TNF-alpha/IFN-gamma-induced iNOS expression increased by prostaglandin E2 in rat primary astrocytes via EP2-evoked cAMP/PKA and intracellular calcium signaling.
Astrocytes, the most abundant glia in the central nervous system (CNS), produce a large amount of prostaglandin E(2) (PGE(2)) in response to proinflammatory mediators after CNS injury. However, it is unclear whether PGE(2) has a regulatory role in astrocytic activity under the inflamed condition. In the present work, we showed that PGE(2) increased inducible nitric oxide synthase (iNOS) production by tumor necrosis factor-alpha and interferon-gamma (T/I) in astrocytes. Pharmacological and RNA interference approaches further indicated the involvement of the receptor EP2 in PGE(2)-induced iNOS upregulation in T/I-treated astrocytes. Quantitative real-time polymerase chain reaction and gel mobility shift assays also demonstrated that PGE(2) increased iNOS transcription through EP2-induced cAMP/protein kinase A (PKA)-dependent pathway. Consistently, the effect of EP2 was significantly attenuated by the PKA inhibitor KT-5720 and partially suppressed by the inhibitor (SB203580) of p38 mitogen-activated protein kinase (p38MAPK), which serves as one of the downstream components of the PKA-dependent pathway. Interestingly, EP2-mediated PKA signaling appeared to increase intracellular Ca(2+) release through inositol triphosphate (IP3) receptor activation, which might in turn stimulate protein kinase C (PKC) activation to promote iNOS production in T/I-primed astrocytes. By analyzing the expression of astrocytic glial fibrillary acidic protein (GFAP), we found that PGE(2) alone only triggered the EP2-induced cAMP/PKA/p38MAPK signaling pathway in astrocytes. Collectively, PGE(2) may enhance T/I-induced astrocytic activation by augmenting iNOS/NO production through EP2-mediated cross-talk between cAMP/PKA and IP3/Ca(2+) signaling pathways.
Hsiao
Han-Yun
HY
Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan.
Mak
Oi-Tong
OT
Yang
Chung-Shi
CS
Liu
Yu-Peng
YP
Fang
Kuan-Ming
KM
Tzeng
Shun-Fen
SF
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000276:immunology / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016207:Cytokines / Q000276:immunology / Q000378:metabolism*; D015232:Dinoprostone / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D004660:Encephalitis / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005911:Gliosis / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000187:drug effects / Q000378:metabolism; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D007424:Intracellular Fluid / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D052247:Nitric Oxide Synthase Type II / Q000276:immunology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018078:Receptors, Prostaglandin E / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D058307:Receptors, Prostaglandin E, EP2 Subtype; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D016207:Cytokines; D004791:Enzyme Inhibitors; D053496:Inositol 1,4,5-Trisphosphate Receptors; C545646:Ptger2 protein, rat; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D000242:Cyclic AMP; D052247:Nitric Oxide Synthase Type II; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone