Expression Of P38 Mitogen-Activated Protein Kinase And Bax/Bcl-2, Caspase-3 In Neural Tube Defects Induced By Hyperthermia

Objective Neural tube defects is one of the most common birth defects, which comprises a series of defects such as anencephalia, encephalocoele, myeloschisis and so on. The development and differentiation of neural tube is a very complicated biological process. This process is regulated and affected by various teratogens, and one notable environmental teratogen is fetal exposure to hyperthermia. Homeothermic animals, including humans, can experience body temperature elevations induced by febrile infections, heavy exercise and hot environments which are known to cause a syndrome of embryonic resorptions, abortions, and malformations in experimental animals. Early embryonic damage is vulnerable to high temperature of the environment, which will prevents cell proliferation and the development of organization, and fetal central nervous system is particularly vulnerable to hyperthermia.High temperature had effects on the expression of genes in embryonic development, especially the enzyme and transduction protein, and resulted in neural tube defects.Recent studies had found that high temperature had an effect on stimulation of mitogen-activated protein kinase (mitogen-activated protein kinases, MAPK) family of ERK1/2 and JNK1/2 and activation of Caspase-3, which confirmed the high temperature had effects on cell apoptosis in congenital neural tube defects. The JNK/SAPK and p38MAPK are MAPK-activated protein kinase family, and the activation of these two pathways are involved in many stress-mediated apoptosis, which indicats that p38MAPK may also be involved in the occurrence of neural tube defects. In this study, on the base of animal models of NTD induced by hyperthermia, we use RT-PCR and Western blotting to detect the expression of p38MAPK and Bax/Bcl-2, Caspase-3 in the development of the neural tube.Methods In-vivo we have used the NTDs animal model to research MAPKs pathway activation in the neural tube defects induced by hyperthermia.30 hyperthermia-and 30 control-treated pregnant females were treated on gestational day 8.5. At 8,16,24, 48 h and 72 hours after the 20-minute exposure (either 37℃or 42℃) and the animals of both groups were terminated by cervical dislocation, and the embryos were removed from the fetal membrane under anatomical lens, we use RT-PCR and Western blotting to detect the expression of p38MAPK and Bax/Bcl-2, Caspase-3 in the development of the neural tube.Results 1. P-p38MAPK was steadily expressed in each control group, the expression of P-p38MAPK increased and had a significant difference from that in the control group at 8-48h(P<0.05), and the peak appeared at 16h(p<0.01), the level of the total p38MAPKmRNA and p38MAPK protein was not changed in the whole course of experiment.2. Bax steadily expressed in each control group;the expression of Bax increased and had a significant difference from that in the corresponding control group in the hyperthermia group at 8-48h(p<0.05), and the peak appeared at 8h and 16h(P<0.01).3. Bcl-2 steadily expressed in each control group;the expression of Bcl-2 decreased and had a significant difference from that in the corresponding control group in the hyperthermia group at 8-24h(P<0.05), and the peak appeared at 8h and 16h(p<0.01).4. Caspase-3 steadily expressed in each control group;activation of Caspase-3 (proteolytic cleavage of the inactive p32 proenzyme and the appearance of the p17 mature subunit of active Caspase-3) at 8-72h(P<0.05).Conclusion We show that hyperthermia induces a dramatic increase in the activation of P-p38MAPK in embryos. On the other hand, increased expression of Bax/Ba1-2, and activation of Caspase-3 was found to be critical for the induction of apoptosis in the neural tube defects induced by hyperthermia. In addition, we observed heat-induced activation of P-p38MAPK are consistent with the expression of Bax/Ba1-2, Caspase-3. And we speculate HS-induced activation of p38MAPKand Bax/Ba1-2, Caspase-3 play a critical role in the process of hyperthermia-induced apoptosis in the neural tube defects.