Protein thiol oxidation in the rat lung following e-cigarette exposure

Nicotine and Vape: Drugs of the Same Profile Flock Together

Smoking, a major behavioral health burden, causes preventable and premature deaths globally. Nicotine, the addictive component present in tobacco products and Electronic cigarettes (E-cigarettes, vape), can bind to nicotinic acetylcholine receptors in the brain to trigger a dopamine release that reinforces smoking. Despite the widespread usage of nicotine, its mechanisms of toxicity, particularly in e-cigarettes, are poorly understood. Using Drosophila melanogaster as a model organism, this study aims to investigate the mechanism of the toxicity of nicotine and vape. Behavioral parameters, oxidative stress indicators, mRNA expression levels of Dopamine 1- receptor 1 (Dop1R1), Acetyl-coenzyme A synthetase (AcCoAs), and apoptotic proteins were assessed in the flies after a 5-day exposure to varying concentrations of nicotine (0.15, 0.25, and 0.35 mg/mL diet) and vape (0.06, 0.08, and 0.12 mg/mL diet). Furthermore, Gas Chromatography-Mass Spectrometry (GC/MS) and Gas Chromatography-Flame Ionization Detection (GC/FID) analyzes were conducted to gain more insight on the composition of the vape used in study. Findings indicate that both nicotine and vape exposure significantly reduced lifespan, impaired locomotor activity, and disrupted sleep patterns. Notably, nicotine exposure stimulated Dop1R1 transcription and altered Acetyl-CoA gene expression, impacting the viability and behavior of the flies. Elevated levels of reactive oxygen biomarkers were observed, contributing to cellular damage through oxidative stress and apoptotic mechanisms mediated by the Reaper and DIAP1 proteins. Additionally, the composition analysis of vape liquid revealed the presence of propylene glycol, nicotine, methyl esters, and an unidentified compound. This study highlights the complex interplay between nicotine, gene expression, and physiological responses in Drosophila.

A synergistic mechanism of Liquiritin and Licochalcone B from Glycyrrhiza uralensis against COPD

BACKGROUND

Chronic Obstructive Pulmonary Disease (COPD) is a refractory respiratory disease mainly attributed to multiple pathological factors such as oxidative stress, infectious inflammation, and idiopathic fibrosis for decades. The medicinal plant Glycyrrhiza uralensis extract (ULE) was widely used to control respiratory diseases in China. However, the regulatory mechanism of scientific evidence to support the therapeutic benefits of ULE in the management of COPD is greatly limited.

PURPOSE

This study aims to discover the potential protection mechanism of ULE on COPD via a muti-targets strategy.

STUDY DESIGN AND METHODS

The present study set out to determine the potential protective effects of ULE on COPD through a multi-target strategy. In vivo and in vitro models of COPD were established using cigarette smoke and lipopolysaccharide to assess the protective effects of ULE. It was evaluated by measuring inflammatory cytokines and assessing pulmonary pathological changes. HPLC was used to verify the active compounds of the potential compounds that were collected and screened using HERB, works of literature, and ADME tools. The mechanisms of ULE in the treatment of COPD were explored using transcriptomics, connectivity-map, and network pharmacology approaches. The relevant targets were further investigated using RT-PCR, western blot, and immunohistochemistry. The HCK inhibitor (iHCK-37) was used to evaluate the potential mechanism of ULE's active compounds in the prevention of COPD.

RESULTS

ULE effectively protected the lungs of COPD mice from oxidative stress, inflammation, and fibrosis damage. After screening and verification using ADME properties and HPLC, 4 active compounds were identified in ULE: liquiritin (LQ), licochalcone B (LCB), licochalcone A (LCA), and echinatin (ET). Network pharmacology integrated with transcriptomics analysis showed that ULE mitigated oxidative stress, inflammation, and fibrosis in COPD by suppressing HCK. The combination of LCB and LQ was optimized for anti-inflammation, antioxidation, and anti-fibrosis activities. The iHCK-37 further validated the preventive treatment of LCB and LQ on COPD by inhibiting HCK to exert antioxidant, anti-inflammatory, and anti-fibrotic effects. The combination of LCB and LQ, in a 1:1 ratio, exerted synergistic antioxidative, anti-inflammatory, and anti-fibrotic effects in the treatment of COPD by downregulating HCK.

