The benefits of oral glucose-lowering agents: GLP-1 receptor agonists, DPP-4 and SGLT-2 inhibitors on myocardial ischaemia/reperfusion injury.

Myocardial infarction (MI) is a life-threatening cardiovascular disease that, on average, results in 8.5 million deaths worldwide each year. Timely revascularization of occluded vessels is a critical method of myocardial salvage. However, reperfusion paradoxically leads to the worsening of myocardial damage known as myocardial ischaemia/reperfusion injury (MI/RI). Therefore, reducing the size of myocardial infarction after reperfusion is critical and remains an important therapeutic goal. The susceptibility of the myocardium to MI/RI may be increased by diabetes. Currently, some traditional antidiabetic agents such as metformin reduce MI/RI by decreasing inflammation, inhibiting oxidative stress, and improving vascular endothelial function. This appears to be a new direction for the treatment of MI/RI. Recent cardiovascular outcome trials have shown that several oral antidiabetic agents, including glucagon-like peptide-1 receptor agonists (GLP-1RAs), dipeptidyl peptidase-4 inhibitors (DPP-4is), and sodium-glucose-linked transporter-2 inhibitors (SGLT-2is), not only have good antidiabetic effects but also have a protective effect on myocardial protection. This article aims to discuss the mechanisms and effects of oral antidiabetic agents, including GLP-1RAs, DPP-4is, and SGLT-2is, on MI/RI to facilitate their clinical application.

SMYD2-Methylated PPARγ Facilitates Hypoxia-Induced Pulmonary Hypertension by Activating Mitophagy.

BACKGROUND: Hyperproliferation of pulmonary arterial smooth muscle cells (PASMCs) and consequent pulmonary vascular remodeling are the crucial pathological features of pulmonary hypertension (PH). Protein methylation has been shown to be critically involved in PASMC proliferation and PH, but the underlying mechanism remains largely unknown. METHODS: PH animal models were generated by treating mice/rats with chronic hypoxia for 4 weeks. SMYD2-vTg mice (vascular smooth muscle cell-specific suppressor of variegation, enhancer of zeste, trithorax and myeloid Nervy DEAF-1 (deformed epidural auto-regulatory factor-1) domain-containing protein 2 transgenic) or wild-type rats and mice treated with LLY-507 (3-cyano-5-{2-[4-[2-(3-methylindol-1-yl)ethyl]piperazin-1-yl]-phenyl}-N-[(3-pyrrolidin-1-yl)propyl]benzamide) were used to investigate the function of SMYD2 (suppressor of variegation, enhancer of zeste, trithorax and myeloid Nervy DEAF-1 domain-containing protein 2) on PH development in vivo. Primary cultured rat PASMCs with SMYD2 knockdown or overexpression were used to explore the effects of SMYD2 on proliferation and to decipher the underlying mechanism. RESULTS: We demonstrated that the expression of the lysine methyltransferase SMYD2 was upregulated in the smooth muscle cells of pulmonary arteries from patients with PH and hypoxia-exposed rats/mice and in the cytoplasm of hypoxia-induced rat PASMCs. More importantly, targeted inhibition of SMYD2 by LLY-507 significantly attenuated hypoxia-induced pulmonary vascular remodeling and PH development in both male and female rats in vivo and reduced rat PASMC hyperproliferation in vitro. In contrast, SMYD2-vTg mice exhibited more severe PH phenotypes and related pathological changes than nontransgenic mice after 4 weeks of chronic hypoxia treatment. Furthermore, SMYD2 overexpression promoted, while SMYD2 knockdown suppressed, the proliferation of rat PASMCs by affecting the cell cycle checkpoint between S and G2 phases. Mechanistically, we revealed that SMYD2 directly interacted with and monomethylated PPARγ (peroxisome proliferator-activated receptor gamma) to inhibit the nuclear translocation and transcriptional activity of PPARγ, which further promoted mitophagy to facilitate PASMC proliferation and PH development. Furthermore, rosiglitazone, a PPARγ agonist, largely abolished the detrimental effects of SMYD2 overexpression on PASMC proliferation and PH. CONCLUSIONS: Our results demonstrated that SMYD2 monomethylates nonhistone PPARγ and inhibits its nuclear translocation and activation to accelerate PASMC proliferation and PH by triggering mitophagy, indicating that targeting SMYD2 or activating PPARγ are potential strategies for the prevention of PH.

