Acid In Epidermis Research Articles

Non-Invasive Method for Quantitative Evaluation of Exogenous Compound Deposition on Skin

Topical application of active compounds on skin is common to both pharmaceutical and cosmetic industries. Quantification of the concentration of a compound deposited on the skin is important in determining the optimum formulation to deliver the pharmaceutical or cosmetic benefit. The most commonly used techniques to date are either invasive or not easily reproducible. In this study, we have developed a noninvasive alternative to these techniques based on spectrofluorimetry. A mathematical model based on diffusion approximation theory is utilized to correct fluorescence measurements for the attenuation caused by endogenous skin chromophore absorption. The limitation is that the compound of interest has to be either fluorescent itself or fluorescently labeled. We used the method to detect topically applied salicylic acid. Based on the mathematical model a calibration curve was constructed that is independent of endogenous chromophore concentration. We utilized the method to localize salicylic acid in epidermis and to follow its dynamics over a period of 3 d.

13-Hydroxyoctadecadienoic Acid (13-HODE) Reverses Epidermal Hyperproliferation via Selective Inhibition of Protein Kinase C-β Activity

13-Hydroxyoctadecadienoic acid (13-HODE) is a major lipoxygenase metabolite of linoleic acid in epidermis. Employing a docosahexaenoic acid (22:6n-3) induced model of hyperproliferative guinea pig epidermis, we demonstrated reversal of hyperproliferation by topical 13-HODE. To delineate a possible mechanism for 13-HODE effect, we demonstrated that topical 13-HODE was incorporated into 13-HODE-containing diacylglycerol (13HODE-DAG). This novel substituted-DAG which was markedly depleted in the hyperproliferative skin paralleled the increased activities of PKC-alpha and beta. Replenishment of the hyperproliferative epidermis with topical 13-HODE resulted in the accumulation of tissue 13HODE-DAG and the selective suppression of PKC-beta activity. These data taken together suggest that the generation of putative 13-HODE-DAG and the selective suppression of PKC-beta isozyme activity may play a role in modulating epidermal hyperproliferation.

Identification, isolation and characterization of epidermal lipids containing linoleic acid

Three specific linoleate-rich lipids have been identified in pig epidermis and are referred to as O-acylglucosyl ceramide, O-acyl ceramide, and O-acyl acid. The acid moiety is up to 70% linoleic acid and linked via the hydroxyl group of a omega-OH long-chain fatty acid, which itself is linked to sphingosine or glucosyl sphingosine. The identification of O-acyl ceramide confirmed the findings of another group, whereas the structural configuration of the O-acylglucosyl ceramide is different to previous reports. The identification of an O-acyl acid in epidermis is novel. Our evidence allows us to speculate that a hydroxylated derivative of the O-acyl ceramide may be intimately involved in the permeability barrier of skin, perhaps providing sufficient polarity to maintain a lamellar phase in the intercellular space of the lower stratum corneum region, and that it is specifically in this form that linoleic acid is involved in skin barrier function. Alternatively, or concurrently, this species may act as a signal for late keratinisation events.

Amount of Ascorbic Acid in Normal Epidermis

In undertaking investigations of the function of ascorbic acid in the skin no reference could be found in the literature concerning the amount of ascorbic acid in epidermis. Jensen and Poulsen in 1942 made an extensive study of the concentration of ascorbic acid in 181 specimens of skin obtained by punch biopsy from 72 persons. They extracted the tissue with 8% metaphosphoric acid solution TABLE I Specimen Area Cause of Amputation Ascorbic Acid, mg. per 100 gm. wet weight Epidermis Corium Whole Skin 1 2 3 4 5 6 7 8 9* 10 Breast Breast Leg Leg Breast Leg Breast Breast Breast Breast Carcinoma Carcinoma Sarcoma of bone Arterial thrombosis Carcinoma Diabetic gangrene Carcinoma Carcinoma Carcinoma Carcinoma 8.35 8.26 4.94 6.64 6.63 6.89 12.80 5.41 11.31 13.40 3.48 1.00 0.18 3.37 4.98 3.08 6.40 3.23 4.25 7.00 7.30 9.90 Negro and titrated this extract with a solution of 2,6-dichlorophenol indophenol which had been standardized with an aqueous solution of ascorbic acid of known concentration. In 95% of the specimens of normal skin they found concentrations of ascorbic acid varying from 0 to 10 mg. per 100 grams of skin (wet weight). At that time no satisfactory method was available for separating epidermis from corium without some chemical alteration (1).