Vitamin D Inhibits IL-6 Pro-Atherothrombotic Effects in Human Endothelial Cells: A Potential Mechanism for Protection against COVID-19 Infection?

BACKGROUND: Thrombosis with cardiovascular involvement is a crucial complication in COVID-19 infection. COVID-19 infects the host by the angiotensin converting enzyme-2 receptor (ACE2r), which is expressed in endothelial cells too. Thus, COVID-related thrombotic events might be due to endothelial dysfunction. IL-6 is one of the main cytokines involved in the COVID-19 inflammatory storm. Some evidence indicates that Vitamin D (VitD) has a protective role in COVID-19 patients, but the molecular mechanisms involved are still debated. Thus, we investigated the effect of VitD on Tissue Factor and adhesion molecules (CAMs) in IL-6-stimulated endothelial cells (HUVEC). Moreover, we evaluated levels of the ACE2r gene and proteins. Finally, we studied the modulation of NF-kB and STAT3 pathways. METHODS: HUVEC cultivated in VitD-enriched medium were stimulated with IL-6 (0.5 ng/mL). The TF gene (RT-PCR), protein (Western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. Similarly, CAMs soluble values (ELISA) and ACE2r (RT-PCR and Western blot) levels were assessed. NF-kB and STAT3 modulation (Western blot) were also investigated. RESULTS: VitD significantly reduced TF expression at both gene and protein levels as well as TF-procoagulant activity in IL-6-treated HUVEC. Similar effects were observed for CAMs and ACE2r expression. IL-6 modulates these effects by regulating NF-κB and STAT3 pathways. CONCLUSIONS: IL-6 induces endothelial dysfunction with TF and CAMs expression via upregulation of ACE2r. VitD prevented these IL-6 deleterious effects. Thus, it might be speculated that this is one of the hypothetical mechanism(s) by which VitD exerts its beneficial effects in COVID-19 infection.

Effects of colchicine on tissue factor in oxLDL-activated T-lymphocytes.

Several studies have shown that T-cells might be involved in pathophysiology of acute coronary syndromes (ACS). Tissue factor (TF) plays a key role in ACS. Many evidences have indicated that some statins reduce TF expression in several cell types. However, literature about rosuvastatin and TF and about statins effects on T-cells is still scanty. Colchicine is an anti-inflammatory drug recently proven to have beneficial effects in ACS via unknown mechanisms. This study investigates the effects of colchicine and rosuvastatin on TF expression in oxLDL-activated T-cells. T-cells, isolated from buffy coats of healthy volunteers, were stimulated with oxLDL (50 µg/dL). T-cells were pre-incubated with colchicine (10 µM) or rosuvastatin (5 µM) for 1 h and then stimulated with oxLDL (50 µg/mL). TF gene (RT-PCR), protein (western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. NF-κB/IκB axis was examined by western blot analysis and translocation assay. Colchicine and rosuvastatin significantly reduced TF gene, and protein expression and procoagulant activity in oxLDL stimulated T-cells. This effect was associated with a significant reduction in TF surface expression as well as its procoagulant activity. These phenomena appear modulated by drug effects on the transcription factor NF-kB. Rosuvastatin and colchicine prevent TF expression in oxLDL-stimulated T-cells by modulating the NF-κB/IκB axis. Thus, we speculate that this might be another mechanism by which these drugs exert benefic cardiovascular effects.

Colchicine inhibits the prothrombotic effects of oxLDL in human endothelial cells.

