Aging of mice is associated with p16(Ink4a)- and β-galactosidase-positive macrophage accumulation that can be induced in young mice by senescent cells

Senescent cells (SCs) have been considered a source of age-related chronic sterile systemic inflammation and a target for anti-aging therapies. To understand mechanisms controlling the amount of SCs, we analyzed the phenomenon of rapid clearance of human senescent fibroblasts implanted into SCID mice, which can be overcome when SCs were embedded into alginate beads preventing them from immunocyte attack. To identify putative SC killers, we analyzed the content of cell populations in lavage and capsules formed around the SC-containing beads. One of the major cell types attracted by secretory factors of SCs was a subpopulation of macrophages characterized by p16(Ink4a) gene expression and β-galactosidase activity at pH6.0 (β-gal(pH6)), thus resembling SCs. Consistently, mice with p16(Ink4a) promoter-driven luciferase, developed bright luminescence of their peritoneal cavity within two weeks following implantation of SCs embedded in alginate beads. p16(Ink4a)/β-gal(pH6)-expressing cells had surface biomarkers of macrophages F4/80 and were sensitive to liposomal clodronate used for the selective killing of cells capable of phagocytosis. At the same time, clodronate failed to kill bona fide SCs generated in vitro by genotoxic stress. Old mice with elevated proportion of p16(Ink4a)/β-gal(pH6)-positive cells in their tissues demonstrated reduction of both following systemic clodronate treatment, indicating that a significant proportion of cells previously considered to be SCs are actually a subclass of macrophages. These observations point at a significant role of p16(Ink4a)/β-gal(pH6)-positive macrophages in aging, which previously was attributed solely to SCs. They require re-interpretation of the mechanisms underlying rejuvenating effects following eradication of p16(Ink4a)/β-gal(pH6)-positive cells and reconsideration of potential cellular target for anti-aging treatment.

Abstract 1178: Unbiased efficacy-based screening of small molecules highly selective against hematological malignancies revealed inhibitor of NAD synthesis

Effective anticancer drugs can be directed against cell lineage-specific, rather than tumor-specific, targets (i.e., androgen receptor, CD20, etc.). We sought to conduct systematic search for novel agents that are selectively cytotoxic to hematopoietic (HP) malignancies presumably targeting HP lineage-specific survival factors. Cell-based screening and subsequent validation of small-molecules in a broad panel of HP and non-HP cancer cell lines followed by a hit-to lead optimization of the selected class of compounds has led to a molecule named OT-82 characterized by highly selective cytotoxicity against all HP-derived cancers tested (14 cell lines, representing human AML, ALL, CML and lymphoma cells) active within single nanomolar range of concentrations. OT-82 killed sensitive cells by induction of apoptosis and was up-to 20-fold more toxic to HP-derived than to solid tumor-derived cell lines and normal primary cells of HP and non-HP origin. OT-82-based affinity chromatography of cell lysates followed by mass spectrometry led to the identification of nicotinamide phosphorybosyltransferase (NAMPT) as the OT-82 target. NAMPT catalyzes the rate limiting step in a major pathway of synthesis of NAD, an energy metabolism mediator and essential cofactor of PARP and sirtuins. NAMPT treatment caused dramatic reductions in cellular NAD levels. Nicotinic acid (NA, vitamin B3), a substrate for the alternative NAD synthesis pathway, protected cells from the cytotoxic effects of OT-82. Oral administration of OT-82 was efficacious in subcutaneous and systemic xenograft models of human AML, ALL, erythroleukemia and multiple myeloma including complete response in several models. Therapeutic doses of OT-82 in mice were significantly lower than maximal tolerated dose (MTD); toxicities observed at doses above MTD were largely limited to HP and lymphoid organs. Toxicity profile of OT-82 determined in GLP in mice and non-human primates was favorably different from that reported for other reported clinical stage NAMPT inhibitors and did not involve any detectable retinal or cardiac toxicity. These results indicate high lineage specific and malignant transformation-specific dependence of HP neoplastic cells on NAMPT, presumably due to the strong addiction of this cell type on the NAD levels, and highlight OT-82 as a prospective clinical candidate for the treatment of hematological malignancies.

