Glycolic Acid Silences Inflammasome Complex Genes,NLRC4andASC, by Inducing DNA Methylation in HaCaT Cells

Abstract

AHAs (α-hydroxy acids), including glycolic acid (GA), have been widely used in cosmetic products and superficial chemical peels. Inflammasome complex has been shown to play critical roles in inflammatory pathways in human keratinocytes. However, the anti-inflammatory mechanism of GA is still unknown. The aim of this study is to investigate the relationship between the expression of the inflammasome complex and epigenetic modification to elucidate the molecular mechanism of the anti-inflammatory effect of GA in HaCaT cells. We evaluated NLRP3, NLRC4, AIM2, and ASC inflammasome complex gene expression on real-time polymerase chain reaction (PCR). Methylation changes were detected in these genes following treatment with DNA methyltransferase (DNMT) inhibitor 5-aza-2'-deoxycytidine (5-Aza) with or without the addition of GA using methylation-specific PCR (MSP). GA inhibited the expressions of these inflammasome complex genes, and the decreases in the expressions of mRNA were reversed by 5-Aza treatment. Methylation was detected in NLRC4 and ASC on MSP, but not in NLRP3 or AIM2. GA decreased NLRC4 and ASC gene expression by increasing not only DNA methyltransferase 3B (DNMT-3B) protein level, but also total DNMT activity. Furthermore, silencing of DNMT-3B (shDNMT-3B) increased the expressions of NLRC4 and ASC. Our data demonstrated that GA treatment induces hypermethylation of promoters of NLRC4 and ASC genes, which may subsequently lead to the hindering of the assembly of the inflammasome complex in HaCaT cells. These results highlight the anti-inflammatory potential of GA-containing cosmetic agents in human skin cells and demonstrate for the first time the role of aberrant hypermethylation in this process.

Increased incidence of non‐alcoholic fatty liver disease in male rat offspring exposed to fluoxetine during fetal and neonatal life involves the NLRP3 inflammasome and augmented de novo hepatic lipogenesis

“…Maternal fluoxetine exposure has been shown to result in posttranslational histone modifications and altered DNA methylation in the offspring (Boulle et al, 2016;Toffoli et al, 2014). There is also some evidence in the literature that demonstrates epigenetic regulation of Elovl6 and core components of NLRP3 inflammasome (Corominas et al, 2015;Meier, Drexler, Eberle, Lefort, & Yazdi, 2016;Tang et al, 2016). Moreover, knockdown of sirtuin 1 (SIRT1), a NAD + -dependent deacetylase has been demonstrated to enhance activation of the NLRP3 inflammasome in HUVEC cells (Li et al, 2017) and inhibition of SIRT1 in hepatocytes results in an upregulation of de novo lipogenesis related genes (Nassir & Ibdah, 2016).…”

Dual Effects of Alpha-Hydroxy Acids on the Skin

“…We demonstrated that GA at a low concentration (0.1 mM) either alone or with UVB radiation reduced the expression of inflammasome genes in NHEKs and HaCaT cells. These genes include NLRC4 and ASC, and are downregulated through epigenetic modification by increasing total DNA methyltransferase activity [ 10 ]. Through this mechanism, GA can reduce NLRC4 and ASC gene expression, thereby resulting in inflammasome collapse and decreasing the quantity of inflammasome downstream cytokine interleukin (IL)-1β released.…”

“…Our laboratory has analyzed a series of related studies on AHAs, which we also highlight in this article [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. GA regulates several signaling pathways, such as epigenetic factors and apoptotic mediators.…”

Chromatin modifiers in human disease: from functional roles to regulatory mechanisms

“…In addition, other studies have shown that HDAC6 and HDAC2 are also involved in the activation of NLRP3 inflammasomes in inflammatory diseases such as tuberculosis infection [ 119 , 120 ]. Glycolic acid stimulation of human immortalized keratinocytes induces DNMT3B recruitment in NLRC4 inflammasome and inhibits the transcriptional expression of NLRC4 and ASC, which may lead to the blockage of NLRC4 inflammasome assembly [ 121 ].…”