Redox-sensitive factors as targets of thiol compounds to hinder SARS-CoV-2 replication and inflammatory response.

SARS-CoV-2 has undergone rapid genetic evolution, leading to the emergence of new variants with distinct mutations impacting global public health. Upon infection, the virus triggers a robust inflammatory response characterized by the release of pro-inflammatory cytokines, which play a central role in lung injury. It also alters the host antioxidant response, causing oxidative stress that supports viral replication and cytokine overproduction. This study investigated key pathogenic effectors in Calu-3 and A549-ACE2/TMPRSS2 cells infected with SARS-CoV-2 variants, focusing on replication kinetics, cellular redox state, and inflammatory cytokine profile. A dramatic redox alteration in terms of glutathione (GSH) and Cysteine (Cys) was observed at 48 h p.i., along with a strong pro-inflammatory cytokine response , likely via activation of the JNK/AP-1 signaling pathway. To counteract these effects, two thiol molecules were tested: I-152, a monothiol conjugate of N-Acetyl-Cysteine (NAC) and β-mercaptoethylamine (MEA) and its dithiol derivative, I-152SdAc. Thiols restored GSH balance by enhancing the expression of Nrf2-mediated genes, such as glutamate-Cys ligase modifier subunit (GCLM), and counteracted AP-1-mediated pathway, resulting in a significant reduction of inflammation and viral replication. Antiviral and anti-inflammatory activities of thiols were confirmed in NHBE cells. These findings highlight that redox imbalance is a key pathogenetic event in SARS-CoV-2 infection. Notably, besides Nrf2 and AP-1, other redox-sensitive factors, such as the CHAC glutathione-specific gamma-glutamyl-cyclotransferase 1 (CHAC1), seem to contribute to the pathogenesis and may represent a new potential therapeutic target of redox active compounds. Therefore, the thiol-derived molecules act as broadly effective compounds by limiting virus replication and inflammation.