Viaminate ameliorates Propionibacterium acnes-induced acne via inhibition of the TLR2/NF-κB and MAPK pathways in rats

Viaminate, a retinoic acid derivative developed in China, has been clinically used for acne treatment to regulate and control keratinocyte cell differentiation and proliferation, inhibit keratinization, reduce sebum secretion, and regulate immune and anti-inflammatory functions; however, its potential molecular mechanism has not yet been elucidated. Therefore, we induced ear acne in rats using Propionibacterium acnes and sebum application. Symptoms of ear redness, epidermal thickening, inflammatory reaction, keratin overproduction, subcutaneous oil, and triglyceride (TG) accumulation improved significantly in acne model rats treated with viaminate for 30 days. Transcriptome analysis of rat skin tissues suggested that viaminate had significant regulatory effects on fatty acid metabolism and cellular keratinization pathways. Molecular target prediction suggested that toll-like receptor 2 (TLR2) may be a key target of viaminate's therapeutic mechanism. Western blotting results confirmed that viaminate inhibited the TLR2 and its downstream pathways, nuclear factor-kappa B (NF-κB) [NF-κB inhibitor alpha (IκBα)/NF-κB-p65] and mitogen-activated protein kinases (MAPKs) [MAPK p38/c-Jun N-terminal kinase (JNK)/extracellular regulated kinase 1/2 (ERK1/2)] in acne vulgaris rats. In vitro studies revealed that viaminate treatment attenuated P. acnes proliferation and P. acnes-induced inflammatory response in human keratinocytes and has an inhibitory effect on the activation of NF-κB and MAPKs, while overexpression of TLR2 attenuated these effects. In conclusion, viaminate ameliorates P. acnes-induced acne by inhibiting the proliferation and inflammatory response of keratinocytes, ascribed to the deactivation of the TLR2-mediated NF-κB and MAPK pathways.

Viaminate Inhibits Propionibacterium Acnes-induced Abnormal Proliferation and Keratinization of HaCat Cells by Regulating the S100A8/S100A9- MAPK Cascade

BACKGROUND

Viaminate, a vitamin A acid drug developed in China, has been clinically used in acne treatment to regulate epithelial cell differentiation and proliferation, inhibit keratinization, reduce sebum secretion, and control immunological and anti-inflammatory actions; however, the exact method by which it works is unknown.

METHODS

In the present study, acne was induced in the ears of rats using Propionibacterium acnes combined with sebum application.

RESULTS

After 30 days of treatment with viaminate, the symptoms of epidermal thickening and keratin overproduction in the ears of rats were significantly improved. Transcriptomic analysis of rat skin tissues suggested that viaminate significantly regulated the biological pathways of cellular keratinization. Gene differential analysis revealed that the S100A8 and S100A9 genes were significantly downregulated after viaminate treatment. The results of qPCR and Western blotting confirmed that viaminate inhibited the expression of S100A8 and S100A9 genes and proteins in rat and HaCat cell acne models, while its downstream pathway MAPK (MAPK p38/JNK/ERK1/2) protein expression levels were suppressed. Additional administration of the S100A8 and S100A9 complex protein significantly reversed the inhibitory effect of viaminate on abnormal proliferation and keratinization levels in acne cell models.

CONCLUSION

In summary, viaminate can improve acne by modulating S100A8 and S100A9 to inhibit MAPK pathway activation and inhibit keratinocyte proliferation and keratinization levels.

Models and methods to characterise levonorgestrel release from intradermally administered contraceptives

Microneedle (MN)-based technologies have been proposed as a means to facilitate minimally invasive sustained delivery of long-acting hormonal contraceptives into the skin. Intradermal administration is a new route of delivery for these contraceptives and therefore no established laboratory methods or experimental models are available to predict dermal drug release and pharmacokinetics from candidate MN formulations. This study evaluates an in vitro release (IVR) medium and a medium supplemented with ex vivo human skin homogenate (SH) as potential laboratory models to investigate the dermal release characteristics of one such hormonal contraceptive that is being tested for MN delivery, levonorgestrel (LNG), and provides details of an accompanying novel two-step liquid–liquid drug extraction procedure and sensitive reversed-phase HPLC–UV assay. The extraction efficiency of LNG was 91.7 ± 3.06% from IVR medium and 84.6 ± 1.6% from the medium supplemented with SH. The HPLC–UV methodology had a limit of quantification of 0.005 µg/mL and linearity between 0.005 and 25 µg/mL. Extraction and detection methods for LNG were exemplified in both models using the well-characterised, commercially available sustained-release implant (Jadelle®). Sustained LNG release from the implant was detected in both media over 28 days. This study reports for the first time the use of biologically relevant release models and a rapid, reliable and sensitive methodology to determine release characteristics of LNG from intradermally administered long-acting drug delivery systems.