Hypotensive mechanism of [Leu13]motilin in dogs in vivo and in vitro.

The effects of [Leu13]motilin were examined in vivo after its intravenous administration into anesthetized dogs and in vitro with isolated preparations of canine mesenteric artery. [Leu13]Motilin (0.1-10 nmol x kg(-1), i.v.) induced both strong and clustered phasic contractions in the gastric antrum and duodenum. At doses of over 1 nmol x kg(-1), [Leu13]motilin also produced transient decreases in arterial blood pressure, left ventricular pressure, maximum rate of rise of left ventricular pressure, and total peripheral resistance, and an increase in aortic blood flow and heart rate. A selective motilin antagonist, GM-109 (Phe-cyclo[Lys-Tyr(3-tBu)-betaAla] trifluoroacetate), completely abolished the gastric antrum and duodenal motor responses induced by [Leu13]motilin. In contrast, hypotension induced by [Leu13]motilin (1 nmol x kg(-1)) was unchanged in the presence of GM-109. In isolated mesenteric artery preparations precontracted with U-46619 (10(-7) M), [Leu13]motilin (10(-8)-10(-5) M) induced an endothelium-dependent relaxation, and this was inhibited by a pretreatment with N(omega)-nitro-L-arginine, a competitive inhibitor of NO synthase (10(-4) M). A high dose (10(-4) M) of GM-109 slightly decreased [Leu13]motilin-induced relaxation, and shifted the concentration-response curve of [Leu13]motilin to the right. However, the pA2 value (4.09) of GM-109 for [Leu13]motilin in the present study was conspicuously lower than that previously demonstrated in the rabbit duodenum (7.37). These results suggest that [Leu13]motilin induces hypotension via the endothelial NO-dependent relaxation mechanism and not through the receptor type that causes upper gastrointestinal contractions.     

High level production of a peptide hormone analogue [Leu13]motilin inE. coli

Summary A peptide hormone analogue [Leu¹³]motilin has been produced in high yield by recombinant DNA techniques. The peptide was expressed from a multicopied [Leu¹³]motilin gene fused to a salmon growth hormone gene fragment. The monomeric [Leu¹³]motilin was obtained by treatment of the fusion protein with cyanogen bromide, carboxypeptidase A and B. [Leu¹³]motilin showed the equivalent biological activity to that of the natural form.     

Hydrolysis of [Leu]enkephalin by chick brain in vitro.

Using high-performance liquid chromatography with electrochemical detection to measure substrate disappearance and metabolite accumulation following addition of [Leu]enkephalin to samples prepared from chick brain in vitro, the following were found: 1. [Leu]enkephalin hydrolysis by whole forebrain homogenates is almost solely attributable to aminopeptidase MII activity. 2. [Leu]enkephalin hydrolysis by whole forebrain P2 membrane fractions is attributable to both aminopeptidase MII and dipeptidyl carboxypeptidase activity. 3. Differences are apparent in both [Leu]enkephalin disappearance and Tyr-Gly-Gly accumulation in P2 membrane fractions, but not in homogenate fractions, prepared from several regions of the chick brain.     

Synthesis and antiproliferative evaluation of 13-aryl-13H-benzo[g]benzothiazolo [2,3-b]quinazoline-5,14-diones

A simple synthesis of novel 13-aryl-13H-benzo[g]benzothiazolo [2,3-b]quinazoline-5,14-dione derivatives was accomplished in excellent yields via the reaction of 2-aminobenzothiazole, aromatic aldehydes and 2-hydroxy-1,4-naphthoquinone in the presence of amberlyst-15. The antiproliferative activities of all the synthesized compounds were assessed on two different human cancer cell lines (HepG2 and Hela), and the results showed that most of the new compounds showed good to potent cytotoxic activities.     

Synthesis of biologically active porcine secretin and [ITyr10] porcine secretin.

Porcine secretin, [Tyr10] secretin, and [Tyr13] secretin were synthesized by solid phase methodology and purified by stepwise gradient elution from a short reversed-phase column with ethanol and acetic acid as organic modifiers. [Tyr10] secretin and [Tyr13] secretin were iodinated by the chloramine-T method and nonmono-, and di-iodinated products separated and isolated by reversed-phase HPLC. Batch incubation analysis is isolated mouse pancreatic islets revealed that secretin and the [Tyr10] analogue were indistinguishable in their effect on the glucose-induced insulin release and cAMP accumulation. [Tyr13] secretin in contrast was significantly less potent in its effect on the glucose-induced insulin release.     

