HDAC4 represses ER stress induced chondrocyte apoptosis by inhibiting ATF4 and attenuates cartilage degeneration in an osteoarthritis rat model.

BACKGROUND: The present study evaluated whether the lack of histone deacetylase 4 (HDAC4) increases endoplasmic reticulum stress-induced chondrocyte apoptosis by releasing activating transcription factor 4 (ATF4) in human osteoarthritis (OA) cartilage degeneration. METHODS: Articular cartilage from the tibial plateau was obtained from patients with OA during total knee replacement. Cartilage extracted from severely damaged regions was classified as degraded cartilage, and cartilage extracted from a relatively smooth region was classified as preserved cartilage. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining was used to detect chondrocyte apoptosis. HDAC4, ATF4, and C/EBP homologous protein (CHOP) expression levels were measured using immunohistochemistry staining and real-time quantitative PCR. Chondrocytes were transfected with HDAC4 or HDAC4 siRNA for 24 h and stimulated with 300 µM H2O2 for 12 h. The chondrocyte apoptosis was measured using flow cytometry. ATF4, CHOP, and caspase 12 expression levels were measured using real-time quantitative PCR and western blotting. Male Sprague-Dawley rats (n = 15) were randomly divided into three groups and transduced with different vectors: ACLT + Ad-GFP, ACLT + Ad-HDAC4-GFP, and sham + Ad-GFP. All rats received intra-articular injections 48 h after the operation and every three weeks thereafter. Cartilage damage was assessed using Safranin O staining and quantified using the Osteoarthritis Research Society International score. ATF4, CHOP, and collagen II expression were detected using immunohistochemistry, and chondrocyte apoptosis was detected using terminal deoxynucleotidyl transferase dUTP nick end labeling staining. RESULTS: The chondrocyte apoptosis was higher in degraded cartilage than in preserved cartilage. HDAC4 expression was lower in degraded cartilage than in preserved cartilage. ATF4 and CHOP expression was increased in degraded cartilage. Upregulation of HDAC4 in chondrocytes decreased the expression of ATF4, while the expression of ATF4 was increased after downregulation of HDAC4. Upregulation of HDAC4 decreased the chondrocyte apoptosis under endoplasmic reticulum stress, and chondrocyte apoptosis was increased after downregulation of HDAC4. In a rat anterior cruciate ligament transection OA model, adenovirus-mediated transduction of HDAC4 was administered by intra-articular injection. We detected a stronger Safranin O staining with lower Osteoarthritis Research Society International scores, lower ATF4 and CHOP production, stronger collagen II expression, and lower chondrocyte apoptosis in rats treated with Ad-HDAC4. CONCLUSION: The lack of HDAC4 expression partially contributes to increased ATF4, CHOP, and endoplasmic reticulum stress-induced chondrocyte apoptosis in OA pathogenesis. HDAC4 attenuates cartilage damage by repressing ATF4-CHOP signaling-induced chondrocyte apoptosis in a rat model of OA.

Activation of CaMKII/HDAC4 by SDF1 contributes to pulmonary arterial hypertension via stabilization Runx2.

Stromal derived factor 1 (SDF1) has been shown to be involved in the pathogenesis of pulmonary artery hypertension (PAH). However, the detailed molecular mechanisms remain unclear. To address this, we utilized primary cultured rat pulmonary artery smooth muscle cells (PASMCs) and monocrotaline (MCT)-induced PAH rat models to investigate the mechanisms of SDF1 driving PASMCs proliferation and pulmonary arterial remodeling. SDF1 increased runt-related transcription factor 2 (Runx2) acetylation by Calmodulin (CaM)-dependent protein kinase II (CaMKII)-dependent HDAC4 cytoplasmic translocation, elevation of Runx2 acetylation conferred its resistance to proteasome-mediated degradation. The accumulation of Runx2 further upregulated osteopontin (OPN) expression, finally leading to PASMCs proliferation. Blocking SDF1, suppression of CaMKII, inhibition the nuclear export of HDAC4 or silencing Runx2 attenuated pulmonary arterial remodeling and prevented PAH development in MCT-induced PAH rat models. Our study provides novel sights for SDF1 induction of PASMCs proliferation and suggests that targeting SDF1/CaMKII/HDAC4/Runx2 axis has potential value in the management of PAH.

Berberine ameliorates contrast-induced acute kidney injury by regulating HDAC4-FoxO3a axis-induced autophagy: In vivo and in vitro.

In hospitals, contrast-induced acute kidney injury (CI-AKI) is a major cause of renal failure. This study evaluates berberine's (BBR) renal protection and its potential HDAC4 mechanism. CI-AKI in rats was induced with 10 mL kg-1 ioversol. Rats were divided into five groups: Ctrl, BBR, CI-AKI, CI-AKI + BBR, and CI-AKI + Tasq. The renal function of CI-AKI rats was determined by measuring serum creatinine and blood urea nitrogen. Histopathological changes and apoptosis of renal tubular epithelial cells were observed by HE and terminal deoxynucleotidyl transferase (TdTase)-mediated dUTP-biotin nick end labeling (TUNEL) staining. Transmission electron microscopy was used to observe autophagic structures. In vitro, a CI-AKI cell model was created with ioversol-treated HK-2 cells. Treatments included BBR, Rapa, HCQ, and Tasq. Analyses focused on proteins and genes associated with kidney injury, apoptosis, autophagy, and the HDAC4-FoxO3a axis. BBR showed significant protective effects against CI-AKI both in vivo and in vitro. It inhibited apoptosis by increasing Bcl-2 protein levels and decreasing Bax levels. BBR also activated autophagy, as indicated by changes in autophagy-related proteins and autophagic flux. The study further revealed that the contrast agent ioversol increased the expression of HDAC4, which led to elevated levels of phosphorylated FoxO3a (p-FoxO3a) and acetylated FoxO3a (Ac-FoxO3a). However, BBR inhibited HDAC4 expression, resulting in decreased levels of p-FoxO3a and Ac-FoxO3a. This activation of autophagy-related genes, regulated by the transcription factor FoxO3a, played a role in BBR's protective effects. BBR, a traditional Chinese medicine, shows promise against CI-AKI. It may counteract CI-AKI by modulating HDAC4 and FoxO3a, enhancing autophagy, and limiting apoptosis.

ABHD5 protects cardiac function in alcoholic cardiomyopathy via HDAC4-NT to inhibit CAMKII/MEF2 axis.

Excessive intake of Alcohol is associated with a high incidence of alcoholic cardiomyopathy (ACM), which may impair cardiac function. In our study, we explored the Abhydrolase Domain Containing 5 (ABHD5) mechanism in ACM about histone deacetylase 4 (HDAC4) and CaM-CaMKII/MEF2 signaling pathway. Rat models of ACM were established in Wistar rats, and in vitro cell models were constructed in rat cardiomyocytes H9C2 utilizing 12-h of treatment of Alcohol (200 mM) to study the regulatory role of ABHD5 in ACM with the involvement of HDAC4 and CaM-CaMKII/MEF2 signaling pathway, as evidenced by determination of cardiac function, myocardial fibrosis, apoptosis of cardiomyocytes and oxidative stress condition. We found that both ABHD5 mRNA and protein expression was significantly lower in the ACM rats and rat cardiomyocytes H9C2. ACM rats with oe-ABHD5 injection showed repressed myocardial hypertrophy and myocardial fibrosis. Also, overexpression of ABHD5 reduced apoptosis and oxidative stress in H9C2 cells. Mechanistic studies demonstrated that ABHD5 via HDAC4-NT inhibits CAMKII/MEF2 axis. This study highlighted that ABHD5 decreased cardiac hypertrophy and myocardial fibrosis and limited cardiomyocyte apoptosis and oxidative stress injury in ACM.

Inhibitory Effects of Ginsenoside Compound K on Lipopolysaccharide-Stimulated Inflammatory Responses in Macrophages by Regulating Sirtuin 1 and Histone Deacetylase 4.

Inflammation, an innate immune response mediated by macrophages, has been a hallmark leading to the pathophysiology of diseases. In this study, we examined the inhibitory effects of ginsenoside compound K (CK) on lipopolysaccharide (LPS)-induced inflammation and metabolic alteration in RAW 264.7 macrophages by regulating sirtuin 1 (SIRT1) and histone deacetylase 4 (HDAC4). LPS suppressed SIRT1 while promoting HDAC4 expression, accompanied by increases in cellular reactive oxygen species accumulation and pro-inflammatory gene expression; however, the addition of CK elicited the opposite effects. CK ameliorated the LPS-induced increase in glycolytic genes and abrogated the LPS-altered genes engaged in the NAD+ salvage pathway. LPS decreased basal, maximal, and non-mitochondrial respiration, reducing ATP production and proton leak in macrophages, which were abolished by CK. SIRT1 inhibition augmented Hdac4 expression along with increased LPS-induced inflammatory and glycolytic gene expression, while decreasing genes that regulate mitochondrial biogenesis; however, its activation resulted in the opposite effects. Inhibition of HDAC4 enhanced Sirt1 expression and attenuated the LPS-induced inflammatory gene expression. In conclusion, CK exerted anti-inflammatory and antioxidant properties with the potential to counteract the alterations of energy metabolism, including glycolysis and mitochondrial respiration, through activating SIRT1 and repressing HDAC4 in LPS-stimulated macrophages.

