Name: automated image-based quantification of neutrophil extracellular traps using netquant
Uploaded: 2019-11-27T12:00:00
Description: Watch this Scientific Journal Video about Automated Image-Based Quantification of Neutrophil Extracellular Traps Using NETQUANT at JoVE.com

The work was funded by the Crafoord Foundation (TM and PN), Swedish Government Research grant (PN, TM), Swedish research council (PN) and Groschinsky Foundation (TM, PN).

The ethics committee of Lund University approved the collection of venous blood from healthy volunteers in accordance with the Declaration of Helsinki (2013/728). All volunteers provided their written informed consent.
1. Isolation of Peripheral Blood Neutrophils using Density-Gradient Centrifugation
<ol>
	<li>Collect human venous blood in tubes containing heparin and allow the tubes to reach room temperature. 
	Note: A minimum of 16 mL of blood from a healthy donor is required to yield...

<ol>
	<li>Nauseef, W. M., Borregaard, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophils+at+work.">Neutrophils at work.</a> Nature Immunology. 15 (7), 602-611 (2014).</li><li>Borregaard, N., Cowland, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Granules+of+the+human+neutrophilic+polymorphonuclear+leukocyte.">Granules of the human neutrophilic polymorphonuclear leukocyte.</a> Blood. 89 (10), 3503-3521 (1997).</li><li>Nordenfelt, P., Tapper, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phagosome+dynamics+during+phagocytosis+by+neutrophils.">Phagosome dynamics during phagocytosis by neutrophils.</a> Journal of Leukocyte Biology. 90 (2), 271-284 (2011).</li><li>Brinkmann, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+extracellular+traps+kill+bacteria.">Neutrophil extracellular traps kill bacteria.</a> Science. 303 (5663), 1532-1535 (2004).</li><li>Sorensen, O. E., Borregaard, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+extracellular+traps+-+the+dark+side+of+neutrophils.">Neutrophil extracellular traps - the dark side of neutrophils.</a> Journal of Clinical Investigation. 126 (5), 1612-1620 (2016).</li><li>Yipp, B. G., Kubes, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NETosis:+how+vital+is+it?.">NETosis: how vital is it?.</a> Blood. 122 (16), 2784-2794 (2013).</li><li>Jorch, S. K., Kubes, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+emerging+role+for+neutrophil+extracellular+traps+in+noninfectious+disease.">An emerging role for neutrophil extracellular traps in noninfectious disease.</a> Nature Medicine. 23 (3), 279-287 (2017).</li><li>Fuchs, T. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+cell+death+program+leads+to+neutrophil+extracellular+traps.">Novel cell death program leads to neutrophil extracellular traps.</a> J Cell Biol. 176 (2), 231-241 (2007).</li><li>Mohanty, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+mechanism+for+NETosis+provides+antimicrobial+defense+at+the+oral+mucosa.">A novel mechanism for NETosis provides antimicrobial defense at the oral mucosa.</a> Blood. 126 (18), 2128-2137 (2015).</li><li>Hakkim, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+the+Raf-MEK-ERK+pathway+is+required+for+neutrophil+extracellular+trap+formation.">Activation of the Raf-MEK-ERK pathway is required for neutrophil extracellular trap formation.</a> Nature Chemical Biology. 7 (2), 75-77 (2011).</li><li>Brinkmann, V., Goosmann, C., Kuhn, L. I., Zychlinsky, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automatic+quantification+of+in+vitro+NET+formation.">Automatic quantification of in vitro NET formation.</a> Frontiers in Immunology. 3, 413 (2012).</li><li>Coelho, L. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automatic+determination+of+NET+(neutrophil+extracellular+traps)+coverage+in+fluorescent+microscopy+images.">Automatic determination of NET (neutrophil extracellular traps) coverage in fluorescent microscopy images.</a> Bioinformatics. 31 (14), 2364-2370 (2015).</li><li>Mohanty, T., Sorensen, O. E., Nordenfelt, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NETQUANT:+Automated+Quantification+of+Neutrophil+Extracellular+Traps.">NETQUANT: Automated Quantification of Neutrophil Extracellular Traps.</a> Frontiers in Immunology. 8, 1999 (2017).</li><li>Kaplan, M. J., Radic, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+extracellular+traps:+double-edged+swords+of+innate+immunity.">Neutrophil extracellular traps: double-edged swords of innate immunity.</a> Journal of Immunology. 189 (6), 2689-2695 (2012).</li><li>Cedervall, J., Olsson, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunity+Gone+Astray+-+NETs+in+Cancer.">Immunity Gone Astray - NETs in Cancer.</a> Trends in Cancer. 2 (11), 633-634 (2016).</li><li>Ginley, B. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computational+detection+and+quantification+of+human+and+mouse+neutrophil+extracellular+traps+in+flow+cytometry+and+confocal+microscopy.">Computational detection and quantification of human and mouse neutrophil extracellular traps in flow cytometry and confocal microscopy.</a> Scientific Reports. 7 (1), 17755 (2017).</li></ol>

