Targeting the AMPK signalling pathway: Honokiol modulated energy metabolism to mitigate pulmonary injury induced by airborne microplastics through regulating autophagy and mitophagy.
Microplastics (MPs) pollution represents a pressing global environmental challenge, with studies increasingly highlighting their associated health risks. Although MPs have been detected in human lung tissues, the majority of existing research has concentrated on their physicochemical characteristics, environmental distribution and pulmonary health risks. Consequently, our understanding of the specific biological targets and effective intervention strategies against these risks remains limited. To identify therapeutic targets, we screened for pulmonary differential metabolites between normal mice and mice exposed to airborne MPs, derived from dust fall of 10 cities in China. Proteomics results showed adenosine 5'-monophosphate-activated protein kinase (AMPK) signalling pathway was one of critical targets. Through molecular docking and molecular dynamics stimulation, honokiol (HNK) was selected as therapeutic drug to regulate AMPK. In vitro results demonstrated that HNK significantly ameliorated autophagy inhibition in RAW264.7 cell, and alleviated mitochondrial dysfunction in BEAS-2B cell. Drug mechanism research revealed that HNK activated autophagy via the AMPK/mammalian target of rapamycin (AMPK/mTOR) pathway, and promoted mitophagy through the AMPK/E3 ubiquitin protein ligase parkin (AMPK/Parkin) pathway, thereby restoring mitochondrial function. Further targeted energy metabolomics analysis illustrated that HNK regulated the guanosine triphosphate to guanosine diphosphate (GTP/GDP) ratio, adenosine triphosphate (ATP) production, and nucleotide metabolism. These functions accelerated the restoration of autophagic flux, mitophagy reactivation and DNA repair. In conclusion, HNK effectively alleviates airborne MPs-induced autophagy inhibition, mitochondrial dysfunction and energy metabolism disorder via AMPK signalling, providing a promising intervention strategy for pulmonary injury caused by airborne MPs.