Altered expression of the Smad signalling pathway: implications for COPD pathogenesis.

Pulmonary emphysema, as a feature of chronic obstructive pulmonary disease (COPD), is characterised by destruction of alveolar tissue. The present authors previously demonstrated reduced decorin expression in the peribronchial area of COPD patients, reflecting an altered extracellular matrix (ECM) modulation. Decorin transcription is regulated by the transforming growth factor (TGF)-beta-Smad pathway, the key intracellular signal route for initiation of ECM component gene transcription. Whether this pathway is aberrantly expressed in COPD is not known. An immunohistochemical study was performed to compare protein expression of TGF-beta1 and TGF-beta receptors, Smad 2, 3, 4 and 7, and decorin in lung tissue of Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages II and IV COPD patients and controls. Epithelial expression of the inhibitory Smad 7 was significantly lower in patients with GOLD stages II and IV than in controls, with other Smad protein expressions being similar in the groups. The expression of TGF-beta1 and TGF-beta receptor type I was significantly lower in stage II patients. Decorin staining of the adventitia and alveolar walls was significantly reduced in COPD stage IV. In conclusion, the transforming growth factor-beta-Smad pathway is aberrantly expressed in chronic obstructive pulmonary disease patients, implying an abnormal tissue repair ultimately resulting in reduced decorin production. The results of the present study contribute to better understanding of the pathogenesis of emphysema and the airway fibrosis observed in chronic obstructive pulmonary disease patients.

High ICAM-1 gene expression in pulmonary fibroblasts of COPD patients: a reflection of an enhanced immunological function.

Chronic obstructive pulmonary disease (COPD) is characterised by destruction of extracellular matrix (ECM) in parenchymal areas, whereas the bronchial walls can show fibrosis. In addition, an extensive inflammatory process is observed. CD8+ T-cells, located throughout the lung, and epithelial cells in centrally located airways, produce cytokines involved in the inflammatory process. These cytokines may influence the present fibroblasts, the key effectors in the defective ECM repair and maintenance in COPD. The current authors explored the effects of the cytokine microenvironment on cell-cell interaction gene expression in pulmonary fibroblasts of controls (n = 6), and Global Initiative for Chronic Obstructive Lung Disease stage II (n = 7) and stage IV (n = 7) COPD patients. The current authors simulated the in vivo microenvironment using supernatants of CD3/CD28 stimulated CD8+ T-cells isolated from peripheral blood of COPD patients, supernatant of a bronchial-epithelial cell line, or a combination of both. The present data show that fibroblasts of chronic obstructive pulmonary disease patients display an altered response to the cytokine microenvironment, depending on both the disease stage and the central or peripheral location in the lung. Especially adhesion-related genes are upregulated in fibroblasts of chronic obstructive pulmonary disease patients, which can indicate a more pronounced role of fibroblasts in the inflammatory process in chronic obstructive pulmonary disease, possibly resulting in reduced function as effectors of extracellular matrix repair.

Inflammatory cell distribution in guinea pig airways and its relationship to airway reactivity.

Although airway inflammation and airway hyperreactivity are observed after allergen inhalation both in allergic humans and animals, little is known about the mechanisms by which inflammatory cells can contribute to allergen-induced airway hyperreactivity. To understand how inflammatory cell infiltration can contribute to airway hyperreactivity, the location of these cells within the airways may be crucial Using a guinea pig model of acute allergic asthma, we investigated the inflammatory cell infiltration in different airway compartments at 6 and 24 h (i.e. after the early and the late asthmatic reaction, respectively) after allergen or saline challenge in relation to changes in airway reactivity (AR) to histamine. At 6 h after allergen challenge, a threefold (p < 0.01) increase in the AR to histamine was observed. At 24 h after challenge, the AR to histamine was lower, but still significantly enhanced (1.6-fold, p < 0.05). Adventitial eosinophil and neutrophil numbers in both bronchi and bronchioli were significantly increased at 6 h post-allergen provocation as compared with saline (p < 0.01 for all), while there was a strong tendency to enhanced eosinophils in the bronchial submucosa at this time point (p = 0.08). At 24h after allergen challenge, the eosinophilic and neutrophilic cell infiltration was reduced. CD3+ T lymphocytes were increased in the adventitial compartment of the large airways (p < 0.05) and in the parenchyma (p < 0.05) at 24h post-allergen, while numbers of CD8+ cells did not differ from saline treatment at any time point post-provocation. The results indicate that, after allergen provocation, inflammatory cell numbers in the airways are mainly elevated in the adventitial compartment. The adventitial inflammation could be important for the development of allergen-induced airway hyperreactivity.

