MiR-4787-5p Regulates Vascular Smooth Muscle Cell Apoptosis by Targeting PKD1 and Inhibiting the PI3K/Akt/FKHR Pathway.

ABSTRACT: Vascular smooth muscle cell (VSMC) dysfunction is the main cause of aortic dissection (AD). In this study, we focused on the role and mechanism of miR-4787-5p in regulating VSMC apoptosis. Real-time fluorescence quantitative polymerase chain reaction was used to detect the expression of miR-4787-5p in aorta tissues of AD (n = 10) and normal aortic tissues of donors (n = 10). Cell apoptosis was tested by TUNEL assay and Annexin V FITC/PI staining flow cytometry. The expression of PC1 and the PI3K/Akt/FKHR signaling pathway associated proteins in VSMCs was measured by Western blot. We found that the miR-4787-5p was highly expressed in aorta tissues of AD compared with 10 healthy volunteers. Meanwhile, PI3K/Akt/FKHR signaling pathway was inactive in the aortic tissue of AD. The overexpression of miR-4787-5p significantly induced VSMC apoptosis, and miR-4787-5p knockdown showed the opposite results. In addition, polycystic kidney disease 1 gene, which encodes polycystin-1 (PC1), was found to be a direct target of miR-4787-5p in the VSMCs and this was validated using a luciferase reporter assay. Overexpression of PC1 by a lentivirus packaging PC1-overexpression plasmid (LV-PC1) plasmids markedly eliminated the promotion of miR-4787-5p overexpression on VSMC apoptosis. Finally, it was found that miR-4787-5p deactivated the PI3K/Akt/FKHR pathway, as demonstrated by the down-regulation of phosphorylated (p-)PI3K, p-Akt, and p-FKHR. In conclusion, these findings confirm an important role for the miR-4787-5p/polycystic kidney disease 1 axis in AD pathobiology.

Aortic Aneurysms, Chronic Kidney Disease and Metalloproteinases.

Metalloproteinases (MPs) are proteolytic enzymes involved in extracellular matrix deposition, regulation of cellular signals of inflammation, proliferation, and apoptosis. Metalloproteinases are classified into three families: Matrix-MPs (MMPs), A-Disintegrin-and-Metalloprotease (ADAMs), and the A-Disintegrin-and-Metalloproteinase-with-Thrombospondin-1-like-Domains (ADAMTS). Previous studies showed that MPs are involved in the development of aortic aneurysms (AA) and, concomitantly, in the onset of chronic kidney disease (CKD). CKD has been, per se, associated with an increased risk for AA. The aim of this review is to examine the pathways that may associate MPs with CKD and AA. Several MMPs, such as MMP-2, -8, -9, and TIMP-1 have been shown to damage the AA wall and to have a toxic effect on renal tubular cells, leading to fibrosis. Similarly, ADAM10 and 17 have been shown to degrade collagen in the AA wall and to worsen kidney function via pro-inflammatory stimuli, the impairment of the Renin-Angiotensin-Aldosterone System, and the degradation of structural proteins. Moreover, MMP-2 and -9 inhibitors reduced aneurysm growth and albuminuria in experimental and human studies. It would be important, in the future, to expand research on MPs from both a prognostic, namely, to refine risk stratification in CKD patients, and a predictive perspective, likely to improve prognosis in response to targeted treatments.

Upregulated Kynurenine Pathway Enzymes in Aortic Atherosclerotic Aneurysm: Macrophage Kynureninase Downregulates Inflammation.

