RESUMO
[Figure: see text].
Assuntos
Diástole , Sarcômeros/fisiologia , Trifosfato de Adenosina/metabolismo , Animais , Masculino , Sarcômeros/metabolismo , Suínos , Porco MiniaturaRESUMO
Mutations in ß-cardiac myosin, the predominant motor protein for human heart contraction, can alter power output and cause cardiomyopathy. However, measurements of the intrinsic force, velocity, and ATPase activity of myosin have not provided a consistent mechanism to link mutations to muscle pathology. An alternative model posits that mutations in myosin affect the stability of a sequestered, super relaxed state (SRX) of the protein with very slow ATP hydrolysis and thereby change the number of myosin heads accessible to actin. Here we show that purified human ß-cardiac myosin exists partly in an SRX and may in part correspond to a folded-back conformation of myosin heads observed in muscle fibers around the thick filament backbone. Mutations that cause hypertrophic cardiomyopathy destabilize this state, while the small molecule mavacamten promotes it. These findings provide a biochemical and structural link between the genetics and physiology of cardiomyopathy with implications for therapeutic strategies.
Assuntos
Benzilaminas/química , Uracila/análogos & derivados , Miosinas Ventriculares/química , Animais , Benzilaminas/farmacologia , Cardiomegalia/enzimologia , Cardiomegalia/genética , Humanos , Músculo Esquelético/enzimologia , Mutação , Suínos , Porco Miniatura , Uracila/química , Uracila/farmacologia , Miosinas Ventriculares/genética , Miosinas Ventriculares/metabolismoRESUMO
Although alterations in fatty acid (FA) metabolism have been shown to have a negative impact on contractility of the hypertrophied heart, the targets of action remain elusive. In this study we compared the function of skinned fiber bundles from transgenic (Tg) mice that overexpress a relatively low level of the peroxisome proliferator-activated receptor α (PPARα), and nontransgenic (NTg) littermates. The mice (NTg-T and Tg-T) were stressed by transverse aortic constriction (TAC) and compared with shams (NTg-S and Tg-S). There was an approximate 4-fold increase in PPARα expression in Tg-S compared with NTg-S, but Tg-T hearts showed the same PPARα expression as NTg-T. Expression of PPARα did not alter the hypertrophic response to TAC but did reduce ejection fraction (EF) in Tg-T hearts compared with other groups. The rate of actomyosin ATP hydrolysis was significantly higher in Tg-S skinned fiber bundles compared with all other groups. Tg-T hearts showed an increase in phosphorylation of specific sites on cardiac myosin binding protein-C (cMyBP-C) and ß-myosin heavy chain isoform. These results advance our understanding of potential signaling to the myofilaments induced by altered FA metabolism under normal and pathological states. We demonstrate that chronic and transient PPARα activation during pathological stress alters myofilament response to Ca2+ through a mechanism that is possibly mediated by MyBP-C phosphorylation and myosin heavy chain isoforms.NEW & NOTEWORTHY Data presented here demonstrate novel signaling to sarcomeric proteins by chronic alterations in fatty acid metabolism induced by PPARα. The mechanism involves modifications of key myofilament regulatory proteins modifying cross-bridge dynamics with differential effects in controls and hearts stressed by pressure overload.
Assuntos
Cardiomegalia/fisiopatologia , Miofibrilas , PPAR alfa/biossíntese , PPAR alfa/genética , Adenosina Trifosfatases/metabolismo , Animais , Sinalização do Cálcio/genética , Cardiomegalia/etiologia , Proteínas de Transporte/metabolismo , Ácidos Graxos/metabolismo , Coração/fisiopatologia , Hipertensão/complicações , Hipertensão/fisiopatologia , Masculino , Camundongos , Camundongos Transgênicos , Miocárdio/citologia , Miocárdio/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Fosforilação , Volume SistólicoRESUMO
We focus here on the modulation of thin filament activity by cardiac troponin I phosphorylation as an integral and adaptive mechanism in cardiac homeostasis and as a mechanism vulnerable to maladaptive response to stress. We discuss a current concept of cardiac troponin I function in the A-band region of the sarcomere and potential signaling to cardiac troponin I in a network involving the ends of the thin filaments at the Z-disk and the M-band regions. The cardiac sarcomere represents a remarkable set of interacting proteins that functions not only as a molecular machine generating the heartbeat but also as a hub of signaling. We review how phosphorylation signaling to cardiac troponin I is integrated, with parallel signals controlling excitation-contraction coupling, hypertrophy, and metabolism.
