Adsorptive-mediated endocytosis of a basic peptide in enterocyte-like Caco-2 cells

Challenges and strategies for collagen delivery for tissue regeneration

Background: Aged skin is characterized by wrinkles, hyperpigmentation, and roughness. Collagen is the most abundant protein in our body and it’s responsible for skin health and it’s mostly influenced by factors that accelerated aging such as UV. Objective: This study aimed to identify the potential use of collagen as skin supplementation and the challenges and strategies for its delivery. Methods: The articles were first searched through the existing database with the keyword of “collagen antiaging”. The 585 articles were then screened by year of publication (2012-2022) resulted in 475 articles. The articles were then selected based on the delivery of collagen either orally or topically, resulted in 12 articles for further analysis. Results: Collagen has important roles in skin physiology by involving some mechanisms through inhibition of Mitogen-Activated Protein Kinase, induction of Tissue Growth Factor β (TGF-β), and inhibition of Nuclear Factor kappa beta (NF-κβ). The oral administration of collagen has an effective biological activity but requires large doses (up to 5 g daily). Meanwhile, the topical administration of collagen is limited by poor permeability due to high molecular weight (±300 kDa). Several strategies need to be carried out mainly by physical modification such as hydrolyzed collagen or entrapment of collagen using a suitable delivery system. Conclusions: Collagen could improve the skin properties, but further research should be conducted to increase its penetration either by physical modification or entrapment into suitable carrier.

Bioavailability of Peptides Derived from the In Vitro Digestion of Human Milk Assessed by Caco-2 Cell Monolayers

Human milk-protein-derived peptides exhibit an array of bioactivities. Certain bioactivities cannot be exerted unless the peptides are absorbed across the gastrointestinal lumen into the bloodstream. The purpose of study was to determine which peptides derived from in vitro digestion of human milk could cross human intestinal Caco-2 cell monolayers. Our results showed that the numbers of peptides absorbed by the Caco-2 cell monolayer were different at different concentrations (44 peptides out of 169 peptides detected at 10 μg/mL, 124 peptides out of 204 peptides detected at 100 μg/mL, and 175 peptides out of 236 peptides detected at 1000 μg/mL). Four peptides (NLHLPLP (β-casein [138-144]), PLAPVHNPI (β-casein [216-224]), PLMQQVPQPIPQ (β-casein [148-159]), and FDPQIPK (β-casein [126-132])) crossed to the basolateral chamber of the Caco-2 monolayer incubated with peptides at all three concentrations. Among the peptides identified in the basolateral chambers, three peptides (NLHLPLP (β-casein [138-144]), LENLHLPLP (β-casein [136-144]), and QVVPYPQ (β-casein [182-188])) are known ACE-inhibitors; one peptide (LLNQELLLNPTHQIYPV (β-casein [197-213])) is antimicrobial, and another peptide (QVVPYPQ (β-casein [182-188])) has antioxidant activity. These findings indicate that specific milk peptides may be able to reach the bloodstream and exert bioactivity.

N-trimethyl chitosan coated nano-complexes enhance the oral bioavailability and chemotherapeutic effects of gemcitabine

N-trimethyl chitosan (TMC) is a multifunctional polymer that can be used in various nanoparticle forms in the pharmaceutical, nutraceutical and biomedical fields. In this study, TMC was used as a mucoadhesive adjuvant to enhance the oral bioavailability and hence antitumour effects of gemcitabine formulated into nanocomplexes composed of poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) conjugated with d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). A central composite design was applied to achieve the optimal formulation. Cellular uptake and drug transportation studies revealed the nanocomplexes permeate over the intestinal cells via adsorptive-mediated and caveolae-mediated endocytosis. Pharmacokinetic studies demonstrated the oral drug bioavailability of the nanocomplexes was increased 5.1-fold compared with drug solution. In pharmacodynamic studies, the formulation reduced tumour size 3.1-fold compared with the drug solution. The data demonstrates that TMC modified nanocomplexes can enhance gemcitabine oral bioavailability and promote the anticancer efficacy.

