Dynamic autophagic activity affected the development of thoracic aortic dissection by regulating functional properties of smooth muscle cells

Enhanced expression of miR-20a driven by nanog exacerbated the degradation of extracellular matrix in thoracic aortic dissection

Thoracic aortic dissection (TAD) is a life-threatening vascular disease manifested as intramural bleeding in the medial layers of the thoracic aorta. The key histopathologic feature of TAD is medial degeneration, characterized by depletion of vascular smooth muscle cells (VSMCs) and degradation of extracellular matrix (ECM). MicroRNA, as essential epigenetic regulators, can inhibit the protein expression of target genes without modifying the sequences. This study aimed to elucidate the role and underlying mechanism of miR-20a, a member of the miR-17-92 cluster, in regulating ECM degradation during the pathogenesis of TAD. The expression of the miR-17-92 cluster was significantly increased in synthetic VSMCs derived from TAD lesions compared to contractile VSMCs isolated from normal thoracic aortas. Notably, the expression of miR-20a was increased in VSMCs in response to serum exposure and various stimuli. In TAD lesions, the expression of miR-20a was significantly negatively correlated with that of elastin. Elevated expression of miR-20a was also observed in thoracic aortas of TAD mice induced by β-aminopropionitrile fumarate and angiotensin II. Overexpression of miR-20a via mimic transfection enhanced the growth and invasive capabilities of VSMCs, with no significant impact on their migratory activity or the expression of phenotypic markers (α-SMA, SM22, and OPN). Silencing of miR-20a with inhibitor transfection mitigated the hyperactivation of MMP2 in VSMCs stimulated by PDGF-bb, as evidenced by reduced levels of active-MMP2 and increased levels of pro-MMP2. Subsequently, TIMP2 was identified as a novel target gene of miR-20a. The role of miR-20a in promoting the activation of MMP2 was mediated by the suppression of TIMP2 expression in VSMCs. In addition, the elevated expression of miR-20a was found to be directly driven by Nanog in VSMCs. Collectively, these findings indicate that miR-20a plays a crucial role in maintaining the homeostasis of the thoracic aortic wall during TAD pathogenesis and may represent a potential therapeutic target for TAD.

Role of EZH2-mediated epigenetic modification on vascular smooth muscle in cardiovascular diseases: A mini-review

Vascular smooth muscle cells (VSMCs) are integral to the pathophysiology of cardiovascular diseases (CVDs). Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, plays a crucial role in epigenetic regulation of VSMCs gene expression. Emerging researches suggest that EZH2 has a dual role in VSMCs, contingent on the pathological context of specific CVDs. This mini-review synthesizes the current knowledge on the mechanisms by which EZH2 regulates VSMC proliferation, migration and survival in the context of CVDs. The goal is to underscore the potential of EZH2 as a therapeutic target for CVDs treatment. Modulating EZH2 and its associated epigenetic pathways in VSMCs could potentially ameliorate vascular remodeling, a key factor in the progression of many CVDs. Despite the promising outlook, further investigation is warranted to elucidate the epigenetic mechanisms mediated by EZH2 in VSMCs, which may pave the way for novel epigenetic therapies for conditions such as atherosclerosis and hypertension.

S-adenosylmethionine attenuates angiotensin II-induced aortic dissection formation by inhibiting vascular smooth muscle cell phenotypic switch and autophagy

