Evaluation of the occurrence of venous thromboembolic events in COVID-19 outpatients

Introduction

Thrombotic events are present at higher rates among COVID-19 patients. Prophylactic use of parenteral anticoagulants during hospitalisation is recommended to reduce the risk of complications. In this context, the Tunisian Anticoagulation Survey in COVID-19 patient General Practice experience (TASC-GP) was conducted.

Objective

The evaluation of the incidence of venous thromboembolic events (VTE) and bleedings in COVID-19 patients treated in ambulatory.

Method

The TASC-GP is an observational, multicenter study included 3,383 patients from July to October 2021. The following up of patients was done 35 days after inclusion date with investigation of VTE and bleeding events. The four main enrolment criteria were: 1) age ≥ 18 years; 2) confirmed COVID-19 infection; 3) treated as an outpatient; 4) initiation of Rivaroxaban 10 mg/d. Patients were excluded if any of the following criteria applied: 1) the use of anticoagulant or thrombolytic drugs other than Rivaroxaban on admission or within days of admission; 2) the use of any dosage other than that specified in the study protocol.

Results

The mean age of the population was 51.6 ± 15.5 years with a sex ratio of 0.67, 30.7% of the population had hypertension, 23.4% were diabetic and 34.9% were obese. At least one cardiovascular comorbidity was observed in 40% of cases and 9.5% had chronic respiratory disease. The mean IMPROVE and IMPROVE DDimer scores were 0.65 ± 0.9 and 1.4 ± 1.4, respectively. The mean Improve bleeding score was 1.4 ± 1.5. A VTE was reported during follow-up in 39 patients (1.15%). Diabetes and chronic respiratory disease were independent factors for the occurrence of VTE with an odd ratio of 2.2 [95% CI 1.1–4.2] (P = 0.017) and 3.2 [95% CI 1.5–6.4] (P = 0.002) respectively. IMPROVE and IMPROVE DDimer scores were comparable in patients with and without VTE. There was no statistically significant increase in the rate of major bleeding (0.001%). The IMPROVE Bleeding score was comparable in the bleeding and non-bleeding groups at follow-up. There were no predictive factors for bleeding.

Conclusion

Our study is in agreement with the literature concerning a decrease in the rate of thrombembolic complications when using prophylactic anticoagulation versus placebo. Other VTE estimation scores including chronic respiratory disease and diabetes can be proposed. The use of Rivaroxaban in this population was not associated with increased bleeding.

[Primary breast sarcomas: About 30 cases treated at Salah-Azaiez institute in Tunisia]

PURPOSE

To identify retrospectively prognostic factors of primary breast sarcoma and review its treatment modalities.

MATERIALS AND METHODS

This is a descriptive study on 30 cases of primary breast sarcoma. We carried out a univariate and multivariate analysis correlating clinical, pathological and therapeutic parameters with disease-free survival and overall survival.

RESULTS

The mean age was 46.8 years. The mean tumour size was 10cm. The 30 cases were 18 phyllodes sarcomas, eight angiosarcomas, three liposarcomas and a case of granulocytic sarcoma. Sixteen patients had adjuvant radiotherapy and only seven patients received adjuvant chemotherapy. The median follow-up was 64 months. Overall survival rates at 3 and 5 years were 49.1% and 33.7%. Disease-free survival rates at 3 and 5 years were 22.8% and 15.2% respectively. The analytical study of the following parameters: tumour size and presence or absence of node or distant metastases, showed no correlation with overall survival nor with disease-free survival. Furthermore, adjuvant radiotherapy did not improve overall survival (P=0.298; hazard ratio [HR]=1 [0.982-1.04]) nor disease-free survival (P=0.61; HR=0.942 [0.862-1.029]). By univariate analyses, we identified a correlation between overall survival, surgical margins (>1cm) (P=0005; HR=3.4 [1.217-9.919]) and tumour necrosis (P=0.028; HR=0.099 [0.014-0.682]). We did not find any independent prognostic factor by multivariate analysis.

CONCLUSION

The prognosis of primary breast sarcoma seems to depend essentially on optimal surgical excision (margin over 1cm). The only potential histological parameter correlated with the prognosis is the presence of tumour necrosis. The histological subtype should not be considered as a prognostic marker for overall or disease-free survival in patients with primary breast sarcoma.

