Bioanalysis of selinexor in mouse plasma micro-samples utilizing UPLC-MS/MS

Selinexor, a first-in-class inhibitor of the nuclear export protein Exportin-1 (XPO1), was recently approved for the treatment of multiple myeloma in combination with dexamethasone, and as monotherapy for diffuse large B-cell lymphoma. To enable investigations of selinexor in mice, we established and validated an ultrahigh-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) assay in the plasma concentration range of 1-1000 ng/mL using plasma microsamples of 5 µL. Protein depletion with acetonitrile was used for efficient isolation of selinexor which was followed by a dilution step, resulting in a scalable sample processing. Quantification was performed with positive electrospray ionization tandem mass spectrometry in the selected reaction monitoring mode. Due to the high sensitivity of the quantification and the scalable sample processing procedure, the assay can be used for different concentration ranges to either further decrease the achievable lower limit of quantification or to reduce the amount of plasma used. The assay showed interday and intraday accuracy of 89.0-109.0% with a corresponding precision ≤ 14.1%. Suitability for investigations of selinexor in small animal experiments was demonstrated by determination of plasma selinexor in mice after oral administration.

LC-MS Quantification of Malondialdehyde-Dansylhydrazine Derivatives in Urine and Serum Samples

We developed a robust analytical method for quantification of malondialdehyde (MDA) in urine and serum samples using dansylhydrazine (DH) as a derivatizing reagent. The derivatization procedure was partially carried out using an autosampler injection program to minimize errors associated with the low-volume addition of reagents and was optimized to yield a stable hydrazone derivative of MDA and its labeled d2-MDA analogue. The target MDA-DH derivatives were separated on an Agilent Zorbax Eclipse Plus Phenyl-Hexyl (3.0 × 100 mm, 3.5 μm) column. The mass-to-charge ratios of the target derivatives [(M+H)+ of 302 and 304 for MDA-DH and d2-MDA-DH, respectively] were analyzed in single ion monitoring mode using a single quadrupole mass spectrometer operated under positive electrospray ionization. The method limits of quantification were 5.63 nM (or 0.405 ng/mL) for urine analysis and 5.68 nM (or 0.409 ng/mL) for serum analysis. The quantification range for urine analysis was 5.63-500 nM (0.405-36.0 ng/mL) while the quantification range for serum analysis was 5.68-341 nM (0.409-24.6 ng/mL). The method showed good relative recoveries (98-103%), good accuracies (92-98%), and acceptable precisions (relative standard deviations 1.8-7.3% for inter-day precision; 1.8-6.1% for intra-day precision) as observed from the repeat analysis of quality control samples prepared at different concentrations. The method was used to measure MDA in individual urine samples (n = 287) and de-identified archived serum samples (n = 22) to assess the overall performance of the method. The results demonstrated that our method is capable of measuring urinary and serum levels of MDA, allowing its future application in epidemiologic investigations.

Studies on the Disposition and Metabolism of Hydrazine in Rats in vivo

1 Rats were given various doses of hydrazine orally and their plasma and liver hydrazine levels were determined (at various times up to 270 min after dosing) by gas chromatography/ mass spectrometry.

2 The increase in the peak plasma level and in the area under the plasma concentration-time curve (AUC) were not directly proportional to the dose.

3 The ratio of plasma to liver hydrazine varied with dose suggesting saturation of an uptake mechanism might be occurring.

4 In a separate experiment hydrazine was still detectable in the plasma and liver 24 h after dosing with hydrazine i.p.

5 Rats were given the same doses of hydrazine and urine was collected for 24 h after dosing and assayed for hydrazine and acetylhydrazine. The proportion of hydrazine and acetylhydrazine excreted declined with dose.

6 Liver samples were taken for histopathological examination 96 h after dosing. Only after the highest dose (81 mg kg-1) was there evidence of fatty liver, 96 h after a single dose, and a reduction in both liver and body weight.

[Studying of hepatoprotective properties of dry extract from apricot leaves on the model of liver lesion by tetrachloromethane]

The results of the pharmacological investigation of the properties of apricot leaves dry extract are indicated in the article. It is proved that the extract belongs to the group of "relatively harmless" substances, exclusion of the ulcerogenic effect on the stomach, local irritating and allergenic effect on animals. It is found minimal reacting dose of the extract, which is 70 mg/kg of body weight. On the model of liver lesion by tetrachlormethane it is proved the antioxidant properties of the extract, which is manifested by the decreasing of the activity of oxidative processes and the resumption of the activity of the endogenous antioxidant system. At the studying of the bile formation and bile secretion functions in the conditions of the toxic tetrachlormethane lesion the hepatoprotective effect of the dosage form was confirmed, which was realized by the increasing of the speed of bile secretion and its volume. It is proved a positive effect of the extract on the detoxification function of the liver, that is confirmed by the reducing of the hexenal sleep in rats after toxicant exposure.

