Ephedrine Neurotoxicity

John H. johnh at faraway.xxx
Sun May 25 06:33:41 EST 2003


03/02/02 20:05

Neuroreport 1999 Oct 19;10(15):3155-8Related Articles,  Influence of NOS
inhibitors on changes in ACH release and NO level in the brain elicited by
amphetamine neurotoxicity.

Bashkatova V, Kraus M, Prast H, Vanin A, Rayevsky K, Philippu A.

Institute of Pharmacology, Russian Academy of Medical Sciences, Moscow.

We studied the possible role of neurotoxicity in the d,l-amphetamine
(AMPH)-induced release of acetylcholine (ACH) in the nucleus accumbens (Nac)
and the involvement of endogenous NO in this process. For determination of
ACH release the Nac was superfused using the push-pull-technique. NO was
directly measured using the electron paramagnetic resonance technique.
Repeated administration of AMPH increased ACH release by about 400%.
N-nitro-L-arginine (L-NNA) and 7-nitroindazole (7-NI) nearly abolished the
AMPH-induced increase in ACH release. AMPH increased NO as well as lipid
peroxidation (LPO) products in the cortex. L-NNA and 7-NI substantially
diminished NO increase. AMPH-evoked LPO was only slightly reduced by these
compounds. It is concluded that AMPH enhances ACH release through increased
NO synthesis and induces neurotoxicity via NO and by LPO independent NO
generation.

PMID: 10574552 [PubMed - indexed for MEDLINE]

Article: Molecular Mechanism of the Inactivation of Tryptophan Hydroxylase
by Nitric Oxide: Attack on Critical Sulfhydryls that Spare the Enzyme Iron
Center
Authors: Donald M. Kuhn 1,2 and Robert Arthur Jr 1
Journal: The Journal of Neuroscience, October 1, 1997, 17(19):7245-7251
Location:
N\Ni
NOS inhibits serotonin via tryto hyrodrox
Date obtained: 31/01/00
Web Page:
Date Read: 27/02/00
Date to Review: 15/10/00
Keywords:
Key words: tryptophan hydroxylase; nitric oxide; sulfhydryls;
catalytic iron site; serotonin; neurotoxic amphetamines, nos, flf, ros,
aspartmane,
ecstasy, mdma, 5ht neurons, depression,
Printed:
Notes:
Tryptophan hydroxylase (TPH), the initial and rate-limiting en-zyme in the
biosynthesis of the neurotransmitter serotonin (5- HT), is irreversibly
inactivated by nitric oxide (NO). We have expressed brain TPH as a
recombinant glutathione-S-transferase fusion protein and delineated the
catalytic domain of the enzyme as the region spanning amino acids 99-444.
Highly purified TPH catalytic core, like the native enzyme from brain, is
inactivated by NO in a concentration-dependent man-ner. Removal of iron from
TPH produces an apoenzyme with low activity that can be reconverted to its
highly active holo-form by the addition of ferrous iron. Apo-TPH exposed to
NO cannot be reactivated by iron. Treatment of holo-TPH (iron-loaded) with
the disulfide 5,59-dithio-bis (2-nitrobenzoic acid) (DTNB) causes an
inactivation of TPH that is readily reversed by dithiothreitol (DTT).
DTNB-treated TPH [sulfhydryl (SH)-protected] exposed to NO is returned to
full activity by thiol reduction with DTT. The inactivation of native TPH by
NO cannot be reversed by either iron or DTT. These data indicate that NO
inactivates TPH by selective action on critical SH groups (i.e., cysteine
residues) while sparing catalytic iron sites within the enzyme. The results
are interpreted with reference to the substituted amphetamines, which are
neurotoxic to 5-HT neurons, that inactivate TPH in vivo and are now known to
produce NO and other reactive oxygen species in vivo.
--
Selected amphetamines have profound effects on the 5-HT neuronal system.
Methylenedioxymethamphetamine (ecstasy) (MDMA) and p-chloroamphetamine cause
extensive destruction of 5-HT neurons. An early manifestation of their
effects is a significant inactivation of TPH (for reviews, see Gibb et al.,
1993; Steele et al., 1994; Seiden and Sabol, 1996). The mechanisms
underlying these effects on TPH are not known, but emerging data implicate
drug-induced production of reactive oxygen species (ROS) and nitric oxide
(NO). The cellular effects of ROS or NO cannot be predicted a priori: NO can
be toxic to some cells (Lipton et al., 1993; Dawson et al., 1994), it is a
neurotransmitter- neuromodulator in other cells (Jaffrey and Snyder, 1996),
and it can protect still other cells from known toxins (Wink et al., 1995,
1996). The recent demonstration that TPH is inactivated by NO in vitro (Kuhn
and Arthur, 1996, 1997) establishes the possibility that this important
brain enzyme is susceptible to inactivation by NO in vivo and could form the
basis for loss of TPH activity when NO levels are elevated in brain (e.g.,
amphetamine-induced).
--
 By altering independently the iron or SH status of TPH, we demon-strate
that NO inactivates TPH by selective attack on critical SH groups, sparing
catalytic iron sites altogether.
--
These experiments establish the importance of iron in TPH f unc-tion and
demonstrate that TPH can be reversibly converted be-tween the apo- and
holo-forms.
--
The present results lead to several interesting conclusions about TPH.
First, they reaffirm the importance of iron and SH groups (free cysteines)
in TPH catalytic f unction. Second, they establish the feasibility and value
of using highly purified, recom-binant TPH to probe the molecular mechanisms
regulating this enzyme. Finally, they point to SH groups as targets for
NO-induced inactivation of the enzyme.
--
 A distinction must be drawn between amphetamine-induced inactivation of TPH
and 5-HT neurotoxicity. Although drugs such as MDMA cause both pro-cesses to
occur, we are not implying that TPH inactivation itself is the direct cause
of 5-HT depletion. These two processes may be linked to the same causal
event (e.g., NO or ROS), or they could be independent. In either case, the
similarities between NO-inactivated TPH (Kuhn and Arthur, 1996, 1997;
present results) and MDMA-inactivated TPH (Stone et al., 1989a,b) are
compel-ling. Furthermore, the potential role of NO in mediating apopto-sis
(Brune et al., 1996; Jacobson, 1996; Simonian and Coyle, 1996) and the
recent claim that MDMA induces apoptosis in a human serotonergic cell line
(Simantov and Tauber, 1997) draws another interesting parallel between NO
and amphetamine-induced alter-ations in 5-HT neurons. We are presently
developing probes for NO-modified TPH in an attempt to identif y
amphetamine-modified TPH in vivo.

