Activation of endothelial cells in thrombosis and vasculitis

Disconnect between COX-2 selective inhibition and cardiovascular risk in preclinical models

INTRODUCTION

Secondary pharmacology profiling is routinely applied in pharmaceutical drug discovery to investigate the pharmaceutical effects of a drug at molecular targets distinct from (off-target) the intended therapeutic molecular target (on-target). Data from a randomized, placebo-controlled clinical trial, the APPROVe (Adenomatous Polyp Prevention on VIOXX, rofecoxib) trial, raised significant concerns about COX-2 inhibition as a primary or secondary target, shaping the screening and decision-making processes of some pharmaceutical companies. COX-2 is often included in off-target screens due to cardiovascular (CV) safety concerns about secondary interactions with this target. Several potential mechanisms of COX-2-mediated myocardial infarctions have been considered including, effects on platelet stickiness/aggregation, vasal tone and blood pressure, and endothelial cell activation. In the present study, we focused on each of these mechanisms as potential effects of COX-2 inhibitors, to find evidence of mechanism using various in vitro and in vivo preclinical models.

METHODS

Compounds tested in the study, with a range of COX-2 selectivity, included rofecoxib, celecoxib, etodolac, and meloxicam. Compounds were screened for inhibition of COX-2 vs COX-1 enzymatic activity, ex vivo platelet aggregation (using whole blood from multiple species), ex vivo canine femoral vascular ring model, in vitro human endothelial cell activation (with and without COX-2 induction), and in vivo cardiovascular assessment (anesthetized dog).

RESULTS

The COX-2 binding assessment generally confirmed the COX-2 selectivity previously reported. COX-2 inhibitors did not have effects on platelet function (spontaneous aggregation or inhibition of aggregation), cardiovascular parameters (mean arterial pressure, heart rate, and left ventricular contractility), or endothelial cell activation. However, rofecoxib uniquely produced an endothelial mediated constriction response in canine femoral arteries.

CONCLUSION

Our data suggest that rofecoxib-related cardiovascular events in humans are not predicted by COX-2 potency or selectivity. In addition, the vascular ring model suggested possible adverse cardiovascular effects by COX-2 inhibitors, although these effects were not seen in vivo studies. These results may also suggest that COX-2 inhibition alone is not responsible for rofecoxib-mediated adverse cardiovascular outcomes.

Autoimmune complications of COVID-19 and potential consequences for long-lasting disease syndromes

The latest WHO report determined the increasing diversity within the CoV-2 omicron and its descendent lineages. Some heavily mutated offshoots of BA.5 and BA.2, such as BA.4.6, BF.7, BQ.1.1, and BA.2.75, are responsible for about 20% of infections and are spreading rapidly in multiple countries. It is a sign that Omicron subvariants are now developing a capacity to be more immune escaping and may contribute to a new wave of COVID-19. Covid-19 infections often induce many alterations in human physiological defense and the natural control systems, with exacerbated activation of the inflammatory and homeostatic response, as for any infectious diseases. Severe activation of the early phase of hemostatic components, often occurs, leading to thrombotic complications and often contributing to a lethal outcome selectively in certain populations. Development of autoimmune complications increases the disease burden and lowers its prognosis. While the true mechanism still remains unclear, it is believed to mainly be related to the host autoimmune responses as demonstrated, only in some patients suffering from the presence of autoantibodies that worsens the disease evolution. In fact in some studies the development of autoantibodies to angiotensin converting enzyme 2 (ACE2) was identified, and in other studies autoantibodies, thought to be targeting interferon or binding to annexin A1, or autoantibodies to phospholipids were seen. Moreover, the occurrence of autoimmune heparin induced thrombocytopenia has also been described in infected patients treated with heparin for controlling thrombogenicity. This commentary focuses on the presence of various autoantibodies reported so far in Covid-19 diseases, exploring their association with the disease course and the durability of some related symptoms. Attempts are also made to further analyze the potential mechanism of actions and link the presence of antibodies with pathological complications.

