Reactive oxygen species as potential antiviral targets

Viral inactivation of murine coronavirus via multiple gas plasma-derived reactive species

The recent pandemic has highlighted the urgent need to elucidate the pathophysiological mechanisms underlying viral effects in humans and is driving the search for innovative antiviral therapies. Several studies have investigated the ability of gas plasma, a partially ionized gas that simultaneously generates several reactive species, to be a new antiviral tool. However, several aspects of the mechanisms of antiviral action of gas plasma remained elusive. In this study, we, for the first time, used a gas plasma device approved for medical purposes and routinely applied in the clinics, especially for wound healing, to test its antiviral activity against a murine corona-virus in vitro (MHV-GFP), a research model analogous to human coronaviruses such as SARS-CoV-2. For this, we established a novel high-content imaging assay that gave quantitative and kinetic information about infection and reduced viral activity in murine fibroblasts (17Cl-1) host cells. Gas plasma treatment delayed viral infectivity and reduced overall infection and toxicity in 17Cl1 cells. Various antioxidants at different concentrations were screened to identify ROS relevant to antiviral effects. Catalase provided no virus protection, and DMSO, mannitol, histidine, Trolox, and ascorbic acid only modestly reduced gas plasma virucidal efficacy. By contrast, glutathione, tyrosine, and cysteine showed profound but not complete protection of MHV from gas plasma-derived reactive species, suggesting pivotal roles of superoxide radicals and peroxynitrite gas in plasma-driven viral inactivation. At extended gas plasma exposure times, fewer intact MHV RNA were detected, indicative of reactive species-driven RNA modifications or degradation as an additional mechanism of action. Virus particle size changes measured by electron microscopy were moderate. Collectively, we identified the potent antiviral activity of a clinically approved argon plasma jet along with potential mechanisms of action.

Shrimp Virus Regulates ROS Dynamics via the Nrf2 Pathway to Facilitate Viral Replication

Reactive oxygen species (ROS) of hosts are widely involved in intracellular signaling and against pathogens. Viruses manipulate ROS homeostasis of hosts as a strategy to evade ROS-mediated negative effects of their infection, but the mechanisms remain unclear. The economically important aquaculture shrimp, Litopenaeus vannamei, is selected to investigate the molecular mechanism of how white spot syndrome virus (WSSV) regulates ROS dynamics and enhances viral replication. WSSV protein wsv220 binds to the repressor of shrimp nuclear factor erythroid 2-related factor 2 (LvNrf2), called Kelch-like ECH-associated protein 1 (LvKeap1), disrupting LvNrf2/LvKeap1 complex and facilitating LvNrf2 nuclear translocation. This activation of LvNrf2 causes up-regulation of antioxidant genes, including glucose-6-phosphate dehydrogenase (LvG6PDH), which increases nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH) production, effectively eliminating excessive ROS. Moreover, WSSV exploits LvNrf2 to establish a positive feedback loop by up-regulating viral immediate early gene wsv051, which further enhances wsv220 expression. Knockdown of LvNrf2 or LvG6PDH reduces WSSV replication and increases host ROS levels. Therefore, WSSV hijacks LvNrf2 pathway to maintain ROS homeostasis and establishes a positive feedback loop to facilitate WSSV replication. These findings reveal a novel molecular mechanism of viral manipulation of host ROS dynamics and suggest potential antiviral strategies targeting LvNrf2 pathway.

Effects of oxidative stress on viral infections: an overview

Viral infections can trigger increased reactive oxygen species (ROS) production and a reduced antioxidant response in the host, leading to redox stress, inflammation, apoptosis, and ultimately, cell and tissue damage, which contribute to disease development. A better understanding of how ROS contributes to viral pathogenesis is critical for the development of novel therapeutic interventions. In this review, we discuss the current knowledge on ROS production and its effects across various viral infections, including severe acute respiratory syndrome-coronavirus-2, influenza A virus, dengue virus, Zika virus, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus infections, to improve future therapeutic and preventive strategies for these infections.

Targeting respiratory virus-induced reactive oxygen species in airways diseases

The immune response to virus infection in the respiratory tract must be carefully balanced to achieve pathogen clearance without excessive immunopathology. For chronic respiratory diseases where there is ongoing inflammation, such as in asthma and COPD, airway immune balance is perturbed, and viral infection frequently worsens (exacerbates) these conditions. Reactive oxygen species (ROS) are critical to the induction and propagation of inflammation, and when appropriately regulated, ROS are vital cell signalling molecules and contribute to innate immunity. However, extended periods of high ROS concentration can cause excessive cellular damage that dysregulates antiviral immunity and promotes inflammation. Traditional antioxidant therapeutics have had limited success treating inflammatory diseases such as viral exacerbations of asthma or COPD, owing to nonspecific pharmacology and poorly understood pharmacokinetic properties. These drawbacks could be addressed with novel drug delivery technologies and pharmacological agents. This review summarises current research on ROS imbalances during virus infection, discusses the commercially available mitochondrial antioxidant drugs that have progressed to clinical trial and assesses novel drug delivery approaches for antioxidant delivery to the airways. Additionally, it provides a perspective on future research into pharmacological targeting of ROS for the treatment of respiratory virus infection and disease.

