The effect of various durations of cigarette smoke exposure on muscle fibre remodeling in rat diaphragms

Cellular senescence contributes to mechanical ventilation-induced diaphragm dysfunction by upregulating p53 signalling pathways

BACKGROUND

Mechanical ventilation can cause acute atrophy and injury in the diaphragm, which are related to adverse clinical results. However, the underlying mechanisms of ventilation-induced diaphragm dysfunction (VIDD) have not been well elucidated. The current study aimed to explore the role of cellular senescence in VIDD.

METHODS

A total of twelve New Zealand rabbits were randomly divided into 2 groups: (1) spontaneously breathing anaesthetized animals (the CON group) and (2) mechanically ventilated animals (for 48 h) in V-ACV mode (the MV group). Respiratory parameters were collected during ventilation. Diaphragm were collected for further analyses.

RESULTS

Compared to those in the CON group, the percentage and density of sarcomere disruption in the MV group were much higher (p < 0.001, both). The mRNA expression of MAFbx and MuRF1 was upregulated in the MV group (p = 0.003 and p = 0.006, respectively). Compared to that in the CON group, the expression of MAFbx and MuRF1 detected by western blotting was also upregulated (p = 0.02 and p = 0.03, respectively). Moreover, RNA-seq showed that genes associated with senescence were remarkably enriched in the MV group. The mRNA expression of related genes was further verified by q-PCR (Pai1: p = 0.009; MMP9: p = 0.008). Transverse cross-sections of diaphragm myofibrils in the MV group showed more intensive positive staining of SA-βGal than those in the CON group. p53-p21 axis signalling was elevated in the MV group. The mRNA expression of p53 and p21 was significantly upregulated (p = 0.02 and p = 0.05, respectively). The western blot results also showed upregulation of p53 and p21 protein expression (p = 0.03 and p = 0.05, respectively). Moreover, the p21-positive staining in immunofluorescence and immunohistochemistry in the MV group was much more intense than that in the CON group (p < 0.001, both).

CONCLUSIONS

In a rabbit model, we demonstrated that mechanical ventilation in A/C mode for 48 h can still significantly induce ultrastructural damage and atrophy of the diaphragm. Moreover, p53-dependent senescence might play a role in mechanical ventilation-induced dysfunction. These findings might provide novel therapeutic targets for VIDD.

Skeletal Muscle Mitochondrial Dysfunction in Chronic Obstructive Pulmonary Disease: Underlying Mechanisms and Physical Therapy Perspectives

Skeletal muscle dysfunction (SMD) is a prevalent extrapulmonary complication and a significant independent prognostic factor in patients with chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction is one of the core factors that damage structure and function in COPD skeletal muscle and is closely related to smoke exposure, hypoxia, and insufficient physical activity. The currently known phenotypes of mitochondrial dysfunction are reduced mitochondrial content and biogenesis, impaired activity of mitochondrial respiratory chain complexes, and increased mitochondrial reactive oxygen species production. Significant progress has been made in research on physical therapy (PT), which has broad prospects for treating the abovementioned potential mitochondrial-function changes in COPD skeletal muscle. In terms of specific types of PT, exercise therapy can directly act on mitochondria and improve COPD SMD by increasing mitochondrial density, regulating mitochondrial biogenesis, upregulating mitochondrial respiratory function, and reducing oxidative stress. However, improvements in mitochondrial-dysfunction phenotype in COPD skeletal muscle due to different exercise strategies are not entirely consistent. Therefore, based on the elucidation of this phenotype, in this study, we analyzed the effect of exercise on mitochondrial dysfunction in COPD skeletal muscle and the regulatory mechanism thereof. We also provided a theoretical basis for exercise programs to rehabilitate this condition.

Endoplasmic Reticulum Stress in Chronic Obstructive Pulmonary Disease: Mechanisms and Future Perspectives

The endoplasmic reticulum (ER) is an integral organelle for maintaining protein homeostasis. Multiple factors can disrupt protein folding in the lumen of the ER, triggering ER stress and activating the unfolded protein response (UPR), which interrelates with various damage mechanisms, such as inflammation, apoptosis, and autophagy. Numerous studies have linked ER stress and UPR to the progression of chronic obstructive pulmonary disease (COPD). This review focuses on the mechanisms of other cellular processes triggered by UPR and summarizes drug intervention strategies targeting the UPR pathway in COPD to explore new therapeutic approaches and preventive measures for COPD.

