Aloin isoforms (A and B) selectively inhibits proteolytic and deubiquitinating activity of papain like protease (PLpro) of SARS-CoV-2 in vitro

Devin S M Lewis,Shashidharamurthy Taval,Savannah Wills,Anasha Kawall,Avini Sharma,Ajay Singh,Stefania Evoli,Maximilian C C J C Ebert,Krishna Chavada,Srujana Rayalam,Vicky Mody,Joanna Ho

doi:10.1038/s41598-022-06104-y

Devin S M Lewis, Shashidharamurthy Taval + Show 10 more

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https://doi.org/10.1038/s41598-022-06104-y

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Abstract

The most common host entry point of human adapted coronaviruses (CoV) including SARS-CoV-2 is through the initial colonization in the nostril and mouth region which is responsible for spread of the infection. Most recent studies suggest that the commercially available oral and nasal rinse products are effective in inhibiting the viral replication. However, the anti-viral mechanism of the active ingredients present in the oral rinses have not been studied. In the present study, we have assessed in vitro enzymatic inhibitory activity of active ingredients in the oral mouth rinse products: aloin A and B, chlorhexidine, eucalyptol, hexetidine, menthol, triclosan, methyl salicylate, sodium fluoride and povidone, against two important proteases of SARS-CoV-2 PLpro and 3CLpro. Our results indicate only aloin A and B effectively inhibited proteolytic activity of PLpro with an IC50 of 13.16 and 16.08 μM. Interestingly, neither of the aloin isoforms inhibited 3CLpro enzymatic activity. Computational structural modelling of aloin A and B interaction with PLpro revealed that, both aloin isoforms form hydrogen bond with Tyr268 of PLpro, which is critical for their proteolytic activity. Furthermore, 100 ns molecular dynamics (MD) simulation studies predicted that both aloin isoforms have strong interaction with Glu167, which is required for PLpro deubiquitination activity. Our results from the in vitro deubiquitinase inhibition assay show that aloin A and B isomers exhibit deubiquitination inhibitory activity with an IC50 value of 15.68 and 17.51 µM, respectively. In conclusion, the isoforms of aloin inhibit both proteolytic and the deubiquitinating activity of SARS-CoV-2 PLpro, suggesting potential in inhibiting the replication of SARS-CoV-2 virus.

Highlights

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulting in coronavirus disease 19 (COVID-19) pandemic claimed millions of lives worldwide
Two proteases encoded by the viral genome, papain like proteases (PLpro) and 3-chymotrypsin like protease (3CLpro), auto-cleave the newly formed PP chain to generate several non-structural proteins (NSPs) required for the viral replication
It has been shown that SARS-CoV-2 PLpro mediates deISGylation of interferon-sensitive gene-15 (ISG-15) to the host signaling molecules that leads to the inhibition of the host anti-viral innate immune r esponse[7,10]

Summary

Introduction

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulting in coronavirus disease 19 (COVID-19) pandemic claimed millions of lives worldwide. It has been shown that SARS-CoV-2 PLpro mediates deISGylation of ISG-15 to the host signaling molecules that leads to the inhibition of the host anti-viral innate immune r esponse[7,10]. The possible mechanism of pro-inflammatory cytokine storm upon SARS-CoV-2 infection might be due to the dysregulated interferon-mediated anti-viral response (Fig. 1). PLpro serves as a drug target to inhibit the viral replication and to suppress the cytokine storm during SARS-CoV-2 infection. The drugs that can target DUB activity of SARS-CoV-2 PLpro may prevent the cytokine storm mediated tissue damage. The high initial viral loads are concentrated in mouth and nasopharyngeal r egion[15] It has become a huge risk factor for healthcare workers such as dentists, physicians, nurses who come in close contact with asymptomatic or infected patients. The specific target of the active components used in the mouthwash to prevent the viral replication is still not clear

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