GPR4 signaling is essential for the promotion of acid-mediated angiogenic capacity of endothelial progenitor cells by activating STAT3/VEGFA pathway in patients with coronary artery disease

M2 macrophages activate the IL-10/JAK2/STAT3 pathway to induce pathological microangiogenesis in the nucleus pulposus exacerbating intervertebral disc degeneration

BACKGROUND

Macrophage infiltration accompanied by pathological microangiogenesis in the nucleus pulposus (NP) plays a critical role in the progression of intervertebral disc degeneration (IDD). However, the involvement of M2 macrophages in mediating NP pathological angiogenesis and their underlying mechanisms remain unclear.

METHODS

Firstly, the expression of M2 macrophage (CD206) and microangiogenic (CD34) markers in human degenerated NP was observed by immunohistochemical staining, subsequently, a co-culture system of M2 macrophages and NP cells was established. IL-10 expression was silenced using siRNA to assess the pro-angiogenic effects of M2 macrophages in IDD via IL-10 and its downstream janus kinase (JAK) 2/ signal transducer and activator of transcription (STAT) 3 pathway. AG490, a specific JAK2/STAT3 inhibitor, was applied to determine whether IL-10 exerts its effects through this pathway and to evaluate its impact on angiogenesis and extracellular matrix (ECM) metabolism in NP pathology.

RESULTS

CD206 and CD34 were co-expressed in degenerated NP tissue. Degenerated NP cells secreted CCL17, CCL18, and CD206, exhibiting M2-like characteristics. Co-culture of M2 macrophages with degenerated NP cells led to IL-10 secretion to promote CD34 expression, and downregulated anabolic genes (type II collagen (COL2), aggrecan), and upregulated catabolic genes (matrix metalloproteinase (MMP)-3, MMP-7). JAK2 and STAT3 expression was significantly increased following co-culture. Activation of the JAK2/STAT3 pathway enhanced vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor (VEGFR), and CD34 expression and induced further downregulation of COL2 and aggrecan and upregulation of MMP-3 and MMP-7.

CONCLUSION

M2 macrophage infiltration and pathological neovascularization are prominent in degenerated NP tissue. IL-10 secreted by M2 macrophages activates the JAK2/STAT3 pathway to promote pathological microangiogenesis by up-regulate the expression of VEGF/VEGFR. This process disrupts ECM and accelerates the progression of IDD.

CLINICAL TRIAL NUMBER

Not applicable.

Fatty acid binding protein 3 activates endothelial adhesion of circulating monocytes and impairs endothelial angiogenesis

BACKGROUND AND PURPOSE

Vascular inflammation and endothelial dysfunction cause the development of atherosclerotic cardiovascular diseases including coronary artery disease (CAD). While elevated fatty acid binding protein 3 (FABP3) may be associated with the presence of cardiovascular diseases, its mechanistic effects remain unclear. This study aimed to investigate the role of FABP3 in impaired angiogenesis and the development of atherosclerosis in CAD.

EXPERIMENTAL APPROACH

In total, 1104 patients were enrolled in a clinical observational study and the correlation between serum FABP3 and cardiovascular events were analysed. Another group of CAD patients and non-CAD subjects were enrolled, and their plasma FABP3 concentrations were measured. Primary cultured mononuclear cells endothelial progenitor cells and human coronary artery endothelial cells were used in vitro. Matrigel plug neovascularisation assay and the aortic ring assay were used in wild-type and apolipoprotein E-knockout mice in vivo.

KEY RESULTS

Circulating FABP3 was up-regulated in the cardiovascular event-positive group and in the CAD patients. Mononuclear cells from the CAD patients presented increased expression of FABP3. FABP3 enhanced the expression of adhesion molecules, including integrin β2, integrin α4 and PSGL1 in mononuclear cells. FABP3 caused endothelial cell dysfunction through the ERK/p38/STAT1/VEGF signalling pathway. Moreover, oxLDL or TNF-α stimulations impaired endothelial cell function through FABP3-dependent signalling pathways. FABP3 also impaired in vivo angiogenesis.

CONCLUSION AND IMPLICATIONS

This study elucidates the clinical and pathological impact of FABP3 on atherosclerotic CAD. Future research may be necessary to evaluate whether FABP3 could be a therapeutic target, especially with regard to stable CAD.

