Glial and glutamatergic markers in depression, alcoholism, and their comorbidity.
BACKGROUND
Alteration of glutamatergic neurotransmission in the prefrontal cortex (PFC) may contribute to the pathophysiology of alcoholism and major depressive disorder (MDD). Among glial cells, astrocytes are mostly responsible for recycling synaptic glutamate by uptake through excitatory amino acid transporters 1 and 2 (EAAT1 and EAAT2), and conversion to glutamine with glutamine synthetase (GS). Low density of astrocytes in the PFC of "uncomplicated' alcoholics and MDD subjects may parallel altered glutamate transporters and GS in the PFC.


METHODS
Immunohistochemistry and Western blotting for glutamate transporters, GS and glial fibrillary acidic protein (GFAP) were applied to postmortem tissue of the left orbitofrontal cortex from 13 subjects with MDD, 13 with alcoholism, 10 with comorbid alcoholism plus MDD (MDA), and 13 non-psychiatric controls. Area fraction of immunoreactivity was measured in sections, and protein levels in Western blots.


RESULTS
EAAT2 immunoreactivity was significantly lower in MDD and MDA subjects than in controls. EAAT1 levels were lower in MDA and MDD subjects as compared to controls, while GS levels in MDA were significantly lower than in alcoholics and controls, and lower in MDD subjects than in alcoholics. Area fraction of GFAP was lower in MDD, but not in MDA subjects as compared to controls or alcoholics.


CONCLUSIONS
High variability of protein levels in some groups and effects of antidepressant treatment, although appearing to be limited, cannot be fully evaluated.


CONCLUSIONS
There are differential changes in the expression of glial glutamatergic markers in depression and alcoholism, suggesting a depletion of certain aspects of glutamatergic processing in depression.
Miguel-Hidalgo
José Javier
JJ
Division of Neurobiology and Behavior Research, Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS 39216, USA. jmiguel-hidalgo@umc.edu
Waltzer
Robert
R
Whittom
Angela A
AA
Austin
Mark C
MC
Rajkowska
Grazyna
G
Stockmeier
Craig A
CA
D000328:Adult; D000368:Aged; D000437:Alcoholism / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology*; D001253:Astrocytes / Q000473:pathology / Q000502:physiology*; D015897:Comorbidity; D003865:Major Depressive Disorder / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology*; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism*; D027342:Excitatory Amino Acid Transporter 2; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D050491:Glutamate Plasma Membrane Transport Proteins / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D005973:Glutamine / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000473:pathology / Q000503:physiopathology*; D012016:Reference Values; D009435:Synaptic Transmission / Q000502:physiology*
D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D005904:Glial Fibrillary Acidic Protein; D050491:Glutamate Plasma Membrane Transport Proteins; C493397:SLC1A2 protein, human; C493394:SLC1A3 protein, human; D005973:Glutamine; D005974:Glutamate-Ammonia Ligase