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Biomedical subjects

R J Faull

Publications and source records attributed to R J Faull.

At least 19 recordsLinked to original sources
PubMed2001

HB-EGF is produced in the peritoneal cavity and enhances mesothelial cell adhesion and migration.

BACKGROUND: The mesothelial cell monolayer lining the peritoneal membrane needs constant repair in response to peritonitis and to the toxicity of peritoneal dialysate. In many continuous ambulatory peritoneal dialysis (CAPD) patients, the repair process progressively fails, and membrane dysfunction and fibrosis occur. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has an important role in wound repair and is also fibrogenic, and thus may be involved in these processes in the peritoneal cavity. METHODS: The presence of HB-EGF, its receptors, and its associated proteins was determined in peritoneal membrane biopsies, cultured human peritoneal mesothelial cells (HPMCs), and peritoneal macrophages from CAPD patients by reverse transcription-polymerase chain reaction, flow cytometry, and immunofluorescence immunocytochemistry with confocal microscopy. HB-EGF effects on HPMC adhesion were measured by a static adhesion assay, on integrin expression by flow cytometry, and on migration by wound healing and chemotaxis assays. RESULTS: HB-EGF, its receptors HER-1 and HER-4, and the associated proteins CD9, CD44, and integrin alpha(3)beta(1) were expressed by HPMCs and peritoneal macrophages. HB-EGF colocalized with HER-1 and HER-4 in HPMCs and induced their adhesion to collagen type I, expression of beta 1 integrins, and migration. CONCLUSIONS: HB-EGF is produced by cells in the peritoneal cavity of CAPD patients and has functional effects on HPMCs that would facilitate repair of the mesothelial layer.

Cell Adhesion↗
PubMed2000

Excellent long-term graft survival in low risk, primary renal allografts treated with prednisolone-avoidance immunosuppression.

Primary avoidance of oral corticosteroids for renal transplant recipients is uncommon. The South Australian renal transplant service used a double therapy (DT) regimen of cyclosporin and azathioprine from August 1986 to July 1996 for low risk (first graft, PRA < 50%) allografts. Oral corticosteroid, prednisolone (P), was reserved for severe rejection or two mild rejection episodes, but could be later withdrawn at the physician's discretion. This regimen is associated with more early acute rejection (Russ et al., Clin Transplant 1990: 4: 26). We have now analysed long-term patient survival (PS) and graft survival (GS) for this group. Of 448 transplants in South Australia between August 1986 and July 1996, 295 commenced DT regimen. Ninety-four (31.8%) never received P at any stage post-transplantation (group 1), 96 (32.5%) were placed on P and later weaned (group 2), and 97 (33%) remained on long-term P (group 3). Technical losses, eight (2.7%), within 30 d of transplantation, were excluded from sub-group analysis. PS for the total DT cohort at 1, 5 and 9 yr post-transplantation was 97, 88 and 74%, respectively. GS over the same time period was 88, 75 and 55%, respectively. There was no statistically significant difference in survival compared to other 'low risk' grafts in the rest of Australia during the same time period. Mean serum creatinine concentration (CrC) for the DT group at 3 and 6 months and 1, 3, 5 and 10 yr was not significantly different to the rest of the Australian 'low risk' grafts. In the DT cohort, there were 334 acute rejections ( < 90 d) in 206 patients (70%), but only 42 (12.5%) required anti-lymphocyte antibody therapy (OKT3 or ATG) for rejection. PS at 9 yr was not statistically significantly different between groups 1 and 2, but both groups survived better than group 3 (p < 0.0043). GS for group 1 at 1, 5 and 9 yr post-transplantation was 90, 81 and 73%, respectively; for group 2, 98, 87 and 66%, respectively; and for group 3, 84, 63 and 29%, respectively. Statistical significance was reached in group 1 versus 3 (p < 0.001) and group 2 versus 3 (p < 0.001). In summary, a DT regimen in low risk, first renal allografts gives excellent long-term patient and GS and minimises long-term P, despite a high rate of early acute rejection.

