👤 Mireia Tondo

Low-density lipoprotein (LDL) aggregation is nowadays considered a therapeutic target in atherosclerosis. DP3, the retro-enantio version of the sequence Gly Tg mice were fed an HFD for 21 days to induce atherosclerosis and then randomized into three groups that received a daily subcutaneous administration (10 mg/kg) of i) vehicle, ii) DP3 peptide, or iii) a non-active peptide (IP321). The in vivo biodistribution of a fluorescent-labeled peptide version (TAMRA-DP3), and its colocalization with ApoB100 in the arterial intima, was analyzed by imaging system (IVIS) and confocal microscopy. Heart aortic roots were used for atherosclerosis detection and quantification. LDL functionality was analyzed by biochemical, biophysical, molecular, and cellular studies. Intimal neutral lipid accumulation in the aortic root was reduced in the DP3-treated group as compared to control groups. ApoB100 in LDLs from the DP3 group exhibited an increased percentage of α-helix secondary structures and decreased immunoreactivity to anti-ApoB100 antibodies. LDL from DP3-treated mice were protected against passive and sphingomyelinase (SMase)-induced aggregation, although they still experienced SMase-induced sphingomyelin phospholysis. In patients with familial hypercholesterolemia (FH), DP3 efficiently inhibited both SMase-induced phospholysis and aggregation. DP3 peptide administration inhibits atherosclerosis by preserving the α-helix secondary structures of ApoB100 in a humanized ApoB100 murine model that mimicks the hallmark of human hypercholesterolemia. Show less

The HDL (high-density lipoprotein)-mediated stimulation of cellular cholesterol efflux initiates macrophage-specific reverse cholesterol transport (m-RCT), which ends in the fecal excretion of macrophage-derived unesterified cholesterol (UC). Early studies established that LDL (low-density lipoprotein) particles could act as efficient intermediate acceptors of cellular-derived UC, thereby preventing the saturation of HDL particles and facilitating their cholesterol efflux capacity. However, the capacity of LDL to act as a plasma cholesterol reservoir and its potential impact in supporting the m-RCT pathway in vivo both remain unknown. We investigated LDL contributions to the m-RCT pathway in hypercholesterolemic mice. Macrophage cholesterol efflux induced in vitro by LDL added to the culture media either alone or together with HDL or ex vivo by plasma derived from subjects with familial hypercholesterolemia was assessed. In vivo, m-RCT was evaluated in mouse models of hypercholesterolemia that were naturally deficient in CETP (cholesteryl ester transfer protein) and fed a Western-type diet. LDL induced the efflux of radiolabeled UC from cultured macrophages, and, in the simultaneous presence of HDL, a rapid transfer of the radiolabeled UC from HDL to LDL occurred. However, LDL did not exert a synergistic effect on HDL cholesterol efflux capacity in the familial hypercholesterolemia plasma. The m-RCT rates of the LDLr (LDL receptor)-KO (knockout), LDLr-KO/APOB100, and PCSK9 (proprotein convertase subtilisin/kexin type 9)-overexpressing mice were all significantly reduced relative to the wild-type mice. In contrast, m-RCT remained unchanged in HAPOB100 Tg (human APOB100 transgenic) mice with fully functional LDLr, despite increased levels of plasma APO (apolipoprotein)-B-containing lipoproteins. Hepatic LDLr plays a critical role in the flow of macrophage-derived UC to feces, while the plasma increase of APOB-containing lipoproteins is unable to stimulate m-RCT. The results indicate that, besides the major HDL-dependent m-RCT pathway via SR-BI (scavenger receptor class B type 1) to the liver, a CETP-independent m-RCT path exists, in which LDL mediates the transfer of cholesterol from macrophages to feces. Graphical Abstract: A graphical abstract is available for this article. Show less