Methamphetamine is a potent and addictive psychostimulant abused by 12 million people in the US at least once (NSDUH, 2012) but also FDA-approved to treat ADHD and obesity. Parkinson’s disease (PD) is a neurodegenerative movement disorder affecting ~4 million people;1 risk for developing PD is increased 2-3 fold by methamphetamine use.2-4 This correlation suggests that methamphetamine use promotes the loss or dysfunction of dopaminergic neurons in the substantia nigra pars compacta (SNc). Loss of these neurons is responsible for the core motor symptoms of PD.5,6 That said, methamphetamine use could trigger dysfunction in other neuronal populations as well. How methamphetamine might promote neurodegeneration is not clear. Two major obstacles to gaining this understanding are 1) the lack of optical probes that allow key physiological parameters to be assessed in relevant subcellular regions and 2) the inability to selectively express probes in relevant neuronal populations. The P30 is addressing the second obstacle by generating transgenic BAC-Cre mice. But to fully take advantage of these mice, the first obstacle needs to be addressed. The proposed project will do that by generating Credependent, genetically encoded optical probes for cytosolic and mitochondrial redox status. Why a redox probe? DA metabolism has long been thought to increase oxidant stress, but the evidence for this has largely been indirect.7-12 Under normal conditions, DA metabolism is likely quite low due to sequestration of DA into vesicles; however, methamphetamine administration dramatically elevates extracellular and intracellular DA.13-18 We hypothesize that methamphetamine-induced elevation of cytosolic DA leads to mitochondrial – but not cytosolic – oxidant stress in dopaminergic terminals (Fig. 1). We think that elevated mitochondrial oxidant stress is driven by monoamine oxidase B (MAO-B) metabolism of cytosolic DA; MAO-B is hypothesized to increase mitochondrial oxidant stress by shuttling electrons to the electron transport chain. This hypothesis runs completely counter to current theories of how DA causes oxidant stress, which posit (without relevant data) that DA metabolism either increases cytosolic quinones or increases cytosolic hydrogen peroxide production by MAO-B. Both these models predict an elevation in cytosolic oxidant stress, not mitochondrial oxidant stress. As outlined above, the lack of clarity in the field is a consequence of our poor tools. In the last 5 years, we have characterized a ratiometric, reversible redox probe that is suitable for two-photon laser microscopy in ex vivo brain slices. This probe – roGFP – can be target to the cytosol or to the mitochondrial matrix. Using this probe, we have generated strong preliminary data in favor of our hypothesis (see below). But what we need to do is to generate Cre-dependent expression constructs that can be packaged into an adenoassociated virus vector. These constructs could then be used in appropriate BAC-Cre mice being generated by the P30 to interrogate relevant populations of neuron before and after methamphetamine treatment. Having these tools will advance the mission of the P30 and NIDA.
|Effective start/end date||7/1/15 → 2/28/17|
- Rockefeller University (5P30DA035756-03)
- National Institute on Drug Abuse (5P30DA035756-03)
Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.