Solid-in-oil nanodispersion as a novel topical transdermal delivery to enhance stability and skin permeation and retention of hydrophilic drugs l-ascorbic acid

l-ascorbic acid （Vitamin C, VC） is the most abundant antioxidant in human skin. But its poor penetration into the skin and unstability limit the application. The aim of the study was to promote the topical skin permeation and retention of VC, increase the stability as well as effectiveness by a novel solid in oil nanodispersion. In the nanodispersions system, nano-sized particles of hydrophilic molecules are dispersed in an oil vehicle with the assistance of hydrophobic surfactants. The optimized formula composed of O170 and S1570 (12.5:1, w/w) showed high EE% of 98% and good stability. FTIR analysis confirmed that there may be hydrogen bond between VC and surfactants. The results of DSC, and XRD revealed that the drug was successfully encapsulated in the surfactants, which maintained the stability of drug. By analyzing and fitting the release data in vitro, the drug release mechanism of SONDs was predicted as a multi-dynamic model. Skin permeation of VC was improved 3.43-fold for SONDs compared with VC aqueous solution, highlighting that the lipophilicity and nano size of the carrier more easily penetrated into the skin. Finally, the photoaging study revealed that topical application of VC-SONDs provided the highest skin protection compared UV and VC aqueous solution treated group which was evident by the normal thick epidermal morphology, no obvious melanocytes and the densely arranged dermal elastic fibers. These results demonstrated that the solid-in-oil nanodispersions may be a potential transdermal delivery system for hydrophilic bioactive ingredients.

Tacrolimus and paclitaxel co-loaded O/O ointment without surfactant: Synergistic combinations for the treatment of psoriasis

Psoriasis is an autoimmune disorder disease with abnormally activated T lymphocytes and thickening of the epidermis. The mechanism of the action of tacrolimus and paclitaxel are matched with the two only known pathogenesis of psoriasis. However, there has been no report on tacrolimus combined with paclitaxel in the treatment of psoriasis until now. The O/O ointment was prepared for the topical application to overcome poor solubility, poor skin penetration, and erratic absorption of the two drugs. A high-speed shearing method was adopted to prepare the ointment, in which propylene carbonate was used to solve tacrolimus and paclitaxel completely. The ointment showed excellent stability, slow release of the drugs, better retention in psoriatic skin, and good skin tolerance. The therapeutic efficacy of ointment was evaluated with imiquimod induced psoriatic model, and the level of expression of psoriatic biochemical markers was evaluated using the PASI score and immunohistochemistry. The cumulative PASI score was 10.8 for the imiquimod induced group, 7.8 for the tacrolimus ointment group, 8.3 for the paclitaxel ointment and 5.3 for the tacrolimus-paclitaxel (1:1) ointment group, respectively. Ointment group with tacrolimus and paclitaxel indicated a significant improvement in the phenotypic features of the psoriatic skin treated. Compared with the imiquimod group, tacrolimus-paclitaxel (1:1) ointment group was significantly reduced the level of IL-17. The results confirm that tacrolimus and paclitaxel co-loaded ointment can be an effective strategy for the treatment of psoriasis.

Solid-in-oil nanodispersions as a novel delivery system to improve the oral bioavailability of bisphosphate, risedronate sodium

The aim of the current study was to modify the oral absorption of risedronate sodium (RS) using solid-in-oil nanodispersions (SONDs) technology. The oral therapeutic effect of RS is limited in vivo because of its low membrane permeability and the formation of insoluble precipitates with bivalent cations (such as Ca²⁺) in the gastrointestinal (GI) tract.We used SONDs to prepare medium-chain triglyceride (MCT)-based nanodispersions of the hydrophilic drug, which used the oral absorption mechanism of MCT digestion to improve bioavailability of RS in vivo. SONDs exhibited high encapsulation efficiency of RS and excellent enzymatic degradation-dependent release behavior. The result of an everted gut sac test showed that the P_app value of the SONDs was 6.29-fold (p<0.05) higher than that of RS aqueous solutions in simulated intestinal fluid containing 5 mM Ca²⁺, this was because MCT can be digested to form the fatty acids C₈ and C₁₀, which have an adsorption-promoting effect on RS. Further, solid-in-oil-in-water (S/O/W) emulsion droplets formedafter emulsification by bile salts and MCT digestionwere effective in disrupting epithelial tight junctions (TJs), facilitating the paracellular permeation of RS throughout the intestine. Moreover, in vivo absorption study in rats revealed that the AUC_0-12h of RS in SONDs was approximately 4.56-fold (p<0.05) higher than with RS aqueous solutions at the same dose (15 mg/kg). This approach demonstrates a potential drug delivery system to improve the bioavailability of risedronate sodium.

