Liquid Chromatography-tandem Mass Spectrometry Assay Research Articles

Identification of a novel mutation in chibby family member 2 in a non-obstructive azoospermic patient

Azoospermia constitutes a significant factor in male infertility, defined by the absence of spermatozoa in the ejaculate, afflicting 15% of infertile men. However, a subset of azoospermic cases remains unattributed to known genetic variants. Prior investigations have identified the chibby family member 2 (CBY2) as prominently and specifically expressed in the testes of both humans and mice, implicating its potential involvement in spermatogenesis. In this study, we conducted whole exome sequencing (WES) on an infertile family to uncover novel genetic factors contributing to azoospermia. Our analysis revealed a homozygous c .355 C>A variant of CBY2 in a non-obstructive azoospermic patient. This deleterious variant significantly diminished the protein expression of CBY2 both in vivo and in vitro, leading to a pronounced disruption of spermatogenesis at the early round spermatid stage post-meiosis. This disruption was characterized by a nearly complete loss of elongating and elongated spermatids. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and co-immunoprecipitation assays demonstrated the interaction between CBY2 and Piwi-like protein 1 (PIWIL1). Immunofluorescence staining further confirmed the co-localization of CBY2 and PIWIL1 in the testes during the spermatogenic process in both humans and mice. Additionally, diminished PIWIL1 expression was observed in the testicular tissue from the affected patient. Our findings suggest that the homozygous c .355 C>A variant of CBY2 compromises CBY2 function, contributing to defective spermatogenesis at the round spermiogenic stage and implicating its role in the pathogenesis of azoospermia.

Ultra-high performance liquid chromatography-tandem mass spectrometry assay for simultaneous determination of 22 marker compounds in traditional herbal medicine Ojeoksan

Traditional herbal medicines (THMs) have long been in use worldwide and are considered safe for use as tonics or complementary treatments for many diseases. Advanced quality control methods for THMs are required in the regulatory framework of modern medicines. In this study, an ultra-high performance liquid chromatography-tandem mass spectrometry assay was established for the simultaneous determination of 22 marker compounds in Ojeoksan (OJS), which is composed of 15 herbal substances. All marker compounds were analyzed within 20 min and successfully identified via scheduled multiple reaction monitoring. The method validation revealed excellent performance characteristics of the method such as specificity, linearity, sensitivity, precision, and accuracy, demonstrating its suitability for intended use. The developed method was applied to samples of commercial OJS tablet and soft-extract dosage forms. The 14 marker compounds corresponding to 12 component herbal substances were determined in the samples; ephedirine, albiflorin, paeoniflorin, ferulic acid, hesperidine, neohesperidin, cinnamic acid, platycodin D, 6-gingerol, atractylenolide III, glycyrrhizin, honokiol, decursin, and magnolol. A fast and easy assay method with sufficient discrimination power was established. As a novel assay, this method can contribute to the quality control of OJS products.

New plasma LC-MS/MS assays for the quantitation of beta-amyloid peptides and identification of apolipoprotein E proteoforms for Alzheimer's disease risk assessment.

Early detection of Alzheimer's disease (AD) represents an unmet clinical need. Beta-amyloid (Aβ) plays an important role in AD pathology, and the Aβ42/40 peptide ratio is a good indicator for amyloid deposition. In addition, variants of the apolipoprotein E (APOE) gene are associated with variable AD risk. Here, we describe the development and validation of high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for plasma Aβ40 and Aβ42 quantitation, as well as apolipoprotein E (ApoE) proteotype determination as a surrogate for APOE genotype. Aβ40 and Aβ42 were simultaneously immunoprecipitated from plasma, proteolytically digested, and quantitated by LC-MS/MS. ApoE proteotype status was qualitatively assessed by targeting tryptic peptides from the ApoE2, ApoE3, and ApoE4 proteoforms. Both assays were validated according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Within-run precision was 1.8%-4.2% (Aβ40), 1.9%-7.2% (Aβ42), and 2.6%-8.3% (Aβ42/40 ratio). Between-run precision was 3.5%-5.9% (Aβ40), 3.8%-8.0% (Aβ42), and 3.3%-8.7% (Aβ42/40 ratio). Both Aβ40 and Aβ42 were linear from 10 to 2500 pg/mL. Identified ApoE proteotypes had 100% concordance with APOE genotypes. We have developed a precise, accurate, and sensitive high-throughput LC-MS/MS assay for plasma Aβ40, Aβ42, and proteoforms of ApoE.

A high performance liquid chromatography-tandem mass spectrometry assay for therapeutic drug monitoring of 10 drug compounds commonly used for antimicrobial therapy in plasma and serum of critically ill patients: Method optimization, validation, cross-validation and clinical application

Background and aimsIntensive care antibiotic treatment faces challenges due to substantial pharmacokinetic differences in critically ill patients. Individualized antibiotic dosing guided by therapeutic drug monitoring (TDM) is considered to minimize the risk of treatment failure and toxicity. This study aimed to develop a valid method for simultaneous LC-MS/MS quantification of 10 drugs frequently used in intensive care antibiotic therapy for which TDM-guided dosing is recommended: piperacillin, meropenem, flucloxacillin, cefuroxime, vancomycin, colistin A and B, linezolid, ciprofloxacin and tazobactam. Methods and ResultsThorough optimization of sample preparation and chromatography resulted in a fast and simple method based on protein precipitation of 50 µL plasma or serum and gradient elution using an Acquity UPLC HSS-T3 column. Electrospray ionization-triple quadrupole mass spectrometry in dynamic multiple reaction monitoring was used for quantification, covering the therapeutic range of each drug compound. Validation following EMA and FDA recommendations, including inter-platform validation and inter-laboratory comparison, demonstrated high accuracy, precision and robustness of the new method. The assay was successfully used to monitor plasma antibiotic levels of critically ill patients (n = 35). ConclusionThe established multiplex method covers major drug classes with documented dosing challenges, provides a reliable basis for the implementation of high-throughput TDM, and its application confirmed the clinical impact of TDM in a real-world setting.

Assessing potential drug-drug interactions between clofazimine and other frequently used agents to treat drug-resistant tuberculosis.

Clofazimine is included in drug regimens to treat rifampicin/drug-resistant tuberculosis (DR-TB), but there is little information about its interaction with other drugs in DR-TB regimens. We evaluated the pharmacokinetic interaction between clofazimine and isoniazid, linezolid, levofloxacin, and cycloserine, dosed as terizidone. Newly diagnosed adults with DR-TB at Klerksdorp/Tshepong Hospital, South Africa, were started on the then-standard treatment with clofazimine temporarily excluded for the initial 2 weeks. Pharmacokinetic sampling was done immediately before and 3 weeks after starting clofazimine, and drug concentrations were determined using validated liquid chromatography-tandem mass spectrometry assays. The data were interpreted with population pharmacokinetics in NONMEM v7.5.1 to explore the impact of clofazimine co-administration and other relevant covariates on the pharmacokinetics of isoniazid, linezolid, levofloxacin, and cycloserine. Clofazimine, isoniazid, linezolid, levofloxacin, and cycloserine data were available for 16, 27, 21, 21, and 6 participants, respectively. The median age and weight for the full cohort were 39 years and 52 kg, respectively. Clofazimine exposures were in the expected range, and its addition to the regimen did not significantly affect the pharmacokinetics of the other drugs except levofloxacin, for which it caused a 15% reduction in clearance. A posteriori power size calculations predicted that our sample sizes had 97%, 90%, and 87% power at P < 0.05 to detect a 30% change in clearance of isoniazid, linezolid, and cycloserine, respectively. Although clofazimine increased the area under the curve of levofloxacin by 19%, this is unlikely to be of great clinical significance, and the lack of interaction with other drugs tested is reassuring.

Sex steroid levels in women with hypopituitarism: A case-controlled observational study.

