High levels of eicosanoids and docosanoids in the lungs of intubated COVID-19 patients

A complex immune communication between eicosanoids and pulmonary macrophages

Respiratory viral infections represent a constant threat for human health and urge for a better understanding of the pulmonary immune response to prevent disease severity. Macrophages are at the center of pulmonary immunity, where they play a pivotal role in orchestrating beneficial and/or pathological outcomes during infection. Eicosanoids, the host bioactive lipid mediators, have re-emerged as important regulators of pulmonary immunity during respiratory viral infections. In this review, we summarize the current knowledge linking eicosanoids' and pulmonary macrophages' homeostatic and antimicrobial functions and discuss eicosanoids as emerging targets for immunotherapy in viral infection.

Prostaglandin E2/Leukotriene B4 balance and viral load in distinct clinical stages of COVID-19: A cross-sectional study

BACKGROUND

Prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) are eicosanoids involved in modulation of the antiviral immune response. Recent studies have identified increased levels of several eicosanoids in the plasma and bronchoalveolar lavage of patients with coronavirus disease (COVID-19). This study investigated correlations between plasma levels of PGE2 and LTB4 and clinical severity of COVID-19.

METHODS

This cross-sectional study involved non-infected (n = 10) individuals and COVID-19 patients classified as cured (n = 13), oligosymptomatic (n = 29), severe (n = 15) or deceased (n = 11). Levels of D-dimer a, known COVID-19 severity marker, PGE2 and LTB4 were measured by ELISAs and data were analysed with respect to viral load.

RESULTS

PGE2 plasma levels were decreased in COVID-19 patients compared to the non-infected group. Changes in PGE2 and LTB4 levels did not correlate with any particular clinical presentations of COVID-19. However, LTB4 was related to decreased SARS-CoV-2 burden in patients, suggesting that only LTB4 is associated with control of viral load.

CONCLUSIONS

Our data indicate that PGE2/LTB4 plasma levels are not associated with COVID-19 clinical severity. Hospitalized patients with COVID-19 are treated with corticosteroids, which may influence the observed eicosanoid imbalance. Additional analyses are required to fully understand the participation of PGE2 receptors in the pathophysiology of COVID-19.

Pla2g5 contributes to viral-like-induced lung inflammation through macrophage proliferation and LA/Ffar1 lung cell recruitment

Macrophages expressing group V phospholipase A2 (Pla2g5) release the free fatty acid (FFA) linoleic acid (LA), potentiating lung type 2 inflammation. Although Pla2g5 and LA increase in viral infections, their role remains obscure. We generated Pla2g5flox/flox mice, deleted Pla2g5 by using the Cx3cr1cre transgene, and activated bone marrow-derived macrophages (BM-Macs) with poly:IC, a synthetic double-stranded RNA that triggers a viral-like immune response, known Pla2g5-dependent stimuli (IL-4, LPS + IFNγ, IL-33 + IL-4 + GM-CSF) and poly:IC + LA followed by lipidomic and transcriptomic analysis. Poly:IC-activated Pla2g5flox/flox;Cx3cr1cre/+ BM-Macs had downregulation of major bioactive lipids and critical enzymes producing those bioactive lipids. In addition, AKT phosphorylation was lower in poly:IC-stimulated Pla2g5flox/flox;Cx3cr1cre/+ BM-Macs, which was not restored by adding LA to poly:IC-stimulated BM-Macs. Consistently, Pla2g5flox/flox;Cx3cr1cre/+ mice had diminished poly:IC-induced lung inflammation, including inflammatory macrophage proliferation, while challenging Pla2g5flox/flox;Cx3cr1cre/+ mice with poly:IC + LA partially restored lung inflammation and inflammatory macrophage proliferation. Finally, mice lacking FFA receptor-1 (Ffar1)-null mice had reduced poly:IC-induced lung cell recruitment and tissue macrophage proliferation, not corrected by LA. Thus, Pla2g5 contributes to poly:IC-induced lung inflammation by regulating inflammatory macrophage proliferation and LA/Ffar1-mediated lung cell recruitment and tissue macrophage proliferation.

Resolution pharmacology and the treatment of infectious diseases

Inflammation is elicited by the host in response to microbes, and is believed to be essential for protection against infection. However, we have previously hypothesized that excessive or misplaced inflammation may be a major contributor to tissue dysfunction and death associated with viral and bacterial infections. The resolutive phase of inflammation is a necessary condition to achieve homeostasis after acute inflammation. It is possible that targeting inflammation resolution may be beneficial for the host during infection. In this review, we summarize the evidence demonstrating the expression, roles and effects of the best described pro-resolving molecules in the context of bacterial and viral infections. Pro-resolving molecules play a pivotal role in modulating a spectrum of pathways associated with tissue inflammation and damage during both viral and bacterial infections. These molecules offer a blend of anti-inflammatory, pro-resolving and sometimes anti-infective benefits, all the while circumventing the undesired and immune-suppressive unwanted effects associated with glucocorticoids. Whether these beneficial effects will translate into benefits to patients clearly deserve further investigation.

Changes in the innate immune response to SARS-CoV-2 with advancing age in humans

BACKGROUND

Advancing age is a major risk factor for respiratory viral infections. The infections are often prolonged and difficult to resolve resulting hospitalizations and mortality. The recent COVID-19 pandemic has highlighted this as elderly subjects have emerged as vulnerable populations that display increased susceptibility and severity to SARS-CoV-2. There is an urgent need to identify the probable mechanisms underlying this to protect against future outbreaks of such nature. Innate immunity is the first line of defense against viruses and its decline impacts downstream immune responses. This is because dendritic cells (DCs) and macrophages are key cellular elements of the innate immune system that can sense and respond to viruses by producing inflammatory mediators and priming CD4 and CD8 T-cell responses.

RESULTS

We investigated the changes in innate immune responses to SARS-CoV-2 as a function of age. Our results using human PBMCs from aged, middle-aged, and young subjects indicate that the activation of DCs and monocytes in response to SARS-CoV-2 is compromised with age. The impairment is most apparent in pDCs where both aged and middle-aged display reduced responses. The secretion of IL-29 that confers protection against respiratory viruses is also decreased in both aged and middle-aged subjects. In contrast, inflammatory mediators associated with severe COVID-19 including CXCL-8, TREM-1 are increased with age. This is also apparent in the gene expression data where pathways related host defense display an age dependent decrease with a concomitant increase in inflammatory pathways. Not only are the inflammatory pathways and mediators increased after stimulation with SARS-CoV-2 but also at homeostasis. In keeping with reduced DC activation, the induction of cytotoxic CD8 T cells is also impaired in aged subjects. However, the CD8 T cells from aged subjects display increased baseline activation in accordance with the enhanced baseline inflammation.

CONCLUSIONS

Our results demonstrate a decline in protective anti-viral immune responses and increase in damaging inflammatory responses with age indicating that dysregulated innate immune responses play a significant role in the increased susceptibility of aged subjects to COVID-19. Furthermore, the dysregulation in immune responses develops early on as middle-aged demonstrate several of these changes.

Small Molecules for the Treatment of Long-COVID-Related Vascular Damage and Abnormal Blood Clotting: A Patent-Based Appraisal

People affected by COVID-19 are exposed to, among others, abnormal clotting and endothelial dysfunction, which may result in deep vein thrombosis, cerebrovascular disorders, and ischemic and non-ischemic heart diseases, to mention a few. Treatments for COVID-19 include antiplatelet (e.g., aspirin, clopidogrel) and anticoagulant agents, but their impact on morbidity and mortality has not been proven. In addition, due to viremia-associated interconnected prothrombotic and proinflammatory events, anti-inflammatory drugs have also been investigated for their ability to mitigate against immune dysregulation due to the cytokine storm. By retrieving patent literature published in the last two years, small molecules patented for long-COVID-related blood clotting and hematological complications are herein examined, along with supporting evidence from preclinical and clinical studies. An overview of the main features and therapeutic potentials of small molecules is provided for the thromboxane receptor antagonist ramatroban, the pan-caspase inhibitor emricasan, and the sodium-hydrogen antiporter 1 (NHE-1) inhibitor rimeporide, as well as natural polyphenolic compounds.

