The proinflammatory actions of angiotensin II are dependent on p65 phosphorylation by the IkappaB kinase complex.
The vasoactive hormone angiotensin II (Ang II) probably triggers inflammatory cardiovascular diseases by activating transcription factors such as NF-kappaB. We describe here a novel mode of NF-kappaB activation in cultured vascular smooth muscle cells exposed to Ang II. Ang II treatment resulted in an increase in the phosphotransferase activity of the IKK complex, which was mediated through the AT1 receptor subtype. The typical phosphorylation and proteasome-dependent degradation of the NF-kappaB inhibitor IkappaBalpha were not observed. Rather, Ang II treatment of vascular smooth muscle cells led to the phosphorylation of p65 on serine 536, a signal detected in both the cytoplasm and the nuclear compartments. The use of pharmacological inhibitors that inhibit the activation of MEK by Ang II revealed that phosphorylation of p65 on serine 536 did not require the MEK-ERK-RSK signaling pathway. On the other hand, specifically targeting the IKKbeta subunit of the IKK complex by overexpression of a dominant negative version of IKKbeta (IKKbeta K44A) or silencing RNA technology demonstrated that the IKKbeta subunit of the IKK complex was responsible for the detected phosphoserine 536 signal in Ang II-treated cells. Characterization of the signaling pathway leading to activation of the IKK complex by Ang II revealed that neither epidermal growth factor receptor transactivation nor the phosphatidylinositol 3-kinase-AKT signaling cascade were involved. Collectively, our data demonstrate that the proinflammatory activity of Ang II is independent of the classical pathway leading to IkappaBalpha phosphorylation and degradation but clearly depends on the recruitment of an IKK complex signaling cascade leading to phosphorylation of p65 on serine 536.
Douillette
Annie
A
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Bibeau-Poirier
Annie
A
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Gravel
Simon-Pierre
SP
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Clément
Jean-François
JF
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Chénard
Valérie
V
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Moreau
Pierre
P
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Servant
Marc J
MJ
Faculty of Pharmacy, University of Montreal, Montreal, Quebec H3C 3J7, Canada. Electronic address: marc.servant@umontreal.ca.
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D007249:Inflammation / Q000139:chemically induced*; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D051996:Transcription Factor RelA / Q000378:metabolism*
D051996:Transcription Factor RelA; D000804:Angiotensin II; D051550:I-kappa B Kinase