In situ expression and soluble form of P-selectin in human glomerulonephritis

Platelets in Renal Disease

Kidney disease is a major global health concern, affecting millions of people. Nephrologists have shown interest in platelets because of coagulation disorders caused by renal diseases. With a better understanding of platelets, it has been found that these anucleate and abundant blood cells not only play a role in hemostasis, but also have important functions in inflammation and immunity. Platelets are not only affected by kidney disease, but may also contribute to kidney disease progression by mediating inflammation and immune effects. This review summarizes the current evidence regarding platelet abnormalities in renal disease, and the multiple effects of platelets on kidney disease progression. The relationship between platelets and kidney disease is still being explored, and further research can provide mechanistic insights into the relationship between thrombosis, bleeding, and inflammation related to kidney disease, and elucidate targeted therapies for patients with kidney disease.

P-Selectin preserves immune tolerance in mice and is reduced in human cutaneous lupus

Mice deficient in P-Selectin presented altered immunity/tolerance balance. We have observed that the absence of P-Selectin promotes splenomegaly with reduced naïve T cell population, elevated activated/effector T cell subset, increased germinal center B and Tfh populations and high production of autoreactive antibodies. Moreover, 1.5-3-month-old P-selectin KO mice showed reduced IL-10-producing leukocytes in blood and a slightly reduced Treg population in the skin. With aging and, coinciding with disease severity, there is an increase in the IL17⁺ circulating and dermal T cell subpopulations and reduction of dermal Treg. As a consequence, P-Selectin deficient mice developed a progressive autoimmune syndrome showing skin alterations characteristic of lupus prone mice and elevated circulating autoantibodies, including anti-dsDNA. Similar to human SLE, disease pathogenesis was characterized by deposition of immune complexes in the dermoepidermal junction and renal glomeruli, and a complex pattern of autoantibodies. More important, skin biopsies of cutaneous lupus erythematosus patients did not show increased expression of P-Selectin, as described for other inflammatory diseases, and the number of vessels expressing P-Selectin was reduced.

CD16+CD56+ cells are a potential culprit for hematuria in IgA nephropathy

BACKGROUND

Hematuria is the first manifestation of urinary abnormality in immunoglobulin A nephropathy (IgAN). Hematuria has recently been reported as a risk factor for deterioration of renal function; however, its cause remains unknown.

METHODS

We analyzed the surface marker of peripheral blood mononuclear cells before and immediately after tonsillectomy in IgAN patients and controls (chronic tonsillitis or tonsillar hypertrophy) by flow cytometry and investigated the association with hematuria. To prove our hypothesis that NK cells induce hematuria, we administered IL-12, activator of NK cells, to HIGA mice. In addition, we transferred cultured NK cells to nude rats and transferred the CD16(+)CD56(+) cells, including NK cells, that are derived from the peripheral blood of IgAN patients immediately after tonsillectomy to nude rats to assess the hematuria level and renal histology of the recipients. We also performed cytotoxicity assays against glomerular endothelial cells by NK cells.

RESULTS

We found that IgAN patients who showed rapid deterioration of hematuria after tonsillectomy also displayed a significant increase in CD16(+)CD56(+) cells in the peripheral blood immediately after tonsillectomy. Exogenous administration of IL-12 to HIGA mice induced hematuria. Adoptive transfer of either cells of an NK cell line, or of CD16(+)CD56(+) cells derived from IgAN patients, into nude rats induced hematuria in the recipients. In vitro analysis showed that NK cells exert cytotoxic activity toward human glomerular endothelial cells in a dose-dependent manner.

CONCLUSIONS

CD16(+)CD56(+) cells seem to be responsible for hematuria in IgAN.

Endothelium-neutrophil interactions in ANCA-associated diseases

The two salient features of ANCA-associated vasculitis (AAV) are the restricted microvessel localization and the mechanism of inflammatory damage, independent of vascular immune deposits. The microvessel localization of the disease is due to the ANCA antigen accessibility, which is restricted to the membrane of neutrophils engaged in β2-integrin-mediated adhesion, while these antigens are cytoplasmic and inaccessible in resting neutrophils. The inflammatory vascular damage is the consequence of maximal proinflammatory responses of neutrophils, which face cumulative stimulations by TNF-α, β2-integrin engagement, C5a, and ANCA by the FcγRII receptor. This results in the premature intravascular explosive release by adherent neutrophils of all of their available weapons, normally designed to kill IgG-opsonized bacteria after migration in infected tissues.

Urine sVCAM-1 and sICAM-1 levels are elevated in lupus nephritis

AIM

We sought to evaluate the relationship of urine levels of soluble cellular adhesion molecules sVCAM-1 (vascular) and sICAM-1 (intercellular) in systemic lupus erythematosus (SLE) patients with or without lupus nephritis, and to explore their correlation with renal disease activity.

