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R C Atkins

Publications and source records attributed to R C Atkins.

At least 19 recordsLinked to original sources
PubMed2001

Interleukin-1 induces tubular epithelial-myofibroblast transdifferentiation through a transforming growth factor-beta1-dependent mechanism in vitro.

Interleukin-1 (IL-1) has been shown to exert profibrotic activity in a number of disease models, including crescentic glomerulonephritis and pulmonary fibrosis, but the mechanisms by which this operates are poorly understood. Recent studies have identified a novel mechanism promoting renal fibrosis: tubular epithelial-myofibroblast transdifferentiation (TEMT). The present study examined whether IL-1 can stimulate TEMT in vitro. Cells of the normal rat kidney tubular epithelial cell line (NRK52E) were grown to confluence on collagen-coated plates and cultured for 5 days in the presence 1 to 20 ng/mL of IL-1alpha. Doses of 10 to 20 ng/mL of IL-1 caused transdifferentiation of NRK52E cells into myofibroblast-like cells. Scanning electron microscopy identified IL-1-induced morphological changes as a loss of apical-basal polarity and microvilli, cell hypertrophy, and the development of an elongated and invasive appearance. Phenotypically, IL-1-induced TEMT was characterized by de novo messenger RNA and protein expression of the mesenchymal marker alpha-smooth muscle actin, shown by Northern blotting, immunohistochemistry, and Western blotting. This was accompanied by loss of the epithelial marker E-cadherin. The addition of an excess of IL-1-receptor antagonist completely inhibited IL-1-induced TEMT. IL-1 was shown to stimulate the secretion of active transforming growth factor-beta1 (TGF-beta1) by NRK52E cells. Furthermore, the addition of a neutralizing anti-TGF-beta1 antibody inhibited IL-1-induced TEMT. In conclusion, IL-1 is a profibrogenic cytokine capable of inducing TEMT through a TGF-beta1-dependent mechanism. This may represent a novel mechanism by which IL-1 induces renal fibrosis in vivo.

Actins↗
PubMed2001

PDGF signal transduction inhibition ameliorates experimental mesangial proliferative glomerulonephritis.

BACKGROUND: Platelet-derived growth factor (PDGF) has been consistently implicated in the cell proliferation and extracellular matrix accumulation, which characterize progressive glomerular disease. In the present study, the effects of a potent and selective inhibitor of PDGF receptor tyrosine kinase, STI 571, were examined in vitro and in vivo. METHODS: Cultured mesangial cells were incubated with PDGF (50 ng/mL) and fibroblast growth factor-2 (FGF-2; 50 ng/mL) and treated with STI 571 (0.13 to 2.0 micromol/L). Experimental mesangial proliferative glomerulonephritis was induced in male Wistar rats with monoclonal OX-7, anti-rat Thy-1.1 antibody with rats randomized to receive either STI 571 (50 mg/kg intraperitoneally daily) or vehicle. Animals were examined six days later. RESULTS: In vitro, both PDGF and FGF-2 induced a threefold increase in mesangial cell 3H-thymidine incorporation. STI 571 reduced PDGF but not FGF-2-stimulated mesangial cell proliferation in a dose-dependent manner, with complete abolition at 0.4 micromol/L. In animals with Thy-1.1 glomerulonephritis, PDGF receptor tyrosine kinase blockade was associated with significant reductions in mesangial cell proliferation (P < 0.001), the number of activated (alpha-smooth muscle positive) mesangial cells, and glomerular type IV collagen deposition (P < 0.001). CONCLUSION: The amelioration of the pathological findings of experimental mesangial proliferative glomerulonephritis by blockade of PDGF receptor activity suggests the potential clinical utility of this approach as a therapeutic strategy in glomerular disease.

Animals↗
PubMed2000

Characteristics of albumin processing during renal passage in anti-Thy1 and anti-glomerular basement membrane glomerulonephritis.

