MECHANISM OF TRH EFFECTS IN FETAL LUNG DEVELOPMENT

TRH 对胎儿肺发育的影响机制

• 批准号: 2609335
• 负责人: UDAY P DEVASKAR
• 金额: $ 15.81万
• 依托单位: MAGEE-WOMEN'S HOSPITAL OF UPMC
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-12-12 至 1999-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2609335
• 关键词: adrenal medulla; bronchopulmonary dysplasia; corticosteroids; embryo /fetus; enzyme activity; epinephrine; growth /development; hormone regulation /control mechanism; laboratory mouse; lung; neural transmission; northern blottings; ornithine decarboxylase; phosphatidylcholines; pituitary thyroid axis; protein biosynthesis; radioimmunoassay; respiratory distress syndrome of newborn; statistics /biometry; thyrotropin releasing hormone; western blottings

HMD and BPD remain the major causes of neonatal mortality and norbidity. Maternal Thyrotropin Releasing Hormone (TRH) treatment enhances fetal lung maturation, but inhibits antioxidant enzyme (AOE). Nevertheless, there is an increasing use of prenatal TRH=corticosteroids (CS) for the prevention of HMD & BPD. The mechanism of TRH effects on fetal lung are unclear, it may be due to its neuroendocrine or neurotransmitter actions. To investigate these possibilities, we will use the HYT/HYT mouse where primary hypothyroidism occurs due to a mutation (ProyieldsLeu,a.a.556) in the TM4 domain of the beta subunit of the TSH receptor, & is transmitted as an autosomal recessive trait. We will test alternative hypotheses that TRH mediates its effect through 1 of 3 pathways: 1) Fetal pituitary-thyroid (TH), 2) Fetal CNS autonomic sympathetic or parasympathetic neurotransmission, or 3) Fetal adrenal medullary release of Epinephrine (beta-a drenergic effect). We will perform fetal lung ultrastructural analysis, quantitate disaturated phosphatidylcholine (DSPC), the rate of 3H-choline incorporation into phosphatidaylcholine (PC) & DSPC, & AOE activity, as indices of TRH effects. Clinically TRH is used with CS, & TRH=CS therapy increases fetal ling SP-A in animals. We have observed altered protein (SP-A & C) & gene expression (SP-C) in HYT/HYT mouse fetal lungs. We will study the effect of prenatal CS, TRH or CS+TRH on fetal lung SP-A & SP-C mRNA (Northern) & protein expression (Western & immunostaining), along with other indices of TRH effects. Plasma TSH & free T4 levels (RIA) will determine the TH status of the Mice. The role of each pathway will be determined as follows: 1) Pituitary-thyroid-lung axis: Comparison of the effect on the fetal lung of maternal TRH treatment in the HYT/HYT & Balb-C mouse; presence of TRH effects in Balb-C & their absence in the HYT/HYT mouse will indicate a role for the pituitary-thyroid axis. 2) CNS sympathetic or adrenal medullary Epinephrine (beta adrenergic) stimulation: Comparison of the effect in the fetal lung of maternal TRH therapy in the HYT/HYT mouse with & without prior treatment with 6- hydroxydopamine (6-OHDA, chemical sympathectomy) or Propranolol (beta- adrenergic blockade) respectively: Absence of TRH effects on the lung in 6-OHDA or Propranolol treated fetuses will suggest a role for the Cnz sympathetic or beta-adrenergic system respectively. 3) CNS parasympathetic stimulation: Comparison of the effect on fetal lung of maternal TRH treatment in the HYT/HYT & Balb-C mouse with & without prior atropine treatment for cholinergic blockade: A lack of TRH effect on lungs of Atropine treated fetuses will indicate a role for the cholinergic system. TRH (24mug/dose) will administered (IP, d16 & 17, b.i.d.) & 18 (1 h prior to killing) of pregnancy. The vehicle, 6-OHDA, Propranolol or Atropine will be infused by Alzet pumps starting on d 14. For TRH+CS studies, vehicle+saline, TRH (24mug/dose) in saline+vehicle, TRH+Beta. (0.6 mg/dose), or saline+Beta. will be injected on d 16 & 17 (b.i.d.) & 18 of pregnancy. All pregnant mice will be killed on d 18, (term about 20 d). These studies will further establish the efficacy, & clarify the mechanism of TRH & TRH+CS~s effect on the fetal lung, & may provide clues for the prevention of AOE inhibition after TRH treatment & improved management of neonates prenatally treated with CS+TRH.

