HDL drug carriers for targeted therapy

Quantitative Raman chemical imaging of intracellular drug-membrane aggregates and small molecule drug precipitates in cytoplasmic organelles

Raman confocal microscopes have been used to visualize the distribution of small molecule drugs within different subcellular compartments. This visualization allows the discovery, characterization, and detailed analysis of the molecular transport phenomena underpinning the Volume of Distribution - a key parameter governing the systemic pharmacokinetics of small molecule drugs. In the specific case of lipophilic small molecules with large Volumes of Distribution, chemical imaging studies using Raman confocal microscopes have revealed how weakly basic, poorly soluble drug molecules can accumulate inside cells by forming stable, supramolecular complexes in association with cytoplasmic membranes or by precipitating out within organelles. To study the self-assembly and function of the resulting intracellular drug inclusions, Raman chemical imaging methods have been developed to measure and map the mass, concentration, and ionization state of drug molecules at a microscopic, subcellular level. Beyond the field of drug delivery, Raman chemical imaging techniques relevant to the study of microscopic drug precipitates and drug-lipid complexes which form inside cells are also being developed by researchers with seemingly unrelated scientific interests. Highlighting advances in data acquisition, calibration methods, and computational data management and analysis tools, this review will cover a decade of technological developments that enable the conversion of spectral signals obtained from Raman confocal microscopes into new discoveries and information about previously unknown, concentrative drug transport pathways driven by soluble-to-insoluble phase transitions occurring within the cytoplasmic organelles of eukaryotic cells.

Lipoproteins-Nanocarriers as a Promising Approach for Targeting Liver Cancer: Present Status and Application Prospects

The prevalence of liver cancer is increasing over the years and it is the fifth leading cause of mortality worldwide. The intrusive features and burden of low survival rate make it a global health issue in both developing and developed countries. The recommended chemotherapy drugs for patients in the intermediate and advanced stages of various liver cancers yield a low response rate due to the nonspecific nature of drug delivery, thus warranting the search for new therapeutic strategies and potential drug delivery carriers. There are several new drug delivery methods available to ferry the targeted molecules to the specific biological environment. In recent years, the nano assembly of lipoprotein moieties (lipidic nanoparticles) has emerged as a promising and efficiently tailored drug delivery system in liver cancer treatment. This increased precision of nano lipoproteins conjugates in chemotherapeutic targeting offers new avenues for the treatment of liver cancer with high specificity and efficiency. This present review is focused on concisely outlining the knowledge of liver cancer diagnosis, existing treatment strategies, lipoproteins, their preparation, mechanism and their potential application in the treatment of liver cancer.

Artificial High Density Lipoprotein Nanoparticles in Cardiovascular Research

Lipoproteins are endogenous nanoparticles which are the major transporter of fats and cholesterol in the human body. They play a key role in the regulatory mechanisms of cardiovascular events. Lipoproteins can be modified and manipulated to act as drug delivery systems or nanocarriers for contrast agents. In particular, high density lipoproteins (HDL), which are the smallest class of lipoproteins, can be synthetically engineered either as nascent HDL nanodiscs or spherical HDL nanoparticles. Reconstituted HDL (rHDL) particles are formed by self-assembly of various lipids and apolipoprotein AI (apo-AI). A variety of substances including drugs, nucleic acids, signal emitting molecules, or dyes can be loaded, making them efficient nanocarriers for therapeutic applications or medical diagnostics. This review provides an overview about synthesis techniques, physicochemical properties of rHDL nanoparticles, and structural determinants for rHDL function. We discuss recent developments utilizing either apo-AI or apo-AI mimetic peptides for the design of pharmaceutical rHDL formulations. Advantages, limitations, challenges, and prospects for clinical translation are evaluated with a special focus on promising strategies for the treatment and diagnosis of atherosclerosis and cardiovascular diseases.

The immune functions of PCSK9: Local and systemic perspectives

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low-density lipoprotein receptor (LDLR) to trigger endocytosis and lysosome degradation in hepatocytes, regulating intracellular and plasma cholesterol levels. The discovery of PCSK9 has provided a new target for the management of hypercholesterolemia and cardiovascular risk reduction. There is emerging evidence that shows that PCSK9 may influence the activity of various cell types through either LDLR-dependent or LDLR-independent mechanisms. Changes in the circulating PCSK9 levels have been observed during infection and proinflammatory conditions. Furthermore, PCSK9 as a secreted protein has both local and systemic effects on cellular function. In this review, we summarize the roles of PCSK9 in inflammation.

A high-density lipoprotein-mediated drug delivery system

High-density lipoprotein (HDL) is a comparatively dense and small lipoprotein that can carry lipids as a multifunctional aggregate in plasma. Several studies have shown that increasing the levels or improving the functionality of HDL is a promising target for treating a wide variety of diseases. Among lipoproteins, HDL particles possess unique physicochemical properties, including naturally synthesized physiological components, amphipathic apolipoproteins, lipid-loading and hydrophobic agent-incorporating characteristics, specific protein-protein interactions, heterogeneity, nanoparticles, and smaller size. Recently, the feasibility and superiority of using HDL particles as drug delivery vehicles have been of great interest. In this review, we summarize the structure, constituents, biogenesis, remodeling, and reconstitution of HDL drug delivery systems, focusing on their delivery capability, characteristics, applications, manufacturing, and drug-loading and drug-targeting characteristics. Finally, the future prospects are presented regarding the clinical application and challenges of using HDL as a pharmacodelivery carrier.

