Statins 對由陰電性低密度脂蛋白引起巨噬細胞介白素-6產生的影響

Abstract

在2016年心血管疾病為世界十大死因之首，動脈粥狀硬化是造成心血管疾病的主因之一。而血液中介白素 (interleukin-6, IL-6) 的濃度對於動脈粥狀硬化及心血管疾病的發生或是預後都扮演重要角色。 LDL(-)是在血液中一種氧化程度較輕微且帶負電性的oxLDL，現今已被人認為是一個心血管疾病的指標。過去研究顯示，LDL(-)被發現存在於動脈粥狀硬化、糖尿病、高膽固醇血脂症以及心肌梗塞患者的血液中。先前實驗室研究發現ST-時段上升心肌梗塞 (STEMI) 病患血液中所分離出的LDL(-)會誘導巨噬細胞產生IL-1β、G-CSF及GM-CSF，並且會增加巨噬細胞IL-1β、TNF-α及IL-6 mRNA表現。而在這個研究我們探討LDL(-)是否會誘導巨噬細胞產生IL-6。結果顯示，與Cu-oxLDL相比，STEMI病人的LDL(-)會誘導巨噬細胞產生更大量的促發炎因子IL-6至胞外，並且LDL(-)會誘導NF-κB及C/EBP-β的活化，而LDL(-)誘導巨噬細胞產生IL-6會在ERK路徑抑制時會大幅被降低。 Statins是臨床上治療心血管疾病的常見用藥，作用為抑制HMG-CoA還原酶(reductase) 來達到降低血液中膽固醇的效果。近年研究發現Statins除了具有降低血液膽固醇的功能之外，還具有抗發炎作用。在臨床上，Statins能夠降低血液中的IL-6及C-反應蛋白 (C-reactive protein, CRP)，以及能降低心血管疾病發生和死亡率。第二個主題我們探討Statins是否具有抑制LDL(-)誘導巨噬細胞所產生的IL-6。首先，我們以不同濃度及不同種類的Statins預處理巨噬細胞並加入LDL(-)後測量細胞分泌IL-6的產量。結果顯示，疏水性及親水性Statins皆能夠抑制LDL(-)引起巨噬細胞產生的IL-6。此外，我們也探討了Statins對於LDL(-)誘導巨噬細胞產生IL-1β的影響，結果發現Statins並不會抑制LDL(-)所刺激產生的IL-1β。接著，我們也探討Statins是透過那些途徑來抑制LDL(-)所刺激細胞分泌IL-6。結果顯示，Statins能夠顯著抑制C/EBP-β的表現及活化並降低巨噬細胞IL-6的產量，但是Statins並沒有抑制NF-κB活化的效果。 總結，在我們的研究中發現LDL(-)能夠刺激巨噬細胞產生IL-6，而Statins能夠有效抑制LDL(-)所誘導細胞產生IL-6，並且可能是透過抑制C/EBP-β活化而非抑制NF-κB活化來降低IL-6的產生。本篇論文可以部份解釋為何心血管疾病患者血液中會有較高的IL-6濃度，並且瞭解Statins能夠抗發炎的分子機制。

Cardiovascular disease (CVD) is a leading cause of death worldwide, and atherosclerosis is one of the main causes of CVD. The concentration of interleukin-6 (IL-6) plays an important role in the development and prognosis of atherosclerosis and cardiovascular disease. Naturally occurring LDL(-) is a mildly oxidized and negatively charged oxLDL that is now considered an indicator of cardiovascular disease. In past studies, LDL(-) was found present in the blood of patients with atherosclerosis, diabetes, hypercholesterolemia, and myocardial infarction. We have recently reported that LDL(-), isolated from patients with ST-segment elevation myocardial infarction (STEMI), induced production of IL-1β, G-CSF, and GM-CSF, and increases mRNA expression of IL-1β, TNF-α and IL-6 in human macrophages. In this study, we explore whether LDL(-) induces production of IL-6 in macrophages. Our results showed that LDL(-) isolated from STEMI significantly increased IL-6 protein production compared to nLDL and Cu-oxLDL. In addition, LDL (-) induced activation of NF-κB and C/EBP-β in human macrophages. We also found that LDL(-)-induced IL-6 production was significantly reduced when cells were pre-treated with U0126, a MEK inhibitor. Statins have long been used for the treatment of CVD. In addition to reducing circulating cholesterol levels, statins also exert anti-inflammatory effects. Clinical studies showed that statin reduces plasma levels of IL-6 and C-reactive protein (CRP) and reduces development and mortality of CVD. The second aim of this study is to investigate whether statins inhibit LDL(-)-induced IL-6 production in macrophages. We pretreated macrophages with different concentrations and types of Statins and then LDL(-) was added and incubated for 24 h, the levels of IL-6 were determined by ELISA . The results show that both hydrophobic and hydrophilic Statins can inhibit the LDL(-)-induced IL-6 production in human macrophages. However, Statins did not inhibit LDL(-)-induced IL-1β production. Furthermore, we showed that Statins suppressed production of IL-6 probably through inhibiting C/EBP-β but not NF-κB activation. In summary, we found that LDL(-) significantly increased IL-6 protein production, and Statins inhibited LDL(-)-induced IL-6 through inhibiting C/EBP-β but not NF-κB in human macrophages. These results can partly explain that patients with STEMI have higher levels of plasma IL-6, and provide possible molecular mechanisms for the anti-inflammatory effects of statins.