Studying Effects of Cigarette Smoke on Pseudomonas Infection in Lung Epithelial Cells

Summary

Described here is a protocol to study how cigarette smoke extract affects bacterial colonization in lung epithelial cells.

Abstract

Cigarette smoking is the major etiological cause for lung emphysema and chronic obstructive pulmonary disease (COPD). Cigarette smoking also promotes susceptibility to bacterial infections in the respiratory system. However, the effects of cigarette smoking on bacterial infections in human lung epithelial cells have yet to be thoroughly studied. Described here is a detailed protocol for the preparation of cigarette smoking extracts (CSE), treatment of human lung epithelial cells with CSE, and bacterial infection and infection determination. CSE was prepared with a conventional method. Lung epithelial cells were treated with 4% CSE for 3 h. CSE-treated cells were, then, infected with Pseudomonas at a multiplicity of infection (MOI) of 10. Bacterial loads of the cells were determined by three different methods. The results showed that CSE increased Pseudomonas load in lung epithelial cells. This protocol, therefore, provides a simple and reproducible approach to study the effect of cigarette smoke on bacterial infections in lung epithelial cells.

Introduction

Cigarette smoking affects the public health of millions of people worldwide. Many deleterious diseases, including lung cancer and chronic obstructive pulmonary disease (COPD), are reported to be related to cigarette smoking^1,2. Cigarette smoking increases susceptibility to acute microbial infections in the respiratory system^3,4,5. Furthermore, mounting evidence proves that cigarette smoking enhances the pathogenesis of many chronic disorders^6,7,

Protocol

1. 100% CSE preparation

1. Draw 10 mL of serum-free cell culture media (DMEM/F12 for BEAS-2B cells; airway epithelial cell basal medium for HSAEC cells) into a 60 mL syringe.
2. Reversely attach an appropriately trimmed 1 mL pipette tip to the nozzle of the syringe as an adapter to hold the cigarette (3R4F).
3. Remove the filter of the cigarette. Attach a cigarette to the tip adaptor and combust the cigarette.
4. Draw 40 mL of smoke-containing air into 10 mL of serum-free media. Mix the smoke with the medium by vigorously shaking (30 s per draw).
5. Repeat step 1.4 about 11x in ~7 min until the cigarette is completely burned out.

Results

A diagram is used to illustrate the protocol in Figure 1. Lung epithelial BEAS-2B cells were treated with CSE and challenged with Pseudomonas. Pseudomonas in the culture medium were killed by the added gentamycin and the cells were subjected to the drop plate assay, RT-qPCR detection of Pseudomonas ribosome 16S RNA, and flow cytometry. Compared with control, CSE treatment substantially increased bacterial infection in drop plate methods (Figure.......

Discussion

Bacterial invasion into lung epithelial cells is a crucial step in the pathogenesis of bacterial infections. The process of bacterial invasion into the cells can be broken down into the following three steps: First, the bacteria contact and adhere to the surface of the epithelial cell using their flagella. Second, the bacteria either undergo internalization or penetrate the cellular membrane. Finally, the bacteria replicate and colonize the cells if they successfully escape cellular defense mechanisms^25.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
50mL syringe	BD Biosciences
airway epithelial cell basal medium	ATCC	PCS-300-030
Bacteria shaker	ThermoFisher Scientific
bronchial epithelial cell growth kit	ATCC	PCS-300-040
Cell Counter	Bio-Rad
CFX96 Real-Time PCR System	Bio-Rad
High-Capacity RNA-to-DNA KIT	ThermoFisher Scientific	4387406
HITES medium	ATCC	ATCC 30-2004
human BEAS-2B cells	ATCC	ATCC CRL-9609
human primary small airway epithelial cells	ATCC	ATCC PCS-300-030
LSRII flow cytometer	BD Biosciences
Nikkon confocal microscope	Nikkon
OD reader	USA Scientific
PCR primers	ITD
Pseudomonas aeruginosa	ATCC	ATCC 47085	PAO1-LAC
Pseudomonas fluorescens Migula	ATCC	ATCC 27853	P.aeruginosa GFP
Research-grade cigarettes (3R4F)	University of Kentucky	TP-7-VA
RNeasy Mini Kit	Qiagen	74106
Transprent PET Transwell Insert	Corning Costar
Tryptic Soy Broth	BD Biosciences