Infusion of anti-Nogo-A antibodies in adult rats increases growth and synapse related proteins in the absence of behavioral alterations.

Restricted structural re-growth in the adult CNS is a major limitation to fully functional recovery following extensive CNS trauma. This limitation is partly due to the presence of growth inhibitory proteins, in particular, Nogo-A. Pre-clinical studies have demonstrated that intrathecally infused anti-Nogo-A antibodies are readily distributed via the cerebrospinal fluid penetrating throughout the spinal cord and brain, where they promote sprouting, axonal regeneration and improved functional recovery after CNS injury. Whether anti-Nogo-A treatments of intact animals might induce behavioral alterations has not been systematically tested. This is addressed here in an adult rat model of chronic intrathecal infusion of function-blocking anti-Nogo-A antibodies for 2 to 4weeks. We observed by proteomic and immunohistochemical techniques that chronic Nogo-A neutralization in the intact CNS increased expression of cytoskeletal, fiber-growth-related, and synaptic proteins in the hippocampus, a brain region which might be particularly sensitive to Nogo-A depletion due to the high expression level of Nogo-A. Despite such molecular and proteomic changes, Nogo-A blockade was not associated with any pronounced cognitive-behavioral changes indicative of hippocampal functional deficiency across several critical tests. Our results suggest that the plastic changes induced by Nogo-A blockade in the adult hippocampus are counter-balanced by homeostatic mechanisms in the intact and the injured CNS. The data indicate that anti-Nogo-A therapy appears safe in the adult CNS over 4weeks of continuous administration.

Neutralization of the membrane protein Nogo-A enhances growth and reactive sprouting in established organotypic hippocampal slice cultures.

The reduced ability of central axons to regenerate after injury is significantly influenced by the presence of several molecules that inhibit axonal growth. Nogo-A is one of the most studied and most potent of the myelin-associated growth inhibitory molecules. Its neutralization, as well as interference with its signalling, allows for enhanced axonal sprouting and growth following injury. Using differentiated rat organotypic hippocampal slice cultures treated for 5 days with either of two different function-blocking anti-Nogo-A antibodies, we show an increase in CA3 fibre regeneration after lesion. In intact slices, 5 days of anti-Nogo-A antibody treatment led to increased sprouting of intact CA3 fibres that are positive for neurofilament 68. A transcriptomic approach confirmed the occurrence of a growth response on the molecular level upon Nogo-A neutralization in intact cultures. Our results demonstrate that Nogo-A neutralization for 5 days is sufficient for the induction of growth in mature CNS tissue without the prerequisite of an injury. Nogo-A may therefore act as a tonic growth suppressor/stabilizer in the adult intact hippocampus.

Phosphorylated FTY720 promotes astrocyte migration through sphingosine-1-phosphate receptors.

Sphingosine-1-phosphate (S1P) receptors are widely expressed in the central nervous system where they are thought to regulate glia cell function. The phosphorylated version of fingolimod/FTY720 (FTY720P) is active on a broad spectrum of S1P receptors and the parent compound is currently in phase III clinical trials for the treatment of multiple sclerosis. Here, we aimed to identify which cell type(s) and S1P receptor(s) of the central nervous system are targeted by FTY720P. Using calcium imaging in mixed cultures from embryonic rat cortex we show that astrocytes are the major cell type responsive to FTY720P in this assay. In enriched astrocyte cultures, we detect expression of S1P1 and S1P3 receptors and demonstrate that FTY720P activates Gi protein-mediated signaling cascades. We also show that FTY720P as well as the S1P1-selective agonist SEW2871 stimulate astrocyte migration. The data indicate that FTY720P exerts its effects on astrocytes predominantly via the activation of S1P1 receptors, whereas S1P signals through both S1P1 and S1P3 receptors. We suggest that this distinct pharmacological profile of FTY720P, compared with S1P, could play a role in the therapeutic effects of FTY720 in multiple sclerosis.