C1q/TNF-Related Protein 9 Attenuates Atherosclerosis by Inhibiting Hyperglycemia-Induced Endothelial Cell Senescence Through the AMPKα/KLF4 Signaling Pathway

Abstract

Hyperglycemia-induced endothelial cell senescence has been widely reported to be involved in the pathogenesis of type 2 diabetes mellitus‒accelerated atherosclerosis. Thus, understanding the underlying mechanisms and identifying potential therapeutic targets for endothelial cell senescence are valuable for attenuating atherosclerosis progression. C1q/tumor necrosis factor-related protein 9 (CTRP9), an emerging potential cardiokine, exerts a significant protective effect with respect to atherosclerosis, particularly in endothelial cells. However, the exact mechanism by which CTRP9 prevents endothelial cells from hyperglycemia-induced senescence remains unclear. This study aimed to investigate the effects of CTRP9 on hyperglycemia-induced endothelial cell senescence and atherosclerotic plaque formation in diabetic apolipoprotein E knockout (ApoE KO) mice. Human umbilical vein endothelial cells (HUVECs) were cultured in normal glucose (5.5 mM) and high glucose (40 mM) with or without recombinant human CTRP9 protein (3 μg/ml) for 48 h. Purified lentiviruses overexpressing CTRP9 (Lv-CTRP9) and control vectors containing green fluorescent protein (Lv-GFP) were injected via the tail vein into streptozotocin-induced diabetic ApoE KO mice. Results revealed that exposure of HUVECs to HG significantly increased the expression of Krüppel-like factor 4 (KLF4) and cyclin-dependent kinase inhibitor p21 (p21) and decreased that of telomerase reverse transcriptase (TERT). Treatment with recombinant human CTRP9 protein protected HUVECs from HG-induced premature senescence and dysfunction. CTRP9 promoted the phosphorylation of AMP-activated kinase (AMPK), attenuated the expression of KLF4 and p21 induced by HG, and increased the expression of TERT in HUVECs. Furthermore, in the background of AMPKα knockdown or KLF4 activation, the protective effects of CTRP9 were abolished. In-vivo experiments showed that the overexpression of CTRP9 inhibited vascular senescence and reduced atherosclerotic plaque formation in ApoE KO mice with diabetes. In conclusion, we demonstrate that KLF4 upregulation plays a crucial role in HG-induced endothelial senescence. This anti-atherosclerotic effect of CTRP9 may be partly attributed to the inhibition of HG-induced endothelial senescence through an AMPKα/KLF4-dependent mechanism, suggesting that CTRP9 could benefit further therapeutic approaches for type 2 diabetes mellitus‒accelerated atherosclerosis.

Hyperglycemia Promotes Endothelial Cell Senescence through AQR/PLAU Signaling Axis

“…The inflammation, ROS overproduction, and advanced glycation end-products (AGEs) caused by hyperglycemia were considered as major contributors to the complications’ etiologically, as they impair vascular function directly [ 19 ]. On the other hand, inflammation, ROS, and AGEs are well-known to promote cellular senescence, and actually, hyperglycemia-induced endothelial cell senescence was observed in vascular cells, such as endothelial cells [ 10 , 20 , 21 , 22 , 23 ], smooth muscle cells [ 11 ], endothelial progenitor cells [ 12 ], and mesenchymal stem cells [ 13 ]. These observations suggest that senescence may be serving as a shared downstream link to diabetic complications.…”

“…These observations suggest that senescence may be serving as a shared downstream link to diabetic complications. Since the endothelial cell is critical to vascular functions, including the maintenance of vessel integrity, secretion, and participation of immune response [ 24 ], and is directly exposed to high glucose in T2DM, the senescent endothelial cell may have a profound impact on the pathogenesis of diabetic complications [ 20 , 21 , 22 , 23 ]. HUVEC is a widely used cellular model to investigate the regulation of endothelial function, for example, senescence and angiogenesis [ 25 , 26 ].…”

Factors and Pathways Modulating Endothelial Cell Senescence in Vascular Aging

“…Deficiency in developmentally regulated GTP-binding protein 2 (DRG2) increases NOX2 expression, ROS generation, and senescence in ECs [ 142 ]. C1q/tumor necrosis factor-related protein 9 (CTRP9), an emerging potential cardiokine, contributes to the inhibition of hyperglycemia-induced endothelial senescence through an AMPKα/ Krüppel-like factor 4 (KLF4)-dependent signaling pathway [ 143 ]. Soluble dipeptidyl peptidase 4 (DPP4), secreted from visceral adipose tissue, induces EC senescence through the protease-activated receptor 2 (PAR2)–cyclooxygenase2 (COX-2)–thromboxane receptor (TP) axis and activates the NLRP3 inflammasome [ 144 ].…”

Pro‐inflammatory cytokines mediating senescence of vascular endothelial cells in atherosclerosis

“…Kim et al reported that tetraspanin‐29 (CD9) aggravates atherosclerotic plaque formation by inducing endothelial cell senescence, while CD9 knockdown or CD9 antibody treatment can noticeably prevent it in apolipoprotein E (ApoE)−/− mice and Ldlr−/− mice [22, 26]. Hou et al found that CTRP9 inhibited hyperglycemia‐induced endothelial cell senescence and reduced atherosclerotic plaque formation in vivo [27]. In addition, Xiong et al reported that overexpression of the circular RNA circGNAQ inhibited the senescence of VECs and the development of AS in vivo and in vitro [23].…”