Abstract 648: Alternative Macrophages Promote Atherosclerosis Progression by Increasing Intraplaque Angiogenesis and Vascular Permeability via HIF-1 alpha/VEGF-A-dependent Pathway

Background: Alternative macrophages exist in human atherosclerosis but their role in atherogenesis remains uncertain. Intraplaque hemorrhage (IPH) is an important stimulus driving alternative macrophage polarization. Intake of hemoglobin (Hb) by the hemoglobin: haptoglobin receptor CD163 leads to a distinct non-foam cell phenotype termed M(Hb). These cells demonstrate upregulation of CD163, lack of lipid retention, and anti-oxidative properties, characteristics considered ‘atheroprotective’. Here we reveal an unexpected but important pathogenic role for M(Hb) in atherosclerosis.

Objectives: To determine the role of M(Hb) macrophages in human intraplaque angiogenesis and vascular permeability.

Methods: Using human atherosclerotic samples, cultured cells, and a mouse model of IPH, we investigated the role of IPH on macrophage function with respect to angiogenesis and vascular permeability.

Results: Within M(Hb) activation of hypoxia-inducible factor-1 alpha (HIF-1) via inhibition of prolyl hydroxylases promotes intraplaque angiogenesis and vascular permeability. In human carotid plaques, alternative CD163 positive macrophages were found to be highly associated with plaque vascularity and expressed high levels of HIF1- and vascular endothelial growth factor-A (VEGF-A). Supernatants from hemoglobin:haptoglobin differentiated M(Hb) macrophages increased endothelial permeability and led to internalization of the endothelial barrier protein vascular endothelial cadherin (VE-cadherin) via activation of VEGF receptor 2 (VEGFR2). Areas of plaque demonstrating high density CD163 high macrophage subsets showed irregular VE-cadherin immunostaining and diffuse perivascular collections of von Willebrand factor suggesting microvessel incompetence. Finally, in brachiocephalic plaques of one-year-old apoE -/- and apoE -/- CD163 -/- mice, CD163 deficiency significantly reduced plaque progression, lesion size, and intraplaque hemorrhage, but had little effect on lesions uncomplicated by hemorrhage.

Conclusions: Our findings provide a novel non-lipid driven mechanism by which alterative M(Hb) macrophages promote plaque neoangiogenesis and microvessel incompetence via a HIF-1/VEGF-A-dependent pathway.

The role of epigenetics in the endothelial cell shear stress response and atherosclerosis

Currently in the field of vascular biology, the role of epigenetics in endothelial cell biology and vascular disease has attracted more in-depth study. Using both in vitro and in vivo models of blood flow, investigators have recently begun to reveal the underlying epigenetic regulation of endothelial gene expression. Recently, our group, along with two other independent groups, have demonstrated that blood flow controls endothelial gene expression by DNA methyltransferases (DNMT1 and 3A). Disturbed flow (d-flow), characterized by low and oscillating shear stress (OS), is pro-atherogenic and induces expression of DNMT1 both in vivo and in vitro. D-flow regulates genome-wide DNA methylation patterns in a DNMT-dependent manner. The DNMT inhibitor 5-Aza-2'deoxycytidine (5Aza) or DNMT1 siRNA reduces OS-induced endothelial inflammation. Moreover, 5Aza inhibits the development of atherosclerosis in ApoE(-/-) mice. Through a systems biological analysis of genome-wide DNA methylation patterns and gene expression data, we found 11 mechanosensitive genes which were suppressed by d-flow in vivo, experienced hypermethylation in their promoter region in response to d-flow, and were rescued by 5Aza treatment. Interestingly, among these mechanosensitive genes, the two transcription factors HoxA5 and Klf3 contain cAMP-response-elements (CRE), which may indicate that methylation of CRE sites could serve as a mechanosensitive master switch in gene expression. These findings provide new insight into the mechanism by which flow controls epigenetic DNA methylation patterns, which in turn alters endothelial gene expression, regulates vascular biology, and induces atherosclerosis. These novel findings have broad implications for understanding the biochemical mechanisms of atherogenesis and provide a basis for identifying potential therapeutic targets for atherosclerosis. This article is part of a Directed Issue entitled: Epigenetics dynamics in development and disease.