The Neuroprotective Peptide Poly-Arginine-12 (R12) Reduces Cell Surface Levels of NMDA NR2B Receptor Subunit in Cortical Neurons; Investigation into the Involvement of Endocytic Mechanisms

We have previously reported that cationic poly-arginine and arginine-rich cell-penetrating peptides display high-level neuroprotection and reduce calcium influx following in vitro excitotoxicity, as well as reduce brain injury in animal stroke models. Using the neuroprotective peptides poly-arginine R12 (R12) and the NR2B9c peptide fused to the arginine-rich carrier peptide TAT (TAT-NR2B9c; also known as NA-1), we investigated the mechanisms whereby poly-arginine and arginine-rich peptides reduce glutamate-induced excitotoxic calcium influx. Using cell surface biotin protein labeling and western blot analysis, we demonstrated that R12 and TAT-NR2B9c significantly reduced cortical neuronal cell surface expression of the NMDA receptor subunit NR2B. Chemical endocytic inhibitors used individually or in combination prior to glutamate excitotoxicity did not significantly affect R12 peptide neuroprotective efficacy. Similarly, pretreatment of neurons with enzymes to degrade anionic cell surface proteoglycans, heparan sulfate proteoglycan (HSPG), and chondroitin sulfate proteoglycan (CSPG), as well as sialic acid residues, did not significantly affect peptide neuroprotective efficacy. While the exact mechanisms responsible for R12 peptide-mediated NMDA receptor NR2B subunit cell surface downregulation were not identified, an endocytic process could not be ruled out. The study supports our hypothesis that arginine-rich peptides reduce excitotoxic calcium influx by reducing the levels of cell surface ion channels.

Current strategies for targeted delivery of bio-active drug molecules in the treatment of brain tumor

Brain tumor is one of the most challenging diseases to treat. The major obstacle in the specific drug delivery to brain is blood-brain barrier (BBB). Mostly available anti-cancer drugs are large hydrophobic molecules which have limited permeability via BBB. Therefore, it is clear that the protective barriers confining the passage of the foreign particles into the brain are the main impediment for the brain drug delivery. Hence, the major challenge in drug development and delivery for the neurological diseases is to design non-invasive nanocarrier systems that can assist controlled and targeted drug delivery to the specific regions of the brain. In this review article, our major focus to treat brain tumor by study numerous strategies includes intracerebral implants, BBB disruption, intraventricular infusion, convection-enhanced delivery, intra-arterial drug delivery, intrathecal drug delivery, injection, catheters, pumps, microdialysis, RNA interference, antisense therapy, gene therapy, monoclonal/cationic antibodies conjugate, endogenous transporters, lipophilic analogues, prodrugs, efflux transporters, direct conjugation of antitumor drugs, direct targeting of liposomes, nanoparticles, solid-lipid nanoparticles, polymeric micelles, dendrimers and albumin-based drug carriers.

Daily consumption of the collagen supplement Pure Gold Collagen® reduces visible signs of aging

With age, changes in the metabolic processes of structural components of the skin lead to visible signs of aging, such as increased dryness and wrinkle formation. The nutritional supplement, Pure Gold Collagen(®), which consists of hydrolyzed collagen, hyaluronic acid, vitamins, and minerals, was developed to counteract these signs. An open-label study was conducted to investigate the effects of this nutritional supplement on skin properties. Supplementation with 50 mL of Pure Gold Collagen on a daily basis for 60 days led to a noticeable reduction in skin dryness, wrinkles, and nasolabial fold depth. In addition, a significant increase in collagen density and skin firmness was observed after 12 weeks. The data from this study suggest that Pure Gold Collagen can counteract signs of natural aging.

Current approaches to enhance CNS delivery of drugs across the brain barriers

Although many agents have therapeutic potentials for central nervous system (CNS) diseases, few of these agents have been clinically used because of the brain barriers. As the protective barrier of the CNS, the blood–brain barrier and the blood–cerebrospinal fluid barrier maintain the brain microenvironment, neuronal activity, and proper functioning of the CNS. Different strategies for efficient CNS delivery have been studied. This article reviews the current approaches to open or facilitate penetration across these barriers for enhanced drug delivery to the CNS. These approaches are summarized into three broad categories: noninvasive, invasive, and miscellaneous techniques. The progresses made using these approaches are reviewed, and the associated mechanisms and problems are discussed.

