Molecular Mechanism of Epidermal Barrier Dysfunction as Primary Abnormalities

Abstract

Epidermal barrier integrity could be influenced by various factors involved in epidermal cell differentiation and proliferation, cell-cell adhesion, and skin lipids. Dysfunction of this barrier can cause skin disorders, including eczema. Inversely, eczema can also damage the epidermal barrier. These interactions through vicious cycles make the mechanism complicated in connection with other mechanisms, particularly immunologic responses. In this article, the molecular mechanisms concerning epidermal barrier abnormalities are reviewed in terms of the following categories: epidermal calcium gradients, filaggrin, cornified envelopes, desquamation, and skin lipids. Mechanisms linked to ichthyoses, atopic dermatitis without exacerbation or lesion, and early time of experimental irritation were included. On the other hand, the mechanism associated with epidermal barrier abnormalities resulting from preceding skin disorders was excluded. The molecular mechanism involved in epidermal barrier dysfunction has been mostly episodic. Some mechanisms have been identified in cultured cells or animal models. Nonetheless, research into the relationship between the causative molecules has been gradually increasing. Further evidence-based systematic data of target molecules and their interactions would probably be helpful for a better understanding of the molecular mechanism underlying the dysfunction of the epidermal barrier.may not be the primary events in lesional skin. However, they can play a role in part as primary abnormalities because abnormalities in the epidermal barrier are already present in non-lesional skin of atopic dermatitis [1]. Epidermal trauma from tape stripping or irritant application also leads to initial disruption of the barrier, although the result at certain time points may be combined with compensatory reactions followed by trauma.Causative mechanisms involved in primary epidermal barrier dysfunction might be more valuable for the prevention of skin diseases induced by barrier abnormalities. However, the underlying mechanism has been discussed mainly in connection with immunologic responses, including cytokine production [1,9,10]. Accordingly, this review covers molecular mechanisms of epidermal barrier dysfunction as primary abnormalities by focusing on the causative factors of skin diseases (atopic dermatitis and ichthyoses) and experimental skin conditions (tape stripping and irritant application) associated with skin barrier abnormalities. Molecular Mechanisms Related to Epidermal Barrier DysfunctionFormation and maintenance of skin barrier integrity could be influenced by genetic and environmental factors involved in epidermal cell differentiation and proliferation, cell-cell adhesion, and skin lipids. Mechanisms related to epidermal barrier dysfunction at molecular levels have commonly illustrated filaggrin mutations [3,11]. Regarding the mechanism behind skin barrier integrity, the role of epidermal calcium gradients could be considered based on their influence on keratinocyte proliferation and dif...

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“…It is highly relevant for the absorption process of the vast majority of drugs by passive diffusion. It consists of corneocytes which are connected via corneodesmosomes and TJ remnants, and intercellular lipids [ 1 , 6 ] (see Figure 1 A).…”

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The Role of MicroRNAs in Epidermal Barrier

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“…Desquamation is determined by de novo synthesis and degradation of corneodesmosomal proteins. The key role of desquamation in epidermal barrier integrity and homeostasis has been attributed to accelerated desquamation either via reduced corneodesmosome synthesis or increased corneodesmosome degradation linked to skin disorders with barrier dysfunction [105]. The association between miRNAs and structural proteins of corneodesmosome or proteases and inhibitors involved in corneodesmosome degradation has been reviewed (Table 4).…”

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