Nobunori Satoh

Acute nephrotoxicity of aristolochic acids in mice

Aristolochic acids (AA), present in Aristolochia plants, are the toxin responsible for Chinese herbs nephropathy (CHN), a rapidly progressive tubulointerstitial nephritis (TIN). To clarify the mechanisms of the development of CHN, we tried to induce TIN in mice using AA. Three strains of inbred mice, BALB/c, C3H/He and C57BL/6, received 2.5 mg kg−1 of AA or AA sodium salt (AANa) daily by intraperitoneal or oral administration, 5 days a week for 2 weeks. Serum and renal tissue were obtained at sacrifice. Twelve‐hour urine samples were individually collected in a metabolic cage at one‐week intervals. In the AA‐injected groups, severe tubular injury, with the appearance of acute tubular necrosis, and rare cell infiltration into the interstitium, were seen in BALB/c mice. C3H/He mice also developed TIN with prominent cell infiltration into the interstitium and interstitial fibrosis. In C57BL/6 mice, only mild and focal tubulointerstitial changes were seen. Serum creatinine and blood urea nitrogen increased in BALB/c and C3H/He mice. Immunofluorescent study revealed no deposition of immune components in kidneys. In the AANa‐treated groups, TIN was also seen in all groups, but even more severe tubulointerstitial changes were induced by intraperitoneal injection. Further examination using purified AAI, AAII, AAIVa and aristolactam I (ALI) revealed that AAI induced strong nephrotoxicity in mice, and that AAII resulted in mild nephrotoxicity. However, AAIVa and ALI caused no nephrotoxicity in this experimental system. There are strain differences in mice in their susceptibility to AA nephropathy. AAI exerted the strongest nephrotoxic effect in mice.

Selective Inhibitors of Membrane-Bound Semicarbazide-Sensitive Amine Oxidase (SSAO) Activity in Mammalian Tissues

Semicarbazide-sensitive amine oxidase (SSAO, EC 1.4.3.6) is a group of enzymes highly sensitive to inhibition by semicarbazide. This high sensitivity distinguishes these enzymes from monoamine oxidase (MAO). Various mammalian tissues contain membrane-bound SSAO which metabolizes only the primary monoamines. Vascular and non-vascular smooth muscle cells have particularly high SSAO activity, but recently the enzyme activity has also been found in non-vascular smooth muscle cells. The substrate specificity of SSAO shows considerable species-related variations. A variety of compounds inhibiting MAO activity has also been identified as SSAO inhibitors. Among inhibitors, there is no specific SSAO inhibitor so far tested. Many studies reinforce the conclusion that inhibitory properties of some compounds against MAO activities has been markedly differed from their properties as SSAO inhibitors. 2-bromoethylamine has been recently developed with a potent, selective and suicide SSAO inhibitor without any inhibitory effect on MAO activity Using this inhibitor, it is possible to study the role of the enzyme in mammalian tissues. As physiological role the increased concentrations of SSAO, especially in blood plasma, have been found in diabetic patients and experimental animals. This enzyme was found to be associated with translocation of the glucose transporter GLUT 4 into the adipose cell surface and involved in the signaling of glucose uptake. Recent studies showed that vascular SSAO metabolizes endogenous primary amines, allylamine, methylamine and aminoacetone, to the corresponding cytotoxic aldehydes. These aldehydes have been linked to the ability of diabetic complications such as neuropathy, retinopathy and nephropathy. Overproduction of such toxic aldehydes produced by increased SSAO activity was proposed to be potentially hazardous in diabetic complications. Thus, reduction or inhibition of SSAO may be beneficial in these pathological conditions. Clearly species-related differences in properties of SSAO must be taken into account in this respect, particularly when assessing if SSAO inhibition may have great application in human.

Behavioral and biochemical changes following acute administration of MPTP and MPP

The acute effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium ion (MPP+) on mouse locomotor activity and striatal dopamine (DA) and 5-hydroxytryptamine (5-HT) levels were investigated. A single dose of either MPTP (10-30 mg/kg, i.p.) or MPP+ (5-20 ug/mouse, i.c.v.) decreased locomotor activity 10-40 min after injection: this locomotor effect was significantly suppressed by either pretreatment with nomifensine or 1-deprenyl alone, or by the combination of desmethylimipramine and 6-hydroxydopamine. Pretreatment with clorgyline did not suppress this behavior and a single dose of haloperidol enhanced the effect. The striatal levels of DA, 3-methoxytyramine and 5-HT increased in parallel with the decrease in locomotor activity caused by MPTP or MPP+. In contrast, levels of 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid were decreased by injection of either MPTP or MPP+. Possible mechanism(s) of the behavioral and biochemical changes caused by the acute actions of MPTP and MPP+ with respect to their neurotoxic effects on the nigrostriatal DA system are discussed.

