Exposure to aerosolized staphylococcal enterotoxin B potentiated by lipopolysaccharide modifies lung transcriptomes and results in lung injury in the mouse model.

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 Vß 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.

Mechanism of pulmonary plague biphasic syndrome: inhibition or activation of NF-κB signaling pathway.

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.

Gdf15 deletion exacerbates acute lung injuries induced by intratracheal inoculation of aerosolized ricin in mice.

Ricin toxin (RT) is a potent toxin derived from castor beans and has a high risk of mortality following inhalation-induced acute lung injury (ALI). Growth differentiation factor 15 (GDF15) is a member of the transforming growth factor ß superfamily and acts as a protective effect in diverse inflammatory diseases. Yet, the role of GDF15 in ALI has not been evaluated. In this study, we investigated the intrinsic role of Gdf15 in ALI induced by intratracheal inoculation of a 1.5 × LD50 (lethal dose for 50%) of aerosolized RT in Gdf15 knockout (KO) mice compared to wild-type (WT) mice. In this model, Gdf15 deletion significantly increased pathology in lung tissues for RT-induced ALI in mice, led to significantly decreased body weights and survival rates and increased expression of inflammatory-related cytokine and chemokine levels at 24 and 72 h post-exposure. Infiltration of myeloid cells in lung tissue were quantified using flow cytometry. Although a similar infiltration pattern of inflammatory cells was observed in Gdf15 KO and WT groups, Gdf15 KO mice had elevated levels of neutrophils and decreased levels of Ly6Clo monocytes (cells with distinct destructive and protective roles, respectively) in the early stage of ALI. Gene expression profiles revealed similar effects as observed through RNA-seq. Bioinformatics analysis confirmed that pro-inflammatory signaling pathways were activated and the expression of inflammatory genes was significantly up-regulated after RT exposure compared to the corresponding baseline control in Gdf15 KO and WT mice. Compared to WT mice, inflammatory genes were more pronounced in Gdf15 KO groups after RT exposure. To our knowledge, this study presents the first research to systematically evaluate the role of Gdf15 in RT-induced ALI. These results collectively uncovered an immune response signature in lung tissues and reveal a critical role of Gdf15 in this ALI mice model. Our findings expose novel opportunities to investigate the contribution of GDF15 for the treatment of lung inflammatory diseases.

Csf2ra deletion attenuates acute lung injuries induced by intratracheal inoculation of aerosolized ricin in mice.

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.