Epigenetic suppression of iNOS expression in human endothelial cells: A potential role of Ezh2-mediated H3K27me3

EZH2 Inhibition to Counteract Oral Cancer Progression through Wnt/β-Catenin Pathway Modulation

Oral squamous cell carcinoma (OSCC) is one of the most common human malignancies worldwide. The molecular mechanisms of OSCC pathogenesis are still unknown; however, in recent years, several reports have focused on the role of enhancer of zeste homolog 2 (EZH2) in OSCC. Therefore, in this study we aimed to investigate the effects of GSK343, a selective EZH2 inhibitor, and its impact on the signaling pathways in OSCC, using an in vitro and in vivo orthotopic model. In the in vitro model, GSK343 (1, 10, and 25 μM) significantly decreased OSCC cell viability and cell migration through EZH2 inhibition, modulating NF-κB/IκBα pathway activation and eNOS, VEGF, and TGFβ expression, important markers of angiogenesis. In the in vivo model, GSK343 (5 mg/kg and 10 mg/kg) restored tongue tissue architecture and reduced tumor progression through EZH2 inhibition and Wnt/β-catenin signaling pathway modulation. Moreover, GSK343 reduced the expression of inflammatory mediators; eNOS and TGFβ, markers of angiogenesis; and CD31 and CD34, markers of micro vessel density, respectively. In conclusion, our data demonstrate that GSK343 counteracts oral cancer progression through EZH2/Wnt/β-catenin pathway modulation, suggesting that it could be a promising therapeutic approach for OSCC management.

Single cell atlas of human gastric muscle immune cells and macrophage-driven changes in idiopathic gastroparesis

Gastrointestinal immune cells, particularly muscularis macrophages (MM) interact with the enteric nervous system and influence gastrointestinal motility. Here we determine the human gastric muscle immunome and its changes in patients with idiopathic gastroparesis (IG). Single cell sequencing was performed on 26,000 CD45+ cells obtained from the gastric tissue of 20 subjects. We demonstrate 11 immune cell clusters with T cells being most abundant followed by myeloid cells. The proportions of cells belonging to the 11 clusters were similar between IG and controls. However, 9/11 clusters showed 578-11,429 differentially expressed genes. In IG, MM had decreased expression of tissue-protective and microglial genes and increased the expression of monocyte trafficking and stromal activating genes. Furthermore, in IG, IL12 mediated JAK-STAT signaling involved in the activation of tissue-resident macrophages and Eph-ephrin signaling involved in monocyte chemotaxis were upregulated. Patients with IG had a greater abundance of monocyte-like cells. These data further link immune dysregulation to the pathophysiology of gastroparesis.

Melatonin mediated inhibition of EZH2-NOS2 crosstalk attenuates inflammatory bowel disease in preclinical in vitro and in vivo models

AIMS

Inflammatory Bowel Disease is characterised by abdominal pain, diarrhoea, rectal bleeding and weight loss. Sometimes it may leads to severe health complications resulting in death of an individual. Current research efforts to highlight the role of melatonin in regulating EZH2, a master epigenetic regulator and its beneficiary effect in case of IBD management.

MATERIAL METHODS

Murine macrophages (RAW 264.7) were treated with lipopolysaccharides (LPS) to activate them for generating inflammatory response to investigate efficacy of melatonin in-vitro models. Similarly, for developing in vivo models, Dextran sodium sulphate (36-50 kDa) was used. Evaluations of anti-inflammatory activities were carried out by nitrite assay, western blotting, q-PCR, immunofluorescence, and histological studies.

KEY FINDINGS

Reduction of epigenetic target, EZH2 by melatonin significantly improves the clinical symptoms of dextran sodium sulphate induced colitis and may be implicated as a potential therapeutic target in IBD management. The present study evaluates the efficacy of melatonin by epigenetic regulation in IBD models. Down regulation of EZH2 by melatonin reduced the chemical induced inflammatory insults in in vitro and in vivo models. Exploration of molecular pathways has revealed interlink of EZH2 and NOS2, a hallmark of inflammation. Molecular mechanistic action of melatonin is attributed to inhibition of the expression and physical interaction of EZH2 and NOS2.

