Biomedical subjects

L Sterin-Borda

Publications and source records attributed to L Sterin-Borda.

At least 19 recordsLinked to original sources

PubMed2006

Signaling pathways leading to prostaglandin E(2) production by rat cerebral frontal cortex.

In this paper, we have determined the effect of both muscarinic acetylcholine receptor (mAChR) and exogenous prostaglandin E(2) (PGE(2)) on PGE(2) production and cyclooxygenases (COX) mRNA gene expression on rat cerebral frontal cortex. Carbachol and PGE(2) increase endogenous PGE(2) production and the COX-1 mRNA levels by activation of PLA(2)s. The COX-1 and COX-2 activity participated in the production of PGE(2) triggered by exogenous PGE(2). While in carbachol-PGE(2) only COX-1 activity is affected. The specific inhibition of PGE(2) receptor was able to impair the increase of endogenous PGE(2) production triggered by both carbachol and exogenous PGE(2). These results suggest that carbachol-activation mAChR increased PGE(2) production that in turn interacting with its own receptor triggers an additional production of PGE(2). Both mechanisms appear to occur by using PLA(2) signaling system. This data should be able to contribute to understand the involvement of PGE(2) in normal brain function and its participation in neuroinflammatory processes.

Animals↗

PubMed2006

Muscarinic cholinoceptor activation modulates DNA synthesis and CD40 expression in fibroblast cells.

1 The aim of the present work was to examine the role of muscarinic acetylcholine receptors (mAChR) on DNA synthesis and CD40 expression in human fibroblast cells. Neonatal human skin fibroblast cultures were stimulated with carbachol in presence or absence of specific antagonists and the following parameters were measured: identification of mAChR subtypes, DNA synthesis, inositol phosphates (InsP) production and CD40 expression. 2 Human fibroblasts express mAChR with Kd 0.47 +/- 0.11 nm and Bmax 236 +/- 22 fmol mg protein(-1). Carbachol stimulates DNA synthesis, InsP and the expression of CD40. All these effects were inhibited by atropine, mustard hydrochloride (4-DAMP) and pirenzepine but not by AF-DX 116 and tropicamide, indicating that M3 and M1 mAChR are implicated in carbachol action. The relative Ki of the antagonists obtained by competition binding assay was in parallel to the relative potency for blocking both carbachol-stimulated InsP accumulation and DNA synthesis. 3 The intracellular pathway leading to carbachol-induced biological effects involved phospholipase C and calcium/calmodulin, as U-73122 and trifluoroperazine blocked carbachol effects, respectively. Calphostin C, a protein kinase C inhibitor, had no effect, indicating that this enzyme does not participate in the system. 4 These results may contribute to a better understanding of the modulatory role of the parasympathetic muscarinic system on normal human fibroblast function.

Atropine↗

PubMed2006

Endogenous signalling system involved in parotid gland adenosine A(1) receptor-amylase release.

AIM: In this study, we have determined signalling pathways involved in adenosine A(1) receptor (A(1) receptor)-dependent stimulation of amylase release in rat parotid gland. METHODS: Amylase release, binding and cyclic adenosine monophosphate (cAMP) assays, inositol phosphates (IPs) production and nitric oxide synthase (NOS) activity in the presence of cyclopentyl-1,3-dipropylxanthine (CPA) alone or in the presence of different inhibitory drugs were performed. RESULTS: The binding parameters of specific A(1) antagonist [(3)H]-cyclopentyl 1,3-dipropilxanthine ([(3)H]-DPCPX) in parotid gland membranes show a population of high affinity sites with K(d) (nm) 0.53 +/- 0.06 and B(max) (fmol mg(-1) protein) 122.6 +/- 10.2. CPA stimulation of A(1) receptor exerts an increase in amylase release, IPs accumulation, cAMP production and NOS activity. All these A(1) agonist effects were blocked by the A(1) receptor antagonist DPCPX. Inhibitors of phospholipase C (PLC), calcium/calmodulin (CaM), protein kinase C (PKC), and adenylate cyclase, but not NOS, activities attenuated the CPA stimulatory effect on amylase release. The effect of CPA on amylase release significantly correlated with its action either on cAMP or on IPs accumulation. CONCLUSION: These results suggest that CPA activation of parotid gland A(1) receptor induces a stimulatory effect on amylase release associated with increased production of cAMP and IPs accumulation. The mechanism appears to occur secondarily to stimulation of phosphoinositide turnover via PLC activation. This, in turn, triggers cascade reactions involving CaM and PKC. The CPA stimulation of NOS does not appear to participate in amylase release.

