HDAC Inhibitors: Therapeutic Potential in Fibrosis-Associated Human Diseases

HDAC Inhibitor Abrogates LTA-Induced PAI-1 Expression in Pleural Mesothelial Cells and Attenuates Experimental Pleural Fibrosis

Lipoteichoic acid (LTA) stimulates pleural mesothelial cell (PMC) to overproduce plasminogen activator inhibitor-1 (PAI-1), and thus may promote pleural fibrosis in Gram-positive bacteria (GPB) parapneumonic effusion (PPE). Histone deacetylase inhibitor (HDACi) was found to possess anti-fibrotic properties. However, the effects of HDACi on pleural fibrosis remain unclear. The effusion PAI-1 was measured among 64 patients with GPB PPE. Pleural fibrosis was measured as radiographical residual pleural thickening (RPT) and opacity at a 12-month follow-up. The LTA-stimulated human PMCs and intrapleural doxycycline-injected rats were pretreated with or without the pan-HDACi, m-carboxycinnamic acid bis-hydroxamide (CBHA), then PAI-1 and collagen expression and activated signalings in PMCs, and morphologic pleural changes in rats were measured. Effusion PAI-1 levels were significantly higher in GPB PPE patients with RPT > 10 mm (n = 26) than those without (n = 38), and had positive correlation with pleural fibrosis shadowing. CBHA significantly reduced LTA-induced PAI-1 and collagen expression via inhibition of JNK, and decreased PAI-1 promoter activity and mRNA levels in PMCs. Furthermore, in doxycycline-treated rats, CBHA substantially repressed PAI-1 and collagen synthesis in pleural mesothelium and minimized pleural fibrosis. Conclusively, CBHA abrogates LTA-induced PAI-1 and collagen expression in PMCs and attenuates experimental pleural fibrosis. PAI-1 inhibition by HDACi may confer potential therapy for pleural fibrosis.

Butyrate administration strengthens the intestinal epithelium and improves intestinal dysbiosis in a cholestasis fibrosis model

AIM

Intestinal dysfunction in cirrhosis patients is linked to death by bacterial infections. Currently, there is no effective therapy for this complication. This study aims to evaluate butyrate, a novel postbiotic, on the intestinal inflammatory response, tight junction proteins and the microbiota in the cholestasis model.

METHODS AND RESULTS

Wistar rats underwent 15 days of bile duct ligation (BDL). We administered butyrate at a concentration of 1%. The BDL group did not receive treatment. The results showed that butyrate could significantly reduce pro-inflammatory cytokines (IL-17A, IFN-γ, TNF-α) in the ileum and colon while promoting IL-10 expression in the colon. Moreover, it significantly promotes tight junction protein (cld-1, occludin and ZO-1) expression in the ileum. A similar effect was observed in the colon except for ZO-1. Additionally, butyrate limited taxa diversity loss and promoted probiotic genera expansion such as Lachnospira, Prevotella and Lactobacillus. The increase in Turicibacter and Clostridiaceae distinguished the BDL group.

CONCLUSIONS

Butyrate is effective in regulating the inflammatory response, tight junction proteins and limits bacterial diversity loss.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research reveals that butyrate could represent an interesting postbiotic metabolomic intervention for intestinal epithelium dysfunction in liver disease.

Selective HDAC8 Inhibition Attenuates Isoproterenol-Induced Cardiac Hypertrophy and Fibrosis via p38 MAPK Pathway

Histone deacetylase (HDAC) expression and enzymatic activity are dysregulated in cardiovascular diseases. Among Class I HDACs, HDAC2 has been reported to play a key role in cardiac hypertrophy; however, the exact function of HDAC8 remains unknown. Here we investigated the role of HDAC8 in cardiac hypertrophy and fibrosis using the isoproterenol-induced cardiac hypertrophy model system.Isoproterenol-infused mice were injected with the HDAC8 selective inhibitor PCI34051 (30 mg kg⁻¹ body weight). Enlarged hearts were assessed by HW/BW ratio, cross-sectional area, and echocardiography. RT-PCR, western blotting, histological analysis, and cell size measurements were performed. To elucidate the role of HDAC8 in cardiac hypertrophy, HDAC8 knockdown and HDAC8 overexpression were also used. Isoproterenol induced HDAC8 mRNA and protein expression in mice and H9c2 cells, while PCI34051 treatment decreased cardiac hypertrophy in isoproterenol-treated mice and H9c2 cells. PCI34051 treatment also reduced the expression of cardiac hypertrophic markers (Nppa, Nppb, and Myh7), transcription factors (Sp1, Gata4, and Gata6), and fibrosis markers (collagen type I, fibronectin, and Ctgf) in isoproterenol-treated mice. HDAC8 overexpression stimulated cardiac hypertrophy in cells, whereas HDAC8 knockdown reversed those effects. HDAC8 selective inhibitor and HDAC8 knockdown reduced the isoproterenol-induced activation of p38 MAPK, whereas HDAC8 overexpression promoted p38 MAPK phosphorylation. Furthermore, p38 MAPK inhibitor SB203580 significantly decreased the levels of p38 MAPK phosphorylation, as well as ANP and BNP protein expression, induced by HDAC8 overexpression.Here we show that inhibition of HDAC8 activity or expression suppresses cardiac hypertrophy and fibrosis. These findings suggest that HDAC8 could be a promising target to treat cardiac hypertrophy and fibrosis by regulating p38 MAPK.

