Annette Palmer

Blunt chest trauma induces mediator-dependent monocyte migration to the lung.

Objective:This study was designed to determine whether lung contusion induces an increased pulmonary recruitment of monocytes as a source of alveolar macrophages and which mediators are involved. Setting and Design:Prospective animal study. Subjects and Interventions:Male Sprague-Dawley rats were subjected to chest trauma by a single blast wave. Measurements:Chemokine concentrations in bronchoalveolar lavage fluids and supernatants of alveolar macrophages, chemokine and chemokine receptor mRNA expressions in monocytes, pulmonary interstitial macrophages, and alveolar macrophages isolated after trauma or sham procedure were evaluated. Immigration of monocytes was determined by staining alveolar macrophages with the fluorescent marker PKH26 before chest trauma. Chemotaxis of naïve monocytes in response to bronchoalveolar lavage or supernatants from alveolar macrophages isolated after trauma or sham procedure and the migratory response of monocytes isolated after trauma/sham to recombinant chemokines were measured. Main Results:Chemokine levels in bronchoalveolar lavage and alveolar macrophage supernatants and the percentage of monocytes migrated to the lungs were increased after chest trauma. Lung contusion enhanced the mRNA expression for CCR2 in monocytes and interstitial macrophages and for monocyte chemotactic protein-1 in alveolar macrophages. Migration of naïve monocytes vs. bronchoalveolar lavage or alveolar macrophage supernatants from traumatized animals was increased when compared with samples from shams. Monocytes isolated 2 hrs after trauma showed a reduced migration to CINC-1 or monocyte chemotactic protein-1 compared with sham. Conclusions:Alveolar macrophages seem to contribute to increased chemokine concentrations in alveoli of animals subjected to blunt chest trauma. Mediators released by alveolar macrophage are potent stimuli for monocyte migration. Monocytes alter their chemokine receptor expression and are recruited to the lungs.

Role of alveolar macrophages in the inflammatory response after trauma.

ABSTRACT Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), can result from both direct and indirect pulmonary damage caused by trauma and shock. In the course of ALI/ARDS, mediators released from resident cells, such as alveolar macrophages, may act as chemoattractants for invading cells and stimulate local cells to build up a proinflammatory micromilieu. Depending on the trauma setting, the role of alveolar macrophages is differentially defined. This review focuses on alveolar macrophage function after blunt chest trauma, ischemia/reperfusion, hemorrhagic shock, and thermal burns.

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

ABSTRACT The treatment of acute lung injury and septic complications after blunt chest trauma remains a challenge. Inhaled hydrogen sulfide (H2S) may cause a hibernation-like metabolic state, which refers to an attenuated systemic inflammatory response. Therefore, we tested the hypothesis that inhaled H2S–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 H2S (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 H2S, whereas the trauma-induced increase in neutrophil counts was unaltered. Furthermore, H2S 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 H2S induced a reduced metabolic expenditure and partially attenuated inflammation after trauma. Nevertheless, in contrast to hypoxic- or pathogen-induced lung injury, H2S treatment appears to have no protective effect after blunt chest trauma.

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

ABSTRACT 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 (AM&PHgr;). We hypothesized that chest trauma alters the phagocytic response of AM&PHgr; as well as the mediator release of AM&PHgr; during phagocytosis. To study this, male Sprague-Dawley rats were subjected to blunt chest trauma. Phagocytosis assays were performed in AM&PHgr; isolated 2 or 24 h after trauma with apoptotic cells or opsonized beads. Phagocytosis of apoptotic AT2 cells by unstimulated AM&PHgr; was significantly increased 2 h after trauma. At 24 h, AM&PHgr; from traumatized animals, stimulated with phorbol-12-myristate-13-acetate, ingested significantly more apoptotic polymorphonuclear neutrophils than AM&PHgr; from sham animals. Alveolar macrophages after trauma released significantly higher levels of tumor necrosis factor &agr;, macrophage inflammatory protein 1&agr;, and cytokine-induced neutrophil chemoattractant 1 when they incorporated latex beads, but significantly lower levels of interleukin 1&bgr; and macrophage inflammatory protein 1&agr; 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 AM&PHgr;. 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.

Complement therapeutic strategies in trauma, hemorrhagic shock and systemic inflammation – closing Pandora’s box?

After severe trauma, the immune system is challenged with a multitude of endogenous and exogenous danger molecules. The recognition of released danger patterns is one of the prime tasks of the innate immune system. In the last two decades, numerous studies have established the complement cascade as a major effector system that detects and processes such danger signals. Animal models with engineered deficiencies in certain complement proteins have demonstrated that widespread complement activation after severe injury culminates in complement dysregulation and excessive generation of complement activation fragments. Such exuberant pro-inflammatory signaling evokes systemic inflammation, causes increased susceptibility to infections and is associated with a detrimental course of the disease after injury. We discuss the underlying processes of such complementopathy and recapitulate different intervention strategies within the complement cascade. So far, several orthogonal anti-complement approaches have been tested with varying success in a large number of rodent, in several porcine and few simian studies. We illustrate the different features among those intervention strategies and highlight those that hold the greatest promise to become potential therapeutic options for the intricate disease of traumatic injury.

