Uptake and metabolism of ciclesonide and retention of desisobutyryl-ciclesonide for up to 24 hours in rabbit nasal mucosa.

BACKGROUND: The nasal tissue uptake and metabolism of ciclesonide, a new-generation corticosteroid under investigation for treatment of allergic rhinitis, to its active metabolite, desisobutyryl-ciclesonide (des-CIC), was evaluated when administered to rabbits in a hypotonic versus an isotonic ciclesonide suspension. Nasal mucosa extracts from normal Japanese white rabbits were evaluated by high-performance liquid chromatography with tandem mass spectrometry detection after a single 143-mug dose of ciclesonide. Retention and formation of fatty acid conjugates of des-CIC were also measured in nasal mucosa extracts postadministration of a hypotonic ciclesonide suspension (143-mug single dose). RESULTS: Versus an isotonic suspension, the hypotonic suspension achieved higher concentrations of des-CIC (5.6-fold, 11.4-fold, and 13.4-fold; p < 0.05 for all) and ciclesonide (25.3-fold, 34.2-fold [p = not significant], and 16-fold [p < 0.05]) at 30, 120, and 240 min postadministration. Additionally, when administered via a hypotonic suspension, des-CIC was retained up to 24 h postadministration (45.46 pmol/g tissue). Highest concentration of major fatty acid ester conjugate, des-CIC-oleate, was detected in nasal mucosa at 8 h postadministration. CONCLUSION: These data suggest that a hypotonic ciclesonide suspension provides higher intracellular concentrations of des-CIC up to 24 h, thereby providing a rationale for investigation of ciclesonide as a convenient once-daily nasal spray for treatment of allergic rhinitis.

In vitro metabolism of ciclesonide in human nasal epithelial cells.

Ciclesonide, a corticosteroid in development for allergic rhinitis, is converted to the pharmacologically active metabolite, desisobutyryl-ciclesonide (des-CIC), and des-CIC is subsequently esterified with fatty acids. Various experiments were performed to investigate ciclesonide metabolism in human nasal epithelial cells (HNEC). Human nasal epithelial cells were incubated with (a) 0.1 microM ciclesonide for 1 h and medium without ciclesonide for up to 24 h, (b) esterase inhibitors for 0.5 h followed by 5 microM ciclesonide for 6 h, or (c) 1 microM des-CIC for 6 h followed by medium without des-CIC for up to 24 h. Ciclesonide, des-CIC and des-CIC fatty acid conjugate concentrations were determined by high-performance liquid chromatography with tandem mass spectrometry. The amount of ciclesonide in HNEC decreased approximately 93-fold from 0.5 to 24 h. In contrast, des-CIC was present at constant levels throughout the post-treatment period. Furthermore, fatty acid conjugates of des-CIC were retained in HNEC up to 24 h post-treatment. Carboxylesterase and cholinesterase inhibitors decreased ciclesonide metabolism > or =50%. The total amounts of des-CIC fatty acid conjugates decreased and the extracellular amounts of des-CIC increased with time. In conclusion, ciclesonide was rapidly converted to des-CIC by carboxylesterases and cholinesterases, and des-CIC underwent reversible fatty acid conjugation in HNEC.

Flow cytometric analysis of erythropoietic abnormality: changes in the cell maturity index of reticulocytes and retic distribution index are useful as indicators of erythropoietic toxicity in non-clinical studies.

We performed a flow cytometric (FCM) analysis of the maturity of reticulocytes using peripheral blood obtained from rats administered 5-fluorouracil (5-FU) at 10, 50 and 100 mg/kg or acethylphenyl hydrazine (APHZ) at 1 and 3 mg/kg to clarify whether the FCM method is useful for assessing toxicity. In the 5-FU-administered rats, a decrease and recovery of the immature reticulocyte fraction (Cell Maturity Index, CMI; Retic Distribution Index, RDI) was observed more rapidly (several days prior to changes in the reticulocyte ratio), and sensitively regarding dose-dependency (clear changes were observed at 10 mg/kg, whereas the reticulocyte ratio was only slightly affected). In addition, there was good agreement between the microscopic results obtained by counting Heilmyer's reticulocyte maturation groups, especially for type I and II, and CMI/RDI assessed by the FCM method after the administration of 50 and 100 mg/kg of 5-FU, the dose at which clear changes were obtained with the microscopic method. In the APHZ-administered rats, a dose-dependent increase in CMI/RDI coinciding with the enhancement of reticulocyte production was observed. The results suggested that the automated FCM method could be a useful and valuable tool to assess and predict impairments of erythropoiesis, especially for CMI and RDI, and could help in the diagnosis of hematological disorders in experimental animals.

Enhancement of transformed foci and induction of prostaglandins in Balb/c 3T3 cells by palytoxin: in vitro model reproduces carcinogenic responses in animal models regarding the inhibitory effect of indomethacin and reversal of indomethacin's effect by exogenous prostaglandins.

