Chemoattractants provoke monocyte adhesion to human mesangial cells and mesangial cell injury

The role of the mesangium in glomerular function

When discussing glomerular function, one cell type is often left out, the mesangial cell (MC), probably since it is not a part of the filtration barrier per se. The MCs are instead found between the glomerular capillaries, embedded in their mesangial matrix. They are in direct contact with the endothelial cells and in close contact with the podocytes and together they form the glomerulus. The MCs can produce and react to a multitude of growth factors, cytokines, and other signaling molecules and are in the perfect position to be a central hub for crosstalk communication between the cells in the glomerulus. In certain glomerular diseases, for example, in diabetic kidney disease or IgA nephropathy, the MCs become activated resulting in mesangial expansion. The expansion is normally due to matrix expansion in combination with either proliferation or hypertrophy. With time, this expansion can lead to fibrosis and decreased glomerular function. In addition, signs of complement activation are often seen in biopsies from patients with glomerular disease affecting the mesangium. This review aims to give a better understanding of the MCs in health and disease and their role in glomerular crosstalk and inflammation.

Monosodium urate crystals induced ICAM-1 expression and cell-cell adhesion in renal mesangial cells: Implications for the pathogenesis of gouty nephropathy

BACKGROUND

Renal disease is prevalent in gouty patients and monosodium urate (MSU) crystal deposition in the kidney can be detected in some gouty nephropathy patients. MSU crystals can induce inflammatory events, we investigated the MSU-induced expression of intercellular adhesion molecule (ICAM)-1 on human renal mesangial cells (HRMCs) and the involved signal transduction mechanisms.

METHODS

The HRMCs cell line was purchased from ScienCell Research Laboratories. MSU crystals were made by dissolving uric acid in sodium hydroxide (NaOH) solution. The involvement of MAPKs, apoptosis-associated speck-like protein containing a CARD domain (ASC), and Toll-like receptor (TLR) was investigated using pharmacological inhibitors, transfection with short hairpin RNA (shRNA), or monoclonal antibodies. Protein expression was evaluated by Western blotting. The functional activity of ICAM-1 was evaluated with cell-cell adhesion assay and immunofluorescence analysis.

RESULTS

MSU stimulation increased expression of ICAM-1 and adhesion between HRMCs and human monocytic THP-1 cells. The interaction between HRMCs and THP-1 was suppressed by ICAM-1 neutralizing antibodies. MSU stimulation induced activation of mitogen-activated protein kinases, including c-Jun N-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK), but only p38 was responsible for MSU-induced expression of ICAM-1 and cell-cell adhesion. ASC also play a role in MSU-induced effects. Pretreatment with monoclonal antibodies against toll-like receptor (TLR)2 or TLR4 reduced MSU-induced ICAM-1 expression, cell-cell adhesion, p38 phosphorylation but the reduction of ASC activation is insignificant.

CONCLUSION

The MSU induced ICAM-1 expression on HRMCs and cell-cell adhesion involved TLR2/4-p38-ICAM1 pathway and TLR2/4 independent ASC-p38-ICAM1 axis. These findings might partly explain the mechanisms underlying gouty nephropathy.

Crossing the Vascular Wall: Common and Unique Mechanisms Exploited by Different Leukocyte Subsets during Extravasation

Leukocyte extravasation is one of the essential and first steps during the initiation of inflammation. Therefore, a better understanding of the key molecules that regulate this process may help to develop novel therapeutics for treatment of inflammation-based diseases such as atherosclerosis or rheumatoid arthritis. The endothelial adhesion molecules ICAM-1 and VCAM-1 are known as the central mediators of leukocyte adhesion to and transmigration across the endothelium. Engagement of these molecules by their leukocyte integrin receptors initiates the activation of several signaling pathways within both leukocytes and endothelium. Several of such events have been described to occur during transendothelial migration of all leukocyte subsets, whereas other mechanisms are known only for a single leukocyte subset. Here, we summarize current knowledge on regulatory mechanisms of leukocyte extravasation from a leukocyte and endothelial point of view, respectively. Specifically, we will focus on highlighting common and unique mechanisms that specific leukocyte subsets exploit to succeed in crossing endothelial monolayers.

Potential association between membranous nephropathy and sargramostim therapy for pulmonary alveolar proteinosis

We present the case of a 43-year-old woman with a diagnosis of pulmonary alveolar proteinosis, on chronic treatment with sargramostim, a recombinant granulocyte-macrophage colony-stimulating factor, who presented with the nephrotic syndrome secondary to biopsy-proven membranous nephropathy. We discuss potential underlying mechanisms, including speculated effects of sargramostim on mesangial cells and the kidney resident macrophages, and review the existing literature on the potential association between these two disorders.

Neutrophil transmigration: emergence of an adhesive cascade within venular walls

Recruitment of neutrophils from the blood circulation to sites of infection or injury is a key innate immune response against invading pathogens and tissue injury. However, if inappropriately triggered, excessive and/or prolonged, this host defence response can also lead to severe pathological disorders. The migration of all leucocytes out of the vasculature is classically described by the leucocyte adhesion cascade that depicts a well-characterised sequence of cellular and molecular events within the vascular lumen. Recent findings have now illustrated that beyond the vascular lumen, the breaching of the venular wall can also involve an analogous cascade of adhesive events. For neutrophils this involves a tightly regulated and sequential series of responses within venular walls, initiating with adhesive steps that guide neutrophils through endothelial cells lining the venular wall, followed by responses that mediate and regulate their migration through the pericyte sheath and the venular basement membrane. The present review aims to provide a brief summary of novel additions to the classical adhesion cascade within the vascular lumen and then to discuss the emergence of a second adhesion cascade for neutrophils within venular walls, the latter illustrating the intricacies and complexities of neutrophil transmigration.

The leukotriene B4 receptor antagonist ONO-4057 inhibits mesangioproliferative changes in anti-Thy-1 nephritis

OBJECTIVE

ONO-4057 is a specific leukotriene B4 (LTB4) receptor antagonist which inhibits human neutrophil aggregation, chemotaxis and degranulation induced by LTB4. This study was conducted to evaluate the role of LTB4 in glomerulonephritis, and to examine whether ONO-4057 moderated anti-Thy-1 nephritis.

METHODS

Experiment 1: Sixty Wistar rats were divided into three groups. Rats of Group A (n = 20) underwent intraperitoneal administration of placebo as a control group, rats of Group B (n = 20) first underwent intraperitoneal administration of 100 mg/kg ONO-4057 and rats of Group C (n = 20) first underwent intraperitoneal administration of 300 mg/kg ONO-4057 daily from day 3 before anti-Thy-1 antibody (OX7) injection to day 14 after OX7 injection, respectively. Experiment 2: Forty rats were divided into two groups. ONO-group (n = 20) was treated with 300 mg/kg BW of ONO-4057 and placebo-group (n = 20) with placebo daily from days 1 to 13 after OX7 injection. Urine and blood samples were collected and the kidneys were extirpated from five rats of each group sacrificed at 3 h, 24 h, day 7 or day 14 after the injection of OX7 in both experiments. Urinary protein excretion, renal function and pathological findings were analysed in each group of both experiments.

