Abstract

Defective LDL-C clearance and hence its elevation in the circulation is an established risk factor for cardiovascular diseases (CVDs) such as myocardial infarction (MI). A soluble LDL-receptor (sLDL-R) has been detected in human plasma which correlates strongly with circulating LDL-C and classical conditions that promote chronic inflammation. However, the mechanistic interplay between sLDL-R, inflammation, and CVDs remains to be investigated. Here, we report that stimulation of HepG2 cells with TNF-α induces the release of sLDL-R into culture supernatants. In addition, TNF-α induces gene expression of peptidases ADAM-17 and MMP-14 in HepG2 cells, and inhibiting these peptidases using TMI 1 significantly reduces the TNF-α induced sLDL-R release. We found that a soluble form of recombinant LDL-R (100 nM) can strongly bind to LDL-C and form a stable complex (KD = E-12). Moreover, incubation of HepG2 cells with this recombinant LDL-R resulted in reduced LDL-C uptake in a dose-dependent manner. In a nested case-control study, we found that baseline sLDL-R in plasma is positively correlated with plasma total cholesterol level. Furthermore, a twofold increase in plasma sLDL-R was associated with a 55% increase in the risk of future MI [AOR = 1.55 (95% CI = 1.10–2.18)]. Nevertheless, mediation analyses revealed that a significant proportion of the association is mediated by elevation in plasma cholesterol level (indirect effect β = 0.21 (95% CI = 0.07–0.38). Collectively, our study shows that sLDL-R is induced by a pro-inflammatory cytokine TNF-α via membrane shedding. Furthermore, an increase in sLDL-R could inhibit hepatic clearance of LDL-C increasing its half-life in the circulation and contributing to the pathogenesis of MI.

Key messages

• TNF-α causes shedding of hepatocytic LDL-R through induction of ADAM-17 and MMP-14.

• sLDL-R binds strongly to LDL-C and inhibits its uptake by hepatocytic cells.

• Plasma sLDL-R is positively correlated with TNF-α and cholesterol.

• Plasma sLDL-R is an independent predictor of myocardial infarction (MI).

• Plasma cholesterol mediates the association between sLDL-R and MI.

中文翻译：

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可溶性 LDL 受体由 TNF-α 诱导并抑制肝细胞清除 LDL 胆固醇

摘要

LDL-C 清除缺陷及其在循环中的升高是心肌梗塞 (MI) 等心血管疾病 (CVD) 的既定危险因素。在人血浆中检测到可溶性 LDL 受体 (sLDL-R)，它与循环 LDL-C 和促进慢性炎症的经典病症密切相关。然而，sLDL-R、炎症和 CVD 之间的机制相互作用仍有待研究。在这里，我们报告用 TNF-α 刺激 HepG2 细胞会诱导 sLDL-R 释放到培养上清液中。此外，TNF-α 诱导 HepG2 细胞中肽酶 ADAM-17 和 MMP-14 的基因表达，使用 TMI 1 抑制这些肽酶可显着减少 TNF-α 诱导的 sLDL-R 释放。我们发现可溶形式的重组 LDL-R (100 nM) 可以与 LDL-C 强烈结合并形成稳定的复合物 (KD = E-12)。此外，用这种重组 LDL-R 孵育 HepG2 细胞会导致 LDL-C 摄取以剂量依赖性方式减少。在一项巢式病例对照研究中，我们发现血浆中基线 sLDL-R 与血浆总胆固醇水平呈正相关。此外，血浆 sLDL-R 增加两倍与未来 MI 风险增加 55% 相关 [AOR = 1.55 (95% CI = 1.10–2.18)]。然而，中介分析显示，很大一部分关联是由血浆胆固醇水平升高介导的（间接效应β  = 0.21 (95% CI = 0.07–0.38)。总的来说，我们的研究表明 sLDL-R 是由 pro 诱导的。 -通过膜脱落产生炎症细胞因子 TNF-α。此外，sLDL-R 的增加可以抑制 LDL-C 的肝脏清除，从而增加其在循环中的半衰期，从而促进 MI 的发病机制。

关键信息

• TNF-α 通过诱导 ADAM-17 和 MMP-14 导致肝细胞 LDL-R 脱落。

• sLDL-R 与 LDL-C 强烈结合并抑制肝细胞对其的摄取。

• 血浆sLDL-R与TNF-α和胆固醇呈正相关。

• 血浆 sLDL-R 是心肌梗塞 (MI) 的独立预测因子。

• 血浆胆固醇介导 sLDL-R 和 MI 之间的关联。