Recent studies have shown that glomerular-filtered albumin appears to be processed by two distinct cellular pathways. The major pathway, a high-capacity retrieval pathway, returns most of the filtered albumin to the blood supply intact. The albumin not taken up by the retrieval pathway is degraded by lysosomes during renal passage and excreted as fragments in urine. We studied the interplay of the albumin retrieval pathway and the degradation pathway in the disease models of anti-Thy1 nephritis, a model of mild proteinuria, and anti-glomerular basement membrane (anti-GBM) disease, a model of severe proteinuria. This is achieved by investigating the integrity of urinary albumin and its excretion rate. Total albumin excretion (intact plus fragments) did not change significantly in the rats with anti-Thy1 nephritis. However, it was established that intact albumin excretion had a strong positive correlation with increasing total-protein excretion, which showed that the degradation pathway was being predominantly affected in this disease. For the rats with anti-GBM disease, total protein excretion increased 26-fold compared with the control group, and intact albumin excretion increased 250-fold. The profound changes in albumin excretion in anti-GBM disease are consistent with inhibition primarily of the retrieval pathway.

Albumins↗
PubMed2000

Up-regulation of the tumour-associated marker CD44V6 in experimental kidney disease.

CD44 is an adhesion molecule involved in a wide range of cell-cell and cell-matrix interactions. The standard form of CD44 (CD44S) is a 85-90-kD glycoprotein, but alternative splicing of RNA encoding 10 variable exons (V1-V10) can give rise to many different CD44 variant protein isoforms of higher molecular weight. CD44 isoforms containing the V6 exon play a crucial role in tumour metastasis and lymphocyte activation. However, the role of CD44V6 in the kidney is unknown. The aim of this study was to examined renal CD44V6 expression in health, disease and in vitro. Immunohistochemistry staining with the V6-specific 1.1ASML antibody identified constitutive CD44V6 expression by occasional cortical tubular epithelial cells and medullary tubules in normal rat kidney. In immune-induced kidney disease (rat anti-glomerular basement membrane glomerulonephritis), there was a marked increase in CD44V6 expression by cortical tubules, particularly in areas of tubulointerstitial damage, which was associated with focal macrophage infiltration. There was also a marked increase in CD44V6 expression by damaged tubules in a model of non-immune kidney disease (unilateral ureteric obstruction). Reverse transcription-polymerase chain reaction revealed a complex pattern of CD44V6-containing mRNA isoforms in normal rat kidney. This pattern of CD44V6 splicing was essentially unaltered in disease. The NRK52E normal rat kidney tubular epithelial cell line expresses both CD44S and CD44V6. Stimulation of NRK52E cells with IL-1 or transforming growth factor-beta 1 induced a two-to-five-fold increase in the expression of both CD44S and CD44V6. Furthermore, triggering of NRK52E cells by antibodies to CD44S or CD44V6, but not isotype control antibodies, induced secretion of monocyte chemoattractant protein-1. In conclusion, this study has identified expression of the tumour-associated marker CD44V6 in tubular epithelial cells in normal and diseased rat kidney, and suggests that signalling through the CD44V6 molecule may participate in the pathogenesis of experimental kidney disease.

Animals↗
PubMed2000

Expression of macrophage migration inhibitory factor in human glomerulonephritis.

