Low molecular weight protamine (LMWP) as nontoxic heparin/low molecular weight heparin antidote (II): in vitro evaluation of efficacy and toxicity

Self-assembled redox-responsive BRD4 siRNA nanoparticles: fomulation and its in vitro delivery in gastric cancer cells

With the development of newer biomarkers in the diagnosis of gastric cancer (GC), therapeutic targets are emerging and molecular-targeted therapy is in progress RNA interference has emerged as a promising method of gene targeting therapy. However, naked small interfering RNA (siRNA) is unstable and susceptible to degradation, so employing vectors for siRNA delivery is the focus of our research. Therefore, we developed LMWP modified PEG-SS-PEI to deliver siRNA targeting BRD4 (L-NPs/siBRD4) for GC therapy. L-NPs/siBRD4 were prepared by electrostatic interaction and characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The release characteristics, cellular uptake and intracellular localization were also investigated. The in vitro anticancer activity of the prepared nanoparticles was analysed by MTT, Transwell invasion and wound healing assay. Quantitative real time-polymerase chain reaction (qRT-PCR) and Western blot were used to detect the effect of gene silencing. The results showed that the optimal N/P was 30 and the prepared L-NPs/siBRD4 uniformly distributed in the system with a spherical and regular shape. L-NPs/siBRD4 exhibited an accelerated release in GSH-containing media from 12h to 24h. The uptake of L-NPs/siBRD4 was enhanced and mainly co-localized in the lysosomes. After 6h incubation, LMWP modified PEG-SS-PEI helped siRNA escape from the lysosomes and diffused into the cytoplasm. L-NPs/siBRD4 significantly inhibited the proliferation, migration and invasion of cells. This might be related with the silence of BRD4, then inhibition of PI3K/Akt and c-Myc. Our results demonstrate that L-NPs/siBRD4 are a novel delivery system with anticancer, which may provide a more effective strategy for GC treatment.

In vitro and in vivo safety studies indicate that R15, a synthetic polyarginine peptide, could safely reverse the effects of unfractionated heparin

Unfractionated heparin (UFH) is an anionic glycosaminoglycan that is widely used to prevent blood clotting. However, in certain cases, unwanted side effects can require it to be neutralized. Protamine sulfate (PS), a basic peptide rich in arginine, is the only approved antagonist for UFH neutralization. Many adverse reactions occur with the clinical application of PS, including systemic hypotension, pulmonary hypertension, and anaphylaxis. We previously described R15, a linear peptide composed of 15 arginine molecules, as a potential UFH antagonist. In this study, the in-depth safety of R15 was explored to reveal its merits and associated risks in comparison with PS. In vitro safety studies investigated the interactions of R15 with erythrocytes, fibrin, complement, and rat plasma. In vivo safety studies explored potential toxicity and immunogenicity of R15 and the UFH-R15 complex. Results showed that both PS and R15 can induce erythrocyte aggregation, thicken fibrin fibers, activate complement, and cause anticoagulation in a concentration-dependent manner. However, those influences weakened in whole blood or in live animals and were avoided when R15 was in a complex with UFH. We found dramatically enhanced complement activation when there was excess UFH in analyses involving UFH-PS complexes, and a slight increase in those involving UFH-R15 complexes. Within 2 h, R15 was degraded in rat plasma in vitro, whereas PS was not. Enhanced creatinine was found after a single intravenous injection of PS or R15 (900 U·kg^-1 , body weight), suggesting possible abnormal renal function. The UFH-PS complex, but not the UFH-R15 complex, exhibited obvious immunogenicity. In conclusion, R15 is nonimmunogenic and potentially safe at a therapeutic dose to reverse the effects of UFH.