Exploring the antimicrobial, anti-inflammatory, antioxidant, and immunomodulatory properties of Chrysanthemum morifolium and Chrysanthemum indicum: a narrow review

Infectious diseases continue to be a major global public health concern, which is exacerbated by the increasing prevalence of antimicrobial resistance. This review investigates the potential of herbal medicine, particularly Chrysanthemum morifolium (CM) and Chrysanthemum indicum (CI), in addressing these challenges. Both herbs, documented in traditional Chinese medicine (TCM) and the Pharmacopoeia of the People's Republic of China (2020 edition), are renowned for their heat-clearing and detoxifying properties. Phytochemical studies reveal that these botanicals contain diverse bioactive compounds, including flavonoids, terpenoids, and phenylpropanoids, which exhibit antimicrobial, anti-inflammatory, and antioxidant properties, among other effects. Comparative analysis reveals that distinct compound profiles and differential concentrations of core phytochemicals between CM and CI may lead to differentiated therapeutic advantages in anti-infective applications. By systematically examining their ethnopharmacological origins, phytochemical fingerprints, and pharmacological mechanisms, this review highlights their synergistic potential with conventional antimicrobial therapies through multi-target mechanisms, proposing novel integrative approaches for global health challenges.

Porcine reproductive and respiratory syndrome virus activates lipid synthesis through a ROS-dependent AKT/PCK1/INSIG/SREBPs axis

The porcine reproductive and respiratory syndrome virus (PRRSV) is a highly contagious pathogen in pigs. This study aimed to investigate the impact of PRRSV infection on cellular metabolism, particularly focusing on lipid metabolism to understand its role in promoting viral replication. We conducted a metabolic analysis on MARC-145 cells before and after PRRSV infection. Our results demonstrated that the most significant alterations in cellular metabolism, accounting for 40.8 % of total changes, were related to lipid metabolism. These changes were primarily driven by the activation of sterol regulatory-element binding proteins (SREBPs), critical regulators of lipid biosynthesis. To understand the mechanisms behind SREBPs activation by PRRSV, we investigated the involvement of upstream effectors, specifically protein kinase B (AKT) and phosphoenolpyruvate carboxykinase 1 (PCK1). Our findings indicated that PRRSV infection triggered AKT activation, leading to the subsequent activation of PCK1. Activated PCK1 then phosphorylated insulin-induced genes (INSIGs), resulting in their degradation. This degradation facilitated the translocation of SREBPs from the endoplasmic reticulum to the nucleus. Additionally, we observed that PRRSV infection stimulated the production of reactive oxygen species (ROS), which played a critical role in activating AKT. Collectively, our findings demonstrate that PRRSV enhances lipid synthesis through a ROS-dependent AKT/PCK1/INSIG/SREBPs signaling axis, which provides new insights into the metabolic strategies employed by PRRSV.

The role of reactive oxygen species in severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection-induced cell death

Coronavirus disease 2019 (COVID-19) represents the novel respiratory infectious disorder caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is characterized by rapid spread throughout the world. Reactive oxygen species (ROS) account for cellular metabolic by-products, and excessive ROS accumulation can induce oxidative stress due to insufficient endogenous antioxidant ability. In the case of oxidative stress, ROS production exceeds the cellular antioxidant capacity, thus leading to cell death. SARS-CoV-2 can activate different cell death pathways in the context of infection in host cells, such as neutrophil extracellular trap (NET)osis, ferroptosis, apoptosis, pyroptosis, necroptosis and autophagy, which are closely related to ROS signalling and control. In this review, we comprehensively elucidated the relationship between ROS generation and the death of host cells after SARS-CoV-2 infection, which leads to the development of COVID-19, aiming to provide a reasonable basis for the existing interventions and further development of novel therapies against SARS-CoV-2.

Mitochondrial Dysfunction and Metabolic Disturbances Induced by Viral Infections

Viruses are intracellular parasites that utilize organelles, signaling pathways, and the bioenergetics machinery of the cell to replicate the genome and synthesize proteins to build up new viral particles. Mitochondria are key to supporting the virus life cycle by sustaining energy production, metabolism, and synthesis of macromolecules. Mitochondria also contribute to the antiviral innate immune response. Here, we describe the different mechanisms involved in virus-mitochondria interactions. We analyze the effects of viral infections on the metabolism of glucose in the Warburg phenotype, glutamine, and fatty acids. We also describe how viruses directly regulate mitochondrial function through modulation of the activity of the electron transport chain, the generation of reactive oxygen species, the balance between fission and fusion, and the regulation of voltage-dependent anion channels. In addition, we discuss the evasion strategies used to avoid mitochondrial-associated mechanisms that inhibit viral replication. Overall, this review aims to provide a comprehensive view of how viruses modulate mitochondrial function to maintain their replicative capabilities.