Acute Disease↗
PubMed1999

Clozapine-induced acute interstitial nephritis.

Drug hypersensitivity reactions commonly cause acute interstitial nephritis (AIN). Clozapine, a new antipsychotic, can cause fatal bone-marrow toxicity. We report clozapine-induced AIN as another serious adverse drug reaction.

Acute Disease↗
PubMed1999

Epidermal growth factor modifies the expression and function of extracellular matrix adhesion receptors expressed by peritoneal mesothelial cells from patients on CAPD.

BACKGROUND: Efficient peritoneal dialysis depends on an intact layer of mesothelial cells that line the peritoneal membrane. This layer is disrupted in patents on continuous ambulatory peritoneal dialysis during episodes of peritonitis (acute injury) and replaced by fibrous tissue during extended dialysis (chronic injury). Little is understood of human peritoneal mesothelial cell (HPMC) responses to wounding and episodes of peritonitis. METHODS: HPMC were harvested from spent peritoneal dialysis effluent and maintained under defined in vitro conditions. Adhesive interactions with extracellular matrix (ECM) molecules and chemotactic and wound-healing responses were measured in vitro using purified ECM molecules. RESULTS: HPMC express multiple functional cell receptors recognizing and binding to ECM molecules, including several members of the integrin family. HPMC exhibit directed migration in wound healing and chemotaxis assays with ECM molecules. Epidermal growth factor (EGF) stimulates a reversible change to a fibroblastic phenotype, accompanied by increased expression of beta1 integrins, particularly alpha2beta1, increased adhesion to type I collagen, and significantly greater HPMC migration on type I collagen in wound healing and chemotaxis assays. CONCLUSIONS: HPMC possess the migratory capacity to contribute to the efficient repair of damaged peritoneal membrane after acute injury, and growth factors, such as EGF, facilitate peritoneal membrane healing by augmenting cell adhesion and migration.

Cell Movement↗
PubMed1998

During human thymic development, beta 1 integrins regulate adhesion, motility, and the outcome of RHAMM/hyaluronan engagement.

During human thymic differentiation, interactions between fibronectin (Fn)/beta1 integrins and hyaluronan (HA)/RHAMM control motility and Fn/beta1 integrins mediate spontaneous Fn-dependent adhesion. Multinegative (MN, CD3-4-8-) thymocytes exhibit strong spontaneous adherence to Fn (75%) that was efficiently inhibited by anti-alpha5beta1 and only weakly inhibited by anti-alpha4beta1. The relatively weak adherence of unfractionated thymocytes to Fn required both alpha4beta1 and alpha5beta1. Video time-lapse microscopy indicates that a subset of thymocytes also undergo spontaneous Fn-dependent motility mediated by alpha5beta1, alpha4beta1, and the HA-receptor RHAMM, but not by CD44. The loss of motility after hyaluronidase treatment of thymocytes indicated that motility is strongly dependent on HA. Of motile cells, 55% were DP, 19% were DN, and 24% were CD4+SP, but only 1% were CD8+SP. Overall, for MN thymocytes, beta1 integrin mediated Fn-adhesion, but after expression of CD4/CD8, beta1 integrins mediated Fn-dependent motility. Treatment with the activating anti-beta1 mAb QE.2E5 inhibited thymic motility and converted otherwise nonadherent thymocytes to an adherent state. High-avidity interactions via integrins appear to supercede the motogenicity of RHAMM and HA, suggesting that integrin avidity may regulate RHAMM. During thymic development, changes in adhesion or motility appear to be mediated by integrin avidity modulation.

Adult↗
PubMed1996

A novel activating anti-beta1 integrin monoclonal antibody binds to the cysteine-rich repeats in the beta1 chain.

The functional status of an integrin depends on the conformation of its extracellular domain, which is controlled by the cell expressing that receptor. The transmission of regulatory signals from within the cell is considered to be via propagated conformational changes from the receptor's cytoplasmic tails to the extracellular ligand binding "pocket." The end result is increased accessibility of the ligand binding pocket in the high affinity ("active") form of integrins. We report a novel monoclonal antibody (QE.2E5) that binds within the cysteine-rich repeats in the integrin beta1 chain and induces high affinity binding of fibronectin to the integrin alpha5beta1. The QE.2E5 epitope is located approximately 200 residues both from the predicted binding site for fibronectin and from the epitopes recognized by other activating anti-beta1 monoclonal antibodies. It is also expressed on beta1 integrins from a number of nonhuman species. Although they have the same functional effects, the binding of QE.2E5 and another activating antibody (8A2) to the receptor have contrasting effects on the expression of an activation-dependent epitope in the beta1 chain. We propose that the cysteine-rich repeats contain a regulatory region that is distinct from those previously described in the integrin beta1 chain.

Amino Acid Sequence↗
PubMed1996

Changes in the expression of adhesion molecules as peripheral blood monocytes differentiate into peritoneal macrophages.

Peritoneal macrophages, derived from peripheral blood monocytes, are the chief cellular defenders against invasion of the peritoneal cavity by infectious organisms. Monocyte migration into the peritoneal cavity depends upon a coordinated series of adhesive events, utilizing cell surface receptors known as adhesion molecules. In order to better understand the mechanisms of leucocyte infiltration of the peritoneum during peritonitis, we studied the relative expression of adhesion molecules on monocytes and peritoneal macrophages from patients on continuous ambulatory peritoneal dialysis (CAPD). Peripheral blood and spent peritoneal dialysis fluid were obtained from patients undergoing CAPD, and the level of expression of various adhesion molecules on the monocytes/macrophages analysed by flow cytometry using receptor-specific monoclonal antibodies. Monocytes were also purified from the peripheral blood of volunteer donors, cultured in vitro for varying periods, and analysed in the same manner. Consistent differences in expression of certain adhesion molecules were found between monocytes and peritoneal macrophages, and similar changes occurred on monocytes cultured in vitro. Concurrent infection had no clear effect. Several receptors (integrins alpha 4 beta 1, alpha 6 beta 1, alpha L beta 2 and alpha IIb beta 3, and platelet endothelial cell adhesion molecule-1) were significantly decreased on peritoneal macrophages, while only the integrin alpha v beta 5 increased. It is concluded that monocyte differentiation into peritoneal macrophages is accompanied by characteristic alterations in the adhesion molecule repertoire on the cell surface, emphasizing the different adhesive requirements of these two cell types.

Aged↗
PubMed1996

Inside-out signaling through integrins.

Rapid and yet precisely controlled changes in cell adhesion are a hallmark of a number of basic physiological processes. Many of these processes directly impact upon nephrology, including: (1) cell migration, which occurs during leukocyte infiltration into inflammatory sites (e.g., in glomerulonephritis, interstitial nephritis, and renal transplant rejection) and during embryogenesis (e.g., in development of the genitourinary system): and (2) platelet aggregation at sites of clot formation (e.g., in glomerulonephritis). The integrins are a family of adhesion molecules whose function is controlled by the cells that express them, and this properly makes them eminently suitable receptors for those situations that demand flexibility of the cellular adhesive phenotype. The control of integrin function occurs via regulatory signals that originate within the cell cytoplasm and are then transmitted to the external ligand-binding domain of the receptor. The generation and transmission of these "inside-out" signals are the subjects of intensive research that will be summarized in this review article.

Carrier Proteins↗
PubMed1995

Dynamic regulation of integrins.

