Ultra-Sensitive Quantification of Corticosteroids in Plasma Samples Using Selective Solid-Phase Extraction and Reversed-Phase Capillary High-Performance Liquid Chromatography/Tandem Mass Spectrometry

Development of a UPLC-ESI-MS/MS method for the determination of triamcinolone acetonide in human plasma and evaluation of its bioequivalence after a single intramuscular injection in healthy volunteers

Introduction: Triamcinolone acetonide (TA) is commonly used in the treatment of various inflammatory conditions. To ensure its efficacy and safety, it is important to accurately determine its concentration in human plasma and evaluate its bioequivalence. In this study, an efficient ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed for the quantification of TA in human plasma after a single intramuscular injection. The internal standard used in this method was cortisone acetate (CA). Methods: TA and CA were extracted from plasma using ethyl acetate and N-hexane (4:1, v/v), separated on a C18 reverse-phase column with a mobile phase of acetonitrile-water containing 1% formic acid (55:45, v/v), and analyzed by UPLC-ESI-MS/MS. Multiple-reaction monitoring was performed using the transitions m/z 435.4→397.3 for TA and m/z 403.4→163.1 for CA. Results: The developed UPLC-ESI-MS/MS method demonstrated linearity over a concentration range of 0.53-21.20 ng/mL, with a lower limit of quantification of 0.53 ng/mL. The intra- and inter-run precision values ranged from 3.007% to 9.960% and 3.528% to 11.26%, respectively. The intra- and inter-run accuracy ranges were -1.962% to -6.577% and -3.371% to 0.348%, respectively. The matrix effect, extraction recovery, and stability of TA all met the acceptance criteria recommended by the National Medical Products Administration (NMPA) for bioassays. In healthy volunteers who received a single intramuscular injection of 80 mg of either the test or reference formulation of TA, various pharmacokinetic parameters were determined. C _max was found to be 8.616 ± 1.232 and 8.285 ± 1.218 ng/mL for the test and reference formulations, respectively. T _max was approximately 1.833 ± 0.243 and 1.861 ± 0.230 h. The t _1/2 was calculated to be 181.249 ± 78.585 and 201.782 ± 83.551 h. AUC _0-720 was 835.642 ± 297.209 and 830.684 ± 331.168 ng h/mL, AUC _0-∞ was 991.859 ± 355.939 and 1018.665 ± 420.769 ng h/mL for the test and reference formulations, respectively. The average relative bioavailability of TA, determined using AUC _0-720, was 105.4 ± 26.9%. Bioequivalence was evaluated through variance analysis and a double unilateral test, and the 90% confidence intervals of AUC _0-720, C _max, and AUC _0-∞ were 92.8%-113.4%, 99.1%-109.1%, and 89.7%-110.9%, respectively (all p > 0.05). Discussion: These results met the bioequivalence criteria set by the NMPA, indicating that the developed UPLC-ESI-MS/MS method accurately determined TA concentrations in the plasma of healthy Chinese volunteers and that the test and reference formulations exhibited bioequivalence in these individuals.

Dose identification of triamcinolone acetonide for noninvasive pre-corneal administration in the treatment of posterior uveitis using a rapid, sensitive HPLC method with photodiode-array detector

Triamcinolone acetonide (TAA) is the drug of choice in the management of ocular inflammations due to its anti-inflammatory and immuno-suppressant activity. Available marketed formulations (Triesence, Trivaris, Kenalog) are in the suspension form recommended to be administered via intravitreal injection, which has many major complications. In the present study, we have designed and evaluated Hydroxypropyl-β-cyclodextrin (HP-β-CD),) based conventional formulations of TAA (aqueous suspensions) with different dose strengths to identify the dose strength required for achieving the effective concentrations in vitreous humor following pre-corneal administration of the formulations. Ocular pharmacokinetic studies of conventional formulations of triamcinolone acetonide (TAA) with different dose strengths (1 mg/30µL, 2 mg/30µL, 4 mg/30µL) were performed to identify the dose strength required to produce effective concentrations of TAA in the aqueous and vitreous humor. A rapid, sensitive, selective, accurate and precise bioanalytical method utilizing a small sampling volume (<45 µL) was developed and validated for quantification of TAA in the samples obtained from the ocular pharmacokinetic studies. Aqueous suspensions of TAA with 20% HP-β-CD produced time course profiles in the aqueous humor at all the dose strengths. However, measurable concentrations and time course of TAA in vitreous humor were achieved only with 4 mg/30µL dose strength.

Evaluation of OptiFlow™-MS/MS for bioanalysis of pharmaceutical drugs and metabolites

Aim: Microflow tandem mass spectrometry-based methods have been proposed as options to improve sensitivity and selectivity while improving sample utility and solvent consumption. Here, we evaluate a newly introduced microflow source, OptiFlow™, for quantitative performance. Results/methodology: We performed a comparison of the OptiFlow and IonDrive™ sources, respectively, on the same triple quadrupole mass spectrometer. The comparison used a neat cocktail of commercially available drugs and extracted plasma samples monitoring midazolam and alprazolam metabolites. Microflow produced a 2–4× signal increase for the neat drug cocktail and a 5–10× increase for extracted plasma samples. Conclusion: The OptiFlow method consistently gave increased signal response relative to the IonDrive method and enabled a better lower limit of quantitation for defining phamacokinetics.