Regulation of Monocyte Adhesion and Type I Interferon Signaling by CD52 in Patients With Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is characterized by dysregulation of type I interferon (IFN) signaling. CD52 is known for its immunosuppressive functions in T cells. This study was undertaken to investigate the role of CD52 in monocyte adhesion and type I IFN signaling in patients with SSc.

METHODS

Transcriptome profiles of circulating CD14+ monocytes from patients with limited cutaneous SSc (lcSSc), patients with diffuse cutaneous SSc (dcSSs), and healthy controls were analyzed by RNA sequencing. Levels of CD52, CD11b/integrin αΜ, and CD18/integrin β2 in whole blood were assessed by flow cytometry. CD52 expression was analyzed in relation to disease phenotype (early, lcSSc, dcSSc) and autoantibody profiles. The impact of overexpression, knockdown, and antibody blocking of CD52 was analyzed by gene and protein expression assays and functional assays.

RESULTS

Pathway enrichment analysis indicated an increase in adhesion- and type I IFN-related genes in monocytes from SSc patients. These cells displayed up-regulated expression of CD11b/CD18, reduced expression of CD52, and enhanced adhesion to intercellular adhesion molecule 1 and endothelial cells. Changes in CD52 expression were consistent with the SSc subtypes, as well as with immunosuppressive treatments, autoantibody profiles, and monocyte adhesion properties in patients with SSc. Overexpression of CD52 led to decreased levels of CD18 and monocyte adhesion, while knockdown of CD52 increased monocyte adhesion. Experiments with the humanized anti-CD52 monoclonal antibody alemtuzumab in blood samples from healthy controls increased monocyte adhesion and CD11b/CD18 expression, and enhanced type I IFN responses. Monocytic CD52 expression was up-regulated by interleukin-4 (IL-4)/IL-13 via the STAT6 pathway, and was down-regulated by lipopolysaccharide and IFNs α, β, and γ in a JAK1 and histone deacetylase IIa (HDAC IIa)-dependent manner.

CONCLUSION

Down-regulation of the antiadhesion CD52 antigen in CD14+ monocytes represents a novel mechanism in the pathogenesis of SSc. Targeting of the IFN-HDAC-CD52 axis in monocytes might represent a new therapeutic option for patients with early SSc.

Epigenomic Evaluation of Cholangiocyte Transforming Growth Factor-β Signaling Identifies a Selective Role for Histone 3 Lysine 9 Acetylation in Biliary Fibrosis

BACKGROUND & AIMS

Transforming growth factor β (TGFβ) upregulates cholangiocyte-derived signals that activate myofibroblasts and promote fibrosis. Using epigenomic and transcriptomic approaches, we sought to distinguish the epigenetic activation mechanisms downstream of TGFβ that mediate transcription of fibrogenic signals.

METHODS

Chromatin immunoprecipitation (ChIP)-seq and RNA-seq were performed to assess histone modifications and transcriptional changes following TGFβ stimulation. Histone modifications and acetyltransferase occupancy were confirmed using ChIP assays. Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) was used to investigate changes in chromatin accessibility. Cholangiocyte cell lines and primary cholangiocytes were used for in vitro studies. Mdr2-/- and 3,5-diethoxycarboncyl-1,4-dihydrocollidine (DDC)-fed mice were used as animal models.

RESULTS

TGFβ stimulation caused widespread changes in histone 3 lysine 27 acetylation (H3K27ac), and was associated with global TGFβ-mediated transcription. In contrast, H3K9ac was gained in a smaller group of chromatin sites and was associated with fibrosis pathways. These pathways included overexpression of hepatic stellate cell (HSC) activators such as fibronectin 1 (FN1) and SERPINE1. The promoters of these genes showed H3K9ac enrichment following TGFβ. Of the acetyltransferases responsible for H3K9ac, cholangiocytes predominantly express Lysine Acetyltransferases 2A (KAT2A). Small interfering RNA knockdown of KAT2A or H3K9ac inhibition prevented the TGFβ-mediated increase in FN1 and SERPINE1. SMAD3 ChIP-seq and ATAC-seq suggested that TGFβ-mediated H3K9ac occurs through SMAD signaling, which was confirmed using colocalization and genetic knockdown studies. Pharmacologic inhibition or cholangiocyte-selective deletion of Kat2a was protective in mouse models of biliary fibrosis.

