This work was supported partially by the University of Louisville start-up funds and National Cancer Institute (Bethesda, MD) grants R01CA177679, R01CA180986.

The protocol was approved by the Institutional Animal Care and Use Committee (IACUC) of University of Louisville.
1. Mouse Bone Marrow Derived Macrophages (BMDMs)
<ol>
	<li>Euthanize a 6- to 8-week-old, healthy wild type mouse using CO2. Pin it down to a foam board and spray it with 70% ethanol until it is soaked. Remove the tibia/femur bones with forceps and scissors. Put them in a petri dish with 5 mL 1x phosphate-buffered saline (PBS). Perform all procedures under sterile conditions.</li>
	<li>Cut open both ends of the tibia/femur bone with a scissor in a sterile tissue culture hood. Flush the bone with a 25 G needle with PBS + 2% fetal bovine serum (FBS) into a 15 mL tube.</li>
	<li>Centrifuge the bone marrow cells at 500 x g, 4 &#176;C for 5 min.</li>
	<li>Resuspend the cell pellet in 1 mL red blood cell lysis buffer to lyse red blood cells (RBC) for less than 1 min. Dilute immediately with 9 mL 1x PBS. Centrifuge again as in step 1.3. Decant the supernatants.</li>
	<li>Resuspend the cell pellet in 10 mL 1x PBS, filter the cell suspension through a sterile 40 &#956;m&#160;nylon mesh into another 15 mL tube to remove cell debris/clumps. Centrifuge again as in 1.3. Decant the supernatants.</li>
	<li>Resuspend the cell pellet in 15 mL Roswell Park Memorial Institute medium (RPMI) 1640 with 5% FBS and 10 &#956;g/mL gentamicin, plate the cells in a 100-mm tissue culture dish at 37 oC incubator for 60 min. Gently swirl the dish, take out the floating cells, and count them.</li>
	<li>Plate 6x106 cells in a 100-mm dish with 12 mL macrophage differentiating media (RPMI 1640 with 5% FBS and 10 &#956;g/mL gentamicin, mixed with 30% L929 conditioned media10) with 10 ng/mL recombinant mouse macrophage colony-stimulating factor (M-CSF) for 2 days.</li>
	<li>After culturing for 2 days in a 37 &#176;C incubator with 5% CO2, feed each dish with 6 mL fresh macrophage differentiating media with 10 ng/mL M-CSF.</li>
	<li>On day 5, take 8 mL of the old media out without disturbing the cells and add 10 mL fresh macrophage differentiating media with 10 ng/mL M-CSF.</li>
	<li>On day 7, harvest the bone marrow-derived macrophages (BMDMs) using a cell lifter. 
	NOTE: Attached macrophages can also be dissociated with 5 mL 1 mM EDTA in 1x PBS for 5 to 10 min after removing the float cells and washing plate twice with 5 mL 1x PBS. Centrifuge the cells as in step 1.3., resuspend them in fresh macrophage differentiating media, and count them with a hemocytometer.
	<ol>
		<li>Confirm the BMDMs&#39; phenotype by flow cytometry as described5. Prepare the derived mouse macrophages in a certain concentration for the following studies.</li>
	</ol>
	</li>
</ol>
2. BSA-fatty Acid Conjugate Preparation
<ol>
	<li>Prepare 2 mM BSA in sterile PBS. For example, weigh 6.65 g BSA, add 30 mL 1x PBS to dissolve, then add more PBS until 50 mL, scaling components to make 2 mM BSA in 1x PBS.</li>
	<li>Prepare 5 mM individual sodium salt of fatty acids in 2 mM BSA. Heat to 37 &#176;C or higher, if necessary, and sonicate the mixture of 2 mM BSA and sodium salt of fatty acids until a clear solution is obtained. 
	NOTE: Compared to unsaturated fatty acids, saturated fatty acids need a higher temperature and more sonication time for dissolving.</li>
	<li>Filter the fatty-acid-BSA solution through a 0.22 &#956;m filter, aliquot it into 1.5 mL sterile microcentrifuge tubes, and store them at 4 &#176;C for short term use or at -20 &#176;C for long term storage. No precipitation should be observed after storage at 4 &#176;C in the refrigerator.</li>
</ol>
3. Saturated Fatty Acids Induce Cell Death of Mouse Bone Marrow Derived Macrophages
<ol>
	<li>Plate the BMDMs in a 24-well tissue culture plate with 0.4 x 106/mL in macrophage differentiating media.</li>
	<li>Treat the cells with the 0.4 mM palmitic acid and stearic acid for 16 to 24 h at a 37 &#176;C incubator with 5% CO2. Use BSA as the negative control.</li>
	<li>Harvest the cells with a cell lifter after treatment and spin down the cells at 500 x g, 4 &#176;C for 5 min.</li>
	<li>Stain the cells with Annexin V-Alexa 488 and 7-aminoactinomycin D (7-AAD) in 100 &#956;L annexin V binding buffer for 15 min at room temperature.</li>
	<li>Dilute the sample with 200 &#181;L of annexin-binding buffer, mix gently, then keep the samples on ice after the incubation period.</li>
	<li>Analyze the stained cells as soon as possible by flow cytometry5. Annexin V-Alexa 488 is detected in FITC channel and 7-AAD is detected in PerCP/PerCP-Cy5.5 channel.</li>
</ol>
4. Intracellular Ceramide Staining
<ol>
	<li>After fatty acid treatment, harvest the cells as in step 3.3. Then fix the cells in 4% paraformaldehyde for 30 min.</li>
	<li>Wash the sample with 1 mL 1x PBS, spin down as step in 3.3, and decant the supernatant.</li>
	<li>Stain the cells with anti-ceramide primary antibody (1:200 dilution) in 100 &#956;L 1x permeabilization buffer for 30 min.</li>
	<li>Wash and spin down the cells again as in step 4.2.</li>
	<li>Stain the cells with anti-mouse IgM secondary antibody (1:500 dilution) in 100 &#956;L 1x permeabilization buffer for 30 min.</li>
	<li>Wash and spin down the cells again as in step 4.2. Add 250 &#956;L 1x PBS and analyze the stained cells by flow cytometry5. 
	NOTE: See the detailed reagent list in the Table of equipment and reagents.</li>
</ol>

