5-HT2A-mGlu2/3 receptor complex in rat spinal cord glutamatergic nerve endings: A 5-HT2A to mGlu2/3 signalling to amplify presynaptic mechanism of auto-control of glutamate exocytosis

Olivero, Guendalina; Grilli, Massimo; Vergassola, Matteo; Bonfiglio, Tommaso; Padolecchia, Cristina; Garrone, Beatrice; Giorgio, Francesco Paolo Di; Tongiani, Serena; Usai, Cesare; Marchi, Mario; Pittaluga, Anna

doi:10.1016/j.neuropharm.2018.02.030

Cited by 24 publications

(43 citation statements)

References 41 publications

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“…Animal studies showed that experimental nerve injuries provoke the upregulation of the 5-HT 2A receptor in dorsal horn neurons promoting spinal hyperexcitation [17]. Recent studies suggested a cross-talk mechanism between 5-HT 2A and mGlu2/3 receptors both in the brain and in the spinal cord [18,19]. In particular, in the spinal cord, mGlu2/3 and 5-HT 2A receptors colocalize at a presynaptic level and 5-HT 2A antagonists trigger positive allosteric modulations of mGlu2/3 autoreceptors in controlling glutamate exocytosis [19].…”

Section: Discussionmentioning

confidence: 99%

“…Recent studies suggested a cross-talk mechanism between 5-HT 2A and mGlu2/3 receptors both in the brain and in the spinal cord [18,19]. In particular, in the spinal cord, mGlu2/3 and 5-HT 2A receptors colocalize at a presynaptic level and 5-HT 2A antagonists trigger positive allosteric modulations of mGlu2/3 autoreceptors in controlling glutamate exocytosis [19]. Accordingly, TRZ might modulate nociceptive second-order activation and thus reduce pain.…”

Section: Discussionmentioning

confidence: 99%

“…Recent preclinical studies suggested a potential role of 5-HT 2A and the mGlu2/3 heterodimer both in the brain and the spinal cord accounting for hyperexcitability and a cellular signaling cascade related to glutamate exocytosis and neuropathic pain [ 17 – 19 ]. Based on this cross-talk mechanism, it has been proposed that TRZ, a potent 5-HT 2A antagonist, could possibly modulate the glutamate exocytosis [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

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Efficacy and Safety of Low Doses of Trazodone in Patients Affected by Painful Diabetic Neuropathy and Treated with Gabapentin: A Randomized Controlled Pilot Study

Lipone

Ehler²,

Nastaj³

et al. 2020

CNS Drugs

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Background Painful diabetic neuropathy is an important therapeutic challenge as the efficacy of analgesic drugs in this setting is still unsatisfactory. Monotherapy with available treatments is often not sufficient and a combination of drugs is necessary. Trazodone (TRZ) is a compound with a multi-modal mechanism of action, being a serotonin-2 antagonist/reuptake inhibitor developed and approved for the treatment of depression in several countries. Previous clinical trials suggest a possible beneficial effect of low doses of trazodone for the treatment of patients affected by painful diabetic neuropathy. Objective This phase II study was designed to collect data on the efficacy and safety of low doses of TRZ combined with gabapentin after 8 weeks of treatment in patients affected by painful diabetic neuropathy. Methods This was a randomized, double-blind, placebo-controlled, multi-center, international, prospective study. Male and female diabetic patients aged 18-75 years and affected by painful diabetic neuropathy were eligible for enrollment. Subjects were randomized (1:1:1 ratio) to TRZ30 (10 mg three times daily for 8 weeks) or TRZ60 (20 mg three times daily for 8 weeks) or placebo. Gabapentin as background therapy was administered in open-label conditions to all patients. The primary endpoint was the change from baseline of the Brief Pain Inventory Short Form item 5 to week 8. Secondary endpoints included the other Brief Pain Inventory Short Form items, and the assessment of anxiety, sleep, quality of life, patient's improvement, and safety. Results One hundred and forty-one patients were included in the intention-to-treat population: 43 allocated to the TRZ30 group, 50 to the TRZ60 group, and 48 to the placebo group. After 8 weeks, the mean changes of Brief Pain Inventory Short Form item 5 from baseline were − 3.1, − 2.6, and − 2.5 in the TRZ30, TRZ60, and placebo groups, respectively. No statistically significant differences between groups were seen. Nevertheless, a better trend was observed for TRZ30 vs placebo (95% confidence interval − 1.30, 0.15; p = 0.1179), on top of the background effect of gabapentin administered to all study groups. 62.8% of patients achieved a ≥ 50% reduction in the TRZ30 group, 54% in the TRZ60 group, and 45.8% in the placebo group. At the same time, a statistically significant improvement was observed in Brief Pain Inventory Short Form item 6 for TRZ30 vs placebo (95% confidence interval − 1.54, − 0.07; p = 0.0314). No serious adverse event occurred during the trial and the most frequent treatment-emergent adverse events involved nervous system, QT prolongation, and gastrointestinal disorders. Conclusions All treatment groups showed a clinically meaningful pain improvement; nevertheless, patients in the TRZ30 treatment group reported better efficacy outcomes. This finding suggests that low doses of TRZ could be useful for treating painful diabetic neuropathy, and support further adequately powered confirmatory trials investigating the efficacy of TRZ. Clinical Trial Registratio...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Efficacy and Safety of Low Doses of Trazodone in Patients Affected by Painful Diabetic Neuropathy and Treated with Gabapentin: A Randomized Controlled Pilot Study

