Fecal Microbiota Transfer from Young Mice Reverts Vascular Aging Hallmarks and Metabolic Impairments in Aged Mice.

As a major risk factor for cardiometabolic diseases, aging refers to a gradual decline in physiological function, characterized with 12 conspicuous hallmarks, like telomere attrition, chronic inflammation, and dysbiosis. Common vascular aging hallmarks include endothelial dysfunction, telomere dysfunction, and vascular inflammation. In this study, we sought to test the hypothesis that young-derived gut microbiota retards vascular aging hallmarks and metabolic impairments in aged hosts. We also aimed to study the therapeutic efficacy of young microbiota in hosts of different ages. Fecal microbiota transplantation (FMT) from young to aged or middle-aged C57BL/6 mice was conducted for 6 consecutive weeks after antibiotic pretreatment. Endothelium-dependent relaxations (EDRs) in mouse arteries were determined by wire myography. Inflammation and AMPK/SIRT1 signaling in mouse aortas and intestines were studied by biochemical assays. The telomere function of aortas and intestines, in terms of telomerase reverse transcriptase expression, telomerase activity, and relative telomere length, were also studied. FMT significantly reverted vascular dysfunction and metabolic impairments in middle-aged mice than in aged mice. Besides, FMT significantly reverted inflammation and telomere dysfunction in aortas and intestines of middle-aged mice. Improved intestinal barrier function and activated AMPK/SIRT1 signaling potentially underlie benefits of FMT. The findings imply gut-vascular connection as potential target against age-associated cardiometabolic disorders, highlight crosstalk among aging hallmarks, and suggest a critical timepoint for efficacy of anti-aging interventions.

Activation of Nrf2 inhibits atherosclerosis in ApoE-/- mice through suppressing endothelial cell inflammation and lipid peroxidation.

BACKGROUND: Nuclear erythroid 2-related factor 2 (Nrf2), a transcription factor, is critically involved in the regulation of oxidative stress and inflammation. However, the role of endothelial Nrf2 in atherogenesis has yet to be defined. In addition, how endothelial Nrf2 is activated and whether Nrf2 can be targeted for the prevention and treatment of atherosclerosis is not explored. METHODS: RNA-sequencing and single-cell RNA sequencing analysis of mouse atherosclerotic aortas were used to identify the differentially expressed genes. In vivo endothelial cell (EC)-specific activation of Nrf2 was achieved by injecting adeno-associated viruses into ApoE-/- mice, while EC-specific knockdown of Nrf2 was generated in Cdh5CreCas9floxed-stopApoE-/- mice. RESULTS: Endothelial inflammation appeared as early as on day 3 after feeding of a high cholesterol diet (HCD) in ApoE-/- mice, as reflected by mRNA levels, immunostaining and global mRNA profiling, while the immunosignal of the end-product of lipid peroxidation (LPO), 4-hydroxynonenal (4-HNE), started to increase on day 10. TNF-α, 4-HNE, and erastin (LPO inducer), activated Nrf2 signaling in human ECs by increasing the mRNA and protein expression of Nrf2 target genes. Knockdown of endothelial Nrf2 resulted in augmented endothelial inflammation and LPO, and accelerated atherosclerosis in Cdh5CreCas9floxed-stopApoE-/- mice. By contrast, both EC-specific and pharmacological activation of Nrf2 inhibited endothelial inflammation, LPO, and atherogenesis. CONCLUSIONS: Upon HCD feeding in ApoE-/- mice, endothelial inflammation is an earliest event, followed by the appearance of LPO. EC-specific activation of Nrf2 inhibits atherosclerosis while EC-specific knockdown of Nrf2 results in the opposite effect. Pharmacological activators of endothelial Nrf2 may represent a novel therapeutic strategy for the treatment of atherosclerosis.

Pien Tze Huang (PZH) protects endothelial function in diabetic mice.

