Inhibition by two lavendustins of the tyrosine kinase activity of pp60F527 in vitro and in intact cells

Effects of the phytoestrogen, genistein, and protein tyrosine kinase inhibitor-dependent mechanisms on steroidogenesis and estrogen receptor expression in porcine granulosa cells of medium follicles

The use of soy-based products in pig diets had raised concerns regarding the reproductive toxicity of genistein, the predominant isoflavone in soybeans. Genistein was reported to exhibit weak estrogenic activity but its mechanism of action is not fully recognized. The aim of the study was to examine the in vitro effects of genistein on (1) progesterone (P(4)) and estradiol (E(2)) secretion by porcine granulosa cells harvested from medium follicles, (2) the viability of cultured granulosa cells, and (3) the mRNA and protein expression of estrogen receptors α and β (ERα and ERβ) in these cells. In addition, to verify the role of protein tyrosine kinase (PTK)-dependent mechanisms possibly involved in genistein biological action, we tested the effects of lavendustin C, the nonsteroidal PTK inhibitor, on granulosa cell steroidogenesis. We found that genistein inhibited (P < 0.05) basal P(4) secretion by granulosa cells harvested from medium follicles of pigs. In contrast, lavendustin C did not affect basal P(4) secretion by the cells. Moreover, genistein increased (P < 0.05) basal granulosal secretion of E(2). In contrast, lavendustin C did not alter basal E(2) secretion by porcine granulosa cells. In addition, we demonstrated that genistein increased mRNA and protein expression of ERβ (P < 0.05) in the examined cells. The expression of ERα mRNA was not affected by genistein and ERα protein was not detected in the cultured granulosa cells of pigs. In summary, the genistein action on follicular steroidogenesis in pigs involved changes in the granulosal expression of ERβ. However, the genistein action on P(4) and E(2) production by granulosa cells harvested from medium follicles did not seem to be associated with PTK.

Glycopyrrolate for treatment of clozapine-induced sialorrhea in three adolescents

OBJECTIVE

The aim of this case study was to report preliminary data on the effectiveness and tolerability of glycopyrrolate for the treatment of clozapine-induced sialorrhea, or excessive flow of saliva, in an adolescent population.

METHOD

Three adolescent females (age 13-16), who developed sialorrhea secondary to clozapine treatment, received an open-label trial of glycopyrrolate (4-8 mg) during inpatient hospitalization for treatment-resistant psychotic illness.

RESULTS

The target symptom of sialorrhea was improved in all three cases, with patient self-reports of decreased production of saliva confirmed by staff observation. Glycopyrrolate was generally well tolerated by the patients. One patient reported constipation, which improved with symptomatic treatment. A second patient reported dry mouth, which improved with a reduction in dose of glycopyrrolate.

CONCLUSIONS

These three cases provide support for the potential effectiveness and tolerability of glycopyrrolate for clozapine-induced sialorrhea in adolescents. Further controlled studies are required to determine the safety, efficacy and tolerability of glycopyrrolate in this age group and in adults for clozapine-induced sialorrhea.

N-desmethylclozapine, an allosteric agonist at muscarinic 1 receptor, potentiates N-methyl-D-aspartate receptor activity

