Carbon dioxide, an important messenger molecule for small cell lung cancer

Carbon dioxide and MAPK signalling: towards therapy for inflammation

Inflammation, although necessary to fight infections, becomes a threat when it exceeds the capability of the immune system to control it. In addition, inflammation is a cause and/or symptom of many different disorders, including metabolic, neurodegenerative, autoimmune and cardiovascular diseases. Comorbidities and advanced age are typical predictors of more severe cases of seasonal viral infection, with COVID-19 a clear example. The primary importance of mitogen-activated protein kinases (MAPKs) in the course of COVID-19 is evident in the mechanisms by which cells are infected with SARS-CoV-2; the cytokine storm that profoundly worsens a patient's condition; the pathogenesis of diseases, such as diabetes, obesity, and hypertension, that contribute to a worsened prognosis; and post-COVID-19 complications, such as brain fog and thrombosis. An increasing number of reports have revealed that MAPKs are regulated by carbon dioxide (CO2); hence, we reviewed the literature to identify associations between CO2 and MAPKs and possible therapeutic benefits resulting from the elevation of CO2 levels. CO2 regulates key processes leading to and resulting from inflammation, and the therapeutic effects of CO2 (or bicarbonate, HCO3-) have been documented in all of the abovementioned comorbidities and complications of COVID-19 in which MAPKs play roles. The overlapping MAPK and CO2 signalling pathways in the contexts of allergy, apoptosis and cell survival, pulmonary oedema (alveolar fluid resorption), and mechanical ventilation-induced responses in lungs and related to mitochondria are also discussed. Video Abstract.

Machine learning strengthened prediction of tracheal, bronchus, and lung cancer deaths due to air pollution

This work pointed out the use of machine learning tools to predict the effect of CO, O3, CH4, and CO2 on TBL (tracheal, bronchus, and lung cancer) deaths from 1990 to 2019. In this study, data from 203 countries/locations were used. We used evaluation metrics like accuracy, area under curve (AUC), recall, precision, and Matthews correlation coefficient (MCC) to determine the prediction efficiency of the models. The models that yielded accuracy between 89 and 90 were selected in this study. The essential features in the prediction process were extracted, and it was found that CO influenced the prediction process. Extra trees classifier, random forest classifier, gradient boosting classifier, and light gradient boosting machine were selected from 14 other classifiers based on the accuracy metric. The best-performing models, according to our benchmark standards, are the extra trees classifier (90.83%), random forest classifier (89.17%), gradient boosting classifier (89.17%), and light gradient boosting machine (89.17). We conclude that machine learning models can be used in predicting mortality, i.e., the number of deaths, and could assist us in predicting the role of air pollutants on TBL deaths globally.

THE ENERGY–POLLUTION–HEALTH NEXUS: A PANEL DATA ANALYSIS OF LOW- AND MIDDLE-INCOME ASIAN COUNTRIES

Increased consumption of nonrenewable energy sources may lead to more air pollution, resulting in negative health impacts in a society. The main purpose of this study is to investigate the relationship between fossil fuel energy consumption and health issues using generalized method of moments estimation technique for data from 18 Asian countries (both low- and middle-income) over the period 1991–2018. The findings demonstrate that fossil fuel energy consumption increases the risk of lung and respiratory diseases. In addition, the results demonstrate the significant effect of CO2 emissions and fossil fuel consumption on undernourishment and death rates. Furthermore, we find that increases in the gross domestic product per capita and healthcare expenditure may help reduce undernourishment and death ratio. The conclusion recommends that diversification of energy in low- and middle-income countries from too much reliance on fossil fuels to more renewable energy sources can improve energy insecurity, at the same time reduce greenhouse gas emissions and minimize the negative impacts on human health.