Endothelial dysfunction is the most common pathological feature of cardiovascular diseases, including diabetes mellitus, hypertension and atherosclerosis. It affects both macro- and micro-vasculatures, causing functional impairment of multiple organs. Pien Tze Huang (PZH) is a well-studied traditional Chinese medicine (TCM) with multiple pharmacological properties that produces therapeutic benefits against colorectal cancer, non-alcoholic steatohepatitis and neurodegenerative diseases. However, it is unknown how PZH affects vascular function under pathological conditions. Therefore, this study aimed to investigate the effect of PZH on endothelial function and the underlying mechanisms in db/db diabetic mice. The results showed that chronic treatment of PZH (250 mg/kg/day, 5 weeks) improved endothelial function by restoring endothelium-dependent relaxation through the activation of the Akt-eNOS pathway and inhibition of endothelial oxidative stress, which increased nitric oxide bioavailability. Furthermore, PZH treatment increased insulin sensitivity and suppressed inflammation in diabetic mice. These new findings suggest that PZH may have vaso-protective properties and the potential to protect against diabetic vasculopathy by preserving endothelial function.

Endogenous and microbial biomarkers for periodontitis and type 2 diabetes mellitus.

It has been well documented that there is a two-way relationship between diabetes mellitus and periodontitis. Diabetes mellitus represents an established risk factor for chronic periodontitis. Conversely, chronic periodontitis adversely modulates serum glucose levels in diabetic patients. Activated immune and inflammatory responses are noted during diabetes and periodontitis, under the modulation of similar biological mediators. These activated responses result in increased activity of certain immune-inflammatory mediators including adipokines and microRNAs in diabetic patients with periodontal disease. Notably, certain microbes in the oral cavity were identified to be involved in the occurrence of diabetes and periodontitis. In other words, these immune-inflammatory mediators and microbes may potentially serve as biomarkers for risk assessment and therapy selection in diabetes and periodontitis. In this review, we briefly provide an updated overview on different potential biomarkers, providing novel diagnostic and therapeutic insights on periodontal complications and diabetes mellitus.

Oral microbiome: a doubtful predictor but potential target of cardiovascular diseases.

Our oral cavity houses various types of microbes including bacteria, protozoa, fungi and viruses, harboring over 700 bacterial species. Oral dysbiosis refers to the imbalance between symbionts and pathobionts in the oral cavity, posing potential threats to host cardiovascular health. Importantly, oral dysbiosis promotes cardiovascular pathophysiology through different mechanisms. Although overgrowth of certain pathogenic bacteria have been indicated in some cardiometabolic diseases, it is still premature to consider oral microbiome as a suitable predictor for non-invasive diagnostic purpose. However, targeting oral microbiome might still provide preventive and therapeutic insights on cardiovascular diseases. Further extensive efforts are needed to deepen our understanding on oral-cardiovascular connection in the context of diagnostic and therapeutic perspectives.

Tubular injury in diabetic kidney disease: molecular mechanisms and potential therapeutic perspectives.

Diabetic kidney disease (DKD) is a chronic complication of diabetes and the leading cause of end-stage renal disease (ESRD) worldwide. Currently, there are limited therapeutic drugs available for DKD. While previous research has primarily focused on glomerular injury, recent studies have increasingly emphasized the role of renal tubular injury in the pathogenesis of DKD. Various factors, including hyperglycemia, lipid accumulation, oxidative stress, hypoxia, RAAS, ER stress, inflammation, EMT and programmed cell death, have been shown to induce renal tubular injury and contribute to the progression of DKD. Additionally, traditional hypoglycemic drugs, anti-inflammation therapies, anti-senescence therapies, mineralocorticoid receptor antagonists, and stem cell therapies have demonstrated their potential to alleviate renal tubular injury in DKD. This review will provide insights into the latest research on the mechanisms and treatments of renal tubular injury in DKD.

Induction of KLF2 by Exercise Activates eNOS to Improve Vasodilatation in Diabetic Mice.