<ol>
	<li>Martins de Lima, T., Cury-Boaventura, M. F., Giannocco, G., Nunes, M. T., Curi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+toxicity+of+fatty+acids+on+a+macrophage+cell+line+(J774).">Comparative toxicity of fatty acids on a macrophage cell line (J774).</a> Clin Sci (Lond). 111 (5), 307-317 (2006).</li><li>Simard, J. R., Zunszain, P. A., Hamilton, J. A., Curry, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Location+of+high+and+low+affinity+fatty+acid+binding+sites+on+human+serum+albumin+revealed+by+NMR+drug-competition+analysis.">Location of high and low affinity fatty acid binding sites on human serum albumin revealed by NMR drug-competition analysis.</a> J Mol Biol. 361 (2), 336-351 (2006).</li><li>Penn, A. H., Dubick, M. A., Torres Filho, I. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fatty+Acid+Saturation+of+Albumin+Used+in+Resuscitation+Fluids+Modulates+Cell+Damage+in+Shock:+In+Vitro+Results+Using+a+Novel+Technique+to+Measure+Fatty+Acid+Binding+Capacity.">Fatty Acid Saturation of Albumin Used in Resuscitation Fluids Modulates Cell Damage in Shock: In Vitro Results Using a Novel Technique to Measure Fatty Acid Binding Capacity.</a> Shock. , (2017).</li><li>Vusse, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Albumin+as+fatty+acid+transporter.">Albumin as fatty acid transporter.</a> Drug Metab Pharmacokinet. 24 (4), 300-307 (2009).</li><li>Zhang, Y., 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=Adipose+Fatty+Acid+Binding+Protein+Promotes+Saturated+Fatty+Acid-Induced+Macrophage+Cell+Death+through+Enhancing+Ceramide+Production.">Adipose Fatty Acid Binding Protein Promotes Saturated Fatty Acid-Induced Macrophage Cell Death through Enhancing Ceramide Production.</a> J Immunol. 198 (2), 798-807 (2017).</li><li>Zhang, Y., 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=Epidermal+Fatty+Acid+binding+protein+promotes+skin+inflammation+induced+by+high-fat+diet.">Epidermal Fatty Acid binding protein promotes skin inflammation induced by high-fat diet.</a> Immunity. 42 (5), 953-964 (2015).</li><li>Wen, H., 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=Fatty+acid-induced+NLRP3-ASC+inflammasome+activation+interferes+with+insulin+signaling.">Fatty acid-induced NLRP3-ASC inflammasome activation interferes with insulin signaling.</a> Nat Immunol. 12 (5), 408-415 (2011).</li><li>Zhang, Y., 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=Fatty+acid-binding+protein+E-FABP+restricts+tumor+growth+by+promoting+IFN-beta+responses+in+tumor-associated+macrophages.">Fatty acid-binding protein E-FABP restricts tumor growth by promoting IFN-beta responses in tumor-associated macrophages.</a> Cancer Res. 74 (11), 2986-2998 (2014).</li><li>Ulloth, J. E., Casiano, C. A., De Leon, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Palmitic+and+stearic+fatty+acids+induce+caspase-dependent+and+-independent+cell+death+in+nerve+growth+factor+differentiated+PC12+cells.">Palmitic and stearic fatty acids induce caspase-dependent and -independent cell death in nerve growth factor differentiated PC12 cells.</a> J Neurochem. 84 (4), 655-668 (2003).</li><li>Weischenfeldt, J., Porse, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+Marrow-Derived+Macrophages+(BMM):+Isolation+and+Applications.">Bone Marrow-Derived Macrophages (BMM): Isolation and Applications.</a> CSH Protoc. , (2008).</li><li>Dansen, T. B., 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=High-affinity+binding+of+very-long-chain+fatty+acyl-CoA+esters+to+the+peroxisomal+non-specific+lipid-transfer+protein+(sterol+carrier+protein-2).">High-affinity binding of very-long-chain fatty acyl-CoA esters to the peroxisomal non-specific lipid-transfer protein (sterol carrier protein-2).</a> Biochem J. 339 (Pt 1), 193-199 (1999).</li><li>Ulloth, J. E., 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=Characterization+of+methyl-beta-cyclodextrin+toxicity+in+NGF-differentiated+PC12+cell+death.">Characterization of methyl-beta-cyclodextrin toxicity in NGF-differentiated PC12 cell death.</a> Neurotoxicology. 28 (3), 613-621 (2007).</li></ol>

