Different inflammatory responses in the remote organs after tourniquet-induced ischemia-reperfusion in mouse hindlimb

Tourniquet use is the most effective tool for controlling life-threatening extremity hemorrhage before other treatments and for creating bloodless operating fields in surgical procedures. However, tourniquet-induced ischemia-reperfusion (tourniquet/IR) also causes skeletal muscle injury and is associated with secondary remote organ injuries. Our previous studies have demonstrated that there is involvement of inflammatory cytokines in tourniquet-induced skeletal muscle IR injuries. In this study, we investigated the inflammatory responses and tissue injuries in remote organs after tourniquet/IR. The unilateral hindlimbs of mice were subjected to 3 h of tourniquet application by placing a rubber band at the hip joint. Then the rubber bands were released to initiate reperfusion, and tissues were harvested after 1, 3, 7, 14, and 28 days of reperfusion. The data from real-time RT-PCR and western blot showed that the levels of IL-1β and TNFα (two pro-inflammatory cytokines) mRNAs and proteins increased in the lungs and livers, whereas these cytokines did not rise in hearts and kidneys during 28 days of tourniquet/IR, compared to the sham tissues. Histological images also confirmed the infiltration of inflammatory cells in lungs and livers, but not in hearts and kidneys during 28 days of tourniquet/IR. Tourniquet/IR induced tissue structural injuries in the lungs but not the livers, hearts, and kidneys. Additionally, 21.8 % (12/55) of mice died at 1 day and 3 days of tourniquet/IR. These results suggest that inflammatory responses and severity of tissue injuries are different among remote organs and tourniquet/IR-related lung injuries could be a major cause of death during tourniquet/IR, which can help to develop therapeutic strategies for reducing mortality and improving outcomes after the use of tourniquet.