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1.
PLoS One ; 7(5): e36315, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22649491

RESUMO

Huntingtin Interacting Protein 14 (HIP14) is a palmitoyl acyl transferase (PAT) that was first identified due to altered interaction with mutant huntingtin, the protein responsible for Huntington Disease (HD). HIP14 palmitoylates a specific set of neuronal substrates critical at the synapse, and downregulation of HIP14 by siRNA in vitro results in increased cell death in neurons. We previously reported that mice lacking murine Hip14 (Hip14-/-) share features of HD. In the current study, we have generated human HIP14 BAC transgenic mice and crossed them to the Hip14-/- model in order to confirm that the defects seen in Hip14-/- mice are in fact due to loss of Hip14. In addition, we sought to determine whether human HIP14 can provide functional compensation for loss of murine Hip14. We demonstrate that despite a relative low level of expression, as assessed via Western blot, BAC-derived human HIP14 compensates for deficits in neuropathology, behavior, and PAT enzyme function seen in the Hip14-/- model. Our findings yield important insights into HIP14 function in vivo.


Assuntos
Aciltransferases/deficiência , Aciltransferases/farmacologia , Proteínas Adaptadoras de Transdução de Sinal/farmacologia , Locomoção/efeitos dos fármacos , Proteínas do Tecido Nervoso/metabolismo , Aciltransferases/genética , Aciltransferases/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Análise de Variância , Animais , Western Blotting , Peso Corporal , Cromossomos Artificiais Bacterianos/genética , Cruzamentos Genéticos , Primers do DNA/genética , Humanos , Imuno-Histoquímica , Lipoilação , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/farmacologia , Reação em Cadeia da Polimerase , Reação em Cadeia da Polimerase em Tempo Real , Teste de Desempenho do Rota-Rod
2.
Hum Mol Genet ; 21(9): 1954-67, 2012 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-22262731

RESUMO

Apoptosis, or programmed cell death, is a cellular pathway involved in normal cell turnover, developmental tissue remodeling, embryonic development, cellular homeostasis maintenance and chemical-induced cell death. Caspases are a family of intracellular proteases that play a key role in apoptosis. Aberrant activation of caspases has been implicated in human diseases. In particular, numerous findings implicate Caspase-6 (Casp6) in neurodegenerative diseases, including Alzheimer disease (AD) and Huntington disease (HD), highlighting the need for a deeper understanding of Casp6 biology and its role in brain development. The use of targeted caspase-deficient mice has been instrumental for studying the involvement of caspases in apoptosis. The goal of this study was to perform an in-depth neuroanatomical and behavioral characterization of constitutive Casp6-deficient (Casp6-/-) mice in order to understand the physiological function of Casp6 in brain development, structure and function. We demonstrate that Casp6-/- neurons are protected against excitotoxicity, nerve growth factor deprivation and myelin-induced axonal degeneration. Furthermore, Casp6-deficient mice show an age-dependent increase in cortical and striatal volume. In addition, these mice show a hypoactive phenotype and display learning deficits. The age-dependent behavioral and region-specific neuroanatomical changes observed in the Casp6-/- mice suggest that Casp6 deficiency has a more pronounced effect in brain regions that are involved in neurodegenerative diseases, such as the striatum in HD and the cortex in AD.


Assuntos
Caspase 6/fisiologia , Degeneração Neural/enzimologia , Envelhecimento/patologia , Envelhecimento/fisiologia , Doença de Alzheimer/enzimologia , Doença de Alzheimer/patologia , Animais , Apoptose/fisiologia , Sequência de Bases , Comportamento Animal/fisiologia , Encéfalo/enzimologia , Encéfalo/patologia , Caspase 6/deficiência , Caspase 6/genética , Humanos , Doença de Huntington/enzimologia , Doença de Huntington/patologia , Camundongos , Camundongos Knockout , Atividade Motora/fisiologia , Degeneração Neural/genética , Degeneração Neural/patologia , Neurônios/enzimologia , Neurônios/patologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de N-Metil-D-Aspartato/fisiologia
3.
J Huntingtons Dis ; 1(2): 243-60, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-25063333

RESUMO

BACKGROUND: The amelioration of behavioral and neuropathological deficits in mice expressing caspase-6-resistant (C6R) mutant huntingtin (mhtt), despite the presence of an expanded polyglutamine tract, highlights proteolysis of htt at the 586aa caspase-6 (casp6) site may be an important mechanism in the pathogenesis of Huntington disease (HD). One possible explanation of these effects is that C6R mhtt could act as a dominant negative on mhtt. OBJECTIVE AND METHODS: To determine if the neuroprotective effect observed in the C6R mice is due to dominant negative effects, we crossed the C6R mice to the YAC128 HD mouse model to generate mice expressing both caspase-cleavable and C6R mhtt (YAC/C6R) concurrently and assessed previously defined behavioral and neuropathological endpoints. RESULTS: Our results demonstrate that YAC/C6R animals exhibit similar motor abnormalities and learning deficits as the YAC128 mice. Neuropathological analysis reveals a significant decrease in brain weight and striatal volume in the YAC/C6R mice comparable to the YAC128 mice. In contrast, and similar to previous findings, C6R mice demonstrate preserved brain weight and striatal volume. As expected, body weight is significantly increased in the YAC/C6R mice due to the increased levels of htt. CONCLUSIONS: The results of this study suggest that the lack of an HD phenotype in the C6R mice is most likely due to the absence of cleavage of htt and not due to suppression of expression of mhtt.


