This work was supported in part by a National Institutes of Health R01 grants HL125435 and HL142997 (to CZ).

1. 100% CSE preparation
<ol>
	<li>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.</li>
	<li>Reversely attach an appropriately trimmed 1 mL pipette tip to the nozzle of the syringe as an adapter to hold the cigarette (3R4F).</li>
	<li>Remove the filter of the cigarette. Attach a cigarette to the tip adaptor and combust the cigarette.</li>
	<li>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).</li>
	<li>Repeat step 1.4 about 11x in ~7 min until the cigarette is completely burned out.</li>
	<li>Filter the 10 mL of smoked media with a 0.22 &#181;m filter to exclude any microorganisms and insoluble particles. Transfer to a closed sterile tube. Prepare the 100% CSE no more than 30 min before the subsequent assay.</li>
</ol>
2. Pseudomonas culture
<ol>
	<li>Inoculate frozen P. aeruginosa (strain PAO1) or P. fluorescens Migula (strain PAO143) into a Tryptic Soy Broth&#160;(TSB) agar plate for overnight culture at 37 &#176;C. 
	NOTE: To obtain enough bacteria for culturing, spread as much bacteria onto the TSB agar plate as possible.</li>
	<li>Collect a bacterial smear and incubate in 20 mL of TSB with 5% of glycerol as the carbon source.</li>
	<li>Shake the bacterial suspension in a 37 &#176;C incubator at 200 rpm for 1 h until the OD600 value = 0.6. 
	CAUTION: Do not let the shaking speed exceed 200 rpm. Higher shaking speeds may damage the morphology of the bacterial flagella and impact the bacterial invasion into lung epithelia. Likewise, limit the shaking time to 1 h to obtain highly invasive bacteria. Measure the OD600 value to estimate the number of bacteria. An OD600&#160;= 1 corresponds to ~109&#160;colony forming units (CFU)/mL.</li>
</ol>
3. Human lung epithelial cell culture and CSE treatment
<ol>
	<li>Culture human&#160;BEAS-2B cells in HITES medium (500&#8197;mL of DMEM/F12, 2.5&#8197;mg insulin, 2.5&#8197;mg transferrin, 2.5&#8197;mg sodium selenite, 2.5&#8197;mg transferrin, 10&#8197;&#956;M hydrocortisone, 10&#8197;&#956;M &#946;-estradiol, 10&#8197;mM HEPES, and 2&#8197;mM L-glutamine) supplemented with 10% fetal bovine serum (FBS) as previously described24.</li>
	<li>Culture human primary small airway epithelial cells (HSAEC) in the airway epithelial cell culture medium (500 mL of Airway Cell Basal Medium, 500 &#181;g/mL HSA, 0.6 &#181;M linoleic acid, 0.6 &#181;g/mL lecithin, 6 mM L-glutamine, 0.4% extract P, 1.0 &#181;M epinephrine, 5 &#181;g/mL transferrin, 10 nM T3, 1 &#181;g/mL hydrocortisone, rh EGF 5 ng/mL, and 5 &#181;g/mL rh insulin). Incubate the cells at 37&#8239;&#176;C in 5% CO2.</li>
	<li>Dissociate the cells with 1 mL of 0.25% trypsin for 5 min until the cells completely detach from the bottom of the plate.</li>
	<li>Add 10 mL of complete HITES medium to neutralize trypsin and collect the cells in a 15 mL tube. Centrifuge at 4 &#176;C at 300 x g for 5 min. 
	CAUTION: Carefully monitor the time for trypsin digestion by microscopy, because overdigestion may cause cell death.</li>
	<li>Discard the supernatant and resuspend the cells in 2 mL of HITES medium with 10% FBS.</li>
	<li>Pipette 10 &#181;L of the above cell suspension onto the plate and insert it into an automated cell counter to obtain the concentration in cells/mL.</li>
	<li>Plate BEAS-2B cells at a concentration of 3 &#215; 105 cells/mL into 6 well plates in a total volume of 2 mL in HITES medium supplemented with 10% of FBS for overnight culture.</li>
	<li>Treat the cells at approximately 80% confluency, or 5 x 105 cells/mL, with 4% CSE for 3 h. Before CSE treatment, change the medium with HITES medium with 1% of FBS.</li>
</ol>
4. Bacterial infection
<ol>
	<li>Add P. aeruginosa or P. fluorescens Migula&#160;(~1 &#215; 107&#160;CFU/mL) to each well of the CSE-treated cells and incubate for 1 h at 37 &#176;C in 5% CO2.</li>
	<li>Aspirate the supernatants and replace with 2 mL of fresh HITES medium to treat with 4% CSE and 100 &#181;g/mL gentamicin. 
