Peroxynitrite Footprint in Circulating Neutrophils of Abdominal Aortic Aneurysm Patients is Lower in Statin than in Non-statin Users

Abstract

Objectives: Extensive reactive oxygen and nitrogen species (also reactive species) production is a mechanism involved in abdominal aortic aneurysm (AAA) development. White blood cells (WBCs) are a known source of reactive species. Their production may be decreased by statins, thereby reducing the AAA growth rate. Reactive species production in circulating WBCs of AAA patients and the effect of statins on their production was investigated.

Methods: This observational study investigated reactive species production in vivo and ex vivo in circulating WBCs of AAA patients, using venous blood from patients prior to elective AAA repair (n = 34; 18 statin users) and from healthy volunteers (n = 10). Reactive species production was quantified in circulating WBCs using immunofluorescence microscopy: nitrotyrosine (footprint of peroxynitrite, a potent reactive nitrogen species) in snap frozen blood smears; mitochondrial superoxide and cytoplasmic hydrogen peroxide (both reactive oxygen species) by live cell imaging. Neutrophils, lymphocytes, and monocytes were examined individually.

Results: In AAA patients using statins, the median nitrotyrosine level in neutrophils was 646 (range 422-2059), in lymphocytes 125 (range 74-343), and in monocytes 586 (range 291-663). Median levels in AAA patients not using statins were for neutrophils 928 (range 552-2095, p = .03), lymphocytes 156 (101-273, NS), and for monocytes 536 (range 535-1635, NS). The statin dose tended to correlate negatively with nitrotyrosine in neutrophils (R_s -0.32, p = .06). The median levels in controls were lower for neutrophils 466 (range 340-820, p < .01) and for monocytes 191 (range 102-386, p = .03), but similar for lymphocytes 99 (range 82-246) when compared to the AAA patients. There were no differences in mitochondrial superoxide and cytoplasmic hydrogen peroxide between statin and non-statin users within AAA patients.

Conclusions: It was found that the peroxynitrite footprint in circulating neutrophils and monocytes of AAA patients is higher than in controls. AAA patients treated with statins had a lower peroxynitrite footprint in neutrophils than non-statin users.

Keywords: Abdominal aortic aneurysms; Reactive nitrogen species; Reactive oxygen species; Statin; White blood cells.