Mechanisms of stretch-induced electro-anatomical remodeling and atrial arrhythmogenesis.

Atrial fibrillation (AF) is the most common cardiac rhythm disorder, often occurring in the setting of atrial distension 4and elevated myocardial stretch. While various mechano-electrochemical signal transduction pathways have been linked to AF development and progression, the underlying molecular mechanisms remain poorly understood, hampering AF therapies. In this review, we describe different aspects of stretch-induced electro-anatomical remodeling as seen in animal models and in patients with AF. Specifically, we focus on cellular and molecular mechanisms that are responsible for mechano-electrochemical signal transduction and the development of ectopic beats triggering AF from pulmonary veins, the most common source of paroxysmal AF. Furthermore, we describe structural changes caused by stretch occurring before and shortly after the onset of AF as well as during AF progression, contributing to longstanding forms of AF. We also propose mechanical stretch as a new dimension to the concept "AF begets AF", in addition to underlying diseases. Finally, we discuss the mechanisms of these electro-anatomical alterations in a search for potential therapeutic strategies and the development of novel antiarrhythmic drugs targeted at the components of mechano-electrochemical signal transduction not only in cardiac myocytes, but also in cardiac non-myocyte cells.

Identification of potential inhibitors of cholinergic and ß-secretase enzymes from phytochemicals derived from Gongronema latifolium Benth leaf: an integrated computational analysis.

Neurodegenerative disorders (NDDs) are associated with increased activities of the brain acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and ß-secretase enzyme (BACE1). Inhibition of these enzymes affords therapeutic option for managing NDDs such as Alzheimer's disease (AD) and Parkinson's disease (PD). Although, Gongronema latifolium Benth (GL) has been widely documented in ethnopharmacological and scientific reports for the management of NDDs, there is paucity of information on its underlying mechanism and neurotherapeutic constituents. Herein, 152 previously reported Gongronema latifolium derived-phytochemicals (GLDP) were screened against hAChE, hBChE and hBACE-1 using molecular docking, molecular dynamics (MD) simulations, free energy of binding calculations and cluster analysis. The result of the computational analysis identified silymarin, alpha-amyrin and teraxeron with the highest binding energies (-12.3, -11.2, -10.5 Kcal/mol) for hAChE, hBChE and hBACE-1 respectively as compared with those of the reference inhibitors (-12.3, -9.8 and - 9.4 for donepezil, propidium and aminoquinoline compound respectively). These best docked phytochemicals were found to be orientated in the hydrophobic gorge where they interacted with the choline-binding pocket in the A-site and P-site of the cholinesterase and subsites S1, S3, S3' and flip (67-75) residues of the pocket of the BACE-1. The best docked phytochemicals complexed with the target proteins were stable in a 100 ns molecular dynamic simulation. The interactions with the catalytic residues were preserved during the simulation as observed from the MMGBSA decomposition and cluster analyses. The presence of these phytocompounds most notably silymarin, which demonstrated dual high binding tendencies to both cholinesterases, were identified as potential neurotherapeutics subject to further investigation.

Antimalarial phytochemicals as potential inhibitors of SARS-CoV-2 guanine N7-methyltransferase (nsp 14): an integrated computational approach.

The inhibition of capping enzymes such as guanine-N7-methyltransferase (GMT) is an attractive target for regulating viral replication, transcription, virulence, and pathogenesis. Thus, compounds that target the Severe Acute Respiratory Syndrome Corona Virus 2 GMT (S2GMT) will enhance drug development against COVID-19. In this study, an in-house library of 249 phytochemicals from African medicinal plants was screened using computational approaches including homology modeling, molecular docking, molecular dynamic simulations, binding free energy calculations based on molecular mechanics/Poisson-Boltzmann surface area (MMPBSA) and Absorption-Distribution-Metabolism-Excretion-Toxicity (ADMET) analysis for inhibitors of S2GMT. The top-ten ranked phytochemicals (TTRP) obtained from the docking analysis to S2GMT were further docked to SARS-COV N7-MTase. Among the TTRP, the top-four ranked phytocompounds (TFRP) viz: 3 alkaloids (Isocryptolepine, 10'-Hydroxyusambarensine and Isostrychnopentamine) and a flavonoid (Mulberrofuran F) interacted strongly with critical catalytic residues whose interference either reduce or completely abolish N7-MTase activity, indicating their potential as capping machinery disruptors. The interactions of TFRP with the catalytic residues of S2GMT were preserved in a 100 ns simulated dynamic environment, thereby, demonstrating high degree of structural stability. The MMPBSA binding free energy calculations corroborated the docking scores with biscryptolepine having the highest binding free energy to S2GMT. The TFRP showed favourable drug-likeness and ADMET properties over a wide range of molecular descriptors. Therefore, the TFRP can be further explored as potential S2GMT inhibitors in in vitro and in vivo experiments.Communicated by Ramaswamy H. Sarma.

African derived phytocompounds may interfere with SARS-CoV-2 RNA capping machinery via inhibition of 2'-O-ribose methyltransferase: An in silico perspective.

Despite the ongoing vaccination against the life-threatening COVID-19, there is need for viable therapeutic interventions. The S-adenosyl-l-Methionine (SAM) dependent 2-O'-ribose methyltransferase (2'-O-MTase) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents a therapeutic target against COVID-19 infection. In a bid to profile bioactive principles from natural sources, a custom-made library of 226 phytochemicals from African medicinal plants with especially anti-malarial activity was screened for direct interactions with SARS-CoV-2 2'-O-MTase (S2RMT) using molecular docking and molecular dynamics (MD) simulations as well as binding free energies methods. Based on minimal binding energy lower than sinefungin (a reference methyl-transferase inhibitor) and binding mode analysis at the catalytic site of S2RMT, a list of 26 hit phytocompounds was defined. The interaction of these phytocompounds was compared with the 2'-O-MTase of SARS-CoV and MERS-CoV. Among these compounds, the lead phytocompounds (LPs) viz: mulberrofuran F, 24-methylene cycloartenol, ferulate, 3-benzoylhosloppone and 10-hydroxyusambarensine interacted strongly with the conserved KDKE tetrad within the substrate binding pocket of the 2'-O-MTase of the coronavirus strains which is critical for substrate binding. The thermodynamic parameters analyzed from the MD simulation trajectories of the LPs-S2RMT complexes presented an eminent structural stability and compactness. These LPs demonstrated favorable druggability and in silico ADMET properties over a diverse array of molecular computing descriptors. The LPs show promising prospects in the disruption of S2RMT capping machinery in silico. However, these LPs should be validated via in vitro and in vivo experimental models.

Prevention of SARS-CoV-2 cell entry: insight from in silico interaction of drug-like alkaloids with spike glycoprotein, human ACE2, and TMPRSS2.

COVID-19 is a respiratory disease caused by SARS-CoV-2, an enveloped positive sense RNA virus. The SARS-CoV-2 spike glycoprotein, human angiotensin-converting enzyme 2 (ACE2) and human transmembrane protease serine 2 (TMPRSS2) are essential for the host cell-mediated viral entry. Targeting these proteins represent viable options to stop the first stage of infection and transmission. Hence, 97 alkaloids from African medicinal plants with reported antiviral activity were evaluated for this purpose via in silico studies. These alkaloids were docked for their interactions with SARS-CoV-2 spike glycoprotein, ACE2, and TMPRSS2. Top 20 alkaloids with highest binding affinities were further screened for their interactions with spike glycoprotein of SARS-CoV and MERS-CoV, and with ACE2-SARS-CoV-2 receptor-binding domain complex (ACE2-RBD). The energy profiling, molecular dynamics simulation (MDS), binding free energy base on Molecular Mechanics/Generalized Born Surface Area (MMGBSA), clustering of MDS trajectories, and virtual physicochemical and pharmacokinetic screening of the best docked alkaloids were performed. Results revealed that more than 15 alkaloids interacted better than the reference compounds. 10-Hydroxyusambarensine and Cryptospirolepine were docked in a similar binding pattern to the S1-specificy pocket of TMPRSS2 as camostat (reference inhibitor). The strong binding affinities, stability of the alkaloid-protein complexes and amino acid interactions displayed by cryptospirolepine, 10-hydroxyusambarensine, and cryptoquindoline with important binding hotspots of the proteins suggest these alkaloids have the potential of altering the capacity of SARS-CoV-2 membrane mediated host cell entry. Further in vitro and in vivo evaluation of these "drug-like" alkaloids as potential inhibitors of coronavirus cell entry is proposed.Communicated by Ramaswamy H. Sarma.

SARS-CoV-2 host cell entry: an in silico investigation of potential inhibitory roles of terpenoids.

BACKGROUND: Targeting viral cell entry proteins is an emerging therapeutic strategy for inhibiting the first stage of SARS-CoV-2 infection. In this study, 106 bioactive terpenoids from African medicinal plants were screened through molecular docking analysis against human angiotensin-converting enzyme 2 (hACE2), human transmembrane protease serine 2 (TMPRSS2), and the spike (S) proteins of SARS-CoV-2, SARS-CoV, and MERS-CoV. In silico absorption-distribution-metabolism-excretion-toxicity (ADMET) and drug-likeness prediction, molecular dynamics (MD) simulation, binding free energy calculations, and clustering analysis of MD simulation trajectories were performed on the top docked terpenoids to respective protein targets. RESULTS: The results revealed eight terpenoids with high binding tendencies to the catalytic residues of different targets. Two pentacyclic terpenoids (24-methylene cycloartenol and isoiguesteri) interacted with the hACE2 binding hotspots for the SARS-CoV-2 spike protein, while the abietane diterpenes were found accommodated within the S1-specificity pocket, interacting strongly with the active site residues TMPRSS2. 3-benzoylhosloppone and cucurbitacin interacted with the RBD and S2 subunit of SARS-CoV-2 spike protein respectively. These interactions were preserved in a simulated dynamic environment, thereby, demonstrating high structural stability. The MM-GBSA binding free energy calculations corroborated the docking interactions. The top docked terpenoids showed favorable drug-likeness and ADMET properties over a wide range of molecular descriptors. CONCLUSION: The identified terpenoids from this study provides core structure that can be exploited for further lead optimization to design drugs against SARS-CoV-2 cell-mediated entry proteins. They are therefore recommended for further in vitro and in vivo studies towards developing entry inhibitors against the ongoing COVID-19 pandemic.

Dual targeting of cytokine storm and viral replication in COVID-19 by plant-derived steroidal pregnanes: An in silico perspective.

The high morbidity and mortality rate of Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) infection arises majorly from the Acute Respiratory Distress Syndrome and "cytokine storm" syndrome, which is sustained by an aberrant systemic inflammatory response and elevated pro-inflammatory cytokines. Thus, phytocompounds with broad-spectrum anti-inflammatory activity that target multiple SARS-CoV-2 proteins will enhance the development of effective drugs against the disease. In this study, an in-house library of 117 steroidal plant-derived pregnanes (PDPs) was docked in the active regions of human glucocorticoid receptors (hGRs) in a comparative molecular docking analysis. Based on the minimal binding energy and a comparative dexamethasone binding mode analysis, a list of top twenty ranked PDPs docked in the agonist conformation of hGR, with binding energies ranging between -9.8 and -11.2 kcal/mol, was obtained and analyzed for possible interactions with the human Janus kinases 1 and Interleukins-6 and SARS-CoV-2 3-chymotrypsin-like protease, Papain-like protease and RNA-dependent RNA polymerase. For each target protein, the top three ranked PDPs were selected. Eight PDPs (bregenin, hirundigenin, anhydroholantogenin, atratogenin A, atratogenin B, glaucogenin A, glaucogenin C and glaucogenin D) with high binding tendencies to the catalytic residues of multiple targets were identified. A high degree of structural stability was observed from the 100 ns molecular dynamics simulation analyses of glaucogenin C and hirundigenin complexes of hGR. The selected top-eight ranked PDPs demonstrated high druggable potentials and favourable in silico ADMET properties. Thus, the therapeutic potentials of glaucogenin C and hirundigenin can be explored for further in vitro and in vivo studies.

