Lethal Acute Lung Injury Research Articles

Loss of neutrophil Shp1 produces hemorrhagic and lethal acute lung injury.

The acute respiratory distress syndrome (ARDS) is associated with significant morbidity and mortality and neutrophils are critical to its pathogenesis. Neutrophil activation is closely regulated by inhibitory tyrosine phosphatases including Src homology region 2 domain containing phosphatase-1 (Shp1). Here, we report that loss of neutrophil Shp1 in mice produced hyperinflammation and lethal pulmonary hemorrhage in sterile inflammation and pathogen-induced models of acute lung injury (ALI) through a Syk kinase-dependent mechanism. We observed large intravascular neutrophil clusters, perivascular inflammation, and excessive neutrophil extracellular traps in neutrophil-specific Shp1 knockout mice suggesting an underlying mechanism for the observed pulmonary hemorrhage. Targeted immunomodulation through the administration of a Shp1 activator (SC43) reduced agonist-induced reactive oxygen species in vitro and ameliorated ALI-induced alveolar neutrophilia and NETs in vivo. We propose that the pharmacologic activation of Shp1 has the potential to fine-tune neutrophil hyperinflammation that is central to the pathogenesis of ARDS.

Programming of neutrophil transcriptome by endothelial ERG maintains anti-inflammatory vascular niche in the lungs

Neutrophils, the predominant blood leukocyte and first responders to the infection, reside as the marginated pool in the lungs. Vascular hyperpermeability and activation of infiltrating neutrophils is the hallmark of lethal acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, signaling nodes that govern crosstalk among these ontologically distinct cell types to maintain tissue homeostasis remain unclear. Here, we identify the ERG transcription factor, which maintains endothelial cell (EC) lineage, as the instructor of anti-inflammatory neutrophils. We show that ERG is highly expressed in lung EC, but the expression was reduced markedly during neutrophilic injury by bacterial pneumonia. Intravital imaging and FACS analysis of mice lungs conditionally lacking ERG in the endothelium (iEC-ERG−/−mice) showed increased neutrophil retention and activation due to rewiring of their transcriptome (hereafter referred to as EC-ERG null neutrophils). RNA sequencing of EC-ERG null neutrophils showed genes enriched with inflammation (IL-1β, TNF-α, MIP-2α), survival (RelB, CD47), and retention (CXCR4) markers. Neutrophils isolated from the blood of ARDS patients similarly showed increased expression of IL-8, TNF-α, and CXCR4 expression. EC-ERG null neutrophils induced lung injury when adoptively transferred into a naïve mouse. EC-ERG loss elicited an immune migratory and chemotactic program by activating the NF-κB-IL8 cascade, exacerbating ALI in a mouse model. We show that ERG in endothelium preserves neutrophil activation and infiltration by upregulating the multipurpose deubiquitinase A20 expression in mouse and human lung endothelial cells (EC). Rescuing A20 deubiquitinase or suppressing IL8-CXCR2 axis through small molecule inhibitor, Reparixin, reversed hyperpermeability, and neutrophilic injury. In summary, our study identifies specialized ERG-instructed anti-inflammatory ‘immune niche’ to prevent neutrophilic inflammation and lung injury. National Institutes of Health (NIH) Grants HL060678, HL084153. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Bronchoscopic light delivery method for peripheral lung cancer photodynamic therapy.

BackgroundTrans-bronchoscope treatment for early stage small peripheral lung cancer, such as photodynamic therapy (PDT), has been investigated. However, despite the efficacy of PDT, light delivery issues limit its application. A method of administering mineral oil with a high refractive index (RI) was previously proposed to enhance light delivery in branched or bent anatomic structures. Lipiodol has a high RI and an exhaustive history of use as a contrast medium for bronchography. We aimed to determine whether the use of lipiodol, like mineral oil, could enhance the illumination effect and therapeutic range of PDT for peripheral lung tumors.MethodsWe injected lipiodol into a pig lung model, guided by a bronchoscope under fluorescent surveillance, to simulate future treatment in humans, and then illuminated with PDT laser fiber to the lipiodol-infused lung to test the technique feasibility in a pig orally administered 20 mg/kg of 5-aminolevulinicc acid (5-ALA) 2 hours before treatment. We also attempted to determine the maximal tolerable light dose in this pilot study for the future studies in human.ResultsWe successfully injected lipiodol into peripheral lungs by this technique. The pig could tolerate up to a total of 40 mL of lipiodol and 800 J of red light, without severe acute fetal injury in a non-cancerous lung.ConclusionsThe technique of injecting lipiodol using bronchoscopy under fluorescent guidance was feasible in a pig model. We can apply the guide sheath through bronchoscopy under fluoroscope inspection. Lipiodol can be used as a light diffuser for the peripheral lung tumor PDT model. No severe lethal acute lung injury was caused by this PDT model under careful manipulation. Additional studies evaluating the dose correlation of the photosensitizer and light are needed.