Quantifying neutrophil extracellular trap release in a combined infection-inflammation NET-array device

Excessive release of neutrophil extracellular traps (NETs) has been reported in various human pathologies, including COVID-19 patients. Elevated NET levels serve as a biomarker, indicating increased coagulopathy and immunothrombosis risks in these patients. Traditional immunoassays employed to quantify NET release focus on bulk measurements of released chromatin in simplified microenvironments. In this study, we fabricated a novel NET-array device to quantify NET release from primary human neutrophils with single-cell resolution in the presence of the motile bacteria Pseudomonas aeruginosa PAO1 and inflammatory mediators. The device was engineered to have wide chambers and constricted loops to measure NET release in variably confined spaces. Our open NET-array device enabled immunofluorescent labeling of citrullinated histone H3, a NET release marker. We took time-lapse images of primary healthy human neutrophils releasing NETs in clinically relevant infection and inflammation-rich microenvironments. We then developed a computer-vision-based image processing method to automate the quantification of individual NETs. We showed a significant increase in NET release to Pseudomonas aeruginosa PAO1 when challenged with inflammatory mediators tumor necrosis factor-α [20 ng mL-1] and interleukin-6 [50 ng mL-1], but not leukotriene B4 [20 nM], compared to the infection alone. We also quantified the temporal dynamics of NET release and differences in the relative areas of NETs, showing a high percentage of variable size NET release with combined PAO1 - inflammatory mediator treatment, in the device chambers. Importantly, we demonstrated reduced NET release in the confined loops of our combined infection-inflammation microsystem. Ultimately, our NET-array device stands as a valuable tool, facilitating experiments that enhance our comprehension of the spatiotemporal dynamics of NET release in response to infection within a defined microenvironment. In the future, our system can be used for high throughput and cost-effective screening of novel immunotherapies on human neutrophils in view of the importance of fine-tuning NET release in controlling pathological neutrophil-driven inflammation.

Lipid Metabolism Modulation during SARS-CoV-2 Infection: A Spotlight on Extracellular Vesicles and Therapeutic Prospects

Extracellular vesicles (EVs) have a significant impact on the pathophysiological processes associated with various diseases such as tumors, inflammation, and infection. They exhibit molecular, biochemical, and entry control characteristics similar to viral infections. Viruses, on the other hand, depend on host metabolic machineries to fulfill their biosynthetic requirements. Due to potential advantages such as biocompatibility, biodegradation, and efficient immune activation, EVs have emerged as potential therapeutic targets against the SARS-CoV-2 infection. Studies on COVID-19 patients have shown that they frequently have dysregulated lipid profiles, which are associated with an increased risk of severe repercussions. Lipid droplets (LDs) serve as organelles with significant roles in lipid metabolism and energy homeostasis as well as having a wide range of functions in infections. The down-modulation of lipids, such as sphingolipid ceramide and eicosanoids, or of the transcriptional factors involved in lipogenesis seem to inhibit the viral multiplication, suggesting their involvement in the virus replication and pathogenesis as well as highlighting their potential as targets for drug development. Hence, this review focuses on the role of modulation of lipid metabolism and EVs in the mechanism of immune system evasion during SARS-CoV-2 infection and explores the therapeutic potential of EVs as well as application for delivering therapeutic substances to mitigate viral infections.

The effect of SARS-CoV-2 variants on the plasma oxylipins and PUFAs of COVID-19 patients

Oxylipins are important signalling compounds that are significantly involved in the regulation of the immune system and the resolution of inflammation. Lipid metabolism is strongly activated upon SARS-CoV-2 infection, however the modulating effects of oxylipins induced by different variants remain unexplored. Here, we compare the plasma profiles of thirty-seven oxylipins and four PUFAs in subjects infected with Wild-type, Alpha (B.1.1.7), Delta (B.1.617.2), and Omicron (B.1.1.529) variants. The results suggest that oxidative stress and inflammation resulting from COVID-19 were highly dependent on the SARS-CoV-2 variant, and that the Wild-type elicited the strongest inflammatory storm. The Alpha and Delta variants induced a comparable lipid profile alteration upon infection, which differed significantly from Omicron. The latter variant increased the levels of pro-inflammatory mediators and decreased the levels of omega-3 PUFA in infected patients. We speculate that changes in therapeutics, vaccination, and prior infections may have a role in the alteration of the oxylipin profile besides viral mutations. The results shed new light on the evolution of the inflammatory response in COVID-19.

The therapeutic potential of resolvins in pulmonary diseases

Uncontrolled inflammation leads to nonspecific destruction and remodeling of tissues and can contribute to many human pathologies, including pulmonary diseases. Stimulation of inflammatory resolution is considered an important process that protects against the progression of chronic inflammatory diseases. Resolvins generated from essential omega-3 polyunsaturated fatty acids have been demonstrated to be signaling molecules in inflammation with important pro-resolving and anti-inflammatory capabilities. By binding to specific receptors, resolvins can modulate inflammatory processes such as neutrophil migration, macrophage phagocytosis and the presence of pro-inflammatory mediators to reduce inflammatory pathologies. The discovery of these pro-resolving mediators has led to a shift in drug research from suppressing pro-inflammatory molecules to investigating compounds that promote resolution to treat inflammation. The exploration of inflammatory resolution also provided the opportunity to further understand the pathophysiology of pulmonary diseases. Alterations of resolution are now linked to both the development and exacerbation of diseases such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, acute respiratory distress syndrome, cancer and COVID-19. These findings have resulted in the rise of novel design and testing of innovative resolution-based therapeutics to treat diseases. Hence, this paper reviews the generation and mechanistic actions of resolvins and investigates their role and therapeutic potential in several pulmonary diseases that may benefit from resolution-based pharmaceuticals.

Deep phenotyping of the lipidomic response in COVID-19 and non-COVID-19 sepsis

BACKGROUND

Lipids may influence cellular penetrance by viral pathogens and the immune response that they evoke. We deeply phenotyped the lipidomic response to SARs-CoV-2 and compared that with infection with other pathogens in patients admitted with acute respiratory distress syndrome to an intensive care unit (ICU).

METHODS

Mass spectrometry was used to characterise lipids and relate them to proteins, peripheral cell immunotypes and disease severity.

RESULTS

Circulating phospholipases (sPLA2, cPLA2 (PLA2G4A) and PLA2G2D) were elevated on admission in all ICU groups. Cyclooxygenase, lipoxygenase and epoxygenase products of arachidonic acid (AA) were elevated in all ICU groups compared with controls. sPLA2 predicted severity in COVID-19 and correlated with TxA2, LTE4 and the isoprostane, iPF2α-III, while PLA2G2D correlated with LTE4. The elevation in PGD2, like PGI2 and 12-HETE, exhibited relative specificity for COVID-19 and correlated with sPLA2 and the interleukin-13 receptor to drive lymphopenia, a marker of disease severity. Pro-inflammatory eicosanoids remained correlated with severity in COVID-19 28 days after admission. Amongst non-COVID ICU patients, elevations in 5- and 15-HETE and 9- and 13-HODE reflected viral rather than bacterial disease. Linoleic acid (LA) binds directly to SARS-CoV-2 and both LA and its di-HOME products reflected disease severity in COVID-19. In healthy marines, these lipids rose with seroconversion. Eicosanoids linked variably to the peripheral cellular immune response. PGE2, TxA2 and LTE4 correlated with T cell activation, as did PGD2 with non-B non-T cell activation. In COVID-19, LPS stimulated peripheral blood mononuclear cell PGF2α correlated with memory T cells, dendritic and NK cells while LA and DiHOMEs correlated with exhausted T cells. Three high abundance lipids - ChoE 18:3, LPC-O-16:0 and PC-O-30:0 - were altered specifically in COVID. LPC-O-16:0 was strongly correlated with T helper follicular cell activation and all three negatively correlated with multi-omic inflammatory pathways and disease severity.

CONCLUSIONS

A broad based lipidomic storm is a predictor of poor prognosis in ARDS. Alterations in sPLA2, PGD2 and 12-HETE and the high abundance lipids, ChoE 18:3, LPC-O-16:0 and PC-O-30:0 exhibit relative specificity for COVID-19 amongst such patients and correlate with the inflammatory response to link to disease severity.

