High-throughput screening for anti-influenza A virus drugs and study of the mechanism of procyanidin on influenza A virus-induced autophagy

Anti-influenza drug screening and inhibition of apigetrin on influenza A virus replication via TLR4 and autophagy pathways

Activation of Toll-like receptor (TLR) 4 plays important roles in the influenzaA virus (IAV) infection. To explore TLR4 inhibitors, 161 traditional Chinese medicines (TCMs) were screened. Further, we screened out Ixeris sonchifolia Hance, and its active compound, Apigetrin (apigenin-7-O-glucoside). Antiviral activity of Apigetrin was determined by plaque assay. We also further investigated the influence of Apigetrin on immune signaling pathways including TLRs, MAPK, NF-κB and autophagy pathways. The in-vitro results showed that the extract and its several ingredients could significantly inhibit IAV replication. Apigetrin significantly improved IAV-induced oxidative stress, inhibited the IAV-induced cytokine storm by suppressing the excessive activation of TLR3/4/7, JNK/p38 MAPK and NF-κB. Apigetrin decreased autophagosome accumulation and promoted degradation of IAV protein. Interestingly, Apigetrin antiviral activity was reversed by using H2O2 and the agonists of TLR4, JNK/p38, NF-κB and autophagy. Most important, the in-vitro effective concentration is higher than the reported plasma concentration. The in-vivo test showed that Apigetrin significantly increased the average survival time, reduced the lung edema and IAV replication. In conclusion, we have found that Ixeris sonchifolia Hance and its several ingredients can inhibit IAV infection, and the mechanisms of action of Apigetrin against IAV is by regulating TLR4 and autophagy signaling pathways.

Inhibitory effects and mechanisms of proanthocyanidins against enterovirus 71 infection

Proanthocyanidins (PC), a natural flavonoid compound, was reported to possess a variety of pharmacological activities such as anti-tumor and anti-viral effects. In this study, the anti-Enterovirus 71 (EV71) activities and mechanisms of PC were investigated both in vitro and in vivo. The results showed that PC possessed anti-EV71 activities in different cell lines with low toxicity. PC can block both the adsorption and entry processes of EV71 via directly binding to virus VP1 protein. PC may competitively interfere with the binding of VP1 to its receptor SCARB2. PC can also regulate three different MAPK signaling pathways to reduce EV71 infection and attenuate virus induced inflammatory responses. Importantly, intramuscular therapy of EV71-infected mice with PC markedly improved their survival and attenuated the severe clinical symptoms. Therefore, the natural compound PC has potential to be developed into a novel anti-EV71 agent targeting viral VP1 protein and MAPK pathways.

The battle for autophagy between host and influenza A virus

Influenza A virus (IAV) is an infectious pathogen, threatening the population and public safety with its epidemics. Therefore, it is essential to better understand influenza virus biology to develop efficient strategies against its pathogenicity. Autophagy is an important cellular process to maintain cellular homeostasis by cleaning up the hazardous substrates in lysosome. Accumulating research has also suggested that autophagy is a critical mechanism in host defense responses against IAV infection by degrading viral particles and activating innate or acquired immunity to induce viral clearance. However, IAV has conversely hijacked autophagy to strengthen virus infection by blocking autophagy maturation and further interfering host antiviral signalling to promote viral replication. Therefore, how the battle for autophagy between host and IAV is carried out need to be known. In this review, we describe the role of autophagy in host defence and IAV survival, and summarize the role of influenza proteins in subverting the autophagic process as well as then concentrate on how host utilize antiviral function of autophagy to prevent IAV infection.

Essential Oils and Their Compounds as Potential Anti-Influenza Agents

Essential oils (EOs) are chemical substances, mostly produced by aromatic plants in response to stress, that have a history of medicinal use for many diseases. In the last few decades, EOs have continued to gain more attention because of their proven therapeutic applications against the flu and other infectious diseases. Influenza (flu) is an infectious zoonotic disease that affects the lungs and their associated organs. It is a public health problem with a huge health burden, causing a seasonal outbreak every year. Occasionally, it comes as a disease pandemic with unprecedentedly high hospitalization and mortality. Currently, influenza is managed by vaccination and antiviral drugs such as Amantadine, Rimantadine, Oseltamivir, Peramivir, Zanamivir, and Baloxavir. However, the adverse side effects of these drugs, the rapid and unlimited variabilities of influenza viruses, and the emerging resistance of new virus strains to the currently used vaccines and drugs have necessitated the need to obtain more effective anti-influenza agents. In this review, essential oils are discussed in terms of their chemistry, ethnomedicinal values against flu-related illnesses, biological potential as anti-influenza agents, and mechanisms of action. In addition, the structure-activity relationships of lead anti-influenza EO compounds are also examined. This is all to identify leading agents that can be optimized as drug candidates for the management of influenza. Eucalyptol, germacrone, caryophyllene derivatives, eugenol, terpin-4-ol, bisabolene derivatives, and camphecene are among the promising EO compounds identified, based on their reported anti-influenza activities and plausible molecular actions, while nanotechnology may be a new strategy to achieve the efficient delivery of these therapeutically active EOs to the active virus site.

Investigating the active compounds and mechanism of HuaShi XuanFei formula for prevention and treatment of COVID-19 based on network pharmacology and molecular docking analysis

Traditional Chinese medicine (TCM) has exerted positive effects in controlling the COVID-19 pandemic. HuaShi XuanFei Formula (HSXFF) was developed to treat patients with mild and general COVID-19 in Zhejiang Province, China. The present study seeks to explore its potentially active compounds and pharmacological mechanisms against COVID-19 based on network pharmacology, molecular docking, and molecular dynamics (MD) simulation. All components of HSXFF were harvested from the pharmacology database of the TCMSP system. COVID-19-related targets were retrieved from using OMIM and GeneCards databases. The herb-compound-targets network was constructed by Cytoscape. The target protein-protein interaction (PPI) network, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed to discover the potential key target genes and mechanism. The main active compounds of HSXFF were docked with 3C-like (3CL) protease hydrolase and angiotensin-converting enzyme 2 (ACE2). The MD simulation confirmed the binding stability of docking results. The herbs-targets network mainly contained 52 compounds and 70 corresponding targets, including key targets such as RELA, TNF, TP53, IL6, MAPK1, CXCL8, IL-1β, and MAPK14. The GO and KEGG indicated that HSXFF may be mainly acting on the IL-17 signaling pathway, TNF signaling pathway, NF-κB signaling pathway, etc. The molecular docking results indicated that isovitexin and procyanidin B1 showed the highest affinity with 3CL and ACE2, respectively, which were confirmed by MD simulation. These findings suggested HSXFF exerted therapeutic effects involving "multi-compounds and multi-targets." It might be working through directly inhibiting the virus, improving immune function, and reducing the inflammatory in response to anti-COVID-19. In summary, the present study would provide a valuable direction for further research of HSXFF.

