The two orphan Na+/Cl(-)-dependent transporters Rxt1 and V-7-3-2 have an overlapping expression pattern in the rat central nervous system

The messenger RNA expression patterns of two orphan Na+/Cl(-)-dependent transporters, Rxt1 and V-7-3-2, were compared in the adult rat CNS by in situ hybridization histochemistry. The sites of synthesis of both orphan transporters were found to largely overlap. The highest concentrations of Rxt1 and V-7-3-2 mRNAs were present in the olfactory bulb, cerebral cortex, hippocampus, habenular and pontine nuclei, and cerebellum. Low levels of orphan transporters mRNAs were observed in the basal ganglia (caudate-putamen, nucleus accumbens, globus pallidus), septum nuclei, substantia nigra, colliculi and brainstem. Only few regions were found to express only one of these two orphan transporters: Rxt1 mRNA in the thalamic area and the hilus of the dentate gyrus. V-7-3-2 mRNA in motoneurons of the most ventral zone of the spinal cord. Rxt1 mRNA was generally more abundant than V-7-3-2 mRNA, except in few areas (piriform cortex, horizontal limb of the diagonal band, medial habenular nucleus, pyramidal and granular cell layers in the hippocampus) where the levels of both mRNAs were similar. The overall parallelism between both distributions was further confirmed at the cellular level on emulsion-coated sections, especially in the hippocampus where pyramidal and granular neurons very probably synthesize both Rxt1 and V-7-3-2. These data provide a further demonstration of the synthesis of the orphan transporters Rxt1 and V-7-3-2 exclusively in neurons whose locations suggest that they might correspond to glutamatergic neurons and subsets of GABAergic neurons.

Functional specialization in the ruminant placenta: evidence for two populations of fetal binucleate cells of different selective synthetic capacity

Trophoblast binucleate cells (BNC) in the ruminant placenta demonstrate a characteristic development, mature structure and migratory capacity whether situated in cotyledonary or intercotyledonary regions of the placenta. However, previous immunocytochemical studies demonstrated clear differences in gene expression in granule contents of BNC according to their anatomical location with some proteins being expressed in all BNC (e.g. ovine placental lactogen) whereas others were unique to a particular origin (e.g. SBU3 antigen in cotyledonary BNC only). We have used enriched preparations of binucleate cells and showed differences in steroid metabolic capacity in vitro which is more related to their species origin (sheep or goat) than to their anatomical location. The predominant product from [3H]pregnenolone is progesterone (sheep) and 5 beta-pregnane-3 alpha, 20 alpha-diol (goat) and the amount formed (corrected for the number of BNC) is similar irrespective of whether BNC were derived from the cotyledonary or intercotyledonary regions. These studies indicate specific forms of regional functional specialization of BNC and emphasize their multifunctional role in the ruminant placenta.

NO synthesis is involved in structural and functional effects of ACE inhibitors in injured arteries

Angiotensin-converting enzyme (ACE) inhibitors reduce intimal hyperplasia after balloon injury. A role for nitric oxide (NO) has been suggested in this effect. Because recent data suggest that NO may modulate some features of endothelial cells and because endothelial cells are involved in the control of intimal hyperplasia, we investigated the role of NO synthesis in the effect of an ACE inhibitor, perindopril, on neoendothelial dysfunction and intimal hyperplasia in a rabbit model of unilateral iliac balloon injury. New Zealand White male rabbits received placebo, perindopril, or cotreatment with perindopril and NG-nitro-L-arginine methyl ester (L-NAME) and were evaluated 4 wk after the injury. Fifteen rabbits (5 in each group) were used to assess in vitro vasoreactivity and twenty-four (8 in each group) for morphometric analysis. In injured vessels, neoendothelium-dependent relaxation in ACE inhibitor-treated animals was improved compared with placebo (P < 0.05) and restored to the level of noninjured vessels (NS). The improvement observed with ACE inhibitor was abolished by cotreatment with L-NAME (P < 0.05). In the same vessels, no effect was observed on neoendothelium-independent vasoreactivity. The improved neoendothelial dysfunction with ACE inhibitor was associated with a 66% reduction in intimal thickening (P < 0.01). The effect was also reversed by cotreatment with L-NAME (P < 0.01). In noninjured vessels, treatment did not alter vasoreactivity or morphology of the vessel wall. These results suggest that NO synthesis may play a key role in the improvement of vascular function seen with ACE inhibitor in balloon-injured vessels.

Basic fibroblast growth factor restores endothelium-dependent responses after balloon injury of rabbit arteries

BACKGROUND

After experimental angioplasty, partial or complete reendothelialization of the denuded surface occurs; the function of the regenerated endothelium has, however, been shown to be abnormal. Basic fibroblast growth factor (bFGF) is mitogenic for endothelial cells in vitro and in vivo. We investigated whether chronic administration of bFGF in a rabbit model of balloon denudation might not only improve endothelial regrowth but also restore normal physiological responses to endothelium-dependent agonists.

