This work has been partially supported by the research grants FIS (PS12/00866) from Instituto de Salud Carlos III, Madrid, Spain; Fondo Europeo para el Desarrollo Regional (FEDER); Red de Investigaci&#243;n en SIDA (RIS), ISCIII-RETIC (RD16/0025/0002) and CERCA Programme / Generalitat de Catalunya. The authors thank the Retrovirology and Viral Immunopathology Laboratory of the Institut d&#39;Investigacions Biom&#232;diques August Pi I Sunyer (IDIBAPS). We thank T. Escrib&#224;, C. Rovira, and C. Hurtado for their assistance and S. Cuf&#237; from the Knowledge and Technology Transfer Office for her guidance in protecting the invention.

For this study, ethical committee approval (Comit&#232; &#200;tic d&#39;Investigaci&#243; Cl&#237;nica, Hospital Clinic, Barcelona; approval number HCB/2014/0756) and written, informed consent from all subjects were obtained.
1. NBD-cholesterol Preparation
<ol>
	<li>Dissolve the NBD-cholesterol (MW 494.63; see Table of Materials) in pure ethanol to obtain the stock (2 mM). For a 10 mg vial, dissolve the entire vial contents in a 10.1 mL volume of ethanol to obtain a 2 mM sto...

<ol>
	<li>Hansson, G. K., Hermansson, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+immune+system+in+atherosclerosis.">The immune system in atherosclerosis.</a> Nature Immunology. 12 (3), 204-212 (2011).</li><li>Libby, P., Ridker, P. M., Hansson, G. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progress+and+challenges+in+translating+the+biology+of+atherosclerosis.">Progress and challenges in translating the biology of atherosclerosis.</a> Nature. 473 (7347), 317-325 (2011).</li><li>Ilhan, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atherosclerosis+and+the+role+of+immune+cells.">Atherosclerosis and the role of immune cells.</a> World Journal of Clinical Cases. 3 (4), 345 (2015).</li><li>Greaves, D. R., Gordon, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunity,+atherosclerosis+and+cardiovascular+disease.">Immunity, atherosclerosis and cardiovascular disease.</a> Trends Immunol. 22, (2001).</li><li>Yamamoto, S., Narita, I., Kotani, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+macrophage+and+its+related+cholesterol+efflux+as+a+HDL+function+index+in+atherosclerosis.">The macrophage and its related cholesterol efflux as a HDL function index in atherosclerosis.</a> Clinica Chimica Acta. 457, 117-122 (2016).</li><li>Escol&#224;-Gil, J. C., Rotllan, N., Julve, J., Blanco-Vaca, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+macrophage-specific+RCT+and+antioxidant+and+antiinflammatory+HDL+activity+measurements:+New+tools+for+predicting+HDL+atheroprotection.">In vivo macrophage-specific RCT and antioxidant and antiinflammatory HDL activity measurements: New tools for predicting HDL atheroprotection.</a> Atherosclerosis. 206 (2), 321-327 (2009).</li><li>Santos-Gallego, C. G., Ibanez, B., Badimon, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HDL-cholesterol:+Is+it+really+good?+Differences+between+apoA-I+and+HDL.">HDL-cholesterol: Is it really good? Differences between apoA-I and HDL.</a> Biochemical Pharmacology. 76 (4), 443-452 (2008).</li><li>Rothblat, G. H., Phillips, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-density+lipoprotein+heterogeneity+and+function+in+reverse+cholesterol+transport.">High-density lipoprotein heterogeneity and function in reverse cholesterol transport.</a> Current Opinion in Lipidology. 21 (3), 229-238 (2010).</li><li>Hafiane, A., Genest, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HDL-mediated+cellular+cholesterol+efflux+assay+method.">HDL-mediated cellular cholesterol efflux assay method.</a> Annals of Clinical and Laboratory Science. 45 (6), 659-668 (2015).</li><li>Szalaia, R., Hadzsiev, K., Melegh, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytochrome+P450+Drug+Metabolizing+Enzymes+in+Roma+Population+Samples:+Systematic+Review+of+the+Literature.">Cytochrome P450 Drug Metabolizing Enzymes in Roma Population Samples: Systematic Review of the Literature.</a> Current Medicinal Chemistry. 23, 1-26 (2016).</li><li>Mcintosh, A. L., 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=Fluorescent+Sterols+for+the+Study+of+Cholesterol+Trafficking+in+Living+Cells.">Fluorescent Sterols for the Study of Cholesterol Trafficking in Living Cells.