In human airway smooth muscle (hASM), mitochondrial volume density is greater in asthmatic patients compared to normal controls. There is also an increase in mitochondrial fragmentation in hASM of moderate asthmatics associated with an increase in Drp1 and a decrease in Mfn2 expression, mitochondrial fission and fusion proteins, respectively. Pro-inflammatory cytokines such TNFα contribute to hASM hyperreactivity and cell proliferation associated with asthma. However, the involvement of pro-inflammatory cytokines in mitochondrial remodeling is not clearly established. In non-asthmatic hASM cells, mitochondria were labeled using MitoTracker Red and imaged in 3-D using a confocal microscope. After 24-h TNFα exposure, mitochondria in hASM cells were more fragmented, evidenced by decreased form factor, aspect ratio and increased sphericity. Associated with increased mitochondrial fragmentation, Drp1 expression increased while Mfn2 expression was reduced. TNFα also increased mitochondrial biogenesis in hASM cells reflected by increased PGC1α expression and increased mitochondrial DNA copy number. Associated with mitochondrial biogenesis, TNFα exposure also increased mitochondrial volume density and porin expression, resulting in an increase in maximum O₂ consumption rate. However, when normalized for mitochondrial volume density, O₂ consumption rate per mitochondrion was reduced by TNFα exposure. Associated with mitochondrial fragmentation and biogenesis, TNFα also increased hASM cell proliferation, an effect mimicked by siRNA knockdown of Mfn2 expression and mitigated by Mfn2 overexpression. The results of this study support our hypothesis that in hASM cells exposed to TNFα mitochondria are more fragmented, with an increase in mitochondrial biogenesis and mitochondrial volume density resulting in reduced O₂ consumption rate per mitochondrion.

中文翻译：

---

TNFα 诱导人气道平滑肌线粒体断裂和生物发生


在人类气道平滑肌（hASM）中，哮喘患者的线粒体体积密度比正常对照者更大。中度哮喘患者 hASM 中线粒体碎片的增加分别与 Drp1 的增加和 Mfn2 表达、线粒体裂变和融合蛋白的减少相关。 TNFα 等促炎细胞因子会导致与哮喘相关的 hASM 高反应性和细胞增殖。然而，促炎细胞因子在线粒体重塑中的参与尚不清楚。在非哮喘 hASM 细胞中，使用 MitoTracker Red 标记线粒体，并使用共焦显微镜进行 3D 成像。暴露于 TNFα 24 小时后，hASM 细胞中的线粒体更加破碎，表现为形状因子、长宽比降低和球形度增加。与线粒体碎片增加相关，Drp1 表达增加，而 Mfn2 表达减少。 TNFα 还增加了 hASM 细胞中的线粒体生物合成，表现为 PGC1α 表达增加和线粒体 DNA 拷贝数增加。与线粒体生物合成相关，TNFα 暴露还增加了线粒体体积密度和孔蛋白表达，导致最大 O ₂消耗率增加。然而，当线粒体体积密度标准化时，每个线粒体的 O ₂消耗率因 TNFα 暴露而降低。 TNFα 与线粒体断裂和生物发生相关，还可以增加 hASM 细胞增殖，这种效应可通过 siRNA 敲低 Mfn2 表达来模拟，并通过 Mfn2 过表达来减轻。 这项研究的结果支持我们的假设，即在暴露于 TNFα 的 hASM 细胞中，线粒体更加破碎，线粒体生物发生和线粒体体积密度增加，导致每个线粒体 O ₂消耗率降低。