In Vitro-In Vivo Correlation for Solid Dispersion of a Poorly Water-Soluble Drug Efonidipine Hydrochloride

The aim of this present study was to investigate the ability of different dissolution methods to predict the in vivo performance of efonidipine hydrochloride (EFH). The solid dispersions of EFH were prepared by solvent evaporation method with HPMC-AS as matrix and urea as a pH adjusting agent. The paddle method, the open-loop, and the closed-loop flow-through cell methods were studied. In the study, Weibull's model was the best fit to explain release profiles. The pharmacokinetics behaviors of two kinds of solid dispersions with different release rate were investigated in comparison to the EFH after oral administration in rats. In vivo absorption was calculated by a numerical deconvolution method. In the study, the level A in vivo and in vitro correlation (IVIVC) was utilized. The correlation coefficient was calculated and interpreted by means of linear regression analysis (Origin.Pro.8.5 software). As a result, excellent IVIVC for solid dispersions and crude drug (r² = 0.9352-0.9916) was obtained for the dissolution rate determined with flow-through cell open-loop system in phosphate buffer solution with 0.1% (w/v) polysorbate 80 at pH 6.5, the flow-rate of 4 mL/min. In addition, the self-assembled flow cell system had good repeatability and accuracy. The dissolution rate of the solid dispersion could be slowed down by the flow-through method, and the difference caused by preparation was significantly distinguished. The study demonstrated that flow-through cell method of the open-loop, compared with paddle method, was suitable for predicting in vivo performance of EFH solid dispersions.

The characteristics and mechanism of co-administration of lovastatin solid dispersion with kaempferol to increase oral bioavailability

Lovastatin shows low bioavailability (lower than 5%) after oral administration because of the poor aqueous solubility and widely metabolized by CYP3A4.Lovastatin solid dispersion was designed to enhance the dissolution. The in vitro intestinal absorption study indicated an increase in the apparent permeability of different intestinal segments compared with crude lovastatin. In the range of 12.5-50 μg/ml, the absorption of both lovastatin and lovastatin solid dispersion were found to be a passive process in rat's jejunum and ileum, but not endocytosis process. CYP3A4 inhibitor (ketoconazole) significantly increased the intestinal absorption of lovastatin and lovastatin solid dispersion. However, P-glycoprotein efflux inhibitor (verapamil) had little effect on them.The absolute bioavailability of lovastatin and lovastatin acid after oral administration of lovastatin solid dispersion were increased by about 2.01-fold and 1.40-fold than that of lovastatin suspension. The oral bioavailability of lovastatin and lovastatin acid after oral administration of lovastatin solid dispersion with 10 mg/kg kaempferol (CYP3A4 inhibitor) were increased about 3.79-fold and 2.51-fold than that of lovastatin suspension, and the absolute bioavailability of lovastatin was up to 33.0%.As a result, co-administration of lovastatin solid dispersion with kaempferol could be a promising delivery system to improve the oral bioavailability of lovastatin.

A Novel Surfactant-Free O/O Paclitaxel Ointment for the Topical Treatment of Psoriasis

Psoriasis is an autoimmune disorder disease with pink-colored plaques and excessive proliferation which is hard to be cured completely. The study focuses on the anti-psoriatic efficacy of O/O paclitaxel ointment which can promote the assembly of microtubules and lead to death of overproliferation cells of the psoriasis epidermal. A high-speed shearing method was adopted in preparing the ointment, in which propylene carbonate was used as the internal oil phase to solve paclitaxel completely. It was characterized by the appearance, particle size, rheological behavior, and in vitro release. The amount of paclitaxel retained in normal skin and psoriatic skin was 1.00 ± 0.50 versus 1.53 ± 0.48 μg/g for 0.03% PTX ointment, 1.30 ± 0.39 versus 2.77 ± 0.49 μg/g for 0.1% PTX ointment, and 2.22 ± 0.92 versus 6.65 ± 0.87 μg/g for 0.3% PTX ointment, respectively, which implied that paclitaxel could better retain in inflamed skin than in normal skin; also the amount of drug retained in the skin was proportional to drug content. Paclitaxel ointment displayed good topical tolerance after repeated application on normal mice skin. The therapeutic efficacy of paclitaxel ointment was evaluated with an imiquimod-induced psoriatic model. A significant improvement has been shown both in the phenotypic and histopathological features of psoriatic skin treated with the ointment. There was also a significant reduction in the epidermal thickness compared to the imiquimod group. The findings confirm that the O/O PTX ointment without any surfactant appears to be a promising approach for the treatment of psoriasis.

Improved Oral Absorption of Poorly Soluble Curcumin via the Concomitant Use of Borneol

In this study, borneol, a natural active compound was applied to improve the bioavailability of curcumin (CUR). In order to increase CUR solubility and dissolution, solid dispersions (SDs) were prepared with the matrix of polyvinylpyrrolidone (PVP) at various ratios by solvent evaporation method. CUR was evidenced to exist as amorphous state in solid dispersion by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Fourier-transform infrared spectroscopy (FT-IR) was utilized to confirm intermolecular hydrogen bonding. The SD at the ratio of 1:3 (CUR:PVP) exhibited the optimal solubility and dissolution rate in various media. The results of ex vivo permeability studies by everted gut sac method showed that the apparent permeability coefficients (P_app) of CUR in SD across the duodenum, jejunum, and ileum had been significantly improved by co-incubation of borneol, and the improvement degree relied on the concentration of borneol. The pharmacokinetic results in rats indicated that the AUC_0-t of CUR-SD (40 mg/kg) co-administration of borneol (90 mg/kg) were 2.53-fold higher than CUR-SD alone, and 19.41-fold higher than pure CUR (200 mg/kg) with borneol (90 mg/kg). Therefore, the combination of borneol and solid dispersion strategy provide a potential approach to enhance the oral bioavailability of CUR.

TRIP12 as a mediator of human papillomavirus/p16-related radiation enhancement effects

Patients with human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) have better responses to radiotherapy and higher overall survival rates than do patients with HPV-negative HNSCC, but the mechanisms underlying this phenomenon are unknown. p16 is used as a surrogate marker for HPV infection. Our goal was to examine the role of p16 in HPV-related favorable treatment outcomes and to investigate the mechanisms by which p16 may regulate radiosensitivity. HNSCC cells and xenografts (HPV/p16-positive and -negative) were used. p16-overexpressing and small hairpin RNA-knockdown cells were generated, and the effect of p16 on radiosensitivity was determined by clonogenic cell survival and tumor growth delay assays. DNA double-strand breaks (DSBs) were assessed by immunofluorescence analysis of 53BP1 foci; DSB levels were determined by neutral comet assay; western blotting was used to evaluate protein changes; changes in protein half-life were tested with a cycloheximide assay; gene expression was examined by real-time polymerase chain reaction; and data from The Cancer Genome Atlas HNSCC project were analyzed. p16 overexpression led to downregulation of TRIP12, which in turn led to increased RNF168 levels, repressed DNA damage repair (DDR), increased 53BP1 foci and enhanced radioresponsiveness. Inhibition of TRIP12 expression further led to radiosensitization, and overexpression of TRIP12 was associated with poor survival in patients with HPV-positive HNSCC. These findings reveal that p16 participates in radiosensitization through influencing DDR and support the rationale of blocking TRIP12 to improve radiotherapy outcomes.

Comparison of two self-assembled macromolecular prodrug micelles with different conjugate positions of SN38 for enhancing antitumor activity

7-Ethyl-10-hydroxycamptothecin (SN38), an active metabolite of irinotecan (CPT-11), is a remarkably potent antitumor agent. The clinical application of SN38 has been extremely restricted by its insolubility in water. In this study, we successfully synthesized two macromolecular prodrugs of SN38 with different conjugate positions (chitosan-(C₁₀-OH)SN38 and chitosan-(C₂₀-OH)SN38) to improve the water solubility and antitumor activity of SN38. These prodrugs can self-assemble into micelles in aqueous medium. The particle size, morphology, zeta potential, and in vitro drug release of SN38 and its derivatives, as well as their cytotoxicity, pharmacokinetics, and in vivo antitumor activity in a xenograft BALB/c mouse model were studied. In vitro, chitosan-(C₁₀-OH)SN38 (CS-(10s)SN38) and chitosan-(C₂₀-OH) SN38 (CS-(20s)SN38) were 13.3- and 25.9-fold more potent than CPT-11 in the murine colon adenocarcinoma cell line CT26, respectively. The area under the curve (AUC)_0–24 of SN38 after intravenously administering CS-(10s)SN38 and CS-(20s)SN38 to Sprague Dawley rats was greatly improved when compared with CPT-11 (both P<0.01). A larger AUC_0–24 of CS-(20s)SN38 was observed when compared to CS-(10s)SN38 (P<0.05). Both of the novel self-assembled chitosan-SN38 prodrugs demonstrated superior anticancer activity to CPT-11 in the CT26 xenograft BALB/c mouse model. We have also investigated the differences between these macromolecular prodrug micelles with regards to enhancing the antitumor activity of SN38. CS-(20s)SN38 exhibited better in vivo antitumor activity than CS-(10s)SN38 at a dose of 2.5 mg/kg (P<0.05). In conclusion, both macromolecular prodrug micelles improved the in vivo conversion rate and antitumor activity of SN38, but the prodrug in which C₂₀-OH was conjugated to macromolecular materials could be a more promising platform for SN38 delivery.

Development of an osmotically-driven pellet coated with acrylic copolymers (Eudragit® RS 30 D) for the sustained release of oxymatrine, a freely water soluble drug used to treat stress ulcers (I): in vitro and in vivo evaluation in rabbits

PURPOSE

To develop an osmotically-driven pellet coated with polymeric film for sustained release of oxymatrine (OMT), a freely water soluble drug.

METHODS

Pellet containing OMT and sodium chloride (NaCl), an osmotically active agent, were prepared by extrusion/spheronization and then coated with acrylic copolymers (Eudragit(®) RS 30 D) by the fluidized bed coating process. In vitro release and swelling behavior studies were employed to optimize and to evaluate the sustained-release behavior from the osmotically-driven pellets with film coated. Finally, in vivo evaluation in rabbits was employed to investigate the sustained plasma level of OMT and its active metabolite matrine.

RESULTS

It was found that the F3 formulation, prepared with 20% NaCl and an 8% coating level, showed a continuous NaCl-induced water influx into the pellets providing a gradual sustained release of OMT for over 12 h. Finally, we confirmed that oral OMT with sustained release led to a gradual sustained plasma profile of both OMT, with a reduction in its bioavailability, and MT with an increase in the bioavailability compared with that of oral OMT with immediate release.

CONCLUSIONS

The pharmaceutical parameters obtained suggested the potential usefulness of oral OMT with sustained release for the treatment of stress ulcers, as well as reducing the risk of MT-induced side effects.

α-Tocopherol succinate-modified chitosan as a micellar delivery system for paclitaxel: preparation, characterization and in vitro/in vivo evaluations

α-Tocopherol succinate hydrophobically modified chitosan (CS-TOS) containing 17 α-tocopherol groups per 100 anhydroglucose units was synthesized by coupling reaction. The formation of CS-TOS was confirmed by (1)H NMR and FT-IR analysis. In aqueous medium, the polymer could self-aggregate to form micelles, and the critical micelle concentration (CMC) was determined to be 5.8 × 10(-3) mg/ml. Transmission electron microscopy (TEM) observation revealed that both bare and paclitaxel-loaded micelles were near spherical in shape. The mean particle size and zeta potential of drug-loaded micelles were about 78 nm and +25.7 mV, respectively. The results of DSC and XRD analysis indicated that paclitaxel was entrapped in the micelles in molecular or amorphous state. In vitro cytotoxicity and hemolysis study revealed the effectiveness and safety of this delivery system, which was further confirmed by the in vivo antitumor evaluations. It can be concluded that the CS-TOS was a potential micellar carrier for paclitaxel.

Nitrendipine nanocrystals: its preparation, characterization, and in vitro-in vivo evaluation

The present investigation was undertaken with the objective of developing a solid formulation containing nitrendipine nanocrystals for oral delivery. Nitrendipine nanocrystals were prepared using a tandem precipitation-homogenization process. Then, spray drying, a cost-effective method very popular in industrial situations, was employed to convert the nanocrystals into a solid form. The parameters of the preparation process were investigated and optimized. The optimal process was as follows: firstly, nitrendipine/acetone solution (100 mg/ml) was added to a polyvinyl alcohol solution (1 mg/ml) at 10°C, then the pre-suspension was homogenized for 20 cycles at 1,000 bar. Both differential scanning calorimetry and X-ray diffraction analysis indicated that nitrendipine was present in crystalline form. The in vitro dissolution rate of the nanocrystals was significantly increased compared with the physical mixture and commercial tablet. The in vivo testing demonstrated that the C(max) of the nanocrystals was approximately 15-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively. In addition, the AUC(0→24) of the nanocrystals was approximately 41-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively.

In vitro-in vivo study of CoQ10-loaded lipid nanoparticles in comparison with nanocrystals

The present work described the effect of CoQ10 dissolution characteristics in nanocrystals and lipid nanoparticles (LNs) on its oral absorption in rats. Nanocrystals and LNs were prepared by melt-high pressure homogenization and sucrose monolaurate was used as a stabilizer in all formulations. Witepsol(®)W35 and medium-chain triglycerides (MCT) were selected as lipid additives to form LN(CoQ10+W35) and LN(CoQ10+MCT), respectively. From the results obtained, the particle size of CoQ10 nanocrystals was 285 nm, while it was reduced to 150 nm by mixture with an equal amount of lipid additives due to their lower melting points. In vitro dissolution results indicated that the drug release from two LNs was delayed compared with that from nanocrystals, and LN(CoQ10+W35) exhibited the highest drug release over 4h. Finally, in vivo evaluation demonstrated that the oral absorption of CoQ10 was markedly increased by using nanocrystals and LNs compared with a coarse suspension. A good relationship was found between the in vitro dissolution and in vivo evaluation. The enhanced oral absorption of CoQ10 by nanocrystals and LNs was due to improved dissolution. In conclusion, Witepsol(®)W35 was shown to be a better lipid additive for the preparation of LNs to increase the oral absorption of CoQ10.

Effect of crystal size on the in vitro dissolution and oral absorption of nitrendipine in rats

PURPOSE

To investigate the effect of crystal size on the dissolution and oral absorption of nitrendipine, a poorly soluble drug, in rats.

METHODS

Five types of nitrendipine crystal suspensions with different particle sizes (200 nm, 620 nm, 2.7 microm, 4.1 microm, 20.2 microm) were prepared either by the precipitation-ultrasonication or the anti-solvent precipitation method. The simulated intestinal fluid in the fasted state (FaSSIF) was selected as the dissolution medium, and the dissolution behaviors of different nitrendipine crystals were simulated based on a Noyes-Whitney type equation. The in vivo absorption and the absolute bioavailability of the different nitrendipine crystals were evaluated in Wistar rats.

RESULTS

The dissolution rate of nitrendipine was significantly increased by a reduction in particle size. The dissolution test in FaSSIF could discriminate between the differences in the dissolution rates of the different particle sizes, and the simulated results were in agreement with the observed dissolution curves. From the simulated T(50%) values (50% dissolution time), the dissolution rates of crystals with particle sizes of 200 nm, 620 nm, 2.7 microm, 4.1 microm and 20.2 microm were calculated to be 5.1 x 10(4), 1.0 x 10(4), 237, 64 and 11-fold greater than that of the raw crystals and resulted in absolute bioavailability of 61.4% 51.5%, 29.4%, 26.7%, 24.7%, respectively. The reduction in the drug particle size correlated well with incremental improvements in oral absorption. A good linear relationship was observed between the Log (T(50%)) and the absolute bioavailability of nitrendipine.

CONCLUSIONS

The dissolution rate and the oral bioavailability of nitrendipine were significantly affected by the crystal size, and the oral bioavailability could be improved significantly by preparing it as nanocrystals. FaSSIF can be used to predict differences in oral absorption of crystals with different particle sizes.

Hypoxia-ischemia brain damage disrupts brain cholesterol homeostasis in neonatal rats

PURPOSE

The first 3 weeks of life is the peak time of oligodendrocytes development and also the critical period of cholesterol increasing dramatically in central nervous system in rats. Neonatal hypoxia-ischemia (HI) brain damage happening in this period may disturb the brain cholesterol balance as well as white matter development.

MATERIALS AND METHODS

To test this hypothesis, postnatal day 7 (P7) Sprague-Dawley rats were subjected to HI insult. Cholesterol concentrations from brain and plasma were measured. White matter integrity was evaluated by densitometric analysis of myelin basic protein (MBP) immunostaining and electron microscopy. Brain TNF-alpha and IL-6 levels were also measured.

RESULTS

HI-induced brain cholesterol, but not the plasma cholesterol, levels decreased significantly during the first three days after HI compared with naïve and sham operated rats (p<0.05). Obvious hypomyelination was indicated by marked reductions in MBP immunostaining on both P10 and P14 (p<0.01) and less and thinner myelinated axons were detected on P21 by electron microscopy observation. High expressions of brain TNF-alpha and IL-6 12 h after HI (p<0.05) were also observed.

DISCUSSION

The present work provides evidence that HI insult destroyed brain cholesterol homeostasis, which might be important in the molecular pathology of hypoxic-ischemic white matter injury. Proinflammatory cytokines insulting oligodendrocytes, may cause cholesterol unbalance. Furthermore, specific therapeutic interventions to maintain brain cholesterol balance may be effective for the recovery of white matter function.

Reduction of Gastric Ulcerogenicity During Multiple Administration of Diclofenac Sodium by a Novel Solid-in-Oil Suspension

This article reports a significant reduction of gastric ulcerogenicity by complex formation of a nonsteroidal anti-inflammatory drug with surfactants. Diclofenac sodium (DFNa) was suspended in medium chain triglyceride (MCT) by forming a complex with an edible lipophilic surfactant. Two types of suspensions, prepared through a membrane emulsification with different pore sizes, were evaluated according to the degree of gastric damage following multiple oral administration in rats. It was shown that gastric ulcerogenicity of DFNa was reduced by the surfactant-drug complexes, at doses up to 12 mg/kg, whereas severe gastric damage was observed upon oral administration of the aqueous solution at doses of 6 mg/kg. Comparable blood levels of DFNa were observed after administration of solution and suspension formulations.

Ghrelin stimulates milk intake by affecting adult type feeding behaviour in postnatal rats

The influence of ghrelin on feeding behaviour during infancy is unknown. To determine whether ghrelin influences milk intake in rat pups, newborn rats received a single i.p. injection of either rat ghrelin (100 microg/kg) or rabbit anti-ghrelin immunoglobulin G (100 microg/kg) every 5 days from postpartum day 5 to day 30 (P5-P30). Milk intake was then assessed by body weight gain following a 2-h suckling period. Ghrelin significantly increased weight gain relative to vehicle-injected controls in P20, P25 and P30 pups, but not in younger animals. Similarly, after 8 h of milk restriction, anti-ghrelin injections significantly decreased weight gain in P25 and P30, but not in younger pups. Interestingly, however, ghrelin did increase independent feeding in P10 and P15 pups using a paradigm in which pups consumed milk from a milk-soaked paper towel. We therefore conclude that ghrelin stimulates milk intake at an early postnatal stage, primarily by affecting adult-type feeding behaviour.

A Novel Solid-in-oil Nanosuspension for Transdermal Delivery of Diclofenac Sodium

PURPOSE

We formulated a solid-in-oil nanosuspension (SONS) as a novel transdermal delivery carrier for diclofenac sodium (DFNa). The basic transdermal characteristics of the SONS were evaluated using a Yucatan micropig (YMP) skin model.

