Antiapoptotic effects of leptin in human neuroblastoma cells.
Many factors regulate nervous system development, including complex cross-talk between local neuroendocrine systems. The adipocyte-secreted hormone leptin, mainly known for its key roles in nutrition and reproductive balance, may also be involved in neuroanatomical organization, myelination processes, and neuronal/glia maturation. SK-N-SH-SY5Y neuroblastoma cells were employed as an in vitro model of human neuronal cells to determine whether leptin exerts neuroprotective activities. We show that SH-SY5Y cells express leptin, the long and short isoforms of the leptin receptor (ObRl, ObRs). In SH-SY5Y cells, leptin induced signal transducer and activator of transcription (STAT)-3 phosphorylation and suppressor of cytokine signaling-3 mRNA expression. Leptin dose-dependently increased cell number (up to 200% at 1 microm by 48 h, P < 0.01), and at 24-48 h, leptin at 100 nm increased SH-SY5Y cell number by 30-50%, respectively. SH-SY5Y cell viability was reduced in serum-free conditions at 24 h, and addition of leptin at 100 nm significantly reduced apoptosis by approximately 20% (P < 0.001). Leptin's antiapoptotic activity required Janus kinase/STAT, MAPK, and phosphatidylinositol-3-kinase activation because the antiapoptotic effects of leptin were abolished, and caspase-3 immunoreactivity increased in the presence of the specific blockers AG490, U0126, or LY294002. Gene array demonstrated that leptin inhibits apoptosis via potent down-regulation of caspase-10 and TNF-related apoptosis-inducing ligand. Our data thus demonstrate, for the first time, that leptin stimulates, in a time- and dose-dependent manner, neuroblastoma cell proliferation and that the underlying mechanisms involve suppression of apoptosis via the Janus kinase-STAT, phosphatidylinositol-3 kinase, and MAPK pathways that culminate altogether in the down-regulation of the apoptotic factors caspase-10 and TNF-related apoptosis-inducing ligand.
Russo
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Centre for Hormone Research, Murdoch Childrens Research Institute, Parkville 3052, Victoria, Australia. vince.russo@mcri.edu.au.
Metaxas
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Kobayashi
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Harris
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Werther
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GA
D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D001798:Blood Proteins / Q000494:pharmacology; D053455:Caspase 10; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D048031:JNK Mitogen-Activated Protein Kinases; D020738:Leptin / Q000378:metabolism / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology* / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D050796:STAT3 Transcription Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; D015534:Trans-Activators / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D001798:Blood Proteins; D004268:DNA-Binding Proteins; D020738:Leptin; D008562:Membrane Glycoproteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D053455:Caspase 10; D020169:Caspases; C506438:CASP10 protein, human