Potential inhibitors of coronavirus 3-chymotrypsin-like protease (3CLpro): an in silico screening of alkaloids and terpenoids from African medicinal plants.

The novel coronavirus disease 2019 (COVID-19) caused by SARS-COV-2 has raised myriad of global concerns. There is currently no FDA approved antiviral strategy to alleviate the disease burden. The conserved 3-chymotrypsin-like protease (3CLpro), which controls coronavirus replication is a promising drug target for combating the coronavirus infection. This study screens some African plants derived alkaloids and terpenoids as potential inhibitors of coronavirus 3CLpro using in silico approach. Bioactive alkaloids (62) and terpenoids (100) of plants native to Africa were docked to the 3CLpro of the novel SARS-CoV-2. The top twenty alkaloids and terpenoids with high binding affinities to the SARS-CoV-2 3CLpro were further docked to the 3CLpro of SARS-CoV and MERS-CoV. The docking scores were compared with 3CLpro-referenced inhibitors (Lopinavir and Ritonavir). The top docked compounds were further subjected to ADEM/Tox and Lipinski filtering analyses for drug-likeness prediction analysis. This ligand-protein interaction study revealed that more than half of the top twenty alkaloids and terpenoids interacted favourably with the coronaviruses 3CLpro, and had binding affinities that surpassed that of lopinavir and ritonavir. Also, a highly defined hit-list of seven compounds (10-Hydroxyusambarensine, Cryptoquindoline, 6-Oxoisoiguesterin, 22-Hydroxyhopan-3-one, Cryptospirolepine, Isoiguesterin and 20-Epibryonolic acid) were identified. Furthermore, four non-toxic, druggable plant derived alkaloids (10-Hydroxyusambarensine, and Cryptoquindoline) and terpenoids (6-Oxoisoiguesterin and 22-Hydroxyhopan-3-one), that bind to the receptor-binding site and catalytic dyad of SARS-CoV-2 3CLpro were identified from the predictive ADME/tox and Lipinski filter analysis. However, further experimental analyses are required for developing these possible leads into natural anti-COVID-19 therapeutic agents for combating the pandemic.Communicated by Ramaswamy H. Sarma.

Alkaloids and flavonoids from African phytochemicals as potential inhibitors of SARS-Cov-2 RNA-dependent RNA polymerase: an in silico perspective.

Corona Virus Disease 2019 (COVID-19) is a pandemic caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Exploiting the potentials of phytocompounds is an integral component of the international response to this pandemic. In this study, a virtual screening through molecular docking analysis was used to screen a total of 226 bioactive compounds from African herbs and medicinal plants for direct interactions with SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). From these, 36 phytocompounds with binding affinities higher than the approved reference drugs (remdesivir and sobosivir), were further docked targeting the active sites of SARS-CoV-2, as well as SARS-CoV and HCV RdRp. A hit list of 7 compounds alongside two positive controls (remdesivir and sofosbuvir) and two negative controls (cinnamaldehyde and Thymoquinone) were further docked into the active site of 8 different conformations of SARS-CoV-2 RdRp gotten from molecular dynamics simulation (MDS) system equilibration. The top docked compounds were further subjected to predictive druglikeness and ADME/tox filtering analyses. Drugable alkaloids (10'-hydroxyusambarensine, cryptospirolepine, strychnopentamine) and flavonoids (usararotenoid A, and 12α-epi-millettosin), were reported to exhibit strong affinity binding and interactions with key amino acid residues in the catalytic site, the divalent-cation-binding site, and the NTP entry channel in the active region of the RdRp enzyme as the positive controls. These phytochemicals, in addition to other promising antivirals such as remdesivir and sofosbuvir, may be exploited towards the development of a cocktail of anti-coronavirus treatments in COVID-19. Experimental studies are recommended to validate these study.