Neochlorogenic acid: an anti-HIV active compound identified by screening of Cortex Mori [Morus Alba L. (Moraceae)]

CONTEXT

Chinese herbs such as Cortex Mori [Morus alba L. (Moraceae)] may inhibit human immunodeficiency virus (HIV), but active compounds are unknown.

OBJECTIVE

Screening of Cortex Mori and other herbs for anti-HIV active compounds.

MATERIALS AND METHODS

HIV-1 virus (multiplicity of infection: 20), and herbs (dissolved in dimethyl sulfoxide, working concentrations: 10, 1, and 0.1 mg/mL) such as Cortex Mori, etc., were added to 786-O cells (10⁵ cell/well). Zidovudine was used as a positive control. Cell survival and viral inhibition rates were measured. The herb that was the closest inactivity to zidovudine was screened. Mass spectrometry identified the active compounds in herbs (mobile phase: 0.05% formic acid aqueous solution and acetonitrile, gradient elution, detection wavelength: 210 nm). The effect of the compounds on reverse transcriptase (RT) products were evaluated by real-time PCR. Gene enrichment was used to analyse underlying mechanisms.

RESULTS

With a dose of 1 mg/mL of Cortex Mori, the cell survival rate (57.94%) and viral inhibition rate (74.95%) were closest to the effect of zidovudine (87.87%, 79.81%, respectively). Neochlorogenic acid, one of the active ingredients, was identified by mass spectrometry in Cortex Mori. PCR discovery total RT products of neochlorogenic acid group (mean relative gene expression: 6.01) significantly inhibited (control: 35.42, p < 0.0001). Enrichment analysis showed that neochlorogenic acid may act on haemopoietic cell kinase, epidermal growth factor receptor, sarcoma, etc., thus inhibiting HIV-1 infection.

CONCLUSIONS

For people of low socioeconomic status affected by HIV, Chinese medicine (such as Cortex Mori) has many advantages: it is inexpensive and does not easily produce resistance. Drugs based on active ingredients may be developed and could have important value.

Grape Seed Proanthocyanidin Ameliorates FB1-Induced Meiotic Defects in Porcine Oocytes

Fumonisin B₁ (FB₁), as the most prevalent and toxic fumonisin, poses a health threat to humans and animals. The cytotoxicity of FB₁ is closely related to oxidative stress and apoptosis. The purpose of this study is to explore whether Grape seed proanthocyanidin (GSP), a natural antioxidant, could alleviate the meiotic maturation defects of oocytes caused by FB₁ exposure. Porcine cumulus oocyte complexes (COCs) were treated with 30 μM FB₁ alone or cotreated with 100, 200 and 300 μM GSP during in vitro maturation for 44 h. The results show that 200 μM GSP cotreatment observably ameliorated the toxic effects of FB₁ exposure, showing to be promoting first polar body extrusion and improving the subsequent cleavage rate and blastocyst development rate. Moreover, 200 μM GSP cotreatment restored cell cycle progression, reduced the proportion of aberrant spindles, improved actin distribution and protected mitochondrial function in FB₁-exposed oocytes. Furthermore, reactive oxygen species (ROS) generation was significantly decreased and the mRNA levels of CAT, SOD2 and GSH-PX were obviously increased in the 200 μM GSP cotreatment group. Notably, the incidence of early apoptosis and autophagy level were also significantly decreased after GSP cotreatment and the mRNA expression levels of BAX, CASPASE3, LC3 and ATG5 were markedly decreased, whereas BCL2 and mTOR were observably increased in the oocytes after GSP cotreatment. Together, these results indicate that GSP could exert significant preventive effects on FB₁-induced oocyte defects by ameliorating oxidative stress through repairing mitochondrial dysfunction.

Targeting autophagy with natural products to prevent SARS-CoV-2 infection

Autophagy is a catabolic process that maintains internal homeostasis and energy balance through the lysosomal degradation of redundant or damaged cellular components. During virus infection, autophagy is triggered both in parenchymal and in immune cells with different finalistic objectives: in parenchymal cells, the goal is to destroy the virion particle while in macrophages and dendritic cells the goal is to expose virion-derived fragments for priming the lymphocytes and initiate the immune response. However, some viruses have developed a strategy to subvert the autophagy machinery to escape the destructive destiny and instead exploit it for virion assembly and exocytosis. Coronaviruses (like SARS-CoV-2) possess such ability. The autophagy process requires a set of proteins that constitute the core machinery and is controlled by several signaling pathways. Here, we report on natural products capable of interfering with SARS-CoV-2 cellular infection and replication through their action on autophagy. The present study provides support to the use of such natural products as adjuvant therapeutics for the management of COVID-19 pandemic to prevent the virus infection and replication, and so mitigating the progression of the disease.

Indirect-Acting Pan-Antivirals vs. Respiratory Viruses: A Fresh Perspective on Computational Multi-Target Drug Discovery

Respiratory viruses continue to afflict mankind. Among them, pathogens such as coronaviruses [including the current pandemic agent known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)] and the one causing influenza A (IAV) are highly contagious and deadly. These can evade the immune system defenses while causing a hyperinflammatory response that can damage different tissues/organs. Simultaneously targeting immunomodulatory proteins is a plausible antiviral strategy since it could lead to the discovery of indirect-acting pan-antiviral (IAPA) agents for the treatment of diseases caused by respiratory viruses. In this context, computational approaches, which are an essential part of the modern drug discovery campaigns, could accelerate the identification of multi-target immunomodulators. This perspective discusses the usefulness of computational multi-target drug discovery for the virtual screening (drug repurposing) of IAPA agents capable of boosting the immune system through the activation of the toll-like receptor 7 (TLR7) and/or the stimulator of interferon genes (STING) while inhibiting key pro-inflammatory proteins, such as caspase-1 and tumor necrosis factor-alpha (TNF-α).

