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Wang H, Zhang F, Wen H, Shi W, Huang Q, Huang Y, Xie J, Li P, Chen J, Qin L, Zhou Y. Tumor- and mitochondria-targeted nanoparticles eradicate drug resistant lung cancer through mitochondrial pathway of apoptosis. J Nanobiotechnology 2020; 18:8. [PMID: 31918714 PMCID: PMC6950814 DOI: 10.1186/s12951-019-0562-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 12/17/2019] [Indexed: 01/24/2023] Open
Abstract
Chemotherapeutic drugs frequently encounter multidrug resistance. ATP from mitochondria helps overexpression of drug efflux pumps to induce multidrug resistance, so mitochondrial delivery as a means of "repurposing'' chemotherapeutic drugs currently used in the clinic appears to be a worthwhile strategy to pursue for the development of new anti-drug-resistant cancer agents. TPP-Pluronic F127-hyaluronic acid (HA) (TPH), with a mitochondria-targeting triphenylphosphine (TPP) head group, was first synthesized through ester bond formation. Paclitaxel (PTX)-loaded TPH (TPH/PTX) nanomicelles exhibited excellent physical properties and significantly inhibited A549/ADR cells. After TPH/PTX nanomicelles entered acidic lysosomes through macropinocytosis, the positively charged TP/PTX nanomicelles that resulted from degradation of HA by hyaluronidase (HAase) in acidic lysosomes were exposed and completed lysosomal escape at 12 h, finally localizing to mitochondria over a period of 24 h in A549/ADR cells. Subsequently, TPH/PTX caused mitochondrial outer membrane permeabilization (MOMP) by inhibiting antiapoptotic Bcl-2, leading to cytochrome C release and activation of caspase-3 and caspase-9. In an A549/ADR xenograft tumor model and a drug-resistant breast cancer-bearing mouse model with lung metastasis, TPH/PTX nanomicelles exhibited obvious tumor targeting and significant antitumor efficacy. This work presents the potential of a single, nontoxic nanoparticle (NP) platform for mitochondria-targeted delivery of therapeutics for diverse drug-resistant cancers.
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Affiliation(s)
- He Wang
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China.,Center of Cancer Research, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, Guangdong, China
| | - Fangke Zhang
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Huaying Wen
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Wenwen Shi
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Qiudi Huang
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Yugang Huang
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Jiacui Xie
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Peiyin Li
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China
| | - Jianhai Chen
- Nanfang Hospital, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Linghao Qin
- School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou, 510006, Guangdong, China.
| | - Yi Zhou
- Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, 511436, Guangdong, China.
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Sil D, Heinbockel L, Kaconis Y, Rössle M, Garidel P, Gutsmann T, David SA, Brandenburg K. Biophysical mechanisms of the neutralization of endotoxins by lipopolyamines. Open Biochem J 2013; 7:82-93. [PMID: 24133550 PMCID: PMC3795406 DOI: 10.2174/1874091x01307010082] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 07/30/2013] [Accepted: 08/08/2013] [Indexed: 01/05/2023] Open
Abstract
Endotoxins (lipopolysaccharides, LPS) are one of the strongest immunostimulators in nature, responsible for beneficial effects at low, and pathophysiological effects at high concentrations, the latter frequently leading to sepsis and septic shock associated with high mortality in critical care settings. There are no drugs specifically targeting the pathophysiology of sepsis, and new therapeutic agents are therefore urgently needed. The lipopolyamines are a novel class of small molecules designed to sequester and neutralize LPS. To understand the mechanisms underlying the binding and neutralization of LPS toxicity, we have performed detailed biophysical analyses of the interactions of LPS with candidate lipopolyamines which differ in their potencies of LPS neutralization. We examined gel-to-liquid crystalline phase behavior of LPS and of its supramolecular aggregate structures in the absence and presence of lipopolyamines, the ability of such compounds to incorporate into different membrane systems, and the thermodynamics of the LPS:lipopolyamine binding. We have found that the mechanisms which govern the inactivation process of LPS obey similar rules as found for other active endotoxin neutralizers such as certain antimicrobial peptides.