Eicosanoids Signals in SARS-CoV-2 Infection: A Foe or Friend

SARS-CoV-2 mediated infection instigated a scary pandemic state since 2019. They created havoc comprising death, imbalanced social structures, and a wrecked global economy. During infection, the inflammation and associated cytokine storm generate a critical pathological situation in the human body, especially in the lungs. By the passage of time of infection, inflammatory disorders, and multiple organ damage happen which might lead to death, if not treated properly. Until now, many pathological parameters have been used to understand the progress of the severity of COVID-19 but with limited success. Bioactive lipid mediators have the potential of initiating and resolving inflammation in any disease. The connection between lipid storm and inflammatory states of SARS-CoV-2 infection has surfaced and got importance to understand and mitigate the pathological states of COVID-19. As the role of eicosanoids in COVID-19 infection is not well defined, available information regarding this issue has been accumulated to address the possible network of eicosanoids related to the initiation of inflammation, promotion of cytokine storm, and resolution of inflammation, and highlight possible strategies for treatment and drug discovery related to SARS-CoV-2 infection in this study. Understanding the involvement of eicosanoids in exploration of cellular events provoked by SARS-CoV-2 infection has been summarized as an important factor to deescalate any upcoming catastrophe imposed by the lethal variants of this micro-monster. Additionally, this study also recognized the eicosanoid based drug discovery, treatment, and strategies for managing the severity of SARS-COV-2 infection.

Specialized pro-resolving lipid mediators and resolution of viral diseases

The COVID-19 pandemics has made sparkly evident the importance of acute inflammation and its timely resolution to protect humans from pathogenic viruses while sparing them from collateral damages due to an uncontrolled immune response. It is clear now that resolution of inflammation is an active process regulated by endogenous specialized proresolving lipid mediators (SPM) biosynthesized from essential polyunsaturated fatty acids. Accruing evidence indicates that SPM are produced during viral infections and play key roles in controlling the magnitude and duration of the inflammatory response and in regulating adaptive immunity. Here, we reviewed biosynthesis and bioactions of SPM in virus-mediated human diseases. Harnessing SPM and their proresolutive actions can help in providing new therapeutic approaches to current and future human viral diseases by controlling infection, stimulating host immunity, and protecting from organ damage.

Metabolomics-directed nanotechnology in viral diseases management: COVID-19 a case study

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently regarded as the twenty-first century's plague accounting for coronavirus disease 2019 (COVID-19). Besides its reported symptoms affecting the respiratory tract, it was found to alter several metabolic pathways inside the body. Nanoparticles proved to combat viral infections including COVID-19 to demonstrate great success in developing vaccines based on mRNA technology. However, various types of nanoparticles can affect the host metabolome. Considering the increasing proportion of nano-based vaccines, this review compiles and analyses how COVID-19 and nanoparticles affect lipids, amino acids, and carbohydrates metabolism. A search was conducted on PubMed, ScienceDirect, Web of Science for available information on the interrelationship between metabolomics and immunity in the context of SARS-CoV-2 infection and the effect of nanoparticles on metabolite levels. It was clear that SARS-CoV-2 disrupted several pathways to ensure a sufficient supply of its building blocks to facilitate its replication. Such information can help in developing treatment strategies against viral infections and COVID-19 based on interventions that overcome these metabolic changes. Furthermore, it showed that even drug-free nanoparticles can exert an influence on biological systems as evidenced by metabolomics.

Eicosapentaenoic Acid Influences the Lipid Profile of an In Vitro Psoriatic Skin Model Produced with T Cells

Psoriasis is a skin disease characterized by epidermal hyperplasia and an inappropriate activation of the adaptive immunity. A dysregulation of the skin's lipid mediators is reported in the disease with a predominance of the inflammatory cascade derived from n-6 polyunsaturated fatty acids (n-6 PUFAs). Bioactive lipid mediators derived from arachidonic acid (AA) are involved in the inflammatory functions of T cells in psoriasis, whereas n-3 PUFAs' derivatives are anti-inflammatory metabolites. Here, we sought to evaluate the influence of a supplementation of the culture media with eicosapentaenoic acid (EPA) on the lipid profile of a psoriatic skin model produced with polarized T cells. Healthy and psoriatic skin substitutes were produced following the auto-assembly technique. Psoriatic skin substitutes produced with or without T cells presented increased epidermal and dermal linolenic acid (LA) and AA levels. N-6 PUFA lipid mediators were strongly measured in psoriatic substitutes, namely, 13-hydroxyoctadecadienoic acid (13-HODE), prostaglandin E2 (PGE2) and 12-hydroxyeicosatetraenoic acid (12-HETE). The added EPA elevated the amounts of EPA, n-3 docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) in the epidermal and dermal phospholipids. The EPA supplementation balanced the production of epidermal lipid mediators, with an increase in prostaglandin E3 (PGE3), 12-hydroxyeicosapentaenoic acid (12-HEPE) and N-eicosapentaenoyl-ethanolamine (EPEA) levels. These findings show that EPA modulates the lipid composition of psoriatic skin substitutes by encouraging the return to a cutaneous homeostatic state.

Chronic inflammation, neuroglial dysfunction, and plasmalogen deficiency as a new pathobiological hypothesis addressing the overlap between post-COVID-19 symptoms and myalgic encephalomyelitis/chronic fatigue syndrome

After five waves of coronavirus disease 2019 (COVID-19) outbreaks, it has been recognized that a significant portion of the affected individuals developed long-term debilitating symptoms marked by chronic fatigue, cognitive difficulties ("brain fog"), post-exertional malaise, and autonomic dysfunction. The onset, progression, and clinical presentation of this condition, generically named post-COVID-19 syndrome, overlap significantly with another enigmatic condition, referred to as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Several pathobiological mechanisms have been proposed for ME/CFS, including redox imbalance, systemic and central nervous system inflammation, and mitochondrial dysfunction. Chronic inflammation and glial pathological reactivity are common hallmarks of several neurodegenerative and neuropsychiatric disorders and have been consistently associated with reduced central and peripheral levels of plasmalogens, one of the major phospholipid components of cell membranes with several homeostatic functions. Of great interest, recent evidence revealed a significant reduction of plasmalogen contents, biosynthesis, and metabolism in ME/CFS and acute COVID-19, with a strong association to symptom severity and other relevant clinical outcomes. These bioactive lipids have increasingly attracted attention due to their reduced levels representing a common pathophysiological manifestation between several disorders associated with aging and chronic inflammation. However, alterations in plasmalogen levels or their lipidic metabolism have not yet been examined in individuals suffering from post-COVID-19 symptoms. Here, we proposed a pathobiological model for post-COVID-19 and ME/CFS based on their common inflammation and dysfunctional glial reactivity, and highlighted the emerging implications of plasmalogen deficiency in the underlying mechanisms. Along with the promising outcomes of plasmalogen replacement therapy (PRT) for various neurodegenerative/neuropsychiatric disorders, we sought to propose PRT as a simple, effective, and safe strategy for the potential relief of the debilitating symptoms associated with ME/CFS and post-COVID-19 syndrome.

Lipid Mediators and Cytokines/Chemokines Display Differential Profiles in Severe versus Mild/Moderate COVID-19 Patients

Host immune responses play a key role in COVID-19 pathogenesis. The underlying phenomena are orchestrated by signaling molecules such as cytokines/chemokines and lipid mediators. These immune molecules, including anti-SARS-CoV-2 antibodies, interact with immune cells and regulate host responses, contributing to inflammation that drives the disease. We investigated 48 plasma cytokines/chemokines, 21 lipid mediators, and anti-S protein (RBD) antibodies in COVID-19 patients (n = 56) and non-COVID-19 respiratory disease controls (n = 49), to identify immune-biomarker profiles. Cytokines/chemokines (IL-6, CXCL-10 (IP-10), HGF, MIG, MCP-1, and G-CSF) and lipid mediators (TxB2, 11-HETE, 9-HODE, 13-HODE, 5-HETE, 12-HETE, 15-HETE, 14S-HDHA, 17S-HDHA, and 5-oxo ETE) were significantly elevated in COVID-19 patients compared to controls. In patients exhibiting severe disease, pro-inflammatory cytokines/chemokines (IL-6, CXCL-10, and HGF) and anti-SARS-CoV-2 antibodies were significantly elevated. In contrast, lipid mediators involved in the reduction/resolution of inflammation, in particular, 5-HETE, 11-HETE, and 5-oxoETE, were significantly elevated in mild/moderate disease. Taken together, these immune-biomarker profiles provide insight into immune responses related to COVID-19 pathogenesis. Importantly, our findings suggest that elevation in plasma concentrations of IL-6, CXCL-10, HGF, and anti-SARS-CoV-2 antibodies can predict severe disease, whereas elevation in lipid mediators peaks early (compared to cytokines) and includes induction of mechanisms leading to reduction of inflammation, associated complications, and maintenance of homeostasis.