CONCLUSION

The combination of LCB and LQ performed a significant anti-COPD effect via downregulating HCK.

Health outcomes of electronic cigarettes

ABSTRACT

The usage of electronic cigarettes (e-cigarettes) sparked an outbreak of unidentified vaping-related lung disease in the US during late 2019. With e-cigarettes becoming more and more popular, smokers have more options other than conventional cigarettes. Under these circumstances, a comprehensive evaluation of the general safety of new tobacco and tobacco-related products, represented by e-cigarettes, to human health is necessary. In this review, we summarize the current research on potential negative impacts of e-cigarette exposure on human health. In particular, studies detailing the relationship between e-cigarettes and the digestive system are summarized, with mechanisms mainly including hepatic metabolic dysfunction, impaired gut barrier, and worsened outcomes of inflammatory bowel disease (IBD). Although believed to be safer than traditional cigarettes, e-cigarettes exert adverse effects on systemic health and induce the development of multiple diseases including asthma, cardiovascular disease, and IBD. Moreover, nicotine-containing e-cigarettes have a negative impact on the childhood development and increase the risk of arterial stiffness compared to the non-nicotine e-cigarettes. However, non-nicotine e-cigarette components have detrimental effects including promoting liver damage and metabolic disorders.

Global approaches for protein thiol redox state detection

Due to its nucleophilicity, the thiol group of cysteine is chemically very versatile. Hence, cysteine often has important functions in a protein, be it as the active site or, in extracellular proteins, as part of a structural disulfide. Within the cytosol, cysteines are typically reduced. But the nucleophilicity of its thiol group makes it also particularly prone to post-translational oxidative modifications. These modifications often lead to an alteration of the function of the affected protein and are reversible in vivo, e.g. by the thioredoxin and glutaredoxin system. The in vivo-reversible nature of these modifications and their genesis in the presence of localized high oxidant levels led to the paradigm of thiol-based redox regulation, the adaptation, and modulation of the cellular metabolism in response to oxidative stimuli by thiol oxidation in regulative proteins. Consequently, the proteomic study of these oxidative posttranslational modifications of cysteine plays an indispensable role in redox biology.

Electronic nicotine delivery systems (ENDS): A convenient means of smoking?

Electronic nicotine delivery systems (ENDS), which are becoming increasingly popular in many parts of the world, have recently become more sophisticated in terms of their more active content and better controlled vaporisation. This review begins by describing how cigarette smoking led to the development of ENDS as a means of combatting nicotine addiction. ENDS are usually categorised as belonging to one of only three main generations, but a fourth has been added in order to differentiate the latest, most powerful, most advanced and innovative that have improved heating efficiency. Descriptions of the principal substances contained in ENDS are followed by considerations concerning the risk of toxicity due to the presence of albeit low concentrations of such a variety of compounds inhaled over a long time, and the increasingly widespread use of ENDS as a means of smoking illicit drugs. We also review the most widely used pharmacotherapeutic approaches to smoking cessation, and recent epidemiological data showing that ENDS can help some people to stop smoking. However, in order to ensure their appropriate regulation, there is a need for higher-quality evidence concerning the health effects and safety of ENDS, and their effectiveness in discouraging tobacco smoking.