</a> Probes and Tags to Study Biomolecular Function: for Proteins, RNA, and Membranes. , 1-33 (2008).</li><li>Osta&#353;ov, 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=FLIM+studies+of+22-+and+25-NBD-cholesterol+in+living+HEK293+cells:+Plasma+membrane+change+induced+by+cholesterol+depletion.">FLIM studies of 22- and 25-NBD-cholesterol in living HEK293 cells: Plasma membrane change induced by cholesterol depletion.</a> Chemistry and Physics of Lipids. 167, 62-69 (2013).</li><li>Song, W., 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+fluorescent+NBD-cholesterol+efflux+in+THP-1-derived+macrophages.">Characterization of fluorescent NBD-cholesterol efflux in THP-1-derived macrophages.</a> Molecular Medicine Reports. 12 (4), 5989-5996 (2015).</li><li>Liu, N., Wu, C., Sun, L., Zheng, J., Guo, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sesamin+enhances+cholesterol+efflux+in+RAW264.7+macrophages.">Sesamin enhances cholesterol efflux in RAW264.7 macrophages.</a> Molecules. 19 (6), 7516-7527 (2014).</li><li>Qin, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+THP-1+cells+as+a+model+for+mimicking+the+function+and+regulation+of+monocytes+and+macrophages+in+the+vasculature.">The use of THP-1 cells as a model for mimicking the function and regulation of monocytes and macrophages in the vasculature.</a> Atherosclerosis. 221 (1), 2-11 (2012).</li><li>Low, H., Hoang, A., Sviridov, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cholesterol+Efflux+Assay.">Cholesterol Efflux Assay.</a> Journal of Visualized Experiments. (61), 5-9 (2012).</li><li>Gimpl, G., Gehrig-Burger, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cholesterol+reporter+molecules.">Cholesterol reporter molecules.</a> Bioscience Reports. 27 (6), 335-358 (2007).</li><li>Zhang, J., Cai, S., Peterson, B. R., Kris-Etherton, P. M., Heuvel, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vanden+Development+of+a+Cell-Based,+High-Throughput+Screening+Assay+for+Cholesterol+Efflux+Using+a+Fluorescent+Mimic+of+Cholesterol.">Vanden Development of a Cell-Based, High-Throughput Screening Assay for Cholesterol Efflux Using a Fluorescent Mimic of Cholesterol.</a> ASSAY and Drug Development Technologies. 9 (2), 136-146 (2011).</li><li>Rader, D. D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+regulation+of+HDL+metabolism+and+function:+implications+for+novel+therapies.">Molecular regulation of HDL metabolism and function: implications for novel therapies.</a> Journal of Clinical Investigation. 116 (12), 3090-3100 (2006).</li><li>Davidson, W. S., 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=The+effects+of+apolipoprotein+B+depletion+on+HDL+subspecies+composition+and+function.">The effects of apolipoprotein B depletion on HDL subspecies composition and function.</a> Journal of Lipid Research. 57 (4), 674-686 (2016).</li><li>Park, S. 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=Sage+weed+(Salvia+plebeia)+extract+antagonizes+foam+cell+formation+and+promotes+cholesterol+efflux+in+murine+macrophages.">Sage weed (Salvia plebeia) extract antagonizes foam cell formation and promotes cholesterol efflux in murine macrophages.</a> International Journal of Molecular Medicine. 30 (5), 1105-1112 (2012).</li><li>Litvinov, Y., Savushkin, E. V., Garaeva, E. A. D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cholesterol+Efflux+and+Reverse+Cholesterol+Transport:+Experimental+Approaches.">Cholesterol Efflux and Reverse Cholesterol Transport: Experimental Approaches.</a> Current Medicinal Chemistry. 371 (25), 2383-2393 (2016).</li><li>Phillips, A., Mucksavage, M. L., Wilensky, R. L., Mohler, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cholesterol+efflux+capacity,+high-density+lipoprotein+function,+and+atherosclerosis.">Cholesterol efflux capacity, high-density lipoprotein function, and atherosclerosis.</a> N Engl J Med. 364 (2), 127-135 (2011).</li><li>Rohatgi, 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=HDL+Cholesterol+Efflux+Capacity+and+Incident+Cardiovascular+Events.">HDL Cholesterol Efflux Capacity and Incident Cardiovascular Events.</a> New England Journal of Medicine. 371 (25), 2383-2393 (2014).</li></ol>