BACKGROUND: We have recently demonstrated that macrophage migration inhibitory factor (MIF) plays a pathogenic role in experimental glomerulonephritis (GN). The aim of the current study was to investigate MIF expression in human GN. METHODS: MIF expression was examined by in situ hybridization and immunohistochemistry staining in 65 biopsies from a variety of glomerulonephridities. RESULTS: There is constitutive expression of MIF mRNA and protein in normal human kidney that is largely restricted to tubular epithelial cells and to some glomerular epithelial cells. There was little change in the pattern of MIF expression in nonproliferative forms of GN such as minimal change disease and membranous GN. However, there was a marked increase in both glomerular and tubular MIF expression in proliferative forms of GN, including focal segmental glomerulosclerosis (FGS), lupus nephritis, crescentic GN, and mesangiocapillary proliferative GN. The prominent macrophage and T-cell infiltrate in these diseases were largely restricted to areas with marked up-regulation of MIF expression, contributing to glomerular hypercellularity, glomerular focal segmental lesions, crescent formation, tubulitis, and granulomatous lesions. De novo MIF expression was evident in glomerular endothelial cells and mesangial cells in proliferative forms of GN. In addition, many infiltrating macrophages and T cells showed MIF mRNA and protein expression. Quantitative analysis found that increased glomerular and tubular MIF expression gave a highly significant correlation with macrophage and T-cell accumulation, the severity of histologic lesions, and the loss of creatinine clearance. CONCLUSIONS: Renal MIF expression is markedly up-regulated in proliferative forms of human GN, and this correlates with leukocyte infiltration, histologic damage, and renal function impairment. These results suggest that MIF may be an important mediator of renal injury in progressive forms of human GN. Based on these findings, together with the known pathogenic role of MIF in experimental GN, we propose that MIF is an attractive therapeutic target in the treatment of progressive forms of GN.

Adolescent↗
PubMed2000

The Irbesartan type II diabetic nephropathy trial: study design and baseline patient characteristics. For the Collaborative Study Group.

BACKGROUND: Diabetic nephropathy is the most common cause of end-stage renal disease in the developed world. Angiotensin-converting enzyme inhibitors have been demonstrated to be renoprotective in type I diabetes and are now the standard of care for both hypertensive and non-hypertensive type I diabetic patients with any level of proteinuria. The role of blockade of the renin-angiotensin system in type II diabetic patients is not defined. The Collaborative Study Group has initiated the Irbesartan Type II Diabetic Nephropathy Trial (IDNT), studying the effect of the angiotensin II receptor antagonist irbesartan on progression of renal disease and mortality in type II diabetic patients with overt nephropathy and hypertension. Here we report the study design and baseline patient characteristics. METHODS: To qualify, hypertensive type II patients, age 30-70 years, must have a 24 h urinary protein excretion of >900 mg and a serum creatinine 90-265 micromol/l (1.0-3. 0 mg/dl) in women and 110-265 micromol/l (1.2-3.0 mg/dl) in men. Three treatment arms include irbesartan, placebo and amlodipine, with every attempt made to achieve similar blood pressure levels in all treatment arms. A total of 1650 patients will be enrolled utilizing approximately 225 clinics worldwide. The primary outcome measure is time to event to the composite end-point of doubling of serum creatinine, end-stage renal disease or death. The secondary outcome measure is time to composite end-point of fatal or non-fatal cardiovascular events. The average length of patient follow-up is expected to be approximately 36 months. RESULTS: The baseline characteristics of the study subjects are: age 59+/-8 years, duration of diabetes 15+/-9 years, height 168+/-11 cm (5 ft 6 in), weight 87+/-19 kg (192 lb), body mass index 31+/-7 kg/m(2), blood pressure 156+/-18 mmHg/85+/-11 mmHg, serum creatinine 150+/-53 micromol/l (1.7+/-0.6 mg/dl), creatinine clearance 66+/-34 ml/min and 24 h urine protein 4.0+/-3.5 g/day.

Adult↗
PubMed2000

CD44-mediated neutrophil apoptosis in the rat.

