Angiotensin II antagonism fails to ameliorate bleomycin-induced pulmonary fibrosis in mice

Based on current evidence, transforming growth factor (TGF)-beta plays a central pathogenic role in the development of pulmonary fibrosis. There is growing evidence that angiotensin II can serve as a stimulus for TGF-beta-mediated lung fibrosis. However, the role of angiotensin II in the pathobiology of pulmonary fibrosis in vivo remains unclear and the therapeutic potential for targeting angiotensin II in a bleomycin-induced pulmonary fibrosis model is not well known. Therefore, the aim of this study was to test whether the angiotensin II antagonist, losartan, attenuated the development of bleomycin-induced pulmonary fibrosis in two distinct murine strains, C57/BL6 and Sv129. This was determined by histopathology and quantification of collagen content by hydroxyproline assay. Despite demonstrable angiotensin II antagonism in vivo and a reduction in measures of acute lung injury, losartan therapy, at a dose shown to reduce renal and cardiac fibrosis in mice, failed to significantly ameliorate bleomycin-induced pulmonary fibrosis. In conclusion, these data suggest that the pulmonary fibrotic disease process in vivo is not solely dependent on angiotensin II activity and the potential for angiotensin II receptor blockers as a therapeutic strategy in patients with pulmonary fibrosis may be limited.

Characterization of Pneumocystis carinii PHR1, a pH-regulated gene important for cell wall Integrity

Pneumocystis carinii remains an important opportunistic fungal pathogen causing life-threatening pneumonia in patients with AIDS and malignancy. Currently, little is known about how the organism adapts to environmental stresses and maintains its cellular integrity. We recently discovered an open reading frame approximately 600 bp downstream of the region coding GSC-1, a gene mediating beta-glucan cell wall synthesis in P. carinii. The predicted amino acid sequence of this new gene, termed P. carinii PHR1, exhibited 38% homology to Saccharomyces cerevisiae GAS1, a glycosylphosphatidylinositol-anchored protein essential to maintaining cell wall integrity, and 37% homology to Candida albicans PHR1/PHR2, pH-responsive genes encoding proteins recently implicated in cross-linking beta-1,3- and beta-1,6-glucans. In view of its homology to these related fungal genes, the pH-dependent expression of P. carinii PHR1 was examined. As in C. albicans, P. carinii PHR1 expression was repressed under acidic conditions but induced at neutral and more alkaline pH. PHR1-related proteins have been implicated in glucan cell wall stability under various environmental conditions. Although difficulties with P. carinii culture and transformation have traditionally limited assessment of gene function in the organism itself, we have successfully used heterologous expression of P. carinii genes in related fungi to address functional correlates of P. carinii-encoded proteins. Therefore, the potential role of P. carinii PHR1 in cell wall integrity was examined by assessing its ability to rescue an S. cerevisiae gas1 mutant with absent endogenous Phr1p-like activity. Interestingly, P. carinii PHR1 DNA successfully restored proliferation of S. cerevisiae gas1 mutants under lethal conditions of cell wall stress. These results indicate that P. carinii PHR1 encodes a protein responsive to environmental pH and capable of mediating fungal cell wall integrity.

Vitronectin and fibronectin function as glucan binding proteins augmenting macrophage responses to Pneumocystis carinii

beta-glucans represent major structural components of fungal cell walls. We recently reported that Pneumocystis carinii beta-glucans stimulate alveolar macrophages to release proinflammatory cytokines. Macrophage activation by beta-glucan is augmented by serum, implying the presence of circulating factors that interact with beta-glucans and enhance their ability to stimulate macrophages. Using beta-glucan-enriched cell wall fractions from P. carinii and Saccharomyces cerevisiae, two prominent proteins were precipitated from serum and demonstrated to be vitronectin (VN) and fibronectin (FN) by immune analysis. Preincubation of beta-glucan with VN or FN enhanced macrophage activation in response to this cell wall component. Because VN and FN accumulate in the lungs during P. carinii pneumonia, we further investigated hepatic and pulmonary expression of VN and FN messenger RNA during infection. P. carinii pneumonia in rodents is associated with increased hepatic expression of VN and FN as well as increased local expression of FN in the lung. Because interleukin (IL)-6 represents the major regulator of VN and FN expression during inflammatory conditions, we measured macrophage IL-6 release in response to stimulation with P. carinii beta-glucan. Stimulation of macrophages with P. carinii beta-glucan induced significant release of IL-6. Elevated concentrations of IL-6 were noted in the blood of infected animals compared with uninfected control animals. These studies indicate that VN and FN bind to beta-glucan components of P. carinii and augment macrophage inflammatory responses. P. carinii cell wall beta-glucan stimulates secretion of IL-6 by macrophages, thereby enhancing hepatic synthesis of both VN and FN, and lung synthesis of FN during pneumonia.

