Antiphospholipid antibodies attenuate endothelial repair and promote neointima formation in mice

Exploration of the Effect on Genome-Wide DNA Methylation by miR-143 Knock-Out in Mice Liver

MiR-143 play an important role in hepatocellular carcinoma and liver fibrosis via inhibiting hepatoma cell proliferation. DNA methyltransferase 3 alpha (DNMT3a), as a target of miR-143, regulates the development of primary organic solid tumors through DNA methylation mechanisms. However, the effect of miR-143 on DNA methylation profiles in liver is unclear. In this study, we used Whole-Genome Bisulfite Sequencing (WGBS) to detect the differentially methylated regions (DMRs), and investigated DMR-related genes and their enriched pathways by miR-143. We found that methylated cytosines increased 0.19% in the miR-143 knock-out (KO) liver fed with high-fat diet (HFD), compared with the wild type (WT). Furthermore, compared with the WT group, the CG methylation patterns of the KO group showed lower CG methylation levels in CG islands (CGIs), promoters and hypermethylation in CGI shores, 5'UTRs, exons, introns, 3'UTRs, and repeat regions. A total of 984 DMRs were identified between the WT and KO groups consisting of 559 hypermethylation and 425 hypomethylation DMRs. Furthermore, DMR-related genes were enriched in metabolism pathways such as carbon metabolism (serine hydroxymethyltransferase 2 (Shmt2), acyl-Coenzyme A dehydrogenase medium chain (Acadm)), arginine and proline metabolism (spermine synthase (Sms), proline dehydrogenase (Prodh2)) and purine metabolism (phosphoribosyl pyrophosphate synthetase 2 (Prps2)). In summary, we are the first to report the change in whole-genome methylation levels by miR-143-null through WGBS in mice liver, and provide an experimental basis for clinical diagnosis and treatment in liver diseases, indicating that miR-143 may be a potential therapeutic target and biomarker for liver damage-associated diseases and hepatocellular carcinoma.

Antiphospholipid antibodies in end-stage renal disease: A systematic review and meta-analysis

INTRODUCTION

The relationship between autoimmune hemolytic anemia and antiphospholipid antibodies (aPL) and/or antiphospholipid syndrome has never been systematically addressed.

METHODS

Systematic review of EMBASE and PubMed databases performed according to PRISMA guidelines from inception to March 2020; meta-analysis performed by Peto's odds ratio for rare events.

FINDINGS

Forty-five studies with different outcomes met the inclusion/exclusion criteria. The pooled prevalence (PP) of IgG anticardiolipin antibodies (aCL) positivity was greater in end-stage renal disease (ESRD) than controls (20.2% vs. 2.6%, P = 0.001, I²  >80%; I² = heterogeneity), particularly in hemodialysis patients (18.3% vs. 8%, I² = 0%). The PP of lupus anticoagulant was greater in ESRD than controls (8.7% vs. 0.2%, P < 0.0001, I² = 0%). The standardized mean difference of IgG aCL favored ESRD rather than controls (P < 0.0001, I² =97%). The PP of fistula occlusion was greater in IgG aCL-positive patients than negative patients (39% vs. 27%, I² =97%); the PP of IgG aCL positivity was greater in patients with fistula occlusion than without fistula occlusion (26.9% vs. 23.2%, P = 0.01, I² =72%); the same applied to the PP of lupus anticoagulant positivity (23% vs. 0.3%, P < 0.0001, I² = 0%). The standardized mean difference of IgG aCL favored fistula occlusion (P = 0.004, I² = 91%).

DISCUSSION

Lupus anticoagulant relates to ESRD regardless of management whereas IgG aCL relates specifically to ESRD on hemodialysis, but only lupus anticoagulant associates with fistula occlusion. The expression of aPL as patients positive for aPL rather than as titers precludes further assumptions on the relationship.