Assuntos
Fenômenos Fisiológicos Cardiovasculares , Miócitos Cardíacos/metabolismo , Troponina I/metabolismo , Animais , Cardiomegalia/metabolismo , Cardiomegalia/fisiopatologia , Humanos , Miócitos Cardíacos/patologia , Miócitos Cardíacos/fisiologia , Fosforilação/fisiologia , Troponina I/fisiologiaRESUMO
Previous structural studies indicated a special functional role for an acidic region composed of residues 1-10 in the unique N-terminal peptide of cardiac troponin I (cTnI). Employing LC-MS/MS, we determined the presence of phosphorylation sites at S5/S6 in cTnI from wild type mouse hearts as well as in hearts of mice chronically expressing active protein kinase C-ε (PKCε) and exhibiting severe dilated cardiomyopathy (DCM). To determine the functional significance of these phosphorylations, we cloned and expressed wild-type cTnI, (Wt), and cTnI variants expressing pseudo-phosphorylation cTnI-(S5D), cTnI(S6D), as well as cTnI(S5A) and cTnI(S6A). We exchanged native Tn of detergent-extracted (skinned) fiber bundles with Tn reconstituted with the variant cTnIs and measured tension and cross-bridge dynamics. Compared to controls, myofilaments controlled by cTnI with pseudo-phosphorylation (S6D) or Ala substitution (S6A) demonstrated a significant depression in maximum tension, ATPase rate, and ktr, but no change in half-maximally activating Ca(2+). In contrast, pseudo-phosphorylation at position 5 (S5D) had no effects, although S5A induced an increase in Ca(2+)-sensitivity with no change in maximum tension or ktr. We further tested the impact of acidic domain modifications on myofilament function in studies examining the effects of cTnI(A2V), a mutation linked to DCM. This mutation significantly altered the inhibitory activity of cTnI as well as cooperativity of activation of myofilament tension, but not when S23/S24 were pseudo-phosphorylated. Our data indicate a new functional and pathological role of amino acid modifications in the N-terminal acidic domain of cTnI that is modified by phosphorylations at cTnI(S23/S24). This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.
Assuntos
Cardiomiopatia Dilatada/metabolismo , Miocárdio/metabolismo , Miofibrilas/metabolismo , Troponina I/metabolismo , Adenosina Trifosfatases/metabolismo , Animais , Cálcio/metabolismo , Cardiomiopatia Dilatada/patologia , Expressão Gênica , Humanos , Contração Isométrica , Cinética , Masculino , Camundongos , Camundongos Transgênicos , Tono Muscular , Mutação , Miocárdio/patologia , Miofibrilas/patologia , Fosforilação , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteína Quinase C-épsilon/genética , Proteína Quinase C-épsilon/metabolismo , Estrutura Terciária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Troponina I/química , Troponina I/genéticaRESUMO
Up to 40% of patients with heart failure develop depression, and depression is an independent risk factor for cardiovascular mortality in this patient population. Consequently, increasing numbers of patients with heart failure are treated with antidepressants. Selective serotonin reuptake inhibitors are typically the antidepressant of choice since this drug class has limited cardiovascular toxicity. However, little is known about the effects of selective serotonin reuptake inhibitors on autonomic cardiac regulation in congestive heart failure (CHF). Here, indexes of cardiac autonomic control were evaluated before and during chronic fluoxetine (FLX) treatment (20 mg·kg(-1)·day(-1), 5 wk) in rats that developed CHF after coronary artery ligation. FLX reduced the low-frequency (LF) component of heart rate variability (HRV; P < 0.01) as well as the sympathetic contribution to LF HRV (P < 0.01) in both CHF and sham-operated rats. Both FLX and CHF reduced high-frequency HRV (P < 0.01). Spontaneous baroreflex gain was decreased in CHF rats 8 wk after ligation (P < 0.01). Cross-spectral coherence between the interbeat interval and mean arterial pressure was reduced in the LF domain 3 wk after ligation in CHF rats (P < 0.01) and was further reduced after chronic FLX treatment (P < 0.01). Plasma catecholamines and LF blood pressure variability were not affected by FLX. Chronotropic responses to both efferent vagal nerve stimulation and isoproterenol administration were reduced in CHF rats and by FLX (P < 0.01), whereas inotropic responses to isoproterenol were reduced only in CHF rats (P < 0.01). These data indicate that chronic FLX reduces the responsiveness to autonomic output controlling cardiac rhythm and may further compromise autonomic regulation of cardiac function in CHF.
Assuntos
Sistema Nervoso Autônomo/efeitos dos fármacos , Fluoxetina/farmacologia , Insuficiência Cardíaca/fisiopatologia , Coração/efeitos dos fármacos , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Animais , Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/fisiopatologia , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Catecolaminas/sangue , Vasos Coronários/fisiologia , Interpretação Estatística de Dados , Ecocardiografia , Eletrodos Implantados , Coração/inervação , Frequência Cardíaca/efeitos dos fármacos , Ligadura , Masculino , Contração Miocárdica/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Sistema Nervoso Simpático/efeitos dos fármacos , Telemetria , Nervo Vago/fisiologiaRESUMO
In the present study, we compared the cardioprotective effects of TRV120023, a novel angiotensin II (ANG II) type 1 receptor (AT1R) ligand, which blocks G protein coupling but stimulates ß-arrestin signaling, against treatment with losartan, a conventional AT1R blocker in the treatment of cardiac hypertrophy and regulation of myofilament activity and phosphorylation. Rats were subjected to 3 wk of treatment with saline, ANG II, ANG II + losartan, ANG II + TRV120023, or TRV120023 alone. ANG II induced increased left ventricular mass compared with rats that received ANG II + losartan or ANG II + TRV120023. Compared with saline controls, ANG II induced a significant increase in pCa50 and maximum Ca(2+)-activated myofilament tension but reduced the Hill coefficient (nH). TRV120023 increased maximum tension and pCa50, although to lesser extent than ANG II. In contrast to ANG II, TRV120023 increased nH. Losartan blocked the effects of ANG II on pCa50 and nH and reduced maximum tension below that of saline controls. ANG II + TRV120023 showed responses similar to those of TRV120023 alone; compared with ANG II + losartan, ANG II + TRV120023 preserved maximum tension and increased both pCa50 and cooperativity. Tropomyosin phosphorylation was lower in myofilaments from saline-treated hearts compared with the other groups. Phosphorylation of cardiac troponin I was significantly reduced in ANG II + TRV120023 and TRV120023 groups versus saline controls, and myosin-binding protein C phosphorylation at Ser(282) was unaffected by ANG II or losartan but significantly reduced with TRV120023 treatment compared with all other groups. Our data indicate that TRV120023-related promotion of ß-arrestin signaling and enhanced contractility involves a mechanism promoting the myofilament response to Ca(2+) via altered protein phosphorylation. Selective activation of ß-arrestin-dependent pathways may provide advantages over conventional AT1R blockers.
