NO Production In Microglial Cells Research Articles

Glutamine Cooperatively Upregulates Lipopolysaccharide-Induced Nitric Oxide Production in BV2 Microglial Cells through the ERK and Nrf-2/HO-1 Signaling Pathway

Glutamine (Gln) is a nonessential α-amino acid for protein biosynthesis. However, the mechanism through which Gln regulates NO production in microglial cells is still unclear. In this study, we investigated whether the presence or absence of Gln affects NO production in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. Our data revealed that Gln depletion decreased cell viability accompanied by mild cytotoxicity, and blocked LPS-induced NO production concomitant with a significant decrease in inducible NO synthase (iNOS) expression. Additionally, Gln depletion for 24 h blocked the restoration of LPS-mediated NO production in the presence of Gln, suggesting that Gln depletion caused long-term immune deprivation. In particular, sodium-coupled amino acid transporter 1 and 2 (SNAT1 and SNAT2), which are the main Gln transporters, were highly upregulated in LPS-stimulated BV2 microglial cells, in the presence of Gln accompanied by NO production. Regardless of the presence of Gln, LPS positively stimulated nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression, and transient Nrf2 knockdown and HO-1 inhibition stimulated LPS-induced NO production and iNOS expression; however, transient Nrf2 knockdown did not affect SNAT1 and SNAT2 expression, indicating that Gln transporters, SNAT1 and SNAT2, were not regulated by Nrf2, which downregulated the HO-1-mediated NO production. Moreover, Gln depletion significantly reduced LPS-induced extracellular signal-regulated kinase (ERK) phosphorylation; furthermore, a specific ERK inhibitor, PD98059, and transient ERK knockdown attenuated LPS-stimulated NO production and iNOS expression, in the presence of Gln, accompanied by downregulation of SNAT1 and SNAT2, suggesting that the ERK signaling pathway was related to LPS-mediated NO production via SNAT1 and SNAT2. Altogether, our data indicated that extracellular Gln is vital for NO production from microglia in inflammatory conditions.

Mn(III)‐Salen Protect Against Different ROS Species Generated by the Aβ16‐Cu Complex

AbstractAβ‐Cu complex generates different reactive oxygen species (ROS) which are responsible for oxidative stress in neuronal cells. We studied the effect of Mn(III)‐salen on Aβ‐Cu catalyzed ROS generation using different assays. Mn(III)‐salen reacts with O2•−generated by Aβ‐Cu and delay H2O2production. Mn(III)‐salen significantly inhibits the formation of HO•generated by Aβ‐Cu which is further confirmed using mass spectrometry analysis. Our results indicate that H2O2generated by Aβ‐Cu activates Mn(III)‐salen to oxomanganese which in turn detoxify Aβ‐Cu‐induced NO production in microglial cells. Overall, Mn(III)‐salen complex can efficiently inhibits different ROS generated by Aβ‐Cu due to its redox flexibility.

Inhibition of interferon‐gamma‐induced nitric oxide production in BV‐2 microglial cells by polyphenolic compounds

Microglial cells are known to play an important role in mediating the host defense functions in the brain. These cells respond readily to pro‐inflammatory cytokines, which stimulate signalling pathways and induction of many genes, including the inducible nitric oxide synthase (iNOS). In the immortalized BV‐2 microglial cells, our studies have demonstrated that interferon gamma (IFNγ) alone could stimulate the induction of iNOS through activation of the nuclear factor‐kappa B (NF‐κB) pathway. Increased NO production in the brain has been implicated in enhanced oxidative stress associated with many neurodegenerative diseases. Many polyphenolic compounds in vegetables and fruits, including resveratrol, catechin, quercetin, genistein are regarded as phytoestrogens and are known to possess potent antioxidant properties. However, whether these compounds also offer anti‐inflammatory effects and inhibit cytokine‐induced NO production in microglial cells have not been examined in detail. The major goal for this project is to use BV‐2 microglial cells as cell model to investigate the effects of these polyphenolic compounds on IFNγ induction of NO. Results show that all the polyphenolic compounds tested could inhibit NO production albeit to different extents, with quercetin having the lowest IC50 and catechin the highest IC50. Surprising, daidzin, a non‐tyrosine kinase analog of genistein, also inhibited IFNγ‐induced NO production, suggesting that the inhibitory effects may not be due entirely to their action on the tyrosine kinase pathway. These results lead to the conclusion that polyphenolic compounds tested not only possess antioxidative but also anti‐inflammatory properties.Acknowledgements: Supported by 5 P01 ES10535 from NIH.