Effects of intrathecal injection of SOCS3 on pain behavior and expression of proinflammatory cytokines in mice with neuropathic pain

Abstract

Objective To evaluate the role of suppressor of cytokine signaling 3 (SOCS3) in the spinal cord of chronic sciatic constriction injury (CCI) mice. Methods Part one: four Kunming mice were selected to receive the CCI operation by sciatic nerve ligation. Seven days after operation the mice were sacrificed and L4~6 segments of the spinal cord were removed.The co-expression of SOCS3 with NeuN (for neurons), GFAP (for astrocytes), or IBA1 (for microglia) in spinal were detected by immunohistofluorescence. Part two: thirty-two Kunming mice were divided into 4 groups according to random number table: sham operation group (group SH), CCI group (group BP), CCI+ Lenti-SOCS3 group (group BS), CCI + Lenti-vector group (group BV). Group BS were intrathcal injected of Lenti-SOCS3 (2 μl) and group BV were intrathcal injected of Lenti-vector (2 μl) on 7 d, 8 d, 9 d after operation.Paw withdrawal latency (PWL) and paw withdrawal threshold (PWT) were measured at 1 d before operation and 5, 7, 10, 12, 14 d after operation. Mice were then sacrificed and L4~6 segments of the spinal cord were removed for determination of GFAP, IBA-1 by Western blot and IL-6, IL-1β, TNF-α by Elisa on 14 d. Results SOCS3 was distributed in dorsal horn, and expressed in astrocytes and microglia, but hardly colocalized with neurons. Compared with group SH, the PWL and PWT of group BP and BV were significantly decreased after operation (all P<0.05), and the expression of GFAP, IBA-1, IL-6, IL-1β and TNF-α was significantly increased (all P<0.05). Compared with group BV, the PWL (5.1±0.9, 7.5±0.8, 7.2±1.4) and PWT (6.1±1.4, 8.9±1.1, 8.2±2.1) of group BS was significantly increased on 10, 12, 14 d (all P<0.05), and the expression of GFAP (1.69±0.45), IBA-1(1.76±0.25), IL-6 (181±8), IL-1β (151±7), TNF-α (216±9) was significantly downregulated (P<0.05). Conclusion SOCS3 alleviates neuropathic pain by inhibiting the glial activation and the expression of proinflammatory cytokines IL-6, IL-1β, TNF-α. Key words: Suppressor of cytokine signaling-3; Neuropathic pain; Glia; Spinal cord; Mice