Crebinostat: a novel cognitive enhancer that inhibits histone deacetylase activity and modulates chromatin-mediated neuroplasticity

Long-term memory formation is known to be critically dependent upon de novo gene expression in the brain. As a consequence, pharmacological enhancement of the transcriptional processes mediating long-term memory formation provides a potential therapeutic strategy for cognitive disorders involving aberrant neuroplasticity. Here we focus on the identification and characterization of small molecule inhibitors of histone deacetylases (HDACs) as enhancers of CREB (cAMP response element-binding protein)-regulated transcription and modulators of chromatin-mediated neuroplasticity. Using a CREB reporter gene cell line, we screened a library of small molecules structurally related to known HDAC inhibitors leading to the identification of a probe we termed crebinostat that produced robust activation of CREB-mediated transcription. Further characterization of crebinostat revealed its potent inhibition of the deacetylase activity of recombinant class I HDACs 1, 2, 3, and class IIb HDAC6, with weaker inhibition of the class I HDAC8 and no significant inhibition of the class IIa HDACs 4, 5, 7, and 9. In cultured mouse primary neurons, crebinostat potently induced acetylation of both histone H3 and histone H4 as well as enhanced the expression of the CREB target gene Egr1 (early growth response 1). Using a hippocampus-dependent, contextual fear conditioning paradigm, mice systemically administered crebinostat for a ten day time period exhibited enhanced memory. To gain insight into the molecular mechanisms of memory enhancement by HDAC inhibitors, whole genome transcriptome profiling of cultured mouse primary neurons treated with crebinostat, combined with bioinformatic analyses of CREB-target genes, was performed revealing a highly connected protein-protein interaction network reflecting modules of genes important to synaptic structure and plasticity. Consistent with these findings, crebinostat treatment increased the density of synapsin-1 punctae along dendrites in cultured neurons. Finally, crebinostat treatment of cultured mouse primary neurons was found to upregulate Bdnf (brain-derived neurotrophic factor) and Grn (granulin) and downregulate Mapt (tau) gene expression-genes implicated in aging-related cognitive decline and cognitive disorders. Taken together, these results demonstrate that crebinostat provides a novel probe to modulate chromatin-mediated neuroplasticity and further suggests that pharmacological optimization of selective of HDAC inhibitors may provide an effective therapeutic approach for human cognitive disorders. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Control of larval-pupal-adult molt in the moth Sesamia nonagrioides by juvenile hormone and ecdysteroids

Sesamia nonagrioides (Lepidoptera: Noctuidae) larvae reared under long day (LD; 16L:8D) conditions pupate after 5 or 6 larval instars, whereas under short day (SD; 12L:12D) conditions they undergo up to 12 additional molts before pupating. This extended period of repeated molting is maintained by high levels of juvenile hormone (JH). Previous work demonstrated that both LD and SD larvae decapitated in the 6th instar pupate but further development is halted. By contrast, about one-third of SD larvae from which only the brain has been removed, undergo first a larval molt, then pupate and subsequently developed to the adult stage. Debrained LD larvae molt to larvae exceptionally but regularly pupate and produce adults. Implanted brains may induce several larval molts in debrained recipient larvae irrespectively of the photoperiodic conditions. The results of present work demonstrate that the prothoracic glands (PGs) and the corpora allata (CA) of debrained larvae continue to produce ecdysteroids and JHs, respectively. PGs are active also in the decapitated larvae that lack JH, consistent with the paradigm that CA, which are absent in the decapitated larvae, are the only source of this hormone. Completion of the pupal-adult transformation in both LD and SD debrained insects demonstrates that brain is not crucial for the development of S. nonagrioides but is required for diapause maintenance. Application of JH to headless pupae induces molting, presumably by activating their PGs. It is likely that JH plays this role also in the induction of pupal-adult transformation in debrained insects. Application of the ecdysteroid agonist RH 2485 (methoxyfenozide) to headless pupae also elicits molting: newly secreted cuticle is in some cases thin and indifferent, in other cases it bears distinct pupal or adult features.

No effect of cigarette smoking dose on oxidized plasma proteins

Cigarette smoking is a major source of oxidative stress. Protein carbonyls have been used as a biomarker of oxidative stress because of the relative stability of carbonylated proteins and the high protein concentration in blood. Increased levels of carbonyl groups have been found in serum proteins of smokers compared to nonsmokers. However, neither the dose effect of current cigarette smoke nor other predictors of oxidative stress have been studied. Hence, we used an Enzyme-Linked Immunosorbent Assay (ELISA) to evaluate plasma protein carbonyls in smokers recruited in the Early Lung Cancer Action Project (ELCAP) program. The lung cancer screening program enrolled current and former smokers age 60 years and over without a prior cancer diagnosis. A total of 542 participants (282 men and 260 women) completed a baseline questionnaire and provided blood samples for the biomarker study. Protein oxidation was measured by derivatization of the carbonyl groups with 2,4-dinitrophenylhydrazine (DNPH) and ELISA quantitation of the DNPH group. Current smoking status was confirmed with urinary cotinine. The mean (+/-S.D.) protein carbonyl level was 17.9+/-2.9 nmol carbonyl/ml plasma. Protein carbonyls did not differ significantly by gender. Carbonyl levels were higher among current than former smokers, but these differences did not attain statistical significance, nor did differences by urine cotinine levels, pack-years, pack/day among current smokers, and smoking duration. In a multiple regression analysis, higher protein carbonyl levels were independently associated with increasing age (0.59 nmol/ml increase per 10 years, 95% CI 0.14, 1.05, p=0.01), African-American vs. white race/ethnicity, (1.30 nmol/ml, 95% CI 0.4, 2.19, p=0.008), and lower educational attainment (0.75 nmol/ml, 95% CI 0.12, 1.38, p=0.02). Although we found no significant difference between current vs. past cigarette smoking and protein carbonyls in this older group of smokers, associations were found for age, ethnicity, and educational attainment. Our results indicate that the measurement of plasma carbonyls by this ELISA technique is still an easy and suitable method for studies of diseases related to oxidative stress.

Cloud point formation based on mixed micelle in the presence of electrolyte for extraction, preconcentration, and spectrophotometric determination of trace amounts of hydrazine in water and biological samples

A cloud point extraction process using mixed micelle of the anionic surfactant sodium dodecyl sulfate and the nonionic surfactant Triton X-114 to extract hydrazine from aqueous solutions was investigated. The method is based on the condensation reaction of hydrazine with p-(dimethylamino)benzaldehyde, azine formation, and mixed micelle-mediated extraction of azine in the presence of NaCl electrolyte as an inducing phase separation. An azine product was concentrated in surfactant-rich phase after separation. The optimal extraction and reaction conditions (e.g., surfactant, reagent and electrolyte concentrations, and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.50-110ngml(-1) of hydrazine and the detection limit of the method is 0.08ngml(-1). The interference effect of some cations, anions, and organic compounds was also tested. The method was successfully applied to the determination of hydrazine in water and biological samples.

