Chronic cigarette smoke exposure induces systemic hypoxia that drives intestinal dysfunction

Area of Science:

• Gastroenterology
• Pulmonology
• Pathology

Background:

• Crohn's disease (CD) is a chronic gastrointestinal inflammatory condition.
• Cigarette smoke (CS) exposure and chronic obstructive pulmonary disease (COPD) are known risk factors for CD, but underlying mechanisms remain unclear.

Purpose of the Study:

• To investigate the mechanisms linking CS exposure, COPD, and CD development.
• To examine the effects of CS on the gastrointestinal tract, focusing on hypoxia, inflammation, and barrier function.

Main Methods:

• Utilized a mouse model of CS-induced COPD and clinical studies.
• Assessed gut mucosal hypoxia, HIF-2 stabilization, inflammation, microvasculature, epithelial turnover, and intestinal barrier function in mice.
• Examined ileum biopsies from human CD patients who smoke versus non-smokers.

Main Results:

• CS-exposed mice developed CD-like pathology, including gut hypoxia, HIF-2 stabilization, inflammation, and reduced barrier function.
• Smoking cessation improved gastrointestinal tract pathology, especially in the ileum.
• A prolyl hydroxylase inhibitor ameliorated CS-induced gastrointestinal tract pathology.
• Vascular endothelial growth factor levels correlated with CS exposure and CD in mice and humans.
• Smokers with CD showed increased ileal vascularization compared to non-smokers.

Conclusions:

• Chronic CS exposure and impaired gas exchange lead to systemic and intestinal ischemia, promoting angiogenesis and gut barrier dysfunction.
• These mechanisms contribute to the increased risk and severity of Crohn's disease.
• Targeting ischemia and barrier dysfunction may offer therapeutic strategies for CS-related CD.