N- and C-terminal modifications of nociceptin/orphanin FQ generate highly potent NOP receptor ligands

Previous structure-activity studies on nociceptin/orphanin FQ (N/OFQ) identified [Phe(1)Psi(CH(2)NH)Gly(2)]N/OFQ(1-13)-NH(2) and [Nphe(1)]N/OFQ(1-13)-NH(2) as a N/OFQ peptide receptor (NOP) partial agonist and pure antagonist, respectively. The addition of fluorine to the Phe(4) or the insertion of a further pair of basic amino acids Arg(14)-Lys(15) generate potent agonists. On the basis of these findings, we combined in the N/OFQ-NH(2) template the chemical modifications Arg(14)-Lys(15) and (pF)Phe(4) that increase the agonist potency with those conferring partial agonist (Phe(1)Psi(CH(2)NH)Gly(2)) or pure antagonist (Nphe(1)) properties. Twelve peptides were synthesized and pharmacologically evaluated in Chinese hamster ovary cells expressing the human recombinant NOP and in electrically stimulated mouse vas deferens and guinea pig ileum assays. All peptides behaved as NOP ligands; the chemical modifications Arg(14)-Lys(15) and (pF)Phe(4) increased ligand affinity/potency. Peptides with the normal Phe(1)-Gly(2) peptide bond behaved as full agonists, and those with the Phe(1)Psi(CH(2)NH)Gly(2) modification behaved as partial agonists, while those with the Nphe(1) modification behaved as partial agonists or pure antagonists depending on the presence or absence of the (pF)Phe(4) modification, respectively. The full agonist [(pF)Phe(4),Arg(14),Lys(15)]N/OFQ-NH(2), the partial agonist [Phe(1)Psi(CH(2)NH)Gly(2),(pF)Phe(4),Arg(14),Lys(15)]N/OFQ-NH(2), and the pure antagonist [Nphe(1),Arg(14),Lys(15)]N/OFQ-NH(2) represent the most potent peptide ligands for NOP.     

Design of monocyclic (1-3) and dicyclic (1-3/4-10) gonadotropin releasing hormone (GnRH) antagonists

Careful analysis of the NMR structures of cyclo(4-10)[Ac-Delta(3)Pro(1),DFpa(2),DTrp(3),Asp(4),DNal (6), Dpr(10)]GnRH, dicyclo(4-10/5-8)[Ac-DNal(1),DCpa(2),DTrp(3), Asp(4), Glu(5),DArg(6),Lys(8),Dpr(10)]GnRH, and dicyclo(4-10/5, 5'-8)[Ac-DNal(1),DCpa(2),DPal(3),Asp(4), Glu(5)(Gly),DArg(6),Dbu(8), Dpr(10)]GnRH showed that, in the N-terminal tripeptide, a type II beta-turn around residues 1 and 2 was probable along with a gamma-turn around DTrp(3)/DPal(3). This suggested the possibility of constraining the N-terminus by the introduction of a cyclo(1-3) scaffold. Optimization of ring size and composition led to the discovery of cyclo(1-3)[Ac-DAsp(1),DCpa(2),DLys(3),DNal(6), DAla(10)]GnRH (5, K(i) = 0.82 nM), cyclo(1,1'-3)[Ac-DAsp(1)(Gly), DCpa(2),DOrn(3),DNal(6),DAla(10)]GnRH (13, K(i) = 0.34 nM), cyclo(1, 1'-3)[Ac-DAsp(1)(Gly),DCpa(2),DLys(3),DNal(6),DA la(10)]GnRH (20, K(i) = 0.14 nM), and cyclo(1,1'-3)[Ac-DAsp(1)(betaAla), DCpa(2), DOrn(3),DNal(6),DAla(10)]GnRH (21, K(i) = 0.17 nM), which inhibited ovulation significantly at doses equal to or lower than 25 microgram/rat. These results were particularly unexpected in view of the critical role(s) originally ascribed to the side chains of residues 1 and 3.(1) Other closely related analogues, such as those where the [DAsp(1)(betaAla), DOrn(3)] cycle of 21 was changed to [DOrn(1)(betaAla), DAsp(3)] of cyclo(1,1'-3)[Ac-DOrn(1)(betaAla), DCpa(2),DAsp(3),DNal(6),DAla(10)]GnRH (22, K(i) = 2.2 nM) or where the size of the cycle was conserved and [DAsp(1)(betaAla), DOrn(3)] was replaced by [DGlu(1)(Gly), DOrn(3)] as in cyclo(1, 1'-3)[Ac-DGlu(1)(Gly),DCpa(2),DOrn(3),DNal(6),DA la(10)]GnRH (23, K(i) = 4.2 nM), were approximately 100 and 25 times less potent in vivo, respectively. Analogues with ring sizes of 18 ?cyclo(1, 1'-3)[Ac-DGlu(1)(Gly),DCpa(2),DLys(3),DNal(6),DA la(10)]GnRH (24)? and 19 ?cyclo(1,1'-3)[Ac-DGlu(1)(betaAla),DCpa(2),DLys( 3),DNal(6), DAla(10)]GnRH (25)? atoms were also less potent than 21 with slightly higher K(i) values (1.5 and 2.2 nM, respectively). These results suggested that the N-terminal tripeptide was likely to assume a folded conformation favoring the close proximity of the side chains of residues 1 and 3. The dicyclic analogue dicyclo(1-3/4-10)[Ac-DAsp(1),DCpa(2),DLys(3),Asp (4),DNal(6), Dpr(10)]GnRH (26) was fully active at 500 microgram, with a K(i) value of 1 nM. The in vivo potency of 26 was at least 10-fold less than that of monocyclic cyclo(1-3)[Ac-DAsp(1),DCpa(2),DLys(3),DNal(6), DAla(10)]GnRH (5); this suggested the existence of unfavorable interactions between the now optimized and constrained (1-3) and (4-10) cyclic moieties that must interact as originally hypothesized. Tricyclo(1-3/4-10/5-8)[Ac-DGlu(1),DCpa(2), DLys(3),Asp(4),Glu(5), DNal(6),Lys(8),Dpr(10)] GnRH (27) was inactive at 500 microgram/rat with a corresponding low affinity (K(i) = 4.6 nM) when compared to those of the most potent analogues (K(i) < 0.5 nM).     