The Impacts of Air Pollution on Health and Economy in Southeast Asia

The accessibility of cheap fossil fuels, due to large government subsidies, promotes the accelerated gross domestic product (GDP) per capita growth in Southeast Asia. However, the ambient air pollution from fossil fuel combustion has a latent cost, which is the public health issues such as respiratory diseases, lung cancer, labor loss, and economic burden in the long-run. In Southeast Asia, lung cancer is the leading and second leading cause of cancer-related death in men, and women, respectively. This nexus study employs the panel vector error correction model (VECM) and panel generalized method of moments (GMM) using data from ten Southeast Asian countries from the period (2000–2016) to explore the possible association between emissions, lung cancer, and the economy. The results confirm that CO2 and PM2.5 are major risk factors for lung cancer in the region. Additionally, the increasing use of renewable energy and higher healthcare expenditure per capita tend to reduce the lung cancer prevalence. Governments specially in low oil price era, have to transfer subsidies from fossil fuels to renewable energy to create a healthy environment. Furthermore, cost creation for fossil fuel consumption through carbon taxation, especially in the power generation sector, is important to induce private sector investment in green energy projects.

Pulmonary neuroepithelial bodies are polymodal airway sensors: Evidence for CO2/H+ sensing

Pulmonary neuroepithelial bodies (NEB) in mammalian lungs are thought to function as airway O2 sensors that release serotonin (5-HT) in response to hypoxia. Direct evidence that NEB cells also respond to airway hypercapnia/acidosis (CO2/H+) is presently lacking. We tested the effects of CO2/H+ alone or in combination with hypoxia on 5-HT release from intact NEB cells in a neonatal hamster lung slice model. For the detection of 5-HT release we used carbon fiber amperometry. Fluorescence Ca2+ imaging method was used to assess CO2/H+-evoked changes in intracellular Ca2+. Exposure to 10 and 20% CO2 or pH 6.8–7.2 evoked significant release of 5-HT with a distinct rise in intracellular Ca2+ in hamster NEBs. This secretory response was dependent on the voltage-gated entry of extracellular Ca2+. Moreover, the combined effects of hypercapnia and hypoxia were additive. Critically, an inhibitor of carbonic anhydrase (CA), acetazolamide, suppressed CO2/H+-mediated 5-HT release. The expression of mRNAs for various CA isotypes, including CAII, was identified in NEB cells from human lung, and protein expression was confirmed by immunohistochemistry using a specific anti-CAII antibody on sections of human and hamster lung. Taken together our findings provide strong evidence for CO2/H+ sensing by NEB cells and support their role as polymodal airway sensors with as yet to be defined functions under normal and disease conditions.

Can mitochondrial dysfunction be initiated by dissociative electron attachment to xenobiotics?

Resonance attachment of low-energy electrons to xenobiotic molecules, 2,4-dichlorophenoxyacetic acid (2,4-D), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE), was investigated under gas-phase conditions by means of complementary experimental techniques. Electron transmission spectroscopy (ETS) and dissociative electron attachment spectroscopy (DEAS), in the 0-6 eV and 0-15 eV energy range, respectively, were applied with the aim of modeling the behavior of these pesticide molecules under reductive conditions in vivo. Formation of long-lived parent molecular anions and fragment negative ions was observed at incident electron energies very close to zero, in agreement with the results of density functional theory calculations. The gas-phase DEA process, analogous to dissociative electron transfer in solution, was considered as a model for the initial step which occurs in the intermembrane space of mitochondria when a xenobiotic molecule captures an electron "leaked" from the respiratory chain. A possible involvement of the fragments produced by DEA to the pesticides under investigation into cellular processes is discussed. It is concluded that the free radicals and potential DNA adducts formed by DEA are expected to be dangerous for mitochondrial functionalities, while several of the products observed could act as messenger molecules, thus interfering with the normal cellular signaling pathways.

Toxicity of carbon dioxide: a review

The toxicity of carbon dioxide has been established for close to a century. A number of animal experiments have explored both acute and long-term toxicity with respect to the lungs, the cardiovascular system, and the bladder, showing inflammatory and possible carcinogenic effects. Carbon dioxide also induces multiple fetal malformations and probably reduces fertility in animals. The aim of the review is to recapitulate the physiological and metabolic mechanisms resulting from CO(2) inhalation. As smokers are exposed to a high level of carbon dioxide (13%) that is about 350 times the level in normal air, we propose the hypothesis that carbon dioxide plays a major role in the long term toxicity of tobacco smoke.