Assuntos
Caspase 6/metabolismo , Modelos Animais de Doenças , Doença de Huntington/patologia , Doença de Huntington/fisiopatologia , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Animais , Corpo Estriado/patologia , Ativação Enzimática , Feminino , Proteína Huntingtina , Camundongos , Camundongos Transgênicos , Especificidade da Espécie
4.
Mol Neurodegener ; 6: 59, 2011 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-21854568

RESUMO

BACKGROUND: Huntington Disease (HD) is a neurodegenerative disorder in which caspase activation and cleavage of substrates, including the huntingtin protein, has been invoked as a pathological mechanism. Specific changes in caspase-2 (casp2) activity have been suggested to contribute to the pathogenesis of HD, however unique casp2 cleavage substrates have remained elusive. We thus utilized mice completely lacking casp2 (casp2-/-) to examine the role played by casp2 in the progression of HD. This 'substrate agnostic' approach allows us to query the effect of casp2 on HD progression without pre-defining proteolytic substrates of interest. RESULTS: YAC128 HD model mice lacking casp2 show protection from well-validated motor and cognitive features of HD, including performance on rotarod, swimming T-maze, pre-pulse inhibition, spontaneous alternation and locomotor tasks. However, the specific pathological features of the YAC128 mice including striatal volume loss and testicular degeneration are unaltered in mice lacking casp2. The application of high-resolution magnetic resonance imaging (MRI) techniques validates specific neuropathology in the YAC128 mice that is not altered by ablation of casp2. CONCLUSIONS: The rescue of behavioral phenotypes in the absence of pathological improvement suggests that different pathways may be operative in the dysfunction of neural circuitry in HD leading to behavioral changes compared to the processes leading to cell death and volume loss. Inhibition of caspase-2 activity may be associated with symptomatic improvement in HD.

5.
Hum Mol Genet ; 20(20): 3899-909, 2011 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-21775500

RESUMO

Huntingtin interacting protein 14 (HIP14, ZDHHC17) is a huntingtin (HTT) interacting protein with palmitoyl transferase activity. In order to interrogate the function of Hip14, we generated mice with disruption in their Hip14 gene. Hip14-/- mice displayed behavioral, biochemical and neuropathological defects that are reminiscent of Huntington disease (HD). Palmitoylation of other HIP14 substrates, but not Htt, was reduced in the Hip14-/- mice. Hip14 is dysfunctional in the presence of mutant htt in the YAC128 mouse model of HD, suggesting that altered palmitoylation mediated by HIP14 may contribute to HD.


Assuntos
Aciltransferases/deficiência , Doença de Huntington/etiologia , Lipoilação/genética , Proteínas do Tecido Nervoso/deficiência , Aciltransferases/genética , Aciltransferases/metabolismo , Animais , Morte Celular/genética , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Modelos Animais de Doenças , Fosfoproteína 32 Regulada por cAMP e Dopamina/metabolismo , Encefalinas/metabolismo , Doença de Huntington/genética , Doença de Huntington/patologia , Camundongos , Camundongos Knockout , Atividade Motora/genética , Proteínas Mutantes/metabolismo , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Neurônios/patologia , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Sinapses/metabolismo
6.
Neurobiol Dis ; 43(1): 257-65, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21458571

RESUMO

Models of Huntington disease (HD) recapitulate some neuropathological features of the disease. However, a global natural history of neuroanatomy in a mouse expressing full-length huntingtin has not been conducted. We investigated neuropathological changes in the YAC128 murine model of HD using magnetic resonance imaging (MRI). Structures affected in human HD are reduced in the YAC128 mice both in absolute terms and in terms of percentage of brain volume. Structures resistant to degeneration in HD, including the cerebellum and hippocampus, are spared in the YAC128 mice. Segmentation of major white matter structures confirms specific, progressive, loss of white matter in HD. In parallel with their specific volume loss, the YAC128 mice also show progressive increases in total ventricular volume, similarly to human HD patients. Cortical atrophy in the YAC128 mice is layer specific, which is the observed pattern of cortical loss in human HD patients. Finally, we have used a classification tree analysis to maximize separation of genotypes using all 62 structure volumes in an objective manner. This analysis demonstrates that sub-cortical gray matter structures (striatum, globus pallidus, thalamus) and cerebral white matter structures (corpus callosum, anterior commisure, fimbria) are the most discriminatory. The high resolution of the current study enables robust measurement of subtle early pathological changes. The use of mice furthermore enables us to address questions difficult to address in humans, including the sequential changes of HD from baseline and the relation between MRI and stereological measures.


