RESUMEN

Apolipoprotein E (APOE) is a strong genetic risk factor for late-onset Alzheimer's disease (LOAD). APOE4 increases and APOE2 decreases risk relative to APOE3. In the P301S mouse model of tauopathy, ApoE4 increases tau pathology and neurodegeneration when compared with ApoE3 or the absence of ApoE. However, the role of ApoE isoforms and lipid metabolism in contributing to tau-mediated degeneration is unknown. We demonstrate that in P301S tau mice, ApoE4 strongly promotes glial lipid accumulation and perturbations in cholesterol metabolism and lysosomal function. Increasing lipid efflux in glia via an LXR agonist or Abca1 overexpression strongly attenuates tau pathology and neurodegeneration in P301S/ApoE4 mice. We also demonstrate reductions in reactive astrocytes and microglia, as well as changes in cholesterol biosynthesis and metabolism in glia of tauopathy mice in response to LXR activation. These data suggest that promoting efflux of glial lipids may serve as a therapeutic approach to ameliorate tau and ApoE4-linked neurodegeneration.

Asunto(s)

Enfermedad de Alzheimer , Tauopatías , Ratones , Animales , Apolipoproteína E4/genética , Apolipoproteína E4/metabolismo , Apolipoproteína E3/genética , Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Tauopatías/tratamiento farmacológico , Tauopatías/genética , Colesterol , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Ratones Transgénicos

RESUMEN

Spastic paraplegia type 11 (SPG11) is a common autosomal recessive form of hereditary spastic paraplegia (HSP) characterized by the degeneration of cortical motor neuron axons, leading to muscle spasticity and weakness. Impaired lipid trafficking is an emerging pathology in neurodegenerative diseases including SPG11, though its role in axonal degeneration of human SPG11 neurons remains unknown. Here, we established a pluripotent stem cell-based SPG11 model by knocking down the SPG11 gene in human embryonic stem cells (hESCs). These stem cells were then differentiated into cortical projection neurons (PNs), the cell types affected in HSP patients, to examine axonal defects and cholesterol distributions. Our data revealed that SPG11 deficiency led to reduced axonal outgrowth, impaired axonal transport, and accumulated swellings, recapitulating disease-specific phenotypes. In SPG11-knockdown neurons, cholesterol was accumulated in lysosome and reduced in plasma membrane, revealing impairments in cholesterol trafficking. Strikingly, the liver-X-receptor (LXR) agonists restored cholesterol homeostasis, leading to the rescue of subsequent axonal defects in SPG11-deficient cortical PNs. To further determine the implication of impaired cholesterol homeostasis in SPG11, we examined the cholesterol distribution in cortical PNs generated from SPG11 disease-mutation knock-in hESCs, and observed a similar cholesterol trafficking impairment. Moreover, LXR agonists rescued the aberrant cholesterol distribution and mitigated the degeneration of SPG11 disease-mutated neurons. Taken together, our data demonstrate impaired cholesterol trafficking underlying axonal degeneration of SPG11 human neurons, and highlight the therapeutic potential of LXR agonists for SPG11 through restoring cholesterol homeostasis.

Asunto(s)

Paraplejía Espástica Hereditaria , Humanos , Paraplejía Espástica Hereditaria/genética , Paraplejía Espástica Hereditaria/metabolismo , Proteínas/metabolismo , Neuronas/metabolismo , Mutación , Colesterol/metabolismo , Hígado/patología