Circulating HDAC4 reflects lipid profile, coronary stenosis and inflammation in coronary heart disease patients.

Aim: To investigate the clinical value of HDAC4 in coronary heart disease (CHD) patients. Methods: The serum HDAC4 levels were determined by ELISA in 180 CHD patients and 50 healthy controls. Results: HDAC4 was decreased in CHD patients compared with healthy controls (p < 0.001). HDAC4 was negatively linked with serum creatinine (p = 0.014), low-density lipoprotein cholesterol (p = 0.027) and C-reactive protein (p = 0.006) in CHD patients. Moreover, HDAC4 was inversely related to TNF-α (p = 0.012), IL-1ß (p = 0.002), IL-6 (p = 0.034), IL-17A (p = 0.023), VCAM1 (p = 0.014) and Gensini score (p = 0.001). Unfortunately, neither HDAC4 high (vs low) (p = 0.080) nor HDAC4 quartile (p = 0.268) estimated major adverse cardiovascular event risk. Conclusion: Circulating HDAC4 levels have disease monitoring value but are less valuable in estimating prognosis in CHD patients.

What was this article about? This study aimed to assess the clinical significance of identifying a marker named histone deacetylase 4 (HDAC4) in coronary heart disease (CHD) patients. What was done? Blood was taken from 180 CHD patients and 50 healthy controls, and their blood HDAC4 levels were evaluated. What were the results? HDAC4 levels were higher in CHD patients than in the controls. The CHD patients with a higher HDAC4 level had good kidney health and lower lipid profile, milder inflammation, good vascular status and less narrowing in their blood vessels. However, the HDAC4 level was not found to predict the risk of future cardiovascular disease. What do the results mean? A higher HDAC4 level in the blood of CHD patients suggests a better symptomatic disease status.

Serum histone deacetylase 4 longitudinal change for estimating major adverse cardiovascular events in acute coronary syndrome patients receiving percutaneous coronary intervention.

OBJECTIVE: Histone deacetylase 4 (HDAC4) regulates lipid accumulation, inflammation, endothelial injury, and atherosclerosis to participate in the pathogenesis of cardiovascular diseases. This study aimed to explore the value of serum HDAC4 change before and after percutaneous coronary intervention (PCI) in predicting major adverse cardiovascular events (MACE) risk in acute coronary syndrome (ACS) patients. METHODS: HDAC4 from serum was detected by enzyme-linked immunosorbent assay in 340 ACS patients at baseline, day (D)1, D3, and D7 after PCI, and from 30 healthy controls (HCs). MACE was recorded during follow-up. RESULTS: HDAC4 was decreased in ACS patients versus HCs (P < 0.001). In ACS patients, HDAC4 was negatively related to total cholesterol (P = 0.025), low-density lipoprotein cholesterol (P = 0.007), C-reactive protein (P < 0.001), cardiac troponin I (P < 0.001), and hyperlipidemia history (P = 0.015). Additionally, HDAC4 was lowest in ST-elevation myocardial infarction (STEMI) patients, followed by non-STEMI patients, and highest in unstable angina patients (P = 0.010). After PCI, HDAC4 was decreased from baseline to D1, then increased until D7 (P < 0.001). Furthermore, HDAC4 at baseline (P = 0.002), D1 (P < 0.001), D3 (P < 0.001), and D7 (P < 0.001) were all reduced in patients who experienced MACE versus those who did not. Meanwhile, high HDAC4 at baseline (P = 0.036), D1 (P = 0.010), D3 (P = 0.012), and D7 (P = 0.012) estimated decreased accumulating MACE risk by Kaplan-Meier curve. Multivariate logistic analysis revealed that HDAC4 at D1 was independently linked to lower MACE risk (odds ratio = 0.957, P = 0.039). CONCLUSION: Serum HDAC4 is decreased from baseline to D1, then elevated until D7, and its increased level correlates with lower MACE risk in ACS patients receiving PCI.