BACKGROUND: Apoptosis is an important mechanism by which neutrophils are removed from sites of inflammation, including the kidney. This study investigated whether ligation of the cell-surface adhesion molecule, CD44, can trigger neutrophil apoptosis. METHODS: The anti-rat CD44 antibody OX-50 was used to induce apoptosis of cultured blood neutrophils, as determined by flow cytometry using annexin V staining and by transmission electron microscopy. The functional consequences of OX-50-mediated neutrophil depletion were examined in a rat model of accelerated antiglomerular basement membrane glomerulonephritis. RESULTS: Flow cytometric analysis using the OX-50 antibody, which recognizes the common amino terminal domain of CD44, showed that rat blood neutrophils express very high levels of CD44. The addition of OX-50, but not control antibodies, rapidly induced neutrophil apoptosis in cultured rat blood leukocytes, as demonstrated by annexin V staining and by electron microscopy. Cross-linking of CD44 was essential since F(ab) fragments of the OX-50 antibody failed to induce neutrophil apoptosis. The CD44 ligand hyaluronan and an antibody to the CD44v6 isoform failed to induce neutrophil apoptosis, indicating that OX-50 antibody-mediated neutrophil apoptosis is epitope specific. This effect was specific to neutrophils since the OX-50 antibody did not induce apoptosis in other CD44-expressing cell types (lymphocytes, mesangial cells, or tubular epithelial cells). An injection of OX-50 antibody into normal rats caused a rapid and profound neutropenia, and apoptotic neutrophils could be seen in the blood by electron microscopy. Furthermore, the administration of OX-50 antibody abrogated neutrophil-dependent glomerular injury (proteinuria) on day 1 of rat antiglomerular basement membrane glomerulonephritis, whereas injury on day 10 of the disease (neutrophil independent) was largely unaffected. CONCLUSIONS: The cross-linking of specific epitopes of the CD44 molecule can rapidly induce neutrophil apoptosis in vitro and inhibit neutrophil-dependent renal injury in vivo. This finding suggests that physiological ligands of the CD44 molecule may play an important role in eliminating neutrophils from sites of inflammation, including inflammatory kidney disease.

Animals↗
PubMed2000

Nutritional therapies for ulcerative colitis: literature review, chart review study, and future research.

Few clinical studies suggest a significant influence of diet or nutritional supplementation on ulcerative colitis. One reason is that ulcerative colitis, like many chronic diseases, is multifactorial. This article will describe and review the relevant literature on ulcerative colitis, including studies of (1) diet and intravenous therapy, (2) nutritional status and nutritional supplementation, and (3) bowel flora and immune function and their influences. Also, results of a retrospective chart review study that was done at a complementary medicine office will be presented. Finally, suggestions for future research will be discussed based on a nutritional model of ulcerative colitis. Taken together, it is hoped that these areas will clarify the current status of ulcerative colitis research and promote the types of investigations that are necessary to establish the validity of nutritional influences on ulcerative colitis as well as the mechanisms that are involved.

Adolescent↗
PubMed2000

Heroin overdose and myoglobinuric acute renal failure.

BACKGROUND: Heroin abuse is an increasing problem in Australia. In our hospitals we have noted an apparent increase in drug-related admissions. In this study we aimed to examine the incidence of renal failure due to heroin-related rhabdomyolysis and to determine any predisposing factors to the requirement for dialysis in these patients. PATIENTS AND METHODS: We identified a group of 27 patients who developed renal failure after recent intravenous heroin use. There was a significant rise in the incidence during 1997-1998 compared with the previous seven years (p < 0.05). RESULTS: Rhabdomyolysis was the likely cause of renal failure in all cases. Eight patients required dialysis for an average of 14 days (range 3-26). Patients who required dialysis had a higher admission creatine kinase (115 x 10(3) U/l (1-316), median (range), versus 9 x 10(3) (0-91 ), p < 0.05 ), a higher admission creatinine (3.8 mg/dl (2.1- 6.7) versus 2.4 (1.4-8.1), p < 0.05 ), a higher peak creatinine kinase (129 x 10(3) U/l (2-316) versus 22 x 10(3) (3-197), p < 0.05), a lower urine output in the initial 24 hours (0.91/24 hrs (0.1-1.5) versus 3.9(1.0-11.1), p < 0.005) and a longer length of hospitalization (37 days (17-112) versus 12 (5-87), p < 0.05). No patient died and all patients had independent renal function at last review. The majority of patients had significant comorbidities. The incidence of serological evidence of exposure to blood-borne viruses was HIV 5% (n = 1), hepatitis B 10% (n = 2) and hepatitis C 74% (n = 17) of patients tested. Pneumonia occurred in 52% (n = 14) and 26% (n = 7) developed respiratory failure requiring intubation. 22% (n = 6) developed a compartment syndrome requiring fasciotomy and 37% (n = 10) had significant residual limb weakness at discharge. CONCLUSION: There is an increase in patients admitted with rhabdomyolysis-induced renal failure associated with heroin use in our hospitals. We found a varied approach to an increasing clinical problem and suggest that a consistent investigative and therapeutic approach be introduced. Although renal recovery can be expected, long-term disability may occur due to potential serious complications.

