Alveolar macrophage phagocytosis is enhanced after blunt chest trauma and alters the posttraumatic mediator release

Blunt chest trauma is known to induce a pulmonary invasion of short-lived polymorphonuclear neutrophils and apoptosis of alveolar epithelial type 2 (AT2) cells. Apoptotic cells are removed by alveolar macrophages (AMΦ). We hypothesized that chest trauma alters the phagocytic response of AMΦ as well as the mediator release of AMΦ during phagocytosis. To study this, male Sprague-Dawley rats were subjected to blunt chest trauma. Phagocytosis assays were performed in AMΦ isolated 2 or 24 h after trauma with apoptotic cells or opsonized beads. Phagocytosis of apoptotic AT2 cells by unstimulated AMΦ was significantly increased 2 h after trauma. At 24 h, AMΦ from traumatized animals, stimulated with phorbol-12-myristate-13-acetate, ingested significantly more apoptotic polymorphonuclear neutrophils than AMΦ from sham animals. Alveolar macrophages after trauma released significantly higher levels of tumor necrosis factor α, macrophage inflammatory protein 1α, and cytokine-induced neutrophil chemoattractant 1 when they incorporated latex beads, but significantly lower levels of interleukin 1β and macrophage inflammatory protein 1α when they ingested apoptotic cells. In vivo, phagocytosis of intratracheally instilled latex beads was decreased in traumatized rats. The bronchoalveolar lavage concentrations of the phagocytosis-supporting surfactant proteins A and D after blunt chest trauma were slightly decreased, whereas surfactant protein D mRNA expression in AT2 cells was significantly increased after 2 h. These findings indicate that chest trauma augments the phagocytosis of apoptotic cells by AMΦ. Phagocytosis of opsonized beads enhances and ingestion of apoptotic cells downregulates the immunologic response following lung contusion. Our data emphasize the important role of phagocytosis during posttraumatic inflammation after lung contusion.     

Pulmonary contusion induces alveolar type 2 epithelial cell apoptosis: role of alveolar macrophages and neutrophils

Alveolar type 2 (AT-2) cell apoptosis is an important mechanism during lung inflammation, lung injury, and regeneration. Blunt chest trauma has been shown to activate inflammatory cells such as alveolar macrophages (AMs) or neutrophils (polymorphonuclear granulocytes [PMNs]), resulting in an inflammatory response. The present study was performed to determine the capacity of different components/cells of the alveolar compartment (AMs, PMNs, or bronchoalveolar lavage [BAL] fluids) to induce apoptosis in AT-2 cells following blunt chest trauma. To study this, male Sprague-Dawley rats were subjected to either sham procedure or blunt chest trauma induced by a single blast wave. Various time points after injury (6 h to 7 d), the lungs were analyzed by immunohistochemistry, for AT-2 cells, or with antibodies directed against caspase 3, caspase 8, Fas, Fas ligand (FasL), BAX, and BCL-2. Bronchoalveolar lavage concentrations of TNF-alpha, IL-1beta, and soluble FasL were determined by enzyme-linked immunosorbent assay. Furthermore, cultures of AT-2 cells isolated from healthy rats were incubated with supernatants of AMs, PMNs, or BAL fluids obtained from either trauma or sham-operated animals in the presence or absence of oxidative stress. Annexin V staining or TUNEL (terminal deoxynucleotidyl transferase) assay was used to detect apoptotic AT-2 cells. Histological evaluation revealed that the total number of AT-2 cells was significantly reduced at 48 h following trauma. Fas, FasL, active caspase 8, and active caspase 3 were markedly up-regulated in AT-2 cells after chest trauma. BAX and BCL-2 did not show any significant changes between sham and trauma. IL-1beta, but not TNF-alpha, levels were markedly increased at 24 h after the injury, and soluble FasL concentrations were significantly enhanced at 6, 12, 24, and 48 h after the insult. Apoptosis of AT-2 cells incubated with supernatants from cultured AMs, isolated at 48 h following chest trauma was markedly increased when compared with shams. In contrast, no apoptosis was induced in AT-2 cells incubated with supernatants of activated PMNs or BAL fluids of traumatized animals. In summary, blunt chest trauma induced apoptosis in AT-2 cells, possibly involving the extrinsic death receptor pathway. Furthermore, mediators released by AMs appeared to be involved in the induction of AT-2 cell apoptosis.     

