This work was funded by the National Institutes of Health NIGMS 056062.

There is nothing to disclose.

The design of this gene-environment interaction study allowed us to gain new information regarding the dual nature of the 5-LOX isozyme in the nigrostriatal pathway.&#160;By performing HPLC to measure striatal monoamines after saline or MPTP treatment in transgenics lacking the 5-LOX isozyme and their wildtype littermates, we were able to note that its deficiency appears to be protective under toxic conditions (Figure 1), but under normal conditions, lack of the enzyme reduces striatal dopamine levels an...

Use of gene-environment interaction models provides an approach to mimic risk factors that likely influence idiopathic Parkinson&#8217;s disease (PD) and affords an opportunity to discern mechanistic insights that are unlikely to be elucidated by use of a genetic or toxicant system alone1,2. Here we illustrate this point and describe application of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of nigrostriatal degeneration3&#160;to better understand the selectivity of lipoxygenase (LOX) isozyme activity on neuroinflammation and toxicity4. While a role for LOX isozymes has been widely evaluated in peripheral disorders5,6 as well as CNS disease including stroke7 and Alzheimer&#8217;s disease8,9, the role of the family of isozymes in nigrostriatal function and degeneration related to PD is not well understood and warrants study. The MPTP neurotoxin demonstrates preferential degeneration of the nigrostriatal pathway and recapitulates the striatal dopamine depletion and nigral dopaminergic cell loss that underlie motoric impairments in PD patients10. While this model does not reproduce the full cadre of nonmotor and motor PD behaviors and frank &#945;-synuclein-positive Lewy body pathology, it has been useful to elucidate novel mechanistic targets that contribute to nigrostriatal damage and for early-stage translational testing as it is the best characterized noninvasive model available to reliably produce nigral cell death accompanied by striatal dopamine loss11-15. Wide use of the MPTP mouse, with paradigms ranging from acute, subacute to chronic16-18, has allowed for standardization of dosing to result in mild to severe nigrostriatal damage19,20&#160;with activation of different mechanisms of toxicity depending on the treatment regimen18,21,22. Consequently, this permits a &#8216;window of lesioning&#8217; to be targeted that may result in enhanced or reduced nigrostriatal injury depending on the therapeutic agent or transgenic model utilized23-25.
Also essential for translational and discovery biology studies are the techniques used to assess damage and the evidence such methods provide.&#160;For the MPTP mouse model, established metrics to evaluate lesioning are measurement of markers of striatal dopaminergic tone, including dopamine and its metabolites by HPLC, and Western blot analysis of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine synthesis, and indicators of degenerative events such as glial activation using Western blot analysis and immunohistochemistry4.&#160;Although these are classical neurochemical, biochemical, and histological procedures, the techniques provide critical and reproducible readouts on the extent of damage within the nigrostriatal dopaminergic pathway, indicate mechanisms of toxicity, and have proven to be valuable tools in understanding degenerative events in PD.

