Organ culture mimics the effects of hypoxia on membrane potential, K(+) channels and vessel tone in pulmonary artery

BACKGROUND AND PURPOSE

Blood vessel culture is gaining interest for use with transfection-based techniques, but alters the contractile properties of the vessels. The present study tested the effects of culture on the intrinsic tone of rat pulmonary arteries (PAs) and examined the function and expression of K(+) channels regulating the resting membrane potential (E(m)) and tone of pulmonary artery smooth muscle cells (PASMCs).

EXPERIMENTAL APPROACH

Rat intrapulmonary arteries were isolated and cultured under standard and modified conditions. Contractile responses of fresh and cultured PA were compared using vessel myograph. Electrophysiology experiments on isolated PASMCs used the patch-clamp technique. K(+) channel expression was quantified using reverse transcription and real-time PCR.

KEY RESULTS

After 4 days in culture vessels contracted to phenylephrine, but relaxation to carbachol was significantly impaired. Contractile responses to 10 mM KCl, 4-aminopyridine and tetraethylammonium increased, and vessels developed an uncharacteristic relaxation response to Ca(2+)-free solution, nifedipine and levcromakalim. PASMCs from cultured vessels were depolarized and K(+) currents reduced, in association with down-regulation of K(v)1.5, K(v)2.1 and TWIK-related acid-sensitive K(+) channel-1 mRNA. These changes were partially reversed by increased oxygenation of the culture medium or removing the endothelium before culture.

CONCLUSIONS AND IMPLICATIONS

Culture of PA for 3-4 days induced loss of functional K(+) channels, depolarization of PASMCs, Ca(2+) influx, intrinsic tone and spontaneous constrictions, similar to the effects of chronic hypoxia. This limits the use of cultured vessels for studying excitation-contraction coupling, although oxygenating the culture medium and removing the endothelium can help to retain normal smooth muscle function.

σ2-Receptor Ligand-Mediated Inhibition of Inwardly Rectifying K+ Channels in the Heart

The sigma(2)-receptor agonist, ifenprodil, was suggested as an inhibitor of G protein-coupled inwardly rectifying potassium channels. Nevertheless, an analysis of the role of sigma(2) receptors in cardiac electrophysiology has never been done. This work aims i) to identify the roles of cardiac sigma(2) receptors in the regulation of cardiac K(+) channel conductances and ii) to check whether sigma(2)-receptor agonists exhibit class III antiarrhythmic properties. The sigma(2)-receptor agonists ifenprodil, threo-ifenprodil, LNP250A [threo-8-[1-(4-hydroxyphenyl)-1-hydroxy-propan-2-yl]-1-phenyl-1,3,8-triazaspiro[4,5]decane-4-one] (a derivative of ifenprodil devoid of alpha(1)-adrenergic and N-methyl-d-aspartate glutamate receptor-blocking properties), and 1,3-di(2-tolyl)guanidine were used to discriminate the effects linked to sigma(2) receptors from those of the sigma(1) subtype, induced by (+/-)-N-allylnormetazocine (SKF-10,047). The sigma(2)-receptor antagonist 3-alpha-tropanyl-2(pCl-phenoxy)butyrate (SM-21) was employed to characterize sigma(2)-mediated effects in patch-clamp experiments. In rabbits, all sigma(2)-receptor agonists reduced phenylephrine-induced cardiac arrhythmias. They prolonged action potential duration in rabbit Purkinje fibers and reduced human ether-a-go-go-related gene (HERG) K(+) currents. (+)-SKF-10,047 was completely inactive in the last two tests. The effects of threo-ifenprodil were not antagonized by SM-21. In HERG-transfected COS-7 cells, SM-21 potentiated the ifenprodil-induced blockade of the HERG current. These data suggest that sigma(2)-receptor ligands block I(Kr) and that this effect could explain part of the antiarrhythmic properties of this ligands family. Nevertheless, an interaction with HERG channels not involving sigma(2) receptors seems to share this pharmacological property. This work shows for the first time that particular caution has to be taken toward ligands with affinity for sigma(2) receptors. The repolarization prolongation and the early-afterdepolarization can be responsible for "torsades de pointe" and sudden cardiac death.

