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Targeting Systems to the Brain Obtained by Merging Prodrugs, Nanoparticles, and Nasal Administration. Pharmaceutics 2021; 13:pharmaceutics13081144. [PMID: 34452105 PMCID: PMC8399330 DOI: 10.3390/pharmaceutics13081144] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 07/13/2021] [Accepted: 07/23/2021] [Indexed: 01/27/2023] Open
Abstract
About 40 years ago the lipidization of hydrophilic drugs was proposed to induce their brain targeting by transforming them into lipophilic prodrugs. Unfortunately, lipidization often transforms a hydrophilic neuroactive agent into an active efflux transporter (AET) substrate, with consequent rejection from the brain after permeation across the blood brain barrier (BBB). Currently, the prodrug approach has greatly evolved in comparison to lipidization. This review describes the evolution of the prodrug approach for brain targeting considering the design of prodrugs as active influx substrates or molecules able to inhibit or elude AETs. Moreover, the prodrug approach appears strategic in optimization of the encapsulation of neuroactive drugs in nanoparticulate systems that can be designed to induce their receptor-mediated transport (RMT) across the BBB by appropriate decorations on their surface. Nasal administration is described as a valuable alternative to obtain the brain targeting of drugs, evidencing that the prodrug approach can allow the optimization of micro or nanoparticulate nasal formulations of neuroactive agents in order to obtain this goal. Furthermore, nasal administration is also proposed for prodrugs characterized by peripheral instability but potentially able to induce their targeting inside cells of the brain.
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Barlow N, Chalmers DK, Williams-Noonan BJ, Thompson PE, Norton RS. Improving Membrane Permeation in the Beyond Rule-of-Five Space by Using Prodrugs to Mask Hydrogen Bond Donors. ACS Chem Biol 2020; 15:2070-2078. [PMID: 32628005 DOI: 10.1021/acschembio.0c00218] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A wide range of drug targets can be effectively modulated by peptides and macrocycles. Unfortunately, the size and polarity of these compounds prevents them from crossing the cell membrane to reach target sites in the cell cytosol. As such, these compounds do not conform to standard measures of drug-likeness and exist in beyond the rule-of-five space. In this work, we investigate whether prodrug moieties that mask hydrogen bond donors can be applied in the beyond rule-of-five domain to improve the permeation of macrocyclic compounds. Using a cyclic peptide model, we show that masking hydrogen bond donors in the natural polar amino acid residues (His, Ser, Gln, Asn, Glu, Asp, Lys, and Arg) imparts membrane permeability to the otherwise impermeable parent molecules, even though the addition of the masking group increases the overall compound molecular weight and the number of hydrogen bond acceptors. We demonstrate this strategy in PAMPA and Caco2 membrane permeability assays and show that masking with groups that reduce the number of hydrogen-bond donors at the cost of additional mass and hydrogen bond acceptors, a donor-acceptor swap, is effective.
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Affiliation(s)
- Nicholas Barlow
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - David K. Chalmers
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Billy J. Williams-Noonan
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Philip E. Thompson
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Raymond S. Norton
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
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Prokai-Tatrai K, De La Cruz DL, Nguyen V, Ross BP, Toth I, Prokai L. Brain Delivery of Thyrotropin-Releasing Hormone via a Novel Prodrug Approach. Pharmaceutics 2019; 11:E349. [PMID: 31323784 PMCID: PMC6680701 DOI: 10.3390/pharmaceutics11070349] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 07/14/2019] [Accepted: 07/16/2019] [Indexed: 12/28/2022] Open
Abstract
Using thyrotropin-releasing hormone (TRH) as a model, we explored whether synergistic combination of lipoamino acid(s) and a linker cleaved by prolyl oligopeptidase (POP) can be used as a promoiety for prodrug design for the preferential brain delivery of the peptide. A representative prodrug based on this design principle was synthesized, and its membrane affinity and in vitro metabolic stability, with or without the presence of a POP inhibitor, were studied. The in vivo formation of TRH from the prodrug construct was probed by utilizing the antidepressant effect of the peptide, as well as its ability to increase acetylcholine (ACh) synthesis and release. We found that the prototype prodrug showed excellent membrane affinity and greatly increased metabolic stability in mouse blood and brain homogenate compared to the parent peptide, yet a POP inhibitor completely prevented prodrug metabolism in brain homogenate. In vivo, administration of the prodrug triggered antidepressant-like effect, and microdialysis sampling showed greatly increased ACh release that was also antagonized upon a POP inhibitor treatment. Altogether, the obtained promising exploratory data warrant further investigations on the utility of the prodrug approach introduced here for brain-enhanced delivery of small peptides with neurotherapeutic potential.
