RESUMEN
This study demonstrated the tracking of ulcerative colitis, which is considered a stressful immune disease. Although there are many ways to test for this disease including dependence on gases, dyes, and painful anal endoscopy, these treatment modalities have many disadvantages. Hence, it is the utmost need of time to discover new methods to detect this chronic immune disease and to avoid the defects of traditional methodologies. Sulfasalazine (SSD) was labeled with iodine-131 (half-life: 8 days, Energy: 971 keV) under optimum reaction conditions including the amount of reducing agent, pH factor, chloramine-T (Ch-T) amount, and incubation period. Characterization was performed using 1 H/ 13 C-NMR, ESI-MS, and HPLC (UV/ Radio) techniques. The biodistribution study was performed in normal and ulcerative mice models, and in silico molecular docking study was performed to evaluate the possible mechanism of action to target peroxisome proliferator-activated receptor gamma (PPARγ). The high radiolabeling yield of [131 I]-sulfasalazine ([131 I]-SSD) was achieved ≥90% through the direct labeling method with radioactive iodine-131 in the presence of chloramine-T (100 µg). The radiotracer [131 I]-SSD was observed to be stable in normal saline and freshly eluted serum up to 12 hr at ambient temperature (37â ± 2â). The radiotracer [131 I]-SSD showed the highest uptake in the targeted organ (i.e., ulcerative colon) which was observed to be ≥75% injected dose per gram (% ID/g) organ for 24 hr postinjection (p.i). Furthermore, in silico data collected from molecular modeling analysis of SSD and [131 I]-SSD with antimicrobial protein (PDB code: 3KEG) and peroxisome proliferator-activated receptor gamma (PPARγ) (PDB code: 4XTA) showed azoreductase activity and high binding potential for PPAR-γ site, respectively. The results of biological studies obtained in this study enlighten the usefulness of radiotracer [131 I]-SSD as a potential imaging agent for ulcerative colitis.
Asunto(s)
Colitis Ulcerosa/radioterapia , Isótopos de Yodo/química , Sulfasalazina/química , Animales , Cloraminas/química , Defensinas/química , Modelos Animales de Enfermedad , Humanos , Concentración de Iones de Hidrógeno , Isótopos de Yodo/farmacología , Cinética , Masculino , Ratones , Simulación del Acoplamiento Molecular , Nitrorreductasas/química , Oxidación-Reducción , PPAR gamma/metabolismo , Proteínas de Plantas/química , Tomografía de Emisión de Positrones , Unión Proteica , Conformación Proteica , Coloración y Etiquetado , Distribución TisularRESUMEN
OBJECTIVE: To assess the diagnostic accuracy of iodine map computed tomography pulmonary angiography (CTPA), for segment-based evaluation of lung perfusion in patients with acute pulmonary embolism (PE), using perfusion single-photon emission CT (SPECT) imaging as a reference standard. METHODS: Thirty participants who have been diagnosed with acute pulmonary embolism on CTPA underwent perfusion SPECT/CT within 24 h. Perfusion SPECT and iodine map were independently interpreted by 2 nuclear medicine physicians and 2 radiologists. For both modalities, each segment was classified as normoperfused or hypoperfused, as defined by a perfusion defect of more than 25% of a segment. The primary end point was the diagnostic accuracy (sensitivity and specificity) of iodine map for segment-based evaluation of lung perfusion, using perfusion SPECT imaging as a reference standard. Following blinded interpretation, a retrospective explanatory analysis was performed to determine potential causes of misinterpretation. RESULTS: The median time between CTPA with iodine maps and perfusion SPECT was 14 h (range 2-23 h). A total of 597 segments were analyzed. Sensitivity and specificity of iodine maps with CTPA for the detection of segmental perfusion defects were 231/284 = 81.3% (95% CI 76.4 to 85.4%) and 247/313 = 78.9% (95% CI 74.1 to 83.1%), respectively. In retrospect, false results were explained in 48.7%. CONCLUSION: Iodine map CTPA showed promising results for the assessment of pulmonary perfusion in patients with acute PE, with sensitivity of 81.3% and specificity of 78.9%, respectively. Recognition of typical pitfalls such as atelectasis, fissures, or beam-hardening artifacts may further improve the accuracy of the test. KEY POINTS: ⢠Sensitivity and specificity of iodine subtraction maps for the detection of segmental perfusion defects were 81.3% (95% CI 76.4 to 85.4%) and 78.9% (95% CI 74.1 to 83.1%), respectively. ⢠Recognition of typical pitfalls such as atelectasis, fissures, or beam-hardening artifacts may further improve the diagnostic accuracy of the test.
