SP600125 Attenuates Nicotine-Related Aortic Aneurysm Formation by Inhibiting Matrix Metalloproteinase Production and CC Chemokine-Mediated Macrophage Migration

The roles and regulatory mechanisms of cigarette smoke constituents in vascular remodeling

Vascular remodeling is a dynamic process involving cellular and molecular changes, including cell proliferation, migration, apoptosis and extracellular matrix (ECM) synthesis or degradation, which disrupt the homeostasis of endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). Cigarette smoke exposure (CSE) is thought to promote vascular remodeling, but the components are complex and the mechanisms are unclear. In this review, we overview the progression of major components of cigarette smoke (CS), such as nicotine and acrolein, involved in vascular remodeling in terms of ECs injury, VSMCs proliferation, migration, apoptosis, and ECM disruption. The aim was to elucidate the effects of different components of CS on different cells of the vascular system, to discover the relevance of their actions, and to provide new references for future studies.

Angiotensin II Type 1 Receptor Blocker Prevents Abdominal Aortic Aneurysm Progression in Osteoprotegerin-Deficient Mice via Upregulation of Angiotensin (1-7)

Background Angiotensin II type 1 receptor blockers (ARBs) have been shown to limit the growth of abdominal aortic aneurysm (AAA), but their efficacy is controversial. This study aimed to investigate the molecular mechanism underlying the protective effect of ARBs against AAA progression. Methods and Results Olmesartan, an ARB, was administered to wild-type and osteoprotegerin-knockout (Opg-KO) mice starting 2 weeks before direct application of CaCl₂ to aortas to induce AAA. The protective effect of olmesartan against AAA in wild-type and Opg-KO mice was compared at 6 weeks after AAA induction. Olmesartan prevented AAA progression in Opg-KO mice, including excessive aortic dilatation and collapse of tunica media, but not in wild-type mice. Deficiency of the Opg gene is known to cause excessive activation of the tumor necrosis factor-related apoptosis-inducing ligand-induced c-Jun N-terminal kinase/matrix metalloproteinase 9 pathway, resulting in prolonged AAA progression. Olmesartan attenuated the upregulation of phosphorylated c-Jun N-terminal kinase and matrix metalloproteinase 9 expression in the aortic wall of Opg-KO mice. In cultured vascular smooth muscle cells, tumor necrosis factor-related apoptosis-inducing ligand-induced c-Jun N-terminal kinase phosphorylation and matrix metalloproteinase 9 expression were inhibited by angiotensin (1-7), the circulating levels of which are increased by ARBs. Furthermore, administering an angiotensin (1-7) antagonist to Opg-KO mice diminished the protective effect of olmesartan against AAA progression. Conclusions Olmesartan prevented AAA progression in Opg-KO mice by upregulating angiotensin (1-7), suggesting that angiotensin (1-7) may be a key factor that mediates the protective effect of ARBs.

Nicotine Exacerbates TAAD Formation Induced by Smooth Muscle-Specific Deletion of the TGF-β Receptor 2

Tobacco smoke is an established risk factor for thoracic aortic aneurysms and dissections (TAAD). However, little is known about its underlying mechanisms due to the lack of validated animal models. The present study developed a mouse model that may be utilized to investigate exacerbation of TAAD formation by mimetics of tobacco smoke. TAADs were created via inducible deletion of smooth muscle cell-specific Tgfbr2 receptors. Using this model, the first set of experiments evaluated the efficacy of nicotine salt (34.0 mg/kg/day), nicotine free base (NFB, 5.0 mg 90-day pellets), and cigarette smoke extract (0.1 ml/mouse/day). Compared with their respective control groups, only NFB pellets promoted TAAD dilation (23 ± 3% vs. 12 ± 2%, P = 0.014), and this efficacy was achieved at a cost of >50% acute mortality. Infusion of NFB with osmotic minipumps at extremely high, but nonlethal, doses (15.0 or 45.0 mg/kg/day) failed to accelerate TAAD dilation. Interestingly, costimulation with β-aminopropionitrile (BAPN) promoted TAAD dilation and aortic rupture at dosages of 3.0 and 45.0 mg/kg/day, respectively, indicating that BAPN sensitizes the response of TAADs to NFB. In subsequent analyses, the detrimental effects of NFB were associated with clustering of macrophages, neutrophils, and T-cells in areas with structural destruction, enhanced matrix metalloproteinase- (MMP-) 2 production, and pathological angiogenesis with attenuated fibrosis in the adventitia. In conclusion, modeling nicotine exacerbation of TAAD formation requires optimization of chemical form, route of delivery, and dosage of the drug as well as the pathologic complexity of TAADs. Under the optimized conditions of the present study, chronic inflammation and adventitial mal-remodeling serve as critical pathways through which NFB exacerbates TAAD formation.

