Endosomal NOX2 oxidase exacerbates virus pathogenicity and is a target for antiviral therapy

Natural and socio-environmental factors in the transmission of COVID-19: a comprehensive analysis of epidemiology and mechanisms

PURPOSE OF REVIEW

There are significant differences in the transmission rate and mortality rate of COVID-19 under environmental conditions such as seasons and climates. However, the impact of environmental factors on the role of the COVID-19 pandemic and the transmission mechanism of the SARS-CoV-2 is unclear. Therefore, a comprehensive understanding of the impact of environmental factors on COVID-19 can provide innovative insights for global epidemic prevention and control policies and COVID-19 related research. This review summarizes the evidence of the impact of different natural and social environmental factors on the transmission of COVID-19 through a comprehensive analysis of epidemiology and mechanism research. This will provide innovative inspiration for global epidemic prevention and control policies and provide reference for similar infectious diseases that may emerge in the future.

RECENT FINDINGS

Evidence reveals mechanisms by which natural environmental factors influence the transmission of COVID-19, including (i) virus survival and transport, (ii) immune system damage, (iii) inflammation, oxidative stress, and cell death, and (iiii) increasing risk of complications. All of these measures appear to be effective in controlling the spread or mortality of COVID-19: (1) reducing air pollution levels, (2) rational use of ozone disinfection and medical ozone therapy, (3) rational exposure to sunlight, (4) scientific ventilation and maintenance of indoor temperature and humidity, (5) control of population density, and (6) control of population movement. Our review indicates that with the continuous mutation of SARS-CoV-2, high temperature, high humidity, low air pollution levels, and low population density more likely to slow down the spread of the virus.

NADPH oxidase in B cells and macrophages protects against murine lupus by regulation of TLR7

Loss of NADPH oxidase (NOX2) exacerbates systemic lupus erythematosus (SLE) in mice and humans, but the mechanisms underlying this effect remain unclear. To identify the cell lineages in which NOX2 deficiency drives SLE, we employed conditional KO and chimeric approaches to delete Cybb in several hematopoietic cell lineages of MRL.Faslpr SLE-prone mice. Deletion of Cybb in macrophages/monocytes exacerbated SLE nephritis, though not to the degree observed in the Cybb global KOs. Unexpectedly, the absence of Cybb in B cells resulted in profound glomerulonephritis and interstitial nephritis, rivaling that seen with global deletion. Furthermore, we identified that NOX2 is a key regulator of TLR7, a driver of SLE pathology, both globally and specifically in B cells. This is mediated in part through suppression of TLR7-mediated NF-κB signaling in B cells. Thus, NOX2's immunomodulatory effect in SLE is orchestrated not only by its function in the myeloid compartment, but through a pivotal role in B cells by selectively inhibiting TLR7 signaling.

Virus versus host: influenza A virus circumvents the immune responses

Influenza A virus (IAV) is a highly contagious pathogen causing dreadful losses to humans and animals around the globe. As is known, immune escape is a strategy that benefits the proliferation of IAVs by antagonizing, blocking, and suppressing immune surveillance. The HA protein binds to the sialic acid (SA) receptor to enter the cytoplasm and initiate viral infection. The conserved components of the viral genome produced during replication, known as the pathogen-associated molecular patterns (PAMPs), are thought to be critical factors for the activation of effective innate immunity by triggering dependent signaling pathways after recognition by pattern recognition receptors (PRRs), followed by a cascade of adaptive immunity. Viral infection-induced immune responses establish an antiviral state in the host to effectively inhibit virus replication and enhance viral clearance. However, IAV has evolved multiple mechanisms that allow it to synthesize and transport viral components by "playing games" with the host. At its heart, this review will describe how host and viral factors interact to facilitate the viral evasion of host immune responses.

Inhibition of NADPH oxidase 2 enhances resistance to viral neuroinflammation by facilitating M1-polarization of macrophages at the extraneural tissues

BACKGROUND

Macrophages play a pivotal role in the regulation of Japanese encephalitis (JE), a severe neuroinflammation in the central nervous system (CNS) following infection with JE virus (JEV). Macrophages are known for their heterogeneity, polarizing into M1 or M2 phenotypes in the context of various immunopathological diseases. A comprehensive understanding of macrophage polarization and its relevance to JE progression holds significant promise for advancing JE control and therapeutic strategies.

METHODS

To elucidate the role of NADPH oxidase-derived reactive oxygen species (ROS) in JE progression, we assessed viral load, M1 macrophage accumulation, and cytokine production in WT and NADPH oxidase 2 (NOX2)-deficient mice using murine JE model. Additionally, we employed bone marrow (BM) cell-derived macrophages to delineate ROS-mediated regulation of macrophage polarization by ROS following JEV infection.

RESULTS

NOX2-deficient mice exhibited increased resistance to JE progression rather than heightened susceptibility, driven by the regulation of macrophage polarization. These mice displayed reduced viral loads in peripheral lymphoid tissues and the CNS, along with diminished infiltration of inflammatory cells into the CNS, thereby resulting in attenuated neuroinflammation. Additionally, NOX2-deficient mice exhibited enhanced JEV-specific Th1 CD4 + and CD8 + T cell responses and increased accumulation of M1 macrophages producing IL-12p40 and iNOS in peripheral lymphoid and inflamed extraneural tissues. Mechanistic investigations revealed that NOX2-deficient macrophages displayed a more pronounced differentiation into M1 phenotypes in response to JEV infection, thereby leading to the suppression of viral replication. Importantly, the administration of H2O2 generated by NOX2 was shown to inhibit M1 macrophage polarization. Finally, oral administration of the ROS scavenger, butylated hydroxyanisole (BHA), bolstered resistance to JE progression and reduced viral loads in both extraneural tissues and the CNS, along with facilitated accumulation of M1 macrophages.

CONCLUSION

In light of our results, it is suggested that ROS generated by NOX2 play a role in undermining the control of JEV replication within peripheral extraneural tissues, primarily by suppressing M1 macrophage polarization. Subsequently, this leads to an augmentation in the viral load invading the CNS, thereby facilitating JE progression. Hence, our findings ultimately underscore the significance of ROS-mediated macrophage polarization in the context of JE progression initiated JEV infection.

Low dose aspirin prevents endothelial dysfunction in the aorta and foetal loss in pregnant mice infected with influenza A virus

Influenza A virus (IAV) infection in pregnancy resembles a preeclamptic phenotype characterised by vascular dysfunction and foetal growth retardation. Given that low dose aspirin (ASA) is safe in pregnancy and is used to prevent preeclampsia, we investigated whether ASA or NO-conjugated aspirin, NCX4016, resolve vascular inflammation and function to improve offspring outcomes following IAV infection in pregnant mice. Pregnant mice were intranasally infected with a mouse adapted IAV strain (Hkx31; 104 plaque forming units) and received daily treatments with either 200µg/kg ASA or NCX4016 via oral gavage. Mice were then culled and the maternal lungs and aortas collected for qPCR analysis, and wire myography was performed on aortic rings to assess endothelial and vascular smooth muscle functionality. Pup and placentas were weighed and pup growth rates and survival assessed. IAV infected mice had an impaired endothelial dependent relaxation response to ACh in the aorta, which was prevented by ASA and NCX4016 treatment. ASA and NCX4016 treatment prevented IAV dissemination and inflammation of the aorta as well as improving the pup placental ratios in utero, survival and growth rates at post-natal day 5. Low dose ASA is safe to use during pregnancy for preeclampsia and this study demonstrates that ASA may prove a promising treatment for averting the significant vascular complications associated with influenza infection during pregnancy.

