Simultaneous determination of fluvoxamine isomers and quetiapine in human plasma by means of high-performance liquid chromatography

An original HPLC-UV method has been developed for the simultaneous determination of the atypical antipsychotic quetiapine and the geometric isomers of the second-generation antidepressant fluvoxamine. The analytes were separated on a reversed-phase C8 column (150 mm x 4.6mm i.d., 5 microm) using a mobile phase composed of acetonitrile (30%) and a 10.5mM, pH 3.5 phosphate buffer containing 0.12% triethylamine (70%). The flow rate was 1.2 mL min(-1) and the detection wavelength was 245 nm. Sample pretreatment was carried out by an original solid-phase extraction procedure using mixed-mode cation exchange (DSC-MCAX) cartridges; only 300 microL of plasma were needed for one analysis. Citalopram was used as the internal standard. The method was validated in terms of linearity, extraction yield, precision and accuracy. Good linearity was obtained in plasma over the 5.0-160.0 ng mL(-1) concentration range for each fluvoxamine isomer and over the 2.5-400.0 ng mL(-1) concentration range for quetiapine. Extraction yield values were always higher than 93%, with precision (expressed as relative standard deviation values) better than 4.0%. The method was successfully applied to human plasma samples drawn from patients undergoing polypharmacy with the two drugs. Satisfactory accuracy values were obtained, with mean recovery higher than 94%.     

Leucine-rich diet supplementation modulates foetal muscle protein metabolism impaired by Walker-256 tumour

Background

Cancer-cachexia induces a variety of metabolic disorders of protein turnover and is more pronounced when associated with pregnancy. Tumour-bearing pregnant rats have impaired protein balance, which decreases protein synthesis and increases muscle breakdown. Because branched-chain amino acids, especially leucine, stimulate protein synthesis, we investigated the effect of a leucine-rich diet on protein metabolism in the foetal gastrocnemius muscles of tumour-bearing pregnant rats.

Methods

Foetuses of pregnant rats with or without Walker 256 tumours were divided into six groups. During the 20 days of the experiment, the pregnant groups were fed with either a control diet (C, control rats; W, tumour-bearing rats; Cp, rats pair-fed the same normoprotein-diet as the W group) or with a leucine-rich diet (L, leucine rats; LW, leucine tumour-bearing rats; and Lp, rats pair-fed the same leucine-rich diet as the LW group). After the mothers were sacrificed, the foetal gastrocnemius muscle samples were resected, and the protein synthesis and degradation and tissue chymotrypsin-like, cathepsin and calpain enzyme activities were assayed. The muscle oxidative enzymes (catalase, glutathione-S-transferase and superoxide dismutase), alkaline phosphatase enzyme activities and lipid peroxidation (malondialdehyde) were also measured.

Results

Tumour growth led to a reduction in foetal weight associated with decreased serum protein, albumin and glucose levels and low haematocrit in the foetuses of the W group, whereas in the LW foetuses, these changes were less pronounced. Muscle protein synthesis (measured by L-[3H]-phenylalanine incorporation) was reduced in the W foetuses but was restored in the LW group. Protein breakdown (as assessed by tyrosine release) was enhanced in the L and W groups, but chymotrypsin-like activity increased only in group W and tended toward an increase in the LW foetuses. The activity of cathepsin H was significantly higher in the W group foetuses, but the proteolytic calcium-dependent pathway showed similar enzyme activity. In parallel, an intense oxidative stress process was observed only in the group W foetuses.

Conclusions

These data suggested that the proteasomal and lysosomal proteolytic pathways and oxidative stress are likely to participate in the process of foetal muscle catabolism of Walker’s tumour-bearing pregnant rats. The present work shows that foetal muscle can be protected by supplementation with a leucine-rich diet.     

Depressive Symptoms Are Associated with Mental Stress-Induced Myocardial Ischemia after Acute Myocardial Infarction

Objectives

Depression is an adverse prognostic factor after an acute myocardial infarction (MI), and an increased propensity toward emotionally-driven myocardial ischemia may play a role. We aimed to examine the association between depressive symptoms and mental stress-induced myocardial ischemia in young survivors of an MI.

Methods

We studied 98 patients (49 women and 49 men) age 38–60 years who were hospitalized for acute MI in the previous 6 months. Patients underwent myocardial perfusion imaging at rest, after mental stress (speech task), and after exercise or pharmacological stress. A summed difference score (SDS), obtained with observer-independent software, was used to quantify myocardial ischemia under both stress conditions. The Beck Depression Inventory-II (BDI-II) was used to measure depressive symptoms, which were analyzed as overall score, and as separate somatic and cognitive depressive symptom scores.

