Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The psychoactive properties of Cannabis sativa and its major biologically active constituent, delta 9-tetrahydrocannabinol, have been known for years. The recent identification and cloning of a specific cannabinoid receptor suggest that cannabinoids mimic endogenous compounds affecting neural signals for mood, memory, movement, and pain. Using whole-cell voltage clamp and the cannabinomimetic aminoalkylindole WIN 55,212-2, we have found that cannabinoid receptor activation reduces the amplitude of voltage-gated calcium currents in the neuroblastoma-glioma cell line NG108-15. The inhibition is potent, being half-maximal at less than 10 nM, and reversible. The inactive enantiomer, WIN 55,212-3, does not reduce calcium currents even at 1 microM. Of the several types of calcium currents in NG108-15 cells, cannabinoids predominantly inhibit an omega-conotoxin-sensitive, high-voltage-activated calcium current. Inhibition was blocked by incubation with pertussis toxin but was not altered by prior treatment with hydrolysis-resistant cAMP analogues together with a phosphodiesterase inhibitor, suggesting that the transduction pathway between the cannabinoid receptor and calcium channel involves a pertussis toxin-sensitive GTP-binding protein and is independent of cAMP metabolism. However, the development of inhibition is considerably slower than a pharmacologically similar pathway used by an alpha 2-adrenergic receptor in these cells. Our results suggest that inhibition of N-type calcium channels, which could decrease excitability and neurotransmitter release, may underlie some of the psychoactive effects of cannabinoids.
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PMID:Cannabinoids inhibit N-type calcium channels in neuroblastoma-glioma cells. 131 42

Anandamide (arachidonyl ethanolamide) has been identified as an endogenous ligand of cannabinoid receptors on the basis of its ability to displace 3H-labeled synthetic cannabinoid in a binding assay. One well characterized cellular action of cannabinoids is inhibition of hormonally stimulated adenylyl cyclase. Another action of synthetic cannabinoids is potent, stereospecific, and reversible inhibition of N-type calcium currents (ICa) in the NG108-15 neuroblastoma-glioma cell line via a pertussis toxin (PTX)-sensitive pathway, independently of cAMP metabolism. Here we used the N18 neuroblastoma cell line and the whole-cell voltage-clamp technique to show that anandamide also potently inhibits N-type ICa in a PTX-sensitive fashion. As with the cannabinomimetic aminoalkylindole WIN 55,212-2, inhibition by anandamide was voltage dependent and N-ethylmaleimide sensitive. However, anandamide was less efficacious than either WIN 55,212-2 or the nonclassical cannabinoid CP 55,940. Indeed, anandamide appears to act as a partial agonist at the cannabinoid receptor. Application of WIN 55,212-2 always caused further inhibition of ICa in cells exposed to a maximally effective concentration of anandamide, and application of anandamide always caused a partial recovery of ICa in cells exposed to a maximally effective concentration of WIN 55,212-2. This partial agonist property of anandamide suggests that, although anandamide inhibits N-type ICa via a PTX-sensitive G protein, its action as a neuromodulator in the intact animal may be more complex than would be inferred by extrapolating the results of in vivo studies with (-)-delta 9-tetra-hydrocannabinol or synthetic cannabinoids.
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PMID:Anandamide, an endogenous cannabinoid, inhibits calcium currents as a partial agonist in N18 neuroblastoma cells. 837 11

Translocation of [3H]dopamine and binding of [3H]WIN 35,428 were measured in intact C6 glioma cells expressing the cloned human dopamine transporter (hDAT) under identical conditions of assay buffer (phosphate-Krebs) and temperature (25 degrees C) with uptake at initial velocity and binding at equilibrium. In the intact cells, [3H]dopamine uptake was a one-component process; in contrast, [3H]WIN 35,428 binding included both a high-affinity component, inhibitable by micromolar concentrations of dopamine, and a low-affinity component only partially inhibited by millimolar concentrations of dopamine. Binding (high-affinity) over uptake Ki ratios were on the average 2.3 for the inhibitors WIN 35,428, cocaine, GBR 12909, and BTCP. The potency of dopamine in inhibiting its own translocation was close to that in inhibiting [3H]WIN 35,428 binding consonant with a more rapid reorientation step of the DAT in the C6-hDAT system than in rat striatal synaptosomes. The similarity in turnover values of the DAT estimated in the current experiments with the C6-hDAT system and in our previous study on rat striatal synaptosomes, performed under comparable conditions, suggest that all DAT's inserted into the C6 cell membrane are functionally active.
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PMID:Translocation of dopamine and binding of WIN 35,428 measured under identical conditions in cells expressing the cloned human dopamine transporter. 887 59