Innate immune response to pulmonary contusion: identification of cell type-specific inflammatory responses

Lung injury from pulmonary contusion is a common traumatic injury, predominantly seen after blunt chest trauma, such as in vehicular accidents. The local and systemic inflammatory response to injury includes activation of innate immune receptors, elaboration of a variety of inflammatory mediators, and recruitment of inflammatory cells to the injured lung. Using a mouse model of pulmonary contusion, we had previously shown that innate immune Toll-like receptors 2 and 4 (TLR2 and TLR4) mediate the inflammatory response to lung injury. In this study, we used chimeric mice generated by adoptive bone marrow transfer between TLR2 or TLR4 and wild-type mice. We found that, in the lung, both bone marrow-derived and nonmyeloid cells contribute to TLR-dependent inflammatory responses after injury in a cell type-specific manner. We also show a novel TLR2-dependent injury mechanism that is associated with enhanced airway epithelial cell apoptosis and increased pulmonary FasL and Fas expression in the lungs from injured mice. Thus, in addition to cardiopulmonary physiological dysfunction, cell type-specific TLR and their differential response to injury may provide novel specific targets for management of patients with pulmonary contusion.     

Inhaled hydrogen sulfide induces suspended animation, but does not alter the inflammatory response after blunt chest trauma

The treatment of acute lung injury and septic complications after blunt chest trauma remains a challenge. Inhaled hydrogen sulfide (H?S) may cause a hibernation-like metabolic state, which refers to an attenuated systemic inflammatory response. Therefore, we tested the hypothesis that inhaled H?S-induced suspended animation may attenuate the inflammation after pulmonary contusion. Male Sprague-Dawley rats were subjected to blunt chest trauma (blast wave) or sham procedure and subsequently exposed to a continuous flow of H?S (100 ppm) or control gas for 6 h. Body temperature and activity were measured by an implanted transmitter. At 6, 24, or 48 h after trauma, animals were killed, and the cellular contents of bronchoalveolar lavage (BAL) as well as cytokine concentrations in BAL, plasma, and culture supernatants of blood mononuclear cells, Kupffer cells, splenic macrophages, and splenocytes were determined. Hydrogen sulfide inhalation caused a significant reduction in body temperature and activity. The trauma-induced increase in alveolar macrophage counts was abrogated 48 h after trauma when animals received H?S, whereas the trauma-induced increase in neutrophil counts was unaltered. Furthermore, H?S inhalation partially attenuated the mediator release in BAL and culture supernatants of Kupffer cells as well as splenic cells; it altered plasma cytokine concentrations but did not affect the trauma-induced changes in mononuclear cell culture supernatants. These findings indicate that inhaled H?S induced a reduced metabolic expenditure and partially attenuated inflammation after trauma. Nevertheless, in contrast to hypoxic- or pathogen-induced lung injury, H?S treatment appears to have no protective effect after blunt chest trauma.     

Blunt chest trauma induces delayed splenic immunosuppression

Severe blunt chest trauma is frequently associated with multiple organ failure and sepsis. Posttraumatic immunosuppression seems to play a major role in their development. However, the immunologic alterations following pulmonary contusion are insufficiently elucidated. Specifically, it remains unknown whether immunocompetent cells located distant from the site of the impact are affected. We therefore aimed to characterize the influence of pulmonary contusion on lymphocytes and splenic macrophages. Male C3H/HeN mice (n = 8-10/group) were anesthetized and subjected to trauma or sham procedure. Blunt chest trauma was induced by a blast wave focused on the thorax. Two or 24 h later, splenocytes and splenic macrophages were isolated and stimulated for 48 h. The cytokine release (IFN-gamma, IL-2, IL-3, IL-10, IL-12, IL-18) from splenocytes as well as from splenic macrophages (TNF-alpha, IL-10, IL-12, IL-18) and plasma levels of TNF-alpha and IL-6 were quantified by ELISA. The results indicate that at 2 h after blunt chest trauma, plasma TNF-alpha and IL-6 were markedly increased. At the same time, no differences in splenocyte cytokine production were detectable. However, at 24 h a significantly depressed cytokine release was observed in trauma animals. Furthermore, splenic macrophages showed a significantly decreased production of TNF-alpha, IL-10, and IL-12 at 24 h and markedly increased release of IL-18 at 2 h after trauma. These results indicate that blunt chest trauma causes severe immunodysfunction of lymphocytes and splenic macrophages. Thus, lung contusion as a localized type of trauma causes dysfunction of immunocompetent cell populations, which are located distant from the site of injury.     

