The phenotypic properties of the endothelium are subject to modulation by o
xidative stress, and the c-dun N-terminal kinase (JNK) pathway is important
in mediating cellular responses to stress, although activation of this pat
hway in endothelial cells has not been fully characterized. Therefore, we e
xposed endothelial cells to hydrogen peroxide (H2O2) and observed rapid act
ivation of JNK within 15 min that involved phosphorylation of JNK and c-Jun
and induction of AP-1 DNA binding activity, Inhibition of protein kinase C
and phosphoinositide 3-kinase did not effect JNK activation. In contrast,
the tyrosine kinase inhibitors, genistein, herbimycin A, and 4-amino-5-(4-c
hlorophenyl)-7-(t-butyl)pyrazolo[3,4-D]pyrimidine (PP2) significantly atten
uated H2O2-induced JNK activation as did endothelial cell adenoviral transf
ection with a dominant-negative form of Src, implicating Src as an upstream
activator of JNK, Activation of JNK by H2O2 was also inhibited by AG1478 a
nd antisense oligonucleotides directed against the epidermal growth factor
receptor (EGFR), implicating the EGFR in this process. Consistent with this
observation, H2O2 stimulated EGFR tyrosine phosphorylation and complex for
mation with Shc-Grb2 that was abolished by PP2, implicating Src in H2O2-ind
uced EGFR activation. Tyrosine phosphorylation of the EGFR by H2O2 did not
involve receptor autophosphorylation at Tyr(1173) as assessed by an autopho
sphorylation-specific antibody. These data indicate that H2O2-induced JNK a
ctivation in endothelial cells involves the EGFR through an Src-dependent p
athway that is distinct from EGFR ligand activation. These data represent o
ne potential pathway for mediating oxidative stress-induced phenotypic chan
ges in the endothelium.