AIMS: Inflammation and hypertension contribute to the progression of atherosclerotic aneurysm in the aorta. Vascular cell metabolism is regarded to modulate atherogenesis, but the metabolic alterations that occur in atherosclerotic aneurysm remain unknown. The present study aimed to identify metabolic pathways and metabolites in aneurysmal walls and examine their roles in atherogenesis. METHODS: Gene expression using microarray and metabolite levels in the early atherosclerotic lesions and aneurysmal walls obtained from 42 patients undergoing aortic surgery were investigated (early lesion n=11, aneurysm n=35) and capillary electrophoresis-time-of-flight mass spectrometry (early lesion n=14, aneurysm n=38). Using immunohistochemistry, the protein expression and localization of the identified factors were examined (early lesion n=11, non-aneurysmal advanced lesion n=8, aneurysm n=11). The roles of the factors in atherogenesis were analyzed in macrophages derived from human peripheral blood mononuclear cells. RESULTS: Enrichment analysis using 35 significantly upregulated genes (log2 ratio, ＞3) revealed the alteration of the kynurenine pathway. Metabolite levels of tryptophan, kynurenine, and quinolinic acid and the kynurenine-to-tryptophan ratio were increased in the aneurysmal walls. Gene and protein expression of kynureninase and kynurenine 3-monooxygenase were upregulated and localized in macrophages in the aneurysmal walls. The silencing of kynureninase in the cultured macrophages enhanced the expression of interleukin-6 and indoleamine 2,3-dioxygenase 1. CONCLUSION: Our study suggests the upregulation of the kynurenine pathway in macrophages in aortic atherosclerotic aneurysm. Kynureninase may negatively regulate inflammation via the kynurenine pathway itself in macrophages.

Bicuspid aortopathy - molecular involvement of microRNAs and MMP-TIMP.

OBJECTIVES: We aimed to elucidate the correlation between expression patterns of aortic tissue microRNAs and the aortopathy formation in bicuspid aortic valve (BAV) disease. METHODS: All 65 patients who underwent elective aortic valve repair/replacement +/- proximal aortic replacement due to BAV disease with or without concomitant aortic aneurysm were identified from our BAV registry. Aortic tissue was collected intraoperatively from the ascending aorta at the greater and lesser curvature. Aortic tissue microRNAs analysis included 11 microRNAs (miR-1, miR-17, miR-18a, miR-19a, miR-20a, miR-21, miR-29b, miR-106a, miR-133a, miR-143 and miR-145). Furthermore, analysis of MMP2, TIMP1/2 mRNA and the protein expression was subsequently performed. The primary study endpoint was the correlation between microRNAs and MMP2, TIMP1/2 mRNA/protein expression. RESULTS: We found a significant association between miR-133a and TIMP1 mRNA (r = 0.870, p < 0.001), an inverse correlation between miR-143a and MMP2 protein expression (r= -0.614, p = 0.044) and a positive correlation between miR-133a and TIMP-2 protein expression (r = 0.583, p = 0.036) at the greater curvature. CONCLUSION: Our findings indicate that aortic tissue microRNAs may reflect remodelling processes of the proximal aorta in BAV aortopathy. Specific aortic tissue microRNAs may exert their regulatory effects on the aortopathy through their impact on MMPs/TIMPs homeostasis at the level of the greater curvature.

Resveratrol Attenuates Aortic Dissection by Increasing Endothelial Barrier Function Through the SIRT1 Pathway.

Aortic dissection (AD) is a serious condition and a health issue on a global scale. ß-Aminopropionitrile-induced AD in mice is similar to the pathogenesis of AD in humans. Resveratrol (RSV) is a natural polyphenolic substance that provides anti-inflammatory and cardiovascular effects, but the role of RSV in AD is unclear. In this study, we investigated the effects and mechanisms of RSV on ß-aminopropionitrile-induced AD in mice. Our results indicate that RSV can prevent the occurrence of AD. More meaningfully, we found that the protective effect comprises an increase in sirtuin 1 (SIRT1) expression in endothelial cells for the reconstruction of their structure, reducing the recruitment of inflammatory cells by endothelial cells and inhibiting the inflammation response, thereby suppressing the occurrence of AD.

Inactivation of cysteine 674 in the SERCA2 accelerates experimental aortic aneurysm.

Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) is vital to maintain intracellular calcium homeostasis. SERCA2 cysteine 674 (C674) is highly conservative and its irreversible oxidation is upregulated in human and mouse aortic aneurysms, especially in smooth muscle cells (SMCs). The contribution of SERCA2 and its redox C674 in the development of aortic aneurysm remains enigmatic. Objective: Our goal was to investigate the contribution of inactivation of C674 to the development of aortic aneurysm and the mechanisms involved. Approach and results: Using SERCA2 C674S knock-in (SKI) mouse line, in which half of C674 was substituted by serine 674 (S674) to represent partial irreversible oxidation of C674 in aortic aneurysm, we found that in aortic SMCs the replacement of C674 by S674 resulted in SMC phenotypic modulation. In SKI SMCs, the increased intracellular calcium activated calcium-dependent calcineurin, which promoted the nuclear translocation of nuclear factor of activated T-lymphocytes (NFAT) and nuclear factor kappa-B (NFκB), while inhibition of calcineurin blocked SMC phenotypic modulation. Besides, the replacement of C674 by S674 accelerated angiotensin II-induced aortic aneurysm. Conclusions: Our results indicate that the inactivation of C674 by causing the accumulation of intracellular calcium to activate calcineurin-mediated NFAT/NFκB pathways, resulted in SMC phenotypic modulation to accelerate aortic aneurysm, which highlights the importance of C674 redox state in the development of aortic aneurysms.

Matrix metalloproteinases and acute aortic dissection: Et Tu, Brute?

OBJECTIVES: To summarize the present evidence for the association of matrix metalloproteinases (MMPs) with acute aortic dissection (AAD), we performed the first meta-analysis of all currently available case-control studies comparing circulating MMP levels between AAD patients and control subjects. METHODS: To identify all studies investigating the levels of circulating MMPs in AAD patients, PubMed and Web of Science were searched up to July 2019. The levels of MMPs in AAD patients and control subjects were extracted from each study, and the standardized mean differences (SMDs) in MMP levels were generated. The study-specific estimates were combined in the random-effects model. RESULTS: Twelve studies enrolling a total of 458 AAD patients and 711 control subjects were identified and included. Pooled analyses demonstrated no significant differences in MMP-1 (4 studies; P = 0.21), MMP-2 (5 studies; P = 0.62) and MMP-3 levels (2 studies; P = 0.94) between AAD patients and control subjects; and significantly higher MMP-8 (2 studies; SMD 2.11; P = 0.020), MMP-9 (9 studies; SMD 1.54; P < 0.001) and MMP-12 levels (2 studies; SMD 1.33; P < 0.001) in AAD patients than in control subjects. CONCLUSION: High circulating MMP-9 levels are associated with AAD, and MMP-8 and MMP-12 levels may be related to AAD.

Involvement of DHX9/YB-1 complex induced alternative splicing of Krüppel-like factor 5 mRNA in phenotypic transformation of vascular smooth muscle cells.

Phenotypic transformation of vascular smooth muscle cells is a key phenomenon in the development of aortic dissection disease. However, the molecular mechanisms underlying this phenomenon have not been fully understood. We used ß-BAPN combined with ANG II treatment to establish a disease model of acute aortic dissection (AAD) in mice. We first examined the gene expression profile of aortic tissue in mice with AAD using a gene chip, followed by confirmation of DExH-box helicase 9 (DHX9) expression using RT-PCR, Western blot, and immunofluorescence analysis. We further developed vascular smooth muscle cell-specific DHX9 conditional knockout mice and conducted differential and functional analysis of gene expression and alternative splicing in mouse vascular smooth muscle cells. Finally, we examined the involvement of DHX9 in Krüppel-like factor 5 (KLF5) mRNA alternative splicing. Our study reported a significant decrease in the expression of DHX9 in the vascular smooth muscle cells (VSMCs) of mice with AAD. The smooth muscle cell-specific knockout of DHX9 exacerbated the development of AAD and altered the transcriptional level expression of many smooth muscle cell phenotype-related genes. Finally, we reported that DHX9 may induce alternative splicing of KLF5 mRNA by bridging YB-1. These results together suggested a new pathogenic mechanism underlying the development of AAD, and future research of this mechanism may help identify effective therapeutic intervention for AAD.

