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Z Vogel

Publications and source records attributed to Z Vogel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Inhibition of adenylyl cyclase isoforms V and VI by various Gbetagamma subunits.

An intriguing development in the G-protein signaling field has been the finding that not only the Galpha subunit, but also Gbetagamma subunits, affect a number of downstream target molecules. One of the downstream targets of Gbetagamma is adenylyl cyclase, and it has been demonstrated that a number of isoforms of adenylyl cyclase can be either inhibited or stimulated by Gbetagamma subunits. Until now, adenylyl cyclase type I has been the only isoform reported to be inhibited by free Gbetagamma. Here we show by transient cotransfection into COS-7 cells of either adenylyl cyclase V or VI, together with Ggamma2 and various Gbeta subunits, that these two adenylyl cyclase isozymes are markedly inhibited by Gbetagamma. In addition, we show that Gbeta1 and Gbeta5 subunits differ in their activity. Gbeta1 transfected alone markedly inhibited adenylyl cylcase V and VI (probably by recruiting endogenous Ggamma subunits). On the other hand, Gbeta5 produced less inhibition of these isozymes, and its activity was enhanced by the addition of Ggamma2. These results demonstrate that adenylyl cyclase types V and VI are inhibited by Gbetagamma dimers and that Gbeta1 and Gbeta5 subunits differ in their capacity to regulate these adenylyl cyclase isozymes.

Adenylyl Cyclase Inhibitors↗
PubMed1998

Regulation of adenylyl cyclase isozymes on acute and chronic activation of inhibitory receptors.

Adenylyl cyclase superactivation, a phenomenon by which chronic activation of inhibitory Gi/o-coupled receptors leads to an increase in cAMP accumulation, is believed to play an important role as a compensatory response of the cAMP signaling system in the cell. However, to date, the mechanism by which adenylyl cyclase activity is regulated by chronic exposure to inhibitory agonists and the nature of the adenylyl cyclase isozymes participating in this process remain largely unknown. Here we show, using COS-7 cells transfected with the various AC isozymes, that acute activation of the D2 dopaminergic and m4 muscarinic receptors inhibited the activity of adenylyl cyclase isozymes I, V, VI, and VIII, whereas types II, IV, and VII were stimulated and type III was not affected. Conversely, chronic receptor activation led to superactivation of adenylyl cyclase types I, V, VI, and VIII and to a reduction in the activities of types II, IV, and VII. The activity of AC-III also was reduced. This pattern of inhibition/stimulation of the various adenylyl cyclase isozymes is similar to that we recently observed on acute and chronic activation of the mu-opioid receptor, suggesting that isozyme-specific adenylyl cyclase superactivation may represent a general means of cellular adaptation to the activation of inhibitory receptors and that the presence/absence and intensity of the adenylyl cyclase response in different brain areas (or cell types) could be explained by the expression of different adenylyl cyclase isozyme types in these areas.

Adenylyl Cyclase Inhibitors↗
PubMed1997

Cannabinol derivatives: binding to cannabinoid receptors and inhibition of adenylylcyclase.

Several derivatives of cannabinol and the 1,1-dimethylheptyl homolog (DMH) of cannabinol were prepared and assayed for binding to the brain and the peripheral cannabinoid receptors (CB1 and CB2), as well as for activation of CB1- and CB2-mediated inhibition of adenylylcyclase. The DMH derivatives were much more potent than the pentyl (i.e., cannabinol) derivatives. 11-Hydroxycannabinol (4a) was found to bind potently to both CB1 and CB2 (Ki values of 38.0 +/- 7.2 and 26.6 +/- 5.5 nM, respectively) and to inhibit CB1-mediated adenylylcyclase with an EC50 of 58.1 +/- 6.2 nM but to cause only 20% inhibition of CB2-mediated adenylylcyclase at 10 microM. It behaves as a specific, though not potent, CB2 antagonist. 11-Hydroxycannabinol-DMH (4b) is a very potent agonist for both CB1 and CB2 (Ki values of 100 +/- 50 and 200 +/- 40 pM; EC50 of adenylylcyclase inhibition 56.2 +/- 4.2 and 207.5 +/- 27.8 pM, respectively).

