Headache medication and the COVID-19 pandemic.

The world is currently dominated by the Corona Virus Disease 2019 (COVID-19) pandemic. Besides the obvious concerns about limitation of virus spread and providing the best possible care to infected patients, a concomitant concern has now arisen in view of a putative link between the use of certain drugs, such as Renin-Angiotensin System (RAS) inhibitors and ibuprofen, and an increased risk for COVID-19 infection. We here discuss this concern in relation to headache treatment and conclude that, based on current evidence, there is no reason to abandon treatment of headache patients with RAS inhibitors or ibuprofen.

Prevention and therapy of COVID-19 via exogenous estrogen treatment for both male and female patients.

The presented work summarizes the results of studies underlining the crucial role of estrogen receptor (ER) signaling in both innate and adaptive immune responses as well as in tissue repairing processes during respiratory virus infection. Experimental studies justify that among respiratory virus infected mice, a weaker ER signaling leads to increased morbidity and mortality in both males and females. In animal experiments, estrogen treatment silences the inflammatory reactions and decreases virus titers leading to improved survival rate; it seems to be an ideal prevention and therapy against COVID-19. We should overcome the widespread reluctance to estrogen therapy as we have a unique estrogen formula; conjugated estrogens, or conjugated equine estrogens available under the brand name of Premarin deriving from natural sources. Premarin can exert similar ER upregulative and gene repairing power like endogenous estrogen without any risk for adverse reactions. Premarin is capable of stopping the COVID-19 pandemic.

Ozone exposure upregulates the expression of host susceptibility protein TMPRSS2 to SARS-CoV-2.

SARS-CoV-2, a novel coronavirus and an etiologic agent for the current global health emergency, causes acute infection of the respiratory tract leading to severe disease and significant mortality. Ever since the start of SARS-CoV-2, also known as the COVID-19 pandemic, countless uncertainties have been revolving around the pathogenesis and epidemiology of the SARS-CoV-2 infection. While air pollution has been shown to be strongly correlated to increased SARS-CoV-2 morbidity and mortality, whether environmental pollutants such as ground-level ozone affects the susceptibility of individuals to SARS-CoV-2 is not yet established. To investigate the impact of ozone inhalation on the expression levels of signatures associated with host susceptibility to SARS-CoV-2, we analyzed lung tissues collected from mice that were sub-chronically exposed to air or 0.8 ppm ozone for three weeks (4 h/night, 5 nights/week), and analyzed the expression of signatures associated with host susceptibility to SARS-CoV-2. SARS-CoV-2 entry into the host cells is dependent on the binding of the virus to the host cellular receptor, angiotensin-converting enzyme (ACE2), and its subsequent proteolytic priming by the host-derived protease, transmembrane protease serine 2 (TMPRSS2). The Ace2 transcripts were significantly elevated in the parenchyma, but not in the extrapulmonary airways and alveolar macrophages, from ozone-exposed mice. The TMPRSS2 protein and Tmprss2 transcripts were significantly elevated in the extrapulmonary airways, parenchyma, and alveolar macrophages from ozone-exposed mice. A significant proportion of additional known SARS-CoV-2 host susceptibility genes were upregulated in alveolar macrophages and parenchyma from ozone-exposed mice. Our data indicate that the unhealthy levels of ozone in the environment may predispose individuals to severe SARS-CoV-2 infection. Given the severity of this pandemic and the challenges associated with direct testing of host-environment interactions in clinical settings, we believe that this ozone exposure-based study informs the scientific community of the potentially detrimental effects of the ambient ozone levels in determining the host susceptibility to SARS-CoV-2.

The spike protein of SARS-CoV-2 induces heme oxygenase-1: Pathophysiologic implications.

