RESUMEN
Angioimmunoblastic T-cell lymphoma (AITL) is proposed to be initiated by age-related clonal hematopoiesis (ACH) with TET2 mutations, whereas the G17V RHOA mutation in immature cells with TET2 mutations promotes the development of T follicular helper (TFH)-like tumor cells. Here, we investigated the mechanism by which TET2-mutant immune cells enable AITL development using mouse models and human samples. Among the 2 mouse models, mice lacking Tet2 in all the blood cells (Mx-Cre × Tet2flox/flox × G17V RHOA transgenic mice) spontaneously developed AITL for approximately up to a year, while mice lacking Tet2 only in the T cells (Cd4-Cre × Tet2flox/flox × G17V RHOA transgenic mice) did not. Therefore, Tet2-deficient immune cells function as a niche for AITL development. Single-cell RNA-sequencing (scRNA-seq) of >50 000 cells from mouse and human AITL samples revealed significant expansion of aberrant B cells, exhibiting properties of activating light zone (LZ)-like and proliferative dark zone (DZ)-like germinal center B (GCB) cells. The GCB cells in AITL clonally evolved with recurrent mutations in genes related to core histones. In silico network analysis using scRNA-seq data identified Cd40-Cd40lg as a possible mediator of GCB and tumor cell cluster interactions. Treatment of AITL model mice with anti-Cd40lg inhibitory antibody prolonged survival. The genes expressed in aberrantly expanded GCB cells in murine tumors were also broadly expressed in the B-lineage cells of TET2-mutant human AITL. Therefore, ACH-derived GCB cells could undergo independent clonal evolution and support the tumorigenesis in AITL via the CD40-CD40LG axis.
Asunto(s)
Linfadenopatía Inmunoblástica , Linfoma de Células T , Humanos , Ratones , Animales , Linfocitos T Colaboradores-Inductores , Linfadenopatía Inmunoblástica/genética , Linfoma de Células T/patología , Centro Germinal/patología , Ratones TransgénicosRESUMEN
Ductal stenting has transformed the care of neonates with ductal-dependent critical CHD, especially in low-income countries. In small infants, a 3.5- or 4-mm stent may lead to too much pulmonary blood flow resulting in pulmonary oedema. We herein presented a novel technique to restrict ductal stent flow in a premature neonate with pulmonary atresia and intact ventricular septum following radiofrequency perforation of the pulmonary valve.
RESUMEN
The brain exchanges nutrients and small molecules with blood via the blood-brain barrier (BBB). Approximately 20% energy intake for the body is consumed by the brain. Glucose is known for its critical roles for energy production and provides substrates for biogenesis in neurons. The brain takes up glucose via glucose transporters GLUT1 and 3, which are expressed in several neural cell types. The brain is also equipped with various transport systems for acquiring amino acids, lactate, ketone bodies, lipids, and cofactors for neuronal functions. Unraveling the mechanisms by which the brain takes up and metabolizes these nutrients will be key in understanding the nutritional requirements in the brain. This could also offer opportunities for therapeutic interventions in several neurological disorders. For instance, emerging evidence suggests a critical role of lactate as an alternative energy source for neurons. Neuronal cells express monocarboxylic transporters to acquire lactate. As such, treatment of GLUT1-deficient patients with ketogenic diets to provide the brain with alternative sources of energy has been shown to improve the health of the patients. Many transporters are present in the brain, but only a small number has been characterized. In this review, we will discuss about the roles of solute carrier (SLC) transporters at the blood brain barrier (BBB) and neural cells, in transport of nutrients and metabolites in the brain.