<table border="0" cellpadding="0" cellspacing="0" width="1227">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:481px;">1-Methyl-4-phenyl-1,2,3,6-tetra-hydropyridine hydrochloride (MPTP-HCL)</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:121px;">M0896</td>
			<td style="width:351px;">for PD modeling</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">4% Formaldehyde (paraformaldehyde) solution, phosphate-buffered (PFA)</td>
			<td>American MasterTech Scientific</td>
			<td>BUP0157</td>
			<td>for immersion fixation</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Perchloric acid ACS reagent, 70% (PCA)</td>
			<td>Sigma-Aldrich</td>
			<td>244252</td>
			<td>for HPLC acid extraction</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tris Base</td>
			<td>Sigma-Aldrich</td>
			<td>T1503</td>
			<td>for tissue homogenization</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ethylenediaminotetraacetic acid disodium salt dihydrate (EDTA)</td>
			<td>Sigma-Aldrich</td>
			<td>E1644</td>
			<td>for tissue homogenization</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Protease inhibitor cocktail</td>
			<td>Sigma-Aldrich</td>
			<td>P8340</td>
			<td>for tissue homogenization</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Phosphatase inhibitor cocktail</td>
			<td>Sigma-Aldrich</td>
			<td>P5726</td>
			<td>for tissue homogenization</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium Hydroxide (NaOH)</td>
			<td>Sigma-Aldrich</td>
			<td>S5881</td>
			<td>for Lowry protein assay</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sucrose, molecular biology, &#8805;99.5% (GC)&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>S0389</td>
			<td>for cryoprotection</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Phosphate buffered saline, powder, pH 7.4 (for 0.01 M PBS)</td>
			<td>Sigma-Aldrich</td>
			<td>P3813</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">BCA Protein Assay Kit</td>
			<td>Pierce/Thermo</td>
			<td>23225</td>
			<td>for protein determination</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Novex 12% Tris-Glycine Mini Gels 1.0 mm, 12-well</td>
			<td>Invitrogen/Life Technologies</td>
			<td>EC60052BOX</td>
			<td>for SDS-PAGE</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">NuPAGE LDS Sample Buffer (4x)</td>
			<td>Invitrogen/Life Technologies</td>
			<td>NP0007</td>
			<td>for SDS-PAGE</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Novex Sharp Prestained Protein Standard&#160;</td>
			<td>Invitrogen/Life Technologies</td>
			<td>LC5800</td>
			<td>protein ladder</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Glycine</td>
			<td>Sigma-Aldrich</td>
			<td>G7126</td>
			<td>for SDS-PAGE</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium dodecyl sulfate, electrophoresis, 98.5% (SDS)</td>
			<td>Sigma-Aldrich</td>
			<td>L3771</td>
			<td>for SDS-PAGE</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Methyl Alcohol, Anhydrous, Reagent&#160;</td>
			<td>American MasterTech Scientific</td>
			<td>SPM1057C</td>
			<td>methanol for transfer</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium chloride (NaCl), ACS reagent</td>
			<td>Sigma-Aldrich</td>
			<td>S9888</td>
			<td>saline and buffers</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nonfat dry milk powder</td>
			<td>Carnation</td>
			<td>n/a</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ponceau S solution in 5% acetic acid&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>P7170</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Anti-Tyrosine Hydroxylase (TH), sheep polyclonal</td>
			<td>Chemicon/Millipore</td>
			<td>AB1542</td>
			<td>for immunofluorescence&#160;</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Anti-Tyrosine Hydroxylase (TH), rabbit polyclonal</td>
			<td>Pel-Freez Biologicals</td>
			<td>P40101-0</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Anti-&#946; Actin, rabbit</td>
			<td>Sigma-Aldrich</td>
			<td>A2066</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Anti-Glial Fibrillary Acidic Protein (GFAP), rabbit polyclonal</td>
			<td>Chemicon/Millipore</td>
			<td>AB5804</td>
			<td>for immunofluorescence</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Anti-Glial Fibrillary Acidic Protein (GFAP), mouse monoclonal</td>
			<td>Covance Inc.</td>
			<td>SMI-22R</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Tween-20</td>
			<td>Sigma-Aldrich</td>
			<td>P1379</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Goat Anti-Rabbit IgG (H+L), Peroxidase Conjugated&#160;</td>
			<td>Fisher Scientific</td>
			<td>31462</td>
			<td>for immunofluorescence</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">goat anti-sheep, peroxidase conjugated</td>
			<td>Pierce/Thermo</td>
			<td>31480</td>
			<td>for immunofluorescence</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">goat anti-mouse, peroxidase conjugated</td>
			<td>Pierce/Thermo</td>
			<td>31430</td>
			<td>for immunofluorescence</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">SuperSignal West Pico Chemiluminescent Substrate</td>
			<td>Pierce/Thermo</td>
			<td>34078</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">CL-XPosure Film 7 in x 9.5 in&#160;</td>
			<td>Pierce/Thermo</td>
			<td>34089</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Restore Western Blot Stripping Buffer&#160;</td>
			<td>Pierce/Thermo</td>
			<td>21059</td>
			<td>for immunoblotting</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Citric acid monohydrate, ACS reagent, &#8805;99.0%&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>C1909</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Normal Donkey Serum</td>
			<td>Millipore</td>
			<td>S30-100ML</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Polyvinylpyrrolidone (PVP)</td>
			<td>Sigma-Aldrich</td>
			<td>P5288</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Bovine Serum Albumin (BSA), lyophilized</td>
			<td>Sigma-Aldrich</td>
			<td>A3294</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Triton X-100</td>
			<td>Fisher Scientific</td>