Results

There was a significant positive association between depressive symptoms and SDS with mental stress, denoting more ischemia. After adjustment for demographic and lifestyle factors, disease severity and medications, each incremental depressive symptom was associated with 0.14 points higher SDS. When somatic and cognitive depressive symptoms were examined separately, both somatic [β = 0.17, 95% CI: (0.04, 0.30), p = 0.01] and cognitive symptoms [β = 0.31, 95% CI: (0.07, 0.56), p = 0.01] were significantly associated with mental stress-induced ischemia. Depressive symptoms were not associated with ischemia induced by exercise or pharmacological stress.

Conclusion

Among young post-MI patients, higher levels of both cognitive and somatic depressive symptoms are associated with a higher propensity to develop myocardial ischemia with mental stress, but not with physical (exercise or pharmacological) stress.     

A substrate ambiguous enzyme facilitates genome reduction in an intracellular symbiont

Background

Genome evolution in intracellular microbial symbionts is characterized by gene loss, generating some of the smallest and most gene-poor genomes known. As a result of gene loss these genomes commonly contain metabolic pathways that are fragmented relative to their free-living relatives. The evolutionary retention of fragmented metabolic pathways in the gene-poor genomes of endosymbionts suggests that they are functional. However, it is not always clear how they maintain functionality. To date, the fragmented metabolic pathways of endosymbionts have been shown to maintain functionality through complementation by host genes, complementation by genes of another endosymbiont and complementation by genes in host genomes that have been horizontally acquired from a microbial source that is not the endosymbiont. Here, we demonstrate a fourth mechanism.

Results

We investigate the evolutionary retention of a fragmented pathway for the essential nutrient pantothenate (vitamin B5) in the pea aphid, Acyrthosiphon pisum endosymbiosis with Buchnera aphidicola. Using quantitative analysis of gene expression we present evidence for complementation of the Buchnera pantothenate biosynthesis pathway by host genes. Further, using complementation assays in an Escherichia coli mutant we demonstrate functional replacement of a pantothenate biosynthesis enzyme, 2-dehydropantoate 2-reductase (E.C. 1.1.1.169), by an endosymbiont gene, ilvC, encoding a substrate ambiguous enzyme.

Conclusions

Earlier studies have speculated that missing enzyme steps in fragmented endosymbiont metabolic pathways are completed by adaptable endosymbiont enzymes from other pathways. Here, we experimentally demonstrate completion of a fragmented endosymbiont vitamin biosynthesis pathway by recruitment of a substrate ambiguous enzyme from another pathway. In addition, this work extends host/symbiont metabolic collaboration in the aphid/Buchnera symbiosis from amino acid metabolism to include vitamin biosynthesis.

     

The Deuterator: software for the determination of backbone amide deuterium levels from H/D exchange MS data

Background  

The combination of mass spectrometry and solution phase amide hydrogen/deuterium exchange (H/D exchange) experiments is an effective method for characterizing protein dynamics, and protein-protein or protein-ligand interactions. Despite methodological advancements and improvements in instrumentation and automation, data analysis and display remains a tedious process. The factors that contribute to this bottleneck are the large number of data points produced in a typical experiment, each requiring manual curation and validation, and then calculation of the level of backbone amide exchange. Tools have become available that address some of these issues, but lack sufficient integration, functionality, and accessibility required to address the needs of the H/D exchange community. To date there is no software for the analysis of H/D exchange data that comprehensively addresses these issues.     

Utility of the Framingham risk score to predict the presence of coronary atherosclerosis in patients with rheumatoid arthritis