Acute Kidney Injury↗
PubMed1999

IL-1 up-regulates osteopontin expression in experimental crescentic glomerulonephritis in the rat.

Osteopontin (OPN) is a macrophage chemotactic and adhesion molecule that acts to promote macrophage infiltration in rat anti-glomerular basement membrane (GBM) glomerulonephritis. The present study investigated the role of interleukin-1 (IL-1) in the up-regulation of renal OPN expression in this disease model. Accelerated anti-GBM glomerulonephritis was induced in groups of six rats. Animals were treated by a constant infusion of the IL-1 receptor antagonist or saline (control) over days -1 to 14 (induction phase) or days 7 to 21 (established disease). In normal rat kidney, OPN was expressed in a few tubules (<5%) and absent from glomeruli. During the development of rat anti-GBM disease (days 7 to 21), there was substantial up-regulation of OPN mRNA and protein expression in glomeruli (>5 cells per glomerular cross-section) and tubular epithelial cells (50-75% OPN-positive). Up-regulation of OPN expression was associated with macrophage accumulation within the kidney, severe proteinuria, loss of renal function, and severe histological damage including glomerular crescentic formation and tubulointerstitial fibrosis. In contrast, IL-1 receptor antagonist treatment of either the induction phase of disease or established disease significantly reduced OPN mRNA and protein expression in glomeruli (/75-85%, P < 0.001) and tubules (/45-60%, P < 0.001). The reduction in OPN expression was associated with significant inhibition of macrophage accumulation and progressive renal injury. In vitro, the addition of IL-1 to the normal rat tubular epithelial cell line NRK52E up-regulated OPN mRNA and protein levels, an effect that was dose-dependent and inhibited by the addition of IL-1 receptor antagonist, thus demonstrating that IL-1 can act directly to up-regulate renal OPN expression. In conclusion, this study provides in vivo and in vitro evidence that IL-1 up-regulates OPN expression in experimental kidney disease and support for the argument that inhibition of OPN expression is one mechanism by which IL-1 receptor antagonist treatment suppresses macrophage-mediated renal injury.

Animals↗
PubMed1999

Up-regulation of macrophage migration inhibitory factor in acute renal allograft rejection in the rat.

Recent studies have identified a key role for macrophage migration inhibitory factor (MIF) in a number of immune cell-mediated diseases. The current study investigated the potential role of MIF in acute allograft rejection. Lewis rats underwent bilateral nephrectomy and then received an orthotopic DA renal allograft or an orthotopic Lewis renal isograft. Groups of six animals were killed at day 1 or 5 after transplantation. No immunosuppression was used. Animals receiving a renal allograft exhibited severe rejection on day 5, as shown by high levels of serum creatinine, very low rates of creatinine clearance, and severe tubulitis with a dense macrophage and T cell infiltrate. In contrast, isografts had normal renal function on day 5 with no histological evidence of rejection. Northern blotting showed that renal MIF mRNA expression was unchanged at day 1, but was increased 3.5-fold on day 5. In situ hybridization showed a marked increase in MIF mRNA expression by tubular cells and MIF mRNA expression by many infiltrating mononuclear cells in day 5 allografts. Immunostaining confirmed an increase in tubular MIF protein expression, particularly in areas of severe tubular damage with prominent leucocytic infiltration. Double staining showed that many infiltrating macrophages and T cells expressed the MIF protein in day 5 allografts. There was only a minor increase in MIF expression in day 5 isografts, demonstrating that neither surgical injury nor stress cause significant up-regulation of MIF expression in allograft rejection. In conclusion, this study has demonstrated that local MIF production is specifically increased in acute renal allograft rejection. These results suggest that MIF may play an important role in the cellular immune response mediating acute allograft rejection.