Diabetic endothelial dysfunction associated with diminished endothelial nitric oxide (NO) synthase (eNOS) activity accelerates the development of atherosclerosis and cardiomyopathy. However, the approaches to restore eNOS activity and endothelial function in diabetes remain limited. The current study shows that enhanced expression of Krüppel-like factor 2 (KLF2), a shear stress-inducible transcription factor, effectively improves endothelial function through increasing NO bioavailability. KLF2 expression is suppressed in diabetic mouse aortic endothelium. Running exercise and simvastatin treatment induce endothelial KLF2 expression in db/db mice. Adenovirus-mediated endothelium-specific KLF2 overexpression enhances both endothelium-dependent relaxation and flow-mediated dilatation, while it attenuates oxidative stress in diabetic mouse arteries. KLF2 overexpression increases the phosphorylation of eNOS at serine 1177 and eNOS dimerization. RNA-sequencing analysis reveals that KLF2 transcriptionally upregulates genes that are enriched in the cyclic guanosine monophosphate-protein kinase G-signaling pathway, cAMP-signaling pathway, and insulin-signaling pathway, all of which are the upstream regulators of eNOS activity. Activation of the phosphoinositide 3-kinase-Akt pathway and Hsp90 contributes to KLF2-induced increase of eNOS activity. The present results suggest that approaches inducing KLF2 activation, such as physical exercise, are effective to restore eNOS activity against diabetic endothelial dysfunction. ARTICLE HIGHLIGHTS: Exercise and statins restore the endothelial expression of Krüppel-like factor 2 (KLF2), which is diminished in diabetic db/db mice. Endothelium-specific overexpression of KLF2 improves endothelium-dependent relaxation and flow-mediated dilation through increasing nitric oxide bioavailability. KLF2 promotes endothelial nitric oxide synthase (eNOS) coupling and phosphorylation in addition to its known role in eNOS transcription. KLF2 upregulates the expression of several panels of genes that regulate eNOS activity.

Thioridazine protects against disturbed flow-induced atherosclerosis by inhibiting RhoA/YAP-mediated endothelial inflammation.

Atherosclerotic diseases remain the leading cause of adult mortality and impose heavy burdens on health systems globally. Our previous study found that disturbed flow enhanced YAP activity to provoke endothelial activation and atherosclerosis, and targeting YAP alleviated endothelial inflammation and atherogenesis. Therefore, we established a luciferase reporter assay-based drug screening platform to seek out new YAP inhibitors for anti-atherosclerotic treatment. By screening the FDA-approved drug library, we identified that an anti-psychotic drug thioridazine markedly suppressed YAP activity in human endothelial cells. Thioridazine inhibited disturbed flow-induced endothelial inflammatory response in vivo and in vitro. We verified that the anti-inflammatory effects of thioridazine were mediated by inhibition of YAP. Thioridazine regulated YAP activity via restraining RhoA. Moreover, administration of thioridazine attenuated partial carotid ligation- and western diet-induced atherosclerosis in two mouse models. Overall, this work opens up the possibility of repurposing thioridazine for intervention of atherosclerotic diseases. This study also shed light on the underlying mechanisms that thioridazine inhibited endothelial activation and atherogenesis via repression of RhoA-YAP axis. As a new YAP inhibitor, thioridazine might need further investigation and development for the treatment of atherosclerotic diseases in clinical practice.

Molecular mechanisms and therapeutic perspectives of peroxisome proliferator-activated receptor α agonists in cardiovascular health and disease.

The prevalence of cardiovascular disease (CVD) has been rising due to sedentary lifestyles and unhealthy dietary patterns. Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor regulating multiple biological processes, such as lipid metabolism and inflammatory response critical to cardiovascular homeostasis. Healthy endothelial cells (ECs) lining the lumen of blood vessels maintains vascular homeostasis, where endothelial dysfunction associated with increased oxidative stress and inflammation triggers the pathogenesis of CVD. PPARα activation decreases endothelial inflammation and senescence, contributing to improved vascular function and reduced risk of atherosclerosis. Phenotypic switch and inflammation of vascular smooth muscle cells (VSMCs) exacerbate vascular dysfunction and atherogenesis, in which PPARα activation improves VSMC homeostasis. Different immune cells participate in the progression of vascular inflammation and atherosclerosis. PPARα in immune cells plays a critical role in immunological events, such as monocyte/macrophage adhesion and infiltration, macrophage polarization, dendritic cell (DC) embedment, T cell activation, and B cell differentiation. Cardiomyocyte dysfunction, a major risk factor for heart failure, can also be alleviated by PPARα activation through maintaining cardiac mitochondrial stability and inhibiting cardiac lipid accumulation, oxidative stress, inflammation, and fibrosis. This review discusses the current understanding and future perspectives on the role of PPARα in the regulation of the cardiovascular system as well as the clinical application of PPARα ligands.