Biochemical impact of ALAEm supplementation in late gestation on the reproductive performance of sows

Adding plant extracts to diets to enhance sow performance and health is widely regarded as a healthy and sustainable practice. In promoting antibiotic-free farming, plant extracts have emerged as a leading solution for enhancing sow fertility through nutritional strategies. The aim of this study was to investigate the biochemical impacts of supplementation of sows with ALAEm (composed of nine plant extracts) on blood and placental indices of sows in late gestation. The components of ALAEm were determined by UPLC-MS/MS. 196 normal gestation parturient sows were randomly allocated into two groups (n = 98 per group): the control group and the test group fed 20 g/d ALAEm supplementation at 74-114 d of gestation. The study examined the various clinical indexes in the blood, the expression of genes and proteins and metabolomics in the placenta. Dietary ALAEm supplementation improved sow reproductive performance (total number of piglets born alive, number of piglets weaned, wean weight), serum biochemical indices, placental structure and increased gene and protein expression of ZO-1, Claudin-1 and other placental junction-associated factors. ALAEm attenuated placental tissue oxidation, inflammation, and apoptosis, promoted placental growth (EGF and IGF-1) and angiogenesis factors (VEGFA, PIGF and other factors), and increased the nutrient transport in placental (GLUT1 and SNAT2). Dietary ALAEm supplementation decreased the number of metabolites associated with lipid metabolism through alpha-linolenic acid metabolism. Therefore, dietary supplementation of ALAEm in the late gestation may improve fertility by reducing the levels of inflammation, oxidation and apoptosis in placental tissues via the EGFR/VEGFR2-PI3K-AKT1 pathway, promoting placental growth, angiogenesis and nutrient transport, and altering the levels of placental lipid metabolites via α-linolenic acid metabolism.

LncRNA Growth Arrest Specific 5 Promotes Glucose Metabolism Reprogramming Via the IGF2BP1/SIX1 Axis and Inhibits Ferroptosis of Endothelial Progenitor Cells Via the miR-23a-3p/SLC7A11 Axis in Coronary Heart Disease

BACKGROUND

Growth arrest specific 5 (GAS5) is a long noncoding RNA (lncRNA) that regulates the function of cardiovascular cells in various cardiovascular diseases. The current study delved into the regulation of GAS5 on the function of endothelial progenitor cells (EPCs) and its potential regulatory mechanism in coronary heart disease (CHD).

METHODS

Reverse transcription-quantitative polymerase chain reaction was used to detect GAS5 expression in the blood samples and EPCs from CHD patients and healthy controls. Cell Counting Kit-8, colony formation, flow cytometry, and transwell assays were performed to evaluate cell phenotype of EPCs. Ferroptosis was detected by the measurement of Fe2+, malondialdehyde, GSH, and reactive oxygen species (ROS) levels. Glycolysis was determined by extracellular acidification rate (ECAR), oxygen consumption rate (OCR), glucose uptake and lactate production.

RESULTS

Growth arrest specific 5 was downregulated in the blood samples and EPCs from CHD patients. Growth arrest specific 5 deficiency suppressed EPC proliferative capacity, migration, invasion and facilitated EPC apoptosis while GAS5 overexpression showed contrary effects. Moreover, GAS5 silencing inhibited the glucose metabolic reprogramming, as evidenced by the reduced ECAR, glycolysis capacity, ATP, glucose uptake and lactate production, and elevated OCR. Additionally, GAS5 overexpression attenuated the erastin-induced ferroptosis of EPCs. Growth arrest specific 5 could bind to IGF2BP1 to enhance the mRNA stability of glycolysis transcriptional regulator SIX1. Growth arrest specific 5 interacted with miR-23a-3p to regulate SLC7A11 expression. GAS5 promoted glucose metabolic reprogramming of EPCs by upregulating SIX1 and inhibited EPC ferroptosis by elevating SLC7A11.

CONCLUSION

Growth arrest specific 5 promotes glucose metabolic reprogramming and represses ferroptosis of EPCs via the IGF2BP1/SIX1 and miR-23a-3p/SLC7A11 dual-regulatory pathways in CHD.