SIGNIFICANCE

Our study highlights melatonin therapeutic effect via attenuating interaction between EZH2 and NOS2 which is beneficial in managing IBD treatment.

Histone methyltransferase enhancer of zeste 2 polycomb repressive complex 2 subunit exacerbates inflammation in depression rats by modulating microglia polarization

Depression is a major cause of emotional agony and degraded living quality. Enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) is involved in histone methylation in human diseases. This experiment was designed to investigate the mechanism of EZH2 on depression. Depression rat model was established via the treatment of chronic unpredictable mild stress (CUMS) to identify rat depression-like behaviors. EZH2 expression was determined and then silenced to assess its effect on depression-like behaviors and neuroinflammation. Microglia were isolated, cultured, identified and activated to assess EZH2 expression. Effect of EZH2 on microglia polarization was evaluated. Next, the binding relation between microRNA (miR)-29b-3p and EZH2 or matrix metallopeptidase 2 (MMP2) was analyzed. Levels of miR-29b-3p expression and MMP2 transcription were examined. Additionally, the role of miR-29b-3p in microglia polarization was tested. Depression-like behaviors were exhibited after CUMS induction. EZH2 was overexpressed in CUMS-treated rats and lipopolysaccharide (LPS)-induced microglia. EZH2 silencing reversed depression-like behaviors. EZH2 silencing mitigated inflammation in depression by manipulating microglia M2-type polarization. EZH2 targeted miR-29b-3p expression to promote MMP2 transcription. Inhibition of miR-29b-3p reversed the role of EZH2 silencing in microglia M2-type polarization and promoted inflammation. EZH2 inhibited miR-29b-3p expression by combining with miR-29b-3p promoter and trimethylation of histone H3-lysine 27-trimethylated upregulation, and then elevated MMP2 transcription and triggered microglia M1-type polarization, thus exacerbating depression-like behaviors and neuroinflammation of depression.

Production of NOS2 and inflammatory cytokines is reduced by selected protein kinase inhibitors with partial repolarization of HL-60 derived and human blood macrophages

JAK/STAT pathway plays a well-known role in macrophage polarization, but other signaling routes may also be involved. The aim of this study was to identify new signaling pathways and repolarize macrophages by selected protein kinase inhibitors. HL-60 derived macrophages were chosen as model cells and human blood macrophages were used for comparison. M1 and M2 polarization of HL60 derived and human blood macrophages was promoted by LPS + IFNγ (LIF) and IL-4 treatments, respectively. In HL-60 derived macrophages, M1 polarization was mediated by Erk1/2 and p38 phosphorylation, while HSP27 phosphorylation was involved in M2 polarization. The inhibition of both MAPK and JAK/STAT pathways reduced the expression of NOS2, IP-10 and TNFα, IL-8 production was decreased by the inhibition of AMPK and PKD, the upstream kinase of HSP27. HSP27 phosphorylation was inhibited by NB 142, a PKD inhibitor. The expression of CD80 (M1 marker) was reduced by MAPK and JAK/STAT inhibitors, without increasing CD206 (M2 marker). On the other hand, CD206 was reduced by PKD and AMPK inhibitors, without increasing CD80 marker. Phagocytic capacity of HL-60 derived macrophages was higher in M1 macrophages and decreased by trametinib and a p38 inhibitor, while in human blood macrophages, where AT 9283, a JAK/STAT inhibitor also caused a significant decrease in M1 polarized macrophages, no difference was observed between M1 and M2 macrophages. Our results suggest that the repolarization of macrophages cannot be achieved by inhibiting their signaling pathways; nevertheless, the expression of certain polarization markers was decreased, therefore a "depolarization" could be observed both in M1 and M2 polarized cells. Selected protein kinase inhibitors of M1 polarization, decreasing NOS 2 and inflammatory cytokines may be potential candidates for therapeutical trials against inflammatory diseases.