CONCLUSIONS

Cholangiocyte expression of HSC-activating signals occurs through SMAD-dependent, KAT2A-mediated, H3K9ac, and can be targeted to prevent biliary fibrosis.

Repurposing of histone deacetylase inhibitors: A promising strategy to combat pulmonary fibrosis promoted by TGF-β signalling in COVID-19 survivors

Coronavirus disease 2019 (COVID-19) has rapidly spread around the world causing global public health emergency. In the last twenty years, we have witnessed several viral epidemics such as severe acute respiratory syndrome coronavirus (SARS-CoV), Influenza A virus subtype H1N1 and most recently Middle East respiratory syndrome coronavirus (MERS-CoV). There were tremendous efforts endeavoured globally by scientists to combat these viral diseases and now for SARS-CoV-2. Several drugs such as chloroquine, arbidol, remdesivir, favipiravir and dexamethasone are adopted for use against COVID-19 and currently clinical studies are underway to test their safety and efficacy for treating COVID-19 patients. As per World Health Organization reports, so far more than 16 million people are affected by COVID-19 with a recovery of close to 10 million and deaths at 600,000 globally. SARS-CoV-2 infection is reported to cause extensive pulmonary damages in affected people. Given the large number of recoveries, it is important to follow-up the recovered patients for apparent lung function abnormalities. In this review, we discuss our understanding about the development of long-term pulmonary abnormalities such as lung fibrosis observed in patients recovered from coronavirus infections (SARS-CoV and MERS-CoV) and probable epigenetic therapeutic strategy to prevent the development of similar pulmonary abnormalities in SARS-CoV-2 recovered patients. In this regard, we address the use of U.S. Food and Drug Administration (FDA) approved histone deacetylase (HDAC) inhibitors therapy to manage pulmonary fibrosis and their underlying molecular mechanisms in managing the pathologic processes in COVID-19 recovered patients.

Epigenetic regulation of the epithelial mesenchymal transition induced by synergistic action of TNF-α and TGF-β in retinal pigment epithelial cells

To clarify the influence of tumor necrosis factor (TNF)-α on fibrotic phenotypes induced by transforming growth factor (TGF)-β in retinal pigment epithelial cells (RPECs) by epigenetic regulation. Human primary retinal pigment epithelial cells (RPECs including ARPE19) were used in cultures in the presence or absence of TNF-α and/or TGF-β2. RT2 Profiler™ (Qiagen) was used for PCR Array for fibrosis and epithelial mesenchymal transition (EMT). Microarray analysis by 3D gene DNA chip was outsourced to Toray Industries Inc. Quantification of histone acetyl transferase (HAT)-related and histone deacetylase (HDAC) related gene expression were also analyzed. HDAC and HAT activity was measured using an EpiQuik HDAC and HAT Activity/Inhibition Assay Kit (Epigentek). CD44, MMP-9, HAT, and HDAC in RPECs were analyzed by western blotting. Analysis of expression of the EMT/fibrosis related CD44 and MMP-9 phenotypes induced by TNF-α+TGF-β2 revealed four alterations in RPECs: 1) abolition of TGF-β2-induced α-SMA by TNF-α; 2) synergy between TNF-α+TGF-β2 for induction of CD44 and MMP-9 phenotypes 3) no inhibition of HDAC activity by either TNF-α or TGF-β2; and 4) significant inhibition of HAT activity by either TNF-α or TGF-β2, but no synergy. The HDAC activation through HAT inhibition by TNF-α+TGF-β was counteracted by HDAC inhibitors, leading to the inhibition of EMT/fibrosis. EMT/fibrotic CD44 and MMP-9 phenotypes were epigenetically upregulated by concerted action of TNF-α and TGF-β in RPECs. The intervention in epigenetic regulation may hold potential in preventing intraocular proliferative diseases.

Ski promotes proliferation and inhibits apoptosis in fibroblasts under high-glucose conditions via the FoxO1 pathway

OBJECTIVES

The present study clarified the role and signalling pathway of Ski in regulating proliferation and apoptosis in fibroblasts under high-glucose (HG) conditions.

