title: Modulation of angiotensin II-induced inflammatory cytokines by the Epac1-Rap1A-NHE3 pathway: implications in renal tubular pathobiology.
abstract: Besides the glomerulus, the tubulointerstitium is often concomitantly affected in certain diseases, e.g., diabetic nephropathy, and activation of the renin-angiotensin system, to a certain extent, worsens its outcome because of perturbations in hemodynamics and possibly tubuloglomerular feedback. Certain studies suggest that pathobiology of the tubulointerstitium is influenced by small GTPases, e.g., Rap1. We investigated the effect of ANG II on inflammatory cytokines, while at the same time focusing on upstream effector of Rap1, i.e., Epac1, and some of the downstream tubular transport molecules, i.e., Na/H exchanger 3 (NHE3). ANG II treatment of LLC-PK1 cells decreased Rap1a GTPase activity in a time- and dose-dependent manner. ANG II treatment led to an increased membrane translocation of NHE3, which was reduced with Epac1 and PKA activators. ANG II-induced NHE3 translocation was notably reduced with the transfection of Rap1a dominant positive mutants, i.e., Rap1a-G12V or Rap1a-T35A. Transfection of cells with dominant negative Rap1a mutants, i.e., Rap1a-S17A, or Epac1 mutant, i.e., EPAC-ΔcAMP, normalized ANG II-induced translocation of NHE3. In addition, ANG II treatment led to an increased expression of inflammatory cytokines, i.e., IL-1β, IL-6, IL-8, and TNF-α, which was reduced with Rap1a-G12V or Rap1a-T35A transfection, while it reverted to previous comparable levels following transfection of Rap1a-S17A or EPAC-ΔcAMP. ANG II-induced expression of cytokines was reduced with the treatment with NHE3 inhibitor S3226 or with Epac1 and PKA activators. These data suggest that this novel Epac1-Rap1a-NHE3 pathway conceivably modulates ANG II-induced expression of inflammatory cytokines, and this information may yield the impetus for developing strategies to reduce tubulointertstitial inflammation in various renal diseases.
authors.affiliation: Departments of Pathology and Medicine, Northwestern University, Chicago, Illinois; and.
authors.forename: Ping
authors.initials: P
authors.lastname: Xie
authors.affiliation: Departments of Pathology and Medicine, Northwestern University, Chicago, Illinois; and.
authors.forename: Darukeshwara
authors.initials: D
authors.lastname: Joladarashi
authors.affiliation: Department of Medicine, University of Illinois, Chicago, Illinois.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Dudeja
authors.affiliation: Departments of Pathology and Medicine, Northwestern University, Chicago, Illinois; and.
authors.forename: Lin
authors.initials: L
authors.lastname: Sun
authors.affiliation: Departments of Pathology and Medicine, Northwestern University, Chicago, Illinois; and y-kanwar@northwestern.edu.
authors.forename: Yashpal S
authors.initials: YS
authors.lastname: Kanwar
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism*; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012084:Renin-Angiotensin System / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013552:Swine; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D016207:Cytokines; D020662:Guanine Nucleotide Exchange Factors; C526973:Rapgef3 protein, rat; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D000804:Angiotensin II; D020827:rap1 GTP-Binding Proteins
keywords: AKI; Epac1-Rap1a; NHE3; angiotensin II; cytokines; diabetic nephropathy; inflammation; tubulointerstitium