The Role of Anthocyanins in Drug Discovery: Recent Developments

Natural compounds have always played a key role in drug discovery. Anthocyanins are secondary metabolites belonging to the flavonoids family responsible for the purple, blue, and red colour of many vegetables and fruits. These phytochemicals have attracted the interest of researchers for their important implications in human health and for their use as natural colorants. Many in vitro and in vivo studies demonstrated the potential effects of anthocyanins and anthocyanins-rich foods in the prevention and/or treatment of diabetes, cancer, and cardiovascular and neurodegenerative diseases. This review reports the recent literature data and focuses on the potential role of anthocyanins in drug discovery. Their biological activity, analysis of structure-activity relationships, bioavailability, metabolism, and future prospects of their uses are critically described.

Potentials of Antitussive Traditional Persian Functional Foods for COVID-19 Therapy†

Coronavirus disease 2019 is a worldwide pandemic resulting in a severe acute respiratory syndrome. Remdesivir is the only FDA-approved drug for hospitalized patients older than age 12. It shows the necessity of finding new therapeutic strategies. Functional foods (FFs) could have co-therapeutic and protective effects against COVID-19 infection. Traditional Persian medicine (TPM), one of the safest and most popular schools of medicine for hundreds of years, has recommended potential FF candidates to manage such a global pandemic. To reveal the potential of TPM in terms of antitussive FFs, traditional Persian pharmacopoeia "Qarabadin-e-Salehi" was searched using the keywords "Soaal" and "Sorfeh." Also, a search of MEDLINE, PubMed Central, Google Scholar, and Science Direct was performed for the relevant literature published from the inception up to March 2021. A combination of search terms including "cough, antitussive, antioxidant, anti-inflammation, antiviral, COVID-19, mucoactive, mucolytic, expectorant, and mucoregulatory" was also applied. The potential mechanism of action in SARS-CoV-2 infection was discussed. Twelve TPM FFs were found including Laooqs, Morabbas, a Saviq, a soup, and a syrup. They are combinations of two to seven ingredients. Natural compounds of mentioned formulations have the main pharmacological mechanisms including antiviral, anti-inflammatory, antioxidant, antihistamine, bronchodilator, immunomodulatory, and mucoactive effects as well as central or peripheral antitussive activities. FFs are cost-effective, easily accessible, and safe options for both treatment and prevention of COVID-19. They might have positive psychological effects along with their pharmacological effects and nutritional virtues. They could also manage persistent respiratory discomforts after recovery from COVID-19.

Overview of Viral Pneumonia Associated With Influenza Virus, Respiratory Syncytial Virus, and Coronavirus, and Therapeutics Based on Natural Products of Medicinal Plants

Viral pneumonia has been a serious threat to global health, especially now we have dramatic challenges such as the COVID-19 pandemic. Approximately six million cases of community-acquired pneumonia occur every year, and over 20% of which need hospital admission. Influenza virus, respiratory virus, and coronavirus are the noteworthy causative agents to be investigated based on recent clinical research. Currently, anaphylactic reaction and inflammation induced by antiviral immunity can be incriminated as causative factors for clinicopathological symptoms of viral pneumonia. In this article, we illustrate the structure and related infection mechanisms of these viruses and the current status of antiviral therapies. Owing to a set of antiviral regiments with unsatisfactory clinical effects resulting from side effects, genetic mutation, and growing incidence of resistance, much attention has been paid on medicinal plants as a natural source of antiviral agents. Previous research mainly referred to herbal medicines and plant extracts with curative effects on viral infection models of influenza virus, respiratory virus, and coronavirus. This review summarizes the results of antiviral activities of various medicinal plants and their isolated substances, exclusively focusing on natural products for the treatment of the three types of pathogens that elicit pneumonia. Furthermore, we have introduced several useful screening tools to develop antiviral lead compounds.

Procyanidins mediates antineoplastic effects against non-small cell lung cancer via the JAK2/STAT3 pathway

Background

Lung cancer is a malignant tumor with one of the highest rates of cancer-related morbidity and mortality worldwide. Non-small cell lung cancer (NSCLC) account for 85% of all lung cancers and have a poor prognosis. Proanthocyanidins (PCs) are polyphenolic compounds that are found widely in natural plants. The present study aimed to determine the effects of PC on lung cancer and identify its possible mechanism.

Methods

A cell growth assay was used to detect the cell growth ability of A549 cancer cells, and a clonal formation assay was used to detect the cloning ability of A549 cancer cells. Flow cytometry was used to detect the effect of PCs on apoptosis and the cell cycle. The wound healing test, Transwell migration, and invasion test were used to detect the migration and invasion of human NSCLC A549 cells. Western blotting was utilized to detect the expression levels of N-cadherin, E-cadherin, vimentin, Janus kinase 2 (JAK2), p-signal transducer and activator of transcription 3 (p-STAT3), STAT3, matrix metalloproteinase 2 (MMP-2), MMP-9, and the apoptosis-related proteins, B-cell lymphoma-2 (Bcl-2) and BCL2-associated X (Bax). Cell immunofluorescence was used to detect the expression levels of the p-STAT3 primary antibody.

Results

PCs reduced the proliferation and cloning ability of A549 cells and significantly inhibited the migration and invasion of A549 cells in a dose-dependent manner. At the same time, PCs induced apoptosis in A549 cells and G2/M cell cycle arrest. PCs increased the pro-apoptotic protein expression, Bax, and down-regulated the anti-apoptotic protein expression, Bcl-2. PCs also inhibited the epithelial-mesothermal transition (EMT) process of A549 cells. We also found that the JAK2/STAT3 signaling pathway inhibitor, AG490, cooperated with PCs to inhibit A549 cell invasion and migration. Our results demonstrated that PCs could mediate the antitumor effect of NSCLC via the JAK2/STAT3 pathway.

Conclusions

PCs can inhibit NSCLC A549 cell proliferation, invasion, metastasis, clone formation, EMT, and induced apoptosis and G2/M cell cycle arrest. They work by inhibiting the JAK2/STAT3 signaling pathway. As a novel antitumor drug, PCs have broad application prospects for the treatment of NSCLC.