In-vitro Transcribed mRNA Delivery Using PLGA/PEI Nanoparticles into Human Monocyte-derived Dendritic Cells

Induction of protein synthesis by the external delivery of in-vitro transcription-messenger RNA (IVT-mRNA) has been a useful approach in the realm of cell biology, disease treatment, ‎reprogramming of cells, and vaccine design. Therefore, the development of new formulations for ‎protection of mRNA against nucleases is required to maintain its activity in-vivo. It was the aim of the present study to ‎investigate the uptake, toxicity, transfection efficiency as well as phenotypic consequences of ‎a nanoparticle (NP) in cell culture. NP consists of poly D, L-lactide-co-glycolide (PLGA) and polyethyleneimine (PEI) ‎for delivery of in-vitro transcription-messenger RNA (IVT- mRNA) encoded green fluorescent protein (GFP) in human monocyte-derived ‎dendritic cells (moDCs). Nanoparticles that were synthesized and encapsulated with synthetic GFP mRNA, exhibited size distribution in this formulation, with mean particle sizes ranging between 415 and 615 nm. Zeta potential was positive (above 12-13 mV) and the encapsulation efficiency exceeded 73.5%. Our results demonstrated that PLGA/PEI NPs encapsulation of GFP mRNA had ‎no toxic effect on immature monocyte-derived ‎dendritic cells and was capable of delivering of IVT-mRNA into moDCs and was highly effective. The expression of GFP protein 48 h after transfection was confirmed by flow cytometry, microscopic examination and western blotting assay. This NP can make a way to target moDCs to express a variety of antigens by IVT- mRNA. The ‎present study introduced the PLGA/PEI NP, which provided effective delivery of ‎IVT-mRNA that encodes the GFP protein.

Targeting heparin and heparan sulfate protein interactions

Heparin and heparan sulfate glycosaminoglycans are long, linear polysaccharides that are made up of alternating dissacharide sequences of sulfated uronic acid and amino sugars. Unlike heparin, which is only found in mast cells, heparan sulfate is ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These negatively-charged glycans play essential roles in important cellular functions such as cell growth, adhesion, angiogenesis, and blood coagulation. These biomolecules are also involved in pathophysiological conditions such as pathogen infection and human disease. This review discusses past and current methods for targeting these complex biomolecules as a novel therapeutic strategy to treating disorders such as cancer, neurodegenerative diseases, and infection.

Heparin-Regulated Prodrug-Type Macromolecular Theranostic Systems for Cancer Therapy

Heparin is a kind of naturally occurring polymer with excellent biocompatibility and solubility. It is characterized by dense of negative charge, higher than any endogenous components. Heparin can bind with various cationic peptides and proteins, thereby providing a useful noncovalent linkage for building a drug delivery system. As a case in point, heparin/cell-penetrating peptides (CPP) interaction is strong, and remains stable in vivo. They can be used to modify different proteins, respectively, and subsequently, by simply mixing the modified proteins, a protein-protein conjugate can be form via the stable heparin/CPP linkage. This linkage could not be broken unless addition of protamine that bears higher cationic charge density than CPP, and CPP thus can be substituted and released. Of note, heparin is a potent antagonist of CPP, and their binding naturally inhibits CPP-mediated drug cell penetration. Based on this method, we developed a heparin-regulated macromolecular prodrug-type system, termed ATTEMPTS, for drug targeting delivery. In this review article, we mainly summary the application of ATTEMPTS in delivery of various macromolecular drugs for cancer therapy, and also introduce the heparin-regulated nanoprobes for tumor imaging.

Nose-to-brain delivery of macromolecules mediated by cell-penetrating peptides

Brain delivery of macromolecular therapeutics (e.g., proteins) remains an unsolved problem because of the formidable blood–brain barrier (BBB). Although a direct pathway of nose-to-brain transfer provides an answer to circumventing the BBB and has already been intensively investigated for brain delivery of small drugs, new challenges arise for intranasal delivery of proteins because of their larger size and hydrophilicity. In order to overcome the barriers and take advantage of available pathways (e.g., epithelial tight junctions, uptake by olfactory neurons, transport into brain tissues, and intra-brain diffusion), a low molecular weight protamine (LMWP) cell-penetrating peptide was utilized to facilitate nose-to-brain transport. Cell-penetrating peptides (CPP) have been widely used to mediate macromolecular delivery through many kinds of biobarriers. Our results show that conjugates of LMWP–proteins are able to effectively penetrate into the brain after intranasal administration. The CPP-based intranasal method highlights a promising solution for protein therapy of brain diseases.