METHODS

Paired serum and urine samples of 121 Asian SLE patients, and urine samples of 19 normal healthy controls were collected. Demographic data, disease activity and damage scores, and selected laboratory parameters, including levels of anti-double stranded DNA antibody, complements C3, C4, and creatinine were captured. Renal disease activity was scored with renal SLE Activity Measure revised (rSLAM-R). Serum and urine sVCAM-1 and sICAM-1 levels were assayed by enzyme-linked immunosorbent assay.

RESULTS

Urinary sVCAM-1 and sICAM-1 were elevated in SLE patients compared to controls. Significantly higher levels of urine sVCAM-1 found in patients with active lupus nephritis correlated with rSLAM-R. In addtion, significantly more patients with active lupus nephritis had detectable levels of urine sICAM-1, but no correlation with renal activity was observed.

CONCLUSION

Urinary sVCAM-1 may serve as a potential biomarker for early diagnosis of lupus nephritis as levels correlated with even mild abnormalities of urine sediment. In addition, both urine sVCAM-1 and sICAM-1 levels may be useful in identifying patients at risk of lupus nephritis.

Dysregulated neutrophil--endothelial interaction in antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides: implications for pathogenesis and disease intervention

The interplay between neutrophils and endothelial cells allows ANCA to become pathogenic and results in uncontrolled inflammation in the vessel wall. This review presents an overall view on neutrophil-endothelial interaction during inflammation with a focus on ANCA-associated vasculitis, and summarizes the effector mechanisms which cause vascular damage in AAV. In addition, potential elements for disease intervention based on this process are discussed.

Fractalkine and its receptor, CX3CR1, promote hypertensive interstitial fibrosis in the kidney

Hypertension promotes and escalates kidney injury, including kidney fibrosis. Fractalkine/CX3CL1 is a unique chemokine that works as a leukocyte chemoattractant and an adhesion molecule. Recently, fractalkine/CX3CL1 has been reported to promote tissue fibrosis via its cognate receptor, CX3CR1. However, the involvement of the fractalkine-CX3CR1 axis in the pathogenesis of hypertensive kidney fibrosis remains unclear. The impacts of the fractalkine-CX3CR1 axis on hypertensive kidney fibrosis were investigated in a deoxycorticosterone acetate (DOCA)-salt hypertensive model in CX3CR1-deficient mice, which were sacrificed on day 28. The blood pressure levels were similarly elevated in both CX3CR1-/- C57BL/6 and wild-type C57BL/6 mice. Fractalkine and CX3CR1 were upregulated in kidneys that were damaged by hypertension. Deficiency in CX3CR1 inhibited kidney fibrosis, as evidenced by a decrease in the presence of interstitial fibrotic area detected by type I collagen in Mallory-Azan staining, concomitant with the downregulation of transforming growth factor (TGF)-β(1) and type I procollagen mRNA expression in damaged kidneys. The CX3CR1 blockade also decreased the number of infiltrating F4/80-positive macrophages in damaged kidneys. These results suggest that the fractalkine-CX3CR1 axis contributes to kidney fibrosis in a hypertensive mouse model, possibly by the upregulation of macrophage infiltration and the expression of TGF-β(1) and type I collagen.

Variation in the upstream region of P-Selectin (SELP) is a risk factor for SLE

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Genome-wide linkage studies implicated a region containing the adhesion molecule P-Selectin. This family-based study revealed two regions of association within P-Selectin. The strongest signal, from a 21.4-kb risk haplotype, stretched from the promoter into the first two consensus repeat (CR) regions (P=8 × 10⁻⁴), with a second association from a 14.6-kb protective haplotype covering CR 2–9 (P=0.0198). The risk haplotype is tagged by the rare C allele of rs3753306, which disrupts the binding site of the trans-activating transcription factor HNF-1. One other variant (rs3917687) on the risk haplotype was significant after permutation (P₁₀₀₀₀<1 × 10⁻⁵), replicated in independent pseudo case-control analysis and was significant by meta-analysis (P=4.37 × 10⁻⁶). A third associated variant on the risk haplotype (rs3917657) replicated in 306 US SLE families and was significant in a joint UK-SLE data set after permutation. The protective haplotype is tagged by rs6133 (a non-synonymous variant in CR8 (P=9.00 × 10⁻⁴), which also shows association in the pseudo case-control analysis (P=1.09 × 10⁻³) and may contribute to another signal in P-Selectin. We propose that polymorphism in the upstream region may reduce expression of P-Selectin, the mechanism by which this promotes autoimmunity is unknown, although it may reduce the production of regulatory T cells.