NOX-2 Inhibitors may be Potential Drug Candidates for the Management of COVID-19 Complications

COVID-19 is an RNA virus that attacks the targeting organs, which express angiotensin- converting enzyme-2 (ACE-2), such as the lungs, heart, renal system, and gastrointestinal tract. The virus that enters the cell by endocytosis triggers ROS production within the confines of endosomes via a NOX-2 containing NADPH-oxidase. Various isoforms of NADPH oxidase are expressed in airways and alveolar epithelial cells, endothelial and vascular smooth muscle cells, and inflammatory cells, such as alveolar macrophages, monocytes, neutrophils, and Tlymphocytes. The key NOX isoform expressed in macrophages and neutrophils is the NOX-2 oxidase, whereas, in airways and alveolar epithelial cells, it appears to be NOX-1 and NOX-2. The respiratory RNA viruses induce NOX-2-mediated ROS production in the endosomes of alveolar macrophages. The mitochondrial and NADPH oxidase (NOX) generated ROS can enhance TGF-β signaling to promote fibrosis of the lungs. The endothelium-derived ROS and platelet-derived ROS, due to activation of the NADPH-oxidase enzyme, play a crucial role in platelet activation. It has been observed that NOX-2 is generally activated in COVID-19 patients. The post-COVID complications like pulmonary fibrosis and platelet aggregation may be due to the activation of NOX-2. NOX-2 inhibitors may be a useful drug candidate to prevent COVID-19 complications like pulmonary fibrosis and platelet aggregation.

TLR7 promotes smoke-induced experimental lung damage through the activity of mast cell tryptase

Toll-like receptor 7 (TLR7) is known for eliciting immunity against single-stranded RNA viruses, and is increased in both human and cigarette smoke (CS)-induced, experimental chronic obstructive pulmonary disease (COPD). Here we show that the severity of CS-induced emphysema and COPD is reduced in TLR7-deficient mice, while inhalation of imiquimod, a TLR7-agonist, induces emphysema without CS exposure. This imiquimod-induced emphysema is reduced in mice deficient in mast cell protease-6, or when wild-type mice are treated with the mast cell stabilizer, cromolyn. Furthermore, therapeutic treatment with anti-TLR7 monoclonal antibody suppresses CS-induced emphysema, experimental COPD and accumulation of pulmonary mast cells in mice. Lastly, TLR7 mRNA is increased in pre-existing datasets from patients with COPD, while TLR7+ mast cells are increased in COPD lungs and associated with severity of COPD. Our results thus support roles for TLR7 in mediating emphysema and COPD through mast cell activity, and may implicate TLR7 as a potential therapeutic target.

Redox-active endosomes mediate α5β1 integrin signaling and promote chondrocyte matrix metalloproteinase production in osteoarthritis

Mechanical cues sensed by integrins induce cells to produce proteases to remodel the extracellular matrix. Excessive protease production occurs in many degenerative diseases, including osteoarthritis, in which articular cartilage degradation is associated with the genesis of matrix protein fragments that can activate integrins. We investigated the mechanisms by which integrin signals may promote protease production in response to matrix changes in osteoarthritis. Using a fragment of the matrix protein fibronectin (FN) to activate the α5β1 integrin in primary human chondrocytes, we found that endocytosis of the integrin and FN fragment complex drove the production of the matrix metalloproteinase MMP-13. Activation of α5β1 by the FN fragment, but not by intact FN, was accompanied by reactive oxygen species (ROS) production initially at the cell surface, then in early endosomes. These ROS-producing endosomes (called redoxosomes) contained the integrin-FN fragment complex, the ROS-producing enzyme NADPH oxidase 2 (NOX2), and SRC, a redox-regulated kinase that promotes MMP-13 production. In contrast, intact FN was endocytosed and trafficked to recycling endosomes without inducing ROS production. Articular cartilage from patients with osteoarthritis showed increased amounts of SRC and the NOX2 complex component p67phox. Furthermore, we observed enhanced localization of SRC and p67phox at early endosomes, suggesting that redoxosomes could transmit and sustain integrin signaling in response to matrix damage. This signaling mechanism not only amplifies the production of matrix-degrading proteases but also establishes a self-perpetuating cycle that contributes to the ongoing degradation of cartilage matrix in osteoarthritis.

Sphingosine-1-Phosphate as Lung and Cardiac Vasculature Protecting Agent in SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may cause severe respiratory illness with high mortality. SARS-CoV-2 infection results in a massive inflammatory cell infiltration into the infected lungs accompanied by excessive pro-inflammatory cytokine production. The lung histology of dead patients shows that some areas are severely emphysematous, with enormously dilated blood vessels and micro-thromboses. The inappropriate inflammatory response damaging the pulmonary interstitial arteriolar walls suggests that the respiratory distress may come in a large part from lung vasculature injuries. It has been recently observed that low plasmatic sphingosine-1-phosphate (S1P) is a marker of a worse prognosis of clinical outcome in severe coronavirus disease (COVID) patients. S1P is an angiogenic molecule displaying anti-inflammatory and anti-apoptotic properties, that promote intercellular interactions between endothelial cells and pericytes resulting in the stabilization of arteries and capillaries. In this context, it can be hypothesized that the benefit of a normal S1P level is due to its protective effect on lung vasculature functionality. This paper provides evidence supporting this concept, opening the way for the design of a pharmacological approach involving the use of an S1P lyase inhibitor to increase the S1P level that in turn will rescue the lung vasculature functionality.

Picolinic acid is a broad-spectrum inhibitor of enveloped virus entry that restricts SARS-CoV-2 and influenza A virus in vivo

The COVID-19 pandemic highlights an urgent need for effective antivirals. Targeting host processes co-opted by viruses is an attractive antiviral strategy with a high resistance barrier. Picolinic acid (PA) is a tryptophan metabolite endogenously produced in mammals. Here, we report the broad-spectrum antiviral activity of PA against enveloped viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus (IAV), flaviviruses, herpes simplex virus, and parainfluenza virus. Mechanistic studies reveal that PA inhibits enveloped virus entry by compromising viral membrane integrity, inhibiting virus-cellular membrane fusion, and interfering with cellular endocytosis. More importantly, in pre-clinical animal models, PA exhibits promising antiviral efficacy against SARS-CoV-2 and IAV. Overall, our data establish PA as a broad-spectrum antiviral with promising pre-clinical efficacy against pandemic viruses SARS-CoV-2 and IAV.

Polydopamine-based nanomedicines for efficient antiviral and secondary injury protection therapy

Viral infections continue to threaten human health. It remains a major challenge to efficiently inhibit viral infection while avoiding secondary injury. Here, we designed a multifunctional nanoplatform (termed as ODCM), prepared by oseltamivir phosphate (OP)-loaded polydopamine (PDA) nanoparticles camouflaged by the macrophage cell membrane (CM). OP can be efficiently loaded onto the PDA nanoparticles through the π-π stacking and hydrogen bonding interactions with a high drug-loading rate of 37.6%. In particular, the biomimetic nanoparticles can accumulate actively in the damaged lung model of viral infection. At the infection site, PDA nanoparticles can consume excess reactive oxygen species and be simultaneously oxidized and degraded to achieve controlled release of OP. This system exhibits enhanced delivery efficiency, inflammatory storm suppression, and viral replication inhibition. Therefore, the system exerts outstanding therapeutic effects while improving pulmonary edema and protecting lung injury in a mouse model of influenza A virus infection.

Endothelial dysfunction, oxidative stress and low-grade endotoxemia in COVID-19 patients hospitalised in medical wards

BACKGROUND

Endothelial dysfunction, assessed by flow-mediated dilation (FMD), is related to poor prognosis in patients with COVID-19 pneumonia (CP). In this study, we explored the interplay among FMD, NADPH oxidase type 2 (NOX-2) and lipopolysaccharides (LPS) in hospitalised patients with CP, community acquired pneumonia (CAP) and controls (CT).

METHODS

We enrolled 20 consecutive patients with CP, 20 hospitalised patients with CAP and 20 CT matched for sex, age, and main cardiovascular risk factors. In all subjects we performed FMD and collected blood samples to analyse markers of oxidative stress (soluble Nox2-derived peptide (sNOX2-dp), hydrogen peroxide breakdown activity (HBA), nitric oxide (NO), hydrogen peroxide (H2O2)), inflammation (TNF-α and IL-6), LPS and zonulin levels.