Assuntos
Doença de Huntington/genética , Doença de Huntington/patologia , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares/genética , Animais , Atrofia , Encéfalo/metabolismo , Encéfalo/patologia , Cerebelo/metabolismo , Cerebelo/patologia , Modelos Animais de Doenças , Progressão da Doença , Regulação da Expressão Gênica/genética , Humanos , Proteína Huntingtina , Doença de Huntington/etiologia , Imageamento por Ressonância Magnética/métodos , Camundongos , Camundongos Transgênicos , Proteínas do Tecido Nervoso/biossíntese , Proteínas Nucleares/biossíntese
7.
J Neurosci ; 30(45): 15019-29, 2010 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-21068307

RESUMO

Caspase cleavage of huntingtin (htt) and nuclear htt accumulation represent early neuropathological changes in brains of patients with Huntington's disease (HD). However, the relationship between caspase cleavage of htt and caspase activation patterns in the pathogenesis of HD remains poorly understood. The lack of a phenotype in YAC mice expressing caspase-6-resistant (C6R) mutant htt (mhtt) highlights proteolysis of htt at the 586 aa caspase-6 (casp6) site as a key mechanism in the pathology of HD. The goal of this study was to investigate how proteolysis of htt at residue 586 plays a role in the pathogenesis of HD and determine whether inhibiting casp6 cleavage of mhtt alters cell-death pathways in vivo. Here we demonstrate that activation of casp6, and not caspase-3, is observed before onset of motor abnormalities in human and murine HD brain. Active casp6 levels correlate directly with CAG size and inversely with age of onset. In contrast, in vivo expression of C6R mhtt attenuates caspase activation. Increased casp6 activity and apoptotic cell death is evident in primary striatal neurons expressing caspase-cleavable, but not C6R, mhtt after NMDA application. Pretreatment with a casp6 inhibitor rescues the apoptotic cell death observed in this paradigm. These data demonstrate that activation of casp6 is an early marker of disease in HD. Furthermore, these data provide a clear link between excitotoxic pathways and proteolysis and suggest that C6R mhtt protects against neurodegeneration by influencing the activation of neuronal cell-death and excitotoxic pathways operative in HD.


Assuntos
Apoptose/genética , Caspase 6/metabolismo , Doença de Huntington/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Análise de Variância , Animais , Apoptose/efeitos dos fármacos , Western Blotting , Caspase 6/genética , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Progressão da Doença , Humanos , Proteína Huntingtina , Doença de Huntington/genética , Doença de Huntington/patologia , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , N-Metilaspartato/farmacologia , Proteínas do Tecido Nervoso/genética , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Proteínas Nucleares/genética
8.
J Neurosci ; 30(43): 14318-29, 2010 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-20980587

RESUMO

YAC transgenic mice expressing poly(Q)-expanded full-length huntingtin (mhtt) recapitulate many behavioral and neuropathological features of Huntington disease (HD). We have previously observed a reduction in phosphorylation of mhtt at S421 in the presence of the mutation for HD. In addition, phosphorylation of normal S421-htt is reduced after excitotoxic stimulation of NMDA receptors (NMDARs). To test whether NMDAR stimulation contributes to reduced pS421-htt levels in HD, we determined phosphorylation of htt at Ser421 after NMDA-induced excitotoxicity in neurons from YAC128 mice. Here, we report that the total level of pS421-htt is reduced in YAC128 primary neurons after excitotoxic NMDAR stimulation. Similarly, the total level of pS421-htt is reduced in YAC128 transgenic mice after quinolinic acid injection into the striatum. In contrast, loss of phosphorylation of pS421-htt is prevented in YAC mice that never develop clinical or neuropathological features of HD [the caspase 6-resistant YAC128 transgene (C6R)]. To gain insight into the mechanisms underlying these findings, we determined that the Ser/Thr protein phosphatases PP1 and PP2A dephosphorylate pS421-htt in situ and after excitotoxic stimulation of NMDARs in neurons. Furthermore, increasing the phosphorylation of htt at S421 by blocking PP1 and PP2A activity protects YAC128 striatal neurons from NMDA-induced cell death. These results, together with the observed modulation of pS421-htt levels by dopamine, the reduced expression of PP1 inhibitor Darpp-32 in the striatum of YAC128 mice, and the reduced phosphorylation of PP1 substrate CreB, point to altered regulation of phosphatase activity in HD and highlight enhancing phosphorylation of htt at S421 as a therapeutic target.


