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E Borrelli

Publications and source records attributed to E Borrelli.

At least 55 records · Page 3Linked to original sources
PubMed1997

Antiproliferative role of dopamine: loss of D2 receptors causes hormonal dysfunction and pituitary hyperplasia.

The function of dopamine (DA) in the nervous system is paralleled by its neuroendocrine control of pituitary gland functions. Here, we document the neuroendocrine function of dopamine by studying the pituitary gland of mice lacking DA D2 receptors (D2R). These mice present a striking, progressive increase in lactotroph number, which ultimately leads to tumors in aged animals. Females develop tumors much earlier than males. An estrogen-mediated lactotroph proliferation cannot account for this sexual dimorphism, since D2R-null females are hypoestrogenic and, thus, have estrogen levels similar to males. In contrast, prolactin levels are six times higher in females than in males. We show that active prolactin receptors are present in the pituitary and their expression increases in concomitance with tumor expansion. These results point to prolactin as an autocrine proliferative factor in the pituitary gland. Additionally, they demonstrate an antiproliferative function for DA regulated through D2 receptor activation.

Animals↗
PubMed1997

Reduction of oxidative stress does not affect recovery of myocardial function: warm continuous versus cold intermittent blood cardioplegia.

OBJECTIVE: To compare oxidative stress after cardiac surgery in patients treated with two different methods of myocardial protection: warm continuous versus cold intermittent blood cardioplegia. To correlate oxidative stress with postoperative myocardial dysfunction. DESIGN: Prospective, randomised, double blind, trial. SETTING: Institutional centre of cardiovascular surgery. PATIENTS: 20 patients were selected for coronary artery bypass surgery (CABG) on the following basis: stable angina, ejection fraction > 50%, double or triple vessel disease, no previous CABG or associated disease. Patients were randomised to two groups of 10 patients each. INTERVENTIONS: Patients underwent CABG with one of two different methods of myocardial protection and cardiopulmonary bypass. CBC group: intermittent cold blood antegrade-retrograde cardioplegia with moderate hypothermic cardiopulmonary bypass; WBC group: continuous warm blood antegrade-retrograde cardioplegia with mild hypothermic cardiopulmonary bypass. MAIN OUTCOME MEASURE: The index of oxidative stress used was the alteration of whole blood and plasma glutathione redox status. Samples were collected from the coronary sinus and peripheral vein before anaesthesia (T1), before aortic unclamping (T2), 15 minutes (T3), and 30 minutes (T4) after unclamping. Haemodynamic parameters were measured with thermodilution techniques. RESULTS: Oxidised glutathione and glutathione-cysteine mixed disulphide significantly increased in the coronary sinus plasma in the CBC group, and the overall redox balance of glutathione was decreased (P < 0.01) at T2-T4 versus T1, and compared with the WBC group. Comparable results were obtained for coronary sinus blood. There was no correlation between postoperative haemodynamic measurements and oxidative stress markers. CONCLUSIONS: Oxidative stress was significant in patients undergoing CABG using cold blood cardioplegia, while the warm technique minimised the effects of ischaemia. However, oxidative stress was not correlated with myocardial dysfunction following CABG.

Analysis of Variance↗
PubMed1997

Dopamine D2 receptors in signal transduction and behavior.

The dopamine D2 receptor belongs to the family of seven transmembrane domain G-protein-coupled receptors and is highly expressed in the central nervous system and the pituitary gland. The binding of dopamine to the D2 receptor is crucial for the regulation of diverse physiological functions, such as the control of locomotor activity and the synthesis of peptide hormones. Two alternatively spliced transcripts are generated from the D2 receptor gene and code for the D2L and D2S isoforms, which are 444 and 415 amino acids in length, respectively. These isoforms exhibit similar pharmacological characteristics and are expressed in the same cell types, with a ratio that normally favors expression of the longer isoform. The D2L isoform differs from D2S by the insertion of 29 amino acids in the putative third intracellular loop of the receptor. This loop is involved in the coupling of the receptor to different G proteins. Experiments have shown that the D2 isoforms have different G-protein-coupling affinities, suggesting that these receptors might serve different functions in vivo. Additionally, this difference in coupling affinity could be a mechanism to amplify the signal transduced by the binding of dopamine to D2 receptors. Important insights into D2 receptor function in vivo have been obtained by knocking out the D2 gene in mice. The Parkinsonian-like phenotype of D2-null mice demonstrates the importance of the D2 receptor for locomotor function.

