Amelioration of influenza virus-induced reactive oxygen species formation by epigallocatechin gallate derived from green tea

Pre-Clinical Evaluation of the Antiviral Activity of Epigalocatechin-3-Gallate, a Component of Green Tea, against Influenza A(H1N1)pdm Viruses

Influenza antiviral drugs are important tools in our fight against both annual influenza epidemics and pandemics. Polyphenols are a group of compounds found in plants, some of which have demonstrated promising antiviral activity. Previous in vitro and mouse studies have outlined the anti-influenza virus effectiveness of the polyphenol epigallocatechin-3-gallate (EGCG); however, no study has utilised the ferret model, which is considered the gold-standard for influenza antiviral studies. This study aimed to explore the antiviral efficacy of EGCG in vitro and in ferrets. We first performed studies in Madin-Darby Canine Kidney (MDCK) and human lung carcinoma (Calu-3) cells, which demonstrated antiviral activity. In MDCK cells, we observed a selective index (SI, CC50/IC50) of 77 (290 µM/3.8 µM) and 96 (290 µM/3.0 µM) against A/California/07/2009 and A/Victoria/2570/2019 (H1N1)pdm09 influenza virus, respectively. Calu-3 cells demonstrated a SI of 16 (420 µM/26 µM) and 18 (420 µM/24 µM). Ferrets infected with A/California/07/2009 influenza virus and treated with EGCG (500 mg/kg/day for 4 days) had no change in respiratory tissue viral titres, in contrast to oseltamivir treatment, which significantly reduced viral load in the lungs of treated animals. Therefore, we demonstrated that although EGCG showed antiviral activity in vitro against influenza viruses, the drug failed to impair viral replication in the respiratory tract of ferrets.

In silico screening of SARS-CoV2 helicase using African natural products: Docking and molecular dynamics approaches

In the current medical era, there is an urgent necessity to identify new effective drugs to enrich the COVID-19's therapeutic arsenal. The SARS-COV-2 NSP13/helicase enzyme has been identified as a potential target for developing novel COVID-19 inhibitors. In this work, we aimed at endorsing effective natural products with potential inhibitory action towards the NSP13 through the virtual screening of 1012 natural products of botanical and marine origin from the South African Natural Compounds Database (SANCDB). The molecules were docked into the NTPase active site, and the best twelve compounds were chosen for further analysis. Thereafter, a combination of molecular dynamics simulations and MM-GBSA free energy calculations were carried out for a subset of best hits complexed with NSP13 helicase. We believe that the findings of this work will pave the way for additional research and experimental validation of some natural products as viable NSP13 helicase inhibitors.

Reducing lipid peroxidation attenuates stress-induced susceptibility to herpes simplex virus type 1

Psychological stress increases the susceptibility to herpes simplex virus type 1 (HSV-1) infection. There is no effective intervention due to the unknown pathogenesis mechanisms. In this study we explored the molecular mechanisms underlying stress-induced HSV-1 susceptibility and the antiviral effect of a natural compound rosmarinic acid (RA) in vivo and in vitro. Mice were administered RA (11.7, 23.4 mg·kg-1·d-1, i.g.) or acyclovir (ACV, 206 mg·kg-1·d-1, i.g.) for 23 days. The mice were subjected to restraint stress for 7 days followed by intranasal infection with HSV-1 on D7. At the end of RA or ACV treatment, mouse plasma samples and brain tissues were collected for analysis. We showed that both RA and ACV treatment significantly decreased stress-augmented mortality and alleviated eye swelling and neurological symptoms in HSV-1-infected mice. In SH-SY5Y cells and PC12 cells exposed to the stress hormone corticosterone (CORT) plus HSV-1, RA (100 μM) significantly increased the cell viability, and inhibited CORT-induced elevation in the expression of viral proteins and genes. We demonstrated that CORT (50 μM) triggered lipoxygenase 15 (ALOX15)-mediated redox imbalance in the neuronal cells, increasing the level of 4-HNE-conjugated STING, which impaired STING translocation from the endoplasmic reticulum to Golgi; the abnormality of STING-mediated innate immunity led to HSV-1 susceptibility. We revealed that RA was an inhibitor of lipid peroxidation by directly targeting ALOX15, thus RA could rescue stress-weakened neuronal innate immune response, thereby reducing HSV-1 susceptibility in vivo and in vitro. This study illustrates the critical role of lipid peroxidation in stress-induced HSV-1 susceptibility and reveals the potential for developing RA as an effective intervention in anti-HSV-1 therapy.

Specialized metabolites from plants as a source of new multi-target antiviral drugs: a systematic review

Viral infections have always been the main global health challenge, as several potentially lethal viruses, including the hepatitis virus, herpes virus, and influenza virus, have affected human health for decades. Unfortunately, most licensed antiviral drugs are characterized by many adverse reactions and, in the long-term therapy, also develop viral resistance; for these reasons, researchers have focused their attention on investigating potential antiviral molecules from plants. Natural resources indeed offer a variety of specialized therapeutic metabolites that have been demonstrated to inhibit viral entry into the host cells and replication through the regulation of viral absorption, cell receptor binding, and competition for the activation of intracellular signaling pathways. Many active phytochemicals, including flavonoids, lignans, terpenoids, coumarins, saponins, alkaloids, etc., have been identified as potential candidates for preventing and treating viral infections. Using a systematic approach, this review summarises the knowledge obtained to date on the in vivo antiviral activity of specialized metabolites extracted from plant matrices by focusing on their mechanism of action.

Anti-influenza A virus activity of flavonoids in vitro: a structure-activity relationship

Secondary plant metabolites from food extracts, namely daidzein, quercetin, and luteolin, exhibit anti-influenza virus effects, with IC₅₀ values of 143.6, 274.8, and 8.0 μM, respectively. The activities of these metabolites differ depending on the functional groups. Therefore, in this study, we focused on members of the flavonoid group, and investigated the anti-influenza viral effects of different flavonoid classes (flavone, isoflavone, flavonol, flavanone, and flavan-3-ol) in vitro. The IC₅₀ values were 4.9-82.8 μM, 143.6 μM, 62.9-477.8 μM, 290.4-881.1 μM, and 22.9-6717.2 μM, respectively, confirming their activity. The modifying group factors (number, position, type) in the flavonoid skeleton may be significantly related to the anti-influenza virus activity. Moreover, time-of-addition assay revealed that the mechanism of inhibition varied for the different classes; for example, flavonoids that inhibit virus adsorption or the early stage of viral growth. Interestingly, all the examined flavonoids inhibited the late stages of viral growth, suggesting that flavonoids mainly inhibit the late events in viral growth before the release of viral particles. Additionally, apigenin might be effective against oseltamivir-resistant strains. Our results may be important in the development of anti-influenza virus therapeutic strategies in the future.