Characterization of murine cytomegalovirus infection and induction of calcification in Murine Aortic Vascular Smooth Muscle Cells (MOVAS)

Human cytomegalovirus (HCMV) is a widespread pathogen that causes lifelong latent infection in the majority of the world population. HCMV is associated with increased incidence and severity of many cardiovascular diseases including myocarditis, atherosclerosis, and transplant vasculopathy. Due to the species-restricted nature of cytomegalovirus infection, murine cytomegalovirus (MCMV) is a useful model that recapitulates many of the features of HCMV infection of the cardiovascular system. While in vivo MCMV studies are able to answer many questions regarding pathogenesis of infection, in vitro experiments using cell lines are useful tools to further understand the potential underlying mechanisms. In this study, we characterize MCMV infection of the murine aortic smooth muscle cell line (MOVAS). Our findings demonstrate that MOVAS cells are permissive for MCMV infection, form plaques under carboxymethyl cellulose overlay, and produce progeny virus similar to NIH 3T3 murine embryonic fibroblasts. In addition, MCMV infection induces calcification in MOVAS cells similar to that seen in the epicardium of MCMV-infected hearts. We conclude that MOVAS cells are a useful in vitro tool for studying CMV-mediated cardiac calcification.

Immunological therapeutics in acute aortic syndrome

Acute aortic syndrome is a group of interlinked conditions with common presenting symptoms, including aortic dissection, penetrating atherosclerotic ulcer, and intramural hematoma. Pharmacological management of acute aortic syndrome is a growing area, with key themes to address the underlying inflammatory pathways believed to be the cause. Research into interleukins, matrix metalloproteinases, and granulocyte macrophage colony-stimulating factor are just some of the many immunological properties being investigated and translated into medical therapies. Stem cell experiments may indicate further advances in the pathologies of acute aortic syndrome. The study of pharmacogenomics to improve treatment across different genomes is also a novel area outlined in this paper.

Cellular signaling in Abdominal Aortic Aneurysm

Abdominal aortic aneurysms (AAAs) are highly lethal cardiovascular diseases without effective medications. However, the molecular and signaling mechanisms remain unclear. A series of pathological cellular processes have been shown to contribute to AAA formation, including vascular extracellular matrix remodeling, inflammatory and immune responses, oxidative stress, and dysfunction of vascular smooth muscle cells. Each cellular process involves complex cellular signaling, such as NF-κB, MAPK, TGFβ, Notch and inflammasome signaling. In this review, we discuss how cellular signaling networks function in various cellular processes during the pathogenesis and progression of AAA. Understanding the interaction of cellular signaling networks with AAA pathogenesis as well as the crosstalk of different signaling pathways is essential for the development of novel therapeutic approaches to and personalized treatments of AAA diseases.

