Human Horny Layer Research Articles

Comparative Evaluation of the Effect of Permeation Enhancers, Lipid Nanoparticles and Colloidal Silica on in vivo Human Skin Penetration of Quercetin

Background/Aim: The aim of this study was to evaluate emulsions containing a penetration enhancer, lipid nanoparticles (LNs) or colloidal silica as systems to improve the topical delivery of the flavonoid quercetin. Methods: The skin penetration of quercetin was investigated in vivo on human volunteers by tape stripping. Quercetin-loaded LNs were prepared using hot high-pressure homogenization and characterized by means of dynamic light scattering and release studies. The location of the silica nanoparticles in the skin was determined by inductively coupled plasma mass spectrometry assay of silicon in the stratum corneum strips. Results and Conclusions: The penetration enhancer diethylene glycol monoethyl ether did not produce any significant increase in the fraction of the applied quercetin dose permeated in vivo into human stratum corneum (17.1 ± 3.2%) compared to the control emulsion (18.1 ± 2.3%). A greater but statistically nonsignificant accumulation of the flavonoid in the human horny layer (21.2 ± 2.9% of the applied dose) was measured following topical application of quercetin-loaded LNs (mean particle size: 527 nm). On the other hand, the addition of colloidal silica (average particle diameter: 486 nm) to the emulsion (2%, w/w) significantly increased the in vivo uptake of quercetin by the human stratum corneum to 26.7 ± 4.1% of the applied dose, the enhancing effect on permeation being more marked in the deepest horny layer strips. The measured in vivo skin penetration profile of colloidal silica showed that silica particles diffused down to the intermediate region of the human horny layer and hence could act as carrier for quercetin.

Influence of cleansing on stratum corneum tryptic enzyme in human skin

Desquamation in human skin is a well-balanced process of de novo production of corneocytes and their shedding from the skin surface. The proteolysis of corneodesmosomes is an important step in the final desquamation process. In the degradation of these adhesion molecules, the stratum corneum tryptic enzyme (SCTE) plays a key role. In initial studies with extracts of porcine epidermis, SCTE was shown to be inactivated by low concentrations of sodium lauryl ether sulphate (SLES). These in vitro findings were supported by in situ results obtained by measuring the release of fluorescent dyes coupled to trypsin-specific substrates incubated on human skin cross-sections. Moreover, in further studies, it could be demonstrated that the SCTE activity in the human horny layer decreases after in vivo application of cleansing products containing SLES. After repeated washing of human volunteers with tap water, a standard market cleansing product (SLES/betaine system) or a new improved cleansing product (SLES/betaine/disodium cocoyl glutamate system), the specific SCTE activity was determined in extracts from the uppermost layers of the stratum corneum. It could be shown that after application of the new formula the remaining SCTE activity was significantly higher than after use of the standard market formula. This ex vivo approach has proven to be very helpful for measuring surfactant effects on human skin enzymes. Using this assay, we developed an improved shower gel formula, which leads to a significantly higher skin enzyme activity after application, compared to a standard market formula.

Elafin: an elastase-specific inhibitor of human skin. Purification, characterization, and complete amino acid sequence.

A potent inhibitor of human leukocyte elastase (EC 3.4.21.37) and porcine pancreatic elastase (EC 3.4.21.36) was purified to homogeneity from human horny layers. It inhibits human leukocyte elastase and porcine pancreatic elastase in a 1:1 molar ratio and shows equilibrium dissociation constants of 6 x 10(-10) M and 1 x 10(-9) M, respectively. Inhibition of plasmin, trypsin, alpha-chymotrypsin, and cathepsin G was not observed. This inhibitor proved to be an acid stable basic peptide with an isoelectric point of 9.7. The complete amino acid sequence appears to be unique with 38% homology to the C-terminal half of antileukoprotease. The sequence shows that the inhibitor is composed of 57 amino acids and predicts a Mr of 7017. The high affinity as well as the apparent specificity for elastases suggests a functional role in preventing elastase-mediated tissue proteolysis. It is suggested that the term "elafin" be used to designate this inhibitor.

Cumulative effect of surfactants on cutaneous horny layers: lysosomal activity of human keratin layers in vivo.

Anionic surfactants have various degrees of membrane labilizing action on isolated lysosome in vitro. This action has been found to correlate with the degrees of skin roughness induced by the surfactants using the circulation method applied to the forearm of human subjects. It has been shown that the acid phosphatase activity in the human horny layer decreases during the in vivo application of the surfactants by the circulation method. The magnitude of the decrease in acid phosphatase activity has been found to correlate to the degree of skin roughness and to in vitro lysosome labilization induced by the surfactants.

Cumulative effect of surfactants on cutaneous horny layers: adsorption onto human keratin layers in vivo.

An attempt has been made to determine the adsorption ability of surfactants by the human horny layers in vivo. For this purpose, a technique utilizing an acidic dye such as indigo carmine was applicable and convenient. Our in vivo study estimating adsorbing residual amounts of surfactants has revealed that there is a positive correlation between adsorbing and roughening effects. It is suggested that the pathogenesis of hand roughness is primarily related to the cumulative injury of the stratum corenum by adsorbing residual surfactant molecules.

Exfoliative cytology of human horny layer. Methods of cell removal and microscopic techniques

A procedure for studying the cytology and morphology of the horny cells of the skin has been described. It is based upon removal of horny cells directly onto adhesive coated glass slides. By viewing the cells in their broad axes, many details may be seen which are concealed in traditional transverse sections. Optical systems and staining procedures are described to facilitate examination of normal and abnormal horny cells.

