Biomedical subjects

G Cremaschi

Publications and source records attributed to G Cremaschi.

At least 19 recordsLinked to original sources

PubMed2000

Intracellular signals coupled to muscarinic acetylcholine receptor activation in cerebral frontal cortex from hypoxic mice.

1. The aim of the present work was to determine hypoxia-induced modifications in the cascade of intracellular events coupled to muscarinic acetylcholine receptor (mAChR) activation in brain. For this purpose, enzymatic activities were measured on normoxically incubated frontal cortical slices from mice exposed to hypobaric hypoxia for 72 hr. 2. We found that hypoxia induced alterations in several cerebral enzymatic basal activities: it increased nitric oxide synthase (NOS), but it decreased both membrane protein kinase C (PKC) and phospholipase C activities. 3. The mAChR agonist carbachol was found to increase phosphoinositide hydrolysis to greater values in hypoxic tissues than those found in normoxic conditions. Furthermore, a greater translocation of PKC in response to carbachol was observed in hypoxic tissues than in normoxic ones. 4. Besides, carbachol induced a drastic reduction of NOS activity in hypoxic brains, at concentrations that stimulated this enzyme activity in normoxic preparations. In the latter, inhibition is obtained only with high concentrations of the cholinergic muscarinic agonist. 5. These results pointed to a carbachol-mediated mAChR hyperactivity induced by hypoxic insult. 6. The possibility that these effects would account for a compensatory mechanism to diminish NOS hyperactivity, probably protecting for NO neurotoxic action in hypoxic brain, is also discussed.

Air Pressure↗

PubMed2000

Zinc status and immune system relationship: a review.

The essentiality of zinc for humans was first documented by Prasad in the 1960s. The main clinical manifestations associated with zinc deficiency are growth retardation, hypogonadism, diarrhea, and increased susceptibility to infectious diseases. Thus, in the past 25 yr, there was an increased interest of researchers in studying the role of zinc in human immunity. Although mechanistic research has been carried out using animal models, there are several studies in humans with similar results. This work is an attempt to review the information available in this field to understand the important role that zinc plays in the normal development and function of the immune system.

Aged↗

PubMed1999

Antimitogenic effect of Larrea divaricata Cav.: participation in arachidonate metabolism.

Aqueous extracts of the leaves of Larrea divaricata Cav. exert antimitogenic effects on tumor cells (BW 5147 murine immature T-lymphoma) and normal, stimulated lymphocytes. The effective concentration was four times smaller in the case of tumor cells than in the case of normal, stimulated lymphocytes. Inhibitor studies of arachidonate pathway suggest that the proliferative effect of the extract is due to the activation of lipoxygenase metabolism, while the inhibitory action could be a direct effect.

Animals↗

PubMed1999

Haloperidol effect on intracellular signals system coupled to alpha1-adrenergic receptor in rat cerebral frontal cortex.

The induction of intracellular signals coupled to alpha1-adrenoceptor by haloperidol, were studied in rat cerebral frontal cortex. The neuroleptic exerts a biphasic effect on nitric oxide synthase (NOS), inhibiting the enzymatic activity at low concentrations (10(-9) M), while higher concentrations (10(-5) M) increased it. Protein kinase C (PKC) and phosphoinositol turnover (PIs) were involved in these actions, as haloperidol induced PKC translocation at low concentrations, and increased PIs turnover at high concentrations. All the effects of haloperidol were blocked by the alpha-adrenoceptor antagonist prazosin and the phospholipase C (PLC) inhibitor NCDC. The possibility that a cross-talk between both enzymatic pathways depending on the neuroleptic concentration used in rat cerebral frontal cortex, is also discussed.

Adrenergic alpha-1 Receptor Agonists↗

PubMed1999

Haloperidol-mediated phosphoinositide hydrolysis via direct activation of alpha1-adrenoceptors in frontal cerebral rat cortex.

In addition to its effect on D2 dopamine receptor blockades, haloperidol is able to interact with multiple neurotransmitters (NTs). Its action on phosphoinositide (PI) turnover was studied on cerebral cortex preparations. It induces an increase in inositol phosphate (IP) accumulation, which was only blunted by the alpha1-adrenoceptor blocker prazosin. Haloperidol maximal effect (Emax) was less than the effect of the full agonist norepinephrine (NE), and dose-response curves for both NE in the presence of submaximal doses of haloperidol and haloperidol in the presence of Emax doses of NE showed that haloperidol behaves as a partial agonist of cerebral alpha1-adrenoceptors. Its effect on PI hydrolysis is mediated through phospholipase C activation, as 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC) and 1-[6-([(17beta)-3-methoxyestra- 1,3,5(10)-trien-17-yl]amino)hexyl]-1H-pyrrole-2,5-dione) (U-73122) were able to abrogate both haloperidol and NE actions. Further, the typical neuroleptic exerts a direct activation of alpha1-adrenoceptors as its actions were not modified by cocaine and persisted in spite of chemical rat cerebral denervation with 6-hydroxydopamine (6-OHDA). The possibility that this agonistic action on alpha1-adrenoceptors would be involved in haloperidol side effects is also discussed.

Animals↗

PubMed1998

Involvement of endogenous nitric oxide signalling system in brain muscarinic acetylcholine receptor activation.

Biochemical signalling events coupled to muscarinic cholinergic receptors (mAChR), specifically those related to nitric oxide (NO) production, were studied on rat cerebral frontal cortex. The mAChR agonist carbachol was found to exert a specific biphasic action on NO synthase (NOS) activity: low doses ranging between 10(-9) M to 10(-7) M lead to NOS activation while higher doses (>10(-6) M) inhibited enzymatic activity. Carbachol stimulatory action was blunted by agents that interfere with calcium-calmodulin while a protein kinase (PKC) inhibitor, staurosporine was able to abrogate the inhibitory effect. Moreover, PKC activity showed maximum translocation to cerebral frontal cortex membranes with carbachol concentrations that inhibited NO production. Products from phosphoinosite (PI) hydrolysis are involved in these actions as carbachol was found to increase PI turnover in a dose dependent manner. These results would serve as an example of cross-talk between both enzymatic pathways.

Animals↗

PubMed1998

Role of nitric oxide in cardiac beta-adrenoceptor-inotropic response.

We examined some of the signalling events in the negative modulation of isoproterenol-induced stimulation of contractility in rat isolated atria. Isoproterenol-mediated positive inotropic response is accompanied by the stimulation of nitric oxide synthase (NOS) and an increase in the production of cyclic GMP (cGMP). Inhibition of NOS and guanylate cyclase increased the dose-response curve of isoproterenol on contractility. Inhibitors of calcium flux or calcium calmodulin, but not of protein kinase C, abrogated these mechanisms. The existence of a modulatory negative inotropic-cyclic GMP-mediated mechanism limiting the effect of beta-adrenergic stimulation in myocardium is discussed.

Animals↗

PubMed1998

Fluoxetine action on murine T-lymphocyte proliferation: participation of PKC activation and calcium mobilisation.

The present study was undertaken to analyse the effect of fluoxetine upon murine T-lymphocyte proliferation. We found that fluoxetine exerted a dual effect, which depended on the degree of lymphocyte activation: at mitogenic concentration (2 microg/mL) of concavalin A (Con A), we observed an inhibitory effect on cellular proliferation, whereas, on submitogenic Con A concentration (1 microg/mL), fluoxetine stimulated the cellular response. Given these facts, we studied PKC activation and calcium mobilisation in both stimulatory and inhibitory effects of fluoxetine on T-cell proliferation. We observed that fluoxetine increased PKC translocation obtained with 1 microg/mL Con A concentration, whereas PKC was degraded when 2 microg/mL was used. This mechanism is thought to be mediated by calcium mobilisation. According to our results, fluoxetine seemed to modulate calcium influx, which, in turn, would influence PKC translocation, modulating the immune response.

