A specific combined long-chain polyunsaturated fatty acid supplementation reverses fatty acid profile alterations in a mouse model of chronic asthma

The Effects of High-Fat Diet and Flaxseed Oil-Enriched Diet on the Lung Parenchyma of Obese Mice

Omega-3 (ω3) fatty acids are widely investigated for their anti-inflammatory potential, however, there is little evidence regarding their action in the lung parenchyma in the context of obesity. The objective is to investigate the effects of flaxseed oil (FS), rich in α-linolenic (C18:3 - ω3), on the lungs of obese mice. Mice were fed a high-fat diet (HF) for 8 weeks to induce obesity. Subsequently, a part of these animals received HF containing FS oil for another 8 weeks. The HF consumption induced weight gain and hyperglycemia. The lung parenchyma shows a complete fatty acids profile, compared to the control group (CT). In the lung parenchyma, FS increases the ω3 content and, notwithstanding a reduction in the interleukins (IL) IL1β and IL18 contents compared to HF. However, FS promoted increased alveolar spaces, followed by MCP1 (Monocytes Chemoattractant Protein-1) positive cell infiltration and a dramatic reduction in the anti-inflammatory cytokine, IL10. Despite reducing the pulmonary inflammatory response, the consumption of a food source of ω3 was associated with alterations in the lipid profile and histoarchitecture of the lung parenchyma, which can lead to the development of pulmonary complications. This study brings an alert against the indiscriminate use of ω3 supplements, warranting caution.

Fatty acids metabolism in ozone-induced pulmonary inflammatory injury: Evidence, mechanism and prevention

Ozone (O3) is a major air pollutant that directly threatens the respiratory system, lung fatty acid metabolism disorder is an important molecular event in pulmonary inflammatory diseases. Liver kinase B1 (LKB1) and nucleotide-binding domain leucine-rich repeat-containing protein 3 (NLRP3) inflammasome not only regulate inflammation, but also have close relationship with fatty acid metabolism. However, the role and mechanism of LKB1 and NLRP3 inflammasome in lung fatty acid metabolism, which may contribute to ozone-induced lung inflammation, remain unclear, and effective strategy for preventing O3-induced pulmonary inflammatory injury is lacking. To explore these, mice were exposed to 1.00 ppm O3 (3 h/d, 5 days), and pulmonary inflammation was determined by airway hyperresponsiveness, histopathological examination, total cells and cytokines in bronchoalveolar lavage fluid (BALF). Targeted fatty acids metabolomics was used to detect medium and long fatty acid in lung tissue. Then, using LKB1-overexpressing adenovirus and NLRP3 knockout (NLRP3-/-) mice to explore the mechanism of O3-induced lung fatty acid metabolism disorder. Results demonstrated that O3 exposure caused pulmonary inflammatory injury and lung medium and long chain fatty acids metabolism disorder, especially decreased dihomo-γ-linolenic acid (DGLA). Meanwhile, LKB1 expression was decreased, and NLRP3 inflammasome was activated in lung of mice after O3 exposure. Additionally, LKB1 overexpression alleviated O3-induced lung inflammation and inhibited the activation of NLRP3 inflammasome. And we found that pulmonary fatty acid metabolism disorder was ameliorated of NLRP3 -/- mice compared with those in wide type mice after O3 exposure. Furthermore, administrating DGLA intratracheally prior to O3 exposure significantly attenuated O3-induced pulmonary inflammatory injury. Taken together, these findings suggest that fatty acids metabolism disorder is involved in O3-induced pulmonary inflammation, which is regulated by LKB1-mediated NLRP3 pathway, DGLA supplement could be a useful preventive strategy to ameliorate ozone-associated lung inflammatory injury.

Metabolomics in Animal Models of Bronchial Asthma and Its Translational Importance for Clinics

Bronchial asthma is an extremely heterogenous chronic respiratory disorder with several distinct endotypes and phenotypes. These subtypes differ not only in the pathophysiological changes and/or clinical features but also in their response to the treatment. Therefore, precise diagnostics represent a fundamental condition for effective therapy. In the diagnostic process, metabolomic approaches have been increasingly used, providing detailed information on the metabolic alterations associated with human asthma. Further information is brought by metabolomic analysis of samples obtained from animal models. This article summarizes the current knowledge on metabolomic changes in human and animal studies of asthma and reveals that alterations in lipid metabolism, amino acid metabolism, purine metabolism, glycolysis and the tricarboxylic acid cycle found in the animal studies resemble, to a large extent, the changes found in human patients with asthma. The findings indicate that, despite the limitations of animal modeling in asthma, pre-clinical testing and metabolomic analysis of animal samples may, together with metabolomic analysis of human samples, contribute to a novel way of personalized treatment of asthma patients.