Assuntos
Agonistas de Aminoácidos Excitatórios/toxicidade , N-Metilaspartato/antagonistas & inibidores , N-Metilaspartato/toxicidade , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Proteínas Nucleares/metabolismo , Proteína Fosfatase 1/fisiologia , Proteína Fosfatase 2/fisiologia , Animais , Morte Celular/fisiologia , Células Cultivadas , Cerebelo/efeitos dos fármacos , Cerebelo/metabolismo , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Maleato de Dizocilpina/farmacologia , Fosfoproteína 32 Regulada por cAMP e Dopamina/biossíntese , Fosfoproteína 32 Regulada por cAMP e Dopamina/genética , Antagonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Proteína Huntingtina , Masculino , Camundongos , Mutação , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares/genética , Fosforilação , Proteína Fosfatase 1/antagonistas & inibidores , Proteína Fosfatase 2/antagonistas & inibidores , Ácido Quinolínico/farmacologia , Receptores de Dopamina D1/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Técnicas Estereotáxicas
9.
Hum Mol Genet ; 19(8): 1528-38, 2010 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-20097678

RESUMO

Levels of full-length huntingtin (FL htt) influence organ and body weight, independent of polyglutamine length. The growth hormone-insulin like growth factor-1 (GH-IGF-1) axis is well established as a regulator of organ growth and body weight. In this study, we investigate the involvement of the IGF-1 pathway in mediating the effect of htt on body weight. IGF-1 expression was examined in transgenic mouse lines expressing different levels of FL wild-type (WT) htt (YAC18 mice), FL mutant htt (YAC128 and BACHD mice) and truncated mutant htt (shortstop mice). We demonstrate that htt influences body weight by modulating the IGF-1 pathway. Plasma IGF-1 levels correlate with body weight and htt levels in the transgenic YAC mice expressing human htt. The effect of htt on IGF-1 expression is independent of CAG size. No effect on body weight is observed in transgenic YAC mice expressing a truncated N-terminal htt fragment (shortstop), indicating that FL htt is required for the modulation of IGF-1 expression. Treatment with 17beta-estradiol (17beta-ED) lowers the levels of circulating IGF-1 in mammals. Treatment of YAC128 with 17beta-ED, but not placebo, reduces plasma IGF-1 levels and decreases the body weight of YAC128 animals to WT levels. Furthermore, given the ubiquitous expression of IGF-1 within the central nervous system, we also examined the impact of FL htt levels on IGF-1 expression in different regions of the brain, including the striatum, cerebellum of YAC18, YAC128 and littermate WT mice. We demonstrate that the levels of FL htt influence IGF-1 expression in striatal tissues. Our data identify a novel function for FL htt in influencing IGF-1 expression.


Assuntos
Peso Corporal , Doença de Huntington/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Animais , Encéfalo/metabolismo , Modelos Animais de Doenças , Expressão Gênica , Humanos , Proteína Huntingtina , Doença de Huntington/genética , Fator de Crescimento Insulin-Like I/genética , Masculino , Camundongos , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares/genética , Transdução de Sinais
10.
Biochim Biophys Acta ; 1791(12): 1166-72, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19695343

RESUMO

Absence of stearoyl-CoA desaturase-1 (SCD1) in mice leads to chronic inflammation of the skin and increased susceptibility to atherosclerosis, while also increasing plasma inflammatory markers. A recent report suggested that SCD1 deficiency also increases disease severity in a mouse model of inflammatory bowel disease, induced by dextran sulfate sodium (DSS). However, SCD1-deficient mice are known to consume increased amounts of water, which would also be expected to increase the intake of DSS-treated water. The aim of this study was to determine the effect of SCD1 deficiency on DSS-induced acute colitis with DSS dosing adjusted to account for genotype differences in fluid consumption. Wild-type controls were treated with 3.5% DSS for 5 days to induce moderately severe colitis, while the concentration of DSS given to SCD1-deficient mice was lowered to 2.5% to control for increased fluid consumption. Colonic inflammation was assessed by clinical and histological scoring. Although SCD1-deficient mice consumed a total intake of DSS that was greater than that of wild-type controls, colonic inflammation, colon length and fecal blood were not altered by SCD1-deficiency in DSS-induced colitis, while diarrhea and total weight loss were modestly improved. Despite SCD1 deficiency leading to chronic inflammation of the skin and increased susceptibility to atherosclerosis, it does not accelerate inflammation in the DSS-induced model of acute colitis when DSS intake is controlled. These observations suggest that SCD1 deficiency does not play a significant role in colonic inflammation in this model.


