[T lymphocyte immunological response to different antigenic fractions of Mycobacterium bovis in juvenile chronic polyarthritis]

BACKGROUND

The possible relationship of stress or heat-shock proteins (hsp) with the pathogenesis of autoimmune disease has been intensely studied recently. In adult rheumatoid arthritis, a bacterial hsp (65 kDa hsp from Mycobacterium tuberculosis or bovis) would have a cross reactivity with a hsp of ARTICULAR cartilage.

AIM

To assess the cellular immune response to the 65 kA hsp from M Bovis in children.

PATIENTS AND METHODS

The proliferative response of peripheral mononuclear cells of 20 children with juvenile chronic polyarthritis and 20 healthy controls, against the 65 kDa hsp and other antigenic fractions from M bovis, was studied.

RESULTS

Patients with juvenile chronic polyarthritis had a intense reaction against 65 kDa fraction and a second fraction located between 32.5 and 27.5 kDa. Patients with a prolonged evolution of the disease (more than five years), reacted preferentially to an antigenic segment located between 32.5 and 27.5 kDa and those with a shorter evolution did so with an antigen of 27.5-18.5 kDa.

CONCLUSIONS

These results support the hypothesis that 65 kDa hsp from M bovis is involved in the pathogenesis of chronic juvenile polyarthritis and suggest that patients with short or prolonged evolutions of the disease would react to different antigenic fractions.

ACE inhibitor quinapril reduces the arterial expression of NF-kappaB-dependent proinflammatory factors but not of collagen I in a rabbit model of atherosclerosis

Increasing evidence supports an association between inflammation and plaque rupture. Macrophages and vascular smooth muscle cells are a source of cytokines and growth factors, which contribute to ongoing inflammation during atherogenesis. In a rabbit model of atherosclerosis, we evaluated the effect of the ACE inhibitor quinapril on different parameters implicated in the pathogenesis of the plaque, such as the presence of chemokines (interleukin-8, monocyte chemoattractant protein-1), collagen I, and vascular smooth muscle cell proliferation (PDGF-B). Since nuclear factor kappaB (NF-kappaB) has been implicated in the control of chemokine transcription and cell proliferation, we also investigated its activation and localization in the lesion. Quinapril administration for 28 days caused a down-regulation in arterial expression of interleukin-8 and monocyte chemoattractant protein-1 (mRNA and protein). However, collagen I expression (mRNA and protein) was not modified. PDGF-B expression was reduced in both the intima and the media. Active NF-kappaB, found in both macrophages and vascular smooth muscle cells, was also reduced by quinapril. Nevertheless, no significant changes were noted in the mild neointima formation, although a certain trend toward normalization was found in the quinapril-treated group. In conclusion, our results show that quinapril treatment attenuates several parameters associated with inflammation within the atherosclerotic lesions that are controlled by NF-kappaB, although it has no effect on collagen I expression. Both effects could contribute to the stabilization of the atherosclerotic plaque.

HMG-CoA reductase inhibition by atorvastatin reduces neointimal inflammation in a rabbit model of atherosclerosis

OBJECTIVES

To study the effect of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)-reductase inhibitor atorvastatin on the potential mechanisms involved in the recruitment of monocytic cells into the vessel wall.

BACKGROUND

Inhibitors of HMG-CoA-reductase reduce cardiovascular mortality though the mechanisms yet elucidated. Most ischemic events are secondary to disruption of atherosclerotic plaques highly infiltrated by macrophages.

METHODS

Atherosclerosis was induced in the femoral arteries of rabbits by endothelial damage and atherogenic diet for 4 weeks. Then, animals were switched to standard chow and randomized to receive either no treatment or atorvastatin (5 mg/kg/d) and killed after 4 weeks.

RESULTS

Atorvastatin induced a significant reduction in serum lipids and in lesion size. Arterial macrophage infiltration was abolished by the treatment, and monocyte chemoattractant protein-1 (MCP-1) was significantly diminished in the neointima and in the media. Nuclear factor kappa-B (NF-kappaB) was activated in the 60% of the lesions, both in macrophages and vascular smooth muscle cells (VSMC), of the untreated group while only in 30% of the atorvastatin group. NF-kappaB activity was also lower in the uninjured aorta and liver of treated compared with untreated rabbits. In cultured VSMC, MCP-1 expression and NF-kappaB activity induced by tumor necrosis factor alpha were downregulated by atorvastatin.