Serum levels of matrix metalloproteinase 9 and toll-like receptor 4 in acute aortic dissection: a case-control study.

BACKGROUND: Matrix metalloproteinase 9 (MMP9) and Toll-like receptor 4 (TLR4) play important roles in aortic pathophysiology. However, there is lacking research on serum TLR4 levels in acute aortic dissection (AAD) patients, and the performance of serum MMP9 and TLR4 for the diagnosis of AAD is still unknown. This study aimed to evaluate the serum levels of MMP9 and TLR4 in AAD patients, identify their associations with circulating C-reactive protein (CRP) and D-dimer, which are well-known classical biomarkers of AAD, and further explore the potential diagnostic role of MMP9 and TLR4 in AAD. METHODS: Serum levels of MMP9 and TLR4 were measured by enzyme-linked immunosorbent assay (ELISA) in 88 AAD patients and 88 controls. The clinical test related information was collected from patients' electronic medical records. RESULTS: Serum MMP9 and TLR4 levels were significantly higher in AAD patients than those in healthy controls in the general and stratified comparisons. Either serum MMP9 or TLR4 was independently associated with the risk of AAD (all p < 0.001). There was a positive significant association between serum MMP9 and TLR4 (r = 0.518, p < 0.001). Both MMP9 and TLR4 levels were statistically correlated with circulating CRP, but not D-dimer. Based on receiver-operating characteristic (ROC) analysis, the area under the curves (AUCs) of MMP9 and TLR4 alone for the diagnosis of AAD were 0.810 and 0.799 with optimal cut-off points of 379.47 ng/ml and 7.83 ng/ml, respectively. Moreover, a combination of serum MMP9 and TLR4 increased the AUC to 0.89 with a sensitivity of 60.2% and specificity of 94.3%. CONCLUSIONS: Serum MMP9 and TLR4 could be potential biomarkers for identifying AAD, while the combined diagnostic value was higher in safely ruling out AAD.

Ectopic Expression of PCSK9 by Smooth Muscle Cells Contributes to Aortic Dissection.

BACKGROUND: Acute aortic dissection (AAD) is a common disease among the elderly. Although several risk factors of AAD have been reported, the molecular mechanism underlying AAD development remains to be elucidated. Proprotein convertase subtilisin/kexin type 9 (PCSK9) increases low-density lipoprotein cholesterol levels in blood by preventing its clearance. Therefore, PCSK9 inhibition is a promising therapeutic approach to treat cardiovascular diseases (CVDs). The objective of this study was to elucidate the role of PCSK9 in the pathogenesis of AAD. METHODS: We used fluorescence immunohistochemistry to assess PCSK9 expression in aortic tissues resected from 10 AAD patients and in the normal aorta from 5 autopsy samples as well as in spontaneously hyperlipidemic apolipoprotein E-deficient mice used as an experimental AD model. RESULTS: We revealed a characteristic distribution pattern of PCSK9 in atherosclerotic plaques and the degenerated tunica media in AAD tissues, which was rarely observed in normal aortic tissues. Furthermore, PCSK9 was notably expressed around calcification areas formed by vascular smooth muscle cells, especially those of the synthetic phenotype. The results obtained in the animal model were consistent with PCSK9 expression in AAD tissues. CONCLUSIONS: Our findings suggest that PCSK9 overexpression in the aorta may promote AAD. This study adds to the growing body of evidence supporting the use of PCSK9 inhibitors for the management of CVDs.

Overexpression of microRNA-30a contributes to the development of aortic dissection by targeting lysyl oxidase.