Lipone

Ehler²,

Nastaj³

et al. 2020

CNS Drugs

View full text Add to dashboard Cite

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“…This approach represents therefore a method of choice to highlight the functional cross-talk linking presynaptic receptors ( Pittaluga et al, 2000 , 2005 ; Musante et al, 2011 ; Summa et al, 2011 ; Grilli et al, 2012 ; Di Prisco et al, 2016 ). By a functional point of view, the receptor–receptor interaction can be evidentiated in release studies as change(s) in transmitter release efficiency observed when exposing concomitantly synaptosomes to exogenous ligands acting at the colocalized receptors ( Longordo et al, 2006 ; Luccini et al, 2007 ; Olivero et al, 2018 ). In general, it is proposed that two receptors coexist and functional couple when the releasing activity due to their concomitant activations differs quantitatively from the sum of the releasing effects elicited by each receptor ( Pittaluga and Raiteri, 1992 ).…”

Section: Discussionmentioning

confidence: 99%

Presynaptic mGlu1 Receptors Control GABAB Receptors in an Antagonist-Like Manner in Mouse Cortical GABAergic and Glutamatergic Nerve Endings

Vergassola

Olivero

Cisani

et al. 2018

Front. Mol. Neurosci.

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Mouse cortical GABAergic synaptosomes possess presynaptic inhibitory GABAB autoreceptors. Accordingly, (±)baclofen (3 μM) inhibits in a CGP53423-sensitive manner the 12 mM KCl-evoked release of preloaded [3H]GABA. Differently, the existence of presynaptic release-regulating metabotropic glutamate type 1 (mGlu1) heteroreceptors in these terminals is still matter of discussion, although confocal microscopy unveiled the existence of mGlu1α with GABAB1 or GABAB2 proteins in cortical VGAT-positive synaptosomes. The group I mGlu agonist 3,5-DHPG failed to modify on its own the 12 mM KCl-evoked [3H]GABA exocytosis from cortical nerve endings, but, when added concomitantly to the GABAB agonist, it significantly reduced the 3 μM (±)baclofen-induced inhibition of [3H]GABA exocytosis. Conversely, the mGlu1 antagonist LY367385 (0.03–1 μM), inactive on its own on GABA exocytosis, amplified the 3 μM (±)baclofen-induced inhibition of [3H]GABA overflow. The ( ± )baclofen-induced inhibition of [3H]GABA exocytosis was more pronounced in cortical synaptosomes from Grm1crv4/crv4 mice, which bear a spontaneous mutation of the Grm1 gene leading to the functional inactivation of the mGlu1 receptor. Inasmuch, the expression of GABAB2 receptor protein in cortical synaptosomal lysates from Grm1crv4/crv4 mice was increased when compared to controls. Altogether, these observations seem best interpreted by assuming that mGlu1 coexist with GABAB receptors in GABAergic cortical synaptosomes, where they control GABA receptors in an antagonist-like manner. We then asked whether the mGlu1-mediated control of GABAB receptors is restricted to GABAergic terminals, or if it occurs also in other subpopulations of nerve endings. Release-regulating GABAB receptors also exist in glutamatergic nerve endings. (±)baclofen (1 μM) diminished the 12 mM KCl-evoked [3H]D-aspartate overflow. Also in these terminals, the concomitant presence of 1 μM LY367385, inactive on its own, significantly amplified the inhibitory effect exerted by (±)baclofen on [3H]D-aspartate exocytosis. Confocal microscopy confirmed the colocalization of mGlu1 with GABAB1 and GABAB2 labeling in vesicular glutamate type1 transporter-positive particles. Our results support the conclusion that mGlu1 receptors modulate in an antagonist-like manner presynaptic release-regulating GABAB receptors. This receptor–receptor interaction could be neuroprotective in central disease typified by hyperglutamatergicity.