Perivascular adipose tissue: Fine-tuner of vascular redox status and inflammation.

Perivascular adipose tissue (PVAT) refers to the aggregate of adipose tissue surrounding the vasculature, exhibiting the phenotypes of white, beige and brown adipocytes. PVAT has emerged as an active modulator of vascular homeostasis and pathogenesis of cardiovascular diseases in addition to its structural role to provide mechanical support to blood vessels. More specifically, PVAT is closely involved in the regulation of reactive oxygen species (ROS) homeostasis and inflammation along the vascular tree, through the tight interaction between PVAT and cellular components of the vascular wall. Furthermore, the phenotype-genotype of PVAT at different regions of vasculature varies corresponding to different cardiovascular risks. During ageing and obesity, the cellular proportions and signaling pathways of PVAT vary in favor of cardiovascular pathogenesis by promoting ROS generation and inflammation. Physiological means and drugs that alter PVAT mass, components and signaling may provide new therapeutic insights in the treatment of cardiovascular diseases. In this review, we aim to provide an updated understanding towards PVAT in the context of redox regulation, and to highlight the therapeutic potential of targeting PVAT against cardiovascular complications.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: The Novel Therapeutic Option for Regenerative Dentistry.

Dental mesenchymal stem cells (MSCs) are characterized by unlimited self-renewal ability and high multidirectional differentiation potential. Since dental MSCs can be easily isolated and exhibit a high capability to differentiate into odontogenic cells, they are considered as attractive therapeutic agents in regenerative dentistry. Recently, MSC-derived extracellular vesicles (MSC-EVs) have attracted widespread attention as carriers for cell-free therapy due to their potential functions. Many studies have shown that MSC-EVs can mediate microenvironment at tissue damage site, and coordinate the regeneration process. Additionally, MSC-EVs can mediate intercellular communication, thus affecting the phenotypes and functions of recipient cells. In this review, we mainly summarized the types of MSCs that could be potentially applied in regenerative dentistry, the possible molecular cargos of MSC-EVs, and the major effects of MSC-EVs on the therapeutic induction of osteogenic differentiation.

SOX4 is a novel phenotypic regulator of endothelial cells in atherosclerosis revealed by single-cell analysis.

INTRODUCTION: Atherosclerotic complications represent the leading cause of cardiovascular mortality globally. Dysfunction of endothelial cells (ECs) often initiates the pathological events in atherosclerosis. OBJECTIVES: In this study, we sought to investigate the transcriptional profile of atherosclerotic aortae, identify novel regulator in dysfunctional ECs and hence provide mechanistic insights into atherosclerotic progression. METHODS: We applied single-cell RNA sequencing (scRNA-seq) on aortic cells from Western diet-fed apolipoprotein E-deficient (ApoE-/-) mice to explore the transcriptional landscape and heterogeneity of dysfunctional ECs. In vivo validation of SOX4 upregulation in ECs were performed in atherosclerotic tissues, including mouse aortic tissues, human coronary arteries, and human renal arteries. Single-cell analysis on human aortic aneurysmal tissue was also performed. Downstream vascular abnormalities induced by EC-specific SOX4 overexpression, and upstream modulators of SOX4 were revealed by biochemical assays, immunostaining, and wire myography. Effects of shear stress on endothelial SOX4 expression was investigated by in vitro hemodynamic study. RESULTS: Among the compendium of aortic cells, mesenchymal markers in ECs were significantly enriched. Two EC subsets were subsequently distinguished, as the 'endothelial-like' and 'mesenchymal-like' subsets. Conventional assays consistently identified SOX4 as a novel atherosclerotic marker in mouse and different human arteries, additional to a cancer marker. EC-specific SOX4 overexpression promoted atherogenesis and endothelial-to-mesenchymal transition (EndoMT). Importantly, hyperlipidemia-associated cytokines and oscillatory blood flow upregulated, whereas the anti-diabetic drug metformin pharmacologically suppressed SOX4 level in ECs. CONCLUSION: Our study unravels SOX4 as a novel phenotypic regulator during endothelial dysfunction, which exacerbates atherogenesis. Our study also pinpoints hyperlipidemia-associated cytokines and oscillatory blood flow as endogenous SOX4 inducers, providing more therapeutic insights against atherosclerotic diseases.