Synthesis and evaluation of antimigratory and antiproliferative activities of lipid-linked [13]-macro-dilactones

The biological activities of a family of novel, lipid-linked 13-membered-ring macro-dilactones are reported. These [13]-macro-dilactones were synthesized by diacylation of functionalized diols, followed by ring-closing metathesis under conditions we had previously reported. Antimigratory, cytostatic and cytotoxic activities of the compounds against cancer cells were evaluated. Compound 13 was the most potent in the series, while compound 10 had the broadest concentration range of subtoxic antiproliferative activity. These compounds share common structural components, namely the [13]-macro-dilactone templated by an octyl α-glucoside 4,6-diol.     

Synthesis and in vitro evaluation of 7-dialkylaminomethylbenzo[g]quinoxaline-5,10-diones

A series of benzo[g]quinoxaline-5,10-dione derivatives carrying a 7-dialkylaminomethyl substituent was synthesized and their in vitro cytotoxic activities were evaluated against four human cancer cell lines (HCT-15, SK-OV-3, MD-MB-468 and T-47D). The most active compound 9d showed cytotoxic activity comparable to that of doxorubicin against HCT-15 cancer cell line.     

Synthesis and biological activity of [Leu5]enkephalin derivatives containing D-glucose

The synthesis of some [Leu5]enkephalin derivatives is described in which D-glucose has been linked to the opioid pentapeptide through the ester bond involving the carboxyl function at the C-terminal with C-1 or C-6 of the D-glucopyranose moiety. Enkephalin derivatives were assayed for opioid activity and found to be full agonists in bioassays based on inhibition of electrically evoked contractions of the guinea pig ileum (GPI) and of the mouse vas deferens (MVD). The obtained results suggest that the opioid activity of the tested glucoconjugates depend upon the ester bond position in the molecule. Whereas 1-O conjugate 5 was somewhat more potent than [Leu5]enkephalin in the GPI assay, the 6-O conjugates, with the exception of 1-O-benzyl derivative 11, were considerably less potent. All enkephalin derivatives were delta-receptor selective; in particular, the acetylated analog 8 was three times more delta-receptor selective than [Leu5]enkephalin.     

Synthesis and in vitro evaluation of [18F]fluoroethyl triazole labelled [Tyr3]octreotate analogues using click chemistry

A novel class of alkyne linked [Tyr³]octreotate analogues have been labelled by a copper catalysed azide-alkyne cycloaddition reaction (CuAAC) to form a 1,4-substituted triazole using the reagent [¹⁸F]2-fluoroethyl azide. An unexpected variability in reactivity during the CuAAC reaction was observed for each alkyne analogue which has been investigated. Two lead alkyne linked [Tyr³]octreotate analogues, G-TOCA (3a) and βAG-TOCA (5a) have been identified to be highly reactive in the click reaction showing complete conversion to the [¹⁸F]2-fluoroethyl triazole linked [Tyr³]octreotate analogues FET-G-TOCA (3b) and FET-βAG-TOCA (5b) under mild conditions and with short synthesis times (5 min at 20 °C). As well as ease of synthesis, in vitro binding to the pancreatic tumour AR42J cells showed that both FET-G-TOCA and FET-βAG-TOCA have high affinity for the somatostatin receptor with IC₅₀ of 4.0 ± 1.4, and 1.6 ± 0.2 nM, respectively.     

Solution conformation of enkephalin. A nuclear magnetic resonance study of 13C-enriched carbonyl carbons in [Leu5]-enkephalin.

By using 13C enrichment in [Leu5]-enkephalin, it has been possible to improve the assignment of carbonyl resonances in the nuclear resonance spectrum and to remove some of the ambiguities in the derived phi and chi dihedral angles, thereby providing information about the conformation of this molecule in solution. The combined use of 13C and 1H nuclear magnetic resonance experiments leads to the conclusion that [Leu5]0enkephalin contains a type I beta bend at residues Gly3-Phe4 in dimethyl-d6 sulfoxide (Me2SO0d6) solution. Furthermore, the side chains of Tyr1, Phe4, and Leu5 exist predominantly in one conformation (tg-) in this solvent. A comparison is made between the conformation found in Me2SO-d6 and those determined by X-ray diffraction and conformational energy calculations.     

Synthesis and biological activity of a lysine-containing cyclic analog of [Leu5]enkephalin

The cyclic analogue of [Leu5]enkephalin--cyclo (Lys-Tyr-Gly-Gly-Phe-Leu) and two corresponding linear hexapeptides with lysine residue attached to the N- or C-terminus of the molecule have been synthesized by classical methods of peptide chemistry. The addition of lysine residue to the N-terminus of cyclization of the molecule reduce the interaction of these analogues with both central and peripheral opiate receptors. The addition of lysine residue to the C-terminus of the molecule through the epsilon-amino group does not affect the interaction of the analogue with mu-receptors but reduces approximately tenfold its affinity for delta-receptors. All three analogues have analgesic potency similar to that of [Leu5]enkephalin as assayed after intracisternal administration to mice.     