BACKGROUND: Tissue Factor (TF) plays a pivotal role in coronary thrombosis. Oxidized low-density lipoproteins (oxLDL) are crucial in development of atherosclerosclerosis. Moreover, oxLDL are known to induce TF expression on several cell types including endothelial cells. The lectin-type oxidized LDL receptor 1 (LOX-1) represent the oxLDL receptor. Colchicine is an anti-mitotic drug recently proven to have beneficial effects in cardiovascular disease via unknown mechanisms. Thus, we aim at investigating colchicine effects on TF expression in oxLDL stimulated human vascular endothelial cells (HUVEC). Some molecular mechanism(s) potentially involved were investigated. METHODS: HUVEC were pre-incubated with colchicine 10 µM for 1 h and then stimulated with oxLDL (50 µg/mL). TF gene (RT-PCR), protein (western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. TF translocation to cell surface was investigated by immunofluorescence. NF-κB/IκB axis was examined by western blot analysis and translocation assay. Finally, LOX-1 expression was also investigated. RESULTS: Colchicine significantly reduced TF gene and protein expression as well as its procoagulant activity in oxLDL-treated HUVEC. These effects seem to be related mainly to action of colchicine on microtubules that, in turn, modulate TF trafficking in the cytoplasm, NF-κB/IκB pathway and LOX-1 expression. CONCLUSIONS: Data of the present study, although in vitro, indicate that one of the hypothetical mechanisms by which colchicine exert protective cardiovascular effects might be its ability to inhibit the pro-thrombotic activity of oxLDL.

Vitamin D inhibits Tissue Factor and CAMs expression in oxidized low-density lipoproteins-treated human endothelial cells by modulating NF-κB pathway.

Epidemiologic studies have clearly demonstrated the correlation existing between Vitamin D (Vit. D) deficiency and increased risk of developing cardiovascular disease, suggesting that it might have a protective role in this clinical setting. Although many experimental studies have investigated the molecular mechanisms by which Vit. D might exert these effects, its potential role in protecting against athero-thrombosis is still partially unknown. We have investigated whether Vit. D might exert anti athero-thombotic effects by preventing expression of adhesion molecules (CAMs) and Tissue Factor (TF), molecules involved in atherothrombotic pathophysiology, in oxLDL stimulated endothelial cells (HUVEC). Moreover, we have investigated whether Vit. D effects might be due to the NF-kB modulation. HUVEC cultivated in medium enriched with Vit. D (10 nM) were stimulated with oxLDL (50 µg/ml). TF gene (RT-PCR), protein (Western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. Similarly, CAMs gene (RT-PCR), surface expression (FACS) and soluble values (ELISA) were measured. NF-kB translocation was also investigated. Vit. D significantly reduced TF gene as well protein expression and procoagulant activity in oxLDL-treated HUVEC. Similar effects were observed for CAMs. These effects were associated with Vit. D modulation of NF-κB pathway. This study, although in vitro, indicate that Vit. D has protective effect on endothelial cells by inhibiting expression of TF and CAMs, proteins involved in atherothrombotic pathophysiology. Further studies will be necessary to translate these findings to a clinical scenario to better define the potential therapeutical role of Vit. D supplementation in the management of cardiovascular disease in patients with Vit. D deficiency.

Effects of colchicine on platelet aggregation in patients on dual antiplatelet therapy with aspirin and clopidogrel.

Platelets aggregation leading to thrombosis plays a pivotal role in the pathophysiology of acute coronary syndrome (ACS) and of stent thrombosis. Antiplatelet therapy with aspirin plus an ADP-receptor inhibitor (ticagrerol, prasugrel or clopidogrel) is recommended to reduce the risk of other platelet-mediated events. Clopidogrel is recommended in patients with Chronic Coronary Syndromes (CCS) or in ACS patients at high bleeding risk. Unfortunately, up to 30% of patients are non-responders to clopidogrel and show residual high platelet reactivity (HPR). Colchicine (COLC) is a drug with cardiovascular effects. We have demonstrated that COLC might exert protective cardiovascular effects by interfering with cytoskeleton rearrangement, a phenomenon involved in platelet aggregation. Here, we investigate in vitro the effects of colchicine on platelet aggregation of patients on DAPT with clopidogrel. Platelets obtained from 35 CCS patients on therapy with clopidogrel were pre-incubated with COLC 10 µM before being stimulated with ADP (20 µM), or TRAP (25 µM) at 0, 30, 60 and 90 min to measure max aggregation by LTA. Platelets not COLC-preincubated served as controls. Seven patients were pre-selected as clopidogrel non-responders. COLC significantly reduced TRAP-induced platelet aggregation in clopidogrel responders and non-responders. Interestingly, COLC inhibited ADP-induced platelet aggregation in clopidogrel non-responders in which ADP still caused activation despite DAPT. We demonstrate that COLC inhibits platelet aggregation in clopidogrel non-responders with HPR despite DAPT with this ADP receptor-inhibitor. Further in vivo studies should be designed to evaluate the opportunity to prescribe colchicine after ACS/CCS to overcome the clopidogrel limitations in the DAPT therapy.