MATERIALS AND METHODS

The proliferation and apoptosis of rat primary fibroblasts were assessed using EdU incorporation and TUNEL assays. The protein and phosphorylation levels of the corresponding factors were measured using immunofluorescence staining and Western blotting. Immunoprecipitation was used to determine the interactions between Ski and FoxO1 or Ski and HDAC1. The Ski protein was overexpressed via recombinant adenovirus transfection, and FoxO1 and HDAC1 were knocked down using targeted small-interfering RNA.

RESULTS

The present study found that HG inhibited fibroblast proliferation, increased apoptosis and reduced Ski levels in rat primary fibroblasts. Conversely, increasing Ski protein levels alleviated HG-induced proliferation inhibition and apoptosis promotion. Increasing Ski protein levels also increased Ski binding to FoxO1 to decrease FoxO1 acetylation, and interfering with FoxO1 caused loss of the regulatory effect of Ski in fibroblasts under HG. Increasing Ski protein levels decreased FoxO1 acetylation via HDAC1-mediated deacetylation.

CONCLUSIONS

Therefore, these findings confirmed for the first time that Ski regulated fibroblast proliferation and apoptosis under HG conditions via the FoxO1 pathway.

Dual Pharmacological Targeting of HDACs and PDE5 Inhibits Liver Disease Progression in a Mouse Model of Biliary Inflammation and Fibrosis

Liver fibrosis, a common hallmark of chronic liver disease (CLD), is characterized by the accumulation of extracellular matrix secreted by activated hepatic fibroblasts and stellate cells (HSC). Fibrogenesis involves multiple cellular and molecular processes and is intimately linked to chronic hepatic inflammation. Importantly, it has been shown to promote the loss of liver function and liver carcinogenesis. No effective therapies for liver fibrosis are currently available. We examined the anti-fibrogenic potential of a new drug (CM414) that simultaneously inhibits histone deacetylases (HDACs), more precisely HDAC1, 2, and 3 (Class I) and HDAC6 (Class II) and stimulates the cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway activity through phosphodiesterase 5 (PDE5) inhibition, two mechanisms independently involved in liver fibrosis. To this end, we treated Mdr2-KO mice, a clinically relevant model of liver inflammation and fibrosis, with our dual HDAC/PDE5 inhibitor CM414. We observed a decrease in the expression of fibrogenic markers and collagen deposition, together with a marked reduction in inflammation. No signs of hepatic or systemic toxicity were recorded. Mechanistic studies in cultured human HSC and cholangiocytes (LX2 and H69 cell lines, respectively) demonstrated that CM414 inhibited pro-fibrogenic and inflammatory responses, including those triggered by transforming growth factor β (TGFβ). Our study supports the notion that simultaneous targeting of pro-inflammatory and fibrogenic mechanisms controlled by HDACs and PDE5 with a single molecule, such as CM414, can be a new disease-modifying strategy.

Nanoapproaches to Modifying Epigenetics of Epithelial Mesenchymal Transition for Treatment of Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronically progressive interstitial lung that affects over 3 M people worldwide and rising in incidence. With a median survival of 2-3 years, IPF is consequently associated with high morbidity, mortality, and healthcare burden. Although two antifibrotic therapies, pirfenidone and nintedanib, are approved for human use, these agents reduce the rate of decline of pulmonary function but are not curative and do not reverse established fibrosis. In this review, we discuss the prevailing epithelial injury hypothesis, wherein pathogenic airway epithelial cell-state changes known as Epithelial Mesenchymal Transition (EMT) promotes the expansion of myofibroblast populations. Myofibroblasts are principal components of extracellular matrix production that result in airspace loss and mortality. We review the epigenetic transition driving EMT, a process produced by changes in histone acetylation regulating mesenchymal gene expression programs. This mechanistic work has focused on the central role of bromodomain-containing protein 4 in mediating EMT and myofibroblast transition and initial preclinical work has provided evidence of efficacy. As nanomedicine presents a promising approach to enhancing the efficacy of such anti-IPF agents, we then focus on the state of nanomedicine formulations for inhalable delivery in the treatment of pulmonary diseases, including liposomes, polymeric nanoparticles (NPs), inorganic NPs, and exosomes. These nanoscale agents potentially provide unique properties to existing pulmonary therapeutics, including controlled release, reduced systemic toxicity, and combination delivery. NP-based approaches for pulmonary delivery thus offer substantial promise to modify epigenetic regulators of EMT and advance treatments for IPF.

