Lysyl Oxidase Induces Vascular Oxidative Stress and Contributes to Arterial Stiffness and Abnormal Elastin Structure in Hypertension: Role of p38MAPK

Reactive Oxygen Species and Oxidative Stress in the Pathogenesis and Progression of Genetic Diseases of the Connective Tissue

Connective tissue is known to provide structural and functional “glue” properties to other tissues. It contains cellular and molecular components that are arranged in several dynamic organizations. Connective tissue is the focus of numerous genetic and nongenetic diseases. Genetic diseases of the connective tissue are minority or rare, but no less important than the nongenetic diseases. Here we review the impact of reactive oxygen species (ROS) and oxidative stress on the onset and/or progression of diseases that directly affect connective tissue and have a genetic origin. It is important to consider that ROS and oxidative stress are not synonymous, although they are often closely linked. In a normal range, ROS have a relevant physiological role, whose levels result from a fine balance between ROS producers and ROS scavenge enzymatic systems. However, pathology arises or worsens when such balance is lost, like when ROS production is abnormally and constantly high and/or when ROS scavenge (enzymatic) systems are impaired. These concepts apply to numerous diseases, and connective tissue is no exception. We have organized this review around the two basic structural molecular components of connective tissue: The ground substance and fibers (collagen and elastic fibers).

Magnesium, Oxidative Stress, Inflammation, and Cardiovascular Disease

Hypomagnesemia is commonly observed in heart failure, diabetes mellitus, hypertension, and cardiovascular diseases. Low serum magnesium (Mg) is a predictor for cardiovascular and all-cause mortality and treating Mg deficiency may help prevent cardiovascular disease. In this review, we discuss the possible mechanisms by which Mg deficiency plays detrimental roles in cardiovascular diseases and review the results of clinical trials of Mg supplementation for heart failure, arrhythmias and other cardiovascular diseases.

Lysyl Oxidase (LOX): Functional Contributions to Signaling Pathways

Cu-dependent lysyl oxidase (LOX) plays a catalytic activity-related, primary role in the assembly of the extracellular matrix (ECM), a dynamic structural and regulatory framework which is essential for cell fate, differentiation and communication during development, tissue maintenance and repair. LOX, additionally, plays both activity-dependent and independent extracellular, intracellular and nuclear roles that fulfill significant functions in normal tissues, and contribute to vascular, cardiac, pulmonary, dermal, placenta, diaphragm, kidney and pelvic floor disorders. LOX activities have also been recognized in glioblastoma, diabetic neovascularization, osteogenic differentiation, bone matrix formation, ligament remodeling, polycystic ovary syndrome, fetal membrane rupture and tumor progression and metastasis. In an inflammatory context, LOX plays a role in diminishing pluripotent mesenchymal cell pools which are relevant to the pathology of diabetes, osteoporosis and rheumatoid arthritis. Most of these conditions involve mechanisms with complex cell and tissue type-specific interactions of LOX with signaling pathways, not only as a regulatory target, but also as an active player, including LOX-mediated alterations of cell surface receptor functions and mutual regulatory activities within signaling loops. In this review, we aim to provide insight into the diverse ways in which LOX participates in signaling events, and explore the mechanistic details and functional significance of the regulatory and cross-regulatory interactions of LOX with the EGFR, PDGF, VEGF, TGF-β, mechano-transduction, inflammatory and steroid signaling pathways.

Interleukin-17A induces vascular remodeling of small arteries and blood pressure elevation

An important link exists between hypertension and inflammation. Hypertensive patients present elevated circulating levels of proinflammatory cytokines, including interleukin-17A (IL-17A). This cytokine participates in host defense, autoimmune and chronic inflammatory pathologies, and cardiovascular diseases, mainly through the regulation of proinflammatory factors. Emerging evidence also suggests that IL-17A could play a role in regulating blood pressure and end-organ damage. Here, our preclinical studies in a murine model of systemic IL-17A administration showed that increased levels of circulating IL-17A raised blood pressure induced inward remodeling of small mesenteric arteries (SMAs) and arterial stiffness. In IL-17A-infused mice, treatment with hydralazine and hydrochlorothiazide diminished blood pressure elevation, without modifying mechanical and structural properties of SMA, suggesting a direct vascular effect of IL-17A. The mechanisms of IL-17A seem to involve an induction of vascular smooth muscle cell (VSMC) hypertrophy and phenotype changes, in the absence of extracellular matrix (ECM) proteins accumulation. Accordingly, treatment with an IL-17A neutralizing antibody diminished SMA remodeling in a model of angiotensin II (Ang II) infusion. Moreover, in vitro studies in VSMCs reported here, provide further evidence of the direct effects of IL-17A on cell growth responses. Our experimental data suggest that IL-17A is a key mediator of vascular remodeling of the small arteries, which might contribute, at least in part, to blood pressure elevation.

