Analyzing the Effects of Cigarette Smoke on Antimicrobial Defense in Lung Epithelial Cells

Take cultures of human lung epithelial cells. These cells secrete antimicrobial peptides (AMPs), which act as a defense barrier against respiratory pathogens.

Treat one group with cigarette smoke extract (CSE); add media to the untreated.

CSE components enter the cells, bind to intracellular receptors, and trigger signaling that reduces AMP production, weakening the cells’ defense.

Incubate both cultures with a respiratory pathogenic bacterium.

In the untreated group, AMPs kill most bacteria, keeping infection levels low.

In the CSE-treated group, fewer AMPs allow more bacteria to survive and invade the epithelial cells.

Add an antibiotic to eliminate the extracellular bacteria and wash to remove the antibiotic.

Add a lysis buffer to disrupt the host cells and release the internalized bacteria. Plate the diluted lysates and incubate to allow bacterial growth.

A higher colony count in the CSE-treated group indicates that cigarette smoke exposure impairs the AMP-mediated bacterial killing.

Plate the lung epithelial cells at a concentration of three times 10 to the fifth cells per milliliter, in a total volume of two milliliters of medium per well. Incubate the plates overnight. When the cells