Mammalian lipid droplets: structural, pathological, immunological and anti-toxicological roles

Mammalian lipid droplets (LDs) are specialized cytosolic organelles consisting of a neutral lipid core surrounded by a membrane made up of a phospholipid monolayer and a specific population of proteins that varies according to the location and function of each LD. Over the past decade, there have been significant advances in the understanding of LD biogenesis and functions. LDs are now recognized as dynamic organelles that participate in many aspects of cellular homeostasis plus other vital functions. LD biogenesis is a complex, highly-regulated process with assembly occurring on the endoplasmic reticulum although aspects of the underpinning molecular mechanisms remain elusive. For example, it is unclear how many enzymes participate in the biosynthesis of the neutral lipid components of LDs and how this process is coordinated in response to different metabolic cues to promote or suppress LD formation and turnover. In addition to enzymes involved in the biosynthesis of neutral lipids, various scaffolding proteins play roles in coordinating LD formation. Despite their lack of ultrastructural diversity, LDs in different mammalian cell types are involved in a wide range of biological functions. These include roles in membrane homeostasis, regulation of hypoxia, neoplastic inflammatory responses, cellular oxidative status, lipid peroxidation, and protection against potentially toxic intracellular fatty acids and lipophilic xenobiotics. Herein, the roles of mammalian LDs and their associated proteins are reviewed with a particular focus on their roles in pathological, immunological and anti-toxicological processes.

Specialized Pro-Resolving Lipid Mediators: Endogenous Roles and Pharmacological Activities in Infections

During an infection, inflammation mobilizes immune cells to eliminate the pathogen and protect the host. However, inflammation can be detrimental when exacerbated and/or chronic. The resolution phase of the inflammatory process is actively orchestrated by the specialized pro-resolving lipid mediators (SPMs), generated from omega-3 and -6 polyunsaturated fatty acids (PUFAs) that bind to different G-protein coupled receptors to exert their activity. As immunoresolvents, SPMs regulate the influx of leukocytes to the inflammatory site, reduce cytokine and chemokine levels, promote bacterial clearance, inhibit the export of viral transcripts, enhance efferocytosis, stimulate tissue healing, and lower antibiotic requirements. Metabolomic studies have evaluated SPM levels in patients and animals during infection, and temporal regulation of SPMs seems to be essential to properly coordinate a response against the microorganism. In this review, we summarize the current knowledge on SPM biosynthesis and classifications, endogenous production profiles and their effects in animal models of bacterial, viral and parasitic infections.

Metabolic alterations upon SARS-CoV-2 infection and potential therapeutic targets against coronavirus infection

The coronavirus disease 2019 (COVID-19) caused by coronavirus SARS-CoV-2 infection has become a global pandemic due to the high viral transmissibility and pathogenesis, bringing enormous burden to our society. Most patients infected by SARS-CoV-2 are asymptomatic or have mild symptoms. Although only a small proportion of patients progressed to severe COVID-19 with symptoms including acute respiratory distress syndrome (ARDS), disseminated coagulopathy, and cardiovascular disorders, severe COVID-19 is accompanied by high mortality rates with near 7 million deaths. Nowadays, effective therapeutic patterns for severe COVID-19 are still lacking. It has been extensively reported that host metabolism plays essential roles in various physiological processes during virus infection. Many viruses manipulate host metabolism to avoid immunity, facilitate their own replication, or to initiate pathological response. Targeting the interaction between SARS-CoV-2 and host metabolism holds promise for developing therapeutic strategies. In this review, we summarize and discuss recent studies dedicated to uncovering the role of host metabolism during the life cycle of SARS-CoV-2 in aspects of entry, replication, assembly, and pathogenesis with an emphasis on glucose metabolism and lipid metabolism. Microbiota and long COVID-19 are also discussed. Ultimately, we recapitulate metabolism-modulating drugs repurposed for COVID-19 including statins, ASM inhibitors, NSAIDs, Montelukast, omega-3 fatty acids, 2-DG, and metformin.

Serum lipid mediator profiles in COVID-19 patients and lung disease severity: a pilot study

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection is highly heterogeneous, ranging from asymptomatic to severe and fatal cases. COVID-19 has been characterized by an increase of serum pro-inflammatory cytokine levels which seems to be associated with fatal cases. By contrast, the role of pro-resolving lipid mediators (SPMs), involved in the attenuation of inflammatory responses, has been scarcely investigated, so further studies are needed to understand SPMs metabolism in COVID-19 and other infectious diseases. Our aim was to analyse the lipid mediator metabolome, quantifying pro- and anti-inflammatory serum bioactive lipids by LC-MS/MS in 7 non-infected subjects and 24 COVID-19 patients divided into mild, moderate, and severe groups according to the pulmonary involvement, to better understand the disease outcome and the severity of the pulmonary manifestations. Statistical analysis was performed with the R programming language (R Foundation for Statistical Computing, Vienna, Austria). All COVID-19 patients had increased levels of Prostaglandin E₂. Severe patients showed a significant increase versus controls, mild- and moderate-affected patients, expressed as median (interquartile range), in resolvin E1 [112.6 (502.7) vs 0.0 (0.0) pg/ml in the other groups], as well as in maresin 2 [14.5 (7.0) vs 8.1 (4.2), 5.5 (4.3), and 3.0 (4.0) pg/ml, respectively]. Moreover, 14-hydroxy docosahexaenoic acid (14-HDHA) levels were also increased in severe vs control and mild-affected patients [24.7 (38.2) vs 2.4 (2.2) and 3.7 (6.4) ng/mL, respectively]. Resolvin D5 was also significantly elevated in both moderate [15.0 (22.4) pg/ml] and severe patients [24.0 (24.1) pg/ml] versus controls [0.0 (0.0) pg/ml]. These results were confirmed by sparse partial least squares discriminant analysis which highlighted the contribution of these mediators to the separation between each of the groups. In conclusion, the potent inflammatory response to SARS-CoV-2 infection involves not only pro- but also anti-inflammatory lipid mediators that can be quantified in easily accessible serum samples, suggesting the need to perform future research on their generation pathways that will help us to discover new therapeutic targets.

Explanatory predictive model for COVID-19 severity risk employing machine learning, shapley addition, and LIME

The rapid spread of SARS-CoV-2 threatens global public health and impedes the operation of healthcare systems. Several studies have been conducted to confirm SARS-CoV-2 infection and examine its risk factors. To produce more effective treatment options and vaccines, it is still necessary to investigate biomarkers and immune responses in order to gain a deeper understanding of disease pathophysiology. This study aims to determine how cytokines influence the severity of SARS-CoV-2 infection. We measured the plasma levels of 48 cytokines in the blood of 87 participants in the COVID-19 study. Several Classifiers were trained and evaluated using Machine Learning and Deep Learning to complete missing data, generate synthetic data, and fill in any gaps. To examine the relationship between cytokine storm and COVID-19 severity in patients, the Shapley additive explanation (SHAP) and the LIME (Local Interpretable Model-agnostic Explanations) model were applied. Individuals with severe SARS-CoV-2 infection had elevated plasma levels of VEGF-A, MIP-1b, and IL-17. RANTES and TNF were associated with healthy individuals, whereas IL-27, IL-9, IL-12p40, and MCP-3 were associated with non-Severity. These findings suggest that these cytokines may promote the development of novel preventive and therapeutic pathways for disease management. In this study, the use of artificial intelligence is intended to support clinical diagnoses of patients to determine how each cytokine may be responsible for the severity of COVID-19, which could lead to the identification of several cytokines that could aid in treatment decision-making and vaccine development.

Mixed storm in SARS-CoV-2 infection: A narrative review and new term in the Covid-19 era

Coronavirus disease 2019 (Covid-19) is caused by a novel severe acute respiratory syndrome coronavirus virus type 2 (SARS-CoV-2) leading to the global pandemic worldwide. Systemic complications in Covid-19 are mainly related to the direct SARS-CoV-2 cytopathic effects, associated hyperinflammation, hypercytokinemia, and the development of cytokine storm (CS). As well, Covid-19 complications are developed due to the propagation of oxidative and thrombotic events which may progress to a severe state called oxidative storm and thrombotic storm (TS), respectively. In addition, inflammatory and lipid storms are also developed in Covid-19 due to the activation of inflammatory cells and the release of bioactive lipids correspondingly. Therefore, the present narrative review aimed to elucidate the interrelated relationship between different storm types in Covid-19 and the development of the mixed storm (MS). In conclusion, SARS-CoV-2 infection induces various storm types including CS, inflammatory storm, lipid storm, TS and oxidative storm. These storms are not developing alone since there is a close relationship between them. Therefore, the MS seems to be more appropriate to be related to severe Covid-19 than CS, since it develops in Covid-19 due to the intricate interface between reactive oxygen species, proinflammatory cytokines, complement activation, coagulation disorders, and activated inflammatory signaling pathway.

Formation of lipoxins and resolvins in human leukocytes

Specialized pro-resolving lipid mediators (SPMs) such as lipoxins or resolvins are formed by the consecutive action of 5-lipoxygenase (5-LO, ALOX5) and different types of arachidonic acid 12- or 15-lipoxygenases using arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid as substrate. Lipoxins are trihydroxylated oxylipins which are formed from arachidonic and eicosapentaenoic acid. The latter can also be converted to di- and trihydroxylated resolvins of the E series, whereas docosahexaenoic acid is the substrate for the formation of di- and trihydroxylated resolvins of the D series. Here, we summarize the formation of lipoxins and resolvins in leukocytes. From the data published so far, it becomes evident that FLAP is required for the biosynthesis of most of the lipoxins and resolvins. Even in the presence of FLAP, formation of the trihydroxylated SPMs (lipoxins, RvD1-RvD4, RvE1) in leukocytes is very low or undetectable which is obviously due to the extremely low epoxide formation by 5-LO from oxylipins such as 15-H(p)ETE, 18-H(p)EPE or 17-H(p)DHA. As a result, only the dihydroxylated oxylipins (5 S,15S-diHETE, 5 S,15S-diHEPE) and resolvins (RvD5, RvE2, RvE4) can be consistently detected using leukocytes as SPM source. However, the reported levels of these dihydroxylated lipid mediators are still much lower than those of the typical pro-inflammatory mediators including the monohydroxylated fatty acid derivatives (e.g. 5-HETE), leukotrienes or cyclooxygenase-derived prostaglandins. Since 5-LO expression is mainly restricted to leukocytes these cells are considered as the main source of SPMs. The low formation of trihydroxylated SPMs in leukocytes, the fact that they are hardly detected in biological samples as well as the lack of functional signaling by their receptors make it highly questionable that trihydroxylated SPMs play a role as endogenous mediators in the resolution of inflammation.

Factors affecting variability in free oxylipins in mammalian tissues

PURPOSE OF THE REVIEW

Along with the growing interest in oxylipins is an increasing awareness of multiple sources of variability in oxylipin data. This review summarizes recent findings that highlight the experimental and biological sources of variation in free oxylipins.

RECENT FINDINGS

Experimental factors that affect oxylipin variability include different methods of euthanasia, postmortem changes, cell culture reagents, tissue processing conditions and timing, storage losses, freeze-thaw cycles, sample preparation techniques, ion suppression, matrix effects, use and availability of oxylipin standards, and postanalysis procedures. Biological factors include dietary lipids, fasting, supplemental selenium, vitamin A deficiency, dietary antioxidants and the microbiome. Overt, but also more subtle differences in health affect oxylipin levels, including during resolution of inflammation and long-term recovery from disease. Sex, genetic variation, exposure to air pollution and chemicals found in food packaging and household and personal care products, as well as many pharmaceuticals used to treat health conditions also affect oxylipin levels.

SUMMARY

Experimental sources of oxylipin variability can be minimized with proper analytical procedures and protocol standardization. Fully characterizing study parameters will help delineate biological factors of variability, which are rich sources of information that can be used to probe oxylipin mechanisms of action and to investigate their roles in health.

Evaluation of urinary cysteinyl leukotrienes as biomarkers of severity and putative therapeutic targets in COVID-19 patients

BACKGROUND

Cysteinyl leukotrienes (CysLT) are potent inflammation-promoting mediators, but remain scarcely explored in COVID-19. We evaluated urinary CysLT (U-CysLT) relationship with disease severity and their usefulness for prognostication in hospitalized COVID-19 patients. The impact on U-CysLT of veno-venous extracorporeal membrane oxygenation (VV-ECMO) and of comorbidities such as hypertension and obesity was also assessed.

METHODS

Blood and spot urine were collected in "severe" (n = 26), "critically ill" (n = 17) and "critically ill on VV-ECMO" (n = 17) patients with COVID-19 at days 1-2 (admission), 3-4, 5-8 and weekly thereafter, and in controls (n = 23) at a single time point. U-CysLT were measured by ELISA. Routine markers, prognostic scores and outcomes were also evaluated.

RESULTS

U-CysLT did not differ between groups at admission, but significantly increased along hospitalization only in critical groups, being markedly higher in VV-ECMO patients, especially in hypertensives. U-CysLT values during the first week were positively associated with ICU and total hospital length of stay in critical groups and showed acceptable area under curve (AUC) for prediction of 30-day mortality (AUC: 0.734, p = 0.001) among all patients.

CONCLUSIONS

U-CysLT increase during hospitalization in critical COVID-19 patients, especially in hypertensives on VV-ECMO. U-CysLT association with severe outcomes suggests their usefulness for prognostication and as therapeutic targets.

Cryo-EM reveals binding of linoleic acid to SARS-CoV-2 spike glycoprotein, suggesting an antiviral treatment strategy

The COVID-19 pandemic and concomitant lockdowns presented a global health challenge and triggered unprecedented research efforts to elucidate the molecular mechanisms and pathogenicity of SARS-CoV-2. The spike glycoprotein decorating the surface of SARS-CoV-2 virions is a prime target for vaccine development, antibody therapy and serology as it binds the host cell receptor and is central for viral cell entry. The electron cryo-microscopy structure of the spike protein revealed a hydrophobic pocket in the receptor-binding domain that is occupied by an essential fatty acid, linoleic acid (LA). The LA-bound spike protein adopts a non-infectious locked conformation which is more stable than the infectious form and shields important immunogenic epitopes. Here, the impact of LA binding on viral infectivity and replication, and the evolutionary conservation of the pocket in other highly pathogenic coronaviruses, including SARS-CoV-2 variants of concern (VOCs), are reviewed. The importance of LA metabolic products, the eicosanoids, in regulating the human immune response and inflammation is highlighted. Lipid and fatty-acid binding to a hydrophobic pocket in proteins on the virion surface appears to be a broader strategy employed by viruses, including picornaviruses and Zika virus. Ligand binding stabilizes their protein structure and assembly, and downregulates infectivity. In the case of rhinoviruses, this has been exploited to develop small-molecule antiviral drugs that bind to the hydrophobic pocket. The results suggest a COVID-19 antiviral treatment based on the LA-binding pocket.

Leukotrienes in Innate Immunity: Still Underappreciated after All These Years?

Leukotrienes (LTs) are lipid mediators derived from the 5-lipoxygenase pathway of arachidonate metabolism. Though best known for their role in asthma, they have broad actions that touch on virtually every aspect of mammalian biology. In a Brief Review published in the journal in 2005, we presented the existing evidence supporting a role for LTs in host defense. In this updated Brief Review, we focus on selected advances since then. We detail new insights into mechanisms and regulation of LT biosynthesis; the protective roles of LTs in the host response to diverse classes of pathogens, with an emphasis on viruses, including SARS-CoV-2; the phagocyte signal transduction mechanisms by which LTs exert their antimicrobial actions; the capacity for overexuberant LT production to promote tissue damage; and roles of LTs in the noninfectious immune-relevant conditions neuroinflammation and cancer.

Endotoxin tolerance and low activation of TLR-4/NF-κB axis in monocytes of COVID-19 patients

Higher endotoxin in the circulation may indicate a compromised state of host immune response against coinfections in severe COVID-19 patients. We evaluated the inflammatory response of monocytes from COVID-19 patients after lipopolysaccharide (LPS) challenge. Whole blood samples of healthy controls, patients with mild COVID-19, and patients with severe COVID-19 were incubated with LPS for 2 h. Severe COVID-19 patients presented higher LPS and sCD14 levels in the plasma than healthy controls and mild COVID-19 patients. In non-stimulated in vitro condition, severe COVID-19 patients presented higher inflammatory cytokines and PGE-2 levels and CD14 + HLA-DR^low monocytes frequency than controls. Moreover, severe COVID-19 patients presented higher NF-κB p65 phosphorylation in CD14 + HLA-DR^low, as well as higher expression of TLR-4 and NF-κB p65 phosphorylation in CD14 + HLA-DR^high compared to controls. The stimulation of LPS in whole blood of severe COVID-19 patients leads to lower cytokine production but higher PGE-2 levels compared to controls. Endotoxin challenge with both concentrations reduced the frequency of CD14 + HLA-DR^low in severe COVID-19 patients, but the increases in TLR-4 expression and NF-κB p65 phosphorylation were more pronounced in both CD14 + monocytes of healthy controls and mild COVID-19 patients compared to severe COVID-19 group. We conclude that acute SARS-CoV-2 infection is associated with diminished endotoxin response in monocytes. KEY MESSAGES: Severe COVID-19 patients had higher levels of LPS and systemic IL-6 and TNF-α. Severe COVID-19 patients presented higher CD14+HLA-DRlow monocytes. Increased TLR-4/NF-κB axis was identified in monocytes of severe COVID-19. Blunted production of cytokines after whole blood LPS stimulation in severe COVID-19. Lower TLR-4/NF-κB activation in monocytes after LPS stimulation in severe COVID-19.

