Exercise induced release of von Willebrand factor: evidence for hypoxic reperfusion microvascular injury in rheumatoid arthritis

Endothelial cells of different organs exhibit heterogeneity in von Willebrand factor expression in response to hypoxia

BACKGROUND AND AIMS

We have previously demonstrated that in response to hypoxia, von Willebrand factor (VWF) expression is upregulated in lung and heart endothelial cells both in vitro and in vivo, but not in kidney endothelial cells. The aim of our current study was to determine whether endothelial cells of different organs employ distinct molecular mechanisms to mediate VWF response to hypoxia.

METHODS

We used cultured human primary lung, heart and kidney endothelial cells to determine the activation of endogenous VWF as well as exogenously expressed VWF promoter in response to hypoxia. Chromatin immunoprecipitation and siRNA knockdown analyses were used to determine the roles of VWF promoter associated transacting factors in mediating its hypoxia response. Platelet aggregates formations in vascular beds of mice were used as a marker for potential functional consequences of hypoxia-induced VWF upregulation in vivo.

RESULTS

Our analyses demonstrated that while Yin Yang 1 (YY1) and specificity protein 1 (Sp1) participate in the hypoxia-induced upregulation of VWF specifically in lung endothelial cells, GATA6 mediates this process specifically in heart endothelial cells. In both cell types, the response to hypoxia involves the decreased association of the NFIB repressor with the VWF promoter, and the increased acetylation of the promoter-associated histone H4. In mice exposed to hypoxia, the upregulation of VWF expression was concomitant with the presence of thrombi in heart and lung, but not kidney vascular beds.

CONCLUSIONS

Heart and lung endothelial cells demonstrated VWF upregulation in response to hypoxia, using distinct mechanisms, while this response was lacking in kidney endothelial cells.

Metabolomics to identify biomarkers and as a predictive tool in inflammatory diseases

There is an overwhelming need for a simple, reliable tool that aids clinicians in diagnosing, assessing disease activity and treating rheumatic conditions. Identification of biomarkers in partially understood inflammatory disorders has long been sought after as the Holy Grail of Rheumatology. Given the complex nature of inflammatory conditions, it has been difficult to earmark the potential biomarkers. Metabolomics, however, is promising in providing new insights into inflammatory conditions and also identifying such biomarkers. Metabolomic studies have generally revealed increased energy requirements for by-products of a hypoxic environment, leading to a characteristic metabolic fingerprint. Here, we discuss the significance of such studies and their potential as a biomarker.

Combined genetic effects of EGLN1 and VWF modulate thrombotic outcome in hypoxia revealed by Ayurgenomics approach

BACKGROUND

Extreme constitution "Prakriti" types of Ayurveda exhibit systemic physiological attributes. Our earlier genetic study has revealed differences in EGLN1, key modulator of hypoxia axis between Prakriti types. This was associated with differences in high altitude adaptation and susceptibility to high altitude pulmonary edema (HAPE). In this study we investigate other molecular differences that contribute to systemic attributes of Prakriti that would be relevant in predictive marker discovery.

METHODS

Genotyping of 96 individuals of the earlier cohort was carried out in a panel of 2,800 common genic SNPs represented in Indian Genomic Variation Consortium (IGVC) panel from 24 diverse populations. Frequency distribution patterns of Prakriti differentiating variations (FDR correction P < 0.05) was studied in IGVC and 55 global populations (HGDP-CEPH) panels. Genotypic interactions between VWF, identified from the present analysis, and EGLN1 was analyzed using multinomial logistic regression in Prakriti and Indian populations from contrasting altitudes. Spearman's Rank correlation was used to study this genotypic interaction with respect to altitude in HGDP-CEPH panel. Validation of functional link between EGLN1 and VWF was carried out in a mouse model using chemical inhibition and siRNA studies.

RESULT

Significant differences in allele frequencies were observed in seven genes (SPTA1, VWF, OLR1, UCP2, OR6K3, LEPR, and OR10Z1) after FDR correction (P < 0.05). A non synonymous variation (C/T, rs1063856) associated with thrombosis/bleeding susceptibility respectively, differed significantly between Kapha (C-allele) and Pitta (T-allele) constitution types. A combination of derived EGLN1 allele (HAPE associated) and ancestral VWF allele (thrombosis associated) was significantly high in Kapha group compared to Pitta (p < 10(-5)). The combination of risk-associated Kapha alleles was nearly absent in natives of high altitude. Inhibition of EGLN1 using (DHB) and an EGLN1 specific siRNA in a mouse model lead to a marked increase in vWF levels as well as pro-thrombotic phenotype viz. reduced bleeding time and enhanced platelet count and activation.