RESUMEN

INTRODUCTION: Liver X receptors (LXRs) are master regulators of atherogenesis. Their anti-atherogenic potential has been attributed to their role in the inhibition of macrophage-mediated inflammation and promotion of reverse cholesterol transport. Owing to the significance of their anti-atherogenic potential, it is essential to develop and test new-generation LXR agonists, both synthetic and natural, to identify potential LXR-targeted therapeutics for the future. AREAS COVERED: This review describes the role of LXRs in atherosclerotic development, and provides a summary of LXR agonists and future directions for atherosclerosis research. We searched PubMed, Scopus, and Google Scholar for relevant reports, from last 10 years, using atherosclerosis, liver X receptor, and LXR agonist as keywords. EXPERT OPINION: LXRα has gained widespread recognition as a regulator of cholesterol homeostasis and expression of inflammatory genes. Further research using models of cell type-specific knockout and specific agonist-targeted LXR isoforms is warranted. Enthusiasm for therapeutic value of LXR agonists has been tempered due to LXRα-mediated induction of hepatic lipogenesis. LXRα agonism and LXRß targeting, gut-specific inverse LXR agonists, investigations combining LXR agonists with other lipogenesis-mitigating agents, like IDOL antagonists and synthetic HDL, and targeting ABCA1, M2 macrophages, and LXRα phosphorylation remain as promising possibilities.

Asunto(s)

Aterosclerosis , Receptores Nucleares Huérfanos , Aterosclerosis/tratamiento farmacológico , Colesterol/metabolismo , Colesterol/uso terapéutico , Humanos , Hígado/metabolismo , Receptores X del Hígado/agonistas , Receptores X del Hígado/metabolismo , Macrófagos/metabolismo , Receptores Nucleares Huérfanos/agonistas , Receptores Nucleares Huérfanos/genética , Receptores Nucleares Huérfanos/metabolismo

RESUMEN

Age-related macular degeneration (AMD) is a progressive disease of the macula characterized by atrophy of the retinal pigment epithelium (RPE) and photoreceptor degeneration, leading to severe vision loss at advanced stages in the elderly population. Impaired reverse cholesterol transport (RCT) as well as intracellular lipid accumulation in the RPE are implicated in AMD pathogenesis. Here, we focus on ATP-binding cassette transporter A1 (ABCA1), a major cholesterol transport protein in the RPE, and analyze conditions that lead to ABCA1 dysregulation in induced pluripotent stem cell (iPSC)-derived RPE cells (iRPEs). Our results indicate that the risk-conferring alleles rs1883025 (C) and rs2740488 (A) in ABCA1 are associated with increased ABCA1 mRNA and protein levels and reduced efficiency of cholesterol efflux from the RPE. Hypoxia, an environmental risk factor for AMD, reduced expression of ABCA1 and increased intracellular lipid accumulation. Treatment with a liver X receptor (LXR) agonist led to an increase in ABCA1 expression and reduced lipid accumulation. Our data strengthen the homeostatic role of cholesterol efflux in the RPE and suggest that increasing cellular cholesterol export by stimulating ABCA1 expression might lessen lipid load, improving RPE survival and reducing the risk of developing AMD.

Asunto(s)

Células Madre Pluripotentes Inducidas , Degeneración Macular , Transportador 1 de Casete de Unión a ATP/genética , Transportador 1 de Casete de Unión a ATP/metabolismo , Anciano , Colesterol/metabolismo , Humanos , Hipoxia/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Degeneración Macular/metabolismo , Epitelio Pigmentado de la Retina/metabolismo

RESUMEN

Obesity is associated with hypercholesterolemia and is a global epidemic. Epidemiological and animal studies revealed cholesterol is an essential regulator of estrogen receptor positive (ER+) breast cancer progression while inhibition of cholesterol accumulation was found to prevent breast tumor growth. Individually, vitamin D and LXR agonist T0901317 showed anticancer properties. The present study investigated the effects of vitamin D3 (VD3, calcitriol), LXR agonist (T0901317) and a combination of VD3 + T0901317 on cholesterol metabolism and cancer progression in ER+ breast cancer (MCF-7) cells. VD3 or T0901317 alone reduced cholesterol accumulation significantly in MCF-7 cells concomitant with an induction of ABCA1 protein and gene expression compared to the control treatment. Most importantly, VD3 + T0901317 combination showed higher effects in reducing cholesterol levels and increasing ABCA1 protein and gene expression compared to individual treatments. Importantly, VD3 + T0901317 combination showed higher effects in increasing apoptosis as measured by annexin apoptosis assay, cell viability and was associated with induction of CHOP protein and gene expression. Additionally, the VD3 + T0901317 exerted higher effects in reducing antiapoptotic BCL-2 while increased pro-apoptotic BAX gene expression compared to the individual treatments. The present results suggest that VD3 and T0901317 combination may have an important therapeutic application to prevent obesity and hyperlipidemia mediated ER+ breast cancer progression.

