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J J Weening

Publications and source records attributed to J J Weening.

At least 19 recordsLinked to original sources
PubMed2001

Beta1 integrin activation on human neutrophils promotes beta2 integrin-mediated adhesion to fibronectin.

Although the importance of beta1 integrin-mediated binding to adhesion molecules and extracellular matrix (ECM) molecules is well established for most types of leukocytes, the expression patterns and functional importance of beta1 integrins on neutrophils have remained controversial. Using flow cytometry, we found that human neutrophils express the alpha4, alpha5, alpha9 and beta1 integrin subunits. To examine whether the integrins VLA-4 (alpha4/beta1) and VLA-5 (alpha5/beta1) have a functional role on neutrophils, we studied adhesion to their ligand fibronectin. Treatment of neutrophils with antibody 8A2, which specifically binds and activates beta1 integrins, resulted in increased binding to fibronectin. However, addition of blocking mAb revealed that 8A2-induced adhesion did not depend on beta1 integrins, but on the beta2 integrin CD11b/CD18. Similarly, activation of beta1 integrins by 8A2 resulted in CD11b-dependent binding of neutrophils to fibrinogen. 8A2 treatment increased expression of an activation epitope of CD11b/CD18, which depended on phosphoinositide 3-OH kinase activity and an adequate concentration of intracellular free Ca2+. These data suggest that engagement of beta1 integrins on neutrophils results in a cross-talk signal that leads to activation of the beta2 integrin CD11b/CD18, followed by CD11b-mediated adhesion. As transmigrated neutrophils are surrounded by both beta1 and beta2 ligands in the ECM, this integrin cross-talk could play a role in modifying migration and cellular activation in inflamed tissues.

Androstadienes↗
PubMed2001

Henoch-Schönlein purpura nephritis: an update.

UNLABELLED: Henoch-Schönlein purpura (HSP) is a form of systemic vasculitis characterised by vascular wall deposits of predominally IgA typically involving small vessels in skin, gut and glomeruli and associated with purpura, colic, haematuria and arthralgia or arthritis. HSP nephritis (HSPN) leads to chronic renal failure in up to 20% of paediatric patients after 20 years of follow-up in selected series. The risk is related to the initial clinical presentation and the percentage of glomeruli presenting with epithelial crescents. The pathogenesis of HSPN might be related to an increased production of abnormally glycosylated IgA, which is not sufficiently cleared by the liver and leads to the formation of IgA macromolecules, accumulating in the circulation with subsequent deposition in vessel walls and in the glomerular mesangium. HSPN is related to IgA nephropathy. These two diseases can be encountered consecutively in the same patient, have been described in identical twins and bear similar pathological and biological abnormalities. No consensus about treatment has been reached up to now. Recent studies indicate that early treatment with methylprednisolone or a combination of steroids and cytotoxic drugs might prevent evolution to chronic renal failure. CONCLUSION: Despite numerous studies, the pathogeny of Henoch-Schönlein nephritis remains incompletely elucidated and controlled therapeutic trials are still needed.

Age Factors↗
PubMed2001

The immune dysregulatory compound mercuric chloride induces integrin-mediated T-lymphocyte adhesion.

Exposure of Brown Norway rats to mercuric chloride induces systemic autoimmunity, involving T- and B-lymphocyte activation, (auto-)antibody production and multiorgan inflammation. Several divalent metal ions, such as Mg2+ and Mn2+, can activate binding of integrins to their ligands, thus causing lymphocyte adhesion. To test the hypothesis that Hg2+ acts in a similar way, we studied the effect of HgCl2 on integrin-mediated T-cell adhesion. HgCl2 induced cell-cell aggregation of human T lymphoblasts. Exposure of a human T-cell clone to HgCl2 for 1 hr enhanced, in a dose-dependent way, cell binding to fibronectin (FN) and to intercellular adhesion molecules (ICAM) -1, -2 and -3. Furthermore, HgCl2 induced strong binding of Jurkat T cells to FN. These effects of HgCl2 were of similar magnitude as the effects of phorbol 12-myristate 13-acetate (PMA) or MnCl2. Studies using blocking antibodies indicated the involvement of CD11a in binding to ICAMs, and of CD49d, CD49e, and CD29 in binding to FN. Adhesion to FN induced by HgCl2 or by PMA, but not by MnCl2, was dependent on temperature and on extracellular Ca2+ or Mg2+. Addition of cytochalasin B enhanced synergistically the FN adhesion induced by MnCl2, whereas the effects of PMA and HgCl2 were not modified. These results indicate that Hg2+ is a potent activator of T-cell adhesion, mediated by several integrins and ligands. In contrast to the effect of MnCl2, HgCl2-induced cell adhesion probably involves an intracellular pathway. Activation of integrins by HgCl2 may play an important role in activation and migration of leucocytes involved in HgCl2-induced immune dysregulation in vivo.

