Mechanisms of Neutrophil Transmigration Across Renal Proximal Tubular HK-2 Cells

Abstract

Background: Adhesion of intratubular leukocytes to proximal tubules in biopsies of patients with rapidly progressive glomerulonephritis and the appearance of leukocytes in the urine in interstitial nephritis suggest interactions between leukocytes and tubular epithelia in renal diseases. The aim of this study was to investigate the effect of cytokines and endotoxin on leukocyte migration through proximal tubular epithelial cells and also to determine the role of the transmembrane adhesion molecules ICAM-1 and CD47 in this process. Methods: Experiments determined transepithelial migration (TEM) of PMN (polymorphonuclear) leukocytes through monolayers of HK-2. Expression of ICAM-1 and CD47 was assessed via confocal immunofluorescence, FACS analysis and western blotting. The effect of antibodies against ICAM-1 and CD47 on TEM was examined. Furthermore measurements of cytokine release (IL- 6 and IL-8) were performed. Results: Preincubation of HK-2 cells with either TNFα or LPS resulted in stimulation of PMN migration through monolayers of HK-2 cells. There was no preferred direction of transmigration. ICAM-1 was expressed by HK-2 cells and expression was increased after 4 h stimulation with TNFα or LPS. Application of ICAM-1 antibodies inhibited TEM. CD47 was expressed in both HK-2 cells and PMN. CD47 antibodies inhibited predominantly basolateral-to-apical TEM. HK-2 cells released IL-8 and IL-6 preferably into the apical compartment. Additionally, we showed that fMLP induced transmigration through monolayers of HK-2 cells was associated with significant increased CD47 expression on PMN cell surfaces. Conclusions: Inflammatory mediators stimulate TEM of PMN through monolayers of HK-2 cells without a clearly discernible preference of direction. Mechanisms involved in TEM stimulated by cytokines or endotoxin appear to be mainly changes in surface receptor densities of HK-2 cells with ICAM-1 and CD47 playing an essential role.

Shiga Toxin Activates Complement and Binds Factor H: Evidence for an Active Role of Complement in Hemolytic Uremic Syndrome

“…In addition, serum IL-8 levels were significantly increased and serum monocyte chemoattractant protein-1 levels were slightly increased in HUS patients (20) when compared with the levels observed in the control subjects. Renal epithelial cells can be stimulated to release IL-8 both into the urine and the interstitial space by several proinflammatory mediators (e.g., TNF-␣) and activate PMN migration (21). These findings corroborate the hypothesis that chemokines, such as monocyte chemoattractant protein-1 and IL-8, may be implicated in the pathogenesis of HUS through the recruitment and activation of monocytes and PMNs, respectively.…”

Uromodulin Facilitates Neutrophil Migration Across Renal Epithelial Monolayers

“…In this study, using a trans-epithelial neutrophil migration assay previously described [23][24][25], we investigated the epithelial expression of uromodulin on neutrophil migration. We demonstrate for the first time that uromodulin expression facilitates neutrophil trans-epithelial migration.…”

Cyclosporin A inhibits CD11a/CD18 adhesion molecules due to inhibition of TNF-α and IL-1β levels in the mouse model of pleurisy induced by carrageenan

“…4 Furthermore, adhesion molecules control the trafficking of leukocytes to the site of the inflammatory process by means of a firm membrane adhesion between leukocyte and endothelium. 1,5 In this context, Wilson et al 6 and also Carlos and Harlan 7 had demonstrated that CD11a/ CD18 is an important adhesion molecule involved in the leukocyte chemotaxis during the inflammatory process. Further, Takeshita et al 8 had also shown that this heterodimer protein is the most important adhesion molecule involved in the leukocyte influx at the site of the inflammatory reaction.…”

“…The complex adhesion molecule CD11a/ CD18 heterodimer are expressed in neutrophils, 1 monocytes, 2 macrophages and other cells. 3 In fact, these adhesion molecules have an essential role in leukocyte recognition through the endothelium and extracellular matrix at the site of inflammation.…”