The molecular and neuronal substrates conferring on clozapine its unique and superior efficacy in the treatment of schizophrenia remain elusive. The interaction of clozapine with many G protein-coupled receptors is well documented but less is known about its biologically active metabolite, N-desmethylclozapine. Recent clinical and preclinical evidences of the antipsychotic activity of the muscarinic agonist xanomeline prompted us to investigate the effects of N-desmethylclozapine on cloned human M1-M5 muscarinic receptors. N-desmethylclozapine preferentially bound to M1 muscarinic receptors with an IC50 of 55 nM and was a more potent partial agonist (EC50, 115 nM and 50% of acetylcholine response) at this receptor than clozapine. Furthermore, pharmacological and site-directed mutagenesis studies suggested that N-desmethylclozapine preferentially activated M1 receptors by interacting with a site that does not fully overlap with the acetylcholine orthosteric site. As hypofunction of N-methyl-d-aspartate (NMDA) receptor-driven neuronal ensembles has been implicated in psychotic disorders, the neuronal activity of N-desmethylclozapine was electrophysiologically investigated in hippocampal rat brain slices. N-desmethylclozapine was shown to dose-dependently potentiate NMDA receptor currents in CA1 pyramidal cells by 53% at 100 nM, an effect largely mediated by activation of muscarinic receptors. Altogether, our observations provide direct evidence that the brain penetrant metabolite N-desmethylclozapine is a potent, allosteric agonist at human M1 receptors and is able to potentiate hippocampal NMDA receptor currents through M1 receptor activation. These observations raise the possibility that N-desmethylclozapine contributes to clozapine's clinical activity in schizophrenics through modulation of both muscarinic and glutamatergic neurotransmission.

Involvement of Ca2+/calmodulin-dependent protein kinase II in endothelial NO production and endothelium-dependent relaxation

Nitric oxide (NO) is synthesized from l-arginine by the Ca(2+)/calmodulin-sensitive endothelial NO synthase (NOS) isoform (eNOS). The present study assesses the role of Ca(2+)/calmodulin-dependent protein kinase II (CaMK II) in endothelium-dependent relaxation and NO synthesis. The effects of three CaMK II inhibitors were investigated in endothelium-intact aortic rings of normotensive rats. NO synthesis was assessed by a NO sensor and chemiluminescence in culture medium of cultured porcine aortic endothelial cells stimulated with the Ca(2+) ionophore A23187 and thapsigargin. Rat aortic endothelial NOS activity was measured by the conversion of l-[(3)H]arginine to l-[(3)H]citrulline. Three CaMK II inhibitors, polypeptide 281-302, KN-93, and lavendustin C, attenuated the endothelium-dependent relaxation of endothelium-intact rat aortic rings in response to acetylcholine, A23187, and thapsigargin. None of the CaMK II inhibitors affected the relaxation induced by NO donors. In a porcine aortic endothelial cell line, KN-93 decreased NO synthesis and caused a rightward shift of the concentration-response curves to A23187 and thapsigargin. In rat aortic endothelial cells, KN-93 significantly decreased bradykinin-induced eNOS activity. These results suggest that CaMK II was involved in NO synthesis as a result of Ca(2+)-dependent activation of eNOS.

Synthesis, anticancer activity, and inhibition of tubulin polymerization by conformationally restricted analogues of lavendustin A

Compounds in the lavendustin A series have been shown to inhibit both protein-tyrosine kinases (PTKs) and tubulin polymerization. Since certain lavendustin A derivatives can exist in conformations that resemble both the trans-stilbene structure of the PTK inhibitor piceatannol and the cis-stilbene structure of the tubulin polymerization inhibitor combretastatin A-4, the possibility exists that the ratio of the two types of activities of the lavendustins could be influenced through the synthesis of conformationally restricted analogues. Accordingly, the benzylaniline structure of a series of pharmacologically active lavendustin A fragments was replaced by either their cis- or their trans-stilbene relatives, and effects on both inhibition of tubulin polymerization and cytotoxicity in cancer cell cultures were monitored. Both dihydrostilbene and 1,2-diphenylalkyne congeners were also prepared and evaluated biologically. Surprisingly, conformational restriction of the bridge between the two aromatic rings of the lavendustins had no significant effect on biological activity. On the other hand, conversion of the three phenolic hydroxyl groups of the lavendustin A derivatives to their corresponding methyl ethers consistently abolished their ability to inhibit tubulin polymerization and usually decreased cytotoxicity in cancer cell cultures as well, indicating the importance of at least one of the phenolic hydroxyl groups. Further investigation suggested that the phenolic hydroxyl group in the salicylamide ring was required for activity, while the two phenol moieties in the hydroquinone ring could be methylated with retention of activity. Two of the lavendustin A derivatives displayed IC(50) values of 1.4 microM for inhibition of tubulin polymerization, which ranks them among the most potent of the known tubulin polymerization inhibitors.