Further characterization of the in vitro hydrolysis of [Leu]- and [Met]enkephalin in rat plasma: HPLC-ECD measurement of substrate and metabolite concentrations.

Hydrolysis of [Leu]- and [Met]enkephalin was determined in whole rat plasma in vitro by using HPLC-ECD to measure Tyr, Tyr-Gly and Tyr-Gly-Gly formation. Although [Leu]- and [Met]enkephalin did not differ in Tyr or Tyr-Gly accumulation, the amount of Tyr-Gly-Gly resulting from [Met]enkephalin hydrolysis was greater than that resulting from [Leu]enkephalin hydrolysis, and [Met]enkephalin's half-life in plasma was slightly shorter than that of [Leu]enkephalin. By comparing metabolite formation in the presence and absence of peptidase inhibitors with high selectivity for their respective enzymes, these studies demonstrated that aminopeptidase M and angiotensin converting enzyme are the major peptidases that hydrolyze enkephalins in rat plasma.     

Synthesis and evaluation of [11C]cyanoimipramine

[¹¹C]Cyanoimipramine has been prepared by methylation of the desmethyl cyanoimipramine with [¹¹C]methyl iodide. The chemically and radiochemically pure labelled product was obtained with a high specific activity (> 300 mCi/μmol). When ¹¹C (or ³H)-cyanoimipramine was intravenously administered in mice, high accumulations were shown in brain and lung. Thirty minutes after injection of the tracer, differences were found in the radioactivity between the cerebral cortex and the cerebellum. The regional distribution of radioactivity in the rat brain 30 min after i.v. injection of [¹¹C]cyanoimipramine was also examined, and the radioactivity was high in receptor rich areas (striatum, cerebral cortex etc.) but low in receptor poor area (cerebellum). The in vivo stability of [³H]cyanoimipramine was quite stable in the mouse brain for at least 30 min. Thirty minutes after injection, the radioactivity in the cerebral cortex of the carrier-added state was reduced as compared with the carrier-free state. Taken together, the in vivo specific binding of [³H]cyanoimipramine in the cerebral cortex was estimated at about 40–50% of the total radioactivity. Furthermore, the distribution of [³H]cyanoimipramine in the mice forced to swim was examined. Significant changes in the distribution of [³H]cyanoimipramine were observed in the cerebral cortex.     

Synthesis and pharmacological evaluation of 2,5-cycloamino-5H-[1]benzopyrano[4,3-d]pyrimidines endowed with in vitro antiplatelet activity

A series of new 2,5-cycloamino-5H-[1]benzopyrano[4,3-d]pyrimidines 3a-i have been synthesized and tested in vivo for the anti-inflammatory/analgesic/antipyretic effects and in vitro to evaluate the antiplatelet activity on guinea-pig platelet-rich plasma aggregated by collagen, adenosine-5'-diphosphate (ADP) and arachidonic acid (AA). Title compounds were ineffective in vivo; however, the pyrrolidino derivatives 3a and 3c exhibited an antiplatelet activity against all the aggregants differing from that of acetylsalicylic acid (ASA) while the 5-morpholino derivatives 3g-i showed the most potent ASA-like antiplatelet activity.     

Synthesis and in vitro antitumor evaluation of some new thiophenes and thieno[2,3-d]pyrimidine derivatives

New thiophene (2–13) and thienopyrimidine (15–27) derivatives have been synthesized. Twenty three compounds were screened against five cell lines namely; hepatocellular carcinoma (liver) HepG-2, epidermoid carcinoma (larynx) Hep-2, mammary gland (breast) MCF-7, human prostate cancer PC-3 and epithelioid cervix carcinoma HeLa. The results revealed that compounds 15,16,17,24 and 25 showed the highest antitumor activity against all tested cell lines compared to Doxorubicin. In order to explain the expected mode of action of the observed anticancer activity, compounds 15,16,17,24 and 25 were selected to screen their DNA binding affinity and enzyme inhibitory activity against DNA polymerase, thymidylate synthase and tyrosine kinase. The results revealed that the tested compounds showed good DNA binding affinity as well as good inhibitory activity against the three enzymes which might explain the observed anticancer activity of the target compounds.     

