Luteolin Inhibits Hepatitis B Virus Replication through Extracellular Signal-Regulated Kinase-Mediated Down-Regulation of Hepatocyte Nuclear Factor 4α Expression

Antiviral activity of luteolin against porcine epidemic diarrhea virus in silico and in vitro

BACKGROUND

Porcine epidemic diarrhea virus (PEDV) mainly causes acute and severe porcine epidemic diarrhea (PED), and is highly fatal in neonatal piglets. No reliable therapeutics against the infection exist, which poses a major global health issue for piglets. Luteolin is a flavonoid with anti-viral activity toward several viruses.

RESULTS

We evaluated anti-viral effects of luteolin in PEDV-infected Vero and IPEC-J2 cells, and identified IC50 values of 23.87 µM and 68.5 µM, respectively. And found PEDV internalization, replication and release were significantly reduced upon luteolin treatment. As luteolin could bind to human ACE2 and SARS-CoV-2 main protease (Mpro) to contribute viral entry, we first identified that luteolin shares the same core binding site on pACE2 with PEDV-S by molecular docking and exhibited positive pACE2 binding with an affinity constant of 71.6 µM at dose-dependent increases by surface plasmon resonance (SPR) assay. However, pACE2 was incapable of binding to PEDV-S1. Therefore, luteolin inhibited PEDV internalization independent of PEDV-S binding to pACE2. Moreover, luteolin was firmly embedded in the groove of active pocket of Mpro in a three-dimensional docking model, and fluorescence resonance energy transfer (FRET) assays confirmed that luteolin inhibited PEDV Mpro activity. In addition, we also observed PEDV-induced pro-inflammatory cytokine inhibition and Nrf2-induced HO-1 expression. Finally, a drug resistant mutant was isolated after 10 cell culture passages concomitant with increasing luteolin concentrations, with reduced PEDV susceptibility to luteolin identified at passage 10.

CONCLUSIONS

Our results push forward that anti-PEDV mechanisms and resistant-PEDV properties for luteolin, which may be used to combat PED.

Bushen Formula promotes the decrease of HBsAg levels in patients with CHB by regulating Tfh cells and B-cell subsets

ETHNOPHARMACOLOGICAL RELEVANCE

Bushen Formula (BSF) is the effective traditional Chinese medicine (TCM) for chronic hepatitis B (CHB) according to our previous researches. However, the special effectiveness of BSF treating CHB patients in different stages and the immunoregulatory mechanisms remain to be explored.

AIM OF THE STUDY

To compare the therapeutic effects of BSF in both treatment-naive patients and Peg-IFN-α-treated patients, and explore the potential mechanism of immunomodulation.

MATERIALS AND METHODS

Ultra-high performance liquid chromatography-quadrupole electrostatic field-orbital trap high resolution mass spectrometry and the TCMSP database were used to determine the main components of BSF. Two hundred and sixty-six patients were enrolled in the retrospective study, and they were divided into the treatment group (T-Group, BSF plus Peg-IFN-α) and the control group (C-Group, Peg-IFN-α monotherapy). Within each group, patients were further grouped into subgroups, namely T1/C1 groups (treatment-naive patients, T1 = 34, C1 = 94) and T2/C2 groups (Peg-IFN-α-treated patients, T2 = 56, C2 = 82). Serum HBV markers, serum HBV DNA levels, serum ALT/AST and TCM symptoms were obtained from the record. Bioinformatics analysis was employed to obtain the potential immunoregulatory mechanisms of BSF treating CHB patients. Among patients in T2 and C2 group, peripheral mononuclear cells from 36 patients were used to analyze the characteristics of peripheral follicular helper T (Tfh) cells and B-cell subtypes by flow cytometry. Preparation of BSF-containing serum in rats. In vitro, the co-culture system of CXCR5+ cells and HepG2.2.15 cells was built to investigate the immunoregulatory effects of BSF.

RESULTS

A total of 14 main active compounds were detected in BSF, which were deemed critical for the treatment of CHB. Our findings indicated that the T2-Group exhibited the higher percentage of HBsAg decline ≥ 1-log10 IU/ml and rate of HBeAg seroclearance compared to the C2-Group (35.7% vs. 15.9%, P = 0.033; 33.9% vs. 11.0%, P = 0.002). Additionally, the T2-Group demonstrated the higher percentage of HBsAg decline ≥ 1-log10 IU/ml and rate of HBeAg seroclearance compared to the T1-Group (35.7% vs. 14.7%, P = 0.031; 33.9% vs. 2.9%, P = 0.000). The total effective rate based on TCM clinical syndrome in T1-Group and T2-Group were significantly greater than those in C1-Group and C2-Group (85.3% vs. 61.7%, P = 0.012; 89.1% vs. 63.4%, P = 0.000). Bioinformatics analysis indicated that the immunoregulatory mechanisms of BSF treating CHB patients were mainly linked to the growth and stimulation of B-cell, T-cell differentiation, and the signaling pathway of the B-cell receptor. Furthermore, the frequencies of Tfh cells and its IL-21 level, and the IL-21R expressed by B-cell were all increased after BSF treatment. Additionally, in the co-culture system of CXCR5+ cells and HepG2.2.15 cells, HBsAg and HBeAg levels were decreased after BSF-containing serum treatment，as well as the up-regulating of Tfh cell frequencies and down-regulating of B-cell frequencies.

CONCLUSIONS

BSF have the higher percentage of HBsAg decline and HBeAg seroclearance in Peg-IFN-α-treated patients compared with treatment-naive patients. The potential immunoregulatory mechanism may correlate with promoting the interaction between Tfh cells and B-cell through IL-21/IL-21R signaling pathway.

Antimicrobial Activities of Natural Bioactive Polyphenols

Secondary metabolites, polyphenols, are widespread in the entire kingdom of plants. They contain one or more hydroxyl groups that have a variety of biological functions in the natural environment. These uses include polyphenols in food, beauty products, dietary supplements, and medicinal products and have grown rapidly during the past 20 years. Antimicrobial polyphenols are described together with their sources, classes, and subclasses. Polyphenols are found in different sources, such as dark chocolate, olive oil, red wine, almonds, cashews, walnuts, berries, green tea, apples, artichokes, mushrooms, etc. Examples of benefits are antiallergic, antioxidant, anticancer agents, anti-inflammatory, antihypertensive, and antimicrobe properties. From these sources, different classes of polyphenols are helpful for the growth of internal functional systems of the human body, providing healthy fats, vitamins, and minerals, lowering the risk of cardiovascular diseases, improving brain health, and rebooting our cellular microbiome health by mitochondrial uncoupling. Among the various health benefits of polyphenols (curcumin, naringenin, quercetin, catechin, etc.) primarily different antimicrobial activities are discussed along with possible future applications. For polyphenols and antimicrobial agents to be proven safe, adverse health impacts must be substantiated by reliable scientific research as well as in vitro and in vivo clinical data. Future research may be influenced by this evaluation.