	NOTE: Gentamicin is used because it is unable to penetrate human lung epithelial cellular membranes. Thus, it can kill all the bacteria in the medium but not those that invaded the lung epithelial cells.</li>
	<li>After 1 h of CSE/gentamicin treatment at 37 &#176;C in 5% CO2, aspirate the supernatants and wash the cells 3x with PBS for the subsequent bacterial concentration determination. 
	NOTE: To confirm the internalized bacteria, cells infected with GFP-labeled P. fluorescens Migula&#160;were observed under fluorescent microscopy.</li>
</ol>
5. Determination of bacterial concentration using the drop plate method
<ol>
	<li>To determine bacterial load in infected cells with the drop plate method, wash the gentamycin-treated cells 2x with 2 mL of cold PBS.</li>
	<li>Add 1 mL of cell lysis buffer (0.5% triton X-100 in PBS) to each well.</li>
	<li>Dilute the cell lysates containing the internalized bacteria in a gradient (1:10, 1:100, 1:1,000, and 1:10,000) for the following inoculation to the TSB agar plate.</li>
	<li>After 16 h of incubation, obtain the results of CFU by counting the bacterial colonies.</li>
</ol>
6. RT-qPCR detection of bacterial 16S rRNA
<ol>
	<li>Treat the Pseudomonas-infected lung epithelial cells (~1 x 106 cells/mL) with gentamycin as described above. Aspirate the medium and wash the cells 2x with 2 mL of cold PBS.</li>
	<li>Add 0.35 mL of the guanidium thiocyanate lysis buffer per well of a 6 well plate. Collect the cells with a cell scraper. Pipette the lysate into a microcentrifuge tube and mix gently with the pipette.</li>
	<li>Add the same volume (0.35 mL) of freshly prepared 70% ethanol into the lysate and mix well. Transfer all samples to a spin column placed in a 2 mL collection tube. Centrifuge at 10,000 x g for 30 s at 20&#8211;25 &#176;C. Then, discard the buffer in the collection tube.</li>
	<li>Wash the column with 0.7 mL of wash buffer 1. Centrifuge the column at 10,000 x g for 30 s. Wash the column 2x with 0.5 mL of buffer to wash the membrane-bound RNA. Repeat the centrifugation at 10,000 x g for 2 min.</li>
	<li>Place the column into a new 1.5 mL collection tube. Add 30&#8211;50 &#181;L RNase-free water. Centrifuge at 10,000 x g for 1 min. Collect the flow-through and measure the RNA concentration.</li>
	<li>Perform a reverse transcription reaction according to the manufacturer&#39;s protocol. Mix 1 &#181;g of total RNA with 10 mL of reaction buffer, 1 &#181;L of reverse transcriptase, and RNase-free water for a 20 &#181;L reaction. Conduct the reverse transcription reaction at 37 &#176;C for 1 h and then 95 &#176;C for 5 min.</li>
	<li>Mix together the cDNA templates (1 &#181;L of each reverse transcription reaction above), 5 &#181;L of the Master Mix containing SYBR dye, 1 &#181;L of each 200 nM specific primers, and water in a 20 &#181;L mixture for the following PCR analysis, according to the manufacturer&#39;s recommendations. 
	NOTE: The following are the primers targeting the 16S rRNA of P. aeruginosa: forward 5&#8242;-CAAAACTACTGAGCTAGAGTACG-3&#8242;; reverse 5&#8242;-TAAGATCTCAAG GATCCCAACGGC-3&#8242;. GAPDH was used as a loading control with the following primers: forward: 5&#8242;-GGCATGGACTGGTCATGA-3&#8242;; reverse: 5&#8217;-TTCACCATGGAGAAGGC-3&#8242;.</li>
	<li>Use the comparative CT method to determine the expression.</li>
</ol>
7. Detection of fluorescent Pseudomonas with flow cytometry
<ol>
	<li>Treat the above fluorescent Pseudomonas-infected lung epithelial cells (~1 x 106 cells/mL) with gentamycin as previously described. Aspirate the medium and wash the cells 2x with 2 mL of cold PBS.</li>
	<li>Analyze the samples with a flow cytometer at a wavelength of 509 nm for the detection of GFP. Terminate each read at 100,000 counts. Analyze the acquired data with related software.</li>
</ol>

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The authors have nothing to disclose.