Asunto(s)

Transportador 1 de Casete de Unión a ATP/metabolismo , Apoptosis/efectos de los fármacos , Neoplasias de la Mama/metabolismo , Colesterol/metabolismo , Hidrocarburos Fluorados/farmacología , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Transducción de Señal/efectos de los fármacos , Sulfonamidas/farmacología , Factor de Transcripción CHOP/metabolismo , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/patología , Femenino , Humanos , Receptores X del Hígado/agonistas , Células MCF-7

RESUMEN

Endogenous hydrogen sulfide (H2S) affects cholesterol homeostasis and liver X receptor α (LXRα) expression. However, whether low-density lipoprotein (LDL) receptor (LDLR), a key player in cholesterol homeostasis, is regulated by exogenous H2S through LXRα signaling has not been determined. We investigated the effects of sodium hydrosulfide (NaHS, H2S donor) on LDLR expression in the presence or absence of LXR agonists, T0901317 or GW3965 in HepG2 cells. We found that H2S strongly accumulated LDLR precursor in the presence of T0901317. Hence, LDLR transcription and the genes involved in LDLR precursor maturation and degradation were studied. T0901317 increased the LDLR mRNA level, whereas H2S did not affect LDLR transcription. H2S had no significant effect on the expression of LXRα and inducible degrader of LDLR (IDOL). H2S and T0901317 altered mRNA levels of several enzymes for N- and O-glycosylation and endoplasmic reticulum (ER) chaperones assisting LDLR maturation, but did not affect their protein levels. H2S decreased proprotein convertase subtilisin/kexin type 9 (PCSK9) protein levels and its mRNA level elevated by T0901317. T0901317 with PCSK9 siRNA also accumulated LDLR precursor as did T0901317 with H2S. High glucose increased PCSK9 protein levels and attenuated LDLR precursor accumulation induced by T0901317 with H2S. Taken together, H2S accumulates LDLR precursor by downregulating PCSK9 expression but not through the LXRα-IDOL pathway, LDLR transcriptional activation, or dysfunction of glycosylation enzymes and ER chaperones. These results also indicate that PCSK9 plays an important role in LDLR maturation in addition to its well-known effect on the degradation of LDLR mature form.

Asunto(s)

Sulfuro de Hidrógeno/metabolismo , Receptores X del Hígado/metabolismo , Proproteína Convertasa 9/metabolismo , Receptores de LDL/metabolismo , Benzoatos/farmacología , Bencilaminas/farmacología , Línea Celular Tumoral , Colesterol/metabolismo , Retículo Endoplásmico/fisiología , Glicosilación/efectos de los fármacos , Células Hep G2 , Homeostasis/fisiología , Humanos , Hidrocarburos Fluorados/farmacología , Receptores X del Hígado/agonistas , Proproteína Convertasa 9/genética , Interferencia de ARN , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Sulfuros/farmacología , Sulfonamidas/farmacología , Transcripción Genética/efectos de los fármacos , Activación Transcripcional/genética

