Increased Serum Thromboxane A2 and Prostacyclin but Lower Complement C3 and C4 Levels in COVID-19: Associations with Chest CT Scan Anomalies and Lowered Peripheral Oxygen Saturation

COVID-19 patients suffer from hypercoagulation and activated immune-inflammatory pathways. The current study examined the relationship between specific complements and coagulation abnormalities associated with chest CT scan anomalies (CCTAs) and peripheral oxygen saturation (SpO2) in COVID-19 patients. Serum levels of complement C3 and C4, and thromboxane A2 (TxA2) and prostacyclin (PGI2) were measured using an ELISA and albumin, calcium, and magnesium by using the spectrophotometric method in 60 COVID-19 patients and 30 controls. C3 and C4 were significantly decreased (p < 0.001), and TxA2 and PGI2 significantly increased (p < 0.001) in the COVID-19 patients compared with the controls with the highest levels in the CCTA patients’ group. Neural networks showed that a combination of C3, albumin, and TxA2 yielded a predictive accuracy of 100% in detecting COVID-19 patients. SpO2 was significantly decreased in the COVID-19 patients and was inversely associated with TxA2 and PGI2, and positively with C3, C4, albumin, and calcium. Patients with positive IgG results show significantly higher SpO2, TxA2, PGI2, and C4 levels than IgG-negative patients. CCTAs were accompanied by lower SpO2 and albumin and increased PGI2 and TxA2 levels, suggesting that interactions between immune-inflammatory pathways and platelet hyperactivity participate in the pathophysiology of COVID-19 and, consequently, may play a role in an enhanced risk of hypercoagulability and venous thromboembolism. These mechanisms are aggravated by lowered calcium and magnesium levels.

Platelet-specific deletion of acetyl-CoA carboxylase 1 decreases phospholipid content and impairs platelet functions

Background Acetyl-CoA carboxylase (ACC), the first enzyme regulating lipid synthesis, promotes thrombus formation by increasing platelet phospholipid content and thromboxane A2 generation. Purpose Our study sought to evaluate whether ACC1 platelet-specific deletion may affect platelet functions by decreasing phospholipid content. Methods We generated a new Cre transgenic mouse strain that allows megakaryocyte/platelet specific ACC1 deletion (GpIbCre+/− x ACC1 flx/flx mouse). In vitro, platelet functions were assessed by aggregometry and flow cytometry. In vivo, hemostasis was assessed via the measurement of bleeding time. Lipidomics analysis was carried out on the commercial Lipidyzer platform. Thromboxane A2 secretion was evaluated by ELISA. Results As expected, ACC1 deletion was restricted to the megakaryocytic lineage. Hematological parameters in platelet-specific ACC1 knockout mice showed a decrease in platelet count by 30% and an increase in platelet volume by 31%, compared to ACC1 flx/flx platelets. In vitro, platelets from platelet-specific ACC1 knockout mice displayed a decrease in thrombin and CRP-induced platelet aggregation, associated with impaired dense granules secretion. In contrast, ADP-induced platelet aggregation was higher in the absence of ACC1. In vivo, platelet-specific ACC1 knockout mice showed a normal bleeding time. In agreement with our hypothesis, lipidomics analyses showed that ACC1 deletion in platelets was associated with a significant decrease in arachidonic acid-contaning phosphatidylethanolamine plasmalogen, and subsequently with a reduced production of thromboxane A2 upon thrombin or CRP stimulation. Conclusion Platelet-specific ACC1 deletion led to a decrease in phospholipid content which, in turn, decreased platelet thromboxane A2 generation, dense granules secretion and aggregation upon thrombin and CRP, but not ADP stimulation. Further studies are needed to elucidate the impact of ADP on platelet functions FUNDunding Acknowledgement Type of funding sources: Other. Main funding source(s): Fonds pour la formation à la Recherche dans l'Industrie et l'Agriculture (FRIA)

Pulmonary artery radiofrequency ablation in an acute porcine model of pulmonary arterial hypertension