BACKGROUND: Acute kidney injury (AKI) is both a consequence and determinant of outcomes in COVID-19. The kidney is one of the major organs infected by the causative virus, SARS-CoV-2. Viral entry into cells requires the viral spike protein, and both the virus and its spike protein appear in the urine of COVID-19 patients with AKI. We examined the effects of transfecting the viral spike protein of SARS-CoV-2 in kidney cell lines. METHODS: HEK293, HEK293-ACE2+ (stably overexpressing ACE2), and Vero E6 cells having endogenous ACE2 were transfected with SARS-CoV-2 spike or control plasmid. Assessment of gene and protein expression, and syncytia formation was performed, and the effects of quercetin on syncytia formation examined. FINDINGS: Spike transfection in HEK293-ACE2+ cells caused syncytia formation, cellular sloughing, and focal denudation of the cell monolayer; transfection in Vero E6 cells also caused syncytia formation. Spike expression upregulated potentially nephrotoxic genes (TNF-α, MCP-1, and ICAM1). Spike upregulated the cytoprotective gene HO-1 and relevant signaling pathways (p-Akt, p-STAT3, and p-p38). Quercetin, an HO-1 inducer, reduced syncytia formation and spike protein expression. INTERPRETATION: The major conclusions of the study are: 1) Spike protein expression in kidney cells provides a relevant model for the study of maladaptive and adaptive responses germane to AKI in COVID-19; 2) such spike protein expression upregulates HO-1; and 3) quercetin, an HO-1 inducer, may provide a clinically relevant/feasible protective strategy in AKI occurring in the setting of COVID-19. FUNDING: R01-DK119167 (KAN), R01-AI100911 (JPG), P30-DK079337; R01-DK059600 (AA).

Identification of hub genes associated with COVID-19 and idiopathic pulmonary fibrosis by integrated bioinformatics analysis.

INTRODUCTION: The coronavirus disease 2019 (COVID-19), emerged in late 2019, was caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The risk factors for idiopathic pulmonary fibrosis (IPF) and COVID-19 are reported to be common. This study aimed to determine the potential role of differentially expressed genes (DEGs) common in IPF and COVID-19. MATERIALS AND METHODS: Based on GEO database, we obtained DEGs from one SARS-CoV-2 dataset and five IPF datasets. A series of enrichment analysis were performed to identify the function of upregulated and downregulated DEGs, respectively. Two plugins in Cytoscape, Cytohubba and MCODE, were utilized to identify hub genes after a protein-protein interaction (PPI) network. Finally, candidate drugs were predicted to target the upregulated DEGs. RESULTS: A total of 188 DEGs were found between COVID-19 and IPF, out of which 117 were upregulated and 71 were downregulated. The upregulated DEGs were involved in cytokine function, while downregulated DEGs were associated with extracellular matrix disassembly. Twenty-two hub genes were upregulated in COVID-19 and IPF, for which 155 candidate drugs were predicted (adj.P.value < 0.01). CONCLUSION: Identifying the hub genes aberrantly regulated in both COVID-19 and IPF may enable development of molecules, encoded by those genes, as therapeutic targets for preventing IPF progression and SARS-CoV-2 infections.

Diet Impact on Obesity beyond Calories and Trefoil Factor Family 2 (TFF2) as an Illustration: Metabolic Implications and Potential Applications.

Obesity is a health problem with increasing impacts on public health, economy and even social life. In order to reestablish the energy balance, obesity management focuses mainly on two pillars; exercise and diet. Beyond the contribution to the caloric intake, the diet nutrients and composition govern a variety of properties. This includes the energy balance-independent properties and the indirect metabolic effects. Whereas the energy balance-independent properties are close to "pharmacological" effects and include effects such as antioxidant and anti-inflammatory, the indirect metabolic effects represent the contribution a diet can have on energy metabolism beyond the caloric contribution itself, which include the food intake control and metabolic changes. As an illustration, we also described the metabolic implication and hypothetical pathways of the high-fat diet-induced gene Trefoil Factor Family 2. The properties the diet has can have a variety of applications mainly in pharmacology and nutrition and further explore the "pharmacologically" active food towards potential therapeutic applications.

Correlation of ACE2 with RAS components after Losartan treatment in light of COVID-19.

