The p38 mitogen-activated protein kinase pathway is involved in the regulation of heme oxygenase-1 by acidic extracellular pH in aortic smooth muscle cells.
Extracellular acidosis (EA) regulates Heme Oxygenase-1 (HO-1) expression in vascular smooth muscle cells via transcriptional and posttranscriptional mechanisms but the signaling pathways involved are not known. We examined the role of Mitogen-Activated Protein Kinase (MAPK) pathways in HO-1 regulation by EA. Primary rat aortic smooth muscle cells were exposed to EA or physiologic pH. Levels of the total and phosphorylated forms of p38, extracellular signal-regulated protein kinases1/2 (ERK1/2), c-Jun N-terminal kinases/stress-activated protein kinases (JNK1/2), and HO-1 protein were assessed by Western analysis and HO-1 mRNA levels were assessed by quantitative PCR. Inhibition of p38 MAPK was achieved with the chemical inhibitor SB203580, or adenoviral infection of a dominant-negative form of p38alpha. Phospho p38 MAPK activity was evaluated with an in vitro kinase activity assay. Binding of Activator Protein-1 (AP-1), a known target of MAPK pathways, was assessed by Electromobility shift assay (EMSA). EA induced phosphorylation of p38 MAPK in a biphasic manner while total p38 was unchanged. EA did not alter levels of phospho ERK 1/2 and phospho JNK 1/2. There was increased phospho p38 MAPK activity in the setting of EA which preceded the induction of HO-1. Inhibition of phospho p38 activity with either SB20358 or a dominant negative p38alpha oligonucleotide abrogated the induction of HO-1 by EA. Increased specific binding of AP-1 in the setting of EA was shown by EMSA. Increased phospho p38 activity precedes and likely mediates HO-1 induction by EA. Increased AP-1 binding may underlie the transcriptional regulation of HO-1 by EA.
Division of Newborn Medicine, Brigham and Women's and Children's Hospitals, Boston, Massachusetts 02115, USA.
Jason
J
Guan
Xinqi
X
Wu
Elena
E
Arons
Helen
H
Christou
D000818:Animals; D001011:Aorta / Q000166:cytology; D001665:Binding Sites; D002465:Cell Movement; D049109:Cell Proliferation; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology*; D032389:Myocytes, Smooth Muscle / Q000201:enzymology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D018808:Transcription Factor AP-1 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D007093:Imidazoles; D011725:Pyridines; D018808:Transcription Factor AP-1; D051547:Heme Oxygenase-1; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580