Effects of mucopolysaccharide polysulphate on tight junction barrier in human epidermal keratinocytes

Tight junctions (TJs) play important roles in epidermal barrier function and their dysfunction is involved in the pathogenesis of various skin diseases, including atopic dermatitis (AD). Mucopolysaccharide polysulphate (MPS) is the active ingredient of a moisturizing agent used to treat xerosis in patients with AD; however, its mechanism of action on TJ barrier function remains unclear. To elucidate the effects of MPS on TJs, adult human epidermal keratinocyte (HEKa) cells were exposed to MPS, subjected to Western blotting and quantitative PCR analyses for the investigation of TJ‐related factors. MPS treatment significantly increased the mRNA and protein expression of claudin‐1 (CLDN1) and zonula occludens‐1, and significantly increased transepithelial electrical resistance (TEER), which indicates TJ integrity. Conversely, the sulphated and non‐sulphated glycosaminoglycans, chondroitin sulphate and hyaluronic acid, respectively, had little effect on TEER or the expression of mRNAs or TJ‐related proteins. Interestingly, MPS treatment also inactivated the extracellular signal‐regulated kinase signalling pathway, which is known to negatively regulate CLDN1 expression. Furthermore, MPS notably improved the reduction in CLDN1 expression and TEER caused by histamine, which is upregulated in the skin of patients with AD and is known to disrupt the TJ barrier function. Taken together, these findings demonstrate that treatment with the moisturizing agent, MPS, can repair TJ dysfunction and could therefore represent a new therapeutic option for treating patients with AD.