Paul Waltz

Lipopolysaccaride induces autophagic signaling in macrophages via a TLR4, heme oxygenase-1 dependent pathway

Toll-like receptor (TLR) signaling is an important part of the innate immune response. One of the downstream responses to TLR4 signaling upon lipopolysaccharide (LPS) stimulation is the induction of autophagy, which is a key response to multiple stressors. An additional adaptive signaling molecule that is involved in the response to stress is heme oxygenase-1 (HO-1). HO-1 signaling is essential to limit inflammation and restore homeostasis. We found that LPS induced autophagic signaling in macrophages via a TLR4, HO-1 dependent pathway in macrophages. These data add to the developing contribution of autophagic signaling as part of the inflammatory response.

Sepsis results in an altered renal metabolic and osmolyte profile

BACKGROUND Sepsis remains a major health-care burden and source of morbidity and mortality. Acute kidney injury and failure frequently accompanies severe sepsis and contributes to this burden. Despite a great deal of research, the exact mechanisms underlying renal failure in sepsis are poorly understood. This study aims to further understand metabolic changes in renal tissue during sepsis. MATERIALS AND METHODS Experimental sepsis was induced by cecal ligation and puncture (CLP) in C57BL/6 mice. Serum and organs were harvested 8 h after CLP. Markers of renal function including serum creatinine, blood urea nitrogen, and cystatin C were measured. Whole kidneys were analyzed for a global biochemical profile via liquid chromatography/tandem mass spectrometry by Metabolon. RESULTS CLP induced renal injury as evidenced by elevated serum creatinine, blood urea nitrogen, and cystatin C. Global energetic profile in sepsis showed an increase in glycolytic intermediates with decreased flux through the tricarboxylic acid (TCA) cycle. Multiple inflammatory markers were elevated in response to CLP. Levels of osmotic regulators varied, with an overall increase in pinitol, urea, and taurine in response to CLP. CONCLUSIONS CLP resulted in dramatic changes in the renal macromolecular milieu. There appears to be an increased dependence on glycolysis and diminished flush through the TCA cycle. In addition, changes in renal osmolytes including pinitol, urea, and taurine were observed, perhaps uncovering an additional change with implications on renal function during sepsis.

Novel therapies for severe Clostridium difficile colitis.

Purpose of reviewClostridium difficile infection (CDI) is becoming a large healthcare burden with increasing incidence, high recurrence rates, and associated morbidity and mortality. Disease severity varies from mild to severe and complicated presentations. Current mainstays of therapy in severe CDI include: fluid resuscitation, support of organ dysfunction, discontinuation of inciting agents, and antibiotic treatment. Recent findingsRecent focus on the impact of the microbiome and targeted therapies to reconstitute biodiversity may provide alternative therapeutic modalities with higher success and lower recurrence rates. Newer antibiotics are under development, along with targeted immunotherapies that attempt to neutralize pathogenic toxins. Alternative surgical options from traditional subtotal colectomy may provide a less morbid surgical option for those requiring intervention. SummaryWith further understanding of the pathogenesis and shortcomings of current therapies, the future of management of CDI may include a multimodal approach focusing on microbiota and immunologic therapies that could result in improved cure with reduced recurrence.

Sirtuin 1 Agonist Minimizes Injury and Improves the Immune Response Following Traumatic Shock.

ABSTRACT Survival from traumatic injury requires a coordinated and controlled inflammatory and immune response. Mitochondrial and metabolic responses to stress have been shown to play a role in these inflammatory and immune responses. We hypothesized that increases in mitochondrial biogenesis via a sirtuin 1 agonist would decrease tissue injury and partially ameliorate the immunosuppression seen following trauma. C57Bl/6 mice were subjected to a multiple trauma model. Mice were pretreated with either 100 mg/kg per day of the sirtuin 1 agonist, Srt1720, via oral gavage for 2 days prior to trauma and extended until the day the animals were killed, or they were pretreated with peroxisome proliferator-activated receptor &ggr; coactivator 1&agr; (PGC1&agr;) siRNA via hydrodynamic tail vein injection 48 h prior to trauma. Markers for mitochondrial function and biogenesis were measured in addition to splenocyte proliferative capacity and bacterial clearance. Srt1720 was noted to improve mitochondrial biogenesis, mitochondrial function, and complex IV activity following traumatic injury (P < 0.05), whereas knockdown of PGC1&agr; resulted in exacerbation of mitochondrial dysfunction (P < 0.05). These changes in mitochondrial function were associated with altered severity of hepatic injury with significant reductions in serum alanine aminotransferase levels seen in mice treated with srt1720. Splenocyte proliferative capacity and intraperitoneal bacterial clearance were evaluated as markers for overall immune function following trauma-hemorrhage. Treatment with Srt1720 minimized the trauma-induced decreases in splenocyte proliferation (P < 0.05), whereas treatment with PGC1&agr; siRNA led to diminished bacterial clearance. The PGC1&agr; signaling pathway is an important regulator of mitochondrial function and biogenesis, which can potentially be harnessed to protect against hepatic injury and minimize the immunosuppression that is seen following trauma-hemorrhage.

1379: BLUE LIGHT THERAPY MODULATES THE SYSTEMIC RESPONSE TO SEPSIS IN MICE AND HUMANS.

