Oxygen-Dependent Changes in the N-Glycome of Murine Pulmonary Endothelial Cells

Supplemental oxygen is frequently used together with mechanical ventilation to achieve sufficient blood oxygenation. Despite the undoubted benefits, it is vigorously debated whether too much oxygen can also have unpredicted side-effects. Uncertainty is also due to the fact that the molecular mechanisms are still insufficiently understood. The lung endothelium is covered with an exceptionally broad glycocalyx, carrying N- and O-glycans, proteoglycans, glycolipids and glycosaminoglycans. Glycan structures are not genetically determined but depend on the metabolic state and the expression level and activity of biosynthetic and glycan remodeling enzymes, which can be influenced by oxygen and the redox status of the cell. Altered glycan structures can affect cell interactions and signaling. In this study, we investigated the effect of different oxygen conditions on aspects of the glycobiology of the pulmonary endothelium with an emphasis on N-glycans and terminal sialylation using an in vitro cell culture system. We combined a proteomic approach with N-glycan structure analysis by LC-MS, qRT-PCR, sialic acid analysis and lectin binding to show that constant and intermittent hyperoxia induced time dependent changes in global and surface glycosylation. An siRNA approach identified St6gal1 as being primarily responsible for the early transient increase of α2-6 sialylated structures in response to hyperoxia.

E-Cigarette Use: Device Market, Study Design, and Emerging Evidence of Biological Consequences

Electronic cigarettes are frequently viewed as a safer alternative to conventional cigarettes; however, evidence to support this perspective has not materialized. Indeed, the current literature reports that electronic cigarette use is associated with both acute lung injury and subclinical dysfunction to the lung and vasculature that may result in pathology following chronic use. E-cigarettes can alter vascular dynamics, polarize innate immune populations towards a proinflammatory state, compromise barrier function in the pulmonary endothelium and epithelium, and promote pre-oncogenic phenomena. This review will summarize the variety of e-cigarette products available to users, discuss current challenges in e-cigarette study design, outline the range of pathologies occurring in cases of e-cigarette associated acute lung injury, highlight disease supporting tissue- and cellular-level changes resulting from e-cigarette exposure, and briefly examine how these changes may promote tumorigenesis. Continued research of the mechanisms by which e-cigarettes induce pathology benefit users and clinicians by resulting in increased regulation of vaping devices, informing treatments for emerging diseases e-cigarettes produce, and increasing public awareness to reduce e-cigarette use and the onset of preventable disease.

The Role of Endothelial Superoxide Dismutase 2 in Modulating Sickle Pathology

Sickle cell disease (SCD) patients suffer from hemolysis in microcirculation. On the one hand, hemoglobin and heme released from sickled red blood cells catalyze reactive oxygen species (ROS) generation by Fenton chemistry. On the other hand, sickled red blood cells occlude capillaries, creating a hypoxic condition that exacerbates ROS production. As an essential antioxidant mechanism, superoxide dismutase 2 (SOD2) detoxifies superoxide by converting it to hydrogen peroxide (H 2O 2) in the mitochondria. In SCD patients, despite the elevated ROS production, we found that SOD2 expression is suppressed in the pulmonary endothelium (Figure 1A,B). Therefore, we hypothesize the depletion of endothelial SOD2 compromises endothelial function and exacerbates the progression of SCD. To examine the role of endothelial SOD2, we silenced SOD2 gene expression (SOD2 KD) with siRNA in primary human pulmonary microvascular endothelial cells (hPMVECs). Knocking down SOD2 in hPMVECs accelerated mitochondrial superoxide production and compromised mitochondrial potential. However, mitochondrial respiration, the activity of respiratory complexes, and the cellular ATP content were not affected by SOD2 KD. An important function of endothelial cells is to form a barrier and sequester cellular and molecular contents in the blood. SOD2 KD hPMVECs exhibited increased albumin leakage and decreased transendothelial resistance, indicating a disrupted endothelial barrier(Figure 1C). The defect in the endothelial barrier was rescued by adding 4 mM H 2O 2(Figure 1D), suggesting SOD2-derived H 2O 2 may serve as a critical signaling molecule. Moreover, cell migration or proliferation was inhibited in SOD2 KD hPMVECs, which was examined by a scratch assay. Since both cell migration and barrier maintenance require focal adhesion assembly, we next investigated the role of SOD2 in focal adhesion dynamics. In an attachment assay, SOD2 KD reduced cell attachment rate on uncoated plates, which was blunted by fibronectin precoating, indicating a fibronectin-dependent defect in cell adhesion(Figure 1E,F). Notably, although fibronectin protein expression in hPMVECs was not altered, SOD2 KD decreased the dimer/monomer ratio. Furthermore, confocal images showed that fibronectin was retained in SOD2 KD cells(Figure 1G), highlighting the importance of SOD2 in fibronectin assembly. In conclusion, we demonstrated for the first time that SOD2 expression is diminished in the pulmonary endothelium of SCD patients and that endothelial SOD2 is crucial for endothelial function by facilitating fibronectin assembly. The importance of SOD2 in endothelial function may prove therapeutic value in SCD patients, which requires further investigation. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Interferon-alpha or -beta facilitates SARS-CoV-2 pulmonary vascular infection by inducing ACE2