Targeted Therapy of Acute Chest Syndrome with Recombinant Heme Oxygenase-1 Revealed By the Resistance of Young Transgenic Sickle Cell Mice to Heme-Induced Acute Lung Injury

Acute chest syndrome (ACS) is a major pulmonary complication of sickle cell disease (SCD) with currently no mechanistic-based therapies. Although ACS is more frequent in childhood, survival among children 1-9 years is ~10-fold higher compared to adults 20 years and older. Hitherto, mechanisms responsible for the high ACS survival in children have not been defined. We previously reported that acute elevation of circulating heme causes a TLR4-dependant lethal acute lung injury (ALI) in transgenic mice with homozygous SCD (SS) reminiscent of severe ACS (Ghosh et al., J Clin Invest, 2013). In the current study we discovered that young (4-6 weeks) and adult (12 weeks) SS mice suffer comparable severity of hemolytic crises when challenged with intravenous hemin (35 μmoles/kg bw). However, virtually none of the young mice develop ALI while nearly all the adults succumb with respiratory failure. We discovered that young SS mice rapidly clear excess heme from the circulation suggesting this was the reason for their resistance to intravenous hemin. Interestingly, young SS mice have significantly lower plasma hemopexin levels than adult SS mice, which excludes the classical heme scavenging pathway as the reason for their heme resistance. Previous studies have linked genetically high heme oxygenase-1 (HO-1) expression with low-risk of ACS, and raised steady-state levels of plasma heme with high-risk ACS in children. To explore these associations further, we studied a large cohort of patients and discovered for the first time that the concentration of plasma HO-1 in SCD children 1-9 yrs is 2-fold higher than adults 20 yrs and older (23.6±1.1, n=191 versus mean 10.7±0.6, n=67); these findings were phenocopied in transgenic SS mice. Plasma fractionization experiments revealed that HO-1 co-localizes with the enzymatic and co-factor machinery required for heme degradation indicating that heme can be degraded in the blood circulation. To test this idea ~3 weeks old SS mice were treated with the HO-1 inhibitor tin protoporphyrin (SnPP) or vehicle, and challenged with intravenous hemin five days later to induce ALI/ACS. Plasma HO activity declined by ~76% in SnPP-treated mice and was unchanged in the vehicle treated animals (n=12-14, p<0.001). A significant majority (10/12; 83%) of the vehicle-treated mice survived, while a majority of the SnPP-treated mice (10/14; 71%) developed lethal ALI/ACS. In another series of experiments young SS mice were treated for three months with Nrf2 activator to block age-dependent HO-1 decline, and then treated with vehicle or SnPP prior to ALI/ACS induction. The SnPP-treated group had 58% reduction in plasma HO-1 (p<0.05), failed to clear heme and developed lethal ALI/ACS, while a majority (63%) of the vehicle treated SS mice with persistently raised HO-1 activity in adulthood survived. Finally, adult SS mice were treated acutely with novel truncated human HO-1 recombinant proteins or a carrier vehicle immediately prior to induction of ALI/ACS. Recombinant variant 4 (V4) possessing an Fc component that enhances protein half-life provided 100% protection while 70% of vehicle treated mice succumbed with ALI/ACS (Mantel-Cox log-rank p<0.001). While the arterial oxygen saturation level (% SpO2) in vehicle treated SS mice declined sharply reflecting severe respiratory distress, V4-treated mice maintained normal SpO2 (p<0.001). In conclusion, we have determined that HO-1 activity in blood plasma declines with aging in SCD patients and identify this phenomenon as the basis of poor survival among adult SS mice with induced ALI/ACS. Furthermore, we provide proof-of-principle in mice that a novel human recombinant HO-1 protein can attenuate lung injury and improve survival from ALI/ACS in SCD. Disclosures Ofori-Acquah: Shire Human Genetic Therapies Inc: Other: Financial Relationship.