It is well known that aortic dissection (AD) is a very aggressive class of vascular diseases. S-adenosylmethionine (SAM) is an autophagy inhibitor with anti-inflammatory and anti-oxidative stress effects; however, the role of SAM in AD is unknown. In this study, we constructed an animal model of AD using subcutaneous minipump continuous infusion of AngII-induced ApoE-/-mice and a cytopathic model using AngII-induced primary vascular smooth muscle cells (VSMCs) to investigate the possible role of SAM in AD. The results showed that mice in the AngII + SAM group had significantly lower AD incidence, significantly prolonged survival, and reduced vascular elastic fiber disruption compared with mice in the AngII group. In addition, SAM significantly inhibited autophagy in vivo and in vitro. Meanwhile, SAM also inhibited the cellular phenotypic switch, mainly by up regulating the expression levels of contractile marker proteins [α-smooth muscle actin (α-SMA) and smooth muscle 22α (SM22α)] and down regulating the expression levels of synthetic marker proteins [osteoblast protein (OPN), matrix metalloproteinase-2 (MMP2), and matrix metalloproteinase-9 (MMP9)]. Molecularly, SAM inhibited AD formation mainly by activating the PI3K/AKT/mTOR signaling pathway. Using a PI3K inhibitor (LY294002) significantly reversed the protective effect of SAM in AngII-induced mice and VSMCs.Our study demonstrates the protective effect of SAM on mice under AngII-induced AD for the first time. SAM prevented AD formation mainly by inhibiting cellular phenotypic switch and autophagy, and activation of the PI3K/AKT/mTOR signaling pathway is a possible molecular mechanism. Thus, SAM may be a novel strategy for the treatment of AD.

HIF-1α Contributes to Hypoxia-induced VSMC Proliferation and Migration by Regulating Autophagy in Type A Aortic Dissection

Type A aortic dissection (AD) is a catastrophic cardiovascular disease. Hypoxia-inducible factor-1α (HIF-1α) and autophagy are reported to be upregulated in the AD specimens. However, the interaction between HIF-1α and autophagy in the pathogenesis of AD remains to be explored. HIF-1α and LC3 levels are evaluated in 10 AD and 10 normal aortic specimens. MDC staining, autophagic vacuoles, and autophagic flux are detected in human aortic smooth muscle cells (HASMCs) under hypoxia treatment. CCK-8, transwell, and wound healing assay are used to identify proliferation and migration under hypoxia treatment. Furthermore, 3-MA is used to inhibit autophagy in hypoxia-treated HASMCs. This study reveals that AD tissues highly express HIF-1α and the LC3. Autophagy is induced under hypoxia in a time-dependent manner, and autophagy is positively related to HIF-1α in HASMCs. Moreover, the proliferation and migration of HASMCs are enhanced by hypoxia, whereas the knockdown of HIF-1α attenuates this effect. Additionally, inhibiting autophagy with 3-MA ameliorates hypoxia-induced proliferation and migration of HASMCs. In summary, the above results indicate that HIF-1α facilitates HASMC proliferation and migration by upregulating autophagy in a hypoxic microenvironment. Thus, inhibition of autophagy may be a novel therapeutic target for the prevention and treatment of AD.

Unbalanced Redox With Autophagy in Cardiovascular Disease

Precise redox balance is essential for the optimum health and physiological function of the human body. Furthermore, an unbalanced redox state is widely believed to be part of numerous diseases, ultimately resulting in death. In this review, we discuss the relationship between redox balance and cardiovascular disease (CVD). In various animal models, excessive oxidative stress has been associated with increased atherosclerotic plaque formation, which is linked to the inflammation status of several cell types. However, various antioxidants can defend against reactive oxidative stress, which is associated with an increased risk of CVD and mortality. The different cardiovascular effects of these antioxidants are presumably due to alterations in the multiple pathways that have been mechanistically linked to accelerated atherosclerotic plaque formation, macrophage activation, and endothelial dysfunction in animal models of CVD, as well as in in vitro cell culture systems. Autophagy is a regulated cell survival mechanism that removes dysfunctional or damaged cellular organelles and recycles the nutrients for the generation of energy. Furthermore, in response to atherogenic stress, such as the generation of reactive oxygen species, oxidized lipids, and inflammatory signaling between cells, autophagy protects against plaque formation. In this review, we characterize the broad spectrum of oxidative stress that influences CVD, summarize the role of autophagy in the content of redox balance-associated pathways in atherosclerosis, and discuss potential therapeutic approaches to target CVD by stimulating autophagy.