ICOS controls effector function but not trafficking receptor expression of kidney-infiltrating effector T cells in murine lupus

Renal pathology in systemic lupus erythematosus involves both autoantibody deposition and a cellular inflammatory response, both of which are mediated by effector CD4 T cells. MRL(lpr) mice spontaneously develop massive perivascular infiltrates, but the pathways that regulate the development, trafficking, and effector functions of kidney-infiltrating T cells are poorly defined. To address these questions, we first surveyed inflammatory chemokine protein levels in nephritic kidneys from lupus-prone MRL(lpr) mice. After identifying highly elevated levels of the CXCR3 ligand CXCL9, we found that kidney-infiltrating effectors are enriched for expression of CXCR3, as well as P-selectin ligand and ICOS. Using genetic ablation, we demonstrate that ICOS plays an essential role in the establishment of renal perivascular infiltrates, although a small number of infiltrating cells remain around the blood vessels. Interestingly, though IgG autoantibody production is substantially reduced in Icos(-/-) MRL(lpr) mice, the progression of immune complex glomerulonephritis is only modestly diminished and the production of inflammatory chemokines, such as CXCL9, remains high in the kidney. We find that Icos(-/-) effector cell numbers are only slightly reduced and these have normal expression of CXCR3 and P-selectin ligand with intact migration to CXCL9. However, they have impaired production of inflammatory cytokines and fail to show evidence of efficient proliferation in the kidney. Thus, while dispensable for acquisition of renal trafficking receptor expression, ICOS is strictly required for local inflammatory functions of autoreactive CD4 T cells in murine lupus.

Review article: Leukocyte-endothelial dysregulation in systemic small vessel vasculitis

Aberrant interaction between the leukocyte and the endothelial cell (EC) results in the uncontrolled inflammation seen in systemic small vessel vasculitis. This review discusses our current understanding of this process and includes consideration of the role of adhesion molecules, proteases and the neutrophil respiratory burst. The effects of anti-neutrophil cytoplasm antibodies and anti-endothelial cell antibodies and their pathogenic roles are examined, and we look at experimental disease models. Specificity of disease-targetted endothelial beds and the role of circulating EC are discussed.

Fibrocytes: a new insight into kidney fibrosis

Fibrocytes are supposed to be a circulating connective tissue cell progenitor, which consists of a novel population of peripheral blood cells. This distinct population of blood-borne cells shares markers of leukocytes as well as mesenchymal cells. Accumulating evidence indicates that fibrosis is characteristic of progressive chronic kidney diseases of any etiologies, resulting in kidney failure. We have uncovered that CCR7-positive fibrocytes migrate into the kidney in response to secondary lymphoid tissue chemokine (SLC/CCL21) and contribute to kidney fibrosis induced by unilateral ureteral obstruction in mice. In addition, the blockade of CCL21/CCR7 signaling by anti-CCL21 antibodies reduced kidney fibrosis, which was confirmed by a decrease in fibrosis in CCR7-null mice with concomitant reduction in macrophage recruitment along with reduced renal transcripts of monocyte chemoattractant protein-1 (MCP-1/CCL2). These findings suggest that fibrocytes dependent on CCL21/CCR7 signaling pathways contribute to the pathogenesis of kidney fibrosis, thereby providing that regulating fibrocytes may provide a novel therapeutic benefit for kidney fibrosis.

Deficiency of P-selectin or P-selectin glycoprotein ligand-1 leads to accelerated development of glomerulonephritis and increased expression of CC chemokine ligand 2 in lupus-prone mice

The selectins and their ligands mediate leukocyte rolling on endothelial cells, the initial step in the emigration cascade leading to leukocyte infiltration of tissue. These adhesion molecules have been shown to be key promoters of acute leukocyte emigration events; however, their roles in the development of long-term inflammatory responses, including those that occur during chronic inflammatory diseases such as systemic lupus erythematosus, are unclear. To assess participation of P-selectin in such disorders, we studied the progression of systemic lupus erythematosus-like disease in P-selectin-deficient and control MRL/MpJ-Fas(lpr) (Fas(lpr)) mice. Surprisingly, we found that P-selectin deficiency resulted in significantly earlier mortality, characterized by a more rapid development of glomerulonephritis and dermatitis. Expression of CCL2 (MCP-1) was increased in the kidneys of P-selectin mutant mice and in supernatants of LPS-stimulated primary renal endothelial cell cultures from these mice. A closely similar phenotype, including elevated renal expression of CCL2, was also observed in Fas(lpr) mice deficient in the major P-selectin ligand, P-selectin glycoprotein ligand-1. These results indicate that P-selectin and P-selectin glycoprotein ligand-1 are not required for leukocyte infiltration and the development of autoimmune disease in Fas(lpr) mice, but rather expression of these adhesion molecules is important for modulating the progression of glomerulonephritis, possibly through down-regulation of endothelial CCL2 expression.

Excreted urinary mediators in an animal model of experimental immune nephritis with potential pathogenic significance

OBJECTIVE

Currently, proteinuria is viewed as the earliest indicator of renal disease in immune-mediated nephritis. The objective of this study was to determine whether additional mediators may be excreted in the urine during immune-mediated nephritis, using an experimental model with a well-defined disease course.