Flow-Dependent Epigenetic DNA Methylation in Endothelial Gene Expression and Atherosclerosis

Epigenetic mechanisms that regulate endothelial cell gene expression are now emerging. DNA methylation is the most stable epigenetic mark that confers persisting changes in gene expression. Not only is DNA methylation important in rendering cell identity by regulating cell type-specific gene expression throughout differentiation, but it is becoming clear that DNA methylation also plays a key role in maintaining endothelial cell homeostasis and in vascular disease development. Disturbed blood flow causes atherosclerosis, whereas stable flow protects against it by differentially regulating gene expression in endothelial cells. Recently, we and others have shown that flow-dependent gene expression and atherosclerosis development are regulated by mechanisms dependent on DNA methyltransferases (1 and 3A). Disturbed blood flow upregulates DNA methyltransferase expression both in vitro and in vivo, which leads to genome-wide DNA methylation alterations and global gene expression changes in a DNA methyltransferase-dependent manner. These studies revealed several mechanosensitive genes, such as HoxA5, Klf3, and Klf4, whose promoters were hypermethylated by disturbed blood flow, but rescued by DNA methyltransferases inhibitors such as 5Aza-2-deoxycytidine. These findings provide new insight into the mechanism by which flow controls epigenomic DNA methylation patterns, which in turn alters endothelial gene expression, regulates vascular biology, and modulates atherosclerosis development.

Abstract 18: The Role of Matrix Metalloproteinase 12 in Vascular Stiffness, Inflammation and Hypertension

Vascular wall remodeling and inflammation contribute to hypertension. These processes decrease arterial elasticity due to a loss of elastin and deposition of collagen. Metalloproteinase-12 (MMP12) is an elastase produced by macrophages and vascular cells. Cleavage of elastin by MMP12 could increase vascular stiffness and lead to release of pro-inflammatory elastin fragments. We sought to determine if MMP12 contributes to hypertension and vascular stiffness in response to angiotensin II and to understand mechanisms responsible for its expression. To determine if mechanical stretch activates MMP12 we subjected cultured murine endothelial cells to 0%, 5% (normotensive) or 10% (hypertensive) uniaxial stretch for 48 hours. Real-time RT-PCR showed that 10% stretch increases MMP12 mRNA by 4 fold compared to 0% or 5% stretch. Western blots and casein zymography indicated that 10% stretch significantly increases MMP12 protein expression and activity, respectively. Western blots also revealed an increase in elastin fragments in the media of cells exposed to 10% stretch compared to those exposed to 5% stretch. To understand the role of MMP12 in hypertension, we infused angiotensin II in wild-type and MMP12 -/- mice. In keeping with the studies of cultured endothelial cells, angiotensin II markedly increased vascular MMP12 mRNA (10-fold) and protein levels. The hypertension caused by angiotensin II was markedly blunted in MMP12 -/- mice (122 ± 3 vs. 173 ± 5, p < 0.0001). Immunohistochemistry with a CD68 specific antibody indicated a significant decrease in macrophages accumulation in the perivascular tissues of MMP12 -/- compared to WT mice. We also examined distensibility of aortic segments in vitro, and quantified this as the percent change in diameter over a pressure change from 75 to 125 mmHg. Angiotensin II markedly decreased this distensibility index from 24 ± 3 to 9 ± 2%, but only to 16 ± 3% in MMP12 -/- mice (p < 0.05). In conclusion, these studies show that mechanical stretch in vitro and hypertension in vivo cause a striking increase in endothelial cell and vascular MMP12 expression and activity. MMP12 activation promotes aortic stiffening and ultimately hypertension. Thus, modulation of MMP12 might be a therapeutic target in hypertension.

Abstract 14: T Cells Mediate Angiotensin II-induced Aortic Stiffening

Clinical studies show an association between inflammation and arterial stiffness. We and others have shown that T cells are involved in hypertension; however their role in aortic stiffening is unknown. We hypothesized that T cells mediate angiotensin II-induced aortic stiffening. Using a pressurized myograph system, we determined aortic stiffness and quantified this using a distensibility index (DI), defined as the percent change in aortic outer diameter from 75 mmHg to 125 mmHg. Angiotensin II (490ng/kg/min for 14 days) markedly decreased the distensibility index in C57Bl/6 mice (23.8±5.5 v.s. 8.9±4.1, p<0.01, n=8), and this was almost completely prevented in RAG-1 -/- mice (18.3±4.0, p<0.01 compared with C57Bl/6, n=8). Adoptive transfer of pan T cells into RAG-1 -/- mice restored aortic stiffness in RAG-1 -/- (11.9±2.6, p<0.05, n=5). The effect of T cell-derived pro-inflammatory cytokines on aortic stiffening was examined using interferon-γ (IFN-γ -/- ) and IL-6 -/- mice. Deficiency of INF-γ partially restored aortic distensibility (17.0±3.5 v.s. 8.9±4.1, p<0.01, n=8) compared C57Bl/6 mice treated with angiotensin II. Aortic distensibility was also preserved in IL-6 -/- mice (19.9±5.9 v.s. 8.9±4.1, p<0.01, n=8) treated with angiotensin II. In contrast to these functional alterations, the increase in collagen caused by angiotensin II was similar between wild-type and RAG-1 -/- mice. There was no change in elastin abundance with angiotensin II treatment or in different mouse strains. In conclusion, T cells are essential for angiotensin II-induced collagen deposition, vascular hypertrophy and aortic stiffening. Part of these effects could be mediated by pro-inflammatory cytokines such as INF-γ and IL-6. These likely mediate aortic stiffening by altering properties of elastin and collagen such as crosslinking, rather than alter total abundance of these proteins.