Deficiency of the novel high mobility group protein HMGXB4 protects against systemic inflammation-induced endotoxemia in mice

Sepsis is a major cause of mortality in intensive care units, which results from a severely dysregulated inflammatory response that ultimately leads to organ failure. While antibiotics can help in the early stages, effective strategies to curtail inflammation remain limited. The high mobility group (HMG) proteins are chromosomal proteins with important roles in regulating gene transcription. While HMGB1 has been shown to play a role in sepsis, the role of other family members including HMGXB4 remains unknown. We found that expression of HMGXB4 is strongly induced in response to lipopolysaccharide (LPS)-elicited inflammation in murine peritoneal macrophages. Genetic deletion of Hmgxb4 protected against LPS-induced lung injury and lethality and cecal ligation and puncture (CLP)-induced lethality in mice, and attenuated LPS-induced proinflammatory gene expression in cultured macrophages. By integrating genome-wide transcriptome profiling and a publicly available ChIP-seq dataset, we identified HMGXB4 as a transcriptional activator that regulates the expression of the proinflammatory gene, Nos2 (inducible nitric oxide synthase 2) by binding to its promoter region, leading to NOS2 induction and excessive NO production and tissue damage. Similar to Hmgxb4 ablation in mice, administration of a pharmacological inhibitor of NOS2 robustly decreased LPS-induced pulmonary vascular permeability and lethality in mice. Additionally, we identified the cell adhesion molecule, ICAM1, as a target of HMGXB4 in endothelial cells that facilitates inflammation by promoting monocyte attachment. In summary, our study reveals a critical role of HMGXB4 in exacerbating endotoxemia via transcriptional induction of Nos2 and Icam1 gene expression and thus targeting HMGXB4 may be an effective therapeutic strategy for the treatment of sepsis.

Role of Nitric Oxide in Gene Expression Regulation during Cancer: Epigenetic Modifications and Non-Coding RNAs

Nitric oxide (NO) has been identified and described as a dual mediator in cancer according to dose-, time- and compartment-dependent NO generation. The present review addresses the different epigenetic mechanisms, such as histone modifications and non-coding RNAs (ncRNAs), miRNA and lncRNA, which regulate directly or indirectly nitric oxide synthase (NOS) expression and NO production, impacting all hallmarks of the oncogenic process. Among lncRNA, HEIH and UCA1 develop their oncogenic functions by inhibiting their target miRNAs and consequently reversing the inhibition of NOS and promoting tumor proliferation. The connection between miRNAs and NO is also involved in two important features in cancer, such as the tumor microenvironment that includes key cellular components such as tumor-associated macrophages (TAMs), cancer associated fibroblasts (CAFs) and cancer stem cells (CSCs).

High Glucose Induces Endothelial COX2 and iNOS Expression via Inhibition of Monomethyltransferase SETD8 Expression

Cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS) overexpression results in endothelial apoptosis, thus mediating vascular endothelial injury in hyperglycaemia. E26 transformation-specific sequence transcription factor-1 (ESE-1), which belongs to the E26 transformation-specific family of transcription factors, has been demonstrated to be involved in COX2 and iNOS gene transcription. Our previous study indicated that SET domain-containing protein 8 (SETD8) downregulation is involved in high glucose-mediated endothelial inflammation in human umbilical vein endothelial cells (HUVECs). Here, we report that SETD8 plays a major role in hyperglycaemia-induced COX2 and iNOS expression. In HUVECs, upregulation of ESE-1 expression was related to high glucose-mediated apoptosis and COX2 and iNOS expression. High glucose inhibited SETD8 expression, and overexpression of SETD8 diminished the effects of high glucose treatment. Consistently, RNA silencing of SETD8 led to the opposite effect. Furthermore, SETD8 was found to interact with specificity protein 1 (SP1). Blockade of SP1 protected against high glucose-mediated endothelial injury. Mechanistically, we showed that H4K20me1, a downstream target of SETD8, and SP1 were enriched at the ESE-1 promoter region by ChIP assay. Luciferase reporter assays indicated that SETD8 overexpression attenuated ESE-1 promoter activity and augmented the inhibitory effect of siSP1 on ESE-1 promoter activity. In general, our data indicate that SETD8 interacts with SP1 to coregulate ESE-1 expression, which is involved in hyperglycaemia-mediated endothelial apoptosis in HUVECs.