Determination of Cloretazine (VNP40101M) and its active metabolite (VNP4090CE) in human plasma by liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS)

A sensitive method for the determination of Cloretazine (VNP40101M) and its metabolite (VNP4090CE) with an internal standard (ISTD) in human plasma was developed using high-performance liquid chromatographic separation with tandem mass spectrometric detection. Acidified plasma samples (500 microL) were prepared using solid phase extraction (SPE) columns, and 25 microL of the reconstituted sample was injected onto an Ascentis C18 HPLC column (3 microm, 5 cmx2.1 mm) with an isocratic mobile phase. Analytes were detected with an API-3000 LC-MS/MS System at unit (Q1) and low (Q3) resolution in negative multiple reaction monitoring mode: m/z 249.0 (precursor ion) to m/z 114.9 (product ion) for both Cloretazine (at 3.64 min) and VNP4090CE (at 2.91 min), and m/z 253.0 (precursor ion) to m/z 116.9 (product ion) for the ISTD. The mean recovery for Cloretazine (VNP40101M) and its metabolite (VNP4090CE) was greater than 87% with a lower limit of quantification of 1.0 ng/mL for Cloretazine (S/N=9.7, CV<or=12%) and 0.5 ng/mL for VNP4090CE (S/N=11.3, CV<or=9.7%). This method was validated over a linear range of 1.0-1000 ng/mL for Cloretazine and 0.5-100 ng/mL for VNP4090CE, and results from a five day validation study demonstrated good within-day and between-day precision and accuracy. This method has been used to measure plasma Cloretazine and its metabolite concentrations in a Phase I study in children with recurrent progressive or refractory primary brain tumors.

Chemoselective hydrazone formation between HYNIC-functionalized peptides and (18)F-fluorinated aldehydes

INTRODUCTION

Since the demand for (18)F-fluorinated peptides for quantitative in vivo receptor imaging using PET has increased, a new chemoselective two-step (18)F-labeling strategy based on hydrazone formation between an unprotected hydrazine-functionalized peptide and an (18)F-labeled aldehyde was developed.

METHODS

First, 4-[(18)F]fluorobenzaldehyde ([(18)F]FB-CHO) was prepared from 4-formyl-N,N,N-trimethylanilinium triflate via direct no-carrier-added (18)F-fluorination (dimethyl sulfoxide, 90 degrees C, 5 min) and purified by RP-HPLC. Hydrazone formation between [(18)F]FB-CHO and 6-hydrazinonicotinic acid (HYNIC) and the unprotected HYNIC-functionalized peptides (HYNIC-d-Phe(1))-Tyr(3)-Thr(8)-octreotide and (HYNIC-Arg(1))-substance P was evaluated with respect to the dependence of radiochemical yield on pH, precursor concentration and temperature. The stability of [(18)F]FB-CH=N-HYNIC-Tyr(3)-Thr(8)(NH(2))-octreotide in aqueous solution at various pH (4.0, 5.5 and 7.5) as well as the in vivo stability of [(18)F]FB-CH=N-HYNIC-Tyr(3)-Thr(8)-octreotide in mouse blood (30 min p.i.) was investigated.

RESULTS

Yields of the hydrazone formation were independent of pH between pH 0.5 and 5.5. Optimal labeling yields of 85% were obtained with a precursor concentration of 2.1 mM at 70 degrees C for 10 min. The labeling products were stable at pH 7.5 at 37 degrees C, while in more acidic media (pH 4.0) the product slowly decomposed to form up to 31+/-2% [(18)F]FB-CHO within 5 h. Metabolite studies showed no detectable degradation of [(18)F]FB-CH=N-HYNIC-Tyr(3)-Thr(8)-octreotide in mouse blood (30 min p.i.).

CONCLUSIONS

In conclusion, chemoselective hydrazone formation between unprotected HYNIC-functionalized peptides and [(18)F]FB-CHO is a fast and straightforward radiolabeling method leading to high yields under mild acidic conditions. In addition, it represents a powerful and versatile radiolabeling strategy that is applicable to a variety of radionuclides and peptide precursors already available for (99m)Tc labeling.

Bisaryloxime ethers as potent inhibitors of transthyretin amyloid fibril formation

Amyloid fibril formation by the plasma protein transthyretin (TTR), requiring rate-limiting tetramer dissociation and monomer misfolding, is implicated in several human diseases. Amyloidogenesis can be inhibited through native state stabilization, mediated by small molecule binding to TTR's primarily unoccupied thyroid hormone binding sites. New native state stabilizers have been discovered herein by the facile condensation of arylaldehydes with aryloxyamines affording a bisarylaldoxime ether library. Of the library's 95 compounds, 31 were active inhibitors of TTR amyloid formation in vitro. The bisaryloxime ethers selectively stabilize the native tetrameric state of TTR over the dissociative transition state under amyloidogenic conditions, leading to an increase in the dissociation activation barrier. Several bisaryloxime ethers bind selectively to TTR in human blood plasma over the plethora of other plasma proteins, a necessary attribute for efficacy in vivo. While bisarylaldoxime ethers are susceptible to degradation by N-O bond cleavage, this process is slowed by their binding to TTR. Furthermore, the degradation rate of many of the bisarylaldoxime ethers is slow relative to the half-life of plasma TTR. The bisaryloxime ether library provides valuable structure-activity relationship insight for the development of structurally analogous inhibitors with superior stability profiles, should that prove necessary.