HMD和BPD仍然是新生儿死亡率和发病率的主要原因。 母体促甲状腺激素释放激素(TRH)治疗促进胎儿 肺成熟，但抑制抗氧化酶(AOE)。不过， 越来越多的孕妇使用TRH=皮质类固醇(CS)治疗 预防HMD和BPD。TRH对胎肺的作用机制如下 尚不清楚，可能是由于其神经内分泌或神经递质 行为。为了研究这些可能性，我们将使用HYT/HYT 因突变而发生原发性甲状腺功能减退症的小鼠 (ProyeeldsLeu，a.a.556)在TSH的Beta亚基的TM4结构域中 受体&以常染色体隐性遗传方式传递。我们会 检验TRH通过1/3调节其效应的替代假设 途径：1)胎儿垂体-甲状腺(TH)，2)胎儿中枢自主神经 交感或副交感神经传递，或3)胎儿肾上腺 肾上腺素的延髓释放(β-a兴奋效应)。我们会 进行胎肺超微结构分析，定量饱和 磷脂酰胆碱(DSPc)，~3H-胆碱参入率 卵磷脂(PC)、DSPC和AOE活性作为TRH的指标 效果。临床上TRH用于CS，TRH=CS治疗增加 动物体内的胎儿型SP-A。我们观察到了改变的蛋白质(SP-A和C) &基因表达(SP-C)在HYT/HYT小鼠胎肺中的表达。我们会研究 产前应用CS、TRH或CS+TRH对胎肺SP-A、SP-C基因表达的影响 (Northern)和蛋白质表达(Western和免疫染色)，以及 TRH效应的其他指数。血浆TSH和游离T4水平(RIA)将 确定鼠标的状态。每条路径的作用将是 确定如下：1)垂体轴-甲状腺-肺轴：比较 HYT/HYT母体TRH治疗对胎肺的影响 Balb-C小鼠；Balb-C中TRH效应的存在及其在小鼠中的缺失 HYT/HYT小鼠将指示垂体轴-甲状腺轴的作用。2) 中枢交感或肾上腺延髓肾上腺素(β肾上腺素能) 促甲状腺激素释放激素对胎儿肺的刺激作用比较 6-羟色胺对HYT/HYT小鼠的治疗作用 羟基多巴胺(6-OHDA，化学交感神经切除术)或普萘洛尔(β- 肾上腺素能受体阻滞剂)：无TRH对肺的影响 6-OHDA或心得安治疗的胎儿将提示Cnz的作用 交感神经或β-肾上腺素能系统。3)中枢神经系统 副交感神经刺激对胎肺影响的比较 HYT/HYT和Balb-C小鼠母体TRH治疗前后的比较 阿托品治疗胆碱能阻断：缺乏TRH效应 对阿托品治疗的胎儿肺的影响将表明 胆碱能系统。TRH(24微克/剂)将被给予(ip，d16和17， B.I.D.)和18(杀人前1小时)怀孕。这辆车，6-OHDA， 从第14天开始，心得安或阿托品将由阿尔茨海默病泵输注。 对于TRH+CS研究，赋形剂+生理盐水，TRH(24mug/剂)在生理盐水+赋形剂中， TRH+Beta。(0.6 mg/剂量)，或生理盐水+Beta。将在16天和17天注射 (b.i.d)&怀孕18天。所有怀孕的小鼠都将在第18天被杀， (期限约20天)。这些研究将进一步确定疗效，& 阐明TRH、TRH+CS~S对胎肺的作用机制 为TRH治疗后AOE抑制的预防提供线索 加强CS+TRH产前治疗新生儿的管理。