MicroRNA-24 inhibits the oxidative stress induced by vascular injury by activating the Nrf2/Ho-1 signaling pathway

BACKGROUND AND AIMS

The process of endothelial repair in diabetic patients after stent implantation was significantly delayed compared with that in non-diabetic patients, and oxidative stress is increasingly considered to be relevant to the pathogenesis of diabetic endothelial repair. However, the mechanisms linking diabetes and reendothelialization after vascular injury have not been fully elucidated. The aim of this study was to evaluate the effect of microRNA-24 (miR-24) up-regulation in delayed endothelial repair caused by oxidative stress after balloon injury in diabetic rats.

METHODS

In vitro, vascular smooth muscle cells (VSMCs) isolated from the thoracic aorta were stimulated with high glucose (HG) after miR-24 recombinant adenovirus (Ad-miR-24-GFP) transfection for 3 days. In vivo, diabetic rats induced using high-fat diet (HFD) and low-dose streptozotocin (30 mg/kg) underwent carotid artery balloon injury followed by Ad-miR-24-GFP transfection for 20 min.

RESULTS

The expression of miR-24 was decreased in HG-stimulated VSMCs and balloon-injured carotid arteries of diabetic rats, which was accompanied by increased expression of Ogt and Keap1 and decreased expression of Nrf2 and Ho-1. Up-regulation of miR-24 suppressed VSMC oxidative stress induced by HG in vitro, and miR-24 up-regulation promoted reendothelialization in balloon-injured diabetic rats. The underlying mechanism was related to the activation of the Nrf2/Ho-1 signaling pathway, which subsequently suppressed intracellular reactive oxidative species (ROS) production and malondialdehyde (MDA) and NADPH oxidase (Nox) activity, and to the restoration of Sod and Gsh-px activation.

CONCLUSIONS

The up-regulation of miR-24 significantly promoted endothelial repair after balloon injury through inhibition of oxidative stress by activating the Nrf2/Ho-1 signaling pathway.

Oxidative/nitrative stress in the pathogenesis of systemic sclerosis: are antioxidants beneficial?

Systemic sclerosis (SSc) is a multisystem autoimmune disease: characterised from the clinical side by progressive vasculopathy and fibrosis of the skin and different organs and from the biochemical side by fibroblast deregulation with excessive production of collagen and increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). The latter contributes to an overproduction of reactive oxygen species that through an autocrine loop maintains NOX4 in a state of activation. Reactive oxygen and nitrogen species are implicated in the origin and perpetuation of several clinical manifestations of SSc having vascular damage in common; attempts to dampen oxidative and nitrative stress through different agents with antioxidant properties have not translated into a sustained clinical benefit. Objective of this narrative review is to describe the origin and clinical implications of oxidative and nitrative stress in SSc, with particular focus on the central role of NOX4 and its interactions, to re-evaluate the antioxidant approaches so far used to limit disease progression, to appraise the complexity of antioxidant treatment and to touch on novel pathways elements of which may represent specific treatment targets in the not so distant future.

Antibiotic-induced acceleration of type 1 diabetes alters maturation of innate intestinal immunity

The early-life intestinal microbiota plays a key role in shaping host immune system development. We found that a single early-life antibiotic course (1PAT) accelerated type 1 diabetes (T1D) development in male NOD mice. The single course had deep and persistent effects on the intestinal microbiome, leading to altered cecal, hepatic, and serum metabolites. The exposure elicited sex-specific effects on chromatin states in the ileum and liver and perturbed ileal gene expression, altering normal maturational patterns. The global signature changes included specific genes controlling both innate and adaptive immunity. Microbiome analysis revealed four taxa each that potentially protect against or accelerate T1D onset, that were linked in a network model to specific differences in ileal gene expression. This simplified animal model reveals multiple potential pathways to understand pathogenesis by which early-life gut microbiome perturbations alter a global suite of intestinal responses, contributing to the accelerated and enhanced T1D development.

