Colon-targeted cell-permeable NFκB inhibitory peptide is orally active against experimental colitis

N-benzyl-N-methyldecan-1-amine and its derivative mitigate 2,4- dinitrobenzenesulfonic acid-induced colitis and collagen-induced rheumatoid arthritis

As our previous study revealed that N-benzyl-N-methyldecan-1-amine (BMDA), a new molecule originated from Allium sativum, exhibits anti-neoplastic activities, we herein explored other functions of the compound and its derivative [decyl-(4-methoxy-benzyl)-methyl-amine; DMMA] including anti-inflammatory and anti-oxidative activities. Pretreatment of THP-1 cells with BMDA or DMMA inhibited tumor necrosis factor (TNF)-α and interleukin (IL)-1β production, and blocked c-jun terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), MAPKAP kinase (MK)2 and NF-κΒ inflammatory signaling during LPS stimulation. Rectal treatment with BMDA or DMMA reduced the severity of colitis in 2,4-dinitrobenzenesulfonic acid (DNBS)-treated rat. Consistently, administration of the compounds decreased myeloperoxidase (MPO) activity (representing neutrophil infiltration in colonic mucosa), production of inflammatory mediators such as cytokine-induced neutrophil chemoattractant (CINC)-3 and TNF-α, and activation of JNK and p38 MAPK in the colon tissues. In addition, oral administration of these compounds ameliorated collagen-induced rheumatoid arthritis (RA) in mice. The treatment diminished the levels of inflammatory cytokine transcripts, and protected connective tissues through the expression of anti-oxidation proteins such as nuclear factor erythroid-related factor (Nrf)2 and heme oxygenase (HO)1. Additionally, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels did not differ between the BMDA- or DMMA-treated and control animals, indicating that the compounds do not possess liver toxicity. Taken together, these findings propose that BMDA and DMMA could be used as new drugs for curing inflammatory bowel disease (IBD) and RA.

Nanomedicine based potentially transformative strategies for colon targeting of peptides: State-of-the-art

Recently, peptides have attracted tremendous attention among researchers attributed to their high target specificity and efficacy compared to conventional therapeutics. The ease of self-administration and non-invasiveness confers oral as the most desirable route. However, numerous challenges associated with peptide delivery through the oral route like harsh gastrointestinal environment, enzymatic degradation, and absorption barriers hinder its clinical translation. Protease activity is more pronounced in the proximal segments of the gastrointestinal tract (GIT). Distal segments like the colon possess lower proteolytic activity, enhanced retention time, etc. which could facilitate easy absorption. However, traversing of the upper segments to reach the colon requires the circumvention of the pitfalls of the GIT. The advent of nanomedicine strategies could help in overcoming the said challenges associated with oral delivery, colon-specific targeting, and improving stability and bioavailability at the active site. Furthermore, the classification of peptides and various nanomedicine strategies for oral delivery of peptides to the colon has been conveyed. Regulatory hurdles and ways to accomplish clinical translation have been addressed.

A Colon-Targeted Prodrug of Riluzole Improves Therapeutic Effectiveness and Safety upon Drug Repositioning of Riluzole to an Anti-Colitic Drug

Riluzole (RLZ) is a neuroprotective drug indicated for amyotrophic lateral sclerosis. To examine the feasibility of RLZ for repositioning as an anti-inflammatory bowel disease (IBD) drug, RLZ (2, 5, and 10 mg/kg) was administered orally to rats with colitis induced by 2,4-dinitrobenzenesulfonic acid. Oral RLZ was effective against rat colitis in a dose-dependent manner, which was statistically significant at doses over 5 mg/kg. To address safety issues upon repositioning and further improve anti-colitic effectiveness, RLZ was coupled with salicylic acid (SA) via an azo-bond to yield RLZ-azo-SA (RAS) for the targeted colonic delivery of RLZ. Upon oral gavage, RAS (oral RAS) was efficiently delivered to and activated to RLZ in the large intestine, and systemic absorption of RLZ was substantially reduced. Oral RAS ameliorated colonic damage and inflammation in rat colitis and was more effective than oral RLZ and sulfasalazine, a current anti-IBD drug. Moreover, oral RAS potently inhibited glycogen synthase kinase 3β (GSK3β) in the inflamed distal colon, leading to the suppression of NFκB activity and an increase in the level of the anti-inflammatory cytokine interleukin-10. Taken together, RAS, which enables RLZ to be delivered to and inhibit GSK3β in the inflamed colon, may facilitate repositioning of RLZ as an anti-IBD drug.

Design, Synthesis and In Vivo Fluorescence Imaging Study of a Cytochrome P450 1B1 Targeted NIR Probe Containing a Chelator Moiety

Cytochrome P450 (CYP) 1B1 has been found to be overexpressed specifically in tumor tissues at early stage, which makes it a potential cancer biomarker for molecular imaging of cancer. Multimodal imaging combines different imaging modalities and offers more comprehensive information. Thus, imaging probes bearing more than one kind of signal fragment have been extensively explored and displayed great promise. Herein, we developed a near infrared (NIR) probe with a chelator moiety targeting CYP1B1 by conjugating α-naphthoflavone (ANF) derivatives with both a NIR dye and a chelator for potential application in bimodal imaging. Enzymatic inhibitory studies demonstrated inhibitory activity against CYP1B1 and selectivity among CYP1 were successfully retained after chemical modification. Cell-based saturation study indicated nanomolar range binding affinity between the probe and CYP1B1 overexpressed cancer cells. In vitro competitive binding assay monitored by confocal microscopy revealed that the probe could specifically accumulate in tumor cells. In vivo and ex vivo imaging studies demonstrated the probe could effectively lighten up the tumor tissues as early as 2 hours post injection. Besides, the fluorescence was significantly blocked by co-injection of CYP1B1 inhibitor, which indicated the probe accumulation in tumor sites was due to specific binding towards CYP1B1.

