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Andrew H Limper

Publications and source records attributed to Andrew H Limper.

At least 37 records · Page 2Linked to original sources
PubMed2004

Transforming growth factor-beta 1 and extracellular matrix-associated fibronectin expression in pulmonary lymphangioleiomyomatosis.

STUDY OBJECTIVES: Lymphangioleiomyomatosis (LAM) is a rare disorder of unknown etiology, affecting almost exclusively women of childbearing age, that is associated with the proliferation of spindle cells and cystic changes in the affected lung. The underlying processes that contribute to this disease are poorly understood. Transforming growth factor (TGF)-beta(1) is a potent cytokine that promotes mesenchymal cell proliferation and regulates the synthesis of extracellular matrix (ECM) components, particularly fibronectins. Herein, we evaluate the expression of TGF beta(1) and matrix-associated fibronectin in lung specimens demonstrating LAM. DESIGN: Lung biopsy specimens that were confirmed to contain pathologic LAM cells were obtained from 13 patients. The specimens were submitted to immunohistochemical evaluation for TGF beta(1) and fibronectin, as well as the typical markers of LAM cells. Healthy lung parenchyma surrounding resected neoplasms was studied in a parallel fashion as control tissues. MEASUREMENTS AND RESULTS: In all 13 LAM cases and in healthy lung parenchyma, we demonstrated that TGF beta(1) localized consistently to airway epithelial cells. However, in LAM tissues, matrix-associated TGF beta(1) was also consistently found in regions containing pathologic LAM cells. Notably, more abundant TGF beta(1) was observed in highly cellular areas compared to the walls of chronic cystic regions in LAM tissues. Fibronectin, a matrix component that is strongly expressed in response to active TGF beta(1) was found to consistently colocalize with this protein in these highly cellular regions, supporting TGF beta(1) activity in these regions. The markers of proliferating LAM cells, including proliferating cell nuclear antigen, were also markedly present in these highly cellular LAM regions. CONCLUSION: These studies suggest that the proliferation of aberrant LAM cells may be associated with altered regional expression of TGF beta(1) and related ECM proteins.

Actins↗
PubMed2003

Pneumocystis carinii BCK1 functions in a mitogen-activated protein kinase cascade regulating fungal cell-wall assembly.

Pneumocystis pneumonia remains the most common AIDS-defining opportunistic infection in people with HIV. The process by which Pneumocystis carinii constructs its cell wall is not well known, although recent studies reveal that molecules such as beta-1-3-glucan synthetase (GSC1) and environmental pH-responsive genes such as PHR1 are important for cell-wall integrity. In closely related fungi, a specific mitogen-activated protein kinase (MAPK) cascade regulates cell-wall assembly in response to elevated temperature. The upstream mitogen-activated protein kinase kinase kinase (MAPKKK, or MEKK), BCK1, is an essential component in this pathway for maintaining cell-wall integrity and preventing fungal cell lysis. We have identified a P. carinii MEKK gene and have expressed it in Saccharomyces cerevisiae to gain insights into its function. The P. carinii MEKK, PCBCK1, corrects the temperature-sensitive cell lysis defect of bck1Delta yeast. Further, at elevated temperature PCBCK1 restored the signaling defect in bck1Delta yeast to maintain expression of the temperature-inducible beta-1-3-glucan synthetase gene, FKS2. PCBCK1, as a functional kinase, is capable of autophosphorylation and substrate phosphorylation. Since glucan machinery is not present in mammals, a better understanding of this pathway in P. carinii might aid in the development of novel medications which interfere with the integrity of the Pneumocystis cell wall.

Base Sequence↗
PubMed2003

Pneumocystis carinii STE11, an HMG-box protein, is phosphorylated by the mitogen activated protein kinase PCM.

A pheromone-induced mitogen activated protein kinase (MAPK) pathway controls mating in fungi by regulating gene transcription. In the opportunistic fungus Pneumocystis carinii, we have identified a protein containing a high-mobility group (HMG) motif which is homologous to the transcriptional activators STE11 of Schizosaccharomyces pombe and STE12 of Saccharomyces cerevisiae. In fungi, this transcriptional activator functions in sexual development, filamentous growth, and pathogenicity. The fungal pheromone-activated MAPK phosphorylates the transcriptional activator to allow binding to pheromone-response elements in the promoter regions of certain genes. We have previously identified a P. carinii MAPK, PCM, which has significant homology to fungal MAPKs involved in mating. As an initial step in understanding the downstream molecules which interact with the PCM kinase, we have cloned a STE11 homologue in P. carinii. PCSTE11 has an open-reading frame of 1.5 kb which encodes a protein of 501 amino acids with a molecular weight of 56 kDa. Greatest homology was to S. pombe STE11 (52%). We have expressed a His-tag fusion of PCSTE11 and purified the protein with nickel affinity resin. PCM phosphorylates the purified protein indicating that PCSTE11 is associated with the MAPK cascade in P. carinii.