Endothelial UCP2 Is a Mechanosensitive Suppressor of Atherosclerosis.

BACKGROUND: Inflamed endothelial cells (ECs) trigger atherogenesis, especially at arterial regions experiencing disturbed blood flow. UCP2 (Uncoupling protein 2), a key mitochondrial antioxidant protein, improves endothelium-dependent relaxation in obese mice. However, whether UCP2 can be regulated by shear flow is unknown, and the role of endothelial UCP2 in regulating inflammation and atherosclerosis remains unclear. This study aims to investigate the mechanoregulation of UCP2 expression in ECs and the effect of UCP2 on endothelial inflammation and atherogenesis. METHODS: In vitro shear stress simulation system was used to investigate the regulation of UCP2 expression by shear flow. EC-specific Ucp2 knockout mice were used to investigate the role of UCP2 in flow-associated atherosclerosis. RESULTS: Shear stress experiments showed that KLF2 (Krüppel-like factor 2) mediates fluid shear stress-dependent regulation of UCP2 expression in human aortic and human umbilical vein ECs. Unidirectional shear stress, statins, and resveratrol upregulate whereas oscillatory shear stress and proinflammatory stimuli inhibit UCP2 expression through altered KLF2 expression. KLF2 directly binds to UCP2 promoter to upregulate its transcription in human umbilical vein ECs. UCP2 knockdown induced expression of genes involved in proinflammatory and profibrotic signaling, resulting in a proatherogenic endothelial phenotype. EC-specific Ucp2 deletion promotes atherogenesis and collagen production. Additionally, we found endothelial Ucp2 deficiency aggravates whereas adeno-associated virus-mediated EC-Ucp2 overexpression inhibits carotid atherosclerotic plaque formation in disturbed flow-enhanced atherosclerosis mouse model. RNA-sequencing analysis revealed FoxO1 (forkhead box protein O1) as the major proinflammatory transcriptional regulator activated by UCP2 knockdown, and FoxO1 inhibition reduced vascular inflammation and disturbed flow-enhanced atherosclerosis. We showed further that UCP2 level is critical for phosphorylation of AMPK (AMP-activated protein kinase), which is required for UCP2-induced inhibition of FoxO1. CONCLUSIONS: Altogether, our studies uncover that UCP2 is novel mechanosensitive gene under the control of fluid shear stress and KLF2 in ECs. UCP2 expression is critical for endothelial proinflammatory response and atherogenesis. Therapeutic strategies enhancing UCP2 level may have therapeutic potential against atherosclerosis.

Activation of AMPK/miR-181b Axis Alleviates Endothelial Dysfunction and Vascular Inflammation in Diabetic Mice.

Hyperglycemia in diabetes mellitus impairs endothelial function and disrupts microRNA (miRNA) profiles in vasculature, increasing the risk of diabetes-associated complications, including coronary artery disease, diabetic retinopathy, and diabetic nephropathy. miR-181b was previously reported to be an anti-inflammatory mediator in vasculature against atherosclerosis. The current study aimed to investigate whether miR-181b ameliorates diabetes-associated endothelial dysfunction, and to identify potential molecular mechanisms and upstream inducer of miR-181b. We found that miR-181b level was decreased in renal arteries of diabetic patients and in advanced glycation end products (AGEs)-treated renal arteries of non-diabetic patients. Transfection of miR-181b mimics improved endothelium-dependent vasodilation in aortas of high fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice, accompanied by suppression of superoxide overproduction and vascular inflammation markers. AMPK activator-induced AMPK activation upregulated miR-181b level in human umbilical vein endothelial cells (HUVECs). Chronic exercise, potentially through increased blood flow, activated AMPK/miR-181b axis in aortas of diabetic mice. Exposure to laminar shear stress upregulated miR-181b expression in HUVECs. Overall, our findings highlight a critical role of AMPK/miR-181b axis and extend the benefits of chronic exercise in counteracting diabetes-associated endothelial dysfunction.