Tandem mass tag-based quantitative proteomic analysis identification of succinylation related proteins in pathogenesis of thoracic aortic aneurysm and aortic dissection

Background

Thoracic aortic aneurysm and dissection (TAAD) are devastating cardiovascular diseases with a high rate of disability and mortality. Lysine succinylation, a newly found post-translational modification, has been reported to play an important role in cardiovascular diseases. However, how succinylation modification influences TAAD remains obscure.

Methods

Ascending aortic tissues were obtained from patients with thoracic aortic aneurysm (TAA, n = 6), thoracic aortic dissection (TAD) with pre-existing aortic aneurysm (n = 6), and healthy subjects (n = 6). Global lysine succinylation level was analyzed by Western blotting. The differentially expressed proteins (DEPs) were analyzed by tandem mass tag (TMT) labeling and mass spectrometry. Succinylation-related proteins selected from the literature review and AmiGO database were set as a reference inventory for further analysis. Then, the pathological aortic sections were chosen to verify the proteomic results by Western blotting and qRT-PCR.

Results

The level of global lysine succinylation significantly increased in TAA and TAD patients compared with healthy subjects. Of all proteins identified by proteomic analysis, 197 common DEPs were screened both in TAA and TAD group compared with the control group, of which 93 proteins were significantly upregulated while 104 were downregulated. Among these 197 DEPs, OXCT1 overlapped with the succinylation-related proteins and was selected as the target protein involved in thoracic aortic pathogenesis. OXCT1 was further verified by Western blotting and qRT-PCR, and the results showed that OXCT1 in TAA and TAD patients was significantly lower than that in healthy donors (p < 0.001), which was consistent with the proteomic results.

Conclusions

OXCT1 represents novel biomarkers for lysine succinylation of TAAD and might be a therapeutic target in the future.

Myocardin/microRNA-30a/Beclin1 signaling controls the phenotypic modulation of vascular smooth muscle cells by regulating autophagy

Upon vascular injury, vascular smooth muscle cells (VSMCs) change from a contractile phenotype to a synthetic phenotype, thereby leading to atherogenesis and arterial restenosis. Myocardin (MYOCD) is essential for maintaining the contractile phenotype of VSMCs. Deletion of MYOCD in VSMCs triggers autophagy. However, the molecular mechanism underlying the effect of MYOCD on autophagy is not clear. In this study, knockdown of MYOCD in human aortic VSMCs (HA-VSMCs) triggered autophagy and diminished the expression of SMC contractile proteins. Inhibition of autophagy in MYOCD-knockdown cells restored the expression of contractile proteins. MYOCD activated the transcription of miR-30a by binding to the CArG box present in its promoter, as confirmed by luciferase reporter and chromatin immune coprecipitation assays, while miR-30a decreased the expression of autophagy protein-6 (ATG6, also known as beclin1) by targeting its 3′UTR. Restoring the expression of miR-30a in MYOCD-knockdown cells upregulated the levels of contractile proteins. Treatment of VSMCs with platelet-derived growth factor type BB (PDGF-BB) resulted in the transformation of VSMCs to a proliferative phenotype. A low level of miR-30a was observed in PDGF-BB-treated HA-VSMCs, and re-expression of miR-30a led to a decrease in proliferative marker expression. Furthermore, using a wire injury mouse model, we found that miR-30a expression was significantly downregulated in the arterial tissues of mice and that restoration of miR-30a expression at the injured site abolished neointimal formation. Herein, MYOCD could inhibit autophagy by activating the transcription of miR-30a and that miR-30a-mediated autophagy defects could inhibit intimal hyperplasia in a carotid arterial injury model.

DAPK1 may be a potential biomarker for arterial aneurysm in clinical treatment and activated inflammation levels in arterial aneurysm through NLRP3 inflammasome by Beclin1

BACKGROUND

Death-associated protein kinase (DAPK1) is one of the positive regulators of apoptosis, and it is widely involved in apoptosis induced by multiple pathways. We examined that the function of DAPK1 in Clinical treatment of arterial aneurysm and its underlying mechanisms. Arterial aneurysm is a common cerebrovascular disease with high disability and fatality rate.