RESULTS

Compared with controls, CP had significant higher values of LPS, sNOX-2-dp, H2O2,TNF-α, IL-6 and zonulin; conversely FMD, HBA and NO bioavailability were significantly lower in CP. Compared to CAP patients, CP had significantly higher levels of sNOX2-dp, H2O2, TNF-α, IL-6, LPS, zonulin and lower HBA. Simple linear regression analysis showed that FMD inversely correlated with sNOX2-dp, H2O2, TNF-α, IL-6, LPS and zonulin; conversely FMD was directly correlated with NO bioavailability and HBA. Multiple linear regression analysis highlighted LPS as the only predictor of FMD.

CONCLUSION

This study shows that patients with COVID-19 have low-grade endotoxemia that could activate NOX-2, generating increased oxidative stress and endothelial dysfunction.

Carboxymethyl Cellulose as a Food Emulsifier: Are Its Days Numbered?

Carboxymethyl cellulose use in industry is ubiquitous. Though it is recognized as safe by the EFSA and FDA, newer works have raised concerns related to its safety, as in vivo studies showed evidence of gut dysbiosis associated with CMC's presence. Herein lies the question, is CMC a gut pro-inflammatory compound? As no work addressed this question, we sought to understand whether CMC was pro-inflammatory through the immunomodulation of GI tract epithelial cells. The results showed that while CMC was not cytotoxic up to 25 mg/mL towards Caco-2, HT29-MTX and Hep G2 cells, it had an overall pro-inflammatory behavior. In a Caco-2 monolayer, CMC by itself increased IL-6, IL-8 and TNF-α secretion, with the latter increasing by 1924%, and with these increases being 9.7 times superior to the one obtained for the IL-1β pro-inflammation control. In co-culture models, an increase in secretion in the apical side, particularly for IL-6 (692% increase), was observed, and when RAW 264.7 was added, data showed a more complex scenario as stimulation of pro-inflammatory (IL-6, MCP-1 and TNF-α) and anti-inflammatory (IL-10 and IFN-β) cytokines in the basal side was observed. Considering these results, CMC may exert a pro-inflammatory effect in the intestinal lumen, and despite more studies being required, the incorporation of CMC in foodstuffs must be carefully considered in the future to minimize potential GI tract dysbiosis.

Disruptions in endocytic traffic contribute to the activation of the NLRP3 inflammasome

Inflammation driven by the NLRP3 inflammasome is coordinated through multiple signaling pathways and is regulated by subcellular organelles. Here, we tested the hypothesis that NLRP3 senses disrupted endosome trafficking to trigger inflammasome formation and inflammatory cytokine secretion. NLRP3-activating stimuli disrupted endosome trafficking and triggered localization of NLRP3 to vesicles positive for endolysosomal markers and for the inositol lipid PI4P. Chemical disruption of endosome trafficking sensitized macrophages to the NLRP3 activator imiquimod, driving enhanced inflammasome activation and cytokine secretion. Together, these data suggest that NLRP3 can sense disruptions in the trafficking of endosomal cargoes, which may explain in part the spatial activation of the NLRP3 inflammasome. These data highlight mechanisms that could be exploited in the therapeutic targeting of NLRP3.

Toll-Like Receptor 4-Dependent Platelet-Related Thrombosis in SARS-CoV-2 Infection

BACKGROUND

SARS-CoV-2 is associated with an increased risk of venous and arterial thrombosis, but the underlying mechanism is still unclear.

METHODS

We performed a cross-sectional analysis of platelet function in 25 SARS-CoV-2 and 10 healthy subjects by measuring Nox2 (NADPH oxidase 2)-derived oxidative stress and thromboxane B₂, and investigated if administration of monoclonal antibodies against the S protein (Spike protein) of SARS-CoV-2 affects platelet activation. Furthermore, we investigated in vitro if the S protein of SARS-CoV-2 or plasma from SARS-CoV-2 enhanced platelet activation.

RESULTS

Ex vivo studies showed enhanced platelet Nox2-derived oxidative stress and thromboxane B₂ biosynthesis and under laminar flow platelet-dependent thrombus growth in SARS-CoV-2 compared with controls; both effects were lowered by Nox2 and TLR4 (Toll-like receptor 4) inhibitors. Two hours after administration of monoclonal antibodies, a significant inhibition of platelet activation was observed in patients with SARS-CoV-2 compared with untreated ones. In vitro study showed that S protein per se did not elicit platelet activation but amplified the platelet response to subthreshold concentrations of agonists and functionally interacted with platelet TLR4. A docking simulation analysis suggested that TLR4 binds to S protein via three receptor-binding domains; furthermore, immunoprecipitation and immunofluorescence showed S protein-TLR4 colocalization in platelets from SARS-CoV-2. Plasma from patients with SARS-CoV-2 enhanced platelet activation and Nox2-related oxidative stress, an effect blunted by TNF (tumor necrosis factor) α inhibitor; this effect was recapitulated by an in vitro study documenting that TNFα alone promoted platelet activation and amplified the platelet response to S protein via p47phox (phagocyte oxidase) upregulation.

CONCLUSIONS

The study identifies 2 TLR4-dependent and independent pathways promoting platelet-dependent thrombus growth and suggests inhibition of TLR4. or p47phox as a tool to counteract thrombosis in SARS-CoV-2.

Innate sensing and cellular metabolism: role in fine tuning antiviral immune responses

Several studies over the last decade have identified intimate links between cellular metabolism and macrophage function. Metabolism has been shown to both drive and regulate macrophage function by producing bioenergetic and biosynthetic precursors as well as metabolites (and other bioactive molecules) that regulate gene expression and signal transduction. Many studies have focused on lipopolysaccharide-induced reprogramming, assuming that it is representative of most inflammatory responses. However, emerging evidence suggests that diverse pathogen-associated molecular patterns (PAMPs) are associated with unique metabolic profiles, which may drive pathogen specific immune responses. Further, these metabolic pathways and processes may act as a rheostat to regulate the magnitude of an inflammatory response based on the biochemical features of the local microenvironment. In this review, we will discuss recent work examining the relationship between cellular metabolism and macrophage responses to viral PAMPs and describe how these processes differ from lipopolysaccharide-associated responses. We will also discuss how an improved understanding of the specificity of these processes may offer new insights to fine-tune macrophage function during viral infections or when using viral PAMPs as therapeutics.

The therapeutic potential of quercetin for cigarette smoking-induced chronic obstructive pulmonary disease: a narrative review

Quercetin is a flavonoid with antioxidant and anti-inflammatory properties. Quercetin has potentially beneficial therapeutic effects for several diseases, including cigarette smoking-induced chronic obstructive pulmonary disease (CS-COPD). Many studies have shown that quercetin's antioxidant and anti-inflammatory properties have positive therapeutic potential for CS-COPD. In addition, quercetin's immunomodulatory, anti-cellular senescence, mitochondrial autophagy-modulating, and gut microbiota-modulating effects may also have therapeutic value for CS-COPD. However, there appears to be no review of the possible mechanisms of quercetin for treating CS-COPD. Moreover, the combination of quercetin with common therapeutic drugs for CS-COPD needs further refinement. Therefore, in this article, after introducing the definition and metabolism of quercetin, and its safety, we comprehensively presented the pathogenesis of CS-COPD related to oxidative stress, inflammation, immunity, cellular senescence, mitochondrial autophagy, and gut microbiota. We then reviewed quercetin's anti-CS-COPD effects, performed by influencing these mechanisms. Finally, we explored the possibility of using quercetin with commonly used drugs for treating CS-COPD, providing a basis for future screening of excellent drug combinations for treating CS-COPD. This review has provided meaningful information on quercetin's mechanisms and clinical use in treating CS-COPD.

