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Supplemental Digital Content is available in the text., Objectives: Mesenchymal stromal cells are being investigated as a cell-based therapy for a number of disease processes, with promising results in animal models of systemic inflammation and sepsis. Studies are ongoing to determine ways to further improve the therapeutic potential of mesenchymal stromal cells. A gas molecule that improves outcome in experimental sepsis is carbon monoxide. We hypothesized that preconditioning of mesenchymal stromal cells with carbon monoxide ex vivo would promote further therapeutic benefit when cells are administered in vivo after the onset of polymicrobial sepsis in mice. Design: Animal study and primary cell culture. Setting: Laboratory investigation. Subjects: BALB/c mice. Interventions: Polymicrobial sepsis was induced by cecal ligation and puncture. Mesenchymal stromal cells, mesenchymal stromal cells-conditioned with carbon monoxide, fibroblasts, or fibroblasts-conditioned with carbon monoxide were delivered by tail vein injections to septic mice. The mice were assessed for survival, bacterial clearance, and the inflammatory response during sepsis in each of the groups. Mesenchymal stromal cells were also assessed for their ability to promote bacterial phagocytosis by neutrophils, the production of specialized proresolving lipid mediators, and their importance for mesenchymal stromal cells function using gene silencing. Measurements and Main Results: Ex vivo preconditioning with carbon monoxide allowed mesenchymal stromal cells to be administered later after the onset of sepsis (6 hr), and yet maintain their therapeutic effect with increased survival. Carbon monoxide preconditioned mesenchymal stromal cells were also able to alleviate organ injury, improve bacterial clearance, and promote the resolution of inflammation. Mesenchymal stromal cells exposed to carbon monoxide, with docosahexaenoic acid substrate, produced specialized proresolving lipid mediators, particularly D-series resolvins, which promoted survival. Silencing of lipoxygenase pathways (5-lipoxygenase and 12/15-lipoxygenase), which are important enzymes for specialized proresolving lipid mediator biosynthesis, resulted in a loss of therapeutic benefit bestowed on mesenchymal stromal cells by carbon monoxide. Conclusions: Taken together, these data suggest that production of specialized proresolving lipid mediators contribute to improved mesenchymal stromal cell efficacy when exposed to carbon monoxide, resulting in an improved therapeutic response during sepsis.

High-mobility group (HMG) proteins are architectural factors that have been shown to play a role in the transcriptional regulation of various mammalian genes. One family of HMG proteins, HMG-I/Y, is known to facilitate the initiation of gene transcription by modifying the conformation of DNA and recruiting transcription factors into an organized complex on transcriptional regulatory regions of specific genes. In many circumstances, the nuclear factor-kappaB family of transcription factors is involved in gene regulation that is mediated by HMG-I/Y. We will review the mechanisms by which HMG-I/Y proteins regulate gene transcription, give an overview of selected genes regulated by HMG-I/Y, summarize the potential roles of these genes in critical illnesses, and provide more detailed information about the role of HMG-I/Y in the regulation of nitric oxide synthase-2 during an inflammatory response, such as endotoxemia/sepsis.

Plasma gelsolin is a circulating actin-binding protein that serves a protective role against tissue injuries. Depletion of plasma gelsolin in systemic inflammation may contribute to adverse outcomes. We examined the role of plasma gelsolin in animal models of sepsis.Animal and laboratory experiments.Academic research laboratory.Adult male mice.Mice subjected to endotoxin or cecal ligation and puncture (CLP) were treated with exogenous plasma gelsolin or placebo.We document the depletion of plasma gelsolin (25-50% of normal) in murine models of sepsis associated with the presence of circulating actin within 6 hrs of septic challenge. Repletion of plasma gelsolin leads to solubilization of circulating actin aggregates and significantly reduces mortality in endotoxemic mice (survival rates were 88% in the gelsolin group vs. 0% in the saline group, p.001) and in CLP-challenged mice (survival rates were 30% in the gelsolin group vs. 0% in the saline group, p = .001). Plasma gelsolin repletion also shifted the cytokine profile of endotoxemic mice toward anti-inflammatory (plasma interleukin-10 levels were 205 +/- 108 pg/mL in the gelsolin group vs. 39 +/- 29 pg/mL in the saline group, p = .02).We propose that circulation of particulate actin is a marker for sepsis-induced cell injury, that plasma gelsolin has a crucial protective role in sepsis, and that gelsolin replacement represents a potential therapy for this common lethal condition.

High-mobility group (HMG) proteins are architectural factors that have been shown to play a role in the transcriptional regulation of various mammalian genes. One family of HMG proteins, HMG-I/Y, is known to facilitate the initiation of gene transcription by modifying the conformation of DNA and recruiting transcription factors into an organized complex on transcriptional regulatory regions of specific genes. In many circumstances, the nuclear factor-kappa B family of transcription factors is involved in gene regulation that is mediated by HMG-I/Y. We will review the mechanisms by which HMG-I/Y proteins regulate gene transcription, give an overview of selected genes regulated by HMG-I/Y, summarize the potential roles of these genes in critical illnesses, and provide more detailed information about the role of HMG-I/Y in the regulation of nitric oxide synthase-2 during an inflammatory response, such as endotoxemia/sepsis.