The rat model of COPD skeletal muscle dysfunction induced by progressive cigarette smoke exposure: a pilot study

Aerobic exercise training engages the canonical wnt pathway to improve pulmonary function and inflammation in COPD

BACKGROUND

We studied whether the exercise improves cigarette smoke (CS) induced chronic obstructive pulmonary disease (COPD) in mice through inhibition of inflammation mediated by Wnt/β-catenin-peroxisome proliferator-activated receptor (PPAR) γ signaling.

METHODS

Firstly, we observed the effect of exercise on pulmonary inflammation, lung function, and Wnt/β-catenin-PPARγ. A total of 30 male C57BL/6J mice were divided into the control group (CG), smoke group (SG), low-intensity exercise group (LEG), moderate-intensity exercise group (MEG), and high-intensity exercise group (HEG). All the groups, except for CG, underwent whole-body progressive exposure to CS for 25 weeks. Then, we assessed the maximal exercise capacity of mice from the LEG, MEG, and HEG, and performed an 8-week treadmill exercise intervention. Then, we used LiCl (Wnt/β-catenin agonist) and XAV939 (Wnt/β-catenin antagonist) to investigate whether Wnt/β-catenin-PPARγ pathway played a role in the improvement of COPD via exercise. Male C57BL/6J mice were randomly divided into six groups (n = 6 per group): CG, SG, LiCl group, LiCl and exercise group, XAV939 group, and XAV939 and exercise group. Mice except those in the CG were exposed to CS, and those in the exercise groups were subjected to moderate-intensity exercise training. All the mice were subjected to lung function test, lung histological assessment, and analysis of inflammatory markers in the bronchoalveolar lavage fluid, as well as detection of Wnt1, β-catenin and PPARγ proteins in the lung tissue.

RESULTS

Exercise of various intensities alleviated lung structural changes, pulmonary function and inflammation in COPD, with moderate-intensity exercise exhibiting significant and comprehensive effects on the alleviation of pulmonary inflammation and improvement of lung function. Low-, moderate-, and high-intensity exercise decreased β-catenin levels and increased those of PPARγ significantly, and only moderate-intensity exercise reduced the level of Wnt1 protein. Moderate-intensity exercise relieved the inflammation aggravated by Wnt agonist. Wnt antagonist combined with moderate-intensity exercise increased the levels of PPARγ, which may explain the highest improvement of pulmonary function observed in this group.

CONCLUSIONS

Exercise effectively decreases COPD pulmonary inflammation and improves pulmonary function. The beneficial role of exercise may be exerted through Wnt/β-catenin-PPARγ pathway.

Lung transcriptomics reveals the underlying mechanism by which aerobic training enhances pulmonary function in chronic obstructive pulmonary disease

BACKGROUND

Aerobic training is the primary method of rehabilitation for improving respiratory function in patients with chronic obstructive pulmonary disease (COPD) in remission. However, the mechanism underlying this improvement is not yet fully understood. The use of transcriptomics in rehabilitation medicine offers a promising strategy for uncovering the ways in which exercise training improves respiratory dysfunction in COPD patients. In this study, lung tissue was analyzed using transcriptomics to investigate the relationship between exercise and lung changes.

METHODS

Mice were exposed to cigarette smoke for 24 weeks, followed by nine weeks of moderate-intensity treadmill exercise, with a control group for comparison. Pulmonary function and structure were assessed at the end of the intervention and RNA sequencing was performed on the lung tissue.

RESULTS

Exercise training was found to improve airway resistance and lung ventilation indices in individuals exposed to cigarette smoke. However, the effect of this treatment on damaged alveoli was weak. The pair-to-pair comparison revealed numerous differentially expressed genes, that were closely linked to inflammation and metabolism.

CONCLUSIONS

Further research is necessary to confirm the cause-and-effect relationship between the identified biomarkers and the improvement in pulmonary function, as this was not examined in the present study.

Main Pathogenic Mechanisms and Recent Advances in COPD Peripheral Skeletal Muscle Wasting