Assuntos
Arrestinas/metabolismo , Cálcio/metabolismo , Cardiomegalia/tratamento farmacológico , Cardiomegalia/fisiopatologia , Ventrículos do Coração/fisiopatologia , Miofibrilas/efeitos dos fármacos , Oligopeptídeos/administração & dosagem , Angiotensina II , Animais , Cardiomegalia/induzido quimicamente , Cardiotônicos/administração & dosagem , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/patologia , Masculino , Contração Miocárdica/efeitos dos fármacos , Tamanho do Órgão/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Resultado do Tratamento , Regulação para Cima/efeitos dos fármacos , beta-ArrestinasRESUMO
AIMS: Both left ventricular (LV) and left atrial (LA) dysfunction and remodelling contribute to adverse outcomes in heart failure with reduced ejection fraction (HFrEF). Danicamtiv is a novel, cardiac myosin activator that enhances cardiomyocyte contraction. METHODS AND RESULTS: We studied the effects of danicamtiv on LV and LA function in non-clinical studies (ex vivo: skinned muscle fibres and myofibrils; in vivo: dogs with heart failure) and in a randomized, double-blind, single- and multiple-dose phase 2a trial in patients with stable HFrEF (placebo, n = 10; danicamtiv, n = 30; 50-100 mg twice daily for 7 days). Danicamtiv increased ATPase activity and calcium sensitivity in LV and LA myofibrils/muscle fibres. In dogs with heart failure, danicamtiv improved LV stroke volume (+10.6 mL, P < 0.05) and LA emptying fraction (+10.7%, P < 0.05). In patients with HFrEF (mean age 60 years, 25% women, ischaemic heart disease 48%, mean LV ejection fraction 32%), treatment-emergent adverse events, mostly mild, were reported in 17 patients (57%) receiving danicamtiv and 4 patients (40%) receiving placebo. Danicamtiv (at plasma concentrations ≥2000 ng/mL) increased stroke volume (up to +7.8 mL, P < 0.01), improved global longitudinal (up to -1.0%, P < 0.05) and circumferential strain (up to -3.3%, P < 0.01), decreased LA minimal volume index (up to -2.4 mL/m2 , P < 0.01) and increased LA function index (up to 6.1, P < 0.01), when compared with placebo. CONCLUSIONS: Danicamtiv was well tolerated and improved LV systolic function in patients with HFrEF. A marked improvement in LA volume and function was also observed in patients with HFrEF, consistent with pre-clinical findings of direct activation of LA contractility.
Assuntos
Insuficiência Cardíaca , Idoso , Antagonistas de Receptores de Angiotensina , Inibidores da Enzima Conversora de Angiotensina , Animais , Miosinas Cardíacas , Cães , Feminino , Insuficiência Cardíaca/tratamento farmacológico , Humanos , Masculino , Pessoa de Meia-Idade , Volume Sistólico , Função Ventricular EsquerdaRESUMO
PYK2 is a Ca(2+)-dependent, nonreceptor protein tyrosine kinase that is involved in the induction of left ventricular hypertrophy (LVH) and its transition to heart failure. We and others have previously investigated PYK2's function in vitro using cultured neonatal and adult rat ventricular myocytes as model systems. However, the function of PYK2 in the in vivo adult heart remains unclear. Here we evaluate the effect of PYK2 inhibition following myocardial infarction (MI) using adenoviral (Adv) overexpression of the C-terminal domain of PYK2, known as CRNK. First we demonstrate that CRNK functions as a dominant-negative inhibitor of PYK2-dependent signaling, presumably by displacing PYK2 from focal adhesions and costameres. Then, male Sprague-Dawley rats (~300 g) underwent permanent left anterior descending coronary artery ligation. One wk post-MI, either Adv-GFP (n=34) or Adv-CRNK (n=28) was administered (10(10) pfu, 0.1 ml) via catheter-based, Optison-mediated gene transfer. LV structure and function were evaluated by echocardiography 1 and 3 wk after gene transfer, and LV tissue was analyzed by real-time RT-PCR and Western blotting. CRNK overexpression was readily detected by Western blotting 1 wk following gene transfer. Adv-CRNK improved overall survival (P=0.03; Logrank Test) and LV fractional shortening (23+/-2% vs. 31+/-2% for Adv-GFP vs. Adv-CRNK infected animals, respectively; P<0.05). Whereas MI hearts exhibited increased beta-, and decreased alpha-myosin heavy chain (MHC) mRNA expression characteristic of LVH, Adv-CRNK reversed the MHC isoenzyme switch (3.3+/-1.4 fold increase in alpha MHC; 0.4+/-0.1 fold decrease in beta MHC; P<0.05 for both). In summary, CRNK gene transfer improves survival, increases LV function, and alters MHC gene expression suggesting an attenuation of LV remodeling post-MI.