Asunto(s)
Encefalopatías/metabolismo , Encéfalo/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Animales , Astrocitos/metabolismo , Barrera Hematoencefálica/metabolismo , Humanos , Ácido Láctico/metabolismoRESUMEN
Huntington disease (HD) is a neurodegenerative disorder caused by a CAG expansion in the HTT gene that codes for an elongated polyglutamine tract in the huntingtin (HTT) protein. HTT is subject to multiple post-translational modifications (PTMs) that regulate its cellular function. Mutating specific PTM sites within mutant HTT (mHTT) in HD mouse models can modulate disease phenotypes, highlighting the key role of HTT PTMs in the pathogenesis of HD. These findings have led to increased interest in developing small molecules to modulate HTT PTMs in order to decrease mHTT toxicity. However, the therapeutic efficacy of pharmacological modulation of HTT PTMs in preclinical HD models remains largely unknown. HTT is palmitoylated at cysteine 214 by the huntingtin-interacting protein 14 (HIP14 or ZDHHC17) and 14-like (HIP14L or ZDHHC13) acyltransferases. Here, we assessed if HTT palmitoylation should be regarded as a therapeutic target to treat HD by (1) investigating palmitoylation dysregulation in rodent and human HD model systems, (2) measuring the impact of mHTT-lowering therapy on brain palmitoylation, and (3) evaluating if HTT palmitoylation can be pharmacologically modulated. We show that palmitoylation of mHTT and some HIP14/HIP14L-substrates is decreased early in multiple HD mouse models, and that mHTT palmitoylation decreases further with aging. Lowering mHTT in the brain of YAC128 mice is not sufficient to rescue aberrant palmitoylation. However, we demonstrate that mHTT palmitoylation can be normalized in COS-7 cells, in YAC128 cortico-striatal primary neurons and HD patient-derived lymphoblasts using an acyl-protein thioesterase (APT) inhibitor. Moreover, we show that modulating palmitoylation reduces mHTT aggregation and mHTT-induced cytotoxicity in COS-7 cells and YAC128 neurons.
Asunto(s)
Proteína Huntingtina/genética , Proteína Huntingtina/toxicidad , Lipoilación/efectos de los fármacos , Lipoilación/genética , Aciltransferasas/genética , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Células COS , Línea Celular , Chlorocebus aethiops , Cisteína/química , Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/uso terapéutico , Femenino , Humanos , Linfocitos/efectos de los fármacos , Linfocitos/metabolismo , Masculino , Ratones , Mutación , Proteínas del Tejido Nervioso/genética , Neuronas/efectos de los fármacos , Neuronas/metabolismo , RatasRESUMEN
Immune cells harboring somatic mutations reportedly infiltrate cancer tissues in patients with solid cancers and accompanying clonal hematopoiesis. Loss-of-function TET2 mutations are frequently observed in clonal hematopoiesis in solid cancers. Here, using a mouse lung cancer model, we evaluated the activity of Tet2-deficient immune cells in tumor tissues. Myeloid-specific Tet2 deficiency enhanced tumor growth in mice relative to that seen in controls. Single-cell sequencing analysis of immune cells infiltrating tumors showed relatively high expression of S100a8/S100a9 in Tet2-deficient myeloid subclusters. In turn, treatment with S100a8/S100a9 promoted Vegfa production by cancer cells, leading to a marked increase in the tumor vasculature in Tet2-deficient mice relative to controls. Finally, treatment of Tet2-deficient mice with an antibody against Emmprin, a known S100a8/S100a9 receptor, suppressed tumor growth. These data suggest that immune cells derived from TET2-mutated clonal hematopoiesis exacerbate lung cancer progression by promoting tumor angiogenesis and may provide a novel therapeutic target for lung cancer patients with TET2-mutated clonal hematopoiesis.