Therapeutic Effects of Green Tea Polyphenol (‒)-Epigallocatechin-3-Gallate (EGCG) in Relation to Molecular Pathways Controlling Inflammation, Oxidative Stress, and Apoptosis

(‒)-Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenol in green tea. Thanks to multiple interactions with cell surface receptors, intracellular signaling pathways, and nuclear transcription factors, EGCG possesses a wide variety of anti-inflammatory, antioxidant, antifibrotic, anti-remodelation, and tissue-protective properties which may be useful in the treatment of various diseases, particularly in cancer, and neurological, cardiovascular, respiratory, and metabolic disorders. This article reviews current information on the biological effects of EGCG in the above-mentioned disorders in relation to molecular pathways controlling inflammation, oxidative stress, and cell apoptosis.

Research progress on antiviral constituents in traditional Chinese medicines and their mechanisms of action

CONTEXT

Viruses have the characteristics of rapid transmission and high mortality. At present, western medicines still lack an ideal antiviral. As natural products, many traditional Chinese medicines (TCM) have certain inhibitory effects on viruses, which has become the hotspot of medical research in recent years.

OBJECTIVE

The antiviral active ingredients and mechanisms of TCM against viral diseases was studied in combination with the pathogenesis of viral diseases and antiviral effects.

MATERIALS AND METHODS

English and Chinese literature from 1999 to 2021 was collected from databases including Web of Science, PubMed, Elsevier, Chinese Pharmacopoeia 2020 (CP), and CNKI (Chinese). Traditional Chinese medicines (TCM), active ingredients, antiviral, mechanism of action, and anti-inflammatory effect were used as the key words.

RESULTS

The antiviral activity of TCM is clarified to put forward a strategy for discovering active compounds against viruses, and provide reference for screening antivirus drugs from TCM. TCM can not only directly kill viruses and inhibit the proliferation of viruses in cells, but also prevent viruses from infecting cells and causing cytophilia. It can also regulate the human immune system, enhance human immunity, and play an indirect antiviral role.

DISCUSSION AND CONCLUSION

Based on the experimental study and antiviral mechanism of TCM, this paper can provide analytical evidence that supports the effectiveness of TCM in treating virus infections, as well as their mechanisms against viruses. It could be helpful to provide reference for the research and development of innovative TCMs with multiple components, multiple targets and low toxicity.

(-)-Epigallocatechin-3-Gallate Prevents IL-1β-Induced uPAR Expression and Invasiveness via the Suppression of NF-κB and AP-1 in Human Bladder Cancer Cells

(-)-Epigallocatechin-3-O-gallate (EGCG), a primary green tea polyphenol, has powerful iron scavengers, belongs to the family of flavonoids with antioxidant properties, and can be used to prevent cancer. Urokinase-type plasminogen activator receptors (uPARs) are glycosylphosphatidylinositol (GPI)-anchored cell membrane receptors that have crucial roles in cell invasion and metastasis of several cancers including bladder cancer. The mechanism of action of EGCG on uPAR expression has not been reported clearly yet. In this study, we investigated the effect of EGCG on interleukin (IL)-1β-induced cell invasion and uPAR activity in T24 human bladder cancer cells. Interestingly, nuclear factor (NF)-κB and activator protein (AP)-1 transcription factors were critically required for IL-1β-induced high uPAR expression, and EGCG suppressed the transcriptional activity of both the ERK1/2 and JNK signaling pathways with the AP-1 subunit c-Jun. EGCG blocked the IL-1β-stimulated reactive oxygen species (ROS) production, in turn suppressing NF-κB signaling and anti-invasion effects by inhibiting uPAR expression. These results suggest that EGCG may exert at least part of its anticancer effect by controlling uPAR expression through the suppression of ERK1/2, JNK, AP-1, and NF-κB.

Anti-influenza virus activity of the REV-ERBα agonist SR9009 and related analogues

REV-ERBα is a member of the nuclear receptor superfamily of transcription factors that aids in the regulation of many diseases. However, the prospect of using REV-ERBα for anti-influenza virus treatment remains poorly described, and there is an urgent need to develop effective anti-influenza agents due to the emergence of drug-resistant influenza viruses. In this study, eight SR9009 analogues were designed, synthesized, and evaluated for their biological activities against multiple influenza virus strains (H1N1, H3N2, adamantane- and oseltamivir-resistant H1N1 and influenza B virus), using ribavirin as the positive control. SR9009 and its analogues showed low micromolar or submicromolar EC₅₀ values and exhibited modestly improved antiviral potency compared to that of ribavirin. In particular, compound 5a possessed the most potent inhibitory activity (EC₅₀ = 0.471, 0.644, 1.644, 0.712 and 0.661 μM for A/PR/8/34, A/WSN/33, A/Wisconsin/67/2005, B/Yamagata/16/88 and Hebei/SWL1/2006, respectively). Cotransfection assays showed that all synthesized derivatives efficaciously suppressed transcription driven by the Bmal1 promoter. Mechanistic study results indicated that 5a efficiently inhibited IAV replication and interfered with the ealry stage of influenza virus life cycle. In addition, we found that 5a upregulated the key antiviral interferon-stimulated genes MxA, OAS2 and CH25H. Further in-depth transcriptome analysis revealed a series of upregulated genes that may contribute to the antiviral activities of 5a. These findings may provide an important direction for the development of new host-targeted broad-spectrum antiviral agents.

Green Tea Polyphenol (-)-Epigallocatechin-3-Gallate (EGCG): A Time for a New Player in the Treatment of Respiratory Diseases?

(-)-Epigallocatechin-3-gallate (EGCG) is a major polyphenol of green tea that possesses a wide variety of actions. EGCG acts as a strong antioxidant which effectively scavenges reactive oxygen species (ROS), inhibits pro-oxidant enzymes including NADPH oxidase, activates antioxidant systems including superoxide dismutase, catalase, or glutathione, and reduces abundant production of nitric oxide metabolites by inducible nitric oxide synthase. ECGC also exerts potent anti-inflammatory, anti-fibrotic, pro-apoptotic, anti-tumorous, and metabolic effects via modulation of a variety of intracellular signaling cascades. Based on this knowledge, the use of EGCG could be of benefit in respiratory diseases with acute or chronic inflammatory, oxidative, and fibrotizing processes in their pathogenesis. This article reviews current information on the biological effects of EGCG in those respiratory diseases or animal models in which EGCG has been administered, i.e., acute respiratory distress syndrome, respiratory infections, COVID-19, bronchial asthma, chronic obstructive pulmonary disease, lung fibrosis, silicosis, lung cancer, pulmonary hypertension, and lung embolism, and critically discusses effectiveness of EGCG administration in these respiratory disorders. For this review, articles in English language from the PubMed database were used.

LOW PREVALENCE OF COVID-19 IN LAOS AND CAMBODIA: DOES DIET PLAY A ROLE?

