SARS-CoV-2 Mediated Endothelial Dysfunction: The Potential Role of Chronic Oxidative Stress

Targeting Oxidative Stress and Endothelial Dysfunction Using Tanshinone IIA for the Treatment of Tissue Inflammation and Fibrosis

Salvia miltiorrhiza Burge (Danshen), a member of the Lamiaceae family, has been used in traditional Chinese medicine for many centuries as a valuable medicinal herb with antioxidative, anti-inflammatory, and antifibrotic potential. Several evidence-based reports have suggested that Salvia miltiorrhiza and its components prevent vascular diseases, including myocardial infarction, myocardial ischemia/reperfusion injury, arrhythmia, cardiac hypertrophy, and cardiac fibrosis. Tanshinone IIA (TanIIA), a lipophilic component of Salvia miltiorrhiza, has gained attention because of its possible preventive and curative activity against cardiovascular disorders. TanIIA, which possesses antioxidative, anti-inflammatory, and antifibrotic properties, could be a key component in the therapeutic potential of Salvia miltiorrhiza. Vascular diseases are often initiated by endothelial dysfunction, which is accompanied by vascular inflammation and fibrosis. In this review, we summarize how TanIIA suppresses tissue inflammation and fibrosis through signaling pathways such as PI3K/Akt/mTOR/eNOS, TGF-β1/Smad2/3, NF-κB, JNK/SAPK (stress-activated protein kinase)/MAPK, and ERK/Nrf2 pathways. In brief, this review illustrates the therapeutic value of TanIIA in the alleviation of oxidative stress, inflammation, and fibrosis, which are critical components of cardiovascular disorders.

Impact of SARS-CoV-2 on Host Factors Involved in Mental Disorders

COVID-19, caused by SARS-CoV-2, is a systemic illness due to its multiorgan effects in patients. The disease has a detrimental impact on respiratory and cardiovascular systems. One early symptom of infection is anosmia or lack of smell; this implicates the involvement of the olfactory bulb in COVID-19 disease and provides a route into the central nervous system. However, little is known about how SARS-CoV-2 affects neurological or psychological symptoms. SARS-CoV-2 exploits host receptors that converge on pathways that impact psychological symptoms. This systemic review discusses the ways involved by coronavirus infection and their impact on mental health disorders. We begin by briefly introducing the history of coronaviruses, followed by an overview of the essential proteins to viral entry. Then, we discuss the downstream effects of viral entry on host proteins. Finally, we review the literature on host factors that are known to play critical roles in neuropsychiatric symptoms and mental diseases and discuss how COVID-19 could impact mental health globally. Our review details the host factors and pathways involved in the cellular mechanisms, such as systemic inflammation, that play a significant role in the development of neuropsychological symptoms stemming from COVID-19 infection.

Loop Between NLRP3 Inflammasome and Reactive Oxygen Species

Significance: Inflammasomes are cytosolic multiprotein complexes that mediate innate immune pathways. Inflammasomes activate inflammatory caspases and regulate inflammatory cytokines interleukin (IL)-1β and IL-18 as well as inflammatory cell death (pyroptosis). Among known inflammasomes, NLRP3 (NLR family pyrin domain containing 3) inflammasome is unique and well studied owing to the fact that it senses a broad range of stimuli and is implicated in the pathogenesis of both microbial and sterile inflammatory diseases. Recent Advances: Reactive oxygen species (ROS), especially derived from the mitochondria, are one of the critical mediators of NLRP3 inflammasome activation. Furthermore, NLRP3 inflammasome-driven inflammation recruits inflammatory cells, including macrophages and neutrophils, which in turn cause ROS production, suggesting a feedback loop between ROS and NLRP3 inflammasome. Critical Issues: The precise mechanism of how ROS affects NLRP3 inflammasome activation still need to be addressed. This review will summarize the current knowledge on the molecular mechanisms underlying the activation of NLRP3 inflammasome with particular emphasis on the intricate balance of feedback loop between ROS and inflammasome activation. Future Directions: Understanding that this relationship is loop rather than traditionally understood linear mechanism will enable to fine-tune inflammasome activation under varied pathological settings. Antioxid. Redox Signal. 36, 784-796.

Targeting Arginine in COVID-19-Induced Immunopathology and Vasculopathy

Coronavirus disease 2019 (COVID-19) represents a major public health crisis that has caused the death of nearly six million people worldwide. Emerging data have identified a deficiency of circulating arginine in patients with COVID-19. Arginine is a semi-essential amino acid that serves as key regulator of immune and vascular cell function. Arginine is metabolized by nitric oxide (NO) synthase to NO which plays a pivotal role in host defense and vascular health, whereas the catabolism of arginine by arginase to ornithine contributes to immune suppression and vascular disease. Notably, arginase activity is upregulated in COVID-19 patients in a disease-dependent fashion, favoring the production of ornithine and its metabolites from arginine over the synthesis of NO. This rewiring of arginine metabolism in COVID-19 promotes immune and endothelial cell dysfunction, vascular smooth muscle cell proliferation and migration, inflammation, vasoconstriction, thrombosis, and arterial thickening, fibrosis, and stiffening, which can lead to vascular occlusion, muti-organ failure, and death. Strategies that restore the plasma concentration of arginine, inhibit arginase activity, and/or enhance the bioavailability and potency of NO represent promising therapeutic approaches that may preserve immune function and prevent the development of severe vascular disease in patients with COVID-19.

