Matrix metalloproteinases in aortic dissection.

Aortic dissection, characterized by a high immediate mortality, is primarily caused by excessive bleeding within the walls of the aorta or a severe tear within the intimal layer of the aorta. Inflammation, as well as oxidative stress and the degradation of extracellular matrix (ECM), are significant factors in the development and occurrence of aortic dissection. Matrix metalloproteinases (MMPs) are pivotal enzymes responsible for degrading the ECM. Inflammatory factors and oxidants can interact with MMPs, indicating the potential significance of MMPs in aortic dissection. A substantial body of evidence indicates that numerous MMPs are significantly upregulated in aortic dissection, playing a critical role in ECM degradation and the pathogenesis of aortic dissection. Furthermore, targeting these enzymes has demonstrated potential in facilitating ECM restoration and reducing the incidence of aortic dissection. This review initially provides a brief overview of MMP biology before delving into their expression patterns, regulatory mechanisms, and therapeutic applications in aortic dissection. A profound comprehension of the catabolic pathways associated with aortic dissection is imperative for the future development of potential preventive or therapeutic bio-interventions for aortic dissection.

SLC44A2-mediated phenotypic switch of vascular smooth muscle cells contributes to aortic aneurysm.

The phenotypic switch of vascular smooth cells (VSMCs) from a contractile to a synthetic state is associated with the development and progression of aortic aneurysm (AA). However, the mechanism underlying this process remains unclear. In this issue of the JCI, Song et al. identified SLC44A2 as a regulator of the phenotypic switch in VSMCs. Inhibition of SLC44A2 facilitated the switch to the synthetic state, contributing to the development of AA. Mechanistically, SLC44A2 interacted with NRP1 and ITGB3 to activate the TGF-ß/SMAD signaling pathway, resulting in VSMCs with a contractile phenotype. Furthermore, VSMC-specific SLC44A2 overexpression by genetic or pharmacological manipulation reduced AA in mouse models. These findings suggest the potential of targeting the SLC44A2 signaling pathway for AA prevention and treatment.

RBM15 activates glycolysis in M1-type macrophages to promote the progression of aortic aneurysm and dissection.

Aortic aneurysm and dissection (AD) represent a critical cardiovascular emergency with an alarmingly high mortality rate. Recent research has spotlighted the overexpression of genes associated with the m6A modification in AD patients, linking them to the presence of inflammatory M1-type macrophages. Moreover, glycolysis is widely recognized as a key feature of inflammatory M1-type macrophages, but biomarkers linking glycolysis and macrophage function to promote disease progression in AD have not been reported. We conducted an analysis of aortic immune cell infiltration, macrophages, and m6A-related biomarkers in AD patients using bioinformatics techniques. Subsequently, we employed a combination of RT-PCR, WB, and immunofluorescence assays to elucidate the alterations in the expression of M1- and M2-type macrophages, as well as markers of glycolysis, following the overexpression of key biomarkers. These findings were further validated in vivo through the creation of a rat model of AD with knockdown of the aforementioned key biomarkers. The findings revealed that the m6A-modified related gene RBM15 exhibited heightened expression in AD samples and was correlated with macrophage polarization. Upon overexpression of RBM15 in macrophages, there was an observed increase in the expression of M1-type macrophage markers CXCL9 and CXCL10, alongside a decrease in the expression of M2-type macrophage markers CCL13 and MRC1. Furthermore, there was an elevation in the expression of glycolytic enzymes GLUT1 and Hexokinase, as well as HIF1α, GAPDH, and PFKFB3 after RBM15 overexpression. Moreover, in vivo knockdown of RBM15 led to an amelioration of aortic aneurysm in the rat AD model. This knockdown also resulted in a reduction of the M1-type macrophage marker iNOS, while significantly increasing the expression of the M2-type macrophage marker CD206. In conclusion, our findings demonstrate that RBM15 upregulates glycolysis in macrophages, thus contributing to the progression of AD through the promotion of M1-type macrophage polarization. Conversely, downregulation of RBM15 suppresses M1-type macrophage polarization, thereby decelerating the advancement of AD. These results unveil potential novel targets for the treatment of AD.

Ciprofloxacin Accelerates Angiotensin-II-Induced Vascular Smooth Muscle Cells Senescence Through Modulating AMPK/ROS pathway in Aortic Aneurysm and Dissection.