Eletrophilic Chemistry of Tranilast Is Involved in Its Anti-Colitic Activity via Nrf2-HO-1 Pathway Activation

Tranilast (TRL), a synthetic derivative of a tryptophan metabolite, is an anti-allergic drug used to treat bronchial asthma. We investigated how TRL activated the nuclear factor-erythroid 2 p45-related factor 2 (Nrf2)-hemeoxygenase-1 (HO-1) pathway based on the electrophilic chemistry of the drug and whether TRL activity contributed to the treatment of rat colitis. In human colon carcinoma cells, TRL activated Nrf2, as represented by an increase in nuclear Nrf2 and induction of Nrf2-dependent luciferase and, subsequently, HO-1, a target gene product of Nrf2. TRL activation of Nrf2 and induction of HO-1 were completely prevented by chemical reduction of the electrophilic functional group (α, β-unsaturated carbonyl group) in the drug. In parallel, TRL was reactive with the nucleophilic thiol group in N-acetylcysteine, forming a covalent adduct. Moreover, TRL, but not reduced TRL, binds to Kelch-like ECH-associated protein 1 (KEAP1), releasing Nrf2. TRL administration ameliorated colonic damage and inflammation in rats with dinitrobenzene sulfonic acid-induced colitis, which was partly compromised by the chemical reduction of TRL or co-treatment with an HO-1 inhibitor. Our results suggest that TRL activated the Nrf2-HO-1 pathway via covalent binding to KEAP1, partly contributing to TRL amelioration in rat colitis.

Design and evaluation of IKK-activated GSK3β inhibitory peptide as an inflammation-responsive anti-colitic therapeutic

Glycogen synthase kinase-3β (GSK3β), a multi-functional kinase, is a promising therapeutic target for the treatment of inflammation. Inhibitory κB kinase (IKK)-activated GSK3β inhibitory peptide (IAGIP) was designed as an inflammation-responsive anti-colitic therapeutic. To optimize therapeutic efficiency, IAGIP was tested using two different drug delivery techniques: colon-targeted delivery and cell-permeable peptide modification. In cell-based experiments, in response to tumor necrosis factor (TNF)- and lipopolysaccharide (LPS)-mediated activation of IKK, cell-permeable IAGIP (CTP-IAGIP) inhibited GSK3β, leading to increased production of anti-inflammatory cytokine interleukin-10 (IL-10) and suppression of TNF- and LPS-induced NFκB activity. Oral gavage of CTP-IAGIP loaded in the colon-targeted capsule attenuated 2,4,6-trinitrobenzene sulfonic acid-induced rat colitis and lowered the expression levels of NFκB-regulated proteins in the inflamed colons. CTP-IAGIP further induced IL-10 production in the inflamed colonic tissues; however, the levels of IL-10 were not affected in the normal colonic tissue or colonic tissue in which inflammation had subsided. Collectively, our data suggest that IAGIP administered using the aforementioned drug delivery techniques is an orally active anti-colitic drug selectively responding to inflammation.

Preparation and Evaluation of Colon-Targeted Prodrugs of the Microbial Metabolite 3-Indolepropionic Acid as an Anticolitic Agent

Microbial metabolites play a critical role in mucosal homeostasis by mediating physiological communication between the host and colonic microbes, whose perturbation may lead to gut inflammation. The microbial metabolite 3-indolepropionic acid (3-IPA) is one such communication mediator with potent antioxidative and anti-inflammatory activity. To apply the metabolite for the treatment of colitis, 3-IPA was coupled with acidic amino acids to yield colon-targeted 3-IPA, 3-IPA-aspartic acid (IPA-AA) and 3-IPA-glutamic acid (IPA-GA). Both conjugates were activated to 3-IPA in the cecal contents, which occurred faster for IPA-AA. Oral gavage of IPA-AA (oral IPA-AA) delivered a millimolar concentration of IPA-AA to the cecum, liberating 3-IPA. In a 2,4-dinitrobenzene sulfonic acid (DNBS)-induced rat colitis model, oral IPA-AA ameliorated rat colitis and was less effective than sulfasalazine (SSZ), a current anti-inflammatory bowel disease drug. To enhance the anticolitic activity of 3-IPA, it was azo-linked with the GPR109 agonist 5-aminonicotinic acid (5-ANA) to yield IPA-azo-ANA, expecting a mutual anticolitic action. IPA-azo-ANA (activated to 5-ANA and 2-amino-3-IPA) exhibited colon specificity in in vitro and in vivo experiments. Oral IPA-azo-ANA mitigated colonic damage and inflammation and was more effective than SSZ. These results suggest that colon-targeted 3-IPA ameliorated rat colitis and its anticolitic activity could be enhanced by codelivery of the GPR109A agonist 5-ANA.

Functional Hybrid Molecules for the Visualization of Cancer: PESIN-Homodimers Combined with Multimodal Molecular Imaging Probes for Positron Emission Tomography and Optical Imaging: Suited for Tracking of GRPR-Positive Malignant Tissue*

We describe multimodal imaging probes for gastrin-releasing peptide receptor (GRPR)-specific targeting suited for positron emission tomography and optical imaging (PET/OI), consisting of PESIN (PEG3 -BBN7-14 ) dimers connected to multimodal imaging subunits. These multimodal agents comprise a fluorescent dye for OI and the chelator ((1,4,7-triazacyclononane-4,7-diyl)diacetic acid-1-glutaric acid) (NODA-GA) for PET radiometal isotope labelling. Special focus was put on the influence of the used dyes on the properties of the whole bioconjugates. For this, several compounds with different fluorescent dyes and non-dye carrying subunits were synthesized and investigated. As fluorescent dyes, dansyl, NBD, derivatives of fluorescein, coumarin and rhodamine as well as three pyrilium-based dyes were employed. Considerable influence of the charge of the colored unit on hydrophilicity as well as in vitro target receptor binding was observed and classified. High radiochemical yields and purities were found during radiolabeling of the multimodal imaging subunits as well as their GRPR-specific bioconjugates with 68 Ga. Examinations of the photophysical properties of both molecule species displayed no loss or alteration of fluorescence characteristics.

