Sirt6 regulates autophagy in AGE-treated endothelial cells via KLF4

Abstract Aims To explore Sirt6 regulating autophagy in endothelial cells and the specific mechanism of this function with involvement of KLF4. Materials and methods Human umbilical vein endothelial cells were cultured with advanced glycation end products (AGE) treatment. Adv-Sirt6, LV-Sirt6 and LV-KLF4 were used to knockup Sirt6 and knockdown Sirt6 and KLF4 respectively. qPCR and Western Blotting were used to detect the mRNA and protein expression of Sirt6 and KLF4. Laser scanning confocal microscope was used to observe the LC3-II marked autophagosomes. Wildlife BALB/c mice were treated with STZ to produce diabetic mice model. AAV-Sirt6 was injected by tail vein injection to achieve Sirt6 knockdown. HE staining and scanning electron microscope were used to observe the aortic intima condition and autophagosomes number respectively. Results In AGE treated HUVECs, knockdown of Sirt6 led to impaired autophagy level along with less expression of autophagic markers LC3-II, Beclin-1, Lamp2 and autophagic marker p62. Knockdown and knockup of Sirt6 directly affected KLF4 expression level but KLF4 didn't have any effect on Sirt6 expression. Knockout of KLF4 offset the augmented autophagy caused by overexpression of Sirt6. In high-fat fed diabetic mice, downregulation of Sirt6 led to better cardiac function along with less autophagosomes and impaired aortic intima integrity. Conclusions Sirt6 improves autophagy both in vivo and in vitro and Sirt6 regulates autophagy via KLF4 in HUVECs. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Natural Science Foundation of China