Biliverdin Improved Angiogenesis and Suppressed Apoptosis Via PI3K/Akt-mediated Nrf2 Antioxidant System to Promote Ischemic Flap Survival

Plastic and reconstructive surgeons frequently utilize random skin flap transplantation to repair skin defects. However, the procedure carries a substantial risk of necrosis. Previous research has suggested that Biliverdin (Bv), the main component of Calculus Bovis, possessed potent anti-ischemic properties, making it a potential therapeutic agent for skin flap survival. Hence, in this study, the potential of Bv in promoting flap survival has been comprehensively investigated. Network pharmacology analysis revealed that the pharmacological effects of Bv on ischemic diseases may be attributed to its modulation of various signaling molecules, including the PI3K-Akt pathway. In vitro results demonstrated that Bv treatment significantly promoted angiogenesis in human umbilical vein endothelial cells (HUVEC), even in the presence of HO. This was evident by the increased cell proliferation, enhanced migration, and improved tube formation. Bv also effectively attenuated the intracellular generation of reactive oxygen species (ROS) induced by HO, which was achieved by suppressing mitochondrial ROS production through the PI3K/Akt-mediated activation of Nrf2/HO-1 signaling pathway. Consequently, Bv treatment led to a significant reduction in apoptosis and an increase in cell viability of HUVEC. Furthermore, in vivo experiment demonstrated that Bv treatment vastly elevated flap survival through enhancing angiogenesis while decreasing oxidative stress and apoptosis, which was comparable to the results of positive control of N-acetylcysteine (Nac). In conclusion, this study not only established a solid foundation for future study on therapeutic potential of Bv, but also proposed a promising treatment approach for enhancing the success rate of flap transplants and other ischemic-related tissue repair.