Extracellular matrix dynamics in vascular remodeling

Vascular remodeling is the adaptive response to various physiological and pathophysiological alterations that are closely related to aging and vascular diseases. Understanding the mechanistic regulation of vascular remodeling may be favorable for discovering potential therapeutic targets and strategies. The extracellular matrix (ECM), including matrix proteins and their degradative metalloproteases, serves as the main component of the microenvironment and exhibits dynamic changes during vascular remodeling. This process involves mainly the altered composition of matrix proteins, metalloprotease-mediated degradation, posttranslational modification of ECM proteins, and altered topographical features of the ECM. To date, adequate studies have demonstrated that ECM dynamics also play a critical role in vascular remodeling in various diseases. Here, we review these related studies, summarize how ECM dynamics control vascular remodeling, and further indicate potential diagnostic biomarkers and therapeutic targets in the ECM for corresponding vascular diseases.

The biology of vascular calcification

Vascular calcification (VC), characterized by different mineral deposits (i.e., carbonate apatite, whitlockite and hydroxyapatite) accumulating in blood vessels and valves, represents a relevant pathological process for the aging population and a life-threatening complication in acquired and in genetic diseases. Similarly to bone remodeling, VC is an actively regulated process in which many cells and molecules play a pivotal role. This review aims at: (i) describing the role of resident and circulating cells, of the extracellular environment and of positive and negative factors in driving the mineralization process; (ii) detailing the types of VC (i.e., intimal, medial and cardiac valve calcification); (iii) analyzing rare genetic diseases underlining the importance of altered pyrophosphate-dependent regulatory mechanisms; (iv) providing therapeutic options and perspectives.

Potential Molecular Pathways Related to Pulmonary Artery Aneurysm Development: Lessons to Learn from the Aorta

Pulmonary arterial hypertension (PAH) is a rare disease caused by pulmonary vascular remodeling. Current vasodilator treatments have substantially improved patients’ survival. This improved survival has led to the appearance of complications related to conditions previously underdiagnosed or even ignored, such as pulmonary artery aneurysm (PAA). The presence of a dilated pulmonary artery has been shown to be related to an increased risk of sudden cardiac death among PAH patients. This increased risk could be associated to the development of left main coronary artery compression or pulmonary artery dissection. Nevertheless, very little is currently known about the molecular mechanisms related to PAA. Thoracic aortic aneurysm (TAA) is a well-known condition with an increased risk of sudden death caused by acute aortic dissection. TAA may be secondary to chronic exposure to classic cardiovascular risk factors. In addition, a number of genetic variants have been shown to be related to a marked risk of TAA and dissection as part of multisystemic syndromes or isolated familial TAA. The molecular pathways implied in the development of TAA have been widely studied and described. Many of these molecular pathways are involved in the pathogenesis of PAH and could be involved in PAA. This review aims to describe all these common pathways to open new research lines that could help lead to a better understanding of the pathophysiology of PAH and PAA and their clinical implications.

Brain mural cell loss in the parietal cortex in Alzheimer's disease correlates with cognitive decline and TDP-43 pathology

AIMS

Brain mural cells (BMC), smooth muscle cells and pericytes, interact closely with endothelial cells and modulate numerous cerebrovascular functions. A loss of BMC function is suspected to play a role in the pathophysiology of Alzheimer's Disease (AD).

METHODS

BMC markers, namely smooth muscle alpha actin (α-SMA) for smooth muscle cells, as well as platelet-derived growth factor receptor β (PDGFRβ) and aminopeptidase N (ANPEP or CD13) for pericytes, were assessed by Western immunoblotting in microvessel extracts from the parietal cortex of 60 participants of the Religious Orders study, with ages at death ranging from 75 to 98 years old.

RESULTS

Participants clinically diagnosed with AD had lower vascular levels of α-SMA, PDGFRβ and CD13. These reductions were correlated with lower cognitive scores for global cognition, episodic and semantic memory, perceptual speed and visuospatial ability. In addition, α-SMA, PDGFRβ and CD13 were negatively correlated with vascular Aβ40 concentrations. Vascular levels of BMC markers were also inversely correlated with insoluble cleaved phosphorylated transactive response DNA binding protein 43 (TDP-43) (25 kDa) and positively correlated with soluble cleaved phosphorylated TDP-43 (35 kDa) in cortical homogenates, suggesting strong association between BMC loss and cleaved phosphorylated TDP-43 aggregation.

CONCLUSIONS

The results of this study highlight a loss of BMC in AD. The associations between α-SMA, PDGFRβ and CD13 vascular levels with cognitive scores, TDP-43 aggregation and cerebrovascular accumulation of Aβ in the parietal cortex suggest that BMC loss contributes to both AD symptoms and pathology, further strengthening the link between cerebrovascular defects and dementia.