Evolutionary study and structural basis of proton sensing by Mus GPR4 and Xenopus GPR4

Animals have evolved pH-sensing membrane receptors, such as G-protein-coupled receptor 4 (GPR4), to monitor pH changes related to their physiology and generate adaptive reactions. However, the evolutionary trajectory and structural mechanism of proton sensing by GPR4 remain unresolved. Here, we observed a positive correlation between the optimal pH of GPR4 activity and the blood pH range across different species. By solving 7-cryoelectron microscopy (cryo-EM) structures of Xenopus tropicalis GPR4 (xtGPR4) and Mus musculus GPR4 (mmGPR4) under varying pH conditions, we identified that protonation of HECL2-45.47 and H7.36 enabled polar network establishment and tighter association between the extracellular loop 2 (ECL2) and 7 transmembrane (7TM) domain, as well as a conserved propagating path, which are common mechanisms underlying protonation-induced GPR4 activation across different species. Moreover, protonation of distinct extracellular HECL2-45.41 contributed to the more acidic optimal pH range of xtGPR4. Overall, our study revealed common and distinct mechanisms of proton sensing by GPR4, from a structural, functional, and evolutionary perspective.

Inhibition of GPR4 Attenuates the Formation of Abdominal Aortic Aneurysm Through Inhibiting the SP-1/VEGF-A Signaling

Abdominal aortic aneurysm (AAA) is a severe cardiovascular disease (CVD) that is partly attributable to endothelial dysfunction, inflammatory response, and angiogenesis. G protein-coupled receptor 4 (GPR4), a proton-sensitive G protein-coupled receptor that is abundantly expressed in vascular endothelial cells, has been associated with numerous physiological functions. Nevertheless, its potential involvement in the development of AAA remains unexplored. In this study, we examined the impact of GPR4 deletion on the development of AAA in ApoE-deficient mice. The mice were categorized into four distinct groups: the ApoE-/- with saline group, the ApoE-/-GPR4-/- with saline group, the ApoE-/- with Ang II group, and the ApoE-/-GPR4-/- with Ang II group. AAA were induced in the ApoE-/- mice through the perfusion of angiotensin II (Ang II). Notably, GPR4 was substantially elevated in the AAA tissues from both human subjects and experimental mice. The deletion of GPR4 substantially decreased the formation of Ang II-induced AAA, damages to elastin, and the expression of aortic inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α), as well as vascular endothelial growth factor A/vascular endothelial growth factor receptor 2 (VEGF-A/VEGF-R2), in ApoE-/- mice. Human aortic endothelial cells (HAECs) were transfected with lenti-viral GPR4 shRNA and subsequently stimulated with Ang II. Our findings indicate that the knockout of GPR4 attenuated Ang II-induced angiogenic tube formation in HAECs by decreasing the expression of VEGF-A and VEGF-R2. Furthermore, GPR4 knockout also hindered the activation of specificity protein-1 (SP-1) by reducing its expression and transcriptional activity. Notably, the overexpression of SP-1 reversed the inhibitory effects of GPR4 knockout on angiogenic tube formation and the expression of VEGF-A/VEGF-R2. This suggests that the protective effects of GPR4 knockout are achieved through the inhibition of SP-1. In summary, the absence of GPR4 impeded AAA formation, indicating that GPR4 could potentially serve as a therapeutic target for AAA.

The beneficial health effects of puerarin in the treatment of cardiovascular diseases: from mechanisms to therapeutics

Cardiovascular diseases (CVDs) are the leading causes of death globally that seriously threaten human health. Although novel western medicines have continued to be discovered over the past few decades to inhibit the progression of CVDs, new drug research and development for treating CVDs with less side effects and adverse reactions are continuously being desired. Puerarin is a natural product found in a variety of medicinal plants belonging to the flavonoid family with potent biological and pharmacological activities. Abundant research findings in the literature have suggested that puerarin possesses a promising prospect in treating CVDs. In recent years, numerous new molecular mechanisms of puerarin have been explored in experimental and clinical studies, providing new evidence for this plant metabolite to protect against CVDs. This article systematically introduces the history of use, bioavailability, and various dosage forms of puerarin and further summarizes recently published data on the major research advances and their underlying therapeutic mechanisms in treating CVDs. It may provide references for researchers in the fields of pharmacology, natural products, and internal medicine.

