Tumor Radiotherapy-Induced Sympathetic Hyperactivation Orchestrates Rapid Systemic Bone Loss

Area of Science:

• Oncology
• Bone Biology
• Neuroscience

Background:

• Radiation therapy (RT) is a cornerstone of cancer treatment but can lead to bone fractures.
• The mechanisms behind RT-induced bone loss are not fully understood.
• The sympathetic nervous system's (SNS) role in this process requires investigation.

Purpose of the Study:

• To investigate radiation therapy-induced bone loss in an esophageal carcinoma mouse model.
• To examine the role of the sympathetic nervous system (SNS) in RT-induced bone loss.
• To explore the potential of targeting the SNS to mitigate bone loss and enhance antitumor effects.

Main Methods:

• Utilized an esophageal carcinoma mouse model with localized RT (20 Gy in four fractions).
• Administered chemical sympathectomy using 6-OHDA to assess SNS involvement.
• Employed Micro-CT, histology, and molecular analyses to evaluate bone structure, cellular activity, and inflammatory markers.

Main Results:

• RT increased bone norepinephrine levels and adrenergic receptor expression, indicating SNS activation.
• Significant trabecular bone loss was observed post-RT, with sympathectomy mitigating these effects.
• RT enhanced osteoclast activity and osteocyte apoptosis while suppressing osteoblast function; these were reversed by sympathectomy.
• Sympathetic ablation also enhanced the antitumor effect of RT.

Conclusions:

• Localized radiotherapy can induce systemic bone loss via excessive SNS activation.
• Mechanisms include increased osteocyte apoptosis, enhanced osteoclastogenesis, and impaired osteoblast activity.
• Targeting the SNS presents a potential strategy for preventing radiation-associated bone loss and may enhance cancer treatment efficacy.