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 mechanisms25...

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 smoking1,2. Cigarette smoking increases susceptibility to acute microbial infections in the respiratory system3,4,5. Furthermore, mounting evidence proves that cigarette smoking enhances the pathogenesis of many chronic disorders6,7,8. For instance, cigarette smoking may increase viral or bacterial infections that cause COPD exacerbation9. Among the bacterial pathogens that etiologically contribute to acute exacerbation of COPD, an opportunistic gram-negative bacillus pathogen, Pseudomonas aeruginosa, causes infections that correlate with poor prognoses and higher mortalities10,11. COPD exacerbation worsens the disease by accelerating pathological progression. There are no effective therapies against COPD exacerbation except for the antisymptomatic management12. COPD exacerbation promotes patient mortality, decreases quality of life, and increases economic burden on society13.
The respiratory airway is an open system, continuously subjected to various microbial pathogens present externally. Opportunistic bacterial pathogens are usually detected in the upper airways but sometimes are observed in the lower airways14,15. In animal models P. aeruginosa can be detected in alveolar sacs as soon as 1 h after infection16. As a major defense mechanism, immune cells such as macrophages or neutrophils eliminate the bacteria in the airways. Lung epithelial cells, as the first physiological barrier, perform a unique role in the host defense against microbial infections. Lung epithelial cells may regulate microbial invasion, colonization, or replication independent of immune cells17. Some molecules found in epithelial cells, including PPARg, exert antibacterial functions, thereby regulating bacterial colonization and replication in lung epithelial cells18. Cigarette smoking may alter the molecules and impair normal defense function in lung epithelial cells19,20. Recent studies reported direct exposure of cigarette smoke to lung epithelial cells using robot smoking apparatus21,22. Exposure to smoke can be performed in other ways, however, including application of CSE. Preparation of CSE is a reproducible approach with potential applications in other cell types, including vascular endothelial cells that are indirectly exposed to cigarette smoke.
This report describes a protocol to generate cigarette smoke extract to alter bacterial load in lung epithelial cells. CSE increases the bacterial load of P. aeruginosa, and it may contribute to the recurrence of bacterial infections usually seen in COPD exacerbation. A conventional method is used for the preparation of CSE. Lung epithelial cells, at their exponential growth stage, are treated with 4% CSE for 3 h. Alternatively, monolayer-cultured lung epithelial cells can be directly exposed to cigarette smoke in an air-liquid interface. CSE-treated cells are then challenged with Pseudomonas at a multiplicity of infection (MOI) of 10. The bacteria are propagated at a particular shaking speed to ensure the morphology of their flagella remains intact to retain their full invasive capacity. Gentamycin is employed to kill the bacteria left in the culture medium, thereby reducing the potential contamination during the subsequent determination of the bacterial load. The protocol also uses&#160;GFP-labeled Pseudomonas, which has been utilized&#160;as&#160;a powerful tool in studying Pseudomonas infection in different models. A representative strain is P. fluorescens Migula23. The degree of infection or bacterial load after CSE treatment is determined in three ways: the drop plate method with colony counting, quantitative PCR using Pseudomonas 16S rRNA-specific primers, or flow cytometry in cells infected with fluorescent Pseudomonas. This protocol is a simple and reproducible approach to study the effect of cigarette smoke on bacterial infections in lung epithelial cells.