Assuntos
Colite/enzimologia , Colite/patologia , Estearoil-CoA Dessaturase/deficiência , Doença Aguda , Animais , Peso Corporal , Colite/induzido quimicamente , Colo/enzimologia , Colo/patologia , Sulfato de Dextrana , Comportamento de Ingestão de Líquido , Fezes , Camundongos , Camundongos Endogâmicos C57BL , Estearoil-CoA Dessaturase/metabolismo
11.
J Neurosci ; 29(11): 3579-89, 2009 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-19295162

RESUMO

The expression of the cholesterol transporter ATP-binding cassette transporter A1 (ABCA1) in the brain and its role in the lipidation of apolipoproteins indicate that ABCA1 may play a critical role in brain cholesterol metabolism. To investigate the role of ABCA1 in brain cholesterol homeostasis and trafficking, we characterized mice that specifically lacked ABCA1 in the CNS, generated using the Cre/loxP recombination system. These mice showed reduced plasma high-density lipoprotein (HDL) cholesterol levels associated with decreased brain cholesterol content and enhanced brain uptake of esterified cholesterol from plasma HDL. Increased levels of HDL receptor SR-BI in brain capillaries and apolipoprotein A-I in brain and CSF of mutant mice were evident. Cholesterol homeostasis changes were mirrored by disturbances in motor activity and sensorimotor function. Changes in synaptic ultrastructure including reduced synapse and synaptic vesicle numbers were observed. These data show that ABCA1 is a key regulator of brain cholesterol metabolism and that disturbances in cholesterol transport in the CNS are associated with structural and functional deficits in neurons. Moreover, our findings also demonstrate that specific changes in brain cholesterol metabolism can lead to alterations in cholesterol uptake from plasma to brain.


Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Encéfalo/metabolismo , Encéfalo/ultraestrutura , Colesterol/metabolismo , Neurônios/fisiologia , Neurônios/ultraestrutura , Regulação para Cima/genética , Transportador 1 de Cassete de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/fisiologia , Animais , Comportamento/fisiologia , Colesterol/biossíntese , Homeostase/genética , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Sinapses/fisiologia
12.
Arterioscler Thromb Vasc Biol ; 29(4): 548-54, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19201688

RESUMO

OBJECTIVE: The ATP-binding cassette transporter, subfamily A, member 1 (ABCA1) plays a key role in HDL cholesterol metabolism. However, the role of ABCA1 in modulating susceptibility to atherosclerosis is controversial. METHODS AND RESULTS: We investigated the role of ABCA1 in atherosclerosis using a combination of overexpression and selective deletion models. First, we examined the effect of transgenic overexpression of a full-length human ABCA1-containing bacterial artificial chromosome (BAC) in the presence or absence of the endogenous mouse Abca1 gene. ABCA1 overexpression in the atherosclerosis-susceptible Ldlr(-/-) background significantly reduced the development of atherosclerosis in both the presence and absence of mouse Abca1. Next, we used mice with tissue-specific inactivation of Abca1 to dissect the discrete roles of Abca1 in different tissues on susceptibility to atherosclerosis. On the Apoe(-/-) background, mice lacking hepatic Abca1 had significantly reduced HDL cholesterol and accelerated atherosclerosis, indicating that the liver is an important site at which Abca1 plays an antiatherogenic role. In contrast, mice with macrophage-specific inactivation of Abca1 on the Ldlr(-/-) background displayed no change in atherosclerotic lesion area. CONCLUSIONS: These data indicate that physiological expression of Abca1 modulates the susceptibility to atherosclerosis and establish hepatic Abca1 expression as an important site of atheroprotection. In contrast, we show that selective deletion of macrophage Abca1 does not significantly modulate atherogenesis.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Aterosclerose/metabolismo , HDL-Colesterol/metabolismo , Fígado/metabolismo , Transportador 1 de Cassete de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Aterosclerose/genética , Aterosclerose/patologia , Aterosclerose/prevenção & controle , HDL-Colesterol/sangue , LDL-Colesterol/metabolismo , VLDL-Colesterol/metabolismo , Cromossomos Artificiais Bacterianos , Gorduras na Dieta/administração & dosagem , Modelos Animais de Doenças , Predisposição Genética para Doença , Humanos , Macrófagos Peritoneais/metabolismo , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Fenótipo , Receptores de LDL/deficiência , Receptores de LDL/genética
13.
Arterioscler Thromb Vasc Biol ; 29(3): 341-7, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19095997

RESUMO

OBJECTIVE: Absence of stearoyl-CoA desaturase-1 (SCD1) in mice reduces plasma triglycerides and provides protection from obesity and insulin resistance, which would be predicted to be associated with reduced susceptibility to atherosclerosis. The aim of this study was to determine the effect of SCD1 deficiency on atherosclerosis. METHODS AND RESULTS: Despite an antiatherogenic metabolic profile, SCD1 deficiency increases atherosclerosis in hyperlipidemic low-density lipoprotein receptor (LDLR)-deficient mice challenged with a Western diet. Lesion area at the aortic root is significantly increased in males and females in two models of SCD1 deficiency. Inflammatory changes are evident in the skin of these mice, including increased intercellular adhesion molecule (ICAM)-1 and ulcerative dermatitis. Increases in ICAM-1 and interleukin-6 are also evident in plasma of SCD1-deficient mice. HDL particles demonstrate changes associated with inflammation, including decreased plasma apoA-II and apoA-I and paraoxonase-1 and increased plasma serum amyloid A. Lipopolysaccharide-induced inflammatory response and cholesterol efflux are not altered in SCD1-deficient macrophages. In addition, when SCD1 deficiency is limited to bone marrow-derived cells, lesion size is not altered in LDLR-deficient mice. CONCLUSIONS: These studies reinforce the crucial role of chronic inflammation in promoting atherosclerosis, even in the presence of antiatherogenic biochemical and metabolic characteristics.


Assuntos
Aterosclerose/enzimologia , Hiperlipidemias/enzimologia , Inflamação/enzimologia , Estearoil-CoA Dessaturase/deficiência , Animais , Apolipoproteínas/sangue , Arildialquilfosfatase/sangue , Aterosclerose/genética , Aterosclerose/imunologia , Aterosclerose/patologia , Modelos Animais de Doenças , Progressão da Doença , Feminino , Hiperlipidemias/genética , Hiperlipidemias/imunologia , Hiperlipidemias/patologia , Inflamação/genética , Inflamação/imunologia , Inflamação/patologia , Mediadores da Inflamação/sangue , Molécula 1 de Adesão Intercelular/sangue , Interleucina-6/sangue , Lipoproteínas HDL/sangue , Macrófagos/enzimologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de LDL/deficiência , Receptores de LDL/genética , Proteína Amiloide A Sérica/metabolismo , Úlcera Cutânea/enzimologia , Úlcera Cutânea/patologia , Estearoil-CoA Dessaturase/genética , Fatores de Tempo
14.
J Lipid Res ; 49(1): 217-29, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17960025

RESUMO

A combination of the interrelated metabolic risk factors obesity, insulin resistance, dyslipidemia, and hypertension, often described as the "metabolic syndrome," is known to increase the risk of developing cardiovascular disease and diabetes. Stearoyl-coenzyme A desaturase (SCD) activity has been implicated in the metabolic syndrome, but detailed studies of the beneficial metabolic effects of SCD deficiency have been limited. Here, we show that absence of the Scd1 gene product reduces plasma triglycerides and reduces weight gain in severely hyperlipidemic low density lipoprotein receptor (LDLR)-deficient mice challenged with a Western diet. Absence of SCD1 also increases insulin sensitivity, as measured by intraperitoneal glucose and insulin tolerance testing. SCD1 deficiency dramatically reduces hepatic lipid accumulation while causing more modest reductions in plasma apolipoproteins, suggesting that in conditions of sustained hyperlipidemia, SCD1 functions primarily to mediate lipid stores. In addition, absence of SCD1 partially ameliorates the undesirable hypertriglyceridemic effect of antiatherogenic liver X receptor agonists. Our results demonstrate that constitutive reduction of SCD activity improves the metabolic phenotype of LDLR-deficient mice on a Western diet.


Assuntos
Hepatócitos/metabolismo , Hiperlipidemias/metabolismo , Lipídeos/sangue , Síndrome Metabólica/metabolismo , Receptores de LDL/metabolismo , Estearoil-CoA Dessaturase/metabolismo , Adiposidade/fisiologia , Animais , Peso Corporal , Células Cultivadas , Dieta/efeitos adversos , Fígado Gorduroso/metabolismo , Hiperlipidemias/sangue , Resistência à Insulina , Metabolismo dos Lipídeos , Camundongos , Camundongos Mutantes , Receptores de LDL/deficiência , Receptores de LDL/genética , Estearoil-CoA Dessaturase/deficiência , Estearoil-CoA Dessaturase/genética
15.
J Neurosci ; 27(9): 2298-308, 2007 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-17329427

RESUMO

Huntingtin-interacting protein 1 (HIP1) is an endocytic adaptor protein that plays a role in clathrin-mediated endocytosis and the ligand-induced internalization of AMPA receptors (AMPARs) (Metzler et al., 2003). In the present study, we investigated the role of HIP1 in NMDA receptor (NMDAR) function by analyzing NMDA-dependent transport and NMDA-induced excitotoxicity in neurons from HIP1-/- mice. HIP1 colocalizes with NMDARs in hippocampal and cortical neurons and affinity purifies with NMDARs by GST (glutathione S-transferase) pull down and coimmunoprecipitation. A profound decrease in NMDA-induced AMPAR internalization of 75% occurs in neurons from HIP1-/- mice compared with wild type, using a quantitative single-cell-based internalization assay. This defect in NMDA-dependent removal of surface AMPARs is in agreement with the observed defect in long-term depression induction in hippocampal brain slices of HIP1-/- mice and supports a role of HIP1 in AMPAR internalization in vivo. HIP1-/- neurons are partially protected from NMDA-induced excitotoxicity as assessed by LDH (lactate dehydrogenase) release, TUNEL (terminal deoxynucleotidyl transferase-mediated biotinylated dUTP nick end labeling) and caspase-3 activation assays, which points to a role of HIP1 in NMDA-induced cell death. Interestingly, phosphorylation of Akt and its substrate huntingtin (htt) decreases during NMDA-induced excitotoxicity by 48 and 31%, respectively. This decrease is significantly modulated by HIP1, resulting in 94 and 48% changes in P-Akt and P-htt levels in HIP1-/- neurons, respectively. In summary, we have shown that HIP1 influences important NMDAR functions and that both HIP1 and htt participate in NMDA-induced cell death. These findings may provide novel insights into the cellular mechanisms underlying enhanced NMDA-induced excitotoxicity in Huntington's disease.


Assuntos
Córtex Cerebral/metabolismo , Proteínas de Ligação a DNA/metabolismo , Hipocampo/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Receptores de N-Metil-D-Aspartato/fisiologia , Animais , Técnicas de Cultura de Células , Morte Celular , Glutationa Transferase/metabolismo , Proteína Huntingtina , Camundongos , Neurônios/metabolismo , Fosforilação
16.
Circulation ; 114(12): 1301-9, 2006 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-16940190

RESUMO

BACKGROUND: Extrahepatic tissues have long been considered critical contributors of cholesterol to nascent HDL particles in the reverse cholesterol transport pathway, in which ABCA1 plays the crucial role. Recent studies, however, including both overexpression and deletion of ABCA1 selectively in the liver, have highlighted the primary role of the liver in the maintenance of HDL levels in vivo. METHODS AND RESULTS: The availability of mice with complete deletion of ABCA1 (total knockout [TKO]) and with liver-specific deletion of ABCA1 (LSKO) has enabled us to dissect the discrete roles of hepatic relative to extrahepatic ABCA1 in HDL biogenesis. Delivery of adenoviral ABCA1 resulted in selective expression of physiological levels of ABCA1 in the livers of both LSKO and TKO mice, resulting in increased HDL cholesterol (HDL-C). Expression of ABCA1 in the liver of LSKO mice resulted in plasma HDL-C levels that were similar to those in wild-type mice and significantly above those seen in similarly treated TKO mice. HDL particles from ABCA1-expressing LSKO mice were larger and contained significantly increased cholesterol compared with TKO mice. Infusion of human apolipoprotein A-I/phospholipid reconstituted HDL particles normalized plasma HDL-C levels in LSKO mice but had no effect on HDL-C levels in TKO mice. CONCLUSIONS: Although hepatic ABCA1 appears crucial for phospholipid transport, extrahepatic tissues play an important role in cholesterol transfer to nascent HDL particles. These data highlight the discrete and specific roles of both liver and extrahepatic ABCA1 in HDL biogenesis in vivo and indicate that ABCA1 shows lipid cargo selectivity depending on its site of expression.


Assuntos
Transportadores de Cassetes de Ligação de ATP/fisiologia , HDL-Colesterol/sangue , Fígado/metabolismo , Transportador 1 de Cassete de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Adenoviridae , Animais , Apolipoproteína A-I/farmacologia , HDL-Colesterol/genética , Feminino , Regulação da Expressão Gênica , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout
17.
Cell ; 125(6): 1179-91, 2006 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-16777606

RESUMO

Cleavage of huntingtin (htt) has been characterized in vitro, and accumulation of caspase cleavage fragments represents an early pathological change in brains of Huntington's disease (HD) patients. However, the relationship between htt proteolysis and the pathogenesis of HD is unknown. To determine whether caspase cleavage of htt is a key event in the neuronal dysfunction and selective neurodegeneration in HD, we generated YAC mice expressing caspase-3- and caspase-6-resistant mutant htt. Mice expressing mutant htt, resistant to cleavage by caspase-6 but not caspase-3, maintain normal neuronal function and do not develop striatal neurodegeneration. Furthermore, caspase-6-resistant mutant htt mice are protected against neurotoxicity induced by multiple stressors including NMDA, quinolinic acid (QA), and staurosporine. These results are consistent with proteolysis of htt at the caspase-6 cleavage site being an important event in mediating neuronal dysfunction and neurodegeneration and highlight the significant role of htt proteolysis and excitotoxicity in HD.


Assuntos
Caspases/metabolismo , Doença de Huntington/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Proteínas Nucleares/metabolismo , Transporte Ativo do Núcleo Celular , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/patologia , Caspase 6 , Caspases/genética , Núcleo Celular/metabolismo , Humanos , Proteína Huntingtina , Doença de Huntington/patologia , Hidrólise , Camundongos , Camundongos Transgênicos , Mutação , N-Metilaspartato/toxicidade , Degeneração Neural/induzido quimicamente , Degeneração Neural/metabolismo , Degeneração Neural/patologia , Proteínas do Tecido Nervoso/genética , Neurônios/patologia , Proteínas Nucleares/genética , Ácido Quinolínico/toxicidade , Estaurosporina/toxicidade
18.
Arterioscler Thromb Vasc Biol ; 26(8): 1821-7, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16728652