METHODS AND RESULTS

Thirty-nine New Zealand White rabbits underwent balloon denudation of the right iliac artery. Twenty rabbits received intravenous administration of bFGF (2.5 micrograms twice a week for 2 weeks). Nineteen rabbits receiving saline injections served as controls. Animals were killed on day 28 for assessment of reendothelialization and neointimal thickening and for analysis of in vitro vasoreactivity. Animals in the bFGF group had a significantly (P<.005) greater degree of reendothelialization than controls (115 +/- 13 versus 55 +/- 6 mm2). Neointimal thickening was similar in the two groups. Four weeks after denudation, endothelium-independent responses did not differ significantly between the two groups. In contrast, the maximal endothelium-dependent acetylcholine-induced relaxation of the bFGF-treated animals (Emax, 40 +/- 7%) was significantly greater than that of the control group (Emax, 11 +/- 9%; P<.05).

CONCLUSIONS

Systemic administration of bFGF restores, in large part, the responses of previously denuded arterial segments to endothelium-dependent vasodilators. Angiogenic growth factors may help to reestablish normal endothelial cell function in patients who have undergone angioplasty.

VLA-6 (CDw49f) is an important adhesion molecule in NK cell-mediated cytotoxicity following autologous or allogeneic bone marrow transplantation

Graft-vs.-leukemia (GVL) is postulated to be the principal mechanism responsible for continued remission after allogeneic bone marrow transplantation (BMT). The specific cytotoxic effectors mediating this effect are as yet undefined, but the major histocompatibility complex (MHC)-nonrestricted lysis of tumor cell lines by natural killer (NK) and lymphokine-activated killer (LAK) cells from recipients of allogeneic BMTs has been proposed as an in vitro correlate of GVL. In vitro culture or treatment in vivo with interleukin-2 (IL-2) is associated with enhanced NK cytotoxicity and lysis of NK-resistant targets (LAK cytotoxicity). NK, LAK, and cytotoxic T lymphocytes (CTL) have cytotoxic properties against autologous and allogeneic leukemic targets. These immune effector cells require receptor-ligand interaction for target recognition and adhesion via specific molecules such as integrins, a group of heterodimeric transmembrane glycoproteins. The integrins include the very late activation (VLA) subfamily, which all share the same beta 1 subunit but have distinct chains. VLA-6 (CDw49f) has been identified on NK cells and binds to laminin, a basement membrane protein found on malignant tumor cells but not normal cells. Monoclonal antibodies (mAbs) to laminin have been found to inhibit in vitro cytotoxicity of the tumor cell line K562, suggesting an important role for VLA-6 in this interaction. The specific aim of this study was to investigate the role of VLA-6 in the interactions of the tumor cell lines K562 and Daudi with peripheral blood lymphocytes (PBL) acting as effectors in cell-mediated cytotoxicity from normal volunteers, patients recovering from chemotherapy, and patients recovering from autologous or allogeneic BMT. In over 96% of assays, incubation of effector cells with anti-CDw49f mAbs led to detectable inhibition of NK and LAK cell-mediated cytotoxicity. More notably, the degree of anti-VLA6-induced suppression of LAK activity was significantly greater in the normal donors than in any of the patient groups, despite a significantly lower incidence of expression of VLA-6 on NK cells from controls than from patients. This implies a reduced role for this adhesion molecule in LAK activity following some form of in vivo stimulation. This hypothesis is supported by the observation that addition of exogenous IL-2 to the cultures ameliorated the effect of VLA-6 blockade, although the incidence and level of VLA-6 expression was unchanged by IL-2. In contrast, VLA-6 blocking led to a greater reduction in NK activity of BMT recipients than of normal donors, demonstrating that the VLA-6 adhesion pathway is important in this group of patients. These results indicate that the VLA-6-laminin interaction is important in normal NK-target interaction but may play a less significant role in the innate cytotoxic response post-BMT, perhaps reflecting subtle differences in the subsets of NK cells present in BMT recipients compared with normal donors.

