Transcriptional profiling and functional characterization of Schistosoma japonicum-stimulated Alternatively Activated Macrophages. Mus musculus

Alternatively activated macrophages (AAMφs) play important roles in a number of Th2 driven pathologies including asthma and allergy, and a number of parasitic infections. Our studies, and those of others, investigating the pathologies associated with infection with the helminth Schistosoma japonicum implicate a role for AAMφs in fibrosis and immunomodulation.. In the present study we show that S. japonicum-secreted egg antigens are able to induce the alternative activation of macrophages as characterised by the induction of Chi3l3 and Arg1 expression. Retnla, another common marker of AAMφs, was not consistently induced in these macrophages suggesting that the specific function of these cells may differ to those induced by S. mansoni and other parasites. Closer examination of the gene expression profile and functionality of these cells identified pathways independent of Retnla expression that could be important for their immunomodulatory activity such as modulating expression of T-cell co-stimulatory molecules and chemokines. In vivo generated S. japonicum soluble egg antigen stimulated AAMφs also exhibited a reduction in their phagocytic ability likely related to the induction of IL4 and decreased expression of cell surface receptors. Additionally these macrophages exhibited reduced expression of Toll-like receptors (TLRs) and an associated reduction in responsiveness to stimulation with TLR ligands. We did not observe pathways that would suggest that AAMφs have a direct profibrotic activity. Taken together, these data describe a mechanism by which alternative activation of macrophages may be induced during S. japonicum infection and highlight the importance of the context of activation in directing AAMφ phenotype and function. Overall design: The gene expression profile of Schistosoma japonicum soluble egg antigen (SEA)-stimulated macrophages was compared with that of PBS stimulated controls. Macrophages were isolated from the peritoneal cavity of BALB/c mice (n=6 per group) stimulated by intraperitoneal injection with SEA or PBS. The macrophages were pooled and RNA was extracted from these cells. Microarray analysis was performed on cRNA synthesised from total RNA derived from these macrophages. The experiment was performed twice creating two biological replicates. Fold-change (relative to the respective PBS control) reported in supplementary file linked below.

交替激活的巨噬细胞（Alternatively activated macrophages, AAMφs）在多种由Th2细胞驱动的病理状态中发挥关键作用，包括哮喘、过敏与多种寄生虫感染。本课题组及其他学者针对日本血吸虫（Schistosoma japonicum）感染相关病理的研究证实，AAMφs在纤维化发生与免疫调节中具有重要作用。
本研究显示，日本血吸虫分泌的卵抗原可诱导巨噬细胞发生交替激活，该激活效应可通过几丁质酶3样蛋白3（Chi3l3）与精氨酸酶1（Arg1）的表达上调得以验证。而AAMφs的另一经典标志物抵抗素样分子α（Retnla）在这类巨噬细胞中未出现稳定诱导表达，提示此类细胞的特定功能或与曼氏血吸虫（S. mansoni）及其他寄生虫诱导的AAMφs存在差异。
对这类细胞的基因表达谱与功能进行更细致的分析后，我们发现了不依赖Retnla表达的通路，这类通路可能与其免疫调节活性密切相关，例如可调控T细胞共刺激分子与趋化因子的表达。体内诱导的日本血吸虫可溶性卵抗原（SEA）刺激的AAMφs，其吞噬能力出现下降，该现象可能与白细胞介素4（IL4）的诱导表达以及细胞表面受体表达下调有关。此外，这类巨噬细胞的Toll样受体（TLRs）表达水平降低，且对TLR配体刺激的响应能力也随之减弱。本研究未观察到提示AAMφs具有直接促纤维化活性的通路。
综上，本研究阐明了日本血吸虫感染期间巨噬细胞交替激活的潜在诱导机制，并强调了激活环境在决定AAMφs表型与功能中的重要性。
整体实验设计：将日本血吸虫可溶性卵抗原（SEA）刺激的巨噬细胞的基因表达谱与PBS刺激的对照组进行对比。实验对象为BALB/c小鼠，通过腹腔注射SEA或PBS进行刺激，每组取6只小鼠，分离其腹腔巨噬细胞并混合，随后提取细胞总RNA。以该总RNA合成cRNA后进行基因芯片分析。本实验重复两次，获得两个生物学重复。倍数变化（相对于对应PBS对照组）详见下文附件补充文件。