PG102 Upregulates IL-37 through p38, ERK, and Smad3 Pathways in HaCaT Keratinocytes

Abstract

IL-37 is an immunomodulatory cytokine that suppresses inflammation in various cell types and disease models. However, its role in keratinocytes has not been clearly understood, and there has been no report on the agents that can increase the expression of IL-37 in keratinocytes. In this study, we investigated the effects of silencing IL37 in HaCaT keratinocytes and the molecular mechanisms involved in the upregulation of IL-37 by PG102, a water-soluble extract from Actinidia arguta. It was found that knockdown of IL37 resulted in the augmented expression of antimicrobial peptides (AMPs) in response to cytokine stimulation. PG102 increased the expression of IL-37 at both mRNA and protein levels presumably by enhancing the phosphorylation of Smad3, ERK, and p38. Indeed, when cells were treated with specific inhibitors for these signaling molecules, the expression level of IL-37 was reduced. PG102 also promoted colocalization of phospho-Smad3 and IL-37. Our results suggest that IL-37 inhibits the expression of AMPs and that PG102 upregulates IL-37 through p38, ERK, and Smad3 pathways in HaCaT cells.

Natural Compounds Tapinarof and Galactomyces Ferment Filtrate Downregulate IL-33 Expression via the AHR/IL-37 Axis in Human Keratinocytes

“…To further determine the cellular localization of IL-37 in NHEKs, we performed immunofluorescent analysis using anti-IL-37 antibody on NHEKs treated with either tapinarof (500 nM) or 5% GFF for 24 h. We observed both cellular and nuclear IL-37 expression in NHEKs treated with either tapinarof or GFF ( Figure 1M ). In accordance with a previous study using human keratinocytes ( 23 ), using ELISA we could not detect secreted IL-37 in the culture supernatant of NHEKs treated with either tapinarof or GFF (data not shown).…”

“…PG102, a plant-derived substance extracted from Actinidia arguta , has also been reported to increase IL-37 expression in human keratinocytes ( 23 ). The A. arguta extract contains many polyphenols, with quercetin derivatives and kaempferol derivatives having been identified as the main components ( 33 , 34 ).…”

IL-1 Family Antagonists in Mouse and Human Skin Inflammation

“…Only few studies have addressed potential effects of IL-37 in the context of human skin inflammation, but their results concur to suggest anti-inflammatory activity of this cytokine. Indeed, overexpression of IL-37b in the human HaCat keratinocyte cell line decreased the expression of pro-inflammatory mediators, while, conversely, siRNA knockdown of IL37 in HaCaT cells resulted in increased AMP expression ( 183 , 184 ). Finally, in vitro treatment of inflammatory skin lesions of Behçet's disease patients with recombinant IL-37 also decreased cytokine expression ( 185 ).…”

Enhanced Wound Healing- and Inflammasome-Associated Gene Expression in TNFAIP3-Interacting Protein 1- (TNIP1-) Deficient HaCaT Keratinocytes Parallels Reduced Reepithelialization

“…HaCaT keratinocytes, a spontaneously immortalized, nontumorigenic line [18], were cultured as previously described [13]. The HaCaT keratinocyte line has been extensively used to model human keratinocyte inflammatory pathway signaling, cytokine production, and reepithelialization [19][20][21][22][23][24][25][26]. TNIP1-targeting siRNA or nontargeting negative control siRNA was used to transfect HaCaT keratinocytes (triplicate wells plated as follows: 6well, 480,000 cells/well; 12-well, 160,000 cells/well; 24-well, 80,000 cells/well) 24 hr postplating.…”