Influence of Th2 Cytokines on the Cornified Envelope, Tight Junction Proteins, and β-Defensins in Filaggrin-Deficient Skin Equivalents

Abstract

Atopic dermatitis is a chronic skin condition with complex etiology. It is characterized by skin barrier defects and T helper type 2 (Th2)-polarized inflammation. Although mutations in the filaggrin gene are known to be prominent genetic risk factors for the development of atopic dermatitis, the interdependency between these and an altered cytokine milieu is not fully understood. In this study, we evaluated the direct effects of filaggrin deficiency on the cornified envelope, tight junction proteins, and innate immune response, and report the effects of Th2 cytokines in normal and filaggrin-deficient skin equivalents. Supplementation with IL-4 and IL-13 led to distinct histologic changes and significantly increased skin surface pH, both of which were enhanced in filaggrin knockdown skin equivalents. We detected a compensatory up-regulation of involucrin and occludin in filaggrin-deficient skin that was dramatically disturbed when simultaneous inflammation occurred. Furthermore, we found that a lack of filaggrin triggered an up-regulation of human ?-defensin 2 via an unknown mechanism, which was abolished by Th2 cytokine supplementation. Taken together, these results indicate that defects in the epidermal barrier, skin permeability, and cutaneous innate immune response are not primarily linked to filaggrin deficiency but are rather secondarily induced by Th2 inflammation.

Development of a Perfusion Platform for Dynamic Cultivation of in vitro Skin Models

“…Additionally, they are accepted for testing skin absorption taking into account the generally higher permeability of in vitro skin models [6,7,8]. Moreover, skin models are used for the assessment of drugs' pharmacodynamics or side effects [9] and for fundamental studies on the (patho)-physiological mechanism [10,11,12]. Nevertheless, in vitro skin models clearly have limitations compared to native human skin such as lower mechanical resistance, impaired maturation and differentiation, altered skin lipid composition and organization [13,14], increased skin permeability [15] and a lack of complexity, e.g.…”

Reconstructed Human Epidermis Predicts Barrier-Improving Effects of <b><i>Lactococcus lactis</i></b> Emulsion in Humans

“…A high expression of filaggrin is associated with an improved barrier function [29], while its deficiency causes barrier disruption [6]. Filaggrin is essential for stratum corneum formation and skin hydration, and elevated filaggrin levels reduce substance permeation and xerosis [29].…”

“…Human β-defensin-2 inhibits S. aureus, Streptococcus pyogenes , and C. albicans [44]. Moreover, this protein is downregulated in both atopic dermatitis patients and the respective 3-D disease model [6], being frequently accompanied by filaggrin deficiency. Although Lactococcus itself is not part of the physiological skin flora, dysbiotic effects can be safely excluded since the test formulations contained a lysate.…”

“…Antibodies against the following antigens were purchased from Abcam (Cambridge, UK): claudin-1 (1: 300; ab15098), involucrin (1: 500; ab111781), filaggrin (1: 1,000; ab81468), and human β-defensin-2 (1: 1,000; ab63982). Immunofluorescence staining was performed according to the standard protocols [6]. Fluorophore-linked secondary antibody obtained from Cell Signaling Technology (1: 400; 8889S; Cambridge, UK) was incubated for 1 h at room temperature.…”

“…Its degradation products essentially contribute to the natural moisturizing factor [4], which frequently declines in aged male skin [5]. Moreover, a reduced filaggrin expression, as seen in 42% of atopic dermatitis patients, is associated with impairment of the skin barrier function [6]. Keratinocytes also provide antimicrobial peptides like human β-defensin-2, which are released into the outermost skin layers.…”