Anti-inflammatory action of exendin-4 in human islets is enhanced by phosphodiesterase inhibitors: potential therapeutic benefits in diabetic patients.

AIMS/HYPOTHESIS: Exendin-4, a glucagon-like peptide-1 (GLP-1) analogue, is reported to have modest anti-inflammatory effects in addition to that of improving beta cell survival. We therefore sought to determine whether exendin-4 decreases expression of the gene encoding chemokine (C-X-C motif) ligand (CXCL)10, which plays a role in initiating insulitis in type 1 diabetes. METHODS: The expression of CXCL10 in human islets was determined at the mRNA level by real-time RT-PCR analysis and at the protein level by western blotting. The level of CXCL10 in culture medium was measured by ELISA. Pathway-specific gene expression profiling was carried out to determine the expression of a panel of genes encoding chemokines and cytokines in human islets exposed to cytokines. RESULTS: IFN-γ induced expression of CXCL10 through activation of signal transducer and activator of transcription-1 (STAT-1). A combination of cytokines (IL-1ß, TNF-α and IFN-γ) showed strong synergy in the induction of numerous chemokines and cytokines through nuclear factor kappa B and STAT-1. Exendin-4 suppressed basal expression of several inflammatory mediators. In combination with phosphodiesterase inhibitors, exendin-4 also decreased IFN-γ-induced CXCL10 expression in human islets and in MIN6 cells (a mouse beta cell line), and its secretion into the culture medium. Exendin-4 action was mimicked by forskolin, an activator of adenylyl cyclase, and by dibutyryl cyclic AMP. Protein kinase A was not involved in mediating exendin-4 action on CXCL10. The mechanism of exendin-4's anti-inflammatory action involved decreases in STAT-1 levels. CONCLUSIONS/INTERPRETATION: These findings suggest that the GLP-1-cyclic AMP pathway decreases islet inflammation in addition to its known effects on beta cell survival.

Sequential cytotoxicity: a theory evaluated using novel 2-[4-(3-aryl-2-propenoyloxy)phenylmethylene]cyclohexanones and related compounds.

Five series of novel compounds were synthesized in order to evaluate the theory of sequential cytotoxicity which seeks to exploit the view that various cancer cells are particularly susceptible to successive attacks by cytotoxic agents. The compounds prepared were various 2-[4-(3-aryl-2-propenoyloxy)phenylmethylene]cyclohexanone s 1 and the related Mannich bases 2. In addition the analogues 3-5 lacking an olefinic bond in the ester group were also synthesized, which were predicted to be less cytotoxic than the compounds of series 1 and 2. The atomic charges at the potential sites for interaction with cellular constituents were determined by molecular modeling calculations. The biodata obtained from murine and human neoplastic cells revealed that the predictions made regarding the viability of the theory were fulfilled in approximately two-thirds of the cases indicating that further investigation of this hypothesis is warranted. In addition, the significant potencies of some of the Mannich bases toward human tumor cell lines, in particular coupled to their selective toxicity toward human leukemic and colon cancer cells, confirms their usefulness in serving as lead molecules for further development. A preliminary investigation into the mode of action of representative compounds revealed their ability to induce apoptosis and inhibit the biosyntheses of ribonucleic acid and proteins.

4-(beta-Arylvinyl)-3-(beta-arylvinylketo)-1-ethyl-4-piperidinols and related compounds: a novel class of cytotoxic and anticancer agents.