Adenylyl Cyclase Inhibitors↗
PubMed1997

Structural requirements for binding of anandamide-type compounds to the brain cannabinoid receptor.

In order to establish the structural requirements for binding to the brain cannabinoid receptor (CB1), we have synthesized numerous fatty acid amides, ethanolamides, and some related simple derivatives and have determined their Ki values. A few alpha-methyl- or alpha, alpha-dimethylarachidonoylalkylamides were also examined. In the 20:4, n-6 series, the unsubstituted amide is inactive; N-monoalkylation, at least up to a branched pentyl group, leads to significant binding. N,N-Dialkylation, with or without hydroxylation on one of the alkyl groups, leads to elimination of activity. Hydroxylation of the N-monoalkyl group at the omega carbon atom retains activity. In the 20x, n-6 series, x has to be either 3 or 4; the presence of only two double bonds leads to inactivation. In the n-3 series, the limited data reported suggest that the derived ethanolamides are either inactive or less active than comparable compounds in the n-6 series. Alkylation or dialkylation of the alpha carbon adjacent to the carbonyl group retains the level of binding in the case of anandamide (compounds 48, 49); however, alpha-monomethylation or alpha,alpha-dimethylation of N-propyl derivatives (50-53) potentiates binding and leads to the most active compounds seen in the present work (Ki values of 6.9 +/- 0.7 to 8.4 +/- 1.1 nM). We have confirmed that the presence of a chiral center on the N-alkyl substituent may lead to enantiomers which differ in their levels of binding (compounds 54, 57 and 55, 56).

Amides↗
PubMed1997

Opiate-induced adenylyl cyclase superactivation is isozyme-specific.

While acute activation of inhibitory Gi/o-coupled receptors leads to inhibition of adenylyl cyclase, chronic activation of such receptors leads to an increase in cAMP accumulation. This phenomenon, observed in many cell types, has been referred to as adenylyl cyclase superactivation. At this stage, the mechanism leading to adenylyl cyclase superactivation and the nature of the isozyme(s) responsible for this phenomenon are largely unknown. Here we show that transfection of adenylyl cyclase isozymes into COS-7 cells results in an isozyme-specific increase in AC activity upon stimulation (e.g. with forskolin, ionomycin, or stimulatory receptor ligands). However, independently of the method used to activate specific adenylyl cyclase isozymes, acute activation of the mu-opioid receptor inhibited the activity of adenylyl cyclases I, V, VI, and VIII, while types II, IV, and VII were stimulated and type III was not affected. Chronic mu-opioid receptor activation followed by removal of the agonist was previously shown, in transfected COS-7 cells, to induce superactivation of adenylyl cyclase type V. Here we show that it also leads to superactivation of adenylyl cyclase types I, VI, and VIII, but not of type II, III, IV, or VII, demonstrating that the superactivation is isozyme-specific. Not only were isozymes II, IV, and VII not superactivated, but a reduction in the activities of these isozymes was actually observed upon chronic opiate exposure. These results suggest that the phenomena of tolerance and withdrawal involve specific adenylyl cyclase isozymes.

Adenylyl Cyclases↗
PubMed1997

Distinct components of morphine effects on cardiac myocytes are mediated by the kappa and delta opioid receptors.

Morphine exerts direct effects on cultured cardiac myocytes from neonatal rats. These effects are mediated via the delta and the kappa opioid receptors, as mu opioid receptors are not present in neonatal cardiomyocyte cultures. Binding parameters to the delta and kappa opioid receptors were determined in membrane preparations from these cultures by heterologous competition to [3H]diprenorphine binding, with [D-Pen2, D-Pen5]-enkephalin (DPDPE) and trans-(dl)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate (U-50,488H) as specific displacers respectively. To define the components of morphine effects mediated via activation of either the delta or the kappa opioid receptor alone, cardiac myocytes were exposed to morphine in the presence of specific antagonists to the kappa or delta opioid receptor respectively. Activation of the kappa opioid receptors by morphine caused a transient increase in Ca2+ influx, leading to increase in amplitudes of [Ca2+]i transients and contraction, with no change in the intracellular pH. Activation of the delta opioid receptors alone by morphine caused a decrease in the amplitude of contraction. This decrease was mediated by a decrease in the intracellular pH leading to reduced responsiveness of the myofilaments to Ca2+. There was no change in Ca2+ influx and in the amplitude of [Ca2+]i transients. The effects mediated through the delta opioid but not through the kappa opioid receptors were pertussis toxin sensitive, indicating coupling of the delta opioid receptors to pertussis toxin sensitive GTP-binding proteins. The overall effects of morphine on the neonatal cardiac myocytes were the sum of the effects exerted by morphine when it activated each of the opioid receptors alone.

