Inhibition of H3K9 methyltransferase G9a ameliorates methylglyoxal-induced peritoneal fibrosis

EZH2 as a major histone methyltransferase in PDGF-BB-activated orbital fibroblast in the pathogenesis of Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an extra-thyroidal complication of Graves' disease which can lead to vision loss in severe cases. Currently, treatments of GO are not sufficiently effective, so novel therapeutic strategies are needed. As platelet-derived growth factor (PDGF)-BB induces several effector mechanisms in GO orbital fibroblasts including cytokine production and myofibroblast activation, this study aims to investigate the roles of histone lysine methyltransferases (HKMTs) in PDGF-BB-activated GO orbital fibroblasts by screening with HKMTs inhibitors library. From the total of twelve selective HKMT inhibitors in the library, EZH2, G9a and DOT1L inhibitors, DZNeP, BIX01294 and Pinometostat, respectively, prevented PDGF-BB-induced proliferation and hyaluronan production by GO orbital fibroblasts. However, only EZH2 inhibitor, DZNeP, significantly blocked pro-inflammatory cytokine production. For the HKMTs expression in GO orbital fibroblasts, PDGF-BB significantly and time-dependently induced EZH2, G9a and DOT1L mRNA expression. To confirm the role of EZH2 in PDGF-BB-induced orbital fibroblast activation, EZH2 silencing experiments revealed suppression of PDGF-BB-induced collagen type I and α-SMA expression along with decreasing histone H3 lysine 27 trimethylation (H3K27me3) level. In a more clinically relevant model than orbital fibroblast culture experiments, DZNeP treated GO orbital tissues significantly reduced pro-inflammatory cytokine production while slightly reduced ACTA2 mRNA expression. Our data is the first to demonstrate that among all HKMTs EZH2 dominantly involved in the expression of myofibroblast markers in PDGF-BB-activated orbital fibroblast from GO presumably via H3K27me3. Thus, EZH2 may represent a novel therapeutics target for GO.

BET Protein Inhibitor JQ1 Ameliorates Experimental Peritoneal Damage by Inhibition of Inflammation and Oxidative Stress

Peritoneal dialysis (PD) is a current replacement therapy for end-stage kidney diseases (ESKDs). However, long-term exposure to PD fluids may lead to damage of the peritoneal membrane (PM) through mechanisms involving the activation of the inflammatory response and mesothelial-to-mesenchymal transition (MMT), leading to filtration failure. Peritoneal damage depends on a complex interaction among external stimuli, intrinsic properties of the PM, and subsequent activities of the local innate-adaptive immune system. Epigenetic drugs targeting bromodomain and extra-terminal domain (BET) proteins have shown beneficial effects on different experimental preclinical diseases, mainly by inhibiting proliferative and inflammatory responses. However the effect of BET inhibition on peritoneal damage has not been studied. To this aim, we have evaluated the effects of treatment with the BET inhibitor JQ1 in a mouse model of peritoneal damage induced by chlorhexidine gluconate (CHX). We found that JQ1 ameliorated the CHX-induced PM thickness and inflammatory cell infiltration. Moreover, JQ1 decreased gene overexpression of proinflammatory and profibrotic markers, together with an inhibition of the nuclear factor-κB (NF-κB) pathway. Additionally, JQ1 blocked the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and restored changes in the mRNA expression levels of NADPH oxidases (NOX1 and NOX4) and NRF2/target antioxidant response genes. To corroborate the in vivo findings, we evaluated the effects of the BET inhibitor JQ1 on PD patients' effluent-derived primary mesothelial cells and on the MeT-5A cell line. JQ1 inhibited tumor necrosis factor-α (TNF-α)-induced proinflammatory gene upregulation and restored MMT phenotype changes, together with the downmodulation of oxidative stress. Taken together, these results suggest that BET inhibitors may be a potential therapeutic option to ameliorate peritoneal damage.

A review of research progress on mechanisms of peritoneal fibrosis related to peritoneal dialysis

Peritoneal dialysis (PD) is an effective alternative treatment for patients with end-stage renal disease (ESRD) and is increasingly being adopted and promoted worldwide. However, as the duration of peritoneal dialysis extends, it can expose problems with dialysis inadequacy and ultrafiltration failure. The exact mechanism and aetiology of ultrafiltration failure have been of great concern, with triggers such as biological incompatibility of peritoneal dialysis solutions, uraemia toxins, and recurrent intraperitoneal inflammation initiating multiple pathways that regulate the release of various cytokines, promote the transcription of fibrosis-related genes, and deposit extracellular matrix. As a result, peritoneal fibrosis occurs. Exploring the pathogenic factors and molecular mechanisms can help us prevent peritoneal fibrosis and prolong the duration of Peritoneal dialysis.

