Nrf2 deficiency impairs atherosclerotic lesion development but promotes features of plaque instability in hypercholesterolemic mice
Anna-Kaisa Ruotsalainen, Jari P Lappalainen, Emmi Heiskanen, Mari Merentie, Virve Sihvola, Juha Näpänkangas, Line Lottonen-Raikaslehto, Emilia Kansanen, Simone Adinolfi, Kai Kaarniranta, Seppo Ylä-Herttuala, Matti Jauhiainen, Eija Pirinen, Anna-Liisa LevonenCardiovascular Research2018
AIMS: Oxidative stress and inflammation play an important role in the progression of atherosclerosis. Transcription factor NF-E2-related factor 2 (Nrf2) has antioxidant and anti-inflammatory effects in the vessel wall, but paradoxically, global loss of Nrf2 in apoE deficient mice alleviates atherosclerosis. In this study, we investigated the effect of global Nrf2 deficiency on early and advanced atherogenesis in alternative models of atherosclerosis, LDL receptor deficient mice (LDLR-/-) and LDLR-/- mice expressing apoB-100 only (LDLR-/-ApoB100/100) having a humanized lipoprotein profile. METHODS AND RESULTS: LDLR-/- mice were fed a high fat diet (HFD) for 6 or 12 weeks and LDLR-/-ApoB100/100 mice a regular chow diet for 6 or 12 months. Nrf2 deficiency significantly reduced early and more advanced atherosclerosis assessed by lesion size and coverage in the aorta in both models. Nrf2 deficiency in LDLR-/- mice reduced total plasma cholesterol after 6 weeks of HFD and triglycerides in LDLR-/-ApoB100/100 mice on a chow diet. Nrf2 deficiency aggravated aortic plaque maturation in aged LDLR-/-ApoB100/100 mice as it increased plaque calcification. Moreover, approximately 36% of Nrf2-/-LDLR-/-ApoB100/100 females developed spontaneous myocardial infarction or sudden death at 5 to 12 months of age. Interestingly, Nrf2 deficiency increased plaque instability index, enhanced plaque inflammation and calcification, and reduced fibrous cap thickness in brachiocephalic arteries of LDLR-/-ApoB100/100 female mice at age of 12 months. CONCLUSION(S): Absence of Nrf2 reduced atherosclerotic lesion size in both atherosclerosis models, likely via systemic effects on lipid metabolism. However, Nrf2 deficiency in aged LDLR-/-ApoB100/100 mice led to an enhanced atherosclerotic plaque instability likely via increased plaque inflammation and oxidative stress, which possibly predisposed to myocardial infarction and sudden death.