Analgesics, Opioid↗
PubMed1997

Differential distribution of synapsin IIa and IIb mRNAs in various brain structures and the effect of chronic morphine administration on the regional expression of these isoforms.

Quantitative reverse transcriptase-polymerase chain reaction and in situ hybridization techniques were used to determine the regional distribution of synapsin IIa and IIb mRNAs in rat central nervous system and to assess the effect of chronic morphine administration on the gene expression of these two isoforms of synapsin II. These isoforms are members of a family of neuron-specific phosphoproteins thought to be involved in the regulation of neurotransmitter release. Our data demonstrate the widespread distribution, yet regionally variable expression, of synapsin IIa and IIb mRNAs throughout the adult rat brain and spinal cord. The ratios of the relative abundance of synapsins IIa and IIb differed by up to 4.5-fold among the various regions studied. Synapsin IIa and IIb mRNAs were shown to be highly concentrated in the thalamus and in the hippocampus, whereas lower concentrations were found in most other central nervous system structures. In this study, we show differential regulation by morphine of synapsins IIa and IIb in various regions of the brain. In the striatum, a 2.4-fold increase was observed in the levels of synapsin IIa mRNA following chronic morphine regime, whereas no change was found for synapsin IIb. On the other hand, mRNA levels of synapsin IIb in spinal cord of chronically treated rats were markedly decreased (by 62%), while no alterations were observed in synapsin IIa. Selective regulation by morphine has also been demonstrated in several other central nervous system structures. The opiate-induced regulation of the gene expression of synapsin II isoforms could be viewed as one of the cellular adaptations to the persistent opiate effects and may be involved in the molecular mechanism underlying opiate tolerance and/or dependence.

Animals↗
PubMed1997

Ras-GRF, the activator of Ras, is expressed preferentially in mature neurons of the central nervous system.

In rodents, the Ras-specific guanine-nucleotide exchange factor (Ras-GRF) is expressed in different areas of the brain and, at a reduced level, also in the spinal cord. No expression of the 140 kDa Ras-GRF was detected in dorsal root ganglia and all other tissues tested. Analysis of primary cultures derived from brain reveals that this exchange factor is only present in neurons of the central nervous system. In primary hippocampal cultures, the expression of Ras-GRF increases in parallel with the onset of a neuronal network and in the whole brain it increases sharply after birth.

Animals↗
PubMed1997

Acupuncture and the opioid system: implications in management of migraine.

We investigated the effectiveness of acupuncture in childhood migraine in 22 children with migraine, randomly divided into two groups: a true acupuncture group (12 children) and a placebo acupuncture group (10 children). Ten healthy children served as a control group. Opioid activity in blood plasma was assayed by two methods: (1) determination of total (panopioid) activity with an opiate radioreceptor assay, and (2) determination of beta-endorphinlike immunoreactivity by radioimmunoassay. The true acupuncture treatment led to significant clinical reduction in both migraine frequency and intensity. At the beginning of the study, significantly greater panopioid activity was evident in plasma of the control group than in plasma of the migraine group. The true acupuncture group showed a gradual increase in the panopioid activity in plasma, which correlated with the clinical improvement. After the tenth treatment, the values of opioid activity of the true acupuncture group were similar to those of the control group, whereas the plasma of the placebo acupuncture group exhibited insignificant changes in plasma panopioid activity. In addition, a significant increase in beta-endorphin levels was observed in the migraine patients who were treated in the true acupuncture group as compared with the values before treatment or with the values of the placebo acupuncture group. The results suggest that acupuncture may be an effective treatment in children with migraine headaches and that it leads to an increase in activity of the opioidergic system.