Preliminary study on the E-liquid and aerosol on the neurobehavior of C. elegans

E-cigarettes, also known as electronic nicotine delivery systems (ENDS), are mainly used among adolescents and young adults. Similar to traditional cigarettes, different concentrations of nicotine are also added to E-cigarette's liquid (E-liquid), but due to the supplementation of chemicals such as propylene glycol (PG), vegetable glycerin (VG) and flavors, it is difficult to determine the risk after using E-cigarettes. And given to the specificity of the aerosol particle composition and atomization process of E-cigarettes, it is necessary to assess the neurotoxic effects of long-term E-cigarettes use. In this study, two commercial nicotine-containing (5%) and nicotine-free E-liquids were diluted to investigate the neurobehavioral changes and addictive tendencies of developing C. elegans after sub-chronic exposure to E-liquid. The results showed that sub-chronic exposure of E-liquid could lead to impaired growth and development of nematodes, abnormal general neuromotor behavior and advanced learning and memory behavior, and nicotine-containing E-liquid could also lead to increased addiction tendency of nematodes. Although the damage effect of nicotine free E-liquid is smaller than that of the nicotine-containing group, its toxic effect cannot be ignored. Further analysis of the neurotoxicity mechanism found that redox imbalance-mediated mitochondrial stress and aging may be important causes of E-liquid-induced biological damage. The biosafety of e-cigarette aerosols was also included in the assessment. The study found that the heated atomization process did not alter the E-liquid components, and E-cigarette aerosols still have the effect of interfering with the growth and development of nematodes and neurobehavior, and its addictive nature is also of concern. This study can provide new ideas for future studies on the neurotoxic effects and safety assessment of the E-cigarettes, and provide theoretical reference for the study on the injury mechanism of E-cigarettes.

Thiol redox proteomics: Characterization of thiol-based post-translational modifications

Redox post-translational modifications on cysteine thiols (redox PTMs) have profound effects on protein structure and function, thus enabling regulation of various biological processes. Redox proteomics approaches aim to characterize the landscape of redox PTMs at the systems level. These approaches facilitate studies of condition-specific, dynamic processes implicating redox PTMs and have furthered our understanding of redox signaling and regulation. Mass spectrometry (MS) is a powerful tool for such analyses which has been demonstrated by significant advances in redox proteomics during the last decade. A group of well-established approaches involves the initial blocking of free thiols followed by selective reduction of oxidized PTMs and subsequent enrichment for downstream detection. Alternatively, novel chemoselective probe-based approaches have been developed for various redox PTMs. Direct detection of redox PTMs without any enrichment has also been demonstrated given the sensitivity of contemporary MS instruments. This review discusses the general principles behind different analytical strategies and covers recent advances in redox proteomics. Several applications of redox proteomics are also highlighted to illustrate how large-scale redox proteomics data can lead to novel biological insights.

Rat bronchoalveolar lavage proteome changes following e-cigarette aerosol exposures

E-cigarette liquids are complex mixtures of chemicals consisting of humectants, such as propylene glycol (PG) and vegetable glycerin (VG), with nicotine or flavorings added. Published literature emphasizes the toxicity of e-cigarette aerosols with flavorings whereas much less attention has been given to the biologic effects of humectants. The purpose of the current study was to provide a comprehensive view of the acute biologic effects of e-cigarette aerosols on rat bronchoalveolar lavage (BAL) using mass spectrometry-based global proteomics. Sprague-Dawley rats were exposed to e-cigarette aerosol for 3 h/day for three consecutive days. Groups included: PG/VG alone, PG/VG + 2.5% nicotine (N), or PG/VG + N + 3.3% vanillin (V). Right lung lobes were lavaged for BAL and supernatants prepared for proteomics. Extracellular BAL S100A9 concentrations and BAL cell staining for citrullinated histone H3 (citH3) were also performed. From global proteomics, ∼2,100 proteins were identified from rat BAL. The greatest change in number of BAL proteins occurred with PG/VG exposures alone compared with controls with biological pathways enriched for acute phase responses, extracellular trap formation, and coagulation. Extracellular BAL S100A9 concentrations and the number of citH3 + BAL cells also increased significantly in PG/VG and PG/VG + 2.5% N. In contrast to PG/VG or PG/VG + N, the addition of vanillin to PG/VG + N increased BAL neutrophilia and downregulated lipid transport proteins. In summary, global proteomics support e-cigarette aerosol exposures to PG/VG alone as having a significant biologic effect on the lung independent of nicotine or flavoring with increased markers of extracellular trap formation.