Toll-like receptor 4-dependent responses to lung injury in a murine model of pulmonary contusion

Blunt chest trauma resulting in pulmonary contusion with an accompanying acute inflammatory response is a common but poorly understood injury. We previously demonstrated that toll-like receptor 2 (TLR-2) participates in the inflammatory response to lung injury. We hypothesized that the TLR-4, in an MyD88-dependent manner, may also participate in the response to lung injury. To investigate this, we used a model of pulmonary contusion in the mouse that is similar to that observed clinically in humans and evaluated postinjury lung function, pulmonary neutrophil recruitment, and the systemic innate immune response. Comparisons were made between wild-type mice and mice deficient in TLR-4 or MyD88. We found TLR-4-dependent responses to pulmonary contusion that include hypoxemia, edema, and neutrophil infiltration. Increased expression of IL-6 and chemokine (C-X-C motif) ligand 1 in the bronchoalveolar lavage and serum was also dependent on TLR-4 activation. We further demonstrated that these responses to pulmonary contusion were dependent on MyD88, an adapter protein in the signal transduction pathway mediated by TLRs. These results show that TLRs have a primary role in the response to acute lung injury. Lung inflammation and systemic innate immune responses are dependent on TLR activation by pulmonary contusion.     

Divergent effects of activated neutrophils on inflammation, Kupffer cell/splenocyte activation, and lung injury following blunt chest trauma

Polymorphonuclear granulocytes (PMNs) have been attributed a primarily deleterious role in the pathogenesis of acute lung injury (ALI). However, evidence exists that PMNs might also act beneficially in certain types of ALI. In this regard, we investigated the role of activated neutrophils in the pathophysiology of lung contusion-induced ALI. We used the model of blunt chest trauma accompanied by PMN-depletion in male C3H/HeN mice. Animals received 25 μg/g body weight PMN-depleting antibody Gr-1 intravenously 48 h before trauma. Bronchoalveolar lavage (BAL) and lung tissue interleukin 6 (IL-6) were similarly elevated in PMN-depleted and control animals after trauma, whereas macrophage inflammatory protein 2 and monocyte chemoattractant protein 1 in BAL and lungs, IL-10 in BAL, and lung keratinocyte chemoattractant (KC) were even further increased in the absence of PMNs. Plasma IL-6 and KC were also increased in response to the insult and even further in the absence of PMNs. Chest trauma induced an enhanced release of IL-6, tumor necrosis factor α, macrophage inflammatory protein 2, monocyte chemoattractant protein 1, and IL-10 from isolated KU, which was blunted in the absence of PMNs. In the presence of PMNs, BAL protein was further increased at 30 h when compared with the 3-h time point, which was not the case in the absence of PMNs. Taken together, in response to lung trauma, activated neutrophils control inflammation including mediator release from distant immune cells but simultaneously mediate pulmonary tissue damage. Thus, keeping in mind potential inflammatory adverse effects, modulation of neutrophil activation or trafficking might be a reasonable therapeutic approach in chest trauma-induced lung injury.     

Toll-like receptor 2 participates in the response to lung injury in a murine model of pulmonary contusion

Blunt chest trauma resulting in pulmonary contusion with an accompanying acute inflammatory response is a common but poorly understood injury. We report that Toll-like receptor (TLR) 2 participates in the inflammatory response to lung injury. To show this, we use a model of pulmonary contusion in the mouse that is similar to that observed clinically in humans based on histologic, morphologic, and biochemical criteria of acute lung injury. The inflammatory response to pulmonary contusion in our mouse model is characterized by pulmonary edema, neutrophil transepithelial migration, and increased expression of the innate immunity proinflammatory cytokines IL 1beta and IL 6, the adhesion intracellular adhesion molecule 1, and chemokine (CXC motif) ligand 1. Compared with wild-type animals, contused Tlr2(-/-) mice have significantly reduced pulmonary edema and neutrophilia. These findings are associated with decreased levels of circulating chemokine (CXC motif) ligand 1. In contrast, systemic IL 6 levels remain elevated in the TLR2-deficient phenotype. These results show that TLR2 has a primary role in the neutrophil response to acute lung injury. We suggest that an unidentified noninfectious ligand generated by pulmonary contusion acts via TLR2 to generate inflammatory responses.     