An analysis of lncRNA-miRNA-mRNA networks to investigate the effects of HDAC4 inhibition on skeletal muscle atrophy caused by peripheral nerve injury.

Background: Muscle atrophy caused by peripheral nerve injury is a common clinical disease, with no effective treatments currently available. Our previous studies have found that denervation-induced muscle atrophy can be alleviated by inhibiting histone deacetylase 4 (HDAC4). An increasing amount of evidence shows that microRNA (miRNA) and long noncoding RNA (lncRNA) are involved in the occurrence of muscle atrophy. This study aimed to find the mechanism by which HDAC4 regulates denervation-induced muscle atrophy based on lncRNA-associated competing endogenous RNA (ceRNA) networks. Methods: We analyzed the influence of short hairpin RNA (shRNA) knockdown of HDAC4 on lncRNAs and miRNAs after denervated muscle atrophy using RNA sequencing. A Pearson's correlation heat map and principal component analysis were employed to analyze differentially expressed miRNAs and lncRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses of target genes were conducted. The ceRNA network of lncRNA-miRNA-mRNA was constructed, and the core regulatory molecules in the ceRNA network were analyzed. Results: We found 32 miRNAs and 111 lncRNAs related to denervated muscle atrophy regulated by HDAC4. Moreover, 15 downregulated lncRNAs, 14 upregulated miRNAs, and 61 downregulated mRNAs constituted a ceRNA regulatory network, participating in the biological processes including response to denervation involved in regulation of muscle adaptation, along with the signaling pathways including autophagy, FoxO signaling pathways, and Jak-STAT signaling pathways. Additionally, 6 upregulated lncRNAs, 8 downregulated miRNAs, and 66 upregulated mRNAs constituted another ceRNA regulatory network, which was mainly involved in cell cycle-related biological processes and pathways. Finally, 3 lncRNAs, 4 miRNAs, and 12 mRNAs constituted a ceRNA sub-network, and XR_377582.2 and ENSMUST00000143649 were considered to be the key lncRNAs. Conclusions: In the ceRNA network, all nodes are directly or indirectly involved in the process by which HDAC4 regulates skeletal muscle atrophy caused by peripheral nerve injury. XR_377582.2 and ENSMUST00000143649 may be the key lncRNAs related to HDAC4 involved in the regulation of muscle atrophy.

Pharmacological and Genetic Inhibition of HDAC4 Alleviates Renal Injury and Fibrosis in Mice.

Histone deacetylase 4 (HDAC4) has been shown to be involved in cell proliferation, differentiation, and migration and is associated with a variety of cancers. However, the role of HDAC4 in renal fibrogenesis and its mechanisms are unclear. We assessed the role of HDAC4 and possible mechanisms of fibrosis in a murine model of kidney injury induced by unilateral ureteral obstruction (UUO) using tasquinimod, a highly selective HDAC4 inhibitor, and knockout mice with depletion of HDAC4 in renal tubular cells. UUO injury resulted in increased expression of HDAC4 and fibrotic proteins fibronectin and α-smooth muscle actin, while treatment with tasquinimod or knockout of HDAC4 significantly reduced their expression. Pharmacological and genetic inhibition of HDAC4 also decreased tubular epithelial cell arrest in the G2/M phase of the cell cycle, expression of transforming growth factor-ß1 and phosphorylation of Smad3, signal transducer and activator of transcription 3, and extracellular signal-regulated kinase 1/2 in the injured kidney. Moreover, tasquinimod treatment or HDAC4 deletion inhibited UUO-induced renal tubular cell injury and apoptosis as indicated by reduced expression of neutrophil gelatinase-associated lipocalin, Bax, and inhibition of caspase-3. Finally, administration of tasquinimod or knockdown of HDAC4 prevented injury-related repression of Klotho, a renoprotective protein. Our results indicate that HDAC4 is critically involved in renal tubular injury and fibrosis and suggest that HDAC4 is a potential therapeutic target for treatment of chronic fibrotic kidney disease.

Formoxanthone C Inhibits Malignant Tumor Phenotypes of Human A549 Multidrug Resistant-cancer Cells through Signal Transducer and Activator of Transcription 1-Histone Deacetylase 4 Signaling.

