Leptin-induced IL-6 production is mediated by leptin receptor, insulin receptor substrate-1, phosphatidylinositol 3-kinase, Akt, NF-kappaB, and p300 pathway in microglia.
Leptin, the adipocyte-secreted hormone that centrally regulates weight control, is known to function as an immunomodulatory regulator. We investigated the signaling pathway involved in IL-6 production caused by leptin in microglia. Microglia expressed the long (OBRl) and short (OBRs) isoforms of the leptin receptor. Leptin caused concentration- and time-dependent increases in IL-6 production. Leptin-mediated IL-6 production was attenuated by OBRl receptor antisense oligonucleotide, PI3K inhibitor (Ly294002 and wortmannin), Akt inhibitor (1L-6-hydroxymethyl-chiro-inositol-2-((R)-2-O-methyl-3-O-octadecylcarbonate)), NF-kappaB inhibitor (pyrrolidine dithiocarbamate), IkappaB protease inhibitor (L-1-tosylamido-2-phenylenylethyl chloromethyl ketone), IkappaBalpha phosphorylation inhibitor (Bay 117082), or NF-kappaB inhibitor peptide. Transfection with insulin receptor substrate (IRS)-1 small-interference RNA or the dominant-negative mutant of p85 and Akt also inhibited the potentiating action of leptin. Stimulation of microglia with leptin activated IkappaB kinase alpha/IkappaB kinase beta, IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation at Ser(276), p65 and p50 translocation from the cytosol to the nucleus, and kappaB-luciferase activity. Leptin-mediated an increase of IkappaB kinase alpha/IkappaB kinase beta activity, kappaB-luciferase activity, and p65 and p50 binding to the NF-kappaB element was inhibited by wortmannin, Akt inhibitor, and IRS-1 small-interference RNA. The binding of p65 and p50 to the NF-kappaB elements, as well as the recruitment of p300 and the enhancement of histone H3 and H4 acetylation on the IL-6 promoter was enhanced by leptin. Our results suggest that leptin increased IL-6 production in microglia via the leptin receptor/IRS-1/PI3K/Akt/NF-kappaB and p300 signaling pathway.
Tang
Chih-Hsin
CH
Department of Pharmacology, China Medical University, Taichung, Taiwan.
Lu
Da-Yuu
DY
Yang
Rong-Sen
RS
Tsai
Huei-Yann
HY
Kao
Ming-Ching
MC
Fu
Wen-Mei
WM
Chen
Yuh-Fung
YF
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D005434:Flow Cytometry; D047468:Immunoprecipitation; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6 / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000378:metabolism*; D054411:Receptors, Leptin; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D050880:p300-CBP Transcription Factors / Q000378:metabolism
D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; C526295:Irs1 protein, mouse; D020738:Leptin; D016328:NF-kappa B; D010750:Phosphoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; C515447:leptin receptor, mouse; D050880:p300-CBP Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt