Human pancreatic polypeptide in a phospholipid-based micellar formulation

BH3-mimetics: recent developments in cancer therapy

The hopeful outcomes from 30 years of research in BH3-mimetics have indeed served a number of solid paradigms for targeting intermediates from the apoptosis pathway in a variety of diseased states. Not only have such rational approaches in drug design yielded several key therapeutics, such outputs have also offered insights into the integrated mechanistic aspects of basic and clinical research at the genetics level for the future. In no other area of medical research have the effects of such work been felt, than in cancer research, through targeting the BAX-Bcl-2 protein-protein interactions. With these promising outputs in mind, several mimetics, and their potential therapeutic applications, have also been developed for several other pathological conditions, such as cardiovascular disease and tissue fibrosis, thus highlighting the universal importance of the intrinsic arm of the apoptosis pathway and its input to general tissue homeostasis. Considering such recent developments, and in a field that has generated so much scientific interest, we take stock of how the broadening area of BH3-mimetics has developed and diversified, with a focus on their uses in single and combined cancer treatment regimens and recently explored therapeutic delivery methods that may aid the development of future therapeutics of this nature.

Inhibition of Amyloid β Aggregation Using Optimized Nano-Encapsulated Formulations of Plant Extracts with High Metal Chelator Activities

Background:

The role of Fe+2, Cu+2 and Zn+2 in facilitating aggregation of Amyloid β (Aβ) and consequently, the progression of Alzheimer's disease (AD) is well established.

Objective:

Development of non-toxic metal chelators is an emerging era in the treatment of AD, in which complete success has not been fully achieved. The purpose of this study was to determine plant extracts with high metal chelator and to encapsulate them in nano-micellar systems with the ability to pass through the Blood Brain Barrier (BBB).

Method:

Extracts of 36 different Anatolian plants were prepared, total phenolic and flavonoid contents were determined, and the extracts with high content were examined for their Fe+2, Cu+2 and Zn+2 chelating activities. Apolipoprotein E4 (Apo E) decorated nano-formulations of active extracts were prepared using Poly (Lactide-co-Glycolide) (PLGA) (final product ApoEPLGA) to provide BBB penetrating property.

Results:

Verbascum flavidum aqueous extract was found as the most active sample, incubation of which, with Aβ before and after metal-induced aggregation, resulted in successful inhibition of aggregate formation, while re-solubilization of pre-formed aggregates was not effectively achieved. The same results were obtained using ApoEPLGA.

Conclusion:

An optimized metal chelator nano-formulation with BBB penetrating ability was prepared and presented for further in-vivo studies.

Nanoparticle-Loaded Hydrogel for the Light-Activated Release and Photothermal Enhancement of Antimicrobial Peptides

Rising concerns over multidrug-resistant bacteria have necessitated an expansion to the current antimicrobial arsenal and forced the development of novel delivery strategies that enhance the efficacy of existing treatments. Antimicrobial peptides (AMPs) are a promising antibiotic alternative that physically disrupts the membrane of bacteria, resulting in rapid bactericidal activity; however, clinical translation of AMPs has been hindered by their susceptibility to protease degradation. Through the co-loading of liposomes encapsulating model AMP, IRIKIRIK-CONH₂ (IK8), and gold nanorods (AuNRs) into a poly(ethylene glycol) (PEG) hydrogel, we have demonstrated the ability to protect encapsulated materials from proteolysis and provide the first instance of the triggered AMP release. Laser irradiation at 860 nm, at 2.1 W cm^-2, for 10 min led to the photothermal triggered release of IK8, resulting in bactericidal activity against Gram-negative Pseudonomas aeruginosa and Gram-positive Staphylococcus aureus. Furthermore, by increasing the laser intensity to 2.4 W cm^-2, we have shown the thermal enhancement of AMP activity. The photothermal triggered release, and enhancement of AMP efficacy, was demonstrated to treat two rounds of fresh S. aureus, indicating that the therapeutic gel has the potential for multiple rounds of treatment. Taken together, this novel therapeutic hydrogel system demonstrates the stimuli-responsive release of AMPs with photothermal enhanced antimicrobial efficacy to treat pathogenic bacteria.

