Recombinant arginine deiminase reduces inducible nitric oxide synthase iNOS-mediated neurotoxicity in a coculture of neurons and microglia

✍ Scribed by Hao-Hsin Yu; Fe-Lin Lin Wu; Shan-Erh Lin; Li-Jiuan Shen

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 337 KB
• Volume: 86
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/jnr.21740

✦ Synopsis

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‐γ (IFN‐γ) 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‐γ 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 μM 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. © 2008 Wiley‐Liss, Inc.