Iron deficiency in Yemeni patients with sickle-cell disease

Despite the general view that patients with sickle-cell disease (SCD) have iron overload, there are reports of iron deficiency in a proportion of these patients. We studied Yemeni patients aged 1-30 years with homozygous SCD to determine their iron status using a set of 4 criteria (low serum iron, low transferrin saturation, high total iron binding capacity and low mean corpuscular volume for age). Of the 75 patients, 44 had never been transfused while 31 patients had received blood transfusions but not during the 3-month period prior to the study. Of the patients, 10 (13.3%) met the criteria for iron deficiency, 9 of whom were from the non-transfused patients (20.5%). The sensitivity and specificity were 40% and 98% respectively for reticulocyte count and 80% and 90% respectively for reticulocyte index. We recommend screening non-transfused SCD patients for iron deficiency.

T lymphocytes and vascular inflammation contribute to stress-dependent hypertension

BACKGROUND

Psychological stress is a significant risk factor for hypertension and also directly affects the immune system. We have previously reported that T lymphocytes are essential for development of hypertension and that the central nervous system contributes to peripheral T-lymphocyte activation and vascular inflammation in this disease; however, the role of T-cell activation in stress-related hypertension remains unclear.

METHODS

Wild-type and T-cell-deficient (RAG-1(-/-)) mice were subjected to daily episodes of stress and blood pressure was measured. Circulating T-cell activation markers and vascular infiltration of immune cells were analyzed, as were stress hormone levels and gene expression changes in the brain. The effects angiotensin II infusion in the presence of chronic stress was also studied.

RESULTS

Repeated daily stress contributed to acute elevations in blood pressure that were associated with increased activation of circulating T cells and increased vascular infiltration of T cells. Repeated stress increased blood pressure in wild-type but not RAG-1(-/-) mice. Adoptive transfer of T cells to RAG-1(-/-) mice restored blood pressure elevation in response to stress. Stress-related hypertension and vascular infiltration of T cells was markedly enhanced by angiotensin II. Moreover, angiotensin II-infused mice exposed to chronic stress exhibited greater blood pressure reactivity to an episode of acute stress.

CONCLUSIONS

These data demonstrate that stress-dependent hypertension triggers an inflammatory response that raises blood pressure at baseline and augments the hypertension caused by angiotensin II. These data provide insight as to how psychological stress contributes to hypertension.

Role of increased guanosine triphosphate cyclohydrolase-1 expression and tetrahydrobiopterin levels upon T cell activation

Tetrahydrobiopterin (BH(4)) is an essential co-factor for the nitric-oxide (NO) synthases, and in its absence these enzymes produce superoxide (O(2)(·-)) rather than NO. The rate-limiting enzyme for BH(4) production is guanosine triphosphate cyclohydrolase-1 (GTPCH-1). Because endogenously produced NO affects T cell function, we sought to determine whether antigen stimulation affected T cell GTPCH-1 expression and ultimately BH(4) levels. Resting T cells had minimal expression of inducible NOS (NOS2), endothelial NOS (NOS3), and GTPCH-1 protein and nearly undetectable levels of BH(4). Anti-CD3 stimulation of T cells robustly stimulated the coordinated expression of NOS2, NOS3, and GTPCH-1 and markedly increased both GTPCH-1 activity and T cell BH(4) levels. The newly expressed GTPCH-1 was phosphorylated on serine 72 and pharmacological inhibition of casein kinase II reduced GTPCH-1 phosphorylation and blunted the increase in T cell BH(4). Inhibition of GTPCH-1 with diaminohydroxypyrimidine (1 mmol/liter) prevented T cell BH(4) accumulation, reduced NO production, and increased T cell O(2)(·-) production, due to both NOS2 and NOS3 uncoupling. GTPCH-1 inhibition also promoted TH(2) polarization in memory CD4 cells. Ovalbumin immunization of mice transgenic for an ovalbumin receptor (OT-II mice) confirmed a marked increase in T cell BH(4) in vivo. These studies identify a previously unidentified consequence of T cell activation, promoting BH(4) levels, NO production, and modulating T cell cytokine production.