Dysregulated Neutrophil Phenotype and Function in Hospitalised Non-ICU COVID-19 Pneumonia.

Rationale: Infection with the SARS-CoV2 virus is associated with elevated neutrophil counts. Evidence of neutrophil dysfunction in COVID-19 is based on transcriptomics or single functional assays. Cell functions are interwoven pathways, and understanding the effect across the spectrum of neutrophil function may identify therapeutic targets. Objectives: Examine neutrophil phenotype and function in 41 hospitalised, non-ICU COVID-19 patients versus 23 age-matched controls (AMC) and 26 community acquired pneumonia patients (CAP). Methods: Isolated neutrophils underwent ex vivo analyses for migration, bacterial phagocytosis, ROS generation, NETosis and receptor expression. Circulating DNAse 1 activity, levels of cfDNA, MPO, VEGF, IL-6 and sTNFRI were measured and correlated to clinical outcome. Serial sampling on day three to five post hospitalization were also measured. The effect of ex vivo PI3K inhibition was measured in a further cohort of 18 COVID-19 patients. Results: Compared to AMC and CAP, COVID-19 neutrophils demonstrated elevated transmigration (p = 0.0397) and NETosis (p = 0.0332), and impaired phagocytosis (p = 0.0036) associated with impaired ROS generation (p < 0.0001). The percentage of CD54+ neutrophils (p < 0.001) was significantly increased, while surface expression of CD11b (p = 0.0014) and PD-L1 (p = 0.006) were significantly decreased in COVID-19. COVID-19 and CAP patients showed increased systemic markers of NETosis including increased cfDNA (p = 0.0396) and impaired DNAse activity (p < 0.0001). The ex vivo inhibition of PI3K γ and δ reduced NET release by COVID-19 neutrophils (p = 0.0129). Conclusions: COVID-19 is associated with neutrophil dysfunction across all main effector functions, with altered phenotype, elevated migration and NETosis, and impaired antimicrobial responses. These changes highlight that targeting neutrophil function may help modulate COVID-19 severity.

High Induction of IL-6 Secretion From hUCMSCs Optimize the Potential of hUCMSCs and TCZ as Therapy for COVID-19-Related ARDS.

Biological and cellular interleukin-6 (IL-6)-related therapies have been used to treat severe COVID-19 pneumonia with hyperinflammatory syndrome and acute respiratory failure, which prompted further exploration of the role of IL-6 in human umbilical cord mesenchymal stem cell (hUCMSC) therapy. Peripheral blood mononuclear cells (PBMCs) were responders cocultured with hUCMSCs or exogenous IL-6. A PBMC suppression assay was used to analyze the anti-inflammatory effects via MTT assay. The IL-6 concentration in the supernatant was measured using ELISA. The correlation between the anti-inflammatory effect of hUCMSCs and IL-6 levels and the relevant roles of IL-6 and IL-6 mRNA expression was analyzed using the MetaCore functional network constructed from gene microarray data. The location of IL-6 and IL-6 receptor (IL-6R) expression was further evaluated. We reported that hUCMSCs did not initially exert any inhibitory effect on PHA-stimulated proliferation; however, a potent inhibitory effect on PHA-stimulated proliferation was observed, and the IL-6 concentration reached approximately 1000 ng/mL after 72 hours. Exogenous 1000 ng/mL IL-6 inhibited PHA-stimulated inflammation but less so than hUCMSCs. The inhibitory effects of hUCMSCs on PHA-stimulated PBMCs disappeared after adding an IL-6 neutralizing antibody or pretreatment with tocilizumab (TCZ), an IL-6R antagonist. hUCMSCs exert excellent anti-inflammatory effects by inducing higher IL-6 levels, which is different from TCZ. High concentration of IL-6 cytokine secretion plays an important role in the anti-inflammatory effect of hUCMSC therapy. Initial hUCMSC therapy, followed by TCZ, seems to optimize the therapeutic potential to treat COVID-19-related acute respiratory distress syndrome (ARDS).

Interleukin-6 as potential mediator of long-term neuropsychiatric symptoms of COVID-19.

The majority of COVID-19 survivors experience long-term neuropsychiatric symptoms such as fatigue, sleeping difficulties, depression and anxiety. We propose that neuroimmune cross-talk via inflammatory cytokines such as interleukin-6 (IL-6) could underpin these long-term COVID-19 symptoms. This hypothesis is supported by several lines of research, including population-based cohort and genetic Mendelian Randomisation studies suggesting that inflammation is associated with fatigue and sleeping difficulties, and that IL-6 could represent a possible causal driver for these symptoms. Immune activation following COVID-19 can disrupt T helper 17 (TH17) and regulatory T (Treg) cell responses, affect central learning and emotional processes, and lead to a vicious cycle of inflammation and mitochondrial dysfunction that amplifies the inflammatory process and results in immuno-metabolic constraints on neuronal energy metabolism, with fatigue being the ultimate result. Increased cytokine activity drives this process and could be targeted to interrupt it. Therefore, whether persistent IL-6 dysregulation contributes to COVID-19-related long-term fatigue, sleeping difficulties, depression, and anxiety, and whether targeting IL-6 pathways could be helpful for treatment and prevention of long COVID are important questions that require investigation. This line of research could inform new approaches for treatment and prevention of long-term neuropsychiatric symptoms of COVID-19. Effective treatment and prevention of this condition could also help to stem the anticipated rise in depression and other mental illnesses ensuing this pandemic.

