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DNA G-quadruplexes in human telomeres and gene promoters are being extensively studied for their role in controlling the growth of cancer cells. G-quadruplexes have been unambiguously shown to exist both in vitro and in vivo, including in the guanine (G)-rich DNA genes encoding pre-ribosomal RNA (pre-rRNA), which is transcribed in the cell's nucleolus. Recent studies strongly suggest that these DNA sequences ("rDNA"), and the transcribed rRNA, are a potential anticancer target through the inhibition of RNA polymerase I (Pol I) in ribosome biogenesis, but the structures of ribosomal G-quadruplexes at atomic resolution are unknown and very little biophysical characterization has been performed on them to date. In the present study, circular dichroism (CD) spectroscopy is used to show that two putative rDNA G-quadruplex sequences, NUC 19P and NUC 23P and their counterpart rRNAs, predominantly adopt parallel topologies, reminiscent of the analogous telomeric quadruplex structures. Based on this information, we modeled parallel topology atomistic structures of the putative ribosomal G-quadruplexes. We then validated and refined the modeled ribosomal G-quadruplex structures using all-atom molecular dynamics (MD) simulations with the CHARMM36 force field in the presence and absence of stabilizing K+. Motivated by preliminary MD simulations of the telomeric parallel G-quadruplex (TEL 24P) in which the K+ ion is expelled, we used updated CHARMM36 force field K+ parameters that were optimized, targeting the data from quantum mechanical calculations and the polarizable Drude model force field. In subsequent MD simulations with optimized CHARMM36 parameters, the K+ ions are predominantly in the G-quadruplex channel and the rDNA G-quadruplexes have more well-defined, predominantly parallel-topology structures as compared to rRNA. In addition, NUC 19P is more structured than NUC 23P, which contains extended loops. Results from this study set the structural foundation for understanding G-quadruplex functions and the design of novel chemotherapeutics against these nucleolar targets and can be readily extended to other DNA and RNA G-quadruplexes.
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G-Cuádruplex , ADN Ribosómico/genética , Humanos , Simulación de Dinámica Molecular , ARN Ribosómico/genética , TelómeroRESUMEN
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Connections between the gut and brain monitor the intestinal tissue and its microbial and dietary content1, regulating both physiological intestinal functions such as nutrient absorption and motility2,3, and brain-wired feeding behaviour2. It is therefore plausible that circuits exist to detect gut microorganisms and relay this information to areas of the central nervous system that, in turn, regulate gut physiology4. Here we characterize the influence of the microbiota on enteric-associated neurons by combining gnotobiotic mouse models with transcriptomics, circuit-tracing methods and functional manipulations. We find that the gut microbiome modulates gut-extrinsic sympathetic neurons: microbiota depletion leads to increased expression of the neuronal transcription factor cFos, and colonization of germ-free mice with bacteria that produce short-chain fatty acids suppresses cFos expression in the gut sympathetic ganglia. Chemogenetic manipulations, translational profiling and anterograde tracing identify a subset of distal intestine-projecting vagal neurons that are positioned to have an afferent role in microbiota-mediated modulation of gut sympathetic neurons. Retrograde polysynaptic neuronal tracing from the intestinal wall identifies brainstem sensory nuclei that are activated during microbial depletion, as well as efferent sympathetic premotor glutamatergic neurons that regulate gastrointestinal transit. These results reveal microbiota-dependent control of gut-extrinsic sympathetic activation through a gut-brain circuit.
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Microbioma Gastrointestinal/fisiología , Intestinos/inervación , Neuronas/fisiología , Sistema Nervioso Simpático/citología , Sistema Nervioso Simpático/fisiología , Animales , Disbiosis/fisiopatología , Femenino , Ganglios Simpáticos/citología , Ganglios Simpáticos/fisiología , Motilidad Gastrointestinal , Vida Libre de Gérmenes , Intestinos/microbiología , Masculino , Ratones , Ratones Endogámicos C57BL , Modelos Animales , Vías Nerviosas/fisiología , Proteínas Proto-Oncogénicas c-fos/metabolismo , TranscriptomaRESUMEN
Studies of the relationship between the gastrointestinal microbiota and outcomes in allogeneic hematopoietic stem cell transplantation (allo-HCT) have thus far largely focused on early complications, predominantly infection and acute graft-versus-host disease (GVHD). We examined the potential relationship of the microbiome with chronic GVHD (cGVHD) by analyzing stool and plasma samples collected late after allo-HCT using a case-control study design. We found lower circulating concentrations of the microbe-derived short-chain fatty acids (SCFAs) propionate and butyrate in day 100 plasma samples from patients who developed cGVHD, compared with those who remained free of this complication, in the initial case-control cohort of transplant patients and in a further cross-sectional cohort from an independent transplant center. An additional cross-sectional patient cohort from a third transplant center was analyzed; however, serum (rather than plasma) was available, and the differences in SCFAs observed in the plasma samples were not recapitulated. In sum, our findings from the primary case-control cohort and 1 of 2 cross-sectional cohorts explored suggest that the gastrointestinal microbiome may exert immunomodulatory effects in allo-HCT patients at least in part due to control of systemic concentrations of microbe-derived SCFAs.
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Butiratos/sangre , Microbioma Gastrointestinal , Enfermedad Injerto contra Huésped/microbiología , Propionatos/sangre , Adulto , Aloinjertos , Bacterias/aislamiento & purificación , Bacterias/metabolismo , Estudios de Casos y Controles , Enfermedad Crónica , Disbiosis/etiología , Disbiosis/microbiología , Heces/microbiología , Enfermedad Injerto contra Huésped/sangre , Enfermedad Injerto contra Huésped/etiología , Trasplante de Células Madre Hematopoyéticas/efectos adversos , Humanos , Metaboloma , RibotipificaciónRESUMEN
BACKGROUND: Tranexamic acid (TXA) is an antifibrinolytic drug. Topical administration of TXA during total knee arthroplasty (TKA) is favored for certain patients because of concerns about thrombotic complications, despite a lack of supporting literature. We compared local and systemic levels of thrombogenic markers, interleukin (IL)-6, and TXA between patients who received intravenous (IV) TXA and those who received topical TXA. METHODS: Seventy-six patients scheduled for TKA were enrolled in this randomized double-blinded study. The IV group received 1.0 g of IV TXA before tourniquet inflation and again 3 hours later; a topical placebo was administered 5 minutes before final tourniquet release. The topical group received an IV placebo before tourniquet inflation and again 3 hours later; 3.0 g of TXA was administered topically 5 minutes before final tourniquet release. Peripheral and wound blood samples were collected to measure levels of plasmin-anti-plasmin (PAP, a measure of fibrinolysis), prothrombin fragment 1.2 (PF1.2, a marker of thrombin generation), IL-6, and TXA. RESULTS: At 1 hour after tourniquet release, systemic PAP levels were comparable between the IV group (after a single dose of IV TXA) and the topical group. At 4 hours after tourniquet release, the IV group had lower systemic PAP levels than the topical group (mean and standard deviation, 1,117.8 ± 478.9 µg/L versus 1,280.7 ± 646.5 µg/L; p = 0.049), indicative of higher antifibrinolytic activity after the second dose. There was no difference in PF1.2 levels between groups, indicating that there was no increase in thrombin generation. The IV group had higher TXA levels at all time points (p < 0.001). Four hours after tourniquet release, wound blood IL-6 and TXA levels were higher than systemic levels in both groups (p < 0.001). Therapeutic systemic TXA levels (mean, 7.2 ± 7.4 mg/L) were noted in the topical group. Calculated blood loss and the length of the hospital stay were lower in the IV group (p = 0.026 and p = 0.025). CONCLUSIONS: Given that therapeutic levels were reached with topical TXA and the lack of a major difference in the mechanism of action, coagulation, and fibrinolytic profile between topical TXA and a single dose of IV TXA, it may be a simpler protocol for institutions to adopt the use of a single dose of IV TXA when safety is a concern. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.