Immunolabeling of central serotonin 5-HT1D beta receptors in the rat, mouse, and guinea pig with a specific anti-peptide antiserum

A synthetic peptide (25 amino acids) corresponding to a specific portion of the third intracytoplasmic loop of the rat serotonin 5-HT1B/1D beta receptor was coupled to keyhole limpet hemocyanin and injected monthly into rabbits. Anti-peptide antibodies were detected by enzyme-linked immunosorbent assay and characterized by immunoprecipitation of the 5-HT1B/1D beta receptor in CHAPS-solubilized extracts from rat striatal membranes. Up to 60% of solubilized striatal serotonin-O-carboxymethylglycyl[125I]iodotyrosinamide ([125I]GTI; a selective 5-HT1B/1D radioligand) binding sites were immunoprecipitated and subsequently pharmacologically identified as 5-HT1B receptors. The remaining 40% of [125I]GTI binding sites were shown to be 5-HT1D receptors. In addition, these antibodies were successfully used in immunofluorescence experiments to detect the 5-HT1B/1D beta, but not the 5-HT1D/1D alpha, receptor in transiently transfected LLC-PK1 cells. Immunoautoradiographic experiments performed with brain sections from the rat, mouse, and guinea pig showed that the substantia nigra and globus pallidus contained the highest densities of 5-HT1D beta receptor-like immunoreactivity. Comparison of the regional distribution of immunolabeling with that of the specific binding of [125I]GTI in the brain of these species further confirmed that the anti-peptide antibodies selectively recognized only the 5-HT1D beta component of [125I]GTI specific receptor binding sites.

Electrophysiological, biochemical, neurohormonal and behavioural studies with WAY-100635, a potent, selective and silent 5-HT1A receptor antagonist

Although considerable progress has been made in characterising the 5-HT1A receptor using agonists, partial agonists or non-selective antagonists, further studies of 5-HT1A receptor function have been hindered by the lack of highly selective antagonists. The term 'silent' antagonist has been used for such compounds in order to distinguish them unequivocally from several 5-HT1A receptor partial agonists which were initially designated 'antagonists'. In this report we provide a comprehensive review of the biochemical, pharmacological and behavioural properties of the first potent, selective and silent 5-HT1A receptor antagonist, WAY-100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-(2- pyridinyl)cyclohexanecarboxamide trihydrochloride). WAY-100635 had an IC50 (displacement of specific [3H]8-OH-DPAT binding to 5-HT1A receptors in the rat hippocampus) of 1.35 nM and was > 100-fold selective for the 5-HT1A site relative to a range of other CNS receptors. [3H]WAY-100635 was also characterised as the first 5-HT1A antagonist radioligand, displaying the same regional distribution of binding sites as [3H]8-OH-DPAT in rat brain. As would be expected for the binding of an antagonist to a G-protein-coupled receptor, the Bmax of [3H]WAY-100635 specific binding was consistently 50-60% greater than that of the agonist radioligand, [3H]8-OH-DPAT. Mn2+, but not guanine nucleotides, inhibited [3H]WAY-100635-specific binding. [3H]WAY-100635 was also shown to bind selectively to brain 5-HT1A receptors in vivo, following intravenous administration to mice. In vitro electrophysiological studies demonstrated that WAY-100635 had no 5-HT1A receptor agonist actions, but dose-dependently blocked the effects of agonists at both the postsynaptic 5-HT1A receptor in the CA1 region of the hippocampus, and the somatodendritic 5-HT1A receptor located on dorsal raphe 5-HT neurones. In vivo, WAY-100635 also dose-dependently blocked the ability of 8-OH-DPAT to inhibit the firing of dorsal raphe 5-HT neurones, and to induce the '5-HT syndrome', hypothermia, hyperphagia and to elevate plasma ACTH levels. In the mouse light/dark box anxiety model, WAY-100635 induced anxiolytic-like effects. WAY-100635 had no intrinsic effect on cognition in the delayed-matching-to-position model of short-term memory in the rat, but reversed the disruptive effects of 8-OH-DPAT on motor motivational performance. These data clearly demonstrate that WAY-100635 is the first potent, selective and silent 5-HT1A receptor antagonist. Furthermore, [3H]WAY-100635 is the first antagonist radioligand to become available for 5-HT1A receptor binding studies both in vitro and in vivo. The positive effects of WAY-100635 in an anxiety model also indicate that a postsynaptic 5-HT1A receptor antagonist action may contribute to the anxiolytic properties of 5-HT1A receptor partial agonists.

Differentiation alters the expression of the two splice variants of the serotonin 5-HT3 receptor-A mRNA in NG108-15 cells

The serotonin 5-HT3-A receptor (5-HT3R-A) mRNA has been shown recently to be expressed as two forms (5-HT3R-AL and 5-HT3R-AS) varying by the presence or the absence of a sequence of 18 bases in the region corresponding to the second cytoplasmic domain of the receptor, and generated by alternative splicing at the level of the 3' acceptor site of exon 9. As the long form of the receptor exhibits a potential phosphorylation site that is disrupted by the alternative splicing, the hypothesis of functional identity and stochastic expression of these two variants was questioned. In the present study, we used quantitative reverse transcriptase-polymerase chain reaction to examine the possible influence of culture conditions on the expression and the alternative splicing of 5-HT3R-A mRNA in NG108-15 clonal cells. Cell differentiation induced by dibutyryl cyclic AMP or theophyllin plus prostaglandin E1 in the presence of 10% serum reduced by threefold the expression of total 5-HT3R-A mRNA, and favored the short form of the message as the ratio S/L (5-HT3R-AS mRNA/5-HT3R-AL mRNA) shifted from 2.23 to 7.33 after 9 days of treatment. Culture with 0.3% serum (instead of 10%) lowered by 10-fold the level of expression of total 5-HT3R-A mRNA, but only slightly reduced the S/L ratio. However, this ratio fell to 0.06 in the presence of 0.3% serum plus 10 ng/ml basic fibroblast growth factor. These results demonstrate that external factors can influence the differential expression of the two variants of the 5-HT3R-A in NG108-15 cells. Appropriate culture conditions for the almost exclusive expression of 5-HT3R-AS mRNA or 5-HT3R-AL mRNA in NG108-15 cells should allow the identification of possible differences in the respective functional properties of each of these two forms of the native 5-HT3 receptor.

