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

Exploiting the chikungunya virus capsid protein: a focused target for antiviral therapeutic development

Chikungunya disease is spread by the bite of infected Aedes mosquitoes. It is considered a neglected tropical disease that has the potential to cause sporadic epidemics in naive populations. Despite the substantial investment in research, there are no approved antiviral treatments for chikungunya. Several screening approaches have been used to identify potential antiviral molecules that target the whole virus, viral proteins, and viral-host interactions, often in conjunction with computational studies. The genome of chikungunya virus (CHIKV) encodes four nonstructural and five structural proteins. The capsid protein (CP) is a small structural protein with enzymatic activity. Owing to its critical role in different stages of the viral life cycle, the CP can be targeted at multiple stages, thereby impeding viral multiplication. There is evidence suggesting that the CP may be a promising target for drug development, and this has led to the discovery of various inhibitors through diverse in vitro and in silico analyses. Both cell-based and cell-free assays have been widely used to identify and evaluate CHIKV CP inhibitors. Computer-based studies targeting CHIKV proteins, including CP, have identified several lead compounds, which are being further evaluated in various in vitro systems. No review has been published on the CHIKV CP, and papers have focused on drug development and the targeting of viral proteins and associated factors. In this review, we summarize the research that has been conducted on the CHIKV CP, including structural studies, antiviral research, and prospects for the use of the CP as an antiviral target.

Diverse Physiological Roles of Kynurenine Pathway Metabolites: Updated Implications for Health and Disease

Tryptophan is an essential amino acid critical for human health. It plays a pivotal role in numerous physiological and biochemical processes through its metabolism. The kynurenine (KYN) pathway serves as the principal metabolic route for tryptophan, producing bioactive metabolites, including KYN, quinolinic acid, and 3-hydroxykynurenine. Numerous studies are actively investigating the relationship between tryptophan metabolism and physiological functions. These studies are highlighting the interactions among metabolites that may exert synergistic or antagonistic effects, such as neuroprotective or neurotoxic, and pro-oxidative or antioxidant activities. Minor disruptions in the homeostasis of these metabolites can result in immune dysregulation, contributing to a spectrum of diseases. These diseases include neurological disorders, mental illnesses, cardiovascular conditions, autoimmune diseases, and chronic kidney disease. Therefore, understanding the physiological roles of the KYN pathway metabolites is essential for elucidating the contribution of tryptophan metabolism to health regulation. The present review emphasizes the physiological roles of KYN pathway metabolites and their mechanisms in disease development, aiming to establish a theoretical basis for leveraging dietary nutrients to enhance human health.

Molecular Insights into the Interaction of Tryptophan Metabolites with the Human Aryl Hydrocarbon Receptor in Silico: Tryptophan as Antagonist and no Direct Involvement of Kynurenine

BACKGROUND

A direct link between the tryptophan (Trp) metabolite kynurenine (Kyn) and the aryl hydrocarbon receptor (AhR) is not supported by metabolic considerations and by studies demonstrating the failure of Kyn concentrations of up to 100 μM to activate the receptor in cell culture systems using the proxy system of cytochrome P-450-dependent metabolism. The Kyn metabolite kynurenic acid (KA) activates the AhR and may mediate the Kyn link. Recent studies demonstrated down regulation and antagonism of activation of the AhR by Trp. We have addressed the link between Kyn and the AhR by looking at their direct molecular interaction in silico.

METHODS

Molecular docking of Kyn, KA, Trp and a range of Trp metabolites to the crystal structure of the human AhR was performed under appropriate docking conditions.

RESULTS

Trp and 30 of its metabolites docked to the AhR to various degrees, whereas Kyn and 3-hydroxykynurenine did not. The strongest docking was observed with the Trp metabolite and photooxidation product 6-Formylindolo[3,2-b]carbazole (FICZ), cinnabarinic acid, 5-hydroxytryptophan, N-acetyl serotonin and indol-3-yllactic acid. Strong docking was also observed with other 5-hydroxyindoles.

CONCLUSIONS

We propose that the Kyn-AhR link is mediated by KA. The strong docking of Trp and its recently reported down regulation of the receptor suggest that Trp is an AhR antagonist and may thus play important roles in body homeostasis beyond known properties or simply being the precursor of biologically active metabolites. Differences in AhR activation reported in the literature are discussed.

In silico molecular screening of bioactive natural compounds of rosemary essential oil and extracts for pharmacological potentials against rhinoviruses

Rhinoviruses (RVs) cause upper respiratory tract infections and pneumonia in children and adults. These non-enveloped viruses contain viral coats of four capsid proteins: VP1, VP2, VP3, and VP4. The canyon on VP1 used cell surface receptor ICAM-1 as the site of attachment and for the internalization of viruses. To date, there has been no drug or vaccine available against RVs. In this study, bioactive natural compounds of rosemary (Salvia rosmarinus L.), which are known for their pharmacological potential, were considered to target the VP1 protein. A total of 30 bioactive natural compounds of rosemary were taken as ligands to target viral proteins. The PkCSM tool was used to detect their adherence to Lipinski's rule of five and the ADMET properties of the selected ligands. Further, the CB-Dock tool was used for molecular docking studies between the VP1 protein and ligands. Based on the molecular docking and ADMET profiling results, phenethyl amine (4 methoxy benzyl) was selected as the lead compound. A comparative study was performed between the lead compound and two antiviral drugs, Placonaril and Nitazoxanide, to investigate the higher potential of natural compounds over synthetic drugs. Placonaril also targets VP1 but failed in clinical trials while Nitazoxanide was examined in clinical trials against rhinoviruses. It was discovered from this study that the (4 methoxy benzyl) phenethyl amine exhibited less toxicity in comparison to other tested drugs against RVs. More research is needed to determine its potential and make it a good medication against RVs.

Novel Anti-Viral Properties of the Herbal Extract of Davallia mariesii against Influenza A Virus

Gu-Sui-Bu, the dried rhizome of Davallia mariesii, is a traditional Chinese herbal remedy with a significant history of treating osteoporosis and inflammatory conditions. However, its potential as an anti-influenza agent and its underlying mechanisms of action remain unexplored. To obtain a more potent extract from D. mariesii and gain insights into its mechanism of action against influenza A virus (IAV), we utilized a partitioning process involving organic solvents and water, resulting in the isolation of butanolic subfractions of the D. mariesii extract (DMBE). DMBE exhibited a broad anti-viral spectrum, effectively inhibiting IAV, with an EC50 of 24.32 ± 6.19 µg/mL and a selectivity index of 6.05. We subsequently conducted a series of in vitro assays to evaluate the antiviral effects of DMBE and to uncover its mechanisms of action. DMBE was found to inhibit IAV during the early stages of infection by hindering the attachment of the virus onto and its penetration into host cells. Importantly, DMBE was observed to hinder IAV-mediated cell-cell fusion. It also inhibited neuraminidase activity, plaque size, and the expression levels of phospho-AKT. In summary, this study provides evidence for the effectiveness of D. mariesii as a complementary and alternative herbal remedy against IAV. Specifically, our data highlight DMBE's capabilities in inhibiting viral entry and the release of virions.