Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA.
Biochem J. 2012 Feb 15;442(1):127-37. doi: 10.1042/BJ20111269.
Airway inflammation in allergen-induced asthma is associated with eicosanoid release. These bioactive lipids exhibit anti- and pro-inflammatory activities with relevance to pulmonary pathophysiology. We hypothesized that sensitization/challenge using an extract from the ubiquitous fungus Aspergillus fumigatus in a mouse model of allergic asthma would result in altered phospholipase gene expression, thus modulating the downstream eicosanoid pathway. We observed the most significant induction in the group IVC PLA2 (phospholipase A2) [also known as cPLA2γ (cytosolic PLA2γ) or PLA2G4C]. Our results infer that A. fumigatus extract can induce cPLA2γ levels directly in eosinophils, whereas induction in lung epithelial cells is most likely to be a consequence of TNFα (tumour necrosis factor α) secretion by A. fumigatus-activated macrophages. The mechanism of TNFα-dependent induction of cPLA2γ gene expression was elucidated through a combination of promoter deletions, ChIP (chromatin immunoprecipitation) and overexpression studies in human bronchoepithelial cells, leading to the identification of functionally relevant CRE (cAMP-response element), NF-κB (nuclear factor κB) and E-box promoter elements. ChIP analysis demonstrated that RNA polymerase II, ATF-2 (activating transcription factor 2)-c-Jun, p65-p65 and USF (upstream stimulating factor) 1-USF2 complexes are recruited to the cPLA2γ enhancer/promoter in response to TNFα, with overexpression and dominant-negative studies implying a strong level of co-operation and interplay between these factors. Overall, our results link cytokine-mediated alterations in cPLA2γ gene expression with allergic asthma and outline a complex regulatory mechanism.
变应原诱导的哮喘中的气道炎症与类二十烷酸释放有关。这些生物活性脂质具有抗炎和促炎活性，与肺病理生理学有关。我们假设，在过敏性哮喘的小鼠模型中，使用无处不在的真菌烟曲霉提取物进行致敏/挑战，将导致磷脂酶基因表达的改变，从而调节下游类二十烷酸途径。我们观察到 IVC PLA2（磷脂酶 A2）[也称为 cPLA2γ（胞质 PLA2γ）或 PLA2G4C]的表达显著上调。我们的结果推断，烟曲霉提取物可以直接在嗜酸性粒细胞中诱导 cPLA2γ 水平，而肺上皮细胞中的诱导很可能是烟曲霉激活的巨噬细胞分泌 TNFα（肿瘤坏死因子α）的结果。通过组合使用启动子缺失、ChIP（染色质免疫沉淀）和人支气管上皮细胞中的过表达研究，阐明了 TNFα 依赖性诱导 cPLA2γ 基因表达的机制，从而确定了功能相关的 CRE（cAMP 反应元件）、NF-κB（核因子κB）和 E-box 启动子元件。ChIP 分析表明，RNA 聚合酶 II、ATF-2（激活转录因子 2）-c-Jun、p65-p65 和 USF（上游刺激因子）1-USF2 复合物被募集到 cPLA2γ 增强子/启动子，以响应 TNFα，过表达和显性负突变研究暗示这些因素之间存在很强的合作和相互作用。总体而言，我们的研究结果将细胞因子介导的 cPLA2γ 基因表达改变与过敏性哮喘联系起来，并概述了一个复杂的调节机制。