The authors declare no financial conflicts of interest.

The proper preparation of fatty acid solution is of critical importance to study the biological function of fatty acids. The neutralization of fatty acid increases its solubility in aqueous solution. However, sodium salts of fatty acids, especially saturated fatty acids, are still of low solubility in water or PBS as we observed. One method is to use 95 - 100% ethanol to help dissolve fatty acid1. Using this method, higher toxicity to cells may be observed even at lower concentrations for less tox...

Fatty acids play a critical role in energy metabolism and in the synthesis of membrane phospholipids in different kinds of cells. Fatty acids have a low aqueous solubility. Appropriate preparation of fatty acid is of critical importance for studying the biological functions of fatty acids in mammalian cells. When fatty acids are prepared with ethanol, many fatty acids may show their toxic soap (detergent) effect on the cell membrane, even at relatively low concentrations1. As a natural, major transporter for free fatty acids in the serum, serum albumin is considered a good carrier for fatty acid delivery in vitro for fatty acid function assays2,3,4. However, the details of the preparation of fatty acid and serum albumin conjugate are usually not available even though many research papers using fatty acids have been published.
Macrophages highly express epidermal fatty acid-binding protein and adipose fatty acid-binding protein5,6,7,8. They actively uptake saturated and unsaturated fatty acids which may regulate their immune functions. To study the impact of fatty acids on macrophages and other cells, different methods of fatty acid preparation were applied1,7,9. Using appropriately prepared fatty acid/serum albumin conjugates to investigate the impact of fatty acids on macrophage function is of critical importance in obtaining biologically meaningful data. Studies on the impact of fatty acids on macrophage function can provide basic knowledge and potential therapeutic targets relating to fatty acid metabolism in macrophage-involved diseases.

