Drug Pharmacokinetics Determined by Real-Time Analysis of Mouse Breath

BreathXplorer: Processing Online Breathomics Data Generated from Direct Analysis Using High-Resolution Mass Spectrometry

Nontargeted breath analysis in real time using high-resolution mass spectrometry (HRMS) is a promising approach for high coverage profiling of metabolites in human exhaled breath. However, the information-rich and unique non-Gaussian metabolic signal shapes of real-time HRMS-based data pose a significant challenge for efficient data processing. This work takes a typical real-time HRMS technique as an example, i.e. secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS), and presents BreathXplorer, an open-source Python package designed for the processing of real-time exhaled breath data comprising multiple exhalations. BreathXplorer is composed of four main modules. The first module applies either a topological algorithm or a Gaussian mixture model (GMM) to determine the start and end points of each exhalation. Next, density-based spatial clustering of applications with noise (DBSCAN) is employed to cluster m/z values belonging to the same metabolic feature, followed by applying an intensity relative standard deviation (RSD) filter to extract real breath metabolic features. BreathXplorer also offers functions of (1) feature alignment across the samples and (2) associating MS/MS spectra with their corresponding metabolic features for downstream compound annotation. Manual inspection of the metabolic features extracted from SESI-HRMS breath data suggests that BreathXplorer can achieve 100% accuracy in identifying the start and end points of each exhalation and acquire accurate quantitative measurements of each breath feature. In a proof-of-concept study on exercise breathomics using SESI-HRMS, BreathXplorer successfully reveals the significantly changed metabolites that are pertinent to exercise. BreathXplorer is publicly available on GitHub (https://github.com/HuanLab/breathXplorer). It provides a powerful and convenient-to-use tool for the researchers to process breathomics data obtained by directly analysis using HRMS.

Memantine inhibits cortical spreading depolarization and improves neurovascular function following repetitive traumatic brain injury

Cortical spreading depolarization (CSD) is a promising target for neuroprotective therapy in traumatic brain injury (TBI). We explored the effect of NMDA receptor antagonism on electrically triggered CSDs in healthy and brain-injured animals. Rats received either one moderate or four daily repetitive mild closed head impacts (rmTBI). Ninety-three animals underwent craniectomy with electrocorticographic (ECoG) and local blood flow monitoring. In brain-injured animals, ketamine or memantine inhibited CSDs in 44 to 88% and 50 to 67% of cases, respectively. Near-DC/AC-ECoG amplitude was reduced by 44 to 75% and 52 to 67%, and duration by 39 to 87% and 61 to 78%, respectively. Daily memantine significantly reduced spreading depression and oligemia following CSD. Animals (N = 31) were randomized to either memantine (10 mg/kg) or saline with daily neurobehavioral testing. Memantine-treated animals had higher neurological scores. We demonstrate that memantine improved neurovascular function following CSD in sham and brain-injured animals. Memantine also prevented neurological decline in a blinded, preclinical randomized rmTBI trial.

Non-invasive monitoring of microbiota and host metabolism using secondary electrospray ionization-mass spectrometry

The metabolic "handshake" between the microbiota and its mammalian host is a complex, dynamic process with major influences on health. Dissecting the interaction between microbial species and metabolites found in host tissues has been a challenge due to the requirement for invasive sampling. Here, we demonstrate that secondary electrospray ionization-mass spectrometry (SESI-MS) can be used to non-invasively monitor metabolic activity of the intestinal microbiome of a live, awake mouse. By comparing the headspace metabolome of individual gut bacterial culture with the "volatilome" (metabolites released to the atmosphere) of gnotobiotic mice, we demonstrate that the volatilome is characteristic of the dominant colonizing bacteria. Combining SESI-MS with feeding heavy-isotope-labeled microbiota-accessible sugars reveals the presence of microbial cross-feeding within the animal intestine. The microbiota is, therefore, a major contributor to the volatilome of a living animal, and it is possible to capture inter-species interaction within the gut microbiota using volatilome monitoring.

Correlation of theophylline levels in rat exhaled breath and lung tissue after its intravenous injection

It is important to know the drug level in the target tissue to determine its dose. Some methods rely on blood levels of a drug to estimate its concentration in the tissues, which can be inaccurate. We thought that drug levels in exhaled breath aerosol (EBA) to give a more accurate value of the level of a test drug in the lung. Rats were intravenously injected with the bronchodilator theophylline and exhaled breath was collected up to 10-20 min after administration. Immediately after breath collection, lung, liver, kidney, and blood were collected and the pharmacokinetics were examined using these samples. Awake free-moving rats were used to efficiently collect exhaled breath from rats with low tidal volume. The amount of exhaled breath of rats was estimated by the amount of exhaled water vapor, and the drug concentration in exhaled breath sample was expressed by the amount of water vapor as the denominator. By using the active sampling method in which the adsorbent is sucked by a pump, theophylline in rat exhaled breath could be measured accurately. When the correlation of theophylline concentration in each sample was examined, a high correlation (r²= 0.74) was found only in exhaled breath and lung tissue. EBA was considered better than blood in pharmacokinetic analysis of lung tissue.