Phospholipid Micelles for Peptide Drug Delivery

Sterically stabilized micelle (SSM) is a self-assembled nanoparticle ideal for the delivery of therapeutic peptides. The PEGylated phospholipid forming the particle, DSPE-PEG₂₀₀₀, is a safe, biocompatible, and biodegradable ingredient already approved for human use in the marketed product Doxil^®. SSM can overcome formulation difficulties such as instability associated with peptide drugs, enabling their development for clinical application. The key advantage of this lipid-based nanocarrier is its simple preparation even at large scales, which allows easy transition to the clinics and the pharmaceutical market. In this chapter, we describe methods for preparation and characterization of peptides self-associated with SSM (peptide-SSM). We also discuss approaches to evaluate the biological activity of the peptide nanomedicines in vitro and in vivo.

Cytotoxic, Apoptotic and Genotoxic Effects of Lipid-Based and Polymeric Nano Micelles, an In Vitro Evaluation

Self-assembly systems (SAS) mainly consist of micelles, and liposomes are the classes of Nano Drug Delivery Systems with superior properties compared to traditional therapeutics in targeting cancer tumors. All commercially available nano-formulations of chemotherapeutics currently consist of SAS. According to our knowledge, a specific toxicity comparison based on material differences has not yet been performed. The purpose of this study was to evaluate and compare the toxicity of two SAS consisting of Sterically Stabilized Micelles (SSM) made of a lipid-based amphiphilic distearoyl-sn-glycero-phosphatidylethanolamine-polyethylene glycol (PEG)-2000 and a polymeric micelle (PM) consisting of Y-shape amphiphilic block copolymer, synthesized using poly ε-caprolactone and PEG. The mechanism of cytotoxicity and genotoxicity of micelles on L-929 healthy mouse fibroblast cells was assessed using Sulforhodamine-B, WST-1, Acridine Orange/Ethidium Bromide and alkaline single-cell gel electrophoresis assays. Results showed that SSM in conc. of 40 mg/mL shows very low cytotoxicity at the end of 24, 48 and 72 h. The DNA damage caused by SSM was much lower than PM while the latter one showed significant toxicity by causing apoptosis with the ED50 value of 3 mg/mL. While the DNA damage caused by SSM was ignorable, some DNA chain breaks were detected on cells treated with PM.

When Is It Important to Measure Unbound Drug in Evaluating Nanomedicine Pharmacokinetics?

Nanoformulations have become important tools for modifying drug disposition, be it from the perspective of enabling prolonged drug release, protecting the drug molecule from metabolism, or achieving targeted delivery. When examining the in vivo pharmacokinetic properties of these formulations, most investigations either focus on systemic concentrations of total (encapsulated plus unencapsulated) drug, or concentrations of encapsulated and unencapsulated drug. However, it is rare to find studies that differentiate between protein-bound and unbound (free) forms of the unencapsulated drug. In light of the unique attributes of these formulations, we cannot simply assume it appropriate to rely upon the protein-binding properties of the traditionally formulated or legacy drug when trying to define the pharmacokinetic or pharmacokinetic/pharmacodynamic characteristics of these nanoformulations. Therefore, this commentary explores reasons why it is important to consider not only unencapsulated drug, but also the portion of unencapsulated drug that is not bound to plasma proteins. Specifically, we highlight those situations when it may be necessary to include measurement of unencapsulated, unbound drug concentrations as part of the nanoformulation pharmacokinetic evaluation.

Glucagon-like peptide-1 loaded phospholipid micelles for the treatment of type 2 diabetes: improved pharmacokinetic behaviours and prolonged glucose-lowering effects

GLP-1-SSM, a sterically stabilized GLP-1 in phospholipid micelles, exhibited improved hypoglycemic activity and long-acting antidiabetic ability.

The role of pancreatic polypeptide in the regulation of energy homeostasis

Imbalances in normal regulation of food intake can cause obesity and related disorders. Inadequate therapies for such disorders necessitate better understanding of mechanisms that regulate energy homeostasis. Pancreatic polypeptide (PP), a robust anorexigenic hormone, effectively modulates food intake and energy homeostasis, thus potentially aiding anti-obesity therapeutics. Intra-gastric and intra-intestinal infusion of nutrients stimulate PP secretion from the gastrointestinal tract, leading to vagal stimulation that mediates complex actions via the neuropeptide Y4 receptor in arcuate nucleus of the hypothalamus, subsequently activating key hypothalamic nuclei and dorsal vagal complex of the brainstem to influence energy homeostasis and body composition. Novel studies indicate affinity of PP for the relatively underexplored neuropeptide y6 receptor, mediating actions via the suprachiasmatic nucleus and pathways involving vasoactive intestinal polypeptide and insulin like growth factor 1. This review highlights detailed mechanisms by which PP mediates its actions on energy balance through various areas in the brain.

VIP-targeted Cytotoxic Nanomedicine for Breast Cancer

Cancer chemotherapy is hampered by serious toxicity to healthy tissues. Conceivably, encapsulation of cytotoxic drugs in actively-targeted, biocompatible nanocarriers could overcome this problem. Accordingly, we used sterically stabilized mixed micelles (SSMM) composed of biocompatible and biodegradable phospholipids to solubilize paclitaxel (P), a hydrophobic model cytotoxic drug, and deliver it to breast cancer in rats. To achieve active targeting, the surface of SSMM was grafted with a ligand, human vasoactive intestinal peptide (VIP) that selectively interacts with its cognate receptors overexpressed on breast cancer cells. We found that even in vitro cytotoxicity of P-SSMM-VIP was 2-fold higher that that of free paclitaxel (p<0.05). Given the unique attributes of P-SSMM and P-SSMM-VIP, most notable small hydrodynamic diameter (~15nm) and stealth properties, biodistribution of paclitaxel was significantly altered. Accumulation of paclitaxel in breast tumor was highest for P-SSMM-VIP, followed by P-SSMM and Cremophor based paclitaxel (PTX). Importantly, bone marrow accumulation of paclitaxel encapsulated in both SSMM-VIP and SSMM was significantly less than that of PTX. Administration of clinically-relevant dose of paclitaxel (5mg/kg) as P-SSMM-VIP and P-SSMM eradicated carcinogen-induced orthotopic breast cancer in rats, whereas PTX decreased tumor size by only 45%. In addition, a 5-fold lower dose (1mg/kg) of paclitaxel in actively targeted P-SSMM-VIP was associated with ~80% reduction in tumor size while the response to PTX and P-SSMM was significantly less. Hypotension was not observed when VIP was grafted onto SSMM. Based on our findings, we propose further development of effective and safe VIP-grafted phospholipid micelle nanomedicines of anti-cancer drugs for targeted treatment of solid tumors in humans.

A new lipid-based nano formulation of vinorelbine

Vinorelbine (VLB) is a semi-synthetic Vinca alkaloid which is currently used in treatment of different cancer types mainly advanced breast cancer (ABC) and advanced/metastatic non-small cell lung cancer (NSCLC). However, its marketed formulation has been reported to have serious side effects, such as granulocytopenia, which is the major dose-limiting toxicity. Other unwanted effects include venous discoloration and phlebitis proximal to the site of injection, as well as localized rashes and urticaria, blistering, and skin sloughing. Our long-term aim in synthesizing a novel nanomicellar vinorelbine formulation is to reduce or even eliminate these side effects and increase drug activity by formulating the drug in a lipid-based system as a nanomedicine targeted to the site of action. To this end, the purpose of this study was to prepare, characterize, and determine the in vitro efficacy of vinorelbine-loaded sterically stabilized, biocompatible, and biodegradable phospholipid nanomicelles (SSM; size, ∼15 nm). Our results indicated that vinorelbine incorporate at high quantities and within the interface between the core and palisade sections of the micelles. Incorporation ratio of drug within sterically stabilized micelles increased as the total amount of drug in the system increased, and no drug particles were formed at the highest drug concentrations tested. The nanomicellar formulation of vinorelbine was ∼6.7-fold more potent than vinorelbine dissolved in DMSO on MCF-7 cell line. Collectively, these data indicate that vinorelbine-loaded SSM can be developed as a new, safe, stable, and effective nanomedicine for the treatment of breast and lung cancers.

