n-3 Fatty acids regulate the inflammatory-state related genes in the lung epithelial cells exposed to polycyclic aromatic hydrocarbons

N-3 PUFAs and their specialized pro-resolving lipid mediators on airway inflammatory response: beneficial effects in the prevention and treatment of respiratory diseases

Respiratory diseases include a wide range of pathologies with different clinical manifestations, affecting the normal airways and lung function. An increase in the inflammatory response is considered a characteristic hallmark of these diseases, being also a critical factor for their progression. The n-3 polyunsaturated fatty acids (n-3 PUFAs) eicosapentaenoic acid (C20:4n-3, EPA), docosahexaenoic acid (C22:6n-3, DHA) and their lipid mediators are known to have an inflammation pro-resolution effect. The effects of these n-3 PUFAs in the prevention and treatment of respiratory diseases are beginning to be understood. Consequently, this article aims to analyze the influence of n-3 PUFAs and their lipid mediators on the inflammatory response in respiratory health, emphasizing recent data concerning their beneficial effects in the prevention and possible treatment of different respiratory diseases, particularly asthma, airway allergic syndromes and chronic obstructive pulmonary disease. The review includes studies regarding the effects of EPA, DHA, and their specialized pro-resolving lipid mediators (SPMs) on in vivo and in vitro models of respiratory disease, concluding that EPA and DHA have a positive impact in attenuating the pro-inflammatory response in respiratory diseases, reducing symptoms like nasal congestion, fever and difficulty in breathing. Controversial data reported are probably due to differences in several factors, including the dosages, administration vehicles, and the supplementation times employed, which are aspects that remain to be addressed in future studies.

Air Pollution and the Airways: Lessons from a Century of Human Urbanization

Since the industrial revolution, air pollution has become a major problem causing several health problems involving the airways as well as the cardiovascular, reproductive, or neurological system. According to the WHO, about 3.6 million deaths every year are related to inhalation of polluted air, specifically due to pulmonary diseases. Polluted air first encounters the airways, which are a major human defense mechanism to reduce the risk of this aggressor. Air pollution consists of a mixture of potentially harmful compounds such as particulate matter, ozone, carbon monoxide, volatile organic compounds, and heavy metals, each having its own effects on the human body. In the last decades, a lot of research investigating the underlying risks and effects of air pollution and/or its specific compounds on the airways, has been performed, involving both in vivo and in vitro experiments. The goal of this review is to give an overview of the recent data on the effects of air pollution on healthy and diseased airways or models of airway disease, such as asthma or chronic obstructive pulmonary disease. Therefore, we focused on studies involving pollution and airway symptoms and/or damage both in mice and humans.

Cross-Sectional Estimation of Endogenous Biomarker Associations with Prenatal Phenols, Phthalates, Metals, and Polycyclic Aromatic Hydrocarbons in Single-Pollutant and Mixtures Analysis Approaches

BACKGROUND

Humans are exposed to mixtures of toxicants that can impact several biological pathways. We investigated the associations between multiple classes of toxicants and an extensive panel of biomarkers indicative of lipid metabolism, inflammation, oxidative stress, and angiogenesis.

METHODS

We conducted a cross-sectional study of 173 participants (median 26 wk gestation) from the LIFECODES birth cohort. We measured exposure analytes of multiple toxicant classes [metals, phthalates, phenols, and polycyclic aromatic hydrocarbons (PAHs)] in urine samples. We also measured endogenous biomarkers (eicosanoids, cytokines, angiogenic markers, and oxidative stress markers) in either plasma or urine. We estimated pair-wise associations between exposure analytes and endogenous biomarkers using multiple linear regression after adjusting for covariates. We used adaptive elastic net regression, hierarchical Bayesian kernel machine regression, and sparse-group LASSO regression to evaluate toxicant mixtures associated with individual endogenous biomarkers.

RESULTS

After false-discovery adjustment (q<0.2), single-pollutant models yielded 19 endogenous biomarker signals associated with phthalates, 13 with phenols, 17 with PAHs, and 18 with trace metals. Notably, adaptive elastic net revealed that phthalate metabolites were selected for several positive signals with the cyclooxygenase (n=7), cytochrome p450 (n=7), and lipoxygenase (n=8) pathways. Conversely, the toxicant classes that exhibited the greatest number of negative signals overall in adaptive elastic net were phenols (n=20) and metals (n=21).

DISCUSSION

This study characterizes cross-sectional endogenous biomarker signatures associated with individual and mixtures of prenatal toxicant exposures. These results can help inform the prioritization of specific pairs or clusters of endogenous biomarkers and exposure analytes for investigating health outcomes. https://doi.org/10.1289/EHP7396.

