Eicosapentaenoic acid suppresses PDGF-induced DNA synthesis in rat mesangial cells: involvement of thromboxane A2.
BACKGROUND
The administration of eicosapentaenoic acid (EPA) derived from marine oils has been shown to suppress vascular myocyte, lymphocyte, keratinocyte, and mesangial cell proliferation in vitro, although the effects are variable and most reports provide fragmented insight into the mechanism(s) responsible for altering cell growth, particularly the relationship of membrane lipid remodeling to changes in cell proliferation. Thus, these studies were designed to elucidate the effects of mesangial cell membrane fatty acid remodeling (induced by EPA) on cell growth, and to define the relevance of changes in the synthesis of growth-modulating eicosanoids.


METHODS
Mesangial cells were grown in RPMI and 17% fetal calf serum, and were subcultured and grown for 48 hours in 17% delipidated serum or delipidated serum supplemented with 0 to 50 micrograms/mL of EPA. Quiescent EPA-loaded and control mesangial cells were subjected to stimulation with 20 ng/mL of platelet-derived growth factor (PDGF) followed by measurement of 3H-thymidine incorporation and cell number.


RESULTS
Mesangial cells remodeled with EPA exhibited a significant decrease in PDGF-stimulated 3H-thymidine incorporation and cell number associated with a reduction in thromboxane A2 (TXA2) in the media. Importantly, the phospholipid fatty acid composition of mesangial cells grown in media enriched with EPA revealed an increase in EPA (0.5 +/- 0.02% to 17.02 +/- 0.52%) coupled with a reciprocal decrease in the precursor for TXA2, arachidonic acid (18.9 +/- 3.17% to 3.55 +/- 0.30%). Blockade of TXA2 synthesis in mesangial cells treated with indomethacin (0.1 to 100 mumol/L) or the specific TXA2 synthase inhibitor, U-63557A (0.1 to 100 mumol/L), evoked a similar reduction in PDGF-stimulated proliferation and TXA2 synthesis. Coincubation of PDGF with the TXA2 mimetic, U-46619 (1 mumol/L), reversed the growth suppression induced by cell membrane remodeling.


CONCLUSIONS
These studies suggest that changes in membrane fatty acid composition induced by EPA modulates PDGF-stimulated proliferation by engendering a change in PDGF-stimulated TXA2 synthesis. Furthermore, we conclude that TXA2 functions as a comitogen for PDGF-stimulated mesangial cell growth.
Schmitz
P G
PG
Department of Internal Medicine, St. Louis University Health Sciences Center, Missouri, USA.
Zhang
K
K
Dalal
R
R
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001572:Benzofurans / Q000494:pharmacology; D002452:Cell Count / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media / Q000378:metabolism; D004247:DNA / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D007213:Indomethacin / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013928:Thromboxane A2 / Q000378:metabolism / Q000502:physiology; D013936:Thymidine / Q000378:metabolism
D001572:Benzofurans; D003470:Culture Media; D004791:Enzyme Inhibitors; D010982:Platelet-Derived Growth Factor; D016718:Arachidonic Acid; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D004247:DNA; D015118:Eicosapentaenoic Acid; C039936:furegrelate; D013936:Thymidine; D007213:Indomethacin