The second messengers cAMP and cGMP are important mediators of signal transduction and hence a wide range of cellular processes including vasodilation and synaptic plasticity. Type 2 cyclic nucleotide phosphodiesterases (PDE2) isoforms inactivate cAMP and cGMP by hydrolyzing the phosphodiester bond. BAY 60-7550 is a potent PDE2 inhibitor with IC50 values of 2.0 nM (bovine) and 4.7 nM (human). It is 50-fold more selective for PDE2 compared to PDE1 and greater than 100-fold selective compared to PDE5 PDE3B, PDE4B, PDE7B, PDE8A, PDE9A, PDE10A, and PDE11A. At 3 mg/kg BAY 60-7550 antagonizes oxidative stress-induced anxiety-like behavioral effects in mice by increasing cGMP signaling. At 1 mg/kg BAY 60-7550 improves the performance of rats in an object location task, enhancing cAMP/cGMP-mediated object and spatial memory consolidation.
BAY 60-7550 is an orally active, potent and selective cGMP-dependent phosphodiesterase PDE2 (PDE2A) inhibitor (human/bovine PDE2 IC50 = 4.7/2.0 nM; bovine PDE1 IC50 = 108 nM, human PDE5/5A/10A/4B IC50 = 240/580/704/940/1830 nM, human PDE3B/7B/8A/9A/11A IC50 >4 μM) with little activity (IC50 >10 μM) toward acetylcholinesterase, mAO-A/B, adenosine deaminase, and many receptor subtypes tested. Bay 60-7550 effectively upregulates cGMP and cAMP level in cultured rat and murine neurons (1 nM-1 μM) exposed to guanylyl cyclase (GC) or adenylyl cyclase (AC) stimulator (1 μM Bay 41-8543 or 2 μM forskolin), respectively, as well as exhibits learning and memory-improving efficacy in rats (0.6-3 mg/kg p.o.) and mice (0.3-1 mg/kg p.o.) in vivo.
This selective cGMP/cAMP phosphodiesterase PDE2A inhibitor (FW = 476.60 g/mol; CAS 439083-90-6; Solubility: 10 mM DMSO), systematically named 2-[(3,4-dimethoxyphenyl)methyl]-7-[(1R)-1- hydroxyethyl]-4-phenylbutyl]-5-methyl-imidazo[5,1-f][1,2,4]triazin-4(1H)- one, targets Type 2 cyclic nucleotide phosphodiesterase (human, IC50 = 4.7 nM; bovine, IC50 = 2.0 nM), a dual-function enzyme that, when stimulated by 3’,5’-cyclicGMP (cGMP), preferentially catalyzes hydrolysis of 3’,5’- cyclicAMP (cAMP). BAY 60-7550 is 50x more selective for PDE2 than PDE1 and >100x selective relative to PDE5 PDE3B, PDE4B, PDE7B, PDE8A, PDE9A, PDE10A, and PDE11A. Use of BAY-60-7550 also indicates that PDE2 is responsible for the degradation of newly synthesized cGMP in cultured neurons and hippocampal slices. Inhibition of PDE2 enhanced long-term potentiation of synaptic transmission without altering basal synaptic transmission. Inhibition of PDE2 also improved the performance of rats in social and object recognition memory tasks, and reversed MK801-induced deficits in spontaneous alternation in mice in a T maze. Treatment of mice with L-buthionine-(S,R)-sulfoximine (300 mg/kg) induces oxidative stress and also causes anxiety-like behavioral effects in elevated plus-maze, open-field, and hole-board tests, most likely through the NADPH oxidase pathway. These effects are antagonized by Bay 60-7550 (3 mg/kg), which decreases oxidative stress and expression of NADPH oxidase subunits in amygdala, hypothalamus, and cultured neurons. The resulting increase in cGMP also promotes phosphorylation of vasodilator-stimulated phosphoprotein (VASP) at Ser-239, suggesting a role of cGMP-Protein Kinase G signaling in the reduction of anxiety. PDE inhibitors also enhance object recognition, and the effects of PDE inhibition on cognitive functions may result from higher cerebrovascular function. In the spatial location task, PDE5 inhibition of cGMP hydrolysis by vardenafil only enhances early-phase consolidation, and PDE4 inhibition of cAMP hydrolysis by rolipram only enhances late-phase consolidation; on the other hand, PDE2 inhibition of cAMP and cGMP hydrolysis by Bay 60- 7550, enhances both. These results underscore the specific effects of cAMP and cGMP on memory consolidation (object and spatial memory) and provide evidence that the underlying mechanisms of PDE inhibition on cognition are independent of cerebrovascular effects. Bay 60-7550 treatment also indicates that phosphodiesterase 2A is a major negative regulator of iNOS expression in lipopolysaccharide-treated mouse alveolar macrophages. BAY 60-7550 reverses functional impairments induced by brain ischemia by decreasing hippocampal neurodegeneration and enhancing hippocampal neuronal plasticity.
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