Oxidized low-density lipoproteins induce tissue factor expression in T-lymphocytes via activation of lectin-like oxidized low-density lipoprotein receptor-1.

AIMS: T-lymphocytes plays an important role in the pathophysiology of acute coronary syndromes. T-cell activation in vitro by pro-inflammatory cytokines may lead to functional tissue factor (TF) expression, indicating a possible contribution of immunity to thrombosis. Oxidized low-density lipoproteins (oxLDLs) are found abundantly in atherosclerotic plaques. We aimed at evaluating the effects of oxLDLs on TF expression in T cells and the role of the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1). METHODS AND RESULTS: CD3+ cells were isolated from healthy volunteers. Gene, protein, and surface expression of TF, as well as of LOX-1, were assessed at different time-points after oxLDL stimulation. To determine whether oxLDL-induced TF was LOX-1 dependent, T cells were pre-incubated with an LOX-1 inhibiting peptide (L-RBP) or with an anti-LOX-1 blocking antibody. To exclude that TF expression was mediated by reactive oxygen species (ROS) generation, oxLDL-stimulated T cells were pre-incubated with superoxide dismutase + catalase or with 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol), an intracellular free radical scavenger. Finally, to determine if the observed findings in vitro may have a biological relevance, the presence of CD3+/TF+/LOX-1+ cells was evaluated by immunofluorescence in human carotid atherosclerotic lesions. oxLDLs induced functionally active TF expression in T cells in a dose- and time-dependent manner, independently on ROS generation. No effect was observed in native LDL-treated T cells. LOX-1 expression was also induced by oxLDLs in a time- and dose-dependent manner. Pre-incubation with L-RBP or anti-LOX-1 antibody almost completely inhibited oxLDL-mediated TF expression. Interestingly, human carotid plaques showed significant infiltration of CD3+ cells (mainly CD8+ cells), some of which were positive for both TF and LOX-1. CONCLUSION: oxLDLs induce functional TF expression in T-lymphocytes in vitro via interaction of oxLDLs with LOX-1. Human carotid atherosclerotic plaques contain CD3+/CD8+cells that express both TF and LOX-1, indicating that also in patients these mechanisms may play an important role.

Effects of Hypobaric Hypoxia on Endothelial Function and Adiponectin Levels in Airforce Aviators.

Background: Hypobaric hypoxia (HH) increases the risk of high altitude-related illnesses (HARI). The pathophysiological mechanism(s) involved are still partially unknown. Altered vascular reactivity as consequence of endothelial dysfunction during HH might play a role in this phenomenon. Adiponectin exerts protective effect on cardiovascular system since it modulates NO release, antagonizing endothelial dysfunction. Aims of this study, performed in a selected population of airforce aviators, were (1) to investigate whether exposure to acute HH might be associated with endothelial dysfunction and (2) to evaluate whether adiponectin might be involved in modulating this phenomenon. Methods: Twenty aviators were exposed to acute HH in a hypobaric chamber by simulating altitude of 8000 and then 6000 m for 2 hours. Vascular reactivity was evaluated by the EndoPAT test immediately before and after the HH; salivary and blood adiponectin levels were measured. Results: EndoPAT performed immediately after HH divided pilots in two groups: 12 pilots with preserved vascular reactivity and 8 pilots with reduction of vascular reactivity, indicating that HH exposure might cause endothelial dysfunction. Salivary and blood adiponectin levels increased post-HH in a time-dependent manner in all aviators, but the significant increase was observed only in those with preserved vascular reactivity suggesting that HH stimulated release of adiponectin that, in turn, by exerting a protective effect, might reduce endothelial dysfunction. Conclusions: Acute HH may cause endothelial dysfunction due, at least in part, to reduced release of adiponectin. This phenomenon might be involved in pathophysiology of HARI.