Recent developments in protein and peptide parenteral delivery approaches

Discovery of insulin in the early 1900s initiated the research and development to improve the means of therapeutic protein delivery in patients. In the past decade, great emphasis has been placed on bringing protein and peptide therapeutics to market. Despite tremendous efforts, parenteral delivery still remains the major mode of administration for protein and peptide therapeutics. Other routes such as oral, nasal, pulmonary and buccal are considered more opportunistic rather than routine application. Improving biological half-life, stability and therapeutic efficacy is central to protein and peptide delivery. Several approaches have been tried in the past to improve protein and peptide in vitro/in vivo stability and performance. Approaches may be broadly categorized as chemical modification and colloidal delivery systems. In this review we have discussed various chemical approaches such as PEGylation, hyperglycosylation, mannosylation, and colloidal carriers including microparticles, nanoparticles, liposomes, carbon nanotubes and micelles for improving protein and peptide delivery. Recent developments on in situ thermosensitive gel-based protein and peptide delivery have also been described. This review summarizes recent developments on some currently existing approaches to improve stability, bioavailability and bioactivity of peptide and protein therapeutics following parenteral administration.

The future role of gut hormones in the treatment of obesity

The obesity pandemic presents a significant burden, both in terms of healthcare and economic outcomes, and current medical therapies are inadequate to deal with this challenge. Bariatric surgery is currently the only therapy available for obesity which results in long-term, sustained weight loss. The favourable effects of this surgery are thought, at least in part, to be mediated via the changes of gut hormones such as GLP-1, PYY, PP and oxyntomodulin seen following the procedure. These hormones have subsequently become attractive novel targets for the development of obesity therapies. Here, we review the development of these gut peptides as current and emerging therapies in the treatment of obesity.

Solubilization of therapeutic agents in micellar nanomedicines

We use atomistic molecular dynamics simulations to reveal the binding mechanisms of therapeutic agents in PEG-ylated micellar nanocarriers (SSM). In our experiments, SSM in buffer solutions can solubilize either ≈11 small bexarotene molecules or ≈6 (2 in low ionic strength buffer) human vasoactive intestinal peptide (VIP) molecules. Free energy calculations reveal that molecules of the poorly water-soluble drug bexarotene can reside at the micellar ionic interface of the PEG corona, with their polar ends pointing out. Alternatively, they can reside in the alkane core center, where several bexarotene molecules can self-stabilize by forming a cluster held together by a network of hydrogen bonds. We also show that highly charged molecules, such as VIP, can be stabilized at the SSM ionic interface by Coulombic coupling between their positively charged residues and the negatively charged phosphate headgroups of the lipids. The obtained results illustrate that atomistic simulations can reveal drug solubilization character in nanocarriers and be used in efficient optimization of novel nanomedicines.

Biomarkers of Alzheimer's disease among Mexican Americans

BACKGROUND

Mexican Americans are the fastest aging segment of the U.S. population, yet little scientific literature exists regarding the Alzheimer's disease (AD) among this segment of the population. The extant literature suggests that biomarkers of AD will vary according to race/ethnicity though no prior work has explicitly studied this possibility. The aim of this study was to create a serum-based biomarker profile of AD among Mexican American.

METHODS

Data were analyzed from 363 Mexican American participants (49 AD and 314 normal controls) enrolled in the Texas Alzheimer's Research & Care Consortium (TARCC). Non-fasting serum samples were analyzed using a luminex-based multi-plex platform. A biomarker profile was generated using random forest analyses.

RESULTS

The biomarker profile of AD among Mexican Americans was different from prior work from non-Hispanic populations with regards to the variable importance plots. In fact, many of the top markers were related to metabolic factors (e.g., FABP, GLP-1, CD40, pancreatic polypeptide, insulin-like-growth factor, and insulin). The biomarker profile was a significant classifier of AD status yielding an area under the receiver operating characteristic curve, sensitivity, and specificity of 0.77, 0.92, and 0.64, respectively. Combining biomarkers with clinical variables yielded a better balance of sensitivity and specificity.

