Central Nervous System Toxicity Induced by Particulate Matter

Epidemiological and toxicological studies have shown that particulate matter may not only have adverse effects in the cardiovascular system but also in the central nervous system (CNS). Most toxicological studies suggested that particulate matter may cause neuroinflammation and behavioral changes. Here, we used diesel exhaust particles (DEPs) to explore its acute CNS toxicity and also used ambient fine particles (PM2.5) to discuss sub-chronic exposure induced CNS toxicity. There are two parts in this study. In the first part of study, C57BL/6 mice were given DEPs by intratracheal instillation. One week after exposure, Morris water maze was conducted. Escape latency, distanced moved and cumulative distance from the center of platform quadrant or platform in acquisition phase, percentage of time spent in target area, area crossing and average proximity from the center of platform quadrant or platform were calculated to examine spatial learning and memory. Histopathological examination was then conducted in the brain using H&E stain. In the second part of study, C57BL/6 mice were exposed to ambient PM2.5 by inhalation for 12 weeks (3 months). Morris water maze was then conducted one week after the end of exposure. Spatial learning and memory ability were tested. Histopathological examination was also conducted in the brain using H&E stain. In the first part of study, results in Morris water maze test showed that acute exposure to DEPs may impair performance in acquisition phase. Mice required longer escape latency and distance moved to find the platform. Cumulative distance from the center of platform quadrant or platform was also longer. Mice histopathological examination found no significant difference between exposure and control group and was within normal limit. In the second part of study, the mean mass concentration for exposed ambient PM2.5 was 11.9 μg/ m3 during the exposure duration. Sub-chronic exposure to low concentration ambient PM2.5 may also impair performance in acquisition phase in Morris water maze test. Histopathological examination found no significant difference between exposure and control group and was within normal limit. Previous studies found that behavioral changes after PM exposure may associated with neuroinflammation. We found that both acute exposure to DEPs and low concentration sub-chronic exposure to ambient PM2.5 may affect performance in acquisition phase in Morris water maze test in mice. Further biochemical examination, inflammatory cells staining in the brain and detailed histopathological were required to explore the mechanism and support current findings in behavioral changes.