Membrane Fas Ligand Kills Human Peripheral Blood T Lymphocytes, and Soluble Fas Ligand Blocks the Killing

It has been believed that the Fas expressed on human peripheral blood T cells (PBT) is nonfunctional, because these cells are insensitive to agonistic anti-Fas/Apo-1 mAbs that efficiently kill in vitro–activated T cells and many Fas-expressing cell lines. Here, we demonstrate that membrane-bound Fas ligand (FasL) kills both fresh and in vitro–activated PBT, indicating that the Fas expressed on fresh PBT is functional. In contrast, soluble FasL kills only the latter. Naive T cells in umbilical cord blood do not express Fas, but can be induced to express Fas by IFN-γ or by a combination of IL-2 and anti-CD28 mAb, after which they acquire sensitivity to membrane but not to soluble FasL. Soluble FasL inhibited the killing of fresh PBT by membrane FasL. These results indicate that the shedding of FasL from the membrane is a mechanism for downregulating at least part of its killing activity.     

干扰素α对慢性髓系白血病来源的树突状细胞表达Fas／FasL的影响

本研究探讨干扰素α对慢性髓系白血病（CML）来源的树突状细胞（DC）表达Fas／FasL的影响。在CML—DCs的培养液中除加入SCF，GM—CSF，TNF—α及IL-4外，还加入IFN—α。培养10-14天，除了鉴定细胞免疫表型和Ph^1染色体比例外，还应用流式细胞仪检测细胞表达Fas／FasL比例，用PI染色分析细胞凋亡，ELISA法检测上清液sFas含量。结果表明：加入IFN-α后，CML—DC共刺激分子的表达显著改善，Ph^1（＋）细胞比例随IFN—α浓度增加而减低；培养细胞Fas的表达上调，sFas含量却下降，FasL表达阴性，细胞凋亡比例增加。结论：IFN—α在改善CML-DC表型同时，可通过Fas途径促进Ph^1（＋）细胞凋亡，使Ph^1（-）细胞数量相对增加。     

IFN-γ and Fas/FasL are required for the antitumor and antiangiogenic effects of IL-12/pulse IL-2 therapy

Systemic administration of IL-12 and intermittent doses of IL-2 induce complete regression of metastatic murine renal carcinoma. Here, we show that overt tumor regression induced by IL-12/pulse IL-2 is preceded by recruitment of CD8(+) T cells, vascular injury, disrupted tumor neovascularization, and apoptosis of both endothelial and tumor cells. The IL-12/IL-2 combination synergistically enhances cell surface FasL expression on CD8(+) T lymphocytes in vitro and induces Fas and FasL expression within tumors via an IFN-gamma-dependent mechanism in vivo. This therapy also inhibits tumor neovascularization and induces tumor regression by mechanisms that depend critically on endogenous IFN-gamma production and an intact Fas/FasL pathway. The ability of IL-12/pulse IL-2 to induce rapid destruction of tumor-associated endothelial cells and regression of established metastatic tumors is ablated in mice with a dysregulated Fas/FasL pathway. The common, critical role for endogenous IFN-gamma and the Fas/FasL pathway in early antiangiogenic effects and in antitumor responses suggests that early, cytokine-driven innate immune mechanisms and CD8(+) T cell-mediated responses are interdependent. Definition of critical early molecular events engaged by IL-12/IL-2 may provide new perspective into optimal therapeutic engagement of a productive host-antitumor immune response.     

缺氧缺血肺损伤新生鼠肺组织细胞凋亡及Fas／FasL mRNA的表达和意义

目的：探讨细胞凋亡与缺氧缺血肺损伤发生、发展的关系以及Fas／FasL系统表达的意义。方法：通过复制缺氧、缺氧后吸入纯氧大鼠肺损伤模型,采用TUNEL法、原位杂交检测、SqRT-PCR技术观察肺组织细胞凋亡情况、FasmRNA、FasLmRNA表达强度。结果：缺氧组或缺氧吸入纯氧组在缺氧4h后即可见大鼠肺泡上皮细胞和肺血管内皮细胞出现凋亡现象,并随着时间延长,细胞凋亡指数增高(P=0．003,P=0．005),同时FasmRNA、FasLmRNA表达上调,且缺氧后吸入纯氧组大鼠FasmRNA、FasLmRNA表达较单纯缺氧组明显增强(P<0．05)。结论：细胞凋亡与FasmRNA、FasLmRNA表达的上调可能参与缺氧和缺氧后吸入纯氧时导致的肺损伤。     

