Eicosapentaenoic acid inhibits Ca2+ mobilization and PKC activity in vascular smooth muscle cells.
BACKGROUND
Eicosapentaenoic acid is a fish oil fatty acid that has been shown to decrease blood pressure (BP) in humans. The mechanism by which this fatty acid produces this effect is unknown. Angiotensin II increases BP by inducing vasoconstriction of vascular smooth muscle cells, an event that is mediated by an increase of intracellular calcium and an increase of protein kinase C activity.


METHODS
We determined the effects of eicosapentaenoic acid on angiotensin II-induced calcium signaling, and protein kinase C activity in cultured rat aortic smooth muscle cells. Incorporation of eicosapentaenoic acid into cell phospholipids was determined by gas chromatography/mass spectrometry. Intracellular calcium concentration was determined using fura-2, and protein kinase C activity was assessed by an ELISA assay using a phospho-specific antiserum for protein kinase C substrates.


RESULTS
We found that eicosapentaenoic acid was incorporated into cell phospholipids within 20 min. Eicosapentaenoic acid (10 or 25 micromol/L) did not alter basal intracellular calcium concentration, but decreased the peak response to 100 nmol/L angiotensin II. Eicosapentaenoic acid also decreased the amount of calcium released by thapsigargin, a drug that releases calcium from the sarcoplasmic reticulum, and decreased cation influx after angiotensin II stimulation. Angiotensin II stimulated phosphorylation of protein kinase C substrates. Preincubation of cells with 10 or 25 micromol/L eicosapentaenoic acid significantly inhibited this phosphorylation.


CONCLUSIONS
Our results demonstrate that acute incorporation of eicosapentaenoic acid into vascular smooth muscle cell phospholipids inhibits intracellular calcium mobilization and protein kinase C activation. These are potential mechanisms by which eicosapentaenoic acid reduces vasoconstriction.
Nyby
Michael D
MD
UCLA School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA. mnyby@ucla.edu
Hori
Mark T
MT
Ormsby
Bernard
B
Gabrielian
Ara
A
Tuck
Michael L
ML
D000804:Angiotensin II / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001013:Aorta, Thoracic / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D023421:Models, Animal; D008955:Models, Cardiovascular; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D010743:Phospholipids; D000804:Angiotensin II; D015118:Eicosapentaenoic Acid; D011493:Protein Kinase C; D002118:Calcium