Isolation of recombinant apolipoprotein E4 N-terminal domain by foam fractionation

Apolipoprotein (apo) E functions in lipoprotein metabolism as a low density lipoprotein receptor ligand. ApoE is comprised of two structural domains, a 22 kDa N-terminal (NT) domain that adopts a helix bundle conformation and a 10 kDa C-terminal domain with strong lipid binding affinity. The NT domain is capable of transforming aqueous phospholipid dispersions into discoidal reconstituted high density lipoprotein (rHDL) particles. Given the utility of apoE-NT as a structural component of rHDL, expression studies were conducted. A plasmid construct encoding a pelB leader sequence fused to the N-terminus of human apoE4 (residues 1-183) was transformed into Escherichia coli. Upon expression, the fusion protein is directed to the periplasmic space where leader peptidase cleaves the pelB sequence, generating mature apoE4-NT. In shaker flask expression cultures, apoE4-NT escapes the bacteria and accumulates in the medium. In a bioreactor setting, however, apoE4-NT was found to combine with gas and liquid components in the culture medium to generate large quantities of foam. When this foam was collected in an external vessel and collapsed into a liquid foamate, analysis revealed that apoE4-NT was the sole major protein present. The product protein was further isolated by heparin affinity chromatography (60-80 mg/liter bacterial culture), shown to be active in rHDL formulation, and documented to serve as an acceptor of effluxed cellular cholesterol. Thus, foam fractionation provides a streamlined process to produce recombinant apoE4-NT for biotechnology applications.

Foam fractionation of a recombinant biosurfactant apolipoprotein

Locusta migratoria apolipophorin III (apoLp-III) possesses the ability to exist as a water soluble amphipathic α-helix bundle and a lipid surface seeking apolipoprotein. The intrinsic ability of apoLp-III to transform phospholipid vesicles into reconstituted discoidal high-density lipoproteins (rHDL) has led to myriad applications. To improve the yield of recombinant apoLp-III, studies were performed in a bioreactor. Induction of apoLp-III expression generated a protein product that is secreted from E. coli into the culture medium. Interaction of apoLp-III with gas and liquid components in media produced large quantities of thick foam. A continuous foam fractionation process yielded a foamate containing apoLp-III as the sole major protein component. The yield of recombinant apoLp-III was ~0.2 g / liter bacterial culture. Mass spectrometry analysis verified the identity of the target protein and indicated no modifications or changes to apoLp-III occurred as a result of foam fractionation. The functional ability of apoLp-III to induce rHDL formation was evaluated by incubating foam fractionated apoLp-III with phosphatidylcholine vesicles. FPLC size exclusion chromatography revealed a single major population of particles in the size range of rHDL. The results described offer a novel approach to bioreactor-based apoLp-III production that takes advantage of its intrinsic biosurfactant properties.

A dual-targeting reconstituted high density lipoprotein leveraging the synergy of sorafenib and antimiRNA21 for enhanced hepatocellular carcinoma therapy

Sorafenib (So) is a multi-target kinase inhibitor extensively used in clinic for hepatocellular carcinoma therapy. It demonstrated strong inhibition both in tumor proliferation and tumor angiogenesis, while hampered by associated cutaneous side-effect and drug resistance. The knockdown of miR-21 with antisense oligonucleotides (antimiRNA21) was regarded as an efficient strategy for increasing tumor sensibility to chemotherapy, which could be employed to appreciate the efficacy of So. Herein, we successfully formulated a dual-targeting delivery system for enhanced hepatocellular carcinoma therapy by encapsulating So and antimiRNA21 in RGD pentapeptide-modified reconstituted high-density lipoprotein (RGD-rHDL/So/antimiRNA21). The RGD and apolipoprotein A-I (ApoA-I) on nanoparticles (NPs) could drive the system simultaneously to tumor neovascular and parenchyma by binding to the overexpressed ανβ3-integrin and SR-B1 receptors, achieving precise delivery of therapeutics to maximize the efficacy. A series in vitro and in vivo experiments revealed that co-delivery of So and antimiRNA21 by RGD-rHDL significantly strengthened the anti-tumor and anti-angiogenic effect of So with negligible toxicity towards major organs, reversed drug-resistance and was capable of remodeling tumor environments. The constructed RGD-rHDL/So/antimiRNA21 with improved efficacy and excellent tumor targeting ability provided new idea for chemo-gene combined therapy in hepatocellular carcinoma.

STATEMENT OF SIGNIFICANCE

Sorafenib (So) is a multi-target kinase inhibitor which was approved by FDA as first-line drug for hepatocellular carcinoma (HCC) therapy. However, long term application of So in clinic was hampered by serious dermal toxicity and drug resistance. Although numerous researchers were devoted to finding alternatives or therapies as combination treatments with So to reach more desired therapeutic efficacy, the therapeutic options were still limited. The present study prepares RGD pentapeptide decorated biomimic reconstituted high-density lipoprotein (rHDL) loaded with So and antimiRNA21 (RGD-rHDL/So/antimiRNA21) for enhanced HCC therapy. The RGD-rHDL/So/antimiRNA21 NPs offer an effective platform for anti-tumor and anti-angiogenesis therapy in HCC and provide new approach to reverse drug-resistance of So for feasible clinical application.

Reconstituted high density lipoprotein mediated targeted co-delivery of HZ08 and paclitaxel enhances the efficacy of paclitaxel in multidrug-resistant MCF-7 breast cancer cells

In the past decades, reconstituted high density lipoprotein (rHDL) has been successfully developed as a drug carrier since the enhanced HDL-lipids uptake is demonstrated in several human cancers. In this paper, rHDL, for the first time, was utilized to co-encapsulate two hydrophobic drugs: an anticancer drug, paclitaxel (PTX), and a new reversal agent for P-gp (P-glycoprotein)-mediated multidrug resistance (MDR) of cancer, N-cyano-1-[(3,4-dimethoxyphenyl)methyl]-3,4-dihydro-6,7-dimethoxy-N'-octyl-2(1H)-isoquinoline-carboximidamide (HZ08). We proposed this drug co-delivery strategy to reverse PTX resistance. The study aimed to develop a biomimetic nanovector, reconstituted high density lipoprotein (rHDL), mediating targeted PTX-HZ08 delivery for cancer therapy. Using sodium cholate dialysis method, we successfully formulated dual-agent co-delivering rHDL nanoparticles (PTX-HZ08-rHDL NPs) with a typical spherical morphology, well-distributed size (~100nm), high drug encapsulation efficiency (approximately 90%), sustained drug release properties and exceptional stability even after storage for 1month or incubation in 10% fetal bovine serum (FBS) DMEM for up to 2days. Results demonstrated that PTX-HZ08-rHDL NPs significantly enhanced anticancer efficacy in vitro, including higher cytotoxicity and better ability to induce cell apoptosis against both PTX-sensitive and -resistant MCF-7 human breast cancer cell lines (MCF-7 and MCF-7/PTX cells). Mechanism studies demonstrated that these improvements could be correlated with increased cellular uptake of PTX mediated by scavenger receptor class B type I (SR-BI) as well as prolonged intracellular retention of PTX due to the HZ08 mediated drug-efflux inhibition. In addition, in vivo investigation showed that the PTX-HZ08-rHDL NPs were substantially safer, have higher tumor-targeted capacity and have stronger antitumor activity than the corresponding dosage of paclitaxel injection. These findings suggested that rHDL NPs could be an ideal tumor-targeted nanovector for simultaneous transfer of insoluble anticancer drug and drug resistance reversal agents. The PTX-HZ08-rHDL NPs co-delivery system might be a new promising strategy to overcome tumor drug resistance.