Roles of Ca2+ and the Ca2+-sensing receptor (CASR) in the expression of inducible NOS (nitric oxide synthase)-2 and its BH4 (tetrahydrobiopterin)-dependent activation in cytokine-stimulated adult human astrocytes

✍ Scribed by Ilaria Dal Pra; Anna Chiarini; Edward F. Nemeth; Ubaldo Armato; James F. Whitfield

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 331 KB
• Volume: 96
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.20511

✦ Synopsis

Abstract

Since NO production by NOS‐2 made by astrocytes activated by proinflammatory cytokines contributes to the killing of neurons in variously damaged human brains, knowing the mechanisms responsible for NOS‐2 expression should contribute to developing effective therapeutics. The expression and activation of NOS‐2 in normal adult human cerebral cortical astrocytes treated with three proinflammatory cytokines, IL‐1β, TNF‐α, and IFN‐γ, are driven by two separable mechanisms. NOS‐2 expression requires a burst of p38 MAPK activity, while the activation of the resulting enzyme protein requires MEK/ERK‐dependent BH~4~ (tetrahydrobiopterin) synthesis between 24 and 24.5 h after adding the cytokines to the culture medium. Here we show that NOS‐2 expression in the activated astrocytes requires that the culture medium contain 1.8 mM Ca^2+^, but it is unaffected by inhibiting calcium‐sensing receptors (CASRs) with NPS 89636. However, NOS‐2 activation is inhibited by NPS 89626 during the MEK/ERK‐dependent stage between 24 and 24.5 h after adding the cytokines, and this inhibition can be overridden by exogenous BH~4~. Therefore, NOS‐2 expression and the subsequent BH~4~‐dependent NOS‐2‐activation in human astrocytes need 1.8 mM Ca^2+^ to be in the culture medium, while NOS‐2 activation also needs functional CASRs between 24 and 24.5 h after cytokine addition. These findings raise the possibility that calcilytic drugs prevent NO‐induced damage and death of human neurons. © 2005 Wiley‐Liss, Inc.