The combination of Schisandrin C and Luteolin synergistically attenuates hepatitis B virus infection via repressing HBV replication and promoting cGAS-STING pathway activation in macrophages

BACKGROUND

HBV infection can result in severe liver diseases and is one of the primary causes of liver cell carcinoma-related mortality. Liuwei Wuling tablet (LWWL) is a traditional Chinese medicine formula, with a protecting liver and decreasing enzyme activity, usually used to treat chronic hepatitis B with NAs in clinic. However, its main active ingredients and mechanism of action have not been fully investigated. Hence, we aimed to screen the active ingredient and effective ingredient combinations from Liuwei Wuling tablet to explore the anti-herpatitis B virus activity and mechanism.

METHODS

Analysis and screening of effective antiviral components in LWWL by network pharmacology, luteolin (Lut) may be a compound with significant antiviral activity. The mechanism of antiviral action of Lut was also found by real-time PCR detection and western blotting. Meanwhile, we established a co-culture model to investigate the antiviral mechanism of Schisandrin C (SC), one of the main active components of Schisandra chinensis fructus (the sovereign drug of LWWL). Next, HBV-infected mice were established by tail vein injection of pAAV-HBV1.2 plasmid and administered continuously for 20 days. And their antiviral capacity was evaluated by checking serum levels of HBsAg, HBeAg, levels of HBV DNA, and liver levels of HBcAg.

RESULTS

In this study, we conducted network pharmacology analysis on LWWL, and through in vitro experimental validation and data analysis, we found that luteolin (Lut) possessed obviously anti-HBV activity, inhibiting HBV replication by downregulating hepatocyte nuclear factor 4α (HNF4α) via the ERK pathway. Additionally, we established a co-culture system and proved that SC promoted activation of cGAS-STINIG pathway and IFN-β production in THP-1 cells to inhibit HBV replication in HepG2.2.15 cells. Moreover, we found the combination of SC and Lut shows a greater effect in inhibiting HBV compared to SC or Lut alone in HBV-infected mice.

CONCLUSION

Taken together, our study suggests that combination of SC and Lut may be potential candidate drug for the prevention and treatment of chronic hepatitis B.

The role of Traditional Chinese medicine in anti-HBV: background, progress, and challenges

Chronic hepatitis B (CHB) remains a major world's most serious public health issues. Despite the remarkable effect of nucleos(t)ide analogues (NAs) in inhibiting hepatitis B virus (HBV) deoxyribonucleic acid (DNA) as the first-line drug, there are several limitations still, such as poor antigen inhibition, drug resistance, low-level viremia, restricting patients' functional cure. Due to the constraints of NAs, traditional medicines, such as traditional Chinese medicine (TCM), have become more prevalently used and researched in the clinical treatment of CHB as complementary alternative therapies. As a consequence, the review focuses on the background based on HBV's life cycle as well as the NAs' limitations, progress based on direct and indirect pathway of targeting HBV of TCM, and challenges of TCM. We found TCMs play an increasingly important role in anti-HBV. In a direct antiviral way, they regulate HBV infection, replication, assembly, and other aspects of the HBV life cycle. As for indirect way, TCMs can exert anti-HBV effects through targeting the host, including immune regulation, apoptosis, autophagy, oxidative stress, etc. Especially, TCMs have the advantages of strong antigenic inhibition compared to NAs. Specifically, we can combine the benefits of TCMs in strong HBV antigen inhibition with the benefits of NAs in targeted antiviral effects, in order to find a suitable combination of "TCM + NAs" to contribute to Chinese knowledge of the realisation of the "global elimination of HBV by 2030" goal of the World Health Organization.

Comprehensive in silico screening of flavonoids against SARS-CoV-2 main protease

In the current pandemic caused by the new coronavirus (SARS-CoV-2), computational drug discovery can play an essential role in finding potential therapeutic agents. Thanks to its anti-viral, antibacterial, and anti-inflammatory properties, sage (Salvia officinalis) is used in traditional medicine. In this study, drugs proposed against COVID-19, including Lopinavir, Remdesivir, Favipiravir, and main flavonoids of sage, were docked favorably against novel coronavirus main protease. Molecular docking findings indicate that Rutin, Luteolin-7-glucoside, Apigenin, and Hispidulin make strong interactions with better binding affinity than selected commercial drugs in the study. But Rutin is the only flavonoid that makes strong hydrogen bond interactions with catalytic dyad and crucial Mpro residues and has more binding affinity than protease inhibitor PF-07321332 as an oral antiviral (PAXLOVID™). Further analysis of Molecular Dynamics and MM-PBSA predicted that chosen ligands could form stable complexes with the main protease. Also, ADMET analysis shows that main flavonoids are expected to have appropriate pharmacokinetic and no toxic properties. The results of the in silico study suggest that Salvia officinalis as a rich source of potent anti-coronavirus flavonoids may play a significant role in counteracting the replication of SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Luteolin is a potential inhibitor of COVID-19: An in silico analysis

The severe respiratory syndrome 2019 novel coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread explosively, raising global health concerns. Luteolin shows antiviral properties, but its effect on SARS-CoV-2 and the associated mechanisms are not elucidated. We used network pharmacology, molecular docking and molecular dynamics to provide potential molecular support of luteolin (3,4,5,7-tetrahydroxyflavone) (LUT) against COVID-19. We employed network pharmacology, molecular docking, and molecular dynamics techniques to investigate how LUT affected COVID-19. Several databases were queried to determine potential target proteins related to LUT and COVID-19. Protein-protein interaction network was constructed, and core targets were filtered by degree value. Following that, functional enrichment was conducted. Molecular docking was utilized to ensure LUT was compatible with core target proteins. Finally, molecular dynamics was used to analyze the effects of the LUT on the optimal hub target. A total of 64 potential target genes for treating COVID-19 were identified, of which albumin, RAC-alpha serine/threonine-protein kinase, caspase-3, epidermal growth factor receptor, heat shock protein HSP 90-alpha, and mitogen-activated protein kinase 1 might be the most promising. In addition, molecular docking results showed that LUT could interact with SARS-CoV-2 major protease 3CL. LUT can bind to the active sites of 3CL protease and mitogen-activated protein kinase 1, showing an anti-SARS-CoV-2 potential.