Pelargonium Extract EPs 7630 in the Treatment of Human Corona Virus-Associated Acute Respiratory Tract Infections - A Secondary Subgroup-Analysis of an Open-Label, Uncontrolled Clinical Trial

Background: Experience in treating human coronavirus (HCoV) infections might help to identify effective compounds against novel coronaviruses. We therefore performed a secondary subgroup-analysis of data from an open-label, uncontrolled clinical trial published in 2015 investigating the proanthocyanidin-rich Pelargonium sidoides extract EPs 7630 in patients with the common cold.

Methods: 120 patients with common cold and at least 2 out of 10 common cold symptoms received one film-coated 20 mg tablet EPs 7630 thrice daily for 10 days in an uncontrolled, interventional multicentre trial (ISRCTN65790556). At baseline, viral nucleic acids were detected by polymerase chain reaction. Common cold-associated symptoms and treatment satisfaction were evaluated after 5 days and at treatment end. Based on the data of patients with proof of viral nucleic acids, we compared the course of the disease in patients with or without HCoV infection.

Results: In 61 patients, viral nucleic acids were detected. Of these, 23 (37.7%) were tested positive for at least one HCoV (HCoV subset) and 38 (62.3%) for other viruses only (non-HCoV subset). Patients of both subsets showed a significant improvement of common cold symptoms already after 5 days of treatment, although the observed change tended to be more pronounced in the HCoV subset. At treatment end, more than 80% of patients of both groups were completely recovered or majorly improved. In both subsets, less than 22% of patients took concomitant paracetamol for antipyresis. The mean number of patients’ days off work or school/college was similar (0.9 ± 2.6 days in HCoV subset vs 1.3 ± 2.8 days in non-HCoV subset). In both groups, most patients were satisfied or very satisfied with EPs 7630 treatment.

Conclusion: EPs 7630 treatment outcomes of common cold patients with confirmed HCoV infection were as favourable as in patients with other viral infections. As this trial was conducted before the pandemic, there is currently no evidence from clinical trials for the efficacy of EPs 7630 in patients with SARS-CoV-2 infection. Dedicated non-clinical studies and clinical trials are required to elucidate the potential of EPs 7630 in the early treatment of HCoV infections.

Anti-influenza A Virus Effects and Mechanisms of Emodin and Its Analogs via Regulating PPARα/γ-AMPK-SIRT1 Pathway and Fatty Acid Metabolism

The peroxisome proliferator-activated receptor (PPAR) α/γ-adenosine 5'-monophosphate- (AMP-) activated protein kinase- (AMPK-) sirtuin-1 (SIRT1) pathway and fatty acid metabolism are reported to be involved in influenza A virus (IAV) replication and IAV-pneumonia. Through a cell-based peroxisome proliferator responsive element- (PPRE-) driven luciferase bioassay, we have investigated 145 examples of traditional Chinese medicines (TCMs). Several TCMs, such as Polygonum cuspidatum, Rheum officinale Baillon, and Aloe vera var. Chinensis (Haw.) Berg., were found to possess high activity. We have further detected the anti-IAV activities of emodin (EMO) and its analogs, a group of common important compounds of these TCMs. The results showed that emodin and its several analogs possess excellent anti-IAV activities. The pharmacological tests showed that emodin significantly activated PPARα/γ and AMPK, decreased fatty acid biosynthesis, and increased intracellular ATP levels. Pharmaceutical inhibitors, siRNAs for PPARα/γ and AMPKα1, and exogenous palmitate impaired the inhibition of emodin. The in vivo test also showed that emodin significantly protected mice from IAV infection and pneumonia. Pharmacological inhibitors for PPARα/γ and AMPK signal and exogenous palmitate could partially counteract the effects of emodin in vivo. In conclusion, emodin and its analogs are a group of promising anti-IAV drug precursors, and the pharmacological mechanism of emodin is linked to its ability to regulate the PPARα/γ-AMPK pathway and fatty acid metabolism.

An Evaluation of Traditional Persian Medicine for the Management of SARS-CoV-2

A new coronavirus causing severe acute respiratory syndrome (SARS-CoV-2) has emerged and with it, a global investigation of new antiviral treatments and supportive care for organ failure due to this life-threatening viral infection. Traditional Persian Medicine (TPM) is one of the most ancient medical doctrines mostly known with the manuscripts of Avicenna and Rhazes. In this paper, we first introduce a series of medicinal plants that would potentially be beneficial in treating SARS-CoV-2 infection according to TPM textbooks. Then, we review medicinal plants based on the pharmacological studies obtained from electronic databases and discuss their mechanism of action in SARS-CoV-2 infection. There are several medicinal plants in TPM with cardiotonic, kidney tonic, and pulmonary tonic activities, protecting the lung, heart, and kidney, the three main vulnerable organs in SARS-CoV-2 infection. Some medicinal plants can prevent "humor infection", a situation described in TPM which has similar features to SARS-CoV-2 infection. Pharmacological evaluations are in line with the therapeutic activities of several plants mentioned in TPM, mostly through antiviral, cytoprotective, anti-inflammatory, antioxidant, and anti-apoptotic mechanisms. Amongst the primarily-introduced medicinal plants from TPM, rhubarb, licorice, garlic, saffron, galangal, and clove are the most studied plants and represent candidates for clinical studies. The antiviral compounds isolated from these plants provide novel molecular structures to design new semisynthetic antiviral agents. Future clinical studies in healthy volunteers as well as patients suffering from pulmonary infections are necessary to confirm the safety and efficacy of these plants as complementary and integrative interventions in SARS-CoV-2 infection.