Women with hypopituitarism remain at increased risk of morbidity and mortality. Insufficient replacement of sex steroids has been suggested as a contributing factor, but sex steroid levels in women with hypopituitarism have not been comprehensively mapped. To quantify sex steroids in women with hypopituitarism by a high-sensitivity assay. Using a combination of clinical and biochemical criteria, women with hypopituitarism (n = 104) who started growth hormone replacement 1995-2014 at a single center were categorized as eugonadal or having hypogonadotropic hypogonadism (HH). A population-based cohort of women (n = 288) served as controls. Eugonadal women and controls were categorized as pre-/postmenopausal and HH women as younger/older (≤ or >52 years). Dehydroepiandrosterone (DHEA), androstenedione, testosterone, dihydrotestosterone, progesterone, 17αOH-progesterone, estradiol and estrone were analyzed by a validated liquid chromatography-tandem mass spectrometry assay. Among both premenopausal/younger and postmenopausal/older women, women with HH had lower levels of sex steroid precursors (DHEA, androstenedione) and androgens (testosterone and dihydrotestosterone) than controls. Progesterone, 17αOH-progesterone, estrone and estradiol showed similar patterns. Women with HH and adrenocorticotropic hormone (ACTH) deficiency had markedly lower concentrations of all sex hormones than those without ACTH deficiency. This study demonstrates for the first time a broad and severe sex steroid deficiency in both younger and older women with HH, particularly in those with combined gonadotropin and ACTH deficiency. The health impact of low sex steroid levels in women with hypopituitarism requires further study and women with combined gonadotropin and ACTH deficiency should be a prioritized group for intervention studies with sex hormone replacement.

Chickpea proteins are potential sources of bioactive peptides that induce glucose uptake via AMP-activated protein kinase

Food proteins are a critical source of nutraceutical bioactive peptides that promote health and prevent diseases. Legume seed proteins have been extensively studied to produce peptides with diverse biological activities. Several legume protein hydrolysates and bioactive peptides have been identified that inhibit the activity of α-amylase, α-glucosidase, and dipeptidyl peptidase IV for the purpose of preventing diabetes. Herein, we observed that chickpea peptides (CPP), prepared using the enzymatic digestion of chickpea protein, induced glucose uptake in C2C12 myotubes. Further, liquid chromatography-tandem mass spectrometry and 2-deoxyglucose uptake assay were used to identify a bioactive CPP, defined as CPP737, REGDIIAVPTGVVF, a part of the legumin A-like protein. CPP737 induced AMP-activated protein kinase phosphorylation and glucose transporter type 4 membrane translocation, but not protein kinase B in C2C12 myotubes. Thus, chickpea protein is a potential source of bioactive peptides that can prevent insulin resistance and hyperglycemia through glucose uptake in the skeletal muscle.

Long-Term Oral Tamoxifen Administration Decreases Brain-Derived Neurotrophic Factor in the Hippocampus of Female Long-Evans Rats.

Tamoxifen, a selective estrogen receptor modulator (SERM), is commonly used as an adjuvant drug therapy for estrogen-receptor-positive breast cancers. Though effective at reducing the rate of cancer recurrence, patients often report unwanted cognitive and affective side effects. Despite this, the impacts of chronic tamoxifen exposure on the brain are poorly understood, and rodent models of tamoxifen exposure do not replicate the chronic oral administration seen in patients. We, therefore, used long-term ad lib consumption of medicated food pellets to model chronic tamoxifen exposure in a clinically relevant way. Adult female Long-Evans Hooded rats consumed tamoxifen-medicated food pellets for approximately 12 weeks, while control animals received standard chow. At the conclusion of the experiment, blood and brain samples were collected for analyses. Blood tamoxifen levels were measured using a novel ultra-performance liquid chromatography-tandem mass spectrometry assay, which found that this administration paradigm produced serum levels of tamoxifen similar to those in human patients. In the brain, brain-derived neurotrophic factor (BDNF) was visualized in the hippocampus using immunohistochemistry. Chronic oral tamoxifen treatment resulted in a decrease in BDNF expression across several regions of the hippocampus. These findings provide a novel method of modeling and measuring chronic oral tamoxifen exposure and suggest a putative mechanism by which tamoxifen may cause cognitive and behavioral changes reported by patients.

Relation between Polygenic Risk Score, Vitamin D Status and BMI-for-Age z Score in Chinese Preschool Children.