Peptides used in the delivery of small noncoding RNA

RNA interference (RNAi) is an endogenous process in which small noncoding RNAs, including small interfering RNAs (siRNAs) and microRNAs (miRNAs), post-transcriptionally regulate gene expressions. In general, siRNA and miRNA/miRNA mimics are similar in nature and activity except their origin and specificity. Although both siRNAs and miRNAs have been extensively studied as novel therapeutics for a wide range of diseases, the large molecular weight, anionic surface charges, instability in blood circulation, and intracellular trafficking to the RISC after cellular uptake have hindered the translation of these RNAs from bench to clinic. As a result, a great variety of delivery systems have been investigated for safe and effective delivery of small noncoding RNAs. Among these systems, peptides, especially cationic peptides, have emerged as a promising type of carrier due to their inherent ability to condense negatively charged RNAs, ease of synthesis, controllable size, and tunable structure. In this review, we will focus on three major types of cationic peptides, including poly(l-lysine) (PLL), protamine, and cell penetrating peptides (CPP), as well as peptide targeting ligands that have been extensively used in RNA delivery. The delivery strategies, applications, and limitations of these cationic peptides in siRNA/miRNA delivery will be discussed.

Inactivation of heparin by cationically modified chitosan

This study was performed to evaluate the ability of N-(2-hydroxypropyl)-3-tri methylammonium chitosan chloride (HTCC), the cationically modified chitosan, to form biologically inactive complexes with unfractionated heparin and thereby blocking its anticoagulant activity. Experiments were carried out in rats in vivo and in vitro using the activated partial thromboplastin time (APTT) and prothrombin time (PT) tests for evaluation of heparin anticoagulant activity. For the first time we have found that HTCC effectively neutralizes anticoagulant action of heparin in rat blood in vitro as well as in rats in vivo. The effect of HTCC on suppression of heparin activity is dose-dependent and its efficacy can be comparable to that of protamine-the only agent used in clinic for heparin neutralization. HTCC administered i.v. alone had no direct effect on any of the coagulation tests used. The potential adverse effects of HTCC were further explored using rat experimental model of acute toxicity. When administered i.p. at high doses (250 and 500 mg/kg body weight), HTCC induced some significant dose-dependent structural abnormalities in the liver. However, when HTCC was administered at low doses, comparable to those used for neutralization of anticoagulant effect of heparin, no histopathological abnormalities in liver were observed.

De novo design of self-assembling foldamers that inhibit heparin-protein interactions

A series of self-associating foldamers have been designed as heparin reversal agents, as antidotes to prevent bleeding due to this potent antithrombotic agent. The foldamers have a repeating sequence of Lys-Sal, in which Sal is 5-amino-2-methoxy-benzoic acid. These foldamers are designed to self-associate along one face of an extended chain in a β-sheet-like interaction. The methoxy groups were included to form intramolecular hydrogen bonds that preclude the formation of very large amyloid-like aggregates, while the positively charged Lys side chains were introduced to interact electrostatically with the highly anionic heparin polymer. The prototype compound (Lys-Sal)₄ carboxamide weakly associates in aqueous solution at physiological salt concentration in a monomer-dimer-hexamer equilibrium. The association is greatly enhanced at either high ionic strength or in the presence of a heparin derivative, which is bound tightly. Variants of this foldamer are active in an antithrombin III–factor Xa assay, showing their potential as heparin reversal agents.