RESULTS

(1) Glomerular infiltration by polymorphonuclear leucocytes (PMNs) and macrophages at 3 h was less in Groups B and C than in Group A, and matrix scores at day 7 were lower in Groups B and C than in Group A. Injury scores did not differ among the groups. (2) Urinary protein excretion at day 7 was less in Group C than in Group A. (3) Neither pathological findings nor urinary protein excretion differed between ONO-group and placebo-group.

CONCLUSION

These results suggest that LTB4 is associated not with the pathogenesis of complement-dependent mesangial cell lysis but with that of mesangial proliferative change in anti-Thy-1 nephritis.

Connective tissue growth factor [CTGF]/CCN2 stimulates mesangial cell migration through integrated dissolution of focal adhesion complexes and activation of cell polarization

Connective tissue growth factor [CTGF]/CCN2 is a prototypic member of the CCN family of regulatory proteins. CTGF expression is up-regulated in a number of fibrotic diseases, including diabetic nephropathy, where it is believed to act as a downstream mediator of TGF-beta function; however, the exact mechanisms whereby CTGF mediates its effects remain unclear. Here, we describe the role of CTGF in cell migration and actin disassembly in human mesangial cells, a primary target in the development of renal glomerulosclerosis. The addition of CTGF to primary mesangial cells induced cell migration and cytoskeletal rearrangement but had no effect on cell proliferation. Cytoskeletal rearrangement was associated with a loss of focal adhesions, involving tyrosine dephosphorylation of focal adhesion kinase and paxillin, increased activity of the protein tyrosine phosphatase SHP-2, with a concomitant decrease in RhoA and Rac1 activity. Conversely, Cdc42 activity was increased by CTGF. These functional responses were associated with the phosphorylation and translocation of protein kinase C-zeta to the leading edge of migrating cells. Inhibition of CTGF-induced protein kinase C-zeta activity with a myristolated PKC-zeta inhibitor prevented cell migration. Moreover, transient transfection of human mesangial cells with a PKC-zeta kinase inactive mutant (dominant negative) expression vector also led to a decrease in CTGF-induced migration compared with wild-type. Furthermore, CTGF stimulated phosphorylation and activation of GSK-3beta. These data highlight for the first time an integrated mechanism whereby CTGF regulates cell migration through facilitative actin cytoskeleton disassembly, which is mediated by dephosphorylation of focal adhesion kinase and paxillin, loss of RhoA activity, activation of Cdc42, and phosphorylation of PKC-zeta and GSK-3beta. These changes indicate that the initial stages of CTGF mediated mesangial cell migration are similar to those involved in the process of cell polarization. These findings begin to shed mechanistic light on the renal diabetic milieu, where increased CTGF expression in the glomerulus contributes to cellular dysfunction.

The role of p42/44 MAPK and protein kinase B in connective tissue growth factor induced extracellular matrix protein production, cell migration, and actin cytoskeletal rearrangement in human mesangial cells

Connective tissue growth factor (CTGF) is a member of an emerging family of immediate-early gene products that coordinate complex biological processes during differentiation and tissue repair. Here we describe the role of CTGF in integrin-mediated adhesive signaling and the production of extracellular matrix components in human mesangial cells. The addition of CTGF to primary mesangial cells induced fibronectin production, cell migration, and cytoskeletal rearrangement. These functional responses were associated with recruitment of Src and phosphorylation of p42/44 MAPK and protein kinase B. The inhibition of CTGF-induced p42/44 MAPK or phosphatidylinositol 3-kinase (PI3K)/protein kinase B pathway activities abrogated the induction of fibronectin expression. In addition, anti-beta(3) integrin antibodies attenuated the activation of both the p42/44 MAPK and protein kinase B and the increase in fibronectin levels. CTGF also induced mesangial cell migration via a beta(3) integrin-dependent mechanism that was similarly sensitive to the inhibition of the p42/44 MAPK and PI3K pathways, and it promoted the adhesion of the mesangial cells to type I collagen via up-regulation of alpha(1) integrin. Transient actin cytoskeletal disassembly was observed following treatment with the ligand over the course of a 24-h period. CTGF induced the loss of focal adhesions from the mesangial cell as evidenced by the loss of punctate vinculin. However, these processes are p42/44 MAPK and PI3K pathway-independent. Our data support the hypothesis that CTGF mediates a number of its biological effects by the induction of signaling processes via beta(3) integrin. However, others such as actin cytoskeleton disassembly are modulated in a beta(3) integrin/MAPK/PI3K-independent manner, indicating that CTGF is a complex pleiotropic factor with the potential to amplify primary pathophysiological responses.

Induction of nephrotoxic serum nephritis in inbred mice and suppressive effect of colchicine on the development of this nephritis

Accelerated nephrotoxic serum (NTS) nephritis is successfully produced in C57BL/6 mice, using anti-murine glomerular basement membrane (GBM) rabbit antiserum. Anti-murine GBM rabbits antiserum was obtained by immunization of New Zealand white rabbit with trypsinized GBM antigen from normal C57BL/6 mice. Preimmunization with normal rabbit IgG and injection with 150 microl of NTS induced typical NTS nephritis with cellular proliferation in glomeruli, occlusion of glomerular loops, crescents, tubulointerstitial changes and hyperazotemia within 14 days. Polymorphonuclear leucocytes (PMN) have an important role in induction and development of NTS nephritis. Furthermore, clinically used colchicine is thought to suppress functions of PMN. Therefore, the therapeutic effect of colchicine on NTS nephritis was examined. The histological score (HS) of the group treated with 60 microg kg (-1) of colchicine (2.8 +/- 0.5) was significantly lower than that of positive control group (4.03 +/- 0.3).The direct immunofluorescent microscopic study revealed that there is no quantitative difference in the deposition of rabbit IgG, mouse IgG and C3 in GBM between these two groups. Urinary protein excretion and hyperazotemia were significantly suppressed by treatment with 60 microg kg (-1) of colchicine. A NTS nephritis model was established, it was found that colchicine may have a suppressive effect on the development of glomerular nephritis.