Antiviral Medicinal Plants of Veterinary Importance: A Literature Review

Viruses have a high mutation rate, and, thus, there is a continual emergence of new antiviral-resistant strains. Therefore, it becomes imperative to explore and develop new antiviral compounds continually. The search for pharmacological substances of plant origin that are effective against animal viruses, which have a high mortality rate or cause large economic losses, has garnered interest in the last few decades. This systematic review compiles 130 plant species that exhibit antiviral activity on 37 different virus species causing serious diseases in animals. The kind of extract, fraction, or compound exhibiting the antiviral activity and the design of the trial were particularly considered for review. The literature revealed details regarding plant species exhibiting antiviral activities against pathogenic animal virus species of the following families-Herpesviridae, Orthomyxoviridae, Paramyxoviridae, Parvoviridae, Poxviridae, Nimaviridae, Coronaviridae, Reoviridae, and Rhabdoviridae-that cause infections, among others, in poultry, cattle, pigs, horses, shrimps, and fish. Overall, 30 plant species exhibited activity against various influenza viruses, most of them causing avian influenza. Furthermore, 30 plant species were noted to be active against Newcastle disease virus. In addition, regarding the pathogens most frequently investigated, this review provides a compilation of 20 plant species active against bovine herpesvirus, 16 against fowlpox virus, 12 against white spot syndrome virus in marine shrimps, and 10 against suide herpesvirus. Nevertheless, some plant extracts, particularly their compounds, are promising candidates for the development of new antiviral remedies, which are urgently required.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.

Unraveling the Molecular Mechanism of Traditional Chinese Medicine: Formulas Against Acute Airway Viral Infections as Examples

Herbal medicine, including traditional Chinese medicine (TCM), is widely used worldwide. Herbs and TCM formulas contain numerous active molecules. Basically, they are a kind of cocktail therapy. Herb-drug, herb-food, herb-herb, herb-microbiome, and herb-disease interactions are complex. There is potential for both benefit and harm, so only after understanding more of their mechanisms and clinical effects can herbal medicine and TCM be helpful to users. Many pharmacologic studies have been performed to unravel the molecular mechanisms; however, basic and clinical studies of good validity are still not enough to translate experimental results into clinical understanding and to provide tough evidence for better use of herbal medicines. There are still issues regarding the conflicting pharmacologic effects, pharmacokinetics, drug interactions, adverse and clinical effects of herbal medicine and TCM. Understanding study validation, pharmacologic effects, drug interactions, indications and clinical effects, adverse effects and limitations, can all help clinicians in providing adequate suggestions to patients. At present, it would be better to use herbs and TCM formulas according to their traditional indications matching the disease pathophysiology and their molecular mechanisms. To unravel the molecular mechanisms and understand the benefits and harms of herbal medicine and TCM, there is still much work to be done.

Oxymatrine Inhibits Influenza A Virus Replication and Inflammation via TLR4, p38 MAPK and NF-κB Pathways

Oxymatrine (OMT) is a strong immunosuppressive agent that has been used in the clinic for many years. In the present study, by using plaque inhibition, luciferase reporter plasmids, qRT-PCR, western blotting, and ELISA assays, we have investigated the effect and mechanism of OMT on influenza A virus (IAV) replication and IAV-induced inflammation in vitro and in vivo. The results showed that OMT had excellent anti-IAV activity on eight IAV strains in vitro. OMT could significantly decrease the promoter activity of TLR3, TLR4, TLR7, MyD88, and TRAF6 genes, inhibit IAV-induced activations of Akt, ERK1/2, p38 MAPK, and NF-κB pathways, and suppress the expressions of inflammatory cytokines and MMP-2/-9. Activators of TLR4, p38 MAPK and NF-κB pathways could significantly antagonize the anti-IAV activity of OMT in vitro, including IAV replication and IAV-induced cytopathogenic effect (CPE). Furthermore, OMT could reduce the loss of body weight, significantly increase the survival rate of IAV-infected mice, decrease the lung index, pulmonary inflammation and lung viral titter, and improve pulmonary histopathological changes. In conclusion, OMT possesses anti-IAV and anti-inflammatory activities, the mechanism of action may be linked to its ability to inhibit IAV-induced activations of TLR4, p38 MAPK, and NF-κB pathways.

Inhibition of curcumin on influenza A virus infection and influenzal pneumonia via oxidative stress, TLR2/4, p38/JNK MAPK and NF-κB pathways

Oxidative stress, Nrf2-HO-1 and TLR-MAPK/NF-κB signaling pathways have been proved to be involved in influenza A virus (IAV) replication and influenzal pneumonia. In the previous studies, we have performed several high-throughput drug screenings based on the TLR pathways. In the present study, through plaque inhibition test, luciferase reporter assay, TCID₅₀, qRT-PCR, western blotting, ELISA and siRNA assays, we investigated the effect and mechanism of action of curcumin against IAV infection in vitro and in vivo. The results showed that curcumin could directly inactivate IAV, blocked IAV adsorption and inhibited IAV proliferation. As for the underlying mechanisms, we found that curcumin could significantly inhibit IAV-induced oxidative stress, increased Nrf2, HO-1, NQO1, GSTA3 and IFN-β production, and suppressed IAV-induced activation of TLR2/4/7, Akt, p38/JNK MAPK and NF-κB pathways. Suppression of Nrf2 via siRNA significantly abolished the stimulatory effect of curcumin on HO-1, NQO1, GSTA3 and IFN-β production and meanwhile blocked the inhibitory effect of curcumin on IAV M2 production. Oxidant H₂O₂ and TLR2/4, p38/JNK and NF-κB agonists could significantly antagonize the anti-IAV activity of curcumin in vitro. Additionally, curcumin significantly increased the survival rate of mice, reduced lung index, inflammatory cytokines and lung IAV titer, and finally improved pulmonary histopathological changes after IAV infection. In conclusion, curcumin can directly inactivate IAV, inhibits IAV adsorption and replication; and its inhibition on IAV replication may be via activating Nrf2 signal and inhibiting IAV-induced activation of TLR2/4, p38/JNK MAPK and NF-κB pathways.

Anti-influenza A virus activity of rhein through regulating oxidative stress, TLR4, Akt, MAPK, and NF-κB signal pathways

Rhein, an anthraquinone compound existing in many traditional herbal medicines, has anti-inflammatory, antioxidant, antitumor, antiviral, hepatoprotective, and nephroprotective activities, but its anti-influenza A virus (IAV) activity is ambiguous. In the present study, through plaque inhibition assay, time-of-addition assay, antioxidant assay, qRT-PCR, ELISA, and western blotting assays, we investigated the anti-IAV effect and mechanism of action of rhein in vitro and in vivo. The results showed that rhein could significantly inhibit IAV adsorption and replication, decrease IAV-induced oxidative stress, activations of TLR4, Akt, p38, JNK MAPK, and NF-κB pathways, and production of inflammatory cytokines and matrix metalloproteinases in vitro. Oxidant H2O2 and agonists of TLR4, Akt, p38/JNK and IKK/NF-κB could significantly antagonize the inhibitory effects of rhein on IAV-induced cytopathic effect (CPE) and IAV replication. Through an in vivo test in mice, we also found that rhein could significantly improve the survival rate, lung index, pulmonary cytokines, and pulmonary histopathological changes. Rhein also significantly decreased pulmonary viral load at a high dose. In conclusion, rhein can inhibit IAV adsorption and replication, and the mechanism of action to inhibit IAV replication may be due to its ability to suppress IAV-induced oxidative stress and activations of TLR4, Akt, p38, JNK MAPK, and NF-κB signal pathways.