Therapeutic Promises of Plant Metabolites against Monkeypox Virus: An In Silico Study

The monkeypox virus was still spreading in May 2022, with the first case identified in a person with travel ties to Nigeria. Using molecular docking-based techniques, we evaluated the efficiency of different bioactive chemicals obtained from plants against the monkeypox virus. A total of 56 plant compounds were evaluated for antimonekypox capabilities, with the top four candidates having a higher binding affinity than the control. We targeted the monkeypox profilin-like protein, which plays a key role in viral replication and assembly. Among the metabolites, curcumin showed the strongest binding affinity with a value of -37.43 kcal/mol, followed by gedunin (-34.89 kcal/mol), piperine (-34.58 kcal/mol), and coumadin (-34.14 kcal/mol). Based on ADME and toxicity assessments, the top four substances had no negative impacts. Furthermore, four compounds demonstrated resistance to deformability, which was corroborated by normal mode analysis. According to the bioactivity prediction study, the top compound target class was an enzyme, membrane receptor, and oxidoreductase. Furthermore, the study discovered that wortmannin, a gedunin analogue, can behave as an orthopoxvirus. The study found that these bioactive natural drug candidates could potentially work as monkeypox virus inhibitors. We recommended further experimental validation to confirm the promising findings of the study.

Luteolin Isolated from Juncus acutus L., a Potential Remedy for Human Coronavirus 229E

The COVID-19 pandemic, caused by SARS-CoV-2, addressed the lack of specific antiviral drugs against coronaviruses. In this study, bioguided fractionation performed on both ethyl acetate and aqueous sub-extracts of Juncus acutus stems led to identifying luteolin as a highly active antiviral molecule against human coronavirus HCoV-229E. The apolar sub-extract (CH₂Cl₂) containing phenanthrene derivatives did not show antiviral activity against this coronavirus. Infection tests on Huh-7 cells, expressing or not the cellular protease TMPRSS2, using luciferase reporter virus HCoV-229E-Luc showed that luteolin exhibited a dose-dependent inhibition of infection. Respective IC₅₀ values of 1.77 µM and 1.95 µM were determined. Under its glycosylated form (luteolin-7-O-glucoside), luteolin was inactive against HCoV-229E. Time of addition assay showed that utmost anti-HCoV-229E activity of luteolin was achieved when added at the post-inoculation step, indicating that luteolin acts as an inhibitor of the replication step of HCoV-229E. Unfortunately, no obvious antiviral activity for luteolin was found against SARS-CoV-2 and MERS-CoV in this study. In conclusion, luteolin isolated from Juncus acutus is a new inhibitor of alphacoronavirus HCoV-229E.

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.

A comprehensive perspective of traditional Arabic or Islamic medicinal plants as an adjuvant therapy against COVID-19

COVID-19 is a pulmonary disease caused by SARS-CoV-2. More than 200 million individuals are infected by this globally. Pyrexia, coughing, shortness of breath, headaches, diarrhoea, sore throats, and body aches are among the typical symptoms of COVID-19. The virus enters into the host body by interacting with the ACE2 receptor. Despite many SARS-CoV-2 vaccines manufactured by distinct strategies but any evidence-based particular medication to combat COVID-19 is not available yet. However, further research is required to determine the safety and effectiveness profile of the present therapeutic approaches. In this study, we provide a summary of Traditional Arabic or Islamic medicinal (TAIM) plants' historical use and their present role as adjuvant therapy for COVID-19. Herein, six medicinal plants Aloe barbadensis Miller, Olea europaea, Trigonella foenum-graecum, Nigella sativa, Cassia angustifolia, and Ficus carica have been studied based upon their pharmacological activities against viral infections. These plants include phytochemicals that have antiviral, immunomodulatory, antiasthmatic, antipyretic, and antitussive properties. These bioactive substances could be employed to control symptoms and enhance the development of a possible COVID-19 medicinal synthesis. To determine whether or if these TAIMs may be used as adjuvant therapy and are appropriate, a detailed evaluation is advised.

Dihydromyricetin inhibits Hepatitis B virus replication by activating NF-κB, MAPKs, and autophagy in HepG2.2.15 cells

BACKGROUND

Hepatitis B virus (HBV) infection is a severe global health problem, and there has been no effective method to eliminate HBV. This study was designed to explore the pharmacological mechanism of Dihydromyricetin (DHM) treatment on HBV replication in vitro.

METHODS AND RESULTS

DHM is a flavonoid compound from Ampelopsis grossedentata. Using HepG2.2.15 cells, which can stably express HBV in vitro, we demonstrated that DHM treatment dramatically reduced HBV replication and secretions of HBsAg and HBeAg. Meanwhile, DHM inhibited mRNA expression of HBV RNAs in HepG2.2.15 cells, including Total HBV RNA, HBV pregenomic RNA (pgRNA), and HBV precore mRNA (pcRNA). Also, DHM elevated the mRNA expressions of inflammatory cytokines and antiviral effectors. In contrast, DHM decreased the mRNA level of HNF4α, which positively correlated with HBV replication. Further studies show that the activation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathway played a critical role in DHM-initiated inhibition of HBV replication in HepG2.2.15 cells. Besides, activated autophagy was another contributor that may accelerate the clearance of HBV components.

CONCLUSION

In summary, DHM could suppress HBV replication by activating NF-κB, MAPKs, and autophagy in HepG2.2.15 cells. Our studies shed light on the future application of DHM for the clinical treatment of HBV infection.

Phytochemicals, Biological Activities, Molecular Mechanisms, and Future Prospects of Plantago asiatica L

Plantago asiatica L. has been used as a vegetable and nutritious food in Asia for thousands of years. According to recent phytochemical and pharmacological research, the active compositions of the plant contribute to various health benefits, such as antioxidant, anti-inflammatory, antibacterial, antiviral, and anticancer. This article reviews the 87 components of the plant and their structures, as well as their biological activities and molecular research progress, in detail. This review provides valuable reference material for further study, production, and application of P. asiatica, as well as its components in functional foods and therapeutic agents.