Adenosine A1 Receptor Antagonists↗

PubMed2005

Neuronal nitric oxide synthase activity in rat urinary bladder detrusor: participation in M3 and M4 muscarinic receptor function.

1. The aim of this paper was to determine the different signalling cascades involved in contraction of the rat urinary bladder detrusor muscle mediated via muscarinic acetylcholine receptors (muscarinic AChR). Contractile responses, phosphoinositides (IPs) accumulation, nitric oxide synthase (NOS) activity and cyclic GMP (cGMP) production were measured to determine the reactions associated with the effect of cholinergic agonist carbachol. The specific muscarinic AChR subtype antagonists and different inhibitors of the enzymatic pathways involved in muscarinic receptor-dependent activation of NOS and cGMP were tested. 2. Carbachol stimulation of M(3) and M(4) muscarinic AChR increased contractility, IPs accumulation, NOS activity and cGMP production. All of these effects were selectively blunted by 4-DAMP and tropicamide, M(3) and M(4) antagonists respectively. 3. The inhibitors of phospholipase C (PLC), calcium/calmodulin (CaM), neuronal NOS (nNOS) and soluble guanylate cyclase, but not of protein kinase C and endothelial NOS (eNOS), inhibited the carbachol action on detrusor contractility. These inhibitors also attenuated the muscarinic receptor-dependent increase in cGMP and activation of NOS. 4. In addition, sodium nitroprusside and 8-bromo-cGMP, induced negative relaxant effect. 5. The results obtained suggest that carbachol activation of M(3) and M(4) muscarinic AChRs, exerts a contractile effect on rat detrusor that is accompanied by an increased production of cGMP and nNOS activity. The mechanism appears to occur secondarily to stimulation of IPs turnover via PLC activation. This in turn, triggers cascade reactions involving CaM, leading to activation of nNOS and soluble guanylate cyclase. They, in turn, exert a modulator inhibitory cGMP-mediated mechanism limiting the effect of muscarinic AChR stimulation of the bladder.

Animals↗

PubMed2002

Nitric oxide synthase/PGE(2) cross-talk in rat submandibular gland.

It is known that nitric oxide modulates the prostaglandin generation. However, little is known about the regulatory action of prostaglandin on nitric oxide production. There is a molecular cross-talk between nitric oxide and prostaglandin. Here, we examined biochemical signalling pathways coupled to the prostaglandin E(2) (PGE(2)) receptor related to nitric oxide synthase stimulation in rat submandibular gland. PGE(2) through the stimulation of its own receptor, triggered activation of phosphoinositide turnover (IPs), translocation of protein kinase C (PKC), stimulation of nitric oxide synthase activity (NOS) and increased production of cyclic GMP (cGMP). PGE(2) stimulation of NOS and cGMP production was blunted by agents interfering with calcium influx, calcium/calmodulin and phospholipase C (PLC) activities; while PKC inhibitor was able to stimulate PGE(2) effects. PGE(2) did not evoke amylase release, indicating that NOS/ cGMP pathway were not associated with this enzyme secretion. Our results suggest that this prostanoid could act as vasoactive chemical mediator through its ability to activate NOS-cGMP pathway via own gland membrane receptor.

Amylases↗

PubMed2001

Autoantibodies against neonatal heart M1 muscarinic acetylcholine receptor in children with congenital heart block.