黄芪皂苷钠治疗后烫伤鼠肺组织细胞凋亡及Fas／FasL的表达

目的探讨黄芪皂苷治疗后烫伤鼠肺组织细胞凋亡及基因调控变化机制,为进一步阐明烫伤鼠肺组织细胞凋亡机制和在细胞凋亡水平防治烧伤后脏器损伤提供理论依据.方法采用Tunel法及免疫组化技术观察黄芪皂苷治疗后烫伤鼠肺组织细胞凋亡,同时测定肺组织Fas/FasL的表达的变化.结果鼠烫伤后肺组织细胞凋亡明显增加,表现为肺泡上皮细胞和肺血管内皮细胞凋亡增加(P＜0.05);Fas抗原、FasL在烫伤鼠肺组织表达明显上调(P＜0.01),Fas抗原、FasL表达的增加与肺组织细胞凋亡增加呈平行关系;用黄芪皂苷治疗后凋亡明显减少,Fas抗原、FasL表达减弱.结论黄芪皂苷治疗后可在一定程度上防治烫伤鼠肺泡上皮和肺血管内皮细胞凋亡,其机理可能与Fas/FasL系统参与有关.     

Opposing effects of transmembrane and soluble Fas ligand expression on inflammation and tumor cell survival

Fas ligand (FasL) has been shown to mediate both apoptotic and inflammatory reactions. To rigorously assess the physiological role of different forms of the FasL molecule with regard to these two distinct processes, we isolated stably transfected lymphoma cell lines that expressed either murine wild-type FasL, membrane-only FasL, or functionally distinct forms of soluble FasL. First, the ability of these lines to induce an inflammatory response was assessed in vivo by injecting the transfectants intraperitoneally and measuring subsequent neutrophil extravasation into the peritoneal cavity. Second, lines were assessed by injecting the transfectants subcutaneously and monitoring their growth as solid tumors. Our study clearly demonstrated that the extent of inflammation induced by the transfectants directly correlated with their relative cytotoxic activities. A neutrophil response could only be elicited in mice with intact Fas death domains although Fas expression by the neutrophils was not essential. Lymphoma cells expressing the soluble FasL form corresponding to the natural cleavage product could not trigger apoptosis and did not induce a neutrophil response. In contrast to the other FasL transfectants, these cells survived as tumor transplants. However, expression of soluble FasL was not benign, but actually suppressed the inflammatory response and protected other transfectants from the effector mechanisms elicted by membrane-bound FasL.     

中性粒细胞凋亡调控基因表达异常在全身炎症反应综合征中的作用

目的观察全身炎症反应综合征（SIRS）时中性粒细胞（PMN）凋亡的异常变化及其凋亡调控基因的表达情况，评价其临床意义。方法8例SIRS患者（均为急性胰腺炎患者）作为SIRS组。6名健康献血者作为正常对照组。分别观察两组外周血PMN凋亡率、凋亡调控基因Fas／FasL和凋亡信号转导分子天冬氨酸特异性半胱氨酸蛋白酶-3（caspase-3）及血清白细胞介素-6（IL-6）、IL8的水平。结果SIRS组外周血血清IL-6和IL-8水平均明显高于正常对照组（P均＜0．01）。SIRS组患者外周血PMN细胞凋亡率较正常对照组明显减少（P＜0．01）；两组PMN在体外培养24h后，用蛋白质免疫印迹法（Western blotting）没有检测到FasL表达；SIRS组患者外周血PMN的Fas、caspase-3表达水平与正常对照组比较明显降低（P均＜0．01）。结论SIRS患者存在PMN的凋亡异常和Fas、caspase-3表达水平下调，PMN凋亡延迟在SIRS的发生发展中有着重要意义。     

Enhanced interleukin-8 release and gene expression in macrophages after exposure to Mycobacterium tuberculosis and its components.

