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Redkiewicz P, Dyniewicz J, Misicka A. Biphalin-A Potent Opioid Agonist-As a Panacea for Opioid System-Dependent Pathophysiological Diseases? Int J Mol Sci 2021; 22:11347. [PMID: 34768778 PMCID: PMC8582929 DOI: 10.3390/ijms222111347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/11/2021] [Accepted: 10/13/2021] [Indexed: 11/16/2022] Open
Abstract
Biphalin, one of the opioid agonists, is a dimeric analog of enkephalin with a high affinity for opioid receptors. Opioid receptors are widespread in the central nervous system and in peripheral neuronal and non-neuronal tissues. Hence, these receptors and their agonists, which play an important role in pain blocking, may also be involved in the regulation of other physiological functions. Biphalin was designed and synthesized in 1982 by Lipkowski as an analgesic peptide. Extensive further research in various laboratories on the antinociceptive effects of biphalin has shown its excellent properties. It has been demonstrated that biphalin exhibits an analgesic effect in acute, neuropathic, and chronic animal pain models, and is 1000 times more potent than morphine when administered intrathecally. In the course of the broad conducted research devoted primarily to the antinociceptive effect of this compound, it has been found that biphalin may also potentially participate in the regulation of other opioid system-dependent functions. Nearly 40 years of research on the properties of biphalin have shown that it may play a beneficial role as an antiviral, antiproliferative, anti-inflammatory, and neuroprotective agent, and may also affect many physiological functions. This integral review analyzes the literature on the multidirectional biological effects of biphalin and its potential in the treatment of many opioid system-dependent pathophysiological diseases.
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Affiliation(s)
- Patrycja Redkiewicz
- Department of Neuropeptides, Mossakowski Medical Research Institute Polish Academy of Sciences, 02106 Warsaw, Poland;
| | - Jolanta Dyniewicz
- Department of Neuropeptides, Mossakowski Medical Research Institute Polish Academy of Sciences, 02106 Warsaw, Poland;
| | - Aleksandra Misicka
- Department of Neuropeptides, Mossakowski Medical Research Institute Polish Academy of Sciences, 02106 Warsaw, Poland;
- Faculty of Chemistry, University of Warsaw, 02093 Warsaw, Poland
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Popiolek-Barczyk K, Piotrowska A, Makuch W, Mika J. Biphalin, a Dimeric Enkephalin, Alleviates LPS-Induced Activation in Rat Primary Microglial Cultures in Opioid Receptor-Dependent and Receptor-Independent Manners. Neural Plast 2017; 2017:3829472. [PMID: 28573049 PMCID: PMC5442438 DOI: 10.1155/2017/3829472] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 03/12/2017] [Accepted: 04/03/2017] [Indexed: 01/23/2023] Open
Abstract
Neuropathic pain is relatively less responsive to opioids than other types of pain, which is possibly due to a disrupted opioid system partially caused by the profound microglial cell activation that underlines neuroinflammation. We demonstrated that intrathecally injected biphalin, a dimeric enkephalin analog, diminished symptoms of neuropathy in a preclinical model of neuropathic pain in rats (CCI, chronic constriction injury of the sciatic nerve) at day 12 postinjury. Using primary microglial cell cultures, we revealed that biphalin did not influence cell viability but diminished NO production and expression of Iba1 in LPS-stimulated cells. Biphalin also diminished MOP receptor level, as well as pronociceptive mediators (iNOS, IL-1β, and IL-18) in an opioid receptor-dependent manner, and it was correlated with diminished p-NF-κB, p-IκB, p-p38MAPK, and TRIF levels. Biphalin reduced IL-6, IL-10, TNFα, p-STAT3, and p-ERK1/2 and upregulated SOCS3, TLR4, and MyD88; however, this effect was not reversed by naloxone pretreatment. Our study provides evidence that biphalin diminishes neuropathy symptoms, which might be partially related to reduced pronociceptive mediators released by activated microglia. Biphalin may be a putative drug for future pain therapy, especially for the treatment of neuropathic pain, when the lower analgesic effects of morphine are correlated with profound microglial cell activation.