OBJECTIVES

Male C57BL/6 mice or DAPK1-/- mice were injected with 50 mg/kg pentobarbital sodium and then were injected with angiotensin II (AngII) infusion for vivo model. hASMCs (Human artery smooth muscle cell) were treated with murine recombinant IL-6 (20  ng ml-1; Cell Signaling) for vitro model.

RESULTS

DAPK1 gene, mRNA expression, and protein expression were induced in mice of arterial aneurysm. DAPK1 mRNA expression was increased and Area Under Curve was 0.9075 in patients with arterial aneurysm. Knockout of DAPK1 decreased inflammation and vascular injury in mice model of arterial aneurysm. Beclin1/NLRP3 (NACHT, LRR, and PYD domains-containing protein 3) signal pathway is a critical downstream effector of DAPK1 by TAP production. The regulation of Beclin1 participated in the effects of DAPK1 on inflammation of arterial aneurysm by ATP-dependent NLRP3 inflammasome. The regulation of NLRP3 participated in the effects of DAPK1 on inflammation of arterial aneurysm.

CONCLUSION

Collectively, our data indicated that DAPK1 may be a potential biomarker for arterial aneurysm in clinical treatment and activated inflammation levels in arterial aneurysm through NLRP3 inflammasome by Beclin1. DAPK1 might be a key pathogenic event underlying excess inflammation of arterial aneurysm.

OCT4 regulated neointimal formation in injured mouse arteries by matrix metalloproteinase 2-mediated smooth muscle cells proliferation and migration

The excessive proliferation and migration of vascular smooth muscle cells (VSMCs) play vital roles in neointimal hyperplasia and vascular restenosis. In the present study, we aimed to investigate the function and mechanism of octamer-binding transcription factor 4 (OCT4, a key transcription factor for maintaining stem cells in de-differentiated state) on neointima formation in response to vascular injury. Quantitative reverse-transcription polymerase chain reaction and western blot results displayed a significant increase of OCT4 levels in injured carotid arteries. Immunohistochemistry and immunofluorescence assays confirmed that the increased OCT4 expression was primarily localized in α-SMA-positive VSMCs from neointima, and colocalized with PCNA in the nuclei of VSMCs. Adenovirus-mediated OCT4 overexpression in injured carotid arteries exacerbated intimal thickening, while OCT4 knockdown significantly inhibited intimal thickening. In-vitro experiments confirmed that the increased OCT4 expression in VMSCs could be induced by platelet-derived growth factor-BB (PDGF-BB) in a time-dependent manner. Overexpression of OCT4 greatly promoted VSMCs proliferation and migration, while OCT4 knockdown significantly retarded the PDGF-BB-induced excessive proliferation and migration of VSMCs. Bioinformatics analysis, dual-luciferase reporter assay, and chromatin immunoprecipitation assay confirmed that OCT4 could upregulate matrix metalloproteinases 2 (MMP2) expression through promoting its transcription. Moreover, knockdown of MMP2 significantly attenuated OCT4-mediated VSMCs proliferation and migration. These results indicated that OCT4 facilitated neointimal formation in response to vascular injury by MMP2-mediated VSMCs proliferation and migration, and targeting OCT4 in VSMCs might be a novel therapeutic strategy for vascular restenosis.

All-Trans Retinoic Acid Prevented Vein Grafts Stenosis by Inhibiting Rb-E2F Mediated Cell Cycle Progression and KLF5-RARα Interaction in Human Vein Smooth Muscle Cells

PURPOSE

Vein graft failure (VGF) is an important limitation for coronary artery bypass graft (CABG) surgery. Inhibition of the excessive proliferation and migration of venous smooth muscle cells (SMCs) is an effective strategy to alleviate VGF during the CABG perioperative period. In the present study, we aimed to explore the role and potential mechanism of all-trans retinoic acid (ATRA) on preventing vein grafts stenosis.