<table width="828">
	<tbody>
		<tr height="20">
			<td height="20" style="width:357px;height:20px;">CPX Ultrasonic Bath&#160;</td>
			<td style="width:208px;">Bransonic</td>
			<td style="width:153px;">Model 2800</td>
			<td style="width:111px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium palmitate (PA)</td>
			<td>Nu-Chek Prep, Inc.</td>
			<td>S-1109</td>
			<td>M.W. 278</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium stearate (SA)</td>
			<td>Nu-Chek Prep, Inc.</td>
			<td>S-1111</td>
			<td>M.W. 306</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bovine serum albumin (BSA), fatty acid-free</td>
			<td>Fisher Scientific</td>
			<td>9048-46-8</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Mouse macrophage colony stimulating factor (mM-CSF)&#160;</td>
			<td>Cell Signaling Technology,&#160; Inc.</td>
			<td>5228</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">RPMI 1640</td>
			<td>VWR International</td>
			<td>71002-878</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Annexin V, Alexa Fluor 488 conjugate</td>
			<td>Fisher Scientific</td>
			<td>A13201</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">7-AAD</td>
			<td>BD Biosciences</td>
			<td>559925</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Monoclonal anti-ceramide antibody (mouse IgM)</td>
			<td>Sigma</td>
			<td>C8104-50TST</td>
			<td>Clone: MID 15B4</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Goat Anti-Mouse IgM Antibody, &#181; chain, FITC conjugate</td>
			<td>Sigma</td>
			<td>AP128F</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fixation buffer</td>
			<td>Biolegend</td>
			<td>420801</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Permeabilization buffer</td>
			<td>Ebioscience</td>
			<td>4307693</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Red Blood Cell Lysis Buffer&#160;</td>
			<td>Sigma</td>
			<td>11814389001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Annexin V Binding Buffer</td>
			<td>BD Biosciences</td>
			<td>556454</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">L929 cells</td>
			<td>ATCC</td>
			<td>CCL-1</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Corning&#160;Cell Lifter&#160;</td>
			<td>Fisher Scientific</td>
			<td>07-200-364</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="width:357px;height:21px;">Note: M.W. is for molecular weight.</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

saturated fatty acids induce ceramide-associated macrophage cell death

Macrophages highly express epidermal fatty acid-binding protein and adipose fatty acid-binding protein. They actively uptake saturated and unsaturated fatty acids, which might play a critical role in regulating their immune functions. Numerous studies have shown that various fatty acids, saturated or unsaturated, may possess different impacts on cell growth and function. However, the approaches used for fatty acid preparation vary, which may lead to non-physiological results. Serum albumin, a natural carrier for fatty acids in mammalian peripheral blood, is recommended for forming a conjugate complex with the sodium salt of fatty acids to study fatty acid function in mammalian cells, thus minimizing the toxicity of fatty acid soap. Thus, a simple, relatively quick heating and sonicating method is developed and presented here for BSA-fatty acid conjugate formation. We describe a protocol using saturated fatty acids, especially stearic acids to induce severe cell death in mouse bone-marrow derived macrophages. We further demonstrate that saturated fatty acid-induced cell death is positively associated with accumulated cellular ceramide levels. This method can be extended for studies of the impact of fatty acid on other mammalian cells.

Obesity increases free fatty acid concentrations in serum. As professional phagocytes, macrophages actively take up fatty acids to maintain host homeostasis. During these processes, overloaded lipids may induce macrophage cell death. To this end, we cultured BMDMs in vitro with obese levels of dietary fatty acids and measured macrophage cell death using flow cytometric staining. Compared to the BSA control, saturated fatty acids, in particular stearic acids, induced significant c...