Animals↗

PubMed1998

Trypanosoma cruzi antigens down-regulate T lymphocyte proliferation by muscarinic cholinergic receptor-dependent release of PGE2.

Here we demonstrate that T. cruzi antigen molecule SAPA (shed acute phase antigen) with neuraminidase-trans sialidase activity triggers down-regulation of T lymphocyte proliferation by interacting with T lymphocyte muscarinic acetylcholine receptors (mAChR). SAPA attachment to mAChR from Lyt 2.2+ T cells resulted in synthesis of cyclic GMP (cGMP) and secretion of PGE2, an immunoregulator effector substance. These T suppressor cell signals were blunted by atropine and by indomethacin. Cell sorter analysis showed that the interaction of SAPA with purified T cells, affected the ratio of L3T4+/Lyt 2.2+ T cells increasing the percentage of Lyt 2.2+ T cells, effect that was inhibited by the mAChR antagonist, atropine. The interaction between SAPA and mAChR from Lyt 2.2+ T cells may result, therefore, in the down-regulation of the host immune response as consequence of T suppressor/cytotoxic cells activation and PGE2 release as they were observed. These results support the theory of an immunosuppressive state that contribute to the chronic course of Chagas' disease.

Animals↗

PubMed1997

Participation of nitric oxide signaling system in the cardiac muscarinic cholinergic effect of human chagasic IgG.

The possible role of altered humoral immune response in the pathogenesis of the chronic chagasic cardioneuromyopathy was examined by analyzing the interaction of IgG from T. cruzi infected patients with cardiac muscarinic acetylcholine receptors (mAChR). Human chagasic IgG by activating cardiac M2 mAChR, simulated the agonist actions triggering negative inotropic effect, inositol phosphate accumulation, nitric oxide synthase stimulation and increased production of cyclic GMP. Inhibitors of phospholipase C, protein kinase C, calcium/calmodulin, nitric oxide synthase and guanylate cyclase activities; prevented chagasic IgG effects on signaling pathways involved in M2 mAChR activation. In addition, sodium nitroprusside or 8-bromo cyclic GMP, mimicked the chagasic IgG effect associated with cholinergic-mediated cellular transmembrane signals. Moreover, these chagasic IgG immunoprecipitated the mAChRs solubilized from cardiac membranes. By means of SDS-PAGE and immunoblotting analysis, chagasic sera recognized a band of 70-75 kDa. The major protein recognized by chagasic IgG had an Rf coincident with the peak of [3H] propylbenzilylcholine mustard with an apparent molecular weight similar to that of mAChRs, which disappeared in the presence of atropine. The specificity of this interaction was checked by immunoprecipitation of rat cardiac mAChR and immunoblotting of pure human M2 mAChRs. Chronic interaction of chagasic IgG with myocardial mAChRs, behaving as a muscarinic agonist, might lead to cell dysfunction or tissue damage. Also, these antibodies could produce desensitization, internalization or degradation of mAChRs; explaining the progressive blockade of mAChRs in myocardium with parasympathetic denervation, a phenomenon that has been described in the course of Chagas' cardioneuromyopathy.

Adult↗

PubMed1997

Multireceptor interactions of haloperidol on rat cerebral frontal cortex "in vitro".

As several side effects of neuroleptics would be related to their interactions with several neurotransmitter receptors (R) haloperidol action on muscarinic cholinergic (mACh) R on frontal cerebral cortex preparations was analyzed. Here we show that haloperidol was able to inhibit in a concentration dependent manner the binding of specific mAChR radiolabeled antagonist on cerebral cortex membranes. This effect would be related to its interaction on mAChR of the M1 subtype as haloperidol blocked the stimulation of phosphoinositides (PIs) turnover induced by low concentrations of carbachol similarly as the M1 antagonist pirenzepine. However at high carbachol concentrations haloperidol triggered a potentiating stimulation of PIs hydrolysis that was only blocked by the alpha 1 adrenergic antagonist prazosin indicating an alpha 1 agonistic action of haloperidol on these Rs. These multireceptor actions of haloperidol found "in vitro" would strengthen its association with "in vivo" neuroleptic-induced side effects.