Lipoprotein-Related and Apolipoprotein-Mediated Delivery Systems for Drug Targeting and Imaging

The integration of lipoprotein-related or apolipoprotein-targeted nanoparticles as pharmaceutical carriers opens new therapeutic and diagnostic avenues in nanomedicine. The concept is to exploit the intrinsic characteristics of lipoprotein particles as being the natural transporter of apolar lipids and fat in human circulation. Discrete lipoprotein assemblies and lipoprotein-based biomimetics offer a versatile nanoparticle platform that can be manipulated and tuned for specific medical applications. This article reviews the possibilities for constructing drug loaded, reconstituted or artificial lipoprotein particles. The advantages and limitations of lipoproteinbased delivery systems are critically evaluated and potential future challenges, especially concerning targeting specificity, concepts for lipoprotein rerouting and design of innovative lipoprotein mimetic particles using apolipoprotein sequences as targeting moieties are discussed. Finally, the review highlights potential medical applications for lipoprotein-based nanoparticle systems in the fields of cardiovascular research, cancer therapy, gene delivery and brain targeting focusing on representative examples from literature.

Synthetic high-density lipoprotein-like nanoparticles as cancer therapy

High-density lipoproteins (HDL) are diverse natural nanoparticles that carry cholesterol and are best known for the role that they play in cardiovascular disease. However, due to their unique targeting capabilities, diverse molecular cargo, and natural functions beyond cholesterol transport, it is becoming increasingly appreciated that HDLs are critical to cancer development and progression. Accordingly, this chapter highlights ongoing research focused on the connections between HDL and cancer in order to design new drugs and targeted drug delivery vehicles. Research is focused on synthesizing biomimetic HDL-like nanoparticles (NP) that can be loaded with diverse therapeutic cargo (e.g., chemotherapies, nucleic acids, proteins) and specifically targeted to cancer cells. Beyond drug delivery, new data is emerging that HDL-like NPs may be therapeutically active in certain tumor types, for example, B cell lymphoma. Overall, HDL-like NPs are becoming increasingly appreciated as targeted, biocompatible, and efficient therapies for cancer, and may soon become indispensable agents in the cancer therapeutic armamentarium.

High-density lipoproteins for the systemic delivery of short interfering RNA

INTRODUCTION

RNA interference (RNAi) is a powerful mechanism for gene silencing with the potential to greatly impact the development of new therapies for many human diseases. Short interfering RNAs (siRNAs) may be the ideal molecules for therapeutic RNAi. However, therapeutic siRNAs face significant challenges that must be overcome prior to widespread clinical use. Many efforts have been made to overcome the hurdles associated with systemic administration of siRNA; however, current approaches are still limited. As such, there is an urgent need to develop new strategies for siRNA delivery that have the potential to impact a broad spectrum of systemic diseases.

AREAS COVERED

This review focuses on the promise of siRNA therapies and highlights current siRNA delivery methods. With an eye toward new strategies, this review first introduces high-density lipoprotein (HDL) and describes its natural biological functions, and then transitions into how HDLs may provide significant opportunities as next-generation siRNA delivery vehicles. Importantly, this review describes how synthetic HDLs leverage the natural ability of HDL to stabilize and deliver siRNAs.

EXPERT OPINION

HDLs are natural nanoparticles that are critical to understanding the systemic delivery of therapeutic nucleic acids, like siRNA. Methods to synthesize biomimetic HDLs are being explored, and data demonstrate that this type of delivery vehicle may be highly beneficial for targeted and efficacious systemic delivery of siRNAs.

Recombinant lipoproteins reinforce cytotoxicity of doxorubicin to hepatocellular carcinoma

Cancer nanotherapeutics are changing the landscape of tumor treatment and used to circumvent limitations of conventional chemotherapy, such as non-specificity and low bioavailability. Reconstituted high density lipoproteins (rHDL) system is one of the most promising targeting delivery systems of chemotherapeutic drugs toward tumors. Here, we developed recombined high-density lipoprotein which can be functionalized to deliver doxorubicin intracellular with a higher efficiency. The cellular viability assay showed that the rHDL/Dox nanovectors had an enhanced efficiency in inhibiting the cell viability of hepatocellular carcinoma cell lines HepG2 and SMMC-7721. FACS and confocal microscopy was used to observe the doxorubicin delivery into cancer cells. Intracellular drug accumulation analysis confirmed that treatment of rHDL/Dox nanovectors resulted in higher intracellular doxorubicin concentration to the levels exceeding that of free drug. On the premise of efficient drug delivery, rHDL/Dox nanovectors have been preliminarily demonstrated effective inducing of cytotoxic effect and cell apoptosis to both of the cell lines in vitro. Tissue distribution experiment showed that rHDL/Dox nanovectors could also deliver doxorubicin to liver effectively. So, we proposed that this lipoprotein-based strategy holds promise for a safer and more efficient delivery of chemotherapeutic agents in the treatment of hepatocellular carcinoma.