Cell transforming activity of palytoxin, a non-TPA type tumor-promoter, was investigated with the two-stage transformation assay using Balb/c 3T3 cells. Palytoxin showed potent promoting activity; treatment at 1.9 pM or more increased the number of transformed foci after initiation by 3-methylcholanthrene (MCA). Determination of prostaglandin (PG) E2 and PGF(2alpha) concentrations in the culture medium revealed that palytoxin (1.9-3.7 pM for 24 h) stimulated the production of PG in Balb/c 3T3 cells (the concentration reached 3-4 microM), and treatment with PGE2 or PGF(2alpha) itself increased the number of transformed foci of Balb/c 3T3 cells after initiation by MCA. Neither palytoxin nor PGs showed initiating activity. Indomethacin suppressed the promoting activity of palytoxin, but not that of PGE2 and PGF(2alpha). Interestingly, concomitant treatment with PGE2 or PGF(2alpha) in addition to indomethacin markedly reversed the suppressive effect of indomethacin. These findings indicated that the in vitro transformation model could reproduce experiments that have been performed in animal models regarding the inhibitory effect of indomethacin on carcinogenic responses and reversal of indomethacin's effect by exogenous prostaglandin and, therefore, may provide insight into molecular modes of action of palytoxin. In the present study, palytoxin also induced prostaglandin synthesis, and therefore, the Balb/c 3T3 cell model should provide insight into the molecular mechanism by which palytoxin regulates prostaglandin biosynthesis.

Signet-ring cell ependymoma with intratumoral hemorrhage in the medulla oblongata.

We report a case of signet-ring cell ependymoma of the medulla oblongata. The patient presented with acute paralysis of the soft palate and absent gag reflex resulting in respiratory distress after accidental inhalation of water. MRI revealed a large intra-axial mass with foci of intratumoral hemorrhage in the medulla oblongata. A subtotal resection was performed as histopathological findings on the frozen section were consistent with metastatic carcinoma. However, the final paraffin section showed an ependymoma with signet-ring cells. A total removal was then performed with preservation of the lower cranial nerves. Postoperatively, the patient made a slow but steady recovery, and was able to swallow both water and food within 3 months. Signet-ring cell ependymoma must be included in the differential diagnosis of metastatic carcinoma to the central nervous system.

Selectivity of febuxostat, a novel non-purine inhibitor of xanthine oxidase/xanthine dehydrogenase.

The purine analogue, allopurinol, has been in clinical use for more than 30 years as an inhibitor of xanthine oxidase (XO) in the treatment of hyperuricemia and gout. As consequences of structural similarities to purine compounds, however, allopurinol, its major active product, oxypurinol, and their respective metabolites inhibit other enzymes involved in purine and pyrimidine metabolism. Febuxostat (TEI-6720, TMX-67) is a potent, non-purine inhibitor of XO, currently under clinical evaluation for the treatment of hyperuricemia and gout. In this study, we investigated the effects of febuxostat on several enzymes in purine and pyrimidine metabolism and characterized the mechanism of febuxostat inhibition of XO activity. Febuxostat displayed potent mixed-type inhibition of the activity of purified bovine milk XO, with Ki and Ki' values of 0.6 and 3.1 nM respectively, indicating inhibition of both the oxidized and reduced forms of XO. In contrast, at concentrations up to 100 muM, febuxostat had no significant effects on the activities of the following enzymes of purine and pyrimidine metabolism: guanine deaminase, hypoxanthine-guanine phosphoribosyltransferase, purine nucleoside phosphorylase, orotate phosphoribosyltransferase and orotidine-5'-monophosphate decarboxylase. These results demonstrate that febuxostat is a potent non-purine, selective inhibitor of XO, and could be useful for the treatment of hyperuricemia and gout.

An extremely potent inhibitor of xanthine oxidoreductase. Crystal structure of the enzyme-inhibitor complex and mechanism of inhibition.

TEI-6720 (2-(3-cyano-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid) is an extremely potent inhibitor of xanthine oxidoreductase. Steady state kinetics measurements exhibit mixed type inhibition with K(i) and K(i)' values of 1.2 +/- 0.05 x 10(-10) m and 9 +/- 0.05 x 10(-10) m, respectively. Fluorescence-monitored titration experiments showed that TEI-6720 bound very tightly to both the active and the inactive desulfo-form of the enzyme. The dissociation constant determined for the desulfo-form was 2 +/- 0.03 x 10(-9) m; for the active form, the corresponding number was too low to allow accurate measurements. The crystal structure of the active sulfo-form of milk xanthine dehydrogenase complexed with TEI-6720 and determined at 2.8-A resolution revealed the inhibitor molecule bound in a long, narrow channel leading to the molybdenum-pterin active site of the enzyme. It filled up most of the channel and the immediate environment of the cofactor, very effectively inhibiting the activity of the enzyme through the prevention of substrate binding. Although the inhibitor did not directly coordinate to the molybdenum ion, numerous hydrogen bonds as well as hydrophobic interactions with the protein matrix were observed, most of which are also used in substrate recognition.

Detection and characterization of the evolution of cerebral abscesses with diffusion-weighted magnetic resonance imaging--two case reports.

A 57-year-old man and a 45-year-old woman presented with cerebral abscesses. Diffusion-weighted magnetic resonance (MR) imaging and conventional MR imaging clearly showed the different stages of the course of the brain abscesses. As the abscess matured, the signal intensity of the center gradually increased to the typical high value with a low apparent diffusion coefficient (ADC) on diffusion-weighted MR imaging, and enhancement of the capsule on T1-weighted MR imaging with gadolinium. Healing of the abscess was revealed by the signal intensity of the center returning to isointense and an increase in ADC to the baseline. Surrounding edema showed an increase in ADC, followed by a return to the baseline. These changes probably reflect the pathological processes occurring in the abscesses.