Acupuncture Therapy↗
PubMed1996

Chronic morphine administration enhances the expression of Kv1.5 and Kv1.6 voltage-gated K+ channels in rat spinal cord.

Prolonged opiate administration leads to the development of tolerance and dependence. These phenomena are accompanied by selective regulation of distant cellular proteins and mRNAs, including ionic channels. Acute opiate administration differentially affects voltage-dependent K+ currents. Whereas, opiate activation of K+ channels is well established opioid-induced inhibition of K+ conductance has also been studied. In this study, we focused on the effect of chronic morphine exposure on voltage-dependent Shaker-related Kv1.5 and Kv1.6 K+ channel gene expression and on Kv1.5 protein levels in the rat spinal cord. Several experimental approaches including in-situ hybridization, RNAse protection, reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry were employed. We found that motor neurons are highly enriched in Kv1.5 and Kv1.6 mRNA and in Kv1.5 channel protein. Moreover, we found significant increases in the amount of mRNA encoding for these two K+ channels and in Kv1.5 channel protein in the spinal cord of morphine-treated rats, compared with controls. For example, quantitative in-situ hybridization, revealed a 2.1 +/- 0.15- and 2.3 +/- 0.5-fold increase in Kv1.5 and Kv1.6 channel mRNA levels, respectively. Similar results were obtained by semiquantitative RT-PCR analyses. Kv1.5 protein level was increased by 1.9-fold in the spinal cord or morphine-treated rats. Our results suggest that Kv1.5 and Kv1.6 Shaker K+ channels play an important role in regulating motor activity that increases in mRNA and protein levels of the spinal cord K+ channels after chronic morphine exposure could be viewed as a cellular adaptation which compensates for a persistent opioid-induced inhibition of K+ channel activity. These alterations may account, in part, for the cellular events leading to opiate tolerance and dependence.

Animals↗
PubMed1996

Chronic opioid treatment induces adenylyl cyclase V superactivation. Involvement of Gbetagamma.

It has been known for some time that chronic treatment of neuronal cells and tissues with opioids, contrary to their acute effect, leads to an increase in cAMP accumulation. This phenomenon, defined as adenylyl cyclase superactivation, has been implicated in opiate addiction, yet the mechanism by which it is induced remains unclear. Here, we show that this phenomenon can be reproduced and studied in COS-7 cells cotransfected with adenylyl cyclase type V and mu-opioid receptor cDNAs. These cells display acute opioid inhibition of adenylyl cyclase activity, whereas prolonged exposure to the mu-agonist morphine or [-Ala2, N-methyl-Phe4, Gly-ol5]enkephalin leads to a time-dependent superactivation of adenylyl cyclase. This superactivated state is reversible, because it is gradually lost following agonist withdrawal. Adenylyl cyclase superactivation can be prevented by pertussis toxin pretreatment, indicating the involvement of Gi/o proteins, or by cotransfection with the carboxyl terminus of beta-adrenergic receptor kinase or with alpha-transducin (scavengers of Gbetagamma dimers), indicating a role for the G protein betagamma dimers in adenylyl cyclase superactivation. However, contrary to several other Gbetagamma-dependent signal transduction mechanisms (e.g. the extracellular signal-regulated kinase 2/MAP kinase pathway), adenylyl cyclase superactivation is not affected by the Ras dominant negative mutant N17-Ras.

Adenylate Cyclase Toxin↗
PubMed1996

(-)-Delta9-tetrahydrocannabinol antagonizes the peripheral cannabinoid receptor-mediated inhibition of adenylyl cyclase.