Novel Aspects of the Immune Response Involved in the Peritoneal Damage in Chronic Kidney Disease Patients under Dialysis

Chronic kidney disease (CKD) incidence is growing worldwide, with a significant percentage of CKD patients reaching end-stage renal disease (ESRD) and requiring kidney replacement therapies (KRT). Peritoneal dialysis (PD) is a convenient KRT presenting benefices as home therapy. In PD patients, the peritoneum is chronically exposed to PD fluids containing supraphysiologic concentrations of glucose or other osmotic agents, leading to the activation of cellular and molecular processes of damage, including inflammation and fibrosis. Importantly, peritonitis episodes enhance peritoneum inflammation status and accelerate peritoneal injury. Here, we review the role of immune cells in the damage of the peritoneal membrane (PM) by repeated exposure to PD fluids during KRT as well as by bacterial or viral infections. We also discuss the anti-inflammatory properties of current clinical treatments of CKD patients in KRT and their potential effect on preserving PM integrity. Finally, given the current importance of coronavirus disease 2019 (COVID-19) disease, we also analyze here the implications of this disease in CKD and KRT.

Natural phytochemicals that affect autophagy in the treatment of oral diseases and infections: A review

Autophagy is a critical factor in eukaryotic evolution. Cells provide nutrition and energy during autophagy by destroying non-essential components, thereby allowing intracellular material conversion and managing temporary survival stress. Autophagy is linked to a variety of oral disorders, including the type and extent of oral malignancies. Furthermore, autophagy is important in lymphocyte formation, innate immunity, and the regulation of acquired immune responses. It is also required for immunological responses in the oral cavity. Knowledge of autophagy has aided in the identification and treatment of common oral disorders, most notably cancers. The involvement of autophagy in the oral immune system may offer a new understanding of the immune mechanism and provide a novel approach to eliminating harmful bacteria in the body. This review focuses on autophagy creation, innate and acquired immunological responses to autophagy, and the status of autophagy in microbial infection research. Recent developments in the regulatory mechanisms of autophagy and therapeutic applications in oral illnesses, particularly oral cancers, are also discussed. Finally, the relationship between various natural substances that may be used as medications and autophagy is investigated.

Inhibition of histone methyltransferase G9a effectively protected the kidney against ischemia-reperfusion injury

This study examined whether BIX01294, a histone methyltransferase G9a inhibitor, effectively preserves the renal function following acute kidney ischemia-reperfusion (AKIR) injury. Adult-male-SD rats (n = 24) were equally categorized into Group 1 (sham-operated control), Group 2 (AKIR + 1.0 cc N/S I.P. injection), and Group 3 (AKIR + BIX01294/5 mg/Kg by I.P. administration at 3 h after the procedure) and the kidneys were harvested at day-3 post-IR procedure. The results showed that by day 3, the levels of creatinine and the blood urea nitrogen (BUN) were significantly higher in group 3 and more significantly higher in group 2 than in group 1 (all P < 0.0001). The protein expression of upstream (TLR-2/TLR-4/MyD88/TRAF6/p-NF-κB) and downstream (IL-1ß/IL-6/TNF-α) inflammatory signaling molecules exhibited a pattern identical to that of creatinine levels among the groups (all P < 0.0001). The protein expression of oxidative stress (NOX-1/NOX-2), MAP kinase family members (ASK1/MKK4/MKK7/JNK/p-38/p-ERK1/2), apoptosis (cleaved-caspase3/cleaved-caspase8/cleaved-PARP/mitochondrial-Bax), fibrosis (Smad3/TGF-ß), and mitochondrial-damaged markers (cyclophilin D/cytosolic-cytochrome-C) displayed a pattern identical to that of creatinine levels among the groups (all P < 0.0001). The kidney injury score, fibrosis, cellular expression of inflammation (CD68+cells), and glomerulus/renal-tubular damaged markers (Snail/KIM-1/WT-1) exhibited an identical pattern, whereas the cellular expression of podocyte component (synaptopodin) displayed an opposite pattern of creatinine levels among the groups (all P < 0.0001). Therefore, the G9a inhibitor effectively protected kidneys against IR injury.