Dynamic regulation of receptor function is a distinguishing feature of the integrin family of adhesion molecules and makes a significant contribution to alterations in cellular adhesive properties. The best characterized example is that of the platelet receptor alpha IIb beta 3 (glycoprotein IIb-IIIa), which does not bind soluble fibrinogen on resting platelets. Following platelet activation, the alpha IIb beta 3 binds soluble fibrinogen with moderately high affinity and platelet aggregation ensues. Similar regulation of receptor function has also been directly demonstrated for alpha 5 beta 1 and alpha M beta 2, and it is likely that it is a general property of all members of the family. The altered ligand binding affinity is due to a change in the conformation of the external domain of the receptor, in response to intracellular signals that are transmitted the length of the molecule. The cytoplasmic tails of the integrins are active participants in this regulation, and they also mediate interactions with the cytoskeleton. A number of anti-integrin monoclonal antibodies have been described which induce high affinity ligand binding, and certain of these preferentially bind to the high affinity conformation of the receptor. The alteration in conformation allows better access for macromolecular ligands to the ligand binding pocket, which has been mapped (in alpha IIb beta 3) to the amino terminal globular head of the receptor. The precise mechanism by which the activating signal is transferred from within the cell to the distal external domain remains the subject of active research.

Animals↗
PubMed1994

Stimulation of integrin-mediated adhesion of T lymphocytes and monocytes: two mechanisms with divergent biological consequences.

We show that the adhesion of T lymphoid cells to immobilized fibronectin can be increased by two distinct mechanisms. The first is by increasing the affinity of the fibronectin receptor/ligand interaction using the anti-beta 1 integrin monoclonal antibody 8A2. The second is by treating the cells with phorbol 12-myristate 13-acetate (PMA), which alters events that occur after receptor occupancy (e.g., cell spreading) without affecting receptor affinity. The effects of these two mechanisms on adhesion in the presence of physiological concentrations of soluble fibronectin suggest that they have different biological consequences. Under these conditions, the net effect of increasing the affinity of the fibronectin receptors is to decrease cell adhesion, whereas the increase in adhesion induced by PMA is unaffected. This suggests that the high affinity receptors are not primarily available for cell adhesion under these circumstances, and that they have an alternative function. We further show that high affinity binding of soluble fibronectin can be induced by either differentiation of the monocytic cell line THP-1 or by cross-linking the T cell receptor complexes on the T lymphoid cell line HUT-78. The differentiated monocytic cells express two populations of fibronectin receptors: a minority in a high affinity state, and the majority in a low affinity state. Thus they will both continue to adhere in the presence of physiological concentrations of soluble fibronectin and bind significant amounts of soluble fibronectin at the cell surface.

Animals↗
PubMed1994

Integrin cytoplasmic domains mediate inside-out signal transduction.

We analyzed the binding of fibronectin to integrin alpha 5 beta 1 in various cells; in some cells fibronectin bound with low affinity (e.g., K562 cells) whereas in others (e.g., CHO), it bound with high affinity (Kd approximately 100 nM) in an energy-dependent manner. We constructed chimeras of the extracellular and transmembrane domains of alpha IIb beta 3 joined to the cytoplasmic domains of alpha 5 beta 1. The affinity state of these chimeras was assessed by binding of fibrinogen or the monoclonal antibody, PAC1. The cytoplasmic domains of alpha 5 beta 1 conferred an energy-dependent high affinity state on alpha IIb beta 3 in CHO but not K562 cells. Three additional alpha cytoplasmic domains (alpha 2, alpha 6A, alpha 6B) conferred PAC1 binding in CHO cells, while three others (alpha M, alpha L, alpha v) did not. In the high affinity alpha chimeras, cotransfection with a truncated (beta 3 delta 724) or mutated (beta 3(S752-->P)) beta 3 subunit abolished high affinity binding. Thus, both cytoplasmic domains are required for energy-dependent, cell type-specific affinity modulation. In addition, mutations that disrupted a highly conserved alpha subunit GFFKR motif, resulted in high affinity binding of ligands to alpha IIb beta 3. In contrast to the chimeras, the high affinity state of these mutants was independent of cellular metabolism, cell type, and the bulk of the beta subunit cytoplasmic domain. Thus, integrin cytoplasmic domains mediate inside-out signaling. Furthermore, the highly conserved GFFKR motif of the alpha subunit cytoplasmic domain maintains the default low affinity state.

Amino Acid Sequence↗