Primary Study On The Influence Of P38 Mitogen Activated Protein Kinase Signaling Pathway On Estradiol-mediated Protection Following Ischemia Reperfusion Injury Of Flaps

Object: p38 MAPK plays a crucial role in the process of ischemia-reperfusion injury of flaps in response to inflammatory stimuli, such as inflammatory and cytokines, which can regulating inflammation, apoptosis and proliferation of cells. The aim of this study was to evaluate the effects of p38 mitogen-activated protein kinase signaling pathway(MAPK)on ischemia-reperfusion(I/R) injury of epigastric axial flaps of rats.To investigate the adjustment changes of estrogen on p38 MAPK in I/R injury of flap. Provide a theoretical basis for the clinical treatment of skin flap I/R injury.Methods: The superficial epigastric artery flap ischemia reperfusion injury model was created in Forty-eight male Wistar specific pathogen free(SPF) rats which were randomly divided into control group(groupⅠ), ischemia-reperfusion group(groupⅡ),saline group(group Ⅲ), estradiol group(group Ⅳ). All procedures were performed in accordance with protocols approved by the SPF laboratory. In groupⅠ, the flaps were sutured back without ischemic insult. The flaps were exposed to ischemia for 6 hours in groupⅡ,Ⅲand Ⅳ. During experiment, group Ⅲ was treated by abdominal cavity application of saline, groupⅣwas treated by estradiol and groupⅡwas left untreated. The general condition of the flap was observed at 3, 5, and 7 days after operation. Seven days postoperatively, the survival rate of the flap was detected by image analysis software(Media Cybernetics, USA), the expression of p38 MAPK, p-p38 MAPK, MKP-2 were quantified with Western Blot and immunohistochemistry. The flaps were harvested to receive histology, immunohistochemistry and ultrastructural observation. The neutrophils(NEU) level, TNF-α level and IL-10 level of the superficial epigastric vein were tested.Results:Treatment with estradiol significantly increased flap survival(P<0.05) when compared to the groupⅡ and groupⅢ. The histological and ultrastructure observationshowed that the degree of inflammatory exudation and necrotic area in the flap of groupⅡ,Ⅲ was more serious than that of groupⅣ. The NEU and TNF-α level in group Ⅳwas lower than that in groupⅡ and Ⅲ(P<0.05). The IL-10 level in groupⅡ,Ⅲ,Ⅳ is higher than that in control group, Particularly in the group Ⅳ. The expression of p38 MAPK and p-p38 MAPK in groupⅣ is lower than that in groupⅡ、Ⅲ(P<0.05),the MKP-2 expression in groupⅣ is higher than that in groupⅠ、Ⅱ、Ⅲ(P<0.05). Pearson correlation analysis between the flap survival rates and TNF-α level showed that there was a significant negative correlation between flap survival rates and TNF-α level. The same negative correlation exists between the skin flap survival and NEU.Conclusions: 1. The estradiol can significantly protect axial flap from the ischemiareperfusion injury and increase axial flap survival rates by inhibit neutrophil infiltration in flap and decreasing of the plasma TNF-α level. Therefore, the estradiol can improved the pathological changes of organization structure, which provides new evidence and direction for estradiol treatment on ischemia- reperfusion injury of flaps.2. Study results suggested that estradiol inhibited the expression of p38 MAPK, which can regulate the expression of pro-inflammatory gene, mitigated neutrophils-mediated inflammatory cascade, reduce the release of inflammatory mediators. The therapeutic effect of estradiol on ischemia-reperfusion injury of flaps may be related to MKP-2, which can inhibit the activity of p38 MAPK.