Role of NAD(P)H oxidase in angiotensin II-induced JAK/STAT signaling and cytokine induction

Abstract

Inflammatory processes involve both synthesis of inflammatory cytokines, such as interleukin-6 (IL-6), and the activation of their distinct signaling pathways, eg, the janus kinases (JAKs) and signal transducers and activators of transcription (STAT). Superoxide (O2-) anions activate this signaling cascade, and the vasoconstrictor angiotensin II (Ang II) enhances the formation of O2- anions via the NAD(P)H oxidase system in rat aortic smooth muscle cells. Ang II activates the JAK/STAT cascade via its type 1 (AT1) receptor and induces synthesis and release of IL-6. Therefore, we investigated the role of O2- anions generated by the NAD(P)H oxidase system on the Ang II activation of the JAK/STAT cascade and its impact on IL-6 synthesis. Ang II stimulation of rat aortic smooth muscle cells induced a rapid increase in O2- anions determined by laser fluoroscopy, which can be abolished by DPI, a flavoprotein inhibitor. Ang II-induced phosphorylation of JAK2, STAT1α/β, STAT3, and IL-6-synthesis can be abolished by DPI, as determined by immunoprecipitations and Northern blot analysis. Electroporation of neutralizing antisera targeted against p47(phox), a NAD(P)H oxidase subunit, abolished Ang II-induced JAK/STAT activation and IL-6 synthesis. Inhibition of JAK2 by its inhibitor AG490 (10 μmol/L) blocked not only JAK2 activation but also IL-6 synthesis. These results suggest that stimulation of the JAK/STAT cascade by Ang II requires O2- anions generated by the NAD(P)H oxidase system, and O2- anion-dependent activation of the JAK/STAT cascade seems to be additionally involved in Ang II-induced IL-6 synthesis. Thus, Ang II-induced inflammatory effects seem to require O2- anions generated by the NAD(P)H oxidase system.