Sensitive, High-Throughput, and Robust Trapping-Micro-LC-MS Strategy for the Quantification of Biomarkers and Antibody Biotherapeutics

For LC-MS-based targeted quantification of biotherapeutics and biomarkers in clinical and pharmaceutical environments, high sensitivity, high throughput, and excellent robustness are all essential but remain challenging. For example, though nano-LC-MS has been employed to enhance analytical sensitivity, it falls short because of its low loading capacity, poor throughput, and low operational robustness. Furthermore, high chemical noise in protein bioanalysis typically limits the sensitivity. Here we describe a novel trapping-micro-LC-MS (T-μLC-MS) strategy for targeted protein bioanalysis, which achieves high sensitivity with exceptional robustness and high throughput. A rapid, high-capacity trapping of biological samples is followed by μLC-MS analysis; dynamic sample trapping and cleanup are performed using pH, column chemistry, and fluid mechanics separate from the μLC-MS analysis, enabling orthogonality, which contributes to the reduction of chemical noise and thus results in improved sensitivity. Typically, the selective-trapping and -delivery approach strategically removes >85% of the matrix peptides and detrimental components, markedly enhancing sensitivity, throughput, and operational robustness, and narrow-window-isolation selected-reaction monitoring further improves the signal-to-noise ratio. In addition, unique LC-hardware setups and flow approaches eliminate gradient shock and achieve effective peak compression, enabling highly sensitive analyses of plasma or tissue samples without band broadening. In this study, the quantification of 10 biotherapeutics and biomarkers in plasma and tissues was employed for method development. As observed, a significant sensitivity gain (up to 25-fold) compared with that of conventional LC-MS was achieved, although the average run time was only 8 min/sample. No appreciable peak deterioration or loss of sensitivity was observed after >1500 injections of tissue and plasma samples. The developed method enabled, for the first time, ultrasensitive LC-MS quantification of low levels of a monoclonal antibody and antigen in a tumor and cardiac troponin I in plasma after brief cardiac ischemia. This strategy is valuable when highly sensitive protein quantification in large sample sets is required, as is often the case in typical biomarker validation and pharmaceutical investigations of antibody therapeutics.

Selective separation and determination of glucocorticoids in cosmetics using dual-template magnetic molecularly imprinted polymers and HPLC

Molecularly imprinting polymers (MIPs) are typically prepared using a single template molecule, which allows selective separation and enrichment of only one target analyte. It is not suitable for determination of complex real samples containing multiple analytes. In order to expand the practical application of imprinted polymers, novel dual-template magnetic molecularly imprinted polymers (MMIPs) were synthesized by surface polymerization using hydrocortisone and dexamethasone as the dual-template molecules in this study. The dual-template MMIPs were prepared by copolymerization on the surface of Fe₃O₄@ SiO₂-NH₂, the template molecules, the functional monomer acrylamide (AM), the cross-linking agent ethylene glycol dimethacrylate (EGDMA), and the initiator 2,2-azobisisobutyronitrile. The morphology, magnetic properties and adsorption characteristics of the obtained dual-template MMIPs were studied by field emission scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and vibrating sample magnetometry, and re-binding experiments. The results indicated that dual-template MMIPs had uniform particle size, strong magnetic properties, high thermal stability, and good mass transfer rate. To investigate the selectivity of dual-template MMIPs, the template molecules were mixed along with their structural analogs. The dual-template MMIPs revealed a significantly higher adsorption amount for the template molecule than its structure analog. The dual-template MMIPs can be used for the enrichment and determination of hydrocortisone and dexamethasone in cosmetic products with the recoveries of spiked cosmetic samples ranging from 86.8-107.5% and 91.2-104.3%, respectively. The relative standard deviation (RSD) for hydrocortisone was <2.89%, and RSD for dexamethasone was <2.62%.

A remodeled protein arginine methyltransferase 1 (PRMT1) generates symmetric dimethylarginine

Protein arginine methylation is emerging as a significant post-translational modification involved in various cell processes and human diseases. As the major arginine methylation enzyme, protein arginine methyltransferase 1 (PRMT1) strictly generates monomethylarginine and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA). The two types of dimethylarginines can lead to distinct biological outputs, as highlighted in the PRMT-dependent epigenetic control of transcription. However, it remains unclear how PRMT1 product specificity is regulated. We discovered that a single amino acid mutation (Met-48 to Phe) in the PRMT1 active site enables PRMT1 to generate both ADMA and SDMA. Due to the limited amount of SDMA formed, we carried out quantum mechanical calculations to determine the free energies of activation of ADMA and SDMA synthesis. Our results indicate that the higher energy barrier of SDMA formation (ΔΔG(‡) = 3.2 kcal/mol as compared with ADMA) may explain the small amount of SDMA generated by M48F-PRMT1. Our study reveals unique energetic challenges for SDMA-forming methyltransferases and highlights the exquisite control of product formation by active site residues in the PRMTs.

Validated assay for the simultaneous determination of cortisol and budesonide in human plasma using ultra high performance liquid chromatography-tandem mass spectrometry

An ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC/MS/MS) method was developed and validated for the quantification of cortisol and budesonide in human plasma. Charcoal stripped human plasma was used as the blank matrix during validation. Cortisol, budesonide, and dexamethasone (internal standard) were extracted from human plasma with methyl-tert-butyl ether, and the chromatographic separation of the peaks was achieved using a Waters Acquity UPLC BEH C18, 1.7 μm, 2.1 mm × 50 mm column with a run time of 4.0 min. Cortisol, budesonide, and dexamethasone were monitored at the total ion current of their respective multiple reaction monitoring transition signals. The UHPLC/MS/MS system consisted of an Agilent 1290 Infinity ultra high performance liquid chromatograph coupled with an AB Sciex Qtrap(®) 5500 hybrid linear ion-trap triple quadrupole mass spectrometer. The method was validated for accuracy, precision, linearity, range, selectivity, lower limit of quantification (LLOQ), recovery, matrix effect, dilution integrity, and evaluation of carry-over. All validation parameters met the acceptance criteria according to regulatory guidelines. The LLOQ was 1.0 ng/mL for both compounds requiring 100 μL of sample. To our knowledge, this is the first validated LC/MS/MS method for the simultaneous quantitative analysis of cortisol and budesonide in human plasma. The method was applied successfully in a clinical investigation of the impact of nasally administered Pulmicort (budesonide) on the hypothalamic-pituitary-adrenal axis of patients with chronic rhinosinusitis.