Early Mechanistic Events Induced by Low Molecular Weight Polycyclic Aromatic Hydrocarbons in Mouse Lung Epithelial Cells: A Role for Eicosanoid Signaling

Low molecular weight polycyclic aromatic hydrocarbons (LMW PAHs; < 206.3 g/mol) are under regulated environmental contaminants (eg, secondhand smoke) that lead to gap junction dysregulation, p38 MAPK activation, and increased mRNA production of inflammatory mediators, such as cytokines and cyclooxygenase (COX2), in lung epithelial cells. However, the early mechanisms involving lipid signaling through the arachidonic acid pathway and subsequent eicosanoid production leading to these downstream events are not known. Common human exposures are to mixtures of LMW PAHs, thus C10 cells (a mouse lung epithelial cell line) were exposed to a representative binary PAH mixture, 1-methylanthracene (1-MeA) and fluoranthene (Flthn), for 30 min-24 h with and without p38 and cytosolic phospholipase A2 (cPLA2) inhibitors. Cytosolic phospholipase A2 inhibition reversed PAH-induced phospho-p38 MAPK activation and gap junction dysregulation at 30 min. A significant biphasic increase in cPLA2 protein was observed at 30 min, 2, and 4 h, as well as COX2 protein at 2 and 8 h. Untargeted metabolomics demonstrated a similar trend with significantly changing metabolites at 30 min and 4 h of exposure relative to 1 h; a "cPLA2-like" subset of metabolites within the biphasic response were predominately phospholipids. Targeted metabolomics showed several eicosanoids (eg, prostaglandin D2 (PGD2), PGE2α) were significantly increased at 4, 8, and 12 h following exposure to the binary PAH mixture and this effect was p38-dependent. Finally, PAH metabolism was not observed until after 8 h. These results indicate an early lipid signaling mechanism of LMW PAH toxicity in lung epithelial cells due to parent PAH compounds.

Fatty acids and selected endocannabinoids content in cerebrospinal fluids from patients with neuroinfections

Neuroinfections are a significant medical problem and can have serious health consequences for patients. Their outcome, if not fatal, can be associated with permanent residual deficits. Cerebrospinal fluid (CSF) examination is commonly used for meningitis confirmation. Fatty acids (FA) are precursors of lipid mediators with pharmacological activity. They actively modulate inflammation as well as contribute to its resolution. Therefore the aim of this study was to determine the FA and selected endocannabinoids (ECB) content in the CSF obtained from patients with bacterial (BM) and viral meningitis (VM) using chromatographic techniques. A significantly lower level of saturated FA was found in patients with BM and VM as compared to controls. There was a significantly higher concentration of long-chain monounsaturated FA and polyunsaturated n-6 FA in the CSF obtained from patients with neuroinfection. Moreover, a significant reduction of n-3 FA in CSF obtained from patients with BM and VM was demonstrated. The highest amount of ECB was detected in the CSF of patients with VM: eicosapentaenoyl ethanolamide (1.65 pg/mL), docosahexaenoyl ethanolamide (655.5 pg/mL) and nervonoyl ethanolamide (3.09 ng/mL). Results indicate the participation of long-chain monounsaturated and polyunsaturated FA and their derivatives in the inflammatory process and likely in the process of resolution of inflammation during neuroinfection. It seems that the determination of the FA and ECB profile in CSF may be a valuable biomarker of health and may allow the development of new pharmacological strategies, therapeutic goals and fatty acids supplementation necessary in the fight against inflammation of the central nervous system.

Chronic antidepressant-like effect of EMD386088, a partial 5-HT6 receptor agonist, in olfactory bulbectomy model may be connected with BDNF and/or CREB signalling pathway

BACKGROUND

The removal of the olfactory bulbs has been attributed to behavioral changes and neuroplasticity manifesting themselves among others like increases in brain neurotrophin expression and neurogenesis. Earlier data presented that EMD386088, a 5-HT6 receptor partial agonist, exerts antidepressant-like properties after chronic administration in olfactory bulbectomy (OB) model as was it compared with amitriptyline (AMI). The aim of this study was to compare acute and chronic biochemical effects of EMD386088, administered in its antidepressant active (2.5mg/kg) and non-active (1.25mg/kg) doses, found in the open field test in OB rats, with those of AMI (10mg/kg). The levels of 5-HT6 receptor protein and selected neurotrophins in prefrontal cortex (PFC) and hippocampus (Hp) of rats have been examined.

METHODS

5-HT6 receptor protein and selected neurotrophins: brain-derived neurotrophic factor (BDNF), cAMP-response element binding protein (CREB), the product of the immediate early gene c-fos (cFos) protein levels were assessed using a Western blot analysis in PFC and Hp of bulbectomized rats after acute or chronic (14-day) EMD386088 or AMI intraperitoneal (ip) treatment.

