Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Brody School of Medicine- East Carolina University, Greenville, NC, United States.
Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt.
Front Immunol. 2020 Sep 18;11:553949. doi: 10.3389/fimmu.2020.553949. eCollection 2020.
Sarcoidosis is a chronic inflammatory disease of unknown cause characterized by granuloma formation. Mechanisms for chronic persistence of granulomas are unknown. Matrix Metalloproteinase-12 (MMP12) degrades extracellular matrix elastin and enables infiltration of immune cells responsible for inflammation and granuloma formation. Previous studies report increased MMP12 in sarcoidosis patients and association between MMP12 expression and disease severity. We also observed elevated MMP12 in our multiwall carbon nanotube (MWCNT) murine model of granulomatous inflammation. Here we hypothesized that MMP12 is important to acute and late phases of granuloma pathogenesis. To test this hypothesis, we analyzed granulomatous and inflammatory responses of (KO) mice at 10 (acute) and 60 days (late) after MWCNT instillation.
C57BL/6 (wildtype) and KO mice underwent oropharyngeal instillation of MWCNT. Lungs were harvested at 3, 10, 20, and 60 days post instillation for evaluation of MMP12 expression and granulomatous changes. Bronchoalveolar lavage (BAL) cells were analyzed 60 days after MWCNT instillation for expression of mediators thought to play a role in sarcoid granulomatosis: peroxisome proliferator-activated receptor-gamma (PPARγ), interferon-gamma (IFN-γ), and CCL2 (MCP-1).
Pulmonary granuloma appearance at 10 days after MWCNT instillation showed no differences between wildtype and KO mice. In contrast, by 60 days after MWCNT instillation, KO mice revealed markedly attenuated granuloma formation together with elevated PPARγ and reduced IFNγ expression in BAL cells compared to wildtype. Unexpectedly, KO mice further demonstrated increased alveolar macrophages with increased CCL2 at 60 days.
The striking reduction of granuloma formation at day 60 in KO mice suggests that MMP12 is required to maintain chronic granuloma pathophysiology. The increased PPARγ and decreased IFNγ findings suggest that these mediators also may be involved since previous studies have shown that PPARγ suppresses IFNγ and PPARγ deficiency amplifies granuloma formation. Interestingly, a role of MMP12 in granuloma resolution is also suggested by increases in both macrophage influx and CCL2. Overall, our results strongly implicate MMP12 as a key factor in granuloma persistence and as a possible therapeutic target in chronic pulmonary sarcoidosis.
结节病是一种病因不明的慢性炎症性疾病,其特征是肉芽肿形成。肉芽肿持续存在的机制尚不清楚。基质金属蛋白酶 12(MMP12)降解细胞外基质弹性蛋白,并使负责炎症和肉芽肿形成的免疫细胞浸润。先前的研究报告表明,结节病患者的 MMP12 增加,并且 MMP12 表达与疾病严重程度之间存在关联。我们还观察到我们的多壁碳纳米管(MWCNT)肉芽肿性炎症小鼠模型中 MMP12 的升高。在这里,我们假设 MMP12 对肉芽肿发病的急性和晚期阶段很重要。为了验证这一假设,我们分析了 MWCNT 注入后 10 天(急性)和 60 天(晚期)的 (KO) 小鼠的肉芽肿和炎症反应。
C57BL/6(野生型)和 KO 小鼠进行口咽部 MWCNT 滴注。MWCNT 滴注后 3、10、20 和 60 天采集肺组织,评估 MMP12 表达和肉芽肿变化。MWCNT 滴注 60 天后分析支气管肺泡灌洗液(BAL)细胞中被认为在结节性肉芽肿病中起作用的介质的表达:过氧化物酶体增殖物激活受体-γ(PPARγ)、干扰素-γ(IFN-γ)和 CCL2(MCP-1)。
MWCNT 注入后 10 天,肺部肉芽肿外观在野生型和 KO 小鼠之间没有差异。相比之下,MWCNT 注入后 60 天,与野生型相比, KO 小鼠的肉芽肿形成明显减弱,BAL 细胞中的 PPARγ 升高,IFNγ 表达降低。出乎意料的是, KO 小鼠在 60 天时还显示出肺泡巨噬细胞增加,CCL2 增加。
在 KO 小鼠中,60 天时肉芽肿形成的明显减少表明 MMP12 是维持慢性肉芽肿病理生理学所必需的。PPARγ 降低和 IFNγ 降低的发现表明这些介质也可能参与其中,因为先前的研究表明 PPARγ 抑制 IFNγ,PPARγ 缺乏会放大肉芽肿形成。有趣的是,MMP12 在肉芽肿消退中的作用也通过巨噬细胞流入和 CCL2 的增加得到提示。总的来说,我们的结果强烈表明 MMP12 是肉芽肿持续存在的关键因素,并且可能是慢性肺结节病的潜在治疗靶点。