Division of Pulmonary, Critical Care, Allergy, Sleep Medicine, Dept of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, University of Washington, Seattle, Washington, United States of America.
PLoS One. 2022 May 12;17(5):e0268398. doi: 10.1371/journal.pone.0268398. eCollection 2022.
Acute injury of the lung involves damage to the epithelium and its underlying extracellular matrix (ECM), the basement membrane (BM). How BMs contribute to injury resolution is poorly understood. Nephronectin (NPNT) is a high-affinity ligand for integrin α8β1 and, although first identified in the mouse kidney, is prominently expressed in the lung, where it localizes to BMs in the alveoli. To determine if NPNT plays a role in acute injury and inflammation of the lung, we developed a model for postnatal deletion of NPNT using mice with a floxed allele of Npnt in combination with a tamoxifen-inducible Cre recombinase expressed at the ROSA locus. Expression of NPNT was substantially reduced in lungs from tamoxifen-treated Cre+ animals. Cre+ mice and Cre- controls were given E. coli LPS by oropharyngeal aspiration to induce injury and inflammation. In Cre- lungs, although both Npnt and Itga8 (integrin α8) transcripts were downregulated at the peak of inflammation, NPNT protein was still detectable. While the onset of inflammation was similar for Cre+ and Cre-, NPNT-deficient lungs still had thickened alveolar septa and there were increased macrophages in the bronchoalveolar lavage fluid (BALF) in the resolution phase. BALF from Cre+ lungs was more chemotactic for bone marrow-derived macrophages than Cre- in in vitro experiments, but there were no differences in the elaboration of chemokines in vivo. We speculate that absence of NPNT in BMs of the alveoli impairs or delays inflammatory and injury resolution in this model, but further studies are needed to establish the precise role of NPNT in tissue repair.
肺的急性损伤涉及到上皮细胞及其下的细胞外基质（ECM）和基底膜（BM）的损伤。BM 如何促进损伤的恢复还不太清楚。肾细胞黏附分子（NPNT）是整合素α8β1的高亲和力配体，尽管最初在小鼠肾脏中被鉴定出来，但在肺中表达丰富，在那里它定位于肺泡的 BM 中。为了确定 NPNT 是否在肺的急性损伤和炎症中发挥作用，我们使用带有 Npnt 基因 floxed 等位基因的小鼠与在 ROSA 基因座表达的可诱导 Cre 重组酶的组合，开发了一种用于出生后 NPNT 缺失的模型。在经他莫昔芬处理的 Cre+动物的肺中，NPNT 的表达显著降低。用 E. coli LPS 通过口咽吸入给予 Cre+小鼠和 Cre-对照小鼠，以诱导损伤和炎症。在 Cre-肺中，尽管炎症高峰期时 Npnt 和 Itga8（整合素α8）转录本均下调，但仍可检测到 NPNT 蛋白。尽管 Cre+和 Cre-肺的炎症起始相似，但 NPNT 缺乏的肺仍然有增厚的肺泡间隔，在恢复阶段支气管肺泡灌洗液（BALF）中的巨噬细胞增加。体外实验中，来自 Cre+肺的 BALF 对骨髓来源的巨噬细胞的趋化性比 Cre-更强，但体内趋化因子的产生没有差异。我们推测，肺泡 BM 中 NPNT 的缺失会损害或延迟该模型中的炎症和损伤恢复，但需要进一步的研究来确定 NPNT 在组织修复中的精确作用。