The combination of G9a histone methyltransferase inhibitors with erythropoietin protects heart against damage from acute myocardial infarction

BACKGROUND

This study tested the hypothesis that combined histone methyltransferase G9a inhibitor (i.e., UNC0638) and erythropoietin (EPO) was superior to either one alone for protecting myocardium from acute myocardial infarction (AMI) damage.

METHODS AND RESULTS

Adult-male SD rats (n=30) were equally categorized into group 1 (sham-operated control), group 2 (AMI), group 3 (AMI-EPO/1000 IU/kg, I.M./3 h after AMI), group 4 (AMI- UNC0638/5 mg/kg I.P./3 h after AMI) and group 5 [AMI-UNC0638-EPO 3 h after AMI] treatment. Animals were euthanized at day 21 after AMI induction. By day 21, left-ventricular-ejection-fraction (LVEF) was highest in group 1, lowest in group 2, significantly higher in group 5 than in groups 3 and 4, but no difference between the latter two groups (all P<0.0001). The protein expressions of inflammatory (MMP-2/MM-9), fibrotic (fibronectin/Smad3/TGF-ß), apoptotic/DNA-damaged (caspas-3/PARP/γ-H2AX), cell-stress response (HIF-1α/p-Akt/p-mTOR) and autophagic (beclin-1/ratio of LC3B-II to LC3B-I) biomarkers exhibited an opposite pattern, whereas the protein expressions of endothelial integrity (CD31/vWF) and anti-oxidant (SIRT1/SIRT3) exhibited an identical pattern of LVEF among the five groups (all P<0.0001). The protein expressions (SDF-1α/VEGF/CXCR4) and cellular expressions (C-kit/CD31+//Sca-1/CD31+//KDR/CD34+) of angiogenesis biomarkers were significantly progressively increased from groups 1 to 5 (all P<0.0001). The infarction/fibrotic areas, myocyte size and number of G9a cells exhibited an opposite pattern, whereas the small-vessel density displayed an identical trend of LVEF among the groups (all P<0.0001). Flow cytometric analysis showed cellular levels of inflammation (Ly6G+/MPO+/CD11b/c+), oxidative-stress (DCFDA+) and apoptosis (early+/late+) exhibited an opposite pattern to LVEF among the groups (all P<0.0001).

CONCLUSION

EPO-BIX01294 effectively protected myocardium against AMI-induced damage.

Peritoneal fibrosis and epigenetic modulation

Peritoneal dialysis (PD) is an effective treatment for patients with end-stage renal disease. However, peritoneal fibrosis (PF) is a common complication that ultimately leads to ultrafiltration failure and discontinuation of PD after long-term PD therapy. There is currently no effective therapy to prevent or delay this pathologic process. Recent studies have reported epigenetic modifications involved in PF, and accumulating evidence suggests that epigenetic therapies may have the potential to prevent and treat PF clinically. The major epigenetic modifications in PF include DNA methylation, histone modification, and noncoding RNAs. The mechanisms of epigenetic regulation in PF are complex, predominantly involving modification of signaling molecules, transcriptional factors, and genes. This review will describe the mechanisms of epigenetic modulation in PF and discuss the possibility of targeting them to prevent and treat this complication.

GSK343, an inhibitor of EZH2, mitigates fibrosis and inflammation mediated by HIF-1α in human peritoneal mesothelial cells treated with high glucose

Inflammation and fibrosis in peritoneal mesothelial cells caused by long-term peritoneal dialysis (PD) are the main reasons why patients withdraw from peritoneal dialysis treatment. However, the related mechanism is still unclear. In the current study, we revealed that the expression of EZH2 was positively related to EMT and fibrosis in an in vitro model using human peritoneal mesothelial cells (HPMCs) stimulated with high glucose. Moreover, EZH2 also exhibited a positive correlation with HIF-1α expression. Using an sh-RNA lentivirus specific to EZH2, the EZH2 inhibitor GSK343 and rescue experiments of HIF-1α, we showed that EZH2 was an inducer of inflammation and fibrosis mediated by HIF-1α. Mechanistically, we revealed that on the one hand, EZH2 could increase the trimethylation of H3K4 at the HIF-1α gene promoter and directly activate HIF-1α transcription, as demonstrated by co-IP and ChIP-RT-PCR experiments. On the other hand, we verified that EZH2 could increase the trimethylation of H3K27 at the miR-142 gene promoter, which repressed the expression of miR-142. Combining bioanalysis and dual-luciferase assays, we found that miR-142 could regulate HIF-1α expression by directly binding to its mRNA 3'-UTR. Inhibition of miR-142 could rescue the protective effect of GSK343 on inflammation and fibrosis. In conclusion, our current study revealed that EZH2 plays a vital role in peritoneal fibrosis mediated by HIF-1α and related mechanisms. To our knowledge, this is the first study to demonstrate the effect of the EZH2-HIF-1α interaction and miR-142 on peritoneal fibrosis and inflammation and to suggest EZH2 and miR-142 as potential targets for the treatment of peritoneal fibrosis in patients with PD.

