c-Myc Upregulated by High Glucose Inhibits HaCaT Differentiation by S100A6 Transcriptional Activation

Abstract

Keratinocyte differentiation dysfunction in diabetic skin is closely related to impaired skin barrier functions. We investigated the effects of c-Myc and S100A6 on Human immortal keratinocyte line (HaCaT) or keratinocyte differentiation and potential mechanisms. The expression levels of differentiation makers such as transglutaminase 1 (TGM1), loricrin (LOR), and keratin 1 (K1) were significantly reduced, while the expression of c-Myc was significantly increased in HaCaT cells cultured in high glucose and wound margin keratinocytes from diabetic rats and human patients. Overexpression of c-Myc caused differentiation dysfunction of HaCaT, while knocking down c-Myc promoted differentiation. High glucose increased the expression of c-Myc and inhibited differentiation in HaCaT cells by activating the WNT/β-catenin pathway. Moreover, inhibition of c-Myc transcriptional activity alleviated the differentiation dysfunction caused by high glucose or overexpression of c-Myc. c-Myc binds to the S100A6 promoter to directly regulate S100A6 expression and high glucose promoted S100A6 transcription. The expression of S100A6 was increased in HaCaT cultured with high glucose and wound margin keratinocytes from diabetic rats and human patients. However, the expression of S100A6 was decreased during normal HaCaT differentiation. HaCaT cells treated with S100A6 recombinant protein showed differentiation dysfunction. The expressions of TGM1, LOR and K1 in knockdown S100A6 HaCaT cells were higher than those in the control group. Overexpression of c-Myc or high glucose caused differentiation dysfunction of HaCaT cells, and was rescued by knocking down S100A6. These findings illustrate a new mechanism by which c-Myc upregulated by high glucose inhibits HaCaT differentiation by directly activating S100A6 transcription. Thus, c-Myc and S100A6 may be potential targets for the treatment of chronic diabetic wounds.

Moringa oleifera Leaf Extract Promotes Healing of Infected Wounds in Diabetic Rats: Evidence of Antimicrobial, Antioxidant and Proliferative Properties

“…HaCaT cells, which are cultured human keratinocyte cells, are commonly used to study inflammation and immunological responses in the skin [ 32 ]. In the present study, HaCaT cells were cultured under high glucose concentrations to simulate diabetic conditions [ 33 ]. M. oleifera extract did not show any cytotoxic effect on HaCaT cells in the MTT assay, confirming the results of its safety on the skin in the skin irritation test.…”

Impaired Function in Diabetic Patient iPSCs-derived Blood Vessel Organoids Stem from a Subpopulation of Vascular Cells

“…It has been reported that endothelial MYC overexpression results in severe defects in the human coronary artery (Pinheiro-de-Sousa et al ., 2022) and the embryonic vascular system (Kokai et al ., 2009). Similarly, high glucose has been shown to activate MYC target genes in different cell types (Jonas et al ., 2001; Zhang et al ., 2021), resulting in exaggerated cell proliferation. Of note, Myc is not only an oxidative stress-responsive gene (Elouil et al ., 2005), but it can also induce ROS production (Vafa et al ., 2002; Liu et al ., 2017).…”

Alterations in epidermal function in type 2 diabetes: Implications for the management of this disease

“…34 In vitro study showed that high glucose inhibited the expression levels of transglutaminase 1 and loricrin in keratinocyte cultures. 35 Thus, decreased expression levels of differentiation-related marker proteins can contribute to delayed permeability barrier recovery. The delayed permeability barrier recovery in mice and humans with type 2 diabetes can be attributed to elevated skin surface pH (discussed later), 15,16,36 and reduced hyaluronic acid, 37 which is required for epidermal lipid production, keratinocyte differentiation, and proliferation.…”

“…In addition, expression levels of loricrin and filaggrin are decreased in diabetic mice 34 . In vitro study showed that high glucose inhibited the expression levels of transglutaminase 1 and loricrin in keratinocyte cultures 35 . Thus, decreased expression levels of differentiation‐related marker proteins can contribute to delayed permeability barrier recovery.…”