Long-term prognosis of vascular access in hemodialysis patients with systemic lupus erythematosus: a retrospective cohort study

Patients with systemic lupus erythematosus (SLE) have a higher risk of vascular complications. This retrospective cohort study aimed to analyze the differences in the risk of arteriovenous fistula or graft (AVF/AVG) dysfunction in hemodialysis patients with and without SLE from Taiwan's National Health Insurance Database over a 10-year period. AVF/AVG dysfunction is defined as the occurrence of the first episode of intervention after vascular access creation. A total of 1366 HD patients with SLE had higher incidence rates of AVF/AVG dysfunction than 4098 non-SLE HD patients in the following 4 periods: (1) after 1 year (incidence rates = 15.21% and 13.01%, respectively; subdistribution hazard ratio (SHR) = 1.16; P = 0.007), (2) 1st-to-10th-year period (15.36% and 13.25%; SHR = 1.16; P = 0.007), (3) 5th-to-10th-year period (11.91% and 8.1%; SHR = 1.42; P = 0.003), and (4) overall period (23.53% and 21.66%; SHR = 1.09; P = 0.027). In conclusion, there were significantly higher incidence rates of AVF/AVG dysfunction in SLE patients during the long-term follow-up period. Vascular access function should be monitored regularly by clinical examinations, especially after 1 year and during 5 to 10 years, to improve AVF/AVG patency and dialysis adequacy in SLE patients undergoing maintenance hemodialysis.

Phenazine methosulphate-treated red blood cells activate NF-κB and upregulate endothelial ICAM-1 expression

Although enhanced Red Blood Cell (RBC) - Endothelial Cell (EC) interaction, as well as RBC induced EC activation, have been extensively studied in several RBC-linked pathologies, the specific individual effects of oxidatively modified RBC on EC activation has not yet been documented. However, increasing evidence in both experimental and clinical studies suggests that oxidatively modified RBC could be considered potential pathogenic determinants in several acute and chronic diseases displaying systemic oxidative stress. Therefore, the present study aimed to explore the specific effects of oxidized RBC interaction with endothelial cells on intracellular signaling pathways that promote EC activation. RBC were exposed to oxidative stress induced by phenazine methosulphate (PMS). It is shown that the interaction of oxidatively modified RBC with cultured human umbilical vein endothelial cells (HUVEC) results in: a) EC activation as indicated by the increased surface expression of intercellular adhesion molecule -1 (ICAM-1); b) the activation of transcription factor NF-κB, an indicator of cellular oxidant stress. These results emphasize the specific contribution of oxidatively modified RBC interaction to EC activation and their possible pathological role in vascular diseases and oxidative stress.

Thrombophilia Associated with Early Post-angioplasty Thrombosis of Dialysis Vascular Access

AIM

Percutaneous transluminal angioplasty (PTA) is widely used as the primary treatment for dialysis vascular access dysfunction. Nonetheless, many patients develop early occlusion after angioplasty. Thus, we investigated the role of thrombophilia in access occlusion within 30 days of angioplasty.

MATERIALS AND METHODS

This case-control study included patients who underwent PTA for dialysis vascular access dysfunction. Patients who experienced occlusion within 30 days of angioplasty were included in the case group and those without occlusion for at least 30 days after angioplasty were included in the control group. All patients were tested for protein C, protein S, antithrombin III, lupus anticoagulant, and anticardiolipin antibodies.

RESULTS

From February to October 2015, 462 patients underwent PTA for dialysis vascular access dysfunction. Forty-one patients (8.9%) had early occlusion within 30 days of angioplasty. The case group had more graft accesses (73 vs. 31%, P < 0.001) and thrombotic occlusions (67 vs. 15%, P < 0.001). A higher incidence of protein C (10 vs. 2%), protein S (15 vs. 5%), and antithrombin III (10 vs. 2%) deficiency and elevated anticardiolipin antibody (22 vs. 10%) levels were observed in the case group. Overall, 26 patients (63%) in the case group had at least one thrombophilic factor, compared with 15 patients (37%) in the control group (unadjusted odds ratio [OR], 3.004; 95% confidence interval [CI], 1.223-7.380; P = 0.027). After adjustment for confounding factors, the association between thrombophilic factors and early occlusion remained (adjusted OR, 3.806; 95% CI, 1.018-14.220; P = 0.047).

