Robust Microfluidic Technology and New Lipid Composition for Fabrication of Curcumin-Loaded Liposomes: Effect on the Anticancer Activity and Safety of Cisplatin.

Curcumin exhibits potent anticancer activity via various mechanisms, but its in vivo efficacy has been hampered by poor solubility. Nanotechnology has been employed to deliver curcumin, but most of the reported systems suffered from low drug loading capacity and poor stability. Here, we report the development and optimization of a liposomal formulation for curcumin (Lipo-Cur) using an automated microfluidic technology. Lipo-Cur exhibited a mean diameter of 120 nm with a low polydispersity index (<0.2) and superior loading capacity (17 wt %) compared to other reported liposomal systems. Lipo-Cur increased the water solubility of curcumin by 700-fold, leading to 8-20-fold increased systemic exposure compared to the standard curcumin suspension formulation. When coadministered with cisplatin to tumor-bearing mice, Lipo-Cur augmented the antitumor efficacy of cisplatin in multiple mouse tumor models and decreased the nephrotoxicity. This is the first report demonstrating the dual effects of curcumin enabled by a nanoformulation in enhancing the efficacy and reducing the toxicity of a chemo-drug in animal models under a single and low dose administration.

Preparation of Lipid Nanodisks Containing Apolipoprotein E-Derived Synthetic Peptides for Biocompatible Delivery Vehicles Targeting Low-Density Lipoprotein Receptor.

High-density lipoprotein (HDL) particles that are formed in vivo adopt a disk-shaped structure, in which the periphery of the discoidal phospholipid bilayer is surrounded by apolipoprotein. Such discoidal nanoparticles can be reconstituted with certain apolipoproteins and phospholipids and are commonly called lipid nanodisks. Apolipoprotein E (apoE), one of the HDL constituent proteins, serves as a ligand for the low-density lipoprotein (LDL) receptor. Thus, it is considered that biocompatible delivery vehicles targeting LDL receptors could be prepared by incorporating apoE as the protein component of lipid nanodisks. To enhance targeting efficiency, we designed lipid nanodisks with a large number of ligands using a peptide with the LDL receptor-binding region of apoE combined with a high lipid affinity sequence (LpA peptide). In our study, the LpA peptide spontaneously formed discoidal complexes (LpA nanodisks) of approximately 10 nm in size, equivalent to native HDL. LpA peptides on nanodisks adopted highly α-helical structures, a competent conformation capable of interacting with LDL receptors. As anticipated, the uptake of LpA nanodisks into LDL receptor-expressing cells (HepG2) was higher than that of apoE nanodisks, suggesting an enhanced targeting efficiency via the enrichment of LDL receptor-binding regions on the particle. Biodistribution studies using 111In-labeled LpA nanodisks showed little splenic accumulation and prolonged retention in blood circulation, reflecting the biocompatibility of LpA nanodisks. High accumulation of 111In-labeled LpA nanodisks was observed in the liver as well as in implanted tumors, which abundantly express LDL receptors. Thus, LpA nanodisks are potential biocompatible delivery vehicles targeting LDL receptors.

Polymersome-mediated delivery of combination anticancer therapy to head and neck cancer cells: 2D and 3D in vitro evaluation.

Polymersomes have the potential to encapsulate and deliver chemotherapeutic drugs into tumor cells, reducing off-target toxicity that often compromises anticancer treatment. Here, we assess the ability of the pH-sensitive poly 2-(methacryloyloxy)ethyl phosphorylcholine (PMPC)- poly 2-(diisopropylamino)ethyl methacrylate (PDPA) polymersomes to encapsulate chemotherapeutic agents for effective combinational anticancer therapy. Polymersome uptake and ability to deliver encapsulated drugs into healthy normal oral cells and oral head and neck squamous cell carcinoma (HNSCC) cells was measured in two and three-dimensional culture systems. PMPC-PDPA polymersomes were more rapidly internalized by HNSCC cells compared to normal oral cells. Polymersome cellular uptake was found to be mediated by class B scavenger receptors. We also observed that these receptors are more highly expressed by cancer cells compared to normal oral cells, enabling polymersome-mediated targeting. Doxorubicin and paclitaxel were encapsulated into pH-sensitive PMPC-PDPA polymersomes with high efficiencies either in isolation or as a dual-load for both singular and combinational delivery. In monolayer culture, only a short exposure to drug-loaded polymersomes was required to elicit a strong cytotoxic effect. When delivered to three-dimensional tumor models, PMPC-PDPA polymersomes were able to penetrate deep into the center of the spheroid resulting in extensive cell damage when loaded with both singular and dual-loaded chemotherapeutics. PMPC-PDPA polymersomes offer a novel system for the effective delivery of chemotherapeutics for the treatment of HNSCC. Moreover, the preferential internalization of PMPC polymersomes by exploiting elevated scavenger receptor expression on cancer cells opens up the opportunity to target polymersomes to tumors.