NET formation is a relatively recent addition to the diverse neutrophil armamentarium4 and there has been a noticeable surge of interest to study the implication of NETs in a wide array of research areas5,7,14,15. Acquisition of images using Immunofluorescence microscopy and subsequent image-based quantification is a widely used method to quantify NETs. This approach has...

Neutrophils are crucial mediators of innate host defense responses against a wide variety of microbial pathogens1. They execute their antimicrobial functions by releasing their granules containing a wide array of antimicrobial proteins2, producing reactive oxygen species (ROS) and hypochlorite1, and through phagocytosis3. In addition, Brinkmann et al.4 described neutrophil extracellular traps (NETs) as a novel mechanism by which neutrophils trap and eliminate invading pathogens. Since their discovery a little over a decade ago4, NETs have been implicated in a wide variety of infectious5,6 and non-infectious7 morbidities. NET formation is an active process and results in the extrusion of chromatin DNA coated with granule-derived antimicrobial proteins8. Some of the key changes in cellular and nuclear morphology associated with NET formation include the loss of nuclear morphology, chromatin decondensation, mobilization of granule proteins from cytoplasm to the nucleus and an increase in the nuclear and cellular diameter8,9.
The web-like NETs, which may appear as diffuse structures slightly larger than the cell or as structures several times larger than a single neutrophil are considered as indicators of NETosis5,10. Using fluorescence microscopy, NETs can be detected by probing DNA with a fluorescent probe such as 4&#39;,6-diamidino-2-phenylindole (DAPI) and by immunofluorescence staining against NET-bound proteins such as neutrophil elastase. Quantification of overlapping areas of staining for DNA and NET-bound proteins determines the total area under NETs in an image11.
A number of image analysis options are available to perform fluorescence image-based quantification of NETs11,12. But these software options present limitations in not being user-friendly and/or fully automated. In this article, we demonstrate the operation of NETQUANT13, a freely available app that can perform unbiased fully automated immunofluorescence microscopy image-based NET quantification. The app has a user friendly graphical interface (GUI) and can perform single-cell analysis. The software quantifies NETosis in an image by detecting the morphological changes in the area of DNA-NET-bound marker, chromatin decondensation associated deformation of the nucleus and increase in the DNA:NET-bound protein ratio. Taken together, the multiple NET definition criteria allows for stringent NET quantification across several data sets in an unbiased fashion.

