Differential regulation of the superoxide dismutase family in the rodent aneurysm model and rat aortic smooth muscle cells

Abstract

Objective. Oxidative stress has been implicated in abdominal aortic aneurysm pathogenesis. This study sought to characterize the relevance of specific superoxide dismutases (SOD) within a family of reactive oxygen catalyzing metalloenzymes, in the rodent aneurysm model and rat aortic smooth muscle cells (RA-SMCs), including Manganese SOD (Mn-SOD), Copper-zinc SOD (Cu, Zn-SOD), and Extracellular SOD (ecSOD). Methods. Male rat infrarenal abdominal aortas were measured and perfused with either porcine pancreatic elastase (6 U/mL) or saline (control). Subsequently, aortic diameters were measured and harvested on postperfusion days 1, 2, 4,∗∗ and 7 ( N = 5–6 per treatment group per day). Male RA-SMCs were incubated for 24 and 72 h in the presence of interleukin-1β (IL-1β, 2 ng/mL). MnSOD, Cu,ZnSOD, and ecSOD, and β-actin expression in aortic tissue and in RA-SMCs was determined by quantitative real-time PCR. Data were analyzed by t-test. Results. Elastase perfused aortic diameters were significantly increased compared to control aortas at postperfusion days 2 (76% versus 39%, P = 0.004), 4 (86% versus 50%, P = 0.04), and 7 (263% versus 46%, P = 0.016). MnSOD mRNA levels in elastase perfused aortas were 6.0 ( P = 0.005), 7.4 ( P < 0.001), and 4.1 times ( P = 0.005) greater than control aortas at postperfusion days 1, 2, and 4, respectively. In RA-SMCs, MnSOD mRNA expression in IL-1β stimulated male were 152.2 ( P = 0.029) and 15.3 times ( P = 0.037) greater than control cells at 24 and 72 h, respectively. No significant differences were observed in Cu, Zn-SOD, and ecSOD expression at any time point studied in elastase perfused aortas; however, there was a slight increase in ecSOD and Cu, Zn-SOD expression in RA-SMCs. Conclusion. Elastase perfused aortic aneurysm formation is associated with early increases in MnSOD expression, which primarily occurs in the mitochondria. Strategies aimed at inhibiting oxidative stress during aneurysm formation should focus on this specific SOD isoform.