title: Endothelial apoptosis induced by inhibition of integrins alphavbeta3 and alphavbeta5 involves ceramide metabolic pathways.
abstract: Matrix ligation of integrins alphavbeta3/alphavbeta5 is critical for endothelial survival and angiogenesis. We have previously shown that ceramide, a proapoptotic lipid second messenger, increases during endothelial anoikis (detachment-induced apoptosis). We now show that RGDfV, an integrin alphavbeta3/alphavbeta5 cyclic function-blocking peptide, increased ceramide and decreased sphingomyelin in human brain microvascular endothelial cells (HBMECs) plated on vitronectin, suggesting that sphingomyelin hydrolysis contributes to RGDfV-induced ceramide increase. Desipramine and imipramine, inhibitors of acid sphingomyelinase (ASMase), suppressed RGDfV-induced ceramide increase. Importantly, desipramine, imipramine, and a third ASMase inhibitor, SR33557, but not inhibitors of neutral sphingomyelinase, suppressed RGDfV-induced apoptosis, suggesting that ASMase was required for integrin-mediated apoptosis. Myriocin, an inhibitor of de novo ceramide synthesis, had no effect on RGDfV-induced HBMEC apoptosis. Interestingly, ASMase inhibitors also suppressed the RGDfV-induced loss of spreading on vitronectin. RGDfV induced a similar increase in ceramide and apoptosis in HBMECs on poly-l-lysine or vitronectin, although cells detached only from vitronectin, indicating that cell detachment was not required for RGDfV-induced apoptosis. Our results suggest involvement of ASMase and ceramide in endothelial apoptosis induced by inhibition of integrins alphavbeta3/alphavbeta5, and propose a novel molecular mechanism for the antiangiogenic effect of RGDfV.
authors.affiliation: Division of Hematology-Oncology, Department of Pediatrics, The Saban Research Institute at Childrens Hospital Los Angeles, 4650 Sunset Blvd, Mailstop No. 57, Los Angeles, CA 90027, USA. epstein@usc.edu
authors.forename: Anat
authors.initials: A
authors.lastname: Erdreich-Epstein
authors.forename: Linda B
authors.initials: LB
authors.lastname: Tran
authors.forename: Orla T
authors.initials: OT
authors.lastname: Cox
authors.forename: Elaine Y
authors.initials: EY
authors.lastname: Huang
authors.forename: Walter E
authors.initials: WE
authors.lastname: Laug
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shimada
authors.forename: Melissa
authors.initials: M
authors.lastname: Millard
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D017209:Apoptosis; D001921:Brain / Q000098:blood supply / Q000166:cytology; D002518:Ceramides / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology*; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors* / Q000502:physiology; D016023:Integrins / Q000037:antagonists & inhibitors* / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology; D019030:Receptors, Vitronectin / Q000037:antagonists & inhibitors* / Q000502:physiology; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000502:physiology; D013109:Sphingomyelins / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D002518:Ceramides; D039302:Integrin alphaVbeta3; D016023:Integrins; D009842:Oligopeptides; D019030:Receptors, Vitronectin; D013109:Sphingomyelins; C064660:integrin alphaVbeta5; C086684:arginyl-glycyl-aspartyl-valine; C112980:acid sphingomyelinase-1; D013108:Sphingomyelin Phosphodiesterase