Cigarette smoking is the main cause of chronic obstructive pulmonary disease (COPD). Diaphragm injury is observed in patients with COPD. However, the potential role of smoking in triggering or perpetuating muscle injury is unknown. The present study was aimed at evaluating the potential role of commercial tobacco smoke as a direct cause of skeletal muscle injury in experimental conditions. Seventy Wistar rats (170 - 250 g) were assigned to smoking (n = 49) or non-smoking (n = 21) groups. The smoking groups were submitted to a single or multiple (i.e., five or thirty) daily sessions of cigarette smoking in an inhalatory chamber (time length: 2 h each session). The level of exposure was constant and assessed by CO concentrations (50 ppm) and serum cotinine analysis. Animals submitted to a single smoke exposure and the corresponding controls were euthanized in groups at 0 h, 2 h, 4 h, 24 h or 48 h after completing the exposure. Animals submitted to multiple exposures were euthanized at 0 h after smoking. Samples from vastus lateralis muscle were obtained and processed for assessing cell injury and selected protein expression. Monoclonal anti-albumin antibodies were used to identify muscle fibers with sarcolemmal (membrane) injury. Subcellular muscle injury was assessed using transmission electron microscopy (EM). MyoD, myogenin and α-tubulin were immunodetected using western blot techniques. Exposure to cigarette smoke associated with significant membrane damage (mean relative difference (MRD) with controls: +181%, p = 0.004) and sarcomere disruptions (MRD: +226%, p = 0.001). Expression of MyoD and myogenin (normalized to α-tubulin) were significantly increased at 4 h and remained increased at 48 h post-exposure. We conclude that not only a single but also consecutive exposure to tobacco smoke have acute deleterious effects on peripheral muscle structure. A rapid induction of subrogate markers of skeletal muscle stress and repair processes associates to sarcolemmal and sarcomere damage.

Oxidative stress may differentially regulate protein loss within peripheral muscles of severe chronic obstructive pulmonary disease (COPD) patients exhibiting different body composition. Oxidation levels of proteins, myosin heavy chain (MyHC) and myonuclei, superoxide anion, antioxidants, actin, creatine kinase, carbonic anhydrase-3, ubiquitin-proteasome system, redox-signalling pathways, inflammation and muscle structure, and damage were quantified in limb muscles of severe COPD patients with and without muscle wasting, and in sedentary controls. Compared with controls, in the quadriceps of muscle-wasted COPD patients, levels of protein carbonylation, oxidation of MyHC and myonuclei, superoxide anion production, superoxide dismutase, total protein ubiquinitation, E2(14k), atrogin-1, FoxO1 and p65 were higher, while content of MyHC, creatine kinase, carbonic anhydrase-3, myogenin, and fast-twitch fibre size were decreased. Importantly, in nonwasted COPD patients, where MyHC was more oxidised than in controls, its content was preserved. Muscle inflammation and glutathione levels did not differ between patients and controls. In all patients, muscle structure abnormalities were increased, while muscle force and exercise capacity were reduced. In severe COPD, while muscle oxidative stress increases regardless of their body composition, protein ubiquitination and loss of MyHC were enhanced only in patients exhibiting muscle atrophy. Oxidative stress does not seem to directly modulate muscle protein loss in these patients.

Muscle injury has clinical relevance in diseased individuals because it is associated with muscle dysfunction in terms of decreased strength and/or endurance. This study was aimed at answering three questions: whether the presence of chronic obstructive pulmonary disease (COPD) is associated with peripheral muscle injury; whether muscle injury is associated with some of the relevant functional impairment in the muscles; and whether muscle injury can be solely justified by deconditioning. Twenty-one male COPD patients were eligible for the study. Seven healthy volunteers recruited from the general population were included as controls. Function of the quadriceps muscle was assessed through specific single-leg exercise (strength and endurance). Cellular (light microscopy) and subcellular (electron microscopy) techniques were used to evaluate muscle injury on biopsies from the vastus lateralis muscle. Signs of injury were found in muscles from both control and COPD patients, not only in cases showing severe airflow obstruction but also in the mild or moderate stages of the disease. Current smoking and presence of COPD were significantly associated with increased injury of the muscle as assessed by light and electron microscopy techniques. The authors conclude that peripheral muscle injury is evident in mild, moderate, and severe stages of COPD even in the absence of respiratory failure, hypercapnia, chronic steroid treatment, low body weight, or some coexisting disease. These findings support the theory that systemic factors with deleterious effect are acting on peripheral muscles of smokers with COPD, increasing the susceptibility of the muscle fibers to membrane and sarcomere injury.

