SARS-CoV2 infection impairs the metabolism and redox function of cellular glutathione

Abstract

Viral infections sustain their replication cycle promoting a pro-oxidant environment in the host cell. In this context, specific alterations of the levels and homeostatic function of the tripeptide glutathione have been reported to play a causal role in the pro-oxidant and cytopathic effects (CPE) of the virus. In this study, these aspects were investigated for the first time in SARS-CoV2-infected Vero E6 cells, a reliable and well-characterized in vitro model of this infection. SARS-CoV2 markedly decreased the levels of cellular thiols, essentially lowering the reduced form of glutathione (GSH). Such an important defect occurred early in the CPE process (in the first 24 hpi). Thiol analysis in N-acetyl-Cys (NAC)-treated cells and membrane transporter expression data demonstrated that both a lowered uptake of the GSH biosynthesis precursor Cys and an increased efflux of cellular thiols, could play a role in this context. Increased levels of oxidized glutathione (GSSG) and protein glutathionylation were also observed along with upregulation of the ER stress marker PERK. The antiviral drugs Remdesivir (Rem) and Nelfinavir (Nel) influenced these changes at different levels, essentially confirming the importance or blocking viral replication to prevent GSH depletion in the host cell. Accordingly, Nel, the most potent antiviral in our in vitro study, produced a timely activation of Nrf2 transcription factor and a GSH enhancing response that synergized with NAC to restore GSH levels in the infected cells. Despite poor in vitro antiviral potency and GSH enhancing function, Rem treatment was found to prevent the SARS-CoV2-induced glutathionylation of cellular proteins. In conclusion, SARS-CoV2 infection impairs the metabolism of cellular glutathione. NAC and the antiviral Nel can prevent such defect in vitro. Their role in COVID-19 therapy worth investigating.

Inhibiting ACSL1-Related Ferroptosis Restrains Murine Coronavirus Infection

“…Several reviews mentioned the possibility of ROS elimination for treatment of COVID-19. Although in one case, the application of N-acetylcysteine (NAC), a ferroptosis inhibitor that promotes glutathione supplementation, restored glutathione levels in the SARS-CoV-2-infected cells, and markedly reduced C-reactive protein (CRP) levels in a severe COVID-19 patient, and another randomized clinical trial indicated that a high dose of NAC brought little benefit to hindering the evolution of severe COVID-19 [65][66][67]. However, our results here showed that the ferroptosis inhibitor suppressed inflammatory cytokines release and MHV-A59 propagation in murine macrophages.…”

Implication of COVID-19 on Erythrocytes Functionality: Red Blood Cell Biochemical Implications and Morpho-Functional Aspects

“…In these conditions, the non-oxidative phase of PPP is increased, in which glycolysis intermediates are converted into the ribose-5-phosphate required for the synthesis of the nucleic acids, which is necessary for the virus replication [25,26]. In addition, high levels of oxidized glutathione and a significant decrease in enzymes forming part of the cellular defense line against oxidative stress were found, including superoxide dismutase 1 (SOD1), glucose-6-phosphate dehydrogenase, and peroxiredoxin [27][28][29]. RBCs from COVID-19 could, therefore, be more exposed to the attack of reactive oxygen species (ROS), resulting in induced cellular lysis and inability to carry oxygen.…”

Metabolic Reprogramming in COVID-19

“…However, blocking glutathione synthesis did not change the progress of SARS-CoV-2 infection, suggesting increased GSH may be an epiphenomenon or can only function in a microenvironment in vivo [ 42 ]. In contrast, the detection of SARS-CoV-2 infected cells 24 h after infection indicated impaired biosynthesis of GSH [ 45 ]. A possible explanation is that increased methylation demands caused by SARS-CoV-2 infection give priority to utilize substrates for glutathione synthesis to generate methyl-groups [ 46 ].…”