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“…Mouse cortical purified synaptosomes were prepared as previously described (Olivero et al, 2018). The tissue was homogenized in 10 volumes of 0.32 M sucrose, buffered to pH 7.4 with Tris-(hydroxymethyl)amino methane (Tris, final concentration 0.01 M) using a glass/Teflon tissue grinder (clearance 0.25 mm).…”

Section: Preparation Of Synaptosomesmentioning

confidence: 99%

The depolarization-evoked, Ca2+-dependent release of exosomes from mouse cortical nerve endings: new insights into synaptic transmission.

Olivero

Cisani

Marimpietri

et al. 2020

Preprint

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Background and purpose Exosomes, nanosized extracellular vesicles, emerged as players in the cell-to-cell communication in the central nervous system (CNS), having a role in the modulation of the synaptic activity. This study aimed at evaluating whether exosomes can be actively released from presynaptic nerve terminals. Experimental Approach Mouse cortical synaptosomes were exposed to a depolarizing stimulus (25 mM KCl medium) and exosomes were isolated from the synaptosomal supernatants. Exosomes were characterized by dynamic light scattering, transmission electron microscopy, western blot and flow cytometry analyses. We also evaluated whether and how removing external Ca2+ ions or activating presynaptic GABAB receptors by exposing synaptosomes to (±)-baclofen (10 μM) affects the 25 mM KCl-evoked release of exosomes. Key Results The structural and biochemical analysis unveiled that synaptosomal supernatants contained vesicles having the size and the shape of exosomes, immunopositive for the exosomal markers TSG101, flotillin-1, CD63 and CD9. The content of these proteins in the exosomal fraction isolated from synaptosomal supernatants increased upon the exposure of nerve terminals to a depolarizing stimulus and occurred in a Ca2+-dependent fashion, mimicking the release of glutamate. (±)-Baclofen significantly reduced glutamate exocytosis but failed to affect the release of exosomes from cortical synaptosomes. Finally, presynaptic exosomes were shown to carry selected NMDA and AMPA receptors subunits. Conclusion and implications Our study unveils the Ca2+-dependent, depolarization-evoked release of exosomes from mouse cortical nerve terminals, which is insensitive to presynaptic releaseregulating GABAB receptors. These findings add new insights into the mechanisms of exosomes-mediated communication in CNS. Background and purpose Exosomes, nanosized extracellular vesicles, emerged as players in the cell-to-cell communication in the central nervous system (CNS), having a role in the modulation of the synaptic activity. This study aimed at evaluating whether exosomes can be actively released from presynaptic nerve terminals. Experimental Approach Mouse cortical synaptosomes were exposed to a depolarizing stimulus (25 mM KCl medium) and exosomes were isolated from the synaptosomal supernatants. Exosomes were characterized by dynamic light scattering, transmission electron microscopy, western blot and flow cytometry analyses. We also evaluated whether and how removing external Ca 2+ ions or activating presynaptic GABA B receptors by exposing synaptosomes to (±)-baclofen (10 μM) affects the 25 mM KCl-evoked release of exosomes.

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5-HT2A-mGlu2/3 receptor complex in rat spinal cord glutamatergic nerve endings: A 5-HT2A to mGlu2/3 signalling to amplify presynaptic mechanism of auto-control of glutamate exocytosis

Cited by 24 publications

References 41 publications

Efficacy and Safety of Low Doses of Trazodone in Patients Affected by Painful Diabetic Neuropathy and Treated with Gabapentin: A Randomized Controlled Pilot Study

Efficacy and Safety of Low Doses of Trazodone in Patients Affected by Painful Diabetic Neuropathy and Treated with Gabapentin: A Randomized Controlled Pilot Study

Presynaptic mGlu1 Receptors Control GABAB Receptors in an Antagonist-Like Manner in Mouse Cortical GABAergic and Glutamatergic Nerve Endings

The depolarization-evoked, Ca2+-dependent release of exosomes from mouse cortical nerve endings: new insights into synaptic transmission.

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