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D Rueda

Publications and source records attributed to D Rueda.

11 recordsLinked to original sources
PubMed2001

Inhibition of glioma growth in vivo by selective activation of the CB(2) cannabinoid receptor.

The development of new therapeutic strategies is essential for the management of gliomas, one of the most malignant forms of cancer. We have shown previously that the growth of the rat glioma C6 cell line is inhibited by psychoactive cannabinoids (I. Galve-Roperh et al., Nat. Med., 6: 313-319, 2000). These compounds act on the brain and some other organs through the widely expressed CB(1) receptor. By contrast, the other cannabinoid receptor subtype, the CB(2) receptor, shows a much more restricted distribution and is absent from normal brain. Here we show that local administration of the selective CB(2) agonist JWH-133 at 50 microg/day to Rag-2(-/-) mice induced a considerable regression of malignant tumors generated by inoculation of C6 glioma cells. The selective involvement of the CB(2) receptor in this action was evidenced by: (a) the prevention by the CB(2) antagonist SR144528 but not the CB(1) antagonist SR141716; (b) the down-regulation of the CB(2) receptor but not the CB(1) receptor in the tumors; and (c) the absence of typical CB(1)-mediated psychotropic side effects. Cannabinoid receptor expression was subsequently examined in biopsies from human astrocytomas. A full 70% (26 of 37) of the human astrocytomas analyzed expressed significant levels of cannabinoid receptors. Of interest, the extent of CB(2) receptor expression was directly related with tumor malignancy. In addition, the growth of grade IV human astrocytoma cells in Rag-2(-/-) mice was completely blocked by JWH-133 administration at 50 microg/day. Experiments carried out with C6 glioma cells in culture evidenced the internalization of the CB(2) but not the CB(1) receptor upon JWH-133 challenge and showed that selective activation of the CB(2) receptor signaled apoptosis via enhanced ceramide synthesis de novo. These results support a therapeutic approach for the treatment of malignant gliomas devoid of psychotropic side effects.

Animals↗
PubMed2001

The CB(1) cannabinoid receptor of astrocytes is coupled to sphingomyelin hydrolysis through the adaptor protein fan.

Cannabinoids exert most of their effects through the CB(1) receptor. This G protein-coupled receptor signals inhibition of adenylyl cyclase, modulation of ion channels, and stimulation of mitogen- and stress-activated protein kinases. In this article, we report that Delta(9)-tetrahydrocannabinol (THC), the major active component of marijuana, induces sphingomyelin hydrolysis in primary astrocytes but not in other cells expressing the CB(1) receptor, such as primary neurons, U373 MG astrocytoma cells, and Chinese hamster ovary cells transfected with the CB(1) receptor cDNA. THC-evoked sphingomyelin breakdown in astrocytes was also exerted by the endogenous cannabinoid anandamide and the synthetic cannabinoid HU-210 and was prevented by the selective CB(1) antagonist SR141716. By contrast, the effect of THC was not blocked by pertussis toxin, pointing to a lack of involvement of G(i/o) proteins. A role for the adaptor protein FAN in CB(1) receptor-coupled sphingomyelin breakdown is supported by two observations: 1) coimmunoprecipitation experiments show that the binding of FAN to the CB(1) receptor is enhanced by THC and prevented by SR141716; 2) cells expressing a dominant-negative form of FAN are refractory to THC-induced sphingomyelin breakdown. This is the first report showing that a G-protein-coupled receptor induces sphingomyelin hydrolysis through FAN and that the CB(1) cannabinoid receptor may signal independently of G(i/o) proteins.

Adenylate Cyclase Toxin↗
PubMed2000

The CB(1) cannabinoid receptor is coupled to the activation of c-Jun N-terminal kinase.

Cannabinoids exert most of their effects through the CB(1) receptor. This G-protein-coupled receptor has been shown to be functionally coupled to inhibition of adenylyl cyclase, modulation of ion channels, and activation of extracellular signal-regulated kinase. Using Chinese hamster ovary cells stably transfected with the CB(1) receptor cDNA, we show here that Delta(9)-tetrahydrocannabinol (THC), the major active component of marijuana, induces the activation of c-Jun N-terminal kinase (JNK). Western blot analysis showed that both JNK-1 and JNK-2 were stimulated by THC. The effect of THC was also exerted by endogenous cannabinoids (anandamide and 2-arachidonoylglycerol) and synthetic cannabinoids (CP-55,940, HU-210, and methanandamide), and was prevented by the selective CB(1) antagonist SR141716. Pertussis toxin, wortmannin, and a Ras farnesyltransferase inhibitor peptide blocked, whereas mastoparan mimicked, the CB(1) receptor-evoked activation of JNK, supporting the involvement of a G(i)/G(o)-protein, phosphoinositide 3'-kinase and Ras. THC-induced JNK stimulation was prevented by tyrphostin AG1296, pointing to the implication of platelet-derived growth factor receptor transactivation, and was independent of ceramide generation. Experiments performed with several types of neural cells that endogenously express the CB(1) receptor suggested that long-term JNK activation may be involved in THC-induced cell death. The CB(1) cannabinoid receptor was also shown to be coupled to the activation of p38 mitogen-activated protein kinase. Data indicate that activation of JNK and p38 mitogen-activated protein kinase may be responsible for some of the cellular responses elicited by the CB(1) cannabinoid receptor.

