Spontaneous apoptosis in primary cultures of human and rat hepatocytes: molecular mechanisms and regulation by dexamethasone.
To elucidate the biochemical pathways leading to spontaneous apoptosis in primary cultures of human and rat hepatocytes, we examined the activation of the caspase cascade, the expression of Bcl-2-related-proteins and heat shock proteins. Comparisons were made before and after dexamethasone (DEX) treatment. We show that DEX inhibited spontaneous apoptosis in a dose-dependent manner. DEX increases the expression of anti-apoptotic Bcl-2 and Bcl-x(L) proteins, decreases the expression of pro-apoptotic Bax and inhibits Bad translocation thereby preventing the release of cytochrome c, the activation of caspases, and cell death. Although, the expression of Hsp27 and Hsp70 proteins remained unchanged, the oncogenic protein c-Myc is upregulated upon DEX-treatment. These results indicate that DEX mediates its survival effect against spontaneous apoptosis by acting upstream of the mitochondrial changes. Thus, the mitochondrial apoptotic pathway plays a major role in regulating spontaneous apoptosis in these cells. Blocking this pathway therefore may assist with organ preservation for transplant, drug screening, and other purposes.
Laboratoire de Pharmaco-Toxicologie Cellulaire et Moléculaire, INRA, 06606 Antibes, France.
B
B
Bailly-Maitre
G
G
de Sousa
N
N
Zucchini
J
J
Gugenheim
K E
KE
Boulukos
R
R
Rahmani
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D029563:Cellular Apoptosis Susceptibility Protein / Q000187:drug effects / Q000378:metabolism; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D053222:Fas Ligand Protein; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D008107:Liver Diseases / Q000378:metabolism* / Q000503:physiopathology; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
C494819:BAD protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C494821:Bad protein, rat; C494828:Bax protein, rat; C494813:Bcl2l1 protein, rat; D002352:Carrier Proteins; D029563:Cellular Apoptosis Susceptibility Protein; D003574:Cytochrome c Group; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; C489427:MYC protein, human; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D003907:Dexamethasone; D020169:Caspases