Boosting efferocytosis in alveolar space using BCG vaccine to protect host against influenza pneumonia.

Efferocytosis by alveolar phagocytes (APs) is pivotal in maintenance of lung homeostasis. Increased efferocytosis by APs results in protection against lethal acute lung injury due to pulmonary infections whereas defective efferocytosis by APs results in chronic lung inflammation. In this report, we show that pulmonary delivery of Bacillus Calmette-Guerin (BCG) significantly enhances efferocytosis by APs. Increased efferocytosis by APs maintains lung homeostasis and protects mice against lethal influenza pneumonia. Intranasally treated wild type C57Bl/6 (WT) mice with BCG showed significant increase in APs efferocytosis in vivo compared to their PBS-treated counterparts. All BCG-treated WT mice survived lethal influenza A virus (IAV) infection whereas all PBS-treated mice succumbed. BCG-induced resistance was abrogated by depleting AP prior to IAV infection. BCG treatment increased uptake, and digestion/removal of apoptotic cells by APs. BCG significantly increased the expression of TIM4 on APs and increased expression of Rab5 and Rab7. We demonstrated that increased efferocytosis by APs through pulmonary delivery of BCG initiated rapid clearance of apoptotic cells from the alveolar space, maintained lung homeostasis, reduced inflammation and protected host against lethal IAV pneumonia.

A Novel Role for P-Selectin in the Pathogenesis of Acute Chest Syndrome

Acute chest syndrome (ACS) is a potentially fatal lung complication of sickle cell disease (SCD). There are currently no mechanistic based therapies for ACS and it continues to be a leading cause of death in SCD. Recent studies have identified independent links between extracellular heme with ACS, and with vaso-occlusive crisis (VOC) a common prodrome of ACS. Our experimental ACS model involves intravenous injection of purified hemin typically 35 µmoles/kg, which raises total plasma heme to a clinically relevant pathophysiologic level equivalent to ~0.5g/dl of hemoglobin, and causes respiratory failure exclusively in transgenic SCD mice of both the Townes and Berkeley strains (Ghosh et al., J Clin Invest, 2013). We have determined using time-lapse video microscopy and electrical cell impedance that hemin rapidly disrupts the pulmonary endothelial barrier in vitro. Hemopexin blocks hemin-induced pulmonary endothelial barrier disruption in vitro and respiratory failure in hemin-challenged SS mice. Importantly, genetic polymorphisms in the gene encoding heme oxygenase-1 the rate-limiting heme degradation enzyme are associated with ACS risk in the Cooperative Study of Sickle Cell Disease and the Silent Infarct Transfusion cohorts. These human data and our mechanistic results in SS mice support the heme hypothesis for ACS pathogenesis. P-selectin is a cell adhesion molecule involved in vascular inflammation. It is normally sequestered inside quiescent endothelium. However, recent evidence indicates extracellular heme activates the release of P-selectin unto the endothelial surface wall. Thus, in this study, we tested the hypothesis that P-selectin promotes ACS development. Infusion of a function blocking anti-P-selectin antibody protected SS mice (n=3) from hemin-induced ACS while all control SS mice (n=3) pretreated with IgG before the hemin challenge died (p=0.03) with severe hypoxemia and postmortem evidence of alveolar flooding. The apparent requirement for P-selectin in heme-induced lethal acute lung injury was confirmed by a 100% survival of P-selectin-/- (n=5) and 100% lethality of congenic P-selectin+/+ (n=5) mice challenged with hemin infusions (p=0.005). To identify the cell population involved in this disease process we generated bone marrow chimeric C57BL/6 mice lacking P-selectin in hematopoietic (P-selectinPLT-/-) and non-hematopoietic (P-selectinEC-/-) compartments. Seventy-five percent of P-selectinEC-/- mice were protected while all P-selectinPLT-/- congenic controls succumbed to hemin (n=3-4). The severity of lung injury in the P-selectinPLT-/- C57BL/6 mice was reflected by severe hypoxemia (SpO2: 82.75±2.14%) and a significantly higher lung wet/dry weight ratio compared to the ratio of the P-selectinEC-/- mouse lungs (p<0.05). Next, we transplanted congenic P-selectin-/- and P-selectin+/+ mice with SS mouse bone marrow to generate chimeric SS mice lacking endothelial P-selectin or expressing endothelial P-selectin respectively. Induction of ACS resulted in 40% lethality in the SS/P-selectinEC-/- mice (n=7) and 100% lethality in SS/P-selectinEC+/+ mice (n=7; p<0.01). The development of respiratory failure in the hemin modelinvolves de novo heme release from acute intravascular hemolysis. In this study, we found that SS/P-selectinEC-/- mice cleared ~70% of the hemin bolus within 30 min, which attenuated intravascular hemolysis and damped de novo heme release, while total plasma heme increased over 2-fold in the SS/P-selectinEC+/+ mice during the same time interval. Together these results demonstrate a critical intermediary role for P-selectin in the ACS triggered by acute intravascular hemolysis and elevated extracellular heme. In addition, we provide proof-of-principle in mice that antagonists of P-selectin can prevent and potentially treat ACS. DisclosuresNo relevant conflicts of interest to declare.

