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1.
Annu Rev Cell Dev Biol ; 39: 277-305, 2023 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-37540844

RESUMO

Cells must tightly regulate their gene expression programs and yet rapidly respond to acute biochemical and biophysical cues within their environment. This information is transmitted to the nucleus through various signaling cascades, culminating in the activation or repression of target genes. Transcription factors (TFs) are key mediators of these signals, binding to specific regulatory elements within chromatin. While live-cell imaging has conclusively proven that TF-chromatin interactions are highly dynamic, how such transient interactions can have long-term impacts on developmental trajectories and disease progression is still largely unclear. In this review, we summarize our current understanding of the dynamic nature of TF functions, starting with a historical overview of early live-cell experiments. We highlight key factors that govern TF dynamics and how TF dynamics, in turn, affect downstream transcriptional bursting. Finally, we conclude with open challenges and emerging technologies that will further our understanding of transcriptional regulation.


Assuntos
Regulação da Expressão Gênica , Fatores de Transcrição , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Cromatina/genética , Sequências Reguladoras de Ácido Nucleico
2.
Immunity ; 55(8): 1402-1413.e4, 2022 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-35882235

RESUMO

The differentiation of innate lymphoid cells (ILCs) from hematopoietic stem cells needs to go through several multipotent progenitor stages. However, it remains unclear whether the fates of multipotent progenitors are predefined by epigenetic states. Here, we report the identification of distinct accessible chromatin regions in all lymphoid progenitors (ALPs), EILPs, and ILC precursors (ILCPs). Single-cell MNase-seq analyses revealed that EILPs contained distinct subpopulations epigenetically primed toward either dendritic cell lineages or ILC lineages. We found that TCF-1 and GATA3 co-bound to the lineage-defining sites for ILCs (LDS-Is), whereas PU.1 binding was enriched in the LDSs for alternative dendritic cells (LDS-As). TCF-1 and GATA3 were indispensable for the epigenetic priming of LDSs at the EILP stage. Our results suggest that the multipotency of progenitor cells is defined by the existence of a heterogeneous population of cells epigenetically primed for distinct downstream lineages, which are regulated by key transcription factors.


Assuntos
Imunidade Inata , Linfócitos , Diferenciação Celular , Linhagem da Célula , Epigênese Genética , Células-Tronco Hematopoéticas
3.
Cell ; 165(3): 593-605, 2016 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-27062924

RESUMO

The estrogen receptor (ER), glucocorticoid receptor (GR), and forkhead box protein 1 (FoxA1) are significant factors in breast cancer progression. FoxA1 has been implicated in establishing ER-binding patterns though its unique ability to serve as a pioneer factor. However, the molecular interplay between ER, GR, and FoxA1 requires further investigation. Here we show that ER and GR both have the ability to alter the genomic distribution of the FoxA1 pioneer factor. Single-molecule tracking experiments in live cells reveal a highly dynamic interaction of FoxA1 with chromatin in vivo. Furthermore, the FoxA1 factor is not associated with detectable footprints at its binding sites throughout the genome. These findings support a model wherein interactions between transcription factors and pioneer factors are highly dynamic. Moreover, at a subset of genomic sites, the role of pioneer can be reversed, with the steroid receptors serving to enhance binding of FoxA1.


Assuntos
Fator 3-alfa Nuclear de Hepatócito/metabolismo , Cromatina/metabolismo , Desoxirribonucleases/metabolismo , Humanos , Células MCF-7 , Receptores de Estrogênio/genética , Receptores de Glucocorticoides/genética , Fatores de Transcrição/metabolismo
4.
Mol Cell ; 81(7): 1484-1498.e6, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-33561389

RESUMO

Transcription factors (TFs) regulate gene expression by binding to specific consensus motifs within the local chromatin context. The mechanisms by which TFs navigate the nuclear environment as they search for binding sites remain unclear. Here, we used single-molecule tracking and machine-learning-based classification to directly measure the nuclear mobility of the glucocorticoid receptor (GR) in live cells. We revealed two distinct and dynamic low-mobility populations. One accounts for specific binding to chromatin, while the other represents a confinement state that requires an intrinsically disordered region (IDR), implicated in liquid-liquid condensate subdomains. Further analysis showed that the dwell times of both subpopulations follow a power-law distribution, consistent with a broad distribution of affinities on the GR cistrome and interactome. Together, our data link IDRs with a confinement state that is functionally distinct from specific chromatin binding and modulates the transcriptional output by increasing the local concentration of TFs at specific sites.


