Regulator of G-protein signalling 5 protects against atherosclerosis in apolipoprotein E-deficient mice

Single-Cell Analyses Offer Insights into the Different Remodeling Programs of Arteries and Veins

Arteries and veins develop different types of occlusive diseases and respond differently to injury. The biological reasons for this discrepancy are not well understood, which is a limiting factor for the development of vein-targeted therapies. This study contrasts human peripheral arteries and veins at the single-cell level, with a focus on cell populations with remodeling potential. Upper arm arteries (brachial) and veins (basilic/cephalic) from 30 organ donors were compared using a combination of bulk and single-cell RNA sequencing, proteomics, flow cytometry, and histology. The cellular atlases of six arteries and veins demonstrated a 7.8× higher proportion of contractile smooth muscle cells (SMCs) in arteries and a trend toward more modulated SMCs. In contrast, veins showed a higher abundance of endothelial cells, pericytes, and macrophages, as well as an increasing trend in fibroblasts. Activated fibroblasts had similar proportions in both types of vessels but with significant differences in gene expression. Modulated SMCs and activated fibroblasts were characterized by the upregulation of MYH10, FN1, COL8A1, and ITGA10. Activated fibroblasts also expressed F2R, POSTN, and COMP and were confirmed by F2R/CD90 flow cytometry. Activated fibroblasts from veins were the top producers of collagens among all fibroblast populations from both types of vessels. Venous fibroblasts were also highly angiogenic, proinflammatory, and hyper-responders to reactive oxygen species. Differences in wall structure further explain the significant contribution of fibroblast populations to remodeling in veins. Fibroblasts are almost exclusively located outside the external elastic lamina in arteries, while widely distributed throughout the venous wall. In line with the above, ECM-targeted proteomics confirmed a higher abundance of fibrillar collagens in veins vs. more basement ECM components in arteries. The distinct cellular compositions and transcriptional programs of reparative populations in arteries and veins may explain differences in acute and chronic wall remodeling between vessels. This information may be relevant for the development of antistenotic therapies.

LETMD1, a target of KLF4, hinders endothelial inflammation and pyroptosis: A protective mechanism in the pathogenesis of atherosclerosis

Atherosclerosis (AS), a metabolic disorder, is usually caused by chronic inflammation. LETM1 Domain-Containing Protein 1 (LETMD1) is a mitochondrial outer membrane protein required for mitochondrial structure. This study aims to evaluate the functional role of LETMD1 in endothelial pathogenesis of AS. Oxidized low-density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs) and high-fat diet apolipoprotein E-deficient (ApoE-/-) mice were used to establish in vitro and in vivo models, respectively. Recombinant adenovirus vectors were constructed to investigate the role of LETMD1 in AS. mRNA sequencing was used to explore the effect of LETMD1 overexpression on gene expression in ox-LDL-induced HUVECs. A dual-luciferase reporting assay and chromatin immunoprecipitation (ChIP)-PCR were further conducted to verify the relationship between KLF4 and LETMD1. Results showed that LETMD1 was highly expressed in the aortas of atherosclerotic animals. LETMD1 overexpression reduced the expression of inflammatory factors, pyroptosis, ROS production, and NF-κB activation in ox-LDL-induced HUVECs, whereas LETMD1 knockdown had the opposite impact. LETMD1 overexpression was involved in regulating gene expression in ox-LDL-induced HUVECs. Overexpression of LETMD1 in mice reduced serum lipid levels as well as atherosclerotic lesions in the aortic roots. Furthermore, LETMD1 overexpression suppressed inflammatory reactions, cell pyroptosis, nuclear p65 protein level, cell apoptosis, and ROS generation in the aortas of AS mice. KLF4 (Krüppel-like factor 4) was found to be the transcriptional regulator of LETMD1. In conclusion, LETMD1, a target of KLF4, hinders endothelial inflammation and pyroptosis, which is a mechanism inhibiting the development of atherosclerosis.

RGS5 maintaining vascular homeostasis is altered by the tumor microenvironment

BACKGROUND

Regulator of G protein signaling 5 (RGS5), as a negative regulator of G protein-coupled receptor (GPCR) signaling, is highly expressed in arterial VSMCs and pericytes, which is involved in VSMC phenotypic heterogeneity and vascular remodeling in tumors. However, its role in normal and tumor vascular remodeling is controversial.

METHODS

RGS5 knockout (Rgs5-KO) mice and RGS5 overexpression or knockdown in VSMCs in vivo by adeno-associated virus type 9 (AAV) carrying RGS5 cDNA or small hairpin RNA (shRNA) targeting RGS5 were used to determine the functional significance of RGS5 in vascular inflammation. RGS5 expression in the triple-negative (TNBCs) and non-triple-negative breast cancers (Non-TNBCs) was determined by immunofluorescent and immunohistochemical staining. The effect of breast cancer cell-conditioned media (BC-CM) on the pro-inflammatory phenotype of VSMCs was measured by phagocytic activity assays, adhesion assay and Western blot.

RESULTS

We identified that knockout and VSMC-specific knockdown of RGS5 exacerbated accumulation and pyroptosis of pro-inflammatory VSMCs, resulting in vascular remodeling, which was negated by VSMC-specific RGS5 overexpression. In contrast, in the context of breast cancer tissues, the role of RGS5 was completely disrupted. RGS5 expression was increased in the triple-negative breast cancer (TNBC) tissues and in the tumor blood vessels, accompanied with an extensive vascular network. VSMCs treated with BC-CM displayed enhanced pro-inflammatory phenotype and higher adherent with macrophages. Furthermore, tumor-derived RGS5 could be transferred into VSMCs.

CONCLUSIONS

These findings suggest that tumor microenvironment shifts the function of RGS5 from anti-inflammation to pro-inflammation and induces the pro-inflammatory phenotype of VSMCs that is favorable for tumor metastasis.