Multifunctional Nanocarriers for diagnostics, drug delivery and targeted treatment across blood-brain barrier: perspectives on tracking and neuroimaging

Nanotechnology has brought a variety of new possibilities into biological discovery and clinical practice. In particular, nano-scaled carriers have revolutionalized drug delivery, allowing for therapeutic agents to be selectively targeted on an organ, tissue and cell specific level, also minimizing exposure of healthy tissue to drugs. In this review we discuss and analyze three issues, which are considered to be at the core of nano-scaled drug delivery systems, namely functionalization of nanocarriers, delivery to target organs and in vivo imaging. The latest developments on highly specific conjugation strategies that are used to attach biomolecules to the surface of nanoparticles (NP) are first reviewed. Besides drug carrying capabilities, the functionalization of nanocarriers also facilitate their transport to primary target organs. We highlight the leading advantage of nanocarriers, i.e. their ability to cross the blood-brain barrier (BBB), a tightly packed layer of endothelial cells surrounding the brain that prevents high-molecular weight molecules from entering the brain. The BBB has several transport molecules such as growth factors, insulin and transferrin that can potentially increase the efficiency and kinetics of brain-targeting nanocarriers. Potential treatments for common neurological disorders, such as stroke, tumours and Alzheimer's, are therefore a much sought-after application of nanomedicine. Likewise any other drug delivery system, a number of parameters need to be registered once functionalized NPs are administered, for instance their efficiency in organ-selective targeting, bioaccumulation and excretion. Finally, direct in vivo imaging of nanomaterials is an exciting recent field that can provide real-time tracking of those nanocarriers. We review a range of systems suitable for in vivo imaging and monitoring of drug delivery, with an emphasis on most recently introduced molecular imaging modalities based on optical and hybrid contrast, such as fluorescent protein tomography and multispectral optoacoustic tomography. Overall, great potential is foreseen for nanocarriers in medical diagnostics, therapeutics and molecular targeting. A proposed roadmap for ongoing and future research directions is therefore discussed in detail with emphasis on the development of novel approaches for functionalization, targeting and imaging of nano-based drug delivery systems, a cutting-edge technology poised to change the ways medicine is administered.

Mechanisms of alveolar epithelial translocation of a defined population of nanoparticles

To explore mechanisms of nanoparticle interactions with and trafficking across lung alveolar epithelium, we utilized primary rat alveolar epithelial cell monolayers (RAECMs) and an artificial lipid bilayer on filter model (ALBF). Trafficking rates of fluorescently labeled polystyrene nanoparticles (PNPs; 20 and 100 nm, carboxylate (negatively charged) or amidine (positively charged)-modified) in the apical-to-basolateral direction under various experimental conditions were measured. Using confocal laser scanning microscopy, we investigated PNP colocalization with early endosome antigen-1, caveolin-1, clathrin heavy chain, cholera toxin B, and wheat germ agglutinin. Leakage of 5-carboxyfluorescein diacetate from RAECMs, and trafficking of (22)Na and (14)C-mannitol across ALBF, were measured in the presence and absence of PNPs. Results showed that trafficking of positively charged PNPs was 20-40 times that of negatively charged PNPs across both RAECMs and ALBF, whereas translocation of PNPs across RAECMs was 2-3 times faster than that across ALBF. Trafficking rates of PNPs across RAECMs did not change in the presence of EGTA (which decreased transepithelial electrical resistance to zero) or inhibitors of endocytosis. Confocal laser scanning microscopy revealed no intracellular colocalization of PNPs with early endosome antigen-1, caveolin-1, clathrin heavy chain, cholera toxin B, or wheat germ agglutinin. Leakage of 5-carboxyfluorescein diacetate from alveolar epithelial cells, and sodium ion and mannitol flux across ALBF, were not different in the presence or absence of PNPs. These data indicate that PNPs translocate primarily transcellularly across RAECMs, but not via known major endocytic pathways, and suggest that such translocation may take place by diffusion of PNPs through the lipid bilayer of cell plasma membranes.

Transport of interleukin-1 across cerebromicrovascular endothelial cells

BACKGROUND AND PURPOSE

The inflammatory cytokine interleukin-1 (IL-1) has profound actions in the brain, causing neuronal cell death and exacerbating brain damage. While circulating levels are normally low, IL-1 can be produced on the vascular side of the brain endothelium, and within the brain. The naturally occurring IL-1 receptor antagonist has been administered peripherally in a Phase II trial in acute stroke patients; understanding how IL-1 and IL-1 receptor antagonist penetrate the brain is, therefore, of considerable importance.

EXPERIMENTAL APPROACH

An in vitro blood-brain barrier model was generated by co-culture of porcine brain microvascular endothelial cells with astrocytes. The mechanisms of transcellular transport of IL-1beta and IL-1 receptor antagonist were characterized in this model, using endocytosis inhibitors and IL-1 receptor-blocking antibodies.

KEY RESULTS

Transcellular IL-1beta and IL-1 receptor antagonist transport was temperature-dependent and IL-1beta was transported with higher affinity than IL-1 receptor antagonist. IL-1beta inhibited IL-1 receptor antagonist transport more potently than IL-1 receptor antagonist inhibited IL-1beta transport. Transport of IL-1beta and IL-1 receptor antagonist was not via adsorptive-mediated endocytosis, although inhibition of microtubule assembly significantly attenuated transport of both cytokines. An antibody directed to the type II IL-1 receptor significantly reduced IL-1beta transport.

CONCLUSIONS AND IMPLICATIONS

These results are consistent with IL-1 and IL-1 receptor antagonist being transported across cultured cerebromicrovascular endothelial cells and suggest that IL-1beta transport may occur via a type II IL-1 receptor-dependent mechanism. Understanding IL-1 transport into the brain may have benefits, particularly in enhancing penetration of IL-1 receptor antagonist into the brain.

Comparative uptake studies of bioadhesive and non-bioadhesive nanoparticles in human intestinal cell lines and rats: the effect of mucus on particle adsorption and transport

PURPOSE

The interaction of nanoparticles (NP), consisting of hydrophobic polystyrene, bioadhesive chitosan, and stealth PLA-PEG with two human intestinal cell lines, the enterocyte-like Caco-2 and mucus-secreting MTX-E12, was investigated and compared to the in vivo NP uptake in rats.

METHODS

The extent and mechanism of cellular association of different NP with Caco-2 and MTX-E12 was investigated using confocal laser scanning microscopy (CLSM) and a cellular association assay. In vitro results were compared to gastrointestinal distribution of chitosan NP in rats after intra-duodenal injection.

RESULTS

Cellular association of NP with Caco-2 cell monolayers showed the following rank order: polystyrene > chitosan >> PLA-PEG. Mucus (MTX-E12) significantly decreased the association of hydrophobic polystyrene NP. While no mucus binding was observed for PLA-PEG, association of chitosan NP with mucus strongly increased. Intra-duodenal administration of chitosan NP in rats confirmed these in vitro results, demonstrating that NP could be detected in both epithelial cells and Peyer's patches. Chitosan NP internalization was saturable, as well as energy- and temperature-dependent. It could be inhibited by an excess of protamine and by removal of anionic sites of the apical membrane. By contrast, polystyrene NP uptake was found to be largely independent of these factors, except for a temperature-dependency.

CONCLUSIONS

In contrast to Caco-2 cells, the presence of mucus presented a major barrier for the uptake of hydrophobic polystyrene NP and showed an even more profound effect upon the uptake of chitosan NP. A correlation between the uptake in cell culture models and in vivo rat epithelial cells was confirmed for chitosan NP. Moreover, chitosan NP seemed to be taken up and transported by adsorptive transcytosis, while polystyrene NP uptake was probably mediated by non-adsorptive transcytosis.

Comparative uptake studies of bioadhesive and non-bioadhesive nanoparticles in human intestinal cell lines and rats: the effect of mucus on particle adsorption and transport

PURPOSE

The interaction of nanoparticles (NP), consisting of hydrophobic polystyrene, bioadhesive chitosan, and stealth PLA-PEG with two human intestinal cell lines, the enterocyte-like Caco-2 and mucus-secreting MTX-E12, was investigated and compared to the in vivo NP uptake in rats.

