Effect of electroacupuncture regulating BDNF/NRF2 signaling pathway on oxidative stress in dorsal root ganglion of rabbits with lumbar intervertebral disc degeneration

To observe the protective function and mechanism of electroacupuncture (EA) “Jiaji” (EX-B2) on dorsal root ganglion (DRG) in rabbits with pressure-induced lumbar intervertebral disc degeneration (IVDD).

Twenty-five male New Zealand rabbits with mature bones were divided into control, sham operation, model, EA, and acupuncture groups, with 5 rabbits in each group. The IVDD model was established by inserting kirschner wires to the vertebral bone surface between the lumbar (L) 4 and L5 vertebrae, followed by applying continuous axial pressure for 28 days. EA (2 Hz/15 Hz, 1 mA) or acupuncture (only insertion of acupuncture needles into bilateral EX-B2, but without electrical stimulation) was applied to bilateral EX-B2 for 20 min, once daily for 28 days.The general conditions and weight changes of rabbits in each group were observed, and the free walking pain score was calculated after interventions. The morphology and structure of DRG cells were observed by HE staining. The activities of superoxide dismutase (SOD), glycine peroxidase (GSH-Px) catalase (CAT) and content of malondialdehyde (MDA) in DRG were detected by ELISA. The concentration of calcium ions in DRG was measured by flow cytometry. The protein expression levels of brain-derived neurotrophic factor (BDNF), nuclear factor E2 related factor 2 (NRF2), heme oxygenase-1 (HO-1) and NAD (P) quinone oxidoreductase 1 (NQO1) in DRG were detected by Western blot.

Compared with the sham operation group, the free walking pain score of rabbifs in the model group was significantly increased (P<0.01), and the concentration of calcium ion and content of MDA in DRG were significantly increased (P<0.01), the contents of SOD, GSH-PX and CAT and the protein expressions of BDNF, NRF2, NQO1 and HO-1 in DRG were significantly decreased (P<0.01). Compared with the model group, the free walking pain score of rabbits in the EA group was significantly decreased (P<0.01), the concentration of calcium ions and the content of MDA in DRG were decreased (P<0.01), the contents of SOD, GSH-PX and CAT and the protein expressions of BDNF, NRF2, NQO1 and HO-1 were significantly increased (P<0.01). The effect of EA was better than acupuncture (P<0.01, P<0.05). HE staining showed atrophied cell bodies, disordered cellular arrangement, dissolved nuclei, and indistinct borders of DRG cells in the model group, which was milder in both acupuncture and EA groups.

EA at EX-B2 may inhibit oxidative stress in DRG cells by regulating BDNF/NRF2 signaling pathway, protect DRG cell damage, reduce nerve pain, thus delay the progression of IVDD.