METHODS

Urine samples from mice with anti-glomerular basement membrane (anti-GBM) antibody-induced experimental nephritis were screened using a focused immunoproteome array bearing 62 cytokines/chemokines/soluble receptors. Molecules identified through this screening assay were validated using an enzyme-linked immunosorbent assay. One of these molecules was further evaluated for its pathogenic role in disease, using antibody-blocking studies.

RESULTS

Compared with B6 and BALB/c mice, in which moderately severe immune-mediated nephritis develops, the highly nephritis-susceptible 129/Sv and DBA/1 mice exhibited significantly increased urinary levels of vascular cell adhesion molecule 1 (VCAM-1), P-selectin, tumor necrosis factor receptor I (TNFRI), and CXCL16, particularly at the peak of disease. Whereas some of the mediators appeared to be serum derived early in the disease course, local production in the kidneys appeared to be an important source of these mediators later in the course of disease. Both intrinsic renal cells and infiltrating leukocytes appeared to be capable of producing these mediators. Finally, antibody-mediated blocking of CXCL16 ameliorated experimental immune nephritis.

CONCLUSION

These studies identified VCAM-1, P-selectin, TNFRI, and CXCL16 as a quartet of molecules that have potential pathogenic significance; the levels of these molecules are significantly elevated during experimental immune nephritis. The relevance of these molecules in spontaneous immune nephritis warrants investigation.

Podocalyxin in human haematopoietic cells

Podocalyxin-like protein (PCLP) is a sialomucin-type membrane protein structurally related to CD34 and endoglycan. It was first described in glomerular podocytes and endothelial cells. In mice, PCLP is present in haemangioblasts, and in both chicken and mice it is a marker of early haematopoietic stem cells and lineage-restricted haematopoietic progenitors. Its expression decreases during differentiation of haematopoietic cells. Of mature blood cells, only chicken and rat thrombocytes express PCLP protein. PCLP expression in human haematopoietic cells has not been studied. Here we demonstrate PCLP mRNA in human CD34+ cells, in lineage committed erythroid, megakaryocyte and myeloid progenitors, in K562 leukaemia cells, and in peripheral blood leucocytes. The mRNA expression level was higher in developing cells than in mature leucocytes. By Northern blotting and cDNA sequencing, the haematopoietic and renal PCLP mRNAs were identical. Of the mobilized CD34+ cells, 28% (mean; range 14-61%) expressed PCLP protein and the majority of PCLP+ cells were CD117+. Almost all of the K562 cells expressed PCLP protein. Surprisingly, PCLP protein was not detected in any mature blood cells. These results suggest that human PCLP may be a valuable marker for a subset of haematopoietic stem cells.

Blockade of p38alpha MAPK ameliorates acute inflammatory renal injury in rat anti-GBM glomerulonephritis

The p38 mitogen-activated protein kinase (MAPK) pathway is a pro-inflammatory signal transduction pathway. The aim of this study was to examine the role of this pathway in acute renal inflammation. Immunostaining localized components of the p38 MAPK pathway (p38alpha, p-p38, p-ATF-2) in normal glomeruli, to podocytes, and occasional endothelial cells. This study identified an eightfold increase in glomerular activation of p38 MAPK (phosphorylated p38, p-p38) within 3 h of the induction of rat anti-glomerular basement membrane (GBM) glomerulonephritis and localized p-p38 and p-ATF-2 to infiltrating neutrophils, with increased staining of podocytes and endothelial cells. The relevance of these findings to human acute inflammatory renal disease was determined by examination of biopsy specimens. In patients with post-infectious glomerulonephritis, there was an increased number of positive p-p38 glomerular cells, including p-p38 staining of infiltrating neutrophils, compared with normal human kidney. In rats, administration of a specific p38 MAPK inhibitor, NPC 31145, before induction of anti-GBM disease prevented a loss of renal function and substantially reduced proteinuria. The reduction in renal injury was attributed to a 55% reduction in glomerular neutrophil infiltration and a 68% reduction in platelet accumulation. This was associated with an abrogation of glomerular P-selectin immunostaining and inhibition of glomerular P-selectin gene expression. In summary, this study has localized the components of the p38 MAPK pathway to cells in normal and diseased rat and human kidney and identified a number of important mechanisms by which signaling through the p38 MAPK pathway induces inflammatory renal disease. Blockade of the p38 pathway may be a novel therapeutic strategy for the treatment of acute renal inflammation.