Colitis-targeted hybrid nanoparticles-in-microparticles system for the treatment of ulcerative colitis

Nanoparticle (NP)-based drug delivery systems accumulate in the disrupted epithelium of inflamed colon tissue in ulcerative colitis. However, premature early drug release and uptake or degradation of NPs during their passage through the harsh gastric or intestinal environment compromise their therapeutic outcomes. This study aimed to develop an advanced colitis-targeted hybrid nanoparticles-in-microparticles (NPsinMPs) drug delivery system to overcome the aforementioned challenges. First, sustained drug releasing poly(lactic-co-glycolic acid) NPs were generated and further encapsulated in pH-sensitive Eudragit FS30D MPs to ensure complete drug protection in a gastric-like pH and for selective delivery of NPs to the colon. SEM and confocal microscopy for the NPsinMPs revealed successful NP encapsulation. NPsinMPs prevented drug release in an acidic gastric-like and intestinal-like pH and presented a sustained release thereafter at an ileal and colonic pH, indicating the degradation of the outer pH-sensitive MPs and release of NPs. Furthermore, in vivo imaging of gastrointestinal tract of a colitis mouse orally administered with fluorescent NPsinMPs revealed higher fluorescence intensities selectively in the colon, demonstrating the release of loaded NPs and their concomitant accumulation at the site of colon inflammation. NPsinMPs markedly mitigated experimental colitis in mice indicated by improved histopathological analysis, decreased myeloperoxidase activity, neutrophils and macrophage infiltration, and expression of proinflammatory cytokines in colonic tissues compared with NP-treated mice. The present results show the successful formulation of an NPsinMP-based drug delivery system and provide a platform to improve NP-based colon-targeted drug delivery through improved protection of encapsulated NPs and their payload in the early small intestine.

A Colon-Targeted Prodrug, 4-Phenylbutyric Acid-Glutamic Acid Conjugate, Ameliorates 2,4-Dinitrobenzenesulfonic Acid-Induced Colitis in Rats

An elevated level of endoplasmic reticulum (ER) stress is considered an aggravating factor for inflammatory bowel disease (IBD). To develop an ER-stress attenuator that is effective against colitis, 4-phenylbutyric acid (4-PBA), a chemical chaperone that alleviates ER stress, was conjugated with acidic amino acids to yield 4-PBA-glutamic acid (PBA-GA) and 4-PBA-aspartic acid (PBA-AA) conjugates. The PBA derivatives were converted to 4-PBA in the cecal contents, and the conversion was greater with PBA-GA than that with PBA-AA. After oral administration of PBA-GA (oral PBA-GA), up to 2.7 mM PBA was detected in the cecum, whereas 4-PBA was not detected in the blood, indicating that PBA-GA predominantly targeted the large intestine. In 2,4-dinitrobenzenesulfonic acid-induced colitis in rats, oral PBA-GA alleviated the damage and inflammation in the colon and substantially reduced the elevated levels of ER stress marker proteins in the inflamed colon. Moreover, PBA-GA was found to be as effective as the currently used anti-IBD drug, sulfasalazine. In conclusion, PBA-GA is a colon-targeted prodrug of 4-PBA and is effective against rat colitis probably via the attenuation of ER stress in the inflamed colon.

Mesalazine Activates Adenosine Monophosphate-activated Protein Kinase: Implication in the Anti-inflammatory Activity of this Anti-colitic Drug

OBJECTIVE

Mesalazine, 5-aminosalicylic acid (5-ASA), is an anti-inflammatory drug that is most widely used for the treatment of Inflammatory Bowel Disease (IBD). Despite extensive clinical use, the exact pharmacological mechanism underlying the anti-colitic effects of 5-ASA has not yet been elucidated. A potential molecular mechanism underlying 5-ASA-mediated anti-colitic activity was investigated.

METHODS

An anti-inflammatory pharmacology of 5-ASA was scrutinized in human colon carcinoma cells and murine macrophages and in a TNBS-induced rat colitis model.

RESULTS

5-ASA induced phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and its substrate acetyl-CoA carboxylase in cells. 5-ASA activation of AMPK occurred regardless of the presence of the pro-inflammatory mediators, Tumor Necrosis Factor Alpha (TNF-α) and lipopolysaccharide. 5-ASA inhibits TNF-α-dependent Nuclear Factor-Kappa B (NF-κB) activation, which was dampened by AMPK inhibition. Oral gavage of sulfasalazine (a colon-specific prodrug of 5- ASA) or rectal administration of 5-ASA ameliorated 2,4,6-trinitrobenzene sulfonic acid (TNBS)- induced rat colitis and activated AMPK in the inflamed colonic tissues while markedly diminishing the levels of NF-κB-regulated pro-inflammatory mediators cyclooxygenase-2, inducible nitric oxide synthase, and cytokine-induced neutrophil chemoattractant-3, elevated by the induction of inflammation. Rectal co-administration of 5-ASA and an AMPK inhibitor undermined 5-ASA-mediated activation of AMPK and its anti-colitic effects.

CONCLUSION

These findings suggest that the activation of AMPK is involved in 5-ASA-mediated anticolitic effects at least partly via interference with pro-inflammatory NF-κB signaling.

pH-dependent ileocolonic drug delivery, part II: preclinical evaluation of novel drugs and novel excipients

Novel drugs and novel excipients in pH-dependent ileocolonic drug delivery systems have to be tested in animals. Which animal species are suitable and what in vivo methods are used to verify ileocolonic drug delivery?