Both genetics and vitamin D deficiency are associated with childhood obesity. However, the role of vitamin D status between polygenic and childhood obesity has been unknown. The current study aimed to determine the relation between genetic factors, vitamin D status, and BMI-for-age z score (zBMI) in Chinese preschool children. A total of 1046 participants aged 3.7 to 6.6 years old from the Long-term Health Effects Assessment Project of Infants and Toddlers Nutritional Pack (LHEAPITNP) were included in this study. The polygenic risk score (PRS) was established based on 55 BMI-related single nucleotide polymorphisms (SNPs) derived from a published genome-wide association study (GWAS) for BMI. Serum 25(OH)D was used as an index of vitamin D status and measured with liquid chromatography-tandem mass spectrometry (LC/MS-MS) assay. The Wilcoxon test or Kruskal-Wallis test was used to compare the differences of variables between different groups and Spearman correlation analysis was used for analyzing the correlations between the PRS, 25(OH)D levels, and zBMI. The PRS showed a positive relation to zBMI (rs = 0.0953, p = 0.0022) and 25(OH)D showed a negative relation to zBMI (rs = -0.1082, p = 0.0005) in the full-adjustment model. In addition, the differences in zBMI at different vitamin D statuses in the low-risk PRS group and the intermediate-risk PRS group were both statistically significant (plow = 0.0308, pintermediate = 0.0121), the median zBMI was both higher at vitamin D insufficiency status. And the difference in zBMI between different genetic risk groups was also statistically significant at vitamin D sufficiency status (p = 0.0077). Furthermore, genetic risk showed a positive relation to zBMI at vitamin D sufficiency status, and the p for trend was 0.0028. Our findings suggested that vitamin D was related to zBMI negatively in Chinese preschoolers and maintaining adequate vitamin D levels may only contribute to lower the zBMI in preschoolers with low and intermediate genetic susceptibility.

Shen Yuan extract exerts a hypnotic effect via the tryptophan/5-hydroxytryptamine/melatonin pathway in mice

Ethnopharmacological relevanceSleep plays a critical role in several physiologic processes, and sleep disorders increase the risk of depression, dementia, stroke, cancer, and other diseases. Stress is one of the main causes of sleep disorders. Ginseng Radix et Rhizoma and Polygalae Radix have been reported to have effects of calming the mind and intensifying intelligence in Chinese Pharmacopoeia. Traditional Chinese medicine prescriptions composed of Ginseng Radix et Rhizoma and Polygalae Radix (Shen Yuan, SY) are commonly used to treat insomnia, depression, and other psychiatric disorders in clinical practice. Unfortunately, the underlying mechanisms of the SY extract's effect on sleep are still unknown. Aim of the studyThis study aimed to investigate the hypnotic effect of the SY extract in normal mice and mice with chronic restraint stress (CRS)-induced sleep disorders and elucidate the underlying mechanisms. Materials and methodsThe SY extract (0.5 and 1.0 g/kg) was intragastrically administered to normal mice for 1, 14, and 28 days and to CRS-treated mice for 28 days. The open field test (OFT) and pentobarbital sodium-induced sleep test (PST) were used to evaluate the hypnotic effect of the SY extract. Liquid chromatography-tandem mass spectrometry and enzyme-linked immunosorbent assay were utilized to detect the levels of neurotransmitters and hormones. Molecular changes at the mRNA and protein levels were determined using real-time quantitative polymerase chain reaction and Western blot analysis to identify the mechanisms by which SY improves sleep disorders. ResultsThe SY extract decreased sleep latency and increased sleep duration in normal mice. Similarly, the sleep duration of mice subjected to CRS was increased by administering SY. The SY extract increased the levels of tryptophan (Trp) and 5-hydroxytryptamine (5-HT) and the expression of tryptophan hydroxylase 2 (TPH2) in the cortex of normal mice. The SY extract increased the Trp level, transcription and expression of estrogen receptor beta and TPH2 in the cortex in mice with sleep disorders by decreasing the serum corticosterone level, which promoted the synthesis of 5-HT. Additionally, the SY extract enhanced the expression of arylalkylamine N-acetyltransferase, which increased the melatonin level and upregulated the expressions of melatonin receptor-2 (MT2) and Cryptochrome 1 (Cry1) in the hypothalamus of mice with sleep disorders. ConclusionsThe SY extract exerted a hypnotic effect via the Trp/5-HT/melatonin pathway, which augmented the synthesis of 5-HT and melatonin and further increased the expressions of MT2 and Cry1.