Common Molecular Pathways Between Post-COVID19 Syndrome and Lung Fibrosis: A Scoping Review

The pathogenetic mechanism of post-Covid-19 pulmonary fibrosis is currently a topic of intense research interest, but still largely unexplored. The aim of this work was to carry out a systematic exploratory search of the literature (Scoping review) to identify and systematize the main pathogenetic mechanisms that are believed to be involved in this phenomenon, in order to highlight the same molecular aspect of the lung. These aims could be essential in the future for therapeutic management. We identified all primary studies involving in post COVID19 syndrome with pulmonary fibrosis as a primary endpoint by performing data searches in various systematic review databases. Two reviewers independently reviewed all abstracts (398) and full text data. The quality of study has been assess through SANRA protocol. A total of 32 studies involving were included, included the possible involvement of inflammatory cytokines, concerned the renin-angiotensin system, the potential role of galectin-3, epithelial injuries in fibrosis, alveolar type 2 involvement, Neutrophil extracellular traps (NETs) and the others implied other specific aspects (relationship with clinical and mechanical factors, epithelial transition mesenchymal, TGF-β signaling pathway, midkine, caspase and macrophages, genetics). In most cases, these were narrative reviews or letters to the editor, except for 10 articles, which presented original data, albeit sometimes in experimental models. From the development of these researches, progress in the knowledge of the phenomenon and hopefully in its prevention and therapy may originate.

COVID-19-Associated Endothelial Dysfunction and Microvascular Injury: From Pathophysiology to Clinical Manifestations

Coronavirus-19 disease (COVID-19) affects more people than previous coronavirus infections and has a higher mortality. Higher incidence and mortality can probably be explained by COVID-19 causative agent's greater affinity (about 10-20 times) for angiotensin-converting enzyme 2 (ACE2) receptor compared with other coronaviruses. Here, the authors first summarize clinical manifestations, then present symptoms of COVID-19 and the pathophysiological mechanisms underlying specific organ/system disease. The worse clinical outcome observed in COVID-19 patients with diabetes may be in part related to the increased ADAM17 activity and its unbalanced interplay with ACE2. Therefore, strategies aimed to inhibit ADAM17 activity may be explored to develop new effective therapeutic approaches.

Mitochondrial hijacking: A potential mechanism for SARS-CoV-2 to impair female fertility

As well as causing respiratory lesions, the multi-organ complications caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are also well known. Combined with the epidemiological characteristics of SARS-CoV-2 with high transmission rate and low lethality, the impact of complications caused by its infection on infected individuals seems to be of greater concern. There has been evidence that viral infection is complicated by female reproductive impairment, but the mechanism by which SARS-CoV-2 impairs female fertility is unclear. In addition, RNA-GPS technology has revealed that the SARS-CoV-2 genome resides in mitochondria of the host cells and affects mitochondrial function. Considering the close relationship between mitochondria and female fertility, this paper takes mitochondrial hijacking as an entry point to elucidate the possible mechanisms by which SARS-CoV-2 affects female fertility through the mitochondrial hijacking pathway, which will be important for timely preventive measures and identification of therapeutic targets for infected women with reproductive needs, especially those with asymptomatic infection.

Populations in Low-Magnesium Areas Were Associated with Higher Risk of Infection in COVID-19's Early Transmission: A Nationwide Retrospective Cohort Study in the United States

Many studies have confirmed the important roles of nutritional status and micronutrients in the COVID-19 pandemic. Magnesium is a vital essential trace element that is involved in oxidative stress, inflammation, and many other immunological functions and has been shown to be associated with the outcome of COVID-19 infection. Here, we conducted a nationwide retrospective cohort study in the United States involving 1150 counties, 287,326,503 individuals, and 5,401,483 COVID-19 confirmed cases as of 30 September 2020 to reveal the infection risk of the populations distributed in low-magnesium areas in the early transmission of COVID-19. Our results indicate that the average county-level COVID-19 cumulative incidence in low-magnesium areas was significantly higher than in the control areas. Additionally, a significant negative nonlinear association was found between environmental magnesium concentration and the county-level COVID-19 cumulative incidence. Furthermore, the populations distributed in low environmental magnesium areas faced a higher COVID-19 infection risk (RR: 1.066; CI: 1.063-1.068), among which females (RR: 1.07; CI: 1.067-1.073), the 0-17 years subgroup (RR: 1.125; CI: 1.117-1.134), the 65+ years subgroup (RR: 1.093; CI: 1.087-1.098), black people (RR: 1.975; CI: 1.963-1.986), populations outside metro areas, and counties with a smaller population experienced higher risk of infection by COVID-19 than other subgroups. Considering that the magnesium intake of about half the population of the United States is below the daily required dose, our study will contribute to the creation of long-term public health strategies to help protect against COVID-19.