Histone Methyltransferases as Therapeutic Targets for Kidney Diseases

Emerging evidence has demonstrated that epigenetic regulation plays a vital role in gene expression under normal and pathological conditions. Alterations in the expression and activation of histone methyltransferases (HMTs) have been reported in preclinical models of multiple kidney diseases, including acute kidney injury, chronic kidney disease, diabetic nephropathy, polycystic kidney disease, and renal cell carcinoma. Pharmacological inhibition of these enzymes has shown promise in preclinical models of those renal diseases. In this review, we summarize recent knowledge regarding expression and activation of various HMTs and their functional roles in some kidney diseases. The preclinical activity of currently available HMT inhibitors and the mechanisms of their actions are highlighted.

Recent progress in histone methyltransferase (G9a) inhibitors as anticancer agents

Epigenetics is the study of heritable changes in gene expression without changing the DNA sequence - a change in phenotype without a change in genotype. Epigenetic abnormalities can lead to serious diseases such as cancer in organisms. Histone methylation is one of the several manifestations of epigenetics, and requires specific enzymes to catalyze, for example, G9a, which is a histone methyl transferase. G9a catalyzes the methylation of histone 3 lysine 9 (H3K9) and histone 3 lysine 27 (H3K27). In addition, G9a also plays an essential role in DNA replication, damage and repair, and gene expression by regulating DNA methylation. Moreover, G9a has been found to be overexpressed in many tumor cells and is associated with the occurrence and development of tumors. Because of its unique characteristics, G9a has become a very promising target for anti-cancer agents. Over the last decade, dozens of G9a inhibitors have been discovered as potential anticancer therapeutic agents. In this review, we summarize and classify current G9a inhibitors, the challenges and future direction are also discussed in detail.

CXCR4-Receptor-Targeted Liposomes for the Treatment of Peritoneal Fibrosis

Peritoneal fibrosis (PF) is a common complication of long-term peritoneal dialysis (PD). It is considered as the main reason for dialysis inadequacy and PD withdrawal. Transforming growth factor beta (TGF-β) regulates the expression of stromal cell-derived factor 1 (SDF-1α) and its receptor C-X-C chemokine receptor type 4 (CXCR4) on human peritoneal mesothelial cells (HPMCs), resulting in an increased migratory potential of HPMCs and extracellular matrix (ECM) deposition in the scar tissue and eventually fibrosis. Because SDF-1α/CXCR4 activation has a vital role in the pathogenesis of PF, codelivery of a CXCR4-receptor targeting agent with an antifibrotic agent in a single nanocarrier can be a promising strategy for treating PF. Here, for the first time, AMD3100 (AMD), a CXCR4-receptor antagonist, was coformulated with sulfotanshinone IIA sodium (STS IIA) into a liposome (STS-AMD-Lips) to develop a CXCR4 receptor targeting form of combination therapy for PF. CXCR4 targeting increased the ability of liposomes to target fibrotic peritoneal mesothelial cells overexpressing CXCR4 and facilitated the ability of STS IIA treatment at the fibrotic site. The liposome had an average diameter of 103 nm with encapsulated efficiencies of above 50%. The in vivo studies confirmed the reversal of PD solution-induced epithelial-to-mesenchymal transition by STS-AMD-Lips in HPMCs. The in vivo studies also revealed the precise biodistribution of the liposomes to peritoneum. Significant reduction of the morphological lesions and decreased level of ECM proteins were observed in rats treated with STS-AMD-Lips, proving that the liposomal nanocarrier has excellent ability to reverse PF. It has been concluded that the STS-AMD-Lips exhibit specific peritoneal targeting ability and could be used to improve STS-AMD combination delivery for the treatment of PF.