Assuntos
Proteínas Intrinsicamente Desordenadas/química , Receptores de Glucocorticoides/química , Fatores de Transcrição/química , Animais , Feminino , Proteínas Intrinsicamente Desordenadas/genética , Proteínas Intrinsicamente Desordenadas/metabolismo , Camundongos , Ratos , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
5.
Cell ; 155(7): 1507-20, 2013 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-24360274

RESUMO

A key finding of the ENCODE project is that the enhancer landscape of mammalian cells undergoes marked alterations during ontogeny. However, the nature and extent of these changes are unclear. As part of the NIH Mouse Regulome Project, we here combined DNaseI hypersensitivity, ChIP-seq, and ChIA-PET technologies to map the promoter-enhancer interactomes of pluripotent ES cells and differentiated B lymphocytes. We confirm that enhancer usage varies widely across tissues. Unexpectedly, we find that this feature extends to broadly transcribed genes, including Myc and Pim1 cell-cycle regulators, which associate with an entirely different set of enhancers in ES and B cells. By means of high-resolution CpG methylomes, genome editing, and digital footprinting, we show that these enhancers recruit lineage-determining factors. Furthermore, we demonstrate that the turning on and off of enhancers during development correlates with promoter activity. We propose that organisms rely on a dynamic enhancer landscape to control basic cellular functions in a tissue-specific manner.


Assuntos
Linfócitos B/metabolismo , Células-Tronco Embrionárias/metabolismo , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica no Desenvolvimento , Regiões Promotoras Genéticas , Regulon , Animais , Linhagem da Célula , Células Cultivadas , Ilhas de CpG , Metilação de DNA , Técnicas Genéticas , Camundongos , Especificidade de Órgãos , RNA Longo não Codificante/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica
6.
Immunity ; 49(3): 427-437.e4, 2018 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-30217409

RESUMO

How cytotoxic T lymphocytes (CTLs) sense T cell receptor (TCR) signaling in order to specialize an area of plasma membrane for granule secretion is not understood. Here, we demonstrate that immune synapse formation led to rapid localized changes in the phosphoinositide composition of the plasma membrane, both reducing phosphoinositide-4-phosphate (PI(4)P), PI(4,5)P2, and PI(3,4,5)P3 and increasing diacylglycerol (DAG) and PI(3,4)P2 within the first 2 min of synapse formation. These changes reduced negative charge across the synapse, triggering the release of electrostatically bound PIP5 kinases that are required to replenish PI(4,5)P2. As PI(4,5)P2 decreased, actin was depleted from the membrane, allowing secretion. Forced localization of PIP5Kß across the synapse prevented actin depletion, blocking both centrosome docking and secretion. Thus, PIP5Ks act as molecular sensors of TCR activation, controlling actin recruitment across the synapse, ensuring exquisite co-ordination between TCR signaling and CTL secretion.


Assuntos
Actinas/metabolismo , Membrana Celular/metabolismo , Grânulos Citoplasmáticos/metabolismo , Sinapses Imunológicas/metabolismo , Fosfatidilinositóis/metabolismo , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Linfócitos T Citotóxicos/imunologia , Animais , Degranulação Celular , Linhagem Celular , Citotoxicidade Imunológica , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais
7.
Mol Cell ; 75(6): 1161-1177.e11, 2019 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-31421980

RESUMO

Genes are transcribed in a discontinuous pattern referred to as RNA bursting, but the mechanisms regulating this process are unclear. Although many physiological signals, including glucocorticoid hormones, are pulsatile, the effects of transient stimulation on bursting are unknown. Here we characterize RNA synthesis from single-copy glucocorticoid receptor (GR)-regulated transcription sites (TSs) under pulsed (ultradian) and constant hormone stimulation. In contrast to constant stimulation, pulsed stimulation induces restricted bursting centered around the hormonal pulse. Moreover, we demonstrate that transcription factor (TF) nuclear mobility determines burst duration, whereas its bound fraction determines burst frequency. Using 3D tracking of TSs, we directly correlate TF binding and RNA synthesis at a specific promoter. Finally, we uncover a striking co-bursting pattern between TSs located at proximal and distal positions in the nucleus. Together, our data reveal a dynamic interplay between TF mobility and RNA bursting that is responsive to stimuli strength, type, modality, and duration.