Direct detection of Legionella species from bronchoalveolar lavage and open lung biopsy specimens: comparison of LightCycler PCR, in situ hybridization, direct fluorescence antigen detection, and culture

We developed a rapid thermocycling, real-time detection (also known as real-time PCR) method for the detection of Legionella species directly from clinical specimens. This method uses the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and requires approximately 1 to 2 h to perform. Both a Legionella genus PCR assay and Legionella pneumophila species-specific PCR assay were designed. A total of 43 archived specimens from 35 patients were evaluated, including 19 bronchoalveolar lavage (BAL) specimens and 24 formalin-fixed, paraffin-embedded open lung biopsy specimens. Twenty-five of the specimens were culture-positive for Legionella (9 BAL specimens and 16 tissue specimens). BAL specimens were tested by LightCycler PCR (LC-PCR) methods and by a direct fluorescent antibody (DFA) assay, which detects L. pneumophila serogroups 1 to 6 and several other Legionella species. Tissue sections were tested by the two LC-PCR methods, by DFA, by an in situ hybridization (ISH) assay, specifically designed to detect L. pneumophila, and by Warthin-Starry (WS) staining. The results were compared to the "gold standard" method of bacterial culture. With BAL specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by Legionella genus LC-PCR, 100 and 100%; Legionella genus detection by DFA assay, 33 and 100%; and L. pneumophila detection by L. pneumophila species-specific LC-PCR, 100 and 100%. With open lung biopsy specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by LC-PCR 68.8 and 100%; Legionella genus detection by DFA assay, 44 and 100%; Legionella genus detection by WS staining, 63 and 100%; L. pneumophila species-specific detection by LC-PCR, 17 and 100%; and L. pneumophila species-specific detection by ISH, 100 and 100%. The analytical sensitivity of both LC-PCR assays was <10 CFU/reaction. LC-PCR is a reliable method for the direct detection of Legionella species from BAL specimens. The Legionella genus LC-PCR assay could be performed initially; if positive, L. pneumophila species-specific LC-PCR could then be performed (if species differentiation is desired). The speed with which the LC-PCR procedure can be performed offers significant advantages over both culture-based methods and conventional PCR techniques. In contrast, for the methods evaluated, culture was the best for detecting multiple Legionella species in lung tissue. WS staining, Legionella genus LC-PCR, and L. pneumophila species-specific ISH were useful as rapid tests with lung tissue.

Carbohydrate recognition domain of surfactant protein D mediates interactions with Pneumocystis carinii glycoprotein A

Pneumocystis carinii continues to cause severe pneumonia in immunocompromised patients. Surfactant protein D (SP-D), a lung collectin, markedly accumulates during P. carinii pneumonia and binds to glycoprotein A (gpA) on the surface of P. carinii, thereby enhancing interactions with alveolar macrophages. Herein, we report the structural basis of the interaction of SP-D with gpA. We demonstrate that natural SP-D binds to purified gpA in the presence of 2 mM calcium in a saturable, concentration-dependent manner, which is abolished by 10 mM ethylenediaminetetraacetic acid. Increasing concentrations of calcium under otherwise cation-free conditions significantly enhance SP-D binding to gpA, whereas manganese and magnesium cations have minimal effect. Maximal SP-D binding occurs at pH 7.4, with significant inhibition at pH 4. SP-D binding to gpA is also competitively inhibited by maltose>glucose>mannose>N-acetyl-glucosamine. Comparison of the binding of various natural and recombinant forms of SP-D to gpA reveals that the number of carbohydrate recognition domains (CRDs) in a given SP-D form determines the relative extent of binding to gpA. Maximal binding is observed with natural SP-D (dodecamers and higher order SP-D complexes) followed by recombinant dodecamers. In contrast, recombinant full-length trimers exhibit substantially less binding, which is similar to that observed with a recombinant truncated molecule consisting of the CRD and neck regions, and containing trimers of this portion of the molecule. Taken together, these findings strongly indicate that the CRD of SP-D mediates interaction with P. carinii gpA through its attached oligosaccharides and that the extent of SP-D binding to P. carinii is greatest with dodecamers and higher order forms of SP-D.

Differential regulation of growth and checkpoint control mediated by a Cdc25 mitotic phosphatase from Pneumocystis carinii

Pneumocystis carinii is an opportunistic fungal pathogen phylogenetically related to the fission yeast Schizosaccharomyces pombe. P. carinii causes severe pneumonia in immunocompromised patients with AIDS and malignancies. Although the life cycle of P. carinii remains poorly characterized, morphologic studies of infected lung tissue indicate that P. carinii alternates between numerous small trophic forms and fewer large cystic forms. To understand further the molecular mechanisms that regulate progression of the cell cycle of P. carinii, we have sought to identify and characterize genes in P. carinii that are important regulators of eukaryotic cell cycle progression. In this study, we have isolated a cDNA from P. carinii that exhibits significant homology, but unique functional characteristics, to the mitotic phosphatase Cdc25 found in S. pombe. P. carinii Cdc25 was shown to rescue growth of the temperature-sensitive S. pombe cdc25-22 strain and thus provides an additional tool to investigate the unique P. carinii life cycle. Although P. carinii Cdc25 could also restore the DNA damage checkpoint in cdc25-22 cells, it was unable to restore fully the DNA replication checkpoint. The dissociation of checkpoint control at the level of Cdc25 indicates that Cdc25 may be under distinct regulatory control in mediating checkpoint signaling.

