Norihiro Shinkai

Intra-articular penetration of ketoprofen and analgesic effects after topical patch application in rats

The purpose of this study was to evaluate percutaneous penetration and pharmacological effects of ketoprofen after transdermal administration, compared to the oral route. Skin and knee joint penetration of ketoprofen was tested by a microdialysis technique in rats and in vivo recovery was determined by retrodialysis. After oral and transdermal administration of ketoprofen, dialysate was sampled at 60 min intervals up to 360 min, for determination of concentrations of ketoprofen and prostaglandin E2. Analgesic effects of ketoprofen in iodoacetate and adjuvant-induced arthritis models were evaluated using the weight bearing method. The average recoveries of ketoprofen over 360 min in the skin and knee joint were 60.2+/-3 and 15.8+/-9%, respectively. Cmax values for ketoprofen absorbed within the skin after oral and transdermal administration were 20.1+/-5 and 297.5+/-478 ng/mL, respectively, and within the knee joint, 4.4+/-0.4 and 2.7+/-0.9 ng/mL. The Cmax value for the plasma concentration of ketoprofen after oral administration was approximately 80 times higher than with the transdermal route. Both transdermal and oral administration of ketoprofen significantly decreased PGE2 production in the skin and knee joint and improved weight bearing after exposure to iodoacetate and adjuvant. These results indicate that the transdermal ketoprofen patch is a useful formulation that can deliver the drug in sufficient amounts to inhibit prostaglandin E2 production in the skin and knee joint.

Camptothecin disrupts androgen receptor signaling and suppresses prostate cancer cell growth

The androgen receptor (AR) is the main therapeutic target for treatment of metastatic prostate cancers. The present study demonstrates that the topoisomerase I inhibitor camptothecin selectively inhibits androgen-responsive growth of prostate cancer cells. Camptothecin strikingly inhibited mutated and wild-type AR protein expression in LNCaP and PC-3/AR cells. This inhibition coincided with decreased androgen-mediated AR phosphorylation at Ser(81) and reduced androgen-mediated AR transcriptional activity in a dose-dependent manner. Additionally, camptothecin disrupted the association between AR and heat shock protein 90 and impeded binding of the synthetic androgen [3H]R1881 to AR in LNCaP cells. Camptothecin also blocked androgen-induced AR nuclear translocation, leading to downregulation of the AR target gene PSA. In addition to decreasing the intracellular and secreted prostate-specific antigen (PSA) levels, camptothecin markedly inhibited androgen-stimulated PSA promoter activity. Collectively, our data reveal that camptothecin not only serves as a traditional genotoxic agent but, by virtue of its ability to target and disrupt AR, may also be a novel candidate for the treatment of prostate cancer.

Microdialysis assessment of percutaneous penetration of ketoprofen after transdermal administration to hairless rats and domestic pigs.

The study was performed to evaluate the percutaneous penetration of ketoprofen after transdermal administration using a microdialysis technique in pigs, in comparison with rats. Ketoprofen release from patches was determined by analysis of the remaining drug content after application to hairless rats and pigs. Skin and knee joint penetration of ketoprofen was tested by microdialysis, and recovery was determined by retrodialysis. Residual rates in hairless rats and pigs were 68.1 ± 1.6% and 81.7 ± 4.4%, respectively, at 10h. The average recoveries of ketoprofen over 480 min in the skin and knee joint cases were 72.0 ± 3.4% and 9.8 ± 6.2% in rats and 72.3 ± 2.5% and 57.6 ± 3.1% in pigs, respectively. In rats, ketoprofen was rapidly absorbed with transdermal administration, with C(max) values of 191.7 ± 76.2 and 35.5 ± 21.7 ng/mL and AUC(0-8h) values of 918.2 ± 577.5 and 195.9 ± 137.1 ngh/mL, respectively, for the skin and knee joint. The C(max) values for the pig were 20.9 ± 18.5 and 3.7 ± 3.0 ng/mL, with AUC(0-8h) values of 73.1 ± 69.2 and 16.1 ± 16.1 ngh/mL. Ketoprofen concentrations within skin and knee joint of non-application sites in rats and pigs were less than 0.8 ng/mL. Transdermal administration of ketoprofen significantly reduced prostaglandin E2 levels in the skin of the application site and showed a tendency for inhibition in the knee joint. We thus demonstrated that topical patches containing ketoprofen can deliver the drug through the skin and knee joint of pigs and rats via direct diffusion, and microdialysis data with the pig may be useful for the prediction of human tissue penetration of drugs with transdermal administration.

