Project description:Heart disease remains the leading cause of death globally. Although reperfusion following myocardial ischemia can prevent death by restoring nutrient flow, ischemia/reperfusion injury can cause significant heart damage. The mechanisms that drive ischemia/reperfusion injury are not well understood; currently, few methods can predict the state of the cardiac muscle cell and its metabolic conditions during ischemia. Here, we explored the energetic sustainability of cardiomyocytes, using a model for cellular metabolism to predict the levels of ATP following hypoxia. We modeled glycolytic metabolism with a system of coupled ordinary differential equations describing the individual metabolic reactions within the cardiomyocyte over time. Reduced oxygen levels and ATP consumption rates were simulated to characterize metabolite responses to ischemia. By tracking biochemical species within the cell, our model enables prediction of the cell’s condition up to the moment of reperfusion. The simulations revealed a distinct transition between energetically sustainable and unsustainable ATP concentrations for various energetic demands. Our model illustrates how even low oxygen concentrations allow the cell to perform essential functions. We found that the oxygen level required for a sustainable level of ATP increases roughly linearly with the ATP consumption rate. An extracellular O2 concentration of ~0.007 mM could supply basic energy needs in non-beating cardiomyocytes, suggesting that increased collateral circulation may provide an important source of oxygen to sustain the cardiomyocyte during extended ischemia. Our model provides a time-dependent framework for studying various intervention strategies to change the outcome of reperfusion.
Project description:Intestinal ischemia-reperfusion (IR) injury is initiated when natural IgM antibodies recognize neo-epitopes that are revealed on ischemic cells. The target molecules and mechanisms whereby these neo-epitopes become accessible to recognition are not well understood. Proposing that isolated intestinal epithelial cells (IEC) may carry IR-related neo-epitopes, we used in vitro IEC binding assays to screen hybridomas created from B cells of unmanipulated wild type C57BL/6 mice. We identified a novel IgM monoclonal antibody (mAb B4) that reacted with the surface of IEC by flow cytometric analysis and was alone capable of causing complement activation, neutrophil recruitment and intestinal injury in otherwise IR-resistant Rag1-/- mice. Monoclonal Ab B4 was found to specifically recognize mouse annexin IV. Pre-injection of recombinant annexin IV blocked IR injury in wild type C57BL/6 mice, demonstrating the requirement for recognition of this protein in order to develop IR injury in the context of a complex natural antibody repertoire. Humans were also found to exhibit IgM natural antibodies that recognize annexin IV. These data in toto identify annexin IV as a key ischemia-related target antigen that is recognized by natural Abs in a pathologic process required in vivo to develop intestinal IR injury. Keywords: Natural antibodies, Annexin, Ischemia Reperfusion, Inflammation, Complement In the study presented here, a total of 4 custom spotted antigen slides were hybridized with known antibodies.
Project description:The intestinal epithelium constitutes a crucial defense to the potentially life-threatening effects of gut microbiota. However, due to a complex underlying vasculature, hypoperfusion and resultant tissue ischemia pose a particular risk to function and integrity of the epithelium. The small ubiquitin-like modifier (SUMO) conjugation pathway critically regulates adaptive responses to metabolic stress and is of particular significance in the gut, as inducible knockout of the SUMO-conjugating enzyme Ubc9 results in rapid intestinal epithelial disintegration. Here we analyzed the pattern of individual SUMO isoforms in intestinal epithelium and investigated their roles in intestinal ischemia/reperfusion (I/R) damage. Immunostaining revealed that epithelial SUMO2/3 expression was almost exclusively limited to crypt epithelial nuclei in unchallenged mice. However, intestinal I/R or overexpression of Ubc9 caused a remarkable enhancement of epithelial SUMO2/3 staining along the crypt-villus axis. Unexpectedly, a similar pattern was found in SUMO1 knockout mice. Ubc9 transgenic mice, but also SUMO1 knockout mice were protected from I/R injury as evidenced by better preserved barrier function and blunted inflammatory responses. PCR array analysis of microdissected villus-tip epithelia revealed a specific epithelial contribution to reduced inflammatory responses in Ubc9 transgenic mice, as key chemotactic signaling molecules such as IL17A were significantly downregulated. Together, our data indicate a critical role particularly of the SUMO2/3 isoforms in modulating responses to I/R and provide the first evidence that SUMO1 deletion activates a compensatory process that protects from ischemic damage.