The Role of Lysyl Oxidase Enzymes in Cardiac Function and Remodeling

Lysyl oxidase (LOX) proteins comprise a family of five copper-dependent enzymes (LOX and four LOX-like isoenzymes (LOXL1-4)) critical for extracellular matrix (ECM) homeostasis and remodeling. The primary role of LOX enzymes is to oxidize lysyl and hydroxylysyl residues from collagen and elastin chains into highly reactive aldehydes, which spontaneously react with surrounding amino groups and other aldehydes to form inter- and intra-catenary covalent cross-linkages. Therefore, they are essential for the synthesis of a mature ECM and assure matrix integrity. ECM modulates cellular phenotype and function, and strikingly influences the mechanical properties of tissues. This explains the critical role of these enzymes in tissue homeostasis, and in tissue repair and remodeling. Cardiac ECM is mainly composed of fibrillar collagens which form a complex network that provides structural and biochemical support to cardiac cells and regulates cell signaling pathways. It is now becoming apparent that cardiac performance is affected by the structure and composition of the ECM and that any disturbance of the ECM contributes to cardiac disease progression. This review article compiles the major findings on the contribution of the LOX family to the development and progression of myocardial disorders.

Transcriptional control of a novel long noncoding RNA Mymsl in smooth muscle cells by a single Cis-element and its initial functional characterization in vessels

Differentiated vascular smooth muscle cells (VSMCs) are crucial in maintaining vascular homeostasis. While the coding transcriptome of the differentiated VSMC phenotype has been defined, we know little about its noncoding signature. Herein, we identified a Myocardin-induced muscle specific long noncoding RNA (lncRNA) (Mymsl) downregulated upon VSMC phenotypic modulation. We demonstrated an essential role of a proximal consensus CArG element in response to MYOCD/SRF in vitro. To validate the in vivo role of this CArG element, we generated CArG mutant mice via CRISPR-Cas9 genome editing. While the CArG mutation had no impact on the expression of surrounding genes, it abolished Mymsl expression in SMCs, but not skeletal and cardiac muscle. Chromatin immunoprecipitation assays (ChIPs) showed decreased SRF binding to CArG region in mutants whereas the enrichment of H3K79Me2 remained the same. RNA-seq analysis showed a downregulation of matrix genes in aortas from Mymsl knockout mice, which was further validated in injured carotid arteries. Our study defined the transcriptional control of a novel lncRNA in SMCs via a single transcription factor binding site, which may offer a new strategy for generating SMC-specific knockout mouse models. We also provided in vivo evidence supporting the potential importance of Mymsl in vascular pathophysiology.

Co-administration of resveratrol and beta-aminopropionitrile attenuates liver fibrosis development via targeting lysyl oxidase in CCl4-induced liver fibrosis in rats

Objectives: In the current study, we aimed to investigate the effect of administration of resveratrol (RES) and beta-aminopropionitrile (BAPN) separately and together on the liver fibrosis progression via regulation of the gene expression and protein level of lysyl oxidase (LOX).Materials and methods: The six-week old Wistar rats received carbon tetrachloride (CCl₄) intraperitoneally and RES and BAPN were administrated orally for eight weeks. The hepatoprotective effects of RES, BAPN, and combination treatment were evaluated. Then the hepatic protein and gene expression levels of LOX were measured.Results: Both RES and BAPN showed the antifibrotic effect through the reduction of collagen fiber bundles, hepatic hydroxyproline content, and protein level of LOX. The antifibrotic effect increased when RES and BAPN up-taken together.Conclusion: The co-administration of RES and BAPN can be considered as a promising therapeutic approach via targeting LOX.

Lysyl oxidase promotes liver metastasis of gastric cancer via facilitating the reciprocal interactions between tumor cells and cancer associated fibroblasts

Background

Liver is one of the most preferred destinations of distant metastasis in gastric cancer (GC). As effective treatment is still limited, the prognosis of GC patients bearing liver metastasis is poor. We filter out lysyl oxidase (LOX) to study its function in the tumor microenvironment (TME) and seek for potential therapeutic targets.

Methods

Transcription analysis on 6 cases of liver metastasis of GC patients with respective paired primary tumors and adjacent normal livers was performed. The filtration out of LOX was done using 5 datasets. 69 GC liver metastasis tissues were utilized to perform immunohistochemistry (IHC) and analyze prognosis. Computed Tomography (CT) combined 3D organ reconstruction bioluminescence imaging was performed to precisely evaluate the metastatic tumor burden on liver of intrasplenic injection mouse model. Human and mouse cancer associated fibroblasts (CAFs) in liver metastasis were separated to culture to study the interaction of LOX and TGF-β1. Patients-derived xenograft (PDX) model was established using liver metastasis of patients to evaluate the therapeutic value of LOX inhibitor β‐aminopropionitrile (BAPN).

Results

CAFs-derived LOX at liver metastatic niche of GC promotes niche formation and outgrowth thus predicts poor prognosis. Meanwhile tumor cells in niche secrete TGF-β1 to nourish CAFs and stimulate them to produce more LOX in turn. The mechanism involved in LOX-mediated proliferation facilitation is enhancement of Warburg effect. The inhibitor of LOX, BPAN could hamper the effect brought by LOX in vivo and in vitro.

Interpretation

Our study has unveiled a positive feedback loop between CAFs and tumor cells in liver metastasis niche of GC. The core molecule is LOX which facilitates Warburg effect. Targeting LOX with its inhibitor BAPN might serve as a potential therapeutic strategy.

