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GABA receptors ameliorate Hcy-mediated integrin shedding and constrictive collagen remodeling in microvascular

Suresh Shastry1, Neetu Tyagi, Karni S Moshal

  • 1Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, KY, USA.

Cell Biochemistry and Biophysics
|June 8, 2006
PubMed

Insights

High homocysteine (Hcy) levels damage brain endothelial cells by increasing metalloproteinase activity and shedding beta-1 integrin. Gamma-aminobutyric acid (GABA) receptors protect against Hcy-induced cerebrovascular remodeling.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Biochemistry

Background:

  • Mammalian endothelial cells lack cystathionine beta-synthetase (CBS), leading to homocysteine (Hcy) accumulation and endothelial toxicity.
  • Hcy increases matrix metalloproteinase (MMP) activity, causing integrin shedding in microvascular endothelial cells (MVEC).
  • Hcy interferes with inhibitory gamma-aminobutyric acid (GABA)-A receptors, suggesting a potential role in cerebrovascular remodeling.

Purpose of the Study:

  • To investigate the hypothesis that Hcy induces MVEC remodeling by increasing metalloproteinase activity and beta-1 integrin shedding through GABA-A/B receptor inactivation.
  • To explore Hcy's role as an excitatory neurotransmitter in cerebrovascular remodeling.
  • To elucidate the mechanisms underlying Hcy-induced endothelial dysfunction.

Main Methods:

  • Isolation and culture of mouse brain MVEC.
  • Immunolabeling and Western blot analysis to detect GABA-A receptors.
  • Zymography to measure MMP-2 activity.
  • Western blot analysis for Tissue Inhibitor of Metalloproteinase (TIMP) and A Disintegrin and Metalloproteinase (ADAM)-12 levels.
  • Measurement of beta-1 integrin in the cell medium.

Main Results:

  • Hcy dose- and time-dependently increased MMP-2 activity.
  • GABA-A/B receptor agonists (muscimol, baclofen) ameliorated Hcy-induced MMP-2 activation and beta-1 integrin shedding.
  • Hcy increased TIMP-1 and TIMP-3, decreased TIMP-4, and robustly increased ADAM-12.
  • Hcy facilitated beta-1 integrin shedding, which was reversed by GABA receptor agonists.
  • GABA receptor activation counteracted Hcy's effects on metalloproteinase expression, integrin shedding, and collagen remodeling.

Conclusions:

  • Hcy acts as an excitatory neurotransmitter in the cerebrovasculature, promoting remodeling.
  • Hcy-induced endothelial damage is mediated by increased metalloproteinase activity and beta-1 integrin shedding.
  • GABA receptors play a protective role against Hcy-induced cerebrovascular remodeling.

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