Spring pollen from the Mongolian Plateau amplifies macrophage inflammation through mitochondrial transfer from damaged nasal epithelium

Pollen is a prevalent environmental bioaerosol and allergen. To investigate its cytotoxicity and mechanisms, human nasal epithelial cells (HNEpC) and THP-1-derived macrophages were exposed to spring pollen from the Mongolian Plateau at environmentally relevant concentrations (1-100X ambient; 1X = 3.5 µg/cm²). Cell viability was measured by CCK-8. Mitochondrial function was assessed by JC-1, MitoSOX, 8-OHdG, and Seahorse XF analysis. Mitochondrial transfer was traced with MitoTracker and quantified by flow cytometry. NLRP3 inflammasome activation was determined by Western blot. THP-1 viability remained > 75% up to 100X pollen, whereas HNEpC viability decreased significantly at 20X and above (P < 0.05). At 10X pollen, HNEpC showed reduced mitochondrial membrane potential, dynamic mROS changes (peaking at 12 h), increased mitochondrial 8-OHdG, suppressed oxidative phosphorylation, and enhanced glycolysis (P < 0.05). In co-culture, the proportion of double-positive THP-1 cells containing HNEpC-derived mitochondria increased from 2.78% ± 0.17-46.72% ± 2.23% after 72 h of pollen exposure, and this increase was reduced to 8.33% ± 1.25% by the EV secretion inhibitor GW4869 (P < 0.05). Pollen exposure upregulated NLRP3, ASC, PRO-CASPASE-1, IL-1β, and IL-18, and increased cleaved CASPASE-1 (p20) and cleaved IL-1β (p17) in THP-1 macrophages; these effects were blocked by the NLRP3 inhibitor MCC950 (P < 0.05). These data indicate that pollen induces mitochondrial damage in HNEpC and promotes potential EV-associated mitochondrial transfer to macrophages, leading to metabolic reprogramming and NLRP3-dependent inflammatory activation.