Fund

This research was supported by the National Natural Science Foundation of China (31872740), the 100-member plan of the Shanghai Municipal Commission of Health and Family Planning (2017BR043), Shanghai Science and Technology Commission Project(17ZR1416800), Renji Hospital Training Fund (PYMDT-003, PYIII-17–015), National Natural Science Foundation of China (81672358), the Shanghai Municipal Education Commission—Gao feng Clinical MedicineGrant Support (20181708), Program of Shanghai Academic/Technology Research Leader(19XD1403400), Science and Technology Commission of Shanghai Municipality (18410721000), Shanghai Municipal Health Bureau (2018BR32), China Postdoctoral Science Foundation (2018M640403), National Natural Science Foundation of China (81701945) and Youth project of Shanghai Municipal Health Commission(20164Y0045).

Emerging Roles of Lysyl Oxidases in the Cardiovascular System: New Concepts and Therapeutic Challenges

Lysyl oxidases (LOX and LOX-likes (LOXLs) isoenzymes) belong to a family of copper-dependent enzymes classically involved in the covalent cross-linking of collagen and elastin, a pivotal process that ensures extracellular matrix (ECM) stability and provides the tensile and elastic characteristics of connective tissues. Besides this structural role, in the last years, novel biological properties have been attributed to these enzymes, which can critically influence cardiovascular function. LOX and LOXLs control cell proliferation, migration, adhesion, differentiation, oxidative stress, and transcriptional regulation and, thereby, their dysregulation has been linked to a myriad of cardiovascular pathologies. Lysyl oxidase could modulate virtually all stages of the atherosclerotic process, from endothelial dysfunction and plaque progression to calcification and rupture of advanced and complicated plaques, and contributes to vascular stiffness in hypertension. The alteration of LOX/LOXLs expression underlies the development of other vascular pathologies characterized by a destructive remodeling of the ECM, such as aneurysm and artery dissections, and contributes to the adverse myocardial remodeling and dysfunction in hypertension, myocardial infarction, and obesity. This review examines the most recent advances in the study of LOX and LOXLs biology and their pathophysiological role in cardiovascular diseases with special emphasis on their potential as therapeutic targets.

The interrelationship between cerebral ischemic stroke and glioma: a comprehensive study of recent reports

Glioma and cerebral ischemic stroke are two major events that lead to patient death worldwide. Although these conditions have different physiological incidences, ~10% of ischemic stroke patients develop cerebral cancer, especially glioma, in the postischemic stages. Additionally, the high proliferation, venous thrombosis and hypercoagulability of the glioma mass increase the significant risk of thromboembolism, including ischemic stroke. Surprisingly, these events share several common pathways, viz. hypoxia, cerebral inflammation, angiogenesis, etc., but the proper mechanism behind this co-occurrence has yet to be discovered. The hypercoagulability and presence of the D-dimer level in stroke are different in cancer patients than in the noncancerous population. Other factors such as atherosclerosis and coagulopathy involved in the pathogenesis of stroke are partially responsible for cancer, and the reverse is also partially true. Based on clinical and neurosurgical experience, the neuronal structures and functions in the brain and spine are observed to change after a progressive attack of ischemia that leads to hypoxia and atrophy. The major population of cancer cells cannot survive in an adverse ischemic environment that excludes cancer stem cells (CSCs). Cancer cells in stroke patients have already metastasized, but early-stage cancer patients also suffer stroke for multiple reasons. Therefore, stroke is an early manifestation of cancer. Stroke and cancer share many factors that result in an increased risk of stroke in cancer patients, and vice-versa. The intricate mechanisms for stroke with and without cancer are different. This review summarizes the current clinical reports, pathophysiology, probable causes of co-occurrence, prognoses, and treatment possibilities.

Reprint of "The complex dynamics of myocardial interstitial fibrosis in heart failure. Focus on collagen cross-linking"

Myocardial interstitial fibrosis (MIF) is a common finding in heart failure (HF) patients, both with preserved and reduced ejection fraction, as well as in HF animal models. MIF is associated with impaired cardiac function and worse clinical outcome. The impact of MIF is influenced not only by the quantity but also by changes in the quality of collagen fibers and in the extracellular matrix components, such as a shift in collagen types proportion, increased fibronectin polymerization and increased degree of collagen cross-linking (CCL). In particular, CCL, a process that renders collagen fibers stiffer and more resistant to degradation, is increased both in patients and animal models of HF. Importantly, in HF patients increased cardiac CCL is directly associated with increased left ventricular stiffness and a higher risk of hospitalization for HF. The aim of this review is to address the complexity of MIF in HF, focusing on CCL.

The complex dynamics of myocardial interstitial fibrosis in heart failure. Focus on collagen cross-linking

Myocardial interstitial fibrosis (MIF) is a common finding in heart failure (HF) patients, both with preserved and reduced ejection fraction, as well as in HF animal models. MIF is associated with impaired cardiac function and worse clinical outcome. The impact of MIF is influenced not only by the quantity but also by changes in the quality of collagen fibers and in the extracellular matrix components, such as a shift in collagen types proportion, increased fibronectin polymerization and increased degree of collagen cross-linking (CCL). In particular, CCL, a process that renders collagen fibers stiffer and more resistant to degradation, is increased both in patients and animal models of HF. Importantly, in HF patients increased cardiac CCL is directly associated with increased left ventricular stiffness and a higher risk of hospitalization for HF. The aim of this review is to address the complexity of MIF in HF, focusing on CCL.

