Analysis of adverse drug events in patients with bipolar disorders using the Japanese Adverse Drug Event Report database

The aim of the present study was to survey adverse drug events (ADEs) in patients with bipolar disorders and identify risk factors using the Japanese Adverse Drug Event Report (JADER) database, a spontaneous reporting system. Data on patients with bipolar disorders were extracted from the JADER database. The Medical Dictionary for Regulatory Activities (MedDRA) preferred terms (PT) and standardized MedDRA queries (SMQ) were used to define ADEs. A multiple logistic regression analysis was performed to identify risk factors for ADEs. A total of 8653 reports of 1108 types of ADEs (PT) were registered in data collected on 3521 patients with bipolar disorders. Rash (PT) was the most frequently reported in 549 patients, followed by drug eruption (PT) in 387, fever (PT) in 364, toxicity to various agents (PT) in 291, and Stevens-Johnson syndrome (PT) in 261. Among 24 ADEs (PT) that were reported in more than 50 patients, lamotrigine was associated with increased risks of 13 ADEs (PT), followed by carbamazepine with increased risks of 8 ADEs (PT). The majority of these ADEs belonged to hypersensitivity (SMQ) or hepatic disorder (SMQ). Lithium carbonate was associated with increased risks of rash (PT), drug interaction (PT), and tubulointerstitial diseases (SMQ). All antipsychotics increased the adjusted odds ratio for neuroleptic malignant syndrome (PT). The risk of hyperglycemia/new onset diabetes mellitus (SMQ) was increased by olanzapine, quetiapine fumarate, and risperidone. We are presenting the profiles of ADEs in patients with bipolar disorders using the JADER database, and propose risk factors for 19 ADEs (PT) and 4 ADEs (SMQ).

Analysis of sex difference in the tubular reabsorption of lithium in rats

Lithium is used in the treatment of bipolar disorder. We previously demonstrated that two types of transporters mediate the tubular reabsorption of lithium in rats, and suggested that sodium-dependent phosphate transporters play a role in lithium reabsorption with high affinity. In the present study, we examined sex differences in lithium reabsorption in rats. When lithium chloride was infused at 60 µg/min, creatinine clearance and the renal clearance of lithium were lower, and the plasma concentration of lithium was higher in female rats. These values reflected the higher fractional reabsorption of lithium in female rats. In rats infused with lithium chloride at 6 µg/min, the pharmacokinetic parameters of lithium examined were all similar in both sexes. The fractional reabsorption of lithium was decreased by foscarnet, a representative inhibitor of sodium-dependent phosphate transporters, in male and female rats when lithium chloride was infused at the low rate. Among the candidate transporters mediating lithium reabsorption examined herein, the mRNA expression of only PiT2, a sodium-dependent phosphate transporter, exhibited sexual dimorphism. The present results demonstrated sex differences in the tubular reabsorption of lithium with low affinity in rats.

Potent Inhibition of Biphasic Tubular Reabsorption of Lithium by Acetazolamide and Foscarnet in Rats

Lithium is mainly excreted into urine, and a large fraction of lithium filtered through glomeruli is reabsorbed in the proximal tubule. However, the mechanisms responsible for lithium reabsorption remain unclear. We previously reported that the reabsorption of lithium was biphasic in rats, and that foscarnet inhibited lithium reabsorption with a high affinity type. We herein evaluated the effects of acetazolamide and foscarnet on the renal excretion of lithium in rats treated with lithium chloride at 2 doses. In rats intravenously injected with a bolus of 25 mg/kg lithium chloride, acetazolamide facilitated the urinary excretion of lithium, and increased the fractional excretion of lithium from 0.446 to 0.953, near the theoretically maximum value. At a dose of 2.5 mg/kg lithium chloride, the fractional excretion of lithium was 0.241 in control rats, 0.420 in rats administered acetazolamide, and 0.976 in rats administered acetazolamide and foscarnet. These results showed the potent inhibition of lithium reabsorption by acetazolamide and foscarnet in rats. And, it was exhibited that the effects of acetazolamide on lithium reabsorption differed with the dosages of lithium administered.

Effect of acetazolamide on lithium reabsorption and lithium-induced GSK3β phosphorylation in rat kidney

Lithium promotes the phosphorylation of glycogen synthase kinase-3β (GSK3β), and this reaction protects against acute kidney injury mediated by renal apoptosis. Lithium is considered to be reabsorbed by sodium-phosphate cotransporters and sodium-proton exchanger NHE3. This study evaluated the relation between the lithium reabsorption and the phosphorylation of GSK3β, by using acetazolamide, an NHE3 inhibitor. In rats infused with lithium chloride, the plasma concentration of lithium was 4.77 mEq/l, and the renal clearance of lithium and its fractional excretion were calculated to be 2.29 ml/min/kg and 0.405, respectively. Coadministration of acetazolamide decreased creatinine clearance and the reabsorption rate of lithium, increased the fractional excretion of lithium, and did not affect its plasma concentration. Western blot analysis exhibited the facilitation of GSK3β phosphorylation in the kidney cortex by lithium infusion, and acetazolamide inhibited the lithium-induced phosphorylation of GSK3β. Lithium did not affect GSK3β phosphorylation in the liver and did not affect Akt in the kidney cortex and liver. These data show that lithium reabsorption contributes to GSK3β phosphorylation in the kidney cortex.