Emodin Inhibition of Influenza A Virus Replication and Influenza Viral Pneumonia via the Nrf2, TLR4, p38/JNK and NF-kappaB Pathways

Lasting activations of toll-like receptors (TLRs), MAPK and NF-κB pathways can support influenza A virus (IAV) infection and promote pneumonia. In this study, we have investigated the effect and mechanism of action of emodin on IAV infection using qRT-PCR, western blotting, ELISA, Nrf2 luciferase reporter, siRNA and plaque inhibition assays. The results showed that emodin could significantly inhibit IAV (ST169, H1N1) replication, reduce IAV-induced expressions of TLR2/3/4/7, MyD88 and TRAF6, decrease IAV-induced phosphorylations of p38/JNK MAPK and nuclear translocation of NF-κB p65. Emodin also activated the Nrf2 pathway, decreased ROS levels, increased GSH levelss and GSH/GSSG ratio, and upregulated the activities of SOD, GR, CAT and GSH-Px after IAV infection. Suppression of Nrf2 via siRNA markedly blocked the inhibitory effects of emodin on IAV-induced activations of TLR4, p38/JNK, and NF-κB pathways and on IAV-induced production of IL-1β, IL-6 and expression of IAV M2 protein. Emodin also dramatically increased the survival rate of mice, reduced lung edema, pulmonary viral titer and inflammatory cytokines, and improved lung histopathological changes. In conclusion, emodin can inhibit IAV replication and influenza viral pneumonia, at least in part, by activating Nrf2 signaling and inhibiting IAV-induced activations of the TLR4, p38/JNK MAPK and NF-κB pathways.

Role of Autophagy and Apoptosis in the Postinfluenza Bacterial Pneumonia

The risk of influenza A virus (IAV) is more likely caused by secondary bacterial infections. During the past decades, a great amount of studies have been conducted on increased morbidity from secondary bacterial infections following influenza and provide an increasing number of explanations for the mechanisms underlying the infections. In this paper, we first review the recent research progress that IAV infection increased susceptibility to bacterial infection. We then propose an assumption that autophagy and apoptosis manipulation are beneficial to antagonize post-IAV bacterial infection and discuss the clinical significance.

Review of the Pharmacological Effects of Vitis vinifera (Grape) and its Bioactive Constituents: An Update

Vitis vinifera fruit (grape) contains various phenolic compounds, flavonoids and stilbenes. In recent years, active constituents found in the fruits, seeds, stems, skin and pomaces of grapes have been identified and some have been studied. In this review, we summarize the active constituents of different parts of V. vinifera and their pharmacological effects including skin protection, antioxidant, antibacterial, anticancer, antiinflammatory and antidiabetic activities, as well as hepatoprotective, cardioprotective and neuroprotective effects in experimental studies published after our 2009 review. Clinical and toxicity studies have also been examined. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of Edible Films Containing Procyanidin on the Preservation of Pork Meat during Chilled Storage

Procyanidins, which are natural antioxidants and antimicrobials found in grapes, enhance the quality and extend the shelf life of meat. We explored the effects of edible films incorporating procyanidins on pork loin stored for various times. Procyanidins (0, 0.1, and 0.3%, w/w) were incorporated into the edible films. We assessed meat color, pH, levels of volatile basic nitrogen (VBN) and 2-thiobarbituric acid-reactive substances (TBARS), and microbial populations for 14 d. The chromaticities and pH values of pork loin wrapped in film containing procyanidins (0.1% and 0.3%) generally increased (p<0.05) with storage time. VBN and TBARS levels, and total bacterial and Escherichia coli (E. coli) counts, significantly decreased (p<0.05) in the procyanidin groups. In particular, procyanidins strongly inhibited TBARS formation. Thus, our findings suggest that edible film impregnated with procyanidins inhibits lipid oxidation and microbial growth, thereby enhancing the quality and shelf life of pork meat.

Validation of Antiviral Potential of Herbal Ethnomedicine

Natural products are the basis of treatment since the dawn of human civilization, and modern medicine has gradually developed, over the years, by scientific and observational efforts from traditional medicine. Today most of the synthetic drugs showed adverse and unacceptable side effects, however, impressive bioactivities with reduced toxicities were reported for many botanicals against several chronic or difficult-to-treat diseases. A whole range of viral diseases including human immunodeficiency virus/acquired immunodeficiency syndrome, severe acute respiratory syndrome, Rabies, Dengue, and Herpes need effective drugs. Considerable research has been carried out on the pharmacognosy, chemistry, pharmacology, and therapeutics of traditional medicines of diverse cultures, and many pharmaceutical companies have renewed their strategies for antiviral drug development where no effective drugs or vaccine exist. Thus, phytochemicals with antiviral potentials need to be studied in depth with standardization, chemical isolation, effectivity, molecular mechanism, along with in vivo toxicity and efficacy to reduce cost and time. This review will portray the scientific approaches and methodologies used for the development of antiviral leads from traditional medicines against selected genetically and functionally diverse viral infections.

Panax notoginseng saponins inhibit areca nut extract-induced oral submucous fibrosis in vitro

BACKGROUND

Oral submucous fibrosis (OSF) is a premalignant and fibrosing disease, which is closely associated with the habit of chewing areca nut. Panax notoginseng Buck F. H. Chen is an often used antifibrotic and antitumor agent. To treat areca nut-induced OSF, we have developed a chewable tablet, in which one of the major medicines is total Panax notoginseng saponins (PNS). In this study, we have investigated the antifibrotic effect and mechanism of PNS on areca nut-induced OSF in vitro.

