Astaxanthin Modulates Autophagy, Apoptosis, and Neuronal Oxidative Stress in a Rat Model of Compression Spinal Cord Injury

Abstract

The effects of astaxanthin (AST) were evaluated on oxidative mediators, neuronal apoptosis, and autophagy in functional motor recovery after spinal cord injury (SCI). Rats were divided into three groups of sham, SCI + DMSO (dimethyl sulfoxide), and SCI + AST. Rats in the sham group only underwent a laminectomy at thoracic 8-9. While, the SCI + DMSO and SCI + AST groups had a compression SCI with an aneurysm clip. Then, this groups received an intrathecal (i.t.) injection of 5% DMSO and AST (10 μl of 0.005 mg/kg), respectively. The rat motor functions were assessed weekly until the 28th day using a combined behavioral score (CBS). Total antioxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were measured in spinal tissue to evaluate oxidative stress-related parameters. Besides, autophagy-related proteins (P62, LC3B, and Beclin1) and apoptosis-associated proteins (Bax and Bcl2) were determined using western blotting on the 1st and 7th days after surgery. Hematoxylin-eosin and Fluoro-Jade B staining were performed to detect the histological alterations and neuronal degeneration. As the result, treatment with AST potentially attenuated rat CBS scores (p < 0.001) towards a better motor performance. AST significantly reduced the spinal level of oxidative stress by increasing TAC, SOD, and GPx, while decreasing MDA (p < 0.001). Furthermore, AST treatment remarkably upregulated expression of LC3B (p < 0.001), and Beclin1 (p < 0.05) in the spinal cord, but downregulated P62 (p < 0.05) and the Bax/Bcl2 ratio (p < 0.001). Consequently, AST reduced SCI-induced histological alterations and neuronal degeneration (p < 0.001). In conclusion, AST can improve motor function after SCI by reducing oxidative stress/apoptosis and increasing neuronal autophagy.

Keywords: Apoptosis; Astaxanthin; Autophagy; Oxidative stress; Rats; Spinal cord injury.