The syntheses of a series of 1-aryl-5-diethylamino-1-penten-3-one hydrochlorides 1 and 1-aryl-3-diethylamino-1-propanone hydrochlorides 4 were accomplished. Attempts to prepare the corresponding bis(5-aryl-3-oxo-4-pentenyl)ethylamine hydrochlorides 2 and bis(3-aryl-3-oxopropyl)ethylamine hydrochlorides 5 led to the formation of a series of 4-(beta-arylvinyl)-3-(beta-arylvinylketo)-1-ethyl-4-piperidi nol hydrochlorides 9 and 4-aryl-3-arylketo-1-ethyl-4-piperidinol hydrochlorides 11, most of which were converted subsequently into the corresponding quaternary ammonium salts 10 and 12, respectively. The structures of these compounds were determined by 1H NMR spectroscopy and confirmed by X-ray crystallography of representative molecules. Most compounds displayed significant cytotoxicity toward murine P388 and L1210 cells as well as human tumors. In general, Mannich bases containing olefinic bonds were more cytotoxic than the analogues without this functional group, while the piperidines 9 and 11 were more potent than the acyclic analogues 1 and 4, respectively. Correlations were noted between various physicochemical constants in the aryl rings and cytotoxicity. Compound 9d displayed promising in vivo activity against colon cancers. This study has revealed that the piperidines 9 and 11 constitute new classses of cytotoxic agents.

Cytotoxic activities of Mannich bases of chalcones and related compounds.

Various Mannich bases of chalcones and related compounds displayed significant cytotoxicity toward murine P388 and L1210 leukemia cells as well as a number of human tumor cell lines. The most promising lead molecule was 21 that had the highest activity toward L1210 and human tumor cells. In addition, 21 exerted preferential toxicity to human tumor lines compared to transformed human T-lymphocytes. Other compounds of interest were 38, with a huge differential in cytotoxicity between P388 and L1210 cells, and 42, with a high therapeutic index when cytotoxicity to P388 cells and Molt 4/C8 T-lymphocytes were compared. In general, the Mannich bases were more cytotoxic than the corresponding chalcones toward L1210 but not P388 cells. A ClusCor analysis of the data obtained from the in vitro human tumor screen revealed that the mode of action of certain groups of compounds was similar. For some groups of compounds, cytotoxicity was correlated with the sigma, pi, or molar refractivity constants in the aryl ring attached to the olefinic group. In addition, the IC50 values in all three screens correlated with the redox potentials of a number of Mannich bases. X-ray crystallography and molecular modeling of representative compounds revealed various structural features which were considered to contribute to cytotoxicity. While a representative compound 15 was stable and unreactive toward glutathione (GSH) in buffer, the Mannich bases 15, 18, and 21 reacted with GSH in the presence of the pi isozyme of glutathione S-transferase, suggesting that thiol alkylation may be one mechanism by which cytotoxicity was exerted in vitro. Representative compounds were shown to be nonmutagenic in an intrachromosomal recombination assay in yeast, devoid of antimicrobial properties and possessing anticonvulsant and neurotoxic properties. Thus Mannich bases of chalcones represent a new group of cytotoxic agents of which 21 in particular serves as an useful prototypic molecule.

(Aryloxy)aryl semicarbazones and related compounds: a novel class of anticonvulsant agents possessing high activity in the maximal electroshock screen.

A number of (aryloxy)aryl semicarbazones and related compounds were synthesized and evaluated for anticonvulsant activities. After intraperitoneal injection to mice, the semicarbazones were examined in the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ), and neurotoxicity (NT) screens. The results indicated that greater protection was obtained in the MES test than the scPTZ screen. Quantitation of approximately one-third of the compounds revealed an average protection index (PI, i.e. TD50/ED50) of approximately 9. After oral administration to rats, a number of compounds displayed significant potencies in the MES screen (ED50 of 1-5 mg/kg) accompanied by very high protection indices. In fact over half the compounds had PI figures of greater than 100, and two were in excess of 300. The compounds were essentially inactive in the scPTZ and NT screens after oral administration to rats. Various compounds displayed greater potencies and PI figures in the mouse intraperitoneal and rat oral screens than three reference clinically used drugs. The data generated supported a binding site hypothesis. Quantitative structure-activity relationships indicated a number of physicochemical parameters which contributed to activity in the MES screen. X-ray crystallography of five compounds suggested the importance of certain interatomic distances and bond angles for activity in the mouse and rat MES screens.