RGS5 augments astrocyte activation and facilitates neuroinflammation via TNF signaling

Astrocytes contribute to chronic neuroinflammation in a variety of neurodegenerative diseases, including Parkinson's disease (PD), the most common movement disorder. However, the precise role of astrocytes in neuroinflammation remains incompletely understood. Herein, we show that regulator of G-protein signaling 5 (RGS5) promotes neurodegenerative process through augmenting astrocytic tumor necrosis factor receptor (TNFR) signaling. We found that selective ablation of Rgs5 in astrocytes caused an inhibition in the production of cytokines resulting in mitigated neuroinflammatory response and neuronal survival in animal models of PD, whereas overexpression of Rgs5 had the opposite effects. Mechanistically, RGS5 switched astrocytes from neuroprotective to pro-inflammatory property via binding to the receptor TNFR2. RGS5 also augmented TNFR signaling-mediated pro-inflammatory response by interacting with the receptor TNFR1. Moreover, interrupting RGS5/TNFR interaction by either RGS5 aa 1-108 or small molecular compounds feshurin and butein, suppressed astrocytic cytokine production. We showed that the transcription of astrocytic RGS5 was controlled by transcription factor early B cell factor 1 whose expression was reciprocally influenced by RGS5-modulated TNF signaling. Thus, our study indicates that beyond its traditional role in G-protein coupled receptor signaling, astrocytic RGS5 is a key modulator of TNF signaling circuit with resultant activation of astrocytes thereby contributing to chronic neuroinflammation. Blockade of the astrocytic RGS5/TNFR interaction is a potential therapeutic strategy for neuroinflammation-associated neurodegenerative diseases.

SRC-3 deficiency prevents atherosclerosis development by decreasing endothelial ICAM-1 expression to attenuate macrophage recruitment

Steroid receptor coactivator 3 (SRC-3) is a member of the p160 SRC family. This factor can interact with multiple nuclear hormone receptors and transcription factors to regulate the expression of their target genes. Although many physiological roles of SRC-3 have been revealed, its role in atherosclerosis is not clear. In this study, we found that SRC-3^-/-ApoE^-/- mice have reduced atherosclerotic lesions and necrotic areas in their aortas and aortic roots compared with SRC-3^+/+ApoE^-/- mice after Western diet (WD) feeding for 12 weeks. RNA-Seq and Western blot analyses of the aorta revealed that SRC-3 was required for maintaining the expression of ICAM-1, which was required for macrophage recruitment and atherosclerosis development. siRNA-mediated knockdown of SRC-3 in endothelial cells significantly reduced WD-induced atherosclerotic plaque formation. Additionally, treatment of ApoE^-/- mice with SRC-3 inhibitor bufalin prevented atherosclerotic plaque development. SRC-3 deficiency reduced aortic macrophage recruitment. Accordingly, ICAM-1 expression was markedly decreased in the aortas of SRC-3^-/-ApoE^-/- mice and ApoE^-/- mice with endothelial SRC-3 knockdown mediated by AAV9-shSRC-3 virus. Mechanistically, SRC-3 coactivated NF-κB p65 to increase ICAM-1 transcription in endothelial cells. Collectively, these findings demonstrate that inhibiting SRC-3 ameliorates atherosclerosis development, at least in part through suppressing endothelial activation by decreasing endothelial ICAM-1 expression via reducing NF-κB signaling.

Inducing vascular normalization: A promising strategy for immunotherapy

In solid tumors, the vasculature is highly abnormal in structure and function, resulting in the formation of an immunosuppressive tumor microenvironment by limiting immune cells infiltration into tumors. Vascular normalization is receiving much attention as an alternative strategy to anti-angiogenic therapy, and its potential therapeutic targets include signaling pathways, angiogenesis-related genes, and metabolic pathways. Endothelial cells play an important role in the formation of blood vessel structure and function, and their metabolic processes drive blood vessel sprouting in parallel with the control of genetic signals in cancer. The feedback loop between vascular normalization and immunotherapy has been discussed extensively in many reviews. In this review, we summarize the impact of aberrant tumor vascular structure and function on drug delivery, metastasis, and anti-tumor immune responses. In addition, we present evidences for the mutual regulation of immune vasculature. Based on the importance of endothelial metabolism in controlling angiogenesis, we elucidate the crosstalk between endothelial cells and immune cells from the perspective of metabolic pathways and propose that targeting abnormal endothelial metabolism to achieve vascular normalization can be an alternative strategy for cancer treatment, which provides a new theoretical basis for future research on the combination of vascular normalization and immunotherapy.

Deletion of Macrophage-Specific Glycogen Synthase Kinase (GSK)-3α Promotes Atherosclerotic Regression in Ldlr−/− Mice

Recent evidence from our laboratory suggests that impeding ER stress–GSK3α/β signaling attenuates the progression and development of atherosclerosis in mouse model systems. The objective of this study was to determine if the tissue-specific genetic ablation of GSK3α/β could promote the regression of established atherosclerotic plaques. Five-week-old low-density lipoprotein receptor knockout (Ldlr^−/−) mice were fed a high-fat diet for 16 weeks to promote atherosclerotic lesion formation. Mice were then injected with tamoxifen to induce macrophage-specific GSK3α/β deletion, and switched to standard diet for 12 weeks. All mice were sacrificed at 33 weeks of age and atherosclerosis was quantified and characterized. Female mice with induced macrophage-specific GSK3α deficiency, but not GSK3β deficiency, had reduced plaque volume (~25%) and necrosis (~40%) in the aortic sinus, compared to baseline mice. Atherosclerosis was also significantly reduced (~60%) in the descending aorta. Macrophage-specific GSK3α-deficient mice showed indications of increased plaque stability and reduced inflammation in plaques, as well as increased CCR7 and ABCA1 expression in lesional macrophages, consistent with regressive plaques. These results suggest that GSK3α ablation promotes atherosclerotic plaque regression and identify GSK3α as a potential target for the development of new therapies to treat existing atherosclerotic lesions in patients with cardiovascular disease.