CONCLUSIONS

In a rabbit atherosclerosis model, atorvastatin diminishes the neointimal inflammation, and this could contribute to the stabilization of the atherosclerotic plaque. This may be an additional explanation for the reduction of acute ischemic events in patients treated with statins.

Angiotensin II participates in mononuclear cell recruitment in experimental immune complex nephritis through nuclear factor-kappa B activation and monocyte chemoattractant protein-1 synthesis

Angiotensin-converting enzyme (ACE) inhibitors reduce macrophage infiltration in several models of renal injury. We approached the hypothesis that angiotensin II (AngII) could be involved in inflammatory cell recruitment during renal damage through the synthesis of monocyte chemoattractant protein-1 (MCP-1). In a model of immune complex nephritis, we observed an up-regulation of renal MCP-1 (mRNA and protein) coincidentally with mononuclear cell infiltration that were markedly reduced by treatment with the ACE inhibitor quinapril. Exposure of cultured rat mesangial cells to AngII increased MCP-1 mRNA expression (2.7-fold) and synthesis (3-fold), similar to that observed with TNF-alpha. Since NF-kappaB is involved in the regulation of MCP-1 gene, we explored whether the effects of AngII were mediated through NF-kappaB activation. Untreated nephritic rats showed increased renal NF-kappaB activity (3.5-fold) that decreased in response to ACE inhibition. In mesangial cells, AngII activated NF-kappaB (4.3-fold), and the NF-kappaB inhibitor pyrrolidine dithiocarbamate abolished the AngII-induced NF-kappaB activation and MCP-1 gene expression. Our results suggest that AngII could participate in the recruitment of mononuclear cells through NF-kappaB activation and MCP-1 expression by renal cells. This could be a novel mechanism that might further explain the beneficial effects of ACE inhibitors in progressive renal diseases.

Overexpression of extracellular matrix proteins in renal tubulointerstitial cells by platelet-activating-factor stimulation

BACKGROUND

One common feature of renal diseases is the development of interstitial fibrosis, but the mechanism of this process remains undefined. We hypothesized that platelet-activating factor (PAF), a classical acute inflammatory mediator involved in the pathogenesis of renal damage, acts on renal tubulointerstitial cells, contributing to the development of fibrosis. For this reason we evaluated the effect of PAF on matrix regulation and cell-growth-related events in tubulointerstitial cells.

METHODS

In vitro studies were conducted with two tubulointerstitial cell lines: renal tubuloepithelial cells (NRK 52E) and interstitial fibroblasts (NRK 49F). The effect of PAF on extracellular matrix gene expression was determined by Northern blot. Fibronectin synthesis was quantified by metabolic labelling and immunoprecipitation. Cell growth changes were evaluated by fluorescence-activated cell-sorting analysis (cell cycle and size) and total protein content by 3[H]leucine incorporation.

RESULTS

In renal tubuloepithelial cells and interstitial fibroblasts, PAF increased fibronectin mRNA expression. PAF-effect on the expression of collagen genes differed depending on the cell type studied. In tubuloepithelial cells there was an increase in type I and IV collagen mRNA levels, while only type I collagen was increased in fibroblasts. The overexpression of matrix proteins induced by PAF was completely blocked by preincubation of cells with the PAF receptor antagonist, BN52021. The PAF-induced upregulation of fibronectin expression was correlated with the increase in fibronectin synthesis. These effects were not associated with an increase in hyperplasia (characterized by changes in cell cycle) either in tubuloepithelial cells or in interstitial fibroblasts. Moreover, PAF did not induce tubular hypertrophy (changes in protein content and cell size).

CONCLUSIONS

Our data suggest that PAF could be a mediator involved in extracellular matrix accumulation and, therefore, participate in the formation of renal interstitial fibrosis.

