SUMMARY Resveratrol, a polyphenol in red wine, has been reported as a calorie restriction mimetic with potential antiaging and antidiabetogenic properties. It is widely consumed as a nutritional supplement, but its mechanism of action remains a mystery. Here, we report that the metabolic effects of resveratrol result from competitive inhibition of cAMP-degrading phosphodiesterases, leading to elevated cAMP levels. The resulting activation of Epac1, a cAMP effector protein, increases intracellular Ca2+ levels and activates the CamKKβ-AMPK pathway via phospholipase C and the ryanodine receptor Ca2+-release channel. As a consequence, resveratrol increases NAD+ and the activity of Sirt1. Inhibiting PDE4 with rolipram reproduces all of the metabolic benefits of resveratrol, including prevention of diet-induced obesity and an increase in mitochondrial function, physical stamina, and glucose tolerance in mice. Therefore, administration of PDE4 inhibitors may also protect against and ameliorate the symptoms of metabolic diseases associated with aging.

Mast cells play a pivotal role in inflammatory and immediate-type allergic reactions by secreting a variety of potent inflammatory mediators, including sphingosine-1-phosphate (S1P). However, it is not known how S1P is released from cells. Here, we report that S1P is exported from mast cells independently of their degranulation and demonstrate that it is mediated by ATP binding cassette (ABC) transporters. Constitutive and antigen-stimulated S1P release was inhibited by MK571, an inhibitor of ABCC1 (MRP1), but not by inhibitors of ABCB1 (MDR-1, P-glycoprotein). Moreover, downregulation of ABCC1 with small interfering RNA, which decreased its cell surface expression, markedly reduced S1P export from both rat RBL-2H3 and human LAD2 mast cells. Transport of S1P by ABCC1 influenced migration of mast cells toward antigen but not degranulation. These findings have important implications for S1P functions in mast cell-mediated immune responses.secretion ͉ sphingolipids ͉ multidrug resistance ͉ allergic responses ͉ sphingosine kinase S phingosine-1-phosphate (S1P) is a pleiotropic lipid mediator that has been implicated in cancer, immunity, and allergy (1-4). S1P is a ligand for a family of five specific G protein-coupled receptors, designated S1P 1-5 (collectively referred to as S1PRs) (5), through which it regulates many different biological responses, including growth, survival, differentiation, cytoskeleton rearrangements, motility, angiogenesis, vascular maturation, lymphocyte trafficking, and mast cell functions (reviewed in refs. 1-3, 5, and 6). Moreover, like its precursors, sphingosine (Sph) and ceramide, S1P may also have intracellular functions (1, 2, 7). S1P is produced in cells by phosphorylation of Sph, the backbone of all sphingolipids, catalyzed by two closely related Sph kinase (SphK) isoenzymes. SphK1 activity is enhanced by numerous external stimuli, including growth factors, ligands for G protein-coupled receptors, and proinflammatory cytokines, and by cross-linking of Ig receptors (reviewed in refs. 1 and 6). To date, only EGF (8) and cross-linking of Ig receptors (4) have been shown to stimulate SphK2.Although S1P secretion has been demonstrated in only a few types of cells (platelets, astroglial cells, and mast cells) activation of SphK1 involves its translocation to the plasma membrane where its substrate Sph resides (9 -11). Increased S1P formation, in turn, activates S1P receptors on the same and͞or neighboring cells in an autocrine or paracrine manner. It has been demonstrated that this type of ''inside-out'' signaling by S1P is critical for migratory responses of fibroblasts and smooth muscle cells toward PDGF (9, 12) and human breast cancer cells toward EGF (8). Similarly, S1P secreted by mast cells is important for migration of mast cells toward antigen (Ag) and might be involved in the movement of mast cells to sites of inf lammation (13). In addition, S1P provokes human airway smooth muscle contraction and may promote inf lammation and airway remodeling in asthma (14). Because S1P's level...

Park et al.: Resveratrol ameliorates aging-related metabolic phenotypes by inhibiting cAMP phosphodiesterases. BMC Proceedings 2012 6(Suppl 3):P73.