Isolated congenital heart block may be associated with autoimmune disorder such as Sjögren Syndrome and systemic lupus erythematosus. In this work we demonstrate circulating autoantibodies against neonatal heart M1 muscarinic acetylcholine receptor (mAChR) in the sera of children with congenital heart block. This antibody were able to react with the second extracellular loop of the human M1 mAChR as demonstrated using a synthetic peptide in enzyme immune assay and binding assay. Affinity purified anti-peptide IgG as well as total IgG from children with congenital heart block, interfered with the specific radioligand occupancy from neonatal heart M1 mAChR, interacting irreversibly. The antipeptide antibodies also displayed an 'agonist-like' activity, i.e. decreased contractility, activated nitric oxide synthase activity and increased production of cyclic GMP. All of these effects were selectively blunted by pirenzepine and neutralized by the synthetic M1 peptide. Both binding and biological effects were obtained using neonatal rat heart instead adult heart and were independent of Ro/SS-A and La/SS-B antibodies and were also absent in the sera of normal children. A clinical relevance of these findings is demonstrated by a strong association between the existence of circulating M1 mAChR antipeptide antibodies and the presence of isolated congenital heart block, making these antibodies a proper marker of this disease.

Amino Acid Sequence↗

PubMed2001

Interaction of human chagasic IgG with human colon muscarinic acetylcholine receptor: molecular and functional evidence.

BACKGROUND AND AIMS: Gastrointestinal disorders is one of the clinical manifestations of chronic Chagas' disease. The pathogenesis seems to be associated with autonomic dysfunction. Here, we consider the muscarinic cholinoceptor mediated alteration in distal colon function in chagasic megacolon. PATIENTS: Patients were divided into four groups: group I, chronic chagasic patients with megacolon; group II, chronic chagasic patients without megacolon; group III, non-chagasic patients with megacolon; and group IV, normal healthy volunteers (control). METHODS: Binding assay and immunoblot of cholinoceptors from human and rat colon and enzyme immunoassay (ELISA) using a synthetic 24mer peptide corresponding to the second extracellular loop of human M2 muscarinic acetylcholine receptors (mAChR) were used to detect the presence of serum antibodies. The effect of antibodies on basal tone and 3',5'-cyclic monophosphate (cAMP) production of human and rat distal colon strips were also tested. RESULTS: Group I but not the other groups had circulating antibodies capable of interacting with human colon activating M2 mAChR, as they competed with binding of specific radioligand to mAChR and interacted with the second extracellular loop of human M2 mAChR. Moreover, affinity purified anti-M2 peptide IgG from group I, in common with monoclonal antihuman M2 mAChR, recognised bands with a molecular weight corresponding to colon mAChR. This antibody also displayed an agonist-like activity, increasing basal tone and decreasing cAMP accumulation. Both effects were blunted by AF-DX 116 and neutralised by the synthetic peptide. CONCLUSIONS: In chagasic patients with megacolon there are antibodies that can recognise and activate M2 mAChR. The implications of these autoantibodies in the pathogenesis of chagasic megacolon is discussed.

Adult↗

PubMed2001

Muscarinic acetylcholine receptor antibodies as a new marker of dry eye Sjögren syndrome.

PURPOSE: The authors investigated whether circulating autoantibodies against M(3) muscarinic acetylcholine receptors (mAChRs) could be a new marker for diagnosis for primary and secondary Sjögren syndrome (SS) dry eye. METHODS: Enzyme-linked immunosorbent assay (ELISA) using both rat exorbital lacrimal gland acinar cell membranes and synthetic 25-mer peptide as antigens was used to determine autoantibodies against acinar cells and M(3) mAChRs. Also, nitric oxide synthase (NOS) activity was assessed to determine the biological effect of these autoantibodies in relation to the M(3) mAChR. RESULTS: Sera from dry eye primary SS (pSS) or secondary SS (sSS) patients tested by ELISA recognized membrane lacrimal gland acinar cells antigens and the synthetic 25-mer peptide, corresponding to the second extracellular loop of human M(3) mAChRs. Moreover, the IgG fraction and the corresponding affinity-purified anti-M(3) peptide autoantibodies from the same patients were able to activate NOS coupled to lacrimal gland M(3) mAChRs. As controls, IgG and sera from women without dry eye with or without rheumatoid arthritis and from normal control subjects gave negative results on ELISA and biological assay; thus demonstrating the specificity of the reaction. CONCLUSIONS: Autoantibodies against mAChR may be considered among the serum factors implicated in the pathophysiology of the development of pSS dry eyes and could be a new marker to differentiate SS dry eyes from non-SS dry eyes.