miR-320a targeting RGS5 aggravates atherosclerosis by promoting migration and proliferation of ox-LDL-stimulated vascular smooth muscle cells

ABSTRACT

MicroRNAs (miRNAs) have been implicated in atherosclerosis (AS) progression. Here, we focused on how miR-320a affect AS progression via vascular smooth muscle cells (VSMCs). Oxidized low-density lipoproteins (ox-LDL)-stimulated VSMCs were used as an AS cell model and qRT-PCR was performed to measure miR-320a and RGS5 levels. CCK-8 and wound healing assays were used to detect the viability and migration of VSMCs. Western blotting was used to measure the protein expression levels of PCNA, Bax, and Bcl-2. The interaction of miR-320a and RGS5 was determined by dual-luciferase and RNA pull-down assays. MiR-320a was highly expressed while RGS5 showed low levels of expression in the arterial plaque tissues. Silencing of miR-320a blocked cell viability and migration, inhibited expression of the proliferation-specific protein PCNA in ox-LDL-treated VSMCs, promoted Bax protein expression and inhibited Bcl-2 protein expression. Furthermore, miR-320a was found to exert these effects by inhibiting RGS5 expression. Collectively, miR-320a promoted cell viability, migration, and proliferation while reducing apoptosis of ox-LDL-stimulated VSMCs by inhibiting RGS5.

A regulator of G protein signaling 5 marked subpopulation of vascular smooth muscle cells is lost during vascular disease

Vascular smooth muscle cell (VSMC) subpopulations relevant to vascular disease and injury repair have been depicted in healthy vessels and atherosclerosis profiles. However, whether VSMC subpopulation associated with vascular homeostasis exists in the healthy artery and how are their nature and fate in vascular remodeling remains elusive. Here, using single-cell RNA-sequencing (scRNA-seq) to detect VSMC functional heterogeneity in an unbiased manner, we showed that VSMC subpopulations in healthy artery presented transcriptome diversity and that there was significant heterogeneity in differentiation state and development within each subpopulation. Notably, we detected an independent subpopulation of VSMCs that highly expressed regulator of G protein signaling 5 (RGS5), upregulated the genes associated with inhibition of cell proliferation and construction of cytoskeleton compared with the general subpopulation, and mainly enriched in descending aorta. Additionally, the proportion of RGS5^high VSMCs was markedly decreased or almost disappeared in the vascular tissues of neointimal formation, abdominal aortic aneurysm and atherosclerosis. Specific spatiotemporal characterization of RGS5^high VSMC subpopulation suggested that this subpopulation was implicated in vascular homeostasis. Together, our analyses identify homeostasis-relevant transcriptional signatures of VSMC subpopulations in healthy artery, which may explain the regional vascular resistance to atherosclerosis at some extent.

Hepatic Regulator of G Protein Signaling 5 Ameliorates Nonalcoholic Fatty Liver Disease by Suppressing Transforming Growth Factor Beta-Activated Kinase 1-c-Jun-N-Terminal Kinase/p38 Signaling

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease, which has no specific pharmacological treatments partially because of the unclear pathophysiological mechanisms. Regulator of G protein signaling (RGSs) proteins are proteins that negatively regulate G protein-coupled receptor (GPCR) signaling. The members of the R4/B subfamily are the smallest RGS proteins in size, and RGS5 belongs to this family, which mediates pluripotent biological functions through canonical G protein-mediated pathways and non-GPCR pathways. This study combined a genetically engineered rodent model and a transcriptomics-sequencing approach to investigate the role and regulatory mechanism of RGS5 in the development of NAFLD.

APPROACH AND RESULTS

This study found that RGS5 protects against NAFLD and nonalcoholic steatohepatitis. Using RNA sequencing and an unbiased systematic investigative approach, this study found that the activation of mitogen-activated protein kinase signaling cascades in response to metabolic challenge is negatively associated with hepatic RGS5 expression. Mechanistically, we found that the 64-181 amino-acid-sequence (aa) fragment of RGS5 directly interacts with transforming growth factor beta-activated kinase 1 (TAK1) through the 1-300aa fragment and inhibits TAK1 phosphorylation and the subsequent c-Jun-N-terminal kinase (JNK)/p38 pathway activation.

CONCLUSIONS

In hepatocytes, RGS5 is an essential molecule that protects against the progression of NAFLD. RGS5 directly binds to TAK1, preventing its hyperphosphorylation and the activation of the downstream JNK/p38 signaling cascade. RGS5 is a promising target molecule for fine-tuning the activity of TAK1 and for the treatment of NAFLD.

Down-regulated RGS5 by genetic variants impairs endothelial cell function and contributes to coronary artery disease

AIMS

Genetic contribution to coronary artery disease (CAD) remains largely unillustrated. Although transcriptomic profiles have identified dozens of genes that are differentially expressed in normal and atherosclerotic vessels, whether those genes are genetically associated with CAD remains to be determined. Here, we combined genetic association studies, transcriptome profiles and in vitro and in vivo functional experiments to identify novel susceptibility genes for CAD.

METHODS AND RESULTS

Through an integrative analysis of transcriptome profiles with genome-wide association studies for CAD, we obtained 18 candidate genes and selected one representative single nucleotide polymorphism (SNP) for each gene for multi-centred validations. We identified an intragenic SNP, rs1056515 in RGS5 gene (odds ratio = 1.17, 95% confidence interval =1.10-1.24, P = 3.72 × 10-8) associated with CAD at genome-wide significance. Rare genetic variants in linkage disequilibrium with rs1056515 were identified in CAD patients leading to a decreased expression of RGS5. The decreased expression was also observed in atherosclerotic vessels and endothelial cells treated by various cardiovascular risk factors. Through siRNA knockdown and adenoviral overexpression, we further showed that RGS5 regulated endothelial inflammation, vascular remodelling, as well as canonical NF-κB signalling activation. Moreover, CXCL12, a specific downstream target of the non-canonical NF-κB pathway, was strongly affected by RGS5. However, the p100 processing, a well-documented marker for non-canonical NF-κB pathway activation, was not altered, suggesting an existence of a novel mechanism by which RGS5 regulates CXCL12.

