Myeloperoxidase-derived hypochlorous acid targets human airway epithelial plasmalogens liberating protein modifying electrophilic 2-chlorofatty aldehydes

Comprehensive analysis of resilience of human airway epithelial barrier against short-term PM2.5 inorganic dust exposure using in vitro microfluidic chip and ex vivo human airway models

BACKGROUND AND OBJECTIVE

The updated World Health Organization (WHO) air quality guideline recommends an annual mean concentration of fine particulate matter (PM2.5) not exceeding 5 or 15 μg/m3 in the short-term (24 h) for no more than 3-4 days annually. However, more than 90% of the global population is currently exposed to daily concentrations surpassing these limits, especially during extreme weather conditions and due to transboundary dust transport influenced by climate change. Herein, the effect of respirable

METHODS

Silica particles at an average size of 1 μm, referred to as

RESULTS

In the AEB-on-a-chip platform, short-term exposure to 800 μg/mL PM2.5 disrupted AEB integrity via increasing barrier permeability, decreasing cell adhesion-barrier markers such as ZO-1, Vinculin, ACE2, and CD31, impaired cell viability and increased the expression levels of proinflammatory markers; IFNs, IL-6, IL-1s, TNF-α, CD68, CD80, and Inos, mostly under dynamic conditions. Besides, decreased tissue viability, impaired tissue integrity via decreasing of Vinculin, ACE2, β-catenin, and E-cadherin, and also proinflammatory response with elevated CD68, IL-1α, IL-6, IFN-Ɣ, Inos, and CD80 markers, were observed after PM2.5 exposure in ex vivo tissue.

CONCLUSION

The duration and concentration of PM2.5 that can be exposed during extreme weather conditions and natural events aligns with our exposure model (0-800 μg/mL 72 h). At this level of exposure, the resilience of the epithelial barrier is demonstrated by both AEB-on-a-chip platform emulating dynamic forces in the body and ex vivo bronchial biopsy slices. Lung-on-a-chip models will serve as reliable exposure models in this context.

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Key Words

• PM2.5
• airway epithelial barrier
• microfluidic systems
• particulate matter
• silica particles

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MESH Headings

• Humans
• Particulate Matter/analysis
• Epithelial Cells/metabolism
• Dust
• Respiratory Mucosa/metabolism
• Lab-On-A-Chip Devices
• Cell Line

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Grants

• 2019K12-149080 Presidency of the Republic of Turkey Strategy and Budget Department
• 1139B412102522 Scientific and Technological Research Council of Turkey (TUBITAK)

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Affiliation(s)

Ozlem Goksel Department of Pulmonary Medicine, Division of Immunology and Allergy, Laboratory of Occupational & Environmental Respiratory Diseases and Asthma, Faculty of Medicine, Ege University, Izmir, Turkey Translational Pulmonary Research Center (EgeSAM), Ege University, Izmir, Turkey
Meryem Irem Sipahi Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
Sena Yanasik Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey
Pelin Saglam-Metiner Translational Pulmonary Research Center (EgeSAM), Ege University, Izmir, Turkey Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey
Sema Benzer Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey
Leila Sabour-Takanlou Department of Medical Biology, Faculty of Medicine, Ege University, Izmir, Turkey
Maryam Sabour-Takanlou Department of Medical Biology, Faculty of Medicine, Ege University, Izmir, Turkey
Cigir Biray-Avci Department of Medical Biology, Faculty of Medicine, Ege University, Izmir, Turkey
Ozlem Yesil-Celiktas Translational Pulmonary Research Center (EgeSAM), Ege University, Izmir, Turkey Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey METU MEMS Center, Ankara, Turkey

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Lipoxin A4 yields an electrophilic 15-oxo metabolite that mediates FPR2 receptor-independent anti-inflammatory signaling