Role of Nitric Oxide and Hydrogen Sulfide in Ischemic Stroke and the Emergent Epigenetic Underpinnings

Nitric oxide (NO) and hydrogen sulfide (H₂S) are the key gasotransmitters with an imperious role in the maintenance of cerebrovascular homeostasis. A decline in their levels contributes to endothelial dysfunction that portends ischemic stroke (IS) or cerebral ischemia/reperfusion (CI/R). Nevertheless, their exorbitant production during CI/R is associated with exacerbation of cerebrovascular injury in the post-stroke epoch. NO-producing nitric oxide synthases are implicated in IS pathology and their activity is regulated, inter alia, by various post-translational modifications and chromatin-based mechanisms. These account for heterogeneous alterations in NO production in a disease setting like IS. Interestingly, NO per se has been posited as an endogenous epigenetic modulator. Further, there is compelling evidence for an ingenious crosstalk between NO and H₂S in effecting the canonical (direct) and non-canonical (off-target collateral) functions. In this regard, NO-mediated S-nitrosylation and H₂S-mediated S-sulfhydration of specific reactive thiols in an expanding array of target proteins are the principal modalities mediating the all-pervasive influence of NO and H₂S on cell fate in an ischemic brain. An integrated stress response subsuming unfolded protein response and autophagy to cellular stressors like endoplasmic reticulum stress, in part, is entrenched in such signaling modalities that substantiate the role of NO and H₂S in priming the cells for stress response. The precis presented here provides a comprehension on the multifarious actions of NO and H₂S and their epigenetic underpinnings, their crosstalk in maintenance of cerebrovascular homeostasis, and their "Janus bifrons" effect in IS milieu together with plausible therapeutic implications.

EZH2-mediated suppression of lncRNA-LET promotes cell apoptosis and inhibits the proliferation of post-burn skin fibroblasts

Although the upregulation of enhancer of zeste homolog 2 (EZH2) expression and downregulation of long non-coding RNA (lncRNA) LET expression are known to be associated with cell apoptosis and proliferation, little is known about the interaction of EZH2 with lncRNA LET. The present study aimed to investigate the interaction of EZH2 and lncRNA LET, and the mechanism of human dermal fibroblast (HDF) proliferation and apoptosis. Tissue samples from 33 burn patients with second- and third-degree burns and 8 controls were collected. mRNA was extracted from the burn tissues for analysis. Isolated primary HDFs were treated with heat or transfected with LET overexpression vectors, and the cell functions and associated proteins in the HDFs were analyzed. Decreased lncRNA LET expression was detected in burn tissues compared with normal skin. Heat-treated HDFs exhibited a reduction in lncRNA LET expression and increase in EZH2 expression. LET gain-of-function experiments in primary HDFs revealed increases in cell proliferation, the proportion of cells in the S stage, and cyclin D1 and cyclin-dependent kinase 4 (CDK4) expression, and reductions in the percentage of apoptotic cells, the Bax/Bcl-2 ratio and caspase-3 expression. RNA immunoprecipitation and chromatin immunoprecipitation assays demonstrated the interaction of ZH2 with lncRNA LET, and of EZH2 with H3K27me3 in HDFs. Furthermore, a negative correlation between lncRNA LET and EZH2 expression was identified. It may be concluded that increased lncRNA-LET expression promoted cell proliferation and inhibited cell apoptosis via the cyclin D1-CDK4 and Bax/Bcl-2/caspase-3 signaling pathways, respectively. Furthermore, the inhibition of lncRNA LET may be regarded as an option for use in the healing of burns.

Endothelial nitric oxide synthase modulates Toll-like receptor 4-mediated IL-6 production and permeability via nitric oxide-independent signaling