Integration of transcriptomics and metabolomics to reveal the effect of ginsenoside Rg3 on allergic rhinitis in mice

Increasing studies have demonstrated that ginsenoside Rg3 (Rg3) plays an important role in the prevention and treatment of various diseases, including allergic lower airway inflammation such as asthma. To investigate the role of Rg3 in allergic upper airway disease, the effect and therapeutic mechanism of Rg3 in allergic rhinitis (AR) were studied. Ovalbumin-induced AR model mice were intragastrically administered with Rg3. Nasal symptoms, levels of IgE, IL-4, IL-5, IL-13, SOD and MDA in serum, and histopathological analysis of nasal mucosa were used to evaluate the effect of Rg3 on ameliorating AR in mice. Moreover, nasal mucosa samples from the normal control group, AR model group and high dosage of Rg3 were collected to perform omics analysis. The differentially expressed genes and significantly changed metabolites were screened based on transcriptomics and metabolomics analyses, respectively. Integrative analysis was further performed to confirm the hub genes, metabolites and pathways. After Rg3 intervention, the nasal symptoms and inflammatory infiltration were effectively improved, the levels of IgE, IL-4, IL-5, IL-13 and MDA were significantly reduced, and the level of SOD was obviously increased. The results of the qRT-PCR assay complemented the transcriptomic findings. Integrated analysis showed that Rg3 played an anti-AR role mainly by regulating the interaction network, which was constructed by 12 genes, 8 metabolites and 4 pathways. Our findings suggested that Rg3 had a therapeutic effect on ovalbumin-induced AR in mice by inhibiting inflammation development and reducing oxidative stress. The present study could provide a potential natural agent for the treatment of AR.

Dihomo-γ-Linolenic Acid (20:3n-6)-Metabolism, Derivatives, and Potential Significance in Chronic Inflammation

Dihomo-γ-linolenic acid (DGLA) has emerged as a significant molecule differentiating healthy and inflamed tissues. Its position at a pivotal point of metabolic pathways leading to anti-inflammatory derivatives or via arachidonic acid (ARA) to pro-inflammatory lipid mediators makes this n-6 polyunsaturated fatty acid (PUFA) an intriguing research subject. The balance of ARA to DGLA is probably a critical factor affecting inflammatory processes in the body. The aim of this narrative review was to examine the potential roles of DGLA and related n-6 PUFAs in inflammatory conditions, such as obesity-associated disorders, rheumatoid arthritis, atopic dermatitis, asthma, cancers, and diseases of the gastrointestinal tract. DGLA can be produced by cultured fungi or be obtained via endogenous conversion from γ-linolenic acid (GLA)-rich vegetable oils. Several disease states are characterized by abnormally low DGLA levels in the body, while others can feature elevated levels. A defect in the activity of ∆6-desaturase and/or ∆5-desaturase may be one factor in the initiation and progression of these conditions. The potential of GLA and DGLA administrations as curative or ameliorating therapies in inflammatory conditions and malignancies appears modest at best. Manipulations with ∆6- and ∆5-desaturase inhibitors or combinations of long-chain PUFA supplements with n-3 PUFAs could provide a way to modify the body's DGLA and ARA production and the concentrations of their pro- and anti-inflammatory mediators. However, clinical data remain scarce and further well-designed studies should be actively promoted.

Deuterated Arachidonic Acid Ameliorates Lipopolysaccharide-Induced Lung Damage in Mice

Arachidonic acid (ARA) is a major component of lipid bilayers as well as the key substrate for the eicosanoid cascades. ARA is readily oxidized, and its non-enzymatic and enzymatic oxidation products induce inflammatory responses in nearly all tissues, including lung tissues. Deuteration at bis-allylic positions substantially decreases the overall rate of ARA oxidation when hydrogen abstraction is an initiating event. To compare the effects of dosing of arachidonic acid (H-ARA) and its bis-allylic hexadeuterated form (D-ARA) on lungs in conventionally healthy mice and in an acute lung injury model, mice were dosed with H-ARA or D-ARA for six weeks through dietary supplementation and then challenged with intranasal lipopolysaccharide (LPS) for subsequent analysis of bronchoalveolar lavage fluid and lung tissue. Dosing on D-ARA resulted in successful incorporation of D-ARA into various tissues. D-ARA significantly reduced LPS-induced adverse effects on alveolar septal thickness and the bronchoalveolar area. Oral deuterated ARA is taken up efficiently and protects against adverse LPS-induced pathology. This suggests novel therapeutic avenues for reducing lung damage during severe infections and other pathological conditions with inflammation in the pulmonary system and other inflammatory diseases.

