Glaesserella parasuis serotype 4 HPS4-YC disrupts the integrity of the swine tracheal epithelial barrier and facilitates bacterial translocation

Glaesserella parasuis (G. parasuis) is a commensal bacterium in the upper respiratory tract of pigs that can also cause the swine Glässer disease, which induces an intensive inflammatory response and results in significant economic losses to the swine industry worldwide. G. parasuis can cause disease through infection of the respiratory tract, resulting in systemic infection, but the mechanism is largely unknown. Recently we showed that Glaesserella parasuis serotype 4 (GPS4) increased swine tracheal epithelial barrier permeability, resulting in easier bacterial translocation. Tight junction proteins (TJ) play a crucial role in maintaining the integrity and impermeability of the epithelial barrier. GPS4 decreased the expression of the TJ ZO-1 and occludin in swine tracheal epithelial cells (STEC). Furthermore, the proinflammatory cytokines IL-6, IL-8 and TNF-α were significantly upregulated in GPS4-infected STEC, and both the MAPK and NF-κB signaling pathways were activated and contributed to the expression of TNF-α. We demonstrate that the production of proinflammatory cytokines, especially TNF-α, during GPS4 infection was involved in barrier dysfunction. Additionally, animal challenge experiments confirmed that GPS4 infection downregulated TJ in the lungs of piglets and induced a severe inflammatory response. In general, G. parasuis infection downregulated the expression of TJ and induced massive secretion of proinflammatory cytokines, resulting in epithelial barrier disruption and favoring bacterial infection. This study allowed us to better understand the mechanism by which G. parasuis crosses the respiratory tract of pigs.

Protective effects of theaflavins and epigallocatechin gallate against ZnO-NP-induced apoptosis in rat tracheal epithelial cells

Zinc oxide nanoparticles (ZnO-NPs) can affect human health primarily via inhalation. This study evaluated the protective effects of theaflavins (TFs) and epigallocatechin gallate (EGCG) against ZnO-NP-induced cytotoxicity in rat tracheal epithelial (RTE) cells. After exposure to ZnO-NPs (100 µg/L), treatment with TFs and EGCG (10, 100 and 1000 µg/L) significantly inhibited the levels of reactive oxygen species (ROS), and the content of malondialdehyde (MDA). Treatment also alleviated apoptosis induced by oxidative stress, which was achieved by inhibiting cytochrome C (CytoC) and Caspase 3/8/9 mRNA expression. Upon treatment with the highest concentrations of TFs and EGCG (1000 µg/L), CytoC gene expression was downregulated by 59.10% and 77.27%, Caspase 3 gene expression by 50.03% and 60.01%, Caspase 8 gene expression by 45.11% and 55.57%, and Caspase 9 gene expression by 51.33% and 66.67%. In addition, about the interleukin family as interleukin 1β (IL-1β) and interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and the other inflammatory chemokines like C-C motif chemokine 2 (CCL2), C-X-C motif chemokine 8 (CXCL8) were upregulated in RTE cells in the presence of ZnO-NPs. All factors were gradually rescued after the addition of TFs and EGCG. These results showed that TFs and EGCG could effectively protect RTE cells from oxidative damage induced by ZnO-NPs through antiapoptotic and antioxidant effects.

Transcriptome Differences in Pig Tracheal Epithelial Cells in Response to Pasteurella Multocida Infection

