Neuronal and perineuronal changes of cerebral cortex after exposure to inhaled particulate matter

The inhalation of particulate matter (PM) increases the perineuronal nets (PNNs) in the cerebral cortex; however, little is known about the related molecular changes. We explored how PM exposure impacted cognitive function and the levels of PNN-related genes. BALB/c mice (6-week-old females, n = 32) were exposed to 1-5-μm diesel-extracted particles (DEPs) (100 µg/m³, 5 hours per day, 5 days per week) and categorized into the following four groups: 1) 4-week DEP exposure (n = 8); 2) 4-week control (n = 8); 3) 8-week DEP exposure (n = 8); and 4) 8-week control (n = 8). The Y-maze test and olfactory function test were conducted after 4 and 8 weeks of DEP exposure. The prefrontal cortex, olfactory bulb and temporal cortex were harvested from the animals in each group. The expression of genes related to PNNs (Tenascin C, matrix metalloproteinase [MMP]14, MMP9) and synaptic vesicular transporters of vesicular glutamergic transporter 1 (VGLUT1), VGLUT2, vesicular GABAergic transporter (VGAT) were measured. The temporal cortex was immunostained for neurocan, VGLUT1, and VGAT. The 4-week DEP group had lower total arm entry in the Y-maze test and olfactory sensitivity. These impaired behavioral functions recovered in the 8-week DEP group. Expression of tenascin C and MMP9 were increased in the cerebral cortex in the 8-week DEP group compared with the control group. The levels of VGLUT1, VGLUT2, and VGAT were elevated in the cerebral cortex of the 8-week DEP group compared with the control group. In immunostaining of the temporal cortex, the expression of neurocan, VGLUT1, and GAD67 were increased in the 8-week DEP group compared with the control group. The 4-week DEP inhalation impaired spatial activities and olfactory sensitivities. After 8 weeks of DEP exposure, the PNN components and their proteolytic enzymes and the vesicular transporters increased in the cerebral cortex.