Adult↗

PubMed2000

Differential effects of fluoxetine on murine B-cell proliferation depending on the biochemical pathways triggered by distinct mitogens.

The effect of fluoxetine on mitogen-induced B-cell proliferation was studied. In particular, we analyzed the influence of fluoxetine on the signal transduction pathways triggered after stimulation with lipopolysaccharide (LPS) and anti-immunoglobulin M antibodies (anti-IgM). We showed that fluoxetine had a dual effect on anti-IgM-stimulated B-cell proliferation: at optimal anti-IgM concentration, fluoxetine inhibited proliferation, whereas at suboptimal anti-IgM concentration, the drug enhanced proliferation. Fluoxetine exerted only an inhibitory effect on LPS-induced B-cell proliferation. Calcium influx seemed to be involved in these effects.

Animals↗

PubMed2000

Altered beta-adrenoceptor function associated to protein kinase C activation in hyperproliferative T lymphocytes.

beta-Adrenoceptor (betaAR) expression and function as well as its modulation via intracellular transduction signals, were analyzed on the T cell lymphoma BW5147. Independently to the kinetic of proliferation and relative to the number of receptors displayed in normal T lymphocytes, BW5147 cells displayed a decreased number of betaAR, uncoupled to adenylate cyclase, but coupled to protein kinase C stimulation. This last effect was impaired by a beta-antagonist and by blockers of the enzymatic pathways involved in T lymphocyte proliferation, inducing a recovery of betaAR sites. Down-regulation of betaAR would implicate the loss of a negative neuroimmune control mechanism for lymphocyte proliferation. The coupling of the remaining sites to a positive signal for cellular activation, would contribute to establish an hyperproliferative state.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed2000

Differential activation of nitric oxide synthase through muscarinic acetylcholine receptors in rat salivary glands.

Muscarinic receptors play an important role in secretory and vasodilator responses in rat salivary glands. Nitric oxide synthase (NOS) appears to be one of the multiple effectors coupled to muscarinic receptors in both submandibular and sublingual glands although some differences have been found depending on the gland studied. First, submandibular glands had a lower basal activity of nitric oxide synthase than sublingual glands and the concentration-response curve for carbachol was bell-shaped in the former but not in sublingual glands. Second, cGMP levels displayed a similar profile to that observed for NOS activity in both glands. Third, protein kinase C also coupled to muscarinic receptor activation in the glands might have a regulatory effect on nitric oxide production since its activity was higher in basal conditions in submandibular than sublingual glands and it also increased in the presence of the agonist at a concentration that inhibited NOS activity in submandibular glands. The effects appear to be partly related to the expression of a minor population of M(1) receptors in submandibular glands absent in sublingual as determined in binding and signaling experiments with the muscarinic receptor antagonist pirenzepine.

Animals↗

PubMed2000

Fluoxetine modulates norepinephrine contractile effect on rat vas deferens.

The aim of this study was to evaluate whether the antidepressant drug fluoxetine could modify rat vas deferens response to norepinephrine (NE), and to compare its effect with that of desipramine and cocaine. Results showed that 10(-5)m fluoxetine produced a super-sensibility of vas deferens to NE. This result was the same as those obtained for 10(-6)m desipramine or cocaine. Since the effect was Na(+)- and Cl(-)-dependent, an inhibitory mechanism of neuronal NE transport was suggested. Fluoxetine did not modify [(3)H]prazosin K(d) or B(max) in rat vas deferens, reinforcing the hypothesis of a pre-synaptic site of action. On the other hand fluoxetine inhibited NE maximal effect. This inhibitory effect could be related to an antagonism of calcium entry through the voltage-dependent calcium channel, since it was partially reverted by increasing calcium concentration and, besides, the drug was able to inhibit the calcium concentration-response curve also. Contractions induced by 5-hydroxytryptamine (5-HT) were not modified in the presence of fluoxetine. It is concluded that fluoxetine modulates rat vas deferens response to low NE concentrations in the same manner as the selective inhibitor of NE neuronal uptake desipramine. This peripheral effect could participate in the modulation of the male reproductive tract observed by these drugs when used in clinical trials.