Network-based pharmacology and molecular docking exploring the "Bupleuri Radix-Scutellariae Radix" mechanism of action in the viral hepatitis B treatment

Viral hepatitis B is caused by the hepatitis B virus, which is characterized by liver lesions. Bupleuri Radix and Scutellariae Radix are the main traditional medicine pairs with remarkable efficacy in hepatitis B. However, their molecular mechanisms are incompletely understood. The main active components of Bupleuri Radix and Scutellariae Radix, as well as therapeutic targets for the treatment of hepatitis B, were identified through network pharmacology techniques. We identified viral hepatitis B targets using the GeneCards, online mendelian inheritance in man, and therapeutic target databases. We discovered the active components of Bupleuri Radix and Scutellariae Radix as well as therapeutic targets using the encyclopedia of traditional Chinese medicine, HERB, traditional Chinese medicine systems pharmacology database, and a bioinformatics analysis tool for molecular mechanism of traditional Chinese medicine databases. VENNY obtained the intersections. Cytoscape and STRING were used to create the "active ingredient-potential target" network and protein interaction network. The DAVID database was used to enrich GO and KEGG pathways. The results were confirmed using the molecular docking method. There were 1827 viral hepatitis B targets, and 37 active ingredients for Bupleuri and Scutellariae Radix, with the main components being quercetin, wogonin, baicalein, and kaempferol. Tumor necrosis factor (TNF), mitogen-activated protein kinase 3 (MAPK3), interleukin-6 (IL-6), vascular endothelial growth factor A, cysteinyl aspartate specific proteinase 3, transcription factor AP-1 (JUN), RAC-alpha serine/threonine-protein kinase, and cellular tumor antigen p53 are among the 78 common targets of Bupleuri Radix and Scutellariae Radix intervention in viral hepatitis B. KEGG enrichment resulted in 107 pathways, including cancer, hepatitis B, and TNF signaling pathways. According to the molecular docking technique, quercetin, wogonin, baicalein, and kaempferol had strong binding activities with TNF, MAPK3, and IL-6. In this study, we initially identified various molecular targets and multiple pathways involved in hepatitis B treatment with Bupleuri Radix and Scutellariae Radix.

Prevalence and associated factors of complementary and integrative medicine use in patients afflicted with COVID-19

Background

Complementary and Integrative Medicine (CIM) is often taken up by individuals seeking relief from different diseases. This study investigates the prevalence and associated factors of CIM use in patients with COVID-19.

Methods

In this telephone-based, cross-sectional study, data on CIM usage were collected from COVID-19 patients from February till June 2020 in Fars province, Iran using a researcher-made checklist. Additionally, we asked about the patients’ attitudes toward these treatments.

Results

Out of 453 patients diagnosed with COVID-19, 400 (88.30%) responded to our calls and agreed to participate in the study. Among them, 276 patients reported using CIM to treat COVID-19 [prevalence: 69% (95% CI: 64.2 to 73.5)]. The most frequently used herbal medicine among COVID-19 patients was ginger (n = 273, 98.9%), thyme (n = 263, 95.3%), and black cumin (n = 205, 74.3%). Most of these patients were recommended to use herbal medicine by their families and friends (n = 96, 34.8%). Univariable logistic regression revealed that age under 50 years old, residency in urban areas (including the capital of the province and small cities), employment, academic education, and being an outpatient were statistically significant factors resulting in CIM usage. Multivariable logistic regression revealed that CIM use among outpatients was 3.65 times more than among inpatients. In addition, patients under 50 years old used CIM 85% more than older patients. Ultimately, only 9 (3.3%) patients consulted with their doctors regarding these medications. No side effects due to CIM use were reported.

Conclusion

Many patients with COVID-19 used CIM, but few consulted with their physicians in this regard. Therefore, physicians should ask their patients about CIM usage, and patients should also report their use of CIM therapies during their medical visits. Furthermore, age and hospitalization status affected CIM use among patients with COVID-19.

Exploring the phytochemicals of Platycodon grandiflorus for TMPRSS2 inhibition in the search for SARS-CoV-2 entry inhibitors

Platycodon grandiflorus (Jacq.) A. DC. (Campanulaceae) is commonly known as a balloon flower whose rhizomes have been widely utilized in traditional Chinese medicine (TCM) and in various Japanese prescriptions for the treatment of respiratory diseases, diabetes, and inflammatory disorders. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19) global pandemic requires priming of the virus's spike (S) protein by cleavage of the S proteins by a multi-domain type II transmembrane serine protease, transmembrane protease serine 2 (TMPRSS2) to gain entry into the host cell. The current research aims at the screening of active phytocompounds of P. grandiflorus as potential inhibitors of cellular TMPRSS2 using molecular docking and molecular dynamics simulations approach. In silico toxicity analyses show that out of a total of 34 phytocompounds selected for the study, 12 compounds obey Lipinski’s rule of five and have favourable pharmacokinetic properties. The top three lead molecules identified here were Apigenin, Luteolin and Ferulic acid which exhibited binding energies of −7.47 kcal/mol, −6.8 kcal/mol and −6.62 kcal/mol respectively with corresponding inhibition constants of 3.33 µM, 10.39 µM and 13.95 µM. The complexes between the lead molecules and the receptor were held by hydrogen bond interactions with key residues such as Gly383, Gly385, Glu389, Lys390, Asp435, Ser436, Ser441, Cys465 and Lys467, and hydrophobic interactions with surrounding residues. The stability of the protein–ligand complexes was evaluated during 100 ns molecular dynamics (MD) simulation by analysing key geometric properties such as RMSD, RMSF, radius of gyration, total solvent accessible surface area and the number of hydrogen bonds. The binding free energies analysis using MD simulations revealed that the compounds and TMPRSS2 have favourable thermodynamic interactions, which are primarily driven by van der Waals forces. As a result, the selected bioactive phytochemicals from P. grandiflorus that target the cellular TMPRSS2 could offer an alternative treatment option against SARS-CoV-2 infections.

