Formation of eicosanoids and other oxylipins in human macrophages.

In this review it is attempted to summarize current studies about formation of eicosanoids and other oxylipins in different human macrophages. There are several reports on M1 and M2 cells, also other phenotypes have been described. The eicosanoids formed in the largest amounts are the COX products TxB₂ and PGE₂. Thus shortlived bioactive TxA₂ is a dominating product both in M1- and in M2-lineages, one exception seems to be M_{GM-CSF, TGFß} cells. 5-LOX products are produced in both M1 and M2 macrophages, as well as in not fully polarized cells of both lineages. M_M-CSF as well as M2 macrophages produced LTC₄ more readily compared to M1 lineage cells. In M_{GM-CSF, TGFß} cells LTB₄ is a major eicosanoid, in line with high expression of LTA₄ hydrolase. Recent reports described increased formation of leukotrienes in macrophages subjected to trained immunity with inflammatory transcriptional reprogramming. Also in macrophages derived from monocytes collected from post-COVID-19 patients. 15-LOX-1 is strongly upregulated in CD206⁺ M2 cells (M2a), differentiated in presence of IL-4. These macrophages also express 15-LOX-2. In incubations with pathogenic E. coli as well as other stimuli 15(S)-HETE and 17(S)-HDHA were major oxylipins formed. Also, the SPM precursor 5,15-diHETE and the SPM RvD5 were produced in considerable amounts, while other SPMs were less abundant. In M2 macrophages incubated with E. coli or S. aureus the cytosolic 15-LOX-1 enzyme accumulated to punctuate structures in a Ca²⁺ dependent manner with a relatively slow time course, leading to formation of mediators from endogenous substrate. Chalcones, flavone-like anti-inflammatory natural products, induced translocation of 15-LOX-1 in M2 cells, with high formation of 15-LOX derived oxylipins.

Commercially Available Flavonols Are Better SARS-CoV-2 Inhibitors than Isoflavone and Flavones.

Despite the fast development of vaccines, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still circulating and generating variants of concern (VoC) that escape the humoral immune response. In this context, the search for anti-SARS-CoV-2 compounds is still essential. A class of natural polyphenols known as flavonoids, frequently available in fruits and vegetables, is widely explored in the treatment of different diseases and used as a scaffold for the design of novel drugs. Therefore, herein we evaluate seven flavonoids divided into three subclasses, isoflavone (genistein), flavone (apigenin and luteolin) and flavonol (fisetin, kaempferol, myricetin, and quercetin), for COVID-19 treatment using cell-based assays and in silico calculations validated with experimental enzymatic data. The flavonols were better SARS-CoV-2 inhibitors than isoflavone and flavones. The increasing number of hydroxyl groups in ring B of the flavonols kaempferol, quercetin, and myricetin decreased the 50% effective concentration (EC50) value due to their impact on the orientation of the compounds inside the target. Myricetin and fisetin appear to be preferred candidates; they are both anti-inflammatory (decreasing TNF-α levels) and inhibit SARS-CoV-2 mainly by targeting the processability of the main protease (Mpro) in a non-competitive manner, with a potency comparable to the repurposed drug atazanavir. However, fisetin and myricetin might also be considered hits that are amenable to synthetic modification to improve their anti-SARS-CoV-2 profile by inhibiting not only Mpro, but also the 3'-5' exonuclease (ExoN).

Naturally Available Flavonoid Aglycones as Potential Antiviral Drug Candidates against SARS-CoV-2.

Flavonoids are important secondary plant metabolites that have been studied for a long time for their therapeutic potential in inflammatory diseases because of their cytokine-modulatory effects. Five flavonoid aglycones were isolated and identified from the hydrolyzed aqueous methanol extracts of Anastatica hierochuntica L., Citrus reticulata Blanco, and Kickxia aegyptiaca (L.) Nabelek. They were identified as taxifolin (1), pectolinarigenin (2), tangeretin (3), gardenin B (4), and hispidulin (5). These structures were elucidated based on chromatographic and spectral analysis. In this study, molecular docking studies were carried out for the isolated and identified compounds against SARS-CoV-2 main protease (Mpro) compared to the co-crystallized inhibitor of SARS-CoV-2 Mpro (α-ketoamide inhibitor (KI), IC50 = 66.72 µg/mL) as a reference standard. Moreover, in vitro screening against SARS-CoV-2 was evaluated. Compounds 2 and 3 showed the highest virus inhibition with IC50 12.4 and 2.5 µg/mL, respectively. Our findings recommend further advanced in vitro and in vivo studies of the examined isolated flavonoids, especially pectolinarigenin (2), tangeretin (3), and gardenin B (4), either alone or in combination with each other to identify a promising lead to target SARS-CoV-2 effectively. This is the first report of the activity of these compounds against SARS-CoV-2.

Structural Bioinformatics Used to Predict the Protein Targets of Remdesivir and Flavones in SARS-CoV-2 Infection.

BACKGROUND: During the current SARS-CoV-2 pandemic, the identification of effective antiviral drugs is crucial. Unfortunately, no specific treatment or vaccine is available to date. OBJECTIVE: Here, we aimed to predict the interactions with SARS-CoV-2 proteins and protein targets from the human body for some flavone molecules (kaempferol, morin, pectolinarin, myricitrin, and herbacetin) in comparison to synthetic compounds (hydroxychloroquine, remdesivir, ribavirin, ritonavir, AMD-070, favipiravir). METHODS: Using MOE software and advanced bioinformatics and cheminformatics portals, we conducted an extensive analysis based on various structural and functional features of compounds, such as their amphiphilic field, flexibility, and steric features. The structural similarity analysis of natural and synthetic compounds was performed using Tanimoto coefficients. The interactions of some compounds with SARS-CoV-2 3CLprotease or RNA-dependent RNA polymerase were described using 2D protein-ligand interaction diagrams based on known crystal structures. The potential targets of considered compounds were identified using the SwissTargetPrediction web tool. RESULTS: Our results showed that remdesivir, pectolinarin, and ritonavir present a strong structural similarity which may be correlated to their similar biological activity. As common molecular targets of compounds in the human body, ritonavir, kaempferol, morin, and herbacetin can activate multidrug resistance-associated proteins, while remdesivir, ribavirin, and pectolinarin appear as ligands for adenosine receptors. CONCLUSION: Our evaluation recommends remdesivir, pectolinarin, and ritonavir as promising anti- SARS-CoV-2 agents.

Hairy Roots of Scutellaria spp. (Lamiaceae) as Promising Producers of Antiviral Flavones.

We measured and studied the growth parameters and the qualitative and quantitative composition of the flavones of hairy roots of the Scutellaria genus: S. lateriflora, S. przewalskii and S. pycnoclada. Hairy roots were obtained using wild-type Agrobacterium rhizogenes A4 by co-cultivation of explants (cotyledons) in a suspension of Agrobacterium. The presence of the rol-genes was confirmed by PCR analysis. The hairy roots of the most studied plant from the Scutellaria genus, S. baicalensis, were obtained earlier and used as a reference sample. HPLC-MS showed the predominance of four main flavones (baicalin, baicalein, wogonin and wogonoside) in the methanol extracts of the studied hairy roots. In addition to the four main flavones, the other substances which are typical to the aerial part of plants were found in all the extracts: apigenin, apigetrin, scutellarin and chrysin-7-O-ß-d-glucuronide. According to the total content of flavones, the hairy roots of the studied skullcaps form the following series: S. przewalskii (33 mg/g dry weight) > S. baicalensis (17.04 mg/g dry weight) > S. pycnoclada (12.9 mg/g dry weight) > S. lateriflora (4.57 mg/g dry weight). Therefore, the most promising producer of anti-coronavirus flavones is S. przewalskii.

Discovery of naturally occurring inhibitors against SARS-CoV-2 3CLpro from Ginkgo biloba leaves via large-scale screening.

3-Chymotrypsin-like protease (3CLpro) is a virally encoded main proteinase that is pivotal for the viral replication across a broad spectrum of coronaviruses. This study aims to discover the naturally occurring SARS-CoV-2 3CLpro inhibitors from herbal constituents, as well as to investigate the inhibitory mechanism of the newly identified efficacious SARS-CoV-2 3CLpro inhibitors. Following screening of the inhibitory potentials of eighty herbal products against SARS-CoV-2 3CLpro, Ginkgo biloba leaves extract (GBLE) was found with the most potent SARS-CoV-2 3CLpro inhibition activity (IC50 = 6.68 µg/mL). Inhibition assays demonstrated that the ginkgolic acids (GAs) and the bioflavones isolated from GBLE displayed relatively strong SARS-CoV-2 3CLpro inhibition activities (IC50 < 10 µM). Among all tested constituents, GA C15:0, GA C17:1 and sciadopitysin displayed potent 3CLpro inhibition activities, with IC50 values of less than 2 µM. Further inhibition kinetic studies and docking simulations clearly demonstrated that two GAs and sciadopitysin strongly inhibit SARS-CoV-2 3CLprovia a reversible and mixed inhibition manner. Collectively, this study found that both GBLE and the major constituents in this herbal product exhibit strong SARS-CoV-2 3CLpro inhibition activities, which offer several promising leading compounds for developing novel anti-COVID-19 medications via targeting on 3CLpro.

Rutin and flavone analogs as prospective SARS-CoV-2 main protease inhibitors: In silico drug discovery study.

Coronavirus disease 2019 (COVID-19) is a new pandemic characterized by quick spreading and illness of the respiratory system. To date, there is no specific therapy for Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2). Flavonoids, especially rutin, have attracted considerable interest as a prospective SARS-CoV-2 main protease (Mpro) inhibitor. In this study, a database containing 2017 flavone analogs was prepared and screened against SARS-CoV-2 Mpro using the molecular docking technique. According to the results, 371 flavone analogs exhibited good potency towards Mpro with docking scores less than -9.0 kcal/mol. Molecular dynamics (MD) simulations, followed by molecular mechanics-generalized Born surface area (MM/GBSA) binding energy calculations, were performed for the top potent analogs in complex with Mpro. Compared to rutin, PubChem-129-716-607 and PubChem-885-071-27 showed better binding affinities against SARS-CoV-2 Mpro over 150 ns MD course with ΔGbinding values of -69.0 and -68.1 kcal/mol, respectively. Structural and energetic analyses demonstrated high stability of the identified analogs inside the SARS-CoV-2 Mpro active site over 150 ns MD simulations. The oral bioavailabilities of probable SARS-CoV-2 Mpro inhibitors were underpinned using drug-likeness parameters. A comparison of the binding affinities demonstrated that the MM/GBSA binding energies of the identified flavone analogs were approximately three and two times less than those of lopinavir and baicalein, respectively. In conclusion, PubChem-129-716-607 and PubChem-885-071-27 are promising anti-COVID-19 drug candidates that warrant further clinical investigations.

Structure-Based Identification of Natural Products as SARS-CoV-2 Mpro Antagonist from Echinacea angustifolia Using Computational Approaches.

Coronavirus disease-19 (COVID-19) pandemic, caused by the novel SARS-CoV-2 virus, continues to be a global threat. The number of cases and deaths will remain escalating due to the lack of effective therapeutic agents. Several studies have established the importance of the viral main protease (Mpro) in the replication of SARS-CoV-2 which makes it an attractive target for antiviral drug development, including pharmaceutical repurposing and other medicinal chemistry approaches. Identification of natural products with considerable inhibitory potential against SARS-CoV-2 could be beneficial as a rapid and potent alternative with drug-likeness by comparison to de novo antiviral drug discovery approaches. Thereof, we carried out the structure-based screening of natural products from Echinacea-angustifolia, commonly used to prevent cold and other microbial respiratory infections, targeting SARS-CoV-2 Mpro. Four natural products namely, Echinacoside, Quercetagetin 7-glucoside, Levan N, Inulin from chicory, and 1,3-Dicaffeoylquinic acid, revealed significant docking energy (>-10 kcal/mol) in the SARS-CoV-2 Mpro catalytic pocket via substantial intermolecular contacts formation against co-crystallized ligand (<-4 kcal/mol). Furthermore, the docked poses of SARS-CoV-2 Mpro with selected natural products showed conformational stability through molecular dynamics. Exploring the end-point net binding energy exhibited substantial contribution of Coulomb and van der Waals interactions to the stability of respective docked conformations. These results advocated the natural products from Echinacea angustifolia for further experimental studies with an elevated probability to discover the potent SARS-CoV-2 Mpro antagonist with higher affinity and drug-likeness.

Neuroprotective effects of flavone luteolin in neuroinflammation and neurotrauma.

Neuroinflammation leads to neurodegeneration, cognitive defects, and neurodegenerative disorders. Neurotrauma/traumatic brain injury (TBI) can cause activation of glial cells, neurons, and neuroimmune cells in the brain to release neuroinflammatory mediators. Neurotrauma leads to immediate primary brain damage (direct damage), neuroinflammatory responses, neuroinflammation, and late secondary brain damage (indirect) through neuroinflammatory mechanism. Secondary brain damage leads to chronic inflammation and the onset and progression of neurodegenerative diseases. Currently, there are no effective and specific therapeutic options to treat these brain damages or neurodegenerative diseases. Flavone luteolin is an important natural polyphenol present in several plants that show anti-inflammatory, antioxidant, anticancer, cytoprotective, and macrophage polarization effects. In this short review article, we have reviewed the neuroprotective effects of luteolin in neurotrauma and neurodegenerative disorders and pathways involved in this mechanism. We have collected data for this study from publications in the PubMed using the keywords luteolin and mast cells, neuroinflammation, neurodegenerative diseases, and TBI. Recent reports suggest that luteolin suppresses systemic and neuroinflammatory responses in Coronavirus disease 2019 (COVID-19). Studies have shown that luteolin exhibits neuroprotective effects through various mechanisms, including suppressing immune cell activation, such as mast cells, and inflammatory mediators released from these cells. In addition, luteolin can suppress neuroinflammatory response, activation of microglia and astrocytes, oxidative stress, neuroinflammation, and the severity of neuroinflammatory diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and TBI pathogenesis. In conclusion, luteolin can improve cognitive decline and enhance neuroprotection in neurodegenerative diseases, TBI, and stroke.