CONCLUSIONS

We identified RGS5 as a novel susceptibility gene for CAD and showed that the decreased expression of RGS5 impaired endothelial cell function and functionally contributed to atherosclerosis through a variety of molecular mechanisms. How RGS5 regulates the expression of CXCL12 needs further studies.

RGS5 rs4657251 polymorphism is associated with small vessel occlusion stroke in Taiwan Han Chinese

BACKGROUND

The regulator of G-protein signaling protein 5 (RGS5) has been demonstrated to play a role in regulating blood pressure and cardiovascular function. Studies have shown that RGS5 polymorphisms exhibit susceptibility to hypertension. However, no study has yet been performed among stroke patients.

METHODS

To evaluate whether RGS5 rs4657251 is a susceptibility gene for stroke, we performed a case-control association study involving 714 large-artery atherosclerosis (LAA) patients, 383 small vessel occlusion (SVO) patients, 401 hypertensive intracranial hemorrhages (HICH), and 626 controls. The RGS5 rs4657251 polymorphism was analyzed through polymerase chain reaction.

RESULTS

The TC genotype was significantly higher in the SVO group compared with that in the control group (odds ratio [OR] = 1.34, 95% confidence interval [CI] = 1.02-1.76, p = 0.035). In addition, the dominant phenotype (TC + CC vs TT) was also significantly different between the SVO and the control groups (OR = 1.31, 95% CI = 1.01-1.70, p = 0.046). However, no association was found between RGS5 rs4657251 and LAA an HICH. After adjustment with gender, diabetes, smoking, cholesterol and low-density lipoprotein levels, RGS5 rs4657251 polymorphism remained an independent risk factor for SVO (OR = 1.49; 95% CI = 1.12-1.98) but not for LAA or HICH.

CONCLUSION

Our findings, obtained among Taiwan Han Chinese subjects, provide the first evidence that RGS5 rs4657251 polymorphism is an independent risk factor for SVO.

Low-dose ethanol intake prevents high-fat diet-induced adverse cardiovascular events in mice

This study aimed to clarify whether low-dose ethanol intake could prevent high-fat diet-induced adverse effects on cardiomyocytes in mice.

Tumor Vasculatures: A New Target for Cancer Immunotherapy

Immune cells rely on a functional vascular network to enter tissues. In solid tumors, blood vessels are abnormal and dysfunctional and, thus, immune effector cell infiltration is impaired. Although normalizing the tumor vasculature has been shown to improve the efficacy of cancer immunotherapies, recent studies suggest that enhanced immune stimulation also, in turn, improves tumor vascular normalization. Thus, this new paradigm of immune system-tumor vasculature mutual reprogramming opens the possibility of identifying new cancer treatment strategies that combine vascular targeting and immunotherapies. Here, we highlight current evidence supporting immune system-tumor vasculature crosstalk and outline how this relationship can provide new rationales for developing more effective combination immunotherapy strategies for treating human cancers.

Genetic Analysis of Rare Human Variants of Regulators of G Protein Signaling Proteins and Their Role in Human Physiology and Disease

Regulators of G protein signaling (RGS) proteins modulate the physiologic actions of many neurotransmitters, hormones, and other signaling molecules. Human RGS proteins comprise a family of 20 canonical proteins that bind directly to G protein-coupled receptors/G protein complexes to limit the lifetime of their signaling events, which regulate all aspects of cell and organ physiology. Genetic variations account for diverse human traits and individual predispositions to disease. RGS proteins contribute to many complex polygenic human traits and pathologies such as hypertension, atherosclerosis, schizophrenia, depression, addiction, cancers, and many others. Recent analysis indicates that most human diseases are due to extremely rare genetic variants. In this study, we summarize physiologic roles for RGS proteins and links to human diseases/traits and report rare variants found within each human RGS protein exome sequence derived from global population studies. Each RGS sequence is analyzed using recently described bioinformatics and proteomic tools for measures of missense tolerance ratio paired with combined annotation-dependent depletion scores, and protein post-translational modification (PTM) alignment cluster analysis. We highlight selected variants within the well-studied RGS domain that likely disrupt RGS protein functions and provide comprehensive variant and PTM data for each RGS protein for future study. We propose that rare variants in functionally sensitive regions of RGS proteins confer profound change-of-function phenotypes that may contribute, in newly appreciated ways, to complex human diseases and/or traits. This information provides investigators with a valuable database to explore variation in RGS protein function, and for targeting RGS proteins as future therapeutic targets.

RGS5 decreases the proliferation of human ovarian carcinoma‑derived primary endothelial cells through the MAPK/ERK signaling pathway in hypoxia

