Cold-inducible RNA-binding Protein Induces Neutrophil Extracellular Traps in the Lungs during Sepsis.

Extracellular cold-inducible RNA-binding protein (CIRP) exaggerates inflammation and tissue injury in sepsis. Neutrophil extracellular traps (NETs) are released by activated neutrophils during sepsis. NETs contribute to pathogen clearance, but excessive NET formation (NETosis) causes inflammation and tissue damage. Peptidylarginine deiminase 4 (PAD4) is associated with NETosis by increasing histone citrullination and chromatin decondensation. We hypothesized that CIRP induces NETosis in the lungs during sepsis via upregulating PAD4 expression. Sepsis was induced in C57BL/6 wild-type (WT) and CIRP-/- mice by cecal ligation and puncture (CLP). After 20 h of CLP induction, NETs in the lungs of WT and CIRP-/- mice were quantified by flow cytometry by staining the single cell suspensions with MPO and CitH3 Abs. PAD4 expression in the lungs of WT and CIRP-/- mice after sepsis was assessed by Western blotting. In vitro effects of recombinant mouse (rm) CIRP for NETosis and PAD4 expression in the bone marrow-derived neutrophils (BMDN) were assessed by flow cytometry and Western blotting, respectively. After 20 h of CLP, NETosis in the lungs was significantly decreased in CIRP-/- mice compared to WT mice, which also correlated with the decreased PAD4 expression. Intratracheal administration of rmCIRP into WT mice significantly increased NETosis and PAD4 expression in the lungs compared to vehicle-injected mice. In vitro culture of BMDN with rmCIRP significantly increased NETosis and PAD4 expression compared to PBS-treated control. Fluorescence microscopy revealed typical web-like structures consistent with NETs in rmCIRP-treated BMDN. Thus, CIRP serves as a novel inducer of NETosis via PAD4 during sepsis.

CIRP Induces Neutrophil Reverse Transendothelial Migration in Sepsis.

Extracellular cold-inducible RNA-binding protein (CIRP) exaggerates inflammation in sepsis. Neutrophil reverse transendothelial migration (rTEM) allows neutrophils to migrate from tissues into the circulation. The phenotype of neutrophils after reverse migration is CD54CXCR1. We hypothesize that CIRP induces neutrophil rTEM in sepsis. Sepsis was induced in male C57BL/6 mice by cecal ligation and puncture (CLP), and at 5, 10, or 20 h after CLP the frequencies of reversely migrated (RM) neutrophils were assessed in the blood by flow cytometry. As 20 h of CLP showed highest increase in the frequency of RM neutrophils, we further assessed RM neutrophils in the blood of WT and CIRP mice at this time point. The effect of CIRP on neutrophil rTEM was determined by injecting mice with recombinant mouse CIRP (rmCIRP) intratracheally (i.t.) and assessed the frequencies of RM neutrophils. The expression of neutrophil elastase (NE) and junctional adhesion molecule-C (JAM-C) in the lungs was measured by Western blot. The mean frequency of RM neutrophils in sham mice was 0.4%, whereas the frequencies were significantly increased to 1%, 3%, and 7% at 5, 10, and 20 h of CLP, respectively. The mean frequency of RM neutrophils in the blood of CIRP mice was significantly lower than that of WT mice at 20 h of CLP. The RM neutrophils in the blood was significantly increased after administration of rmCIRP i.t. into mice in a time- and dose-dependent manners. NE expression was upregulated, whereas JAM-C expression was downregulated in the lungs after CLP or rmCIRP administration. For the first time, we have showed that CIRP induces neutrophil rTEM in sepsis by increasing NE and decreasing JAM-C.

Targeting junctional adhesion molecule-C ameliorates sepsis-induced acute lung injury by decreasing CXCR4+ aged neutrophils.