Aortic aneurysm and dissection (AAD) is a cardiovascular disease that poses a severe threat to life and has high morbidity and mortality rates. Clinical and animal-based studies have irrefutably shown that fluoroquinolones, a commonly prescribed antibiotic for treating infections, significantly increase the risk of AAD. Despite this, the precise mechanism by which fluoroquinolones cause AAD remains unclear. Therefore, this study aims to investigate the molecular mechanism and role of Ciprofloxacin definitively-a type of fluoroquinolone antibiotic-in the progression of AAD. Aortic transcriptome data were collected from GEO datasets to detect the genes and pathways expressed differently between healthy donors and AAD patients. Human primary Vascular Smooth Muscle Cells (VSMCs) were isolated from the aorta. After 72 h of exposure to 110ug/ml Ciprofloxacin or 100 nmol/L AngII, either or combined, the senescent cells were identified through SA-ß-gal staining. MitoTracker staining was used to examine the morphology of mitochondria in each group. Cellular Reactive Oxygen Species (ROS) levels were measured using MitoSox and DCFH-DA staining. Western blot assay was performed to detect the protein expression level. We conducted an analysis of transcriptome data from both healthy donors and patients with AAD and found that there were significant changes in cellular senescence-related signaling pathways in the latter group. We then isolated and identified human primary VSMCs from healthy donors (control-VSMCs) and patients' (AAD-VSMCs) aortic tissue, respectively. We found that VSMCs from patients exhibited senescent phenotype as compared to control-VSMCs. The higher levels of p21 and p16 and elevated SA-ß-gal activity demonstrated this. We also found that pretreatment with Ciprofloxacin promoted angiotensin-II-induced cellular senescence in control-VSMCs. This was evidenced by increased SA-ß-gal activity, decreased cell proliferation, and elevation of p21 and p16 protein levels. Additionally, we found that Angiotensin-II (AngII) induced VSMC senescence by promoting ROS generation. We used DCFH-DA and mitoSOX staining to identify that Ciprofloxacin and AngII pretreatment further elevated ROS levels than the vehicle or alone group. Furthermore, JC-1 staining showed that mitochondrial membrane potential significantly declined in the Ciprofloxacin and AngII combination group compared to others. Compared to the other three groups, pretreatment of Ciprofloxacin plus AngII could further induce mitochondrial fission, demonstrated by mitoTracker staining and western blotting assay. Mechanistically, we found that Ciprofloxacin impaired the balance of mitochondrial fission and fusion dynamics in VSMCs by suppressing the phosphorylation of AMPK signaling. This caused mitochondrial dysfunction and ROS generation, thereby elevating AngII-induced cellular senescence. However, treatment with the AMPK activator partially alleviated those effects. Our data indicate that Ciprofloxacin may accelerate AngII-induced VSMC senescence through modulating AMPK/ROS signaling and, subsequently, hasten the progression of AAD.

The S-Nitrosylation of Septin2 (SNO-Septin2) axis: A novel potential therapeutic target for treating aneurysms and dissection.

Aortic aneurysm and aortic dissection (AAD) are severe life-threatening cardiovascular disorders for which no approved pharmaceutical therapies are currently available. Protein S-nitrosylation (SNO) is a typical redox-dependent posttranslational modification whose role in AAD has yet to be described. Recently, Zhang et al. revealed for the first time that SNO modification of macrophage cytoskeletal protein septin2 promotes vascular inflammation and extracellular matrix degradation in aortic aneurysm. Mechanically, the TIAM1-RAC1(T lymphoma invasion and metastasis-inducing protein 1-Ras-related C3 botulinum toxin substrate 1) axis participates in the progression of AAD induced with S-nitrosylated septin2. More importantly, developing R-ketorolac and NSC23766 compounds that specifically target the TIAM1-RAC1 pathway may be new a potential strategy for alleviating AAD.

Aging aggravates aortic aneurysm and dissection via miR-1204-MYLK signaling axis in mice.

The mechanism by which aging induces aortic aneurysm and dissection (AAD) remains unclear. A total of 430 participants were recruited for the screening of differentially expressed plasma microRNAs (miRNAs). We found that miR-1204 is significantly increased in both the plasma and aorta of elder patients with AAD and is positively correlated with age. Cell senescence induces the expression of miR-1204 through p53 interaction with plasmacytoma variant translocation 1, and miR-1204 induces vascular smooth muscle cell (VSMC) senescence to form a positive feedback loop. Furthermore, miR-1204 aggravates angiotensin II-induced AAD formation, and inhibition of miR-1204 attenuates ß-aminopropionitrile monofumarate-induced AAD development in mice. Mechanistically, miR-1204 directly targets myosin light chain kinase (MYLK), leading to the acquisition of a senescence-associated secretory phenotype (SASP) by VSMCs and loss of their contractile phenotype. MYLK overexpression reverses miR-1204-induced VSMC senescence, SASP and contractile phenotypic changes, and the decrease of transforming growth factor-ß signaling pathway. Our findings suggest that aging aggravates AAD via the miR-1204-MYLK signaling axis.

Smooth muscle cell phenotypic switching occurs independent of aortic dilation in bicuspid aortic valve-associated ascending aortas.

