Botanical C-glucosylated isoflavone puerarin suppresses nitric oxide-induced neurotoxicity via inducing arginase-2 expression

Abstract

Aberrant production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is implicated in the ageing process and the pathogenesis of neurodegenerative diseases, major depression, schizophrenia and bipolar disorder. Puerarin is an antioxidant and neuroprotective C-glycosylated isoflavonone derived from a group of edible plants in the genus of pueraria native to much of Asia and Pacific Islands such as Radix Puerariae (the dried root of Pueraria lobata (Wild.) Ohwi). The present study was designed to elucidate the puerarin target protein networks in regulating the survival and differentiation of neurons. A proteomic response fingerprinting (ProReF) approach was employed to profile the cellular responses to puerarin in differentiated PC12 cells. The protein spots with the change of more than 1.5-fold were selected and analyzed by MALDI-TOF mass spectrometry. Of a total of 16 proteins identified, mitochondrial enzyme arginase-2 is well-known to hydrolyze L-arginine to L-ornithine. Thus, arginase-2 is of importance for its potential role in the control of nitric oxide (NO)-mediated neuronal injury via competing the substrate L-arginine with nitric oxide synthase (NOS) in mitochondria. We confirmed that arginase II was up-regulated by puerarin in a dose and time dependent manner by Western blotting technique. By inhibiting arginase-2 with specific inhibitor BEC, puerarin lost its activity against neurotoxin 6-hydroxydopamine (6-OHDA)-induced formation in the intracellular nitric oxide (NO) in differentiated PC12 cells and primary culture of rat midbrain neurons. These results suggest that pharmacological induction of arginase-2 expression represents a novel neuroprotective mechanism. Puerarin may serve as a lead molecule for future development of neuroprotective therapiess in neurodegenerative diseases and psychiatric disorders.