Leptin induces apoptosis via ERK/cPLA2/cytochrome c pathway in human bone marrow stromal cells.
Leptin, the Ob gene product, has emerged recently as a key regulator of bone mass. However, the mechanism mediating leptin effect remains controversial. Because the action of leptin is dependent on its receptors, we analyzed their expression in osteoblast-lineage primary human bone marrow stromal cells (hBMSC). Both the short and long forms of leptin receptors were detected in hBMSC. Leptin significantly decreased the viability of hBMSC. This cytotoxic effect was prevented by Z-Val-Ala-Asp-fluoromethylketone, a pan-caspase inhibitor, implicating that leptin-induced hBMSC death was caspase-dependent. Further investigation demonstrated that leptin activated caspase-3 and caspase-9, but not caspase-8, and increased the cleavage of poly-(ADP-ribose) polymerase and cytochrome c release into cytosol. Leptin activated ERK, but not p38 and JNK, and up-regulated cPLA2 activity; the latter was abolished by pre-treatment of cells with the MEK inhibitor (PD98059 or U0126) or cPLA2 inhibitor (AACOCF3). PD98059, U0126, and AACOCF3 also diminished the leptin-induced cytochrome c release into cytosol, cell death, and caspase-3 activation. These data indicated that leptin induced hBMSC apoptosis via ERK/cPLA2/cytochrome c pathway with activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase. To our knowledge, this is the first study demonstrating the direct detrimental effect of leptin on bone cells.
Kim
Ghi Su
GS
Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Gu, Seoul 138-736, Republic of Korea. gskim3@amc.seoul.kr
Hong
Jeong Soo
JS
Kim
Seung Wook
SW
Koh
Jung-Min
JM
An
Chung Sun
CS
Choi
Je-Yong
JY
Cheng
Su-Li
SL
D000469:Alkaline Phosphatase / Q000378:metabolism; D017209:Apoptosis; D016718:Arachidonic Acid / Q000378:metabolism; D001391:Azo Compounds / Q000494:pharmacology; D015152:Blotting, Northern; D001854:Bone Marrow Cells / Q000378:metabolism* / Q000473:pathology*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D004396:Coloring Agents / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D020738:Leptin / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D015675:Osteocalcin / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D017154:Stromal Cells / Q000166:cytology*; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism
D001391:Azo Compounds; D004396:Coloring Agents; D003574:Cytochrome c Group; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D020738:Leptin; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D014157:Transcription Factors; D015675:Osteocalcin; D016718:Arachidonic Acid; D011065:Poly(ADP-ribose) Polymerases; D020928:Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; C011049:oil red O