Hypoxia predisposes neonatal rat ventricular myocytes to apoptosis induced by activation of the Fas (CD95/Apo-1) receptor: Fas activation and apoptosis in hypoxic myocytes.
OBJECTIVE
Since apoptosis is an important contributor to heart diseases in which ischemia and hypoxia are key elements, we tested the hypothesis that hypoxia predisposes neonatal rat ventricular myocytes (NRVM) to Fas-mediated apoptosis, by shifting the balance between antiapoptotic and proapoptotic proteins towards the latter.


METHODS
Normoxic or hypoxic (22 h, 1% O(2)) cultured NRVM were exposed to recombinant Fas L (rFasL) for 7 h, and apoptosis measured thereafter.


RESULTS
Whereas in normoxic NRVM, rFasL did not cause apoptosis measured by the TUNEL assay (4.8+/-0.5% in control versus 4.5+/-0.9% in rFasL), in hypoxic cultures rFasL increased the background apoptosis level by 100%. That Fas was functional in normoxic NRVM, despite its inability to mediate apoptosis, was evidenced by the finding that Fas activation increased the diastolic [Ca(2+)](i) levels measured by Fura 2 fluorescence, and caused arrhythmias. In support of our working hypothesis, hypoxia increased Fas expression by 200% (measured by quantitative Western blot), and the expression of the proapoptotic proteins ARTS and FADD by 323 and 250%, respectively, and decreased the expression of the antiapoptotic proteins ARC and FLIP by 90 and 60%, respectively.


CONCLUSIONS
By upregulating Fas expression and key proapoptotic proteins, and by downregulating antiapoptotic proteins, hypoxia predisposes ventricular myocytes to Fas-induced apoptosis.
Yaniv
Gal
G
Bruce Rappaport Faculty of Medicine, The Bernard Katz Minerva Center for Cell Biophysics, Technion-Israel Institute of Technology, Haifa, Israel.
Shilkrut
Mark
M
Lotan
Rona
R
Berke
Gideon
G
Larisch
Sarit
S
Binah
Ofer
O
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D029681:Arabidopsis Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D053222:Fas Ligand Protein; D044943:Fatty Acid Desaturases / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D009124:Muscle Proteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D019014:fas Receptor / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D029681:Arabidopsis Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D009124:Muscle Proteins; C491788:Nol3 protein, rat; D011994:Recombinant Proteins; D019014:fas Receptor; D044943:Fatty Acid Desaturases; C084083:Fad7 protein, Arabidopsis