Nicotinamide Phosphoribosyltransferase Regulates Cell Survival Through NAD+ Synthesis in Cardiac Myocytes

Rationale: NAD+ acts not only as a cofactor for cellular respiration but also as a substrate for NAD+-dependent enzymes, such as Sirt1. The cellular NAD+ synthesis is regulated by both the de novo and the salvage pathways. Nicotinamide phosphoribosyltransferase (Nampt) is a rate-limiting enzyme in the salvage pathway. Objective: Here we investigated the role of Nampt in mediating NAD+ synthesis in cardiac myocytes and the function of Nampt in the heart in vivo. Methods and Results: Expression of Nampt in the heart was significantly decreased by ischemia, ischemia/reperfusion and pressure overload. Upregulation of Nampt significantly increased NAD+ and ATP concentrations, whereas downregulation of Nampt significantly decreased them. Downregulation of Nampt increased caspase 3 cleavage, cytochrome c release, and TUNEL-positive cells, which were inhibited in the presence of Bcl-xL, but did not increase hairpin 2–positive cells, suggesting that endogenous Nampt negatively regulates apoptosis but not necrosis. Downregulation of Nampt also impaired autophagic flux, suggesting that endogenous Nampt positively regulates autophagy. Cardiac-specific overexpression of Nampt in transgenic mice increased NAD+ content in the heart, prevented downregulation of Nampt, and reduced the size of myocardial infarction and apoptosis in response to prolonged ischemia and ischemia/reperfusion. Conclusions: Nampt critically regulates NAD+ and ATP contents, thereby playing an essential role in mediating cell survival by inhibiting apoptosis and stimulating autophagic flux in cardiac myocytes. Preventing downregulation of Nampt inhibits myocardial injury in response to myocardial ischemia and reperfusion. These results suggest that Nampt is an essential gatekeeper of energy status and survival in cardiac myocytes.

[1]  M. Matsuda,et al.  Visfatin: a protein secreted by visceral fat that mimics the effects of insulin. , 2005, Science.

[2]  L. Guarente.  Sirtuins as potential targets for metabolic syndrome , 2006, Nature.

[3]  L. Gille,et al.  The existence of a lysosomal redox chain and the role of ubiquinone. , 2000, Archives of biochemistry and biophysics.

[4]  W. Tao,et al.  Lats2 Is a Negative Regulator of Myocyte Size in the Heart , 2008, Circulation research.

[5]  S. Vatner,et al.  Silent Information Regulator 2&agr;, a Longevity Factor and Class III Histone Deacetylase, Is an Essential Endogenous Apoptosis Inhibitor in Cardiac Myocytes , 2004, Circulation research.

[6]  S. Imai,et al.  The regulation of nicotinamide adenine dinucleotide biosynthesis by Nampt/PBEF/visfatin in mammals , 2007, Current opinion in gastroenterology.

[7]  S. Vatner,et al.  Activation of Mst1 causes dilated cardiomyopathy by stimulating apoptosis without compensatory ventricular myocyte hypertrophy. , 2003, The Journal of clinical investigation.

[8]  S. Vatner,et al.  Sirt1 Regulates Aging and Resistance to Oxidative Stress in the Heart , 2007, Circulation research.

[9]  Yasushi Matsumura,et al.  The role of autophagy in cardiomyocytes in the basal state and in response to hemodynamic stress , 2007, Nature Medicine.

[10]  G. Bjørkøy,et al.  p62/SQSTM1: A Missing Link between Protein Aggregates and the Autophagy Machinery , 2006, Autophagy.

[11]  P. Bernardi,et al.  Opening of the Mitochondrial Permeability Transition Pore Causes Depletion of Mitochondrial and Cytosolic NAD+and Is a Causative Event in the Death of Myocytes in Postischemic Reperfusion of the Heart* , 2001, The Journal of Biological Chemistry.

[12]  D. Torella,et al.  Senescence and Death of Primitive Cells and Myocytes Lead to Premature Cardiac Aging and Heart Failure , 2003, Circulation research.

[13]  S. Imai,et al.  The NAD Biosynthesis Pathway Mediated by Nicotinamide Phosphoribosyltransferase Regulates Sir2 Activity in Mammalian Cells* , 2004, Journal of Biological Chemistry.

[14]  R. Billington,et al.  NAD depletion by FK866 induces autophagy , 2008, Autophagy.

[15]  Dudley Lamming,et al.  Nutrient-Sensitive Mitochondrial NAD+ Levels Dictate Cell Survival , 2007, Cell.

[16]  D. Sinclair,et al.  Nicotinamide and PNC1 govern lifespan extension by calorie restriction in Saccharomyces cerevisiae , 2003, Nature.

[17]  J. Sadoshima,et al.  Inhibition of Endogenous Mst1 Prevents Apoptosis and Cardiac Dysfunction Without Affecting Cardiac Hypertrophy After Myocardial Infarction , 2007, Circulation research.

[18]  E. Zocchi,et al.  Connexin 43 hemichannels mediate Ca2+‐regulated transmembrane NAD+ fluxes in intact cells , 2001, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[19]  S. Vatner,et al.  Chelerythrine rapidly induces apoptosis through generation of reactive oxygen species in cardiac myocytes. , 2001, Journal of molecular and cellular cardiology.

[20]  L. Guarente,et al.  Transcriptional silencing and longevity protein Sir2 is an NAD-dependent histone deacetylase , 2000, Nature.

[21]  Nicholas E. Bruns,et al.  A role for the NAD-dependent deacetylase Sirt1 in the regulation of autophagy , 2008, Proceedings of the National Academy of Sciences.

[22]  C. Brenner,et al.  NAD+ metabolism in health and disease. , 2007, Trends in biochemical sciences.

[23]  S. Imai,et al.  Poly(ADP-ribose) Polymerase-1-dependent Cardiac Myocyte Cell Death during Heart Failure Is Mediated by NAD+ Depletion and Reduced Sir2α Deacetylase Activity* , 2005, Journal of Biological Chemistry.

[24]  Chengqun Huang,et al.  A method to measure cardiac autophagic flux in vivo , 2008, Autophagy.

[25]  J. Sadoshima,et al.  Sirt1 protects the heart from aging and stress , 2008, Biological chemistry.

[26]  D. Klionsky,et al.  Protein turnover via autophagy: implications for metabolism. , 2007, Annual review of nutrition.

[27]  G. Condorelli,et al.  The Akt-Glycogen Synthase Kinase 3β Pathway Regulates Transcription of Atrial Natriuretic Factor Induced by β-Adrenergic Receptor Stimulation in Cardiac Myocytes* , 2000, The Journal of Biological Chemistry.

[28]  Samuel H. Wilson,et al.  Involvement of poly(ADP-ribose) polymerase activity in regulating Chk1-dependent apoptotic cell death. , 2005, DNA repair.

[29]  Ileana M. Cristea,et al.  Induction of Autophagy in Axonal Dystrophy and Degeneration , 2006, The Journal of Neuroscience.

[30]  D. Sinclair.  Toward a unified theory of caloric restriction and longevity regulation , 2005, Mechanisms of Ageing and Development.

[31]  T. Asano,et al.  Distinct Roles of Autophagy in the Heart During Ischemia and Reperfusion: Roles of AMP-Activated Protein Kinase and Beclin 1 in Mediating Autophagy , 2007, Circulation research.

[32]  S. Vatner,et al.  The MEKK1-JNK pathway plays a protective role in pressure overload but does not mediate cardiac hypertrophy. , 2002, The Journal of clinical investigation.

[33]  J. Denu.  Vitamins and Aging: Pathways to NAD+ Synthesis , 2007, Cell.