Nanoparticles Containing a Liver X Receptor Agonist Inhibit Inflammation and Atherosclerosis

Liver X receptor (LXR) signaling pathways regulate lipid metabolism and inflammation, which has generated widespread interest in developing synthetic LXR agonists as potential therapeutics for the management of atherosclerosis. In this study, we demonstrate that nanoparticles (NPs) containing the synthetic LXR agonist GW3965 (NP-LXR) exert anti-inflammatory effects and inhibit the development of atherosclerosis without causing hepatic steatosis. These NPs were engineered through self-assembly of a biodegradable diblock poly(lactide-co-glycolide)-b-poly(ethylene glycol) (PLGA-b-PEG) copolymer. NP-LXR was significantly more effective than free GW3965 at inducing LXR target gene expression and suppressing inflammatory factors in macrophages in vitro and in vivo. Addtionally, the NPs elicited negligible lipogenic gene stimulation in the liver. Using the Ldlr−/− mouse model of atherosclerosis, we saw abundant co-localization of fluorescently labeled NPs within plaque macrophages following systemic administration. Notably, six intravenous injections of NP-LXR over two weeks markedly reduced the CD68-positive cell (macrophage) content of plaques (by 50%) without increasing total cholesterol or triglycerides in the liver and plasma. Together, these findings identify GW3965-encapsulated PLGA-b-PEG NPs as a promising nanotherapeutic approach to combat atherosclerosis, providing the benefits of LXR agonists without their adverse effects on hepatic and plasma lipid metabolism

Function and Distribution of Apolipoprotein A1 in The Artery Wall Are Markedly Distinct From Those in Plasma

Background—Prior studies show that apolipoprotein A1 (apoA1) recovered from human atherosclerotic lesions is highly oxidized. Ex vivo oxidation of apoA1 or high-density lipoprotein (HDL) cross-links apoA1 and impairs lipid binding, cholesterol efflux, and lecithin-cholesterol acyltransferase activities of the lipoprotein. Remarkably, no studies to date directly quantify either the function or HDL particle distribution of apoA1 recovered from the human artery wall. Methods and Results—A monoclonal antibody (10G1.5) was developed that equally recognizes lipid-free and HDL-associated apoA1 in both native and oxidized forms. Examination of homogenates of atherosclerotic plaque–laden aorta showed \u3e100-fold enrichment of apoA1 compared with normal aorta (P\u3c0.001). Surprisingly, buoyant density fractionation revealed that only a minority (\u3c3% of total) of apoA1 recovered from either lesions or normal aorta resides within an HDL-like particle (1.063≤d≤1.21). In contrast, the majority (\u3e90%) of apoA1 within aortic tissue (normal and lesions) was recovered within the lipoprotein-depleted fraction (d\u3e1.21). Moreover, both lesion and normal artery wall apoA1 are highly cross-linked (50% to 70% of total), and functional characterization of apoA1 quantitatively recovered from aorta with the use of monoclonal antibody 10G1.5 showed ≈80% lower cholesterol efflux activity and ≈90% lower lecithin-cholesterol acyltransferase activity relative to circulating apoA1. Conclusions—The function and distribution of apoA1 in human aorta are quite distinct from those found in plasma. The lipoprotein is markedly enriched within atherosclerotic plaque, predominantly lipid-poor, not associated with HDL, extensively oxidatively cross-linked, and functionally impaired

Function and Distribution of Apolipoprotein A1 in The Artery Wall Are Markedly Distinct From Those in Plasma

Background—Prior studies show that apolipoprotein A1 (apoA1) recovered from human atherosclerotic lesions is highly oxidized. Ex vivo oxidation of apoA1 or high-density lipoprotein (HDL) cross-links apoA1 and impairs lipid binding, cholesterol efflux, and lecithin-cholesterol acyltransferase activities of the lipoprotein. Remarkably, no studies to date directly quantify either the function or HDL particle distribution of apoA1 recovered from the human artery wall. Methods and Results—A monoclonal antibody (10G1.5) was developed that equally recognizes lipid-free and HDL-associated apoA1 in both native and oxidized forms. Examination of homogenates of atherosclerotic plaque–laden aorta showed \u3e100-fold enrichment of apoA1 compared with normal aorta (P\u3c0.001). Surprisingly, buoyant density fractionation revealed that only a minority (\u3c3% of total) of apoA1 recovered from either lesions or normal aorta resides within an HDL-like particle (1.063≤d≤1.21). In contrast, the majority (\u3e90%) of apoA1 within aortic tissue (normal and lesions) was recovered within the lipoprotein-depleted fraction (d\u3e1.21). Moreover, both lesion and normal artery wall apoA1 are highly cross-linked (50% to 70% of total), and functional characterization of apoA1 quantitatively recovered from aorta with the use of monoclonal antibody 10G1.5 showed ≈80% lower cholesterol efflux activity and ≈90% lower lecithin-cholesterol acyltransferase activity relative to circulating apoA1. Conclusions—The function and distribution of apoA1 in human aorta are quite distinct from those found in plasma. The lipoprotein is markedly enriched within atherosclerotic plaque, predominantly lipid-poor, not associated with HDL, extensively oxidatively cross-linked, and functionally impaired