RESUMEN

Temporal multi-omics data can provide information about the dynamics of disease development and therapeutic response. However, statistical analysis of high-dimensional time-series data is challenging. Here we develop a novel approach to model temporal metabolomic and transcriptomic data by combining machine learning with metabolic models. ADAPT (Analysis of Dynamic Adaptations in Parameter Trajectories) performs metabolic trajectory modeling by introducing time-dependent parameters in differential equation models of metabolic systems. ADAPT translates structural uncertainty in the model, such as missing information about regulation, into a parameter estimation problem that is solved by iterative learning. We have now extended ADAPT to include both metabolic and transcriptomic time-series data by introducing a regularization function in the learning algorithm. The ADAPT learning algorithm was (re)formulated as a multi-objective optimization problem in which the estimation of trajectories of metabolic parameters is constrained by the metabolite data and refined by gene expression data. ADAPT was applied to a model of hepatic lipid and plasma lipoprotein metabolism to predict metabolic adaptations that are induced upon pharmacological treatment of mice by a Liver X receptor (LXR) agonist. We investigated the excessive accumulation of triglycerides (TG) in the liver resulting in the development of hepatic steatosis. ADAPT predicted that hepatic TG accumulation after LXR activation originates for 80% from an increased influx of free fatty acids. The model also correctly estimated that TG was stored in the cytosol rather than transferred to nascent very-low density lipoproteins. Through model-based integration of temporal metabolic and gene expression data we discovered that increased free fatty acid influx instead of de novo lipogenesis is the main driver of LXR-induced hepatic steatosis. This study illustrates how ADAPT provides estimates for biomedically important parameters that cannot be measured directly, explaining (side-)effects of pharmacological treatment with LXR agonists.

RESUMEN

Anti-angiogenic therapy triggers metabolic alterations in experimental and human tumors, the best characterized being exacerbated glycolysis and lactate production. By using both Liquid Chromatography-Mass Spectrometry (LC-MS) and Nuclear Magnetic Resonance (NMR) analysis, we found that treatment of ovarian cancer xenografts with the anti-Vascular Endothelial Growth Factor (VEGF) neutralizing antibody bevacizumab caused marked alterations of the tumor lipidomic profile, including increased levels of triacylglycerols and reduced saturation of lipid chains. Moreover, transcriptome analysis uncovered up-regulation of pathways involved in lipid metabolism. These alterations were accompanied by increased accumulation of lipid droplets in tumors. This phenomenon was reproduced under hypoxic conditions in vitro, where it mainly depended from uptake of exogenous lipids and was counteracted by treatment with the Liver X Receptor (LXR)-agonist GW3965, which inhibited cancer cell viability selectively under reduced serum conditions. This multi-level analysis indicates alterations of lipid metabolism following anti-VEGF therapy in ovarian cancer xenografts and suggests that LXR-agonists might empower anti-tumor effects of bevacizumab.

Asunto(s)

Metabolismo de los Lípidos/efectos de los fármacos , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/metabolismo , Factor A de Crecimiento Endotelial Vascular/metabolismo , Apoptosis/efectos de los fármacos , Benzoatos/uso terapéutico , Bencilaminas/uso terapéutico , Bevacizumab/uso terapéutico , Western Blotting , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Femenino , Humanos , Inmunohistoquímica , Espectroscopía de Resonancia Magnética , Factor A de Crecimiento Endotelial Vascular/antagonistas & inhibidores , Ensayos Antitumor por Modelo de Xenoinjerto

RESUMEN

BACKGROUND: Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) may be used to depict tumour vascular structure and for therapy response assessment in various tumour sites. The purpose of the current work is to examine whether ultra-early changes in tumour physiology following cytotoxic treatment with doxorubicin and liver X receptor (LXR) agonist GW3965 are detectable by DCE-MRI. METHODS: 36 female, athymic nude foxn1nu mice with bilaterally implanted breast cancer xenografts (17 with ER-positive HBCx34, 19 with triple-negative HBCx39) were randomised in the following treatment groups; control, GW3965 (40 mg/kg p.o.), doxorubicin (8 mg/kg i.v.) and a combination therapy of GW3965 and doxorubicin. DCE-MRI (3D FLASH on a 7 T preclinical scanner) was performed at baseline and one and six days after onset of treatment. Wash-in (30 s p.i.) and wash-out (300 s p.i.) enhancement were quantified from dynamic uptake curves, before voxel-by-voxel fitting to the pharmacokinetic Tofts model and generation of maps for the resulting parameters Ktrans, νe and νB. Treatment effect was evaluated by univariate repeated measures mixed-effects maximum likelihood regression models applied to median tumour data. RESULTS: We found no effects of any treatment 24 h post treatment. After 6 days, doxorubicin given as both mono- and combination therapy gave significant increases of ~ 30% in wash-in enhancement (p < 0.011) and Ktrans (p < 0.017), and 40-50% in νB (p < 0.024) for HBCx34, but not for HBCx39. No effects of GW3965 were observed at any time (p > 0.1). CONCLUSIONS: Twenty-four h after onset of treatment was too early to evaluate treatment effects by DCE-MRI. Early enhancement and Ktrans were approximately equally sensitive metrics to capture treatment effects six days pt. Pharmacokinetic modelling however allowed us to attribute the observed effect to changes in tumour perfusion rather than increased retention.

