title: Inhibition of Methylglyoxal-Induced AGEs/RAGE Expression Contributes to Dermal Protection by N-Acetyl-L-Cysteine.
abstract: Accumulation of advanced glycation end products (AGEs) is a major cause of diabetes mellitus (DM) skin complications. Methylglyoxal (MGO), a reactive dicarbonyl compound, is a crucial intermediate of AGEs generation. N-acetyl-L-cysteine (NAC), an active ingredient of some medicines, can induce endogenous GSH and hydrogen sulfide generation, and set off a condensation reaction with MGO. However, there is rare evidence to show NAC can alleviate DM-induced skin injury through inhibition of AGEs generation or toxicity. The present study aimed to observe the effects of NAC on MGO-induced inflammatory injury and investigate the roles of AGEs and its receptor (RAGE) in NAC's dermal protection in human HaCaT keratinocytes.
  
  
  
  The cells were exposed to MGO to simulate a high MGO status in diabetic blood or tissues. The content of AGEs in serum or cell medium was measured with ELISA. The protective effects of NAC against MGO-induce injury were evaluated by administration before MGO one hour, in virtue of cell viability, mitochondrial membrane potential, inflammation reaction, nuclear factor (NF)-κB activation, matrix metalloproteinase (MMP)-9 expression, as well as cellular behavioral function.
  
  
  
  We found the AGEs levels of patients with DM were elevated comparing with healthy volunteers. The in vitro AGEs generation was also able to be enhanced by the exposure of HaCaT cells to MGO, which reduced dose-dependently cellular viability, damaged mitochondrial function, triggered secretion of interleukin (IL)-6 and IL-8, activated NF-κB and upregulated MMP-9 expression. Furthermore, the exposure caused cellular adhesion and migration dysfunction, as well as collagen type I inhibition. Importantly, before the exposure to MGO, the preconditioning with NAC significantly attenuated MGO-induced AGEs generation, improved cellular viability and mitochondrial function, partially reversed the overexpression of proinflammatory factors and MMP-9, as well as the activation of NF-κB. Lastly, NAC blocked MGO-induced RAGE upregulation, and inhibition of RAGE with its neutralizing antibody significantly alleviated MGO-induced NF-κB activation, MMP-9 upregulation and inflammatory injury in HaCaT cells.
  
  
  
  The present work indicates the administration of NAC can prevent MGO-induced dermal inflammatory injury through inhibition of AGEs/RAGE signal, which may provide a basal support for the treatment of diabetic skin complications with NAC-containing medicines in the future.
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China|Affiliated Cancer Hospital & Institute, Guangzhou, China
authors.forename: Chun-Tao
authors.initials: CT
authors.lastname: Yang
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China
authors.forename: Fu-Hui
authors.initials: FH
authors.lastname: Meng
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China
authors.forename: Lai-Jian
authors.initials: LJ
authors.lastname: Cen
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Wen
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China
authors.forename: Cai-Chen
authors.initials: CC
authors.lastname: Li
authors.affiliation: Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou, China|Affiliated Cancer Hospital & Institute, Guangzhou, China|Quality Control Section of Academic Affairs, Guangzhou Medical University, Guangzhou, China
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D000368:Aged; D016022:Case-Control Studies; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000473:pathology; D005260:Female; D017127:Glycation End Products, Advanced / Q000032:analysis* / Q000097:blood; D006801:Humans; D015850:Interleukin-6 / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008875:Middle Aged; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D020011:Protective Agents / Q000494:pharmacology*; D011765:Pyruvaldehyde / Q000494:pharmacology*; D000067759:Receptor for Advanced Glycation End Products / Q000032:analysis* / Q000097:blood; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D017127:Glycation End Products, Advanced; D015850:Interleukin-6; D016209:Interleukin-8; D020011:Protective Agents; D000067759:Receptor for Advanced Glycation End Products; D011765:Pyruvaldehyde; D020780:Matrix Metalloproteinase 9; D000111:Acetylcysteine
keywords: Advanced glycation end products; Delayed wound healing; Diabetes mellitus; Inflammation; Keratinocytes; N-acetyl-L-cysteine