Alternative Splicing↗
PubMed1996

Plasma concentrations of cytokines, their soluble receptors, and antioxidant vitamins can predict the development of multiple organ failure in patients at risk.

OBJECTIVES: The aims of this study were: a) to evaluate plasma concentrations of cytokines and their soluble receptors, as well as antioxidant substances in patients at high risk of developing multiple organ failure; b) to investigate early change: and c) to examine the possible prognostic value of these elements. DESIGN: Prospective analysis. SETTING: Surgical intensive care unit (ICU) of a university hospital. PATIENTS: sixteen patients at risk for multiple organ failure. MEASUREMENTS AND MAIN RESULTS: Ten patients developed multiple organ failure and five of them died. Whereas tumor necrosis factor-alpha (TNF-alpha) plasma concentrations were only borderline higher in patients developing multiple organ failure, TNF-soluble receptors 55 and 75 were significantly increased during all ICU days compared with patients not going into organ failure. Interleukin-6 plasma concentrations were higher in patients developing multiple organ failure during the first 2 days after ICU admission. The antioxidant vitamin C was significantly decreased in patients going into multiple organ failure during all ICU days. Other biochemical markers of antioxidant activity, such as vitamin E, copper, and zinc plasma concentrations, did not differ between the two groups. CONCLUSIONS: Our data suggest that there is a marked increase in anti-TNF activity and a decrease of antioxidant defense in patients at risk of developing multiple organ failure. The predictive value of plasma concentrations of circulating TNF-soluble receptors and vitamin C in this type of patient needs further evaluation.

Adult↗
PubMed1995

Parkinsonian-like locomotor impairment in mice lacking dopamine D2 receptors.

Dopaminergic neuronal pathways arise from mesencephalic nuclei and project axons to the striatum, cortex, limbic system and hypothalamus. Through these pathways dopamine affects many physiological functions, such as the control of coordinated movement and hormone secretion. Here we have studied the physiological involvement of the dopamine D2 receptors in dopaminergic transmission, using homologous recombination to generate D2-receptor-deficient mice. Absence of D2 receptors leads to animals that are akinetic and bradykinetic in behavioural tests, and which show significantly reduced spontaneous movements. This phenotype presents analogies with symptoms characteristic of Parkinson's disease. Our study shows that D2 receptors have a key role in the dopaminergic control of nervous function. These mice have therapeutic potential as a model for investigating and correcting dysfunctions of the dopaminergic system.

Animals↗
PubMed1995

Alternative splicing of the dopamine D2 receptor directs specificity of coupling to G-proteins.

Two isoforms of the dopamine D2 receptor have been characterized, D2L (long) and D2S (short), generated by alternative splicing from the same gene. They differ by an in-frame insert of 29 amino acids specific to D2L within the putative third intracytoplasmic loop of the receptor. We have previously demonstrated (Montmayeur, J.-P., Guiramand, J., and Borelli, E. (1993) Mol. Endocrinol. 7, 161-170) that D2S and D2L, although presenting very similar pharmacological profiles, couple differently to the alpha-subunit of guanine nucleotide-binding regulatory proteins (G-proteins). In particular, D2L, but not D2S, requires the presence of the alpha-subunit of the inhibitory G-protein (G alpha i2) to elicit greater inhibition of adenylyl cyclase activity. The insert present in D2L must therefore confer the specificity of interaction with G alpha i2. Thus, we introduced substitution mutations within the D2L insert. These mutant receptors were expressed in JEG3 cells, a G alpha i2-deficient cell line, scoring for those presenting an increased inhibition of adenylyl cyclase by dopamine. Our analysis identified two mutants, S259/262A and D249V, with these properties. These results clearly show that the insert present in D2L plays a critical role in the selectivity for the G-proteins interacting with the receptor.

Adenylyl Cyclase Inhibitors↗
PubMed1995

In vitro cytokine production and T-cell proliferation in patients undergoing cardiopulmonary by-pass.

Cardiac surgery, employing cardiopulmonary by-pass (CPB), has long been associated with a generalized immunosuppression. To further understand the complex physiological and immunological changes related to CPB, we decided to investigate whether CPB affects the immune response, with regard to T-cell activation and cytokine production. Using phytohaemagglutinin (PHA) as mitogen and peripheral blood mononuclear cells (PBMC) isolated from patients undergoing CPB, we investigated whether this procedure has any effect on interferon-gamma(IFN-gamma) and other cytokine production and/or PBMC proliferation. Comparisons were made between the responsiveness of PBMC obtained before, during and at the end of CPB. In all patients, CPB significantly reduces IFN-gamma and interleukin 2 (IL-2) production in response to PHA. On the other hand, tumour necrosis factor-alpha (TNF-alpha) production was also significantly diminished, while interleukin 6 (IL-6), interleukin 1 beta (IL-1 beta) and interleukin 8 (IL-8) release in response to PHA was not significantly affected. Reduced IFN-gamma, IL-2 and TNF-alpha production was associated with a significant decrease in PBMC proliferation. These results might be related to the mechanical damage on blood cells described during extracorporeal circulation procedures as well as the release of immunosuppressive factors during surgery. The immunosuppression observed during CPB may play an important role in the development of infectious complications after CPB.