Sofalcone, a gastroprotective drug, covalently binds to KEAP1 to activate Nrf2 resulting in anti-colitic activity

Sofalcone is a synthetic chalcone being used as a gastric mucosa protective agent in Japan. Sofalcone contains a 1,3-diaryl-2-propen-1-one moiety, which is a common chemical scaffold in naturally occurring chalcones. The α,β-unsaturated carbonyl group (Michael reaction acceptor) has electrophilic properties. We investigated the biochemical mechanisms by which sofalcone activated the cytoprotective and anti-inflammatory nuclear factor-erythroid 2 (NF-E2) p45-related factor 2 (Nrf2)-heme oxygenase (HO)-1 pathway. Furthermore, we investigated whether the activation of this pathway was involved in sofalcone -mediated protective effects in an experimental colitis model. Sofalcone induced HO-1 protein expression, which was dependent on increased nuclear accumulation of Nrf2 in human colon carcinoma cells. In addition, Sofalcone reacted with nucleophilic thiol compounds to form Michael adducts. A reduced form of sofalcone (SFCR) in which the Michael reaction acceptor was deactivated, did not exert biological or chemical activity. Biotin-tagged sofalcone bound to Kelch-like ECH-associated protein 1 (KEAP1), a cytosolic repressor of Nrf2. This binding was prevented by pretreatment with sofalcone and a thiol compound but not with SFCR. Furthermore, sofalcone treatment induced dissociation of the Nrf2-KEAP1 complex. Rectal administration of sofalcone alleviated colon damage and inflammation and increased colon nuclear accumulation of Nrf2 and HO-1 levels in a dinitrobenzene sulfonic acid-induced rat colitis model. The protective effects of sofalcone against colon damage and inflammation were significantly inhibited by co-administration of an HO-1 inhibitor. In conclusion, sofalcone activated the Nrf2-HO-1 pathway by covalently binding to KEAP1 via Michael addition, and may confer anti-colitic effects by inducing Nrf2 activation.

NEMO-binding domain peptides alleviate perihematomal inflammation injury after experimental intracerebral hemorrhage

Inflammation aggravates the lethal consequences of intracerebral hemorrhage. Recently, many studies have found that nuclear factor-κB (NF-κB) is a crucial transcription factor that initiates inflammation in the perihematomal region of ICH. NF-κB essential modulator (NEMO)-binding domain (NBD) peptide, a cell-permeable peptide spanning the NBD of IKKα or IKKβ, functions as a highly specific inhibitor of NF-κB. This peptide can negatively regulate the NF-κB pathway. The present study aimed to explore the effects and underlying pathomechanisms of NBD peptides after ICH. Striatum infusion of whole blood or saline was performed on C57BL/6 mice (n = 198). Experimental animals were administered NBD or control (mutated) peptides 2 h before or after ICH by intracerebroventricular injection (icv.). NBD peptides significantly inhibited edema formation, ameliorated the neurological deficits, markedly reduced IκBα and p65 phosphorylation, blocked nuclear translocation of p65, and upregulated IκBα expression by NF-κB after ICH induction. Using an in vitro hemin toxicity model, we investigated the effects of NBD peptides on microglial inflammation. We found that NBD peptides suppressed microglia inflammation and lowered the expression of TNF-α and IL-1β in both in vivo and in vitro experiments. Further experiments were performed in mice and cultured microglia, which treated with NBD peptides in the presence of p65 siRNA confirmed that the specificity of NBD peptides inhibit ICH-induced NF-κB activation. This study demonstrated that NBD peptides exert a neuroprotective role after ICH and might be a potential candidate for a novel therapeutic strategy for ICH.

pH-triggered surface charge-reversal nanoparticles alleviate experimental murine colitis via selective accumulation in inflamed colon regions

In this study, we developed pH-triggered surface charge-reversal lipid nanoparticles (LNPs), loaded with budesonide, which could precisely deliver the drug to inflamed colon segments for the treatment of ulcerative colitis. Polyethyleneimine (PEI) was used to render LNPs cationic (PEI-LNPs), and Eudragit® S100 (ES) was coated on PEI-LNPs to obtain pH-triggered charge-reversal LNPs (ES-PEI-LNPs). ES coating avoided a burst drug release under acidic conditions mimicking the stomach and early small intestine environments and showed a sustained release in the colon. The surface charge of ES-PEI-LNPs switched from negative to positive under colonic conditions owing to pH-triggered removal of the ES coating. Bioimaging of the mouse gastrointestinal tract and confocal analysis of colon tissues revealed that ES-PEI-LNPs selectively accumulated in an inflamed colon. Furthermore, ES-PEI-LNPs mitigated experimental colitis in mice. These results suggest that the pH-triggered charge-reversal LNPs could be a promising drug carrier for ulcerative colitis therapy and other colon-targeted treatments.

Oxidized 5-aminosalicylic acid activates Nrf2-HO-1 pathway by covalently binding to Keap1: Implication in anti-inflammatory actions of 5-aminosalicylic acid

Mesalazine (5-aminosalicylic acid, 5-ASA), a currently used drug for anti-inflammatory bowel disease, is easily oxidized by HOCl, a strong oxidant generated in gut inflammation, to produce electrophilic quinones. We investigated whether this chemical feature has an implication in the anti-inflammatory pharmacology of 5-ASA. Human colon carcinoma HCT116 cells were treated with HOCl-reacted 5-ASA. Oxidized 5-ASA activated Nrf2 while 5-ASA itself was not effective. Activation of Nrf2 led to induction of hemeoxygenase (OH)-1, an anti-inflammatory enzyme. Western blot analysis of Keap1, a cytosolic repressor of Nrf2, following precipitation of biotin-labeled proteins in cell lysates treated with biotin-tagged 5-ASA, revealed a much greater amount of Keap1 when biotin-tagged 5-ASA was oxidized with HOCl. Precipitation of Keap1 was attenuated markedly by pretreatment with oxidized 5-ASA or a sulfhydryl donor. In addition, treatment with oxidized 5-ASA in cell lysates reduced the Keap1 amount that coimmunoprecipitated with Nrf2. In parallel, rectal administration of 5-ASA increased the level of HO-1 and nuclear Nrf2 in the inflamed colonic tissues, but not in normal colonic tissues. Moreover, oral gavage of sulfasalazine, a colon-specific prodrug of 5-ASA currently used clinically, activated the Nrf2-HO-1 pathway in the colonic tissues where inflammation was in progress, which was not observed when inflammation subsided. Collectively, our data suggest that Nrf2-HO-1 pathway is involved in the anti-inflammatory pharmacology of 5-ASA, which was likely being exerted exclusively in the inflammatory state.