Emerging roles of inflammation-mediated endothelial–mesenchymal transition in health and disease

Endothelial–mesenchymal transition (EndoMT), a cellular differentiation process in which endothelial cells (ECs) lose their properties and differentiate into mesenchymal cells, has been observed not only during development but also in various pathological states in adults, including cancer progression and organ/tissue fibrosis. Transforming growth factor-β (TGF-β), an inflammation-related cytokine, has been shown to play central roles in the induction of EndoMT. TGF-β induces EndoMT by regulating the expression of various transcription factors, signaling molecules, and cellular components that confer ECs with mesenchymal characteristics. However, TGF-β by itself is not necessarily sufficient to induce EndoMT to promote the progression of EndoMT-related diseases to a refractory extent. In addition to TGF-β, additional activation by other inflammatory factors is often required to stabilize the progression of EndoMT. Since recent lines of evidence indicate that inflammatory signaling molecules act as enhancers of EndoMT, we summarize the roles of inflammatory factors in the induction of EndoMT and related diseases. We hope that this review will help to develop therapeutic strategies for EndoMT-related diseases by targeting inflammation-mediated EndoMT.

Effect of Cysteine Oxidation in SARS-CoV-2 Receptor-Binding Domain on Its Interaction with Two Cell Receptors: Insights from Atomistic Simulations

Binding of the SARS-CoV-2 S-glycoprotein to cell receptors is vital for the entry of the virus into cells and subsequent infection. ACE2 is the main cell receptor for SARS-CoV-2, which can attach to the C-terminal receptor-binding domain (RBD) of the SARS-CoV-2 S-glycoprotein. The GRP78 receptor plays an anchoring role, which attaches to the RBD and increases the chance of other RBDs binding to ACE2. Although high levels of reactive oxygen and nitrogen species (RONS) are produced during viral infections, it is not clear how they affect the RBD structure and its binding to ACE2 and GRP78. In this research, we apply molecular dynamics simulations to study the effect of oxidation of the highly reactive cysteine (Cys) amino acids of the RBD on its binding to ACE2 and GRP78. The interaction energy of both ACE2 and GRP78 with the whole RBD, as well as with the RBD main regions, is compared in both the native and oxidized RBDs. Our results show that the interaction energy between the oxidized RBD and ACE2 is strengthened by 155 kJ/mol, increasing the binding of the RBD to ACE2 after oxidation. In addition, the interaction energy between the RBD and GRP78 is slightly increased by 8 kJ/mol after oxidation, but this difference is not significant. Overall, these findings highlight the role of RONS in the binding of the SARS-CoV-2 S-glycoprotein to host cell receptors and suggest an alternative mechanism by which RONS could modulate the entrance of viral particles into the cells.

The impact of dawn to sunset fasting on immune system and its clinical significance in Covid-19 pandemic

Dawn to sunset fasting, a type of intermittent fasting commonly practiced in the month of Ramadan, requires fasting from dawn to sunset without food or liquid intake. Dawn and dusk are two transition time zones of the day that play a critical role in the human circadian rhythm. Practicing dawn to sunset fasting requires the alignment of mealtimes and wake-sleep times with the human biological dawn and dusk. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) impairs immune cell responses at multiple levels and leads to severe Coronavirus Disease 2019 (COVID-19). It generates high levels of pro-inflammatory cytokines and chemokines, also known as a cytokine storm, leads to mitochondrial dysfunction and generation of excessive amounts of mitochondrial reactive oxygen species, downregulates autophagy to escape detection for unchecked replication, and alters gut microbiome composition. Severe cases of COVID-19 have been associated with several comorbidities that impair immune responses (e.g., obesity, diabetes, malignancy) and blood laboratory abnormalities (e.g., elevated procalcitonin, C-reactive protein, interleukin-6 (IL-6), leukocytosis, lymphopenia). Several studies of dawn to sunset fasting showed anti-inflammatory effect by suppressing several pro-inflammatory cytokines, reducing oxidative stress, inducing a proteome response associated with increased autophagy, remodeling the gut microbiome, and improving the components of metabolic syndrome (e.g., obesity, blood glucose levels, blood pressure, lipids). In conclusion, dawn to sunset fasting has the potential to optimize the immune system function against SARS-CoV-2 during the COVID-19 pandemic as it suppresses chronic inflammation and oxidative stress, improves metabolic profile, and remodels the gut microbiome. This review presents scientific literature related to the effects of dawn to sunset fasting on the immune system. Studies are needed to assess and confirm the potential benefits of dawn to sunset fasting against SARS-CoV-2.

Pannexin-1 channel opening is critical for COVID-19 pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly rampaged worldwide, causing a pandemic of coronavirus disease (COVID -19), but the biology of SARS-CoV-2 remains under investigation. We demonstrate that both SARS-CoV-2 spike protein and human coronavirus 229E (hCoV-229E) or its purified S protein, one of the main viruses responsible for the common cold, induce the transient opening of Pannexin-1 (Panx-1) channels in human lung epithelial cells. However, the Panx-1 channel opening induced by SARS-CoV-2 is greater and more prolonged than hCoV-229E/S protein, resulting in an enhanced ATP, PGE₂, and IL-1β release. Analysis of lung lavages and tissues indicate that Panx-1 mRNA expression is associated with increased ATP, PGE₂, and IL-1β levels. Panx-1 channel opening induced by SARS-CoV-2 spike protein is angiotensin-converting enzyme 2 (ACE-2), endocytosis, and furin dependent. Overall, we demonstrated that Panx-1 channel is a critical contributor to SARS-CoV-2 infection and should be considered as an alternative therapy.