High glucose-altered gene expression in mesangial cells. Actin-regulatory protein gene expression is triggered by oxidative stress and cytoskeletal disassembly

High extracellular glucose plays a pivotal role in the pathophysiology of diabetic nephropathy. Here we report 200 genes, identified using suppression-subtractive hybridization, that are differentially expressed when human mesangial cells are propagated in high ambient glucose in vitro. The major functional classes of genes identified included modulators and products of extracellular matrix protein metabolism, regulators of cell growth and turnover, and a cohort of actin cytoskeleton regulatory proteins. Actin cytoskeletal disassembly is a prominent feature of diabetic nephropathy. The induction of actin cytoskeleton regulatory gene expression by high glucose was attenuated by the inhibitor of reactive oxygen species generation, carbonyl cyanide m-chlorophenylhydrazone but not by the protein kinase C inhibitor GF 109203X and was not mimicked by the addition of transforming growth factor beta. Enhanced expression of actin cytoskeleton regulatory genes was also observed following disruption of the mesangial cell actin cytoskeleton by cytochalasin D. In aggregate, these results suggest that the induction of genes encoding actin cytoskeleton regulatory proteins (a) is a prominent component of the mesangial cell transcriptomic response in diabetic nephropathy and (b) is dependent on oxidative stress, is independent of protein kinase C and transforming growth factor-beta, and represents an adaptive response to actin cytoskeleton disassembly.

Transmembrane signalling in human monocyte/mesangial cell co-cultures: role of cytosolic Ca(2+)

BACKGROUND

Adhesion of monocytes triggers apoptosis, cytotoxicity, cytokine release, and later proliferation of cultured human mesangial cells (HMC). In the search for transmembrane signals transducing the interaction of HMC adhesion molecules with leukocyte counterreceptors, we measured variations of cytosolic Ca(2+) ([Ca(2+)](i)) in HMC and monocytes of the U937 cell line during 6-h co-cultures.

METHODS

Monolayer cultures of HMC and suspensions of U937 cells were loaded with the fluoroprobe fura 2-AM and subsequently co-cultured for 6 h while separately monitoring by microfluorometry the Ca(2+)-dependent 500 nm fluorescent emission of each cell line at fixed intervals upon excitation at 340/380 nm.

RESULTS

U937 and peripheral blood monocyte adhesion was followed in HMC by a slow, progressive rise of [Ca(2+)](i) from basal levels of 96+/-9 nM to 339+/-54 at 60 min and 439+/-44 nM at 3 h. The [Ca(2+)](i) elevation reached a steady state thereafter, while parallel monolayers incubated with control media maintained resting levels throughout the co-culture with stable fluoroprobe retention. Receptor sensitivity to vasoconstrictor agents, including compounds not released by monocytes, such as angiotensin II, was rapidly downregulated in HMC co-cultured with U937 cells. No [Ca(2+)](i) changes could be elicited by the octapeptide or by the TxA(2) analogue, U-46619, as early as 30 min after exposure to U937 cells. No [Ca(2+)](i) changes were observed in U937 cells throughout the co-culture. Conditioned media from monocytes and from co-cultured HMC+U937 cells had no effect on [Ca(2+)](i) of HMC. Ca(2+) entry leading to fura 2 saturation was still inducible by Ca(2+) ionophores, such as ionomycin and 4-Br-A23187, which also inhibited the responses to vasoconstrictors. Ca(2+)-free solutions prevented the [Ca(2+)](i) rise as well as subsequent receptor inactivation, implicating Ca(2+) influx through store-operated Ca(2+) channels (SOC), a major pathway for Ca(2+) entry in these cultured cells. Ca(2+) influx was confirmed by Mn(2+)-quenching of fura 2.

CONCLUSIONS

In HMC, early changes in [Ca(2+)](i) signal for monocyte adhesion in a co-culture model of glomerular inflammation. This signalling mechanism may mediate the functional responses elicited in glomerular cells by leukocytes, including downregulation of receptors for vasoactive agents.

Enhanced expression of complement C5a receptor mRNA in human diseased kidney assessed by in situ hybridization

BACKGROUND

Anaphylatoxin C5a mediates inflammatory responses through interaction with a specific C5a receptor (C5aR), the expression of which is thought to be restricted to peripheral blood leukocytes. Although the presence of C5aR on cultured mesangial cells and tubular epithelial cells has recently been documented, the tissue distribution of C5aR in diseased kidney has not yet been determined.

METHODS

Immunohistochemistry and nonradioactive in situ hybridization for C5aR were performed in 34 tissue samples of kidneys from patients with various renal diseases, including 4 with minimal change nephrotic syndrome (MCNS), 5 with membranous nephropathy (MN), and 25 with mesangial proliferative glomerulonephritis (mesGN; 15 patients with IgA nephropathy, 5 with non-IgA mesGN, and 5 with lupus nephritis). Normal portions of surgically resected kidney served as the control.

RESULTS

In normal kidneys, C5aR protein was detected in tubular epithelial cells, while C5aR mRNA was detected in a few glomerular cells, tubular epithelial cells, and vascular endothelial and smooth muscle cells. In MCNS, the distribution of C5aR protein and mRNA was similar to that in normal kidneys. In MN and mesGN, C5aR protein and mRNA were detected in mesangial cells, glomerular epithelial and endothelial cells, Bowman's capsule cells, tubular cells, infiltrating cells, and vascular endothelial and smooth muscle cells. The glomerular expression of C5aR mRNA and protein correlated positively with the degree of mesangial hypercellularity and mesangial matrix expansion in mesGN. In the tubulointerstitium, interstitial expression of C5aR mRNA correlated positively with the degree of tubular atrophy and interstitial broadening in mesGN. Furthermore, the interstitial expression of C5aR mRNA correlated positively with the level of serum creatinine.

CONCLUSIONS

Our results indicate that renal cells produce C5aR and that activation of C5a/C5aR pathway on renal cells may be involved in tissue injury in mesGN.

IHG-2, a mesangial cell gene induced by high glucose, is human gremlin. Regulation by extracellular glucose concentration, cyclic mechanical strain, and transforming growth factor-beta1

We used cloning in silico coupled with polymerase chain reaction to demonstrate that IHG-2 is part of the 3'-untranslated region of gremlin, a member of the DAN family of secreted proteins that antagonize the bioactivities of members of the transforming growth factor (TGF)-beta superfamily. Mesangial cell gremlin mRNA levels were induced by high glucose, cyclic mechanical strain, and TGF-beta1 in vitro, and gremlin mRNA levels were elevated in the renal cortex of rats with streptozotocin-induced diabetic nephropathy in vivo. gremlin expression was observed in parallel with induction of bone morphogenetic protein-2 (BMP-2), a target for gremlin in models of cell differentiation. Together these data indicate that (a) IHG-2 is gremlin, (b) gremlin is expressed in diabetic nephropathy in vivo, (c) both glycemic and mechanical strain stimulate mesangial cell gremlin expression in vitro, (d) high glucose induces gremlin, in part, through TGFbeta-mediated pathways, and (e) Gremlin is a potential endogenous antagonist of BMPs within a diabetic glomerular milieu.

