THE MELATONIN PROTECTIVE ROLE IN AN ORGANOTYPIC MODEL OF SPINAL CORD INJURY SECONDARY DAMAGE

Spinal cord injury (SCI) is characterized to be a two-step process composed by the primary lesion consisting of the initial trauma and the secondary damage, characterized by multiple processes including inflammation, oxidative stress and cell death that lead to a significant expansion of the original damage and to an increase of the functional deficit. Among the aforementioned processes, the oxidative stress plays a significant role in pathophysiology of SCI. In this study, we evaluated the role of melatonin, potent antioxidant and immunomodulator indoleamin, on the oxidative stress, the tissue viability and the neuritic plasticity deriving from the gray matter in an experimental model of organotypic cultures. These cultures consisted of Sprague Dawley rat spinal cord slice treated with hydrogen peroxide (H2O2). In five experimental groups, A) Control Group (CTR) – Organotypic spinal cord slice culture (350μm); B) Stressed Group (H2O2) – Organotypic spinal cord slice culture (350μm) exposed to H2O2 (50 μM); C) Control Group treated with melatonin (10-5M) of 24 hours (CTR+MEL) – Organotypic spinal cord slice culture (350μm) treated with melatonin for 24 hours; D) Treated Group (H2O2+MEL-POST) – Organotypic spinal cord slice culture (350μm) exposed to H2O2 (50 μM) and treated after 24 hours with melatonin (10-5M) for 24 hours; E) Treated Group (H2O2+MEL-PRE) – Organotypic spinal cord slice culture (350μm) pre-treated with melatonin (10-5M) for 24 hours (50 μM) and exposed to H2O2 for other 24 hours. We investigated the slice cellular death by propidium iodide (PI) assay, the slice vitality by MTT assay, the superoxide dismutase (SOD) and total thiols (SH) levels for the contrast to the oxidative stress, the neuronal (NeuN) and the synaptophysin (Syp) immunopositivity. Melatonin significantly decreased the number of dead cells, increased slice vitality, mainly in slices treated before H2O2 exposition. Melatonin enhanced SOD immunopositivity, contrasted total thiols decrease, attenuated Syp reduction and increased NeuN immunopositivity. Overall, these findings suggest that melatonin may exert a potentially beneficial effect upon the progression of SCI secondary damage, protecting the tissue from a further degeneration.