Santina Chiechio

Lmx1b is required for maintenance of central serotonergic neurons and mice lacking central serotonergic system exhibit normal locomotor activity

Central serotonergic neurons have been implicated in numerous animal behaviors and psychiatric disorders, but the molecular mechanisms underlying their development are not well understood. Here we generated Lmx1b (LIM homeobox transcription factor 1 β) conditional knock-out mice (Lmx1bf/f/p) in which Lmx1b was only deleted in Pet1 (pheochromocytoma 12 ETS factor-1)-expressing 5-HT neurons. In Lmx1bf/f/p mice, the initial generation of central 5-HT neurons appeared normal. However, the expression of both 5-HT-specific and non-5-HT-specific markers was lost in these neurons at later stages of development. The loss of gene expression is concomitant with downregulation of Lmx1b expression, with the exception of serotonin transporter Sert and tryptophan hydroxylase TPH2, whose expression appears to be most sensitive to Lmx1b. Interestingly, the expression of Pet1 is tightly coupled with expression of Lmx1b during later stages of embryonic development, indicating that Lmx1b maintains Pet1 expression. In Lmx1bf/f/p mice, almost all central 5-HT neurons failed to survive. Surprisingly, Lmx1bf/f/p mice survived to adulthood and exhibited normal locomotor activity. These data reveal a critical role of Lmx1b in maintaining the differentiated status of 5-HT neurons. Lmx1bf/f/p mice with normal locomotor function should provide a unique animal model for examining the roles of central 5-HT in a variety of animal behaviors.

Epigenetic Modulation of mGlu2 Receptors by Histone Deacetylase Inhibitors in the Treatment of Inflammatory Pain

Knowing that expression of metabotropic glutamate 2 (mGlu2) receptors in the dorsal root ganglia is regulated by acetylation mechanisms, we examined the effect of two selective and chemically unrelated histone deacetylase (HDAC) inhibitors, N-(2-aminophenyl)-4-[N-(pyridine-3-ylmethoxy-carbonyl)aminomethyl]benzamide (MS-275) and suberoylanilide hydroamic acid (SAHA), in a mouse model of persistent inflammatory pain. Although a single subcutaneous injection of MS-275 (3 mg/kg) or SAHA (5-50 mg/kg) was ineffective, a 5-day treatment with either of the two HDAC inhibitors substantially reduced the nociceptive response in the second phase of the formalin test, which reflects the development of central sensitization in the dorsal horn of the spinal cord. Analgesia was abrogated by a single injection of the mGlu2/3 receptor antagonist (αS)-α-amino-α-[(1S,2S)-2-carboxycyclopropyl]-9H-xantine-9-propanoic acid (LY341495; 1 mg/kg, i.p.), which was inactive per se. Both MS-275 and SAHA up-regulated the expression of mGlu2 receptors in the dorsal root ganglion (DRG) and spinal cord under conditions in which they caused analgesia, without changing the expression of mGlu1a, mGlu4, or mGlu5 receptors. Induction of DRG mGlu2 receptors in response to SAHA was associated with increased acetylation of p65/RelA on lysine 310, a process that enhances the transcriptional activity of p65/RelA at nuclear factor-κB-regulated genes. Transcription of the mGlu2 receptor gene is known to be activated by p65/RelA in DRG neurons. We conclude that HDAC inhibition produces analgesia by up-regulating mGlu2 receptor expression in the DRG, an effect that results from the amplification of NF-κB transcriptional activity. These data provide the first evidence that HDAC inhibitors cause analgesia and suggest that HDACs are potential targets for the epigenetic treatment of pain.

Mice Lacking Central Serotonergic Neurons Show Enhanced Inflammatory Pain and an Impaired Analgesic Response to Antidepressant Drugs

A large body of literature has implicated serotonin [5-hydroxytryptamine (5-HT)] in descending modulation of nociceptive transmission. Here, we have studied the pain behavior of Lmx1b conditional knock-out mice (Lmx1bf/f/p), which lack 5-HT neurons in the CNS. Lmx1bf/f/p mutant mice showed normal thermal and visceral pain responses but were less sensitive to mechanical stimuli and exhibited enhanced inflammatory pain compared with their littermate control mice. Importantly, the analgesic effect of several antidepressant drugs, including selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants, was either abolished or greatly attenuated in Lmx1bf/f/p mice. Moreover, in the acute versus persistent pain settings, the analgesic actions of the SNRI duloxetine and the SSRI fluoxetine were differentially affected. Together, our results provide in vivo genetic evidence demonstrating that although the predominant role of the central 5-HT system in inflammatory pain is inhibitory, its role in acute mechanical pain is facilitatory. The findings that the analgesic effects of various antidepressant drugs are differentially dependent on the central 5-HT system should help us to understand the mechanism of the analgesic action of different classes of antidepressants in the management of persistent pain.