Regulator of G-protein signaling 5 (RGS5), a tissue-specific signal-regulating molecule, plays a key role in the development of the vasculature. It was recently found that RGS5 is abundantly expressed in epithelial ovarian cancer (EOC) compared with the normal ovaries. However, the distribution of RGS5 in EOC and its significance require further investigation. The aim of the present study was to investigate the expression of RGS5 in EOC, as well as its association with cancer differentiation, metastasis and clinicopathological parameters. Immunohistochemistry (IHC), western blotting, RT-PCR, wound-healing, cell proliferation and flow cytometric assays were the methods used in the present study. RGS5 was highly expressed in the cytoplasm of ovarian carcinoma cells and in microvascular structures. The expression of RGS5 in EOC was negatively associated with peritoneal metastasis (P=0.004), but it was not found to be associated with age, tumor size, clinical stage or lymph node metastasis (P>0.05). EOC patients with high RGS5 expression had a prolonged progression-free survival (72.34±8.41 vs. 43.56±5.41 months, P<0.001). High expression of RGS5 was correlated with significantly lower microvascular density (MVD) as indicated by the expression of CD34, whereas the opposite was observed in tissues with low RGS5 expression (P<0.05). Hypoxia increased RGS5 expression in ovarian carcinoma-derived endothelial cells (ODMECs), whereas the proliferative capacity of ODMECs exhibited a significant increase following RNAi-mediated reduction of RGS5 expression. These data indicated that RGS5 plays a key role in angiogenesis in ovarian carcinoma. In addition, RGS5 downregulated the expression of the downstream proteins CDC25A, CDK2 and cyclin E, which are mediated by the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, causing ODMEC arrest in the G1 phase of the cell cycle under hypoxic conditions. Collectively, our data indicated that RGS5 is crucial for the occurrence and development of ovarian cancer, and that RGS5 and its signaling pathway may serve as anti-angiogenesis targets for the treatment of ovarian cancer.

Reduced atherosclerosis lesion size, inflammatory response in miR-150 knockout mice via macrophage effects

Atherosclerosis is considered to be a chronic inflammatory disease that can lead to severe clinically important cardiovascular events. miR-150 is a small noncoding RNA that significantly enhances inflammatory responses by upregulating endothelial cell proliferation and migration, as well as intravascular environmental homeostasis. However, the exact role of miR-150 in atherosclerosis remains unknown. Here, we investigated the effect of miR-150 deficiency on atherosclerosis development. Using double-knockout (miR-150^-/- and ApoE^-/-) mice, we measured atherosclerotic lesion size and stability. Meanwhile, we conducted in vivo bone marrow transplantation to identify cellular-level components of the inflammatory response. Compared with mice deficient only in ApoE, the double-knockout mice had significantly smaller atherosclerotic lesions and displayed an attenuated inflammatory response. Moreover, miR-150 ablation promoted plaque stabilization via increases in smooth muscle cell and collagen content and decreased macrophage infiltration and lipid accumulation. The in vitro experiments indicated that an inflammatory response with miR-150 deficiency in atherosclerosis results directly from upregulated expression of the cytoskeletal protein, PDZ and LIM domain 1 (PDLIM1), in macrophages. More importantly, the decreases in phosphorylated p65 expression and inflammatory cytokine secretion induced by miR-150 ablation were reversed by PDLIM1 knockdown. These findings suggest that miR-150 is a promising target for the management of atherosclerosis.

eNOS S-nitrosylation mediated OxLDL-induced endothelial dysfunction via increasing the interaction of eNOS with β‑catenin

Protein S-nitrosylation plays an important role in the progression of cardiovascular diseases. eNOS can be S-nitrosylated in endothelial cells, and this modification reversibly attenuates enzyme activity. Under physiological conditions, eNOS directly interacts with β‑catenin. However, whether and how eNOS S-nitrosylation regulates the β‑catenin signal pathway and participates in endothelial dysfunction remains unknown. Here, we show that OxLDL induces the S-nitrosylation of eNOS, which enhances the interaction between eNOS and β‑catenin, transcriptional activity of β‑catenin, cell migration and adhesion molecule expression in endothelial cells. In addition, these effects are partially abolished after eNOS is mutated at Cys94 and Cys99, but not Cys441, in endothelial cells. Furthermore, OxLDL increases iNOS expression. The specific iNOS inhibitor 1400 W decreases eNOS S-nitrosylation and the association of eNOS and β‑catenin, thereby blocking the β‑catenin signal pathway to alleviate OxLDL-induced endothelial dysfunction. Taken together, OxLDL induces eNOS S-nitrosylation at Cys94 and Cys99 via an iNOS-dependent manner, which may increase β‑catenin activation and trigger endothelial injury. This study describes a novel mechanism of endothelial dysfunction.

RGS3 inhibits TGF-β1/Smad signalling in adventitial fibroblasts

Recent evidence suggests that adventitial fibroblasts (AFs) are crucially implicated in atherosclerosis. However, the mechanisms by which AFs are dysfunctional and contribute to atherosclerosis remain unclear. This study aimed to investigate the role of regulator of G-protein signalling 3 (RGS3) in the regulation of AFs using apoE knockout mouse as the model. Pathological changes in aortic arteries of apoE knockout mice fed with hyperlipid diet were examined by Movat staining. The expression of RGS3, α-SMA, TGF-β1, Smad2, and Smad3 in the adventitia was detected by immunohistochemistry. Adventitial fibroblasts were isolated from aortic arteries of apoE knockout mice and infected with RGS3 overexpression lentivirus or empty lentivirus. The expression of RGS3, α-SMA, TGF-β1, Smad2, and Smad3 in AFs was detected by real-time polymerase chain reaction and Western blot analysis. We found that hyperlipidic diet caused significant aortic intima thickening and atherosclerotic plaques in 15-week-old apoE knockout mice. Compared to wild-type mice, RGS3 expression was lower while α-SMA, TGF-β1, Smad2, and Smad3 expression was higher in the adventitia of apoE knockout mice. In addition, lentivirus mediated overexpression of RGS3 caused decreased expression of α-SMA, TGF-β1, Smad2, and Smad3 in AFs derived from apoE(-/-) mice. In conclusion, these results suggest that RGS3 may provide protection against pathological changes of AFs and the development of atherosclerosis by inhibiting TGF-β1/Smad signalling. RGS3 may be a potential therapeutic target for atherosclerosis.

