GCH1/BH4轴调控乳酸脱氢酶A（LDHA）S-亚硝基化修饰影响放射性肺损伤进展的机制研究

放射性肺损伤是肿瘤放疗常见并发症，与氧自由基（ROS）损伤密切相关。四氢生物蝶呤（BH4）是一氧化氮合成酶的必要辅因子，影响一氧化氮合成。本项目前期研究发现受照射肺细胞和动物肺组织中BH4合成限速酶GCH1的表达和磷酸化水平均明显下调，引起BH4合成抑制，降低乳酸脱氢酶A（LDHA）的S-亚硝基化水平，影响LDHA与NADH互作及自由基生成。据此，我们提出假说：GCH1/BH4轴通过调控LDHA的S-亚硝基化，影响其与NADH的相互作用，从而影响放射性肺损伤的进展。本项目拟进一步探索：1）GCH1表达、S81位磷酸化和BH4合成对肺和支气管细胞及小鼠模型放射敏感性的影响；2）采用纳米胶束负载BH4防治放射性肺损伤；3）BH4调控LDHA的S-亚硝基化影响受照射细胞自由基产生和损伤的分子机制。本项目有望从LDHA的亚硝基化修饰调控角度阐明放射性肺损伤进展的新机制，为其防治提供新的靶点和策略。

Radiation-induced pulmonary injury is a common complication of tumor radiotherapy, which is closely related to reactive oxygen species (ROS) damage. Tetrahydrobiopterin (BH4) is an essential cofactor of nitric oxide synthase (NOS), which affects nitric oxide (NO) synthesis. The preliminary study of this project found that the expression and phosphorylation levels of the rate-limiting enzyme GCH1 of BH4 synthesis were significantly down-regulated in irradiated lung cells and animal lung tissues, which resulted in inhibition of BH4 synthesis, decreased S-nitrosolation level of lactate dehydrogenase A (LDHA), and affected LDHA-NADH interaction and free radical generation. Based on this, we hypothesized that the GCH1/BH4 axis affects the interaction between LDHA and NADH by regulating the S-nitrosolation of LDHA, thereby influencing the progression of radiation lung injury. This project aims to further explore: 1) the effects of GCH1 expression, S81 phosphorylation, and BH4 synthesis on radiosensitivity of lung and bronchial cells and mouse models; 2) Nano-micellar loaded BH4 was used to prevent and treat radiation lung injury; 3) The molecular mechanism that BH4 regulates the S-nitrosolation of LDHA to affect the production of ROS and damage the irradiated cells. This project is expected to elucidate the new mechanism of the progression of radiation lung injury from the perspective of LDHA S-nitrosylation modification and regulation, and provide new targets and strategies for its prevention and treatment.