Cellular and Molecular Mechanisms of Anti-Phospholipid Syndrome

The primary anti-phospholipid syndrome (APS) is characterized by the production of antibodies that bind the phospholipid-binding protein β2 glycoprotein I (β2GPI) or that directly recognize negatively charged membrane phospholipids in a manner that may contribute to arterial or venous thrombosis. Clinically, the binding of antibodies to β2GPI could contribute to pathogenesis by formation of immune complexes or modification of coagulation steps that operate along cell surfaces. However, additional events are likely to play a role in pathogenesis, including platelet and endothelial cell activation. Recent studies focus on neutrophil release of chromatin in the form of neutrophil extracellular traps as an important disease contributor. Jointly, the participation of both the innate and adaptive arms of the immune system in aspects of the APS make the complete understanding of crucial steps in pathogenesis extremely difficult. Only coordinated and comprehensive analyses, carried out in different clinical and research settings, are likely to advance the understanding of this complex disease condition.

Antiphospholipid antibodies induce thrombosis by PP2A activation via apoER2-Dab2-SHC1 complex formation in endothelium

In the antiphospholipid syndrome (APS), antiphospholipid antibody (aPL) recognition of β2 glycoprotein I promotes thrombosis, and preclinical studies indicate that this is due to endothelial nitric oxide synthase (eNOS) antagonism via apolipoprotein E receptor 2 (apoER2)-dependent processes. How apoER2 molecularly links these events is unknown. Here, we show that, in endothelial cells, the apoER2 cytoplasmic tail serves as a scaffold for aPL-induced assembly and activation of the heterotrimeric protein phosphatase 2A (PP2A). Disabled-2 (Dab2) recruitment to the apoER2 NPXY motif promotes the activating L309 methylation of the PP2A catalytic subunit by leucine methyl transferase-1. Concurrently, Src homology domain-containing transforming protein 1 (SHC1) recruits the PP2A scaffolding subunit to the proline-rich apoER2 C terminus along with 2 distinct regulatory PP2A subunits that mediate inhibitory dephosphorylation of Akt and eNOS. In mice, the coupling of these processes in endothelium is demonstrated to underlie aPL-invoked thrombosis. By elucidating these intricacies in the pathogenesis of APS-related thrombosis, numerous potential new therapeutic targets have been identified.

New Insights in the Pathophysiology of Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by an elevated risk for arterial and venous thrombosis and pregnancy-related morbidity. Since the discovery of the disease in 1980s, numerous studies in cell culture systems, in animal models, and in patient populations have been reported, leading to a deeper understanding of the pathogenesis of APS. These studies have determined that circulating autoantibodies, collectively called antiphospholipid antibodies (aPL), the majority of which recognize cell surface proteins attached to the plasma membrane phospholipids, play a causal role in the development of the disease. The binding of aPL to the cell surface antigens triggers interaction of the complex with transmembrane receptors to initiate intracellular signaling in critical cell types, including platelets, monocytes, endothelial cells, and trophoblasts. Subsequent alteration of various cell functions results in inflammation, thrombus formation, and pregnancy complications. Apolipoprotein E receptor 2 (apoER2), a lipoprotein receptor family member, has been implicated as a mediator for aPL actions in platelets and endothelial cells. Nitric oxide (NO) is a signaling molecule known to exert potent antithrombotic, anti-inflammatory, and anti-atherogenic effects. NO insufficiency and oxidative stress have been linked to APS pathogenesis. This review will focus on the recent findings on how apoER2 and dysregulation of NO production contribute to aPL-mediated pathologies in APS.

Delayed reendothelialization with rapamycin is rescued by the addition of nicorandil in balloon-injured rat carotid arteries

Rapamycin is an immunosuppressive agent that is added to drug eluting stents. It prevents restenosis, but it also impairs reendothelialization. Nicorandil is a hybrid agent with adenosine triphosphated (ATP)-sensitive K+ (KATP) channel opener and nitrate properties. It prevents oxidative stress and cell apoptosis induced by rapamycin in endothelial cells in vitro. However, whether nicorandil promotes reendothelialization after angioplasty delayed by rapamycin remains to be determined. Balloon injury model was established in SD rats. Nicorandil increased reendothelialization impaired by rapamycin, and it decreased xanthine oxidase (XO)-generated reactive oxygen species (ROS) induced by rapamycin. In addition, eNOS expression inhibited by rapamycin was increased by nicorandil in vivo. In vitro, rapamycin-impeded cardiac microvascular endothelial cells (CMECs) migration, proliferation and rapamycin-induced ROS production were reversed by nicorandil. Knockdown of XO partially inhibited rapamycin-induced ROS production and cell apoptosis in CMECs, and it promoted CMECs migration and proliferation suppressed by rapamycin. Knockdown of Akt partially prevents eNOS upregulation promoted by nicorandil. The beneficial effect of nicorandil is exhibited by inhibiting XO and up-regulating Akt pathway. Nicorandil combined with rapamycin in effect rescue the deficiencies of rapamycin alone in arterial healing after angioplasty.

