Obstructive sleep apnea in pulmonary fibrosis

Intermittent hypoxia induces myofibroblast differentiation and extracellular matrix production of MRC5s via HIF-1α-TGF-β/Smad pathway

PURPOSE

To investigate whether or not intermittent hypoxia (IH), the main characteristic of obstructive sleep apnea (OSA) may affect the myofibroblast differentiation and extracellular matrix (ECM) production of lung fibroblast through the HIF-1α-TGF-β/Smad pathway and assess the interventional role of a HIF-1α inhibitor, 2-methoxyestradiol (2-ME2).

METHOD

The human lung fibroblast MRC5 cells were exposed to normoxia or IH conditions, and the expression of myofibroblast differentiation marker α-smooth muscle actin (α-SMA) and ECM protein collagen I were evaluated. To clarify the underlying mechanism, the expression level of HIF-1α, TGF-β, and p-Smads/Smads were measured and the effects of inhibiting HIF-1α with 2-ME2 on the α-SMA expression level and ECM production through the TGF-β/Smad pathway were assessed. Si HIF-1α was applied to genetically inhibit HIF-1α in MRC5 cells, and the related proteins were assessed.

RESULTS

IH increased the protein and mRNA expression of Collagen I and α-SMA of MRC5 cells in a time-dependent manner. IH activated the protein and mRNA level of HIF-1α and TGF-β and increased the phosphorylation of Smad2/Smad3 of MRC5 cells in a time-dependent manner. 2-ME2 inhibited the activation of HIF-1α induced by IH and decreased overexpression of TGF-β, p-Smad2/Smad2, and p-Smad3/Smad3, which in turn partially reversed the upregulation of α-SMA and Collagen I induced by IH in MRC5 cells. When HIF-1α was successfully silenced by si-HIF-1α, upregulation of TGF-β induced by intermittent hypoxia was partially decreased.

CONCLUSIONS

This study showed that IH contributes to myofibroblast differentiation and excessive ECM production of MRC5 cells through activation of the HIF-1α-TGF-β/Smad pathway. 2-ME2 partially attenuated myofibroblast differentiation induced by IH by inhibiting the HIF-1α-TGF-β/Smad pathway.

Treatable traits: a comprehensive precision medicine approach in interstitial lung disease

Interstitial lung disease (ILD) is a diverse group of inflammatory and fibrotic lung conditions causing significant morbidity and mortality. A multitude of factors beyond the lungs influence symptoms, health-related quality of life, disease progression and survival in patients with ILD. Despite an increasing emphasis on multidisciplinary management in ILD, the absence of a framework for assessment and delivery of comprehensive patient care poses challenges in clinical practice. The treatable traits approach is a precision medicine care model that operates on the premise of individualised multidimensional assessment for distinct traits that can be targeted by specific interventions. The potential utility of this approach has been described in airway diseases, but has not been adequately considered in ILD. Given the similar disease heterogeneity and complexity between ILD and airway diseases, we explore the concept and potential application of the treatable traits approach in ILD. A framework of aetiological, pulmonary, extrapulmonary and behavioural and lifestyle treatable traits relevant to clinical care and outcomes for patients with ILD is proposed. We further describe key research directions to evaluate the application of the treatable traits approach towards advancing patient care and health outcomes in ILD.

Causal associations between obstructive sleep apnea and COVID-19: A bidirectional Mendelian randomization study

BACKGROUNDS

The COVID-19 pandemic has caused significant impact on human health. Whether obstructive sleep apnea (OSA) increases the risk of COVID-19 remains unclear. We sought to clarify this issue using two-sample Mendelian randomization (TSMR) analysis in large cohorts.

METHODS

Bidirectional two-sample Mendelian randomization (MR) was used to evaluate the potential causality between OSA and COVID-19 by selecting single-nucleotide polymorphisms (SNPs) as instrumental variables (IVs) from genome-wide association studies (GWAS). The inverse-variance weighted (IVW) method was selected as the main approach for data analysis to estimate the possible causal effects. Alternative methods such as MR-Egger, the MR pleiotropy residual sum and outlier (MR-PRESSO), and leave-one-out analysis methods were implemented as sensitivity analysis approaches to ensure the robustness of the results.

RESULTS

All forward MR analyses consistently indicated the absence of a causal relationship between OSA and any COVID-19 phenotype. In the reverse MR analysis, the IVW mode demonstrated that severe respiratory confirmed COVID-19 was correlated with a 4.9% higher risk of OSA (OR, 1.049; 95%CI, 1.018-1.081; P = 0.002), consistent in MR-PRESSO (OR = 1.049, 95%CI 1.018-1.081, P = 0.004), weighted median (OR = 1.048, 95%CI 1.003-1.095, P = 0.035), and MR-Egger (OR = 1.083, 95%CI 1.012-1.190, P = 0.041) methods.

