GP73 enhances the ox-LDL-induced inflammatory response in THP-1 derived macrophages via affecting NLRP3 inflammasome signaling.

Background: Atherosclerosis is a chronic inflammatory disease with its molecular basis incompletely understood. Here, we determined whether the Golgi phosphoprotein 73 (GP73), a novel protein highly related to inflammation and disrupted lipid metabolism, was involved in the development of atherosclerosis.

Methods: Public microarray databases of human vascular samples were analyzed for expression patterns. Apolipoprotein-E-gene-deficient (ApoE-/-) mice (8-week-old) were randomly assigned to either a chow diet group or a high-fat diet group. The levels of serum GP73, lipid profiles and key inflammatory cytokines were determined by ELISA. The aortic root plaque was isolated and used for by Oil Red O staining. PMA-differentiated THP-1 macrophages were transfected with GP73 small interfering RNA (siRNA) or infected with adenovirus expressing GP73, and then stimulated with oxidized low density lipoprotein (ox-LDL). The expressions of pro-inflammatory cytokines and signal pathway key targets were determined by ELISA kit and Western blot respectively. In addition, ichloro-dihydro-fluorescein diacetate (DCFH-DA) was used to measure the intracellular ROS levels.

Results: The expressions of GP73 and NLRP3 were substantially upregulated in human atherosclerotic lesions. There were significant linear correlations between GP73 and inflammatory cytokines expressions. High-fat diet-induced atherosclerosis and increased levels of plasma inflammatory mediators (IL-1β, IL-18, and TNF-α) were observed in ApoE-/- mice. Besides, the expressions of GP73 in the aorta and serum were significantly upregulated and positively correlated with the NLRP3 expression. In the THP-1 derived macrophages, ox-LDL treatment upregulated the expressions of GP73 and NLRP3 proteins and activated the inflammatory responses in a concentration-dependent and time-dependent manner. Silencing of GP73 attenuated the inflammatory response and rescued the decreased migration induced by ox-LDL, inhibiting the NLRP3 inflammasome signaling and the ROS and p-NF-κB activation.

Conclusions: We demonstrated that GP73 promoted the ox-LDL-induced inflammation in macrophages by affecting the NF-κB/NLRP3 inflammasome signaling, and may play a role in atherosclerosis.