Fibroblast growth factor 2 modulates extracellular purine metabolism by upregulating ecto-5′-nucleotidase and adenosine deaminase in cultured rat spinal cord astrocytes

Alpha and beta adrenoceptors activate interleukin-6 transcription through different pathways in cultured astrocytes from rat spinal cord

In brain astrocytes, noradrenaline (NA) has been shown to up-regulate IL-6 production via β-adrenoceptors (ARs). However, the underlying intracellular mechanisms for this regulation are not clear, and it remains unknown whether α-ARs are involved. In this study, we investigated the AR-mediated regulation of IL-6 mRNA levels in the cultured astrocytes from rat spinal cord. NA, the α1-agonist phenylephrine, and the β-agonist isoproterenol increased IL-6 mRNA levels. The phenylephrine-induced IL-6 increase was accompanied by an increase in ERK phosphorylation, and these effects were blocked by inhibitors of PKC and ERK. The isoproterenol-induced IL-6 increase was accompanied by an increase in CREB phosphorylation, and these effects were blocked by a PKA inhibitor. Our results indicate that IL-6 increases by α1- and β-ARs are mediated via the PKC/ERK and cAMP/PKA/CREB pathways, respectively. Moreover, conditioned medium collected from astrocytes treated with the α2-AR agonist dexmedetomidine, increased IL-6 mRNA in other astrocytes. In this study, we elucidate that α1- and α2-ARs, in addition to β-ARs, promote IL-6 transcription through different pathways in spinal cord astrocytes.

Fibroblast growth factor 2 upregulates ecto-5'-nucleotidase and adenosine deaminase via MAPK pathways in cultured rat spinal cord astrocytes

Adenosine triphosphate (ATP) and adenosine are neurotransmitters and neuromodulators in the central nervous system. Astrocytes regulate extracellular concentration of purines via ATP release and its metabolisms via ecto-enzymes. The expression and activity of purine metabolic enzymes in astrocytes are increased under pathological conditions. We previously showed that fibroblast growth factor 2 (FGF2) upregulates the expression and activity of the enzymes ecto-5'-nucleotidase (CD73) and adenosine deaminase (ADA). Here, we further demonstrate that this occurs in concentration- and time-dependent manners in cultured rat spinal cord astrocytes and is suppressed by inhibitors of the FGF receptor as well as the mitogen-activated protein kinases (MAPKs). We also found that FGF2 increased the phosphorylation of MAPKs, including extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAPK, leading to the increased expression and activity of CD73 and ADA. Our findings reveal the involvement of FGF2/MAPK pathways in the regulation of purine metabolic enzymes in astrocytes. These pathways may contribute to the control of extracellular purine concentrations under physiological and pathological conditions.