Asunto(s)
Carcinoma Pulmonar de Lewis/patología , Proteínas de Unión al ADN/genética , Dioxigenasas/genética , Perfilación de la Expresión Génica/métodos , Mutación con Pérdida de Función , Factor A de Crecimiento Endotelial Vascular/metabolismo , Animales , Basigina/administración & dosificación , Basigina/farmacología , Calgranulina A/efectos de los fármacos , Calgranulina A/genética , Calgranulina B/efectos de los fármacos , Calgranulina B/genética , Carcinoma Pulmonar de Lewis/tratamiento farmacológico , Carcinoma Pulmonar de Lewis/genética , Carcinoma Pulmonar de Lewis/metabolismo , Estudios de Casos y Controles , Línea Celular Tumoral , Progresión de la Enfermedad , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Ratones , Análisis de Secuencia de ARN , Análisis de la Célula IndividualRESUMEN
Huntington disease (HD) is a progressive neurodegenerative disease that initially affects the striatum and leads to changes in behavior and loss of motor coordination. It is caused by an expansion in the polyglutamine repeat at the N terminus of huntingtin (HTT) that leads to aggregation of mutant HTT. The loss of wild-type function, in combination with the toxic gain of function mutation, initiates various cell death pathways. Wild-type and mutant HTT are regulated by different posttranslational modifications that can positively or negatively regulate their function or toxicity. In particular, we have previously shown that caspase cleavage of mutant HTT at amino acid position aspartate 586 (D586) by caspase-6 is critical for the pathogenesis of the disease in an HD mouse model. Herein, we describe the identification of a new caspase cleavage site at position D572 that is mediated by caspase-1. Inhibition of caspase-1 also appeared to decrease proteolysis at D586, likely by blocking the downstream activation of caspase-6 through caspase-1. Inhibition of caspase cleavage at D572 significantly decreased mutant HTT aggregation and significantly increased the turnover of soluble mutant HTT. This suggests that caspase-1 may be a viable target to inhibit caspase cleavage of mutant HTT at both D572 and D586 to promote mutant HTT clearance.-Martin, D. D. O., Schmidt, M. E., Nguyen, Y. T., Lazic, N., Hayden, M. R. Identification of a novel caspase cleavage site in huntingtin that regulates mutant huntingtin clearance.
Asunto(s)
Proteína Huntingtina/química , Proteína Huntingtina/genética , Proteínas Mutantes/química , Proteínas Mutantes/genética , Animales , Sitios de Unión/genética , Caspasa 1/metabolismo , Células HeLa , Humanos , Proteína Huntingtina/metabolismo , Enfermedad de Huntington/genética , Enfermedad de Huntington/metabolismo , Ratones , Mutagénesis Sitio-Dirigida , Proteínas Mutantes/metabolismo , Agregación Patológica de Proteínas/genética , Agregación Patológica de Proteínas/metabolismo , Procesamiento Proteico-Postraduccional , Proteolisis , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , SolubilidadRESUMEN
This study evaluated the capacity to remove lead by an indigenous consortium of five sulfate-reducing bacteria (SRB): Desulfobacterium autotrophicum, Desulfomicrobium salsugmis, Desulfomicrobium escambiense, Desulfovibrio vulgaris, and Desulfovibrio carbinolicus, using continuous moving bed biofilm reactor systems. Four continuous moving bed biofilm reactors (referred as R1-R4) were run in parallel for 40 days at lead loading rates of 0, 20, 30 and 40 mg l-1 day-1, respectively. The impact of lead on community structure of the SRB consortium was investigated by dsrB gene-based denaturing gradient gel electrophoresis (dsrB-based DGGE), fluorescence in situ hybridization (FISH) and chemical analysis. These results indicated that D. escambiense and D. carbinolicus were dominant in all analyzed samples and played a key role in lead removal in R2 (20 mg l-1 day-1) and R3 (30 mg l-1 day-1). However, in R4 (40 mg l-1 day-1), these two strains were barely detected by FISH and dsrB-based DGGE. As a result, SRB activity was severely affected by lead toxicity. High lead removal efficiencies of lead (99-100%) were observed in R2 and R3 throughout the operation, whereas that in R4 was significantly decreased (91%) after 40 days of operation. This data strongly implied that the investigated SRB consortium might have potential application for lead removal. Moreover, to improve the efficiency of the lead treatment process, the lead loading rates below the inhibitory level to SRB activity should be selected.