Watch this Scientific Journal Video about Saturated Fatty Acids Induce Ceramide-associated Macrophage Cell Death at JoVE.com

Saturated Fatty Acids Induce Ceramide-associated Macrophage Cell Death

We illustrate a straight-forward method to derive murine primary macrophages from bone marrow cells and a simple method to prepare BSA-fatty acid conjugates. Then we demonstrate that saturated fatty acids can induce macrophage cell death, and such cell death is positively associated with cellular accumulation of ceramide levels.

Macrophages highly express epidermal fatty acid-binding protein and adipose fatty acid-binding protein. They actively uptake saturated and unsaturated ...

saturated-fatty-acids-induce-ceramide-associated-macrophage-cell-death

Research

JoVE Journal

Immunology and Infection

9.2K Views.  University of Louisville. We illustrate a straight-forward method to derive murine primary macrophages from bone marrow cells and a simple method to prepare BSA-fatty acid conjugates. Then we demonstrate that saturated fatty acids can induce macrophage cell death, and such cell death is positively associated with cellular accumulation of ceramide levels.

Video: Saturated Fatty Acids Induce Ceramide-associated Macrophage Cell Death

Methods to Assess Beta Cell Death Mediated by Cytotoxic T Lymphocytes

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease. During the pathogenesis, patients become progressively more insulinopenic as 
insulin production is lost, presumably this results from the destruction of pancreatic beta cells by T cells. Understanding the mechanisms of beta cell death during 
the development of T1D will provide insights to generate an effective cure for this disease. Cell-mediated lymphocytotoxicity (CML) assays have historically used the 
radionuclide Chromium 51 (51Cr) to label target cells. These targets are then exposed to effector cells and the release of 51Cr from target 
cells is read as an indication of lymphocyte-mediated cell death. Inhibitors of cell death result in decreased release of 51Cr.
 As effector cells, we used an activated autoreactive clonal population of CD8+ Cytotoxic T lymphocytes (CTL) isolated from a mouse stock transgenic for both the alpha and beta chains of the AI4 T cell receptor (TCR). Activated AI4 T cells were co-cultured with 51Cr labeled target NIT cells for 16 hours, release of 51Cr was recorded to calculate specific lysis 
Mitochondria participate in many important physiological events, such as energy production, regulation of signaling transduction, and apoptosis. The study of beta cell mitochondrial functional changes during the development of T1D is a novel area of research. Using the mitochondrial membrane potential dye Tetramethyl Rhodamine Methyl Ester (TMRM) and confocal microscopic live cell imaging, we monitored mitochondrial membrane potential over time in the beta cell line NIT-1. For imaging studies, effector AI4 T cells were labeled with the fluorescent nuclear staining dye Picogreen. NIT-1 cells and T cells were co-cultured in chambered coverglass and mounted on the microscope stage equipped with a live cell chamber, controlled at 37&deg;C, with 5% CO2, and humidified. During these experiments images were taken of each cluster every 3 minutes for 400 minutes.
Over a course of 400 minutes, we observed the dissipation of mitochondrial membrane potential in NIT-1 cell clusters where AI4 T cells were attached. In the simultaneous control experiment where NIT-1 cells were co-cultured with MHC mis-matched human lymphocyte Jurkat cells, mitochondrial membrane potential remained intact. This technique can be used to observe real-time changes in mitochondrial membrane potential in cells under attack of cytotoxic lymphocytes, cytokines, or other cytotoxic reagents.

Cell-mediated lymphocytotoxicity (CML) assays can be used to test autoreactive responses and study mechanisms of cell death in vitro. However, using live-cell confocal microscopic imaging techniques with fluorescent dyes, the type and kinetics of cell death as well as the pathways utilized can be studied in greater detail.

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease.  During the pathogenesis, patients become progressively more insulinopenic as 
insulin ...

Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic stem/progenitor cells from the bone marrow are directed into monocytic differentiation, followed by M1 or M2 stimulation. The activation status can be tracked by changes in cell surface antigens, gene expression and cell signaling pathways.

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic stem/progenitor cells from the bone marrow are directed into monocytic differentiation, followed by M1 or M2 stimulation. The activation status can be tracked by changes in cell surface antigens, gene expression and cell signaling pathways.

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic ...