In Silico and In Vitro Identification of Pan-Coronaviral Main Protease Inhibitors from a Large Natural Product Library

The main protease (Mpro or 3CLpro) in coronaviruses represents a promising specific drug target as it is essential for the cleavage of the virus polypeptide and has a unique cleavage site that does not exist in human host proteases. In this study, we explored potential natural pan-coronavirus drugs using in vitro and in silico approaches and three coronavirus main proteases as treatment targets. The PyRx program was used to screen 39,442 natural-product-like compounds from the ZINC database and 121 preselected phytochemicals from medicinal plants with known antiviral activity. After assessment with Lipinski's rule of five, molecular docking was performed for the top 33 compounds of both libraries. Enzymatic assays were applied for the top candidates from both in silico approaches to test their ability to inhibit SARS-CoV-2 Mpro. The four compounds (hypericin, rosmarinic acid, isorhamnetin, and luteolin) that most efficiently inhibited SARS-CoV-2 Mpro in vitro were further tested for their efficacy in inhibiting Mpro of SARS-CoV-1 and MERS-CoV. Microscale thermophoresis was performed to determine dissociation constant (Kd) values to validate the binding of these active compounds to recombinant Mpro proteins of SARS-CoV-2, SARS-CoV-1, and MERS-CoV. The cytotoxicity of hypericin, rosmarinic acid, isorhamnetin, and luteolin was assessed in human diploid MRC-5 lung fibroblasts using the resazurin cell viability assay to determine their therapeutic indices. Sequence alignment of Mpro of SARS-CoV-2 demonstrated 96.08%, 50.83%, 49.17%, 48.51%, 44.04%, and 41.06% similarity to Mpro of other human-pathogenic coronaviruses (SARS-CoV-1, MERS-CoV, HCoV-NL63, HCoV-OC43, HCoV-HKU1, and HCoV-229E, respectively). Molecular docking showed that 12 out of 121 compounds were bound to SARS-CoV-2 Mpro at the same binding site as the control inhibitor, GC376. Enzyme inhibition assays revealed that hypericin, rosmarinic acid, isorhamnetin, and luteolin inhibited Mpro of SARS-CoV-2, while hypericin and isorhamnetin inhibited Mpro of SARS-CoV-1; hypericin showed inhibitory effects toward Mpro of MERS-CoV. Microscale thermophoresis confirmed the binding of these compounds to Mpro with high affinity. Resazurin assays showed that rosmarinic acid and luteolin were not cytotoxic toward MRC-5 cells, whereas hypericin and isorhamnetin were slightly cytotoxic. We demonstrated that hypericin represents a potential novel pan-anti-coronaviral agent by binding to and inhibiting Mpro of several human-pathogenic coronaviruses. Moreover, isorhamnetin showed inhibitory effects toward SARS-CoV-2 and SARS-CoV-1 Mpro, indicating that this compound may have some pan-coronaviral potential. Luteolin had inhibitory effects against SARS-CoV-2 Mpro.

Chinese Patent Medicine Liuweiwuling Tablet had Potent Inhibitory Effects on Both Wild-Type and Entecavir-Resistant Hepatitis B Virus (HBV) in vitro and Effectively Suppressed HBV Replication in Mouse Model

Liuweiwuling Tablet (LWWL) is a licensed Chinese patent medicine (approval number: Z20060238) included in the national health insurance for anti-inflammation of chronic HBV infection, whereas its anti-HBV effect remains clarification. The study aimed to clarify its antiviral effect and related mechanisms. HepG2.2.15 cells (wild-type HBV-replicating cells) and HepG2. A64 cells (entecavir-resistant HBV-replicating cells) were used for in vitro test. Hydrodynamic injection-mediated HBV-replicating mouse model was used for in vivo test. Active compounds and related mechanisms for antiviral effect of LWWL were analyzed using network pharmacology and transcriptomics. The inhibition rates of LWWL (0.8 mg/ml) on HBV DNA, HBsAg, and pgRNA were 57.06, 38.55, and 62.49% in HepG2.2.15 cells, and 51.57, 17.57, and 53.88% in HepG2. A64 cells, respectively. LWWL (2 g kg^-1 d^-1 for 4 weeks)-treated mice had 1.16 log₁₀ IU/mL decrease of serum HBV DNA, and more than 50% decrease of serum HBsAg/HBeAg and hepatic HBsAg/HBcAg. Compared to tenofovir control, LWWL was less effective in suppressing HBV DNA but more effective in suppressing HBV antigens. Thirteen differentially-expressed genes were found in relation to HBV-host interaction and some of them were enriched in interferon (IFN)-β pathway in LWWL-treated HepG2.2.15 cells. CD3⁺CD4⁺ T-cell frequency and serum IFN-γ were significantly increased in LWWL-treated mice compared to LWWL-untreated mice. Among 26 compounds with potential anti-HBV effects that were predicted by network pharmacology, four compounds (quercetin, luteolin, wogonin, and kaempferol) were experimentally confirmed to have antiviral potency. In conclusion, LWWL had potent inhibitory effect on both wild-type and entecavir-resistant HBV, which might be associated with increasing IFN-β and IFN-γ production.

Disruption of Tumor Suppressors HNF4α/HNF1α Causes Tumorigenesis in Liver

The hepatocyte nuclear factor-4α (HNF4α) and hepatocyte nuclear factor-1α (HNF1α) are transcription factors that influence the development and maintenance of homeostasis in a variety of tissues, including the liver. As such, disruptions in their transcriptional networks can herald a number of pathologies, such as tumorigenesis. Largely considered tumor suppressants in liver cancer, these transcription factors regulate key events of inflammation, epithelial-mesenchymal transition, metabolic reprogramming, and the differentiation status of the cell. High-throughput analysis of cancer cell genomes has identified a number of hotspot mutations in HNF1α and HNF4α in liver cancer. Such results also showcase HNF1α and HNF4α as important therapeutic targets helping us step into the era of personalized medicine. In this review, we update current findings on the roles of HNF1α and HNF4α in liver cancer development and progression. It covers the molecular mechanisms of HNF1α and HNF4α dysregulation and also highlights the potential of HNF4α as a therapeutic target in liver cancer.

GATA binding protein 4 promotes the expression and transcription of hepatitis B virus by facilitating hepatocyte nuclear factor 4 alpha in vitro

Background

GATA binding protein 4 (GATA4) has been reported as a potential target of gene therapy for hepatocellular carcinoma (HCC). It is well known that the main cause of HCC is the chronic infection of hepatitis B virus (HBV). However, whether the effect of GATA4 on HBV has not yet been reported.