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Antifibrinolíticos/administración & dosificación , Artroplastia de Reemplazo de Rodilla/métodos , Interleucina-6/sangre , Osteoartritis de la Rodilla/cirugía , Ácido Tranexámico/administración & dosificación , Trombosis de la Vena/prevención & control , Administración Tópica , Anciano , Método Doble Ciego , Femenino , Estudios de Seguimiento , Humanos , Infusiones Intravenosas , Masculino , Persona de Mediana Edad , Osteoartritis de la Rodilla/diagnóstico por imagen , Seguridad del Paciente/estadística & datos numéricos , Complicaciones Posoperatorias/prevención & control , Medición de Riesgo , Ácido Tranexámico/sangre , Resultado del TratamientoRESUMEN
Despite evidence linking the human microbiome to health and disease, how the microbiota affects human physiology remains largely unknown. Microbiota-encoded metabolites are expected to play an integral role in human health. Therefore, assigning function to these metabolites is critical to understanding these complex interactions and developing microbiota-inspired therapies. Here, we use large-scale functional screening of molecules produced by individual members of a simplified human microbiota to identify bacterial metabolites that agonize G-protein-coupled receptors (GPCRs). Multiple metabolites, including phenylpropanoic acid, cadaverine, 9-10-methylenehexadecanoic acid, and 12-methyltetradecanoic acid, were found to interact with GPCRs associated with diverse functions within the nervous and immune systems, among others. Collectively, these metabolite-receptor pairs indicate that diverse aspects of human health are potentially modulated by structurally simple metabolites arising from primary bacterial metabolism.
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Bacterias/metabolismo , Interacciones Microbiota-Huesped/inmunología , Interacciones Microbiota-Huesped/fisiología , Microbiota/inmunología , Microbiota/fisiología , Receptores Acoplados a Proteínas G/agonistas , Proteínas Angiogénicas/agonistas , Animales , Cadaverina/metabolismo , Cadaverina/farmacología , Ácidos Grasos/metabolismo , Ácidos Grasos/farmacología , Fermentación , Vida Libre de Gérmenes , Agonistas de los Receptores Histamínicos , Humanos , Sistema Inmunológico , Ligandos , Ratones , Ratones Endogámicos C57BL , Modelos Animales , Propionatos/metabolismo , Propionatos/farmacología , Receptores Acoplados a Proteínas G/metabolismo , Receptores Histamínicos/efectos de los fármacos , Receptores de Neurotransmisores/agonistasRESUMEN
Klebsiella pneumoniae, Escherichia coli, and other members of the Enterobacteriaceae family are common human pathogens that have acquired broad antibiotic resistance, rendering infection by some strains virtually untreatable. Enterobacteriaceae are intestinal residents, but generally represent <1% of the adult colonic microbiota. Antibiotic-mediated destruction of the microbiota enables Enterobacteriaceae to expand to high densities in the colon, markedly increasing the risk of bloodstream invasion, sepsis, and death. Here, we demonstrate that an antibiotic-naive microbiota suppresses growth of antibiotic-resistant clinical isolates of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis by acidifying the proximal colon and triggering short chain fatty acid (SCFA)-mediated intracellular acidification. High concentrations of SCFAs and the acidic environment counter the competitive edge that O2 and NO3 respiration confer upon Enterobacteriaceae during expansion. Reestablishment of a microbiota that produces SCFAs enhances clearance of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis from the intestinal lumen and represents a potential therapeutic approach to enhance clearance of antibiotic-resistant pathogens.