Towards an integrated systems-based modelling framework for drug transport and its effect on tumour cells

Background

A systematic understanding of chemotherapeutic influence on solid tumours is highly challenging and complex as it encompasses the interplay of phenomena occurring at multiple scales. It is desirable to have a multiscale systems framework capable of disentangling the individual roles of multiple contributing factors, such as transport and extracellular factors, and purely intracellular factors, as well as the interactions among these factors. Based on a recently developed systems-based modelling framework, we have developed a coupled system in order to further elucidate the role of drug transport, and its interplay with cellular signalling by incorporating intra- and extra-vascular drug transport in tumour, dynamic descriptions of intracellular signalling and tumour cell density dynamics.

Results

Different aspects of the interaction between transport and cell signalling and the effects of transport parameters have been investigated in silico. Limited drug penetration is found to be a major constraint in inducing drug effect; many aspects of the interaction of transport with cell signalling are independent of the details of cell signalling. A sensitivity analysis indicates that the effect of drug diffusivity depends on the balance between interstitial drug transport and the specific requirement for triggering apoptosis (governed by highly nonlinear signalling networks), suggesting that the effect of drug diffusivity in such cases must be considered in conjunction with descriptions of cellular dynamics.

Conclusions

The modelling framework developed in this study provides qualitative and mechanistic insights into the effect of drug on tumour cells. It provides an in silico experimental platform to investigate the interplay between extracellular factors (e.g. transport) and intracellular factors. Such a platform is essential to understanding the individual and combined effects of transport and cellular factors in solid tumour.

Cell-penetrating peptides meditated encapsulation of protein therapeutics into intact red blood cells and its application

Red blood cells (RBCs) based drug carrier appears to be the most appealing for protein drugs due to their unmatched biocompatability, biodegradability, and long lifespan in the circulation. Numerous methods for encapsulating protein drugs into RBCs were developed, however, most of them induce partial disruption of the cell membrane, resulting in irreversible alterations in both physical and chemical properties of RBCs. Herein, we introduce a novel method for encapsulating proteins into intact RBCs, which was meditated by a cell penetrating peptide (CPP) developed in our lab-low molecular weight protamine (LMWP). l-asparaginase, one of the primary drugs used in treatment of acute lymphoblastic leukemia (ALL), was chosen as a model protein to illustrate the encapsulation into erythrocytes mediated by CPPs. In addition current treatment of ALL using different l-asparaginase delivery and encapsulation methods as well as their associated problems were also reviewed.

Chemically and biologically synthesized CPP-modified gelonin for enhanced anti-tumor activity

The ineffectiveness of small molecule drugs against cancer has generated significant interest in more potent macromolecular agents. Gelonin, a plant-derived toxin that inhibits protein translation, has attracted much attention in this regard. Due to its inability to internalize into cells, however, gelonin exerts only limited tumoricidal effect. To overcome this cell membrane barrier, we modified gelonin, via both chemical conjugation and genetic recombination methods, with low molecular weight protamine (LMWP), a cell-penetrating peptide (CPP) which was shown to efficiently ferry various cargoes into cells. Results confirmed that gelonin-LMWP chemical conjugate (cG-L) and recombinant gelonin-LMWP chimera (rG-L) possessed N-glycosidase activity equivalent to that of unmodified recombinant gelonin (rGel); however, unlike rGel, both gelonin-LMWPs were able to internalize into cells. Cytotoxicity studies further demonstrated that cG-L and rG-L exhibited significantly improved tumoricidal effects, with IC50 values being 120-fold lower than that of rGel. Moreover, when tested against a CT26 s.c. xenograft tumor mouse model, significant inhibition of tumor growth was observed with rG-L doses as low as 2 μg/tumor, while no detectable therapeutic effects were seen with rGel at 10-fold higher doses. Overall, this study demonstrated the potential of utilizing CPP-modified gelonin as a highly potent anticancer drug to overcome limitations of current chemotherapeutic agents.

