Argon Alleviates Bone Cancer Pain by Mitigating Neuronal Ferroptosis via the TLR2-COX-2 Pathway

Bone cancer pain (BCP) related neuronal damage is associated with ferroptosis, a regulated cell death dependent on iron. The noble gas argon is known to have neuroprotective effects, reducing neuroinflammation and enhancing neuronal recovery. However, its potential role in alleviating BCP through the modulation of neuronal ferroptosis remains unexplored.

Ferroptosis was induced by Erastin in SH-SY5Y human neuroblastoma cells. Plasmids were used to overexpress or knock down toll-like receptor (TLR) 2 and cyclooxygenase-2 (COX-2). The effects of argon treatment were evaluated in SH-SY5Y cells in which TLR2 and COX-2 expression was manipulated using viability assays, oxidative stress markers (reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH)), and ferroptosis-related proteins (acyl-CoA synthetase long-chain family member 4 (ACSL4), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11)). In vivo, a murine BCP model was developed by injecting Lewis lung carcinoma cells into the femoral cavity. Pain behaviors were analyzed, and spinal cord ferroptosis features were evaluated using histology, immunofluorescence, and transmission electron microscopy (TEM).

In vitro experiments showed that argon treatment restored SH-SY5Y cell viability after Erastin exposure, suppressed ROS and MDA production, and boosted GSH levels. It also downregulated ACSL4 and upregulated GPX4 and SLC7A11. In vivo, argon improved pain behaviors, reduced tumor burden, preserved neuronal integrity, and mitigated ferroptosis-induced damage to the spinal cords of BCP model mice. Argon also significantly suppressed TLR2 and COX-2 expression, disrupting the ferroptosis and inflammation cascades. However, overexpression of TLR2 or COX-2 reversed these protective effects, confirming the pivotal role of the TLR2-COX-2 axis in neuronal ferroptosis and pain modulation.

These findings demonstrate that argon effectively mitigates neuronal ferroptosis and alleviates BCP by downregulating the TLR2-COX-2 pathway, highlighting its therapeutic potential for conditions involving ferroptosis, such as cancer-related pain and neurodegenerative diseases.