Project description:Background: We hypothesized that spleen microarray gene expression profiles analyzed with contemporary pathway analysis software would provide molecular pathways of interest and target genes that might help explain the affect of bcl-2 on improving survival during sepsis. Methods: Two mouse models of sepsis, cecal ligation and puncture and tracheal instillation of Pseudomonas aeruginosa, were tested in both wild-type mice and mice that overexpress bcl-2. Whole spleens were obtained 6 hours after septic injury. DNA microarray transcriptional profiles were obtained using the Affymetrix 430A GeneChip, containing 22,690 elements. Ingenuity Pathway Analysis software was used to construct hypothetical transcriptional networks that changed in response to sepsis and expression of the bcl-2 transgene. Results: A conservative approach was used wherein only changes induced by both abdominal and pulmonary sepsis were studied. At 6 hours, sepsis induced alterations in the abundance of hundreds of spleen genes, including a number of proinflammatory mediators (e.g., IL-6). These sepsis-induced alterations were blocked by expression of the bcl-2 transgene. Network analysis implicated a number of bcl-2-related apoptosis genes, including bcl2L11 (bim), bcl-2L2 (bcl-w), bmf, and mcl-1. Sepsis in bcl-2 transgenic animals resulted in alteration of RNA abundance for only a single gene, ceacam1. Conclusion: These findings are consistent with sepsis-induced alterations in the balance of pro- and anti-apoptotic transcriptional networks. In addition, our data suggest that the ability of bcl-2 overexpression to improve survival in sepsis in this model is related in part to prevention of sepsis-induced alterations in spleen transcriptional responses. Experiment Overall Design: To determine the splenic response in these lethal models of CLP and Pseudomonas pneumonia, microarray analysis was performed on each spleen harvested from wild-type animals 6 hours after CLP or tracheal instillation of bacteria. The responses of the CLP or Pseudomonas spleens were compared concurrently to those of the wild-type controls, sham laparotomy and tracheal instillation of saline, respectively. This study was repeated in animals overexpressing bcl-2. Thus, the splenocyte effect of sepsis secondary to CLP (n=6) or Pseudomonas pneumonia (n=5) could be determined compared to their controls (n=6 and 5, respectively), and the effect of bcl-2 overexpression in turn also could be determined in both CLP (n=5) and pneumonia models (n=5) compared to controls (n=5 and 5, respectively).

Project description:Sepsis is the most common cause of hospitalization worldwide. Millions of people survive sepsis each year and are at risk for rehospitalization and death. Pulmonary complications such as respiratory failure due to pneumonia and exacerbation of chronic respiratory disease are among the most common reasons for rehospitalization in sepsis survivors. In order to prevent additional morbidity and death in patients surviving sepsis, we must establish biomarkers to identify patients at risk for pulmonary complications and develop treatments. Late complications in sepsis survivors, particularly nosocomial infections, are proposed to occur through persistent immune reprogramming after sepsis known as immunoparalysis. However, pro-inflammatory immune reprogramming in the form of primed or enhanced responses to secondary stimuli has also been described and could directly contribute to tissue injury and death. Primed immune responses and their contribution to long-term sepsis complications remains understudied. We hypothesize that primed immune responses to inflammatory stimuli in the lung after sepsis are associated with pulmonary complications in survivors of sepsis. To this end, we developed a model of antibiotic treated sepsis induced by cecal ligation and puncture followed three weeks later by secondary challenge with intranasal lipopolysaccharide to induce inflammatory lung injury. We find that mice surviving sepsis have enhanced lung injury responses in the setting of an exaggerated proinflammatory immune response, including primed Ly6Chi monocyte Tnf expression. Using RNA sequencing, we identified derangements in lung gene expression after CLP prior to LPS administration which may mediate enhanced lung injury in this model. One potential mediator, S100A8/A9, was also found to be elevated in the circulation of human sepsis survivors for up to 180 days after sepsis. These findings validate our model and identify S100A8/A9 as one of many potential biomarkers and therapeutic targets for patients at risk for long-term pulmonary complications after sepsis. The role of S100A8/A9, monocyte priming, and other factors predisposing to enhanced lung injury responses and pulmonary complications after sepsis warrant further investigation in humans and mice.

Dataset Information

Mus musculus

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets