LC-ESI-MS method for the determination of dexamethasone acetate in skin of nude mouse

Simultaneous quantification of dexamethasone and 6β-hydroxydexamethasone in rabbit plasma, aqueous and vitreous humor, and retina by UHPLC-MS/MS

Aim: To develop and validate a fit for purpose method for the simultaneous determination of dexamethasone and its major metabolite, 6β-hydroxydexamethasone, in rabbit plasma and ocular matrices to measure the in vivo release and distribution profile of dexamethasone from intravitreal implants. Materials & methods: An UHPLC-MS/MS system was employed to perform the bioanalysis. The method was validated according to the US FDA Bioanalytical Method Validation Guidance for Industry. Results & conclusion: The method was found to be fit-for-purpose for the described biological matrices and had a LLOQ of 0.1 ng/ml.

The anti-inflammatory potential of Cinnamomum camphora (L.) J.Presl essential oil in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Borneol was widely used in traditional Chinese medicine formulas due to its pharmacological activities, e.g. sedative, anti-inflammatory, and anti-ischemic properties. Cinnamomum camphora (L.) J.Presl essential oil (BEO) is a by-product of natural crystalline borneol (NCB) production obtained by steam distillation of Cinnamomum camphora (L.) J.Presl leaves, and borneol was the main component of BEO. This study aims to investigate the anti-inflammatory effect of BEO and its corresponding mechanisms through in vitro and in vivo studies.

MATERIALS AND METHODS

Human erythrocyte membrane stability assay and the acute inflammation murine model (xylene-induced ear edema) were chosen to evaluate the anti-inflammatory effect of BEO. Expression of inflammatory mediators, including interleukin (IL)-1β, IL-6, and tumor necrosis factor α (TNF-α) was determined by real-time quantitative polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assays (ELISA). The functional compounds in the BEO were identified by using gas chromatography-mass spectrometry (GC-MS). The steady-state transdermal diffusion rates of BEO and BEO nano-emulsion with were also determined in this study. Cytotoxicity of BEO was analyzed by cell counting kit-8 (CCK-8) assay.

RESULTS

The BEO showed a high human erythrocyte membrane stabilization by inhibiting heat-induced hemolysis (IC50 = 5.29 mg/mL) and hypotonic solution-induced hemolysis (IC50 = 0.26 mg/mL) in vitro. The BEO was topically applied to mice auricles, both single and repeated administration significantly reduced xylene-induced auricle swelling (p < 0.0001). Expression of inflammatory mediators, including interleukin (IL)-1β, IL-6, and tumor necrosis factor α (TNF-α) in serum and tissue was significantly downregulated (p < 0.05), so as to the mRNA expression of IL-1β (p＜0.05) and TNF-α (p < 0.001). A total of 43 components were identified and quantified by GC-MS. The most abundant was borneol [178.3 mg/mL, 20.9% (m/v)], followed by β-caryophyllene (116.3 mg/mL), camphor (115.2 mg/mL), and limonene (89.4 mg/mL). For determining the skin permeability of BEO, the steady-state transdermal diffusion rates of BEO and BEO nano-emulsion were determined to be 6.7 and 8.9 mg/cm2·h, respectively.

CONCLUSION

It is suspected that the anti-inflammatory effects in vivo and in vitro were derived from the above-mentioned components in the BEO. These findings will facilitate the development of BEO as a new and natural therapeutic agent for inflammatory skin conditions.

Skin tissue sample collection, sample homogenization, and analyte extraction strategies for liquid chromatographic mass spectrometry quantification of pharmaceutical compounds

Quantification of pharmaceutical compounds in skin tissue is challenging because of low expected concentrations, small typical sample volumes, and the hard nature of the skin structure itself. This review provides a comprehensive overview of sample collection, sample homogenization and analyte extraction methods that have been used to quantify pharmaceutical compounds in skin tissue, obtained from animals and humans, using liquid chromatography-mass spectrometry. For each step in the process of sample collection to sample extraction, methods are compared to discuss challenges and provide practical guidance. Furthermore, liquid chromatographic-mass spectrometry considerations regarding the quality and complexity of skin tissue sample measurements are discussed, with emphasis on analyte recovery and matrix effects. Given that the true recovery of analytes from skin tissue is difficult to assess, the extent of homogenization plays a crucial role in the accuracy of quantification. Chemical or enzymatic solubilization of skin tissue samples would therefore be preferable as homogenization method.

The combination of acyclovir and dexamethasone protects against Alzheimer's disease-related cognitive impairments in mice

Alzheimer's disease (AD) is the most common neurodegenerative disease. However, effective drugs for this disease have not yet been developed. The analysis of big data indicated that childhood herpes virus infection may be associated with the incidence of AD, suggesting that anti-herpetic drugs, such as acyclovir, may have preventive and suppressive effects in AD therapy. Moreover, short-term use of dexamethasone (DXMT), a clinical used synthetic corticosteroid, could effectively inhibit AD-related neuroinflammation. In this study, we have found that the combination of acyclovir and DXMT, but not acyclovir or DXMT alone, could protect against AD causing β-amyloid (Aβ) oligomer-induced spatial cognitive impairments. Moreover, acyclovir and DXMT could prevent Aβ oligomer-induced over-activation of microglia and astrocytes, and over-expression of pro-inflammatory cytokines, indicating that anti-AD effects of drug combination might be at least partially via neuroinflammation inhibition and immunomodulation. Furthermore, Aβ oligomer-induced decrease of PSD-95 and increase of pTau expression was prevented by the combination of acyclovir and DXMT, suggesting the involvement of synaptic protective effects of the drug combination. Taken together, our studies indicated that the combination of acyclovir and DXMT might be an alternative therapy for the treatment of AD.

An LC-MS Method for Determination of Betamethasone in Tissue Engineering Skin and Application to Dermatopharmacokinetic Study

Background and Objectives:

Tissue engineering skin is a three-dimensional skin substitute cultured in the gas-liquid interface using the immortalized keratinocytes (HaCaT cells). In this study, the preliminary metabolism of betamethasone dipropionate by tissue engineering skin was studied and the pharmacokinetics methodology was established using betamethasone dipropionate gel as the target drug.

Methods:

The betamethasone dipropionate gel was applied on the tissue engineering skin after the skin was cultured. Then the medium (receiving liquid) and skin were taken on 0.25, 0.75, 1.75, 3, 5, 8, 12, 24, 36, 48 h time points. The betamethasone concentration in the medium and skin was determinated by the LC-MS method. Chromatographic analysis was conducted using isocratic elution on a C18 column (150 mm × 2.0 mm, 5 µm) in mobile phase consisting of methanol and water (70 : 30, v/v). The mobile phase was pumped at a flow rate of 0.2 mL/min.

Results:

This method exhibited linearity within the concentration range of 0. 1 to 50 µg /mL of betamethasone. The LLOQ was 0. 1 µg /mL. The intra- and inter-day precisions of betamethasone in the blank medium were all less than 10.69 % (RSD, %), while in the blank, skin homogenates were all less than 13.96 % (RSD, %). As a result, the betamethasone concentration in the medium and skin could both be detected, which suggested that betamethasone dipropionate could be metabolized to betamethasone through the tissue engineering skin.

Conclusion:

It was feasible to use tissue engineering skin as a model to study the dermatopharmacokinetics of topical betamethasone dipropionate gel. The research could build a foundation for the dermato-pharmacokinetic study approach.

Development of a simple method for simultaneous determination of tazarotene and betamethasone dipropionate and their metabolites using LC-MS method and its application to dermatopharmacokinetic study

In our study, a method for the determination for tazarotene and betamethasone dipropionate in human tissue-engineered skin was established. Tazarotene gel, betamethasone dipropionate cream or a combination cream was administered to the skin. Then the skin was taken off at 0.25, 0.75, 1.75, 3, 5, 8, 12, 24, 36, 48 h time points after the residual drug was removed. The concentrations of tazarotene, betamethasone dipropionate and their major metabolites in skin were determined by LC-MS. Tazarotene and tazarotenic acid were detected in the concentration range of 2-200 μg/mL with an LLOQ of 2 μg/mL. Betamethasone dipropionate was detected in the concentration range 0.5-300 μg/mL with an LLOQ of 0.5 μg/mL, and betamethasone was detected at 2-200 μg/mL with an LLOQ of 2 μg/mL. The intra- and inter-day precisions of the four analytes in the skin homogenate were all <15% (RSD, %). The results showed that tazarotene could be metabolized to tazarotenic acid and betamethasone dipropionate could be metabolized to betamethasone in tissue-engineered skin. The results also revealed that this method was suitable for the simultaneous determination of tazarotene, betamethasone dipropionate and their metabolites in tissue-engineered skin.

Topical delivery of dexamethasone acetate from hydrogel containing nanostructured liquid carriers and the drug

The potential of hydrogel containing nanostructured lipid carriers (NLC) to enhance the skin permeation rate and skin deposition of dexamethasone acetate (DEA) was investigated. The particle size of obtained NLCs was around 224.4 nm. NLCs had core-shell structure and DEA existed in amorphous state in NLCs. The permeation rate of DEA through excised mouse skins from hydrogel containing DEA-NLC (DEA-NLC-hydrogel) was 7.3 times higher than DEA-ointment. The skin deposition of DEA from DEA-NLC-hydrogel increased 3.8 folds compared to that from solution of DEA in hydrogel (DEA-hydrogel).