title: PACAP and its receptor VPAC1 regulate megakaryocyte maturation: therapeutic implications.
abstract: Megakaryocytes and platelets express the Gs-coupled VPAC1 receptor, for which the pituitary adenylyl cyclase-activating peptide (PACAP) and the vasointestinal peptide (VIP) are agonists. We here demonstrate a regulatory role for VPAC1 signaling during megakaryopoiesis. A total of 2 patients with trisomy 18p with PACAP overexpression and transgenic mice overexpressing PACAP in megakaryocytes have thrombopathy, a mild thrombocytopenia, and a reduced number of mature megakaryocytes in their bone marrow. In vitro differentiation of hematopoietic stem cells from the patient and transgenic mice shows a reduced number of megakaryocyte colonies compared with controls. The addition of PACAP, VIP, or the adenylyl cyclase activator forskolin to CD34(+) cells inhibits megakaryocyte differentiation. In contrast, neutralizing monoclonal anti-PACAP (PP1A4) or anti-VPAC1 (23A11) antibodies inhibit cAMP formation and stimulate megakaryopoiesis in a thrombopoietin-independent manner. Moreover, wild-type mice obtain an increased platelet count after subcutaneous injection of PP1A4 or 23A11. These antibodies also elevate platelet numbers in animal models of myelosuppressive therapy and in GATA1-deficient mice with congenital thrombocytopenia. Furthermore, 23A11 stimulates the in vitro megakaryocyte differentiation of both normal and GATA1-deficient human CD34(+) cells. Together, our data strongly suggest that VPAC1 signaling tempers normal megakaryopoiesis, and that inhibition of this pathway stimulates megakaryocyte differentiation, enhancing platelet recovery after myelosuppressive therapy and in GATA1 deficiency.
authors.affiliation: Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium. kathleen.freson@med.kuleuven.be
authors.forename: Kathleen
authors.initials: K
authors.lastname: Freson
authors.forename: Karen
authors.initials: K
authors.lastname: Peeters
authors.forename: Rita
authors.initials: R
authors.lastname: De Vos
authors.forename: Christine
authors.initials: C
authors.lastname: Wittevrongel
authors.forename: Chantal
authors.initials: C
authors.lastname: Thys
authors.forename: Marc F
authors.initials: MF
authors.lastname: Hoylaerts
authors.forename: Jos
authors.initials: J
authors.lastname: Vermylen
authors.forename: Chris
authors.initials: C
authors.lastname: Van Geet
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D045744:Cell Line, Tumor; D002887:Chromosomes, Human, Pair 18; D000242:Cyclic AMP / Q000502:physiology; D006801:Humans; D008533:Megakaryocytes / Q000166:cytology* / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000235:genetics* / Q000502:physiology; D011817:Rabbits; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I / Q000235:genetics* / Q000502:physiology; D013921:Thrombocytopenia / Q000235:genetics; D014314:Trisomy / Q000235:genetics
chemical_list: C495401:ADCYAP1 protein, human; D015703:Antigens, CD; D018952:Antigens, CD34; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D000242:Cyclic AMP