title: A2B adenosine receptor contributes to penile erection via PI3K/AKT signaling cascade-mediated eNOS activation.
abstract: Normal penile erection is under the control of multiple factors and signaling pathways. Although adenosine signaling is implicated in normal and abnormal penile erection, the exact role and the underlying mechanism for adenosine signaling in penile physiology remain elusive. Here we report that shear stress leads to increased adenosine release from endothelial cells. Subsequently, we determined that ecto-5'-nucleotidase (CD73) is a key enzyme required for the production of elevated adenosine from ATP released by shear-stressed endothelial cells. Mechanistically, we demonstrate that shear stress-mediated elevated adenosine functions through the adenosine A(2B) receptor (A(2B)R) to activate the PI3K/AKT signaling cascade and subsequent increased endothelial nitric oxide synthase (eNOS) phosphorylation. These in vitro studies led us to discover further that adenosine was induced during sustained penile erection and contributes to PI3K/AKT activation and subsequent eNOS phosphorylation via A(2B)R signaling in intact animal. Finally, we demonstrate that lowering adenosine in wild-type mice or genetic deletion of A(2B)R in mutant mice significantly attenuated PI3K/AKT activation, eNOS phosphorylation, and subsequent impaired penile erection featured with the reduction of ratio of maximal intracavernosal pressure to systemic arterial pressure from 0.49 ± 0.03 to 0.41 ± 0.05 and 0.38 ± 0.04, respectively (both P<0.05). Overall, using biochemical, cellular, genetic, and physiological approaches, our findings reveal that adenosine is a novel molecule signaling via A(2B)R activation, contributing to penile erection via PI3K/AKT-dependent eNOS activation. These studies suggest that this signaling pathway may be a novel therapeutic target for erectile disorders.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, 6431 Fannin St., MSB 6.200, Houston, TX 77030, USA.
authors.forename: Jiaming
authors.initials: J
authors.lastname: Wen
authors.forename: Almut
authors.initials: A
authors.lastname: Grenz
authors.forename: Yujin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yingbo
authors.initials: Y
authors.lastname: Dai
authors.forename: Rodney E
authors.initials: RE
authors.lastname: Kellems
authors.forename: Michael R
authors.initials: MR
authors.lastname: Blackburn
authors.forename: Holger K
authors.initials: HK
authors.lastname: Eltzschig
authors.forename: Yang
authors.initials: Y
authors.lastname: Xia
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism; D000241:Adenosine / Q000502:physiology; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D002460:Cell Line; D004558:Electric Stimulation; D042783:Endothelial Cells / Q000502:physiology; D004789:Enzyme Activation; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D052250:Nitric Oxide Synthase Type III / Q000502:physiology*; D010410:Penile Erection / Q000502:physiology*; D010413:Penis / Q000294:innervation / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D043704:Receptor, Adenosine A2B / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical
chemical_list: D043704:Receptor, Adenosine A2B; D000255:Adenosine Triphosphate; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D015720:5'-Nucleotidase; D000241:Adenosine