Thomas L. Clanton

Increased Susceptibility to Pulmonary Emphysema among HIV-Seropositive Smokers

Several reports (1-3) have suggested that before recognized AIDS-related respiratory complications develop, some HIV-seropositive persons may develop an accelerated form of lung injury that has physiologic features or findings on computed tomography of the chest that are consistent with pulmonary emphysema. Emphysema, defined as enlargement of the terminal air spaces and destruction of the alveolar walls (4), is uniquely characterized by disappearance of lung tissue (4). Insight into the cellular mechanisms critical to pathogenesis of this condition in humans has been limited by the lengthy course over which the disease develops and by the fact that only a minority of smokers develops significant disease (5). The possibility that HIV-seropositive persons may have a greater risk for developing accelerated lung destruction may have broad biological relevance regarding emphysema pathogenesis. With this in mind, we sought to extend previous anecdotal studies and attempted to prospectively characterize a group of HIV-infected persons exhibiting evidence of emphysema-like destructive lung disease. Methods The study sample consisted of 114 consecutive HIV-seropositive persons who underwent high-resolution computed tomography of the chest (1994 through 1997). This group was a sample of a larger cohort of 321 HIV-seropositive persons who had undergone a detailed assessment of respiratory symptoms and pulmonary function. Most participants were from Columbus, Ohio, and were recruited through advertisements, by word of mouth, and by the Ohio State University Medical Center AIDS-Clinical Trials Unit. Less than 10% of the participants were receiving protease inhibitors at the time of this study. Persons with a history of Pneumocystis carinii pneumonia and other pulmonary complications of AIDS were excluded. Controls consisted of 44 HIV - seronegative volunteers matched for age, sex, and smoking history; they were recruited from the general population by advertisements. All participants completed a modified American Thoracic Society Questionnaire (6) for symptoms, smoking history, drug use, history of pneumonia, and medications. Nonsmokers were identified as having a history of cumulative cigarette smoking of 1 pack-year or less. Pulmonary function studies were performed according to American Thoracic Society standards. The study was approved by the Ohio State University human subjects review board. Informed consent was obtained from all participants. Computed tomography was performed with a GE 9800 CT scanner (GE Medical Systems, Milwaukee, Wisconsin) or a Picker PQ 2000 CT scanner (Picker International, Solon, Ohio) with 1.5-mm collimation at 10-mm intervals through the chest. Scans were obtained at total lung capacity in the supine position. Images were reconstructed by using the high spatial frequency algorithm and were photographed at a lung window width of 1500 Hounsfield units (brightness level, 700 Hounsfield units). Emphysema was considered present if the scans showed evidence of bullae, thin-walled cystic spaces, or abnormal decreases in attenuation, accompanied by vascular disruption. Emphysema severity was estimated by assigning an emphysema score (0 to 10) for each lobe according to the percentage of the lobe that was affected. The lingula was considered a separate lobe. The total score represented the sum for all lobes. Scans were interpreted by two experienced chest radiologists, who were blinded to the patients HIV status and physiologic data. Participants were considered to have clear evidence of at least early emphysema if 1) the computed tomography emphysema score was 6 or higher [for example, 25% of two lobes involved with emphysema] or 2) pulmonary function tests demonstrated a total lung capacity greater than 120% of the predicted value, a diffusing capacity less than 60% of predicted, and computed tomographic evidence of emphysema in more than two lobes. Bronchoalveolar lavage and differential cell counts were performed according to standard techniques (7) on consenting participants. This included 46 HIV-seropositive smokers and 14 control smokers. A sample containing more than 1 000 000 cells was analyzed by a fluorescence-activated cell sorter for T-lymphocyte subtyping. An experienced microbiologist, who was blinded to HIV status, examined all lavage samples for the presence of fungi, acid-fast bacilli, P. carinii, and bacteria. Statistical analyses were performed by using the SAS JMP package (8). Analysis of variance was used to compare groups, and post hoc analysis was performed by using the Dunnett procedure (8). The Pearson chi-square test was used for equality of proportions; exact P values were calculated for small samples (9). Results With the exception of a lower CD4 count and diffusing capacity in the HIV-seropositive group, the two study groups had similar baseline characteristics (Table). Of note, 25% of the HIV-seropositive group had a