Assuntos
Adenoviridae , Quinase 2 de Adesão Focal/biossíntese , Infarto do Miocárdio/enzimologia , Cadeias Pesadas de Miosina/metabolismo , Transdução Genética , Miosinas Ventriculares/metabolismo , Remodelação Ventricular , Animais , Animais Recém-Nascidos , Células Cultivadas , Quinase 2 de Adesão Focal/genética , Terapia Genética , Insuficiência Cardíaca/enzimologia , Insuficiência Cardíaca/genética , Hipertrofia Ventricular Esquerda/enzimologia , Hipertrofia Ventricular Esquerda/genética , Isoenzimas/genética , Isoenzimas/metabolismo , Masculino , Infarto do Miocárdio/genética , Infarto do Miocárdio/terapia , Cadeias Pesadas de Miosina/genética , Estrutura Terciária de Proteína/genética , Ratos , Ratos Sprague-Dawley , Função Ventricular Esquerda/genética , Miosinas Ventriculares/genética , Remodelação Ventricular/genéticaRESUMO
While significantly reduced glucose metabolism in fronto-temporo-parietal and cingulate cortices has been demonstrated in Alzheimer's disease (AD) compared with controls, cerebral glucose metabolism in patients with mild cognitive impairment who subsequently develop AD is less well-defined. In the present study we measured cerebral glucose metabolism by positron emission tomography (PET) with (18)F-2-fluoro-2-deoxy-D-glucose in 14 patients with aging-associated cognitive decline (AACD), 44 patients with AD, and 14 healthy control subjects at baseline. The AACD patients were clinically followed up, and conversion to AD was determined. Compared with controls, AACD patients had significantly reduced glucose metabolism in the right precuneus, posterior cingulate, right angular gyrus, and bilateral middle temporal cortices, while the respective deficits were more pronounced in AD patients and also involved the frontal cortices. AACD patients who subsequently converted to AD (AACD-converters) showed more extended metabolic changes which also involved the frontal and temporal cortices, right cingulate gyrus, right thalamus, and bilateral precuneus.
Assuntos
Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Transtornos Cognitivos/metabolismo , Glucose/metabolismo , Tomografia por Emissão de Pósitrons/estatística & dados numéricos , Idoso , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Mapeamento Encefálico , Córtex Cerebral/diagnóstico por imagem , Córtex Cerebral/metabolismo , Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/diagnóstico por imagem , Progressão da Doença , Feminino , Fluordesoxiglucose F18/metabolismo , Seguimentos , Lobo Frontal/diagnóstico por imagem , Lobo Frontal/metabolismo , Lateralidade Funcional/fisiologia , Giro do Cíngulo/diagnóstico por imagem , Giro do Cíngulo/metabolismo , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Tomografia por Emissão de Pósitrons/métodos , Índice de Gravidade de Doença , Lobo Temporal/diagnóstico por imagem , Lobo Temporal/metabolismo , Distribuição TecidualRESUMO
PURPOSE: To evaluate the influence of 68-Ga-labeled DOTA (0)-D-Phe (1)-Tyr (3)-Octreotide positron emission tomography ([68Ga]-DOTATOC-PET) for target definition for fractionated stereotactic radiotherapy (FSRT) as a complementary modality to computed tomography (CT) and magnetic resonance imaging (MRI). Because meningiomas show a high expression of somatostatin receptor subtype 2, somatostatin analogs such as DOTATOC offer the possibility of receptor-targeted imaging. PATIENTS AND METHODS: Twenty-six patients received stereotactic CT, MRI, and [68Ga]-DOTATOC-PET as part of their treatment planning. Histology was: World Health Organization (WHO) Grade 1 61.5%, WHO Grade 2 7.7%, WHO Grade 3 3.9%, and undetermined 26.9%. Six patients received radiotherapy as primary treatment, 2 after subtotal resection; 17 patients were treated for recurrent disease. Dynamic PET scans were acquired before radiotherapy over 60 min after intravenous injection of 156 +/- 29 MBq [68Ga]-DOTATOC. These PET images were imported in the planning software for FSRT. Planning target volume (PTV)-I outlined on CT and contrast-enhanced MRI was compared with PTV-II outlined on PET. PTV-III was defined with CT, MRI, and PET and was actually used for radiotherapy treatment. RESULTS: PTV-III was smaller than PTV-I in 9 patients, the same size in 7 patients, and larger in 10 patients. Median PTV-I was 49.6 cc, median PTV-III was 57.2 cc. In all patients [68Ga]-DOTATOC-PET delivered additional information concerning tumor extension. PTV-III was significantly modified based on DOTATOC-PET data in 19 patients. In 1 patient no tumor was exactly identified on CT/MRI but was visible on PET. CONCLUSION: These data demonstrate that [68Ga]-DOTATOC-PET improves target definition for FSRT in patients with intracranial meningiomas. Radiation targeting with fused DOTATOC-PET, CT, and MRI resulted in significant alterations in target definition in 73%.
