Genetic deletion of Sphk2 confers protection against Pseudomonas aeruginosa mediated differential expression of genes related to virulent infection and inflammation in mouse lung

Abstract

AbstractBackgroundPseudomonas aeruginosa(PA) is an opportunistic Gram-negative bacterium that causes serious life threatening and nosocomial infections including pneumonia.PAhas the ability to alter host genome to facilitate its invasion, thus increasing the virulence of the organism. Sphingosine-1- phosphate (S1P), a bioactive lipid, is known to play a key role in facilitating infection. Sphingosine kinases (SPHK) 1&2 phosphorylate sphingosine to generate S1P in mammalian cells. We reported earlier thatSphk2−/−mice offered significant protection against lung inflammation, compared to wild type (WT) animals. Therefore, we profiled the differential expression of genes between the protected group ofSphk2−/−and the wild type controls to better understand the underlying protective mechanisms related to theSphk2deletion in lung inflammatory injury. Whole transcriptome shotgun sequencing (RNA-Seq) was performed on mouse lung tissue using NextSeq 500 sequencing system.ResultsTwo-way analysis of variance (ANOVA) analysis was performed and differentially expressed genes followingPAinfection were identified using whole transcriptome ofSphk2−/−mice and their WT counterparts. Pathway (PW) enrichment analyses of the RNA seq data identified several signaling pathways that are likely to play a crucial role in pneumonia caused byPAsuch as those involved in: 1. Immune response toPAinfection and NF-κB signal transduction; 2. PKC signal transduction; 3. Impact on epigenetic regulation; 4. Epithelial sodium channel pathway; 5. Mucin expression; and 6. Bacterial infection related pathways.Our genomic data suggests a potential role for SPHK2 inPA-induced pneumonia through elevated expression of inflammatory genes in lung tissue. Further, validation by RT-PCR on 10 differentially expressed genes showed 100% concordance in terms of vectoral changes as well as significant fold change.ConclusionUsingSphk2−/−mice and differential gene expression analysis, we have shown here that S1P/SPHK2 signaling could play a key role in promotingPApneumonia. The identified genes promote inflammation and suppress others that naturally inhibit inflammation and host defense. Thus, targeting SPHK2/S1P signaling inPA-induced lung inflammation could serve as a potential therapy to combatPA-induced pneumonia.