METHODS

DFNa-sucrose erucate (i.e. surfactant) complexes were prepared via the formation of a water-in-oil emulsion. The complexes were suspended in isopropyl myristate (IPM) to form a SONS. The basic transdermal characteristics of the SONS were examined using full-thickness YMP dorsal skin in a Franz-type diffusion cell. DFNa powder suspended in IPM without complex formation was used as a control. The effect of the weight ratio of surfactant to DFNa on DFNa penetration of the skin was evaluated.

RESULTS

DFNa was successfully dispersed into IPM as a nanosized suspension via complex formation with sucrose erucate. The resultant SONS increased the permeability flux of DFNa across the YMP skin by up to 3.8-fold compared with the control. The size of the SONS depended on the weight ratio of the surfactant to DFNa. The optimal weight ratio for the highest DFNa permeation was 8.8, at which point the mean diameter of the SONS was 14.4 nm.

CONCLUSION

The SONS formulation can enhance the percutaneous absorption of DFNa.

Biotransformation of letrozole in rat liver microsomes: effects of gender and tamoxifen

The in vitro metabolic kinetics of letrozole were investigated by incubating letrozole (10-500 microM) in female or male rat liver microsomes to assess the effect of gender and to predict the in vivo biotransformation characteristics of letrozole in rats. The effects of tamoxifen (TAM) on the metabolic kinetics of letrozole were also examined by incubating letrozole in female rat liver microsomes in the presence or absence of TAM. The effects of chronic pretreatment of female rats with TAM (0.5, 1.0, 5.0 mg/kg/day, i.p. for 7 consecutive days) on liver microsomal protein content and metabolic activity were also examined. The formation rate of the carbinol metabolite of letrozole, CGP44 645, was significantly higher (p<0.05) in male rat liver microsomes in comparison to female. The V(max)/K(m) ratio for letrozole metabolism in female rat liver microsomes did not change significantly (p>0.05) in the presence of TAM. After chronic pretreatment of female rats with TAM (up to a dose of 1.0mg/kg/day), the hepatic microsomal protein content was significantly increased but the formation rate of CGP44 645, when normalized for protein content, did not change significantly. These results suggest that there is a marked gender difference in letrozole metabolism in rats. It also appears that acute treatment of female rat liver microsomes with TAM produces negligible inhibitory effect on the CYP mediated metabolic clearance of letrozole. However, chronic pretreatment of female rats with TAM appear to induce CYPs, but does not significantly impact the metabolic activities of the enzymes associated with the formation of the carbinol metabolite of letrozole.

Oral delivery of diclofenac sodium using a novel solid-in-oil suspension

The present work reports on a new pharmaceutical formulation for oral delivery of diclofenac sodium (DFNa), a non-steroidal anti-inflammatory drug (NSAID). Although DFNa itself is water-soluble at neutral pH, it was readily suspended in soybean oil via complex formation with an edible lipophilic surfactant and a matrix protein. The resulting solid-in-oil (S/O) suspension containing stably encapsulated DFNa in an oil phase markedly reduced the risks for gastrointestinal ulcers upon oral administration even at the LD(50) level in rats (ca. 50 mg/kg DFNa). In addition, plasma concentration of DFNa upon administration of an S/O suspension was comparable with that of the aqueous counterpart at the same DFNa dose. These results indicate the potential use of S/O suspensions as novel oil-based pharmaceutical formulations for oral delivery of water-soluble drugs without causing severe mucitis.

Determinant role of membrane helices in K ATP channel gating

The ATP-sensitive K(+) (K(ATP)) channels couple chemical signals to cellular activity, in which the control of channel opening and closure (i.e., channel gating) is crucial. Transmembrane helices play an important role in channel gating. Here we report that the gating of Kir6.2, the core subunit of pancreatic and cardiac K(ATP) channels, can be switched by manipulating the interaction between two residues located in transmembrane domains (TM) 1 and 2 of the channel protein. The Kir6.2 channel is gated by ATP and proton, which inhibit and activate the channel, respectively. The channel gating involves two residues, namely, Thr71 and Cys166, located at the interface of the TM1 and TM2. Creation of electrostatic attraction between these sites reverses the channel gating, which makes the ATP an activator and proton an inhibitor of the channel. Electrostatic repulsion with two acidic residues retains or even enhances the wild-type channel gating. A similar switch of the pH-dependent channel gating was observed in the Kir2.1 channel, which is normally pH- insensitive. Thus, the manner in which the TM1 and TM2 helices interact appears to determine whether the channels are open or closed following ligand binding.