The Roles of Proton-Sensing G-Protein-Coupled Receptors in Inflammation and Cancer

The precise regulation of pH homeostasis is crucial for normal physiology. However, in tissue microenvironments, it can be impacted by pathological conditions such as inflammation and cancer. Due to the overproduction and accumulation of acids (protons), the extracellular pH is characteristically more acidic in inflamed tissues and tumors in comparison to normal tissues. A family of proton-sensing G-protein-coupled receptors (GPCRs) has been identified as molecular sensors for cells responding to acidic tissue microenvironments. Herein, we review the current research progress pertaining to these proton-sensing GPCRs, including GPR4, GPR65 (TDAG8), and GPR68 (OGR1), in inflammation and cancer. Growing evidence suggests that GPR4 and GPR68 are mainly pro-inflammatory, whereas GPR65 is primarily anti-inflammatory, in various inflammatory disorders. Both anti- and pro-tumorigenic effects have been reported for this family of receptors. Moreover, antagonists and agonists targeting proton-sensing GPCRs have been developed and evaluated in preclinical models. Further research is warranted to better understand the roles of these proton-sensing GPCRs in pathophysiology and is required in order to exploit them as potential therapeutic targets for disease treatment.

The Role of Progenitor Cells in the Pathogenesis of Arteriosclerosis

The increasing incidence of arteriosclerosis has become a significant global health burden. Arteriosclerosis is characterized by the thickening and hardening of arterial walls, which can lead to the narrowing or complete blockage of blood vessels. However, the pathogenesis of the disease remains incompletely understood. Recent research has shown that stem and progenitor cells found in the bone marrow and local vessel walls play a role in the development of arteriosclerosis by differentiating into various types of vascular cells, including endothelial cells, smooth muscle cells, fibroblasts, and inflammatory cells. This review aims to provide a comprehensive understanding of the role of stem and progenitor cells in the pathogenesis of arteriosclerosis, shedding light on the underlying mechanisms and potential therapeutic approaches for this disease.

Immunomodulation of Proton-activated G Protein-coupled Receptors in Inflammation

Proton-activated G protein-coupled receptors (GPCRs), initially discovered by Ludwig in 2003, are widely distributed in various tissues. These receptors have been found to modulate the immune system in several inflammatory diseases, including inflammatory bowel disease, atopic dermatitis, and asthma. Proton-activated GPCRs belong to the G protein-coupled receptor family and can detect alternations in extracellular pH. This detection triggers downstream signaling pathways within the cells, ultimately influencing the function of immune cells. In this review, we specifically focused on investigating the immune response of proton-activated GPCRs under inflammatory conditions.

Recent advances in acid sensing by G protein coupled receptors

Changes in extracellular proton concentrations occur in a variety of tissues over a range of timescales under physiological conditions and also accompany virtually all pathologies, notably cancers, stroke, inflammation and trauma. Proton-activated, G protein coupled receptors are already partially active at physiological extracellular proton concentrations and their activity increases with rising proton concentrations. Their ability to monitor and report changes in extracellular proton concentrations and hence extracellular pH appears to be involved in a variety of processes, and it is likely to mirror and in some cases promote disease progression. Unsurprisingly, therefore, these pH-sensing receptors (pHR) receive increasing attention from researchers working in an expanding range of research areas, from cellular neurophysiology to systemic inflammatory processes. This review is looking at progress made in the field of pHRs over the past few years and also highlights outstanding issues.