Snapshot of an enzyme reaction intermediate in the structure of the ATP-Mg2+-oxalate ternary complex of Escherichia coli PEP carboxykinase.

We report the 1.8 A crystal structure of adenosine triphosphate (ATP)-magnesium-oxalate bound phosphoenolpyruvate carboxykinase (PCK) from Escherichia coli. ATP binding induces a 20 degree hinge-like rotation of the N- and C-terminal domains which closes the active-site cleft. PCK possesses a novel nucleotide-binding fold, particularly in the adenine-binding region, where the formation of a cis backbone torsion angle in a loop glycine residue promotes intimate contacts between the adenine-binding loop and adenine, while stabilizing a syn conformation of the base. This complex represents a reaction intermediate analogue along the pathway of the conversion of oxaloacetate to phosphoenolpyruvate, and provides insight into the mechanistic details of the chemical reaction catalysed by this enzyme.

Cytotoxic evaluation of some 3,5-diarylidene-4-piperidones and various related quaternary ammonium compounds and analogs.

A number of 3,5-diarylidene-4-piperidones (1) and some related quaternary ammonium salts (5) as well as closely related analogs were prepared principally as candidate cytotoxic agents in two screens. The first test system used an average of 54 human tumor cell lines from eight neoplastic diseases, namely leukemia, melanoma, colon, non-small-cell lung, small-cell lung, central nervous system, ovarian, and renal cancers. Selective toxicity was demonstrated by some of the compounds, especially toward leukemia. The second screen used L1210 lymphoid leukemia cells. In general, the compounds were less cytotoxic than the reference drug melphalan in both screens. Linear plots were made between the Hammett (sigma), fragment (f), and molar refractivity (MR) constants of the nuclear substituents in series 1 and 5 with the IC50 figures of both the human tumor cell lines and L1210 cells. Evaluation against the human tumor cell lines revealed that increases in the f values were correlated with elevation of cytotoxicity in both series 1 and 5; MR constants were also important in series 5. In the L1210 screen, sigma and MR constants were positively correlated with cytotoxicity. X-ray crystallography was undertaken on 3,5-bis-[[4'-(methylthio)phenyl]methylene]-1-methyl-4-piperidone methiodide (5d), which had significant cytotoxicity, and 3,5-bis(4-pyridylmethylene)-1-methyl-4-piperidone methiodide (6), which was virtually inactive in both screens.(ABSTRACT TRUNCATED AT 250 WORDS)

2',3'-Didehydro-2',3'-dideoxy-5-hydroxymethyluridine.

The furanose ring in C10H12N2O5 adopts the O(4')-endo envelope conformation (0E) and the glycosidic torsion angle C(2)--N(1)--C(1')--O(4'), chi, is 245.2 (3) degrees. The pseudo-rotational parameters are P = 102.7 degrees and tau m = 5.2 degrees. The CH2OH group on C(5') has the t conformation [gamma = 179.2 (2) degrees].

Anticonvulsant activities of some arylsemicarbazones displaying potent oral activity in the maximal electroshock screen in rats accompanied by high protection indices.

Various semicarbazones derived from aryl aldehydes, phenylalkyl aldehydes, and phenylalkyl ketones as well as some related compounds were evaluated for anticonvulsant activity. Most of the compounds displayed anticonvulsant activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens accompanied by neurotoxicity when given to mice by the intraperitoneal route. However quantitative data revealed protection indices (TD50/ED50) of less than 4 in general. Oral administration of the compounds to rats led to excellent potency in the MES screen accompanied by high protection indices while virtually no activity in the scPTZ test was displayed. These observations support the theory that one large hydrophobic group (in this case the aryl ring) and two electron donor atoms (present in the semicarbazono group) are requirements for protection in the MES screen. In general, the semicarbazones had rapid onsets of action, and one of the ways in which these compounds displayed their anticonvulsant activity is likely to be interaction with chloride channels. Empirical and semiempirical conformational calculations indicated that certain molecular fragments and hydrophobicity of these molecules affect bioactivity.