Cigarette Smoke and DNA Cleavage Promote Lung Inflammation and Emphysema

Area of Science:

• Pulmonary Medicine
• Immunology
• Toxicology

Background:

• Smoking causes preventable and incurable lung diseases like COPD, emphysema, and lung cancer.
• Persistent inflammation and lung function decline in former smokers suggest acquired immunity plays a role.
• Cigarette smoke contains nano-sized carbon black (nCB) that accumulates in lung myeloid cells.

Purpose of the Study:

• To investigate the pathogenic role of nano-sized carbon black (nCB) in smoking-induced lung diseases.
• To understand the mechanisms by which nCB contributes to lung inflammation and emphysema.

Main Methods:

• Intra-nasal instillation of nCB in mice to induce airway inflammation and emphysema.
• High-throughput analysis of macrophages engulfing nCB to identify activated enzymes.
• Histological studies to detect DNA double-stranded breaks in lung cells.
• Analysis of cytokine expression in nCB-containing myeloid dendritic cells and their effect on T cell differentiation.

Main Results:

• Intra-nasal nCB instillation caused airway inflammation and emphysema in mice.
• Macrophages exposed to nCB showed activation of DNA repair enzymes and DNA double-stranded breaks.
• nCB-containing myeloid dendritic cells expressed pro-inflammatory cytokines.
• These cells promoted the differentiation of naive CD4 T cells into T helper 1 and interleukin 17A expressing subsets.

Conclusions:

• nCB accumulation in lung innate immune cells initiates and sustains lung inflammation.
• nCB contributes to the development and progression of emphysema.
• Targeting nCB accumulation or its downstream effects may offer therapeutic strategies for smoking-related lung diseases.