Binding sites for 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)[3H]tropane ([3H]WIN 35,428) on the human dopamine transporter expressed in C6 glioma cells were alkylated with N-ethylmaleimide (NEM), and the protective potency of the blockers cocaine, N[1-(2-benzo[b]thiophenyl) cyclohexyl]piperidine (BTCP), and benztropine, and of the substrates dopamine, d-amphetamine, and norepinephrine was measured. In general, the protective potency was lower (at least 4-5 times) than the potency in inhibiting [3H]WIN 35,428 binding with the compounds present under the same experimental conditions used for the NEM alkylation. However, the disparity was substantially greater for all substrates tested (23- to 44-fold) than for the blockers (4- to 11-fold), especially cocaine (5-fold) and BTCP (4-fold). Benztropine took an intermediate place (11-fold) between cocaine (5-fold) and BTCP (4-fold), on the one hand, and dopamine (23-fold), on the other hand. [3H]WIN 35,428 binding was best described by a one-site model under the present conditions. The results are discussed in terms of models involving blocker-induced conformational changes and overlapping nonidentical binding domains for blockers and substrates.
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PMID:Binding domains for blockers and substrates on the cloned human dopamine transporter studied by protection against N-ethylmaleimide-induced reduction of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)[3H]tropane ([3H]WIN 35,428) binding. 893 55

The role of arachidonic acid was examined in the regulation of dopamine transport in C6 glioma cells stably expressing the human dopamine transporter. Exogenously added arachidonic acid (20-160 microM) stimulated [3H]dopamine uptake when pre-incubated for short times (15-30 min); 160 microM arachidonic acid inhibited following longer pre-exposures (45-60 min). Under the same conditions, only decreases were observed in the binding of the cocaine analog [3H]2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane ([3H]WIN 35,428). The reduction in dopamine transporter activity by arachidonic acid (at 160 microM for 60 min) was caused by a decrease in the Vmax (from 202 to 44 pmol/mg/min) opposed by a smaller reduction in K(m) (from 1.2 to 0.8 microM), whereas the effect of arachidonic acid (at 160 microM for 15 min) on [3H]WIN 35,428 binding was caused by a reduction in the Bmax (from 1.8 to 1.3 pmol/mg) without a change in Kd (7.2 nM). Upon 15-min exposure, melittin, an activator of phospholipase A2, and nordihydroguaiaretic acid, a lipooxygenase inhibitor, both expected to cause enhanced endogenous arachidonic acid, inhibited [3H]dopamine uptake and [3H]WIN 35,428 binding with an IC50 value close to 1 microM, whereas thimerosal, which raises arachidonic acid by inhibiting lipid reacylation, caused similar reductions at the sub-millimolar level. Co-presence of stauroporine (0.3-2 microM), an inhibitor of protein kinase C, had little or no effect on the melittin- or arachidonic acid-induced inhibition of [3H]dopamine uptake. Both the melittin- and arachidonic acid-, but not phorbol 12-myristate 13-acetate-induced inhibition of uptake were counteracted by bovine serum albumin (0.1 and 1 mg/ml) which binds arachidonic acid. The data taken together suggest that the inhibitory effects of arachidonic acid activators and those of protein kinase C activators on dopamine uptake are mediated by separate mechanisms.
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PMID:Regulation of the functional activity of the human dopamine transporter by the arachidonic acid pathway. 898 75

The role of protein kinase C (PKC) was examined in the regulation of dopamine transport in C6 glioma cells stably expressing the human dopamine transporter. The PKC activating phorbol esters phorbol 12-myristate 13-acetate (PMA) and 4 beta-12,13-dibutyrate phorbol-ester (PDBu) inhibited [3H]dopamine uptake concentration dependently. These effects were attenuated by the PKC inhibitor staurosporine but were unaltered by another inhibitor, chelerythrine, or the phosphatase inhibitor okadaic acid. The potency of PMA in inhibiting [3H]dopamine uptake was similar to that in inhibiting the binding of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane ([3H]WIN 35,428), and again staurosporine, but not chelerythrine, weakened the effect of PMA. The reduction in dopamine transporter activity by PMA was caused by a decrease in the Vmax value of [3H]dopamine uptake, opposed by a smaller reduction in the Km value, whereas the effect of PMA on [3H]WIN 35,428 binding was caused by a reduction in the Bmax value without a change in the Kd value. The lower Km value in the presence of PMA was accompanied by a higher IC50 of dopamine in inhibiting [3H]WIN 35,428 binding; the latter effect was attenuated by the co-presence of staurosporine. The results are discussed in the context of transporter loss from the cell surface, or a model with phosphorylation affecting the shared dopamine and WIN 35,428 binding domain on the transporter as well as affecting a part of the dopamine binding domain lying outside that for WIN 35,428.
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PMID:Regulation of the functional activity of the human dopamine transporter by protein kinase C. 911 87