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	<tbody>
		<tr>
			<td>BD Vacutainer Heparinised plastic tubes</td>
			<td>BD Biosciences</td>
			<td>367885</td>
			<td></td>
		</tr>
		<tr>
			<td>Lymphoprep</td>
			<td>Axis-Shield</td>
			<td>114547</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI-1640 with L-Glutamine</td>
			<td>Gibco</td>
			<td>11835-030</td>
			<td></td>
		</tr>
		<tr>
			<td>50mL conical flasks</td>
			<td>Sarstedt</td>
			<td>62.547.004</td>
			<td></td>
		</tr>
		<tr>
			<td>15mL conical flasks</td>
			<td>Sarstedt</td>
			<td>62.554.002</td>
			<td></td>
		</tr>
		<tr>
			<td>12-well Tissue culture plates</td>
			<td>Falcon</td>
			<td>10626491</td>
			<td></td>
		</tr>
		<tr>
			<td>#1 Coverslips 10mm</td>
			<td>Menzel Glaser</td>
			<td>CS10100</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass slides</td>
			<td>Menzel Glaser</td>
			<td>631-0098</td>
			<td></td>
		</tr>
		<tr>
			<td>Primary anti-human elastase</td>
			<td>DAKO</td>
			<td>DAKO rabbit 1373, contract immunization</td>
			<td></td>
		</tr>
		<tr>
			<td>Secondary fluorophore conjugated goat anti-rabbit</td>
			<td>Life technologies</td>
			<td>A-11072, A-11070</td>
			<td></td>
		</tr>
		<tr>
			<td>PROLONG-Gold Antifade reagent with DAPI</td>
			<td>Life technologies</td>
			<td>P36930</td>
			<td>Mounting medium</td>
		</tr>
		<tr>
			<td>Goat serum</td>
			<td>Sigma-Aldrich</td>
			<td>G9023</td>
			<td></td>
		</tr>
		<tr>
			<td>Phorbol 12-myristate 13-acetate (PMA)</td>
			<td>Sigma-Aldrich</td>
			<td>79346</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma-Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon Ti-E Epifluorescence microscope</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CCD camera</td>
			<td>Andor Zyla</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plan Apochromat 20x, 40x objectives</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Windows 10</td>
			<td>Microsoft</td>
			<td></td>
			<td>Operating system</td>
		</tr>
		<tr>
			<td>macOS Sierra 10.12</td>
			<td>Apple</td>
			<td></td>
			<td>Operating system</td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>Mathworks</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

automated image-based quantification of neutrophil extracellular traps using netquant

Neutrophil extracellular traps (NETs) are web-like antimicrobial structures consisting of DNA and granule derived antimicrobial proteins. Immunofluorescence microscopy and image-based quantification methods remain important tools to quantitate neutrophil extracellular trap formation. However, there are key limitations to the immunofluorescence-based methods that are currently available for quantifying NETs. Manual methods of image-based NET quantification are often subjective, prone to error and tedious for users, especially non-experienced users. Also, presently available software options for quantification are either semi-automatic or require training prior to operation. Here, we demonstrate the implementation of an automated immunofluorescence-based image quantification method to evaluate NET formation called NETQUANT. The software is easy to use and has a user-friendly graphical user interface (GUI). It considers biologically relevant parameters such as an increase in the surface area and DNA:NET marker protein ratio, and nuclear deformation to define NET formation. Furthermore, this tool is built as a freely available app, and allows for single-cell resolution quantification and analysis.

5 x 105 neutrophils/mL were seeded onto coverslips placed in a 12-well plate and stimulated with either 20 nM PMA or left unstimulated for 150 min. The samples were then stained using primary rabbit anti-human neutrophil elastase antibodies, secondary goat anti-rabbit fluorophore conjugated antibodies and DAPI - a fluorescently labelled dye that stains DNA (See the Table of Materials for details). A minimum of 5 images were then acquired using an epifluorescenc...

Watch this Scientific Journal Video about Automated Image-Based Quantification of Neutrophil Extracellular Traps Using NETQUANT at JoVE.com

Automated Image-Based Quantification of Neutrophil Extracellular Traps Using NETQUANT

Here, we present a protocol for generating neutrophil extracellular traps (NETs) and operating NETQUANT, a fully automatic software option for quantification of NETs in immunofluorescence images.

Neutrophil extracellular traps (NETs) are web-like antimicrobial structures consisting of DNA and granule derived antimicrobial proteins. ...

