Lysophosphatidylcholine inhibits endothelial cell migration by increasing intracellular calcium and activating calpain

Abstract

Objective - Endothelial cell (EC) migration, essential for reestablishing arterial integrity after vascular injury, is inhibited by oxidized LDL (oxLDL) and lysophosphatidylcholine (lysoPC) that are present in the arterial wall. We tested the hypothesis that a mechanism responsible for lysoPC-induced inhibition is increased intracellular free calcium concentration ([Ca2+]i). Methods and Results - LysoPC, at concentrations that inhibit in vitro EC migration to 35% of control, increased [Ca2+]i levels 3-fold. These effects of lysoPC were concentration dependent and reversible. LysoPC induced Ca2+ influx within 10 minutes, and [Ca2+]i remained elevated for 2 hours. The calcium ionophore A23187 also increased [Ca2+]i and inhibited EC migration. Chelators of intracellular Ca2+ (BAPTA/AM and EGTA/AM) and nonvoltage-sensitive channel blockers (lanthanum chloride and gadolinium chloride) blunted the lysoPC-induced [Ca2+]i rise and partially preserved EC migration. After lysoPC treatment, calpain, a calcium-dependent cysteine protease, was activated, and cytoskeletal changes occurred. Calpain inhibitors (calpastatin, MDL28170, and calpeptin) added before lysoPC prevented cytoskeletal protein cleavage and preserved EC migration at 60% of control levels. Conclusions - LysoPC increases [Ca2+]i. In turn, activating calpains that can alter the cytoskeleton are activated and EC migration is inhibited.