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P-selectin-dependent macrophage migration into the tubulointerstitium in unilateral ureteral obstruction
Tomohiko Naruse1, Yukio Yuzawa, Toshiyuki Akahori
1The Third Department of Internal Medicine, Nagoya University School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466, Japan.
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).
Conclusion:
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.
Insights
Vasa recta in the kidneys express P-selectin, facilitating macrophage infiltration during unilateral ureteral obstruction. Blocking P-selectin significantly reduces this inflammatory cell migration, highlighting its role in tubulointerstitial injury.
Area of Science:
- Nephrology
- Immunology
- Cell Biology
Background:
- Macrophage (Mø) infiltration into the kidney interstitium is a key driver of tubulointerstitial injury.
- The precise mechanisms governing Mø infiltration into the tubulointerstitium remain incompletely understood.
Purpose of the Study:
- To investigate the role of selectins in acute macrophage infiltration in a rat model of unilateral ureteral obstruction (UUO).
- To determine if vasa recta act as specialized vessels facilitating massive Mø influx into the renal interstitium.
Main Methods:
- Immunohistochemistry and immunoelectron microscopy were used to examine selectin and L-selectin ligand expression.
- Functional roles of P-selectin in vasa recta were assessed using Stamper-Woodruff assays, in vivo Mø migration assays, and blocking experiments with monoclonal antibodies (mAbs).
Main Results:
- P-selectin expression was selectively detected in vasa recta starting one hour after UUO and increased over 96 hours.
- Blocking P-selectin with mAb ARP2-4 significantly inhibited Mø adhesion to vasa recta in vitro and reduced Mø infiltration in vivo.
- In vivo experiments showed labeled macrophages accumulating around and infiltrating the outer medulla, with reduced numbers following P-selectin blockade.
Conclusions:
- The study suggests that vasa recta, through P-selectin expression, function as specialized post-capillary venules that promote massive macrophage infiltration.
- These findings implicate P-selectin expressed by vasa recta as a critical mediator in the inflammatory response contributing to tubulointerstitial injury.