Here we present NETQUANT, a fully automated approach to quantify NETS and immunofluorescence images. This will help researchers in making comparable image analysis from data generated by multiple users and conditions. The advantages of this technique are the ease of use, single-cell data analysis, multiple criteria to evaluate NET formation, and an unbiased analysis of multiple images.Install and open the analysis software. An up-to-date version can be found on the Zenodo GitHub archive, or the Nordonfelt Lab website. In the setup tab, choose a source folder for analysis by clicking the get path option in the source menu.Select the folder containing the image sequences to be analyzed. Again, click on the get path option in the target menu, and select the target folder for saving the data following image analysis. Next, when using separate channel images, name the channel folders so that the DNA channel corresponds with the nuclear DNA stain, and the NET channel depicts the neutrophil elastase stain in the images.Also, name the folder containing the control image files as control. Next, click the load image information button and load the image metadata into the software. Then in the channel order sub-menu, select the correct channel order contained in the images.This helps to prevent accidental mismatches. Now click on the prepare data button to acquire primary image properties from the raw data and convert the images. The converted images will then appear in the sample types sub-menu.Click on the sample type menu, select an image from the sub-menu and click on display image data to display the images split into the DNA and Neutrophil Extracellular Trap, or NET channel, respectively. To segment the cells into their respective channels, select the segmentation method tab, and select a method in the method sub-menu for both the DNA and the NET channels. The default method of segmentation is set to adaptive and is the recommended setting.Other options are available in the software including global edge and chanverse. A watershed option has also been included to help distinguish between closely-placed cells or NETs. Also in the segmentation tab, click on the segment control samples option.Then select PMA from sample type sub-menu and click on the batch option to begin segmentation of all images included in the data set. Next, select the images in the sample type menu and click on the display image data button to visualize and validate the binary image masks for both the DNA and NET masks generated post-segmentation. Now, in the analysis tab, click on the determine threshold button to analyze the control samples.Then, on the right hand side, change the sample type to PMA and click the get cell properties button to complete analysis of the stimulated samples. Next, select an image from the sample type sub-menu and click on the display image data button to display the overlay and the number of cells and NET forming cells in the image. Begin by selecting the sample from the sample type sub-menu.Individual images can be selected from the sample type sub-menu for analysis or the entire batch of images can be analyzed by selecting the batch option. Once selected, click on the analyze NETs button to complete the analysis. Adjust NET criteria manually to yield optimal results for a given sample.Compare identified NETs with the original images to assess the quality of identification. Once this step has been completed, the NET criteria can be applied across all images in the dataset. Any changes made to the NET criteria are also simultaneously applied to all control samples.Inspect the data summary in the cell data sub-menu, where the number of images, cell count per image, and percentage of NETs per image are displayed. Enter the output tab to select and view the result outputs. Explore and compare the various data outputs generated from the analysis of control and PMA-treated samples by selecting the form of the output and clicking on the output results button.Next, launch the results data table CSV file to explore single-cell data and click on the results PDF files to visualize the NET area distribution and DNA to NET ratio in the samples. The red line indicates the threshold value in the graphs. Finally, click on the results bivariate distribution file to determine the NET area versus shape of DNA.Here, 15 images of control neutrophils and 15 images of PMA-stimulated neutrophils were analyzed in under ten minutes. The total number of cells were counted and the percentage of cells with Neutrophil Extracellular Traps was determined using the automated quantification method described in this article. These results shows that PMA-stimulated neutrophils have a larger area, an increase in nuclear deformation, and a higher DNA to NET ratio than control samples.When combined into a 3D graph, the PMA-stimulated samples tend to show areas of tighten groupings than the control samples. While attempting the procedure, it's important to remember that although the workflow was tested using multiple donors, it is recommended that the user should decide on the software parameters appropriately based on the individual data set.

automated-image-based-quantification-neutrophil-extracellular-traps

Research

JoVE Journal

Immunology and Infection

Neutrophil Extracellular Traps: How to Generate and Visualize Them

Neutrophil granulocytes are the most abundant group of leukocytes in the peripheral blood. As professional phagocytes, they engulf bacteria and kill them intracellularly when their antimicrobial granules fuse with the phagosome. We found that neutrophils have an additional way of killing microorganisms: upon activation, they release granule proteins and chromatin that together form extracellular fibers that bind pathogens. These novel structures, or Neutrophil Extracellular Traps (NETs), degrade virulence factors and kill bacteria1, fungi2 and parasites3. The structural backbone of NETs is DNA, and they are quickly degraded in the presence of DNases. Thus, bacteria expressing DNases are more virulent4. Using correlative microscopy combining TEM, SEM, immunofluorescence and live cell imaging techniques, we could show that upon stimulation, the nuclei of neutrophils lose their shape and the eu- and heterochromatin homogenize. Later, the nuclear envelope and the granule membranes disintegrate allowing the mixing of NET components. Finally, the NETs are released as the cell membrane breaks. This cell death program (NETosis) is distinct from apoptosis and necrosis and depends on the generation of Reactive Oxygen Species by NADPH oxidase5. 
Neutrophil extracellular traps are abundant at sites of acute inflammation. NETs appear to be a form of innate immune response that bind microorganisms, prevent them from spreading, and ensure a high local concentration of antimicrobial agents to degrade virulence factors and kill pathogens thus allowing neutrophils to fulfill their antimicrobial function even beyond their life span. There is increasing evidence, however, that NETs are also involved in diseases that range from auto-immune syndromes to infertility6.
We describe methods to isolate Neutrophil Granulocytes from peripheral human blood7 and stimulate them to form NETs. Also we include protocols to visualize the NETs in light and electron microscopy.