Very low-density lipoprotein stimulates the expression of monocyte chemoattractant protein-1 in mesangial cells

BACKGROUND

Elevated plasma levels of very low-density lipoprotein (VLDL) are associated with an increased risk for focal glomerulosclerosis, which is analogous to atherosclerosis. One feature of focal glomerulosclerosis is the presence of foam cells derived from the infiltration of circulating monocytes. Mesangial cells are able to express monocyte chemoattractant protein-1 (MCP-1). In this study, the ability of VLDL to stimulate MCP-1 expression in mesangial cells and consequent monocyte adhesion was investigated.

METHODS

For adhesion studies, mesangial cells isolated from Sprague-Dawley rats were treated with VLDL for six hours, followed by a one-hour incubation with Tamm-Horsfall protein-1 (THP-1) cells. Mesangial MCP-1 mRNA levels were determined by reverse transcription-polymerase chain reaction. MCP-1 protein was determined by solid-phase immunoassay.

RESULTS

VLDL (100 to 300 microg/mL) significantly enhanced the expression and secretion of MCP-1 (54 to 285 ng/well) in mesangial cells. Such an effect was accompanied by the increased adhesion of monocytes to mesangial cells and later the formation of foam cells from monocytes after ingesting excessive amounts of VLDL lipids. VLDL-induced MCP-1 expression and monocyte adhesion were blocked by a protein kinase C inhibitor (staurosporine), as well as a calcium channel blocker (diltiazem).

CONCLUSIONS

Our results demonstrate that elevated levels of VLDL, through the action of MCP-1, may contribute to the infiltration of monocytes into the mesangium and subsequent foam cell formation. Hence, VLDLs may play a role in the pathogenesis of focal glomerulosclerosis. One of the mechanisms of such effect may be mediated through the calcium-dependent protein kinase C pathway.

Regulation of leukocyte trafficking by lipoxins

Lipoxins are lipoxygenase interaction products formed by transcellular metabolism during host defence and inflammation. In model systems, lipoxins modulate polymorphonuclear leukocytes (PMN) chemotaxis, adhesion molecule expression, inhibit PMN-endothelial cell adhesion, and attenuate cytokine release from epithelial cells. These observations raise the possibility that lipoxins are 'stop signals' for PMN-mediated tissue injury and promote the resolution of acute inflammation.

Suppression subtractive hybridization identifies high glucose levels as a stimulus for expression of connective tissue growth factor and other genes in human mesangial cells

Accumulation of mesangial matrix is a pivotal event in the pathophysiology of diabetic nephropathy. The molecular triggers for matrix production are still being defined. Here, suppression subtractive hybridization identified 15 genes differentially induced when primary human mesangial cells are exposed to high glucose (30 mM versus 5 mM) in vitro. These genes included (a) known regulators of mesangial cell activation in diabetic nephropathy (fibronectin, caldesmon, thrombospondin, and plasminogen activator inhibitor-1), (b) novel genes, and (c) known genes whose induction by high glucose has not been reported. Prominent among the latter were genes encoding cytoskeleton-associated proteins and connective tissue growth factor (CTGF), a modulator of fibroblast matrix production. In parallel experiments, elevated CTGF mRNA levels were demonstrated in glomeruli of rats with streptozotocin-induced diabetic nephropathy. Mannitol provoked less mesangial cell CTGF expression in vitro than high glucose, excluding hyperosmolality as the key stimulus. The addition of recombinant CTGF to cultured mesangial cells enhanced expression of extracellular matrix proteins. High glucose stimulated expression of transforming growth factor beta1 (TGF-beta1), and addition of TGF-beta1 to mesangial cells triggered CTGF expression. CTGF expression induced by high glucose was partially suppressed by anti-TGF-beta1 antibody and by the protein kinase C inhibitor GF 109203X. Together, these data suggest that 1) high glucose stimulates mesangial CTGF expression by TGFbeta1-dependent and protein kinase C dependent pathways, and 2) CTGF may be a mediator of TGFbeta1-driven matrix production within a diabetic milieu.

The leukotriene B4 receptor antagonist ONO-4057 inhibits nephrotoxic serum nephritis in WKY rats

To evaluate the role of leukotriene B4 (LTB4) in glomerulonephritis, this study was conducted to examine whether ONO-4057, an LTB4 receptor antagonist, moderated nephritis caused by the injection of nephrotoxic serum (NTS) into Wistar-Kyoto rats. Rats were given intraperitoneal injections of ONO-4057 or phosphate-buffered saline 24 h before the injection of NTS. These rats subsequently received equal doses of ONO-4057 or phosphate-buffered saline 3 h and 1, 2, 3, 4, 5, and 6 d later. Compared with the control groups, ONO-4057 treatment significantly reduced proteinuria and hematuria, suppressed the glomerular accumulation of monocytes/macrophages, and reduced the formation of crescentic glomeruli in a dose-dependent manner. These results suggest that LTB4 is responsible for the crescentic formations and renal dysfunction associated with NTS nephritis. The LTB4 receptor antagonist ONO-4057 may thus be beneficial in the treatment of crescentic glomerulonephritis.

Expression of adhesion molecules in chronic serum sickness in rats

Peripheral blood leukocytes infiltrate the kidney in chronic serum sickness (CSS). We therefore studied the expression of CD54 and its ligands CD18 and CD11b/c in CSS in 10 rats with CSS, 6 rats immunized similarly who did not developed proteinuria (no-CSS group), and 10 normal rats (control group). Intense (6 to 35 times more than controls) leukocyte infiltration was observed in CSS. The CSS group over-expressed CD54 in glomeruli and interstitium in association with increments in CD18- and CD11b/c-positive cells ranging 2.5 to 7 times the number found in controls. 75% of infiltrating leukocytes expressed CD18 and 87% expressed CD11b/c. The non-CSS group had leukocyte infiltration and expression of adhesion molecules similar to control group. Adherence of CD43-positive cells to renal tissues was 4 times higher in renal tissue from CSS rats than to normal kidney. Pretreatment with corresponding Mabs reduced adherence by half. We concluded that over-expression of CD54 and its ligands CD18 and CD11b/c in infiltrating leukocytes occur in CSS. Binding experiments suggest the functional relevance of these molecules.

Cultured human glomerular mesangial cells express the C5a receptor

BACKGROUND

While the association of complement activation and glomerulonephritis has been recognized for decades, the pathogenic mechanisms of complement-mediated glomerular damage are incompletely understood. Expression of the C5a receptor in the kidney suggests that C5a could play a direct role in initiating or promoting glomerulonephritis.