Cardiopulmonary Bypass↗
PubMed1994

Targeting of G alpha i2 to the Golgi by alternative spliced carboxyl-terminal region.

Heterotrimeric guanosine triphosphate (GTP)-binding proteins (G proteins) may participate in membrane traffic events. A complementary DNA (cDNA) was isolated from a mouse pituitary cDNA library that corresponded to an alternatively spliced form of the gene encoding the G protein alpha subunit G alpha i2. The cDNA was identical to that encoding G alpha i2 except that the region encoding for the carboxyl-terminal 24 amino acids was replaced by a longer region encoding 35 amino acids that have no sequence similarity with G alpha i2 or other members of the G protein family. This alternative spliced product and the corresponding protein (sGi2) were present in several tissues. Specific antibodies revealed that sGi2 was localized in the Golgi apparatus, suggesting a role in membrane transport. Thus, alternative splicing may generate from a single gene two G protein alpha subunits with differential cellular localization and function.

Alternative Splicing↗
PubMed1993

Preferential coupling between dopamine D2 receptors and G-proteins.

The D2 dopamine receptor, an inhibitor of adenylyl cyclase, belongs to the family of seven transmembrane domain G-protein-coupled receptors. This receptor is encoded by two mRNAs produced from the same gene by alternative splicing, here referred to as D2L and D2S. The resultant proteins are identical except for an insertion of 29 amino acids in the putative third intracytoplasmic domain. This domain has been shown to be important for the coupling of this family of receptors to G-proteins. We have previously shown that there is differential inhibition of the adenylyl cyclase activity when these two receptors are produced in JEG3 cells; D2S is more efficient than D2L. To understand the molecular basis of such differential activity, we analyzed the G-proteins expressed in these cells. Here we show that G alpha i2 is absent in this cell line. Moreover, it is possible to restore the same inhibitory activity obtained by D2S when an expression vector encoding this alpha-subunit is cotransfected with D2L. In addition, transfections of the two receptors in a recipient cell line containing the three G alpha i subtypes confirm that the two receptors behave similarly. We conclude that the 29-amino acid insertion present in D2L allows it to interact specifically with G alpha i2. These data suggest that in vivo the function of activated D2 receptors is exerted by specific interactions with Gi-protein subtypes.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Pituitary hyperplasia induced by ectopic expression of nerve growth factor.

Nerve growth factor (NGF) cDNA was fused to the rat prolactin promoter to induce its ectopic expression in pituitary lactotrophs of transgenic mice. High-level expression of both RNA and functional protein was achieved in two pedigrees. Pituitary cells from these animals secreted biologically active NGF that was capable of inducing rapid differentiation of cocultured PC12 pheochromocytoma cells. Despite this robust expression, transgenic pituitaries failed to show any detectable increase in neuronal innervation. Unexpectedly, we observed a dramatic hyperplasia of lactotrophs resulting in pituitaries 10-100 times larger than normal. These results suggest that NGF, in addition to its previously described effects, may act as a new class of mitogen, with a potential role in oncogenesis.

Adrenal Gland Neoplasms↗
PubMed1992

NKD, a developmentally regulated tachykinin receptor in Drosophila.

A number of neuropeptides have been described which are present in the insect nervous system. The physiological role of these neuropeptides has not yet been clarified. We have characterized a Drosophila melanogaster cDNA coding for a protein, NKD, whose sequence resembles that of mammalian G protein-coupled neuropeptide receptors. This protein shows 38% homology with the mammalian tachykinin NK3 receptor within the transmembrane domain region. Stable cell lines expressing this cDNA are responsive to Locusta migratoria tachykinin but not to other peptides of the tachykinin family. The expression of this gene is detected principally in adult fly heads, but also in the adult body and in embryos. Interestingly, NKD mRNA is detected at very early stages of Drosophila embryonic development (3 h) and reaches the highest level of expression at 12-16 h, a time which correlates with the period of major neuronal development. In situ hybridization experiments demonstrate that NKD is expressed in the central nervous system, as well as in subsets of neurons in each segment of the developing ventral ganglia. The cytological localization of this gene is at position 86C on the Drosophila third chromosome.