Acute Disease↗
PubMed1999

Transforming growth factor-beta regulates tubular epithelial-myofibroblast transdifferentiation in vitro.

BACKGROUND: We recently found evidence of tubular epithelial-myofibroblast transdifferentiation (TEMT) during the development of tubulointerstitial fibrosis in the rat remnant kidney. This study investigated the mechanisms that induce TEMT in vitro. METHODS: The normal rat kidney tubular epithelial cell line (NRK52E) was cultured for six days on plastic or collagen type I-coated plates in the presence or absence of recombinant transforming growth factor-beta1 (TGF-beta1). Transdifferentiation of tubular cells into myofibroblasts was assessed by electron microscopy and by expression of alpha-smooth muscle actin (alpha-SMA) and E-cadherin. RESULTS: NRK52E cells cultured on plastic or collagen-coated plates showed a classic cobblestone morphology. Culture in 1 ng/ml TGF-beta caused only very minor changes in morphology, but culture in 10 or 50 ng/ml TGF-beta1 caused profound changes. This involved hypertrophy, a loss of apical-basal polarity and microvilli, with cells becoming elongated and invasive, the formation of a new front-end back-end polarity, and the appearance of actin microfilaments and dense bodies. These morphological changes were accompanied by phenotypic changes. Double immunohistochemistry staining showed that the addition of TGF-beta1 to confluent cell cultures caused a loss of the epithelial marker E-cadherin and de novo expression of alpha-SMA. An intermediate stage in transdifferentiation could be seen with hypertrophic cells expressing both E-cadherin and alpha-SMA. De novo alpha-SMA expression was confirmed by Northern blotting, Western blotting, and flow cytometry. In particular, cells with a transformed morphology showed strong alpha-SMA immunostaining of characteristic microfilament structures along the cell axis. There was a dose-dependent increase in the percentage of cells expressing alpha-SMA with increasing concentrations of TGF-beta1, which was completely inhibited by the addition of a neutralizing anti-TGF-beta1 antibody. Compared with growth on plastic, cell culture on collagen-coated plates showed a threefold increase in the percentage of cells expressing alpha-SMA in response to TGF-beta1. CONCLUSION: TGF-beta1 is a key mediator that regulates, in a dose-dependent fashion, transdifferentiation of tubular epithelial cells into alpha-SMA+ myofibroblasts. This transdifferentiation is markedly enhanced by growth on collagen type I. These findings have identified a novel pathway that may contribute to renal fibrosis associated with overexpression of TGF-beta1 within the diseased kidney.

Actins↗
PubMed1999

Mechanisms of glomerular macrophage infiltration in lipid-induced renal injury.

BACKGROUND: A number of studies have demonstrated an important role for macrophages (M phi) in lipid-induced glomerular injury; however, little is known of the mechanisms that facilitate M phi infiltration in this disease. This study examined the expression of M phi chemotactic molecules M phi migration inhibitory factor (MIF) and leukocyte adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) during the induction of glomerular M phi infiltration in ExHC rats, a strain that is susceptible to lipid-induced glomerular injury. METHODS: Groups of five ExHC rats were fed a high-cholesterol diet (HCD) containing 3% cholesterol, 0.6% sodium cholate, and 15% olive oil and were killed after three days or one, two, or six weeks. Control animals were killed on day 0 or after six weeks on a normal diet. RESULTS: ExHC rats fed an HCD showed marked hypercholesterolemia in the absence of any increase in plasma triglyceride levels from day 3 and developed mild proteinuria and segmental glomerular lesions at week 6. Immunoperoxidase staining identified a significant increase in glomerular ED1+ M phi at week 1, which was further increased at week 6, when M phi-derived foam cells were seen in almost all glomeruli. Many of the infiltrating glomerular M phi expressed lymphocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4), which are ligands for ICAM-1 and VCAM-1, respectively. Coincident with the induction of hypercholesterolemia on day 3 and prior to significant M phi infiltration, combined in situ hybridization and immunohistochemistry staining demonstrated a marked up-regulation of M-CSF and MIF mRNA expression by glomerular mesangial cells and podocytes. There was also a significant increase in ICAM-1 and VCAM-1 mRNA expression by intrinsic glomerular cells, including endothelial cells, on day 3 of the HCD. CONCLUSION: These results suggest that hypercholesterolemia can induce a classic proinflammatory response within the kidney glomerulus, involving production of well-described M phi chemotactic and adhesion molecules, which results in M phi recruitment and the development of glomerular injury.

