Citations

Abstract 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-α 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-α generation and is associated with neutrophilic infiltration of the lungs. Digestion of the P. carinii cell wall isolate with zymolyase, a preparation containing predominantly β-1,3 glucanase, substantially reduces the ability of this P. carinii cell wall fraction to activate alveolar macrophages, thus suggesting that β-glucan components of the P. carinii cell wall largely mediate TNF-α release. Furthermore, the soluble carbohydrate β-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 α-mannan, a preparation that antagonizes macrophage mannose receptors, had minimal effect on TNF-α release induced by the P. carinii cell wall fraction. P. carinii β-glucan-induced TNF-α 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 β-glucan cell wall components can directly stimulate alveolar macrophages to release proinflammatory cytokines mainly through interaction with cognate β-glucan receptors on the phagocyte.

Abstract Dendritic cells (DC) are key regulators of immune responses. In the current study, we hypothesized that cigarette smoke-induced aberrance in DC function is an important mechanism by which smokers develop cancer, infection, and allergy—diseases common in smokers. We demonstrate that cigarette smoke extract (CSE) inhibits DC-mediated priming of T cells, specifically inhibiting the secretion of IFN-γ whereas enhancing the production of IL-4 in the MLR. Conditioning with CSE did not effect cytokine (IL-10, IL-6, or IL-12) production from immature DCs, but significantly inhibited IL-12p70 release by LPS-matured DCs. In contrast, IL-10 secretion by LPS-activated CSE-conditioned DCs was enhanced when compared with control DCs. CSE also induced cyclooxygenase-2 protein levels in maturing DCs and significantly augmented endogenous PGE2 release. Conditioning of DCs with CSE also suppressed LPS-mediated induction of CD40, CD80, and CD86, and suppressed maturation-associated CCR7 expression. Although CSE has been reported to induce apoptosis of fibroblasts and epithelial cells, the immunomodulatory effects observed with CSE were not due to diminished DC viability. The effects of CSE on DC function were not exclusively mediated by nicotine, because equivalent, or even higher concentrations of nicotine than those found in CSE, failed to suppress DC-induced T cell priming. These data provide evidence that soluble components extracted from cigarette smoke suppress key DC functions and favor the development of Th-2 immunity.

Abstract Respiratory failure during Pneumocystis pneumonia is mainly a consequence of exaggerated inflammatory responses to the organism. Dendritic cells (DCs) are the most potent APCs in the lung and are key to the regulation of innate and adaptive immune responses. However, their participation in the inflammatory response directed against Pneumocystis infection has not been fully elucidated. Therefore, we studied the role of Pneumocystis carinii, as well as Saccharomyces cerevisiae, cell wall-derived β-glucans, in DC costimulatory molecule expression. We further studied the impact of β-glucans on subsequent T cell activation. Because cytokine secretion by DCs has recently been shown to be regulated by Fas ligand (FasL), its role in β-glucan activation of DCs was also investigated. β-Glucan-induced DC activation occurred in part through dectin-1 receptors. We demonstrated that DC activation by β-glucans elicits T cell activation and polarization into a Th1 patterned response, but with the conspicuous absence of IL-12. These observations differed from LPS-driven T cell polarization, suggesting that β-glucans and LPS signal DC activation through different mechanisms. We additionally determined that IL-1β and TNF-α secretion by β-glucan-stimulated DCs was partially regulated by Fas-FasL. This suggests that dysregulation of FasL could further enhance exuberant and prolonged cytokine production by DCs following DC-T cell interactions, further promoting lung inflammation typical of Pneumocystis pneumonia.

Abstract IL-12p70, a heterodimer composed of p35 and p40 subunits, is a key polarizing cytokine produced by maturing dendritic cells (DCs). We report that cigarette smoke extract (CSE), an extract of soluble cigarette smoke components, suppresses both p35 and p40 production by LPS or CD40L-matured DCs. Suppression of IL-12p70 production from maturing DCs was not observed in the presence of nicotine concentrations achievable in CSE or in the circulation of smokers. The suppressed IL-12p70 protein production by CSE-conditioned DCs was restored by pretreatment of DCs or CSE with the antioxidants N-acetylcysteine and catalase. Inhibition of DC IL-12p70 by CSE required activation of ERK-dependent pathways, since inhibition of ERK abrogated the suppressive effect of CSE on IL-12 secretion. Oxidative stress and sustained ERK phosphorylation by CSE enhanced nuclear levels of the p40 transcriptional repressor c-fos in both immature and maturing DCs. Suppression of the p40 subunit by CSE also resulted in diminished production of IL-23 protein by maturing DCs. Using a murine model of chronic cigarette smoke exposure, we observed that systemic and lung DCs from mice “smokers” produced significantly less IL-12p70 and p40 protein upon maturation. This inhibitory effect was selective, since production of TNF-α during DC maturation was enhanced in the smokers. These data imply that oxidative stress generated by cigarette smoke exposure suppresses the generation of key cytokines by maturing DCs through the activation of ERK-dependent pathways. Some of the cigarette smoke-induced inhibitory effects on DC function may be mitigated by antioxidants.