The study aims to review the involvement of different dietary habits in Laotian, Cambodian, and Vietnamese populations in reducing COVID19 impact. Materials and Methods. The methods of collection, systematization, analysis and generalization of information data have been used. The analysis of literature in scientific databases and analytical platforms by the listed keywords has been performed; all relevant references in the found sources have also been reviewed. Results and Discussion. Coronavirus disease (COVID-19) outbreak is an ongoing pandemic caused by a highly pathogenic human coronavirus known as SARS-CoV2. Current epidemiology reported that more than 500 million cases of COVID-19 occurred in more than 180 countries worldwide. When the upper respiratory tract gets infected by low pathogenetic HCoVs, it typically triggers a mild respiratory disease. In contrast, when the lower airways get infected by highly pathogenic HCoVs, such as SARS-CoV2, acute respiratory distress syndrome (ARDS) may occur and even fatal pneumonia. Such a situation causes the need for an urgent search of effective treatment measures. A very low incidence of SARS-CoV-2 in Laos and Cambodia, as well as low mortality rate due to COVID-19 in Vietnam and Laos, are extremely interesting, especially because of their early exposure to the virus, continuing ties to China, relative poverty, and high population density. The use of several spices and aromatic herbs as natural treatments for several illnesses, including viral infections, has been reported since a long time ago. The research reviewed three integral elements of Laotian, Cambodian, and Vietnamese diets, such as special culinary spices and herbs, coconut oil, and palm oil-rich for saturated fatty acids as well as fermented shrimp paste. Environmental and population genetic causes may be forwarded but moreover local dietary habits may have even a role in this evidence. Therefore, all these items highlight the possibility of a significant contribution of local cuisine and diet into the impact on appropriate anti-inflammatory and immune-resistant mechanisms of the human population. Conclusions. The review on Vietnam, Cambodia, and Laos inhabitants' diet helped to suggest the dietary factors having the contributing potential of reducing the severity of SARS-CoV-2 symptoms.

Epigallocatechin-3-Gallate Ameliorates Acute Lung Damage by Inhibiting Quorum-Sensing-Related Virulence Factors of Pseudomonas aeruginosa

The superbug Pseudomonas aeruginosa is among the most formidable antibiotic-resistant pathogens. With declining options for antibiotic-resistant infections, new medicines are of utmost importance to combat with P. aeruginosa. In our previous study, we demonstrated that Epigallocatechin-3-gallate (EGCG) can inhibit the production of quorum sensing (QS)-regulated virulence factors in vitro. Accordingly, the protective effect and molecular mechanisms of EGCG against P. aeruginosa-induced pneumonia were studied in a mouse model. The results indicated that EGCG significantly lessened histopathological changes and increased the survival rates of mice infected with P. aeruginosa. EGCG effectively alleviated lung injury by reducing the expression of virulence factors and bacterial burden. In addition, EGCG downregulated the production of pro-inflammatory cytokines, such as TNF-α, IL-1, IL-6, and IL-17, and increased the expression of anti-inflammatory cytokines IL-4 and IL-10. Thus, the experimental results supported for the first time that EGCG improved lung damage in P. aeruginosa infection by inhibiting the production of QS-related virulence factors in vivo.

Functional foods with antiviral activity

Viruses are known to cause a variety of diseases, ranging from mild respiratory diseases, such as the common cold, to fatal illnesses. Although the development of vaccines and targeted drugs have significantly improved the mortality rate and disease severity against a number of viral infections, there are still many viruses without proper treatment/prevention options and newly emerging viruses can pose serious health threats. For instance, the coronavirus disease 2019 (COVID-19) pandemic is producing significant healthcare and socio-economic burden worldwide, which may jeopardize the lives and livelihoods for years to come. Studies have identified functional foods with antiviral activity. Certain foods may target the viral life cycle or modulate the host immune system to enhance defense against viral infections. In this review, we will discuss some of the food products reported to display protective effects against viruses including the influenza virus, human immunodeficiency virus, and severe acute respiratory syndrome coronavirus 2.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Modulating Neurological Complications of Emerging Infectious Diseases: Mechanistic Approaches to Candidate Phytochemicals

Growing studies are revealing the critical manifestations of influenza, dengue virus (DENV) infection, Zika virus (ZIKV) disease, and Ebola virus disease (EVD) as emerging infectious diseases. However, their corresponding mechanisms of major complications headed for neuronal dysfunction are not entirely understood. From the mechanistic point of view, inflammatory/oxidative mediators are activated during emerging infectious diseases towards less cell migration, neurogenesis impairment, and neuronal death. Accordingly, the virus life cycle and associated enzymes, as well as host receptors, cytokine storm, and multiple signaling mediators, are the leading players of emerging infectious diseases. Consequently, chemokines, interleukins, interferons, carbohydrate molecules, toll-like receptors (TLRs), and tyrosine kinases are leading orchestrates of peripheral and central complications which are in near interconnections. Some of the resulting neuronal manifestations have attracted much attention, including inflammatory polyneuropathy, encephalopathy, meningitis, myelitis, stroke, Guillain-Barré syndrome (GBS), radiculomyelitis, meningoencephalitis, memory loss, headaches, cranial nerve abnormalities, tremor, and seizure. The complex pathophysiological mechanism behind the aforementioned complications urges the need for finding multi-target agents with higher efficacy and lower side effects. In recent decades, the natural kingdom has been highlighted as promising neuroprotective natural products in modulating several dysregulated signaling pathways/mediators. The present study provides neuronal manifestations of some emerging infectious diseases and underlying pathophysiological mechanisms. Besides, a mechanistic-based strategy is developed to introduce candidate natural products as promising multi-target agents in combating major dysregulated pathways towards neuroprotection in influenza, DENV infection, ZIKV disease, and EVD.

An Overview on the Potential Roles of EGCG in the Treatment of COVID-19 Infection

Coronavirus disease-19 (COVID-19) pandemic is currently ongoing worldwide and causes a lot of deaths in many countries. Although different vaccines for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection have been developed and are now available, there are no effective antiviral drugs to treat the disease, except for Remdesivir authorized by the US FDA to counteract the emergency. Thus, it can be useful to find alternative therapies based on the employment of natural compounds, with antiviral features, to circumvent SARS-CoV-2 infection. Pre-clinical studies highlighted the antiviral activities of epigallocatechin-3-gallate (EGCG), a catechin primarily found in green tea, against various viruses, including SARS-CoV-2. In this review, we summarize this experimental evidence and highlight the potential use of EGCG as an alternative therapeutic choice for the treatment of SARS-CoV-2 infection.

Nanotechnology-Based Approaches and Investigational Therapeutics against COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus which is currently responsible for the global pandemic since December 2019. This class of coronavirus has affected 217 countries around the world. Most of the countries have taken some non-remedial preventive actions like country lockdown, work from home, travel bans, and the most significant one is social isolation. Pharmacists, doctors, nurses, technologists, and all other healthcare professionals are playing a pivotal role during this pandemic. Unluckily, there is no specific drug that can treat patients who are confirmed with COVID-19, though favipiravir and remdesivir have appeared as favorable antiviral drugs. Some vaccines have already developed, and vaccination has started worldwide. Different nanotechnologies are in the developing stage in many countries for preventing SARS-COV-2 and treating COVID-19 conditions. In this article, we review the COVID-19 pandemic situation as well as the nanotechnology-based approaches and investigational therapeutics against COVID-19.

