Sinomenine Liposomes Alleviate Neuropathic Pain in a Spared Nerve Injury Model by Regulating Astrocyte Reactivity Associated with Inhibition of the JAK2/STAT3 Pathway

Abstract

Neuropathic pain (NP) is chronic pain caused by injury or disease affecting the nervous system. SIN@Lip-HA was prepared and characterised for particle size, zeta potential, encapsulation efficiency and morphology. Sprague-Dawley rats with spared nerve injury (SNI) were randomly divided into the six groups. Analgesic effects were assessed via behavioural tests. Histopathological changes were examined using H&E staining. Astrocyte polarisation was detected using immunofluorescence, and Western blotting was used to assess related protein expression. qRT-PCR measured mRNA level of genes, while ELISA evaluated inflammatory cytokines and oxidative stress markers. The study showed that the particle size of SIN@Lip-HA was 111 ± 5.13 nm, with an encapsulation efficiency of 85.47% and a zeta potential of -24.86 ± 1.20 mV. The in vitro release profile showed sustained drug release, and the formulation remained stable for 3 months. Compared with the model group, SIN@Lip-HA significantly increased PWT and PWL, alleviated spinal cord pathology and was associated with a shift in astrocyte reactivity, as indicated by a reduction in A1-related markers and an increase in A2-related markers. SIN@Lip-HA downregulated CGRP/SP and GFAP. It was also found to inhibit JAK2/STAT3 pathway activation by reducing p-JAK2/p-STAT3 expression and decrease TNF-α, IL-1β and IL-6 whilst increasing IL-10. It also mitigated oxidative stress. Concomitant use with gabapentin markedly enhanced therapeutic efficacy. These findings suggest that sinomenine liposomes alleviate NP in SNI rats in a manner associated with inhibition of JAK2/STAT3 signaling and correlated with astrocyte reactivity, and reduced pain mediators.