METHODS

The autogenous vein grafts model was established in the right jugular artery of rabbits. Immunohistochemistry staining and western blot assays were used to detected the protein expression, while real-time PCR assay was applied for mRNAs expression detection. The interaction between proteins was identified by co-immunoprecipitation assay. The Cell Counting Kit-8 and wound-healing assays were used to investigate the role of ATRA on human umbilical vein smooth muscle cells (HUVSMCs) function. Cell cycle progression was identified by flow cytometry assay.

RESULTS

Vein graft stenosis and SMCs hyperproliferation were confirmed in vein grafts by histological and Ki-67 immunohistochemistry assays. Treatment of ATRA (10 mg/kg/day) significantly mitigated the stenosis extent of vein grafts, demonstrated by the decreased thickness of intima-media, and decreased Ki-67 expression. ATRA could repress the PDGF-bb-induced excessive proliferation and migration of HUVSMCs, which was mediated by Rb-E2F dependent cell cycle inhibition. Meanwhile, ATRA could reduce the interaction between KLF5 and RARα, thereby inhibiting the function of cis-elements of KLF5. KLF5-induced inducible nitric oxide synthase (iNOS) expression activation could be significantly inhibited by ATRA.

CONCLUSIONS

These results suggested that ATRA treatment may represent an effective prevention and therapy avenue for VGF.

Induction of thoracic aortic dissection: a mini-review of β-aminopropionitrile-related mouse models

Thoracic aortic dissection (TAD) is one of the most lethal aortic diseases due to its acute onset, rapid progress, and high rate of aortic rupture. The pathogenesis of TAD is not completely understood. In this mini-review, we introduce three emerging experimental mouse TAD models using β-aminopropionitrile (BAPN) alone, BAPN for a prolonged duration (four weeks) and then with added infusion of angiotensin II (AngII), or co-administration of BAPN and AngII chronically. We aim to provide insights into appropriate application of these three mouse models, thereby enhancing the understanding of the molecular mechanisms of TAD.

Role of autophagy in aneurysm and dissection of the ascending aorta

Maintenance of physiologically balanced levels of autophagy is crucial for cellular homeostasis and in the normal vessel wall, balanced autophagy can be considered a cytoprotective mechanism that preserves endothelial function and prevents cardiovascular disease. Recent studies pointed out the importance of the modulation of the autophagic flux in the pathogenesis of aortic dissection and aneurysms of the ascending aorta. Notably, shear stress (and its receptor p62), IL-6, Rab7 and Atg5/IRE1α pathways of autophagy may be considered the novel super-selective therapeutic target for the preventive and postoperative treatment of aortic aneurysm and aortic dissection. This review intends to summarize current evidences in this field trying to enlighten new avenues for future researches.

Inhibition of HIF1A-AS1 promoted starvation-induced hepatocellular carcinoma cell apoptosis by reducing HIF-1α/mTOR-mediated autophagy

BACKGROUND

Hepatocellular carcinoma (HCC) is still a major health burden in China considering its high incidence and mortality. Long non-coding RNAs (lncRNAs) were found playing vital roles in tumor progression, suggesting a new way of diagnosis and prognosis prediction, or treatment of HCC. This study was designed to investigate the role of HIF1A-AS1 during the progression of HCC and to explore its related mechanisms.

METHODS

The expression of HIF1A-AS1 was detected in 50 paired carcinoma tissues and adjacent normal tissues by quantitative real-time PCR assay. HCC cell apoptosis was induced by nutrient-deficient culture medium and detected by Cell Counting Kit-8 and flow cytometer assays. HIF1A-AS1 inhibition in HCC cells was accomplished by small interfering RNA transfection.