Novel liposomes composed of dimyristoylphosphatidylcholine and trehalose surfactants inhibit the growth of tumor cells along with apoptosis.

Novel liposomes composed of L-α-dimyristoylphosphatidylcholine (DMPC) and trehalose surfactant (DMTre) were produced and inhibitory effects of DMTre on the growth of human colon carcinoma (HCT116) and gastric carcinoma (MKN45) in vitro were examined. The remarkably high inhibitory effects of DMTre on the growth of HCT116 and MKN45 cells were obtained without affecting the growth of normal cells. The thickness of fixed aqueous layer of DMTre was larger than that of DMPC liposomes and increased in a dose-dependent manner. The induction of apoptosis by DMTre was revealed on the basis of flow cytometric analysis. DMTre induced apoptosis through the activation of caspases and mitochondria via Bax. It is noteworthy that remarkable inhibitory effects of DMTre on the growth of human colon and gastric carcinoma cells leading to apoptosis were obtained for the first time.

Anti-tumor effects of cationic hybrid liposomes against colon carcinoma along with apoptosis in vitro.

New-type three-component cationic hybrid liposomes (HLs) composed of dimyristoylphosphatidylcholine (DMPC), polyoxyethylene(21)dodecyl ether (C(12)(EO)(21)) and O,O'-ditetradecanoyl-N-(α-trimethylammonioacetyl) diethanolamine chloride (2C(14)ECl) were produced. Cationic HLs were smaller and more stable than pure DMPC liposomes. It is noteworthy that cationic HLs could remarkably inhibit the growth of human colon cancer (HCT116) cells along with apoptosis in vitro for the first time in this study.

Loading and release of a phospholipid from contact lenses.

PURPOSE: Dry eye syndrome has been associated with the lack of phospholipids in the tear film, leading to disruption of the tear film and subsequent irritation. This study explores the feasibility of loading a phospholipid into contact lenses for controlled release to the eye. METHODS: Silicone hydrogel contact lenses were loaded with 33 µg of radio-labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. The loaded lenses were soaked at 35°C in either water or artificial tear solution (ATF), and the elution of DMPC was quantified by scintillation counting. RESULTS: About 33 µg of DMPC was loaded into the lenses. An average of nearly 1 µg of DMPC was eluted into ATF within the first 10 h. Elution was about five times faster in ATF than in water. The elution appears to be controlled by the diffusivity of DMPC in the contact lens and the properties of the elution solution. CONCLUSIONS: This type of lens technology may have the potential to deliver phospholipids to help address contact lens-related dryness through lipid layer stabilization.

[Marked therapeutic effects of hybrid liposomes on the hepatic metastasis of colon carcinoma].

Hybrid liposomes (HLs) composed of vesicular and micellar surfactants have inhibitory effects on the growth of tumor cells in vitro and in vivo. Successful clinical chemotherapy with drug-free HLs to patient with lymphoma has been reported after approval by the Committe of Bioethics. However, the therapeutic effects of HLs on the metastasis of colon carcinoma cells have not yet been elucidated. In this study, the therapeutic effects of HLs composed of L-alpha-dimyristoylphosphatidylcholine (DMPC) and polyoxyethylene (23) dodecyl ether [C(12)(EO)(23)] on the metastasis of colon carcinoma (Colon26) cells were examined in vivo. Marked high therapeutic effects were obtained in the hepatic metastasis mice model after the treatment with HLs. Furthermore, optical microscopic analysis indicated that HLs could induce the apoptosis of colon carcinoma cells in vivo. No toxicity was observed in the hepatic metastasis mice model after intravenously injecting HLs. Therapeutic effects along with the induction of apoptosis by HLs without any drugs on hepatic metastasis were revealed on the basis of optical microscopic analysis for the first time in vivo.

Effect of bicellar systems on skin properties.