Colchicine reduces platelet aggregation by modulating cytoskeleton rearrangement via inhibition of cofilin and LIM domain kinase 1.

INTRODUCTION: Platelets activation/aggregation with subsequent thrombus formation is the main event in the pathophysiology of acute coronary syndrome. Once activated, platelets show an extensive cytoskeleton rearrangement that leads to recruitment of additional platelets to finally cause haemostatic plug formation. Thus, the cytoskeleton plays a pivotal role in this phenomenon. Colchicine (COLC) is an anti-inflammatory drug proven to reduce major cardiovascular events in patients with coronary artery disease. The molecular mechanisms by which COLC exerts these protective effects remain partially still unknown. Since COLC causes disruption of tubulin, a component of cell cytoskeleton, we investigated whether this drug might interfere with platelet aggregation by acting on cytoskeleton rearrangement. METHODS AND RESULTS: Platelets isolated from healthy volunteers were activated with Adenosine Diphosphate (ADP, 20 µM) Collagen (COLL, 60 µg/ml) and Thrombin Activating Receptor Peptide (TRAP 25 µM) with/without COLC 10 µM pretreatment. After stimulus, aggregation was measured by light aggregometry overtime. Microtubules structure was assessed by immunohistochemistry and key proteins involved in regulation of actin-filament assembly and contractility such as Myosin Phosphatase Targeting subunit (MYPT), LIM domain kinase 1(LIMK1) and cofilin were evaluated by Western Blot analysis. Colchicine pretreatment significantly blunted ADP/COLL/TRAP-induced platelet aggregation (up to 40%). COLC effects appeared mediated by microtubules depolymerization and cytoskeleton disarrangement associated to inactivation of MYPT and LIMK1 that finally interfered with cofilin activity. CONCLUSIONS: Our data indicate that colchicine exerts anti-platelet effects in vitro via inhibition of key proteins involved in cytoskeleton rearrangement, suggesting that its beneficial cardiovascular properties may be due, at least in part, to an inhibitory effect of platelet activity.

Nobiletin inhibits oxidized-LDL mediated expression of Tissue Factor in human endothelial cells through inhibition of NF-κB.

INTRODUCTION: Flavonoids are nutrients usually included in human diet with several significant biological activities. Nobiletin is a flavonoid that, besides having anti-inflammatory and anti-tumoral activity, seems to exert protective effects on cardiovascular system. Several studies investigated nobiletin as a natural drug to antagonize the atherosclerotic disease. On the contrary, literature about its potential role in modulating the main acute complication of atherosclerosis, thrombosis, is still scanty. Several studies have indicated that Tissue Factor (TF) plays a pivotal role in the pathophysiology of cardiovascular thrombotic events by triggering the formation of intracoronary thrombi. Oxidized-LDL have an important role in promoting athero-thrombotic events. This study investigates whether nobiletin might exert protective cardiovascular effects by preventing the oxidized-LDL mediated expression of TF in human endothelial cells in vitro. Moreover, we have studied whether the nobiletin effects might be modulated by the inhibition of the NF-κB pathway. METHODS AND RESULTS: In HUVEC, ox-LDL induced TF-mRNA transcription as demonstrated by real time PCR and expression of functionally active TF as demonstrated by Western-blot, FACS analysis and pro-coagulant activity assay. Nobiletin prevented these ox-LDL-mediated effects by exerting antioxidant effects, finally leading to inhibition of the transcription factor NF-κB. CONCLUSIONS: These data suggest that nobiletin might be a potential antithrombotic agent of dietary origin. This flavonoid, through its antioxidant proprieties, might potentially exert an antithrombotic activity by inhibiting TF expression/activity in a cell population never investigated before in this context and that is normally represented in vessel wall such as endothelial cells.

Expression of functional tissue factor in activated T-lymphocytes in vitro and in vivo: A possible contribution of immunity to thrombosis?

