Rosmarinic Acid Increases Macrophage Cholesterol Efflux through Regulation of ABCA1 and ABCG1 in Different Mechanisms.

Lipid dysregulation in diabetes mellitus escalates endothelial dysfunction, the initial event in the development and progression of diabetic atherosclerosis. In addition, lipid-laden macrophage accumulation in the arterial wall plays a significant role in the pathology of diabetes-associated atherosclerosis. Therefore, inhibition of endothelial dysfunction and enhancement of macrophage cholesterol efflux is the important antiatherogenic mechanism. Rosmarinic acid (RA) possesses beneficial properties, including its anti-inflammatory, antioxidant, antidiabetic and cardioprotective effects. We previously reported that RA effectively inhibits diabetic endothelial dysfunction by inhibiting inflammasome activation in endothelial cells. However, its effect on cholesterol efflux remains unknown. Therefore, in this study, we aimed to assess the effect of RA on cholesterol efflux and its underlying mechanisms in macrophages. RA effectively reduced oxLDL-induced cholesterol contents under high glucose (HG) conditions in macrophages. RA enhanced ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) expression, promoting macrophage cholesterol efflux. Mechanistically, RA differentially regulated ABCA1 expression through JAK2/STAT3, JNK and PKC-p38 and ABCG1 expression through JAK2/STAT3, JNK and PKC-ERK1/2/p38 in macrophages. Moreover, RA primarily stabilized ABCA1 rather than ABCG1 protein levels by impairing protein degradation. These findings suggest RA as a candidate therapeutic to prevent atherosclerotic cardiovascular disease complications related to diabetes by regulating cholesterol efflux in macrophages.

Rosmarinic acid inhibits oxLDL-induced inflammasome activation under high-glucose conditions through downregulating the p38-FOXO1-TXNIP pathway.

Elevated glucose levels in diabetes mellitus is associated with increased oxidized low density lipoprotein (oxLDL). High glucose (HG) and oxLDL are key inducers of oxidative stress and inflammatory processes responsible for diabetic vascular disorders. Rosmarinic acid is a polyphenol with antioxidant, anti-inflammatory and insulin-sensitizing effects. However, whether rosmarinic acid protects against diabetic atherosclerosis remains unknown. In this study, we aimed to investigate the protective effect of rosmarinic acid against diabetic atherosclerosis and the related signaling pathway. oxLDL-mediated oxidative stress upregulated thioredoxin-interacting protein (TXNIP) and subsequently induced binding of TXNIP to NLRP3 to mediate NLRP3 inflammasome assembly and activation under HG conditions in ECs. Reactive oxygen species (ROS) scavengers, p38 and FOXO1 inhibitors and TXNIP siRNA inhibited TXNIP protein upregulation and NLRP3 inflammasome assembly and activation. Rosmarinic acid abrogated TXNIP protein upregulation and the interaction between TXNIP and NLRP3 to attenuate NLRP3 inflammasome assembly and activation and eventually IL-1ß secretion in ECs through downregulating ROS production, p38 phosphorylation and FOXO1 protein induction in ECs. These findings show that rosmarinic acid inhibits endothelial dysfunction which is shown in diabetic atherosclerosis through downregulating the p38-FOXO1-TXNIP pathway and inhibiting inflammasome activation.