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Affiliation(s)
| | - Anna Piotrowska
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland
| | - Wioletta Makuch
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland
| | - Joanna Mika
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland
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Lesniak A, Bochynska-Czyz M, Sacharczuk M, Benhye S, Misicka A, Bujalska-Zadrozny M, Lipkowski AW. Biphalin preferentially recruits peripheral opioid receptors to facilitate analgesia in a mouse model of cancer pain - A comparison with morphine. Eur J Pharm Sci 2016; 89:39-49. [DOI: 10.1016/j.ejps.2016.04.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 04/07/2016] [Accepted: 04/11/2016] [Indexed: 01/30/2023]
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Garbuz O, Gulea A, Dyniewicz J, Zablocka B, Lipkowski AW. The non-opioid receptor, antioxidant properties of morphine and the opioid peptide analog biphalin. Peptides 2015; 63:1-3. [PMID: 25453981 DOI: 10.1016/j.peptides.2014.09.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 10/24/2022]
Abstract
Opioids participate in a broad spectrum of regulatory effects. The discovery of the opioid receptor system led to the initial belief that all of the observed effects in this system were associated with receptor activation. However, it must be considered that certain opioid properties are the result of the properties of other chemicals and their distribution. The presence of a tyramine moiety in opioids is suggestive of their potential antioxidant properties. Therefore, this study evaluated the antioxidant properties of opioids that are not related to opioid receptor activation. The morphine antioxidant capacity (IC50=81μM) was 2.8 times lower than that of the reference ascorbic acid (IC50=29μM). Surprisingly, the biphalin antioxidant capacity (IC50=8μM) was 3.6 times higher than that of ascorbic acid and over 10 times higher than that of morphine. This unexpectedly high biphalin antioxidant capacity correlates with its neuroprotective properties.
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Affiliation(s)
- Olga Garbuz
- Moldova Coordination Chemistry Department, Moldova State University, Chisinau, Republic of Moldova.
| | - Aurelian Gulea
- Moldova Coordination Chemistry Department, Moldova State University, Chisinau, Republic of Moldova.
| | - Jolanta Dyniewicz
- Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw 02106, Poland.
| | - Barbara Zablocka
- Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw 02106, Poland.
| | - Andrzej W Lipkowski
- Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw 02106, Poland.
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5
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Chen WH, Janout V, Kondo M, Mosoian A, Mosoyan G, Petrov RR, Klotman ME, Regen SL. A fine line between molecular umbrella transport and ionophoric activity. Bioconjug Chem 2009; 20:1711-5. [PMID: 19689127 DOI: 10.1021/bc900246u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A persulfated molecular umbrella derived from one spermine, four lysine, and eight deoxycholic acid molecules was found to exhibit ionophoric activity, as shown by pH discharge and Na(+) and Cl(-) transport experiments. In sharp contrast, a moderately more hydrophilic analogue derived from cholic acid showed no such ionophoric activity. Both molecular umbrellas crossed liposomal membranes by passive transport with experimental rates that were similar. These findings show how the interactions between such amphomorphic molecules and phospholipid bilayers are a sensitive function of the umbrella's hydrophilic/lipophilic balance (HLB). They also raise the possibility of exploiting molecular umbrellas in fundamentally new ways.
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Affiliation(s)
- Wen-Hua Chen
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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Gardiner J, Thomae AV, Mathad RI, Seebach D, Krämer SD. Comparison of permeation through phosphatidylcholine bilayers of N-dipicolinyl-alpha- and -beta-oligopeptides. Chem Biodivers 2007; 3:1181-201. [PMID: 17193232 DOI: 10.1002/cbdv.200690120] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cell-membrane permeation of small therapeutic peptides and peptidomimetics is a fundamental issue in pharmaceutical research. Using a Tb(3+)-based permeation assay, we have examined the ability of alpha- and beta-peptides, bearing proteinogenic side chains and an N-terminal dipicolinic acid (DPA) monoamide group, to enter liposomes composed of egg phosphatidylcholine bilayers. A series of 12 DPA-peptides of increasing chain length was prepared and characterized by CD and NMR analysis. An interesting destabilizing effect of the N-terminal DPA group on the helical structure of a beta-hexapeptide was discovered. Significant differences in permeation were observed between the DPA-alpha- and the DPA-beta-peptides, with all beta-peptidic compounds permeating better than their alpha-analogs. Thus, beta-peptides have been shown to interact with lipid bilayers in a manner that is distinctly different from that of alpha-peptides. Together with the fact that beta-peptides are proteolytically stable in mammalian organisms, and that they fold to form helices and hairpin turns with short chain lengths, the new results further emphasize the biomedical potential of beta-peptides.