Subchronic exposure to Kafura; its neurotoxic potentials in young adult female Wistar rats.

BACKGROUND: Kafura pelebe (camphor) {C10H16O} is a chemical substance used mostly amongst the Yoruba ethnic group in Western Nigeria to treat infantile colic during early childhood. This study assess the neurotoxic potentials of Kafura following sub-chronic exposure in female albino Wistar rats. METHODS: Twenty-eight female rats (mean weight of 130 g) were randomly selected and assigned into four (4) groups. Control, received 1ml coconut oil while the treatment groups received 79, 158 and 237. mg/kg b.wt (d ose p.o) of Kafura for the period of 14 days. On day fifteen, animals were dissected and the brain organ excised for the homogenate and histopathologic assay, blood samples were also collected for haematological analysis. Morris Water Maze experiment for reference memory was also carried out to ascertain effect of Kafura in the Central Nervous system (CNS). RESULTS: A trend toward decreased body-weight gain and increase brain weight was observed in Kafura-treated rats but was statistically not significant, compared to control. The biochemical assessment of the antioxidant status of brains of Kafura-treated rats showed significant (p ≤ 0.05) increase in activities of some anti-oxidant enzymes (Superoxide dismutase (SOD), Glutathione peroxide (GPx), and Catalase (CAT)). There was increase in acetylcholinesterase (AChE), Malondialdehyde (MDA), and Total protein activities in the brain of treated rats compared to control. Alterations of the haematological parameters were observed, with the plasma granulocytes, lymphocytes, and haemoglobin (HGB), showing significant decrease in the treated rats compared to control. The water maze test showed a marked increase in spatial learning and memory time (seconds) in kafura-treated rats, compared to control and across treated groups. CONCLUSIONS: The present study provides indication that kafura Pelebe shows apparent neurotoxicity in experimental animals. Incessant exposure in humans though may lead to development of some central nervous system defects.

Polyalthia longifolia Extract Triggers ER Stress in Prostate Cancer Cells Concomitant with Induction of Apoptosis: Insights from In Vitro and In Vivo Studies.

Plant-based therapies are being explored to prevent or treat several cancer types. The antioxidant properties of Polyalthia longifolia plant are well established. In our previous work, we demonstrated the presence of cytotoxic compounds in the methanol extract of Polyalthia longifolia (MEP) with potent activity against human leukemia cells. In the present study, we evaluated the efficacy of MEP against prostate cancer (PCa) and established the molecular basis of its effect in in vitro and in vivo models. We observed that MEP treatment resulted in a significant decrease in the growth and viability of PCa cells, associated with arrest in the G1/S phase of the cell cycle. Apoptosis was confirmed as the primary mode of MEP-induced cell death through activation of the intrinsic apoptotic machinery. Proteomic and biochemical studies identified BiP as an important target of MEP with the activation of the ER stress pathway, as a potential mechanism driving MEP-induced apoptosis. The extract exhibited strong efficacy in the PCa xenograft mouse model with significant inhibition of tumor growth and reduced tumor burden. Taken together, our findings indicate that MEP-induced apoptosis in PCa cells concomitant with the activation of the ER stress pathways results in the inhibition of tumor growth, in vitro and in vivo. Our studies provide initial evidence of the efficacy of MEP against PCa and advocate for in-depth studies in other preclinical models for its possible use in clinical settings.

Safety effect of fractions from methanolic leaf extract of Ocimum gratissimum on reproduction in male wistar rats.

