Name: targeting drugs to larval zebrafish macrophages by injecting drug-loaded liposomes
Uploaded: 2020-02-18T13:00:00
Description: Watch this Scientific Journal Video about Targeting Drugs to Larval Zebrafish Macrophages by Injecting Drug-Loaded Liposomes at JoVE.com

This work was supported by grants awarded to C.J.H. (Health research Council of New Zealand and Marsden Fund, Royal Society of New Zealand) and Z.W. (Faculty Research Development Fund from the University of Auckland). The authors thank Alhad Mahagaonkar for expert management of the zebrafish facility, the Biomedical Imaging Research Unit, School of Medical Sciences, University of Auckland for assistance with confocal imaging and Graham Lieschke for gifting the Tg(mpeg1:EGFP) reporter line.

1. Preparation of Drug-loaded Marina Blue-labeled Liposomes
NOTE: Liposomes carrying the blue fluorescent dye, Marina Blue and drug are prepared using a thin film hydration method with post insertion of poloxamer 188. All procedures are performed at room temperature unless otherwise specified. Control liposomes only carry Marina blue and PBS. The example here describes loading liposomes with a mitochondria-targeting antioxidant drug25 that is used in the representative re...

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Here, we have provided a detailed protocol to formulate drug-loaded liposomes to specifically target macrophages in larval zebrafish. This method can be used to dissect the role of macrophages in certain disease models by ensuring direct targeted delivery of drugs specifically to macrophages. Moreover, it can be used when general toxicity of drugs limits their use when delivered by more conventional routes, like immersion. The protocol described here provides an alternative to other nanoparticulate systems that have been...