Determination of Tolerable Fatty Acids and Cholera Toxin Concentrations Using Human Intestinal Epithelial Cells and BALB/c Mouse Macrophages

The positive role of fatty acids in the prevention and alleviation of non-human and human diseases have been and continue to be extensively documented. These roles include influences on infectious and non-infectious diseases including prevention of inflammation as well as mucosal immunity to infectious diseases. Cholera is an acute intestinal illness caused by the bacterium Vibrio cholerae. It occurs in developing nations and if left untreated, can result in death. While vaccines for cholera exist, they are not always effective and other preventative methods are needed. We set out to determine tolerable concentrations of three fatty acids (oleic, linoleic and linolenic acids) and cholera toxin using mouse BALB/C macrophages and human intestinal epithelial cells, respectively. We solubilized the above fatty acids and used cell proliferation assays to determine the concentration ranges and specific concentrations of the fatty acids that are not detrimental to human intestinal epithelial cell viability. We solubilized cholera toxin and used it in an assay to determine the concentration ranges and specific concentrations of cholera toxin that do not statistically decrease cell viability in BALB/C macrophages. 
We found the optimum fatty acid concentrations to be between 1-5 ng/&mu;l, and that for cholera toxin to be &lt; 30 ng per treatment. This data may aid future studies that aim to find a protective mucosal role for fatty acids in prevention or alleviation of cholera infections.

We set out to determine tolerable concentrations of three fatty acids (oleic, linoleic and linolenic acids) and cholera toxin that did not significantly and adversely affect cell survival by solubilizing the fatty acids and the toxin and using them in cell survival assays.

The positive role of fatty acids in the prevention and alleviation of non-human and  human diseases have been and continue to be extensively documented. ...

Bone Marrow-derived Macrophage Production

Macrophages are critical components of the innate and adaptive immune responses, and they are the first line of defense against foreign invaders because of their powerful microbicidal activities. Macrophages are widely distributed throughout the body and are present in the lymphoid organs, liver, lungs, gastrointestinal tract, central nervous system, bone, and skin. Because of their repartition, they participate in a wide range of physiological and pathological processes. Macrophages are highly versatile cells that are able to recognize microenvironmental alterations and to maintain tissue homeostasis. Numerous pathogens have evolved mechanisms to use macrophages as Trojan horses to survive, replicate in, and infect both humans and animals and to propagate throughout the body. The recent explosion of interest in evolutionary, genetic, and biochemical aspects of host-pathogen interactions has renewed scientific attention regarding macrophages. Here, we describe a procedure to isolate and cultivate macrophages from murine bone marrow that will provide large numbers of macrophages for studying host-pathogen interactions as well as other processes.

Macrophages have long been recognized as a critical component of the innate and adaptive immune responses. The recent explosion of knowledge pertaining to evolutionary, genetic, and biochemical aspects of the interaction between macrophages and microbes has renewed scientific attention to macrophages. This article describes a method to differentiate macrophages from mouse bone marrow.

Macrophages are critical components of the innate and adaptive immune responses, and they are the first line of defense against foreign invaders because ...

RNA Purification from Intracellularly Grown Listeria monocytogenes in Macrophage Cells

Analysis of the transcriptome of bacterial pathogens during mammalian infection is a valuable tool for studying genes and factors that mediate infection. However, isolating bacterial RNA from infected cells or tissues is a challenging task, since mammalian RNA mostly dominates the lysates of infected cells. Here we describe an optimized method for RNA isolation of Listeria monocytogenes bacteria growing within bone marrow derived macrophage cells. Upon infection, cells are mildly lysed and rapidly filtered to discard most of the host proteins and RNA, while retaining intact bacteria. Next, bacterial RNA is isolated using hot phenol-SDS extraction followed by DNase treatment. The extracted RNA is suitable for gene transcription analysis by multiple techniques. This method is successfully employed in our studies of Listeria monocytogenes gene regulation during infection of macrophage cells 1-4. The protocol can be easily modified to study other bacterial pathogens and cell types.