Simultaneous quantification of 22R and 22S epimers of budesonide in human plasma by ultra-high-performance liquid chromatography-tandem mass spectrometry: application in a stereoselective pharmacokinetic study

Budesonide (BUD) is used as a mixture of 22R and 22S epimers for the topical treatment of asthma, rhinitis, and inflammatory bowel disease. To study stereoselectivity in the pharmacokinetics of each epimer, we developed a stereoselective and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method for the quantitative determination of 22R and 22S epimers of BUD in human plasma. The epimers of BUD were extracted from plasma using n-hexane/dichloromethane/isopropanol (2:1:0.1, v/v/v) under alkaline conditions. Baseline separation was obtained within 7min on an Acquity UPLC BEH C18 (50mm×2.1mm, 1.7μm) column using an isocratic mobile phase consisting of acetonitrile/5mM ammonium acetate/acetic acid (29:71:0.142, v/v/v) at a flow rate of 0.7mL/min. Mass spectrometric detection was performed in a multiple reaction monitoring mode using the m/z 489→357 transition for BUD epimers and the m/z 497→357 transition for the internal standard d8-BUD epimers. Calibration curves were linear over the concentration ranges of 5.0-500 and 5.0-3000pg/mL for 22R-BUD and 22S-BUD, respectively. The lower limit of quantification was 5.0pg/mL for both epimers. The method was successfully applied in a pharmacokinetic study of BUD controlled-release capsules in humans. Consistent differences in the pharmacokinetics of the 22R and 22S epimers were observed, the AUC(0-∞) of 22S-BUD was approximately six times higher than that of 22R-BUD, and the 22S-/22R-BUD ratio of total body clearance was 0.17.

Simultaneous determination of montelukast as sparing therapy with some inhaled corticosteroids in plasma of asthmatic patients

Montelukast (MKST) is a leukotriene receptor antagonist that has been concomitantly used with inhaled corticosteroids (ICS) for its steroid-sparing effect in the long-term management of asthma. However, the simultaneous determination of MKST, when used as ICS tapering therapy, with ICS in human plasma has not yet been reported. A fast and efficient reversed phase monolith HPLC method was developed for simultaneous determination of MKST with some ICS in plasma of asthmatic patients. The separation was achieved on monolith reversed phase column by isocratic mode at a flow rate of 1.0 ml min(-1) using a mobile phase consisted of a mixture of acetonitrile and 10mM phosphate buffer adjusted to pH 3.5 (40:60, v/v) and detected at 240 nm. Betamethasone dipropionate (BDP) was used as the internal standard. All the studied ICS and MKST were efficiently separated within less than 6 min. The obtained linearity range for the developed HPLC method was 0.03-10 μg ml(-1) with correlation coefficients>0.9995 and the detection limits were 0.009-0.016 μg ml(-1) in plasma for all the studied drugs. The method was validated in agreement with the requirements of US-FDA guideline and was recommended for the target applications. The method is valuable for investigations concerned with the effective tapering of ICS therapy with MKST in patients with chronic asthma in clinical practice without loss of asthma control.

Metabolite profiling identified methylerythritol cyclodiphosphate efflux as a limiting step in microbial isoprenoid production

Isoprenoids are natural products that are all derived from isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). These precursors are synthesized either by the mevalonate (MVA) pathway or the 1-Deoxy-D-Xylulose 5-Phosphate (DXP) pathway. Metabolic engineering of microbes has enabled overproduction of various isoprenoid products from the DXP pathway including lycopene, artemisinic acid, taxadiene and levopimaradiene. To date, there is no method to accurately measure all the DXP metabolic intermediates simultaneously so as to enable the identification of potential flux limiting steps. In this study, a solid phase extraction coupled with ultra performance liquid chromatography mass spectrometry (SPE UPLC-MS) method was developed. This method was used to measure the DXP intermediates in genetically engineered E. coli. Unexpectedly, methylerythritol cyclodiphosphate (MEC) was found to efflux when certain enzymes of the pathway were over-expressed, demonstrating the existence of a novel competing pathway branch in the DXP metabolism. Guided by these findings, ispG was overexpressed and was found to effectively reduce the efflux of MEC inside the cells, resulting in a significant increase in downstream isoprenoid production. This study demonstrated the necessity to quantify metabolites enabling the identification of a hitherto unrecognized pathway and provided useful insights into rational design in metabolic engineering.

