title: Epac/Rap1 pathway regulates microvascular hyperpermeability induced by PAF in rat mesentery.
abstract: Experiments in cultured endothelial cell monolayers demonstrate that increased intracellular cAMP strongly inhibits the acute permeability responses by both protein kinase A (PKA)-dependent and -independent pathways. The contribution of the PKA-independent pathways to the anti-inflammatory mechanisms of cAMP in intact mammalian microvessels has not been systematically investigated. We evaluated the role of the cAMP-dependent activation of the exchange protein activated by cAMP (Epac), a guanine nucleotide exchange factor for the small GTPase Rap1, in rat venular microvessels exposed to the platelet-activating factor (PAF). The cAMP analog 8-pCPT-2'-O-methyl-cAMP (O-Me-cAMP), which stimulates the Epac/Rap1 pathway but has no effect on PKA, significantly attenuated the PAF increase in microvessel permeability as measured by hydraulic conductivity (Lp). We also demonstrated that PAF induced a rearrangement of vascular endothelial (VE)-cadherin seen as numerous lateral spikes and frequent short breaks in the otherwise continuous peripheral immunofluorescent label. Pretreatment with O-Me-cAMP completely prevented the PAF-induced rearrangement of VE-cadherin. We conclude that the action of the Epac/Rap1 pathway to stabilize cell-cell adhesion is a significant component of the activity of cAMP to attenuate an acute increase in vascular permeability. Our results indicate that increased permeability in intact microvessels by acute inflammatory agents such as PAF is the result of the decreased effectiveness of the Epac/Rap1 pathway modulation of cell-cell adhesion.
authors.affiliation: Physiology and Membrane Biology, School of Medicine, University of California at Davis, Davis, CA 95616, USA. rhadamson@ucdavis.edu
authors.forename: R H
authors.initials: RH
authors.lastname: Adamson
authors.forename: J C
authors.initials: JC
authors.lastname: Ly
authors.forename: R K
authors.initials: RK
authors.lastname: Sarai
authors.forename: J F
authors.initials: JF
authors.lastname: Lenz
authors.forename: A
authors.initials: A
authors.lastname: Altangerel
authors.forename: D
authors.initials: D
authors.lastname: Drenckhahn
authors.forename: F E
authors.initials: FE
authors.lastname: Curry
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D007202:Indicators and Reagents; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D018613:Microscopy, Confocal; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020889:Rolipram / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013152:Splanchnic Circulation / Q000187:drug effects / Q000502:physiology*; D020827:rap1 GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D000318:Adrenergic beta-Agonists; D015820:Cadherins; D007202:Indicators and Reagents; C483758:N(6)-phenyl-cAMP; D010726:Phosphodiesterase Inhibitors; D010972:Platelet Activating Factor; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D020827:rap1 GTP-Binding Proteins; D020889:Rolipram; D007545:Isoproterenol