Endothelial Glycocalyx Injury in SARS-CoV-2 Infection: Molecular Mechanisms and Potential Targeted Therapy.

This review aims at summarizing state-of-the-art knowledge on glycocalyx and SARS-CoV-2. The endothelial glycocalyx is a dynamic grid overlying the surface of the endothelial cell (EC) lumen and consists of membrane-bound proteoglycans and glycoproteins. The role of glycocalyx has been determined in the regulation of EC permeability, adhesion, and coagulation. SARS-CoV-2 is an enveloped, single-stranded RNA virus belonging to ß-coronavirus that causes the outbreak and the pandemic of COVID-19. Through the respiratory tract, SARS-CoV-2 enters blood circulation and interacts with ECs possessing angiotensin-converting enzyme 2 (ACE2). Intact glycolyx prevents SARS-CoV-2 invasion of ECs. When the glycocalyx is incomplete, virus spike protein of SARS-CoV-2 binds with ACE2 and enters ECs for replication. In addition, cytokine storm targets glycocalyx, leading to subsequent coagulation disorder. Therefore, it is intriguing to develop a novel treatment for SARS-CoV-2 infection through the maintenance of the integrity of glycocalyx. This review aims to summarize state-of-the-art knowledge of glycocalyx and its potential function in SARS-CoV-2 infection.

VWF, Platelets and the Antiphospholipid Syndrome.

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with the persistent presence of antiphospholipid antibodies (aPLs). Laboratory criteria for the classification of APS include the detection of lupus anticoagulant (LAC), anti-cardiolipin (aCL) antibodies and anti-ß2glycoprotein I (aß2GPI) antibodies. Clinical criteria for the classification of thrombotic APS include venous and arterial thrombosis, along with microvascular thrombosis. Several aPLs, including LAC, aß2GPI and anti-phosphatidylserine/prothrombin antibodies (aPS/PT) have been associated with arterial thrombosis. The Von Willebrand Factor (VWF) plays an important role in arterial thrombosis by mediating platelet adhesion and aggregation. Studies have shown that aPLs antibodies present in APS patients are able to increase the risk of arterial thrombosis by upregulating the plasma levels of active VWF and by promoting platelet activation. Inflammatory reactions induced by APS may also provide a suitable condition for arterial thrombosis, mostly ischemic stroke and myocardial infarction. The presence of other cardiovascular risk factors can enhance the effect of aPLs and increase the risk for thrombosis even more. These factors should therefore be taken into account when investigating APS-related arterial thrombosis. Nevertheless, the exact mechanism by which aPLs can cause thrombosis remains to be elucidated.

E-selectin in vascular pathophysiology.

Selectins are a group of Ca2+-dependent, transmembrane type I glycoproteins which attract cell adhesion and migration. E-selectin is exclusively expressed in endothelial cells, and its expression is strongly enhanced upon activation by pro-inflammatory cytokines. The interaction of E-selectin with its ligands on circulating leukocytes captures and slows them down, further facilitating integrin activation, firm adhesion to endothelial cells and transmigration to tissues. Oxidative stress induces endothelial cell injury, leading to aberrant expression of E-selectin. In addition, the elevated level of E-selectin is positively related to high risk of inflammation. Dysregulation of E-selectin has been found in several pathological conditions including acute kidney injury (AKI), pulmonary diseases, hepatic pathology, Venous thromboembolism (VTE). Deletion of the E-selectin gene in mice somewhat ameliorates these complications. In this review, we describe the mechanisms regulating E-selectin expression, the interaction of E-selectin with its ligands, the E-selectin physiological and pathophysiological roles, and the therapeutical potential of targeting E-selectin.

Symmetrical peripheral gangrene: potential mechanisms and therapeutic approaches in severe COVID-19.