A Phase I and Pharmacokinetic Study of VNP40101M, a Novel Sulfonylhydrazine Alkylating Agent, in Patients with Refractory Leukemia

PURPOSE

VNP40101M is a novel sulfonylhydrazine alkylating agent with broad antitumor activity in animal models. As alkylating agents are important antileukemia drugs, a Phase I and pharmacokinetic study of VNP40101M was conducted in patients with refractory or relapsed leukemias or poor-risk myelodysplastic syndromes (MDS).

EXPERIMENTAL DESIGN

VNP40101M was given as a single i.v. infusion over 15-70 min on day 1. Courses were repeated every 4 weeks according to antileukemic activity. The starting dose of 220 mg/m(2) was escalated by approximately 33% in cohorts of 3-6 patients until a maximum-tolerated dose was established. One additional cohort was treated with the maximum-tolerated dose divided over days 1 and 8.

RESULTS

Thirty-eight patients, including 28 with acute myeloid leukemia and 5 with MDS, received 52 courses of treatment. Nondose-limiting, reversible infusion-related toxicities were the most frequent adverse event, occurring in 24 (63%) patients on the first course. Dose escalation was terminated at 708 mg/m(2) for prolonged myelosuppression in 1 of 7 patients, and 600 mg/m(2) was selected as the recommended Phase II dose, with no significant extramedullary toxicity at this dose level. Two patients, 1 with MDS treated with 300 mg/m(2) and 1 with acute myeloid leukemia treated with 600 mg/m(2), achieved complete remission.

CONCLUSIONS

VNP40101M had significant antileukemic activity and minimal extramedullary toxicity in patients with relapsed or refractory disease.

CYP2E1 mediated isoniazid-induced hepatotoxicity in rats

AIM

To investigate the role of CYP2E1 in isoniazid (INH)-induced hepatotoxicity and the influence of rifampicin (RFP) on INH-induced liver injury.

METHODS

Rats were treated with INH alone (100 mg/kg, ip) or co-administered with RFP (100 mg/kg, ig) for 10 d and 21 d. Hepatotoxicity was assayed by plasma enzymes (sALT, sAST) and histopathological examinations. Hepatic CYP2E1 activity was measured by aniline hydroxylase (ANH), and CYP2E1 mRNA expression was determined by RT-PCR. Plasma hydrazine concentration was determined by RP-HPLC.

RESULTS

For a 10 d INH-treatment, hepatic CYP2E1 level was increased to 3.7-fold over the control; liver impairment appeared after 21 d treatment, while CYP2E1 and plasma hydrazine were, respectively, increased to 4.6-fold and 1.7-fold. However, in INH-RFP group for 10 d, CYP2E1 and plasma hydrazine were, respectively, decreased by 13 % and 18 % over INH group; similarly, hepatic injury is equal to INH group appeared after 21 d, and CYP2E1 was further decreased by 26 %. Correlation analysis showed that sALT had a positive correlation with plasma hydrazine and with CYP2E1 activity; CYP2E1 activity was also markedly correlated with plasma hydrazine. And compared with control, there is no difference in changes of CYP2E1 mRNA expression in INH and INH-RFP treatment for 21 d.

CONCLUSION

The metabolite of INH, hydrazine, plays an important role in INH-induced hepatotoxicity in rats. The induction of CYP2E1 by hydrazine is involved in the hepatotoxicity of INH. RFP does not exacerbate INH-induced hepatotoxicity in short term, which relates to down-regulation of CYP2E1.

Pharmacokinetics, mass balance, and tissue distribution of a novel DNA alkylating agent, VNP40101M, in rat

VNP40101M (1,2-Bis(methylsulfonyl)-1-(2-chloroethyl)-2-[(2 methylamino)carbonyl] hydrazine), a novel DNA alkylating agent, is currently under clinical development for the treatment of cancer in Phase I clinical trials. This study investigated the pharmacokinetics, mass balance, and tissue distribution of [14C]-VNP40101M in rats following a single intravenous dose of 10 mg/kg. After 7 days, the total recovery of radioactivity was 85% for males and 79% for females. Most of the radioactivity was eliminated within 48 hours through urine (70%), with less excreted in feces (6%). Tissue contained relatively high radioactive residues with the highest concentrations in kidneys, liver, lung, and spleen. After 7 days, tissue still contained 9% of the dose. At both 5 minutes and 1 hour post-dose, brain contained relatively high radioactivity (5.9 and 3.3 micro g equivalence/g and 50% and 30% of the blood concentration, respectively), suggesting that VNP40101M penetrated the blood-brain barrier. The elimination half-life of VNP40101M was approximately 20 minutes, the peak plasma concentration (Cmax) averaged 11.3 micro g/mL, the volume of distribution (Vss) averaged 0.91 L/kg, and the total body clearance (Cl) averaged 33.5 mL/min/kg. The metabolite profile in urine was complex, indicating VNP40101M was extensively metabolized. There were no apparent sex differences in pharmacokinetic parameters of VNP40101M in the rat.

