LDL Receptor Regulates the Reverse Transport of Macrophage-Derived Unesterified Cholesterol via Concerted Action of the HDL-LDL Axis: Insight From Mouse Models.

RATIONALE: 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. OBJECTIVE: We investigated LDL contributions to the m-RCT pathway in hypercholesterolemic mice. METHODS AND RESULTS: 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. CONCLUSIONS: 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.

Impaired HDL (High-Density Lipoprotein)-Mediated Macrophage Cholesterol Efflux in Patients With Abdominal Aortic Aneurysm-Brief Report.

Objective- The ability of HDL (high-density lipoprotein) to promote macrophage cholesterol efflux is considered the main HDL cardioprotective function. Abdominal aortic aneurysm (AAA) is usually characterized by cholesterol accumulation and macrophage infiltration in the aortic wall. Here, we aim to evaluate the composition of circulating HDL particles and their potential for promoting macrophage cholesterol efflux in AAA subjects. Approach and Results- First, we randomly selected AAA and control subjects from Spain. The AAA patients in the Spanish cohort showed lower plasma apoA-I levels concomitantly associated with low levels of plasma HDL cholesterol and the amount of preß-HDL particles. We determined macrophage cholesterol efflux to apoB-depleted plasma, which contains mature HDL, preß-HDL particles and HDL regulatory proteins. ApoB-depleted plasma from AAA patients displayed an impaired ability to promote macrophage cholesterol efflux. Next, we replicated the experiments with AAA and control subjects derived from Danish cohort. Danish AAA patients also showed lower apoA-I levels and a defective HDL-mediated macrophage cholesterol efflux. Conclusions- AAA patients show impaired HDL-facilitated cholesterol removal from macrophages, which could be mechanistically linked to AAA.

T22-PE24-H6 Nanotoxin Selectively Kills CXCR4-High Expressing AML Patient Cells In Vitro and Potently Blocks Dissemination In Vivo.

Despite advances in the development of targeted therapies for acute myeloid leukemia (AML), most patients relapse. For that reason, it is still necessary to develop novel therapies that improve treatment effectiveness and overcome drug resistance. We developed T22-PE24-H6, a protein nanoparticle that contains the exotoxin A from the bacterium Pseudomonas aeruginosa and is able to specifically deliver this cytotoxic domain to CXCR4+ leukemic cells. Next, we evaluated the selective delivery and antitumor activity of T22-PE24-H6 in CXCR4+ AML cell lines and BM samples from AML patients. Moreover, we assessed the in vivo antitumor effect of this nanotoxin in a disseminated mouse model generated from CXCR4+ AML cells. T22-PE24-H6 showed a potent, CXCR4-dependent antineoplastic effect in vitro in the MONO-MAC-6 AML cell line. In addition, mice treated with nanotoxins in daily doses reduced the dissemination of CXCR4+ AML cells compared to buffer-treated mice, as shown by the significant decrease in BLI signaling. Furthermore, we did not observe any sign of toxicity or changes in mouse body weight, biochemical parameters, or histopathology in normal tissues. Finally, T22-PE24-H6 exhibited a significant inhibition of cell viability in CXCR4high AML patient samples but showed no activity in CXCR4low samples. These data strongly support the use of T22-PE24-H6 therapy to benefit high-CXCR4-expressing AML patients.

Potent Anticancer Activity of CXCR4-Targeted Nanostructured Toxins in Aggressive Endometrial Cancer Models.

Patients with advanced endometrial cancer (EC) show poor outcomes. Thus, the development of new therapeutic approaches to prevent metastasis development in high-risk patients is an unmet need. CXCR4 is overexpressed in EC tumor tissue, epitomizing an unexploited therapeutic target for this malignancy. The in vitro antitumor activity of two CXCR4-targeted nanoparticles, including either the C. diphtheriae (T22-DITOX-H6) or P. aeruginosa (T22-PE24-H6) toxin, was evaluated using viability assays. Apoptotic activation was assessed by DAPI and caspase-3 and PARP cleavage in cell blocks. Both nanotoxins were repeatedly administrated to a subcutaneous EC mouse model, whereas T22-DITOX-H6 was also used in a highly metastatic EC orthotopic model. Tumor burden was assessed through bioluminescence, while metastatic foci and toxicity were studied using histological or immunohistochemical analysis. We found that both nanotoxins exerted a potent antitumor effect both in vitro and in vivo via apoptosis and extended the survival of nanotoxin-treated mice without inducing any off-target toxicity. Repeated T22-DITOX-H6 administration in the metastatic model induced a dramatic reduction in tumor burden while significantly blocking peritoneal, lung and liver metastasis without systemic toxicity. Both nanotoxins, but especially T22-DITOX-H6, represent a promising therapeutic alternative for EC patients that have a dismal prognosis and lack effective therapies.

