Drug repurposing to face Covid-19: Celastrol, a potential leading drug capable of inhibiting SARS-CoV-2 replication and induced inflammation

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Abstract

The global emergence of Covid-19 has caused huge human casualties. Clinical manifestations of the disease vary from asymptomatic to lethal, and the symptomatic form can be associated with cytokine storm and non-homeostatic inflammatory response. In face of the urgent demand for effective drugs to treat Covid-19, we have searched for candidate compounds using a drug repurposing approach based on in silico analysis followed by biological validation. Here we identified celastrol, a pentacyclic triterpene isolated from Tripterygium wilfordii Hook F – a plant used in traditional Chinese medicine – as one of the best compounds out of 39 repurposed drug candidates. Celastrol reverted gene expression signature from SARS-CoV-2-infected cells; bound with high-affinity energy to viral molecular targets such as main protease (M pro ) and receptor-biding domain (RBD); inhibited SARS-CoV-2 replication in monkey (Vero and Vero-ACE2) and human (Caco-2 and Calu-3) cell lines; and decreased interleukin-6 (IL-6) secretion in SARS-CoV-2-infected human cell lines. Interestingly, celastrol acted in a concentration-dependent manner, with undetectable signs of cytotoxicity. Therefore, celastrol is a promising lead drug candidate to treat Covid-19 due to its ability to suppress SARS-CoV-2 replication and IL-6 production in infected cells, two critical events in the pathophysiology of this disease.

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  1. SciScore for 10.1101/2021.04.20.439992: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Experimental Models: Cell Lines
    SentencesResources
    Finally, virus titration was performed on Vero CCL81 cells using standard limiting dilution to determine the 50% tissue culture infectious dose (TCID50) of viral stock47,48. 2.5.
    Vero CCL81
    suggested: None
    Photomicrographs were taken using the Olympus ix51 inverted microscope and analyzed using the QCapture Pro 6.0 software under 200× magnification (QImaging)49, in order to examine whether celastrol interfered with SARS-CoV-2 cytopathic effects in Vero CCL-81 cells.
    Vero CCL-81
    suggested: None
    Cell viability: Cytotoxicity of celastrol (Sigma-Aldrich) to Vero CCL-81, Vero CCL-81-ACE2, Calu-3, and Caco-2 was determined using the Alamar Blue Cell Viability protocol (Thermo Scientific, Waltham, USA), according to the manufacturer's instructions.
    Vero
    suggested: None
    Caco-2
    suggested: CLS Cat# 300137/p1665_CaCo-2, RRID:CVCL_0025)
    Interleukin 6 quantification: IL-6 levels were quantified in Caco-2 and Calu-3 cell culture supernatants using the Human DuoSet ELISA assay kit (R&D Systems, USA), according to the manufacturer’s instructions.
    Calu-3
    suggested: KCLB Cat# 30055, RRID:CVCL_0609)
    Software and Algorithms
    SentencesResources
    The signature was submitted to over-representation analysis using Reactome pathways34 and clusterProfiler R package35 to find biological pathways that were enriched due to viral infection, within BH adjusted p-value < 0.05.
    Reactome
    suggested: (Reactome, RRID:SCR_003485)
    clusterProfiler
    suggested: (clusterProfiler, RRID:SCR_016884)
    The graphical representation of drug signatures data and scores were generated with pheatmap36 and ggplot2 packages37 in R software38.
    ggplot2
    suggested: (ggplot2, RRID:SCR_014601)
    Docking analysis was carried out using Autodock Vina43 with exhaustiveness parameter equal to 20.
    Autodock
    suggested: (AutoDock, RRID:SCR_012746)
    Graphical representations of energy results were plotted with ggplot2 R package and molecular model structures were drawn with Pymol44 and Discovery Studio Visualizer® (version-2020)45. 2.3.
    Pymol44
    suggested: None
    All the experimental data are expressed as mean ± standard error of the mean (SEM), and they were plotted and analyzed using GraphPad Prism 7 software52.
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)

    Results from OddPub: Thank you for sharing your data.


    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Despite its potential therapeutic effects, there are still some limitations to the use of celastrol, such as its low solubility that results in poor bioavailability, in vitro and in vivo toxicity, and adverse effects that remain to be evaluated107,108. Celastrol was not cytotoxic to all cell lines tested herein, even at the highest concentration (1000 nM), corroborating other reports using Caco-2 cells109. At 1000 nM, this compound reduced the SARS-CoV-2-cytopathic effect on Vero CCL-81 cells. A recent study using a mouse model of acute toxicity has demonstrated that celastrol is safe even when orally administered at a high dose (62.5 mg/kg body weight)110. Intraperitoneal administration of celastrol (0.25 mg/kg body weight) increases the gamma irradiated-mice survival rate by around 7078. To surpass celastrol toxicity, solubility, and pharmacokinetic issues, several pharmaceutical approaches have been proposed, such as nanoencapsulation, liposomes, and sugar-silica nanoparticles111–113. Celastrol has been considered a lead drug for several human illnesses, but its toxicity to humans remains to be determined64,73,114. To the best of our knowledge, the present study is the pioneer to use the combination between bioinformatic tools and biological approaches to demonstrate that celastrol inhibits the SARS-CoV-2 replication in non-human and human cell lines, and down-regulates IL-6 secretion from infected-human cell lines, reinforcing that celastrol is a potential repurposed drug...

    Results from TrialIdentifier: No clinical trial numbers were referenced.


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: We did not find any issues relating to colormaps.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • No funding statement was detected.
    • No protocol registration statement was detected.

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