title: ASH1L Suppresses Matrix Metalloproteinase through Mitogen-activated Protein Kinase Signaling Pathway in Pulpitis.
abstract: BACKGROUND
  Pulpitis is an inflammation of dental pulp produced by a response to external stimuli. The response entails substantial cellular and molecular activities. Both genetic and epigenetic regulators contribute to the occurrence of pulpitis. However, the epigenetic mechanisms are still poorly understood. In this research, we studied the role of the absent, small, or homeotic-like (ASH1L) gene in the process of pulpitis.
  
  
  METHODS
  Human dental pulp cells (HDPCs) were stimulated with proinflammatory cytokine tumor necrosis factor alpha (TNF-α). Gene expression profiling was performed to assess the occurrence of epigenetic regulators. Pulp tissue from rat experimental pulpitis was subjected to immunofluorescence to detect the occurrence of ASH1L and trimethylation of lysine 4 histone 3 (H3K4me3). The presence of ASH1L in HDPCs that had been generated by TNF-α stimulation was analyzed by Western blot procedures and cellular immunofluorescence. Once detected, ASH1L was silenced through the use of specific small interfering RNA. The effects of ASH1L on the occurrence and operation of matrix metalloproteinases (MMPs) were then tested by analysis of quantitative polymerase chain reactions, Western blotting, and zymography. Chromatin immunoprecipitation was performed to detect whether ASH1L and H3K4me3 were present in the promoter regions of MMPs. We then used Western blot procedures to examine the nuclear factor kappa B and the mitogen-activated protein kinase (MAPK) responses to the silencing of ASH1L. We also examined the specific pathway involved in ASH1L regulation of the MMPs.
  
  
  RESULTS
  After stimulating HDPCs with TNF-α, ASH1L emerged as 1 of the most strongly induced epigenetic mediators. We found that TNF-α treatment induced the expression of ASH1L through the nuclear factor kappa B and MAPK signal pathways. ASH1L was found in both the nucleus and the cytoplasm. TNF-α treatment was particularly active in inducing the accumulation of ASH1L in cellular cytoplasm. As is also consistent with in vitro results, ASH1L was found in increased quantities in experimental dental pulpitis tissue. ASH1L knockdown markedly up-regulated the occurrence of MMP-1, MMP-2, and MMP-13. It also exercised an impact on the enzymatic activity of MMP-2 in HDPCs that had been stimulated with TNF-α. ASH1L knockdown activated the MAPK signal pathway in TNF-α-triggered HDPCs, the inhibition of which reversed the induction of MMPs.
  
  
  CONCLUSIONS
  Our research identifies a mechanism by which ASH1L suppresses the occurrence and operation of MMPs during pulpitis. It does this through the MAPK pathway.
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Bei
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tianqian
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Fanyuan
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Luo
authors.initials: L
authors.lastname: Haiyun
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Liao
authors.initials: L
authors.lastname: Xueyang
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Jing
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Wang
authors.initials: W
authors.lastname: Chenglin
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China. Electronic address: ling-ye@hotmail.com.
authors.forename: Ye
authors.initials: Y
authors.lastname: Ling
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000502:physiology*; D003782:Dental Pulp / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D055785:Gene Knockdown Techniques; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020781:Matrix Metalloproteinase 1 / Q000502:physiology; D053509:Matrix Metalloproteinase 13 / Q000502:physiology; D020778:Matrix Metalloproteinase 2 / Q000502:physiology; D020782:Matrix Metalloproteinases / Q000502:physiology*; D011671:Pulpitis / Q000378:metabolism*; D051381:Rats; D014157:Transcription Factors / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C490911:ASH1L protein, human; D011495:Histone-Lysine N-Methyltransferase; D053509:Matrix Metalloproteinase 13; D020782:Matrix Metalloproteinases; D020778:Matrix Metalloproteinase 2; D020781:Matrix Metalloproteinase 1
keywords: ASH1L; epigenetic; matrix metalloproteinase; pulpitis