RNA Purification from Intracellularly Grown Listeria monocytogenes in Macrophage Cells

Here we describe a method for bacterial RNA isolation from Listeria monocytogenes bacteria growing inside murine macrophages. This technique can be used with other intracellular pathogens and mammalian host cells.

Analysis of the transcriptome of bacterial pathogens during mammalian infection is a valuable tool for studying genes and factors that mediate infection. ...

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 ...

Detection of Inflammasome Activation and Pyroptotic Cell Death in Murine Bone Marrow-derived Macrophages

Inflammasomes are innate immune signaling platforms that are required for the successful control of many pathogenic organisms, but also promote inflammatory and autoinflammatory diseases. Inflammasomes are activated by cytosolic pattern recognition receptors, including members of the NOD-like receptor (NLR) family. These receptors oligomerize upon the detection of microbial or damage-associated stimuli. Subsequent recruitment of the adaptor protein ASC forms a microscopically visible inflammasome complex, which activates caspase-1 through proximity-induced auto-activation. Following the activation, caspase-1 cleaves pro-IL-1&#946; and pro-IL-18, leading to the activation and secretion of these pro-inflammatory cytokines. Caspase-1 also mediates the inflammatory form of cell death termed pyroptosis, which features the loss of membrane integrity and cell lysis. Caspase-1 cleaves gasdermin D, releasing the N-terminal fragment which forms plasma membrane pores, leading to osmotic lysis.
In vitro, the activation of caspase-1 can be determined by labeling bone marrow-derived macrophages with the caspase-1 activity probe FAM-YVAD-FMK and by labeling the cells with antibodies against the adaptor protein ASC. This technique allows the identification of inflammasome formation and caspase-1 activation in individual cells using fluorescence microscopy. Pyroptotic cell death can be detected by measuring the release of cytosolic lactate dehydrogenase into the medium. This procedure is simple, cost effective and performed in a 96-well plate format, allowing adaptation for screening. In this manuscript, we show that activation of the NLRP3 inflammasome by nigericin leads to the co-localization of the adaptor protein ASC and active caspase-1, leading to pyroptosis.

We describe the detection of NLRP3 inflammasome activation on cellular basis using fluorescence microscopy and staining for active caspase-1 and the adaptor, ASC. A lactate dehydrogenase release assay is presented to detect pyroptotic lysis on a population basis. These techniques can be adapted to study many aspects of inflammasome biology.

Inflammasomes are innate immune signaling platforms that are required for the successful control of many pathogenic organisms, but also promote ...

An Immunohistopathologic Study to Profile the Folate Receptor Beta Macrophage and Vascular Immune Microenvironment in Giant Cell Arteritis

Giant cell arteritis (GCA) is a chronic immune-mediated disease of medium-to-large sized arteries that affects older adults. GCA manifests with arthritis and occlusive symptoms of headaches, stroke or vision loss. Macrophages and T-helper lymphocytes infiltrate the vascular wall and produce a pro-inflammatory response that lead to vessel damage and ischemia. To date, there is no GCA biomarker that can monitor disease activity and guide therapeutic response.
Folate receptor beta (FRB) is a glycosylphosphatidylinositol protein that is anchored on cell membranes and normally expressed in the myelomonocytic lineage and in the majority of myeloid leukemia cells as well as in tumor and rheumatoid synovial macrophages, where its expression correlates with disease severity. The ability of FRB to bind folate compounds, folic acid-conjugates and antifolate drugs has made it a druggable target in cancer and inflammatory disease research. This report describes the histopathologic and immunohistochemical methods used to assess expression and distribution of FRB in relation to GCAimmunopathology.
Formalin-fixed and paraffin-embedded temporal artery biopsies from GCA and normal controls were stained with Hematoxylin and Eosin to review tissue histology and identify pathognomonic features.Immunohistochemistry was used to detect FRB, CD68 and CD3 expression. A microscopic analysis was performed to quantify the number of positively stained cells on 10 selected high-power-field sections and their respective locations in the arterial wall.
Lymphohistiocytic (LH) inflammation accompanied by intimal hyperplasia and disrupted elastic lamina was seen in GCA with none found in controls. The LH infiltrate was composed of approximately 60% lymphocytes and 40% macrophages. FRB expression was restricted to macrophages, comprising 31% of the total CD68+ macrophage population and localized to the media and adventitia. No FRB was seen in controls.
This protocol demonstrated a distinct numerical and spatial pattern of the FRB macrophage relative to the vascular immune microenvironment in GCA.