Nano-scale liquid chromatography/mass spectrometry and on-the-fly orthogonal array optimization for quantification of therapeutic monoclonal antibodies and the application in preclinical analysis

Therapeutic monoclonal antibodies (mAbs) constitute a group of highly effective agents for treating various refractory diseases. Nonetheless it is challenging to achieve selective and accurate quantification of mAb in pharmaceutical matrices, which is required by PK studies. Liquid chromatography/mass spectrometry under selected reaction monitoring mode (LC/SRM-MS) is emerging as an attractive alternative to immunoassays because of the high specificity and multiplexing capacity it provides, but may fall short in terms of sensitivity, reliability and quantitative accuracy. Moreover, the strategy for optimization of the MS conditions for many candidates of signature peptides (SP) and the selection of the optimal SP for quantification remains elusive. In this study, we employed a suite of technical advances to overcome these difficulties, which include: (i) a nano-LC/SRM-MS approach to achieve high analytical sensitivity, (ii) a high-resolution nano-LC/LTQ/Orbitrap for confident identification of candidate peptides, (iii) an on-the-fly orthogonal array optimization (OAO) method for the high-throughput, accurate and reproducible optimization for numerous candidate peptides in a single LC/MS run without using synthesized peptides, (iv) a comprehensive evaluation of stability of candidates in matrix using the optimized SRM parameters, (v) the use of two unique SP for quantification of one mAb to gauge possible degradation/modification in biological system and thus enhancing data reliability (e.g. rejection of data if the deviation between the two SP is greater than 25%) and (vi) the utilization of purified target protein as the calibrator to eliminate the risk of severe negative biases that could occur when a synthesized peptide is used as calibrator. To show a proof of concept, this strategy is applied in the quantification of cT84.66, a chimeric, anti-CEA antibody, in preclinical mouse models. A low detection limit of the mAb down to 3.2 ng/mL was achieved, which is substantially more sensitive than established immunoassay methods for anti-CEA antibodies. The quantitative method showed good linearity (within the range of 12.9 ng/mL to 32.3 μg/mL in plasma), accuracy and precision. Additionally, the ultra-low sample consumption (2 μL plasma per preparation) permits the acquisition of an entire set of time course data from the same mouse, which represents a prominent advantage for PK study using small-animal models. The developed method enabled an accurate PK investigation of cT84.66 in mice following intravenous and subcutaneous administrations at relatively low doses over an extended period of time. The strategy employed in this study can be easily adapted to the sensitive and accurate analysis of other mAb and therapeutic proteins.

Discovery pharmacokinetic studies in mice using serial microsampling, dried blood spots and microbore LC–MS/MS

Background: Initial pharmacokinetic (PK) studies of discovery compounds are conducted in mice to demonstrate exposure prior to conducting efficacy studies. PK information obtained from a single mouse by serial blood microsampling, dried blood spot collection and analyses using microbore (1 mm internal diameter column) LC–MS/MS is presented. Ex vivo blood to plasma concentration ratios (BPRs) from mouse PK studies were compared with in vitro BPRs for 15 compounds. Results: Two compounds were orally dosed and blood was collected at time points via serial blood sampling. The calculated PK parameters (AUC, Tmax and Cmax) were comparable across liquid blood, dried blood spot and plasma matrices. The BPR results from both methods were comparable. Conclusion: Serial blood microsampling has led to reduced animal and compound usage with improved PK data. Ex vivo BPR is suitable in a discovery setting. Microbore LC–MS/MS is well suited in instances where sample volume is limited, and enables faster analyses, reduced solvent use, and less frequent MS source cleaning.

High-throughput method development for sensitive, accurate, and reproducible quantification of therapeutic monoclonal antibodies in tissues using orthogonal array optimization and nano liquid chromatography/selected reaction monitoring mass spectrometry

Although liquid chromatography/mass spectrometry using selected reaction monitoring (LC/SRM-MS) holds great promise for targeted protein analysis, quantification of therapeutic monoclonal antibody (mAb) in tissues represents a daunting challenge due to the extremely low tissue levels, complexity of tissue matrixes, and the absence of an efficient strategy to develop an optimal LC/SRM-MS method. Here we describe a high-throughput, streamlined strategy for the development of sensitive, selective, and reliable quantitative methods of mAb in tissue matrixes. A sensitive nano-LC/nanospray-MS method was employed to achieve a low lower limit of quantification (LOQ). For selection of signature peptides (SP), the SP candidates were identified by a high-resolution Orbitrap and then optimal SRM conditions for each candidate were obtained using a high-throughput, on-the-fly orthogonal array optimization (OAO) strategy, which is capable of optimizing a large set of SP candidates within a single nano-LC/SRM-MS run. Using the optimized conditions, the candidates were experimentally evaluated for both sensitivity and stability in the target matrixes, and SP selection was based on the results of the evaluation. Two unique SP, respectively from the light and heavy chain, were chosen for quantification of each mAb. The use of two SP improves the quantitative reliability by gauging possible degradation/modification of the mAb. Standard mAb proteins with verified purities were utilized for calibration curves, to prevent the quantitative biases that may otherwise occur when synthesized peptides were used as calibrators. We showed a proof of concept by rapidly developing sensitive nano-LC/SRM-MS methods for quantifying two mAb (8c2 and cT84.66) in multiple preclinical tissues. High sensitivity was achieved for both mAb with LOQ ranged from 0.156 to 0.312 μg/g across different tissues, and the overall procedure showed a wide dynamic range (≥500-fold) and good accuracy [relative error (RE) < 18.8%] and precision [interbatch relative standard deviation (RSD) < 18.1%, intrabatch RSD < 17.2%]. The quantitative method was applied to a comprehensive investigation of the steady-state tissue distribution of 8c2 in wild-type mice versus those deficient in FcRn α-chain, FcγIIb, and FcγRI/FcγRIII, following a chronic dosing regimen. This work represents the first extensive quantification of mAb in tissues by an LC/MS-based method.

