Protective Effects Of Vitamin D₃ On Umbilical Cord Vascular Injury In Pregnant Rats Caused By Cooking Oil Fumes-derived PM_2.5 And Its Related Mechanism

Objective To establish the exposure model of the SD rats under the intervention of VD₃and COFs-PM_2.5,observe the effects of COFs-PM_2.5exposure on intrauterine growth and development of fetal rats after VD₃intervention,and further to detect the damage of umbilical cord blood vessels.To explore the possible molecular mechanisms of umbilical cord vascular damage,and provide a new thought and a method for preventing and controlling the damage of the umbilical cord blood vessel caused by the exposure of COFs-PM_2.5.Methods SPF-class SD rats（7-8 weeks old）were caged after adaptive feeding for 7days.After successful mating,the female rats were randomly divided into 4 groups:control group,PM_2.5group,VD₃group and VD₃+PM_2.5group.In the PM_2.5group and the VD₃+PM_2.5group,female rats were treated with 1.0 mg/m L COFs-PM_2.5（3 m L/kg body weight）every 3 days by intratracheal instillation,while in the control group and the VD₃group,the corresponding volume of physiological saline was given.In the VD₃group and VD₃+PM_2.5group,female rats were treated with 5μg/kg body weight VD₃per day by intragastric administration,while in the control group and the PM_2.5group,the corresponding volume of original emulsion without VD₃was given.All female rats were anesthetized and killed at 21 days of gestation.Observe the intrauterine growth and development of the fetus,and calculate the number of live births,the number of stillbirths and the number of resorbed fetuses.Weigh the weight of the fetus,the weight of the placenta and the weight of the brain,heart,liver,kidneys,lungs,etc.;measure the length of crown-rump length,tail length and placental diameter;collect fetal rat blood and umbilical cord blood vessels.HE staining was used to observe morphological changes of umbilical cord blood vessels.The microstructural damage of umbilical cord endothelial cells and smooth muscle cells was assessed with transmission electron microscopy.The changes of oxidative and inflammatory levels in umbilical cord blood vessels were detected.The levels of related proteins and m RNA involved in umbilical cord blood vessels were measured by western blot and RT-PCR.Results 1.Exposure to COFs-derived PM_2.5could induce the occurrence of intrauterine growth restriction in fetal rats.Comparing with the control group,the gestational weight gain in the PM_2.5group was significantly reduced,the weight of fetus,the length of crown-rump length,placental weight and placental diameter were significantly decreased,and the organ coefficient of brain and heart were increased in PM_2.5group（P<0.05）.However,after VD₃intervention,the effects of PM_2.5exposure on the growth and development of fetal rats were significantly improved.2. Exposure to COFs-PM_2.5could lead to changes in the vascular morphology of the umbilical cord.Light microscopy showed that compared with the normal control group,the umbilical vein and umbilical artery wall thickened and the lumen diameter decreased in the PM_2.5group（P<0.05）.Electron microscopic showed that mitochondria in umbilical cord vascular smooth muscle cells and endothelial cells in PM_2.5group were swollen,mitochondria kurtosis was disordered and partially fractured,vacuolar changes in matrix increased,endoplasmic reticulum significantly expanded,and the particle-like substance in the cytoplasm increased.After VD₃intervention,the effects of PM_2.5exposure on umbilical cord blood vessels were significantly improved.3. Exposure to COFs-PM_2.5could lead to changes in the vascular function of the umbilical cord.Compared with the normal control group,the NO level in the umbilical cord tissue of the PM_2.5group increased slightly,and the expression level of ET-1increased significantly.After VD₃intervention,the abnormally elevated level of ET-1expression was significantly reduced.4. Compared with the normal control group,COFs-PM_2.5exposure could induce the increase of oxidative stress（Cu Zn-SOD/T-SOD/GSH/MDA）and inflammatory response（TNF-α/IL-1β）in umbilical cord blood vessel tissue,and VD₃could protect the effects of COFs-PM_2.5on the oxidative stress and inflammatory response of the umbilical cord.5. Western Blot and RT-PCR results showed that exposure to COFs-PM_2.5activated the HIF-1α/e NOS/NO and VEGF/VEGFR2/e NOS signaling pathway in umbilical cord blood vessels,and up-regulated the expression levels of HIF-1α,VEGF and VEGFR2.After VD₃intervention,the expression levels of HIF-1α,VEGF and VEGFR2 were reduced.Conclusion Exposure to COFs-PM_2.5could significantly damage umbilical cord blood vessels,caused excessive oxidative stress and inflammatory response levels,leading to disordered expression of related vascular factors.After VD₃intervention,the adverse effects of PM_2.5exposure on umbilical cord blood vessels were significantly improved.This study revealed the partial toxicity mechanism of COFs-PM_2.5exposure on umbilical cord blood vessels,indicated that VD₃intervention can protect umbilical cord blood vessel injury caused by COFs-PM_2.5exposure,and provided a new strategy for preventing umbilical cord blood vessel injury caused by PM_2.5exposure.