Targeting endothelial dysfunction and inflammation.

Vascular endothelium maintains vascular homeostasis through liberating a spectrum of vasoactive molecules, both protective and harmful regulators of vascular tone, structural remodeling, inflammation and atherogenesis. An intricate balance between endothelium-derived relaxing factors (nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor) and endothelium-derived contracting factors (superoxide anion, endothelin-1 and constrictive prostaglandins) tightly regulates vascular function. Disruption of such balance signifies endothelial dysfunction, a critical contributor in aging and chronic cardiometabolic disorders, such as obesity, diabetes, hypertension, dyslipidemia and atherosclerotic vascular diseases. Among many proposed cellular and molecular mechanisms causing endothelial dysfunction, oxidative stress and inflammation are often the pivotal players and they are naturally considered as useful targets for intervention in patients with cardiovascular and metabolic diseases. In this article, we provide a recent update on the therapeutic values of pharmacological agents, such as cyclooxygenase-2 inhibitors, renin-angiotensin-system inhibitors, bone morphogenic protein 4 inhibitors, peroxisome proliferator-activated receptor δ agonists, and glucagon-like peptide 1-elevating drugs, and the physiological factors, particularly hemodynamic forces, that improve endothelial function by targeting endothelial oxidative stress and inflammation.

Endothelial dysfunction after androgen deprivation therapy and the possible underlying mechanisms.

INTRODUCTION: Androgen deprivation therapy (ADT) is a key treatment modality in the management of prostate cancer (PCa), especially for patients with metastatic disease. Increasing evidences suggest that patients who received ADT have increased incidence of diabetes, myocardial infarction, stroke, and even mortality. It is important to understand the pathophysiological mechanisms on how ADT increases cardiovascular risk and induces cardiovascular events, which would provide important information for potential implementation of preventive measures. METHODS: Twenty-six 12-week-old male SD rats were divided into four groups for different types of ADTs including: the bilateral orchidectomy group (Orx), LHRH agonist group (leuprolide), LHRH antagonist group (degarelix), and control group. After treated with drug or adjuvant injection every 3 weeks for 24 weeks, all rats were sacrificed and total blood were collected. Aorta, renal arteries, and kidney were preserved for functional assay, immunohistochemistry, western blot, and quantitative reverse-transcription polymerase chain reaction. RESULTS: In vascular reactivity assays, aorta, intrarenal, and coronary arteries of all three ADT groups showed endothelial dysfunction. AT1R and related molecules at protein and messenger RNA (mRNA) level were tested, and AT1R pathway was shown to be activated and played a role in endothelial dysfunction. Both ACE and AT1R mRNA levels were doubled in the aorta in the leuprolide group while Orx and degarelix groups showed upregulation of AT1R in the kidney tissues. By immunohistochemistry, our result showed higher expression of AT1R in the intrarenal arteries of leuprolide and degarelix groups. The role of reactive oxygen species in endothelial dysfunction was confirmed by DHE fluorescence, nitrotyrosine overexpression, and upregulation of NOX2 in the different ADT treatment groups. CONCLUSION: ADT causes endothelial dysfunction in male rats. GnRH receptor agonist compared to GnRH receptor antagonist, showed more impairment of endothelial function in the aorta and intrarenal arteries. Such change might be associated with upregulation and activation of AngII-AT1R-NOX2 induced oxidative stress in the vasculature. These results help to explain the different cardiovascular risks and outcomes related to different modalities of ADT treatment.

KLF2 Mediates the Suppressive Effect of Laminar Flow on Vascular Calcification by Inhibiting Endothelial BMP/SMAD1/5 Signaling.

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A high methionine and low folate diet alters glucose homeostasis and gut microbiome.

