The tamoxifen cation reacts to give indene products

2000 ◽  
Vol 78 (9) ◽  
pp. 1186-1193
Author(s):  
Cristina Sanchez ◽  
Robert A McClelland
Keyword(s):  
Intramolecular Cyclization ◽  
Phenyl Ring ◽  
Irreversible Process ◽  
Total Yield ◽  
Cellular Systems ◽  
Acid Solutions ◽  
Allylic Cation ◽  
Super Acid ◽  
Acidic Conditions

The tamoxifen carbocation (Ph(Ar)C=CPh-CH+-CH3, Ar = 4-Me2NCH2CH2OC6H4) is generated from acetate and sulfate precursors by SN1 ionization in water. The cation exists in (E) and (Z) forms which equilibrate before reaction. The major products are the α-hydroxytamoxifens Ph(Ar)C=CPh-CHOH-CH3, both (E) 64% and (Z) 29%, with the ratio independent of the configuration of the starting ester. Two minor products with a total yield of 7% account for the rest of the products. These have been characterized as indenes derived from intramolecular cyclization, a 4.5% yield of the indene derived from cyclization into the Ar ring with 2.5% due to cyclization into the phenyl ring. Experiments in acid solutions (0.01-0.1 M HCl) starting with pure (E)- or (Z)-α-hydroxytamoxifen reveal that the two alcohols equilibrate. This occurs by H+-catalyzed formation of the carbocation followed by water capture. Occurring about 10-fold slower than this isomerization is an irreversible process resulting in the two indenes. This cyclization will result in the destruction of the α-hydroxytamoxifens upon exposure to acidic conditions and also makes the direct observation of the tamoxifen carbocation under super-acid conditions difficult, if not impossible. The indenes do form in low yield whenever the tamoxifen carbocation is generated from an SN1 precursor. Thus these products could serve as markers for the formation of the tamoxifen carbocation in cellular systems or in in vivo experiments.Key words: carbocation, indene, allylic cation, isomerization.

A Sensitive Method for Assay of Mixed-Function Oxygenase (p-450 complex) in Cell Culture

1988 ◽  
Vol 15 (3) ◽  
pp. 219-223
Author(s):  
Jørgen Clausen ◽  
Søren Achim Nielsen
Keyword(s):  
Human Lymphocytes ◽  
Cellular Systems ◽  
Metabolic Effects ◽  
Assay Method ◽  
Related Family ◽  
Oxygenase Activity ◽  
Metabolic Transformation ◽  
Mixed Function Oxygenase

The mixed-function oxygenase system involved in the metabolism of drugs and xenobiotics has been extensively studied in various animal species and in various organs (1). It is now apparent that in humans the p-450 complex is one representative of a related family, expressed by 13 c-DNA genes showing approximately 36% similarity between the different subfamilies (2). In order to compare the in vivo and in vitro metabolic effects of drugs and xenobiotics, the induction capabilities of the mixed-function oxygenase must be known. The most sensitive non-isotopic assay system for determination of mixed-function oxygenase activity is the method of Nebert & Gelboin (3,4), which is based on the metabolic transformation of benzo-(a)-pyrene to its fluorescent hydroxyl derivatives (5). However, the levels of the mixed-function oxygenase enzymes in different cellular systems show great variations, with the highest activities in liver cells. Therefore, in order to use human lymphocytes and other cellular systems with low mixed-function oxygenase activities, the assay method for determining oxygenase activity must have the highest possible sensitivity. The present communication is devoted to a study aimed at increasing the sensitivity of Nebert & Gelboin's methods for assay of mixed-function oxygenase subfamilies using benzo-(a)-pyrene as a substrate.

scholarly journals Doxorubicin loaded magnetism nanoparticles based on cyclodextrin dendritic-graphene oxide inhibited MCF-7 cell proliferation

2021 ◽  
Vol 12 (1) ◽  
pp. 8-15
Author(s):  
Ainaz Mihanfar ◽  
Niloufar Targhazeh ◽  
Shirin Sadighparvar ◽  
Saber Ghazizadeh Darband ◽  
Maryam Majidinia ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Anticancer Drug Delivery ◽  
Release Studies ◽  
Anti Cancer ◽  
Acidic Conditions ◽  
Mcf 7