Cell wall assembly by Pneumocystis carinii. Evidence for a unique gsc-1 subunit mediating beta -1,3-glucan deposition

Pneumocystis carinii remains a persistent cause of severe pneumonia in immune compromised patients. Recent studies indicate that P. carinii is a fungal species possessing a glucan-rich cyst wall. Pneumocandin antagonists of beta-1,3-glucan synthesis rapidly suppress infection in animal models of P. carinii pneumonia. We, therefore, sought to define the molecular mechanisms of beta-glucan cell wall assembly by P. carinii. Membrane extracts derived from freshly purified P. carinii incorporate uridine 5'-diphosphoglucose into insoluble carbohydrate, in a manner that was completely inhibited by the pneumocandin L733-560, an antagonist of Gsc-1-type beta-glucan synthetases. Using degenerative polymerase chain reaction and library screening, the P. carinii Gsc-1 catalytic subunit of beta-1,3-glucan synthetase was cloned and characterized. P. carinii gsc1 exhibited homology to phylogenetically related fungal beta-1,3-glucan synthetases, encoding a predicted 214-kDa integral membrane protein with 12 transmembrane domain structure. Immunoprecipitation of P. carinii extracts, with a synthetic peptide anti-Gsc-1 antibody, specifically yielded a protein of 219.4 kDa, which was also capable of incorporating 5'-diphosphoglucose into insoluble glucan carbohydrate. As opposed to other fungi, the expression of gsc-1 mRNA is uniquely regulated over P. carinii's life cycle, having minimal expression in trophic forms, but substantial expression in the thick-walled cystic form of the organism. These results indicate that P. carinii contains a unique catalytic subunit of beta-1,3-glucan synthetase utilized in cyst wall formation. Because synthesis of beta-1,3-glucan is absent in mammalian cells, inhibition of the P. carinii Gsc-1 represents an attractive molecular target for therapeutic exploitation.

Mechanisms of defence in the lung: lessons from Pneumocystis carinii pneumonia

Pneumocystis carinii continues to represent an important complication of individuals with compromised immunity. P. carinii interacts with immune and non-immune cells in the lung and mediates lung injury through a variety of mechanisms. CD4+ T lymphocytes are the cornerstone in defence against P. carinii. Recent studies indicate that alveolar macrophages provide essential functions that significantly enhance clearance of P. carinii infection. P. carinii also attaches to alveolar epithelial cells, causing inhibition of epithelial growth and replication. In addition to cellular interactions, P. carinii organisms bind to a variety of host adhesive proteins present in the lower respiratory tract. Binding of these proteins to P. carinii modulates host cell recognition and immune responses to the parasite. During the course of P. carinii pneumonia, several inflammatory mediators are produced in the lung. Although necessary for control of infection, exuberant inflammatory responses also predispose the host to the development of acute lung injury. Thus, host defences against P. carinii depend on complex interactions between immune and non-immune cells as well as several mediators that facilitate host recognition and eventual elimination of infection. Understanding these complex processes may enable development of novel therapeutic approaches for management of this important infection.

Pneumocystis carinii uses a functional cdc13 B-type cyclin complex during its life cycle

Pneumocystis carinii causes severe pneumonia in immunocompromised patients. Recent studies indicate that P. carinii uses a Cdc2 cyclin-dependent kinase to control its proliferation. To further study the regulation of the life cycle of P. carinii, we characterized the P. carinii B-type cyclin termed Cdc13, whose binding to Cdc2 is necessary for kinase activity. Antibodies to B-type cyclins (Cdc13) specifically immunoprecipitated Cdc2/ Cdc13 complexes with associated kinase activity from P. carinii extracts. To clone P. carinii cdc13, degenerate polymerase chain reaction was undertaken using primers generated from amino-acid motifs conserved in fungal Cdc13 proteins. This amplicon was used to obtain full-length genomic and complementary DNA (cDNA) clones. A specific synthetic peptide antibody generated to P. carinii Cdc13 further demonstrated differential Cdc2/Cdc13 activity over the life cycle of P. carinii, with greater activity in cysts compared with trophic forms of the organism. Finally, P. carinii cdc13 cDNA was used to rescue mutant Schizosaccharomyces pombe strains containing temperature-sensitive deficiencies of endogenous Cdc13 activity, thus verifying function of the P. carinii Cdc13 protein. Therefore, P. carinii contains a Cdc13 cyclin, which is variably active over its life cycle and which promotes fungal proliferation.

Isolated Pneumocystis carinii cell wall glucan provokes lower respiratory tract inflammatory responses

Macrophage-induced lung inflammation contributes substantially to respiratory failure during Pneumocystis carinii pneumonia. We isolated a P. carinii cell wall fraction rich in glucan carbohydrate, which potently induces TNF-alpha and macrophage-inflammatory protein-2 generation from alveolar macrophages. Instillation of this purified P. carinii carbohydrate cell wall fraction into healthy rodents is accompanied by substantial increases in whole lung TNF-alpha generation and is associated with neutrophilic infiltration of the lungs. Digestion of the P. carinii cell wall isolate with zymolyase, a preparation containing predominantly beta-1,3 glucanase, substantially reduces the ability of this P. carinii cell wall fraction to activate alveolar macrophages, thus suggesting that beta-glucan components of the P. carinii cell wall largely mediate TNF-alpha release. Furthermore, the soluble carbohydrate beta-glucan receptor antagonists laminariheptaose and laminarin also substantially reduce the ability of the P. carinii cell wall isolate to stimulate macrophage-inflammatory activation. In contrast, soluble alpha-mannan, a preparation that antagonizes macrophage mannose receptors, had minimal effect on TNF-alpha release induced by the P. carinii cell wall fraction. P. carinii beta-glucan-induced TNF-alpha release from alveolar macrophages was also inhibited by both dexamethasone and pentoxifylline, two pharmacological agents with potential activity in controlling P. carinii-induced lung inflammation. These data demonstrate that P. carinii beta-glucan cell wall components can directly stimulate alveolar macrophages to release proinflammatory cytokines mainly through interaction with cognate beta-glucan receptors on the phagocyte.