end.
Project:


[[31/03/01 11:56

Ann Neurol 2001 Jan;49(1):79-89 Related Articles, Books


Role of mitochondrial dysfunction and dopamine-dependent oxidative stress in
amphetamine-induced toxicity.

Lotharius J, O'Malley KL

Department of Anatomy and Neurobiology, Washington University School of
Medicine, St Louis, MO, USA.

To define the molecular mechanisms underlying amphetamine (AMPH)
neurotoxicity, primary cultures of dopaminergic neurons were examined for
drug-induced changes in dopamine (DA) distribution, oxidative stress,
protein damage, and cell death. As in earlier studies, AMPH rapidly
redistributed vesicular DA to the cytoplasm, where it underwent outward
transport through the DA transporter. DA was concurrently oxidized to
produce a threefold increase in free radicals, as measured by the
redox-sensitive dye dihydroethidium. Intracellular DA depletion using the DA
synthesis inhibitor alpha-methyl-p-tyrosine or the vesicular monoamine
transport blocker reserpine prevented drug-induced free radical formation.
Despite these AMPH-induced changes, neither protein oxidation nor cell death
was observed until 1 and 4 days, respectively. AMPH also induced an early
burst of free radicals in a CNS-derived dopaminergic cell line. However,
AMPH-mediated attenuation of ATP production and mitochondrial function was
not observed in these cells until 48 to 72 hours. Thus, neither metabolic
dysfunction nor loss of viability was a direct consequence of AMPH
neurotoxicity. In contrast, when primary cultures of dopaminergic neurons
were exposed to AMPH in the presence of subtoxic doses of the mitochondrial
complex I inhibitor rotenone, cell death was dramatically increased,
mimicking the effects of a known parkinsonism-inducing toxin. Thus,
metabolic stress may predispose dopaminergic neurons to injury by free
radical-promoting insults such as AMPH.

PMID: 11198300
[[1/04/01 15:37

: Brain Res 1998 Dec 14;814(1-2):120-6 Related Articles, Books


Microgliosis and down-regulation of adenosine transporter induced by
methamphetamine in rats.

Escubedo E, Guitart L, Sureda FX, Jimenez A, Pubill D, Pallas M, Camins A,
Camarasa J

Unitat de Farmacologia i Farmacognosia, Facultat de Farmacia, Nucli
Universitari de Pedralbes, 08028, Barcelona, Spain. escubedo at far.ub.es

[Record supplied by publisher]

Chronic administration of methamphetamine to rats induces neurotoxicity
characterized by a loss of striatal dopaminergic terminals and reactive
gliosis. Subcutaneous administration of methamphetamine in a scheduled
procedure of four doses (10 mg/kg) at 2 h interval also induces a
significant increase in the peripheral-type benzodiazepine receptor (PBR)
density. This increase is maximum (76%) at 72 h post-treatment in the
striatum and disappears at 7 days, suggesting that microglia may have a
predominant role in necrosis-phagocytosis of neuronal debris rather than
acting in a restorative manner. Microgliosis is not restricted to the
striatum since it is also evident in cerebellum (75.4% of PBR increase) and
hippocampus (37.2% of PBR increase). In the areas with high density of
adenosine transporter, the microgliosis phenomenon correlates well with a
decrease of this nucleoside transporter (about 39%). Although the
microgliosis and the decrease in adenosine transporter could be parallel and
not related events, we can speculate that when microglia are activated, a
down-regulation of adenosine transporter occurs, playing a role in tissue
homeostasis. With the same dosing schedule, methamphetamine induces HSP72
expression in both cytoplasmic and nuclear fractions of the striatum,
cerebellum and hippocampus. This expression is also evident in the cerebral
cortex, where adenosine transporter population did not show any variation.
Copyright 1998 Elsevier Science B.V.

PMID: 9838075


"anon" <anon at no.com> wrote in message news:BAF5FF86.5F0%anon at no.com...
>
> Can you site any studies showing neurotoxicity from amphetamines?
>
>
> > Interesting...
> >
> > I does anyone know the mechanism of amphetamine neurotoxicity? Is it the
> > same as the hypothesised MDMA-esque MAO-B degrading DA, releasing ROS?
>
>





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