Angiotensin-converting enzyme 2 (ACE2) is an important factor in coronavirus disease (COVID-19) interactions. Losartan (LOS) belongs to the angiotensin receptor blocker (ARB) family. Additionally, the protective role of ACE2 restored by LOS has been suggested and clinically examined in the treatment of COVID-19 patients. Furthermore, clinical trials with LOS have been conducted. However, the mechanism through which LOS enhances ACE2 expression remains unclear. In addition, the response of ACE2 to LOS differs among patients. Our LOS-treated patient data revealed a correlated mechanism of ACE2 with components of the renin-angiotensinogen system. We observed a significant positive regulation of MAS1 and ACE2 expression. In the context of LOS treatment of COVID-19, ACE2 expression could depend on LOS regulated MAS1. Thus, MAS1 expression could predict the COVID-19 treatment response of LOS.

The effect of renin-angiotensin-aldosterone system inhibitors on organ-specific ace2 expression in zebrafish and its implications for COVID-19.

Among cases of SARS-CoV-2 infections that result in serious conditions or death, many have pre-existing conditions such as hypertension and are on renin-angiotensin-aldosterone system (RAAS) inhibitors. The angiotensin-converting-enzyme-2 (ACE2), a key protein of the RAAS pathway, also mediates cellular entry of SARS-CoV-2. RAAS inhibitors might affect the expression levels of ace2, which could impact patient susceptibility to SARS-CoV-2. However, multi-organ-specific information is currently lacking and no species other than rodents have been examined. To address this knowledge gap, we treated adult zebrafish with the RAAS inhibitors aliskiren, olmesartan, and captopril for 7 consecutive days and performed qRT-PCR analysis of major RAAS pathway genes in the brain, gill, heart, intestine, kidney, and liver. Both olmesartan and captopril significantly increased ace2 expression in the heart, gill, and kidney. Olmesartan also increased ace2 expression in the intestine. Conversely, aliskiren significantly decreased ace2 expression in the heart. Discontinuation of compound treatments for 7 days did not return ace2 expression to baseline levels. While potential risks or benefits of antihypertensive RAAS inhibitors to SARS-CoV-2 infections in humans remain uncertain, this study provides new insights regarding the impact of RAAS inhibitors on organ-specific ace2 expression in another vertebrate model, thereby providing comparative data and laying scientific groundwork for future clinical decisions of RAAS inhibitor use in the context of COVID-19.

Hemin as a novel candidate for treating COVID-19 via heme oxygenase-1 induction.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the coronavirus disease-19 (COVID-19). More than 143 million cases of COVID-19 have been reported to date, with the global death rate at 2.13%. Currently, there are no licensed therapeutics for controlling SARS-CoV-2 infection. The antiviral effects of heme oxygenase-1 (HO-1), a cytoprotective enzyme that inhibits the inflammatory response and reduces oxidative stress, have been investigated in several viral infections. To confirm whether HO-1 suppresses SARS-CoV-2 infection, we assessed the antiviral activity of hemin, an effective and safe HO-1 inducer, in SARS-CoV-2 infection. We found that treatment with hemin efficiently suppressed SARS-CoV-2 replication (selectivity index: 249.7012). Besides, the transient expression of HO-1 using an expression vector also suppressed the growth of the virus in cells. Free iron and biliverdin, which are metabolic byproducts of heme catalysis by HO-1, also suppressed the viral infection. Additionally, hemin indirectly increased the expression of interferon-stimulated proteins known to restrict SARS-CoV-2 replication. Overall, the findings suggested that HO-1, induced by hemin, effectively suppressed SARS-CoV-2 in vitro. Therefore, HO-1 could be potential therapeutic candidate for COVID-19.

Topoisomerase 2 inhibitor etoposide promotes interleukin-10 production in LPS-induced macrophages via upregulating transcription factor Maf and activating PI3K/Akt pathway.