Asunto(s)
Angiografía de Substracción Digital/métodos , Angiografía por Tomografía Computarizada/métodos , Isótopos de Yodo/farmacología , Pulmón/diagnóstico por imagen , Embolia Pulmonar/diagnóstico , Tomografía Computarizada de Emisión de Fotón Único/métodos , Enfermedad Aguda , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Yodo , Masculino , Persona de Mediana Edad , Curva ROC , Reproducibilidad de los Resultados , Estudios RetrospectivosRESUMEN
The expression of telomerase in approximately 85% of cancers and its absence in the majority of normal cells makes it an attractive target for cancer therapy. However the lag period between initiation of telomerase inhibition and growth arrest makes direct inhibition alone an insufficient method of treatment. However, telomerase inhibition has been shown to enhance cancer cell radiosensitivity. To investigate the strategy of simultaneously inhibiting telomerase while delivering targeted radionuclide therapy to cancer cells, 123I-radiolabeled inhibitors of telomerase were synthesized and their effects on cancer cell survival studied. An 123I-labeled analogue of the telomerase inhibitor MST-312 inhibited telomerase with an IC50 of 1.58 µM (MST-312 IC50: 0.23 µM). Clonogenic assays showed a dose dependant effect of 123I-MST-312 on cell survival in a telomerase positive cell line, MDA-MB-435.
Asunto(s)
Quimioradioterapia/métodos , Tolerancia a Radiación/efectos de los fármacos , Telomerasa/antagonistas & inhibidores , Antineoplásicos/farmacología , Benzamidas/farmacología , Benzamidas/uso terapéutico , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/efectos de la radiación , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/uso terapéutico , Humanos , Isótopos de Yodo/farmacología , Isótopos de Yodo/uso terapéutico , Radioisótopos/farmacología , Radioisótopos/uso terapéutico , Telomerasa/metabolismoRESUMEN
Although antigen-binding fragments (Fabs) of antibodies constitute established tracers for in vivo radiodiagnostics, their functionality is hampered by a very short circulation half-life. PASylation, the genetic fusion with a long, conformationally disordered amino acid chain comprising Pro, Ala and Ser, provides a convenient way to expand protein size and, consequently, retard renal filtration. Humanized αHER2 and αCD20 Fabs were systematically fused with 100 to 600 PAS residues and produced in E. coli. Cytofluorimetric titration analysis on tumor cell lines confirmed that antigen-binding activities of the parental antibodies were retained. The radio-iodinated PASylated Fabs were studied by positron emission tomography (PET) imaging and biodistribution analysis in mouse tumor xenograft models. While the unmodified αHER2 and αCD20 Fabs showed weak tumor uptake (0.8% and 0.2% ID/g, respectively; 24 h p.i.) tumor-associated radioactivity was boosted with increasing PAS length (up to 9 and 26-fold, respectively), approaching an optimum for Fab-PAS400. Remarkably, 6- and 5-fold higher tumor-to-blood ratios compared with the unmodified Fabs were measured in the biodistribution analysis (48 h p.i.) for αHER2 Fab-PAS100 and Fab-PAS200, respectively. These findings were confirmed by PET studies, showing high imaging contrast in line with tumor-to-blood ratios of 12.2 and 5.7 (24 h p.i.) for αHER2 Fab-PAS100 and Fab-PAS200. Even stronger tumor signals were obtained with the corresponding αCD20 Fabs, both in PET imaging and biodistribution analysis, with an uptake of 2.8% ID/g for Fab-PAS100 vs. 0.24% ID/g for the unmodified Fab. Hence, by engineering Fabs via PASylation, plasma half-life can be tailored to significantly improve tracer uptake and tumor contrast, thus optimally matching reagent/target interactions.