Asunto(s)
Plomo/metabolismo , Bacterias Reductoras del Azufre/clasificación , Bacterias Reductoras del Azufre/aislamiento & purificación , Aguas Residuales/microbiología , Contaminantes Químicos del Agua/metabolismo , Biodegradación Ambiental , Reactores Biológicos/microbiología , ADN Bacteriano/genética , Electroforesis en Gel de Gradiente Desnaturalizante , Hibridación Fluorescente in Situ , Oxidación-Reducción , Filogenia , ARN Ribosómico 16S/genética , Bacterias Reductoras del Azufre/genéticaRESUMEN
Activation of caspase-6 in the striatum of both presymptomatic and affected persons with Huntington's disease (HD) is an early event in the disease pathogenesis. However, little is known about the role of caspase-6 outside the central nervous system (CNS) and whether caspase activation might play a role in the peripheral phenotypes, such as muscle wasting observed in HD. We assessed skeletal muscle tissue from HD patients and well-characterized mouse models of HD. Cleavage of the caspase-6 specific substrate lamin A is significantly increased in skeletal muscle obtained from HD patients as well as in muscle tissues from two different HD mouse models. p53, a transcriptional activator of caspase-6, is upregulated in neuronal cells and tissues expressing mutant huntingtin. Activation of p53 leads to a dramatic increase in levels of caspase-6 mRNA, caspase-6 activity and cleavage of lamin A. Using mouse embryonic fibroblasts (MEFs) from YAC128 mice, we show that this increase in caspase-6 activity can be mitigated by pifithrin-α (pifα), an inhibitor of p53 transcriptional activity, but not through the inhibition of p53's mitochondrial pro-apoptotic function. Remarkably, the p53-mediated increase in caspase-6 expression and activation is exacerbated in cells and tissues of both neuronal and peripheral origin expressing mutant huntingtin (Htt). These findings suggest that the presence of the mutant Htt protein enhances p53 activity and lowers the apoptotic threshold, which activates caspase-6. Furthermore, these results suggest that this pathway is activated both within and outside the CNS in HD and may contribute to both loss of CNS neurons and muscle atrophy.
Asunto(s)
Caspasa 6/metabolismo , Músculo Esquelético/metabolismo , Proteínas del Tejido Nervioso/genética , Proteína p53 Supresora de Tumor/metabolismo , Animales , Benzotiazoles/farmacología , Caspasa 6/genética , Células Cultivadas , Modelos Animales de Enfermedad , Femenino , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Humanos , Proteína Huntingtina , Enfermedad de Huntington/genética , Enfermedad de Huntington/metabolismo , Enfermedad de Huntington/patología , Lamina Tipo A/metabolismo , Masculino , Ratones , Ratones Transgénicos , Músculo Esquelético/patología , Mutación , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Neuronas/patología , Tolueno/análogos & derivados , Tolueno/farmacología , Proteína p53 Supresora de Tumor/genéticaRESUMEN
For the first time, ultrasonic emulsification was studied for cinnamon essential oil (CEO) Pickering emulsion, stabilized by cellulose nanocrystal (CNC) from rice straw. Sonication proved to be an effective method for emulsifying CEO, creating small emulsion droplets around 700 nm in size, with an even dispersion characterized through a low polydispersity index. The biomass-derived CNC exhibits high encapsulation efficiency (> 95 %) with varying CEO concentration (5-25 vol%), creating droplets with negative surface charge with limited aggregation of emulsions. Optimization through the Box Behnken design using response surface methodology provides a model for the interaction and effects of variables towards the formulation. Optimal condition was concluded to be at 11.47 vol% CEO, 0.84 wt/vol% CNC and at 6 sonication cycles. The optimized Pickering emulsions retain the antimicrobial properties of CEO, with a large inhibition zone and low MIC value of around 0.048 vol% CEO. DPPH inhibition assay indicates that the emulsification process enhances the antioxidation properties of cinnamon essential oil, expressed through a lower IC50 of 0.90 vol% CEO, in comparison to pure essential oil at 1.33 vol% CEO. Overall, this research proposes a novel approach towards using nanocellulose as carriers for essential oil with potential in a large variety of applications.
Asunto(s)
Celulosa , Cinnamomum zeylanicum , Emulsiones , Nanopartículas , Aceites Volátiles , Oryza , Aceites Volátiles/química , Aceites Volátiles/farmacología , Nanopartículas/química , Celulosa/química , Emulsiones/química , Cinnamomum zeylanicum/química , Oryza/química , Antioxidantes/química , Antioxidantes/farmacología , Tamaño de la PartículaRESUMEN
Few T cells infiltrate into primary brain tumors, fundamentally hampering the effectiveness of immunotherapy. We hypothesized that Toxoplasma gondii, a microorganism that naturally elicits a Th1 response in the brain, can promote T cell infiltration into brain tumors despite their immune suppressive microenvironment. Using a mouse genetic model for medulloblastoma, we found that T. gondii infection induced the infiltration of activatable T cells into the tumor mass and led to myeloid cell reprogramming toward a T cell-supportive state, without causing severe health issues in mice. The study provides a concrete foundation for future studies to take advantage of the immune modulatory capacity of T. gondii to facilitate brain tumor immunotherapy.