Molecular Docking Simulations on Histone Deacetylases (HDAC)-1 and -2 to Investigate the Flavone Binding

Histone modifications through acetylation are fundamental for remodelling chromatin and consequently activating gene expression. The imbalance between acetylation and deacetylation activity causes transcriptional dysregulation associated with several disorders. Flavones, small molecules of plant origin, are known to interfere with class I histone deacetylase (HDAC) enzymes and to enhance acetylation, restoring cell homeostasis. To investigate the possible physical interactions of flavones on human HDAC1 and 2, we carried out in silico molecular docking simulations. Our data have revealed how flavone, and other two flavones previously investigated, i.e., apigenin and luteolin, can interact as ligands with HDAC1 and 2 at the active site binding pocket. Regulation of HDAC activity by dietary flavones could have important implications in developing epigenetic therapy to regulate the cell gene expression.

Epigenetic modification mechanisms involved in keloid: current status and prospect

Keloid, a common dermal fibroproliferative disorder, is benign skin tumors characterized by the aggressive fibroblasts proliferation and excessive accumulation of extracellular matrix. However, common therapeutic approaches of keloid have limited effectiveness, emphasizing the momentousness of developing innovative mechanisms and therapeutic strategies. Epigenetics, representing the potential link of complex interactions between genetics and external risk factors, is currently under intense scrutiny. Accumulating evidence has demonstrated that multiple diverse and reversible epigenetic modifications, represented by DNA methylation, histone modification, and non-coding RNAs (ncRNAs), play a critical role in gene regulation and downstream fibroblastic function in keloid. Importantly, abnormal epigenetic modification manipulates multiple behaviors of keloid-derived fibroblasts, which served as the main cellular components in keloid skin tissue, including proliferation, migration, apoptosis, and differentiation. Here, we have reviewed and summarized the present available clinical and experimental studies to deeply investigate the expression profiles and clarify the mechanisms of epigenetic modification in the progression of keloid, mainly including DNA methylation, histone modification, and ncRNAs (miRNA, lncRNA, and circRNA). Besides, we also provide the challenges and future perspectives associated with epigenetics modification in keloid. Deciphering the complicated epigenetic modification in keloid is hopeful to bring novel insights into the pathogenesis etiology and diagnostic/therapeutic targets in keloid, laying a foundation for optimal keloid ending.

Rectification of cavernosal fibrosis and veno-occlusive dysfunction by administration of suberoylanilide hydroxamic acid in a rat model of cavernosal nerve injury: Comparison with a PDE5 inhibitor

BACKGROUND

Cavernosal fibrosis, which is induced by cavernosal nerve (CN) injury and progresses with time, is the main cause of cavernosal veno-occlusive dysfunction (CVOD) after radical prostatectomy.

OBJECTIVES

To determine whether daily oral administration of suberoylanilide hydroxamic acid (SAHA; vorinostat) for 5-weeks from the immediate post-injury period after CN injury would rectify CVOD by suppressing cavernosal fibrosis and normalizing HDAC pathway in a rat model of CN crush injury (CNCI) and to compare the results with those obtained using chronic administration of PDE5-inhibitors (a positive control).

METHODS

Fifty-six 12-week-old rats were randomized into the four groups: sham surgery (S), CNCI (I), and CNCI treated with daily administration of 25.0 mg/kg SAHA (V) or 20.0 mg/kg udenafil (P). Group-V and Group-P received the respective treatment for 5-weeks from the following day after CNCI. At 5 weeks after surgery, dynamic infusion cavernosometry (DIC), histological staining, and Western blot analysis were performed.

RESULTS

Group-I had a significantly decreased papaverine response, higher maintenance rate or drop rate, lower smooth muscle (SM)/collagen ratio, decreased SM content, and increased protein expression of HDAC2, HDAC3, TGF-β1, and collagen-1, compared with Group-S. The three DIC parameters in Group-V and Group-P significantly improved compared to those in Group-I. Except for the maintenance rate, the improvement in papaverine response and drop rate in Group-V was not significantly different from that in Group-P. Group-V and Group-P showed the rectification of SM/collagen ratio and protein expression of TGF-β1 or collagen-1. SM content was improved in Group-P, but not in Group-V. Group-V showed the normalization of protein expression of both HDAC2 and HDAC3, whereas protein expression of only HDAC2 was partially restored in Group-P.

DISCUSSION

Treatment strategies targeting the HDAC pathway might be helpful to alleviate CVOD induced by CN injury.

CONCLUSIONS

According to our data, chronic administration of SAHA improves post-injury CVOD by suppressing cavernosal fibrosis via rectifying the HDAC/TGF-β1 pathway in nerve-injured rats, comparable to that with PDE5 inhibitors.