Histone acetyltransferase P300 deficiency promotes ferroptosis of vascular smooth muscle cells by activating the HIF-1α/HMOX1 axis.

BACKGROUND: E1A-associated 300-kDa protein (P300), an endogenous histone acetyltransferase, contributes to modifications of the chromatin landscape of genes involved in multiple cardiovascular diseases. Ferroptosis of vascular smooth muscle cells (VSMCs) is a novel pathological mechanism of aortic dissection. However, whether P300 regulates VSMC ferroptosis remains unknown. METHODS: Cystine deprivation (CD) and imidazole ketone erastin (IKE) were used to induce VSMC ferroptosis. Two different knockdown plasmids targeting P300 and A-485 (a specific inhibitor of P300) were used to investigate the function of P300 in the ferroptosis of human aortic smooth muscle cells (HASMCs). Cell counting kit-8, lactate dehydrogenase and flow cytometry with propidium iodide staining were performed to assess the cell viability and death under the treatment of CD and IKE. BODIPY-C11 assay, immunofluorescence staining of 4-hydroxynonenal and malondialdehyde assay were conducted to detect the level of lipid peroxidation. Furthermore, co-immunoprecipitation was utilized to explore the interaction between P300 and HIF-1α, HIF-1α and P53. RESULTS: Compared with normal control, the protein level of P300 was significantly decreased in HASMCs treated with CD and IKE, which was largely nullified by the ferroptosis inhibitor ferrostatin-1 but not by the autophagy inhibitor or apoptosis inhibitor. Knockdown of P300 by short-hairpin RNA or inhibition of P300 activity by A-485 promoted CD- and IKE-induced HASMC ferroptosis, as evidenced by a reduction in cell viability and aggravation of lipid peroxidation of HASMCs. Furthermore, we found that hypoxia-inducible factor-1α (HIF-1α)/heme oxygenase 1 (HMOX1) pathway was responsible for the impacts of P300 on ferroptosis of HASMCs. The results of co-immunoprecipitation demonstrated that P300 and P53 competitively bound HIF-1α to regulate the expression of HMOX1. Under normal conditions, P300 interacted with HIF-1α to inhibit HMOX1 expression, while reduced expression of P300 induced by ferroptosis inducers would favor HIF-1α binding to P53 to trigger HMOX1 overexpression. Furthermore, the aggravated effects of P300 knockdown on HASMC ferroptosis were largely nullified by HIF-1α knockdown or the HIF-1α inhibitor BAY87-2243. CONCLUSION: Thus, our results revealed that P300 deficiency or inactivation facilitated CD- and IKE-induced VSMC ferroptosis by activating the HIF-1α/HMOX1 axis, which may contribute to the development of diseases related to VSMC ferroptosis.

BRD4770 inhibits vascular smooth muscle cell proliferation via SUV39H2, but not EHMT2 to protect against neointima formation.

The behavior of vascular smooth muscle cells (VSMCs) contributes to the formation of neointima. We previously found that EHMT2 suppressed autophagy activation in VSMCs. BRD4770, an inhibitor of EHMT2/G9a, plays a critical role in several kinds of cancers. However, whether and how BRD4770 regulates the behavior of VSMCs remain unknown. In this study, we evaluate the cellular effect of BRD4770 on VSMCs by series of experiments in vivo and ex vivo. We demonstrated that BRD4770 inhibited VSMCs' growth by blockage in G2/M phase in VSMCs. Moreover, our results demonstrated that the inhibition of proliferation was independent on autophagy or EHMT2 suppression which we previous reported. Mechanistically, BRD4770 exhibited an off-target effect from EHMT2 and our further study reveal that the proliferation inhibitory effect by BRD4770 was associated with suppressing on SUV39H2/KTM1B. In vivo, BRD4770 was also verified to rescue VIH. Thus, BRD4770 function as a crucial negative regulator of VSMC proliferation via SUV39H2 and G2/M cell cycle arrest and BRD4770 could be a molecule for the therapy of vascular restenosis.