Potent somatostatin undecapeptide agonists selective for somatostatin receptor 1 (sst1)

A family of analogues of des-AA(1,2,5)-[DTrp(8)/D2Nal(8)]-SRIF that contain a 4-(N-isopropyl)-aminomethylphenylalanine (IAmp) at position 9 was identified that has high affinity and selectivity for human somatostatin receptor subtype 1 (sst1). The binding affinities of des-AA(1,2,5)-[DTrp(8),IAmp(9)]-SRIF (c[H-Cys-Lys-Phe-Phe-DTrp-IAmp-Thr-Phe-Thr-Ser-Cys-OH], CH-275) (7), des-AA(1,5)-[Tyr(2),DTrp(8),IAmp(9)]-SRIF (CH-288) (16), des-AA(1,2,5)-[Tyr(7),DTrp(8),IAmp(9)]-SRIF (23), and des-AA(1,2,5)-[DTrp(8),IAmp(9),Tyr(11)]-SRIF (25) are about (1)/(7), (1)/(4), (1)/(125), and (1)/(4) that of SRIF-28 (1) to sst1, respectively, about (1)/(65), (1)/(130), <(1)/(1000), and <(1)/(150) that of 1 to sst3, respectively, and about or less than (1)/(1000) that of 1 to the other three human SRIF receptor subtypes. A substitution of DTrp(8) by D2Nal(8) in 7 to yield des-AA(1,2,5)-[D2Nal(8),IAmp(9)]-SRIF (13) and in 16 to yield des-AA(1,5)-[Tyr(2),D2Nal(8),IAmp(9)]-SRIF (17) was intended to increase chemical stability, selectivity, and affinity and resulted in two analogues that were less potent or equipotent with similar selectivity, respectively. Carbamoylation of the N-terminus as in des-AA(1,2,5)-[DTrp(8),IAmp(9),Tyr(11)]-Cbm-SRIF (27) increased affinity slightly as well as improved selectivity. Monoiodination of 25 to yield 26 and of 27 to yield 28 resulted in an additional 4-fold increase in affinity at sst1. Desamination of the N-terminus of 17 to yield 18, on the other hand, resulted in significant loss of affinity. Attempts at reducing the size of the ring with maintenance of selectivity failed in that des-AA(1,4,5,13)-[Tyr(2),DTrp(8),IAmp(9)]-SRIF (33) and des-AA(1,4,5,6,12,13)-[Tyr(2),DTrp(8),IAmp(9)]-SRIF (34) progressively lost affinity for all receptors. Both des-AA(1,2,5)-[DTrp(8),IAmp(9),Tyr(11)]-Cbm-SRIF (27) and des-AA(1,2,5)-[DCys(3),DTrp(8),IAmp(9),Tyr(11)]-Cbm-SRIF (29) show agonistic activity in a cAMP assay; therefore, the structural basis for the agonist property of this family of analogues is not contingent upon the chirality of the Cys residue at position 3 as shown to be the case in 18-membered ring SRIF octapeptides. None of the high affinity structures described here showed receptor antagonism. We have prepared the radiolabeled des-AA(1,2,5)-[DTrp(8),IAmp(9),(125)ITyr(11)]-SRIF ((125)I-25) and des-AA(1,2,5)-[DTrp(8),IAmp(9), (125)ITyr(11)]-Cbm-SRIF ((125)I-27), used them as in vitro tracers, and found them to be superior to des-AA(1,5)-[(125)ITyr(2),DTrp(8),IAmp(9)]-SRIF ((125)I-16) for the detection of sst1 tumors in receptor autoradiography studies.     

Structure-activity studies of the Phe(4) residue of nociceptin(1-13)-NH(2): identification of highly potent agonists of the nociceptin/orphanin FQ receptor.

A total of 32 compounds was prepared to investigate the functional role of Phe(4) in NC(1-13)-NH(2), the minimal sequence maintaining the same activity as the natural peptide nociceptin. These compounds could be divided into three series in which Phe(4) was replaced with residues that would (i) alter aromaticity or side chain length, (ii) introduce steric constraint, and (iii) modify the phenyl ring. Compounds were tested for biological activity as (a) inhibitors of the electrically stimulated contraction of the mouse vas deferens; (b) competitors of the binding of [(3)H]-NC-NH(2) to mouse brain membranes; and (c) inhibitors of forskolin-stimulated cAMP accumulation in CHO cells expressing the recombinant human OP(4) receptor. Results indicate that all compounds of the first and second series were inactive or very weak with the exception of [N(CH(3))Phe(4)]NC(1-13)-NH(2), which was only 3-fold less potent than NC(1-13)-NH(2). Compounds of the third series showed higher, equal, or lower potencies than NC(1-13)-NH(2). In particular, [(pF)Phe(4)]NC(1-13)-NH(2) (pF) and [(pNO(2))Phe(4)]NC(1-13)-NH(2) (pNO(2)) were more active than NC(1-13)-NH(2) by a factor of 5. In the mVD, these compounds showed the following order of potency: (pF) = (pNO(2)) > or = (pCN) > (pCl) > (pBr) > (pI) = (pCF(3)) = (pOCH(3)) > (pCH(3)) > (pNH(2)) = (pOH). (oF) and especially (mF) maintained high potencies but were less active than (pF). Similar orders of potency were observed in binding competition and cAMP accumulation studies. There was a strong (r(2) > or = 0.66) correlation between data observed in these assays. Biological activity data of compounds of the third series were plotted against some Hansch parameters that are currently used to quantify physicochemical features of the substituents. In the three biological assays agonist potency/affinity positively correlates with the electron withdrawal properties of the groups in the p-position of Phe(4) and inversely with their size.     

