Glutamine and interleukin‐1β interact at the level of Sp1 and nuclear factor‐κB to regulate argininosuccinate synthetase gene expression

Abstract

We previously demonstrated that the expression of the argininosuccinate synthetase (ASS) gene, a key step in nitric oxide production, is stimulated either by interleukin‐1β[Brasse‐Lagnel et al. (2005) Biochimie 87, 403–9] or by glutamine in Caco‐2 cells [Brasse‐Lagnel et al. (2003) J. Biol. Chem. 278, 52504–10], through the activation of transcription factors nuclear factor‐κB and Sp1, respectively. In these cells, the fact that glutamine stimulated the expression of a gene induced by pro‐inflammatory factors appeared paradoxical as the amino acid is known to exert anti‐inflammatory properties in intestinal cells. We therefore investigated the effect of simultaneous addition of both glutamine and interleukin‐1β on ASS gene expression in Caco‐2 cells. In the presence of both compounds for 4 h, the increases in ASS activity, protein amount and mRNA level were almost totally inhibited, implying a reciprocal inhibition between the amino acid and the cytokine. The inhibition was exerted at the level of the transcription factors Sp1 and nuclear‐κB: (a) interleukin‐1β inhibited the glutamine‐stimulated DNA‐binding of Sp1, which might be related to a decrease of its glutamine‐induced O‐glycosylation, and (b) glutamine induced per se a decrease in the amount of nuclear p65 protein without affecting the stimulating effect of interleukin‐1β on nuclear factor‐κB, which might be related to the metabolism of glutamine into glutamate. The present results constitute the first demonstration of a reciprocal inhibition between the effects of an amino acid and a cytokine on gene expression, and provide a molecular basis for the protective role of glutamine against inflammation in the intestine.

Potential for amino acids supplementation during inflammatory bowel diseases

“…35,46 The action of glutamine on cytokine production is mediated by different signaling pathways (Fig. 2), including nuclear factor kappa B (NF-jB), 16,46,47,50,51 signal transducer and activator of transcription (STAT), 37,47 Jun N-terminal kinase (JNK), 48 or peroxisome proliferator-activated receptor-c (PPARc). 49 During IBD, oxidative stress is increased in intestinal mucosa and antioxidative defenses, especially glutathione, are reduced.…”

To Give or Not to Give? Lessons from the Arginine Paradox

“…Glutamine and arginine are excellent substrates for the citric acid cycle because both may be efficient precursors of α-ketoglutarate, and this explains why, in demanding metabolic conditions such as in sepsis, both these AA can be found substantially decreased in plasma [26]. Moreover, elevated concentrations of glutamine increase ASsynth expression and activity in intestinal cells, similarly to interleukin (IL)-1β, but the simultaneous presence of glutamine and IL-1 suppresses ASsynth expression and activity [27]. In contrast, glutamine inhibits arginine synthesis in endothelial cells by directly decreasing ASsynth activity and also through a competitive inhibition of citrulline uptake [28].…”

IKKβ promotes metabolic adaptation to glutamine deprivation via phosphorylation and inhibition of PFKFB3

“…This is not entirely surprising, as p65 Ser536 phosphorylation does not necessarily affect p65 transcriptional activity (Okazaki et al 2003). Interestingly, previous reports have indicated that glutamine level affects LPS or interleukin 1-β function via modulation of p65 nuclear activity (Liboni et al 2005;Brasse-Lagnel et al 2007), indicating that glutamine level may play a role in coordinating cytokine-regulated NF-κB activity and cell survival.…”