Blue light impairs the repair of UVB-induced pyrimidine dimers in a human skin model.

In recent years, interest is growing in the biological cutaneous effects of high-energy visible light (400-450 nm). In the present study, we explored the impact of blue light (BL) on the repair of pyrimidine dimers, the major class of premutagenic DNA damage induced by exposure to sunlight. We unambiguously demonstrate that the exposure of invitro reconstructed human epidermis to environmentally relevant doses of BL strongly decreases the rate of repair of cyclobutane pyrimidine dimers and pyrimidine (6-4) pyrimidone photoproducts induced by a subsequent UVB irradiation. Using the highly sensitive and specific liquid chromatography-tandem mass spectrometry assay, we did not observe induction of pyrimidine dimers by BL alone. Finally, we showed that application, during the BL exposure step, of a formula containing a new filter, named TriAsorB and affording BL photoprotection, prevented the decrease in DNA repair efficiency. These results emphasize the potential deleterious effects of BL on DNA repair and the interest in providing adequate skin protection against this wavelength range of sunlight.

A validated liquid chromatography-tandem mass spectrometry assay for the analysis of isoniazid and its metabolite acetyl-isoniazid in urine

IntroductionIsoniazid (INH) is one of the most effective and potent first-line anti-tubercular drug. INH is also effectively administered as a preventative monotherapy and has been shown to significantly reduce TB incidence. INH is primarily metabolised to acetyl-isoniazid (AcINH) in the liver. AcINH is mainly excreted in urine presenting as a target for monitoring adherence to INH therapy. ObjectiveThe study aimed to develop and fully validate a bioanalytical method using liquid chromatography-tandem mass spectrometry for the quantification of INH and AcINH in human urine. MethodsThe samples were prepared using solid phase extraction, with the internal standards isoniazid-d4 and acetyl-isoniazid-d4 being used. The extracts were chromatographed on an Atlantis T3 analytical column with an isocratic mobile phase. For detection, a AB Sciex™ API 5500 triple quadrupole mass spectrometer was used at unit resolution in the multiple reaction monitoring mode, following positive electrospray ionization. ResultsThe analytical method demonstrated sufficient sensitivity, as indicated by average signal-to-noise ratios of 7.07 and 6.23 at the lower limit of quantification for INH and AcINH, respectively. Validation was performed over three consecutive batches, demonstrating accuracy, precision, and overall robustness based on peak area ratios within the analytical range of 0.234–30.0 µg/mL for both INH and AcINH. All required validation experiments were assessed and met the acceptance criteria guidelines of the US Food and Drug Administration and European Medicines Agency. The validated method was utilized to measure concentrations of AcINH in urine as a means of assessing adherence to the intake of isoniazid in order to prevent TB infection during a phase III open-label multicenter trial. ConclusionA bioanalytical method was developed and fully validated for quantifying isoniazid (INH) and acetyl-isoniazid (AcINH) in 100 µL of human urine.

Maternal Ezetimibe Concentrations Measured in Breast Milk and Its Use in Breastfeeding Infant Exposure Predictions.

Lactating mothers taking ezetimibe, an antihyperlipidemic agent, may be hesitant to breastfeed despite the known benefit of breastfeeding to both mother and infant. Currently, no data exist on the presence or concentration of ezetimibe and its main active metabolite, ezetimibe-glucuronide (EZE-glucuronide), in human breast milk. Voluntary breast milk samples containing ezetimibe and EZE-glucuronide were attained from lactating mothers taking ezetimibe as part of their treatment. An assay was developed and validated to measure ezetimibe and EZE-glucuronide concentrations in breast milk. A workflow that utilized a developed and evaluated pediatric physiologically based pharmacokinetic (PBPK) model, the measured concentrations in milk, and weight-normalized breast milk intake volumes was applied to predict infant exposures and determine the upper area under the curve ratio (UAR). Fifteen breast milk samples from two maternal-infant pairs were collected. The developed liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay showed an analytical range of 0.039-5.0 ng/mL and 0.39-50.0 ng/mL for ezetimibe and EZE-glucuronide, respectively. The measured concentrations in the breast milk samples were 0.17-1.02 ng/mL and 0.42-2.65 ng/mL of ezetimibe and EZE-glucuronide, respectively. The evaluated pediatric PBPK model demonstrated minimal exposure overlap in adult therapeutic dose and breastfed infant simulated area under the concentration-time curve from time zero to 24h (AUC24). Calculated UAR across infant age groups ranged from 0.0015 to 0.0026. PBPK model-predicted ezetimibe and EZE-glucuronide exposures and UAR suggest that breastfeeding infants would receive non-therapeutic exposures. Future work should involve a 'mother-infant pair study' to ascertain breastfed infant plasma ezetimibe and EZE-glucuronide concentrations to confirm the findings of this work.