RESULTS

HIF1A-AS1 was overexpressed in HCC tissues and was associated with tumor size, TNM stage, and lymph node metastasis. Compared with the low HIF1A-AS1 group, the high HIF1A-AS1 group had a shorter overall survival and a worse disease-free survival. HIF1A-AS1 expression was significantly higher in HCC cell lines (7721 and Huh7) than that in normal hepatocyte cell line L02 under normal culture condition. However, under nutrient-deficient condition, HIF1A-AS1 expression was significantly increased in both HCC and normal hepatocyte cell lines and was increased with the prolongation of nutrient-free culture. Inhibition of HIF1A-AS1 promoted starvation-induced HCC cell apoptosis. Furthermore, inhibition of HIF1A-AS1 could also reduce starvation-induced HCC cell autophagy. The expression of HIF-1α and phosphorylated mTOR was significantly decreased in HCC cells after HIF1A-AS1 inhibition.

CONCLUSIONS

HIF1A-AS1, overexpressed in HCC and associated with HCC prognosis, could regulate starvation-induced HCC cell apoptosis by reducing HIF-1α/mTOR-mediated autophagy, promoting HCC cell progression.

Therapeutic Effect of Rapamycin on Aortic Dissection in Mice

Aortic dissection (AD) is a serious clinical condition that is unpredictable and frequently results in fatal outcome. Although rapamycin, an inhibitor of mechanistic target of rapamycin (mTOR), has been reported to be effective in preventing aortopathies in mouse models, its mode of action has yet to be clarified. A mouse AD model that was created by the simultaneous administration of β-aminopropionitrile (BAPN) and angiotensin II (AngII) for 14 days. Rapamycin treatment was started either at day 1 or at day 7 of BAPN+AngII challenge, and continued throughout the observational period. Rapamycin was effective both in preventing AD development and in suppressing AD progression. On the other hand, gefitinib, an inhibitor of growth factor signaling, did not show such a beneficial effect, even though both rapamycin and gefitinib suppressed cell cycle activation in AD. Rapamycin suppressed cell cycle-related genes and induced muscle development-related genes in an AD-related gene expression network without a major impact on inflammation-related genes. Rapamycin augmented the activation of Akt1, Akt2, and Stat3, and maintained the contractile phenotype of aortic smooth muscle cells. These findings indicate that rapamycin was effective both in preventing the development and in suppressing the progression of AD, indicating the importance of the mTOR pathway in AD pathogenesis.

GAA compound heterozygous mutations associated with autophagic impairment cause cerebral infarction in Pompe disease

Clinical manifestations of the late-onset adult Pompe disease (glycogen storage disease type II) are heterogeneous. To identify genetic defects of a special patient population with cerebrovascular involvement as the main symptom, we performed whole-genome sequencing (WGS) analysis on a consanguineous Chinese family of total eight members including two Pompe siblings both had cerebral infarction. Two novel compound heterozygous variants were found in GAA gene: c.2238G>C in exon 16 and c.1388_1406del19 in exon 9 in the two patients. We verified the function of the two mutations in leading to defects in GAA protein expression and enzyme activity that are associated with autophagic impairment. We further performed a gut microbiome metagenomics analysis, found that the child’s gut microbiome metagenome is very similar to his mother. Our finding enriches the gene mutation spectrum of Pompe disease, and identified the association of the two new mutations with autophagy impairment. Our data also indicates that gut microbiome could be shared within Pompe patient and cohabiting family members, and the abnormal microbiome may affect the blood biochemical index. Our study also highlights the importance of deep DNA sequencing in potential clinical applications.

EHMT2/G9a Inhibits Aortic Smooth Muscle Cell Death by Suppressing Autophagy Activation

Although EHMT2 (also known as G9a) plays a critical role in several kinds of cancers and cardiac remodeling, its function in vascular smooth muscle cells (VSMCs) remains unknown. In the present study, we revealed a novel function of EHMT2 in regulating autophagic cell death (ACD) of VSMC. Inhibition of EHMT2 by BIX01294 or knockdown of EHMT2 resulted in reduced VSMC numbers which were independent of proliferation and apoptosis. Interestingly, EHMT2 protein levels were significantly decreased in VSMCs treated with autophagic inducers. Moreover, more autophagic vacuoles and accumulated LC3II were detected in VSMCs treated with BIX01294 or lenti-shEHMT2 than their counterparts. Furthermore, we found that EHMT2 inhibited the ACD of VSMCs by suppressing autophagosome formation. Mechanistically, the pro-autophagic effect elicited by EHMT2 inhibition was associated with SQSTM1 and BECN1 overexpression. Moreover, these detrimental effects were largely nullified by SQSTM1 or BECN1 knockdown. More importantly, similar results were observed in primary human aortic VSMCs. Overall, these findings suggest that EHMT2 functions as a crucial negative regulator of ACD via decreasing SQSTM1 or BECN1 expression and that EHMT2 could be a potent therapeutic target for cardiovascular diseases (e.g., aortic dissection).