Changes in diaphragm contractility in cigarette smoking-exposed and smoking cessation rats are associated with alterations in mitochondrial morphology and homeostasis

The effects of cigarette smoking (CS) cessation on the diaphragm are unknown, as are the CS-induced diaphragmatic mitochondrial changes. We examined the changes in diaphragm contractility, as well as alterations in mitochondrial morphology, function and homoeostasis during CS exposure and after cessation. Rats were randomly divided into CS exposure and CS cessation groups: 3-month CS (S3), 6-month CS (S6), 6-month CS followed by 3-month cessation (S6N3). The changes in the diaphragm were investigated, including contractile properties, the ultrastructure, mitochondrial function and the expression of markers of mitochondrial homoeostasis. CS caused irreversible histological disruption and functional depression in the lungs, along with significantly declines in diaphragmatic contractility and more severely in extensor digitorum longus muscular contractility. Such declines were recovered after 3-month CS cessation. CS exposure disrupted the diaphragmatic mitochondrial morphology and function (S6), which was significantly alleviated in the S6N3 group. The mitochondrial homoeostasis was depressed (S6), as indicated by the downregulation of Pink1 and Mfn1. Interestingly, the Mfn1 level was recovered after smoking cessation (S6N3). In conclusion, smoking cessation eased CS-induced diaphragmatic dysfunction and mitochondrial deregulation, which are likely associated with deregulated mitochondrial homoeostasis.

Assessments and Targeted Rehabilitation Therapies for Diaphragmatic Dysfunction in Patients with Chronic Obstructive Pulmonary Disease: A Narrative Review

Purpose

This review summarizes the characteristics, assessment methods, and targeted rehabilitation therapies of diaphragm dysfunction in patients with chronic obstructive pulmonary disease (COPD).

Methods

Extensive literature was searched in PubMed, the Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure Database, Wanfang, and SinoMed.

Results

Under the influence of oxidative stress, inflammation, and other factors, the diaphragm function of patients with COPD changes in mobility, muscle strength, thickness, and thickening. In patients with COPD, diaphragm mobility can be assessed using ultrasound, X-ray fluoroscopy, and magnetic resonance imaging. Diaphragmatic strength can be measured by transdiaphragmatic pressure and maximal inspiratory pressure. Diaphragmatic thickness and thickening can be assessed using ultrasound. Rehabilitation therapies targeting the diaphragm include diaphragmatic breathing, diaphragm-related manual therapy, and phrenic nerve electrical stimulation. Diaphragmatic breathing is safe, simple, and not limited by places. Diaphragmatic manual therapies, which require patient cooperation and one-on-one operation by a professional therapist, are effective. Phrenic nerve electrical stimulation is suitable for patients with severe conditions. These therapies improve the diaphragmatic function, lung function, dyspnea, and exercise capacity of patients with COPD.

Conclusion

The diaphragmatic function is commonly assessed in terms of mobility, strength, thickness, and thickening. Diaphragmatic targeted rehabilitation therapies have proven to be efficient, which are recommended to be included in the pulmonary rehabilitation strategy for patients with COPD.

Gasping for Sulfide: A Critical Appraisal of Hydrogen Sulfide in Lung Disease and Accelerated Aging

Hydrogen sulfide (H₂S) is a gaseous signaling molecule involved in a plethora of physiological and pathological processes. It is primarily synthesized by cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase as a metabolite of the transsulfuration pathway. H₂S has been shown to exert beneficial roles in lung disease acting as an anti-inflammatory and antiviral and to ameliorate cell metabolism and protect from oxidative stress. H₂S interacts with transcription factors, ion channels, and a multitude of proteins via post-translational modifications through S-persulfidation ("sulfhydration"). Perturbation of endogenous H₂S synthesis and/or levels have been implicated in the development of accelerated lung aging and diseases, including asthma, chronic obstructive pulmonary disease, and fibrosis. Furthermore, evidence indicates that persulfidation is decreased with aging. Here, we review the use of H₂S as a biomarker of lung pathologies and discuss the potential of using H₂S-generating molecules and synthesis inhibitors to treat respiratory diseases. Furthermore, we provide a critical appraisal of methods of detection used to quantify H₂S concentration in biological samples and discuss the challenges of characterizing physiological and pathological levels. Considerations and caveats of using H₂S delivery molecules, the choice of generating molecules, and concentrations are also reviewed. Antioxid. Redox Signal. 35, 551-579.

Functional, Ultrastructural, and Transcriptomic Changes in Rat Diaphragms with Different Durations of Cigarette Smoke Exposure

Aims

The aim of the study was to explore the functional and structural changes of the diaphragm and underlying mechanisms in response to 12 or 24 weeks of cigarette smoke (CS) exposure in rats.

Materials and Methods

Rats were exposed to CS to develop a COPD model and the rats exposed to room air served as a control group. Rats were randomly divided into four groups: CS12W, CON12W, CS24W, and CON24W. Pulmonary function, lung histopathology, and the contractile properties and ultrastructure of diaphragm muscle were examined in these rats. The changes of transcriptomic profiling of diaphragm muscle were further compared between CS and control rats by the RNA Seq.

