ABSTRACT
Ischemia-reperfusion injury is the leading cause of acute renal failure and determinant of renal-transplant outcome. Although many experimental studies show decreased injury and preserved renal function after dampening of the inflammatory response, surprisingly little progress has been made in the development of novel therapies.
Subject(s)
Graft Rejection/prevention & control , Kidney/blood supply , Nephritis/prevention & control , Renal Insufficiency/prevention & control , Reperfusion Injury/therapy , Animals , Chemokines/metabolism , Cytokines/metabolism , Graft Rejection/etiology , Graft Rejection/metabolism , Humans , Kidney/metabolism , Kidney Transplantation , Mice , Nephritis/etiology , Nephritis/metabolism , Renal Insufficiency/etiology , Renal Insufficiency/metabolism , Reperfusion Injury/complications , Reperfusion Injury/metabolismABSTRACT
The urokinase plasminogen activator receptor (uPAR) is expressed at the cell surface of inflammatory cells and plays an important role in neutrophil migration. To investigate the in vivo role of uPAR during urinary tract infection, acute pyelonephritis was induced in uPAR-/- and wild-type (WT) mice by intravesical inoculation with 1 x 10(9) colony-forming units (CFU) of uropathogenic Escherichia coli. Mice were killed after 24 and 48 h, after which bacterial outgrowth and cytokine levels in kidney homogenates were determined. Influx of neutrophils was quantified by myeloperoxidase-enzyme-linked immunosorbent assay. uPAR-/- kidneys had significantly higher numbers of E. coli CFU, accompanied by higher levels of interleukin-1beta (IL-1beta), IL-6, keratinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2), and tumor necrosis factor-alpha (TNF-alpha). However, the number of infiltrating neutrophils was similar in uPAR-/- and WT mice at both time points, suggesting that uPAR-/- neutrophils have a lower ability to eliminate E. coli. To further investigate this, neutrophil oxidative burst and phagocytosis was measured. The generation of reactive oxygen species upon stimulation with E. coli was not diminished in uPAR-/- neutrophils compared with WT. Interestingly, uPAR-/- neutrophils displayed significantly impaired phagocytosis of E. coli organisms compared with WT neutrophils. We conclude that uPAR is crucially involved in host defense through phagocytosis during E. coli induced acute pyelonephritis.
Subject(s)
Pyelonephritis/immunology , Receptors, Cell Surface/physiology , Animals , Chemokines/metabolism , Cytokines/metabolism , Escherichia coli Infections/immunology , Kidney/metabolism , Mice , Mice, Inbred C57BL , Neutrophil Infiltration/physiology , Neutrophils/physiology , Pyelonephritis/metabolism , Pyelonephritis/microbiology , Receptors, Urokinase Plasminogen ActivatorABSTRACT
As CD44 is involved in the activation, proliferation, adhesion, and extravasation of lymphocytes, we hypothesized that CD44 could be involved in the pathogenesis of acute renal allograft rejection. Renal biopsies and plasma were collected from patients suffering an episode of acute renal allograft rejection. CD44 and its ligands, hyaluronic acid (HA) and osteopontin, were analyzed retrospectively by immunohistochemistry and, computer-aided, morphometric analysis. Soluble CD44 (sCD44) and osteopontin in the plasma were determined by enzyme-linked immunosorbent assay. During acute rejection episodes, CD44 and its ligands, HA and osteopontin, were upregulated in the renal allograft. Also, increased sCD44 plasma levels were observed, which correlated with both tubular expression of CD44 and the extent of infiltrate. No differences could be detected between the different pathologic grades of rejection. Upregulation of tubular CD44 and increased levels of circulating sCD44 may reflect a common pathogenic mechanism during acute renal rejection and could be useful markers in the diagnosis of acute renal rejection.