Combined biological effects and lung proteomics analysis in mice reveal different toxic impacts of electronic cigarette aerosol and combustible cigarette smoke on the respiratory system

Combustible cigarettes produce many toxic substances that have been linked to diseases, such as lung cancer and chronic obstructive pulmonary disease. For those smokers unable or unwilling to quit, electronic cigarettes (e-cigarettes) could be used as an alternative to cigarettes. However, the effects and mechanisms of e-cigarette aerosol (ECA) on respiratory function have not been fully elucidated, and in vivo studies of its safety are limited compared to cigarette smoke (CS). In this article, we chose nicotine levels as dosing references and C57BL/6 mice for a 10-week subchronic inhalation toxicity study. A comprehensive set of toxicological endpoints was used to study the effect of exposure. Both CS (6 mg/kg) and ECA (6 or 12 mg/kg) inhalation had decreased the animal's lung function and increased levels of inflammation markers, along with pathological changes in the airways and lungs, with ECA displaying a relatively small effect at the same dose. Proteomic analysis of lung tissue showed greater overall protein changes by CS than that of ECA, with more severe inflammatory network perturbations. Compared with ECA, KEGG analysis of CS revealed upregulation of more inflammatory and virus-related pathways. Protein-protein interactions (PPI) showed that both ECA and CS significantly changed ribosome and complement system-related proteins in mouse lung tissue. The results support that e-cigarette aerosol is less harmful to the respiratory system than cigarette smoke at the same dose using this animal model, thus providing additional evidence for the relative safety of e-cigarettes.

Acute vaping in a golden Syrian hamster causes inflammatory response transcriptomic changes

E-cigarette vaping is a major aspect of nicotine consumption, especially for children and young adults. Although it is branded as a safer alternative to cigarette smoking, murine and rat models of subacute and chronic e-cigarette vaping exposure have shown many proinflammatory changes in the respiratory tract. An acute vaping exposure paradigm has not been demonstrated in the golden Syrian hamster, and the hamster is a readily available small animal model that has the unique benefit of becoming infected with and transmitting respiratory viruses, including SARS-CoV-2, without genetic alteration of the animal or virus. Using a 2-day, whole body vaping exposure protocol in male golden Syrian hamsters, we evaluated serum cotinine, bronchoalveolar lavage cells, lung, and nasal histopathology, and gene expression in the nasopharynx and lung through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Depending on the presence of nonnormality or outliers, statistical analysis was performed by ANOVA or Kruskal-Wallis tests. For tests that were statistically significant (P < 0.05), post hoc Tukey-Kramer and Dunn's tests, respectively, were performed to make pairwise comparisons between groups. In nasal tissue, RT-qPCR analysis revealed nicotine-dependent increases in gene expression associated with type 1 inflammation (CCL-5 and CXCL-10), fibrosis [transforming growth factor-β (TGF-β)], nicotine-independent increase oxidative stress response (SOD-2), and a nicotine-independent decrease in vasculogenesis/angiogenesis (VEGF-A). In the lung, nicotine-dependent increases in the expression of genes involved in the renin-angiotensin pathway [angiotensin-converting enzyme (ACE), ACE2], coagulation (tissue factor, Serpine-1), extracellular matrix remodeling (MMP-2, MMP-9), type 1 inflammation (IL-1β, TNF-α, and CXCL-10), fibrosis (TGF-β and Serpine-1), oxidative stress response (SOD-2), neutrophil extracellular traps release (ELANE), and vasculogenesis and angiogenesis (VEGF-A) were identified. To our knowledge, this is the first demonstration that the Syrian hamster is a viable model of e-cigarette vaping. In addition, this is the first report that e-cigarette vaping with nicotine can increase tissue factor gene expression in the lung. Our results show that even an acute exposure to e-cigarette vaping causes significant upregulation of mRNAs in the respiratory tract from pathways involving the renin-angiotensin system, coagulation, extracellular matrix remodeling, type 1 inflammation, fibrosis, oxidative stress response, neutrophil extracellular trap release (NETosis), vasculogenesis, and angiogenesis.

