Rapid and transient inhibition of mitochondrial function following methamphetamine or 3,4-methylenedioxymethamphetamine administration

Abstract

Metabolic mapping of discrete brain regions using cytochrome oxidase histochemistry was used as a marker for alterations in mitochondrial function and cytochrome oxidase enzymatic activity in response to high doses of amphetamine derivatives. The activity of cytochrome oxidase, complex IV of the electron transport chain, was determined at three different time-points following administration of high doses of methamphetamine or 3,4-methylenedioxymethamphetamine (MDMA) (four injections of 10–15 mg/kg administered over 8 h). There was a rapid decrease in cytochrome oxidase staining in the striatum (23–29%), nucleus accumbens (29–30%) and substantia nigra (31–43%), 2 h following administration of either methamphetamine and MDMA. This decrease in cytochrome oxidase activity was transient and returned to control levels within 24 h. Since the methamphetamine and MDMA-induced decrease in cytochrome oxidase activity was localized to dopamine-rich regions, increased extracellular concentrations of dopamine may contribute to the inhibition of metabolic function via its metabolism to form quinones or other reactive oxygen species. These results support previous studies demonstrating that psychostimulants induce a rapid and transient decrease in striatal ATP stores and provide further evidence that these drugs of abuse can disrupt mitochondrial function.

Introduction

Increased metabolic stress compromises bioenergetic processes and has been hypothesized to contribute to lasting changes in the dopamine and serotonin (5-hydroxytryptamine, 5-HT) systems following high-dose methamphetamine administration. Evidence of metabolic stress following methamphetamine includes increased extracellular concentrations of lactate (Stephans et al., 1998) and a decrease in striatal ATP concentrations (Chan et al., 1994). Poblete and Azmitia (1995) have reported that 3,4-methylenedioxymethamphetamine (MDMA) increases the breakdown of glycogen in vitro, indicating that similar changes in metabolic function occur following administration of other substituted amphetamines. Acute administration of methamphetamine or its parent compound amphetamine, has been shown to rapidly (within 1 h) increase local cerebral glucose utilization in multiple brain regions Pontieri et al., 1990, Porrino et al., 1984. In addition, high-dose treatment with methamphetamine or MDMA results in decreased cerebral glucose metabolism weeks to months following drug administration, suggesting lasting impairments in metabolic systems Huang et al., 1999, McBean et al., 1990, Sharkey et al., 1991. Although these studies indicate that energy metabolism is altered following methamphetamine or MDMA administration, no studies have demonstrated directly that mitochondrial function itself is acutely or chronically compromised following high doses of psychostimulants.

Metabolic mapping using cytochrome oxidase histochemistry can be used to compare relative levels of enzymatic activity in discrete brain regions (Hevner et al., 1995). The density of cytochrome oxidase staining is highly correlated with cytochrome oxidase activity as measured in tissue homogenates, but the histochemical technique has the advantage of higher anatomic resolution compared with biochemical measurements in tissue homogenates (Hevner et al., 1995). Unlike mapping using 2-deoxyglucose, which measures rapid changes in glucose utilization, cytochrome oxidase histochemistry can be used to measure changes in energy usage over a period of hours to weeks (Wong-Riley, 1989). The degree of cytochrome oxidase staining is believed to reflect the overall functional activity of neurons in that intense staining is associated with areas that have both a high level of excitatory input and high tonic firing rates Kageyama and Wong-Riley, 1982, Mjaatvedt and Wong-Riley, 1991.

The primary goal of this study was to identify and characterize mitochondrial dysfunction following methamphetamine or MDMA administration. Specifically, the activity of complex IV (cytochrome oxidase) was determined following administration of high doses of methamphetamine or MDMA to determine if these psychostimulants had rapid or lasting effects on mitochondrial enzyme function. Based on the suggestion that psychostimulants increase the formation of nitric oxide Abekawa et al., 1996, Zheng and Laverty, 1998, a known complex IV inhibitor Cleeter et al., 1994, Lizasoain et al., 1996, and the finding of depleted energy stores following methamphetamine administration (Chan et al., 1994), it was hypothesized that high-dose methamphetamine or MDMA would decrease cytochrome oxidase histochemical staining in a brain region specific manner correlating with the ability of these drugs to increase extracellular concentrations of dopamine and 5-HT. Cytochrome oxidase activity was examined 2 h, 24 h, and 7 days following administration of the last dose of methamphetamine or MDMA. These time-points were chosen, in part, based on a previous study demonstrating a loss of striatal ATP at 1.5 h, but not 24 h following the same course of methamphetamine treatment (Chan et al., 1994). In addition, several studies have demonstrated that substituted amphetamines result in a rapid depletion of neurotransmitter content, followed by a transitory recovery (24 h post drug), and a lasting monoamine loss (generally measured 3 or 7 days post drug). Therefore, these time-points were also chosen to determine if changes in cytochrome oxidase activity correlate temporally with the known time-course of methamphetamine- and MDMA-induced monoamine loss.