The mononuclear phagocyte system provides a first line of defense against invading pathogens. This system consists of monocytes, monocyte-derived dendritic cells and macrophages, which actively phagocytoze foreign pathogens, thereby limiting pathogen spread. In addition to these phagocytic and microbicidal effector functions, dendritic cells and macrophages are also capable of cytokine production and antigen-presentation to activate the adaptive immune system1. Of these cells, macrophages have received particular attention due to their diverse functional heterogeneity and involvement in multiple inflammatory diseases, from autoimmunity and infectious diseases to cancer2,3,4,5,6,7. The plasticity of macrophages and their ability to functionally adapt to the needs to their tissue environment necessitates experimental approaches to directly observe and interrogate these cells in vivo.
Larval zebrafish are an ideal model organism by which to study the function and plasticity of macrophages in vivo8. The optical transparency of larval zebrafish provides a window to directly observe the behavior of macrophages, especially when coupled with macrophage-marking transgenic reporter lines. Exploiting the live imaging potential and experimental tractability of larval zebrafish has led to many significant insights into macrophage function that have direct relevance to human disease9,10,11,12,13,14,15. Many of these studies have also taken advantage of the high conservation of drug activity in zebrafish (an attribute that underpins their use as a whole animal drug discovery platform16,17,18), by utilizing chemical interventions to pharmacologically manipulate macrophage function. To date, these pharmacological treatments have been mostly delivered either through immersion, which requires the drug to be water soluble, or by direct microinjection of free drug (Figure 1A). Limitations of these passive delivery strategies include off-target effects and general toxicity that may preclude assessing any impact on macrophage function. Additionally, when investigating drug effects on macrophages it is unknown whether the drugs are acting on the macrophages themselves or through more indirect mechanisms. When performing similar chemical intervention studies to investigate macrophage function, we recognized there was an unmet need to develop an inexpensive and straightforward delivery method to target drugs specifically to macrophages.
Liposomes are microscopic, biocompatible, lipid bilayered vesicles that can encapsulate proteins, nucleotides and drug cargo19. The unilamellar or multilamellar lipid bilayer structure of liposomes forms an aqueous inner lumen where water-soluble drugs can be incorporated while hydrophobic drugs can be integrated into the lipid membranes. In addition, the physicochemical properties of liposomes, including size, charge and surface modifications can be manipulated to tailor their targeting to specific cells20,21. These features of liposomes have made them an attractive vehicle to deliver drugs and enhance the precision of current treatment regimens20. As liposomes are naturally phagocytozed by macrophages (a feature exploited by their routine use in delivering clodronate specifically to macrophages for ablation experiments22), they present as an attractive option for macrophage-specific drug delivery (Figure 1B).
This protocol describes the formulation of drugs into blue fluorescent liposomes coated with the hydrophilic polymer poloxamer 188, that forms a protective layer on the liposome surface and has been shown to enhance drug retention and have superior biocompatibility23. Poloxamer was chosen for surface coating of liposomes as our previous research had shown that, when compared to polyethylene glycol modified liposomes, poloxamer modified liposomes showed better biocompatibility following subcutaneous injection of rat paws and similar pharmacokinetics in rabbits following intravenous infusion23. Protocols are also described for their microinjection into larval zebrafish and live imaging to assess their macrophage-targeting ability and localization to intracellular compartments necessary for liposome degradation and cytoplasmic drug delivery. As a proof-of-concept we have previously used this technique to target two drugs to macrophages to suppress their activation in a larval zebrafish model of acute gouty inflammation24. This drug delivery technique expands the chemical &#34;toolkit&#34; available to zebrafish researchers wanting to ensure macrophage-targeting of their drugs of interest.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)</td>
			<td>Avanti Polar Lipids, Inc.</td>
			<td>850355P</td>
			<td></td>
		</tr>
		<tr>
			<td>1,2-diseteroyl-sn-glycero-3-phosphocholine (DSPE)</td>
			<td>Avanti Polar Lipids, Inc.</td>
			<td>850367P</td>
			<td></td>
		</tr>
		<tr>
			<td>1.0 &#181;m Whatman Nuclepore Track-Etched polycarbonate membranes</td>
			<td>GE Healthcare Life Sciences</td>
			<td>110610</td>
			<td></td>
		</tr>
		<tr>
			<td>25 mL round-bottom flask</td>
			<td>Sigma-Aldrich</td>
			<td>Z278262</td>
			<td></td>
		</tr>
		<tr>
			<td>35 mm culture dish</td>
			<td>Thermo Scientific</td>
			<td>150460</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>Sigma-Aldrich</td>
			<td>34998</td>
			<td></td>
		</tr>
		<tr>
			<td>Agilent 1260 Infinity Diode Array Detector</td>
			<td>Agilent Technologies</td>
			<td>G4212B</td>
			<td></td>
		</tr>
		<tr>
			<td>Agilent 1260 Infinity Quaternary Pump</td>
			<td>Agilent Technologies</td>
			<td>G1311B</td>
			<td></td>
		</tr>
		<tr>
			<td>Agilent 1290 Infinity Series Thermostat</td>
			<td>Agilent Technologies</td>
			<td>G1330B</td>
