Post on 16-Dec-2015
Bryan Yamamoto
Addiction Therapy-2014Chicago, USA
August 4 - 6, 2014
Bryan Yamamoto, Ph.D.Department of Neurosciences
University of Toledo College of Medicine and Life SciencesAugust 4, 2014
Volkow et al, Am. J. Psychiatry, 2001
Callaghan et al., Drug and Alcohol Dependence, 2011
Meth abuse increases risk of Parkinson’s Disease by 76% compared to age-matched controls and cocaine-abusers
Methamphetamine Neurotoxicity in Humans
Overarching Hypothesis
Excitotoxicity and oxidation of proteins and lipids are mechanisms underlying the neurotoxicity of Methamphetamine
Glutamate Release
Calcium
NOS
NO
ONOO-
(peroxynitrite)
O2-
Protein oxidation, Mitochondrial Dysfunction
Lipid Peroxidation
H2O2
Calpain
Proteolysis
Identified Events Leading to a Loss of Dopamine and 5HT
Glu Receptor Activation
Dopamine Release
Fe++
X
X
X
X
XX
MAO
OH*
But, there are caveats to the proposition that the
neurotoxicity/excitotoxicity of METH is a result of its direct action
on the brain……..
Local administration of METH does not increase glutamate
0
50
100
150
200
-1 0 1 2 3 4 5 6 7 8
Do
pa
min
e (p
g/2
0 u
l)
Time (hours)
Systemic MA
Local MA
Systemic and Local Administration of METH:
Burrows
Glu
tam
ate
(pg/
20
l)
0100020003000400050006000700080009000
10000
-1 0 1 2 3 4 5 6 7 8
PerfusionGlu
tam
ate
(pg
/20
l
Dop
amin
e (p
g/g
pro
tein
)
Without Glutamate With Glutamate
Glutamate Synergizes with Local METHTo Deplete Dopamine Content
No Meth Meth Meth/Heat No Meth Meth Meth/Heat
*
#
Burrows
If it is not the direct effect of METH alone on the brain (striatum), what other systems could be responsible for the neurotoxicity?
Another target of METH is the liverLiver damage can produce encephalopathy
(i.e. hepatic encephalopathy) Tremor, movement disorders Delirium, stupor, confusion, and coma
Thinking Outside the Brain……
METH and Evidence of Hepatotoxicity
Halpin
ALT(IU/L)
Saline METH
*
AST(IU/L)
Saline METH
*
Alanine Aminotransferase Aspartate Aminotransferase
Methamphetamine Increases Liver Enzymes in Plasma
Halpin
Liver Damage and Ammonia
The liver normally removes excess ammonia from the blood via the urea cycle.
This is important because ammonia is a neurotoxic byproduct of protein metabolism and other metabolic reactions.
If the liver damaged, there is an accumulation of ammonia that is thought to cause hepatic encephalopathy
Ammonia Toxicity Excitotoxicity (Fan and Szerb, 1993, Hermenegildo et al., 1996) Oxidative stress (Kosenko et al., 1997 and Kosenko et al., 1995) Metabolic compromise (Hawkins et al., 1973, McCandless
and Schenker, 1981)
Similar mechanisms that mediate the toxicity to ammonia and the neurotoxicity to METH
Unknown whether peripheral organ (e.g. liver) damage is produced by METH and if it contributes to METH neurotoxicity
Overarching Hypothesis
Liver Damage
Hyperammonemia
Methamphetamine
Neurotoxicity
LactuloseX
Saline Lactulose METH METH + Lactulose
Plas
ma
Amm
onia
(M
)
*
#
Methamphetamine Increases Ammonia in Plasma
Halpin
400
300
200
500
100
Methamphetamine Increases Ammonia in Striatum:Blocked by Lactulose
Halpin
2
3
1
METH METH + Lactulose
0
Lactulose Does Not Affect METH Concentrations in the Brain
Halpin
(pg/
g p
rote
in)
Vehicle VehicleVehicleVehicleLactulose Lactulose LactuloseLactulose
Saline Saline SalineSaline METHMETHMETH METH
(pg/
g p
rote
in)
* *
* #
#
Lactulose Attenuates METH-induced Long-term Depletions of Dopamine and 5HT Content
Dopamine Serotonin
