Quantitative analysis of 11-dehydrocorticosterone and corticosterone for preclinical studies by liquid chromatography/triple quadrupole mass spectrometry.

RATIONALE: The activity of the glucocorticoid activating enzyme 11ß-hydroxysteroid dehydrogenase type-1 (11ßHSD1) is altered in diseases such as obesity, inflammation and psychiatric disorders. In rodents 11ßHSD1 converts inert 11-dehydrocorticosterone (11-DHC) into the active form, corticosterone (CORT). A sensitive, specific liquid chromatography/tandem mass spectrometry method was sought to simultaneously quantify total 11-DHC and total and free CORT in murine plasma for simple assessment of 11ßHSD1 activity in murine models. METHODS: Mass spectrometry parameters were optimised and a method for the chromatographic separation of CORT and 11-DHC was developed. Murine plasma was prepared by 10:1 chloroform liquid-liquid extraction (LLE) for analysis. Limits of quantitation (LOQs), linearity and other method criteria were assessed, according to bioanalytical method validation guidelines. RESULTS: Reliable separation of 11-DHC and CORT was achieved using an ACE Excel 2 C18-AR (2.1 × 150 mm; 2 µm) fused core column at 25°C, with an acidified water/acetonitrile gradient over 10 min. Analytes were detected by multiple reaction monitoring after positive electrospray ionisation (m/z 345.1.1 ➔ 121.2, m/z 347.1 ➔ 121.1 for 11-DHC and CORT, respectively). The LOQs were 0.25 and 0.20 ng/mL for 11-DHC and CORT, respectively. CONCLUSIONS: This LC/MS method is suitable for the reliable analysis of 11-DHC and CORT following simple LLE of murine plasma, bringing preclinical analysis in line with recommendations for clinical endocrinology and biochemistry.

The depth of anaesthesia associated with the administration of isoflurane 2.5% during cardiopulmonary bypass.

BACKGROUND: Administering isoflurane 2.5% into the oxygenator during cardiopulmonary bypass results in no patient movement. However, doing so may result in an excessive depth of anaesthesia particularly, when hypothermia is induced. Bispectral index and arterial blood and oxygenator exhaust concentrations of volatile anaesthetics should be related to depth of anaesthesia. The primary aim of this study was to measure the depth of anaesthesia using bispectral index, resulting from administering isoflurane 2.5% into the oxygenator during cardiopulmonary bypass, and secondary aims were to examine the relationships between blood and oxygenator exhaust isoflurane concentrations and bispectral index. METHODS: Arterial and mixed-venous blood samples were aspirated at three time points during cardiopulmonary bypass and measured for isoflurane concentration using mass spectrometry. Simultaneously, oxygenator exhaust isoflurane concentration, nasopharyngeal temperature and bispectral index were recorded. RESULTS: When averaged across the three time points, all patients had a bispectral index score below 40 (binomial test, p < 0.001). There were no significant correlations between bispectral index score and arterial or mixed-venous blood isoflurane concentrations (r = -0.082, p = 0.715; r = -0.036, p = 0.874) and oxygenator exhaust gas concentration of isoflurane (r = -0.369, p = 0.091). CONCLUSION: When 2.5% isoflurane was administered into the sweep gas supply to the oxygenator during cardiopulmonary bypass, all patients experienced a bispectral index score less than 40 and no significant relationship was found between either arterial or mixed-venous blood or oxygenator exhaust concentrations of isoflurane and bispectral index.

Assessing the depth of isoflurane anaesthesia during cardiopulmonary bypass.

INTRODUCTION: Bispectral index (BIS) and monitoring of end-tidal concentration may be associated with a reduction in the incidence of awareness during volatile-based general anaesthesia. An analogue of end-tidal concentration during cardiopulmonary bypass (CPB) is measuring exhausted isoflurane concentration from the oxygenator as an estimate to blood and, so, brain concentration. The aim of this study was to determine the relationships between oxygenator exhaust and blood concentrations of isoflurane and the BIS score during CPB when administering isoflurane into the sweep gas supply to the oxygenator. METHODS: Seventeen patients undergoing elective cardiac surgery using CPB and isoflurane with BIS monitoring were recruited in a single-centre university hospital. Isoflurane gas was delivered via a calibrated vaporiser at the beginning of anaesthetic induction. Radial arterial blood samples were collected after the initiation of CPB and before aortic cross-clamping, which were analysed for isoflurane by gas chromatography and mass spectrometry. The BIS score and the concentration of exhausted isoflurane from the oxygenator membrane, as measured by an anaesthetic gas analyser, were recorded at the time of blood sampling. RESULTS: The mean duration of anaesthetic induction to arterial blood sampling was 90 min (95%CI: 80,100). On CPB, the median BIS was 39 (range, 7-43) and the mean oxygenator exhaust isoflurane concentration was 1.24 ± 0.21%. No significant correlation was demonstrated between BIS with arterial isoflurane concentration (r=-0.19, p=0.47) or oxygenator exhaust isoflurane concentration (r=0.07, p=0.80). Mixed-venous blood temperature was moderately correlated to BIS (r=0.50, p=0.04). Oxygenator exhaust isoflurane concentration was moderately, positively correlated with its arterial concentration (r=0.64, p<0.01). DISCUSSION: In conclusion, in patients undergoing heart surgery with CPB, the findings of this study indicate that, whilst oxygenator exhaust concentrations were significantly associated with arterial concentrations of isoflurane, neither had any association with the BIS scores, whereas body temperature has moderate positive correlation.

