-

Cell Type Specific CD40(L) Signaling in Vascular Disease

D. Lievens1, A. Zernecke2, L. Beckers1, M. Donners1, E. Wijnands1, M. de Winther1, I. Munnix1, A. Daugherty3, R. Noelle4, A. Newby5, J. Heemskerk1, C. Weber2, M. Daemen1, E. Lutgens1

1Pathology, CARIM; Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands; 2Institut fur Kardiovasculare Molekular Biology, Universitatsklinikum Aachen, Aachen, Germany; 3Cardiovascular Research Center, University of Kentucky, Lexington, United States of America; 4Microbiology and Immunology, Dartmouth Medical School, Lebanon, United States of America; 5Bristol Heart Institute, Bristol, United Kingdom;

CD40-CD40L signaling plays a crucial role in atherosclerosis. Its inhibition results in the formation of stable atherosclerotic plaques. In the present study we determined which CD40(L) expressing cell-types are pivotal in atherosclerosis and explored the role of CD40-CD40L interactions in aneurysm and neointima formation. To investigate which CD40(L) expressing cell-type is crucial in atherosclerosis, we performed a bone marrow transplantation in which we injected CD40-/- bone marrow into lethally irradiated LDLR-/- mice, and found a 2.1-fold decrease in atherosclerosis. This decrease was due to a dimished leukocyte adhesion to the endothelium. In a second experiment, we injected activated CD40L-/-/ApoE-/-, ApoE-/- platelets or PBS every 5 days in ApoE-/- mice that were fed a normal chow diet from wk 5-19 (initial lesions), or in diet fed ApoE-/- mice that underwent a bilateral collar placement to induce advanced atherosclerosis (7 wk injection). Deficiency of platelet CD40L reduced atherosclerotic lesion development and progression. Absence of CD40L resulted in an impaired platelet aggregation on collagen I, and in a 54% decrease in the formation of platelet-leukocyte aggregates. Moreover, we confirmed that in these platelet-leukocyte aggregates, platelet CD40L binds to leukocyte CD40. Abdominal dissecting aneurysms were induced in CD40L-/-/ApoE-/- mice by angiotensin II infusion. Absence of CD40L resulted in a 3.5 fold decrease in the incidence of aneurysm formation. In CD40L-/-/ApoE-/- mice, abdominal aorta’s showed a decrease in mRNA levels of MCP-1, TNFα, IL6, MIP1α, as well as in MMP-2, -9, -13 and -14, whereas TIMP-2 and -3 levels had increased. Neointima formation was induced in CD40(L)-/- mice, C57Bl6 mice, and in CD40-/- mice with a chimeric CD40 transgene with mutations in the TRAF2/3/5 and/or TRAF6 binding sites, thereby omitting CD40-TRAF2/3/5 and/or CD40-TRAF6 interactions. Neointimal volume and vascular remodeling were significantly reduced in absence of CD40. In CD40-/- mice, neointimal lesions contained less inflammation and more fibrosis. This was dependent on CD40-TRAF6, but not on CD40-TRAF2/3/5 signaling. Zymography showed that active MMP2 levels in the neointima were reduced in absence of CD40. From these data it becomes clear that CD40-CD40L interactions are very powerful players in vascular disease. The functional outcome of activation of the CD40(L) system is dependent on the cell-type and signaling intermediates that are involved.

-/YIA139.htm