Increased risk of Parkinson's disease in individuals hospitalized with conditions related to the use of methamphetamine or other amphetamine-type drugs

BACKGROUND

Since methamphetamine and other amphetamine-type stimulants (meth/amphetamine) can damage dopaminergic neurons, researchers have long speculated that these drugs may predispose users to develop Parkinson's disease (PD), a dopamine deficiency neurological disorder.

METHODS

We employed a retrospective population-based cohort study using all linked statewide California inpatient hospital episodes and death records from January 1, 1990 through December 31, 2005. Patients at least 30 years of age were followed for up to 16 years. Competing risks analysis was used to determine whether the meth/amphetamine cohort had elevated risk of developing PD (ICD-9 332.0; ICD-10 G20) in comparison to a matched population-proxy appendicitis group and a matched cocaine drug control group. Individuals admitted to hospital with meth/amphetamine-related conditions (n=40,472; ICD-9 codes 304.4, 305.7, 969.7, E854.2) were matched on age, race, sex, date of index admission, and patterns of hospital admission with patients with appendicitis conditions (n=207,831; ICD-9 codes 540-542) and also individuals with cocaine-use disorders (n=35,335; ICD-9 codes 304.2, 305.6, 968.5).

RESULTS

The meth/amphetamine cohort showed increased risk of PD compared to both that of the matched appendicitis group [hazard ratio (HR)=1.76, 95% CI: 1.12-2.75, p=0.017] and the matched cocaine group [HR=2.44, 95% CI: 1.32-4.41, p=0.004]. The cocaine group did not show elevated hazard of PD compared to the matched appendicitis group [HR=1.04, 95% CI: 0.56-1.93, p=0.80].

CONCLUSION

These data provide evidence that meth/amphetamine users have above-normal risk for developing PD.

New medications for drug addiction hiding in glutamatergic neuroplasticity

The repeated use of drugs that directly or indirectly stimulate dopamine transmission carry addiction liability and produce enduring pathological changes in the brain circuitry that normally regulates adaptive behavioral responding to a changing environment. This circuitry is rich in glutamatergic projections, and addiction-related behaviors in animal models have been linked to impairments in excitatory synaptic plasticity. Among the best-characterized glutamatergic projection in this circuit is the prefrontal efferent to the nucleus accumbens. A variety of molecular adaptations have been identified in the prefrontal glutamate synapses in the accumbens, many of which are induced by different classes of addictive drugs. Based largely on work with cocaine, we hypothesize that the drug-induced adaptations impair synaptic plasticity in the cortico-accumbens projection, and thereby dysregulate the ability of addicts to control their drug-taking habits. Accordingly, we go on to describe the literature implicating the drug-induced changes in protein content or function that impinge upon synaptic plasticity and have been targeted in preclinical models of relapse and, in some cases, in pilot clinical trials. Based upon modeling drug-induced impairments in neuroplasticity in the cortico-accumbens pathway, we argue for a concerted effort to clinically evaluate the hypothesis that targeting glial and neuronal proteins regulating excitatory synaptic plasticity may prove beneficial in treating addiction.

Neurologic manifestations of chronic methamphetamine abuse

Methamphetamine abuse has reached epidemic proportions in the United States. The repetitive use of methamphetamine causes massive and sustained elevations in central monoamines. These elevations, particularly in dopamine, can cause changes in the function of the central nervous system that can manifest as a variety of neurologic disorders. This article focuses on these disorders, such as neurocognitive disorders and mental illness, including drug-induced psychosis; motor disorders, including the possible risk of Parkinson's disease, the development of choreoathetoid movements, and punding; and changes in the physical appearance of the methamphetamine users, including dental caries.

Biphasic dopamine regulation in mesoaccumbens pathway in response to non-contingent binge and escalating methamphetamine regimens in the Wistar rat

RATIONALE

Methamphetamine (MA) increases extracellular dopamine (DA) and at chronic high doses induces toxicity as indicated by decreased expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT). Notably, rats will self-administer MA in escalating quantities producing such toxicity. However, the impact of MA at sub-toxic doses on DA regulation is not well established.

OBJECTIVE

The temporal dynamics of DA regulation following cessation of sub-toxic escalating and binge doses of non-contingent MA were investigated as changes therein may be associated with escalation of MA intake.

MATERIALS AND METHODS

MA was administered 3×/day using an established 14-day escalating-dose regimen (0.1-4.0 mg/kg) or a single-day binge-style administration (3 × 4 mg/kg). DA tissue content, DA turnover, TH protein, TH phosphorylation, DAT, and vesicular monoamine transporter 2 were measured in nigrostriatal and mesoaccumbens pathways 48 h and 2 weeks after MA cessation.