LILRB4 deficiency aggravates the development of atherosclerosis and plaque instability by increasing the macrophage inflammatory response via NF-κB signaling

Atherosclerosis is a chronic inflammatory disease. LILRB4 is associated with the pathological processes of various inflammatory diseases. However, the potential function and underlying mechanisms of LILRB4 in atherogenesis remain to be investigated. In this study, LILRB4 expression was examined in both human and mouse atherosclerotic plaques. The effects and possible mechanisms of LILRB4 in atherogenesis and plaque instability were evaluated in LILRB4^-/-ApoE^-/- and ApoE^-/- mice fed a high-fat diet. We found that LILRB4 was located primarily in macrophages, and its expression was up-regulated in atherosclerotic lesions from human coronary arteries and mouse aortic roots. LILRB4 deficiency significantly accelerated the development of atherosclerotic lesions and increased the instability of plaques, as evidenced by the increased infiltration of lipids, decreased amount of collagen components and smooth muscle cells. Moreover, LILRB4 deficiency in bone marrow-derived cells promoted the development of atherosclerosis. In vivo and in vitro analyses revealed that the pro-inflammatory effects of LILRB4 deficiency were mediated by the increased activation of NF-κB signaling due to decreased Shp1 phosphorylation. In conclusion, the present study indicates that LILRB4 deficiency promotes atherogenesis, at least partly, through reduced Shp1 phosphorylation, which subsequently enhances the NF-κB-mediated inflammatory response. Thus, targeting the "LILRB4-Shp1" axis may be a novel therapeutic approach for atherosclerosis.

Regulator of G protein signaling 5 (RGS5) inhibits sonic hedgehog function in mouse cortical neurons

Regulator of G protein signaling 5 (RGS5) acts as a GTPase-activating protein (GAP) for the Gαi subunit and negatively regulates G protein-coupled receptor signaling. However, its presence and function in postmitotic differentiated primary neurons remains largely uncharacterized. During neural development, sonic hedgehog (Shh) signaling is involved in cell signaling pathways via Gαi activity. In particular, Shh signaling is essential for embryonic neural tube patterning, which has been implicated in neuronal polarization involving neurite outgrowth. Here, we examined whether RGS5 regulates Shh signaling in neurons. RGS5 transcripts were found to be expressed in cortical neurons and their expression gradually declined in a time-dependent manner in culture system. When an adenovirus expressing RGS5 was introduced into an in vitro cell culture model of cortical neurons, RGS5 overexpression significantly reduced neurite outgrowth and FM4-64 uptake, while cAMP-PKA signaling was also affected. These findings suggest that RGS5 inhibits Shh function during neurite outgrowth and the presynaptic terminals of primary cortical neurons mature via modulation of cAMP.

Oncostatin M receptor β deficiency attenuates atherogenesis by inhibiting JAK2/STAT3 signaling in macrophages

Oncostatin M (OSM) is a secreted cytokine mainly involved in chronic inflammatory and cardiovascular diseases through binding to OSM receptor β (OSMR-β). Recent studies demonstrated that the presence of OSM contributed to the destabilization of atherosclerotic plaque. To investigate whether OSMR-β deficiency affects atherosclerosis, male OSMR-β^−/−ApoE^−/− mice were generated and utilized. Here we observed that OSMR-β expression was remarkably upregulated in both human and mouse atherosclerotic lesions, which were mainly located in macrophages. We found that OSMR-β deficiency significantly ameliorated atherosclerotic burden in aorta and aortic root relative to ApoE-deficient littermates and enhanced the stability of atherosclerotic plaques by increasing collagen and smooth muscle cell content, while decreasing macrophage infiltration and lipid accumulation. Moreover, bone marrow transplantation of OSMR-β^−/− hematopoietic cells to atherosclerosis-prone mice displayed a consistent phenotype. Additionally, we observed a relatively reduced level of JAK2 and signal transducer and activator of transcription (STAT)3 in vivo and under Ox-LDL stimulation in vitro. Our findings suggest that OSMR-β deficiency in macrophages improved high-fat diet-induced atherogenesis and plaque vulnerability. Mech­anistically, the protective effect of OSMR-β deficiency on atherosclerosis may be partially attributed to the inhibition of the JAK2/STAT3 activation in macrophages, whereas OSM stimulation can activate the signaling pathway.

Vinexin β Ablation Inhibits Atherosclerosis in Apolipoprotein E-Deficient Mice by Inactivating the Akt-Nuclear Factor κB Inflammatory Axis

Background

Vinexin β is a novel adaptor protein that regulates cellular adhesion, cytoskeletal reorganization, signal transduction, and transcription; however, the exact role that vinexin β plays in atherosclerosis remains unknown.

Methods and Results

Immunoblot analysis showed that vinexin β expression is upregulated in the atherosclerotic lesions of both patients with coronary heart disease and hyperlipemic apolipoprotein E–deficient mice and is primarily localized in macrophages indicated by immunofluorescence staining. The high‐fat diet–induced double‐knockout mice exhibited lower aortic plaque burdens than apolipoprotein E^−/− littermates and decreased macrophage content. Vinexin β deficiency improved plaque stability by attenuating lipid accumulation and increasing smooth muscle cell content and collagen. Moreover, the bone marrow transplant experiment demonstrated that vinexin β deficiency exerts atheroprotective effects in hematopoietic cells. Consistent with these changes, the mRNA expression of proinflammatory cytokines were downregulated in vinexin β^−/− apolipoprotein E^−/− mice, whereas the anti‐inflammatory M2 macrophage markers were upregulated. The immunohistochemical staining and in vitro experiments showed that deficiency of vinexin β inhibited the accumulation of monocytes and the migration of macrophages induced by tumor necrosis factor α–stimulated human umbilical vein endothelial cells as well as macrophage proliferation. Finally, the inhibitory effects exerted by vinexin β deficiency on foam cell formation, nuclear factor κB activation, and inflammatory cytokine expression were largely reversed by constitutive Akt activation, whereas the increased expression of the nuclear factor κB subset promoted by adenoviral vinexin β was dramatically suppressed by inhibition of AKT.