The protocol illustrates the use of histopathologic examination and immunohistochemistry to profile the folate receptor beta macrophage and its relationship with the total immune cell infiltrate in temporal artery biopsies in giant cell arteritis.

Giant cell arteritis (GCA) is a chronic immune-mediated disease of medium-to-large sized arteries that affects older adults. GCA manifests with arthritis ...

Processing of Bronchoalveolar Lavage Fluid and Matched Blood for Alveolar Macrophage and CD4+ T-cell Immunophenotyping and HIV Reservoir Assessment

Bronchoscopy is a medical procedure whereby normal saline is injected into the lungs via a bronchoscope and then suction is applied, removing bronchoalveolar lavage (BAL) fluid. The BAL fluid is rich in cells and can thus provide a 'snapshot' of the pulmonary immune milieu. CD4 T cells are the best characterized HIV reservoirs, while there is strong evidence to suggest that tissue macrophages, including alveolar macrophages (AMs), also serve as viral reservoirs. However, much is still unknown about the role of AMs in the context of HIV reservoir establishment and maintenance. Therefore, developing a protocol for processing BAL fluid to obtain cells that may be used in virological and immunological assays to characterize and evaluate the cell populations and subsets within the lung is relevant for understanding the role of the lungs as HIV reservoirs. Herein, we describe such a protocol, employing standard techniques such as simple centrifugation and flow cytometry. The CD4 T cells and AMs may then be used for subsequent applications, including immunophenotyping and HIV DNA and RNA quantification.

Processing of Bronchoalveolar Lavage Fluid and Matched Blood for Alveolar Macrophage and CD4+ T-cell Immunophenotyping and HIV Reservoir Assessment

We describe a method for processing bronchoalveolar lavage fluid and matched peripheral blood from chronically HIV-infected individuals on antiretroviral therapy to assess pulmonary HIV reservoirs. These methods result in the acquisition of highly pure CD4 T cells and alveolar macrophages that may subsequently be used for immunophenotyping and HIV DNA/RNA quantifications by ultrasensitive polymerase chain reaction.

Bronchoscopy is a medical procedure whereby normal saline is injected into the lungs via a bronchoscope and then suction is applied, removing ...

Visualization of Macrophage Lytic Cell Death During Mycobacterial Infection in Zebrafish Embryos via Intravital Microscopy

Zebrafish is an excellent model organism for studying innate immune cell behavior due to its transparent nature and reliance solely on its innate immune system during early development. The Zebrafish Mycobacterium marinum (M. marinum) infection model has been well-established in studying host immune response against mycobacterial infection. It has been suggested that different macrophage cell death types will lead to the diverse outcomes of mycobacterial infection. Here we describe a protocol using intravital microscopy to observe macrophage cell death in zebrafish embryos following M. marinum infection. Zebrafish transgenic lines that specifically label macrophages and neutrophils are infected via intramuscular microinjection of fluorescently labeled M. marinum in either the midbrain or the trunk. Infected zebrafish embryos are subsequently mounted on low melting agarose and observed by confocal microscopy in X-Y-Z-T dimensions. Because long-term live imaging requires using low laser power to avoid photobleaching and phototoxicity, a strongly expressing transgenic is highly recommended. This protocol facilitates the visualization of the dynamic processes in vivo, including immune cell migration, host pathogen interaction, and cell death.

This protocol describes a technique for visualizing macrophage behavior and death in embryonic zebrafish during Mycobacterium marinum infection. Steps for the preparation of bacteria, infection of the embryos, and intravital microscopy are included. This technique may be applied to the observation of cellular behavior and death in similar scenarios involving infection or sterile inflammation.

Zebrafish is an excellent model organism for studying innate immune cell behavior due to its transparent nature and reliance solely on its innate immune ...