Systemic isotretinoin therapy normalizes exaggerated TLR-2-mediated innate immune responses in acne patients

Retinoids are used in the treatment of inflammatory skin diseases and malignancies, but studies characterizing the in vivo actions of these drugs in humans are lacking. Isotretinoin is a pro-drug for all-trans retinoic acid that can induce long-term remissions of acne; however, its complete mechanism of action is unknown. We hypothesized that isotretinoin induces remission of acne by normalizing the innate immune response to the commensal bacterium P. acnes. Compared to normal subjects, peripheral blood monocytes from acne patients expressed significantly higher levels of TLR-2 and exhibited significantly greater induction of TLR-2 expression following P. acnes stimulation. Treatment of patients with isotretinoin significantly decreased monocyte TLR-2 expression and subsequent inflammatory cytokine response to P. acnes by one week of therapy. This effect was sustained six months following cessation of therapy, indicating that TLR-2 modulation may be involved in the durable therapeutic response to isotretinoin. This study demonstrates that isotretinoin exerts immunomodulatory effects in patients and sheds light on a potential mechanism for its long-term effects in acne. The modulation of TLR-2 expression on monocytes has important implications in other inflammatory disorders characterized by TLR-2 dysregulation.

Combinatorial peptide ligand library treatment followed by a dual-enzyme, dual-activation approach on a nanoflow liquid chromatography/orbitrap/electron transfer dissociation system for comprehensive analysis of swine plasma proteome

The plasma proteome holds enormous clinical potential, yet an in-depth analysis of the plasma proteome remains a daunting challenge due to its high complexity and the extremely wide dynamic range in protein concentrations. Furthermore, existing antibody-based approaches for depleting high-abundance proteins are not adaptable to the analysis of the animal plasma proteome, which is often essential for experimental pathology/pharmacology. Here we describe a highly comprehensive method for the investigation of the animal plasma proteome which employs an optimized combinatorial peptide ligand library (CPLL) treatment to reduce the protein concentration dynamic range and a dual-enzyme, dual-activation strategy to achieve high proteomic coverage. The CPLL treatment enriched the lower abundance proteins by >100-fold when the samples were loaded in moderately denaturing conditions with multiple loading-washing cycles. The native and the CPLL-treated plasma were digested in parallel by two enzymes (trypsin and GluC) carrying orthogonal specificities. By performing this differential proteolysis, the proteome coverage is improved where peptides produced by only one enzyme are poorly detectable. Digests were fractionated with high-resolution strong cation exchange chromatography and then resolved on a long, heated nano liquid chromatography column. MS analysis was performed on a linear triple quadrupole/orbitrap with two complementary activation methods (collisionally induced dissociation (CID) and electron transfer dissociation). We applied this optimized strategy to investigate the plasma proteome from swine, a prominent animal model for cardiovascular diseases (CVDs). This large-scale analysis results in identification of a total of 3421 unique proteins, spanning a concentration range of 9-10 orders of magnitude. The proteins were identified under a set of commonly accepted criteria, including a precursor mass error of <15 ppm, Xcorr cutoffs, and ≥2 unique peptides at a peptide probability of ≥95% and a protein probability of ≥99%, and the peptide false-positive rate of the data set was 1.8% as estimated by searching the reversed database. CPLL treatment resulted in 55% more identified proteins over those from native plasma; moreover, compared with using only trypsin and CID, the dual-enzyme/activation approach enabled the identification of 2.6-fold more proteins and substantially higher sequence coverage for most individual proteins. Further analysis revealed 657 proteins as significantly associated with CVDs (p < 0.05), which constitute five CVD-related pathways. This study represents the first in-depth investigation of a nonhuman plasma proteome, and the strategy developed here is adaptable to the comprehensive analysis of other highly complex proteomes.

Determination of triamcinolone in human plasma by a sensitive HPLC-ESI-MS/MS method: application for a pharmacokinetic study using nasal spray formulation

A liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method for the quantitation of triamcinolone in human plasma after nasal spray application was developed and validated. Betamethasone was used as internal standard (IS). The analytes were extracted by a liquid-liquid procedure and separated on a Zorbax Eclipse XDB C(18) column with a mobile phase composed of 2 mM aqueous ammonium acetate pH 3.2 and acetonitrile (55:45). Selected reaction monitoring was performed using the transitions m/z 435 → 415 and m/z 393 → 373 to quantify triamcinolone acetonide and betamethasone, respectively. Calibration curve was constructed over the range of 20-2000 pg/ml for triamcinolone acetonide. The lower limit of quantitation was 20 pg/ml. The mean RSD values were 4.6% and 5.7% for the intra-run and inter-run precision, respectively. The mean accuracy value was 98.5% and a recovery rate corresponding to 97.5% was achieved. No matrix effect was detected in the samples. The validated method was successfully applied to determine the plasma concentrations of triamcinolone acetonide in healthy volunteers, in a pharmacokinetic study with nasal spray formulation.

Simultaneous HPLC analysis of triamcinolone acetonide and budesonide in microdialysate and rat plasma: application to a pharmacokinetic study

A specific and reliable HPLC-PDA method for the quantitative determination of triamcinolone acetonide, budesonide and fluticasone propionate (as internal standards) in small volumes of microdialysate and rat plasma was developed. An efficient solid-phase extraction (SPE) procedure for plasma samples yielded extremely clean extracts with overall recovery of 104.3% and 95.7% for triamcinolone acetonide (TA) and fluticasone propionate, respectively. Plasma extracts obtained after SPE and microdialysis samples were directly injected on a C18 column to separation. The method has been validated with good linearity, sensitivity, specificity and high accuracy (RE -5.28% to 9.14%) and precision (CV 0.50% to 6.62%) on both matrices. In stability studies, TA and budesonide were stable during storage and assay procedures. The method was applied to a pharmacokinetic study in rodents using microdialysis to determine protein unbound TA concentrations in blood and muscle.

