Intrathecal Lentivirus-mediated Transfer of Interleukin-10 Attenuates Chronic Constriction Injury-induced Neuropathic Pain through Modulation of Spinal High-mobility Group Box 1 in Rats

Background: Neuropathic pain is a complex state of chronic pain that is usually accompanied byperipheral and central nervous system damage or dysfunction. Previous studies have indicated thatneuroinflammation in the spinal cord is an important contributor to neuropathological and behavioralabnormalities. A series of early inflammatory markers, such as IL-1, TNF-α, and IFN-γ, and advancedinflammatory markers, such as high-mobility group box 1 (HMGB1), are involved in neuroinflammation.Study Design: A randomized, double blind, controlled animal trial.Objective: In this study, a lentivirus delivering human IL-10 (LV/hIL-10) was administeredintrathecally to determine the effects of IL-10 on allodynia and hyperalgesia in a chronic constrictioninjury-induced (CCI) rat model of neuropathic pain.Methods: Sprague-Dawley rats weighting 260 - 320 g were randomly divided into 4 groups.Group Sham (Sham), Group CCI±Normal Saline (NS), Group CCI±LV/hIL-10 (LV/hIL-10), and GroupCCI±LV/control (vector). Rats in each group were intrathecally administered NS, LV/control, orrecombinant vector LV/hIL-10 in a total volume of 10 μl. Paw withdrawal mechanical thresholds(PWMT) and paw withdrawal thermal latency PWTL were measured one day before CCI (baseline)and 0, 3, 7, 14, and 28 days after intrathecal administration. Cerebrospinal fluid (CSF) sampleswere collected during surgical plane anesthesia and the collected CSF samples were used toassay for human IL-10, rat IL-1β, rat IL-6, and rat TNF-α by enzyme-linked immunosorbent assay(ELISA). Animals were sacrificed and the L4-5 lumbar segment of the spinal cord was removed fordetermination of green fluorescent protein (GFP) expression. Immunohistochemical analysis wasperformed using anti HMGB1 antibodies and the expression of HMGB1 protein in the spinal cordwas determined by Western blot analysis after intrathecal delivery (n = 8 each).Results: The results show that intrathecal LV/hIL-10 reverses enhanced pain states. Moreover,the increased level of HMGB1 exhibited in a late stage of CCI was inhibited by exogenousoverexpression of hIL-10 in the CCI model. Expression of HMGB1, RAGE, and pAkt were lowerin CCI-induced rats treated with LV/hIL-10 than in those treated with LV/control (vector) or saline(NS). Our results showed that IL-10 inhibits activation of the inflammatory HMGB1-RAGE pathwayin the CCI rat model.Limitations: Further experimental investigations are needed to clarify the specific biological rolesplayed by HMGB1 in IL-10-mediated regulation of neuropathic pain.Conclusion: Our results indicate that intrathecal lentiviral-mediated transfer of IL-10 attenuatesCCI-induced neuropathic pain in rats. The anti-thermal hyperalgesia and anti-mechanical allodyniamay be partly attributable to the decreased expression of HMGB1 and inhibition of HMGB1-RAGEpathway.Key words: Analgesia, interleukin-10, lentiviral, HMGB1, intrathecal, randomized, controlled trial