Bicelles are discoidal aggregates formed by a flat dimyristoyl-glycero-phosphocholine (DMPC) bilayer, stabilized by a rim of dihexanoyl-glycero-phosphocholine (DHPC) in water. Given the structure, composition and the dimensions of these aggregates around 10-50 nm diameter, their use for topical applications is a promising strategy. This work evaluates the effect of DMPC/DHPC bicelles with molar ratio (2/1) on intact skin. Biophysical properties of the skin, such as transepidermal water loss (TEWL), elasticity, skin capacitance and irritation were measured in healthy skin in vivo. To study the effect of the bicellar systems on the microstructure of the stratum corneum (SC) in vitro, pieces of native tissue were treated with the aforementioned bicellar system and evaluated by freeze substitution applied to transmission electron microscopy (FSTEM). Our results show that bicelles increase the TEWL, the skin elastic parameters and, decrease skin hydration without promoting local signs of irritation and without affecting the SC lipid microstructure. Thus, a permeabilizing effect of bicelles on the skin takes place possibly due to the changes in the phase behaviour of the SC lipids by effect of phospholipids from bicelles.

Multimodal Image-Guided Surgical and Photodynamic Interventions in Head and Neck Cancer: From Primary Tumor to Metastatic Drainage.

PURPOSE: The low survival rate of head and neck cancer (HNC) patients is attributable to late disease diagnosis and high recurrence rate. Current HNC staging has inadequate accuracy and low sensitivity for effective diagnosis and treatment management. The multimodal porphyrin lipoprotein-mimicking nanoparticle (PLP), intrinsically capable of positron emission tomography (PET), fluorescence imaging, and photodynamic therapy (PDT), shows great potential to enhance the accuracy of HNC staging and potentially HNC management. EXPERIMENTAL DESIGN: Using a clinically relevant VX-2 buccal carcinoma rabbit model that is able to consistently develop metastasis to regional lymph nodes after tumor induction, we investigated the abilities of PLP for HNC diagnosis and management. RESULTS: PLPs facilitated accurate detection of primary tumor and metastatic nodes (their PET image signal to surrounding muscle ratios were 10.0 and 7.3, respectively), and provided visualization of the lymphatic drainage from tumor to regional lymph nodes by both preoperative PET and intraoperative fluorescence imaging, allowing the identification of unknown primaries and recurrent tumors. PLP-PDT significantly enhanced cell apoptosis in mouse tumors (73.2% of PLP-PDT group vs 7.1% of PLP alone group) and demonstrated complete eradication of primary tumors and obstruction of tumor metastasis in HNC rabbit model without toxicity in normal tissues or damage to adjacent critical structures. CONCLUSIONS: PLPs provide a multimodal imaging and therapy platform that could enhance HNC diagnosis by integrating PET/computed tomography and fluorescence imaging, and improve HNC therapeutic efficacy and specificity by tailoring treatment via fluorescence-guided surgery and PDT.

New lipid formulation of amphotericin B: spectral and microscopic analysis.

UV-visible and dichroic spectrum analysis and electron microscopy have been used to characterize a new amphotericin B (AmB) lipid formulation prepared by a solvent displacement process. The composition was dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylglycerol (DMPG) in molar ratio DMPC/DMPG/AmB 7:3:5, a similar composition to that of Abelcet. Although the latter has a "ribbon-like" structure, our process gave a thin disc-like structure. Analysis of circular dichroism (CD) and UV-visible spectra of formulations containing different percentages of AmB revealed that a minimum of AmB self-association was observed with 7:3:5 molar ratio. Varying the lipid ratio (DMPC/DMPG) while maintaining the fixed ratio of AmB yielded similar results when DMPC was in excess (DMPC/DMPG from 10:0 to 6:4). However, when the ratio was between 5:5 to 3:7, AmB self-aggregation increased. For compositions rich in DMPG (2:8 and 0:10), inversion of the CD spectrum was observed. The influence of the lipid composition on the morphology of the complex was also evident in electron microscopy. DMPC/DMPG/AmB (10:0:5) gave large unfracturable lamellae. The presence of DMPG shortened the lamellae, which often appeared as disc-like structures. AmB content, the presence of DMPG and the preparation process all contribute to generating these original structures with particular CD spectra.

Oral synthetic phospholipid (DMPC) raises high-density lipoprotein cholesterol levels, improves high-density lipoprotein function, and markedly reduces atherosclerosis in apolipoprotein E-null mice.

