Department of Surgery, University of Texas Southwestern, Dallas, TX, USA.
Department of Surgery, University of Texas Southwestern, Dallas, TX, USA.
Burns. 2022 Feb;48(1):168-175. doi: 10.1016/j.burns.2021.04.007. Epub 2021 Apr 18.
Damage associated molecular patterns (DAMPs) are pathological mediators linking local tissue damage to systemic inflammation in various diseases. Some DAMPs, such as mitochondrial DNA (mtDNA), can be recognized by the cytoplasmic cGAS protein to trigger the activation of the stimulator of interferon genes (STING)-dependent innate immune pathway responsible for infection or sterile inflammation. The objective of our study was to evaluate the association between circulating mtDNA and cGAS-STING pathway activation in mediating inflammation following burn injury.
48 adult Sprague-Dawley male rats were divided into eight groups (Sham, 2, 4, 8, 12, 24, 48, 72 h after burn injury). The animals underwent 40% total body surface area scald injury to produce a full-thickness burn. Plasma samples were collected via cardiac puncture under deep anesthesia. Tissues were harvested and placed in formalin, followed by paraffin embedment. Total plasma DNA was isolated followed by measurement of mtDNA using quantitative polymerase chain reaction. Haemotoxylin-Eosin stain and Western blot was used for lung histology and protein assays, respectively. Statistical analyses were performed using ANOVA and student's t-test and represented as mean ± s.d.
Plasma mtDNA trended upward at early time-points following burn injury with peak levels at 8 h after burn when compared to the control group (345 ± 83.4 copies/μl vs. 239 ± 43.1 copies/μl, p = 0.07) and followed a bell-shaped distribution. Lung slices from burned rats showed acute injury marked by increased inflammatory infiltrate, with the maximum changes seen at 24 h, accompanied with significant upregulation of neutrophil elastase (p = 0.04). Compared with sham animals, cGAS and STING protein levels in lung tissue were up-regulated at 4 and 8 h after burn (p = 0.03 and p < 0.001, respectively).
Activation of the cGAS-STING pathway by increased plasma mtDNA is an important pathway driving neutrophil infiltration in burn-induced acute lung injury in rats. A further understanding of the STING-mediated immunopathology in lung and other susceptible organs may be important for the development of novel therapies for burn injury.
损伤相关分子模式（DAMPs）是将局部组织损伤与各种疾病中的全身炎症联系起来的病理介质。一些 DAMPs，如线粒体 DNA（mtDNA），可以被细胞质 cGAS 蛋白识别，从而触发干扰素基因刺激物（STING）依赖性先天免疫途径的激活，该途径负责感染或无菌性炎症。我们的研究目的是评估循环 mtDNA 与 cGAS-STING 通路激活在介导烧伤后炎症中的相关性。
将 48 只成年 Sprague-Dawley 雄性大鼠分为 8 组（假手术、烧伤后 2、4、8、12、24、48、72 h）。动物接受 40%总体表面积烫伤损伤以产生全层烧伤。在深度麻醉下通过心脏穿刺采集血浆样本。采集组织并置于福尔马林中，然后进行石蜡包埋。分离总血浆 DNA 后，通过定量聚合酶链反应测量 mtDNA。苏木精-伊红染色和 Western blot 分别用于肺组织学和蛋白质检测。使用方差分析和学生 t 检验进行统计分析，并表示为均值±标准差。
与对照组相比，烧伤后早期血浆 mtDNA 呈上升趋势，烧伤后 8 小时达到峰值（345±83.4 拷贝/μl 比 239±43.1 拷贝/μl，p=0.07），呈钟形分布。烧伤大鼠的肺切片显示急性损伤，以炎症浸润增加为特征，最大变化发生在 24 小时，伴有中性粒细胞弹性蛋白酶的显著上调（p=0.04）。与假手术动物相比，烧伤后 4 小时和 8 小时肺组织中 cGAS 和 STING 蛋白水平上调（p=0.03 和 p<0.001）。
循环 mtDNA 增加激活 cGAS-STING 途径是驱动大鼠烧伤后急性肺损伤中性粒细胞浸润的重要途径。进一步了解 STING 介导的肺和其他易感器官的免疫病理学可能对烧伤损伤的新型治疗方法的发展很重要。