Characterization of a rat glomerular visceral epithelial cell line.

Cultures of glomerular epithelial cells (GEC) are currently used to identify important cellular and molecular mechanisms involved in the pathogenesis of renal diseases. However, there is still controversy in the literature as to the visceral or parietal origin of cultured GEC. Our aim was to firmly establish the nature of a GEC cell line. The reactivity of cultured GEC was investigated with a large panel of mono- and polyclonal antibodies by using immunofluorescent techniques and compared with literature data on the in vivo expression of these antigens on podocytes. In addition, the podocyte specific 5A (podocalyxin), 13A and 27A (9-O-acetylated GD3) antigen expression was investigated in immuno-overlay experiments with isolated gangliosides and in immunoprecipitations with metabolically labelled cells. In general, immunoreactivities between cultured GEC and literature data on GEC in vivo expressions were similar. Important podocyte epitopes in vivo were expressed by cultured GEC such as podocalyxin, gp330 and the 13A antigen. Cultured GEC however differed from their in vivo counterparts in their expression of keratin-18, their lack of expression of pp44 and no detectable immunohistological expression of the ganglioside 9-O-acetylated GD3. Interestingly, the podocyte-specific epitope 9-O-acetylated GD3 was detected by the 27A antibodies in immuno-overlays of isolated GEC gangliosides. Moreover, by using the 27A antibody, we were able to precipitate the podocyte-specific 103-kD protein from 35S-methionine metabolically labelled GEC. From our immunohistological data together with the detectability of the 27A antigen we conclude that the cell line we use very probably originates from glomerular visceral epithelial cells.

Biological alterations of rat podocytes cultured under basolateral hydrostatic pressure.

In vivo, glomerular visceral epithelial cells (GVEC), or podocytes, are morphologically highly differentiated cells which are in close contact with adjacent cells by complex interdigitating foot processes. In vitro, the dedifferentiated appearance of podocytes hampers investigations on podocyte structure and function. Cultured podocytes resemble simple epithelium in several ways with apical tight junctions and absence of foot processes. The morphological resemblances between GVEC early in embryonic development, in proteinuric diseases and in cultured cells are striking, but the mechanisms involved in these (de)differentiation processes are poorly understood. A common feature of GVEC in these various states of dedifferentiation is their altered exposure to or even total lack of hydrostatic pressure, suggesting that this may be one of the parameters involved in GVEC differentiation. In this study we investigated whether basolateral hydrostatic pressure could affect GVEC biology in vitro. We therefore exposed cultured GVEC grown on porous supports to basolateral hydrostatic pressure and investigated morphology with scanning and transmission electron microscopy, expression of specific podocyte markers and their biological responses to a model stimulus, the cytokine IFN-gamma. Morphologically, monolayers of pressurized GVEC contained large regions of whirl-like, raised cell formations. Individual cells in these formations had a rounded morphology and pore-like indentations between adjacent cells were observed. Cell-cell contacts were often found more basally and intercellular spaces were widened. Moreover, protein expression of pressurized monolayers was altered, as demonstrated by regions of cells with decreased keratin expression. Finally, upon exposure to the model stimulus IFN-gamma, the pressurized as compared to the control GVEC demonstrated a 3-fold increased expression of MHC class II and a strongly decreased sensitivity to the toxic effects of IFN-gamma. In conclusion, we found several indications that hydrostatic pressure can affect podocyte biology in vitro and similar mechanisms may account for podocyte biology in vivo. The strikingly altered morphology and biology of pressurized GVEC suggest that this culture system can be quite relevant for future studies with cultured GVEC.

Interferon-gamma (IFN-gamma) and IL-4 expressed during mercury-induced membranous nephropathy are toxic for cultured podocytes.