Thrombo-Inflammation in COVID-19 and Sickle Cell Disease: Two Faces of the Same Coin

People with sickle cell disease (SCD) are at greater risk of severe illness and death from respiratory infections, including COVID-19, than people without SCD (Centers for Disease Control and Prevention, USA). Vaso-occlusive crises (VOC) in SCD and severe SARS-CoV-2 infection are both characterized by thrombo-inflammation mediated by endothelial injury, complement activation, inflammatory lipid storm, platelet activation, platelet-leukocyte adhesion, and activation of the coagulation cascade. Notably, lipid mediators, including thromboxane A2, significantly increase in severe COVID-19 and SCD. In addition, the release of thromboxane A2 from endothelial cells and macrophages stimulates platelets to release microvesicles, which are harbingers of multicellular adhesion and thrombo-inflammation. Currently, there are limited therapeutic strategies targeting platelet-neutrophil activation and thrombo-inflammation in either SCD or COVID-19 during acute crisis. However, due to many similarities between the pathobiology of thrombo-inflammation in SCD and COVID-19, therapies targeting one disease may likely be effective in the other. Therefore, the preclinical and clinical research spurred by the COVID-19 pandemic, including clinical trials of anti-thrombotic agents, are potentially applicable to VOC. Here, we first outline the parallels between SCD and COVID-19; second, review the role of lipid mediators in the pathogenesis of these diseases; and lastly, examine the therapeutic targets and potential treatments for the two diseases.

Dissecting Platelet's Role in Viral Infection: A Double-Edged Effector of the Immune System

Platelets play a major role in the processes of primary hemostasis and pathological inflammation-induced thrombosis. In the mid-2000s, several studies expanded the role of these particular cells, placing them in the "immune continuum" and thus changing the understanding of their function in both innate and adaptive immune responses. Among the many receptors they express on their surface, platelets express Toll-Like Receptors (TLRs), key receptors in the inflammatory cell-cell reaction and in the interaction between innate and adaptive immunity. In response to an infectious stimulus, platelets will become differentially activated. Platelet activation is variable depending on whether platelets are activated by a hemostatic or pathogen stimulus. This review highlights the role that platelets play in platelet modulation count and adaptative immune response during viral infection.

Home as the new frontier for the treatment of COVID-19: the case for anti-inflammatory agents

COVID-19, caused by SARS-CoV-2, is characterised by a broad spectrum of symptom severity that requires varying amounts of care according to the different stages of the disease. Intervening at the onset of mild to moderate COVID-19 symptoms in the outpatient setting would provide the opportunity to prevent progression to a more severe illness and long-term complications. As early disease symptoms variably reflect an underlying excessive inflammatory response to the viral infection, the use of anti-inflammatory drugs, especially non-steroidal anti-inflammatory drugs (NSAIDs), in the initial outpatient stage of COVID-19 seems to be a valuable therapeutic strategy. A few observational studies have tested NSAIDs (especially relatively selective COX-2 inhibitors), often as part of multipharmacological protocols, for early outpatient treatment of COVID-19. The findings from these studies are promising and point to a crucial role of NSAIDs for the at-home management of people with initial COVID-19 symptoms.

Home as the new frontier for the treatment of COVID-19: the case for anti-inflammatory agents

COVID-19, caused by SARS-CoV-2, is characterised by a broad spectrum of symptom severity that requires varying amounts of care according to the different stages of the disease. Intervening at the onset of mild to moderate COVID-19 symptoms in the outpatient setting would provide the opportunity to prevent progression to a more severe illness and long-term complications. As early disease symptoms variably reflect an underlying excessive inflammatory response to the viral infection, the use of anti-inflammatory drugs, especially non-steroidal anti-inflammatory drugs (NSAIDs), in the initial outpatient stage of COVID-19 seems to be a valuable therapeutic strategy. A few observational studies have tested NSAIDs (especially relatively selective COX-2 inhibitors), often as part of multipharmacological protocols, for early outpatient treatment of COVID-19. The findings from these studies are promising and point to a crucial role of NSAIDs for the at-home management of people with initial COVID-19 symptoms.

Deletion of macrophage Gpr101 disrupts their phenotype and function dysregulating host immune responses in sterile and infectious inflammation

We recently found that the G protein coupled receptor GPR101 mediates the phagocyte-directed pro-resolving activities of RvD5_{n-3 DPA} (n-3 docosapentaenoic acid-derived Resolvin D5). Herein, we investigated the endogenous role of this pro-resolving receptor in modulating macrophage biology using a novel mouse line where the expression of Gpr101 was conditionally deleted in macrophages (Mac^Gpr101KO). Peritoneal macrophages obtained from naïve Mac^Gpr101KO mice displayed a marked shift in the expression of phenotypic and activation markers, including the Interleukin (IL)-10 and IL-23 receptors. Loss of Gpr101 on macrophages was also associated with a significant disruption in their cellular metabolism and a decreased ability to migrate towards the chemoattractant Mcp-1. The alterations in macrophage phenotype observed in Gpr101 deficient macrophages were maintained following inflammatory challenge. This was linked with an increased inflammatory response in the Gpr101 deficient animals and a reduced ability of phagocytes, including macrophages, to clear bacteria. Loss of Gpr101 on macrophages disrupted host pro-resolving responses to zymosan challenge with Mac^Gpr101KO mice exhibiting significantly higher neutrophil numbers and a delay in the resolution interval when compared with control mice. These observations were linked with a marked dysregulation in peritoneal lipid mediator concentrations in Gpr101 deficient mice, with a downregulation of pro-resolving mediators including MaR2_{n-3 DPA}, Resolvin (Rv) D3 and RvE3. Together these findings identify Gpr101 as a novel regulator of both macrophage phenotype and function, modulating key biological activities in both limiting the propagation of inflammation and expediting its resolution.

Right atrial thrombus, junctional tachycardia, and critical lower limb ischemia: three rare complications of severe acute respiratory syndrome coronavirus 2 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can engender multi-system inflammatory syndrome. Its main symptoms are cardiovascular and thromboembolic problems that can develop into severe complications. The present case is about a 55-year-old patient who was admitted for critical ischemia of the right lower limb and necrosis of the right forefoot. The patient was infected with coronavirus disease 2019 (COVID-19) one month before her admission. The patient also has cardiovascular risks including type 2 diabetes and hypertension. The performance of ultrasounds revealed a thrombus in the right atrium and the pulmonary artery, and arteriography detected an occlusion of the right popliteal joint for which she had an endovascular recanalization and amputation of the right forefoot. This case highlights that SARS-CoV-2 infection could be considered a serious cardiovascular disease requiring cardiovascular explorations to initiate hospital management and avoid severe complications.

Decrease in serum levels of autotaxin in COVID-19 patients

INTRODUCTION

In order to identify therapeutic targets in Coronavirus disease 2019 (COVID-19), it is important to identify molecules involved in the biological responses that are modulated in COVID-19. Lysophosphatidic acids (LPAs) are involved in the pulmonary inflammation and fibrosis are one of the candidate molecules. The aim of this study was to evaluate the association between the serum levels of autotaxin (ATX), which are enzymes involved in the synthesis of lysophosphatidic acids.

MATERIAL AND METHODS

We enrolled 134 subjects with COVID-19 and 58 normal healthy subjects for the study. We measured serum ATX levels longitudinally in COVID-19 patients and investigated the time course and the association with severity and clinical parameters.

RESULTS

The serum ATX levels were reduced in all patients with COVID-19, irrespective of the disease severity, and were negatively associated with the serum CRP, D-dimer, and anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody levels.

DISCUSSION

Considering the biological properties of LPAs in the pulmonary inflammation and fibrosis, modulation of ATX might be compensatory biological responses to suppress immunological overreaction especially in the lung, which is an important underlying mechanism for the mortality of the disease.