			<td></td>
		</tr>
		<tr>
			<td>Avanti mini-extruder Avanti Polar Lipids Inc.</td>
			<td>Avanti Polar Lipids Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>borosilicate microinjection needles</td>
			<td>Warner Instruments</td>
			<td>203-776-0664</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma-Aldrich</td>
			<td>C4901-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>cholesterol</td>
			<td>Sigma-Aldrich</td>
			<td>C8667</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont No.5 fine tip forceps</td>
			<td>Fine Science Tools</td>
			<td>11251-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Microloader pipette tip</td>
			<td>Eppendorf</td>
			<td>5242956003</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf SmartBlock 1.5 mL, thermoblock for 24 reaction vessels</td>
			<td>Eppendorf</td>
			<td>4053-6038</td>
			<td></td>
		</tr>
		<tr>
			<td>eyelash manipulator</td>
			<td>Ted Pella Inc.</td>
			<td>113</td>
			<td></td>
		</tr>
		<tr>
			<td>hemocytometer</td>
			<td>Hawksley</td>
			<td>BS.748</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>BDH Chemicals</td>
			<td>441474J</td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC system</td>
			<td>Agilent Technologies</td>
			<td>1260 series HPLC system</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma-Aldrich</td>
			<td>P9541-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>low melting point agarose</td>
			<td>Invitrogen</td>
			<td>16520-100</td>
			<td></td>
		</tr>
		<tr>
			<td>LysoTracker Deep Red</td>
			<td>Invitrogen</td>
			<td>L12492</td>
			<td>1 mM stock solution in DMSO, keep at -20 &#176;C and protect from light.</td>
		</tr>
		<tr>
			<td>LysoTracker Deep Red</td>
			<td>Thermo Scientific</td>
			<td>L12492</td>
			<td></td>
		</tr>
		<tr>
			<td>magnetic stand</td>
			<td>Narishige</td>
			<td>GJ-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Marina Blue 1,2-dihexadecanoyl-sn-glycero-phosphoethanolamine (Marina Blue DHPE)</td>
			<td>Invitrogen</td>
			<td>M12652</td>
			<td>Keep at -20 &#176;C and protect from light.</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma-Aldrich</td>
			<td>34860</td>
			<td></td>
		</tr>
		<tr>
			<td>methyl cellulose</td>
			<td>Sigma-Aldrich</td>
			<td>M0387-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>methylene blue</td>
			<td>Alfa Aesar</td>
			<td>42771</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Sigma-Aldrich</td>
			<td>230391-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>micromanipulator</td>
			<td>Narishige</td>
			<td>M-152</td>
			<td></td>
		</tr>
		<tr>
			<td>mineral oil</td>
			<td>Sigma-Aldrich</td>
			<td>M-3516</td>
			<td></td>
		</tr>
		<tr>
			<td>Mitochondria-targeting antioxidant MitoTEMPO</td>
			<td>Sigma-Aldrich</td>
			<td>SML0737</td>
			<td></td>
		</tr>
		<tr>
			<td>MitoSOX Red Mitochondrial Superoxide Indicator</td>
			<td>Thermo Scientific</td>
			<td>M36008</td>
			<td></td>
		</tr>
		<tr>
			<td>MitoTEMPO</td>
			<td>Sigma-Aldrich</td>
			<td>SML0737</td>
			<td>Keep at -20 &#176;C and protect from light.</td>
		</tr>
		<tr>
			<td>N-Phenylthiourea (PTU)</td>
			<td>Sigma-Aldrich</td>
			<td>P7629-10G</td>
			<td>Take care when handling, toxic.</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>BDH Chemicals</td>
			<td>27810.295</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS (pH 7.4)</td>
			<td>Gibco</td>
			<td>10010-023</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish (100 mm x 20 mm)</td>
			<td>Corning Inc.</td>
			<td>430167</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenomenex C18 Gemini-NZ 3 mm 250 mm x 4.6 mm column</td>
			<td>Phenomenex</td>
			<td>00G-4439-E0</td>
			<td></td>
		</tr>
		<tr>
			<td>pHrodo Red Escherichia coli BioParticles Conjugate</td>
			<td>Thermo Scientific</td>
			<td>P35361</td>
			<td></td>
		</tr>
		<tr>
			<td>pHrodo Red Escherichia coli BioParticles Conjugate</td>
			<td>Invitrogen</td>
			<td>P35361</td>
			<td>Keep at -20 &#176;C and protect from light. Make 1 mg/mL stock solution by dissolving 2 mg lyophilized product in 2 mL of PBS supplemented with 20 mM HEPES, pH 7.4.</td>
		</tr>
		<tr>
			<td>plastic transfer pipette</td>
			<td>Medi&#39;Ray</td>
			<td>RL200C</td>
			<td></td>
		</tr>
		<tr>
			<td>poloxamer 188</td>
			<td>BASF Corporation</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pressure injector</td>
			<td>Applied Scientific Instruments</td>
			<td>MPPI-2</td>
			<td></td>
		</tr>
		<tr>
			<td>rotary evaporator</td>
			<td>B&#252;chi, Flawil, Switzerland</td>
			<td>B&#252;chi R-215 Rotavapor</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanning confocal microscope</td>
			<td>Olympus</td>
			<td>Olympus FV1000 FluoView</td>
			<td></td>
		</tr>
		<tr>
			<td>Sorvall WX+ Ultracentrifuge</td>
			<td>Thermo Scientific</td>
			<td>75000090</td>
			<td></td>
		</tr>
		<tr>
			<td>stereomicroscope</td>
			<td>Leica</td>
			<td>MZ12</td>
			<td></td>
		</tr>
		<tr>
			<td>Tricaine</td>
			<td>Sigma-Aldrich</td>
			<td>A5040-25G</td>
			<td>Make 4 mg/mL stock solution (in deionzed H2O) and keep at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>triton-X100</td>
			<td>Sigma-Aldrich</td>
			<td>X100-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonic bath</td>
			<td>Thermo Scientific</td>
			<td>FB-11205</td>
			<td></td>
		</tr>
		<tr>
			<td>Volocity Image Analysis Software</td>
			<td>PerkinElmer</td>
			<td>version 6.3</td>
			<td></td>
		</tr>
		<tr>
			<td>water bath</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zetasizer Nano</td>
			<td>Malvern Instruments Ltd</td>
			<td>Zetasizer Nano ZS ZEN 3600</td>
			<td></td>
		</tr>
	</tbody>
</table>