Influence of early neutrophil depletion on MMPs/TIMP-1 balance in bleomycin-induced lung fibrosis

Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix in interstitium resulting in respiratory failure associated with inflammation showing mainly neutrophil (PMN) recruitment. The turn over of extracellular matrix is partially regulated by proteases such as metalloproteinases (MMPs) and their inhibitors (TIMPs). We investigated the impact of PMN depletion on the MMP/TIMP-1 imbalance and the development of fibrosis in mice induced by bleomycin (0.3 mg/mouse). Administration of 200 microL of rabbit anti-mouse PMN antibody i.p. blunted the neutrophil influx detected in BAL and in whole blood one day after bleomycin administration. At day(14), hydroxyproline content was increased both in anti-PMN treated and control mice, without any difference between groups. At day one, bleomycin elicited a raise in pro-MMP-9 level in BAL that was significantly attenuated in anti-PMN depleted mice, whereas TIMP-1 and MMP-2 release were similar in both groups at day(1) and day(14). Higher RNA levels were observed in PMN-treated mice at day(1) for MMP-9 and MMP-2 and at day(14) for MMP-2 only. At day(14), bleomycin elicited a raise of TIMP-1 protein and RNA levels regardless of anti-PMN treatment, whereas MMP-9 returned to basal level. Bleomycin enhanced MMP-8 level in BAL at day(14) only for the control group. The amount of MMP-8 was more important in BAL from anti-PMN treated mice than in control mice at day(1) and day(14). PMN-depletion and the associated modifications in pro-MMP-9/TIMP-1 imbalance in lung during the early inflammatory phase do not alter susceptibility to bleomycin-induced pulmonary fibrosis.

TIMP-1 is a key factor of fibrogenic response to bleomycin in mouse lung

Pulmonary fibrosis is characterized by the excessive deposition of extracellular matrix in the interstitium, resulting in respiratory failure. The role of remodeling mediators such as metalloproteinases (MMPs) and their inhibitors (TIMPs) in the fibrogenic process remains misunderstood. We investigated MMP-9, MMP-2, TIMP-1, TIMP-2 and TIMP-3 in the fibrotic response to bleomycin of fibrosis prone C57BL/6J and fibrosis resistant BALB/c mice. Mice were administered with 0.1 mg bleomycin by intranasal administration. Either 24 h or 14 days after, the mice were anesthetized and underwent either bronchoalveolear lavage (BAL) or lung removal. Collagen deposition in lung tissue was determined by hydroxyproline measurement, MMP activity was analyzed by zymography, and other mediators were analyzed by ELISA. TIMP-1 was localized in lung sections by immunohistochemistry and real time PCR was performed to gene expression in lung. Non parametric Mann-Whitney and Spearman tests were used for statistical analysis. Fourteen days after bleomycin administration, hydroxyproline assay and histological study revealed that BALB/c mice developed significantly less fibrosis compared to C57BL/6J mice. At day 1, bleomycin enhanced TIMP-1, MMP-2 and MMP-9 protein levels in BALF, and induced corresponding genes in lung tissue of both strains. The rise of Timp-1, Mmp-9 and Mmp-2 gene levels were significantly stronger in lungs of C57BL/6J, whereas gelatinase activities of MMP-2 and MMP-9 were similar. Immunohistochemistry revealed that TIMP-1 macrophages and epithelial cells were prominent TIMP-1 producers in both strains. At day 14, neither MMP-2 nor MMP-9 levels exhibited strain-dependent protein level or gene expression, although TIMP-1 was strongly associated with fibrosis. Interestingly, bleomycin induced neither Timp-2 nor Timp-3 in lung tissue at any time of the study. The present study shows that early altered regulation of TIMP-1 following bleomycin administration may be involved in bleomycin-induced pulmonary fibrosis.

Macrophage metalloelastase (MMP-12) deficiency does not alter bleomycin-induced pulmonary fibrosis in mice

BACKGROUND

Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix in the interstitium resulting in respiratory failure. The role of remodeling mediators such as metalloproteinases (MMPs) and their inhibitors (TIMPs) in the fibrogenic process remains misunderstood. In particular, macrophage metalloelastase, also identified as MMP-12, is known to be involved in remodeling processes under pathological conditions. However, MMP-12 involvement in pulmonary fibrosis is unknown. Here we investigated fibrotic response to bleomycin in MMP-12 deficient mice.

MATERIALS AND METHODS

C57BL/6 mice, Balb/c mice and MMP-12 -/- mice with a C57BL/6 background received 0.3 mg bleomycin by intranasal administration. 14 days after, mice were anesthetized and underwent either bronchoalveolear lavage (BAL) or lung removal. Collagen deposition in lung tissue was determined by Sircoltrade mark collagen assay, MMP activity in BAL fluid was analyzed by zymography, and other mediators were quantified in BAL fluid by ELISA. Real time PCR was performed to assess gene expression in lung removed one or 14 days after bleomycin administration. Student t test or Mann & Whitney tests were used when appropriate for statistical analysis.