Abstract Doxorubicin (DOX) is an effective chemotherapeutic agent used for the treatment of various types of cancer. However, its poor solubility, undesirable side effects, and short half-life have remained a challenge. We used a formulation based on graphene oxide as an anticancer drug delivery system for DOX in MCF-7 breast cancer cells, to address these issues. In vitro release studies confirmed that the synthesized formulation has an improved release profile in acidic conditions (similar to the tumor microenvironment). Further in vitro studies, including MTT, uptake, and apoptosis assays were performed. The toxic effects of the nanocarrier on the kidney, heart and liver of healthy rats were also evaluated. We observed that the DOX-loaded carrier improved the cytotoxic effect of DOX on the breast cell line compared to free DOX. In summary, our results introduce the DOX-loaded carrier as a potential platform for in vitro targeting of cancer cells and suggest further studies are necessary to investigate its in vivo anti-cancer potential.

scholarly journals EJE Prize 2013: Regulation of aldosterone secretion: from physiology to disease

2013 ◽  
Vol 168 (6) ◽  
pp. R85-R93 ◽  
Author(s):  
Felix Beuschlein
Keyword(s):  
High Throughput Sequencing ◽  
Secondary Hypertension ◽  
Small Sample ◽  
Cellular Systems ◽  
Common Disease ◽  
Aldosterone Secretion ◽  
Technical Developments ◽  
Starting Point

Arterial hypertension is a major cardiovascular risk factor that affects between 10 and 40% of the population in industrialized countries. Primary aldosteronism (PA) is the most common form of secondary hypertension with an estimated prevalence of around 10% in referral centers and 4% in a primary care setting. Despite its high prevalence until recently, the underlying genetic and molecular basis of this common disease had remained largely obscure. Over the past decade, a number of insights have been achieved that have relied onin vitrocellular systems, wild-type and genetically modifiedin vivomodels, as well as clinical studies in well-characterized patient populations. This progress has been made possible by a number of independent technical developments including that of specific hormone assays that allow measurement in small sample volumes as well as genetic techniques that enable high-throughput sequencing of a large number of samples. Furthermore, animal models have provided important insights into the physiology of aldosterone regulation that have served as a starting point for investigation of mechanisms involved in autonomous aldosterone secretion. Finally, national and international networks that have built up registries and biobanks have been instrumental in fostering translational research endeavors in PA. Therefore, it is to be expected that in the near future, further pathophysiological mechanisms that result in autonomous aldosterone secretion will be unraveled.

scholarly journals Analysis of free and protein-bound nitrotyrosine in human plasma by a gas chromatography/mass spectrometry method that avoids nitration artifacts

2000 ◽  
Vol 345 (3) ◽  
pp. 453-458 ◽  
Author(s):  
Matthew T. FROST ◽  
Barry HALLIWELL ◽  
Kevin P. MOORE
Keyword(s):  
Reactive Nitrogen Species ◽  
Plasma Proteins ◽  
Biological Fluids ◽  
Plasma Concentrations ◽  
Normal Subjects ◽  
Gas Chromatography Mass Spectrometry ◽  
Highly Sensitive ◽  
Acidic Conditions ◽  
First Time

Measurement of nitrotyrosine in biological fluids and tissues is increasingly being used to monitor the production of reactive nitrogen species in vivo. The detection of nitrotyrosine in vivo has been reported with the use of a variety of methods including immunoassay, HPLC and GLC/MS. The validity of HPLC and immunoassays have been questioned with regard to their selectivity and sensitivity limits. In principle, the measurement of nitrotyrosine by GLC/MS permits a highly specific, highly sensitive and fully quantitative assay. The nitration of tyrosine under acidic conditions in the presence of nitrite is well documented. Derivatization for the full quantification of nitrotyrosine by using GLC/MS can lead to the artifactual nitration of tyrosine if performed under acidic conditions in the presence of nitrite. We describe a novel alkaline method for the hydrolysis and derivatization of nitrotyrosine and tyrosine, and demonstrate its applicability to the measurement of plasma concentrations of both free and protein-bound nitrotyrosine and tyrosine. A detection limit of 1 pg for nitrotyrosine and 100 pg for tyrosine has been achieved. Our method allows, for the first time, the analysis of free and protein-bound nitrotyrosine and tyrosine in biological samples. The plasma concentrations (means±S.E.M.) of free tyrosine and nitrotyrosine in eight normal subjects were 12±0.6 μg/ml and 14±0.7 ng/ml respectively. Plasma proteins contained tyrosine and nitrotyrosine at 60.7±1.7 μg/mg and 2.7±0.4 ng/mg respectively.

scholarly journals Genome-wide imaging screen uncovers molecular determinants of arsenite-induced protein aggregation and toxicity

2021 ◽  
Author(s):  
Stefanie Andersson ◽  
Antonia Romero ◽  
Joana Isabel Rodrigues ◽  
Sansan Hua ◽  
Xinxin Hao ◽  
...  
Keyword(s):  
Protein Aggregation ◽  
Translational Control ◽  
Protein Biosynthesis ◽  
Cellular Systems ◽  
Genome Wide ◽  
A Genome ◽  
Toxic Metalloid ◽  
Arsenic Stress

The toxic metalloid arsenic causes widespread misfolding and aggregation of cellular proteins. How these protein aggregates are formed in vivo, the mechanisms by which they affect cells, and how cells prevent their accumulation is not fully understood. To find components involved in these processes, we performed a genome-wide imaging screen and identified yeast deletion mutants with either enhanced or reduced protein aggregation levels during arsenite exposure. We show that many of the identified factors are crucial to safeguard protein homeostasis (proteostasis) and to protect cells against arsenite toxicity. The hits were enriched for various functions including protein biosynthesis and transcription, and dedicated follow-up experiments highlight the importance of accurate transcriptional and translational control for mitigating protein aggregation and toxicity during arsenite stress. Some of the hits are associated with pathological conditions, suggesting that arsenite-induced protein aggregation may affect disease processes. The broad network of cellular systems that impinge on proteostasis during arsenic stress identified in this current study provides a valuable resource and a framework for further elucidation of the mechanistic details of metalloid toxicity and pathogenesis.

scholarly journals Manganese transport by Streptococcus sanguinis in acidic conditions and its impact on growth in vitro and in vivo

2021 ◽  
Author(s):  
Tanya Puccio ◽  
Alexander C Schultz ◽  
Claudia A Lizarraga ◽  
Ashley S Bryant ◽  
David J Culp ◽  
...  
Keyword(s):  
Streptococcus Sanguinis ◽  
Manganese Uptake ◽  
Zip Family ◽  
Oral Environment ◽  
Colonization Model ◽  
Acidic Conditions ◽  
Oral Colonization ◽  
Manganese Transport

Streptococcus sanguinis is an oral commensal and an etiological agent of infective endocarditis. Previous studies have identified the SsaACB manganese transporter as essential for endocarditis virulence; however, the significance of SsaACB in the oral environment has never been examined. Here we report that a ΔssaACB mutant of strain SK36 exhibits reduced growth and manganese uptake under acidic conditions. Further studies revealed that these deficits resulted from the decreased activity of TmpA, shown in the accompanying paper to function as a ZIP-family manganese transporter. Transcriptomic analysis of fermentor-grown cultures of SK36 WT and ΔssaACB strains identified pH-dependent changes related to carbon catabolite repression in both strains, though their magnitude was generally greater in the mutant. In strain VMC66, which possesses a MntH transporter, loss of SsaACB did not significantly alter growth or cellular manganese levels under the same conditions. Interestingly, there were only modest differences between SK36 and its ΔssaACB mutant in competition with Streptococcus mutans in vitro and in a murine oral colonization model. Our results suggest that the heterogeneity of the oral environment may provide a rationale for the variety of manganese transporters found in S. sanguinis and point to strategies for enhancing the safety of oral probiotics.

scholarly journals Enzymes and Substrates Are Balanced at Minimal Combined Mass Concentration in vivo

2017 ◽  
Author(s):  
Hugo Dourado ◽  
Veronica G. Maurino ◽  
Martin J. Lercher
Keyword(s):  
Fundamental Problem ◽  
Geometric Mean ◽  
Physiological State ◽  
Cellular Systems ◽  
Cellular Growth ◽  
Metabolic Efficiency ◽  
E Coli ◽  
Molecular Masses ◽  
Enzyme Molecules

AbstractA fundamental problem in biology is how cells organize their resource investment. Cellular metabolism, for example, typically involves hundreds of enzymes and metabolites, but it is unclear according to which principles their concentrations are set. Reasoning that natural selection will drive cells towards achieving a given physiological state at minimal cost, we derive a general equation that predicts the concentration of a metabolite from the concentration of the most abundant and costly enzyme consuming it. Simulations of cellular growth as well as experimental data demonstrate that costs are approximately proportional to molecular masses. For effectively irreversible reactions, the cell maximizes its metabolic efficiency by investing equally into substrate and unbound enzyme molecules. Without fitting any free parameters, the resulting model predicts in vivo substrate concentrations from enzyme concentrations and substrate affinities with high accuracy across data from E. coli and diverse eukaryotes (R2=0.79, geometric mean fold-error 1.74). The corresponding organizing principle – the minimization of the summed mass concentrations of solutes – may facilitate reducing the complexity of kinetic models and will contribute to the design of more efficient synthetic cellular systems.