Inhibition of regulated cell death by cell-penetrating peptides

Development of the means to efficiently and continuously renew missing and non-functional proteins in diseased cells remains a major goal in modern molecular medicine. While gene therapy has the potential to achieve this, substantial obstacles must be overcome before clinical application can be considered. A promising alternative approach is the direct delivery of non-permeant active biomolecules, such as oligonucleotides, peptides and proteins, to the affected cells with the purpose of ameliorating an advanced disease process. In addition to receptor-mediated endocytosis, cell-penetrating peptides are widely used as vectors for rapid translocation of conjugated molecules across cell membranes into intracellular compartments and the delivery of these therapeutic molecules is generally referred to as novel prospective protein therapy. As a broad coverage of the enormous amount of published data in this field is unrewarding, this review will provide a brief, focused overview of the technology and a summary of recent studies of the most commonly used protein transduction domains and their potential as therapeutic agents for the treatment of cellular damage and the prevention of regulated cell death.

Dual PET and Near-Infrared Fluorescence Imaging Probes as Tools for Imaging in Oncology

OBJECTIVE

The purpose of this article is to summarize advances in PET fluorescence resolution, agent design, and preclinical imaging that make a growing case for clinical PET fluorescence imaging.

CONCLUSION

Existing SPECT, PET, fluorescence, and MRI contrast imaging techniques are already deeply integrated into the management of cancer, from initial diagnosis to the observation and management of metastases. Combined positron-emitting fluorescent contrast agents can convey new or substantial benefits that improve on these proven clinical contrast agents.

5-Aminosalicylic Acid Azo-Linked to Procainamide Acts as an Anticolitic Mutual Prodrug via Additive Inhibition of Nuclear Factor kappaB

To improve the anticolitic efficacy of 5-aminosalicylic acid (5-ASA), a colon-specific mutual prodrug of 5-ASA was designed. 5-ASA was coupled to procainamide (PA), a local anesthetic, via an azo bond to prepare 5-(4-{[2-(diethylamino)ethyl]carbamoyl}phenylazo)salicylic acid (5-ASA-azo-PA). 5-ASA-azo-PA was cleaved to 5-ASA and PA up to about 76% at 10 h in the cecal contents while remaining stable in the small intestinal contents. Oral gavage of 5-ASA-azo-PA and sulfasalazine, a colon-specific prodrug currently used in clinic, to rats showed similar efficiency in delivery of 5-ASA to the large intestine, and PA was not detectable in the blood after 5-ASA-azo-PA administration. Oral gavage of 5-ASA-azo-PA alleviated 2,4,6-trinitrobenzenesulfonic acid-induced rat colitis. Moreover, combined intracolonic treatment with 5-ASA and PA elicited an additive ameliorative effect. Furthermore, combined treatment with 5-ASA and PA additively inhibited nuclear factor-kappaB (NFκB) activity in human colon carcinoma cells and inflamed colonic tissues. Finally, 5-ASA-azo-PA administered orally was able to reduce inflammatory mediators, NFκB target gene products, in the inflamed colon. 5-ASA-azo-PA may be a colon-specific mutual prodrug acting against colitis, and the mutual anticolitic effects occurred at least partly through the cooperative inhibition of NFκB activity.

Evaluation of glycine-bearing celecoxib derivatives as a colon-specific mutual prodrug acting on nuclear factor-κB, an anti-inflammatory target

In an inflammatory state where HOCl is generated, glycine readily reacts with HOCl to produce glycine chloramine, an anti-inflammatory oxidant. Colonic delivery of celecoxib elicits anticolitic effects in a trinitrobenzene sulfonic acid-induced rat colitis model. Glycine-bearing celecoxib derivatives were prepared and evaluated as a colon-specific mutual prodrug acting on nuclear factor-κB (NFκB), an anticolitic target. Glycylcelecoxib (GC), N-glycylaspart-1-ylcelecoxib (N-GA1C), and C-glycylaspart-1-ylcelecoxib (C-GA1C) were synthesized and their structures identified using infrared and proton nuclear magnetic resonance spectrometer. The celecoxib derivatives were chemically stable in pH 6.8 and 1.2 buffers. GC and C-GA1C were resistant to degradation in the small intestinal contents, while N-GA1C was substantially cleaved to release celecoxib. In contrast, all the celecoxib derivatives were degraded to liberate celecoxib in the cecal content. These results suggest that GC and C-GA1C could be delivered to and liberate celecoxib and glycine in the large intestine. In human colon carcinoma HCT116 and murine macrophage RAW264.7 cells, combined celecoxib–glycine chloramine treatment additively suppressed the production of proinflammatory NFκB target gene products. Collectively, our data suggest that C-GA1C is a potential colon-specific mutual prodrug acting against NFκB.