Asunto(s)
Anticuerpos Antineoplásicos , Antígenos CD20 , Fragmentos Fab de Inmunoglobulinas , Marcaje Isotópico , Neoplasias Experimentales , Tomografía de Emisión de Positrones , Receptor ErbB-2 , Animales , Anticuerpos Antineoplásicos/química , Anticuerpos Antineoplásicos/farmacología , Línea Celular Tumoral , Femenino , Xenoinjertos , Humanos , Fragmentos Fab de Inmunoglobulinas/química , Fragmentos Fab de Inmunoglobulinas/genética , Fragmentos Fab de Inmunoglobulinas/farmacología , Isótopos de Yodo/química , Isótopos de Yodo/farmacocinética , Isótopos de Yodo/farmacología , Ratones , Trasplante de Neoplasias , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/metabolismo , Neoplasias Experimentales/patologíaRESUMEN
The recent identification of a novel binding site for angiotensin (Ang) II as the peptidase neurolysin (E.C. 3.4.24.16) has implications for the renin-angiotensin system (RAS). This report describes the distribution of specific binding of 125I-Sarcosine1, Isoleucine8 Ang II (125I-SI Ang II) in neurolysin knockout mouse brains compared to wild-type mouse brains using quantitative receptor autoradiography. In the presence of p-chloromercuribenzoic acid (PCMB), which unmasks the novel binding site, widespread distribution of specific (3 µM Ang II displaceable) 125I-SI Ang II binding in 32 mouse brain regions was observed. Highest levels of binding >700 fmol/g initial wet weight were seen in hypothalamic, thalamic and septal regions, while the lowest level of binding <300 fmol/g initial wet weight was in the mediolateral medulla. 125I-SI Ang II binding was substantially higher by an average of 85% in wild-type mouse brains compared to neurolysin knockout brains, suggesting the presence of an additional non-AT1, non-AT2, non-neurolysin Ang II binding site in the mouse brain. Binding of 125I-SI Ang II to neurolysin in the presence of PCMB was highest in hypothalamic and ventral cortical brain regions, but broadly distributed across all regions surveyed. Non-AT1, non-AT2, non-neurolysin binding was also highest in the hypothalamus but had a different distribution than neurolysin. There was a significant reduction in AT2 receptor binding in the neurolysin knockout brain and a trend towards decreased AT1 receptor binding. In the neurolysin knockout brains, the size of the lateral ventricles was increased by 56% and the size of the mid forebrain (-2.72 to +1.48 relative to Bregma) was increased by 12%. These results confirm the identity of neurolysin as a novel Ang II binding site, suggesting that neurolysin may play a significant role in opposing the pathophysiological actions of the brain RAS and influencing brain morphology.
Asunto(s)
Angiotensina II , Metaloendopeptidasas/metabolismo , Prosencéfalo/metabolismo , Sistema Renina-Angiotensina/fisiología , Sarcosina , Angiotensina II/farmacocinética , Angiotensina II/farmacología , Animales , Isótopos de Yodo/farmacocinética , Isótopos de Yodo/farmacología , Metaloendopeptidasas/genética , Ratones , Ratones Noqueados , Receptor de Angiotensina Tipo 2/genética , Receptor de Angiotensina Tipo 2/metabolismo , Sarcosina/farmacocinética , Sarcosina/farmacologíaRESUMEN
Dopamine D3 receptors are implicated in cue-induced relapse to drug seeking. We have previously shown that systemic administration of a selective D3 antagonist reduces cue-induced reinstatement of nicotine seeking in rats. The current study sought to investigate potential neural substrates mediating this effect. The D3 antagonist SB-277011-A (0.01-1 µg/0.5 µl/side) infused into the basolateral amygdala or the lateral habenula, but not the nucleus accumbens, significantly attenuated cue-induced reinstatement of nicotine seeking. Moreover, infusion of SB-277011-A (1 µg/0.5 µl/side) into the basolateral amygdala or lateral habenula had no effect on food self-administration. Together with the finding that systemic SB-277011-A had no effect on extinction responding, this suggests that the effects observed here were on reinstatement and cue seeking, and not due to nonspecific motor activation or contextual-modified residual responding. The further finding of binding of [(125)I]7-OH-PIPAT to D3 receptors in the lateral habenula and in the basolateral amygdala is consistent with an important role of D3 receptors in these areas in nicotine seeking. It was also found that systemic administration of the selective D2 antagonist L741626 decreased cue-induced reinstatement, consistent with a role of D2 and D3 receptors in modulating this behavior. The current study supports an important role for D3 receptors in the basolateral amygdala and lateral habenula in cue-induced reinstatement.
