Organic osmolytes preserve the function of the developing tight junction in ultraviolet B-irradiated rat epidermal keratinocytes

Abstract

Epidermal barrier function is provided by the highly keratinised stratum corneum and also by tight junctions (TJs) in the granular layer of skin. The development of the TJ barrier significantly deteriorates in response to ultraviolet B radiation (UVB). Following exposure to UVB, keratinocytes accumulate organic osmolytes, which are known to preserve cell volume during water stress. Since TJs are intimately associated with control of water homeostasis in skin, we hypothesised that there may be a direct influence of osmolytes on TJ development. Exposure of rat epidermal keratinocytes (REKs) to a single dose of UVB reduced the function of developing TJs. This was concomitant with dislocalisation of claudin-1 and claudin-4 from the keratinocyte plasma membrane, phosphorylation of occludin and elevation of reactive oxygen species (ROS). In the presence of organic osmolytes, these effects were negated but were independent of the effects of these molecules on cell volume, elevation of ROS or the gene expression of TJ proteins. These data suggest that organic osmolytes affect TJs via post-translational mechanism(s) possibly involving protection of the native conformation of TJ proteins.

Brazilian Green Propolis Rescues Oxidative Stress-Induced Mislocalization of Claudin-1 in Human Keratinocyte-Derived HaCaT Cells

“…There was no apparent change in CLDN4 localization, but the amount of CLDN4 protein increased transiently after 6 h of H 2 O 2 treatment. Recently, El-Chami et al [27] reported that H 2 O 2 (1 mM, a higher concentration than in our study) induced the mislocalization of CLDN1, CLDN4, and occludin in a continuous cell line of rat epidermal keratinocytes. We suggest that oxidative stress selectively induces the mislocalization of CLDN1 in low-level cell toxic conditions.…”

Increased osmolality enhances the tight junction‐mediated barrier function in a cultured renal epithelial cell line

“…All these processes can potentially affect and modulate TJ proteins. Interestingly, taurine, one of these osmolytes, has been shown to enhance the TJ barrier in different epithelia (El-Chami et al, 2018). Interestingly, taurine, one of these osmolytes, has been shown to enhance the TJ barrier in different epithelia (El-Chami et al, 2018).…”

“…In addition, an increase in extracellular osmolality can lead to a longterm increase in cytoplasmic osmolytes, as a compensatory process to preserve cell volume (Alfieri and Petronini, 2007). Interestingly, taurine, one of these osmolytes, has been shown to enhance the TJ barrier in different epithelia (El-Chami et al, 2018). Assessment of all these potential mechanisms of regulating TJ under hyperosmolarity is an attractive area for future research.…”

Weak Ultraviolet B Enhances the Mislocalization of Claudin-1 Mediated by Nitric Oxide and Peroxynitrite Production in Human Keratinocyte-Derived HaCaT Cells

“…Recently, El-Chami et al [ 29 ] reported that a single dose of UVB (10 mJ/cm 2 ) induces the elevation of ROS and disruption of the TJ barrier in rat epidermal keratinocyte. Our results indicated that the total amount of CLDN1 protein is constant for 24 h, but CLDN1 dissociates from the TJ ( Figure 1 ).…”