Volatile organic compounds in exhaled breath are independent of systemic inflammatory syndrome caused by intravenous lipopolysaccharide infusion in humans: results from an experiment in healthy volunteers

Breath biomarkers in Non-Carcinogenic diseases

The analysis of volatile organic compounds (VOCs) from human matrices like breath, perspiration, and urine has received increasing attention from academic and medical researchers worldwide. These biological-borne VOCs molecules have characteristics that can be directly related to physiologic and pathophysiologic metabolic processes. In this work, gathers a total of 292 analytes that have been identified as potential biomarkers for the diagnosis of various non-carcinogenic diseases. Herein we review the advances in VOCs with a focus on breath biomarkers and their potential role as minimally invasive tools to improve diagnosis prognosis and therapeutic monitoring.

Diagnosis by Volatile Organic Compounds in Exhaled Breath in Exhaled Breath from Patients with Gastric and Colorectal Cancers

One in three cancer deaths worldwide are caused by gastric and colorectal cancer malignancies. Although the incidence and fatality rates differ significantly from country to country, the rates of these cancers in East Asian nations such as South Korea and Japan have been increasing each year. Above all, the biggest danger of this disease is how challenging it is to recognize in its early stages. Moreover, most patients with these cancers do not present with any disease symptoms before receiving a definitive diagnosis. Currently, volatile organic compounds (VOCs) are being used for the early prediction of several other diseases, and research has been carried out on these applications. Exhaled VOCs from patients possess remarkable potential as novel biomarkers, and their analysis could be transformative in the prevention and early diagnosis of colon and stomach cancers. VOCs have been spotlighted in recent studies due to their ease of use. Diagnosis on the basis of patient VOC analysis takes less time than methods using gas chromatography, and results in the literature demonstrate that it is possible to determine whether a patient has certain diseases by using organic compounds in their breath as indicators. This study describes how VOCs can be used to precisely detect cancers; as more data are accumulated, the accuracy of this method will increase, and it can be applied in more fields.

Volatolomic urinary profile analysis for diagnosis of the early stage of lung cancer

Nowadays in clinical practice there is a pressing need for potential biomarkers that can identify lung cancer at early stage before becoming symptomatic or detectable by conventional means. Several researchers have independently pointed out that the volatile organic compounds (VOCs) profile can be considered as a lung cancer fingerprint useful for diagnosis. In particular, 16% of volatiles contributing to the human volatilome are found in urine, which is therefore an ideal sample medium. Its analysis through non-invasive, relatively low-cost and straightforward techniques could offer great potential for the early diagnosis of lung cancer. In this study, urinary VOCs were analysed with a gas chromatography-ion mobility spectrometer (GC-IMS) and an electronic nose (e-nose) made by a matrix of twelve quartz microbalances (QMBs) complemented by a photoionization detector (PID). This clinical prospective study involved 127 individuals, divided into two groups: 46 with lung cancer stage I-II-III confirmed by computerized tomography (CT) or positron emission tomography-(PET) imaging techniques and histology (biopsy), and 81 healthy controls. Both instruments provided a multivariate signal which, after being analysed by a machine learning algorithm, identified eight VOCs that could distinguish lung cancer patients from healthy ones. The eight VOCs are 2-pentanone, 2-hexenal, 2-hexen-1-ol, hept-4-en-2-ol, 2-heptanone, 3-octen-2-one, 4-methylpentanol, 4-methyl-octane. Results show that GC-IMS identifies lung cancer with respect to the control group with a diagnostic accuracy of 88%. Sensitivity resulted as being 85%, and specificity was 90% - Area Under the Receiver Operating Characteristics (AUROC): 0.91. The contribution made by the e-nose was also important, even though the results were slightly less sensitive with an accuracy of 71.6%. Moreover, of the eight VOCs identified as potential biomarkers, five VOCs had a high sensitivity (p≤ 0.06) for early stage (stage I) lung cancer.

