School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Western Australia, Australia.
Centre for Neonatal Research and Education, School of Paediatrics and Child Health, University of Western Australia, Perth, Western Australia, Australia.
Respirology. 2015 Nov;20(8):1255-62. doi: 10.1111/resp.12615. Epub 2015 Aug 26.
In utero infection may critically influence diaphragm development and predispose preterm infants to postnatal respiratory failure. We aimed to determine how frequency and gestational age (GA) at time of intra-amniotic (IA) lipopolysaccharide (LPS) exposure affects preterm diaphragm function.
Pregnant ewes received IA injections of saline or 10-mg LPS at 7 days or 21 days or weekly injections 21, 14 and 7 days before delivery at 121-day GA. Foetal lambs were killed with pentobarbitone (150 mg/kg; intravenous). Diaphragm contractile function was measured in vitro. Muscle fibre type, activation of protein synthesis and degradation pathways, pro-inflammatory signalling and oxidative stress were evaluated using immunofluorescence staining, RT-qPCR, ELISA, Western blotting and biochemical assay.
In utero LPS exposure significantly impaired diaphragm contractile function. LPS exposure 7 days before delivery caused maximum specific twitch and tetanic forces 30% lower than controls. When the initial LPS exposure occurred 21 days before delivery maximum specific forces were 40% lower than controls. Earlier LPS exposure also prolonged twitch contraction time, increased fatigue resistance and elevated protein carbonyl content. Despite increased white blood cell counts and interleukin-6 mRNA expression following weekly LPS exposure, there were no significant differences in contractile properties between exposure 21 days before delivery and repeated LPS groups suggesting that frequency of inflammatory exposure does not influence the severity of contractile dysfunction.
GA at time of initial LPS exposure, rather than frequency of exposure, determines the extent of inflammation-induced diaphragm dysfunction.
宫内感染可能严重影响膈肌发育，并使早产儿易发生出生后呼吸衰竭。本研究旨在确定羊膜内（IA）脂多糖（LPS）暴露的频率和胎龄（GA）如何影响早产儿膈肌功能。
怀孕的母羊在 GA 为 121 天时，在第 7 天或第 21 天接受 IA 生理盐水或 10mg LPS 注射，或在分娩前 21、14 和 7 天每周接受 IA 注射。戊巴比妥（150mg/kg；静脉内）处死胎羊。体外测量膈肌收缩功能。采用免疫荧光染色、RT-qPCR、ELISA、Western blot 和生化分析评估肌纤维类型、蛋白合成和降解途径的激活、促炎信号和氧化应激。
宫内 LPS 暴露显著损害膈肌收缩功能。分娩前 7 天的 LPS 暴露使比目鱼肌的最大特定颤搐和强直力比对照组低 30%。当最初的 LPS 暴露发生在分娩前 21 天时，最大特定力比对照组低 40%。早期 LPS 暴露还延长了颤搐收缩时间，增加了疲劳抵抗力，并升高了蛋白质羰基含量。尽管每周 LPS 暴露后白细胞计数和白细胞介素-6 mRNA 表达增加，但在分娩前 21 天的暴露与重复 LPS 组之间，收缩性能没有显著差异，这表明炎症暴露的频率不会影响收缩功能障碍的严重程度。
初始 LPS 暴露时的 GA 而非暴露频率决定了炎症诱导的膈肌功能障碍的程度。