A threonine residue (Thr71) at the intracellular end of the M1 helix plays a critical role in the gating of Kir6.2 channels by intracellular ATP and protons

ATP-sensitive K+ (K(ATP)) channels are known to be gated by several intracellular molecules, but the gating mechanisms remain unclear. To understand the relationship of channel gating to ligand binding, we studied Kir6.2 channel gating by ATP and protons, which inhibit and activate the channel, respectively. We have previously shown that a threonine residue (Thr71) is critical for the pH sensitivity of Kir6.2 channel. If this site is involved in channel gating rather than ligand binding, it should affect channel gating by both ATP and proton. To test this hypothesis we performed a mutation analysis. Site-specific mutations of Thr71 to a bulky residue reduced the ATP sensitivity by >100-fold and eliminated the pH sensitivity. Single-channel activity of these mutants was stabilized at the open state with no detectable rundown. Mutations to a small amino acid had little effect on the ATP and pH sensitivities. Mutations to intermediate amino acids reduced but did not abolish the ATP and pH sensitivities. Hydrophobicity is not critical, as both polar and nonpolar amino acids are found in each group. Mutation to a positively charged lysine markedly exacerbated the pH- but not ATP-sensitivity, whereas mutation to glutamate moderately reduced ATP and pH sensitivities. These results indicate that the residue mass is critical for Kir6.2 channel gating, a mass that should be below 120 daltons with no charge. The existence of such a site as Thr71 involved in channel gating by both ATP and proton suggests that channel gating in the K(ATP) channel likely is separate from ligand binding.

Requirement of multiple protein domains and residues for gating K(ATP) channels by intracellular pH

ATP-sensitive K(+) channels (K(ATP)) are regulated by pH in addition to ATP, ADP, and phospholipids. In the study we found evidence for the molecular basis of gating the cloned K(ATP) by intracellular protons. Systematic constructions of chimerical Kir6.2-Kir1.1 channels indicated that full pH sensitivity required the N terminus, C terminus, and M2 region. Three amino acid residues were identified in these protein domains, which are Thr-71 in the N terminus, Cys-166 in the M2 region, and His-175 in the C terminus. Mutation of any of them to their counterpart residues in Kir1.1 was sufficient to completely eliminate the pH sensitivity. Creation of these residues rendered the mutant channels clear pH-dependent activation. Thus, critical players in gating K(ATP) by protons are demonstrated. The pH sensitivity enables the K(ATP) to regulate cell excitability in a number of physiological and pathophysiological conditions when pH is low but ATP concentration is normal.

Cloning of rabbit alpha(1b)-adrenoceptor and pharmacological comparison of alpha(1a)-, alpha(1b)- and alpha(1d)-adrenoceptors in rabbit

We have isolated a cDNA clone of the rabbit alpha(1b)-adrenoceptor which has an open reading frame of 1557 nucleotides encoding a protein of 518 amino acids. The sequence shows higher identity to those of hamster, human, and rat alpha(1b)-adrenoceptors than to those of rabbit alpha(1a)- and alpha(1d)-adrenoceptors. The pharmacological binding properties of this clone expressed in Cos-7 cells showed a characteristic profile as alpha(1b)-adrenoceptor; high affinity for prazosin (pK(i)=10.3), relatively high affinity for tamsulosin (9.5) and low affinity for (-)-(R)-1-(3-hydroxypropyl)-5-[2-[[2-[2-(2,2, 2-trifluoroethoxy)phenoxy]ethyl]amino]propyl]indoline-7-carboxamid e (KMD3213) (8.5), 2-(2,6-dimethoxy-phenoxyethyl)-aminomethyl-1, 4-benzodioxane hydrochloride (WB4101) (8.7), and 8-[2-[4-(2-methoxy-phenyl)-L-piperazinyl]-8-azaspiro[4,5]decane-7, 9-dione dihydrochloride (BMY7378) (7.3). We have compared the levels of mRNA expression of three alpha(1)-adrenoceptor subtypes in rabbit tissues using the competitive reverse transcription/polymerase chain reaction (RT/PCR) assay. In most rabbit tissues except heart, alpha(1a)-adrenoceptor mRNA was expressed 10 folds more than the other two subtypes. However, binding experiments with [3H]prazosin and [3H]KMD3213 in rabbit tissues revealed a poor relationship between binding density and mRNA level. Especially, alpha(1b) binding sites were exclusively predominant in spleen, whereas the alpha(1b) subtype was minor at the mRNA level. These results indicate a high identity of structural and pharmacological profiles of three distinct alpha(1)-adrenoceptor subtypes between rabbit and other species, but there are species differences in their distribution.

[Usefulness of galea suturing method for scalp closure]

A method for scalp closure to prevent alopecia along a suture line is described. Only the galea is sutured. By tacking a sufficient width of the galea on both sides with an absorbable suture material, the sutured wound forms a ridge. The outer layer is then closed with skin staples to keep the blood circulation undisturbed. This procedure contrasts with the traditional method in which the galea is sutured with the overlying subcutaneous tissue and consequently the hair follicles are strangled. By adopting the method of suturing the galea, development of alopecia along a suture line has been effectively prevented and scarring has become less conspicuous.