history of oral thrush; however, other HIV-related opportunistic infections were rarely reported (<2%). The percentage of HIV-seropositive persons who reported any use of intravenous drugs was low (approximately 10%), and no significant differences in the use of intravenous drugs, crack cocaine, or marijuana were found between the HIV-seropositive group and the control group. Table. Clinical and Demographic Characteristics of the Study Groups Clinical variables did not significantly differ between the HIV-seropositive group of this study and the 321 persons in the overall HIV cohort (Table). For example, the median age of the overall cohort was 33 years (range, 20 to 66 years), the median CD4 count was 348 cells/mm3 (range, 0 to 1188 cells/mm3), and the median diffusing capacity was 83.7% of predicted (range, 38.8% to 153%). Sixty-three percent of the overall cohort smoked cigarettes. Emphysema was identified in 17 of 114 HIV-seropositive participants compared with 1 of 44 HIV-seronegative controls (P=0.025). Only one HIV-seronegative participant had a computed tomography emphysema score as high as 6, whereas 14 HIV-seropositive participants had scores between 6 and 23. The mean (SE) emphysema score for the HIV-seropositive group with emphysema was 10.5 1.7, the mean total lung capacity was 110% 6.9% of predicted, and the diffusing capacity was 60.1% 11.3% of predicted. Of note, persons with emphysema had only mild airflow obstruction (ratio of FEV1 to FVC, 69.2% 9.4%), which may relate to a higher than expected number of persons (approximately 30%) demonstrating subpleural or peripheral lesions (10). The Figure shows examples of precocious emphysema in HIV-seropositive persons, with accompanying emphysema scores. Figure. High-resolution computed tomographic scans of the chest.A. arrows B. Because a relatively high proportion of cigarette smokers appeared to be susceptible to early destructive changes, we specifically studied the role of smoking history. Thirty-seven percent (14 of 38) of HIV-seropositive smokers with a smoking history of 12 pack-years or more met criteria for emphysema, compared with 0% (0 of 14) HIV-seronegative controls (P=0.011). Furthermore, 46% (11 of 24) of HIV-seropositive participants with a smoking history of 25 pack-years or more met criteria for emphysema, compared with 0% (0 of 10) in the HIV-seronegative controls (P=0.013). Next, using current pack-year of cigarette smoking as a covariate, we compared lung-cell populations among three groups of smokers: HIV-seronegative smokers (n=14), HIV-seropositive smokers without emphysema (n=34), and HIV-seropositive smokers with emphysema (n=12). The numbers of alveolar macrophages and neutrophils in the lavage fluid were similar among the three groups. Although the two HIV-seropositive groups were found to have threefold more lymphocytes than the uninfected controls, no significant difference in lymphocyte numbers were noted between HIV-seropositive persons with and those without emphysema. However, when lymphocyte subtypes were examined, HIV-seropositive persons with emphysema were found to have the highest percentage of lavage lymphocytes bearing the cytotoxic phenotype; the mean (SE) value in this group was 58% 4.6%, compared with 46.6% 2.3% in HIV-seropositive smokers without emphysema (P<0.05) and 32.2% 4.6% in HIV-seronegative smokers (P<0.01). Of note, no pathogens were observed in microbiological stains of lavage fluid from study participants. Discussion This prospective study demonstrates the development of an accelerated form of pulmonary emphysema in a stable HIV-seropositive outpatient sample. Furthermore, the results suggest that the lesion is related to a heightened susceptibility to cigarette smoke. We hypothesize that HIV infection or secondary inflammatory abnormalities directly accelerate the process of smoking-induced parenchymal lung destruction. The cellular mechanisms predisposing HIV-seropositive smokers to emphysema are unclear. However, immunologic aspects of HIV disease may be relevant to understanding emphysema pathogenesis in the general population. Of particular interest are the many bronchoalveolar lavage and lung pathology studies that have demonstrated increased numbers of cytotoxic lymphocytes in the lungs of HIV-seropositive persons (11-13). Although prevailing theories for emphysema have focused on smoking-induced production of proteolytic enzymes by neutrophils and macrophages (4, 5), recent morphometric analyses of lung biopsy sections from non-HIV-infected smokers have demonstrated a high correlation between lung lymphocytes and the presence of emphysema (14, 15). Furthermore, experimental evidence suggests that viral activation of cytotoxic lymphocytes may contribute to parenchymal lung destruction (16). Another potential mechanism recently hypothesized is that latent viral infections may be an important cofactor in the development of chronic obstructive pulmonary disease (17). Adenoviral proteins, latently expressed in host epithelial cells, a