RESUMO

OBJECTIVE: Mutations in ATP-binding cassette transporter A1 (ABCA1), the cellular lipid transport molecule mutated in Tangier disease, result in the rapid turnover of high-density lipoprotein (HDL)-associated apolipoproteins that presumably are cleared by the kidneys. However, the role of ABCA1 in the liver for HDL apolipoprotein and cholesteryl ester (CE) catabolism in vivo is unknown. METHODS AND RESULTS: Murine HDL was radiolabeled with 125I in its apolipoprotein and with [3H]cholesteryl oleyl ether in its CE moiety. HDL protein and lipid metabolism in plasma and HDL uptake by tissues were investigated in ABCA1-overexpressing bacterial artificial chromosome (BAC)-transgenic (BAC+) mice and in mice harboring deletions of total (ABCA1-/-) and liver-specific ABCA1 (ABCA1(-L/-L)). In BAC+ mice with elevated ABCA1 expression, fractional catabolic rates (FCRs) of both the protein and the lipid tracer were significantly decreased in plasma and in the liver, yielding a diminished hepatic selective CE uptake from HDL. In contrast, ABCA1-/- or ABCA1(-L/-L) mice had significantly increased plasma and liver FCRs for both HDL tracers. An ABCA1 deficiency was associated with increased selective HDL CE uptake by the liver under all experimental conditions. CONCLUSIONS: Hepatic ABCA1 has a critical role for HDL catabolism in plasma and for HDL selective CE uptake by the liver.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Ésteres do Colesterol/metabolismo , Lipoproteínas HDL/metabolismo , Fígado/metabolismo , Transportador 1 de Cassete de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Animais , Colesterol/sangue , Cromossomos Artificiais Bacterianos/genética , Cromossomos Artificiais Bacterianos/metabolismo , Lipoproteínas HDL/farmacocinética , Camundongos , Camundongos Knockout/genética , Camundongos Transgênicos/genética , Receptores Depuradores Classe B/metabolismo , Distribuição Tecidual
19.
J Clin Invest ; 116(4): 1052-62, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16543947

RESUMO

Plasma HDL cholesterol levels are inversely related to risk for atherosclerosis. The ATP-binding cassette, subfamily A, member 1 (ABCA1) mediates the rate-controlling step in HDL particle formation, the assembly of free cholesterol and phospholipids with apoA-I. ABCA1 is expressed in many tissues; however, the physiological functions of ABCA1 in specific tissues and organs are still elusive. The liver is known to be the major source of plasma HDL, but it is likely that there are other important sites of HDL biogenesis. To assess the contribution of intestinal ABCA1 to plasma HDL levels in vivo, we generated mice that specifically lack ABCA1 in the intestine. Our results indicate that approximately 30% of the steady-state plasma HDL pool is contributed by intestinal ABCA1 in mice. In addition, our data suggest that HDL derived from intestinal ABCA1 is secreted directly into the circulation and that HDL in lymph is predominantly derived from the plasma compartment. These data establish a critical role for intestinal ABCA1 in plasma HDL biogenesis in vivo.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , HDL-Colesterol/metabolismo , Mucosa Intestinal/metabolismo , Transportador 1 de Cassete de Ligação de ATP , Animais , HDL-Colesterol/sangue , Imunofluorescência , Intestinos/enzimologia , Linfa/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos
20.
Neurobiol Dis ; 21(2): 444-55, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16230019

RESUMO

Huntington disease (HD) is a devastating neuropsychiatric disease caused by expansion of a trinucleotide repeat (CAG) in the HD gene. Neuropathological changes include the appearance of N-terminal huntingtin fragments, decreased brain weight and apoptotic neuronal loss in a select subset of neurons located in the striatum. There is still controversy over whether homozygosity for the mutation in HD is associated with a more severe phenotype. In humans, resolution of this issue has been complicated by the small number of homozygous patients and difficulty in the definition of reliable phenotypic endpoints. In order to definitively determine whether there is a correlation between phenotypic severity and expression levels of mutant huntingtin, we undertook a behavioral and neuropathological assessment of YAC128 mice with varying levels of mutant huntingtin. The results reveal a clear relationship between levels of mutant huntingtin and phenotype defined by earlier age of onset, more rapid progression, enhanced striatal volume loss, acceleration of nuclear huntingtin fragment accumulation and increased sensitivity to NMDAR-mediated excitotoxicity. These results provide clear evidence in vivo supporting a more severe phenotype associated with increased levels of mutant huntingtin as seen in homozygotes for HD.


Assuntos
Homozigoto , Doença de Huntington/genética , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Fenótipo , Idade de Início , Animais , Western Blotting , Encéfalo/metabolismo , Encéfalo/patologia , Cromossomos Artificiais de Levedura , Modelos Animais de Doenças , Progressão da Doença , Proteína Huntingtina , Doença de Huntington/metabolismo , Hibridização in Situ Fluorescente , Camundongos , Camundongos Transgênicos , Atividade Motora/fisiologia , RNA Mensageiro/análise , Receptores de N-Metil-D-Aspartato/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Expansão das Repetições de Trinucleotídeos
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