It has been suggested that cocaine and mazindol bind to separate sites on the dopamine transporter. In the present study, we address this issue by examining the inhibition by mazindol of the binding of [3H]WIN 35,428 ([3H]2beta-carbomethyoxy-3beta-(4-fluorophenyl)-tropane), a phenyltropane analog of cocaine, and the inhibition by WIN 35,428 of [3H]mazindol binding to the cloned human dopamine transporter expressed in C6 glioma cells. The design involved the construction of inhibition curves at six widely different radioligand levels, enabling the distinction between the nonlinear hyperbolic competition (i.e., negative allosteric) model and the competitive (i.e., mutually exclusive binding) model. Nonlinear computer curve-fitting analysis indicated no difference in the goodness of fit between the two models; the negative allosteric model indicated an extremely high allosteric constant of approximately > or = 100, which practically equates to the competitive model. The present results suggest that complex interactions reported between cocaine and mazindol in inhibiting dopamine transport are beyond the level of ligand recognition.
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PMID:WIN 35,428 and mazindol are mutually exclusive in binding to the cloned human dopamine transporter. 926 59

The present study addresses the possibility that there are different cocaine-related and mazindol-related binding domains on the dopamine transporter (DAT) that show differential sensitivity to cations. The effects of Zn2+, Mg2+, Hg2+, Li+, K+, and Na+ were assessed on the binding of [3H]mazindol and [3H]WIN 35,428 to the human (h) DAT expressed in C6 glioma cells under identical conditions for intact cell and membrane assays. The latter were performed at both 0 and 21 degrees C. Zn2+ (30-100 microM) stimulated binding of both radioligands to membranes, with a relatively smaller effect for [3H]mazindol; Mg2+ (0.1-100 microM) had no effect; Hg2+ at approximately 3 microM stimulated binding to membranes, with a relatively smaller effect for [3H]mazindol than [3H]WIN 35,428 at 0 degrees C, and at 30-100 microM inhibited both intact cell and membrane binding; Li+ and K+ substitution (30-100 mM) inhibited binding to membranes more severely than to intact cells; and Na+ substitution was strongly stimulatory. With only a few exceptions, the patterns of ion effects were remarkably similar for both radioligands at both 0 and 21 degrees C, suggesting the involvement of common binding domains on the hDAT impacted similarly by cations. Therefore, if there are different binding domains for WIN 35,428 and mazindol, these are not affected differentially by the cations studied in the present experiments, except for the stimulatory effect of Zn2+ at 0 and 21 degrees C and Hg2+ at 0 degrees C.
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PMID:Cations affect [3H]mazindol and [3H]WIN 35,428 binding to the human dopamine transporter in a similar fashion. 928 33

1. Aminoalkylindoles, typified by WIN 55212-2, bind to G protein-coupled cannabinoid receptors in brain. Although cannabinoids inhibit adenylyl cyclase in NG108-15 neuroblastoma x glioma hybrid cells, cannabinoid receptor binding in these cells has not been described previously. This study compares pharmacological characteristics of [3H]WIN 55212-2 binding sites in rat cerebellar membranes and in NG108-15 membranes. 2. Although the KD of specified [3H]WIN 55212-2 binding was similar in brain and NG108-15 membranes, the Bmax was 10 times lower in NG108-15 than in cerebellar membranes. In both brain and NG108-15 membranes, aminoalkylindole analogues were relatively potent in displacing [3H]WIN 55212-2 binding. However, IC50 values for more traditional cannabinoids were significantly higher in NG108-15 membranes than in brain, e.g., the Ki values for CP55,940 were 1.2 nM in brain and > 5000nM in NG108-15 membranes. Moreover, sodium and GTP-gamma-S decreased [3H]WIN 55212-2 binding in brain but not in NG108-15 membranes. 3. These data suggest that WIN 55212-2 does not label traditional cannabinoid receptors in NG108-15 cells and that these novel aminoalkylindole binding sites are not coupled to G proteins.
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PMID:Binding of aminoalkylindoles to noncannabinoid binding sites in NG108-15 cells. 935 90

Delta9-Tetrahydrocannabinol, the main active component of marijuana, induces apoptosis of transformed neural cells in culture. Here, we show that intratumoral administration of Delta9-tetrahydrocannabinol and the synthetic cannabinoid agonist WIN-55,212-2 induced a considerable regression of malignant gliomas in Wistar rats and in mice deficient in recombination activating gene 2. Cannabinoid treatment did not produce any substantial neurotoxic effect in the conditions used. Experiments with two subclones of C6 glioma cells in culture showed that cannabinoids signal apoptosis by a pathway involving cannabinoid receptors, sustained ceramide accumulation and Raf1/extracellular signal-regulated kinase activation. These results may provide the basis for a new therapeutic approach for the treatment of malignant gliomas.
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PMID:Anti-tumoral action of cannabinoids: involvement of sustained ceramide accumulation and extracellular signal-regulated kinase activation. 1070 Feb 20


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