Comparative uptake behavior of trace elements in adult and suckling rat lens

The multitracer technique was applied to the determination of the uptake of trace elements in the lenses of adult and suckling rats to investigate the transport mechanisms of trace elements during developmental maturation. Be, Sc, V, Mn, Fe, Co, Zn, As, Se, Rb, Sr, Y, Zr, Ru and Rh accumulate in adult and suckling rat lenses. The rates of uptake of trace elements differ among each species and also differ between adult and suckling rat lenses. The uptakes of Fe and Sr are greater in adult rat lenses, while the uptakes of Se and Rb are greater in suckling rat lenses. High concentrations of Zn are transported into the lenses of both adult and suckling rats in comparison with other elements, and the content of Zn in suckling rat lens is higher than in adult lens. The present study suggests that different mechanisms depending on the stage of development act to transport trace elements into lenses.

Expression of plasma membrane Ca(2+)-ATPase in lenses from normal and hereditary cataract UPL rats

PURPOSE

The regulation of calcium concentration in lens cells is important in the mechanisms of cataractogenesis. The Ca( 2+) level in cells is controlled by plasma membrane Ca(2+)-ATPase (PMCA). PMCA has several isoforms that are distributed in various cell types in the body. In this study, we investigated the PMCA mRNA expression in normal lenses and in lenses from rats with newly developed hereditary cataracts.

METHODS

The rats used were the UPL strain of Sprague-Dawley rats, with (UPL) and without (normal) the dominant gene for cataracts. PMCA mRNA expression in the lens, brain, liver and kidney in the normal and UPL rats was detected by reverse transcription-PCR using isoform specific primers. Partial cDNA sequences of the lens PMCA were also determined.

RESULTS

PMCA1, 2, 3 and 4 were expressed in the brain and kidney. Distinct from the brain, liver and kidney, only one isoform of PMCA, PMCA1b, was expressed in both normal and UPL rat lenses. Sequences of PMCA in normal and UPL rat lenses were not different.

CONCLUSIONS

The present study demonstrated that PMCA1b is the only form of PMCA present in both normal and UPL rat lenses.

Nitric oxide participates in cataract development in selenite-treated rats

PURPOSE

The role of nitric oxide in the development of selenite-induced cataracts in rats was examined using nitric oxide synthase (NOS) inhibitors.

METHODS

Subcutaneous injection of sodium selenite was used to induce cataracts in rats, with or without pretreatment with NOS inhibitors. The anterior eye segment analysis system (EAS-1000, Nidek) was used to measure lens opacity. The glutathione content of the lenses was determined by an HPLC method and the Ca2+ content by atomic absorption spectrometry. Nitrite, a stable metabolite of nitric oxide, was determined fluorometrically. NADPH-diaphorase activity staining and Western blot analysis were used to determine NOS levels.

RESULTS

Administration of the NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), inhibited lens opacification in selenite-treated rats. NG-nitro-d-arginine methyl ester, an inactive enantiomer of l-NAME, had no effect. Aminoguanidine, another NOS inhibitor, also inhibited the development of cataracts in a dose-dependent manner. On the other hand, L-arginine, a substrate of NOS, accelerated the development of cataracts. Although the opacification of the lenses was apparent approximately 3 days after selenite injection, the nitrite level was increased within one day. In addition, NOS was induced in the eye within one day of selenite injection.

CONCLUSIONS

The present study demonstrated that NOS inhibitors prevented the development of cataracts in selenite-treated rats. The results also suggest that nitric oxide had an important role in the development of selenite-induced cataracts.

Preparation and in vivo ocular absorption studies of disulfiram solid dispersion

Disulfiram, a dimer of diethyldithiocarbamate (DDC) which is a strong radical scavenger, is known to prevent cataract development. However, disulfiram is hardly absorbed from the cornea and its bioavailability is extremely low. In this study, we attempted to prepare disulfiram solid dispersion for the improvement of ocular bioavailability. Solid dispersions of disulfiram were prepared by either an evaporation method or a spray-drying method, using polyvinylpyrrolidone (PVP) as a carrier. Preparations were analyzed by scanning electron microscopy, powder X-ray diffractometry and differential scanning calorimetry, and confirmed to be a solid dispersion. The particle size of the solid dispersion prepared by the spray-drying method was smaller than the preparation by the evaporation method (spray-drying: 3.3+/-0.04 microm, evaporation: 34.3+/-18.0 microm). An in vivo ocular absorption experiment was conducted by instilling solid dispersions to rabbit eye and measuring the DDC in the aqueous humor. After instillation of disulfiram and PVP physical mixture, DDC was not detected in the aqueous humor. On the other hand, DDC appeared in the aqueous humor after the instillation of a solid dispersion. Maximal concentration and the area under the aqueous humor concentration-time curve were greater in the solid dispersion prepared by the spray-drying method than the preparation by the evaporation method. Disulfiram solid dispersion, especially prepared by the spray-drying method, improved ocular bioavailability.