Changes of breath volatile organic compounds in healthy volunteers following segmental and inhalation endotoxin challenge

Background It is still unclear how airway inflammation affects the breath volatile organic compounds (VOC) profile in exhaled air. We therefore analyzed breath following well-defined pulmonary endotoxin (lipopolysaccharide, LPS) challenges. Methods Breath was collected from 10 healthy non-smoking subjects at eight time points before and after segmental and whole lung LPS inhalation challenge. Four Tenax-TA® adsorption tubes were simultaneously loaded from an aluminum reservoir cylinder and independently analyzed by two research groups using gas chromatography - mass spectrometry. Airway inflammation was assessed in bronchoalveolar lavage (BAL) and in sputum after segmental and inhaled LPS challenge, respectively. Results Segmental LPS challenge significantly increased the median (interquartile range, IQR) percentage of neutrophils in BAL from 3.0 (4.2) % to 64.0 (7.3) %. The inhalation challenge increased sputum neutrophils from 33.9 (26.8) % to 78.3 (13.5) %. We observed increases in breath aldehydes at both time points after segmental and inhaled LPS challenge. These results were confirmed by an independent laboratory. The longitudinal breath analysis also revealed distinct VOC patterns related to environmental exposures, clinical procedures, and to metabolic changes after food intake. Conclusions Changes in breath aldehydes suggest a relationship to LPS induced inflammation compatible with lipid peroxidation processes within the lung. Findings from our longitudinal data highlight the need for future studies to better consider the potential impact of the multiple VOCs from detergents, hygiene or lifestyle products a subject is continuously exposed to. We suspect that this very individual "owncloud" exposure is contributing to an increased variability of breath aldehydes, which might limit a use as inflammatory markers in daily clinical practice.

Targeted exhaled breath analysis for detection of Pseudomonas aeruginosa in cystic fibrosis patients

BACKGROUND

Pseudomonas aeruginosa (PA) is an important respiratory pathogen for cystic fibrosis (CF) patients. Routine microbiology surveillance is time-consuming, and is best performed on expectorated sputum. As alternative, volatile organic compounds (VOCs) may be indicative of PA colonisation. In this study, we aimed to identify VOCs associated with PA in literature and perform targeted exhaled breath analysis to recognize PA positive CF patients non-invasively.

METHODS

This study consisted of 1) a literature review to select VOCs of interest, and 2) a cross-sectional CF study. Definitions used: A) PA positive, PA culture at visit/chronically; B) PA free, no PA culture in ≥12 months. Exhaled VOCs were identified via quadrupole MS. The primary endpoint was the area under the receiver operating characteristics curve (AUROCC) of individual VOCs as well as combined VOCs against PA culture.

RESULTS

241 VOCs were identified in literature, of which 56 were further evaluated, and 13 could be detected in exhaled breath in our cohort. Exhaled breath of 25 pediatric and 28 adult CF patients, PA positive (n=16) and free (n=28) was available. 3/13 VOCs were significantly (p<0.05) different between PA groups in children; none were in adults. Notably, a composite model based on 5 or 1 VOC(s) showed an AUROCC of 0.86 (CI 0.71-1.0) and 0.87 (CI 0.72-1.0) for adults and children, respectively.

CONCLUSIONS

Targeted VOC analysis appears to discriminate children and adults with and without PA positive cultures with clinically acceptable sensitivity values.

A literature survey of all volatiles from healthy human breath and bodily fluids: the human volatilome

This paper comprises an updated version of the 2014 review which reported 1846 volatile organic compounds (VOCs) identified from healthy humans. In total over 900 additional VOCs have been reported since the 2014 review and the VOCs from semen have been added. The numbers of VOCs found in breath and the other bodily fluids are: blood 379, breath 1488, faeces 443, milk 290, saliva 549, semen 196, skin 623 and urine 444. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been included in a single table with the source reference(s) for each VOC, an update on our 2014 paper. VOCs have also been grouped into tables according to their chemical class or functionality to permit easy comparison. Careful use of the database is needed, as a number of the identified VOCs only have level 2-putative assignment, and only a small fraction of the reported VOCs have been validated by standards. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces and breath. However, the lack of compounds from matrices such a semen and milk compared to breath for example could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from milk and semen compared to a large number for breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. by collecting skin sebum (with dissolved VOCs and semi VOCs) onto glass beads or cotton pads and then heating to a high temperature to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this work will not only be a useful database of VOCs listed in the literature but will stimulate further study of VOCs from healthy individuals; for example more work is required to confirm the identification of these VOCs adhering to the principles outlined in the metabolomics standards initiative. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.