(-)-Delta9-Tetrahydrocannabinol ((-)-Delta9-THC) is the major active psychotropic component of the marijuana plant, Cannabis sativa. The membrane proteins that have been found to bind this material or its derivatives have been called the cannabinoid receptors. Two GTP-binding protein-coupled cannabinoid receptors have been cloned. CB1 or the neuronal cannabinoid receptor is found mostly in neuronal cells and tissues while CB2 or the peripheral cannabinoid receptor has been detected in spleen and in several cells of the immune system. It has previously been shown that activation of CB1 or CB2 receptors by cannabinoid agonists inhibits adenylyl cyclase activity. Utilizing Chinese hamster ovary cells and COS cells transfected with the cannabinoid receptors we report that (-)-Delta9-THC binds to both receptors with similar affinity. However, in contrast to its capacity to serve as an agonist for the CB1 receptor, (-)-Delta9-THC was only able to induce a very slight inhibition of adenylyl cyclase at the CB2 receptor. Morever, (-)-Delta9-THC antagonizes the agonist-induced inhibition of adenylyl cyclase mediated by CB2. Therefore, we conclude that (-)-Delta9-THC constitutes a weak antagonist for the CB2 receptor.

Adenylyl Cyclase Inhibitors↗
PubMed1996

Expression of opioid receptors during heart ontogeny in normotensive and hypertensive rats.

BACKGROUND: The opioidergic systems are involved in modulating nociceptive stimuli. In addition, the recent results suggest that endogenous and exogenous opioids could play a role in the modulation of blood pressure and cardiac functions. However, little is known regarding the expression and role of opioid-binding sites in the heart. The decreased sensitivity to noxious stimuli in hypertensive rats raises the possibility of different developmental pattern expression of opioid-binding sites in normotensive versus hypertensive rats. METHODS AND RESULTS: Opioid receptor expression in hearts from hypertensive and normotensive rats was studied during heart development by binding assays. From P1 until P90, the development of the heart in the two rat strains was accompanied by a gradual increase in the density of kappa-opioid receptors. Hearts from hypertensive rats expressed significantly higher levels of kappa receptors compared with those of normotensive rats. At ages older than P7, mu-opioid receptors could not be detected in hearts of both strains, whereas delta-opioid-binding sites gradually increased until reaching adult levels. Seven-day-old cardiomyocyte cultures of both rat strains expressed similar densities of delta or kappa receptors to those observed in hearts from 7-day-old neonates. The mu-binding sites were not detected in cardiomyocytes cultures. Similar to the in vivo state, cultured myocytes from hypertensive rats had significantly higher levels of kappa-binding sites (1.5 fold) compared with those of normotensive rats. The kappa sites are pertussis toxin sensitive, and the state of coupling of the receptor to G protein is similar for the two rat strains. CONCLUSION: The role of opioid-binding sites in the heart is not completely clear. Hypertensive rats are known to be less sensitive to noxious stimuli compared with normotensive rats. It is controversial whether the site if application of noxious stimuli plays an important role in the sensitivity to pain in hypertensive rats. We suggest that the opioidergic system could play a role in the modulation of blood pressure in addition to its known effect on nociception.

Animals↗
PubMed1996

Pharmacological basis for functional selectivity of partial muscarinic receptor agonists.

Muscarinic receptor agonists activate phosphoinositide hydrolysis and adenylate cyclase in Chinese hamster ovary cells transfected with cDNAs encoding the human muscarinic ml and m3 receptors. Whereas carbachol activates similarly both receptor subtypes, 4-[3-chlorophenyl-carbamoyloxy]-2-butynyltrimethyl ammonium chloride (McN-A-343) preferentially activates the m1 subtype over m3, in regard to both phosphoinositide hydrolysis and adenylate cyclase activity. On the other hand, oxotremorine activates phosphoinositide hydrolysis to a similar extent in both cell lines, but it activates preferentially adenylate cyclase in m1 versus m3 receptor expressing cells. Relative to carbachol, both McN-A-343 and oxotremorine activate preferentially phosphoinositide hydrolysis over adenylate cyclase in both cell lines. Prolonged incubation of cells with either carbachol, McN-A-343, or oxotremorine down-regulated the m1 receptors. This was accompanied by a parallel decrease in adenylate cyclase activity, whereas phosphoinositide hydrolysis remained relatively high. Inactivation of the receptors by alkylation with acetylethylcholine mustard, or by blocking with atropine, reduced carbachol-stimulated adenylate cyclase activity more effectively than carbachol-induced phosphoinositide hydrolysis in both m1 and m3 receptor expressing cells. These findings imply that the receptor reserve in these cell lines is greater for phosphoinositide hydrolysis response than for adenylate cyclase response. Yet, the receptor reserve for each of these responses is similar in both m1 and m3 receptor expressing cells. Since the binding affinities of McN-A-343 and of oxotremorine to m1 and m3 receptors are very similar, and since both cell lines contain similar amounts of spare receptors, we propose that the preferential activation of muscarinic m1 over m3 receptor by partial agonists is related to differences in the abilities of the two receptor subtypes to undergo conformational changes following agonist binding. This hypothesis is supported by results showing that the muscarinic m1 but not m3 receptor exhibits two affinity states in a competition binding assay.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1996

