Exploring the Bone–Liver Axis: Impact of Acute Ethanol Intoxication on Post-Traumatic Liver Inflammation and Damage Following Femur Fracture

Abstract

Bone fracture activates the immune system and induces inflammation crucial for fracture healing but may also affect trauma-distant organs like the liver. Acute alcohol intoxication (AAI) dysregulates immune responses and affects organ damage post-trauma. However, the bone–liver axis and alcohol’s role in this process remain poorly understood. This study explores liver inflammation and damage following fracture, with and without prior AAI. Twenty-four male C57BL/6J mice were randomly assigned to four groups (n = 6) and received either NaCl (control) or 35% ethanol via gavage. Mice underwent femur osteotomy with external fixation or sham surgery. After 24 h, liver damage was assessed using hematoxylin–eosin and activated caspase-3 staining. Liver inflammation was evaluated through CXCL1 and polymorphonuclear leukocyte (PMNL) immunostaining, cytokine gene and protein expression analyses, and immune cell profiling in the liver via flow cytometry. Western blotting assessed NF-κB and Wnt signaling. Neither fracture alone nor with AAI caused significant liver damage. However, fracture significantly increased PMNL infiltration and altered monocyte populations, effects that were amplified by AAI. The hepatic neutrophil-to-monocyte ratio significantly decreased after fracture and was absent in the fracture AAI group. CXCL1 increased post-fracture, while MCP-1 and IL-10 decreased significantly, with AAI further significantly amplifying these changes. Wnt1 and Wnt3a levels increased significantly after fracture and were further strongly elevated by AAI. AAI completely abolished fracture-induced significant β-catenin reduction and significantly increased its phosphorylation, effects that potentially involve an AAI-induced β-catenin stabilization as well as its increased degradation. NF-κB activation was significantly decreased, while A20 expression significantly increased after fracture and AAI. Fracture influences the inflammatory liver response and signaling pathways, effects which were further modulated by AAI.