Synergistic enhancement of matrix metalloproteinase-9 expression and pro-inflammatory cytokines by influenza virus infection and oxidized-LDL treatment in human endothelial cells

Influenza and cardiovascular disease pathophysiology: strings attached

A link between influenza infection and cardiovascular morbidity has been known for almost a century. This narrative review examined the cardiovascular complications associated with influenza and the potential mechanisms behind this relationship. The most common reported cardiovascular complications are cardiovascular death, myocardial infarction, and heart failure hospitalization. There are multiple proposed mechanisms driving the increased risk of cardiovascular complications. These mechanics involve influenza-specific effects such as direct cardiac infection and endothelial dysfunction leading to plaque destabilization and rupture, but also hypoxaemia and systemic inflammatory responses including increased metabolic demand, biomechanical stress, and hypercoagulability. The significance of the individual effects is unclear, and thus whether influenza directly or indirectly causes cardiovascular events is unknown. In conclusion, the risk of acute cardiovascular morbidity and mortality is elevated during influenza infection. The proposed underlying pathophysiological mechanisms support this association, but systemic responses to infection may drive this relationship.

Protective Effect of Uric Acid on ox-LDL-Induced HUVECs Injury via Keap1-Nrf2-ARE Pathway

Uric acid is an effective antioxidant. Oxidized low-density lipoprotein (ox-LDL) is derived from circulating LDL and promotes atherosclerosis. The Keap1-Nrf2-ARE pathway is a key body pathway involved in protection against internal and external oxidative damages. The role of uric acid on vascular endothelial function damaged by ox-LDL, and its effect on the Keap1-Nrf2-ARE pathway has not been fully explored. HUVECs were treated with different concentrations of uric acid and ox-LDL to explore the effect of uric acid in vitro. Cell phenotype was determined by cytometry and Western blot. Nuclear translocation of Nrf2 was determined by immunofluorescence. Coimmunoprecipitation was used to determine the level of Nrf2 ubiquitination. A microfluidic device was used to mimic the vascular environment in the body, and the level of mRNA levels of inflammatory factors was determined by RT-PCR. The findings of this study show that suitable uric acid can significantly reduce endothelial damage caused by ox-LDL, such as oxidative stress, inflammation, and increased adhesion. In addition, uric acid reduced Nrf2 ubiquitination and increased nuclear translocation of Nrf2 protein, thus activating the Keap1-Nrf2-ARE pathway and playing a protective role. Interestingly, the effects of UA were significantly inhibited by administration of Brusatol, an inhibitor of Nrf2. In summary, suitable concentrations of uric acid can alleviate the oxidative stress level of endothelial cells through Nrf2 nuclear translocation and further protect cells from damage.

Anti-high mobility group box 1 monoclonal antibody suppressed hyper-permeability and cytokine production in human pulmonary endothelial cells infected with influenza A virus

Objective

High mobility group box-1 (HMGB1) has been reported to be involved in influenza A virus-induced acute respiratory distress syndrome (ARDS). We studied the efficacy of an anti-HMGB1 mAb using an in vitro model of TNF-α stimulation or influenza A virus infection in human pulmonary microvascular endothelial cells (HMVECs).

Methods

Vascular permeability of HMVECs was quantified using the Boyden chamber assay under tumor necrosis factor-α (TNF-α) stimulation or influenza A virus infection in the presence of anti-HMGB1 mAb or control mAb. The intracellular localization of HMGB1 was assessed by immunostaining. Extracellular cytokine concentrations and intracellular viral mRNA expression were quantified by the enzyme-linked immunosorbent assay and quantitative reverse transcription PCR, respectively.

Results

Vascular permeability was increased by TNF-α stimulation or influenza A infection; HMVECs became elongated and the intercellular gaps were extended. Anti-HMGB1 mAb suppressed both the increase in permeability and the cell morphology changes. Translocation of HMGB1 to the cytoplasm was observed in the non-infected cells. Although anti-HMGB1 mAb did not suppress viral replication, it did suppress cytokine production in HMVECs.

Conclusion

Anti-HMGB1 mAb might be an effective therapy for severe influenza ARDS.