Expression of endogenous epitope-tagged GPR4 in the mouse brain

GPR4 is a proton-sensing G protein-coupled receptor implicated in many peripheral and central physiological processes. GPR4 expression has previously been assessed only via detection of the cognate transcript or indirectly, by use of fluorescent reporters. In this work, CRISPR/Cas9 knock-in technology was used to encode a hemagglutinin (HA) epitope tag within the endogenous locus of Gpr4 and visualize GPR4-HA in the mouse central nervous system using a specific, well characterized HA antibody; GPR4 expression was further verified by complementary Gpr4 mRNA detection. HA immunoreactivity was found in a limited set of brain regions, including in the retrotrapezoid nucleus (RTN), serotonergic raphe nuclei, medial habenula, lateral septum, and several thalamic nuclei. GPR4 expression was not restricted to cells of a specific neurochemical identity as it was observed in excitatory, inhibitory, and aminergic neuronal cell groups. HA immunoreactivity was not detected in brain vascular endothelium, despite clear expression of Gpr4 mRNA in endothelial cells. In the RTN, GPR4 expression was detected at the soma and in proximal dendrites along blood vessels and the ventral surface of the brainstem; HA immunoreactivity was not detected in RTN projections to two known target regions. This localization of GPR4 protein in mouse brain neurons corroborates putative sites of expression where its function has been previously implicated (e.g., CO2-regulated breathing by RTN), and provides a guide for where GPR4 could contribute to other CO2/H+ modulated brain functions. Finally, GPR4-HA animals provide a useful reagent for further study of GPR4 in other physiological processes outside of the brain.Significance Statement GPR4 is a proton-sensing G-protein coupled receptor whose expression is necessary for a number of diverse physiological processes including acid-base sensing in the kidney, immune function, and cancer progression. In the brain, GPR4 has been implicated in the hypercapnic ventilatory response mediated by brainstem neurons. While knockout studies in animals have clearly demonstrated its necessity for normal physiology, descriptions of GPR4 expression have been limited due to a lack of specific antibodies for use in mouse models. In this paper, we implemented a CRISPR/Cas9 knock-in approach to incorporate the coding sequence for a small epitope tag into the locus of GPR4. Using these mice, we were able to describe GPR4 protein expression directly for the first time.

LncRNA-mediated Modulation of Endothelial Cells: Novel Progress in the Pathogenesis of Coronary Atherosclerotic Disease

Coronary atherosclerotic disease (CAD) is a common cardiovascular disease and an important cause of death. Moreover, endothelial cells (ECs) injury is an early pathophysiological feature of CAD, and long noncoding RNAs (lncRNAs) can modulate gene expression. Recent studies have shown that lncRNAs are involved in the pathogenesis of CAD, especially by regulating ECs. In this review, we summarize the novel progress of lncRNA-modulated ECs in the pathogenesis of CAD, including ECs proliferation, migration, adhesion, angiogenesis, inflammation, apoptosis, autophagy, and pyroptosis. Thus, as lncRNAs regulate ECs in CAD, lncRNAs will provide ideal and novel targets for the diagnosis and drug therapy of CAD.

Versatile lactate signaling via HCAR1: a multifaceted GPCR involved in many biological processes

G-coupled protein receptors (GPCRs) are the ultimate refuge of pharmacology and medicine as more than 40% of all marketed drugs are directly targeting these receptors. Through cell surface expression, they are at the forefront of cellular communication with the outside world. Metabolites among the conveyors of this communication are becoming more prominent with the recognition of them as ligands for GPCRs. HCAR1 is a GPCR conveyor of lactate. It is a class A GPCR coupled to Gαi which reduces cellular cAMP along with the downstream Gβγ signaling. It was first found to inhibit lipolysis, and lately has been implicated in diverse cellular processes, including neural activities, angiogenesis, inflammation, vision, cardiovascular function, stem cell proliferation, and involved in promoting pathogenesis for different conditions, such as cancer. Other than signaling from the plasma membrane, HCAR1 shows nuclear localization with different location-biased activities therein. Although different functions for HCAR1 are being discovered, its cell and molecular mechanisms are yet ill understood. Here, we provide a comprehensive review on HCAR1, which covers the literature on the subject, and discusses its importance and relevance in various biological phenomena.

GPR4 Knockout Attenuates Intestinal Inflammation and Forestalls the Development of Colitis-Associated Colorectal Cancer in Murine Models

GPR4 is a proton-sensing G protein-coupled receptor highly expressed in vascular endothelial cells and has been shown to potentiate intestinal inflammation in murine colitis models. Herein, we evaluated the proinflammatory role of GPR4 in the development of colitis-associated colorectal cancer (CAC) using the dextran sulfate sodium (DSS) and azoxymethane (AOM) mouse models in wild-type and GPR4 knockout mice. We found that GPR4 contributed to chronic intestinal inflammation and heightened DSS/AOM-induced intestinal tumor burden. Tumor blood vessel density was markedly reduced in mice deficient in GPR4, which correlated with increased tumor necrosis and reduced tumor cell proliferation. These data demonstrate that GPR4 ablation alleviates intestinal inflammation and reduces tumor angiogenesis, development, and progression in the AOM/DSS mouse model.