Citation Format: Lioubov Korotchkina, Sangeeta Joshi, Slavoljub Vujcic, Ilya Toshkov, Mikhail Chernov, Denis Kazyulkin, Katerina Andrianova, Alexander Polinsky, Olga Chernova, Andrei V. Gudkov. Unbiased efficacy-based screening of small molecules highly selective against hematological malignancies revealed inhibitor of NAD synthesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1178. doi:10.1158/1538-7445.AM2017-1178

High-throughput screening identifies Ceefourin 1 and Ceefourin 2 as highly selective inhibitors of multidrug resistance protein 4 (MRP4)

Multidrug resistance protein 4 (MRP4/ABCC4), a member of the ATP-binding cassette (ABC) transporter superfamily, is an organic anion transporter capable of effluxing a wide range of physiologically important signalling molecules and drugs. MRP4 has been proposed to contribute to numerous functions in both health and disease; however, in most cases these links remain to be unequivocally established. A major limitation to understanding the physiological and pharmacological roles of MRP4 has been the absence of specific small molecule inhibitors, with the majority of established inhibitors also targeting other ABC transporter family members, or inhibiting the production, function or degradation of important MRP4 substrates. We therefore set out to identify more selective and well tolerated inhibitors of MRP4 that might be used to study the many proposed functions of this transporter. Using high-throughput screening, we identified two chemically distinct small molecules, Ceefourin 1 and Ceefourin 2, that inhibit transport of a broad range of MRP4 substrates, yet are highly selective for MRP4 over other ABC transporters, including P-glycoprotein (P-gp), ABCG2 (Breast Cancer Resistance Protein; BCRP) and MRP1 (multidrug resistance protein 1; ABCC1). Both compounds are more potent MRP4 inhibitors in cellular assays than the most widely used inhibitor, MK-571, requiring lower concentrations to effect a comparable level of inhibition. Furthermore, Ceefourin 1 and Ceefourin 2 have low cellular toxicity, and high microsomal and acid stability. These newly identified inhibitors should be of great value for efforts to better understand the biological roles of MRP4, and may represent classes of compounds with therapeutic application.

New nanoformulation of rapamycin Rapatar extends lifespan in homozygous p53-/- mice by delaying carcinogenesis

The nutrient-sensing mTOR (mammalian Target of Rapamycin) pathway regulates cellular metabolism, growth functions, and proliferation and is involved in age-related diseases including cancer, type 2 diabetes, neurodegeneration and cardiovascular disease. The inhibition of mTOR by rapamycin, or calorie restriction, has been shown to extend lifespan and delays tumorigenesis in several experimental models suggesting that rapamycin may be used for cancer prevention. This requires continuous long-term treatment making oral formulations the preferred choice of administration route. However, rapamycin by itself has very poor water solubility and low absorption rate. Here we describe pharmacokinetic and biological properties of novel nanoformulated micelles of rapamycin, Rapatar. Micelles of Rapatar were rationally designed to increase water solubility of rapamycin to facilitate oral administration and to enhance its absorption. As a result, bioavailability of Rapatar was significantly increased (up to 12%) compared to unformulated rapamycin, which concentration in the blood following oral administration remained below level of detection. We also demonstrated that the new formulation does not induce toxicity during lifetime administration. Most importantly, Rapatar extended the mean lifespan by 30% and delayed tumor development in highly tumor-prone p53^−/− mice. Our data demonstrate that water soluble Rapatar micelles represent safe, convenient and efficient form of rapamycin suitable for a long-term treatment and that Rapatar may be considered for tumor prevention.

Identification of alkylidene hydrazides as glucagon receptor antagonists

High throughput screening of our small molecule combinatorial library identified a class of benzoylnaphthalenehydrazones with modest affinity for the human glucagon receptor. Optimization of this initial hit through a series of targeted libraries and traditional medicinal chemistry led to ligands with nanomolar affinities. Pharmacological evaluation demonstrated that these ligands were competitive glucagon receptor antagonists. Intravenous administration of a representative benzoylnaphthalenehydrazone into rats attenuated glucagon-stimulated glucose levels.