Leukotriene B4 receptor type 2 protects against pneumolysin-dependent acute lung injury

Although pneumococcal infection is a serious problem worldwide and has a high mortality rate, the molecular mechanisms underlying the lethality caused by pneumococcus remain elusive. Here, we show that BLT2, a G protein-coupled receptor for leukotriene B4 and 12(S)-hydroxyheptadecatrienoic acid (12-HHT), protects mice from lung injury caused by a pneumococcal toxin, pneumolysin (PLY). Intratracheal injection of PLY caused lethal acute lung injury (ALI) in BLT2-deficient mice, with evident vascular leakage and bronchoconstriction. Large amounts of cysteinyl leukotrienes (cysLTs), classically known as a slow reactive substance of anaphylaxis, were detected in PLY-treated lungs. PLY-dependent vascular leakage, bronchoconstriction, and death were markedly ameliorated by treatment with a CysLT1 receptor antagonist. Upon stimulation by PLY, mast cells produced cysLTs that activated CysLT1 expressed in vascular endothelial cells and bronchial smooth muscle cells, leading to lethal vascular leakage and bronchoconstriction. Treatment of mice with aspirin or loxoprofen inhibited the production of 12-HHT and increased the sensitivity toward PLY, which was also ameliorated by the CysLT1 antagonist. Thus, the present study identifies the molecular mechanism underlying PLY-dependent ALI and suggests the possible use of CysLT1 antagonists as a therapeutic tool to protect against ALI caused by pneumococcal infection.

BLT2 receptor protects against lethal acute lung injury induced by a pneumococcal toxin pneumolysin

Pneumonia is one of the major causes of death over the world, and the capital cause of infectious pneumonia is S. pneumoniae (pneumococcus). The key virulence factor of pneumococcus is a pore‐forming toxin pneumolysin (PLY). By its direct cytotoxic effect, PLY is known to cause acute lung injury, leading to pneumococcal invasion and subsequent severe bacteremia. Leukotriene B4 (LTB4) receptor type 2 (BLT2) is a G‐protein coupled receptor that was originally identified as a low‐affinity receptor for LTB4, and recently we elucidated that the high affinity endogenous ligand for BLT2 is 12‐hydroxyheptadecatrienoic acid (12‐HHT), an arachidonic acid metabolite by cyclooxygenase. Previously we reported that BLT2 is expressed in intestinal epithelial cells and skin keratinocytes, and that 12‐HHT/BLT2 signaling exhibits important roles in maintaining mucosal integrity and in accelerating skin wound healing. However, the biological roles of BLT2 in other organs are still uncertified. In this study, we investigated the protective role of BLT2 in mouse lung using PLY‐induced acute lung injury model. Interestingly, BLT2‐deficient mice were more susceptible to PLY administration, and also exhibited increased vascular permeability and potent bronchoconstriction by PLY administration when compared to wild‐type mice. We found BLT2 in mouse lung is expressed in alveolar type II cells and vascular endothelial cells. The molecular mechanisms of how BLT2 exhibits the protective role for PLY‐induced acute lung injury are now under investigation.Support or Funding InformationThis work was supported by Grants‐in‐Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT) Nos. 22116001, 22116002, 15H05901, 15H05904, and 15H04708.