OBJECTIVE: To explore the role of microRNA (miR)-30a in the development of aortic dissection. METHODS: Human aortic specimens of aortic dissections and aneurysms were harvested. Aortic specimens from donors for heart transplantation served as controls. Rat aortic vascular smooth muscle cells (VSMCs) were transfected with agomiR-30a or antagomiR-30a, and control cells were incubated with empty vectors. Rats were pretreated with agomiR-30a or antagomiR-30a (5 × 107 transfection units every 3 days for 4 weeks), and empty vectors were infused to controls. Acute aortic dissection was induced by subcutaneous infusion of angiotensin II (1 µg · kg-1 · min-1 for 24 hours). Protein expressions of lysyl oxidase (LOX) and elastin and gene expression of miR-30a were measured in VSMCs and human and rat aortic specimens by Western blot analysis and quantitative real-time polymerase chain reaction. RESULTS: Gene expression of miR-30a was much higher, and protein abundance of LOX and elastin was significantly lower, in the aortic dissection specimens (P < .05 vs controls). Transfection of agomiR-30a markedly decreased the luciferase activity of LOX in VSMCs of wild type, but not of LOX 3'-UTR mutant (P = .002). In cultured VSMCs, transfection of agomiR-30a dramatically enhanced the gene expression of miR-30a and down-regulated the protein abundance of LOX and elastin (P < .05 vs controls). Pretreatment with agomiR-30a in vivo enhanced miR-30a expression and down-regulated the protein abundance of LOX and elastin in rat aortas (P < .05 vs controls). The rate of dissection was significantly higher in rats pretreated with agomiR-30a (P = .003 vs controls). CONCLUSIONS: Overexpression of miR-30a contributes to the development of aortic dissection, possibly by targeting LOX.

The Role Matrix Metalloproteinases in the Production of Aortic Aneurysm.

Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of aortic aneurysm because the histology of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) is characterized by the loss of smooth muscle cells in the aortic media and the destruction of extracellular matrix (ECM). Furthermore, AAA have evidence of inflammation and the cellular elements involved in inflammation such as macrophages can produce and/or activate MMPs This chapter focuses on human aortic aneurysm that are not due to specific known genetic causes because this type of aneurysm is the more common type. This chapter will also focus on MMP protein expression rather than on genetic data which may not necessarily translate to increased MMP protein expression. There are supporting data that certain MMPs are increased in the aortic wall. For TAA, it is most notably MMP-1, -9, -12, and -14 and MMP-2 when a bicuspid aortic valve is present. For AAA, it is MMP-1, -2, -3, -9, -12, and -13. The data are weaker or insufficient for the other MMPs. Several studies of gene polymorphisms support MMP-9 for TAA and MMP-3 for AAA as potentially important factors. The signaling pathways in the aorta that can lead to MMP activation include JNK, JAK/stat, osteopontin, and AMP-activated protein kinase alpha2. Substrates in the human vasculature for MMP-3, MMP-9, or MMP-14 include collagen, elastin, ECM glycoprotein, and proteoglycans. Confirmed and potential substrates for MMPs, maintain aortic size and function so that a reduction in their content relative to other components of the aortic wall may produce a failure to maintain aortic size leading to dilatation and aneurysm formation.

P38 MAPK Signaling Pathway Mediates Angiotensin II-Induced miR143/145 Gene Cluster Downregulation during Aortic Dissection Formation.