The interaction between ferroptosis and inflammatory signaling pathways.

Ferroptosis is an iron-dependent regulated cell death driven by excessive lipid peroxidation. Inflammation is one common and effective physiological event that protects against various stimuli to maintain tissue homeostasis. However, the dysregulation of inflammatory responses can cause imbalance of the immune system, cell dysfunction and death. Recent studies have pointed out that activation of inflammation, including the activation of multiple inflammation-related signaling pathways, can lead to ferroptosis. Among the related signal transduction pathways, we focused on five classical inflammatory pathways, namely, the JAK-STAT, NF-κB, inflammasome, cGAS-STING and MAPK signaling pathways, and expounded on their roles in ferroptosis. To date, many agents have shown therapeutic effects on ferroptosis-related diseases by modulating the aforementioned pathways in vivo and in vitro. Moreover, the regulatory effects of these pathways on iron metabolism and lipid peroxidation have been described in detail, contributing to further understanding of the pathophysiological process of ferroptosis. Taken together, targeting these pathways related to inflammation will provide appropriate ways to intervene ferroptosis and diseases.

Methyltransferase-like 3 suppresses phenotypic switching of vascular smooth muscle cells by activating autophagosome formation.

Prevention of neointima formation is the key to improving long-term outcomes after stenting or coronary artery bypass grafting. RNA N6 -methyladenosine (m6 A) methylation has been reported to be involved in the development of various cardiovascular diseases, but whether it has a regulatory effect on neointima formation is unknown. Herein, we revealed that methyltransferase-like 3 (METTL3), the major methyltransferase of m6 A methylation, was downregulated during vascular smooth muscle cell (VSMC) proliferation and neointima formation. Knockdown of METTL3 facilitated, while overexpression of METTL3 suppressed the proliferation of human aortic smooth muscle cells (HASMCs) by arresting HASMCs at G2/M checkpoint and the phosphorylation of CDC2 (p-CDC2) was inactivated by METTL3. On the other hand, the migration and synthetic phenotype of HASMCs were enhanced by METTL3 knockdown, but inhibited by METTL3 overexpression. The protein levels of matrix metalloproteinase 2 (MMP2), MMP7 and MMP9 were reduced, while the expression level of tissue inhibitor of metalloproteinase 3 was increased in HASMCs with METTL3 overexpression. Moreover, METTL3 promoted the autophagosome formation by upregulating the expression of ATG5 (autophagy-related 5) and ATG7. Knockdown of either ATG5 or ATG7 largely reversed the regulatory effects of METTL3 overexpression on phenotypic switching of HASMCs, as evidenced by increased proliferation and migration, and predisposed to synthetic phenotype. These results indicate that METTL3 inhibits the phenotypic switching of VSMCs by positively regulating ATG5-mediated and ATG7-mediated autophagosome formation. Thus, enhancing the level of RNA m6 A or the formation of autophagosomes is the promising strategy to delay neointima formation.

Targeting autophagy in aortic aneurysm and dissection.