BACKGROUND: Lecithin has been widely sold as a dietary supplement. 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) is a phospholipid that does not exist in nature and has been used in vitro to study lipid binding. We tested DMPC in vivo in apolipoprotein (apo) E-null mice. METHODS AND RESULTS: DMPC or soy or egg lecithin at 1.0 mg/mL was added to the drinking water of 4-week-old apoE-null female mice. Eight weeks later, HDL cholesterol levels and apoA-I levels were markedly increased in the mice that received DMPC. HDL function was also dramatically improved in the mice receiving DMPC, and there was a significant reduction in aortic lesions (P=0.021) in the DMPC mice but not in those receiving lecithin. Adding 1.0 mg/mL of DMPC to the drinking water of 10-month-old apoE-null female mice for 5 weeks caused regression of aortic sinus lesions (P=0.003). Adding 1.0 mg/mL DMPC to the drinking water of 6-month-old apoE-null male mice for 8 weeks significantly reduced aortic sinus lesion area (P=0.0031) and en face whole aorta lesion area (P=0.001), whereas adding the same concentrations of soy or egg lecithin did not significantly alter lesion area. Jejunal apoA-I synthesis and plasma apoA-I levels were increased 2- to 3-fold in mice receiving DMPC but not soy or egg lecithin. CONCLUSIONS: DMPC (but not lecithin) raises HDL cholesterol and apoA-I, improves HDL function, and prevents lesions or causes their regression in apoE-null mice.

Kupffer cells do not play a role in governing the efficacy of liposomal mitoxantrone used to treat a tumor model designed to assess drug delivery to liver.

A tumor model designed to assess liposome-mediated drug delivery to liver has been used in an attempt to better understand the mechanism of activity of liposomal mitoxantrone, a liposomal anticancer drug formulation that appears to be uniquely effective in treating this tumor model. Reductions in liposomal mitoxantrone accumulation in the liver were achieved either by use of poly(ethylene)glycol (PEG)-modified lipids or by methods designed to deplete liver phagocytes, a method referred to as hepatic mononuclear phagocytic system (MPS) blockade. A 2-fold reduction in mitoxantrone delivery to the liver was obtained using a mitoxantrone formulation with PEG-modified lipids, and a 3-fold reduction was obtained when liposomal mitoxantrone was given to animals pretreated to induce hepatic MPS blockade. Results demonstrate that the liposomal mitoxantrone formulation prepared with PEG-modified lipids was significantly less active than the formulations that did not contain PEG lipids, with median survival times of 17 days and 100% 60-day survival, respectively. In contrast, hepatic MPS blockade had no effect on the therapeutic activity of 1,2-dimyristoyl phosphatidylcholine/cholesterol (DMPC/Chol) mitoxantrone (100% 60-day survival). These data suggest that the hepatic MPS does not play a role in mediating the therapeutic activity of DMPC/Chol mitoxantrone in the treatment of liver localized disease. Results with formulations prepared with a PEG-stabilized surface, however, suggest that nonspecific methods to decrease liposome cell interactions inhibit the therapeutic activity of DMPC/Chol mitoxantrone.

Disseminated visceral fusariosis treated with amphotericin B-phospholipid complex.

Fusariosis, a rare infectious disease of the immunocompromised host, is relatively resistant to amphotericin B (AmB) or other antifungal agents. We describe a 5-year follow-up of a 40 year old woman with T-type acute lymphoblastic leukemia who following chemotherapy developed prolonged high fever, chills, night sweats, and severe weakness. Liver function tests were impaired and abdominal computerized tomography (CT) showed multiple lesions in the liver and abnormal structure of the spleen. A laparotomy revealed multiple granulomas containing Fusarium sp. in the liver, and the spleen was heavily infiltrated by the same fungus. The patient failed to respond to the conventional AmB dosage form (Fungizone) even after a total dose of 3.0 g was given, and developed significant renal impairment. AmB was complexed (in a mole ratio of 1:16) with a mixture of the phospholipids dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol (mixed in 7:3 mole ratio). The resulting drug complex, AmB-PLC, was then administered (1-4 mg/kg/day, total dose 4.2 g) and subsequently the patient was cured of all symptoms of fusariosis. There were only mild side effects and no nephrotoxicity was evident. On the contrary, marked improvement of the renal function tests occurred during AmB-PLC treatment. Eight months later, she developed a spinal lesion with dense consistency in L5 and S1, and after receiving another course of AmB-PLC (3.1 g) she recovered completely. In a 2 year follow-up period the patient had no further relapse of the fungal disease. Subsequent chemotherapy given for relapse of the leukemia was followed by a new fungal infection, which was treated with AmB-cholesteryl sulfate complex (Amphocil).(ABSTRACT TRUNCATED AT 250 WORDS)

The preparation of norfloxacin-loaded liposomes and their in-vitro evaluation in pig's eye.