Topoisomerase (TOP) inhibitors were commonly used as chemotherapeutic agents in the treatment of cancers. In our present study, we found that etoposide (ETO), a topoisomerase 2 (TOP2) inhibitor, upregulated the production of Interleukin 10 (IL-10) in lipopolysaccharide (LPS)-stimulated macrophages. Besides, other TOP2 inhibitors including doxorubicin hydrochloride (DOX) and teniposide (TEN) were also able to augment IL-10 production. Meanwhile, the expression levels of pro-inflammatory factors, for example IL-6 and TNF-α, were also decreased accordingly by the treatment of the TOP2 inhibitors. Of note, ETO facilitated IL-10 secretion, which might be regulated by transcription factor Maf via PI3K/AKT pathway, as pharmaceutic blockage of kinase PI3K or AKT attenuated ETO-induced Maf and IL-10 expression. Further, in LPS-induced mice sepsis model, the enhanced generation of IL-10 was observed in ETO-treated mice, whereas pro-inflammatory cytokines were decreased, which significantly reduced the mortality of mice from LPS-induced lethal cytokine storm. Taken together, these results indicated that ETO may exhibit an anti-inflammatory role by upregulating the alteration of transcription factor Maf and promoting subsequential IL-10 secretion via PI3K/Akt pathway in LPS-induced macrophages. Therefore, ETO may serve as a potential anti-inflammatory agent and employed to severe pro-inflammatory diseases including COVID-19.

Interferon and Toll-Like Receptor 7 Response in COVID-19: Implications of Topical Imiquimod for Prophylaxis and Treatment.

BACKGROUND: The innate immune system is recognized as an essential aspect of COVID-19 pathogenesis. Toll-like receptors (TLRs) are important in inducing antiviral response, triggering downstream production of interferons (IFNs). Certain loss-of-function variants in TLR7 are associated with increased COVID-19 disease severity, and imiquimod (ImiQ) is known to have immunomodulating effects as an agonist of TLR7. Given that topical imiquimod (topImiQ) is indicated for various dermatologic conditions, it is necessary for dermatologists to understand the interplay between innate immunity mechanisms and the potential role of ImiQ in COVID-19, with a particular focus on TLR7. SUMMARY: Our objective was to survey recent peer-reviewed scientific literature in the PubMed database, examine relevant evidence, and elucidate the relationships between IFNs, TLR7, the innate immune system, and topImiQ in the context of COVID-19. Despite limited studies on this topic, current evidence supports the critical role of TLRs in mounting a strong immune response against COVID-19. Of particular interest to dermatologists, topImiQ can result in systemic upregulation of the immune system via activation of TLR7. Key Message: Given the role of TLR7 in the systemic activation of the immune system, ImiQ, as a ligand of the TLR7 receptor, may have potential therapeutic benefit as a topical immunomodulatory treatment for COVID-19.

Targeting of the CD80/86 proinflammatory axis as a therapeutic strategy to prevent severe COVID-19.

An excessive immune response known as cytokine storm is the hallmark of severe COVID-19. The cause of this cytokine rampage is yet not known. Based on recent epidemiological evidence, we hypothesized that CD80/86 signaling is essential for this hyperinflammation, and that blocking this proinflammatory axis could be an effective therapeutic approach to protect against severe COVID-19. Here we provide exploratory evidence that abatacept, a drug that blocks CD80/86 co-stimulation, produces changes at the systemic level that are highly antagonistic of the proinflammatory processes elicited by COVID-19. Using RNA-seq from blood samples from a longitudinal cohort of n = 38 rheumatic patients treated with abatacept, we determined the immunological processes that are significantly regulated by this treatment. We then analyzed available blood RNA-seq from two COVID19 patient cohorts, a very early cohort from the epicenter of the pandemic in China (n = 3 COVID-19 cases and n = 3 controls), and a recent and larger cohort from the USA (n = 49 severe and n = 51 mild COVD-19 patients). We found a highly significant antagonism between SARS-CoV-2 infection and COVID-19 severity with the systemic response to abatacept. Analysis of previous single-cell RNA-seq data from bronchoalveolar lavage fluid from mild and severe COVID-19 patients and controls, reinforce the implication of the CD80/86 proinflammatory axis. Our functional results further support abatacept as a candidate therapeutic approach to prevent severe COVID-19.

Sulforaphane inhibits the expression of interleukin-6 and interleukin-8 induced in bronchial epithelial IB3-1 cells by exposure to the SARS-CoV-2 Spike protein.

