Cyclic helix B peptide promotes random-pattern skin flap survival via TFE3-mediated enhancement of autophagy and reduction of ROS levels.

BACKGROUND AND PURPOSE Necrosis of random-pattern skin flaps limits their clinical application. Helix B surface peptide (HBSP) protects tissues from ischemia-reperfusion injury; however, the short plasma half-life of HBSP limits its applications. Cyclic helix B peptide (CHBP) was synthesized in the present study, and the role of CHBP in flap survival and the underlying mechanism were investigated. EXPERIMENTAL APPROACH Flap viability was evaluated by survival area analysis, laser doppler blood flow, and histological analysis. RNA sequencing was used to identify the mechanisms relevant to the role of CHBP. Western blotting, real-time quantitative PCR, immunohistochemistry, and immunofluorescence were used to assay the levels of autophagy, oxidative stress, pyroptosis, necroptosis, and molecules related to the adenosine 5'-monophosphate-activated protein kinase (AMPK)-transient receptor potential mucolipin 1 (TRPML1)-calcineurin signaling pathway. KEY RESULTS The results indicated that CHBP promoted the survival of random-pattern skin flaps. The results of RNA sequencing analysis indicated that autophagy, oxidative stress, pyroptosis, and necroptosis were involved in the ability of CHBP to promote skin flap survival. Restoration of autophagy flux and enhanced resistance to oxidative stress contributed to inhibition of pyroptosis and necroptosis. Increased autophagy and inhibition of oxidative stress in the ischemic flaps are regulated by transcription factor E3 (TFE3). A decrease in the levels of TFE3 caused a reduction in autophagy flux and accumulation of ROS and eliminated the protective effect of CHBP. Moreover, CHBP regulated the activity of TFE3 via the AMPK-TRPML1-calcineurin signaling pathway. CONCLUSION AND IMPLICATIONS CHBP promotes skin flap survival by upregulating autophagy and inhibiting oxidative stress in the ischemic flap and may have potential clinical applications.