Pathophysiology and Genetics of Bronchiectasis Unrelated to Cystic Fibrosis

Bronchiectasis-COPD Overlap Syndrome: A Comprehensive Review of its Pathophysiology and Potential Cardiovascular Implications

Bronchiectasis-Chronic Obstructive Pulmonary Disease Overlap Syndrome (BCOS) is a complex pulmonary condition that merges bronchiectasis and chronic obstructive pulmonary disease (COPD), presenting unique clinical challenges. Patients with BCOS typically exhibit a range of symptoms from both conditions, including a chronic productive cough, reduced lung function, frequent exacerbations, and diminished exercise tolerance. The etiology of BCOS involves multiple factors such as genetic predisposition, respiratory infections, tobacco smoke, air pollutants, and other inflammatory mediators. Accurate diagnosis requires a comprehensive approach, incorporating pulmonary function tests to evaluate airflow limitation, radiographic imaging to identify structural lung abnormalities, and blood eosinophil counts to detect underlying inflammation. Treatment strategies are tailored to individual symptom profiles and severity, potentially including bronchodilators, inhaled corticosteroids, and pulmonary therapy to improve lung function and quality of life. Patients with BCOS are also at an increased risk for cardiovascular complications, such as stroke, ischemic heart disease, and cor pulmonale. Additionally, medications like beta-agonists and muscarinic antagonists used in COPD treatment can further affect cardiac risk by altering heart rate. This paper aims to provide a thorough understanding of BCOS, addressing its development, diagnosis, treatment, and associated cardiovascular complications, to aid healthcare providers in managing this multifaceted condition and improving patient outcomes.

Prevalence of pulmonary artery dilation in non-cystic fibrosis bronchiectasis: A CT analysis from a cohort of the US Bronchiectasis and Nontuberculous Mycobacteria Research Registry

Although pulmonary artery (PA) dilation is independently associated with significant morbidity and mortality in patients with pulmonary diseases irrespective of diagnosed pulmonary hypertension, its relationship to nontuberculous mycobacteria (NTM) is unknown. To determine the prevalence of PA dilation in patients with NTM-predominant non-CF bronchiectasis, we evaluated the chest computed tomography (CT) scans from 321 patient in the United States based Bronchiectasis and NTM Research Registry. The majority of our cohort had NTM infection. We measured the severity of bronchiectasis using modified Reiff criteria and measured the diameters of the PA and aorta (Ao), with PA dilation defined as a PA:Ao ratio > 0.9. Forty-two patients (13%) were found to have PA dilation. PA dilation was positively associated with the use of supplemental oxygen (p < 0.001), but there was no association between PA dilation and NTM infection.

Rituximab-Induced Immune Dysregulation Leading to Organizing Pneumonia, Bronchiectasis, and Pulmonary Fibrosis

We present a case of rituximab-induced organizing pneumonia (OP) along with bronchiectasis and pulmonary fibrosis, in a patient with a history of granulomatosis with polyangiitis (GPA), on long-term maintenance therapy with rituximab. T-cell dysregulation and B-cell depletion associated with the chronic use of rituximab often lead to a profound immunosuppressed state with hypogammaglobulinemia and unbalanced T-cell response. This acquired immunodeficient state with severe immune dysregulation predisposed this patient to recurrent pulmonary infection and ultimately led to bronchiectasis and pulmonary fibrosis.

The Impact of Endoplasmic Reticulum-Associated Protein Modifications, Folding and Degradation on Lung Structure and Function

The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and induces the unfolded protein response (UPR) and other mechanisms to restore ER homeostasis, including translational shutdown, increased targeting of mRNAs for degradation by the IRE1-dependent decay pathway, selective translation of proteins that contribute to the protein folding capacity of the ER, and activation of the ER-associated degradation machinery. When ER stress is excessive or prolonged and these mechanisms fail to restore proteostasis, the UPR triggers the cell to undergo apoptosis. This review also examines the overlooked role of post-translational modifications and their roles in protein processing and effects on ER stress and the UPR. Finally, these effects are examined in the context of lung structure, function, and disease.

Aberrant Epithelial Cell Proliferation in Peripheral Airways in Bronchiectasis

Dilation of bronchi and bronchioles caused by destruction and excessive epithelial remodeling is a characteristic feature of bronchiectasis. It is not known how epithelial progenitor cells contribute to these pathologic conditions in peripheral airways (bronchioles) in bronchiectasis. We aimed to explore the expression levels of signature airway progenitor cells in the dilated bronchioles in patients with bronchiectasis. We obtained the surgically resected peripheral lung tissues from 43 patients with bronchiectasis and 33 control subjects. Immunostaining was performed to determine the expression patterns of thyroid transcription factor-1 (TTF-1, for labeling progenitor cells in distal airways), P63 (basal cells), club cell 10 kDa protein (CC10, club cells), and surfactant protein C (SPC, alveolar type II epithelial cells) in epithelium or sub-epithelium. Here, we reported significantly lower percentage of TTF-1⁺ cells and CC10⁺ cells, and higher percentage of P63⁺ cells within the epithelium of dilated bronchioles compared with control bronchioles. In airway sub-epithelium of the dilated bronchioles, epithelial hyperplasia with disarrangement of TTF-1⁺ cells yielded cuboidal (100%) and columnar (93.0%) type among bronchiectasis patients. Most progenitor cell markers co-localized with TTF-1. The median (the 1st, 3rd quartile) percentage of P63⁺TTF-1⁺, CC10⁺TTF-1⁺, and SPC⁺TTF-1⁺ cells was 16.0% (8.9, 24.0%), 14.5% (7.1, 20.8%), and 52% (40.3, 64.4%), respectively. For cuboidal epithelial hyperplasia, 91.0% (86.5, 94.0%) of areas co-stained with SPC and TTF-1. Columnar epithelial hyperplasia was characterized by TTF-1 co-staining with P63⁺TTF-1⁺ and CC10⁺TTF-1⁺ cells. Taken together, aberrant proliferation of airway progenitor cells in both epithelium and sub-epithelium are implicated in bronchiectasis.