The enzymatic oxidation of arachidonic acid is proposed to yield trihydroxytetraene species (termed lipoxins) that resolve inflammation via ligand activation of the formyl peptide receptor, FPR2. While cell and murine models activate signaling responses to synthetic lipoxins, primarily 5S,6R,15S-trihydroxy-7E,9E,11Z,13E-eicosatetraenoic acid (lipoxin A4, LXA4), there are expanding concerns about the biological formation, detection and signaling mechanisms ascribed to LXA4 and related di- and tri-hydroxy ω-6 and ω-3 fatty acids. Herein, the generation and actions of LXA4 and its primary 15-oxo metabolite were assessed in control, LPS-activated and arachidonic acid supplemented RAW 264.7 macrophages. Despite protein expression of all enzymes required for LXA4 synthesis, both LXA4 and its 15-oxo-LXA4 metabolite were undetectable. Moreover, synthetic LXA4 and the membrane permeable 15-oxo-LXA4 methyl ester that is rapidly de-esterified to 15-oxo-LXA4, displayed no ligand activity for the putative LXA4 receptor FPR2, as opposed to the FPR2 ligand WKYMVm. Alternatively, 15-oxo-LXA4, an electrophilic α,β-unsaturated ketone, alkylates nucleophilic amino acids such as cysteine to modulate redox-sensitive transcriptional regulatory protein and enzyme function. 15-oxo-LXA4 activated nuclear factor (erythroid related factor 2)-like 2 (Nrf2)-regulated gene expression of anti-inflammatory and repair genes and inhibited nuclear factor (NF)-κB-regulated pro-inflammatory mediator expression. LXA4 did not impact these macrophage anti-inflammatory and repair responses. In summary, these data show an absence of macrophage LXA4 formation and receptor-mediated signaling actions. Rather, if LXA4 were present in sufficient concentrations, this, and other more abundant mono- and poly-hydroxylated unsaturated fatty acids can be readily oxidized to electrophilic α,β-unsaturated ketone products that modulate the redox-sensitive cysteine proteome via G-protein coupled receptor-independent mechanisms.

Development of an activatable far-red fluorescent probe for rapid visualization of hypochlorous acid in live cells and mice with neuroinflammation

Recent investigations have suggested that abnormally elevated levels of HOCl may be tightly related to the severity of neuroinflammation. Although some successes have been achieved, fluorescent probes with far-red fluorescence emission and capable of detecting HOCl with high specificity in pure aqueous solution are still urgently needed. Herein, a responsive far-red fluorescent probe, DCI-H, has been constructed to monitor HOCl activity in vivo and in vitro. DCI-H could rapidly respond to HOCl within 120 s and had a low detection limit for HOCl of 1.5 nM. Importantly, physiologically common interfering species, except for HOCl, did not cause a change in the fluorescence intensity of DCI-HOCl at 655 nm. The results of confocal imaging demonstrated the ability of DCI-H to visualize endogenous HOCl produced by MPO-catalyzed H2O2/Cl- and LPS stimulation. With the assistance of DCI-H, upregulation of HOCl levels was observed in the mice model of LPS-induced neuroinflammation. Thus, we believed that DCI-H provided a valuable tool for HOCl detection and diagnosis of inflammation-related diseases.

Characterization of N-Acetyl Cysteine Adducts with Exogenous and Neutrophil-Derived 2-Chlorofatty Aldehyde

Hypochlorous acid is produced by leukocyte myeloperoxidase activity. 2-Chlorofatty aldehydes (2-ClFALDs) are formed when hypochlorous acid attacks the plasma membrane phospholipid plasmalogen molecular subclass and are thus produced following leukocyte activation as well as in the lungs of mice exposed to chlorine gas. The biological role of 2-ClFALD is largely unknown. Recently, we used an alkyne analog (2-ClHDyA) of the 2-ClFALD molecular species, 2-chlorohexadecanal (2-ClHDA), to identify proteins covalently modified by 2-ClHDyA in endothelial cells and epithelial cells. Here, we demonstrate that 2-ClHDA reduces the metabolic activity of RAW 264.7 cells in a dose-dependent manner. 2-ClHDyA localizes to the mitochondria, endoplasmic reticulum and Golgi in RAW 264.7 cells and modifies many proteins. The thiol-containing precursor of glutathione, N-acetyl cysteine (NAC), was shown to produce an adduct with 2-ClHDA with the loss of Cl^- (HDA-NAC). This adduct was characterized in both positive and negative ion modes using LC-MS/MS and electrospray ionization. NAC treatment of neutrophils reduced the 2-ClFALD levels in PMA-stimulated cells with subsequent increases in HDA-NAC. NAC treatments reduced the 2-ClHDA-elicited loss of metabolic activity in RAW 264.7 cells as well as 2-ClHDA protein modification. These studies demonstrate that 2-ClFALD toxic effects can be reduced by NAC, which reduces protein modification.