Asunto(s)
Complejo Nuclear Basolateral/efectos de los fármacos , Señales (Psicología) , Comportamiento de Búsqueda de Drogas/efectos de los fármacos , Habénula/efectos de los fármacos , Nicotina/administración & dosificación , Agonistas Nicotínicos/administración & dosificación , Receptores de Dopamina D3/metabolismo , Refuerzo en Psicología , Animales , Autorradiografía , Complejo Nuclear Basolateral/metabolismo , Condicionamiento Operante/efectos de los fármacos , Antagonistas de Dopamina/farmacología , Extinción Psicológica/efectos de los fármacos , Habénula/metabolismo , Indoles/farmacología , Isótopos de Yodo/farmacología , Masculino , Nitrilos/farmacología , Piperidinas/farmacología , Ratas , Ratas Long-Evans , Autoadministración , Tetrahidroisoquinolinas/farmacología , Tetrahidronaftalenos/farmacocinéticaRESUMEN
Long-term treatment with nicotine or selective α7 nicotinic acetylcholine receptor (nAChR) agonists increases the number of α7 nAChRs and this up-regulation may be involved in the mechanism underlying the sustained procognitive effect of these compounds. Here, we investigate the influence of type I and II α7 nAChR positive allosteric modulators (PAMs) on agonist-induced α7 nAChR up-regulation. We show that the type II PAMs, PNU-120596 (10 µM) or TQS (1 and 10 µM), inhibit up-regulation, as measured by protein levels, induced by the α7 nAChR agonist A-582941 (10 nM or 10 µM), in SH-EP1 cells stably expressing human α7 nAChR, whereas the type I PAMs AVL-3288 or NS1738 do not. Contrarily, neither type I nor II PAMs affect 10 µM nicotine-induced receptor up-regulation, suggesting that nicotine and A-582941 induce up-regulation through different mechanisms. We further show in vivo that 3 mg/kg PNU-120596 inhibits up-regulation of the α7 nAChR induced by 10 mg/kg A-582941, as measured by [(125)I]-bungarotoxin autoradiography, whereas 1 mg/kg AVL-3288 does not. Given that type II PAMs decrease desensitization of the receptor, whereas type I PAMs do not, these results suggest that receptor desensitization is involved in A-582941-induced up-regulation. Our results are the first to show an in vivo difference between type I and II α7 nAChR PAMs, and demonstrate an agonist-dependent effect of type II PAMs occurring on a much longer time scale than previously appreciated. Furthermore, our data suggest that nicotine and A-582941 induce up-regulation through different mechanisms, and that this confers differential sensitivity to the effects of α7 nAChR PAMs. These results may have implications for the clinical development of α7 nAChR PAMs.