Severe viral pneumonia caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is characterized by a hyperinflammatory state typified by elevated circulating pro-inflammatory cytokines, frequently leading to potentially lethal vascular complications including thromboembolism, disseminated intracellular coagulopathy and vasculitis. Though endothelial infection and subsequent endothelial damage have been described in patients with fatal COVID-19, the mechanism by which this occurs remains elusive, particularly given that, under naïve conditions, pulmonary endothelial cells demonstrate minimal cell surface expression of the SARS-CoV-2 binding receptor ACE2. Herein we describe SARS-CoV-2 infection of the pulmonary endothelium in postmortem lung samples from individuals who died of COVID-19, demonstrating both heterogeneous ACE2 expression and endothelial damage. In primary endothelial cell cultures, we show that SARS-CoV-2 infection is dependent on the induction of ACE2 protein expression and that this process is facilitated by type 1 interferon-alpha (IFNα) or -beta(β)—two of the main anti-viral cytokines induced in severe SARS-CoV-2 infection—but not significantly by other cytokines (including interleukin 6 and interferon γ/λ). Our findings suggest that the stereotypical anti-viral interferon response may paradoxically facilitate the propagation of COVID-19 from the respiratory epithelium to the vasculature, raising concerns regarding the use of exogenous IFNα/β in the treatment of patients with COVID-19.

Infrequent Placental and Fetal Involvement in SARS-CoV-2 Infection: Pathology Data from a Large Medical Center

In order to determine the frequency of SARS-CoV-2 placental and fetal involvements, we analyzed placentas of 197 women positive for infection at delivery and fetal tissues in cases of pregnancy loss in women positive by SARS-CoV-2 PCR (N = 2) and COVID-19 serology (N = 4), using in situ hybridization (ISH), immunohistochemistry (IHC) and, in selected cases, RT-PCR of tissue homogenates. The virus was identified in situ, accompanied by intervillositis, in 2 of 197 placentas (1.02%). In three more cases, SARS-CoV-2 was detected by tissue PCR without in situ localization and placental inflammation. There were no maternal mortality or association of placental infection with the clinical severity of COVID-19. All tested neonates born to SARS-CoV-2-positive women (N = 172) were negative for the virus. There were three pregnancy losses among 197 infected women and in two cases available fetal tissues were negative for SARS-CoV-2. In one of four fetal autopsies performed in women with positive COVID-19 serology, the mother-to-child transmission (MTCT) could be inferred based on positive SARS-CoV-2 nucleocapsid IHC in fetal pulmonary endothelium. Placental involvement by SARS-CoV-2 is rare, but may be underestimated due to its transient nature. MTCT is even rarer, supporting the protective role of placenta in SARS-CoV-2 infection.

