Abstract
Activity of H3K9 histone methyltransferase G9a is reportedly induced by transforming growth factor-β1 (TGF-β1) and plays an important role in the progression of cancer and fibrosis. In this study, we investigated whether inhibition of G9a-mediated H3K9 methylation attenuates peritoneal fibrosis in mice and human peritoneal mesothelial cells (HPMCs). Nonadherent cells of peritoneal dialysis (PD) patients were isolated from PD effluent to examine expression of G9a. Peritoneal fibrosis was induced by peritoneal injection of methylglyoxal (MGO) in male C57/B6 mice for 3 weeks. BIX01294, a G9a inhibitor, was administered by subcutaneous injection. Effects of BIX01294 on MGO-induced pathological and functional changes in mice were evaluated by immunohistochemistry and a peritoneal equilibration test. HPMCs were isolated from human omentum, and the inhibitory effect of BIX01294 on TGF-β1-induced fibrotic changes was investigated in the HPMCs by western blotting. G9a was upregulated in nonadherent cells of human PD effluent, the peritoneum of MGO-injected mice, and TGF-β1-stimulated HPMCs. BIX01294 significantly reduced the submesothelial zone thickness and cell density in MGO-injected mice. Immunohistochemical staining revealed that BIX01294 treatment decreased not only mono-methylation of H3K9 (H3K9me1), but also the number of mesenchymal cells, accumulation of collagen, and infiltration of monocytes. In addition to the pathological changes, BIX01294 reduced the level of TGF-β1 in peritoneal fluid and improved peritoneal functions. Furthermore, BIX01294 inhibited TGF-β1-induced fibrotic changes along with suppression of H3K9me1 in HPMCs. Therefore, inhibition of H3K9 methyltransferase G9a suppresses peritoneal fibrosis through a reduction of H3K9me1.
Highlights
Peritoneal dialysis (PD) is an effective replacement therapy for end-stage kidney disease, and many patients benefit from PD treatment
In nonadherent cells of human PD effluents, we found elevation of G9a expression levels in PD patients compared with human peritoneal mesothelial cells (HPMCs) derived from non-PD patients (Fig 1C)
We found increased expression of G9a in a mouse model of MGOinduced peritoneal fibrosis, and nonadherent cells isolated from PD effluent of patients
Summary
Peritoneal dialysis (PD) is an effective replacement therapy for end-stage kidney disease, and many patients benefit from PD treatment. Long-term exposure to PD fluid eventually leads to peritoneal fibrosis that is clinically observed as a decrease in water removal [1, 2]. G9a-induced H3K9me in peritoneal fibrosis study design, data collection and analysis, decision to publish, or preparation of the manuscript
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