A Key Role for the Endothelium in NOD1 Mediated Vascular Inflammation: Comparison to TLR4 Responses

Understanding the mechanisms by which pathogens induce vascular inflammation and dysfunction may reveal novel therapeutic targets in sepsis and related conditions. The intracellular receptor NOD1 recognises peptidoglycan which features in the cell wall of Gram negative and some Gram positive bacteria. NOD1 engagement generates an inflammatory response via activation of NFκB and MAPK pathways. We have previously shown that stimulation of NOD1 directly activates blood vessels and causes experimental shock in vivo. In this study we have used an ex vivo vessel-organ culture model to characterise the relative contribution of the endothelium in the response of blood vessels to NOD1 agonists. In addition we present the novel finding that NOD1 directly activates human blood vessels. Using human cultured cells we confirm that endothelial cells respond more avidly to NOD1 agonists than vascular smooth muscle cells. Accordingly we have sought to pharmacologically differentiate NOD1 and TLR4 mediated signalling pathways in human endothelial cells, focussing on TAK1, NFκB and p38 MAPK. In addition we profile novel inhibitors of RIP2 and NOD1 itself, which specifically inhibit NOD1 ligand induced inflammatory signalling in the vasculature. This paper is the first to demonstrate activation of whole human artery by NOD1 stimulation and the relative importance of the endothelium in the sensing of NOD1 ligands by vessels. This data supports the potential utility of NOD1 and RIP2 as therapeutic targets in human disease where vascular inflammation is a clinical feature, such as in sepsis and septic shock.

阐明病原体诱导血管炎症与功能障碍的机制，或可为脓毒症及相关疾病发掘全新治疗靶点。细胞内受体核苷酸结合寡聚化结构域蛋白1（NOD1）可识别存在于革兰氏阴性菌及部分革兰氏阳性菌细胞壁中的肽聚糖。NOD1激活可通过活化核因子κB（NFκB）与丝裂原活化蛋白激酶（MAPK）通路引发炎症反应。本团队此前研究证实，NOD1刺激可直接激活血管，并在活体中诱导实验性休克。本研究采用离体血管器官培养模型，解析血管内皮细胞在血管对NOD1激动剂应答过程中的相对作用。此外本研究还报道了一项全新发现：NOD1可直接激活人源血管。通过使用人源培养细胞，本团队证实内皮细胞相较于血管平滑肌细胞，对NOD1激动剂的应答更为强烈。据此，本研究旨在通过药理学手段区分人源内皮细胞中NOD1与Toll样受体4（TLR4）介导的信号通路，重点关注转化生长因子β激活激酶1（TAK1）、核因子κB（NFκB）以及p38丝裂原活化蛋白激酶（p38 MAPK）。此外本研究还筛选得到针对受体相互作用蛋白激酶2（RIP2）及NOD1本身的新型抑制剂，这类抑制剂可特异性抑制血管中NOD1配体诱导的炎症信号通路。本研究为首项证实NOD1刺激可激活完整人源动脉，并明确血管感知NOD1配体过程中内皮细胞相对重要性的研究。本研究数据支持将NOD1与RIP2作为治疗靶点的潜在应用价值，适用于以血管炎症为临床特征的人类疾病，例如脓毒症与脓毒性休克。