Conclusions

Vinexin β deficiency attenuates atherogenesis primarily by suppressing vascular inflammation and inactivating Akt–nuclear factor κB signaling. Our data suggest that vinexin β could be a therapeutic target for the treatment of atherosclerosis.

Ablation of Interferon Regulatory Factor 3 Protects Against Atherosclerosis in Apolipoprotein E-Deficient Mice

The secretion of adhesion molecules by endothelial cells, as well as the subsequent infiltration of macrophages, determines the initiation and progression of atherosclerosis. Accumulating evidence suggests that IRF3 (interferon regulatory factor 3) is required for the induction of proinflammatory cytokines and for endothelial cell proliferation. However, the effect and underlying mechanism of IRF3 on atherogenesis remain unknown. Our results demonstrated a moderate-to-strong immunoreactivity effect associated with IRF3 in the endothelium and macrophages of the atherosclerotic plaques in patients with coronary heart disease and in hyperlipidemic mice. IRF3^-/-ApoE^-/- mice showed significantly decreased atherosclerotic lesions in the whole aorta, aortic sinus, and brachiocephalic arteries. The bone marrow transplantation further suggested that the amelioration of atherosclerosis might be attributed to the effects of IRF3 deficiency mainly in endothelial cells, as well as in macrophages. The enhanced stability of atherosclerotic plaques in IRF3^-/-ApoE^-/- mice was characterized by the reduction of necrotic core size, macrophage infiltration, and lipids, which was accompanied by increased collagen and smooth muscle cell content. Furthermore, multiple proinflammatory cytokines showed a marked decrease in IRF3^-/-ApoE^-/- mice. Mechanistically, IRF3 deficiency suppresses the secretion of VCAM-1 (vascular cell adhesion molecule 1) and the expression of ICAM-1 (intercellular adhesion molecule 1) by directly binding to the ICAM-1 promoter, which subsequently attenuates macrophage infiltration. Thus, our study suggests that IRF3 might be a potential target for the treatment of atherosclerosis development.

Loss of Caspase-Activated DNase Protects Against Atherosclerosis in Apolipoprotein E-Deficient Mice

Background

Atherosclerosis is a chronic disease that is closely related to inflammation and macrophage apoptosis, which leads to secondary necrosis and proinflammatory responses in advanced lesions. Caspase‐activated DNase (CAD) is a double‐strand specific endonuclease that leads to the subsequent degradation of chromosome DNA during apoptosis. However, whether CAD is involved in the progression of atherosclerosis remains elusive.

Methods and Results

CAD^−/−ApoE^−/− and ApoE^−/− littermates were fed a high‐fat diet for 28 weeks to develop atherosclerosis. Human specimens were collected from coronary heart disease (CHD) patients who were not suitable for transplantation. CAD expression was increased in the atheromatous lesions of CHD patients and high‐fat diet‐treated ApoE‐deficient mice. Further investigation demonstrated that CAD deficiency inhibited high‐fat diet‐induced atherosclerosis, as evidenced by decreased atherosclerotic plaques, inhibited inflammatory response, and macrophage apoptosis, as well as enhanced stability of plaques in CAD^−/−ApoE^−/− mice compared to the ApoE^−/− controls. Bone marrow transplantation verified the effect of CAD on atherosclerosis from macrophages. Mechanically, the decrease in the phosphorylated levels of mitogen‐activated protein kinase (MAPK) kinase/extracellular signal‐regulated kinase 1 and 2 (MEK‐ERK1/2) that resulted from CAD knockout and the activation of nuclear factor kappa B signaling mediated by CAD stimulation that was suppressed by inhibiting ERK1/2 phosphorylation revealed the potential association between the role of CAD in atherosclerosis and the MAPK signaling pathway.

Conclusions

In conclusion, CAD deficiency protects against atherosclerosis through inhibiting inflammation and macrophage apoptosis, which is partially through inactivation of the MEK‐ERK1/2 signaling pathway. This finding provides a promising therapeutic target for treating atherosclerosis.

Hydrogen Sulfide Induces Keap1 S-sulfhydration and Suppresses Diabetes-Accelerated Atherosclerosis via Nrf2 Activation

Hydrogen sulfide (H2S) has been shown to have powerful antioxidative and anti-inflammatory properties that can regulate multiple cardiovascular functions. However, its precise role in diabetes-accelerated atherosclerosis remains unclear. We report here that H2S reduced aortic atherosclerotic plaque formation with reduction in superoxide (O2 (-)) generation and the adhesion molecules in streptozotocin (STZ)-induced LDLr(-/-) mice but not in LDLr(-/-)Nrf2(-/-) mice. In vitro, H2S inhibited foam cell formation, decreased O2 (-) generation, and increased nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and consequently heme oxygenase 1 (HO-1) expression upregulation in high glucose (HG) plus oxidized LDL (ox-LDL)-treated primary peritoneal macrophages from wild-type but not Nrf2(-/-) mice. H2S also decreased O2 (-) and adhesion molecule levels and increased Nrf2 nuclear translocation and HO-1 expression, which were suppressed by Nrf2 knockdown in HG/ox-LDL-treated endothelial cells. H2S increased S-sulfhydration of Keap1, induced Nrf2 dissociation from Keap1, enhanced Nrf2 nuclear translocation, and inhibited O2 (-) generation, which were abrogated after Keap1 mutated at Cys151, but not Cys273, in endothelial cells. Collectively, H2S attenuates diabetes-accelerated atherosclerosis, which may be related to inhibition of oxidative stress via Keap1 sulfhydrylation at Cys151 to activate Nrf2 signaling. This may provide a novel therapeutic target to prevent atherosclerosis in the context of diabetes.

