Nox2 and Nox4 mediate tumour necrosis factor-α-induced ventricular remodelling in mice

Abstract

Reactive oxygen species (ROS) and pro-inflammatory cytokines are crucial in ventricular remodelling, such as inflammation-associated myocarditis. We previously reported that tumour necrosis factor-α (TNF-α)-induced ROS in human aortic smooth muscle cells is mediated by NADPH oxidase subunit Nox4. In this study, we investigated whether TNF-α-induced ventricular remodelling was mediated by Nox2 and/or Nox4. An intravenous injection of murine TNF-α was administered to a group of mice and saline injection was administered to controls. Echocardiography was performed on days 1, 7 and 28 post-injection. Ventricular tissue was used to determine gene and protein expression of Nox2, Nox4, ANP, interleukin (IL)-1β, IL-2, IL-6, TNF-α and to measure ROS. Nox2 and Nox4 siRNA were used to determine whether or not Nox2 and Nox4 mediated TNF-α-induced ROS and upregulation of IL-1β and IL-6 in adult human cardiomyocytes. Echocardiography showed a significant increase in left ventricular end-diastolic and left ventricular end-systolic diameters, and a significant decrease in the ejection fraction and fractional shortening in mice 7 and 28 days after TNF-α injection. These two groups of mice showed a significant increase in ventricular ROS, ANP, IL-1β, IL-2, IL-6 and TNF-α proteins. Nox2 and Nox4 mRNA and protein levels were also sequentially increased. ROS was significantly decreased by inhibitors of NADPH oxidase, but not by inhibitors of other ROS production systems. Nox2 and Nox4 siRNA significantly attenuated TNF-α-induced ROS and upregulation of IL-1β and IL-6 in cardiomyocytes. Our study highlights a novel TNF-α-induced chronic ventricular remodelling mechanism mediated by sequential regulation of Nox2 and Nox4 subunits.

Signalling mechanisms underlying doxorubicin and Nox2 NADPH oxidase‐induced cardiomyopathy: involvement of mitofusin‐2

“…Similar studies have reported the effective use of siRNAs to knockdown both Nox and Mfn2 and inhibit ROS production and apoptosis in cardiac cells, including HL‐1 cardiomyocytes (Yeh et al, 2011), H9c2 cardiomyocytes, (Shen et al, 2007), cultured neonatal rat cardiomyocytes (Papanicolaou et al, 2011) and mouse ventricular cells (Moe et al, 2011). However, while this investigation found no changes in apoptosis in DOX‐treated HL‐1 cardiomyocytes in the presence of Nox2 or Mfn2 knockdown, it is possible that efficacy of transfection may have influenced the measured endpoint.…”

Endothelial Dysfunction in Tristetraprolin-deficient Mice Is Not Caused by Enhanced Tumor Necrosis Factor-α Expression

“…TNF-␣ has been described to be an important mediator of atherogenesis (42), as well as to regulate Nox expression in cell culture (43) and mouse models (44). Therefore we expected that genetic inactivation of the Tnf-␣ gene in TTP Ϫ/Ϫ mice normalizes the atherogenic phenotype.…”

Role of Tumor Necrosis Factor-α in the Pathogenesis of Atrial Fibrosis and Development of an Arrhythmogenic Substrate

“…The dose of TNF-α injection was chosen from previous studies in mice that have reliably induced systemic and hepatic inflammation 13, 14 and from our pilot studies (described later) to avoid any significant detrimental effects on left ventricular (LV) function. After 16 weeks, animals were killed by being placed in a box connected to a CO2 gas cylinder in which the inflow of gas could be precisely regulated.…”

“…We had previously demonstrated that a single bolus injection of 8 μg/kg TNF-α in mice resulted in an increase in LV size and a decrease in systolic function after 28 days. 14 We therefore used 2 lower doses of TNF-α (2 and 4 μg/kg) in 18 mice (6 for each dose and 6 controls, which received saline injection). Echocardiographic measurements of LV size and function and LA diameter were assessed at baseline and after 4 weeks.…”