Animals↗

PubMed1996

"In vivo" and "in vitro" antitumoral action of Larrea divaricata Cav.

We previously reported that aqueous extract of Larrea divaricata Cav. had an antiproliferative activity upon tumoral lymphoid cells (BW 5147), without affecting normal immunity. To determine the probable mechanism of the inhibitory action of the extract upon cell growth, the participation of intracellular signals involved in the inhibition of cell proliferation, namely the activation of adenylate cyclase system was studied. The production of cyclic 3', 5 adenosine monophosphate (cAMP) in presence and absence of extract was analized. The extract increased the cAMP levels, but neither the cAMP production nor the inhibitory effect of the extract on proliferation were blocked by a beta adrenergic receptor antagonist (propranolol) or by histaminergic receptor antagonists (cimetidine and mepyramine). So, we concluded that the antiproliferative activity of the extract of BW 5147 cells would be mediated by an increase in cAMP intracellular levels no related to the activation of the membrane receptors here studied. In parallel, the extract was administered to a pregnant rat with a spontaneous mammarian carcinoma and "in vivo" antitumoral activity was found.

Analysis of Variance↗

PubMed1995

Modulation of cardiac physiology by an anti-Trypanosoma cruzi monoclonal antibody after interaction with myocardium.

Circulating antibodies from human and murine chagasic sera are able to interact with myocardium, activating neurotransmitter receptors. Here, we studied the effects of a monoclonal antibody (MAb CAK20.12), which recognizes a 150 kilodalton antigen of Trypanosoma cruzi and reacts with normal human and murine striated muscles and with cardiac tissue. The MAb CAK20.12 binds to purified cardiac membranes and interferes with the binding of beta-adrenergic receptor radioligand ([125I]CYP) and muscarinic cholinergic receptor (mAChR) radioligand ([3H]QNB) in a noncompetitive way. As a consequence of this interaction, beta-adrenergic receptor and mAChR were activated, leading to increased intracellular levels of cyclic AMP as a result of beta-adrenergic receptor-coupled adenylate cyclase triggering. When its sympathetic action was abrogated, it also induced an mAChR-mediated increase in cyclic GMP. Furthermore, cardiac physiology was modified by MAb CAK20.12, as it was able to increase cardiac contractility through beta-adrenoceptor activation and to decrease atrial frequency as a result of mAChR activation. The fact that this MAb modulates and modifies the mechanical and biochemical activity of normal murine heart established an important basis for future research and understanding of how the host's humoral immune response acts on the course and development of the chronic chagasic myocardiopathy.

Animals↗

PubMed1995

[Relation between cell proliferation and beta adrenergic receptor expression in activated T lymphocytes].

beta adrenergic receptors (R) on murine lymphocytes stimulated with concanavalin A (Con A) and tumor lymphoid cell line (BW5147) were characterized by beta radioligand binding of 125Icyanopindolol (125I-CYP). The functionality was also assesses by hormone-dependent changes in cyclic 3', 5', adenosine monophosphate (cAMP) levels on intact cell. Both types of cells displayed a reduced number of beta adrenergic receptors by 125I-CYP specific binding. However BW5147 cell line were unable to respond to beta agonist stimulation meanwhile the response of lymphocytes stimulated with Con A was lower than normal lymphocytes. Despite this difference both kind of cells displayed an increase in cAMP production induced by Prostaglandin E1 (PGE1). It can be concluded that functional beta R are absent in BW5147 cell line. The possible implication of alternative transmission pathway and neuroendocrine control in tumor lymphoid cells is discussed.

Animals↗

PubMed1992

Modification of G regulatory protein mediated actions by the interaction of histocompatibility antigens with cardiac muscarinic cholinergic receptors.