Induction of the Coxsackievirus and Adenovirus Receptor in Macrophages During the Formation of Atherosclerotic Plaques

Multiple viruses are implicated in atherosclerosis, but the mechanisms by which they infect cells and contribute to plaque formation in arterial walls are not well understood. Based on reports showing the presence of enterovirus in atherosclerotic plaques we hypothesized that the coxsackievirus and adenovirus receptor (CXADR/CAR), although absent in normal arteries, could be induced during plaque formation. Large-scale microarray and mass spectrometric analyses revealed significant up-regulation of CXADR messenger RNA and protein levels in plaque-invested carotid arteries compared with control arteries. Macrophages were identified as a previously unknown cellular source of CXADR in human plaques and plaques from Ldr-/-Apob100/100 mice. CXADR was specifically associated with M1-polarized macrophages and foam cells and was experimentally induced during macrophage differentiation. Furthermore, it was significantly correlated with receptors for other viruses linked to atherosclerosis. The results show that CXADR is induced in macrophages during plaque formation, suggesting a mechanism by which enterovirus infect cells in atherosclerotic plaques.

Immune Mechanisms in Cardiovascular Diseases Associated With Viral Infection

Influenza virus infection causes 3-5 million cases of severe illness and 250,000-500,000 deaths worldwide annually. Although pneumonia is the most common complication associated with influenza, there are several reports demonstrating increased risk for cardiovascular diseases. Several clinical case reports, as well as both prospective and retrospective studies, have shown that influenza can trigger cardiovascular events including myocardial infarction (MI), myocarditis, ventricular arrhythmia, and heart failure. A recent study has demonstrated that influenza-infected patients are at highest risk of having MI during the first seven days of diagnosis. Influenza virus infection induces a variety of pro-inflammatory cytokines and chemokines and recruitment of immune cells as part of the host immune response. Understanding the cellular and molecular mechanisms involved in influenza-associated cardiovascular diseases will help to improve treatment plans. This review discusses the direct and indirect effects of influenza virus infection on triggering cardiovascular events. Further, we discussed the similarities and differences in epidemiological and pathogenic mechanisms involved in cardiovascular events associated with coronavirus disease 2019 (COVID-19) compared to influenza infection.

Astragaloside IV Protects Against Oxidized Low-Density Lipoprotein (ox-LDL)-Induced Endothelial Cell Injury by Reducing Oxidative Stress and Inflammation

Background

Endothelial injury is the main mechanism of atherosclerosis, and is caused by oxidized low-density lipoprotein (ox-LDL). Astragaloside IV (AS-IV) is the primary active ingredient of the Chinese herb Huangqi, and exhibits antioxidant and anti-inflammatory properties in cardiovascular diseases. This study investigated the protective effect of AS-IV in human umbilical vein endothelial cells (HUVECs).

Material/Methods

HUVEC cells were induced with ox-LDL to establish an in vitro atherosclerosis model. Then HUVECs were pretreated for 1 h with AS-IV at different concentrations (10, 20, and 50 μM) and then exposed to ox-LDL (100 μg/mL) for 48 h. The cell viability, lactate dehydrogenase (LDH) release, apoptosis, migration, intracellular reactive oxygen species (ROS), and NADPH oxidase activity of HUVECs were measured. qRT-PCR was performed to measure the mRNA expressions of Nrf2, HO-1, TNFα, and IL-6. Enzyme-linked immunosorbent assay (ELISA) was performed to measure the supernatant contents of TNFα and IL-6.

Results

Exposure of HUVECs to ox-LDL reduced cell viability and migration, induced apoptosis, and increased intracellular ROS production and NADPH oxidase. Pretreatment with AS-IV (10, 20, and 50 μM) significantly enhanced the cell viability and migration, suppressed LDH release, apoptosis, ROS production, and NADPH oxidase in HUVECs, in a concentration-dependent manner. The AS-IV (50 μM) alone did not show significant differences from control. AS-IV increased mRNA expressions of Nrf2 and HO-1 and decreased mRNA expressions of TNFα and IL-6 in the ox-LDL-HUEVC cells. Furthermore, AS-IV reduced supernatant contents of TNFα and IL-6.

Conclusions

Astragaloside IV prevents ox-LDL-induced endothelial cell injury by reducing apoptosis, oxidative stress, and inflammatory response.