METHODS

Expression of the C5a receptor by cultured human glomerular mesangial cells (HGMC) was examined by immunofluorescence, by FACS analysis and by reverse transcriptase-polymerase chain reaction (RT-PCR). Potential mitogenic effects were examined by analysis of neutral red dye uptake after treatment with recombinant C5a (rC5a). The production of cytokines [interleukin-1 (IL-1), interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1)] and growth factors [transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF-AB)] by mesangial cells stimulated with rC5a was examined by ELISA of cell culture supernatants.

RESULTS

Expression of the C5a receptor by the cultured HGMC was demonstrated by both immunofluorescence and FACS. The presence of mRNA encoding the receptor was confirmed by RT-PCR. Treatment of HGMC in vitro with rC5a resulted in mild cellular proliferation. No IL-1 was detected despite stimulation with up to 100 nM rC5a. Concentrations of IL-8 and TGF-beta did not increase beyond basal levels in control samples at any level of stimulation. Mean MCP-1 concentrations and PDGF-AB concentrations increased by 40% and 70% above control values 48 hours post-stimulation (P = 0.01 and P = 0.003, respectively).

CONCLUSIONS

These data indicate that the C5a receptor is expressed on HGMC in vitro, and may play a role in mediating glomerular injury by promoting cellular proliferation and the production of cytokines and growth factors.

Adhesion molecules and urinary tumor necrosis factor-alpha in idiopathic membranous glomerulonephritis

Adhesion molecules are required in several physiological processes, but their altered function/expression is associated with the pathogenesis of inflammatory diseases. In the present study on idiopathic membranous glomerulonephritis (MGN) the expression of adhesion molecules (ICAM-1, VCAM-1, PECAM-1, E-selectin, LFA-1, Mac-1) was analyzed in different cellular compartments of the kidney using an indirect immunoperoxidase technique and monoclonal antibodies. Relationships between the expression of these molecules and the clinical and morphological activity of the disease and the urinary excretion of tumor necrosis factor alpha (TNF-alpha) were studied in 20 patients. The results were compared with the findings in ten normal kidneys and urinary TNF-alpha in 17 healthy subjects. The expression of adhesion molecules in glomeruli and tubules was unchanged apart from a diminished expression of VCAM-1 (P = 0.014) in glomerular parietal epithelial cells and PECAM-1 in glomerular endothelial cells (P < 0.01). Interstitial peritubular capillaries expressed significantly (P = 0.009) more E-selectin compared with the controls. The interstitial compartment had a highly increased number of cells expressing ICAM-1 in MGN (32.4 +/- 4.6 cells/high power field) compared with the controls (9.4 +/- 1.2; P < 0.001). Also, cells expressing VCAM-1 (10.2 +/- 1.6 vs. 2.8 +/- 1.9; P = 0.005). PECAM-1 (25.9 +/- 5.3 vs. 7.4 +/- 2.1; P = 0.006), and LFA-1 (20.4 +/- 3.6 vs. 8.3 +/- 1.5; P = 0.041) were increased in the interstitium. Proteinuria correlated particularly with the expression of E-selectin in peritubular capillaries (r = 0.63, P = 0.004). The number of LFA-1 expressing inflammatory cells in the interstitium correlated with peritubular capillary E-selectin (r = 0.8, P < 0.001) and interstitial ICAM-1 (r = 0.61, P = 0.009) expression, but histological alterations did not correlate with the expression of adhesion molecules. Tumor necrosis factor-alpha excretion was significantly increased in MGN (41 +/- 8 pg/mg creatinine) compared with the controls (13 +/- 2; P = 0.001), and in particular, it correlated with the interstitial expression of LFA-1 (r = 0.71, P = 0.002). This study suggests that active MGN leads not only to proteinuria but also to increased urinary TNF-alpha excretion. These may serve as triggers for the up-regulation of adhesion molecules in the peritubular capillaries and interstitial cells thus enhancing the development of the interstitial injury.

Induction of mesangial interleukin-6 synthesis by apoptotic U937 cells and monocytes

Infiltration of the glomerular mesangium by monocytes and macrophages is a central pathologic feature in various forms of glomerulonephritis. Dependent on the presence and activity of local survival factors, monocytes may undergo apoptosis. Therefore, we looked for the interaction between cultured human mesangial cells (HMC) and intact, necrotic or apoptotic monocytic cells with different stages of programmed cell death (U937 cells and blood-derived human monocytes) and the possible evoked secretory responses of HMC. Interleukin-6 (IL-6) synthesis of HMC after a two hour co-culture with late apoptotic U937 cells was significantly increased (505 +/- 55 pg/ml) as compared to intact U937 cells (349 +/- 27 pg/ml; HMC alone, 319 +/- 62 pg/ml), and was further elevated after 20 hours (815 +/- 108 pg/ml). U937 cells alone, after incubation in HMC-conditioned medium or after coincubation with HMC, did not produce any detectable IL-6. A high mesangial IL-6 synthesis in response to apoptotic U937 cells was dependent on the cellular contact between HMC and U937 and could not be mimicked by apoptotic U937 culture supernatants. Radiolabeling studies indicated that HMC bound (16.6 +/- 2.4%) and ingested (12.5 +/- 1.9%) apoptotic U937 cells to a much higher amount as compared to intact U937 (5.3 +/- 2.0% binding; 5.0 +/- 1.1% phagocytosis). Binding and ingestion of monocytic cells undergoing apoptosis was confirmed by morphologic studies using electron microscopy. Incubation of HMC with a blocker of the CD36/ vitronectin receptor (VnR) dependent recognition mechanism of phagocytes for apoptotic leukocytes (RGDS peptide) did not alter binding, phagocytosis or IL-6 synthesis of HMC in response to apoptotic U937. Phospho-L-serine as an antagonist of the phosphatidylserine (PS) mediated recognition pathway for apoptotic cell disposal was able to reduce binding and IL-6 production by HMC but not phagocytosis. Thus, binding of apoptotic monocytic cells by HMC rather than ingestion may be the prerequisite for a stimulated secretory response. To elucidate whether binding and phagocytosis of particles in general might stimulate HMC to produce IL-6, we looked for mesangial IL-6 production after binding and ingestion of opsonized zymosan particles. In this case, IL-6 synthesis was markedly down-regulated. Furthermore, HMC proliferated after zymosan treatment, whereas after apoptotic cell uptake the mesangial cell number remained constant. In conclusion, apoptotic monocytic cells provoked an enhanced mesangial IL-6 synthesis by a PS-dependent recognition mechanism. This secretory response may have secondary implications for humoral or cellular processes within the mesangium.