Pathogenetic bases of the use of antifibrotic therapy with Bovhyaluronidazum azoximerum in patients with new coronavirus infection COVID-19

One of the most likely and serious complications of the novel coronavirus infection (COVID-19) is pneumofibrosis, which can negatively affect the duration and quality of life of patients who have suffered from this disease. The appearance of fibrotic changes in COVID-19 is due to a number of pathological processes that occur in the lungs after the pathogen, the SARS- CoV-2 virus, enters there. First of all, an inflammatory response is triggered, which is mediated by macrophages and granulocytes, due to which the synthesis of pro-inflammatory cytokines, incl. IL-1, TNF, which are potent inducers of hyaluronic acid synthetase. There is a decrease in the content of fibrinolysis activators in the pulmonary endothelium, which contributes to the accumulation of fibrin in the vessels of the lungs. Fibrin can escape into the interstitial space and cause the formation of sclerosing alveolitis. The increasing defeat of pneumocytes favors the release of fibrin into the lumen of the alveoli, which causes the formation of hyaline membranes. The regulation of the fibrotic process involves immunocompetent cells, primarily CD4 + T-lymphocytes, which are capable of producing cytokines, chemokines and growth factors, and these, in turn, stimulate the proliferation and differentiation of fibroblasts, as well as their production of collagen. The more severe forms of infectious process can lead to the greater risk of developing fibrotic changes. Risk factors are a large area of lung damage, the use of artificial pulmonary ventilation, ARDS, fibrosis in anamnesis. An additional role in the pathomorphogenesis of pneumofibrosis is played by smoking, external inhalation effects (inhalation of organic and inorganic dust), gastroesophageal reflux, type II diabetes mellitus, genetic factors (familial idiopathic pulmonary fibrosis). The pathogenetic features of COVID-19 require administration of anti-fibrotic treatment. Bovhyaluronidazum azoximerum, a drug that is a conjugate of the proteolytic enzyme hyaluronidase, is considered as an antifibrotic agent. The treatment regimens with this drug recommended in the period of convalescence for patients who have undergone COVID-19 are given.

Flow-dependent regulation of endothelial Tie2 by GATA3 in vivo

Background Reduced endothelial Tie2 expression occurs in diverse experimental models of critical illness, and experimental Tie2 suppression is sufficient to increase spontaneous vascular permeability. Looking for a common denominator among different critical illnesses that could drive the same Tie2 suppressive (thereby leak inducing) phenotype, we identified “circulatory shock” as a shared feature and postulated a flow-dependency of Tie2 gene expression in a GATA3 dependent manner. Here, we analyzed if this mechanism of flow-regulation of gene expression exists in vivo in the absence of inflammation. Results To experimentally mimic a shock-like situation, we developed a murine model of clonidine-induced hypotension by targeting a reduced mean arterial pressure (MAP) of approximately 50% over 4 h. We found that hypotension-induced reduction of flow in the absence of confounding disease factors (i.e., inflammation, injury, among others) is sufficient to suppress GATA3 and Tie2 transcription. Conditional endothelial-specific GATA3 knockdown (B6-Gata3tm1-Jfz VE-Cadherin(PAC)-cerERT2) led to baseline Tie2 suppression inducing spontaneous vascular leak. On the contrary, the transient overexpression of GATA3 in the pulmonary endothelium (jet-PEI plasmid delivery platform) was sufficient to increase Tie2 at baseline and completely block its hypotension-induced acute drop. On the functional level, the Tie2 protection by GATA3 overexpression abrogated the development of pulmonary capillary leakage. Conclusions The data suggest that the GATA3–Tie2 signaling pathway might play a pivotal role in controlling vascular barrier function and that it is affected in diverse critical illnesses with shock as a consequence of a flow-regulated gene response. Targeting this novel mechanism might offer therapeutic opportunities to treat vascular leakage of diverse etiologies.