NOX2 oxidase inhibitor GSK2795039 possess antiviral activity against H1N1 influenza A virus in vitro and vivo

The continuous zoonotic circulation and reassortment potential of influenza A viruses (IAV) in nature represents an enormous public health threat to humans. Beside vaccination antivirals are needed to efficiently control spreading of the disease. The previous research has shown that NOX2 involved in IAV replication, but the detailed mechanism has not been reported. In the present study we investigated the roles of NOX2 in host inflammatory response and IAV replication using a novel inhibitor GSK2795039. The drug significantly reduced H1N1 virus induced NOX2 activity and ROS release in human lung epithelial cells. The results of time course experiments suggested that GSK2795039 inhibited an early post-entry step of viral infection. Concomitantly, there was a decreased expression of pro-inflammatory cytokines (tumor necrosis factor (TNF)-α, interferon (IFN)-β and interleukin (IL)-6) in NOX2 suppressed cells. In vivo, compared with control groups, suppression of NOX2 improved the survival rate of mice infected with H1N1 virus (42.9% in GSK2795039 treated mice versus >0% of control mice) and viral burden also decreased in the GSK2795039 treated group. Thus, our data demonstrated a critical role for NOX2 in the establishment of H1N1 infection and subsequent inflammatory reactions, which suggest that GSK2795039 may be a potential therapeutic drug for IAV infection.

Influenza Virus Infection during Pregnancy as a Trigger of Acute and Chronic Complications

Influenza A virus (IAV) infection during pregnancy disrupts maternal and fetal health through biological mechanisms, which are to date poorly characterised. During pregnancy, the viral clearance mechanisms from the lung are sub-optimal and involve hyperactive innate and adaptive immune responses that generate wide-spread inflammation. Pregnancy-related adaptations of the immune and the cardiovascular systems appear to result in delayed recovery post-viral infection, which in turn promotes a prolonged inflammatory phenotype, increasing disease severity, and causing maternal and fetal health problems. This has immediate and long-term consequences for the mother and fetus, with complications including acute cardiopulmonary distress syndrome in the mother that lead to perinatal complications such as intrauterine growth restriction (IUGR), and birth defects; cleft lip, cleft palate, neural tube defects and congenital heart defects. In addition, an increased risk of long-term neurological disorders including schizophrenia in the offspring is reported. In this review we discuss the pathophysiology of IAV infection during pregnancy and its striking similarity to other well-established complications of pregnancy such as preeclampsia. We discuss general features of vascular disease with a focus on vascular inflammation and define the "Vascular Storm" that is triggered by influenza infection during pregnancy, as a pivotal disease mechanism for short and long term cardiovascular complications.

Comparison of renal histopathology in three patients with gross hematuria after SARS-CoV-2 vaccination

We present three cases of IgA nephropathy with gross hematuria following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccination. Case 1 was a 60-year-old woman who has previously experienced transient proteinuria. Case 2 was a 22-year-old woman with no history of urinary abnormality. Finally, case 3 was a 66-year-old woman who has had microscopic hematuria since she was in her 50s. They were all diagnosed as IgA nephropathy with little histological active lesion. Their renal function and proteinuria improved without the use of corticosteroids. There were differences in the findings of vascular endothelial damage based on the time between the appearance of gross hematuria and renal biopsy. Glomerular endocapillary damage could be a part of the mechanism triggered by mRNA vaccination. When a patient presents with gross hematuria following vaccination, a comprehensive approach including renal biopsy should be considered.

Disengaging the COVID-19 Clutch as a Discerning Eye Over the Inflammatory Circuit During SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the cytokine release syndrome (CRS) and leads to multiorgan dysfunction. Mitochondrial dynamics are fundamental to protect against environmental insults, but they are highly susceptible to viral infections. Defective mitochondria are potential sources of reactive oxygen species (ROS). Infection with SARS-CoV-2 damages mitochondria, alters autophagy, reduces nitric oxide (NO), and increases both nicotinamide adenine dinucleotide phosphate oxidases (NOX) and ROS. Patients with coronavirus disease 2019 (COVID-19) exhibited activated toll-like receptors (TLRs) and the Nucleotide-binding and oligomerization domain (NOD-), leucine-rich repeat (LRR-), pyrin domain-containing protein 3 (NLRP3) inflammasome. The activation of TLRs and NLRP3 by SARS-CoV-2 induces interleukin 6 (IL-6), IL-1β, IL-18, and lactate dehydrogenase (LDH). Herein, we outline the inflammatory circuit of COVID-19 and what occurs behind the scene, the interplay of NOX/ROS and their role in hypoxia and thrombosis, and the important role of ROS scavengers to reduce COVID-19-related inflammation.

Detecting free radicals post viral infections

Free radical generation plays a key role in viral infections. While free radicals have an antimicrobial effect on bacteria or fungi, their interplay with viruses is complicated and varies greatly for different types of viruses as well as different radical species. In some cases, radical generation contributes to the defense against the viruses and thus reduces the viral load. In other cases, radical generation induces mutations or damages the host tissue and can increase the viral load. This has led to antioxidants being used to treat viral infections. Here we discuss the roles that radicals play in virus pathology. Furthermore, we critically review methods that facilitate the detection of free radicals in vivo or in vitro in viral infections.

Surface cysteines could protect the SARS-CoV-2 main protease from oxidative damage

The SARS-CoV-2 main protease (Mpro) is responsible for cleaving twelve nonstructural proteins from the viral polyprotein. Mpro, a cysteine protease, is characterized by a large number of noncatalytic cysteine (Cys) residues, none involved in disulfide bonds. In the absence of a tertiary-structure stabilizing role for these residues, a possible alternative is that they are involved in redox processes. We report experimental work in support of a proposal that surface cysteines on Mpro can protect the active-site Cys145 from oxidation by reactive oxygen species (ROS). In investigations of enzyme kinetics, we found that mutating three surface cysteines to serines did not greatly affect activity, which in turn indicates that these cysteines could protect Cys145 from oxidative damage.

Reactive Oxygen Species Scavenging Nanomedicine for the Treatment of Ischemic Heart Disease

Ischemic heart disease (IHD) is the leading cause of disability and mortality worldwide. Reactive oxygen species (ROS) have been shown to play key roles in the progression of diabetes, hypertension, and hypercholesterolemia, which are independent risk factors that lead to atherosclerosis and the development of IHD. Engineered biomaterial-based nanomedicines are under extensive investigation and exploration, serving as smart and multifunctional nanocarriers for synergistic therapeutic effect. Capitalizing on cell/molecule-targeting drug delivery, nanomedicines present enhanced specificity and safety with favorable pharmacokinetics and pharmacodynamics. Herein, the roles of ROS in both IHD and its risk factors are discussed, highlighting cardiovascular medications that have antioxidant properties, and summarizing the advantages, properties, and recent achievements of nanomedicines that have ROS scavenging capacity for the treatment of diabetes, hypertension, hypercholesterolemia, atherosclerosis, ischemia/reperfusion, and myocardial infarction. Finally, the current challenges of nanomedicines for ROS-scavenging treatment of IHD and possible future directions are discussed from a clinical perspective.

Recent Developments in the Understanding of Immunity, Pathogenesis and Management of COVID-19

Coronaviruses represent a diverse family of enveloped positive-sense single stranded RNA viruses. COVID-19, caused by Severe Acute Respiratory Syndrome Coronavirus-2, is a highly contagious respiratory disease transmissible mainly via close contact and respiratory droplets which can result in severe, life-threatening respiratory pathologies. It is understood that glutathione, a naturally occurring antioxidant known for its role in immune response and cellular detoxification, is the target of various proinflammatory cytokines and transcription factors resulting in the infection, replication, and production of reactive oxygen species. This leads to more severe symptoms of COVID-19 and increased susceptibility to other illnesses such as tuberculosis. The emergence of vaccines against COVID-19, usage of monoclonal antibodies as treatments for infection, and implementation of pharmaceutical drugs have been effective methods for preventing and treating symptoms. However, with the mutating nature of the virus, other treatment modalities have been in research. With its role in antiviral defense and immune response, glutathione has been heavily explored in regard to COVID-19. Glutathione has demonstrated protective effects on inflammation and downregulation of reactive oxygen species, thereby resulting in less severe symptoms of COVID-19 infection and warranting the discussion of glutathione as a treatment mechanism.