Chemical, metabolic and immunological characterization of gangliosides of human glioma cells

The patterns of ganglioside profiles were studied in 10 human glioma and one melanoma cell lines. Ganglio-series gangliosides, GM3 (NeuAc alpha2-3Gal beta1-4Glc beta1-Cer) and GM2 (GalNAc beta 1-4 (NeuAc alpha2-3)Gal beta1-4Glc beta 1-1Cer), and a neolacto-series ganglioside, sialylparagloboside (SPG) (NeuAc alpha 2-3Gal beta1-4GlcNAc beta1-3Gal beta1-4Glc beta1-1Cer), were the predominant constituents. The activities of the two key enzymes, GM3 synthetase and lactotriaosyl ceramide (Lc3Cer) synthetase, alone did not account for the ganglioside profile. Metabolic labeling with the use of [3H]glucosamine-HCl showed more pronounced difference in the synthetic rate of each ganglioside type, in which GM2 was the most strongly labeled in 7 out of the 10 glioma cell lines. On quantifying the chemical content of GM3 and GM2, the GM3/GM2 molar ratio of above 2.0 was arbitrarily classified into GM3 dominant type (KG-1C and Mewo); the ratio below 0.5 was designated as GM2 dominant type (H4, U138MG, U373MG, T98G and A172); and the ratio between 0.5 and 2.0 was regarded as GM3 and GM2-co-dominant type (U87MG, Hs683, SW1088 and U118MG). Subsequently, the capabilities of the antibody binding to these gangliosides were examined in native forms in the cell membrane and in chemically-isolated forms. The intensity of reaction against chemically isolated GM3 and GM2 gangliosides was dependent on the quantity, and GM2 was more reactive than GM3; however, the reactivities on the cell surface did not correlate with the chemical content indicating other factors to influence their immunoreactivities.

[Effects of basic fibroblast growth factor on anoxia/reoxygenation injury of rat neonatal cardiomyocytes]

The effects of basic fibroblast growth factor (bFGF) on anoxia/reoxygenation (A/R) injury and protein kinase C (PKC) activity were studied on a model of A/R injury of neonatal rat cardiomyocytes to investigate the possibility of its using as a substrate for pharmacological preconditioning. The data indicated that bFGF improved the viability of cardiomyocytes, lowered the deplection of ATP and leakage of intracellular lactate dehydrogenase (LDH) in a concentration-dependent manner. PKC inhibitor, H7, completely abolished the protective effects. It was also found that bFGF directely activated PKC in cardiomyocytes in a time course similar to that in hypoxic preconditioning. The data suggested that the protective effect of bFGF on cardiomyocyte A/R injury might be mediated by PKC.

Cell density regulates crypticity of GM3 ganglioside on human glioma cells

Human glioma cell line KG-1C contains GM3 ganglioside as its sole glycolipid. The degree of M2590 antibody binding to GM3 was found to be regulated by the cell density; the percentage of positive cells in FACS analysis decreased from approximately 20% to close to none as the cells increased their density from sparse to confluent. The contents of GM3 with different cell densities were consistent, being more than 0.4 micromol/g of the cellular weight, which was high enough to be recognized by the antibody. Trypsin treatment of the cells did not increase antibody reactivity. The extracted GM3 retained its antigenicity, being intensely stained with M2590 on a TLC plate; there was no change in chromatographic mobility either, indicating no modification of its chemical structure. The fluorescent microscope disclosed scattered dot-like staining of GM3, particularly at the periphery of the cells. We were able to expose cryptic GM3 fully within 12 h by dispersion of the cells to a sparse density. Surface labeling of GM3 with the use of limited sodium periodate oxidation of sialylated residue equally labeled GM3 either from the confluent cells or the sparse cells. Disassembly of actin filaments with cytochalasin B (10 microM) partially exposed cryptic GM3 of confluent cells, indicating reversibility of the crypticity. All together, the results indicate that cryptic GM3 actually exists on the cell surface, hidden from the surface not by other molecules but by other mechanisms associated with the cellular architecture. We are beginning to explore the possibility of selective localization of GM3 in small caves or folds of the cell membrane produced upon cell-to-cell contact.

[Protective effects of methanolic extract of Oenanthe stolonifera (Roxb.) Wall. ex DC. on myocardial injury induced by ischemia and reperfusion in rats]

The methanolic extract Oenanthe stoloni fera iv, pretreatment can significantly prevent the arrhythmias induced by myocardial ischemia and reduce the myocardial infarct size in rats. It can also markedly prevent myocardial ischemia and reperfusion-induced arrhythmias. In addition, the methanolic extract of Oenanthe stoloni fera (100 mg/kg i.v.) helps significantly to decrease the MDA content and preserve the SOD activity in plasma.

[Chemical constituents of Ledebouriella seseloides Wolff]

Eleven compounds were isolated from the methanolic extraction of the radix of Ledebouriella seseloides. They were identified as beta-sitosterol, bergapten, hamaudol, daucosterine sec-O-glucosylhamaudol, 5-O-methylvisamminol, cimifugin, sucrose, 4-O-beta-glucopyranosyl-5-O-methyl-visamminol, prim-O-glucosylcimifugin and mannitol by physico-chemical constants and spectroscopic analysis.