Salvianolic acid B inhibits atherosclerosis and TNF-α-induced inflammation by regulating NF-κB/NLRP3 signaling pathway

Abstract

Background: Inflammation is critical in the pathophysiology of atherosclerosis (AS). The aim of this study was to investigate the protective effect of salvianolic acid B (Sal B) on AS and to explore the molecular mechanism of tumor necrosis factor-α (TNF-α)-induced damage in human umbilical vein endothelial cells (HUVECs).

Methods: In vivo studies, LDLR^-/- mice were fed a high-fat diet (HFD) for 14 weeks to establish an AS model to evaluate the protective effect of Sal B on the development of AS. Total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) levels were determined in the blood serum. En face and cross section lipid deposits were measured and quantified with Oil Red O staining. Hematoxylin and eosin (H&E) and Masson's trichrome staining were used to quantify atherosclerotic plaque size and collagen fiber content in aortic root sections. Reactive oxygen species (ROS) were detected in aortic root using dihydroethylenediamine (DHE) staining. Apoptosis rate was determined by TdT-mediated dUTP nick end labeling (TUNEL) staining. Immunofluorescence (IF) staining was used to detect the expression of the nuclear factor kappa-B (NF-κB) p65 and NOD-like receptor family pyrin domain containing 3 (NLRP3). To further investigate the protective effect of Sal B, we used TNF-α induced HUVECs inflammation model. We examined cell viability, lactate dehydrogenase (LDH) content, and ROS production. The transcription of NF-κB was evaluated by immunofluorescence. The mRNA levels of NLRP3, caspase-1, and IL-1β were detected by RT-PCR. Pyroptosis related proteins were detected by Western blot.

Results: The change in the weight of the mice over time was an indication that Sal B had an effect on weight gain.

In vivo studies: we were able to show that the serum lipids TC, TG and LDL-C were increased in the model group and that the treatment with Sal B reduced the levels of serum lipids. Histological staining showed that the LDLR^-/- mice had a large amount of foam cell deposition accompanied by inflammatory cell infiltration and the formation of atherosclerotic plaques in theMOD group. The pathological abnormalities were significantly improved by Sal B treatment. ROS release and apoptosis were significantly increased after HFD in aortic root, which was attenuated by Sal B. IF results showed that the expression of NF-κB p65 and NLRP3 was significantly increased in the MOD group and significantly decreased in the Sal B group, suggesting that Sal B may act through the NF-κB/NLRP3 pathway. And in vitro studies: inflammatory damage of HUEVCs was induced by TNF-α, and Sal B treatmented significantly increased cell viability and reduced LDH release. It was also found that Sal B inhibited ROS level increase after TNF-α-induced HUEVCs. Activation of NF-κB p65 by TNF-α stimulation, NF-κB p65 is transferred to the nucleus. Sal B treatment could reverse this effect. RT-PCR and Western blot showed that Sal B affected NF-κB transcription and NLRP3 inflammasome activation and could significantly inhibit TNF-α-induced NLRP3 inflammasome activation. These results suggest that Sal B may participate in antiatherosclerotic and inflammatory responses through the NF-κB/NLRP3 pathway.

Conclusions: This study shows that Sal B ameliorates the development of AS lesions in HFD-induced LDLR^-/- mice. Furthermore, under TNF-α conditions, Sal B reduced ROS release and reversed nuclear translocation of NF-κB, and inhibited atherosclerosis and inflammation by modulating the NF-κB/NLRP3 pathway.

Keywords: Atherosclerosis; HUVECs; Inflammation; Salvianolic acid B; TNF-α, pyroptosis.