BACKGROUND: We endeavored to prove that angiotensin II (Ang II) regulates both the expression of micro-RNA143/145 (miR143/145) and differentiation of vascular smooth muscle cells (VSMCs) during the formation of aortic dissection (AD). We also studied the contribution of p38 mitogen-activated protein kinase (MAPK) signaling pathway toward this process. METHODS: Ascending aortic tissues were harvested from the patients with AD and organ donors. Tissues were immunostained with labeled antibodies targeting p38 MAPK, phospho-p38 MAPK, alpha-smooth muscle actin (α-SMA), and osteopontin (OPN). Next, we treated mouse aortic VSMCs with different regimens of Ang II (duration and dosages) in vitro and determined expression levels of miR143/145 and VSMC phenotype marker proteins (α-SMA and OPN) by quantitative polymerase chain reaction and/or western blotting. SB203580 was used to inhibit the p38 MAPK signaling pathway. Finally, the VSMC phenotype was validated by immunofluorescence microscopy. RESULTS: Expression of phospho-p38 MAPK was significantly greater in the AD tissue. Ang II induced the phenotypic switching of VSMCs along with the downregulation of an miR143/145 gene cluster. Expression of OPN and phospho-p38 was significantly increased in VSMCs treated with 0.1 µM Ang II for 12 hr. Furthermore, the expression of miR143 and miR145 was downregulated by Ang II treatment. When the p38 MAPK signaling pathway was blocked by pretreatment with an SB203580 inhibitor, the expression of miR143, miR145, and VSMC phenotypic markers was not affected by Ang II. Immunohistochemical staining of aortic tissues donated by AD patients and healthy donors showed that the expression of α-SMA decreased in pathological tissue, while the OPN increased and the arrangement of the smooth muscle cells of the media was dysregulated, which we verified in vitro. CONCLUSIONS: Ang II could regulate the expression of miR143/145 gene cluster and the phenotypic switching of VSMCs via the p38 MAPK signaling pathway. This may play an important role in the pathogenesis of AD.

The expression of inhibitor of nuclear factor kappa-B kinase epsilon (IKKe) in human aortic aneurysm.

BACKGROUND: Aortic aneurysm (AA) is one of the most common causes of sudden death among elderly people. Although AA can be detected by non-invasive imaging techniques, there are no pharmacological treatments currently available to prevent progression at any stage of the disease. In this study we will explore the expression of inhibitor of nuclear factor kappa-B kinase epsilon (IKKe) in AA and its potential underlying molecular mechanism in AA. MATERIALS AND METHODS: Human aortic tissue was taken from 14 patients who underwent surgical repair of AA for the AA group and another 11 patients with normal aorta who underwent aortic valve replacement surgery for the control group. After excision, we used haematoxylin-eosin staining, Masson staining, immunohistochemistry analysis and Western blot analysis to observe the expres-sion, location and morphological changes of the IKKe, P50 and the extracellular matrix within the AA. RESULTS: In the AA group, haematoxylin-eosin staining revealed a loss of medial integrity and inflammatory cell infiltration. Masson staining confirmed the degradation of the extracellular matrix in the AA group. Immunohistochemistry analysis showed increased infiltration of inflammatory cells and up-regulation of proinflammatory cytokines in the AA group when compared to the control group. Based on immunohistochemistry and Western blot analysis, there was clearly over-expression of IKKe, P50 and MMP2 in AA group, mainly in the intrinsic aortic cells of the media. CONCLUSIONS: The over-expression of IKKe may play an important role in the ori-gination and progression of AA and might be a vital target for their treatment.

The Effect of Nicotine and Tobacco on Aortic Matrix Metalloproteinases in the Production of Aortic Aneurysm.

BACKGROUND: Aortic aneurysms (AAs) are without effective pharmacologic therapy, in clinical usage, in part because of the limited understanding of factors leading to AA development. OBJECTIVE: The objectives of this study were to examine the evidence that cigarette smoking induces AAs through altering matrix metalloproteinases (MMP) and the molecular biology/pharmacology that maybe involved in this effect. METHODS: A systematic search was conducted to identify studies that examined the links between cigarette smoke, MMP and AAs. RESULTS: Eleven studies were identified. There was consistency, between studies. They found that cigarette smoke, nicotine or tobacco products increased aortic dimension and the proportion of AAs. Nicotine and tobacco constituents induced MMPs: MMP-1, MMP-2, MMP-8, MMP-9 and MMP-12 but with different levels of consistency. The molecular mechanisms involved in the pathogenesis of cigarette-induced AA formation, ranked according to the consistency of evidence include JNK, AMPK-α2, Jak Stat, and mTOR/p70Sk and PTEN pathways. CONCLUSION: Nicotine and tobacco constituents translate the exposure to cigarette smoke into increased MMP expression through various molecular mechanisms whose interruption can form the basis for pharmacologic management of AAs.