Symmetrical peripheral gangrene is a rare condition that is characterized by ischemic damage and tissue death (gangrene) in the extremities. Recent reports have shed light on SPG in patients with severe COVID-19. This condition presents with symmetrical cyanosis of the extremities and common COVID-19 symptoms and what the most frightening is within a few days, cutaneous necrosis occurred and patients died. Skin biopsy results have shown the presence of microthrombi in small vessels. The formation of SPG in COVID-19 patients results from immunothrombosis, endothelial dysfunction, and procoagulant platelets, leading to a hypercoagulation state and microvascular thrombosis. Thrombotic microangiopathy, shock, disseminated intravascular coagulation, and anticoagulant depletion promote the development of SPG in COVID-19. At the early stage, SPG patients with COVID-19 exhibit similar clinical manifestations. TMA causes early damage to microvasculature in SPG, and the shock state further exacerbates the ischemic injury due to local hypo-perfusion. The disturbed procoagulant-anticoagulant balance caused by DIC and anticoagulant depletion, combined with the pre-ischemic state brought on by TMA and shock, leads to the rapid formation of extensive microthrombi in the late stage of COVID-19 associated SPG. This review will delve into the clinical features, possible mechanisms, and potential therapeutic managements for COVID-19 associated SPG.

Complement factor H inhibits endothelial cell migration through suppression of STAT3 signaling.

Complement factor H (CFH), a major soluble inhibitor of complement, is a plasma protein that directly interacts with the endothelium of blood vessels. Mutations in the CFH gene lead to diseases associated with excessive angiogenesis; however, the underlying mechanisms are unknown. The present study aimed to determine the effects of CFH on endothelial cells and to explore the underlying mechanisms. The adenoviral plasmid expressing CFH was transduced into HepG2 cells, and the culture medium supernatant was collected and co-cultured with human umbilical vein endothelial cells (HUVECs). Cell proliferation was measured by CCK8 and MTT assays, and cell migration was measured by wound healing and Transwell assays. Reverse transcription-quantitative PCR was performed to detect gene transcription. Western blotting was used to determine protein levels. The results revealed that CFH can inhibit migration, but not viability, of HUVECs. In addition, CFH did not significantly alter MAPK or TGF-ß signaling, whereas it decreased STAT3 phosphorylation in HUVECs. Furthermore, CFH failed to reduce migration of HUVECs, with inhibition of STAT3 signaling by STATTIC or activation of STAT3 signaling by overexpression of STAT3 (Y705D) compromising CFH-inhibited HUVEC migration. CFH also decreased the expression levels of vascular endothelial growth factor receptor 2, a downstream effector of STAT3 mediating endothelial cell migration. In conclusion, the present study suggested that CFH may be a potential therapeutic target for angiogenesis-related diseases.

Abacavir use is associated with increased prothrombin conversion.

There is ongoing debate as to whether abacavir (ABC) increases the risk for cardiovascular disease(CVD) in people living with HIV (PLHIV) and the mechanisms underlying this possible association. We recently showed that the use of an ABC-containing regimen was independently associated with increased thrombin generation (TG). In the present study, we aim to explore these findings further, by studying the mechanistical processes that underly the global thrombin generation test via thrombin dynamics analysis. Thrombin dynamics analysis can pinpoint the cause of increased thrombin generation associated with ABC-use either to the procoagulant prothrombin conversion pathway or the anticoagulant thrombin inactivation pathway. In this cross-sectional study, 208 virally suppressed PLHIV were included, of whom 94 were on a ABC-containing regimen, 92 on a tenofovir disoproxil fumarate (TDF)-containing regimen, and the remainder on other regimens. We used Calibrated Automated Thrombinography to measure thrombin generation and perform thrombin dynamics analysis. The total amount of prothrombin conversion, as well as the maximum rate of prothrombin conversion were significantly increased in PLHIV on an ABC containing regimen compared to other treatment regimens. The levels of pro- and anticoagulant factors were comparable, indicating that the ABC-induced changes affect the kinetics of prothrombin conversion rather than procoagulant factor levels. Moreover, Von Willebrand Factor (VWF), active VWF and VWF pro-peptide levels were significantly higher in PLHIV than controls without HIV. However, they did not differ between ABC and non-ABC treated participants.

Functional changes in hemostasis during asexual and sexual parasitemia in a controlled human malaria infection.

