TRPV4/β-catenin通过上调气道上皮HMGB1表达参与调控哮喘气道炎症

Toluene-2,4-diisocyanate (TDI) is an important cause of asthma, which is often dominated by granulocytic inflammation in the airway. Emerging evidence suggests that dysfunction of airway epithelial cells plays an important role in the pathogenesis of TDI-induced asthma. The epithelial adherent junction protein β-catenin exerts dual roles in asthma. We’ve found that blocking β-catenin signaling could attenuate TDI-induced airway inflammation. .High mobility group box 1 (HMGB1) is a DNA-binding protein that is abundantly expressed in most tissues. Recently, HMGB1 has gained much attention for its regulation of immunity and inflammation. Researchers have already demonstrated the critical role of HMGB1 in the initiation of asthmatic airway inflammation and hyperresponsiveness, yet the upstream signaling of HMGB1 is largely unknown. .Transient receptor potential vanilloid 4 (TRPV4) is one of the ion channels found to be expressed in the airway, the role of which in airway diseases has attracted much attention. Recently, it has been proposed to contribute to the pathogenesis of asthma. But the exact functions as well as mechanisms involved are yet to be discovered. In our preliminary experiments, we found that TDI-induced neutrophilc and eosinophilic airway inflammation together with airway hyperreactivity was significantly decreased by treatment with TRPV4 inhibitor. Immunohistochemistry revealed that cytoplasmic and nuclear translocation of β-catenin in airway epithelia was also alleviated, accompanied by decreased pulmonary HMGB1 expression. Previously we’ve demonstrated that β-catenin signaling also participates in the increase of HMGB1 expression in TDI-induced asthma model. Hereby, we proposed that TRPV4/β-catenin axis orchestrates TDI-induced airway inflammation through upregulating HMGB1 expression in airway epithelial cell. .This study will be further conducted in animal models and airway epithelial cell lines to test and to identify whether and how TRPV4/β-catenin signaling mediates the TDI-induced airway inflammation and HMGB1 expression. The study will add to our understanding of the role of TRPV4/β-catenin signaling in asthma.

HMGB1是哮喘发病的关键因子，气道上皮细胞是其主要来源之一。我们前期研究发现TDI哮喘肺组织HMGB1升高，气道上皮HMGB1表达亦增多，拮抗β-catenin信号可抑制TDI哮喘气道炎症及肺组织HMGB1表达，然β-catenin信号是否参与气道上皮细胞HMGB1表达及其上游调控机制尚不清楚。前期我们发现TRPV4激动剂可上调气道上皮细胞HMGB1的蛋白水平，体内拮抗TRPV4不仅减轻了TDI诱导的哮喘小鼠气道炎症，抑制了气道上皮β-catenin核转位，也同时下调了肺组织HMGB1的表达，免疫组化显示气道上皮HMGB1表达也显著减少。因此，我们猜想：TRPV4/β-catenin信号可通过促进气道上皮释放HMGB1参与调控TDI哮喘发病。本项目拟从动物和细胞水平探讨TRPV4/β-catenin对TDI哮喘中HMGB1的调控作用和机制，找出新药作用靶点，为哮喘防控提供新的理论依据。

甲苯二异氰酸酯（TDI）是引起成人哮喘非常重要的致病因素之一，不仅可单独诱发以大量中性粒细胞和少量嗜酸性粒细胞浸润为特征的气道炎症，而且还能加重原有哮喘。临床及动物实验数据均显示TDI哮喘对激素治疗的反应性较差，探讨TDI哮喘的发生发展机理对于寻找激素不敏感型哮喘新的治疗策略具有重要意义。.气道上皮细胞是机体抵御“外敌”的第一道防线，不仅构成物理屏障，且在哮喘致敏及炎症启动、维持过程中发挥着最为根本的作用。HMGB1是哮喘发病的关键因子，气道上皮细胞是其主要来源之一。本项目的研究目的是探讨TRPV4/β-catenin信号是否可通过调节气道上皮HMGB1生成而参与TDI哮喘发病。研究内容分两部分：1、明确TRPV4在TDI哮喘气道炎症中的作用；2、探讨TRPV4/β-catenin调控气道上皮HMGB1生成的分子机制。结果显示：TDI暴露可上调模型小鼠肺组织及气道上皮TRPV4表达、活化β-catenin信号，并促进HMGB1释放；阻断TRPV4可显著减轻TDI诱导的哮喘气道炎症及气道高反应性，抑制β-catenin活化及HMGB1释放；用药物阻断β-catenin信号同样可以减少肺组织及气道上皮HMGB1表达。体外实验发现，TDI可以刺激气道上皮细胞β-catenin入核及HMGB1分泌，干预TRPV4可抑制β-catenin入核及HMGB1分泌，干预β-catenin信号也可以干扰HMGB1的生成；而予TRPV4激动剂4α-PDD单独处理气道上皮细胞后，可观察到β-catenin信号被激活。这些实验结果证明了TRPV4/β-catenin信号通过调控气道上皮HMGB1生成参与TDI哮喘发病。本项目揭示了哮喘发病的新机制，为寻找激素不敏感型哮喘新的治疗靶点提供了更多理论依据。