Asunto(s)
Colinérgicos/farmacología , Receptores Nicotínicos/fisiología , Regulación hacia Arriba/efectos de los fármacos , Regulación Alostérica/efectos de los fármacos , Análisis de Varianza , Animales , Autorradiografía , Encéfalo/anatomía & histología , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Bungarotoxinas/metabolismo , Relación Dosis-Respuesta a Droga , Isótopos de Yodo/farmacología , L-Lactato Deshidrogenasa/metabolismo , Masculino , Nicotina/farmacología , Unión Proteica/efectos de los fármacos , Ratas , Ratas Wistar , Transfección , Receptor Nicotínico de Acetilcolina alfa 7RESUMEN
Prostate cancer (PCa) is the second most commonly diagnosed and sixth leading cause of cancer death in American men and one for which no curative therapy exists after metastasis. To meet this need for novel therapies, our laboratory has previously generated conditionally replicating adenovirus (CRAd) vectors expressing the sodium iodide symporter (hNIS). This virus transduced PCa cells and induced functional NIS expression, allowing for noninvasive tumor imaging and combination therapy with radioiodide, referred to as radiovirotherapy. We have now generated two new modified vectors to further improve efficacy. Ad5/3PB-ADP-hNIS and Ad5/3PB-hNIS include a hybrid Ad5/3 fiber knob to improve transduction efficiency, and express NIS from the endogenous major late promoter to restrict NIS expression to target cells. Additionally, Ad5/3PB-ADP-hNIS includes the adenovirus death protein (ADP), which hastens the release of viral particles after assembly. These two vectors specifically induce radioisotope uptake, cytopathic effect, and viral replication in androgen receptor-expressing PCa cell lines with Ad5/3PB-ADP-hNIS showing earlier (131)I uptake and cytolysis at low multiplicity of infection. SPECT-CT imaging of xenograft tumors infected with Ad5/3PB-hNIS showed steady uptake, whereas infection with Ad5/3PB-ADP-hNIS led to increasing uptake, indicating viral spread. Radiovirotherapy of xenograft LNCaP tumors with Ad5/3PB-ADP-hNIS showed the most significant survival extension versus control tumors (p=0.001), but the benefit of radiovirotherapy was not statistically significant compared with virotherapy alone in this model. These results show the potential of Ad5/3PB-ADP-hNIS as a vector for treatment of prostate cancer.
Asunto(s)
Adenoviridae , Vectores Genéticos , Neoplasias de la Próstata/terapia , Simportadores/biosíntesis , Animales , Línea Celular Tumoral , Humanos , Isótopos de Yodo/farmacología , Masculino , Ratones , Trasplante de Neoplasias , Receptores Androgénicos/biosíntesis , Simportadores/genética , Trasplante Heterólogo , Replicación Viral/genéticaRESUMEN
BACKGROUND AND AIM: In internal radiotherapy, the variable distribution of target receptors within the tumoral tissue, and the variable ranges of electrons may be responsible for a heterogeneous dose distribution at the cellular level. The aim of the present study was to use Monte Carlo simulations to assess (131)I electron dose in a model of heterogeneous tumor containing multiple clusters of cancer cells, targeted by (131)I-labeled molecules. METHODS: The model consisted of 150-µm-diameter spherical tumor cell clusters, in which (131)I was homogeneously distributed. Clusters were placed 24 µm apart, separated by septa of nonradioactive connective tissue. The electron dose distribution to tumor cells in a single cluster was first assessed. Then was assessed the dose increase to these targets after adding multiple layers of neighboring clusters (total number of clusters = 15,624). RESULTS: Dose distribution within a single isolated cluster follows a decreasing gradient, the dose for the outermost cell layer being about half that at the center. When radioactive neighbors were added, the dose to the central cluster increased. The most important contribution was given by the nearest neighbors, whereas the contribution from neighbors beyond a distance of 1 mm was only for 5% of the final dose. If the central cluster was unlabeled, the absorbed dose to the outermost cell layer of this cluster was reduced by 27%, and that at the center by 45%. CONCLUSIONS: The electron cross-dose of (131)I falls rapidly as a function of distance and becomes negligible after just 1 mm. Small clusters of tumor cells that are not radiolabeled may receive a very small dose. Therefore, in internal radiotherapy it is important to aim at targeting tumor cells as homogeneously as possible, rather than relying on the cross-dose to achieve a therapeutic effect.