Inhibition of Brain Type A Monoamine Oxidase and 5‐Hydroxytryptamine Uptake by Two Amphetamine Metabolites, p‐Hydroxyamphetamine and p‐Hydroxynorephedrine

Two amphetamine metabolites, p‐hydroxyam‐phetamine (p‐OHA) and p‐hydroxynorephedrine (p‐OHN), selectively inhibited the A form of monoamine oxidase (MAO) in rat and mouse forebrain homogenates. Of these two metabolites, p‐OHA inhibited MAO‐A more strongly than p‐OHN. This MAO‐A‐selective inhibition by p‐OHA or p‐OHN was found to be competitive with respect to deamination of its substrate, 5‐hydroxytryptamine (5‐HT). The degree of MAO‐A inhibition was not changed by 90 min of preincubation of the enzyme preparations with either metabolite, and the activity inhibited by p‐OHA after the preincubation recovered completely to the control level after repeated washing. Uptake of 5‐HT or dopamine into mouse forebrain synaptosomes was highly reduced by both p‐OHA and p‐OHN. Both metabolites were more potent in reducing dopamine uptake than in reducing 5‐HT uptake. In reduction of 5‐HT and of dopamine uptake, p‐OHA was more potent than p‐OHN. These results indicate that p‐OHA is a more selective inhibitor of brain MAO‐A activity and 5‐HT uptake than its subsequent metabolite, p‐OHN. These two actions of p‐OHA might, together with possible 5‐HT efflux into the synaptic cleft, greatly contribute to head twitch, a brain 5‐HT‐mediated animal behavior induced by p‐OHA.

Inhibition of rat brain monoamine oxidase by some analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 1-methyl-4-phenylpyridinium ion

To clarify the essential chemical structures of the neurotoxins, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its oxidized product, 1-methyl-4-phenylpyridinium ion (MPP+), that govern nigrostriatal dopamine neuron toxicity, interactions of several structurally related compounds of MPTP or MPP+ with monoamine oxidase (MAO) in rat forebrain homogenates were studied. Of the compounds tested, 4-phenyl-1,2,3,6-tetrahydropyridine (PTP), 4-phenylpyridine and 4-phenylpiperidine strongly and dose-dependently inhibited MAO-A and -B activity. Inhibition of PTP and 4-phenylpiperidine was MAO-A-selective, while that by 4-phenylpyridine was MAO-B-selective. Of these 3 compounds, only PTP time-dependently inhibited MAO-B, but not -A. Without preincubation, the modes of inhibition of MAO-A and -B by PTP were competitive. After 1 h preincubation, the mode of MAO-B inhibition changed to non-competitive, while inhibition of -A remained unchanged. PTP was oxidized by MAO-B, but not by -A, under these conditions. In contrast, 4-phenylpyridine and 4-phenylpiperidine were not substrates for either form of MAO in rat forebrain homogenates. These results, along with the other observations, indicate that PTP may essentially cause a neurotoxic effect on the nigrostriatal dopamine pathway.

Effects of Bupleurum scorzoneraefolium, Bupleurum falcatum, and saponins on nephrotoxic serum nephritis in mice.

ETHNOPHARMACOLOGICAL SIGNIFICANCE Bupleuri radix is a commonly prescribed Oriental herbal medicine containing extracts of different Bupleuri species. We wished to determine whether two of these species, Bupleurum scorzoneraefolium and Bupleurum falcatum, or their active ingredients, saikosaponins a, c, and d, could prevent the development of immune-complex nephritis in nephrotoxic serum treated mice. MATERIALS AND METHODS Immune-complex nephritis was created in C57BL/6 mice by administration of nephrotoxic serum containing anti-basement membrane antibodies. Mice were next given one of five treatments: Bupleurum scorzoneraefolium, Bupleurum falcatum, saikosaponin a, saikosaponin c, or saikosaponin d. Proteinuria, blood urea nitrogen, creatinine, and renal histological changes were then examined. RESULTS Saikosaponin c almost completely prevented the development of nephritis, although immune-complex deposition was not affected. Bupleurum falcatum and saikosaponin d had a significant, although lesser effect, and Bupleurum falcatum and saikosaponin a showed no effect. CONCLUSIONS The mechanism of action of saikosaponin c and the reasons for the difference between the two bupleuri species should be investigated further in order to find the best way to utilize the therapeutic effect of Bupleuri radix on nephritis.

