Lipopolysaccharide Lowers Cholesteryl Ester Transfer Protein by Activating F4/80+Clec4f+Vsig4+Ly6C- Kupffer Cell Subsets.

BACKGROUND: Lipopolysaccharide (LPS) decreases hepatic CETP (cholesteryl ester transfer protein) expression albeit that the underlying mechanism is disputed. We recently showed that plasma CETP is mainly derived from Kupffer cells (KCs). In this study, we investigated the role of KC subsets in the mechanism by which LPS reduces CETP expression. METHODS AND RESULTS: In CETP-transgenic mice, LPS markedly decreased hepatic CETP expression and plasma CETP concentration without affecting hepatic macrophage number. This was paralleled by decreased expression of the resting KC markers C-type lectin domain family 4, member f (Clec4f) and V-set and immunoglobulin domain containing 4 (Vsig4), while expression of the infiltrating monocyte marker lymphocyte antigen 6 complex locus C (Ly6C) was increased. Simultaneously, the ratio of plasma high-density lipoprotein-cholesterol over non-high-density lipoprotein-cholesterol transiently increased. After ablation hepatic macrophages via injection with liposomal clodronate, the reappearance of hepatic gene and protein expression of CETP coincided with Clec4f and Vsig4, but not Ly6C. Double-immunofluorescence staining showed that CETP co-localized with Clec4f+ KCs and not Ly6C+ monocytes. In humans, microarray gene-expression analysis of liver biopsies revealed that hepatic expression and plasma level of CETP both correlated with hepatic VSIG4 expression. LPS administration decreased the plasma CETP concentration in humans. In vitro experiments showed that LPS reduced liver X receptor-mediated CETP expression. CONCLUSIONS: Hepatic expression of CETP is exclusively confined to the resting KC subset (ie, F4/80+Clec4f+Vsig4+Ly6C-). LPS activated resting KCs, leading to reduction of Clec4f and Vsig4 expression and reduction of hepatic CETP expression, consequently decreasing plasma CETP and raising high-density lipoprotein (HDL)-cholesterol. This sequence of events is consistent with the anti-inflammatory role of HDL in the response to LPS and may be relevant as a defense mechanism against bacterial infections.

Anacetrapib reduces (V)LDL cholesterol by inhibition of CETP activity and reduction of plasma PCSK9.

Recently, we showed in APOE*3-Leiden cholesteryl ester transfer protein (E3L.CETP) mice that anacetrapib attenuated atherosclerosis development by reducing (V)LDL cholesterol [(V)LDL-C] rather than by raising HDL cholesterol. Here, we investigated the mechanism by which anacetrapib reduces (V)LDL-C and whether this effect was dependent on the inhibition of CETP. E3L.CETP mice were fed a Western-type diet alone or supplemented with anacetrapib (30 mg/kg body weight per day). Microarray analyses of livers revealed downregulation of the cholesterol biosynthesis pathway (P < 0.001) and predicted downregulation of pathways controlled by sterol regulatory element-binding proteins 1 and 2 (z-scores -2.56 and -2.90, respectively; both P < 0.001). These data suggest increased supply of cholesterol to the liver. We found that hepatic proprotein convertase subtilisin/kexin type 9 (Pcsk9) expression was decreased (-28%, P < 0.01), accompanied by decreased plasma PCSK9 levels (-47%, P < 0.001) and increased hepatic LDL receptor (LDLr) content (+64%, P < 0.01). Consistent with this, anacetrapib increased the clearance and hepatic uptake (+25%, P < 0.001) of [(14)C]cholesteryl oleate-labeled VLDL-mimicking particles. In E3L mice that do not express CETP, anacetrapib still decreased (V)LDL-C and plasma PCSK9 levels, indicating that these effects were independent of CETP inhibition. We conclude that anacetrapib reduces (V)LDL-C by two mechanisms: 1) inhibition of CETP activity, resulting in remodeled VLDL particles that are more susceptible to hepatic uptake; and 2) a CETP-independent reduction of plasma PCSK9 levels that has the potential to increase LDLr-mediated hepatic remnant clearance.

Anacetrapib reduces progression of atherosclerosis, mainly by reducing non-HDL-cholesterol, improves lesion stability and adds to the beneficial effects of atorvastatin.

BACKGROUND: The residual risk that remains after statin treatment supports the addition of other LDL-C-lowering agents and has stimulated the search for secondary treatment targets. Epidemiological studies propose HDL-C as a possible candidate. Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from atheroprotective HDL to atherogenic (V)LDL. The CETP inhibitor anacetrapib decreases (V)LDL-C by ∼15-40% and increases HDL-C by ∼40-140% in clinical trials. We evaluated the effects of a broad dose range of anacetrapib on atherosclerosis and HDL function, and examined possible additive/synergistic effects of anacetrapib on top of atorvastatin in APOE*3Leiden.CETP mice. METHODS AND RESULTS: Mice were fed a diet without or with ascending dosages of anacetrapib (0.03; 0.3; 3; 30 mg/kg/day), atorvastatin (2.4 mg/kg/day) alone or in combination with anacetrapib (0.3 mg/kg/day) for 21 weeks. Anacetrapib dose-dependently reduced CETP activity (-59 to -100%, P < 0.001), thereby decreasing non-HDL-C (-24 to -45%, P < 0.001) and increasing HDL-C (+30 to +86%, P < 0.001). Anacetrapib dose-dependently reduced the atherosclerotic lesion area (-41 to -92%, P < 0.01) and severity, increased plaque stability index and added to the effects of atorvastatin by further decreasing lesion size (-95%, P < 0.001) and severity. Analysis of covariance showed that both anacetrapib (P < 0.05) and non-HDL-C (P < 0.001), but not HDL-C (P = 0.76), independently determined lesion size. CONCLUSION: Anacetrapib dose-dependently reduces atherosclerosis, and adds to the anti-atherogenic effects of atorvastatin, which is mainly ascribed to a reduction in non-HDL-C. In addition, anacetrapib improves lesion stability.