Neurochemical and histologic characterization of striatal excitotoxic lesions produced by the mitochondrial toxin 3-nitropropionic acid

Abstract

An impairment of energy metabolism may underlie slow excitotoxic neuronal death in neurodegenerative diseases. We therefore examined the effects of intrastriatal, subacute systemic, or chronic systemic administration of the mitochondrial toxin 3-nitropropionic acid (3-NP) in rats. Following intrastriatal injection 3-NP produced dose-dependent striatal lesions. Neurochemical and histologic evaluation showed that markers of both spiny projection neurons (GABA, substance P, calbindin) and aspiny interneurons (somatostatin, neuropeptide Y, NADPH-diaphorase) were equally affected. Subacute systemic administration of 3-NP produced age-dependent bilateral striatal lesions with a similar neurochemical profile. However, in contrast to the intrastriatal injections, striatal dopaminergic afferent projections were spared. Both freeze-clamp measurements and chemical shift magnetic resonance spectroscopy showed that 3-NP impairs energy metabolism in the striatum in vivo. Microdialysis showed no increase in extracellular glutamate concentrations after systemic administration of 3-NP. The lesions produced by intrastriatal injection or systemic administration of 3-NP were blocked by prior decortication. However, the NMDA antagonist MK-801 did not block the effects of intrastriatal 3-NP, consistent with a non-NMDA excitotoxic mechanism. In contrast to subacute systemic administration of 3-NP, chronic (1 month) administration produced lesions confined to the striatum in which there was relative sparing of NADPH-diaphorase interneurons, consistent with an NMDA excitotoxic process. Chronic administration showed growth-related proliferative changes in dendrites of spiny neurons similar to changes in Huntington's disease (HD). These results are consistent with in vitro studies showing that mild metabolic compromise can selectively activate NMDA receptors while more severe compromise activates both NMDA and non-NMDA receptors. Chronic administration of 3-NP over 1 month produces selective striatal lesions that replicate many of the characteristic histologic and neurochemical features of HD.

Mechanisms of Cell Death Induced by the Mitochondrial Toxin 3-Nitropropionic Acid: Acute Excitotoxic Necrosis and Delayed Apoptosis

“…In our hippocampal neuronal cultures, the basal level of extracellular glutamate was 4.3 M, similar to the estimates of normal extracellular glutamate levels in the CNS and in cultures used by others (Mitani et al, 1990;Dickie et al, 1996;Didier et al, 1996). 3-NP does not result in an increase in extracellular glutamate (Zeevalk and Nicklas, 1991;Beal et al, 1993;Fu et al, 1995). In the absence of added glutamate, 3-NP resulted in ϳ60% neuronal loss over 48 hr, of which approximately 20% was necrosis and 80% apoptosis.…”

Sp1 and Sp3 Are Oxidative Stress-Inducible, Antideath Transcription Factors in Cortical Neurons

“…Sp1 and Sp3 were similarly induced in cells in the region adjacent to neuronal loss in response to the 3-NP. 3-NP is a mitochondrial toxin that produces striatal lesions that mimic HD and that are mediated by excitotoxicity-induced oxidative stress mechanisms (Beal et al, 1993;Kim and Chan, 2002). Taken together, these results are consistent with the notion that Sp1 and Sp3 are induced by stimuli that lead to oxidative stress in vivo.…”

Effects of Mitochondrial Toxins on the Brain Amino Acid Concentrations

“…On the other hand no behavioural or motoric changes are detectable after toxin administration, despite the prolonged depression of the amino acid levels. The microdialysis studies showed no changes in the levels of Glu and Asp following 3NP administration in the striatum (15,16). We did not detect changes in hte Glu levels, but found a significant reduction of Asp levels.…”