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Colon/metabolismo , Farmacorresistencia Bacteriana , Infecciones por Enterobacteriaceae/metabolismo , Enterobacteriaceae/crecimiento & desarrollo , Microbioma Gastrointestinal , Animales , Colon/microbiología , Colon/patología , Infecciones por Enterobacteriaceae/microbiología , Infecciones por Enterobacteriaceae/patología , Ácidos Grasos/metabolismo , Femenino , Humanos , Concentración de Iones de Hidrógeno , Masculino , RatonesRESUMEN
Respiratory viral infections are frequent in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT) and can potentially progress to lower respiratory tract infection (LRTI). The intestinal microbiota contributes to resistance against viral and bacterial pathogens in the lung. However, whether intestinal microbiota composition and associated changes in microbe-derived metabolites contribute to the risk of LRTI following upper respiratory tract viral infection remains unexplored in the setting of allo-HCT. Fecal samples from 360 allo-HCT patients were collected at the time of stem cell engraftment and subjected to deep, 16S ribosomal RNA gene sequencing to determine microbiota composition, and short-chain fatty acid levels were determined in a nested subset of fecal samples. The development of respiratory viral infections and LRTI was determined for 180 days following allo-HCT. Clinical and microbiota risk factors for LRTI were subsequently evaluated using survival analysis. Respiratory viral infection occurred in 149 (41.4%) patients. Of those, 47 (31.5%) developed LRTI. Patients with higher abundances of butyrate-producing bacteria were fivefold less likely to develop viral LRTI, independent of other factors (adjusted hazard ratio = 0.22, 95% confidence interval 0.04-0.69). Higher representation of butyrate-producing bacteria in the fecal microbiota is associated with increased resistance against respiratory viral infection with LRTI in allo-HCT patients.
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Bacterias/metabolismo , Butiratos/metabolismo , Microbioma Gastrointestinal , Trasplante de Células Madre Hematopoyéticas/efectos adversos , Infecciones del Sistema Respiratorio/etiología , Infecciones del Sistema Respiratorio/microbiología , Virosis/etiología , Virosis/microbiología , Adulto , Heces/microbiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Factores Protectores , Infecciones del Sistema Respiratorio/metabolismo , Trasplante Homólogo/efectos adversos , Virosis/metabolismoRESUMEN
This corrects the article DOI: 10.1038/nature23874.
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Bone marrow transplantation (BMT) offers curative potential for patients with high-risk hematologic malignancies, but the post-transplantation period is characterized by profound immunodeficiency. Recent studies indicate that the intestinal microbiota not only regulates mucosal immunity, but can also contribute to systemic immunity and hematopoiesis. Using antibiotic-mediated microbiota depletion in a syngeneic BMT mouse model, here we describe a role for the intestinal flora in hematopoietic recovery after BMT. Depletion of the intestinal microbiota resulted in impaired recovery of lymphocyte and neutrophil counts, while recovery of the hematopoietic stem and progenitor compartments and the erythroid lineage were largely unaffected. Depletion of the intestinal microbiota also reduced dietary energy uptake and visceral fat stores. Caloric supplementation through sucrose in the drinking water improved post-BMT hematopoietic recovery in mice with a depleted intestinal flora. Taken together, we show that the intestinal microbiota contribute to post-BMT hematopoietic reconstitution in mice through improved dietary energy uptake.
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Trasplante de Médula Ósea , Microbioma Gastrointestinal , Apoyo Nutricional , Animales , Médula Ósea/fisiología , Hematopoyesis , Ratones , Modelos Animales , Resultado del TratamientoRESUMEN
Commensal bacteria are believed to have important roles in human health. The mechanisms by which they affect mammalian physiology remain poorly understood, but bacterial metabolites are likely to be key components of host interactions. Here we use bioinformatics and synthetic biology to mine the human microbiota for N-acyl amides that interact with G-protein-coupled receptors (GPCRs). We found that N-acyl amide synthase genes are enriched in gastrointestinal bacteria and the lipids that they encode interact with GPCRs that regulate gastrointestinal tract physiology. Mouse and cell-based models demonstrate that commensal GPR119 agonists regulate metabolic hormones and glucose homeostasis as efficiently as human ligands, although future studies are needed to define their potential physiological role in humans. Our results suggest that chemical mimicry of eukaryotic signalling molecules may be common among commensal bacteria and that manipulation of microbiota genes encoding metabolites that elicit host cellular responses represents a possible small-molecule therapeutic modality (microbiome-biosynthetic gene therapy).