CONCLUSION

We demonstrate for the first time a genetic link between EGLN1 and VWF in a constitution specific manner which could modulate thrombosis/bleeding susceptibility and outcomes of hypoxia. Integration of Prakriti in population stratification may help assemble common variations in key physiological axes that confers differences in disease occurrence and patho-phenotypic outcomes.

The danger model approach to the pathogenesis of the rheumatic diseases

The danger model was proposed by Polly Matzinger as complement to the traditional self-non-self- (SNS-) model to explain the immunoreactivity. The danger model proposes a central role of the tissular cells' discomfort as an element to prime the immune response processes in opposition to the traditional SNS-model where foreignness is a prerequisite. However recent insights in the proteomics of diverse tissular cells have revealed that under stressful conditions they have a significant potential to initiate, coordinate, and perpetuate autoimmune processes, in many cases, ruling over the adaptive immune response cells; this ruling potential can also be confirmed by observations in several genetically manipulated animal models. Here, we review the pathogenesis of rheumatic diseases such as systemic lupus erythematous, rheumatoid arthritis, spondyloarthritis including ankylosing spondylitis, psoriasis, and Crohn's disease and provide realistic approaches based on the logic of the danger model. We assume that tissular dysfunction is a prerequisite for chronic autoimmunity and propose two genetically conferred hypothetical roles for the tissular cells causing the disease: (A) the Impaired cell and (B) the paranoid cell. Both roles are not mutually exclusive. Some examples in human disease and in animal models are provided based on current evidence.

Chronic arthritis and cardiovascular disease: altered blood parameters give rise to a prothrombotic propensity

OBJECTIVE

Rheumatoid arthritis, and to a lesser extent ankylosing spondylitis and psoriatic arthritis, associates with increased morbidity and mortality due to cardiovascular complications. We hypothesized that the increased risk of cardiovascular disease is reflected by changes in blood parameters that are compatible with a prothrombotic propensity. To substantiate this notion, we performed an extensive literature search identifying such parameters.

METHODS

A search through PubMed (1970-2013) was done to find primary articles with the following search terms: rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis or synovial fluid. These were combined with keywords reflecting processes of atherothrombosis: atherosclerosis, cardiovascular disease, coagulation, endothelial, fibrinolysis, mean platelet volume, microparticle, platelet, platelet count and mass, thrombosis, and thrombus.

RESULTS

The published studies point to a multitude of blood-related processes that can contribute to a prothrombotic propensity in chronic inflammatory diseases. These include an increase in platelet mass; low-level platelet activation, enforced by interaction with leukocytes and the formation of proinflammatory cytokines; a locally activated endothelium; and an increased coagulant activity. Patient treatment with methotrexate or TNF-α blockers appears to result in normalization of several of these prothrombotic parameters.

CONCLUSION

This analysis provides a first identification of the mechanisms by which inflammatory arthritis can aggravate cardiovascular disease.

Increased von Willebrand factor antigen and high molecular weight multimers in sickle cell disease associated with nocturnal hypoxemia

We evaluated vWF profiles in children and adolescents with SCD and sleep hypoxemia. Mean vWF:Ag levels were significantly elevated in the SCD-hypoxemia group when compared with SCD-normoxia and control groups (p=0.007); and correlated inversely with pulse oximetry (r=-0.54, p=0.01). Densitographic analyses of vWF multimer distribution also showed an inverse correlation between %HMW-multimers and oxygen saturation (r=-0.62, p=0.03). The previously reported association between nocturnal desaturation and SCD vascular complications, including stroke, may be influenced by hypoxemic modulation of vWF as noted in this study.

Safety of exercise in patients with rheumatoid arthritis

PURPOSE OF REVIEW

Patients with rheumatoid arthritis benefit from long-term moderate or high-intensity exercises. Moderate or high-intensity exercises were found to improve aerobic capacity, muscle strength, functional ability, and psychological well-being, and slow the age-related and sex-related decrease in bone mineral density of the hip. Despite these positive findings, there is also concern about its risks. Studies on the effects of exercise on disease activity and joint damage are reviewed.

