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高氧降低新生大鼠肺泡Ⅱ型上皮细胞中 STX17 的表达并抑制自噬流。

Hyperoxia reduces STX17 expression and inhibits the autophagic flux in alveolar type II epithelial cells in newborn rats.

机构信息

Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China.

出版信息

Int J Mol Med. 2020 Aug;46(2):773-781. doi: 10.3892/ijmm.2020.4617. Epub 2020 May 27.

Abstract

Supplemental oxygen therapy can be life‑saving for premature infants. Our previous study revealed a defect in the autophagic flux in the lung tissues of neonatal rats with hyperoxia‑induced bronchopulmonary dysplasia (BPD), but the underlying mechanism remains unknown. Moreover, there are few innovative treatments that can completely alter the course of BPD. The present study examined the expression of Syntaxin 17 (STX17), a protein necessary for autophagosome‑lysosome binding, in alveolar type II (AT‑II) epithelial cells of neonatal rats with BPD. Neonatal Sprague‑Dawley rats were randomly exposed to elevated O2 levels [fraction of inspired oxygen (FiO2), 0.8; model group] or normal room air (FiO2, 0.21; control group), and the expression levels of STX17, autophagy‑related [Microtubule‑associated protein 1A/1B‑light chain 3B (LC3B)‑II, p62, lysosomal‑associated membrane protein 1)] and apoptosis‑related (cleaved caspase3) mRNA and proteins were examined in lung tissues. Moreover, the expression levels of the aforementioned proteins were measured in isolated primary AT‑II cells cultured in vitro under hyperoxic conditions in the presence or absence of pharmacological modulators of autophagy. Transmission electron microscopy identified that AT‑II cell apoptosis and autophagosome aggregation were elevated in the lungs of BPD rats compared with control rats on postnatal day 7. STX17 mRNA and protein expression levels were decreased in lung tissue and isolated AT‑II cells as early as postnatal day 3 in BPD rats, while the expression levels of LC3B‑II, p62 and cleaved caspase3 were increased, reaching a peak on postnatal day 7. This early reduction in STX17 expression, followed by increased expression in autophagy‑ and apoptosis‑related proteins, was also observed in isolated AT‑II cells exposed to hyperoxia in vitro. However, treatment with the autophagy inducers rapamycin or LiCl eliminated the hyperoxia‑induced reduction in STX17, partially restored the autophagy flux and increased the survival of AT‑II cells exposed to hyperoxia. Collectively, these results indicated that STX17 expression in AT‑II cells was reduced in the early stages of BPD in neonatal rats and may be related to the subsequent hyperoxia‑induced block in autophagic flux.

摘要

补充氧气治疗对早产儿可能有救命作用。我们之前的研究表明,高氧诱导的支气管肺发育不良(BPD)新生大鼠肺组织的自噬流存在缺陷,但潜在机制尚不清楚。此外,几乎没有创新的治疗方法可以完全改变 BPD 的进程。本研究检测了突触结合蛋白 17(STX17)在患有 BPD 的新生大鼠肺泡 II 型(AT-II)上皮细胞中的表达。将新生 Sprague-Dawley 大鼠随机暴露于高氧水平[吸入氧分数(FiO2),0.8;模型组]或正常室内空气(FiO2,0.21;对照组],并检测肺组织中 STX17、自噬相关[微管相关蛋白 1A/1B-轻链 3B(LC3B)-II、p62、溶酶体相关膜蛋白 1]和凋亡相关[裂解的半胱天冬酶 3]mRNA 和蛋白的表达水平。此外,还在体外高氧条件下培养的分离原代 AT-II 细胞中测量了上述蛋白的表达水平,并使用自噬的药理学调节剂进行了处理。透射电子显微镜观察到,与对照组大鼠相比,BPD 大鼠在生后第 7 天肺组织中 AT-II 细胞凋亡和自噬体聚集增加。在 BPD 大鼠中,从生后第 3 天开始,肺组织和分离的 AT-II 细胞中 STX17 mRNA 和蛋白表达水平降低,而 LC3B-II、p62 和裂解的半胱天冬酶 3 的表达水平增加,在生后第 7 天达到高峰。在体外高氧暴露的分离 AT-II 细胞中也观察到 STX17 表达的这种早期减少,随后自噬和凋亡相关蛋白的表达增加。然而,用自噬诱导剂雷帕霉素或 LiCl 处理可消除高氧诱导的 STX17 减少,部分恢复自噬流,并增加暴露于高氧的 AT-II 细胞的存活率。综上所述,这些结果表明,在新生大鼠 BPD 的早期阶段,AT-II 细胞中的 STX17 表达减少,这可能与随后的高氧诱导自噬流阻断有关。

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