IGF-1 Deficiency Promotes Pathological Remodeling of Cerebral Arteries: A Potential Mechanism Contributing to the Pathogenesis of Intracerebral Hemorrhages in Aging

Clinical and experimental studies show that age-related decline in circulating insulin-like growth factor-1 (IGF-1) levels promotes the pathogenesis of intracerebral hemorrhages, which critically contribute to the development of vascular cognitive impairment and disability in older adults. Yet, the mechanisms by which IGF-1 deficiency compromises structural integrity of the cerebral vasculature are not completely understood. To determine the role of IGF-1 deficiency in pathological remodeling of middle cerebral arteries (MCAs), we compared alterations in vascular mechanics, morphology, and remodeling-related gene expression profile in mice with liver-specific knockdown of IGF-1 (Igf1f/f + TBG-Cre-AAV8) and control mice with or without hypertension induced by angiotensin-II treatment. We found that IGF-1 deficiency resulted in thinning of the media and decreased wall-to-lumen ratio in MCAs. MCAs of control mice exhibited structural adaptation to hypertension, manifested as a significant increase in wall thickness, vascular smooth muscle cell (VSMC) hypertrophy, decreased internal diameter and up-regulation of extracellular matrix (ECM)-related genes. IGF-1 deficiency impaired hypertension-induced adaptive media hypertrophy and dysregulated ECM remodeling, decreasing elastin content and attenuating adaptive changes in ECM-related gene expression. Thus, circulating IGF-1 plays a critical role in maintenance of the structural integrity of cerebral arteries. Alterations of VSMC phenotype and pathological remodeling of the arterial wall associated with age-related IGF-1 deficiency have important translational relevance for the pathogenesis of intracerebral hemorrhages and vascular cognitive impairment in elderly hypertensive patients.

In Vivo Detection and Measurement of Aortic Aneurysm and Dissection in Mouse Models Using Microcomputed Tomography with Contrast Agent

Objectives

The aim of this study was to evaluate the potential of microcomputed tomography (micro-CT) using the intravascular contrast agent ExiTron nano 12000 for aorta imaging and monitoring the dynamic changing process of the aorta in mouse models with aortic aneurysm and dissection.

Materials and Methods

Experiments were performed on healthy mice and mice with aortic dissection. Mice that were developing aortic dissection and healthy mice underwent micro-CT imaging after injection of ExiTron nano 12000. Time-dependent signal enhancement (at 1, 2, 3, 6, and 12 hours after intravenous injection of the contrast agent, respectively) in the aorta of healthy mice was measured to confirm the optimal imaging time of aorta. Various contrast agent doses (70, 100, and 150 μl per 25 g mouse, respectively) were investigated to determine the optimal required dose for imaging of the aorta. The mice were scanned with micro-CT at 1, 14, and 28 days after onset of aneurysm and dissection to monitor the dynamic changing process of the aorta. Mouse aortas were stained with hematoxylin and eosin staining, and the diameter of the aorta was measured and compared with those obtained by micro-CT.

Results

Time-dependent signal enhancement in the aorta shows that the contrast agent has a long blood half-life of 6 hours, with a peak enhancement at 2 hours after injection. Injection of 100 μl ExiTron nano 12000 per 25 g mouse allows for effective visualization of the aorta. Micro-CT combined with contrast agent can monitor the changing process of the aorta in the mouse model of aortic aneurysm and dissection dynamically. The values of the diameter of the aortas obtained from the in vivo micro-CT imaging were compared with those obtained from histology and showed a significant correlation (R² = 0.96).

Conclusions

These data demonstrate that in vivo micro-CT is an accurate and feasible technique to detect aortic aneurysm or dissection in a mouse model, and the micro-CT technique using the innovative contrast agent ExiTron nano 12000 allows for monitoring various processes dynamically such as aortic remodeling in longitudinal studies.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Vascular Oxidative Stress: Impact and Therapeutic Approaches

Oxidative stress has been defined as an imbalance between oxidants and antioxidants and more recently as a disruption of redox signaling and control. It is generally accepted that oxidative stress can lead to cell and tissue injury having a fundamental role in vascular dysfunction. Physiologically, reactive oxygen species (ROS) control vascular function by modulating various redox-sensitive signaling pathways. In vascular disorders, oxidative stress instigates endothelial dysfunction and inflammation, affecting several cells in the vascular wall. Vascular ROS are derived from multiple sources herein discussed, which are prime targets for therapeutic development. This review focuses on oxidative stress in vascular physiopathology and highlights different strategies to inhibit ROS production.