miR-27a regulates vascular remodeling by targeting endothelial cells' apoptosis and interaction with vascular smooth muscle cells in aortic dissection

Rationale: Aortic dissection (AD) is caused by functional disorder of cells in the aortic wall, which is largely attributed to vascular remodeling. Therapeutic strategies for AD remain limited due to our incomplete understanding of the role of endothelial cells (ECs) in AD pathogenesis. This study aimed to identify the regulatory role of miR-27a in AD and provide a mechanistic basis for a non-invasive treatment of AD.

Methods: We harvested aortas from normal and AD patients to explore the expression of miR-27a. In vitro and in vivo assays were preformed to explore the biological effects of differential expression of miR-27a in ECs and its regulatory effect on AD.

Results: MiR-27a was lower in intima of AD samples than in healthy individuals. Downregulation of miR-27a in EC was due to up-regulated expression of fas-associated protein with death domain (FADD) and the activation of apoptosis pathway, which led to apoptosis of ECs. Migration of vascular smooth muscle cells was promoted by EC after downregulation of miR-27a due to enhancement of growth/differentiation factor 8 (GDF8) and repression of matrix metalloproteinase-20 (MMP20) in the co-culture system supernatants. Increase in FADD and apoptosis of ECs to induce AD was shown using mouse models of AD in which miR-27a was stably knocked-down by antagomir. Up-regulation of miR-27a by agomir led to a protective effect on AD.

Conclusion: Treatment with miR-27a activator that targets apoptosis of ECs strongly diminished occurrence of AD, providing a new strategy for this disease.

Microarray analysis and functional characterization revealed NEDD4-mediated cardiomyocyte autophagy induced by angiotensin II

Autophagy is a highly regulated intracellular process to maintain cellular homeostasis by degrading damaged proteins and organelles. Dysregulation of autophagic activity in cardiomyocytes is implicated in various heart diseases. However, the underlying mechanisms of cardiomyocyte autophagy are not yet known. In this study, the enhanced cardiomyocyte autophagy was induced by angiotensin II (0.1 μmol/L), demonstrated by the increase of double-membraned autophagosomes, BECN1 expression, and the conversion of LC3-I to LC3-II. Microarray assay showed that a total of 197 genes were differentially expressed in angiotensin II-treated cardiomyocytes, including 22 upregulated and 175 downregulated. Gene ontology functional enrichment analysis showed that nearly 50% of differentially expressed genes were related to metabolism and energy maintenance in biological process. Pathway analysis showed that most frequently represented pathways were involved in metabolism and the citric acid cycle and respiratory electron transport. Based on KEGG database, 10 differentially expressed genes were found to be involved in autophagic signaling pathways. The hub genes with high degree were predicted to regulate cardiomyocyte autophagy activity by PPI network analysis. NEDD4, the top focus hub gene, showed a clear time-dependent increased expression pattern in cardiomyocytes during angiotensin II treatment. Moreover, inhibition of NEDD4 could significantly reduce cardiomyocyte autophagy induced by angiotensin II. In summary, the cardiomyocyte autophagy-related genes were screened by microarray assay combining with bioinformatics analysis. The role of NEDD4 on cardiomyocyte autophagy might provide valuable clues to finding therapeutic targets for heart diseases.