Assuntos
Glucocorticoides/farmacologia , Regiões Promotoras Genéticas , RNA/biossíntese , Receptores de Glucocorticoides/metabolismo , Sítio de Iniciação de Transcrição , Transcrição Gênica/efeitos dos fármacos , Animais , Camundongos , RNA/genética
8.
Immunity ; 47(2): 298-309.e5, 2017 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-28801231

RESUMO

Despite the widespread use of glucocorticoids (GCs), their anti-inflammatory effects are not understood mechanistically. Numerous investigations have examined the effects of glucocorticoid receptor (GR) activation prior to inflammatory challenges. However, clinical situations are emulated by a GC intervention initiated in the midst of rampant inflammatory responses. To characterize the effects of a late GC treatment, we profiled macrophage transcriptional and chromatinscapes with Dexamethasone (Dex) treatment before or after stimulation by lipopolysaccharide (LPS). The late activation of GR had a similar gene-expression profile as from GR pre-activation, while ameliorating the disruption of metabolic genes. Chromatin occupancy of GR was not predictive of Dex-regulated gene expression, contradicting the "trans-repression by tethering" model. Rather, GR activation resulted in genome-wide blockade of NF-κB interaction with chromatin and directly induced inhibitors of NF-κB and AP-1. Our investigation using GC treatments with clinically relevant timing highlights mechanisms underlying GR actions for modulating the "inflamed epigenome."


Assuntos
Anti-Inflamatórios/farmacologia , Dexametasona/farmacologia , Glucocorticoides/farmacologia , Inflamação/tratamento farmacológico , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Receptores de Glucocorticoides/metabolismo , Animais , Anti-Inflamatórios/uso terapêutico , Células Cultivadas , Cromatina/metabolismo , Montagem e Desmontagem da Cromatina , Dexametasona/uso terapêutico , Glucocorticoides/uso terapêutico , Humanos , Inflamação/imunologia , Lipopolissacarídeos/imunologia , Ativação de Macrófagos , Camundongos , Camundongos Endogâmicos C57BL , NF-kappa B/genética , NF-kappa B/metabolismo , Fator de Transcrição AP-1/genética , Fator de Transcrição AP-1/metabolismo , Transcriptoma
9.
Cell ; 146(4): 544-54, 2011 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-21835447

RESUMO

The glucocorticoid receptor (GR), like other eukaryotic transcription factors, regulates gene expression by interacting with chromatinized DNA response elements. Photobleaching experiments in living cells indicate that receptors transiently interact with DNA on the time scale of seconds and predict that the response elements may be sparsely occupied on average. Here, we show that the binding of one receptor at the glucocorticoid response element (GRE) does not reduce the steady-state binding of another receptor variant to the same GRE. Mathematical simulations reproduce this noncompetitive state using short GR/GRE residency times and relatively long times between DNA binding events. At many genomic sites where GR binding causes increased chromatin accessibility, concurrent steady-state binding levels for the variant receptor are actually increased, a phenomenon termed assisted loading. Temporally sparse transcription factor-DNA interactions induce local chromatin reorganization, resulting in transient access for binding of secondary regulatory factors.