The balance between mitochondrial fission and fusion is crucial for mitochondria to perform its normal cellular functions. We hypothesized that cigarette smoke (CS) disrupts this balance and enhances mitochondrial dysfunction in the airway. In nonasthmatic human airway smooth muscle (ASM) cells, CS extract (CSE) induced mitochondrial fragmentation and damages their networked morphology in a concentration-dependent fashion, via increased expression of mitochondrial fission protein dynamin-related protein 1 (Drp1) and decreased fusion protein mitofusin (Mfn) 2. CSE effects on Drp1 vs. Mfn2 and mitochondrial network morphology involved reactive oxygen species (ROS), activation of extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), protein kinase C (PKC) and proteasome pathways, as well as transcriptional regulation via factors such as NF-κB and nuclear erythroid 2-related factor 2. Inhibiting Drp1 prevented CSE effects on mitochondrial networks and ROS generation, whereas blocking Mfn2 had the opposite, detrimental effect. In ASM from asmatic patients, mitochondria exhibited substantial morphological defects at baseline and showed increased Drp1 but decreased Mfn2 expression, with exacerbating effects of CSE. Overall, these results highlight the importance of mitochondrial networks and their regulation in the context of cellular changes induced by insults such as inflammation (as in asthma) or CS. Altered mitochondrial fission/fusion proteins have a further potential to influence parameters such as ROS and cell proliferation and apoptosis relevant to airway diseases.

Purpose To develop a rapid proton MR elastography (MRE) technique that can quantify the absolute shear stiffness of lung parenchyma, to investigate the ability to differentiate respiration‐dependent stiffness variations of the lung, and to demonstrate clinical feasibility. Materials and Methods A spin‐echo echo planar imaging MRE sequence (SE‐EPI MRE) with a very short echo time was developed and tested in a series of five healthy volunteers at three different lung volumes: (i) residual volume (RV), (ii) total lung capacity (TLC), (iii) and midway between RV and TLC (MID). At each volume, lung density was quantified using a MR‐based density mapping sequence. For reference, data were acquired using the previously described spin‐echo lung MRE sequence (SE‐MRE). MRE data were also acquired in a patient with proven Idiopathic Pulmonary Fibrosis (IPF) to test clinical feasibility. Results The SE‐EPIMRE sequence reduced total acquisition time by a factor of 2 compared with the SE‐MRE sequence. Lung parenchyma median shear stiffness for the 5 volunteers quantified with the SE‐EPI MRE sequence was 0.9 kPa, 1.1 kPa, and 1.6 kPa at RV, MID, and TLC, respectively. The corresponding values obtained with the SE‐MRE sequence were 0.9 kPa, 1.1 kPa, and 1.5 kPa. Absolute shear stiffness was also successfully measured in the IPF patient. Conclusion The results indicate that stiffness variations due to respiration could be measured with the SE‐EPIMRE technique and were equivalent to values generated by the previously described SE‐MRE approach. Preliminary data obtained from the patient demonstrate clinical feasibility. J. Magn. Reson. Imaging 2014;40:1230–1237 . © 2013 Wiley Periodicals, Inc .

Abstract β -glucans represent major structural components of fungal cell walls. We recently reported that Pneumocystis carinii β -glucans stimulate alveolar macrophages to release proinflammatory cytokines. Macrophage activation by β -glucan is augmented by serum, implying the presence of circulating factors that interact with β -glucans and enhance their ability to stimulate macrophages. Using β -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 β -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 β -glucan. Stimulation of macrophages with P. carinii β -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 β -glucan components of P. carinii and augment macrophage inflammatory responses. P. carinii cell wall β -glucan stimulates secretion of IL-6 by macrophages, thereby enhancing hepatic synthesis of both VN and FN, and lung synthesis of FN during pneumonia.

ObjectivePulmonary disease represents an important extraarticular manifestation of rheumatoid arthritis (RA). While the association of RA and interstitial lung disease is widely acknowledged, obstructive lung disease (OLD) in RA is less well understood. We therefore aimed to assess the incidence, risk factors, and mortality of OLD in patients with RA.MethodsWe examined a population‐based incident cohort of patients with RA and a comparison cohort of individuals without RA. OLD was defined using a strict composite criterion. Cox proportional hazards models were used to compare OLD incidence between the RA and comparator cohorts to investigate risk factors and to explore the impact of OLD on patient survival.ResultsA total of 594 patients with RA and 596 subjects without RA were followed for a mean of 16.3 and 19.4 years, respectively. The lifetime risk of developing OLD was 9.6% for RA patients and 6.2% for subjects without RA (hazard ratio [HR] 1.54, 95% confidence interval [95% CI] 1.01–2.34). The risk of developing OLD was higher among male patients, among current or former smokers, and for individuals with more severe RA. Survival of RA patients diagnosed with OLD was worse compared to those without OLD (HR 2.09, 95% CI 1.47–2.97).ConclusionPatients with RA are at higher risk of developing OLD, which is significantly associated with premature mortality. Effective diagnostic and therapeutic strategies to detect and manage OLD in patients with RA may help to improve survival in these patients.