Autophagy is a well-conserved biological process that maintains homeostasis. Accumulating evidence has revealed that autophagy plays an important role in various cardiovascular diseases, such as aneurysm, aortic dissection, atherosclerosis, and myocardial ischemia-reperfusion injury. Here, we summarize the current experimental evidence on the function of autophagy and autophagy proteins in aortic aneurysm and dissection (AAD). AAD is a very serious aortic disease, and there are currently no effective drug treatment options. Studies have shown that autophagy is activated during AAD. However, the role of autophagy in AAD is still controversial. For example, knocking out autophagy related 5 (ATG5) or ATG7 to inhibit autophagy and excessive autophagy activation can promote the occurrence of AAD. Recently, multiple studies have demonstrated that rapamycin and metformin, which are autophagy activators, can delay the progression of AAD. Thus, targeting autophagy has the potential to become a new therapeutic strategy for AAD. In addition, we discuss the recent research progress on AAD from the perspective of single-cell RNA sequencing. Moreover, we offer our perspective on current challenges and barriers in this research field.

JIB-04, a histone demethylase Jumonji C domain inhibitor, regulates phenotypic switching of vascular smooth muscle cells.

BACKGROUND: Vascular smooth muscle cell (VSMC) phenotype switching is critical for neointima formation, which is the major cause of restenosis after stenting or coronary artery bypass grafting. However, the epigenetic mechanisms regulating phenotype switching of VSMCs, especially histone methylation, are not well understood. As a main component of histone lysine demethylases, Jumonji demethylases might be involved in VSMC phenotype switching and neointima formation. METHODS AND RESULTS: A mouse carotid injury model and VSMC proliferation model were constructed to investigate the relationship between histone methylation of H3K36 (downstream target molecule of Jumonji demethylase) and neointima formation. We found that the methylation levels of H3K36 negatively correlated with VSMC proliferation and neointima formation. Next, we revealed that JIB-04 (a pan-inhibitor of the Jumonji demethylase superfamily) could increase the methylation levels of H3K36. Furthermore, we found that JIB-04 obviously inhibited HASMC proliferation, and a cell cycle assay showed that JIB-04 caused G2/M phase arrest in HASMCs by inhibiting the phosphorylation of RB and CDC2 and promoting the phosphorylation of CHK1. Moreover, JIB-04 inhibited the expression of MMP2 to suppress the migration of HASMCs and repressed the expression of contraction-related genes. RNA sequencing analysis showed that the biological processes associated with the cell cycle and autophagy were enriched by using Gene Ontology analysis after HASMCs were treated with JIB-04. Furthermore, we demonstrated that JIB-04 impairs autophagic flux by downregulating STX17 and RAB7 expression to inhibit the fusion of autophagosomes and lysosomes. CONCLUSION: JIB-04 suppresses the proliferation, migration, and contractile phenotype of HASMCs by inhibiting autophagic flux, which indicates that JIB-04 is a promising reagent for the treatment of neointima formation.

Integrating Bulk Transcriptome and Single-Cell RNA Sequencing Data Reveals the Landscape of the Immune Microenvironment in Thoracic Aortic Aneurysms.

Thoracic aortic aneurysm (TAA) is a life-threatening cardiovascular disease whose formation is reported to be associated with massive vascular inflammatory responses. To elucidate the roles of immune cell infiltration in the pathogenesis underlying TAA, we utilized multiple TAA datasets (microarray data and scRNA-seq data) and various immune-related algorithms (ssGSEA, CIBERSORT, and Seurat) to reveal the landscapes of the immune microenvironment in TAA. The results exhibited a significant increase in the infiltration of macrophages and T cells, which were mainly responsible for TAA formation among the immune cells. To further reveal the roles of immunocytes in TAA, we inferred the intercellular communications among the identified cells of aortic tissues. Notably, we found that in both normal aortic tissue and TAA tissue, the cells that interact most frequently are macrophages, endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells (VSMCs). Among the cells, macrophages were the most prominent signal senders and receivers in TAA and normal aortic tissue. These findings suggest that macrophages play an important role in both the physiological and pathological conditions of the aorta. The present study provides a comprehensive evaluation of the immune cell composition and reveals the intercellular communication among aortic cells in human TAA tissues. These findings improve our understanding of TAA formation and progression and facilitate the development of effective medications to treat these conditions.

BRD4770 functions as a novel ferroptosis inhibitor to protect against aortic dissection.