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Amidas/metabolismo , Bacterias/metabolismo , Mimetismo Biológico , Tracto Gastrointestinal/microbiología , Receptores Acoplados a Proteínas G/metabolismo , Transducción de Señal , Simbiosis , Amidas/química , Animales , Bacterias/enzimología , Bacterias/genética , Glucemia/metabolismo , Femenino , Microbioma Gastrointestinal/genética , Microbioma Gastrointestinal/fisiología , Tracto Gastrointestinal/metabolismo , Células HEK293 , Homeostasis , Humanos , Ligandos , Masculino , RatonesRESUMEN
The prevalence of mutant isocitrate dehydrogenase 1 (IDH1) brain tumors has generated significant efforts to understand the role of the mutated enzyme product d-2-hydroxyglutarate (D2HG), an oncometabolite, in tumorigenesis, as well as means to eliminate it. Glymphatic clearance was proposed as a pathway that could be manipulated to accelerate D2HG clearance and dictated the study design that consisted of two cohorts of mice bearing U87/mutant IDH1 intracerebral tumors that underwent two microdialysis - providing D2HG interstitial fluid concentrations - sampling periods of awake and asleep (activate glymphatic clearance) in a crossover manner. Glymphatic clearance was found not to have a significant effect on D2HG brain tumor interstitial fluid concentrations that were 126.9 ± 74.8 µM awake and 117.6 ± 98.6 µM asleep. These concentrations, although low relative to total brain tumor concentrations of 6.8 ± 3.6 mM, were considered sufficient to be transported by interstitial fluid and taken up into normal cells to cause deleterious effects. A model of D2HG CNS distribution supported this contention and was further supported by in vitro studies that showed D2HG could interfere with immune cell function. The study provides insight into the compartmental distribution of D2HG in the brain, wherein the interstitial fluid serves as a dynamic pathway for D2HG to enter normal cells and contribute to tumorigenesis.
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BACKGROUND/AIM: The alkylating agent, temozolomide (TMZ), is considered the standard-of-care for high-grade astrocytomas -known as glioblastoma multiforme (GBM)- an aggressive type of tumor with poor prognosis. The therapeutic benefit of TMZ is attributed to formation of DNA adducts involving the methylation of purine bases in DNA. We investigated the effects of TMZ on arginine and lysine amino acids, histone H3 peptides and histone H3 proteins. MATERIALS AND METHODS: Chemical modification of amino acids, histone H3 peptide and protein by TMZ was performed in phosphate buffer at physiological pH. The reaction products were examined by mass spectrometry and western blot analysis. RESULTS: Our results showed that TMZ following conversion to a methylating cation, can methylate histone H3 peptide and histone H3 protein, suggesting that TMZ exerts its anticancer activity not only through its interaction with DNA, but also through alterations of protein post-translational modifications. CONCLUSION: The possibility that TMZ can methylate histones involved with epigenetic regulation of protein indicates a potentially unique mechanism of action. The study will contribute to the understanding the anticancer activity of TMZ in order to develop novel targeted molecular strategies to advance the cancer treatment.
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Antineoplásicos Alquilantes/farmacología , Metilación de ADN/efectos de los fármacos , Dacarbazina/análogos & derivados , Histonas/metabolismo , Animales , Arginina/metabolismo , Dacarbazina/farmacología , Humanos , Lisina/metabolismo , Espectrometría de Masas , Metilación/efectos de los fármacos , Temozolomida , XenopusRESUMEN
Thiourea-modified 3-chloro-4-fluoroanilino-quinazoline derivatives have been studied as potential receptor-targeted carrier ligands in linear gold(I) complexes. The molecules mimic the epidermal growth factor receptor (EGFR) tyrosine kinase-targeted inhibitor gefitinib. Thiourea groups were either directly attached to quinazoline-C6 (compounds 4, 5, and 7) or linked to this position via a flexible ethylamino chain (compound 9). Compound 7 acts as a thiourea-S/quinazoline-N1 mixed-donor ligand, giving the unexpected dinuclear complex [{Au(µ-7-S,N)}2]X2 (X = Cl(-), SCN(-)) (12a,b) (X-ray crystallography, electrospray mass spectrometry). Derivative 9 forms a stable linear complex, [Au(PEt3)(9-S)](NO3) (13). The biological activity of the carrier ligands and corresponding gold(I) complexes was studied in NCI-H460 and NCI-H1975 lung cancer cells. Compound 9 partially overcomes resistance to gefitinib in NCI-H1975, a lung cancer cell line characterized by a L858R/T790M mutation in EGFR (IC50 values of 1.7 and 30 µM, respectively). The corresponding gold complex (13) maintains activity in the low-micromolar concentration range similar to the metal-free carrier. Compound 9 and the corresponding [Au(PEt3)] complex, 13, inhibit EGFR kinase-mediated phosphorylation with sub-micromolar IC50 values similar to those observed for gefitinib under the same assay conditions. Potential mechanisms of action and reactions in biological media of this new type of hybrid agent, as well as shortcomings of the current design are discussed.
