Upregulation of Nox4 promotes angiotensin II-induced epidermal growth factor receptor activation and subsequent cardiac hypertrophy by increasing ADAM17 expression.

BACKGROUND: Activation of epidermal growth factor receptor (EGFR) plays an important role in angiotensin II (Ang II)-induced cardiac hypertrophy, but little is known about the underlying mechanism that results in EGFR activation. In this study, we aimed to confirm the important role of nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) in Ang II-induced EGFR activation and subsequent cardiac hypertrophy by upregulating expression of a disintegrin and metalloproteinase (MMP)-17 (ADAM17).

METHODS: Small interference RNA (siRNA) was adopted to knock down ADAM17 or Nox4 expression. Nox4 plasmid was used to construct cardiomyocytes with Nox4 overexpression.

RESULTS: Nox4 and ADAM17 increased in an abdominal artery coarctation-induced model of myocardial hypertrophy. In vitro studies showed that Nox4 was required in Ang II-induced EGFR activation and subsequent myocardial hypertrophy. Nox4 siRNA and Nox4 overexpression demonstrated that Nox4 controlled the transcription and translation of ADAM17. Furthermore, we observed that the ratio of phosphor-EGFR (p-EGFR) to EGFR was significantly reduced by ADAM17 siRNA in hypertrophic cardiomyocytes. Enzyme-linked immunosorbent assay studies revealed that Nox4 and ADAM17 mediated the release of mature heparin-binding EGF-like growth factor (HB-EGF), which played a critical role in the Ang II-induced EGFR activation. Moreover, the results of reactive oxygen species (ROS) scavenging by N-acetyl cysteine (NAC) indicated that ROS were required in the Nox4-mediated upregulation of ADAM17 expression.

CONCLUSIONS: In summary, Nox4 is required in Ang II-induced EGFR activation and subsequent cardiac hypertrophy; it increased the expression of ADAM17, which induced the release of mature HB-EGF. ROS were also required in the Nox4-mediated upregulation of ADAM17 expression.