Hydrogen-rich saline attenuated neuropathic pain by reducing oxidative stress.

Background: Reactive oxygen species (ROS) are often associated with persistent pains such as neuropathic and inflammatory pain. Hydrogen gas can reduce ROS and alleviate cerebral, myocardial, and hepatic ischemia/reperfusion injuries. in the present study, we aim to investigate whether hydrogen-rich saline can reduce neuropathic pain in a rat model of chronic constriction injury (CCI). Methods: thirty SD rats were randomly divided into three groups: sham group was administered sodium chloride by intrathecal injection (n = 10); control groups underwent CCI surgery and were administered sodium chloride by intrathecal injection (n = 10); vehicle group underwent CCI surgery and was administered hydrogen-rich saline by intrathecal injection (n = 10). Drugs were administered in the dose of 100ul/kg once a day at 0.5 hours before and 1-7 day after CCI surgery. the mechanical thresholds were tested at one day before and 3-14 day after CCI surgery. Results: We found that hydrogen-rich saline significantly elevated the mechanical thresholds of neuropathic pain compared to vehicle (physiologic saline) control in CCI rats (p < 0.05); it also decreased the levels of myeloperoxidase, maleic dialdehyde, and protein carbonyl in spinal cord by 7 days post-chronic constriction injury(p < 0.05). in addition, hydrogen-rich saline also suppressed the expression of p38-mitogen-activated protein kinase (p38MAPK) and brain-derived neurotrophic factor (BDNF) in the spinal cord by 7 days post-chronic constriction injury (p < 0.01, p < 0.01, respectively), but had no effect on P2X4R (p > 0.05), an ATP receptor. Conclusion: intrathecal injection of hydrogen-rich saline can decrease oxidative stress and the expression of p38MAPK and BDNF that may contribute to the elevated threshold of neuropathic pain in rat CCI model.