BACKGROUND: A key clinical feature of COVID-19 is a deep inflammatory state known as "cytokine storm" and characterized by high expression of several cytokines, chemokines and growth factors, including IL-6 and IL-8. A direct consequence of this inflammatory state in the lungs is the Acute Respiratory Distress Syndrome (ARDS), frequently observed in severe COVID-19 patients. The "cytokine storm" is associated with severe forms of COVID-19 and poor prognosis for COVID-19 patients. Sulforaphane (SFN), one of the main components of Brassica oleraceae L. (Brassicaceae or Cruciferae), is known to possess anti-inflammatory effects in tissues from several organs, among which joints, kidneys and lungs. PURPOSE: The objective of the present study was to determine whether SFN is able to inhibit IL-6 and IL-8, two key molecules involved in the COVID-19 "cytokine storm". METHODS: The effects of SFN were studied in vitro on bronchial epithelial IB3-1 cells exposed to the SARS-CoV-2 Spike protein (S-protein). The anti-inflammatory activity of SFN on IL-6 and IL-8 expression has been evaluated by RT-qPCR and Bio-Plex analysis. RESULTS: In our study SFN inhibits, in cultured IB3-1 bronchial cells, the gene expression of IL-6 and IL-8 induced by the S-protein of SARS-CoV-2. This represents the proof-of-principle that SFN may modulate the release of some key proteins of the COVID-19 "cytokine storm". CONCLUSION: The control of the cytokine storm is one of the major issues in the management of COVID-19 patients. Our study suggests that SFN can be employed in protocols useful to control hyperinflammatory state associated with SARS-CoV-2 infection.

SARS-CoV-2 Viral Entry Proteins in Hyperandrogenemic Female Mice: Implications for Women with PCOS and COVID-19.

SARS-CoV-2, the causative agent of COVID-19, infects host cells using the angiotensin I converting enzyme 2 (ACE2) as its receptor after priming by host proteases, including TMPRSS2. COVID-19 affects multiple organ systems, and male patients suffer increased severity and mortality. Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder in reproductive-age women and is characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology. PCOS is associated with obesity and cardiometabolic comorbidities, both being risk factors associated with severe COVID-19 pathology. We hypothesize that elevated androgens in PCOS regulate SARS-CoV-2 entry proteins in multiple tissues increasing the risk for this population. Female mice were treated with dihydrotestosterone (DHT) for 90 days. Body composition was measured by EchoMRI. Fasting glucose was determined by an enzymatic method. mRNA and protein levels of ACE2, Tmprss2, Cathepsin L, Furin, Tmprss4, and Adam17 were quantified by RT-qPCR, Western-blot, or ELISA in tissues, serum, and urine. DHT treatment increased body weight, fat and lean mass, and fasting glucose. Ace2 mRNA was upregulated in the lung, cecum, heart, and kidney, while downregulated in the brain by DHT. ACE2 protein was upregulated by DHT in the small intestine, heart, and kidney. The SARS-CoV-2 priming proteases Tmprss2, Cathepsin L, and Furin mRNA were upregulated by DHT in the kidney. ACE2 sheddase Adam17 mRNA was upregulated by DHT in the kidney, which corresponded with increased urinary ACE2 in DHT treated mice. Our results highlight the potential for increased cardiac, renal, and gastrointestinal dysfunction in PCOS women with COVID-19.

Lipid-induced endothelial vascular cell adhesion molecule 1 promotes nonalcoholic steatohepatitis pathogenesis.