Potential Beneficial Role of Nitric Oxide in SARS-CoV-2 Infection: Beyond Spike-Binding Inhibition

SARS-CoV-2, the causative virus for the COVID-19 disease, uses its spike glycoprotein to bind to human ACE2 as a first step for viral entry into the cell. For this reason, great efforts have been made to find mechanisms that disrupt this interaction, avoiding the infection. Nitric oxide (NO) is a soluble endogenous gas with known antiviral and immunomodulatory properties. In this study, we aimed to test whether NO could inhibit the binding of the viral spike to ACE2 in human cells and its effects on ACE2 enzymatic activity. Our results show that ACE2 activity was decreased by the NO donors DETA-NONOate and GSNO and by the NO byproduct peroxynitrite. Furthermore, we found that DETA-NONOate could break the spike-ACE2 interaction using the spike from two different variants (Alpha and Gamma) and in two different human cell types. Moreover, the same result was obtained when using NO-producing murine macrophages, while no significant changes were observed in ACE2 expression or distribution within the cell. These results support that it is worth considering NO as a therapeutic agent for COVID-19, as previous reports have suggested.

Borna disease virus 1 induces ferroptosis, contributing to lethal encephalitis

Borna disease virus 1 (BoDV-1) is a neurotropic RNA virus that has been linked to fatal BoDV-1 encephalitis (BVE) in humans. Ferroptosis represents a newly recognized kind of programmed cell death that marked by iron overload and lipid peroxidation. Various viral infections are closely related to ferroptosis. However, the link between BoDV-1 infection and ferroptosis, as well as its role in BVE pathogenesis, remains inadequately understood. Herein, we used primary rat cortical neurons, human microglial HMC3 cells, and Sprague‒Dawley rats as models. BoDV-1 infection induced ferroptosis, as ferroptosis characteristics were detected (iron overload, reactive oxygen species buildup, decreased antioxidant capacity, lipid peroxidation, and mitochondrial damage). Analysis via qRT-PCR and Western blot demonstrated that BoDV-1-induced ferroptosis was mediated through Nrf2/HO-1/SLC7a11/GPX4 antioxidant pathway suppression. Nrf2 downregulation was due to BoDV-1 infection promoting Nrf2 ubiquitination and degradation. Following BoDV-1-induced ferroptosis, the PTGS2/PGE2 signaling pathway was activated, and various intracellular lipid peroxidation products and damage-associated molecular patterns were released, contributing to BVE occurrence and progression. More importantly, inhibiting ferroptosis or the ubiquitin‒proteasome system effectively alleviated BVE. Collectively, these findings demonstrate the interaction between BoDV-1 infection and ferroptosis and reveal BoDV-1-induced ferroptosis as an underlying pathogenic mechanism of BVE.

8-Oxoguanine DNA Glycosylase1 conceals oxidized guanine in nucleoprotein-associated RNA of respiratory syncytial virus

Respiratory syncytial virus (RSV), along with other prominent respiratory RNA viruses such as influenza and SARS-CoV-2, significantly contributes to the global incidence of respiratory tract infections. These pathogens induce the production of reactive oxygen species (ROS), which play a crucial role in the onset and progression of respiratory diseases. However, the mechanisms by which viral RNA manages ROS-induced base oxidation remain poorly understood. Here, we reveal that 8-oxo-7,8-dihydroguanine (8-oxoGua) is not merely an incidental byproduct of ROS activity but serves as a strategic adaptation of RSV RNA to maintain genetic fidelity by hijacking the 8-oxoguanine DNA glycosylase 1 (OGG1). Through RNA immunoprecipitation and next-generation sequencing, we discovered that OGG1 binding sites are predominantly found in the RSV antigenome, especially within guanine-rich sequences. Further investigation revealed that viral ribonucleoprotein complexes specifically exploit OGG1. Importantly, inhibiting OGG1's ability to recognize 8-oxoGua significantly decreases RSV progeny production. Our results underscore the viral replication machinery's adaptation to oxidative challenges, suggesting that inhibiting OGG1's reading function could be a novel strategy for antiviral intervention.

Resveratrol inhibits rabies virus infection in N2a cells by activating the SIRT1/Nrf2/HO-1 pathway

Rabies is a highly lethal infectious disease with no existing treatment available, thus investigating effective antiviral compounds to control rabies virus (RABV) infection is of utmost importance. Resveratrol is a natural phenolic compound that, as a phytoalexin, exhibits several biological activities, including antiviral activity. In this study, we evaluated the inhibitory effect of resveratrol on RABV infection and investigated its molecular antiviral mechanism. We found that resveratrol significantly inhibited RABV infection, including the phases of adsorption, replication, and release, and also directly inactivated RABV and inhibited its infectivity. However, resveratrol had no significant effect on RABV internalization. Resveratrol also reduced RABV-induced oxidative stress, specifically reactive oxygen species and malondialdehyde levels. Western blotting analysis revealed that resveratrol enhanced antioxidant signaling via the SIRT1/Nrf2/HO-1 pathway and inhibited viral replication. Viral infection was enhanced after SIRT1 knockdown, which inhibited the SIRT1/Nrf2/HO-1 antioxidant signaling pathway, suggesting that this pathway plays an important role in RABV replication. Overall, resveratrol prevented the adsorption, replication, and release of RABV and directly inactivated RABV, but failed to inhibit RABV internalization. Furthermore, resveratrol activated the SIRT1/Nrf2/HO-1 pathway to inhibit RABV replication and suppressed RABV-induced oxidative stress. These findings highlight the therapeutic potential of resveratrol for fighting RABV infections.