A rapid, reproducible, on-the-fly orthogonal array optimization method for targeted protein quantification by LC/MS and its application for accurate and sensitive quantification of carbonyl reductases in human liver

Liquid chromatography (LC)/mass spectrometry (MS) in selected-reactions-monitoring (SRM) mode provides a powerful tool for targeted protein quantification. However, efficient, high-throughput strategies for proper selection of signature peptides (SP) for protein quantification and accurate optimization of their SRM conditions remain elusive. Here we describe an on-the-fly, orthogonal array optimization (OAO) approach that enables rapid, comprehensive, and reproducible SRM optimization of a large number of candidate peptides in a single nanoflow-LC/MS run. With the optimized conditions, many peptide candidates can be evaluated in biological matrixes for selection of the final SP. The OAO strategy employs a systematic experimental design that strategically varies product ions, declustering energy, and collision energy in a cycle of 25 consecutive SRM trials, which accurately reveals the effects of these factors on the signal-to-noise ratio of a candidate peptide and optimizes each. As proof of concept, we developed a highly sensitive, accurate, and reproducible method for the quantification of carbonyl reductases CBR1 and CBR3 in human liver. Candidate peptides were identified by nano-LC/LTQ/Orbitrap, filtered using a stringent set of criteria, and subjected to OAO. After evaluating both sensitivity and stability of the candidates, two SP were selected for quantification of each protein. As a result of the accurate OAO of assay conditions, sensitivities of 80 and 110 amol were achieved for CBR1 and CBR3, respectively. The method was validated and used to quantify the CBRs in 33 human liver samples. The mean level of CBR1 was 93.4 +/- 49.7 (range: 26.2-241) ppm of total protein, and of CBR3 was 7.69 +/- 4.38 (range: 1.26-17.9) ppm. Key observations of this study: (i) evaluation of peptide stability in the target matrix is essential for final selection of the SP; (ii) utilization of two unique SP contributes to high reliability of target protein quantification; (iii) it is beneficial to construct calibration curves using standard proteins of verified concentrations to avoid severe biases that may result if synthesized peptides alone are used. Overall, the OAO method is versatile and adaptable to high-throughput quantification of validated biomarkers identified by proteomic discovery experiments.

Proteomic expression profiling of Haemophilus influenzae grown in pooled human sputum from adults with chronic obstructive pulmonary disease reveal antioxidant and stress responses

Background

Nontypeable Haemophilus influenzae colonizes and infects the airways of adults with chronic obstructive pulmonary disease, the fourth most common cause of death worldwide.Thus, H. influenzae, an exclusively human pathogen, has adapted to survive in the hostile environment of the human airways.To characterize proteins expressed by H. influenzae in the airways, a prototype strain was grown in pooled human sputum to simulate conditions in the human respiratory tract.The proteins from whole bacterial cell lysates were solubilized with a strong buffer and then quantitatively cleaned with an optimized precipitation/on-pellet enzymatic digestion procedure.Proteomic profiling was accomplished by Nano-flow liquid chromatography/mass spectroscopy with low void volume and high separation efficiency with a shallow, long gradient.

Results

A total of 1402 proteins were identified with high confidence, including 170 proteins that were encoded by genes that are annotated as conserved hypothetical proteins.Thirty-one proteins were present in greater abundance in sputum-grown conditions at a ratio of > 1.5 compared to chemically defined media.These included 8 anti-oxidant and 5 stress-related proteins, suggesting that expression of antioxidant activity and stress responses is important for survival in the airways.Four proteins involved in uptake of divalent anions and 9 proteins that function in uptake of various molecules were present in greater abundance in sputum-grown conditions.

Conclusions

Proteomic expression profiling of H. influenzae grown in pooled human sputum revealed increased expression of antioxidant, stress-response proteins and cofactor and nutrient uptake systems compared to media grown cells.These observations suggest that H. influenzae adapts to the oxidative and nutritionally limited conditions of the airways in adults with chronic obstructive pulmonary disease by increasing expression of molecules necessary for survival in these conditions.

Database-dependent metabolite profiling focused on steroid and fatty acid derivatives using high-temperature gas chromatography-mass spectrometry

BACKGROUND

A database-dependent gas chromatography-mass spectrometry (GC-MS) based approach was developed for non-targeted metabolite profiling, focusing on 232 steroids, 24 fatty acids, 10 eicosanoids, 10 cannabinoids and 22 steroid-fatty acid esters in biological specimens.

METHODS

This method, used to search for potent biomarkers in lipid metabolism, included MS based analysis combined with high-temperature gas chromatographic (HTGC) separation of biological metabolites, statistical clustering and an in-house database (DB) searching.

RESULTS

The HTGC technique showed better detectability of high lipophilic compounds, particularly steroid-fatty acid esters, which generally have poor chromatographic properties on a conventional GC column. The in-house DB search consisted of the retention index and mass spectrum corresponding to each compound selected. The method was applied to tissue samples obtained from cardiac hypertrophy-induced mice. Increased levels of palmitic, linoleic, oleic, and stearic acids and cholesterol were detected and identified.