Amino Acid Sequence↗
PubMed2003

Pneumocystis carinii cell wall beta-glucans initiate macrophage inflammatory responses through NF-kappaB activation.

beta-Glucans are major structural components of fungi. We have recently reported that the pathogenic fungus Pneumocystis carinii assembles a beta-glucan-rich cell wall that potently activates alveolar macrophages to release pro-inflammatory cytokines and chemokines. Purified P. carinii beta-glucans predictably induce both cytokine generation and associated neutrophilic lung inflammation. Herein, we demonstrate that P. carinii beta-glucan-induced macrophage stimulation results from activation of NF-kappaB. Although analogous to macrophage activation induced by bacterial lipopolysaccharide (LPS), P. carinii beta-glucan-induced macrophage NF-kappaB activation exhibits distinctly different kinetics, with slower induction and longer duration compared with LPS stimulation. Macrophage activation in response to P. carinii beta-glucan was also substantially inhibited with the NF-kappaB antagonist pyrrolidine dithiocarbamate. In addition to different kinetics of NF-kappaB activation, P. carinii beta-glucan and LPS also utilize different receptor systems to induce macrophage activation. Macrophages from Toll-like receptor 4-deficient and wild type mice produced equivalent amounts of tumor necrosis factor alpha when stimulated with P. carinii beta-glucan. However, Toll-like receptor 4-deficient macrophages were refractory to stimulation with LPS. In contrast, MyD88-deficient macrophages exhibited a significant (though partial) blunted response to P. carinii beta-glucan. These data demonstrate that P. carinii beta-glucan acts as potent inducer of macrophage activation through NF-kappaB utilizing cellular receptors and signaling pathways distinct from LPS.

Animals↗
PubMed2003

Characterization of a lanosterol 14 alpha-demethylase from Pneumocystis carinii.

Pneumocystis carinii (PC) causes severe pneumonia in immunocompromised patients. PC is intrinsically resistant to treatment with azole antifungal medications. The enzyme lanosterol 14 alpha-demethylase (Erg11) is the target for azole antifungals. We cloned PCERG11 and compared its sequence to Erg11 proteins present in azole-resistant organisms, and performed chromosomal and Northern blot analysis for PCERG11. Of 13 potential sites which could confer resistance to azoles, two were identical to azole-resistant Candida. By site-directed mutagenesis we changed these two sites in PCERG11 to those present in azole-sensitive Candida to generate PCERG11-SDM (E113D, T125K). We tested the susceptibility of ERG11 deletion strains of Saccharomyces cerevisiae (SC) expressing PCERG11, PCERG11-SDM, and wild-type SCERG11 to three azole antifungals: fluconazole, itraconazole, and voriconazole. PCERG11 required a 2.2-fold higher dose of voriconazole and 3.5-fold higher dose of fluconazole than SCERG11 for a 50% reduction in growth. No difference was observed in the sensitivity to itraconazole. PCERG11-SDM has increased sensitivity to fluconazole and voriconazole, but not itraconazole. We believe that the molecular structure of the lanosterol 14 alpha-demethylase encoded by PCERG11 confers inherent resistance to azole antifungals and plays an integral part in the overall resistance of this PC to azole therapy.

Amino Acid Sequence↗
PubMed2003

The role of inflammation in respiratory impairment during Pneumocystis carinii pneumonia.

Pneumocystis carinii remains an important cause of pneumonia in immunosuppressed hosts. Severe Pneumocystis pneumonia is characterized by an intense neutrophilic inflammatory response resulting in gas exchange abnormalities, diffuse alveolar damage, and respiratory failure. The inflammatory response directed against P. carinii involves a complex series of interactions between alveolar macrophages, CD4+ T lymphocytes, polymorphonuclear cells, and their various products. CD4+ T lymphocytes are crucial to host defense against P. carinii. Alveolar macrophages also provide essential functions that significantly enhance clearance of P. carinii infection. In addition, host proteins play an important role in augmenting the host inflammatory responses to this organism. Although essential for effective clearance of infection, excessive inflammatory responses also predispose the host to the development of lung injury and respiratory compromise. Understanding the complex processes involved in the host inflammatory response and its potential for causing lung injury may enable development of novel therapeutic approaches for this and other important fungal lung infections.

Humans↗
PubMed2003

Drug-induced lung disease: a pragmatic classification incorporating HRCT appearances.