M1 agonists for the treatment of Alzheimer's disease. Novel properties and clinical update.

The AF series compounds, AF102B and congeners of AF150(S), are functionally selective agonists for m1 muscarinic receptors (m1AChRs). This is shown in stable transfected CHO and PC12 cells (PC12M1) with m1m5AChRs and m1AChRs, respectively. AF102B and AF150(S) are partial agonists, but AF150, AF151, and AF151 (S) are full agonists in stimulating phosphoinositides hydrolysis or arachidonic acid release in these cells. Yet, all these compounds behave as antagonists when compared with carbachol in elevating cAMP levels. In PC12M1 cells, unlike carbachol, the AF series compounds induce only minimal to moderate neurite outgrowth. Yet, these agonists synergize strongly with NGF, which by itself mediates only a mild response. Stimulation of m1AChRs by AF102B, AF150(S) and AF151(S) in PC12M1 cells enhances secretion of beta/A4 amyloid precursor protein derivatives (APPs). The enhanced APPs secretion induced by AF102B is potentiated by NGF. AF102B also stimulates APPs secretion from rat cortical slices. Stimulation of m1AChR in PC12M1 cells with carbachol or AF102B decreases tau phosphorylation as indicated by specific tau-1 mAb and alkaline phosphatase treatment. Due to the above mentioned properties m1 agonists may be of unique value in delaying the progression of Alzheimer's disease (AD). The AF series compounds show a wide safety margin and improve memory and learning deficits in animal models for AD. There is a dearth of clinical reports on m1 agonists. These include studies on AF102B and xanomeline, another m1 selective agonist. We tested AF102B in escalating doses of 20, 40, 60 mg, tid, po, (each dose for 2 weeks) for a total of 10 weeks. This was a single-blind placebo-controlled, parallel-group study in patients with probable AD. AF102B was significantly effective at 40 and 60 mg, tid in the ADAS, ADAS-cognitive and ADAS-word recognition scales.

Alzheimer Disease↗
PubMed1996

Correlation between secretagogue-induced Ca2+ influx, intracellular Ca2+ levels and secretion of catecholamines in cultured adrenal chromaffin cells.

Catecholamine secretion induced by various secretagogues in cultured bovine chromaffin cells has been correlated with Ca2+ influx and intracellular Ca2+ concentrations. Nicotine and high K+ caused prompt secretion of catecholamines from cells. Coincidently, both secretagogues evoked 45[Ca2+] influx with a parallel increase in free intracellular Ca2+ concentration, as determined by Quin 2 fluorescence. However, the rate of return of Ca2+ level to baseline after nicotine stimulation was more rapid than after K+ stimulation. In comparison, stimulation with veratridine produced a slow and prolonged Ca2+ influx accompanied by lower levels of intracellular Ca2+ than those observed after nicotine or K+ stimulation. Yet, during 15 min of stimulation, veratridine induced a substantial catecholamine release, which was larger than that obtained after nicotine or K+ stimulations. The Ca2+ ionophore A23187 (1 microM) induced a pronounced increase in intracellular Ca2+ levels, but did not evoke any significant catecholamine release. Finally, addition of the Ca2+ channel blocker verapamil following stimulation, at a time when intracellular Ca2+ concentration was at its peak level, did not affect the rate of decline in intracellular free Ca2+ concentration but promptly blocked Ca2+ uptake and catecholamine secretion. These findings suggest that the rate of Ca2+ influx, rather than the absolute level of intracellular Ca2+ concentration, determines the rate and extent of catecholamine release.

Aminoquinolines↗