CONCLUSIONS

This data-dependent non-targeted metabolite profiling technique could be more effective in biomarker studies associated with the steroid and lipid metabolism than commercially available DBs.

Characterization of ecdysteroids in Drosophila melanogaster by enzyme immunoassay and nano-liquid chromatography-tandem mass spectrometry

Ecdysteroids are polyhydroxylated steroids that function as molting hormones in insects. 20-Hydroxyecdysone (a 27C-ecdysteroid) is classically considered as the major steroid hormone of Drosophilamelanogaster, but this insect also contains 28C-ecdysteroids. This arises from both the use of several dietary sterols as precursors for the synthesis of its steroid hormones, and its inability to dealkylate the 28C-phytosterols to produce cholesterol. The nature of Drosophila ecdysteroids has been re-investigated using both high-performance liquid chromatography coupled to enzyme immunoassay and a particularly sensitive nano-liquid chromatography-mass spectrometry methodology, while taking advantage of recently available ecdysteroid standards isolated from plants. In vitro incubations of the larval steroidogenic organ, the ring-gland, reveals the synthesis of ecdysone, 20-deoxy-makisterone A and a third less polar compound identified as the 24-epimer of the latter, while wandering larvae contain the three corresponding 20-hydroxylated ecdysteroids. This pattern results from the simultaneous use of higher plant sterols (from maize) and fungal sterols (from yeast). The physiological relevance of all these ecdysteroids, which display different affinities to the ecdysteroid receptors, is still a matter of debate.

Simultaneous determination of corticosteroids, androgens, and progesterone in river water by liquid chromatography-tandem mass spectrometry

The assessment of steroidal hormones in the environment requires sensitive and selective analytical techniques suitable for sample matrices. This paper reports a simple method to analyze simultaneously six corticosteroids (triamcinolone, cortisol, dexamethasone, flumethasone, prednisolone, triamcinolone acetonide), four androgens (boldenone, epitestosterone, methyltestosterone, nortestosterone), and progesterone in river and drinking water sources. The developed method is based on a single solid-phase extraction (SPE) followed by liquid chromatography/tandem mass spectrometry (LC-MS/MS) with atmospheric pressure chemical ionization (APCI). The main advantage of this method over other methods includes the use of a single SPE with a low volume cartridge for sample preparation, separation of steroids on alkyl-amide stationary phase with no matrix interferences by LC-MS/MS analysis, and simultaneous analysis of more than two groups of steroids. The method was characterized by generally good performance, analyzing three groups of steroids using 100 and 1000mL samples with average recovery ranges of 80-109% and 68-126%, respectively at a level of 1ngL(-1). The limit of detection (LOD) ranged from 0.06 to 0.2 and 0.01-0.21ngL(-1) for 100mL and 1000mL samples volumes, respectively. Sixty samples of Danube River and drinking water sources from different regions of Hungary were collected to analyze target steroids in two sampling periods in 2008 and 2009. Steroids, except cortisol, dexamethasone, flumethasone, prednisolone, epitestosterone and progesterone were below detection limits. Endogenous steroids (cortisol, epitestosterone, progesterone) were present in the concentration range of 0.08-2.67ngL(-1) while synthetic corticosteroids (dexamethasone, flumethasone, and prednisolone) varied from 0.064 to 1.43ngL(-1). Steroids were present in river water, except progesterone, which was present only in ground water. Levels of steroids are compared with other rivers in the world and were briefly discussed.

Comparison of electron capture-atmospheric pressure chemical ionization and electrospray ionization for the analysis of gambogic acid and its main circulating metabolite in dog plasma

Gambogic acid (GA), a promising anticancer candidate, is a polyprenylated xanthone abundant in the resin of Garcinia morella and Garcinia hanburyi. Electron capture-atmospheric pressure chemical ionization (EC- APCI) and electrospray ionization (ESI) techniques, both in the negative ion mode, were evaluated regarding ionization, fragmentation patterns and sensitivity for simultaneous liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of GA and its main circulating metabolite, 10-hydroxygambogic acid (10-OHGA) in dog plasma. Both analytes underwent extensive in-source fragmentation in EC-APCI, which was not desirable for reliable quantification of these analytes, whereas the substitution of ESI for EC-APCI almost eliminated the source instability of both analytes. Negative ion ESI was, therefore, chosen for the development of an LC-MS/MS method for simultaneous determination of these analytes. After protein precipitation by acetonitrile, all analytes were separated on a Luna C18 HST column (50 x 2.0 mm i.d., 2.5 microm) with a mobile phase of 20 mmol L(-1) ammonium acetate water solution containing 0.2% acetic acid:acetonitrile (18:82, v/v). The detection was performed on a tandem mass spectrometer using selective reaction monitoring mode. Calibration curves were linear over the range of 10-6000 ng mL(-1) for GA and 3-2000 ng mL(-1) for 10-OHGA. The method was successfully applied to the pharmacokinetics study of GA injection in six beagle dogs.

Systemic absorption of triamcinolone acetonide after posterior sub-Tenon injection

PURPOSE

To study systemic absorption of triamcinolone acetonide (TA) after posterior sub-Tenon injection.

DESIGN

Prospective, interventional case series.

METHODS

The study was conducted in a tertiary care teaching hospital on 35 eyes in which posterior sub-Tenon injection of 40 mg TA was administered after conventional extracapsular cataract extraction. Patients who had received any systemic steroid over 6 weeks preceding the period of study or had inflammatory ocular conditions were excluded. Serum TA levels were estimated by high-performance liquid chromatography at 1, 2, 3, 24, and 48 hours and 1, 2, and 6 weeks after injection.