Mycobacterium tuberculosis infection is accompanied by acute and chronic inflammatory infiltrates associated with necrotizing granulomas in lung tissue. The cellular infiltrate is characterized by inflammatory cells which include neutrophils, lymphocytes, and macrophages. In animal and in vitro models of mycobacterial infection, cytokines including tumor necrosis factor-alpha (TNF-alpha), interferon gamma (IFN-gamma), and interleukin-1 beta (IL-1 beta) participate in granulomatous inflammation. We hypothesized that interleukin-3, a potent chemoattractant for neutrophils and lymphocytes, could be released by activated alveolar macrophages after exposure to M. tuberculosis or its components and contribute to granulomatous lung inflammation. A quantitative immunoassay revealed that IL-8 protein release was significantly elevated in supernatants of macrophages and in lavage fluid obtained from patients with pulmonary tuberculosis compared to normal controls. In addition, Northern blots demonstrated striking up-regulation of IL-8 mRNA in macrophages from these patients. M. tuberculosis and its cell wall components lipoarabinomannan (LAM), lipomannan (LM), and phosphoinositolmannoside (PIM) stimulated IL-8 protein release and mRNA expression in vitro from alveolar macrophages, but deacylated LAM did not. Neutralizing antibodies to TNF-alpha and/or IL-1-alpha and beta blocked 83% of the stimulation. IL-8 synthesis and release is an early response of macrophages after phagocytosis of M. tuberculosis. Its production serves to attract both acute and chronic inflammatory cells of active infection and thus participates in the process of containment of the pathogen.     

Pulmonary contusion causes impairment of macrophage and lymphocyte immune functions and increases mortality associated with a subsequent septic challenge

OBJECTIVE AND DESIGN: Pulmonary contusion is frequently followed by acute respiratory distress syndrome, pneumonia, and sepsis. However, immunologic alterations of circulating and resident immune cell populations contributing to the posttraumatic immunosuppression are poorly understood. We therefore characterized the influence of pulmonary contusion on peripheral blood mononuclear cells, peritoneal macrophages, splenocytes, and splenic macrophages. To address the significance of the immunosuppression associated with lung contusion, we investigated how the consecutive addition of moderate or severe sepsis affected survival after blunt chest trauma. SUBJECTS: Male C3H/HeN mice (n = 10 per group) were anesthetized and subjected to chest trauma or sham procedure. MEASUREMENTS: The cytokine release of cultured peripheral blood mononuclear cells, peritoneal macrophages, splenocytes, and splenic macrophages and plasma levels of tumor necrosis factor-alpha and interleukin-6 from those animals were quantified. Sepsis was induced via cecal ligation and puncture 24 hrs after lung contusion. MAIN RESULTS: Two hours after blunt chest trauma, plasma tumor necrosis factor-alpha and interleukin-6 were markedly increased, as was peripheral blood mononuclear cell cytokine production, lung myeloperoxidase activity, and lung chemokine concentrations. At 24 hrs and, in part, already at 2 hrs, cytokine release from peritoneal macrophages, splenic macrophages, and splenocytes was significantly suppressed. Furthermore, pulmonary contusion when followed by moderate sepsis significantly diminished survival rate when compared with chest trauma or moderate sepsis alone. CONCLUSIONS: These results indicate that pulmonary contusion causes severe immunodysfunction of splenocytes, macrophages, and monocytes in different local compartments and systemically. Moreover, this immunosuppression is associated with an increased susceptibility to infectious complications, which results in a decreased survival rate if blunt chest trauma is followed by a septic insult.     

The pulmonary and hepatic immune microenvironment and its contribution to the early systemic inflammation following blunt chest trauma

OBJECTIVE: Blunt chest trauma is accompanied by an early increase in plasma cytokine concentrations. However, the local sources of these mediators are poorly defined. We investigated the impact of blunt chest trauma on the inflammatory mediator milieu in different compartments (lung tissue, bronchoalveolar lavage, liver tissue, Kupffer cells, plasma) along with the time course of trauma-induced pulmonary endothelial barrier dysfunction to elucidate potential relationships. In addition, the correlation between intratracheally instilled interleukin-6 and its systemic release were studied. DESIGN: Prospective, randomized, controlled animal study. SETTING: Basic science laboratory of a university affiliated level 1 trauma center. SUBJECTS: Male C3H/HeN mice, 8-9 wks old, n = 141. INTERVENTIONS: Blunt chest trauma induced by a focused blast wave, intravenous injection of Evans blue, and intratracheal instillation of recombinant human interleukin-6. MEASUREMENTS AND MAIN RESULTS: Two hours after blunt chest trauma, plasma interleukin-6 was markedly increased. Simultaneously, interleukin-6, tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemotactic polypeptide-1 and neutrophil/monocyte accumulation in bronchoalveolar lavage and interleukin-6, monocyte chemotactic polypeptide-1, and myeloperoxidase activity in lung tissue were significantly increased. This was accompanied by a coinciding elevation in the Evans blue lung-plasma ratio. Recombinant human interleukin-6, instilled intratracheally before blunt chest trauma, was detected in a dose-dependent manner in the plasma of the mice. Additionally, Kupffer cell interleukin-6, tumor necrosis factor-alpha, and interleukin-10 production was significantly augmented as early as 30 mins after the insult. CONCLUSIONS: These results indicate that early increased cytokine concentrations in the lung, particularly interleukin-6, are important mediator sources as their local peak coincides with the systemic inflammatory response and is accompanied by a simultaneous impaired function of the pulmonary endothelial barrier. A direct relationship between their local and systemic concentrations can be established. Furthermore, this is the first study to show that Kupffer cells are activated early after blunt chest trauma.     