Effects of the properties of short peptides conjugated with cell-penetrating peptides on their internalization into cells

Peptides, especially intracellular functional peptides that can play a particular role inside a cell, have attracted attention as promising materials to control cell fate. However, hydrophilic materials like peptides are difficult for cells to internalize. Therefore, the screening and design of intracellular functional peptides are more difficult than that of extracellular ones. An effective high-throughput screening system for intracellular functional peptides has not been reported. Here, we demonstrate a novel peptide array system for screening intracellular functional peptides, in which both cell-penetrating peptide (CPP) domain and photo-cleavable linkers are used. By using this screening system, we determined how the cellular uptake properties of CPP-conjugated peptides varied depending on the properties of the conjugated peptides. We found that the internalization ability of CPP-conjugated peptides varied greatly depending on the property of the conjugated peptides, and anionic peptides drastically decreased the uptake ability. We summarized our data in a scatter diagram that plots hydrophobicity versus isoelectric point (pI) of conjugated peptides. These results define a peptide library suitable for screening of intracellular functional peptides. Thus, our system, including the diagram, is a promising tool for searching biological active molecules such as peptide-based drugs.

Colon-targeted delivery of piceatannol enhances anti-colitic effects of the natural product: potential molecular mechanisms for therapeutic enhancement

Piceatannol (PCT), an anti-colitic natural product, undergoes extensive Phase II hepatic metabolism, resulting in very low bioavailability. We investigated whether colon-targeted delivery of PCT could enhance anti-colitic effects and how therapeutic enhancement occurred at the molecular level. Molecular effects of PCT were examined in human colon carcinoma cells and inflamed colons. The anti-colitic effects of PCT in a colon-targeted capsule (colon-targeted PCT) were compared with PCT in a gelatin capsule (conventional PCT) in a trinitrobenzene sulfonic acid-induced rat colitis model. Colon-targeted PCT elicited greatly enhanced recovery of the colonic inflammation. In HCT116 cells, PCT inhibited nuclear factor kappaB while activating anti-colitic transcription factors, nuclear factor-erythroid 2 (NF-E2) p45-related factor 2, and hypoxia-inducible factor-1. Colon-targeted PCT, but not conventional PCT, modulated production of the target gene products of the transcription factors in the inflamed colonic tissues. Rectal administration of PCT, which simulates the therapeutic action of colon-targeted PCT, also ameliorated rat colitis and reproduced the molecular effects in the inflamed colonic tissues. Colon-targeted delivery increased therapeutic efficacy of PCT against colitis, likely resulting from multitargeted effects exerted by colon-targeted PCT. The drug delivery technique may be useful for therapeutic optimization of anti-colitic lead compounds including natural products.

Enhanced therapeutic efficacy of budesonide in experimental colitis with enzyme/pH dual-sensitive polymeric nanoparticles

Current colon-targeted drug-delivery approaches for colitis therapy often utilize single pH-triggered systems, which are less reliable due to the variation of gut pH in individuals and in disease conditions. Herein, we prepared budesonide-loaded dual-sensitive nanoparticles using enzyme-sensitive azo-polyurethane and pH-sensitive methacrylate copolymer for the treatment of colitis. The therapeutic potential of the enzyme/pH dual-sensitive nanoparticles was evaluated using a rat colitis model and compared to single pH-triggered nanoparticles. Clinical activity scores, colon/body weight ratios, myeloperoxidase activity, and proinflammatory cytokine levels were markedly decreased by dual-sensitive nanoparticles compared to single pH-triggered nanoparticles and budesonide solution. Moreover, dual-sensitive nanoparticles accumulated selectively in inflamed segments of the colon. In addition, dual-sensitive nanoparticle plasma concentrations were lower than single pH-triggered nanoparticles, and no noticeable in vitro or in vivo toxicity was observed. Our results demonstrate that enzyme/pH dual-sensitive nanoparticles are an effective and safe colon-targeted delivery system for colitis therapy.

Colonic delivery of celecoxib is a potential pharmaceutical strategy for repositioning the selective COX-2 inhibitor as an anti-colitic agent

Celecoxib is a selective cyclooxygenase-2 inhibitor applied to the treatment of arthritis. Repositioning the anti-inflammatory drug as an anti-inflammatory bowel disease drug has obstacles such as controversial anti-colitic efficacy and potential side effects. We examined whether colonic delivery of celecoxib could circumvent the therapeutic limitations. N-succinylglutam-1-yl celecoxib (SG1C), a colon-specific prodrug of celecoxib), was administered orally to rats with colitis and the anti-inflammatory activity and pharmacologic mechanisms were investigated. SG1C alleviated the colonic injury and lowered myeloperoxidase activity in the inflamed colonic tissues much more effectively than conventional celecoxib. While suppressing expression of pro-inflammatory nuclear factor kappaB gene products including cyclooxygenase-2, SG1C elevated an anti-inflammatory nuclear factor-erythroid 2 p45 (NF-E2)-related factor 2 (Nrf2) and its target gene product heme oxygenase (HO)-1 in the inflamed colon. In contrast, no significant molecular effects were observed with conventional celecoxib. Unlike conventional celecoxib, SG1C did not lower the serum level of 6-keto-PGF1α, an inverse indicator of cardiovascular adverse effects. Collectively, colonic delivery of celecoxib, likely improving therapeutic and toxicological properties of celecoxib, may be a feasible pharmaceutical strategy to therapeutically switch celecoxib to an anti-colitic drug.

HIF-prolyl hydroxylase is a potential molecular target for esculetin-mediated anti-colitic effects

We investigated a potential molecular target for anti-colitic effects of esculetin, 6,7-dihydroxycoumarin. Esculetin administered rectally effectively ameliorated TNBS-induced rat colitis and attenuated the expression of pro-inflammatory mediators in the inflamed colon. In human colon carcinoma HCT116 cells, esculetin induced hypoxia-inducible factor-1α (HIF-1α), leading to secretion of vascular endothelial growth factor, a HIF-1 target gene product involved in ulcer healing of the gastrointestinal mucosa. Esculetin directly inhibited HIF prolyl hydroxylase-2 (HPH-2), an enzyme playing a major role in negatively regulating HIF-1α protein stability. Esculetin inhibition of HPH and consequent induction of HIF-1α were attenuated by escalating dose of either ascorbate or 2-ketoglutarate, the required factors of the enzyme. Structurally, the catechol moiety in esculetin was required for HPH inhibition. Collectively, HPH may be a molecular target for esculetin-mediated anti-colitic effects and the catechol moiety in esculetin is the pharmacophore for HPH inhibition.