Anti-Influenza with Green Tea Catechins: A Systematic Review and Meta-Analysis

Influenza is one of the most serious respiratory viral infections worldwide. Although several studies have reported that green tea catechins (GTCs) might prevent influenza virus infection, this remains controversial. We performed a systematic review and meta-analysis of eight studies with 5048 participants that examined the effect of GTC administration on influenza prevention. In a random-effects meta-analysis of five RCTs, 884 participants treated with GTCs showed statistically significant effects on the prevention of influenza infection compared to the control group (risk ratio (RR) 0.67, 95% CIs 0.51–0.89, p = 0.005) without evidence of heterogeneity (I² = 0%, p = 0.629). Similarly, in three cohort studies with 2223 participants treated with GTCs, there were also statistically significant effects (RR 0.52, 95% CIs 0.35–0.77, p = 0.001) with very low evidence of heterogeneity (I² = 3%, p = 0.358). Additionally, the overall effect in the subgroup analysis of gargling and orally ingested items (taking capsules and drinking) showed a pooled RR of 0.62 (95% CIs 0.49–0.77, p = 0.003) without heterogeneity (I² = 0%, p = 0.554). There were no obvious publication biases (Egger’s test (p = 0.138) and Begg’s test (p = 0.103)). Our analysis suggests that green tea consumption is effective in the prophylaxis of influenza infections. To confirm the findings before implementation, longitudinal clinical trials with specific doses of green tea consumption are warranted.

Antiviral Effects of Green Tea EGCG and Its Potential Application against COVID-19

(–)-Epigallocatechin-3-O-gallate (EGCG), the most abundant component of catechins in tea (Camellia sinensis (L.) O. Kuntze), plays a role against viruses through inhibiting virus invasiveness, restraining gene expression and replication. In this paper, the antiviral effects of EGCG on various viruses, including DNA virus, RNA virus, coronavirus, enterovirus and arbovirus, were reviewed. Meanwhile, the antiviral effects of the EGCG epi-isomer counterpart (+)-gallocatechin-3-O-gallate (GCG) were also discussed.

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.

Insights into RNA-dependent RNA Polymerase Inhibitors as Antiinfluenza Virus Agents

BACKGROUND

Influenza is a seasonal disease that affects millions of people every year and has a significant economic impact. Vaccines are the best strategy to fight this viral pathology, but they are not always available or administrable, prompting the search for antiviral drugs. RNA-dependent RNA polymerase (RdRp) recently emerged as a promising target because of its key role in viral replication and its high conservation among viral strains.

DISCUSSION

This review presents an overview of the most interesting RdRp inhibitors that have been discussed in the literature since 2000. Compounds already approved or in clinical trials and a selection of inhibitors endowed with different scaffolds are described, along with the main features responsible for their activity.

RESULTS

RdRp inhibitors are emerging as a new strategy to fight viral infections and the importance of this class of drugs has been confirmed by the FDA approval of baloxavir marboxil in 2018. Despite the complexity of the RdRp machine makes the identification of new compounds a challenging research topic, it is likely that in the coming years, this field will attract the interest of a number of academic and industrial scientists because of the potential strength of this therapeutic approach.

Micronutrients and bioactive substances: Their potential roles in combating COVID-19

OBJECTIVES

The coronavirus disease 2019 (COVID-19) pandemic is seriously threatening public health and setting off huge economic crises across the world. In the absence of specific drugs for COVID-19, there is an urgent need to look for alternative approaches. Therefore, the aim of this paper was to review the roles of micronutrients and bioactive substances as potential alternative approaches in combating COVID-19.

METHODS

This review was based on the literature identified using electronic searches in different databases.

RESULTS

Vitamins (A, B, C, D, and E), minerals (selenium and zinc), and bioactive substances from curcumin, echinacea, propolis, garlic, soybean, green tea, and other polyphenols were identified as having potential roles in interfering with spike glycoproteins, angiotensin converting enzyme 2, and transmembrane protease serine 2 at the entry site, and inhibiting activities of papain-like protease, 3 chymotrypsin-like protease, and RNA-dependent RNA polymerase in the replication cycle of severe acute respiratory syndrome coronavirus 2. Having immunomodulating, antiinflammatory, antioxidant, and antiviral properties, such micronutrients and bioactive substances are consequently promising alterative nutritional approaches to combat COVID-19.

CONCLUSIONS

The roles of micronutrients and bioactive substances in the fight against COVID-19 are exciting areas of research. This review may suggest directions for further study.

Study on the mechanism of active components of Liupao tea on 3CLpro based on HPLC-DAD fingerprint and molecular docking technique

Liupao tea, a drink homologous to medicine and food. It can treat dysentery, relieve heat, remove dampness, and regulate the intestines and stomach. The objective of this study is to explore the material basis and mechanism of Liupao tea intervention in COVID-19 and to provide a new prevention and treatment programme for COVID-19. We used high performance liquid chromatography to analyze the extract of Liupao tea and establish its fingerprint. The main index components of the fingerprint were determined using SARS-COV-2 3-chymotrypsin-like protease (3CL^pro ), and an in vitro drug screening model based on fluorescence resonance energy transfer was used to evaluate its inhibitory activity in vitro. The fingerprint results showed that the alcohol extract of Liupao tea contained gallic acid, epigallocatechin gallate (EGCG), caffeine, epicatechin gallate, rutin, and ellagic acid. The molecular docking binding energies of the six index components of SARS-CoV-2 3Cl^pro were all less than -5.0 kJ/mol and showed strong binding affinity. The results of in vitro activity showed that the IC₅₀ of EGCG was 8.84 μmol/L, which could inhibit SARS-CoV-2 3Cl^pro to a certain extent. This study unleashed that EGCG has a certain inhibitory effect on SARS-CoV-2 3CL^pro , and Liupao tea has a certain significance as a tea drink for the prevention of COVID-19. PRACTICAL APPLICATIONS: The objective of this study was to explore the material basis and mechanism of Liupao tea intervention in COVID-19 and to provide a new prevention and treatment programme for COVID-19. The molecular docking binding energies of the six index components of Liupao tea with SARS-CoV-2 3CL^pro were all less than -5.0 kJ/mol, among them, the enzyme activity experiment shows that EGCG has a certain inhibitory effect on SARS-CoV-2 3CL^pro , it can be used as a potential SARS-CoV-2 3CL^pro inhibitor. We predicted that the understandings gained in the current research may evidence that Liupao tea has a certain significance as a tea drink for the prevention of COVID-19.