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Affiliation(s)
- James Gardiner
- Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich
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Cavazza A, Marini M, Spagnoli GC, Adamina M, Roda LG. Permeability of Phospholipid Vesicles to the Tumor Antigen Epitope gp100280–288. ChemMedChem 2006; 1:816-20. [PMID: 16902935 DOI: 10.1002/cmdc.200600019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Antonella Cavazza
- Dipartimento di Neuroscienze, Università degli Studi di Roma Tor Vergata, Via Montpellier 1, 00133 Roma, Italy
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Witt KA, Davis TP. CNS drug delivery: opioid peptides and the blood-brain barrier. AAPS JOURNAL 2006; 8:E76-88. [PMID: 16584136 PMCID: PMC2751425 DOI: 10.1208/aapsj080109] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Peptides are key regulators in cellular and intercellular physiological responses and possess enormous promise for the treatment of pathological conditions. Opioid peptide activity within the central nervous system (CNS) is of particular interest for the treatment of pain owing to the elevated potency of peptides and the centrally mediated actions of pain processes. Despite this potential, peptides have seen limited use as clinically viable drugs for the treatment of pain. Reasons for the limited use are primarily based in the physiochemical and biochemical nature of peptides. Numerous approaches have been devised in an attempt to improve peptide drug delivery to the brain, with variable results. This review describes different approaches to peptide design/modification and provides examples of the value of these strategies to CNS delivery of peptide drugs. The various modes of modification of therapeutic peptides may be amalgamated, creating more efficacious "hybrid" peptides, with synergistic delivery to the CNS. The ongoing development of these strategies provides promise that peptide drugs may be useful for the treatment of pain and other neurologically-based disease states in the future.
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Affiliation(s)
- Ken A. Witt
- />Pharmaceutical Sciences, School of Pharmacy, Southern Illinois University, Edwardsville, 200 University Park Drive, 62026 Edwardsville, IL. USA
| | - Thomas P. Davis
- />Department of Medical Pharmacology, College of Medicine, The University of Arizona, LSN 542, 1501 N. Campbell Avenue, P.O. Box 245050, 85724 Tucson, Arizona
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Chakraborty T, Krishna Mohan B, Uday Kumar S, Prabhakar A, Jagadeesh B. Synthesis of 3,4-di- O -acylated glucose-derived furanoid sugar amino acids (Gaa): conformational analysis of a Leu-enkephalin analog containing di- O -myristoylated Gaa. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2004.05.118] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Boguslavsky V, Hruby VJ, O'Brien DF, Misicka A, Lipkowski AW. Effect of peptide conformation on membrane permeability. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 2003; 61:287-97. [PMID: 12753376 DOI: 10.1034/j.1399-3011.2003.00047.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The effect of peptide conformational constraint on the peptide permeation across the model membranes was examined by determining the permeability of pairs of cyclic and acyclic peptides related to c[d-Pen2, d-Pen5] enkephalin (DPDPE). The peptides were cyclized by formation of an intramolecular disulfide bridge between the second and fifth residues composed of either d-penicillamine or cysteine. In each case the acyclic peptide was three to seven times more permeable than corresponding cyclic peptide. The possibility that the differences in permeability of cyclic and acyclic peptides is based on the greater conformational freedom of the acyclic peptides in the presence of membrane was examined in more detail by isothermal titration calorimetric studies of Trp6-DPDPE and its acyclic analog. The membrane binding of the acyclic peptide is a more exothermic process than binding of its cyclic Trp6-DPDPE. The transfer of acyclic peptide from water to membrane is an enthalpy driven process, whereas the transfer of the cyclic peptide is driven by entropy.
