Anti-inflammatory effects of differential molecular weight hyaluronic acids on UVB-induced calprotectin-mediated keratinocyte inflammation

Background: The biological functions of HA are related to its molecular weight and binding to its receptor TLR4 or CD44. Recent studies have shown that LMW-HA exhibits proinflammatory effects, while HMW-HA functions as an anti-inflammatory factor. UVB-induced epidermal inflammation is mainly mediated by endogenous molecules, such as DAMPs, that cause severe skin damage by activating TLR signaling pathways. Objective: Since both LMW- and HMW-HA have inhibitory functions on TLR-mediated macrophage inflammation, HA is assumed to suppress UVB-induced DAMP-mediated inflammation in the skin. In this study, both uLMW-HA and HMW-HA were found to inhibit UVB-induced keratinocyte inflammation. Methods: To elucidate whether HAs have anti-inflammatory effects on inflammation induced by UVB exposure, we performed whole transcriptome analysis in HaCaT cells treated with or without HAs after UVB exposure. Results: UV radiation induced upregulation or downregulation of genes (FC>1.2 or FC<0.8, q<0.05) were obtained. We analyzed network of these genes with Ingenuity Pathway analysis using information collected from databases on protein interactions. IL-6 was detected as an upstream factor of HA suppressing UV-radiation effects on HaCaT cells. Canonical pathway analysis also shows uLMW-HA downregulated NF-?B, which is located downstream of TLR4 signaling pathway, although HMW-HA did not show downregulation of NF-?B signaling pathway. Conclusions: Both uLMW-HA and HMW-HA were found to inhibit UVB-induced keratinocyte inflammation. Overall design: RNAseq analysis of HaCaT cells treated with or without HAs after UVB exposure.