Time-Prolonged Release of Tumor-Targeted Protein-MMAE Nanoconjugates from Implantable Hybrid Materials.

The sustained release of small, tumor-targeted cytotoxic drugs is an unmet need in cancer therapies, which usually rely on punctual administration regimens of non-targeted drugs. Here, we have developed a novel concept of protein-drug nanoconjugates, which are packaged as slow-releasing chemically hybrid depots and sustain a prolonged secretion of the therapeutic agent. For this, we covalently attached hydrophobic molecules (including the antitumoral drug Monomethyl Auristatin E) to a protein targeting a tumoral cell surface marker abundant in several human neoplasias, namely the cytokine receptor CXCR4. By this, a controlled aggregation of the complex is achieved, resulting in mechanically stable protein-drug microparticles. These materials, which are mimetics of bacterial inclusion bodies and of mammalian secretory granules, allow the slow leakage of fully functional conjugates at the nanoscale, both in vitro and in vivo. Upon subcutaneous administration in a mouse model of human CXCR4+ lymphoma, the protein-drug depots release nanoconjugates for at least 10 days, which accumulate in the tumor with a potent antitumoral effect. The modification of scaffold cell-targeted proteins by hydrophobic drug conjugation is then shown as a novel transversal platform for the design of slow releasing protein-drug depots, with potential application in a broad spectrum of clinical settings.

A diphtheria toxin-based nanoparticle achieves specific cytotoxic effect on CXCR4+ lymphoma cells without toxicity in immunocompromised and immunocompetent mice.

High rates of relapsed and refractory diffuse large B-cell lymphoma (DLBCL) patients and life-threatening side effects associated with immunochemotherapy make an urgent need to develop new therapies for DLBCL patients. Immunotoxins seem very potent anticancer therapies but their use is limited because of their high toxicity. Accordingly, the self-assembling polypeptidic nanoparticle, T22-DITOX-H6, incorporating the diphtheria toxin and targeted to CXCR4 receptor, which is overexpressed in DLBCL cells, could offer a new strategy to selectively eliminate CXCR4+ DLBCL cells without adverse effects. In these terms, our work demonstrated that T22-DITOX-H6 showed high specific cytotoxicity towards CXCR4+ DLBCL cells at the low nanomolar range, which was dependent on caspase-3 cleavage, PARP activation and an increase of cells in early/late apoptosis. Repeated nanoparticle administration induced antineoplastic effect, in vivo and ex vivo, in a disseminated immunocompromised mouse model generated by intravenous injection of human luminescent CXCR4+ DLBCL cells. Moreover, T22-DITOX-H6 inhibited tumor growth in a subcutaneous immunocompetent mouse model bearing mouse CXCR4+ lymphoma cells in the absence of alterations in the hemogram, liver or kidney injury markers or on-target or off-target organ histology. Thus, T22-DITOX-H6 demonstrates a selective cytotoxicity towards CXCR4+ DLBCL cells without the induction of toxicity in non-lymphoma infiltrated organs nor hematologic toxicity.

Engineering non-antibody human proteins as efficient scaffolds for selective, receptor-targeted drug delivery.

Self-assembling non-immunoglobulin scaffold proteins are a promising class of nanoscale carriers for drug delivery and interesting alternatives to antibody-based carriers that are not sufficiently efficient in systemic administration. To exploit their potentialities in clinics, protein scaffolds need to be further tailored to confer appropriate targeting and to overcome their potential immunogenicity, short half-life in plasma and proteolytic degradation. We have here engineered three human scaffold proteins as drug carrier nanoparticles to target the cytokine receptor CXCR4, a tumoral cell surface marker of high clinical relevance. The capability of these scaffolds for the selective delivery of Monomethyl auristatin E has been comparatively evaluated in a disseminated mouse model of human, CXCR4+ acute myeloid leukemia. Monomethyl auristatin E is an ultra-potent anti-mitotic drug used against a range of hematological neoplasias, which because of its high toxicity is not currently administered as a free drug but as payload in antibody-drug conjugates. The protein nanoconjugates generated here offer a collective strength of simple manufacturing process, high proteolytic and structural stability and multivalent ligand receptor interactions that result in a highly efficient and selective delivery of the payload drug and in a potent anticancer effect. The approach shown here stresses this class of human scaffold proteins as promising alternatives to antibodies for targeted drug delivery in the rapidly evolving drug development landscape.