Therapeutic effect of sulphated hyaluronic acid, a potential selectin-blocking agent, on experimental progressive mesangial proliferative glomerulonephritis

The initial event in the process of leukocyte infiltration is characterized by leukocyte rolling on the surface of the endothelium, which is mediated by selectins. P- and L-selectin bind to the sulphated sugar chains of their natural ligands, including sulphated glycolipids such as sulphatide. Recently, it has been demonstrated that sulphated glycolipids and sulphated oligosaccharides interfere with selectin binding pathways. This study synthesized sulphated hyaluronic acid (SHA), which is a potential selectin-blocking agent, and examined its therapeutic effect on the experimental progressive mesangial proliferative glomerulonephritis induced by anti-Thy-1 monoclonal antibody (1-22-3 MAb) after unilateral nephrectomy. The selectin-inhibitory effect of SHA in vitro was confirmed. SHA inhibited the binding of P- and L-selectin to sulphatide, which is a glycolipid ligand for P- and L-selectin, at a concentration of 1.5 micro g/ml and 100 micro g/ml. Immunohistochemical examination showed that P-selectin was up-regulated in the glomeruli in the 1-22-3 MAb nephritis model, while the ligands for L-selectin were not detected in the glomerular tufts. A single administration of SHA ameliorated proteinuria and glomerular leukocyte infiltration in 24 h after the injection of anti-Thy-1 MAb. Anti-P-selectin MAb, but not anti-L-selectin MAb, inhibited proteinuria and glomerular leukocyte infiltration. To examine further the therapeutic effect of SHA on chronic glomerulonephritis, SHA was administered daily from day 3 to day 14 in this model. Proteinuria and glomerular leukocyte infiltration were significantly diminished in SHA-treated rats on day 14. These results suggest that SHA ameliorated rat progressive mesangial proliferative glomerulonephritis by inhibiting P-selectin-dependent leukocyte infiltration in glomeruli. Sulphated oligosaccharides may be beneficial for the therapy of mesangial proliferative glomerulonephritis.

Preventive effect of sulphated colominic acid on P-selectin-dependent infiltration of macrophages in experimentally induced crescentic glomerulonephritis

Leucocytes infiltrate into renal tissue and are involved in the pathogenesis of crescentic glomerulonephritis. The initial event in the process of leucocyte infiltration is characterized by selectin-mediated leucocyte rolling on endothelial surface. Role of selectins in pathogenesis of glomerulonephritis has still been controversial. Sulphated glycolipids and sulphated polysaccharides interfere with the binding of P- and L-selectin with carbohydrate ligands on endothelial cells or on leucocytes. Here we evaluated the role of selectins and the preventive effects of sulphated colominic acid (SCA), a synthetic sulphated polysaccharide, on experimental crescentic glomerulonephritis in Wistar-Kyoto (WKY) rats. Crescentic glomerulonephritis was induced by injection of nephrotoxic serum (NTS) in WKY rats. Rats subsequently received intraperitoneal injection of saline, neutralizing or non-neutralizing monoclonal antibody (mAb) to rat P-selectin and L-selectin, SCA (5 or 10mg/kg/day) or nonsulphated colominic acid (CA) (10mg/kg/day) for 2 weeks. Localization of P-, E-selectin, ligands for L-selectin and intraglomerular leucocytes was examined by immunohistochemistry. Gene expression of platelet-derived growth factor (PDGF) B chain in glomeruli was quantified using real-time RT-PCR. P-selectin was highly expressed on glomerular endothelial cells after injection of NTS, whereas E-selectin and L-selectin ligands were not detected. Anti-P-selectin mAb, but not anti-L-selectin mAb, significantly reduced glomerular infiltration of macrophages, crescent formation, and proteinuria. SCA also reduced proteinuria, macrophage infiltration, and crescent formation in a dose-dependent manner. Furthermore, SCA suppressed gene expression of PDGF B chain in glomeruli. Our results indicate that P-selectin partially mediates glomerular infiltration of macrophage in experimental crescentic glomerulonephritis. Moreover, SCA may inhibit intraglomerular infiltration of macrophages by interfering with P-selectin-dependent adhesion pathway, and progression of experimental crescentic glomerulonephritis.

Gene structure and alternative splicing of murine podocalyxin: a member of the CD34 sialomucin family

Podocalyxin is a sialoglycoprotein of the glomerular podocytes, vascular endothelial cells, platelets, and hemopoietic stem cells. The function of podocalyxin is unknown, but it contains most of the protein bound sialic acid in the glomerulus and is considered vital in the structure and function of the glomerular filtration apparatus. The murine podocalyxin full-length cDNA has been determined and is 5,318 base pairs. The gene localizes to chromosome 6B1 by FISH analysis and contains eight major exons with one additional alternatively spliced exon. The alternatively spliced isoform of podocalyxin codes for a truncated intracellular domain and is expressed in a tissue specific pattern in parallel with full-length podocalyxin. The organization of the gene structure of murine podocalyxin is similar to the murine CD34 gene and suggests a distant evolutionary relationship to CD34.