Histone deacetylase 8 inhibition alleviates cholestatic liver injury and fibrosis

Cholestasis is a pathological condition involving blockage of bile flow that results in hepatotoxicity, inflammation, and fibrosis. Although recent studies have shown that histone deacetylases (HDACs) are involved in the progression of fibrosis in various organs, the role of HDAC8 on liver fibrosis has until now remained unexplored. This study presents a newly-synthesized, selective HDAC8 inhibitor SPA3014 composed of a vinyl disulfide-sulfoxide core, and evaluates its therapeutic efficacy against cholestatic liver injury and fibrosis in bile duct-ligated (BDL) mice. We first observed the increase in HDAC8 protein levels in mice with BDL and patients with cholestatic liver disease. Mice with BDL that were pretreated with SPA3014 had lower liver damage and fibrosis, based on gross examination, histopathologic findings, and biochemical analyses, than did vehicle-treated mice. Studies with LX-2 human hepatic stellate cells showed that SPA3014 exerted protective effects by inhibiting TGF-β-mediated activation of MAPK-Smad2/3 and JAK2-STAT3 pathways and by upregulating PPARγ expression. Overall, these results strongly suggest that HDAC8 inhibition constitutes a new therapeutic strategy for treatment of cholestatic liver injury.

Phlorotannins ameliorate extracellular matrix production in human vocal fold fibroblasts and prevent vocal fold fibrosis via aerosol inhalation in a laser-induced fibrosis model

Vocal fold fibrosis is an abnormal condition characterized by unfavorable changes in the organization of the extracellular matrix in vocal fold lamina propria. To prevent and treat vocal fold fibrosis, a number of synthetic drugs, such as mitomycin C and the glucocorticoid family, are used after surgery, but these are known to have some side effects. Therefore, using both in vitro and in vivo studies, this study investigated whether phlorotannins extracted from Ecklonia cava have the potential to prevent vocal fold fibrosis with minimal side effects. The results show that phlorotannins suppressed both the expression of the fibrotic phenotypic marker and cell migration by inhibiting the activation of the mitogen-activated protein kinase (MAPK) and Smad2/3 signaling pathways in human vocal fold fibroblasts stimulated by transforming growth factor-β. Additionally, phlorotannins exhibited antifibrotic efficacy without an excessive inflammatory response in a laser-induced fibrosis rabbit model when delivered as an aerosol via inhalation. Based on these results, phlorotannins should be considered a promising candidate for use in the prevention of vocal fold fibrosis.

Protein acetylation and deacetylation: An important regulatory modification in gene transcription (Review)

Cells primarily rely on proteins to perform the majority of their physiological functions, and the function of proteins is regulated by post-translational modifications (PTMs). The acetylation of proteins is a dynamic and highly specific PTM, which has an important influence on the functions of proteins, such as gene transcription and signal transduction. The acetylation of proteins is primarily dependent on lysine acetyltransferases and lysine deacetylases. In recent years, due to the widespread use of mass spectrometry and the emergence of new technologies, such as protein chips, studies on protein acetylation have been further developed. Compared with histone acetylation, acetylation of non-histone proteins has gradually become the focus of research due to its important regulatory mechanisms and wide range of applications. The discovery of specific protein acetylation sites using bioinformatic tools can greatly aid the understanding of the underlying mechanisms of protein acetylation involved in related physiological and pathological processes.

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.

CMH-Small Molecule Docks into SIRT1, Elicits Human IPF-Lung Fibroblast Cell Death, Inhibits Ku70-deacetylation, FLIP and Experimental Pulmonary Fibrosis

Regenerative capacity in vital organs is limited by fibrosis propensity. Idiopathic pulmonary fibrosis (IPF), a progressive lung disease linked with aging, is a classic example. In this study, we show that in flow cytometry, immunoblots (IB) and in lung sections, FLIP levels can be regulated, in vivo and in vitro, through SIRT1 activity inhibition by CMH (4-(4-Chloro-2-methylphenoxy)-N-hydroxybutanamide), a small molecule that, as we determined here by structural biology calculations, docked into its nonhistone substrate Ku70-binding site. Ku70 immunoprecipitations and immunoblots confirmed our theory that Ku70-deacetylation, Ku70/FLIP complex, myofibroblast resistance to apoptosis, cell survival, and lung fibrosis in bleomycin-treated mice, are reduced and regulated by CMH. Thus, small molecules associated with SIRT1-mediated regulation of Ku70 deacetylation, affecting FLIP stabilization in fibrotic-lung myofibroblasts, may be a useful strategy, enabling tissue regeneration.

