Caracterización de la aparición y desarrollo de tolerancia a la morfina en un modelo de inflamación monoarticular en ratón

Consultable des del TDXTítol obtingut de la portada digitalitzadaLos opioides se utilizan en el tratamiento del dolor osteoarticular crónico, pero se desconocen las características de aparición de tolerancia a sus efectos durante estos procesos. Postulamos que la inflamación puede alterar la aparición / desarrollo de tolerancia opioide ya que se inducen cambios en la transmisión nociceptiva y en la expresión de receptores opioides. METODOLOGÍA: En un modelo de monoartritis producida por adyuvante de Freund (CFA) en ratones control y tolerantes (con la implantación de un comprimido s.c. de morfina), se evaluaron: peso corporal, diámetro de la articulación, respuesta nociceptiva a estímulos térmicos (plantar test) y mecánicos (Randall y Selitto, Von Frey), extravasación de plasma y tránsito intestinal. También se estudiaron los efectos de la administración sistémica de morfina y la reversión por naloxona y naloxona metiodada. Finalmente se estudió la expresión de receptores opioides m en tejidos periféricos (plantar, ganglios de la raíz dorsal y médula espinal) mediante Western Blot. RESULTADOS: El CFA indujo una inflamación localizada, cuantificable entre las 4 horas y los 14 días. El efecto anti-nociceptivo y anti-inflamatorio de la morfina fue significativamente mayor en presencia de inflamación (x2), sin modificar el efecto anti-alodínico. La implantación de un comprimido de morfina produjo una disminución de la sensibilidad nociceptiva a los estímulos térmicos y mecánicos, induciendo tolerancia opioide a los efectos anti-nociceptivos y anti-inflamatorios de la morfina. Asimismo en presencia de inflamación el desarrollo de tolerancia fue mayor. Los resultados de conducta obtenidos se relacionaron con los obtenidos a nivel molecular. La inflamación periférica aumentó la expresión de receptores opioides, y en presencia de tolerancia a la morfina los resultados sugirieron la no-funcionalidad de estos receptores.Opioids are clinically used in the management of chronic osteoarticular pains, but tolerance to analgesia has not been reported. The aim of our study was to characterise morphine tolerance in a mice model of monoarthritis that mimics the clinical condition. We postulate that inflammation could alter the development of opioid tolerance, because of the changes induced in the nociceptive transmission and opioid-receptor expression. METHODS: Inflammation was induced by the subplantar injection of Freund's adjuvant (CFA) in control and tolerant mice (tolerance was induced by the subcutaneous implantation of a 75-mg morphine pellet). We assessed changes in body weight, paw diametre, nocicpetive response to thermic (plantar test) and mechanic (Randall & Selitto, Von Frey) estimoulous, plasma extravasation and gastrointestinal transit. We also studied the anti-hyperalgesic (thermal, mechanical), anti-allodynic and anti-extravasation effects of morphine and its reversibility with morphine antagonists (naloxone), and the expression of m opioid receptors (western blot) in paw tissue, dorsal root ganglia and spinal cord. RESULTS: CFA-inflammation induced a localised inflammation, from 4 hours to 14 days since the injection of CFA. Inflammation increased the anti-nociceptive and anti-inflammatory effects of acute morphine (x2), without modify the anti-allodynic effects. The implantation of a morphine pellet decreased nociceptive sensibility, inducing tolerance to anti-nociceptive and anti-inflammatory effects, demonstrating tolerance. Inflammation and sustained exposure (pellet) to morphine, each individually, similarly increased m opioid receptor levels in all tissues tested; in the paw, opioid receptors expression was further enhanced in the presence of inflammation plus tolerance. The results suggested an up-regulation of non-functional m opioid receptors in tolerant mice, with and without inflammation