Quantification of volatile organic compounds by secondary electrospray ionization-high resolution mass spectrometry

Secondary electrospray ionization coupled with high resolution mass spectrometry (SESI-HRMS) is a direct mass spectrometry technique, which can identify trace volatile organic compounds (VOCs) in real time without sample pretreatment and chromatographic separation. SESI-HRMS has been successfully applied in multiple applications, including breath analysis, animals and plants VOCs emissions, analysis of headspace of cell cultures and indoor and outdoor air. The range of areas where the technique can potentially have a substantial impact is very broad. However, one critical aspect that requires further development to consolidate the technique is absolute quantification. Therefore, in this study we aim to develop a quantitative method for eight representative VOCs, including ketones (acetone, 2-butanone and 2-pentanone), alkenes (isoprene and α-terpinene) and aromatics (toluene, styrene and mesitylene). The mass spectrometric platform includes a commercial SESI source hyphenated with a Q-Exactive hybrid quadrupole Orbitrap high resolution mass spectrometer. Within the concentration range of 0-100 ppbv studied, the optimal coefficient of determination for linear regression (R² = 0.993-0.999) between signal intensity and concentration is obtained in the range of 0-10 ppbv for all eight VOCs. The detection limits range between 3 (2-Pentanone) and 15 (Acetone) pptv. The intra-day (n = 10) and inter-day (n = 30) coefficients of variation (CV) are ≤ 6% and ≤10%, respectively. Finally the method is applied for the fast evaluation (<5 min) of different materials widely used for the collection, storage or pretreatment of gas sample. Better recovery of trace levels of eight VOCs is observed for PTFE gas sampling bag as compared to Nalophan and Tedlar bags; when Nafion tube is used to pretreat the gas sample, recovery of ≤50% are obtained for 2-pentanone, α-terpinene and all three aromatics.

Real-time pharmacokinetics via online analysis of exhaled breath

The advantages that on-line breath analysis has shown in different fields have already made it stand as an interesting tool for pharmacokinetic studies. This review summarizes recent progress in the field, diving into the different analytical methods and the different advantages and hurdles encountered. We conclude that there is a wealth of limitations in the application of this technique, and key aspects like standardization are still outstanding. Nevertheless, this is an experimental field that has not yet been fully explored; and the advantages it offers for animal welfare, decrease in the amount of drug needed in experimental studies, and complementary insights to current pharmacological studies, warrant further exploration. Further studies are needed to overcome current limitations and incorporate this technique into the toolbox of pharmacological studies, both at an industrial and academic level.

Personalised therapeutic management of epileptic patients guided by pathway-driven breath metabolomics

BACKGROUND

Therapeutic management of epilepsy remains a challenge, since optimal systemic antiseizure medication (ASM) concentrations do not always correlate with improved clinical outcome and minimal side effects. We tested the feasibility of noninvasive real-time breath metabolomics as an extension of traditional therapeutic drug monitoring for patient stratification by simultaneously monitoring drug-related and drug-modulated metabolites.

METHODS

This proof-of-principle observational study involved 93 breath measurements of 54 paediatric patients monitored over a period of 2.5 years, along with an adult's cohort of 37 patients measured in two different hospitals. Exhaled breath metabolome of epileptic patients was measured in real time using secondary electrospray ionisation-high-resolution mass spectrometry (SESI-HRMS).

RESULTS

We show that systemic ASM concentrations could be predicted by the breath test. Total and free valproic acid (VPA, an ASM) is predicted with concordance correlation coefficient (CCC) of 0.63 and 0.66, respectively. We also find (i) high between- and within-subject heterogeneity in VPA metabolism; (ii) several amino acid metabolic pathways are significantly enriched (p < 0.01) in patients suffering from side effects; (iii) tyrosine metabolism is significantly enriched (p < 0.001), with downregulated pathway compounds in non-responders.

CONCLUSIONS

These results show that real-time breath analysis of epileptic patients provides reliable estimations of systemic drug concentrations along with risk estimates for drug response and side effects.

Cu2O nanoparticles anchored on carbon for the efficient removal of propofol from operating room wastewater via peroxymonosulfate activation: efficiency, mechanism, and pathway

Anesthetic drug wastage has increasingly become the main resource of operating room sewage, which poses a great risk to the safety of humans and other organisms. Propofol is the most widely used anesthetic drug in the world, and also occupies the largest proportion of the total anesthetic wastage in the operating room. In this work, a 2D Cu2O anchored carbon catalyst (Cu2O@NC) was prepared by the assembly-pyrolysis process and successfully applied to peroxymonosulfate (PMS) activation. We took propofol as a typical example and investigated the removal activity through heterostructure-enhanced advanced oxidation processes (AOPs). Through the degradation process, propofol can be removed from 20 ppm to ultralow levels within 5 min using the PMS/Cu2O@NC system. The degradation pathway of propofol was deduced through quantum chemical calculation and LC/GC-MS results. The final products were verified as CO2 and H2O. Moreover, sulfate radicals (SO4˙-) proved to be the dominant reactive oxidation species by radical scavenger experiments and ESR results. In addition, it has great universality for various pharmaceuticals such as tetracycline (TC), amoxicillin (AMX), cephalexin (CPX), and norfloxacin (NFX). Our work provided the possibility to treat operation room sewage in a rapid, high-efficiency, and feasible way.

In vivo monitoring of volatile metabolic trajectories enables rapid diagnosis of influenza A infection

We report that influenza A virus infection induces changes in odor traits that could be captured by real-time high-resolution mass spectrometry in a living mouse model. The most striking changes in the volatile metabolites may be associated mostly to glyoxylate/dicarboxylate metabolism.