Prevention of Wogonin on Colorectal Cancer Tumorigenesis by Regulating p53 Nuclear Translocation

The tumor suppressor protein p53 plays an important role in the development and progression of colon cancer, and the subcellular organelle localization directly affects its function. Wogonin (5,7-dihydroxy-8-methoxyflavone), a mono-flavonoid extracted from root of Scutellaria baicalensis Georgi, possesses acceptable toxicity and has been used in colorectal cancer (CRC) chemoprevention in pre-clinical trials by oncologist. However, the underlying anti-colon cancer mechanisms of wogonin are not yet fully understood. In the present study, the effect of wogonin on the initiation and development of colitis-associated cancer through p53 nuclear translocation was explored. AOM-DSS CRC animal model and human CRC HCT-116 cell model were used to evaluate the in vivo and in vitro anti-colon cancer action of wogonin. We observed that wogonin showed a dramaticlly preventive effect on colon cancer. Our results showed that wogonin caused apoptotic cell death in human CRC HCT-116 cell through increased endoplasmic reticulum (ER) stress. Meanwhile, excessive ER stress facilitated the cytoplasmic localization of p53 through increasing phosphor-p53 at S315 and S376 sites, induced caspase-dependent apoptosis and inhibited autophagy. Furthermore, we verified the chemoprevention effect and toxicity of wogonin in vivo by utilizing an AOM-DSS colon cancer animal model. We found that wogonin not only reduced tumor multiplicity, preserved colon length to normal (6.79 ± 0.34 to 7.41 ± 0.56, P < 0.05) but also didn’t induce side effects on various organs. In conclusion, these results explain the anti-tumor effect of wogonin in CRC and suggest wogonin as a potential therapeutic candidate for the therapeutic strategy in CRC treatment.

Lysyl oxidase (LOX) limits VSMC proliferation and neointimal thickening through its extracellular enzymatic activity

Lysyl oxidase (LOX) plays a critical role in extracellular matrix maturation and limits VSMC proliferation and vascular remodeling. We have investigated whether this anti-proliferative effect relies on the extracellular catalytically active LOX or on its biologically active propeptide (LOX-PP). High expression levels of both LOX and LOX-PP were detected in the vascular wall from transgenic mice over-expressing the full-length human LOX cDNA under the control of SM22α promoter (TgLOX), which targets the transgene to VSMC without affecting the expression of mouse LOX isoenzymes. TgLOX VSMC also secrete high amounts of both mature LOX and LOX-PP. Wild-type (WT) mouse VSMC exposed to VSMC supernatants from transgenic animals showed reduced proliferative rates (low [³H]-thymidine uptake and expression of PCNA) than those incubated with conditioned media from WT cells, effect that was abrogated by β-aminopropionitrile (BAPN), an inhibitor of LOX activity. Lentiviral over-expression of LOX, but not LOX-PP, decreased human VSMC proliferation, effect that was also prevented by BAPN. LOX transgenesis neither impacted local nor systemic inflammatory response induced by carotid artery ligation. Interestingly, in this model, BAPN normalized the reduced neointimal thickening observed in TgLOX mice. Therefore, extracellular enzymatically active LOX is required to limit both VSMC proliferation and vascular remodeling.

Contribution of Heme Oxygenase 2 to Blood Pressure Regulation in Response to Swimming Exercise and Detraining in Spontaneously Hypertensive Rats

Background

We aimed to determine the effects of exercise followed by detraining on systolic blood pressure (SBP), heme oxygenase 2 (HO-2) expression, and carboxyhemoglobin (COHb) concentration in spontaneously hypertensive rats (SHR) to explain the role of carbon monoxide (CO) in this process.

Material/Methods

Animals were randomized into exercised and detrained groups. Corresponding sedentary rats were grouped as Time 1–2. Swimming of 60 min/5 days/week for 10 weeks was applied. Detraining rats discontinued training for an additional 5 weeks. Gene and protein expressions were determined by real-time PCR and immunohistochemistry.

Results

Aorta HO-2 histological scores (HSCORE) of hypertensive rats were lower, while SBP was higher. Swimming caused enhancement of HO-2 immunostaining in aorta endothelium and adventitia of SHR. Exercise induced elevation of blood COHb index in SHR. Synchronous BP lowering effect of exercise was observed. HO-2 mRNA expression, HSCORE, and blood COHb index were unaltered during detraining, while SBP was still low in SHR.

Conclusions

CO synthesized by HO-2 at least partly plays a role in SBP regulation in the SHR- and BP-lowering effect of exercise. Regular exercise with short-term pauses may be advised to both hypertensives and individuals who are at risk.

Quantitative Micro-CT Analysis of Aortopathy in a Mouse Model of β-aminopropionitrile-induced Aortic Aneurysm and Dissection

Aortic aneurysm and dissection is associated with significant morbidity and mortality in the population and can be highly lethal. While animal models of aortic disease exist, in vivo imaging of the vasculature has been limited. In recent years, micro-computerized tomography (micro-CT) has emerged as a preferred modality for imaging both large and small vessels both in vivo and ex vivo. In conjunction with a method of vascular casting, we have successfully used micro-CT to characterize the frequency and distribution of aortic pathology in β-aminopropionitrile-treated C57/Bl6 mice. Technical limitations of this method include variations in the quality of the perfusion introduced by poor animal preparation, the application of proper methodologies for vessel size quantification, and the non-survivability of this procedure. This article details a methodology for the intravascular perfusion of a lead-based radiopaque silicone rubber for the quantitative characterization of aortopathy in a mouse model of aneurysm and dissection. In addition to visualizing aortic pathology, this method may be used for examining other vascular beds in vivo or vascular beds removed post-mortem.