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Affiliation(s)
- V Boguslavsky
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
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Witt KA, Huber JD, Egleton RD, Davis TP. Pluronic p85 block copolymer enhances opioid peptide analgesia. J Pharmacol Exp Ther 2002; 303:760-7. [PMID: 12388663 DOI: 10.1124/jpet.102.039545] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Peptide-based drug development is a rapidly growing field within pharmaceutical research. Nevertheless, peptides have found limited clinical use due to several physiological and pathological factors. Pluronic block copolymers represent a growing technology with the potential to enhance efficacy of peptide therapeutics. This investigation assesses Pluronic P85 (P85) and its potential to enhance opioid peptide analgesia. Two opioid peptides, [D-Pen(2),D-Pen(5)]-enkephalin (DPDPE) and biphalin, were examined as to the benefits of P85 coadministration, above (1.0%) and below (0.01%) the critical micelle concentration, with morphine as a nonpeptide control. P85 was examined in vitro to assess blood-brain barrier uptake in association with P-glycoprotein effect, DPDPE and morphine being P-glycoprotein substrates. P85 coadministration with DPDPE and biphalin showed increased (p < 0.01) analgesia with both 0.01 and 1.0% P85. Morphine showed increased (p < 0.01) analgesia with 0.01% P85 only. This increase in analgesia is due to both an increase in peak effect, as well as a prolongation of effect. P85 increased cellular uptake of (125)I-DPDPE and [(3)H]morphine at 0.01% (p < 0.01) and 1.0% (p < 0.01 and p < 0.05, respectively). Cyclosporin-A coadministration with (125)I-DPDPE and [(3)H]morphine increased cellular uptake (p < 0.01 and p < 0.05, respectively). (125)I-DPDPE and [(3)H]morphine coadministered with 0.01% P85 and cyclosporin-A increased cellular uptake compared with control (p < 0.01) and compared with cyclosporin-A coadministration without P85 (p < 0.01 and p < 0.05, respectively). This indicates that, in addition to P-gp inhibition, 0.01% P85 increased (125)I-DPDPE and [(3)H]morphine uptake. In our examination, we determined that P85 enhanced the analgesic profile of biphalin, DPDPE, and morphine, both above and below the critical micelle concentration.
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Affiliation(s)
- Ken A Witt
- Department of Pharmacology, College of Medicine, The University of Arizona, Tucson, AZ 85724, USA
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12
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Flippen-Anderson JL, Deschamps JR, George C, Hruby VJ, Misicka A, Lipkowski AW. Crystal structure of biphalin sulfate: a multireceptor opioid peptide. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 2002; 59:123-33. [PMID: 11985706 DOI: 10.1034/j.1399-3011.2002.01967.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Biphalin is a dimeric opioid peptide, composed of two tetrapeptides connected 'tail-to-tail', that exhibits a high affinity for all three opioid receptor types (i.e. mu, delta and kappa). This study presents the X-ray crystal structure of biphalin sulfate and compares it to other opioids that interact with the same biological targets. Both halves of the molecule have a folded backbone conformation but differ significantly from one another. Residues 1-4 in biphalin, which compare well with the delta selective opioid peptide DADLE, fold into a random coil. Residues 5-8, which can be fit to the mu selective peptide D-TIPP-NH2, exhibit a fairly normal type III' beta bend. Biphalin also exhibits structural similarities with two naltrexone analogs, naltrexonazine and norbinaltorphamine, that are specific to mu and kappa receptor sites.
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Affiliation(s)
- J L Flippen-Anderson
- Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, DC 20375-5000, USA.