Synthesis and investigation of conformationally restricted analogues of lavendustin A as cytotoxic inhibitors of tubulin polymerization

A series of conformationally restricted analogues were synthesized in order to elucidate the possible effects of different amide conformations of lavendustin A derivatives on cytotoxicity in cancer cell cultures and on inhibition of tubulin polymerization. The conformationally restricted analogues were based on the oxazinedione and isoindolone ring systems. In addition, the amide bond was replaced by both cis and trans alkene moieties. Surprisingly, the results indicated very little effect of conformational restriction on biological activity. Because all of the compounds synthesized had similar cytotoxicities and potencies as tubulin polymerization inhibitors, the side chain present on the aniline ring system does not appear to be important in the biological effects of the lavendustins. The hydroquinone ring of lavendustin A may be a more important determinant of the biological activity than the structure surrounding the aniline ring.

Myocardial protection by insulin at reperfusion requires early administration and is mediated via Akt and p70s6 kinase cell-survival signaling

The "metabolic cocktail" comprising glucose-insulin-potassium administrated at reperfusion reduces infarct size in the in vivo rat heart. We propose that insulin is the major component mediating this protection and acts via Akt prosurvival signaling. This hypothesis was studied in isolated perfused rat hearts (measuring infarct size to area of risk [%]) subjected to 35 minutes regional myocardial ischemia and 2 hours reperfusion. Insulin administered at the onset of reperfusion attenuated infarct size by >/=45% versus control hearts (P<0.001). Insulin-mediated cardioprotection was found to be independent of the presence of glucose at reperfusion. Moreover, the cell survival benefit of insulin is temporally dependent, in that insulin administration from the onset of reperfusion and maintained for either 15 minutes or for the duration of reperfusion reduced infarct size. In contrast, protection was abrogated if insulin administration was delayed until 15 minutes into reperfusion. Pharmacological inhibition of both upstream and downstream signals in the Akt prosurvival pathway abolished the cardioprotective effects of insulin. Here coadministration of insulin with the tyrosine kinase inhibitor lavendustin A, the phosphatidylinositol3-kinase (PI3-kinase) inhibitor wortmannin, and mTOR/p70s6 kinase inhibitor rapamycin abolished cardioprotection. Steady-state levels of activated/phosphorylated Akt correlated with insulin administration. Finally, downstream prosurvival targets of Akt including p70s6 kinase and BAD were modulated by insulin. In conclusion, insulin administration at reperfusion reduces myocardial infarction, is dependent on early administration during reperfusion, and is mediated via Akt and p70s6 kinase dependent signaling pathway. Moreover, BAD is maintained in its inert phosphorylated state in response to insulin therapy.

Design, synthesis, and biological evaluation of a series of lavendustin A analogues that inhibit EGFR and Syk tyrosine kinases, as well as tubulin polymerization

A series of N-alkylamide analogues of the lavendustin A pharmacophore were synthesized and tested for inhibition of the epidermal growth factor receptor (EGFR) protein tyrosine kinase and the nonreceptor protein tyrosine kinase Syk. Although several compounds in the series were effective inhibitors of both kinases, it seemed questionable whether their inhibitory effects on these kinases were responsible for the cytotoxic properties observed in a variety of human cancer cell cultures. Accordingly, a COMPARE analysis of the cytotoxicity profile of the most cytotoxic member of the series was performed, and the results indicated that its cytotoxicity profile was similar to that of antitubulin agents. This mechanism of action was supported by demonstrating that most compounds in the series were moderately effective as inhibitors of tubulin polymerization. This suggests that the lavendustin A analogues reported here, as well as some of the previously reported lavendustin A analogues, may be acting as cytotoxic agents by a mechanism involving the inhibition of tubulin polymerization.