Assuntos
Neoplasias Meníngeas/diagnóstico por imagem , Meningioma/diagnóstico por imagem , Octreotida/análogos & derivados , Compostos Radiofarmacêuticos , Radiocirurgia , Adulto , Idoso , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Neoplasias Meníngeas/diagnóstico , Neoplasias Meníngeas/cirurgia , Meningioma/diagnóstico , Meningioma/cirurgia , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/diagnóstico por imagem , Recidiva Local de Neoplasia/cirurgia , Tomografia por Emissão de Pósitrons , Receptores de Somatostatina/análise , Tomografia Computadorizada por Raios XRESUMO
Hypertrophic cardiomyopathy (HCM) is an inherited disease of heart muscle that can be caused by mutations in sarcomere proteins. Clinical diagnosis depends on an abnormal thickening of the heart, but the earliest signs of disease are hyperdynamic contraction and impaired relaxation. Whereas some in vitro studies of power generation by mutant and wild-type sarcomere proteins are consistent with mutant sarcomeres exhibiting enhanced contractile power, others are not. We identified a small molecule, MYK-461, that reduces contractility by decreasing the adenosine triphosphatase activity of the cardiac myosin heavy chain. Here we demonstrate that early, chronic administration of MYK-461 suppresses the development of ventricular hypertrophy, cardiomyocyte disarray, and myocardial fibrosis and attenuates hypertrophic and profibrotic gene expression in mice harboring heterozygous human mutations in the myosin heavy chain. These data indicate that hyperdynamic contraction is essential for HCM pathobiology and that inhibitors of sarcomere contraction may be a valuable therapeutic approach for HCM.
Assuntos
Adenosina Trifosfatases/antagonistas & inibidores , Benzilaminas/administração & dosagem , Miosinas Cardíacas/antagonistas & inibidores , Cardiomiopatia Hipertrófica Familiar/tratamento farmacológico , Contração Miocárdica/efeitos dos fármacos , Cadeias Pesadas de Miosina/antagonistas & inibidores , Sarcômeros/efeitos dos fármacos , Uracila/análogos & derivados , Animais , Benzilaminas/química , Miosinas Cardíacas/genética , Cardiomiopatia Hipertrófica Familiar/patologia , Cardiomiopatia Hipertrófica Familiar/fisiopatologia , Células Cultivadas , Modelos Animais de Doenças , Fibrose , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/patologia , Heterozigoto , Humanos , Masculino , Camundongos , Camundongos Endogâmicos , Mutação , Miocárdio/patologia , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/patologia , Cadeias Pesadas de Miosina/genética , Ratos , Uracila/administração & dosagem , Uracila/químicaRESUMO
UNLABELLED: Because biopsy has a high risk of hemorrhage and the findings of CT and MRI are often ambiguous, especially at the base of the skull, additional methods for the characterization of intracranial tumors are needed. Meningiomas show high expression of the somatostatin receptor subtype 2 and thus offer the possibility of receptor-targeted imaging. We used the somatostatin analog (68)Ga-DOTA-d-Phe(1)-Tyr(3)-octreotide (DOTA-TOC) labeled with the positron emitter (68)Ga (half-life, 68 min), obtained from a (68)Ge/(68)Ga generator, for PET of these tumors. In contrast to (18)F-FDG, this ligand shows high meningioma-to-background ratios. The aim was to evaluate kinetic parameters in meningiomas before radiotherapy. METHODS: Dynamic PET scans (3-dimensional mode; 28 frames; ordered-subsets expectation maximization reconstruction) were acquired for 21 patients (mean age +/- SD, 51 +/- 13 y) before radiotherapy during the 60 min after intravenous injection of 156 +/- 29 MBq of (68)Ga-DOTA-TOC. We analyzed 28 meningiomas (median grade [I] according to the system of the World Health Organization) with volumes of at least 0.5 mL (mean volume, 13.1 mL) and nasal mucosa as reference tissue, showing a slight to moderate physiologic uptake. For evaluation of the (68)Ga-DOTA-TOC kinetics, the vascular fraction (vB) and the rate constants (k1, k2, k3, and k4 [1/min]) were computed using a 2-tissue-compartment model. Furthermore, receptor binding (RB) (k1 - k1 x k2) and the ratios k1/k2 and k3/k4 were calculated. RESULTS: Significant differences (P < 0.05; t test) between meningiomas and the reference tissue were found for the mean standardized uptake value (10.5 vs.1.3), vB (0.42 vs. 0.11), k2 (0.12 vs. 0.56), k3 (0.024 vs. 0.060), k4 (0.004 vs. 0.080), and RB (0.49 vs. 0.13). Although there was no significant difference for k1 (0.54 vs. 0.40), the ratios k1/k2 (4.50 vs. 0.71) and k3/k4 (6.00 vs. 0.75) were markedly greater in meningiomas than in reference tissue. CONCLUSION: The high uptake of (68)Ga-DOTA-TOC in meningiomas can be explained by the high values for vB and by the remarkably low values for k2 and k4, leading to significantly greater k1/k2 and k3/k4 ratios and RB in meningiomas than in reference tissue. Thus, pharmacokinetic modeling offers a more detailed analysis of biologic properties of meningiomas. In further studies, these data might serve as a basis for monitoring the somatostatin receptors of meningiomas after radiotherapy.