The authors wish to declare that they are inventors of the patent application (EPO; 18382337.6-1118; 17th May 2018) entitled &#34;Method for determining cholesterol efflux&#34; based on this method.

Fluorescent-labelled cholesterol is a promising strategy to analyze and investigate the properties and metabolism of natural cholesterol in vitro. Its main advantages are that it can be taken up by cells, allows for intracellular and membrane distribution studies, and can be applied to cholesterol efflux assays such as in this protocol (Figure 7). Some fluorescent-labelled sterols allow cholesterol tracking in vitro including BODIPY-cholesterol, dansyl-cholesterol, dehydroegrosterol, and 22-...

According to the World Health Organization, the current principal causes of death worldwide are ischemic heart disease and stroke (accounting for a total of 15.2 million deaths)1. Both are cardiovascular diseases (CVD) that can be preceded by atherosclerosis and the rupture of atheroma plaques in the blood vessels2,3.
Atherosclerosis is a vessel wall inflammatory disease in which macrophages, T cells, mast cells, and dendritic cells infiltrate the endothelium and accumulate from the blood, eventually forming atherosclerotic plaques. Atherosclerotic plaques present a lipid core and cholesterol crystals, evidenced by high-resolution B-mode ultrasonography measurements of the carotid intima media thickness4,5. In macrophages, cholesterol efflux towards lipid acceptor particles is carried out by means of the ATP-binding cassette (ABC) receptors ABCA1, ATP binding cassette subfamily G member 1 (ABCG1), and the scavenger receptor SR-BI. The imbalance of cholesterol influx and efflux in macrophages is considered a key process in atherosclerosis initiation6. Cholesterol efflux is considered a key step in cholesterol elimination from peripheral tissue to the plasma and liver in a process called reverse cholesterol transport (RCT). Cholesterol is transferred from macrophages mainly to apolipoprotein A1 (ApoA1) found on the surface of high-density lipoprotein (HDL) particles. HDLs then transport cholesterol to the liver for excretion and re-utilization7,8,9.
Traditionally, tritium (3H) radio-labelled cholesterol has been used in cholesterol efflux10. The emission signal of radioisotopes is highly sensitive10; however, radio-labelled cholesterol presents obvious handicaps such as long protocols, risk of exposure to ionizing radiation, and the need for special radioactivity facilities and equipment to ensure safe handling of radioactive emission. On the contrary, fluorescence has been successfully incorporated in diagnostic techniques due to its simplicity in fluorescent signal detection, the wide variety of fluorophores available, and its safety11. Several fluorescent-labelled sterols have been used to study cholesterol metabolism including dehydroergosterol (with intrinsic fluorescence), dansyl cholesterol, 4,4-difluoro-3a,4adiaza-s-indacene (BODIPY)-cholesterol, and 22-(N-(7-Nitrobenz-2-Oxa-1,3-Diazol-4-yl)Amino)-23,24-Bisnor-5-Cholen-3&#946;-Ol (NBD-cholesterol). Particularly, NBD-cholesterol presents an efficient uptake in human cells12. Two different NBD labelled-cholesterol are currently available: 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3b-ol (22-NBD) and 25-(N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-methyl]amino)-27-norcholesterol (25-NBD; Figure 1). Cholesterol labelled with 22-NBD moiety may best suit cholesterol efflux studies, while 25-NBD-cholesterol is mainly used in cellular membrane dynamics research13,14.
Cell lines typically used in in vitro cholesterol efflux assays are monocyte-like cells such as human leukemia-derived THP-1 cells, murine Raw 264.7 cells15, or J774.1. All of these cells can be differentiated into macrophages in vitro using phorbol 12-myristate 13-acetate (PMA), but THP-1-derived macrophages (dmTHP-1) best reflect and mimic the human macrophages16.
In the present study, we optimize and standardize a fluorescent high-throughput method to determine the cholesterol efflux capacity of serum samples on dmTHP-1, using 22-NBD-cholesterol as an alternative to [3H]-cholesterol. In addition, we compare the optimized fluorescent technique with the standard radioactive analog.

