Hao H, Cohen D A, Jennings C D, Bryson J S, Kaplan A M
Department of Microbiology and Immunology, the Graduate Center for Toxicology, University of Kentucky, College of Medicine, Lexington 40536-0084, USA.
J Leukoc Biol. 2000 Oct;68(4):515-21.
Eosinophils have been shown to increase in tissues during many fibrotic conditions and consequently have been suggested to contribute to the development of fibrosis. This study tested the hypothesis that eosinophils are essential in the development of lung fibrosis in mice in response to bleomycin (BLM). Anti-IL-5 antibody was administered intraperitoneally into mice 2 h prior to endotracheal BLM inoculation and thereafter, every other day. Lung eosinophilia was evaluated by measurement of eosinophil peroxidase activity and confirmed by eosinophil counts in histologic sections. Lung fibrosis was evaluated by hydroxyproline content and confirmed by collagen staining in histological sections. Results demonstrated that BLM induced pronounced lung eosinophilia, which was maximal 7 days after BLM treatment and remained elevated through day 14, in C57B1/6 SCID mice and CBA/J mice. In contrast, eosinophilia was a minor component in the lungs of wildtype C57B1/6 mice after BLM treatment, although lung fibrosis developed similarly in all three strains of mice. Treatment with anti-IL-5 completely abrogated eosinophilia but failed to block pulmonary fibrosis induced by BLM in all mouse strains, including C57B1/6 SCID, wildtype C57B1/6 mice, and CBA/J mice. Analysis of cytokine mRNA by RNase-protection assay in C57B1/6 SCID mice indicated that BLM treatment caused enhanced expression of the cytokines, TNF-alpha, and IL-6 at days 3, 7, and 14 post-BLM inoculation, regardless of whether eosinophils were depleted by anti-IL-5. Finally, the importance of eosinophils in lung fibrosis was examined in IL-5 gene knockout mice (IL-5tm1Kopf). BLM treatment induced significant lung fibrosis in IL-5 knockout mice in the absence of eosinophilia. These findings indicate that eosinophils are not an absolute requirement for BLM-induced pulmonary fibrosis in the mouse.
在许多纤维化疾病中，嗜酸性粒细胞已被证明会在组织中增多，因此有人认为它们会促进纤维化的发展。本研究检验了以下假设：嗜酸性粒细胞在小鼠对博来霉素（BLM）产生反应而发生肺纤维化的过程中起关键作用。在内气管接种BLM前2小时，给小鼠腹腔注射抗IL-5抗体，此后每隔一天注射一次。通过测量嗜酸性粒细胞过氧化物酶活性评估肺嗜酸性粒细胞增多情况，并通过组织学切片中的嗜酸性粒细胞计数进行确认。通过羟脯氨酸含量评估肺纤维化情况，并通过组织学切片中的胶原染色进行确认。结果表明，在C57B1/6 SCID小鼠和CBA/J小鼠中，BLM诱导了明显的肺嗜酸性粒细胞增多，在BLM治疗后7天达到峰值，并在第14天一直保持升高。相比之下，虽然所有三种小鼠品系的肺纤维化发展情况相似，但在野生型C57B1/6小鼠中，BLM治疗后嗜酸性粒细胞增多只是肺部的一个次要成分。用抗IL-5治疗完全消除了嗜酸性粒细胞增多，但未能阻止所有小鼠品系中由BLM诱导的肺纤维化，包括C57B1/6 SCID、野生型C57B1/6小鼠和CBA/J小鼠。通过核糖核酸酶保护试验对C57B1/6 SCID小鼠的细胞因子mRNA进行分析表明，无论嗜酸性粒细胞是否被抗IL-5清除，BLM治疗在接种BLM后第3、7和14天都会导致细胞因子TNF-α和IL-6的表达增强。最后，在IL-5基因敲除小鼠（IL-5tm1Kopf）中研究了嗜酸性粒细胞在肺纤维化中的重要性。在没有嗜酸性粒细胞增多的情况下，BLM治疗在IL-5基因敲除小鼠中诱导了显著的肺纤维化。这些发现表明，嗜酸性粒细胞并非小鼠中BLM诱导的肺纤维化的绝对必要条件。