<table border="0" cellpadding="0" cellspacing="0" style="width:691px;" width="690">
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	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">50mL syringe</td>
			<td style="width:148px;">BD Biosciences</td>
			<td style="width:161px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">airway epithelial cell basal medium</td>
			<td style="width:148px;">ATCC</td>
			<td>PCS-300-030</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Bacteria shaker</td>
			<td style="width:148px;">ThermoFisher Scientific</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">bronchial epithelial cell growth kit</td>
			<td style="width:148px;">ATCC</td>
			<td>PCS-300-040</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Cell Counter</td>
			<td style="width:148px;">Bio-Rad</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">CFX96 Real-Time PCR System</td>
			<td style="width:148px;">Bio-Rad</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">High-Capacity RNA-to-DNA KIT</td>
			<td style="width:148px;">ThermoFisher Scientific</td>
			<td align="right" style="width:161px;">4387406</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">HITES medium</td>
			<td style="width:148px;">ATCC</td>
			<td style="width:161px;">ATCC 30-2004</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">human BEAS-2B cells</td>
			<td style="width:148px;">ATCC</td>
			<td style="width:161px;">ATCC CRL-9609</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">human primary small airway epithelial cells</td>
			<td style="width:148px;">ATCC</td>
			<td style="width:161px;">ATCC PCS-300-030</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LSRII flow cytometer</td>
			<td style="width:148px;">BD Biosciences</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Nikkon confocal microscope</td>
			<td style="width:148px;">Nikkon</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">OD reader</td>
			<td style="width:148px;">USA Scientific</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">PCR primers</td>
			<td style="width:148px;">ITD</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Pseudomonas aeruginosa</td>
			<td style="width:148px;">ATCC</td>
			<td style="width:161px;">ATCC 47085</td>
			<td style="width:167px;">PAO1-LAC</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Pseudomonas fluorescens Migula</td>
			<td style="width:148px;">ATCC</td>
			<td style="width:161px;">ATCC 27853</td>
			<td>P.aeruginosa GFP</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Research-grade cigarettes (3R4F)</td>
			<td style="width:148px;">University of Kentucky</td>
			<td style="width:161px;">TP-7-VA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNeasy Mini Kit</td>
			<td style="width:148px;">Qiagen</td>
			<td align="right" style="width:161px;">74106</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Transprent PET Transwell Insert</td>
			<td style="width:148px;">Corning Costar</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Tryptic Soy Broth</td>
			<td style="width:148px;">BD Biosciences</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

studying effects of cigarette smoke on pseudomonas infection in lung epithelial cells

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.

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...

Watch this Scientific Journal Video about Studying Effects of Cigarette Smoke on Pseudomonas Infection in Lung Epithelial Cells at JoVE.com

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

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

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

Cigarette smoking is the major etiological cause for lung emphysema and chronic obstructive pulmonary disease (COPD). Cigarette smoking also promotes ...

studying-effects-cigarette-smoke-on-pseudomonas-infection-lung

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JoVE Journal

Immunology and Infection

5.8K Views.  University of Pittsburgh School of Medicine. Described here is a protocol to study how cigarette smoke extract affects bacterial colonization in lung epithelial cells.

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

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

Bacterial biofilms have been associated with a number of different human diseases, but biofilm development has generally been studied on non-living surfaces. In this paper, we describe protocols for forming Pseudomonas aeruginosa biofilms on human airway epithelial cells (CFBE cells) grown in culture. In the first method (termed the Static Co-culture Biofilm Model), P. aeruginosa is incubated with CFBE cells grown as confluent monolayers on standard tissue culture plates. Although the bacterium is quite toxic to epithelial cells, the addition of arginine delays the destruction of the monolayer long enough for biofilms to form on the CFBE cells. The second method (termed the Flow Cell Co-culture Biofilm Model), involves adaptation of a biofilm flow cell apparatus, which is often used in biofilm research, to accommodate a glass coverslip supporting a confluent monolayer of CFBE cells. This monolayer is inoculated with P. aeruginosa and a peristaltic pump then flows fresh medium across the cells. In both systems, bacterial biofilms form within 6-8 hours after inoculation. Visualization of the biofilm is enhanced by the use of P. aeruginosa strains constitutively expressing green fluorescent protein (GFP). The Static and Flow Cell Co-culture Biofilm assays are model systems for early P. aeruginosa infection of the Cystic Fibrosis (CF) lung, and these techniques allow different aspects of P. aeruginosa biofilm formation and virulence to be studied, including biofilm cytotoxicity, measurement of biofilm CFU, and staining and visualizing the biofilm.

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

This paper describes different methods of growing Pseudomonas aeruginosa biofilms on cultured human airway epithelial cells. These protocols can be adapted to study different aspects of biofilm formation, including visualization of the biofilm, staining of the biofilm, measuring the colony forming units (CFU) of the biofilm, and studying biofilm cytotoxicity.

Bacterial biofilms have been associated with a number of different human diseases, but biofilm development has generally been studied on non-living ...