Identification of 5 hub genes for diagnosis of coronary artery disease

Background

Coronary artery disease (CAD) is a main cause leading to increasing mortality of cardiovascular disease (CVD) worldwide. We aimed to discover marker genes and develop a diagnostic model for CAD.

Methods

CAD-related target genes were searched from DisGeNET. Count expression data and clinical information were screened from the GSE202626 dataset. edgeR package identified differentially expressed genes (DEGs). Using online STRING tool and Cytoscape, protein-protein reactions (PPI) were predicted. WebGestaltR package was employed to functional enrichment analysis. We used Metascape to conduct module-based network analysis. VarElect algorithm provided genes-phenotype correlation analysis. Immune infiltration was assessed by ESTIMATE package and ssGSEA analysis. mRNAsi was determined by one class logistic regression (OCLR). A diagnostic model was constructed by SVM algorithm.

Results

162 target genes were screened by intersection 1,714 DEGs and 1,708 CAD related target genes. 137 target genes of the 162 target genes were obtained using PPI analysis, in which those targets were enriched in inflammatory cytokine pathways, such as chemokine signaling pathway, and IL-17 signaling pathway. From the above 137 target genes, four functional modules (MCODE1-4) were extracted. From the 162 potential targets, CAD phenotype were directly and indirectly associated with 161 genes and 22 genes, respectively. Finally, 5 hub genes (CCL2, PTGS2, NLRP3, VEGFA, LTA) were screened by intersections with the top 20, directly and indirectly, and genes in MCODE1. PTGS2, NLRP3 and VEGFA were positively, while LTA was negatively correlated with immune cells scores. PTGS2, NLRP3 and VEGFA were negatively, while LTA was positively correlated with mRNAsi. A diagnostic model was successfully established, evidenced by 92.59% sensitivity and AUC was 0.9230 in the GSE202625 dataset and 94.11% sensitivity and AUC was 0.9706 in GSE120774 dataset.

Conclusion

In this work, we identified 5 hub genes, which may be associated with CAD development.

Acidosis-related pain and its receptors as targets for chronic pain

Sensing acidosis is an important somatosensory function in responses to ischemia, inflammation, and metabolic alteration. Accumulating evidence has shown that acidosis is an effective factor for pain induction and that many intractable chronic pain diseases are associated with acidosis signaling. Various receptors have been known to detect extracellular acidosis and all express in the somatosensory neurons, such as acid sensing ion channels (ASIC), transient receptor potential (TRP) channels and proton-sensing G-protein coupled receptors. In addition to sense noxious acidic stimulation, these proton-sensing receptors also play a vital role in pain processing. For example, ASICs and TRPs are involved in not only nociceptive activation but also anti-nociceptive effects as well as some other non-nociceptive pathways. Herein, we review recent progress in probing the roles of proton-sensing receptors in preclinical pain research and their clinical relevance. We also propose a new concept of sngception to address the specific somatosensory function of acid sensation. This review aims to connect these acid-sensing receptors with basic pain research and clinical pain diseases, thus helping with better understanding the acid-related pain pathogenesis and their potential therapeutic roles via the mechanism of acid-mediated antinociception.