3T3 Cells↗
PubMed1992

Chronic administration of NMDA antagonists induces D2 receptor synthesis in rat striatum.

Dopamine D2 receptor gene expression was examined in rat striatum after chronic treatment with N-methyl-D-aspartate (NMDA) receptor antagonists (ketamine at 15 mg/kg/day or MK-801 at 0.1, 0.2 and 0.4 mg/kg/day per os, for 50 days). The long-isoform mRNA, as well as the total D2 mRNA expression were induced. No change was noticed in striatal dopamine release or turnover. D2 binding studies carried out in MK-801 chronically treated (0.3 mg/kg/day per os, for 50 days) and control rats revealed an increased receptor density in treated animals without a significant change in receptor affinity. These results suggest that the synthesis of both striatal D2 receptor isoforms is postsynaptically regulated at the transcriptional level, by events triggered by glutamate through the NMDA-type receptor.

Animals↗
PubMed1992

Induction of D2 dopamine receptor mRNA synthesis in a 6-hydroxydopamine parkinsonian rat model.

By injecting 6-hydroxydopamine into the pars compacta of the substantia nigra, we produced a hemiparkinsonian rat model in which there is almost complete destruction of the dopaminergic nigrostriatal pathway but sparing of the dopaminergic mesolimbic system. The lesion has been characterized by several criteria: a rotational behavior in response to apomorphine, a complete loss of tyrosine hydroxylase immunoreactivity in the lesioned substantia nigra, a near total depletion of dopamine and metabolites in the striatum ipsilateral to the lesion, and a supersensitivity of the dopamine D2 receptors in the ipsilateral striatum. Dopaminergic striatal deafferentation was accompanied by an increase of D2 receptor mRNA synthesis in the striatum ipsilateral to the lesion, suggesting that the increased D2 receptor density observed after the lesion is due to an increase of the synthesis of receptor molecules. This synthesis appears to be regulated at the transcriptional level.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Mutations in signal transduction pathways and inherited diseases.

Intracellular signal transduction pathways have central roles in processes such as growth, differentiation, neurotransmission and development. The aberrant expression of components of various signal transduction pathways has profound consequences for cellular functions. Recent findings indicate that many cases of neoplasia and inherited diseases have, at their roots, mutations in key steps of signalling pathways.

Animals↗
PubMed1992

Signal transduction and gene control: the cAMP pathway.

The transcriptional activity of a gene can be regulated by a multitude of trans-acting factors that interact with specific cis-acting elements, mostly located in the promoter regions. The function of transcription factors is modulated by intracellular signal transduction pathways, which are activated by specific ligands binding to the appropriate membrane receptors. Here we discuss the links between the activation of the adenylyl cyclase pathway and the transcriptional response of cAMP-inducible genes that is achieved by the interplay of a multitude of nuclear transcription factors such as CREB and CREM.

Adenylyl Cyclases↗
PubMed1991

Transcription mediated by a cAMP-responsive promoter element is reduced upon activation of dopamine D2 receptors.

Dopaminergic D2 receptors mediate the effect of dopamine on cellular effector systems by means of guanine nucleotide-binding proteins (G proteins). The major biochemical effect evoked by these receptors is the inhibition of adenylyl cyclase. As a consequence, the activation of D2 receptors lowers the intracellular cAMP level. Two cDNAs, originated by alternative splicing of the same gene, have been isolated: D2A and D2B. They code for two proteins of 444 and 415 amino acids. These proteins display high affinity for selective D2 dopamine ligands. D2A differs from D2B by an insertion of 87 nucleotides in its cDNA, which is located in a region of the protein considered important for the coupling to G proteins. To investigate functional differences between the two dopamine D2 receptor isoforms, we transiently expressed them in cultured cells. To do so we developed an assay to study membrane receptors that are coupled to the adenylyl cyclase. Using this assay, we were able to show that the stimulation of the adenylyl cyclase induced by the activation of the beta 2-adrenergic receptor is inhibited more efficiently by D2B than D2A. The effects elicited by the D2 receptors are mediated by pertussis toxin-sensitive G proteins. Treatment of transfected cells with pertussis toxin abolishes the inhibitory effects in a dose- and receptor isoform-dependent manner. Our results suggest that the two dopamine receptor isoforms are differentially coupled to G proteins.

Adenylate Cyclase Toxin↗