FTY720 sustains and restores neuronal function in the DA rat model of MOG-induced experimental autoimmune encephalomyelitis.

FTY720 (fingolimod) is an oral sphingosine 1-phosphate (S1P) receptor modulator under development for the treatment of multiple sclerosis (MS). To elucidate its effects in the central nervous system (CNS), we compared functional parameters of nerve conductance in the DA rat model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) after preventive and therapeutic treatment. We demonstrate that prophylactic therapy protected against the emergence of EAE symptoms, neuropathology, and disturbances to visual and somatosensory evoked potentials (VEP, SEP). Moreover, therapeutic treatment from day 25 to 45 markedly reversed paralysis in established EAE and normalized the electrophysiological responses, correlating with decreased demyelination in the brain and spinal cord. The effectiveness of FTY720 in this model is likely due to several contributing factors. Evidence thus far supports its role in the reduction of inflammation and preservation of blood-brain-barrier integrity. FTY720 may also act via S1P receptors in glial cells to promote endogenous repair mechanisms that complement its immunomodulatory action.

Effect of cortical spreading depression on basal forebrain neurons.

During natural sleep and anesthesia, rhythmic hypo- and hyperpolarizations alternate in cortical pyramidal cells and are reflected as slow (<1 Hz) cortical rhythm at the level of the electroencephalogram (EEG). Membrane potential changes in pyramidal neurons were initially attributed to the rhythmic fluctuation of the cholinergic input as the basal forebrain (BF) neurons fire in synchrony with cortical waves, but a more recent proposal suggested that the slow rhythm was of cortical origin. In the present experiments, interaction between the cortex and the BF was examined in urethane-anesthetized rats. BF neuronal activity was inhibited by local infusion of lidocaine into the substantia innominata in one group of rats, while in another group, the slow cortical rhythm was blocked by inducing spreading depression (SD) in the cortex. Slow cortical rhythm persisted after unilateral lidocaine injection, but rhythmic firing in BF neurons disappeared following SD induction. These findings support the view that slow cortical rhythm is generated in the cortex and transmitted to the BF through descending fibers. According to anatomical data, these fibers can excite cholinergic cells only indirectly as they terminate on non-cholinergic neurons. Thus, timing of activity changes in BF neurons during the slow cortical rhythm might give some clue regarding their transmitter specificity.

EEG related neuronal activity in the pedunculopontine tegmental nucleus of urethane anaesthetized rats.

Cholinergic pathways ascending from the brainstem are considered as a decisive part of the reticular activating system. We recorded unit activity from the cholinergic pedunculopontine tegmental nucleus with extracellular microelectrodes in urethane-anesthetized rats and monitored cortical electroencephalogram (EEG) to examine the possible role of the nucleus in cortical activation. We found two types of cells showing EEG-correlated firing patterns. In one group, firing rate increased during cortical activation (F cell), while in another, higher rate was accompanied by cortical slow waves (S cell). Phasic changes in the firing rate of pedunculopontine neurons and in the cortical EEG were also analyzed. Changes of single unit activity in F cells always occurred before short periods of low-voltage fast activity appeared in the cortical EEG. The S cells were more variable with respect to the temporal relation. In some of the S cells, changes in firing rate preceded changes in the EEG patterns, while in others they occurred after a certain delay. Our results indicate that F-cells in the PPT might be involved in the initiation of tonic and phasic changes in cortical activation.

FTY720 rescue therapy in the dark agouti rat model of experimental autoimmune encephalomyelitis: expression of central nervous system genes and reversal of blood-brain-barrier damage.

FTY720 (fingolimod) is an oral sphingosine-1 phosphate (S1P) receptor modulator in phase III development for the treatment of multiple sclerosis. To further investigate its mode of action, we analyzed gene expression in the central nervous system (CNS) during experimental autoimmune encephalomyelitis (EAE). FTY720 downregulated inflammatory genes in addition to vascular adhesion molecules. It decreased the matrix metalloproteinase gene MMP-9 and increased its counterregulator--tissue inhibitor of metalloproteinase, TIMP-1--resulting in a proteolytic balance that favors preservation of blood-brain-barrier (BBB) integrity. Furthermore, FTY720 reduced S1P lyase that increases the S1P concentration in the brain, in line with a marked reversal of neurological deficits and raising the possibility for enhanced triggering of S1P receptors on resident brain cells. This is accompanied by an increase in S1P(1) and S1P(5) in contrast with the attenuation of S1P(3) and S1P(4). Late-stage rescue therapy with FTY720, even up to 1 month after EAE onset, reversed BBB leakiness and reduced demyelination, along with normalization of neurologic function. Our results indicate rapid blockade of ongoing disease processes by FTY720, and structural restoration of the CNS parenchyma, which is likely caused by the inhibition of autoimmune T cell infiltration and direct modulation of microvascular and/or glial cells.

Brain penetration of the oral immunomodulatory drug FTY720 and its phosphorylation in the central nervous system during experimental autoimmune encephalomyelitis: consequences for mode of action in multiple sclerosis.

FTY720 [2-amino-2-[2-(4-octylphenyl) ethyl]propane-1,3-diol hydrochloride] is an oral sphingosine-1-phosphate receptor modulator under development for the treatment of multiple sclerosis (MS). The drug is phosphorylated in vivo by sphingosine kinase 2 to its bioactive form, FTY720-P. Although treatment with FTY720 is accompanied by a reduction of the peripheral lymphocyte count, its efficacy in MS and experimental autoimmune encephalomyelitis (EAE) may be due to additional, direct effects in the central nervous system (CNS). We now show that FTY720 localizes to the CNS white matter, preferentially along myelin sheaths. Brain trough levels of FTY720 and FTY720-P in rat EAE are of the same magnitude and dose dependently increase; they are in the range of 40 to 540 ng/g in the brain tissue at efficacious doses and exceed blood concentrations severalfold. In a rat model of chronic EAE, prolonged treatment with 0.03 mg/kg was efficacious, but limiting the dosing period failed to prevent EAE despite a significant decrease in blood lymphocytes. FTY720 effectiveness is likely due to a culmination of mechanisms involving reduction of autoreactive T cells, neuroprotective influence of FTY720-P in the CNS, and inhibition of inflammatory mediators in the brain.