Nitrosamines as nicotinic receptor ligands

Nitrosamines are carcinogens formed in the mammalian organism from amine precursors contained in food, beverages, cosmetics and drugs. The potent carcinogen, NNK, and the weaker carcinogen, NNN, are nitrosamines formed from nicotine. Metabolites of the nitrosamines react with DNA to form adducts responsible for genotoxic effects. We have identified NNK as a high affinity agonist for the alpha7 nicotinic acetylcholine receptor (alpha7nAChR) whereas NNN bound with high affinity to epibatidine-sensitive nAChRs. Diethylnitrosamine (DEN) bound to both receptors but with lower affinity. High levels of the alpha7nAChR were expressed in human small cell lung cancer (SCLC) cell lines and in hamster pulmonary neuroendocrine cells (PNECs), which serve as a model for the cell of origin of human SCLC. Exposure of SCLC or PNECs to NNK or nicotine increased expression of the alpha7nAChR and caused influx of Ca(2+), activation of PKC, Raf-1, ERK1/2, and c-myc, resulting in the stimulation of cell proliferation. Signaling via the alpha7nAChR was enhanced when cells were maintained in an environment of 10-15% CO(2) similar to that in the diseased lung. Hamsters with hyperoxia-induced pulmonary fibrosis developed neuroendocrine lung carcinomas similar to human SCLC when treated with NNK, DEN, or nicotine. The development of the NNK-induced tumors was prevented by green tea or theophylline. The beta-adrenergic receptor agonist, isoproterenol or theophylline blocked NNK-induced cell proliferation in vitro. NNK and nicotine-induced hyperactivity of the alpha7nAChR/RAF/ERK1/2 pathway thus appears to play a crucial role in the development of SCLC in smokers and could be targeted for cancer prevention.

Receptor-mediated effects of nicotine and its nitrosated derivative NNK on pulmonary neuroendocrine cells

Pulmonary neuroendocrine cells (PNECs) have been implicated in the development of small cell lung carcinoma (SCLC) and pediatric asthma, and smoking is a risk factor for both diseases. We as well as others have shown that the alpha(7) nicotinic acetylcholine receptor (alpha(7) nAChR) regulates the release of 5-hydroxytryptamine (5-HT, serotonin) in PNECs and SCLC. Serotonin is an autocrine growth factor for PNECs and SCLC and acts as broncho-constrictor. We found that nicotine and its nitrosated carcinogenic derivative 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) bind to the alpha(7) nAChR in SCLC and PNECs, resulting in the influx of Ca(2+), release of 5-HT, and activation of a mitogenic pathway mediated by protein kinase C (PKC), Raf-1, mitogen activated protein kinase (MAPK) and c-myc. Exposure to 10% CO(2) acted synergistically. Unstimulated SCLC cells from smokers demonstrated high base levels of 5-HT release and of individual downstream signaling components in comparison to PNECs. Subchronic exposure of PNECs to NNK up-regulated the alpha(7) nAChR and its associated serotonergic mitogenic pathway in PNECs, an effect that may contribute to the development of SCLC in smokers and pediatric asthma in children of mothers who smoke.

Effect of carbon dioxide on human ovarian carcinoma cell growth

OBJECTIVE

Laparoscopy may be associated with increased risk of ovarian carcinoma wound metastases. This study was designed to determine whether carbon dioxide exposure increases the growth of human ovarian cancer cells in vitro.

STUDY DESIGN

Immortalized ovarian epithelial carcinoma cell (SKOV-3 cell line) cultures were exposed to carbon dioxide, nitrous oxide, or culture media with decreased pH for up to 3 hours. Cell growth was determined with the use of a spectrophotometric assay, and the results were compared with control cells by paired t tests and linear regressions analysis.

RESULTS

Carbon dioxide exposure increased SKOV-3 cell growth by 52% after 4 days in culture. The increased cell growth had a linear relationship to the length of carbon dioxide exposure. Cells that were exposed to either nitrous oxide or media with pH 6.3 showed a trend toward decreased growth.

CONCLUSION

Carbon dioxide exposure increases the in vitro growth of human ovarian carcinoma cells by an effect that is independent of the carbon dioxide-related decrease in the culture media pH.

