TNFR1/phox interaction and TNFR1 mitochondrial translocation Thwart silica-induced pulmonary fibrosis.

Macrophages play a fundamental role in innate immunity and the pathogenesis of silicosis. Phagocytosis of silica particles is associated with the generation of reactive oxygen species (ROS), secretion of cytokines, such as TNF, and cell death that contribute to silica-induced lung disease. In macrophages, ROS production is executed primarily by activation of the NADPH oxidase (Phox) and by generation of mitochondrial ROS (mtROS); however, the relative contribution is unclear, and the effects on macrophage function and fate are unknown. In this study, we used primary human and mouse macrophages (C57BL/6, BALB/c, and p47(phox-/-)) and macrophage cell lines (RAW 264.7 and IC21) to investigate the contribution of Phox and mtROS to silica-induced lung injury. We demonstrate that reduced p47(phox) expression in IC21 macrophages is linked to enhanced mtROS generation, cardiolipin oxidation, and accumulation of cardiolipin hydrolysis products, culminating in cell death. mtROS production is also observed in p47(phox-/-) macrophages, and p47(phox-/-) mice exhibit increased inflammation and fibrosis in the lung following silica exposure. Silica induces interaction between TNFR1 and Phox in RAW 264.7 macrophages. Moreover, TNFR1 expression in mitochondria decreased mtROS production and increased RAW 264.7 macrophage survival to silica. These results identify TNFR1/Phox interaction as a key event in the pathogenesis of silicosis that prevents mtROS formation and reduces macrophage apoptosis.

Interleukin 1 receptor antagonist mediates the antiinflammatory and antifibrotic effect of mesenchymal stem cells during lung injury.

Mesenchymal stem cells (MSCs) have been exploited as cellular vectors to treat a wide array of diseases but the mechanisms responsible for their therapeutic effect remain indeterminate. Previously, we reported that MSCs inhibit bleomycin (BLM)-induced inflammation and fibrosis within the lungs of mice. Interrogation of the MSC transcriptome identified interleukin 1 receptor antagonist (IL1RN) as a potential mediator of this effect. Fractionation studies indicated that MSCs are the principal source of IL1RN in murine bone marrow and that its expression is restricted to a unique subpopulation of cells. Moreover, MSC-conditioned media was shown to block proliferation of an IL-1alpha-dependent T cell line and inhibit production of TNF-alpha by activated macrophages in vitro. Studies conducted in mice revealed that MSC administration was more effective than recombinant IL1RN delivered via adenoviral infection or osmotic pumps in inhibiting BLM-induced increases in TNF-alpha, IL-1alpha, and IL1RN mRNA in lung, IL1RN protein in bronchoalveolar lavage (BAL) fluid, and trafficking of lymphocytes and neutrophils into the lung. Therefore, MSCs protect lung tissue from BLM-induced injury by blocking TNF-alpha and IL-1, two fundamental proinflammatory cytokines in lung. Identification of IL1RN-expressing human MSC subpopulations may provide a novel cellular vector for treating chronic inflammatory diseases in humans.

Laparoscopic sleeve gastrectomy in patients with heart failure and left ventricular assist devices as a bridge to transplant.

BACKGROUND: Obesity is an epidemic that is closely associated with heart failure. The ultimate treatment for end-stage heart failure is cardiac transplantation. Patients with morbid obesity are often excluded from receiving donor organs. Many transplant centers use body mass index (BMI) >35 kg/m2 as a contraindication to listing for heart transplant. Left ventricular assist devices (LVADs) were developed as a bridge to transplant for many heart failure patients, but bariatric surgery for LVAD patients has not been well described. OBJECTIVES: The purpose of our study was to evaluate the safety and efficacy of laparoscopic sleeve gastrectomy (LSG) in LVAD patients and the impact on heart failure recovery as a bridge to cardiac transplantation. SETTING: University hospital. METHODS: A retrospective study was conducted to evaluate the outcomes of patients with morbid obesity and LVADs who underwent LSG at a large academic medical center between 2013 and 2017. Age, BMI, percent excess weight loss, cardiac ejection fraction, listing status for transplantation, and success of transplant were reviewed. RESULTS: Eleven patients were identified with morbid obesity and heart failure with LVAD support who underwent LSG. There were no perioperative deaths. Four patients (37%) achieved BMI <35 and were successfully listed for and received cardiac transplantation. An additional 3 patients (27%) achieved BMI <35 kg/m2 and are listed for cardiac transplantation. CONCLUSIONS: LSG can be safely used in patients with morbid obesity and end-stage heart failure requiring LVAD support to lower their BMI and become eligible for cardiac transplantation.

Loss of sirtuin 1 and mitofusin 2 contributes to enhanced ischemia/reperfusion injury in aged livers.