The effectiveness of norfloxacin as an antibacterial agent in ophthalmology is limited by poor drug delivery and limited ocular bioavailability. Liposomes containing norfloxacin have been prepared from different phospholipids using a novel technique with an encapsulation efficiency sixteen times greater than that of a conventional film method. The in-vitro release of the norfloxacin and the transcorneal characteristics of the liposomes have been evaluated. Differential scanning calorimetry was used to determine the interaction occurring between liposomes and cornea. The release of liposome-entrapped norfloxacin was affected by the pH of the environment. In the in-vitro corneal perfusion studies, norfloxacin-loaded liposome was transferred through the cornea at a slower rate than was the free drug. Norfloxacin-loaded liposomes were accumulated primarily in the cornea. The drug corneal retention of the lipids increased in the order dimyristoyl-L-alpha-phosphatidylcholine < dipalmitoyl-L-alpha -phosphatidylcholine < distearoyl-L-alpha-phosphatidylcholine. In the corneal drug-elimination study, liposomal norfloxacin increased the loading of the drug in cornea; the maximum value of the loading occurred 5 h after dosing. The drainage of liposomes from the cornea was somewhat slower than the solution form. Accumulation of norfloxacin in the cornea was greater for the liposome-entrapped drug. The results suggest that norfloxacin-loaded liposomes are absorbed by the cornea via endocytosis.

Chemotherapy with hybrid liposomes for acute lymphatic leukemia leading to apoptosis in vivo.

Hybrid liposomes (HL) composed of 95 mol% l-α-dimyristoylphosphatidylcholine (DMPC) and 5 mol% polyoxyethylene (25) dodecyl ether (C(12)(EO)(25)) were prepared by sonication. A clear solutions of HL-25 having hydrodynamic diameter of about 50 nm could be maintained over 3 weeks. Remarkable reduction of tumor volume in model mice of acute lymphatic leukemia (ALL) intravenously treated with HL-25 without drugs after the subcutaneously inoculation of human ALL (MOLT-4) cells was verified in vivo. Induction of apoptosis in tumor of model mice of ALL treated with HL-25 was observed in micrographs on the basis of TUNEL method. Remarkable decrease of the ascites in ALL model mice treated with HL-25 was observed. It is noteworthy that prolonged survival (>400%) was obtained in model mice of ALL after the treatment with HL-25 without drugs.

Synthetic dimyristoylphosphatidylcholine liposomes assimilating into high-density lipoprotein promote regression of atherosclerotic lesions in cholesterol-fed rabbits.

We have reported recently that enrichment of high-density lipoprotein (HDL) with phosphatidylcholine (PC) liposomes is effective in solubilizing cholesterol from isolated human atherosclerotic plaques. In the present study, we investigated the in vivo effect of enrichment of HDL with PC on regression of diet-induced atherosclerosis in rabbits. As part of the study, a preliminary in vitro study on blood collected from the cholesterol-fed rabbits was performed to assess the capacity of the HDL density (d > 1.063 g/mL) plasma fraction from cholesterol-fed rabbits to assimilate multilamellar liposomes of synthetic dimyristoylphosphatidylcholine (DMPC). This was compared with the capacities of egg- and soy-PC liposomes to be assimilated into the HDL density plasma fraction. The capacity of the HDL density fraction to absorb PC from DMPC liposomes (11.5 mg/mL) was more than 10 times greater than egg or soy liposomes. Therefore, DMPC liposomes were chosen to infuse into cholesterol-fed rabbits. Cholesterol-fed rabbits infused weekly with DMPC liposomes (300 mg/kg body weight) for five weeks had significantly decreased aortic cholesterol contents (P < 0.05) compared with saline-infused cholesterol-fed controls. Atherosclerotic plaque volume, as measured by a type of new magnetic resonance imaging analysis, also decreased significantly (P < 0.05) after DMPC treatment. The present findings suggest that the enrichment of HDL with PC via intravenous infusion of synthetic DMPC liposomes could be a potential therapeutic approach for atherosclerotic plaque regression.

Therapeutic effects of hybrid liposomes on gastric carcinoma involve apoptosis.

