Tumor Necrosis Factor - Alpha Is Essential for Angiotensin II-Induced Ventricular Remodeling: Role for Oxidative Stress

The functional crosstalk between angiotensin II (Ang II) and tumor necrosis factor (TNF)-alpha has been shown to cause adverse left ventricular remodeling and hypertrophy in hypertension. Previous studies from our lab showed that mice lacking TNF-alpha (TNF-alpha(-/-)) have attenuated hypertensive response to Ang II; however, the signaling mechanisms involved are not known. In this study, we investigated the signaling pathways involved in the Ang II and TNF-alpha interaction. Chronic Ang II infusion (1 mu g/kg/min, 14 days) significantly increased cardiac collagen I, collagen III, CTGF and TGF-beta mRNA and protein expression in wild-type (WT) mice, whereas these changes were decreased in TNF-alpha(-/-) mice. TNF-alpha(-/-) mice with Ang II infusion showed reduced myocardial perivascular and interstitial fibrosis compared to WT mice with Ang II infusion. In WT mice, Ang II infusion increased reactive oxygen species formation and the expression of NADPH oxidase subunits, indicating increased oxidative stress, but not in TNF-alpha(-/-) mice. In addition, treatment with etanercept (8 mg/kg, every 3 days) for two weeks blunted the Ang II-induced hypertension (133 +/- 4 vs 154 +/- 3 mmHg, p<0.05) and cardiac hypertrophy (heart weight to body weight ratio, 4.8 +/- 0.2 vs 5.6 +/- 0.3, p<0.05) inWT mice. Furthermore, Ang II-induced activation of NF-kappa B, p38 MAPK, and JNK were reduced in both TNF-alpha(-/-) mice and mice treated with etanercept. Together, these findings indicate that TNF-alpha contributes to Ang II-induced hypertension and adverse cardiac remodeling, and that these effects are associated with changes in the oxidative stress dependent MAPK/TGF-beta/NF-kappa B pathway. These results may provide new insight into the mechanisms of Ang II and TNF-alpha interaction.