Platelet-activating factor stimulates gene expression and synthesis of matrix proteins in cultured rat and human mesangial cells: role of TGF-beta

Platelet-activating factor (PAF) is a potent inflammatory mediator that participates in the pathogenesis of proteinuria and glomerular damage. However, the role of this lipid in glomerular sclerosis remains unknown. This study examines the effect of PAF on the regulation of extracellular matrix proteins by rat and human mesangial cells. PAF increased in a dose-dependent manner the gene expression of fibronectin and type IV collagen, but not type I collagen. Moreover, an increase in cell-associated and soluble fibronectin synthesis was also seen. These effects were abolished by BN52021 and WEB2086, two different PAF receptor antagonists. Because transforming growth factor (TGF)-beta has been considered a profibrogenic cytokine, this study also evaluated whether PAF effects might be mediated by the production of endogenous TGF-beta. PAF caused an increase in TGF-beta1 mRNA expression (by a protein kinase C-dependent pathway) and TGF-beta activity. Moreover, PAF-induced fibronectin synthesis was totally abolished when an anti-TGF-beta-neutralizing antibody was added to the culture medium, suggesting that PAF stimulates fibronectin synthesis, at least in part, through the induction of TGF-beta. Addition of cycloheximide, a protein synthesis inhibitor, upregulated PAF-induced fibronectin mRNA expression but downregulated PAF-induced TGF-beta1 gene expression, suggesting the existence of different regulatory transcriptional factors of the two proteins. These results suggest that PAF may be implicated in matrix accumulation during renal injury and therefore contribute to the pathogenesis of glomerulosclerosis.

Angiotensin-converting enzyme inhibition prevents arterial nuclear factor-kappa B activation, monocyte chemoattractant protein-1 expression, and macrophage infiltration in a rabbit model of early accelerated atherosclerosis

BACKGROUND

The migration of monocytes into the vessel wall is a critical event leading to the development of atherosclerosis. Monocyte chemoattractant protein-1 (MCP-1) is the main chemotactic factor involved in this phenomenon, and nuclear factor-kappa B (NF-kappa B) is one of the nuclear factors controlling its expression. ACE inhibitors have been useful in some experimental models of atherosclerosis. In this work, we addressed the hypothesis that angiotensin II (Ang II) may be implicated in the recruitment of monocytes into the vessel wall through the activation of NF-kappa B and the induction of MCP-1 expression.

METHODS AND RESULTS

Accelerated atherosclerosis was induced in the femoral arteries of rabbits by endothelial desiccation and atherogenic diet for 7 days. Atherosclerotic vessels exhibited an increase in NF-kappa B-like activity, and p50 and p65 NF-kappa B subunits were identified as components of this activity. MCP-1 (mRNA and protein) was also expressed in the injured vessels coincidently with the neointimal macrophage infiltration. ACE inhibition with quinapril reduced these three parameters. In cultured monocytic and vascular smooth muscle cells. Ang II elicited an increase in NF-kappa B activation and MCP-1 expression that was prevented by preincubation of cells with pyrrolidinedithiocarbamate, an inhibitor of NF-kappa B activation.

CONCLUSIONS

The present data support a role for Ang II in neointimal monocyte infiltration through NF-kappa B activation and MCP-1 expression in a model of accelerated atherosclerosis in rabbits. Our results suggest that ACE inhibitors may have a beneficial effect in early atherosclerosis.

Expression of leucocyte chemoattractants by interstitial renal fibroblasts: up-regulation by drugs associated with interstitial fibrosis

Interstitial inflammation is a strong predictor of long-term renal damage. The potential role of renal interstitial fibroblasts in recruitment of inflammatory leucocytes into the interstitium is unclear. We have thus studied the mRNA expression of several leucocyte chemotactic factors by rat renal interstitial fibroblasts and its modulation by cytokines. In addition, the effects of two unrelated drugs associated with the development of interstitial fibrosis, namely puromycin aminonucleoside (PAN) and cyclosporin A (CsA), were also studied. Rat renal interstitial fibroblasts showed constitutive mRNA expression for the chemokines monocyte chemoattractant protein 1 (MCP-1) and interferon-inducible protein 10 (IP-10). In addition, these cells also exhibited constitutive mRNA expression for cyclophilin B, an immunophilin recently found to have leucocyte chemoattractant properties. The inflammatory cytokine tumour necrosis factor-alpha up-regulated IP-10 and MCP-1 mRNA expression (10- and four-fold, respectively), but had no effect on cyclophilin B mRNA levels. IP-10 and MCP-1 produced about a four-fold increase in MCP-1 and cyclophilin B mRNA expression, but did not affect IP-10 mRNA. PAN caused an augmentation in IP-10, MCP-1 and cyclophilin B mRNA levels (12-, 9.5, and two-fold, respectively), while CsA increased only cyclophilin B mRNA in a dose-dependent manner. In conclusion, rat renal interstitial fibroblasts express mRNA for chemotactic factors and this expression is up-regulated by inflammatory cytokines, PAN and CsA. The present findings suggest that renal interstitial fibroblasts may play an active role in the recruitment of inflammatory leucocytes into the interstitium.

Urinary excretion of platelet-activating factor in human and experimental nephrosis

BACKGROUND

Platelet-activating factor (PAF) is a phospholipid that has been implicated in the pathogenesis of glomerulonephritis and can be synthesized by glomerular cells in response to different stimuli. PAF increases glomerular permeability to proteins and urinary PAF has been determined to be of renal origin. In order to assess whether urinary PAF can be found augmented in situations of glomerular damage without glomerular leukocyte infiltration, urinary PAF was quantified in human and experimental nephrosis.

METHODS

Urinary PAF was quantified by platelet bioassay and glomerular PAF by incorporation of 3H-acetate into PAF. PAF was characterized by its behaviour on thin-layer chromatography and high performance liquid chromatography and the blockade of its bioactivity by receptor antagonists.

RESULTS

Urinary PAF excretion was significantly higher in patients with active idiopathic nephrotic syndrome than in controls (5.8+/-1.5 versus 1.7+/-0.75 mg/24 h; P<0.05) and patients in remission (1.63+/-0.75 ng/24 h; P<0.02). In rats with nephrosis induced by puromycin aminonucleoside there was an early increase in urinary PAF excretion (138+/-19 versus 49+/-22 pg/24 h in controls; P<0.035) that coincided with the augmented glomerular PAF synthesis (67+/-3.4 versus 36+/-1.2 DPM/mg protein in controls; P<0.003).

CONCLUSIONS

These results suggest that the synthesis of PAF in the kidney may be involved in the pathogenesis of the proteinuria in idiopathic nephrotic syndrome and that urinary PAF excretion may be a good marker of disease activity.

ACE inhibition reduces proteinuria, glomerular lesions and extracellular matrix production in a normotensive rat model of immune complex nephritis

We studied the effect of the angiotensin converting enzyme (ACE) inhibitor, quinapril, on the clinical and morphological lesions of a normotensive model of immune complex nephritis. Untreated rats developed massive nephrotic syndrome, intense cell proliferation and glomerular and tubulointerstitial lesions. In the renal cortex of nephritic rats there was a significant increase in gene expression of TGF-beta 1, fibronectin and collagens, and ACE activity. Systolic blood pressure remained normal with progression of the disease. Administration of quinapril for three weeks to animals with glomerular lesions (proteinuria 20 to 50 mg/day) avoided the development of intense proteinuria (79 +/- 28 vs. 589 +/- 73 mg/day, P < 0.001) and decreased cell proliferation, glomerulosclerosis, tubulointerstitial lesions, and inflammatory infiltrates. Cortical gene expression of TGF-beta 1 and matrix proteins was also diminished. ACE activity was inhibited by 68% in renal cortex. These results show that quinapril administration to normotensive rats with immune complex nephritis decreases proteinuria and glomerular and tubulointerstitial lesions, probably modulating the local angiotensin II generation and its effects on cell growth, TGF beta and matrix protein synthesis.