Sepsis is a severe inflammatory condition associated with high mortality. Transmigration of neutrophils into tissues increases their lifespan to promote deleterious function. Junctional adhesion molecule-C (JAM-C) plays a pivotal role in neutrophil transmigration into tissues. We aim to study the role of JAM-C on the aging of neutrophils to cause sepsis-induced acute lung injury (ALI). Sepsis was induced in C57BL/6J mice by cecal ligation and puncture (CLP) and JAM-C expression in serum was assessed. Bone marrow-derived neutrophils (BMDN) were treated with recombinant mouse JAM-C (rmJAM-C) ex vivo and their viability was assessed. CLP-operated animals were administrated with either isotype IgG or anti-JAM-C Ab at a concentration of 3 mg/kg and after 20 h, aged neutrophils (CXCR4+ ) were assessed in blood and lungs and correlated with systemic injury and inflammatory markers. Soluble JAM-C level in serum was up-regulated during sepsis. Treatment with rmJAM-C inhibited BMDN apoptosis, thereby increasing their lifespan. CLP increased the frequencies of CXCR4+ neutrophils in blood and lungs, while treatment with anti-JAM-C Ab significantly reduced the frequencies of CXCR4+ aged neutrophils. Treatment with anti-JAM-C Ab significantly reduced systemic injury markers (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) as well as systemic and lung inflammatory cytokines (IL-6 and IL-1ß) and chemokine (macrophage inflammatory protein-2). The blockade of JAM-C improved lung histology and reduced neutrophil contents in lungs of septic mice. Thus, reduction of the pro-inflammatory aged neutrophils by blockade of JAM-C has a novel therapeutic potential in sepsis-induced ALI.

B-1a cells protect mice from sepsis-induced acute lung injury.

BACKGROUND: Sepsis morbidity and mortality are aggravated by acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Mouse B-1a cells are a phenotypically and functionally unique sub-population of B cells, providing immediate protection against infection by releasing natural antibodies and immunomodulatory molecules. We hypothesize that B-1a cells ameliorate sepsis-induced ALI. METHODS: Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). PBS or B-1a cells were adoptively transferred into the septic mice intraperitoneally. After 20 h of CLP, lungs were harvested and assessed by PCR and ELISA for pro-inflammatory cytokines (IL-6, IL-1ß) and chemokine (MIP-2) expression, by histology for injury, by TUNEL and cleaved caspase-3 for apoptosis, and by myeloperoxidase (MPO) assay for neutrophil infiltration. RESULTS: We found that septic mice adoptively transferred with B-1a cells significantly decreased the mRNA and protein levels of IL-6, IL-1ß and MIP-2 in the lungs compared to PBS-treated mice. Mice treated with B-1a cells showed dramatic improvement in lung injury compared to PBS-treated mice after sepsis. We found apoptosis in the lungs was significantly inhibited in B-1a cell injected mice compared to PBS-treated mice after sepsis. B-1a cell treatment significantly down-regulated MPO levels in the lungs compared to PBS-treated mice in sepsis. The protective outcomes of B-1a cells in ALI was further confirmed by using B-1a cell deficient CD19-/- mice, which showed significant increase in the lung injury scores following sepsis as compared to WT mice. CONCLUSIONS: Our results demonstrate a novel therapeutic potential of B-1a cells to treat sepsis-induced ALI.

CIRP increases ICAM-1+ phenotype of neutrophils exhibiting elevated iNOS and NETs in sepsis.