This study evaluates the reproductive toxicity of ethyl acetate and butanolic fractions from crude methanolic leaf extract of Ocimum gratissimum in male Wistar rats. Acute toxicity was assessed to determine the safety dose, Sub-chronic reproductive toxicity studies were carried out by administering daily 25, 100 and 400 mg/kg body weight doses of the fractions to respective group of animals and 1 ml of normal saline daily for the control group for 28 days. Blood, epididymis and testes were harvested for reproductive hormones, sperm parameters, and histopathologic analysis respectively. There was significant (P < 0.05) increase in serum levels of testosterone, body-weight gain, sperm count. There was also apparent increase in mean-testicular weight and preservation of testicular histology with increase spermatogenesis in both the ethyl acetate and butanolic fraction treated groups compared with control. Serum levels of luteinising hormone was however significantly (P < 0.05) decrease across the groups compared to control. These effects were more pronounced in the butanolic fraction group compared to the ethyl acetate treated group. Sperm motility was also significantly (P < 0.05) higher in the ethyl acetate treated group compared to control. Findings from this studies demonstrate that these fractions were non-toxic at the tested doses with regards to male reproduction but, rather, exhibited fertility enhancing effects which was better with the butanolic fraction. Our findings also shows that the ethyl acetate fraction may be safer than the butanolic fraction.

Fisetin targets YB-1/RSK axis independent of its effect on ERK signaling: insights from in vitro and in vivo melanoma models.

The anti-proliferative activity of dietary flavonoid fisetin has been validated in various cancer models. Establishing its precise mechanism of action has proved somewhat challenging given the multiplicity of its targets. We demonstrated that YB-1 promotes epithelial-to-mesenchymal transition and its inhibition suppressed tumor cell proliferation and invasion. The p90 ribosomal S6 kinase (RSK), an important ERK effector, activates YB-1 to drive melanoma growth. We found that fisetin treatment of monolayer/3-D melanoma cultures resulted in YB-1 dephosphorylation and reduced transcript levels. In parallel, fisetin suppressed mesenchymal markers and matrix-metalloproteinases in melanoma cells. Data from cell-free/cell-based systems indicated that fisetin inhibited RSK activity through binding to the kinase. Affinity studies for RSK isoforms evaluated stronger interaction for RSK2 than RSK1. Competition assays performed to monitor binding responses revealed that YB-1 and RSK2 do not compete, rather binding of fisetin to RSK2 promotes its binding to YB-1. Fisetin suppressed YB-1/RSK signaling independent of its effect on ERK, and reduced MDR1 levels. Comparable efficacy of fisetin and vemurafenib for inhibiting melanoma growth was noted albeit through divergent modulation of ERK. Our studies provide insight into additional modes of regulation through which fisetin interferes with melanoma growth underscoring its potential therapeutic efficacy in disease progression.

A 90 day chronic toxicity study of Nigerian herbal preparation DAS-77 in rats.

BACKGROUND: The herbal preparation DAS-77, used for the treatment of various ailments in Nigeria, contains the milled bark of Mangifera indica L. and root of Carica papaya L. Toxicological assessment of the preparation was carried out in this study. METHODS: In the acute toxicity study, DAS-77 was administered to mice p.o. up to 20 g/kg in divided doses and i.p. at 250-3000 mg/kg. Mortality within 24 h was recorded. In the chronic toxicity study, rats were treated p.o. for 90 days at doses of 80, 400 (therapeutic dose, TD) and 2000 mg/kg. By 90 days, animals were sacrificed and blood samples collected for hematological and biochemical analysis. Organs were harvested for weight determination, antioxidants and histopathological assessments. RESULTS: DAS-77 did not produce any lethality administered p.o. up to 20 g/kg in divided doses but the i.p. LD50 was 1122.0 mg/kg. At TD, DAS-77 produced significant (p < 0.05) reductions in body weight, food intake and K+, and increases in ovary weight, neutrophils and HDL, which were reversible. Histopathological presentations were generally normal. Effects at the other doses were comparable to those at TD except for reversible increases in antioxidants in the liver, kidney and testes, and sperm abnormality, and reductions in liver enzymes, sperm motility and count. CONCLUSIONS: Findings in this study revealed that DAS-77 is relatively safe with the potential for enhancing in vivo antioxidant activity. However, possibly reversible side-effects include electrolyte imbalance and sterility in males.