Plasma S-Adenosylmethionine Is Associated with Lung Injury in COVID-19

Objective

S-Adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are indicators of global transmethylation and may play an important role as markers of severity of COVID-19.

Methods

The levels of plasma SAM and SAH were determined in patients admitted with COVID-19 (n = 56, mean age = 61). Lung injury was identified by computed tomography (CT) in accordance with the CT0-4 classification.

Results

SAM was found to be a potential marker of lung damage risk in COVID-19 patients (SAM > 80 nM; CT3,4 vs. CT 0-2: relative ratio (RR) was 3.0; p = 0.0029). SAM/SAH > 6.0 was also found to be a marker of lung injury (CT2-4 vs. CT0,1: RR = 3.47, p = 0.0004). There was a negative association between SAM and glutathione level (ρ = −0.343, p = 0.011). Interleukin-6 (IL-6) levels were associated with SAM (ρ = 0.44, p = 0.01) and SAH (ρ = 0.534, p = 0.001) levels.

Conclusions

A high SAM level and high methylation index are associated with the risk of lung injury in patients with COVID-19. The association of SAM with IL-6 and glutathione indicates an important role of transmethylation in the development of cytokine imbalance and oxidative stress in patients with COVID-19.

Mitochondrial Dynamics in SARS-COV2 Spike Protein Treated Human Microglia: Implications for Neuro-COVID

Emerging clinical data from the current COVID-19 pandemic suggests that ~ 40% of COVID-19 patients develop neurological symptoms attributed to viral encephalitis while in COVID long haulers chronic neuro-inflammation and neuronal damage result in a syndrome described as Neuro-COVID. We hypothesize that SAR-COV2 induces mitochondrial dysfunction and activation of the mitochondrial-dependent intrinsic apoptotic pathway, resulting in microglial and neuronal apoptosis. The goal of our study was to determine the effect of SARS-COV2 on mitochondrial biogenesis and to monitor cell apoptosis in human microglia non-invasively in real time using Raman spectroscopy, providing a unique spatio-temporal information on mitochondrial function in live cells. We treated human microglia with SARS-COV2 spike protein and examined the levels of cytokines and reactive oxygen species (ROS) production, determined the effect of SARS-COV2 on mitochondrial biogenesis and examined the changes in molecular composition of phospholipids. Our results show that SARS- COV2 spike protein increases the levels of pro-inflammatory cytokines and ROS production, increases apoptosis and increases the oxygen consumption rate (OCR) in microglial cells. Increases in OCR are indicative of increased ROS production and oxidative stress suggesting that SARS-COV2 induced cell death. Raman spectroscopy yielded significant differences in phospholipids such as Phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylcholine (PC), which account for ~ 80% of mitochondrial membrane lipids between SARS-COV2 treated and untreated microglial cells. These data provide important mechanistic insights into SARS-COV2 induced mitochondrial dysfunction which underlies neuropathology associated with Neuro-COVID.

Low Brachial Artery Flow-Mediated Dilation Predicts Worse Prognosis in Hospitalized Patients with COVID-19

Background: Endothelial injury can be induced by coronavirus disease 2019 (COVID-19) and seems to exert a crucial pathogenic role in its most severe clinical manifestations. We aimed to investigate the association between brachial artery flow-mediated dilation (bFMD), a potential clinical and non-invasive measure of endothelial function, and in-hospital prognosis of COVID-19 patients. Methods: Brachial artery flow-mediated dilation was assessed in hospitalized COVID-19 patients within 48 h of hospital admission. The association between bFMD and either intensive care unit (ICU) admission or in-hospital death was explored using univariable and multivariable analyses. Results: Four hundred and eight patients were enrolled. Significantly lower bFMD values emerged in COVID-19 patients with either radiographic signs of pneumonia, respiratory distress, or the need for non-invasive ventilation compared with patients without these signs (p < 0.001, p = 0.001, and p < 0.001, respectively). Forty-two (10%) patients were admitted to the ICU, 76 (19%) patients died, and 118 (29%) patients met the composite endpoint of ICU admission/in-hospital death. At unadjusted Cox regression analysis showed that low bFMD (<4.4%, the median value) was associated with a higher risk for the composite endpoint of ICU admission/in-hospital death compared with high bFMD (≥4.4%, the median value) (HR 1.675, 95% CI 1.155–2.428, p = 0.007). Multi-adjusted Cox regression analyses showed that low bFMD was independently associated with a 1.519- to 1.658-fold increased risk for the composite endpoint of ICU admission/in-hospital death. Conclusions: Low bFMD predicts an unfavorable in-hospital prognosis in COVID-19 patients. The measurement of bFMD may be clinically useful in the prognostic stratification of COVID-19 patients upon hospital admission.