Relation of coronary angioscopic findings at coronary angioplasty to angiographic restenosis

BACKGROUND

Discordant results have been reported regarding morphological predictors of restenosis after percutaneous transluminal coronary angioplasty (PTCA). These discrepancies may be related to the limitations of angiography in the study of plaque morphology.

METHODS AND RESULTS

We studied 117 consecutive patients who underwent successful PTCA and who underwent coronary angioscopy before and immediately after the procedure. Angiographic follow-up was performed in 99 (85%) patients. We analyzed the relationship between angioscopic variables at the time of PTCA and the occurrence of restenosis assessed by quantitative coronary angiography. Plaque shape and color had no effect on late loss in luminal diameter (late loss: smooth lesions, 0.55 +/- 0.68 mm; complex lesions, 0.76 +/- 0.60 mm; white plaques, 0.51 +/- 0.56 mm; yellow plaques, 0.65 +/- 0.72 mm; P = NS). An angioscopic protruding thrombus at the PTCA site was associated with significantly greater loss in luminal diameter (late loss: no thrombus, 0.47 +/- 0.54 mm; lining thrombus, 0.59 +/- 0.67 mm; protruding thrombus, 1.07 +/- 0.77 mm; P < .05). Dissection assessed by angioscopy immediately after PTCA had no effect on late loss in luminal diameter (late loss: no dissection, 0.60 +/- 0.60 mm; simple dissection, 0.82 +/- 0.75 mm; complex dissection, 0.57 +/- 0.80 mm; P = NS).

CONCLUSIONS

These results show that coronary angioscopy may be helpful in predicting the risk of restenosis after PTCA. The high rate of angiographic recurrence observed when PTCA is performed at thrombus-containing lesions supports a role for thrombus in the process of luminal renarrowing after PTCA.

[New perspectives in the serotoninergic treatment for depression]

A great deal of data support the view that depression is frequently associated with a decrease in central serotonergic neurotransmission. Furthermore, this neurobiological alteration very probably contributes to depression because treatments known to increase the 'serotonergic tone', such as the chronic administration of selective serotonin reuptake inhibitors (SSRIs), have antidepressant properties. Extensive studies of the mechanisms of action of SSRIs led to the discovery of the key role of somato-dendritic 5-HT1A autoreceptors in a negative control of serotonergic neurotransmission. From this finding, a new treatment of depression has been attempted which consists of the association of an SSRI with an antagonist (non-selective) of these autoreceptors. The potent antidepressant action of this association (with a shorter delay of action, even in depressed patients previously resistant to 'classical' therapies) should promote novel therapeutic strategies consisting of raising the 'serotonergic tone' by acting on different (but convergent) molecular targets.

Immunolabeling of the Na+/Cl(-)-dependent "orphan" transporter Rxt1 in the rat central nervous system

Previous studies have shown that the mRNA encoding the Na+/Cl(-)-dependent "orphan" transporter Rxt1 is expressed exclusively in the central nervous system (CNS). In the present study, specific antibodies were raised in rabbits for the detailed mapping of this transporter in the rat. The C-terminal part of Rxt1 was fused with glutathione-S-transferase (Rxt1ct-GST) and the resulting fusion protein was used as antigen. The specificity of the antiserum toward Rxt1 was confirmed by immunofluorescent, Western blot, and immunoautoradiographic experiments. In cerebral cortex membranes, Rxt1-like material recognized by the antiserum is a glycosylated protein of 97-116 kDa. This protein was the most abundant in the caudate-putamen, followed, in decreasing order, by the cerebral cortex approximately hippocampus > cerebellum > brainstem > spinal cord. In contrast, no immunoreactive material could be detected in peripheral tissues (tongue, thymus, heart, lung, spleen, kidney, adrenals, liver, skeletal muscle, intestine, testis). Immunoautoradiographic labeling with affinity-purified anti-Rxt1ct-GST antibodies showed high levels of Rxt1-like material in the olfactory bulb, cerebral cortex, striatal complex, hippocampal formation, superior layer of the anterior colliculus, cortex, and deep nuclei in the cerebellum. The regional distribution of Rxt1-like material generally matched that of GABAergic and glutamatergic projections in agreement with previous in situ hybridization data.