Decreased platelet count is an early phenomenon in asexual Plasmodium falciparum parasitemia, but its association with acute or long-term functional changes in platelets and coagulation is unknown. Moreover, the impact of gametocytemia on platelets and coagulation remains unclear. We investigated the changes in platelet number and function during early asexual parasitemia, gametocytemia and convalescence in 16 individuals participating in a controlled human malaria infection study, and studied its relationship with changes in total and active von Willebrand factor levels (VWF) and the coagulation system. Platelet activation and reactivity were determined by flow cytometry, and the coagulation system was assessed using different representative assays including antigen assays, activity assays and global functional assays. Platelet count was decreased during asexual blood stage infection but normalized during gametocytemia. Platelet P-selectin expression was slightly increased during asexual parasitemia, gametocytemia and at day 64. In contrast, platelet reactivity to different agonists remained unchanged, except a marked decrease in reactivity to low dose collagen-related peptide-XL. Thrombin generation and antigen assays did not show a clear activation of the coagulation during asexual parasitemia, whereas total and active VWF levels were markedly increased. During gametocytemia and on day 64, the endogenous thrombin potential, thrombin peak and velocity index were increased and prothrombin conversion and plasma prothrombin levels were decreased. We conclude that the decreased platelet count during asexual parasitemia is associated with increased active VWF levels (i.e. endothelial activation), but not platelet hyperreactivity or hypercoagulability, and that the increased platelet clearance in asexual parasitemia could cause spontaneous VWF-platelet complexes formation.

Curdlan sulfate/O-linked quaternized chitosan nanoparticles acting as potential adjuvants promote multiple arms of immune responses.

Nasal immunization to prevent and treat diseases caused by infection through the respiratory tract cannot be actualized because of the lack of effective adjuvants. We have proven that compared with antigens loaded on CS or O-HTCC alone in nasal vaccination, antigens loaded on the nanoparticles of curdlan sulfate/O-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (CS/O-HTCC) can induce stronger systemic and mucosal immune responses. In this study, we evaluated the immunostimulatory activity and mechanisms of CS/O-HTCC nanoparticles. The results showed that CS/O-HTCC nanoparticles can improve the activation of antigen-presenting cells, upregulate the production of inflammatory factors and cytokines, induce cross-presentation, and simultaneously activate type I interferon-related genes. CS/O-HTCC nanoparticles also activated the PI3K/AKT and MAPK pathways and significantly promoted IL-2 transcription to induce the proliferation of lymphocytes. The results revealed that CS/O-HTCC nanoparticles as a type of multifunctional adjuvant can improve multiple arms of immune responses.

Curdlan sulfate-O-linked quaternized chitosan nanoparticles: potential adjuvants to improve the immunogenicity of exogenous antigens via intranasal vaccination.

INTRODUCTION: The development of ideal vaccine adjuvants for intranasal vaccination can provide convenience for many vaccinations. As an ideal intranasal vaccine adjuvant, it should have the properties of assisting soluble antigens to pass the mucosal barrier and potentiating both systemic and mucosal immunity via nasal administration. METHODS: By using the advantages of polysaccharides, which can promote both T-helper 1 and 2 responses, curdlan sulfate (CS)-O-(2-hydroxyl)propyl-3-trimethyl ammonium chitosan chloride (O-HTCC) nanoparticles were prepared by interacting CS with O-HTCC, and the adjuvancy of the nanoparticles was investigated. RESULTS: The results showed that the polysaccharide-based nanoparticles induced the proliferation and activation of antigen-presenting cells. High protein-loading efficiency was obtained by testing with the model antigen ovalbumin (Ova), and the Ova adsorbed onto the cationic CS/O-HTCC complexes was taken up easily by the epithelium. To evaluate the capacity of the Ova/CS/O-HTCC nanoparticles for immune enhancement in vivo, we collected and analyzed immunocytes, serum, and mucosal lavage fluid from intranasally vaccinated mice. The results showed that Ova/CS/O-HTCC nanoparticles induced activation and maturation of antigen-presenting cells and provoked the proliferation and differentiation of lymphocytes more significantly compared to the immunization of Ova mixed with aluminum hydroxide gel. Furthermore, CS/O-HTCC evoked a significantly higher level of Ova-specific antibodies. CONCLUSION: Therefore, these results suggest that CS/O-HTCC nanoparticles are ideal vaccine adjuvants for soluble antigens used in intranasal or mucosal vaccination.