Combichem and chemoinformatics

New developments in cheminformatics are reviewed in the perspective of combinatorial chemistry and drug discovery. One of the most important trends is the realization that the ability to generate compounds in large numbers may not, in isolation, be helpful. It is more important to enrich combinatorial libraries with compounds which, if found to be active, can be quickly developed into viable drug candidates. Library design tools are being created that incorporate an accumulated medicinal chemistry experience necessary to produce compounds with desirable pharmacological properties. The development of methods to ensure chemical accessibility of designed libraries has also become important because of the need to integrate all steps of library generation, from design to synthesis, into one automated high-throughput process.

Synthesis and conformational properties of the lanthionine-bridged opioid peptide [D-AlaL2,AlaL5]enkephalin as determined by NMR and computer simulations

We report the synthesis and conformational analysis by means of NMR and computer simulations of a novel opioid peptide with the sequence [formula: see text], which we write as [formula: see text], abbreviated [D-AlaL2,L-AlaL5]EA, where AlaL denotes each of the lanthionine amino acid ends linked by a monosulfide bridge and EA indicates enkephalinamide. Data from 2D NMR (HOHAHA and ROESY) provide short-range NOEs that are used as constraints in molecular modeling; measurement of coupling constants shows that chi 1 (D-AlaL2) is predominantly in either the t or g- conformation, and temperature coefficient data suggest the participation of the AlaL5 amide proton in an intramolecular hydrogen bond. The use of NOE and hydrogen-bond constraints in a distance-geometry program yields a large number of initial conformations compatible with the data. Energy minimization of these structures using CHARMM results in three families of backbone ring conformations, labled A1, A2, and B. The torsion chi 1 in D-AlaL2 remains close to trans for all three conformations. Molecular dynamics in vacuo at 300 K show that these three families of conformers interconvert, with concerted shifts in two of the three torsions psi(Phe), phi(AlaL5), and chi(AlaL5). The [D-AlaL2,L-AlaL5]EA is superactive in the guinea pig ileum (GPI) and mouse vas deferens (MVD) in vitro tests and also in the rat hot plate test in vivo. At the same time, this analog with a constrained 13-membered ring shows virtually no selectivity with a ratio IC50 (MVD)/IC50 (GPI) of 0.882.

Minimum energy conformations of proline-containing helices

Proline occurs frequently in transmembrane alpha-helices of transport and receptor proteins even though statistical surveys demonstrate the overwhelming preference of this residue for a non-alpha-helical, hydrophilic environment. As a result, membrane-buried proline has been proposed to be functionally important, with function arising from structural discontinuity or destabilization of the helix. Destabilization may occur by Pro-mediated conformational transitions between discrete states, and may be manifested in membrane protein systems through reversible processes such as channel opening and closing or signal transduction. In this study, computer modeling of a model transmembrane alpha-helix, (Ala)8-Leu-Pro-Phe-(Ala)8, in a medium of low polarity (dielectric = 2), is used to examine the occurrence and energetic accessibility of Pro-mediated conformational interconversions. Leu psi and chi 1, Pro psi, and Phe phi and chi 1 torsion angles were assigned random values so that a data base of 200 conformations for each of the cis and trans states was generated. The conformations were minimized and low-energy structures organized into families. This analysis demonstrated that the most populated lowest energy family is the Trans-I conformation, corresponding to proline in a kinked alpha-helix. Two additional trans structures, Trans-II and Trans-III, as well as a cis conformation, Cis-I, are also energetically competitive. Interconversions between the trans states could thus be mediated by changes at a single torsion angle, accompanied by minor local hydrogen-bonding rearrangements. This work substantiates that membrane-buried proline can provide the basis for conformational transitions between discrete alpha-helix-based structures in a nonpolar environment.

A simple gas chromatographic method for the analysis of trace organics in ambient air

A simple method using adsorption, heat desorption, and F.I.D. gas chromatography to determine ppb quantities of various organic vapors in air is described. Laboratory results with chemicals such as bischloromethyl ether, vinyl chloride monomer and volatile ketones are discussed.