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The Parkinsonian mimetic, 6-OHDA, impairs axonal transport in dopaminergic axons.

Lu X, Kim-Han JS, Harmon S, Sakiyama-Elbert SE, O'Malley KL - Mol Neurodegener (2014)

Bottom Line: This appeared to be a general effect on transport function since 6-OHDA also disrupted transport of synaptophysin-tagged vesicles.The effects of 6-OHDA on mitochondrial transport were blocked by the addition of the SOD1-mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), as well as the anti-oxidant N-acetyl-cysteine (NAC) suggesting that free radical species played a role in this process.Temporally, microtubule disruption and autophagy occurred after transport dysfunction yet before DA cell death following 6-OHDA treatment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, Washington University in Saint Louis, 1 Brookings Drive, Campus Box 1097, St, Louis, MO 63130, USA. sakiyama@wustl.edu.

ABSTRACT
6-hydroxydopamine (6-OHDA) is one of the most commonly used toxins for modeling degeneration of dopaminergic (DA) neurons in Parkinson's disease. 6-OHDA also causes axonal degeneration, a process that appears to precede the death of DA neurons. To understand the processes involved in 6-OHDA-mediated axonal degeneration, a microdevice designed to isolate axons fluidically from cell bodies was used in conjunction with green fluorescent protein (GFP)-labeled DA neurons. Results showed that 6-OHDA quickly induced mitochondrial transport dysfunction in both DA and non-DA axons. This appeared to be a general effect on transport function since 6-OHDA also disrupted transport of synaptophysin-tagged vesicles. The effects of 6-OHDA on mitochondrial transport were blocked by the addition of the SOD1-mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), as well as the anti-oxidant N-acetyl-cysteine (NAC) suggesting that free radical species played a role in this process. Temporally, microtubule disruption and autophagy occurred after transport dysfunction yet before DA cell death following 6-OHDA treatment. The results from the study suggest that ROS-mediated transport dysfunction occurs early and plays a significant role in inducing axonal degeneration in response to 6-OHDA treatment.

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6-OHDA rapidly decreases mitochondrial movement in non-DA axons. A) Axonal movement of mitochondria in control and 6-OHDA treated axons. Non-GFP positive axons (non-DA; Top panels) that were labeled with MitoDsRed2 (Middle panels) were selected for imaging 30 minutes after treatment with 6-OHDA. Resulting kymographs are shown below. For additional clarity tracks of moving particles are depicted in the bottom panels: blue lines denote anterograde movement and red lines indicate retrograde trafficking. Scale bar indicates 10 μm. Quantification of B) moving mitochondria in both anterograde and retrograde directions (n = 3–4 devices per group from with 3–5 axons analyzed per device) and C) mitochondrial speeds of motile mitochondria. The latter were calculated as described [10] (n = 90–120 mitochondria per group). In B and C, data are represented as mean ± SEM, *: indicate p < 0.05 versus control.
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Figure 2: 6-OHDA rapidly decreases mitochondrial movement in non-DA axons. A) Axonal movement of mitochondria in control and 6-OHDA treated axons. Non-GFP positive axons (non-DA; Top panels) that were labeled with MitoDsRed2 (Middle panels) were selected for imaging 30 minutes after treatment with 6-OHDA. Resulting kymographs are shown below. For additional clarity tracks of moving particles are depicted in the bottom panels: blue lines denote anterograde movement and red lines indicate retrograde trafficking. Scale bar indicates 10 μm. Quantification of B) moving mitochondria in both anterograde and retrograde directions (n = 3–4 devices per group from with 3–5 axons analyzed per device) and C) mitochondrial speeds of motile mitochondria. The latter were calculated as described [10] (n = 90–120 mitochondria per group). In B and C, data are represented as mean ± SEM, *: indicate p < 0.05 versus control.

Mentions: Because 6-OHDA is easily oxidized in vitro to p-quinones and ROS species such as hydrogen peroxide, 6-OHDA may exert its toxic effect via an extracellular mechanism without the need for uptake via the dopamine transporter [17]. In fact, we have previously shown that even small doses and short time treatments with 6-OHDA lead to death of DA and non-DA neurons in culture [16]. Not surprisingly then, mitochondrial transport in non-DA axons was also significantly decreased in terms of total mitochondrial motility without an effect on anterograde or retrograde velocities (Figure 2). Taken together, 6-OHDA led to a 50% decrease in mitochondrial motility 30 min after treatment in both DA and non-DA axons.


The Parkinsonian mimetic, 6-OHDA, impairs axonal transport in dopaminergic axons.

Lu X, Kim-Han JS, Harmon S, Sakiyama-Elbert SE, O'Malley KL - Mol Neurodegener (2014)

6-OHDA rapidly decreases mitochondrial movement in non-DA axons. A) Axonal movement of mitochondria in control and 6-OHDA treated axons. Non-GFP positive axons (non-DA; Top panels) that were labeled with MitoDsRed2 (Middle panels) were selected for imaging 30 minutes after treatment with 6-OHDA. Resulting kymographs are shown below. For additional clarity tracks of moving particles are depicted in the bottom panels: blue lines denote anterograde movement and red lines indicate retrograde trafficking. Scale bar indicates 10 μm. Quantification of B) moving mitochondria in both anterograde and retrograde directions (n = 3–4 devices per group from with 3–5 axons analyzed per device) and C) mitochondrial speeds of motile mitochondria. The latter were calculated as described [10] (n = 90–120 mitochondria per group). In B and C, data are represented as mean ± SEM, *: indicate p < 0.05 versus control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4016665&req=5

Figure 2: 6-OHDA rapidly decreases mitochondrial movement in non-DA axons. A) Axonal movement of mitochondria in control and 6-OHDA treated axons. Non-GFP positive axons (non-DA; Top panels) that were labeled with MitoDsRed2 (Middle panels) were selected for imaging 30 minutes after treatment with 6-OHDA. Resulting kymographs are shown below. For additional clarity tracks of moving particles are depicted in the bottom panels: blue lines denote anterograde movement and red lines indicate retrograde trafficking. Scale bar indicates 10 μm. Quantification of B) moving mitochondria in both anterograde and retrograde directions (n = 3–4 devices per group from with 3–5 axons analyzed per device) and C) mitochondrial speeds of motile mitochondria. The latter were calculated as described [10] (n = 90–120 mitochondria per group). In B and C, data are represented as mean ± SEM, *: indicate p < 0.05 versus control.
Mentions: Because 6-OHDA is easily oxidized in vitro to p-quinones and ROS species such as hydrogen peroxide, 6-OHDA may exert its toxic effect via an extracellular mechanism without the need for uptake via the dopamine transporter [17]. In fact, we have previously shown that even small doses and short time treatments with 6-OHDA lead to death of DA and non-DA neurons in culture [16]. Not surprisingly then, mitochondrial transport in non-DA axons was also significantly decreased in terms of total mitochondrial motility without an effect on anterograde or retrograde velocities (Figure 2). Taken together, 6-OHDA led to a 50% decrease in mitochondrial motility 30 min after treatment in both DA and non-DA axons.

Bottom Line: This appeared to be a general effect on transport function since 6-OHDA also disrupted transport of synaptophysin-tagged vesicles.The effects of 6-OHDA on mitochondrial transport were blocked by the addition of the SOD1-mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), as well as the anti-oxidant N-acetyl-cysteine (NAC) suggesting that free radical species played a role in this process.Temporally, microtubule disruption and autophagy occurred after transport dysfunction yet before DA cell death following 6-OHDA treatment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, Washington University in Saint Louis, 1 Brookings Drive, Campus Box 1097, St, Louis, MO 63130, USA. sakiyama@wustl.edu.

ABSTRACT
6-hydroxydopamine (6-OHDA) is one of the most commonly used toxins for modeling degeneration of dopaminergic (DA) neurons in Parkinson's disease. 6-OHDA also causes axonal degeneration, a process that appears to precede the death of DA neurons. To understand the processes involved in 6-OHDA-mediated axonal degeneration, a microdevice designed to isolate axons fluidically from cell bodies was used in conjunction with green fluorescent protein (GFP)-labeled DA neurons. Results showed that 6-OHDA quickly induced mitochondrial transport dysfunction in both DA and non-DA axons. This appeared to be a general effect on transport function since 6-OHDA also disrupted transport of synaptophysin-tagged vesicles. The effects of 6-OHDA on mitochondrial transport were blocked by the addition of the SOD1-mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), as well as the anti-oxidant N-acetyl-cysteine (NAC) suggesting that free radical species played a role in this process. Temporally, microtubule disruption and autophagy occurred after transport dysfunction yet before DA cell death following 6-OHDA treatment. The results from the study suggest that ROS-mediated transport dysfunction occurs early and plays a significant role in inducing axonal degeneration in response to 6-OHDA treatment.

Show MeSH
Related in: MedlinePlus