Shi M M, Chong I W, Long N C, Love J A, Godleski J J, Paulauskis J D
Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.
Inflammation. 1998 Feb;22(1):29-43. doi: 10.1023/a:1022391623063.
Chemokines are important inflammatory mediators that function by activating and recruiting leukocytes to an inflamed tissue. We have recently cDNA cloned the rat chemokine macrophage inflammatory protein-1 alpha (MIP-1 alpha) (1). In the present study, we characterize the biological function of recombinant MIP-1 alpha protein and describe expression of its mRNA both in vitro and in a rat model of lung inflammation. In vitro rat rMIP-1 alpha protein was chemotactic for both polymorphonuclear leukocytes (PMNs) and macrophages with maximal activity at 50 nM for both cell types. In in vivo studies, we found that intratracheal instillation of 1 and 5 micrograms of rMIP-1 alpha resulted in a significant (P < 0.05) influx of cells, primarily monocytes/macrophages, into the airspace of the lungs after 6 h. Mean numbers of lavagable PMNs were not elevated significantly (P < 0.05) for either dose of MIP-1 alpha. As a model of inflammation, rats were intratracheally instilled with 0.1 mg/kg bacterial lipopolysaccharide (LPS). Bronchoalveolar lavage (BAL) was performed 3 h later. Instillation of LPS resulted in an acute neutrophilia, but no significant change in lavagable macrophages. BAL cells from control animals (saline instilled) displayed no basal mRNA expression of either MIP-1 alpha or MIP-2 (positive control). In contrast, both MIP-1 alpha and MIP-2 mRNA levels increased markedly in BAL cells from rats instilled with LPS. The rat alveolar macrophage cell line (NR8383) also showed increased MIP-1 alpha mRNA levels in response to LPS (10 micrograms/ml) with a maximal increase after 6-8 h. The induction of MIP-1 alpha mRNA expression by LPS in NR8383 cells was attenuated by cotreatment with the antioxidants N-acetylcysteine and dimethylsulfoxide, suggesting that the induction of MIP-1 alpha mRNA by LPS is mediated via the generation of reactive oxygen species. We conclude that MIP-1 alpha is a potent chemoattractant for macrophages in vivo, and its mRNA expression in macrophages and BAL cells in response to inflammatory stimuli suggests a fundamental role in acute pulmonary inflammation.
趋化因子是重要的炎症介质，通过激活白细胞并将其募集到炎症组织发挥作用。我们最近已对大鼠趋化因子巨噬细胞炎性蛋白-1α（MIP-1α）进行了cDNA克隆（1）。在本研究中，我们对重组MIP-1α蛋白的生物学功能进行了表征，并描述了其mRNA在体外和大鼠肺部炎症模型中的表达情况。在体外，大鼠重组MIP-1α蛋白对多形核白细胞（PMN）和巨噬细胞均具有趋化作用，两种细胞类型在50 nM时活性最高。在体内研究中，我们发现气管内滴注1微克和5微克的重组MIP-1α后，6小时后肺脏气腔内出现明显（P < 0.05）的细胞流入，主要是单核细胞/巨噬细胞。两种剂量的MIP-1α均可使可冲洗出的PMN平均数量未显著升高（P < 0.05）。作为炎症模型，给大鼠气管内滴注0.1 mg/kg细菌脂多糖（LPS）。3小时后进行支气管肺泡灌洗（BAL）。滴注LPS导致急性中性粒细胞增多，但可冲洗出的巨噬细胞无显著变化。对照动物（滴注生理盐水）的BAL细胞未显示MIP-1α或MIP-2（阳性对照）的基础mRNA表达。相反，在滴注LPS的大鼠的BAL细胞中，MIP-1α和MIP-2的mRNA水平均显著升高。大鼠肺泡巨噬细胞系（NR8383）对LPS（10微克/毫升）的反应也显示MIP-1α mRNA水平升高，在6 - 8小时后达到最大增幅。在NR8383细胞中，LPS诱导的MIP-1α mRNA表达可被抗氧化剂N-乙酰半胱氨酸和二甲基亚砜共同处理所减弱，这表明LPS诱导MIP-1α mRNA是通过活性氧的产生介导的。我们得出结论，MIP-1α在体内是巨噬细胞的有效趋化剂，其在巨噬细胞和BAL细胞中对炎症刺激的mRNA表达表明其在急性肺部炎症中起重要作用。
