Fazio R et al. – Neuromyelitis optica (NMO) is a rare demyelinating disease, affecting selectively the optic nerve and the spinal cord. It was previously considered to be a severe variant of multiple sclerosis (MS) due to the similar pathological features and its resemblance to optico–spinal, or Japanese, MS, typical of Asian populations.
With a concentration of 55,000 mM, water is by far the most prevalent molecule in biological systems.
Neuromyelitis optica (NMO) is an inflammatory autoimmune demyelinating disease of the central nervous system (CNS) which in autoantibodies produced by patients with NMO (NMO-IgG) recognize a glial water channel protein, Aquaporin-4 (AQP4) expressed as two major isoforms, M1- and M23-AQP4, in which the plasma membrane form orthogonal arrays of particles (OAPs). AQP4-M23 is the OAP-forming isoform, whereas AQP4-M1 alone is unable to form OAPs.
Discovery of aquaporin water channel proteins has provided insight into the molecular mechanism of membrane water permeability. In mammalian brain, Aquaporin-4 (AQP4) is the main water channel and is distributed with highest density in the perivascular and subpial astrocyte end-feet. AQP4 is a critical component of an integrated water and potassium homeostasis.