Actins↗
PubMed2001

Release of urokinase plasminogen activator receptor during urosepsis and endotoxemia.

BACKGROUND: The urokinase receptor (uPAR; CD87) is a multifunctional molecule involved in fibrinolysis, in proteolysis, in renal tubular functions, and in migration and adhesion of inflammatory cells to the site of infection. METHODS: To gain insight into systemic and local release of uPAR and into its regulation during urosepsis, which is one of the leading causes of chronic renal failure, uPAR was measured in urine and plasma of healthy human controls (N = 20), patients with culture-proven urosepsis (N = 30), and healthy human volunteers intravenously injected with endotoxin (N = 7). RESULTS: Patients had elevated uPAR levels in both plasma and urine. Three hours after endotoxin challenge in volunteers, there was also a significant increase of uPAR in plasma and in urine. The urine/plasma ratio for uPAR was highly elevated during urosepsis and experimental endotoxemia, suggesting local production in the kidney. Accordingly, damaged tubuli strongly expressed uPAR during pyelonephritis. Moreover, tubular epithelial cells produced uPAR in vitro, and this secretion was strongly up-regulated after stimulation with interleukin-1 beta or tumor necrosis factor-alpha. CONCLUSIONS: We found that uPAR is released systemically and in the urinary tract during urosepsis and experimental endotoxemia. This systemic and renal production of uPAR during pyelonephritis may play a central role in eliminating the infection and protecting renal function.

Adult↗
PubMed2001

What is the difference between IgA nephropathy and Henoch-Schönlein purpura nephritis?

Henoch-Schönlein purpura nephritis (HSPN) and IgA nephropathy (IgAN) are considered to be related diseases since both can be encountered consecutively in the same patient, they have been described in twins, and bear identical pathological and biological abnormalities. Apart from the presence of extrarenal clinical signs found only in HSPN, other differences are noticed between the two diseases. The peak age ranges between 15 and 30 years for a diagnosis of IgAN, whereas HSPN is mainly seen in childhood. Nephritic and/or nephrotic syndromes are more often seen at presentation in HSPN. In contrast to IgAN, HSPN has been described in association with hypersensitivity. Endocapillary and extracapillary inflammations as well as fibrin deposits in the glomerulus are more frequent in HSPN. No major biological differences have been found between the two illnesses, except for a larger size of circulating IgA-containing complexes (IgA-CC) and a greater incidence of increased plasma IgE levels in HSPN. As tissue infiltration by leukocytes is a major feature of HSPN vasculitis, a possible role of a more potent activation of the latter cells by IgA-CC and/or circulating chemokines in HSPN should be considered. Further studies are required to elucidate this possible mechanism as well as the role of hypersensitivity in HSPN.

Glomerulonephritis, IGA↗
PubMed2001

Renal vascular changes in renal disease independent of hypertension.

INTRODUCTION: Cardiovascular disease is common in patients with renal disease, but little is known about the effect of renal disease and loss of renal function on vascular morphology. Intima proliferation of small renal arteries, which correlates with atherosclerosis in the aorta, is sometimes present in renal disease and has been shown to increase with age and hypertension. We studied the effect of chronic renal disease and renal function, independent of hypertension, on intima proliferation. METHODS: We retrospectively selected renal biopsies of subjects in whom a glomerular filtration rate (GFR) measurement with [(125)I] iothalamate had been performed. To separate the effects of renal disease and renal function, we selected biopsies from (A) normotensive controls undergoing nephrectomy because of renal carcinomas; (B) normotensive patients with renal disease and GFR > 90 ml/min; (C) normotensive patients with GFR 30-90 ml/min, and (D) hypertensive patients with a GFR < 90 ml/min. The area of the arteriolar lumen, intima, and media were measured. RESULTS: No significant changes from control subjects were observed in group B. Intima proliferation was observed when renal function declined (intima/total vessel surface ratio was 0.262 +/- 0.071 in group C, 0.192 +/- 0.032 in group A, and 0.205 +/- 0.035 in group B, P < 0.05). The intima proliferation was aggravated in patients with renal insufficiency and hypertension (0.333 +/- 0.121, P < 0.05). Media surface area was not different between groups. CONCLUSION: Renal disease with preserved GFR does not cause significant intima proliferation of small renal arteries. Loss of renal function is accompanied by intima proliferation, even in the absence of systemic hypertension.