Attenuation of acute and chronic inflammation using compounds derived from plants

The appearance of excessive inflammatory activity is associated with onset of many disease states. Such non-productive responses are often the basis of the mortality consequent to incurring numerous disorders. The current outbreak of coronavirus disease 2019 caused by the virus "severe acute respiratory syndrome coronavirus 2" is a striking reflection of the inadequacy of current medical science to adequately address this issue. The usefulness of a range of materials of botanical origin in the attenuation of both chronic and acute inflammatory responses to various disease stressors is described. The properties of preparations of plant-based origin often parallel those of synthesized pharmacologics, but differ from them in some key respects. These differences can lead to more traditional preparations having distinct therapeutic advantages but also a number of specific shortcomings. The strengths and weaknesses of these materials are objectively contrasted with that of a more orthodox pharmacological approach. Each of these emphases in style has specific advantages and they should not be considered as competitors, but rather as accomplices in combating adverse states involving derangement of immune function.

The upshot of Polyphenolic compounds on immunity amid COVID-19 pandemic and other emerging communicable diseases: An appraisal

Polyphenols are a large family of more than 10,000 naturally occurring compounds, which exert countless pharmacological, biological and physiological benefits for human health including several chronic diseases such as cancer, diabetes, cardiovascular, and neurological diseases. Their role in traditional medicine, such as the use of a wide range of remedial herbs (thyme, oregano, rosemary, sage, mint, basil), has been well and long known for treating common respiratory problems and cold infections. This review reports on the most highlighted polyphenolic compounds present in up to date literature and their specific antiviral perceptive properties that might enhance the body immunity facing COVID-19, and other viral infectious diseases. In fact, several studies and clinical trials increasingly proved the role of polyphenols in controlling numerous human pathogens including SARS and MERS, which are quite similar to COVID-19 through the enhancement of host immune response against viral infections by different biological mechanisms. Thus, polyphenols ought to be considered as a potential and valuable source for designing new drugs that could be used effectively in the combat against COVID-19 and other rigorous diseases.

COVID-19 Outbreak: Pathogenesis, Current Therapies, and Potentials for Future Management

At the end of 2019, a novel coronavirus (CoV) was found at the seafood market of Hubei province in Wuhan, China, and this virus was officially named coronavirus diseases 2019 (COVID-19) by World Health Organization (WHO). COVID-19 is mainly characterized by severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) and creates public health concerns as well as significant threats to the economy around the world. Unfortunately, the pathogenesis of COVID-19 is unclear and there is no effective treatment of this newly life-threatening and devastating virus. Therefore, it is crucial to search for alternative methods that alleviate or inhibit the spread of COVID-19. In this review, we try to find out the etiology, epidemiology, symptoms as well as transmissions of this novel virus. We also summarize therapeutic interventions and suggest antiviral treatments, immune-enhancing candidates, general supplements, and CoV specific treatments that control replication and reproduction of SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV).

Redox control in the pathophysiology of influenza virus infection

Triggered in response to external and internal ligands in cells and animals, redox homeostasis is transmitted via signal molecules involved in defense redox mechanisms through networks of cell proliferation, differentiation, intracellular detoxification, bacterial infection, and immune reactions. Cellular oxidation is not necessarily harmful per se, but its effects depend on the balance between the peroxidation and antioxidation cascades, which can vary according to the stimulus and serve to maintain oxygen homeostasis. The reactive oxygen species (ROS) that are generated during influenza virus (IV) infection have critical effects on both the virus and host cells. In this review, we outline the link between viral infection and redox control using IV infection as an example. We discuss the current state of knowledge on the molecular relationship between cellular oxidation mediated by ROS accumulation and the diversity of IV infection. We also summarize the potential anti-IV agents available currently that act by targeting redox biology/pathophysiology.

Coronavirus Disease (COVID-19-SARS-CoV-2) and Nutrition: Is Infection in Italy Suggesting a Connection?

Novel coronavirus disease (COVID-19) was declared a global pandemic on March 11, 2020. The outbreak first occurred in Wuhan, Hubei, China, in December 2019 and hit Italy heavily in February 2020. Several countries are adopting complete or partial lockdown to contain the growth of COVID-19 infection. These measures may affect people's mental health and well-being but are necessary to avoid spreading the pandemic. There has been a gradual increase in studies exploring prevention and control measures, and we recommend paying close attention to nutrition, which may contribute to modulating some important consequences of COVID-19 infection, as such pro-inflammatory cytokine storm.

Antiviral Properties of R. tanguticum Nanoparticles on Herpes Simplex Virus Type I In Vitro and In Vivo

Herpes simplex virus type 1 (HSV-1), an enveloped DNA virus, plays a key role in varieties of diseases including recurrent cold sores, keratoconjunctivitis, genital herpes and encephalitis in humans. Great efforts have been made in developing more effective and less side-effects anti-herpes simplex virus agents, including traditional Chinese herbal medicines. In the present study, we evaluated the antiviral efficacy of Rheum tanguticum nanoparticles against HSV-1 in vitro and in vivo. R. tanguticum nanoparticles could inactivate the HSV-1 virions and block the viral attachment and entry into cells. Time-of-addition assay indicated that R. tanguticum nanoparticles could interfere with the entire phase of viral replication. Besides, R. tanguticum nanoparticles showed the ability to inhibit the mRNA expression of HSV-1 immediate early gene ICP4 and early gene ICP8 as well as the expression of viral protein ICP4 and ICP8. Moreover, R. tanguticum nanoparticles have been proved to protect mice against HSV-1 induced lethality by decreasing the viral load and alleviated pathological changes in brain tissues. In conclusion, we demonstrated that R. tanguticum nanoparticles could inhibit HSV-1 infection through multiple mechanisms. These results suggest that R. tanguticum nanoparticles may have novel roles in the treatment of HSV-1 infection.

Metal chelators for the inhibition of the lymphocytic choriomeningitis virus endonuclease domain

Arenaviridae is a viral family whose members are associated with rodent-transmitted infections to humans responsible of severe diseases. The current lack of a vaccine and limited therapeutic options make the development of efficacious drugs of high priority. The cap-snatching mechanism of transcription of Arenavirus performed by the endonuclease domain of the L-protein is unique and essential, so we developed a drug design program targeting the endonuclease activity of the prototypic Lymphocytic ChorioMeningitis Virus. Since the endonuclease activity is metal ion dependent, we designed a library of compounds bearing chelating motifs (diketo acids, polyphenols, and N-hydroxyisoquinoline-1,3-diones) able to block the catalytic center through the chelation of the critical metal ions, resulting in a functional impairment. We pre-screened 59 compounds by Differential Scanning Fluorimetry. Then, we characterized the binding affinity by Microscale Thermophoresis and evaluated selected compounds in in vitro and in cellula assays. We found several potent binders and inhibitors of the endonuclease activity. This study validates the proof of concept that the endonuclease domain of Arenavirus can be used as a target for anti-arena-viral drug discovery and that both diketo acids and N-hydroxyisoquinoline-1,3-diones can be considered further as potential metal-chelating pharmacophores.