Effects of dorsal rhizotomy and selective lesion of serotonergic and noradrenergic systems on 5-HT1A, 5-HT1B, and 5-HT3 receptors in the rat spinal cord

Autoradiographic studies were performed in combination with dorsal rhizotomy or selective lesion of descending serotonergic or noradrenergic systems in an attempt to identify the neuronal cell types endowed with the serotonin 5-HT1A, 5-HT1B and 5-HT3 receptors in the rat spinal cord. Unilateral sectioning of seven dorsal roots (C4-T2) at the cervical level produced a marked decrease (approximately-75%, 10 days after the surgery) in the binding of [125I]iodozacopride to 5-HT3 receptors in the superficial layers of the ipsilateral dorsal horn, further confirming the preferential location of these receptors on primary afferent fibres. In addition, a significant decrease (approximately 20%) in the binding of [3H]8-OH-DPAT to 5-HT1A receptors and of [125I]GTI to 5-HT1B receptors was also observed in the same spinal area in rhizotomized rats, suggesting that a small proportion of these receptors are also located on primary afferent fibres. The labelling of 5-HT1B receptors was significantly decreased (-12%) in the dorsal horn at the cervical (but not the lumbar) level, and that of 5-HT3 receptors was unchanged in the whole spinal cord in rats whose descending serotonergic projections had been destroyed by 5,7-dihydroxytryptamine. Conversely, the labelling of 5-HT1A receptors was significantly increased in the cervical (+13%) and lumbar (+42%) dorsal horn in 5,7-dihydroxytryptamine-lesioned rats. Similarly, [3H]8-OH-DPAT binding to 5-HT1A receptors significantly increased (+26%) in the lumbar (but not the cervical) dorsal horn in rats whose noradrenergic systems had been lesioned by DSP-4. The labelling of 5-HT1B receptors was also increased (+31% at the cervical level; +17% at the lumbar level), whereas that of 5-HT3 receptors remained unchanged in these animals. These data indicate that complex adaptive changes in the expression of 5-HT1A and 5-HT1B receptors occurred in the rat spinal cord following the lesion of descending monoaminergic systems.

Glucocorticoid receptor-mediated inhibition by corticosterone of 5-HT1A autoreceptor functioning in the rat dorsal raphe nucleus

In the rat brain, the dorsal raphe nucleus contains a large proportion of serotoninergic neurons, which are mostly regulated by somato-dendritic 5-HT1A autoreceptors. This nucleus also possesses intracellular glucocorticoid receptors (GR), which may be involved in the well established modulation of serotonin (5-hydroxytryptamine, 5-HT) metabolism by glucocorticoids. Control by corticosteroids of 5-HT1A receptor-mediated inhibitory control of the firing of serotoninergic neurons in the dorsal raphe nucleus was investigated using an in vitro electrophysiological approach. The spontaneous firing rate of serotoninergic neurons recorded in brain stem slices and its inhibition due to 5-HT1A autoreceptor stimulation by 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) were similar in adrenalectomized rats and sham-operated animals. In vitro pretreatment with corticosterone (30-100 nM) significantly reduced 8-OH-DPAT-induced inhibition of the 5-HT cell discharge in slices from adrenalectomized rats. This effect could be prevented by the GR antagonist, 11 beta-(4-dimethyl-amino-phenyl)- 17 beta-hydroxy-17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one (RU) 38486, 30 nM), and mimicked by the GR agonist, 11 beta, 17 beta-dihydroxy-6-methyl-17 alpha (prop-1-ynyl) androsta-1,4,6-trien-3-one (RU 28362, 500 nM). In contrast, the mineralocorticoid receptor (MR) agonist, aldosterone (10 nM), did not alter 8-OH-DPAT-induced inhibition in tissues from adrenalectomized animals. Complementary autoradiographic experiments showed that [3H]8-OH-DPAT specific binding to 5-HT1A sites in the dorsal raphe nucleus (and the hippocampus) was not significantly altered following adrenalectomy and exposure of brain stem slices to corticosterone. These data suggest that GR are involved in the suppressive effects of high levels of corticosterone on the 5-HT1A receptor-dependent regulation of 5-HT neuronal activity in the rat dorsal raphe nucleus.

