title: Recombinant arginine deiminase reduces inducible nitric oxide synthase iNOS-mediated neurotoxicity in a coculture of neurons and microglia.
abstract: Modulation of nitric oxide (NO) production is considered a promising approach to therapy of diseases involving excessive inducible nitric oxide synthase (iNOS) expression, such as certain neuronal diseases. Recombinant arginine deiminase (rADI, EC3.5.3.6) catalyzes the conversion of L-arginine (L-arg), the sole substrate of NOS for NO production, to L-citrulline (L-cit) and ammonia. To understand the effect of the depletion of L-arg by rADI on NO concentration and neuroprotection, a direct coculture of neuron SHSY5Y cells and microglia BV2 cells treated with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) was used as a model of iNOS induction. The results showed that rADI preserved cell viability (4-fold higher compared with the cells treated with LPS/IFN-gamma only) by the MTT assay, corresponding with the results of neuronal viability by neuron-specific immunostaining assay. NO production (mean +/- SD) decreased from 67.0 +/- 1.3 to 19.5 +/- 5.5 microM after a 2-day treatment of rADI by the Griess assay; meanwhile, induction of iNOS protein expression by rADI was observed. In addition, rADI substantially preserved the neuronal function of dopamine uptake in the coculture. The replenishment of L-arg in the coculture eliminated the neuroprotective and NO-suppressive effects of rADI in the coculture, indicating that L-arg played a crucial role in the effects of rADI. These results highlight the important role of L-arg in the neuron-microglia coculture in excessive induction of iNOS. Regulation of L-arg by ADI demonstrated that rADI has a potentially therapeutic role in iNOS-related neuronal diseases.
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Hao-Hsin
authors.initials: HH
authors.lastname: Yu
authors.forename: Fe-Lin Lin
authors.initials: FL
authors.lastname: Wu
authors.forename: Shan-Erh
authors.initials: SE
authors.lastname: Lin
authors.forename: Li-Jiuan
authors.initials: LJ
authors.lastname: Shen
mesh_terms: D001120:Arginine / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018920:Coculture Techniques; D005434:Flow Cytometry; D006801:Humans; D006867:Hydrolases / Q000494:pharmacology*; D007150:Immunohistochemistry; D007371:Interferon-gamma / Q000633:toxicity; D008070:Lipopolysaccharides / Q000633:toxicity; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000187:drug effects*; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D008070:Lipopolysaccharides; D018696:Neuroprotective Agents; D009498:Neurotoxins; D011994:Recombinant Proteins; D009569:Nitric Oxide; D007371:Interferon-gamma; D001120:Arginine; D052247:Nitric Oxide Synthase Type II; D006867:Hydrolases; C019723:arginine deiminase