RGS proteins as targets in the treatment of intestinal inflammation and visceral pain: New insights and future perspectives

Regulators of G protein signaling (RGS) proteins provide timely termination of G protein-coupled receptor (GPCR) responses. Serving as a central control point in GPCR signaling cascades, RGS proteins are promising targets for drug development. In this review, we discuss the involvement of RGS proteins in the pathophysiology of the gastrointestinal inflammation and their potential to become a target for anti-inflammatory drugs. Specifically, we evaluate the emerging evidence for modulation of selected receptor families: opioid, cannabinoid and serotonin by RGS proteins. We discuss how the regulation of RGS protein level and activity may modulate immunological pathways involved in the development of intestinal inflammation. Finally, we propose that RGS proteins may serve as a prognostic factor for survival rate in colorectal cancer. The ideas introduced in this review set a novel conceptual framework for the utilization of RGS proteins in the treatment of gastrointestinal inflammation, a growing major concern worldwide.

YiXin-Shu, a ShengMai-San-based traditional Chinese medicine formula, attenuates myocardial ischemia/reperfusion injury by suppressing mitochondrial mediated apoptosis and upregulating liver-X-receptor α

Positive evidence from clinical trials has fueled growing acceptance of traditional Chinese medicine (TCM) for the treatment of cardiac diseases; however, little is known about the underlying mechanisms. Here, we investigated the nature and underlying mechanisms of the effects of YiXin-Shu (YXS), an antioxidant-enriched TCM formula, on myocardial ischemia/reperfusion (MI/R) injury. YXS pretreatment significantly reduced infarct size and improved viable myocardium metabolism and cardiac function in hypercholesterolemic mice. Mechanistically, YXS attenuated myocardial apoptosis by inhibiting the mitochondrial mediated apoptosis pathway (as reflected by inhibition of mitochondrial swelling, cytochrome c release and caspase-9 activity, and normalization of Bcl-2 and Bax levels) without altering the death receptor and endoplasmic reticulum-stress death pathways. Moreover, YXS reduced oxidative/nitrative stress (as reflected by decreased superoxide and nitrotyrosine content and normalized pro- and anti-oxidant enzyme levels). Interestingly, YXS upregulated endogenous nuclear receptors including LXRα, PPARα, PPARβ and ERα, and in-vivo knockdown of cardiac-specific LXRα significantly blunted the cardio-protective effects of YXS. Collectively, these data show that YXS is effective in mitigating MI/R injury by suppressing mitochondrial mediated apoptosis and oxidative stress and by upregulating LXRα, thereby providing a rationale for future clinical trials and clinical applications.

Regulator of G-Protein Signaling 5 Prevents Smooth Muscle Cell Proliferation and Attenuates Neointima Formation

OBJECTIVE

Regulator of G-protein signaling 5 (RGS5) is abundantly expressed in vascular smooth muscle cells (SMCs) and inhibits G-protein signaling by enhancing the guanosine triphosphate-hydrolyzing activity of Gα-subunits. In the present study, we investigated the effects of RGS5 on vascular SMC function in vitro and neointima formation after wire-induced injury in mice and determined the underlying mechanisms.

APPROACH AND RESULTS

We found a robust expression of RGS5 in native arteries of C57BL/6 mice and a highly significant downregulation within neointimal lesions 10 and 21 days after vascular injury as assessed by quantitative polymerase chain reaction, immunoblotting, and immunohistochemistry. In vitro, RGS5 was found significantly downregulated after mitogenic stimulation of human coronary artery SMCs. To restore RGS5 levels, SMCs were transduced with adenoviral vectors encoding wild-type RGS5 or a nondegradable mutant. RGS5-WT and, even more prominently, the C2A-RGS5 mutant prevented SMC proliferation and migration. In contrast, the siRNA-mediated knockdown of RGS5 significantly augmented SMC proliferation. Following overexpression of RGS5, fluorescence-activated cell sorting analysis of propidium iodide-stained cells indicated cell cycle arrest in G0/G1 phase. Mechanistically, inhibition of the phosphorylation of the extracellular signal-regulated kinase 1/2 and mitogen-activated protein kinase downstream signaling was shown to be responsible for the anti-proliferative effect of RGS5. Following wire-induced injury of the femoral artery in C57BL/6 mice, adenoviral-mediated overexpression of RGS5-WT or C2A-RGS5 significantly reduced SMC proliferation and neointima formation in vivo.

CONCLUSIONS

Downregulation of RGS5 is an important prerequisite for SMC proliferation in vitro and in vivo. Therefore, reconstitution of RGS5 levels represents a promising therapeutic option to prevent vascular remodeling processes.

Chinese innovation in cardiovascular drug discovery

This article is part of a themed section on Chinese Innovation in Cardiovascular Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-23

R4 Regulator of G Protein Signaling (RGS) Proteins in Inflammation and Immunity

G protein-coupled receptors (GPCRs) have important functions in both innate and adaptive immunity, with the capacity to bridge interactions between the two arms of the host responses to pathogens through direct recognition of secreted microbial products or the by-products of host cells damaged by pathogen exposure. In the mid-1990s, a large group of intracellular proteins was discovered, the regulator of G protein signaling (RGS) family, whose main, but not exclusive, function appears to be to constrain the intensity and duration of GPCR signaling. The R4/B subfamily--the focus of this review--includes RGS1-5, 8, 13, 16, 18, and 21, which are the smallest RGS proteins in size, with the exception of RGS3. Prominent roles in the trafficking of B and T lymphocytes and macrophages have been described for RGS1, RGS13, and RGS16, while RGS18 appears to control platelet and osteoclast functions. Additional G protein independent functions of RGS13 have been uncovered in gene expression in B lymphocytes and mast cell-mediated allergic reactions. In this review, we discuss potential physiological roles of this RGS protein subfamily, primarily in leukocytes having central roles in immune and inflammatory responses. We also discuss approaches to target RGS proteins therapeutically, which represents a virtually untapped strategy to combat exaggerated immune responses leading to inflammation.