High-performance liquid chromatographic determination of isoniazid, acetylisoniazid and hydrazine in biological fluids

The basic principle of derivatization of a hydrazide moiety with an aldehyde as applied in the method developed by Lacroix et al. [J. Chromatogr., 307 (1984) 137-144] for the quantitation of isoniazid and acetylisoniazid was improved by modification, standardization and extension to allow quantitation of hydrazine in patient samples. It could be shown that 40 microliters of 1% methanolic cinnamaldehyde per 200 microliters of deproteinized analysate gave maximal chromophoric isoniazid-cinnamaldehyde conjugate, read at 340 nm. The hydrolytic loss of isoniazid, crucial to the quantitation of acetylisoniazid, could be compensated for by introduction of an appropriate set of calibration curves. Although the method described here allows quantitation of monoacetylhydrazine and diacetylhydrazine, in addition to hydrazine, in mono-spiked samples, the method cannot be used for the quantitation of the acetylated metabolites of hydrazine in patient samples because of a lack of specificity. Linear calibration curves in the range 1-25 micrograms/ml for isoniazid and acetylisoniazid, 10-400 ng/ml for hydrazine and 50-1000 ng/ml for monoacetylhydrazine and diacetylhydrazine, could be constructed; analyte recoveries approaching 100% could be achieved in all instances.

Hydrazine production in children receiving isoniazid for the treatment of tuberculous meningitis

OBJECTIVE

To study the generation of the hepatotoxin hydrazine in 32 malnourished children receiving isoniazid for the treatment of tuberculous meningitis.

DESIGN AND SETTING

This observational study was undertaken in the pediatric ward of a teaching hospital admitting children with advanced forms of tuberculous meningitis for treatment and management of complications.

METHODS

Thirty-two children (mean age 2.28 years) receiving isoniazid 20 mg/kg/d were studied. Plasma isoniazid, acetylisoniazid, and hydrazine concentrations were determined by an HPLC method. Fourteen children were studied at weekly intervals for the first month of treatment and again after six months of therapy; 18 additional children were studied on one or more occasions during the first month of treatment only.

RESULTS

The area under the curve for hydrazine two to five hours after the isoniazid dose correlated with the isoniazid elimination rate and with acetylisoniazid generation. Hydrazine production increased significantly during the first month of treatment, but decreased to approximate initial values at six months. No correlation was found between any clinical or biochemical indicator of liver dysfunction and hydrazine production.

CONCLUSIONS

Hydrazine is formed in significant concentrations during the metabolism of isoniazid in young children. However, additional factors such as preexisting liver damage (e.g., from viral hepatitis) may be necessary for it to reach its toxic potential.

Agents combining thromboxane receptor antagonism with thromboxane synthase inhibition: [[[2-(1H-imidazol-1-yl)ethylidene]amino]oxy]alkanoic acids

A new class of compounds combining thromboxane-A2 (TxA2) receptor antagonism and thromboxane synthase inhibition is described. A first series of (E)- and (Z)-[[[2-(1H-imidazol-1-yl)ethylidene]amino]oxy]pentanoic acids showed relevant thromboxane synthase inhibition associated with weak TxA2 receptor antagonism, while a series of (+/-)-(E)-[[[2-(1H-imidazol-1-yl)-3-phenylpropylidene]amino]oxy] pentanoic acids, structurally derived from the former, showed potent and well-balanced dual activity. Structural requirements for significant single and dual activity are discussed. Two close congeners of the latter series, (+/-)-(E)-5-[[[1-cyclohexyl-2-(1H-imidazol-1-yl)-3- phenylpropylidene]amino]oxy]pentanoic acid 23c and its p-fluorophenyl analog 23m, inhibited TxB2 production in vitro, in rat whole blood during clotting, with IC50 of 0.06 and 0.37 microM and antagonized the binding of [3H]SQ 29548 to washed human platelets, with IC50 of 0.08 and 0.02 microM, respectively. These two compounds were selected for further pharmacological evaluation and were shown to antagonize U46619-induced platelet aggregation in human platelet rich plasma with IC50 of 0.30 and 0.44 microM, respectively. They were both orally available, and in particular 23m caused a long lasting ex vivo TxA2 synthase inhibition in the fed rat. The levorotatory enantiomer of 23c, stereospecifically synthesized as a model compound, was found to be more potent than racemic 23c with regard to TxA2 receptor antagonism (IC50 = 0.04 microM) and equivalent to the latter with regard to TxA2 synthase inhibition. A molecular modeling study concerning the levorotatory enantiomer of 23c (S), TxA2, and representative TxA2 antagonists of different classes led to the definition of a putative pharmacophoric model for the TxA2 receptor ligands.

Comprehensive assay for pyrazinamide, rifampicin and isoniazid with its hydrazine metabolites in human plasma by column liquid chromatography

A comprehensive assay for determination of pyrazinamide (PZA), rifampicin (RIF), isoniazid (INH) and hydrazine metabolites is described. The method involves organic solvent extraction of PZA and RIF, followed by derivatization of INH, monoacetylhydrazine (mHYD) and hydrazine (HYD) with salicylaldehyde and extraction with diethyl ether. Acetylisoniazid (acINH) and diacetylhydrazine (dHYD) were hydrolyzed to INH and mHYD, respectively, and processed as above. Using a gradient solvent programmer, PZA and RIF were analyzed on a C8 (5 microns) column at 248 nm, while INH and metabolites were analyzed on a C18 (5 microns) ODS2 column at 280 nm.

Determination of hydrazine in human plasma by high-performance liquid chromatography

A simple and sensitive liquid chromatographic method for the determination of hydrazine in human plasma and serum is described. Samples were prepared in a single-step reaction by protein denaturation with trichloroacetic acid and derivatization to a stable azine with 4-hydroxybenzaldehyde. Chromatographic separation was carried out on a reversed-phase (octadecylsilane) column with methanol-water (60:40) as mobile phase and ultraviolet detection at 340 nm. Linearity was found in the range 5-1000 ng/ml. The detection limit of spiked plasma was 1 ng/ml. The coefficient of variation ranged from 1.7 to 3.8%. No degradation of hydrazine was found in spiked plasma and serum, even after storage at room temperature for one week. An increased hydrazine level was found after in vitro degradation from isoniazid in human serum.