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Affiliation(s)
- Diptesh Sil
- Department. of Medicinal Chemistry, University of Kansas, Lawrence, KS, USA
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3
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Ghosh R, Pan S, Wang L, Lu S. A pulsed tangential-flow ultrafiltration technique for studying protein-drug binding. J Pharm Sci 2013; 102:2679-88. [PMID: 23765403 DOI: 10.1002/jps.23639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 05/17/2013] [Accepted: 05/21/2013] [Indexed: 11/07/2022]
Abstract
We describe a pulsed tangential-flow ultrafiltration technique for rapid analysis of protein-drug binding. A protein-drug pulse was injected into a tangential-flow membrane device and made to flow parallel to the surface of a protein-retaining ultrafiltration membrane. The protein and protein-drug complexes were flushed out of the device in the retentate stream, whereas the free drug present in the permeate stream was quantified using on-line UV detector. The height of the permeate drug peak and its area under the curve were both found to be proportional to the free drug concentration in the injected sample. The fraction of bound drug was determined by comparison with peak obtained with protein-free drug sample. The characteristics of the permeate drug peak such as residence time, peak width, and peak height depended on both feed and permeate flow rates. The proposed technique in addition to being fast was "self-priming" in nature because the injected samples were flushed out of the module along with the retentate and permeate. This feature makes this technique particularly suitable for automated sample analysis. The technique was validated using three-model protein-drug combinations: bovine serum albumin (BSA)-antipyrine, BSA-tryptophan, and BSA-aspirin.
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Affiliation(s)
- Raja Ghosh
- Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada.
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Kokatla HP, Yoo E, Salunke DB, Sil D, Ng CF, Balakrishna R, Malladi SS, Fox LM, David SA. Toll-like receptor-8 agonistic activities in C2, C4, and C8 modified thiazolo[4,5-c]quinolines. Org Biomol Chem 2013; 11:1179-98. [PMID: 23314908 PMCID: PMC3577938 DOI: 10.1039/c2ob26705e] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Toll-like receptor (TLR)-8 agonists typified by the 2-alkylthiazolo[4,5-c]quinolin-4-amine (CL075) chemotype are uniquely potent in activating adaptive immune responses by inducing robust production of T helper 1-polarizing cytokines, suggesting that TLR8-active compounds could be promising candidate vaccine adjuvants, especially for neonatal vaccines. Alkylthiazoloquinolines with methyl, ethyl, propyl and butyl groups at C2 displayed comparable TLR8-agonistic potencies; activity diminished precipitously in the C2-pentyl compound, and higher homologues were inactive. The C2-butyl compound was unique in possessing substantial TLR7-agonistic activity. Analogues with branched alkyl groups at C2 displayed poor tolerance of terminal steric bulk. Virtually all modifications at C8 led to abrogation of agonistic activity. Alkylation on the C4-amine was not tolerated, whereas N-acyl analogues with short acyl groups (other than acetyl) retained TLR8 agonistic activity, but were substantially less water-soluble. Immunization in rabbits with a model subunit antigen adjuvanted with the lead C2-butyl thiazoloquinoline showed enhancements of antigen-specific antibody titers.
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Affiliation(s)
- Hari Prasad Kokatla
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Euna Yoo
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Deepak B. Salunke
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Diptesh Sil
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Cameron F. Ng
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Rajalakshmi Balakrishna
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Subbalakshmi S. Malladi
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Lauren M. Fox
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
| | - Sunil A. David
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence KS 66047
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Shukla NM, Salunke DB, Balakrishna R, Mutz CA, Malladi SS, David SA. Potent adjuvanticity of a pure TLR7-agonistic imidazoquinoline dendrimer. PLoS One 2012; 7:e43612. [PMID: 22952720 PMCID: PMC3429503 DOI: 10.1371/journal.pone.0043612] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 07/26/2012] [Indexed: 01/25/2023] Open
Abstract
Engagement of toll-like receptors (TLRs) serve to link innate immune responses with adaptive immunity and can be exploited as powerful vaccine adjuvants for eliciting both primary and anamnestic immune responses. TLR7 agonists are highly immunostimulatory without inducing dominant proinflammatory cytokine responses. We synthesized a dendrimeric molecule bearing six units of a potent TLR7/TLR8 dual-agonistic imidazoquinoline to explore if multimerization of TLR7/8 would result in altered activity profiles. A complete loss of TLR8-stimulatory activity with selective retention of the TLR7-agonistic activity was observed in the dendrimer. This was reflected by a complete absence of TLR8-driven proinflammatory cytokine and interferon (IFN)-γ induction in human PBMCs, with preservation of TLR7-driven IFN-α induction. The dendrimer was found to be superior to the imidazoquinoline monomer in inducing high titers of high-affinity antibodies to bovine α-lactalbumin. Additionally, epitope mapping experiments showed that the dendrimer induced immunoreactivity to more contiguous peptide epitopes along the amino acid sequence of the model antigen.