HDAC inhibitors promote pancreatic stellate cell apoptosis and relieve pancreatic fibrosis by upregulating miR-15/16 in chronic pancreatitis

In chronic pancreatitis, PSCs are activated by proinflammatory cytokines to induce pancreatic fibrogenesis. HDAC inhibition protected against the pancreatic fibrosis and the apoptosis of PSCs through induced apoptosis and depressed inflammation. In our study, we found that miR-15 and miR-16 decreased significantly in chronic pancreatitis and HDAC inhibition could recover the levels of these two miRNAs. HDAC regulated the transcription of miR-15 and miR-16, which then modulate the apoptosis and fibrosis of PSCs. And we proved that Bcl-2 and Smad5 were the target genes of miR-15 and miR-16, which illustrated how HDAC inhibition alleviated the apoptosis and fibrogenesis of PSCs in chronic pancreatitis. These results suggested that HDAC inhibition protects against CP by promoting apoptosis and TGF-β/Smads signaling pathways, and indicated that HDAC inhibition is a potential therapy to alleviate CP patients in clinic, and these need to be explored further.

CG200745, a Novel HDAC Inhibitor, Attenuates Kidney Fibrosis in a Murine Model of Alport Syndrome

Histone deacetylases have been a target of therapy for organ fibrosis. Here, we report the protective effect of CG200745 (CG), a novel histone deacetylase inhibitor, on tubulointerstitial fibrosis in Col4a3^-/- mice, a murine model of Alport syndrome. Morphological analyses revealed CG treatment markedly alleviated kidney fibrosis in Col4a3^-/- mice at the age of 7 weeks. CG prevented the activation of transforming growth factor β (TGFβ) and its downstream SMAD signaling in the kidney of Col4a3^-/- mice. As critical upstream regulators of TGFβ signaling, immunoblotting of whole kidney lysate of Col4a3^-/- mice reveled that intra-renal renin-angiotensin system (RAS) was activated with concurrent upregulation of inflammation and apoptosis, which were effectively suppressed by CG treatment. CG suppressed both activation of RAS and up-regulation of TGFβ signals in angiotensin II-stimulated HK-2 cells, a human kidney proximal tubular epithelial cell line. CG inhibited activation of TGFβ-driven signals and fibrosis in NRK-49F cells, a rat kidney fibroblast cell line, under angiotensin II-rich conditions. Collectively, CG was found to be effective both in proximal tubular epithelial cells by inhibiting local RAS and TGFβ signaling activation, as well as in fibroblasts by blocking their transition to myofibroblasts, attenuating renal fibrosis in a murine model of Alport syndrome.

Liver-Specific Knockdown of Class IIa HDACs Has Limited Efficacy on Glucose Metabolism but Entails Severe Organ Side Effects in Mice

Histone deacetylases (HDACs) are important regulators of epigenetic gene modification that are involved in the transcriptional control of metabolism. In particular class IIa HDACs have been shown to affect hepatic gluconeogenesis and previous approaches revealed that their inhibition reduces blood glucose in type 2 diabetic mice. In the present study, we aimed to evaluate the potential of class IIa HDAC inhibition as a therapeutic opportunity for the treatment +of metabolic diseases. For that, siRNAs selectively targeting HDAC4, 5 and 7 were selected and used to achieve a combinatorial knockdown of these three class IIa HDAC isoforms. Subsequently, the hepatocellular effects as well as the impact on glucose and lipid metabolism were analyzed in vitro and in vivo. The triple knockdown resulted in a statistically significant decrease of gluconeogenic gene expression in murine and human hepatocyte cell models. A similar HDAC-induced downregulation of hepatic gluconeogenesis genes could be achieved in mice using a liver-specific lipid nanoparticle siRNA formulation. However, the efficacy on whole body glucose metabolism assessed by pyruvate-tolerance tests were only limited and did not outweigh the safety findings observed by histopathological analysis in spleen and kidney. Mechanistically, Affymetrix gene expression studies provide evidence that class IIa HDACs directly target other key factors beyond the described forkhead box (FOXP) transcription regulators, such as hepatocyte nuclear factor 4 alpha (HNF4a). Downstream of these factors several additional pathways were regulated not merely including glucose and lipid metabolism and transport. In conclusion, the liver-directed combinatorial knockdown of HDAC4, 5 and 7 by therapeutic siRNAs affected multiple pathways in vitro, leading in vivo to the downregulation of genes involved in gluconeogenesis. However, the effects on gene expression level were not paralleled by a significant reduction of gluconeogenesis in mice. Combined knockdown of HDAC isoforms was associated with severe adverse effects in vivo, challenging this approach as a treatment option for chronic metabolic disorders like type 2 diabetes.