Considering that presence of cancer stem cell (CSC) subpopulation in tumor tissues confers anticancer drug resistance, we investigated whether human A549 lung cancer cells resistant to etoposide possess CSC-like phenotypes. Furthermore, it is known that these malignant tumor features are the leading cause of treatment failure in cancer. We have thus attempted to explore new therapeutic agents from natural products targeting these malignancies. We found that formoxanthone C (XanX), a 1,3,5,6-tetraoxygenated xanthone from Cratoxylum formosum ssp. pruniflorum, at a non-cytotoxic concentration reduced the expression of the signal transducer and activator of transcription 1 (STAT1) and histone deacetylase 4 (HDAC4) proteins, leading to inhibition of CSC-like phenotypes such as cell migration, invasion, and sphere-forming ability. Moreover, we found that treatment with STAT1 or HDAC4 small interfering RNAs significantly hindered these CSC-like phenotypes, indicating that STAT1 and HDAC4 play a role in the malignant tumor features. Taken together, our findings suggest that XanX may be a potential new therapeutic agent targeting malignant lung tumors.

SP1 Promotes HDAC4 Expression and Inhibits HMGB1 Expression to Reduce Intestinal Barrier Dysfunction, Oxidative Stress, and Inflammatory Response after Sepsis.

As a serious and elusive syndrome caused by infection, sepsis causes a high rate of mortality around the world. Our investigation aims at exploring the role and possible mechanism of specificity protein-1 (SP1) in the development of sepsis. A mouse model of sepsis was established by cecal ligation perforation, and a cellular model was stimulated by lipopolysaccharide (LPS), followed by determination of the SP1 expression. It was determined that SP1 was poorly expressed in the intestinal tissues of septic mice and LPS-treated cells. Next, we examined the interactions among SP1, histone deacetylase 4 (HDAC4), and high mobility group box 1 (HMGB1) and found that SP1 bound to the HDAC4 promoter to upregulate its expression, thereby promoting the deacetylation of HMGB1. Meanwhile, gain- or loss-of-function approaches were applied to evaluate the intestinal barrier dysfunction, oxidative stress, and inflammatory response. Overexpression of SP1 or underexpression of HMGB1 was observed to reduce intestinal barrier dysfunction, oxidative stress, and inflammatory injury. Collectively, these experimental data provide evidence reporting that SP1 could promote the HDAC4-mediated HMGB1 deacetylation to reduce intestinal barrier dysfunction, oxidative stress, and inflammatory response induced by sepsis, providing a novel therapeutic target for sepsis prevention and treatment.

Histone deacetylase 4 reverses cellular senescence via DDIT4 in dermal fibroblasts.

Histone deacetylases (HDACs) remove acetyl groups from lysine chains on histones and other proteins and play a crucial role in epigenetic regulation and aging. Previously, we demonstrated that HDAC4 is consistently downregulated in aged and ultraviolet (UV)-irradiated human skin in vivo. Cellular senescence is a permanent cell cycle arrest induced by various stressors. To elucidate the potential role of HDAC4 in the regulation of cellular senescence and skin aging, we established oxidative stress- and UV-induced cellular senescence models using primary human dermal fibroblasts (HDFs). RNA sequencing after overexpression or knockdown of HDAC4 in primary HDFs identified candidate molecular targets of HDAC4. Integrative analyses of our current and public mRNA expression profiles identified DNA damage-inducible transcript 4 (DDIT4) as a critical senescence-associated factor regulated by HDAC4. Indeed, DDIT4 and HDAC4 expressions were downregulated during oxidative stress- and UV-induced senescence. HDAC4 overexpression rescued the senescence-induced decrease in DDIT4 and senescence phenotype, which were prevented by DDIT4 knockdown. In addition, DDIT4 overexpression reversed changes in senescence-associated secretory phenotypes and aging-related genes, suggesting that DDIT4 mediates the reversal of cellular senescence via HDAC4. Collectively, our results identify DDIT4 as a promising target regulated by HDAC4 associated with cellular senescence and epigenetic skin aging.

Blood HDAC4 Variation Links With Disease Activity and Response to Tumor Necrosis Factor Inhibitor and Regulates CD4+ T Cell Differentiation in Ankylosing Spondylitis.