Assuntos
Montagem e Desmontagem da Cromatina , Receptores de Glucocorticoides/metabolismo , Elementos de Resposta , Trifosfato de Adenosina/metabolismo , Animais , Linhagem Celular Tumoral , Vírus do Tumor Mamário do Camundongo , Camundongos , Modelos Biológicos , Método de Monte Carlo , Nucleossomos/metabolismo , Receptores de Estrogênio/metabolismo , Sequências Reguladoras de Ácido Nucleico , Fatores de Transcrição/metabolismo
10.
Exp Cell Res ; 439(1): 114075, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38710404

RESUMO

Leber's hereditary optic neuropathy (LHON) is a visual impairment associated with mutations of mitochondrial genes encoding elements of the electron transport chain. While much is known about the genetics of LHON, the cellular pathophysiology leading to retinal ganglion cell degeneration and subsequent vision loss is poorly understood. The impacts of the G11778A mutation of LHON on bioenergetics, redox balance and cell proliferation were examined in patient-derived fibroblasts. Replacement of glucose with galactose in the culture media reveals a deficit in the proliferation of G11778A fibroblasts, imparts a reduction in ATP biosynthesis, and a reduction in capacity to accommodate exogenous oxidative stress. While steady-state ROS levels were unaffected by the LHON mutation, cell survival was diminished in response to exogenous H2O2.


Assuntos
DNA Mitocondrial , Fibroblastos , Galactose , Mutação , Atrofia Óptica Hereditária de Leber , Humanos , Fibroblastos/metabolismo , Fibroblastos/efeitos dos fármacos , Atrofia Óptica Hereditária de Leber/genética , Atrofia Óptica Hereditária de Leber/metabolismo , Atrofia Óptica Hereditária de Leber/patologia , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Galactose/metabolismo , Mutação/genética , Proliferação de Células/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/genética , Células Cultivadas , Glucose/metabolismo , Glucose/farmacologia
11.
J Neurosci ; 43(11): 1976-1986, 2023 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-36788030

RESUMO

Recent evidence suggests that, in the absence of any task, spontaneous brain activity patterns and connectivity in the visual and motor cortex code for natural stimuli and actions, respectively. These "resting-state" activity patterns may underlie the maintenance and consolidation (replay) of information states coding for ecological stimuli and behaviors. In this study, we examine whether replay patterns occur in resting-state activity in association cortex grouped into high-order cognitive networks not directly processing sensory inputs or motor outputs. Fifteen participants (7 females) performed four hand movements during an fMRI study. Three movements were ecological. The fourth movement as control was less ecological. Before and after the task scans, we acquired resting-state fMRI scans. The analysis examined whether multivertex task activation patterns for the four movements computed at the cortical surface in different brain networks resembled spontaneous activity patterns measured at rest. For each movement, we computed a vector of r values indicating the strength of the similarity between the mean task activation pattern and frame-by-frame resting-state patterns. We computed a cumulative distribution function of r 2 values and used the 90th percentile cutoff value for comparison. In the dorsal attention network, resting-state patterns were more likely to match task patterns for the ecological movements than the control movement. In contrast, rest-task pattern correlation was more likely for less ecological movement in the ventral attention network. These findings show that spontaneous activity patterns in human attention networks code for hand movements.SIGNIFICANCE STATEMENT fMRI indirectly measures neural activity noninvasively. Resting-state (spontaneous) fMRI signals measured in the absence of any task resemble signals evoked by task performance both in topography and inter-regional (functional) connectivity. However, the function of spontaneous brain activity is unknown. We recently showed that spatial activity patterns evoked by visual and motor tasks in visual and motor cortex, respectively, occur at rest in the absence of any stimulus or response. Here we show that activity patterns related to hand movements replay at rest in frontoparietal regions of the human attention system. These findings show that spontaneous activity in the human cortex may mediate the maintenance and consolidation of information states coding for ecological stimuli and behaviors.


Assuntos
Mapeamento Encefálico , Encéfalo , Feminino , Humanos , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Mãos , Movimento , Análise e Desempenho de Tarefas , Imageamento por Ressonância Magnética
12.
Lancet ; 401(10382): 1079-1090, 2023 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-36868261