			<td>BP151-01</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Donkey anti-Rabbit IgG, Alexa Fluor 568-labeled&#160;</td>
			<td>Invitrogen/Life Technologies</td>
			<td>A10042</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Donkey Anti-Sheep IgG (H+L), FITC&#160;</td>
			<td>Jackson ImmunoResearch</td>
			<td>713-095-147</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">VECTASHIELD Hard-Set Mounting Medium with DAPI</td>
			<td>Vector Laboratories</td>
			<td>H-1500</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Normal Goat Serum</td>
			<td>Millipore</td>
			<td>S26-100ML</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">VECTASTAIN ABC Kit (Rabbit IgG )&#160;</td>
			<td>Vector Laboratories</td>
			<td>PK-4001</td>
			<td>for IHC; 10 &#181;l each of solutions A and B per 1 ml PBS (per instructions )</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">DAB Peroxidase Substrate Kit, 3,3&#8217;-diaminobenzidine</td>
			<td>Vector Laboratories</td>
			<td>SK-4100</td>
			<td>for IHC; per 5 ml cold ddH2O, add 2 drops buffer stock solution, 2 drops DAB, and 1 drop H2O2 (H2O2 is added immediately before use)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Hydrogen peroxide, 30%</td>
			<td>Sigma-Aldrich</td>
			<td>216763</td>
			<td>for quench step in IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Rabbit anti-Iba1</td>
			<td>Biocare Medicals</td>
			<td>CP290A</td>
			<td>for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:481px;">Cresyl Violet Solution, Regular Strength&#160;</td>
			<td>FD Neurotechnologies</td>
			<td>PS102-01&#160;</td>
			<td>counterstain for Iba1 IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">95% Ethanol, reagent alcohol</td>
			<td>Sigma-Aldrich</td>
			<td>R8382</td>
			<td>dehydration for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">100% Absolute ethanol</td>
			<td>Mallinckrodt&#160;</td>
			<td>7019-10</td>
			<td>dehydration for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetic acid</td>
			<td>Sigma-Aldrich</td>
			<td>A6283</td>
			<td>destaining for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Xylene</td>
			<td>Sigma-Aldrich</td>
			<td>534056</td>
			<td>clearing agent for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DPX Mountant</td>
			<td>Sigma-Aldrich</td>
			<td>06522</td>
			<td>mounting medium for DAB IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">O.C.T. Compound - Frozen Section Embedding Medium&#160;</td>
			<td>American MasterTech Scientific</td>
			<td>EMOCTCS</td>
			<td>embeddium medium for cryostat cutting</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Potassium permanganate</td>
			<td>Sigma-Aldrich</td>
			<td>223468</td>
			<td>to decontaminate DAB solution</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dopamine hydrochloride</td>
			<td>Sigma-Aldrich</td>
			<td>H8502</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">3,4-Dihydroxyphenylacetic acid (DOPAC)</td>
			<td>Sigma-Aldrich</td>
			<td>850217</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Homovanillic acid (HVA)</td>
			<td>Sigma-Aldrich</td>
			<td>H1252</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Perchloric acid (PCA) - 70%</td>
			<td>Sigma-Aldrich</td>
			<td>244252</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium dihydrogen phosphate monohydrate</td>
			<td>Sigma-Aldrich</td>
			<td>71504</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Citric acid monohydrate</td>
			<td>Sigma-Aldrich</td>
			<td>C1909</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">1-Octanesulfonic acid sodium salt (OSA)</td>
			<td>Sigma-Aldrich</td>
			<td>O8380</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">EDTA</td>
			<td>Sigma-Aldrich</td>
			<td>E1644</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetonitrile</td>
			<td>EMD</td>
			<td>AX0145-1</td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">HPLC-grade distilled deionized water (ddH2O)</td>
			<td>Millipore</td>
			<td></td>
			<td>for HPLC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">0.22 &#181;m GSTF membrane</td>
			<td>Millipore</td>
			<td></td>
			<td>for filtration</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Corning Netwells</td>
			<td>Sigma-Aldrich</td>
			<td>CLS3477</td>
			<td>polystyrene insert with polyester mesh bottom, for IHC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
			<td>[header]</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ultrasonic cell disrupter (Soniprep 150)</td>
			<td>MSE</td>
			<td>MSE.41371.274</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microcentrifuge</td>
			<td>Eppendorf</td>
			<td>5414R</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">ESA MD-150 reverse-phase column&#160;</td>
			<td>ESA</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">HPLC Pump (Ultimate 3000)</td>
			<td>Dionex</td>
			<td>ISO-3100BM</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">HPLC Autosampler (Ultimate 3000)</td>
			<td>Dionex</td>
			<td>WPS-3000TSL</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Electrochemical detector</td>
			<td>ESA</td>
			<td>Coulochem III</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Guard Cell</td>
			<td>ESA</td>
			<td>5020</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Analytical Cell</td>
			<td>ESA</td>
			<td>5011A</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Chromeleon software</td>
			<td>Dionex</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Eclipse E400</td>
			<td>Nikon</td>
			<td>E400</td>
			<td>light/fluorescent microscope</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Disposable mouse cage</td>
			<td>Ancare</td>
			<td>N10HT</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microfilter top</td>
			<td>Ancare</td>
			<td>N10MBT</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
			<td>[header]</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">5-LOX- deficient mice</td>
			<td>The Jackson Laboratory</td>
			<td>004155</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">12/15-LOX-deficient mice</td>
			<td>The Jackson Laboratory</td>
			<td>002778</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