Proteinase 3 enhances endothelial monocyte chemoattractant protein-1 production and induces increased adhesion of neutrophils to endothelial cells by upregulating intercellular cell adhesion molecule-1

Wegener's granulomatosis is an autoimmune disease that is characterized by systemic vasculitis and granuloma formation. Early influx of polymorphonuclear neutrophils (PMN), followed at a later stage by mononuclear cells, contributes to the granulomatous inflammation. Previous studies have shown that proteinase 3 (PR3), the major autoantigen in Wegener's granulomatosis, specifically binds to endothelial cells and plays a possible role in activation of these cells by enhancing interleukin-8 production, thus providing a chemotactic and activating stimulus for PMN. The present study demonstrated that PR3 enhances the production of monocyte chemoattractant protein-1 (MCP-1) by human umbilical vein endothelial cells (HUVEC) in a dose- and time-dependent manner. The PR3-induced increase in MCP-1 production was demonstrated at both the protein and the mRNA levels and was chemotactic for monocytes. In addition, it was demonstrated that PR3 induces a dose- and time-dependent increase in the expression of intercellular adhesion molecule-1 (ICAM-1) as determined by fluorescence-activated cell sorter analysis. The PR3-induced increase in expression of ICAM-1 was also demonstrated at the mRNA level. PR3 induced a slight increase in vascular cell adhesion molecule-1 expression and had no effect on the expression of both P- and E-selectin. Incubation of HUVEC for 24 h in the presence of PR3 resulted in a significant increase in adhesion of PMN, which was reduced to baseline levels in the presence of blocking monoclonal antibody anti-ICAM-1 or anti-CD18 or a combination of both. Monocytes showed a slight but statistically not significant increase in adhesion. Incubation of HUVEC with PR3 for 4 h did not result in enhanced adhesion of either PMN or monocytes. It was hypothesized that PR3, which may be released locally at inflammatory sites after activation of cytokine primed PMN, plays a role in endothelial cell activation by enhancing both interleukin-8 and MCP-1 production, thus providing a chemotactic and activating stimulus for both PMN and monocytes. In addition, PR3 may contribute to the ongoing inflammation by enhancing the adhesion of PMN to endothelial cells by upregulating ICAM-1 expression.

Chemokines in renal diseases

The interaction of activated leukocytes and renal resident cells is thought to play a crucial role in the pathogenesis of renal diseases. Recent investigations of the pathophysiological roles of chemokines and their cognate receptors have shed light on the detailed molecular mechanisms of leukocyte trafficking and activation in the diseased kidneys. Chemokine/chemokine receptor systems may be essentially involved in the pathogenesis of phase-specific renal disorders and the measurement of urinary levels of chemokines may be clinically useful for monitoring the different disease phases and activities. In addition, chemokine receptors expressed in renal resident cells may be involved in proliferation, fibrogenesis, as well as chemotaxis. The selective intervention of chemokine/chemokine receptor systems (anti-chemokine therapy) may have the potential as the particular therapeutic strategies for renal diseases in future.

Circulating soluble adhesion molecules in ANCA-associated vasculitis

BACKGROUND

To evaluate whether changes in concentrations of soluble (s) E-selectin, sP-selectin, sL-selectin, intercellular adhesion molecule 1 (sICAM-1), and vascular cell adhesion molecule 1 (sVCAM-1) reflect disease activity in patients with ANCA-associated vasculitis and whether serum levels of these adhesion molecules are related to the degree of renal failure in patients with chronic renal failure (CRF).

SUBJECTS AND METHODS

A sandwich ELISA was used to measure these soluble adhesion molecules in (i) sera from 20 patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (10 patients with Wegener's granulomatosis (WG) and 10 patients with microscopic polyangiitis (MPA)), obtained at the time of diagnosis and during the remission period; (ii) sera from 40 patients with CRF not undergoing haemodialysis.

RESULTS

At the time of diagnosis, serum levels of sE-selectin, sICAM-1 and sVCAM-1 (88+/-42 ng/ml, 437+/-184 ng/ml, 1720+/-1174 ng/ml respectively) were significantly higher in patients with ANCA-associated vasculitis than in healthy controls (P<0.0001, P=0.002 and P=0.001 respectively). Serum sP-selectin values did not differ from those obtained in normal donors. In contrast, sL-selectin levels (940+/-349 ng/ml) were significantly lower in patients than those recorded in healthy controls (P<0.0001). A significant decrease in concentrations of sE-selectin, sP-selectin, sICAM-1, and sVCAM-1 was observed between active and remission phases (P<0.0001, P=0.002, P=0.001 and P=0.001 respectively). No significant differences were observed in sL-selectin levels between active and remission phases. sL-selectin concentrations (802+/-306 ng/ml) during the remission phase remained lower than those observed in healthy controls (P<0.0001). No correlation was observed between serum creatinine and sE-selectin, sP-selectin, sICAM-1 and sVCAM-1 in patients of the CRF group. A slight negative correlation was established between creatinine and sL-selectin concentration.