Effects of rifampicin on pharmacokinetics of isoniazid and its metabolite acetylhydrazine in rats

After i.v. and i.p. injections of isoniazid (Iso) 40 mg.kg-1 to male Wistar rats, the plasma levels of Iso, acetylisoniazid (AcIso), and acetylhydrazine (AcHz) were determined by spectrophotometric method and gas chromatography. The results suggested that the pharmacokinetic behavior of Iso in rats belonged to a 2-compartment model. The plasma levels of AcHz in rifampicin (Rif 30 mg.kg-1)-pretreated rats were lowered vs the control (P < 0.05 or < 0.01). The T1/2 of AcHz was shortened by Rif (control group 3.3 h, Rif-pretreated group 1.4 h) after i.v. injection of AcHz 10 mg.kg-1 to rats and the results showed that AcHz was converted to its active metabolites quickly by increasing the oxidative elimination rate of AcHz, which is related to the higher incidence of liver necrosis caused by Iso and Rif in combination.

Factors in hydrazine formation from isoniazid by paediatric and adult tuberculosis patients

An HPLC method is described for measurement of plasma hydrazine (Hz) concentrations (CHz) at the same time as isoniazid (INH) levels (CINH). Study has been made of CHz during 2-5 after dose in healthy adults (A, n = 34), in adult pulmonary TB patients (B, n = 18) and in paediatric tuberculous meningitis patients (C, n = 25). Although the population has about equal proportions of 'slow' (52%) and 'fast' acetylators, in none of the groups could a correlation be shown between CHz levels or rates of Hz accumulation and any measure of acetylator type. Consequently Hz must be derived both from INH and from its metabolites during the first hours post-dose. For group A and ca. 70% of groups B and C a constant and maximal fraction of dose (ca. 0.6% for adults and 0.4% for paediatric patients) appeared as Hz at 4-5 h. For group B patients small pre-dose concentrations increased with duration of treatment. Four patients in group B showed the highest levels of CHz and rates of Hz accumulation some three times greater than the rest; all four had been identified as alcoholics and one showed evidence of hepatotoxicity at CHz (5 h) = 1.3% of dose. Amongst group C (9/25) episodes of high CHz greater than 0.5% of dose occurred during the first weeks of treatment and one developed CHz ca. 100 ng/ml = 1.3% of dose coincidentally with indications of hepatic damage.

Determination of hydrazine in biofluids by capillary gas chromatography with nitrogen-sensitive or mass spectrometric detection

Plasma and liver levels of hydrazine were determined at 10, 30, 90 and 270 min in rats given 0.09, 0.27, 0.84 and 2.53 mmol of hydrazine per kg body weight orally by capillary gas chromatography-mass spectrometry of its pentafluorobenzaldehyde adduct (DFBA, m/z 388) using selected ion monitoring with 15N2-labelled hydrazine as the internal standard (adduct, m/z 390). The mean half-life for hydrazine in the plasma was approximately 2 h but varied with dose. Urinary excretion (0-24 h) of hydrazine and its metabolite acetylhydrazine were determined employing nitrogen-phosphorus detection of the adducts utilising a novel internal standard, pentafluorophenylhydrazine, the adduct of which structurally resembles DFBA. The fraction of the original dose excreted as hydrazine (and acetylhydrazine) declined with increasing dose.

High-performance liquid chromatographic analysis of fatty acid compositions of platelet phospholipids as their 2-nitrophenylhydrazides

A novel high-performance liquid chromatographic method for biologically important fatty acids incorporated into platelet phospholipids in esterified form has been developed. 2-Nitrophenylhydrazine hydrochloride was used as a pre-column labelling agent to convert the saponified platelet phospholipids directly into corresponding fatty acid hydrazides, without a complicated isolation procedure. Isocratic separation was achieved within only 36 min for twenty-five saturated and mono- and polyunsaturated fatty acids (C8:0-C22:6), including cis and trans isomers, on a YMC-FA column. The analytical results showed good quantitative accuracy. Fatty acid compositions were determined in platelet phospholipids obtained from normal subjects and patients with diabetes mellitus. The method is simple, rapid and adequate for labelling esterified fatty acids in biological materials, and has several advantages with regard to resolution, analysis time and sensitivity over previously published methods.

Simultaneous assay for isoniazid and hydrazine metabolite in plasma and cerebrospinal fluid in the rabbit

A simple procedure for the simultaneous determination of isoniazid and hydrazine metabolite in plasma and cerebrospinal fluid in the rabbit is described. The assay involves organic extraction before and after derivatization of the two compounds and the internal standard, phenelzine. The extract of the derivatized compounds was evaporated to dryness at 40 degrees C and the residue redissolved in the mobile phase (50 microliters). A 25-microliters aliquot was injected into the liquid chromatograph and eluted with acetonitrile-water-triethylamine (70:30:0.4, v/v) containing 5 mM heptanesulphonic acid on a 30-microns C8 precolumn linked to a 10-microns C18 microBondapak column at ambient temperature (25 +/- 1 degree C). The eluate was detected by ultraviolet detection at 320 nm.

The pharmacokinetics of isoniazid and hydrazine metabolite in plasma and cerebrospinal fluid of rabbits

The pharmacokinetics of isoniazid (INH) and hydrazine metabolite (HYD) in plasma and cerebrospinal fluid (CSF) of ten rabbits was studied after separate intravenous (i.v.) and oral (p.o.) administration in a crossover study. The concentrations of INH and HYD in the biological fluids were determined by high performance liquid chromatography (HPLC). There was no difference in the area under plasma concentration-time curves, indicating that oral absorption was complete. The mean apparent volume of distribution after i.v. (3.02 +/- 0.55 L) was smaller (p less than 0.01) than that after p.o. (4.29 +/- 1.25 L) dosing. The elimination t1/2 of INH in CSF was longer (p less than 0.005) than that in plasma after either route of administration. There was no significant barrier to the penetration of INH into the CSF from the general circulation. The HYD plasma concentrations were similar after either route. HYD was eliminated at a slower rate (Ke = 0.17 h-1) than INH (Ke = 0.59 h-1). There was prolonged exposure of the body to HYD (greater than 6 h - above 0.1 micrograms/ml).