Validation of a novel direct method to determine reduced adherence to atorvastatin therapy.

Objective methods to determine statin adherence are requested to improve lipid management. We have recently established a method to detect reduced adherence to atorvastatin therapy with cut-off values based on the sum of atorvastatin and its major metabolites in blood. We aimed to validate this method in patients with and without cardiovascular disease, and optimize previous cut-off values. The pharmacokinetic study included 60 participants treated with atorvastatin 20 mg (N=20), 40 mg (N=20), and 80 mg (N=20). Atorvastatin was then stopped and blood samples collected from day zero to day four. Quantification of the parent drug and its metabolites in blood plasma was performed with a liquid chromatography-tandem mass spectrometry assay. The cut-off values for reduced adherence were validated and optimized by calculating diagnostic sensitivity and specificity. Our candidate cut-off value of dose-normalized six-component sum of atorvastatin plus metabolites <0.10 nM/mg provided a sensitivity of 97% and a specificity of 93% for detecting ≥2 omitted doses. An optimized cut-off <0.062 nM/mg provided a sensitivity of 90% and a specificity of 100%. An alternative simplified two-component metabolite sum with cut-off value <0.05 nM/mg provided a sensitivity of 98% and a specificity of 76%. An optimized cut-off <0.02 nM/mg provided a sensitivity of 97% and a specificity of 98%. This validation study confirms that our direct method discriminates reduced adherence from adherence to atorvastatin therapy with high diagnostic accuracy. The method may improve lipid management in clinical practice and serve as a useful tool in future studies.

Adaptive Dosage Strategy of Levetiracetam in Chinese Epileptic Patients: Focus on Pregnant Women

There is presently no efficient dose individualization strategy for the use of antiseizure medications in epileptic pregnant patients. This study aimed to develop a population pharmacokinetics model for levetiracetam and propose a tailored adaptive individualized dosage strategy for epileptic pregnant patients. A total of 322 levetiracetam plasma concentrations from 238 patients with epilepsy were included, including 216 women with epilepsy (20.83% of whom were pregnant). The levetiracetam plasma concentration was measured using a validated ultra-performance liquid chromatography-tandem mass spectrometry assay, and the data were modeled using a nonlinear mixed-effects model. The resultant model served as the basis for simulating the dosage adjustment strategy. A one-compartment model with first-order elimination best described the pharmacokinetic data of levetiracetam. The apparent clearance (CL/F) was 3.43 L/h (95% CI 3.30–3.56) and the apparent volume of distribution was 43.7 L (95% CI 40.4–47.0) for a typical individual of 57.2 kg. Pregnancy and body weight were found to be significant covariates of CL/F of levetiracetam. The recommended regimen of levetiracetam could be predicted by the population pharmacokinetic model based on body weight, gestational age, and the daily dose of levetiracetam taken before pregnancy.

A Liquid Chromatography-Tandem Mass Spectrometry Assay for Quantification of Ethyl Glucuronide and Ethyl Sulfate in Urine.

Ethyl glucuronide and ethyl sulfate emerged as the biomarkers of choice for detection of ethanol use as the required sample is urine, enabling easy and noninvasive collection. Further, these biomarkers have a longer detection window in urine than blood ethanol. A liquid chromatography-tandem mass spectrometry method was developed and clinically validated using electrospray ionization in negative mode and selected reaction monitoring. A simple dilution was used for sample preparation on 100 microliters of urine. Gradient elution had a run time of 7min. The reportable range was established to be 180-100,000ng/mL for ethyl glucuronide and 50-46,600ng/mL for ethyl sulfate and between-run imprecision was <7% for both analytes.