Smooth muscle cell (SMC) loss is the characteristic feature in the pathogenesis of aortic dissection (AD), and ferroptosis is a novel iron-dependent regulated cell death driven by the excessive lipid peroxidation accumulation. However, whether targeting ferroptosis is an effective approach for SMC loss and AD treatment remains unclear. Here, we found that the iron level, ferroptosis-related molecules TFR, HOMX1, ferritin and the lipid peroxidation product 4-hydroxynonenal were increased in the aorta of AD. Then, we screened several inhibitors of histone methyltransferases and found that BRD4770 had a protective effect on cystine deprivation-, imidazole ketone erastin- or RSL3-induced ferroptosis of SMCs. The classic ferroptosis pathways, System Xc--GPX4, FSP1-CoQ10 and GCH1-BH4 pathways which were inhibited by ferroptosis inducers, were re-activated by BRD4770 via inhibiting mono-, di- and tri- methylated histone H3 at lysine 9 (H3K9me1/2/3). RNA-sequencing analysis revealed that there was a positive feedback regulation between ferroptosis and inflammatory response, and BRD4770 can reverse the effects of inflammation activation on ferroptosis. More importantly, treatment with BRD4770 attenuated aortic dilation and decreased morbidity and mortality in a ß-Aminopropionitrile monofumarate-induced mouse AD model via inhibiting the inflammatory response, lipid peroxidation and ferroptosis. Taken together, our findings demonstrate that ferroptosis is a novel and critical pathological mechanism that is involved in SMC loss and AD development. BRD4770 is a novel ferroptosis inhibitor and has equivalent protective effect to Ferrostatin-1 at the optimal concentration. Translating insights into the anti-ferroptosis effects of BRD4770 may reveal a potential therapeutic approach for targeting SMC ferroptosis in AD.

Downregulation of Filamin a Expression in the Aorta Is Correlated With Aortic Dissection.

Filamins (FLNs) are actin cross-linking proteins, and as scaffolding proteins, FLNs are closely associated with the stabilization of the cytoskeleton. Nevertheless, the biological importance of FLNs in aortic dissection (AD) has not been well-elucidated. In this study, we first reanalyzed datasets downloaded from the Gene Expression Omnibus (GEO) database, and we found that in addition to the extracellular matrix, the actin cytoskeleton is a key structure associated with AD. Given that FLNs are involved in remodeling the cytoskeleton to affect cellular functions, we measured their expression levels in the aortas of patients with Stanford type A AD (TAAD). Our results showed that the mRNA and protein levels of FLNA were consistently decreased in dissected aortas of both humans and mice, while the FLNB protein level was upregulated despite decreased FLNB mRNA levels, and comparable expression levels of FLNC were observed between groups. Furthermore, the immunohistochemistry results demonstrated that FLNA was highly expressed in smooth muscle cells (SMCs) of aorta in non-AD samples, and downregulated in the medial layer of the dissected aortas of humans and mice. Moreover, we revealed that FOS and JUN, forming a dimeric transcription factor called AP-1 (activating protein-1), were positively correlated with the expression of FLNA in aorta. Either overexpression of FOS or JUN alone, or overexpression of FOS and JUN together, facilitated the expression of FLNA in primary cultured human aortic SMCs. In the present study, we not only detected the expression pattern of FLNs in aortas of humans and mice with or without AD, but we also found that the expression of FLNA in the AD samples was significantly reduced and that AP-1 might regulate the expression of FLNA. Our findings will contribute to the elucidation of the pathological mechanisms of AD and provide potential therapeutic targets for AD.

The Expression Patterns and Roles of Lysyl Oxidases in Aortic Dissection.

