) in rat myocardium. When tyramine (1 mM) was directly infused through the microdialysis probe, the level of NE significantly increased in the dialysate and the level of NE increased by 128 +/- 43%. Imidaprilat (5, 25 and 50 microM) decreased the level of tyramine (1 mM)-induced NE in a concentration-dependent manner. Tyramine clearly produced an increase in *OH formation. In the presence of imidaprilat (50 microM), tyramine failed to increase both 2,3- and 2,5-dihydroxylation. Therefore, the effects of imidaprilat on the *OH generation in the sympathetic nerve blockaded hearts by reserpine treatment were not observed. Moreover, to examine the effect of imidaprilat on *OH formation by ischemia/reperfusion of the myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery. When the heart was reperfused, elevation of NE and 2,3- and 2,5-DHBA in imidaprilat (50 microM)-pretreated animals was not observed in the heart dialysate. Imidaprilat 2.5 mg/kg i.p. pretreatment at 5 h before coronary occlusion significantly blunted the rise of serum creatine phosphokinase and improved the electrocardiogram 2 h after coronary occlusion. These results suggest that imidaprilat, an ACE inhibitor, is associated with cardioprotective effect due to the suppression of NE-induced *OH generation.

Expression of a dominant negative SHP-2 in transgenic mice induces insulin resistance

To elucidate the roles of SHP-2, we generated transgenic (Tg) mice expressing a dominant negative mutant lacking protein tyrosine phosphatase domain (DeltaPTP). On examining two lines of Tg mice identified by Southern blot, the transgene product was expressed in skeletal muscle, liver, and adipose tissues, and insulin-induced association of insulin receptor substrate 1 with endogenous SHP-2 was inhibited, confirming that DeltaPTP has a dominant negative property. The intraperitoneal glucose loading test demonstrated an increase in blood glucose levels in Tg mice. Plasma insulin levels in Tg mice after 4 h fasting were 3 times greater with comparable blood glucose levels. To estimate insulin sensitivity by a constant glucose, insulin, and somatostatin infusion, steady state blood glucose levels were higher, suggesting the presence of insulin resistance. Furthermore, we observed the impairment of insulin-stimulated glucose uptake in muscle and adipocytes in the presence of physiological concentrations of insulin. Moreover, tyrosine phosphorylation of insulin receptor substrate-1 and stimulation of phosphatidylinositol 3-kinase and Akt kinase activities by insulin were attenuated in muscle and liver. These results indicate that the inhibition of endogenous SHP-2 function by the overexpression of a dominant negative mutant may lead to impaired insulin sensitivity of glucose metabolism, and thus SHP-2 may function to modulate insulin signaling in target tissues.

Prazosin attenuates hydroxyl radical generation in the rat myocardium

The present study examined whether tyramine-induced hydroxyl radical (*OH) generation via noradrenaline release was attenuated by prazosin. A flexibly mounted microdialysis technique was used to detect the generation of *OH in in vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anaesthetized rats and Ringer's solution was used. To measure the level of *OH, sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused directly through a microdialysis probe to detect the generation of *OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Tyramine (0.1, 0.5 and 1.0 mM) increased the level of 2,3-DHBA in a concentration-dependent manner. However, in the presence of prazosin (10 microM), the effect of tyramine was abolished. To confirm the generation of *OH by a Fenton type reaction, iron (II) was infused through a microdialysis probe. A positive linear correlation between iron (II) and the formation of 2,3-DHBA (R2 = 0.982) was observed. To examine the effect of prazosin on ischemic/reperfused rat myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery. When the heart was reperfused, a marked elevation of the level of 2,3-DHBA was observed. However, in the presence of prazosin (10 microM), the elevation of 2,3-DHBA was not observed in ischemic/reperfused rat heart. Prazosin was shown to have a *OH scavenging effect. These results suggest that tyramine-induced noradrenaline causes *OH generation, an effect which is inhibited by prazosin as Na+ channel blocker, but not through its alpha1-adrenoceptor antagonistic action of prazosin.