CONCLUSIONS

COVID-19 patients showed a decrease in the serum levels of ATX, irrespective of the disease severity. Key MessagesAutotaxin (ATX) is an enzyme involved in the synthesis of lysophosphatidic acid (LPA), which has been reported to be involved in pulmonary inflammation and fibrosis. Patients with COVID-19 show decrease in the serum levels of ATX. Modulation of ATX might be compensatory biological responses to suppress immunological overreaction.

The free fatty acid-binding pocket is a conserved hallmark in pathogenic β-coronavirus spike proteins from SARS-CoV to Omicron

As coronavirus disease 2019 (COVID-19) persists, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) emerge, accumulating spike (S) glycoprotein mutations. S receptor binding domain (RBD) comprises a free fatty acid (FFA)-binding pocket. FFA binding stabilizes a locked S conformation, interfering with virus infectivity. We provide evidence that the pocket is conserved in pathogenic β-coronaviruses (β-CoVs) infecting humans. SARS-CoV, MERS-CoV, SARS-CoV-2, and VOCs bind the essential FFA linoleic acid (LA), while binding is abolished by one mutation in common cold-causing HCoV-HKU1. In the SARS-CoV S structure, LA stabilizes the locked conformation, while the open, infectious conformation is devoid of LA. Electron tomography of SARS-CoV-2-infected cells reveals that LA treatment inhibits viral replication, resulting in fewer deformed virions. Our results establish FFA binding as a hallmark of pathogenic β-CoV infection and replication, setting the stage for FFA-based antiviral strategies to overcome COVID-19.

Deuterated Drugs and Biomarkers in the COVID-19 Pandemic

Coronavirus disease 2019 (COVID-19) is a highly contagious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Initially identified in Wuhan (China) in December 2019, COVID-19 rapidly spread globally, resulting in the COVID-19 pandemic. Carriers of the SARS-CoV-2 can experience symptoms ranging from mild to severe (or no symptoms whatsoever). Although vaccination provides extra immunity toward SARS-CoV-2, there has been an urgent need to develop treatments for COVID-19 to alleviate symptoms for carriers of the disease. In seeking a potential treatment, deuterated compounds have played a critical role either as therapeutic agents or as internal MS standards for studying the pharmacological properties of new drugs by quantifying the parent compounds and metabolites. We have identified >70 examples of deuterium-labeled compounds associated with treatment of COVID-19. Of these, we found 9 repurposed drugs and >20 novel drugs studied for potential therapeutic roles along with a total of 38 compounds (drugs, biomarkers, and lipids) explored as internal mass spectrometry standards. This review details the synthetic pathways and modes of action of these compounds (if known), and a brief analysis of each study.

Saliva metabolomic profile of COVID-19 patients associates with disease severity

INTRODUCTION

Coronavirus disease 2019 (COVID-19) is strongly linked to dysregulation of various molecular, cellular, and physiological processes that change abundance of different biomolecules including metabolites that may be ultimately used as biomarkers for disease progression and severity. It is important at early stage to readily distinguish those patients that are likely to progress to moderate and severe stages.

OBJECTIVES

This study aimed to investigate the utility of saliva and plasma metabolomic profiles as a potential parameter for risk stratifying COVID-19 patients.

METHOD

LC-MS/MS-based untargeted metabolomics were used to profile the changes in saliva and plasma metabolomic profiles of COVID-19 patients with different severities.

RESULTS

Saliva and plasma metabolites were screened in 62 COVID-19 patients and 18 non-infected controls. The COVID-19 group included 16 severe, 15 moderate, 16 mild, and 15 asymptomatic cases. Thirty-six differential metabolites were detected in COVID-19 versus control comparisons. SARS-CoV-2 induced metabolic derangement differed with infection severity. The metabolic changes were identified in saliva and plasma, however, saliva showed higher intensity of metabolic changes. Levels of saliva metabolites such as sphingosine and kynurenine were significantly different between COVID-19 infected and non-infected individuals; while linoleic acid and Alpha-ketoisovaleric acid were specifically increased in severe compared to non-severe patients. As expected, the two prognostic biomarkers of C-reactive protein and D-dimer were negatively correlated with sphingosine and 5-Aminolevulinic acid, and positively correlated with L-Tryptophan and L-Kynurenine.

CONCLUSION

Saliva disease-specific and severity-specific metabolite could be employed as potential COVID-19 diagnostic and prognostic biomarkers.

Redox Status Is the Mainstay of SARS-CoV-2 and Host for Producing Therapeutic Opportunities

Over hundreds of years, humans have faced multiple pandemics and have overcome many of them with scientific advancements. However, the recent coronavirus disease (COVID-19) has challenged the physical, mental, and socioeconomic aspects of human life, which has introduced a general sense of uncertainty among everyone. Although several risk profiles, such as the severity of the disease, infection rate, and treatment strategy, have been investigated, new variants from different parts of the world put humans at risk and require multiple strategies simultaneously to control the spread. Understanding the entire system with respect to the commonly involved or essential mechanisms may be an effective strategy for successful treatment, particularly for COVID-19. Any treatment for COVID-19 may alter the redox profile, which can be an effective complementary method for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry and further replication. Indeed, redox profiles are one of the main barriers that suddenly shift the immune response in favor of COVID-19. Fortunately, several redox components exhibit antiviral and anti-inflammatory activities. However, access to these components as support elements against COVID-19 is limited. Therefore, understanding redox-derived species and their nodes as a common interactome in the system will facilitate the treatment of COVID-19. This review discusses the redox-based perspectives of the entire system during COVID-19 infection, including how redox-based molecules impact the accessibility of SARS-CoV-2 to the host and further replication. Additionally, to demonstrate its feasibility as a viable approach, we discuss the current challenges in redox-based treatment options for COVID-19.

In Vitro and In Silico Evaluation of ACE2 and LOX Inhibitory Activity of Origanum Essential Oils and Carvacrol

Origanum spp. are used both for culinary purposes and for their biological activities. In this study, commercial Origanum majorana, Origanum minutiflorum, Origanum vulgare, and Origanum onites essential oils and their prominent constituent carvacrol were evaluated for their in vitro and in silico angiotensin-converting enzyme 2 and lipoxygenase enzyme inhibitory potentials. The essential oils were analysed by gas chromatography-flame ionisation detection and gas chromatography-mass spectrometry, where carvacrol was identified as the major component (62 - 81%), confirming the quality. In vitro enzyme inhibition assays were conducted both with the essential oils (20 µg/mL) and with carvacrol (5 µg/mL). The comparative values of angiotensin-converting enzyme 2 percent inhibition for O. majorana, O. minutiflorum, O. vulgare, and O. onites essential oils were determined as 85.5, 79.1, 74.3, and 42.8%, respectively. As a result of the enzyme assays, carvacrol showed 90.7% in vitro angiotensin-converting enzyme 2 inhibitory activity. The in vitro lipoxygenase inhibition of the essential oils (in the same order) was 89.4, 78.9, 81.1, and 73.5%, respectively, where carvacrol showed 74.8% inhibition. In addition, protein-ligand docking and interaction profiling was used to gain structural and mechanistic insights into the angiotensin-converting enzyme 2 and lipoxygenase inhibitory potentials of major Origanum essential oil constituents. The in silico findings agreed with the significant enzyme inhibition activity observed in vitro. Further in vivo studies are suggested to confirm the safety and efficacy of the oils.

Urinary lipid profile of patients with coronavirus diseases 2019

The coronavirus diseases 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is ongoing. Over 490 million people have been infected with this virus worldwide. Although many patients present with lower respiratory symptoms, some may progress to acute respiratory distress syndrome and even multi-organ damage. Therefore, there is an urgent need to establish treatment and management methods for this infectious disease. Here, we comprehensively analyzed urinary lipid mediators and their metabolites to identify non-invasive biomarkers that reflect the disease status of COVID-19 patients. We diagnosed 16 patients by polymerase chain reaction (PCR) analysis, who presented with mild-to-moderate symptoms, including fever and cough, between May and October 2020 in Japan, and collected their urine samples. Using mass spectrometry, we analyzed the lipid metabolites in these urine samples. In all the urine samples from the patients, 21 types of fatty acids and their metabolites were consistently detected in the samples among the 214 metabolites which were analyzed. Interestingly, urinary levels of fatty acids, docosahexaenoic acid was increased by approximately 3-fold in patients with COVID-19 compared to those in healthy subjects. Metabolites of major proinflammatory lipid mediators, PGE2, TXA2, and PGF2α, were also detected at significantly higher levels in the urine of patients with COVID-19. These observations suggest that urinary lipids can reflect the inflammatory status of patients with COVID-19, which can be a useful index to manage this disease.

