OxLDL induces mitogen-activated protein kinase activation mediated via PI3-kinase/Akt in vascular smooth muscle cells.
Oxidized low-density lipoprotein (OxLDL) is a risk factor in atherosclerosis and stimulates multiple signaling pathways, including activation of phosphatidylinositol 3-kinase (PI3-K)/Akt and p42/p44 mitogen-activated protein kinase (MAPK), which are involved in mitogenesis of vascular smooth muscle cells (VSMCs). We therefore investigated the relationship between PI3-K/Akt and p42/p44 MAPK activation and cell proliferation induced by OxLDL. OxLDL stimulated Akt phosphorylation in a time- and concentration-dependent manner, as determined by Western blot analysis. Phosphorylation of Akt stimulated by OxLDL and epidermal growth factor (EGF) was attenuated by inhibitors of PI3-K (wortmannin and LY294002) and intracellular Ca2+ chelator (BAPTA/AM) plus EDTA. Pretreatment of VSMCs with pertussis toxin, cholera toxin, and forskolin for 24 h also attenuated the OxLDL-stimulated Akt phosphorylation. In addition, pretreatment of VSMCs with wortmannin or LY294002 inhibited OxLDL-stimulated p42/p44 MAPK phosphorylation and [3H]thymidine incorporation. Furthermore, treatment with U0126, an inhibitor of MAPK kinase (MEK)1/2, attenuated the p42/p44 MAPK phosphorylation, but had no effect on Akt activation in response to OxLDL and EGF. Overexpression of p85-DN or Akt-DN mutants attenuated MEK1/2 and p42/p44 MAPK phosphorylation stimulated by OxLDL and EGF. These results suggest that the mitogenic effect of OxLDL is, at least in part, mediated through activation of PI3-K/Akt/MEK/MAPK pathway in VSMCs.
Chien
Ming-Wei
MW
Department of Physiology and Pharmacology, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan.
Chien
Chin-Sung
CS
Hsiao
Li-Der
LD
Lin
Ching-Hsuan
CH
Yang
Chuen-Mao
CM
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology*; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D011944:Receptors, Androgen / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
D002118:Calcium; D002772:Cholera Toxin; D005576:Colforsin; D008077:Lipoproteins, LDL; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011944:Receptors, Androgen; D014157:Transcription Factors; C478359:WDR77 protein, human; C099252:oxidized low density lipoprotein; C494918:AKT1 protein, human; C494920:Akt1 protein, rat