Project description:Purpose:Detection of differentially expressed lncRNA in the infarct zone and the control group in myocardial ischemia-reperfusion injury model tissue. Method: Use 8 weeks of C57BL/6 mice to establish a myocardial ischemia-reperfusion injury model, 45 minutes of ischemia, and 24 hours after reperfusion, the mice were sacrificed to obtain materials. Result: The expression of lncRNAs in the infarct area of myocardial ischemia-reperfusion injury model mice was detected, and it was found that a total of 43 lncRNAs related to myocardial ischemia-reperfusion injury changed in expression, of which 17 were up-regulated (fold change >1.5). 26 expressions are down-regulated (fold change <0.8)
Project description:Liver injury is a common complication of inflammatory bowel disease (IBD). However, the mechanisms of liver injury development are not clear in IBD patients. Gut microbiota is thought to be engaged in IBD pathogenesis. Here, by an integrated analysis of host transcriptome and colonic microbiome, we have attempted to reveal the mechanism of liver injury in colitis mice. In this study, dextran sulfate sodium (DSS) -induced mice colitis model was constructed. Liver and colon transcriptome results showed that immune response and lipid metabolism-related pathways were dramatically altered, while DNA damage repair-related pathways were only significantly down-regulated in the colon. The microbiota of DSS-treated mice underwent strong transitions. Correlation analyses identified genes associated with liver and colon injury, whose expression was associated with the abundance of liver and gut health-related bacteria Collectively, the results indicate that the liver injury in colitis mice may be related to the intestinal dysbiosis and host-microbiota interactions. These findings may provide new insights for identifying potential targets for the treatment of IBD and its induced liver injury.
Project description:Experiments in rodents have shown that kidney ischemia/reperfusion injury (IRI) facilitates lung injury and inflammation. To identify potential ischemia-specific lung molecular pathways involved, we conducted global gene expression profiling of lung 6 or 36 hours following 1) bilateral kidney IRI, 2) bilateral nephrectomy (BNx), and 3) sham laparotomy in C57BL/6J mice. Total RNA from whole lung was isolated and hybridized to 430MOEA (22,626 genes) GeneChips (n=3/group). Experiment Overall Design: All procedures were approved by the Johns Hopkins Animal Care and Use Committee, and were consistent with the National Institutes of Health (NIH) Guide for the Care and Use of Laboratory Animals. Male 6-8 week-old mice (C57BL6/J), weighing approximately 25-30 grams were obtained from Jackson Laboratory (Bar Harbor, ME) and housed under pathogen-free conditions according to NIH guidelines at least five days prior to operative procedures. Experiment Overall Design: Animals were placed on a heating blanket and underwent midline laparotomy with isolation of bilateral renal pedicles. For mice assigned to experimental ischemia-reperfusion injury (IRI), a non-traumatic microvascular clamp was applied across both renal pedicles for 60 minutes. After the allotted ischemia time, the clamps were gently removed, the animals administered 1 ml of sterile saline intraperitoneally, and the incision closed in two layers with 4-0 silk suture. The animals were then allowed to recover with free access to food and water. Sham animals underwent the identical procedure without placement of the vascular clamps. The mice assigned to bilateral nephrectomy (BNx) underwent similar procedures except both renal pedicles were ligated with 5-0 silk suture and the kidneys removed. At 6 or 36 hours following the experimental procedure, the mice were euthanized by exsanguination under pentobarbital anesthesia and lung tissues collected for analysis.
Project description:Hepatic ischemia reperfusion injury is a dynamic process consisting of two stages: ischemia and reperfusion, and triggers a cascade of physiological and biochemical events. Given the important role of microRNAs in regulating gene expression, we analyzed gene expression changes in mouse livers at sham control, ischemia stage, and reperfusion stage. We generated global expression profiles of microRNA and mRNA genes in mouse livers subjected to ischemia reperfusion injury at the three stages, respectively. Comparison analysis showed that reperfusion injury had a distinct expression profile whereas the ischemia sample and the sham control were clustered together. Consistently, there are 69 differentially expressed microRNAs between the reperfusion sample and the sham control whereas 28 differentially expressed microRNAs between the ischemia sample and the sham control. We further identified two modes of microRNA expression changes in ischemia reperfusion injury. Functional analysis of both the differentially expressed microRNAs in the two modes and their target mRNAs revealed that ischemia injury impaired mitochondria function, nutrient consumption, and metabolism process. In contrast, reperfusion injury led to severe tissue inflammation that is predominantly an innate-immune response in the ischemia reperfusion process. Our staged analysis of gene expression profiles provides new insights into regulatory mechanisms of microRNAs in mouse hepatic ischemia reperfusion injury.