A snake cathelicidin enhances transcription factor EB‐mediated autophagy and alleviates ROS‐induced pyroptosis after ischaemia–reperfusion injury of island skin flaps

Background and Purpose Ischaemia–reperfusion (I/R) injury is a major contributor to skin flap necrosis, which presents a challenge in achieving satisfactory therapeutic outcomes. Previous studies showed that cathelicidin‐BF (BF‐30) protects tissues from I/R injury. In this investigation, BF‐30 was synthesized and its role and mechanism in promoting survival of I/R‐injured skin flaps explored. Experimental Approach Survival rate analysis and laser Doppler blood flow analysis were used to evaluate I/R‐injured flap viability. Western blotting, immunofluorescence, TdT‐mediated dUTP nick end labelling (TUNEL) and dihydroethidium were utilized to examine the levels of apoptosis, pyroptosis, oxidative stress, transcription factor EB (TFEB)‐mediated autophagy and molecules related to the adenosine 5′‐monophosphate‐activated protein kinase (AMPK)–transient receptor potential mucolipin 1 (TRPML1)–calcineurin signalling pathway. Key Results The outcomes revealed that BF‐30 enhanced I/R‐injured island skin flap viability. Autophagy, oxidative stress, pyroptosis and apoptosis were related to the BF‐30 capability to enhance I/R‐injured flap survival. Improved autophagy flux and tolerance to oxidative stress promoted the inhibition of apoptosis and pyroptosis in vascular endothelial cells. Activation of TFEB increased autophagy and inhibited endothelial cell oxidative stress in I/R‐injured flaps. A reduction in TFEB level led to a loss of the protective effect of BF‐30, by reducing autophagy flux and increasing the accumulation of reactive oxygen species (ROS) in endothelial cells. Additionally, BF‐30 modulated TFEB activity via the AMPK–TRPML1–calcineurin signalling pathway. Conclusion and Implications BF‐30 promotes I/R‐injured skin flap survival by TFEB‐mediated up‐regulation of autophagy and inhibition of oxidative stress, which may have possible clinical applications.