Enhanced transcriptomic resilience following increased alternative splicing and differential isoform production between air pollution conurbations

Adverse health outcomes caused by ambient particulate matter (PM) pollution occur in a progressive process, with neutrophils eliciting inflammation or pathogenesis. We investigated the toxico-transcriptomic mechanisms of PM in real-life settings by comparing healthy residents living in Beijing and Chengde, the opposing ends of a well-recognised air pollution (AP) corridor in China. Beijing recruits (BRs) uniquely expressed ~12,000 alternative splicing (AS)-derived transcripts, largely elevating the proportion of transcripts significantly correlated with PM concentration. BRs expressed PM-associated isoforms (PMAIs) of PFKFB3 and LDHA, encoding enzymes responsible for stimulating and maintaining glycolysis. PMAIs of PFKFB3 featured different COOH-terminals, targeting PFKFB3 to different sub-cellular functional compartments and stimulating glycolysis. PMAIs of LDHA have longer 3^′ UTRs relative to those expressed in Chengde recruits (CRs), allowing glycolysis maintenance by enhancing LDHA mRNA stability and translational efficiency. PMAIs were directly regulated by different HIF-1A and HIF-1B isoforms. BRs expressed more non-functional Fas isoforms, and a resultant reduction of intact Fas proportion is expected to inhibit the transmission of apoptotic signals and prolong neutrophil lifespan. BRs expressed both membrane-bound and soluble IL-6R isoforms instead of only one in CRs. The presence of both IL-6R isoforms suggested a higher migration capacity of neutrophils in BRs. PMAIs of HIF-1A and PFKFB3 were downregulated in Chronic Obstructive Pulmonary Disease patients compared with BRs, implying HIF-1 mediated defective glycolysis may mediate neutrophil dysfunction. PMAIs could explain large variances of different phenotypes, highlighting their potential application as biomarkers and therapeutic targets in PM-induced diseases, which remain poorly elucidated.