AKT2 Promotes Bone Marrow Cell-Mediated Aortic Protection in Mice.

BACKGROUND: Insufficient aortic protection and repair may contribute to the development of aortic aneurysms and dissections (AAD). However, mechanisms of aortic protection and repair are poorly understood. We have shown that the multifunctional kinase AKT2 plays an important role in protecting the aortic wall. Here, we examined whether AKT2 protects against AAD by promoting bone marrow cell (BMC)-mediated aortic protection. METHODS: Irradiated wild-type mice received green fluorescent protein-expressing BMCs from wild-type mice or Akt2(-/-) mice, followed by challenge with angiotensin II (1000 ng/kg/min) infusion for 4 weeks. We compared BMC recruitment, aortic destruction, and AAD development between groups. The direct effects of wild-type and Akt2(-/-) BMCs on smooth muscle cell survival were examined in coculture experiments. RESULTS: After angiotensin II infusion, no (0 of 14) wild-type BMC recipients had AAD; in contrast, 64% (9 of 14) of Akt2(-/-) BMC recipients had AAD (p = 0.002) with severe aortic destruction. Compared with aortas from challenged wild-type BMC recipients, aortas from challenged Akt2(-/-) BMC recipients showed significantly less BMC recruitment, NG2 (neuron-glial antigen 2) progenitor activation, and FSP1 (fibroblast-specific protein 1) fibroblast activation. In addition, aortas from challenged Akt2(-/-) BMC recipients showed increased apoptosis and inflammation. In coculture experiments, wild-type but not Akt2(-/-) BMCs prevented smooth muscle cells from undergoing oxidative stress-induced apoptosis. CONCLUSIONS: After aortic challenge, BMCs are recruited to the aortic wall and provide protection by activating progenitors and fibroblasts and by promoting aortic cell survival. Our findings indicate that AKT2 is involved in these processes and that defects in this pathway may promote progressive degeneration during AAD development.

A disintegrin and metalloproteinase with thrombospondin motif 1 (ADAMTS1) expression increases in acute aortic dissection.

Acute aortic dissection (AAD) is a life-threatening cardiovascular disease caused by progressive medial degeneration of the aortic wall. A disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) is a recently identified extracellular metalloproteinase participating in the development of vascular disease, such as atherosclerosis. In the present study, we found that ADAMTS1 was significantly elevated in blood samples from AAD patients compared with patients with acute myocardial infarction and healthy volunteers. Based on these findings, we established an AAD model by infusing angiotensin II in older mice. AAD was successfully developed in aorta tissues, with an incidence of 42% after 14 days in the angiotensin II group. Macrophage and neutrophil infiltration was observed in the media of the aorta, and ADAMTS1 overexpression was found in the aorta by Western blot and immunohistochemistry. Double immunofluorescence staining showed the expression of ADAMTS1 in macrophages and neutrophils. Consistent with the upregulation of ADAMTS1 in aortic dissection tissues, versican (a proteoglycan substrate of ADAMTS1) was degraded significantly more in these tissues than in control aortic tissues. These data suggest that the increased expression of ADAMTS1 protein in macrophages and neutrophils that infiltrated aortic tissues may promote the progression of AAD by degrading versican.

Vascular Smooth Muscle Sirtuin-1 Protects Against Aortic Dissection During Angiotensin II-Induced Hypertension.