Role of alveolar macrophages in the regulation of local and systemic inflammation after lung contusion.

BACKGROUND Blunt chest trauma is an injury that enhances the morbidity and mortality rate, particularly in the context of polytrauma. Our previous studies showed local and systemic inflammatory alterations after blunt chest trauma in mice. This study was designed to determine whether alveolar macrophages (AM&PHgr;) have an alleviative role in this posttraumatic inflammation. METHODS AM&PHgr; of male C3H/HeN mice were depleted by instillation of clodronate liposomes into the lung before blunt chest trauma induced by a single blast wave. In bronchoalveolar lavage, lung homogenates, plasma, and cell culture supernatants of Kupffer cells, peripheral blood mononuclear cells, splenic macrophages, and splenocytes isolated 2 hours or 24 hours after chest trauma mediator concentrations were determined by multiplex assay or enzyme-linked immunosorbent assay. RESULTS In bronchoalveolar lavage, AM&PHgr; depletion led to increased monocyte chemoattractant protein 1 and regulated and normal T cell expressed and secreted (RANTES) concentrations as well as an attenuated increase of interleukin 6 concentrations after chest trauma. Bronchoalveolar lavage keratinocyte-derived chemokine concentrations increased in nontraumatized but AM&PHgr;-depleted animals with no further change after chest trauma. Cytokine concentrations in lung homogenates were altered in the same way as in bronchoalveolar lavage early after trauma. In the plasma of AM&PHgr;-depleted animals, interleukin 6 concentrations were slightly decreased after chest trauma. Depletion of AM&PHgr; abrogated the trauma-induced decrease of Kupffer cell chemokine release. Cytokine concentrations of blood monocytes, splenic macrophages, and splenocyte supernatants were not influenced by AM&PHgr; depletion. CONCLUSION These depletion experiments show that AM&PHgr; ameliorate the inflammatory response after blunt chest trauma. Taken together, this study gives relevant insights into the regulative role of AM&PHgr; during the local and systemic inflammation after lung contusion.

Role of Hemorrhagic Shock in Experimental Polytrauma

ABSTRACT Hemorrhagic shock (HS) after tissue trauma increases the complication and mortality rate of polytrauma (PT) patients. Although several murine trauma models have been introduced, there is a lack of knowledge about the exact impact of an additional HS. We hypothesized that HS significantly contributes to organ injury, which can be reliably monitored by detection of specific organ damage markers. Therefore we established a novel clinically relevant PT plus HS model in C57BL/6 mice which were randomly assigned to control, HS, PT, or PT+HS procedure (n = 8 per group). For induction of PT, anesthetized animals received a blunt chest trauma, head injury, femur fracture, and soft tissue injury. HS was induced by pressure-controlled blood drawing (mean arterial blood pressure of 30 mmHg for 60 min) and mice then resuscitated with ionosterile (4 × volume drawn), monitored, and killed for blood and organ harvesting 4 h after injury. After HS and resuscitation, PT+HS mice required earlier and overall more catecholamine support than HS animals to keep their mean arterial blood pressure. HS significantly contributed to the systemic release of interleukin-6 and high mobility group box 1 protein. Furthermore, the histological lung injury score, pulmonary edema, neutrophil influx, and plasma clara cell protein 16 were all significantly enhanced in PT animals in the presence of an additional HS. Although early morphological changes were minor, HS also contributed functionally to remote acute kidney injury but not to early liver damage. Moreover, PT-induced systemic endothelial injury, as determined by plasma syndecan-1 levels, was significantly aggravated by an additional HS. These results indicate that HS adds to the systemic inflammatory reaction early after PT. Within hours after PT, HS seems to aggravate pulmonary damage and to worsen renal and endothelial function which might overall contribute to the development of early multiple organ dysfunction.

Acute ethanol administration results in a protective cytokine and neuroinflammatory profile in traumatic brain injury

