Tanshinone IIA Exerts Anti-Inflammatory and Immune-Regulating Effects on Vulnerable Atherosclerotic Plaque Partially via the TLR4/MyD88/NF-κB Signal Pathway.

Zhuo Chen,Siming Li,Hao Xu,He Zhang,Yanxiang Gao,Anlu Wang,Jing Liu,Weiliang Sun,Yu Qiu,Jingen Li,Fangyuan Che,Jing Guo,Bingyan Cao,Geng Li,Xiang Gao,Mei-Li Yu ,Jiyong Yang ,Pei Lin ,Chen Yu ,Yu Zhu

doi:10.3389/fphar.2019.00850

Abstract

Background: Tanshinone IIA (Tan IIA), a lipophilic constituent from Salvia miltiorrhiza Bunge, has shown a promising cardioprotective effect including anti-atherosclerosis. This study aims at exploring Tan IIA’s anti-inflammatory and immune-regulating roles in stabilizing vulnerable atherosclerotic plaque in ApoE-deficient (ApoE−/−) mice. Methods: Male ApoE−/− mice (6 weeks) were fed with a high-fat diet for 13 weeks and then randomized to the model group (MOD) or Tan IIA groups [high dose: 90 mg/kg/day (HT), moderate dose: 30 mg/kg/day (MT), low dose: 10 mg/kg/day (LT)] or the atorvastatin group (5 mg/kg/day, ATO) for 13 weeks. Male C57BL/6 mice (6 weeks) were fed with ordinary rodent chow as control. The plaque stability was evaluated according to the morphology and composition of aortic atherosclerotic (AS) plaque in H&E staining and Movat staining sections by calculating the area of extracellular lipid, collagenous fiber, and foam cells to the plaque. The expression of the Toll-like receptor 4 (TLR4)/myeloid differentiation factor88 (MyD88)/nuclear factor-kappa B (NF-κB) signal pathway in aorta fractions was determined by immunohistochemistry. Serum levels of blood lipid were measured by turbidimetric inhibition immunoassay. The concentrations of tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) were detected by cytometric bead array. Results: Tan IIA stabilized aortic plaque with a striking reduction in the area of extracellular lipid (ATO: 13.15 ± 1.2%, HT: 12.2 ± 1.64%, MT: 13.93 ± 1.59%, MOD: 18.84 ± 1.46%, P < 0.05) or foam cells (ATO: 16.05 ± 1.26%, HT: 14.88 ± 1.79%, MT: 16.61 ± 1.47%, MOD: 22.08 ± 1.69%, P < 0.05) to the plaque, and an evident increase in content of collagenous fiber (ATO: 16.22 ± 1.91%, HT: 17.58 ± 1.33%, MT: 15.71 ± 2.26%, LT:14.92 ± 1.65%, MOD: 9.61 ± 0.7%, P < 0.05) to the plaque than that in the model group, concomitant with down-regulation of the protein expression of TLR4, MyD88, and NF-κB p65, and serum level of MCP-1 and TNF-α in a dose-dependent manner. There were no differences in serum TC, LDL, HDL, or TG levels between ApoE–/– mice and those treated with atorvastatin. Conclusions: These results suggest that Tan IIA could stabilize vulnerable AS plaque in ApoE−/− mice, and this anti-inflammatory and immune-regulating effect may be achieved via the TLR4/MyD88/NF-κB signaling pathway.

Highlights

Atherosclerosis (AS) is the leading cause of cardiovascular disease worldwide
The rest of the 60 ApoE−/− mice were randomly divided into five groups (n = 12): model group (MOD: high-fat diet), high dose of Tan Tanshinone IIA (IIA) group (HT: high-fat diet and Tanshinone IIA (Tan IIA) 90 mg/kg/day), moderate dose of Tan IIA group (MT: high-fat diet and Tan IIA 30 mg/kg/day), low dose of TanIIA group (LT: high-fat diet and Tan IIA 10 mg/kg/day), and atorvastatin group (ATO: high-fat diet and atorvastatin 5 mg/kg/day) (Tan IIA standard sample was purchased from Nanjing Zelang pharmaceutical technology Co., Ltd, lot number: ZL140508582; atorvastatin was purchased from Pfizer Pharmaceutical Co., Ltd, lot number: 046012K)
It was intuitively plausible that the aorta of the control group (CON) group was smooth and clean, that of MOD group had the most plaque, and other groups using either Tan IIA or Atorvastatin had less plaque than the MOD group to some extent (Figure 2A)

Summary

Introduction

Atherosclerosis (AS) is the leading cause of cardiovascular disease worldwide. It mainly involves aorta and coronary artery. AS is no longer regarded as just a simple disease with smooth muscle cell proliferation and lipid accumulation in the arterial wall, since an increased number of inflammatory cells and mediators have been detected in recent years. The underlying pathogenesis of AS involves imbalanced lipid metabolism and chronic inflammation induced by maladaptive immune response. Both innate and acquired immune responses mediate all stages of AS inflammation from initiation through progression (Libby et al, 2009; Libby, 2012). This study aims at exploring Tan IIA’s anti-inflammatory and immune-regulating roles in stabilizing vulnerable atherosclerotic plaque in ApoE-deficient (ApoE−/−) mice

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Conclusion