RESUMO

BACKGROUND: Hereditary angioedema is a rare and potentially life-threatening genetic disease that is associated with kallikrein-kinin system dysregulation. Garadacimab (CSL312), a novel, fully-human monoclonal antibody that inhibits activated factor XII (FXIIa), is being studied for the prevention of hereditary angioedema attacks. The aim of this study was to evaluate the efficacy and safety of once-monthly subcutaneous administrations of garadacimab as prophylaxis for hereditary angioedema. METHODS: VANGUARD was a pivotal, multicentre, randomised, double-blind, placebo-controlled, phase 3 trial that recruited patients (aged ≥12 years) with type I or type II hereditary angioedema across seven countries (Canada, Germany, Hungary, Israel, Japan, the Netherlands, and the USA). Eligible patients were randomly assigned (3:2) to receive garadacimab or placebo for 6 months (182 days) by an interactive response technology (IRT) system. Randomisation was stratified by age (≤17 years vs >17 years) and baseline attack rate (1 to <3 attacks per month vs ≥3 attacks per month) for the adult group. The randomisation list and code were kept by the IRT provider during the study, with no access by site staff and funding representatives. All patients and investigational site staff, and representatives from the funder (or their delegates) with direct interaction with the study sites or patients, were masked to treatment assignment in a double-blind fashion. Randomly assigned patients received a 400-mg loading dose of subcutaneous garadacimab as two 200-mg injections or volume-matched placebo on day 1 of the treatment period, followed by five additional self-administered (or caregiver-administered) monthly doses of 200-mg subcutaneous garadacimab or volume-matched placebo. The primary endpoint was the investigator-assessed time-normalised number of hereditary angioedema attacks (number of hereditary angioedema attacks per month) during the 6-month treatment period (day 1 to day 182). Safety was evaluated in patients who received at least one dose of garadacimab or placebo. The study is registered with the EU Clinical Trials Register, 2020-000570-25 and ClinicalTrials.gov, NCT04656418. FINDINGS: Between Jan 27, 2021, and June 7, 2022, we screened 80 patients, 76 of whom were eligible to enter the run-in period of the study. Of 65 eligible patients with type I or type II hereditary angioedema, 39 were randomly assigned to garadacimab and 26 to placebo. One patient was randomly assigned in error and did not enter the treatment period (no dose of study drug received), resulting in 39 patients assigned to garadacimab and 25 patients assigned to placebo being included. 38 (59%) of 64 participants were female and 26 (41%) were male. 55 (86%) of 64 participants were White, six (9%) were Asian (Japanese), one (2%) was Black or African American, one (2%) was Native Hawaiian or Other Pacific Islander, and one (2%) was listed as other. During the 6-month treatment period (day 1 to day 182), the mean number of investigator-confirmed hereditary angioedema attacks per month was significantly lower in the garadacimab group (0·27, 95% CI 0·05 to 0·49) than in the placebo group (2·01, 1·44 to 2·57; p<0·0001), corresponding to a percentage difference in means of -87% (95% CI -96 to -58; p<0·0001). The median number of hereditary angioedema attacks per month was 0 (IQR 0·00-0·31) for garadacimab and 1·35 (1·00-3·20) for placebo. The most common treatment-emergent adverse events were upper-respiratory tract infections, nasopharyngitis, and headaches. FXIIa inhibition was not associated with an increased risk of bleeding or thromboembolic events. INTERPRETATION: Monthly garadacimab administration significantly reduced hereditary angioedema attacks in patients aged 12 years and older compared with placebo and had a favourable safety profile. Our results support the use of garadacimab as a potential prophylactic therapy for the treatment of hereditary angioedema in adolescents and adults. FUNDING: CSL Behring.


Assuntos
Angioedemas Hereditários , Adulto , Adolescente , Humanos , Masculino , Feminino , Angioedemas Hereditários/tratamento farmacológico , Angioedemas Hereditários/prevenção & controle , Resultado do Tratamento , Anticorpos Monoclonais , Método Duplo-Cego
13.
Biochem Biophys Res Commun ; 721: 150119, 2024 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-38768545

RESUMO

Mitochondrial dynamics were examined in human dermal fibroblasts biopsied from a confirmed Leber's Hereditary Optic Neuropathy (LHON) patient with a homoplasmic G11778A mutation of the mitochondrial genome. Expression of the G11778A mutation did not impart any discernible difference in mitochondrial network morphology using widefield fluorescence microscopy. However, at the ultrastructural level, cells expressing this mutation exhibited an impairment of mitochondrial morphological plasticity when forced to utilize oxidative phosphorylation (OXPHOS) by transition to glucose-free, galactose-containing media. LHON fibroblasts also displayed a transient increase in mitophagy upon transition to galactose media. These results provide new insights into the consequences of the G11778A mutation of LHON and the pathological mechanisms underlying this disease.