Targeted Treatment Of Acute Chest Syndrome In Transgenic Sickle Mice

Acute chest syndrome (ACS) is a major cause of morbidity and mortality in sickle cell disease (SCD). The diagnosis, prevention and treatment of ACS pose major clinical concerns in SCD partly because the mechanism underlying the pathogenesis of this syndrome remains elusive. Our group first reported that excess intravascular hemin causes a lethal acute lung injury (ALI) in transgenic SCD mice reminiscent of ACS (Ghosh and Ofori-Acquah, Blood 116 Suppl 1:944, 2010). Subsequently, large-scale genomics studies by Bean et al., (Blood 120:3822-8, 2012) and Galarneau et al., (Blood, 122:434-42, 2013) have implicated hemin catabolism and inflammation in the pathogenesis of ACS. In addition, we have reported recently that raised plasma free hemin increases the odds of ACS in children with SCD (Adisa et al., Br J Haematol. 2013). Collectively, these studies support a new theme of ACS pathogenesis involving extracellular hemin. In the current study, we validated the respiratory dysfunction of this ACS model, tested the hypothesis that toll-like receptor 4 (TLR4) mediates the associated lung injury, and examined the efficacy of two strategies to treat the condition in mice. Arterial blood gas analysis of SS mice with the ACS-like disease confirmed severe hypoxemia (PaO2; 40.23 ±3.85 mmHg, SO2; 58.72±6.6%, p<0.001), and revealed worsening hypercapnia (PaCO2; 56.08±3.64 mmHg) and acidosis (mean pH; 7.21), which are all typical of severe ALI. Blood gas parameters remained normal in control AA mice exposed to the same concentration of extracellular hemin. Next, we generated two types of sickle bone marrow chimeric mice that lack expression of TLR4 in non-hematopoietic cells (SSNHTLR4-/-) or express TLR4 on all cell types (SSTLR4+/+). Induction of extracellular hemin crisis with 70 micromoles/kg of hemin resulted in rapid oxygen desaturation, reduced breath rate, pulmonary infiltration, high lung wet/dry weight ratio and sudden death in the SSTLR4+/+ chimeras (n=6). Although all the SSNHTLR4-/- mice acquired a similar phenotype of hemin crisis as the SSTLR4+/+ mice, defined by acute intravascular hemolysis (∼1g/dl drop in Hb, ∼1g/dl increase in cell-free Hb), exhaustion of plasma hemopexin, ∼3-fold increase in plasma free hemin, they did not develop any respiratory symptoms (n=7). Next, we tested two potential therapies, recombinant human hemopexin and TAK-242 a small molecule inhibitor of TLR4. Both agents protected SS mice from developing ACS when they were administered immediately after the induction of hemin crisis. When SS mice were treated after developing respiratory distress evident by significant reductions in oxygen saturation and breath rate, only the recombinant human hemopexin was effective in preventing respiratory failure. In conclusion, we show that TLR4 expressed by the vessel wall, most likely the endothelium, mediates the inflammatory response to excess free hemin associated with severe ACS in mice. Pharmacological inhibition of TLR4 signaling and hemin sequestration may be effective in preventing the development of ACS. In addition, hemin sequestration offers a targeted approach that may halt the progression of ACS in those with more advanced disease. Disclosures:No relevant conflicts of interest to declare.

A Staphylococcus aureus pore-forming toxin subverts the activity of ADAM10 to cause lethal infection in mice

Staphylococcus aureus is a major cause of human disease, responsible for half a million infections and approximately 20,000 deaths per year in the United States alone 1,2. This pathogen secretes α-hemolysin, a pore-forming cytotoxin that contributes to the pathogenesis of pneumonia 3–5. α-hemolysin injures epithelial cells by interacting with its receptor, the zinc-dependent metalloprotease ADAM10 6. We show that mice harboring a conditional disruption of the Adam10 gene in lung epithelium are resistant to lethal pneumonia. Investigation of the molecular mechanism of toxin-receptor function revealed that α-hemolysin upregulates ADAM10 metalloprotease activity in alveolar epithelial cells, resulting in cleavage of the adherens junction protein E-cadherin. Cleavage is associated with disruption of epithelial barrier function, contributing to the pathogenesis of lethal acute lung injury. A metalloprotease inhibitor of ADAM10 prevents E-cadherin cleavage; similarly, E-cadherin proteolysis and barrier disruption is attenuated in ADAM10 knockout mice. Together, these data attest to the function of ADAM10 as the cellular receptor for α-hemolysin. The observation that Hla can usurp the metalloprotease activity of its receptor reveals a novel mechanism of pore-forming cytotoxin action in which pathologic insults are not solely the result of irreversible membrane injury, and defines ADAM10 inhibition as a strategy for disease modification.