Role of activated neutrophils in chest trauma-induced septic acute lung injury

More than 50% of severely injured patients have chest trauma. Second insults frequently result in acute lung injury (ALI), with sepsis being the main underlying condition. We aimed to develop a standardized, reproducible, and clinically relevant double-hit mouse model of ALI induced by chest trauma and polymicrobial sepsis and to investigate the pathophysiologic role of activated neutrophils. Lung contusion was applied to C57Bl/6 mice via a focused blast wave. Twenty-four hours later, sepsis was induced by cecal ligation and puncture. For polymorphonuclear leukocyte (PMN) depletion, animals received intravenous injections of PMN-depleting antibody. In response to blunt chest trauma followed by sepsis as well as after sepsis alone, a significant local and systemic inflammatory response with increased cytokine/chemokine levels in lung and plasma was observed. In contrast, lung apoptosis was markedly elevated only after a double hit. Intra-alveolar neutrophils and total bronchoalveolar lavage protein concentrations were markedly increased following isolated chest trauma or the combined insult, but not after sepsis alone. Lung myeloperoxidase activity was enhanced only in response to the double hit accompanied by histological disruption of the alveolar architecture, lung congestion, and marked cellular infiltrates. Neutrophil depletion significantly diminished lung interleukin 1β and interleukin 6 concentrations and reduced the degree of septic ALI. Here we have established a novel and highly reproducible mouse model of chest trauma-induced septic ALI characterizing a clinical relevant double-hit scenario. In particular, the depletion of neutrophils substantially mitigated the extent of lung injury, indicating a pathomechanistic role for neutrophils in chest trauma-induced septic ALI.     

Expression of Fas (CD95) and Fas ligand on peripheral blood mononuclear cells in critical illness and association with multiorgan dysfunction severity and survival

OBJECTIVE: This was an exploratory study with three goals: a) to quantify the expression of the apoptotic receptor Fas and its ligand (FasL) on peripheral blood mononuclear cells (PBMCs) in patients with, or at risk for, multiple organ dysfunction syndrome (MODS); b) to compare this expression with the respective expression in matched controls; and c) to explore the association with MODS severity and survival. DESIGN: Repeated-measures correlational and cross-sectional design. SETTING: The surgical, medical, and the trauma/burn intensive care unit of an academic institution. PATIENTS: Thirty-five adult, critically ill patients meeting the diagnostic criteria for systemic inflammatory response syndrome (SIRS) with MODS, or at risk for MODS, were followed for 14 days. Thirty-five non-SIRS controls matched with patients for age, gender, and race comprised the control group. INTERVENTIONS: Peripheral blood sampling every 48 hrs. MEASUREMENTS/MAIN RESULTS: T cells were considerably depleted in SIRS/MODS patients (p <.001), and Fas and FasL expression on PBMCs (flow cytometric analysis) was elevated significantly compared with controls (p <.001). In contrast to controls, non-T cells were the major sources of Fas and FasL in SIRS/MODS patients (p <.01). Expression of Fas and FasL exhibited a bimodal correlation with severity (p <.03). High severity patients demonstrated increasing Fas and FasL expression with increasing severity in contrast to declining expression in moderately severe patients. Fas and FasL measurements were significantly and positively associated with the likelihood of survival (p <.05). CONCLUSIONS: Dysregulation in the expression of apoptotic receptors Fas and FasL, at least in PBMCs, may be involved in the pathophysiology of SIRS, the related lymphocytopenia, and the onset of MODS and the related morbidity and mortality rates.