Ischemia/reperfusion (I/R) injury is a causative factor contributing to morbidity and mortality during liver resection and transplantation. Livers from elderly patients have a poorer recovery from these surgeries, indicating reduced reparative capacity with aging. Mechanisms underlying this age-mediated hypersensitivity to I/R injury remain poorly understood. Here, we investigated how sirtuin 1 (SIRT1) and mitofusin 2 (MFN2) are affected by I/R in aged livers. Young (3 months) and old (23-26 months) male C57/BL6 mice were subjected to hepatic I/R in vivo. Primary hepatocytes isolated from each age group were also exposed to simulated in vitro I/R. Biochemical, genetic, and imaging analyses were performed to assess cell death, autophagy flux, mitophagy, and mitochondrial function. Compared to young mice, old livers showed accelerated liver injury following mild I/R. Reperfusion of old hepatocytes also showed necrosis, accompanied with defective autophagy, onset of the mitochondrial permeability transition, and mitochondrial dysfunction. Biochemical analysis indicated a near-complete loss of both SIRT1 and MFN2 after I/R in old hepatocytes, which did not occur in young cells. Overexpression of either SIRT1 or MFN2 alone in old hepatocytes failed to mitigate I/R injury, while co-overexpression of both proteins promoted autophagy and prevented mitochondrial dysfunction and cell death after reperfusion. Genetic approaches with deletion and point mutants revealed that SIRT1 deacetylated K655 and K662 residues in the C-terminus of MFN2, leading to autophagy activation. The SIRT1-MFN2 axis is pivotal during I/R recovery and may be a novel therapeutic target to reduce I/R injury in aged livers.

Computed tomography evidence of fluid in the hernia sac predicts surgical site infection following mesh repair of acutely incarcerated ventral and groin hernias.

BACKGROUND: Mesh placement during repair of acutely incarcerated ventral and groin hernias is associated with high rates of surgical site infection (SSI). The utility of preoperative computed tomography (CT) in this setting is unclear. We hypothesized that CT evidence of bowel wall compromise would predict SSI while accounting for physiologic parameters. METHODS: We performed a 4-year retrospective cohort analysis of 50 consecutive patients who underwent mesh repair of acutely incarcerated ventral or groin hernias. We analyzed chronic disease burden, acute illness severity, CT findings, operative management, and herniorrhaphy-specific outcomes within 180 days. The primary outcome was SSI by the Centers for Disease Control and Prevention criteria. Multiple logistic regression was performed to identify independent predictors of SSI. RESULTS: Eighty-four percent of all patients were American Society of Anesthesiologists class III or IV, 28% were active smokers, and mean body mass index (BMI) was 35 kg/m. Fifty-four percent had ventral hernias, 40% had inguinal hernias, and 6% had femoral or combined inguinal/ femoral hernias. Seventy percent of preoperative CT scans had features suggesting bowel compromise, abdominal free fluid, or fluid in the hernia sac. Surgical site infection occurred in 32% of all patients (8% superficial, 24% deep or organ/space). The strongest predictors of SSI were CT evidence of fluid in the hernia sac (odds ratio [OR], 8.3; 95% confidence interval [CI], 1.7-41), initial heart rate 90 beats/min or greater (OR, 6.3; 95% CI, 1.1-34), and BMI 35 kg/m or greater (OR, 5.8; 95% CI, 1.2-28). Surgical site infection rates were significantly higher among patients who had CT evidence of fluid in the hernia sac (56% vs. 19%, p = 0.012). CONCLUSIONS: More than half of all patients with CT scan evidence of fluid in the hernia sac developed an SSI. Computed tomography evidence of fluid in the hernia sac was the strongest predictor of SSI, followed by heart rate and BMI. Together, these parameters identify high-risk patients for whom better strategies are needed to avoid SSI without sacrificing durability. LEVEL OF EVIDENCE: Prognostic study, level III; Therapeutic, level IV.

Orthotopic Patient-Derived Pancreatic Cancer Xenografts Engraft Into the Pancreatic Parenchyma, Metastasize, and Induce Muscle Wasting to Recapitulate the Human Disease.

OBJECTIVE: Limitations associated with current animal models serve as a major obstacle to reliable preclinical evaluation of therapies in pancreatic cancer (PC). In an effort to develop more reliable preclinical models, we have recently established a subcutaneous patient-derived xenograft (PDX) model. However, critical aspects of PC responsible for its highly lethal nature, such as the development of distant metastasis and cancer cachexia, remain underrepresented in the flank PDX model. The purpose of this study was to evaluate the degree to which an orthotopic PDX model of PC recapitulates these aspects of the human disease. METHODS: Human PDX-derived PC tumors were implanted directly into the pancreas of NOD.Cg-Prkdc Il2rg/SzJ mice. Tumor growth, metastasis, and muscle wasting were then evaluated. RESULTS: Orthotopically implanted PDX-derived tumors consistently incorporated into the murine pancreatic parenchyma, metastasized to both the liver and lungs and induced muscle wasting directly proportional to the size of the tumor, consistent of the cancer cachexia syndrome. CONCLUSIONS: Through the orthotopic implantation technique described, we demonstrate a highly reproducible model that recapitulates both local and systemic aspects of human PC.

Improved outcomes following implementation of an acute gastrointestinal bleeding multidisciplinary protocol.