The response to thromboxane A2 analogues in human platelets. Discrimination of two binding sites linked to distinct effector systems

Thromboxane A2 (TXA2) induces platelet shape change, secretion, and aggregation. Using a novel TXA2/prostaglandin endoperoxide receptor antagonist, [1r-[1 alpha(Z),2 beta,3 beta,5 alpha]]-(+)-7-[5-[[(1,1'- biphenyl)-4-yl]methoxy]-3-hydroxy-2-(1-piperidinyl) cyclopentyl]-4-heptenoic acid hydrochloride (GR32191), we demonstrate that these responses are mediated by at least two receptor-effector systems. GR32191 non-competitively inhibited platelet aggregation to the TXA2 mimetics, (15S)-hydroxy-11,9-(epoxymethano) prostadienoic acid (U46619) and [1S-(1 alpha,2 beta(5Z),3 alpha (1E,-3S), 4 alpha)]-7-[3-(3-hydroxy-4-(p-iodophenoxy)-1-butenyl)7- oxabicyclo[2.2.1]hept-2yl]-5-heptenoic acid by binding irreversibly to a TXA2/prostaglandin endoperoxide receptor. Dissociation of [3H]GR32191 from human platelets demonstrated two specific binding sites, one which was rapidly dissociating and a site to which binding was essentially irreversible. Stimulation by U46619 of platelets incubated with GR32191 and subsequently washed to expose the reversible binding site failed to aggregate or to secrete [3H]5-hydroxy-tryptamine; formation of inositol phosphates and activation of protein kinase C were markedly suppressed. In contrast, platelet shape change and calcium stimulation remained at 90% of control. Furthermore, stimulation of the reversible binding site with U46619 induced aggregation in the presence of ADP, demonstrating its functional importance in amplifying the response to other agonists. These data suggest that TXA2 mediates platelet activation through at least two receptor-effector systems; one linked to phospholipase C activation, resulting in platelet aggregation and secretion and a second site mediating an increase in cytosolic calcium and platelet shape change.

Gas chromatographic analysis of monoalkylhydrazines

A quantitative electron-capture gas chromatographic assay procedure was developed for the analysis of monoalkylhydrazines in biological samples. Application to the analysis of phenelzine was demonstrated. Four monoalkylhydrazines were analyzed in whole blood by reaction with pentafluorobenzaldehyde to form stable hydrazone derivatives which were extracted and subsequently reacted with pentafluoropropionic anhydride to give products which were very sensitive to electron-capture detection when analyzed by gas chromatography. Methylhydrazine, benzylhydrazine, phenelzine and pheniprazine each yielded single derivatives with this procedure suggesting that the analytical procedure has a broad application to the analysis of other monoalkylated hydrazines. The method was applied to monitor whole blood levels of phenelzine in rats treated intravenously with phenelzine sulphate.

The reaction of oxyhemoglobin with 1,1-diphenyl-2-picrylhydrazine and 2,2-diphenyl-1-picrylhydrazyl

In an effort to elucidate the mechanism of the initiation reaction of the denaturation of oxyhemoglobin, I, to methemoglobin, II, by hydrazines, we have investigated by electron paramagnetic resonance, EPR, and visible spectrophotometry at 22 degrees C, pH 7.4, the reaction of I with 1,1-diphenyl-2-picrylhydrazine, III, and 2,2-diphenyl-1-picrylhydrazyl, IV, in dimethylsulphoxide/buffer and methanol/buffer mixtures, these organic solvents included at a concentration of 10 v/v% to render III and IV soluble while not causing appreciable denaturation of I. In both buffer mixtures, the results obtained were the same. For the I/III reaction mixtures, although the spectrophotometric data obtained showed denaturation to occur, there was no EPR evidence for formation of IV, contrary to expectation based on the chemical structure of III. The EPR observations on each I/IV reaction mixture showed a rapid decrease in IV signal intensity to a value that, depending on the initial reactant concentrations, was either below the detection limit or, when measurable, constant with time. The results of similar EPR measurements on analogous II/IV reaction mixtures were the same. These EPR results are compatible with the idea that IV forms a complex with the protein moiety of I and II, and show that the I/III reaction could yield IV and thus involve a one-electron transfer process.

In vitro attachment of mono- and oligosaccharides to surface glycoconjugates of intact cells

We have synthesized glycosylhydrazines of various mono- and oligosaccharides and coupled these to periodate- or galactose oxidase-treated human red cells and K562 erythroleukemia cells. The optimal conditions for this carbohydrate modification of cells have been established. This method makes it possible to specifically elongate oligosaccharide chains of cell surface glycoconjugates with desired carbohydrates. In this way, new antigenic and receptor properties can be conferred to cells, and the functional roles of carbohydrates in cell surface glycoconjugates can be studied. The method has been used to make red cells of blood group O reactive with anti-A and anti-B sera, and in rendering K562 cells or red cells of blood group O agglutinable with the alpha-N-acetylgalactosamine-specific Helix pomatia lectin.

