Acute Injury of Respiratory System in Rats Induced by PM_2.5 Collected from Dushu Lake Higher Education Town in Suzhou

Objective  To investigate the characteristics of acute respiratory system injury in rats induced by PM_2.5 and its possible mechanisms.

Methods  Twenty-four Wistar male rats were randomly divided into four groups, including one control group and three PM_2.5 exposure groups treated with endotracheal instillation of PM_2.5 suspensions (2.5 mg/kg, 5.0 mg/kg and 10.0 mg/kg) for 3 consecutive days. PM_2.5 samples were collected from a campus of Dushu Lake Higher Education Town in Suzhou. Rats were sacrificed 24 hours after the last treatment. The left lung of rats was fixed for pathological examination. Bronchoalveolar lavage fluid (BALF) from the right lung was collected for detecting the activity of enzyme (LDH, ACP, AKP), the level of cytokine related to both pro-inflammation (TNF-ɑ, IL-8) and anti-inflammation (IL-4, IL-10). The level of mitochondrial membrane potential (MMP), Ca²⁺ and reactive oxygen species (ROS) were measured by flow cytometer.

Results  Histopathological examination results indicated that PM_2.5 induced pulmonary inflammatory response, pulmonary interstitial hyperplasia and increased alveolar cavities secretion in a dose dependent way. There were no obvious changes on the level of enzyme and cytokine both in the control and exposure groups except the activity of AKP in 5.0 mg/kg and 10.0 mg/kg groups, which decreased significantly compared with the control group. The level of Ca²⁺ increased while the MMP decreased in the lung cell of exposure groups compared with that of the control group.

Conclusions  Acute exposure of PM_2.5 could induce parenchymal injury, inflammation and oxidative stress of lung in rats; PM_2.5 were collected from Dushu Lake Higher Education Town in Suzhou.