RESULTS

The development of pulmonary fibrosis in "fibrosis prone" (C57BL/6) mice was associated with prominent MMP-12 expression in lung, whereas MMP-12 expression was weak in lung tissue of "fibrosis resistant" (Balb/c) mice. MMP-12 mRNA was not detected in MMP-12 -/- mice, in conformity with their genotype. Bleomycin elicited macrophage accumulation in BAL of MMP-12 -/- and wild type (WT) mice, and MMP-12 deficiency had no significant effect on BAL cells composition. Collagen content of lung was increased similarly in MMP-12 -/- and WT mice 14 days after bleomycin administration. Bleomycin elicit a raise of TGF-beta protein, MMP-2 and TIMP-1 protein and mRNA in BAL fluids and lung respectively, and no significant difference was observed between MMP-12 -/- and WT mice considering those parameters.

CONCLUSION

The present study shows that MMP-12 deficiency has no significant effect on bleomycin-induced fibrosis.

Role of matrix metalloproteinases in the development of airway inflammation and remodeling

Matrix metalloproteinases (MMPs) are a major group of proteases known to regulate extracellular matrix (ECM) turnover and so they have been suggested to be important in the process of lung disease associated with tissue remodeling. This has led to the concept that modulation of airway remodeling including excessive proteolysis damage to the tissue may be of interest for future treatment. Within the MMP family, macrophage elastase (MMP-12) is able to degrade ECM components such as elastin and is involved in tissue remodeling processes in chronic obstructive pulmonary disease including emphysema. Pulmonary fibrosis has an aggressive course and is usually fatal within an average of 3 to 6 years after the onset of symptoms. Pulmonary fibrosis is associated with deposition of ECM components in the lung interstitium. The excessive airway remodeling as a result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of ECM components could justify anti-protease treatments. Indeed, the correlation of the differences in hydroxyproline levels in the lungs of bleomycin-treated mice strongly suggests that a reduced molar pro-MMP-9/TIMP-1 ratio in bronchoalveolar lavage fluid is associated with collagen deposition, beginning as early as the inflammatory events at day 1 after bleomycin administration. Finally, these observations emphasize that effective treatment of these disorders must be started early during the natural history of the disease, prior to the development of extensive lung destruction and fibrosis.

The absence of reactive oxygen species production protects mice against bleomycin-induced pulmonary fibrosis

Background

Reactive oxygen species and tissue remodeling regulators, such as metalloproteinases (MMPs) and their inhibitors (TIMPs), are thought to be involved in the development of pulmonary fibrosis. We investigated these factors in the fibrotic response to bleomycin of p47^phox -/- (KO) mice, deficient for ROS production through the NADPH-oxidase pathway.

Methods

Mice are administered by intranasal instillation of 0.1 mg bleomycin. Either 24 h or 14 days after, mice were anesthetized and underwent either bronchoalveolar lavage (BAL) or lung removal.

Results

BAL cells from bleomycin treated WT mice showed enhanced ROS production after PMA stimulation, whereas no change was observed with BAL cells from p47^phox -/- mice. At day 1, the bleomycin-induced acute inflammatory response (increased neutrophil count and MMP-9 activity in the BAL fluid) was strikingly greater in KO than wild-type (WT) mice, while IL-6 levels increased significantly more in the latter. Hydroxyproline assays in the lung tissue 14 days after bleomycin administration revealed the absence of collagen deposition in the lungs of the KO mice, which had significantly lower hydroxyproline levels than the WT mice. The MMP-9/TIMP-1 ratio did not change at day 1 after bleomycin administration in WT mice, but increased significantly in the KO mice. By day 14, the ratio fell significantly from baseline in both strains, but more in the WT than KO strains.

Conclusions

These results suggest that NADPH-oxidase-derived ROS are essential to the development of pulmonary fibrosis. The absence of collagen deposition in KO mice seems to be associated with an elevated MMP-9/TIMP-1 ratio in the lungs. This finding highlights the importance of metalloproteinases and protease/anti-protease imbalances in pulmonary fibrosis.