Quantitative Micro-CT Analysis of Aortopathy in a Mouse Model of β-aminopropionitrile-induced Aortic Aneurysm and Dissection

Aortic aneurysm and dissection is associated with significant morbidity and mortality in the population and can be highly lethal. While animal models of aortic disease exist, in vivo imaging of the vasculature has been limited. In recent years, micro-computerized tomography (micro-CT) has emerged as a preferred modality for imaging both large and small vessels both in vivo and ex vivo. In conjunction with a method of vascular casting, we have successfully used micro-CT to characterize the frequency and distribution of aortic pathology in β-aminopropionitrile-treated C57/Bl6 mice. Technical limitations of this method include variations in the quality of the perfusion introduced by poor animal preparation, the application of proper methodologies for vessel size quantification, and the non-survivability of this procedure. This article details a methodology for the intravascular perfusion of a lead-based radiopaque silicone rubber for the quantitative characterization of aortopathy in a mouse model of aneurysm and dissection. In addition to visualizing aortic pathology, this method may be used for examining other vascular beds in vivo or vascular beds removed post-mortem.

Role of Magnesium Deficiency in Promoting Atherosclerosis, Endothelial Dysfunction, and Arterial Stiffening as Risk Factors for Hypertension

Arterial hypertension is a disease with a complex pathogenesis. Despite considerable knowledge about this socially significant disease, the role of magnesium deficiency (MgD) as a risk factor is not fully understood. Magnesium is a natural calcium antagonist. It potentiates the production of local vasodilator mediators (prostacyclin and nitric oxide) and alters vascular responses to a variety of vasoactive substances (endothelin-1, angiotensin II, and catecholamines). MgD stimulates the production of aldosterone and potentiates vascular inflammatory response, while expression/activity of various antioxidant enzymes (glutathione peroxidase, superoxide dismutase, and catalase) and the levels of important antioxidants (vitamin C, vitamin E, and selenium) are decreased. Magnesium balances the effects of catecholamines in acute and chronic stress. MgD may be associated with the development of insulin resistance, hyperglycemia, and changes in lipid metabolism, which enhance atherosclerotic changes and arterial stiffness. Magnesium regulates collagen and elastin turnover in the vascular wall and matrix metalloproteinase activity. Magnesium helps to protect the elastic fibers from calcium deposition and maintains the elasticity of the vessels. Considering the numerous positive effects on a number of mechanisms related to arterial hypertension, consuming a healthy diet that provides the recommended amount of magnesium can be an appropriate strategy for helping control blood pressure.

Vascular smooth muscle cells direct extracellular dysregulation in aortic stiffening of hypertensive rats

Aortic stiffening is an independent risk factor that underlies cardiovascular morbidity in the elderly. We have previously shown that intrinsic mechanical properties of vascular smooth muscle cells (VSMCs) play a key role in aortic stiffening in both aging and hypertension. Here, we test the hypothesis that VSMCs also contribute to aortic stiffening through their extracellular effects. Aortic stiffening was confirmed in spontaneously hypertensive rats (SHRs) vs. Wistar‐Kyoto (WKY) rats in vivo by echocardiography and ex vivo by isometric force measurements in isolated de‐endothelized aortic vessel segments. Vascular smooth muscle cells were isolated from thoracic aorta and embedded in a collagen I matrix in an in vitro 3D model to form reconstituted vessels. Reconstituted vessel segments made with SHR VSMCs were significantly stiffer than vessels made with WKY VSMCs. SHR VSMCs in the reconstituted vessels exhibited different morphologies and diminished adaptability to stretch compared to WKY VSMCs, implying dual effects on both static and dynamic stiffness. SHR VSMCs increased the synthesis of collagen and induced collagen fibril disorganization in reconstituted vessels. Mechanistically, compared to WKY VSMCs, SHR VSMCs exhibited an increase in the levels of active integrin β1‐ and bone morphogenetic protein 1 (BMP1)‐mediated proteolytic cleavage of lysyl oxidase (LOX). These VSMC‐induced alterations in the SHR were attenuated by an inhibitor of serum response factor (SRF)/myocardin. Therefore, SHR VSMCs exhibit extracellular dysregulation through modulating integrin β1 and BMP1/LOX via SRF/myocardin signaling in aortic stiffening.