Failure of CCK receptor ligands to modify anxiety-related behavioural suppression in an operant conflict paradigm in rats

The effects of cholecystokinin (CCK) receptor ligands were studied in the rat safety signal withdrawal conflict procedure, an operant paradigm sensitive to both anxiolytic and anxiogenic compounds. In this procedure, behavioural suppression of lever pressing for food was induced by the withdrawal of a conditioned signal for safety without the usual presentation of a conditioned signal for danger. The compounds tested were selective CCK-B antagonists [CI-988 (0.01-1 mg/kg SC), L-365,260 (0.004-2 mg/kg IP) and LY 262,691 (0.001-1 mg/kg SC)], CCK-B agonists [CCK-4 (0.01-1 mg/kg SC) and BC 264 (0.004-1 mg/kg IP)] and CCK-A antagonists [devazepide (0.001-1 mg/kg SC) and lorglumide (0.01-1 mg/kg SC)]. None of these drugs induced the expected behavioural effects, i.e. an anxiolytic-like release of the behavioural suppression with CCK-B and, possibly, CCK-A antagonists and/or a further reduction of lever pressing with CCK-B agonists, indicative of an anxiogenic-like potential. In contrast, the established anxiolytic lorazepam (0.06-0.25 mg/kg IP), as well as diazepam (2 mg/kg IP) and buspirone (0.25 mg/kg SC) used as positive control drugs, released the suppression of pressing for food during the period associated with the safety signal withdrawal, whereas picrotoxin (1 mg/kg IP), used as an anxiogenic control, further reduced responding during this conflict period. The present results contrast with a series of published data suggesting the involvement of CCK processes in anxiety-related behaviour in rodent models such as the elevated plus-maze or the light:dark two compartment test, and in panic disorders in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Accumulation of fetal fibronectin mRNAs after balloon denudation of rabbit arteries

BACKGROUND

Fibronectin (FN), a component of the extracellular matrix, influences cellular migration and differentiation. It is a prominent component of the extracellular matrix of normal arteries and is thought to play an important role in the pathogenesis of restenosis after angioplasty. FN exists in multiple forms that arise from a single RNA transcript that can be alternatively spliced. EIIIA- and EIIIB-containing FN mRNAs predominate in the embryo, whereas in the adult, most of the normal tissue FN lacks these domains. Since few data were available concerning pattern of expression of the different alternatively spliced forms of FN mRNA in arteries after endoluminal injury, we analyzed the expression of EIIIA and EIIIB FN isoforms at different times after experimental angioplasty.

METHODS AND RESULTS

The spatial and temporal alterations in FN expression were studied in an in vivo model of endothelial denudation in the rabbit aorta and iliac artery by a combination of immunochemistry and in situ hybridization methods. Alternatively spliced forms of FN EIIIA and EIIIB were detected in the media and the adventitia of both types of vessels 24 to 48 hours after injury. Two weeks after injury, EIIIA and EIIIB mRNAs were found to accumulate within the luminal layers of the neointima. The cellular form of FN protein was not found until 2 weeks after the injury and accumulated in the inner part of the neointima.

CONCLUSIONS

These data demonstrate that FN upregulation is an early and long-lasting process after arterial injury. These results suggest that the induction of the embryonic FN isoforms may be involved in the restenotic process that follows balloon denudation of arteries.

Chronic alcoholization alters the expression of 5-HT1A and 5-HT1B receptor subtypes in rat brain

The expression of central 5-HT1A and 5-HT1B receptors was studied in several brain areas of rats subjected to a 2-week period of chronic alcoholization, followed by 18 h withdrawal. Quantitative autoradiography indicated that the ethanol treatment provoked an increase (approximately +30%) in the labeling by [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT) and [3H]N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane carboxamide ([3H]WAY-100635) of 5-HT1A autoreceptors in the dorsal raphe nucleus, accompanied by a concomitant decrease in the labeling of postsynaptic 5-HT1A receptors in the hippocampus (approximately -20%), anterior (approximately -30%) and posterior (approximately -32%) cortices. These changes were associated with a tendency toward an increase and decrease in 5-HT1A mRNA levels in the anterior raphe area and hippocampus, respectively, suggesting that the changes observed are due to modifications in 5-HT1A receptor protein synthesis. The autoradiographic labeling of 5-HT1B receptors by serotonin-O-carboxymethylglycyl[125I]iodotyrosinamide ([125I]GTI) was found to increase (+55%) in the globus pallidus of alcoholized rats. Interestingly, a significant increase (+57%) in 5-HT1B receptor mRNA levels was observed in the striatum, which contains cell bodies of neurons projecting into the globus pallidus. These data suggest that altered sensitivity of chronically alcoholized rats to 5-HT1A and 5-HT1B receptor ligands may result from alcohol-induced changes in the transcription of the genes encoding these receptors.