Creation versus destruction of T cell epitopes in the class II MHC pathway

Proteases perform two key roles in the class II MHC antigen processing pathway. They initiate removal of the invariant chain chaperone for class II MHC and they generate peptides from foreign and self proteins for eventual capture and display to T cells. How a balance is achieved between generation of suitable peptides versus their complete destruction in an aggressive proteolytic environment is not known. Nor is it known in most cases which proteases are actually involved in antigen processing. Our recent studies have identified asparagine endopeptidase (AEP or legumain) as an enzyme that contributes to both productive and destructive antigen processing in the class II MHC pathway. The emerging consensus seems to be that individual proteolytic enzymes make clear and non-redundant contributions to antigen processing.

Bm-CPI-2, a cystatin homolog secreted by the filarial parasite Brugia malayi, inhibits class II MHC-restricted antigen processing

While interference with the class I MHC pathway by pathogen-encoded gene products, especially those of viruses, has been well documented, few examples of specific interference with the MHC class II pathway have been reported. Potential targets for such interference are the proteases that remove the invariant chain chaperone and generate antigenic peptides. Indeed, recent studies indicate that immature dendritic cells express cystatin C to modulate cysteine protease activity and the expression of class II MHC molecules [1]. Here, we show that Bm-CPI-2, a recently discovered cystatin homolog produced by the filarial nematode parasite Brugia malayi (W. F. Gregory et al., submitted), inhibits multiple cysteine protease activities found in the endosomes/lysosomes of human B lymphocyte lines. CPI-2 blocked the hydrolysis of synthetic substrates favored by two different families of lysosomal cysteine proteases and blocked the in vitro processing of the tetanus toxin antigen by purified lysosome fractions. Moreover, CPI-2 substantially inhibited the presentation of selected T cell epitopes from tetanus toxin by living antigen-presenting cells. Our studies provide the first example of a product from a eukaryotic parasite that can directly interfere with antigen presentation, which, in turn, may suggest how filarial parasites might inactivate the host immune response to a helminth invader.

Changing heat and moisture exchangers every 48 hours does not increase the incidence of nosocomial pneumonia

This prospective study was conducted to evaluate the risk of nosocomial pneumonia when changing heat and moisture exchangers every 48 hours in 1996 instead of every 24 hours in 1995 for patients needing continuous mechanical ventilation. Medical and surgical patients in the two periods did not differ in terms of demographic characteristics and markers of acute or underlying illnesses. The incidence density of nosocomial pneumonia was not different in the two groups. Extended heat and moisture exchanger use reduces circuit manipulation and cost.

An asparaginyl endopeptidase processes a microbial antigen for class II MHC presentation

Foreign protein antigens must be broken down within endosomes or lysosomes to generate suitable peptides that will form complexes with class II major histocompatibility complex molecules for presentation to T cells. However, it is not known which proteases are required for antigen processing. To investigate this, we exposed a domain of the microbial tetanus toxin antigen (TTCF) to disrupted lysosomes that had been purified from a human B-cell line. Here we show that the dominant processing activity is not one of the known lysosomal cathepsins, which are generally believed to be the principal enzymes involved in antigen processing, but is instead an asparagine-specific cysteine endopeptidase. This enzyme seems similar or identical to a mammalian homologue of the legumain/haemoglobinase asparaginyl endopeptidases found originally in plants and parasites. We designed competitive peptide inhibitors of B-cell asparaginyl endopeptidase (AEP) that specifically block its proteolytic activity and inhibit processing of TTCF in vitro. In vivo, these inhibitors slow TTCF presentation to T cells, whereas preprocessing of TTCF with AEP accelerates its presentation, indicating that this enzyme performs a key step in TTCF processing. We also show that N-glycosylation of asparagine residues blocks AEP action in vitro. This indicates that N-glycosylation could eliminate sites of processing by AEP in mammalian proteins, allowing preferential processing of microbial antigens.

Modulation by epitope-specific antibodies of class II MHC-restricted presentation of the tetanus toxin antigen

Above a certain affinity the dissociation rate of monovalent antigen from antibody becomes slower than the time taken for antigen capture, endocytosis and processing by professional antigen presenting cells. Thus, when high affinity antibodies drive antigen uptake, either directly via B-cell membrane immunoglobulin or indirectly via Fc receptors, the substrate for processing may frequently be an antigen/antibody complex. Here we review studies using the tetanus toxin antigen which show that bound antibodies can dramatically affect proteolytic processing, dependent on the epitope specificity and multiplicity of antibodies bound. Certain antibodies protect or 'footprint' specific domains of the antigen during processing in B-cell clones resulting in modulation of loading of class II MHC-restricted T-cell epitopes. Processing and class II MHC loading of some T-cell epitopes within the footprinted region was hindered, as might be expected, but, surprisingly, presentation of other T-cell epitopes was boosted considerably. These studies show that protein/protein complexes can be processed in an unpredictable fashion by antigen presenting cells and indicate a possible mechanism whereby cryptic T-cell epitopes might be revealed in autoimmune disease.

