Ischemia reperfusion injury induces pyroptosis and mediates injury in steatotic liver thorough Caspase 1 activation.

A steatotic liver is increasingly vulnerable to ischemia reperfusion injury (IRI), and the underlying mechanisms are incompletely defined. Caspases are endo-proteases, which provide critical regulatory connections between cell death and inflammation. Caspase 1 is driven by inflammasomes which are key signaling platforms, that detect sterile stressors (DAMPs), releasing the highly pro-inflammatory cytokine interleukin IL-8 and IL-1ß. To delineate the involvement of Caspase 1 and 11 in hepatocellular injury in steatotic liver undergoing IRI. Male C57BL6/Wild Type and Caspase 1Null, Caspase 11-/- and Caspase 1-/-/11-/- mice were fed a high fat diet (HFD) for 12 weeks. These mice were subjected to 40 min of ischemia followed by 2-24 h of reperfusion. Hepatocellular injury was assessed by histopathologic injury scoring, serum ALT and propidium iodide (PI) uptake, mRNA levels of Caspase 1, IL-1ß by RT PCR, Caspase 1 activity assay and Caspase 1. Specific Caspase 1, inhibitor experiments were carried out. All groups gained similar body weight after a 12-week HFD. Cleaved Caspase 1 protein levels, Caspase 1 mRNA levels were significantly higher in steatotic liver undergoing IRI. Executor of pyroptosis cleaved GSDMD levels were higher in HFD fed mouse compared to lean. In addition, genetic deletion of Caspase 1, Casp1Null mouse expressing Caspase-11 and Caspase 1/11 double knock out demonstrated significant reduction in serum ALT (p < 0.01), Injury Score, (p < 0.0002) but not in Caspase 11 alone. Caspase 1 is the driver of hepatocellular injury in a steatotic liver undergoing IRI, inhibition of which leads to hepatoprotection, thus providing a therapeutic target for clinical use.

Fibroblast growth factor-10 serves a regulatory role in duodenal development.

PURPOSE: Duodenal obstruction occurs in 1 of 6000 live births and requires urgent surgical intervention. Duodenal atresia previously has been ascribed to a developmental failure of luminal recanalization; however, the cause of duodenal atresia remains incompletely understood. Although familial intestinal atresias have been described and syndromic associations are known, no specific genetic link has been established. Fibroblast growth factor-10 (Fgf10) is a known regulatory molecule relevant to mesenchymal-epithelial interactions, and mice deficient in Fgf10 demonstrate congenital anomalies in several organ systems including the gastrointestinal tract. The authors hypothesized that Fgf10 could serve a regulatory role in establishing normal duodenal development. METHODS: Wild-type mice with beta-galactosidase under the control of the Fgf10 promoter were harvested from timed-pregnancy mothers. The expression of Fgf10 in the duodenum during development was evaluated by developing the embryos in X-Gal solution. Wild-type and mutant Fgf10(-/-) embryos were harvested from timed-pregnancy mothers at 18.5 days postconception (near term) and were analyzed for duodenal morphology (Institutional Animal Care and Use Committee-approved protocol 32-02). Photomicrographs were reviewed. RESULTS: Fibroblast growth factor-10 is active in the duodenum at a late stage of development. The Fgf10(-/-) mutants demonstrate duodenal atresia with a variable phenotype similar to clinical findings. The duodenum fails to develop luminal continuity and has proximal dilation. The phenotype occurs in an autosomal recessive pattern with incomplete penetrance (38%). CONCLUSIONS: Fibroblast growth factor-10 serves as a regulator in normal duodenal growth and development. Its deletion leads to duodenal atresia and challenges traditionally accepted theories of pathogenesis. This novel, genetically mediated duodenal malformation reflects an animal model that will allow further evaluation of the pathogenesis of this surgically correctable disease. By studying the mechanism of Fgf10 function in foregut development, the authors hope to better understand these anomalies and to explore possible therapeutic alternatives.

Colonic atresia without mesenteric vascular occlusion. The role of the fibroblast growth factor 10 signaling pathway.

BACKGROUND/PURPOSE: Colonic atresia occurs in 1:20,000 live births, offering a neonatal surgical challenge. Prenatal expression of fibroblast growth factor 10 (Fgf10), acting through fibroblast growth factor receptor 2b (Fgfr2b), is critical to the normal development of the colon. Invalidation of the Fgf10 pathway results in colonic atresia, inherited in an autosomal recessive pattern. Classically, disturbance of the mesenteric vasculature has been thought to cause many forms of intestinal atresia. The purpose of this study was to evaluate the role of vascular occlusion in the pathogenesis of colonic atresia. METHODS: Wild type (Wt), Fgf10(-/-), and Fgfr2b(-/-) mutant mouse embryos were harvested from timed pregnant mothers. Immediately following harvest, filtered India ink was infused via intracardiac microinjection. The gastrointestinal tract was dissected, and photomicrographs of the mesenteric arterial anatomy were taken at key developmental time points. RESULTS: Photomicrographs after India ink microinjections demonstrate normal, patent mesenteric cascades to the atretic colon at the time points corresponding to the failure of colonic development in the Fgf10(-/-) and Fgfr2b(-/-) mutants. The mesenteric arterial anatomy of the colon demonstrates no difference between the Wt and mutant colonic atresia. CONCLUSIONS: The absence of embryonic expression of Fgf10 or its receptor Fgfr2b results in colonic atresia in mice. India ink microinjection is a direct measure of mesenteric arterial patency. Colonic atresia in the Fgf10(-/-) and Fgfr2b(-/-) mutants occurs despite normal mesenteric vascular development. Thus the atresia is not the result of a mesenteric vascular occlusion. The patent colonic mesentery of the Fgf10(-/-) and Fgfr2b(-/-) mutants challenges an accepted pathogenesis of intestinal atresia. Although colonic atresia can occur as a result of vascular occlusion, new evidence exists to suggest that a genetic mechanism may play a role in the pathogenesis of this disease.