miRNA-mediated regulation of LPS tolerance

 描述（由申请人提供）：炎症反应是由基因表达的仔细平衡模式引起的，其设计用于控制微生物感染，同时限制 破坏性炎症炎性细胞因子的过度产生有助于感染触发的全身性炎性病症脓毒症的进展。在可能是针对这种有害结果的保护性反应中，巨噬细胞变得耐受促炎剂如脂多糖（LPS）的长期治疗。耐受性巨噬细胞在再刺激时减少促炎细胞因子的产生，有利于抗炎和抗微生物基因。然而，这种现象的分子基础并没有明确定义。不同的机制可以导致选择性的基因表达过程中看到，如诱导耐受。特别是微小RNA（miRNAs）已经成为选择性基因表达的重要转录后调节因子。到目前为止，还没有发现miRNA选择性地影响转录的方式，概括了在LPS耐受性期间注意到的基因表达变化。然而，我们已经鉴定了许多miRNA种类，它们在长时间暴露于LPS处理后在巨噬细胞中表达，并且似乎选择性地调节炎症相关基因的表达。miR-222是在我们的筛选中鉴定的最高表达的miRNA，并且我们的初步结果表明miR-222靶向巨噬细胞中SWI/SNF重塑复合物的Brg 1亚基。这种靶向导致炎性细胞因子亚群的产生减弱;然而，它使TLR 4信号传导保持完整。考虑到miR-222表达的动力学，以及新定义的miR-222靶点Brg 1已被证明在LPS耐受化过程中介导选择性启动子处的染色质重塑，我们假设miR-222可能是真正的耐受性调节剂。我们计划利用基因组分析和一种新的遗传模型来验证miR-222作为耐受性调节因子的作用。该项目对设计治疗药物以急性诱导耐受和对抗脓毒症进展期间的炎症具有令人兴奋的意义。

 DESCRIPTION (provided by applicant): The inflammatory response results from a carefully balanced pattern of gene expression that is designed to control microbial infection, while limiting damaging inflammation. Excessive production of inflammatory cytokines contributes to the progression of the infection-triggered systemic inflammatory condition, sepsis. In what may be a protective response against this deleterious outcome, macrophages become tolerant to prolonged treatment with pro-inflammatory agents such as lipopolysaccharide (LPS). Tolerant macrophages reduce production of pro-inflammatory cytokines in favor of anti- inflammatory and anti-microbial genes upon re-stimulation. However, the molecular basis of this phenomenon is not clearly defined. Diverse mechanisms can lead to the selective gene expression seen during processes such as the induction of tolerance. MicroRNAs (miRNAs), in particular, have emerged as important post-transcriptional regulators of selective gene expression. Thus far, no miRNA has been found to selectively affect transcription in a way that recapitulates the gene expression changes noted during LPS tolerance. However, we have identified a number of miRNA species that are expressed in macrophages after prolonged exposure to LPS treatment and which appear to selectively modulate the expression of inflammation-related genes. miR-222 was the most highly expressed of the miRNAs identified in our screen, and our preliminary results suggest that miR-222 targets the Brg1 subunit of the SWI/SNF remodeling complex in macrophages. This targeting leads to attenuated production of a subset of inflammatory cytokines; however, it leaves TLR4 signaling intact. Given the kinetics of miR-222 expression, and the fact that the newly defined miR-222 target, Brg1, has been shown to mediate chromatin remodeling at selective promoters during LPS tolerization, we hypothesize that miR-222 may be a bona fide regulator of tolerance. We plan to utilize genomic analysis and a novel genetic model to validate the role of miR-222 as a regulator of tolerance. This project has exciting implications for the design of therapeutics to acutely induce tolerance and combat inflammation during sepsis progression.