CBX5/G9a/H3K9me-mediated gene repression is essential to fibroblast activation during lung fibrosis

Pulmonary fibrosis is a devastating disease characterized by accumulation of activated fibroblasts and scarring in the lung. While fibroblast activation in physiological wound repair reverses spontaneously, fibroblast activation in fibrosis is aberrantly sustained. Here we identified histone 3 lysine 9 methylation (H3K9me) as a critical epigenetic modification that sustains fibroblast activation by repressing the transcription of genes essential to returning lung fibroblasts to an inactive state. We show that the histone methyltransferase G9a (EHMT2) and chromobox homolog 5 (CBX5, also known as HP1α), which deposit H3K9me marks and assemble an associated repressor complex respectively, are essential to initiation and maintenance of fibroblast activation specifically through epigenetic repression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha gene (PPARGC1A, encoding PGC1α). Both TGFβ and increased matrix stiffness potently inhibit PGC1α expression in lung fibroblasts through engagement of the CBX5/G9a pathway. Inhibition of CBX5/G9a pathway in fibroblasts elevates PGC1α, attenuates TGFβ- and matrix stiffness-promoted H3K9 methylation, and reduces collagen accumulation in the lungs following bleomycin injury. Our results demonstrate that epigenetic silencing mediated by H3K9 methylation is essential for both biochemical and biomechanical fibroblast activation, and that targeting this epigenetic pathway may provide therapeutic benefit by returning lung fibroblasts to quiescence.

The histone demethylase Kdm4 suppresses activation of hepatic stellate cell by inducing MiR-29 transcription

One of the hallmark events during liver fibrosis is the transition of quiescent hepatic stellate cells (HSC) into activated myofibroblasts, which are responsible for the production and deposition of pro-fibrogenic proteins. The epigenetic mechanism underlying HSC trans-differentiation is not fully understood. In the present study we investigated the contribution of histone H3K9 demethylase KDM4 in this process. We report that expression levels of KDM4 were down-regulated during HSC activation paralleling the up-regulation of alpha smooth muscle cell actin (Acta2), a marker of mature myofibroblast. Furthermore, HSCs isolated from mice induced to develop liver fibrosis exhibit lowered KDM4 expression compared to the control mice. In accordance, KDM4 depletion with siRNA accelerated HSC activation. Of interest, the loss of KDM4 was mirrored by the repression of miR-29, an antagonist of liver fibrosis, during HSC activation both in vitro and in vivo. KDM4 knockdown resulted in the down-regulation of miR-29 expression. Mechanistically, the sequence-specific transcription factor SREBP2 interacted with KDM4 to activate miR-29 transcription. In conclusion, our data delineate a novel epigenetic mechanism underlying HSC activation. Targeting this axis may yield potential therapeutics against liver fibrosis.

Inhibition of the H3K4 methyltransferase SET7/9 ameliorates peritoneal fibrosis

Transforming growth factor-β1 (TGF-β1) is a major mediator of peritoneal fibrosis and reportedly affects expression of the H3K4 methyltransferase, SET7/9. SET7/9-induced H3K4 mono-methylation (H3K4me1) critically activates transcription of fibrosis-related genes. In this study, we examined the effect of SET7/9 inhibition on peritoneal fibrosis in mice and in human peritoneal mesothelial cells (HPMCs). We also examined SET7/9 expression in nonadherent cells isolated from the effluent of peritoneal dialysis (PD) patients. Murine peritoneal fibrosis was induced by intraperitoneal injection of methylglyoxal (MGO) into male C57/BL6 mice over 21 days. Sinefungin, a SET7/9 inhibitor, was administered subcutaneously just before MGO injection (10 mg/kg). SET7/9 expression was elevated in both MGO-injected mice and nonadherent cells isolated from the effluent of PD patients. SET7/9 expression was positively correlated with dialysate/plasma ratio of creatinine in PD patients. Sinefungin was shown immunohistochemically to suppress expression of mesenchymal cells and collagen deposition, accompanied by decreased H3K4me1 levels. Peritoneal equilibration tests showed that sinefungin attenuated the urea nitrogen transport rate from plasma and the glucose absorption rate from the dialysate. In vitro, sinefungin suppressed TGF-β1-induced expression of fibrotic markers and inhibited H3K4me1. These findings suggest that inhibiting the H3K4 methyltransferase SET7/9 ameliorates peritoneal fibrosis.