Cordycepin ameliorates morphine tolerance by inhibiting spinal cord ferroptosis and inflammation via targeting SIRT1.

Morphine tolerance caused by long-term use of morphine is a major medical problem. Neuroinflammation plays an important role in morphine tolerance, and currently no drugs have been found for clinical use to alleviate neuroinflammation during morphine tolerance. Cordycepin is the main active component of fungus cordycepin militaris, has been demonstrated to have anti-oxidative stress and anti-inflammatory properties in various diseases. In this study, we established a rat model of morphine tolerance, examined the effect of cordycepin on the development of morphine tolerance, and evaluated its potential regulatory mechanisms. We found that cordycepin treatment ameliorated the development of morphine tolerance, improved mitochondrial damage associated with ferroptosis, by reducing the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and Fe(2+), increasing superoxide dismutase (SOD) and glutathione (GSH) levels, and decreasing the secretion of pro-inflammatory factors (IL-1β, IL-6, and TNF-α). Besides, cordycepin upregulated the expression of SIRT1, SLC7A11 and GPX4. Further research found that the above effects of cordycepin on morphine-tolerant rats were abolished by SIRT1 selective inhibitor EX-527. Thus, these findings indicated that cordycepin could ameliorate the development of morphine tolerance by inhibiting spinal cord ferroptosis and inflammation via targeting SIRT1. Collectively, these results demonstrated the protective effects of cordycepin and highlighted its therapeutic potential as a drug component for morphine tolerance treatment and prevention.