Acute Barrier Perturbation Abolishes the Ca2+ and K+ Gradients in Murine Epidermis: Quantitative Measurement Using PIXE

Abstract

Epidermal permeability barrier homeostasis requires the delivery of lipids and hydrolytic enzymes by lamellar body exocytosis from the uppermost granular cells, a process that is upregulated following barrier disruption. As lamellar body secretion is controlled by ionic concentrations, especially Ca2+ and K+, we used a quantitative technique, microbeam proton-induced X-ray emission, to measure Ca2+, K+, Cl-, and P concentrations before and after acute barrier perturbation by acetone applications. We found a steep gradient of Ca2+ in normal tissue, peaking in the outer stratum granulosum, which disappeared after barrier disruption, and partially reformed as the barrier recovered. A similar gradient, peaking somewhat lower in the epidermis (i.e., at the stratum granulosum-stratum corneum interface), was found for K+. Epidermal concentrations of K+ also decreased after barrier abrogation, although to a lesser extent than Ca2+. In contrast, P and Cl- demonstrated distribution gradients at baseline, which remained unchanged after barrier disruption. These studies quantitate the levels of Ca2+, K+, Cl-, and P within specific epidermal cell layers at baseline, and in relation to changes in permeability barrier integrity. Ca2+ and K+, but not Cl- or P, decrease after barrier disruption, consistent with these two ion's role in barrier repair.

Acute Modulations in Permeability Barrier Function Regulate Epidermal Cornification

“…Previous studies by our and other laboratories have demonstrated that disruption of the permeability barrier results in a decrease in calcium and other ions in the outer Ϫ/Ϫ mice 3 hours after tape stripping (E) (n ϭ 5). Scale bars ϭ 10 m. nucleated layers of the epidermis, 10,49 modifying the distinctive calcium gradient of the epidermis 50 -54 and stimulating lamellar body secretion. Yet, although decreases in calcium stimulate lamellar body secretion, they simultaneously inhibit epidermal differentiation 52 ; hence, we suspect that a decrease in calcium in the outer epidermis would not stimulate terminal differentiation.…”

Calcium-induced Matrix Metalloproteinase 9 Gene Expression Is Differentially Regulated by ERK1/2 and p38 MAPK in Oral Keratinocytes and Oral Squamous Cell Carcinoma

“…There is a steep calcium gradient within the oral mucosa, with higher calcium present in the uppermost differentiated layers, and altering extracellular calcium has been used to effectively model keratinocyte differentiation in vitro (13)(14)(15)(16). Immunohistochemical analysis of human keratinocytes indicates a correlation between MMP-9 expression and differentiation.…”

Focal Adhesion Kinase Controls pH-Dependent Epidermal Barrier Homeostasis by Regulating Actin-Directed Na+/H+ Exchanger 1 Plasma Membrane Localization

“…Two enzymes essential for this processing, ␤-GlcCer'ase and acidic sphingomyelinase, require acidic milieu for optimal activity, 29,45 suggesting that epidermal permeability barrier homeostasis is dependent on SC pH. 46,47 When exposed to alkaline or neutral solutions, skin exhibits greater susceptibility to develop irritant/allergic contact dermatitis. 46 -48 A number of exogenous and intrinsic mechanisms have been proposed to contribute to SC acidity.…”