In this work we characterized the interaction of class I histocompatibility (HC) antigens (Ag) with cardiac cholinergic receptors by means of specific radioligand binding and by production of cholinergic-mediated cellular transmembrane signals. Alloimmune as well as anti-class I but not anti-class II antibodies were able to inhibit in an allosteric manner the binding of [3H]quinuclidinyl benzilate to cardiac membrane. Moreover, alloantibody could modify all of the muscarinic cholinergic effects mediated by a G regulatory protein, i.e. decrement of atria contractility, inhibition of cAMP stimulation, and activation of the turnover of phosphoinositides via phospholipase C. The cGMP production was not altered by the alloantibody. The data indirectly indicated that HC-Ag-muscarinic cholinergic interactions trigger all the cholinergic functions related to G proteins. The induction of intracellular second messengers by class I antigens and hormone-receptor interactions is discussed.

Animals↗

PubMed1992

Chagasic IgG stimulates phosphoinositide hydrolysis via neurotransmitter receptor activation: role of calcium.

Induction of polyphosphoinositide hydrolysis in cardiac tissue by IgG from chagasic mice was assayed. BALB/c mice auricles were labelled with myo-[3H]inositol precursor and inositol phosphate production in the presence or absence of chagasic IgG and the corresponding F(ab')2 was measured. Both chagasic IgG and F(ab')2 but not the normal forms specifically increased phosphoinositide turnover. This increment was blocked by muscarinic cholinergic antagonists and to an even greater extent by the phospholipase C inhibitor NCDC. Moreover, calcium channel blocking agents such as diltiazem, verapamil and D-600 also exerted an inhibitory action. A muscarinic cholinergic agonist, carbachol, and the ionophore A-23187, mimicked the action of the chagasic IgG upon phosphoinositide turnover. It is concluded that murine chagasic IgG and its F(ab')2 fragments result in stimulation of phospholipase C-mediated phosphoinositide hydrolysis through the interaction with muscarinic cholinergic receptors requiring the cytosolic calcium concentration to be raised.

Animals↗

PubMed1990

Major histocompatibility complex modulation of beta-adrenoceptor function.

Reciprocal interaction between beta-adrenoceptor specific ligand occupancy and alloantibody binding to specific antigens of cardiac and smooth muscle tissues was observed. Interference of alloimmune antibody fixation to both cardiac and oviductal tract preparations by beta 1 or beta 2 selective blockers, respectively, was obtained by means of indirect immunofluorescence assays. Reciprocally, alloimmune IgG and monoclonal antibodies directed to class I H-2 antigens, behaving as beta-adrenoceptor agonists, modified the contractility of both tissues, increasing intracellular levels of cyclic AMP (cAMP). Additionally, alloantibodies were also capable of inhibiting specific beta-adrenoceptor radioligand binding to purified cardiac and smooth muscle membranes. These data suggested a modulation of beta-adrenoceptor function by antibodies directed against H-2 class I histocompatibility molecules, probably through molecular interactions between both structures.

Animals↗

PubMed1989

Colchicine blocks beta adrenoceptor and class I antigen-specific interactions.

Previously we have demonstrated a molecular relationship between H-2 class I antigens and beta adrenoceptors from cardiac tissue. Here we show this type of interaction taking place with beta adrenoceptors from splenic cells and their purified membranes and the participation of cytoskeletal proteins in the phenomenon. Alloimmune, as well as anti-class I but not anti-class II, antibodies were able to inhibit in a competitive manner the binding of (-)-[3H]dihydroalprenolol to splenic lymphocytes and their purified membranes, and to increase cyclic AMP levels in intact cells as a consequence of beta adrenoceptor activation. Furthermore, colchicine (a microtubule disrupting drug), but not cytochalasin B (a microfilament disrupting drug), was able to abrogate alloimmune antibody inhibition over the beta radioligand binding to its receptor on both intact splenocytes and their membranes. Alloantibody actions were significantly diminished by peripheral protein solubilization in purified spleen cell membranes. These data pointed indirectly to the participation of a colchicine binding protein in class I antigen hormone-receptor associations.

Animals↗