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Many microbial cells have the ability to form sessile microbial communities defined as biofilms that have altered physiological and pathological properties compared to free living microorganisms. Biofilms in nature are often difficult to investigate and reside under poorly defined conditions1. Using a transparent substratum it is possible to device a system where simple biofilms can be examined in a non-destructive way in real-time: here we demonstrate the assembly and operation of a flow cell model system, for in vitro 3D studies of microbial biofilms generating high reproducibility under well-defined conditions2,3.
The system consists of a flow cell that serves as growth chamber for the biofilm. The flow cell is supplied with nutrients and oxygen from a medium flask via a peristaltic pump and spent medium is collected in a waste container. This construction of the flow system allows a continuous supply of nutrients and administration of e.g. antibiotics with minimal disturbance of the cells grown in the flow chamber. Moreover, the flow conditions within the flow cell allow studies of biofilm exposed to shear stress. A bubble trapping device confines air bubbles from the tubing which otherwise could disrupt the biofilm structure in the flow cell.
The flow cell system is compatible with Confocal Laser Scanning Microscopy (CLSM) and can thereby provide highly detailed 3D information about developing microbial biofilms. Cells in the biofilm can be labeled with fluorescent probes or proteins compatible with CLSM analysis. This enables online visualization and allows investigation of niches in the developing biofilm. Microbial interrelationship, investigation of antimicrobial agents or the expression of specific genes, are of the many experimental setups that can be investigated in the flow cell system.

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Protocol describing the application of a flow cell system for growing and analyzing microbial biofilms for Confocal Laser Scanning Microscopy (CLSM).

Many microbial cells have the ability to form sessile microbial communities defined as biofilms that have altered physiological and pathological ...

Application of a Mouse Ligated Peyer&#x2019;s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells

The inside of our gut is inhabited with enormous number of commensal bacteria. The mucosal surface of the gastrointestinal tract is continuously exposed to them and occasionally to pathogens. The gut-associated lymphoid tissue (GALT) play a key role for induction of the mucosal immune response to these microbes1, 2. To initiate the mucosal immune response, the mucosal antigens must be transported from the gut lumen across the epithelial barrier into organized lymphoid follicles such as Peyer's patches. This antigen transcytosis is mediated by specialized epithelial M cells3, 4. M cells are atypical epithelial cells that actively phagocytose macromolecules and microbes. Unlike dendritic cells (DCs) and macrophages, which target antigens to lysosomes for degradation, M cells mainly transcytose the internalized antigens. This vigorous macromolecular transcytosis through M cells delivers antigen to the underlying organized lymphoid follicles and is believed to be essential for initiating antigen-specific mucosal immune responses. However, the molecular mechanisms promoting this antigen uptake by M cells are largely unknown. We have previously reported that glycoprotein 2 (Gp2), specifically expressed on the apical plasma membrane of M cells among enterocytes, serves as a transcytotic receptor for a subset of commensal and pathogenic enterobacteria, including Escherichia coli and Salmonella enterica serovar Typhimurium (S. Typhimurium), by recognizing FimH, a component of type I pili on the bacterial outer membrane 5. Here, we present a method for the application of a mouse Peyer's patch intestinal loop assay to evaluate bacterial uptake by M cells. This method is an improved version of the mouse intestinal loop assay previously described 6, 7. The improved points are as follows: 1. Isoflurane was used as an anesthetic agent. 2. Approximately 1 cm ligated intestinal loop including Peyer's patch was set up. 3. Bacteria taken up by M cells were fluorescently labeled by fluorescence labeling reagent or by overexpressing fluorescent protein such as green fluorescent protein (GFP). 4. M cells in the follicle-associated epithelium covering Peyer's patch were detected by whole-mount immunostainig with anti Gp2 antibody. 5. Fluorescent bacterial transcytosis by M cells were observed by confocal microscopic analysis. The mouse Peyer's patch intestinal loop assay could supply the answer what kind of commensal or pathogenic bacteria transcytosed by M cells, and may lead us to understand the molecular mechanism of how to stimulate mucosal immune system through M cells.

Application of a Mouse Ligated Peyer&#8217;s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells

M cells in a specialized follicle-associated epithelium covering Peyer&#x2019;s patches play an important role for the mucosal immunosurveillance in gut-associated lymphoid tissue. Here we described the evaluation method for bacterial transcytosis by M cells in vivo. This method provides a method to understand M-cell function in the immune system.

The inside of our gut is inhabited with enormous number of commensal bacteria. The mucosal surface of the gastrointestinal tract is continuously exposed ...