Adult↗
PubMed2001

In vitro evidence for differential involvement of CTGF, TGFbeta, and PDGF-BB in mesangial response to injury.

BACKGROUND: Connective tissue growth factor (CTGF) is a profibrotic growth factor, which is upregulated in wound healing and renal fibrosis, including anti-Thy-1.1 nephritis. The kinetics of CTGF mRNA expression in anti-Thy-1.1 nephritis suggested that CTGF regulation might contribute to glomerular response to injury downstream of transforming growth factor-beta (TGFbeta). In anti-Thy-1.1 nephritis the initial damage is followed by mesangial repair and limited sclerosis, which involves mesangial cell (MC) activation (alpha-smooth-muscle actin (alphaSMA) expression), proliferation, migration, and extracellular matrix production. The present in vitro study addresses the possible role of CTGF in these different aspects of mesangial response to injury, and how CTGF activity might relate to effects of TGFbeta and platelet-derived growth factor-BB (PDGF-BB). METHODS AND RESULTS: Immunostaining and ELISA showed that alphaSMA expression and transformation of MC into myofibroblast-like cells was induced by TGFbeta, but not affected by PDGF-BB, CTGF, or neutralizing anti-CTGF antibodies. [(3)H]thymidine incorporation and Ki67 staining demonstrated that, unlike PDGF-BB, neither CTGF nor TGFbeta induced the proliferation of MC. In contrast, both CTGF and TGFbeta induced MC migration, as evidenced by approximation of wound edges in scrape-wounded, non-proliferating rat MC monolayers. In addition, fibronectin expression was upregulated by both CTGF and TGFbeta, as measured by dot-blot analysis. Anti-CTGF completely blocked the effect of added CTGF. Moreover, anti-CTGF significantly reduced TGFbeta-induced increase in fibronectin. CONCLUSION: It thus appears that CTGF is specifically involved in a subset of the adaptive changes of MC involved in mesangial repair and sclerosis, which makes it an interesting candidate target for future intervention strategies.

Actins↗
PubMed2001

Divergent effects of tumor necrosis factor alpha on apoptosis of human neutrophils.

Apoptosis of neutrophils is a key mechanism to control the intensity of the acute inflammatory response. Previously, the cytokine tumor necrosis factor alpha (TNF-alpha) was reported by some to have pro-apoptotic and by others to have antiapoptotic effects on neutrophils. The aim of this study was to explain these contradictory results. We found that TNF-alpha at low concentrations strongly decreased apoptosis of neutrophils. However, at higher concentrations, TNF-alpha lost its protective effects, and also reversed the protective effects of interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF). This pro-apoptotic effect of TNF-alpha was blocked by anti-CD11b and was absent in neutrophils from patients with chronic granulomatous disease, which cannot produce toxic oxygen metabolites. Under these circumstances, we found that TNF-alpha retained its anti-apoptotic effects even at high concentrations. In conclusion, the protective effects against apoptosis of IFN-gamma, GM-CSF, and TNF-alpha itself are overruled when the concentration of TNF-alpha is high enough to produce a respiratory burst. These dual, concentration-dependent effects of TNF-alpha provide an explanation for previous controversial reports and support a dominant role for TNF-alpha in neutrophil apoptosis.

Apoptosis↗
PubMed2001

Acute renal failure caused by Klebsiella pneumoniae pyelonephritis.

We report a 34-year-old male patient without prior medical history who presented with acute renal failure due to acute bacterial pyelonephritis. Both blood and urine cultures grew Klebsiella pneumoniae. Although a kidney biopsy revealed extensive necrosis and no viable glomeruli, renal function recovered to near normal after intermittent hemodialysis and antibiotic therapy. We believe that it is important to include this entity in the differential diagnosis of acute renal failure since proper diagnosis and treatment is essential for recovery of renal function. Furthermore, we would like to draw attention to Klebsiella pneumoniae as an important potential pathogen in such cases, in addition to Escherichia coli.

Acute Kidney Injury↗
PubMed2000

Biomaterial-associated persistence of Staphylococcus epidermidis in pericatheter macrophages.