The role of the gut microbiota in health and cardiovascular diseases

The gut microbiota is critical to human health, such as digesting nutrients, forming the intestinal epithelial barrier, regulating immune function, producing vitamins and hormones, and producing metabolites to interact with the host. Meanwhile, increasing evidence indicates that the gut microbiota has a strong correlation with the occurrence, progression and treatment of cardiovascular diseases (CVDs). In patients with CVDs and corresponding risk factors, the composition and ratio of gut microbiota have significant differences compared with their healthy counterparts. Therefore, gut microbiota dysbiosis, gut microbiota-generated metabolites, and the related signaling pathway may serve as explanations for some of the mechanisms about the occurrence and development of CVDs. Several studies have also demonstrated that many traditional and latest therapeutic treatments of CVDs are associated with the gut microbiota and its generated metabolites and related signaling pathways. Given that information, we summarized the latest advances in the current research regarding the effect of gut microbiota on health, the main cardiovascular risk factors, and CVDs, highlighted the roles and mechanisms of several metabolites, and introduced corresponding promising treatments for CVDs regarding the gut microbiota. Therefore, this review mainly focuses on exploring the role of gut microbiota related metabolites and their therapeutic potential in CVDs, which may eventually provide better solutions in the development of therapeutic treatment as well as the prevention of CVDs.

Regulation of Endothelial Progenitor Cell Functions in Ischemic Heart Disease: New Therapeutic Targets for Cardiac Remodeling and Repair

Ischemic heart disease (IHD) is the leading cause of morbidity and mortality worldwide. Ischemia and hypoxia following myocardial infarction (MI) cause subsequent cardiomyocyte (CM) loss, cardiac remodeling, and heart failure. Endothelial progenitor cells (EPCs) are involved in vasculogenesis, angiogenesis and paracrine effects and thus have important clinical value in alternative processes for repairing damaged hearts. In fact, this study showed that the endogenous repair of EPCs may not be limited to a single cell type. EPC interactions with cardiac cell populations and mesenchymal stem cells (MSCs) in ischemic heart disease can attenuate cardiac inflammation and oxidative stress in a microenvironment, regulate cell survival and apoptosis, nourish CMs, enhance mature neovascularization, alleviate adverse ventricular remodeling after infarction and enhance ventricular function. In this review, we introduce the definition and discuss the origin and biological characteristics of EPCs and summarize the mechanisms of EPC recruitment in ischemic heart disease. We focus on the crosstalk between EPCs and endothelial cells (ECs), smooth muscle cells (SMCs), CMs, cardiac fibroblasts (CFs), cardiac progenitor cells (CPCs), and MSCs during cardiac remodeling and repair. Finally, we discuss the translation of EPC therapy to the clinic and treatment strategies.

Physiological relevance of proton-activated GPCRs

The detection of H+ concentration variations in the extracellular milieu is accomplished by a series of specialized and non-specialized pH-sensing mechanisms. The proton-activated G protein-coupled receptors (GPCRs) GPR4 (Gpr4), TDAG8 (Gpr65), and OGR1 (Gpr68) form a subfamily of proteins capable of triggering intracellular signaling in response to alterations in extracellular pH around physiological values, i.e., in the range between pH 7.5 and 6.5. Expression of these receptors is widespread for GPR4 and OGR1 with particularly high levels in endothelial cells and vascular smooth muscle cells, respectively, while expression of TDAG8 appears to be more restricted to the immune compartment. These receptors have been linked to several well-studied pH-dependent physiological activities including central control of respiration, renal adaption to changes in acid-base status, secretion of insulin and peripheral responsiveness to insulin, mechanosensation, and cellular chemotaxis. Their role in pathological processes such as the genesis and progression of several inflammatory diseases (asthma, inflammatory bowel disease), and tumor cell metabolism and invasiveness, is increasingly receiving more attention and makes these receptors novel and interesting targets for therapy. In this review, we cover the role of these receptors in physiological processes and will briefly discuss some implications for disease processes.

Vascular Stem/Progenitor Cells in Vessel Injury and Repair

Vascular repair upon vessel injury is essential for the maintenance of arterial homeostasis and function. Stem/progenitor cells were demonstrated to play a crucial role in regeneration and replenishment of damaged vascular cells during vascular repair. Previous studies revealed that myeloid stem/progenitor cells were the main sources of tissue regeneration after vascular injury. However, accumulating evidences from developing lineage tracing studies indicate that various populations of vessel-resident stem/progenitor cells play specific roles in different process of vessel injury and repair. In response to shear stress, inflammation, or other risk factors-induced vascular injury, these vascular stem/progenitor cells can be activated and consequently differentiate into different types of vascular wall cells to participate in vascular repair. In this review, mechanisms that contribute to stem/progenitor cell differentiation and vascular repair are described. Targeting these mechanisms has potential to improve outcome of diseases that are characterized by vascular injury, such as atherosclerosis, hypertension, restenosis, and aortic aneurysm/dissection. Future studies on potential stem cell-based therapy are also highlighted.