Simultaneous assay of prostaglandins and thromboxane in the cerebrospinal fluid by gas chromatography-mass spectrometry-selected ion monitoring

A method of simultaneous analysis of prostaglandins (PGs) and thromboxane (TX) B2 in cerebrospinal fluid (CSF) with GC-MS-SIM was established. Deuterated PGs and TXB2 were used as internal standards: tetra-deuterated PGE2 (d4-PGE2) for PGE2, PGE1 and PGD2; d5-PGF2alpha for PGF2alpha and 9alpha,11beta-PGF2 and 8-epi PGF2alpha; d4-TXB2 for TXB2; and d4-6-keto PGF1alpha for 6-keto PGF1alpha. The PGs and TXB2 were derivatized to the methyl ester of the methoxim dimethyisopropylsilyl (DMiPSi) ether form or the methyl ester of the DMiPSi ether form with simultaneous preparation. Samples were extracted with octadecyl silica gel and purified in two steps with silisic acid gel chromatography between derivatization steps. The calibration curve of each PG and TXB2 was linear from 10 pg to 10 ng with the isotope dilution method. The levels of the seven types of PG and of TXB2 were assayed simultaneously in the cerebrospinal fluid (CSF) from patients with aseptic meningitis. The CSF pattern of the PG and TXB2 concentrations in mumps meningitis differed from those in other types of aseptic meningitis and in disease controls.

Eicosapentaenoic acid inhibits prostaglandin D2 generation by inhibiting cyclo-oxygenase-2 in cultured human mast cells

BACKGROUND

Eicosapentaenoic acid (EPA) is catalysed by cyclo-oxygenase (COX), as is arachidonic acid, and is a competitive inhibitor of arachidonate metabolism.

OBJECTIVES

We examined the effect of EPA on prostaglandin (PG) D2 generation in the cultured human mast cells with IgE-anti-IgE challenge incubation.

METHODS

Cultured human mast cells were incubated with EPA (1 micromol/L) for 20 h, then challenged with anti-IgE incubation after treatment with IgE. At the same time, COX inhibitors were tested to identify COX-1 and COX-2 activity. PGD2 synthetic activity was also assayed in a cell-free homogenate of cultured mast cells with COX inhibitors and EPA. Histamine in the culture medium and in cells was assayed with the HPLC-fluorescent method. PGD2 and PGD3 were assayed with gas chromatography-mass spectrometry and the stable isotope dilution method.

RESULTS

Although EPA incubation did not affect histamine release by cultured human mast cells in response to IgE-anti-IgE challenge incubation, it did decrease PGD2 generation by inhibiting the COX-2 pathway. In contrast, in the cell-free homogenate of cultured human mast cells, EPA inhibited both COX-1 and COX-2 activities.

CONCLUSION

Pre-incubation with EPA primarily affects the COX-2 pathway in cultured human mast cells and reduces PGD2 generation in response to IgE-anti-IgE challenge incubation. These findings suggest that COX-1 and COX-2 have different substrate flow systems in mast cells. They also suggest that endogenous EPA diet supplementation would reduce PGD2 production and could serve as an anti-inflammatory substrate in human mast cells.

Protective effect of imidaprilat, a new angiotensin-converting enzyme inhibitor against 1-methyl-4-phenylpyridinium ion-induced *OH generation in rat striatum