Pharmacological characterisation of [(pX)Phe4]nociceptin(1-13)amide analogues. 1. In vitro studies

Phe(4) in the nociceptin (NC) sequence has been identified as the most critical residue for receptor interaction. In the present study, we investigated the pharmacological activity of a series of NC(1-13)NH(2) analogues, in which the hydrogen atom in the para position of Phe(4) was substituted with F, NO(2), CN, Cl, Br, I, CH(3), OH or NH(2).In receptor binding studies, performed using CHO cells expressing the recombinant human NC receptor (CHO(hOP4)) and in rat cerebral cortex membranes, [(pF)Phe(4)]NC(1-13)NH(2), [(pNO(2))Phe(4)]NC(1-13)NH(2), and [(pCN)Phe(4)]NC(1-13)NH(2) displayed higher affinity than NC(1-13)NH(2). The affinity of [(pCl)Phe(4)]NC(1-13)NH(2) was essentially identical to that of NC(1-13)NH(2), while the remaining compounds displayed reduced affinity. In a series of functional assays (stimulation of GTPgammaS binding in CHO(hOP4)cells and rat cerebral cortex membranes and inhibition of cAMP accumulation in CHO(hOP4) cells), the para substituted analogues behaved as full agonists (with the exception of [(pOH)Phe(4)]NC(1-13)NH(2) which acted as a partial agonist in the GTPgammaS binding assays) with the following rank order potency:[(pF)Phe(4)]NC(1-13)NH(2) and [(pNO(2))Phe(4)]NC(1-13)NH(2) were either inactive or displayed micromolar potencies in cAMP accumulation experiments performed on cells expressing classical opioid receptors. All compounds were full agonists in isolated tissues from various species (guinea pig ileum, mouse colon and mouse/rat vas deferens) with the exception of [(pOH)Phe(4)]NC(1-13)NH(2) which displayed partial agonist/weak antagonist activities. The rank order of potency was similar to that found in the other assays. The effects of all analogues were not modified by naloxone. The selective OP(4) receptor antagonist [Nphe(1)]NC(1-13)NH(2), tested in all preparations against one or both of the highly potent derivatives [(pF)Phe(4)]NC(1-13)NH(2) and [(pNO(2))Phe(4)]NC(1-13)NH(2), showed pA(2) values similar to those found against NC, the pA(2) in the GTPgammaS binding/rat cerebral cortex assay being much higher (ca. 7.5) than in the other functional assays (ca. 6).This study further supports the notion that Phe(4) of NC is the critical residue for receptor occupation and activation. Moreover, as part of this study, we have identified two novel, highly potent and selective agonists for the OP(4) receptor, [(pF)Phe(4)]NC(1-13)NH(2) and [(pNO(2))Phe(4)]NC(1-13)NH(2).     

S-allylcysteine scavenges singlet oxygen and hypochlorous acid and protects LLC-PK(1) cells of potassium dichromate-induced toxicity.

It has been found that S-allylcysteine (SAC), a garlic-derived compound, has in vivo and in vitro antioxidant properties. In addition, it is known that SAC is able to scavenge different reactive oxygen or nitrogen species including superoxide anion (O(2)(-)), hydrogen peroxide (H(2)O(2)), hydroxyl radical (OH()), and peroxynitrite anion (ONOO(-)) although the IC(5O) values for each reactive species has not been calculated and the potential ability of SAC to scavenge singlet oxygen ((1)O(2)) and hypochlorous acid (HOCl) has not been explored. The purposes of this work was (a) to explore the potential ability of SAC to scavenge (1)O(2) and HOCl, (b) to further characterize the O(2)(-), H(2)O(2), OH(), and ONOO(-) scavenging ability of SAC by measuring the IC(50) values using in vitro assays, and (c) to explore the potential ability of SAC to ameliorate the potassium dichromate (K(2)Cr(2)O(7))-induced cytotoxicity in LLC-PK1 cells in which oxidative stress is involved. The scavenging activity was compared against the following reference compounds: N-acetylcysteine for O(2)(-), sodium pyruvate for H(2)O(2), dimethylthiourea for OH(), lipoic acid and glutathione for (1)O(2), lipoic acid for HOCl, and penicillamine for ONOO(-). It was found that SAC was able to scavenge concentration-dependently all the species assayed with the following IC(5O) (mean+/-SEM, mM): O(2)(-) (14.49+/-1.67), H(2)O(2) (68+/-1.92), OH() (0.68+/-0.06), (1)O(2) (1.93+/-0.27), HOCl (2.86+/-0.15), and ONOO(-) (0.80+/-0.05). When the ability of SAC to scavenge these species was compared to those of the reference compounds it was found that the efficacy of SAC (a) to scavenge O(2)(-), H(2)O(2), OH(), and ONOO(-) was lower, (b) to scavenge HOCl was similar, and (c) to scavenge (1)O(2) was higher. In addition, it was found that SAC was able to prevent K(2)Cr(2)O(7)-induced toxicity in LLC-PK1 cells in culture. It was showed for the first time that SAC is able to scavenge (1)O(2) and HOCl and to ameliorate the K(2)Cr(2)O(7)-induced toxicity.     