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Affiliation(s)
- Nikunj M. Shukla
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States of America
| | - Deepak B. Salunke
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States of America
| | - Rajalakshmi Balakrishna
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States of America
| | - Cole A. Mutz
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States of America
| | - Subbalakshmi S. Malladi
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States of America
| | - Sunil A. David
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas, United States of America
- * E-mail:
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6
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Interactions between solubilized polymer molecules and blood components. J Control Release 2012; 160:14-24. [DOI: 10.1016/j.jconrel.2012.02.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 02/01/2012] [Indexed: 12/19/2022]
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Agnihotri G, Crall BM, Lewis TC, Day TP, Balakrishna R, Warshakoon HJ, Malladi SS, David SA. Structure-activity relationships in toll-like receptor 2-agonists leading to simplified monoacyl lipopeptides. J Med Chem 2011; 54:8148-60. [PMID: 22007676 DOI: 10.1021/jm201071e] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Toll-like receptor 2-agonistic lipopeptides typified by S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-R-cysteinyl-S-serine (PAM(2)CS) compounds are potential vaccine adjuvants. In continuation of previously reported structure-activity relationships on this chemotype, we have determined that at least one acyl group of optimal length (C(16)) and an appropriately oriented ester carbonyl group is essential for TLR2-agonistic activity. The spacing between one of the palmitoyl ester carbonyl and the thioether is crucial to allow for an important H-bond, which observed in the crystal structure of the lipopeptide:TLR2 complex; consequently, activity is lost in homologated compounds. Penicillamine-derived analogues are also inactive, likely due to unfavorable steric interactions with the carbonyl of Ser 12 in TLR2. The thioether in this chemotype can be replaced with a selenoether. Importantly, the thioglycerol motif can be dispensed with altogether and can be replaced with a thioethanol bridge. These results have led to a structurally simpler, synthetically more accessible, and water-soluble analogue possessing strong TLR2-agonistic activities in human blood.
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Affiliation(s)
- Geetanjali Agnihotri
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Lawrence, KS 66047, United States
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Agnihotri G, Ukani R, Malladi SS, Warshakoon HJ, Balakrishna R, Wang X, David SA. Structure-activity relationships in nucleotide oligomerization domain 1 (Nod1) agonistic γ-glutamyldiaminopimelic acid derivatives. J Med Chem 2011; 54:1490-510. [PMID: 21299227 DOI: 10.1021/jm101535e] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
N-acyl-γ-glutamyldiaminopimelic acid is a prototype ligand for Nod1. We report a detailed SAR of C(12)-γ-D-Glu-DAP. Analogues with glutaric or γ-aminobutyric acid replacing the glutamic acid show greatly attenuated Nod1-agonistic activity. Substitution of the meso-diaminopimelic (DAP) acid component with monoaminopimelic acid, L- or D-lysine, or cadaverine also results in reduced activity. The free amine on DAP is crucial. However, the N-acyl group on the D-glutamyl residue can be substituted with N-alkyl groups with full preservation of activity. The free carboxylates on the DAP and Glu components can also be esterified, resulting in more lipophilic but active analogues. Transcriptomal profiling showed a dominant up-regulation of IL-19, IL-20, IL-22, and IL-24, which may explain the pronounced Th2-polarizing activity of these compounds and also implicate cell signaling mediated by TREM-1. These results may explain the hitherto unknown mechanism of synergy between Nod1 and TLR agonists and are likely to be useful in designing vaccine adjuvants.
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Affiliation(s)
- Geetanjali Agnihotri
- Department of Medicinal Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, United States
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9
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Shukla NM, Malladi SS, Mutz CA, Balakrishna R, David SA. Structure-activity relationships in human toll-like receptor 7-active imidazoquinoline analogues. J Med Chem 2010; 53:4450-65. [PMID: 20481492 DOI: 10.1021/jm100358c] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Engagement of toll-like receptors serve to link innate immune responses with adaptive immunity and can be exploited as powerful vaccine adjuvants for eliciting both primary and anamnestic immune responses. TLR7 agonists are highly immunostimulatory without inducing dominant proinflammatory cytokine responses. A structure-activity study was conducted on the TLR7-agonistic imidazoquinolines, starting with 1-(4-amino-2-((ethylamino)methyl)-1H-imidazo[4,5-c]quinolin-1-yl)-2-methylpropan-2-ol as a lead. Modifications of the secondary amine of the C2 ethylaminomethylene side chain are poorly tolerated. The 4-amino group must be retained for activity. Replacement of the imidazole ring of the scaffold with triazole or cyclic urea led to complete loss of activity. A systematic exploration of N(1)-benzyl-C2-alkyl substituents showed a very distinct relationship between alkyl length and TLR7-agonistic potency with the optimal compound bearing a C2-n-butyl group. Transposition of the N(1) and C2 substituents led to the identification of an extremely active TLR7-agonistic compound with an EC(50) value of 8.6 nM. The relative potencies in human TLR7-based primary reporter gene assays were paralleled by interferon-alpha induction activities in whole human blood models.
