Lack of IκBNS promotes cholate-containing high-fat diet-induced inflammation and atherogenesis in low-density lipoprotein (LDL) receptor-deficient mice

Kenichi Kitamura; Kikuo Isoda; Koji Akita; Katsutoshi Miyosawa; Tomoyasu Kadoguchi; Kazunori Shimada; Hiroyuki Daida

doi:10.1016/j.ijcha.2019.03.004

Lack of IκBNS promotes cholate-containing high-fat diet-induced inflammation and atherogenesis in low-density lipoprotein (LDL) receptor-deficient mice

Int J Cardiol Heart Vasc. 2019 Mar 27:23:100344. doi: 10.1016/j.ijcha.2019.03.004. eCollection 2019 Jun.

Authors

Kenichi Kitamura¹, Kikuo Isoda¹, Koji Akita¹, Katsutoshi Miyosawa¹, Tomoyasu Kadoguchi¹, Kazunori Shimada¹, Hiroyuki Daida¹

Affiliation

¹ Department of Cardiovascular Medicine, Juntendo University Graduate School of Medicine, Hongo, Tokyo, Japan.

Abstract

Background: IκBNS, a nuclear IκB protein, regulates a subset of Toll-like receptor (TLR) dependent genes. A cholate-containing high-fat diet (HFD(CA(+))) induces TLR4 mediated early inflammatory response. The present study aims to clarify that the lack of IκBNS promotes atherogenesis in low-density lipoprotein receptor-deficient (LDLr^-/-) mice fed HFD(CA(+)) compared with those fed a cholate-free HFD (HFD(CA(-))).

Methods and results: Mice that lacked IκBNS (IκBNS^-/-) were crossed with LDLr^-/- mice and formation of atherosclerotic lesions was analyzed after 6-week consumption of HFD(CA(+)) or HFD(CA(-)). IκBNS^-/-/LDLr^-/- mice fed HFD(CA(+)) (IκBNS^-/-/LDLr^-/-(CA(+))) showed a 3.5-fold increase of atherosclerotic lesion size in the aorta compared with LDLr^-/-(CA(+)) mice (p < 0.01), whereas there was no difference between LDLr^-/-(CA(-)) and IκBNS^-/-/LDLr^-/-(CA(-)) mice. Immunohistochemical analysis of the aortic root revealed that HFD(CA(+)) significantly increased Mac-3 (macrophage)-positive area by 1.5-fold (p < 0.01) and TLR4, interleukin-6 (IL-6) expression by 1.7-fold (p < 0.05) and 1.5-fold (p < 0.05), respectively, in IκBNS^-/-/LDLr^-/-(CA(+)) compared with LDLr^-/---(CA(+)) mice. Furthermore, active STAT3 (pSTAT3)-positive cells were significantly increased by 1.7-fold in the lesions of IκBNS^-/-/LDLr^-/-(CA(+)) compared with LDLr^-/-(CA(+)) mice (p < 0.01). These findings suggest that IκBNS deficiency and HFD(CA(+)) promote atherogenesis in LDLr^-/- mice via TLR4/IL-6/STAT3 pathway. Finally, we showed that the monocytes from peripheral blood of IκBNS^-/-/LDLr^-/-(CA(+)) mice were found to contain the highest proportion of Ly6C^hi monocytes among the four groups, suggesting that lack of IκBNS enhanced inflammation in response to HFD(CA(+)) feeding.

Conclusions: The present study is the first to demonstrate that the activation of innate immune system using HFD(CA(+)) induced significant inflammation and atherogenesis in IκBNS^-/-/LDLr^-/- compared with LDLr^-/- mice.

Keywords: Atherosclerosis; Cholate; Inflammation; Innate immune system; IκBNS.