Robotized Noncontact Open-Space Mapping of Volatile Organic Compounds Emanating from Solid Specimens

Analysis of volatile organic compounds (VOCs) is normally preceded by sample homogenization and solvent extraction. This methodology does not provide spatial resolution of the analyzed VOCs in the examined matrix. Here, we present a robotized pen-shaped probe for open-space sampling and mapping of VOCs emanating from solid specimens (dubbed "PENVOC"). The system combines vacuum-assisted suction probe, mass spectrometry, and robotic handling of the probe. The VOCs are scavenged from the sample surface by a gentle hydrodynamic flow of air sustained by a vacuum pump. The sampled gas is transferred to the proximity of corona discharge in an atmospheric pressure chemical ionization source of a tandem mass spectrometer. The PENVOC has been attached to a robotic arm to enable unattended scanning of flat surfaces. The specimens can be placed away from the mass spectrometer during the scan. The robotized PENVOC has been characterized using chemical standards (benzaldehyde, limonene, 2-nonanone, and ethyl octanoate). The limits of detection are in the range from 2.33 × 10^-5 to 2.68 × 10^-4 mol m^-2. The platform has further been used for mapping of VOCs emanating from a variety of specimens: flowers, glove exposed to smoke, fuel stains, worn medical face mask, worn clothing, cheese, ham, and fruits. The chemical maps show unique distributions of the VOCs on the scanned surfaces. Obtaining comparable results (VOC maps) using other techniques (e.g., repetitive headspace sampling prior to offline analysis) would be time-consuming. The presented mapping technique may find applications in environmental, forensic, and food science.

Monitoring peppermint washout in the breath metabolome by secondary electrospray ionization-high resolution mass spectrometry

In this study, a secondary electrospray ionization-high resolution mass spectrometer (SESI-HRMS) system was employed to profile the real-time exhaled metabolome of ten subjects who had ingested a peppermint oil capsule. In total, six time points were sampled during the experiment. Using an untargeted way of profiling breath metabolome, 2333 m/z unique metabolite features were determined in positive mode, and 1322 in negative mode. To benchmark the performance of the SESI-HRMS setup, several additional checks were done, including determination of the technical variation, the biological variation of one subject within three days, the variation within a time point, and the variation across all samples, taking all m/z features into account. Reproducibility was good, with the median technical variation being 18% and the median variation within biological replicates being 34%. Both variations were lower than the variation across individuals. Washout profiles of compounds from the peppermint oil, including menthone, limonene, pulegone, menthol and menthofuran were determined in all subjects. Metabolites of the peppermint oil were also determined in breath, for example, cis/trans-carveol, perillic acid and menthol glucuronide. Butyric acid was found to be the major metabolite that reduce the uptake rate of limonene. Pathways related to limonene metabolism were examined, and meaningful pathways were identified from breath metabolomics data acquired by SESI using an untargeted analysis.

Cortical spreading depolarizations induced by surgical field blood in a mouse model of neurosurgery

OBJECTIVE

Cortical spreading depolarization (CSD) has been linked to poor clinical outcomes in the setting of traumatic brain injury, malignant stroke, and subarachnoid hemorrhage. There is evidence that electrocautery during neurosurgical procedures can also evoke CSD waves in the brain. It is unknown whether blood contacting the cortical surface during surgical bleeding affects the frequency of spontaneous or surgery-induced CSDs. Using a mouse neurosurgical model, the authors tested the hypothesis that electrocautery can induce CSD waves and that surgical field blood (SFB) is associated with more CSDs. The authors also investigated whether CSD can be reliably observed by monitoring the fluorescence of GCaMP6f expressed in neurons.

METHODS

CSD waves were monitored by using confocal microscopy to detect fluorescence increases at the cortical surface in mice expressing GCaMP6f in CamKII-positive neurons. The cortical surface was electrocauterized through an adjacent burr hole. SFB was simulated by applying a drop of tail vein blood to the brain through the same burr hole.

RESULTS

CSD waves were readily detected in GCaMP6f-expressing mice. Monitoring GCaMP6f fluorescence provided far better sensitivity and spatial resolution than detecting CSD events by observing changes in the intrinsic optical signal (IOS). Forty-nine percent of the CSD waves identified by GCaMP6f had no corresponding IOS signal. Electrocautery evoked CSD waves. On average, 0.67 ± 0.08 CSD events were generated per electrocautery episode, and multiple CSD waves could be induced in the same mouse by repeated cauterization (average, 7.9 ± 1.3 events; maximum number in 1 animal, 13 events). In the presence of SFB, significantly more spontaneous CSDs were generated (1.35 ± 0.37 vs 0.13 ± 0.16 events per hour, p = 0.002). Ketamine effectively decreased the frequency of spontaneous CSD waves (1.35 ± 0.37 to 0.36 ± 0.15 CSD waves per hour, p = 0.016) and electrocautery-stimulated CSD waves (0.80 ± 0.05 to 0.18 ± 0.08 CSD waves per electrocautery, p = 0.00002).

CONCLUSIONS

CSD waves are detected with far greater sensitivity and fidelity by monitoring GCaMP6f signals in neurons than by monitoring IOSs. Electrocautery reliably evokes CSD waves, and the frequency of spontaneous CSD waves is increased when blood is applied to the cortical surface. These experimental conditions recapitulate common scenarios in the neurosurgical operating room. Ketamine, a clinically available pharmaceutical agent, can block stimulated and spontaneous CSDs. More research is required to understand the clinical importance of intraoperative CSD.