IN VIVO IL-18 SUPPLEMENTATION AMELIORATES LETHAL ACUTE LUNG INJURY IN BURN-PRIMED ENDOTOXEMIC MICE

Previously, we have found that a prior burn insult induces lethal acute lung injury (ALI) and overproduction of proinflammatory cytokines after LPS challenge in mice. The current study was aimed to determine the role of IL-18 in burn-induced LPS hypersensitivity. Except sham group, mice were subjected to a 15% total body surface area full-thickness burn and either untreated or treated with IL-18 alone, IL-18 + anti-IL-10 antibody or IL-18 + isotype immunoglobulin G. LPS was intravenously administered to all mice on the 11th day, and the mice were killed at the indicated time point, or survival was examined. We additionally examined cytokine production by splenic cells in vitro for the elucidation of immunologic mechanisms. Unexpectedly, the liver IL-18 decreased transiently after burn injury, and in vivo IL-18 supplementation improved survival and ameliorated ALI, as well as reducing the lung contents of all cytokines examined, except IL-10. Neutralization of IL-10 cancelled the protective effect of IL-18. In splenic macrophages obtained from burned mice, the production of macrophage inflammatory protein 2 (MIP-2), TNF-alpha, and IL-10 was augmented, whereas in vivo IL-18 supplementation decreased MIP-2 production, but increased IL-10 production. Furthermore, a physiological concentration of IL-18 directly attenuated MIP-2 production by splenic cells in vitro. Burn injury induces LPS hypersensitivity through augmented production of proinflammatory cytokines by systemic macrophages. IL-18 supplementation is protective for LPS-induced lethal ALI through the direct anti-inflammatory effect on macrophages as well as by in vivo acceleration of IL-10 production, and could thus be an effective prophylactic strategy against septic complications in critically ill patients.

Lethal acute lung injury and hypoglycemia after subcutaneous administration of monochloroacetic acid

Hypoglycemia is suspected in the acute lethal toxicity induced by cutaneous exposure to monochloroacetic acid (MCA). Although it has been shown that hepato-renal dysfunction is involved, the mechanism and the target organs that directly affect mortality remain to be determined. We suspected respiratory failure as a main cause of death in some reported cases. We investigated dose-response effects, hypoglycemia, and lung injury in rats exposed to MCA. Serum glucose, blood gases, and parameters of alveolar injury in bronchoalveolar lavage fluid (BALF) were analysed 2 and 4 h after subcutaneous administration of MCA (108, 135 or 163 mg/kg). Apparent pulmonary injury and hypoglycemia were not identified 2 h after administration, but lactate dehydrogenase (LDH) and total cells in BALF were dose-dependently increased; and severe hypoglycemia was identified 4 h after administration. Blood gas analysis showed remarkable alveolar gas dysfunction as exchange in the 163 mg/kg group. Thus, hypoglycemia and lung injury appear to cause death in response to MCA exposure.

Prior burn insult induces lethal acute lung injury in endotoxemic mice: effects of cytokine inhibition.

Many patients who experience surgical stress, including burn injury, become susceptible to severe sepsis and septic organ dysfunction, which remains the primary contributor to morbidity and mortality in burn patients. In the present study, we developed a murine model of burn-primed sublethal endotoxemia by producing a 15% BSA full-thickness burn on the dorsum of BALB/c mice under ether anesthesia and administering 10 mg/kg of LPS intravenously on day 11 to model endotoxemia. The prior burn injury in this model induced two-peaked production of cytokines, TNF-alpha, and macrophage inflammatory protein-2 at 2 and 12 h after LPS administration, and it was associated with increased mortality. We also assessed the effect of pharmacological modulation with cytokine synthesis inhibitors prednisolone and JTE-607 and found that pretreatment with them attenuated later cytokine production and decreased mortality after LPS administration. We speculate that the prior burn injury primed the mice for the secondary insult via cytokine production. These results also suggested that an anticytokine strategy might serve as a novel prophylactic therapy for septic organ dysfunction in burn-primed patients.