Hybrid liposomes (HLs) composed of 90 mol% dimyristoylphosphatidylcholine (DMPC) and 10 mol% polyoxyethylene(23)dodecyl ether (C(12)(EO)(23)), having a hydrodynamic diameter under 100 nm, were preserved for a period of one month. The inhibitory effects of HLs on the growth of gastric carcinoma (CoRa 622 G6) cells in vitro were investigated. Decrease in mitochondrial membrane potential and activation of caspase-8, caspase-9 and caspase-3 were observed, indicating that apoptotic signals induced by HLs should pass through mitochondria and these caspases. Remarkable inhibitory effects on the metastasis of gastric carcinoma along with apoptosis and prolonged survival were obtained for mouse models of gastric carcinoma with peritoneal dissemination after the treatment with HLs in vivo.

Histological bioanalysis for therapeutic effects of hybrid liposomes on the hepatic metastasis of colon carcinoma in vivo.

Therapeutic effects of hybrid liposomes (HL) composed of l-alpha-dimyristoylphosphatidylcholine (DMPC) and polyoxyethylene (23) dodecylether (C(12)(EO)(23)) on the metastasis of colon carcinoma (Colon26) cells were examined in vivo. Fluorescent labeled Colon26 cells were observed in the liver tissue of hepatic metastasis mouse models after the intrasplenic inoculation of the cells. Remarkably high therapeutic effects were obtained in the hepatic metastasis mouse models after the treatment with HL on the basis of relative liver weight and histological analysis of the liver tissue sections of mouse models with hematoxylin-eosin staining, Masson trichrome staining, and CEA immunostaining as a histochemical marker of metastatic colon carcinoma. Furthermore, no toxicity was observed in the hepatic metastasis mouse models after the intravenous injection of HL. Therapeutic effects of HL without any drugs on the hepatic metastasis were revealed on the basis of histological analysis for the first time in vivo.

Lipid nanostructures: self-assembly and effect on skin properties.

This work evaluates the relation between the composition and the self-assembly of some lipid aggregates with their effects on the skin. To this end, liposomes, bicelles and micelles formed by dipalmitoylphosphatidylcholine (DPPC), dimyristoylphosphatidylcholine (DMPC) and dihexanoylphosphatidylcholine (DHPC) were characterized by electron microscopy and dynamic light scattering techniques, and applied on the skin. The results revealed that nanostructures with similar assembly but different composition caused different effects on the skin parameters. In general, samples containing DMPC affected the barrier function to a greater extent than systems containing DPPC. Additionally, our results showed that samples with the same lipid composition but different assembly exerted different effects on the skin. Liposomes decreased or did not modify the transepidermal water loss (TEWL), while bicelles and micelles increased this parameter. Hydration of the skin diminished especially after the application of micellar and bicellar samples. In vitro experiments showed structures like vesicles inside cutaneous SC (stratum corneum) incubated with DPPC/DHPC bicelles. These structures were not detected in SC samples incubated with DMPC/DHPC bicelles probably due to the different thermotropic behavior of DMPC and DPPC at physiological temperatures. Results reported in this work should be considered in terms of design of more efficient and specific skin delivery systems.

Dimyristoylphosphotidylcholine induces conformational changes in apoB that lowers lipoprotein(a).

Lipoprotein(a) [Lp(a)] is assembled by the binding of apolipoprotein B (apoB) lysine residues on LDL to lysine binding sites in apolipoprotein(a) [apo(a)] and the subsequent formation of a disulphide bond between apoB and apo(a). In this study, we induced changes in apoB conformation by adding phospholipids to LDL and tested the effect of the altered apoB conformation on Lp(a) assembly. The addition of dimyristoylphosphatidylcholine (DMPC) to isolated LDL induced a decrease in the alpha-helical content of apoB and increased the immunoreactivity of the apoB C terminus toward monoclonal antibodies in the region. These conformational changes were associated with a reduction in the ability of the DMPC-modified LDL to form Lp(a) in in vitro assays. Furthermore, administration of DMPC to Lp(a) transgenic mice lead to a significant but transient decrease in Lp(a) levels (18.6% decrease at 2 h, P < 0.001) which coincided with the association of DMPC with LDL in plasma. Our study shows that changes in apoB conformation in the C-terminal region alter the exposure of sequences required for Lp(a) assembly and reduce the formation of Lp(a) both in vitro and in vivo. We conclude that manipulation of LDL surface phospholipids alters Lp(a) levels.