CONCLUSIONS

Increased serum levels of sE-selectin, sICAM-1, and sVCAM-1 and decreased levels of sL-selectin in active ANCA-associated vasculitis, and the normalization of sE-selectin, sICAM-1, and sVCAM-1 during the remission phase suggest that the concentration of soluble levels of these adhesion molecules reflects disease activity. The decrease in sP-selectin levels between active and inactive phases also suggest that this receptor may reflect clinical activity. The lack of correlation between serum levels of sE-selectin, sP-selectin, sICAM-1, and sVCAM-1 and the degree of renal failure in patients with CRF suggests that the mechanism of clearance of these molecules is not renal.

Immunohistochemical localization of P-selectin in the glomeruli from forensic autopsies

The expression of the adhesion molecule P-selectin is known to be up-regulated in several vital organs including the kidney after trauma in experimental animals. We examined the expression of P-selectin in the kidney by immunohistochemistry in 41 forensic autopsies mainly from trauma cases. P-selectin immunoreactivity was present in the glomerular capillary endothelial tufts and cortical interstitial vascular endothelial cells. The P-selectin immunoreactivity in the glomeruli was not co-localized with CD41 (platelet marker) immunoreactivity. The antemortem interval between the onset of injury and death (AMI) was statistically significantly longer in the cases with more P-selectin-positive capillary endothelial tufts in the glomeruli. Our results show that P-selectin immunoreactivity exists in the glomerular capillary endothelial cells rather than platelets. Our results also indicate that the P-selectin expression increases in the glomerular endothelial cells of the human kidney with the longer duration of the state under injury.

The role of selectins in glomerular leukocyte recruitment in rat anti-glomerular basement membrane glomerulonephritis

Leukocytes play a central role in the pathogenesis of anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). Understanding the mechanisms underlying their recruitment in the glomerulus is of critical importance, because this may lead to more specific anti-inflammatory drug design. The requirement for integrins, especially from the beta2 group, and their Ig superfamily counter-receptors has been established, however, the role of selectins remains controversial. An intravital microscopy technique was developed to study concomitantly the glomerular and venular leukocyte kinetics and the hemodynamic alterations in a rat model of anti-GBM GN, induced by injection of 10 mg of nephrotoxic serum (NTS). Histologic studies of the kidney were performed in parallel and urinary protein excretion was measured. The animals received NTS alone or were pretreated with either a monoclonal antibody against the beta2 integrin CD11b (OX42, 4 mg/kg) or fucoidan F7 (FF7, 8 mg/kg), an oligosaccharide that blocks both L- and P-selectin function. Administration of NTS resulted in a time-dependent increase in the number of adherent leukocytes in the glomeruli and a parallel decrease of the perfused glomerular capillary area. Substantial proteinuria was observed. Pretreatment with OX42 significantly attenuated these changes. FF7 almost abolished the rolling of the leukocytes in the venules, thus demonstrating efficient anti-selectin activity. Nevertheless, FF7 had no influence on the glomerular events or on the development of proteinuria. These results confirm that glomerular leukocyte adhesion in anti-GBM GN is CD11b-dependent. However, selectin-mediated interaction between the leukocytes and the glomerular capillary endothelium does not appear to be a prerequisite for leukocyte adhesion in the glomerulus. These results therefore question the potential utility of anti-selectin therapy in the treatment of anti-GBM GN.

MIP-1alpha and MCP-1 contribute to crescents and interstitial lesions in human crescentic glomerulonephritis

BACKGROUND

The precise molecular mechanisms of macrophage (Mphi) recruitment and activation in crescentic glomerulonephritis remain to be investigated. We hypothesized that locally produced macrophage inflammatory protein (MIP)-1alpha and monocyte chemoattractant protein (MCP)-1 via the chemokine receptors participate in the pathophysiology of human crescentic glomerulonephritis by recruiting and activating Mphi.

METHODS

We investigated the levels of MIP-1alpha and MCP-1 by enzyme-linked immunosorbent assay (ELISA) in 20 healthy subjects, 20 patients with crescentic glomerulonephritis, and 41 control patients with various other renal diseases. The presence of MIP-1alpha, MCP-1, and the cognate chemokine receptor for MIP-1alpha, CCR5, in the diseased kidneys was evaluated by immunohistochemical and in situ hybridization analyses.

