A Preliminary Study On The Effect Of Prenatal Cold Stress On Maternal Hippocampus,Placenta And Offspring In Rats

Cold stress is one of the most common sources of environmental stress in the cold regions of the North,and prenatal cold stress is one of initiating factors affecting the benefits of animal husbandry industry,which is reported to increase the rates of unhealthy newborn animals,and leads to growth retardation,immune dysfunction,increasing in the disease susceptibility.However,the underlying mechanism remains unclear.Analyzing the response of maternal and their offspring to prenatal cold stress,and then clarify the corresponding signal transduction mechanism,will help solve the problem of immunocompromised and poor disease resistance of young animals in the cold regions of the north,and look for effective measures to prevent prenatal cold stress by the methods of maternal intervene,and it is of great significance to improve the productivity of livestock and to ensure the sustainable and healthy development of animal husbandry.In order to study the mechanism of prenatal cold stress on pregnant rats and their offspring,rats were selected as subjects to establish prenatal（15-21 days of pregnancy,4°C cold exposure）cold stress model,and normal temperature pregnant rats were used as controls.Rats’rectal temperature,feed intake,body weight gain,and plasma corticosterone（CORT）were measured on the 15th,17th,19th,and 21st days of pregnancy.The results showed that prenatal cold stress induced the level of plasma CORT（P<0.05）and decreased rectal temperature（P<0.05）in pregnant rats.With the extension of cold stress,the feed intake was increased（P<0.05）,but body weight gain was no significant changes（P>0.05）.In order to study the mechanism of cold-stressed pregnant rats’hippocampal regulation of the HPA axis,hippocampal tissues of pregnant rats at the 15th,17th,19th,and 21st days of gestation were collected,detection of MR,GR,brain-derived neurotrophic factor（BDNF）,RNA binding motif protein 3（RBM3）and HSP70/TLR4/MYD88/NF-κB pathway-related proteins in hippocampus.The results showed that prenatal cold stress inhibits the phosphorylation of ERK1/2in the maternal hippocampus,promotes the synthesis of RBM3 protein（P<0.01）,and inhibits the expression of BDNF protein（P<0.05）,promoted the activation of NF-κB through HSP70/TLR4/MYD88/NF-κB signaling pathway,and the response of cold-stressed pregnant rats to cold stress showed a time-varying effect.In order to study the mechanism of cold stress on the placenta,placenta tissues of pregnant rats at the 15th,17th,19th,and 21st days of gestation were collected,detection of GR,MR,11β-hydroxysteroid dehydrogenase type II（11β-HSD2）,HSP70/TLR4/NF-κB pathway-associated proteins,and apoptosis-related proteins such as Bcl-x L in the placenta.The results showed that Prenatal cold stress promoted placenta and CORT response-related proteins GR（P<0.05）,MR（P<0.05）and 11β-HSD2（P<0.01）expression,and activated placental placental HSP70/TLR4/NF-κB signaling pathway,promote the occurrence of inflammatory reactions,induce apoptosis,while the body also through the negative feedback regulation of NF-κB,improve IκBαprotein expression（P<0.01）,inhibit the NF-κB activation,protects the body from harm.To further study the effect of prenatal cold stress on offspring,we performed open-field（OFT）and elevated plus maze（EPMT）behavioral tests on weaned offspring,and collected blood,hippocampus,liver,and small intestine samples.MR,GR,BDNF proteins in hippocampus and serum liver function indexes（AST,ALT,ALKP）were detected and liver and intestinal villi were observed by HE staining.The results showed that prenatal cold stress affected the offspring HPA axis activity,inhibited the expression of MR（P<0.05）in the hippocampus of male offspring rats,and the expression of GR（P<0.05）in female offspring rats;At the same time,prenatal cold stress inhibited the expression of BDNF（P<0.05）and IGF1R proteins（P<0.01）in the hippocampus of the male offspring and inhibited the expression of NEUN（P<0.05）and GFAP（P<0.05）proteins in hippocampus of male and female offspring,these may affected the growth and development of neurons.Moreover,prenatal cold stress inhibited the expression of CRHR1（P<0.01）and GABA_B2（P<0.05）proteins in the hippocampus of male offspring,lead to decreased anxiety-like behavior in offspring and induces offspring behavior abnormalities;In addition,prenatal cold stress reduces the ratio of CD4 and CD8 lymphocyte subsets（P<0.01）in the peripheral blood of male offspring,inhibit offspring cell immunity.In addition,prenatal cold stress promoted the growth of intestinal villi and induced hepatic injury in offspring.The ratio of AST and ALT in serum was significantly higher than that in normal temperature control group（P<0.05）,and the level of ALKP was significantly increased（P<0.01）.The results of this study indicate that prenatal cold stress inhibits the expression of BDNF in the hippocampus of pregnant rats,promotes the synthesis of RBM3 protein,inhibits ERK1/2phosphorylation,and activates HSP70/TLR4/NF-κB signal transduction pathways to promote NF-κB activation;Activate placental HSP70/TLR4/NF-κB pathway,promote the occurrence of inflammatory response;Inhibit the growth and development of hippocampal neurons in weaned offspring rats,induce offspring anxiety-like behavior,and induce weaning offspring offspring damage.