Tandem mass spectrometric assay of N-acetylglucosamine-6-sulfatase for multiplex analysis of mucopolysaccharidosis-IIID in dried blood spots

Previously we developed a multiplex liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay using dried blood spots for all subtypes of mucopolysaccharidoses (MPS) except MPS-IIID. Here we show that the MPS-IIID enzyme N-acetylglucosamine-6-sulfatase (GNS) is inhibited in dried blood spot (DBS) extracts, but activity can be recovered if the extract is diluted to reduce the concentrations of endogenous inhibitors. The new GNS assay displays acceptable characteristics including linearity in product formation with incubation time and amount of enzyme, low variability, and ability to distinguish MPS-IIID-affected from healthy patients using DBS. The assay can be added to the LC-MS/MS multiplex panel for all MPS subtypes requiring ∼2 min per newborn for the LC-MS/MS run.

Application of a Validated Method for Quantifying Circulating Protoporphyrin IX to the Beacon Trial of Bitopertin in Erythropoietic Protoporphyria

Introduction: Accumulation of the photoreactive heme precursor protoporphyrin IX (PPIX) is a signature of the disease pathophysiology for both erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), and PPIX levels correlate with disease severity and light tolerance. Additionally, an elevated ratio of circulating metal-free PPIX vs. metal-bound PPIX is observed in patients with protoporphyrias, and the extent of metal-free elevation is distinguishable between EPP (85-100%) and XLP (50-85%). Therefore, the accurate determination of metal-free PPIX and metal-bound PPIX is of particular interest in patients with EPP or XLP. Methods: Novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays were developed and validated to quantify circulating metal-free and zinc (Zn)-complexed PPIX in whole blood and plasma. Each of the four assays were developed and validated according to applicable regulatory guidance for bioanalytical assay validation with regard to accuracy, precision, sensitivity, and selectivity. The minimum required sample volume for each assay was 200 µL, compared to &amp;gt;1 mL for most currently available protoporphyria-related assays. During bioanalytical method development, rapid degradation of metal-free PPIX (≥90%) and Zn-PPIX (up to 96%) was observed in plasma samples within 24 hours under ambient light conditions. In contrast, whole blood was less susceptible to photodegradation (i.e., ≤20% for both metal-free PPIX and Zn-PPIX) under the same conditions. The most effective method for maintaining sample integrity was reduction of light exposure during sample collection, handling, and processing. Implementation of light-reduction controls was used during method validation and facilitated improved stability of metal-free PPIX and Zn-PPIX in plasma and whole-blood samples. For the metal-free PPIX plasma assay validation, the effect of hemolysis was evaluated due to the apparent sequestration of metal-free PPIX in red blood cells. The bioanalytical work informed specific sample-collection procedures to mitigate instability and hemolysis, such as the use of opaque consumables for sample collection, controls for plasma aliquoting, and operating under low-light conditions for all sample handling and processing. BEACON is a Phase 2, randomized, open-label, parallel-arm trial (ACTRN12622000799752) of approximately 22 participants who will receive oral, once-daily administration of 20 or 60 mg of bitopertin for 6 months. Baseline light tolerance was assessed using 2 patient-reported outcomes measures during a 2- to 4-week screening period. Participants were asked to conduct weekly sun exposure challenges and time to first prodromal symptom (itching, burning, tingling, etc.) was averaged for the screening period. Results: More than 600 clinical samples from 17 participants in the BEACON study have been collected as of 06 June 2023 and analyzed using the validated porphyrin assays. Measured metal-free PPIX baseline values ranged from 1440 - 34,100 ng/mL (2.6 - 61 µM) in whole blood and 177 - 2560 ng/mL (0.31 - 4.5 µM) in plasma ( n=16). Baseline percentage of intra-patient plasma/whole-blood concentrations ranged from 2.5 - 16%. Each participant's baseline values were converted to erythrocyte metal-free PPIX concentrations using measured hematocrit levels and ranged from 3590 - 88400 ng/mL (6.4 - 157 µM). These values were comparable to data previously reported in the literature (6-139 µM 1). Additionally, higher baseline whole-blood metal-free PPIX concentrations were associated with decreased averages for time to prodrome (Table 1). Conclusion: Fully-validated LC-MS/MS assays to quantify metal-free PPIX and Zn-PPIX in plasma and whole blood were used to analyze clinical samples from the BEACON study evaluating bitopertin in EPP. PPIX values were consistent with previously reported values for patients with EPP. The methods also provided improved accuracy and specificity for metal-free vs. metal-complexed PPIX and reduced sample volume requirements. In addition, higher baseline whole-blood PPIX values were associated with decreased light tolerance within the trial population, supporting its use as a measure of disease severity in EPP.