Methods

In this study, the regulation of GATA4 on HBV was analyzed in vitro. In turn, the effect of HBV on GATA4 was also observed in vitro, in vivo, and clinical HCC patients. Subsequently, we analyzed whether the effect of GATA4 on HBV was related to hepatocyte nuclear factor 4 alpha (HNF4α) in vitro.

Results

The results showed that GATA4 significantly promoted the secretion of HBV surface antigen (HBsAg) and HBV e antigen in the cell culture medium, improved the replication of HBV genomic DNA, and increased the level of HBV 3.5 kb pre-genomic RNA and HBV total RNA (P < 0.05). Moreover, it was showed that HBV had no significant effect on GATA4 in vitro and in vivo (P > 0.05). At the same time, GATA4 expression was decreased in 78.9% (15/19) of HCC patients regardless of the HBV and HBsAg status. Among them, there were 76.9% (10/13) in HBV-associated patients with HCC (HBV-HCC), and 83.3% (5/6) in non-HBV-HCC patients. In addition, the expression of HNF4α was also up-regulated or down-regulated accordingly when stimulating or interfering with the expression of GATA4. Furthermore, stimulating the expression of HNF4α could only alleviate the HBsAg level and HBV transcription levels, but had no significant effect on GATA4.

Conclusions

In summary, this study found that GATA4 has a positive effect on HBV, and the potential pathway may be related to another transcription factor HNF4α that regulates HBV.

The Use of Traditional Chinese Medicine in Relieving EGFR-TKI-Associated Diarrhea Based on Network Pharmacology and Data Mining

In this study, the role of traditional Chinese medicine (TCM) in relieving epidermal growth factor receptor-tyrosine kinase inhibitor- (EGFR-TKI-) associated diarrhea was discussed by network pharmacology and data mining. Prediction of drug targets by introducing the EGFR-TKI molecular structures into the SwissTargetPrediction platform and diarrhea-related targets in the DrugBank, GeneCards, DisGeNET, and OMIM databases were obtained. Compounds in the drug-disease target intersection were screened by absorption, distribution, metabolism, and excretion parameters and Lipinski's rule in Traditional Chinese Medicine Systems Pharmacology. TCM-containing compounds were selected, and information on the property, taste, and meridian tropism of these TCMs was summarized and analyzed. A target-compound-TCM network diagram was constructed, and core targets, compounds, and TCMs were selected. The core targets and components were docked by AutoDock Vina (Version 1.1.2) to explore the target combinations of related compounds and evaluate the docking activity of related targets and compounds. Twenty-three potential therapeutic TCM targets for the treatment of EGFR-TKI-related diarrhea were obtained. There were 339 compounds acting on potential therapeutic targets, involving a total of 402 TCMs. The results of molecular docking showed good binding between the core targets and compounds, and the binding between the core targets and compounds was similar to that of the core target and the recommended drug loperamide. TCMs have multitarget characteristics and are present in a variety of compounds used for relieving EGFR-TKI-associated diarrhea. Antitumor activity and the efficacy of alleviating diarrhea are the pharmacological basis of combining TCMs with EGFR-TKI in the treatment of non-small-cell lung cancer. The core targets, compounds, and TCMs can provide data to support experimental and clinical studies on the relief of EGFR-TKI-associated diarrhea in the future.

The inhibition mechanism of luteolin on peroxidase based on multispectroscopic techniques

Luteolin, a plant-derived flavonoid, was found to exert effective inhibitory effect to peroxidase activity in a non-competitive manner with an IC50 of (6.62 ± 0.45) × 10-5 mol L-1. The interaction between luteolin and peroxidase induced the formation of a static complex with a binding constant (Ksv) of 7.31 × 103 L mol-1 s-1 driven by hydrogen bond and hydrophobic interaction. Further, the molecular interaction between luteolin and peroxidase resulted in intrinsic fluorescence quenching, structural and conformational alternations which were determined by multispectroscopic techniques combined with computational molecular docking. Molecular docking results revealed that luteolin bound to peroxidase and interacted with relevant amino acid residues in the hydrophobic pocket. These results will provide information for screening additional peroxidase inhibitors and provide evidence of luteolin's potential application in preservation and processing of fruit and vegetables and clinical disease remedy.

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.

Luteolin inhibits respiratory syncytial virus replication by regulating the MiR-155/SOCS1/STAT1 signaling pathway

Background

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract infection in infants, children, immunocompromised adults, and elderly individuals. Currently, there are few therapeutic options available to prevent RSV infection. The present study aimed to investigate the effects of luteolin on RSV replication and the related mechanisms.

Material and methods

We pretreated cells and mice with luteolin before infection with RSV, the virus titer, expressions of RSV-F, interferon (IFN)-stimulated genes (ISGs), and production of IFN-α and IFN-β were determined by plaque assay, RT-qPCR, and ELISA, respectively. The activation of Janus kinase (JAK)-signal transducer and activator of transcription 1 (STAT1) signaling pathway was detected by Western blotting and luciferase assay. Proteins which negatively regulate STAT1 were determined by Western blotting. Then cells were transfected with suppressor of cytokine signaling 1 (SOCS1) plasmid and virus replication and ISGs expression were determined. Luciferase reporter assay and Western blotting were performed to detect the relationship between SOCS1 and miR-155.

Results

Luteolin inhibited RSV replication, as shown by the decreased viral titer and RSV-F mRNA expression both in vitro and in vivo. The antiviral activity of luteolin was attributed to the enhanced phosphorylation of STAT1, resulting in the increased production of ISGs. Further study showed that SOCS1 was downregulated by luteolin and SOCS1 is a direct target of microRNA-155 (miR-155). Inhibition of miR-155 rescued luteolin-mediated SOCS1 downregulation, whereas upregulation of miR-155 enhanced the inhibitory effect of luteolin.

Conclusion

Luteolin inhibits RSV replication by regulating the miR-155/SOCS1/STAT1 signaling pathway.

