[Antagonistic effect of quercetin on PM_2.5 toxicity in the rat's embryonic development in vitro]

To explore the antagonistic effect of quercetin on fine particulate matter (PM_2.5)-induced embryonic developmental toxicity in vitro.

PM_2.5 was collected on glass fiber filters by PM_2.5 samplers during the heating period of Dec. 2015 to Mar. 2016 in an area of Haidian District, Beijing City. The sampled filters were cut into 1 cm×3 cm pieces followed by sonication. The PM_2.5 suspension was filtered into a 10 cm glass dish through 8 layers of sterile carbasus and stored at -80 °C until freeze drying. Frozen PM_2.5 suspension was dried by vacuum freeze-drying. In vitro post-implantation whole embryo culture was used in this study. Pregnant rats with 9.5 gestation days (GD) were killed by cervical dislocation and the uteri were removed into sterile Hank's solution. The embryos with intact yolk sacs and ecto placental cones were induced by PM_2.5, and then subjected to intervention of quercetin at the doses of 0.1 μmol/L, 0.5 μmol/L, 1.0 μmol/L and 5.0 μmol/L, respectively. At the end of the 48 h culture period, the cultures were terminated, and all embryos were removed from the culture bottles and placed in prewarmed Hank's solution for evaluation. Morphological evaluation of the embryos was conducted under a stereomicroscope using the morphologic scoring system by Brown and Fabro. The mitochondrial reactive oxygen species (ROS) level was detected by FACSCalibur flow cyto-metry using MitoSOX^TM Red staining.

An obvious antagonistic effect was achieved through quercetin at the dose of 1.0 μmol/L, which could result in an increase of visceral yolk sac (VYS) diameter, crown-rump length and head length, somite number, and the differentiation of visceral yolk sac vascular vessels. The scores of allantois, flexion, heart, hind brain, midbrain, forebrain, auditory system, visual system, olfactory system, branchialarch, maxillary process, forelimb bud and hindlimb bud also revealed a significant increase and the relative mitochondrial ROS level of embryonic cells was significantly decreased when compared with PM_2.5 group. Although quercetin at the doses of 0.1 μmol/L, 0.5 μmol/L, 5.0 μmol/L also exhibited protective effects against PM_2.5-induced embryonic developmental toxicity, the protective effect was weaker when compared with the dose of 1.0 μmol/L.

Quercetin at proper dose may be of great benefit for the development of embryos exposed to PM_2.5 in the uterus of the rats. Quercetin provides an effective strategy for the prevention of PM_2.5-induced embryonic developmental toxicity. Clearance of mitochondrial ROS may be one of its mechanisms.