Endothelial dysfunction, characterized by changes in eNOS, is a common finding in chronic inflammatory vascular diseases. These states are associated with increased infectious complications. We hypothesized that alterations in eNOS would enhance the response to LPS-mediated TLR4 inflammation. Human microvascular endothelial cells were treated with sepiapterin or N-nitro-L-arginine methylester (L-NAME) to alter endogenous NO production, and small interfering RNA to knockdown eNOS. Alterations of endogenous NO by sepiapterin, and L-NAME provided no significant changes to LPS inflammation. In contrast, eNOS knockdown greatly enhanced endothelial IL-6 production and permeability in response to LPS. Knockdown of eNOS enhanced LPS-induced p38. Inhibition of p38 with SB203580 prevented IL-6 production, without altering permeability. Knockdown of p38 impaired NF-κB activation. Physical interaction between p38 and eNOS was demonstrated by immunoprecipitation, suggesting a novel, NO-independent mechanism for eNOS regulation of TLR4. In correlation, biopsy samples in patients with systemic lupus erythematous showed reduced eNOS expression with associated elevations in TLR4 and p38, suggesting an in vivo link. Thus, reduced expression of eNOS, as seen in chronic inflammatory disease, was associated with enhanced TLR4 signaling through p38. This may enhance the response to infection in patients with chronic inflammatory conditions.-Stark, R. J., Koch, S. R., Choi, H., Mace, E. H., Dikalov, S. I., Sherwood, E. R., Lamb, F. S. Endothelial nitric oxide synthase modulates Toll-like receptor 4-mediated IL-6 production and permeability via nitric oxide-independent signaling.

Chaetospirolactone reverses the apoptotic resistance towards TRAIL in pancreatic cancer

The pancreatic cancer is one of the most aggressive tumors. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can trigger apoptosis by interaction with death receptors. However, in TRAIL-resistant pancreatic cancer, responsiveness to TRAIL treatment is terribly poor. In current work, we have demonstrated that a natural product chaetospirolactone (CSL) isolated from an endophytic fungus Chaetomium sp. NF00754 can enhance the susceptibility of TRAIL-resistant pancreatic cancer cells to apoptosis. CSL can induce apoptosis in TRAIL-treated pancreatic cancer cells. Furthermore, combined CSL and TRAIL treatment significantly inhibits viability and migration of pancreatic cancer cells. Combinatorial TRAIL and CSL treatment repressed xenograft tumor growth without substantially toxic side effects. CSL can specifically upregulate expression of death receptor 4 (DR4). Further study revealed that CSL represses the activities of an epigenetic regulator enhancer of zeste homolog 2 (EZH2) and consistently reduces histone H3 lysine 27 trimethylation (H3K27me3) to allow DR4 transcription. Taken together, CSL treatment may reverse TRAIL resistance in pancreatic cancer cells via epigenetic regulation of DR4 implying that administration of CSL might represent a putative strategy for pancreatic cancer therapy.

Hypoxia induces TWIST-activated epithelial-mesenchymal transition and proliferation of pancreatic cancer cells in vitro and in nude mice

The epithelial-mesenchymal transition (EMT) plays a crucial role in pancreatic ductal adenocarcinoma (PDAC) development and progression. TWIST activated by intra-tumoral hypoxia functions to promote the EMT. We hypothesized that TWIST and the downstream gene pathway could mediate PDAC progression under hypoxia. Therefore, 90 PDAC tissue specimens were immunostained for TWIST and other proteins. Pancreatic cancer cell lines were used for in vitro experiments and nude mice were used to confirm the in vivo data. Expression of TWIST and HIF-1α proteins was significantly upregulated, whereas expression of E-cadherin and p16 was down-regulated in PDAC tissues compared to that of non-tumor tissues and in tumor tissues obtained from patients with tumor involving splenic artery than those without splenic artery involvement. Up-regulated TWIST in tumor tissues were associated with worse prognosis in PDAC patients. The in vitro data showed that HIF-1α-induced TWIST overexpression promoted tumor cell growth and EMT under a hypoxic condition via TWIST interaction with Ring1B and EZH2. In vivo data showed that TWIST overexpression or a hypoxic condition induce xenograft growth, abdominal metastasis and low mouse survival, whereas knockdown of either Ring1B or EZH2 expression suppressed tumor xenograft growth and metastasis and prolonged survival of nude mice. TWIST was the key player in promotion of pancreatic cancer development and metastasis under a hypoxic condition through interaction with Ring1B and EZH2 to regulate expression of E-cadherin and p16 proteins in pancreatic cancer cells.