Asunto(s)
Isótopos de Yodo/farmacología , Modelos Biológicos , Neoplasias/radioterapia , Simulación por Computador , Electrones , Isótopos de Yodo/química , Método de Montecarlo , Neoplasias/patología , Radiometría/métodos , Dosificación RadioterapéuticaRESUMEN
Accumulating evidence suggests that the alpha7 subtype of nicotinic acetylcholine receptors (nAChRs) plays a role in the pathophysiology of neuropsychiatric diseases, including schizophrenia and Alzheimer's disease. Currently, there are no suitable small molecule radioligands for alpha7 nAChRs in the brain, although [(125)I]alpha-bungarotoxin has been widely used as a radioligand for alpha7 nAChRs. In the present study, we characterized a new radioligand, 4-[(3)H]methylphenyl 2,5-diazabicyclo[3.2.2]nonane-2-carboxylate ([(3)H]CHIBA-1001), a derivative of the selective alpha7 nAChR agonist SSR180711, in brain membranes from rat, monkey, and human. Scatchard analysis revealed an apparent equilibrium dissociation constant (Kd) of 193.4nM in rat brain membranes at 4 degrees C, and the maximal number of binding sites (Bmax) was 346.2fmol/mg protein. The order of drugs for the inhibition of [(3)H]CHIBA-1001 binding to rat brain membranes is SSR180711>A-844606>MG624>epibatidine>DMAB>A-582941, suggesting a similarity of alpha7 nAChR pharmacological profiles. In contrast, alpha-bungarotoxin, MLA, and nicotine were found to be very weak. The distribution of [(3)H]CHIBA-1001 binding to crude membranes from dissected regions of rat, monkey, and human brain was different from that of [(125)I]alpha-bungarotoxin binding, suggesting that [(3)H]CHIBA-1001 binding sites may not be identical to [(125)I]alpha-bungarotoxin binding in the brain. In summary, [(3)H]CHIBA-1001 would be a useful radioligand for alpha7 nAChRs in the brains of rodents, non-human primates, and humans.
Asunto(s)
Encéfalo/metabolismo , Compuestos Bicíclicos Heterocíclicos con Puentes/metabolismo , Colinérgicos/metabolismo , Receptores Nicotínicos/metabolismo , Anciano , Animales , Sitios de Unión/efectos de los fármacos , Unión Competitiva/efectos de los fármacos , Encéfalo/citología , Encéfalo/efectos de los fármacos , Compuestos Bicíclicos Heterocíclicos con Puentes/química , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Bungarotoxinas/metabolismo , Bungarotoxinas/farmacología , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Colinérgicos/química , Colinérgicos/farmacología , Relación Dosis-Respuesta a Droga , Humanos , Isótopos de Yodo/metabolismo , Isótopos de Yodo/farmacología , Macaca fascicularis , Masculino , Unión Proteica/efectos de los fármacos , Ratas , Distribución Tisular/fisiología , Tritio/metabolismo , Receptor Nicotínico de Acetilcolina alfa 7RESUMEN
PURPOSE: Oncolytic adenoviruses are promising tools for cancer therapy. Although several clinical reports have indicated both safety and promising antitumor capabilities for these viruses, there are only a few examples of complete tumor eradication. Thus, the antitumor efficacy of oncolytic adenoviruses needs to be improved. One potentially useful approach is combination with radiotherapy. EXPERIMENTAL DESIGN: To target systemically administered radioiodide to tumors, we created Ad5/3-Delta24-human sodium iodide symporter (hNIS), a Rb-p16 pathway selective infectivity enhanced oncolytic adenovirus encoding hNIS. RESULTS: Ad5/3-Delta24-hNIS replication effectively killed prostate cancer cells in vitro and in vivo. Also, the virus-mediated radioiodide uptake into prostate cancer cells in vitro and into tumors in vivo. Furthermore, Ad5/3-Delta24-hNIS with radioiodide was significantly more effective than virus alone in mice with prostate cancer xenografts. CONCLUSIONS: These results suggest that oncolytic adenovirus-mediated targeted radiotherapy might be a potentially useful option for enhancing the efficacy or adenoviral virotherapy.