Matrix Metalloproteinase in Abdominal Aortic Aneurysm and Aortic Dissection

Abdominal Aortic Aneurysm (AAA) affects 4–5% of men over 65, and Aortic Dissection (AD) is a life-threatening aortic pathology associated with high morbidity and mortality. Initiators of AAA and AD include smoking and arterial hypertension, whilst key pathophysiological features of AAA and AD include chronic inflammation, hypoxia, and large modifications to the extra cellular matrix (ECM). As it stands, only surgical methods are available for preventing aortic rupture in patients, which often presents difficulties for recovery. No pharmacological treatment is available, as such researchers are attempting to understand the cellular and molecular pathophysiology of AAA and AD. Upregulation of matrix metalloproteinase (MMPs), particularly MMP-2 and MMP-9, has been identified as a key event occurring during aneurysmal growth. As such, several animal models of AAA and AD have been used to investigate the therapeutic potential of suppressing MMP-2 and MMP-9 activity as well as modulating the activity of other MMPs, and TIMPs involved in the pathology. Whilst several studies have offered promising results, targeted delivery of MMP inhibition still needs to be developed in order to avoid surgery in high risk patients.

The effect of intravascular interventional embolization and craniotomy on MMP-2, MMP-9 and caspase3 in serum of intracranial aneurysm patients

The effect of intravascular interventional embolization and surgical operation on matrix metalloprotein (MMP)-2, MMP-9 and caspase3 in serum of intracranial aneurysms was analyzed to study the mechanisms. Seventy-nine patients of intracranial aneurysms from September 2011 to August 2014 were divided into the intervention group (n=41) and the craniotomy group (n=38) based on treatment methods, and 40 cases of normal volunteers with normal physical examination were selected as the control group. Patients in the intervention group were treated with intravascular interventional embolization, and the surgical group was treated with craniotomy and no treatment was performed in the control group. The survival rate and adverse reaction rate were calculated. ELISA kit was used to detect the level of reactive oxygen species (ROS), interleukin-6 (IL-6), tumor necrosis factor (TNF-α) and IL-10 in serum; the mRNA and protein expression levels of MMP-2, MMP-9 and caspase3 in serum were detected by qPCR and western blotting; the protein expression levels of p-adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK), Bcl-2 and Bax were also detected. The survival rate of patients in the intervention group was significantly higher than that in the craniotomy group (P<0.05). The ROS level in the intervention and craniotomy groups was significantly higher than that in the control group (P<0.01), while the levels of IL-6 and TNF-α in the serum of the intervention group were lower than those in the craniotomy group (P<0.01). The mRNA and protein expression of MMP-2, MMP-9 and caspase3 of the intervention group was significantly lower than that of the craniotomy group (P<0.01). The protein expression of p-AMPK and Bcl-2/Bax in the intervention group were lower than that in the craniotomy group (P<0.01). Intravascular interventional surgery can significantly increase the patient's survival time, and effectively reduce the expression of MMP-2, MMP-9 and caspase3 in the serum of intracranial aneurysm patients. The mechanism may be through the impact of ROS levels, thereby affecting the p-AMPK and Bcl2/Bax expression.

Nicotine and the renin-angiotensin system

Cigarette smoking is the single most important risk factor for the development of cardiovascular and pulmonary diseases (CVPD). Although cigarette smoking has been in constant decline since the 1950s, the introduction of e-cigarettes or electronic nicotine delivery systems 10 yr ago has attracted former smokers as well as a new generation of consumers. Nicotine is a highly addictive substance, and it is currently unclear whether e-cigarettes are "safer" than regular cigarettes or whether they have the potential to reverse the health benefits, notably on the cardiopulmonary system, acquired with the decline of tobacco smoking. Of great concern, nicotine inhalation devices are becoming popular among young adults and youths, emphasizing the need for awareness and further study of the potential cardiopulmonary risks of nicotine and associated products. This review focuses on the interaction between nicotine and the renin-angiotensin system (RAS), one of the most important regulatory systems on autonomic, cardiovascular, and pulmonary functions in both health and disease. The literature presented in this review strongly suggests that nicotine alters the homeostasis of the RAS by upregulating the detrimental angiotensin-converting enzyme (ACE)/angiotensin (ANG)-II/ANG II type 1 receptor axis and downregulating the compensatory ACE2/ANG-(1-7)/Mas receptor axis, contributing to the development of CVPD.