Animals↗
PubMed1999

Dialyzer performance in the clinic: comparison of six low-flux membranes.

The aim of this study is to assess the clinical performance of 6 different low-flux dialysis membranes under steady-state conditions in terms of urea and phosphate clearances. Ten stable hemodialysis patients were examined. The following dialyzers were studied, all in 1.5- to 1.6-m2 format: cuprammonium, cellulose acetate, cellulose diacetate, hemophane, polysulfone (low-flux), and polysynthane. The following parameters were examined: urea reduction ratio, phosphate reduction ratio, "instantaneous dialyzer clearance" for urea and phosphate, and total amount of urea and phosphate removed in the dialysate over a 1-week (three dialyses) period. Although there were differences between the membranes, all produced results within a narrow range. There was no one membrane that produced superior clearances in all categories. The cellulose acetate membrane was the least satisfactory membrane. Phosphate clearances were at best one third that of urea clearances. When choosing a low-flux dialysis membrane, urea and phosphate clearances are so similar amongst different membranes that other criteria are likely to have a greater influence on the choice of membrane.

Adult↗
PubMed1999

Glomerular epithelial-myofibroblast transdifferentiation in the evolution of glomerular crescent formation.

BACKGROUND: Glomerular cellular crescents consist of epithelial cells and macrophages, which can undergo an irreversible process of fibrous organization. However, the origin of the fibroblast-type cells that mediate this fibrous organization is unclear. METHODS: This study examined glomerular epithelial- myofibroblast transdifferentiation (GEMT) in the formation and evolution of glomerular crescents in two distinct rat models of glomerulonephritis: 5/6 nephrectomy and antiglomerular basement membrane (GBM) disease. RESULTS: Early in the course of both disease models, and prior to crescent formation, immunohistochemistry staining and in-situ hybridization demonstrated de novo expression of alpha-smooth-muscle actin (alpha-SMA), a marker of smooth muscle cells and myofibroblasts, by glomerular parietal epithelial cells (GPEC). The expression of alpha-SMA by GPEC was accompanied by a loss of E-cadherin staining, a marker of epithelial cells. At this early stage of GEMT, ultrastructural studies identified the presence of characteristic actin microfilaments and dense bodies within GPEC which retained a normal epithelial morphology with apical-basal polarity and microvilli. A late stage of transdifferentiation was seen in fibrocellular crescents. In this case, GPEC attached to intact segments of the capsular basement membrane contained large bundles of actin microfilaments throughout the cell, and this was accompanied by a loss of polarity, microvilli, and tight junctions. There was a significant correlation between the presence of alpha-SMA(+) GPEC and glomerular crescent formation. Cellular crescents contained small numbers of alpha-SMA(+) myofibroblasts. These cells become the dominant population in fibrocellular crescents, which was associated with marked local proliferation. Relatively few alpha-SMA(+) myofibroblasts remained in fibrotic/organizing crescents. Most cells within cellular and fibrocellular crescents expressed transforming growth factor-beta (TGF-beta) and basic fibroblast growth factor (FGF-2), suggesting that these growth factors may regulate this GEMT process during the evolution of glomerular crescents. CONCLUSIONS: This study provides the first phenotypic and morphological evidence that glomerular epithelial-myofibroblast transdifferentiation participates in the formation and evolution of glomerular crescents.

Actins↗
PubMed1999

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.

Animals↗