Analysis of Pneumocystis carinii introns

Pneumocystis carinii is an ascomycete phylogenetically related to Schizosaccharomyces pombe. Little is known about gene regulation in P. carinii. The removal of introns from pre-mRNA requires spliceosomal recognition of the intron-exon boundary. In S. pombe and higher eukaryotes, this boundary and a branch site within the intron are conserved. We recently demonstrated that P. carinii cdc2 cDNA can complement S. pombe containing conditional mutations of cdc2, an essential gene involved in cell cycle regulation. We next tested whether P. carinii genomic cdc2 (with six introns) could also complement S. pombe cdc2 mutants and found genomic sequences incapable of this activity. Reverse transcriptase PCR confirmed the inability of the S. pombe cdc2 mutants to splice the P. carinii genomic cdc2. Analysis of 83 introns from 19 P. carinii protein-encoding genes demonstrated that the sequence GTWWDW functions as a donor consensus in P. carinii, whereas YAG serves as an acceptor consensus. These sequences are similar in S. pombe; however, a branch site sequence was not found in the P. carinii genes studied.

Stretch induces cytokine release by alveolar epithelial cells in vitro

Mechanical ventilation can injure the lung, causing edema and alveolar inflammation. Interleukin-8 (IL-8) plays an important role in this inflammatory response. We postulated that cyclic cell stretch upregulates the production and release of IL-8 by human alveolar epithelium in the absence of structural cell damage or paracrine stimulation. To test this hypothesis, alveolar epithelial cells (A549 cells) were cultured on a deformable silicoelastic membrane. When stretched by 30% for up to 48 h, the cells released 49 +/- 34% more IL-8 (P < 0.001) than static controls. Smaller deformations (20% stretch) produced no consistent increase in IL-8. Stretch of 4 h duration increased IL-8 gene transcription fourfold above baseline. Stretch had no effect on cell proliferation, cell viability as assessed by (51)Cr release assay, or the release of granulocyte-macrophage colony-stimulating factor and tumor necrosis factor-alpha. We conclude that deformation per se can trigger inflammatory signaling and that alveolar epithelial cells may be active participants in the alveolitis associated with ventilator-induced lung injury.

Constrictive pericarditis and pleuropulmonary disease linked to ergot dopamine agonist therapy (cabergoline) for Parkinson's disease

Cabergoline is one of several ergoline dopamine agonist medications used in the treatment of Parkinson's disease (PD). We diagnosed constrictive pericarditis (CP) in a patient with PD receiving cabergoline therapy (10 mg daily), who had symptoms and signs of congestive heart failure (CHF). In the absence of previous reported cases of this condition linked to ergoline drugs, cabergoline was not initially identified as the cause. Shortly thereafter, however, the patient developed of a severe pleuropulmonary inflammatory-fibrotic syndrome, a recognized complication of ergoline medications, thus suggesting a common pathogenesis due to cabergoline therapy. To our knowledge, this is the first case in the English literature, although we speculate that CP may be more common than reported among patients with PD who are treated with an ergoline drug (cabergoline, bromocriptine, pergolide, or lisuride). The diagnosis of CP is difficult and requires a high level of suspicion; symptoms may masquerade as CHF due to common mechanisms such as coronary artery disease. In patients with PD who are taking not only cabergoline but also one of the other ergoline drugs, CP should be suspected if symptoms of CHF develop.

Laboratory diagnosis of Pneumocystis carinii infections by PCR directed to genes encoding for mitochondrial 5S and 28S ribosomal RNA

PCR with 5S mitochondrial ribosomal RNA (5S) target is a sensitive and specific assay for the detection of Pneumocystis carinii in clinical specimens from the respiratory tract. We developed an oligonucleotide probe directed to a 200 bp amplicon generated by fungal-specific universal primers that anneals with sequences specific for P. carinii in the 28S ribosomal RNA gene (28S). Of 50 archived bronchoalveolar lavage 1(BAL) specimens, 46 of 50 samples (92% agreement) gave the same result (23 positive, 23 negative) by PCR directed to the 5S and 28S assays. Results of calcofluor white staining of BAL smears on slides indicated agreement with the molecular results in 43 of 46 (93.5%) assays. PCR detection of P. carinii by amplification of 28S ribosomal gene target by fungal-specific primers and an organism-specific probe provides an alternate genomic target for the laboratory diagnosis of this organism.

Alveolar macrophage and glycoprotein responses to Pneumocystis carinii

Pneumocystis carinii continues to represent an important complication of immunosuppression in patients with acquired immune deficiency syndrome, hematological and solid malignancies, organ transplantation, and during corticosteroid and cytotoxic therapy for inflammatory disorders. Although host defenses against this organism center around CD4 lymphocytic function, additional immune mediators in the alveolar spaces contribute substantially to host recognition and elimination of P. carinii. In particular, this review considers the interactions of P. carinii with alveolar macrophages, adhesive glycoproteins including vitronectin and fibronectin, and surfactant lipids and protein components. Recent studies indicate that alveolar macrophages contribute significantly to host responses against this organism by mediating uptake and degradation of P. carinii, and by releasing inflammatory mediators including reactive oxidants, eicosanoids, and the potent proinflammatory cytokine tumor necrosis factor-alpha. Furthermore, the interactions of P. carinii with multiple adhesive proteins and with surfactant components additionally modulate the interactions of P. carinii with macrophages and enhance host recognition of this pathogen. These non-lymphocytic mediators represent additional important mechanisms of host recognition and response to P. carinii infection.

