A two-hit model of sepsis plus hyperoxia causes lung permeability and inflammation

Mouse models of acute lung injury (ALI) have been instrumental for studies of the biologic underpinnings of lung inflammation and permeability, but murine models of sepsis generate minimal lung injury. Our goal was to create a murine sepsis model of ALI that reflects the inflammation, lung edema, histologic abnormalities and physiologic dysfunction that characterize ALI. Using a cecal slurry (CS) model of polymicrobial abdominal sepsis and exposure to hyperoxia (95%), we systematically varied timing and dose of the CS injection, fluids and antibiotics and dose of hyperoxia. We found that CS alone had a high mortality rate that was improved with the addition of antibiotics and fluids. Despite this, we did not see evidence of ALI as measured by bronchoalveolar lavage (BAL) cell count, total protein, CXCL-1 or by lung wet:dry weight ratio. Addition of hyperoxia (95% FiO2) to CS immediately after CS injection increased BAL cell counts and CXCL-1 and lung wet:dry weight ratio but was associated with 40% mortality. Splitting the hyperoxia treatment into two 12 hour exposures (0-12 hours24-36 hours) after CS injection increased survival to 75% and caused significant lung injury compared to CS alone as measured by increased BAL total cell count (92500 vs 240000, p=0.0004), BAL protein (71 vs 103 ug/ml, p=0.0030, and lung wet:dry weight ratio (4.5 vs 5.5 p=0.0005), and compared to sham as measured by increased BAL CXCL-1 (20 vs 2372 pg/ml, p<0.0001), and histologic lung injury score (1.9 vs 4.2, p=0.0077). Additionally, our final model showed evidence of lung epithelial (increased BAL and plasma RAGE) and endothelial (increased Syndecan-1 and sulfated glycosaminoglycans) injury. In conclusion, we have developed a clinically relevant mouse model of sepsis-induced ALI using IP injection of CS, antibiotics and fluids, and hyperoxia. This clinically relevant model can be used for future studies of sepsis-induced ALI.

Targeting S100A9 Reduces Neutrophil Recruitment, Inflammation and Lung Damage in Abdominal Sepsis

S100A9, a pro-inflammatory alarmin, is up-regulated in inflamed tissues. However, the role of S100A9 in regulating neutrophil activation, inflammation and lung damage in sepsis is not known. Herein, we hypothesized that blocking S100A9 function may attenuate neutrophil recruitment in septic lung injury. Male C57BL/6 mice were pretreated with the S100A9 inhibitor ABR-238901 (10 mg/kg), prior to cercal ligation and puncture (CLP). Bronchoalveolar lavage fluid (BALF) and lung tissue were harvested for analysis of neutrophil infiltration as well as edema and CXC chemokine production. Blood was collected for analysis of membrane-activated complex-1 (Mac-1) expression on neutrophils as well as CXC chemokines and IL-6 in plasma. Induction of CLP markedly increased plasma levels of S100A9. ABR-238901 decreased CLP-induced neutrophil infiltration and edema formation in the lung. In addition, inhibition of S100A9 decreased the CLP-induced up-regulation of Mac-1 on neutrophils. Administration of ABR-238901 also inhibited the CLP-induced increase of CXCL-1, CXCL-2 and IL-6 in plasma and lungs. Our results suggest that S100A9 promotes neutrophil activation and pulmonary accumulation in sepsis. Targeting S100A9 function decreased formation of CXC chemokines in circulation and lungs and attenuated sepsis-induced lung damage. These novel findings suggest that S100A9 plays an important pro-inflammatory role in sepsis and could be a useful target to protect against the excessive inflammation and lung damage associated with the disease.

Self-perceived recovery and quality of life in elderly patients surviving ICU-admission for abdominal sepsis

Introduction Concern for loss of physical performance and Health-Related Quality of Life (HRQoL) may raise doubts regarding the meaningfulness of an Intensive Care (ICU) admission in elderly patients. We evaluated self-perceived long-term recovery and satisfaction in elderly surviving an abdominal sepsis related ICU-admission and related this to objective measures of HRQoL. Methods A cross-sectional survey study was performed in all ICU-survivors with age ≥70 admitted with abdominal sepsis. HRQoL, frailty and self-perceived long-term recovery were measured using the EQ-5D-3L, Groningen Frailty Indicator, and a self-developed questionnaire, respectively. Results Of 144 patients admitted, 48 were alive at follow up (2.42 [0.92; 3.83] years), and 29 (60%) returned the survey. Eleven patients out of 29 (38%) recovered to baseline functioning, and reported higher HRQoL compared to unrecovered patients (0.861 [0.807; 1.000] and 0.753 [0.499; 0.779] respectively, p=0.005). Of the unrecovered patients, 53% were satisfied with their functioning, and 94% were willing to return to ICU. Conclusions Mortality in elderly patients with abdominal sepsis is high and ICU-admission should be weighed carefully. However, despite substantial functional decline in survivors, it does not necessarily cause self-perceived unsatisfactory functioning, poor HRQoL and unwillingness to receive life-sustaining therapy again. Caution is advised to use an anticipated loss of functioning as an argument to deny an ICU-admission.

The Pharmacokinetic Profile and Bioavailability of Enteral N-Acetylcysteine in Intensive Care Unit

Background and Objectives: N-acetylcysteine (NAC) is a mucolytic agent used to prevent ventilator-associated pneumonia in intensive care units. This study aimed to evaluate the oral bioavailability of NAC in critically ill patients with pneumonia, isolated acute brain injury and abdominal sepsis. Materials and Methods: This quantitative and descriptive study compared NAC’s pharmacokinetics after intravenous and enteral administration. 600 mg of NAC was administered in both ways, and the blood levels for NAC were measured. Results: 18 patients with pneumonia, 19 patients with brain injury and 17 patients with abdominal sepsis were included in the population pharmacokinetic modelling. A three-compartmental model without lag-time provided the best fit to the data. Oral bioavailability was estimated as 11.6% (95% confidence interval 6.3–16.9%), similar to bioavailability in healthy volunteers and patients with chronic pulmonary diseases. Conclusions: The bioavailability of enteral NAC of ICU patients with different diseases is similar to the published data on healthy volunteers.

c-Abl kinase regulates neutrophil extracellular trap formation and lung injury in abdominal sepsis

Sepsis is associated with exaggerated neutrophil responses although mechanisms remain elusive. The aim of this study was to investigate the role of c-Abelson (c-Abl) kinase in neutrophil extracellular trap (NET) formation and inflammation in septic lung injury. Abdominal sepsis was induced by cecal ligation and puncture (CLP). NETs were detected by electron microscopy in the lung and by confocal microscopy in vitro. Plasma levels of DNA-histone complexes, interleukin-6 (IL-6) and CXC chemokines were quantified. CLP-induced enhanced phosphorylation of c-Abl kinase in circulating neutrophils. Administration of the c-Abl kinase inhibitor GZD824 not only abolished activation of c-Abl kinase in neutrophils but also reduced NET formation in the lung and plasma levels of DNA-histone complexes in CLP mice. Moreover, inhibition of c-Abl kinase decreased CLP-induced lung edema and injury. Administration of GDZ824 reduced CLP-induced increases in the number of alveolar neutrophils. Inhibition of c-Abl kinase also markedly attenuated levels of CXC chemokines in the lung and plasma as well as IL-6 levels in the plasma of septic animals. Taken together, this study demonstrates that c-Abl kinase is a potent regulator of NET formation and we conclude that c-Abl kinase might be a useful target to ameliorate lung damage in abdominal sepsis.