Modulation of Immune-Inflammatory Responses in Abdominal Aortic Aneurysm: Emerging Molecular Targets

Abdominal aortic aneurysm (AAA), a deadly vascular disease in human, is a chronic degenerative process of the abdominal aorta. In this process, inflammatory responses and immune system work efficiently by inflammatory cell attraction, proinflammatory factor secretion and subsequently MMP upregulation. Previous studies have demonstrated various inflammatory cell types in AAA of human and animals. The majority of cells, such as macrophages, CD4+ T cells, and B cells, play an important role in the diseased aortic wall through phenotypic modulation. Furthermore, immunoglobulins also greatly affect the functions and differentiation of immune cells in AAA. Recent evidence suggests that innate immune system, especially Toll-like receptors, chemokine receptors, and complements are involved in the progression of AAAs. We discussed the innate immune system, inflammatory cells, immunoglobulins, immune-mediated mechanisms, and key cytokines in the pathogenesis of AAA and particularly emphasis on a further trend and application of these interventions. This current understanding may offer new insights into the role of inflammation and immune response in AAA.

Autoimmunity in the Abdominal Aortic Aneurysm and its Association with Smoking

Smoking increases the risk of abdominal aortic aneurysm (AAA) in both humans and mice, although the underlying mechanisms are not completely understood. An adventitial aortic antigen, AAAP-40, has been partially sequenced. It has motifs with similarities to all three fibrinogen chains and appears to be connected in evolution to a large family of proteins called fibrinogen-related proteins. Fibrinogen may undergo non-enzymatic nitration, which may result from exposure to nitric oxide in cigarette smoke. Nitration of proteins renders them more immunogenic. It has recently been reported that anti-fibrinogen antibody promotes AAA development in mice. Also, anti-fibrinogen antibodies are present in patients with AAA. These matters are reviewed in the overall context of autoimmunity in AAA. The evidence suggests that smoking amplifies an auto-immune reaction that is critical to the pathogenesis of AAA.

Stimulation of Alpha7 Nicotinic Acetylcholine Receptor Attenuates Nicotine-Induced Upregulation of MMP, MCP-1, and RANTES through Modulating ERK1/2/AP-1 Signaling Pathway in RAW264.7 and MOVAS Cells

Vagus nerve stimulation through alpha7 nicotine acetylcholine receptors (α7-nAChR) signaling had been demonstrated attenuation of inflammation. This study aimed to determine whether PNU-282987, a selective α7-nAChR agonist, affected activities of matrix metalloproteinase (MMP) and inflammatory cytokines in nicotine-treatment RAW264.7 and MOVAS cells and to assess the underlying molecular mechanisms. RAW264.7 and MOVAS cells were treated with nicotine at different concentrations (0, 1, 10, and 100 ng/ml) for 0–120 min. Nicotine markedly stimulated the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) and c-Jun in RAW264.7 cells. Pretreatment with U0126 significantly suppressed phosphorylation of ERK1/2 and further attenuated nicotine-induced activation of c-Jun and upregulation of MMP-2, MMP-9, monocyte chemotactic protein- (MCP-) 1, and regulated upon activation normal T cell expressed and secreted (RANTES). Similarly, nicotine treatment also increased phosphorylation of c-Jun and expressions of MMP-2, MMP-9, MCP-1, and RANTES in MOVAS cells. When cells were pretreated with PNU-282987, nicotine-induced activations of ERK1/2 and c-Jun in RAW264.7 cells and c-Jun in MOVAS cells were effectively inhibited. Furthermore, nicotine-induced secretions of MMP-2, MMP-9, MCP-1, and RANTES were remarkably downregulated. Treatment with α7-nAChR agonist inhibits nicotine-induced upregulation of MMP and inflammatory cytokines through modulating ERK1/2/AP-1 signaling in RAW264.7 cells and AP-1 in MOVAS cells, providing a new therapeutic for abdominal aortic aneurysm.