gene-environment interaction models to unmask susceptibility mechanisms in parkinson's disease

Lipoxygenase (LOX) activity has been implicated in neurodegenerative disorders such as Alzheimer&#39;s disease, but its effects in Parkinson&#39;s disease (PD) pathogenesis are less understood. Gene-environment interaction models have utility in unmasking the impact of specific cellular pathways in toxicity that may not be observed using a solely genetic or toxicant disease model alone.&#160;To evaluate if distinct LOX isozymes selectively contribute to PD-related neurodegeneration, transgenic (i.e. 5-LOX and 12/15-LOX deficient) mice can be challenged with a toxin that mimics cell injury and death in the disorder.&#160;Here we describe the use of a neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces a nigrostriatal lesion to elucidate the distinct contributions of LOX isozymes to neurodegeneration related to PD. The use of MPTP in mouse, and nonhuman primate, is well-established to recapitulate the nigrostriatal damage in PD.&#160;The extent of MPTP-induced lesioning is measured by HPLC analysis of dopamine and its metabolites and semi-quantitative Western blot analysis of striatum for tyrosine hydroxylase (TH), the rate-limiting enzyme for the synthesis of dopamine. To assess inflammatory markers, which may demonstrate LOX isozyme-selective sensitivity, glial fibrillary acidic protein (GFAP) and Iba-1 immunohistochemistry are performed on brain sections containing substantia nigra, and GFAP Western blot analysis is performed on striatal homogenates.&#160;This experimental approach can provide novel insights into gene-environment interactions underlying nigrostriatal degeneration and PD.

This toxin exposure paradigm can produce a significant and detectable 20% striatal dopamine depletion in MPTP- vs. saline-injected animals. It is important to note that different lots of MPTP may yield slightly more or less lesioning; thus, for better precision, a preliminary experiment in wildtype mice is recommended prior to use in transgenics when a new lot of neurotoxin is utilized.&#160;The use of mild-to-moderate lesioning allows for impact of the transgene to be observed; a severe lesion may produce a &#39;floor e...

Watch this Scientific Journal Video about Gene-environment Interaction Models to Unmask Susceptibility Mechanisms in Parkinson's Disease at JoVE.com

Gene-environment Interaction Models to Unmask Susceptibility Mechanisms in Parkinson&#039;s Disease

Lipoxygenase (LOX) isozymes can generate products that may increase or decrease neuroinflammation and neurodegeneration.&#160;A gene-environment interaction study could identify LOX isozyme-specific effects. Using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of nigrostriatal damage in two LOX isozyme-deficient transgenic lines allows for comparison of the contribution of LOX isozymes on dopaminergic integrity and inflammation.

Gene-environment Interaction Models to Unmask Susceptibility Mechanisms in Parkinson's Disease

Lipoxygenase (LOX) activity has been implicated in neurodegenerative disorders such as Alzheimer&#39;s disease, but its effects in Parkinson&#39;s disease ...

gene-environment-interaction-models-to-unmask-susceptibility

Research

JoVE Journal

Medicine

6.6K vues.  SRI International. Les isozymes lipoxygénase (LOX) peuvent générer des produits qui peuvent augmenter ou diminuer la neuroinflammation et la neurodégénérescence. Une étude d’interaction gène-environnement pourrait identifier les effets spécifiques de l’isozyme LOX. L’utilisation du modèle 1-méthyl-4-phényl-1,2,3,6-tétrahydropyridine (MPTP) des dommages nigrostriatal dans deux lignées transgéniques déficientes en isozyme LOX permet de comparer la contribution des isozy...

Vidéo: Gene-environment Interaction Models to Unmask Susceptibility Mechanisms in Parkinson's Disease

Development of a Unilaterally-lesioned 6-OHDA Mouse Model of Parkinson's Disease

The unilaterally lesioned 6-hyroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD) has proved to be invaluable in advancing our understanding of the mechanisms underlying parkinsonian symptoms, since it recapitulates the changes in basal ganglia circuitry and pharmacology observed in parkinsonian patients1-4. However, the precise cellular and molecular changes occurring at cortico-striatal synapses of the output pathways within the striatum, which is the major input region of the basal ganglia remain elusive, and this is believed to be site where pathological abnormalities underlying parkinsonian symptoms arise3,5.
In PD, understanding the mechanisms underlying changes in basal ganglia circuitry following degeneration of the nigro-striatal pathway has been greatly advanced by the development of bacterial artificial chromosome (BAC) mice over-expressing green fluorescent proteins driven by promoters specific for the two striatal output pathways (direct pathway: eGFP-D1; indirect pathway: eGFP-D2 and eGFP-A2a)8, allowing them to be studied in isolation. For example, recent studies have suggested that there are pathological changes in synaptic plasticity in parkinsonian mice9,10. However, these studies utilised juvenile mice and acute models of parkinsonism. It is unclear whether the changes described in adult rats with stable 6-OHDA lesions also occur in these models. Other groups have attempted to generate a stable unilaterally-lesioned 6-OHDA adult mouse model of PD by lesioning the medial forebrain bundle (MFB), unfortunately, the mortality rate in this study was extremely high, with only 14% surviving the surgery for 21 days or longer11. More recent studies have generated intra-nigral lesions with both a low mortality rate &gt;80% loss of dopaminergic neurons, however expression of L-DOPA induced dyskinesia11,12,13,14 was variable in these studies. Another well established mouse model of PD is the MPTP-lesioned mouse15. Whilst this model has proven useful in the assessment of potential neuroprotective agents16, it is less suitable for understanding mechanisms underlying symptoms of PD, as this model often fails to induce motor deficits, and shows a wide variability in the extent of lesion17, 18.
Here we have developed a stable unilateral 6-OHDA-lesioned mouse model of PD by direct administration of 6-OHDA into the MFB, which consistently causes &gt;95% loss of striatal dopamine (as measured by HPLC), as well as producing the behavioural imbalances observed in the well characterised unilateral 6-OHDA-lesioned rat model of PD. This newly developed mouse model of PD will prove a valuable tool in understanding the mechanisms underlying generation of parkinsonian symptoms.

Development of a Unilaterally-lesioned 6-OHDA Mouse Model of Parkinson&#039;s Disease

A protocol for performing unilateral 6-OHDA lesions of the medial forebrain bundle in mice is described. This method has a low mortality rate (13.3 %) with 89% of the surviving animals showing &#62;95% loss of striatal dopamine and 90.63&#177;-4.02 % ipsiversive rotational bias towards the side of the lesion.

The unilaterally lesioned 6-hyroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD) has proved to be invaluable in advancing our ...

MALDI Imaging Mass Spectrometry of Neuropeptides in Parkinson's Disease

MALDI imaging mass spectrometry (IMS) is a powerful approach that facilitates the spatial analysis of molecular species in biological tissue samples2 (Fig.1). A 12 &mu;m thin tissue section is covered with a MALDI matrix, which facilitates desorption and ionization of intact peptides and proteins that can be detected with a mass analyzer, typically using a MALDI TOF/TOF mass spectrometer. Generally hundreds of peaks can be assessed in a single rat brain tissue section. In contrast to commonly used imaging techniques, this approach does not require prior knowledge of the molecules of interest and allows for unsupervised and comprehensive analysis of multiple molecular species while maintaining high molecular specificity and sensitivity2. Here we describe a MALDI IMS based approach for elucidating region-specific distribution profiles of neuropeptides in the rat brain of an animal model Parkinson's disease (PD). 
PD is a common neurodegenerative disease with a prevalence of 1% for people over 65 of age3,4. The most common symptomatic treatment is based on dopamine replacement using L-DOPA5. However this is accompanied by severe side effects including involuntary abnormal movements, termed L-DOPA-induced dyskinesias (LID)1,3,6. One of the most prominent molecular change in LID is an upregulation of the opioid precursor prodynorphin mRNA7. The dynorphin peptides modulate neurotransmission in brain areas that are essentially involved in movement control7,8. However, to date the exact opioid peptides that originate from processing of the neuropeptide precursor have not been characterized. Therefore, we utilized MALDI IMS in an animal model of experimental Parkinson's disease and L-DOPA induced dyskinesia. 
MALDI imaging mass spectrometry proved to be particularly advantageous with respect to neuropeptide characterization, since commonly used antibody based approaches targets known peptide sequences and previously observed post-translational modifications. By contrast MALDI IMS can unravel novel peptide processing products and thus reveal new molecular mechanisms of neuropeptide modulation of neuronal transmission. While the absolute amount of neuropeptides cannot be determined by MALDI IMS, the relative abundance of peptide ions can be delineated from the mass spectra, giving insights about changing levels in health and disease. In the examples presented here, the peak intensities of dynorphin B, alpha-neoendorphin and substance P were found to be significantly increased in the dorsolateral, but not the dorsomedial, striatum of animals with severe dyskinesia involving facial, trunk and orolingual muscles (Fig. 5). Furthermore, MALDI IMS revealed a correlation between dyskinesia severity and levels of des-tyrosine alpha-neoendorphin, representing a previously unknown mechanism of functional inactivation of dynorphins in the striatum as the removal of N-terminal tyrosine reduces the dynorphin's opioid-receptor binding capacity9. This is the first study on neuropeptide characterization in LID using MALDI IMS and the results highlight the potential of the technique for application in all fields of biomedical research.

MALDI Imaging Mass Spectrometry of Neuropeptides in Parkinson&#039;s Disease

Dopamine replacement pharmacotherapy using L-DOPA is the most commonly used symptomatic treatment of Parkinson&#x2019;s disease, but is accompanied by side effects including involuntary abnormal movements, termed dyskinesia 1. Here, a protocol for MALDI imaging mass spectrometry is presented that detects changes in rat brain neuropeptide levels related to dyskinesia.

MALDI imaging mass spectrometry (IMS) is a powerful approach that facilitates the spatial analysis of molecular species in biological tissue samples2 ...

Skin Punch Biopsy Explant Culture for Derivation of Primary Human Fibroblasts

Tissues and cell lines derived from an individual with disease are ideal sources to study disease-related cellular phenotypes. Patient-derived fibroblasts in this protocol have been successfully used in the derivation of induced pluripotent stem cells to model disease1. Early passages of these fibroblasts can also be used for cell-based functional assays to study specific disease pathways, mechanisms2 and subsequent drug screening approaches. The advantage of the presented protocol over enzymatic procedures are 1) the reproducibility of the technique from small amounts of tissue derived from older patients, e.g. patients affected with Parkinson's disease, 2) the technically simple approach over more challenging methodologies using enzymatic treatments, and 3) the time consideration: this protocol takes 15-20 min and can be performed immediately after biopsy arrival. Enzymatic treatments can take up to 4 hr and have the problems of overdigestion, reduction of cell viability and subsequent attachment of cells when not handled properly. This protocol describes the dissection and preparation of a 4-mm human skin biopsy for derivation of a fibroblast culture and has a very high success rate which is important when dealing with patient-derived tissue samples. In this culture, keratinocytes migrate out of the biopsy tissue within the first week after preparation. Fibroblasts appear 7-10 days after the first outgrowth of keratinocytes. DMEM high glucose media supplemented with 20% FBS favors the growth of fibroblasts over keratinocytes and fibroblasts will overgrow the keratinocytes. After 2 passages keratinocytes have been diluted out resulting in relatively homogenous fibroblast cultures which expresses the fibroblast marker SERPINH1 (HSP-47). Using this approach, 15-20 million fibroblasts can be derived in 4-8 weeks for cell banking. The skin dissection takes about 15-20 min, cells are then monitored once a day under the microscope, and media is changed every 2-3 days after attachment and outgrowth of cells.

The fibroblast explant culture protocol from human skin punch biopsies is a technically robust and simple way to derive skin cells within 4-8 weeks for banking of about 15-20 million cells at a low passage number.

Tissues and cell lines derived from an individual with disease are ideal sources to study disease-related cellular phenotypes. Patient-derived fibroblasts ...

The Use of Primary Human Fibroblasts for Monitoring Mitochondrial Phenotypes in the Field of Parkinson's Disease

Parkinson's disease (PD) is the second most common movement disorder and affects 1% of people over the age of 60 1. Because ageing is the most important risk factor, cases of PD will increase during the next decades 2. Next to pathological protein folding and impaired protein degradation pathways, alterations of mitochondrial function and morphology were pointed out as further hallmark of neurodegeneration in PD 3-11.
After years of research in murine and human cancer cells as in vitro models to dissect molecular pathways of Parkinsonism, the use of human fibroblasts from patients and appropriate controls as ex vivo models has become a valuable research tool, if potential caveats are considered. Other than immortalized, rather artificial cell models, primary fibroblasts from patients carrying disease-associated mutations apparently reflect important pathological features of the human disease.
Here we delineate the procedure of taking skin biopsies, culturing human fibroblasts and using detailed protocols for essential microscopic techniques to define mitochondrial phenotypes. These were used to investigate different features associated with PD that are relevant to mitochondrial function and dynamics. Ex vivo, mitochondria can be analyzed in terms of their function, morphology, colocalization with lysosomes (the organelles degrading dysfunctional mitochondria) and degradation via the lysosomal pathway. These phenotypes are highly relevant for the identification of early signs of PD and may precede clinical motor symptoms in human disease-gene carriers. Hence, the assays presented here can be utilized as valuable tools to identify pathological features of neurodegeneration and help to define new therapeutic strategies in PD.

The Use of Primary Human Fibroblasts for Monitoring Mitochondrial Phenotypes in the Field of Parkinson&#039;s Disease

Fibroblasts from patients carrying mutations in Parkinson's disease-causing genes represent an easily accessible ex vivo model to study disease-associated phenotypes. Live cell imaging gives the opportunity to study morphological and functional parameters in living cells. Here we describe the preparation of human fibroblasts and subsequent monitoring of mitochondrial phenotypes.

Parkinson's disease (PD) is the second most  common movement disorder and affects 1% of people over the age of 60 1. Because ageing is  the most important ...

Controlling Parkinson's Disease With Adaptive Deep Brain Stimulation

Adaptive deep brain stimulation (aDBS) has the potential to improve the treatment of Parkinson&#39;s disease by optimizing stimulation in real time according to fluctuating disease and medication state. In the present realization of adaptive DBS we record and stimulate from the DBS electrodes implanted in the subthalamic nucleus of patients with Parkinson&#39;s disease in the early post-operative period. Local field potentials are analogue filtered between 3 and 47 Hz before being passed to a data acquisition unit where they are digitally filtered again around the patient specific beta peak, rectified and smoothed to give an online reading of the beta amplitude. A threshold for beta amplitude is set heuristically, which, if crossed, passes a trigger signal to the stimulator. The stimulator then ramps up stimulation to a pre-determined clinically effective voltage over 250 msec and continues to stimulate until the beta amplitude again falls down below threshold. Stimulation continues in this manner with brief episodes of ramped DBS during periods of heightened beta power.
Clinical efficacy is assessed after a minimum period of stabilization (5 min) through the unblinded and blinded video assessment of motor function using a selection of scores from the Unified Parkinson&#39;s Rating Scale (UPDRS). Recent work has demonstrated a reduction in power consumption with aDBS as well as an improvement in clinical scores compared to conventional DBS. Chronic aDBS could now be trialed in Parkinsonism.

Controlling Parkinson&#039;s Disease With Adaptive Deep Brain Stimulation

Adaptive deep brain stimulation (aDBS) is effective for Parkinson&#8217;s disease, improving symptoms and reducing power consumption compared to conventional deep brain stimulation (cDBS). In aDBS we track a local field potential biomarker (beta oscillatory amplitude) in real time and use this to control the timing of stimulation.

Adaptive deep brain stimulation (aDBS) has the potential to improve the treatment of Parkinson&#39;s disease by optimizing stimulation in real time ...

Adapting Human Videofluoroscopic Swallow Study Methods to Detect and Characterize Dysphagia in Murine Disease Models

This study adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research. Successful outcomes are dependent upon three critical components: test chambers that permit self-feeding while standing unrestrained in a confined space, recipes that mask the aversive taste/odor of commercially-available oral contrast agents, and a step-by-step test protocol that permits quantification of swallow physiology. Elimination of one or more of these components will have a detrimental impact on the study results. Moreover, the energy level capability of the fluoroscopy system will determine which swallow parameters can be investigated. Most research centers have high energy fluoroscopes designed for use with people and larger animals, which results in exceptionally poor image quality when testing mice and other small rodents. Despite this limitation, we have identified seven VFSS parameters that are consistently quantifiable in mice when using a high energy fluoroscope in combination with the new murine VFSS protocol. We recently obtained a low energy fluoroscopy system with exceptionally high imaging resolution and magnification capabilities that was designed for use with mice and other small rodents. Preliminary work using this new system, in combination with the new murine VFSS protocol, has identified 13 swallow parameters that are consistently quantifiable in mice, which is nearly double the number obtained using conventional (i.e., high energy) fluoroscopes. Identification of additional swallow parameters is expected as we optimize the capabilities of this new system. Results thus far demonstrate the utility of using a low energy fluoroscopy system to detect and quantify subtle changes in swallow physiology that may otherwise be overlooked when using high energy fluoroscopes to investigate murine disease models.

This study successfully adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research.

This study adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating ...

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

The epithelial barrier is the first innate defense of the gastrointestinal tract and selectively regulates transport from the lumen to the underlying tissue compartments, restricting the transport of smaller molecules across the epithelium and almost completely prohibiting epithelial macromolecular transport. This selectivity is determined by the mucous gel layer, which limits the transport of lipophilic molecules and both the apical receptors and tight junctional protein complexes of the epithelium. In vitro cell culture models of the epithelium are convenient, but as a model, they lack the complexity of interactions between the microbiota, mucous-gel, epithelium and immune system. On the other hand, in vivo assessment of intestinal absorption or permeability may be performed, but these assays measure overall gastrointestinal absorption, with no indication of site specificity. Ex vivo permeability assays using &#34;intestinal sacs&#34; are a rapid and sensitive method of measuring either overall intestinal integrity or comparative transport of a specific molecule, with the added advantage of intestinal site specificity. Here we describe the preparation of intestinal sacs for permeability studies and the calculation of the apparent permeability (Papp) of a molecule across the intestinal barrier. This technique may be used as a method of assessing drug absorption, or to examine regional epithelial barrier dysfunction in animal models of gastrointestinal disease.

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

This protocol describes the use of excised intestinal tissue preparations or "intestinal sacs" as an ex vivo model of intestinal barrier function. This model may be used to assess integrity of both the epithelial barrier and the mucous gel layer at specific intestinal sites in animal models of digestive disease.

The epithelial barrier is the first innate defense of the gastrointestinal tract and selectively regulates transport from the lumen to the underlying ...