Animals↗

PubMed2000

Role of neurotransmitter autoantibodies in the pathogenesis of chagasic peripheral dysautonomia.

Chagas' disease is caused by a parasite, Trypanosoma cruzi, which is widely distributed in South and Central America. Dysautonomias, derangements of sympathetic and parasympathetic nervous system function, are seen fairly often during the chronic course of Chagas' disease. Many infected subjects developed, in the course of the disease, neurogenic cardiomyopathy or digestive damage. Our investigations show the existence of circulating antibodies in Chagas' disease that bind to beta-adrenergic and muscarinic cholinergic receptor (mAChR). The neurotransmitter receptor-autoantibody interaction triggers in the cells intracellular signal transductions that alter the physiological behavior of the target organs, leading to tissue damage. Moreover, the deposit of autoantibodies behaving as agonists induces desensitization and/or down regulation of the receptors. This in turn can lead to a progressive blockade of them with sympathetic and parasympathetic denervation. Using synthetic peptides for immunoblotting and enzyme immunoassay, we demonstrated that these autoantibodies reacted against the second extracellular loop of the human heart beta 1 adrenoceptor and M2 cholinoceptor. Also, the corresponding affinity-purified antipeptide antibodies displayed an agonist-like activity associated with specific receptor activation. A strong association between circulating antipeptide M2 mAChR autoantibodies and the presence of patients' low heart rate variability index, bradycardia and cardiac or esophageal autonomic dysfunction in chronic chagasic patients was verified. This fact make these antipeptide antibodies a proper marker of cardiac neuromyopathy and achalasia.

Autoantibodies↗

PubMed2000

Downregulation of beta adrenergic receptor expression on B cells by activation of early signals in alloantigen-induced immune response.

Previously we described a decrease in beta-adrenergic receptor expression in B lymphocytes as a consequence of in vivo alloimmunization. This decrease correlates with the highest response of alloantibody production by B cells. In the present report we examined the participation of intracellular signals elicited after alloimmune stimulation. We showed that in vitro stimulation of B cells with mitomycin C-treated allogenic cells induced a reduction in the number of beta-adrenoceptors. This downregulation correlated to changes in basal and in isoproterenol-stimulated intracellular cAMP levels. We found that calcium mobilization and protein kinase C activation triggered after direct allogenic stimulation and/or by the action of T cell-soluble factors induced the reduction in beta-adrenoceptor sites. These findings could be of interest to understand the neuroendocrine mechanisms involved in the regulation of B cell activation.

Animals↗

PubMed1999

Sjögren autoantibodies modify neonatal cardiac function via M1 muscarinic acetylcholine receptor activation.

Isolated congenital heart block may be associated with primary Sjögren syndrome. In this work we describe circulating antibodies in the sera of primary Sjögren syndrome patients that are able to interact with neonatal myocardium by activating muscarinic acetylcholine receptors of M1 subtype. We report on the presence of autoantibodies against the second extracellular loop of human M1 muscarinic acetylcholine receptors in primary Sjögren syndrome mothers whose children have congenital heart block using a synthetic peptide in indirect immunofluorescence technique. Autoantibodies from primary Sjögren syndrome patients gave positive image on neonatal atria but not on adult atria slices. The synthetic M1 peptide selectively abrogated indirect immunofluorescence recognition. The primary Sjögren syndrome-immunoglobulin G also displayed an 'agonist like' activity modifying the intracellular events associated with muscarinic acetylcholine receptor activation. The mechanism appears to occur secondarily to stimulation of phosphoinositides turnover via phospholipase C activation. This, in turn, triggers cascade reactions involving calcium/calmodulin and leads to activation of nitric oxide synthase and soluble guanylate cyclase. All of these effects were selectively blunted by pirenzepine and neutralized by M1 synthetic peptide. These biological effects were not obtained using adult instead of neonatal rat atria and neither occurred with the sera of normal healthy women of childbearing age. It could be concluded that antibodies against neonatal M1 muscarinic acetylcholine receptor may be another serum factor to be considered in the pathophysiology of the development of congenital heart block associated with primary Sjögren syndrome mothers.