Cytomegalovirus-induced peroxynitrite promotes virus entry and contributes to pathogenesis in a murine model of infection

There are no licensed vaccines for human cytomegalovirus (HCMV), and current antiviral drugs that target viral proteins are toxic and prone to resistance. Targeting host pathways essential for virus replication provides an alternate strategy that may reduce opportunities for drug resistance to occur. Oxidative stress is triggered by numerous viruses including HCMV. Peroxynitrite is a reactive nitrogen species that is formed during oxidative stress. Herein, we identified that HCMV rapidly induces the generation of intracellular peroxynitrite upon infection in a manner partially dependent upon xanthine oxidase generation. Peroxynitrite promoted HCMV infection in both cell-free and cell-associated infection systems in multiple cell types. Inhibiting peroxynitrite within the first 24 hours of infection prevented HCMV replication and peroxynitrite promoted cell entry and pp65 translocation into the host cell nuclei. Furthermore, using the murine cytomegalovirus model, we demonstrated that antagonizing peroxynitrite significantly reduces cytomegalovirus replication and pathogenesis in vivo. Overall, our study highlights a proviral role for peroxynitrite in CMV infection and implies that RNS and/or the mechanisms that induce their production could be targeted as a novel strategy to inhibit HCMV infection.

IMPORTANCE

Human cytomegalovirus (HCMV) causes significant disease in individuals with impaired or immature immune systems, such as transplant patients and after congenital infection. Antiviral drugs that target the virus directly are toxic and are susceptible to antiviral drug resistance due to virus mutations. An alternate strategy is to target processes within host cells that are required by the virus for replication. Herein, we show that HCMV infection triggers a highly reactive molecule, peroxynitrite, during the initial stages of infection. Peroxynitrite was required for the initial entry of the virus into the cell and promotes virus replication in multiple cell types, suggesting a broad pro-viral function. Importantly, targeting peroxynitrite dramatically inhibited cytomegalovirus replication in cells in the laboratory and in mice, suggesting that therapeutic targeting of this molecule and/or the cellular functions it regulates could represent a novel strategy to inhibit HCMV infection.

Leucoverdazyls as Novel Potent Inhibitors of Enterovirus Replication

Enteroviruses (EV) are important pathogens causing human disease with various clinical manifestations. To date, treatment of enteroviral infections is mainly supportive since no vaccination or antiviral drugs are approved for their prevention or treatment. Here, we describe the antiviral properties and mechanisms of action of leucoverdazyls-novel heterocyclic compounds with antioxidant potential. The lead compound, 1a, demonstrated low cytotoxicity along with high antioxidant and virus-inhibiting activity. A viral strain resistant to 1a was selected, and the development of resistance was shown to be accompanied by mutation of virus-specific non-structural protein 2C. This resistant virus had lower fitness when grown in cell culture. Taken together, our results demonstrate high antiviral potential of leucoverdazyls as novel inhibitors of enterovirus replication and support previous evidence of an important role of 2C proteins in EV replication.

Non-Thermal Plasma Reduces HSV-1 Infection of and Replication in HaCaT Keratinocytes In Vitro

Herpes simplex virus type 1 (HSV-1) is a lifelong pathogen characterized by asymptomatic latent infection in the trigeminal ganglia (TG), with periodic outbreaks of cold sores caused by virus reactivation in the TG and subsequent replication in the oral mucosa. While antiviral therapies can provide relief from cold sores, they are unable to eliminate HSV-1. We provide experimental results that highlight non-thermal plasma (NTP) as a new alternative therapy for HSV-1 infection that would resolve cold sores faster and reduce the establishment of latent infection in the TG. Additionally, this study is the first to explore the use of NTP as a therapy that can both treat and prevent human viral infections. The antiviral effect of NTP was investigated using an in vitro model of HSV-1 epithelial infection that involved the application of NTP from two separate devices to cell-free HSV-1, HSV-1-infected cells, and uninfected cells. It was found that NTP reduced the infectivity of cell-free HSV-1, reduced viral replication in HSV-1-infected cells, and diminished the susceptibility of uninfected cells to HSV-1 infection. This triad of antiviral mechanisms of action suggests the potential of NTP as a therapeutic agent effective against HSV-1 infection.