OBJECTIVE: T-lymphocyte activation plays an important role in the pathophysiology of acute coronary syndromes (ACS). Plaques from ACS patients show a selective oligoclonal expansion of T-cells, indicating a specific, antigen-driven recruitment of T-lymphocytes within the unstable lesions. At present, however, it is not known whether T-cells may contribute directly to thrombosis by expressing functional tissue factor (TF). Accordingly, the aim of the present study was to investigate whether T-cells are able to express functional TF in their activated status. METHODS: In vitro, CD3(+)-cells, isolated from buffy coats, were stimulated with anti-CD3/CD28 beads, IL-6, TNF-α, IL-17, INF-γ or PMA/ionomycin. Following stimulation, TF expression on cell-surface, at gene and protein levels, as well as its procoagulant activity in whole cells and microparticles was measured. In vivo, TF expression was evaluated in CD3(+)-cells isolated from the aorta and the coronary sinus of ACS-NSTEMI and stable coronary artery disease (SCAD) patients. The presence of CD3(+)-TF(+)cells was also evaluated by immunohistochemistry in thrombi aspirated from ACS-STEMI patients. RESULTS: PMA/ionomycin and IL-17 plus INF-γ stimulation resulted in a significant TF increase at gene and protein levels as well as at cell-surface expression. This was accompanied by a parallel increase in FXa generation, both in whole cells and in microparticles, indicating that the induced membrane-bound TF was active. Furthermore, transcardiac TF gradient was significantly higher in CD3(+)-cells obtained from ACS-patients compared to SCAD-patients. Interestingly, thrombi from ACS-STEMI patients resulted enriched in CD3(+)-cells, most of them expressing TF. CONCLUSIONS: Our data demonstrate that activated T-lymphocytes in vitro express functional TF on their membranes, suggesting a direct pathophysiological role of these cells in the thrombotic process; this hypothesis is further supported by the observations in vivo that CD3(+)-cells from coronary circulation of ACS-NSTEMI patients show increased TF levels and that coronary thrombi from ACS-STEMI patients are enriched in CD3(+)-cells expressing TF.

Pregnancy-associated plasma protein-A promotes TF procoagulant activity in human endothelial cells by Akt-NF-κB axis.

Pregnancy-associated plasma protein-A (PAPP-A) is a metalloproteinase with a controversial role in pathophysiology of cardiovascular disease. It seems involved in progression of atherosclerosis and is widely represented in atherosclerotic plaque. PAPP-A plasma levels are elevated in patients with acute coronary syndromes (ACS), thus it has been suggested that it might be a prognostic marker for developing major cardiovascular events. However, the pathophysiological link(s) between PAPP-A and ACS are still unknown. Several studies have indicated that tissue factor (TF) plays a pivotal role in the pathophysiology of ACS by triggering the formation of intracoronary thrombi following endothelial injury. This study investigates whether PAPP-A, at concentrations measurable in ACS patients, might induce TF expression in human endothelial cells in culture (HUVEC). In HUVEC, PAPP-A induced TF-mRNA transcription as demonstrated by real time PCR and expression of functionally active TF as demonstrated by FACS analysis and pro-coagulant activity assay. PAPP-A induced TF expression through the activation of Akt/NF-κB axis, as demonstrated by luciferase assay and by suppression of TF-mRNA transcription as well as of TF expression/activity by Akt and NF-κB inhibitors. These data indicate that PAPP-A promotes TF expression in human endothelial cells and support the hypothesis that this proteinase, besides being involved in progression of atherosclerosis, does not represent an independent risk factor for adverse cardiovascular events, but it rather might play an "active" role in the pathophysiology of ACS as an effector molecule able to induce a pro-thrombotic phenotype in endothelial cells.

Fructose induces prothrombotic phenotype in human endothelial cells : A new role for "added sugar" in cardio-metabolic risk.