Pneumocystis pneumonia: clinical presentation and diagnosis in patients with and without acquired immune deficiency syndrome

Pneumocystis carinii causes severe pneumonia in immunocompromised hosts. Although this most commonly occurs in patients with the acquired immunodeficiency syndrome (AIDS), other groups of immunocompromised patients without AIDS are also at risk for P. carinii pneumonia. These patients have solid or hematologic malignancies, organ transplantation, or inflammatory conditions requiring chronic immunosuppressive drugs, particularly corticosteroids. There are important differences in the clinical presentation of P. carinii pneumonia in patients with and without AIDS. P. carinii causes an acute fulminate pneumonia in patients without AIDS while patients with AIDS have more insidious involvement. The organism burden and lung inflammatory response are markedly different between these groups, contributing to substantial differences in clinical presentation, outcome, and mortality. The diagnosis of P. carinii pneumonia remains challenging for primary care physicians and specialists alike. The specific diagnosis of P. carinii pneumonia requires demonstration of the organism from a clinically relevant source, such as sputum, bronchoalveolar lavage fluid, or lung tissue. Alternative methods to diagnose P. carinii pneumonia are currently investigational and are an active area of research. The rapid and specific diagnosis of P. carinii pneumonia allows institution of specific treatment and improvement in patient outcome.

Characterization of a mitogen-activated protein kinase from Pneumocystis carinii

The pathogenic fungus Pneumocystis carinii causes severe pneumonia in patients with impaired immunity, particularly patients with acquired immunodeficiency syndrome. The life cycle of P. carinii is poorly understood, and the inability to continuously culture P. carinii is a major limitation in understanding its cell biology. In fungi homologous to P. carinii, pheromone mating factors signal through a mitogen-activated protein kinase (MAPK) signal transduction cascade, resulting in mitotic cell cycle arrest and entry into a pathway of conjugation, cellular differentiation, and proliferation. Using degenerate PCR and library screening, we have identified a MAPK cDNA in P. carinii that is highly homologous to fungal MAPKs involved in the pheromone mating signal transduction cascade, and we demonstrate MAPK activity in P. carinii lysates with a specific antiserum derived from the translated P. carinii MAPK cDNA sequence.

Recognition of Pneumocystis carinii antigen on its surface by immunohistochemistry and immunoelectron microscopy

The aim of this study was to detect the surface antigens in different stages of experimental induced Pneumocystis carinii in Sprague-Dawley rats. Immunohistochemical staining with monoclonal (900, 902 and 904) and polyclonal (SP-D) antibodies demonstrated that the P. carinii organisms were mostly in the alveolar lumina. The binding sites of the monoclonal (900, 902 and 904) and polyclonal (SP-D) antibodies developed against P. carinii were examined at the ultrastructural level by using a post-embedding immunogold labeling. The gold particles were observed evenly on the surface of precyst and cyst stages of the P. carinii. In the trophozoite stage, scattered gold particles were seen on the pellicles and tubular expansions. The monoclonal antibodies reacted mainly with pellicles of P. carinii, whereas SP-D labeled pellicles, intracystic bodies, cytoplasms of alveolar macrophages, free floating surfactant material in the alveolar spaces, and adjacent type II epithelial cells. In the immunogold labeling, basically no significant differences were found in the precyst, cyst, and ruptured cyst stages. These results indicate that the gold particles were observed adhering to every stage of P. carinii, mostly concentrated on the pellicles, and more concentrated in the precyst or cyst stage than trophozoite stage which may be due to an increase in antigen accumulation during development from the trophozoite to the cyst.

Pneumocystis carinii contains a functional cell-division-cycle Cdc2 homologue

Pneumocystis carinii causes life-threatening pneumonia in immunocompromised patients. The inability to culture P. carinii has hampered basic investigations of the organism's life cycle, limiting the development of new therapies directed against it. Recent investigations indicate that P. carinii is a fungus phylogenetically related to other ascomycetes such as Schizosaccharomyces pombe. The cell cycles of S. pombe and homologous fungi are carefully regulated by cell-division-cycle molecules (cdc), particularly cell-division-cycle 2 (Cdc2), a serine-threonine kinase with essential activity at the G1 restriction point and for entry into mitosis. Antibodies to the proline-serine-threonine-alanine-isoleucine-arginine (PSTAIR) amino-acid sequence conserved in Cdc2 proteins specifically precipitated, from P. carinii extracts, a molecule with kinase activity consistent with a Cdc2-like protein. Cdc2 molecules exhibit differential activity throughout the life cycle of the organisms in which they occur. In accord with this, the P. carinii Cdc2 showed greater specific activity in P. carinii trophic forms (trophozoites) than in spore-case forms (cysts). In addition, complete genomic and complementary DNA (cDNA) sequences of P. carinii Cdc2 were cloned and found to be most closely homologus to the corresponding sequences of other pathogenic fungi. The function of P. carinii cdc2 cDNA was further documented through its ability to complement the DNA of mutant strains of S. pombe with temperature-sensitive deficiencies in Cdc2 activity. The P. carinii cdc2 cDNA restored normal Cdc2 function in these mutant strains of S. pombe, and promoted fungal proliferation. These studies represent the first molecular analysis of the cell-cycle-regulatory machinery in P. carinii. Further understanding of P. carinii's life cycle promises novel insights for preventing and treating the intractable infection it causes in immunocompromised patients.