Can a metabolism-targeted therapeutic intervention successfully subjugate SARS-COV-2? A scientific rational

As a process entailing a high turnover of the host cell molecules, viral replication is required for a successful viral infection and requests virus capacity to acquire the macromolecules required for its propagation. To this end, viruses have adopted several strategies to harness cellular metabolism in accordance with their specific demands. Most viruses upregulate specific cellular anabolic pathways and are largely dependent on such alterations. RNA viruses, for example, upregulate both glycolysisand glycogenolysis providing TCA cycle intermediates essential for anabolic lipogenesis. Also, these infections usually induce the PPP, leading to increased nucleotide levels supporting viral replication. SARS-CoV-2 (the cause of COVID-19)that has so far spread from China throughout the world is also an RNA virus. Owing to the more metabolic plasticity of uninfected cells, a promising approach for specific antiviral therapy, which has drawn a lot of attention in the recent years, would be the targeting of metabolic changes induced by viruses. In the current review, we first summarize some of virus-induced metabolic adaptations and then based on these information as well as SARS-CoV-2 pathogenesis, propose a potential therapeutic modality for this calamitous world-spreading virus with the hope of employing this strategy for near-future clinical application.

Research Progress of the Antiviral Bioactivities of Natural Flavonoids

Flavonoids are now considered as an indispensable component in a variety of nutraceutical and pharmaceutical applications. Most recent researches have focused on the health aspects of flavonoids for humans. Especially, different flavonoids have been investigated for their potential antiviral activities, and several natural flavonoids exhibited significant antiviral properties both in vitro and in vivo. This review provides a survey of the literature regarding the evidence for antiviral bioactivities of natural flavonoids, highlights the cellular and molecular mechanisms of natural flavonoids on viruses, and presents the details of most reported flavonoids. Meanwhile, future perspectives on therapeutic applications of flavonoids against viral infections were discussed.

Bioavailability and Pharmaco-therapeutic Potential of Luteolin in Overcoming Alzheimer's Disease

Luteolin is a naturally occurring, yellow crystalline flavonoid found in numerous dietary supplements we frequently have in our meals. Studies in the last 2 decades have revealed its therapeutic potential to reduce the Alzheimer's disease (AD) symptoms in various in vitro and in vivo models. The anti-Alzheimer's potential of luteolin is attributed to its ability to suppress Aβ as well as tau aggregation or promote their disaggregation, down-regulate the expression of COX-2, NOS, MMP-9, TNF-α, interleukins and chemokines, reduce oxidative stress by scavenging ROS, modulate the activities of transcription factors CREB, cJun, Nrf-1, NF-κB, p38, p53, AP-1 and β-catenine and inhibiting the activities of various protein kinases. In several systems, luteolin has been described as a potent antioxidant and anti-inflammatory agent. In addition, we have also discussed about the bio-availability of the luteolin in the plasma. After being metabolized luteolin persists in plasma as glucuronides and sulphate-conjugates. Human clinical trials indicated no dose limiting toxicity when administered at a dose of 100 mg/day. Improvements in the formulations and drug delivery systems may further enhance the bioavailability and potency of luteolin. The current review describes in detail the data supporting these studies.

A bioinformatics investigation into molecular mechanism of Yinzhihuang granules for treating hepatitis B by network pharmacology and molecular docking verification

Yinzhihuang granules (YZHG) is a patented Chinese medicine for the treatment of hepatitis B. This study aimed to investigate the intrinsic mechanisms of YZHG in the treatment of hepatitis B and to provide new evidence and insights for its clinical application. The chemical compounds of YZHG were searched in the CNKI and PUBMED databases, and their putative targets were then predicted through a search of the SuperPred and Swiss Target Prediction databases. In addition, the targets of hepatitis B were obtained from TTD, PharmGKB and DisGeNET. The abovementioned data were visualized using Cytoscape 3.7.1, and network construction identified a total of 13 potential targets of YZHG in the treatment of hepatitis B. Molecular docking verification showed that CDK6, CDK2, TP53 and BRCA1 might be strongly correlated with hepatitis B treatment. Furthermore, GO and KEGG analyses indicated that the treatment of hepatitis B by YZHG might be related to positive regulation of transcription, positive regulation of gene expression, the hepatitis B pathway and the viral carcinogenesis pathway. Network pharmacology intuitively shows the multicomponent, multitarget and multichannel pharmacological effects of YZHG in the treatment of hepatitis B and provides a scientific basis for its mechanism of action.

Rimonabant suppresses RNA transcription of hepatitis B virus by inhibiting hepatocyte nuclear factor 4α

Chronic infection with hepatitis B virus (HBV) sometime induces lethal cirrhosis and hepatocellular carcinoma. Although nucleot(s)ide analogs are used as main treatment for HBV infection, the emergence of the drug-resistant viruses has become a problem. To discover novel antivirals with low side effects and low risk of emergence of resistant viruses, screening for anti-HBV compounds was performed with compound libraries of inhibitors targeting G-protein-coupled receptors (GPCRs). HepG2-hNTCP C4 cells infected with HBV were treated with various GPCR inhibitors and harvested at 14 day postinfection for quantification of core protein in the first screening or relaxed circular DNA in the second screening. Finally, we identified a cannabinoid receptor 1 inhibitor, rimonabant, as a candidate showing anti-HBV effect. In HepG2-hNTCP C4 cells, treatment with rimonabant suppressed HBV propagation at the viral RNA transcription step but had no effect on entry or covalently closed circular DNA level. The values of half maximal inhibitory concentration, half maximal effective concentration, and selectivity index of rimonabant in primary human hepatocyte (PHH) are 2.77 μm, 40.4 μm, and 14.6, respectively. Transcriptome analysis of rimonabant-treated primary hepatocytes by RNA sequencing revealed that the transcriptional activity of hepatocyte nuclear factor 4α (HNF4α), which is known to stimulate viral RNA synthesis, was depressed. By treatment of PHH with rimonabant, the expression level of HNF4α protein and the production of the messenger RNAs (mRNAs) of downstream factors promoted by HNF4α were reduced while the amount of HNF4α mRNA was not altered. These results suggest that treatment with rimonabant suppresses HBV propagation through the inhibition of HNF4α activity.

Role of hepatocyte nuclear factor 4-alpha in gastrointestinal and liver diseases

Hepatocyte nuclear factor 4-alpha (HNF4α) is a highly conserved member of nuclear receptor superfamily of ligand-dependent transcription factors that is expressed in liver and gastrointestinal organs (pancreas, stomach, and intestine). In liver, HNF4α is best known for its role as a master regulator of liver-specific gene expression and essential for adult and fetal liver function. Dysregulation of HNF4α expression has been associated with many human diseases such as ulcerative colitis, colon cancer, maturity-onset diabetes of the young, liver cirrhosis, and hepatocellular carcinoma. However, the precise role of HNF4α in the etiology of these human pathogenesis is not well understood. Limited information is known about the role of HNF4α isoforms in liver and gastrointestinal disease progression. There is, therefore, a critical need to know how disruption of the expression of these isoforms may impact on disease progression and phenotypes. In this review, we will update our current understanding on the role of HNF4α in human liver and gastrointestinal diseases. We further provide additional information on possible use of HNF4α as a target for potential therapeutic approaches.

