Nrf2 in bone marrow-derived cells positively contributes to the advanced stage of atherosclerotic plaque formation

Abstract

Atherosclerosis is the major etiology underlying myocardial infarction and stroke, and strategies for preventing atherosclerosis are urgently needed. In the context of atherosclerosis, the deletion of the Nrf2 gene, which encodes a master regulator of the oxidative stress response in mammals, reportedly attenuates atherosclerosis formation. However, the precise mechanisms of protection against atherosclerosis are largely unknown. To further clarify the role of Nrf2 in atherosclerosis in vivo, we performed a time course analysis of atherosclerosis development utilizing an ApoE knockout (KO) mouse model. The results demonstrate that oil red O-stainable lesions were similar in size 5 weeks after the initiation of an HFC (high fat and high cholesterol) diet, but the lesions were markedly attenuated in the Nrf2 and ApoE double KO mice (A0N0 mice) compared with the lesions in the ApoE KO mice (A0N2 mice) at 12 weeks. Consistent with these results, the immunohistochemical analysis revealed that Nrf2 activation is observed in late-stage atherosclerotic plaques but not in earlier lesions. The RT-qPCR analysis of 12-week atherosclerotic plaques revealed that Nrf2 target genes, such as Ho-1 and SLPI, are expressed at significantly lower levels in the A0N0 mice compared with the A0N2 mice, and this change was associated with a decreased expression of macrophage M1-subtype genes Arginase II and inducible NO synthase in the A0N0 mice. Furthermore, the bone marrow (BM) transplantation (BMT) analysis revealed that the Nrf2 activity in the BM-derived cells contributed to lesion formation. Therefore, our study has characterized the positive role of Nrf2 in the BM-derived cells during the development of atherosclerosis, which suggests that Nrf2 may influence the inflammatory reactions in the plaques.

Keywords: A0N0; A0N2; ApoE; ApoE KO and Nrf2 KO; ApoE KO and Nrf2 WT; ApoE knockout mice; ArgI; ArgII; Atherosclerosis; BM; BMT; CHO; CM; Cholesterol; Gclm; HDL; HFC diet; Ho-1; ICAM-1; IL-6; KO; LDL; Macrophage polarization; NAD(P)H dehydrogenase, quinone 1; NF-E2-related factor 2; Nqo1; Nrf2; SLPI; Srxn1; TG; TNF-α; VCAM-1; VLDL; WT; apolipoprotein E; arginase I; arginase II; bone marrow; bone marrow transplantation; cholesterol; chylomicron; glutamate-cysteine ligase, modifier subunit; heme oxygenase-1; high fat and high cholesterol diet; high-density lipoprotein; iNOS; inducible nitric oxide synthase; intercellular cell adhesion molecule 1; interleukin-6; knockout; low density lipoprotein; oxLDL; oxidized LDL; secretory leukocyte protease inhibitor; sulfiredoxin 1 homolog; triglyceride; tumor necrosis factor α Txnrd1, thioredoxin reductase 1; vascular cell adhesion molecule 1; very low density lipoprotein; wild type.