The use of low molecular weight protamine chemical chimera to enhance monomeric insulin intestinal absorption

Although oral delivery of insulin offers a number of unmatched advantages, it nevertheless is beset by the poor permeability of insulin molecules through the epithelial cell membranes of the intestinal mucosal layer. We previously reported the development of low molecular weight protamine (LMWP) as a non-toxic yet potent cell-penetrating peptide, of which via covalent linkage was capable of translocating protein cargos through the membranes of almost all cell types. It is therefore hypothesized that LMWP could be practically employed as a safe and effective tool to deliver insulin across the intestinal mucosal membrane, thereby augmenting its absorption through the GI tract. However, formulating 1:1 monomeric insulin/LMWP conjugate presents a tall order of challenge, as the acidic insulin and basic LMWP would automatically form tight aggregates through electrostatic interactions. In this paper, we developed an innovative conjugation strategy to solve this problem, by using succinimidyl-[(N-maleimidopropionamido)-polyethyleneglycol] ester (NHS-PEG-MAL) as an intermediate cross-linker during the coupling process. Both SDS-PAGE and MALDI-TOF mass spectroscopy confirmed the formation of a homogenous, monomeric (1:1 ratio) insulin/LMWP conjugate without encountering the conventional problem of substrate aggregation. Cell culture studies demonstrated that transport of the Insulin-PEG-LMWP conjugate across the intestinal mucosal monolayer was augmented by almost five-folds compared to native insulin. Furthermore, results from the in situ loop absorption tests in rats showed that systemic pharmacological bioavailability of insulin was significantly enhanced after its conjugation with LMWP. Overall, the presented chemical conjugation with LMWP could offer a reliable and safe means to improve the intestinal permeability of therapeutic peptides/proteins, shedding light of the possibility for their effective oral delivery.

Magnetic nanoparticles for tumor imaging and therapy: a so-called theranostic system

In this review, we discussed the establishment of a so-called "theranostic" system by instituting the basic principles including the use of: [1] magnetic iron oxide nanoparticles (MION)-based drug carrier; [2] intra-arterial (I.A.) magnetic targeting; [3] macromolecular drugs with unmatched therapeutic potency and a repetitive reaction mechanism; [4] cell-penetrating peptide-mediated cellular drug uptake; and [5] heparin/protamine-regulated prodrug protection and tumor-specific drug re-activation into one single drug delivery system to overcome all possible obstacles, thereby achieving a potentially non-invasive, magnetic resonance imaging-guided, clinically enabled yet minimally toxic brain tumor drug therapy. By applying a topography-optimized I.A. magnetic targeting to dodge rapid organ clearance of the carrier during its first passage into the circulation, tumor capture of MION was enriched by >350 folds over that by conventional passive enhanced permeability and retention targeting. By adopting the prodrug strategy, we observed by far the first experimental success in a rat model of delivering micro-gram quantity of the large β-galactosidase model protein selectively into a brain tumor but not to the ipsi- or contra-lateral normal brain regions. With the therapeutic regimens of most toxin/siRNA drugs to fully (>99.9%) eradicate a tumor being in the nano-molar range, the prospects of reaching this threshold become practically accomplishable.

Nanomedicines based on recombinant fusion proteins for targeting therapeutic siRNA oligonucleotides

The enormous promise of siRNA technology for rational and targeted therapy can only be realized if the inherent problems in terms of pharmaceutical development are overcome. Besides liposomal and polymeric nanoparticles, fusion proteins hold great potential for cell-type specific delivery of siRNA. Consisting of a protein binder and an oligonucleotide complexing domain, fusion proteins are designed for targeted delivery to a certain tissue or organ and subsequent release of the siRNA after cellular uptake. This article focuses on the possibilities and importance of targeting and complexing domains, including polymers and dendrimers. In vitro and in vivo evaluations are discussed with an in-depth view on pharmacokinetic properties. Remaining challenges concerning specificity on the tissue and molecular levels are highlighted.

Evaluation of a chromogenic assay to measure the factor Xa inhibitory activity of unfractionated heparin in canine plasma

BACKGROUND

Unfractionated heparin (UFH) has a complex pharmacologic profile that necessitates patient monitoring to prevent inadequate anticoagulation or overdosage and hemorrhage. Factor Xa inhibitory assays (to measure anti-Xa activity) are used to adjust UFH dosage and define safe and effective regimens for specific thrombotic disorders in humans.

