gms | German Medical Science

Objectives: Multiple injured trauma patients often suffer both bone fractures and hemorrhagic shock, which induce a systemic and local inflammation driven by enhanced NF-kappaB activity. In addition, traumatic injuries are often accompanied by an acute intoxication with alcohol. Due to its immunomodulatory properties, alcohol has a huge clinical impact. The mechanisms behind its NF-kappaB-downregulating role in acute-drinking situation, and thus, immune-suppressive effects after trauma are unknown. A20 protein inhibits NF-kappaB activity by sequestrating its components inactive in the cytoplasm, and thereby modifying the inflammatory response. We aimed to investigate the role of A20 as a modifier of the NF-kappaB-driven inflammatory response in the lung after trauma in alcohol-intoxicated mice.

Methods: Mice were randomly assigned to four groups. Animals received an intragastral gavage of either sodium chloride or ethanol (35%, alcohol) to simulate an acute intoxication. Animals in trauma groups underwent osteotomy with external fixation (Fx) and a pressure-controlled hemorrhagic shock (35 mmHg; 90 minutes) with subsequent resuscitation (H/R). Sham-operated animals underwent surgical procedures. Lung and liver tissues were collected after 24 hours. Oil Red O staining of fatty vacuoles in the liver was performed to assess alcohol intoxication. Lung damage was evaluated by hematoxylin-eosin staining, determination of the total protein concentration in the bronchoalveolar lavage fluid (BALF) and lung injury score (LIS) calculation. Pro-inflammatory changes going together with NF-kappaB-activation were assessed by the determination of lung infiltration with neutrophils and CXCL1 expression. Apoptosis was analyzed by activated caspase-3 expression. A20 expression was determined by immunofluorescence.

Results: The results confirmed that alcohol induced significant fatty changes in the liver. Significantly increased total protein concentration in the BALF and enhanced histomorphological LIS after Fx+H/R compared to sham indicate trauma-induced lung injury and barrier breakdown. Acute alcohol consumption prior trauma decreased both total BALF-protein concentration and the histomorphological LIS compared to the Fx+H/R control group. Fx+H/R increased the lung neutrophil infiltration, expression of CXCL1 as well as the expression of activated caspase-3 compared to sham. These results were paralleled by decreased A20 expression after Fx+H/R. Compared to the control trauma group, the local presence of neutrophils in the lung as well as CXCL1 expression and apoptosis were reduced upon alcohol consumption prior Fx+H/R. Alcohol increased the expression of the NF-kappaB regulating ubiquitin-editing enzyme A20 after trauma.

Conclusion: In this double-hit model, acute alcohol consumption before trauma provides immunosuppressive effects via A20-reduced NF-kappaB activation in the lung.