BACKGROUND: Sirtuin-1 (SirT1), a nicotinamide adenine dinucleotide(+)-dependent deacetylase, is a key enzyme in the cellular response to metabolic, inflammatory, and oxidative stresses; however, the role of endogenous SirT1 in the vasculature has not been fully elucidated. Our goal was to evaluate the role of vascular smooth muscle SirT1 in the physiological response of the aortic wall to angiotensin II, a potent hypertrophic, oxidant, and inflammatory stimulus. METHODS AND RESULTS: Mice lacking SirT1 in vascular smooth muscle (ie, smooth muscle SirT1 knockout) had drastically high mortality (70%) caused by aortic dissection after angiotensin II infusion (1 mg/kg per day) but not after an equipotent dose of norepinephrine, despite comparable blood pressure increases. Smooth muscle SirT1 knockout mice did not show any abnormal aortic morphology or blood pressure compared with wild-type littermates. Nonetheless, in response to angiotensin II, aortas from smooth muscle SirT1 knockout mice had severely disorganized elastic lamellae with frequent elastin breaks, increased oxidant production, and aortic stiffness compared with angiotensin II-treated wild-type mice. Matrix metalloproteinase expression and activity were increased in the aortas of angiotensin II-treated smooth muscle SirT1 knockout mice and were prevented in mice overexpressing SirT1 in vascular smooth muscle or with use of the oxidant scavenger tempol. CONCLUSIONS: Endogenous SirT1 in aortic smooth muscle is required to maintain the structural integrity of the aortic wall in response to oxidant and inflammatory stimuli, at least in part, by suppressing oxidant-induced matrix metalloproteinase activity. SirT1 activators could potentially be a novel therapeutic approach to prevent aortic dissection and rupture in patients at risk, such as those with hypertension or genetic disorders, such as Marfan's syndrome.

Gene polymorphisms as risk factors for predicting the cardiovascular manifestations in Marfan syndrome. Role of folic acid metabolism enzyme gene polymorphisms in Marfan syndrome.

Folic acid metabolism enzyme polymorphisms are believed to be responsible for the elevation of homocysteine (HCY) concentration in the blood plasma, correlating with the pathogenesis of aortic aneurysms and aortic dissection. We studied 71 Marfan patients divided into groups based on the severity of cardiovascular involvement: no intervention required (n=27, Group A); mild involvement requiring intervention (n=17, Group B); severe involvement (n=27, Group C) subdivided into aortic dilatation (n=14, Group C1) and aortic dissection (n=13, Group C2), as well as 117 control subjects. We evaluated HCY, folate, vitamin B12 and the polymorphisms of methylenetetrahydrofolate reductase (MTHFR;c.665C>T and c.1286A>C), methionine synthase (MTR;c.2756A>G) and methionine synthase reductase (MTRR;c.66A>G). Multiple comparisons showed significantly higher levels of HCY in Group C2 compared to Groups A, B, C1 and control group (p<0.0001, p<0.0001, p=0.001 and p=0.003, respectively). Folate was lower in Group C2 than in Groups A, B, C1 and control subjects (p<0.0001, p=0.02, p<0.0001 and p<0.0001, respectively). Group C2 had the highest prevalence of homozygotes for all four gene polymorphisms. Multivariate logistic regression analysis revealed that HCY plasma level was an independent risk factor for severe cardiovascular involvement (Group C; odds ratio [OR] 1.85, 95% confidence interval [CI] 1.28-2.67, p=0.001) as well as for aortic dissection (Group C2; OR 2.49, 95%CI 1.30-4.78, p=0.006). In conclusion, severe cardiovascular involvement in Marfan patients, and especially aortic dissection, is associated with higher HCY plasma levels and prevalence of homozygous genotypes of folic acid metabolism enzymes than mild or no cardiovascular involvement. These results suggest that impaired folic acid metabolism has an important role in the development and remodelling of the extracellular matrix of the aorta.