Extracellular elastolytic activity in human lung lavage: a comparative study between smokers and non-smokers

Area of Science:

• Pulmonary Medicine
• Biochemistry
• Toxicology

Background:

• Emphysema is linked to excessive lung proteolysis, particularly in smokers.
• Extracellular protease activity in human lung lavage is not well-studied.
• Smoking is a major risk factor for emphysema development.

Purpose of the Study:

• To quantify elastase and serine protease activities in bronchoalveolar lavage (BAL) from smokers and non-smokers.
• To investigate the role of protease and antiprotease imbalance in smoking-related lung disease.
• To determine if smoking affects specific protease activities or antiprotease levels.

Main Methods:

• Collected bronchoalveolar lavage (BAL) supernatants from smokers and non-smokers.
• Measured elastolytic activity using insoluble [3H]-elastin.
• Assessed serine protease activity using N-succinyl-L-trialanyl-p-nitroanilide.
• Quantified alpha 1-proteinase inhibitor (alpha 1-PI) and bronchial mucus proteinase inhibitor (BMPI) levels and function.

Main Results:

• Smokers showed significantly higher elastolytic activity in BAL compared to non-smokers.
• Elastolytic activity constituted a larger proportion of total protease activity in smokers (over 30%) versus non-smokers (5%).
• No significant difference in serine protease activity or antiprotease levels/function was observed between groups.

Conclusions:

• The protease/antiprotease imbalance in smokers' lungs is primarily due to enhanced elastolytic protease activity, not reduced antiprotease capacity.
• Smoking selectively enhances elastase activity, suggesting a specific mechanism in emphysema pathogenesis.
• Bronchial mucus proteinase inhibitor (BMPI) is a significant antiprotease in lung lavage.