Asunto(s)
Neoplasias Encefálicas , Toxoplasmosis , Animales , Ratones , Neoplasias Encefálicas/inmunología , Neoplasias Encefálicas/patología , Toxoplasmosis/inmunología , Toxoplasma/inmunología , Meduloblastoma/inmunología , Meduloblastoma/patología , Ratones Endogámicos C57BL , Linfocitos T/inmunología , Linfocitos Infiltrantes de Tumor/inmunología , Ratones Transgénicos , FemeninoRESUMEN
Coronary artery disease requiring surgical revascularization is prevalent in United States Veterans. We aimed to investigate preoperative predictors of 30-day mortality following coronary artery bypass grafting (CABG) in the Veteran population. The Veterans Affairs Surgical Quality Improvement (VASQIP) national database was queried for isolated CABG cases between 2008 and 2018. The primary outcome was 30-day mortality. A multivariable logistic regression was performed to assess for independent predictors of the primary outcome. A P-value of <0.05 was considered statistically significant. A total of 32,711 patients were included. The 30-day mortality rate was 1.37%. Multivariable analysis identified the following predictors of 30-day mortality: African-American race (OR 1.46, 95% CI 1.09-1.96); homelessness (OR 6.49, 95% CI 3.39-12.45); female sex (OR 2.15, 95% CI 1.08-4.30); preoperative myocardial infarction within 7 days (OR 1.49, 95% CI 1.06-2.10) or more than 7 days before CABG (OR 1.34, 95% CI 1.04-1.72); partially/fully dependent functional status (OR 1.44, 95% CI 1.07-1.93); chronic obstructive pulmonary disease (OR 1.54, 95% CI 1.24-1.92); mild (OR 1.48, 95% CI 1.04-2.11) and severe aortic stenosis (OR 2.06, 95% CI 1.37-3.09); moderate (OR 1.88, 95% CI 1.31-2.72), or severe (OR 2.99, 95% CI 1.71-5.22) mitral regurgitation; cardiomegaly (OR 1.73, 95% CI 1.35-2.22); NYHA Class III/IV heart failure (OR 2.05, 95% CI 1.10-3.83); and urgent/emergent operation (OR 1.42, 95% CI 1.08-1.87). The 30-day mortality rate in US Veterans undergoing isolated CABG between 2008 and 2018 was 1.37%. In addition to established clinical factors, African-American race and homelessness were independent demographic predictors of 30-day mortality.
RESUMEN
BACKGROUND: The efficacy of Helicobacter pylori (H. pylori) eradication therapy for children is currently low, and antibiotic resistance is a significant cause of treatment failure. The purpose of this study was to evaluate the H. pylori eradication efficacy of therapy based on antimicrobial susceptibility in pediatric patients with gastritis and peptic ulcer. METHODS: This study was conducted at Can Tho Children's Hospital and Can Tho University of Medicine and Pharmacy Hospital between March 2019 and April 2022. We performed an upper gastrointestinal endoscopy, cultured H. pylori from biopsies of gastric mucosa, determined antibiotic sensitivities to H. pylori by the E-test method, and treated eradication based on the antibiotic susceptibilities of bacteria. After at least 4 weeks of eradication therapy, we assessed the effectiveness of treatment with a breath test. RESULTS: Among 237 children recruited in this study, 48.9% were boys and 51.1% were girls, and the mean age was 10.03 ± 2.53 years. We determined that 80.6% of H. pylori were resistant to clarithromycin, as well as amoxicillin, metronidazole, levofloxacin, and tetracycline, at 71.7%, 49.4%, 45.1%, and 11.4%, respectively. The overall eradication rate of H. pylori was 83.1% (172/207). Among therapies tailored to antimicrobial susceptibility, the bismuth quadruple regimen achieved the greatest success, but the efficacy of triple therapy with esomeprazole + AMX + CLR/MTZ was low. CONCLUSIONS: Tailored eradication therapy was highly successful in our study but did not achieve over 90%. We recommend that in countries with a high prevalence of antibiotic resistance in H. pylori strains, particularly where the amoxicillin-resistance rate of H. pylori is high, therapy tailored to antimicrobial susceptibility should be used as first-line therapy, and bismuth and tetracycline should be added to enhance the eradication efficacy in children.
