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Leukocyte Overexpression of Intracellular NAMPT Attenuates Atherosclerosis by Regulating PPARγ-Dependent Monocyte
Beatriz Bermudez1, Tuva Borresdatter Dahl2, Indira Medina2
1From the Experimental Vascular Pathology Group, Department of Pathology, CARIM, Maastricht University Medical Center, The Netherlands (B.B., I.M., M.G., M.R., J.O., V.H., E.A.L.B.); Department of Cell Biology, School of Biology, University of Seville, Spain (B.B.); Laboratory of Cellular and Molecular Nutrition (LCMN), Instituto de la Grasa, Seville, Spain (S.M.-d.l.P., L.M.V., A.O.-G., R.A., F.J.G.M.); Department of Molecular Biology and Biochemical Engineering, Universidad Pablo de Olavide, Seville, Spain (L.M.V.); Department of Vascular Immunotherapy, Institute for Cardiovascular Prevention, Ludwig Maximilians University Munich, Germany (A.O.-G.); Section of Clinical Immunology and Infectious Diseases (P.A.), and Department of Microbiology for Research Institute of Internal Medicine (T.B.D., S.H., T.R., A.Y., P.A., B.H.), Section of Clinical Immunology and Infectious Diseases (P.A.), and Department of Microbiology, Oslo University Hospital Rikshospitalet, Norway (T.B.D.); Department of Internal Medicine, K.G. Jebsen Inflammatory Research Center, Oslo, Norway (T.B.D., T.R., A.Y., P.A., B.H.); Faculty of Medicine, University of Oslo, Norway (T.R., A.Y., P.A., B.H.); and Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, University of Debrecen Medical and Health Science Center, Hungary (L.N.). bbermudez@us.es.
Objective:
Extracellular nicotinamide phosphoribosyltransferase (eNAMPT) mediates inflammatory and potentially proatherogenic effects, whereas the role of intracellular NAMPT (iNAMPT), the rate limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide (NAD)+ generation, in atherogenesis is largely unknown. Here we investigated the effects of iNAMPT overexpression in leukocytes on inflammation and atherosclerosis.
Approach And Results:
Low-density lipoprotein receptor-deficient mice with hematopoietic overexpression of human iNAMPT (iNAMPThi), on a western type diet, showed attenuated plaque burden with features of lesion stabilization. This anti-atherogenic effect was caused by improved resistance of macrophages to apoptosis by attenuated chemokine (C-C motif) receptor 2-dependent monocyte chemotaxis and by skewing macrophage polarization toward an anti-inflammatory M2 phenotype. The iNAMPThi phenotype was almost fully reversed by treatment with the NAMPT inhibitor FK866, indicating that iNAMPT catalytic activity is instrumental in the atheroprotection. Importantly, iNAMPT overexpression did not induce any increase in eNAMPT, and eNAMPT had no effect on chemokine (C-C motif) receptor 2 expression and promoted an inflammatory M1 phenotype in macrophages. The iNAMPT-mediated effects at least partly involved sirtuin 1-dependent molecular crosstalk of NAMPT and peroxisome proliferator-activated receptor γ. Finally, iNAMPT and peroxisome proliferator-activated receptor γ showed a strong correlation in human atherosclerotic, but not healthy arteries, hinting to a relevance of iNAMPT/peroxisome proliferator-activated receptor γ pathway also in human carotid atherosclerosis.
Conclusions:
This study highlights the functional dichotomy of intracellular versus extracellular NAMPT, and unveils a critical role for the iNAMPT-peroxisome proliferator-activated receptor γ axis in atherosclerosis.