scholarly journals NIR Bioluminescence Probe Enables Discovery of Diet-Induced Modulation of the Tumor Microenvironment via Nitric Oxide

2021 ◽  
Author(s):  
Anuj K Yadav ◽  
Michael C. Lee ◽  
Melissa Lucero ◽  
Christopher J. Reinhardt ◽  
ShengZhang Su ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Tumor Microenvironment ◽  
Tumor Progression ◽  
Critical Role ◽  
Cellular Systems ◽  
Tissue Imaging ◽  
Molecular Evidence ◽  
No Production ◽  
The Impact

<p>Nitric oxide (NO) plays a critical role in acute and chronic inflammation. NO’s contributions to cancer are of particular interest due to its context-dependent bioactivities. For example, immune cells initially produce cytotoxic quantities of NO in response to the nascent tumor. However, it is believed that this fades over time and reaches a concentration that supports the tumor microenvironment (TME). These complex dynamics are further complicated by other factors, such as diet and oxygenation, making it challenging to establish a complete picture of NO’s impact on tumor progression. Although many activity-based sensing (ABS) probes for NO have been developed, only a small fraction have been employed <i>in vivo </i>and fewer yet are practical in cancer models where the NO concentration is < 200 nM. To overcome this outstanding challenge, we have developed BL<sub>660</sub>-NO, the first ABS probe for NIR bioluminescence imaging of NO in cancer. Owing to the low intrinsic background, high sensitivity, and deep tissue imaging capabilities of our design, BL<sub>660</sub>-NO was successfully employed to visualize endogenous NO in cellular systems, a human liver metastasis model, and a murine breast cancer model. Importantly, its exceptional performance facilitated the design of a dietary study to examine the impact of NO on the TME by varying the intake of fat. BL<sub>660</sub>-NO provides the first direct molecular evidence that intratumoral NO becomes elevated in mice fed a high-fat diet who became obese with larger tumors compared to control animals on a low-fat diet. These results indicate that an inflammatory diet can increase NO production via recruitment of macrophages and overexpression of iNOS which in turn can drive tumor progression.<br></p>

Resistance of Acid-Adapted Salmonellae to Organic Acid Rinses on Beef†

1995 ◽  
Vol 58 (9) ◽  
pp. 973-976 ◽  
Author(s):  
J. S. DICKSON ◽  
M. R. KUNDURU
Keyword(s):  
Organic Acid ◽  
Parent Strain ◽  
Good Growth ◽  
Acid Solutions ◽  
Bacterial Populations ◽  
Acid Adaptation ◽  
Ph Values ◽  
Atcc Strain ◽  
Lean Beef ◽  
Acidic Conditions

Four strains of salmonellae, including three bovine isolates and an ATCC strain, were adapted to growth in acidic conditions by sequential transfer in tryptic soy broth with reduced pH values. The cultures were transferred until good growth (approximately log107 CFU/ml) was obtained within 24 h at 37°C at pH 5.0. Lean beef tissue was inoculated by immersion into either the acid-adapted or the homologous parent strain of each bacterium. The inoculated tissue was rinsed for 10s in 1.5% or 3.0% lactic acid solutions at 23°C or 55°C. Reductions in bacterial populations were compared between the parent and acid-adapted strains to determine if the acid-adapted strains were more resistant to the organic acid rinses. Acid-adapted strains had either equal or greater sensitivity to organic acid rinses than their homologous parent strains, indicating that acid adaptation did not result in bacteria which were resistant to organic acid rinses. Acid-adapted strains had significantly lower D55°C− values than their homologous parent strains.

A fluorescent probe operating under weak acidic conditions for the visualization of HOCl in solid tumors in vivo

2020 ◽  
Vol 63 (8) ◽  
pp. 1153-1158 ◽  
Author(s):  
Peng Wei ◽  
Lingyan Liu ◽  
Wei Yuan ◽  
Jiajia Yang ◽  
Ruohan Li ◽  
...  
Keyword(s):  
Solid Tumors ◽  
Fluorescent Probe ◽  
Acidic Conditions
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