targeting drugs to larval zebrafish macrophages by injecting drug-loaded liposomes

Zebrafish (Danio rerio) larvae have developed into a popular model to investigate host-pathogen interactions and the contribution of innate immune cells to inflammatory disease due to their functionally conserved innate immune system. They are also widely used to examine how innate immune cells help guide developmental processes. By taking advantage of the optical transparency and genetic tractability of larval zebrafish, these studies often focus on live imaging approaches to functionally characterize fluorescently marked macrophages and neutrophils within intact animals. Due to their diverse functional heterogeneity and ever-expanding roles in disease pathogenesis, macrophages have received significant attention. In addition to genetic manipulations, chemical interventions are now routinely used to manipulate and examine macrophage behavior in larval zebrafish. Delivery of these drugs is typically limited to passive targeting of free drug through direct immersion or microinjection. These approaches rely on the assumption that any changes to macrophage behavior are the result of a direct effect of the drug on the macrophages themselves, and not a downstream consequence of a direct effect on another cell type. Here, we present our protocols for targeting drugs specifically to larval zebrafish macrophages by microinjecting drug-loaded fluorescent liposomes. We reveal that poloxamer 188-modified drug-loaded blue fluorescent liposomes are readily taken up by macrophages, and not by neutrophils. We also provide evidence that drugs delivered in this way can impact macrophage activity in a manner consistent with the mechanism of action of the drug. This technique will be of value to researchers wanting to ensure targeting of drugs to macrophages and when drugs are too toxic to be delivered by traditional methods like immersion.

The thin film hydration approach described here for the preparation of fluorescent liposomes enclosing drugs is a simple and cost-effective method. With the protocol used in this study, the liposomes are expected to be unilamellar23,24. The size, zeta potential, drug loading and entrapment efficiency of the liposomes produced are summarized in Table 1. The particle size of the liposomes (before and after drug loading) are similar (Table 1...

Watch this Scientific Journal Video about Targeting Drugs to Larval Zebrafish Macrophages by Injecting Drug-Loaded Liposomes at JoVE.com

Targeting Drugs to Larval Zebrafish Macrophages by Injecting Drug-Loaded Liposomes

Here, we describe the synthesis of drug-loaded liposomes and their microinjection into larval zebrafish for the purpose of targeting drug delivery to macrophage-lineage cells.

Zebrafish (Danio rerio) larvae have developed into a popular model to investigate host-pathogen interactions and the contribution of innate immune cells ...

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Non-invasive Imaging of the Innate Immune Response in a Zebrafish Larval Model of Streptococcus iniae Infection

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Quantification of Cytosolic vs. Vacuolar Salmonella in Primary Macrophages by Differential Permeabilization

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Phenotypic Characterization of Macrophages from Rat Kidney by Flow Cytometry

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