Lighting up multiprotein complexes: lessons from GPCR oligomerization

Spatiotemporal characterization of protein protein interactions (PPIs) is essential in determining the molecular mechanisms of intracellular signaling processes. In this review, we discuss how new methodological strategies derived from non-invasive fluorescence- and luminescence-based approaches (FRET, BRET, BiFC and BiLC), when applied to the study of G protein-coupled receptor (GPCR) oligomerization, can be used to detect specific PPIs in live cells. These technologies alone or in concert with complementary methods (SRET, BRET or BiFC, and SNAP-tag or TR-FRET) can be extremely powerful approaches for PPI visualization, even between more than two proteins. Here we provide a comprehensive update on all the biotechnological aspects, including the strengths and weaknesses, of new fluorescence- and luminescence-based methodologies, with a specific focus on their application for studying PPIs

On the role of G protein-coupled receptors oligomerization

The existence of a supramolecular organization of the G protein-coupled receptor (GPCR) is now being widely accepted by the scientific community. Indeed, GPCR oligomers may enhance the diversity and performance by which extracellular signals are transferred to the G proteins in the process of receptor transduction, although the mechanism that underlies this phenomenon still remains unsolved. Recently, it has been proposed that a trans-conformational switching model could be the mechanism allowing direct inhibition/activation of receptor activation/inhibition, respectively. Thus, heterotropic receptor-receptor allosteric regulations are behind the GPCR oligomeric function. In this paper we want to revise how GPCR oligomerization impinges on several important receptor functions like biosynthesis, plasma membrane diffusion or velocity, pharmacology and signaling. In particular, the rationale of receptor oligomerization might lie in the need of sensing complex whole cell extracellular signals and translating them into a simple computational model

Pridopidine Reverses Phencyclidine-Induced Memory Impairment

Pridopidine is in clinical trials for Huntington's diseasetreatment. Originally developedas a dopamine D2receptor (D2R) ligand, pridopidine displays about 100-fold higheraffinity for the sigma-1 receptor (sigma-1R). Interestingly, pridopidine slows diseaseprogression and improves motor function in Huntington's disease model mice and,in preliminarily reports, Huntington's disease patients.The present study examinedthe anti-amnesic potential of pridopidine. Thus, memory impairment was produced inmice by administration of phencyclidine (PCP, 10 mg/kg/day) for 10 days, followedby 14 days' treatment with pridopidine (6 mg/kg/day), or saline. Finally, novel objectrecognition performance was assessed in the animals. Mice receiving PCP andsaline exhibited deficits in novel object recognition, as expected, while pridopidinetreatment counteracted PCP-induced memory impairment. The effect of pridopidine wasattenuated by co-administration of the sigma receptor antagonist, NE-100 (10 mg/kg).Our results suggest that pridopidine exerts anti-amnesic and potentially neuroprotectiveactions. These data provide new insights into the therapeutic potential of pridopidine asa pro-cognitive drug

Adenosine A1-A2A Receptor Heteromer as a Possible Target for Early-Onset Parkinson's Disease

Parkinson's disease (PD) is a progressive, neurodegenerative disorder that affects ~1% of individuals over the age of 60, which turns to 5% in subjects up to 85 years (de Lau and Breteler, 2006). On the other hand, a form of PD, called early-onset PD (EOPD), arises at an earlier age (<45; Bonifati et al., 2005; Ylikotila et al., 2015). EOPD patients generally display a slower progression of the disease and present a better response to dopaminergic treatments; however, they may finally develop a full PD symptomatology (i.e., bradykinesia, resting tremor, muscular rigidity and postural instability, drug-induced dyskinesia; Olgiati et al., 2016)

