Data regarding: Melatonin induces neuroprotection in experimental autoimmune encephalomyelitis by impairing T cell priming and reactivation in the central nervous system
Experimental autoimmune encephalomyelitis (EAE), the pre-clinical animal model of human multiple sclerosis, is triggered by myelin-specific T effector cells that are primed in peripheral lymph nodes and migrate to the central nervous system (CNS) where they are reactivated and induce demyelination. While melatonin ameliorates EAE disease symptoms, modulates encephalitogenic and suppressive responses, and reduces demyelination, its mechanism of action is not clear. Our objective was to study the effects of melatonin on key processes in EAE: the peripheral priming of T cells, their migration to the CNS and their reactivation therein. In this way, the actions of melatonin on co-stimulatory/co-inhibitory and adhesion molecules, on chemokine ligands/receptors expressed by different immune and CNS cell populations, on the blood-brain barrier (BBB) and on brain-derived neurotrophic factor (BDNF) levels in the CNS were studied in EAE. EAE induction protocol and EAE score assessment, and protocols for isolating draining lymph node (dLN) and CNS mononuclear cells and assessing immune subsets cells can be found in Álvarez-Sánchez et al. Brain, Behavior, and Immunity. 2015. Briefly, EAE was induced by s.c. administration of 100 μg of MOG35-55 emulsified in CFA containing 50 μg of heat-killed Mycobacterium tuberculosis (H37Ra), followed by two i.p. doses of 400 ng of pertussis toxin on days 0 and 2. Melatonin (80 mg/kg in ethanol/saline 8%) or vehicle was administered i.p. daily from day 0 onwards. Clinical signs of EAE were assessed as follows: 0: no clinical signs; 1: limp tail; 2: impaired righting reflex; 3: partial hind limb paralysis; 4: complete hind limb paralysis; 5: complete hind limb paralysis + frontal limb paralysis; 6: dead or moribund. Mononuclear cells or RNA were isolated from dLNs and CNS at days 5, 10 and 15 post-induction (p.i.) and analyzed by flow cytometry (co-stimulatory/co-inhibitory molecules, adhesion molecules and chemokyne receptors on APCs and T cells) or real-time quantitative PCR (expression of chemokyne ligands and receptors, adhesion molecules, BDNF). The integrity of the BBB was assessed in spinal cords by the immunohistochemical detection of albumin in the capillaries and by Evans Blue extravasation. Melatonin regulated many of the key pathological steps in EAE by regulating the immune synapse as well as chemoattractant and adhesion molecules and suppressive andneuroprotective responses, both in the periphery and in the CNS.