Microtubules as Major Regulators of Endothelial Function: Implication for Lung Injury

Endothelial dysfunction has been attributed as one of the major complications in COVID-19 patients, a global pandemic that has already caused over 4 million deaths worldwide. The dysfunction of endothelial barrier is characterized by an increase in endothelial permeability and inflammatory responses, and has even broader implications in the pathogenesis of acute respiratory syndromes such as ARDS, sepsis and chronic illnesses represented by pulmonary arterial hypertension and interstitial lung disease. The structural integrity of endothelial barrier is maintained by cytoskeleton elements, cell-substrate focal adhesion and adhesive cell junctions. Agonist-mediated changes in endothelial permeability are directly associated with reorganization of actomyosin cytoskeleton leading to cell contraction and opening of intercellular gaps or enhancement of cortical actin cytoskeleton associated with strengthening of endothelial barrier. The role of actin cytoskeleton remodeling in endothelial barrier regulation has taken the central stage, but the impact of microtubules in this process remains less explored and under-appreciated. This review will summarize the current knowledge on the crosstalk between microtubules dynamics and actin cytoskeleton remodeling, describe the signaling mechanisms mediating this crosstalk, discuss epigenetic regulation of microtubules stability and its nexus with endothelial barrier maintenance, and overview a role of microtubules in targeted delivery of signaling molecules regulating endothelial permeability and inflammation.

COVID-19: A Redox Disease-What a Stress Pandemic Can Teach Us About Resilience and What We May Learn from the Reactive Species Interactome About Its Treatment

Significance: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19), affects every aspect of human life by challenging bodily, socioeconomic, and political systems at unprecedented levels. As vaccines become available, their distribution, safety, and efficacy against emerging variants remain uncertain, and specific treatments are lacking. Recent Advances: Initially affecting the lungs, COVID-19 is a complex multisystems disease that disturbs the whole-body redox balance and can be long-lasting (Long-COVID). Numerous risk factors have been identified, but the reasons for variations in susceptibility to infection, disease severity, and outcome are poorly understood. The reactive species interactome (RSI) was recently introduced as a framework to conceptualize how cells and whole organisms sense, integrate, and accommodate stress. Critical Issues: We here consider COVID-19 as a redox disease, offering a holistic perspective of its effects on the human body, considering the vulnerability of complex interconnected systems with multiorgan/multilevel interdependencies. Host/viral glycan interactions underpin SARS-CoV-2's extraordinary efficiency in gaining cellular access, crossing the epithelial/endothelial barrier to spread along the vascular/lymphatic endothelium, and evading antiviral/antioxidant defences. An inflammation-driven "oxidative storm" alters the redox landscape, eliciting epithelial, endothelial, mitochondrial, metabolic, and immune dysfunction, and coagulopathy. Concomitantly reduced nitric oxide availability renders the sulfur-based redox circuitry vulnerable to oxidation, with eventual catastrophic failure in redox communication/regulation. Host nutrient limitations are crucial determinants of resilience at the individual and population level. Future Directions: While inflicting considerable damage to health and well-being, COVID-19 may provide the ultimate testing ground to improve the diagnosis and treatment of redox-related stress diseases. "Redox phenotyping" of patients to characterize whole-body RSI status as the disease progresses may inform new therapeutic approaches to regain redox balance, reduce mortality in COVID-19 and other redox diseases, and provide opportunities to tackle Long-COVID. Antioxid. Redox Signal. 35, 1226-1268.

Endothelial Dysfunction through Oxidatively Generated Epigenetic Mark in Respiratory Viral Infections

The bronchial vascular endothelial network plays important roles in pulmonary pathology during respiratory viral infections, including respiratory syncytial virus (RSV), influenza A(H1N1) and importantly SARS-Cov-2. All of these infections can be severe and even lethal in patients with underlying risk factors.A major obstacle in disease prevention is the lack of appropriate efficacious vaccine(s) due to continuous changes in the encoding capacity of the viral genome, exuberant responsiveness of the host immune system and lack of effective antiviral drugs. Current management of these severe respiratory viral infections is limited to supportive clinical care. The primary cause of morbidity and mortality is respiratory failure, partially due to endothelial pulmonary complications, including edema. The latter is induced by the loss of alveolar epithelium integrity and by pathological changes in the endothelial vascular network that regulates blood flow, blood fluidity, exchange of fluids, electrolytes, various macromolecules and responses to signals triggered by oxygenation, and controls trafficking of leukocyte immune cells. This overview outlines the latest understanding of the implications of pulmonary vascular endothelium involvement in respiratory distress syndrome secondary to viral infections. In addition, the roles of infection-induced cytokines, growth factors, and epigenetic reprogramming in endothelial permeability, as well as emerging treatment options to decrease disease burden, are discussed.

