Fudala Rafal, Krupa Agnieszka, Matthay Michael A, Allen Timothy C, Kurdowska Anna K
Department of Biochemistry, University of Texas Health Center, Tyler, TX 75708-3154, USA.
Am J Physiol Lung Cell Mol Physiol. 2007 Aug;293(2):L364-74. doi: 10.1152/ajplung.00179.2006. Epub 2007 May 18.
Our previous studies demonstrated that a significant fraction of interleukin-8 (IL-8) in lung fluids from patients with acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 immune complexes). Neutrophils have been implicated in the pathogenesis of ALI/ARDS, and moreover, it is well-established that apoptosis of neutrophils is delayed in patients with ALI/ARDS. The aim of this study was, therefore, to examine the role of anti-IL-8:IL-8 immune complexes in modulating spontaneous apoptosis of normal human neutrophils. Apoptosis was assessed by evaluating morphological changes, measuring enzymatic activity of caspase-3, and determining the extent of DNA degradation. We found that samples containing anti-IL-8:IL-8 immune complexes but not samples from which these complexes were removed inhibited neutrophil apoptosis. Furthermore, the former samples or effectively anti-IL-8:IL-8 complexes induced an increase in the level of antiapoptotic protein, Bcl-X(L). In contrast, levels of proapoptotic proteins Bax and Bak were decreased in the same conditions. Activity of both caspase-3 and caspase-9 was also suppressed by anti-IL-8:IL-8 complex-containing samples. Finally, we established that IgG receptor, FcgammaRIIa, mediates antiapoptotic activity of anti-IL-8:IL-8 complexes and that the key components of the FcgammaRIIa signaling pathway, Src, Syk, PI3 kinase, and ERK, may be involved in regulation of neutrophil apoptosis by the complexes. These studies demonstrate for the first time that anti-IL-8:IL-8 immune complexes have the ability to prolong neutrophil life.
我们之前的研究表明，急性肺损伤（ALI）和急性呼吸窘迫综合征（ARDS）患者肺液中的很大一部分白细胞介素-8（IL-8）与抗IL-8自身抗体（抗IL-8：IL-8免疫复合物）有关。中性粒细胞与ALI/ARDS的发病机制有关，此外，众所周知，ALI/ARDS患者中性粒细胞的凋亡会延迟。因此，本研究的目的是探讨抗IL-8：IL-8免疫复合物在调节正常人中性粒细胞自发凋亡中的作用。通过评估形态变化、测量半胱天冬酶-3的酶活性以及确定DNA降解程度来评估凋亡。我们发现，含有抗IL-8：IL-8免疫复合物的样本而非去除了这些复合物的样本抑制了中性粒细胞凋亡。此外，前者样本或有效的抗IL-8：IL-8复合物诱导抗凋亡蛋白Bcl-X(L)水平升高。相比之下，在相同条件下促凋亡蛋白Bax和Bak的水平降低。含抗IL-8：IL-8复合物的样本也抑制了半胱天冬酶-3和半胱天冬酶-9的活性。最后，我们确定IgG受体FcγRIIa介导抗IL-8：IL-8复合物的抗凋亡活性，并且FcγRIIa信号通路的关键成分Src、Syk、PI3激酶和ERK可能参与复合物对中性粒细胞凋亡的调节。这些研究首次证明抗IL-8：IL-8免疫复合物具有延长中性粒细胞寿命的能力。