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Affiliation(s)
- Nikunj M Shukla
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence, Kansas 66047, USA
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10
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Wu W, Li R, Malladi SS, Warshakoon HJ, Kimbrell MR, Amolins MW, Ukani R, Datta A, David SA. Structure-activity relationships in toll-like receptor-2 agonistic diacylthioglycerol lipopeptides. J Med Chem 2010; 53:3198-213. [PMID: 20302301 DOI: 10.1021/jm901839g] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The N-termini of bacterial lipoproteins are acylated with a (S)-(2,3-bisacyloxypropyl)cysteinyl residue. Lipopeptides derived from lipoproteins activate innate immune responses by engaging Toll-like receptor 2 (TLR2) and are highly immunostimulatory and yet without apparent toxicity in animal models. The lipopeptides may therefore be useful as potential immunotherapeutic agents. Previous structure-activity relationships in such lipopeptides have largely been obtained using murine cells, and it is now clear that significant species-specific differences exist between human and murine TLR responses. We have examined in detail the role of the highly conserved Cys residue as well as the geometry and stereochemistry of the Cys-Ser dipeptide unit. (R)-Diacylthioglycerol analogues are maximally active in reporter gene assays using human TLR2. The Cys-Ser dipeptide unit represents the minimal part-structure, but its stereochemistry was found not to be a critical determinant of activity. The thioether bridge between the diacyl and dipeptide units is crucial, and replacement by an oxoether bridge results in a dramatic decrease in activity.
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Affiliation(s)
- Wenyan Wu
- Department of Medicinal Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
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11
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Survey of the year 2008: applications of isothermal titration calorimetry. J Mol Recognit 2010; 23:395-413. [DOI: 10.1002/jmr.1025] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Purification of human IgG by negative chromatography on ω-aminohexyl-agarose. J Chromatogr B Analyt Technol Biomed Life Sci 2010; 878:557-66. [DOI: 10.1016/j.jchromb.2009.12.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 12/10/2009] [Accepted: 12/18/2009] [Indexed: 11/20/2022]
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Abstract
Sepsis, otherwise referred to as "blood poisoning" is a serious clinical problem, the incidence of which continues to rise in the US and worldwide despite advances in antimicrobial chemotherapy. The primary trigger in Gram-negative sepsis is endotoxin, a lipopolysaccharide (LPS) constituent of the outer membrane of all Gram-negative bacteria. The structurally highly conserved glycolipid called lipid A is the active moiety of LPS. Lipid A is composed of a hydrophilic, bis-phosphorylated di-glucosamine backbone, and a hydrophobic polyacyl domain. The bis-anionic, amphiphilic nature of lipid A enables it to interact with a variety of cationic hydrophobic ligands, including polymyxin B, a toxic peptide antibiotic which binds to lipid A and neutralizes endotoxicity. Having determined the structural basis of the interaction of polymyxin B with lipid A, our long-term goal has been to rationally design non-peptidic, nontoxic, small-molecule LPS-sequestrants. Our efforts began with defining the central pharmacophore that determined LPS-recognition and -neutralization properties in small molecules, which led to the discovery of a novel lipopolyamine lead, DS-96. DS-96 is an effective LPS-neutralizer, rivaling polymyxin B in a panel of vitro assays, as well as in protecting animals against endotoxicosis. Structure-activity relationships in our effort to rationally design endotoxin sequestering agents, preclinical assessment of hits and leads, and approaches to overcoming issues with toxicity are described in this chapter.
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Affiliation(s)
- Sunil A David
- Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence, KS 66047, USA.
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Structure-activity relationships of lipopolysaccharide sequestration in N-alkylpolyamines. Bioorg Med Chem Lett 2009; 19:2478-81. [PMID: 19332373 DOI: 10.1016/j.bmcl.2009.03.055] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 03/10/2009] [Accepted: 03/12/2009] [Indexed: 11/23/2022]
Abstract
We have previously shown that simple N-acyl or N-alkyl polyamines bind to and sequester Gram-negative bacterial lipopolysaccharide, affording protection against lethality in animal models of endotoxicosis. Several iterative design-and-test cycles of SAR studies, including high-throughput screens, had converged on compounds with polyamine scaffolds which have been investigated extensively with reference to the number, position, and length of acyl or alkyl appendages. However, the polyamine backbone itself had not been explored sufficiently, and it was not known if incremental variations on the polymethylene spacing would affect LPS-binding and neutralization properties. We have now systematically explored the relationship between variously elongated spermidine [NH(2)-(CH(2))(3)-NH-(CH(2))(4)-NH(2)] and norspermidine [NH(2)-(CH(2))(3)-NH-(CH(2))(3)-NH(2)] backbones, with the N-alkyl group being held constant at C(16) in order to examine if changing the spacing between the inner secondary amines may yield additional SAR information. We find that the norspermine-type compounds consistently showed higher activity compared to corresponding spermine homologues.
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