Huanglong Antitussive Granule Relieves Acute Asthma Through Regulating Pulmonary Lipid Homeostasis

Background: Asthma is a respiratory disease with chronic airway inflammatory, and individuals with asthma exacerbations is one of the most frequent causes of hospitalization. Huanglong antitussive granule (HL Granule), a Chinese proprietary herbal medicine, has been proved to be effective in the clinical treatment of pulmonary disease. This study is devoted to the pharmacodynamics of HL Granule in acute asthma and the possible mechanism from the perspective of lipidomics. Methods: Mice were divided into four groups, control group, acute asthma model group, HL Granule treatment and montelukast sodium treatment group. Acute asthma was induced by ovalbumin (OVA). Histopathology, pulmonary function and enzyme linked immunosorbent assay (ELISA) were used to validated model and effect of HL Granule. Lipids were detected by ultra-high-performance liquid chromatography coupled to hybrid Quadrupole-Exactive Orbitrap mass spectrometry (UHPLC-Q-Exactive Orbitrap MS) and identified by MS-DAIL and built-in Lipidblast database. Differentially expressed lipids recalled in HL Granule treatment group were extracted for heatmap, enrichment analysis and correlation analysis. Results: HL Granule was effective in decreasing airway hyperresponsiveness (AHR), airway inflammatory and the levels of IL-4 and IL-5. A total of 304 and 167 lipids were identified in positive and negative ion mode, respectively. Among these, 104 and 73 lipids were reserved in HL Granule group (FDR < 0.05), including acylcarnitine (ACar), fatty acid (FA), lysophosphatidylcholine (LPC), phosphatidylcholine (PC), lysophosphatidylethanolamine (LPE), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylserine (PS), diglyceride (DG), triglyceride (TG), sphingomyelin (SM) and ceramide (Cer). Furthermore, 118 and 273 correlations among 47 and 96 lipids in the positive and negative were observed, with ether-linked phosphatidylethanolamine (PEe) and phosphatidylcholine (PCe) (FDR < 0.001, Spearman correlation coefficient r ² > 0.75). Conclusion: HL Granule might improve pulmonary lipid homeostasis and could be used as an alternative or supplementary therapy in clinical for the treatment of asthma.

CFTR Correctors and Antioxidants Partially Normalize Lipid Imbalance but not Abnormal Basal Inflammatory Cytokine Profile in CF Bronchial Epithelial Cells

A deficiency in cystic fibrosis transmembrane conductance regulator (CFTR) function in CF leads to chronic lung disease. CF is associated with abnormalities in fatty acids, ceramides, and cholesterol, their relationship with CF lung pathology is not completely understood. Therefore, we examined the impact of CFTR deficiency on lipid metabolism and pro-inflammatory signaling in airway epithelium using mass spectrometric, protein array. We observed a striking imbalance in fatty acid and ceramide metabolism, associated with chronic oxidative stress under basal conditions in CF mouse lung and well-differentiated bronchial epithelial cell cultures of CFTR knock out pig and CF patients. Cell-autonomous features of all three CF models included high ratios of ω-6- to ω-3-polyunsaturated fatty acids and of long- to very long-chain ceramide species (LCC/VLCC), reduced levels of total ceramides and ceramide precursors. In addition to the retinoic acid analog fenretinide, the anti-oxidants glutathione (GSH) and deferoxamine partially corrected the lipid profile indicating that oxidative stress may promote the lipid abnormalities. CFTR-targeted modulators reduced the lipid imbalance and oxidative stress, confirming the CFTR dependence of lipid ratios. However, despite functional correction of CF cells up to 60% of non-CF in Ussing chamber experiments, a 72-h triple compound treatment (elexacaftor/tezacaftor/ivacaftor surrogate) did not completely normalize lipid imbalance or oxidative stress. Protein array analysis revealed differential expression and shedding of cytokines and growth factors from CF epithelial cells compared to non-CF cells, consistent with sterile inflammation and tissue remodeling under basal conditions, including enhanced secretion of the neutrophil activator CXCL5, and the T-cell activator CCL17. However, treatment with antioxidants or CFTR modulators that mimic the approved combination therapies, ivacaftor/lumacaftor and ivacaftor/tezacaftor/elexacaftor, did not effectively suppress the inflammatory phenotype. We propose that CFTR deficiency causes oxidative stress in CF airway epithelium, affecting multiple bioactive lipid metabolic pathways, which likely play a role in CF lung disease progression. A combination of anti-oxidant, anti-inflammatory and CFTR targeted therapeutics may be required for full correction of the CF phenotype.

