Objective: Ischemia-reperfusion (IR) injury is a leading cause of flap compromise and organ dysfunction during free-tissue transfer, and remains a great challenge for plastic surgeons. Thioredoxin-1 (Trx-1) was proved to protect the IR flap by mitigating the oxidative stress, and inhibiting the activation of apoptosis signal-regulating kinase-1 (ASK-1) and mitogen-activated protein kinase (MAPK) pathway. The aim of this study is to investigate the distinction of Trx-1 expression, apoptosis indices in different layers of IR flaps, and the feasibility of tissue-layer-specific administration of Trx-1. Methods: Ten patients′ specimens of IR flaps for DIEP breast reconstruction were collected and assessed for apoptosis and Trx-1 expression. Twenty mice were used to establish the IR flap model. The mice were sacrificed twenty-four hours after reperfusion. The flap tissues were harvested and tested by immunohistochemistry staining and TUNEL assay. The tissue-layer-specific dermoprotective effect of Trx-1 and the molecular mechanisms were assessed by an in vitro epithelial skin cell hypoxia-reoxygenation model. The statistics were conducted by t test and ANOVA using SPSS 20.0. Results: Trx-1 expression and apoptotic cells were observed mainly located in the basal layer of epidermis and the papillary layer of dermis in human IR flaps and mice models. Trx-1 depletion was 24.19 %± 2.23% in the basal layer of epidermis and the papillary layer of dermis of patient IR flaps, decreasing significantly compared with 70.71% ± 6.38% in control group (t = 27.54, P< 0.001). Similar tissue-layer-specific down regulation of Trx-1 also displayed in mice IR flap models (19.83% ± 2.34% vs. 76.59% ± 4.88%; t = 34.71, P<0.001). The apoptotic index in human samples significantly increased from 1.32% ± 1.52% in control group to 43.71 %± 3.17% in IR group (t =38.23, P<0.001); while it was proved to be dramatically raised in mice models from 0.86% ± 1.15% in control group to 41.14 %± 4.21% in IR group (t= 36.96, P < 0.001). Western Blot analysis revealed Trx-1 down regulation and a significant increase in ASK-1, p-p38, and c-PARP abundance in the hypoxia-reoxygenation-treated HaCaT cells (P < 0.01). Supplementation of recombinant human Trx-1 significantly reduced the apoptosis-related protein expression. Conclusions The basal layer of epidermis and the papillary layer of dermis are the main damaged tissue layers in the early stage of skin flap ischemia-reperfusion injury. The IR flap can be protected by precisely replenishing the vulnerable layers with Trx-1.

The mechanisms underlying autophagic defects in nonalcoholic steatohepatitis (NASH) remain largely unknown. We aimed to elucidate the roles of hepatic cyclooxygenase 1 (COX1) in autophagy and the pathogenesis of diet-induced steatohepatitis in mice. Human nonalcoholic fatty liver disease (NAFLD) liver samples were used to examine the protein expression of COX1 and the level of autophagy. Cox1^Δhepa mice and their wildtype littermates were generated and fed with 3 different NASH models. We found that hepatic COX1 expression was increased in patients with NASH and diet-induced NASH mice models accompanied by impaired autophagy. COX1 was required for basal autophagy in hepatocytes and liver specific COX1 deletion exacerbated steatohepatitis by inhibiting autophagy. Mechanistically, COX1 directly interacted with WD repeat domain, phosphoinositide interacting 2 (WIPI2), which was crucial for autophagosome maturation. Adeno-associated virus (AAV)-mediated rescue of WIPI2 reversed the impaired autophagic flux and improved NASH phenotypes in Cox1^Δhepa mice, indicating that COX1 deletion-mediated steatohepatitis was partially dependent on WIPI2-mediated autophagy. In conclusion, we demonstrated a novel role of COX1 in hepatic autophagy that protected against NASH by interacting with WIPI2. Targeting the COX1-WIPI2 axis may be a novel therapeutic strategy for NASH.