Assuntos
Neoplasias Meníngeas/diagnóstico por imagem , Neoplasias Meníngeas/metabolismo , Meningioma/diagnóstico por imagem , Meningioma/metabolismo , Octreotida/análogos & derivados , Octreotida/farmacocinética , Tomografia por Emissão de Pósitrons/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Feminino , Radioisótopos de Gálio/farmacocinética , Humanos , Cinética , Masculino , Taxa de Depuração Metabólica , Pessoa de Meia-Idade , Especificidade de Órgãos , Compostos Radiofarmacêuticos/farmacocinéticaRESUMO
UNLABELLED: Bombesin (BN), a 14-amino-acid peptide, shows high affinity for the human gastrin-releasing peptide receptor (GRP-r), which is overexpressed on several types of cancer, including prostate, breast, gastrointestinal, and small cell lung cancer. Thus, radiolabeled BN or BN analogs may prove to be specific tracers for diagnostic and therapeutic targeting of GRP-r-positive tumors in nuclear medicine. This study evaluated a novel BN analog labeled with the positron emitter 68Ga for receptor imaging with PET. METHODS: DOTA-PEG2-[D-Tyr6,beta-Ala11,Thi13,Nle14] BN(6-14) amide (BZH3) (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid; PEG is ethyleneglycol (2-aminoethyl)carboxymethyl ether) was synthetized using the Fmoc strategy and radiolabeled with either 67Ga or 177Lu for in vitro and biodistribution experiments. 68Ga for PET was obtained from a 68Ge/68Ga generator. In vitro binding, internalization, and efflux were determined using the pancreatic tumor cell line AR42J. Biodistribution of the peptide as a function of time and dose was studied in AR42J tumor-bearing mice. RESULTS: In vitro assays demonstrated a high affinity of 67Ga-BZH3 (dissociation constant = 0.46 nmol/L), a rapid internalization (70% of total cell-associated activity was endocytosed after a 15-min incubation), and an intracellular retention half-life (t1/2) of the 67Ga activity of 16.5 +/- 2.4 h. Biodistribution indicated a dose-dependent uptake in the tumor and a prolonged tumor residence time (t1/2 approximately 16 h). Clearance from GRP-r-negative tissues was fast, resulting in high tumor-to-tissue ratios as early as 1 h after injection. Replacing 67Ga by 177Lu, a therapeutic radionuclide, for peptide labeling resulted in a slightly reduced (approximately 20%) tumor uptake and tumor residence time of 177Lu-BZH3. In contrast, 177Lu decline in the pancreas was significantly accelerated by a factor of 3 compared with that of 67Ga. PET of mice with 68Ga-BZH3 clearly delineated tumors in the mediastinal area. CONCLUSION: The promising in vivo data of 68Ga-BZH3 indicate its potential for an improved localization of GRP-r-positive tumors and also suggest its application in patients. PET may also be favorably used for GRP-r density determination, a prerequisite for therapeutic applications.
Assuntos
Peptídeo Liberador de Gastrina/metabolismo , Oligopeptídeos/farmacocinética , Compostos Organometálicos/farmacocinética , Neoplasias Pancreáticas/diagnóstico por imagem , Neoplasias Pancreáticas/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Animais , Linhagem Celular Tumoral , Feminino , Taxa de Depuração Metabólica , Camundongos , Camundongos Nus , Especificidade de Órgãos , Compostos Radiofarmacêuticos/farmacocinética , Ratos , Distribuição Tecidual , Transplante HeterólogoRESUMO
UNLABELLED: Differentiation between tumor progression and radiation necrosis is one of the most difficult tasks in oncologic neuroradiology. Functional imaging of tumor metabolism can help with this task, but the choice of tracer is still controversial. This prospective study following up irradiated low-grade astrocytoma (LGA) was, to our knowledge, the first receiver-operating-characteristic (ROC) analysis that intraindividually evaluated the diagnostic performance of the SPECT tracers 3-[(123)I]iodo-alpha-methyl-L-tyrosine (IMT) and (99m)Tc(I)-hexakis(2-methoxyisobutylisonitrile) (MIBI) and the PET tracer (18)F-FDG. METHODS: We examined 17 patients, initially with histologically proven LGA and treated by stereotactic radiotherapy, who presented with new gadolinium-diethylenetriaminepentaacetic acid-enhancing lesions (n = 26) on MRI. At that time, MRI could not differentiate between progressive tumor and nonprogressive tumor. This MRI examination was closely followed by (18)F-FDG PET and by (99m)Tc-MIBI and (123)I-IMT SPECT. Lesions were classified as progressive tumor (n = 17) or nonprogressive tumor (n = 9) on the basis of prospective follow-up (through clinical examination, MRI, and proton MR spectroscopy) for 26.6 +/- 6.6 mo after PET or SPECT. RESULTS: (123)I-IMT yielded the best ROC characteristics and was the most accurate for classification, with an area under the ROC curve (A(z)) of 0.991. The A(z) of (18)F-FDG (0.947) was not significantly lower than that of (123)I-IMT. The difference in the A(z) of (99m)Tc-MIBI (0.713) from the A(z) of the other tracers used in our study was highly significant (P = 0.01). (99m)Tc-MIBI SPECT was of low accuracy and, especially, of poor sensitivity even at modest specificity values. CONCLUSION: (123)I-IMT SPECT imaging of amino acid transport accurately detects tumor progression in patients with irradiated LGA. In contrast to (123)I-IMT, (18)F-FDG PET was slightly less accurate for classification, and (99m)Tc-MIBI SPECT was of limited value. Imaging of amino acid transport with (123)I-IMT is a valuable additional tool for the follow-up of LGA, allowing early, noninvasive differentiation of lesions with ambiguous morphology after irradiation.
Assuntos
Astrocitoma/diagnóstico por imagem , Astrocitoma/radioterapia , Fluordesoxiglucose F18 , Metiltirosinas , Recidiva Local de Neoplasia/diagnóstico por imagem , Curva ROC , Tecnécio Tc 99m Sestamibi , Tomografia Computadorizada de Emissão/métodos , Adulto , Astrocitoma/diagnóstico , Feminino , Humanos , Masculino , Invasividade Neoplásica/diagnóstico , Invasividade Neoplásica/diagnóstico por imagem , Invasividade Neoplásica/prevenção & controle , Recidiva Local de Neoplasia/diagnóstico , Cuidados Pós-Operatórios/métodos , Valor Preditivo dos Testes , Compostos Radiofarmacêuticos , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Resultado do TratamentoRESUMO
PURPOSE: [111In]-DTPAOC (Octreoscan(R)) has been shown to be very useful in the detection of somatostatin receptor (SSTR) positive tumors and their metastases using either conventional scintigraphy or single photon emission computed tomography (SPECT). The main drawback of this method is the limited spatial resolution and a somewhat low receptor affinity of the radiopeptide. Due to the increased spatial resolution and the ability of quantification, an agent for positron emission tomography (PET) imaging of SSTR is desirable. This communication shows our initial experience using [68Ga]-DOTA-D-Phe(1)-Tyr(3)-Octreotide (DOTATOC) in comparison to [111In]-DTPAOC-SPECT in patients with neuroendocrine tumors. PROCEDURES: Four patients, two male and two female (46-55 years old) have been examined by [111In]-DTPAOC scintigraphy and within one month by [68Ga]-DOTATOC-PET. All of them suffered from neuroendocrine tumors and/or their metastases. DOTATOC has been labeled using the positron-emitting generator-nuclide 68Ga (t(1/2) 68 minutes). In two patients with previously known localization of tumor, dynamic PET scans after intravenous bolus-injection of 181+/-17 MBq [68Ga]-DOTATOC until 120 minutes post-injection were acquired. In all patients, the static PET-scans have been acquired after 45 or 60 minutes post-injection (SUV1) and 140 minutes post-injection (SUV2). RESULTS: Similar to [111In]-DTPAOC, [68Ga]-DOTATOC showed the highest uptake in the spleen, followed by the kidneys and the liver. A clear delineation of the pituitary gland could only be achieved by PET. The highest SUVs were found at a plateau between 45 and 90 minutes with a maximum 60 minutes post-injection. Due to the fast tracer accumulation in the tumor and the rapid clearance of the compound, resulting in high tumor to background ratios even 40 minutes after injection, the short half life of 68Ga is reasonable. In two patients more findings have been revealed by [68Ga]-DOTATOC-PET as compared to the [111In]-DTPAOC-SPECT. In comparison to the [111In]-DTPAOC-SPECT [68Ga]-DOTATOC-PET seems to be superior especially concerning small findings with low tracer uptake. Both [111In]-DTPAOC-SPECT and [68Ga]-DOTATOC-PET were less sensitive in the detection of liver metastases of neuroendocrine tumors compared to computerized tomography CT because they showed a lower uptake than the surrounding liver tissue. CONCLUSIONS: According to our initial experiences in a limited number of patients, [68Ga]-DOTATOC is a promising PET tracer for imaging neuroendocrine tumors and their metastases. In comparison to the [111In]-DTPAOC-scan it seems to be superior especially in detecting small tumors or tumors bearing only a low density of SSTRs. It offers excellent imaging properties and very high tumor to background ratios. Further evaluation of [68Ga]-DOTATOC in a larger number of patients is certainly justified.
Assuntos
Neoplasias Gastrointestinais/diagnóstico por imagem , Neoplasias Gastrointestinais/diagnóstico , Octreotida/análogos & derivados , Octreotida/farmacologia , Compostos Radiofarmacêuticos/farmacologia , Somatostatina/análogos & derivados , Somatostatina/farmacologia , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Tomografia Computadorizada de Emissão/métodos , Tumor Carcinoide/diagnóstico , Tumor Carcinoide/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Metástase Neoplásica , Fatores de Tempo , Distribuição TecidualRESUMO
The case of a patient with familial hemiplegic migraine (FHM) suffering from prolonged right sided hemiparesis and aphasia that persisted for more than 10 days is reported. The symptoms were accompanied by slowing of the magnetoencephalogram over the left hemisphere, which normalized parallel to the clinical improvement. Positron emission tomography obtained on the 6th day revealed glucose-hypometabolism (hemispheric difference > or =10%) in left hemisphere's fronto-basal cortex, caudate nucleus, and thalamus. In contrast, magnetic resonance imaging including perfusion and diffusion weighted imaging was normal and did not show significant alterations of cortical perfusion or water mobility during the episode. We hypothesize that this finding provides evidence for a primary neuronal dysfunction causing the prolonged neurological deficits in FHM.