Drug-induced lung disease frequently poses a diagnostic challenge. Knowledge of common radiological patterns of lung involvement and corresponding histopathologic diagnoses can facilitate management of individual patients. We outline a framework for understanding radiological and histologic patterns of drug-induced lung disease. Diffuse forms of drug-induced lung disease include processes that mimic acute respiratory distress syndrome (ARDS) and diffuse alveolar hemorrhage. These patterns of drug-induced lung disease are especially common in patients receiving cytotoxic chemotherapeutic agents. Chronic forms of drug-induced lung disease include many of the interstitial pneumonias seen more commonly in patients with idiopathic disease. Bronchiolitis obliterans organizing pneumonia and eosinophilic pneumonia are nonspecific patterns of drug-induced lung disease that are radiologically and histologically indistinguishable from their idiopathic counterparts. In some patients organizing pneumonia and eosinophilic pneumonia mimic the radiological appearance of neoplastic disease.

Journal Article↗
PubMed2003

Lung epithelial cells and extracellular matrix components induce expression of Pneumocystis carinii STE20, a gene complementing the mating and pseudohyphal growth defects of STE20 mutant yeast.

Pneumocystis carinii causes severe pneumonia in immunocompromised hosts. The binding of P. carinii to alveolar epithelial cells and extracellular matrix constituents such as fibronectin and vitronectin is a central feature of infection, which initiates proliferation of the organism. Herein, we demonstrate that P. carinii binding to lung cells specifically alters the gene expression of the organism, regulating fungal growth. Subtractive hybridization was performed to isolate P. carinii genes expressed following binding to mammalian extracellular matrix constituents. P. carinii STE20 (PCSTE20), a gene participating in mating and pseudohyphal growth of other fungi, was identified following adherence to the extracellular matrix constituents fibronectin, vitronectin, collagen, and lung epithelial cells. The expression of PCSTE20 and a related P. carinii mitogen-activated protein kinase (MAPK) kinase gene, also implicated in signaling of mating, were both specifically upregulated by binding to matrix protein. The expression of general cyclin-dependent kinases and other MAPKs not involved in mating pathways were not altered by organism binding. PCSTE20 expression was also strongly enhanced following organism attachment to A549 lung epithelial cells. When expressed in a Saccharomyces cerevisiae ste20Delta mutant, PCSTE20 suppressed defects in both mating and pseudohyphal growth. These findings are consistent with the observed proliferation and filopodial extension of Pneumocystis organisms adherent to the epithelium in the lungs of immunocompromised hosts. PCSTE20 expression appears to represent a significant component in the regulation of the life cycle of this intractable opportunistic pathogen.

Amino Acid Sequence↗
PubMed2003

Surfactant protein D-mediated aggregation of Pneumocystis carinii impairs phagocytosis by alveolar macrophages.

Pneumocystis carinii remains an important and potentially fatal cause of opportunistic pneumonia. Animal studies reveal that substantial quantities of surfactant protein D (SP-D) accumulate in the airspaces during P. carinii pneumonia and are particularly abundant in aggregates of organisms. Due to the multimeric structure of SP-D, we hypothesized that SP-D mediates aggregation of the organism. From previous clinical studies it is known that aggregated organisms are conspicuous in sections of lung tissue and bronchoalveolar lavage (BAL) fluids of humans with active P. carinii pneumonia. Herein, we observe that SP-D levels increased at least fourfold in BAL fluids of patients with P. carinii pneumonia. Next, a spectrophotometric sedimentation assay was developed to assess the aggregation of P. carinii in vitro by SP-D. P. carinii organisms were first stripped with glutathione to remove bound SP-D and subsequently incubated in the presence of SP-D and 2 mM calcium. P. carinii incubated with natural SP-D (10 micro g/ml) containing dodecamers and higher-order forms exhibited aggregation and enhanced sedimentation compared to that of glutathione-stripped P. carinii. Aggregation was also enhanced by the concentrated supernatant of rat BAL fluid, and this effect was abolished by the selective removal of SP-D from the lavage fluid. P. carinii aggregation was reduced by maltose, mannose, and EDTA, consistent with the role of the SP-D C-type lectin domain (CRD) in the aggregation event. Comparisons of different molecular forms of SP-D showed that dodecamers-but not trimeric subunits-mediate optimal aggregation of P. carinii. Aggregation of P. carinii by SP-D was shown to be responsible for the impaired phagocytosis of the organisms by alveolar macrophages. Thus, SP-D-mediated aggregation of P. carinii may represent one means by which the organism avoids elimination by the host.

Animals↗
PubMed2003

Evidence for a melanin cell wall component in Pneumocystis carinii.

Fluorescein isothiocyanate-labeled monoclonal antibodies specific for fungal melanin were used in this study to visualize melanin-like components of the Pneumocystis carinii cell wall. A colorimetric enzyme assay confirmed these findings. This is the first report of melanin-like pigments in Pneumocystitis.

Animals↗
PubMed2003

Etanercept for the treatment of stage II and III progressive pulmonary sarcoidosis.

