Mg(++)-induced endothelial cell migration: substratum selectivity and receptor-involvement

Area of Science:

• Cell Biology
• Angiogenesis Research
• Extracellular Matrix Interactions

Background:

• Endothelial cell activation, crucial for angiogenesis, involves cell spreading and migration influenced by microenvironmental signals.
• Transmembrane calcium (Ca++) influx is essential for endothelial cell motility and spreading.
• Extracellular divalent cations, specifically Mg++ and Ca++, were investigated for their potential roles in regulating human umbilical vein endothelial cell (HUVEC) behavior.

Purpose of the Study:

• To investigate the hypothesis that extracellular Mg++ and Ca++ regulate HUVEC spreading and act as chemoattractants.
• To elucidate the mechanisms underlying Mg++ and Ca++ mediated endothelial cell responses.

Main Methods:

• Assessing HUVEC spreading on various extracellular matrix substrata with different Mg++ and Ca++ concentrations.
• Utilizing checkerboard analysis to evaluate Mg++ and Ca++ as chemoattractants for HUVEC migration on coated filters.
• Investigating the role of Mg++ in cell motility and energy production using oligomycin.
• Examining the signaling pathways involved in Mg++-stimulated chemotaxis using inhibitors like pertussis toxin, d-erythrosphingosine, and tyrphostin B48.

Main Results:

• Extracellular Mg++ significantly enhanced HUVEC spreading on multiple matrices, while Ca++ promoted spreading only on vitronectin.
• Mg++ demonstrated potent chemoattractant activity for HUVEC migration on gelatin and type IV collagen, but not vitronectin.
• Checkerboard analysis revealed Mg++ induces both chemokinetic and chemotactic migration, with optimal effects at 0.1 mM and 10 mM, respectively.
• Mg++-stimulated chemotaxis was significantly inhibited by pertussis toxin, d-erythrosphingosine, and tyrphostin B48, suggesting involvement of Gi protein-coupled receptors, protein kinase C, and protein tyrosine phosphorylation.

Conclusions:

• Extracellular Mg++ functions as a significant chemoattractant for endothelial cells, distinct from its potential role in cellular energy metabolism.
• Mg++-induced chemotaxis appears to be mediated via a Gi protein-coupled receptor pathway, requiring protein kinase C activity and protein tyrosine phosphorylation.
• These findings identify Mg++ as a novel, receptor-mediated chemoattractant that regulates endothelial cell behavior during angiogenesis.