Modification of behavioral effects of 8-hydroxy-2-(di-n-propylamino)tetralin following chronic ethanol consumption in the rat: evidence for the involvement of 5-HT1A receptors in ethanol dependence

Behavioral effects induced by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; i.e., lower lip retraction, flat body posture, and forepaw treading) were examined in rats during ethanol withdrawal following a 2-week period of access to a liquid diet containing 9% (v/v) ethanol. After an 18 h withdrawal period, tolerance to 8-OH-DPAT-induced flat body posture and, conversely, sensitization to the effects of 8-OH-DPAT on lower lip retraction were observed in the 9% ethanol group as compared to control rats fed an isocaloric diet. In contrast, 8-OH-DPAT-induced forepaw treading in the 9% ethanol group was not significantly different in comparison to control rats. Plasma corticosterone levels were significantly higher in the ethanol-exposed group than in control animals, an effect which was not additive with the increase in corticosterone levels normally observed after the administration of low doses of 8-OH-DPAT. Altered flat body posture and lower lip retraction responses to a submaximal dose of 8-OH-DPAT (2.5 mg/kg i.p.) were still observed as late as 3 days after withdrawal of the 9% ethanol liquid diet, but were no longer apparent at 7 days. Interestingly, prominent ethanol withdrawal signs such as tremor and rigidity, while occurring on the first day, were completely absent on the third day. Taken together, these results indicate that chronic ethanol exposure differentially alters sensitivity to several pharmacological effects of the 5-HT1A receptor ligand 8-OH-DPAT. They further support the involvement of 5-HT (5-hydroxytryptamine, serotonin) systems in alcohol abuse and therapeutic interventions using 5-HT1A ligands.

Developmental changes in the differential expression of two serotonin 5-HT3 receptor splice variants in the rat

PCR was used to isolate identical partial cDNA clones encoding a serotonin 5-HT3 receptor subunit from rat nodose and superior cervical ganglia. The amino acid sequence predicted from these clones, extending from the putative transmembrane domain I to the stop codon, demonstrated a 93% homology with the 5-HT3 receptor A (R-A) subunit cloned from NCB 20 hybridoma mouse neuroblastoma/Chinese hamster embryonic brain cells. Comparison of the sequences of the rat gene and cDNA encoding this subunit revealed a five amino acid deletion, GSLLP, located within the putative second intracellular loop of the receptor subunit. This deletion was shown to occur at an intron/exon junction. Therefore, alternative splicing was probably responsible for the presence of short (5-HT3 R-As) and long (5-HT3 R-AL) forms of 5-HT3 R-A mRNA in these ganglia. PCR experiments, with specific primers located upstream and downstream of the GSLLP deletion, were used to detect reverse transcribed 5-HT3 R-A mRNAs. A short fragment (92 bp), corresponding to the deleted form, and a long fragment (107 bp), corresponding to the nondeleted form, were amplified from various regions of the CNS and peripheral ganglia of the rat, as well as from NG108-15 hybridoma cells. In the adult rat, the ratio of the two forms varied very little from one tissue to another, the long form corresponding to only approximately 10% of the total 5-HT3 R-A mRNA. Study of their respective distributions during ontogeny demonstrated a differential expression of the short and long forms in some tissues during late embryonic development, at embryonic day 17 (E17) or E20.(ABSTRACT TRUNCATED AT 250 WORDS)

Early desensitization of somato-dendritic 5-HT1A autoreceptors in rats treated with fluoxetine or paroxetine

Electrophysiological and autoradiographic approaches were used to assess possible changes in 5-hydroxytryptamine (serotonin) 5-HT1A receptors in the rat dorsal raphe nucleus after a subchronic treatment with fluoxetine or paroxetine, two specific serotonin reuptake inhibitors with antidepressant properties. Fluoxetine or paroxetine were injected daily (5 mg/kg, i.p.) for various time periods up to 21 days. Electrophysiological recordings performed 24 h after the last injection showed that the potency of the 5-HT1A receptor agonist, 8-OH-DPAT, to depress the firing of serotoninergic neurons in the dorsal raphe nucleus within brain stem slices was significantly reduced as early as after a 3-day treatment with either drug. The proportion of recorded neurons showing desensitization of somatodendritic 5-HT1A autoreceptors increased along the treatment from approximately 40% on the 3rd day to 60-80% on the 21st day. At no time during the treatment, was the specific binding of [3H]8-OH-DPAT (agonist radioligand) or [3H]WAY-100 635 (antagonist radioligand) to 5-HT1A receptors modified in the dorsal raphe nucleus or in other brain areas, suggesting that neither the density nor the coupling of these receptors to G-proteins were probably altered in rats injected with fluoxetine or paroxetine for up to 21 days. These results show that adaptive desensitization of somatodendritic 5-HT1A autoreceptors within the dorsal raphe nucleus can already be detected after a 3-day treatment with selective serotonin reuptake inhibitors. Rather than the desensitization per se, it may be the progressive increase in the number of serotoninergic neurons with desensitized 5-HT1A autoreceptors which plays a critical role in the (slowly developing) antidepressant action of these drugs.