Alkaline hydrolysis of oxaliplatin--isolation and identification of the oxalato monodentate intermediate

The alkaline degradation of the chemotherapeutic agent oxaliplatin has been studied using liquid chromatography. The oxalato ligand is lost in two consecutive steps. First, the oxalato ring is opened, forming an oxalato monodentate intermediate, as identified by electrospray ionization mass spectrometry. Subsequently, the oxalato ligand is lost and the dihydrated oxaliplatin complex is formed. The observed rate constants for the first step (k(1)) and the second step (k(2)) follow the equation k(1) or k(2) = k(0) + k(OH(-) )[OH(-)], where k(0) is the rate constant for the degradation catalyzed by water and k(OH(-) ) represents the second-order rate constant for the degradation catalyzed by the hydroxide ion. At 37 degrees C the rate constants for the first step are k(OH(-) ) = 5.5 x 10(-2) min(-1) M(-1) [95% confidence interval (CI), 2.7 x 10(-2) to 8.4 x 10(-2) min(-1) M(-1)] and k(0) = 4.3 x 10(-2) min(-1) (95% CI, 4.0 x 10(-2) to 4.7 x 10(-2) min(-1)). For the second step the rate constants are k(OH(-) ) = 1.1 x 10(-3) min(-1) M(-1) (95% CI, -1.1 x 10(-3) to 3.3 x 10(-3)) min(-1) M(-1) and k(0) = 7.5 x 10(-3) min(-1) (95% CI, 7.2 x 10(-3) to 7.8 x 10(-3) min(-1)). Thus, the ring-opening step is nearly six times faster than the step involving the loss of the oxalato ligand.     

Hydrophilic matrices: application of Placket-Burman screening design to model the effect of POLYOX-carbopol blends on drug release

The aim of the present study was to screen the effect of seven factors--POLYOX molecular weight (X(1)) and amount (X(2)); carbopol (X(3)), lactose (X(4)), sodium chloride (X(5)), citric acid (X(6)); compression pressure (X(7))--on (1) the release of theophylline from hydrophilic matrices, demonstrated by changes in dissolution rate, and (2) their impact on the release exponent [n] indicative of the drug transport mechanism through the diffusion matrix. This objective was accomplished utilizing the Placket-Burman screening design. Theophylline tablets were prepared according to a 7-factor-12-run statistical model and subjected to a 24-h dissolution study in phosphate buffer at pH 7.2. The primary response variable, Y(4), was the cumulative percent of theophylline dissolved in 12h. The regression equation for the response was Y(4)=66.2167 - 17.5833X(1) - 3.3833X(2) - 9.366X(3) - 1.1166X(4) - 0.6166X(5) + 2.6X(6) - 2.783X(7). This polynomial model was validated by the ANOVA and residual analysis. The results showed that only two factors (X(2) and X(3)) had significant effect (p-value<0.10) on theophylline release from the hydrophilic polymer matrix. Factors (X(2) and X(7)) had significant effect (p-value<0.10) on [n], the exponent.     

海洋放线菌Kocuria sp.次级代谢产物的研究

目的 研究海洋放线菌Kocuria sp.的次级代谢产物。方法 菌株摇瓶发酵,采用现代色谱学方法(硅胶柱色谱、Sephadex LH-20凝胶柱色谱、半制备HPLC),对发酵产物进行分离,利用现代波谱学技术对化合物进行结构鉴定。结果 从海洋放线菌Kocuria sp.发酵液的乙酸乙酯萃取部分分离得到16个单体化合物：环(L-苯丙氨酸-L-脯氨酸)2 (1)、环(L-色氨酸-L-脯氨酸) (2)、环(L-色氨酸-D-脯氨酸) (3)、环(L-苯丙氨酸-D-脯氨酸) (4)、环(L-羟脯氨酸-L-苯丙氨酸) (5)、环(D-羟脯氨酸-L-苯丙氨酸) (6)、环(L-羟脯氨酸-L-酪氨酸) (7)、环(L-异亮氨酸-D-脯氨酸) (8)、环(L-亮氨酸-D-脯氨酸) (9)、环(L-亮氨酸-L-脯氨酸) (10)、环(L-苯丙氨酸-L-酪氨酸) (11)、环(L-亮氨酸-D-酪氨酸) (12)、环(L-亮氨酸-L-苯丙氨酸) (13)、环(D-缬氨酸-L-苯丙氨酸) (14)、环(D-亮氨酸-甘氨酸) (15)、环(D-异亮氨酸-甘氨酸) (16)。结论 海洋放线菌Kocuria sp.可产生结构丰富多样的环肽类化合物,所有化合物均首次从Kocuria属放线菌中分离得到。     