Sensitive Blood-Based Detection of HIV-1 and Mycobacterium tuberculosis Peptides for Disease Diagnosis by Immuno-Affinity Liquid Chromatography-Tandem Mass Spectrometry: A Method Development and Proof-of-Concept Study.

Novel approaches that allow early diagnosis and treatment monitoring of both human immunodeficiency virus-1 (HIV-1) and tuberculosis disease (TB) are essential to improve patient outcomes. We developed and validated an immuno-affinity liquid chromatography-tandem mass spectrometry (ILM) assay that simultaneously quantifies single peptides derived from HIV-1 p24 and Mycobacterium tuberculosis (Mtb) 10-kDa culture filtrate protein (CFP10) in trypsin-digested serum derived from cryopreserved serum archives of cohorts of adults and children with/without HIV and TB. ILM p24 and CFP10 results demonstrated good intra-laboratory precision and accuracy, with recovery values of 96.7% to 104.6% and 88.2% to 111.0%, total within-laboratory precision (CV) values of 5.68% to 13.25% and 10.36% to 14.92%, and good linearity (r2 > 0.99) from 1.0 to 256.0 pmol/L and 0.016 to 16.000 pmol/L, respectively. In cohorts of adults (n = 34) and children (n = 17) with HIV and/or TB, ILM detected p24 and CFP10 demonstrated 85.7% to 88.9% and 88.9% to 100.0% diagnostic sensitivity for HIV-1 and TB, with 100% specificity for both, and detected HIV-1 infection earlier than 3 commercial p24 antigen/antibody immunoassays. Finally, p24 and CFP10 values measured in longitudinal serum samples from children with HIV-1 and TB distinguished individuals who responded to TB treatment from those who failed to respond or were untreated, and who developed TB immune reconstitution inflammatory syndrome. Simultaneous ILM evaluation of p24 and CFP10 results may allow for early TB and HIV detection and provide valuable information on treatment response to facilitate integration of TB and HIV diagnosis and management.

The Dsup coordinates grain development and abiotic stress in rice

DNA damage is a serious threat to all living organisms and may be induced by environmental stressors. Previous studies have revealed that the tardigrade (Ramazzotius varieornatus) DNA damage suppressor protein Dsup has protective effects in human cells and tobacco. However, whether Dsup provides radiation damage protection more widely in crops is unclear. To explore the effects of Dsup in other crops, stable Dsup overexpression lines through Agrobacterium-mediated transformation were generated and their agronomic traits were deeply investigated. In this study, the overexpression of Dsup not only enhanced the DNA damage resistance at the seeds and seedlings stages, they also exhibited grain size enlargement and starch granule structure and cell size alteration by the scanning electron microscopy observation. Notably, the RNA-seq revealed that the Dsup plants increased radiation-related and abiotic stress-related gene expression in comparison to wild types, suggesting that Dsup is capable to coordinate normal growth and abiotic stress resistance in rice. Immunoprecipitation enrichment with liquid chromatography-tandem mass spectrometry (IP-LC-MS) assays uncovered 21 proteins preferably interacting with Dsup in plants, suggesting that Dsup binds to transcription and translation related proteins to regulate the homeostasis between DNA protection and plant development. In conclusion, our data provide a detailed agronomic analysis of Dsup plants and potential mechanisms of Dsup function in crops. Our findings provide novel insights for the breeding of crop radiation resistance.