Exacerbations of chronic obstructive pulmonary disease (COPD) are associated with several modifiable (sedentary life style, smoking, malnutrition, hypoxemia) and non modifiable (age co morbidities, severity of pulmonary function, respiratory infections) risk factors We hypothesise that most of these risk factors may have a converging and deleterious effects on both respiratory and peripheral muscle function in COPD patientsMethods A multicentre study was carried out in 121 COPD patients (92% males, 63 +/- 11 yr, FEV1, 49 +/- 17%pred) Assessments included anthropometrics, lung function, body composition using bioelectrical impedance analysis (BIA), and global muscle function (peripheral muscle (dominant and non dominant hand grip strength, HGS), inspiratory (Pl(max)), and expiratory (PEmax) muscle strength) GOLD stage, clinical status (stable vs non stable) and both current and past hospital admissions due to COPD exacerbations were included as covariates in the analysesResults Respiratory and peripheral muscle weakness were observed in all subsets of patients Muscle weakness, was significantly associated with both current and past hospitalisations Patients with history of multiple admissions showed increased global muscle weakness after adjusting by FEV1 (PEmax, OR = 6 8, p < 0 01, Pl(max), OR = 2 9, p < 0 05, HGSd, OR = 2 4, and HGSnd, OR = 2 6, p = 0 05) Moreover, a significant increase in both respiratory and peripheral muscle weakness, after adjusting by FEV1, was associated with current acute exacerbationsConclusions Muscle dysfunction, adjusted by GOLD stage, is associated with an increased risk of hospital admissions due to acute episodes of exacerbation of the disease Current exacerbations further deteriorate muscle dysfunction (C) 2010 Elsevier Ltd All rights reserved

Michael T. Borchers,1,2 Scott C. Wesselkamper,1 Victor Curull,3,4,5 Alba Ramirez-Sarmiento,3,4 Albert Sánchez-Font,3,4 Judith Garcia-Aymerich,6 Carlos Coronell,3 Josep Lloreta,7,8 Alvar G. Agusti,9,10 Joaquim Gea,4,7,9 John A. Howington,11 Michael F. Reed,11 Sandra L. Starnes,11 Nathaniel L. Harris,1 Mark Vitucci,1 Bryan L. Eppert,1 Gregory T. Motz,1 Kevin Fogel,2 Dennis W. McGraw,2 Jay W. Tichelaar,12 and Mauricio Orozco-Levi3,4,7,9

OBJECTIVE:There is disagreement regarding the local action of cytokines in the respiratory muscles of patients with chronic obstructive pulmonary disease (COPD). The objective of this study was to analyze the relationships between cytokine expression and genetic activation of the mechanisms of muscle repair. PATIENTS AND METHODS:Twenty-five patients with severe COPD and in stable condition were enrolled in the study. We performed a biopsy of the external intercostal muscle of the patients and analyzed the specimen for signs of muscle lesion (morphometry), infiltration of inflammatory cells (immunohistochemistry), and expression of selected genes (real-time polymerase chain reaction technique) corresponding to the cytokines (tumor necrosis factor alpha [TNF-alpha] and its type 1 and 2 receptors [TNFR1 and TNFR2], and interleukin [IL] 1beta, IL-6, and IL-10), a pan-leukocyte marker (CD18), and key molecules in the repair-myogenesis pathways (Pax7, M-cadherin, and MyoD). RESULTS:Expression of TNFR2 is directly related to inspiratory muscle function (represented by maximum sustainable inspiratory pressure; r=0.496; P<.05), whereas expression of CD18 is inversely related (r=0.462; P<.05). Moreover, expression of the 2 TNF-alpha receptors was directly related to that of the key molecules of the repair pathways analyzed (TNFR1 to Pax7 [r=0.650; P<.001] and M-cadherin [r=0.678; P<.001]; TNFR2 to Pax7 [r=0.395; P<.05], M-cadherin [r=0.409; P<.05], and MyoD [r=0.418; P<.05]). CONCLUSIONS:Expression of TNF-alpha receptors bears a close relationship both to activation of the myogenesis programs and to inspiratory muscle function. This reinforces our hypothesis that some local cytokines take part in the repair of respiratory muscles in patients with COPD.

