Exploring antiviral and anti-inflammatory effects of thiol drugs in COVID-19

Abstract

The redox status of the cysteine-rich SARS-CoV-2 spike glycoprotein (SARS-2-S) is important for binding of SARS-2-S to ACE2, suggesting that drugs with a functional thiol group ("thiol drugs") may cleave cystines to disrupt SARS-CoV-2 cell entry. In addition, neutrophil-induced oxidative stress is a mechanism of COVID-19 lung injury, and the antioxidant and anti-inflammatory properties of thiol drugs, especially cysteamine, may limit this injury. To first explore antiviral effects of thiol drugs in COVID-19, we used an ACE-2 binding assay and cell entry assays utilizing reporter pseudoviruses and authentic SARS-CoV-2 viruses. We found that multiple thiol drugs inhibit SARS-2-S binding to ACE2 and virus infection. The most potent drugs were effective in the low millimolar range, and IC50 values followed the order of their cystine cleavage rates and lower thiol pKa values. To determine if thiol drugs have antiviral effects in vivo and to explore any anti-inflammatory effects of thiol drugs in COVID-19, we tested the effects of cysteamine delivered intraperitoneally (IP) to hamsters infected with SARS-CoV-2. Cysteamine did not decrease lung viral infection but it significantly decreased lung neutrophilic inflammation and alveolar hemorrhage. We speculate that the concentration of cysteamine achieved in the lungs with IP delivery was insufficient for antiviral effects but sufficient for anti-inflammatory effects. We conclude that thiol drugs decrease SARS-CoV-2 lung inflammation and injury and we provide rationale for future studies to test if direct (aerosol) delivery of thiol drugs to the airways might also result in antiviral effects.

Omicron Spike Protein Is Vulnerable to Reduction

“…Previously the effects of reduction have been demonstrated in both cellular models (Manček-Keber et al 2021;Alonzi et al 2022;Grishin et al 2022;Khanna et al 2022;Murae et al 2022) and mouse models (Khanna et al 2022). Here, we verified the same phenomenon using an in vitro method and elaborated on the involved mechanism.…”

“…Our study clearly demonstrated a significant vulnerability of Omicron variant compared to WT, which was also mentioned by two previous studies(Alonzi et al . 2022; Khanna et al . 2022).…”

“…The copyright holder for this preprint this version posted January 6, 2023. ; https://doi.org/10.1101/2023.01.06.522977 doi: bioRxiv preprint activity toward ACE2-binding (Manček-Keber et al 2021;Alonzi et al 2022;Grishin et al 2022;Khanna et al 2022;Murae et al 2022). However, most of these studies were based on the original Wuhan SARS-CoV-2 wild type (WT) strain or early variants.…”

SARS-CoV-2 Spike Proteins and Cell–Cell Communication Inhibits TFPI and Induces Thrombogenic Factors in Human Lung Microvascular Endothelial Cells and Neutrophils: Implications for COVID-19 Coagulopathy Pathogenesis

“…In fact, DTNB has been shown to reduce the binding, entry, and infection of other envelope viruses into susceptible cells, including human immunodeficiency virus (HIV) [ 68 ], cytomegalovirus [ 69 ], and murine coronavirus [ 64 ]. Thiol-based drugs have also been shown to decrease the binding of SARS-CoV-2 S-proteins to ACE2, inhibit viral entry and infection, and significantly decrease lung neutrophilic inflammation [ 70 , 71 ]. The result of our current study suggests that exposure of HLMEC or neutrophils to S-proteins and endothelial–neutrophil interactions induce/increase TF and pro-thrombogenic factors via mechanisms involving/requiring free and functional thiol groups that likely participate in disulfide bonds formation during virus–cell interactions and binding.…”

Redox medicine in viral infections: focus on AIDS and COVID-19

“…To test this hypothesis, Khanna and colleagues analyzed the effects of cysteamine delivered intraperitoneally to SARS-CoV-2-infected hamsters. Although the reached concentrations of cysteamine in the lung were not sufficient for antiviral effects, they were sufficient for anti-inflammatory effects (Khanna et al, 2022). Accordingly, several in vitro and in vivo studies have suggested that NAC, which reduces the disulfide bonds (-S-S) to sulfhydryl groups (-SH) thus increasing intracellular GSH levels, improves T cell response, inhibits the NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway, and inhibits viral replication (Poe and Corn, 2020).…”