The LEPIS-HuR-TMOD4 axis regulates hepatic cholesterol homeostasis and accelerates atherosclerosis

Long noncoding RNAs (lncRNAs) play important roles in the progression of atherosclerosis. In this study, we identified an uncharacterized lncRNA, Liver Expressions by PSRC1 Induced Specifically (LEPIS). This study aimed to clarify the mechanism though which LEPIS affects atherosclerosis (AS).

The expression of LEPIS and its potential target, tropomodulin 4 (TMOD4), was increased in the livers of ApoE^-/- mice fed a high-fat diet (HFD). An ApoE^-/- mouse model in which LEPIS or TMOD4 was overexpressed in the liver was established. The plaque load in the aorta was assessed, plasma was collected to measure blood lipid levels, and the liver was collected to study cholesterol metabolism.

We found that both LEPIS and TMOD4 increased the AS burden and reduced hepatic cholesterol levels. A further study revealed that LEPIS and TMOD4 affected the expression of genes related to hepatic cholesterol homeostasis, including proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein receptor (LDLR), which are closely related to hypercholesterolemia. Mechanistically, human antigen R (HuR), an RNA-binding protein (RBP), was shown to be critical for the regulation of TMOD4 by LEPIS. Furthermore, we found that verexpression of LEPIS promoted the shuttling of HuR from the nucleus to the cytoplasm, enhanced the stability of TMOD4 mRNA, and in turn promoted the expression of TMOD4. In addition, TMOD4 was found to affect intracellular cholesterol levels through PCSK9.

These results suggest that the LEPIS-HuR-TMOD4 axis is a potential intervention target for dysregulated hepatic cholesterol homeostasis and AS and may provide the basis for further reductions in the circulating LDL-C concentration and arterial plaque burden.