Expression Profiles of Circular RNA in Aortic Vascular Tissues of Spontaneously Hypertensive Rats

Background: Circular RNAs (circRNAs), as a kind of endogenous non-coding RNA, have been implicated in ischemic heart diseases and vascular diseases. Based on theirs high stability with a closed loop structure, circRNAs function as a sponge and bind specific miRNAs to exert inhibitory effects in heart and vasculature, thereby regulating their target gene and protein expression, via competitive endogenous RNA (ceRNA) mechanism. However, the exact roles and underlying mechanisms of circRNAs in hypertension and related cardiovascular diseases remain largely unknown. Methods and Results: High-throughput RNA sequencing (RNA-seq) was used to analyze the differentially expressed (DE) circRNAs in aortic vascular tissues of spontaneously hypertensive rats (SHR). Compared with the Wistar-Kyoto (WKY) rats, there were marked increases in the levels of systolic blood pressure, diastolic blood pressure and mean blood pressure in SHR under awake conditions via the tail-cuff methodology. Totally, compared with WKY rats, 485 DE circRNAs were found in aortic vascular tissues of SHR with 279 up-regulated circRNAs and 206 down-regulated circRNAs. Furthermore, circRNA-target microRNAs (miRNAs) and the target messenger RNAs (mRNAs) of miRNAs were predicted by the miRanda and Targetscan softwares, respectively. Additionally, real-time RT-PCR analysis verified that downregulation of rno_circRNA_0009197, and upregulation of rno_circRNA_0005818, rno_circRNA_0005304, rno_circRNA_0005506, and rno_circRNA_0009301 were observed in aorta of SHR when compared with that of WKY rats. Then, the potential ceRNA regulatory mechanism was constructed via integrating 5 validated circRNAs, 31 predicted miRNAs, and 266 target mRNAs. More importantly, three hub genes (NOTCH1, FOXO3, and STAT3) were recognized according to PPI network and three promising circRNA-miRNA-mRNA regulatory axes were found in hypertensive rat aorta, including rno_circRNA_0005818/miR-615/NOTCH1, rno_circRNA_0009197/ miR-509-5p/FOXO3, and rno_circRNA_0005818/miR-10b-5p/STAT3, respectively. Conclusions: Our results demonstrated for the first time that circRNAs are expressed aberrantly in aortic vascular tissues of hypertensive rats and may serve as a sponge linking with relevant miRNAs participating in pathogenesis of hypertension and related ischemic heart diseases via the circRNA-miRNA-mRNA ceRNAnetwork mechanism.

Effect of Peptidylarginine Deiminase 4 on Endothelial Progenitor Cell Function in Peripheral Arterial Disease

At present, the global prevalence of peripheral arterial disease is increasing year by year, and it has become a worldwide disease. Studies have shown that transplanting endothelial progenitor cells (EPCs) into ischemic tissues can improve the tissue ischemia, thereby having a therapeutic effect on peripheral arterial diseases. This indicates that EPCs play a therapeutic effect in peripheral arterial disease. Recent studies have shown that peptidylarginine deiminase (PAD) is involved in the regulation of epigenetics and its inhibitor Cl-amidine can improve endothelium-dependent vasodilation and significantly reduce the formation of arterial thrombosis. It can also play a role in hematopoietic stem cells that share the same origin with EPCs. Therefore, we speculate that PAD4 may also have an effect on EPCs through a similar mechanism, thereby participating in the damage and repair of peripheral arterial disease. Therefore, we first detected the expression of PAD4 in EPCs of peripheral arterial disease and detected changes in the number and function of endothelial progenitor cells in peripheral blood after injecting the PAD4 inhibitor Cl-amidine into mice. A mouse model of lower limb ischemia was established to explore the effect of PAD4 on the function of EPCs in peripheral arterial disease. The results show that PAD4 is highly expressed in peripheral arterial diseases and the PAD4 inhibitor Cl-amidine can increase the number of EPCs and can treat peripheral arterial diseases by improving the proliferation, migration, and vascularization of EPCs.