Exosomal Interferon-Induced Transmembrane Protein 2 Transmitted to Dendritic Cells Inhibits Interferon Alpha Pathway Activation and Blocks Anti-Hepatitis B Virus Efficacy of Exogenous Interferon Alpha

The negative regulators in the interferon (IFN) signaling pathway inhibit intrahepatic immune response, resulting in suboptimal therapeutic response to IFNα treatment in chronic hepatitis B (CHB) patients. Identifying the key negative factors and elucidating the regulating mechanism are essential for improving anti-HBV (hepatitis B virus) efficacy of IFNα. From the Gene Expression Omnibus (GEO) database, we downloaded and analyzed gene expression profiles of CHB patients with different responses to IFNα (GSE54747), and found that innate immune status was associated with the IFNα-based therapeutic response in CHB patients. Through PCR array, we found higher baseline level of IFN-induced transmembrane protein 2 (IFITM2) mRNA and lower baseline level of IFNα mRNA in peripheral blood mononuclear cells (PBMCs) of CHB patients with suboptimal response to IFNα treatment. Increased IFITM2 protein was also found in the serum of IFNα nonresponsive patients. With further experiments, we found that overexpressing IFITM2 in Huh7 cells suppressed endogenous IFNα synthesis by inhibiting phosphorylation of extracellular signal-regulated kinase (ERK), TANK-binding kinase 1 (TBK1), and interferon regulatory factor 3 (IRF3); knocking out IFITM2 enhanced activation of the endogenous IFNα synthesis pathway, exhibiting better inhibition on HBV replication. We also found that IFITM2 protein was shuttled by exosomes to dendritic cells (DCs), the main source of endogenous IFNα. Exosome-mediated transport of IFITM2 inhibited synthesis of endogenous IFNα in DCs whereas the inhibitory effect was abolished when IFITM2 was knocked out. Furthermore, we demonstrated that both palmitoylation inhibitor and mutation on 70/71 sites of IFITM2 protein influenced its incorporation into exosomes. Mutated IFITM2 protein increased the effect of IFNα against HBV. Conclusion: Exosome-mediated transport of IFITM2 to DCs inhibits IFNα pathway activation and blocks anti-HBV efficacy of exogenous IFNα. The findings provide an explanation to the suboptimal response of CHB patients to IFNα treatment.

Luteolin, a flavonoid, as an anticancer agent: A review

Many food-derived phytochemicals and their derivatives represent a cornucopia of new anti-cancer compounds. Luteolin (3,4,5,7-tetrahydroxy flavone) is a flavonoid found in different plants such as vegetables, medicinal herbs, and fruits. It acts as an anticancer agent against various types of human malignancies such as lung, breast, glioblastoma, prostate, colon, and pancreatic cancers. It also blocks cancer development in vitro and in vivo by inhibition of proliferation of tumor cells, protection from carcinogenic stimuli, and activation of cell cycle arrest, and by inducing apoptosis through different signaling pathways. Luteolin can additionally reverse epithelial-mesenchymal transition (EMT) through a mechanism that involves cytoskeleton shrinkage, induction of the epithelial biomarker E-cadherin expression, and by down-regulation of the mesenchymal biomarkers N-cadherin, snail, and vimentin. Furthermore, luteolin increases levels of intracellular reactive oxygen species (ROS) by activation of lethal endoplasmic reticulum stress response and mitochondrial dysfunction in glioblastoma cells, and by activation of ER stress-associated proteins expressions, including phosphorylation of eIF2α, PERK, CHOP, ATF4, and cleaved-caspase 12. Accordingly, the present review article summarizes the progress of recent research on luteolin against several human cancers.

Luteolin decreases the yield of influenza A virus in vitro by interfering with the coat protein I complex expression

Influenza is an acute transmissible respiratory infectious disease in humans and animals with high morbidity and mortality. It was reported that luteolin, extracted from Chinese herbs, could potently inhibit influenza virus replication in vitro. To assess the effect and explore the fundamental mechanism of luteolin, we infected several cell lines with two subtypes of influenza A virus (IAV), including A/Jiangxi/312/2006 (H3N2) and A/Fort Monmouth/1/1947 (H1N1) and demonstrated that luteolin suppressed the replication of IAV by cytopathic effect reduction method, qRT-PCR, immunofluorescence and Western blot assays. A time-of-addition assay indicated that this compound interfered with viral replication at the early stage of infection. In addition, we found that luteolin suppressed coat protein I complex expression, which was related to influenza virus entry and endocytic pathway. Overall, our findings demonstrated the antiviral effect of luteolin against IAV and its novel antiviral mechanism.

Inhibitory effects of metachromin A on hepatitis B virus production via impairment of the viral promoter activity

The currently available antiviral agents for chronic infection with hepatitis B virus (HBV) are pegylated interferon-α and nucleoside/nucleotide analogues, although it has been difficult to completely eliminate covalently closed circular DNA (cccDNA) from patients. To identify an antiviral compound targeting HBV core promoter, 15 terpenes originating from marine organisms were screened using a cell line expressing firefly luciferase under the control of the HBV core promoter. Metachromin A, which is a merosesquiterpene isolated from the marine sponge Dactylospongia metachromia, inhibited the viral promoter activity at the highest level among the tested compounds, and suppressed HBV production with an EC₅₀ value of 0.8 μM regardless of interferon signaling and cytotoxicity. The analysis on the structure-activity relationship revealed that the hydroquinone moiety, and the double bonds at carbon numbers-5 and -9 in metachromin A are crucial for anti-HBV activity. Furthermore, metachromin A reduced the protein level but not the RNA level of hepatic nuclear factor 4α, which mainly upregulates the activities of enhancer I/X promoter and enhancer II/core promoter. These results suggest that metachromin A can inhibit HBV production via impairment of the viral promoter activity. Antiviral agents targeting the viral promoter may ameliorate HBV-related disorders regardless of remaining cccDNA.