Results

Both CS groups showed lower FEV_0.3/FVC, elevated mean linear intercept (MLI), and reduced mean alveolar numbers (MAN) vs the control groups. The fatigue index (FI) of the diaphragm muscle from the CS12W group, but not CS24W, was significantly increased. Conversely, the force–frequency curves of the diaphragm muscle from the CS24W group, but not CS12W group, were significantly decreased. Consistently, mitochondrial number density (N_A) and volume density (Vv) were increased in the CS12W diaphragm muscle, while being decreased in the CS24W group. Furthermore, the diaphragm transcriptomic profiling results showed that genes regulating cell proliferation and energy metabolic activity were un-regulated and genes regulating protein degradation were down-regulated in the CS12W diaphragm, while CS24W diaphragm showed opposite changes.

Conclusion

These observations suggested a transition of diaphragm muscle from initial compensatory to decompensatory changes in function, structure, and gene expression during the development of COPD.

A prospective observational study on critically ill children with diaphragmatic dysfunction: clinical outcomes and risk factors

Background

Diaphragmatic dysfunction (DD) has a great negative impact on clinical outcomes, and it is a well-recognized complication in adult patients with critical illness. However, DD is largely unexplored in the critically ill pediatric population. The aim of this study was to identify risk factors associated with DD, and to investigate the effects of DD on clinical outcomes among critically ill children.

Methods

Diaphragmatic function was assessed by diaphragm ultrasound. According to the result of diaphragmatic ultrasound, all enrolled subjects were categorized into the DD group (n = 24) and the non-DD group (n = 46). Collection of sample characteristics in both groups include age, sex, height, weight, primary diagnosis, complications, laboratory findings, medications, ventilatory time and clinical outcomes.

Results

The incidence of DD in this PICU was 34.3%. The level of CRP at discharge (P = 0.003) in the DD group was higher than the non-DD group, and duration of elevated C-reactive protein (CRP) (P < 0.001), sedative days (P = 0.008) and ventilatory treatment time (P < 0.001) in the DD group was significantly longer than the non-DD group. Ventilatory treatment time and duration of elevated CRP were independently risk factors associated with DD. Patients in the DD group had longer PICU length of stay, higher rate of weaning or extubation failure and higher mortality.

Conclusion

DD is associated with poorer clinical outcomes in critically ill childern, which include a longer PICU length of stay, higher rate of weaning or extubation failure and a higher mortality. The ventilatory treatment time and duration of elevated CRP are main risk factors of DD in critically ill children.

Trial registration

Current Controlled Trials ChiCTR1800020196, Registered 01 Dec 2018.

Hydrogen Sulfide Plays an Important Protective Role through Influencing Endoplasmic Reticulum Stress in Diseases

The endoplasmic reticulum is an important organelle responsible for protein synthesis, modification, folding, assembly and transport of new peptide chains. When the endoplasmic reticulum protein folding ability is impaired, the unfolded or misfolded proteins accumulate to lead to endoplasmic reticulum stress. Hydrogen sulfide is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicate that H₂S plays an important protective role in many diseases through influencing endoplasmic reticulum stress, but its mechanism is not fully understood. This article reviewed the progress about the effect of H₂S on endoplasmic reticulum stress and its mechanisms involved in diseases in recent years to provide theoretical basis for in-depth study.

The predictive value of diaphragm ultrasound for weaning outcomes in critically ill children

Introduction

Multiple studies have shown that diaphragmatic ultrasound can better predict the outcome of weaning in adults. However, there are few studies focusing on children, leading to a lack of sufficient clinical evidence for the application of diaphragmatic ultrasound in children. The purpose of this study was to investigate the predictive value of diaphragm ultrasound for weaning outcomes in critically ill children.

Methods

The study included 50 cases whose mechanical ventilation (MV) time was > 48 h, and all eligibles were divided into either the weaning success group (n = 39) or the weaning failure group (n = 11). Diaphragm thickness, diaphragmatic excursion (DE), and diaphragmatic thickening fraction (DTF) were measured in the zone of apposition. The maximum inspiratory pressure (PImax) was also recorded.

Results

The ventilatory treatment time (P = 0.002) and length of PICU stay (P = 0.013) in the weaning failure group was longer than the success group. Cut-off values of diaphragmatic measures associated with successful weaning were ≥ 21% for DTF with a sensitivity of 0.82 and a specificity of 0.81, whereas it was ≥0.86 cm H₂O/kg for PImax with a sensitivity of 0.51 and a specificity of 0.82. The linear correlation analysis showed that DTF had a significant positive correlation with PImax in children (P = 0.003).

Conclusions

Diaphragm ultrasound has potential value in predicting the weaning outcome of critically ill children. DTF and PImax presented better performance than other diaphragmatic parameters. However, DE has limited value in predicting weaning outcomes of children with MV.

Trial registration

Current Controlled Trials ChiCTR1800020196, (Dec 2018).