Chloride secretion in kidney distal epithelial cells (A6) evoked by cadmium

The effect of Cd(2+) on chloride secretion was examined in A6 renal epithelia cells by chloride-sensitive fluorescence (SPQ probe) and by the short-circuit-current (I(sc)) technique. Depleting the cells of Cl(-) suggests that the Cd(2+)-activated I(sc) (DeltaI(sc(Cd))) is dependent on the presence of Cl(-) ions. Among the Cl(-)-channel inhibitors the fenemates, flufenamic acid (FFA) and niflumic acid (NFA), and 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) significantly lowered DeltaI(sc(Cd)) compared with control level. In SPQ-loaded A6 cells, Cd(2+) evoked an increase in Cl(-) secretion ([DeltaCl(-)](Cd)), which significantly exceeded the basal Cl(-) transport and was blockable by FFA and NFA. The closely related metals, Zn(2+) or Ni(2+), were also able to activate Cl(-) secretion. Preexposure of Zn(2+) or Ni(2+) completely prevented [DeltaCl(-)](Cd), suggesting that Zn(2+) and Ni(2+) probably use similar mechanisms. Like Cd(2+), thapsigargin (TG), an inhibitor of intracellular Ca(2+)-ATPase and the Ca(2+)-ionophore A23187, induced an increase in I(sc). Moreover, TG and Cd(2+) were able to neutralize the responses of the counterparts as also observed in I(sc) measurements, which indicates that Cd(2+) activates Cl(-) secretion in a Ca(2+)-dependent manner. Hence, this study supports the idea that basolateral Cd(2+) (possibly also Zn(2+) and Ni(2+)), probably through a Ca(2+)-sensing receptor, causes calcium mobilization that activates apical fenemate-sensitive chloride channels leading to chloride secretion in A6 cells.     

Nitric oxide and sodium nitroprusside-induced relaxation of the human umbilical artery

In the human umbilical artery (HUA) pre-contracted with the thromboxane mimetic U46619 or with 5-hydroxytryptamine (5-HT), (and pretreated with indomethacin (3 microM) to suppress the synthesis of prostanoids), authentic nitric oxide (NO) evoked concentration-dependent relaxation (pEC(50) 7.05 and 5.99, respectively). In contrast, sodium nitroprusside (SNP) induced relaxation only in U46619 pre-contracted HUA (pEC(50) 6.52). At high (>300 mmHg) vs low (<55 mmHg) oxygen tension the dose-response curves to NO- and SNP-induced relaxations were biphasic and shifted leftward. Preincubation of the arterial rings with the soluble guanylyl cyclase (sGC) inhibitor 1H[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one (ODQ; 10 microM) shifted the concentration-response curve to NO, reduced the maximal relaxation response to NO (E(max) 71%) and to SNP (E(max) 10%). Pre-exposure of HUA rings to high extracellular K(+) (50 mM) reduced E(max) relaxation responses to NO (36%) and SNP (1%). Pretreatment of the HUA with the K(+) channel inhibitors, tetraethylammonium (TEA, 1 mM), 4-aminopyridine (4-AP, 0.5 mM), charybdotoxin (0.1 microM) or iberiotoxin (0.1 microM) increased the pEC(30) for NO and SNP and changed the shape of the dose-response curves from biphasic to monophasic. Pre-incubation of HUA rings with TEA (1 mM), 4-AP (0.5 mM) and ODQ (10 microM) significantly reduced the NO-induced maximal relaxation (E(max) 26%) but not the pEC(50) (5.60). These data indicate that SNP-induced relaxation in the HUA is primarily mediated via sGC-cyclic GMP whereas NO-induced relaxation also involves the activation of K(V) and K(Ca) channels and a cyclic GMP/K(+) channel-independent mechanism(s).     

Characterization of the endothelin-1-induced regulation of L-type Ca2+ current in rabbit ventricular myocytes

The effects of endothelin-1 (ET-1) on the L-type Ca2+ current (I(Ca)) and the interaction of ET-1 with beta-adrenoceptor stimulation were investigated in rabbit ventricular myocytes by the whole-cell patch-clamp technique. ET-1 (10(-8) M) had a biphasic effect on I(Ca) (direct effect), causing a transient decrease that was followed by a long-lasting increase which is much smaller than the increase induced by isoprenaline (ISO). The effect of ET-1 on I(Ca) was abolished by a selective ET(A) receptor antagonist, FR139317 (10(-6) M). The increase in I(Ca) induced by ET-1 (10(-8) M) was enhanced by a selective ET(B) receptor antagonist, BQ-788 (10(-6) M), as the transient decrease but not the increase in I(Ca) induced by ET-1 (10(-8) M) was suppressed by BQ-788. In the presence of ISO (10(-6) M), ET-1 elicited a more pronounced inhibitory effect: at 10(-9)-10(-7) M ET-1 inhibited the ISO-induced increase in I(Ca) in a concentration-dependent manner (anti-adrenergic effect). The maximum inhibition induced by ET-1 at 10(-7) M was approximately 80% of the ISO-induced response, and the IC50 value for anti-adrenergic effect of ET-1 was 4.2x10(-9) M. The anti-adrenergic effect of ET-1 (10(-8) M) was antagonized by the ET(A) antagonist FR139317 (10(-9)-10(-6) M) in a concentration-dependent manner and was partially inhibited by the ET(B) antagonist BQ-788 (10(-6) M). The anti-adrenergic effect of ET-1 was markedly attenuated by pretreatment of ventricular myocytes with pertussis toxin. The increases in I(Ca) induced by forskolin (10(-6) M), 3-isobutyl-1-methylxanthine (10(-4) M), and 8-bromo-cyclic AMP (3x10(-4) M) were also suppressed by ET-1 (10(-8) M). In summary, ET-1 has a differential effect on I(Ca) in the absence and in the presence of ISO: ET- I has a feeble biphasic action on the baseline I(Ca) and, in addition, it elicits a pronounced anti-adrenergic effect on the ISO-induced increase in I(Ca). Pertussis toxin-sensitive G protein is responsible for the anti-adrenergic effect of ET-1 on I(Ca), but the anti-adrenergic effect of ET-1 may involve also the regulation at the level of signaling process beyond the cyclic AMP generation. Anti-adrenergic effect of ET-1 on I(Ca) is mainly due to activation of ET(A) receptors but ET(B) receptors are also involved partially in the anti-adrenergic effect of ET-1 on I(Ca) in rabbit ventricular myocytes.     