Effects of HIV-1 on the surface expression of LFA-1 on cultured monocytes

CD11a, the alpha chain of LFA-1, which is a member of the LeuCAM family of integrins, has been implicated in the formation of HIV-induced syncytia and may contribute to the depletion of CD4-positive lymphocytes seen in patients with HIV infection. In this study, we examined the effects of HIV-1 infection on the expression of CD11a on cultured monocyte-derived macrophages (MDMs). Monocytes isolated from peripheral blood and maintained in suspension culture were infected in vitro with a monocytotropic variant of HIV-1 (Ba-L). Surface expression of CD11a, measured by indirect immunofluorescence and flow cytometry, was significantly higher on HIV-infected cells than on mock-infected cells from the same donor. Upregulation of CD11a expression was unaffected by the HIV reverse transcriptase inhibitor, zidovudine, indicating that it did not depend on reverse transcription. A step before reverse transcription, such as viral binding, appears sufficient to trigger an increase in CD11a expression. This hypothesis is supported by our findings of soluble recombinant CD4 inhibition of HIV-induced CD11a upregulation. It is possible that induction of a cytokine network by HIV underlies this effect, given our findings that exposure of uninfected MDMs to granulocyte-macrophage colony-stimulating factor (GM-CSF) specifically increased CD11a expression and that HIV-infected MDMs secreted more GM-CSF than mock-infected cells.

Monocyte chemoattractant protein-1 mediates monocyte/macrophage influx in anti-thymocyte antibody-induced glomerulonephritis

Chemokines are a family of chemotactic cytokines whose participation in inflammation in vivo remains to be established. To study the role of monocyte-chemoattractant-protein-1 (MCP-1) on the glomerular accumulation of leukocytes, rats received a neutralizing anti-MCP-1 antiserum following the induction of an glomerulonephritis by an anti-thymocyte antibody (ATS). The infiltration of monocytes/macrophages (M/M) and granulocytes was analyzed by immunohistology. When studied by Northern blotting, glomerular mRNA levels of MCP-1, and interleukin 1 beta (IL-1 beta) increased at three hours and 24 hours following the induction of the injury. The glomerular mRNA expression of intercellular adhesion molecule-1 (ICAM-1) only increased marginally, whereas the expression of the chemokine RANTES was not enhanced. In animals that received anti-MCP-1 antibody glomerular MCP-1 mRNA expression increased. However, the chemoattractant activity for monocytes released into supernatants of isolated glomeruli was reduced. The anti-MCP-1 antibody did not affect glomerular IL-1 beta, ICAM-1 or RANTES mRNA levels. The induction of glomerulonephritis was associated with an increased glomerular recruitment of polymorphonuclear granulocytes (PMNs) at three hours and M/M at 24 hours, when compared with controls. The anti-MCP-1 antiserum significantly reduced the glomerular M/M infiltration at 24 hours by 40%, but was without effect on glomerular PMN recruitment or growth of the resident glomerular cells. These studies demonstrate that MCP-1 is an important mediator for monocyte recruitment in this model of glomerulonephritis. The reduction of M/M infiltration might affect this glomerular injury.

Ultrastructural localization of vascular cell adhesion molecule-1 in proliferative and crescentic glomerulonephritis

Recent studies have demonstrated an important role of vascular cell adhesion molecule-1 (VCAM-1) in the pathogenesis of nephritis. In the present study, renal biopsy specimens from patients with proliferative and crescentic glomerulonephritis were subjected to immunoelectron microscopy using an anti-VCAM-1 monoclonal antibody. In control normal kidney tissue, VCAM-1 expression was restricted to the free surface of parietal epithelial cells. In diseased glomeruli, VCAM-1 was expressed on the free surface of parietal and visceral epithelial cells, on the luminal surface of capillary endothelial cells, on infiltrating monocyte/macrophage-like cells, on mesangial cells, and in the matrix of the expanded mesangium. There was also VCAM-1 expression on almost all cell types in the crescents, including macrophage-like cells, fibroblast-like cells, and epithelial cells. Some cells also showed VCAM-1 positivity in the rough endoplasmic reticulum and the perinuclear space. Both the glomerular capillary lumen and urinary spaces of Bowman's capsule contained positive reaction products, which were often associated with exocytosis by the surrounding cells. VCAM-1 was predominantly expressed on the basal and lateral surfaces of a few proximal tubules, but it could not be localized ultrastructurally. These findings suggest that production and secretion of VCAM-1 by both infiltrating monocyte/macrophages and resident glomerular cells may be related to the pathogenesis of proliferative and crescentic glomerulonephritis.

Activation of mesangial cells with TNF-alpha stimulates M-CSF gene expression and monocyte proliferation: evidence for involvement of protein kinase C and protein tyrosine kinase

In this study, we examined the effect of TNF-alpha on mesangial cell gene expression of M-CSF, a colony-stimulating factor associated with monocyte differentiation into macrophages and proliferation. Incubation of mesangial cells with TNF-alpha-stimulated mRNA expression and protein synthesis of M-CSF. Mesangial cell activation with PMA, a PKC activator, stimulated M-CSF mRNA expression while PKC depletion decreased M-CSF mRNA expression to control levels. Stimulation of PKC-depleted mesangial cells with either PMA or TNF-alpha inhibited M-CSF mRNA transcripts. Preincubation of mesangial cells with calphostin C, a PKC inhibitor, reduced both PMA- and TNF-alpha-induced M-CSF mRNA transcripts. Specific protein tyrosine kinase inhibitors blocked TNF-alpha-induced mesangial cell M-CSF mRNA expression. Additional studies showed that pertussis toxin, isoproterenol, and dibutyryl (db)cAMP did not induce mesangial cell M-CSF gene expression. However, coincubation of mesangial cells with TNF-alpha and either dbcAMP, forskolin, or pertussis toxin inhibited TNF-alpha-induced M-CSF gene expression. Finally, TNF-alpha-activated mesangial cell conditioned media stimulated monocyte/macrophage proliferation dose-dependently and was prevented by using anti-M-CSF. These data suggested that M-CSF can regulate monocyte differentiation into macrophages and proliferation within the mesangium induced by proinflammatory cytokines such as TNF-alpha. These cellular events appeared to be modulated by signal transduction pathways mediated by PKC and PTK.