Asunto(s)

Antineoplásicos/uso terapéutico , Benzoatos/uso terapéutico , Bencilaminas/uso terapéutico , Doxorrubicina/uso terapéutico , Imagen por Resonancia Magnética , Neoplasias Mamarias Experimentales/diagnóstico por imagen , Neovascularización Patológica/diagnóstico por imagen , Animales , Terapia Combinada , Medios de Contraste , Femenino , Neoplasias Mamarias Experimentales/tratamiento farmacológico , Neoplasias Mamarias Experimentales/patología , Ratones , Ratones Desnudos , Neovascularización Patológica/tratamiento farmacológico

RESUMEN

Liver-X-receptor (LXR) agonists are known to bear anti-tumor activity. However, their efficacy is limited and additional insights regarding the underlying mechanism are necessary. By performing transcriptome analysis coupled with global polar metabolite screening, we show that LXR agonists, LXR623 and GW3965, enhance synergistically the anti-proliferative effect of BH3 mimetics in solid tumor malignancies, which is predominantly mediated by cell death with features of apoptosis and is rescued by exogenous cholesterol. Extracellular flux analysis and carbon tracing experiments (U-13 C-glucose and U-13 C-glutamine) reveal that within 5 h, activation of LXRß results in reprogramming of tumor cell metabolism, leading to suppression of mitochondrial respiration, a phenomenon not observed in normal human astrocytes. LXR activation elicits a suppression of respiratory complexes at the protein level by reducing their stability. In turn, energy starvation drives an integrated stress response (ISR) that up-regulates pro-apoptotic Noxa in an ATF4-dependent manner. Cholesterol and nucleotides rescue from the ISR elicited by LXR agonists and from cell death induced by LXR agonists and BH3 mimetics. In conventional and patient-derived xenograft models of colon carcinoma, melanoma, and glioblastoma, the combination treatment of ABT263 and LXR agonists reduces tumor sizes significantly stronger than single treatments. Therefore, the combination treatment of LXR agonists and BH3 mimetics might be a viable efficacious treatment approach for solid malignancies.

Asunto(s)

Carcinoma/fisiopatología , Respiración de la Célula/efectos de los fármacos , Glioblastoma/fisiopatología , Receptores X del Hígado/agonistas , Melanoma/fisiopatología , Proteína bcl-X/antagonistas & inhibidores , Animales , Apoptosis/efectos de los fármacos , Benzoatos/metabolismo , Bencilaminas/metabolismo , Carcinoma/tratamiento farmacológico , Proliferación Celular/efectos de los fármacos , Modelos Animales de Enfermedad , Perfilación de la Expresión Génica , Glioblastoma/tratamiento farmacológico , Humanos , Indazoles/metabolismo , Melanoma/tratamiento farmacológico , Metabolómica , Modelos Teóricos , Resultado del Tratamiento

