The Thromboxane-Prostanoid Receptor in Radiation-Induced Pulmonary Fibrosis

项目总结： 放射性肺损伤是接受胸部放射治疗的患者的关键剂量限制因素，影响 即使使用较新的放射治疗技术，也有相当大比例的患者。这项提案调查了一个 可直接靶向限制渐进性辐射诱导的成纤维细胞激活的新途径 肺纤维化。我们发现血栓烷-前列腺素受体(TPR)在人体内有结构性表达。 和小鼠纤维化肺成纤维细胞，以及药物抑制或条件性基因消融 TPR明显减轻电离辐射所致小鼠肺纤维化 氧化应激或Hermansky-Pudlak综合征。尽管血栓烷A2是TPR的主要配体，但我们发现 TPR信号由F2-异前列腺素(F2-Isoprostanes，F2-Isoprostanes)驱动 花生四烯酸的氧化。我们已经证明了电离辐射诱导细胞中F2-IsoP的产生 与博莱霉素一样，在培养和体内的小鼠肺组织中也是如此。特发性高血压患者F2-Isop升高 在这种疾病中，肺纤维化是由于氧化应激引起的，但在发生这种疾病的患者中，肺纤维化是否增加 放射性肺纤维化(RIPF)尚不清楚，尽管临床前和临床研究提供了关键 支持非酶自由基氧化花生四烯酸信号的总体假设 对RIPF有重大贡献。我们假设一个促成因素是通过钙诱导的钙蛋白- 介导转化生长因子β从肺成纤维细胞的潜伏复合体中释放。小分子伊非曲班是TPR 经过广泛的人体测试并具有极好的安全性的拮抗剂。因此，研究 验证TPR拮抗剂抑制RIPF可以通过改变现有和安全的用途而导致快速翻译 毒品。然而，在临床试验之前，我们的知识中有一些关键的空白需要填补。 恰如其分。首先，治疗需要在包括免疫在内的现有护理标准的背景下奏效 检查点疗法。第二，尽管血栓烷或F2-Isop很可能在 RIPF，我们需要验证接受胸部放射治疗的患者实际上显示出一个或多个 这些分子。最后，我们需要更好地了解TPR调节肺功能的机制 辐射背景下肌成纤维细胞的分化和激活。这项提案的目标是填补这些 差距。

Project Summary: Radiation induced lung injury is a crucial dose-limiting factor in patients receiving thoracic radiotherapy, affecting a significant proportion of patients even with use of newer radiotherapy techniques. This proposal investigates a novel pathway regulating fibroblast activation that can be directly targeted to limit progressive radiation-induced lung fibrosis. We found that the thromboxane-prostanoid receptor (TPr) was constitutively expressed in human and murine fibrotic pulmonary fibroblasts and that pharmacological inhibition or conditional genetic ablation of the TPr markedly attenuated pulmonary fibrosis in mice resulting from ionizing radiation, bleomycin-induced oxidative stress or Hermansky-Pudlak syndrome. Although thromboxane A2 is a major ligand for TPr, we found that TPr signaling was being driven by F2-isoprostanes (F2-IsoPs), resulting from non-enzymatic, free-radical oxidation of arachidonic acid. We have demonstrated that ionizing radiation induces F2-IsoP generation in cell culture and in murine pulmonary tissue in vivo, as does bleomycin. F2-IsoPs are increased in idiopathic pulmonary fibrosis due to oxidative stress in this disease, but whether they are increased in patients who develop radiation-induced pulmonary fibrosis (RIPF) is unknown, although preclinical and clinical studies provide key support for the overall hypothesis that non-enzymatic free radical-induced oxidation of arachidonic acid signaling significantly contributes to RIPF. We hypothesize that a contributing factor is via calcium-induced calpain- mediated release of TGFβ from the latent complex in lung fibroblasts. The small molecule ifetroban is a TPr antagonist that has undergone extensive human testing and has an excellent safety profile. Thus, research validating TPr antagonism in inhibiting RIPF could result in rapid translation via repurposing of existing and safe drugs. However, there are key gaps in our knowledge that need to be filled before a clinical trial would be appropriate. First, the therapy would need to work in the context of existing standard of care, including immune checkpoint therapy. Second, although it is likely that there is an increase in either thromboxane or F2-IsoPs in RIPF, we need to verify that patients receiving thoracic radiation actually show an increase in one or more of these molecules. Finally, we need a better understanding of the mechanism by which TPr regulates pulmonary myofibroblast differentiation and activation in the context of radiation. The goal of this proposal is to fill these gaps.