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Hydroxyacids and Moisturisers
Hydroxyacids and Moisturisers
J Am Acad Dermatol. 1996 Feb;34(2 Pt 1):187-95.
Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study.
Ditre CM, Griffin TD, Murphy GF, Sueki H, Telegan B, Johnson WC, Yu RJ, Van Scott EJ.
Department of Dermatology, Hahnemann University School of Medicine, Philadelphia, Pennsylvania, USA.
BACKGROUND: alpha-Hydroxy acids (AHAs) have been reported to improve aging skin. The mechanisms of action of AHAs on epidermal and dermal compartments need clarification.
OBJECTIVE: Our purpose was to determine the effects of AHAs on photoaged human skin by clinical and microanalytic means.
METHODS: Patients applied a lotion containing 25% glycolic, lactic, or citric acid to one forearm and a placebo lotion to the opposite forearm for an average of 6 months. Thickness of forearm skin was measured throughout the study. Biopsy specimens from both forearms were processed for analysis at the end of the study.
RESULTS: Treatment with AHAs caused an approximate 25% increase in skin thickness. The epidermis was thicker and papillary dermal changes included increased thickness, increased acid mucopolysaccharides, improved quality of elastic fibers, and increased density of collagen. No inflammation was evident.
CONCLUSION: Treatment with AHAs produced significant reversal of epidermal and dermal markers of photoaging.
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Arch Dermatol. 1995 Jul;131(7):809-16.
Exogenous nonphysiologic vs physiologic lipids. Divergent mechanisms for correction of permeability barrier dysfunction.
Mao-Qiang M, Brown BE, Wu-Pong S, Feingold KR, Elias PM.
Dermatology Service, Veterans Affairs Medical Center, San Francisco, USA.
BACKGROUND AND DESIGN: Although barrier function requires cholesterol, free fatty acids, and ceramides, applications of one or two of these lipids to damaged skin impedes barrier recovery, while equimolar mixtures allow normal recovery. Both incomplete and complete mixtures appear to be internalized within the epidermal nucleated layers, followed by the secretion of abnormal vs normal lamellar body contents, respectively. We compared the ability of complete physiologic lipid mixtures vs a nonmetabolized hydrophobic lipid, petrolatum, to repair the barrier and the requirement for intracellular processing of these lipids within the epidermis.
RESULTS: Neat petrolatum, which remains restricted to the stratum corneum, produces more rapid improvement in barrier function than the solvent-dispersed physiologic lipids, and its effects are not altered by coapplication of either monensin or brefeldin A (both from Sigma Chemical Co, St Louis, Mo), known inhibitors of exocytosis and organellogenesis, respectively. In contrast, the physiologic lipids enter the nucleated layers in substantial amounts and require longer to produce barrier recovery. Whereas monensin blocks their ability to facilitate barrier recovery, the physiologic lipids overcome brefeldin A-induced delays in barrier recovery, bypassing the subcellular site of brefeldin A blockade, normalizing both lamellar body contents and intercellular bilayers.
CONCLUSIONS: While petrolatum remains restricted to the stratum corneum, physiologic lipid mixtures influence barrier recovery after transport to subjacent, nucleated layers, followed by internalization, apparent transport to the distal Golgi apparatus, and incorporation into nascent lamellar bodies.
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J Am Acad Dermatol. 1997 Sep;37(3 Pt 1):403-8.
Optimal ratios of topical stratum corneum lipids improve barrier recovery in chronologically aged skin.
Zettersten EM, Ghadially R, Feingold KR, Crumrine D, Elias PM.
Department of Dermatology, University of California School of Medicine, San Francisco, USA.
BACKGROUND: Chronologically aged skin exhibits delayed recovery rates after defined barrier insults, with decreased epidermal lipid synthesis, and particularly a reduction in cholesterol synthesis. Prior studies in young mice (< 10 weeks) and humans (20 to 30 years of age) have shown that application of a mixture of cholesterol, ceramides, and essential/nonessential free fatty acids (FFAs) in an equimolar ratio allows normal barrier recovery, whereas any 3:1:1:1 ratio of these four ingredients accelerates barrier recovery.
OBJECTIVE AND METHODS: Our purpose was to compare the ability of equimolar and cholesterol- and FFA-dominant molar lipid mixtures (2% in propylene glycol/n-propanol, 7:3) versus vehicle alone on barrier recovery rates at 0, 3, 6, 24, 48 hours, and 1 week after tape stripping of aged hairless mouse (> 18 months) and chronologically aged human skin (80 +/- 5 years).
RESULTS: Whereas a single topical application of the equimolar mixture only allows normal recovery in young mice, it appeared to improve barrier recovery in chronologically aged mice (p < 0.06). Moreover, a 3:1:1:1 mixture with cholesterol as the dominant lipid further accelerated barrier recovery at 3 and 6 hours (p < 0.01 and p < 0.03, respectively, vs 1:1:1:1). Likewise, the cholesterol-dominant, optimal molar ratio mixture significantly accelerated barrier recovery in chronologically aged human skin at 6 hours (p < 0.005; n = 6). In contrast, in aged mice, an FFA-dominant mixture significantly delayed barrier recovery at 3, 6, and 24 hours (p < 0.005, 0.05, and 0.001, respectively), Finally, ultrastructural studies showed that lipid-induced, accelerated recovery in chronologically aged mice is associated with the accelerated replenishment of the stratum corneum interstices with lamellar unit structures.
CONCLUSION: These findings show that barrier recovery is accelerated in chronologically aged murine epidermis with optimized ratios of physiologic lipids, provided that cholesterol is the dominant lipid and that the same mixture also accelerates barrier recovery in chronologically aged human skin. |
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