Cigarette smoke-initiated autoimmunity facilitates sensitisation to elastin-induced COPD-like pathologies in mice

It is currently not understood whether cigarette smoke exposure facilitates sensitisation to self-antigens and whether ensuing auto-reactive T cells drive chronic obstructive pulmonary disease (COPD)-associated pathologies.To address this question, mice were exposed to cigarette smoke for 2 weeks. Following a 2-week period of rest, mice were challenged intratracheally with elastin for 3 days or 1 month. Rag1^-/- , Mmp12^-/- , and Il17a^-/- mice and neutralising antibodies against active elastin fragments were used for mechanistic investigations. Human GVAPGVGVAPGV/HLA-A*02:01 tetramer was synthesised to assess the presence of elastin-specific T cells in patients with COPD.We observed that 2 weeks of cigarette smoke exposure induced an elastin-specific T cell response that led to neutrophilic airway inflammation and mucus hyperproduction following elastin recall challenge. Repeated elastin challenge for 1 month resulted in airway remodelling, lung function decline and airspace enlargement. Elastin-specific T cell recall responses were dose dependent and memory lasted for over 6 months. Adoptive T cell transfer and studies in T cells deficient Rag1^-/- mice conclusively implicated T cells in these processes. Mechanistically, cigarette smoke exposure-induced elastin-specific T cell responses were matrix metalloproteinase (MMP)12-dependent, while the ensuing immune inflammatory processes were interleukin 17A-driven. Anti-elastin antibodies and T cells specific for elastin peptides were increased in patients with COPD.These data demonstrate that MMP12-generated elastin fragments serve as a self-antigen and drive the cigarette smoke-induced autoimmune processes in mice that result in a bronchitis-like phenotype and airspace enlargement. The study provides proof of concept of cigarette smoke-induced autoimmune processes and may serve as a novel mouse model of COPD.

Neurogenic pulmonary edema following acute stroke: The progress and perspective

Neurogenic pulmonary edema (NPE) following acute stroke is an acute respiratory distress syndrome (ARDS) with clinical characteristics that include acute onset, apparent pulmonary interstitial fluid infiltration and rapid resolution. The pathological process of NPE centers on sympathetic stimulation and fulminant release of catecholamines, which cause contraction of resistance vessels. Elevated systemic resistance forces fluid into pulmonary circulation, while pulmonary circulation overload induces pulmonary capillary pressure that elevates, and in turn damages the alveolar capillary barrier. Damage to the alveolar capillary barrier leads to pulmonary ventilation disorder, blood perfusion disorder and oxygenation disorder. Eventually, NPE will cause post-stroke patients' prognosis to further deteriorate. At present, we lack specific biological diagnostic indicators and a meticulously unified diagnostic criterion, and this results in a situation in which many patients are not recognized quickly and/or diagnosed accurately. There are no drugs that are effective against NPE. Therefore, understanding how to diagnose NPE early by identifying the risk factors and how to apply appropriate treatment to avoid a deteriorating prognosis are important scientific goals. We will elaborate the progress of NPE after acute stroke in terms of its pathophysiological mechanisms, etiology, epidemiology, clinical diagnosis and early prediction, comprehensive treatment strategies, and novel drug development. We also propose our own thinking and prospects regarding NPE.

Autophagy plays an essential role in cigarette smoke-induced expression of MUC5AC in airway epithelium

Mucus hypersecretion is a common pathological feature of chronic airway inflammatory diseases including chronic obstructive pulmonary disease (COPD). However, the molecular basis for this condition remains incompletely understood. We have previously demonstrated a critical role of autophagy in COPD pathogenesis through mediating apoptosis of lung epithelial cells. In this study, we aimed to investigate the function of autophagy as well as its upstream and downstream signals in cigarette smoke-induced mucus production in human bronchial epithelial (HBE) cells and in mouse airways. Cigarette smoke extract (CSE), as well as the classical autophagy inducers starvation or Torin-1, significantly triggered MUC5AC expression, and inhibition of autophagy markedly attenuated CSE-induced mucus production. The CSE-induced autophagy was mediated by mitochondrial reactive oxygen species (mitoROS), which regulated mucin expression through the JNK and activator protein-1 pathway. Epidermal growth factor receptor (EGFR) was also required for CSE-induced MUC5AC in HBE cells, but it exerted inconsiderable effects on the autophagy-JNK signaling cascade. Airways of mice with dysfunctional autophagy-related genes displayed a markedly reduced number of goblet cells and attenuated levels of Muc5ac in response to cigarette smoke exposure. These results altogether suggest that mitoROS-dependent autophagy is essential for cigarette smoke-induced mucus hyperproduction in airway epithelial cells, and reemphasize autophagy inhibition as a novel therapeutic strategy for chronic airway diseases.