Coronary Sinus Isoflurane Concentration in Cardiac Surgery.

OBJECTIVE: Volatile anesthetic agents such as isoflurane may be associated with fewer adverse myocardial events compared with total intravenous anesthesia in cardiac surgery. The authors aimed to determine whether reasonable isoflurane concentrations at tissue level were being achieved to protect the myocardium using this agent. The isoflurane concentration in myocardium has never been measured. The primary aim was to sample coronary sinus (CS) blood and measure its isoflurane concentration. Secondary aims were to determine whether the CS blood concentration would equilibrate with the arterial blood concentration and the relationship of CS blood concentration with oxygenator exhaust isoflurane concentrations during cardiopulmonary bypass (CPB). DESIGN: Prospective, observational study. SETTING: Single-center university hospital. PARTICIPANTS: The study comprised 23 patients undergoing cardiac surgery using CPB and isoflurane. MEASUREMENTS AND MAIN RESULTS: Shortly after initiation of CPB and insertion of a CS retrograde cardioplegia catheter but before aortic cross-clamping, CS blood was aspirated, followed by radial artery blood, which then were analyzed for isoflurane with gas chromatography and mass spectrometry. The oxygenator exhaust isoflurane level was measured with an anesthetic gas analyzer. The mean arterial and CS isoflurane concentrations were 87.7 ± 50.1 and 73.0 ± 42.9 µg/mL, respectively. There was a significant mean difference of 14.7 µg/mL (95% confidence interval 6.7-22.8) between CS and arterial isoflurane concentrations. Oxygenator exhaust isoflurane levels were correlated positively with those in the CS blood (r = 0.68, p < 0.001) and arterial blood (r = 0.72, p < 0.001). CONCLUSIONS: This was the first study in which CS blood was sampled and measured for isoflurane concentration. The CS isoflurane concentration could be estimated from the isoflurane concentration in the oxygenator exhaust gas. However, the value of this relationship is limited because the CS isoflurane concentration does not accurately represent its myocardial levels during CPB.

Kynurenine monooxygenase regulates inflammation during critical illness and recovery in experimental acute pancreatitis.

Kynurenine monooxygenase (KMO) blockade protects against multiple organ failure caused by acute pancreatitis (AP), but the link between KMO and systemic inflammation has eluded discovery until now. Here, we show that the KMO product 3-hydroxykynurenine primes innate immune signaling to exacerbate systemic inflammation during experimental AP. We find a tissue-specific role for KMO, where mice lacking Kmo solely in hepatocytes have elevated plasma 3-hydroxykynurenine levels that prime inflammatory gene transcription. 3-Hydroxykynurenine synergizes with interleukin-1ß to cause cellular apoptosis. Critically, mice with elevated 3-hydroxykynurenine succumb fatally earlier and more readily to experimental AP. Therapeutically, blockade with the highly selective KMO inhibitor GSK898 rescues the phenotype, reducing 3-hydroxykynurenine and protecting against critical illness and death. Together, our findings establish KMO and 3-hydroxykynurenine as regulators of inflammation and the innate immune response to sterile inflammation. During critical illness, excess morbidity and death from multiple organ failure can be rescued by systemic KMO blockade.

On the mechanism of demethylation of 5-methylcytosine in DNA.

DNA methylation is an important biological process that programmes gene expression in vertebrates. The methylation pattern is generated by a combination of methylation and demethylation reactions catalyzed by DNA methyltransferases and putative demethylases. MBD2 binds methylated DNA and possesses DNA demethylase activity. We use here direct analysis of the reaction mixture by GC-MS using a water-tolerant gas chromatographic column to avoid the loss of potential volatile products and identify the leaving residue of the demethylation reaction. We show that the DNA demethylase reaction catalyzed by a recombinant human MBD2 purified from SF9 insect cells releases dideuteroformaldehyde from [Me-(2)H(3)]-5-methylcytosine in DNA. A mechanism of the DNA demethylation reaction is proposed based on this observation.