Ketamine Blocks Morphine-Induced Conditioned Place Preference and Anxiety-Like Behaviors in Mice

Patients suffering from opioid use disorder often relapse during periods of abstinence, which is posited to be caused by negative affective states that drive motivated behaviors. Here, we explored whether conditioning mice with morphine in a conditioned place preference (CPP) training paradigm evoked anxiety-like behavior during morphine abstinence. To do this, mice were conditioned with morphine (10 mg/kg, i.p.) for 5 days. Twenty-four hours following conditioning, anxiety levels were tested by measuring time in the open arms of the elevated plus-maze. The next day, mice were placed in the three-compartment chamber to measure morphine-induced CPP. Our results show that following morphine conditioning, mice spent significantly less time in the open arm of the elevated plus-maze and expressed robust morphine CPP on CPP test day. Furthermore, we found that an acute treatment with (R,S)-ketamine (10 mg/kg, i.p.), a medication demonstrating promise for preventing anxiety-related phenotypes, 30 min before testing on post-conditioning day 1, increased time spent in the open arm of the elevated plus-maze in saline- and morphine-conditioned mice. Additionally, we found that the second injection of ketamine 30 min before CPP tests on post-conditioning day 2 prevented morphine-induced CPP, which lasted for up to 28 days post-conditioning. Furthermore, we found that conditioning mice with 10% (w/v) sucrose using an oral self-administration procedure did not evoke anxiety-like behavior, but elicited robust CPP, which was attenuated by ketamine treatment 30 min before CPP tests. Overall, our results suggest that the ketamine-induced block of morphine CPP may not be attributed solely to alleviating negative affective states, but potentially through impaired memory of morphine-context associations.

Rats Sniff Off Toxic Air

Breathing air is a fundamental human need, yet its safety, when challenged by various harmful or lethal substances, is often not properly guarded. For example, air toxicity is currently monitored only for a single or a limited number of known toxicants, thus failing to warn against possible hazardous air fully. Here, we discovered that, within minutes, living rats emitted distinctive profiles of volatile organic compounds (VOCs) via breath when exposed to various airborne toxicants such as endotoxin, O₃, ricin, and CO₂. Compared to background indoor air, when exposed to ricin or endotoxin aerosols, breath-borne VOC levels, especially that of carbon disulfide, were shown to decrease, while their elevated levels were observed for exposure to O₃ and CO₂. A clear contrast in breath-borne VOC profiles of rats exposed to different toxicants was observed with a statistical significance. Differences in microRNA regulations such as miR-33, miR-146a, and miR-155 from rats' blood samples revealed different mechanisms used by rats in combating different air toxicant challenges. Similar to dogs, rats were found here to be able to sniff off toxic air by releasing a specific breath-borne VOC profile. The discovered science opens a new arena for online monitoring of air toxicity and health effects of pollutants.

Ketamine induces immediate and delayed alterations of OCD-like behavior

RATIONALE

Obsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by intrusive obsessive thoughts and/or compulsive behaviors. Currently, serotonin reuptake inhibitors (SRIs) provide the only pharmacological monotherapy for OCD, but response rates are insufficient. Ketamine, a noncompetitive NMDA receptor antagonist, was reported to have rapid, sustained therapeutic effects in OCD patients. However, the mechanisms remain unknown.

OBJECTIVES

Here, we aimed to provide a platform for investigating mechanisms underlying anti-OCD effects of ketamine treatment by assessing whether ketamine pretreatment could alleviate 5-HT1B receptor (5-HT1BR)-induced OCD-like behavior in mice.

METHODS

We assessed whether acute ketamine (0, 3, 10, 30 mg/kg), administered at two pretreatment time points (30 min, 24 h), would modulate 5-HT1BR-induced OCD-like behavior in mice. Behavioral measures were perseverative hyperlocomotion in the open field and deficits in prepulse inhibition (PPI) induced by acute pharmacological 5-HT1BR challenge.

RESULTS

Three milligrams per kilogram of ketamine reduced 5-HT1BR-induced perseverative hyperlocomotion, but not PPI deficits, 24 h postinjection. In contrast, higher doses of ketamine were either ineffective (10 mg/kg) or exacerbated (30 mg/kg) 5-HT1BR-induced perseverative hyperlocomotion 30 min postinjection. At 24 h postinjection, 30 mg/kg ketamine reduced perseverative hyperlocomotion across all groups.

CONCLUSIONS

Our results suggest that the 5-HT1BR-induced model of OCD-like behavior is sensitive to a low dose of ketamine, a potential fast-acting anti-OCD treatment, and may provide a tool for studying mechanisms underlying the rapid therapeutic effects of ketamine in OCD patients.

Sub-anesthetic and anesthetic ketamine produce different long-lasting behavioral phenotypes (24 h post-treatment) via inducing different brain-derived neurotrophic factor (BDNF) expression level in the hippocampus

Clinical and preclinical researches have shown that sub-anesthetic ketamine elicits sustained antidepressant effects for up to 1-2 weeks. Pharmacokinetics studies (t1/2 = 23 min) in mice showed no ketamine residue at 24 h after sub-anesthetic or anesthetic ketamine administration. Therefore, this study aims to reveal the mechanism underlying these different biological functions at 24 h after sub-anesthetic and anesthetic ketamine treatment. First, at the animal behavioral level, we found that sub-anesthetic ketamine induced antidepressant and anxiolytic effects while anesthetic ketamine induced depressive-like phenotypes and cognitive impairment. Second, we examined the correlation between behavior phenotype and protein expression, and found that the Brain-derived neurotrophic factor (BDNF) level is oppositely regulated by sub-anesthetic and anesthetic ketamine. Sub-anesthetic ketamine significantly increased the BDNF level, correlating to antidepressant effects; whereas anesthetic dose reduced BDNF expression in the hippocampus, correlating to depressive-like behaviors, anxiety-like behaviors and cognitive impairment. Third, the antidepressant effects of sub-anesthetic ketamine were prevented by pre-treatment of ANA-12, a Tropomyosin receptor kinase B (TrkB) inhibitor. Thus, we conclude that BDNF may be the key factor underlying antidepressant and anxiolytic effects of sub-anesthetic ketamine at 24 h after treatment. These results may shed light on future studies and the development of long-lasting anti-depressant drugs and therapies.

