Abstract
Purpose :
Aspirin acetylates lysine residues in cellular and extracellular proteins. Studies have shown that inhibitors of histone deacetylases suppress the epithelial-mesenchymal transition (EMT) in lens epithelial cells (LECs) by increasing acetylation of histones and α-tubulin. Thus, the aim of this study was to determine whether acetylation of proteins by aspirin negatively affects the TGFβ2-induced EMT in human LECs.
Methods :
Human LECs line (FHL124), human lens capsular bags, and lensectomized mice were used to determine the effect of aspirin on TGFβ2-induced EMT. FHL124 cells were treated with 2 mM aspirin for 24 h followed by 10 ng/ml TGFβ2 treatment for another Indicated time. Western blotting and qPCR methods measured specific protein and mRNA levels. The capsular bags were maintained for 19 days, capsular wrinkling was assessed by microscopy the expression of α-SMA and F-actin was evaluated by immunohistochemistry. Mice were orally administered 1 mg/ml aspirin in 25 mM sodium phosphate buffered drinking water for 5 days prior to the lensectomy and after 5 days fresh daily. Eyes were fixed, paraffin embedded, sectioned and subjected to immunofluorescence detection of α-SMA and collagen type IV. LC-MS/MS carried out to verify the specific lysine residues acetylated in histone H3.
Results :
Aspirin (2 mM) inhibited the expression of EMT markers, α-SMA, αB-crystallin and fibronectin in TGFβ2 treated FHL124 cells. Aspirin also halted the EMT response of TGFβ2 when introduced after EMT initiation. In human capsule bags, treatment with 2 mM aspirin completely suppressed posterior capsule wrinkling, and α-SMA and F-actin in capsule adherent LECs. After lensectomy in mice, we observed an increase in proliferation and α-SMA expression in the capsule adherent LECs, which were ameliorated by 1 mg/ml aspirin administration in drinking water. Using LC-MS/MS, we found that the aspirin selectively acetylates K56, K115, and K122 in histone H3 in LECs. These acetylated residues are on the lateral surface of globular domain in histone H3 and directly affect DNA binding affinity.
Conclusions :
The results show that aspirin inhibits TGFβ2-mediated EMT of LECs, and that the inhibition occurs possibly due to epigenetic downregulation of the EMT-related genes via hyperacetylation of histone H3.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.