Asunto(s)
Adenocarcinoma/terapia , Neoplasias Pulmonares/terapia , Viroterapia Oncolítica , Neoplasias de la Próstata/terapia , Simportadores/genética , Adenocarcinoma/radioterapia , Adenoviridae/genética , Animales , Línea Celular Tumoral , Terapia Combinada , Terapia Genética , Humanos , Isótopos de Yodo/farmacología , Isótopos de Yodo/uso terapéutico , Neoplasias Pulmonares/radioterapia , Masculino , Ratones , Virus Oncolíticos/genética , Neoplasias de la Próstata/radioterapia , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
In the CNS, several regulators of G-protein signalling (RGS) modulate the activity of mu-opioid receptors. In pull-down assays performed on membranes from mouse periaqueductal gray matter (PAG), mu-opioid receptors co-precipitated with delta-opioid receptors, Gi/o/z/q proteins, and the regulators of G-protein signalling RGS4, RGS9-2, RGS14, RGSZ1 and RGSZ2. No RGS2, RGS7, RGS10 and RGS11 proteins were associated with the mu receptors in these PAG membranes. In mice, an intracerebroventricular dose of 10 nmol morphine produced acute tolerance at mu receptors but did not disrupt the co-precipitation of mu-delta receptor complexes. However, this opioid reduced by more than 50% the co-precipitation of G alpha i/o/z subunits with mu receptors, and altered their association with some of the RGS proteins at 30 min, 3 h and 24 h after its administration. The association of RGS9-2 with mu receptors diminished by 30-40% 24 h after the administration of morphine, while that of RGSZ2 and of RGSZ1 increased. Morphine treatment recruited RGS4 to the PAG membranes, and 30 min and 3 h after the opioid challenge its association with mu receptors had increased. However, 24 h after morphine administration, the co-precipitation of RGS4 had decreased by about 30%. The opioid produced no change in the membrane levels of RGS9-2, RGS14, RGSZ1 and RGSZ2. Thus, in PAG synaptosomal membranes, a dynamic and selective link exists between, mu-opioid receptors, Gi/o/z proteins and certain RGS proteins.
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Morfina/farmacología , Narcóticos/farmacología , Sustancia Gris Periacueductal/efectos de los fármacos , Proteínas RGS/metabolismo , Receptores Opioides mu/metabolismo , Analgésicos Opioides/farmacología , Animales , Autorradiografía , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Precipitación Química , Cromatografía de Afinidad/métodos , Relación Dosis-Respuesta a Droga , Encefalina Ala(2)-MeFe(4)-Gli(5)/farmacología , Immunoblotting/métodos , Isótopos de Yodo/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Sustancia Gris Periacueductal/metabolismo , Proteínas RGS/clasificación , Receptores Opioides delta/metabolismo , Receptores Opioides mu/deficiencia , Factores de Tiempo , betaendorfina/farmacologíaRESUMEN
The aim of the current study was to elucidate whether the response of the adult rat brain to thyroid hormones is affected by the intensity of neuronal activity. For this purpose, the kinetic characteristics of nuclear T3 binding, the relative expression of thyroid hormone receptor (TR) isoforms and the synaptosomal content of thyroid hormones in adult rat brain were examined after administration of a single convulsion dose of pentylenetetrazole (PTZ). Experiments in adult Wistar rats revealed an increase (33%) of the density of specific T3 nuclear receptors in cerebral hemispheres 4h after PTZ-induced seizures while no changes were observed in the dissociation constant. The relative expression of the T3-binding isoforms of TRs was not affected, while there was a gradual decrease of the relative expression of the TR alpha2 variant (non-T3 binding isoform). The above changes were coupled with an increase of the synaptosomal T3 levels during the epileptic seizures. Our study revealed inversely proportional changes between the nuclear T3 binding sites and the TR alpha2 mRNA levels 4 h after PTZ-induced seizures, suggesting that the regulation of the expression of the non-T3 binding variant of TRs determines the nuclear T3 binding sites in adult rat brain, while the synaptosomal T3 levels could play a novel functional role in the signaling from the synapse to the nucleus.
