Role of Complement C5 in Experimental Blunt Chest Trauma-Induced Septic Acute Lung Injury (ALI).

BACKGROUND: Severe blunt chest trauma is associated with high mortality. Sepsis represents a serious risk factor for mortality in acute respiratory distress syndrome (ARDS). In septic patients with ARDS complement activation products were found to be elevated in the plasma. In single models like LPS or trauma complement has been studied to some degree, however in clinically highly relevant double hit models such as the one used here little data is available. Here, we hypothesized that absence of C5 is correlated with a decreased inflammatory response in trauma induced septic acute lung injury. METHODS: 12 hrs after DH in mice the local and systemic cytokines and chemokines were quantified by multiplex bead array or ELISA, activated caspase-3 by western blot. Data were analyzed using one-way ANOVA followed by post-hoc Sidak's multiple comparison test (significance, p≤ 0.05). RESULTS: In lung tissue interleukin (IL)-6, monocyte chemo attractant protein-1 (MCP-1) and granulocyte-colony stimulating factor (G-CSF) was elevated in both C5-/- mice and wildtype littermates (wt), whereas caspase-3 was reduced in lungs after DH in C5-/- mice. Systemically, reduced keratinocyte-derived chemokine (KC) levels were observed after DH in C5-/- compared to wt mice. Locally, lung myeloperoxidase (MPO), protein, IL-6, MCP-1 and G-CSF in brochoalveolar lavage fluid (BALF) were elevated after DH in C5-/- compared to wt. CONCLUSIONS: In the complex but clinically relevant DH model the local and systemic inflammatory immune response features both, C5-dependent and C5-independent characteristics. Activation of caspase-3 in lung tissue after DH was C5-dependent whereas local inflammation in lung tissue was C5-independent.

Inflammatory and apoptotic alterations in serum and injured tissue after experimental polytrauma in mice: distinct early response compared with single trauma or "double-hit" injury.

BACKGROUND: The exact alterations of the immune system after polytrauma leading to sepsis and multiple-organ failure are poorly understood. Thus, the early local and systemic inflammatory and apoptotic response was characterized in a new polytrauma model and compared with the alterations seen after single or combined injuries. METHODS: Anesthetized C57BL/6 mice were subjected to either blunt bilateral chest trauma (Tx), closed head injury, right femur fracture including contralateral soft tissue injury, or a combination of injuries (PTx). After 2 hours or 6 hours, animals were sacrificed, and the systemic as well as the local pulmonary immune response (bronchoalveolar lavage [BAL]/plasma cytokines, lung myeloperoxidase [MPO] activity, and alveolocapillary barrier dysfunction) were evaluated along with lung/brain apoptosis (lung caspase 3 Western blotting, immunohistochemistry, and polymorphonuclear leukocytes [PMN] Annexin V). RESULTS: Hemoglobin, PO2 saturation, and pH did not differ between the experimental groups. Local BAL cytokines/chemokines were significantly increased in almost all groups, which included Tx. There was no further enhancement of this local inflammatory response in the lungs in case of PTx. At 2 hours, all groups except sham and closed head injury alone revealed an increased activity of lung MPO. However, 6 hours after injury, lung MPO remained increased only in the PTx group. Increased BAL protein levels were found, reflecting enhanced lung leakage in all groups with Tx 6 hours after trauma. Only after PTx was neutrophil apoptosis significantly decreased, whereas lung caspase 3 and plasma interleukin 6/keratinocyte chemoattractant (KC) were substantially increased. CONCLUSION: The combination of different injuries leads to an earlier systemic inflammatory response when compared with the single insults. Interestingly, only after PTx but not after single or double hits was lung apoptosis increased, and PMN apoptosis was decreased along with a prolonged presence of neutrophils in the lungs, which may therefore represent a possible pathomechanism for lung injury after polytrauma.