Inhibition of reactive oxygen species attenuates aneurysm formation in a murine model

Abstract

Reactive oxygen species (ROS) are increased in human abdominal aortic aneurysms (AAA). NADPH oxidases are the predominant source of superoxide anion (O 2 − ) in the vasculature. Inducible nitric oxide synthase (iNOS) produces significant amount of nitric oxide (NO) during inflammatory processes. We hypothesized that ROS produced by NADPH oxidases and iNOS play an important role in aneurysm formation. We examined this hypothesis using selective blockade of NADPH oxidases and iNOS in a murine model of AAA. Mice, including C57BL/6, iNOS knockout (iNOS −/− ) mice, and its background matched control (C57BL/6), underwent AAA induction by periaortic application of CaCl 2 . Aortic diameter was measured at aneurysm induction and harvest. Beginning 1 week prior to aneurysm induction and continuing to aortic harvest 6 weeks later, one group of the C57BL/6 mice were treated with orally administered apocynin (NADPH oxidase inhibitor). Control mice were given water. The mean diameter and change in diameter of each group were compared with concurrent controls. Aortic levels of the NO metabolite, NO x N(NO 2 and NO 3 ), are significantly increased in CaCl 2 -treated wild type mice. INOS −/− mice are resistant to aneurysm induction. This is associated with reduced expression of matrix metalloproteinase (MMP)-2 and MMP-9 and decreased production of NO x in the aortic tissues. Inhibition of NADPH oxidase by apocynin also blocked aneurysm formation. In conclusion, both iNOS deficiency and NADPH oxidase inhibition suppress aneurysm formation in association with decreased NO x levels. These studies suggest that both the NADPH oxidase and iNOS pathways contribute to ROS production and AAA development.

Regulatory T Cells Prevent Angiotensin II–Induced Abdominal Aortic Aneurysm in Apolipoprotein E Knockout Mice

“…13 It has been reported that ROS generation is markedly upregulated in the aortic aneurysmal tissues, whereas inhibition of ROS production attenuates AAA formation. 3,23 In this study, Tregs treatment substantially reduced the production of ROS in the aortic aneurysmal tissues in ApoE −/− mice, suggesting that blunted oxidative stress may be an important mechanism in preventing AAA formation in our mouse model. NF-κB is a key proinflammatory transcription factor responsible for the regulation of the cytokine network in vascular SMCs.…”

Overexpression of Smooth Muscle Myosin Heavy Chain Leads to Activation of the Unfolded Protein Response and Autophagic Turnover of Thick Filament-associated Proteins in Vascular Smooth Muscle Cells

“…It is therefore surprising that the 16p13.1 duplications implicated in aortic disease may result in increased contractility. Both contraction and increased metabolic stress could lead to increased ATP turnover in SM1 cells, potentially driving increased production of reactive oxygen species, which have been previously associated with aortic disease (58,59). Alternatively, vascular SMCs typically retain a large reserve of unphosphorylated myosin light chain to respond rapidly to changes in biomechanical forces.…”

Cytochrome P450 1B1 Contributes to the Development of Angiotensin II–Induced Aortic Aneurysm in Male Apoe−/− Mice

“…35 The infusion of Ang II for 28 days increased aortic ROSs, as indicated by enhanced oxidized DHE fluorescence intensity in AAA ( Figure 5, A and B), and cardiac NADPH oxidase activity and increased plasma levels of 8-isoprostane, another index of oxidative stress, 36 in Apoe À/À /Cyp1b1 þ/þ mice, which was inhibited by treatment with TMS or by Cyp1b1 gene disruption ( Figure 5, C and D). Ang II increases COX-2 expression in VSMCs via p38 mitogen-activated protein kinase, 37 and this pathway been implicated in the pathogenesis of AAA.…”

“…Treatment with TMS or Cyp1b1 Gene Disruption Minimizes MMP Expression and ECM Degradation in Ang IIeInduced AAA in Apoe À/À /Cyp1b1 þ/þ Mice Aneurysm lesions are characterized by degradation of the ECM components by proteolytic enzymes like MMP-2 and -9 35 ; therefore, we assessed the contribution of CYP1B1 in the expression of MMP and ECM components (collagen, elastin, and a smooth muscle actin) in AAA due to Ang II infusion for 28 days. Increased fluorescence intensity of MMP-2 and -9 staining was observed in the aorta sections from Apoe À/À /Cyp1b1 þ/þ mice infused with Ang II but not in mice concurrently treated with TMS or in Apoe À/À / Cyp1b1 À/À mice ( Figure 4, A and B).…”