Neuroprotective Effects of Oxymatrine via Triggering Autophagy and Inhibiting Apoptosis Following Spinal Cord Injury in Rats

Abstract The identification of drugs that promote autophagy and inhibits apoptosis in neurons is critical for improving patient outcomes following spinal cord injury (SCI). Here, we aimed to investigate the neuroprotective effects of oxymatrine (OMT) and the potential mechanism after SCI in rats. Female Sprague-Dawley rats were randomly assigned to either a sham group, SCI group, OMT-treated group (40 mg/kg), and a group treated with both OMT and SIRT1 inhibitor EX527 (10 µg/kg). A modified compressive device (weight 35 g, time 5 min) was applied to induce moderate SCI in all groups except the sham group. After treatment with drugs or vehicle (saline), the neurological functions were evaluated using the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale and footprint analysis. Morphological changes in the spinal cord were assessed using hematoxylin-eosin staining and the number of surviving and apoptotic neurons was determined using Nissl and TUNEL staining, respectively. Neuronal ultrastructures were observed using transmission electron microscope (TEM). Moreover, we investigated the gene and protein expression levels of relevant molecules involved in apoptosis and autophagy, such as SIRT1, AMPK, p62, Beclin-1, LC3B, Bcl-2, Bcl-xL, Bax, Bak and C-caspase-3 using qRT-PCR analysis, Western blotting, or immunofluorescence staining. Our results indicated that OMT treatment significantly reduced the lesion size, promoted survival of motor neurons, and subsequently attenuated motor dysfunction following SCI in rats. OMT significantly enhanced autophagy activity, inhibited apoptosis in neurons, and increased SIRT1 and p-AMPK expression levels. These effects of OMT on SCI were partially prevented by co-treatment with SIRT1 inhibitor EX527. Taken together, these data revealed that OMT exerts a neuroprotective role in functional recovery against SCI in rats, and these effects are potentially associated with OMT-induced activation of autophagy via the SIRT1/AMPK signaling pathway.