RESUMEN

Macrophage infiltration is common to both emphysema and atherosclerosis, and cigarette smoke down-regulates the macrophage cholesterol efflux transporter ATP binding cassette (ABC)A1. This decreased cholesterol efflux results in lipid-laden macrophages. We hypothesize that cigarette smoke adversely affects cholesterol transport via an ABCA1-dependent mechanism in macrophages, enhancing TLR4/myeloid differentiation primary response gene 88 (Myd88) signaling and resulting in matrix metalloproteinase (MMP) up-regulation and exacerbation of pulmonary inflammation. ABCA1 is significantly down-regulated in the lung upon smoke exposure conditions. Macrophages exposed to cigarette smoke in vivo and in vitro exhibit impaired cholesterol efflux correlating with significantly decreased ABCA1 expression, up-regulation of the TLR4/Myd88 pathway, and downstream MMP-9 and MMP-13 expression. Treatment with liver X receptor (LXR) agonist restores ABCA1 expression after short-term smoke exposure and attenuates the inflammatory response; after long-term smoke exposure, there is also attenuated physiologic and morphologic changes of emphysema. In vitro, treatment with LXR agonist decreases macrophage inflammatory activation in wild-type but not ABCA1 knockout mice, suggesting an ABCA1-dependent mechanism of action. These studies demonstrate an important association between cigarette smoke exposure and cholesterol-mediated pathways in the macrophage inflammatory response. Modulation of these pathways through manipulation of ABCA1 activity effectively blocks cigarette smoke-induced inflammation and provides a potential novel therapeutic approach for the treatment of chronic obstructive pulmonary disease.-Sonett, J., Goldklang, M., Sklepkiewicz, P., Gerber, A., Trischler, J., Zelonina, T., Westerterp, M., Lemaître, V., Okada, V., D'Armiento, J. A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure.

RESUMEN

Passive amyloid-ß (Aß) vaccination has shown significant effects on amyloid pathology in pre-depositing amyloid-ß protein precursor (AßPP) mice but the results in older mice are inconsistent. A therapeutic effect of LXR and RXR agonists consisting of improved memory deficits and Aß pathology has been demonstrated in different Alzheimer's disease (AD) mouse models. Here, we report the effect of a combination of N-terminal Aß antibody and synthetic LXR agonist T0901317 (T0) on AD-like phenotype of APP23 mice. To examine the therapeutic potential of this combination, the treatment of mice started at 11 months of age, when amyloid phenotype in this model is fully developed, and continued for 50 days. We show that Aß immunization with or without LXR agonist restored the performance of APP23 transgenic mice in two behavior paradigms without affecting the existing amyloid plaques. Importantly, we did not observe an increase of brain microhemorrhage which is considered a significant side effect of Aß vaccination. Target engagement was confirmed by increased Abca1 and ApoE protein level as well as increased ApoE lipidation in soluble brain extract. In interstitial fluid obtained by microdialysis, we demonstrate that immunization and T0 significantly reduced Aß levels, indicating an increased Aß clearance. We found no interaction between the immunotherapy and T0, suggesting no synergism, at least with these doses. The results of our study demonstrate that anti-Aß treatments can ameliorate cognitive deficits in AßPP mice with advanced AD-like phenotype in conjunction with a decrease of Aß in brain interstitium and increase of ApoE lipidation without affecting the existing amyloid plaques.

Asunto(s)

Enfermedad de Alzheimer/terapia , Péptidos beta-Amiloides/metabolismo , Anticuerpos Monoclonales/uso terapéutico , Hidrocarburos Fluorados/uso terapéutico , Inmunización Pasiva , Trastornos de la Memoria/terapia , Sulfonamidas/uso terapéutico , Transportador 1 de Casete de Unión a ATP/metabolismo , Precursor de Proteína beta-Amiloide/genética , Proteínas Amiloidogénicas/inmunología , Animales , Apolipoproteínas E/metabolismo , Encéfalo/efectos de los fármacos , Encéfalo/patología , Encéfalo/fisiopatología , Terapia Combinada , Condicionamiento Psicológico/efectos de los fármacos , Condicionamiento Psicológico/fisiología , Modelos Animales de Enfermedad , Miedo/efectos de los fármacos , Miedo/fisiología , Femenino , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Aprendizaje por Laberinto/fisiología , Trastornos de la Memoria/patología , Trastornos de la Memoria/fisiopatología , Ratones Endogámicos C57BL , Ratones Transgénicos , Nootrópicos/uso terapéutico , Distribución Aleatoria