The cationic liposome CCS/C adjuvant induces immunity to influenza independently of the adaptor protein MyD88

Traditional non-living vaccines are often least effective in the populations that need them most, such as neonates and elderly adults. Vaccine adjuvants are one approach to boost the immunogenicity of antigens in populations with reduced immunity. Ideally, vaccine adjuvants will increase the seroconversion rates across the population, lead to stronger immune responses, and enable the administration of fewer vaccine doses. We previously demonstrated that a cationic liposomal formulation of the commercial influenza split virus vaccine (CCS/C-HA) enhanced cellular and humoral immunity to the virus, increased seroconversion rates, and improved survival after live virus challenge in a preclinical model, as compared to the commercial vaccine as is (F-HA). We now evaluated vaccine efficacy in different strains and sexes of mice and determined the role of innate immunity in the mechanism of action of the CCS/C adjuvant by testing the response of mice deficient in Toll-like receptors or the TLR/IL-1 adaptor protein MyD88 following immunization with CCS/C-HA vs. F-HA. Although TLR2- and TLR4-deficient mice responded to F-HA immunization, F-HA immunization failed to engender a significant immune response in the absence of MyD88. In contrast, immunization with the CCS/C-HA vaccine overcame the requirement for MyD88 in the response to the commercial vaccine and improved the immune responses and seroconversion rates in all strains of mice tested, including those deficient in TLR2 and TLR4

The complex fate in plasma of gadolinium incorporated into high-density lipoproteins used for magnetic imaging of atherosclerotic plaques

We have previously reported enhancing the imaging of atherosclerotic plaques in mice using reconstituted high density lipoproteins (HDL) as nanocarriers for the MRI contrast agent gadolinium (Gd). This study focuses on the underlying mechanisms of Gd delivery to atherosclerotic plaques. HDL, LDL, and VLDL particles containing Gd chelated to phosphatidyl ethanolamine (DTPA-DMPE) and a lipidic fluorophore were used to demonstrate the transfer of Gd-phospholipids among plasma lipoproteins in vitro and in vivo. To determine the basis of this transfer, the roles of phospholipid transfer protein (PLTP) and lipoprotein lipase (LpL) in mediating the migration of Gd-DTPA-DMPE among lipoproteins were investigated. The results indicated that neither was an important factor, suggesting that spontaneous transfer of Gd-DTPA-DMPE was the most probable mechanism. Finally, two independent mouse models were used to quantify the relative contributions of HDL and LDL reconstituted with Gd-DTPA-DMPE to plaque imaging enhancement by MR. Both sets of results suggested that Gd-DTPA-DMPE originally associated with LDL was about twice as effective as that injected in the form of Gd-HDL, and that some of Gd-HDL's effectiveness in vivo is indirect through transfer of the imaging agent to LDL. In conclusion, the fate of Gd-DTPA-DMPE associated with a particular type of lipoprotein is complex, and includes its transfer to other lipoprotein species that are then cleared from the plasma into tissue

The Complex Fate in Plasma of Gadolinium Incorporated into High-Density Lipoproteins Used for Magnetic Imaging of Atherosclerotic Plaques

We have previously reported enhancing the imaging of atherosclerotic plaques in mice using reconstituted high density lipoproteins (HDL) as nanocarriers for the MRI contrast agent gadolinium (Gd). This study focuses on the underlying mechanisms of Gd delivery to atherosclerotic plaques. HDL, LDL, and VLDL particles containing Gd chelated to phosphatidyl ethanolamine (DTPA-DMPE) and a lipidic fluorophore were used to demonstrate the transfer of Gd-phospholipids among plasma lipoproteins <i>in vitro</i> and <i>in vivo</i>. To determine the basis of this transfer, the roles of phospholipid transfer protein (PLTP) and lipoprotein lipase (LpL) in mediating the migration of Gd-DTPA-DMPE among lipoproteins were investigated. The results indicated that neither was an important factor, suggesting that spontaneous transfer of Gd-DTPA-DMPE was the most probable mechanism. Finally, two independent mouse models were used to quantify the relative contributions of HDL and LDL reconstituted with Gd-DTPA-DMPE to plaque imaging enhancement by MR. Both sets of results suggested that Gd-DTPA-DMPE originally associated with LDL was about twice as effective as that injected in the form of Gd-HDL, and that some of Gd-HDL’s effectiveness <i>in vivo</i> is indirect through transfer of the imaging agent to LDL. In conclusion, the fate of Gd-DTPA-DMPE associated with a particular type of lipoprotein is complex, and includes its transfer to other lipoprotein species that are then cleared from the plasma into tissues