Adhesion of U-937 monocytes induces cytotoxic damage and subsequent proliferation of cultured human mesangial cells

In an in vitro model of monocyte adhesion to glomerular cells, U-937 myelomonocytic leukemia cells irreversibly bind to human mesangial cell monolayers. Adhesion is enhanced in mesangial cells proliferating in response to fetal bovine serum, and in the presence of several cytokines and vasoactive agents. In the present study, co-culture with U-937 followed by removal of non-adherent cells time-dependently decreased viability of mesangial cells, measured either by fluorometry after dual labeling with calcein acetoxymethylester and ethidium homodimer, or by the release of lactate dehydrogenase. The cytotoxic effects of co-culture with U-937 cells were significantly reduced by a combination of free radical scavengers, indicating involvement of reactive oxygen species. U-937 cells also stimulated subsequent proliferation of mesangial cells, assessed by [3H]-TdR incorporation and direct cell counts 24 hours later (from 1,034 +/- 83 to 14,611 +/- 959 and from 2,931 +/- 201 to 19,400 +/- 2,124 cpm/well, quiescent/cycling mesangial cells, respectively, P < 0.01). Controls to rule out TdR incorporation by adherent U-937 cells included selective [3H]-TdR labeling and demecolcine pretreatment. Cell counts at 24 hours confirmed U-937-induced proliferation of quiescent HMC, from 50,575 +/- 3,596 to 143,012 +/- 10,039 cells/cm2 (P < 0.01). Agents that promote U-937 cell adhesion, such as the TxA2 mimetic, U-46619, or angiotensin II, enhanced cytotoxicity while inhibiting the proliferation of both quiescent and cycling mesangial cells, when added during co-culture and the subsequent 24 hours (+1 microM U-46619, 1,875 +/- 131 and 2,546 +/- 125 cpm/well, respectively, 79,793 +/- 5,744 cells/cm2, P < 0.01 vs. U-937 only; +1 microM Ang II, 5066 +/- 560 and 5,784 +/- 306 cpm/well, respectively, 81,068 +/- 4,671 cells/cm2, P < 0.05). Blocking antibodies against the adhesion molecule ICAM-1 and leukocyte counterreceptors (LFA-1, VLA-4) prevented the proliferative response, which could not be duplicated with the conditioned media of U-937 alone or co-cultured with mesangial cells. These findings may reflect the interactions occurring in vivo between infiltrating leukocytes and resident cells during glomerular inflammation.

Increased glomerular and interstitial LFA-1 expression in proteinuric immunoglobulin A nephropathy

The cell populations infiltrating the kidneys and the LFA-1 expression were studied in renal biopsy specimens from patients with proteinuric (n = 15, group 1) and non-proteinuric (n = 12, group 2) immunoglobulin A nephropathy. Both groups were matched for age and renal function at the time of biopsy. Proliferative glomerular changes were more commonly see in group 1. Both groups had similar numbers of intraglomerular and interstitial total leukocytes, monocytes/macrophages, and T cells (P = NS). However, glomerular LFA-1 alpha- and -beta-positive cells were significantly higher in group 1 (2.3 +/- 0.2 and 3.3 +/- 0.1 per glomerulus) than in group 2 (0.2 +/- 0.08 and 0.5 +/- 0.05 per glomerulus) (P < 0.005 and P < 0.01, respectively). Group 1 had much higher interstitial LFA-1 alpha- (109 +/- 20/mm(2)) and -beta-positive cells (157 +/- 40/mm(2)) in comparison with group 2 (29 +/- 12/mm(2) and 42 +/- 17/mm(2)). (P < 0.005 and P < 0.01, respectively). No association between glomerular and interstitial LFA-1-positive cells was seen. In addition, tubular HLA-DR expression was higher in group 1 (29 +/- 6/mm(2)) than in group 2 (9 +/- 2/mm(2)) (P < 0.005), but the interstitial HLA-DR-positive cells were similar in both groups. There was a significant association between interstitial LFA-1 alpha- and -beta-positive cells and tubular HLA-DR expression in group 1 (P < 0.01 and P < 0.005, respectively) but not in group 2. Interestingly, the extent of interstitial but not glomerular LFA-1-alpha and -beta expression was highly related to the degree of proteinuria in group 1 (P < 0.01 and P < 0.002, respectively). In conclusion, proteinuria in immunoglobulin A nephropathy is associated with increased LFA-1 expression by glomerular and interstitial infiltrating cells. However, interstitial but not glomerular LFA-1-positive cells are strongly related with the degree of urinary protein excretion. The exact link between LFA-1 expression and proteinuria needs further investigation.

Intraglomerular and interstitial leukocyte infiltration, adhesion molecules, and interleukin-1 alpha expression in 15 cases of antineutrophil cytoplasmic autoantibody-associated renal vasculitis

In renal biopsy specimens from 15 patients with antineutrophil cytoplasmic autoantibody (ANCA)-associated renal vasculitis, the infiltrating intraglomerular and interstitial leukocytes were localized and the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and the cytokine interleukin-1 alpha (IL-1 alpha) were studied by an immunohistochemical method. Intraglomerular leukocytes were mainly macrophages (13.46 +/- 9.29 cells/glomerular cross-section) and, to a lesser extent, T lymphocytes (4.61 +/- 2.81 cells/glomerular cross-section). Staining with VCAM-1, which was negative in the undamaged tufts, was strongly positive in necrotizing-extracapillary lesions. Staining with ICAM-1 was also present in the damaged tufts, but its pattern was more diffuse. Intraglomerular IL-1 alpha was found in all biopsy specimens. Where the Bowman's capsule was not damaged, the periglomerular infiltrating cells were macrophages (42.6 +/- 25.2 cells/glomerular cross-section) and T lymphocytes (51.06 +/- 33.0 cells/glomerular cross-section). When there was a granulomatous lesion involving the glomerulus, the number of cells per granulomatous area revealed a massive number of CD45-positive leukocytes (345.83 +/- 237.47 cells/granulomatous lesion), many of them positive for activity markers (HLA-DR, IL-2R), adhesion molecules, and IL-1 alpha. Many activated cells were also present in interstitial areas of perivascular clusters of leukocytes, in which T lymphocytes (prevalently CD4+ cells) outnumbered the macrophages (331.55 +/- 207.85 cells/0.05 mm2 area v 125.68 +/- 60.57 cells/0.05 mm2 area). Adhesion molecules and IL-1 alpha were found in both tubular and vascular areas in all biopsy specimens. Our data strongly support the involvement of both the adhesion molecules ICAM-1 and VCAM-1 in the recruitment of intraglomerular leukocytes in renal vasculitis, indicate that VCAM-1 is a very good marker of necrotizing-extracapillary damage, and suggest its crucial connection with the macrophage recruitment in these vasculitic lesions. The presence of histochemically detectable levels of IL-1 alpha in glomeruli, tubules, and vessels and on some inflammatory cells supports its involvement in the vasculitic lesions, probably by triggering a positive feedback that increases the damage.

Butein ameliorates experimental anti-glomerular basement membrane (GBM) antibody-associated glomerulonephritis in rats (1)

Effects of butein on crescentic-type anti-glomerular basement membrane (GBM) nephritis in rats were investigated. When rats were treated with butein from 1 day after i.v. injection of anti-GBM serum, it inhibited the elevation of protein excretion into urine. In the butein-treated rats, cholesterol content in plasma was lower than that of the nephritic control rats. Histological observation demonstrated that this agent suppressed the incidence of crescent formation, adhesion of capillary wall to Bowman's capsule and fibrinoid necrosis in the glomeruli. Furthermore, butein suppressed the accumulation of leukocytes, including CD4-positive cells and CD8-positive cells in the glomeruli. However, butein failed to suppress the production of the antibody against rabbit gamma-globulin and the deposition of rat-IgG on the GBM. These results suggest that butein may be a useful medicine against rapidly progressive glomerulonephritis, which is characterized by severe glomerular lesions with diffuse crescents.