Viroporins Manipulate Cellular Powerhouses and Modulate Innate Immunity

Viruses have a wide repertoire of molecular strategies that focus on their replication or the facilitation of different stages of the viral cycle. One of these strategies is mediated by the activity of viroporins, which are multifunctional viral proteins that, upon oligomerization, exhibit ion channel properties with mild ion selectivity. Viroporins facilitate multiple processes, such as the regulation of immune response and inflammasome activation through the induction of pore formation in various cell organelle membranes to facilitate the escape of ions and the alteration of intracellular homeostasis. Viroporins target diverse membranes (such as the cellular membrane), endoplasmic reticulum, and mitochondria. Cumulative data regarding the importance of mitochondria function in multiple processes, such as cellular metabolism, energy production, calcium homeostasis, apoptosis, and mitophagy, have been reported. The direct or indirect interaction of viroporins with mitochondria and how this interaction affects the functioning of mitochondrial cells in the innate immunity of host cells against viruses remains unclear. A better understanding of the viroporin-mitochondria interactions will provide insights into their role in affecting host immune signaling through the mitochondria. Thus, in this review, we mainly focus on descriptions of viroporins and studies that have provided insights into the role of viroporins in hijacked mitochondria.

Simultaneous Activation of Immunogenic Cell Death and cGAS-STING Pathway by Liver- and Mitochondria-Targeted Gold(I) Complexes for Chemoimmunotherapy of Hepatocellular Carcinoma

Induction of immunogenic cell death (ICD) and activation of the cyclic GMP-AMP synthase stimulator of interferon gene (cGAS-STING) pathway are two potent anticancer immunotherapeutic strategies in hepatocellular carcinoma (HCC). Herein, 12 liver- and mitochondria-targeting gold(I) complexes (9a-9l) were designed and synthesized. The superior complex 9b produced a considerable amount of reactive oxygen species (ROS) and facilitated DNA excretion, the ROS-induced ICD and DNA activated the cGAS-STING pathway, both of which evoked an intense anticancer immune response in vitro and in vivo. Importantly, 9b strongly inhibited tumor growth in a patient-derived xenograft model of HCC. Overall, we present the first case of simultaneous ICD induction and cGAS-STING pathway activation within the same gold-based small molecule, which may provide an innovative strategy for designing chemoimmunotherapies for HCC.

HCV-induced autophagy and innate immunity

The interplay between autophagy and host innate immunity has been of great interest. Hepatitis C virus (HCV) impedes signaling pathways initiated by pattern-recognition receptors (PRRs) that recognize pathogens-associated molecular patterns (PAMPs). Autophagy, a cellular catabolic process, delivers damaged organelles and protein aggregates to lysosomes for degradation and recycling. Autophagy is also an innate immune response of cells to trap pathogens in membrane vesicles for removal. However, HCV controls the autophagic pathway and uses autophagic membranes to enhance its replication. Mitophagy, a selective autophagy targeting mitochondria, alters the dynamics and metabolism of mitochondria, which play important roles in host antiviral responses. HCV also alters mitochondrial dynamics and promotes mitophagy to prevent premature cell death and attenuate the interferon (IFN) response. In addition, the dysregulation of the inflammasomal response by HCV leads to IFN resistance and immune tolerance. These immune evasion properties of HCV allow HCV to successfully replicate and persist in its host cells. In this article, we discuss HCV-induced autophagy/mitophagy and its associated immunological responses and provide a review of our current understanding of how these processes are regulated in HCV-infected cells.

Anastrozole Protects against Human Coronavirus Infection by Ameliorating the Reactive Oxygen Species-Mediated Inflammatory Response

The common human coronavirus (HCoV) exhibits mild disease with upper respiratory infection and common cold symptoms. HCoV-OC43, one of the HCoVs, can be used to screen drug candidates against SARS-CoV-2. We determined the antiviral effects of FDA/EMA-approved drug anastrozole (AZ) on two human coronaviruses, HCoV-OC43 and HCoV-229E, using MRC-5 cells in vitro. The AZ exhibited antiviral effects against HCoV-OC43 and HCoV-229E infection. Subsequent studies focused on HCoV-OC43, which is related to the SARS-CoV-2 family. AZ exhibited anti-viral effects and reduced the secretion of inflammatory cytokines, TNF-α, IL-6, and IL-1β. It also inhibited NF-κB translocation to effectively suppress the inflammatory response. AZ reduced intracellular calcium and reactive oxygen species (ROS) levels, including mitochondrial ROS and Ca2+, induced by the virus. AZ inhibited the expression of NLRP3 inflammasome components and cleaved IL-1β, suggesting that it blocks NLRP3 inflammasome activation in HCoV-OC43-infected cells. Moreover, AZ enhanced cell viability and reduced the expression of cleaved gasdermin D (GSDMD), a marker of pyroptosis. Overall, we demonstrated that AZ exhibits antiviral activity against HCoV-OC43 and HCoV-229E. We specifically focused on its efficacy against HCoV-OC43 and showed its potential to reduce inflammation, inhibit NLRP3 inflammasome activation, mitigate mitochondrial dysfunction, and suppress pyroptosis in infected cells.