Background: Lysyl oxidases (LOXs), including LOX, LOXL1, LOXL2, LOXL3, and LOXL4, catalyze the formation of a cross-link between elastin (ELN) and collagen. Multiple LOX mutations have been shown to be associated with the occurrence of aortic dissection (AD) in humans, and LOX-knockout mice died during the perinatal period due to aortic aneurysm and rupture. However, the expression levels and roles of other LOX members in AD remain unknown. Methods: A total of 33 aorta samples of AD and 15 normal aorta were collected for LOXs mRNA and protein levels detection. We also analyzed the datasets of AD in GEO database through bioinformatics methods. LOXL2 and LOXL3 were knocked down in primary cultured human aortic smooth muscle cells (HASMCs) via lentivirus. Results: Here, we show that the protein levels of LOXL2 and LOXL3 are upregulated, while LOXL4 is downregulated in AD subjects compared with non-AD subjects, but comparable protein levels of LOX and LOXL1 are detected. Knockdown of LOXL2 suppressed MMP2 expression, the phosphorylation of AKT (p-AKT) and S6 (p-S6), but increased the mono-, di-, tri-methylation of H3K4 (H3K4me1/2/3), H3K9me3, and p-P38 levels in HASMCs. These results indicate that LOXL2 is involved in regulation of the extracellular matrix (ECM) in HASMCs. In contrast, LOXL3 knockdown inhibited PCNA and cyclin D1, suppressing HASMC proliferation. Our results suggest that in addition to LOX, LOXL2 and LOXL3 are involved in the pathological process of AD by regulating ECM and the proliferation of HASMCs, respectively. Furthermore, we found that LOXL2 and LOXL4 was inhibited by metformin and losartan in HASMCs, which indicated that LOXL2 and LOXL4 are the potential targets that involved in the therapeutic effects of metformin and losartan on aortic or aneurysm expansion. Conclusions: Thus, differential regulation of LOXs might be a novel strategy to prevent or treat AD.

Histone methyltransferase SMYD2: ubiquitous regulator of disease.

SET (Suppressor of variegation, Enhancer of Zeste, Trithorax) and MYND (Myeloid-Nervy-DEAF1) domain-containing protein 2 (SMYD2) is a protein methyltransferase that methylates histone H3 at lysine 4 (H3K4) or lysine 36 (H3K36) and diverse nonhistone proteins. SMYD2 activity is required for normal organismal development and the regulation of a series of pathophysiological processes. Since aberrant SMYD2 expression and its dysfunction are often closely related to multiple diseases, SMYD2 is a promising candidate for the treatment of these diseases, such as cardiovascular disease and cancer. Here, we present an overview of the complex biology of SMYD2 and its family members and their context-dependent nature. Then, we discuss the discovery, structure, inhibitors, roles, and molecular mechanisms of SMYD2 in distinct diseases, with a focus on cardiovascular disease and cancer.

Disturbed energy and amino acid metabolism with their diagnostic potential in mitral valve disease revealed by untargeted plasma metabolic profiling.

INTRODUCTION: Mitral valve disease (MVD), including mitral valve regurgitation (MR) and mitral valve stenosis (MS), is a chronic and progressive cardiac malady. However, the metabolic alterations in MVD is not well-understood till now. The current gold standard diagnostic test, transthoracic echocardiography, has limitations on high-throughput measurement and lacks molecular information for early diagnosis of the disease. OBJECTIVE: The present study aimed to investigate the biochemical alterations and to explore their diagnostic potential for MVD. METHODS: Plasma metabolic profile derangements and their diagnostic potential were non-invasively explored in 34 MR and 20 MS patients against their corresponding controls, using high-throughput NMR-based untargeted metabolomics. RESULTS: Eighteen differential metabolites were identified for MR and MS patients respectively, on the basis of multivariate and univariate data analysis, which were mainly involved in energy metabolism, amino acid metabolism, calcium metabolism and inflammation. These differential metabolites, notably the significantly down-regulated formate and lactate, showed high diagnostic potential for MVD by using Spearman's rank-order correlation analysis and ROC analysis. CONCLUSIONS: To the best of our knowledge, the present study is the first one that explores the metabolic derangements and their diagnostic values in MVD patients using metabolomics. The findings indicated that metabolic disturbance occurred in MVD patients, with plasma formate and lactate emerged as important candidate biomarkers for MVD.

HDAC6 is associated with the formation of aortic dissection in human.

BACKGROUND: The pathological features of aortic dissection (AD) include vascular smooth muscle cell (VSMC) loss, elastic fiber fraction, and inflammatory responses in the aorta. However, little is known about the post-translational modification mechanisms responsible for these biological processes. METHODS: A total of 72 aorta samples, used for protein detection, were collected from 36 coronary artery disease (CAD, served as the control) patients and 36 type A AD (TAAD) patients. Chromatin immunoprecipitation (ChIP)-PCR was used to identify the genes regulated by H3K23ac, and tubastatin A, an inhibitor of HDAC6, was utilized to clarify the downstream mechanisms regulated by HDAC6. RESULTS: We found that the protein level of histone deacetylase HDAC6 was reduced in the aortas of patients suffering from TAAD and that the protein levels of H4K12ac, and H3K23ac significantly increased, while H3K18ac, H4K8ac, and H4K5ac dramatically decreased when compared with CAD patients. Although H3K23ac, H3K18ac, and H4K8ac increased in the human VSMCs after treatment with the HDAC6 inhibitor tubastatin A, only H3K23ac showed the same results in human tissues. Notably, the results of ChIP-PCR demonstrated that H3K23ac was enriched in extracellular matrix (ECM)-related genes, including Col1A2, Col3A1, CTGF, POSTN, MMP2, TIMP2, and ACTA2, in the aortic samples of TAAD patients. In addition, our results showed that HDAC6 regulates H4K20me2 and p-MEK1/2 in the pathological process of TAAD. CONCLUSIONS: These results indicate that HDAC6 is involved in human TAAD formation by regulating H3K23ac, H4K20me2 and p-MEK1/2, thus, providing a strategy for the treatment of TAAD by targeting protein post-translational modifications (PTMs), chiefly histone PTMs.

EZH2 inhibits autophagic cell death of aortic vascular smooth muscle cells to affect aortic dissection.

Enhancer of zeste homolog 2 (EZH2), a methyltransferase that di- and tri-methylates lysine-27 of histone H3, largely functions as a transcriptional repressor, and plays a critical role in various kinds of cancers. Here we report a novel function of EZH2 in regulating autophagic cell death (ACD) of vascular smooth muscle cells (VSMCs) that affect aortic dissection (AD). Inhibition of EZH2 activity by UNC1999 or knockdown EZH2 resulted in VSMC loss, while overexpression of EZH2 facilitated VSMC growth, and these effects of EZH2 on VSMCs were independent of proliferation and apoptosis. Interestingly, more autophagic vacuoles and increased LC3II protein levels were identified in VSMCs with EZH2 inhibition or deficiency. Moreover, when compared with counterparts, chloroquine alone, or chloroquine with rapamycin treatment led to more LC3II accumulation in EZH2 inhibited or knockdown VSMCs, which indicated that EZH2 negatively regulated autophagosome formation. In conjunction to this, ATG5 and ATG7 protein levels were remarkably increased in EZH2 inhibited or deficient VSMCs, and ATG5 or ATG7 knockdown virtually rescued VSMC loss induced by EZH2 inhibition or knockdown. In addition, we found that the MEK-ERK1/2 signaling pathway, but not AMPKα, mTOR, or AKT pathway, is responsible for the impact of EZH2 on ACD of VSMCs. Additionally, the adverse effects of EZH2 inhibition or knockdown on VSMCs were largely reversed by PD98059, an inhibitor of MEK1. More importantly, decreased EZH2 expression levels in the aortic wall of patients with AD indicated its contribution to VSMC loss and AD occurrence. Overall, these findings revealed that EZH2 affects ACD of VSMCs and the pathologic process of AD via regulating ATG5 and ATG7 expression and MEK-ERK1/2 signaling. Our hitherto unrecognized findings indicate that EZH2 activation has therapeutic or preventive potential for AD.

Short-term MyD88 inhibition ameliorates cardiac graft rejection and promotes donor-specific hyporesponsiveness of skin grafts in mice.

Recognition of evolutionarily conserved ligands by Toll-like receptors (TLRs) triggers signaling cascades in innate immune cells to amplify adaptive immune responses. Nearly all TLRs require MyD88 to transduce downstream signaling. MyD88 deficiency has been shown to promote the allograft acceptance in mice. However, direct evidence for therapeutic potential of MyD88 inhibitors remains lacking. Herein, we used a MyD88 inhibitor, namely ST2825, to explore its therapeutic potential and mechanisms in fully allogeneic skin and heart transplant models. Phenotypic maturation of dendritic cells stimulated by TLR ligands was alleviated by ST2825 in parallel with reduced T-cell proliferation in vitro. A short-course treatment with ST2825 significantly prolonged cardiac graft survival (mean survival time = 18.5 ± 0.92 days vs. 7.25 ± 0.46 days). ST2825-treated group had significantly reduced proinflammatory cytokines in allografts compared with control group. ST2825 combined with anti-CD154 induced long-term skin allograft acceptance in about one-third of recipients (>100 days). 'Skin-tolerant' recipients showed attenuated donor-specific IFN-γ responses, intact IL-4 responses, and compromised alloantibody responses. We conclude that MyD88 inhibitor ST2825 attenuates acute cardiac rejection and promotes donor-specific hyporesponsiveness in stringent skin transplant models. The direct evidence suggests that pharmacological inhibition of MyD88 hold promising potential for transplant rejection.

TIGIT negatively regulates inflammation by altering macrophage phenotype.

Macrophages function as an essential component of innate immune system, contributing to both the initiation and appropriate resolution of inflammation. The exposure of macrophages to the microbial products, such as lipopolysaccharide (LPS), can strongly shift the balance between tissue homeostasis and inflammation in favor of causing systemic damage, in which macrophage M1 polarization play important roles. Strategies aiming at restoring the balance of macrophage polarization remain to be further explored. Herein, we have demonstrated that poliovirus receptor (PVR), the receptor of TIGIT, was dramatically upregulated on the surface of mouse peritoneal macrophages when exposed to LPS. TIGIT-Fc fusion protein not only inhibited the macrophage activation, but also skewed M1/M2 balance toward an anti-inflammatory profile, especially enhanced the secretion of IL-10. The activation of TIGIT/PVR pathway in macrophages correlated with increased nuclear translocation of c-Maf, which promotes IL-10 transcription. Treatment with fibroblasts stably secreting TIGIT-Fc fusion protein significantly reversed the lethal and sublethal endotoxic shock, which facilitated peritoneal macrophages to switch towards anti-inflammatory M2 cytokine profiles. These findings highlight a novel role of the TIGIT/PVR pathway in macrophage M2 polarization and suggest that TIGIT may have the potential to optimize the treatment of macrophage-involved inflammatory diseases.

A new marine bacterial laccase with chloride-enhancing, alkaline-dependent activity and dye decolorization ability.

A bacterial laccase gene designated as lac21 was screened from a marine microbial metagenomic library of the South China Sea based on sequence screening strategy. The protein encoded by lac21 shared less than 40% sequence identities with all of the laccases found. Lac21, which was recombinantly expressed in Escherichia coli, showed high activity toward syringaldazine at an optimum pH of 7.5 and temperature of 45°C. Lac21 was stable at pH values ranging from 5.5 to 9.0 and temperatures lower than 40°C. Interestingly, chloride enhanced the laccase activity, with concomitant increase in substrate affinity. Furthermore, Lac21 has high decolorization capability toward azo dyes in the absence of redox mediators, with 80% of Reactive Deep Blue M-2GE (50mg/L) being decolorized by 15U/L enzyme after 24h incubation at 20°C. These unusual properties demonstrate that the new bacterial laccase Lac21 has potentials in specific industrial or environmental applications.