Allergy Modulation by N-3 Long Chain Polyunsaturated Fatty Acids and Fat Soluble Nutrients of the Mediterranean Diet

The Mediterranean diet, containing valuable nutrients such as n-3 long chain poly-unsaturated fatty acids (LCPUFAs) and other fat-soluble micronutrients, is known for its health promoting and anti-inflammatory effects. Its valuable elements might help in the battle against the rising prevalence of non-communicable diseases (NCD), including the development of allergic diseases and other (chronic) inflammatory diseases. The fat fraction of the Mediterranean diet contains bioactive fatty acids but can also serve as a matrix to dissolve and increase the uptake of fat-soluble vitamins and phytochemicals, such as luteolin, quercetin, resveratrol and lycopene with known immunomodulatory and anti-inflammatory capacities. Especially n-3 LCPUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derived from marine oils can target specific receptors or signaling cascades, act as eicosanoid precursors and/or alter membrane fluidity and lipid raft formation, hereby exhibiting anti-inflammatory properties. Beyond n-3 LCPUFAs, fat-soluble vitamins A, D, E, and K1/2 have the potential to affect pro-inflammatory signaling cascades by interacting with receptors or activating/inhibiting signaling proteins or phosphorylation in immune cells (DCs, T-cells, mast cells) involved in allergic sensitization or the elicitation/effector phase of allergic reactions. Moreover, fat-soluble plant-derived phytochemicals can manipulate signaling cascades, mostly by interacting with other receptors or signaling proteins compared to those modified by fat-soluble vitamins, suggesting potential additive or synergistic actions by applying a combination of these nutrients which are all part of the regular Mediterranean diet. Research concerning the effects of phytochemicals such as polyphenols has been hampered due to their poor bio-availability. However, their solubility and uptake are improved by applying them within the dietary fat matrix. Alternatively, they can be prepared for targeted delivery by means of pharmaceutical approaches such as encapsulation within liposomes or even unique nanoparticles. This review illuminates the molecular mechanisms of action and possible immunomodulatory effects of n-3 LCPUFAs and fat-soluble micronutrients from the Mediterranean diet in allergic disease development and allergic inflammation. This will enable us to further appreciate how to make use of the beneficial effects of n-3 LCPUFAs, fat-soluble vitamins and a selection of phytochemicals as active biological components in allergy prevention and/or symptom reduction.

Oil supplementation with a special combination of n-3 and n-6 long-chain polyunsaturated fatty acids does not protect for exercise induced asthma: a double-blind placebo-controlled trial

BACKGROUND

Many patients suffering from exercise-induced asthma (EIA) have normal lung function at rest and show symptoms and a decline in FEV₁ when they do sports or during exercise-challenge. It has been described that long-chain polyunsaturated fatty acids (LCPUFA) could exert a protective effect on EIA.

METHODS

In this study the protective effect of supplementation with a special combination of n-3 and n-6 LCPUFA (sc-LCPUFA) (total 1.19 g/ day) were investigated in an EIA cold air provocation model.

PRIMARY OUTCOME MEASURE

Decrease in FEV₁ after exercise challenge and secondary outcome measure: anti-inflammatory effects monitored by exhaled NO (eNO) before and after sc-LCPUFA supplementation versus placebo.

RESULTS

Ninety-nine patients with exercise-induced symptoms aged 10 to 45 were screened by a standardized exercise challenge in a cold air chamber at 4 °C. Seventy-three patients fulfilled the inclusion criteria of a FEV₁ decrease > 15% and were treated double-blind placebo-controlled for 4 weeks either with sc-LCPUFA or placebo. Thirty-two patients in each group completed the study. Mean FEV₁ decrease after cold air exercise challenge and eNO were unchanged after 4 weeks sc-LCPUFA supplementation.

CONCLUSION

Supplementation with sc-LCPUFA at a dose of 1.19 g/d did not have any broncho-protective and anti-inflammatory effects on EIA.

TRIAL REGISTRATION

Clinical trial registration number: NCT02410096. Registered 7 February 2015 at Clinicaltrial.gov.

Triacylglycerol-Rich Oils of Marine Origin are Optimal Nutrients for Induction of Polyunsaturated Docosahexaenoic Acid Ester of Hydroxy Linoleic Acid (13-DHAHLA) with Anti-Inflammatory Properties in Mice

SCOPE

The docosahexaenoic acid ester of hydroxy linoleic acid (13-DHAHLA) is a bioactive lipid with anti-inflammatory properties from the family of fatty acid esters of hydroxy fatty acids (FAHFA).