Relation between the deletion polymorphism of the angiotensin-converting enzyme gene and late luminal narrowing after coronary angioplasty

BACKGROUND

The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been implicated in the pathogenesis of coronary artery disease. The deletion allele is strongly associated with the level of circulating ACE and is a potent risk factor for myocardial infarction. Recently, the deletion allele was also associated with the occurrence of visually diagnosed restenosis after percutaneous transluminal coronary angioplasty (PTCA) in a selected population of patients with acute myocardial infarction.

METHODS AND RESULTS

We investigated the influence of the ACE I/D polymorphism on the occurrence of restenosis after PTCA with the use of quantitative coronary angiography. ACE I/D genotypes were characterized in 118 consecutive patients who had one-vessel disease and were undergoing systematic angiographic follow-up. Coronary angiograms were analyzed before and after PTCA and at follow-up (7.4 +/- 3.0 months). Before PTCA, there were no clinical or angiographic differences among the three groups of genotypes (DD, n = 39; ID, n = 62; II, n = 17). After PTCA, the mean differences in minimal luminal diameter between post-PTCA and pre-PTCA angiograms (acute gain) were identical in the three groups, as was the mean percent residual stenosis. At follow-up angiography, the mean difference in minimal coronary luminal diameter between post-PTCA and follow-up angiograms (late loss) was not significantly different in the three groups of genotypes. The percentage of patients with restenosis defined as a > 50% stenosis was identical in the three groups.

CONCLUSIONS

In this quantitative study, the I/D polymorphism of the ACE gene had no influence on the occurrence of restenosis after coronary angioplasty.

Restenosis after coronary angioplasty

The major disadvantage of using percutaneous transluminal coronary angioplasty to treat patients with atherosclerotic coronary disease is the frequent occurrence of restenosis after an initially successful procedure. Studies in animals and histological observations in man have demonstrated that restenosis is characterized by neointimal hyperplasia due to smooth muscle cell proliferation and to the synthesis of extracellular matrix. Improvements in technology or pharmacological interventions have had no significant impact on the rate of restenosis. In spite of our increased understanding of the molecular mechanisms of restenosis. no effective treatment is available at the present time. Gene therapy, which has produced encouraging initial results in experimental models, may provide a solution in the medium term.

Novel, potent, and selective 5-HT3 receptor antagonists based on the arylpiperazine skeleton: synthesis, structure, biological activity, and comparative molecular field analysis studies

Synthesis and pharmacological evaluation of a series of condensed quinoline derivatives bearing a basic nitrogen on piperazine or [(dimethylamino)ethyl]thio moieties attached at the 2-position of the quinoline nucleus are described. 5-HT receptor binding studies revealed, for most of the compounds studied, nanomolar affinity for the 5-HT3 receptor subtype. The most active compound, benzopyrano[3,4-c]quinoline derivative 5f, displayed a Ki value very similar to that reported for quipazine along with an improved selectivity. Functional and in vivo testing carried out on three selected compounds showed that 5f,j,n are potent 5-HT3 receptor antagonists with potencies in the same range as the best known 5-HT3 receptor antagonists ondansetron, tropisetron, and zacopride. The crystal and molecular structures of compounds 5f,j,n were determined by single-crystal X-ray diffraction and used as starting structures for molecular modeling studies. Comparative molecular field analysis (CoMFA) was applied to binding constants of compounds 5a-p and 6a-h. The cross-validated r2, derived from partial least-squares calculations, indicated a good predictive capacity for affinity values in the series of compounds investigated. Evidence for the prediction capacity is provided in the form of plots of actual vs predicted pKi values. The steric and electrostatic features of the CoMFA-derived model are presented as standard coefficient contour maps of steric and electrostatic fields.

[Percutaneous coronary angioscopy: 200 observations in 100 candidates for angioplasty]

Due to the recent technological advances, it is possible to perform percutaneous coronary angioscopy in a straightforward fashion in most patients. To know the safety and usefulness of this technique we present 200 observations in 100 patients candidates for coronary intervention. We used a coronary angioscope (Baxter, Edwards LIS Division), that can be placed using the conventional technique for percutaneous coronary angioplasty. The system incorporates a proximal occluding balloon, and distally a movable optical fiber. Case selection considered non-ostial coronary segments relatively straight. It was possible to obtain adequate images in 86 percent of cases. The technique is safe in experienced hands: there were two cases of ventricular fibrillation, and two cases of local dissection occurred, none of these associated with clinical consequences. No myocardial infarction, surgery or death, related to this procedure occurred. Valuable diagnostic information is derived from angioscopy as the method provides some histopathological correlation. Stable plaques are usually uniformly white or yellow. Unstable plaques are yellow and ulcerated. Thrombus can be easily recognized in acute coronary syndromes. Also in percutaneously treated segments, the final result and the presence of dissection or hemorrhage can be visualized. Coronary percutaneous angioscopy is safe and brings useful clinical information. Its applications in the clinical practice are still to be determined.