RESULTS

Significant levels of the drug were detected in 45.71% of samples (mean serum levels, 6.94 +/- 8.98 ng/ml; P < .001) at 1 hour after sub-Tenon injection, in 85.71% of samples (mean serum levels, 21.83 +/- 12.92 ng/ml; P < .001) at 2 hours after injection, in 100% of samples (mean serum levels, 47.14 +/- 12.20 ng/ml; P < .001) at 3 hours after injection, in 100% of samples (mean serum levels, 35.49 +/- 13.79 ng/ml; P < .001) at 24 hours after injection, in 62.86% of samples (mean serum levels, 10.46 +/- 10.69 ng/ml; P < .001) at 48 hours after injection, and in 28.57% of samples (mean serum levels, 3.74 +/- 6.45 ng/ml; P = .002) at 1 week after injection. The drug was not detected in any of the samples obtained 2 weeks and 6 weeks later.

CONCLUSIONS

Posterior sub-Tenon injection of 40 mg TA adds statistically significant quantities to physiologic concentration of corticosteroids in peripheral blood. This may be detrimental for patients having certain metabolic diseases like diabetes and preferably should be avoided or administered with caution.

Quantitative metabolic profiling of 21 endogenous corticosteroids in urine by liquid chromatography-triple quadrupole-mass spectrometry

Since corticosteroid metabolism may be affected by disease states, the accurate and precise measurement of endogenous corticosteroids in urine is necessary to understand their biochemical roles. An efficient quantitative profiling of 21 endogenous corticosteroids in urine has been validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After enzymatic hydrolysis with beta-glucuronidase, samples were purified using a solid-phase extraction cartridge and then separated through a sub-2 microm particle C18 column (2.1 mm x 50 mm, 1.9 microm) and quantified within 12.1 min using a triple quadrupole MS with electrospray ionization in positive ion mode. All corticosteroids resulted in the base-line separation, which is even achieved for stereo-isomers, such as alpha-/beta-cortol, alpha-/beta-cortolone, and allo-tetrahydrocortisol/tetrahydrocortisol. Overall recoveries ranged from 85% to 106% with limit of quantification ranged from 0.5 to 2.0 ng mL(-1) for the corticosteroids examined. The precision (% CV) and accuracy (% bias) of the assay were 1.7-7.8% and 95.1-105.4%, respectively, in 0.5-200 ng mL(-1) calibration ranges (r(2)>0.9903), for quality-control samples containing 21 endogenous corticosteroids at three different urinary concentrations. Clinical application included quantitative analysis from patients with both prostate cancer and benign prostatic hyperplasia with altered cortisol concentrations. The described LC-MS/MS method eliminates interference from other urine components, has excellent chromatographic resolution achieved by a small particle LC column with a sufficient sensitivity to allow the profiling of both gluco- and mineralo-corticosteroids at a time.

Highly selective and sensitive assay for paclitaxel accumulation by tumor cells based on selective solid phase extraction and micro-flow liquid chromatography coupled to mass spectrometry

The taxanes are among the most important cancer chemotherapy drugs approved for clinical use in the last two decades. Paclitaxel is used as first-line therapy for a variety of cancers, and numerous drug delivery approaches are under investigation to enhance its selectivity and effectiveness against tumors. One strategy is to produce sustained, low drug levels within the tumor to enhance apoptosis and inhibit angiogenesis. The interest in altering drug concentration/time exposure profiles to improve therapeutic outcomes creates the necessity to quantify low concentrations of paclitaxel in cells or tissues. Here, a selective solid phase extraction (SPE) method, coupled with a capillary liquid chromatography-tandem mass spectrometry (microLC-MS/MS) method, was developed to quantify low, therapeutically relevant concentrations of paclitaxel that could not be analyzed using conventional LC-MS/MS. Under optimized SPE wash and elution conditions, paclitaxel was selectively extracted from biological samples, and most matrix components were removed. A 150 x 0.5 mm ID ODS capillary column was used for microLC separation and the flow rate was 12 microL min(-1). Sample extracts were focused at the front of the microLC column and then eluted with a gradient. The lower limits of detection and quantification were 5 and 20 pg mL(-1), respectively, permitting quantification of paclitaxel in small tissue samples or in cultured cells exposed to low drug concentrations. The quantitative linear range was 20-20 000 pg mL(-1). The ability to quantify these low concentrations of paclitaxel provides an important tool to study the concentration-dependent pharmacological effects of this important drug.

Ultra-sensitive quantification of paclitaxel using selective solid-phase extraction in conjunction with reversed-phase capillary liquid chromatography/tandem mass spectrometry

The ability to quantify ultra-low concentrations of biologically active compounds in biological matrices is essential for the study of pharmacological/toxicological effects occurring at low doses. Selective solid-phase extraction (SPE) was combined with highly sensitive capillary LC (microLC)-MS/MS analysis to achieve ultra-sensitive quantification of the anti-cancer drug paclitaxel in cancer cells. The optimized SPE selectively extracted paclitaxel and eliminated undesirable matrix compounds, thus enabling a high sample loading volume on the microLC column without compromising chromatographic performance and operational robustness. The validated lower limit of quantification (LOQ) was 5pg/mL, approx. 20-fold more sensitive than published LC-MS/MS methods. The calibration curve was linear over the range of 5-6250pg/mL. Accuracy was 98-109% and the variation (CV%) was 2.3-7.4%. This method was applied successfully to quantify temporal drug accumulation by A121a ovarian cancer cells treated with sub-ng/mL concentrations of paclitaxel.