Prenatal Exposure To LPS Alters Expression Of DNA Methyltransferase Of Renal In Offspring Rats

Background and objective:The ―Development Origins of Health and Disease(DOHaD)‖ hypothesis has been greatly developed in past two decades. The British Dr. Barker proposed ―Fetal origins of adult disease ‖ hypothesis in last 90’s. A worldwide series of epidemiological studies and a lot of animal experiments researches shown that environmental influences in early life, which impair growth and development of individuals, result in an increased risk for adult chronic disease, include hypertension, obesity, insulin resistance, type Ⅱ diabetes, cardiovascular disease, asthma, chronic kidney disease and cancer.Report On Cardiovascular Diseases China(2013) shows that the main cause of death is cardiovascular disease among urban and rural people. Hypertension is an important risk factor for cardiovascular disease. However, the exact mechanism lead to essential hypertension is not clear. Studies at present shown that prenatal adverse environment exposure may alters the key offspring disease genetic epigenetic modification, leading to genetic imprinting effect and changes the expression of gene in the whole life of the offspring, thus inducing occurrence of adult chronic disease. Prenatal exposure to lipopolysaccharide lead to hypertension in offspring rats and increase of inflammatory factor(e.g. IL-6, TNF-α) in the placenta, amniotic fluid and fetal brain. Currently, it is shown that high level of interleukin-6(IL-6) raise DNA methyltransferase-1(DNMT1) through JAK2 pathway up-regulation transcription factor Fli-1; Moreover, tumor necrosis factor-α(TNF-α) stimulate the production of DNMT3 B by up-regulation transcription factor NK-κB. Methylation, one of the major of epigenetic modification, is important to normal growth and development in individuals. DNMT1 is regarded as the DNMT to carry out maintenance methylation following cell division and replication, while DNMT3 A and DNMT3 B are regarded as the de novo enzymes, basic for setting up new DNA methylation patterns during germ line and embryonic development.Based on these theories and researches, we propose this following hypothesis, maternal inflammation stimulation may changes the DNA methyltransferase level and alters the destination DNA epigenetic modification by raising the expression of inflammatory cytokines in offspring, resulting in abnormal expression of critical genes in temporal and spatial specificity, which leads to the occurrence of hypertension. In the present research, we duplicated the mechanism of hypertension through measure the level of IL-6, Fli-1, DNMT1, DNMT3 in the renal tissue of offspring that maternal exposure to LPS, and investigate whether DNMT is involved in the change of DNA epigenetic modification in the renal tissue.Materials and methods:1. Sixteen gravid Sprague-Dawley(SD) rats were randomly categorized into four groups: a control group, a LPS-treated group, a PDTC-treated group, a LPS+PDTC group. The prenatal rats in these groups were treated with intraperitoneal injection 0.5ml normal saline, 0.79mg/kg LPS, 100mg/kg PDTC or LPS and PDTC. The control group were treated normal saline from the gestation day 8 to day 14; The LPS group were administered LPS on gestation day 8, 10, 12, and given normal saline on the 9th, 11 th, 13 th, 14 th pregnancy day; The PDTC group were treated PDTC from gestation day 8 to day 14; The LPS+PDTC group were given LPS at the same time with the LPS group while PDTC were given from day 8 to day 14 in pregnancy. PDTC were administered after LPS-treated immediately.2. Pups were raised with a lactating mother until 4 weeks of age, and then they lived in cages with 3 rats per cage. The pups’ body weight were measured per two weeks since 4 weeks-old to 12 weeks-old. The blood pressure were measured in the age of 6, 8, 10 and 12 weeks.3. The expression levels of renal cortex cytosine-5-methyltransferases mRNA, IL-6, TNF-α, Fli-1, DNMT1, DNMT3 A, DNMT3 B in offspring rats were assessed with real-time PCR.4. The expression levels of renal cortex cytosine-5-methyltransferases protein, IL-6,Fli-1, DNMTs in offspring rats were assessed with western blot.Results:1. The weight of offspring rats in LPS group were higher than control group at 12 weeks age(P<0.01). While the weight of offspring rats which prenatal exposure to LPS treat with PDTC were reversed.2. Comparing with control group, all offspring rats in LPS group significantly increased blood pressure since 8 weeks old(P<0.01). But prenatal exposure to LPS and PDTC showed a decrease blood pressure than LPS group(P<0.01).3. Prenatal exposure to LPS resulted in increased renal cortex mRNA expression of IL-6, Fli-1, DNMT1, DNMT3 B in offspring rats at 6, 12 weeks of age, and it was markedly reversed by PDTC treatment.4. Prenatal exposure to LPS resulted in increased renal cortex mRNA expression of TNF-α, the difference were not significant in the age of 6 weeks, while the differences in the age of 12 weeks were significant.5.There are not significantly differences in the renal cortex expression of DNMT3 A in offspring rats between LPS-treated and control group.Conclusions:1. Prenatal LPS exposure caused increases in blood pressure and body weight.2. The level of mRNA expression of DNMT1, DNMT3 B were significantly increases in offspring rats of LPS group than control group,.3. Prenatal exposure to LPS leads to increases of IL-6 and Fli-1 in offspring rats than control group. Inflammation increase the expression of DNMT1 through raised IL-6 up-regulate transcription factor Fli-1.