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Affiliation(s)
- Katalin Prokai-Tatrai
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
| | - Daniel L De La Cruz
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Vien Nguyen
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Benjamin P Ross
- School of Pharmacy, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Istvan Toth
- School of Chemistry & Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Laszlo Prokai
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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Glucose Transporters at the Blood-Brain Barrier: Function, Regulation and Gateways for Drug Delivery. Mol Neurobiol 2016; 54:1046-1077. [PMID: 26801191 DOI: 10.1007/s12035-015-9672-6] [Citation(s) in RCA: 201] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 12/17/2015] [Indexed: 12/31/2022]
Abstract
Glucose transporters (GLUTs) at the blood-brain barrier maintain the continuous high glucose and energy demands of the brain. They also act as therapeutic targets and provide routes of entry for drug delivery to the brain and central nervous system for treatment of neurological and neurovascular conditions and brain tumours. This article first describes the distribution, function and regulation of glucose transporters at the blood-brain barrier, the major ones being the sodium-independent facilitative transporters GLUT1 and GLUT3. Other GLUTs and sodium-dependent transporters (SGLTs) have also been identified at lower levels and under various physiological conditions. It then considers the effects on glucose transporter expression and distribution of hypoglycemia and hyperglycemia associated with diabetes and oxygen/glucose deprivation associated with cerebral ischemia. A reduction in glucose transporters at the blood-brain barrier that occurs before the onset of the main pathophysiological changes and symptoms of Alzheimer's disease is a potential causative effect in the vascular hypothesis of the disease. Mutations in glucose transporters, notably those identified in GLUT1 deficiency syndrome, and some recreational drug compounds also alter the expression and/or activity of glucose transporters at the blood-brain barrier. Approaches for drug delivery across the blood-brain barrier include the pro-drug strategy whereby drug molecules are conjugated to glucose transporter substrates or encapsulated in nano-enabled delivery systems (e.g. liposomes, micelles, nanoparticles) that are functionalised to target glucose transporters. Finally, the continuous development of blood-brain barrier in vitro models is important for studying glucose transporter function, effects of disease conditions and interactions with drugs and xenobiotics.
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Prokai-Tatrai K, Nguyen V, Szarka S, Konya K, Prokai L. Design and exploratory neuropharmacological evaluation of novel thyrotropin-releasing hormone analogs and their brain-targeting bioprecursor prodrugs. Pharmaceutics 2013; 5:318-28. [PMID: 24058724 PMCID: PMC3777413 DOI: 10.3390/pharmaceutics5020318] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Efforts to take advantage of the beneficial activities of thyrotropin-releasing hormone (TRH) in the brain are hampered by its poor metabolic stability and lack of adequate central nervous system bioavailability. We report here novel and metabolically stable analogs that we derived from TRH by replacing its amino-terminal pyroglutamyl (pGlu) residue with pyridinium-containing moieties. Exploratory studies have shown that the resultant compounds were successfully delivered into the mouse brain after systemic administration via their bioprecursor prodrugs, where they manifested neuropharmacological responses characteristic of the endogenous parent peptide. On the other hand, the loss of potency compared to TRH in a model testing antidepressant-like effect with a simultaneous preservation of analeptic activity has been observed, when pGlu was replaced with trigonelloyl residue. This finding may indicate an opportunity for designing TRH analogs with potential selectivity towards cholinergic effects.
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Affiliation(s)
- Katalin Prokai-Tatrai
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, USA; E-Mails: (V.N.); (S.S.); (L.P.)
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-817-735-0617; Fax: +1-817-735-2118
| | - Vien Nguyen
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, USA; E-Mails: (V.N.); (S.S.); (L.P.)
| | - Szabolcs Szarka
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, USA; E-Mails: (V.N.); (S.S.); (L.P.)
| | - Krisztina Konya
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, USA; E-Mails: (V.N.); (S.S.); (L.P.)
| | - Laszlo Prokai
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, USA; E-Mails: (V.N.); (S.S.); (L.P.)
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Prokai-Tatrai K, Prokai L. Prodrug design for brain delivery of small- and medium-sized neuropeptides. Methods Mol Biol 2012; 789:313-36. [PMID: 21922418 DOI: 10.1007/978-1-61779-310-3_21] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The blood-brain barrier (BBB) represents multiple barriers for drug delivery from the circulation. Peptides potentially useful to treat maladies of the brain are especially limited in their ability to cross the BBB due to several shortcomings. Specific delivery strategies have been conceived to outwit the BBB to target neuropeptides into the brain. It should be noted, however, that no unified method is possible for true brain-targeting of these fascinating biomolecules due to their structural features, properties, and intricate interplays among factors governing their entrance into and retention within the brain. In most brain-targeting prodrug approaches, a lipophilic and bioreversible moiety(ies) is covalently attached to the peptide that results in the complete loss of the innate biological activity of the parent peptide (prodrugs are inactive per definition) but significantly improves brain uptake and metabolic stability in the plasma and the interstitial fluid. Once the peptide prodrug has crossed the BBB, specific enzymes liberate the parent agent from its prodrug in the brain. To illustrate the applicability of the prodrug strategy for brain delivery of small neuropeptides, pGlu-Glu-Pro-NH(2), [Glu(2)TRH], a thyrotropin-releasing hormone (TRH) analogue with a vast array of central activities, was chosen as an example. An ester prodrug provided significantly improved brain delivery compared to the unmodified parent peptide. The synthesis, in vitro and in vivo evaluations of this prodrug as specific examples are given for typical exploratory prodrug validation.
