Transition of apoptotic resistant vascular smooth muscle cells to troptotic sensitive state is correlated with downregulation of c-FLIP.
Fas and its ligand, FasL, are a receptor-ligand pair identified as promoting cell death in several tissues. Vascular smooth muscle cells (VSMCs) are resistant to FasL or anti-Fas antibody (Ab) signal, and a number of in vitro studies show that VSMC death can only be induced by anti-Fas Ab or FasL in the presence of protein inhibitor or additional inflammatory mediators. It remains to be clarified whether known, constitutively expressed cytoprotective molecules are reduced by protein inhibitor, thereby accounting for sensitization to cell death by Fas/FasL signaling. We found that Fas mRNA and protein exist in several primary VSMCs, as previously reported. We also demonstrated (1) that critical death-signaling molecules, such as FADD, caspase-1/ICE, and caspase-3/YAMA, are present in these VSMCs, (2) that human VSMCs contain high concentrations of c-FLIP (3) and that following treatment with the protein inhibitor, CHX, cell extracts showed a decrease in c-FLIP protein that was dose- and time-dependent on the degree of apoptosis and inversely correlated with both caspase-8 and -3 activity. In contrast, there was neither a change nor an even modest upregulation of Bcl-2 family, even after 12 h of treatment with CHX. Taken together, these results may provide a novel insight into atherogenesis and suggest that c-FLIP may contribute to an apoptosis-resistant state of VSMC, and that a downregulation of c-FLIP may render VSMCs susceptible to apoptosis.
Imanishi
T
T
Division of Cardiology, Department of Medicine, Wakayama Medical College, Wakayama City, Japan. imanashi@wakayama.hosp.gobo.jp
Hano
T
T
Nishio
I
I
Liles
W C
WC
Schwartz
S M
SM
Han
D K
DK
D017209:Apoptosis / Q000187:drug effects; D029681:Arabidopsis Proteins; D001161:Arteriosclerosis / Q000503:physiopathology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020170:Caspase 1 / Q000096:biosynthesis / Q000235:genetics; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004790:Enzyme Induction; D004797:Enzyme-Linked Immunosorbent Assay; D053222:Fas Ligand Protein; D044943:Fatty Acid Desaturases / Q000096:biosynthesis / Q000235:genetics; D005786:Gene Expression Regulation; D019254:Genes, bcl-2; D006801:Humans; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D015398:Signal Transduction; D051020:bcl-X Protein; D019014:fas Receptor / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
D029681:Arabidopsis Proteins; C494811:BCL2L1 protein, human; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D011500:Protein Synthesis Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D051020:bcl-X Protein; D019014:fas Receptor; D003513:Cycloheximide; D044943:Fatty Acid Desaturases; C084083:Fad7 protein, Arabidopsis; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D020170:Caspase 1