The subepithelial immune deposits of Dorus Zadel Black (DZB) rats with mercury-induced membranous nephropathy consist of autoantibodies directed to laminin P1 and of complement. The animals develop massive proteinuria within 10-14 days which is associated with obliteration of foot processes of glomerular visceral epithelial cells (GVEC), or podocytes. Previous studies indicate that these autoantibodies are probably not the sole mediator of proteinuria and GVEC damage. In this study we investigated whether circulating or macrophage-derived cytokines can contribute to the GVEC changes as detected in vivo. In vivo at the height of the proteinuria, increased intraglomerular IFN-gamma immunoreactivity was found. In diseased rats a five-fold increase in intraglomerular macrophages was found, but we could not detect intraglomerular IFN-alpha, IFN-beta, IL-1 beta or tumour necrosis factor-alpha (TNF-alpha) by using immunohistology. Subsequently, we exposed cultured GVEC to these cytokines to investigate their cytotoxic effects on several physiological and structural parameters. IFN-gamma and IL-4 were the only cytokines that exerted toxic effects, resulting in a rapidly decreased transepithelial resistance of confluent monolayers, which was closely associated with altered immunoreactivity of the tight junction protein ZO-1. IL-4 also affected vimentin and laminin immunoreactivity. IFN-gamma and IL-4 only interfered with monolayer integrity when added to the basolateral side of the GVEC, indicating specific (receptor-mediated) effects. Only IL-4 decreased the viability of the cells, and treated monolayers demonstrated an increased passage of the 44-kD protein horseradish peroxidase. From our experiments we concluded that IFN-gamma subtly affected monolayer integrity at the level of the tight junctions, and that IL-4 additionally induced cell death. We hypothesize that the toxic effects of the cytokines IFN-gamma and IL-4 as seen with cultured podocytes are necessary together with the autoantibodies, for the ultimate induction of proteinuria in mercury nephropathy in the DZB rat.

Podocyte expression of MHC class I and II and intercellular adhesion molecule-1 (ICAM-1) in experimental pauci-immune crescentic glomerulonephritis.

We examined immunopathological changes of podocytes in vivo which, based on in vitro studies, are thought to be relevant for the pathogenesis of renal diseases. We investigated the alterations of podocytes in local inflammation in a recently developed model of pauci-immune necrotizing crescentic glomerulonephritis (NCGN) in the rat. Frozen and plastic embedded kidney sections at different time points of the disease were incubated with antibodies directed to MHC class I, MHC class II, ICAM-1 and to relevant cytokines. Strong glomerular expression of MHC class I, II and ICAM-1 was found within 4 days, and plastic embedded sections clearly demonstrated increased cell membrane staining of podocytes. Increased glomerular interferon-gamma (IFN-gamma) was detected within 24 h of induction of NCGN, and IL-1 beta and tumour necrosis factor-alpha (TNF-alpha) were found from day 4. The potency of these cytokines to induce adhesion molecules on podocytes was investigated on rat glomerular epithelial cells in vitro. By using FACS analysis and electron microscopical techniques, we found that the in vivo expression of MHC class I, II and ICAM-1 by podocytes could in vitro be simulated by IFN-gamma. IFN-alpha weakly induced MHC class I, while IL-1 beta and TNF-alpha were ineffective. We hypothesize that podocytes in this in vivo model are important to maintain the local inflammatory process in the glomerulus by expression of relevant adhesion molecules and MHC molecules upon stimulation with specific cytokines.

Thymocytes reacting with heterologous antibodies against GP 330 in autologous immune complex glomerulopathy (AICG) in the rat. The relation between susceptibility for AICG and anti-GP 330-binding thymocytes.

Autologous immune complex glomerulopathy (AICG) is induced by immunizing rats with a crude brushborder fraction of rat kidney tubules (Fx1A) or with the purified GP 330 antigen. In these animals, anti-brushborder antibodies develop, leading to subepithelial immune complexes along the glomerular capillary wall. In rats with AICG, thymocytes sensitized against Fx1A as well as thymocytes recognizing anti-Fx1A are present. These latter cells might play a role in the specific tolerance against the pathogenetic antigen GP 330. To substantiate this notion, immunofluorescence studies were performed in which the number of anti-GP 330 binding cells was quantified in thymus cell suspensions of rats with AICG, in control rats and in naive rats with different genetic background. It is shown that increased numbers of anti-GP 330-binding thymocytes in rats with AICG are associated with a decline in the serum anti-brushborder titer. Furthermore, it appears that the number of anti-GP 330-binding thymocytes in naive rats of the non-responder Brown Norway strain is significantly higher as compared to the PVG/c and Lewis strains, which are susceptible for AICG. The correlation between the numbers of anti-GP 330-binding thymocytes and the susceptibility for AICG suggests a role for these cells in maintaining the tolerance against the Fx1A (GP 330) antigen.