CONCLUSION

The biomarker profile for AD among Mexican American cases is significantly different from that previously identified among non-Hispanic cases from many large-scale studies. This is the first study to explicitly examine and provide support for blood-based biomarkers of AD among Mexican Americans. Areas for future research are highlighted.

Biodistribution of Nanostructured Lipid Carriers (NLCs) after intravenous administration to rats: influence of technological factors

Nanoparticles for medical applications are frequently administered via parenteral administration. In this study, the tissue distribution of three lipid formulations based on Nanostructured Lipid Carriers (NLCs) after intravenous administration to rats was evaluated. NLCs were prepared by a high pressure homogenization method and varied in terms of particle size, surface charge, and surfactant content. The (99m)Tc radiolabeled NLCs were intravenously administered to rats, and radioactivity levels in blood and tissues were measured. Cmax, AUC0-24, and MRT0-24 were obtained from the radioactivity level versus time profiles. The radiolabeled nanocarriers exhibited a long circulation time since radioactivity was detected in blood even 24 h post-injection. No differences on the MRT values in blood among the NLCs were observed, in spite of the different particle size and surface charge. The highest radioactivity levels were measured in the kidney, followed by the bone marrow, the liver, and the spleen. In the kidney, there was a higher accumulation of the positive nanoparticles, and in the liver, uptake of negative nanoparticles was higher than positive ones. NLCs with the largest particle size showed a higher uptake in the lung and lower accumulation in liver and bone marrow, in comparison with the smaller ones.

Novel, biocompatible, and disease modifying VIP nanomedicine for rheumatoid arthritis

Despite advances in rheumatoid arthritis (RA) treatment, efficacious and safe disease-modifying therapy still represents an unmet medical need. Here, we describe an innovative strategy to treat RA by targeting low doses of vasoactive intestinal peptide (VIP) self-associated with sterically stabilized micelles (SSMs). This spontaneous interaction of VIP with SSM protects the peptide from degradation or inactivation in biological fluids and prolongs circulation half-life. Treatment with targeted low doses of nanosized SSM-VIP but not free VIP in buffer significantly reduced the incidence and severity of arthritis in an experimental model, completely abrogating joint swelling and destruction of cartilage and bone. In addition, SSM associated VIP, unlike free VIP, had no side-effects on the systemic functions due to selective targeting to inflamed joints. Finally, low doses of VIP in SSM successfully downregulated both inflammatory and autoimmune components of RA. Collectively, our data clearly indicate that VIP-SSM should be developed to be used as a novel nanomedicine for the treatment of RA.

A novel peptide nanomedicine for treatment of pancreatogenic diabetes

Pancreatogenic diabetes (PD) is a potentially fatal disease that occurs secondary to pancreatic disorders. The current anti-diabetic therapy for PD is fraught with adverse effects that can increase morbidity. Here we investigated the efficacy of novel peptide nanomedicine: pancreatic polypeptide (PP) in sterically stabilized micelles (SSM) for management of PD. PP exhibits significant anti-diabetic efficacy but its short plasma half-life curtails its therapeutic application. To prolong and improve activity of PP in vivo, we evaluated the delivery of PP in SSM. PP-SSM administered to rats with PD, significantly improved glucose tolerance, insulin sensitivity and hepatic glycogen content compared to peptide in buffer. The studies established the importance of micellar nanocarriers in protecting enzyme-labile peptides in vivo and delivering them to target site, thereby enhancing their therapeutic efficacy. In summary, this study demonstrated that PP-SSM is a promising novel anti-diabetic nanomedicine and therefore should be further developed for management of PD.

FROM THE CLINICAL EDITOR

Pancreatic peptide was earlier demonstrated to address pancreatogenic diabetes, but its short half-life represented major difficulties in further development for therapeutic use. PP-SSM (pancreatic polypeptide in sterically stabilized micelles) is a promising novel anti-diabetic nanomedicine that enables prolonged half-life and increased bioactivity of PP, as shown in this novel study, paving the way toward clinical studies in the near future.

