Ion Channel Modulation as a Therapeutic Approach in Multiple Sclerosis.

Ion channel dysfunction has been identified as a contributor to symptom development and neurodegeneration in multiple sclerosis (MS). The molecular insights have been translated into new lines of research, with ion channel modulation now representing a therapeutic approach in MS. Studies of Na+ channel function have demonstrated pathological blockade of Na(+) channels during an acute inflammatory attack. Relapses are typically associated with subsequent alterations in Na+ channel expression and structure. However, these compensatory changes may also be deleterious. Specifically, increased Na(+) channel expression may contribute to neuronal energy insufficiency and a cascade of events that may ultimately lead to neurodegeneration and apoptosis. Pharmacological blockade of Na(+) channels in animal models of MS demonstrated encouraging results, although mixed results were obtained in subsequent clinical trials in MS patient cohorts. The process involved in demyelination, a characteristic event in MS pathology, may also induce complex structural changes mediated by K(+) channels that may in turn hinder neural transmission. From a therapeutic perspective, the potent K(+) channel blocker, 4-aminopyridine (4-AP), has demonstrated neurophysiological and functional improvements in animal models of demyelination. Clinical translation of these results was recently achieved with the advent of Fampridine PR, a modified release form of 4-AP, with phase III clinical trials that demonstrated improvement in neurological symptoms including fatigue, walking speed and strength in MS patients.