Chronic obstructive pulmonary disease (COPD) is a lethal progressive lung disease culminating in permanent airway obstruction and alveolar enlargement. Previous studies suggest CTL involvement in COPD progression; however, their precise role remains unknown. Here, we investigated whether the CTL activation receptor NK cell group 2D (NKG2D) contributes to the development of COPD. Using primary murine lung epithelium isolated from mice chronically exposed to cigarette smoke and cultured epithelial cells exposed to cigarette smoke extract in vitro, we demonstrated induced expression of the NKG2D ligand retinoic acid early transcript 1 (RAET1) as well as NKG2D-mediated cytotoxicity. Furthermore, a genetic model of inducible RAET1 expression on mouse pulmonary epithelial cells yielded a severe emphysematous phenotype characterized by epithelial apoptosis and increased CTL activation, which was reversed by blocking NKG2D activation. We also assessed whether NKG2D ligand expression corresponded with pulmonary disease in human patients by staining airway and peripheral lung tissues from never smokers, smokers with normal lung function, and current and former smokers with COPD. NKG2D ligand expression was independent of NKG2D receptor expression in COPD patients, demonstrating that ligand expression is the limiting factor in CTL activation. These results demonstrate that aberrant, persistent NKG2D ligand expression in the pulmonary epithelium contributes to the development of COPD pathologies.

Oxidative stress is involved in the sarcopenia of aging muscles. On the grounds that ventilatory muscles are permanently active, and their activity may even increase with aging, we hypothesized that the levels of oxidative stress would probably be increased in the external intercostals of elderly healthy individuals. We conducted a case-control study in which reactive carbonyl groups, malondialdehyde-protein adducts, 3-nitrotyrosine immunoreactivity, Mn-superoxide dismutase (Mn-SOD), and catalase were detected using immunoblotting in external intercostals and quadriceps (open muscle biopsies) obtained from 12 healthy elderly and 12 young individuals of both sexes. In elderly subjects, reactive carbonyls, malondialdehyde-protein adducts, 3-nitrotyrosine, Mn-SOD, and catalase were significantly greater in the external intercostals than in the young controls. A post hoc analysis, in which men and women from both groups were analyzed separately, revealed that the external intercostals of elderly women, but not those of elderly men, showed significantly increased levels of reactive carbonyls, malondialdehyde-protein adducts, 3-nitrotyrosine, and Mn-SOD compared to those of control females. This study suggests that differences in muscle activity might explain the differential pattern of oxidative stress observed in human respiratory and limb muscles with aging as well as the likely existence of a sex-related regulation of this phenomenon in these muscles.

OBJECTIVE:Magnetic stimulation of the diaphragm allows its strength to be assessed. The clinical applications of this technique are becoming more widespread given that the patient's cooperation is not required. The aim of the present study was to compare this inhalation technique with traditional voluntary forced inspiration (sniff test) in a group of patients with chronic obstructive pulmonary disease (COPD).PATIENTS AND METHODS:Sixteen men with moderate-to-severe COPD were studied (mean [SD] forced expiratory volume in 1 second, 35% [15%] of the reference value). For all patients, the maximal transdiaphragmatic pressure (a measure of the contractility of the muscle) was determined at peak inspiration and during cervical magnetic stimulation.RESULTS:A moderate correlation between measurements with the 2 techniques was observed. The value obtained with stimulation was approximately 20% of that obtained with the sniff maneuver (22 [7] cm H2O vs 97 [27] cm H2O, respectively). The stimulation technique yielded an intraindividual coefficient of variability of 12% (7%) and an interindividual one of 33% (6%). Very similar values for these coefficients were obtained with the sniff maneuver. Qualitative analysis of the stimulation technique showed it to have a high sensitivity (89%) for diagnosing muscle weakness, with few false negatives. In contrast, specificity was very low (43%), and false positives for muscle weakness were relatively common. The overall effectiveness of the prediction was acceptable (69%).CONCLUSIONS:Cervical magnetic stimulation appears to be a good clinical option for ruling out diaphragm weakness. It is particularly indicated in patients with limited capacity for understanding instructions or those unable to cooperate.

Objetivo La estimulacion magnetica del iafragma es una tecnica que permite evaluar la fuerza de este musculo. Dado que obvia la necesidad de colaboracion del paciente, va extendiendo progresivamente su aplicacion clinica. El objetivo del presente estudio ha sido comparar esta tecnica de estimulacion con la clasica de inhalacion voluntaria forzada (sniff) en un grupo de pacientes con enfermedad pulmonary obstructiva cronica (EPOC). Pacientes y metodos Se estudio a 16 pacientes varones con EPOC de moderada a grave (valor medio ± desviacion estandar del volumen espiratorio forzado en el primer Segundo del 35 ± 15% del valor de referencia). En todos ellos se obtuvo la presion maxima del diafragma (expresion de la fuerza contractil del musculo) por maniobras de inhalacion voluntaria maxima y de estimulacion cervical magnetica. Resultados Se observo una relacion moderada entre ambas tecnicas, siendo los valores obtenidos con estimulacion de aproximadamente un 20% de los obtenidos con la maniobra voluntaria (97 ± 27 y 22 ± 7 cmH2O, respectivamente). La tecnica de estimulacion mostro unos coeficientes de variabilidad intraindividual del 12 ± 7%, e interindividual del 33 ± 6%, muy similares a los del metodo de inhalacion. El analisis cualitativo de la tecnica de estimulacion para el diagnostico de debilidad muscular mostro una elevada sensibilidad (89%), con escasos falsos negativos. Por el contrario, su especificidad fue muy baja (43%), con una tasa relativamente elevada de sobrediagnosticos. La eficacia de la prediccion resulto globalmente aceptable (69%). Conclusiones La tecnica de estimulacion magnetica cervical se muestra como una buena opcion clinica para descartar debilidad del diafragma, con indicacion sobre todo en pacientes con poca capacidad de comprension o incapacidad de colaboracion.