<table>
	<tbody>
		<tr>
			<td>96-well collecting plate</td>
			<td>Corning Inc</td>
			<td>Costar 3912</td>
			<td>white 96-well plate with opaque clear bottom</td>
		</tr>
		<tr>
			<td>96-well culture plate</td>
			<td>Corning Inc</td>
			<td>Costar 3610</td>
			<td>white 96-well plate with flat clear bottom</td>
		</tr>
		<tr>
			<td>Cholesterol Efflux Assay Kit (Cell-based)</td>
			<td>Abcam</td>
			<td>ab196985</td>
			<td>commercial high-throughput cell-based assay kit aimed to determine the cholesterol efflux</td>
		</tr>
		<tr>
			<td>colorless RPMI 1640</td>
			<td>Sigma-Aldrich</td>
			<td>R7509</td>
			<td>RPMI 1640 with no pehnol-red</td>
		</tr>
		<tr>
			<td>Gen5 Data Analysis Software</td>
			<td>BioTek</td>
			<td></td>
			<td>Version 2.0</td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Sigma-Aldrich</td>
			<td>G8790-100G</td>
			<td>Glycine, non-animal use</td>
		</tr>
		<tr>
			<td>Luminometer</td>
			<td>Biotek</td>
			<td>SYNERGY HT</td>
			<td>Multi-Detection Microplate Reader</td>
		</tr>
		<tr>
			<td>Lysis Solution 1</td>
			<td>in-house</td>
			<td></td>
			<td>50 mM Tris Buffer, 150 mM NaCl and H2O</td>
		</tr>
		<tr>
			<td>Lysis Solution 2</td>
			<td>in-house</td>
			<td></td>
			<td>Pure ethanol and Cell Lysis Solution 1:1 (v:v)</td>
		</tr>
		<tr>
			<td>NBD-cholesterol</td>
			<td>Thermo-Fisher</td>
			<td>N1148</td>
			<td>22-(N-(7-Nitrobenz-2-Oxa-1,3-Diazol-4-yl)Amino)-23,24-Bisnor-5-Cholen-3&#946;-Ol</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Sigma-Aldrich</td>
			<td>P3813</td>
			<td>Phosphate-buffered&#160;saline</td>
		</tr>
		<tr>
			<td>PEG 8000</td>
			<td>Sigma-Aldrich</td>
			<td>202452-250G</td>
			<td>polyethylene glycol</td>
		</tr>
		<tr>
			<td>PMA</td>
			<td>Sigma-Aldrich</td>
			<td>79346</td>
			<td>Phorbol 12-merystate B-acetate.</td>
		</tr>
		<tr>
			<td>R10</td>
			<td>in-house</td>
			<td></td>
			<td>RPMI 1640 supplemented with 10 % fetal bovine serum and 5 % Penicillin/Streptomycin.</td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Sigma-Aldrich</td>
			<td>R8758</td>
			<td>RPMI 1640 with 2mM L-glutamine containing 1.5 g/L sodium bicarbonate and 4.5 g/L glucose</td>
		</tr>
		<tr>
			<td>THP-1 cells</td>
			<td>Sigma-Aldrich</td>
			<td>ATCC, #TIB-202</td>
			<td>monocyte-like line derived from leukemia from a one year old baby</td>
		</tr>
		<tr>
			<td>Tween 80</td>
			<td>Sigma-Aldrich</td>
			<td>P1754</td>
			<td></td>
		</tr>
	</tbody>
</table>

