Skin pharmacology : the official journal of the Skin Pharmacology Society
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Two human skin recombinants, the epidermis reconstructed on the deepidermized dermis (RE-DED) or on fibroblast-populated collagen matrix (Living Skin Equivalent, LSE), were used to study the irritating effect of sodium lauryl sulfate (SLS). The extent of cytotoxicity induced after a 24-hour exposure period to increasing concentrations of SLS (0-5%) was evaluated on the basis of (1) morphological perturbations, (2) changes in the expression of differentiation-specific protein markers (keratin 1, 10, 6, 16, involucrin and transglutaminase), (3) cell membrane integrity (LDH leakage) and (4) release of proinflammatory mediators (PGE2, IL-1, IL-6 and IL-8). SLS induced significant changes in epidermal morphology and changes in the expression and localization of differentiation-specific protein markers when applied topically in concentrations higher than 1% on RE-DED and higher than 0.1% on LSE. ⋯ All parameters used in the present study for evaluation of toxicity can serve as useful endpoints for screening of contact skin irritancy in vitro. Compared to RE-DED, the LSE seems to be more susceptible to SLS. The differences in sensitivity between LSE and RE-DEd can be ascribed to reported differences in their stratum corneum barrier function.
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A new argon laser technique was introduced to evaluate the excitability of the free nerve endings in the skin following topical application of capsaicin. Short argon laser pulses can be perceived as distinct, painful pin pricks and the pain threshold can be determined. This gives the possibility to follow changes in sensory and pain thresholds after topical application of various substances. ⋯ Capsaicin was applied to human skin once daily for 21 days, and the pain threshold was significantly increased after 10 days of application, and after 21 days the increase was found to be 260%. After termination of capsaicin treatment the thresholds were monitored for 21 days, and normalization occurred after 7 days. Argon laser stimulation is a reliable method to evaluate sensory and pain thresholds in human skin.