The specificity of nephritogenic antibodies. III. Binding of anti-Fx1A antibodies in glomeruli is dependent on dual specificity.

Rabbit antibodies against rat tubular brushborder antigens (Fx1A) give rise to in situ formation of immune aggregates along the glomerular capillary walls after intravenous injection into rats. These antibodies (anti-Fx1A), able to produce heterologous immune complex glomerulopathy (HIC) in the rat, have previously been shown to bind with brushborders (anti-BB) as well as with rat thymocytes (anti-T). In the present communication, this dual specificity was also demonstrated in antibodies eluted from kidneys of rats with HIC. It further appeared that, when the anti-thymocyte binding activity was selectively removed from these antibodies, using immunoabsorption with rat tissue extracts, these anti-Fx1A antibodies were no longer able to stain glomerular basement membranes (GBM) as demonstrated at the ultrastructural level using the peroxidase technique. Following perfusion of these antibodies in the normal rat kidney ex vivo, binding along the capillary walls was also below the detection level, in contrast to non anti-T depleted anti-Fx1A IgG. Biochemical analysis (including immunoblotting) showed that the anti-T moiety of anti-Fx1A was directed to a 90 kD component of Fx1A, since selective absorption of this specificity prevented staining of this 90 kD component. It is concluded, that this anti-T specificity within rabbit anti-Fx1A plays a crucial role in local immune complex formation in the rat kidney ex vivo. Whether this holds also for its role in the pathogenesis of HIC in vivo awaits further confirmation.

Loss of glomerular polyanion in vitro induced by mononuclear blood cells from patients with minimal-change nephrotic syndrome.

Peripheral mononuclear blood cells isolated from nephrotic subjects with minimal-change nephrotic syndrome (selective proteinuria greater than 3.5 g/24 h) or various other forms of glomerulonephritis (non-selective proteinuria greater than 3.5 g/24 h) were stimulated with concanavalin A and cultured for 20 h in the presence of kidney tissue under standard conditions. Identical cultures were developed with phosphate-buffered saline from normal control donors. Triplicate cultures of each subject (3 X 10(6) cells/ml) were incubated with or without 5, 10, or 20 micrograms/ml concanavalin A per milliliter serum-free tissue culture medium upon cryostat sections from normal rat kidney. The cells were subsequently removed, and the tissue sections were washed and stained for sialoprotein using the colloidal iron method and evaluated for stainability of glomerular polyanion using light microscopy. The results show that peripheral mononuclear blood cells from subjects with minimal-change nephrotic syndrome had affected glomerular polyanion in vitro during incubation with kidney tissue in a significantly (p less than or equal to 0.005) higher number of cases (15/17) as compared with the number of glomerulonephritis patients who scored positive in 4 out of 14 cases, whereas this was the case in 3 out of 18 cases of the normal donors. It is concluded that stimulated cellular immune reactivity of peripheral mononuclear blood cells from subjects with minimal-change nephrotic syndrome in vitro is associated with the potential impairment in vitro of an important part of the glomerular filtration barrier. Since this cellular activity occurred to a significant lesser extent in other nephrotic subjects, this response is not related to the nephrotic state per se.

The glomerular polyanion (GPA) of the rat kidney. III. Further characterization of a vaso-active serum factor which reduces GPA.

