Airborne PM2.5 Induces Embryo Implantation Failure In Rat Via Affecting MMPs/TIMPs Balance

Objectives: Our subject is to discuss the acute toxicity of fine particlulate matter to embryo implantation and the role of MMPs/TIMPs balance in it in SD female rats that trachea instilled by PM2.5.Methods: 75 SD female rats were randomly divided into 5 groups: saline group,PM2.5 low-dose group,medium-dose group,high-dose group and BaP group with 15 rats in each group.After 15 days administration the male and female were mated with a ratio of 2:3.On the sixth day of gestation,all the rats were sacrificed.Body weight,embryos counts and the weight of uteruses were examined.Blood level of heavy metal Pb,Hg,Cd,As,Sb were estimated by ICP-MS.HE staining was used to detect the pathological signs in ovaries and uteruses.Immunohistochemisty was performed to identify the location of MMP2,MMP9,TIMP1,TIMP2 and TIMP3 in the uterine implantation sites.Real-Time PCR and Western Blotting were performed to detect the mRNA and protein level of MMP2,MMP9,TIMP1,TIMP2 and TIMP3 in the uterine implantation sites.Results:1 Compared with saline group,there was a great decrease in the body weight of rats in PM2.5 high-dose group at every contamination time points(P< 0.05).While the dose of PM2.5 raised,the mating and pregnancy index decreased nevertheless rats in BaP group showed no difference.2 In the three PM2.5 group,the lung showed a relative necrosis extent,and was worse with the increasing of the PM2.5 dose while rats in BaP group showed no obvious changes.3 Compared with saline group,rats in other 4 groups had a smaller embryos count even though no significant difference showed.At the same time,the statistical results in uterine weight showed significant difference in the PM2.5 low-dose group and high-dose group(P<0.05).4 The level of serum Pb,Hg,Cd of 5 groups showed no differences while serum As in PM2.5 low-dose,medium-dose,high-dose raised significantly(P< 0.05).There was a negative correlation between serum As and embryos count(rs=-0.405,P < 0.05).The level of serum Sb of 5 groups showed no difference but a negative correlation between serum Sb and embryos number(rs =-0.382,P=0.054)was still found.5 There were no signs for pathological changes in ovaries and uteruses as indicated by HE staining.6 Immunohistomical results showed that MMP2,MMP9,TIMP1,TIMP2,TIMP3 expressed mainly in the deciduas cell cytoplasm and extracellular matrix(ECM).7 In Real-Time PCR analyses,MMP2 mRNA expression of PM2.5low-dose group,middle-dose group,high-dose group,and BaP group was respectively 0.93,1.27,1.33 and 1.07 times as much as the saline group(P<0.05 for PM2.5 high-dose group).MMP9 mRNA expression in the four groups were respectively 1.33,1.97,2.30,1.06 times as much as the saline group(P<0.01 for PM2.5 medium-dose,high-dose group).TIMP1 mRNA expression in the four groups were respectively 1.06,0.85,0.80,0.82 times as much as the saline group.TIMP2 mRNA expression in the four groups were respectively 1.19,1.56,1.90,1.49 times as much as the saline group(P<0.05 for PM2.5 medium-dose,BaP group,P<0.01 for PM2.5 high-dose group).TIMP3 mRNA expression in the four groups were respectively 0.88,1.64,1.07,0.91 times as much as the saline group(P<0.01 for PM2.5 medium-dose group).There was a positive correlation between MMP2/TIMP2 mRNA ratio and embryos count(rs = 0.562,P = 0.029).8 In western blot analyses,MMP2 expression in PM2.5 low-dose group,middle-dose group,high-dose group,and BaP group were respectively 0.93,1.52,1.13 and 1.05 times as much as the saline group(P<0.01 for PM2.5medium-dose group).MMP9 expression in the four groups were respectively0.97,1.26,1.63,1.89 times as much as the saline group(P<0.01 for PM2.5high-dose group and BaP group).TIMP1 expression in the four groups were respectively 0.88,0.51,0.36,0.49 times as much as the saline group(P<0.01 for PM2.5 medium-dose,high-dose group and BaP group).TIMP2 expression in the four groups were respectively 2.33,2.02,3.19,1.85 times as much as the saline group(P<0.05 for PM2.5 medium-dose and BaP group,P<0.01 for low-dose and high-dose group).TIMP3 expression in the four groups were respectively 1.38,1.89,1.61,1.40 times as much as the saline group(P<0.05 for PM2.5 low-dose group,high-dose and BaP group,P<0.01 for PM2.5medium-dose group).Conclusions:1 PM2.5 induces embryo implantation falure via affecting MMPs/TIMPs in uterus.2 As takes the major responsibility for the toxicity of PM2.5 while Sb may act as another important poisonous component.3 BaP impairs the viability of implanted embryos.