Evaluation of EpiDerm full thickness-300 (EFT-300) as an in vitro model for skin irritation: studies on aliphatic hydrocarbons.

The aim of this study was to understand the skin irritation effects of saturated aliphatic hydrocarbons (HCs), C9-C16, found jet fuels using in vitro 3-dimensional EpiDerm full thickness-300 (EFT-300) skin cultures. The EFT-300 cultures were treated with 2.5microl of HCs and the culture medium and skin samples were collected at 24 and 48h to measure the release of various inflammatory biomarkers (IL-1alpha, IL-6 and IL-8). To validate the in vitro results, in vivo skin irritation studies were carried out in hairless rats by measuring trans epidermal water loss (TEWL) and erythema following un-occlusive dermal exposure of HCs for 72h. The MTT tissue viability assay results with the EFT-300 tissue show that 2.5microl/tissue ( approximately 4.1microl/cm(2)) of the HCs did not induce any significant changes in the tissue viability for exposure times up to 48h of exposure. Microscopic observation of the EFT-300 cross-sections indicated that there were no obvious changes in the tissue morphology of the samples at 24h, but after 48h of exposure, tridecane, tetradecane and hexadecane produced a slight thickening and disruption of stratum corneum. Dermal exposures of C12-C16 HCs for 24h significantly increased the expression of IL-1alpha in the skin as well as in the culture medium. Similarly, dermal exposure of all HCs for 24h significantly increased the expression of interleukin-6 (IL-6) and IL-8 in the skin as well as in the culture medium in proportion to the HC chain length. As the exposure time increased to 48h, IL-6 concentrations increased 2-fold compared to the IL-6 values at 24h. The in vivo skin irritation data also showed that both TEWL and erythema scores increased with increased HCs chain length (C9-C16). In conclusion, the EFT-300 showed that the skin irritation profile of HCs was in the order of C9C10C11C12

Dermal microdialysis of inflammatory markers induced by aliphatic hydrocarbons in rats.

In the present study we made an attempt to understand the skin irritation cascade of selected aliphatic hydrocarbons using microdialysis technique. Microdialysis probes were inserted into dermis in the dorsal skin of hairless rats. After 2h of probes insertion, occlusive dermal exposure (2h) was carried out with 230 microl of nonane, dodecane and tetradecane, using Hill top chambers((R)). Inflammatory biomarkers such as substance P (SP), alpha-melanocyte stimulating hormone (alpha-MSH) Interleukin 6 (IL-6) and prostaglandin E2 (PGE(2)) were analyzed in the dialysis samples by enzyme immunoassay (EIA). SP, alpha-MSH and IL6 were released in significant amounts following the dermal exposure of nonane and dodecane, whereas tetradecane did not induce any of these markers in significant amounts compared to control. Nonane increased the PGE(2) levels in significant amounts within 2h of chemical exposure compared to dodecane and tetradecane. IL-6 response was found to be slow and 2-3-fold increase in IL-6 levels was observed after 5h following nonane and dodecane application. The magnitude of skin irritation exerted by all three chemicals was in the order of nonane>or=dodecane>or=tetradecane. The results demonstrate that microdialysis can be used to measure the inflammatory biomarkers in the skin irritation studies and irritation response of chemicals was quantifiable by this method. In conclusion, microdialysis was found to be an excellent tool to measure several inflammatory biomarkers as a function of time after dermal exposures with irritant chemicals.