Tunicamycin potentiates paclitaxel-induced apoptosis through inhibition of PI3K/AKT and MAPK pathways in breast cancer.

PURPOSE: Paclitaxel has been reported to upregulate both AKT and MAPK signaling pathways and thereby compromises its antitumor efficacy. However, tunicamycin has the ability to downregulate AKT and MAPK pathways. The aim of the study is to investigate the antitumor activity of the combination treatment of paclitaxel with tunicamycin and the mechanisms involving the changes of antitumor efficacy. METHODS: Sulforhodamine B (SRB) assay was used to examine the cell viability upon treatment of breast cancer cells with paclitaxel, tunicamycin and the combination of both. Cell cycle distributions and apoptosis were detected by flow cytometry. Western blotting and immunofluorescence staining were used to analyze the effect of drugs on tubulin polymerization. The antitumor growth of combined treatment was measured in nude mice bearing MDA-MB-231 xenograft. Western blotting was performed to explore the alteration of AKT and MAPK pathways in vitro and in vivo. RESULTS: SRB assay and nude mice experiment showed that tunicamycin synergistically enhanced paclitaxel-induced inhibition of cell proliferation and tumor growth. Tunicamycin had no clear effect on paclitaxel-induced cell cycle arrest, demonstrating that cell cycle distribution was not involved in the enhanced antitumor activity. Both annexin V-FITC/propidium iodide assay and TUNEL assay indicated that the combination of tunicamycin with paclitaxel resulted in significant increased cell apoptosis as compared with individual treatment in vitro and in vivo. Tunicamycin decreased paclitaxel-induced microtubulin polymerization, suggesting that enhanced antitumor effect of paclitaxel was not dependent of microtubulin polymerization. Western blotting analysis confirmed that tunicamycin decreased paclitaxel-induced upregulation of survival signal pathways such as AKT and MAPK. CONCLUSION: These results revealed that tunicamycin synergistically enhanced the antitumor effects of paclitaxel through potentiating apoptosis via inhibiting paclitaxel-induced elevation of AKT and MAPK pathways. This study raised the possibility that the combination of paclitaxel with tunicamycin may be a promising approach for improving the clinical activity of paclitaxel.

Tunicamycin enhances the antitumor activity of trastuzumab on breast cancer in vitro and in vivo.

Trastuzumab, a humanized monoclonal antibody targeting HER2, has demonstrated clinical benefits for women with HER2-positive breast cancer; however, trastuzumab resistance remains the biggest clinical challenge. In this study, results showed that tunicamycin, an inhibitor of N-glycosylation, synergistically enhanced the antitumor activity of trastuzumab against HER2-overexpressing breast cancer cells through induction of cell cycle arrest and apoptosis. Combined treatment of tunicamycin with trastuzumab dramatically decreased the expression of EGFR family and its down signaling pathway in SKBR3 and MCF-7/HER2 cells. Tunicamycin dose-dependently inhibited tumor growth in both of SKBR3 xenografts and MCF-7/HER2 xenografts. Optimal tunicamycin without inducing ER stress in liver tissue significantly increased the antitumor effect of trastuzumab in MCF-7/HER2 xenografts. Combinations of trastuzumab with N-glycosylation inhibitors tunicamycin may be a promising approach for improving clinical efficacy of trastuzumab.

Structural insights for the design of new borate-phosphates: synthesis, crystal structure and optical properties of Pb4O(BO3)(PO4) and Bi4O3(BO3)(PO4).

Two new metal borate-phosphates, Pb4O(BO3)(PO4) (1) and Bi4O3(BO3)(PO4) (2), have been successfully designed and synthesized. The structures of the title compounds were determined by single-crystal X-ray diffraction. The title compounds have similar crystal structures consisting of oxygen-centered (OPb4) or (OBi4) tetrahedra as well as isolated BO3 and PO4 groups. Structural comparison and the Madelung energy calculation indicate that the title compounds also exhibit a strong correlation with the known metal borates and phosphates. In addition, a strategy of BO3-PO4 substitution is proposed for designing new borate-phosphates. Thermal analyses, IR spectroscopy and UV-vis-NIR diffuse reflectance spectroscopy have also been performed.