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Complejos de Coordinación/química , Oro/química , Inhibidores de Proteínas Quinasas/síntesis química , Tiourea/química , Afatinib , Línea Celular , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Complejos de Coordinación/síntesis química , Complejos de Coordinación/farmacología , Relación Dosis-Respuesta a Droga , Gefitinib , Humanos , Concentración 50 Inhibidora , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/farmacología , Quinazolinas/síntesis química , Quinazolinas/farmacología , Tiourea/síntesis química , Tiourea/farmacologíaRESUMEN
Platinum-acridine hybrid agents show low-nanomolar potency in chemoresistant non-small cell lung cancer (NSCLC), but high systemic toxicity in vivo. To reduce the promiscuous genotoxicity of these agents and improve their pharmacological properties, a modular build-click-screen approach was used to evaluate a small library of twenty hybrid agents containing truncated and extended chromophores of varying basicities. Selected derivatives were resynthesized and tested in five NSCLC cell lines representing large cell, squamous cell, and adenocarcinomas. 7-Aminobenz[c]acridine was identified as a promising scaffold in a hybrid agent (P1-B1) that maintained submicromolar activity in several of the DNA-repair proficient and p53-mutant cancer models, while showing improved tolerability in mice by 32-fold compared to the parent platinum-acridine (P1-A1). The distribution and DNA/RNA adduct levels produced by the acridine- and benz[c]acridine-based analogues in NCI-H460 cells (confocal microscopy, ICP-MS), and their ability to bind G-quadruplex forming DNA sequences (CD spectroscopy, HR-ESMS) were studied. P1-B1 emerges as a less genotoxic, more tolerable, and potentially more target-selective hybrid agent than P1-A1.
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Acridinas/química , Antineoplásicos/química , Diseño de Fármacos , Sustancias Intercalantes/química , Compuestos Organoplatinos/química , Acridinas/farmacología , Animales , Antineoplásicos/farmacología , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Células Escamosas/tratamiento farmacológico , Carcinoma de Células Escamosas/genética , Línea Celular Tumoral , Aductos de ADN/efectos de los fármacos , Ensayos de Selección de Medicamentos Antitumorales , G-Cuádruplex/efectos de los fármacos , Humanos , Sustancias Intercalantes/farmacología , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/genética , Ratones , Compuestos Organoplatinos/farmacología , Relación Estructura-ActividadRESUMEN
Using a versatile synthetic approach, a new class of potential ester prodrugs of highly potent, but systemically too toxic, platinum-acridine anticancer agents was generated. The new hybrids contain a hydroxyl group, which has been masked with a cleavable lipophilic acyl moiety. Both butanoic (butyric) and bulkier 2-propanepentanoic (valproic) esters were introduced. The goals of this design were to improve the drug-like properties (e.g., logD) and to reduce the systemic toxicity of the pharmacophore. Two distinct pathways by which the target compounds undergo effective ester hydrolysis, the proposed activating step, have been confirmed: platinum-assisted, self-immolative ester cleavage in a low-chloride environment (LC-ESMS, NMR spectroscopy) and enzymatic cleavage by human carboxylesterase-2 (hCES-2) (LC-ESMS). The valproic acid ester derivatives are the first example of a metal-containing agent cleavable by the prodrug-converting enzyme. They show excellent chemical stability and reduced systemic toxicity. Preliminary results from screening in lung adenocarcinoma cell lines (A549, NCI-H1435) suggest that the mechanism of the valproic esters may involve intracellular deesterification.