Use of Artificial Sputum Medium to Test Antibiotic Efficacy Against Pseudomonas aeruginosa in Conditions More Relevant to the Cystic Fibrosis Lung

There is growing concern about the relevance of in vitro antimicrobial susceptibility tests when applied to isolates of P. aeruginosa from cystic fibrosis (CF) patients. Existing methods rely on single or a few isolates grown aerobically and planktonically. Predetermined cut-offs are used to define whether the bacteria are sensitive or resistant to any given antibiotic1. However, during chronic lung infections in CF, P. aeruginosa populations exist in biofilms and there is evidence that the environment is largely microaerophilic2. The stark difference in conditions between bacteria in the lung and those during diagnostic testing has called into question the reliability and even relevance of these tests3.
 Artificial sputum medium (ASM) is a culture medium containing the components of CF patient sputum, including amino acids, mucin and free DNA. P. aeruginosa growth in ASM mimics growth during CF infections, with the formation of self-aggregating biofilm structures and population divergence4,5,6. The aim of this study was to develop a microtitre-plate assay to study antimicrobial susceptibility of P. aeruginosa based on growth in ASM, which is applicable to both microaerophilic and aerobic conditions.
 An ASM assay was developed in a microtitre plate format. P. aeruginosa biofilms were allowed to develop for 3 days prior to incubation with antimicrobial agents at different concentrations for 24 hours. After biofilm disruption, cell viability was measured by staining with resazurin. This assay was used to ascertain the sessile cell minimum inhibitory concentration (SMIC) of tobramycin for 15 different P. aeruginosa isolates under aerobic and microaerophilic conditions and SMIC values were compared to those obtained with standard broth growth. Whilst there was some evidence for increased MIC values for isolates grown in ASM when compared to their planktonic counterparts, the biggest differences were found with bacteria tested in microaerophilic conditions, which showed a much increased resistance up to a &gt;128 fold, towards tobramycin in the ASM system when compared to assays carried out in aerobic conditions.
 The lack of association between current susceptibility testing methods and clinical outcome has questioned the validity of current methods3. Several in vitro models have been used previously to study P. aeruginosa biofilms7, 8. However, these methods rely on surface attached biofilms, whereas the ASM biofilms resemble those observed in the CF lung9 . In addition, reduced oxygen concentration in the mucus has been shown to alter the behavior of P. aeruginosa2 and affect antibiotic susceptibility10. Therefore using ASM under microaerophilic conditions may provide a more realistic environment in which to study antimicrobial susceptibility.

Use of Artificial Sputum Medium to Test Antibiotic Efficacy Against Pseudomonas aeruginosa in Conditions More Relevant to the Cystic Fibrosis Lung

Current diagnostic antimicrobial susceptibility testing relies on the planktonic growth of isolates in nutrient rich, aerobic conditions. Here, we employ an alternative artificial sputum medium to study antimicrobial susceptibility of Pseudomonas aeruginosa biofilms under both aerobic and microaerophilic conditions more representative of the cystic fibrosis lung.

There  is growing concern about the relevance of in vitro antimicrobial  susceptibility tests when applied to isolates of P. aeruginosa from  cystic ...

Flow Cytometric Isolation of Primary Murine Type II Alveolar Epithelial Cells for Functional and Molecular Studies

Throughout the last years, the contribution of alveolar type II epithelial cells (AECII) to various aspects of immune regulation in the lung has been increasingly recognized. AECII have been shown to participate in cytokine production in inflamed airways and to even act as antigen-presenting cells in both infection and T-cell mediated autoimmunity 1-8. Therefore, they are especially interesting also in clinical contexts such as airway hyper-reactivity to foreign and self-antigens as well as infections that directly or indirectly target AECII. However, our understanding of the detailed immunologic functions served by alveolar type II epithelial cells in the healthy lung as well as in inflammation remains fragmentary. Many studies regarding AECII function are performed using mouse or human alveolar epithelial cell lines 9-12. Working with cell lines certainly offers a range of benefits, such as the availability of large numbers of cells for extensive analyses. However, we believe the use of primary murine AECII allows a better understanding of the role of this cell type in complex processes like infection or autoimmune inflammation. Primary murine AECII can be isolated directly from animals suffering from such respiratory conditions, meaning they have been subject to all additional extrinsic factors playing a role in the analyzed setting. As an example, viable AECII can be isolated from mice intranasally infected with influenza A virus, which primarily targets these cells for replication 13. Importantly, through ex vivo infection of AECII isolated from healthy mice, studies of the cellular responses mounted upon infection can be further extended.
Our protocol for the isolation of primary murine AECII is based on enzymatic digestion of the mouse lung followed by labeling of the resulting cell suspension with antibodies specific for CD11c, CD11b, F4/80, CD19, CD45 and CD16/CD32. Granular AECII are then identified as the unlabeled and sideward scatter high (SSChigh) cell population and are separated by fluorescence activated cell sorting 3.
In comparison to alternative methods of isolating primary epithelial cells from mouse lungs, our protocol for flow cytometric isolation of AECII by negative selection yields untouched, highly viable and pure AECII in relatively short time. Additionally, and in contrast to conventional methods of isolation by panning and depletion of lymphocytes via binding of antibody-coupled magnetic beads 14, 15, flow cytometric cell-sorting allows discrimination by means of cell size and granularity. Given that instrumentation for flow cytometric cell sorting is available, the described procedure can be applied at relatively low costs. Next to standard antibodies and enzymes for lung disintegration, no additional reagents such as magnetic beads are required. The isolated cells are suitable for a wide range of functional and molecular studies, which include in vitro culture and T-cell stimulation assays as well as transcriptome, proteome or secretome analyses 3, 4.

We describe the rapid isolation of primary murine type II alveolar epithelial cells (AECII) by flow cytometric negative selection. These AECII show high viability and purity and are suitable for a wide range of functional and molecular studies regarding their role in respiratory conditions such as autoimmune or infectious diseases.

Throughout  the last years, the contribution of alveolar type II epithelial cells (AECII)  to various aspects of immune regulation in the lung has been ...

Pseudomonas aeruginosa Induced Lung Injury Model

In order to study human acute lung injury and pneumonia, it is important to develop animal models to mimic various pathological features of this disease. Here we have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa (P. aeruginosa or PA). Using this model, we were able to show lung inflammation at the early phase of injury. In addition, alveolar epithelial barrier leakiness was observed by analyzing bronchoalveolar lavage (BAL); and alveolar cell death was observed by Tunel assay using tissue prepared from injured lungs. At a later phase following injury, we observed cell proliferation required for the repair process. The injury was resolved 7 days from the initiation of P. aeruginosa injection. This model mimics the sequential course of lung inflammation, injury and repair during pneumonia. This clinically relevant animal model is suitable for studying pathology, mechanism of repair, following acute lung injury, and also can be used to test potential therapeutic agents for this disease.

Pseudomonas aeruginosa Induced Lung Injury Model

We have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa. This model mimics lung injury during pneumonia and is clinically relevant.

In order to study human acute lung injury and pneumonia, it is important to develop animal models to mimic various pathological features of this disease. ...

Analyzing the Effects of Stromal Cells on the Recruitment of Leukocytes from Flow

Stromal cells regulate the recruitment of circulating leukocytes during inflammation through cross-talk with neighboring endothelial cells. Here we describe two in vitro &#8220;vascular&#8221; models for studying the recruitment of circulating neutrophils from flow by inflamed endothelial cells. A major advantage of these models is the ability to analyze each step in the leukocyte adhesion cascade in order, as would occur in vivo. We also describe how both models can be adapted to study the role of stromal cells, in this case mesenchymal stem cells (MSC), in regulating leukocyte recruitment.
Primary endothelial cells were cultured alone or together with human MSC in direct contact on Ibidi microslides or on opposite sides of a Transwell filter for 24 hr. Cultures were stimulated with tumor necrosis factor alpha (TNF&#945;) for 4 hr and incorporated into a flow-based adhesion assay. A bolus of neutrophils was perfused over the endothelium for 4 min. The capture of flowing neutrophils and their interactions with the endothelium was visualized by phase-contrast microscopy.
In both models, cytokine-stimulation increased endothelial recruitment of flowing neutrophils in a dose-dependent manner. Analysis of the behavior of recruited neutrophils showed a dose-dependent decrease in rolling and a dose-dependent increase in transmigration through the endothelium. In co-culture, MSC suppressed neutrophil adhesion to TNF&#945;-stimulated endothelium.
Our flow based-adhesion models mimic the initial phases of leukocyte recruitment from the circulation. In addition to leukocytes, they can be used to examine the recruitment of other cell types, such as therapeutically administered MSC or circulating tumor cells. Our multi-layered co-culture models have shown that MSC communicate with endothelium to modify their response to pro-inflammatory cytokines, altering the recruitment of neutrophils. Further research using such models is required to fully understand how stromal cells from different tissues and conditions (inflammatory disorders or cancer) influence the recruitment of leukocytes during inflammation.

The ability of inflamed endothelium to recruit leukocytes from flow is regulated by mesenchymal stromal cells. We describe two in vitro models incorporating primary human cells that can be used to assess neutrophil recruitment from flow and examine the role that mesenchymal stromal cells play in regulating this process.

Stromal cells regulate the recruitment of circulating leukocytes during inflammation through cross-talk with neighboring endothelial cells. Here we ...

Flow Cytometric Analysis of Particle-bound Bet v 1 Allergen in PM10

Flow cytometry is a method widely used to quantify suspended solids such as cells or bacteria in a size range from 0.5 to several tens of micrometers in diameter. In addition to a characterization of forward and sideward scatter properties, it enables the use of fluorescent labeled markers like antibodies to detect respective structures. Using indirect antibody staining, flow cytometry is employed here to quantify birch pollen allergen (precisely Bet v 1)-loaded particles of 0.5 to 10 &#181;m in diameter in inhalable particulate matter (PM10, particle size &#8804;10 &#181;m in diameter). PM10 particles may act as carriers of adsorbed allergens possibly transporting them to the lower respiratory tract, where they could trigger allergic reactions.
So far the allergen content of PM10 has been studied by means of enzyme linked immunosorbent assays (ELISAs) and scanning electron microscopy. ELISA measures the dissolved and not the particle-bound allergen. Compared to scanning electron microscopy, which can visualize allergen-loaded particles, flow cytometry may additionally quantify them. As allergen content of ambient air can deviate from birch pollen count, allergic symptoms might perhaps correlate better with allergen exposure than with pollen count. In conjunction with clinical data, the presented method offers the opportunity to test in future experiments whether allergic reactions to birch pollen antigens are associated with the Bet v 1 allergen content of PM10 particles &#62;0.5 &#181;m.

Here, we present a protocol to quantify allergen-loaded particles by flow cytometry. Ambient particulate matter particles may act as carriers of adsorbed allergens. We show here that flow cytometry, a method widely used to characterize suspended solids &#62;0.5 &#181;m in diameter, can be used to measure these allergen-loaded particles.

Flow cytometry is a method widely used to quantify suspended solids such as cells or bacteria in a size range from 0.5 to several tens of micrometers in ...

Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the development and persistence of many health related infections. One of the most well described and studied biofilms in human disease occurs in chronic pulmonary infection of cystic fibrosis patients. When studying biofilms in the context of the host, many factors can impact biofilm formation and development. In order to identify how host factors may affect biofilm formation and development, we used a static chambered coverglass method to grow biofilms in the presence of host-derived factors in the form of sputum supernatants. Bacteria are seeded into chambers and exposed to sputum filtrates. Following 48 hr of growth, biofilms are stained with a commercial biofilm viability kit prior to confocal microscopy and analysis. Following image acquisition, biofilm properties can be assessed using different software platforms. This method allows us to visualize key properties of biofilm growth in presence of different substances including antibiotics.

This protocol describes the visualization of biofilm development following exposure to host-factors using a slide chamber model. This model allows for direct visualization of biofilm development as well as analysis of biofilm parameters using computer software programs.

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the ...

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

Bacteria are able to secrete a variety of molecules via various secretory systems. Besides the secretion of molecules into the extracellular space or directly into another cell, Gram-negative bacteria can also form outer membrane vesicles (OMVs). These membrane vesicles can deliver their cargo over long distances, and the cargo is protected from degradation by proteases and nucleases. 
Legionella pneumophila (L. pneumophila) is an intracellular, Gram-negative pathogen that causes a severe form of pneumonia. In humans, it infects alveolar macrophages, where it blocks lysosomal degradation and forms a specialized replication vacuole. Moreover, L. pneumophila produces OMVs under various growth conditions. To understand the role of OMVs in the infection process of human macrophages, we set up a protocol to purify bacterial membrane vesicles from liquid culture. The method is based on differential ultracentrifugation. The enriched OMVs were subsequently analyzed with regard to their protein and lipopolysaccharide (LPS) amount and were then used for the treatment of a human monocytic cell line or murine bone marrow-derived macrophages. The pro-inflammatory responses of those cells were analyzed by enzyme-linked immunosorbent assay. Furthermore, alterations in a subsequent infection were analyzed. To this end, the bacterial replication of L. pneumophila in macrophages was studied by colony-forming unit assays. 
Here, we describe a detailed protocol for the purification of L. pneumophila OMVs from liquid culture by ultracentrifugation and for the downstream analysis of their pro-inflammatory potential on macrophages.

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

Here, we describe the purification of Legionella pneumophila (L. pneumophila) outer membrane vesicles (OMVs) from liquid cultures. These purified vesicles are then used for the treatment of macrophages to analyze their pro-inflammatory potential.

Bacteria are able to secrete a variety of molecules via various secretory systems. Besides the secretion of molecules into the extracellular space or ...

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Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages