苦马豆素致糖基转移酶活性改变对小鼠生殖激素分泌的影响

Swainsonine Poisoning-induced Changes of Glycosyltransferase Activity Affected Secretion of Reproductive Hormone in Mice

苦马豆素是疯草主要有毒成分,抑制α-甘露糖苷酶的活性,引起N-聚糖加工过程失调。笔者课题组前期研究得出:苦马豆素致糖蛋白激素(促卵泡素和促黄体素)糖基化位点上糖链结构发生改变,引起促性腺激素功能发生改变。而苦马豆素中毒对家畜生殖激素分泌的调节机制尚不明确。苦马豆素腹腔注射对小鼠进行染毒,收集妊娠期和分娩期小鼠的血液、子宫和卵巢组织,检测糖基转移酶活性、生殖激素水平及其受体mRNA和类固醇限速酶蛋白质表达量。结果表明:在妊娠和分娩期,苦马豆素致子宫内膜固有层大量低聚糖蓄积,显著抑制N-聚糖加工过程关键糖基转移酶的活性(P<0.05);染毒组小鼠血液的生殖激素包括促卵泡素(FSH)、促黄体素(LH)、雌激素(E2)和孕酮(P4)水平显著低于对照组(P<0.05)。在整个妊娠周期,染毒组小鼠4种激素受体mRNA的表达量显著低于对照组(P<0.05)。在妊娠后期,染毒组小鼠3-β羟基类固醇脱氢酶(3-βHSD)和芳香化酶(CYP19A1)蛋白表达量显著低于对照组(P<0.05)。苦马豆素可使N-聚糖加工紊乱,引起促性腺激素分泌降低,进一步降低生殖激素受体和性类固醇激素限速酶的表达量,致使性类固醇激素分泌下降,导致生殖激素分泌紊乱,最终结果造成机体繁殖性能下降。

Swainsonine is the main toxic component of madweed,inhibiting the activity of α-mannosidase and causing the dysregulation of N-glycan processing.In the previous study,it is found that swainsonine changed the structure of glycosyl chain at the glycosylation site of glycoprotein hormone (i.e.follicle stimulating hormone and luteinizing hormone),which caused the change of gonadotropin function.However,the regulation mechanism of swainsonine poisoning on the secretion of reproductive hormone in livestock is still unclear.Mice were exposed to swainsonine by intraperitoneal injection,and blood,uterus and ovarian tissues were collected from gestational and delivery mice.The glycosyltransferase activity,reproductive hormone levels and their receptor mRNA expressions, and protein expressions of steroid rate-limiting enzymes were investigated.During pregnancy and childbirth,swainsonine poisoning caused a large amount of oligosaccharide accumulation in the lamina propria of the endometrium, which significantly inhibited the activity of key glycosyltransferase during N-glycan processing (P <0.05).The lev- els of reproductive hormones,including follicle-stimulating hormone (FSH),luteinizing hormone (LH),estradiol (E2) and progesterone (P4),in the blood of the exposure groups were significantly lower than those in the control group (P <0.05).During the whole pregnancy cycle,the mRNA expression of four hormone receptors in the poi- soned mice were significantly lower than those in the control group (P <0.05).In the late period of pregnancy,the expression levels of 3-β-hydroxysteroid dehydrogenase (3-βHSD) and aromatase (CYP19A1 ) in the poisoned group were significantly lower than those in the control group (P <0.05).The swainsonine poisoning can reduce the secretion of gonadotropin caused by the disorder of N-glycan processing,further reduce the expression of the hormone- restricting enzymes of reproductive hormone receptors and sex steroids,and cause the decrease in the secretion of sex steroid hormones,leading to the disorder of reproductive hormones secretion.The final result is a decline in reproductive performance.