Monocyte homing to the liver and adhesion to the liver sinusoidal endothelial cells (LSECs) are key elements in nonalcoholic steatohepatitis (NASH) pathogenesis. We reported previously that VCAM-1 mediates monocyte adhesion to LSECs. However, the pathogenic role of VCAM-1 in NASH is unclear. Herein, we report that VCAM-1 was a top upregulated adhesion molecule in the NASH mouse liver transcriptome. Open chromatin landscape profiling combined with genome-wide transcriptome analysis showed robust transcriptional upregulation of LSEC VCAM-1 in murine NASH. Moreover, LSEC VCAM-1 expression was significantly increased in human NASH. LSEC VCAM-1 expression was upregulated by palmitate treatment in vitro and reduced with inhibition of the mitogen-activated protein 3 kinase (MAP3K) mixed lineage kinase 3 (MLK3). Likewise, LSEC VCAM-1 expression was reduced in the Mlk3-/- mice with diet-induced NASH. Furthermore, VCAM-1 neutralizing Ab or pharmacological inhibition attenuated diet-induced NASH in mice, mainly via reducing the proinflammatory monocyte hepatic population as examined by mass cytometry by time of flight (CyTOF). Moreover, endothelium-specific Vcam1 knockout mice were also protected against NASH. In summary, lipotoxic stress enhances the expression of LSEC VCAM-1, in part, through MLK3 signaling. Inhibition of VCAM-1 was salutary in murine NASH and might serve as a potential therapeutic strategy for human NASH.

Upregulation of the Renin-Angiotensin System Pathways and SARS-CoV-2 Infection: The Rationale for the Administration of Zinc-Chelating Agents in COVID-19 Patients.

The article describes the rationale for the administration of zinc-chelating agents in COVID-19 patients. In a previous work I have highlighted that the binding of the SARS-CoV spike proteins to the zinc-metalloprotease ACE2 has been shown to induce ACE2 shedding by activating the zinc-metalloprotease ADAM17, which ultimately leads to systemic upregulation of ACE2 activity. Moreover, based on experimental models, it was also shown the detrimental effect of the excessive systemic activity of ACE2 through its downstream pathways, which leads to "clinical" manifestations resembling COVID-19. In this regard, strong upregulation of circulating ACE2 activity was recently reported in COVID-19 patients, thus supporting the previous hypothesis that COVID-19 may derive from upregulation of ACE2 activity. Based on this, a reasonable hypothesis of using inhibitors that curb the upregulation of both ACE2 and ADAM17 zinc-metalloprotease activities and consequent positive feedback-loops (initially triggered by SARS-CoV-2 and subsequently sustained independently on viral trigger) is proposed as therapy for COVID-19. In particular, zinc-chelating agents such as citrate and ethylenediaminetetraacetic acid (EDTA) alone or in combination are expected to act in protecting from COVID-19 at different levels thanks to their both anticoagulant properties and inhibitory activity on zinc-metalloproteases. Several arguments are presented in support of this hypothesis and based on the current knowledge of both beneficial/harmful effects and cost/effectiveness, the use of chelating agents in the prevention and therapy of COVID-19 is proposed. In this regard, clinical trials (currently absent) employing citrate/EDTA in COVID-19 are urgently needed in order to shed more light on the efficacy of zinc chelators against SARS-CoV-2 infection in vivo.

Expression of the SARS-CoV-2 Receptor ACE2 and Proinflammatory Cytokines Induced by the Periodontopathic Bacterium Fusobacterium nucleatum in Human Respiratory Epithelial Cells.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently a global public health emergency. Periodontitis, the most prevalent disease that leads to tooth loss, is caused by infection by periodontopathic bacteria. Periodontitis is also a risk factor for pneumonia and the exacerbation of chronic obstructive pulmonary disease, presumably because of the aspiration of saliva contaminated with periodontopathic bacteria into the lower respiratory tract. Patients with these diseases have increased rates of COVID-19 aggravation and mortality. Because periodontopathic bacteria have been isolated from the bronchoalveolar lavage fluid of patients with COVID-19, periodontitis may be a risk factor for COVID-19 aggravation. However, the molecular links between periodontitis and COVID-19 have not been clarified. In this study, we found that the culture supernatant of the periodontopathic bacterium Fusobacterium nucleatum (CSF) upregulated the SARS-CoV-2 receptor angiotensin-converting enzyme 2 in A549 alveolar epithelial cells. In addition, CSF induced interleukin (IL)-6 and IL-8 production by both A549 and primary alveolar epithelial cells. CSF also strongly induced IL-6 and IL-8 expression by BEAS-2B bronchial epithelial cells and Detroit 562 pharyngeal epithelial cells. These results suggest that when patients with mild COVID-19 frequently aspirate periodontopathic bacteria, SARS-CoV-2 infection is promoted, and inflammation in the lower respiratory tract may become severe in the presence of viral pneumonia.