Sepsis represents uncontrolled inflammation due to an infection. Cold-inducible RNA-binding protein (CIRP) is a stress-induced damage-associated molecular pattern (DAMP). A subset of neutrophils expressing ICAM-1+ neutrophils was previously shown to produce high levels of reactive oxygen species. The role of CIRP for the development and function of ICAM-1+ neutrophils during sepsis is unknown. We hypothesize that CIRP induces ICAM-1 expression in neutrophils causing injury to the lungs during sepsis. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found increased expression of CIRP and higher frequencies and numbers of ICAM-1+ neutrophils in the lungs. Conversely, the CIRP-/- mice showed significant inhibition in the frequencies and numbers of ICAM-1+ neutrophils in the lungs compared to wild-type (WT) mice in sepsis. In vitro treatment of bone marrow-derived neutrophils (BMDN) with recombinant murine CIRP (rmCIRP) significantly increased ICAM-1+ phenotype in a time- and dose-dependent manner. The effect of rmCIRP on increasing frequencies of ICAM-1+ neutrophils was significantly attenuated in BMDN treated with anti-TLR4 Ab or NF-κB inhibitor compared, respectively, with BMDN treated with isotype IgG or DMSO. The frequencies of iNOS producing and neutrophil extracellular traps (NETs) forming phenotypes in rmCIRP-treated ICAM-1+ BMDN were significantly higher than those in ICAM-1- BMDN. Following sepsis the ICAM-1+ neutrophils in the lungs showed significantly higher levels of iNOS and NETs compared to ICAM-1- neutrophils. We further revealed that ICAM-1 and NETs were co-localized in the neutrophils treated with rmCIRP. CIRP-/- mice showed significant improvement in their survival outcome (78% survival) over that of WT mice (48% survival) in sepsis. Thus, CIRP could be a novel therapeutic target for regulating iNOS producing and NETs forming ICAM-1+ neutrophils in the lungs during sepsis.

Acute lung injury and multiple organ dysfunction syndrome secondary to intra-abdominal hypertension and abdominal decompression in extensively burned patients.

BACKGROUND: Secondary abdominal compartment syndrome (ACS) is a lethal complication after resuscitation from burn shock, even after abdominal decompression (AD) is performed. This study investigated increased susceptibility to multiple organ dysfunction syndrome (MODS) in extensively burned patients with ACS. METHODS: Patients admitted to our burn unit between 2002 and 2005 with burns affecting 40% or more of the total body surface area without severe inhalation injury were analyzed. Hemodynamic parameters, blood gas analysis, and intrabladder pressure as intra-abdominal pressure were recorded. Serum interleukin (IL)-8 and IL-6 concentrations were measured in 20 of these patients. Lung injury score and Sequential Organ Failure Assessment scores were serially determined. RESULTS: Fourteen of 38 patients developed intra-abdominal hypertension in 22.9 +/- 8.9 hours postburn. Hemodynamic parameters in these 14 patients, including peak intra-abdominal pressure (46.6 +/- 11.2 to 19.8 +/- 9.9 cm H2O), peak inspiratory pressure (51.4 +/- 10.5 to 31.8 +/- 7.0 cm H2O), and abdominal perfusion pressure (51.3 +/- 18.3 to 73.9 +/- 13.6 mm Hg), were improved immediately after AD. Despite AD, lung injury score and Sequential Organ Failure Assessment scores increased significantly 2 and 3 days postburn in patients who required AD. Plasma concentration of IL-8 was elevated in intra-abdominal hypertension patients 3 days postburn. CONCLUSION: Intra-abdominal hypertension induced acute lung injury and MODS with IL-8 elevation, even though AD improved hemodynamic parameters in extensively burned patients.

Resuscitation fluid volume and abdominal compartment syndrome in patients with major burns.

Abdominal compartment syndrome (ACS) is rarely reported as a complication of severe burn. This study clarified the risk of burned patients with and without ACS, especially regarding the resuscitation fluid volume. Extensively burned patients admitted to our burn unit from January 2003, through to June 2004, were examined. Vital signs, blood gas analysis, bladder pressure to estimate intra-abdominal pressure (IAP), peak inspiratory pressure (PIP), resuscitation fluid volume, and urine output (UO) were analyzed. Intra-abdominal hypertension (IAH) was defined as an IAP of more than 30 cm of H2O. Eight of 48 patients suffering from a more than 30% total burn surface area developed ACS in 18.3+/-4.9 h. In these patients, IAP (49+/-12 cmH2O), PIP (50+/-16 cmH2O), heart rate (115+/-8/min), and PaCO2 (54.6+/-10.1 mmHg) were higher than normal, and their resuscitation volume was 0.40+/-0.11 L/kg. Also, a significant correlation between the IBP, PIP and resuscitation volume was observed. Most patients with severe burns required more than 300 mL/kg of resuscitation fluid for the first 24 h after injury that led to ACS and had higher HR, IBP, PIP and PaCO2 despite arterial pressure showing no significant difference.