Fractions of normal rat serum were purified using gel chromatography and their molecular weights were analysed using gradient polyacrylamide gel electrophoresis (PAGE). The fractions were tested for their capacity to affect in vitro glomerular polyanion (GPA) in rat kidney tissue whereas their vascular enhancing capacity in vivo after intradermal injection into the rat skin was analysed. GPA impairment in vitro was estimated after incubation of the fractions with tissue sections for 2 h at 37 degrees C and subsequent staining for sialoproteins with colloidal iron. Enhanced vascular responses were assayed using a standard vascular permeability test in the rat skin. The results show that a factor with an estimated molecular weight of 120 000 was responsible for a dose-related activity in both test systems studied. The activity of this fraction could be inhibited by various plasma kallikrein-inhibiting protease inhibitors, whereas in addition the skin response could be inhibited by pyridinolcarbamate and not by histamine- or serotonin-inhibiting drugs. From the inhibition patterns in vivo and in vitro as well as from the estimated molecular weight of the fraction, it is suggested that a plasma kallikrein-like factor might be responsible for the activities observed. We feel that further study of this fraction in rat or human serum is worthwhile in particular with respect to nephrotic conditions associated with GPA loss.

The glomerular polyanion (GPA) of the rat kidney II. GPA loss in vitro by a vasoactive serum fraction.

Fractions from normal rat serum were prepared using gel filtration techniques and tested for their capacity to affect glomerular polyanion (GPA) of normal rat kidney tissue in vitro after incubation for 2 h and 37 degrees with cryostat kidney sections. Subsequently these sections, incubated with serum fractions or neuraminidase solutions, were rinsed with aquadest and stained for sialoprotein using the colloidal-iron method, and evaluated for their stainability of GPA using light microscopy. GPA stainability of these sections was compared with the stainability of GPA of kidney sections from nephrotic rats. The same serum fractions were also tested for their capacity to induce increased vascular permeability in the rat skin in vivo using a standard vascular permeability tests. The results show that a fraction with an estimated mol. wt between 50 and 100 kilodaltons did affect GPA in vitro in a dose-related manner, whereas this fraction also induced increased dose-related vascular skin responses after intradermal injection into rats in contrast to control fractions. Such a vasoactive serum fraction which is able to affect an important part of the glomerular filter barrier in vivo might play a role in conditions of increased glomerular permeability.

The glomerular polyanion (GPA) of the rat kidney. I. Concanavalin-A activated cells affect the glomerular polyanion in vitro.

Rat peritoneal exudate cells (PEC) or human peripheral blood cells stimulated with mitogens in vitro were cultured in tissue culture chambers mounted on rat or human cryostat kidney sections. After 20 h, the cultures were discontinued and the glomerular polyanion (GPA) of the glomeruli was studied using the colloidal iron stain. The results show that in contrast to PHA-stimulated cells, rat PEC or human blood cells stimulated with Con-A are able to reduce GPA stainability. It was further shown that rat PEC activated with Con-A for 20 or 48 h were able to suppress in vitro lymphocyte transformation of syngeneic blood lymphocytes in a co-culture system following mitogenic stimulation. In view of recent concepts according to which disturbance of T cell function is associated with in vivo loss of GPA in some forms of the nephrotic state, we conclude that investigation into the possible in vivo significance of the present observations is worthwhile.

The specificity of nephritogenic antibodies: I. Evidence on anti-T-cell specificity in nephritogenic antibodies detected by cytotoxicity and MIF assays.

Heterologous antibodies directed to brushborder antigens of rat kidney tubules are nephritogenic in that an immediate immune complex glomerulopathy occurs after injection ot these antibodies into normal rats. Since previous observations suggested the presence of anti-T-cell specificity within these antibodies, we now compared the specificities of these antibodies with those of heterologous anti-rat thymocyte antibodies, using immunofluorescence (IF), cytotoxicity and migration inhibition (MIF) assays. The results suggest that anti-brushborder anti-serum contains anti-thymocyte specificities, while antithymocyte antiserum contains anti-brushborder specificity. These specificities could be removed selectively from both of the antisera by absorption with insoluble tissue extracts containing the appropriate antigens, i.e. thymocyte antigens or brushborder antigens respectively, indicating that two specificities are involved rather than only cross-reacting antibodies. Since it is unlikely for several other reasons that this feature is simply the result of an immunologic cross-reaction due to antibodies raised by immunization with purified kidney tissue antigens, this dual specificity of anti-brushborder antibody might play a role in the pathogenesis of experimental glomerulopathy.