RESULTS

MIP-1alpha-positive cells were mainly detected in crescentic lesions, whereas MCP-1 was mainly in the interstitium. In addition, we detected CCR5-positive cells in diseased glomeruli and interstitium. Urinary MIP-1alpha was detected in crescentic glomerulonephritis, even though it was below detectable levels in healthy subjects and in patients with other renal diseases without crescents. Urinary MIP-1alpha levels in the patients with crescentic glomerulonephritis were well correlated with the percentage of cellular crescents and the number of CD68-positive infiltrating cells and CCR5-positive cells in the glomeruli. However, urinary MCP-1 levels were well correlated with the percentage of both total crescents and fibrocellular/fibrous crescents and the number of CD68-positive infiltrating cells in the interstitium. Moreover, elevated urinary levels of both MIP-1alpha and MCP-1 dramatically decreased during glucocorticoid therapy-induced convalescence.

CONCLUSIONS

These observations suggest that locally produced MIP-1alpha may be involved in the development of cellular crescents in the acute phase via CCR5 and that MCP-1 may be involved mainly in the development of interstitial lesions in the chronic phase when fibrocellular/fibrous crescents are present, possibly through Mphi recruitment and activation.

P-selectin deficiency exacerbates experimental glomerulonephritis: a protective role for endothelial P-selectin in inflammation

P-selectin is a leukocyte adhesion receptor present in endothelial cells and platelets. We examined the role of P-selectin in the autologous phase of an accelerated model of anti-glomerular basement membrane (GBM) glomerulonephritis using P-selectin-deficient mice and chimeric mice expressing P-selectin only in platelets or endothelial cells. P-selectin-deficient mice exhibited more severe glomerular damage with increased interstitial mononuclear leukocytic infiltrates, and had significantly increased proteinuria and mortality when compared to wild-type mice. P-selectin on the endothelium was predominantly responsible for protection from the exacerbated disease, because chimeric mice with endothelial P-selectin, and not mice with platelet P-selectin, showed glomerular injury similar to that in wild-type animals. Levels of soluble circulating P-selectin were increased in nephritic wild-type mice and in chimeric mice with endothelial P-selectin, but not platelet P-selectin. Levels of soluble P-selectin, which has been shown to be anti-inflammatory in vitro, were inversely associated with the severity of disease. P-selectin was not expressed in the endothelium of the glomerulus or interstitium. Thus, the protective effect in wild-type mice may be accounted for, in part by soluble P-selectin shed by non-renal endothelial cells, although other endothelial P-selectin-dependent mechanisms cannot be ruled out.

Podocalyxin in rat platelets and megakaryocytes

Podocalyxin is a membrane protein of rat podocytes and endothelial cells. It has not been described in other cell types, and no amino acid or DNA sequence data are available about it. Here we show that podocalyxin antigens are present in rat platelets and megakaryocytes. In resting platelets, the antigens are mainly intracellular but become surface exposed after thrombin stimulation, as shown by immunofluorescence and flow cytometry. By Western blotting, platelet podocalyxin has an apparent Mr of 140,000. Cytocentrifuge slides of rat bone marrow show that anti-podocalyxin antibodies recognize large polyploid cells also expressing CD62P, indicating that the cells are megakaryocytes. From a rat glomerular cDNA library we isolated a clone covering the carboxyl-terminal nucleotides of rat podocalyxin. Its putative transmembrane or intracellular domains are 100% or >93% identical, respectively, with the human and rabbit podocalyxin-like proteins. The truncated extracellular domain extends to include two of the four conserved cysteines shared by podocalyxin-like proteins. By Northern blotting, a 5.5-kb renal cortical transcript is seen. By in situ hybridization, cRNA probes recognize podocytes, endothelial cells, and megakaryocytes, and by reverse transcription polymerase chain reaction, platelets are shown to contain podocalyxin mRNA. Our results show that rat podocalyxin is a homologue of the previously cloned podocalyxin-like proteins and suggest that also in mammals podocalyxin has a role in hematopoiesis, as previously shown in the chicken.

Identification of podocalyxin-like protein as a high endothelial venule ligand for L-selectin: parallels to CD34

The leukocyte adhesion molecule, L-selectin, mediates the recruitment of lymphocytes to secondary lymphoid organs via interactions with specific ligands presented on high endothelial venules (HEV). Although the HEV-derived ligands for L-selectin are still incompletely defined, they share a common sialomucin-like structure which is thought to present clustered oligosaccharides to the lectin domain of L-selectin. Podocalyxin-like protein (PCLP) is a transmembrane sialomucin that is similar in structure to the well-characterized L-selectin ligand CD34. PCLP has been shown previously to be expressed on the foot processes of podocytes in the kidney glomerulus as well as on vascular endothelium at some sites. We have determined that PCLP is present on HEV, where it binds to both recombinant L-selectin and the HEV-specific monoclonal antibody MECA-79. Furthermore, purified HEV-derived PCLP is able to support the tethering and rolling of lymphocytes under physiological flow conditions in vitro. These results suggest a novel function for PCLP as an adhesion molecule and allow the definition of conserved structural features in PCLP and CD34, which may be important for L-selectin ligand function.