RESULTS

The acute treatment with EMD386088 caused significant increases in CREB and BDNF protein levels in PFC, and an increase in BDNF in Hp of OB rats, while AMI injection decreased CREB and did not change BDNF levels. After the chronic administration of EMD386088, the increasing levels of BDNF and CREB were still observed in PFC and Hp.

CONCLUSIONS

The antidepressant-like effect of EMD386088 may be associated with the neuroplasticity activation in PFC and Hp in rats.

A metabolomics strategy to assess the combined toxicity of polycyclic aromatic hydrocarbons (PAHs) and short-chain chlorinated paraffins (SCCPs)

The combined toxicity of mixed chemicals is usually evaluated according to several specific endpoints, and other potentially toxic effects are disregarded. In this study, we provided a metabolomics strategy to achieve a comprehensive understanding of toxicological interactions between mixed chemicals on metabolism. The metabolic changes were quantified by a pseudotargeted analysis, and the types of combined effects were quantitatively discriminated according to the calculation of metabolic effect level index (MELI). The metabolomics strategy was used to assess the combined effects of polycyclic aromatic hydrocarbons (PAHs) and short-chain chlorinated paraffins (SCCPs) on the metabolism of human hepatoma HepG2 cells. Our data suggested that exposure to a combination of PAHs and SCCPs at human internal exposure levels could result in an additive effect on the overall metabolism, whereas diverse joint effects were observed on various metabolic pathways. The combined exposure could induce a synergistic up-regulation of phospholipid metabolism, an additive up-regulation of fatty acid metabolism, an additive down-regulation of tricarboxylic acid cycle and glycolysis, and an antagonistic effect on purine metabolism. SCCPs in the mixture acted as the primary driver for the acceleration of phospholipid and fatty acid metabolism. Lipid metabolism disorder caused by exposure to a combination of PAHs and SCCPs should be an important concern for human health.

Oxidized LDL triggers changes in oxidative stress and inflammatory biomarkers in human macrophages

Oxidized low-density lipoprotein (oxLDL) is a well-recognized proatherogenic particle that functions in atherosclerosis. In this study, we established conditions to generate human oxLDL, characterized according to the grade of lipid and protein oxidation, particle size and oxylipin content. The induction effect of the cellular proatherogenic response was assessed in foam cells by using an oxLDL-macrophage interaction model. Uptake of oxLDL, reactive oxygen species production and expression of oxLDL receptors (CD36, SR-A and LOX-1) were significantly increased in THP-1 macrophages. Analyses of 35 oxylipins revealed that isoprostanes (IsoP) and prostaglandins (PGs) derived from the oxidation of arachidonic, dihomo gamma-linolenic and eicosapentaenoic acids were strongly and significantly induced in macrophages stimulated with oxLDL. Importantly, the main metabolites responsible for the THP1-macrophage response to oxLDL exposure were the oxidative stress markers 5-epi-5-F_2t-IsoP, 15-E_1t-IsoP, 8-F_3t-IsoP and 15-keto-15-F_2t-IsoP as well as inflammatory markers PGDM, 17-trans-PGF_3α, and 11β-PGF_2α, all of which are reported here, for the first time, to function in the interaction of oxLDL with THP-1 macrophages. By contrast, a salvage pathway mediated by anti-inflammatory PGs (PGE₁ and 17-trans-PGF_3α) was also identified, suggesting a response to oxLDL-induced injury. In conclusion, when THP-1 macrophages were treated with oxLDL, a specific induction of biomarkers related to oxidative stress and inflammation was triggered. This work contributes to our understanding of initial atherogenic events mediated by oxLDL-macrophage interactions and helps to generate new approaches for their modulation.

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OxLDL has a potent impact on the oxylipin profiles in THP-1 human macrophages.

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OxLDL induces biomarkers of oxidation and inflammation in THP-1 human macrophages.

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Human Macrophages produce anti-inflammatory prostaglandins after oxLDL exposure.

Docosahexaenoic acid mechanisms of action on the bovine oocyte-cumulus complex

Background

Supplementation of bovine oocyte-cumulus complexes during in vitro maturation (IVM) with 1 μM of docosahexaenoic acid (DHA), C22:6 n-3 polyunsaturated fatty acid, was reported to improve in vitro embryo development. The objective of this paper was to decipher the mechanisms of DHA action.