Purpose: Histone deacetylase 4 (HDAC4) regulates the progression of autoimmune diseases. This study aimed to further investigate the correlation between HDAC4 and Th cells, inflammation, disease activity, and treatment response in patients with ankylosing spondylitis (AS). Methods: A total of 132 active patients with AS were enrolled, of whom 54 patients received TNF inhibitor (TNFi) and 78 patients received NSAID. Serum HDAC4 was measured by ELISA in patients with AS before treatment (W0) and at week (W)4, W8, and W12 after treatment. Meanwhile, serum HDAC4 was detected in 30 patients with osteoarthritis and in 30 healthy controls (HCs) by ELISA. Besides, naïve CD4+ T cells from patients with AS were isolated, followed by modulation of HDAC4 and then polarization toward Th1, Th2, and Th17. Results: Histone deacetylase 4 was reduced in patients with AS compared with HCs and patients with osteoarthritis (both P < 0.01). In patients with AS, HDAC4 was negatively correlated with TNF (P < 0.001), IL-1ß (P = 0.003), Th17 proportion (P = 0.008), C-reactive protein (P < 0.001), and ASDAS (P = 0.038), but not with IL-6, Th1 proportion, or other characteristics. Meanwhile, HDAC4 increased from W0 to W12 (P < 0.001); HDAC4 at W8 (P = 0.014) and W12 (P = 0.006) was raised in ASAS40-response patients than ASAS40-non-response patients; further subgroup analysis showed that HDAC4 at W12 was higher in ASAS40-response patients than ASAS40-non-response patients (P = 0.016) in the TNFi-treated group, but not in the NSAID-treated group. In addition, HDAC4 negatively regulated the polarization of naïve CD4+ T cells toward Th17 (P < 0.01), but not Th1 or Th2. Conclusion: Histone deacetylase 4 is associated with lower inflammation, and the disease activity negatively regulates Th17 polarization, whose increment after treatment reflects favorable outcomes in patients with AS.

circ­LRP6 contributes to osteosarcoma progression by regulating the miR­141­3p/HDAC4/HMGB1 axis.

Circular RNA­lipoprotein receptor 6 (circ­LRP6) serves a role in promoting the tumorigenesis of retinoblastoma, esophageal squamous cell cancer and oral squamous cell carcinoma; however, whether circ­LRP6 demonstrates the same effect in osteosarcoma (OS) is yet to be fully elucidated. The present study aimed to analyze the expression, role and potential molecular mechanism of circ­LRP6 in OS. The expression levels of circ­LRP6, microRNA (miR)­141­3p, histone deacetylase 4 (HDAC4) and high mobility group protein 1 (HMGB1) were evaluated by reverse transcription-quantitative PCR in OS tissues and cell lines. Cell Counting Kit­8, Transwell and Matrigel assays were conducted to evaluate cell proliferation, migration and invasion, respectively. Western blotting was also performed to determine HDAC4 and HMGB1 protein expression levels. Bioinformatics and dual­luciferase reporter assays were used to predict and analyze the interactions between circ­LRP6 and miR­141­3p, miR­141­3p and HDAC4, as well as between miR­141­3p and HMGB1. Additionally, RNA immunoprecipitation was performed to verify the association between circ­LRP6 and miR­141­3p. The results confirmed that circ­LRP6 was highly expressed in OS tissues and cell lines. In addition, circ­LRP6 negatively regulated the expression of miR­141­3p and, in turn, miR­141­3p negatively regulated HDAC4 and HMGB1 expression. Functional assays revealed that circ­LRP6 knockdown inhibited the proliferation, migration and invasion of OS cells, whereas the inhibition of miR­141­3p or the overexpression of either HDAC4 or HMGB1 partly reversed the inhibitory effect of circ­LRP6 knockdown. In summary, the present study determined that circ­LRP6 knockdown inhibited the proliferation, migration and invasion of OS cells by regulating the miR­141­3p/HDAC4/HMGB1 axis.

Promotion of microRNA-146a by histone deacetylase 4 silencing contributes to radiosensitization of esophageal carcinoma.