Cyclosporin A (CsA) modulates the glomerular production of inflammatory mediators and proteoglycans in experimental nephrosis

Nephrosis is characterized by glomerular epithelial cell injury and a decrease in the glomerular basement membrane (GBM) proteoglycan content. Although CsA is a useful treatment for a group of patients with this disease, its mechanism of action is unclear. We have previously shown that in experimental nephrosis there is an increase in the glomerular production of tumour necrosis factor-alpha (TNF-alpha) and platelet-activating factor (PAF). Here we have studied the effect of CsA on kidney generation of TNF-alpha and PAF in puromycin aminonucleoside (PAN) nephrosis as well as on the synthesis of proteoglycans by cultured glomerular epithelial cells. Rats receiving CsA had, on day 8 of PAN injection, a significant reduction in proteinuria, blood cholesterol levels and in interstitial mononuclear cells. A diminution in glomerular production and urinary excretion of TNF-alpha and PAF was also noted. In in vitro studies, at 24 h of incubation PAF and TNF-alpha induced in glomerular epithelial cells a significant decrease in proteoglycan synthesis. Neither PAF nor TNF-alpha had any significant effect on glomerular epithelial cell proliferation. CsA alone induced a dose-response increase in proteoglycan synthesis and a slight decrease in cell proliferation. CsA also reversed the inhibitory effect of PAF and TNF-alpha on proteoglycan synthesis. However, CsA did not alter the pattern of proteoglycan production, remaining around 50% chondroitinase ABC-, 15% heparitinase-sensitive. Our results indicate that PAF and TNF-alpha could be implicated in the pathogenesis of nephrosis through the inhibition of proteoglycan synthesis by glomerular epithelial cells. The beneficial effect of CsA in nephrosis may be due to the recovery of the GBM charge selectivity caused by the normalization of glomerular PAF and TNF-alpha synthesis and the increase in proteoglycan synthesis by glomerular epithelial cells.

Purification and preliminary sequencing of Tc-45, an immunodominant Trypanosoma cruzi antigen: absence of homology with cruzipain, cruzain, and a 46-kilodalton protein

In spite of being separated by more than 20 million years of evolution, the murine and human immune systems share extensive similarities. Thus, experimental results obtained with the murine model may have predictive value for human Chagas' disease. Challenge of the H-2 congenic mouse stains A.SW (H-2s) and A.CA (H-2f) with Trypanosoma cruzi yields different results. The A.CA animals die approximately 12 days postinfection, while A.SW mice survive indefinitely. A 45-kD protein (Tc45), an antigen differentially recognized by the A.SW strain, is present in cultured epimastigotes and blood trypomastigotes. We describe here its purification from epimastigotes. The presence of Tc45 was monitored and a single band was detected. Since the molecular weights of Tc45, cruzipain, cruzain, and a 46-kD parasite polypeptide are similar, it was important to determine if these molecules are related. A complete lack of homology was observed when the sequence of cruzain, cruzipain, and the 46-kD polypeptide were compared with the preliminary sequence of Tc45.

Humoral immune response anti K99 pilus from enterotoxigenic Escherichia coli in experimentally inoculated calves

The bovine model is extremely interesting to study several basic aspects of mucosal local immunity. Many reports have shown that, in young calves, the infectivity of enterotoxigenic Escherichia coli may be inhibited by passively administered antibodies anti K99 pilus. We have measured, by immunoradiometric assays, the IgG response anti K99 pilus in the serum of calves, deprived of colostrum and orally inoculated with enteropathogenic K99+ E. coli. Although variable levels of IgG anti K99 pilus were detected, their protective value could not be ascertained in vivo due to the acute development of the infection. In an effort to correlate the presence of serum antibodies anti K99 pilus with their protective capacity, an ex-vivo assay to monitor the interaction of radiolabeled K99 pilus with the bovine mucosa was standardized. Paradoxically, although K99 pilus, purified by standard procedures, was recognized by polyclonal rabbit and calf antisera, its interaction with the bovine intestinal mucosa, quantitated in the ex-vivo system, was not inhibited by these reagents, indicating that the antibodies did not effectively block those K99 pilus domains involved in the interaction with mucosal receptors.