Pneumocystis carinii inhibits cyclin-dependent kinase activity in lung epithelial cells

Pneumocystis carinii remains an important cause of pneumonia in patients with AIDS. Attachment of the organism to epithelial cells is a central event in establishing infection, impairing the growth potential of lung epithelial cells and thereby slowing repair. In light of investigations documenting a central role for cyclin-dependent kinases in controlling the cell cycle, we addressed the hypothesis that P. carinii inhibits epithelial cell growth by interfering with host epithelial cyclin-dependent kinase (cdk) activity. We observed that P. carinii significantly impaired growth of cultured mink lung epithelial cells, with effects observed after 48-72 h of treatment. However, the kinase activity associated with p34cdc2 or p33cdk2 was maximally inhibited as early as 24 h after P. carinii exposure. The inhibitory effect on cyclin-dependent kinase activity was mediated by the trophozoite form of P. carinii, in that highly purified trophozoites exerted marked inhibition of p34cdc2 activity. Growth impairment was similarly preceded by P. carinii-induced alteration in the state of epithelial cell p34cdc2 phosphorylation, with no change in p34cdc2 or p33cdk2 protein levels. These data strongly suggest that the antiproliferative activity of P. carinii on respiratory epithelium is mediated in part through modulation of the host cell cycle machinery.

Pneumocystis carinii induces ICAM-1 expression in lung epithelial cells through a TNF-alpha-mediated mechanism

Inflammatory cell recruitment contributes to respiratory impairment during Pneumocystis carinii pneumonia. We evaluated expression of intercellular adhesion molecule-1 (ICAM-1), a key participant in leukocyte accumulation, in rats with P. carinii pneumonia. Immunostaining for ICAM-1 was most marked on bronchiolar epithelium but was also evident on type II pneumocytes, endothelium, and macrophages. Lung from normal and dexamethasone-treated uninfected animals exhibited markedly less ICAM-1. We hypothesized that P. carinii promoted ICAM-1 expression in epithelium through tumor necrosis factor-alpha (TNF-alpha) release from macrophages or that P. carinii directly stimulated ICAM-1 expression. Alveolar macrophages were incubated with P. carinii, and the medium was added to A549 epithelial cells. Treatment of macrophages with P. carinii enhanced A549 ICAM-1, which was inhibited with antibody to TNF-alpha. To determine whether P. carinii alone also stimulated ICAM-1, A549 cells were cultured with P. carinii, also augmenting ICAM-1. Of note, A549 ICAM-1 expression from P. carinii alone was less than with P. carinii-exposed macrophages. Thus ICAM-1 is enhanced in lung epithelium during P. carinii infection, in part, through TNF-alpha-mediated mechanisms.

Steady-state effects of vitronectin and fibronectin on the binding, uptake, and degradation of Pneumocystis carinii in rat alveolar macrophages

Pneumocystis carinii pneumonia remains a serious complication of immunodeficiency. Vitronectin (VN) and fibronectin (FN) accumulate in the lung during P. carinii infection and bind to the organism, thereby enhancing macrophage release of TNF alpha. It is not known whether VN and FN also regulate uptake and degradation of P. carinii by macrophage when present in concentrations similar to those in the lung during pneumonia. To address this, macrophages were cultured with 35S-radiolabeled P. carinii and organism binding, phagocytosis, and degradation determined in media alone (control), or in the presence of VN or FN (100 micrograms/ml each). Soluble VN and FN, in concentrations similar to those in the host, did not significantly affect binding uptake or degradation of P. carinii by alveolar macrophages. Thus, although VN and FN enhance macrophage activation during P. carinii pneumonia, phagocytosis of the organism is not increased by these host glycoproteins under steady-state conditions.

The role of alveolar macrophages in Pneumocystis carinii degradation and clearance from the lung

Although studies indicate that alveolar macrophages participate in host defense against Pneumocystis carinii, their role in organism degradation and clearance from the lung has not yet been established. We, therefore, quantified the uptake and degradation of 35S-labeled P. carinii by cultured macrophages, demonstrating significant degradation of P. carinii over 6 h. We further evaluated the role of macrophages in elimination of P. carinii from the living host. Rats received either intratracheal PBS, liposomal PBS (L-PBS), or liposomal dichloromethylene diphosphonate (L-Cl2MDP), a preparation which leads to selective depletion of macrophages. Over 72 h, L-Cl2MDP-treated animals had loss of > 85% of their alveolar macrophages. In contrast, L-PBS-treated rats had cellular differentials identical to rats receiving PBS. Macrophage-depleted rats and controls were next inoculated with P. carinii and organism clearance was determined after 24 h. P. carinii elimination was evaluated with both cyst counts and an ELISA directed against glycoprotein A (gpA), the major antigen of P. carinii. Both assays indicated that macrophage-depleted rats had substantial inpairment of P. carinii clearance compared to L-PBS- or PBS-treated rats. These data provide the first direct evidence that macrophages mediate elimination of P. carinii from the living host.