Chain conformational analysis of beijeran by n-h map calculations

Possible regular helix models of beijeran, a new acidic heteropolysaccharide consisting of a trisaccharide as a repeating unit, were investigated. Conformational analyses of the three component disaccharides were first carried out by calculating their relaxed-residue energy maps with respect to the glycosidic bond rotations, phi and psi. A search for possible beijeran chain conformations was carried out by calculating the two-dimensional map of the helix parameters; n (the number of asymmetric units per a fiber repeat) and h (the axial rise per the unit), on the basis of the phi-psi conformations taken from the low energy regions of each of the three energy maps. The n-h values of the helix models with low steric energies were mostly found to be around the experimental values (n = 2 and h = 1.20-1.25 nm), which may support the present methodology. It was also suggested that the internal flexibility of beijeran chain allowed it to conform in diverse helical structures, each of which were reasonably in accord with the observed n-h values. The three representative helix models were finally proposed for the beijeran chain conformation in the crystal structure.

Cholesterol modulates organic cation transport activity and lipid fluidity in rat renal brush-border membranes

The role of cholesterol in organic cation transport was studied in rat renal brush-border membranes. H+ gradient-dependent uptake of the organic cation tetraethylammonium in brush-border membrane vesicles was stimulated by cholesterol enrichment in a dose-dependent manner. The dissipation rate of the H+ gradient, a driving force for organic cation transport in brush-border membranes, was reduced by cholesterol enrichment. Tetraethylammonium uptake in the absence of H+ gradient was also stimulated by cholesterol enrichment. These findings indicate that cholesterol modulates tetraethylammonium uptake by affecting the intrinsic activity of the organic cation transporter and the H+ gradient dissipation rate. Therefore, cholesterol content should be an important determinant for organic cation transport in renal brush-border membranes.

Modulation of organic cation transport and lipid fluidity by benzyl alcohol in rat renal brush-border membranes

PURPOSE

Organic cations are actively transported in renal brush-border membranes (BBM) by the H+/organic cation antiport system. In the present study, we investigated the relationship between membrane fluidity and organic cation transport in the BBM.

METHODS

The effects of benzyl alcohol, a membrane fluidizing agent, on the organic cation tetraethylammonium (TEA) uptake were studied using renal BBM vesicles isolated from rat kidney. BBM fluidity was assessed by fluorescence polarization technique.

RESULTS

H+ gradient-dependent uptake of TEA in BBM vesicles was inhibited by benzyl alcohol in a dose-dependent manner, with an apparent half inhibitory concentration of 18mM. The decrease in fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene in BBM, which represents the increase in membrane fluidity, was correlated with the decrease in TEA transport activity. The dissipation rate of H+ gradient, a driving force for organic cation transport in BBM, was increased by benzyl alcohol. In addition, H+ gradient-independent TEA-TEA exchange was also inhibited by benzyl alcohol. These findings indicate that benzyl alcohol inhibits the uptake of TEA by affecting the intrinsic activity of the organic cation transporter and the H+ gradient dissipation rate.

CONCLUSIONS

The membrane fluidity should be an important determinant for organic cation transport in renal BBM.

Identification of organic cation transporter in rat renal brush-border membrane by photoaffinity labeling

As an approach to identification of the organic cation transport system in brush-border membranes, we designed a photoaffinity probe, 1-cyano-2-(4-azido[3,5-3H]benzoylethyl)-3-[2-[[(5-methyl-4-imidazo lyl ) methyl]thio]ethyl]-guanidine ([3H]AMC) based on the molecular structure of cimetidine, which is taken up by the organic cation transport system in brush-border membrane vesicles. The effect of nonradioactive 1-cyano-2-(4-azidobenzoylethyl)-3-[2-[[(5-methyl-4- imidazolyl)methyl]thio]ethyl]guanidine (AMC) on tetraethylammonium uptake was investigated in rat renal brush-border membrane vesicles. We examined the photolysis of AMC in which the azido group was converted to an active nitrene group using UV light at a wavelength of 254 nm and established a half-life of 7 s. This half-life duration did not significantly impair brush-border membrane vesicles during the exposure to light for photo-labeling. Photoaffinity labeling of brush-border membrane vesicles from the rat renal cortex with [3H]AMC resulted in the covalent incorporation of radioactivity into membrane polypeptides; an apparent 36 kDa polypeptide was predominantly labeled. Photolabeling specificity was shown by a reduction in the labeling of the 36 kDa polypeptide in the presence of organic cations, cimetidine, tetraethylammonium and N-methylnicotinamide whereas the organic anion, fur osemide, had no effect on labeling patterns. These data demonstrate that AMC, as well as organic cations, cimetidine, tetraethylammonium and N-methylnicotinamide, interact with a common 36 kDa membrane polypeptide, which may be the transport system or one of its brush-border membrane components.