METHODS

Through human procollagen gene promoter luciferase reporter plasmid, hydroxyproline assay, gelatin zymography, qRT-PCR, ELISA, and Western blot, the influences of PNS on areca nut extract (ANE)-induced cell growth, collagen accumulation, procollagen gene transcription, MMP-2/-9 activity, MMP-1/-13 and TIMP-1/-2 expression, cytokine secretion, and the activation of PI3K/AKT, ERK/JNK/p38 MAPK, and TGFβ/Smads pathways were detected.

RESULTS

Panax notoginseng saponins could inhibit the ANE-induced abnormal growth and collagen accumulation of oral mucosal fibroblasts in a concentration-dependent manner. PNS (25 μg/ml) could significantly inhibit the ANE-induced expression of Col1A1 and Col3A1, augment the ANE-induced decrease of MMP-2/-9 activity, inhibit the ANE-induced increase of TIMP-1/-2 expression, and decrease the ANE-induced transcription and release of CTGF, TGFβ1, IL-6, and TNFα. PNS (25 μg/ml) also significantly inhibited the ANE-induced activation of AKT and ERK/JNK/p38 MAPK pathways in oral mucosal fibroblasts and the ANE-induced activation of TGFβ/smad pathway in HaCaT cells.

CONCLUSION

Panax notoginseng saponins possess excellent anti-OSF activity, and its mechanism may be related to its ability to inhibit the ANE-induced activation of PI3K/AKT, ERK/JNK/p38 MAPK, and TGFβ/smad pathways.

Screening and identification of inhibitors against influenza A virus from a US drug collection of 1280 drugs

Infection with influenza A virus is still a global concern since it causes significant mortality, morbidity and economic loss. New burst pandemics and rapid emergence of drug-resistance strains in recent years call for novel antiviral therapies. One promising way to overcome this problem is searching new inhibitors among thousands of drugs approved in the clinic for the treatment of different diseases or approved to be safe by clinical trials. In the present work, a collection of 1280 compounds, most of which have been clinically used in human or animal, were screened for anti-influenza activity and 41 hits (SI>4.0) were obtained. Next the 18 hit compounds with SI >10.0 were tested for antiviral activity against 7 other influenza virus strains in canine-originated MDCK cells, 9 compounds exhibited broad antiviral spectrum. The antiviral effects of the 9 compounds were also confirmed in human-originated A549 cells and chicken-originated DF1 cells, by infectious virus yield reduction assay and indirect immunofluorescent assay. Results from the time of addition assay showed that the 9 candidates impaired different stages of influenza virus life cycle, indicating they are novel inhibitors with different mechanisms compared with the existing M2 ion-channel blockers or neuraminidase (NA) inhibitors. Taken together, our findings provide 9 novel drug candidates for the treatment of influenza virus infection. Further mechanism of action study of these inhibitors may lead to the discovery of new anti-influenza targets and structure-activity relationship (SAR) study can be initiated to improve the efficacy of these new classes of influenza inhibitors.

Genome rearrangement of influenza virus for anti-viral drug screening

Rearrangement of the influenza A genome such that NS2 is expressed downstream of PB1 permits the insertion of a foreign gene in the NS gene segment. In this report, the genome rearranged strategy was extended to A/California/04/2009 (pH1N1), and Gaussia luciferase (GLuc) or GFP was expressed downstream of the full-length NS1 gene (designated GLucCa04 and GFPCa04, respectively). In growth kinetics studies, culture of amantadine sensitive GLucCa04 (Sens/GlucCa04) in the presence of amantadine significantly decreased GLuc expression and viral titers for 48 h post-infection (hpi). When Sens/GlucCa04 was subsequently used in an in vitro anti-viral screening assay, amantadine treatment significantly decreased GLuc expression from amantadine sensitive compared to amantadine resistant GLucCa04 (Res/GlucCa04) as early as 16 hpi. In in vivo screening studies, DBA mice were treated daily with amantadine from 1 day prior to infection and inoculated with either Sens/GlucCa04 or Res/GlucCa04 alone or as a co-infection with the parental strain. On days 3 and 5 post-infection, lung samples were collected and amantadine treatment was shown to decrease GLuc expression by two orders of magnitude (p<0.05) in Sens/GlucCa04 infected mice. Furthermore, while both Sens and Res/GlucCa04 were highly attenuated, addition of the parental strain to the inoculum yielded clinical disease indicative of GLuc expression and pulmonary viral titers. These findings indicate that the use of GLucCa04 can potentially accelerate in vitro and in vivo anti-viral screening by shortening the time required for virus detection.

In Vitro Antiviral Activity of a Series of Wild Berry Fruit Extracts against Representatives of Picorna-, Orthomyxo- and Paramyxoviridae

Wild berry species are known to exhibit a wide range of pharmacological activities. They have long been traditionally applied for their antiseptic, antimicrobial, cardioprotective and antioxidant properties. The aim of the present study is to reveal the potential for selective antiviral activity of total methanol extracts, as well as that of the anthocyanins and the non-anthocyanins from the following wild berries picked in Bulgaria: strawberry ( Fragaria vesca L.) and raspberry ( Rubus idaeus L.) of the Rosaceae plant family, and bilberry ( Vaccinium myrtillis L.) and lingonberry ( Vaccinium vitis-idaea L) of the Ericaceae. The antiviral effect has been tested against viruses that are important human pathogens and for which chemotherapy and/or chemoprophylaxis is indicated, namely poliovirus type 1 (PV-1) and coxsackievirus B1 (CV-B1) from the Picornaviridae virus family, human respiratory syncytial virus A2 (HRSV-A2) from the Paramyxoviridae and influenza virus A/H3N2 of Orthomyxoviridae. Wild berry fruits are freeze-dried and ground, then total methanol extracts are prepared. Further the extracts are fractioned by solid phase extraction and the non-anthocyanin and anthocyanin fractions are eluted. The in vitro antiviral effect is examined by the virus cytopathic effect (CPE) inhibition test. The results reveal that the total extracts of all tested berry fruits inhibit the replication of CV-B1 and influenza A virus. CV-B1 is inhibited to the highest degree by both bilberry and strawberry, as well as by lingonberry total extracts, and influenza A by bilberry and strawberry extracts. Anthocyanin fractions of all wild berries strongly inhibit the replication of influenza virus A/H3N2. Given the obtained results it is concluded that wild berry species are a valuable resource of antiviral substances and the present study should serve as a basis for further detailed research on the matter.