Abstract Ethanol intoxication is a common comorbidity in traumatic brain injury. To date, the effect of ethanol on TBI pathogenic cascades and resulting outcomes remains debated. A closed blunt weight‐drop murine TBI model has been implemented to investigate behavioral (by sensorimotor and neurological tests), and neuro‐immunological (by tissue cytokine arrays and immuno‐histology) effects of ethanol intoxication on TBI. The effect of the occurrence of traumatic intracerebral hemorrhage was also studied. The results indicate that ethanol pretreatment results in a faster and better recovery after TBI with reduced infiltration of leukocytes and reduced microglia activation. These outcomes correspond to reduced parenchymal levels of GM‐CSF, IL‐6 and IL‐3 and to the transient upregulation of IL‐13 and VEGF, indicating an early shift in the cytokine profile towards reduced inflammation. A significant difference in the cytokine profile was still observed 24 h post injury in the ethanol pretreated mice, as shown by the delayed peak in IL‐6 and by the suppression of GM‐CSF, IFN‐&ggr;, and IL‐3. Seven days post‐injury, ethanol‐pretreated mice displayed a significant decrease both in CD45 + cells infiltration and in microglial activation. On the other hand, in the case of traumatic intracerebral hemorrhage, the cytokine profile was dominated by KC, CCL5, M‐CSF and several interleukins and ethanol pretreatment did not produce any modification. We can thus conclude that ethanol intoxication suppresses the acute neuro‐inflammatory response to TBI, an effect which is correlated with a faster and complete neurological recovery, whereas, the presence of traumatic intracerebral hemorrhage overrides the effects of ethanol. HighlightsEthanol intoxication improves neurological recovery after traumatic brain injury.Ethanol suppresses pro‐inflammatory cytokines induced by traumatic brain injury.Ethanol is ineffective in case of concomitant hematoma formation.

Neuroprotective effect of acute ethanol intoxication in TBI is associated to the hierarchical modulation of early transcriptional responses

ABSTRACT Ethanol intoxication is a risk factor for traumatic brain injury (TBI) but clinical evidence suggests that it may actually improve the prognosis of intoxicated TBI patients. We have employed a closed, weight‐drop TBI model of different severity (2 cm or 3 cm falling height), preceded (− 30 min) or followed (+ 20 min) by ethanol administration (5 g/Kg). This protocol allows us to study the interaction of binge ethanol intoxication in TBI, monitoring behavioral changes, histological responses and the transcriptional regulation of a series of activity‐regulated genes (immediate early genes, IEGs). We demonstrate that ethanol pretreatment before moderate TBI (2 cm) significantly reduces neurological impairment and accelerates recovery. In addition, better preservation of neuronal numbers and cFos + cells was observed 7 days after TBI. At transcriptional level, ethanol reduced the upregulation of a subset of IEGs encoding for transcription factors such as Atf3, c‐Fos, FosB, Egr1, Egr3 and Npas4 but did not affect the upregulation of others (e.g. Gadd45b and Gadd45c). While a subset of IEGs encoding for effector proteins (such as Bdnf, InhbA and Dusp5) were downregulated by ethanol, others (such as Il‐6) were unaffected. Notably, the majority of genes were sensitive to ethanol only when administered before TBI and not afterwards (the exceptions being c‐Fos, Egr1 and Dusp5). Furthermore, while severe TBI (3 cm) induced a qualitatively similar (but quantitatively larger) transcriptional response to moderate TBI, it was no longer sensitive to ethanol pretreatment. Thus, we have shown that a subset of the TBI‐induced transcriptional responses were sensitive to ethanol intoxication at the instance of trauma (ultimately resulting in beneficial outcomes) and that the effect of ethanol was restricted to a certain time window (pre TBI treatment) and to TBI severity (moderate). This information could be critical for the translational value of ethanol in TBI and for the design of clinical studies aimed at disentangling the role of ethanol intoxication in TBI. HIGHLIGHTSHigh‐dose Ethanol shows neuroprotective effect on behavioral and histological readouts.Ethanol downregulates the trauma‐associated transcriptional response.Ethanol should be taken/administered before the TBI.Effects of Ethanol are limited to moderate TBI and is not effective on severe TBI.Ethanol sensitivity defines a hierarchy on the activation of transcription factors upon TBI.

MDSCs are induced after experimental blunt chest trauma and subsequently alter antigen-specific T cell responses

Severe blunt chest trauma (TxT) induces a strong inflammatory response with posttraumatic immune suppression pointing to an impaired adaptive immune response. Since CD11b+Gr-1+-expressing myeloid-derived suppressor cells (MDSCs) are induced after inflammation and suppress T cell responses, MDSC induction and their impact on T cell functions was analysed in an experimental TxT model. MDSCs were induced preferentially in the lung until 24 hours after TxT. Although MDSC numbers were only faintly increased in the spleen, splenic MDSCs isolated after TxT strongly inhibited alloantigen-induced T cell proliferation in vitro. Suppressive activity correlated with increased expression of arginase-1 and iNOS. MDSCs also prevented antigen-induced T cell expansion in vivo, since staphylococcus enterotoxin B (SEB)-induced proliferation of vβ8+ T cells was impaired in TxT mice in the presence of CD11b+Gr-1+ cells. Surprisingly, MDSCs were not involved in shifting T cells into Th2 cells, characterized by the secretion of cytokines impairing cell-mediated immunity and promoting immunosuppression. Instead, the presence of CD11b+Gr-1+ cells was required for efficient IL-2, IFN-γ and TNFα production after antigenic stimulation, indicating, that elevation of MDSCs early after traumatic injuries might contribute to restrict the initial inflammatory response by alleviating T cell expansion, however, without impeding Th1 functions.