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

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.