Potential role for ceramide in mitogen-activated protein kinase activation and proliferation of vascular smooth muscle cells induced by oxidized low density lipoprotein.
Proliferation of vascular smooth muscle cells (SMC) is a hallmark in the pathogenesis of atherosclerotic lesions. Mildly oxidized low density lipoproteins (UV-oxLDL), which are mitogenic to cultured AG-08133A SMC, activate the sphingomyelin (SM)-ceramide pathway. We report here the following. (i) UV-oxLDL elicited a biphasic and sustained activation of MBP kinase activity, phosphorylation and nuclear translocation of p44/42 mitogen-activated protein kinase (MAPK), and [3H]thymidine incorporation, which were inhibited by PD-098059, a MAPK kinase inhibitor. (ii) The use of preconditioned media (from SMC pre-activated by UV-oxLDL) transferred to native SMC and blocking antibodies against growth factors suggest that UV-oxLDL-induced activation of MAPK and [3H]thymidine incorporation seem to be independent of any autocrine secretion of growth factors. (iii) UV-oxLDL-induced activation of a neutral sphingomyelinase, SM hydrolysis, ceramide production, and [3H]thymidine incorporation were inhibited by two serine-protease inhibitors (serpins), suggesting that a serpin-sensitive proteolytic pathway is involved in the activation of the SM-ceramide signaling pathway. (iv) UV-oxLDL-induced MAPK activation and [3H]thymidine incorporation were mimicked by ceramide generated in the plasma membrane by bacterial sphingomyelinase treatment or by addition of the permeant C2-ceramide. Serpins did not inhibit the MAPK activation and [3H]thymidine incorporation induced by C2-ceramide, indicating that activation of the MAPK and [3H]thymidine incorporation is subsequent to the stimulation of the SM-ceramide pathway. Taken together, these data suggest that mitogenic concentrations of UV-oxLDL are able to stimulate the SM-ceramide pathway through a protease-dependent mechanism and activate p44/42 MAPK, leading to proliferation of vascular SMC.
Augé
N
N
Laboratory of Biochemistry, INSERM U-466, Institut Louis Bugnard, CHU Rangueil, 1 Avenue Jean Poulhes, 31403 Toulouse Cedex 4, France.
Escargueil-Blanc
I
I
Lajoie-Mazenc
I
I
Suc
I
I
Andrieu-Abadie
N
N
Pieraggi
M T
MT
Chatelut
M
M
Thiers
J C
JC
Jaffrézou
J P
JP
Laurent
G
G
Levade
T
T
Nègre-Salvayre
A
A
Salvayre
R
R
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002417:Cattle; D002455:Cell Division / Q000502:physiology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D010084:Oxidation-Reduction; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D013109:Sphingomyelins / Q000378:metabolism / Q000502:physiology*; D013936:Thymidine / Q000378:metabolism
D008077:Lipoproteins, LDL; D013109:Sphingomyelins; C099252:oxidized low density lipoprotein; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013108:Sphingomyelin Phosphodiesterase; D013936:Thymidine