Inhibition of maternally expressed gene 3 attenuated lipopolysaccharide-induced apoptosis through sponging miR-21 in renal tubular epithelial cells

Acute kidney injury (AKI) results in retention of waste products and dysregulation of extracellular volume and electrolytes, thus leading to a variety of complications. Recent advances in long noncoding RNAs suggested their close relationship with disease progression. In the current study, we investigated the role and mechanism of maternally expressed gene 3 (MEG3) on AKI pathogenesis. Real-time polymerase chain reaction found that the expression of MEG3 was significantly increased in both kidney tissues and TKPTS cells induced by lipopolysaccharide (LPS). Western blot assay showed that the expression of apoptosis regulator Bcl-2 was increased in MEG3-inhibited TKPTS cells. Flow cytometry assay confirmed that LPS-induced apoptosis was significantly attenuated after transfection of si-MEG3. The RNAhybrid informatics algorithm predicted that there was a strong binding capacity between miR-21 and MEG3. Luciferase reporter assay confirmed that MEG3 could function as a competing endogenous RNA of miR-21. The antiapoptotic effect of si-MEG3 could be neutralized by a miR-21 inhibitor, demonstrated by the decreased expression of Bcl-2 and flow cytometry results. Further investigation showed that programmed cell death protein 4 (PDCD4), a validated target of miR-21, was highly expressed in both injured kidney tissues and LPS-stimulated TKPTS cells. Meanwhile, the protein expression of PDCD4 was significantly reduced by inhibition of MEG3, but retrieved by coinhibition of MEG3 and miR-21. In conclusion, our results demonstrated that inhibition of MEG3 could attenuate LPS-induced apoptosis in TKPTS cells by regulating the miR-21/PDCD4 pathway, suggesting that the MEG3/miR-21/PDCD4 axis could be developed as a potential therapeutic target of AKI.

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.

Interleukin-6 downregulated vascular smooth muscle cell contractile proteins via ATG4B-mediated autophagy in thoracic aortic dissection

Interleukin-6 (IL-6) overexpression played an important role in the pathogenesis of thoracic aortic dissection (TAD). Our previous study found enhanced autophagy accompanying with contractile proteins α smooth muscle actin (α-SMA) and smooth muscle 22α (SM22α) degradation in TAD aortic vascular smooth muscle cells (VSMCs). Autophagy is an important way for intracellular proteins degradation, while IL-6 has been found as a contributing factor of autophagy in some cancers. These indicated IL-6 might contribute to the occurrence of TAD by promoting autophagy-induced contractile proteins degradation, which has not been investigated. The aim of the present study is to verify this hypothesis and investigate the mechanism of it. We collected 10 TAD and 10 control aortic specimens from patients underwent TAD surgical repair and coronary artery bypass grafting, respectively. Quantitative real-time polymerase chain reaction was used to detect mRNA expression. Protein expression level was assessed by enzyme-linked immunosorbent assay, western blot, and immunohistochemistry. Microtubule-associated protein 1 light chain 3 beta overexpression adenovirus with green and red fluorescent protein tags and transmission electron microscopy were used to detect autophagy level in VSMCs. 3-Methyladenine (3-MA) and chloroquine were used to block autophagy in human VSMCs. Experiment results showed that the expression of IL-6 was significantly increased accompanying with up-regulated autophagy in TAD aortic wall compared with controls. In vitro results showed that IL-6 stimulation decreased the expression of VSMCs contractile proteins α-SMA and SM22α accompanying with up-regulated autophagy. Blocking autophagy with 3-MA or chloroquine inhibited IL-6 induced α-SMA and SM22α degradation. Further investigation showed that autophagy-related 4B cysteine peptidase (ATG4B) was significantly overexpressed in TAD aortic wall and played important role in IL-6 induced autophagy up-regulation. ATG4B knockdown blocked IL-6-induced autophagy and α-SMA and SM22α degradation, while ATG4B overexpression partly replaced the function of IL-6 in human VSMCs. In conclusion, our study demonstrated that IL-6 downregulated expression of VSMCs contractile proteins α-SMA and SM22α via enhancing ATG4B-mediated autophagy in TAD.