Novel thiocyanato complexes with potent cytotoxic and antimicrobial properties

The aim of the present study was to assess the cytotoxic and antimicrobial properties of seven new thiocyanato complexes: Ni(C(9)H(11)N(2)O)(SCN), Cu(C(9)H(11)N(2)O)(SCN), Pd(C(9)H(11)N(2)O)(SCN), Pt(C(9)H(11)N(2) O) (SCN), K[Ti(C(9)H(11)N(2)O)(SCN)(3)], Au(C(9)H(11)N(2)O)(SCN), and K[V(O)(C(9)H(11)N(2)O)(SCN)] (T(1)-T(7), respectively). All the complexes showed toxicity against brine shrimp nauplii (Artemia salina L.). The titanium-based complex, T(5), exhibited potent toxicity, with a lethal concentration 50% (the concentration of test compound that kills 50% of A. salina) value of 1.59 microg mL(-1). These new complexes also exhibited promising antibacterial and antifungal properties. A macrodilution technique was used to estimate the minimum inhibitory concentrations of the seven bioactive complexes. Minimum inhibitory concentrations were found to be 8-64 microg mL(-1) against the tested bacterial species.     

The mechanism of actions of 3-(5'-(hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) on Ca(2+)-activated K(+) currents in GH(3) lactotrophs

The effects of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), an activator of soluble guanylyl cyclase, on ionic currents have been assessed in rat pituitary GH(3) lactotrophs. In GH(3) cells bathed in normal Tyrode's solution, YC-1 (1 microM) reversibly suppressed the amplitude of the Ca(2+)-activated K(+) current (I(K(Ca))). YC-1 at a concentration above 10 microM produced a biphasic response in the amplitude of I(K(Ca)), i.e., an initial decrease followed by a sustained increase. When the pipette solutions were filled with high EGTA (10 mM), the YC-1-induced stimulatory effect on I(K(Ca)) was abolished. Over a similar concentration range, YC-1 also effectively inhibited the voltage-dependent K(+) current (I(K(V))) in GH(3) cells. The IC(50) value required for the inhibition of I(K(V)) by YC-1 was 1 microM. Unlike YC-1, 8-bromo cGMP did not inhibit I(K(Ca)). However, YC-1 (10 microM) did not affect the amplitude of L-type Ca(2+) current. In the cell-attached configuration, application of YC-1 (10 microM) to the bath did not change the single-channel conductance of the large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels; however, it did increase the opening probability of BK(Ca) channels. In contrast, in the outside-out configuration, YC-1 (10 microM) significantly suppressed the opening probability of BK(Ca) channels. The present study shows dual effects of YC-1 on I(K(Ca)) in GH(3) cells. The YC-1-mediated stimulation of I(K(Ca)) may result from elevated cytosolic Ca(2+), whereas the inhibition of I(K(Ca)) and I(K(V)) by YC-1 appears to be direct and independent of the activation of soluble guanylyl cyclase. Caution thus needs to be used in attributing the YC-1-mediated response to the activation of soluble guanylyl cyclase.     

Pharmacological characterisation of [(pX)Phe4]nociceptin(1-13)NH2 analogues. 2. In vivo studies

As part of a structure-activity study focused on the Phe(4) residue of nociceptin (NC) (1-13)NH(2), we identified two highly potent and selective agonists for the OP(4) receptor, [(pF)Phe(4)]NC(1-13)NH(2) and [(pNO(2))Phe(4)]NC(1-13)NH(2), whose in vitro pharmacological profiles have been described in the companion paper. In the present study, we investigated the actions of [(pF)Phe(4)]NC(1-13)NH(2) and compared it with those of NC(1-13)NH(2) in a battery of vivo assays.In the locomotor activity test in mice, 1 nmol NC(1-13)NH(2) given intracerebroventricularly (i.c.v.) caused a significant decrease (about 70% inhibition) in activity for the first 15 min following injection; [(pF)Phe(4)]NC(1-13)NH(2), at the same dose, exerted a similar inhibitory effect that continued until the end of the observation period (30 min). This effect was prevented by the selective OP(4) receptor antagonist [Nphe(1)]NC(1-13)NH(2) (10 nmol, i.c.v.). In the tail-withdrawal assay in mice, [(pF)Phe(4)]NC(1-13)NH(2) mimicked the effects of NC(1-13)NH(2) producing pronociceptive and antimorphine effects following i.c.v. administration. In both experimental paradigms, the actions of [(pF)Phe(4)]NC(1-13)NH(2) were longer lasting (>60 min) compared to those of NC(1-13)NH(2) (ca. 30 min). In unanaesthetised normotensive mice, bolus intravenous (i.v.) injection of 100 nmol/kg of [(pF)Phe(4)]NC(1-13)NH(2) decreased mean blood pressure and heart rate; these effects were longer lasting than those elicited by the same dose of NC(1-13)NH(2). I.c.v. administration of [(pF)Phe(4)]NC(1-13)NH(2) dose-dependently stimulated feeding in rats, and was about tenfold more potent than NC(1-13)NH(2).Collectively, the present data demonstrate that, in a variety of in vivo assays, NC(1-13)NH(2) and [(pF)Phe(4)]NC(1-13)NH(2) mimicked the actions of NC. [(pF)Phe(4)]NC(1-13)NH(2) was more potent and its in vivo effects were longer lasting than those of NC(1-13)NH(2) and NC.     

