Lysophosphatidic acid positively regulates the fluid flow-induced local Ca(2+) influx in bovine aortic endothelial cells.
Using real-time confocal microscopy, we have demonstrated that lysophosphatidic acid (LPA), a bioactive phospholipid existing in plasma, positively regulates fluid flow-induced [Ca(2+)](i) response in fluo 4-loaded, cultured, bovine aortic endothelial cells. The initial increase in [Ca(2+)](i) was localized to a circular area with a diameter of <4 microm and spread concentrically, resulting in a mean global increase in [Ca(2+)](i). The local increase often occurred in a stepwise manner or repetitively during constant flow. The percentage of cells that responded and the averaged level of increase in [Ca(2+)](i) were dependent on both the concentration of LPA (0.1 to 10 micromol/L) and the flow rate (25 to 250 mm/s). The response was inhibited by removing extracellular Ca(2+) or by the application of Gd(3+), an inhibitor of mechanosensitive (MS) channels, but not by thapsigargin, an inhibitor of the endoplasmic reticular Ca(2+)-ATPASE: It was also inhibited by 8-bromo-cGMP, and the inhibition was completely reversed by KT5823, an inhibitor of protein kinase G (PKG). These results suggest that the [Ca(2+)](i) response arises from Ca(2+) influx through Gd(3+)-sensitive MS channels, which are negatively regulated by the activation of PKG. The spatiotemporal properties of the [Ca(2+)](i) response were completely different from those of a Ca(2+) wave induced by ATP, a Ca(2+)-mobilizing agonist. Therefore, we called the phenomenon Ca(2+) spots. We conclude that LPA positively regulates fluid flow-induced local and oscillatory [Ca(2+)](i) increase, ie, the Ca(2+) spots, in endothelial cells via the activation of elementary Ca(2+) influx through PKG-regulating MS channels. This indicates an important role for LPA as an endogenous factor in fluid flow-induced endothelial function.
Ohata
H
H
Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan. ohata@pharm.showa-u.ac.jp
Ikeuchi
T
T
Kamada
A
A
Yamamoto
M
M
Momose
K
K
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology*; D018613:Microscopy, Confocal; D013314:Stress, Mechanical; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014966:Xanthenes / Q000494:pharmacology
D000814:Aniline Compounds; C409648:Fluo 4; D005456:Fluorescent Dyes; D008246:Lysophospholipids; D014966:Xanthenes; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D005682:Gadolinium; C038958:gadolinium chloride; D002118:Calcium