high-throughput nitrobenzoxadiazole-labeled cholesterol efflux assay

Atherosclerosis leads to cardiovascular disease (CVD). It is still unclear whether cholesterol-HDL (cHDL) concentration plays a causal role in atherosclerosis development. However, an important factor in early stages of atheroma plaque formation is cholesterol efflux capacity to HDL (the ability of HDL particles to accept cholesterol from macrophages) in order to avoid foam cell formation. This is a key step in avoiding the accumulation of cholesterol in the endothelium and a part of reverse cholesterol transport (RCT) to eliminate cholesterol through the liver. Cholesterol efflux capacity to serum or plasma in macrophage cell models is a promising tool that can be used as biomarker for atherosclerosis. Traditionally, [3H]-cholesterol has been used in cholesterol efflux assays. In this study, we aim to develop a safer and faster strategy using fluorescent labelled-cholesterol (NBD-cholesterol) in a cellular assay to trace the cholesterol uptake and efflux process in THP-1-derived macrophages. Finally, we optimize and standardize the NBD-cholesterol efflux method and develop a high-throughput analysis using 96-well plates.

The aim of the cholesterol efflux assay is to determine in vitro the cholesterol efflux capacity of a given serum, plasma, or supernatant containing HDL particles. The method consists of loading labelled-cholesterol into a culture of a standard macrophage cell line and inducing contact with the testing sample diluted into FBS-free media with the cells. Finally, the fluorescent levels from the NBD are measured in the media and cell lysate. To optimize measurements, the effluxed cholesterol from the cells to media is mixed...

Watch this Scientific Journal Video about High-throughput Nitrobenzoxadiazole-labeled Cholesterol Efflux Assay at JoVE.com

High-throughput Nitrobenzoxadiazole-labeled Cholesterol Efflux Assay

Measurement of in vitro cholesterol efflux capacity to serum or plasma in macrophage cell models is a promising tool as a biomarker for atherosclerosis. In the present study, we optimize and standardize a fluorescent NBD-cholesterol efflux method and develop a high-throughput analysis using 96-well plates.

Atherosclerosis leads to cardiovascular disease (CVD). It is still unclear whether cholesterol-HDL (cHDL) concentration plays a causal role in ...

