Most multiple sclerosis (MS) patients develop over time a secondary
progressive disease course, characterized histologically by axonal loss and
atrophy. In early phases of the disease, focal inflammatory demyelination
leads to functional impairment, but the mechanism of chronic progression in MS
is still under debate. Reactive oxygen species generated by invading and
resident central nervous system (CNS) macrophages have been implicated in
mediating demyelination and axonal damage, but demyelination and
neurodegeneration proceed even in the absence of obvious immune cell
infiltration, during clinical recovery in chronic MS. Here, we employ
intravital NAD(P)H fluorescence lifetime imaging to detect functional NADPH
oxidases (NOX1–4, DUOX1, 2) and, thus, to identify the cellular source of
oxidative stress in the CNS of mice affected by experimental autoimmune
encephalomyelitis (EAE) in the remission phase of the disease. This directly
affects neuronal function in vivo, as monitored by cellular calcium levels
using intravital FRET–FLIM, providing a possible mechanism of disease
progression in MS