We examined the antioxidant effects of angiotensin-converting enzyme inhibitor on 1-methyl-4-phenylpyridinium ion (MPP+)-induced hydroxyl radical (*OH) formation in extracellular fluid of rat striatum. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol microl(-1) min(-1) was infused through a microdialysis probe to detect the generation of *OH, as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. MPP+ clearly produced an increase in *OH formation in a concentration-dependent manner. When imidaprilat was infused in MPP+ -pre-treated animals, the formation of dopamine and 2,3-DHBA significantly decreased, as compared with that in the MPP+ -only-treated group. We compared the ability of two non-SH-containing angiotensin-converting enzyme inhibitors (imidaprilat and enalaprilat) with an SH-containing angiotensin-converting enzyme inhibitor (captopril) to scavenge *OH. All three angiotensin-converting enzyme inhibitors were able to scavenge *OH generated by the action of MPP+. However, the changes produced by captopril and enalaprilat were not significant. When dopamine was administered to the MPP+ -pre-treatment group, a marked elevation was observed, showing a positive linear correlation between dopamine and *OH formation (2,3-DHBA) in the dialysate. Moreover, when iron (II) was administered to the MPP+ -pre-treatment group, the same results were obtained: a positive linear correlation (R2 = 0.989) between the release of dopamine and 2,3-DHBA (R2 = 0.989) in the dialysate. When corresponding experiments were performed with imidaprilat-pre-treated animals, the level of 2,3-DHBA decreased. These results suggested that angiotensin-converting enzyme inhibitors may protect against MPP+ -induced *OH formation in the rat striatum.

Protective effect of histidine on hydroxyl radical generation induced by potassium-depolarization in rat myocardium

We investigated the efficacy of histidine on potassium-depolarization induced hydroxyl radical (*OH) generation in the extracellular fluid of rat myocardium by a flexibly mounted microdialysis technique (O system). After the rat was anesthetized, a microdialysis probe was implanted in the left ventricular myocardium, and then sodium salicylate in Ringer's solution (0.5 nmol/microl per minute) was infused to detect the generation of *OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Infusion of KCl (70 mM) clearly produced an increase in *OH formation. However, when KCl in the presence of a high concentration of histidine (25 mM) was infused through the microdialysis probe, KCl failed to increase the 2,3-DHBA formation. To examine the effect of histidine on ischemia-reperfusion of the myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, a marked elevation of the levels of 2,3-DHBA was observed in the heart dialysate. However, when corresponding experiments were performed with histidine (25 mM)-pretreated animals, histidine prevented the ischemia-reperfusion induced *OH formation trapped as 2,3-DHBA. These results indicate that histidine may protect against K+-depolarization-evoked *OH generation in rat myocardium.

Tyramine produces interstitial adenosine-mediated activation of ecto-5'-nucleotidase in rat heart in vivo

We examined the effect of tyramine on the production of adenosine in rat heart. A flexibly mounted microdialysis setup was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in in vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at a rate of 1.0 microl/min. The concentration of adenosine in the effluent (dialysate) was measured by high-performance liquid chromatography (HPLC). Dialysate adenosine obtained during perfusion with the AMP-containing solution through the probe originated from the hydrolysis of AMP by endogenous ecto-5'-nucleotidase, and the level of adenosine reflected the activity of ecto-5'-nucleotidase in the tissue. Tyramine (0-4 mM) increased the adenosine concentration measured during the perfusion of AMP (100 microM) in a concentration-dependent manner. Alpha,beta-methyleneadenosine 5'-diphosphate (alpha,beta-meADP, 100 microM), an inhibitor of ecto-5'-nucleotidase, abolished the AMP-induced increase in dialysate adenosine. Tyramine (1 mM) increased the adenosine concentration measured in the presence of 100 microM AMP (i.e., the activity of ecto-5'-nucleotidase) by 65.8 +/- 19.9% (n = 6, P < 0.05), an increase which was inhibited by an antagonist of the alpha1-adrenoceptor (prazosin, 50 microM) or of protein kinase C (chelerythrine, 10 microM). These data provide the first evidence that alpha1-adrenoceptor stimulation and the subsequent activation of protein kinase C can increase adenosine concentrations in the interstitial space of ventricular muscle in vivo, through activation of endogenous ecto-5'-nucleotidase. To examine the effect of tyramine on the production of adenosine by ischemia-reperfusion of the rat myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery. When the heart was reperfused, elevation of the level of adenosine in the ischemic zone was observed, but this change was not significant. However, when corresponding experiments were performed with a subsequent systemic administration of tyramine (1 mM), a marked elevation in the level of adenosine was observed. The results suggest that tyramine elevates adenosine via stimulation of alpha1-adrenoceptors and protein kinase C-mediated activation of ecto-5'-nucleotidase in rat heart.