Mucus production stimulated by IFN-AhR signaling triggers hypoxia of COVID-19.

Silent hypoxia has emerged as a unique feature of coronavirus disease 2019 (COVID-19). In this study, we show that mucins are accumulated in the bronchoalveolar lavage fluid (BALF) of COVID-19 patients and are upregulated in the lungs of severe respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected mice and macaques. We find that induction of either interferon (IFN)-ß or IFN-γ upon SARS-CoV-2 infection results in activation of aryl hydrocarbon receptor (AhR) signaling through an IDO-Kyn-dependent pathway, leading to transcriptional upregulation of the expression of mucins, both the secreted and membrane-bound, in alveolar epithelial cells. Consequently, accumulated alveolar mucus affects the blood-gas barrier, thus inducing hypoxia and diminishing lung capacity, which can be reversed by blocking AhR activity. These findings potentially explain the silent hypoxia formation in COVID-19 patients, and suggest a possible intervention strategy by targeting the AhR pathway.

Antiviral Activity of Type I, II, and III Interferons Counterbalances ACE2 Inducibility and Restricts SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease 2019 (COVID-19), is a recently emerged respiratory coronavirus that has infected >23 million people worldwide with >800,000 deaths. Few COVID-19 therapeutics are available, and the basis for severe infections is poorly understood. Here, we investigated properties of type I (ß), II (γ), and III (λ1) interferons (IFNs), potent immune cytokines that are normally produced during infection and that upregulate IFN-stimulated gene (ISG) effectors to limit virus replication. IFNs are already in clinical trials to treat COVID-19. However, recent studies highlight the potential for IFNs to enhance expression of host angiotensin-converting enzyme 2 (ACE2), suggesting that IFN therapy or natural coinfections could exacerbate COVID-19 by upregulating this critical virus entry receptor. Using a cell line model, we found that beta interferon (IFN-ß) strongly upregulated expression of canonical antiviral ISGs, as well as ACE2 at the mRNA and cell surface protein levels. Strikingly, IFN-λ1 upregulated antiviral ISGs, but ACE2 mRNA was only marginally elevated and did not lead to detectably increased ACE2 protein at the cell surface. IFN-γ induced the weakest ISG response but clearly enhanced surface expression of ACE2. Importantly, all IFN types inhibited SARS-CoV-2 replication in a dose-dependent manner, and IFN-ß and IFN-λ1 exhibited potent antiviral activity in primary human bronchial epithelial cells. Our data imply that type-specific mechanisms or kinetics shape IFN-enhanced ACE2 transcript and cell surface levels but that the antiviral action of IFNs against SARS-CoV-2 counterbalances any proviral effects of ACE2 induction. These insights should aid in evaluating the benefits of specific IFNs, particularly IFN-λ, as repurposed therapeutics.IMPORTANCE Repurposing existing, clinically approved, antiviral drugs as COVID-19 therapeutics is a rapid way to help combat the SARS-CoV-2 pandemic. Interferons (IFNs) usually form part of the body's natural innate immune defenses against viruses, and they have been used with partial success to treat previous new viral threats, such as HIV, hepatitis C virus, and Ebola virus. Nevertheless, IFNs can have undesirable side effects, and recent reports indicate that IFNs upregulate the expression of host ACE2 (a critical entry receptor for SARS-CoV-2), raising the possibility that IFN treatments could exacerbate COVID-19. Here, we studied the antiviral- and ACE2-inducing properties of different IFN types in both a human lung cell line model and primary human bronchial epithelial cells. We observed differences between IFNs with respect to their induction of antiviral genes and abilities to enhance the cell surface expression of ACE2. Nevertheless, all the IFNs limited SARS-CoV-2 replication, suggesting that their antiviral actions can counterbalance increased ACE2.