Abstract 13040: Repeated Social Defeat Stress Enhances Neutrophil Extracellular Traps Formation in vivo and in vitro: Implication in the Exaggerated Atherosclerosis in Chronic Social Stress-exposed Apoe-/- Mice
Introduction: Neutrophil extracellular traps (NETs) has been reported to promote atherosclerosis through induction of NETosis, a new type of neutrophil cell death; however, the role of NETosis in psychosocial stress-induced atherosclerosis remains undefined.
Methods and Results: Eight-week-old male apoE-/- mice were exposed to the repeated social defeat (RSD) by housing with a larger CD-1 mice in a shared home cage with a clear perforated divider. They were repeatedly subjected to vigorous physical contact for 5-10 min each day on 10 consecutive days. Control mice were housed in the same gage without physical contact. After 6 weeks of high-cholesterol diet feeding, atherosclerotic lesion area of the aortic root was significantly increased in RSD mice compared with control mice (19.4% vs 13.9%, P < 0.05). There was no significant difference in body weight, food intake, mean blood pressure, and lipid profile between the 2 groups. Although both of Ly6G-positive and Mac3-positive area in immunofluorescent staining were comparable between the 2 groups, Ly6G-positive area in RSD mice was much strongly co-localized with MPO (16.4% vs. 6.6%; P < 0.05) and H3Cit (15.1% vs. 9.0%; P < 0.05), suggesting the augmented NETosis in RSD mice. Consistently, serum IL-1β level was markedly higher in RSD mice (2.9-fold; P < 0.05). The percentages of circulating neutrophils (Ly6G+CD11b+F4/80-CD11c-) were significantly increased in RSD mice compared with control mice (27.1% vs. 13.0%; P < 0.05), whereas the fractions of circulating inflammatory monocytes (Lin-CD11b+Ly6C+) and bone marrow (BM) monocyte-lineage progenitor cells were equivalent between the 2 groups. To further examine the NETs formation of individual neutrophils in vitro, BM neutrophils (Ly6G+) were isolated by flow cytometry and stimulated by PMA for 4 hr. The percentages of MPO- and H3Cit-positive cells were significantly increased by 2.5-fold in RSD mice compared with control mice (P < 0.01).
Conclusions: Our findings demonstrated for the first time that RSD promotes NETs formation in BM neutrophils as well as in atherosclerotic lesions, which precede high-cholesterol diet-induced monocytosis, suggesting that NETosis could be a new therapeutic target in psychosocial stress-induced atherosclerosis.
Author Disclosures: K. Yamamoto: None. H. Yamada: None. K. Terada: None. S. Motoyama: None. N. Wada: None. M. Saburi: None. M. Kikai: None. N. Wakana: None. S. Matoba: None.
- © 2016 by American Heart Association, Inc.