A preliminary study for clinical pharmacokinetics of oral fluorine anticancer medicines using the commercial MRI system 19F-MRS

These preliminary studies of dynamic natural abundance 19F-magnetic resonance spectroscopy (19F-MRS) on 5-FU based medicines were performed in the human liver using commercial 1.5 T MRI equipment. A single tuned, custom-made circular shape surface coil with a diameter of 15 cm operating at 60 MHz was used for the 19F-MRS study. Localized proton shimming with a whole body coil was performed with adequate volume to include the observing area of the surface coil, and the line width of the water signal was less than 40 Hz. Very different spectroscopic appearance patterns of 5-FU were observed. We examined whether the pharmacokinetics in the liver of orally administered 1-hexylcarbamoyl-5-fluorouracil (HCFU) differ from those of orally administered 5'-deoxy-5-fluorouridine (5'-DFUR). This preliminary study suggested the 19F-MRS technique could be a useful method of evaluating in vivo the metabolism of 5-FU based medicines.

Reserpine prevents hydroxyl radical formation by MPP+ in rat striatum

The present study investigated the blockage of dopamine (DA) oxidation by reserpine. 1-Methyl-4 phenylpyridinium ion (MPP+) increased the release of DA and the formation of hydroxyl radical ( r22. OH). The r22. OH generated by DA when captured as the hydroxylated derivative of salicylic acid was measured by the high-performance liquid chromatographic-electrochemical (HPLC-EC) procedure. MPP+ concentration for half-maximal effect of DA producing release (EC50) was 5.2 mM. The maximum attainable concentration of dialysate DA (Emax) by MPP+ was 7.7 microM. However, the EC50 and Emax values with reserpinized animal were 5.2 mM and 1.2 microM, respectively. When high concentration of pargyline (10 mM) were infused in MPP+ (5 mM)-pretreated animals, a marked elevation of DA and r22. OH formation was observed. The level of DA and 2, 3-DHBA formations was drastically reduced, as compared with the MPP+-only treated group. Although the levels of MPP+-induced DA and 2,3-DHBA formation after pargyline treatment increased, pargyline failed to increase either the level of MPP+-induced DA or 2,3-DHBA in the reserpinized group. When DA was administered to the MPP+-pretreatment group, a marked elevation was observed, showing a positive linear correlation DA and r22. OH formation trapped as 2,3-DHBA (R2=0.978) in the dialysate. When corresponding experiment were performed with iron (II), the same results were obtained: a positive linear correlation between the release of DA and 2,3-DHBA (R2=0.989) in the dialysate. These results indicated that reserpine-induced DA depletion may reduce MPP+-induced r22. OH formation.

Protective effect of histidine on iron (II)-induced hydroxyl radical generation in rat hearts

We investigated the efficacy of histidine on iron (II)-induced hydroxyl radical (.OH) generation in extracellular fluid of the rat myocardium using a flexibly mounted microdialysis technique (O system). Rats were anesthetized and a microdialysis probe was implanted in the left ventricular, followed by infusion of sodium salicylate in Ringer's solution (0.5 nmol/microL/min) to detect the generation .OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Iron (II) clearly produced a concentration-dependent increase in .OH formation. A positive linear correlation between iron (II) and the formation of 2,3-DHBA (R2 = 0.987) was observed. However, histidine (25 mM) was infused through a microdialysis probe; iron (II) failed to increase the 2,3-DHBA formation obtained. To examine the effect of histidine on ischemia-reperfusion of the myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, a marked elevation of the levels of 2,3-DHBA was observed in the heart dialysate. When corresponding experiments were performed with histidine (25 mM)-pretreated animals, histidine prevented the ischemia-reperfusion induced .OH generation trapped as 2,3-DHBA. These results indicate that histidine protects the myocardium against ischemia-reperfusion damage by .OH generation.