PCR detection of Pneumocystis carinii in bronchoalveolar lavage specimens: analysis of sensitivity and specificity

Although PCR detection of Pneumocystis carinii DNA has been described, little is known about the sensitivity or specificity of the assay in routine laboratory practice. We had the unique opportunity to use a bronchoalveolar lavage (BAL) specimen bank with samples for which the direct examination results for P. carinii were known. DNA purified from 129 selected specimens was amplified by using the primers described previously (A. E. Wakefield, F. J. Pixley, S. Banerji, K. Sinclair, R. F. Miller, E. R. Moton, and J. M. Hopkin, Mol. Biochem. Parasitol. 43:69-76, 1990). Of the 129 specimens, 37 were positive for P. carinii by direct examination. All 37 specimens were positive for P. carinii by PCR, yielding a 100% sensitivity and 100% negative predictive value for the assay. An additional 23 specimens were repeatedly positive for P. carinii by PCR but were not positive by direct examination. Review of the patient charts for these specimens with discordant results demonstrated that five of the patients were actually positive for P. carinii, as determined by either biopsy or examination of repeat or prior BAL specimens. A response to empiric therapy for P. carinii pneumonia was seen in an additional two patients. Of the remaining specimens, 8 produced no significant isolates other than P. carinii, while 12 contained culture-confirmed significant respiratory pathogens in addition to P. carinii (two fungal, nine bacterial, and one viral pathogen). Cytomegalovirus, which was of unknown significance, was isolated from 16 additional specimens. Overall, the specificity of the PCR assay was 79.3% compared to the results of direct examination. We hypothesized that the apparently poor specificity of the PCR assay was due to the increased sensitivity of the assay compared to that of direct examination. The sensitivity of the PCR assay was therefore assessed with BAL specimens containing P. carinii cysts. Serial dilutions of this preparation were evaluated by direct examination and PCR. PCR was found to be 100-fold more sensitive than direct examination, which detected one to two cysts per amplification. No false-positive results were detected in controls containing no DNA or by using target DNA from various fungal, viral, or bacterial respiratory pathogens. We conclude that PCR detection of P. carinii in BAL specimens is very sensitive and should be considered for patients whose specimens do not yield a diagnosis. The increased sensitivity of the PCR assay may help to identify those patients with low-titer infections who might benefit from directed antibiotic therapy for P. carinii and would otherwise be missed by direct examination alone.

Acute eosinophilic pneumonia: histopathologic findings in nine patients

Acute eosinophilic pneumonia is characterized by acute respiratory insufficiency, hypoxemia, fever, diffuse radiographic infiltrates, and eosinophilia in bronchoalveolar lavage fluid (BALF) or lung biopsies in the absence of infection, atopy, or asthma. A rapid response to corticosteroids is characteristic. We reviewed our experience with nine cases of acute lung disease with histologic features of acute and organizing diffuse alveolar damage and prominent interstitial and alveolar eosinophils in order to determine whether this pathology was characteristic of acute eosinophilic pneumonia. The mean age of the patients (four men and five women) was 53 yr (range: 33 to 71 yr). They presented with 2 to 21 d of dyspnea, cough, myalgias, and fever. All were hypoxic and had bilateral infiltrates on chest radiographs. Peripheral blood eosinophilia was present in four of eight patients (peripheral blood count unavailable for one patient). All patients were treated with high-dose corticosteroids with a mean time to symptomatic and radiographic improvement of 4 d. Seven of the nine patients enrolled in the study are alive without relapse; one patient has a mild deficit in diffusing capacity, and one patient died of a myocardial infarct while improving on therapy. The presence of eosinophils in cases of acute respiratory insufficiency due to diffuse alveolar damage (DAD) should suggest the diagnostic possibility of acute eosinophilic pneumonia. Acute eosinophilic pneumonia should be distinguished from other causes of DAD because of important differences in natural history.

Tissue localization of transforming growth factor-beta1 in pulmonary eosinophilic granuloma

Pulmonary eosinophilic granuloma is characterized by infiltration of the lungs with fibronodular lesions containing specialized Langerhans' cells. In some patients, progressive pulmonary fibrosis leads to significant respiratory impairment. Transforming growth factor-beta1 (TGF-beta1) promotes fibrosis by enhancing the synthesis of extracellular matrix components. The role of TGF-beta1 in promoting fibrosis in the setting of pulmonary eosinophilic granuloma is currently unknown. We used immunohistochemistry to evaluate the extent and distribution of TGF-beta1 and the extracellular matrix components type I collagen and decorin, a TGF-beta1-binding proteoglycan. Lung biopsies from 11 patients with pulmonary eosinophilic granuloma were evaluated. In biopsies with active inflammatory lesions containing Langerhans' cells, hyperplastic type 2 pneumocytes and alveolar macrophages within and surrounding the fibronodular lesions contained abundant TGF-beta1. Langerhans' cells were consistently devoid of immunoreactive TGF-beta1. Active inflammatory lesions also exhibited staining for decorin, in a loosely organized distribution. Advanced fibrotic lesions of eosinophilic granuloma, containing minimal inflammatory cells and few or no Langerhans' cells, exhibited weak or absent staining for TGF-beta1 within either hyperplastic type 2 pneumocytes or alveolar macrophages. The fibroconnective tissues of these advanced fibrotic lesions consistently revealed dense staining for decorin. Through their actions on extracellular matrix protein accumulation, TGF-beta1 and the TGF-beta1-binding proteoglycan decorin may modulate fibrotic repair accompanying pulmonary eosinophilic granuloma.