Hyperhomocysteinemia (HHcy) is considered as a risk factor for several complications, including cardiovascular and neurological disorders. A high methionine low folate (HMLF) diet chronically causes HHcy by accumulating homocysteine in the systemic circulation. Elevated Hcy level is also associated with the incidence of diabetes mellitus. However, very few studies focus on the impact of HMLF diet on glucose homeostasis, and that on gut microbiome profile. HHcy was induced by feeding C57BL/6 mice a HMLF diet for 8 weeks. The HMLF diet feeding resulted in a progressive body weight loss, and development of slight glucose intolerance and insulin resistance in HHcy mice. Notably, the HMLF diet alters the gut microbiome profile and increases the relative abundance of porphyromonadaceae family of bacteria in HHcy mice. These findings provide new insights into the roles of dysregulated glucose homeostasis and gut flora in the pathogenesis of HHcy-related complications.

A GLP-1 analog lowers ER stress and enhances protein folding to ameliorate homocysteine-induced endothelial dysfunction.

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases and increases mortality in type 2 diabetic patients. HHcy induces endoplasmic reticulum (ER) stress and oxidative stress to impair endothelial function. The glucagon-like peptide 1 (GLP-1) analog exendin-4 attenuates endothelial ER stress, but the detailed vasoprotective mechanism remains elusive. The present study investigated the beneficial effects of exendin-4 against HHcy-induced endothelial dysfunction. Exendin-4 pretreatment reversed homocysteine-induced impairment of endothelium-dependent relaxations in C57BL/6 mouse aortae ex vivo. Four weeks subcutaneous injection of exendin-4 restored the impaired endothelial function in both aortae and mesenteric arteries isolated from mice with diet-induced HHcy. Exendin-4 treatment lowered superoxide anion accumulation in the mouse aortae both ex vivo and in vivo. Exendin-4 decreased the expression of ER stress markers (e.g., ATF4, spliced XBP1, and phosphorylated eIF2α) in human umbilical vein endothelial cells (HUVECs), and this change was reversed by cotreatment with compound C (CC) (AMPK inhibitor). Exendin-4 induced phosphorylation of AMPK and endothelial nitric oxide synthase in HUVECs and arteries. Exendin-4 increased the expression of endoplasmic reticulum oxidoreductase (ERO1α), an important ER chaperone in endothelial cells, and this effect was mediated by AMPK activation. Experiments using siRNA-mediated knockdown or adenoviral overexpression revealed that ERO1α mediated the inhibitory effects of exendin-4 on ER stress and superoxide anion production, thus ameliorating HHcy-induced endothelial dysfunction. The present results demonstrate that exendin-4 reduces HHcy-induced ER stress and improves endothelial function through AMPK-dependent ERO1α upregulation in endothelial cells and arteries. AMPK activation promotes the protein folding machinery in endothelial cells to suppress ER stress.

Interplay Between Oxidative Stress, Cyclooxygenases, and Prostanoids in Cardiovascular Diseases.

Significance: Endothelial cells lining the lumen of blood vessels play an important role in the regulation of cardiovascular functions through releasing both vasoconstricting and vasodilating factors. The production and function of vasoconstricting factors are largely elevated in hypertension, diabetes, atherosclerosis, and ischemia/reperfusion injuries. Cyclooxygenases (COXs) are the major enzymes producing five different prostanoids that act as either contracting or relaxing substances. Under conditions of increased oxidative stress, the expressions and activities of COX isoforms are altered, resulting in changes in production of various prostanoids and thus affecting vascular tone. This review briefly summarizes the relationship between oxidative stress, COXs, and prostanoids, thereby providing new insights into the pathophysiological mechanisms of cardiovascular diseases (CVDs). Recent Advances: Many new drugs targeting oxidative stress, COX-2, and prostanoids against common CVDs have been evaluated in recent years and they are summarized in this review. Critical Issues: Comprehensive understanding of the complex interplay between oxidative stress, COXs, and prostanoids in CVDs helps develop more effective measures against cardiovascular pathogenesis. Future Directions: Apart from minimizing the undesired effects of harmful prostanoids, future studies shall investigate the restoration of vasoprotective prostanoids as a means to combat CVDs. Antioxid. Redox Signal. 34, 784-799.