Putidaredoxin-cytochrome p450cam interaction. Spin state of the heme iron modulates putidaredoxin structure

During the monooxygenase reaction catalyzed by cytochrome P450cam (P450cam), a ternary complex of P450cam, reduced putidaredoxin, and d-camphor is formed as an obligatory reaction intermediate. When ligands such as CO, NO, and O2 bind to the heme iron of P450cam in the intermediate complex, the EPR spectrum of reduced putidaredoxin with a characteristic signal at 346 millitesla at 77 K changed into a spectrum having a new signal at 348 millitesla. The experiment with O2 was carried out by employing a mutant P450cam with Asp251 --> Asn or Gly where the rate of electron transfer from putidaredoxin to oxyferrous P450cam is considerably reduced. Such a ligand-induced EPR spectral change of putidaredoxin was also shown in situ in Pseudomonas putida. Mutations introduced into the neighborhood of the iron-sulfur cluster of putidaredoxin revealed that a Ser44 --> Gly mutation mimicked the ligand-induced spectral change of putidaredoxin. Arg109 and Arg112, which are in the putative putidaredoxin binding site of P450cam, were essential for the spectral changes of putidaredoxin in the complex. These results indicate that a change in the P450cam active site that is the consequence of an altered spin state is transmitted to putidaredoxin within the ternary complex and produces a conformational change of the 2Fe-2S active center.

Early detection of radiation-induced liver injury in rat by superparamagnetic iron oxide-enhanced MR imaging

The detectability of early liver injury induced by irradiation was studied using magnetic resonance (MR) imaging enhanced with superparamagnetic iron oxide (SPIO), a tissue-specific contrast agent against the reticuloendothelial system (RES). In rat, 3 days after focal irradiation (0-10 Gy), MR imaging was performed and specimens were obtained to observe the phagocytic function of RES. The irradiated portion of the liver was visualized with a clear demarcation from the nonirradiated part by SPIO-enhanced MR images as a decrease in negative enhancement reflecting the function of RES (P < 0.05), whereas this was impossible with nonenhanced MR images. Significant regression was observed as a dose-related change of the signal intensity in the irradiated portion on SPIO-enhanced MR images (R = 0.867, P < 0.0001). SPIO-enhanced MR imaging was reliable for detecting the range and extent of liver injury a few days after low-dose irradiation, and it may be a useful procedure for verifying the target area in clinical cases of radiation therapy.

Analysis of the consensus binding sequence and the DNA-binding domain of ZF5

Murine ZF5 is a transcription factor with five zinc finger motifs that represses the c-myc gene by binding to two GC-rich elements at the promoter region. Because of its ubiquitous expression in a variety of tissues, elucidation of biological functions and cellular target genes of ZF5 is of great interest. As the first step of identifying cellular target genes, we have attempted to determine the consensus binding motif for ZF5. We succeeded in isolating 19 oligonucleotide duplex DNAs to which ZF5 binds and determined the binding sequences with DNase I footprinting analysis. From these sequences, we deduced the consensus binding motif for ZF5 to be GSGCGCGR. In addition, we have analyzed the DNA-binding domain of ZF5 by testing a series of deletion mutants. It turned out that the zinc fingers 3 and 4 of the five finger motifs play a critical role in DNA binding.

A new antidiabetic agent (JTT-501) rapidly stimulates glucose disposal rates by enhancing insulin signal transduction in skeletal muscle