Hypertonic lactated saline resuscitation reduces the risk of abdominal compartment syndrome in severely burned patients.

BACKGROUND: Secondary abdominal compartment syndrome is a lethal complication after resuscitation from burn shock. Hypertonic lactated saline (HLS) infusion reduces early fluid requirements in burn shock, but the effects of HLS on intraabdominal pressure have not been clarified. METHODS: Patients admitted to our burn unit between 2002 and 2004 with burns > or =40% of the total body surface area without severe inhalation injury were entered into a fluid resuscitation protocol using HLS (n = 14) or lactated Ringer's solution (n = 22). Urine output was monitored hourly with a goal of 0.5 to 1.0 mL/kg per hour. Hemodynamic parameters, blood gas analysis, intrabladder pressure as an indicator of intraabdominal pressure (IAP), and the peak inspiratory pressure were recorded. Pulmonary compliance and the abdominal perfusion pressure were also calculated. RESULTS: In the HLS group, the amount of intravenous fluid volume needed to maintain adequate urine output was less at 3.1 +/- 0.9 versus 5.2 +/- 1.2 mL/24 h per kg per percentage of total body surface area, and the peak IAP and peak inspiratory pressure at 24 hours after injury were significantly lower than those in the lactated Ringer's group. Two of 14 patients (14%) in the HLS group and 11 of 22 patients (50%) developed IAH within 20.8 +/- 7.2 hours after injury. CONCLUSION: In patients with severe burn injury, a large intravenous fluid volume decreases abdominal perfusion during the resuscitative period because of increased IAP. Our data suggest that HLS resuscitation could reduce the risk of secondary abdominal compartment syndrome with lower fluid load in burn shock patients.

Effects of escharotomy as abdominal decompression on cardiopulmonary function and visceral perfusion in abdominal compartment syndrome with burn patients.

BACKGROUND: Abdominal compartment syndrome (ACS) can become fatal; however, it has rarely been described as a complication of burn injury. This study clarified the physiologic results of abdominal decompression (AD) for ACS in patients with burn injury in detail. METHODS: Extensively burned patients admitted to our burn unit between January 2003 and February 2004 were prospectively monitored by pulmonary artery catheter. Physiologic parameters from the catheter, blood gas analysis, intrabladder pressure as a parameter of intra-abdominal pressure (IAP), peak inspiratory pressure, and urine output (UO) were compared before and after escharotomy as AD in patients with ACS. RESULTS: Eight of 36 patients who had sustained more than 30% total body surface area burn developed ACS requiring AD in 18.3 +/- 4.9 hours. AD significantly decreased IAP (52 +/- 9 cm H2O vs. 26 +/- 7 cm H2O), peak inspiratory pressure (53 +/- 13 cm H2O vs. 35 +/- 6 cm H2O), heart rate, and Paco2, and increased cardiac index (1.6 +/- 0.7 L/min/m2 vs. 2.5 +/- 0.9 L/min/m2), abdominal perfusion pressure (50 +/- 11 mm Hg vs. 72 +/- 17 mm Hg), UO (0.45 +/- 0.46 mL/h/kg vs. 2.0 +/- 2.1 mL/h/kg), and oxygen delivery index (290 +/- 195 mL/m2/min vs. 455 +/- 218 mL/m2/min). Impaired oxygen consumption index increased (86 +/- 43 mL/m2/min vs. 153 +/- 58 mL/m2/min) after AD. CONCLUSION: In patients with severe burn injury, elevated IAP makes pulmonary artery wedge pressure and UO unreliable indices of preload or intravascular volume, and decreases abdominal perfusion in the resuscitation period. AD in these patients significantly improves the ventilation, hemodynamic parameters, and oxygen metabolism.