El objetivo del presente estudio fue evaluar de forma prospectiva los efectos de una exacerbación clínica de la enfermedad pulmonar obstructiva crónica (EPOC) sobre la función muscular esquelética periférica y respiratoria Se seleccionó a 49 pacientes (todos varones con una edad media [DE] de 63 [11] años), asignados a 3 cohortes para el análisis: a) pacientes con EPOC hospitalizados por exacerbación de su enfermedad en sala convencional; b) pacientes hospitalizados en sala convencional por otra enfermedad pulmonar o nódulo pulmonar, y c) pacientes con EPOC en fase estable (ambulatorios). Se realizaron mediciones secuenciales mediante antropometría, bioquímica sérica y bioimpedancia corporal. En la cohorte de pacientes con EPOC agudizada se evaluaron los cambios en la función de los músculos periféricos (fuerza y resistencia de las manos dominante y no dominante), así como de los músculos inspiratorios y espiratorios Se evaluó a los pacientes durante un período medio de 6 (2) días. Los pacientes con EPOC exacerbada mostraron un deterioro funcional muscular, progresivo y global, expresado como disminución de la presión espiratoria máxima del 17% (12%), de la fuerza máxima de la mano dominante del 6% (9%) y de la no dominante del 7% (8%), así como de la resistencia anaeróbica de la mano dominante del 28% (26%) y de la no dominante del 23% (16%). Estos cambios tuvieron una tendencia lineal. La bioimpedancia corporal expresó una pérdida media de masa magra del 7% (6%) (p < 0,05), que habría pasado inadvertida si se hubiera cuantificado el peso corporal únicamente. Los casos de neumonía mostraron cambios similares en la BIA. Por otra parte, la cohorte de pacientes con EPOC estable no mostró cambios en la función muscular ni la en la bioimpedancia corporal La agudización de la EPOC se asocia a un deterioro agudo y global de la función de los músculos esqueléticos espiratorios y periféricos. Es posible que estos cambios estén relacionados con una pérdida aguda de masa muscular (proteólisis). Esta disfunción muscular no se detecta si se evalúa únicamente la función muscular inspiratoria, probablemente por la coexistencia de factores mecánicos transitorios The purpose of this study was to evaluate on a prospective fashion the effects of clinical relapses of chronic obstructive pulmonary disease (COPD) on both peripheral and respiratory skeletal muscle functions We included 49 patients (males, 63 [11] years) who were assigned to three cohorts: a) COPD patients who were hospitalized in a conventional ward because of a relapse of their disease; b) patients hospitalzed in conventional wards because of another lung disease or a pulmonary nodule; and c) COPD patients whose disease was stabilized (outpatients). Sequential measurements were made by means of anthropometry, serum biochemistry and body bioimpedance (BIA). In COPD patients with a disease relapse, we assessed changes in the function of peripheral muscles [force (Fhand) and resistance (Tlimhand) of hands], inspiratory muscles (PImax) and espiratory muscles (PEmax) Patients were evauluated during a 6 [2] days period. Patients with a COPD relapse displayed a global and progressive functional muscle impairment, which was expressed as a decrease of PEmax (17 [12]%), F hand-D (6 [9]%), F hand-ND (7 [8]%), Tlim hand-D (28 [26]%) and Tlim hand-ND (23 [16]%). These changes showed a linear trend. BIA exhibited a loss of lean mass (7 [6]%, p < 0.05) which would have been unnoticeable if only the body weight was quantified. Pneumonia cases showed similar changes in BIA. On the other hand, the cohort of patients with stable COPD did not have changes in both muscle function and BIA COPD exacerbation is associated with an acute and global impairment of the function of espiratory and peripheral skeletal muscles. It is possible that these changes are related to an acute loss of muscular mass (proteolysis). This muscle dysfunction is not detected if only the inspiratory muscular fucntion is evaluated – possibly because of the coexistence of transitory mechanic factors