CONCLUSION

Thrombophilia is associated with early occlusion after angioplasty for hemodialysis vascular access.

Risk of Vascular access Thrombosis in Patients with Systemic Lupus Erythematosus on Hemodialysis

Introduction

Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis.

Methods

Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups.

Results

Mean age at dialysis was 36±10 years in 36 SLE patients (28 females, 8 males) and was 38±6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p<0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2–8.2).

Conclusion

SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

Biomarkers of endothelial cell activation: candidate markers for drug-induced vasculitis in patients or drug-induced vascular injury in animals

There is a pressing need for vascular biomarkers for studies of drug-induced vasculitis in patients and drug-induced vascular injury (DIVI) in animals. We previously reviewed a variety of candidate biomarkers of endothelial cell (EC) activation (Zhang et al., 2010). Now we update information on EC activation biomarkers from animal data on DIVI and clinical data of vasculitic patients, particularly patients with primary antineutrophil cytoplasmic autoantibody (ANCA)-associated small vessel vasculitis (primary AAVs), including Wegener's granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome and necrotizing crescentic glomerulonephritis. Drug-associated ANCA-positive small vessel vasculitis (drug-AAVs) can closely resemble primary AAVs, suggesting the large overlap between primary idiopathic systemic vasculitis and drug-induced vasculitis. AAVs in patients and DIVI in animals vary considerably; however, there is close resemblance between AAVs and DIVI in some respects: (1) the immunopathogenetic mechanisms (activation of primed neutrophils, ECs and T cells by ANCA in patients and activation of ECs, mast cells, and macrophages by drugs in animals); (2) the morphologic changes (fibrinoid necrosis of the vessel wall and neutrophilic infiltration); (3) the preferable sites (small arteries, arterioles, capillaries and venules); and (4) elevation of vascular biomarkers suggestive of an endothelial origin. The present review discusses soluble and cell component biomarkers and provides a rationale for the potential utility of EC activation biomarkers in nonclinical and clinical studies during new drug development. Further investigation, however, is needed to assess their potential utility.

Biomarkers of endothelial cell activation serve as potential surrogate markers for drug-induced vascular injury

Drug-induced vascular injury (DIVI) is a nonclinical finding that often confounds the toxicological evaluation of investigational drugs, but there is an absence of qualified biomarkers that can be used to detect and monitor its appearance in animals and patients during drug development and clinical use. It is well known that endothelial cell (EC) activation plays a key role in the expression and evolution of DIVI, and the various immunological and inflammatory factors involved in its expression may serve as potential biomarker candidates. Activated ECs change their morphology and gene expression, generating endothelial adhesion molecules, pro-coagulant molecules, cytokines, chemokines, vasodilators, nitric oxide, and acute-phase reactants. This review provides a brief historical background of EC activation and the search for biomarkers of early EC activation for monitoring DIVI. At present, no biomarkers of EC activation have been qualified to predict DIVI in the nonclinical or clinical context, and a robust pathologic foundation for their use is still lacking. We propose three categories of EC activation biomarkers: recommended surrogate markers, potentially useful markers, and emerging candidate markers. This review alerts pharmaceutical companies, research institutions, and regulatory agencies to the continuing need for reliable biomarkers of EC activation in drug development.