Identification of 23-(s)-2-amino-3-phenylpropanoyl-silybin as an antiviral agent for influenza A virus infection in vitro and in vivo

It has been reported that autophagy is involved in the replication of many viruses. In this study, we screened 89 medicinal plants, using an assay based on the inhibition of the formation of the Atg12-Atg5/Atg16 heterotrimer, an important regulator of autophagy, and selected Silybum marianum L. for further study. An antiviral assay indicated that silybin (S0), the major active compound of S. marianum L., can inhibit influenza A virus (IAV) infection. We later synthesized 5 silybin derivatives (S1 through S5) and found that 23-(S)-2-amino-3-phenylpropanoyl-silybin (S3) had the best activity. When we compared the polarities of the substituent groups, we found that the hydrophobicity of the substituent groups was positively correlated with their activities. We further studied the mechanisms of action of these compounds and determined that S0 and S3 also inhibited both the formation of the Atg12-Atg5/Atg16 heterotrimer and the elevated autophagy induced by IAV infection. In addition, we found that S0 and S3 could inhibit several components induced by IAV infection, including oxidative stress, the activation of extracellular signal-regulated kinase (ERK)/p38 mitogen-activated protein kinase (MAPK) and IκB kinase (IKK) pathways, and the expression of autophagic genes, especially Atg7 and Atg3. All of these components have been reported to be related to the formation of the Atg12-Atg5/Atg16 heterotrimer, which might validate our screening strategy. Finally, we demonstrated that S3 can significantly reduce influenza virus replication and the associated mortality in infected mice. In conclusion, we identified 23-(S)-2-amino-3-phenylpropanoyl-silybin as a promising inhibitor of IAV infection.

Xiao-Qing-Long-Tang (Sho-seiryu-to) inhibited cytopathic effect of human respiratory syncytial virus in cell lines of human respiratory tract

ETHNOPHARMACOLOGICAL RELEVANCE

Xiao-Qing-Long-Tang (XQLT, TJ-19, Sho-seiryu-to, so-cheong-ryong-tang) has been used against acute airway diseases for thousands of year in ancient China. Most of the acute airway illnesses are caused by virus. However, without activity against influenza virus, XQLT has been questioned to manage respiratory tract viral infection. Nevertheless, XQLT might be active against airway viruses other than influenza. Human respiratory syncytial virus (HRSV) is one of the most common respiratory viral pathogens without effective management. However, it is unknown whether XQLT has anti-HRSV activity.

AIM OF THE STUDY

We tested the hypothesis that XQLT can effectively minimize HRSV-induced plaque formation in respiratory tract mucosal cell lines.

MATERIALS AND METHODS

Anti-HRSV activity of a hot water extract of XQLT was examined by plaque reduction assay in both human upper (HEp-2) and low (A549) respiratory tract cell lines. Its effects on syncytial formation and viral fusion (F) protein were examined directly by microscopy and by western blot, respectively. Ability of XQLT to stimulate IFN-β was evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Hot water extract of XQLT dose-dependently inhibited HRSV-induced plaque formation in both HEp-2 and A549 cells (P<0.0001), particularly when given before viral inoculation (p<0.0001). XQLT inhibited viral attachment (p<0.0001) and internalization (p<0.0001). 300μg/ml XQLT could decrease both the number and the size of HRSV-induced syncytium without clear effect on the production of viral F protein. XQLT could stimulate epithelial cells to secrete IFN-β before and after viral inoculation to counteract viral infection (p<0.0001).

CONCLUSIONS

XQLT is effective against HRSV infection on airway epithelia by preventing viral attachment, internalization, syncytial formation, and by stimulating interferon secretion.

Drug screening for autophagy inhibitors based on the dissociation of Beclin1-Bcl2 complex using BiFC technique and mechanism of eugenol on anti-influenza A virus activity

Autophagy is involved in many human diseases, such as cancer, cardiovascular disease and virus infection, including human immunodeficiency virus (HIV), hepatitis C virus (HCV), influenza A virus (IAV) and coxsackievirus B3/B4 (CVB3/B4), so a drug screening model targeting autophagy may be very useful for the therapy of these diseases. In our study, we established a drug screening model based on the inhibition of the dissociation of Beclin1-Bcl2 heterodimer, an important negative regulator of autophagy, using bimolecular fluorescence complementation (BiFC) technique for developing novel autophagy inhibitors and anti-IAV agents. From 86 examples of traditional Chinese medicines, we found Syzygium aromaticum L. had the best activity. We then determined the anti-autophagy and anti-IAV activity of eugenol, the major active compound of Syzygium aromaticum L., and explored its mechanism of action. Eugenol could inhibit autophagy and IAV replication, inhibited the activation of ERK, p38MAPK and IKK/NF-κB signal pathways and antagonized the effects of the activators of these pathways. Eugenol also ameliorated the oxidative stress and inhibited the expressions of autophagic genes. We speculated that the mechanism underlying might be that eugenol inhibited the oxidative stress and the activation of ERK1/2, p38MAPK and IKK/NF-κB pathways, subsequently inhibited the dissociation of Beclin1-Bcl2 heterodimer and autophagy, and finally impaired IAV replication. These results might conversely display the reasonableness of the design of our screening model. In conclusion, we have established a drug screening model for developing novel autophagy inhibitor, and find eugenol as a promising inhibitor for autophagy and IAV infection.

Autophagosomal protein dynamics and influenza virus infection

Autophagy is a constitutive, catabolic process leading to the lysosomal degradation of cytosolic proteins and organelles. However, it is also induced under stress conditions, remodeling the eukaryotic cell by regulating energy, protein, and lipid homeostasis. It is likely that the autophagosomal/lysosomal pathway evolved primordially to recycle cell components, but further functionally developed as to become part of the immune system to defend against invading pathogens. Likewise, pathogenic, foreign agents developed strategies to fight back and even to employ the autophagy machinery to their own benefit. Hence, the regulation of autophagy has many implications on human health and disease. This review summarizes the molecular dynamics of autophagosome formation, maturation, and target selection. Membrane dynamics, as well as protein–protein and protein–membrane interactions are particularly addressed. In addition, it recapitulates current knowledge of the influences of influenza virus infection on the process.