Assuntos
Fibroblastos , Mitocôndrias , Mitofagia , Mutação , Atrofia Óptica Hereditária de Leber , Humanos , Mitofagia/genética , Atrofia Óptica Hereditária de Leber/genética , Atrofia Óptica Hereditária de Leber/patologia , Atrofia Óptica Hereditária de Leber/metabolismo , Mitocôndrias/metabolismo , Mitocôndrias/genética , Mitocôndrias/patologia , Fibroblastos/metabolismo , Fibroblastos/patologia , Fosforilação Oxidativa , Células Cultivadas
14.
Trends Immunol ; 42(11): 994-1008, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34649777

RESUMO

How T lymphocytes tune their responses to different strengths of stimulation is a fundamental question in immunology. Recent work using new optogenetic, single-cell genomic, and live-imaging approaches has revealed that stimulation strength controls the rate of individual cell responses within a population. Moreover, these responses have been found to use shared molecular programs, regardless of stimulation strength. However, additional data indicate that stimulation duration or cytokine feedback can impact later gene expression phenotypes of activated cells. In-depth molecular studies have suggested mechanisms by which stimulation strength might modulate the probability of T cell activation. This emerging model allows activating T cells to achieve a wide range of population responses through probabilistic control within individual cells.


Assuntos
Genoma , Ativação Linfocitária , Citocinas/metabolismo , Humanos , Linfócitos T
15.
Mol Pharm ; 21(5): 2406-2414, 2024 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-38639477

RESUMO

The dissolution testing method described in the United States Pharmacopeia (USP) Chapter ⟨711⟩ is widely used for assessing the release of active pharmaceutical ingredients from solid dosage forms. However, extensive use over the years has revealed certain issues, including high experimental intervariability observed in specific formulations and the settling of particles in the dead zone of the vessel. To address these concerns and gain a comprehensive understanding of the hydrodynamic conditions within the USP 2 apparatus, computational fluid dynamic simulations have been employed in this study. The base design employed in this study is the 900 mL USP 2 vessel along with a paddle stirrer at a 50 rpm rotational speed. Additionally, alternative stirrer designs, including the hydrofoil, pitched blade, and Rushton impeller, are investigated. A comparison is also made between a flat-bottom tank and the USP round-bottom vessel of the same volume and diameter. Furthermore, this work examines the impact of various parameters, such as clearance distance (distance between the bottom of the impeller and bottom of the vessel), number of impeller blades, impeller diameter, and impeller attachment angle. The volume-average shear rate (Stv), fluid velocity (Utv), and energy dissipation rates (ϵtv) represent the key properties evaluated in this study. Comparing the USP2 design and systems with the same stirrer but flat-bottom vessel reveals more homogeneous mixing compared to the USP2 design. Analyzing fluid flow streamlines in different designs demonstrates that hydrofoil stirrers generate more suspension or upward movement of fluid compared to paddle stirrers. Therefore, when impellers are of a similar size, hydrofoil designs generate higher fluid velocities in the coning area. Furthermore, the angle of blade attachment to the hub influences the fluid velocity in the coning area in a way that the 60° angle design generates more suspension than the 45° angle design. The findings indicate that the paddle stirrer design leads to a heterogeneous shear rate and velocity distributions within the vessel compared with the other designs, suggesting suboptimal performance. These insights provide valuable guidance for the development of improved in vitro dissolution testing devices, emphasizing the importance of optimized design considerations to minimize hydrodynamic variability, enhance dissolution characterization, and reduce variability in dissolution test results. Ultimately, such advancements hold potential for improving in vitro-in vivo correlations in drug development.