Oligoarginine-linked polymers as a new class of penetration enhancers

Oligoarginines, which are known as cell-penetrating peptides, enhance the cellular uptake of poorly membrane-permeable bioactive molecules that are chemically conjugated to them. We designed a novel polymer: oligoarginine-linked poly(N-vinylacetamide-co-acrylic acid), with the expectation that the polymers will enhance the cellular uptake of the bioactive molecules that are physically mixed with them. Oligoarginines were grafted onto the polymer backbone through the chemical reaction with acrylic acid functional groups. The changes in the blood glucose concentration after nasal administration of insulin with and without the polymer were monitored in mice. The blood glucose concentration was slightly reduced when insulin was given solely at a dose of 10IU/kg. A D-octaarginine-linked poly(N-vinylacetamide-co-acrylic acid) with a grafting degree of 2% significantly enhanced the insulin-induced hypoglycemic effect. A similar enhancement was not observed when the polymer was substituted with intact D-octaarginine. The penetration-enhancing function of D-octaarginine-linked poly(N-vinylacetamide-co-acrylic acid) increased dramatically with an increase in the grafting degree of D-octaarginine. Substitution of D-octaarginine with the corresponding optical isomer and an increase in the number of arginine residues rather reduced the penetration-enhancing function. In vitro cell studies also indicated that a D-octaarginine-linked poly(N-vinylacetamide-co-acrylic acid) with a grafting degree of 17% enabled fluorescein isothiocyanate-dextran to effectively penetrate the cell membrane. Results demonstrated that our oligoarginine-linked polymer has a potential to provide a new class of penetration enhancers.

Percutaneous penetration of felbinac after application of transdermal patches: relationship with pharmacological effects in rats.

We have evaluated the percutaneous penetration of felbinac following application of topical patches using a microdialysis technique, and have examined correlations with pharmacological effects. A linear microdialysis probe with a 20‐mm dialysis fibre was inserted into the skin of anaesthetized rats. Probe perfusion was started at 2.0 μL min−1 with physiological saline and after a 60‐min baseline sampling of dialysate, 0.1 mL croton oil was applied to the skin surface at a concentration of 8%, v/v. A felbinac patch was then applied to the same point 60 min thereafter and dialysate was sampled at 60‐min intervals up to 300 min after patch application, for determination of concentrations of felbinac and prostaglandin (PG) E2. Analgesic effects of felbinac patches in an iodoacetate‐induced osteoarthritis model and an incisional pain model were evaluated using the weight bearing method. After application of patches, felbinac penetration into the skin was rapid, maximum concentrations in the dialysates with 0.07, 0.5 and 3.5% w/w felbinac patches being 0.046 ± 0.02, 0.104 ± 0.06 and 0.244 ± 0.2 μg mL−1, respectively. Dermal administration of croton oil caused an increment in PGE2 levels, which was significantly decreased by 0.5 and 3.5% felbinac patches 2–5 h after application. In pharmacological studies, 3.5% felbinac patches suppressed pain‐associated behaviour induced by iodoacetate injection and plantar incision. These results suggested that the transdermal patch containing 3.5% felbinac may become a useful formulation.

Performance of cell-penetrating peptide-linked polymers physically mixed with poorly membrane-permeable molecules on cell membranes

We are investigating a new class of penetration enhancers that enable poorly membrane-permeable molecules physically mixed with them to effectively penetrate cell membranes without their concomitant cellular uptake. Since we previously revealed that poly(N-vinylacetamide-co-acrylic acid) modified with d-octaarginine, which is a typical cell-penetrating peptide, significantly enhanced the nasal absorption of insulin, we examined the performance of the polymers on cell membranes. When Caco-2 cells were incubated with 5(6)-carboxyfluorescein (CF) for 30 min, approximately 0.1% of applied CF was internalized into the cells. This poor membrane permeability was dramatically enhanced by d-octaarginine-linked polymers; a 25-fold increase in the cellular uptake of CF was observed when the polymer concentration was adjusted to 0.2mg/mL. None of the individual components, for example, d-octaarginine, had any influence on CF uptake, demonstrating that only d-octaarginine anchored chemically to the polymeric platform enhanced the membrane permeation of CF. The polymer-induced CF uptake was consistently high even when the incubation time was extended to 120 min. Confocal laser scanning microphotographs of cells incubated with d-octaarginine-linked polymers bearing rhodamine red demonstrated that the cell outline was stained with red fluorescence. The polymer-induced CF uptake was significantly suppressed by 5-(N-ethyl-N-isopropyl)amiloride, which is an inhibitor of macropinocytosis. Results indicated that d-octaarginine-linked polymers remained on the cell membrane and poorly membrane-permeable CF was continuously internalized into cells mainly via macropinocytosis repeated for the individual peptidyl branches in the polymer backbone.

Automated analysis of fluvoxamine in rat plasma using a column-switching system and ion-pair high-performance liquid chromatography.