A newly synthesized antidiabetic agent, JTT-501 is an isoxazolidinedione rather than a thiazolidinedione. An oral dose of JTT-501 (100 mg x kg(-1) x day(-1)) given to 12-week-old male Zucker fatty rats for 7 days led to the amelioration of both hyperinsulinaemia (40% of non-treated) and hypertriglyceridaemia (23% of non-treated) as well as a 2.4-fold increased insulin sensitivity as determined by a euglycaemic insulin clamp. In our study, we further evaluated the acute effect of JTT-501 on both the glucose infusion rates (GIR) and insulin signalling in skeletal muscle. Male Sprague-Dawley (SD) rats aged 10 weeks were injected intravenously with JTT-501 (5 mg/kg) and then a euglycaemic insulin clamp was initiated and glucose infusion rates monitored for 150 min. We found that this treatment increased the glucose infusion rate by 33% during the last 30 min in SD rats. After the clamp had been initiated for 30 min, the insulin-stimulated phosphatidylinositol 3-kinase (PI3-kinase) activities co-immunoprecipitated with insulin receptor substrate 1 (IRS-1) were also enhanced, resulting in increased glycogen synthase activities in the soleus muscles. Treatment with JTT-501 also enhanced the phosphorylation of insulin receptors and insulin receptor-substrate 1 rapidly as well as the phosphatidylinositol 3-kinase activities, which were stimulated by a bolus injection of insulin. Similarly, JTT-501 stimulated the glucose infusion rate by 30% and enhanced insulin signalling in Zucker fatty rats. In conclusion, a newly developed isoxazolidinedione, JTT-501, rapidly potentiates the insulin sensitivity of skeletal muscle by enhancing insulin signalling and could be useful for the treatment of insulin-resistant diabetic subjects.

Protective effect of histidine on MPP+-induced hydroxyl radical generation in rat striatum

We investigated the efficacy of histidine on MPP+-induced hydroxyl radical (.OH) formation in extracellular fluid of rat striatum. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol microl-1 min-1) was infused through a microdialysis probe to detect the generation of.OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. MPP+ (5 mM) clearly produced an increase in.OH formation. However, histidine (25 mM) reduced the.OH formation by the action of MPP+. These results indicate that histidine protects MPP+-induced.OH formation in rat striatum.

Isolation of deoxycytidine kinase from Ehrlich carcinoma cells by affinity chromatography based on a substrate analog, 2'-C-cyano-2'-deoxy-1-beta-D-arabinofuranosyl-N4-palmitoylcytosine++ +

Deoxycytidine kinase from Ehrlich carcinoma cells was purified 10400-fold by ammonium sulfate fractionation and affinity chromatography using Sepharose 4B coupled to 2'-C-cyano-2'-deoxy-1-beta-D-arabinofuranosyl-N4-palmitoylcytosine , with a yield of 45%. The purified enzyme preparation showed a single major band with a molecular weight of 32000 on SDS-PAGE. The enzyme phosphorylated deoxyadenosine, deoxyguanosine, cytidine, and several deoxycytidine analogues as well as deoxycytidine. Also, the kinetic parameters of the enzyme for the substrates were estimated.

[A case of systemic lupus erythematosus overlapping with progressive systemic sclerosis accompanied by deposition of AA amyloid in the stomach]

A 52-year-old woman was admitted to our department because of fever and dysphasia in November 1994. She had noticed Raynaud's phenomenon, arthralgia, and stiffness in the skin for the past 20 years without receiving specific treatment. A diagnosis of progressive systemic sclerosis (PSS) was made based on the presence of sclerosis of the skin, sclerodactyly, pulmonary fibrosis, and the dilatation of the lower esophagus. It was also confirmed that systemic lupus erythematosus (SLE) overlapped based on the presence of an oral ulcer, polyarthralgia, leukocytopenia, renal dysfunction, positive tests for antinuclear antibodies and anti-DNA antibodies. A gastric biopsy specimen revealed amyloid deposits which showed green birefrigence by Congo red staining under polarized light microscopy. The disappearance of the green birefrigence after potassium permanganate treatment indicated that the deposits consisted of AA amyloid. No amyloid deposits were detected in the rectum or the kidney. The average of the SAA level in active SLE patients is 174 micrograms/ml in our department and the SAA level in the present case was 280 micrograms/ml. Although AA amyloidosis is rarely associated with SLE and PSS, a long-term elevation of SAA level could cause the development of amyloidosis even in the cases of SLE and PSS.