The mechanistic basis linking cytokine storm to thrombosis in COVID-19

It is now well established that infection with SARS-CoV-2 resulting in COVID-19 disease includes a severely symptomatic subset of patients in whom an aggressive and/or dysregulated host immune response leads to cytokine storm syndrome (CSS) that may be further complicated by thrombotic events, contributing to the severe morbidity and mortality observed in COVID-19. This review provides a brief overview of cytokine storm in COVID-19, and then presents a mechanistic discussion of how cytokine storm affects integrated pathways in thrombosis involving the endothelium, platelets, the coagulation cascade, eicosanoids, auto-antibody mediated thrombosis, and the fibrinolytic system.

Treatment of COVID-19 Pneumonia and Acute Respiratory Distress With Ramatroban, a Thromboxane A2 and Prostaglandin D2 Receptor Antagonist: A Four-Patient Case Series Report

Hypoxemia in COVID-19 pneumonia is associated with hospitalization, mechanical ventilation, and mortality. COVID-19 patients exhibit marked increases in fatty acid levels and inflammatory lipid mediators, predominantly arachidonic acid metabolites, notably thromboxane B2 >> prostaglandin E2 > prostaglandin D2. Thromboxane A2 increases pulmonary capillary pressure and microvascular permeability, leading to pulmonary edema, and causes bronchoconstriction contributing to ventilation/perfusion mismatch. Prostaglandin D2-stimulated IL-13 production is associated with respiratory failure, possibly due to hyaluronan accumulation in the lungs. Ramatroban is an orally bioavailable, dual thromboxane A2/TP and prostaglandin D2/DP2 receptor antagonist used in Japan for allergic rhinitis. Four consecutive outpatients with COVID-19 pneumonia treated with ramatroban exhibited rapid relief of dyspnea and hypoxemia within 12–36 h and complete resolution over 5 days, thereby avoiding hospitalization. Therefore, ramatroban as an antivasospastic, broncho-relaxant, antithrombotic, and immunomodulatory agent merits study in randomized clinical trials that might offer hope for a cost-effective pandemic treatment.

Acetylcholine, Fatty Acids, and Lipid Mediators Are Linked to COVID-19 Severity

Lipid and cholinergic mediators are inflammatory regulators, but their role in the immunopathology of COVID-19 is still unclear. Here, we used human blood and tracheal aspirate (TA) to investigate whether acetylcholine (Ach), fatty acids (FAs), and their derived lipid mediators (LMs) are associated with COVID-19 severity. First, we analyzed the perturbation profile induced by SARS-CoV-2 infection in the transcriptional profile of genes related to the ACh and FA/LM pathways. Blood and TA were used for metabolomic and lipidomic analyses and for quantification of leukocytes, cytokines, and ACh. Differential expression and coexpression gene network data revealed a unique transcriptional profile associated with ACh and FA/LM production, release, and cellular signaling. Transcriptomic data were corroborated by laboratory findings: SARS-CoV-2 infection increased plasma and TA levels of arachidonic acid, 5-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid, 11-hydroxy-5Z,8Z,12E,14Z-eicosatetraenoic acid, and ACh. TA samples also exhibited high levels of PGE₂, thromboxane B₂, 12-oxo-5Z,8Z,10E,14Z-eicosatetraenoic acid, and 6-trans-leukotriene B₄ Bioinformatics and experimental approaches demonstrated robust correlation between transcriptional profile in Ach and FA/LM pathways and parameters of severe COVID-19. As expected, the increased neutrophil-to-lymphocyte ratio, neutrophil counts, and cytokine levels (IL-6, IL-10, IL-1β, and IL-8) correlated with worse clinical scores. Glucocorticoids protected severe and critical patients and correlated with reduced Ach levels in plasma and TA samples. We demonstrated that pulmonary and systemic hyperinflammation in severe COVID-19 are associated with high levels of Ach and FA/LM. Glucocorticoids favored the survival of patients with severe/critical disease, and this effect was associated with a reduction in ACh levels.

Platelet activation and partial desensitization are associated with viral xenophagy in patients with severe COVID-19

During severe COVID-19, platelets get activated and become partly desensitized through mechanisms involving glycoprotein shedding.

Platelets from patients with severe COVID-19 internalize SARS-CoV-2 and develop viral xenophagy.

Mild thrombocytopenia, changes in platelet gene expression, enhanced platelet functionality, and presence of platelet-rich thrombi in the lung have been associated with thromboinflammatory complications of patients with COVID-19. However, whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gets internalized by platelets and directly alters their behavior and function in infected patients remains elusive. Here, we investigated platelet parameters and the presence of viral material in platelets from a prospective cohort of 29 patients with severe COVID-19 admitted to an intensive care unit. A combination of specific assays, tandem mass spectrometry, and flow cytometry indicated high levels of protein and lipid platelet activation markers in the plasma from patients with severe COVID-19 associated with an increase of proinflammatory cytokines and leukocyte-platelets interactions. Platelets were partly desensitized, as shown by a significant reduction of αIIbβ3 activation and granule secretion in response to stimulation and a decrease of surface GPVI, whereas plasma from patients with severe COVID-19 potentiated washed healthy platelet aggregation response. Transmission electron microscopy indicated the presence of SARS-CoV-2 particles in a significant fraction of platelets as confirmed by immunogold labeling and immunofluorescence imaging of Spike and nucleocapsid proteins. Compared with platelets from healthy donors or patients with bacterial sepsis, platelets from patients with severe COVID-19 exhibited enlarged intracellular vesicles and autophagolysosomes. They had large LC3-positive structures and increased levels of LC3II with a co-localization of LC3 and Spike, suggesting that platelets can digest SARS-CoV-2 material by xenophagy in critically ill patients. Altogether, these data show that during severe COVID-19, platelets get activated, become partly desensitized, and develop a selective autophagy response.

Cytokines and Lipid Mediators of Inflammation in Lungs of SARS-CoV-2 Infected Mice

Coronavirus disease 19 (COVID-19) is the clinical manifestation of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) infection. A hallmark of COVID-19 is a lung inflammation characterized by an abundant leukocyte infiltrate, elevated levels of cytokines/chemokines, lipid mediators of inflammation (LMI) and microthrombotic events. Animal models are useful for understanding the pathophysiological events leading to COVID-19. One such animal model is the K18-ACE2 transgenic mice. Despite their importance in inflammation, the study of LMI in lung of SARS-CoV-2 infected K18-ACE2 mice has yet to be studied to our knowledge. Using tandem mass spectrometry, the lung lipidome at different time points of infection was analyzed. Significantly increased LMI included N-oleoyl-serine, N-linoleoyl-glycine, N-oleoyl-alanine, 1/2-linoleoyl-glycerol, 1/2-docosahexaenoyl-glycerol and 12-hydroxy-eicosapenatenoic acid. The levels of prostaglandin (PG) E₁, PGF_2α, stearoyl-ethanolamide and linoleoyl-ethanolamide were found to be significantly reduced relative to mock-infected mice. Other LMI were present at similar levels (or undetected) in both uninfected and infected mouse lungs. In parallel to LMI measures, transcriptomic and cytokine/chemokine profiling were performed. Viral replication was robust with maximal lung viral loads detected on days 2-3 post-infection. Lung histology revealed leukocyte infiltration starting on day 3 post-infection, which correlated with the presence of high concentrations of several chemokines/cytokines. At early times post-infection, the plasma of infected mice contained highly elevated concentration of D-dimers suggestive of blood clot formation/dissolution. In support, the presence of blood clots in the lung vasculature was observed during infection. RNA-Seq analysis of lung tissues indicate that SARS-CoV-2 infection results in the progressive modulation of several hundred genes, including several inflammatory mediators and genes related to the interferons. Analysis of the lung lipidome indicated modest, yet significant modulation of a minority of lipids. In summary, our study suggests that SARS-CoV-2 infection in humans and mice share common features, such as elevated levels of chemokines in lungs, leukocyte infiltration and increased levels of circulating D-dimers. However, the K18-ACE2 mouse model highlight major differences in terms of LMI being produced in response to SARS-CoV-2 infection. The potential reasons and impact of these differences on the pathology and therapeutic strategies to be employed to treat severe COVID-19 are discussed.