BACKGROUND: Effective multidisciplinary management of gastrointestinal bleeding (GIB) requires effective communication. We instituted a protocol to standardize communication practices with the hypothesis that outcomes would improve following protocol initiation. METHODS: We performed a retrospective cohort analysis of 442 patients who required procedural management of acute GIB at our institution during a 50-month period spanning 25 months before and 25 months after implementation of a multidisciplinary communication protocol. The protocol stipulates that when a patient with severe GIB is identified, a conference call is coordinated among the gastroenterology, interventional radiology, and acute care surgery teams. A consensus plan is generated and then reassessed following procedural interventions and changes in patients' status. Patients' characteristics, management strategies, and outcomes were compared before and after protocol initiation. RESULTS: Patient populations before and after protocol initiation were similar in age, comorbidities, outpatient use of antiplatelet/anticoagulant medications, admission vital signs, and admission laboratory values. The median interval between admission and the first procedure was significantly shorter in the protocol group (40 vs 47 hours, p = 0.046). The proportion of patients who received packed red blood cell transfusions decreased following protocol initiation (41% vs 50%, p = 0.018). Median hospital length of stay was significantly shorter in the protocol group (5.0 vs 6.0 days, p = 0.014). Readmissions with GIB were decreased after protocol implementation (8% vs. 15%, p = 0.023). CONCLUSION: Implementation of a multidisciplinary protocol for management of acute GIB was associated with earlier intervention, fewer packed red blood cell transfusions, shorter hospital length of stay, and fewer readmissions with GIB. Future research should seek to establish causal relationships between communication practices and outcomes. LEVEL OF EVIDENCE: Therapeutic study, level III.

Deacetylation of mitofusin-2 by sirtuin-1: A critical event in cell survival after ischemia.

Sirtuin-1 (SIRT1) is associated with longevity and cell survival. Recently, we unveiled a new role of SIRT1 in hepatic ischemia/reperfusion (I/R) injury and identified a novel interaction between SIRT1 and mitochondrial outer membrane protein mitofusin-2 (MFN2), in which SIRT1-dependent deacetylation of MFN2 regulates mitochondria and autophagy in the liver.

Autophagy in the liver: cell's cannibalism and beyond.

Chronic liver disease and its progression to liver failure are induced by various etiologies including viral infection, alcoholic and nonalcoholic hepatosteatosis. It is anticipated that the prevalence of fatty liver disease will continue to rise due to the growing incidence of obesity and metabolic disorder. Evidence is accumulating to indicate that the onset of fatty liver disease is causatively linked to mitochondrial dysfunction and abnormal lipid accumulation. Current treatment options for this disease are limited. Autophagy is an integral catabolic pathway that maintains cellular homeostasis both selectively and nonselectively. As mitophagy and lipophagy selectively remove dysfunctional mitochondria and excess lipids, respectively, stimulation of autophagy could have therapeutic potential to ameliorate liver function in steatotic patients. This review highlights our up-to-date knowledge on mechanistic roles of autophagy in the pathogenesis of fatty liver disease and its vulnerability to surgical stress, with an emphasis on mitophagy and lipophagy.

Autophagy in Ischemic Livers: A Critical Role of Sirtuin 1/Mitofusin 2 Axis in Autophagy Induction.

No-flow ischemia occurs during cardiac arrest, hemorrhagic shock, liver resection and transplantation. Recovery of blood flow and normal physiological pH, however, irreversibly injures the liver and other tissues. Although the liver has the powerful machinery for mitochondrial quality control, a process called mitophagy, mitochondrial dysfunction and subsequent cell death occur after reperfusion. Growing evidence indicates that reperfusion impairs mitophagy, leading to mitochondrial dysfunction, defective oxidative phosphorylation, accumulation of toxic metabolites, energy loss and ultimately cell death. The importance of acetylation/deacetylation cycle in the mitochondria and mitophagy has recently gained attention. Emerging data suggest that sirtuins, enzymes deacetylating a variety of target proteins in cellular metabolism, survival and longevity, may also act as an autophagy modulator. This review highlights recent advances of our understanding of a mechanistic correlation between sirtuin 1, mitophagy and ischemic liver injury.

Mitochondrial Dysfunction and Autophagy in Hepatic Ischemia/Reperfusion Injury.

Ischemia/reperfusion (I/R) injury remains a major complication of liver resection, transplantation, and hemorrhagic shock. Although the mechanisms that contribute to hepatic I/R are complex and diverse involving the interaction of cell injury in hepatocytes, immune cells, and endothelium, mitochondrial dysfunction is a cardinal event culminating in hepatic reperfusion injury. Mitochondrial autophagy, so-called mitophagy, is a key cellular process that regulates mitochondrial homeostasis and eliminates damaged mitochondria in a timely manner. Growing evidence accumulates that I/R injury is attributed to defective mitophagy. This review aims to summarize the current understanding of autophagy and its role in hepatic I/R injury and highlight the various therapeutic approaches that have been studied to ameliorate injury.