Prediction of the response to citalopram and reboxetine in post-stroke depressed patients

Rationale and objectiveDepression is a significant complication of stroke. The effectiveness of antidepressant drugs in the management of post-stroke depression (PSD) has been widely investigated. However, the choice of antidepressant drug is critically influenced by its safety and tolerability and by its effect on concurrent pathologies. Here we investigate the efficacy and safety of a selective serotonin reuptake inhibitor (SSRI), citalopram, and a noradrenaline reuptake inhibitor (NARI), reboxetine, in post-stroke patients affected by anxious depression or retarded depression.MethodsThis was a randomized double-blind study. Seventy-four post-stroke depressed patients were diagnosed as affected by anxious or retarded depression by using a synoptic table. Randomisation was planned so that 50% of the patients in each subgroup were assigned for 16 weeks to treatment with citalopram and the remaining 50% were assigned to treatment with reboxetine. The Beck Depression Inventory (BDI), the Hamilton Depression Rating Scale (HDRS) and a synoptic table were used to score depressive symptoms.ResultsBoth citalopram and reboxetine showed good safety and tolerability. Citalopram exhibited greater efficacy in anxious depressed patients, while reboxetine was more effective in retarded depressed patients.ConclusionsCitalopram or other SSRIs and reboxetine may be of first choice treatment in PSD because of their good efficacy and lack of severe side effects. In addition, PSD patients should be classified according to their clinical profile (similarly to patients affected by primary depression) for the selection of SSRIs or reboxetine as drugs of choice in particular subgroups of patients.

The SSRI, citalopram, improves bradykinesia in patients with Parkinson's disease treated with L-dopa.

Idiopathic Parkinsons disease (IPD) is characterized by motor signs such as akinesia, rigidity, and often tremor at rest. In addition to these symptoms, depression is a common finding affecting 40% of patients with IPD. This study evaluates the effect of the selective serotonin reuptake inhibitor, citalopram, on motor and nonmotor symptoms of depressed and nondepressed patients with IPD. Forty-six nondemented patients with IPD (24 men, 22 women; mean age 64 ± 5.3 years; mean ± SD disease duration, 6.4 ± 3.2 years; mean ± SD Hoehn-Yahr stage, 2.8 ± 1.2) were included in the study. Patients were divided in two subgroups: depressed (n = 18) and nondepressed (n = 28). Citalopram was added in an unblinded manner, starting with 10 mg/d, and, after a week, increased up to 20 mg/d in the depressed subgroup (n = 18) and in half of the nondepressed subgroup (n = 14). Parkinsonian and depressive symptoms were evaluated before and after 1 and 4 months of treatment. Statistical evaluation was made by analysis of variance for repeated measures. Citalopram did not worsen motor performance in IPD, but improved bradykinesia and finger taps after 1 month and 4 months of treatment both in patients with and without depression (p < 0.05 versus baseline). A clear improvement in mood was also observed in 15 of 16 patients with depression. Although case reports indicate that citalopram can potentially worsen the motor symptoms in patients with PD, to date this effect has not been confirmed. Many of the symptoms, typically associated with depression, can be observed in nondepressed patients with IPD, because signs thought to represent depression can be produced by Parkinsons disease. In this study, we observed that when combined with levodopa, citalopram induces an improvement of motor performance, in particular of subscores 23 and 31 of Unified Parkinsons Disease Rating Scale both in depressed and in nondepressed patients with IPD.

Metabotropic glutamate receptors and the control of chronic pain

Over the past two decades metabotropic glutamate (mGlu) receptor ligands have been investigated for their potential therapeutic effects in different disorders of the central nervous system (CNS), including anxiety, depression, schizophrenia, and neurodegenerative diseases. In addition, it has been widely demonstrated that mGlu receptors are able to modulate pain transmission both in inflammatory and neuropathic pain models. A large number of preclinical studies combining the use of selective ligands with the knockout strategy have revealed more details about the role of the different mGlu receptor subtypes in the modulation of pain information. This review will address the role of mGlu receptors in pain sensitivity focusing on different strategies to achieve pain control by targeting specific mGlu receptor subtypes. Specifically, pharmacological interventions aimed at inhibiting group I mGlu receptor-mediated signaling and/or potentiating groups II and III mGlu receptor signaling together with an epigenetic approach leading to an increased expression of mGlu2 receptors will be discussed.

