Sex hormones affect the calcium signaling response of human arterial cells to LDL.
The present study was designed to examine the role of calcium-dependent signal transduction as a common link between the atherogenic effect of LDL and the mitigating influence of sex hormones in aortic endothelial (EC) and smooth muscle cells (SMC). Human aortic EC and SMC were pre-incubated for 48 hr in media containing no hormone, 17-beta-estradiol (20 ng/ml) or testosterone (300 ng/ml). Low density lipoprotein (N-LDL) or its minimally oxidized species (Ox-LDL) was added to the media at different concentrations (0, 2, 5, 10, 20, and 40 micrograms protein/ml), and changes in cytosolic calcium [Ca+2]i were measured by spectrofluorometric analysis using a Fura 2-AM indicator. Cell viability was determined with a 51chromium release assay. In EC, exposure to N-LDL resulted in a weak and unsustained increase in [Ca+2]i, (max. 21.9 +/- 4.6%) while a more marked rise was seen in SMC (max. 79.1 +/- 11.5%; P < 0.005). There was an amplified response to the more atherogenic Ox-LDL in both EC (max. 130.9 +/- 22.9%) and SMC (max. 240.5 +/- 14.2%; P < 0.0002). Estrogen was associated with a lower resting level of [Ca+2]i in both cell types, and resulted in a significant, dose-dependent inhibition of cytosolic calcium mobilization in SMC exposed to Ox-LDL (P < 0.05). Alternatively, testosterone increased cytosolic calcium response in SMC exposed to either N-LDL (P < 0.05) or Ox-LDL (P < 0.05). Similar trends were seen in EC, but failed to reach statistical significance. These changes could not be attributed to cell toxicity. Sex hormones may modulate the atherogenic potential of LDL by influencing intracellular, calcium-dependent signaling mechanisms.
Wells
K E
KE
Case Western Reserve University, MetroHealth Medical Center, Cleveland, Ohio 44109, USA.
Miguel
R
R
Alexander
J J
JJ
D000704:Analysis of Variance; D001011:Aorta; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002860:Chromium Radioisotopes; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000378:metabolism* / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D010084:Oxidation-Reduction; D015398:Signal Transduction / Q000187:drug effects; D013739:Testosterone / Q000494:pharmacology*; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
D002860:Chromium Radioisotopes; D008077:Lipoproteins, LDL; D017392:Thiobarbituric Acid Reactive Substances; D013739:Testosterone; D004958:Estradiol; D002118:Calcium