The prevalence of ischemic heart disease and atherosclerosis is increased in patients with rheumatoid arthritis (RA). In the general population, but not in patients with systemic lupus erythematosus, the Framingham risk score identifies patients at increased cardiovascular risk and helps determine the need for preventive interventions. We examined the hypothesis that the Framingham score is increased and associated with coronary-artery atherosclerosis in patients with RA. The Framingham score and the 10-year cardiovascular risk were compared among 155 patients with RA (89 with early disease, 66 with long-standing disease) and 85 control subjects. The presence of coronary-artery calcification was determined by electron-beam computed tomography. The Framingham score was compared in patients with RA and control subjects, and the association between the risk score and coronary-artery calcification was examined in patients. Patients with long-standing RA had a higher Framingham score (14 [11 to 18]) (median [interquartile range]) compared to patients with early RA (11 [8 to 14]) or control subjects (12 [7 to 14], P < 0.001). This remained significant after adjustment for age and gender (P = 0.015). Seventy-six patients with RA had coronary calcification; their Framingham risk score was higher (14 [12 to 17]) than that of 79 patients without calcification (10 [5 to 14]) (P < 0.001). Furthermore, a higher Framingham score was associated with a higher calcium score (odds ratio [OR] = 1.20, 95% confidence interval [CI] 1.12 to 1.29, P < 0.001), and the association remained significant after adjustment for age and gender (OR = 1.15, 95% CI 1.02 to 1.29, P = 0.03). In conclusion, a higher Framingham risk score is independently associated with the presence of coronary calcification in patients with RA.     

HPLC analysis of the novel antidepressant duloxetine in human plasma after an original solid-phase extraction procedure

Duloxetine is the most recent serotonin and norepinephrine reuptake inhibitor (SNRI) drug introduced for the therapy of depression. Thus, it is evident that there is a need for having on hand new reliable analytical methods for the determination of duloxetine plasma levels in depressed patients. The present paper deals with the development of a rapid and sensitive high-performance liquid chromatographic method for duloxetine analysis in human plasma. The assays were carried out using a C8 reversed-phase column and a mobile phase composed of 60% aqueous phosphate buffer containing triethylamine at pH 3.0 and 40% acetonitrile. The UV detector was set at 230 nm and loxapine was used as the internal standard. An original pre-treatment of plasma samples was developed, based on solid-phase extraction (SPE) with mixed-mode reversed phase-strong cation exchange cartridges (30 mg, 1 mL). The extraction yields values were higher than 90%. Linearity was found in the 2-200 ng mL(-1) duloxetine concentration range; the limit of quantitation was 2.0 ng mL(-1) and the limit of detection was 0.7 ng mL(-1). The method was applied to plasma samples from depressed patients undergoing therapy with duloxetine. Precision data and accuracy results were satisfactory and no interference from other drugs was found. Thus, the method seems to be suitable for the therapeutic drug monitoring of duloxetine in depressed patients' plasma.     

Simultaneous determination of the antipsychotic drugs levomepromazine and clozapine and their main metabolites in human plasma by a HPLC-UV method with solid-phase extraction

A HPLC method with UV detection has been developed for the simultaneous determination of levomepromazine, clozapine and their main metabolites: N-desmethyl-levomepromazine, levomepromazine sulphoxide, O-desmethyl-levomepromazine, N-desmethylclozapine and clozapine N-oxide. The analytes were separated on a C8 reversed-phase column using a mobile phase composed of acetonitrile and a pH 2.0, 34 mM phosphate buffer containing 0.3% triethylamine (29:71, v/v). Loxapine was used as the internal standard. A reliable biological sample pre-treatment procedure by means of solid-phase extraction on C1 cartridges was implemented, which allows to obtain good extraction yields (>91%) for all analytes and appropriate sample purification from endogenous interference. The method was validated in terms of extraction yield, precision and accuracy. These assays gave RSD% values for precision always lower than 4.9% and mean accuracy values higher than 92%. The method is suitable for the therapeutic drug monitoring (TDM) of patients undergoing polypharmacy with levomepromazine and clozapine.     

Hes1 Increases the Invasion Ability of Colorectal Cancer Cells via the STAT3-MMP14 Pathway

The Notch pathway contributes to self-renewal of tumor-initiating cell and inhibition of normal colonic epithelial cell differentiation. Deregulated expression of Notch1 and Jagged1 is observed in colorectal cancer. Hairy/enhancer of split (HES) family, the most characterized targets of Notch, involved in the development of many cancers. In this study, we explored the role of Hes1 in the tumorigenesis of colorectal cancer. Knocking down Hes1 induced CRC cell senescence and decreased the invasion ability, whereas over-expression of Hes1 increased STAT3 phosphorylation activity and up-regulated MMP14 protein level. We further explored the expression of Hes1 in human colorectal cancer and found high Hes1 mRNA expression is associated with poor prognosis in CRC patients. These findings suggest that Hes1 regulates the invasion ability through the STAT3-MMP14 pathway in CRC cells and high Hes1 expression is a predictor of poor prognosis of CRC.