Regulation of hyperoxia-induced neonatal lung injury via post-translational cysteine redox modifications

Preterm infants and patients with lung disease often have excess fluid in the lungs and are frequently treated with oxygen, however long-term exposure to hyperoxia results in irreversible lung injury. Although the adverse effects of hyperoxia are mediated by reactive oxygen species, the full extent of the impact of hyperoxia on redox-dependent regulation in the lung is unclear. In this study, neonatal mice overexpressing the beta-subunit of the epithelial sodium channel (β-ENaC) encoded by Scnn1b and their wild type (WT; C57Bl6) littermates were utilized to study the pathogenesis of high fraction inspired oxygen (FiO2)-induced lung injury. Results showed that O2-induced lung injury in transgenic Scnn1b mice is attenuated following chronic O2 exposure. To test the hypothesis that reversible cysteine-redox-modifications of proteins play an important role in O2-induced lung injury, we performed proteome-wide profiling of protein S-glutathionylation (SSG) in both WT and Scnn1b overexpressing mice maintained at 21% O2 (normoxia) or FiO2 85% (hyperoxia) from birth to 11-15 days postnatal. Over 7700 unique Cys sites with SSG modifications were identified and quantified, covering more than 3000 proteins in the lung. In both mouse models, hyperoxia resulted in a significant alteration of the SSG levels of Cys sites belonging to a diverse range of proteins. In addition, substantial SSG changes were observed in the Scnn1b overexpressing mice exposed to hyperoxia, suggesting that ENaC plays a critically important role in cellular regulation. Hyperoxia-induced SSG changes were further supported by the results observed for thiol total oxidation, the overall level of reversible oxidation on protein cysteine residues. Differential analyses reveal that Scnn1b overexpression may protect against hyperoxia-induced lung injury via modulation of specific processes such as cell adhesion, blood coagulation, and proteolysis. This study provides a landscape view of protein oxidation in the lung and highlights the importance of redox regulation in O2-induced lung injury.

The role of synthetic coolants, WS-3 and WS-23, in modulating E-cigarette-induced reactive oxygen species (ROS) in lung epithelial cells

There has been a substantial rise in e-cigarette (e-cig) use or vaping in the past decade, prompting growing concerns about their adverse health effects. Recently, e-cig manufacturers have been using synthetic cooling agents, like WS-23 and WS-3, to provide a cooling sensation without the "menthol taste". Studies have shown that aerosols/vapes generated by e-cigs can contain significant levels of reactive oxygen species (ROS). However, studies investigating the role of synthetic coolants in modulating ROS levels generated by e-cigs are lacking. This study seeks to understand how synthetic coolants, e-cig additives that have become increasingly prevalent in e-liquids sold in the United States (US), impact acellular ROS production from e-liquid aerosols as well as cellular ROS levels from pulmonary epithelial cells exposed to these e-liquids. To further explain, our study aims to understand whether the addition of WS-3 and WS-23 to e-liquid base and e-liquid base with nicotine significantly modifies generated acellular ROS levels within aerosolized e-liquids, as well as cellular ROS within BEAS-2B cells treated with these same e-liquids. Aerosols were generated from e-liquids with and without synthetic coolants through a single-puff aerosol generator; subsequently, acellular ROS was semi-quantified in H2O2 equivalents via fluorescence spectroscopy. Our acellular ROS data suggest that adding WS-3 to e-liquid base (PG:VG), regardless of nicotine content, has a minimal impact on modifying e-cig generated acellular ROS levels. Additionally, we also measured cellular ROS in lung epithelial cells using both e-liquids containing and not containing synthetic coolants via the CellROX Green fluorescent sensor. Similar comparable results were found in BEAS2B cells though ROS was increased by WS-3 and WS-23 treated in e-cig nicotine groups. Altogether, our data suggest that neither the addition of WS-23 nor WS-3 to e-liquid base solution, with and without nicotine, significantly modifies e-cig generated acellular ROS levels within aerosolized e-liquids and cellular ROS levels within treated BEAS-2B cells. Together, our data provide insight into whether synthetic coolants added to e-liquids could impact vaping-induced oxidative stress in the lungs.