Lupus mesenteric vasculitis can cause acute abdominal pain in patients with SLE

Lupus mesenteric vasculitis (LMV) is a unique clinical entity found in patients who present with gastrointestinal manifestations of systemic lupus erythematosus, and is the main cause of acute abdominal pain in these patients. LMV usually presents as acute abdominal pain with sudden onset, severe intensity and diffuse localization. Other causes of abdominal pain, such as acute gastroenteritis, peptic ulcers, acute pancreatitis, peritonitis, and other reasons for abdominal surgery should be ruled out. Prompt and accurate diagnosis of LMV is critical to ensure implementation of appropriate immunosuppressive therapy and avoidance of unnecessary surgical intervention. The pathology of LMV comprises immune-complex deposition and complement activation, with subsequent submucosal edema, leukocytoclastic vasculitis and thrombus formation; most of these changes are confined to small mesenteric vessels. Abdominal CT is the most useful tool for diagnosing LMV, which is characterized by the presence of target signs, comb signs, and other associated findings. The presence of autoantibodies against phospholipids and endothelial cells might provide information about the likelihood of recurrence of LMV. Immediate, high-dose, intravenous steroid therapy can lead to a favorable outcome and prevent serious complications such as bowel ischemia, necrosis and perforation.

Two cases of eosinophilic vasculitis with thrombosis

Vasculitides are characterized by vessel wall inflammation of unknown etiology. We report two cases of eosinophilic vasculitis and hypereosinophilia with thrombosis. They have been treated with a high-dose glucocorticoid and anticoagulation. These cases emphasize that thrombosis should be anticipated in patients with eosinophilic vasculitis.

Anticardiolipin antibody and Taiwanese chronic haemodialysis patients with recurrent vascular access thrombosis

Vascular access failure is a major cause of morbidity in chronic haemodialysis (HD) patients. However, some factors (such as homocysteine levels) are known regarding the risk factors predisposing certain HD patients to vascular access thrombosis (VAT). Immunoglobulin-G anticardiolipin antibody (IgG-ACA) is strongly associated with venous and arterial thrombosis in patients with normal renal function. Previous investigations have reported the characteristics of patients with raised IgG-ACA titre and recurrent VAT of HD in Western countries, but few equivalent studies exist for Taiwan. This retrospective study attempts to determine whether raised IgG-ACA titres are associated with an increased risk of recurrent VAT in chronic HD patients. This study enrolled 483 patients undergoing HD. IgG-ACA titre and hepatitis B&C marker were measured for all patients. A history of recurrent (VAT more than one) and/or VAT was elicited by using information from the patient questionnaires and was verified by means of careful inpatient and outpatient chart review. Raised IgG-ACA titres were present in 21.7% (105/483) of patients. In both groups (raised IgG-ACA and normal IgG-ACA), the type of shunt differed significantly (p = 0.029). In predicting for more or one episodes of VAT by using multiple logistic regression with all significant factors, synthetic graft was also a significant factor (p < 0.0001). The 105 raised IgG-ACA titres and 378 normal IgG-ACA titres were associated between chronic HD patients and recurrent VAT (p = 0.034). In predicting for more or one episode of VAT by using multiple logistic regression with all significant factors, raised IgG-ACA titre was a non-significant factor (p = 0.336). The presence of hepatitis C had a higher percentage in group with raised IgG-ACA titres of HD patients (p = 0.042). In predicting for more or one episode of VAT by using multiple logistic regression with all significant factors, the presence of hepatitis C was also a significant factor (p = 0.022). In conclusion, the prevalence of raised IgG-ACA titres was 21.7% among HD patients. There was a weak association between raised IgG-ACA titre and recurrent VAT and this finding may be the consequence of pathogenetic role of raised IgG-ACA titres in the development of VAT status for chronic HD patients. The presence of hepatitis C was a cofactor.

Anti-neutrophil cytoplasmic antibodies (ANCA) from patients with systemic vasculitis recognize restricted epitopes of proteinase 3 involving the catalytic site

ANCA with specificity for proteinase 3 (PR3), a neutrophil primary granule enzyme, are of diagnostic value in Wegener's granulomatosis (WG) and certain other forms of systemic vasculitis. There is evidence to suggest that they play a pathogenic role in disease, and that the interaction of ANCA with PR3 is likely to be important. We showed, using a resonant mirror biosensor, that C-ANCA from different patients recognized the same or closely related epitopes on PR3. Studies using linear peptides in the SPOT system confirmed the highly restricted nature of this interaction and identified five linear epitopes. Fluid-phase inhibition studies, using a different set of peptides, validated the sequences involved. Using a computer-generated model of the structure of PR3, four of five epitopes were shown to be intimately linked with the catalytic site. The restricted number of epitopes, and their location at the catalytic site, has important implications for the role of C-ANCA in the pathogenesis of vasculitis.

