Extracellular Nucleotides Differentially Regulate Interleukin-1β Signaling in Primary Human Astrocytes: Implications for Inflammatory Gene Expression

Abstract

The cytokine interleukin-1␤ (IL-1␤) is a potent activator of human astrocytes, inducing or modulating expression of multiple proinflammatory genes via activation of the transcription factors nuclear factor-B (NF-B) and activator protein-1 (AP-1). In this study, we examined whether IL-1␤ signaling is regulated in these cells by extracellular nucleotides that are released at high concentrations under inflammatory conditions and act as ligands for members of the P2 receptor family. Using reporter constructs and electromobility shift assays, we found that cotreatment of astrocyte cultures with ATP (1-100 M) significantly potentiated IL-1␤-mediated activation of NF-B and AP-1 and that ATP alone activated AP-1. These effects were blocked by the P2 receptor antagonists XAMR 0721, periodate-oxidized ATP, and suramin. A role for ATP in modulating IL-1␤-mediated inflammatory gene expression was supported further by the observation that ATP potentiated the IL-1␤-induced expression of IL-8 mRNA and protein but strongly downregulated IP-10 expression. Reverse transcription-PCR and cloning demonstrated expression of the ATP-responsive P2 receptor subtypes P2Y 1 , P2Y 2 , and P2X 7 , as well as the ATP-insensitive receptor P2Y 4 . ADP, a selective agonist for P2Y 1 , produced results similar to or greater than those obtained using ATP, whereas 2Ј-3Ј-O-(4-benzoylbenzoyl)-ATP, a selective agonist for P2X 7 , was less effective than ATP. In contrast, UTP, a selective agonist for P2Y 2 and P2Y 4 , was ineffective. These studies indicate that different P2 receptor subtypes play distinct roles in the modulation of IL-1␤-mediated signal transduction in human astrocytes, and that signaling via P2 receptors may fine-tune the transcription of genes involved in inflammatory responses in the human CNS.

The Tryptophan Metabolite 3-Hydroxyanthranilic Acid Plays Anti-Inflammatory and Neuroprotective Roles During Inflammation

“…The lack of effect on IL-8 production in the same culture demonstrated that 3-HAA was not simply inducing cell toxicity and apoptosis, as some studies have suggested. 48 The two ␣-chemokines (IP-10 and IL-8) are often differentially regulated, for example, by extracellular ATP or PI3K/AKT inhibitor, 49,50 in addition to 3-HAA as shown in this study. At present, the basis for the differential regulation is not clear.…”

Adenosine suppresses activation of nuclear factor-κB selectively induced by tumor necrosis factor in different cell types

“…Adenosine blocks TNF-mediated NF-jB activation S Majumdar and BB Aggarwal TNF-induced activation, ATP was also found to potentiate IL-1b-mediated NF-kB activation in human astrocytes (John et al, 2001). Another report showed that ATP suppresses interleukin-12 (IL-12) and TNF release from macrophages (Hasko et al, 2000a, b), which suggests that ATP may suppress NF-kB activation.…”

“…Indeed, suppression of lipopolysaccharide (LPS)-induced TNF production by adenosine has been demonstrated in human cardiac tissue (Wagner et al, 1998a, b). Additionally, adenosine has also been shown to modulate the signaling of inflammatory cytokines, including TNF (de la Harpe and Nathan, 1989;Sullivan et al, 1990;Bergmann et al, 1994;Liu et al, 2000) and interleukin-1 (IL-1) (Pahl 1999;John et al, 2001).…”

Concomitant Recruitment of ERK1/2 and p38 MAPK Signalling Pathway Is Required for Activation of Cytoplasmic Phospholipase A2via ATP in Articular Chondrocytes

“…Thus, ATP and proinflammatory cytokines in articular tissue may well act synergistically and complementarily, because there is a true interplay between the classic inflammatory mediators and ATP in other systems. In astrocytes, P2Y modulates IL-1␤-mediated signal transduction and finetunes the transcription of genes involved in inflammatory responses in the human central nervous system (30). Conversely, IL-1␤ increases the transcription and function of P2Y 2 receptors in vascular smooth muscle cells (31) and in mammalian astrocytes (32).…”