RESUMEN
Rationale: Cancer stem cells (CSCs) are known to cause tumor recurrence and drug resistance. The heat shock protein (HSP) system plays a major role in preserving expression and function of numerous oncoproteins, including those involved in the CSC activities. We explored novel anticancer drugs, especially those targeting HSP components required for the functional role of CSCs. Methods: Investigation of the role of the HSP system in CSCs and screening of a natural product chemical library were performed by utilizing cancer cell lines, primary cultures of patient-derived xenografts (PDXs), and their putative CSC subpopulations (i.e., those grown under sphere-forming conditions, stably transfected with reporter vectors carrying NANOG or POUSF1 promoters, or carrying high ALDH activity) in vitro and PDX and KrasG12D/+-driven tumor models in vivo. Regulation of the HSP system was investigated by immunoprecipitation, drug affinity responsive target stability assay, binding experiments using ATP-agarose beads and biotinylated drug, and docking analysis. Results: The HSP system was activated in CSCs via transcriptional upregulation of the HSP system components, especially HSP70. Evodiamine (Evo) was identified to induce apoptosis in both CSC and bulk non-CSC populations in human lung, colon, and breast cancer cells and their sublines with chemoresistance. Evo administration decreased the multiplicity, volume, and load of lung tumors in KrasG12D/+ transgenic mice and the growth of cancer cell line- and PDX-derived tumors without detectable toxicity. Mechanistically, Evo disrupted the HSP system by binding the N-terminal ATP-binding pocket of HSP70 and causing its ubiquitin-mediated degradation. Conclusions: Our findings illustrate HSP70 as a potential target for eliminating CSCs and Evo as an effective HSP70-targeting anticancer drug eradicating both CSCs and non-CSCs with a minimal toxicity.
Asunto(s)
Antineoplásicos/farmacología , Proteínas HSP70 de Choque Térmico/metabolismo , Neoplasias/tratamiento farmacológico , Células Madre Neoplásicas/efectos de los fármacos , Células Madre Neoplásicas/metabolismo , Quinazolinas/farmacología , Células A549 , Animales , Apoptosis/efectos de los fármacos , Línea Celular , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Células HCT116 , Humanos , Ratones , Ratones Endogámicos NOD , Ratones SCID , Ratones Transgénicos , Neoplasias/metabolismo , Transducción de Señal/efectos de los fármacos , Transcripción Genética/efectos de los fármacos , Regulación hacia Arriba/efectos de los fármacosRESUMEN
Although quantitative surveillance data for immature stages of Aedes aegypti are often used to prioritize containers or specific types of containers for control, the relationship between immature and emergent adult populations under field conditions is largely unknown. We examined the relationships between abundance of III/IV instars and pupae, and emerging adult population for a series of water storage containers in southern Vietnam. A large proportion of III/IV instars failed to progress to adulthood, and the relationships between III/IV instars and adults were poor. Collected IV instars appeared to be nutritionally deprived, although their size and nutrient levels were not reliable indicators of emergence success. Conversely, pupal abundance was a good indicator of emerging adult populations, especially over the ensuing 48-h period. Although there were clear advantages of pupal surveillance over surveillance of III/IV instars for the estimation of adult mosquito productivity, there were practical limitations associated with the enumeration of pupae, and their comparatively low densities may preclude the identification of potentially productive containers.