Low-density lipoprotein stimulates the expression of macrophage colony-stimulating factor in glomerular mesangial cells

Disordered lipoprotein metabolism and the enhanced influx and accumulation of circulating mononuclear leukocytes into vascular tissue are common pathobiological phenomena associated with both atherosclerosis and glomerulosclerosis. Since atherogenic lipoproteins (such as low density lipoprotein, LDL) have been implicated in monocyte migration and proliferation into the glomerular mesangium, we examined the effect of LDL on mesangial cell expression of macrophage colony-stimulating factor (M-CSF), a cytoregulatory peptide associated with monocyte chemoattraction, differentiation and proliferation. Mesangial cell M-CSF gene expression, protein synthesis and secretion, and its biological activity to induce progenitor colony formation and monocyte proliferation were studied in murine mesangial cells. Incubation of either primary cultures or SV-40 transformed murine mesangial cells with LDL (0 to 200 micrograms/ml) induced M-CSF steady-state mRNA expression, in a dose-dependent manner (52 to 183% of control) when Northern blots were analyzed quantitatively by densitometric scanning. Similarly, Western blot analysis showed that LDL-activated SV-40 transformed mesangial cells increased M-CSF protein synthesis and secretion in a dose-dependent manner. The conditioned media obtained by incubating mesangial cells with LDL induced bone marrow progenitor colony formation that could be inhibited by specific neutralizing antibodies against murine M-CSF. Finally, the biological activity of M-CSF secreted by LDL-activated mesangial cells was further confirmed by its enhanced ability to induce monocyte proliferation. These data indicate that LDL, by activating mesangial cells to induce M-CSF and possibly other monocyte chemoattractants, may regulate the migration and proliferation of cells of mononuclear leukocytic origin into the mesangium supporting a pathobiological role for LDL in glomerular injury.

Participation of CR1 (CD35), CR3 (CD11b/CD18) and CR4 (CD11c/CD18) in membranoproliferative glomerulonephritis type I

Intraglomerular expression of complement receptors (CR) was investigated chronologically in 22 repeatedly biopsied patients with membranoproliferative glomerulonephritis (MPGN) type I by indirect immunoperoxidase staining using MoAbs. Patients were divided into two groups based on whether intraglomerular C3c deposition was decreased at the second biopsy (2nd Bx) (group A, n = 12), or not (group B, n = 10). At the first biopsy (1st Bx), the severity of glomerular injury and the degree of glomerular C3c deposition were compatible between the two groups. Four patterns of CR1 (CD35) expression on podocytes were recognized: normal; generally decreased; focally/segmentally lost; and completely lost. The numbers of CR3 (CD11b/CD18)- and CR4 (CD11c/CD18)-positive cells per glomerular cross-section were counted. At the 1st Bx, no significant difference was found in the number of CR3+ or CR4+ cells between the two groups. At the 2nd Bx, the numbers of both the CR3+ and CR4+ cells were significantly decreased only in group A (P < 0.01). The numbers of CR3+ and CR4+ cells were significantly higher in cases with moderate or marked C3c deposits than in those with no or mild C3c deposits. The intensity of CR1 expression in group B was less than that in group A at both the 1st and 2nd Bx (1st, P < 0.05; 2nd, P < 0.01), and chronological improvement of CR1 expression was observed only in group A. The severity of glomerular injury was increased only in group B (P < 0.01), and was associated with persistent massive proteinuria and hypocomplementaemia. Our results suggest that, in cases with an adverse outcome, a more severe defect of CR1 initially exists and the expression of CR1 is not recoverable chronologically. This irreversible decrease or loss of CR1 may partly contribute to the continuous C3c deposition and intraglomerular infiltration of CR3+ and CR4+ cells.

Modulation of neutrophil influx in glomerulonephritis in the rat with anti-macrophage inflammatory protein-2 (MIP-2) antibody

The role of the chemokine, macrophage inflammatory protein-2 (MIP-2), during anti-glomerular basement membrane (GBM) antibody (Ab) glomerulonephritis (GN) was studied. Rat MIP-2 cDNA had been cloned previously. Recombinant rat MIP-2 (rMIP-2) from Escherichia coli exhibited neutrophil chemotactic activity and produced neutrophil influx when injected into the rat bladder wall. By using a riboprobe derived from the cDNA and an anti-rMIP-2 polyclonal Ab, MIP-2 was found to be induced in glomeruli with anti-GBM Ab GN as mRNA by 30 min and protein by 4 h, with both disappearing by 24 h. The expression of MIP-2 correlated with glomerular neutrophil influx. A single dose of the anti-MIP-2 Ab 30 min before anti-GBM Ab was effective in reducing neutrophil influx (40% at 4 h, P < 0.01) and periodic acid-Schiff deposits containing fibrin (54% at 24 h, P < 0.01). The anti-rMIP-2 Ab had no effect on anti-GBM Ab binding (paired-label isotope study). Functional improvement in the glomerular damage was evidenced by a reduction of abnormal proteinuria (P < 0.05). These results suggest that MIP-2 is a major neutrophil chemoattractant contributing to influx of neutrophils in Ab-induced glomerular inflammation in the rat.

Infiltration patterns of macrophages and lymphocytes in chronically rejecting rat kidney allografts

The migration of circulating leukocytes to sites of inflammation or antigen is based, at least in part, on the activities of adhesion molecules. In the context of organ transplantation, some of these have been shown to be upregulated during acute allograft rejection. As their role during chronic rejection has not been examined, we have used an established rat model to compare sequentially the presence of host cells within the grafts, as defined immunohistologically, with patterns of in vitro leukocyte binding and their dependence upon particular adhesion molecules. Various donor populations of peripheral blood lymphocytes (PBL), lymph node lymphocytes (LNL), and splenic monocytes were interacted with snap-frozen sections of allografted, isografted, and native kidneys at serial intervals up to 24 weeks after transplantation. Monocyte binding in the allografts rose at 8 weeks and peaked at 12 weeks, a period preceding the maximum numbers of macrophages noted immunohistologically in the chronically rejecting grafts at 16 weeks. Lymphocyte binding and infiltration patterns were similar, remaining stable throughout the follow-up period and consistently greater than those noted in isografts. In vitro binding of the monocytes was inhibited by mAbs against ICAM-1, LFA-1, CD18, and MAC-1; MAC-1 did not influence lymphocyte binding, although the other mAbs were effective. We conclude that adhesion molecules are responsible, at least in part, for patterns of cell populations infiltrating chronically rejecting renal allografts.