Monoamine oxidase and head-twitch response in mice mechanisms of α-methylated substrate derivatives

It is well known that head-twitch response (HTR) in mice represents hallucinations, since administration of lysergic acid diethylamide (LSD) produces hallucinations in humans, and the HTR in mice is induced by administration of LSD as a hallucinogen. The HTR is produced by excitation of 5-hydroxytryptamine (5-HT)2A receptors. In this paper, we review the mechanisms of HTR induced by various drugs such as 5-HT precursor, 5-HT receptor agonist, 5-HT releaser, hallucinogenic compounds, benzodiazepins and cannabinoid. The response induced by HTR-inducers is significantly enhanced by combined treatment with a non-selective form of monoamine oxidase (MAO) inhibitor. Thus, the relationship between MAO activity and HTR caused by these drugs (especially, alpha-methylated analogous compounds which 5-fluoro-alpha-methyltryptamine, 6-fluoro-alpha-methyltryptamine and p-hydroxyamphetamine) is presented in detail.

Acute effects of a parkinsonism-inducing neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on mouse body temperature

The parkinsonism-inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) given in single systemic doses (i.p.) to mice produced marked hyperthermia, and subsequent long-lasting hypothermia. Administration of MPTP or its oxidized product, 1-methyl-4-phenylpyridinium ion, MPP+, via i.c.v. resulted in only hypothermia. In contrast, i.p. MPP+ administration resulted in only hyperthermia. The MPTP-induced hyperthermia (i.p.) was blocked by quaternary derivatives of anti-cholinergic agents, atropine and scopolamine, but not by the tertiary-derivative of atropine. Duration of this hyperthermic effect was potentiated by neostigmine. Pretreatment with 1-deprenyl did not prevent hypothermia, but nomifensine partially or clorgyline completely prevented the effect without preventing MPTP-induced hyperthermia. The thermic effects by MPTP, unlike its neurotoxicity for the nigrostriatal DA system, may not require metabolism to MPP+. These results indicate that peripheral cholinergic functions are responsible for the MPTP-induced hyperthermia, whereas its hypothermic effect may be centrally mediated via dysregulation of the various neuron systems.

Community pharmacists’ perspectives on generic substitution in Japan

AimThe aim of this study was to evaluate Japanese community pharmacists’ attitudes toward and their recommendation of generic substitution, and to identify the barriers towards performing generic substitution.Subject and methodsA questionnaire survey was conducted from June 2007 to December 2008. A total of 1,590 community pharmacists working for 449 community pharmacies whose owners agreed to participate in the study were involved in the study.ResultsA total of 1,253 community pharmacists responded to the survey (response rate: 78.8%). The majority of respondents (72.1%) were in favor of dispensing generic medicine, but they agreed that they would carefully decide if it is appropriate. In spite of these favorable attitudes, more than half of the respondents (55.6%) seldom or never recommend generic substitution to patients. Respondents indicated four barriers preventing them from performing generic substitution: (1) the generic drug is not in stock or no generic drug equivalent is available yet in the market, (2) only a very small cost savings resulting in patients’ objections, (3) physicians’ objections and (4) presence of skepticism in the quality of generic medicines and inadequate drug information from generic manufacturersConclusionIt is not common for Japanese community pharmacists to recommend generic substitution to patients in spite of their positive attitudes towards generic substitution. Prospective policies on generic substitution are needed to overcome the barriers identified in this study, preventing community pharmacists from performing generic substitutions.

Correlation Between the Administration of Morphine or Oxycodone and the Development of Infections in Patients With Cancer Pain

Morphine and oxycodone are widely used in the therapy for cancer pain. Although some previous studies have reported that morphine induces immunosuppression and oxycodone does not, whether this is true for human infections is unclear. We performed a retrospective study on the correlation between the administration of morphine or oxycodone and the development of infections in patients with cancer pain. This study was undertaken in 841 inpatients receiving only 1 opioid continuously for more than 10 days. Development of infections was based on (1) antibiotic administration and (2) diagnosis of infections, positive microbial culture test, or increase in white blood cells or C-reactive protein. Liver, kidney, and hematological cancer, antineoplastic drugs, radiotherapy, steroid, immunosuppressive agents, granulocyte colony-stimulating factor, and thyroid inhibitors were defined as the exclusion criteria in consideration of influence on immune system or metabolism and excretion of morphine and oxycodone. A total of 60 morphine and 74 oxycodone cases were included, which resulted in 18 and 10 infection cases. Significantly more patients treated with morphine developed infections than those patients treated with oxycodone (odds ratio = 3.60, 95% confidence interval = 1.40-9.26). No significant differences were seen in the other variables analyzed. Although perhaps some confounding variables were included because this was an observational rather than randomized study, these results suggested that morphine’s immunosuppressive effect may contribute to the development of infections in patients with cancer pain.