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Aim: To develop high-throughput screening (HTS) assays for monoamine oxidase (MAO)-A and MAO-B inhibitors. Methods: A fluorescence probe based method measuring MAO-A and MAO-B activity was established and optimized, with its sensitivity, stability and specificity evaluated. Reaction conditions including enzyme sources, substrate concentrations, incubation volume and reaction time in 384-well format were optimized to achieve sensitive and low consumptive goal. Results: In optimized conditions, dynamic parameters of MAO-A and MAO-B were obtained. The Km value of serotonin to MAO-A was 1.66 μmol/L, while that of benzylamine to MAO-B was 0.80 μmol/L. The IC50 value of clorgyline to MAO-A was 2.99 nmol/L, and that of deprenyl to MAO-B was 7.04 nmol/L, matching those obtained from traditional spectrometric assays. Among tested samples, one compound exerted an inhibitory effect on MAO-A activity with IC 50 as 0.36 μmol/L, and three compounds had an inhibitory effect on MAO-B activity with IC 50 as 0.13, 0.19, and 0.13 μmol/L. The Z' factor was 0.71±0.03 and 0.75±0.03 in MAO-A-inhibitor and MAO-B-inhibitor HTS system, respectively. Conclusion: The established assays can be well applied to MAO-A and MAO-B inhibitor screening with high quality, precision and reproducibility.

To study effects of pinocembrin, a natural compound extracted from propolis, on cognitive ability impaired by chronic cerebral hypoperfusion in rats, and if it did so, to investigate its effects on brain mitochondria. Rat chronic cerebral hypoperfusion was achieved by permanent bilateral common carotid arteries ligation, with regional cerebral blood flow evaluated. Cognitive ability was tested by Morris water maze task. Production of reactive oxygen species and origin targets including mitochondria membrane potential, respiratory chain complex I, complex III activities and mitochondria swelling degree were evaluated. Cytochrome oxidase was determined on its expression level by western blotting. Pinocembrin alleviated cognitive impairments in Morris water maze and decreased mitochondria reactive oxygen species production, in accordance with its improvements on complex I activity, membrane potential level, mitochondria swelling degree and cytochrome oxidase deficits. Pinocembrin could improve rat cognitive impairments induced by chronic cerebral hypoperfusion, contributed to its protections on brain mitochondria structure and function.

To observe the damages induced by hydrogen peroxide in cultured bovine cerebral microvascular endothelial cells (BCMEC) and evaluate the protective effects of hydroxyethylpuerarin on hydrogen peroxide-injured BCMEC.BCMEC were cultured and transferred into modified Eagle medium (MEM). The viability of cells was detected by MTT assay. Cell injury was determined by lactate dehydrogenase (LDH) activity in the extracellular medium. Flow cytometry was employed to observe the occurrence of apoptosis. Morphologic changes of cells were visualized under phase contrast and electron microscopes.Hydrogen peroxide (200 micromol x L(-1) for 4 hours) inhibited the viability of cultured BCMEC and stimulated LDH release. Hydrogen peroxide (100 micromol x L(-1) for 4 hours) induced the occurrence of apoptosis. Hydroxyethylpuerarin was shown to increase the survival rate and decrease the activity of LDH of BCMEC damaged by hydrogen peroxide. Hydroxyethylpuerarin was also found to protect BCMEC against apoptosis induced by hydrogen peroxide.Hydrogen peroxide induces BCMEC injury either by apoptosis or through necrosis. Hydroxyethylpuerarin protects BCMEC against hydrogen peroxide-induced injury in a concentration-dependent manner. Its antioxidant effects might be involved as the mechanism protection.