Neutrophil Extracellular Traps (NETs) are an important innate immune mechanism to fight pathogenic bacteria, fungi and parasites. Here we describe methods to isolate neutrophil granulocytes from human blood and to activate them to form NETs. We present preparation techniques to visualize NETs in light and electron microscopy.

Neutrophil granulocytes are the most abundant group of leukocytes in the peripheral blood. As professional phagocytes, they engulf bacteria and kill them ...

Simplified Human Neutrophil Extracellular Traps (NETs) Isolation and Handling

Neutrophil Extracellular Traps (NETs) have been recently identified as part of the neutrophil&#8217;s antimicrobial armamentarium. Apart from their role in fighting infections, recent research has demonstrated that they may be involved in many other disease processes, including cancer progression. Isolating purified NETs is a crucial element to allow the study of these functions.
In this video, we demonstrate a simplified method of cell free NET isolation from human whole blood using readily available reagents. Isolated NETs can then be used for immunofluorescence staining, blotting or various functional assays. This enables an assessment of their biologic properties in the absence of the potential confounding effects of neutrophils themselves.
A density gradient separation technique is employed to isolate neutrophils from healthy donor whole blood. Isolated neutrophils are then stimulated by phorbol 12-myristate 13-acetate (PMA) to induce NETosis. Activated neutrophils are then discarded, and a cell-free NET stock is obtained.
We then demonstrate how isolated NETs can be used in an adhesion assay with A549 human lung cancer cells. The NET stock is used to coat the wells of a 96 well cell culture plate O/N, and after ensuring an adequate NET monolayer formation on the bottom of the wells, CFSE labeled A549 cells are added. Adherent cells are quantified using a Nikon TE300 fluorescent microscope. In some wells, 1000U DNAse1 is added 10 min before counting to degrade NETs

Simplified Human Neutrophil Extracellular Traps NETs Isolation and Handling

In the following protocol, we describe a very simple way to isolate Neutrophil Extracellular traps (NETs) from human whole blood using readily available reagents. We then demonstrate how the isolated NETs can be used in an in vitro adhesion assay with cancer cells.

Neutrophil Extracellular Traps (NETs) have been recently identified as part of the neutrophil&#8217;s antimicrobial armamentarium. Apart from their role ...

Methods to Study Lipid Alterations in Neutrophils and the Subsequent Formation of Neutrophil Extracellular Traps

Lipid analysis performed by high performance thin layer chromatography (HPTLC) is a relatively simple, cost-effective method of analyzing a broad range of lipids. The function of lipids (e.g., in host-pathogen interactions or host entry) has been reported to play a crucial role in cellular processes. Here, we show a method to determine lipid composition, with a focus on the cholesterol level of primary blood-derived neutrophils, by HPTLC in comparison to high performance liquid chromatography (HPLC). The aim was to investigate the role of lipid/cholesterol alterations in the formation of neutrophil extracellular traps (NETs). NET release is known as a host defense mechanism to prevent pathogens from spreading within the host. Therefore, blood-derived human neutrophils were treated with methyl-&#946;-cyclodextrin (M&#946;CD) to induce lipid alterations in the cells. Using HPTLC and HPLC, we have shown that M&#946;CD treatment of the cells leads to lipid alterations associated with a significant reduction in the cholesterol content of the cell. At the same time, M&#946;CD treatment of the neutrophils led to the formation of NETs, as shown by immunofluorescence microscopy. In summary, here we present a detailed method to study lipid alterations in neutrophils and the formation of NETs.

Lipids are known to play an important role in cellular functions. Here, we describe a method to determine the lipid composition of neutrophils, with emphasis on the cholesterol level, by using both HPTLC and HPLC to gain a better understanding of the underlying mechanisms of neutrophil extracellular trap formation.