RECENT FINDINGS

Studies on the effects of moderate or high-intensity exercise in rheumatoid arthritis demonstrate either decreased or stable disease activity. From the few available studies that address exercise and radiologic progression of the small joints, results indicate that exercises are safe for the joints of hands and feet. However, a recent study suggests caution in prescribing long-term high-intensity weight-bearing exercises to patients who have significant radiologic damage of large joints, as some patients might develop additional damage.

SUMMARY

Moderate or high-intensity weight-bearing exercises are safe with respect to disease activity and radiologic damage of the hands and feet. In the absence of sufficient data on exercise and radiologic progression of the large joints, patients with significant radiologic damage of the large joints should not be encouraged to participate in moderate to high-intensity weight-bearing exercise unless individualized to protect affected joints. A broader dissemination of the effectiveness and safety of moderate and high-intensity exercise for patients with rheumatoid arthritis is needed among rheumatologists, physical therapists, and patients.

Injury of the renal microvascular endothelium alters barrier function after ischemia

The role of renal microvascular endothelial cell injury in the pathophysiology of ischemic acute renal failure (ARF) remains largely unknown. No consistent morphological alterations have been ascribed to the endothelium of the renal microvasculature as a result of ischemia-reperfusion injury. Therefore, the purpose of this study was to examine biochemical markers of endothelial injury and morphological changes in the renal microvascular endothelium in a rodent model of ischemic ARF. Circulating von Willebrand factor (vWF) was measured as a marker of endothelial injury. Twenty-four hours after ischemia, circulating vWF peaked at 124% over baseline values (P = 0.001). The FVB-TIE2/GFP mouse was utilized to localize morphological changes in the renal microvascular endothelium. Immediately after ischemia, there was a marked increase in F-actin aggregates in the basal and basolateral aspect of renal microvascular endothelial cells in the corticomedullary junction. After 24 h of reperfusion, the pattern of F-actin staining was more similar to that observed under physiological conditions. In addition, alterations in the integrity of the adherens junctions of the renal microvasculature, as demonstrated by loss of localization in vascular endothelial cadherin immunostaining, were observed after 24 h of reperfusion. This observation temporally correlated with the greatest extent of permeability defect in the renal microvasculature as identified using fluorescent dextrans and two-photon intravital imaging. Taken together, these findings indicate that renal vascular endothelial injury occurs in ischemic ARF and may play an important role in the pathophysiology of ischemic ARF.

Von Willebrand factor propeptide as a marker of disease activity in systemic sclerosis (scleroderma)

In 44 consecutive patients with systemic sclerosis (SSc), plasma concentrations of von Willebrand factor (vWf) were higher than those of the vWf propeptide, but the propeptide showed less variability within patient subgroups. Higher values of the propeptide were observed in patients with early pulmonary involvement. A closer correlation of the propeptide than of vWf to biochemical markers of activity was also evident. Our results suggest that the propeptide, despite a shorter circulating half-time and lower plasma concentrations than vWf, is more useful in the assessment of disease activity in SSc.

Pefloxacin-induced achilles tendon toxicity in rodents: biochemical changes in proteoglycan synthesis and oxidative damage to collagen

Despite a relatively low incidence of serious side effects, fluoroquinolones and the fluoroquinolone pefloxacin have been reported to occasionally promote tendinopathy that might result in the complication of spontaneous rupture of tendons. In the present study, we investigated in rodents the intrinsic deleterious effect of pefloxacin (400 mg/kg of body weight) on Achilles tendon proteoglycans and collagen. Proteoglycan synthesis was determined by measurement of in vivo and ex vivo radiosulfate incorporation in mice. Collagen oxidative modifications were measured by carbonyl derivative detection by Western blotting. An experimental model of tendinous ischemia (2 h) and reperfusion (3 days) was achieved in rats. Biphasic changes in proteoglycan synthesis were observed after a single administration of pefloxacin, consisting of an early inhibition followed by a repair-like phase. The depletion phase was accompanied by a marked decrease in the endogenous serum sulfate level and a concomitant increase in the level of sulfate excretion in urine. Studies of ex vivo proteoglycan synthesis confirmed the in vivo results that were obtained. The decrease in proteoglycan anabolism seemed to be a direct effect of pefloxacin on tissue metabolism rather than a consequence of the low concentration of sulfate. Pefloxacin treatment for several days induced oxidative damage of type I collagen, with the alterations being identical to those observed in the experimental tendinous ischemia and reperfusion model. Oxidative damage was prevented by coadministration of N-acetylcysteine (150 mg/kg) to the mice. These results provide the first experimental evidence of a pefloxacin-induced oxidative stress in the Achilles tendon that altered proteoglycan anabolism and oxidized collagen.