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Antineoplásicos/química , Platino (Metal)/química , Profármacos/química , Adenocarcinoma/tratamiento farmacológico , Adenocarcinoma/metabolismo , Adenocarcinoma del Pulmón , Antineoplásicos/metabolismo , Antineoplásicos/farmacología , Línea Celular Tumoral , Diseño de Fármacos , Humanos , Hidrólisis , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/metabolismo , Platino (Metal)/metabolismo , Platino (Metal)/farmacología , Profármacos/metabolismo , Profármacos/farmacología , Ácido Valproico/química , Ácido Valproico/metabolismo , Ácido Valproico/farmacologíaRESUMEN
The transient nucleolus plays a central role in the up-regulated synthesis of ribosomal RNA (rRNA) to sustain ribosome biogenesis, a hallmark of aberrant cell growth. This function, in conjunction with its unique pathohistological features in malignant cells and its ability to mediate apoptosis, renders this sub-nuclear structure a potential target for chemotherapeutic agents. In this Minireview, structurally and functionally diverse small molecules are discussed that have been reported to either interact with the nucleolus directly or perturb its function indirectly by acting on its dynamic components. These molecules include all major classes of nucleic-acid-targeted agents, antimetabolites, kinase inhibitors, anti-inflammatory drugs, natural product antibiotics, oligopeptides, as well as nanoparticles. Together, these molecules are invaluable probes of structure and function of the nucleolus. They also provide a unique opportunity to develop novel strategies for more selective and therefore better-tolerated chemotherapeutic intervention. In this regard, inhibition of RNA polymerase-I-mediated rRNA synthesis appears to be a promising mechanism for killing cancer cells. The recent development of molecules targeted at G-quadruplex-forming rRNA gene sequences, which are currently undergoing clinical trials, seems to attest to the success of this approach.
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Nucléolo Celular/metabolismo , Antineoplásicos/química , Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Nucléolo Celular/química , ADN/química , ADN/metabolismo , Humanos , Neoplasias/metabolismo , Neoplasias/patología , ARN Ribosómico/genética , ARN Ribosómico/metabolismo , Transcripción Genética/efectos de los fármacosRESUMEN
A combination of biophysical, biochemical, and computational techniques was used to delineate mechanistic differences between the platinum-acridine hybrid agent [PtCl(en)(L)](NO(3))(2) (complex 1, en = ethane-1,2-diamine, L = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea) and a considerably more potent second-generation analogue containing L' = N-[2-(acridin-9-ylamino)ethyl]-N-methylpropionamidine (complex 2). Calculations at the density functional theory level provide a rationale for the binding preference of both complexes for guanine-N7 and the relatively high level of adenine adducts observed for compound 1. A significant rate enhancement is observed for binding of the amidine-based complex 2 with DNA compared with the thiourea-based prototype 1. Studies conducted with chemical probes and on the bending and unwinding of model duplex DNA suggest that adducts of complex 2 perturb B-form DNA more severely than complex 1, however, without denaturing the double strand and significantly less than cisplatin. Circular and linear dichroism spectroscopies and viscosity measurements suggest that subtle differences exist between the intercalation modes and adduct geometries of the two complexes. The adducts formed by complex 2 most efficiently inhibit transcription of the damaged DNA by RNA polymerase II. Not only do complexes 1 and 2 cause less distortion to DNA than cisplatin, they also do not compromise the thermodynamic stability of the modified duplex. This leads to a decreased or negligible affinity of HMG domain proteins for the adducts formed by either Pt-acridine complex. In a DNA repair synthesis assay the lesions formed by complex 2 were repaired less efficiently than those formed by complex 1. These significant differences in DNA adduct formation, structure, and recognition between the two acridine complexes and cisplatin help to elucidate why compound 2 is highly active in cisplatin-resistant, repair proficient cancer cell lines.