Asunto(s)
Corteza Cerebral/efectos de los fármacos , Pentilenotetrazol/farmacología , Convulsiones/metabolismo , Triyodotironina/farmacología , Animales , Northern Blotting/métodos , Corteza Cerebral/citología , Corteza Cerebral/metabolismo , Modelos Animales de Enfermedad , Interacciones Farmacológicas , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Isótopos de Yodo/farmacología , Masculino , Unión Proteica/efectos de los fármacos , Unión Proteica/fisiología , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Convulsiones/inducido químicamente , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismo , Factores de TiempoRESUMEN
Macromolecules that bind beta-amyloid peptide (Abeta) and neutralize Abeta cytotoxicity offer a promising new approach for treating Alzheimer's disease. When the plasma protein, alpha2-macroglobulin (alpha2M), is treated with methylamine (alpha2M-MA), it undergoes conformational change and acquires Abeta-binding activity. In this study, we demonstrate that a chemically stabilized preparation of human alpha2M conformational intermediates (alpha2M-cis-Pt/MA) binds Abeta with greatly increased affinity, compared with alpha2M-MA. alpha2M-cis-Pt/MA was generated by reacting alpha2M with the protein cross-linking reagent, cis-Pt, followed by methylamine. Increased Abeta-binding to alpha2M-cis-Pt/MA was demonstrated by co-migration of radio-iodinated proteins in non-denaturing PAGE, chemical cross-linking, and co-immunoprecipitation. The apparent K(D) for Abeta-binding to alpha2M-cis-Pt/MA was decreased 10-fold, compared with alpha2M-MA, to 29 nm. Native alpha2M demonstrated negligible Abeta-binding, as anticipated. alpha2M-cis-Pt/MA markedly counteracted Abeta-induced C6 cell apoptosis. Essentially complete inhibition of apoptosis was observed even when the Abeta was present at fourfold molar excess to alpha2M-cis-Pt/MA. Under equivalent conditions, alpha2M-MA inhibited apoptosis by 25 +/- 6%. When Abeta and alpha2M-cis-Pt/MA were added to human plasma in vitro, significant binding was detected. No binding was observed when an equivalent concentration of native alpha2M or alpha2M-MA was added to plasma. We propose that alpha2M-cis-Pt/MA is a novel alternative to Abeta-specific antibodies, for studying the efficacy of Abeta-binding agents in vitro and in vivo.
Asunto(s)
Péptidos beta-Amiloides/química , Péptidos beta-Amiloides/metabolismo , alfa-Macroglobulinas/química , alfa-Macroglobulinas/metabolismo , Western Blotting/métodos , Muerte Celular/efectos de los fármacos , Cisplatino/farmacología , Reactivos de Enlaces Cruzados/farmacología , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Electroforesis en Gel de Poliacrilamida/métodos , Ensayo de Inmunoadsorción Enzimática/métodos , Humanos , Inmunoprecipitación/métodos , Isótopos de Yodo/farmacología , Sustancias Macromoleculares/farmacología , Metilaminas/farmacología , Péptidos , Unión Proteica/efectos de los fármacos , Conformación Proteica/efectos de los fármacos , Colorantes de Rosanilina/metabolismoRESUMEN
In order to investigate the possible links connecting beta-amyloid (Abeta) accumulation, tau-hyperphosphorylation and nicotinic receptor expression, rat embryonic primary hippocampal cultures were incubated with amyloidogenic peptides. Exposure to 0.5 microm fibrillar Abeta(1-42) for 3 days caused retraction of dendrites, shrinkage of cell bodies and a decrease in the expression of microtubule-associated proteins 2b (MAP2b), without affecting the total number of neurons and their viability. No impact on the tau-phosphorylation sites Ser-202, Thr231/Ser235, Ser262 and Ser396/Ser404 was found. The total number of homomeric alpha7-nicotinic receptors (alpha7-nAChRs) and their affinity for [(125)I]alpha-bungarotoxin remained unaltered. Upon incubation with the putatively protective tetrapeptide propionyl-isoleucine-isoleucine-glycine-leucine (Pr-IIGL), an analogue of the region [31-34] of Abeta, cell bodies were swollen in the region of the apical dendrite. These morphological alterations, different from those elicited by Abeta(1-42), did not involve MAP2 expression changes. In contrast to Abeta(1-42), Pr-IIGL caused a massive hyperphosphorylation of the tau-protein at Ser-202 and at Ser396/Ser404. The total number of homomeric alpha7-nAChRs and their affinity for [(125)I]alpha-bungarotoxin were unaffected. In conclusion, the present results show a toxic effect of Abeta(1-42) on the cytoskeletal structure at concentrations normally present in the brains of Alzheimer's disease patients, but raise some doubts about the role of Abeta(1-42) fibrils as a direct trigger of tau-hyperphosphorylation. The tetrapeptide Pr-IIGL cannot be considered protective with regard to cell morphology. Although it prevents the Abeta(1-42)-induced retraction of dendrites, it exhibits other toxic properties. The homomeric alpha7-nAChRs were not affected either by Abeta(1-42) incubation or by Pr-IIGL-induced tau-hyperphosphorylation.