Lipid analysis performed by high performance thin layer chromatography (HPTLC) is a relatively simple, cost-effective method of analyzing a broad range of ...

A Simple Fluorescence Assay for Quantification of Canine Neutrophil Extracellular Trap Release

Neutrophil extracellular traps are networks of DNA, histones and neutrophil proteins released in response to infectious and inflammatory stimuli. Although a component of the innate immune response, NETs are implicated in a range of disease processes including autoimmunity and thrombosis. This protocol describes a simple method for canine neutrophil isolation and quantification of NETs using a microplate fluorescence assay. Blood is collected using conventional venipuncture techniques. Neutrophils are isolated using dextran sedimentation and a density gradient using conditions optimized for dog blood. After allowing time for attachment to the wells of a 96 well plate, neutrophils are treated with NET-inducing agonists such as phorbol-12-myristate-13-acetate or platelet activating factor. DNA release is measured by the fluorescence of a cell-impermeable nucleic acid dye. This assay is a simple, inexpensive method for quantifying NET release, but NET formation rather than other causes of cell death must be confirmed with alternative methods.

Neutrophil extracellular traps (NETs) are networks of DNA, histones and neutrophil proteins. Although a component of the innate immune response, NETs are implicated in autoimmunity and thrombosis. This protocol describes a simple method for canine neutrophil isolation and quantification of NETs using a microplate fluorescence assay.

Neutrophil extracellular traps are networks of DNA, histones and neutrophil proteins released in response to infectious and inflammatory stimuli. Although ...

Visualizing Macrophage Extracellular Traps Using Confocal Microscopy

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal microscopy methods to visualize macrophage extracellular traps (METs). These extracellular traps are defined by the presence of extracellular chromatin with co-expression of other components such as granule proteases, citrullinated histones, and peptidyl arginase deiminase (PAD). The expression of METs is generally measured after exposure to a stimulus and compared to un-stimulated samples. Samples are also included for background and isotype control. Cells are analyzed using well-defined image analysis software. Confocal microscopy may be used to define the presence of METs both in vitro and in vivo in lung tissue.

Macrophage extracellular traps are a newly described entity. This article will concentrate on confocal microscopy methods and how they are visualized in vitro and in vivo from lung samples.

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal ...

Identification of Neutrophil Extracellular Traps in Paraffin-Embedded Feline Arterial Thrombi using Immunofluorescence Microscopy

Neutrophil extracellular traps (NETs), composed of cell-free DNA (cfDNA) and proteins like histones and neutrophil elastase (NE), are released by neutrophils in response to systemic inflammation or pathogens. Although NETs have previously been shown to augment clot formation and inhibit fibrinolysis in humans and dogs, the role of NETs in cats with cardiogenic arterial thromboembolism (CATE), a life-threatening complication secondary to hypertrophic cardiomyopathy, is unknown. A standardized method to identify and quantify NETs in cardiogenic arterial thrombi in cats will advance our understanding of their pathological role in CATE. Here, we describe a technique to identify NETs in formaldehyde-fixed and paraffin-embedded thrombi within the aortic bifurcation, extracted during necropsy. Following deparaffinization with xylene, aortic sections underwent indirect heat-induced antigen retrieval. Sections were then blocked, permeabilized, and ex vivo NETs were identified by colocalization of cell-free DNA (cfDNA), citrullinated histone H3 (citH3), and neutrophil elastase (NE) using immunofluorescence microscopy. To optimize the immunodetection of NETs in thrombi, autofluorescence of tissue elements was limited by using an autofluorescence quenching process prior to microscopy. This technique could be a useful tool to study NETs and thrombosis in other species and offers new insights into the pathophysiology of this complex condition.

We describe a method to identify neutrophil extracellular traps (NETs) in formaldehyde-fixed and paraffin-embedded feline cardiogenic arterial thrombi using heat-induced antigen retrieval and a double immunolabeling protocol.

Neutrophil extracellular traps (NETs), composed of cell-free DNA (cfDNA) and proteins like histones and neutrophil elastase (NE), are released by ...

