No Effect of Fibrates on Synthesis of Apolipoprotein(a) in Primary Cultures of Cynomolgus Monkey and Human Hepatocytes: Apolipoprotein A-I Synthesis Increased

Therapeutic antibodies targeting proprotein convertase subtilisin kexin type 9 (PCSK9) (e.g. alirocumab) lower low-density lipoprotein cholesterol (LDL-C) and lipoprotein (a) [Lp(a)] levels in clinical trials. We recently showed that PCSK9 enhances apolipoprotein(a) [apo(a)] secretion from primary human hepatocytes but does not affect Lp(a) cellular uptake. Here, we aimed to determine how PCSK9 neutralization modulates Lp(a) levels in vivo. Six nonhuman primates (NHP) were treated with alirocumab or a control antibody (IgG1) in a crossover protocol. After the lowering of lipids reached steady state, NHP received an intravenous injection of [2H3]-leucine, and blood samples were collected sequentially over 48 h. Enrichment of apolipoproteins in [2H3]-leucine was assessed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Kinetic parameters were calculated using numerical models with the SAAMII software. Compared with IgG1, alirocumab significantly reduced total cholesterol (TC) (−28%), LDL-C (−67%), Lp(a) (−56%), apolipoprotein B100 (apoB100) (−53%), and apo(a) (−53%). Alirocumab significantly increased the fractional catabolic rate of apoB100 (+29%) but not that of apo(a). Conversely, alirocumab sharply and significantly reduced the production rate (PR) of apo(a) (−42%), but not significantly that of apoB100, compared with IgG1, respectively. In line with the observations made in human hepatocytes, the present kinetic study establishes that PCSK9 neutralization with alirocumab efficiently reduces circulating apoB100 and apo(a) levels by distinct mechanisms: apoB primarily by enhancing its catabolism and apo(a) primarily by lowering its production.

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Fibrate-modulated Expression of Fibrinogen, Plasminogen Activator Inhibitor-1 and Apolipoprotein A-I in Cultured Cynomolgus Monkey Hepatocytes

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615393 ◽

1998 ◽

Vol 80 (12) ◽

pp. 942-948 ◽

Cited By ~ 29

Author(s):

M. Kockx ◽

H. M. G. Princen ◽

T. Kooistra

Keyword(s):

Plasminogen Activator ◽

Cynomolgus Monkey ◽

Plasma Concentrations ◽

Plasminogen Activator Inhibitor ◽

Peroxisome Proliferator ◽

Plasminogen Activator Inhibitor 1 ◽

Apolipoprotein A ◽

Activator Inhibitor ◽

Pai 1

SummaryFibrates are used to lower plasma triglycerides and cholesterol levels in hyperlipidemic patients. In addition, fibrates have been found to alter the plasma concentrations of fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and apolipoprotein A-I (apo A-I). We have investigated the in vitro effects of fibrates on fibrinogen, PAI-1 and apo A-I synthesis and the underlying regulatory mechanisms in primary monkey hepatocytes.We show that fibrates time- and dose-dependently increase fibrinogen and apo A-I expression and decrease PAI-1 expression in cultured cynomolgus monkey hepatocytes, the effects demonstrating different potency for different fibrates. After three consecutive periods of 24 h the most effective fibrate, ciprofibrate (at 1 mmol/l), increased fibrinogen and apo A-I synthesis to 356% and 322% of control levels, respectively. Maximum inhibition of PAI-1 synthesis was about 50% of control levels and was reached by 1 mmol/l gemfibrozil or ciprofibrate after 48 h. A ligand for the retinoid-X-receptor (RXR), 9-cis retinoic acid, and specific activators of the peroxisome proliferator-activated receptor-α (PPARα), Wy14,643 and ETYA, influenced fibrinogen, PAI-1 and apo A-I expression in a similar fashion, suggesting a role for the PPARα/RXRα heterodimer in the regulation of these genes. When comparing the effects of the various compounds on PPARα trans-activation activity as determined in a PPARα-sensitive reporter gene system and the ability of the compounds to affect fibrinogen, PAI-1 and apo A-I antigen production, a good correlation (r = 0.80; p <0.01) between PPARα transactivation and fibrinogen expression was found. Apo A-I expression correlated only weakly with PPARα transactivation activity (r = 0.47; p = 0.24), whereas such a correlation was absent for PAI-1 (r = 0.03; p = 0.95). These results strongly suggest an involvement of PPARα in the regulation of fibrinogen gene expression.

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Alpha Interferon Inhibits Hepatitis C Virus Replication in Primary Human Hepatocytes Infected In Vitro

Journal of Virology ◽

10.1128/jvi.76.16.8189-8199.2002 ◽

2002 ◽

Vol 76 (16) ◽

pp. 8189-8199 ◽

Cited By ~ 87

Author(s):

Valérie Castet ◽

Chantal Fournier ◽

Alexandre Soulier ◽

Rozenn Brillet ◽

Joliette Coste ◽

...

Keyword(s):

Chronic Hepatitis ◽

Hepatitis C Virus ◽

Hepatitis C ◽

Chronic Hepatitis C ◽

Primary Cultures ◽

Indirect Evidence ◽

Human Hepatocytes ◽

Alpha Interferon ◽

Healthy Human

ABSTRACT Chronic hepatitis C is a common cause of liver disease, the complications of which include cirrhosis and hepatocellular carcinoma. Treatment of chronic hepatitis C is based on the use of alpha interferon (IFN-α). Recently, indirect evidence based on mathematical modeling of hepatitis C virus (HCV) dynamics during human IFN-α therapy suggested that the major initial effect of IFN-α is to block HCV virion production or release. Here, we used primary cultures of healthy, uninfected human hepatocytes to show that: (i) healthy human hepatocytes can be infected in vitro and support HCV genome replication, (ii) hepatocyte treatment with IFN-α results in expression of IFN-α-induced genes, and (iii) IFN-α inhibits HCV replication in infected human hepatocytes. These results show that IFN-α acts primarily through its nonspecific antiviral effects and suggest that primary cultures of human hepatocytes may provide a good model to study intrinsic HCV resistance to IFN-α.

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