Retinal vessels modifications in acute and post-COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by SARS-CoV-2 primarily affecting the respiratory system which can damage vessels walls virtually in any body district. Changes affecting retinal vessels are a good marker for systemic vascular alterations. This study investigated retinal vessels during the acute phase of COVID-19 and after patients recovery. Fifty-nine eyes from 32 COVID-19 patients and 80 eyes from 53 unexposed subjects were included. Mean arteries diameter (MAD) and mean veins diameter (MVD) were assessed through semi-automatic analysis on fundus color photos at baseline and 6 months later in patients and subjects unexposed to the virus. At baseline MAD and MVD were significantly higher in COVID-19 patients compared to unexposed subjects (p < 0.0001). Both MAD and MVD significantly decreased in COVID-19 patients at follow-up (from 97.5 ± 10.9 to 92.2 ± 11.4 µm, p < 0.0001 and from 133.1 ± 19.3 to 124.6 ± 16.1 µm, p < 0.0001, respectively). Despite this reduction vessels diameter remained significantly higher in severe COVID-19 patients compared to unexposed subjects. Transient retinal vessels dilation could serve a biomarker for systemic inflammation while long-lasting alterations seen in severe COVID-19 likely reflect irreversible structural damage to the vessels walls and should be further investigated for their possible effects on tissues perfusion and function.

Association of Low Molecular Weight Plasma Aminothiols with the Severity of Coronavirus Disease 2019

Objective

Aminothiols (glutathione (GSH), cysteinylglycine (CG)) may play an important role in the pathogenesis of coronavirus disease 2019 (COVID-19), but the possible association of these indicators with the severity of COVID-19 has not yet been investigated.

Methods

The total content (t) and reduced forms (r) of aminothiols were determined in patients with COVID-19 (n = 59) on admission. Lung injury was characterized by computed tomography (CT) findings in accordance with the CT0-4 classification.

Results

Low tGSH level was associated with the risk of severe COVID-19 (tGSH ≤ 1.5 μM, mild vs. moderate/severe: risk ratio (RR) = 3.09, p = 0.007) and degree of lung damage (tGSH ≤ 1.8 μM, CT < 2 vs. CT ≥ 2: RR = 2.14, p = 0.0094). The rGSH level showed a negative association with D-dimer levels (ρ = -0.599, p = 0.014). Low rCG level was also associated with the risk of lung damage (rCG ≤ 1.3 μM, CT < 2 vs. CT ≥ 2: RR = 2.28, p = 0.001). Levels of rCG (ρ = -0.339, p = 0.012) and especially tCG (ρ = -0.551, p = 0.004) were negatively associated with platelet count. In addition, a significant relationship was found between the advanced oxidation protein product level and tGSH in patients with moderate or severe but not in patients with mild COVID-19.

Conclusion

Thus, tGSH and rCG can be seen as potential markers for the risk of severe COVID-19. GSH appears to be an important factor to oxidative damage prevention as infection progresses. This suggests the potential clinical efficacy of correcting glutathione metabolism as an adjunct therapy for COVID-19.

Endothelial Activation and Stress Index (EASIX) as an Early Predictor for Mortality and Overall Survival in Hematological and Non-Hematological Patients with COVID-19: Multicenter Cohort Study

COVID-19, as a disease involving the endothelium of multiple organs, is characterized by high mortality rates among hospitalized patients. Patients with hematological malignancies are particularly at risk of an unfavorable course of COVID-19. The endothelial activation and stress index (EASIX) score has been used as a simple predictor of overall survival (OS) in specific groups of hematological cancer patients. EASIX, as a biomarker of endothelial dysfunction, might play a prognostic role in patients with COVID-19. Here, we performed a comprehensive retrospective analysis of the EASIX score in 523 hospitalized COVID-19 patients with or without coexisting hematological cancer. Hematological cancer COVID-19 patients had higher EASIX scores compared to the overall population with COVID-19. In hematological patients, EASIX was a strong predictor of the occurrence of sepsis during COVID-19. Our findings demonstrated EASIX as a strong predictor of intensive care unit admission, in-hospital mortality, the occurrence of acute renal failure and the need for hemodialysis, both in hematological and non-hematological COVID-19 patients. Patients with a high EASIX score on COVID-19 diagnosis had significantly inferior OS compared to patients with low EASIX. We showed for the first time that EASIX might serve as a simple, universal prognostic tool of OS in both hematological and non-hematological COVID-19 patients.

Biological and Clinical Factors Contributing to the Metabolic Heterogeneity of Hospitalized Patients with and without COVID-19

The Corona Virus Disease 2019 (COVID-19) pandemic represents an ongoing worldwide challenge. The present large study sought to understand independent and overlapping metabolic features of samples from acutely ill patients (n = 831) that tested positive (n = 543) or negative (n = 288) for COVID-19. High-throughput metabolomics analyses were complemented with antigen and enzymatic activity assays on plasma from acutely ill patients collected while in the emergency department, at admission, or during hospitalization. Lipidomics analyses were also performed on COVID-19-positive or -negative subjects with the lowest and highest body mass index (n = 60/group). Significant changes in amino acid and fatty acid/acylcarnitine metabolism emerged as highly relevant markers of disease severity, progression, and prognosis as a function of biological and clinical variables in these patients. Further, machine learning models were trained by entering all metabolomics and clinical data from half of the COVID-19 patient cohort and then tested on the other half, yielding ~78% prediction accuracy. Finally, the extensive amount of information accumulated in this large, prospective, observational study provides a foundation for mechanistic follow-up studies and data sharing opportunities, which will advance our understanding of the characteristics of the plasma metabolism in COVID-19 and other acute critical illnesses.

