Characterization of platelet-derived growth factor-induced p38 mitogen-activated protein kinase activation in vascular smooth muscle cells.
BACKGROUND
The mitogen-activated protein (MAP) kinase super-family plays a crucial role in cell growth and differentiation and even in programmed cell death in response to diverse extracellular stimuli. The platelet-derived growth factor (PDGF)-BB is well known to promote the proliferation of vascular smooth muscle cells (VSMC) via extracellular-regulated protein kinases (ERKs), leading to the development of cardiovascular diseases. However, it has not yet been clarified whether PDGFs that include other isoforms can activate the other parallel signal transduction pathways, c-jun NH2-terminal protein kinase (JNK) and p38 MAP kinase (p38), in VSMC. In this study, we investigated the effect of PDGFs on p38 activation in cultured rat VSMC.


METHODS
After stimulation by PDGFs with SB-203580 or PD-98059, the cells were solubilized, and the expressions of MAP kinases, MAP kinase kinases (MKKs), phosphorylated DNA-binding proteins, and cyclooxigenases (COXs) were examined by immunoblot analysis.


RESULTS
PDGFs activated p38 phosphorylation dose-dependently, and the phosphorylations were specifically inhibited by SB-203580 but not by PD-98059. PDGFs also activated the phosphorylation of MKK 3/MKK 6 but not that of either stress-activated protein kinase/ERK kinase or JNK. PDGFs affected the activation of a cyclic AMP response-element binding protein, which was inhibited by SB-203580. However, the activating transcription factor-2 was not activated by PDGFs. Interestingly, the stimulation of PDGFs for 72 h enhanced the level of COX-2, and these levels were decreased by SB-203580.


CONCLUSIONS
These results have clarified that PDGFs activate the p38 cascade via an MKK 3/6 pathway, independently of the ERK cascade, and subsequently regulate the level of COX-2 in rat VSMC, providing that PDGFs influence the inflammatory process in the vascular wall.
Yamaguchi
H
H
Third Department of Internal Medicine, Yamagata University School of Medicine, Yamagata, Japan.
Igarashi
M
M
Hirata
A
A
Tsuchiya
H
H
Susa
S
S
Tominaga
M
M
Daimon
M
M
Kato
T
T
D051698:Activating Transcription Factor 2; D000818:Animals; D001011:Aorta / Q000166:cytology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015151:Immunoblotting; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6; D020935:MAP Kinase Signaling System; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism* / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D051698:Activating Transcription Factor 2; C497107:Atf2 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D010982:Platelet-Derived Growth Factor; D014157:Transcription Factors; D011451:Prostaglandin-Endoperoxide Synthases; D011505:Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6; D020929:Mitogen-Activated Protein Kinase Kinases