Effects of concentric and eccentric contractions on phosphorylation of MAPK(erk1/2) and MAPK(p38) in isolated rat skeletal muscle

1. Exercise and contractions of isolated skeletal muscle induce phosphorylation of mitogen-activated protein kinases (MAPKs) by undefined mechanisms. The aim of the present study was to determine exercise-related triggering factors for the increased phosphorylation of MAPKs in isolated rat extensor digitorum longus (EDL) muscle. 2. Concentric or eccentric contractions, or mild or severe passive stretches were used to discriminate between effects of metabolic/ionic and mechanical alterations on phosphorylation of two MAPKs: extracellular signal-regulated kinase 1 and 2 (MAPK(erk1/2)) and stress-activated protein kinase p38 (MAPK(p38)). 3. Concentric contractions induced a 5-fold increase in MAPK(erk1/2) phosphorylation. Application of the antioxidants N-acetylcysteine (20 mM) or dithiothreitol (5 mM) suppressed concentric contraction-induced increase in MAPK(erk1/2) phosphorylation. Mild passive stretches of the muscle increased MAPK(erk1/2) phosphorylation by 1.8-fold, whereas the combination of acidosis and passive stretches resulted in a 2.8-fold increase. Neither concentric contractions, nor mild stretches nor acidosis significantly affected phosphorylation of MAPK(p38). 4. High force applied upon muscle by means of either eccentric contractions or severe passive stretches resulted in 5.7- and 9.5-fold increases of phosphorylated MAPK(erk1/2), respectively, whereas phosphorylation of MAPK(p38) increased by 7.6- and 1.9-fold (not significant), respectively. 5. We conclude that in isolated rat skeletal muscle an increase in phosphorylation of both MAPK(erk1/2) and MAPK(p38) is induced by mechanical alterations, whereas contraction-related metabolic/ionic changes (reactive oxygen species and acidosis) cause increased phosphorylation of MAPK(erk1/2) only. Thus, contraction-induced phosphorylation can be explained by the combined action of increased production of reactive oxygen species, acidification and mechanical perturbations for MAPK(erk1/2) and by high mechanical stress for MAPK(p38).

Interaction of tobacco-specific toxicants with the neuronal alpha(7) nicotinic acetylcholine receptor and its associated mitogenic signal transduction pathway: potential role in lung carcinogenesis and pediatric lung disorders

Pulmonary neuroendocrine cells function as hypoxia-sensitive chemoreceptors, and they release peptides and biogenic amines that are important mediators of pulmonary neonatal adaptation. Some of these products additionally act as autocrine growth factors. Increased numbers of pulmonary neuroendocrine cells have been observed in several smoking-associated pediatric lung disorders such as bronchopulmonary dysplasia, cystic fibrosis, sudden infant death syndrome, and asthma. Disturbed pulmonary neuroendocrine function has been implicated in the etiology of this disease complex. One of the most common smoking-associated lung cancer types, small cell lung carcinoma, expresses phenotypic and functional features of pulmonary neuroendocrine cells. We, as well as others, have shown that the release of the autocrine growth factors 5-hydroxytryptamine (5-HT, serotonin) and mammalian bombesin/gastrin releasing peptide (MB/GRP) by cell lines derived from human small cell lung carcinoma or fetal hamster pulmonary neuroendocrine cells are regulated by a neuronal nicotinic acetylcholine receptor comprised of alpha(7) subunits. In radio-receptor assays, nicotine and the nicotine-derived carcinogenic nitrosamines NNNN. Binding of nicotine or NNK to the alpha(7) receptor resulted in calcium influx and overexpression and activation of the serine-threonine protein kinase Raf-1. In turn, this event lead to overexpression and activation of the mitogen activated (MAP) kinases extracellular signal regulated kinase 1 (ERK1) and extracellular signal regulated kinase 2 (ERK2) and stimulation of DNA synthesis accompanied by an increase in cell numbers in fetal pulmonary neuroendocrine cells and small cell carcinoma cells. Exposure of fetal pulmonary neuroendocrine cells for 6 days to NNK caused a prominant up-regulation of Raf-1. Our findings suggest that chronic exposure to nicotine and NNK in pregnant women who smoke may up-regulate the alpha(7) nicotinic receptor as well as components of its associated mitogenic signal transduction pathway, thus increasing the susceptibilities of the infants for the development of pediatric lung disorders. Similarly, up-regulation of one or several components of this nicotinic receptor pathway in smokers may be an important factor for the development of small cell lung carcinoma.