On-Line Analysis of Exhaled Breath Focus Review

On-line analysis of exhaled breath offers insight into a person's metabolism without the need for sample preparation or sample collection. Due to its noninvasive nature and the possibility to sample continuously, the analysis of breath has great clinical potential. The unique features of this technology make it an attractive candidate for applications in medicine, beyond the task of diagnosis. We review the current methodologies for on-line breath analysis, discuss current and future applications, and critically evaluate challenges and pitfalls such as the need for standardization. Special emphasis is given to the use of the technology in diagnosing respiratory diseases, potential niche applications, and the promise of breath analysis for personalized medicine. The analytical methodologies used range from very small and low-cost chemical sensors, which are ideal for continuous monitoring of disease status, to optical spectroscopy and state-of-the-art, high-resolution mass spectrometry. The latter can be utilized for untargeted analysis of exhaled breath, with the capability to identify hitherto unknown molecules. The interpretation of the resulting big data sets is complex and often constrained due to a limited number of participants. Even larger data sets will be needed for assessing reproducibility and for validation of biomarker candidates. In addition, molecular structures and quantification of compounds are generally not easily available from on-line measurements and require complementary measurements, for example, a separation method coupled to mass spectrometry. Furthermore, a lack of standardization still hampers the application of the technique to screen larger cohorts of patients. This review summarizes the present status and continuous improvements of the principal on-line breath analysis methods and evaluates obstacles for their wider application.

Molecular breath analysis supports altered amino acid metabolism in idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Diagnosis of idiopathic pulmonary fibrosis (IPF) is complex and its pathogenesis is poorly understood. Recent findings indicate elevated levels of proline and other amino acids in lung tissue of IPF patients which may also be of diagnostic value. Following these findings, we hypothesized that such altered metabolic profiles would be mirrored in exhaled breath and could therefore be captured non-invasively in real time.

METHODS

We aimed to validate these results using real-time exhaled breath analysis by secondary electrospray ionization-mass spectrometry, which can provide a non-invasive, painless and fast insight into the metabolism. Breath analysis was performed in a matched 1:1 case-control study involving 21 patients with IPF and 21 control subjects.

RESULTS

We found significantly (P < 0.05) elevated levels of proline, 4-hydroxyproline, alanine, valine, leucine/isoleucine and allysine in breath of IPF patients, whereas pyroglutamic acid and phenylalanine did not show significant differences. This coincides with the amino acid's abundance in pulmonary tissue indicating that our observations reflect progressing fibrosis. In addition, amino acid levels correlated across subjects, further supporting a common underlying pathway. We were able to obtain a cross-validated area under the curve of 0.86, suggesting that these increased amino acid levels in exhaled breath have the potential to be used as biomarkers for IPF.

CONCLUSION

We could validate previous findings of elevated lung tissue amino acid levels in IPF and show that online breath analysis might be a practical tool for a rapid screening for IPF.

Positive matrix factorization: A data preprocessing strategy for direct mass spectrometry-based breath analysis

Interest in exhaled breath has grown considerably in recent years, as breath biosampling has shown promise for non-invasive disease diagnosis, therapeutic drug monitoring, and environmental exposure. Real time breath analysis can be accomplished via direct online mass spectrometry (MS)-based methods, which can provide more accurate and detailed data and an enhanced understanding of the temporal evolution of exhaled VOCs in the breath; however, the complicated chemical composition and large raw datasets involved in breath analysis have hindered the discovery of sources contributing to the exhaled VOCs. The positive matrix factorization (PMF) receptor model has been widely used for source apportionment in atmospheric studies. Since the exhaled VOCs contain compounds from various sources, such as alveolar air, mouth air and respiratory dead-space air, PMF may be also helpful for source apportionment of exhaled VOCs in the breath. Thus, this study explores the application of PMF in the pretreatment of direct breath measurement data. The results indicate that (i) endogenous compounds and background contaminants sources can be readily distinguished by PMF in data obtained from replicate measurements of human exhaled breath at single time points (~30 s/measurement), which may benefit both exhalome investigations and the identification of exposure biomarkers; (ii) sources resolved from online measurement data collected over longer periods (1.5 h) can be used to isolate the evolution of exhaled VOCs and investigate processes such as the pharmacokinetics of ketamine and its major metabolites. Therefore, PMF has shown promise for both data processing and subsequent data mining for the ambient MS-based breath analysis.

Automated in Vivo Nanosensing of Breath-Borne Protein Biomarkers

Toxicology and bedside medical condition monitoring is often desired to be both ultrasensitive and noninvasive. However, current biomarker analyses for these purposes are mostly offline and fail to detect low marker quantities. Here, we report a system called dLABer (detection of living animal's exhaled breath biomarker) that integrates living rats, breath sampling, microfluidics, and biosensors for the automated tracking of breath-borne biomarkers. Our data show that dLABer could selectively detect (online) and report differences (of up to 10³-fold) in the levels of inflammation agent interleukin-6 (IL-6) exhaled by rats injected with different ambient particulate matter (PM). The dLABer system was further shown to have an up to 10⁴ higher signal-to-noise ratio than that of the enzyme-linked immunosorbent assay (ELISA) when analyzing the same breath samples. In addition, both blood-borne IL-6 levels analyzed via ELISA in rats injected with different PM extracts and PM toxicity determined by a dithiothreitol (DTT) assay agreed well with those determined by the dLABer system. Video recordings further verified that rats exposed to PM with higher toxicity (according to a DTT assay and as revealed by dLABer) appeared to be less physically active. All the data presented here suggest that the dLABer system is capable of real-time, noninvasive monitoring of breath-borne biomarkers with ultrasensitivity. The dLABer system is expected to revolutionize pollutant health effect studies and bedside disease diagnosis as well as physiological condition monitoring at the single-protein level.