Enteroviral 2B Interacts with VDAC3 to Regulate Reactive Oxygen Species Generation That Is Essential to Viral Replication

Enterovirus (EV) 71 caused episodes of outbreaks in China and Southeast Asia during the last few decades. We have previously reported that EV71 induces reactive oxygen species (ROS). However, the underlying mechanism remains elusive. Co-immunoprecipitation-proteomic analysis revealed that enteroviral 2B protein interacted with mitochondrial voltage-dependent anion channel 3 (VDAC3). Knockdown (KD) of VDAC3 expression specifically inhibited enteroviral replication. Single-round viral replication was also inhibited in KD cells, suggesting that VDAC3 plays an essential role in replication. Consistent with this, VDAC3 gene KD significantly reduced the EV71-induced mitochondrial ROS generation. Exogenous 2B expression could induce the mitochondrial ROS generation that was significantly reduced in VDAC3-KD cells or in the Mito-TEMPO-treated cells. Moreover, VDAC3 appears to be necessary for regulation of antioxidant metabolism. VDAC3 gene KD led to the enhancement of such pathways as hypotaurine/taurine synthesis in the infected cells. Taken together, these findings suggest that 2B and VDAC3 interact to enhance mitochondrial ROS generation, which promotes viral replication.

Reactive oxygen species associated immunoregulation post influenza virus infection

An appropriate level of reactive oxygen species (ROS) is necessary for cell proliferation, signaling transduction, and apoptosis due to their highly reactive character. ROS are generated through multiple metabolic pathways under a fine-tuned control between oxidant and antioxidant signaling. A growing number of evidence has proved their highly relevant role in modulating inflammation during influenza virus infection. As a network of biological process for protecting organism from invasion of pathogens, immune system can react and fight back through either innate immune system or adaptive immune system, or both. Herein, we provide a review about the mechanisms of ROS generation when encounter influenza virus infection, and how the imbalanced level of ROS influences the replication of virus. We also summarize the pathways used by both the innate and adaptive immune system to sense and attack the invaded virus and abnormal levels of ROS. We further review the limitation of current strategies and discuss the direction of future work.

Glycolysis and the Pentose Phosphate Pathway Promote LPS-Induced NOX2 Oxidase- and IFN-β-Dependent Inflammation in Macrophages

Macrophages undergo a metabolic switch from oxidative phosphorylation to glycolysis when exposed to gram-negative bacterial lipopolysaccharide (LPS), which modulates antibacterial host defence mechanisms. Here, we show that LPS treatment of macrophages increased the classical oxidative burst response via the NADPH oxidase (NOX) 2 enzyme, which was blocked by 2-deoxyglucose (2-DG) inhibition of glycolysis. The inhibition of the pentose phosphate pathway with 6-aminonicotinamide (6-AN) also suppressed the LPS-induced increase in NOX2 activity and was associated with a significant reduction in the mRNA expression of NOX2 and its organizer protein p47phox. Notably, the LPS-dependent enhancement in NOX2 oxidase activity was independent of both succinate and mitochondrial reactive oxygen species (ROS) production. LPS also increased type I IFN-β expression, which was suppressed by 2-DG and 6-AN and, therefore, is dependent on glycolysis and the pentose phosphate pathway. The type I IFN-β response to LPS was also inhibited by apocynin pre-treatment, suggesting that NOX2-derived ROS promotes the TLR4-induced response to LPS. Moreover, recombinant IFN-β increased NOX2 oxidase-dependent ROS production, as well as NOX2 and p47phox expression. Our findings identify a previously undescribed molecular mechanism where both glycolysis and the pentose phosphate pathway are required to promote LPS-induced inflammation in macrophages.

The NCF1 variant aggravates autoimmunity by facilitating the activation of plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) are a professional type I IFN producer that play critical roles in the pathogenesis of autoimmune diseases. However, both genetic regulation of the function of pDCs and their relationships with autoimmunity are largely undetermined. Here, we investigated the causality of the neutrophil cytosolic factor 1 (NCF1) missense variant, which is one of the most significant associated risk variants for lupus, and found that the substitution of arginine (R) for histidine (H) at position 90 in the NCF1 protein (NCF1 p.R90H) led to excessive activation of pDCs. A mechanism study demonstrated that p.R90H reduced the affinity of NCF1 for phospholipids, thereby impairing endosomal localization of NCF1. As NCF1 is a subunit of the NADPH oxidase 2 (NOX2) complex, this impairment led to an acidified endosomal pH and facilitated downstream TLR signaling. Consistently, the homozygous knockin mice manifested aggravated lupus progression in a pDC-dependent lupus model. More important, pharmaceutical intervention revealed that hydroxychloroquine (HCQ) could antagonize the detrimental function of NCF1 p.R90H in the lupus model and systemic lupus erythematosus samples, supporting the idea that NCF1 p.R90H could be identified as a genetic biomarker for HCQ application. Therefore, our study provides insights into the genetic control of pDC function and a paradigm for applying genetic variants to improve targeted therapy for autoimmune diseases.

Aryl Hydrocarbon Receptor in Oxidative Stress as a Double Agent and Its Biological and Therapeutic Significance

The aryl hydrocarbon receptor (AhR) has long been implicated in the induction of a battery of genes involved in the metabolism of xenobiotics and endogenous compounds. AhR is a ligand-activated transcription factor necessary for the launch of transcriptional responses important in health and disease. In past decades, evidence has accumulated that AhR is associated with the cellular response to oxidative stress, and this property of AhR must be taken into account during investigations into a mechanism of action of xenobiotics that is able to activate AhR or that is susceptible to metabolic activation by enzymes encoded by the genes that are under the control of AhR. In this review, we examine various mechanisms by which AhR takes part in the oxidative-stress response, including antioxidant and prooxidant enzymes and cytochrome P450. We also show that AhR, as a participant in the redox balance and as a modulator of redox signals, is being increasingly studied as a target for a new class of therapeutic compounds and as an explanation for the pathogenesis of some disorders.

Endothelial NOX4 Oxidase Negatively Regulates Inflammation and Improves Morbidity During Influenza A Virus Lung Infection in Mice

Endosomal NOX2 oxidase-dependent ROS production promotes influenza pathogenicity, but the role of NOX4 oxidase, which is highly expressed in the lung endothelium, is largely unknown. The aim of this study was to determine if endothelial NOX4 expression can influence viral pathology in vivo, using a mouse model of influenza infection. WT and transgenic endothelial NOX4 overexpressing mice (NOX4 TG) were infected intranasally with the Hong Kong H3N2 X-31 influenza A virus (104 PFU; HK x-31) or PBS control. Mice were culled at either 3 or 7 days post-infection to analyse: airway inflammation by bronchoalveolar lavage fluid (BALF) cell counts; NOX4, as well as inflammatory cytokine and chemokine gene expression by QPCR; and ROS production by an L-012-enhanced chemiluminescence assay. Influenza A virus infection of WT mice resulted in a significant reduction in lung NOX4 mRNA at day 3, which persisted until day 7, when compared to uninfected mice. Influenza A virus infection of NOX4 TG mice resulted in significantly less weight loss than that of WT mice at 3-days post infection. Viral titres were decreased in infected NOX4 TG mice compared to the infected WT mice, at both 3- and 7-days post infection and there was significantly less lung alveolitis, peri-bronchial inflammation and neutrophil infiltration. The oxidative burst from BALF inflammatory cells extracted from infected NOX4 TG mice was significantly less than that in the WT mice. Expression of macrophage and neutrophil chemoattractants CXCL10, CCL3, CXCL1 and CXCL2 in the lung tissue were significantly lower in NOX4 TG mice compared to the WT mice at 3-days post infection. We conclude that endothelial NOX4 oxidase is protective against influenza morbidity and is a potential target for limiting influenza A virus-induced lung inflammation.

Do Diet and Dietary Supplements Mitigate Clinical Outcomes in COVID-19?

The coronavirus disease 2019 (COVID-19) has caused a pandemic and upheaval that health authorities and citizens around the globe are still grappling with to this day. While public health measures, vaccine development, and new therapeutics have made great strides in understanding and managing the pandemic, there has been an increasing focus on the potential roles of diet and supplementation in disease prevention and adjuvant treatment. In the literature, the impact of nutrition on other respiratory illnesses, including the common cold, pneumonia, and influenza, has been widely demonstrated in both animal and human models. However, there is much less research on the impact related to COVID-19. The present study discusses the potential uses of diets, vitamins, and supplements, including the Mediterranean diet, glutathione, zinc, and traditional Chinese medicine, in the prevention of infection and severe illness. The evidence demonstrating the efficacy of diet supplementation on infection risk, disease duration, severity, and recovery is mixed and inconsistent. More clinical trials are necessary in order to clearly demonstrate the contribution of nutrition and to guide potential therapeutic protocols.