Development of an Alpha-synuclein Based Rat Model for Parkinson's Disease via Stereotactic Injection of a Recombinant Adeno-associated Viral Vector

In order to study the molecular pathways of Parkinson&#39;s disease (PD) and to develop novel therapeutic strategies, scientific investigators rely on animal models. The identification of PD-associated genes has led to the development of genetic PD models. Most transgenic &#945;-SYN mouse models develop gradual &#945;-SYN pathology but fail to display clear dopaminergic cell loss and dopamine-dependent behavioral deficits. This hurdle was overcome by direct targeting of the substantia nigra with viral vectors overexpressing PD-associated genes. Local gene delivery using viral vectors provides an attractive way to express transgenes in the central nervous system. Specific brain regions can be targeted (e.g. the substantia nigra), expression can be induced in the adult setting and high expression levels can be achieved. Further, different vector systems based on various viruses can be used. The protocol outlines all crucial steps to perform a viral vector injection in the substantia nigra of the rat to develop a viral vector-based alpha-synuclein animal model for Parkinson&#39;s disease.

Development of an Alpha-synuclein Based Rat Model for Parkinson&#039;s Disease via Stereotactic Injection of a Recombinant Adeno-associated Viral Vector

This manuscript describes how viral vector-mediated local gene delivery provides an attractive way to express transgenes in the central nervous system. The protocol outlines all crucial steps to perform a viral vector injection in the substantia nigra of the rat to develop a viral vector-based animal model for Parkinson's disease.

In order to study the molecular pathways of Parkinson&#39;s disease (PD) and to develop novel therapeutic strategies, scientific investigators rely on ...

Quantitative 3D In Silico Modeling (q3DISM) of Cerebral Amyloid-beta Phagocytosis in Rodent Models of Alzheimer's Disease

Neuroinflammation is now recognized as a major etiological factor in neurodegenerative disease. Mononuclear phagocytes are innate immune cells responsible for phagocytosis and clearance of debris and detritus. These cells include CNS-resident macrophages known as microglia, and mononuclear phagocytes infiltrating from the periphery. Light microscopy has generally been used to visualize phagocytosis in rodent or human brain specimens. However, qualitative methods have not provided definitive evidence of in vivo phagocytosis. Here, we describe quantitative 3D in silico modeling (q3DISM), a robust method allowing for true 3D quantitation of amyloid-&#946; (A&#946;) phagocytosis by mononuclear phagocytes in rodent Alzheimer&#39;s Disease (AD) models. The method involves fluorescently visualizing A&#946; encapsulated within phagolysosomes in rodent brain sections. Large z-dimensional confocal datasets are then 3D reconstructed for quantitation of A&#946; spatially colocalized within the phagolysosome. We demonstrate the successful application of q3DISM to mouse and rat brains, but this methodology can be extended to virtually any phagocytic event in any tissue.

Quantitative 3D In Silico Modeling q3DISM of Cerebral Amyloid-beta Phagocytosis in Rodent Models of Alzheimer&#039;s Disease

We developed a methodology for quantitative 3D in silico modeling (q3DISM) of cerebral amyloid-&#946; (A&#946;) phagocytosis by mononuclear phagocytes in rodent models of Alzheimer&#39;s disease. This method can be generalized for the quantitation of virtually any phagocytic event in vivo.

Neuroinflammation is now recognized as a major etiological factor in neurodegenerative disease. Mononuclear phagocytes are innate immune cells responsible ...

Repeated Measurement of Respiratory Muscle Activity and Ventilation in Mouse Models of Neuromuscular Disease

Accessory respiratory muscles help to maintain ventilation when diaphragm function is impaired. The following protocol describes a method for repeated measurements over weeks or months of accessory respiratory muscle activity while simultaneously measuring ventilation in a non-anesthetized, freely behaving mouse. The technique includes the surgical implantation of a radio transmitter and the insertion of electrode leads into the scalene and trapezius muscles to measure the electromyogram activity of these inspiratory muscles. Ventilation is measured by whole-body plethysmography, and animal movement is assessed by video and is synchronized with electromyogram activity. Measurements of muscle activity and ventilation in a mouse model of amyotrophic lateral sclerosis are presented to show how this tool can be used to investigate how respiratory muscle activity changes over time and to assess the impact of muscle activity on ventilation. The described methods can easily be adapted to measure the activity of other muscles or to assess accessory respiratory muscle activity in additional mouse models of disease or injury.

This paper introduces a method for repeated measurements of ventilation and respiratory muscle activity in a freely behaving amyotrophic lateral sclerosis (ALS) mouse model throughout disease progression with whole-body plethysmography and electromyography via an implanted telemetry device.

Accessory respiratory muscles help to maintain ventilation when diaphragm function is impaired. The following protocol describes a method for repeated ...