We have established a robust, fully automated analytical method for the analysis of fluvoxamine in rat plasma using a column-switching ion-pair high-performance chromatography system. The plasma sample was injected onto a precolumn packed with Shim-pack MAYI-ODS (50 microm), where the drug was automatically purified and enriched by on-line solid-phase extraction. After elution of the plasma proteins, the analyte was back-flushed from the precolumn and then separated isocratically on a reversed-phase C18 column (L-column ODS) with a mobile phase (acetonitrile-0.1% phosphoric acid, 36:64, v/v) containing 2 mM sodium 1-octanesulfonate. The analyte was monitored by a UV detector at a wavelength of 254 nm. The calibration line for fluvoxamine showed good linearity in the range of 5-5000 ng/mL (r > 0.999) with the limit of quantification of 5 ng/mL (RSD = 6.51%). Accuracy ranged from -2.94 to 4.82%, and the within- and between-day precision of the assay was better than 8% across the calibration range. The analytical sensitivity and accuracy of this assay is suitable for characterization of the pharmacokinetics of orally-administered fluvoxamine in rats.

Tocolytic Effects of a Long‐acting β2‐Adrenoceptor Agonist, Formoterol, in Rats

We have assessed the tocolytic activity of formoterol, a novel long‐acting and potent β2‐adrenoceptor agonist, through its production of cyclic adenosine monophosphate, in comparison with ritodrine, a β2‐adrenoceptor agonist used clinically to counter premature delivery.

Tocolytic activity of formoterol against premature delivery in mice.

The tocolytic activity of formoterol (eformoterol), a long‐acting potent β2‐adrenoceptor agonist, was assessed in pregnant mice, with determination of uterine effects on the 15th and 16th days of gestation. For examination in the lipopolysaccharide‐induced premature delivery model, osmotic pumps filled with formoterol or saline solution were implanted subcutaneously under the back skin. The mice were sacrificed 18–20 h thereafter, and the numbers of fetuses in the uteri and the newborn were counted. The uteri, amniotic membranes and placenta were also rapidly removed for determination of IL‐6 concentrations. Furthermore, the effect of formoterol on IL‐6 secretion from mouse amnion cells was determined. Formoterol and ritodrine inhibited contraction responses of isolated mouse uteri and their intravenous administration resulted in lowered uterine motility. Lipopolysaccharide (30 μg mL−1/mouse) induced premature delivery, attributable to increased IL‐6 secretion, and formoterol suppressed this. Doses of 5–500 μg/mouse thus reduced the number of prematurely delivered newborn, and 50 μg/mouse also depressed IL‐6 secretion. On histopathologic analysis, the marked oedema and slight haemorrhage in the mouse cervix induced by lipopolysaccharide were reduced by administration of the β2‐adrenoceptor agonist. Neither formoterol (10−7–10−5 m) nor ritodrine (10−7–10−5 m) influenced spontaneous secretion of IL‐6 in amnion cells. However, at 10−7 and 10−5 m, and 10−6 and 10−5 m, respectively, they inhibited lipopolysaccharide‐induced IL‐6 secretion and this inhibitory effect was competitively reversed by addition of ICI‐118,551 (β2‐adrenoceptor antagonist), but not atenolol (β1‐adrenoceptor antagonist). These findings strongly suggest that formoterol can suppress premature delivery mediated by its actions on IL‐6 secretion.

Tocolytic effects of formoterol are associated with local change in the progesterone/estradiol ratio

OBJECTIVE The aim of the study was to determine whether a beta(2)-adrenoceptor agonist, formoterol, inhibits premature delivery in connection with change in estradiol and progesterone concentrations in the amniotic fluid in ovariectomized rats. STUDY DESIGN Pregnant rats at the 15th day of gestation were bilaterally ovariectomized and given injection of 17beta-estradiol immediately after the operation and every 24 h. An osmotic pump filled with a solution of formoterol or saline was also implanted subcutaneously into the back of each. The animals were killed by decapitation under light ether anesthesia 18, 36, 54 or 72 h after ovariectomy, and the numbers of undelivered fetuses and newborn were counted. Amniotic fluid was collected 16, 36, and 54 h after ovariectomy. RESULTS Formoterol (0.15 mg/(kg h)) reversed the decline in premature delivered fetuses due to 17beta-estradiol 54 and 72 h after ovariectomy. Although no influence was evident regarding the progesterone and estradiol concentrations in amniotic fluid in ovariectomized rats supplemented with 17beta-estradiol, formoterol significantly inhibited the increment in the estradiol/progesterone ratio as well as the elevation in prostaglandin F2alpha concentration. CONCLUSION These findings indicate that tocolytic effects of formoterol may be associated with suppression of uterine activity due to modulation of hormone secretion.