Exfoliative Cytology of Human Horny Layer

A procedure for studying the cytology and morphology of the horny cells of the skin has been described. It is based upon removal of horny cells directly onto adhesive coated glass slides. By viewing the cells in their broad axes, many details may be seen which are concealed in traditional transverse sections. Optical systems and staining procedures are described to facilitate examination of normal and abnormal horny cells.

Horny Layer Lipids: II. Further Studies on the Overall Chemical Composition of Lipids from Normal and Pathological Human Stratum Corneum

In a previous report (1) we described some studies of the lipids from human horny layers. We have continued this work using improved extraction and analytical techniques. The results confirm and amplify our previous findings.

Desquamation of the Human Horny Layer

By protecting various portions of the skin surface, the morphology of the shedding process has been discerned. Normal desquamation is neither in the form of subcellular particles nor as a microscopic dust of individual cells. The stratum corneum cracks up in its outermost portion into aggregates of cells to be finally shed as fine scales and flakes.

About the Proof of Urocanic Acid in Callus and in Normal Human Horny Layer

Urocanic acid (UCA) was first demonstrated in human sweat (1), later on in aqueous extracts of superficial (2) and deep human horny layer (barrier” (3)) and in the whole epidermis of guinea pigs (4). The epidermal nature of UCA in guinea pig epidermis, normally exempt from sweat glands, was proven by its existence after X-ray-induced atrophy of sebaceous glands (5). The known origin of UCA from histidine could also be demonstrated in mammalian epidermis by radio-carbon tracers (6). The identity of water soluble ultraviolet-absorbing constituent of normal human horny layer with UCA was confirmed by means of several quite different analyses: as there were characteristic ultraviolet spectra at pH 1 and pH 13 (1, 2), their loss after hydrogenation depending on a transformation to imidazolyl propionic acid (1), ionophoretic mobility (1, 2), Rf-values by paper chromatography in three different solvents (1, 2), coupling reactions with diazosulfanilic acid (Pauly's reagent) (1, 2), and with dianisidine (2), further coloring with eosine-Hg (2), and finally, growing pale after spraying with KMn04 (2).

Isolation of a Glycoproteolipid from Human Horny Layers

The dermatologie literature contains a wide variety of studies on the lipids of human epidermis and horny layers which do not originate from the sebaceous glands (1 to 6). Nevertheless, the composition and role of these substances have not been subjected to systematic investigations.

Water-soluble organic components of psoriatic scales.

During the last 12 years the water-soluble organic components of human horny layers have attracted steadily increasing attention. early reports Rothman, Bolliger, and their co-workers1,2pointed out that in horny structures these components were always present. While originally thought to be derived at least in part from sweat,1the later fundamental works of Szakall, Spier, and others3-18definitely established that the water-soluble compounds were formed by the epidermal cells during the development of the horny layer. These authors and subsequent investigators brought growing evidence that these compounds are not merely by-products of keratinization, but may occupy a central role in the physiology and chemistry of normal and pathologic epidermis. In faulty keratinization, disturbances of the cellular decomposition are probably at least as important as anomalies of keratin formation.19 Experiments with isolated psoriatic epidermis, freed of horny layer, present formidable technical difficulties. Therefore the common approach

The Society for Investigative Dermatology, Inc. 23rd Annual Meeting

PRESIDENTIAL ADDRESS: ADVENTURES WITH THE BASOPHIL. WALTER B. SHELLEY, M.D., Department of Dermatology, School of Medicine, University of Pennsylvania, Philadelphia, Pa. The Superiority of Blister Fluid Over Standard Serum Additives to Tissue Culture Media for the Cultivation of Epidermal Cells. Philip C. Anderson, M.D., Department of Dermatology, University of Michigan Medical Center, Ann Arbor, Mich. Barriers to Skin Penetration. Francis N. Marzulli, Ph.D., Field Toxicology Branch, Chemical Research & Development Laboratories, Army Chemical Center, Maryland. Studies in the Biochemistry of Skin. I. Respiration of Adult Rat Epidermal Tissue. Theodore Rosett, Ph.D., and Joseph Fogg, B.S., Duke University School of Medicine, Durham, N. C. Studies of Epidermal Protein Metabolism. II. Soluble Epidermal Proteins. Howard P. Baden, M.D., and Irwin M. Frcedberg, M.D., Department of Dermatology, Harvard Medical School, at the Massachusetts General Hospital, Boston, Mass., and the Graduate Department of Biochemistry, Brandeis University, Waltham, Mass. Isolation of a Glycoproteolipid from Human Horny Layers. Peter Flesch, M.D., Ph.D., and Elizabeth C. J. Esoda, M.D., Department of Dermatology, School of Medicine, University of Pennsylvania, Philadelphia, Pa. Epidermal Glucose in Health and Disease. Alan H. Schragger, M.D., Department of Dermatology, University of Miami School of Medicine, Miami, Florida. Studies on the Pharmacology of Human Skin. I. Epinephrine and Norepinephrine. D. Joseph Demis, M.D., Ph.D., Phyllis Vcrhonick, Major, ANC, and James G. Zimmer, M.D., Department of Dermatology, Walter Reed Army Institute of Research, Washington, D. C.