METHODS

The extent and mechanism of cellular association of different NP with Caco-2 and MTX-E12 was investigated using confocal laser scanning microscopy (CLSM) and a cellular association assay. In vitro results were compared to gastrointestinal distribution of chitosan NP in rats after intra-duodenal injection.

RESULTS

Cellular association of NP with Caco-2 cell monolayers showed the following rank order: polystyrene > chitosan >> PLA-PEG. Mucus (MTX-E12) significantly decreased the association of hydrophobic polystyrene NP. While no mucus binding was observed for PLA-PEG, association of chitosan NP with mucus strongly increased. Intra-duodenal administration of chitosan NP in rats confirmed these in vitro results, demonstrating that NP could be detected in both epithelial cells and Peyer's patches. Chitosan NP internalization was saturable, as well as energy- and temperature-dependent. It could be inhibited by an excess of protamine and by removal of anionic sites of the apical membrane. By contrast, polystyrene NP uptake was found to be largely independent of these factors, except for a temperature-dependency.

CONCLUSIONS

In contrast to Caco-2 cells, the presence of mucus presented a major barrier for the uptake of hydrophobic polystyrene NP and showed an even more profound effect upon the uptake of chitosan NP. A correlation between the uptake in cell culture models and in vivo rat epithelial cells was confirmed for chitosan NP. Moreover, chitosan NP seemed to be taken up and transported by adsorptive transcytosis, while polystyrene NP uptake was probably mediated by non-adsorptive transcytosis.

[Biopharmaceutical studies on molecular mechanisms of membrane transport]

By incorporating the transporter-mediated or receptor-mediated transport process in physiologically based pharmacokinetic models, we succeeded in the quantitative prediction of plasma and tissue concentrations of beta-lactam antibiotics, insulin, pentazocine, quinolone antibacterial agents, and inaperizone and digoxin. The author's research on transporter-mediated pharmacokinetics focuses on the molecular and functional characteristics of drug transporters such as oligopeptide transporter, monocarboxylic acid transporter, anion antiporter, organic anion transporters, organic cation/carnitine transporters (OCTNs), and the ATP-binding cassette transporters P-glycoprotein and MRP2. We have successfully demonstrated that these transporters play important roles in the influxes and/or effluxes of drugs in intestinal and renal epithelial cells, hepatocytes, and brain capillary endothelial cells that form the blood-brain barrier. In the systemic carnitine deficiency (SCD) phenotype mouse model, juvenile visceral steatosis (jvs) mouse, a mutation in the OCTN2 gene was found. Furthermore, several types of mutation in human SCD patients were found, demonstrating that OCTN2 is a physiologically important carnitine transporter. Interestingly, OCTNs transport carnitine in a sodium-dependent manner and various cationic drugs transport it in a sodium-independent manner. OCTNs are thought to be multifunctional transporters for the uptake of carnitine into tissue cells and for the elimination of intracellular organic cationic drugs.

Regional peptide uptake study in the rat intestinal mucosa: glatiramer acetate as a model drug

PURPOSE

To identify regions of the rat intestine that are able to internalize from the lumen oligopeptides, using the model drug glatiramer acetate (GA).

METHODS

GA was introduced into rat intestinal sacs and the integrity of GA during uptake was monitored using antibody detection. Sodium docecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting of intestinal homogenates that had been exposed to GA were performed to identify GA presence. An enzyme-linked immunosorbent assay (ELISA) protocol was adapted for GA quantification. Immunohistochemistry was undertaken to examine the rat colonic wall for GA uptake, and confocal microscopy was used to differentiate adsorbed and internalized peptide in cultured colorectal adenocarcinoma cells.

RESULTS

The colon and the ileum, respectively, were identified to be the intestinal regions in which GA was maximally preserved during uptake from the lumen. GA was identified to cross the colonic wall from the epithelium to the serosa. Internalization of GA into cultured colonic epithelial cells was demonstrated.

CONCLUSIONS

The rat colonic wall was identified to be less proteolytically active toward GA compared to the wall of the more proximal regions of the small intestine. GA has the capacity to penetrate from the lumen into the colonic wall. The maintenance of GA integrity within the wall of the colon offers the potential for local biological activity of the drug.