Methylene Blue (Basic Blue 9, Tetramethylthionine chloride, methylthioninium chloride, CI-52015) is used as a dye in chromoendoscopy. It Inhibits tau filament formation with IC50 of 1.9μM. Also it inhibits soluble guanylyl cyclase.
MB may inhibit the action of nitric oxide synthase itself and could also inactivate nitric oxide directly, possibly through the generation of superoxide anions. In addition to interfering with the nitric oxide–cyclic guanosine monophosphate pathway, MB has also been shown to directly activate calcium-dependent potassium channels and to enhance release of noradrenaline from intracellular stores[1].
Methylene Blue acts by inhibiting guanylate cyclase, thus decreasing C-GMP and vascular smooth muscle relaxation. When injected intravenously, MB selectively accumulates in parathyroid glands, thereby facilitating the identification of these structures during surgery. Pharmacokinetic studies in rodents revealed that intravascular administration of MB leads to a rapid and extensive accumulation of this drug in the central nervous system (CNS)[1].
[1] Vutskits L, et al. Anesthesiology. 108(4):684-692. [2] Hochgr鋐e K, et al. Acta Neuropathol Commun. 2015, 3:25. [3] Masaki E, et al. Anesth Analg. 1999, 89(2):484-489.