Non-competitive pharmacological antagonism at the rabbit B(1) receptor

The B(1) receptor for kinins, stimulated by kinin metabolites without the C-terminal Arg residue (e.g., des-Arg(9)-bradykinin (BK) and Lys-des-Arg(9)-BK), is an increasingly recognized molecular target for the development of analgesic and anti-inflammatory drugs. Recently developed antagonists of this receptor were compared to a conventional antagonist, Ac-Lys-[Leu(8)]-des-Arg(9)-BK, in pharmacological assays based on the rabbit B(1) receptor. B-9858 (Lys-Lys-[Hyp(3), Igl(5), D-Igl(7), Oic(8)]des-Arg(9)-BK) and three other analogues possessing the alpha-2-indanylglycine(5) (Igl(5)) residue (order of potency B-9858 approximately B-10146>B-10148>B-10050) were partially insurmountable antagonists of des-Arg(9)-BK in the contractility assay based on rabbit aortic rings. B-9858-induced depression of the maximal effect was more pronounced in tissues treated with the protein synthesis inhibitor cycloheximide to block the spontaneous increase of response attributed to the post-isolation formation of B(1) receptors, and only partly reversible on washing. By comparison, Ac-Lys-[Leu(8)]des-Arg(9)-BK was a surmountable antagonist (pA(2) 7. 5), even in cycloheximide-treated tissues. B-9958 (Lys-[Hyp(3), CpG(5), D-Tic(7), CpG(8)]des-Arg(9)-BK) was also surmountable (pA(2) 8.5). The binding of [(3)H]-Lys-des-Arg(9)-BK to recombinant rabbit B(1) receptors expressed in COS-1 cells was influenced by two of the antagonists: while Ac-Lys-[Leu(8)]des-Arg(9)-BK competed for the radioligand binding without affecting the B(max), B-9858 decreased the B(max) in a time-dependent and washout-resistant manner. B-9858 and analogues possessing Igl(5) are the first reported non-competitive, non-equilibrium antagonists of the kinin B(1) receptor.     

Inhibitory effect of PACAP(6–38) on relaxations induced by PACAP, VIP and non-adrenergic, non-cholinergic nerve stimulation in the guinea-pig taenia caeci

The effect of the pituitary adenylate cyclase activating polypeptide (PACAP) receptor antagonist PACAP(6-38) on the relaxant response to exogenous PACAP, vasoactive intestinal polypeptide (VIP) and nonadrenergic, non-cholinergic (NANC) nerve stimulation was tested in the guinea-pig taenia caeci, in the presence of atropine (10(-6) M) and guanethidine (3x10(-6) M). PACAP(6-38) (3x10(-6) M) strongly inhibited sub-maximal relaxations evoked by exogenous PACAP (1-3x 10(-8) M) or VIP (10(-8) M), but not those due to isoprenaline (4-8x10(-8) M) or ATP (10(-6) M). PACAP(6-38) caused a small but significant (approximately 20%) inhibition of the NANC relaxation due to electrical field stimulation (1 Hz or 10 Hz for 20 s). At these frequencies PACAP(6-38) caused no inhibition of the NANC relaxation in the presence of the P2 purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 5x10(-5) M), or PPADS plus the NO-synthase blocker NG-nitro-L-arginine (L-NOARG; 10(-4) M); in preparations pretreated with L-NOARG (10(-4) M) alone PACAP(6-38) retained its inhibitory effect. The PPADS- and L-NOARG-resistant NANC relaxation with 10 Hz electrical stimulation was blocked by apamin (10(-7) M); it was not significantly modified by the tachykinin receptor antagonist spantide (10(-5) M). Tachyphylaxis to PACAP(1-27) (10(-7) M for 10 min) strongly inhibited the relaxation due to PACAP(1-38) (1-3x10(-8) M) and reduced electrical stimulation-evoked relaxations by half. The putative VIP antagonist VIP(10-28) (10(-5) M) failed to significantly reduce the relaxant action of exogenous VIP (1-3x10(-8) M). Relaxation induced by PACAP(1-38) (1-2x10(-8) M) was not influenced by a mixture of PPADS (5x10(-5) M) and L-NOARG (10(-4) M). It is concluded that: (a) PACAP(6-38) is a VIP/PACAP antagonist in the guinea-pig taenia caeci; (b) a release of a VIP/PACAP-like substance from enteric nerves is involved in the NANC relaxation in this preparation, but its contribution is relatively small and seems to depend on the functional integrity of the PPADS-sensitive inhibitory mechanism; (c) the PPADS- plus L-NOARG-resistant NANC relaxation probably involves apamin-sensitive K+ channels.     