Introduction Pulmonary hemodynamics improvement after pulmonary artery denervation (PADN) was demonstrated in PAH. Questions arise regarding PADN perioperative effectiveness and the accuracy of the target nerves damage. The aim of the study was to evaluate whether PADN decreases pulmonary artery pressure (PAP) in acute thromboxane A2 (U46619)–induced PAH, and damages PA perivascular nerve fibers. Materials and methods 10 male Landrace swine (34.7±5.1 kg). In 6 swine acute reversible target mean PAP of 40 mm Hg was induced with synthetic thromboxane A2 infusion (U46619). Control group: 4 swine with PADN. Hemodynamics was assessed throughout the study, PAH modeling was done before and 20 min after PADN (radiofrequency energy, 40 Watts), followed by pathology and immunohistochemical studies. Results The mean number of RF applications was 17.5±3.6. Pulmonary embolism (PE) was observed after PADN in 3 swine with U46619 infusion, which were excluded. There was no differences in mPAP, PVR and U46619 dosage after PADN in PAH model (12.3±3.5 vs 12.1±1 mm Hg, p=0.2; 150.4±48.7 vs 129.2±64.1 dynes s cm–5; p=0.2; 24.9±3.3 vs 22.4±4.1 mcg; p=0.18; respectively). Similar hemodynamic results were observed in the control group after PADN (mPAP; p=0.3; PVR; p=0.58). S100 expression was evident in the majority of RFA PA species and in some species loss in tyrosine hydroxylase and M1 acetylcholine receptors expression was detected with no hemodynamic correlation. Conclusions PADN using an electrophysiological catheter with unipolar energy does not lead to an acute PA perivascular nerve fibers destruction and detectable mPAP changes in U46619-induced PAH. Delayed nerve damage might be attributable to PADN effects observed in previous studies. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Grant from the Ministry of Science and Higher Education of the Russian Federation (agreement #075-15-2020-800).

Tetrahydrocurcumin Downregulates MAPKs/cPLA2 Signaling and Attenuates Platelet Thromboxane A2 Generation, Granule Secretion, and Thrombus Growth

Platelet granule secretion plays a key role in atherothrombosis. Curcumin, a natural polyphenol compound derived from turmeric, exerts multiple biological activities. The current study sought to investigate the efficacy of tetrahydrocurcumin (THC, the major active metabolite of curcumin) on platelet granule secretion in vitro and thrombus formation in vivo. We found that THC significantly attenuated agonist-induced granule secretion in human gel-filtered platelets in vitro, including CD62P and CD63 expression and platelet factor 4, CCL5, and adenosine triphosphate release. These inhibitory effects of THC were partially mediated by the attenuation of cytosolic phospholipase A2 (cPLA2) phosphorylation, leading to a decrease in thromboxane A2 (TxA2) generation. Moreover, the MAPK (Erk1/2, JNK1/2, and p38 MAPK) signaling pathways were downregulated by THC treatment, resulting in reduced cPLA2 activation, TxA2 generation, and granule secretion. Additionally, THC and curcumin attenuated murine thrombus growth in a FeCl3-induced mesenteric arteriole thrombosis model in C57BL/6J mice without prolonging the tail bleeding time. THC exerted more potent inhibitory effects on thrombosis formation than curcumin. Through blocking cyclooxygenase-1 activity and thus inhibiting platelet TxA2 synthesis and granule secretion with aspirin, we found that THC did not further decrease the inhibitory effects of aspirin on thrombosis formation. Thus, through inhibiting MAPKs/cPLA2 signaling, and attenuating platelet TxA2 generation, granule secretion, and thrombus formation, THC may be a potent cardioprotective agent.

Effect of Berberine on Cardiovascular Disease Risk Factors: A Mechanistic Randomized Controlled Trial

Cardiovascular disease (CVD) is a major contributor to the global burden of disease. Berberine, a long-standing, widely used, traditional Chinese medicine, is thought to have beneficial effects on CVD risk factors and in women with polycystic ovary syndrome. The mechanisms and effects, specifically in men, possibly via testosterone, have not been examined previously. To assess the effect of berberine on CVD risk factors and any potential pathway via testosterone in men, we conducted a randomized, double-blind, placebo-controlled, parallel trial in Hong Kong. In total, 84 eligible Chinese men with hyperlipidemia were randomized to berberine (500 mg orally, twice a day) or placebo for 12 weeks. CVD risk factors (lipids, thromboxane A2, blood pressure, body mass index and waist–hip ratio) and testosterone were assessed at baseline, and 8 and 12 weeks after intervention. We compared changes in CVD risk factors and testosterone after 12 weeks of intervention using analysis of variance, and after 8 and 12 weeks using generalized estimating equations (GEE). Of the 84 men randomized, 80 men completed the trial. Men randomized to berberine had larger reductions in total cholesterol (−0.39 mmol/L, 95% confidence interval (CI) −0.70 to −0.08) and high-density lipoprotein cholesterol (−0.07 mmol/L, 95% CI −0.13 to −0.01) after 12 weeks. Considering changes after 8 and 12 weeks together, berberine lowered total cholesterol and possibly low-density lipoprotein-cholesterol (LDL-c), and possibly increased testosterone. Changes in triglycerides, thromboxane A2, blood pressure, body mass index and waist–hip ratio after the intervention did not differ between the berberine and placebo groups. No serious adverse event was reported. Berberine is a promising treatment for lowering cholesterol. Berberine did not lower testosterone but instead may increase testosterone in men, suggesting sex-specific effects of berberine. Exploring other pathways and assessing sex differences would be worthwhile, with relevance to drug repositioning and healthcare.