Increase of tumour necrosis factor alpha synthesis and gene expression in peripheral blood mononuclear cells of children with idiopathic nephrotic syndrome

The pathogenesis of idiopathic nephrotic syndrome (minimal change nephropathy and its variants) is not completely understood. In recent years it has been speculated that a cytokine released by circulating blood mononuclear cells could alter the permeability of the glomerular capillary wall. In this study we have explored the potential participation of tumour necrosis factor alpha (TNF alpha), a cytokine mainly produced by monocytes, in 25 children with idiopathic nephrotic syndrome. TNF alpha was determined by cytotoxicity bioassay in the L-929 cell line and by double antibody/RIA. Patients in activity had higher serum TNF alpha levels and TNF alpha production by monocytes than patients in remission and controls. TNF alpha mRNA expression in blood mononuclear cells was analysed by Northern blot. The TNF alpha mRNA levels in patients in activity were increased compared to controls and to patients in remission. No significant differences in IL-1 beta and IL-6 synthesis were found between patients and controls. Our results suggest that TNF alpha, but not other cytokines such as IL-1 beta and IL-6, could play a role in the pathogenesis of the proteinuria in idiopathic nephrotic syndrome.

Involvement of angiotensin II and endothelin in matrix protein production and renal sclerosis

PURPOSE

To review the evidence that links angiotensin II and endothelin as growth factors and as modifiers of extracellular matrix synthesis in renal cells, with particular reference to the effects of angiotensin converting enzyme (ACE) inhibition in models of renal injury.

IN VITRO STUDIES

In cultured mesangial cells, both angiotensin II and endothelin promote contraction, proliferation/hypertrophy, signal transduction pathways, the activation of early growth genes, and the generation of inflammatory mediators, cytokines and growth factors. Both hormones have been shown to promote the synthesis of fibronectin and collagen in a dose-dependent manner. ACE inhibition attenuates the effect of endothelin-1, one of three isoforms of endothelin.

ANIMAL STUDIES

In experimental models of renal injury, chiefly in those characterized by increased intraglomerular pressure, ACE inhibition has reduced proteinuria and glomerular and interstitial sclerosis.

HUMAN STUDIES

ACE inhibition has been shown to have major beneficial effects in patients with diabetic nephropathy, even in those with normal blood pressure.

CONCLUSIONS

Although the renal-protective effects of ACE inhibitors in experimental and human renal injury may reflect systemic and/or local hemodynamic effects of these drugs, their modulatory actions on extracellular matrix synthesis and proteinuria may contribute to the benefit of ACE-inhibitor therapy.

The potential role of inflammatory and fibrogenic cytokines in the glomerular diseases

In recent years increasing evidence has been accumulated on the role of cytokines in mediating glomerular and renal damage. Many such cytokines are released in the inflamed glomeruli by leukocytes and intrinsic glomerular cells. Cytokines not only recruit inflammatory cells into the injured glomeruli, but also induce a variety of responses on glomerular cells that range from a direct toxic effect to shape changes, proliferation, and induction of the release of inflammatory mediators and extracellular matrix, and could promote further glomerular damage. Moreover, exogenous administration of cytokines has induced glomerular injury in healthy animals and has enhanced renal damage in animals with glomerulonephritis. Anti-cytokine strategies have proved to be effective therapeutical alternatives in experimental models of glomerular diseases and may provide a more specific approach to the management of human glomerulonephritis.

[Thermoactinomyces vulgaris as a cause of extrinsic allergic alveolitis]

Thermoactinomycetes are microorganisms similar to the aerobic actinomycetes that grow at temperatures between 32 65 degrees C and are usually found in soil, hay and warm environment. They are the agent of Extrinsic Allergy Alveolitis producing an interstitial process of immunologic, generated by the inhalation of the environmental dust that contain spores from these fungi. There is one case of a middle age man who works in a boiler of a foundry company of province de Buenos Aires in Argentina. The patient presents a clinical picture compatible with the above mentioned illness and he gets better in vacation periods. The Thermoactinomyces vulgaris was isolated from the dust accumulated in a ceiling light.