Pasteurella multocida generally colonizes mammalian/bird respiratory tracts and mainly causes respiratory disorders in both humans and animals. To date, the effects of P. multocida infection on the respiratory epithelial barriers and molecules in host respiratory epithelial cells in their response to P. multocida infection are still not well-known. In this study, we used newborn pig tracheal epithelial (NPTr) cells as an in vitro model to investigate the effect of P. multocida infection on host respiratory epithelial barriers. By detecting the transepithelial electrical resistance (TEER) values of NPTr cells and the expression of several known molecules associated with cell adherens and junctions, we found that P. multocida infection disrupted the barrier functions of NPTr cells. By performing RNA sequencing (RNA-Seq), we determined 30 differentially expressed genes (DEGs), including the vascular endothelial growth factor A (VEGFA) encoding gene VEGFA, which participated in biological processes (GO:0034330, GO:0045216, and GO:0098609) closely related to epithelial adhesion and barrier functions. These 30 DEGs participated in 22 significant signaling pathways with a p-value < 0.05, including the transforming growth factor (TGF)-beta signaling pathway (KEGG ID: ssc04350), hypoxia-inducible factor 1 (HIF-1) signaling pathway (KEGG ID: ssc04066), epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance (KEGG ID: ssc01521), tumor necrosis factor (TNF) signaling pathway (KEGG ID: ssc04668), and mitogen-activated protein kinase (MAPK) signaling pathway (KEGG ID: ssc04010), which are reported to have roles in contributing to the production of inflammatory factors as well as the regulation of epithelial adhesion and barrier function in other tissues and organisms. The results presented in this study may help improve our understanding of the pathogenesis of P. multocida.

Fucoxanthin Ameliorates Oxidative Stress and Airway Inflammation in Tracheal Epithelial Cells and Asthmatic Mice

Fucoxanthin is isolated from brown algae and was previously reported to have multiple pharmacological effects, including anti-tumor and anti-obesity effects in mice. Fucoxanthin also decreases the levels of inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) of asthmatic mice. The purpose of the present study was to investigate the effects of fucoxanthin on the oxidative and inflammatory responses in inflammatory human tracheal epithelial BEAS-2B cells and attenuated airway hyperresponsiveness (AHR), airway inflammation, and oxidative stress in asthmatic mice. Fucoxanthin significantly decreased monocyte cell adherence to BEAS-2B cells. In addition, fucoxanthin inhibited the production of pro-inflammatory cytokines, eotaxin, and reactive oxygen species in BEAS-2B cells. Ovalbumin (OVA)-sensitized mice were treated by intraperitoneal injections of fucoxanthin (10 mg/kg or 30 mg/kg), which significantly alleviated AHR, goblet cell hyperplasia and eosinophil infiltration in the lungs, and decreased Th2 cytokine production in the BALF. Furthermore, fucoxanthin significantly increased glutathione and superoxide dismutase levels and reduced malondialdehyde (MDA) levels in the lungs of asthmatic mice. These data demonstrate that fucoxanthin attenuates inflammation and oxidative stress in inflammatory tracheal epithelial cells and improves the pathological changes related to asthma in mice. Thus, fucoxanthin has therapeutic potential for improving asthma.

Ultraviolet-A light increases mitochondrial anti-viral signaling protein in confluent human tracheal cells even at a distance from the light source

Mitochondrial antiviral signaling (MAVS) protein mediates innate antiviral responses, including responses to certain coronaviruses such as severe acute respiratory syndrome coronavirus-2 ( SARS-CoV-2 ). We have previously shown that ultraviolet-A (UVA) therapy can prevent virus-induced cell death in human ciliated tracheal epithelial cells (HTEpC) infected with coronavirus-229E, and that UVA treatment results in an increase in intracellular levels of MAVS. In this study, we set out to determine the mechanisms by which UVA light can activate MAVS, and whether local UVA light application can activate MAVS at locations distant from the light source (such as via cell-to-cell communication). MAVS levels were compared in HTEpC exposed to 2 mW/cm 2 narrow band (NB)-UVA for 20 minutes and in unexposed controls, at 30-40% and at 100% confluency. MAVS levels were also compared in unexposed HTEpC treated with supernatants or lysates from UVA-exposed cells or from unexposed controls. Also, MAVS was assessed in different sections of confluent monolayer plates where only one section was exposed to NB-UVA. The results show that UVA increases the expression of MAVS protein. Cells in a confluent monolayer exposed to UVA were able to confer an elevation in MAVS in cells adjacent to the exposed section, and even cells in the most distant sections not exposed to UVA. In this study, human ciliated tracheal epithelial cells exposed to UVA demonstrate increased MAVS protein, and also appear to transmit this influence to distant confluent cells not exposed to light.