BACKGROUND: Tumor necrosis factor (TNF)-alpha is produced by macrophages and other cells, and is believed to participate in granulomatous inflammation. Targeted antagonism of TNF-alpha has been proposed as a novel treatment strategy for sarcoidosis. Etanercept is a dimeric fusion protein that binds specifically to TNF-alpha, rendering it biologically inactive. OBJECTIVE: To assess whether etanercept has potential efficacy in the treatment of progressive pulmonary sarcoidosis. DESIGN: Prospective, open-label, phase-2 treatment trial. SETTING: Mayo Clinic, Rochester, MN. PATIENTS: Stage II or III progressive pulmonary sarcoidosis. INTERVENTION: Etanercept, 25 mg subcutaneously twice weekly. MEASUREMENTS: Pulmonary function, chest radiographs, dyspnea, and TNF-alpha levels in serum and BAL fluid. RESULTS: The study was terminated after the enrollment of 17 patients due to an early-stop clause of the pretrial study design related to excessive treatment failures. Neither absolute levels of TNF-alpha nor TNF-alpha activity in the serum, BAL fluid, or alveolar macrophages were able to predict which patients would respond to etanercept. CONCLUSIONS: In patients with progressive stage II or III pulmonary sarcoidosis, etanercept was frequently associated with early or late treatment failure. These data would not support the design of a large multicenter randomized trial comparing etanercept with conventional corticosteroid therapy.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2003

The overlap between respiratory bronchiolitis and desquamative interstitial pneumonia in pulmonary Langerhans cell histiocytosis: high-resolution CT, histologic, and functional correlations.

OBJECTIVES: To characterize the histologic, high-resolution CT (HRCT), and functional correlates of respiratory bronchiolitis (RB)/desquamative interstitial pneumonia (DIP)-like changes in biopsy specimens of adults with pulmonary Langerhans cell histiocytosis (PLCH). METHODS: We retrospectively identified 14 adult patients with histologically proven PLCH (all smokers) in whom both biopsy specimens and HRCT were available for review. The presence and extent of RB/DIP-like changes on lung biopsy specimens of patients with PLCH were correlated with total pack-years of smoking, lung function variables, and the presence of ground-glass attenuation on HRCT. RESULTS: Varying degrees of RB/DIP-like changes were identified in all biopsy specimens. The extent of involvement with RB/DIP-like changes correlated with the cumulative exposure to cigarettes smoked at the time of biopsy (r = 0.61, p = 0.03). Ground-glass attenuation was detected in three HRCTs, two of which had extensive RB/DIP-like changes (> or = 70% involvement) on histology, suggesting that substantial smoking-induced RB/DIP-like changes may be the cause of ground-glass attenuation on the HRCT of patients with PLCH. No correlation was found between the extent of RB/DIP-like changes and total lung capacity, FEV(1), or diffusion capacity of the lung for carbon monoxide. CONCLUSIONS: RB/DIP-like changes are exceedingly common in PLCH, may be sufficiently severe to cause the appearance of ground-glass attenuation on HRCT, and correlate with the cumulative exposure to cigarettes smoked. This study provides additional evidence that PLCH, RB, and DIP form a spectrum of interstitial patterns of lung injury to cigarette smoke.

Bronchiolitis↗
PubMed2002

Pneumocystis carinii cell wall beta-glucan induces release of macrophage inflammatory protein-2 from alveolar epithelial cells via a lactosylceramide-mediated mechanism.

Infiltration of the lungs with neutrophils promotes respiratory failure during severe Pneumocystis carinii (PC) pneumonia. Recent studies have shown that alveolar epithelial cells (AECs), in addition to promoting PC attachment, also participate in lung inflammation by the release of cytokines and chemokines. Herein, we demonstrate that a PC beta-glucan rich cell wall isolate (PCBG) stimulates the release of macrophage inflammatory protein-2 (MIP-2) from isolated AECs through a lactosylceramide-dependent mechanism. The results demonstrate that MIP-2 mRNA and protein production is significantly increased at both early and late time points after PCBG challenge. Although CD11b/CD18 (Mac-1, CR3) is the most widely studied beta-glucan receptor, we demonstrate that CD11b/CD18 is not present on AECs. This study instead demonstrates that preincubation of AECs with an antibody directed against the membrane glycosphingolipid lactosylceramide (CDw17) results in a significant decrease in MIP-2 secretion. Preincubation of the anti-CDw17 antibody with solubilized lactosylceramide reverses this effect. Furthermore, incubation of AECs with inhibitors of glycosphingolipid biosynthesis, including N-butyldeoxyno jirimycin and d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol-HCl, also results in a significant decrease in AEC MIP-2 production following challenge with PCBG. These data demonstrate that PC beta-glucan induces significant production of MIP-2 from AECs and that CDw17 participates in the glucan-induced inflammatory signaling in lung epithelial cells during PC infection.

Animals↗