Asunto(s)
Aedes/fisiología , Ecosistema , Aedes/crecimiento & desarrollo , Animales , Monitoreo del Ambiente , Artículos Domésticos , Larva/crecimiento & desarrollo , Control de Mosquitos , Densidad de Población , Vietnam , AguaRESUMEN
As solids pyrolyse during combustion, they lose chemical and structural integrity by gradually degrading into residual char and forming defects such as voids, fissures and cracks. The material degradation process, which is coupled to the crack formation process, is described using a theoretical model and is numerically simulated using the finite-element method for a generic, charring, rubber-like material. In this model, a slab of material is subjected to an external, localized heat flux and, as the material degrades, cracks form when the local principal stress exceeds a defined cracking threshold. The magnitude of the cracking threshold σ c is systematically varied in order to examine its influences on crack initiation, evolution, distribution and behaviour over time. When σ c exceeds the maximum principal stress for the entire process, σ m , then no cracks are generated. We quantify how the average crack spacing, total crack length and crack initiation time depend upon the ratio σ c /σ m . Two characteristic domains of crack formation behaviour are identified from the crack initiation behaviour. Correlations are produced for the crack length evolution and final crack length values as functions of σ c /σ m . Crack intersection patterns and behaviour are described and characterized.
RESUMEN
Glutathione (GSH) degradation plays an essential role in GSH homeostasis, which regulates cell survival, especially in cancer cells. Among human GSH degradation enzymes, the ChaC2 enzyme acts on GSH to form 5-l-oxoproline and Cys-Gly specifically in the cytosol. Here, we report the crystal structures of ChaC2 in two different conformations and compare the structural features with other known γ-glutamylcyclotransferase enzymes. The unique flexible loop of ChaC2 seems to function as a gate to achieve specificity for GSH binding and regulate the constant GSH degradation rate. Structural and biochemical analyses of ChaC2 revealed that Glu74 and Glu83 play crucial roles in directing the conformation of the enzyme and in modulating the enzyme activity. Based on a docking study of GSH to ChaC2 and binding assays, we propose a substrate-binding mode and catalytic mechanism. We also found that overexpression of ChaC2, but not mutants that inhibit activity of ChaC2, significantly promoted breast cancer cell proliferation, suggesting that the GSH degradation by ChaC2 affects the growth of breast cancer cells. Our structural and functional analyses of ChaC2 will contribute to the development of inhibitors for the ChaC family, which could effectively regulate the progression of GSH degradation-related cancers.
Asunto(s)
Glutatión/metabolismo , gamma-Glutamilciclotransferasa/química , gamma-Glutamilciclotransferasa/metabolismo , Dominio Catalítico , Proliferación Celular , Células HEK293 , Humanos , Células MCF-7 , Simulación del Acoplamiento Molecular , Mutación , Multimerización de Proteína , Estructura Cuaternaria de Proteína , Alineación de Secuencia , gamma-Glutamilciclotransferasa/genéticaRESUMEN
Aberrant activation of caspase-6 (C6) in the absence of other hallmarks of apoptosis has been demonstrated in cells and tissues from patients with Huntington disease (HD) and animal models. C6 activity correlates with disease progression in patients with HD and the cleavage of mutant huntingtin (mHTT) protein is thought to strongly contribute to disease pathogenesis. Here we show that the mHTT1-586 fragment generated by C6 cleavage interacts with the zymogen form of the enzyme, stabilizing a conformation that contains an active site and is prone to full activation. This shift toward enhanced activity can be prevented by a small-molecule inhibitor that blocks the interaction between C6 and mHTT1-586. Molecular docking studies suggest that the inhibitor binds an allosteric site in the C6 zymogen. The interaction of mHTT1-586 with C6 may therefore promote a self-reinforcing, feedforward cycle of C6 zymogen activation and mHTT cleavage driving HD pathogenesis.