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Affiliation(s)
- Katalin Prokai-Tatrai
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, USA
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Prokai-Tatrai K, Szarka S, Nguyen V, Sahyouni F, Walker C, White S, Talamantes T, Prokai L. "All in the mind"? Brain-targeting chemical delivery system of 17β-estradiol (Estredox) produces significant uterotrophic side effect. ACTA ACUST UNITED AC 2011; Suppl 7. [PMID: 24380028 DOI: 10.4172/2153-2435.s7-002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Here we revisit the peculiarly named redox chemical delivery system concept. This unique prodrug approach has long been claimed to be capable of targeting 17β-estradiol (E2), which has numerous beneficial central effects, into the brain without detrimental peripheral hormonal exposure. Using a well-established protocol to monitor E2's antidepressant-like effect, we show that the administration of this chemical delivery system incorporated into hydroxypropyl-β-cyclodextrin (i.e., Estredox), indeed, triggers a transient antidepressant-like behavior in ovariectomized mice. At the same time, even an acute dose of the carefully purified chemical delivery system produces significant circulating E2 levels and uterotrophic side effects for several days after drug administration. For the first time, we also unequivocally show by liquid chromatography coupled with tandem mass spectrometry that the uterus of the Estredox-treated animals contains a large quantity of E2 compared to that of the control group. These thus far unexposed yet consequential peripheral side effects brought about by Estredox call for a thorough and unbiased reassessment of the extent of brain-targeting of the hormone via the chemical delivery system approach.
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Affiliation(s)
- Katalin Prokai-Tatrai
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States ; Department of Pharmaceutical Sciences, University of North Texas System College of Pharmacy, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Szabolcs Szarka
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Vien Nguyen
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Fatima Sahyouni
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Cary Walker
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Shastazia White
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Tatjana Talamantes
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
| | - Laszlo Prokai
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699, United States
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Abstract
The delivery of drugs to the CNS is hampered by the existence of the blood–brain barrier (BBB). Nowadays, medicinal chemists follow defined rules for the development of drugs able to cross the BBB. At the same time, the parameters needed in order to gain valuable estimates of brain drug delivery are well defined. Despite the limits in molecular weight that allow drugs to cross the BBB, it was shown that nanotech products, in particular properly functionalized nanoparticles, spherical particles of approximately 200 nm in diameter, are able to cross the BBB after intravenous administration and act as drug carriers for CNS. Moreover, peptides as ligands for receptors present on the brain endothelium, or able to cross the BBB and to act as carriers for CNS drug delivery in the form of conjugates with drugs, have been discovered and started to be studied as targeting moieties for nanoparticulate systems. This article will discuss the results obtained so far in the field of nanoparticle drug carriers for CNS and highlight the parameters needed in order to fully characterize these hitherto largely unknown delivery systems. Even if promising results have been obtained, more studies are needed in order to fully evaluate the clinical potential of this drug-delivery system.
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Pavan B, Dalpiaz A, Ciliberti N, Biondi C, Manfredini S, Vertuani S. Progress in drug delivery to the central nervous system by the prodrug approach. Molecules 2008; 13:1035-65. [PMID: 18560328 PMCID: PMC6245073 DOI: 10.3390/molecules13051035] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 04/01/2008] [Accepted: 04/30/2007] [Indexed: 01/09/2023] Open
Abstract
This review describes specific strategies for targeting to the central nervous system (CNS). Systemically administered drugs can reach the brain by crossing one of two physiological barriers resistant to free diffusion of most molecules from blood to CNS: the endothelial blood-brain barrier or the epithelial blood-cerebrospinal fluid barrier. These tissues constitute both transport and enzymatic barriers. The most common strategy for designing effective prodrugs relies on the increase of parent drug lipophilicity. However, increasing lipophilicity without a concomitant increase in rate and selectivity of prodrug bioconversion in the brain will result in failure. In these regards, consideration of the enzymes present in brain tissue and in the barriers is essential for a successful approach. Nasal administration of lipophilic prodrugs can be a promising alternative non-invasive route to improve brain targeting of the parent drugs due to fast absorption and rapid onset of drug action. The carrier-mediated absorption of drugs and prodrugs across epithelial and endothelial barriers is emerging as another novel trend in biotherapeutics. Several specific transporters have been identified in boundary tissues between blood and CNS compartments. Some of them are involved in the active supply of nutrients and have been used to explore prodrug approaches with improved brain delivery. The feasibility of CNS uptake of appropriately designed prodrugs via these transporters is described in detail.
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Affiliation(s)
- Barbara Pavan
- University of Ferrara, Department of Biology, General Physiology Section, via L. Borsari 46, 44100, Ferrara, Italy.
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