Human macrophage-induced vascular smooth muscle cell apoptosis requires NO enhancement of Fas/Fas-L interactions.
OBJECTIVE
We have previously shown that macrophages induce vascular smooth muscle cell (VSMC) apoptosis in vitro by cell-cell proximity and Fas-L/Fas interactions. Because NO is a short-range mediator, we tested whether NO mediates macrophage-induced VSMC apoptosis.


RESULTS
NO synthase (NOS) inhibitors markedly inhibited macrophage-induced apoptosis of carotid plaque VSMCs (apoptotic indices, 81+/-2.9% for control and 28.2+/-3.9% for N(G)-nitro-L-arginine methyl ester [L-NAME] treatment) and coronary medial VSMCs (apoptotic indices, 76+/-5.5% for control and 3.5+/-0.8% for L-NAME treatment). Inactive enantiomers were without effect (P>0.05). Cultured macrophages, but not VSMCs, expressed inducible NOS (but not neuronal NOS or endothelial NOS) concomitant with activation and secreted 1.51+/-0.3 fmol nitrite per cell, which was blocked by L-NAME (100 micro mol/L). Diethylene triamine nitric oxide (DETA/NO) and sodium nitroprusside (NO donors) induced VSMC cell-surface Fas and enhanced plaque VSMC apoptosis induced by agonistic anti-Fas antibody (apoptotic indices, 6.6+/-1.8% for control, 6.3+/-1.5% for DETA/NO, 26+/-1.8% for Fas, and 44+/-6.9% for Fas+DETA/NO). In isolated macrophages, NOS inhibitors reduced and NO donors increased surface Fas-L, indicating an NO-dependent autocrine enhancement of macrophage surface Fas-L.


CONCLUSIONS
Together, these data indicate that macrophage-derived NO is required for macrophage-induced VSMC apoptosis and that it acts by enhancing Fas-L/Fas interactions.
Boyle
Joseph J
JJ
Division of Cardiovascular Medicine, Addenbrooke's Hospital, Cambridge, UK. joseph.boyle@ic.ac.uk
Weissberg
Peter L
PL
Bennett
Martin R
MR
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D019898:Autocrine Communication / Q000502:physiology; D002340:Carotid Artery Diseases / Q000201:enzymology / Q000473:pathology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000473:pathology / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D009599:Nitroprusside / Q000378:metabolism; D011073:Polyamines / Q000378:metabolism; D021381:Protein Transport; D015854:Up-Regulation / Q000502:physiology; D019014:fas Receptor / Q000378:metabolism*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008024:Ligands; D008562:Membrane Glycoproteins; D020030:Nitric Oxide Donors; D011073:Polyamines; D019014:fas Receptor; C005391:diethylenetriamine; D009599:Nitroprusside; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D019331:NG-Nitroarginine Methyl Ester