Assuntos
Hidrodinâmica , Solubilidade , Liberação Controlada de Fármacos , Química Farmacêutica/métodos , Farmacopeias como Assunto , Simulação por Computador , Desenho de Equipamento , Composição de Medicamentos/métodos , Estados Unidos
16.
Mol Pharm ; 21(1): 201-215, 2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38115627

RESUMO

The authors present a steady-state-, particle-size-, and dose-dependent dissolution-permeation model that describes particle dissolution within the concentration boundary layer (CBL) adjacent to a semipermeable surface. It is critical to understand how particle size and dose affect the behavior of dissolving particles in the presence of a CBL adjacent to a semipermeable surface both in vivo and in vitro. Control of particle size is ubiquitous in the pharmaceutical industry; however, traditional pharmaceutical assumptions of particle dissolution typically ignore particle dissolution within the length scale of the CBL. The CBL does not physically prevent particles from traveling to the semipermeable surface (mucus, epithelial barrier, synthetic membrane, etc.), and particle dissolution can occur within the CBL thickness (δC) if the particle is sufficiently small (∼dparticle ≤ δC). The total flux (the time rate transport of molecules across the membrane surface per unit area) was chosen as a surrogate parameter for measuring the additional mass generated by particles dissolving within the donor CBL. Mass transfer experiments aimed to measure the total flux of drug using an ultrathin large-area membrane diffusion cell described by Sinko et al. with a silicone-based membrane ( Mol. Pharmaceutics 2020, 17, (7) 2319-2328, DOI: 10.1021/acs.molpharmaceut.0c00040). Suspensions of ibuprofen, a model weak-acid drug, with three different particle-size distributions with average particle diameters of 6.6, 37.4, and 240 µm at multiple doses corresponding to a range of suspension concentrations with dimensionless dose numbers of 2.94, 14.7, 147, and 588 were used to test the model. Experimentally measured total flux across the semipermeable membrane/CBL region agreed with the predictions from the proposed model, and at a range of relatively low suspension concentrations, dependent on the average particle size, there was a measurable effect on the flux due to the difference in δC that formed at the membrane surface. Additionally, the dose-dependent total flux across the membrane was up to 10% higher than the flux predicted by the standard Higuchi-Hiestand dissolution model where the effects of confinement were ignored as described by Wang et al. ( Mol. Pharmaceutics 2012, 9 (5), 1052-1066, DOI: 10.1021/mp2002818).


Assuntos
Tamanho da Partícula , Solubilidade , Difusão
17.
Pharm Res ; 41(5): 937-945, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38698196

RESUMO

BACKGROUND: Phosphate buffer is often used as a replacement for the physiological bicarbonate buffer in pharmaceutical dissolution testing, although there are some discrepancies in their properties making it complicated to extrapolate dissolution results in phosphate to the in vivo situation. This study aims to characterize these discrepancies regarding solubility and dissolution behavior of ionizable compounds. METHODS: The dissolution of an ibuprofen powder with a known particle size distribution was simulated in silico and verified experimentally in vitro at two different doses and in two different buffers (5 mM pH 6.8 bicarbonate and phosphate). RESULTS: The results showed that there is a solubility vs. dissolution mismatch in the two buffers. This was accurately predicted by the in-house simulations based on the reversible non-equilibrium (RNE) and the Mooney models. CONCLUSIONS: The results can be explained by the existence of a relatively large gap between the initial surface pH of the drug and the bulk pH at saturation in bicarbonate but not in phosphate, which is caused by not all the interfacial reactions reaching equilibrium in bicarbonate prior to bulk saturation. This means that slurry pH measurements, while providing surface pH estimates for buffers like phosphate, are poor indicators of surface pH in the intestinal bicarbonate buffer. In addition, it showcases the importance of accounting for the H2CO3-CO2 interconversion kinetics to achieve good predictions of intestinal drug dissolution.