Improvement of in vivo efficacy of recombinant human erythropoietin by encapsulation in PEG-PLA micelle

To improve the pharmacokinetics and stability of recombinant human erythropoietin (rhEPO), rhEPO was successfully formulated into poly(ethylene glycol)–poly(d,l-lactide) (PEG–PLA) di-block copolymeric micelles at diameters ranging from 60 to 200 nm with narrow polydispersity indices (PDIs; PDI < 0.3) and trace amount of protein aggregation. The zeta potential of the spherical micelles was in the range of −3.78 to 4.65 mV and the highest encapsulation efficiency of rhEPO in the PEG–PLA micelles was about 80%. In vitro release profiles indicated that the stability of rhEPO in the micelles was improved significantly and only a trace amount of aggregate was found. Pharmacokinetic studies in rats showed highly enhanced plasma retention time of the rhEPO-loaded PEG-PLA micelles in comparison with the native rhEPO group. Increased hemoglobin concentrations were also found in the rat study. Native polyacrylamide gel electrophoresis results demonstrated that rhEPO was successfully encapsulated into the micelles, which was stable in phosphate buffered saline with different pHs and concentrations of NaCl. Therefore, PEG–PLA micelles can be a potential protein drug delivery system.

Peptide delivery using phospholipid micelles

Peptide based drugs are an important class of therapeutic agents but their development into commercial products is often hampered due to their inherent physico-chemical and biological instabilities. Phospholipid micelles can be used to address these delivery concerns. Peptides self-associate with micelles that serve to thwart the aggregation of these biomolecules. Self-association with micelles does not modify the peptide chemically; therefore the process does not denature or compromise the bioactivity of peptides. Additionally, many amphiphilic peptides adopt α-helical conformation in phospholipid micelles which is not only the most favorable conformation for receptor interaction but also improves their stability against proteolytic degradation, thus making them long-circulating. Furthermore, the nanosize of micelles enables passive targeting of peptides to the desired site of action through leaky vasculature present at tumor and inflamed tissues. All these factors alter the pharmacokinetic and biodistribution profiles of peptides therefore enhance their efficacy, reduce the dose required to obtain a therapeutic response and prevent adverse effects due to interaction of the peptide with receptors present in other physiological sites of the body. These phospholipid micelle based peptide nanomedicines can be easily scaled-up and lyophilized, thus setting the stage for further development of the formulation for clinical use. All things considered, it can be concluded that phospholipid micelles are a safe, stable and effective delivery option for peptide drugs and they form a great promise for future peptide nanomedicines.

Improvement of drug safety by the use of lipid-based nanocarriers

Drug toxicity is an important factor that contributes significantly to adverse drug events in current healthcare practice. Application of lipid-based nanocarriers in drug formulation is one approach to improve drug safety. Lipid-based delivery systems include micelles, liposomes, solid lipid nanoparticles, nanoemulsions and nanosuspensions. These carriers are generally composed of physiological lipids well tolerated by human body. Delivery of water-insoluble drugs in these formulations increases their solubility and stability in aqueous media and eliminates the need for toxic co-solvents or pH adjustment to solubilize hydrophobic drugs. Association or encapsulation of peptides/proteins within lipid-based carriers protects the labile biologics against enzymatic degradation, hence reducing the therapeutic dose required and risk of dose-dependent toxicity. Most importantly, lipid-based nanocarriers alter the pharmacokinetics and biodistribution of drugs through passive and active targeting, leading to increased drug accumulation at target sites while significantly decreasing non-specific distribution to other tissues. Furthermore, surface modification of these nanocarriers reduces immunogenicity of drug-carrier complexes, imparts stealth by preventing opsonization and removal by phagocytes and minimizes interaction with circulating blood components. In view of heightening attention on drug safety in patient treatment, lipid-based nanocarrier is therefore an important and promising option for formulation of pharmaceutical products to improve treatment safety and efficacy.