Crit Care Med 2016 • Volume 44 • Number 12 (Suppl.) clinical outcomes and add significantly to healthcare burden and cost. Little data is available on CDI complicating patients hospitalized with septic shock (SS). We sought to determine the prevalence of CDI in hospitalized patients with SS and the impact of CDI on clinical outcomes in these patients. Methods: The National Inpatient Sample (NIS) was used to identify hospitalizations from 2007 to 2013 of adults (age > 18 years) with SS. Septic shock was identified by either ICD9-CM code for SS or vasopressor use associated with ICD-9 codes of sepsis, severe sepsis, septicemia, bacteremia, or fungemia. CDI was identified by secondary diagnosis ICD-9-CM code. Demographic data was obtained from NIS database. Primary outcome was prevalence of CDI among patients with SS. Secondary outcomes were: mortality and hospital length of stay (LOS) associated with CDI. Results: There were 2,031,739 hospitalizations with SS between 2007 and 2013. CDI was present in 8.2% of patients with SS. The prevalence of CDI in SS remained stable between 2007 and 2013. Patients with CDI were older (mean age 69.8 (+ 14.7 vs 66.8 (+ 15.9) years, p <0.001). The in-hospital mortality of SS complicated by CDI was comparable to those without CDI (37.1% versus 37.0%, p=0.48). The median LOS was significantly longer for patients with CDI (13 vs 9 days, p<0.001). Prolonged LOS (>75th percentile of LOS for SS cases, 17 days) was observed in 36.9% of SS patients with CDI vs 22.7% without CDI (p<0.001). After adjusting for age, gender, race, and Charlson Comorbidity Index; the odds of prolonged LOS with presence of CDI was significantly greater (OR 2.11, 95%CI 2.06 – 2.15, p<0.001). Conclusions: CDI complicating septic shock is associated with a significant increase in length of stay but no increase in in-hospital mortality.

Heme Oxygenase-2 Localizes to Mitochondria and Regulates Hypoxic Responses in Hepatocytes

Hypoxia occurs as a part of multiple disease states, including hemorrhagic shock. Adaptive responses occur within the cell to limit the consequences of hypoxia. This includes changes in mitochondrial respiration, stress-induced cell signaling, and gene expression that is regulated by hypoxia inducible factor-1α (HIF-1α). Heme oxygenase-2 (HO-2) has been shown to be involved in oxygen sensing in several cell types. The purpose of these experiments was to test the hypothesis that HO-2 is a critical regulator of mitochondrial oxygen consumption and reactive oxygen species (ROS) production to influence hypoxia-adaptive responses such as HIF-1α protein levels and JNK signaling. Methods and Results. In vitro studies were performed in primary mouse hepatocytes. HO-2, but not HO-1, was expressed in mitochondria at baseline. Decreased oxygen consumption and increased mitochondrial ROS production in response to hypoxia were dependent upon HO-2 expression. HO-2 expression regulated HIF-1α and JNK signaling in a mitochondrial ROS-dependent manner. Furthermore, knockdown of HO-2 led to increased organ damage, systemic inflammation, tissue hypoxia, and shock in a murine model of hemorrhage and resuscitation. Conclusion. HO-2 signaling plays a role in hypoxic signaling and hemorrhagic shock. This pathway may be able to be harnessed for therapeutic effects.

Minimally Invasive Approaches to Clostridium Difficile Colitis

Clostridium difficile infection (CDI) has been increasing in incidence over the past three decades. It is now recognized as a major healthcare-associated complication and is the leading nosocomial pathogen. Disease severity ranges from mild diarrhea to severe sepsis with multiple organ dysfunction. Early recognition, diagnosis, and treatment are necessary to prevent disease progression. Despite best effort, some cases progress in severity, and the development of severe, complicated disease (sometimes known as fulminant colitis or the development of toxic megacolon) is associated with a high rate of mortality. Surgical treatment for severe, complicated disease was defined in the 1990s to be subtotal abdominal colectomy and end ileostomy. Although mortality is improved by colectomy in patients that are critically ill compared to those treated with medical therapy alone, outcomes are still poor. There may be opportunity to improve outcomes by more aggressive nonsurgical interventions, earlier surgical intervention, and alternative surgical techniques when managing severe CDI. This chapter highlights some of the minimally invasive surgical and nonsurgical approaches to treat patients with severe, complicated CDI.

The High Stakes of Postoperative Clostridium difficile Infection

30-day postoperative rate of CDI in the Veterans Health Administration Surgery Programs was determined over a 4-year period from 2009 to 2013. The findings in this study demonstrate an overall 0.4% per year rate of CDI with a range of 0.0% to 1.4% by program. This includes outcomes from ambulatory surgery centers. The associated risk factors for the development of CDI were as expected: indices of patient frailty, length of preoperative hospitalization, complexity of surgical procedure, complexity of the surgical program of the facility, and increasing exposure to antibiotics. The strength of the study by Li et al lies within the ability to capture CDI documented in the Veterans Affairs electronic medical record that includes inpatient and outpatient settings; however, it is possible that some patients may have been diagnosed with CDI outside of the Veterans Affairs system. Moreover, while most CDIs occur temporally within 2 weeks of antibiotic exposure during the index hospitalization associated with the surgical procedure, hospital acquired–CDI is considered to be within 3 months following hospitalization. This study was limited to the 30-day postoperative period. Additionally, given the approximately 20% recurrence rate of CDI, inclusion of this end