Effect of Temperature on Dopamine Transporter Function and Intracellular Accumulation of Methamphetamine: Implications for Methamphetamine-Induced Dopaminergic Neurotoxicity

Abstract

Hyperthermia exacerbates and hypothermia attenuates methamphetamine (METH)-induced dopamine (DA) neurotoxicity. The mechanisms underlying these temperature effects are unknown. Given the essential role of the DA transporter (DAT) in the expression of METH-induced DA neurotoxicity, we hypothesized that the effect of temperature on METH-induced DA neurotoxicity is mediated, at least in part, at the level of the DAT. To test this hypothesis, the effects of small, physiologically relevant temperature changes on DAT function were evaluated in two types of cultured neuronal cells: (1) a neuroblastoma cell line stably transfected with human DAT cDNA and (2) rat embryonic mesencephalic primary cells that naturally express the DAT. Temperatures for studies of DAT function were selected based on core temperature measurements in animals exposed to METH under usual ambient (22°C) and hypothermic (6°C) temperature conditions, where METH neurotoxicity was fully expressed and blocked, respectively. DAT function, determined by measuring accumulation of radiolabeled DA and 1-methyl-4-phenylpyridinium (MPP ϩ ), was found to directly correlate with temperature, with higher levels of substrate uptake at 40°C, intermediate levels at 37°C, and lower levels at 34°C. DAT-mediated accumulation of METH also directly correlated with temperature, with greater accumulation at higher temperatures. These findings indicate that relatively small, physiologically relevant changes in temperature significantly alter DAT function and intracellular METH accumulation, and suggest that the effect of temperature on METHinduced DA neurotoxicity is mediated, at least in part, at the level of the DAT.Key words: dopamine; dopamine transporter; temperature; methamphetamine; MPP ϩ ; neurotoxicityThe psychostimulant methamphetamine (METH) is a potent dopamine (DA) neurotoxin in rodents, nonhuman primates (Gibb et al., 1994;Lew et al., 1998) and, possibly, humans (McCann et al., 1998Volkow et al., 1999). METH administration leads to longlasting reductions in a number of DA axonal markers including DA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid, tyrosine hydroxylase activity, and the DA transporter (DAT). Recent studies indicate that the striatal vesicular monoamine transporter is also reduced on a long-term basis after METH (Frey et al., 1997;Villemagne et al., 1998). Morphological studies indicate that loss of these presynaptic DA axonal markers is related to destruction of DA axons and axon terminals (Ellison et al., 1978;Lorez, 1981;Ricaurte et al., 1982Ricaurte et al., , 1984Bowyer et al., 1994;Broening et al., 1997;Fukumura et al., 1998), generally with sparing of DA nerve cell bodies (Ricaurte et al., 1982;Woolverton et al., 1989; but see Sonsalla et al., 1996;Hirata and Cadet, 1997). The mechanism by which METH induces dopaminergic neurotoxicity is not known. However, there is compelling evidence that the DAT plays an essential role (Marek et al., 1990;Pu et al., 1994;Fumagalli et al., 1998). The DAT is an integral membrane protein of DA neu...

Changes in Gene Expression Linked to Methamphetamine-Induced Dopaminergic Neurotoxicity

“…Also, as mentioned above, in situ hybridization studies indicate that although the increase in COX1 expression takes place in the substantia nigra, it occurs in the pars reticulata, in a region where GABA, rather than DA, cell bodies are located (González-Hernández and Rodríguez, 2000). Nevertheless, when we tested the effects of METH given at low ambient temperature, which induces hypothermia and prevents METH-induced DA neurotoxicity (Ali et al, 1995;Xie et al, 2000), no increase in COX1 expression was observed, further attesting to the close link between METHinduced DA neurotoxicity and increased COX1 expression. Clearly, to completely delineate the role of COX1 in METH neurotoxicity, additional studies will be necessary.…”

“…Twelve and 24 hr later, the mice were killed for Northern blot analyses of the COX1 mRNA level. Under these experimental conditions, which completely prevent METH-induced DA neurotoxicity (Xie et al, 2000), there was no increase in COX1 transcription at either 12 or 24 hr (data not shown), further suggesting that increased COX1 expression and METH-induced DA neurotoxicity are closely linked phenomena.…”

“…The importance of temperature has been documented by studies demonstrating that decreases in core temperature protect against METH neurotoxicity, whereas increases in core temperature exacerbate the toxicity (Bowyer et al, 1994;Miller and O'Callaghan, 1994;Albers and Sonsalla, 1995;Ali et al, 1996). Furthermore, there is evidence that at least part of the effect of temperature on METH neurotoxicity is mediated at the level of the DAT (Xie et al, 2000). More recent studies have also implicated energy metabolism (Huang et al, 1997;Stephans et al, 1998;Burrows et al, 2000a) and possibly ion dysregulation in the METH-induced DA neurotoxic process.…”

Brain Hyperthermia Is Induced by Methamphetamine and Exacerbated by Social Interaction

“…Change in brain temperature is a factor that affects various neural functions ranging from the activity of ionic channels and receptor sensitivity (Thompson et al, 1985;Rosen, 2001) to such global neuronal alterations as release and uptake of neurotransmitters (Andersen and Moser, 1995;Xie et al, 2000). Thus, the METH-induced metabolic activation suggested by our temperature measurements could be a "common denominator" for various abnormalities in neural functions (i.e., thermal stress, oxidative stress, abnormal transmitter release, decrease in ATP, etc.)…”

Modeling Human Methamphetamine Exposure in Nonhuman Primates: Chronic Dosing in the Rhesus Macaque Leads to Behavioral and Physiological Abnormalities

“…One of our main goals was to prevent critical hyperthermia in naïve animals, not only as a safety issue, but also because it has been implicated as cause of METH-related neurotoxicity in acute high dose protocols (Xie et al, 2000;Riddle et al, 2002;Brown et al, 2003). One of the long-term goals of this work is to understand how METH-induced hyperther- Figure 3 Effect of METH on average total 24 h urinary cortisol excretion over the course of all three periods, Saline, METH Ramp-up, and METH Maintenance (mean7SEM).…”