Neuron-selective changes in RNA transcripts related to energy metabolism in toxic models of parkinsonism in rodents - PubMed (original) (raw)

James G Greene et al. Neurobiol Dis. 2010 Jun.

Abstract

Dopamine (DA) neurons in the substantia nigra (SNDA neurons) are among the most severely affected in Parkinson's disease (PD). Mitochondrial complex I inhibition by rotenone or MPTP can induce SNDA neurodegeneration and recapitulate motor disability in rodents. We performed a transcriptional analysis of the midbrain response to complex I inhibition focused on selected metabolic transcripts using quantitative real-time RT-PCR in conjunction with laser-capture microdissection (LCM) of immunofluorescently targeted SNDA and ventral tegmental area (VTA) DA neurons. There were DA neuron-selective alterations in metabolic transcripts in response to generalized complex I inhibition dependent on the behavioral response of the animal, and vulnerable SNDA neurons were more dynamic in their metabolic transcriptional response than less vulnerable VTADA neurons. The metabolic transcriptional response of DA neurons may contribute significantly to the ultimate toxicity associated with mitochondrial inhibition, and better understanding of this response may provide insight into potential targets for neuroprotection in PD.

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Figures

Figure 1

Figure 1. Timeline of rotenone experiments

Vehicle-treated rats and rotenone-treated rats were killed at both 1 and 4 weeks after the beginning of rotenone infusion. ‘Sick’ rats were sacrificed at the time points indicated when they became unable to care for themselves appropriately. Three sick rats had decreased tyrosine hydroxylase immunoreactivity in the striatum. One had a diffuse lesion (open arrow) and two had punctate lesions (closed arrows).

Figure 2

Figure 2. Dynamic, neuron-selective metabolic transcriptional responses during rotenone infusion

A. No changes in metabolic transcripts were evident when microdissected midbrain tissue was analyzed by Q-RT-PCR. B. There was a large dynamic range for metabolic transcript level in SNDA neurons. Metabolic transcripts were increased up to 200% in SNDA neurons after 4 weeks of exposure to rotenone. SNDA neurons from sick animals had dramatically lower levels of metabolic transcripts. C. While the trend was similar in VTADA neurons, the magnitude of differences was lower. ND1, complex I ND1 subunit; COX1, cytochrome oxidase subunit 1; LDHB, lactate dehydrogenase B; TPI, triose phosphate isomerase; PDHC, pyruvate dehydrogenase complex E1 subunit. *p < 0.05, **p < 0.01, ***p < 0.001 by post-hoc Bonferroni after two-way ANOVA. N = 12 (Vehicle), 8 (Week 1), 8 (Week 4), and 7 (Sick).

Figure 3

Figure 3. Neuron-selective metabolic transcriptional responses after MPTP treatment

SNDA neurons from MPTP-treated mice had lower levels of metabolic transcripts than those from vehicle-treated mice. There were no significant changes in VTADA neurons after MPTP treatment. Dashed line represents vehicle-treated transcript abundance. ND1, complex I ND1 subunit; LDHB, lactate dehydrogenase B; TPI, triose phosphate isomerase; ANT2, adenine nucleotide translocator 2. *p < 0.05, **p < 0.01 by post-hoc Bonferroni after two-way ANOVA. N = 4 (Vehicle) and 3 (MPTP).

Figure 4

Figure 4. Dopamine neuron subtype-selective metabolic transcriptional responses after complex 1 inhibition

A. When compared in the same mice, the ratio of expression level for metabolic transcripts shifts from favoring SNDA neurons to favoring VTADA neurons in MPTP-treated animals. N = 4 (Vehicle) and 3 (MPTP). B. When compared in the same rats, the ratio of expression level for metabolic transcripts shifts from favoring SNDA neurons to favoring VTADA neurons in sick animals. N = 12 (Vehicle) and 7 (Rotenone). DDCt, delta-delta cycle threshold, ND1, complex I ND1 subunit; LDHB, lactate dehydrogenase B; TPI, triose phosphate isomerase; ANT2, adenine nucleotide translocator 2. *p < 0.05, **p < 0.01 by post-hoc Bonferroni after two-way ANOVA.

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