Plasma von Willebrand factor and intestinal ischaemia-reperfusion injury in rats

The purpose of this study was to determine whether plasma von Willebrand factor concentrations are correlated with the degree of intestinal ischaemia-reperfusion injury. Forty-six anaesthetised adult Wistar rats were divided into five groups. The sham-operated group (S, n=10) had laparotomy and isolation of the superior mesenteric artery without clamping. Three ischaemia-reperfusion groups (n=10 in each) had clamping of the superior mesenteric artery for 15, 30, and 45 minutes, respectively, and reperfusion for 15 minutes. A control group (C, n=6) had direct puncture of the heart to sample blood. Mean arterial pressure was measured continuously. Blood was collected at the end of the study to measure von Willebrand factor. The small bowel injury was graded histologically. There was a significant systemic hypotension after declamping in all ischaemia-reperfusion groups, which had a high negative correlation with the histological score (R=-0.46, F=10.1, p<0.003, simple linear regression). Plasma von Willebrand factor was significantly elevated in the three ischaemia-reperfusion groups compared with the control group but not significantly different from the sham-operated group (mean von Willebrand factor concentration (SEM): 156 (29), 283 (29), 295 (25), 381 (44), and 366 (40)% in C, S, ischaemia-reperfusion 15, ischaemia-reperfusion 30, and ischaemia-reperfusion 45 groups, respectively). The concentration of von Willebrand factor was not correlated to the histological score (R=0.22, F=1.83, p<0.2) or the degree of hypotension after the removal of the clamp (R=-0.22, F=1.8, p<0.2, simple linear regression). This study shows that von Willebrand factor concentration does not correlate with the degree of intestinal ischaemia-reperfusion injury. It is unlikely that von Willebrand factor can be used as a predictor of disease severity.

Immunohistochemical study on type II collagen-induced arthritis in DBA/1J mice

We performed immunohistochemical examinations on type II collagen-induced arthritis (CIA) mice, focusing attention on the changes in distribution of plasma proteins and extracellular matrix materials (ECM) and in expression of adhesion molecules. The limb joints of male DBA/1J mice immunized with bovine type II collagen were obtained at 6 to 20 weeks after the first immunization. In the early stage of CIA, deposition of fibrin, IgG, von Willebrand factor (vWF) and fibronectin was detected on the surface of the synovial lining layer and articular cartilage and in the articular cavity. In the stage of pannus formation, prominent proliferation of ICAM-1-positive capillaries and marked infiltration of LFA-1-positive neutrophils were observed in the pannus. The superficial portion of the pannus and basement membranes of proliferated capillaries were strongly positive for type IV collagen and laminin. In the late stage, the pannus invaded and destroyed articular cartilage and subchondral bone, and strongly positive immunostainabilities for both lysozyme and fibronectin were observed on the surface of the pannus and at the junctional portion between the pannus and the cartilage. The present immunohistochemical findings on the distribution of plasma proteins and ECM materials and the expression of adhesion molecules in CIA mice were similar to those in rheumatoid arthritis (RA) in many aspects. This suggests that CIA is a useful model for the investigation of RA.

Neutrophil elastase, von Willebrand factor, soluble thrombomodulin and percutaneous oxygen in peripheral atherosclerosis

OBJECTIVES

To test the hypothesis that endothelial cell damage and hypoxia are related to the activity of neutrophil elastase in patients with peripheral atherosclerosis.

DESIGN

A cross-sectional serological study in a tertiary referral, University Hospital.

MATERIALS

Venous blood was obtained from 22 patients with peripheral vascular disease and an equal number of age and sex matched controls.

