Role of TGF Beta and PPAR Alpha Signaling Pathways in Radiation Response of Locally Exposed Heart: Integrated Global Transcriptomics and Proteomics Analysis

Epidemiological
data from patients undergoing radiotherapy for
thoracic tumors clearly show the damaging effect of ionizing radiation
on cardiovascular system. The long-term impairment of heart function
and structure after local high-dose irradiation is associated with
systemic inflammatory response, contraction impairment, microvascular
damage, and cardiac fibrosis. The goal of the present study was to
investigate molecular mechanisms involved in this process. C57BL/6J
mice received a single X-ray dose of 16 Gy given locally to the heart
at the age of 8 weeks. Radiation-induced changes in the heart transcriptome
and proteome were investigated 40 weeks after the exposure. The omics
data were analyzed by bioinformatics tools and validated by immunoblotting.
Integrated network analysis of transcriptomics and proteomics data
elucidated the signaling pathways that were similarly affected at
gene and protein level. Analysis showed induction of transforming
growth factor (TGF) beta signaling but inactivation of peroxisome
proliferator-activated receptor (PPAR) alpha signaling in irradiated
heart. The putative mediator role of mitogen-activated protein kinase
cascade linking PPAR alpha and TGF beta signaling was supported by
data from immunoblotting and ELISA. This study indicates that both
signaling pathways are involved in radiation-induced heart fibrosis,
metabolic disordering, and impaired contractility, a pathophysiological
condition that is often observed in patients that received high radiation
doses in thorax.

针对胸部肿瘤接受放射治疗的患者的流行病学数据清晰表明，电离辐射（ionizing radiation）对心血管系统具有损伤作用。局部高剂量照射后出现的心脏功能与结构长期损伤，与全身性炎症反应、收缩功能受损、微血管损伤及心脏纤维化密切相关。本研究旨在探究该过程涉及的分子机制。8周龄的C57BL/6J小鼠接受单次16戈瑞（Gy）的心脏局部X射线（X-ray）照射。于照射后40周，探究了辐射诱导的心脏转录组（transcriptome）与蛋白质组（proteome）变化。借助生物信息学工具对组学（omics）数据进行分析，并通过免疫印迹（immunoblotting）进行验证。对转录组学（transcriptomics）与蛋白质组学（proteomics）数据进行整合网络分析，阐明了在基因与蛋白水平均受到相似影响的信号通路。分析结果显示，受照射的心脏中，转化生长因子β（transforming growth factor beta, TGF-β）信号通路被激活，而过氧化物酶体增殖物激活受体α（peroxisome proliferator-activated receptor alpha, PPARα）信号通路则发生失活。免疫印迹与酶联免疫吸附试验（ELISA）的数据证实，丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）级联反应作为连接PPARα与TGF-β信号通路的潜在介质发挥作用。本研究表明，这两条信号通路均参与了辐射诱导的心脏纤维化、代谢紊乱及收缩功能受损——这是胸部接受高剂量辐射的患者中常见的病理生理状态。