What about the herb? A new metabolomics approach for synthetic cannabinoid drug testing

Synthetic cannabinoids (SCs) are consumed as legal alternative to cannabis and often allow passing drug-screening tests. Their rapid transience on the drug scene, combined with their mostly unknown metabolic profiles, creates a scenario with constantly moving analytical targets, making their monitoring and identification challenging. The development of fast screening strategies for SCs, not directly focused on their chemical structure, as an alternative to the commonly applied target acquisition methods, would be highly appreciated in forensic and public health laboratories. An innovative untargeted metabolomics approach, focused on herbal components commonly used for 'spice' products, was applied. Saliva samples of healthy volunteers were collected at pre-dose and after smoking herbal components and analysed by high-resolution mass spectrometry. The data obtained, combined with appropriate statistical analysis, allowed to highlight and elucidate two markers (scopoletin and N,N-bis(2-hydroxyethyl)dodecylamine), which ratio permitted to differentiate herbal smokers from non-smokers. The proposed strategy will allow discriminating potential positives, on the basis of the analysis of two markers identified in the herbal blends. This work is presented as a step forward in SC drug testing, promoting a smart first-line screening approach, which will allow reducing the number of samples to be further investigated by more sophisticated HRMS methods. Graphical abstract The development of an alternative, generic screening methods of synthetic cannabinoids, not directly based on the chemical structure, in order to provide fast response on its potential consumption.

Development and validation of brain target controlled infusion of propofol in mice

Mechanisms through which anesthetics disrupt neuronal activity are incompletely understood. In order to study anesthetic mechanisms in the intact brain, tight control over anesthetic pharmacology in a genetically and neurophysiologically accessible animal model is essential. Here, we developed a pharmacokinetic model that quantitatively describes propofol distribution into and elimination out of the brain. To develop the model, we used jugular venous catheters to infuse propofol in mice and measured propofol concentration in serial timed brain and blood samples using high performance liquid chromatography (HPLC). We then used adaptive fitting procedures to find parameters of a three compartment pharmacokinetic model such that all measurements collected in the blood and in the brain across different infusion schemes are fit by a single model. The purpose of the model was to develop target controlled infusion (TCI) capable of maintaining constant brain propofol concentration at the desired level. We validated the model for two different targeted concentrations in independent cohorts of experiments not used for model fitting. The predictions made by the model were unbiased, and the measured brain concentration was indistinguishable from the targeted concentration. We also verified that at the targeted concentration, state of anesthesia evidenced by slowing of the electroencephalogram and behavioral unresponsiveness was attained. Thus, we developed a useful tool for performing experiments necessitating use of anesthetics and for the investigation of mechanisms of action of propofol in mice.

Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental exposure in a non-invasive manner. In this work, we present a protocol to characterize the exhaled VOCs in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry (Sec-nanoESI-HRMS). The homemade Sec-nanoESI source was readily set up based on a commercial nanoESI source. Hundreds of peaks were observed in the background-subtracted mass spectra of exhaled breath, and the mass accuracy values are -4.0-13.5 ppm and -20.3-1.3 ppm in the positive and negative ion detection modes, respectively. The peaks were assigned with accurate elemental composition according to the accurate mass and isotopic pattern. Less than 30 s is used for one exhalation measurement, and it takes approximately 7 min for six replicated measurements.

Translating secondary electrospray ionization-high-resolution mass spectrometry to the clinical environment

While there has been progress in making use of breath tests to guide clinical decision making, the full potential of exhaled breath analysis still remains to be exploited. Here we summarize some of the reasons why this is the case, what we have done so far to overcome some of the existing obstacles, and our vision of how we think breath analysis will play a more prominent role in the coming years. In particular, we envision that real-time high-resolution mass spectrometry will provide valuable information in biomarker discovery studies. However, this can only be achieved by a coordinated effort, using standardized equipment and methods in multi-center studies to eventually deliver tangible advances in the field of breath analysis in a clinical setting. Concrete aspects such as sample integrity, compound identification, quantification and standardization are discussed. Novel secondary electrospray ionization developments with the aim of facilitating inter-groups comparisons and biomarker validation studies are also presented.

Diagnosis of acute respiratory distress syndrome by exhaled breath analysis

The acute respiratory distress syndrome (ARDS) is a complication of critical illness that is characterized by acute onset, protein rich, pulmonary edema. There is no treatment for ARDS, other than the reduction of additional ventilator induced lung injury. Prediction or earlier recognition of ARDS could result in preventive measurements and might decrease mortality and morbidity. Exhaled breath contains volatile organic compounds (VOCs), a collection of hundreds of small molecules linked to several physiological and pathophysiological processes. Analysis of exhaled breath through gas-chromatography and mass-spectrometry (GC-MS) has resulted in an accurate diagnosis of ARDS in several studies. Most identified markers are linked to lipid peroxidation. Octane is one of the few markers that was validated as a marker of ARDS and is pathophysiologically likely to be increased in ARDS. None of the currently studied breath analysis methods is directly applicable in clinical practice. Two steps have to be taken before any breath test can be allowed into the intensive care unit. External validation in a multi-center study is a prerequisite for any of the candidate breath markers and the breath test should outperform clinical prediction scores. Second, the technology for breath analysis should be adapted so that it is available at a decentralized lab inside the intensive care unit and can be operated by trained nurses, in order to reduce the analysis time. In conclusion, exhaled analysis might be used for the early diagnosis and prediction of ARDS in the near future but several obstacles have to be taken in the coming years. Most of the candidate markers can be linked to lipid peroxidation. Only octane has been validated in a temporal external validation cohort and is, at this moment, the top-ranking breath biomarker for ARDS.

