Role of JunB in Adenosine A_2BReceptor–Mediated Vascular Endothelial Growth Factor Production

Abstract

Interstitial adenosine stimulates neovascularization in part through A 2B adenosine receptor-dependent upregulation of vascular endothelial growth factor (VEGF). In the current study, we tested the hypothesis that A 2B receptors upregulate JunB, which can contribute to stimulation of VEGF production. Using the human microvascular endothelial cell line, human mast cell line, mouse cardiac Sca1-positive stromal cells, and mouse Lewis lung carcinoma (LLC) cells, we found that adenosine receptordependent upregulation of VEGF production was associated with an increase in VEGF transcription, activator protein-1 (AP-1) activity, and JunB accumulation in all cells investigated. Furthermore, the expression of JunB, but not the expression of other genes encoding transcription factors from the Jun family, was specifically upregulated. In LLC cells expressing A 2A and A 2B receptor transcripts, only the nonselective adenosine agonist NECA (59-N-ethylcarboxamidoadenosine), but not the selective A 2A receptor agonist CGS21680 [2-p-(2-carboxyethyl) phenylethylamino-59-N-ethylcarboxamidoadenosine], significantly increased JunB reporter activity and JunB nuclear accumulation, which were inhibited by the A 2B receptor antagonist PSB603 [(8-[4-[4-((4-chlorophenzyl)piperazide-1-sulfonyl)phenyl]]-1-propylxanthine]. Using activators and inhibitors of intracellular signaling, we demonstrated that A 2B receptor-dependent accumulation of JunB protein and VEGF secretion share common intracellular pathways. NECA enhanced JunB binding to the murine VEGF promoter, whereas mutation of the high-affinity AP-1 site (21093 to 21086) resulted in a loss of NECA-dependent VEGF reporter activity. Finally, NECA-dependent VEGF secretion and reporter activity were inhibited by the expression of a dominant negative JunB or by JunB knockdown. Thus, our data suggest an important role of the A 2B receptor-dependent upregulation of JunB in VEGF production and possibly other AP-1-regulated events.

Expression of adenosine receptors in monocytes from patients with bronchial asthma

“…In agreement with previously documented adenosine actions [14,26,27,28], stimulation of adenosine receptors resulted in the induction of IL-6 , IL-8 and VEGF mRNA expressions in both asthmatics and control subjects (Fig. 4).…”

A2a and a2b adenosine receptors affect HIF‐1α signaling in activated primary microglial cells

“…However, in the present study we have shown that the A 2B subtype is involved in the VEGF secretion not through HIF‐1α stimulation. Several works in literature reported a role for A 2B receptors in VEGF secretion in various cell types in a HIF‐1α‐independent way and recently a role of Jun B in A 2B ‐mediated VEGF secretion has been demonstrated (Feoktistov et al, ; Ryzhov et al, ). Therefore, it is likely that different pathways may be activated by the same receptor depending on the cellular system investigated or the stimulus applied.…”

Impaired adenosine-mediated angiogenesis in preeclampsia: potential implications for fetal programming

“…Further studies, using HMEC-1 demonstrated that adenosine receptor-dependent upregulation of VEGF production was associated with an increase in VEGF transcription, activator protein 1 (AP-1) activity and transcription factor JunB (JunB) accumulation (Ryzhov et al, 2014). …”