A multivalent Ara-C-prodrug nanoconjugate achieves selective ablation of leukemic cells in an acute myeloid leukemia mouse model.

Current therapy in acute myeloid leukemia (AML) is based on chemotherapeutic drugs administered at high doses, lacking targeting selectivity and displaying poor therapeutic index because of severe adverse effects. Here, we develop a novel nanoconjugate that combines a self-assembled, multivalent protein nanoparticle, targeting the CXCR4 receptor, with an Oligo-Ara-C prodrug, a pentameric form of Ara-C, to highly increase the delivered payload to target cells. This 13.4 nm T22-GFP-H6-Ara-C nanoconjugate selectively eliminates CXCR4+ AML cells, which are protected by its anchoring to the bone marrow (BM) niche, being involved in AML progression and chemotherapy resistance. This nanoconjugate shows CXCR4-dependent internalization and antineoplastic activity in CXCR4+ AML cells in vitro. Moreover, repeated T22-GFP-H6-Ara-C administration selectively eliminates CXCR4+ leukemic cells in BM, spleen and liver. The leukemic dissemination blockage induced by T22-GFP-H6-Ara-C is significantly more potent than buffer or Oligo-Ara-C-treated mice, showing no associated on-target or off-target toxicity and, therefore, reaching a highly therapeutic window. In conclusion, T22-GFP-H6-Ara-C exploits its 11 ligands-multivalency to enhance target selectivity, while the Oligo-Ara-C prodrug multimeric form increases 5-fold its payload. This feature combination offers an alternative nanomedicine with higher activity and greater tolerability than current intensive or non-intensive chemotherapy for AML patients.

Cholesterol and 27-hydroxycholesterol promote thyroid carcinoma aggressiveness.

Cholesterol mediates its proliferative and metastatic effects via the metabolite 27-hydroxycholesterol (27-HC), at least in breast and endometrial cancer. We determined the serum lipoprotein profile, intratumoral cholesterol and 27-HC levels in a cohort of patients with well-differentiated papillary thyroid carcinoma (PTC; low/intermediate and high risk), advanced thyroid cancers (poorly differentiated, PDTC and anaplastic thyroid carcinoma, ATC) and benign thyroid tumors, as well as the expression of genes involved in cholesterol metabolism. We investigated the gene expression profile, cellular proliferation, and migration in Nthy-ori 3.1 and CAL-62 cell lines loaded with human low-density lipoprotein (LDL). Patients with more aggressive tumors (high-risk PTC and PDTC/ATC) showed a decrease in blood LDL cholesterol and apolipoprotein B. These changes were associated with an increase in the expression of the thyroid's LDL receptor, whereas 3-hydroxy-3-methylglutaryl-CoA reductase and 25-hydroxycholesterol 7-alpha-hydroxylase were downregulated, with an intratumoral increase of the 27-HC metabolite. Furthermore, LDL promoted proliferation in both the Nthy-ori 3.1 and CAL-62 thyroid cellular models, but only in ATC cells was its cellular migration increased significantly. We conclude that cholesterol and intratumoral accumulation of 27-HC promote the aggressive behavior process of PTC. Targeting cholesterol metabolism could be a new therapeutic strategy in thyroid tumors with poor prognosis.

Characterization of ApoJ-reconstituted high-density lipoprotein (rHDL) nanodisc for the potential treatment of cerebral ß-amyloidosis.

Cerebral ß-amyloidosis is a major feature of Alzheimer's disease (AD), characterized by the accumulation of ß-amyloid protein (Aß) in the brain. Several studies have implicated lipid/lipoprotein metabolism in the regulation of ß-amyloidosis. In this regard, HDL (High Density Lipoprotein)-based therapies could ameliorate pathological features associated with AD. As apolipoprotein J (ApoJ) is a natural chaperone that interacts with Aß, avoiding its aggregation and toxicity, in this study we propose to prepare reconstituted rHDL-rApoJ nanoparticles by assembling phospholipids with recombinant human ApoJ (rApoJ). Hence, rHDL particles were prepared using the cholate dialysis method and characterized by N-PAGE, dynamic light scattering, circular dichroism and electron transmission microscopy. The preparation of rHDL particles showed two-sized populations with discoidal shape. Functionally, rHDL-rApoJ maintained the ability to prevent the Aß fibrillization and mediated a higher cholesterol efflux from cultured macrophages. Fluorescently-labelled rHDL-rApoJ nanoparticles were intravenously administrated in mice and their distribution over time was determined using an IVIS Xenogen® imager. It was confirmed that rHDL-rApoJ accumulated in the cranial region, especially in old transgenic mice presenting a high cerebral Aß load. In conclusion, we have standardized a reproducible protocol to produce rHDL-rApoJ nanoparticles, which may be potentially considered as a therapeutic option for ß-amyloid-related pathologies.