Assuntos
Hemiplegia/genética , Hemiplegia/patologia , Transtornos de Enxaqueca/genética , Transtornos de Enxaqueca/patologia , Doenças do Sistema Nervoso/patologia , Adulto , Afasia/genética , Afasia/patologia , Química Encefálica , Cromossomos Humanos Par 19/genética , Seguimentos , Glucose/metabolismo , Hemiplegia/complicações , Humanos , Imageamento por Ressonância Magnética , Magnetoencefalografia , Masculino , Transtornos de Enxaqueca/complicações , Doenças do Sistema Nervoso/complicações , Tomografia Computadorizada de Emissão , Ultrassonografia Doppler TranscranianaRESUMO
CT, MRI, PET and SPECT provide complementary information for treatment planning in stereotactic radiotherapy. Stereotactic correlation of these images requires commissioning tests to confirm the localization accuracy of each modality. A phantom was developed to measure the accuracy of stereotactic localization for CT, MRI, PET and SPECT in the head and neck region. To this end. the stereotactically measured coordinates of structures within the phantom were compared with their mechanically defined coordinates. For MRI, PET and SPECT, measurements were performed using two different devices. For MRI, T1- and T2-weighted imaging sequences were applied. For each measurement, the mean radial deviation in space between the stereotactically measured and mechanically defined position of target points was determined. For CT, the mean radial deviation was 0.4 +/- 0.2 mm. For MRI, the mean deviations ranged between 0.7 +/- 0.2 mm and 1.4 +/- 0.5 mm, depending on the MRI device and the imaging sequence. For PET, mean deviations of 1.1 +/- 0.5 mm and 2.4 +/- 0.3 mm were obtained. The mean deviations for SPECT were 1.6 +/- 0.5 mm and 2.0 +/- 0.6 mm. The phantom is well suited to determine the accuracy of stereotactic localization with CT, MRI, PET and SPECT in the head and neck region. The obtained accuracy is well below the physical resolution for CT, PET and SPECT, and of comparable magnitude for MRI. Since the localization accuracy may be device dependent, results obtained at one device cannot be generalized to others.
Assuntos
Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Radiocirurgia/métodos , Tomografia Computadorizada de Emissão/métodos , Tomografia Computadorizada por Raios X/métodos , Humanos , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Aumento da Imagem/normas , Controle de Qualidade , Radiocirurgia/instrumentação , Radiocirurgia/normas , Planejamento da Radioterapia Assistida por Computador/instrumentação , Planejamento da Radioterapia Assistida por Computador/métodos , Planejamento da Radioterapia Assistida por Computador/normas , Radioterapia Assistida por Computador/instrumentação , Radioterapia Assistida por Computador/métodos , Padrões de Referência , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Técnica de Subtração , Tomografia Computadorizada de Emissão de Fóton Único/métodosRESUMO
Animal studies indicate that estrogens, such as 17beta-estradiol (E(2)), may enhance hippocampal metabolism and function. In postmenopausal Alzheimer's disease (AD) patients, cerebrospinal fluid (CSF) E(2) levels were significantly lower than in non-demented controls. This finding was inversely correlated with CSF beta-amyloid levels. To address the potential impact of this finding, E(2) levels in CSF were correlated with regional cerebral [18F]2-fluoro-2-deoxy-D-glucose (FDG) uptake as measured using positron emission tomography (PET) in six postmenopausal AD patients. CSF E(2) levels were determined using an electro-chemiluminescence-immunoassay on the Roche Elecsys 2010 immunoassay analyzer. Basic image processing was done by MEDx, using SPM routines for spatial normalization and statistics. CSF E(2) levels were significantly correlated with cerebral glucose metabolism in the left hippocampus. This is the first clinical study indicating an association between CSF E(2) concentration and hippocampal glucose metabolism in postmenopausal women with AD.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Glicemia/metabolismo , Estradiol/líquido cefalorraquidiano , Hipocampo/diagnóstico por imagem , Pós-Menopausa/líquido cefalorraquidiano , Idoso , Doença de Alzheimer/líquido cefalorraquidiano , Dominância Cerebral/fisiologia , Feminino , Fluordesoxiglucose F18 , Humanos , Processamento de Imagem Assistida por Computador , Pessoa de Meia-Idade , Cintilografia , Valores de ReferênciaRESUMO
Alzheimer's disease (AD) is characterized by a variety of cognitive deficits which can be reliably assessed by the neuropsychological test battery of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), but the cerebral changes underlying the respective cognitive deficits are only partly understood. Measures of severity of dementia in AD as well as delayed episodic memory performance in mild cognitive impairment significantly correlated with bihemispheric cerebral glucose hypometabolism. We therefore hypothesized that the CERAD cognitive battery may represent cerebral dysfunction of both hemispheres in patients with AD. In 32 patients with AD, cerebral glucose metabolism was investigated using positron-emission-tomography with 18Fluorodeoxyglucose (FDG PET) and associated with the test scores of the CERAD cognitive battery by statistical parametric mapping. Episodic memory scores significantly correlated with temporopari etal glucose metabolism of both hemispheres while delayed episodic memory significantly was correlated with the right frontotemporal cortices. Verbal fluency and naming scores significantly correlated with glucose metabolism in left temporoparietal and right frontal cortices, whereas constructional praxis predominantly correlated significantly with the bilateral precuneus. In conclusion, the results of our study demonstrate that not only memory function but also functions of language and constructional praxis in AD are associated with glucose metabolism as revealed by FDG PET in subsets of uni- and bilateral brain areas. The findings of our study for the first time demonstrate that in AD neuropsychological deficits as assessed by the CERAD refer to different cerebral sites of both hemispheres.