Therapeutic Targeting of Endosome and Mitochondrial Reactive Oxygen Species Protects Mice From Influenza Virus Morbidity

There is an urgent need to develop effective therapeutic strategies including immunomodulators to combat influenza A virus (IAV) infection. Influenza A viruses increase ROS production, which suppress anti-viral responses and contribute to pathological inflammation and morbidity. Two major cellular sites of ROS production are endosomes via the NOX2-oxidase enzyme and the electron transport chain in mitochondria. Here we examined the effect of administration of Cgp91ds-TAT, an endosome-targeted NOX2 oxidase inhibitor, in combination with mitoTEMPO, a mitochondrial ROS scavenger and compared it to monotherapy treatment during an established IAV infection. Mice were infected with IAV (Hkx31 strain; 10⁴PFU/mouse) and 24 h post infection were treated with Cgp91ds-TAT (0.2 mg/kg), mitoTEMPO (100 μg) or with a combination of these inhibitors [Cgp91ds-TAT (0.2 mg/kg)/mitoTEMPO (100 μg)] intranasally every day for up to 2 days post infection (pi). Mice were euthanized on Days 3 or 6 post infection for analyses of disease severity. A combination of Cgp91ds-TAT and mitoTEMPO treatment was more effective than the ROS inhibitors alone at reducing airway and neutrophilic inflammation, bodyweight loss, lung oedema and improved the lung pathology with a reduction in alveolitis following IAV infection. Dual ROS inhibition also caused a significant elevation in Type I IFN expression at the early phase of infection (day 3 pi), however, this response was suppressed at the later phase of infection (day 6 pi). Furthermore, combined treatment with Cgp91ds-TAT and mitoTEMPO resulted in an increase in IAV-specific CD8⁺ T cells in the lungs. In conclusion, this study demonstrates that the reduction of ROS production in two major subcellular sites, i.e. endosomes and mitochondria, by intranasal delivery of a combination of Cgp91ds-TAT and mitoTEMPO, suppresses the severity of influenza infection and highlights a novel immunomodulatory approach for IAV disease management.

Oxidative Stress-Related Mechanisms in SARS-CoV-2 Infections

The COVID-19 pandemic caused relatively high mortality in patients, especially in those with concomitant diseases (i.e., diabetes, hypertension, and chronic obstructive pulmonary disease (COPD)). In most of aforementioned comorbidities, the oxidative stress appears to be an important player in their pathogenesis. The direct cause of death in critically ill patients with COVID-19 is still far from being elucidated. Although some preliminary data suggests that the lung vasculature injury and the loss of the functioning part of pulmonary alveolar population are crucial, the precise mechanism is still unclear. On the other hand, at least two classes of medications used with some clinical benefits in COVID-19 treatment seem to have a major influence on ROS (reactive oxygen species) and RNS (reactive nitrogen species) production. However, oxidative stress is one of the important mechanisms in the antiviral immune response and innate immunity. Therefore, it would be of interest to summarize the data regarding the oxidative stress in severe COVID-19. In this review, we discuss the role of oxidative and antioxidant mechanisms in severe COVID-19 based on available studies. We also present the role of ROS and RNS in other viral infections in humans and in animal models. Although reactive oxygen and nitrogen species play an important role in the innate antiviral immune response, in some situations, they might have a deleterious effect, e.g., in some coronaviral infections. The understanding of the redox mechanisms in severe COVID-19 disease may have an impact on its treatment.

Oxidative stress-induced endothelial dysfunction and decreased vascular nitric oxide in COVID-19 patients

Background

SARS-CoV-2 targets endothelial cells through the angiotensin-converting enzyme 2 receptor. The resulting endothelial injury induces widespread thrombosis and microangiopathy. Nevertheless, early specific markers of endothelial dysfunction and vascular redox status in COVID-19 patients are currently missing.

Methods

Observational study including ICU and non-ICU adult COVID-19 patients admitted in hospital for acute respiratory failure, compared with control subjects matched for cardiovascular risk factors similar to ICU COVID-19 patients, and ICU septic shock patients unrelated to COVID-19.

Findings

Early SARS-CoV-2 infection was associated with an imbalance between an exacerbated oxidative stress (plasma peroxides levels in ICU patients vs. controls: 1456.0 ± 400.2 vs 436 ± 272.1 mmol/L; P < 0.05) and a reduced nitric oxide bioavailability proportional to disease severity (5-α-nitrosyl-hemoglobin, HbNO in ICU patients vs. controls: 116.1 ± 62.1 vs. 163.3 ± 46.7 nmol/L; P < 0.05). HbNO levels correlated with oxygenation parameters (PaO₂/FiO₂ ratio) in COVID-19 patients (R² = 0.13; P < 0.05). Plasma levels of angiotensin II, aldosterone, renin or serum level of TREM-1 ruled out any hyper-activation of the renin-angiotensin-aldosterone system or leucocyte respiratory burst in ICU COVID-19 patients, contrary to septic patients.

Interpretation

Endothelial oxidative stress with ensuing decreased NO bioavailability appears as a likely pathogenic factor of endothelial dysfunction in ICU COVID-19 patients. A correlation between NO bioavailability and oxygenation parameters is observed in hospitalized COVID-19 patients. These results highlight an urgent need for oriented research leading to a better understanding of the specific endothelial oxidative stress that occurs during SARS-CoV-2.

Funding

Stated in the acknowledgments section.

Pathogenesis of Respiratory Viral and Fungal Coinfections

Individuals suffering from severe viral respiratory tract infections have recently emerged as "at risk" groups for developing invasive fungal infections. Influenza virus is one of the most common causes of acute lower respiratory tract infections worldwide. Fungal infections complicating influenza pneumonia are associated with increased disease severity and mortality, with invasive pulmonary aspergillosis being the most common manifestation. Strikingly, similar observations have been made during the current coronavirus disease 2019 (COVID-19) pandemic. The copathogenesis of respiratory viral and fungal coinfections is complex and involves a dynamic interplay between the host immune defenses and the virulence of the microbes involved that often results in failure to return to homeostasis. In this review, we discuss the main mechanisms underlying susceptibility to invasive fungal disease following respiratory viral infections. A comprehensive understanding of these interactions will aid the development of therapeutic modalities against newly identified targets to prevent and treat these emerging coinfections.

EROS is a selective chaperone regulating the phagocyte NADPH oxidase and purinergic signalling

EROS (essential for reactive oxygen species) protein is indispensable for expression of gp91phox, the catalytic core of the phagocyte NADPH oxidase. EROS deficiency in humans is a novel cause of the severe immunodeficiency, chronic granulomatous disease, but its mechanism of action was unknown until now. We elucidate the role of EROS, showing it acts at the earliest stages of gp91phox maturation. It binds the immature 58 kDa gp91phox directly, preventing gp91phox degradation and allowing glycosylation via the oligosaccharyltransferase machinery and the incorporation of the heme prosthetic groups essential for catalysis. EROS also regulates the purine receptors P2X7 and P2X1 through direct interactions, and P2X7 is almost absent in EROS-deficient mouse and human primary cells. Accordingly, lack of murine EROS results in markedly abnormal P2X7 signalling, inflammasome activation, and T cell responses. The loss of both ROS and P2X7 signalling leads to resistance to influenza infection in mice. Our work identifies EROS as a highly selective chaperone for key proteins in innate and adaptive immunity and a rheostat for immunity to infection. It has profound implications for our understanding of immune physiology, ROS dysregulation, and possibly gene therapy.