Comparative structure-function studies with analogs of dynorphin-(1-13) and [Leu5]enkephalin

Analogs of dynorphin-(1-13) with modifications in the enkephalin segment were compared with correspondingly modified analogs of [Leu5]enkephalin in the guinea pig ileum (GPI) and mouse vas deferens (MVD) assay as well as in mu- and delta-receptor selective binding assays. The obtained results indicate that a) the enkephalin binding domain of the dynorphin (kappa) receptor has structural requirements which are distinct from those of the enkephalin binding site at the mu-receptor and b) the introduction of an identical conformational constraint in [Leu5]enkephalin and in the enkephalin segment of dynorphin-(1-13) produces a superpotent agonist in both cases. Fluorescence energy transfer measurements with the active [4-tryptophan]analogs of dynorphin-(1-13) and [Leu5]enkephalin and with dynorphin-(1-17) demonstrated a more extended conformation of the N-terminal tetrapeptide segment in [Trp4]dynorphin-(1-13) than in [Trp4, Leu5]enkephalin as well as the absence of an interaction between the N- and C-terminal segments of dynorphin-(1-17).     

Synthesis and in vitro cytotoxic evaluation of new 1H-benzo[d]imidazole derivatives of dehydroabietic acid

A series of new 1H-benzo[d]imidazole derivatives of dehydroabietic acid were designed and synthesized as potent antitumor agents. Structures of the target molecules were characterized using MS, IR, ¹H NMR, ¹³C NMR and elemental analyses. In the in vitro cytotoxic assay, most compounds showed significant cytotoxic activities against two hepatocarcinoma cells (SMMC-7721 and HepG2) and reduced cytotoxicity against noncancerous human hepatocyte (LO2). Among them, compound 7b exhibited the best cytotoxicity against SMMC-7721 cells (IC₅₀: 0.36 ± 0.13 μM), while 7e was most potent to HepG2 cells (IC₅₀: 0.12 ± 0.03 μM). The cell cycle analysis indicated that compound 7b caused cell cycle arrest of SMMC-7721 cells at G2/M phase. Further, compound 7b also induced the apoptosis of SMMC-7721 cells in Annexin V-APC/7-AAD binding assay.     

Synthesis and in vitro evaluation of 4-substituted furano[3,2-c] tetrahydroquinolines as potential anti-cancer agents

A convenient and mild method for the synthesis of substituted furano [3,2-c]tetrahydroquinoline derivatives was developed, using the multi-component Povarov reaction. Of the synthesized tetrahydroquinoline derivatives, compound 10a displayed the greatest cellular proliferation inhibitory activities with IC₅₀ values of 2.5–16.7?μmol/l. In addition, 10a induced murine C6 glioma cell apoptosis in a dose-dependent manner by up-regulating the expression of Bax, caspase-3, and caspase-9, and by down-regulating Bcl-2. Our findings suggest that these novel compounds have potential as therapeutic agents via inducing mitochondrial apoptosis.     

Brain-targeted chemical delivery of [Leu2, Pip3]-TRH: synthesis and biological evaluation

A chemical targeting system for [Leu2, Pip3]-TRH (Gln,Leu,Pip) was synthesized in order to allow its specific delivery to the central nervous system (CNS). Sequential metabolism of the obtained 'packaged' chemical delivery system, (CDS), DHT-Pro-Pro-Gln-Leu-Pip-OCh, should yield a 'locked-in' precursor following the oxidative conversion of the dihydrotrigonellyl (DHT) to the trigonellyl (T+) moiety, followed by removal of the cholesteryl function and cleavage of the T+-Pro-Pro by prolyl endopeptidase. The antagonism of barbiturate-induced sleeping time was used to assess the activity of the CDS. The sleeping time after administration of vehicle and [Leu2]-TRH was 100.5 +/- 6.3 min, and 78.2 +/- 4.7 min, respectively. The [Leu2, Pip3]-TRH-CDS showed a significant decrease in sleeping time (58.2 +/- 3.4 min) compared to the vehicle or [Leu2]-TRH. These results indicate successful brain delivery of the precursor construct, and an effective release of the active GlnLeuPip in the brain.     

Synthesis and biological evaluation of pNPY fragments

Peptide fragments of pNPY corresponding to the C-terminal segments (13-36) and (25-36), the N-terminal segments (1-12) and (1-24), the segments (6-14) and (7-20), which contain a putative beta-turn, and the internal segments (13-24) and (20-30) were synthesized using solid phase methodology. These fragments were assayed for NPY receptor binding activity in the rat hypothalamus membrane preparation, enhancement of food intake in the rat following ivt administration and inhibition of electrically stimulated muscle contraction in the rat vas deferens. Only the C-terminal fragment (13-36) retained some of the activities of pNPY, appearing to act as a weak agonist, having an additive effect with pNPY on the inhibition of muscle contraction and prolonging the duration of action of pNPY in the feeding assay. It also had considerable alpha-helical character, as did pNPY. None of the other peptide fragments had any agonist or antagonist activity. These results suggest that the expression of full biological NPY activity requires both the C- and the N-terminal segments as well as a putative amphiphilic alpha-helical segment (14-31).