Identification of a Monoclonal Antibody That Attenuates Antiphospholipid Syndrome-Related Pregnancy Complications and Thrombosis

In the antiphospholipid syndrome (APS), patients produce antiphospholipid antibodies (aPL) that promote thrombosis and adverse pregnancy outcomes. Current therapy with anticoagulation is only partially effective and associated with multiple complications. We previously discovered that aPL recognition of cell surface β2-glycoprotein I (β2-GPI) initiates apolipoprotein E receptor 2 (apoER2)-dependent signaling in endothelial cells and in placental trophoblasts that ultimately promotes thrombosis and fetal loss, respectively. Here we sought to identify a monoclonal antibody (mAb) to β2-GPI that negates aPL-induced processes in cell culture and APS disease endpoints in mice. In a screen measuring endothelial NO synthase (eNOS) activity in cultured endothelial cells, we found that whereas aPL inhibit eNOS, the mAb 1N11 does not, and instead 1N11 prevents aPL action. Coimmunoprecipitation studies revealed that 1N11 decreases pathogenic antibody binding to β2-GPI, and it blocks aPL-induced complex formation between β2-GPI and apoER2. 1N11 also prevents aPL antagonism of endothelial cell migration, and in mice it reverses the impairment in reendothelialization caused by aPL, which underlies the non-thrombotic vascular occlusion provoked by disease-causing antibodies. In addition, aPL inhibition of trophoblast proliferation and migration is negated by 1N11, and the more than 6-fold increase in fetal resorption caused by aPL in pregnant mice is prevented by 1N11. Furthermore, the promotion of thrombosis by aPL is negated by 1N11. Thus, 1N11 has been identified as an mAb that attenuates APS-related pregnancy complications and thrombosis in mice. 1N11 may provide an efficacious, mechanism-based therapy to combat the often devastating conditions suffered by APS patients.

Evaluation of anticardiolipin antibodies in tobacco users and non-tobacco users with severe chronic periodontal disease

Aims:

Many studies have proven that b2-glycoprotein-I-dependent anticardiolipin is elevated in periodontal diseases. Systemic lupus erythematosus and antiphospholipid syndrome, which are usually associated with high antiphospholipid antibodies, are more prone to adverse pregnancy outcomes and cardiovascular sequelae. Therefore, the aim of the present study is to evaluate IgG, IgM anticardiolipin antibodies in tobacco users and non-tobacco users with severe chronic periodontal disease.

Materials and Methods:

Based on the Armitage classification, 2000, 40 severe periodontitis (group D) (mean clinical attachment loss greater than 2.5 mm) male patients were selected for the study with the age range of 35–65 years and good general health from the Department of periodontics, SRM Kattankulathur Dental College, Chennai. They were classified as smokers (20 subjects) and non-smokers (20 subjects). Blood samples were collected and IgG, IgM antibodies were semi-quantitatively analyzed by enzyme-linked immunosorbent assay. The data thus collected were statistically analyzed by independent student's t-test.

Results:

Results showed that smokers with severe periodontitis exhibited marked increase in anticardiolipin IgG, IgM compared to non-smokers. They showed a positive correlation and statistical significance (P < 0.0001) between mean clinical attachment loss and IgG and IgM values.

Conclusions:

Results showed a rise in anticardiolipin antibodies in smokers with severe periodontitis, which indicates that these patients are more prone to coronary heart disease.

Soluble analog of ApoER2 targeting beta2-glycoprotein I in immune complexes counteracts hypertension in lupus-prone mice with spontaneous antiphospholipid syndrome

Essentials (NZWxBXSB)F1 male mice develop antibodies beta2-glycoprotein I (β2GPI) and hypertension. A1-A1 is a soluble analogue of ApoE receptor 2 with a high affinity for β2GPI/antibody complexes. A1-A1 improved blood pressure and arterial elastance in (NZWxBXSB)F1 male mice. A1-A1 had no adverse effects on the hemodynamics of healthy mice.

