In vitro properties of 5-(benzylsulfonyl)-4-bromo-2-methyl-3(2H)-pyridazinone: A novel permeability transition pore inhibitor

Despite the increasing implication of the permeability transition pore (PTP) in the pathophysiology of neurodegenerative diseases, few selective PTP inhibitors have been reported so far. Here, we evaluate the pharmacological properties of a novel PTP inhibitor, BBMP (5-(benzylsulfonyl)-4-bromo-2-methyl-3(2H)-pyridazinone). This drug was discovered from the screening of a compound library against the PTP using a functional assay with isolated mitochondria. Similarly to cyclosporin A, the drug prevented Ca2+-induced permeability transition and mitochondrial depolarization. BBMP appeared more potent that minocycline in both swelling and membrane potential assays displaying pIC50 values of 5.5 ± 0.1 and 5.6 ± 0.0, respectively. Unlike minocycline, BBMP dose-dependently prevented DNA fragmentation induced by KCl 25/5 mM shift and serum deprivation in cerebellar granule neurons with a pIC50 of 5.7 ± 0.6. The inhibition of PTP-mediated cytochrome c release observed in isolated mitochondria at 10 and 100 μM may explain its neuroprotective properties in vitro. These data suggest that the mitochondrial PTP is potentially involved in neuronal cell death and that PTP inhibitors, like BBMP, may possess a therapeutic potential in neurodegenerative disorders.