BACKGROUND: Histone deacetylases (HDACs) have been identified to be implicated in the carcinogenesis and cancer progression. The present study was performed to probe into the effect of HDAC4 on radioresistance of esophageal carcinoma (EC). METHODS: The expression of HDAC4 in responders and non-responders to radiotherapy was characterized by RT-qPCR, immunohistochemistry, and Western blot analysis. EC cells were exposed to continuous fractionated X-ray irradiation, and their proliferation and apoptosis were evaluated by means of colony formation assay and flow cytometry based Annexin V-FITC/PI apoptosis assay in response to HDAC4 overexpression or silencing. Mechanistic investigation was conducted by means of in silico analysis and dual-luciferase reporter gene assay. Tumor xenografts derived from radioresistant EC cells were exposed to local X-ray irradiation in vivo for validation. RESULTS: High expression of HDAC4 was detected in either tumor tissues derived from radiotherapy responders or radioresistant EC cells. Loss of HDAC4 contributed to suppressed proliferation and enhanced apoptosis of radioresistant EC cells. Moreover, our findings revealed that HDAC4 conferred radioresistance of EC by downregulating microRNA-146a (miR-146a). Interleukin-1 receptor-associated kinase 1 (IRAK1) was a target of miR-146a, and its knockdown promoted radiosensitivity. Silencing of HDAC4 radiosensitized EC cells both in vitro and in vivo via the miR-146a/IRAK1 axis. CONCLUSION: Hence, loss of HDAC4 upregulated miR-146a to limit radioresistance. This study aids in the better understanding about mechanism responsible for radioresistance of EC.

Drug Repurposing: Escitalopram attenuates acute lung injury by inhibiting the SIK2/ HDAC4/ NF-κB signaling cascade.

Acute lung injury (ALI) is a significant cause of morbidity and mortality worldwide. To search for a new treatment for acute lung injury, we investigated the effect of escitalopram on lipopolysaccharide (LPS)-induced ALI. Our results showed that escitalopram inhibited salt-inducible kinase 2 (SIK2) activity (IC50 = 6.36 ± 0.93 µM) and triggered histone deacetylase 4 (HDAC4) dephosphorylation. Following its dephosphorylation, HDAC4 translocated into the nucleus, promoted deacetylation and cytoplasmic shuttling of p65, thus inhibited LPS-induced pro-inflammatory cytokine production. Moreover, escitalopram markedly ameliorated the inflammatory responses, reduced neutrophils infiltration and attenuated LPS-induced pulmonary injury in mice. Taken together, we identified a previously unexplored role for escitalopram in SIK2/HDAC4/NF-κB pathway, therefore escitalopram may be considered as a new treatment for ALI.

HDAC4 mutant represses chondrocyte hypertrophy by locating in the nucleus and attenuates disease progression of posttraumatic osteoarthritis.

BACKGROUND: The aim of this study was to evaluate whether histone deacetylase 4 S246/467/632A mutant (m-HDAC4) has enhanced function at histone deacetylase 4 (HDAC4) to attenuate cartilage degeneration in a rat model of osteoarthritis (OA). METHODS: Chondrocytes were infected with Ad-m-HDAC4-GFP or Ad-HDAC4-GFP for 24 h, incubated with interleukin-1ß (IL-1ß 10 ng/mL) for 24 h, and then measured by RT-qPCR. Male Sprague-Dawley rats (n = 48) were randomly divided into four groups and transduced with different vectors: ACLT/Ad-GFP, ACLT/Ad-HDAC4-GFP, ACLT/Ad-m-HDAC4-GFP, and sham/Ad-GFP. All rats received intra-articular injections 48 h after the operation and every 3 weeks thereafter. Cartilage damage was assessed using radiography and Safranin O staining and quantified using the OARSI score. The hypertrophic and anabolic molecules were detected by immunohistochemistry and RT-qPCR. RESULTS: M-HDAC4 decreased the expression levels of Runx-2, Mmp-13, and Col 10a1, but increased the levels of Col 2a1 and ACAN more effectively than HDAC4 in the IL-1ß-induced chondrocyte OA model; upregulation of HDAC4 and m-HDAC4 in the rat OA model suppressed Runx-2 and MMP-13 production, and enhanced Col 2a1 and ACAN synthesis. Stronger Safranin O staining was detected in rats treated with m-HDAC4 than in those treated with HDAC4. The resulting OARSI scores were lower in the Ad-m-HDAC4 group (5.80 ± 0.45) than in the Ad-HDAC4 group (9.67 ± 1.83, P = 0.045). The OARSI scores were highest in rat knees that underwent ACLT treated with Ad-GFP control adenovirus vector (14.93 ± 2.14, P = 0.019 compared with Ad-HDAC4 group; P = 0.003 compared with Ad-m-HDAC4 group). Lower Runx-2 and MMP-13 production, and stronger Col 2a1 and ACAN synthesis were detected in rats treated with m-HDAC4 than in those treated with HDAC4. CONCLUSIONS: M-HDAC4 repressed chondrocyte hypertrophy and induced chondrocyte anabolism in the nucleus. M-HDAC4 was more effective in attenuating articular cartilage damage than HDAC4.