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

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

The role of NADPH oxidases in infectious and inflammatory diseases

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) are enzymes that generate superoxide or hydrogen peroxide from molecular oxygen utilizing NADPH as an electron donor. There are seven enzymes in the NOX family: NOX1-5 and dual oxidase (DUOX) 1-2. NOX enzymes in humans play important roles in diverse biological functions and vary in expression from tissue to tissue. Importantly, NOX2 is involved in regulating many aspects of innate and adaptive immunity, including regulation of type I interferons, the inflammasome, phagocytosis, antigen processing and presentation, and cell signaling. DUOX1 and DUOX2 play important roles in innate immune defenses at epithelial barriers. This review discusses the role of NOX enzymes in normal physiological processes as well as in disease. NOX enzymes are important in autoimmune diseases like type 1 diabetes and have also been implicated in acute lung injury caused by infection with SARS-CoV-2. Targeting NOX enzymes directly or through scavenging free radicals may be useful therapies for autoimmunity and acute lung injury where oxidative stress contributes to pathology.

The role of oxidative stress in HIV-associated neurocognitive disorders

HIV-associated neurocognitive disorders (HAND) are a leading cause of morbidity in up to 50% of individuals living with HIV, despite effective treatment with antiretroviral therapy (ART). Current evidence suggests that chronic inflammation associated with HIV is especially attributed to the dysregulated production of reactive oxygen species (ROS) that contribute to neurodegeneration and poor clinical outcomes. While ROS have beneficial effects in eliciting immune responses to infection, chronic ROS production causes damage to macromolecules such as DNA and lipids that has been linked to altered redox homeostasis associated with antioxidant dysregulation. As a result, this disruption in the balance between antioxidant-dependent mechanisms of ROS inactivation and ROS production by enzymes such as the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family, as well as from the electron transport chain of the mitochondria can result in oxidative stress. This is particularly relevant to the brain, which is exquisitely susceptible to oxidative stress due to its inherently high lipid concentration and ROS levels that have been linked to many neurodegenerative diseases that have similar stages of pathogenesis to HAND. In this review, we discuss the possible role and mechanisms of ROS production leading to oxidative stress that underpin HAND pathogenesis even when HIV is suppressed by current gold-standard antiretroviral therapies. Furthermore, we highlight that pathological ROS can serve as biomarkers for HIV-dependent HAND, and how manipulation of oxidative stress and antioxidant-dependent pathways may facilitate novel strategies for HIV cure.

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Production of reactive oxygen species has been linked to neurodegenerative diseases.

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ROS production contributes to HIV-associated neurocognitive disorders.

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ROS may be used as a biomarker for HIV-associated neurocognitive disorders.

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Manipulation of antioxidant pathways may present novel HIV cure strategies.

Reactive Oxygen Species: Not Omnipresent but Important in Many Locations

Reactive oxygen species (ROS), such as the superoxide anion or hydrogen peroxide, have been established over decades of research as, on the one hand, important and versatile molecules involved in a plethora of homeostatic processes and, on the other hand, as inducers of damage, pathologies and diseases. Which effects ROS induce, strongly depends on the cell type and the source, amount, duration and location of ROS production. Similar to cellular pH and calcium levels, which are both strictly regulated and only altered by the cell when necessary, the redox balance of the cell is also tightly regulated, not only on the level of the whole cell but in every cellular compartment. However, a still widespread view present in the scientific community is that the location of ROS production is of no major importance and that ROS randomly diffuse from their cellular source of production throughout the whole cell and hit their redox-sensitive targets when passing by. Yet, evidence is growing that cells regulate ROS production and therefore their redox balance by strictly controlling ROS source activation as well as localization, amount and duration of ROS production. Hopefully, future studies in the field of redox biology will consider these factors and analyze cellular ROS more specifically in order to revise the view of ROS as freely flowing through the cell.

Beyond the Extra Respiration of Phagocytosis: NADPH Oxidase 2 in Adaptive Immunity and Inflammation

Reactive oxygen species (ROS) derived from the phagocyte NADPH oxidase (NOX2) are essential for host defence and immunoregulation. Their levels must be tightly controlled. ROS are required to prevent infection and are used in signalling to regulate several processes that are essential for normal immunity. A lack of ROS then leads to immunodeficiency and autoinflammation. However, excess ROS are also deleterious, damaging tissues by causing oxidative stress. In this review, we focus on two particular aspects of ROS biology: (i) the emerging understanding that NOX2-derived ROS play a pivotal role in the development and maintenance of adaptive immunity and (ii) the effects of excess ROS in systemic disease and how limiting ROS might represent a therapeutic avenue in limiting excess inflammation.

NOTCH-induced rerouting of endosomal trafficking disables regulatory T cells in vasculitis

The aorta and the large conductive arteries are immunoprivileged tissues and are protected against inflammatory attack. A breakdown of immunoprivilege leads to autoimmune vasculitis, such as giant cell arteritis, in which CD8+ Treg cells fail to contain CD4+ T cells and macrophages, resulting in the formation of tissue-destructive granulomatous lesions. Here, we report that the molecular defect of malfunctioning CD8+ Treg cells lies in aberrant NOTCH4 signaling that deviates endosomal trafficking and minimizes exosome production. By transcriptionally controlling the profile of RAB GTPases, NOTCH4 signaling restricted vesicular secretion of the enzyme NADPH oxidase 2 (NOX2). Specifically, NOTCH4hiCD8+ Treg cells increased RAB5A and RAB11A expression and suppressed RAB7A, culminating in the accumulation of early and recycling endosomes and sequestering of NOX2 in an intracellular compartment. RAB7AloCD8+ Treg cells failed in the surface translocation and exosomal release of NOX2. NOTCH4hiRAB5AhiRAB7AloRAB11AhiCD8+ Treg cells left adaptive immunity unopposed, enabling a breakdown in tissue tolerance and aggressive vessel wall inflammation. Inhibiting NOTCH4 signaling corrected the defect and protected arteries from inflammatory insult. This study implicates NOTCH4-dependent transcriptional control of RAB proteins and intracellular vesicle trafficking in autoimmune disease and in vascular inflammation.

The misunderstood link between SARS-CoV-2 and angiogenesis. A narrative review

Novel Coronavirus Disease 2019 (Covid-19) is associated with multi-systemic derangement, including circulatory dysfunction with features of endothelial dysfunction, microangiopathic thrombosis and angiocentric inflammation. Recently, intussusceptive angiogenesis has been implicated in the pathogenesis of the disease. Herein, we conducted a narrative review according to the SANRA guidelines to review and discuss data regarding splitting angiogenesis including mechanisms, drivers, regulators and putative roles. Relevant angiogenic features in Covid-19, including their potential role in inflammation, endothelial dysfunction and permeability, as well as their use as prognostic markers and therapeutic roles are reviewed. Splitting angiogenesis in Covid-19 involve hypoxia, hypoxia-inducible factors, classic angiogenic mediators, such as the Vascular Endothelial Growth Factor (VEGF), Angiopoietins, hyperinflammation and cytokine storm, and dysregulation of the Renin-Angiotensin-Aldosterone System, which combined, interact to promote intussusception. Data regarding the use of angiogenic mediators as prognostic tools is summarized and suggest that angiopoietins and VEGF are elevated in Covid-19 patients and predictors of adverse outcomes. Finally, we reviewed the scarce data regarding angiogenic mediators as therapeutic targets. These preliminary findings suggest a potential benefit of bevacizumab as an add-on therapy.

Genetically Encoded Fluorescent Redox Indicators for Unveiling Redox Signaling and Oxidative Toxicity

Redox-active molecules play essential roles in cell homeostasis, signaling, and other biological processes. Dysregulation of redox signaling can lead to toxic effects and subsequently cause diseases. Therefore, real-time tracking of specific redox-signaling molecules in live cells would be critical for deciphering their functional roles in pathophysiology. Fluorescent protein (FP)-based genetically encoded redox indicators (GERIs) have emerged as valuable tools for monitoring the redox states of various redox-active molecules from subcellular compartments to live organisms. In the first section of this review, we overview the background, focusing on the sensing mechanisms of various GERIs. Next, we review a list of selected GERIs according to their analytical targets and discuss their key biophysical and biochemical properties. In the third section, we provide several examples which applied GERIs to understanding redox signaling and oxidative toxicology in pathophysiological processes. Lastly, a summary and outlook section is included.