Antiviral Mechanism of Action of Epigallocatechin-3-O-gallate and Its Fatty Acid Esters

Epigallocatechin-3-O-gallate (EGCG) is the major catechin component of green tea (Cameria sinensis), and is known to possess antiviral activities against a wide range of DNA viruses and RNA viruses. However, few studies have examined chemical modifications of EGCG in terms of enhanced antiviral efficacy. This paper discusses which steps of virus infection EGCG interferes with, citing previous reports. EGCG appears most likely to inhibits the early stage of infections, such as attachment, entry, and membrane fusion, by interfering with viral membrane proteins. According to the relationships between structure and antiviral activity of catechin derivatives, the 3-galloyl and 5'-OH group of catechin derivatives appear critical to antiviral activities. Enhancing the binding affinity of EGCG to virus particles would thus be important to increase virucidal activity. We propose a newly developed EGCG-fatty acid derivative in which the fatty acid on the phenolic hydroxyl group would be expected to increase viral and cellular membrane permeability. EGCG-fatty acid monoesters showed improved antiviral activities against different types of viruses, probably due to their increased affinity for virus and cellular membranes. Our study promotes the application of EGCG-fatty acid derivatives for the prevention and treatment of viral infections.

Anti-pandemic influenza A (H1N1) virus potential of catechin and gallic acid

BACKGROUND

The pandemic influenza A (H1N1) virus has spread worldwide and infected a large proportion of the human population. Discovery of new and effective drugs for the treatment of influenza is a crucial issue for the global medical community. According to our previous study, TSL-1, a fraction of the aqueous extract from the tender leaf of Toonasinensis, has demonstrated antiviral activities against pandemic influenza A (H1N1) through the down-regulation of adhesion molecules and chemokine to prevent viral attachment.

METHODS

The aim of the present study was to identify the active compounds in TSL-1 which exert anti-influenza A (H1N1) virus effects. XTT assay was used to detect the cell viability. Meanwhile, the inhibitory effect on the pandemic influenza A (H1N1) virus was analyzed by observing plaque formation, qRT-PCR, neuraminidase activity, and immunofluorescence staining of influenza A-specific glycoprotein.

RESULTS

Both catechin and gallic acid were found to be potent inhibitors in terms of influenza virus mRNA replication and MDCK plaque formation. Additionally, both compounds inhibited neuraminidase activities and viral glycoprotein. The 50% effective inhibition concentration (EC₅₀) of catechin and gallic acid for the influenza A (H1N1) virus were 18.4 μg/mL and 2.6 μg/mL, respectively; whereas the 50% cytotoxic concentrations (CC₅₀) of catechin and gallic acid were >100 μg/mL and 22.1 μg/mL, respectively. Thus, the selectivity indexes (SI) of catechin and gallic acid were >5.6 and 22.1, respectively.

CONCLUSION

The present study demonstrates that catechin might be a safe reagent for long-term use to prevent influenza A (H1N1) virus infection; whereas gallic acid might be a sensitive reagent to inhibit influenza virus infection. We conclude that these two phyto-chemicals in TSL-1 are responsible for exerting anti-pandemic influenza A (H1N1) virus effects.

Green Tea Polyphenol Epigallocatechin-3-gallate-Alleviated Coxsackievirus B3-induced Myocarditis Through Inhibiting Viral Replication but Not Through Inhibiting Inflammatory Responses

Viral myocarditis, which is mainly caused by coxsackievirus B3 (CVB3), affects about 5%-20% of the world population and still lacks efficient treatments. Green tea, a tonic and healthful beverage that was originated in ancient China, has been receiving considerable attention for its protective effect on cardiovascular diseases in recent years. In the present investigation, we aimed to explore the effect of green tea polyphenol epigallocatechin-3-gallate (EGCG) on CVB3-induced myocarditis and its underlying mechanism. Our study showed that EGCG could alleviate CVB3-induced myocarditis as evidenced by less cardiac injury and higher survival rate. Furthermore, we found that EGCG failed to downregulate the expression of inflammatory cytokines but could significantly inhibit the replication of CVB3. Furthermore, we found that EGCG treatment could downregulate the protein expression level of coxsackievirus and adenovirus receptor, the major receptor for CVB3 to infect cardiac myocytes. In conclusion, our data indicated that EGCG could ameliorate CVB3-induced myocarditis through inhibiting viral replication, which might provide a potential novel therapeutic strategy for viral myocarditis.

The role of oxidative stress in influenza virus infection

Virus-induced oxidative stress plays an important role in the regulation of the host immune system. In this review, we provide backgrounds of the pathogenic mechanism of oxidative stress induced by influenza virus and the specific oxidant-sensitive pathways, and highlight that antioxidant is one of the effective strategies against influenza virus infection.

Antivirals for Respiratory Viral Infections: Problems and Prospects

In the past two decades, several newly emerging and reemerging viral respiratory pathogens including several influenza viruses (avian influenza and pandemic influenza), severe acute respiratory syndrome coronavirus (SARS-CoV), and Middle East respiratory syndrome coronavirus (MERS-CoV), have continued to challenge medical and public health systems. Thereafter, the development of cost-effective, broad-spectrum antiviral agents is the urgent mission of both virologists and pharmacologists. Current antiviral developments have focused targets on viral entry, replication, release, and intercellular pathways essential for viral life cycle. Here, we review the current literature on challenges and prospects in the development of these antivirals.

Medicinal plants--prophylactic and therapeutic options for gastrointestinal and respiratory diseases in calves and piglets? A systematic review

BACKGROUND

Gastrointestinal and respiratory diseases in calves and piglets lead to significant economic losses in livestock husbandry. A high morbidity has been reported for diarrhea (calves ≤ 35%; piglets ≤ 50%) and for respiratory diseases (calves ≤ 80%; piglets ≤ 40%). Despite a highly diverse etiology and pathophysiology of these diseases, treatment with antimicrobials is often the first-line therapy. Multi-antimicrobial resistance in pathogens results in international accordance to strengthen the research in novel treatment options. Medicinal plants bear a potential as alternative or additional treatment. Based on the versatile effects of their plant specific multi-component-compositions, medicinal plants can potentially act as 'multi-target drugs'. Regarding the plurality of medicinal plants, the aim of this systematic review was to identify potential medicinal plant species for prevention and treatment of gastrointestinal and respiratory diseases and for modulation of the immune system and inflammation in calves and piglets.

