title: NOX2 activated by α1-adrenoceptors modulates hepatic metabolic routes stimulated by β-adrenoceptors.
abstract: The NADPH oxidase (NOX) family of enzymes oxidase catalyzes the transport of electrons from NADPH to molecular oxygen and generates O(2)(•-), which is rapidly converted into H(2)O(2). We aimed to identify in hepatocytes the protein NOX complex responsible for H(2)O(2) synthesis after α(1)-adrenoceptor (α(1)-AR) stimulation, its activation mechanism, and to explore H(2)O(2) as a potential modulator of hepatic metabolic routes, gluconeogenesis, and ureagenesis, stimulated by the ARs. The dormant NOX2 complex present in hepatocyte plasma membrane (HPM) contains gp91(phox), p22(phox), p40(phox), p47(phox), p67(phox) and Rac 1 proteins. In HPM incubated with NADPH and guanosine triphosphate (GTP), α(1)-AR-mediated H(2)O(2) synthesis required all of these proteins except for p40(phox). A functional link between α(1)-AR and NOX was identified as the Gα(13) protein. Alpha(1)-AR stimulation in hepatocytes promotes Rac1-GTP generation, a necessary step for H(2)O(2) synthesis. Negative cross talk between α(1)-/β-ARs for H(2)O(2) synthesis was observed in HPM. In addition, negative cross talk of α(1)-AR via H(2)O(2) to β-AR-mediated stimulation was recorded in hepatocyte gluconeogenesis and ureagenesis, probably involving aquaporine activity. Based on previous work we suggest that H(2)O(2), generated after NOX2 activation by α(1)-AR lightening in hepatocytes, reacts with cAMP-dependent protein kinase A (PKA) subunits to form an oxidized PKA, insensitive to cAMP activation that prevented any rise in the rate of gluconeogenesis and ureagenesis.
authors.affiliation: Department of Animal Nutrition and Biochemistry, Faculty of Veterinary Medicine and Zootechnics, National Autonomous University of Mexico, Mexico City, Mexico. adc@servidor.unam.mx
authors.forename: Antonio
authors.initials: A
authors.lastname: Diaz-Cruz
authors.forename: Maria Magdalena
authors.initials: MM
authors.lastname: Vilchis-Landeros
authors.forename: Raquel
authors.initials: R
authors.lastname: Guinzberg
authors.forename: Rafael
authors.initials: R
authors.lastname: Villalobos-Molina
authors.forename: Enrique
authors.initials: E
authors.lastname: Piña
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D020346:Aquaporins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005943:Gluconeogenesis; D006160:Guanosine Triphosphate / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D046912:Multiprotein Complexes / Q000378:metabolism; D009249:NADP / Q000494:pharmacology; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000737:chemistry / Q000378:metabolism*; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism*; D014508:Urea / Q000378:metabolism
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D020346:Aquaporins; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; D018340:Receptors, Adrenergic, alpha-1; D018342:Receptors, Adrenergic, beta-1; D009249:NADP; D006160:Guanosine Triphosphate; D014508:Urea; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D017868:Cyclic AMP-Dependent Protein Kinases