Emphysema-like Pulmonary Disease Associated with Human Immunodeficiency Virus Infection

OBJECTIVE To describe a possible association between prolonged infection with human immunodeficiency virus (HIV) and a pathophysiologic process suggestive of pulmonary emphysema. DESIGN Case series. SETTING The Ohio State University Hospital, Columbus, Ohio. MEASUREMENTS AND MAIN RESULTS We describe four HIV-seropositive individuals ranging in age from 32 to 55 years who presented with dyspnea. Radiographic examination of the chest showed no infiltrates. All patients were presumed to have had prolonged HIV infection (mean CD4 count, 99.8 +/- 43 cells/mm3), but none had a previous history of pneumonia or opportunistic infections. Comprehensive examination of bronchoalveolar lavage fluid showed no pathogens or other complications of HIV infection. All patients had markedly abnormal pulmonary function tests that were suggestive of emphysema with air-trapping, hyperinflation, and a markedly decreased diffusing capacity. However, only minimal evidence of airflow obstruction was noted. Three patients subsequently had high-resolution computed tomographic scans of the chest that revealed emphysema-like bullous changes. Known causes of emphysema were not present in these patients. CONCLUSIONS Our findings support an association between prolonged HIV infection and an emphysema-like process. This syndrome may occur in the absence of previous pulmonary infections or apparent pulmonary complications and is characterized by unusual pulmonary function test abnormalities.

Macrophage-Colony-Stimulating Factor-Induced Activation of Extracellular-Regulated Kinase Involves Phosphatidylinositol 3-Kinase and Reactive Oxygen Species in Human Monocytes

We previously reported that activation of the phosphatidylinositol (PI) 3-kinase pathway was important in M-CSF-induced monocyte survival. Because M-CSF also induces activation of the mitogen-activated protein (MAP) kinase extracellular-regulated kinase (Erk), we focused on dissecting the mechanism used by M-CSF to induce Erk activation in human monocytes. We found that, in addition to the MAP/Erk kinase inhibitor PD098059, the PI 3-kinase inhibitors LY294002 and wortmannin both suppressed Erk activation in M-CSF-treated monocytes, suggesting that 3-phosphorylated products of PI 3-kinase played a role in Erk activation. Investigating the biochemical pathways regulated by PI 3-kinase to activate Erk, we found that, in response to M-CSF, normal human monocytes induced reactive oxygen species (ROS), which were suppressed by the PI 3-kinase inhibitor wortmannin but not by the solvent control DMSO or the MAP/Erk kinase inhibitor PD098059. We next found that, in the absence of M-CSF, ROS could induce Erk activation in human monocytes. Exogenous H2O2 induced Erk activation in human monocytes, which was suppressed by exogenous catalase. To determine whether ROS induced by M-CSF played a role in Erk activation, we found that N-acetylcysteine and diphenyleneiodonium both suppressed Erk activation in M-CSF-treated monocytes. Erk activation by M-CSF also seemed to play a role in cellular survival in monocytes. These data suggest that, in M-CSF-stimulated human monocytes, PI 3-kinase products and ROS production play a role in Erk activation and monocyte survival.

Respiratory muscle fiber remodeling in chronic hyperinflation: dysfunction or adaptation?

The diaphragm and other respiratory muscles undergo extensive remodeling in both animal models of emphysema and in human chronic obstructive pulmonary disease, but the nature of the remodeling is different in many respects. One common feature is a shift toward improved endurance characteristics and increased oxidative capacity. Furthermore, both animals and humans respond to chronic hyperinflation by diaphragm shortening. Although in rodent models this clearly arises by deletion of sarcomeres in series, the mechanism has not been proven conclusively in human chronic obstructive pulmonary disease. Unique characteristics of the adaptation in human diaphragms include shifts to more predominant slow, type I fibers, expressing slower myosin heavy chain isoforms, and type I and type II fiber atrophy. Although some laboratories report reductions in specific force, this may be accounted for by decreases in myosin heavy chain content as the muscles become more oxidative and more efficient. More recent findings have reported reductions in Ca(2+) sensitivity and reduced myofibrillar elastic recoil. In contrast, in rodent models of disease, there is no consistent evidence for loss of specific force, no consistent shift in fiber populations, and atrophy is predominantly seen only in fast, type IIX fibers. This review challenges the hypothesis that the adaptations in human diaphragm represent a form of dysfunction, secondary to systemic disease, and suggest that most findings can as well be attributed to adaptive processes of a complex muscle responding to unique alterations in its working environment.

NMR spin trapping: detection of free radical reactions using a phosphorus-containing nitrone spin trap.

This study employs 31P‐nuclear magnetic resonance (NMR) to probe for changes in molecular structure arising from reactions between free radicals and a phosphorus‐containing nitrone spin trap, 5‐diethoxyphosphoryl‐5‐methyl‐1‐pyrroline‐N‐oxide (DEPMPO). A number of biologically relevant free radical reactions were detected: a) reactions of DEPMPO with ⋅OH resulted in a new 31P‐NMR resonance at 27.05 ppm (shifted from the parent compound at 23.67 ppm); evidence suggests that this species is a diamagnetic hydroxy‐pyrrolidone reduction product; b) 31P‐NMR spectra of DEPMPO/⋅CH3 reactions resulted in peaks at 24.54, 30.83, and 32.31 ppm, while DEPMPO/⋅CH2OH produced peaks at 24.05, 30.80 and 32.52 ppm; in the presence of excess ascorbate, only resonances between 30 and 32 ppm were evident, which we have tentatively assigned to the hydroxylamine isomers of their respective adducts; and c) reaction of DEPMPO with O2⋅−, produced by xanthine/xanthine oxidase or stimulated neutrophils, resulted in a single line, indistinguishable from DEPMPO/⋅OH reaction products. We conclude that NMR spin trapping is a useful approach for detecting free radical reaction pathways. It may have future applications for human free radical biology and imaging. Magn Reson Med 42:228–234, 1999.

Respiratory Muscle Fatigue

Ventilatory failure may accompany a variety of pulmonary and neuromuscular diseases. There has been much controversy about whether this failure is due to respiratory muscle fatigue at peripheral sites or a failure of drive at sites within the central nervous system. The chapter reviews this topic.

Hyperthermia induces injury to the intestinal mucosa in the mouse: evidence for an oxidative stress mechanism

Loss of the intestinal barrier is critical to the clinical course of heat illness, but the underlying mechanisms are still poorly understood. We tested the hypothesis that conditions characteristic of mild heatstroke in mice are associated with injury to the epithelial lining of the intestinal tract and comprise a critical component of barrier dysfunction. Anesthetized mice were gavaged with 4 kDa FITC-dextran (FD-4) and exposed to increasing core temperatures, briefly reaching 42.4°C, followed by 30 min recovery. Arterial samples were collected to measure FD-4 concentration in plasma (in vivo gastrointestinal permeability). The small intestines were then removed to measure histological evidence of injury. Hyperthermia resulted in a ≈2.5-fold elevation in plasma FD-4 and was always associated with significant histological evidence of injury to the epithelial lining compared with matched controls, particularly in the duodenum. When isolated intestinal segments from control animals were exposed to ≥41.5°C, marked increases in permeability were observed within 60 min. These changes were associated with release of lactate dehydrogenase, evidence of protein oxidation via carbonyl formation and histological damage. Coincubation with N-acetylcysteine protected in vitro permeability during hyperthermia and reduced histological damage and protein oxidation. Chelation of intracellular Ca(2+) to block tight junction opening during 41.5°C exposure failed to reduce the permeability of in vitro segments. The results demonstrate that hyperthermia exposure in mouse intestine, at temperatures at or below those necessary to induce mild heatstroke, cause rapid and substantial injury to the intestinal lining that may be attributed, in part, to oxidative stress.

