Research On The Expression Of FSH And GnRH And Their Protection Of Ischemia-Reperfusion Injury In Rat Hippocampus

The gonadotropin-releasing hormone (GnRH), also called luteinizing hormone-releasing hormone (LHRH), is a decapeptide. Gonadotropin-releasing hormone receptor (GnRH receptor) is a member of the seven-transmembrane, G-protein-coupled receptor family. GnRH combined with GnRH receptor to regulate secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and plays an important role in reproductive process.Gonadotropine comprise of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). They are heterodimer glycoproteins composed ofαandβsubunits and have important roles in production of gonadal hormone and regulation of reproductive process. FSH receptor and LH receptor are G protein-coupled receptors. The secretion of FSH and LH are all regulated by GnRH secreted from hypothalamus. Increasing evidence suggests that GnRH and its receptor can also exist in other extrahypothalamic regions, such as gastrointestinal tract, submaxillary gland, pancreas and some malignant tumor cells such as prostate cancer cells. At the same time, the function of GnRH is beyond reproduction. GnRH, an upstream hormone of estrogen, which can regulate the secretion of estrogen, also broadly exists in hippocampus with its receptor; but there is no report about the change of expression of GnRH and its receptor in hippocampus with ischemia-reperfusion injury. Many research showed that FSH also exists in other tissues besides pituitary. In reproductive system, FSH exists in prostate, breast, testis and placenta; in non-reproductive system, FSH exists in parietal cells of stomach. Its functions are also beyond reproduction. Besides expressed in gonad, FSH receptor also exists in uterine tubal epithelium and cervix.Recently, research has showed that many hormones and their receptors, including reproductive hormones such as GnRH,LH and their receptors, exist in hippocampal neurons. However, whether FSH and its receptor also exist in hippocampal neurons remained unknown yet. Global ischemia-reperfusion injury elicits selective, delayed neuronal death, and the main reason is apoptosis. Many researches have showed that estrogen can protect neuron injury and neuron apoptosis in hippocampal CA1 region during ischemia and this protection is mediated by estrogen receptors in hippocampus. GnRH and FSH are upstream hormones of estrogen, but there is no report about their protection of ischemia-reperfusion injury in rat hippocampus.On the base of our previous research, we did the following experiments: combined with image analysis system, Immunohistochemistry and in situ hybridization method were used to observe the change of expression of GnRH and its receptor in neurons of CA1 region in rat hippocampus after ischemia-reperfusion injury; in situ hybridization method was used to observe the expression of FSH in rat hippocampus; double label immunofluorescence histochemical staining and confocal laser-scanning microscope were used to study the colocalization of FSH and FSHR in rat hippocampus; in vivo study of middle cerebral artery occlusion model building and TUNEL staining was made and in vitro study of oxygen-glucose deprivation model building and double staining of Annexin V/PI with flow cytometer was made to study the protection of ischemia-reperfusion injury by FSH and GnRH in rat hippocampus.Through these experiments, the results are as follows: the expression of GnRH and GnRH mRNA in CA1 reagion of rat hippocampus decreased with time after ischemia-reperfusion injury. the number of positive cells also decreased with time after injury. The expression of GnRHR and GnRHR mRNA in CA1 reagion of rat hippocampus increased at first and then decreased at last with time after ischemia-reperfusion injury. The number of positive cells decreased with time after injury. Three days after ischemia-reperfusion injury, not only GnRHR positive cells but also GnRH positive cells appeared at stratum oriens and stratum radiatum. Hippocampal neurons from CA1 to CA4 region and dentate gyrus showed both FSH immunoreactivity and FSH mRNA hybridization signal. Hippocampal neurons from CA1 to CA4 region and dentate gyrus showed FSHR immunoreactivity. FSH and FSHR co-located in the same hippocampal neurons. FSH and GnRHR co-located in the same hippocampal neurons. 72h after ischemia-reperfusion injury, mean grey levels of TUNEL stain positive neuron in CA1 region of rat hippocampus in FSH interfere group and GnRH interfere group were higher than that of control group, namely the TUNEL positive product in FSH interfere group and GnRH interfere group were less than that of control group.The number of TUNEL stain positive neuron in FSH interfere group and GnRH interfere group were less than that of control group. Compared with that of control group, the percent of apoptosis neuron in FSH interfere group and GnRH interfere group were increased while the percent of survival neuron decreased. Compared with that of no interfere group, the percent of apoptosis neuron in FSH interfere group and GnRH interfere group were decreased while the percent of survival neuron increased.In conclusion, our research found that the expression of GnRH and GnRHR in CA1 region of rat hippocampus make change after ischemia-reperfusion injury.GnRH might participate in the regulation of brain repair process at CA1 region after injury. Rat hippocampus can express FSH. FSH positive hippocampal neurons were also the FSH target cells. FSH secreted by hippocampal neurons might regulate the function of hippocampus through paracrine or autocrine. GnRH secreted by hippocampal neurons might regulate the FSH positive hippocampal neurons through GnRH receptor. Interfere with certain concentration of FSH or GnRH before ischemia-reperfusion injury can reduce the neuron apoptosis at CA1 region of rat hippocampus.FSH and GnRH have protective effect on neuron ischemia-reperfusion injury.