RESULTS

Based on nine initial sources including standard textbooks and European ethnoveterinary studies, a total of 223 medicinal plant species related to the treatment of gastrointestinal and respiratory diseases was identified. A defined search strategy was established using the PRISMA statement to evaluate 30 medicinal plant species starting from 20'000 peer-reviewed articles published in the last 20 years (1994-2014). This strategy led to 418 references (257 in vitro, 84 in vivo and 77 clinical trials, thereof 48 clinical trials in veterinary medicine) to evaluate effects of medicinal plants and their efficacy in detail. The findings indicate that the most promising candidates for gastrointestinal diseases are Allium sativum L., Mentha x piperita L. and Salvia officinalis L.; for diseases of the respiratory tract Echinacea purpurea (L.) MOENCH, Thymus vulgaris L. and Althea officinalis L. were found most promising, and Echinacea purpurea (L.) MOENCH, Camellia sinensis (L.) KUNTZE, Glycyrrhiza glabra L. and Origanum vulgare L. were identified as best candidates for modulation of the immune system and inflammation.

CONCLUSIONS

Several medicinal plants bear a potential for novel treatment strategies for young livestock. There is a need for further research focused on gastrointestinal and respiratory diseases in calves and piglets, and the findings of this review provide a basis on plant selection for future studies.

The cytokine storm of severe influenza and development of immunomodulatory therapy

Severe influenza remains unusual in its virulence for humans. Complications or ultimately death arising from these infections are often associated with hyperinduction of proinflammatory cytokine production, which is also known as 'cytokine storm'. For this disease, it has been proposed that immunomodulatory therapy may improve the outcome, with or without the combination of antiviral agents. Here, we review the current literature on how various effectors of the immune system initiate the cytokine storm and exacerbate pathological damage in hosts. We also review some of the current immunomodulatory strategies for the treatment of cytokine storms in severe influenza, including corticosteroids, peroxisome proliferator-activated receptor agonists, sphingosine-1-phosphate receptor 1 agonists, cyclooxygenase-2 inhibitors, antioxidants, anti-tumour-necrosis factor therapy, intravenous immunoglobulin therapy, statins, arbidol, herbs, and other potential therapeutic strategies.

(+)-Catechin inhibition of transmissible gastroenteritis coronavirus in swine testicular cells is involved its antioxidation

Transmissible gastroenteritis virus (TGEV) causes transmissible gastroenteritis (TGE), especially in newborn piglets, which severely threatens the worldwide pig industry. In this study, (+)-catechin was evaluated for its antiviral effect against TGEV in vitro. Viability assays revealed that (+)-catechin treatment exerted a dose-dependent rescue effect in TGEV-infected ST cells, and this result was only obtained with the post-treatment application of (+)-catechin. The viral yields in (+)-catechin-treated cultures were reduced by almost three log₁₀ units. Quantitative real-time PCR analysis of the TGEV genome revealed that TGEV RNA replication was restricted after (+)-catechin treatment. Intracellular reactive oxygen species (ROS) detection showed that (+)-catechin alleviated ROS conditions induced by TGEV infection. Our results showed that (+)-catechin exerts an inhibitory effect on TGEV proliferation in vitro and is involved its antioxidation.

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(+)-Catechin has anti-TGEV effect.

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Anti-TGEV effect was working after TGEV infection.

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(+)-Catechin could relieve CPE caused by TGEV in ST cells.

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TGEV proliferation was decreased after (+)-catechin incubation.

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Antioxidation of (+)-catechin is related to its antiviral effect.

Influenza infection induces host DNA damage and dynamic DNA damage responses during tissue regeneration

Influenza viruses account for significant morbidity worldwide. Inflammatory responses, including excessive generation of reactive oxygen and nitrogen species (RONS), mediate lung injury in severe influenza infections. However, the molecular basis of inflammation-induced lung damage is not fully understood. Here, we studied influenza H1N1 infected cells in vitro, as well as H1N1 infected mice, and we monitored molecular and cellular responses over the course of 2 weeks in vivo. We show that influenza induces DNA damage to both, when cells are directly exposed to virus in vitro (measured using the comet assay) and also when cells are exposed to virus in vivo (estimated via γH2AX foci). We show that DNA damage, as well as responses to DNA damage persist in vivo until long after virus has been cleared, at times when there are inflammation associated RONS (measured by xanthine oxidase activity and oxidative products). The frequency of lung epithelial and immune cells with increased γH2AX foci is elevated in vivo, especially for dividing cells (Ki-67-positive) exposed to oxidative stress during tissue regeneration. Additionally, we observed a significant increase in apoptotic cells as well as increased levels of DNA double strand break (DSB) repair proteins Ku70, Ku86 and Rad51 during the regenerative phase. In conclusion, results show that influenza induces DNA damage both in vitro and in vivo, and that DNA damage responses are activated, raising the possibility that DNA repair capacity may be a determining factor for tissue recovery and disease outcome.

The role of cellular oxidoreductases in viral entry and virus infection-associated oxidative stress: potential therapeutic applications

INTRODUCTION

Cellular oxidoreductases catalyze thiol/disulfide exchange reactions in susceptible proteins and contribute to the cellular defense against oxidative stress. Oxidoreductases and oxidative stress are also involved in viral infections. In this overview, different aspects of the role of cellular oxidoreductases and oxidative stress during viral infections are discussed from a chemotherapeutic viewpoint.

AREAS COVERED

Entry of enveloped viruses into their target cells is triggered by the interaction of viral envelope glycoproteins with cellular (co)receptor(s) and depends on obligatory conformational changes in these viral envelope glycoproteins and/or cellular receptors. For some viruses, these conformational changes are mediated by cell surface-associated cellular oxidoreductases, which mediate disulfide bridge reductions in viral envelope glycoprotein(s). Therefore, targeting these oxidoreductases using oxidoreductase inhibitors might yield an interesting strategy to block viral entry of these viruses. Furthermore, since viral infections are often associated with systemic oxidative stress, contributing to disease progression, the enhancement of the cellular antioxidant defense systems might have potential as an adjuvant antiviral strategy, slowing down disease progression.

EXPERT OPINION

Promising antiviral data were obtained for both strategies. However, potential pitfalls have also been identified for these strategies, indicating that it is important to carefully assess the benefits versus risks of these antiviral strategies.

Respiratory protease/antiprotease balance determines susceptibility to viral infection and can be modified by nutritional antioxidants

The respiratory epithelium functions as a central orchestrator to initiate and organize responses to inhaled stimuli. Proteases and antiproteases are secreted from the respiratory epithelium and are involved in respiratory homeostasis. Modifications to the protease/antiprotease balance can lead to the development of lung diseases such as emphysema or chronic obstructive pulmonary disease. Furthermore, altered protease/antiprotease balance, in favor for increased protease activity, is associated with increased susceptibility to respiratory viral infections such as influenza virus. However, nutritional antioxidants induce antiprotease expression/secretion and decrease protease expression/activity, to protect against viral infection. As such, this review will elucidate the impact of this balance in the context of respiratory viral infection and lung disease, to further highlight the role epithelial cell-derived proteases and antiproteases contribute to respiratory immune function. Furthermore, this review will offer the use of nutritional antioxidants as possible therapeutics to boost respiratory mucosal responses and/or protect against infection.