Fungal beta-glucan interacts with vitronectin and stimulates tumor necrosis factor alpha release from macrophages

beta-Glucans are polymers of D-glucose which represent major structural components of fungal cell walls. It was shown previously that fungi interact with macrophages through beta-glucan receptors, thereby inducing release of tumor necrosis factor alpha (TNF-alpha). Additional studies demonstrated that vitronectin, a host adhesive glycoprotein, binds to fungi and enhances macrophage recognition of these organisms. Since vitronectin contains a carbohydrate-binding region, we postulated that vitronectin binds fungal beta-glucans and subsequently augments macrophage TNF-alpha release in response to this fungal component. To study this, we first determined the release of TNF-alpha from alveolar macrophages stimulated with fungal beta-glucan. Maximal TNF-alpha release occurred with moderate concentrations of beta-glucan (100 to 200 micrograms/ml), whereas higher concentrations of beta-glucan (> or = 500 micrograms/ml) caused apparent suppression of the TNF-alpha activity released. This suppression of TNF-alpha activity by high concentrations of beta-glucan was mediated by the particulate beta-glucan binding soluble TNF-alpha, through the lectin-binding domain of the cytokine, rendering the TNF-alpha less available for measurement. Next, we assessed the interaction of vitronectin with beta-glucan. Binding of 125I-vitronectin to particulate fungal beta-glucan was dose dependent and specifically inhibitable by unlabeled vitronectin. Furthermore, treatment of beta-glucan with vitronectin substantially augmented macrophage TNF-alpha release in response to this fungal component. These findings demonstrate that fungal beta-glucan can directly modulate TNF-alpha release from macrophages. Further, these studies indicate that the host adhesive glycoprotein vitronectin specifically binds beta-glucan and augments macrophage cytokine release in response to this fungal element.

Drug-induced interstitial lung disease

Drugs can have multiple different adverse effects on the lungs, airways, pleura, mediastinum, and the interstitium. Their appearance can mimic other interstitial lung diseases and, for the most part, drug-induced interstitial lung disease is a condition of exclusion rather than a specific entity that can be diagnosed with imaging studies or histology. It is important to be aware of all the potential adverse effects of drugs on the lung in order to recognize the condition and to discontinue the drug as soon as possible, as death will result in many of the situations discussed here if appropriate measures are not taken.

Candida albicans induces the release of inflammatory mediators from human peripheral blood monocytes

Candida albicans (C. albicans) is a major nosocomial pathogen. We examined arachidonic acid (AA) and cytokine production by monocytes stimulated with C. albicans. [14C]-AA labeled monocytes released 8.9 +/- 2.3% of the incorporated AA following stimulation with live C. albicans (C. albicans: monocyte of 16:1) (P = 0.0002). Prior studies indicate that soluble alpha-mannans and beta-glucans antagonize mannose and beta-glucan receptors, respectively. Preincubation of monocytes with alpha-mannan (100 micrograms/ml) caused 45.8 +/- 5.7% inhibition of [14C]-AA release, whereas beta-glucan (100 micrograms/ml) yielded 43.7 +/- 6.0% inhibition (P < 0.05 for each compared to control). Additionally, monocytes stimulated with C. albicans also released interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF alpha), interleukin-6 (IL-6) and interleukin-8 (IL-8). However, alpha-mannan or beta-glucan failed to inhibit IL-1 beta release. These data indicate that C. albicans induces monocytes to release AA and inflammatory cytokines. Furthermore, AA, but not cytokine liberation, is partially mediated by alpha-mannan and beta-glucan components of the fungus.

Pneumocystis carinii pneumonia in patients without acquired immunodeficiency syndrome: associated illness and prior corticosteroid therapy

OBJECTIVE

To determine the clinical spectrum of immunosuppressive conditions and systemic corticosteroid therapy associated with the development of Pneumocystis carinii pneumonia in a consecutive series of patients without acquired immunodeficiency syndrome (AIDS).

DESIGN

We retrospectively analyzed a consecutive series of 116 patients without AIDS who were assessed at Mayo Medical Center for a first episode of P. carinii pneumonia between 1985 and 1991.

METHODS

Medical records were examined to determine underlying immunosuppressive disorders, premorbid corticosteroid dosage and duration of therapy, associated infections, and subsequent respiratory failure and in-hospital mortality.

RESULTS

Conditions associated with a first episode of P. carinii pneumonia were hematologic malignant disorders (30.2%), organ transplantation (25.0%), inflammatory disorders (22.4%), solid tumors (12.9%), and miscellaneous conditions (9.5%). Regardless of the associated underlying disease, corticosteroids had been administered systemically in 105 patients (90.5%) within 1 month before the diagnosis of P. carinii pneumonia. The median daily corticosteroid dose was equivalent to 30 mg of prednisone; however, 25% of patients had received as little as 16 mg of prednisone daily. The median duration of corticosteroid therapy was 12 weeks before the development of pneumonia; however, P. carinii pneumonia developed after 8 weeks or less of corticosteroid therapy in 25% of these patients. Respiratory failure occurred in 43%, and in-hospital mortality was 34% for patients with P. carinii pneumonia in conditions other than AIDS.

CONCLUSION

Although these results do not suggest that premorbid administration of corticosteroids is the only factor that contributes to the development of P. carinii pneumonia in these patients, they show that, in this large consecutive series, systemic corticosteroid therapy, even in moderate doses, was administered to most patients during the month preceding the onset of P. carinii pneumonia. Consideration should be given to instituting P. carinii prophylaxis (when not contra-indicated) in patients for whom prolonged systemic corticosteroid therapy is prescribed.