Breath Biopsy and Discovery of Exclusive Volatile Organic Compounds for Diagnosis of Infectious Diseases

Exhaled breath contains thousand metabolites and volatile organic compounds (VOCs) that originated from both respiratory tract and internal organ systems and their microbiomes. Commensal and pathogenic bacteria and virus of microbiomes are capable of producing VOCs of different chemical classes, and some of them may serve as biomarkers for installation and progression of various common human diseases. Here we describe qualitative and quantitative methods for measuring VOC fingerprints generated by cellular and microbial metabolic and pathologic pathways. We describe different chemical classes of VOCs and their role in the host cell-microbial interactions and their impact on infection disease pathology. We also update on recent progress on VOC signatures emitted by isolated bacterial species and microbiomes, and VOCs identified in exhaled breath of patients with respiratory tract and gastrointestinal diseases, and inflammatory syndromes, including the acute respiratory distress syndrome and sepsis. The VOC curated databases and instrumentations have been developed through statistically robust breathomic research in large patient populations. Scientists have now the opportunity to find potential biomarkers for both triage and diagnosis of particular human disease.

Changes in volatile organic compounds provoked by lipopolysaccharide- or alpha toxin-induced inflammation in ventilated rats

Inflammation may alter volatile organic compounds (VOCs) in exhaled breath. We therefore used ion mobility spectrometry (IMS) to evaluate exhaled breath components in two non-infectious inflammatory models. Fifty male Sprague Dawley rats were anesthetized and ventilated for 24 h. Five treatments were randomly assigned: (1) lipopolysaccharide low dose [5 mg/kg]; (2) lipopolysaccharide high dose [10 mg/kg]; (3) alpha toxin low dose [40 µg/kg]; (4) alpha toxin high dose [80 µg/kg]; and, (5) NaCl 0.9% as control group. Gas was sampled from the expiratory line of the ventilator every 20 min and analyzed with IMS combined with a multi-capillary column. VOCs were identified by comparison with an established database. Survival analysis was performed by log-rank test, other analyses by one-way or paired ANOVA-tests and post-hoc analysis according to Holm-Sidak. Rats given NaCl and low-dose alpha toxin survived 24 h. The median survival time in alpha toxin high-dose group was 23 (95%-confidence interval (CI): 21, 24) h. In contrast, the median survival time in rats given high-dose lipopolysaccharide was 12 (95% CI: 9, 14) and only 13 (95% CI: 10, 16) h in those given high-dose lipopolysaccharide. 73 different VOCs were detected, of which 35 were observed only in the rats, 38 could be found both in the blank measurements of ventilator air and in the exhaled air of the rats. Forty-nine of the VOCs were identifiable from a registry of compounds. Exhaled volatile compounds were comparable in each group before injection of lipopolysaccharide and alpha toxin. In the LPS groups, 1-pentanol increased and 2-propanol decreased. After alpha toxin treatment, 1-butanol and 1-pentanol increased whereas butanal and isopropylamine decreased. Induction of a non-infectious systemic inflammation (niSI) by lipopolysaccharide and alpha toxin changes VOCs in exhaled breath. Exhalome analysis may help identify niSI.

In vitro profiling of endothelial volatile organic compounds under resting and pro-inflammatory conditions

INTRODUCTION

The evaluation of volatile organic compounds(VOCs) emitted by human body offers a unique tool to set up new non-invasive devices for early diagnosis and long-lasting monitoring of most human diseases. However, their cellular origin and metabolic fate have not been completely elucidated yet, thus limiting their clinical application. Endothelium acts as an interface between blood and surrounding tissues. As such, it adapts its physiology in response to different environmental modifications thus playing a role in the pathogenesis of many metabolic and inflammatory diseases.

OBJECTIVES

Since endothelium specifically reshapes its physiologic functions upon environmental changes the objective of this study was to evaluate if and how pro-inflammatory stimuli affect VOC metabolism in endothelial cell in culture.

METHODS

Gas chromatography with mass spectrometric detection was applied to profile VOCs in the headspace of cultured endothelial cells (EC) in the absence or presence of the pro-inflammatory stimulus lipopolysaccharide (LPS).