BACKGROUND: Bicuspid aortic valves (BAV) are frequently associated with ascending aortic aneurysms. The etiology is incompletely understood, but genetic factors, in addition to flow perturbations, are likely involved. Since loss of contractility and elaboration of extracellular matrix in the vessel wall are features of BAV-associated aortopathy, phenotypic modulation of smooth muscle cells (SMCs) may play a role. METHODS: Ascending aortic tissue was collected intra-operatively from 25 individuals with normal (i.e., tricuspid) aortic valves (TAV) and from 25 individuals with BAVs. For both TAV and BAV, 10 patients had non-dilated (ND) and 15 patients had dilated (D) aortas. SMCs were isolated and cultured from a subset of patients from each group. Aortic tissue and SMCs were fluorescently immunolabeled for SMC phenotypic markers (i.e., alpha-smooth muscle actin (ASMA, contractile), vimentin (synthetic) and p16INK4a and p21Cip1 (senescence). SMCs were also analyzed for replicative senescence in culture. RESULTS: In normal-sized and dilated BAV aortas, SMCs switched from the contractile state to either synthetic or senescent phenotypes, as observed by loss of ASMA (ND: P = 0.001, D: P = 0.002) and associated increases in vimentin (ND: P = 0.03, D: P = 0.004) or p16/p21 (ND: P = 0.03, D: P<0.0001) compared to TAV. Dilatation of the aorta exacerbated SMC phenotypic switching in both BAV and TAV aortas (all P<0.05). In SMCs cultured from normal and dilated aortas, those isolated from BAV reached replicative senescence faster than those from TAV aortas (all P = 0.02). Furthermore, there was a stark inverse correlation between ASMA and cell passage number in BAV SMCs (ND: P = 0.0006, D: P = 0.01), but not in TAV SMCs (ND: P = 0.93, D: P = 0.20). CONCLUSIONS: The findings of this study provide direct evidence from cell culture studies implying that SMCs switch from the contractile state to either synthetic or senescent phenotypes in the non-dilated BAV aorta. In cultured SMCs from both non-dilated and dilated aortas, we found that this process may precede dilatation and accompany aneurysm development in BAV. Our findings suggest that therapeutically targeting SMC phenotypic modulation in BAV patients may be a viable option to prevent or delay ascending aortic aneurysm formation.

A new procedure to induce aortic aneurysms in mice.

Aortic aneurysms (AAs) are a major public health challenge, featured by a progressive impairs in aortic wall integrity that drives to aortic dilation and, in end stage, to its rupture. Despite important advances in the surgical treatment of aortic aneurysms, there is currently no pharmacological intervention that prevents their development, reduces their expansion, or avoids their rupture. In addition to classic risk factors such age or gender, several heritable connective tissue disorders have been associated with AA developing, highlighting the role of extracellular matrix (ECM) genes alterations in the developing of AA. In this sense, we have recently demonstrated that global deletion of the cellular communicating network factor 2 (CCN2), previously known as connective tissue growth factor (CTGF) due to its role in the extracellular matrix formation, predisposes to early and lethal AAs development after Angiotensin II (Ang II) infusion in mice. Here, we detail the protocol to induce and detect AAs generation in inducible global CCN2 knockout mice after Ang II infusion which allow the characterization of CCN role in AA development and may help to the development of pharmacological target for AA treatment.

Loss of Smooth Muscle Tenascin-X Inhibits Vascular Remodeling Through Increased TGF-ß Signaling.

BACKGROUND: Vascular smooth muscle cells (VSMCs) are highly plastic. Vessel injury induces a phenotypic transformation from differentiated to dedifferentiated VSMCs, which involves reduced expression of contractile proteins and increased production of extracellular matrix and inflammatory cytokines. This transition plays an important role in several cardiovascular diseases such as atherosclerosis, hypertension, and aortic aneurysm. TGF-ß (transforming growth factor-ß) is critical for VSMC differentiation and to counterbalance the effect of dedifferentiating factors. However, the mechanisms controlling TGF-ß activity and VSMC phenotypic regulation under in vivo conditions are poorly understood. The extracellular matrix protein TN-X (tenascin-X) has recently been shown to bind TGF-ß and to prevent it from activating its receptor. METHODS: We studied the role of TN-X in VSMCs in various murine disease models using tamoxifen-inducible SMC-specific knockout and adeno-associated virus-mediated knockdown. RESULTS: In hypertensive and high-fat diet-fed mice, after carotid artery ligation as well as in human aneurysmal aortae, expression of Tnxb, the gene encoding TN-X, was increased in VSMCs. Mice with smooth muscle cell-specific loss of TN-X (SMC-Tnxb-KO) showed increased TGF-ß signaling in VSMCs, as well as upregulated expression of VSMC differentiation marker genes during vascular remodeling compared with controls. SMC-specific TN-X deficiency decreased neointima formation after carotid artery ligation and reduced vessel wall thickening during Ang II (angiotensin II)-induced hypertension. SMC-Tnxb-KO mice lacking ApoE showed reduced atherosclerosis and Ang II-induced aneurysm formation under high-fat diet. Adeno-associated virus-mediated SMC-specific expression of short hairpin RNA against Tnxb showed similar beneficial effects. Treatment with an anti-TGF-ß antibody or additional SMC-specific loss of the TGF-ß receptor reverted the effects of SMC-specific TN-X deficiency. CONCLUSIONS: In summary, TN-X critically regulates VSMC plasticity during vascular injury by inhibiting TGF-ß signaling. Our data indicate that inhibition of vascular smooth muscle TN-X may represent a strategy to prevent and treat pathological vascular remodeling.