METHODS AND RESULTS

To explore the biosynthesis of 13-DHAHLA from dietary oils, C57BL/6N mice are gavaged for 8 days with various corn oil/marine oil mixtures containing the same amount of DHA. Plasma levels of omega-3 FAHFAs are influenced by the lipid composition of the mixtures but do not reflect the changes in bioavailability of polyunsaturated fatty acids in plasma. Triacylglycerol-bound DHA and linoleic acid serve as more effective precursors for 13-DHAHLA synthesis than DHA bound in phospholipids or wax esters. Both 13(S)- and 13(R)-DHAHLA inhibit antigen and PGE₂ -induced chemotaxis and degranulation of mast cells to a comparable extent and 13(S)-DHAHLA is identified as the predominant isomer in mouse adipose tissue.

CONCLUSION

Here, the optimal nutritional source of DHA is identified, which supports production of anti-inflammatory FAHFAs, as triacylglycerol-based marine oil and also reveals a possible role of triacylglycerols in the synthesis of FAHFA lipokines.

Dietary Omega-3 Fatty Acid Dampens Allergic Rhinitis via Eosinophilic Production of the Anti-Allergic Lipid Mediator 15-Hydroxyeicosapentaenoic Acid in Mice

The metabolism and generation of bioactive lipid mediators are key events in the exertion of the beneficial effects of dietary omega-3 fatty acids in the regulation of allergic inflammation. Here, we found that dietary linseed oil, which contains high amounts of alpha-linolenic acid (ALA) dampened allergic rhinitis through eosinophilic production of 15-hydroxyeicosapentaenoic acid (15-HEPE), a metabolite of eicosapentaenoic acid (EPA). Lipidomic analysis revealed that 15-HEPE was particularly accumulated in the nasal passage of linseed oil-fed mice after the development of allergic rhinitis with the increasing number of eosinophils. Indeed, the conversion of EPA to 15-HEPE was mediated by the 15-lipoxygenase activity of eosinophils. Intranasal injection of 15-HEPE dampened allergic symptoms by inhibiting mast cell degranulation, which was mediated by the action of peroxisome proliferator-activated receptor gamma. These findings identify 15-HEPE as a novel EPA-derived, and eosinophil-dependent anti-allergic metabolite, and provide a preventive and therapeutic strategy against allergic rhinitis.

A combination of LCPUFAs regulates the expression of miRNA-146a-5p in a murine asthma model and human alveolar cells

BACKGROUND

LCPUFAs are suggestive of having beneficial effects on inflammatory diseases such as asthma. However, little is known about the modulative capacity of omega-(n)-3 and n-6 LCPUFAs within the epigenetic regulation of inflammatory processes.

OBJECTIVE

The aim of this study was to investigate whether a specific combined LCPUFA supplementation restores disease-dysregulated miRNA-profiles in asthmatic mice. In addition, we determined the effect of the LCPUFA supplementation on the interaction of the most regulated miRNA expression and oxygenase activity in vitro.

METHODS

Sequencing of miRNA was performed by NGS from lung tissue of asthmatic and control mice with normal diet, as well as of LCPUFA supplemented asthmatic mice. Network analysis and evaluation of the biological targets of the miRNAs were performed by DIANA- miRPath v.3 webserver software, TargetScanMouse 7.2, and tool String v.10, respectively. Expression of hsa-miRNA-146a-5p and activity of COX-2 and 5-LO in LCPUFA-treated A549 cells were assessed by qPCR and flow cytometry, respectively.

RESULTS

In total, 62 miRNAs were dysregulated significantly in murine allergic asthma. The LCPUFA combination restored 21 of these dysregulated miRNAs, of which eight (mmu-miR-146a-5p, -30a-3p, -139-5p, -669p-5p, -145a-5p, -669a-5p, -342-3p and -15b-5p) were even normalized compared to the control levels. Interestingly, six of the eight rescued miRNAs are functionally implicated in TGF-β signaling, ECM-receptor interaction and fatty acid biosynthesis. Furthermore, in vitro experiments demonstrated that upregulation of hsa-miRNA-146a-5p is accompanied by a reduction of COX-2 and 5-LO activity. Moreover, transfection experiments revealed that LCPUFAs inhibit 5-LO activity in the presence and absence of anti-miR-146a-5p.

CONCLUSION

Our results demonstrate the modulative capacity of LCPUFAs on dysregulated miRNA expression in asthma. In addition, we pointed out the high regulative potential of LCPUFAs on 5-LO regulation and provided evidence that miR-146a partly controls the regulation of 5-LO.