Animals↗
PubMed1999

Involvement of the cAMP/protein kinase A pathway and of mitogen-activated protein kinase in the anti-proliferative effects of anandamide in human breast cancer cells.

Anandamide (ANA) inhibits prolactin- and nerve growth factor (NGF)-induced proliferation of human breast cancer cells by decreasing the levels of the 100 kDa prolactin receptor (PRLr) and the high affinity trk NGF receptor, respectively, and by acting via CB(1)-like cannabinoid receptors. However, the intracellular signals that mediate these effects are not known. Here, we show that, in MCF-7 cells: (i) forskolin and the mitogen-activated protein kinase (MAPK) kinase inhibitor PD098059 prevent, and the protein kinase A inhibitor RpcAMPs mimics, the inhibitory effects of ANA on cell proliferation and PRLr/trk expression and (ii) ANA inhibits forskolin-induced cAMP formation and stimulates Raf-1 translocation and MAPK activity, in a fashion sensitive to the selective CB(1) antagonist SR141716A. ANA stimulation of MAPK was enhanced by inhibitors of ANA hydrolysis. Forskolin inhibited MAPK and ANA-induced Raf-1 translocation. These findings indicate that, in MCF-7 cells, ANA inhibits adenylyl cyclase and activates MAPK, thereby exerting a down-regulation on PRLr and trk levels and a suppression of cell proliferation.

Arachidonic Acids↗
PubMed1998

Involvement of sphingomyelin hydrolysis and the mitogen-activated protein kinase cascade in the Delta9-tetrahydrocannabinol-induced stimulation of glucose metabolism in primary astrocytes.

The effects of cannabinoids on metabolic pathways and signal transduction systems were studied in primary cultures of rat astrocytes. Delta9-Tetrahydrocannabinol (THC), the major active component of marijuana, increased the rate of glucose oxidation to CO2 as well as the rate of glucose incorporation into phospholipids and glycogen. These effects of THC were mimicked by the synthetic cannabinoid HU-210, and prevented by forskolin, pertussis toxin, and the CB1 receptor antagonist SR 141716. THC did not affect basal cAMP levels but partially antagonized the forskolin-induced elevation of intracellular cAMP concentration. THC stimulated p42/p44 mitogen-activated protein kinase (MAPK) activity, Raf-1 phosphorylation, and Raf-1 translocation to the particulate cell fraction. In addition, the MAPK inhibitor PD 098095 and the phosphoinositide 3-kinase inhibitors wortmannin and LY 294002 were able to antagonize the THC-induced stimulation of glucose oxidation to CO2, phospholipid synthesis and glycogen synthesis. The possible involvement of sphingomyelin breakdown in the metabolic effects of THC was studied subsequently. THC produced a rapid stimulation of sphingomyelin hydrolysis that was concomitant to an elevation of intracellular ceramide levels. This effect was prevented by SR 141716. Moreover, the cell-permeable ceramide analog D-erythro-N-octanoylsphingosine, as well as exogenous sphingomyelinase, were able in turn to stimulate MAPK activity, to increase the amount of Raf-1 bound to the particulate cell fraction, and to stimulate glucose metabolism. The latter effect was prevented by PD 098059 and was not additive to that exerted by THC. Results thus indicate that THC produces a cannabinoid receptor-mediated stimulation of astrocyte metabolism that seems to rely on sphingomyelin hydrolysis and MAPK stimulation.

Animals↗
PubMed1998

Use of the Gamma nail in the treatment of fractures of the proximal femur.

Fractures of the proximal femur are, more than ever, an important challenge in the field of traumatology. The Gamma nail, a combination of advantages of the sliding screw with the intramedullary nail, represents an efficient technique in the management of these fractures. A series of 224 fractures of the proximal femur in which this nail was used is reported. The average age of the patients was 79.2 years. The mean healing time was 68.2 days in 99.4% of the cases. The incidence of perioperative complications was 10.3% showing that, in most of the cases, the complications occurred because of poor technique. Postoperative complications occurred with an incidence of 14.1%. Seven cases of migration of a proximal screw, six shaft fractures, and one broken nail were the most important complications. The device allowed for early mobilization and full weightbearing of the affected hip regardless of the type of fracture. With adequate surgical technique and experience, the advantages of the Gamma nail increases as the complication rate diminishes.

Adult↗
PubMedDate not supplied

In the fluorescent spotlight: global and local conformational changes of small catalytic RNAs.

RNA is a ubiquitous biopolymer that performs a multitude of essential cellular functions involving the maintenance, transfer, and processing of genetic information. RNA is unique in that it can carry both genetic information and catalytic function. Its secondary structure domains, which fold stably and independently, assemble hierarchically into modular tertiary structures. Studies of these folding events are key to understanding how catalytic RNAs (ribozymes) are able to position reaction components for site-specific chemistry. We have made use of fluorescence techniques to monitor the rates and free energies of folding of the small hairpin and hepatitis delta virus (HDV) ribozymes, found in satellite RNAs of plant and the human hepatitis B viruses, respectively. In particular, fluorescence resonance energy transfer (FRET) has been employed to monitor global conformational changes, and 2-aminopurine fluorescence quenching to probe for local structural rearrangements. In this review we illuminate what we have learned about the reaction pathways of the hairpin and HDV ribozymes, and how our results have complemented other biochemical and biophysical investigations. The structural transitions observed in these two small catalytic RNAs are likely to be found in many other biological RNAs, and the described fluorescence techniques promise to be broadly applicable.

2-Aminopurine↗