Lipopolysaccharide (LPS) is one of the main constituents of the cell wall in Gram-negative bacteria. Staphylococcal enterotoxin B (SEB) is produced by the Gram-positive opportunistic pathogen, Staphylococcus aureus. Emerging evidence suggests that intraperitoneal injection of LPS combined with low-dose aerosolized SEB exposure can cause severe lung injury and even death, while SEB or LPS alone cause neither mortality nor severe pulmonary symptoms in mice. However, pulmonary effects from exposure to aerosolized SEB potentiated by LPS have not been evaluated. This study investigates the global transcriptome profile of lung tissue in mice after exposure to aerosolized SEB potentiated by LPS or LPS alone. A mouse model of intratracheal exposure to LPS-potentiated aerosolized SEB is established and described through histological examination. Transcriptome analysis revealed LPS-potentiated aerosolized SEB affected mouse lungs within 72 h post-SEB inhalation, gradually causing lung injury starting from 24 h post inhalation. Hub genes leading to lung injury at 48 h post inhalation have been identified. Flow cytometry revealed that LPS potentiation of low-dose SEB produces a superantigen response that T cells expressing a particular T cell receptor Vβ induces a proliferation response by 72 h post inhalation in the lungs of mice. This study represents the first research to investigate pulmonary transcriptional responses of LPS-potentiated aerosolized low-dose SEB exposure. This research helps to elucidate the molecular mechanisms underlying the process by which the two bacterial components combined to produce lung damage and provides an insight into potential treatments for alleviating inflammation of the lung when coinfection is present.
Specific therapeutics are not available for acute lung injury (ALI) induced by ricin toxin (RT). Inhibiting the host immune response in the course of pulmonary ricinosis is hypothesized to be of benefit and can be achieved by impairing granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling, thereby reducing the pro-inflammatory response to exogenous foreign body invasion. However, it is unknown whether mice with impaired GM-CSF signaling can survive after RT inhalation. To test this, colony stimulating factor 2 receptor alpha (Csf2ra) knockout (KO) mice that lack GM-CSF signaling and wild-type (WT) mice models of intratracheal exposure to a lethal dose (2× LD50) of RT were established. Survival was greater in Csf2ra KO mice 21 days after RT inhalation compared with WT mice. Highly co-expressed genes that probably attenuated the pro-inflammatory response in the lung of Csf2ra KO mice were identified. Bioinformatics analysis revealed that transcriptome changes involved mostly inflammation-related genes after RT exposure in both Csf2ra KO mice and WT mice. However, the activity levels of pro-inflammatory pathways, such as the TNF signaling pathway and NF-κB signaling pathway, in Csf2ra KO mice were significantly decreased and the degree of neutrophil chemotaxis and recruitment inhibited after RT-exposure relative to WT mice. RT-qPCR and flow cytometry validated results of RNA-Seq analysis. This work provides potential avenues for host-directed therapeutic applications that can mitigate the severity of ALI-induced by RT.
Background: Pneumonic plague is a fatal respiratory disease caused by Yersinia pestis. Time-course transcriptome analysis on the mechanism of pneumonic plague biphasic syndrome is lacking in the literature. Materials & methods: This study documented the disease course through bacterial load, histopathology, cytokine levels and flow cytometry. RNA-sequencing technology was used to investigate the global transcriptome profile of lung tissue in mice infected with Y. pestis. Results: Inflammation-related genes were significantly upregulated at 48 h post-infection, while genes related to cell adhesion and cytoskeletal structure were downregulated. Conclusion: NOD-like receptor and TNF signaling pathways play a plausible role in pneumonic plague biphasic syndrome and lung injury by controlling the activation and inhibition of the NF-κB signaling pathway.
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