Complex II ambiguities-FADH2 in the electron transfer system

The prevailing notion that reduced cofactors NADH and FADH2 transfer electrons from the tricarboxylic acid cycle to the mitochondrial electron transfer system creates ambiguities regarding respiratory Complex II (CII). CII is the only membrane-bound enzyme in the tricarboxylic acid cycle and is part of the electron transfer system of the mitochondrial inner membrane feeding electrons into the coenzyme Q-junction. The succinate dehydrogenase subunit SDHA of CII oxidizes succinate and reduces the covalently bound prosthetic group FAD to FADH2 in the canonical forward tricarboxylic acid cycle. However, several graphical representations of the electron transfer system depict FADH2 in the mitochondrial matrix as a substrate to be oxidized by CII. This leads to the false conclusion that FADH2 from the β-oxidation cycle in fatty acid oxidation feeds electrons into CII. In reality, dehydrogenases of fatty acid oxidation channel electrons to the Q-junction but not through CII. The ambiguities surrounding Complex II in the literature and educational resources call for quality control, to secure scientific standards in current communications of bioenergetics, and ultimately support adequate clinical applications. This review aims to raise awareness of the inherent ambiguity crisis, complementing efforts to address the well-acknowledged issues of credibility and reproducibility.

Mitochondrial Reactive Oxygen Species in TRIF-Dependent Toll-like Receptor 3 Signaling in Bronchial Epithelial Cells against Viral Infection

Toll-like receptor 3 (TLR3) plays an important role in double-stranded RNA recognition and triggers the innate immune response by acting as a key receptor against viral infections. Intracellular reactive oxygen species (ROS) are involved in TLR3-induced inflammatory responses during viral infections; however, their relationship with mitochondrial ROS (mtROS) remains largely unknown. In this study, we show that polyinosinic-polycytidylic acid (poly(I:C)), a mimic of viral RNA, induced TLR3-mediated nuclear factor-kappa B (NF-κB) signaling pathway activation and enhanced mtROS generation, leading to inflammatory cytokine production. TLR3-targeted small interfering RNA (siRNA) and Mito-TEMPO inhibited inflammatory cytokine production in poly(I:C)-treated BEAS-2B cells. Poly(I:C) recruited the TLR3 adaptor molecule Toll/IL-1R domain-containing adaptor, inducing IFN (TRIF) and activated NF-κB signaling. Additionally, TLR3-induced mtROS generation suppression and siRNA-mediated TRIF downregulation attenuated mitochondrial antiviral signaling protein (MAVS) degradation. Our findings provide insights into the TLR3-TRIF signaling pathway and MAVS in viral infections, and suggest TLR3-mtROS as a therapeutic target for the treatment of airway inflammatory and viral infectious diseases.

Murine Mast Cells That Are Deficient in IFNAR-Signaling Respond to Viral Infection by Producing a Large Amount of Inflammatory Cytokines, a Low Level of Reactive Oxygen Species, and a High Rate of Cell Death

Mat cells (MCs) are located in the skin and mucous membranes at points where the body meets the environment. When activated, MCs release inflammatory cytokines, which help the immune system to fight viruses. MCs produce, and have receptors for interferons (IFNs), which belong to a family of cytokines recognized for their antiviral properties. Previously, we reported that MCs produced proinflammatory cytokines in response to a recombinant vesicular stomatitis virus (rVSVΔm51) and that IFNAR signaling was required to down-modulate these responses. Here, we have demonstrated that UV-irradiated rVSVΔm51 did not cause any inflammatory cytokines in either in vitro cultured mouse IFNAR-intact (IFNAR+/+), or in IFNAR-knockout (IFNAR-/-) MCs. However, the non-irradiated virus was able to replicate more effectively in IFNAR-/- MCs and produced a higher level of inflammatory cytokines compared with the IFNAR+/+ MCs. Interestingly, MCs lacking IFNAR expression displayed reduced levels of reactive oxygen species (ROS) compared with IFNAR+/+ MCs. Additionally, upon the viral infection, these IFNAR-/- MCs were found to coexist with many dying cells within the cell population. Based on our findings, IFNAR-intact MCs exhibit a lower rate of rVSVΔm51 infectivity and lower levels of cytokines while demonstrating higher levels of ROS. This suggests that MCs with intact IFNAR signaling may survive viral infections by producing cell-protective ROS mechanisms and are less likely to die than IFNAR-/- cells.

The integrated stress response effector ATF4 is an obligatory metabolic activator of NRF2

The redox regulator NRF2 becomes activated upon oxidative and electrophilic stress and orchestrates a response program associated with redox regulation, metabolism, tumor therapy resistance, and immune suppression. Here, we describe an unrecognized link between the integrated stress response (ISR) and NRF2 mediated by the ISR effector ATF4. The ISR is commonly activated after starvation or ER stress and plays a central role in tissue homeostasis and cancer plasticity. ATF4 increases NRF2 transcription and induces the glutathione-degrading enzyme CHAC1, which we now show to be critically important for maintaining NRF2 activation. In-depth analyses reveal that NRF2 supports ATF4-induced cells by increasing cystine uptake via the glutamate-cystine antiporter xCT. In addition, NRF2 upregulates genes mediating thioredoxin usage and regeneration, thus balancing the glutathione decrease. In conclusion, we demonstrate that the NRF2 response serves as second layer of the ISR, an observation highly relevant for the understanding of cellular resilience in health and disease.