Glucocorticoids are lower at delivery in maternal, but not cord blood of obese pregnancies.

Glucocorticoids are vital for lung maturation. We previously showed that cortisol is lower in obese pregnancy. Whether this is maintained at delivery is unknown but is clinically relevant as maternal and cord blood cortisol levels are correlated and offspring of obese are more likely to need neonatal respiratory support. We hypothesized that glucocorticoids are lower in maternal and cord blood at delivery in obese pregnancies. Glucocorticoids (cortisol and corticosterone) and their inactive versions (cortisone and 11-dehydrocorticosterone) were measured by LC-MS/MS in maternal and cord plasma from 259 Caucasian women at delivery (BMI 18-55 kg/m2). Analyses adjusted for labour status, delivery mode, offspring gender, birthweight and gestational age. Cortisol and corticosterone were significantly higher in maternal than cord blood. Inactive versions were significantly higher in cord than maternal blood. Increased maternal BMI associated with lower maternal cortisol, corticosterone and 11-dehydrocorticosterone. Despite significant positive correlations between maternal and cord blood glucocorticoid levels, increased maternal BMI was not associated with lower cord blood glucocorticoid levels. Conditions at delivery may overcome any potential negative effects of low maternal glucocorticoids on the fetus in the short-term. This may not preclude the longer-term effects of fetal exposure to lower glucocorticoid levels during obese pregnancy.

Indolyl-oxazaphosphorine Precursors for Stereoselective Synthesis of Phosphite Triesters and Dithymidinyl Phosphorothioates.

Several novel chiral indolyl-oxazaphosphorines 7 were synthesized, and their potential as precursors to chiral phosphorothioates was evaluated. Reaction of 7 with a thymidine derivative gave phosphite triester 8 with a large degree of stereoselectivity. Sulfurization with Beaucage's reagent provided phosphorothioate triesters 9. The chiral auxiliary 9b containing a cyano group could be easily removed with aqueous ammonia to form dithymidinyl phosphorothioate in more than 97% diastereomeric excess. The chiral indolyl-oxazaphosphorines 7 are a new class of precursors for stereoselective synthesis of phosphorothioates.

The methyl donor S-Adenosylmethionine inhibits active demethylation of DNA: a candidate novel mechanism for the pharmacological effects of S-Adenosylmethionine.

S-Adenosylmethionine (AdoMet) is the methyl donor of numerous methylation reactions. The current model is that an increased concentration of AdoMet stimulates DNA methyltransferase reactions, triggering hypermethylation and protecting the genome against global hypomethylation, a hallmark of cancer. Using an assay of active demethylation in HEK 293 cells, we show that AdoMet inhibits active demethylation and expression of an ectopically methylated CMV-GFP (green fluorescent protein) plasmid in a dose-dependent manner. The inhibition of GFP expression is specific to methylated GFP; AdoMet does not inhibit an identical but unmethylated CMV-GFP plasmid. S-Adenosylhomocysteine (AdoHcy), the product of methyltransferase reactions utilizing AdoMet does not inhibit demethylation or expression of CMV-GFP. In vitro, AdoMet but not AdoHcy inhibits methylated DNA-binding protein 2/DNA demethylase as well as endogenous demethylase activity extracted from HEK 293, suggesting that AdoMet directly inhibits demethylase activity, and that the methyl residue on AdoMet is required for its interaction with demethylase. Taken together, our data support an alternative mechanism of action for AdoMet as an inhibitor of intracellular demethylase activity, which results in hypermethylation of DNA.

Synthesis of antisense oligonucleotides conjugated to a multivalent carbohydrate cluster for cellular targeting.

Carrier-mediated delivery holds great promise for significantly improving the cellular uptake and therefore the therapeutic efficacy of antisense oligonucleotides in vivo. A multivalent carbohydrate recognition motif for the asialoglycoprotein receptor has been designed for tissue- and cell-specific delivery of antisense drugs to parenchymal liver cells. To combine low molecular weight with high receptor affinity, the synthetic ligand contains three galactosyl residues attached to a cholane scaffold via epsilon-aminocapramide linkers. Three-dimensional structural calculations indicate that this unique design provides proper spacing and orientation of the three galactosyl residues to accomplish high affinity binding to the receptor. Covalent conjugation of the bulky carbohydrate cluster to oligonucleotides has been achieved by solid-phase synthesis using low-loaded macroporous resins and optimized synthesis protocols.