The Effect Of Pretreatment Of Oleanolic Acid On The IKK/I-κB/NF-κB Signaling Pathway During Rat's HIRI

[Backgrounds] Hepatic ischemia-reperfusion injury (HIRI) plays an important role that cause hepatic dysfunction or nonfunction after insufficient or discontinuation of the blood flow. Many mechanisms are involved in the procedure of HIRI, in which inflammation is a critical factor, and the activation of NF-κB is an important process of inflammation. The activation of NF-κB during this procedure is mainly regulated by IKK2 and I-κBα. It is reported that HIRI could be attenuated by restraining the signal transduction of IKK/I-κB/NF-κB. Oleanolic acid (OA) has been used for clinical for many years, and it is reported that the pretreatment of OA could attenuate bromobenzene, thioacetamide, carbon tetrachloride and furosemide induced hepatic injury. Our previous works suggested that the pretreatment of OA could improve the storage of glycogen before ischemia, inhibit the production of reactive oxygen species, and attenuate HIRI, but whether the IKK/I-κB/NF-κB signaling pathway was involved in this anti-HIRI's mechanism is unclear.[Objective] To investigate whether the IKK/I-κB/NF-κB signaling pathway is involved in this anti-HIRI's mechanism in rat's 70% hepatic ischemic model using OA as a pretreatment drug.[Methods] One hundred and twenty eight male Sprague-Dawley (SD) rats were randomly divided into sham group (SH),ischemia-reperfusion group (IR),0.5% sodium carboxymethycellulose (CMC-Na) group (CM) and OA+0.5% CMC-Na group (OA) equally. Before the operation, the rats of each group got intragastric administrated of corresponding solution once a day for seven days (OA group with 100 mg/kg of OA+0.5% CMC-Na,SH group and IR group with water of the same volume, CM group with 0.5% CMC-Na of the same volume). At the 8th day,rats were suffered from segmental(70%) hepatic ischemia for 60 min, and then followed with different times of reperfusion (rats of SH group were received laparotomy but no ischemia), then the hepatic tissues were taken at 0 h,3 h,and 6 h after reperfusion (the tissues of rats of SH group were taken at the same time). The expression of IKK2,I-κBαin the cytoplasm and NF-κB p65 in the nucleus were evaluated by western blotting.[Results] No intracytoplasmic IKK2 and only a few of intranuclear NF-κB p65 were detected before operation or at 0h after reperfusion in each group. Meanwhile, the intracytoplasmic I-κBαhas no significant difference between four groups at the same time. The expression of IKK2 and I-κBαin cytoplasm and NF-κB p65 in nucleus had no significant difference between CM and IR groups at each point of time (P>0.05). The intracytoplasmic IKK2 and intranuclear NF-κB p65 in the SH group was much lower than that in each other group at 3h or 6h after reperfusion (P<0.05), while the same protein detected in OA group was less than that in CM or IR group at the same time (P<0.05). The expression of intracytoplasm I-κBαin the SH group was higher than that in each other group (P<0.05), while this protein detected in OA group was more than that in CM or IR group (P<0.05) at the same time.[Conclusion] Our results suggested that the expression of IKK2 in the cell cytoplasm would be increased by HIRI, which induce the phosphorylation of I-κB, then activate NF-κB and make NF-κB translocate into nucleus, so that inflammatory response would be triggered. The activation of the signaling pathway of IKK/I-κB/NF-κB can be inhibited by pretreatment of OA, so this may be one of the mechanisms for OA alleviating HIRI.