The clinical importance of choosing the right assay for detection of HLA-specific donor-reactive antibodies

BACKGROUND

We found earlier that there is a close clinical correlation between the presence of histocompatibility leukocyte antigens (HLA) class I-specific donor-reactive antibodies in cross-match serum and a significantly higher frequency of early acute rejection episodes and graft loss during the first year after the transplant.

METHODS

Specificity determinations of donor-reactive antibodies present in the cross-match serum before allogeneic kidney transplants were performed. In the present study, we compared the suitability and efficiency of (a) platelet absorptions, (b) blocking with anti-HLA monoclonal antibodies in the microcytotoxicity assay, and (c) donor-specific HLA antigen-coated magnetic microbeads in flow cytometric assays for the definition of clinically relevant HLA antibodies and their correlation with early acute rejections and early graft loss.

RESULTS

We found that the microlymphocytoxicity test using donor splenic B lymphocytes often gave positive reactions in the absence of class I or class II antibodies; in other words, a high frequency of false positive reactions was observed. Flow cytometric tests are more sensitive than microlymphocytotoxicity, not only because they are more sensitive, but also because noncomplement-binding antibodies are detected. Platelet absorptions, which detect only reactivity against HLA class I antigens, is insufficient for use in specificity determinations of donor-reactive antibodies. We found that a positive test for HLA antibodies using paramagnetic beads coated with solubilized donor-derived HLA antigens (class I or class II) correlates with early immunological complications after a transplant (P<0.001).

CONCLUSION

Assays to determine the specificity of donor-reactive antibodies are now available for use during an acute transplant situation. The introduction of such methods is expected to enhance graft survival and to reduce significantly the frequencies of acute rejections episodes after a transplant.

Evolving concepts about the role of antineutrophil cytoplasm autoantibodies in systemic vasculitides

This review discusses the main issues of antineutrophil cytoplasm autoantibodies (ANCA) that have emerged from the literature. From January 1997 to August 1998, 216 papers were published on ANCA. Two major themes seem to be evolving from these articles. The first theme concerns the specificity and sensitivity of ANCA testing in clinical practice in relation to diagnosing systemic vasculitic syndromes. We focus on immunofluorescence patterns, ANCA antigens, testing methodology, and the (predictive) value of ANCA in clinical practice. Second, there is the unsolved question of how ANCA are etiologically involved in the development of the vasculitic lesion. Ongoing research questions the role of ANCA in stimulating granulocytes, monocytes, and the endothelium.

Beta2-glycoprotein I as a 'cofactor' for anti-phospholipid reactivity with endothelial cells

Beta2-glycoprotein I (beta2GPI) is a cofactor for anti-phospholipid (aPL) binding to cardiolipin (CL)-coated plates. Beta2GPI is also able to bind to endothelial cell (EC) membranes as supported by in-vivo as well as by in-vitro studies. The PL-binding site in the fifth domain of the molecule is involved in the adhesion to endothelium. Actually, specific mutations in this molecular portion abolish endothelium binding and a synthetic peptide spanning the sequence Glu274-Cys288 of the CL-binding site displays comparable adhesion to EC monolayers. Heparan sulphate appears to be one of the anionic EC membrane structures with which cationic beta2GPI interacts, as supported by studies with heparitinase-treated EC. Beta2GPI binding to EC might be related to its activity as endothelial growth factor or as a lipid-carrying glycoprotein. Adhesion of beta2GPI to endothelial membranes offers suitable epitopes for circulating aPL that, once bound, can induce cell activation