Assuntos
Bicarbonatos , Liberação Controlada de Fármacos , Ibuprofeno , Fosfatos , Solubilidade , Soluções Tampão , Bicarbonatos/química , Concentração de Íons de Hidrogênio , Ibuprofeno/química , Fosfatos/química , Tamanho da Partícula , Simulação por Computador , Pós/química , Cinética , Química Farmacêutica/métodos
18.
Nucleic Acids Res ; 50(22): 13063-13082, 2022 12 09.
Artigo em Inglês | MEDLINE | ID: mdl-36464162

RESUMO

The glucocorticoid receptor (GR) is a ubiquitously expressed transcription factor that controls metabolic and homeostatic processes essential for life. Although numerous crystal structures of the GR ligand-binding domain (GR-LBD) have been reported, the functional oligomeric state of the full-length receptor, which is essential for its transcriptional activity, remains disputed. Here we present five new crystal structures of agonist-bound GR-LBD, along with a thorough analysis of previous structural work. We identify four distinct homodimerization interfaces on the GR-LBD surface, which can associate into 20 topologically different homodimers. Biologically relevant homodimers were identified by studying a battery of GR point mutants including crosslinking assays in solution, quantitative fluorescence microscopy in living cells, and transcriptomic analyses. Our results highlight the relevance of non-canonical dimerization modes for GR, especially of contacts made by loop L1-3 residues such as Tyr545. Our work illustrates the unique flexibility of GR's LBD and suggests different dimeric conformations within cells. In addition, we unveil pathophysiologically relevant quaternary assemblies of the receptor with important implications for glucocorticoid action and drug design.


Assuntos
Glucocorticoides , Receptores de Glucocorticoides , Receptores de Glucocorticoides/metabolismo , Ligantes , Ligação Proteica , Dimerização
19.
PLoS Genet ; 17(8): e1009737, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34375333

RESUMO

Ultradian glucocorticoid rhythms are highly conserved across mammalian species, however, their functional significance is not yet fully understood. Here we demonstrate that pulsatile corticosterone replacement in adrenalectomised rats induces a dynamic pattern of glucocorticoid receptor (GR) binding at ~3,000 genomic sites in liver at the pulse peak, subsequently not found during the pulse nadir. In contrast, constant corticosterone replacement induced prolonged binding at the majority of these sites. Additionally, each pattern further induced markedly different transcriptional responses. During pulsatile treatment, intragenic occupancy by active RNA polymerase II exhibited pulsatile dynamics with transient changes in enrichment, either decreased or increased depending on the gene, which mostly returned to baseline during the inter-pulse interval. In contrast, constant corticosterone exposure induced prolonged effects on RNA polymerase II occupancy at the majority of gene targets, thus acting as a sustained regulatory signal for both transactivation and repression of glucocorticoid target genes. The nett effect of these differences were consequently seen in the liver transcriptome as RNA-seq analysis indicated that despite the same overall amount of corticosterone infused, twice the number of transcripts were regulated by constant corticosterone infusion, when compared to pulsatile. Target genes that were found to be differentially regulated in a pattern-dependent manner were enriched in functional pathways including carbohydrate, cholesterol, glucose and fat metabolism as well as inflammation, suggesting a functional role for dysregulated glucocorticoid rhythms in the development of metabolic dysfunction.


Assuntos
Corticosterona/farmacologia , Fígado/patologia , Receptores de Glucocorticoides/metabolismo , Animais , Expressão Gênica/genética , Perfilação da Expressão Gênica/métodos , Regulação da Expressão Gênica/genética , Glucocorticoides/metabolismo , Fígado/metabolismo , Masculino , Periodicidade , Transporte Proteico/genética , RNA Polimerase II/genética , RNA Mensageiro/genética , Ratos , Ratos Sprague-Dawley , Receptores de Glucocorticoides/fisiologia , Ativação Transcricional/genética , Transcriptoma/genética
20.
J Pers Assess ; : 1-13, 2024 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-38271468

RESUMO

This article introduces a measure of self-condemnatory internal dialogue as an element of the relationship with the self: The Automatic Self-Recrimination Scale (ASRS). Using the construct validation approach to test construction, we describe the initial development of items and report on findings from a clinical and nonclinical sample showing the ASRS is best understood as a multidimensional measure of self-critical internal dialogue composed of one higher-order factor and four lower-order facets: Not Mattering, Self as Failure, Undeserving Self, and Loathsomeness. The overall scale and four subscales demonstrated acceptable internal consistency and test-retest reliability. Moreover, there was evidence of good convergent and incremental validity of the ASRS subscales with measures of perfectionism, self-criticism, and dysfunctional attitudes. Overall, the ASRS appears to be a reliable and valid measure of an automatic self-recriminatory internal dialogue.

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