RESUMEN

Stimulation of the liver X receptor (LXR) is associated with anti-inflammatory and vascular-protective effects under hyperlipemic conditions. We examined whether LXR stimulation influences TNF-α-induced endothelial dysfunction under normolipemic conditions. Endothelium-dependent vasorelaxation of aortic rings was determined in an organ water bath. Human umbilical vein endothelial cells (HUVEC) were exposed to TNF-α (10 ng/ml) in the presence or absence of 5 µM of the LXR agonist T0901317 or GW3965 and changes in TNF-α-induced endothelial cell apoptosis, inflammation, oxidative stress, and NO metabolism were analyzed. T0901317 improved TNF-α-impaired endothelium-dependent relaxation of aortic rings in response to acetylcholine. T0901317 decreased the TNF-α-induced apoptosis and inflammation as indicated by a decrease in caspase 3/7 activity, VCAM-1 mRNA expression and subsequent mononuclear cell adhesion. Furthermore, T0901317 reduced the expression of the oxidative stress markers: AT1R, NOX4, and p22phox and normalized the TNF-α-induced NOX activity to basal levels. In line with the reduced AT1R expression, T0901317 impaired the Ang II responsiveness. T0901317 influenced NO metabolism as indicated by a decrease in TNF-α-upregulated arginase activity, a reversal of TNF-α-induced downregulation of argininosuccinate synthase mRNA expression and eNOS expression to basal levels and a raise in NO production. Furthermore, T0901317 decreased the TNF-α-induced superoxide and nitrotyrosine production, but did not upregulate the TNF-α-downregulated eNOS dimer/monomer ratio. Silencing of LXRß, but not of LXRα, abrogated the anti-apoptotic effects of T0901317. We conclude that LXR agonism improves TNF-α-impaired endothelial function via its anti-apoptotic, anti-inflammatory, and anti-oxidative properties and its capacity to restore TNF-α-impaired NO bioavailability independent of its cholesterol-modulating effects.

Asunto(s)

Colesterol/metabolismo , Hidrocarburos Fluorados/farmacología , Receptores Nucleares Huérfanos/agonistas , Sulfonamidas/farmacología , Factor de Necrosis Tumoral alfa/farmacología , Animales , Antioxidantes/metabolismo , Aorta/metabolismo , Benzoatos/farmacología , Bencilaminas/farmacología , Caspasa 3/metabolismo , Caspasa 7/metabolismo , Endotelio/efectos de los fármacos , Células Endoteliales de la Vena Umbilical Humana , Humanos , Técnicas In Vitro , Receptores X del Hígado , Masculino , NADPH Oxidasas/metabolismo , Óxido Nítrico/metabolismo , Receptores Nucleares Huérfanos/metabolismo , Estrés Oxidativo , ARN Interferente Pequeño/metabolismo , Ratas , Ratas Wistar , Especies Reactivas de Oxígeno

RESUMEN

Vitamin D receptor (VDR) and liver X receptor (LXR) are nuclear receptors, which regulate gene transcription upon binding of their specific ligands. VDR seems to play a role in the regulation of prostate cancer cell proliferation. ATP-binding cassette transporter A1 (ABCA1) is known to be a target gene of LXR and it has been reported to be inhibited by androgen and to be involved in the regulation of LNCaP proliferation. We find that calcitriol (1 alpha,25(OH)(2)D(3)) inhibits both basal and a LXR agonist, TO-901317, induced ABCA1 mRNA expression but has no effect on the mRNA expression of ATP-binding cassette transporter G1 (ABCG1), LXR alpha nor LXR beta. TO-901317 increases both basal and calcitriol induced 25-hydroxyvitamin D(3)-24-hydroxylase (CYP24) mRNA expression and it slightly but significantly inhibits VDR mRNA expression. The inhibition of ABCA1 by calcitriol appears to be androgen-independent. Cell growth assay shows that when each of calcitriol and 5 alpha-dihydrotestosterone (DHT) was co-treated with ABCA1 blocker, glybenclamide, cell-growth is significantly decreased compared to their own treatments respectively. Our study suggests a possible interaction between calcitriol and TO-901317 in LNCaP cells. Alike DHT, the inhibition of ABCA1 by calcitriol may be involved in its regulation of LNCaP growth.