Biomaterial surfaces may be modified to reduce bacterial adhesion. The susceptibility in mice to Staphylococcus epidermidis infection in tissue surrounding the commonly used catheter materials-silicon elastomer (SE), polyamide (PA), and their surface-modified polyvinylpyrrolidone (PVP)-grafted derivatives, SE-PVP and PA-PVP, respectively-was assessed. Abscesses developed around SE-PVP. Around SE, PA, and PA-PVP catheters, no signs of infection were observed, although mice carrying PA-PVP developed septicemia after 14-21 days. S. epidermidis was cultured from the tissue surrounding PA-PVP segments. Cells around PA-PVP segments containing large numbers of bacteria were identified as macrophages by use of immunohistochemistry and electron microscopy. This persistence of intracellular bacteria was also observed around SE-PVP, SE, and PA catheters, although to a lesser extent. The cytokine profiles around the 4 materials were different. Implanted biomaterial induces an inflammatory response favorable to the persistence of S. epidermidis. Intracellular persistence of bacteria inside macrophages may be a pivotal process in the pathogenesis of biomaterial-associated infection.

Animals↗
PubMed2000

ACE inhibition delays development of terminal renal failure in the presence of severe albuminuria.

The hypertensive fawn-hooded (FHH) rat develops progressive albuminuria (UalbV) and focal glomerulosclerosis (FGS). Early-onset angiotensin-converting enzyme inhibition (ACE-i) completely prevented the development of hypertension, UalbV, and FGS. ACE-i was still effective when the start of treatment was delayed, albeit less than early-onset treatment. In this study, we examined whether more advanced renal damage reduces the efficacy of ACE-i, and, if so, which factors dampen the efficacy. ACE-i was started in 36-week-old FHH rats, and follow-up consisted of regular assessment of systolic blood pressure (SBP) and UalbV. Untreated rats, matched for age, SBP, and UalbV, served as controls. In separate groups, untreated or treated with ACE-i from either week 7 or week 36, glomerular hemodynamics and FGS were determined at week 40. ACE-i normalized SBP and markedly reduced UalbV. The Initial UalbV response to ACE-i was inversely correlated with pretreatment UalbV, but despite control of SBP, UalbV rose again. Eventually, rats died of terminal renal failure. Life expectancy was significantly increased in treated rats. In both untreated and treated rats, there was a significant inverse correlation between baseline UalbV and survival time. However, the gain in survival time decreased when pretreatment UalbV was higher. Late-onset ACE-i reduced glomerular capillary pressure to the same extent as early-onset ACE-i. There was a significant linear correlation between FGS and UalbV. We conclude that in FHH rats with advanced renal damage, ACE-i slows down the progression to terminal renal failure. The outcome is an increased survival time that is inversely correlated with baseline UalbV.

Albuminuria↗
PubMed2000

Interleukin-1 receptor type I gene-deficient mice are less susceptible to Staphylococcus epidermidis biomaterial-associated infection than are wild-type mice.

Elevated concentrations of interleukin-1 (IL-1) were found in tissue surrounding biomaterials infected with Staphylococcus epidermidis. To determine the role of IL-1 in biomaterial-associated infection (BAI), IL-1 receptor type I-deficient (IL-1R(-/-)) and wild-type mice received subcutaneous implants of silicon elastomer (SE) or polyvinylpyrrolidone-grafted SE (SEpvp), combined with an injection of 10(6) CFU of S. epidermidis or sterile saline. Neither mouse strain was susceptible to BAI around SE. IL-1R(-/-) mice with SEpvp implants had a no abscess formation and a reduced susceptibility to persistent S. epidermidis infection. The normal foreign body response, characterized by giant-cell formation and encapsulation, was delayed around SEpvp in wild-type mice but not in IL-1R(-/-) mice. This coincided with enhanced local IL-4 production in IL-1R(-/-) mice. These data suggest that inhibition of local IL-1 activity may be beneficial for the outcome of BAI.

Animals↗
PubMed2000

Enhanced susceptibility to subcutaneous abscess formation and persistent infection around catheters is associated with sustained interleukin-1beta levels.

A persistent Staphylococcus epidermidis infection in mice around a subcutaneous polyvinylpyrrolidone-grafted silicon elastomer catheter (SEpvp) but not around a conventional silicon elastomer catheter was observed. With SEpvp pericatheter tissue, protracted and exaggerated interleukin-1beta (IL-1beta) production was found. Apparently, sustained levels of IL-1beta are associated with enhanced susceptibility to biomaterial-associated S. epidermidis infection.

Abscess↗