Morphological and Compositional Analysis of Neutrophil Extracellular Traps Induced by Microbial and Chemical Stimuli

Neutrophils function as the first line of cellular defense in an innate immune response by employing diverse mechanisms, such as the formation of neutrophil extracellular traps (NETs). This study analyzes the morphological and compositional changes in NETs induced by microbial and chemical stimuli using standardized in vitro methodologies for NET induction and characterization with human cells. The procedures described here allow the analysis of NET morphology (lytic or non-lytic) and composition (DNA-protein structures and enzymatic activity), and the effect of soluble factors or cellular contact on such characteristics. Additionally, the techniques described here could be modified to evaluate the effect of exogenous soluble factors or cellular contact on NET composition.
The applied techniques include the purification of polymorphonuclear cells from human peripheral blood using a double density gradient (1.079-1.098 g/mL), guaranteeing optimal purity and viability (&#8805; 95%) as demonstrated by Wright's staining, trypan blue exclusion, and flow cytometry, including FSC versus SSC analysis and 7AAD staining. NET formation is induced with microbial (Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans) and chemical (phorbol myristate acetate, HOCl) stimuli, and the NETs are characterized by DNA-DAPI staining, immunostaining for the antimicrobial peptide cathelicidin (LL37), and quantification of enzymatic activity (neutrophil elastase, cathepsin G, and myeloperoxidase). The images are acquired through fluorescence microscopy and analyzed with ImageJ.

Presented here is a protocol for the induction and analysis of in vitro neutrophil extracellular traps (NETs). Quantification of DNA, cathelicidin (LL37), and enzyme activity yielded data that show the variability in the composition and morphology of NETs induced by microbial and chemical stimuli under similar controlled conditions.

Neutrophils function as the first line of cellular defense in an innate immune response by employing diverse mechanisms, such as the formation of ...

Quantifying Myeloperoxidase-DNA and Neutrophil Elastase-DNA Complexes from Neutrophil Extracellular Traps by Using a Modified Sandwich ELISA

Certain stimuli, such as microorganisms, cause neutrophils to release neutrophil extracellular traps (NETs), which are basically web-like structures composed of DNA with granule proteins, such as myeloperoxidase (MPO) and neutrophil elastase (NE), and cytoplasmic and cytoskeletal proteins. Although interest in NETs has increased recently, no sensitive, reliable assay method is available for measuring NETs in clinical settings. This article describes a modified sandwich enzyme-linked immunosorbent assay to quantitatively measure two components of circulating NETs, MPO-DNA and NE-DNA complexes, which are specific components of NETs and are released into the extracellular space as breakdown products of NETs. The assay uses specific monoclonal antibodies for MPO or NE as the capture antibodies and a DNA-specific detection antibody. MPO or NE binds to one site of the capture antibody during the initial incubation of samples containing MPO-DNA or NE-DNA complexes. This assay shows good linearity and high inter-assay and intra-assay precision. We used it in 16 patients with COVID-19 with accompanying acute respiratory distress syndrome and found that the plasma concentrations of MPO-DNA and NE-DNA were significantly higher than in the plasma obtained from healthy controls. This detection assay is a reliable, highly sensitive, and useful method for investigating the characteristics of NETs in human plasma and culture supernatants.

We present a protocol for a modified sandwich enzyme-linked immunosorbent assay technique to quantitatively measure two components of neutrophil extracellular trap remnants, myeloperoxidase conjugated-DNA and neutrophil elastase conjugated-DNA complexes,derived from activated neutrophils.

Certain stimuli, such as microorganisms, cause neutrophils to release neutrophil extracellular traps (NETs), which are basically web-like structures ...

Staining and Imaging to Visualize Neutrophil Extracellular Traps

Immunofluorescence Imaging of Neutrophil Extracellular Traps in Human and Mouse Tissues