Chronic obstructive pulmonary disease (COPD) is a worldwide prevalent respiratory disease mainly caused by tobacco smoke exposure. COPD is now considered as a systemic disease with several comorbidities. Among them, skeletal muscle dysfunction affects around 20% of COPD patients and is associated with higher morbidity and mortality. Although the histological alterations are well characterized, including myofiber atrophy, a decreased proportion of slow-twitch myofibers, and a decreased capillarization and oxidative phosphorylation capacity, the molecular basis for muscle atrophy is complex and remains partly unknown. Major difficulties lie in patient heterogeneity, accessing patients' samples, and complex multifactorial process including extrinsic mechanisms, such as tobacco smoke or disuse, and intrinsic mechanisms, such as oxidative stress, hypoxia, or systemic inflammation. Muscle wasting is also a highly dynamic process whose investigation is hampered by the differential protein regulation according to the stage of atrophy. In this review, we report and discuss recent data regarding the molecular alterations in COPD leading to impaired muscle mass, including inflammation, hypoxia and hypercapnia, mitochondrial dysfunction, diverse metabolic changes such as oxidative and nitrosative stress and genetic and epigenetic modifications, all leading to an impaired anabolic/catabolic balance in the myocyte. We recapitulate data concerning skeletal muscle dysfunction obtained in the different rodent models of COPD. Finally, we propose several pathways that should be investigated in COPD skeletal muscle dysfunction in the future.

Analysis of serum exosome microRNAs in the rat model of chronic obstructive pulmonary disease

BACKGROUND

MicroRNAs (miRNAs) play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the molecular mechanisms underlying the function of miRNAs remain to be fully understood. This study aimed to explore the profile of serum exosome-derived miRNAs in the rat model of COPD.

METHODS

We established the COPD rat model by cigarette smoke exposure (CSE). The pulmonary function and morphological changes were analyzed. Serum exosomes were examined by transmission electron microscopy (TEM) and western blotting. The differentially expressed miRNAs between COPD and healthy rats were screened from exosome-derived small RNA library using bioinformatics analysis and experimentally verified in rat lung tissues by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

The pulmonary function indexes in COPD rats were significantly decreased compared to control rats. The typical pathological manifestations of emphysema were observed in COPD rats. Marker proteins (CD9, CD63, and TSG101) and characteristic morphology features were detected in serum exosomes. Fifteen differentially expressed miRNAs were identified in the small RNA library. In addition, we confirmed that the expression of miR-185-5p and miR-182-5p was significantly down-regulated in the lung tissues of COPD rats compared to control rats.

CONCLUSION

The expression of miR-185-5p and miR-182-5p was down-regulated in serum-derived exosomes and lung tissues of COPD rats, indicating that these two miRNAs might be involved in the development of COPD and might serve as potential biomarkers for the diagnosis of COPD.

Association between Sleep Duration and Hand Grip Strength among COPD Patients

This study aimed to evaluate the association between night-time sleep duration and hand grip strength (HGS) among patients with chronic obstructive pulmonary disease (COPD). Participants aged ≥45 years were included in a nationally representative investigation clinical study in 2015. HGS was measured using dynamometers. The data on night-time sleep duration, sociodemographic information, and health-related variables were systematically collected. For analysis, sleep duration was categorized as <5 h, 5-7 h, 7 h, 7-9 h, and >9 h. Multivariable linear regression models were used to determine the possible association between the night-time sleep duration and HGS. Our results indicated that the shortest (<5 h) or the longest sleep duration (>9 h) was relevant to high risk of weaker HGS in females. In males, the shortest (<5 h) sleep duration was correlated to lower HGS. Thus, our findings clearly suggest that health care providers should focus on the potential influence of sleep duration on HGS among COPD patients.

Involvement of Parkin-mediated mitophagy in the pathogenesis of chronic obstructive pulmonary disease-related sarcopenia

BACKGROUND

Sarcopenia is characterized by the loss of skeletal muscle mass and strength and is associated with poor prognosis in patients with chronic obstructive pulmonary disease (COPD). Cigarette smoke (CS) exposure, a major cause for COPD, induces mitochondrial damage, which has been implicated in sarcopenia pathogenesis. The current study sought to examine the involvement of insufficient Parkin-mediated mitophagy, a mitochondrion-selective autophagy, in the mechanisms by which dysfunctional mitochondria accumulate with excessive reactive oxygen species (ROS) production in the development of COPD-related sarcopenia.

METHODS

The involvement of Parkin-mediated mitophagy was examined using in vitro models of myotube formation, in vivo CS-exposure model using Parkin^-/- mice, and human muscle samples from patients with COPD-related sarcopenia.

RESULTS

Cigarette smoke extract (CSE) induced myotube atrophy with concomitant 30% reduction in Parkin expression levels (P < 0.05). Parkin-mediated mitophagy regulated myotube atrophy by modulating mitochondrial damage and mitochondrial ROS production. Increased mitochondrial ROS was responsible for myotube atrophy by activating Muscle Ring Finger 1 (MuRF-1)-mediated myosin heavy chain (MHC) degradation. Parkin^-/- mice with prolonged CS exposure showed enhanced limb muscle atrophy with a 31.7% reduction in limb muscle weights (P < 0.01) and 2.3 times greater MuRF-1 expression (P < 0.01) compared with wild-type mice with concomitant accumulation of damaged mitochondria and oxidative modifications in 4HNE expression. Patients with COPD-related sarcopenia exhibited significantly reduced Parkin but increased MuRF-1 protein levels (35% lower and 2.5 times greater protein levels compared with control patients, P < 0.01 and P < 0.05, respectively) and damaged mitochondria accumulation demonstrated in muscles. Electric pulse stimulation-induced muscle contraction prevented CSE-induced MHC reduction by maintaining Parkin levels in myotubes.

