טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentYaniv Gal
SubjectModulation of Fas-Induced Apoptosis in Cultured
Neonatal Rat Ventricular Myocytes by Ischemic
Stresses
DepartmentDepartment of Medicine
Supervisors Professor Emeritus Ofer Binah
Ms. Sarit Larisch


Abstract

The Fas/Fas Ligand system plays an important role in various myocardial diseases. However, recent studies have shown that healthy normoxic cardiomyocytes are resistant to apoptosis induced by Fas activation. In this study we hypothesized that while healthy cardiomyocytes are resistant to Fas-mediated apoptosis, myocardial stresses such as hypoxia or free radical injury sensitize cardiomyocytes to Fas-mediated apoptosis, by altering the balance between pro-apoptotic and anti-apoptotic proteins related to the Fas apoptotic pathway. In an attempt to block Fas deleterious effects, genistein, a broad-spectrum tyrosine kinases inhibitor was administrated during hypoxia and normoxia, before and during Fas activation.

Whereas in normoxic NRVM, rFasL did not cause apoptosis, both hypoxia and H2O2 sensitized NRVM to Fas-mediated apoptosis. That Fas was functional in normoxic NRVM was evidenced by the finding that Fas activation increased diastolic [Ca2+]i levels and caused arrhythmias. In support of our working hypothesis, hypoxia and ROS altered the expression of key pro-apoptotic (Fas, ARTS, FADD, Daxx, ASK-1) and anti-apoptotic proteins (FLIPL, ARC, xIAP), thereby predisposing NRVM to Fas-mediated apoptosis.

Genistein prevented Fas-mediated increase in 1,4,5-IP3 production in NRVM. Accordingly, genistein or herbimycin A abolished the diastolic [Ca2+]i-rise and arrhythmogenic activity in both rat and murine ventricular myocytes. Importantly, genistein attenuated Fas-mediated apoptosis in hypoxic NRVM.

In summary, the finding that NRVM are sensitized to Fas-mediated apoptosis following ischemic stresses as hypoxia and ROS, may play a key role in ischemic heart pathology. As genistein can block both Fas-mediated deleterious effects in hypoxic and normoxic NRVM, tyrosine kinase inhibition should be considered a potential theraputic target in ischemic heart disease.