Neutrophil extracellular traps (NETs) are released by neutrophils as a response to bacterial infection or traumatic tissue damage but also play a role in autoimmune diseases and sterile inflammation. They are web-like structures composed of double-stranded DNA filaments, histones, and antimicrobial proteins. Once released, NETs can trap and kill extracellular pathogens in blood and tissue. Furthermore, NETs participate in homeostatic regulation by stimulating platelet adhesion and coagulation. However, the dysregulated production of NETs has also been associated with various diseases, including sepsis or autoimmune disorders, which makes them a promising target for therapeutic intervention. Apart from electron microscopy, visualizing NETs using immunofluorescence imaging is currently one of the only known methods to demonstrate NET interactions in tissue. Therefore, various staining methods to visualize NETs have been utilized. In the literature, different staining protocols are described, and we identified four key components showing high variability between protocols: (1) the types of antibodies used, (2) the usage of autofluorescence-reducing agents, (3) antigen retrieval methods, and (4) permeabilization. Therefore, in vitro immunofluorescence staining protocols were systemically adapted and improved in this work to make them applicable for different species (mouse, human) and tissues (skin, intestine, lung, liver, heart, spinal disc). After fixation and paraffin-embedding, 3 &#181;m thick sections were mounted onto slides. These samples were stained with primary antibodies for myeloperoxidase (MPO), citrullinated histone H3 (H3cit), and neutrophil elastase (NE) according to a modified staining protocol. The slides were stained with secondary antibodies and examined using a widefield fluorescence microscope. The results were analyzed according to an evaluation sheet, and differences were recorded semi-quantitatively.
Here, we present an optimized NET staining protocol suitable for different tissues. We used a novel primary antibody to stain for H3cit and reduced non-specific staining with an autofluorescence-reducing agent. Furthermore, we demonstrated that NET staining requires a constant high temperature and careful handling of samples.

Author Spotlight: Neutrophil Extracellular Traps Imaging in Human and Mouse Tissues 

Neutrophil extracellular traps (NETs) are associated with various diseases, and immunofluorescence is often used for their visualization. However, there are various staining protocols, and, in many cases, only one type of tissue is examined. Here, we establish a generally applicable protocol for staining NETs in mouse and human tissue.

Neutrophil extracellular traps (NETs) are released by neutrophils as a response to bacterial infection or traumatic tissue damage but also play a role in ...

Immunofluorescence Staining of Neutrophil Extracellular Traps in Tissue Samples

Begin by pipetting one drop of ready-to-use blocking solution with donkey serum onto the tissue samples. Then incubate the samples for 30 minutes at room temperature. Remove the excess blocking solution from the slides by tapping the edge against a hard surface.Dilute the primary antibodies in the antibody dilution buffer to prepare 100 microliters of the final solution for each sample. Set up the antibodies, one tube for each primary antibody and one for each isocontrol antibody. Evenly spread 100 microliters of isocontrol antibodies to one sample, and 100 microliters of myeloperoxidase and citrullinated histone H3, or myeloperoxidase and neutrophil elastase antibody dilution to the other sample.Place the slides in a wet chamber and store them overnight at four degrees Celsius. The following day, tap off excess primary antibody solution from the slides and stack them in a cuvette. Rinse the slides three times for five minutes each using Tris buffered saline with tween To remove the remaining primary antibody solution.Prepare two distinctly fluorescent secondary antibodies, donkey anti-goat for myeloperoxidase and donkey anti-rabbit for citrullinated histone H3 staining. Dilute each antibody to 7.5 micrograms per milliliter concentration in the antibody dilution buffer. Place the slides in a wet chamber and dispense 100 microliters of the secondary antibody solution onto each sample.Incubate them for 30 minutes at room temperature protected from light. Remove excess secondary antibody solution by tapping the slides. Put the slides in a slide rack.Submerge the slides three times for five minutes each in a staining jar filled with PBS to wash off unbound antibodies. Prepare the dappy solution and dilute it to a concentration of one microgram per milliliter with deionized water. Submerge the slide rack in a staining jar containing the dappy solution and incubate for five minutes at room temperature in the dark.Next, submerge the slide rack in a staining jar with PBS for five minutes to wash off any excess dappy solution. Finally, mount the samples using cover slips and mounting medium. The citrullinated histone H3 antibody only bound to the extracellular histones and showed no staining of intracellular histones.The human or mouse specific myeloperoxidase antibody showed no specific staining. While the universal human and mouse antibodies showed consistent good staining for myeloperoxidase. When no blocking agent was used, some mouse samples showed more non-specific and partial positive staining.When blocked, the five minutes blocking time showed good results compared to the 10 minutes blocking time. The higher temperatures in the microwave and water bath showed consistently moderate to good antigen retrieval. Whereas in a 60 degrees Celsius water bath there was only partially positive to no staining.For double staining, more favorable results were obtained for the samples incubated at 96 degrees Celsius water bath. However, exceeding the incubation time of 40 minutes at 96 degrees Celsius resulted in less intense antibody staining.