GABAA receptor agonist mitigates homocysteine-induced cerebrovascular remodeling in knockout mice.
Individuals with homozygous deficiency in cystathionine-beta-synthase (CBS) develop high levels of homocysteine in plasma, a condition known as homocysteinuria. Mental retardation ensues with death in teens; the heterozygous live normally but develop vascular dementia and Alzheimer's disease (AD) in later part of life. The treatment with muscimol, a gamma amino butyric acid receptor-A (GABA(A)) agonist, mitigates the AD syndrome and vascular dementia. We tested the hypothesis that homocysteine (Hcy) antagonizes the GABA(A) receptor and behaves as an excitotoxic neurotransmitter that causes blood brain barrier (BBB) permeability and vascular dementia. The BBB permeability was measured by infusing Evan's blue dye (2% in saline 5 ml/kg concentration) in CBS-/+, GABA(A)-/-, CBS-/+/GABA(A)-/- double knockout, CBS-/+ mice treated with muscimol and wild type (WT) mice. Matrix Metalloproteinase (MMP-2, MMP-9), Tissue Inhibitor of Matrix Metalloproteinase (TIMP-3, TIMP-4), collagen-III and elastin levels were measured in whole brain by Western blot. These results suggested an increase in Evan's blue permeability: CBS-/+<GABA(A)-/-<CBS-/+/GABA(A)-/- compared to WT mice. Interestingly, in CBS-/+ mice treated with muscimol, BBB permeability was significantly decreased compared with the CBS-/+ group. There was a decrease in the TIMP-4 protein expression level, whereas the TIMP-3 level increased in CBS-/+, GABA(A)-/-, and CBS-/+/GABA(A)-/- mice compared to the WT. MMP-2 and MMP-9 expression significantly increased in all the groups compared to the wild type. The results suggested that Hcy caused cerebral interstitial remodeling in brain by distorting the extracellular matrix, thus increasing the blood brain permeability; treatment with muscimol mitigated BBB permeability.
Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
Munish
M
Kumar
Neetu
N
Tyagi
Karni S
KS
Moshal
Utpal
U
Sen
S B
SB
Pushpakumar
Thomas
T
Vacek
David
D
Lominadze
Suresh C
SC
Tyagi
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D001929:Brain Edema / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004396:Coloring Agents / Q000493:pharmacokinetics; D015140:Dementia, Vascular / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D005070:Evans Blue / Q000493:pharmacokinetics; D016326:Extracellular Matrix Proteins / Q000187:drug effects / Q000378:metabolism; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology; D058785:GABA-A Receptor Agonists; D006710:Homocysteine / Q000378:metabolism*; D006712:Homocystinuria / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009118:Muscimol / Q000494:pharmacology / Q000627:therapeutic use; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D004396:Coloring Agents; D016326:Extracellular Matrix Proteins; D018755:GABA Agonists; D058785:GABA-A Receptor Agonists; D011963:Receptors, GABA-A; D006710:Homocysteine; D009118:Muscimol; D005070:Evans Blue