Assessing Collagen and Elastin Pressure-dependent Microarchitectures in Live, Human Resistance Arteries by Label-free Fluorescence Microscopy

The pathogenic contribution of resistance artery remodeling is documented in essential hypertension, diabetes and the metabolic syndrome. Investigations and development of microstructurally motivated mathematical models for understanding the mechanical properties of human resistance arteries in health and disease have the potential to aid understanding how disease and medical treatments affect the human microcirculation. To develop these mathematical models, it is essential to decipher the relationship between the mechanical and microarchitectural properties of the microvascular wall. In this work, we describe an ex vivo method for passive mechanical testing and simultaneous label-free three-dimensional imaging of the microarchitecture of elastin and collagen in the arterial wall of isolated human resistance arteries. The imaging protocol can be applied to resistance arteries of any species of interest. Image analyses are described for quantifying i) pressure-induced changes in internal elastic lamina branching angles and adventitial collagen straightness using Fiji and ii) collagen and elastin volume densities determined using Ilastik software. Preferably all mechanical and imaging measurements are performed on live, perfused arteries, however, an alternative approach using standard video-microscopy pressure myography in combination with post-fixation imaging of re-pressurized vessels is discussed. This alternative method provides users with different options for analysis approaches. The inclusion of the mechanical and imaging data in mathematical models of the arterial wall mechanics is discussed, and future development and additions to the protocol are proposed.

More than a syllable in fib-ROS-is: The role of ROS on the fibrotic extracellular matrix and on cellular contacts

Fibrosis is characterized by excess deposition of extracellular matrix (ECM). However, the ECM changes during fibrosis not only quantitatively but also qualitatively. Thus, the composition is altered as the expression of various ECM proteins changes. Moreover, also posttranslational modifications, secretion, deposition and crosslinkage as well as the proteolytic degradation of ECM components run differently during fibrosis. As several of these processes involve redox reactions and some of them are even redox-regulated, reactive oxygen species (ROS) influence fibrotic diseases. Redox regulation of the ECM has not been studied intensively, although evidences exist that the alteration of the ECM, including the redox-relevant processes of its formation and degradation, may be of key importance not only as a cause but also as a consequence of fibrotic diseases. Myofibroblasts, which have differentiated from fibroblasts during fibrosis, produce most of the ECM components and in return obtain important environmental cues of the ECM, including their redox-dependent fibrotic alterations. Thus, myofibroblast differentiation and fibrotic changes of the ECM are interdependent processes and linked with each other via cell-matrix contacts, which are mediated by integrins and other cell adhesion molecules. These cell-matrix contacts are also regulated by redox processes and by ROS. However, most of the redox-catalyzing enzymes are localized within cells. Little is known about redox-regulating enzymes, especially the ones that control the formation and cleavage of redox-sensitive disulfide bridges within the extracellular space. They are also important players in the redox-regulative crosstalk between ECM and cells during fibrosis.

Cellular mechanisms underlying obesity-induced arterial stiffness

Obesity is an emerging pandemic driven by consumption of a diet rich in fat and highly refined carbohydrates (a Western diet) and a sedentary lifestyle in both children and adults. There is mounting evidence that arterial stiffness in obesity is an independent and strong predictor of cardiovascular disease (CVD), cognitive functional decline, and chronic kidney disease. Cardiovascular stiffness is a precursor to atherosclerosis, systolic hypertension, cardiac diastolic dysfunction, and impairment of coronary and cerebral flow. Moreover, premenopausal women lose the CVD protection normally afforded to them in the setting of obesity, insulin resistance, and diabetes, and this loss of CVD protection is inextricably linked to an increased propensity for arterial stiffness. Stiffness of endothelial and vascular smooth muscle cells, extracellular matrix remodeling, perivascular adipose tissue inflammation, and immune cell dysfunction contribute to the development of arterial stiffness in obesity. Enhanced endothelial cortical stiffness decreases endothelial generation of nitric oxide, and increased oxidative stress promotes destruction of nitric oxide. Our research over the past 5 years has underscored an important role of increased aldosterone and vascular mineralocorticoid receptor activation in driving development of cardiovascular stiffness, especially in females consuming a Western diet. In this review the cellular mechanisms of obesity-associated arterial stiffness are highlighted.

Oxidative Stress in Human Atherothrombosis: Sources, Markers and Therapeutic Targets

Atherothrombosis remains one of the main causes of morbidity and mortality worldwide. The underlying pathology is a chronic pathological vascular remodeling of the arterial wall involving several pathways, including oxidative stress. Cellular and animal studies have provided compelling evidence of the direct role of oxidative stress in atherothrombosis, but such a relationship is not clearly established in humans and, to date, clinical trials on the possible beneficial effects of antioxidant therapy have provided equivocal results. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is one of the main sources of reactive oxygen species (ROS) in human atherothrombosis. Moreover, leukocyte-derived myeloperoxidase (MPO) and red blood cell-derived iron could be involved in the oxidative modification of lipids/lipoproteins (LDL/HDL) in the arterial wall. Interestingly, oxidized lipoproteins, and antioxidants, have been analyzed as potential markers of oxidative stress in the plasma of patients with atherothrombosis. In this review, we will revise sources of ROS, focusing on NADPH oxidase, but also on MPO and iron. We will also discuss the impact of these oxidative systems on LDL and HDL, as well as the value of these modified lipoproteins as circulating markers of oxidative stress in atherothrombosis. We will finish by reviewing some antioxidant systems and compounds as therapeutic strategies to prevent pathological vascular remodeling.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.