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Mehrotra S, Prajapati RK, Haq W, Singh VK. Immunomodulation by biphalin, dimeric synthetic opioid peptide, and its analog. Immunopharmacol Immunotoxicol 2002; 24:83-96. [PMID: 12022447 DOI: 10.1081/iph-120003405] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The opioid pentapeptides called enkephalins were originally described as the endogenous ligands for the opioid receptors. Although their precise physiological significance still remains elusive, the enkephalins have been reported to exhibit analgesic, antidepressant, antianxiety and anticonvulsant activities. In addition, enkephalins have also been shown to act as immunomodulator. The first generation of dimeric peptides was derived from enkephalins. Biphalin [(Tyr-D-Ala-Gly-Phe-NH)2] is a bivalent opioid analog containing two tyrosine residues. We have evaluated the immunomodulatory properties of biphalin and its analogs in various in vitro tests. We report that biphalin and one of its analogs [Tyr-D-Ala-Gly-Phe-NH.NH-Phe(p-Cl)-H] stimulate human T cell proliferation, natural killer (NK) cell cytotoxicity in vitro and interleukin-2 (IL-2) production. Biphalin and its analog also released chemokine like factor in the culture supernatant that was responsible for increased chemotaxis of monocytes. Furthermore, these peptides inhibited tumor necrosis factor (TNF-alpha) production in lipopolysaccharide (LPS) stimulated peripheral blood mononuclear cells (PBMC) and nitric oxide (NO) production in mouse macrophage cells, RAW 264.7. Our observations suggest immunomodulatory property of biphalin and its analog.
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Affiliation(s)
- S Mehrotra
- Department of Immunology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India
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Romanowski M, Zhu X, Kim K, Hruby VJ, O'Brien DF. Interaction of enkephalin peptides with anionic model membranes. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1558:45-53. [PMID: 11750263 DOI: 10.1016/s0005-2736(01)00421-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
According to the model for passive transport across the membranes, the total flow of permeant molecules is related to the product of the water-membrane partition coefficient and the diffusion coefficient, and to the water-membrane interfacial barrier. The effect of membrane surface charge on the permeability and interaction of analgesic peptide ligands with model membranes was investigated. A mixture of zwitterionic phospholipids with cholesterol was used as a model membrane. The lipid membrane charge density was controlled by the addition of anionic 1-palmitoyl-2-oleoylphosphatidylserine. Two classes of highly potent analgesic peptides were studied, c[D-Pen(2),D-Pen(5)]enkephalin (DPDPE) and biphalin, a dimeric analog of enkephalin. The effect of increased surface charge on the permeability of the zwitterionic DPDPE is a relatively modest decrease, that appears to be due to a diminished partition coefficient. On the other hand the binding of the dicationic biphalin ligands to membranes increases proportionally with increased negative surface charge. This effect translates into a significant reduction of biphalin permeability by reducing the diffusion of the peptide across the bilayer. These experiments show the importance of electrostatic effects on the peptide-membrane interactions and suggest that the negative charge naturally present in cell membranes may hamper the membrane transport of some peptide drugs, especially cationic ones, unless there are cationic transporters present.
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Affiliation(s)
- Marek Romanowski
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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Witt KA, Gillespie TJ, Huber JD, Egleton RD, Davis TP. Peptide drug modifications to enhance bioavailability and blood-brain barrier permeability. Peptides 2001; 22:2329-43. [PMID: 11786210 DOI: 10.1016/s0196-9781(01)00537-x] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Peptides have the potential to be potent pharmaceutical agents for the treatment of many central nervous system derived maladies. Unfortunately peptides are generally water-soluble compounds that will not enter the central nervous system, via passive diffusion, due to the existence of the blood-brain barrier. Peptides can also undergo metabolic deactivation by peptidases, thus further reducing their therapeutic benefits. In targeting peptides to the central nervous system consideration must be focused both on increasing bioavailability and enhancing brain uptake. To date multiple strategies have been examined with this focus. However, each strategy comes with its own complications and considerations. In this review we assess the strengths and weaknesses of many of the methods currently being examined to enhance peptide entry into the central nervous system.
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Affiliation(s)
- K A Witt
- Department of Pharmacology, The University of Arizona, College of Medicine, LSN 542, 1501 N. Campbell Avenue, Tucson, Arizona 85724, USA
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