METHODS

Neutrophil elastase and two markers of endothelial cell damage (von Willebrand factor and soluble thrombomodulin) were measured in plasma by ELISA. Hypoxia was measured by percutaneous oxygen (by oximeter) at the dorsum of the foot.

RESULTS

Patients had higher von Willebrand factor, higher soluble thrombomodulin and higher elastase but lower percutaneous oxygen (all p < 0.001). In the patient's group, there were significant inverse correlates between von Willebrand factor and percutaneous oxygen (p = 0.004) and between soluble thrombomodulin and percutaneous oxygen (p = 0.011) while elastase correlated positively with soluble thrombomodulin (p = 0.023).

CONCLUSIONS

Our data support the hypothesis that release of elastase from activated neutrophils relates to endothelial cell damage. This may contribute to hypoxia and may result in the deterioration in clinically assessed atherosclerosis.

Computer based quantitative analysis of capillary abnormalities in systemic sclerosis and its relation to plasma concentration of von Willebrand factor

OBJECTIVES

To evaluate an objective and quantitative method for assessment of capillary abnormalities in systemic sclerosis (SSc).

METHODS

Nailfold capillaries were investigated by capillary microscopy and photographed in 17 consecutive SSc patients (five with diffuse cutaneous systemic sclerosis (dSSc) and 12 with limited cutaneous systemic sclerosis (lSSc)) and in 17 healthy controls. Investigators having no access to clinical data made drawings from magnified projections of coded photographs and analysed them using a computer program. Capillary density (capillary loops/mm in the distal row) and median capillary loop area were calculated. Presence of functional or organic arterial changes was evaluated by measurement of finger pressure with finger cooling. Plasma concentration of von Willebrand factor (VWF) was analysed using an enzyme linked immunosorbent assay (ELISA).

RESULTS

In 16 of 17 SSc patients and 13 of 17 controls the technical quality of the photographs was sufficient for computer analysis. Capillary density was decreased in dSSc (median 6.9 loops/mm) and in lSSc (median 3.8 loops/mm) compared with healthy controls (8.9 loops/mm) and median capillary loop area was increased in dSSc (7.3 x 10(-3) mm2) and in lSSc (8.5 x 10(-3) mm2) compared with healthy controls (5.0 x 10(-3) mm2). An inverse relation was found between capillary density and median capillary loop area in SSc patients. Plasma VWF was increased in patients (median 401 IE/l in dSSc and 409 IE/l in lSSc) compared with controls matched for age and sex (median 276 IE/l). Computer based analysis showed capillary density below the control range and median capillary loop area above the control range in 14 of 16 SSc patients. Measurement of finger pressure with finger cooling showed organic vascular changes in nine of 13 SSc patients.

CONCLUSION

Computer based quantitative analysis has low interobserver variability and is a quantitative and sensitive method of assessing capillary abnormalities in SSc.

Plasma von Willebrand factor, tissue plasminogen activator, plasminogen activator inhibitor, and antithrombin III levels in Behçet's disease

Sixty-three patients with Behçet's disease (BD), 30 patients with recurrent oral ulcer and 30 healthy individuals as control group were included in the study. ISG criteria was used for the diagnosis of BD and patients were classified as active and inactive and evaluated accordingly. In the patient and control groups, von Willebrand factor (vWF), tissue plasminogen activator (tPA), and plasminogen activator inhibitor (PAI) levels were determined using ELISA method and antithrombin III (AT-III) by nephelometric methods. High levels of endothelial product, vWF in the active Behçet patient group (p < 0.005) supports endothelial destruction due to vasculitis related with BD. In the active patient group tPA levels were significantly lower (p < 0.05) than the inactive and control groups with higher levels of PAI (p < 0.05 and p < 0.01) respectively. In Behçet disease, besides the decrease in tPA synthesis, high PAI levels also can affect tPA decrease and lead to inhibition of fibrinolytic activity. In active Behçet group, levels of AT-III were low and no significant difference was observed in recurrent oral ulcer and control groups. This situation may arise from the excessive use of AT-III in active disease. In conclusion, high levels of vWF in Behçet patients is thought to arise from vasculitis and high levels of PAI from the accumulation of thrombocytes on the damaged surface of endothelium leading to a decrease in tPA levels and inhibition of fibrinolytic activity.