This protocol is our cell based method for the cholesterol termination of cholesterol reflux in ceramal plasma. Particularly in screenings. This may be applied to diagnose cardiovascular risk, and to identify or evaluate cholesterol lower maintenance.This technique avoids the risk and burdens as the safety to with handling radiated materials by providing results with comparable quality levels, to the ones of Cholesterol reflux has been reported to associate with Thus, the plasma or ceramal cholesterol reflux of accepted can be compared, to our reference control and may provide the risk to suffer from This method will also be applied to the cell lines, like other human cell lines or even primary macro phases. Macro phases or and human induced spray button stem cells. To begin this procedure, dissolve the NPD cholesterol in pure ethanol to obtain a stock solution with a final concentration of two micromolar.Dilute 25 microliters of the NBD cholesterol stock in AR 10 medium to reach a final concentration of five micromolar. Culture thp-1 cells in our 10 medium at 37 degrees celsius with 5%carbon dioxide. Every three days adjust the cell density to 300000 cells per milliliter.Then obtain a 96-well plate with a flat clear bottom. For better homogenization, prepare a 10 milliliters of thp-1 cells in a 15 milliliter tube, and add 200 microliters of PMA stock. Mix gently and seed 100 microliters of the mixture into the plate wells at 200, 000 cells per well.And incubate at 37 degrees celsius with 5%carbon dioxide for 48 to 72 hours to differentiate the thp-1 cells into DM thp-1 cells. First dilute glycine in 10%PBS with sterile water, to a concentration of 200 micromolar at pH 7.4. Add 40 milliliters of diluted glycine to 10 grams of peg 8000 to prepare a 20%peg solution, and mix vigorously to homogenize.Next apply four parts of 20%per 10 parts of sample to each serum or plasma sample in a 1.5 ml tube. Leave the mixture on ice for 25 minutes. Centrifuge the peg apolipoprotein B precipitated at 13000 times G, and at four degrees celsius for 15 minutes.Discard the precipitate, and transfer the supernatant to a new tube. Retrieve the plate containing the differentiated thp-1 cells. Remove and discard the culture medium, and then wash the cells twice with 1X PBS.Add 100 microliters of 5 micromolar MVD cholesterol in AR-10 medium to each well. Incubate overnight at 37 degrees celsius with 5%carbon dioxide. The next day discard, discard the medium.Wash the cells twice with PBS, and then add 100 microliters ABDS, or purified lipid acceptor diluted in rpmi 1630 medium to the desired concentration to each well. Include a negative control which do not contain cholesterol acceptors in a positive control, as outlined in the text protocol, and incubate at 37 degrees celsius for four to six hours. Meanwhile, prepare a 200 milliliter stock of cell lysis solution one as outlined in the text.Mix this solution with ethanol, at a one-to-one volumetric ratio to obtain lysis solution too. For media and BD cholesterol detection, remove the cell medium from the plates in collected in a new white 96-well plate with an opaque flat bottom. Add 100 microliters of pure ethanol to 100 microliters of each medium sample to obtain a one-to-one ratio in the new plate.Using a illuminometer, measure the fluorescent's intensity at an excitation of 463 nanometers, and an emission of 536 nanometers. For intracellular NBD cholesterol detection, wash the cells twice with PBS. Add 100 microliters of lysis solution too to each well, and incubate at room temperature, while shaking for 25 minutes.After this, measure the fluorescent's intensity while adjusting the sensitivity parameter to 50 in the software. Then determine the cholesterol efflux rate in the final measure of cholesterol efflux as outlined in the text protocol. Diluting NBD cholesterol in pure ethanol produces the highest fluorescent's intensity values while a high content in aqueous solution, lowers the intensity.This suggests that the fluorescent's emission of this molecule is highly dependent on the medium, in which it is contained. When using a mixture of media and ethanol at a one-to-one ratio, the fluorescent's intensity is seem to increase proportionally, with a concentration of the cholesterol analog, suggesting that the probe is behaving appropriate under these conditions. To determine the amount of time required to incubate the loaded cells with cholesterol acceptors, cell media is harvested at different time points.The cholesterol efflux evolved linearly from zero to six hours, with the maximum signal being captured six hours after ABDS is added to the cells. The saturation threshold and dynamic range is tested by measuring the cholesterol efflux at different percentages of HDL containing media. In the high throughput asset, the efflux evolves linearly from one to 7%ABDS, reaching the peak of cholesterol efflux capacity at 7%At concentrations higher than 7%the fluroescent's intensity decreases in an inverse relationship with the ABDS percentage.The performance of the fluorescence based method is then evaluated by comparing it to the standard radio labeled technique. Both techniques are highly correlated when using different concentrations of ABDS. The described method is sensitive to an increase of acceptor concentrations within cholesterol efflux values between five and 15%It is important to ensure that the celluarizer contains no aggregates.Critical point is to grade an aggregate ethanol containing environment, to measure the fluorescence in a homogenous, and optimal weight. Following this procedure, name technical cholesterol can be measured, and the effect of drugs in the cholesterol efflux pathway can be determined. Also the school eventually be used as a diagnostic to asses cardiovascular risk.We believe that this method is much easier and safer than the radioactive standard method. However it is still cell dependent. Please remember that ethanol is inflammable and it should be stored and handled accordingly.

high-throughput-nitrobenzoxadiazole-labeled-cholesterol-efflux-assay

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Medicine

8.8K Views.  Hospital Clínic de Barcelona. This protocol is our cell based method for the cholesterol termination of cholesterol reflux in ceramal plasma. Particularly in screenings. This may be applied to diagnose cardiovascular risk, and to identify or evaluate cholesterol lower maintenance.This technique avoids the risk and burdens as the safety to with handling radiated materials by providing results with comparable quality levels, to the ones of Cholesterol reflux has been reported to associate with Thus, the plasma or cer...