Verbenalin protects against coronavirus pneumonia by promoting host immune homeostasis: Evidences for its mechanism of action.

BACKGROUND

Coronavirus has caused high-mortality viral pneumonia worldwide. The pathogenesis is characterized by hyperinflammatory reactions resulting from immune homeostasis dysregulation. Verbenalin, an iridoid glucoside derived from Verbena officinalis L., is widely used in Traditional Chinese Medicine (TCM) clinical practice for its antioxidant, anti-inflammatory and antiviral properties.

PURPOSE

This study aimed to investigate the pharmacological effects and underlying mechanisms of verbenalin on coronavirus pneumonia both in vivo and in vitro.

METHODS

A coronavirus pneumonia mouse model and macrophage injury models, including mouse alveolar macrophage cell line (MH-S) cells and primary macrophages, were established to initially confirm the antiviral effects of verbenalin. Time-resolved proteomic were then employed to uncover proteomic changes and identify potential therapeutic targets for coronavirus treatment. Subsequently, flow cytometry and Western blot were employed to investigate verbenalin's effects on NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome pathway. Additionally, the targeting regulation of phosphatase and tensin homolog-induced putative kinase 1 (PINK1) / E3 ubiquitin ligase Parkin (Parkin) pathway by verbenalin was validated through molecular docking, surface plasmon resonance (SPR), immunofluorescent staining, RNA interference (RNAi), and mitophagy inhibition both in vivo and in vitro.

RESULTS

Verbenalin reduced cell injury and inflammation in Human coronavirus 229E (HCoV-229E)-infected macrophages and improved lung inflammation in mice. Proteomics analysis highlighted the roles of nucleotide-binding oligomerization domain (NOD)-like receptor signaling and mitophagy pathways in coronavirus pneumonia. Verbenalin bound strongly to PINK1 and Parkin proteins, increased mitochondrial membrane potential (MMP), decreased mitochondrial reactive oxygen species (mtROS) levels, reduced the opening of mitochondrial permeability transition pore (MPTP), maintained mitochondrial mass, promoted mitophagy flux, upregulated the expression of PINK1, Parkin, and microtubule-associated protein 1A/1B-light chain 3BII (LC3BII). Additionally, verbenalin inhibited the activation of the NLRP3 inflammasome and downregulated the expression of Interleukin-1 beta (IL-1β), cysteine aspartate-specific protease 1 (caspase-1), and gasdermin D (GSDMD) both in vivo and in vitro. Furthermore, treatment with a mitophagy inhibitor and RNAi attenuated the inhibitory effects of verbenalin on NLRP3 activation, confirming the involvement of the PINK1/Parkin/NLRP3 pathway in verbenalin's protective effects.

CONCLUSION

Verbenalin enhances PINK1/Parkin-mediated mitophagy to suppress NLRP3 activation, thereby promoting immune homeostasis and mitigating HCoV-229E-induced inflammation.