Histone deacetylase 4 deletion broadly affects cardiac epigenetic repression and regulates transcriptional susceptibility via H3K9 methylation.

Histone deacetylase 4 (HDAC4) is a member of class IIa histone deacetylases (class IIa HDACs) and is believed to possess a low intrinsic deacetylase activity. However, HDAC4 sufficiently represses distinct transcription factors (TFs) such as the myocyte enhancer factor 2 (MEF2). Transcriptional repression by HDAC4 has been suggested to be mediated by the recruitment of other chromatin-modifying enzymes, such as methyltransferases or class I histone deacetylases. However, this concept has not been investigated by an unbiased approach. Therefore, we studied the histone modifications H3K4me3, H3K9ac, H3K27ac, H3K9me2 and H3K27me3 in a genome-wide approach using HDAC4-deficient cardiomyocytes. We identified a general epigenetic shift from a 'repressive' to an 'active' status, characterized by an increase of H3K4me3, H3K9ac and H3K27ac and a decrease of H3K9me2 and H3K27me3. In HDAC4-deficient cardiomyocytes, MEF2 binding sites were considerably overrepresented in upregulated promoter regions of H3K9ac and H3K4me3. For example, we identified the promoter of Adprhl1 as a new genomic target of HDAC4 and MEF2. Overexpression of HDAC4 in cardiomyocytes was able to repress the transcription of the Adprhl1 promoter in the presence of the methyltransferase SUV39H1. On a genome-wide level, the decrease of H3K9 methylation did not change baseline expression but was associated with exercise-induced gene expression. We conclude that HDAC4, on the one hand, associates with activating histone modifications, such as H3K4me3 and H3K9ac. A functional consequence, on the other hand, requires an indirect regulation of H3K9me2. H3K9 hypomethylation in HDAC4 target genes ('first hit') plus a 'second hit' (e.g., exercise) determines the transcriptional response.

Mechanistic Insights into Binding of Ligands with Thiazolidinedione Warhead to Human Histone Deacetylase 4.

Recently, we have reported that non-hydroxamate thiazolidinedione (TZD) analogs are capable of inhibiting human deacetylase 4 (HDAC4). This study aims at the dissection of the molecular determinants and kinetics of the molecular recognition of TZD ligands by HDAC4. For this purpose, a structure activity relationship analysis of 225 analogs was combined with a comprehensive study of the enzyme and binding kinetics of a variety of HDAC4 mutant variants. The experimental data were rationalized by docking to the two major conformations of HDAC4. TZD ligands are competitive inhibitors and bind via a two-step mechanism involving principal molecular recognition and induced fit. The residence time of 24 g is (34 ± 3) min and thus much larger than that of the canonical pan-HDAC inhibitor SAHA ((5 ± 2) min). Importantly, the binding kinetics can be tuned by varying the structure of the CAP group.

A Novel ZIP4-HDAC4-VEGFA Axis in High-Grade Serous Ovarian Cancer.

We have recently identified ZIP4 as a novel cancer stem cell (CSC) marker in high-grade serous ovarian cancer (HGSOC). While it converts drug-resistance to cisplatin (CDDP), we unexpectedly found that ZIP4 induced sensitization of HGSOC cells to histone deacetylase inhibitors (HDACis). Mechanistically, ZIP4 selectively upregulated HDAC IIa HDACs, with little or no effect on HDACs in other classes. HDAC4 knockdown (KD) and LMK-235 inhibited spheroid formation in vitro and tumorigenesis in vivo, with hypoxia inducible factor-1 alpha (HIF1α) and endothelial growth factor A (VEGFA) as functional downstream mediators of HDAC4. Moreover, we found that ZIP4, HDAC4, and HIF1α were involved in regulating secreted VEGFA in HGSOC cells. Furthermore, we tested our hypothesis that co-targeting CSC via the ZIP4-HDAC4 axis and non-CSC using CDDP is necessary and highly effective by comparing the effects of ZIP4-knockout/KD, HDAC4-KD, and HDACis, in the presence or absence of CDDP on tumorigenesis in mouse models. Our results showed that the co-targeting strategy was highly effective. Finally, data from human HGSOC tissues showed that ZIP4 and HDAC4 were upregulated in a subset of recurrent tumors, justifying the clinical relevance of the study. In summary, our study provides a new mechanistic-based targeting strategy for HGSOC.