CONCLUSIONS

Taken together, COPD-related sarcopenia can be attributed to insufficient Parkin-mediated mitophagy and increased mitochondrial ROS causing enhanced muscle atrophy through MuRF-1 activation, which may be at least partly preventable through optimal physical exercise.

Magnesium isoglycyrrhizinate inhibits airway inflammation in rats with chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a kind of chronic lung diseases with the characteristics of airway remodeling and airflow obstruction. Magnesium isoglycyrrhizinate (MgIG) is an anti-inflammatory glycyrrhizic acid preparation for treating hepatitis. However, whether MgIG can treat other diseases and its action mechanism is still obscure. In this study, we evaluated the anti-inflammatory effect of MgIG in rats with COPD and investigated the underlying mechanisms.

Methods

Rat model of COPD was constructed by endotracheal-atomized lipopolysaccharide exposure and cigarette smoke induction. Rats were randomly divided into 5 groups: control group, COPD model group, salmeterol fluticasone comparator group, low dose of MgIG group, and high dose of MgIG group. Except for normal control group, the other four groups received sensitization treatment by cigarette smoking and endotracheal-atomization of endotoxin lipopolysaccharide to construct COPD rats model. After model established successfully, the COPD rats in each group received corresponding dose of endotracheal-atomized normal saline, salmeterol fluticasone, and MgIG every day prior to exposure of cigarette smoke from days 30 to 45. Normal control group were treated with normal saline. Finally, All rats were euthanatized. Pulmonary function was measured. Cells in bronchoalveolar lavage fluid were classified, inflammatory factors IL-6 and TNF-α were determined, histopathological analysis was performed by HE staining, and expression of NLRP3 and cleaved caspase-1 in the lung tissue was also determined by Western blotting.

Results

It showed that MgIG treatment (0.40 or 0.80 mg/kg/day) could recover the weight and the clinical symptoms of rats with COPD, accompanied with lung inflammation infiltration reduction, airway wall attenuation, bronchial mucus secretion reduction. Additionally, MgIG administration reduced inflammatory cells (white blood cells, neutrophils, lymphocytes and monocytes) accumulation in bronchoalveolar lavage fluid and decreased IL-6 and TNF-α production in the serum of COPD rats. Furthermore, MgIG treatment also reduced the expression level of NLRP3 and cleaved caspase-1.

Conclusion

It indicate that MgIG might be an alternative for COPD treatment, and its mechanism of action might be related to the suppression of NLRP3 inflammasome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01745-7.

Factors affecting the severity of fatigue in male patients with chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVES

Fatigue, the second most common symptom after dyspnea in patients with chronic obstructive pulmonary disease, impairs functional capacity and quality of life. This study aims to predict the factors that affect fatigue severity and investigate the effects of fatigue in patients with chronic obstructive pulmonary disease.

METHODS

Data were collected to assess demographic and clinical characteristics, cigarette consumption, fatigue severity (Fatigue Severity Scale), dyspnea severity (Medical Research Council Dyspnea Scale), level of physical activity (International Physical Activity Questionnaire-Short Form), and health-related quality of life (36-Item Short Form Health Survey).

RESULTS

A total of 64 male chronic obstructive pulmonary disease patients were evaluated (mean age 61.1±4.7 years, mean Fatigue Severity Scale score 39.8±14.4). The result of the linear regression model was significant and explained 84% of the variance in fatigue severity (Adjusted R-squared=0.84, F=29.48, df=60, p<.001). It showed that the Medical Research Council Dyspnea Scale score (β=.40), cigarette consumption (β=.35), and physical activity level (β=-.37) were significantly correlated with the severity of fatigue (p<.001 for all) and that they independently contributed to the prediction of severity of fatigue.

CONCLUSION

Dyspnea, cigarette consumption, and physical activity level affect fatigue severity. Additionally, physical activity level, pulmonary function, and health-related quality of life were also associated with fatigue. These findings support the assertion that it is important to measure fatigue and the factors that affect its severity.

