Hyperlipidemia stimulates the extracellular release of the nuclear high mobility group box 1 protein

Our aim was to evaluate the effect of hyperlipidemia on the activation of endogenous alarmin, the high mobility group box 1 (HMGB1) protein, related to systemic inflammation associated with the progression of experimental atherosclerosis and to establish whether statin treatment regulates the HMGB1 signaling pathway. Hyperlipidemia was induced in vivo in golden Syrian hamsters and in monocyte cell culture (U937) by feeding the animals with a high-fat Western diet and by exposing the cells to hyperlipidemic serum. Blood samples, heart, lung and cells were harvested for biochemical, morphological, Western blot, quantitative polymerase chain reaction and enzyme-linked immunosorbent assay analyses. The data revealed that, in the atherosclerotic animal model, the protein HMGB1 and its gene expression were increased and that fluvastatin treatment significantly reduced the release of HMGB1 into the extracellular space. The cell culture experiments demonstrated the relocation of HMGB1 protein from the nucleus to cytoplasm under hyperlipidemic stress. The high level of detected HMGB1 correlated positively with the up-regulation of the advanced glycation end product receptors (RAGE) in the lung tissue from hyperlipidemic animals. During hyperlipidemic stress, the AKT signaling pathway could be activated by HMGB1-RAGE interaction. These results support the existence of a direct correlation between experimentally induced hyperlipidemia and the extracellular release of HMGB1 protein; this might be controlled by statin treatment. Moreover, the data suggest new potentials for statin therapy, with improved effects on patients with systemic inflammation induced by hyperlipidemia.