Impact of diesel particulate matter on the olfactory bulb of mice: insights from behavioral, histological, and molecular assessments

BackgroundDiesel particulate matter (DPM) constitutes a significant air pollutant that adversely affects neurological health through the olfactory pathway. Although extensive human epidemiological and animal research exists, the specific mechanisms underlying DPM-induced olfactory dysfunction have not been definitively elucidated.ObjectiveThis study aimed to conduct a comprehensive analysis of the behavioral, histological, and molecular changes in the olfactory bulb (OB) of mice following intranasal exposure to 10 mg/kg DPM for a duration of four weeks.ResultsExposure to DPM led to notable olfactory impairment in the mice, characterized by an elevation in Iba-1-positive microglia, though without inducing neuronal cell death. Transcriptomic evaluation revealed 84 differentially expressed genes (DEGs) in the OB that met the criteria of fold change greater than 1.5 and a p value less than 0.05. Within this set, 55 genes were upregulated and 29 were downregulated. Gene ontology-based functional analysis revealed that these DEGs were primarily related to sensory organ morphogenesis, energy homeostasis, and the regulation of monocyte aggregation. Subsequent investigation using the Kyoto Encyclopedia of Genes and Genomes database identified enriched pathways connected to neuroactive ligand-receptor interactions and calcium signaling.ConclusionOur findings suggest a plausible association between DPM-induced olfactory dysfunction and disruptions in a range of molecular pathways. This hypothesis is supported by observed alterations in gene expression and the presence of mild neuroinflammation, primarily driven by microglial activation.