Asunto(s)
Caspasa 6/metabolismo , Proteína Huntingtina/genética , Enfermedad de Huntington/metabolismo , Regulación Alostérica/genética , Animales , Apoptosis , Células COS , Caspasa 6/fisiología , Chlorocebus aethiops , Proteína Huntingtina/metabolismo , Enfermedad de Huntington/patología , Simulación del Acoplamiento Molecular/métodos , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Proteínas Nucleares/metabolismoRESUMEN
Huntington disease (HD) is caused by the expression of mutant huntingtin (mHTT) bearing a polyglutamine expansion. In HD, mHTT accumulation is accompanied by a dysfunction in basal autophagy, which manifests as specific defects in cargo loading during selective autophagy. Here we show that the expression of mHTT resistant to proteolysis at the caspase cleavage site D586 (C6R mHTT) increases autophagy, which may be due to its increased binding to the autophagy adapter p62. This is accompanied by faster degradation of C6R mHTT in vitro and a lack of mHTT accumulation the C6R mouse model with age. These findings may explain the previously observed neuroprotective properties of C6R mHTT. As the C6R mutation cannot be easily translated into a therapeutic approach, we show that a scheduled feeding paradigm is sufficient to lower mHTT levels in YAC128 mice expressing cleavable mHTT. This is consistent with a previous model, where the presence of cleavable mHTT impairs basal autophagy, while fasting-induced autophagy remains functional. In HD, mHTT clearance and autophagy may become increasingly impaired as a function of age and disease stage, because of gradually increased activity of mHTT-processing enzymes. Our findings imply that mHTT clearance could be enhanced by a regulated dietary schedule that promotes autophagy.
Asunto(s)
Autofagia/fisiología , Ayuno/fisiología , Proteína Huntingtina/metabolismo , Enfermedad de Huntington/metabolismo , Enfermedad de Huntington/terapia , Proteolisis , Envejecimiento/metabolismo , Animales , Células COS , Células Cultivadas , Corteza Cerebral/metabolismo , Corteza Cerebral/patología , Chlorocebus aethiops , Modelos Animales de Enfermedad , Femenino , Humanos , Proteína Huntingtina/genética , Hígado/metabolismo , Hígado/patología , Masculino , Ratones Transgénicos , Mutación , Neuronas/metabolismo , Neuronas/patología , Distribución AleatoriaRESUMEN
Species of the Culex vishnui subgroup, Cx. fuscocephala and Cx. gelidus, which are known Japanese encephalitis (JE) vectors, are distributed in rice agroecosystems in Asian countries. Hence, although ecological studies of rice agroecosystems in northern Vietnam are necessary, very few integrated studies of breeding habitats of mosquitoes, including JE vectors, have been conducted. We carried out a field study and investigated the mosquito fauna in six rice production areas in northern Vietnam during the rainy and dry seasons of 2009. Mosquitoes and potential mosquito predators were collected from aquatic habitats by using larval dippers. We collected 1780 Culex individuals (including 254 Cx. tritaeniorhynchus; 113 Cx. vishnui, 58 Cx. vishnui complex, consisting of Cx. vishnui and Cx. pseudovishnui; 12 Cx. gelidus; 1 Cx. bitaeniorhynchus; and 1 Cx. fuscocephala), 148 Anopheles individuals (including 5 An. vagus), 1 Mansonia annulifera, and 1 Mimomyia chamberlaini during the rainy season. During the dry season, we collected 176 Culex individuals (including 33 Cx. vishnui, 24 Cx. tritaeniorhynchus, 8 Cx. vishnui complex, and 1 Cx. gelidus) and 186 Anopheles individuals (including 9 An. tessellatus, 2 An. kochi, and 2 An. barbumbrosus). We found mosquitoes in all aquatic habitats, namely, rice fields, ditches, ponds, wetlands, irrigation canals, and rice nurseries, and Cx. tritaeniorhynchus and Cx. vishnui complex were found in all the above six areas. Heteroptera such as Micronecta, Veliidae, and Pleidae were abundant and widely distributed in both the seasons. The abundance of mosquito larvae was higher in the rice fields, ditches, and ponds during the rainy season than during the dry season. Cx. tritaeniorhynchus, Cx. vishnui complex, Cx. fuscocephala, and Cx. gelidus were abundant in rice agroecosystems (rice fields, ditches, ponds, and wetlands) in northern Vietnam, and their abundance was high during the rainy season. These findings deepen our understanding of mosquito ecology and strengthen mosquito control strategies to be applied in rice ecosystems Vietnam in the future.