Comprehensive Real-Time Analysis of the Yeast Volatilome

While yeast is one of the most studied organisms, its intricate biology remains to be fully mapped and understood. This is especially the case when it comes to capture rapid, in vivo fluctuations of metabolite levels. Secondary electrospray ionization-high resolution mass spectrometry SESI-HRMS is introduced here as a sensitive and noninvasive analytical technique for online monitoring of microbial metabolic activity. The power of this technique is exemplarily shown for baker’s yeast fermentation, for which the time-resolved abundance of about 300 metabolites is demonstrated. The results suggest that a large number of metabolites produced by yeast from glucose neither are reported in the literature nor are their biochemical origins deciphered. With the technique demonstrated here, researchers interested in distant disciplines such as yeast physiology and food quality will gain new insights into the biochemical capability of this simple eukaryote.

Investigation on the influence of time-of-day on benzene metabolic pharmacokinetics by direct breath analysis in mice

Benzene, well known as a ubiquitous environmental pollutant, can lead to increasing risk of cancer, bone marrow failure as well as other serious diseases. Benzene has been classified as carcinogenic to humans with no recommended safe level of exposure. In this study, the influence of time-of-day on benzene metabolism has been tentatively explored in a mouse model based on direct real-time breath analysis by using membrane inlet single photon ionization time of flight mass spectrometry (MI-SPI-TOFMS). The exhaled breath of eight mice was monitored at a time resolution of less than 20 s after intraperitoneal (I.P.) injection of benzene in the morning, afternoon and evening on different days, and two rounds of experiments were carried out in total. The pharmacokinetic parameters such as total exposure AUC_0-∞ (h ng/mL), peak level C_max (ng/mL), time of peak level t_max (h), and terminal half-life t_1/2z (h) were calculated and discussed. The values of individual parameter varied greatly among the eight mice, e.g., AUC_0-∞ in the morning of the first round of experiment ranged from 10.66 to 162.17 h ng/mL and the mean ± SD was 103.72 ± 99.72 h ng/mL (n = 8). Significant difference has also been observed between two rounds of experiments, implying the damage in the liver caused by the benzene exposure. However, there is no significant difference among the results from the morning, afternoon and evening for each round of the experiment. In our follow-up study, the influence of time-of-day will be further investigated, in which the metabolites of benzene as well as endogenous metabolites will be considered.

Analysis of volatile compounds by open-air ionization mass spectrometry

This study demonstrates a simple method for rapid and in situ identification of volatile and endogenous compounds in culinary spice samples through mass spectrometry (MS). This method only requires a holder for solid spice sample (2-3 mm) that is placed close to a mass spectrometer inlet, which is applied with a high voltage. Volatile species responsible for the aroma of the spice samples can be readily detected by the mass spectrometer. Sample pretreatment is not required prior to MS analysis, and no solvent was used during MS analysis. The high voltage applied to the inlet of the mass spectrometer induces the ionization of volatile compounds released from the solid spice samples. Furthermore, moisture in the air also contributes to the ionization of volatile compounds. Dried spices including cinnamon and cloves are used as the model sample to demonstrate this straightforward MS analysis, which can be completed within few seconds. Furthermore, we also demonstrate the suitability of the current method for rapid screening of cinnamon quality through detection of the presence of a hepatotoxic agent, i.e. coumarin.

Direct human breath analysis by secondary nano-electrospray ionization ultrahigh-resolution mass spectrometry: Importance of high mass resolution and mass accuracy

RATIONALE

Direct mass spectrometry (MS)-based methods make it possible to monitor the molecular compositions of hundreds of volatile organic compounds (VOCs) in exhaled human breath in real time. Mass resolution and mass accuracy play important roles for direct MS analysis, especially for the low-concentration isobaric compounds in non-target research.

METHODS

Direct detection of VOCs in exhaled breath of four healthy subjects (3 males and 1 female aged between 25 to 35 years old) has been performed by using secondary nano-electrospray ionization mass spectrometry (Sec-nanoESI-UHRMS) at resolutions (R) of 15,000, 30,000, 60,000 and 120,000.

RESULTS

For some low-intensity isobaric ions, they could be distinguished only when R ≥ 60,000, e.g., signals at m/z 96.9591 (sulfate/sulfuric acid), m/z 96.9687 (phosphate/phosphoric acid) and m/z 96.9756 ([C₄ H₂ O₇ S]^- ), m/z 234.1161 ([C₁₀ H₂₀ O₃ NS]⁺ ) and m/z 234.1338 ([C₁₀ H₂₀ O₅ N]⁺ ), m/z 119.0686 (isotope of indole) and m/z 119.0705 (an interfering signal), respectively. At R 120,000, the mass errors were obtained from a set of reference ions, and the values were ≤0.6 mDa for ions detected in positive detection mode and in the range of -1.0-1.1 mDa for the negative mode. These mass errors were used to exclusively identify unknown compounds detected in the breath samples. By utilizing the present setup, besides the normal VOCs reported previously, we detected non-volatile species (sulfate/sulfuric acid, silicate/silicic acid, phosphate/phosphoric acid and nitrate/nitric acid), dichlorobenzene and an ammonium adduct ([(C₂ H₆ SiO)₆  + NH₄ ]⁺ ), which were ascribed to exhaled particles, indoor air pollution and an endogenous source, respectively.