Platelet-Rich Plasma and Bone Marrow-Derived Mesenchymal Stromal Cells Prevent TGF-β1-Induced Myofibroblast Generation but Are Not Synergistic when Combined: Morphological in vitro Analysis

The persistence of activated myofibroblasts is a hallmark of fibrosis of many organs. Thus, the modulation of the generation/functionality of these cells may represent a strategical anti-fibrotic therapeutic option. Bone marrow-derived mesenchymal stromal cell (MSC)-based therapy has shown promising clues, but some criticisms still limit the clinical use of these cells, including the need to avoid xenogeneic compound contamination for ex vivo cell amplification and the identification of appropriate growth factors acting as a pre-conditioning agent and/or cell delivery vehicle during transplantation, thus enabling the improvement of cell survival in the host tissue microenvironment. Many studies have demonstrated the ability of platelet-rich plasma (PRP), a source of many biologically active molecules, to positively influence MSC proliferation, survival, and functionality, as well as its anti-fibrotic potential. Here we investigated the effects of PRP, murine and human bone marrow-derived MSCs, and of the combined treatment PRP/MSCs on in vitro differentiation of murine NIH/3T3 and human HDFα fibroblasts to myofibroblasts induced by transforming growth factor (TGF)-β1, a well-known pro-fibrotic agent. The myofibroblastic phenotype was evaluated morphologically (cell shape and actin cytoskeleton assembly) and immunocytochemically (vinculin-rich focal adhesion clustering, α-smooth muscle actin and type-1 collagen expression). We found that PRP and MSCs, both as single treatments and in combination, were able to prevent the TGF-β1-induced fibroblast-myofibroblast transition. Unexpectedly, the combination PRP/MSCs had no synergistic effects. In conclusion, within the limitations related to an in vitro experimentation, our study may contribute to providing an experimental background for supporting the anti-fibrotic potential of the combination PRP/MSCs which, once translated "from bench to bedside," could potentially offer advantages over the single treatments.

γ-catenin alleviates cardiac fibrosis through inhibiting phosphorylation of GSK-3β

Cardiac fibrosis is a common pathological change of many cardiovascular diseases. β-catenin has been shown to promote fibrosis. However, the precise role of its homolog γ-catenin in the process of fibrosis remains largely unclear. In this study, we found that the expression of γ-catenin was significantly decreased in angiotensin Ⅱ (Ang Ⅱ)-induced cardiac fibrosis model, contrary to most reports of β-catenin. Overexpression of γ-catenin in cardiac fibroblasts (CFs) significantly inhibited the expression of α-smooth muscle actin (α-SMA), whereas knocking down the expression of γ-catenin with siRNA promoted the occurrence of cardiac fibrosis. Mechanistically, γ-catenin could bind to GSK-3β to inhibit the phosphorylation of GSK-3β, therefore preventing cardiac fibrosis. Our study shows that γ-catenin is an important protective factor in cardiac fibrosis, which provides a new potential target for the treatment of cardiac fibrosis.

Circulating levels of butyrate are inversely related to portal hypertension, endotoxemia, and systemic inflammation in patients with cirrhosis

Short-chain fatty acids (SCFAs) are gut microbiota-derived products that participate in maintaining the gut barrier integrity and host's immune response. We hypothesize that reduced SCFA levels are associated with systemic inflammation, endotoxemia, and more severe hemodynamic alterations in cirrhosis. Patients with cirrhosis referred for a hepatic venous pressure gradient (HVPG) measurement (n = 62) or a transjugular intrahepatic portosystemic shunt placement (n = 12) were included. SCFAs were measured in portal (when available), hepatic, and peripheral blood samples by GC-MS. Serum endotoxins, proinflammatory cytokines, and NO levels were quantified. SCFA levels were significantly higher in portal vs. hepatic and peripheral blood. There were inverse relationships between SCFAs and the severity of disease. SCFAs (mainly butyric acid) inversely correlated with the model for end-stage liver disease score and were further reduced in patients with history of ascites, hepatic encephalopathy, and spontaneous bacterial peritonitis. There was an inverse relationship between butyric acid and HVPG values. SCFAs were directly related with systemic vascular resistance and inversely with cardiac index. Butyric acid inversely correlated with inflammatory markers and serum endotoxin. A global reduction in the blood levels of SCFA in patients with cirrhosis is associated with a more advanced liver disease, suggesting its contribution to disease progression.-Juanola, O., Ferrusquía-Acosta, J., García-Villalba, R., Zapater, P., Magaz, M., Marín, A., Olivas, P., Baiges, A., Bellot, P., Turon, F., Hernández-Gea, V., González-Navajas, J. M., Tomás-Barberán, F. A., García-Pagán, J. C., Francés, R. Circulating levels of butyrate are inversely related to portal hypertension, endotoxemia, and systemic inflammation in patients with cirrhosis.