Results

Transcriptomic analysis of 1 μM DHA-treated and control cumulus cells after 4 h IVM showed no significant difference in gene expression. MALDI-TOF mass spectrometry analysis of lipid profiles in DHA-treated and control oocytes and cumulus cells after IVM showed variations of only 3 out of 700 molecular species in oocytes and 7 out of 698 species in cumulus cells (p < 0.01).

We showed expression of free fatty acid receptor FFAR4 in both oocytes and cumulus cells, this receptor is known to be activated by binding to DHA. FFAR4 protein was localized close to the cellular membrane by immunofluorescence. Functional studies demonstrated that supplementation with FFAR4 agonist TUG-891 (1 μM or 5 μM) during IVM led to an increased blastocyst rate (39.5% ± 4.1%, 41.3% ± 4.1%), similar to DHA 1 μM treatment (39.2% ± 4.1%) as compared to control (25.2% ± 3.6%).

FFAR4 activation via TUG-891 led to beneficial effect on oocyte developmental competence and might explain in part similar effects of DHA.

Conclusions

In conclusion, we suggested that low dose of DHA (1 μM) during IVM might activate regulatory mechanisms without evident effect on gene expression and lipid content in oocyte-cumulus complexes, likely through signaling pathways which need to be elucidated in further studies.

Electronic supplementary material

The online version of this article (10.1186/s13048-017-0370-z) contains supplementary material, which is available to authorized users.

Metabolomics analysis reveals that benzo[a]pyrene, a component of PM2.5, promotes pulmonary injury by modifying lipid metabolism in a phospholipase A2-dependent manner in vivo and in vitro

Particulate matter with an aerodynamic diameter less than 2.5μM (PM2.5) is one of the major environmental pollutants in China. In this study, we carried out a metabolomics profile study on PM2.5-induced inflammation. PM2.5 from Beijing, China, was collected and given to rats through intra-tracheal instillation in vivo. Acute pulmonary injury were observed by pulmonary function assessment and H.E. staining. The lipid metabolic profile was also altered with increased phospholipid and sphingolipid metabolites in broncho-alveolar lavage fluid (BALF) after PM2.5 instillation. Organic component analysis revealed that benzo[a]pyrene (BaP) is one of the most abundant and toxic components in the PM2.5 collected on the fiber filter. In vitro, BaP was used to treat A549 cells, an alveolar type II cell line. BaP (4μM, 24h) induced inflammation in the cells. Metabolomics analysis revealed that BaP (4μM, 6h) treatment altered the cellular lipid metabolic profile with increased phospholipid metabolites and reduced sphingolipid metabolites and free fatty acids (FFAs). The proportion of ω-3 polyunsaturated fatty acid (PUFA) was also decreased. Mechanically, BaP (4μM) increased the phospholipase A2 (PLA2) activity at 4h as well as the mRNA level of Pla2g2a at 12h. The pro-inflammatory effect of BaP was reversed by the cytosolic PLA2 (cPLA2) inhibitor and chelator of intracellular Ca2+. This study revealed that BaP, as a component of PM2.5, induces pulmonary injury by activating PLA2 and elevating lysophosphatidylcholine (LPC) in a Ca2+-dependent manner in the alveolar type II cells.

Resolvin D1 down-regulates CYP1A1 and PTGS2 gene in the HUVEC cells treated with benzo(a)pyrene

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) can interact with lipids and their derivatives and have been known to induce atherosclerosis. The aim of this study was to evaluate the impact of Resolvin D1 (RvD1) on inflammatory-state realted proteins and genes in the human primary umbilical vein endothelial HUVEC cells exposed to benzo(a)pyrene (BaP).

METHODS

We analyzed the influence of RvD1 and/or BaP on cyclooxygenase-2 (COX-2), cytosolic prostaglandine E2 synthase (cPGES), glutathione S transferase (GSTM1) and aryl hydrocarbon receptor (AhR) protein expression by Western blot. Additionaly, phospholipase A2 (cPLA2) and cytochrome P450 (CYP1A1) activity, as well as AhR, CYP1A1, phospholipase A2 (PLA2G4A) and prostaglandin synthase 2 (PTGS2) gene expression by qRT-PCR was studied.

RESULTS

RvD1 down-regulates cytochrome P450 (CYP1A1) and prostaglandin synthase 2 (PTGS2) gene expression in HUVEC cells exposed to BaP. Repressesion of COX-2, cPGES and overexpressesion of GSTM1 protein was noted after co-treatment with RvD1 and BaP. After incubation with RvD1 an increase of cPLA2 and a decrease of CYP1A1 activity was observed when compared to BaP treated alone endothelial cells.

CONCLUSIONS

Our data suggests that RvD1 can significantly contributes on vascular function and alleviates the harmful effects caused by BaP, which might potentially aid in the repair of the injured endothelium.