Oligomerización de receptores acoplados a proteína G y enfermedad de Parkinson

La enfermedad de Parkinson es una condición neurodegenerativa del sistema nervioso central que puede aparecer en la madurez pero cuya incidencia aumenta dramáticamente en la tercera edad. Por este motivo, en las sociedades industrializadas, donde la esperanza de vida es alta, la enfermedad tiene un elevado coste socio-económico. El origen de la patología radica en la pérdida selectiva de neuronas dopaminérgicas de una región concreta de los ganglios basales. En consecuencia, se produce un desequilibrio neuroquímico (ej.; glutama to/dopamina/adenosina) que afecta en última instancia a los procesos controlados por los ganglios basales (ej.; el control motor, la cognición, las emociones y el aprendizaje). Recientemente, se ha demostrado que los receptores acoplados a proteína G pueden expresarse en la membrana plasmática como homodímeros y heterómeros. Estos complejos oligoméricos pueden funcionar como procesadores computacionales dinámicos, modulando la señalización celular y por tanto el flujo de información a través de los circuitos neuronales. Así, desde un punto de vista cuantitativo y/o cualitativo la señal generada por la estimulación de un receptor concreto del heterómero puede ser diferente de aquella obtenida mediante la coestimulación de los diferentes integrantes del complejo. Este nuevo concepto, además de exhortar la reinterpretación de la farmacodinámica clásica de receptores acoplados a proteína G, impulsará el diseño de nuevas terapias basadas en la combinación de fármacos cuya diana sean los oligómeros de receptores, por ejemplo, el oligómero formado por los receptores de glutamato, dopamina y adenosina en el tratamiento de la enfermedad de Parkinson

An update on adenosine A2A receptors as drug target in Parkinson's disease

Adenosine receptors are G protein-coupled receptors (GPCRs) that mediate the physiological functions of adenosine. In the central nervous system adenosine A2A receptors (A2ARs) are highly enriched in striatopallidal neurons where they form functional oligomeric complexes with other GPCRs such us the dopamine D2 receptor (D2R). Furthermore, it is assumed that the formation of balanced A2AR/D2R receptor oligomers are essential for correct striatal function as the allosteric receptor-receptor interactions established within the oligomer are needed for properly sensing adenosine and dopamine. Interestingly, A2AR activation reduces the affinity of striatal D2R for dopamine and the blockade of A2AR with specific antagonists facilitates function of the D2R. Thus, it may be postulated that A2AR antagonists are pro-dopaminergic agents. Therefore, A2AR antagonists will potentially reduce the effects associated with dopamine depletion in Parkinson's disease (PD). Accordingly, this class of compounds have recently attracted considerable attention as potential therapeutic agents for PD pharmacotherapy as they have shown potential effectiveness in counteracting motor dysfunctions and also displayed neuroprotective and anti-inflammatory effects in animal models of PD. Overall, we provide here an update of the current state of the art of these A2AR-based approaches that are under clinical study as agents devoted to alleviate PD symptom

Triglyceride Form of Docosahexaenoic Acid Mediates Neuroprotection in Experimental Parkinsonism

Parkinson’s disease (PD) is a neurodegenerative disorder of unknown etiology. The main treatment of PD consists of medication with dopamine-based drugs, which palliate the symptoms but may produce adverse effects after chronic administration. Accordingly, there is a need to develop novel neuroprotective therapies. Several studies suggest that omega-3 polyunsaturated fatty acids (n-3 PUFA) might provide protection against brain damage. Here, we studied several experimental models of PD, using striatal neuronal cultures, striatal slices, and mice, to assess the neuroprotective effects of docosahexaenoic acid (DHA), the main n-3 PUFA in the brain, administered in its triglyceride form (TG-DHA). Hence, we determined the beneficial effects of TG-DHA on neural viability following 6-hydroxydopamine (6-OHDA)-induced neurotoxicity, a well-established PD model. We also implemented a novel mouse behavioral test, the beam walking test, to finely assess mouse motor skills following dopaminergic denervation. This test showed potential as a useful behavioral tool to assess novel PD treatments. Our results indicated that TG-DHA-mediated neuroprotection was independent of the net incorporation of PUFA into the striatum, thus suggesting a tight control of brain lipid homeostasis both in normal and pathological conditions