Therapeutic options in the treatment of clozapine-induced sialorrhea

Clozapine is an effective atypical antipsychotic drug, but its use may be compromised by its side effects. Agranulocytosis may be fatal, but sialorrhea occurs more frequently and plays a major role in patients' noncompliance. A MEDLINE search from 1975-2000 revealed that treatment of clozapine-induced sialorrhea is predominantly based on case reports. Due to its elusive mechanism, physicians have attempted to treat this side effect with agents that counteract clozapine's adrenergic and muscarinic properties. We evaluated reported treatment options and other possible strategies from a pharmacologic standpoint. Antimuscarinic agents and alpha-receptor agonists are both viable options but must be administered and monitored cautiously in patients with psychiatric disorders. Although not yet available in the United States, pirenzepine, a selective muscarinic receptor antagonist, has the most promising mechanism. Other selective, peripherally acting agents must be investigated in controlled clinical trials to determine their efficacy as possible alternatives.

Insulin administered at reoxygenation exerts a cardioprotective effect in myocytes by a possible anti-apoptotic mechanism

The metabolic cocktail of glucose-insulin-potassium (GIK) has been shown to reduce mortality in humans and reduce infarct size in the rat when administered from the onset of reperfusion following an ischemic insult. The mechanisms underlying GIK mediated cardioprotection are, however, still unclear. Recent data implicates insulin "alone" as the major protagonist of cardioprotection when administered at the time of reperfusion. We have therefore begun to investigate an insulin activated signalling pathway and the putative role of apoptosis in this insulin-induced cardioprotection. Simulated ischemia and reoxygenation were induced in rat neonatal cardiocyte experiments. The administration of insulin [0.3 mU/ml] at the moment of reoxygenation (Ins(R)) enhanced myocardial cell viablility as assessed by trypan blue exclusion compared to vehicle alone treated control myocytes (Ins(R)50+/-2%v controls 70+/-1%, P<0.001). This insulin-mediated cardioprotection was due, in part to a reduction in myocyte apoptosis as measured by TUNEL (Ins(R)29+/-2%v controls 49+/-3%, P<0.001) and Annexin V staining (Ins(R)34+/-2%v controls 65+/-3%, P<0.001). These cardioprotective and anti-apoptotic effects of insulin were completely abolished by the tyrosine kinase inhibitor lavendustin A and by the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor wortmannin. Thus, we conclude that the early administration of insulin appears to be an effective modality to reduce reoxgygenation injury in cardiocytes, in part, via the attenuation of ischemia/reoxygenation-induced apoptosis. Moreover, the cardioprotective and anti-apoptotic effects of insulin are mediated via tyrosine kinase and PI3-kinase signalling pathways.

Tyrosine kinase inhibitors block sperm-induced egg activation in Xenopus laevis

Fertilization of Xenopus laevis eggs triggers a wave of increased [Ca2+]i. The exact signal transduction pathway culminating in this Ca2+ wave remains unknown. To determine whether increases in tyrosine kinase activity are part of this pathway, we microinjected tyrosine kinase inhibitors into unfertilized eggs. Upon fertilization, signs of activation were monitored, such as fertilization envelope liftoff and the Ca2+ wave (for eggs microinjected with lavendustin A). Various concentrations of lavendustin A and tyrphostin B46 were microinjected, as well as inactive forms of these compounds (lavendustin B and tyrphostin A1) to provide negative controls. Peptide A, a 20-amino-acid peptide derived from the SH2 region of pp60(v-src) tyrosine kinase, was also microinjected. Peptide A inhibits tyrosine kinase activity but not PKA or PKG activity. Dose-response curves for lavendustin A, tyrphostin B46, and peptide A show clear inhibition of vitelline envelope liftoff by these three compounds. Confocal imaging of eggs coinjected with lavendustin A and Oregon Green-dextran showed that the Ca2+ wave was inhibited under normal insemination conditions but that the block of the Ca2+ wave could be overcome with very high sperm densities. A phenomenon of small local Ca2+ increases termed "hot spots" seen in lavendustin A containing eggs is also described. Since this inhibition of egg activation by tyrosine kinase inhibitors can be overcome by Ca2+ microinjection, the inhibitors must act on a step in the signal transduction cascade that is upstream of the Ca2+ wave.