title: P-selectin-dependent macrophage migration into the tubulointerstitium in unilateral ureteral obstruction.
abstract: BACKGROUND
  Interstitial infiltration of macrophages (Mø) is one of the main causal factors for the tubulointerstitial injury. However, precise mechanisms of Mø infiltration into tubulointerstitium have not been fully explored. The purposes of this study were to assess the role of selectins in the acute infiltration of Mø in rats with unilateral ureteral obstruction (UUO) and to evaluate the role of vasa recta, that is, whether they facilitate massive influx of Mø into the interstitium by functioning as specialized vessels.
  
  
  METHODS
  To evaluate the role of selectins in Mø infiltration into tubulointerstitium, the expression of selectins and L-selectin ligands was examined by immunohistochemistry and immunoelectron microscopy. The functional role of P-selectin in vasa recta was studied by Stamper-Woodruff assay, in vivo p-Mø migration assay and in vivo blocking experiments with the monoclonal antibody (mAb) ARP2-4.
  
  
  RESULTS
  Selective expression of P-selectin was detected in vasa recta as early as one hour after UUO, and the expression increased thereafter for 96 hours. In contrast, endothelial expression of L-selectin ligands and E-selectin were not detectable. In the Stamper-Woodruff assay on kidney sections of rats with UUO, the adhesion of isolated rat peritoneal Mø (p-Mø) to vasa recta was significantly inhibited by the mAb ARP2-4 (P-selectin blocker; P < 0.01), but not by mAb ARE-5 (E-selectin blocker) or rLECIg (rat L-selectin chimeric protein). In the in vivo transfer experiments with fluorescein-labeled p-Mø into rats 48 hours after UUO, labeled p-Mø had accumulated around vasa recta at three minutes and had infiltrated predominantly into the outer medulla at 180 minutes. The number of labeled p-Mø was reduced when the rats were pretreated with ARP2-4 (P < 0.01). Finally, ARP2-4 (10 mg/kg), injected 15 minutes before UUO, reduced the number of infiltrated Mø (P < 0.01).
  
  
  CONCLUSIONS
  The results suggest that vasa recta, which express P-selectin, contribute to massive infiltration of Mø into the interstitium by functioning as specialized post-capillary venules.
authors.affiliation: The Third Department of Internal Medicine, Nagoya University School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Naruse
authors.forename: Yukio
authors.initials: Y
authors.lastname: Yuzawa
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Akahori
authors.forename: Masashi
authors.initials: M
authors.lastname: Mizuno
authors.forename: Shoji
authors.initials: S
authors.lastname: Maruyama
authors.forename: Reiji
authors.initials: R
authors.lastname: Kannagi
authors.forename: Nigishi
authors.initials: N
authors.lastname: Hotta
authors.forename: Seiichi
authors.initials: S
authors.lastname: Matsuo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002465:Cell Movement; D005260:Female; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D007668:Kidney / Q000737:chemistry; D007684:Kidney Tubules / Q000473:pathology*; D019041:L-Selectin / Q000502:physiology; D008264:Macrophages / Q000502:physiology*; D019007:P-Selectin / Q000032:analysis / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014517:Ureteral Obstruction / Q000473:pathology*
chemical_list: D000911:Antibodies, Monoclonal; D019007:P-Selectin; D018799:Intercellular Adhesion Molecule-1; D019041:L-Selectin