Factors affecting the severity of fatigue in male patients with chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVES

Fatigue, the second most common symptom after dyspnea in patients with chronic obstructive pulmonary disease, impairs functional capacity and quality of life. This study aims to predict the factors that affect fatigue severity and investigate the effects of fatigue in patients with chronic obstructive pulmonary disease.

METHODS

Data were collected to assess demographic and clinical characteristics, cigarette consumption, fatigue severity (Fatigue Severity Scale), dyspnea severity (Medical Research Council Dyspnea Scale), level of physical activity (International Physical Activity Questionnaire Short-Form), and health-related quality of life (36-Item Short Form Health Survey).

RESULTS

A total of 64 male COPD patients were evaluated (mean age 61.1 ± 4.7 years, mean FSS score 39.8 ± 14.4). The result of the linear regression model was significant and explained 84% of the variance in fatigue severity (Adjusted R-squared = 0.84, F = 29.48, df = 60, p < .001). It showed that the MRC score (β = .40), cigarette consumption (β = .35), and physical activity level (β = -.37) were significantly correlated with the severity of fatigue (p < .001 for all) and that they independently contributed to the prediction of severity of fatigue.

CONCLUSION

Dyspnea, cigarette consumption, and physical activity level affect fatigue severity. Additionally, physical activity level, pulmonary function, and HRQOL were also associated with fatigue. These findings support the assertion that it is important to measure fatigue and the factors that affect its severity.

Ninjin'yoeito Ameliorates Skeletal Muscle Complications in COPD Model Mice by Upregulating Peroxisome Proliferator-Activated Receptor γ Coactivator-1α Expression

Purpose

Sarcopenia, the loss of skeletal muscle mass and strength, is a common systemic consequence of chronic obstructive pulmonary disease (COPD) and is correlated with higher mortality. Ninjin’yoeito (NYT) is a Japanese herbal medicine used to treat athrepsia and anorexia and is reported to ameliorate weight loss and muscular dysfunction. Recent studies have shown that its crude components upregulate the peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α)-related pathway, which is involved in skeletal muscle functions. Here, we examined whether NYT improves skeletal muscle complications by upregulating PGC-1α in COPD model mice.

Materials and Methods

Mice were divided into four groups: control, NYT, smoking, and smoking + NYT. The smoking and smoking + NYT groups were exposed to cigarette smoke for 60 min once daily. The mice in the NYT and smoking + NYT groups were fed an NYT-containing diet (3% w/w). We performed cellular analysis of bronchoalveolar lavage fluid, assessed pulmonary morphological changes, examined the expression of PGC-1α mRNA and protein in the gastrocnemius and soleus muscle, measured the hindlimb muscle volume with micro-computed tomography, and determined the myofiber proportion in soleus muscle after 12 weeks.

Results

Cigarette smoke exposure resulted in reduced skeletal muscle volume and slow-twitch muscle fibers and development of pulmonary emphysema. NYT feeding induced partial recovery of the damaged alveolar wall; however, NYT did not ameliorate smoke-induced alveolar enlargement. These findings revealed that NYT did not have sufficient efficacy in suppressing pulmonary emphysema. On the other hand, PGC-1α expression in muscle tissue of the NYT-fed mice increased significantly, resulting in suppression of smoke-induced loss of muscle mass and alteration in the muscle fiber distribution.

Conclusion

NYT increases PGC-1α expression in the muscle of COPD model mice and is involved in suppressing cigarette smoke-induced muscle complications. NYT may be a novel preventive and therapeutic medication for muscular dysfunctions in COPD.

Comparative Analyses of mTOR/Akt and Muscle Atrophy-Related Signaling in Aged Respiratory and Gastrocnemius Muscles

Sarcopenia is the degenerative loss of skeletal muscle mass and function associated with aging and occurs in the absence of any underlying disease or condition. A comparison of the age-related molecular signaling signatures of different muscles has not previously been reported. In this study, we compared the age-related molecular signaling signatures of the intercostal muscles, the diaphragm, and the gastrocnemii using 6-month and 20-month-old rats. The phosphorylation of Akt, ribosomal S6, and Forkhead box protein O1 (FoxO1) in diaphragms significantly increased with age, but remained unchanged in the intercostal and gastrocnemius muscles. In addition, ubiquitin-proteasome degradation, characterized by the levels of MuRF1 and Atrogin-1, did not change with age in all rat muscles. Interestingly, an increase in LC3BII and p62 levels marked substantial blockage of autophagy in aged gastrocnemii but not in aged respiratory muscles. These changes in LC3BII and p62 levels were also associated with a decrease in markers of mitochondrial quality control. Therefore, our results suggest that the age-related signaling events in respiratory muscles differ from those in the gastrocnemii, most likely to preserve the vital functions played by the respiratory muscles.