OBJECTIVE

In this study, the accuracy, linearity, and clinical utility of a chromogenic assay were assessed for monitoring UFH anti-Xa activity in canine plasma samples.

METHODS

A commercial assay (Rotachrom Heparin, Diagnostica Stago, Parsippany, NJ, USA) was used to measure anti-Xa activity in canine plasma samples spiked with different concentrations of UFH. Background absorbance and assay linearity were compared for canine and human plasmas. Percentage recovery of UFH anti-Xa activity and intra- and interassay imprecisions were investigated by multiple measurements of canine plasma to which known amounts of UFH were added. The spiked plasma samples also were used to determine the heparin sensitivity of an activated partial thromboplastin time (aPTT) test.

RESULTS

Canine plasma samples were assayed at a higher dilution than were human plasma samples (3:8 versus 4:8) to eliminate higher background anti-Xa activity in canine plasma. Using this modification, the recovery of anti-Xa activity in canine plasma was linear (R2 > .9) at concentrations of 0 - 0.75 U/mL UFH. Intra- and interassay imprecisions for plasma samples containing 0.5 U/mL UFH were <10%, whereas samples containing 0.25 U/mL UFH had imprecisions of 13% and 24%, respectively. The anti-Xa activity range of 0.5 - 0.75 U/mL caused prolongation of aPTTs to 1.5 - 2.5 times the assay mean.

CONCLUSION

Plasma anti-Xa activity of dogs treated with UFH can be accurately monitored using this commercially available chromogenic assay.

Low molecular weight protamine as nontoxic heparin/low molecular weight heparin antidote (III): preliminary in vivo evaluation of efficacy and toxicity using a canine model

Heparin employed in cardiovascular surgeries often leads to a high incidence of bleeding complications. Protamine employed in heparin reversal, however, can cause severe adverse reactions. In an attempt to address this clinical problem, we developed low molecular weight protamine (LMWP) as a potentially effective and less toxic heparin antagonist. A homogeneous 1880-d peptide fragment, termed LMWP-TDSP5 and containing the amino acid sequence of VSRRRRRRGGRRRR, was derived directly from protamine by enzymatic digestion of protamine with thermolysin. In vitro studies demonstrated that TDSP5 was capable of neutralizing various anticoagulant functions of both heparin and commercial low molecular weight heparin preparations. In addition, TDSP5 exhibited significantly reduced crossreactivity toward mouse sera containing antiprotamine antibodies. TDSP5 showed a decrease in its potential in activating the complement system. All of these findings suggested the possibility of markedly reduced protamine toxicity for TDSP5. In this article, we conducted preliminary in vivo studies to further demonstrate the feasibility and utility of using LMWP as a nontoxic clinical protamine substitute. Dogs were chosen as test animals because they were known to magnify the typical human response to protamine. By using a full spectra of biological and clinical assays for heparin, including the anti-IIa and anti-Xa chromogenic assays and the activated partial, thromboplastin time and TCT clotting assays, TDSP5 showed that it could completely neutralize all these different anticoagulant functions of heparin in dogs. Although administration of protamine in dogs produced a significant reduction in mean arterial blood pressure (-14.9 mm Hg) and elevation in pulmonary artery systolic pressure (+5.0 mm Hg), the use of TDSP5 in dogs did not elicit any statistically significant change in any of the variables measured. Furthermore, the use of LMWP also significantly reduced the protamine-induced transient thrombocytopenic and granulocytopenic responses. The white blood cell counts and platelet counts decreased to 82.1% and 60.0% of baseline, respectively, in dogs given intravenous protamine compared to 97.8% and 88.6% of baseline in dogs receiving TDSP5. These preliminary findings indicated that LMWP could potentially provide an effective and safe means to control both heparin- and protamine-induced complications.