Alpha-defensins: risk factor for thrombosis in COVID-19 infection.

The inflammatory response to SARS/CoV-2 (COVID-19) infection may contribute to the risk of thromboembolic complications. α-Defensins, antimicrobial peptides released from activated neutrophils, are anti-fibrinolytic and prothrombotic in vitro and in mouse models. In this prospective study of 176 patients with COVID-19 infection, we found that plasma levels of α-defensins were elevated, tracked with disease progression/mortality or resolution and with plasma levels of interleukin-6 (IL-6) and D-dimers. Immunohistochemistry revealed intense deposition of α-defensins in lung vasculature and thrombi. IL-6 stimulated the release of α-defensins from neutrophils, thereby accelerating coagulation and inhibiting fibrinolysis in human blood, imitating the coagulation pattern in COVID-19 patients. The procoagulant effect of IL-6 was inhibited by colchicine, which blocks neutrophil degranulation. These studies describe a link between inflammation and the risk of thromboembolism, and they identify a potential new approach to mitigate this risk in patients with COVID-19 and potentially in other inflammatory prothrombotic conditions.

Evidence of the pathogenic HERV-W envelope expression in T lymphocytes in association with the respiratory outcome of COVID-19 patients.

BACKGROUND: Despite an impressive effort in clinical research, no standard therapeutic approach for coronavirus disease 2019 (COVID-19) patients has been established, highlighting the need to identify early biomarkers for predicting disease progression and new therapeutic interventions for patient management. The present study aimed to evaluate the involvement of the human endogenous retrovirus -W envelope (HERV-W ENV) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection considering recent findings that HERVs are activated in response to infectious agents and lead to various immunopathological effects. We analysed HERV-W ENV expression in blood cells of COVID-19 patients in correlation with clinical characteristics and have discussed its potential role in the outcome of the disease. METHODS: We analysed HERV-W ENV expression in blood samples of COVID-19 patients and healthy donors by flow cytometry and quantitative reverse transcriptase PCR analysis, and evaluated its correlation with clinical signs, inflammatory markers, cytokine expression, and disease progression. FINDINGS: HERV-W ENV was highly expressed in the leukocytes of COVID-19 patients but not in those of healthy donors. Its expression correlated with the markers of T-cell differentiation and exhaustion and blood cytokine levels. The percentage of HERV-W ENV-positive lymphocytes correlated with inflammatory markers and pneumonia severity in COVID-19 patients. Notably, HERV-W ENV expression reflects the respiratory outcome of patients during hospitalization. INTERPRETATION: Given the known immuno- and neuro-pathogenicity of HERV-W ENV protein, it could promote certain pathogenic features of COVID-19 and therefore serve as a biomarker to predict clinical progression of disease and open to further studies for therapeutic intervention. FUNDING: Information available at the end of the manuscript.

Emerging role of IL-6 and NLRP3 inflammasome as potential therapeutic targets to combat COVID-19: Role of lncRNAs in cytokine storm modulation.

The world has witnessed a high morbidity and mortality caused by SARS-CoV-2, and global death toll is still rising. Exaggerated inflammatory responses are thought to be more responsible for infiltrated immune cells accumulation, organ damage especially lung, dyspnea, and respiratory failure rather than direct effect of viral replication. IL-6 and NLRP3 inflammasome are the major immune components in immune responses stimulation upon pathogen infection. It's noteworthy that the function and expression of these components are remarkably influenced by non-coding RNAs including long non-coding RNAs. Given the potential role of these components in organ damage and pathological manifestations of patients infected with COVID-19, their blockage might be a hopeful and promising treatment strategy. Notably, more study on long non-coding RNAs involved in inflammatory responses could elevate the efficacy of anti-inflammatory therapy. In this review we discuss the potential impact of IL-6 and NLRP3 inflammasome blocker drugs on inflammatory responses, viral clearance, and pathological and clinical manifestations. Collectively, anti-inflammatory strategy might pave the way to diminish clinical and pathological manifestations and thereby discharging patients infected with COVID-19 from hospital.

The bio-mission of interleukin-6 in the pathogenesis of COVID-19: A brief look at potential therapeutic tactics.

Interleukin-6 (IL-6), known as an inflammatory cytokine, can be involved in many innate and adaptive immune responses. The role of IL-6 in the pathogenesis of the novel coronavirus disease 2019 (COVID-19) has recently received much more attention due to the spread of the virus and its pandemic potential. Cytokine storm is among the most critical pathological events in patients affected with coronaviruses (CoVs), i.e., severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and COVID-19, causing inflammation-induced lung injury and also occurring as a result of dysregulation of immune responses to the mentioned viruses. IL-6, along with some other inflammatory cytokines, including IL-1 beta (ß), IL-8, and tumor necrosis factor-alpha (TNF-α), as well as inflammatory chemokines, can significantly contribute to, fever, lymphopenia, coagulation, lung injury, and multi-organ failure (MOF). Therefore, researchers are to explore novel approaches to treat the disease through targeting of IL-6 and its receptors based on prior experience of other disorders. In this review article, the latest findings on the role of IL-6 in the pathogenesis of COVID-19, as well as therapeutic perspectives, were summarized and discussed.