Colon-targeted celecoxib ameliorates TNBS-induced rat colitis: a potential pharmacologic mechanism and therapeutic advantages

The clinical usefulness of celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, for treatment of inflammatory bowel disease (IBD) is controversial in terms of efficacy and toxicity. To overcome these problems, colon-specific drug delivery was adopted, which generally confers therapeutic and toxicological advantages of drugs for treatment of colonic diseases. N-succinylaspart-1-yl celecoxib (SA1C), a colon-specific prodrug of celecoxib, was administered orally to rats with experimental colitis, and the anti-colitic effects and a molecular mechanism were investigated and compared to those of conventional celecoxib. SA1C, which delivered a much greater amount of celecoxib to the inflamed colon, alleviated the colonic injury, lowered myeloperoxidase activity in the inflamed colonic tissues and was much more effective than conventional celecoxib. SA1C but not conventional celecoxib significantly attenuated expression of NFκB target gene products in the inflamed tissues. Consistent with this, SA1C effectively prevented nuclear accumulation of p65 in the inflamed tissues. Moreover, while conventional celecoxib lowered the serum level of 6-keto-PGF1α, an inverse indicator of cardiovascular toxicity, SA1C did not change its serum level. Our data suggest that colonic delivery of celecoxib is a feasible strategy for treatment of IBD with improved therapeutic and toxicological properties.

Proteins and peptides: The need to improve them as promising therapeutics for ulcerative colitis

The present review briefly describes the nature, type and pathogenesis of ulcerative colitis, and explores the potential use of peptides and proteins in the treatment of inflammatory bowel disease, especially ulcerative colitis. Intestinal absorption and the barrier mechanism of peptide and protein drugs are also discussed, with special emphasis on various strategies which make these drugs better therapeutics having high specificity, potency and molecular targeting ability. However, the limitation of such therapeutics are oral administration, poor pharmacokinetic profile and decreased bioavailability. The recent findings illustrated in this review will be helpful in designing the peptide/protein drugs as a promising treatment of choice for ulcerative colitis.

Enzyme/pH dual sensitive polymeric nanoparticles for targeted drug delivery to the inflamed colon

Novel nanoparticles whose drug release profiles are controlled by both enzyme and pH were prepared for the colon-specific drug delivery using a polymeric mixture of enzyme-sensitive azo-polyurethane and pH-sensitive Eudragit S100 (ES-Azo.pu). The enzyme/pH dual sensitive nanoparticles were designed to release a drug based on a two-fold approach which specifically aimed to target drug delivery to the inflamed colon while preventing the burst release of drugs in the stomach and small intestine. Single pH-sensitive (ES) and dual sensitive (ES-Azo.pu) nanoparticles were prepared using an oil-in-water emulsion solvent evaporation method and coumarin-6 (C-6) was used as a model drug. The successful formation of ES and ES-azo.pu nanoparticles that have 214 nm and 244 nm in mean particle size, respectively, was confirmed by scanning electron microscopy and qNano. ES nanoparticles showed almost 100% of burst drug release at pH 7.4, whereas ES-Azo.pu nanoparticles prevented the burst drug release at pH 7.4, followed by a sustained release phase thereafter. Furthermore, ES-Azo.pu nanoparticles exhibited enzyme-triggered drug release in the presence of rat cecal contents obtained from a rat model of colitis. An in vivo localization study in rat gastrointestinal tract demonstrated that ES-Azo.pu nanoparticles were selectively distributed in the inflamed colon, showing 5.5-fold higher C-6 than ES nanoparticles. In conclusion, the enzyme/pH dual sensitive nanoparticles presented in this study can serve as a promising strategy for colon-specific drug delivery against inflammatory bowel disease and other colon disorders.

N-(2-Mercaptopropionyl)-glycine, a diffusible antioxidant, activates HIF-1 by inhibiting HIF prolyl hydroxylase-2: implication in amelioration of rat colitis by the antioxidant

We investigated anti-colitic effects of N-(2-mercaptopropionyl)-glycine (NMPG), a diffusible antioxidant, in TNBS-induced rat colitis model and a potential molecular mechanism underlying the pharmacologic effect of the antioxidant. NMPG alleviated colonic injury and effectively lowered myeloperoxidase activity. Moreover, NMPG substantially attenuated expression of pro-inflammatory mediators in the inflamed colon. NMPG induced hypoxia-inducible factor-1α (HIF-1α) in human colon carcinoma cells, leading to elevated secretion of vascular endothelial growth factor (VEGF), a target gene product of HIF-1 involved in ulcer healing of gastrointestinal mucosa. NMPG induction of HIF-1α occurred by inhibiting HIF prolyl hydroxylase-2 (HPH-2), an enzyme that plays a major role in negatively regulating HIF-1α protein stability. In in vitro Von Hippel-Lindau protein binding assay, the inhibitory effect of NMPG on HPH-2 was attenuated by escalating dose of ascorbate but not 2-ketoglutarate, cofactors of the enzyme. Consistent with this, cell-permeable ascorbate significantly attenuated NMPG induction of HIF-1α in cells. Our data suggest that NMPG is an anti-colitic antioxidant that exerts its pharmacologic effects at least partly through activation of an ulcer healing pathway, HIF-1-VEGF.