The chemistry and toxicology of vaping

Vaping is the process of inhaling and exhaling an aerosol produced by an e-cigarette, vape pen, or personal aerosolizer. When the device contains nicotine, the Food and Drug Administration (FDA) lists the product as an electronic nicotine delivery system or ENDS device. Similar electronic devices can be used to vape cannabis extracts. Over the past decade, the vaping market has increased exponentially, raising health concerns over the number of people exposed and a nationwide outbreak of cases of severe, sometimes fatal, lung dysfunction that arose suddenly in otherwise healthy individuals. In this review, we discuss the various vaping technologies, which are remarkably diverse, and summarize the use prevalence in the U.S. over time by youths and adults. We examine the complex chemistry of vape carrier solvents, flavoring chemicals, and transformation products. We review the health effects from epidemiological and laboratory studies and, finally, discuss the proposed mechanisms underlying some of these health effects. We conclude that since much of the research in this area is recent and vaping technologies are dynamic, our understanding of the health effects is insufficient. With the rapid growth of ENDS use, consumers and regulatory bodies need a better understanding of constituent-dependent toxicity to guide product use and regulatory decisions.

Toxicity of electronic cigarettes: A general review of the origins, health hazards, and toxicity mechanisms

Electronic cigarettes (E-cigarette) are an alternative for traditional cigarette smokers to quit smoking. Based on the current understanding, electronic cigarettes have rapidly become popular among existing smokers and former non-smokers. However, increasing research at different levels reveals that e-cigarettes are unsafe. This review provides an overview of the toxicology of e-cigarettes based on existing in vivo and in vitro studies and compares their toxicity with that of traditional cigarettes. Moreover, we describe the associated toxicity components in e-cigarettes, as well as the potential mechanism by which e-cigarettes exert toxic effects. As is known to all, the nicotine in traditional cigarettes and e-cigarettes has certain toxicity. Besides, a few studies have shown that propylene glycol and vegetable glycerin mixture and flavoring agents in e-cigarettes also are the key components causing adverse effects in animals or cells. There is insufficient scientific evidence on the toxicity of e-cigarettes due to the lack of standardized research methods, prompting the need to conduct a comprehensive toxicity assessment of e-cigarette toxicity to elucidate the safety issues of e-cigarettes. Eventually, a basis for decision-making on whether people use e-cigarettes will be obtained.

Characterization of cellular oxidative stress response by stoichiometric redox proteomics

The thiol redox proteome refers to all proteins whose cysteine thiols are subjected to various redox-dependent posttranslational modifications (PTMs) including S-glutathionylation (SSG), S-nitrosylation (SNO), S-sulfenylation (SOH), and S-sulfhydration (SSH). These modifications can impact various aspects of protein function such as activity, binding, conformation, localization, and interactions with other molecules. To identify novel redox proteins in signaling and regulation, it is highly desirable to have robust redox proteomics methods that can provide global, site-specific, and stoichiometric quantification of redox PTMs. Mass spectrometry (MS)-based redox proteomics has emerged as the primary platform for broad characterization of thiol PTMs in cells and tissues. Herein, we review recent advances in MS-based redox proteomics approaches for quantitative profiling of redox PTMs at physiological or oxidative stress conditions and highlight some recent applications. Considering the relative maturity of available methods, emphasis will be on two types of modifications: 1) total oxidation (i.e., all reversible thiol modifications), the level of which represents the overall redox state, and 2) S-glutathionylation, a major form of reversible thiol oxidation. We also discuss the significance of stoichiometric measurements of thiol PTMs as well as future perspectives toward a better understanding of cellular redox regulatory networks in cells and tissues.