Halpin
1.2
1.0
0.8
0.6
0.4
0.2
Vehicle VehicleLactulose Lactulose
Saline Saline METHMETH
Dopamine Transporter Immunoreactivity
*
% C
ontr
olLactulose Blocks METH-induced Decreases
in Dopamine Transporter Immmunoreactivity
Halpin
Glu
tam
ate
(% B
asel
ine)
200
400
500
600
100
300
B
Time (hrs)
Vehicle-METH
Vehicle-Saline
Lac-METH
Lac-Saline
METH-Induced Increases in Striatal Extracellular Glutamate:
Blocked by Lactulose
Halpin, Northrop
Lactulose Blocks METH-Induced Increases in Striatal Spectrin Proteolysis
Vehicle Lactulose Vehicle LactuloseSaline Saline METH METH
100
40
20
160
140
120
60
80
180 *
Perc
ent C
ontr
ol
Halpin, Northrop
METH-Induced Astroglyosis (GFAP) is Blocked by Lactulose
0
20
40
60
80
100
120
140
160
180
200
Vehicle Lactulose Vehicle LactuloseSaline Saline METH METH
Perc
ent C
ontr
ol
*
Halpin, Northrop
Glu
tam
ate
(% B
asel
ine)
Time (hrs)
TBOA or aCSF
NH3 or aCSF
Local Perfusion of Ammonia on Glutamate:Efflux Through Reversal of the Glutamate Transporter
*
100
300
250
200
150
50
Halpin, Northrop
* *
Vehicle VehicleNH3
Saline Saline METHMETHVehicle Vehicle
Saline Saline METHMETH
(pg/
g p
rote
in)
(pg/
g p
rote
in)
NH3 NH3 NH3
Combined Local Perfusions of Ammonia and METHDopamine and 5HT Content in the Striatum
Dopamine 5HT
Halpin, Northrop
METHGYKI
NH3
METHGYKI
NH3
Are there other targets of ammonia?
Amphetamines
The Blood-Brain Barrier: A Protective Barrier of the Brain
BBB Function in Cortex After Meth
VehicleSaline
LactuloseSaline
LactuloseMeth
VehicleMeth
*
#
Quantification of FITC-Dextran Extravasation
Vehicle+Saline Lactulose+Saline Vehicle+Meth Lactulose+Meth
Northrop
Blood-Brain BarrierTight Junctions
OccludinClaudin 3, 5, 12JAM
*
#
Occludin
VehicleSaline
LactuloseSaline
VehicleMeth
LactuloseMeth
Claudin-5
*
#
VehicleSaline
LactuloseSaline
VehicleMeth
LactuloseMeth
Meth-Induced Disruption of BBB Structure in Cortex
* *
Northrop
Isolated Brain Capillaries
Representative Blot for Nitrotyrosine
Ammonia as a Pro-Oxidant?
Representative Blot for Tight Junction Proteins
Northrop
Isolated Brain Capillaries from Cortex
Cyclooxygenase-2Ammonia as a Pro-Inflammatory Agent?
Northrop
VehicleSaline
VehicleMeth
LactuloseMeth
LactuloseSaline
*
&
CO
X-2
Imm
uno
rea
ctiv
ity(%
Veh
icle
+ S
alin
e)
Summary and Conclusions
Increases in extracellular glutamate and evidence of excitotoxicity and oxidative degradation of proteins
Causes hepatotoxicity and increases ammonia concentrations in peripheral plasma and brain to mediate excitotoxicity
Damages the BBB via ammonia, oxidative stress, and inflammation (COX2-dependent prostaglandin synthesis?)
Opening of the BBB can render the brain vulnerable to toxins by that would otherwise by restricted to the periphery.
Peripheral organ effects should be considered as possible causes of the neurotoxicity associated with psychostimulant drug use
Effects of METH:
Jeffrey Brown, Ph.D.
Kristan Burrows Cline, Ph.D.
David Eyerman, Ph.D.
Amy Ferng, M.S.
Laura Halpin, Ph.D.
John Irlam, D.O.
J. F. Nash, Ph.D.
Arunan Nadarajah, Ph.D.
Nicole Northrop, Ph.D.
Robert Staszewski, M.S.
Despina Tata, Ph.D
Amanda Blaker
Veronica Chiu, Ph.D.
Stuart Collins
Nicole Harless
Katelyn Marchal
Carmen Mitchell
Reka Natarajan, Ph.D.
Allen Schroering, M.S.
Erin Semple
Branden Stansley
CollaboratorsMethamphetamine Project Past and Current
Other Current Lab Members
NIH grants DA007606, DA016866, DA035499
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