Dithiothreitol improves recovery from in vitro diaphragm fatigue.

There is increasing evidence that reactive oxygen species are produced during strenuous skeletal muscle work and that they contribute to the development of muscle fatigue. Although the precise cellular mechanisms underlying such a phenomenon remain obscure, it has been hypothesized that endogenously produced reactive oxygen species may down-regulate force production during fatigue by oxidizing critical sulfhydryl groups on important contractile proteins. To test this hypothesis, we fatigued rat diaphragm strips in vitro for 4 min at 20 Hz stimulation and a duty cycle of 0.33. Following fatigue, the tissue baths were drained and randomly replaced with either physiologic saline or physiologic saline containing the disulfide reducing agent, dithiothreitol (DTT) at varying doses (0.1-5.0 mM). Force-frequency characteristics were then measured over a 90-min recovery period. At the 0.5 and 1.0 mM doses, DTT treatment was associated with significantly greater force production in the recovery period. DTTs effects were observed at most frequencies tested, but appeared more prominent at the higher frequencies. The beneficial effects of DTT were not evident at the 0.1 or 5.0 mM doses and appeared to be specific for fatigued muscle. These recovery-enhancing effects of a potent disulfide reducing agent suggest that important contractile proteins may be oxidized during fatigue; such changes may be readily reversible.

Biological Reactions of Peroxynitrite: Evidence for an Alternative Pathway of Salicylate Hydroxylation

Salicylate hydroxylation has often been used as an assay of hydroxyl radical production in vivo. We have examined here if hydroxylation of salicylate might also occur by its reaction with peroxynitrite. To test this hypothesis, we exposed salicylate to various concentrations of peroxynitrite, in vitro. We observed the hydroxylation of salicylate at 37 degrees C by peroxynitrite at pH 6, 7 and 7.5, where the primary products had similar retention times on HPLC to 2,3- and 2,5-dihydroxybenzoic acid. The product yields were pH dependent with maximal amounts formed at pH 6. Furthermore, the relative concentration of 2,3- to 2,5-dihydroxybenzoic acid increased with decreasing pH. Nitration of salicylate was also observed and both nitration and hydroxylation reaction products were confirmed independently by mass spectrometry. The spin trap N-t-butyl-alpha-phenylnitrone (PBN), with or without dimethyl sulfoxide (DMSO), was incapable of trapping the peroxynitrite decomposition intermediates. Moreover, free radical adducts of the type PBN/.CH3 and PBN/.OH were susceptible to destruction by peroxynitrite (pH 7, 0.1 M phosphate buffer). These results suggest direct peroxynitrite hydroxylation of salicylate and that the presence of hydroxyl radicals is not a prerequisite for hydroxylation reactions.

HIV Infection Increases Susceptibility to Smoking- Induced Emphysema*

2000;117;285S Chest Henk F. Kauffman and Dirkje S. Postma Steven R. Rutgers, Huib AM Kerstjens, Wim Timens, Nikolaos Tzanakis, * -Monophosphate in COPD ′ Hyperresponsiveness to Adenosine 5 Airway Inflammation and http://chestjournal.chestpubs.org/content/117/5_suppl_1/285S.2.full.html services can be found online on the World Wide Web at: The online version of this article, along with updated information and ISSN:0012-3692 ) http://chestjournal.chestpubs.org/site/misc/reprints.xhtml ( written permission of the copyright holder. this article or PDF may be reproduced or distributed without the prior Dundee Road, Northbrook, IL 60062. All rights reserved. No part of Copyright2000by the American College of Chest Physicians, 3300 Physicians. It has been published monthly since 1935. is the official journal of the American College of Chest Chest