Antiproliferative constituents in plants 9. Aerial parts of Lippia dulcis and Lippia canescens

The antiproliferative constituents in the MeOH extracts of the aerial parts of Lippia dulcis Trev. and Lippia canescens Kunth (Verbenaceae) were investigated. Activity-guided chemical investigation of the MeOH extracts resulted in the isolation of the three bisabolane-type sesquiterpenes [(+)-hernandulcin (1), (-)-epihernandulcin (2), and (+)-anymol (3)] and four phenylethanoid glycosides [acteoside (4), isoacteoside (5), martynoside (6), and a new diacetylmartynoside (7)] from the former, and four phenylethanoid glycosides [acteoside (4), isoacteoside (5), arenarioside (8), and leucosceptoside A (9)] and three flavones [desmethoxycentaureidin (10), eupafolin (11), and 6-hydroxyluteolin (12)] from the latter. Antiproliferative activity of the isolated compounds against murine melanoma (B16F10), human gastric adenocarcinoma (MK-1), and human uterine carcinoma (HeLa) cells was estimated. (+)-Anymol (3), acteoside (4), isoacteoside (5), arenarioside (8), eupafolin (11), and 6-hydroxyluteolin (12) had GI50 values of 10-16 microM against B16F10 cell. Desmethoxycentaureidin (10) and eupafolin (11) showed high inhibitory activity against HeLa cell growth (GI50 9 microM, and 6 microM, respectively).     

A cytoplasm-sensitive peptide vector cross-linked with dynein light chain association sequence (DLCAS) enhances gene expression

We previously engineered a novel, non-viral, multifunctional gene vector (STR-CH(2)R(4)H(2)C) containing stearoyl (STR) and a block peptide consisting of Cys (C), His (H), and Arg (R). STR-CH(2)R(4)H(2)C forms a nano-complex with pDNA and is stabilized by electronic interactions and disulfide cross linkages. In blood, pDNA, a cytosol-sensitive gene vector, is released from the complex into the cytosol. The current study aimed to make STR-CH(2)R(4)H(2)C capable of active nuclear localization. The dynein light chain association sequence (DLCAS) was disulfide cross-linked to STR-CH(2)R(4)H(2)C/pDNA through disulfide linkages, and the gene expression ability of this DLCAS cross-linked gene vector was evaluated. We examined the gene transfection efficiency of S-180 cells transfected with the STR-CH(2)R(4)H(2)C/DLCAS/pDNA complex. STR-CH(2)R(4)H(2)C/DLCAS/pDNA showed significantly higher and faster gene expression compared with STR-CH(2)R(4)H(2)C/pDNA. We also evaluated the cellular uptake ability of STR-CH(2)R(4)H(2)C/DLCAS/Cy5-labeled pDNA complex. STR-CH(2)R(4)H(2)C/DLCAS/pDNA showed significantly lower cellular uptake compared with STR-CH(2)R(4)H(2)C/pDNA. This result indicates that high gene expression of STR-CH(2)R(4)H(2)C/DLCAS/pDNA does not facilitate its cellular uptake. In addition, the gene expression of DLCAS/STR-CH(2)R(4)H(2)C/pDNA in S-180 cells pretreated with the tubulin polymerization inhibitor, nocodazole (NCZ), was significantly lower than that in the absence of NCZ. These results indicate that the high transfection efficiency of DLCAS/STR-CH(2)R(4)H(2)C/pDNA is dependent on intra-cellular transport utilizing the microtubule motor protein, dynein. Taken together, our results suggest that DLCAS-modified STR-CH(2)R(4)H(2)C may be a promising gene delivery system.     

Development and characterization of a highly selective neuropeptide Y Y5 receptor agonist radioligand: [125I][hPP1-17, Ala31, Aib32]NPY

(1) The existence of multiple classes of neuropeptide Y (NPY) receptors (Y(1), Y(2), Y(4), Y(5) and y(6)) is now well established. However, one of the major difficulties in the study of these various receptor subtypes is the current lack of highly selective probes to investigate a single receptor class. Up to most recently, this was particularly true for the Y(4) and Y(5) subtypes. (2) [hPP(1-17), Ala(31), Aib(32)]NPY, the first highly selective Y(5) agonist, was iodinated using the chloramine T method and purified by high-pressure liquid chromatography. (3) Binding performed in rat brain homogenates revealed that equilibrium was reached after 120 min (t(1/2)=21 min) and 60 min (t(1/2)=12 min) at 25 and 100 pM [(125)I][hPP(1-17), Ala(31), Aib(32)]NPY, respectively. (4) Isotherm saturation binding experiments demonstrated that [(125)I][hPP(1-17), Ala(31), Aib(32)]NPY binds to an apparent single population with high-affinity (K(D) of 1.2 and 1.7 nM) and low-capacity (B(max) of 14+/-3 fmol/100,000 cells and 20+/-5 fmol/mg protein) sites in Y(5) receptor HEK293-transfected cells and rat brain membrane homogenates, respectively. No specific [(125)I][hPP(1-17), Ala(31), Aib(32)]NPY binding sites could be detected in Y(1), Y(2) or Y(4) receptors transfected HEK293 cells, demonstrating the high selectivity of this ligand for the Y(5) subtype. (5) Competition binding experiments performed in rat brain membrane homogenates and Y(5)-receptor transfected HEK293 cells demonstrated that specific [(125)I][hPP(1-17), Ala(31), Aib(32)]NPY binding was competed with high affinity by Y(5) agonists and antagonists such as [Ala(31), Aib(32)]NPY, [hPP(1-17), Ala(31), Aib(32)]NPY, hPP, CGP71683A and JCF109, but not by Y(1) (BIBP3226), Y(2) (BIIE0246) and Y(1)/Y(4) (GR231118) preferential ligands. (6) Taken together, these data demonstrate that [(125)I][hPP(1-17), Ala(31), Aib(32)]NPY is the first highly selective Y(5) radioligand to be developed. This new probe should prove most useful for further detailed studies of the molecular and pharmacological properties of this receptor subtype in brain and peripheral tissues.