title: Extracellular NAD(+) inhibits human neutrophil apoptosis.
abstract: Regulation of neutrophil apoptosis plays a critical role in the inflammatory response. Inflammation has previously been shown to increase levels of extracellular β-nicotinamide adenine dinucleotide (NAD(+)). The present study demonstrates that extracellular NAD(+) at concentrations found in the inflamed tissues profoundly delays spontaneous apoptosis of human neutrophils as was evidenced by inhibition of phosphatidylserine (PS) exposure, DNA fragmentation and caspase-3 activation. The effect was abrogated by NF157, an antagonist of P2Y11 receptor, and was pertussis toxin-insensitive. The NAD(+)-mediated delay of neutrophil apoptosis was reversed by 2',5'-dideoxyadenosine, an inhibitor of adenylyl cyclase, and Rp-8-Br-cAMPS, an inhibitor of type I cAMP-dependent protein kinase A (PKA). Blocking of NAD(+)-induced influx of extracellular Ca(2+) with EGTA did not abolish the pro-survival effect of NAD(+). Extracellular NAD(+) inhibited proteasome-dependent degradation of Mcl-1 upstream of caspase activation and, furthermore, suppressed Bax translocation to the mitochondria and attenuated both dissipation of mitochondrial transmembrane potential (ΔΨm) and cytochrome c release from the mitochondria into the cytosol. Finally, we found that extracellular NAD(+) inhibited spontaneous activation of caspase-9, but not caspase-8, and the pro-survival effect of extracellular NAD(+) was abrogated by the inhibitor of caspase-9, but not by the inhibitor of caspase-8. Together, these results demonstrate that extracellular NAD(+) inhibits neutrophil apoptosis via P2Y11 receptor and cAMP/PKA pathway by regulating Mcl-1 level, Bax targeting to the mitochondria and mitochondrial apoptotic pathway. Thus, extracellular NAD(+) acts as a neutrophil survival factor that can contribute to prolonged neutrophil lifespan in inflammatory response.
authors.affiliation: Hematology Research Center, Novy Zykovsky Pr. 4, Moscow, 125167, Russia, bpliyev@cardio.ru.
authors.forename: Boris K
authors.initials: BK
authors.lastname: Pliyev
authors.forename: Anna V
authors.initials: AV
authors.lastname: Ivanova
authors.forename: Valery G
authors.initials: VG
authors.lastname: Savchenko
mesh_terms: D017209:Apoptosis; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005110:Extracellular Space / Q000201:enzymology; D006801:Humans; D007249:Inflammation / Q000473:pathology; D008928:Mitochondria / Q000502:physiology; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism; D009243:NAD / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; C109734:P2RY11 protein, human; D018048:Receptors, Purinergic P2; D009243:NAD; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D046988:Proteasome Endopeptidase Complex