Mouse lung slices: An ex vivo model for the evaluation of antiviral and anti-inflammatory agents against influenza viruses

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Mouse lung slices stay alive for at least 5 days ex vivo.

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Influenza viruses can replicate in mouse lung slices and trigger robust cytokine and chemokine responses.

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A positive correlation in cytokine and chemokine responses between ex vivo and in vivo exists.

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Neuraminidase and IP-10 can serve as readouts for antiviral and anti-inflammation activities, respectively.

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This ex vivo model may predict efficacy of drug candidates in antiviral and anti-inflammation activities in vivo.

The influenza A virus is notoriously known for its ability to cause recurrent epidemics and global pandemics. Antiviral therapy is effective when treatment is initiated within 48 h of symptom onset, and delaying treatment beyond this time frame is associated with decreased efficacy. Research on anti-inflammatory therapy to ameliorate influenza-induced inflammation is currently underway and seems important to the impact on the clinical outcome. Both antiviral and anti-inflammatory drugs with novel mechanisms of action are urgently needed. Current methods for evaluating the efficacy of anti-influenza drugs rely mostly on transformed cells and animals. Transformed cell models are distantly related to physiological and pathological conditions. Although animals are the best choices for preclinical drug testing, they are not time- or cost-efficient. In this study, we established an ex vivo model using mouse lung slices to evaluate both antiviral and anti-inflammatory agents against influenza virus infection. Both influenza virus PR8 (H1N1) and A/Human/Hubei/3/2005 (H3N2) can replicate efficiently in mouse lung slices and trigger significant cytokine and chemokine responses. The induction of selected cytokines and chemokines were found to have a positive correlation between ex vivo and in vivo experiments, suggesting that the ex vivo cultured lung slices may closely resemble the lung functionally in an in vivo configuration when challenged by influenza virus. Furthermore, a set of agents with known antiviral and/or anti-inflammatory activities were tested to validate the ex vivo model. Our results suggested that mouse lung slices provide a robust, convenient and cost-efficient model for the assessment of both antiviral and anti-inflammatory agents against influenza virus infection in one assay. This ex vivo model may predict the efficacy of drug candidates’ antiviral and anti-inflammatory activities in vivo.

Pyrrolidine dithiocarbamate inhibits enterovirus 71 replication by down-regulating ubiquitin-proteasome system

Enterovirus 71 (EV71) is the main causative pathogen of hand, foot, and mouth disease (HFMD). The severe neurological complications caused by EV71 infection and the lack of effective therapeutic medicine underline the importance of searching for antiviral substances. Pyrrolidine dithiocarbamate (PDTC), an antioxidant, has been reported to inhibit the replication of coxsackievirus B (CVB) through dysregulating ubiquitin-proteasome system (UPS). In this study, we demonstrated that PDTC exerted potent antiviral effect on EV71. Viral RNA synthesis, viral protein expression, and the production of viral progeny were significantly reduced by the treatment of PDTC in Vero cells infected with EV71. Similar to the previous report about the inhibitory effect of PDTC on UPS, we found that PDTC treatment led to decreased levels of polyubiquitinated proteins in EV71-infected cells. The inhibitory effect of PDTC on UPS was further confirmed by the increased accumulation of cell cycle regulatory proteins p21 and p53, which are normally degraded through UPS, while the expression levels of both proteins remained unchanged. We also showed that PDTC had no impact on the activity of proteasome. Thus, we demonstrated that the down-regulation of PDTC on UPS was the result of its inhibition on ubiquitination. More importantly, this study provides evidence that the inhibition on UPS was required for the antiviral activity of PDTC, since MG132, a potent proteasome inhibitor, significantly inhibited the cytopathic effect and viral protein synthesis in EV71-infected cells. We also found that the antioxidant property of PDTC did not contribute to its antiviral effect, since N-acetyl-l-cysteine, a potent antioxidant, could not inhibit viral replication. In addition, CPE and viral protein synthesis were not inhibited in the cells pretreated with PDTC 2h before viral infection and then cultured in the media with no PDTC supplement, while the antioxidant effect of PDTC was retained. PDTC also showed significant inhibition on apoptosis induced by EV71 infection when it was applied at the early stage of viral infection. Our results collectively suggest that PDTC could be a potential anti-EV71 compound which possesses both antiviral and anti-apoptotic capacity.

In vitro and in vivo studies of the inhibitory effects of emodin isolated from Polygonum cuspidatum on Coxsakievirus B₄

The lack of effective therapeutics for Coxsackievirus B₄ (CVB₄) infection underscores the importance of finding novel antiviral compounds. Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is one of the natural anthraquinone derivatives obtained from the root and rhizome of Polygonum cuspidatum. In the present study, the possibility of using emodin as a potential antiviral to treat CVB₄ infection was explored in vitro and in mice. Emodin reduced CVB₄ entry and replication on Hep-2 cells in a concentration- and time-dependent manner, with a 50% effective concentration (EC₅₀) of 12.06 μM and selectivity index (SI) of 5.08, respectively. The inhibitory effect of emodin for CVB₄ entry and replication was further confirmed by a quantitative real time PCR (qPCR) assay. The results further showed that the mice orally treated with different dosages of emodin displayed a dose dependent increase of survival rate, body weight and prolonged mean time of death (MTD), accompanied by significantly decreased myocardial virus titers and pathologic scores/lesions. Moreover, emodin could inhibit CVB₄-induced apoptosis in vitro and in vivo. Our results indicated that emodin could be used as potential antiviral in the post-exposure prophylaxis for CVB₄ infection.

Regulation of oxidative stress by Nrf2 in the pathophysiology of infectious diseases

The innate immune system, including phagocytic cells, is the first line of defense against pathogens. During infection by microorganisms such as viruses, bacteria, or parasites, phagocytic cells produce an excess of oxidants, a crucial process for the clearance of pathogens. This increase in oxidants creates an imbalance between oxidants and endogenous antioxidants. Left unchecked, this acute or chronic oxidative stress can lead to apoptotic cell-death and oxidative stress-induced diseases including neurodegenerative and cardiovascular disorders, premature aging, secondary infections, and cancer. The activation of nuclear factor E2-related factor 2 (Nrf2) is an efficient antioxidant defensive mechanism used by host cells to counteract oxidative stress. The transcription factor Nrf2 has been identified as the master regulator of several hundred of genes involved in the antioxidant defense response. The review objectives were to collect recent findings on the contribution of oxidative stress to complications of infection, and to highlight the beneficial impact of antioxidants in reducing inflammation and oxidant-related tissue damage. Furthermore, a direct relationship between infection and decline in Nrf2 activity has been demonstrated. Thus, an interesting therapeutic approach in disease prevention and treatment of stress-related diseases may consist in optimizing antibiotic or antiviral therapy with a combination of Nrf2 inducer treatment.