T cell-targeted immunotherapy in murine collagen-induced arthritis

Counteracting the effect of autoimmunity can be achieved by elimination or inactivation of autoreactive T cells. We have focused on two approaches targeting on autoaggressive T cells in the model of collagen-induced arthritis (CIA) in mice. First, type II collagen (CII) primed DBA/1 mice were treated with various monoclonal antibodies (mAb) specific for the beta chains of the T cell receptor (TCR) using a protocol resulting in a long-term elimination of the target T cells. Indeed, CIA could be suppressed by injection of anti-V beta 8.1, 2 mAb and down-regulated by that of anti-V beta 2 and/or anti-V beta 5, presumably by deleting pathogenic T cell clones. In contrast, treatment with either anti-V beta 6 or anti-V beta 11 mAb did not alter CIA. Second, we generated CII-specific T cell hybrid clones that recognize the antigenic peptides in association with Kq and IA(q) molecules respectively for CD8+ and CD4+ cells. Vaccination with the irradiated hybrid clones, 3 weeks prior to immunization, was effective in preventing the development of arthritis. Furthermore, this suppression was antigen and disease specific. Most importantly, one CD8+ clone could reverse the ongoing disease. These new therapeutic approaches derived from animal models may offer a hope of more selective interventions for the treatment of human autoimmune diseases.

T cell regulation of collagen-induced arthritis in mice. II. Immunomodulation of arthritis by cytotoxic T cell hybridomas specific for type II collagen

Injection of native type II collagen (CII) to susceptible strains of mice (H-2q) induces a rheumatoid arthritis-like disease. To study the role of CD8+ T cells in the collagen-induced arthritis (CIA), we generated CII-specific T cell hybridomas by fusion of cells from arthritic C3H. Q mice and an AKR thymoma. Two hybrid clones (P3G8 and P2D9) were selected for their ability to lyse syngeneic CII-pulsed macrophages and recognize different antigenic epitopes in association with Kq molecules. When these T cell clones were irradiated and inoculated into (C3H.Q x AKR)F1 mice 21 days prior to priming with native CII/complete Freund's adjuvant, the incidence and the duration of CIA were significantly reduced in comparison to groups receiving saline or control T cell hybridoma. Furthermore, both anti-CII T cell hybridomas were able to attenuate CIA in highly susceptible inbred strains of mice and this suppression was antigen and disease specific. The protective activity seems to require intact cells as neither membrane fractions nor cytosolic preparations of the hybridoma T cells retained the vaccinating activity. Most importantly, one of the hybrid clones (P3G8) had a therapeutic effect on CIA since its administration to arthritic DBA/1 mice on day 30 after priming down-regulated the ongoing disease. Taken together, these findings suggest that anti-CII cytotoxic T cell clones can vaccinate against CIA and even reverse the disease.

[Laboratory contributions in systemic Candida albicans infections]

The authors have studied Candida albicans' serologies for seven patients in an intensive care unit. The comparison with the clinical evolution and results' laboratory displays an discordance for two cases. For these patients with many risk's factors, the observation of serology seems interesting on a prolonged period.

[Torulopsis glabrata septicemia: apropos of a case]

A 74 year's old patient with cancer of oesophagus has been operated. An atelectasis occurred just after surgery, then a septic shock with a septicaemia. Blood cultures were positive with Torulopsis glabrata. Amphotericin B and flucytosine, followed by flucytosine and miconazole cured septicaemia. These septicaemia happen often to diabetics patients, to patients with malignant tumours, or after wide spectrum antibiotics or during prolonged parenteral nutrition or after surgery.

[Heart conduction disorders in acute maprotiline poisoning]

A case is reported of self-poisoning with maprotiline followed by prolonged disorders of intraventricular conduction. The cardiotoxicity of tetracyclic antidepressants was well established, but few cases were reported. Maprotiline pharmacokinetics explained the duration of the cardiovascular side-effects. The severity of maprotiline overdoses should not be underestimated.