Intake of large amounts of added sweeteners has been associated with the pathogenesis of cardiometabolic risk. Several studies have shown that fructose increases the cardiovascular risk by modulating endothelial dysfunction and promoting atherosclerosis. Recently, a potential role for fructose in cardiovascular thrombosis has been suggested but with controversial results. Tissue factor (TF) plays a pivotal role in the pathophysiology of cardiovascular thrombosis by triggering the formation of intracoronary thrombi following endothelial injury. This study investigates the effects of fructose, in a concentration range usually observed in the plasma of patients with increased cardiovascular risk, on TF in human umbilical endothelial cells (HUVECs). Cells were stimulated with increasing concentrations of fructose (0.25, 1 and 2.5 mM) and then processed to evaluate TF-mRNA levels by real-time PCR as well as TF expression/activity by FACS analysis and procoagulant activity. Finally, a potential molecular pathway involved in modulating this phenomenon was investigated. We demonstrate that fructose induces transcription of mRNA for TF. In addition, we show that this monosaccharide promotes surface expression of TF that is functionally active. Fructose effects on TF appear modulated by the oxygen free radicals through activation of the transcription factor NF-κB since superoxide dismutase and NF-κB inhibitors suppressed TF expression. Data of the present study, although in vitro, indicate that fructose, besides promoting atherosclerosis, induces a prothrombotic phenotype in HUVECs, thus indicating one the mechanism(s) by which this sweetener might increase cardiometabolic risk.

Activating stimuli induce platelet microRNA modulation and proteome reorganisation.

Platelets carry megakaryocyte-derived mRNAs whose translation efficiency before and during activation is not known, although this can greatly affect platelet functions, both under basal conditions and in response to physiological and pathological stimuli, such as those involved in acute coronary syndromes. Aim of the present study was to determine whether changes in microRNA (miRNA) expression occur in response to activating stimuli and whether this affects activity and composition of platelet transcriptome and proteome. Purified platelet-rich plasmas from healthy volunteers were collected and activated with ADP, collagen, or thrombin receptor activating peptide. Transcriptome analysis by RNA-Seq revealed that platelet transcriptome remained largely unaffected within the first 2 hours of stimulation. In contrast, quantitative proteomics showed that almost half of > 700 proteins quantified were modulated under the same conditions. Global miRNA analysis indicated that reorganisation of platelet proteome occurring during activation reflected changes in mature miRNA expression, which therefore, appears to be the main driver of the observed discrepancy between transcriptome and proteome changes. Platelet functions significantly affected by modulated miRNAs include, among others, the integrin/cytoskeletal, coagulation and inflammatory-immune response pathways. These results demonstrate a significant reprogramming of the platelet miRNome during activation, with consequent significant changes in platelet proteome and provide for the first time substantial evidence that fine-tuning of resident mRNA translation by miRNAs is a key event in platelet pathophysiology.

The adipokine apelin-13 induces expression of prothrombotic tissue factor.

Adipocytes are cells able to produce and secrete several active substances (adipokines) with direct effects on vascular cells. Apelin, one of the most recently identified adipokines has been studied in cardiovascular system physiology in regard to vessel vasodilation and myocardial contraction, but it has not yet completely characterised for its pathophysiological role in cardiovascular disease and especially in acute coronary syndromes (ACS). Several studies have indicated that tissue factor (TF) plays a pivotal role in the pathophysiology of ACS by triggering the formation of intracoronary thrombi following endothelial injury. This study investigates the effects of apelin 12 and apelin 13 on TF in human umbilical endothelial cells (HUVECs) and monocytes. Cells were stimulated with increasing concentrations of apelin 12 or apelin 13 and then processed to evaluate TF-mRNA levels by real-time PCR as well as TF expression/activity by FACS analysis and pro-coagulant activity. Finally, a potential molecular pathway involved in modulating this phenomenon was investigated. We demonstrate that apelin 13 but not apelin 12 induces transcription of mRNA for TF. In addition, we show that this adipokine promotes surface expression of TF that is functionally active. Apelin 13 effects on TF appear modulated by the activation of the G-protein-transcription factor nuclear factor (NF)-κB axis since G-protein inhibitors suppressed NF-κB mediated TF expression. Data of the present study, although in vitro, indicate that apelin-13, induces a procoagulant phenotype in HUVECs and monocytes by promoting TF expression. These observations support the hypothesis that this adipokine might play a relevant role as an active partaker in athero-thrombotic disease.