Drug level monitoring: cardiovascular drugs

Methods for the determination of cardiovascular drugs in blood and plasma are critically reviewed with emphasis on gas and liquid chromatographic techniques. The importance of the various procedures is discussed, in particular sample work-up where the conditions for isolation and derivatization of the compounds are decisive for the accuracy and precision of the methods. Compared with other assay techniques chromatographic methods are generally to be preferred owing to their better selectivity. In the review the following groups are discussed: digitalis glycosides, antiarrhythmic agents, beta-adrenoceptor antagonists, vasodilating agents, antihypertensive compounds, and diuretics.

Levels of acetyl hydrazines and rate of acetylation of isoniazid in adult tuberculosis patients

Patients suffering from pulmonary tuberculosis were investigated for the levels of isoniazid (INH) and its metabolites viz. acetyl-INH, mono and diacetyl hydrazines and ammonia. It was observed that 50% of the patients are slow inactivators of INH and almost all show an increase in circulating levels of NH3 at 6 hrs. Mono and diacetyl hydrazine levels in blood and urine were detectable in all the patients up+o 24 hrs though the maximum levels were observed at different intervals after the intake of INH.

Plasma hydrazine concentrations in man after isoniazid and hydralazine administration

By using a specific sensitive stable-isotope dilution gas chromatography-mass spectrometry (GC-MS) assay, hydrazine was detected in the plasma of eight healthy male volunteer subjects taking isoniazid (300 mg daily) for 2 weeks. Accumulation of hydrazine occurred in slow-acetylator phenotypes. Hydrazine was also detected in the plasma of eight out of 14 hypertensive patients treated chronically with hydralazine (200 mg daily). However, the concentrations of hydrazine observed were much lower than in the isoniazid study and were close to the limit of detection. As hydrazine is hepatotoxic, mutagenic and carcinogenic in animals, its presence in human plasma has important toxicological implications.

The haemolytic reactions of 1-acetyl-2-phenylhydrazine and hydrazine: a spin trapping study

Free radical production from the reaction of hydrazine and 1-acetyl-2-phenylhydrazine (AcPhHZ) with oxyhaemoglobin and with human red blood cells, has been observed by the electron spin resonance technique of spin trapping. Using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the free radical intermediates detected depended on the hydrazine derivative, oxyhaemoglobin and the oxyhaem/hydrazine derivative concentration ratio. The reaction of hydrazine with oxyhaemoglobin in the presence of DMPO gave a nitroxide which was identified as a reduced dimer of DMPO. Whereas hydrazine-treated red blood cells, in the presence of DMPO, gave a nitroxide spin adduct which was identified as the hydroxyl radical spin adduct of DMPO, 5,5-dimethyl-1-pyrrolidino-1-oxyl (DMPO-OH). The reaction of AcPhHZ with oxyhaemoglobin, in the presence of DMPO, gave DMPO-OH, the phenyl radical spin adduct of DMPO, 5,5-dimethyl-2-phenylpyrrolidino-1-oxyl (DMPO-Ph) and an oxidised derivative of DMPO, 5,5-dimethyl-2-pyrrolidone-1-oxyl (DMPOX). The amounts of DMPO-Ph, DMPO-OH and DMPOX observed depended on the 1-acetyl-2-phenyl-hydrazine/oxyhaemoglobin concentration ratio; DMPOX replaced DMPO-OH as the concentration of AcPhHZ was decreased. DMPOX production has been previously associated with the production of highly oxidised haem iron-oxygen intermediates. AcPhHZ treated red blood cells gave DMPO-Ph and DMPO-OH spin adducts in the presence of DMPO. DMPO had little to no effect on the rate of oxygen consumption by oxyhaemoglobin with hydrazine and AcPhHZ. Moreover, the rate of oxyhaemoglobin oxidation induced by hydrazine, was not decreased by DMPO whereas the rate of oxyhaemoglobin oxidation induced by AcPhHZ was decreased approx. 40% by DMPO. DMPO (10 mM) gave a small decrease in haemolysis and lipid peroxidation induced by 1 mM hydrazine and AcPhHZ in a 1% suspension of red blood cells.

Quantitative determination of propildazine in rat plasma by gas-liquid chromatography

A gas-liquid chromatographic method for the evaluation of the new anti-hypertensive drug propildazine (ISF 2123) in rat plasma is described. The procedure involves separation of the drug from plasma by cation-exchange chromatography, subsequent acylation of the dried eluate with heptafluorobutyric anhydride and quantitation with electron-capture detection. Propildazine can be determined in concentrations down to ca. 0.4 microgram/ml.

Further studies on the metabolism of carbidopa, (minus)-L-alpha-hydrazino-3,4-dihydroxy-alpha-methylbenzenepropanoic acid monohydrate, in the human, Rhesus monkey, dog, and rat

Major urinary metabolites of carbidopa have been identified. Estimates were made based on the recovery or radio activity or by glc analysis of pooled urine of the amounts of the urinary metabolites II (2-methyl-3'-methoxy-4'-hydroxyphenylpropionic acid), III (2-methyl-3,4-dihydroxyphenylpropionic acid), IV (3,4-dihydroxyphenylacetone), V [2-methyl-3-(3'-methoxy-4'-hydroxyphenyl)lactic acid], VI [2-methyl-3-(3',4-dihydroxyphenyl)lactic acid], and VII (3-hydroxy-alpha-methylphenylpropionic acid). Metabolite II represented similar to 10% of the urinary radioactivity in both man and monkey and 16% in the dog. Metabolite III represented 10, 17, and 19% of the urinary radioactivity in man, monkey, and dog. Metabolite IV represented smaller than 5% of the urinary radioactivity in human and dog. Metabolite VII represented similar to 10% of the urinary radioactivity in man and monkey. The corresponding figure for the rat was similar to 20%. In the dog, compounds V and VI represented smaller than 5% of the urinary radioactivity. It was concluded that the loss of the hydrazine functional group(probably as molecular nitrogen) represents the major metabolic pathway for carbidopa.