Size and surface modification of silica nanoparticles affect the severity of lung toxicity by modulating endosomal ROS generation in macrophages

Background

As the application of silica nanomaterials continues to expand, increasing chances of its exposure to the human body and potential harm are anticipated. Although the toxicity of silica nanomaterials is assumed to be affected by their physio-chemical properties, including size and surface functionalization, its molecular mechanisms remain unclear. We hypothesized that analysis of intracellular localization of the particles and subsequent intracellular signaling could reveal a novel determinant of inflammatory response against silica particles with different physico-chemical properties.

Results

We employed a murine intratracheal instillation model of amorphous silica nanoparticles (NPs) exposure to compare their in vivo toxicities in the respiratory system. Pristine silica-NPs of 50 nm diameters (50 nm-plain) induced airway-centered lung injury with marked neutrophilic infiltration. By contrast, instillation of pristine silica particles of a larger diameter (3 μm; 3 μm-plain) significantly reduced the severity of lung injury and neutrophilic infiltration, possibly through attenuated induction of neutrophil chemotactic chemokines including MIP2. Ex vivo analysis of alveolar macrophages as well as in vitro assessment using RAW264.7 cells revealed a remarkably lower cellular uptake of 3 μm-plain particles compared with 50 nm-plain, which is assumed to be the underlying mechanism of attenuated immune response. The severity of lung injury and neutrophilic infiltration was also significantly reduced after intratracheal instillation of silica NPs with an amine surface modification (50 nm-NH₂) when compared with 50 nm-plain. Despite unchanged efficacy in cellular uptake, treatment with 50 nm-NH₂ induced a significantly attenuated immune response in RAW264.7 cells. Assessment of intracellular redox signaling revealed increased reactive oxygen species (ROS) in endosomal compartments of RAW264.7 cells treated with 50 nm-plain when compared with vehicle-treated control. In contrast, augmentation of endosomal ROS signals in cells treated with 50 nm-NH₂ was significantly lower. Moreover, selective inhibition of NADPH oxidase 2 (NOX2) was sufficient to inhibit endosomal ROS bursts and induction of chemokine expressions in cells treated with silica NPs, suggesting the central role of endosomal ROS generated by NOX2 in the regulation of the inflammatory response in macrophages that endocytosed silica NPs.

Conclusions

Our murine model suggested that the pulmonary toxicity of silica NPs depended on their physico-chemical properties through distinct mechanisms. Cellular uptake of larger particles by macrophages decreased, while surface amine modification modulated endosomal ROS signaling via NOX2, both of which are assumed to be involved in mitigating immune response in macrophages and resulting lung injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00415-0.

Corticosteroid use, myocardial injury and in-hospital cardiovascular events in patients with community-acquired pneumonia

BACKGROUND AND PURPOSE

Corticosteroids are often prescribed to community-acquired pneumonia (CAP) patients, but the relationship with major cardiovascular events (MACEs) is unclear.

EXPERIMENTAL APPROACH

541 CAP patients were recruited (334 males, mean age 71.9 ± 16.2 years). High-sensitivity troponin T (hs-cTnT) was measured at admission, during the hospital stay and at discharge. MACE occurrence was registered during a long-term follow-up.

KEY RESULTS

Overall, 318 patients (59%) showed hs-cTnT elevation >99th percentile (>0.014 μg/L). Age, heart failure and the increasing quintiles of hs-cTnT (hazard ratio [HR] 2.16, 95% confidence interval [CI] 1.82-2.58, P < .001) predicted MACEs. Among patients with hs-cTnT >0.014 μg/L at admission, 102 patients (31%) were on corticosteroids and showed lower hs-cTnT increase (P = .021), (NADPH) oxidase-2 (Nox2) activation (P = .005) and incidence of MACEs than untreated ones (HR 0.64, 95% CI 0.41-0.97, P = .038); no effect of corticosteroids on MACEs was observed in CAP patients with normal troponin. In vitro study showed that glucocorticoids have an antioxidant effect via downregulation of Nox2 activity.

CONCLUSION AND IMPLICATIONS

The study provides evidence that corticosteroid use is associated with lower increase of hs-cTnT and incidence of MACEs in CAP patients.

Raising the 'Good' Oxidants for Immune Protection

Redox medicine is a new therapeutic concept targeting reactive oxygen species (ROS) and secondary reaction products for health benefit. The concomitant function of ROS as intracellular second messengers and extracellular mediators governing physiological redox signaling, and as damaging radicals instigating or perpetuating various pathophysiological conditions will require selective strategies for therapeutic intervention. In addition, the reactivity and quantity of the oxidant species generated, its source and cellular location in a defined disease context need to be considered to achieve the desired outcome. In inflammatory diseases associated with oxidative damage and tissue injury, ROS source specific inhibitors may provide more benefit than generalized removal of ROS. Contemporary approaches in immunity will also include the preservation or even elevation of certain oxygen metabolites to restore or improve ROS driven physiological functions including more effective redox signaling and cell-microenvironment communication, and to induce mucosal barrier integrity, eubiosis and repair processes. Increasing oxidants by host-directed immunomodulation or by exogenous supplementation seems especially promising for improving host defense. Here, we summarize examples of beneficial ROS in immune homeostasis, infection, and acute inflammatory disease, and address emerging therapeutic strategies for ROS augmentation to induce and strengthen protective host immunity.

Potential protective mechanisms of green tea polyphenol EGCG against COVID-19

Background

The world is in the midst of the COVID-19 pandemic. In this comprehensive review, we discuss the potential protective effects of (−)-epigallocatechin-3-gallate (EGCG), a major constituent of green tea, against COVID-19.

Scope and approach

Information from literature of clinical symptoms and molecular pathology of COVID-19 as well as relevant publications in which EGCG shows potential protective activities against COVID-19 is integrated and evaluated.

Key findings and conclusions

EGCG, via activating Nrf2, can suppress ACE2 (a cellular receptor for SARS-CoV-2) and TMPRSS2, which mediate cell entry of the virus. Through inhibition of SARS-CoV-2 main protease, EGCG may inhibit viral reproduction. EGCG via its broad antioxidant activity may protect against SARS-CoV-2 evoked mitochondrial ROS (which promote SARS-CoV-2 replication) and against ROS burst inflicted by neutrophil extracellular traps. By suppressing ER-resident GRP78 activity and expression, EGCG can potentially inhibit SARS-CoV-2 life cycle. EGCG also shows protective effects against 1) cytokine storm-associated acute lung injury/acute respiratory distress syndrome, 2) thrombosis via suppressing tissue factors and activating platelets, 3) sepsis by inactivating redox-sensitive HMGB1, and 4) lung fibrosis through augmenting Nrf2 and suppressing NF-κB. These activities remain to be further substantiated in animals and humans. The possible concerted actions of EGCG suggest the importance of further studies on the prevention and treatment of COVID-19 in humans. These results also call for epidemiological studies on potential preventive effects of green tea drinking on COVID-19.

Reactive oxygen species as potential antiviral targets

Reactive oxygen species (ROS) are by-products of cellular metabolism and can be either beneficial, at low levels, or deleterious, at high levels, to the cell. It is known that several viral infections can increase oxidative stress, which is mainly facilitated by viral-induced imbalances in the antioxidant defence mechanisms of the cell. While the exact role of ROS in certain viral infections (adenovirus and dengue virus) remains unknown, other viruses can use ROS for enhancement of pathogenesis (SARS coronavirus and rabies virus) or replication (rhinovirus, West Nile virus and vesicular stomatitis virus) or both (hepatitis C virus, human immunodeficiency virus and influenza virus). While several viral proteins (mainly for hepatitis C and human immunodeficiency virus) have been identified to play a role in ROS formation, most mediators of viral ROS modulation are yet to be elucidated. Treatment of viral infections, including hepatitis C virus, human immunodeficiency virus and influenza virus, with ROS inhibitors has shown a decrease in both pathogenesis and viral replication both in vitro and in animal models. Clinical studies indicating the potential for targeting ROS-producing pathways as possible broad-spectrum antiviral targets should be evaluated in randomized controlled trials.