Endothelial Dysfunction, Inflammation, and Oxidative Stress in COVID-19-Mechanisms and Therapeutic Targets

The outbreak of the COVID-19 pandemic represents an ongoing healthcare emergency responsible for more than 3.4 million deaths worldwide. COVID-19 is the disease caused by SARS-CoV-2, a virus that targets not only the lungs but also the cardiovascular system. COVID-19 can manifest with a wide range of clinical manifestations, from mild symptoms to severe forms of the disease, characterized by respiratory failure due to severe alveolar damage. Several studies investigated the underlying mechanisms of the severe lung damage associated with SARS-CoV-2 infection and revealed that the respiratory failure associated with COVID-19 is the consequence not only of acute respiratory distress syndrome but also of macro- and microvascular involvement. New observations show that COVID-19 is an endothelial disease, and the consequent endotheliopathy is responsible for inflammation, cytokine storm, oxidative stress, and coagulopathy. In this review, we show the central role of endothelial dysfunction, inflammation, and oxidative stress in the COVID-19 pathogenesis and present the therapeutic targets deriving from this endotheliopathy.

Redox imbalance links COVID-19 and myalgic encephalomyelitis/chronic fatigue syndrome

Although most patients recover from acute COVID-19, some experience postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection (PASC). One subgroup of PASC is a syndrome called "long COVID-19," reminiscent of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). ME/CFS is a debilitating condition, often triggered by viral and bacterial infections, leading to years-long debilitating symptoms including profound fatigue, postexertional malaise, unrefreshing sleep, cognitive deficits, and orthostatic intolerance. Some are skeptical that either ME/CFS or long COVID-19 involves underlying biological abnormalities. However, in this review, we summarize the evidence that people with acute COVID-19 and with ME/CFS have biological abnormalities including redox imbalance, systemic inflammation and neuroinflammation, an impaired ability to generate adenosine triphosphate, and a general hypometabolic state. These phenomena have not yet been well studied in people with long COVID-19, and each of them has been reported in other diseases as well, particularly neurological diseases. We also examine the bidirectional relationship between redox imbalance, inflammation, energy metabolic deficits, and a hypometabolic state. We speculate as to what may be causing these abnormalities. Thus, understanding the molecular underpinnings of both PASC and ME/CFS may lead to the development of novel therapeutics.

Role of ACE2 in pregnancy and potential implications for COVID-19 susceptibility

In times of coronavirus disease 2019 (COVID-19), the impact of severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 infection on pregnancy is still unclear. The presence of angiotensin-converting enzyme (ACE) 2 (ACE2), the main receptor for SARS-CoV-2, in human placentas indicates that this organ can be vulnerable for viral infection during pregnancy. However, for this to happen, additional molecular processes are critical to allow viral entry in cells, its replication and disease manifestation, particularly in the placenta and/or feto-maternal circulation. Beyond the risk of vertical transmission, COVID-19 is also proposed to deplete ACE2 protein and its biological actions in the placenta. It is postulated that such effects may impair essential processes during placentation and maternal hemodynamic adaptations in COVID-19 pregnancy, features also observed in several disorders of pregnancy. This review gathers information indicating risks and protective features related to ACE2 changes in COVID-19 pregnancies. First, we describe the mechanisms of SARS-CoV-2 infection having ACE2 as a main entry door and current evidence of viral infection in the placenta. Further, we discuss the central role of ACE2 in physiological systems such as the renin-angiotensin system (RAS) and the kallikrein-kinin system (KKS), both active during placentation and hemodynamic adaptations of pregnancy. Significant knowledge gaps are also identified and should be urgently filled to better understand the fate of ACE2 in COVID-19 pregnancies and the potential associated risks. Emerging knowledge will be able to improve the early stratification of high-risk pregnancies with COVID-19 exposure as well as to guide better management and follow-up of these mothers and their children.

Mechanics Insights of Alpha-Lipoic Acid against Cardiovascular Diseases during COVID-19 Infection

Coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, in late December 2019. Since then, COVID-19 has spread rapidly worldwide and was declared a global pandemic on 20 March 2020. Cardiovascular complications are rapidly emerging as a major peril in COVID-19 in addition to respiratory disease. The mechanisms underlying the excessive effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on patients with cardiovascular comorbidities remain only partly understood. SARS-CoV-2 infection is caused by binding of the viral surface spike (S) protein to the human angiotensin-converting enzyme 2 (ACE2), followed by the activation of the S protein by transmembrane protease serine 2 (TMPRSS2). ACE2 is expressed in the lung (mainly in type II alveolar cells), heart, blood vessels, small intestine, etc., and appears to be the predominant portal to the cellular entry of the virus. Based on current information, most people infected with SARS-CoV-2 virus have a good prognosis, while a few patients reach critical condition, especially the elderly and those with chronic underlying diseases. The "cytokine storm" observed in patients with severe COVID-19 contributes to the destruction of the endothelium, leading to "acute respiratory distress syndrome" (ARDS), multiorgan failure, and death. At the origin of the general proinflammatory state may be the SARS-CoV-2-mediated redox status in endothelial cells via the upregulation of ACE/Ang II/AT1 receptors pathway or the increased mitochondrial reactive oxygen species (mtROS) production. Furthermore, this vicious circle between oxidative stress (OS) and inflammation induces endothelial dysfunction, endothelial senescence, high risk of thrombosis and coagulopathy. The microvascular dysfunction and the formation of microthrombi in a way differentiate the SARS-CoV-2 infection from the other respiratory diseases and bring it closer to cardiovascular diseases like myocardial infarction and stroke. Due the role played by OS in the evolution of viral infection and in the development of COVID-19 complications, the use of antioxidants as adjuvant therapy seems appropriate in this new pathology. Alpha-lipoic acid (ALA) could be a promising candidate that, through its wide tissue distribution and versatile antioxidant properties, interferes with several signaling pathways. Thus, ALA improves endothelial function by restoring the endothelial nitric oxide synthase activity and presents an anti-inflammatory effect dependent or independent of its antioxidant properties. By improving mitochondrial function, it can sustain the tissues' homeostasis in critical situation and by enhancing the reduced glutathione it could indirectly strengthen the immune system. This complex analysis could open a new therapeutic perspective for ALA in COVID-19 infection.

The zinc finger transcription factor, KLF2, protects against COVID-19 associated endothelial dysfunction

Coronavirus disease 2019 (COVID-19) is regarded as an endothelial disease (endothelialitis) with its patho-mechanism being incompletely understood. Emerging evidence has demonstrated that endothelial dysfunction precipitates COVID-19 and its accompanying multi-organ injuries. Thus, pharmacotherapies targeting endothelial dysfunction have potential to ameliorate COVID-19 and its cardiovascular complications. The objective of the present study is to evaluate whether kruppel-like factor 2 (KLF2), a master regulator of vascular homeostasis, represents a therapeutic target for COVID-19-induced endothelial dysfunction. Here, we demonstrate that the expression of KLF2 was reduced and monocyte adhesion was increased in endothelial cells treated with COVID-19 patient serum due to elevated levels of pro-adhesive molecules, ICAM1 and VCAM1. IL-1β and TNF-α, two cytokines elevated in cytokine release syndrome in COVID-19 patients, decreased KLF2 gene expression. Pharmacologic (atorvastatin and tannic acid) and genetic (adenoviral overexpression) approaches to augment KLF2 levels attenuated COVID-19-serum-induced increase in endothelial inflammation and monocyte adhesion. Next-generation RNA-sequencing data showed that atorvastatin treatment leads to a cardiovascular protective transcriptome associated with improved endothelial function (vasodilation, anti-inflammation, antioxidant status, anti-thrombosis/-coagulation, anti-fibrosis, and reduced angiogenesis). Finally, knockdown of KLF2 partially reversed the ameliorative effect of atorvastatin on COVID-19-serum-induced endothelial inflammation and monocyte adhesion. Collectively, the present study implicates loss of KLF2 as an important molecular event in the development of COVID-19-induced vascular disease and suggests that efforts to augment KLF2 levels may be therapeutically beneficial.

Biological and Clinical Factors contributing to the Metabolic Heterogeneity of Hospitalized Patients with and without COVID-19

The Corona Virus Disease 2019 (COVID-19) pandemic represents an ongoing worldwide challenge. Exploratory studies evaluating the impact of COVID-19 infection on the plasma metabolome have been performed, often with small numbers of patients, and with or without relevant control data; however, determining the impact of biological and clinical variables remains critical to understanding potential markers of disease severity and progression. The present large study, including relevant controls, sought to understand independent and overlapping metabolic features of samples from acutely ill patients (n = 831), testing positive (n = 543) or negative (n = 288) for COVID-19. High-throughput metabolomics analyses were complemented with antigen and enzymatic activity assays on 831 plasma samples from acutely ill patients while in the emergency department, at admission, and during hospitalization. We then performed additional lipidomics analyses of the 60 subjects with the lowest and highest body mass index, either COVID-19 positive or negative. Omics data were correlated to detailed data on patient characteristics and clinical laboratory assays measuring coagulation, hematology and chemistry analytes. Significant changes in arginine/proline/citrulline, tryptophan/indole/kynurenine, fatty acid and acyl-carnitine metabolism emerged as highly relevant markers of disease severity, progression and prognosis as a function of biological and clinical variables in these patients. Further, machine learning models were trained by entering all metabolomics and clinical data from half of the COVID-19 patient cohort and then tested on the other half yielding ~ 78% prediction accuracy. Finally, the extensive amount of information accumulated in this large, prospective, observational study provides a foundation for follow-up mechanistic studies and data sharing opportunities, which will advance our understanding of the characteristics of the plasma metabolism in COVID-19 and other acute critical illnesses.