RESULTS

Changes in striatal DA regulation were limited to increased DA turnover. However, in the mesoaccumbens pathway, escalating MA had biphasic effects. DA was increased in ventral tegmental area (VTA) and decreased in nucleus accumbens at 48 h post-MA while the reverse was seen at 2 weeks. These changes were matched by similar changes in TH protein and, in the VTA, by changes in DAT.

CONCLUSION

Escalation of MA intake produces both transient and long-lasting effects upon DA, TH, and DAT in the mesoaccumbens pathway. The eventual decrease of DA in the VTA is speculated to contribute to craving for MA and, thus, may be associated with MA escalation and resulting dopaminergic toxicity.

Impact of methamphetamine on dopamine neurons in primates is dependent on age: implications for development of Parkinson's disease

Methamphetamine is a CNS stimulant with limited therapeutic indications, but is widely abused. Short-term exposure to higher doses, or long-term exposure to lower doses, of methamphetamine induces lasting damage to nigrostriatal dopamine neurons in man and animals. Strong evidence indicates that the mechanism for this detrimental effect on dopamine neurons involves oxidative stress exerted by reactive oxygen species. This study investigates the relative susceptibility of dopamine neurons in mid-gestation, young, and adult (not aged) monkeys to four treatments with methamphetamine over 2 days. Primate dopamine neurons undergo natural cell death at mid-gestation, and we hypothesized that during this event they are particularly vulnerable to oxidative stress. The results indicated that at mid-gestation and in adults, dopamine neurons were susceptible to methamphetamine-induced damage, as indicated by loss of striatal tyrosine hydroxylase (TH) immunoreactivity and dopamine concentration. However, dopamine neurons in young animals appeared totally resistant to the treatment, despite this group having higher brain levels of methamphetamine 3 h after administration than the adults. As a possible explanation for the protection, striatal glial-derived neurotrophic factor (GDNF) levels were elevated in young animals 1 week after treatment, but not in adults following methamphetamine treatment. Implications of these primate studies are: (1) the susceptibility of dopamine neurons at mid-gestation to methamphetamine warns against the risk of exposing pregnant women to the drug or oxidative stressors, and supports the hypothesis of Parkinson's disease being associated with oxidative stress during development, (2) elucidation of the mechanism of resistance of dopamine neurons in the young animals to methamphetamine-induced oxidative stress may provide targets for slowing or preventing age- or disease-related loss of adult nigrostriatal dopamine (DA) neurons, and (3) the increased striatal production of GDNF in young animals, but not in adults, in response to methamphetamine, suggests the possibility of an age-related change in the neurotrophic capacity of the striatal dopamine system.

Chronic methamphetamine administration causes differential regulation of transcription factors in the rat midbrain

Methamphetamine (METH) is an addictive and neurotoxic psychostimulant widely abused in the USA and throughout the world. When administered in large doses, METH can cause depletion of striatal dopamine terminals, with preservation of midbrain dopaminergic neurons. Because alterations in the expression of transcription factors that regulate the development of dopaminergic neurons might be involved in protecting these neurons after toxic insults, we tested the possibility that their expression might be affected by toxic doses of METH in the adult brain. Male Sprague-Dawley rats pretreated with saline or increasing doses of METH were challenged with toxic doses of the drug and euthanized two weeks later. Animals that received toxic METH challenges showed decreases in dopamine levels and reductions in tyrosine hydroxylase protein concentration in the striatum. METH pretreatment protected against loss of striatal dopamine and tyrosine hydroxylase. In contrast, METH challenges caused decreases in dopamine transporters in both saline- and METH-pretreated animals. Interestingly, METH challenges elicited increases in dopamine transporter mRNA levels in the midbrain in the presence but not in the absence of METH pretreatment. Moreover, toxic METH doses caused decreases in the expression of the dopamine developmental factors, Shh, Lmx1b, and Nurr1, but not in the levels of Otx2 and Pitx3, in saline-pretreated rats. METH pretreatment followed by METH challenges also decreased Nurr1 but increased Otx2 and Pitx3 expression in the midbrain. These findings suggest that, in adult animals, toxic doses of METH can differentially influence the expression of transcription factors involved in the developmental regulation of dopamine neurons. The combined increases in Otx2 and Pitx3 expression after METH preconditioning might represent, in part, some of the mechanisms that served to protect against METH-induced striatal dopamine depletion observed after METH preconditioning.