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

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 Ly6Chi 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: IκBNS, Cholate, Innate immune system, Inflammation, Atherosclerosis