Phytosterol-mediated inhibition of intestinal cholesterol absorption in mice is independent of liver X receptor.

SCOPE: Previous studies have proposed that phytosterols activate liver X receptors (LXR) in the intestine, thereby reducing intestinal cholesterol absorption and promoting fecal cholesterol excretion. METHODS AND RESULTS: In the present study, we examined the effects of dietary phytosterol supplementation on intestinal cholesterol absorption and fecal neutral sterol excretion in LXRαß-deficient mice, and wild-type mice treated with synthetic high-affinity LXRαß agonists. LXRαß deficiency led to an induction of intestinal cholesterol absorption and liver cholesterol accumulation. Phytosterol feeding resulted in an approximately 40% reduction of intestinal cholesterol absorption both in wild-type and LXRαß-deficient mice, reduced dietary cholesterol accumulation in liver and promoted the excretion of fecal cholesterol-derived compounds. Furthermore, phytosterols produced additive inhibitory effects on cholesterol absorption in mice treated with LXRαß agonists. CONCLUSIONS: Our data confirm the effect of LXR in regulating intestinal cholesterol absorption and demonstrate that the cholesterol-lowering effects of phytosterols occur in an LXR-independent manner.

ApoA-I mimetic administration, but not increased apoA-I-containing HDL, inhibits tumour growth in a mouse model of inherited breast cancer.

Low levels of high-density lipoprotein cholesterol (HDLc) have been associated with breast cancer risk, but several epidemiologic studies have reported contradictory results with regard to the relationship between apolipoprotein (apo) A-I and breast cancer. We aimed to determine the effects of human apoA-I overexpression and administration of specific apoA-I mimetic peptide (D-4F) on tumour progression by using mammary tumour virus-polyoma middle T-antigen transgenic (PyMT) mice as a model of inherited breast cancer. Expression of human apoA-I in the mice did not affect tumour onset and growth in PyMT transgenic mice, despite an increase in the HDLc level. In contrast, D-4F treatment significantly increased tumour latency and inhibited the development of tumours. The effects of D-4F on tumour development were independent of 27-hydroxycholesterol. However, D-4F treatment reduced the plasma oxidized low-density lipoprotein (oxLDL) levels in mice and prevented oxLDL-mediated proliferative response in human breast adenocarcinoma MCF-7 cells. In conclusion, our study shows that D-4F, but not apoA-I-containing HDL, hinders tumour growth in mice with inherited breast cancer in association with a higher protection against LDL oxidative modification.

Consumption of polyunsaturated fat improves the saturated fatty acid-mediated impairment of HDL antioxidant potential.

SCOPE: The present study aimed to compare the effects of diets containing high-fat, high-cholesterol and saturated fatty acids (HFHC-SFA) and HFHC-polyunsaturated fatty acids-containing (HFHC-PUFA) diets on two major antiatherogenic functions of HDL, the HDL antioxidant function and the macrophage-to-feces reverse cholesterol transport. METHODS AND RESULTS: Experiments were carried out in mice fed a low-fat, low-cholesterol (LFLC) diet, an HFHC-SFA diet or an HFHC-PUFA diet in which SFAs were partly replaced with an alternative high-linoleic and α-linolenic fat source. The HFHC-SFA caused a significant increase in serum HDL cholesterol and phospholipids as well as elevated levels of oxidized HDL and oxidized LDL. Replacing SFA with PUFA significantly reduced the levels of these oxidized lipoproteins and enhanced the ability of HDL to protect LDL from oxidation. The SFA-mediated impairment of HDL antioxidant potential was not associated with the cholesterol content of the diet, obesity or insulin resistance. In contrast, the effect of the HFHC diets on fecal macrophage-derived cholesterol excretion was independent of the fatty acid source. CONCLUSION: SFA intake impairs the antioxidant potential of HDL and increases serum levels of oxidized lipoprotein species whereas the antioxidant potential of HDL is enhanced after PUFA consumption.