RESULTS

We observed that, under resting conditions, EC affected the amount of 58 VOCs belonging to aldehyde, alkane and ketone families. Among these, LPS significantly altered the amount of 15 VOCs. ROC curves show a perfect performance (AUC = 1) for 10 metabolites including 1-butanol, 3-methyl-1-butanol and 2-ethyl-1-hexanol.

DISCUSSION

The emission and uptake of the aforementioned VOCs disclose potential unexplored metabolic pathways for EC that deserve to be investigated. Overall, we identified new candidate VOC potentially exploitable, upon experimental confirm in in vivo model of disease, as potential biomarkers of sepsis and pro-inflammatory clinical settings.

Volatile organic compound profiles in outlet air from extracorporeal life-support devices differ from breath profiles in critically ill patients

Introduction

It is highly uncertain whether volatile organic compounds (VOCs) in exhaled breath of critically ill intensive care unit patients are formed in the lung locally, in the air compartment or lung tissue, or elsewhere in the body and transported to the lung via the bloodstream. We compared VOC mixtures in exhaled breath and in air coming from extracorporeal support devices in critically ill patients to address this issue.

Methods

First, we investigated whether it was safe to connect an electronic nose (eNose) or a gas sampling pump to extracorporeal support membranes. Then, breath and air from extracorporeal support devices were collected simultaneously for continuous monitoring of VOC mixtures using an eNose. In addition, samples for gas chromatography/mass spectrometry (GC-MS) analysis were taken daily at the two measurement sites.

Results

10 critically ill patients were monitored for a median (interquartile range) duration of 73 (72-113) h; in total, we had 887 h of air sampling. The eNose signals of breath correlated moderately with signals of air from the extracorporeal support devices (R²=0.25-0.44). After GC-MS analysis, 96 VOCs were found both in breath and air from the extracorporeal support devices; of these, 29 (30%) showed a significant correlation (p<0.05) between the two measurement sites, of which 17 were identified. VOCs that did not correlate were found in a higher concentration in breath than in air from the extracorporeal support devices.

Conclusion

This study suggests VOC analysis in the extracorporeal circulation is safe, and that VOCs of nonpulmonary origin can be measured in the breath and in the extracorporeal circulation of critically ill patients. For VOCs that did not correlate between the two measurement sites, the breath concentration was higher, suggesting pulmonary production of these molecules in a highly selected population of patients that received extracorporeal support.

Therapeutic effects of 5,2'-dibromo-2,4',5'-trihydroxydiphenylmethanone (LM49) in an experimental rat model of acute pyelonephritis by immunomodulation and anti-inflammation

Antibiotics are still the primary therapy for acute pyelonephritis (APN); rarely, natural polyphenols are also used. LM49 is a novel marine bromophenol derivative displaying strong anti-inflammatory effects. We investigated the therapeutic efficacy of LM49 in an experimental rat model of APN. The model was established by injecting 0.5 mL Escherichia coli (ATCC 25922, 10⁸ CFU/mL) into the urinary bladders of Sprague Dawley rats. This model showed increased kidney viscera indices and renal bacterial growth scores, as well as pathological changes in kidneys. We also performed a broth microdilution antimicrobial susceptibility test of the E. coli strain. Both norfloxacin and LM49 treatment reduced kidney viscera indices and decreased microbial counts in urine cultures and kidney homogenates in APN rats. However, in vitro experiments showed that LM49 did not directly inhibit bacteria. Rather, LM49 treatment inhibited inflammatory cell infiltration or abscess and improved tissue lesions in the renal medullary junction, renal pelvis, and calyx, and high-dose LM49 treatment inhibited the production of inflammatory interleukin-1β (IL-1β) and interleukin-6 (IL-6) in serum. CD4⁺ T cells were higher in the LM49 groups treated with high, medium, and low doses than in the model group, whereas only high-dose LM49 treatment increased the number of CD8⁺ T cells, as compared with that in the model group. However, LM49 treatment did not influence hematological parameters. Our results show that LM49 therapeutic effects in an APN animal model may be achieved by regulating immune responses and inhibiting inflammatory mediators, suggesting it as a candidate APN treatment.