Reactive oxygen species in biological media are they friend or foe? Major In vivo and In vitro sensing challenges

The role of Reactive Oxygen Species (ROS) on biological media has been shifting over the years, as the knowledge on the complex mechanism that lies in underneath their production and overall results has been growing. It has been known for some time that these species are associated with a number of health conditions. However, they also participate in the immunoactivation cascade process, and can have an active role in theranostics. Macrophages, for example, react to the presence of pathogens through ROS production, potentially allowing the development of new therapeutic strategies. However, their short lifetime and limited spatial distribution of ROS have been limiting factors to the development and understanding of this phenomenon. Even though, ROS have shown successful theranostic applications, e.g., photodynamic therapy, their wide applicability has been hampered by the lack of effective tools for monitoring these processes in real time. Thus the development of innovative sensing strategies for in vivo monitoring of the balance between ROS concentration and the resultant immune response is of the utmost relevance. Such knowledge could lead to major breakthroughs towards the development of more effective treatments for neurodegenerative diseases. Within this review we will present the current understanding on the interaction mechanisms of ROS with biological systems and their overall effect. Additionally, the most promising sensing tools developed so far, for both in vivo and in vitro tracking will be presented along with their main limitations and advantages. This review focuses on the four main ROS that have been studied these are: singlet oxygen species, hydrogen peroxide, hydroxyl radical and superoxide anion.

Unraveling the Intrinsic Biocidal Activity of the SiO2-Ag Composite against SARS-CoV-2: A Joint Experimental and Theoretical Study

The COVID-19 pandemic has emerged as an unprecedented global healthcare emergency, demanding the urgent development of effective materials to inactivate the SARS-CoV-2 virus. This research was planned to disclose the remarkable biocidal activity of SiO2-Ag composites incorporated into low-density polyethylene. For this purpose, a joint experimental and theoretical [based on first-principles calculations at the density functional theory (DFT) level] study is performed. Biological assays showed that this material eliminatesStaphylococcus aureusand SARS-CoV-2 virus in just 2 min. Here, we investigate a previously unexplored process that we postulate may occur along the O2 and H2O adsorption and activation processes of pure and defective SiO2-Ag surfaces for the generation of reactive oxygen species (ROS). The obtained results help us to predict the nature of ROS: superoxide anion radicals, •O2-, hydroxyl radicals, •OH, and hydroperoxyl radicals, •HO2, that destroy and degrade the structure of the SARS-COV-2 virus. This is consistent with the DFT studies, where the energetic, electronic, and magnetic properties of the intermediates show a feasible formation of ROS. Present findings are expected to provide new insights into the relationship among the structure, property, and biocidal activity of semiconductor/metal SiO2-Ag composites.

DUOX2 regulates secreted factors in virus-infected respiratory epithelial cells that contribute to neutrophil attraction and activation

The first line of defense against respiratory viruses relies on the antiviral and proinflammatory cytokine response initiated in infected respiratory epithelial cells. The cytokine response not only restricts virus replication and spreading, but also orchestrates the subsequent immune response. The epithelial Dual Oxidase 2 (DUOX2) has recently emerged as a regulator of the interferon antiviral response. Here, we investigated the role of DUOX2 in the inflammatory cytokine response using a model of A549 cells deficient in DUOX2 generated using Crispr-Cas9 and infected by Sendai virus. We found that the absence of DUOX2 selectively reduced the induction of a restricted panel of 14 cytokines and chemokines secreted in response to Sendai virus by 20 to 89%. The secreted factors produced by epithelial cells upon virus infection promoted the migration, adhesion, and degranulation of primary human neutrophils, in part through the DUOX2-dependent secretion of TNF and chemokines. In contrast, DUOX2 expression did not impact neutrophil viability or NETosis, thereby highlighting a selective impact of DUOX2 in neutrophil functions. Overall, this study unveils previously unrecognized roles of epithelial DUOX2 in the epithelial-immune cells crosstalk during respiratory virus infection.

Vitisin B inhibits influenza A virus replication by multi-targeting neuraminidase and virus-induced oxidative stress

The development of drug-resistant influenza and new pathogenic virus strains underscores the need for antiviral therapeutics. Currently, neuraminidase (NA) inhibitors are commonly used antiviral drugs approved by the US Food and Drug Administration (FDA) for the prevention and treatment of influenza. Here, we show that vitisin B (VB) inhibits NA activity and suppresses H1N1 viral replication in MDCK and A549 cells. Reactive oxygen species (ROS), which frequently occur during viral infection, increase virus replication by activating the NF-κB signaling pathway, downmodulating glucose-6-phosphate dehydrogenase (G6PD) expression, and decreasing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant response activity. VB decreased virus-induced ROS generation by increasing G6PD expression and Nrf2 activity, and inhibiting NF-κB translocation to the nucleus through IKK dephosphorylation. In addition, VB reduced body weight loss, increased survival, decreased viral replication and the inflammatory response in the lungs of influenza A virus (IAV)-infected mice. Taken together, our results indicate that VB is a promising therapeutic candidate against IAV infection, complements existing drug limitations targeting viral NA. It modulated the intracellular ROS by G6PD, Nrf2 antioxidant response pathway, and NF-κB signaling pathway. These results demonstrate the feasibility of a multi-targeting drug strategy, providing new approaches for drug discovery against IAV infection.

Lignin: A Sustainable Antiviral Coating Material

Transmission of viruses through contact with contaminated surfaces is an important pathway for the spread of infections. Antiviral surface coatings are useful to minimize such risks. Current state-of-the-art approaches toward antiviral surface coatings either involve metal-based materials or complex synthetic polymers. These approaches, however, even if successful, will have to face great challenges when it comes to large-scale applications and their environmental sustainability. Here, an antiviral surface coating was prepared by spin-coating lignin, a natural biomass residue of the paper production industry. We show effective inactivation of herpes simplex virus type 2 (>99% after 30 min) on a surface coating that is low-cost and environmentally sustainable. The antiviral mechanism of the lignin surface was investigated and is attributed to reactive oxygen species generated upon oxidation of lignin phenols. This mechanism does not consume the surface coating (as opposed to the release of a specific antiviral agent) and does not require regeneration. The coating is stable in ambient conditions, as demonstrated in a 6 month aging study that did not reveal any decrease in antiviral activity. This research suggests that natural compounds may be used for the development of affordable and sustainable antiviral coatings.

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.

An Analysis of the Effects of In Vitro Photodynamic Therapy on Prostate Cancer Tissue by Histopathological Examination and Magnetic Resonance Imaging

Prostate cancer can significantly shorten the lifetime of a patient, even if he is diagnosed at an early stage. The development of minimally-invasive focal therapies such as photodynamic therapy to reduce the number of neoplastic cells while sparing delicate structures is extremely advantageous for treating prostate cancer. This study investigates the effect of photodynamic therapy performed in prostate tissue samples in vitro, using quantitative magnetic resonance imaging and histopathological analysis. Prostate tissue samples were treated with oxygenated solutions of Rose Bengal (RB) or protoporphyrin IX disodium salt (PpIX), illuminated with visible light, and then analyzed for changes in morphology by microscopy and by measurement of spin–lattice and spin–spin relaxation times at 1.5 Tesla. In the treated prostate tissue samples, histopathological images revealed chromatin condensation and swelling of the stroma, and in some cases, thrombotic necrosis and swelling of the stroma accompanied by pyknotic nuclei occurred. Several samples had protein fragments in the stroma. Magnetic resonance imaging of the treated prostate tissue samples revealed differences in the spin–lattice and spin–spin relaxation times prior to and post photodynamic action.

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.

Long COVID-19 in Children: From the Pathogenesis to the Biologically Plausible Roots of the Syndrome

Long Coronavirus disease-19 (COVID-19) refers to the persistence of symptoms related to the infection with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). This condition is described as persistent and can manifest in various combinations of signs and symptoms, such as fatigue, headache, dyspnea, depression, cognitive impairment, and altered perception of smells and tastes. Long COVID-19 may be due to long-term damage to different organs-such as lung, brain, kidney, and heart-caused by persisting viral-induced inflammation, immune dysregulation, autoimmunity, diffuse endothelial damage, and micro thrombosis. In this review, we discuss the potential and biologically plausible role of some vitamins, essential elements, and functional foods based on the hypothesis that an individual's dietary status may play an important adjunctive role in protective immunity against COVID-19 and possibly against its long-term consequences.

Non-Coding RNAs and Reactive Oxygen Species–Symmetric Players of the Pathogenesis Associated with Bacterial and Viral Infections

Infections can be triggered by a wide range of pathogens. However, there are few strains of bacteria that cause illness, but some are quite life-threatening. Likewise, viral infections are responsible for many human diseases, usually characterized by high contagiousness. Hence, as bacterial and viral infections can both cause similar symptoms, it can be difficult to determine the exact cause of a specific infection, and this limitation is critical. However, recent scientific advances have geared us up with the proper tools required for better diagnoses. Recent discoveries have confirmed the involvement of non-coding RNAs (ncRNAs) in regulating the pathogenesis of certain bacterial or viral infections. Moreover, the presence of reactive oxygen species (ROS) is also known as a common infection trait that can be used to achieve a more complete description of such pathogen-driven conditions. Thus, this opens further research opportunities, allowing scientists to explore infection-associated genetic patterns and develop better diagnosis and treatment methods. Therefore, the aim of this review is to summarize the current knowledge of the implication of ncRNAs and ROS in bacterial and viral infections, with great emphasis on their symmetry but, also, on their main differences.