Erratic expression of DNA polymerases by β-amyloid causes neuronal death

An ectopic reentrance into the cell cycle with ensuing DNA replication is required for neuronal apoptosis induced by β‐amyloid. Here, we investigate the repertoire of DNA polymerases expressed in β‐amyloid‐treated neurons, and their specific role in DNA synthesis and apoptosis. We show that exposure of cultured cortical neurons to β‐amyloid induces the expression of DNA polymerase‐β, proliferating cell nuclear antigen, and the p49 and p58 subunits of DNA primase. Induction requires the activity of cyclin‐dependent kinases. The knockdown of the p49 primase subunit prevents β‐amyloid‐induced neuronal DNA synthesis and apoptosis. Similar effects are observed by knocking down DNA polymerase‐β or by using dideoxycytidine, a preferential inhibitor of this enzyme. Thus, the reparative enzyme DNA polymerase‐β unexpectedly mediates a large component of de novo DNA synthesis and apoptotic death in neurons exposed to βamyloid. These data indicate that DNA polymerases become death signals when erratically expressed by differentiated neurons.

Preparation and analgesic activity of Eudragit RS100 microparticles containing diflunisal

Two different techniques, the quasi-emulsion solvent diffusion method and spray drying that provide polar and nonpolar preparation environments, were used to prepare microspheres from Eudragit RS100 (RS) (acrylic/methacrylic copolymer) incorporating the nonsteroidal anti-inflammatory drug diflunisal. The effects of pH on the preparation medium and drug/polymer ratio on production yield and drug incorporation, as well as on the in vitro drug release at pH 1.2 and 6.8 from tabletted microparticles, were evaluated. The drug-polymer interactions and the effect of diflunisal incorporation in the polymer matrix on drug crystallinity have been evaluated by using differential scanning calorimetry, IR and ultraviolet spectroscopy, x-ray diffraction, and microscopy analysis. A preliminary biological assay confirmed that diflunisal maintains its analgesic activity after intraperitoneal administration to rats.Two different techniques, the quasi-emulsion solvent diffusion method and spray drying that provide polar and nonpolar preparation environments, were used to prepare microspheres from Eudragit RS100® (RS) (acrylic/methacrylic copolymer) incorporating the nonsteroidal anti-inflammatory drug diflunisal. The effects of pH on the preparation medium and drug/polymer ratio on production yield and drug incorporation, as well as on the in vitro drug release at pH 1.2 and 6.8 from tabletted microparticles, were evaluated. The drug-polymer interactions and the effect of diflunisal incorporation in the polymer matrix on drug crystallinity have been evaluated by using differential scanning calorimetry, IR and ultraviolet spectroscopy, x-ray diffraction, and microscopy analysis. A preliminary biological assay confirmed that diflunisal maintains its analgesic activity after intraperitoneal administration to rats.

Evaluation of the Prophylactic Efficacy of Amitriptyline and Citalopram, Alone or in Combination, in Patients with Comorbidity of Depression, Migraine, and Tension-Type Headache

Antidepressants are used to treat chronic daily headache disorders such as migraine and chronic tension-type headache (TTH), which are often associated with depression and anxiety. Here, we studied the efficacy and tolerability of amitriptyline and citalopram, given alone or in combination, in patients with ‘triple’ comorbidity of depression, TTH, and migraine. Eighty-eight patients were enrolled in the study and randomly divided into two groups. The first group received amitriptyline and the second citalopram for 16 weeks. Patients were assessed at weeks 0, 4, 8, and 16. The two drugs were equally efficacious in relieving depressive symptoms, although amitriptyline was more efficacious than citalopram in reducing migraine and TTH attacks. Patients who did not respond to monotherapy (<30% of improvement in the clinical scores) were treated with a combination of the two drugs for 16 additional weeks. In these selected patients, the combined treatment produced a substantial improvement in depression, migraine and TTH without producing major side effects such as those commonly related to the ‘serotonergic’ syndrome. The results indicate that a combined therapy with amitriptyline and citalopram may be particularly beneficial for patients with TTH, migraine and comorbid depression that do not respond to monotherapy.

Pregabalin in the treatment of chronic pain: An overview

Chronic ‘pathological’ pain is sustained by mechanisms of peripheral and central sensitization, which are being increasingly investigated at the molecular and cellular levels. The molecular determinants of nociceptive sensitization are natural targets for potential analgesic drugs used in the treatment of different forms of pain. Most of these determinants are common to all forms of chronic pain, and it is therefore not surprising that drugs specifically targeted for the treatment of neuropathic pain are effective in relieving nociceptive inflammatory pain and vice versa. The molecular mechanisms of sensitization that occur in peripheral nociceptors and the dorsal horns of the spinal cord are putative targets for context-dependent drugs, i.e. drugs that are able to discriminate between ‘normal’ and ‘pathological’ pain transmission. Among these, pregabalin and gabapentin bind to the α2δ subunit of voltage-sensitive Ca2+ channels, which sustain the enhanced release of pain transmitters at the synapses between primary afferent fibres and second-order sensory neurons under conditions of chronic pain. Pregabalin in particular represents a remarkable example of a context-dependent analgesic drug that acts at a critical step of nociceptive sensitization. Preclinical and clinical data suggest that pregabalin is more than a structural and functional analogue of gabapentin and may be effective in the treatment of nociceptive inflammatory pain that is resistant to gabapentin.