SUMMARY

Background Antiphospholipid syndrome (APS) is diagnosed based on the presence of antiphospholipid antibodies and clinical thrombosis or fetal loss during pregnancy. Lupus-prone (NZWxBXSB)F1 male mice are the mouse model of spontaneous APS. They develop anti-β2GPI antibodies, microinfarcts and hypertension. ApoER2 is a receptor that contributes to anti-β2GPI-dependent thrombosis in APS by down-regulating endothelial nitric oxide synthase activation. Objectives A1-A1 is a small protein constructed from two identical ligand-binding modules from ApoER2, containing the binding site for β2GPI. We studied how treatment with A1-A1 affects the development of hypertension in (NZWxBXSB)F1 male mice. Methods We treated (NZWxBXSB)F1 male mice with A1-A1 for up to 4 weeks and examined changes in hemodynamics by left ventricular pressure-volume loop measurements. Results We observed improvements in blood pressure in the A1-A1 treated mice. A1-A1 prevented the deterioration of arterial elastance by decreasing systemic resistance and improving vessel compliance. We did not detect any adverse effects of the treatment in either male mice or in apparently healthy female (NZWxBXSB)F1 mice. Conclusions We demonstrated that A1-A1, which is a soluble analog of ApoER2 that binds pathological β2GPI/anti-β2GPI complexes, has a positive impact on hemodynamics in lupus-prone mice with spontaneous anti-β2GPI antibodies and hypertension.

Loss of Reelin protects against atherosclerosis by reducing leukocyte-endothelial cell adhesion and lesion macrophage accumulation

The multimodular glycoprotein Reelin controls neuronal migration and synaptic transmission by binding to apolipoprotein E receptor 2 (Apoer2) and very low density lipoprotein receptor (Vldlr) on neurons. In the periphery, Reelin is produced by the liver, circulates in blood, and promotes thrombosis and hemostasis. To investigate if Reelin influences atherogenesis, we studied atherosclerosis-prone low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice in which we inducibly deleted Reelin either ubiquitously or only in the liver, thus preventing the production of circulating Reelin. In both types of Reelin-deficient mice, atherosclerosis progression was markedly attenuated, and macrophage content and endothelial cell staining for vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) were reduced at the sites of atherosclerotic lesions. Intravital microscopy revealed decreased leukocyte-endothelial adhesion in the Reelin-deficient mice. In cultured human endothelial cells, Reelin enhanced monocyte adhesion and increased ICAM1, VCAM1, and E-selectin expression by suppressing endothelial nitric oxide synthase (eNOS) activity and increasing nuclear factor κB (NF-κB) activity in an Apoer2-dependent manner. These findings suggest that circulating Reelin promotes atherosclerosis by increasing vascular inflammation, and that reducing or inhibiting circulating Reelin may present a novel approach for the prevention of cardiovascular disease.

An A1-A1 mutant with improved binding and inhibition of β2GPI/antibody complexes in antiphospholipid syndrome

β2 glycoprotein I (β2GPI) is the most common antigen for autoimmune antibodies in antiphospholipid syndrome (APS). Thrombosis is a clinical feature of APS. We created a molecule (A1-A1) that consists of two identical β2GPI-binding modules from ApoE receptor 2 (ApoER2). A1-A1 binds to β2GPI/antibody complexes, preventing their association with ApoER2 and anionic phospholipids, and reducing thrombus size in the mouse model of APS. Here, we describe a mutant of A1-A1 (mA1-A1ND) with improved affinity for β2GPI. mA1-A1ND inhibits the binding of β2GPI to cardiolipin in the presence of anti-β2GPI antibodies, and inhibits the binding to phospholipids in plasma samples of APS patients, affecting the clotting time. Reduction of the clotting time demonstrates the presence of soluble β2GPI/antibody complexes in patients' plasma. These complexes either already exist in patients' plasma or form rapidly in the proximity to phospholipids. All members of the low-density lipoprotein receptor family bind β2GPI. Modeling studies of A1 in a complex with domain V of β2GPI (β2GPI-DV) revealed two possible modes of interaction of a ligand-binding module from lipoprotein receptors with β2GPI-DV. In both orientations, the ligand-binding module interferes with binding of β2GPI to anionic phospholipids; however, it interacts with two different but overlapping sets of lysine residues in β2GPI-DV, depending on the orientation.