Anti-inflammatory effects of S-1-propenyl-L-cysteine, a major constituent of Aged Garlic Extract: reversion of the proinflammatory mRNA up-regulation induced in human bronchial epithelial IB3-1 COVID-19 BNT162b2-vaccine.

The coronavirus disease 2019 (COVID-19) pandemic represented a major global health crisis between 2020 and 2023. During this period, extensive research efforts were dedicated to identifying effective therapeutic strategies to mitigate disease progression and improve patient outcomes. One of the most critical and life-threatening complications of COVID-19 is the onset of a hyperinflammatory state, characterized by the excessive production of proinflammatory cytokines and chemokines, a phenomenon widely referred to as the “cytokine storm”. This uncontrolled immune activation plays a central role in the pathogenesis of severe respiratory distress syndrome and multi-organ failure. Consequently, pharmacological approaches targeting key inflammatory mediators, such as interleukin-6 (IL-6) and interleukin-8 (IL-8), have become a major focus in the management of severe COVID-19 and related complications. As part of broader anti-inflammatory strategies, several biomolecules derived from medicinal plants have been investigated for their potential to mitigate COVID-19-associated cytokine storms and the resulting acute respiratory distress syndrome (ARDS). Garlic (Allium sativum L.), a member of the onion family (Alliaceae), has long been used both as a culinary ingredient and a traditional remedy. Its well-documented antioxidant properties, particularly its ability to scavenge reactive oxygen species (ROS), underpin its broad application in biomedical research. Among the plant-derived extracts with prominent anti-inflammatory properties, Aged Garlic Extract (AGE) has gained increasing scientific attention. One of its main sulfur-containing constituents, S-1-propenyl-L-cysteine (S1PC), has demonstrated the capacity to modulate inflammatory responses, including those characteristic of the cytokine storm observed in COVID-19. This study aimed to evaluate the potential anti-inflammatory effects of S1PC in the human bronchial epithelial cell line IB3-1, used as an in vitro model for inflammatory response following stimulation with the COVID-19 mRNA vaccine BNT162b2, encoding for the SARS-CoV-2 Spike protein. Vaccine-stimulated cells were treated with S1PC at concentrations of 1, 5, 10, 25, 50, and 100 μM for 48 hours. After treatment, reverse transcription quantitative PCR (RT-qPCR) and western blot analyses were conducted to assess changes in the expression of inflammatory genes and proteins. Results showed a notable accumulation of Spike mRNA and protein in IB3-1 cells following BNT162b2 exposure, along with a significant upregulation of the NF-κB transcription factor and its downstream IL-6, IL-8, and granulocyte colony-stimulating factor (G-CSF) target genes. Treatment with S1PC successfully reversed this BNT162b2-mediated induction of proinflammatory gene expression without affecting cell viability, apoptosis, cell cycle, or proliferation efficiency. Molecular docking and molecular dynamics studies suggest that Toll-like receptor-4 (TLR4) might be a biochemical target of S1PC. All together, these findings support the potential of S1PC as a therapeutic candidate for the control of hyperinflammatory responses associated with SARS-CoV-2 vaccination or infection. Further studies are required to identify additional agents capable of acting synergistically with S1PC to enhance its anti-inflammatory effects and to further elucidate the underlying molecular mechanisms od action.