Multi-chamber microfluidic platform for high-precision skin permeation testing.

The established in vitro tool used for testing the absorption and penetration of chemicals through skin in pharmacology, toxicology and cosmetic science is the static Franz diffusion cell. While widespread, Franz cells are relatively costly, low-throughput and results may suffer from poor reproducibility. Microfluidics has the potential to overcome these drawbacks. In this paper, we present a novel microfluidic skin permeation platform and validate it rigorously against the Franz cell by comparing the transport of 3 model chemicals of varying lipophilicity: caffeine, salicylic acid and testosterone. Permeation experiments through silicone membranes show that the chip yields higher sensitivity in permeant cumulative amounts and comparable or lower coefficients of variation. Using a skin organotypic culture, we show that the chip decreases the effect of unstirred water layers that can occur in static Franz cells. The validation reported herein sets the stage for efficient skin permeation and toxicity screening and further development of microfluidic skin-on-chip devices.

Effect of the CYP3A5 and ABCB1 genotype on exposure, clinical response and manifestation of toxicities from sunitinib in Asian patients.

The objective of this study was to determine the effect of the CYP3A5 and ATP binding cassette subfamily B member 1 (ABCB1) single-nucleotide polymorphisms on the disposition of sunitinib and SU12662, on clinical response, and on the manifestation of toxicities in Asian metastatic renal cell carcinoma patients. At week 4 of each treatment cycle, toxicities and plasma steady-state levels were assessed. Clinical response was assessed after two cycles. Genotyping was performed by using the PCR restriction fragment length polymorphism method. The CC genotype for ABCB1 was associated with a higher sunitinib exposure (76.81 vs 56.55 ng ml(-1), P=0.03), higher risk of all-grade rash (RR 3.00, 95% CI 1.17-7.67) and mucositis (RR 1.60, 95% CI 1.10-2.34) and disease progression than compared with the CT/TT genotype. There was a lack of association observed between the CYP3A5 polymorphism and exposure, response and toxicities. The polymorphism of ABCB1 (C3435T) has an important role in the manifestation of toxicities and drug exposure, but not polymorphism of CYP3A5.

Activation of the δ-opioid receptor promotes cutaneous wound healing by affecting keratinocyte intercellular adhesion and migration.

BACKGROUND AND PURPOSE: In addition to its analgesic functions, the peripheral opioid receptor system affects skin homeostasis by influencing cell differentiation, migration and adhesion; also, wound healing is altered in δ-opioid receptor knockout mice (DOPr(-/-) ). Hence, we investigated δ-opioid receptor effects on the expression of several proteins of the desmosomal junction complex and on the migratory behaviour of keratinocytes. EXPERIMENTAL APPROACH: Expression levels of desmosomal cadherins in wild-type and DOPr(-/-) mice, and the morphology of intercellular adhesion in human keratinocytes were analysed by immunofluorescence. To investigate the δ-opioid receptor activation pathway, protein expression was studied using Western blot and its effect on cellular migration determined by in vitro live cell migration recordings from human keratinocytes. KEY RESULTS: Expression of the desmosomal cadherins, desmogleins 1 and 4, was up-regulated in skin from DOPr(-/-) mice, and down-regulated in δ-opioid receptor-overexpressing human keratinocytes. The localization of desmoplakin expression was rearranged from linear arrays emanating from cell borders to puncta in cell periphery, resulting in less stable intercellular adhesion. Migration and wound recovery were enhanced in human keratinocyte monolayers overexpressing δ-opioid receptors in vitro. These δ-opioid receptor effects were antagonized by specific PKCα/ß inhibition indicating they were mediated through the PKC signalling pathway. Finally, cells overexpressing δ-opioid receptors developed characteristically long but undirected protrusions containing filamentous actin and δ-opioid receptors, indicating an enhanced migratory phenotype. CONCLUSION AND IMPLICATIONS: Opioid receptors affect intercellular adhesion and wound healing mechanisms, underlining the importance of a cutaneous neuroendocrine system in wound healing and skin homeostasis. LINKED ARTICLES: This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.