Imaging tumor angiogenesis in breast cancer experimental lung metastasis with positron emission tomography, near-infrared fluorescence, and bioluminescence

The goal of this study was to develop a molecular imaging agent that can allow for both positron emission tomography (PET) and near-infrared fluorescence (NIRF) imaging of CD105 expression in metastatic breast cancer. TRC105, a chimeric anti-CD105 monoclonal antibody, was labeled with both a NIRF dye (i.e., IRDye 800CW) and (64)Cu to yield (64)Cu-NOTA-TRC105-800CW. Flow cytometry analysis revealed no difference in CD105 binding affinity/specificity between TRC105 and NOTA-TRC105-800CW. Serial bioluminescence imaging (BLI) was carried out to non-invasively monitor the lung tumor burden in BALB/c mice, after intravenous injection of firefly luciferase-transfected 4T1 (i.e., fLuc-4T1) murine breast cancer cells to establish the experimental lung metastasis model. Serial PET imaging revealed that fLuc-4T1 lung tumor uptake of (64)Cu-NOTA-TRC105-800CW was 11.9 ± 1.2, 13.9 ± 3.9, and 13.4 ± 2.1 %ID/g at 4, 24, and 48 h post-injection respectively (n = 3). Biodistribution studies, blocking fLuc-4T1 lung tumor uptake with excess TRC105, control experiments with (64)Cu-NOTA-cetuximab-800CW (which served as an isotype-matched control), ex vivo BLI/PET/NIRF imaging, autoradiography, and histology all confirmed CD105 specificity of (64)Cu-NOTA-TRC105-800CW. Successful PET/NIRF imaging of tumor angiogenesis (i.e., CD105 expression) in the breast cancer experimental lung metastasis model warrants further investigation and clinical translation of dual-labeled TRC105-based agents, which can potentially enable early detection of small metastases and image-guided surgery for tumor removal.

PET imaging of CD105/endoglin expression with a ⁶¹/⁶⁴Cu-labeled Fab antibody fragment

PURPOSE

The goal of this study was to generate and characterize the Fab fragment of TRC105, a monoclonal antibody that binds with high affinity to human and murine CD105 (i.e., endoglin), and investigate its potential for PET imaging of tumor angiogenesis in a small-animal model after (61/64)Cu labeling.

METHODS

TRC105-Fab was generated by enzymatic papain digestion. The integrity and CD105 binding affinity of TRC105-Fab was evaluated before NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid) conjugation and (61/64)Cu labeling. Serial PET imaging and biodistribution studies were carried out in the syngeneic 4T1 murine breast cancer model to quantify tumor targeting efficiency and normal organ distribution of (61/64)Cu-NOTA-TRC105-Fab. Blocking studies with unlabeled TRC105 were performed to confirm CD105 specificity of the tracer in vivo. Immunofluorescence staining was also conducted to correlate tracer uptake in the tumor and normal tissues with CD105 expression.

RESULTS

TRC105-Fab was produced with high purity through papain digestion of TRC105, as confirmed by SDS-PAGE, HPLC analysis, and mass spectrometry. (61/64)Cu labeling of NOTA-TRC105-Fab was achieved with about 50 % yield (specific activity about 44 GBq/μmol). PET imaging revealed rapid uptake of (64)Cu-NOTA-TRC105-Fab in the 4T1 tumor (3.6 ± 0.4, 4.2 ± 0.5, 4.9 ± 0.3, 4.4 ± 0.7, and 4.6 ± 0.8 %ID/g at 0.5, 2, 5, 16, and 24 h after injection, respectively; n = 4). Since tumor uptake peaked soon after tracer injection, (61)Cu-labeled TRC105-Fab was also able to provide tumor contrast at 3 and 8 h after injection. CD105 specificity of the tracer was confirmed with blocking studies and histological examination.

CONCLUSION

We report PET imaging of CD105 expression using (61/64)Cu-NOTA-TRC105-Fab, which exhibited prominent and target-specific uptake in the 4T1 tumor. The use of a Fab fragment led to much faster tumor uptake (which peaked at a few hours after tracer injection) compared to radiolabeled intact antibody, which may be translated into same-day immunoPET imaging for clinical investigation.

In vitro and in vivo evaluation of a water-in-oil microemulsion system for enhanced peptide intestinal delivery

Peptide and protein drugs have become the new generation of therapeutics, yet most of them are only available as injections, and reports on oral local intestinal delivery of peptides and proteins are quite limited. The aim of this work was to develop and evaluate a water-in-oil (w/o) microemulsion system in vitro and in vivo for local intestinal delivery of water-soluble peptides after oral administration. A fluorescent labeled peptide, 5-(and-6)-carboxytetramethylrhodamine labeled HIV transactivator protein TAT (TAMRA-TAT), was used as a model peptide. Water-in-oil microemulsions consisting of Miglyol 812, Capmul MCM, Tween 80, and water were developed and characterized in terms of appearance, viscosity, conductivity, morphology, and particle size analysis. TAMRA-TAT was loaded and its enzymatic stability was assessed in modified simulated intestinal fluid (MSIF) in vitro. In in vivo studies, TAMRA-TAT intestinal distribution was evaluated using fluorescence microscopy after TAMRA-TAT microemulsion, TAMRA-TAT solution, and placebo microemulsion were orally gavaged to mice. The half-life of TAMRA-TAT in microemulsion was enhanced nearly three-fold compared to that in the water solution when challenged by MSIF. The treatment with TAMRA-TAT microemulsion after oral administration resulted in greater fluorescence intensity in all intestine sections (duodenum, jejunum, ileum, and colon) compared to TAMRA-TAT solution or placebo microemulsion. The in vitro and in vivo studies together suggested TAMRA-TAT was better protected in the w/o microemulsion in an enzyme-containing environment, suggesting that the w/o microemulsions developed in this study may serve as a potential delivery vehicle for local intestinal delivery of peptides or proteins after oral administration.