Adult↗

PubMed1999

Role of protein kinase C and cAMP in fluoxetine effects on human T-cell proliferation.

In this work, we studied the effect of fluoxetine on human T-lymphocyte proliferation using optimal and suboptimal concanavalin A concentrations. In particular, we analyzed the influence of fluoxetine on the kinases that are involved in intracellular signalling after stimulation with mitogens. We found that fluoxetine promoted the Ca2+ -mediated proteolysis of protein kinase C (PKC) and increased cyclic-AMP (cAMP) levels, thereby impairing lymphocyte proliferation, when optimal concanavalin A concentrations were used. In contrast, when suboptimal concanavalin A concentrations were used, fluoxetine only increased PKC translocation, without modifying cAMP levels, leading to T-cell proliferation. According to our results, fluoxetine has a dual effect on T-cell proliferation by modulating the PKC and protein kinase A pathways. This mechanism is thought to be mediated through Ca2+ mobilization.

Adult↗

PubMed1999

Activation of nitric oxide signaling through muscarinic receptors in submandibular glands by primary Sjögren syndrome antibodies.

Primary Sjögren Syndrome is a chronic autoimmune disease characterized by exocrine gland dysfunction. Here we present evidence of the activation of nitric oxide signaling cascade by circulating antibodies of patients with Sjögren Syndrome in rat submandibular glands. Constitutive nitric oxide synthase and cyclic GMP levels are modulated by Sjögren IgGs through the activation of muscarinic acetylcholine receptors on the glands. The effects are similar to those produced by the agonist carbachol and blocked by the antagonist atropine. The involvement of M1 subtype of muscarinic receptors is proposed since both a synthetic peptide homologous to an extracellular domain of M1 receptor and pirenzepine, a selective M1 antagonist, partially blocked the effects. We conclude that Sjögren Syndrome antibodies can activate nitric oxide signaling in submandibular glands by interacting with muscarinic acetylcholine receptors.

Adult↗

PubMed1999

Alterations in cardiac beta-adrenergic receptors in chagasic mice and their association with circulating beta-adrenoceptor-related autoantibodies.

OBJECTIVE: Cardiac tissue from chagasic mice was studied to evaluate the expression and biological activity of beta-adrenoceptors in association with circulating beta-adrenoceptor-related autoantibodies. METHODS: BALB/c inbred mice that were either treated or not treated with atenolol (2.5 mg/kg) and infected or not infected with 1 x 10(4) trypomastigotes (CA-1 strain) were sacrificed weekly up to week nine. Morphological, binding and contractility studies were performed on the four different groups of animals. The effect of their serum antibodies was also assayed in binding and contractility studies on normal heart preparations. RESULTS: Hearts from chagasic myocarditis mice showed a beta-adrenoceptor-related dysfunction, with a decrease in heart contractility, impaired response to exogenous beta-adrenoceptor agonist and a significant reduction in beta-adrenergic binding sites. Those effects were maximum at eight-nine weeks post-infection and were improved by treating infected mice with atenolol. In addition, serum or IgG from chagasic myocarditis mice was capable of interacting with cardiac beta-adrenoceptors, reducing the number of binding sites and inhibiting the contractile response to exogenous norepinephrine. IgG effects that were observed in normal myocardium, were highest in sera from mice eight-nine weeks post-infection and correlate with the degree of myocarditis. Moreover, chagasic autoantibodies from infected mice recognized a peptide corresponding to the sequence of the second extracellular loop of the human beta 1-adrenoceptor. CONCLUSIONS: (1) The development of alterations in beta-adrenergic receptors, related to cardiac dysfunction, may be associated with the presence of circulating antibodies against these receptors and (2) it is possible that the chronic deposits of these autoantibodies in cardiac beta-adrenoceptors could lead to a progressive blockade with sympathetic denervation, a phenomenon that has been described in the course of chagasic myocarditis.

Adrenergic beta-Antagonists↗