CONCLUSIONS

For direct breath analysis, high mass resolution of ≥60,000 and mass errors of 1.0 mDa (absolute value) covering the mass range of interests (e.g., m/z 50-500) are necessary for the exploration and accurate identification of low-intensity unknown isobaric compounds in non-target research. Copyright © 2017 John Wiley & Sons, Ltd.

Gauging circadian variation in ketamine metabolism by real-time breath analysis

Real-time in vivo pharmacokinetics to investigate time-of-day variation in drug metabolism.

Real-Time Quantification of Amino Acids in the Exhalome by Secondary Electrospray Ionization–Mass Spectrometry: A Proof-of-Principle Study

BACKGROUND

Amino acids are frequently determined in clinical chemistry. However, current analysis methods are time-consuming, invasive, and suffer from artifacts during sampling, sample handling, and sample preparation. We hypothesized in this proof-of-principle study that plasma concentrations of amino acids can be estimated by measuring their concentrations in exhaled breath. A novel breath analysis technique described here allows such measurements to be carried out in real-time and noninvasively, which should facilitate efficient diagnostics and give insights into human physiology.

METHODS

The amino acid profiles in 37 individuals were determined by ion-exchange HPLC in blood plasma and simultaneously in breath by secondary electrospray ionization coupled to high-resolution mass spectrometry. Participants were split into training and test sets to validate the analytical accuracy. Longitudinal profiles in 3 individuals were additionally obtained over a 12-h period.

RESULTS

Concentrations of 8 slightly volatile amino acids (A, V, I, G, P, K, F, Orn) could be determined in exhaled breath with a CV of &lt;10%. Exhalome validation studies yielded high accuracies for each of these amino acids, on average only 3% less compared to plasma concentrations (95% CI ±13%). Higher variations were found only for amino acids with a low plasma concentration.

CONCLUSIONS

This study demonstrates for the first time that amino acids can be quantified in the human breath and that their concentrations correlate with plasma concentrations. Although this noninvasive technique needs further investigation, exhalome analysis may provide significant benefits over traditional, offline analytical methods.

Circadian Metabolism: From Mechanisms to Metabolomics and Medicine

The circadian clock directs nearly all aspects of diurnal physiology, including metabolism. Current research identifies several major axes by which it exerts these effects, including systemic signals as well as direct control of cellular processes by local clocks. This redundant network can transmit metabolic and timing information bidirectionally for optimal synchrony of metabolic processes. Recent advances in cellular profiling and metabolomics technologies have yielded unprecedented insights into the mechanisms behind this control. They have also helped to illuminate individual variation in these mechanisms that could prove important in personalized therapy for metabolic disease. Finally, these technologies have provided platforms with which to screen for the first potential drugs affecting clock-modulated metabolic function.

Dosing-Time Makes the Poison: Circadian Regulation and Pharmacotherapy

Daily rhythms in physiology significantly modulate drug pharmacokinetics and pharmacodynamics according to the time-of-day, a finding that has led to the concept of chronopharmacology. The importance of biological clocks for xenobiotic metabolism has gained increased attention with the discovery of the molecular circadian clockwork. Mechanistic understanding of the cell-autonomous molecular circadian oscillator and the circadian timing system as a whole has opened new conceptual and methodological lines of investigation to understand first, the clock's impact on a specific drug's daily variations or the effects/side effects of environmental substances, and second, how clock-controlled pathways are coordinated within a given tissue or organism. Today, there is an increased understanding of the circadian modulation of drug effects. Moreover, several molecular strategies are being developed to treat disease-dependent and drug-induced clock disruptions in humans.

Capturing in Vivo Plant Metabolism by Real-Time Analysis of Low to High Molecular Weight Volatiles

We have deployed an efficient secondary electrospray ionization source coupled to an Orbitrap mass analyzer (SESI-MS) to investigate the emissions of a Begonia semperflorens. We document how hundreds of species can be tracked with an unparalleled time resolution of 2 min during day-night cycles. To further illustrate the capabilities of this system for volatile organic compounds (VOCs) analysis, we subjected the plant to mechanical damage and monitored its response. As a result, ∼1200 VOCs were monitored displaying different kinetics. To validate the soundness of our in vivo measurements, we fully characterized some key compounds via tandem mass spectrometry (MS/MS) and confirmed their expected behavior based on prior gas chromatography/mass spectrometry (GC/MS) studies. For example, β-caryophyllene, which is directly related to photosynthesis, was found to show a periodic day-night pattern with highest concentrations during the day. We conclude that the capability of SESI-MS to capture highly dynamic VOC emissions and wide analyte coverage makes it an attractive tool to complement GC/MS in plant studies.

Detection and Quantification of Benzothiazoles in Exhaled Breath and Exhaled Breath Condensate by Real-Time Secondary Electrospray Ionization-High-Resolution Mass Spectrometry and Ultra-High Performance Liquid Chromatography

2-Subtituted benzothiazoles are widely used industrial chemicals whose occurrence in environmental samples has been shown to be ubiquitous. However, knowledge about human exposure to these compounds and their excretion route is still scarce. Here, we demonstrate for the first time the detection of benzothiazole derivatives in exhaled breath. Real-time analysis of breath was carried out by means of secondary electrospray ionization coupled to high-resolution mass spectrometry. This coupling allowed not only the detection of these compounds in breath with a sensitivity in the pptv range but also their robust identification by comparing tandem high-resolution mass spectra from breath and standards. For further confirmation, benzothiazoles were also determined in exhaled breath condensate samples by means of ultra high-performance liquid chromatography. This approach strengthened the identification as a result of excellent matches in retention times and also allowed quantification. An estimated total daily exhalation of ca. 20 μg day(-1) was calculated for the six benzothiazole derivatives found in breath.