CONCLUSIONS

There is no significant evidence supporting a causal association between OSA and any COVID phenotype, while we identified potential evidence for a causal effect of severe COVID-19 on an increased risk of OSA.

OSA and Chronic Respiratory Disease: Mechanisms and Epidemiology

Obstructive sleep apnea (OSA) is a highly prevalent disorder that has profound implications on the outcomes of patients with chronic lung disease. The hallmark of OSA is a collapse of the oropharynx resulting in a transient reduction in airflow, large intrathoracic pressure swings, and intermittent hypoxia and hypercapnia. The subsequent cytokine-mediated inflammatory cascade, coupled with tractional lung injury, damages the lungs and may worsen several conditions, including chronic obstructive pulmonary disease, asthma, interstitial lung disease, and pulmonary hypertension. Further complicating this is the sleep fragmentation and deterioration of sleep quality that occurs because of OSA, which can compound the fatigue and physical exhaustion often experienced by patients due to their chronic lung disease. For patients with many pulmonary disorders, the available evidence suggests that the prompt recognition and treatment of sleep-disordered breathing improves their quality of life and may also alter the course of their illness. However, more robust studies are needed to truly understand this relationship and the impacts of confounding comorbidities such as obesity and gastroesophageal reflux disease. Clinicians taking care of patients with chronic pulmonary disease should screen and treat patients for OSA, given the complex bidirectional relationship OSA has with chronic lung disease.

Treating Pulmonary Fibrosis with Non-Viral Gene Therapy: From Bench to Bedside

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease characterized by irreversible lung scarring, which achieves almost 80% five-year mortality rate. Undeniably, commercially available pharmaceuticals, such as pirfenidone and nintedanib, exhibit certain effects on improving the well-being of IPF patients, but the stubbornly high mortality still indicates a great urgency of developing superior therapeutics against this devastating disease. As an emerging strategy, gene therapy brings hope for the treatment of IPF by precisely regulating the expression of specific genes. However, traditional administration approaches based on viruses severely restrict the clinical application of gene therapy. Nowadays, non-viral vectors are raised as potential strategies for in vivo gene delivery, attributed to their low immunogenicity and excellent biocompatibility. Herein, we highlight a variety of non-viral vectors, such as liposomes, polymers, and proteins/peptides, which are employed in the treatment of IPF. By respectively clarifying the strengths and weaknesses of the above candidates, we would like to summarize the requisite features of vectors for PF gene therapy and provide novel perspectives on design-decisions of the subsequent vectors, hoping to accelerate the bench-to-bedside pace of non-viral gene therapy for IPF in clinical setting.

Idiopathic Pulmonary Comorbidities and Mechanisms

Idiopathic pulmonary fibrosis (IPF) is a disease with an unknown etiology mainly characterized by a progressive decline of lung function due to the scarring of the tissue deep in the lungs. The overall survival after diagnosis remains low between 3 and 5 years. IPF is a heterogeneous disease and much progress has been made in the past decade in understanding the disease mechanisms that contributed to the development of two new drugs, pirfenidone and nintedanib, which improved the therapeutic management of the disease. The understanding of the cofactors and comorbidities of IPF also contributed to improved management of the disease outcome. In the present review, we evaluate scientific evidence which indicates IPF as a risk factor for other diseases based on the complexity of molecular and cellular mechanisms involved in the disease development and of comorbidities. We conclude from the existing literature that while much progress has been made in understating the mechanisms involved in IPF development, further studies are still necessary to fully understand IPF pathogenesis which will contribute to the identification of novel therapeutic targets for IPF management as well as other diseases for which IPF is a major risk factor.

The prevalence of obstructive sleep apnea in interstitial lung disease: a systematic review and meta-analysis

PURPOSE

To evaluate the overall prevalence of obstructive sleep apnea (OSA) in interstitial lung disease (ILD).

METHODS

We performed a systematic search of the academic literature while adhering to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines on four scientific databases including EMBASE, CENTRAL, Scopus, and MEDLINE. We performed a meta-analysis to evaluate the prevalence and severity of OSA. Severity was defined by apnea-hypopnea index (AHI) as mild (AHI ≥ 5 to < 15/h), moderate (AHI ≥ 15 to < 30/h), and severe (AHI ≥ 30/h).

RESULTS

From 1397 studies, we found 10 eligible studies with 569 patients with ILD (mean age: 65.3 ± 6.0 years). Among these patients, 332 (61%) suffered from OSA with 32% categorized as mild, 17% moderate, and 9% severe.  CONCLUSION: This systematic review and meta-analysis provides preliminary evidence regarding the high prevalence of OSA in ILD.