Valproate reduces CHOP levels and preserves oligodendrocytes and axons after spinal cord injury.

Spinal cord injury (SCI) is a major cause of disability to which there are not yet effective treatments. We previously reported that degeneration of oligodendrocytes and neurons that occurs after SCI is associated with the development of endoplasmic reticulum (ER) stress and the progressive accumulation of the pro-apoptotic factor CHOP. Since following ER stress, the balance between the pro-survival chaperone BiP and CHOP drives the cell destiny, we aimed to find drugs that modulate this ratio in favour of the former. We found that valproate (VPA) induced a significant reduction of CHOP levels after ER stress in an organotypic-based culture of spinal cord in vitro. We then administered different doses of VPA to rats following spinal cord contusion, and found that the treatment caused a marked reduction of CHOP levels early after the lesion. In addition, VPA administration partially prevented cord tissue, myelin and axonal loss, and significantly increased the relative number of surviving oligodendrocytes in the damaged spinal cord. Besides, VPA-treated rats showed better recovery of the locomotor activity than vehicle-treated rats after SCI. Since VPA is a drug already in clinical use, these results open the avenue for its therapeutical use in SCI as well as in demyelinating disorders.

Selective sigma receptor agonist 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate (PRE084) promotes neuroprotection and neurite elongation through protein kinase C (PKC) signaling on motoneurons.

Neuronal loss and interruption of axonal pathways are occurring after spinal cord injury. This is initiated by the mechanical damage and propagated by secondary events that include the fast rise of glutamate concentration and the subsequent over-activation of glutamate receptors, triggering noxious processes to the cell. Excitotoxic processes are also observed in degenerative diseases that involve motoneuron loss. Sigma-1 receptors (Sig-1Rs) are expressed in the CNS and their ligands have been shown to prevent neuronal death associated to glutamate toxicity. In the present study, we used organotypic cultures of spinal cord slices and dorsal root ganglia (DRG) explants from 7-8 days old postnatal rats to assess whether the agonist of the Sig-1R, 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate (PRE084), protects the spinal cord against glutamate excitotoxicity and promotes neurite elongation. The results showed that PRE084 exerted a bell-shape dose-dependent protective response of the motoneurons, with a significant neuroprotection obtained with 10 microM PRE084. PRE084 also caused an increase in the length of neurites in both motoneurons and neurons in DRG explants. Both effects were abrogated with the addition of BD 1063, an antagonist of Sig-1R, and the use of chelerythrine, a protein kinase C (PKC) pan-inhibitor indicating that PKC is implicated in the observed effects. These results suggest the use of PRE084 as a neuroprotective agent for spinal cord damage.

Analysis of FK506-mediated protection in an organotypic model of spinal cord damage: heat shock protein 70 levels are modulated in microglial cells.

Functional loss after spinal cord injuries is originated by primary and secondary injury phases whose underlying mechanisms include massive release of excitatory amino acids to cytotoxic levels that contribute to neural death. Attenuation of this excitotoxicity is a key point for improving the functional outcome after injury. One of the drugs with potential neuroprotective actions is FK506, a molecule widely used as an immunosuppressant. FK506 may exert neuroprotection via inhibition of calcineurin by binding the FKBP12, or by binding other immunophilins such as FKBP52, leading to modulation of heat shock proteins (Hsp) 90 and 70. In the present study, we used an in vitro model of organotypic culture of rat spinal cord slices to assess whether FK506 is able to protect them against glutamate excitotoxicity. The results showed that FK506 promoted a significant protective effect on the spinal cord tissue at concentrations of 50 and 100 nM. Hsp70 induction was restricted to microglial cells in spinal cord slices treated with either glutamate or FK506. In contrast, the combination of both agents led to a transient reduction in Hsp70 levels in parallel to a marked reduction in IL-1beta precursor production by glial cells. The use of geldanamycin, which promotes persistent induction of Hsp70 in these cells as well as in motoneurons, did not produce tissue neuroprotection. These observations suggest that FK506 might protect spinal cord tissue by targeting on microglial cells and that transient downregulation of Hsp70 on these cells after excitotoxicity is a relevant mechanism of action of FK506.