PM_2.5 Exposure Suppresses Dendritic Maturation in Subgranular Zone in Aged Rats

Detrimental effects of long-term inhalation of fine particulate matter (PM_2.5) on the pulmonary and cardiovascular systems have been widely reported. Recent studies have shown that exposure to PM_2.5 also causes adverse neurocognitive effects. This study investigates the effects of inhaled ammonium sulfate, which is a major compound of inorganic air pollutants in PM_2.5, on adult neurogenesis in aged Sprague-Dawley rats. A total of 20 rats were randomly assigned to experimental (n = 10) and control (n = 10) conditions, wherein they were exposed to either ammonium sulfate or sham air for 2 h per day and for 28 consecutive days. It was observed that ammonium sulfate inhibited the maturation process and diminished dendritic complexity of immature neurons in the subgranular zone (SGZ) of the hippocampus significantly, although the number of neural stem cells or the rates of differentiation were comparable between the two groups. Our findings provide clear evidence on the direct relationship between air quality and advantageous neurogenesis. Exposure to PM leads to specific adverse effects on the maturation process during neurogenesis.