Iron Overload Damages the Endothelial Mitochondria via the ROS/ADMA/DDAHII/eNOS/NO Pathway

Abstract

It has been recognized that iron overload may harm the body's health. Vascular endothelial cells (VECs) are one of the main targets of iron overload injury, and the mechanism involved was thought to be related to the excessive generation of reactive oxygen species (ROS). However, the subcellular and temporal characteristics of ROS generation, potential downstream mechanisms, and target organelles in VECs injured by iron overload have not been expounded yet. In this study, we elucidated the abovementioned issues through both in vivo and in vitro experiments. Mice were fed pellet diets that were supplemented with iron for 4 consecutive months. Results showed that the thoracic aortic strips' endothelium-dependent dilation was significantly impaired and associated with inflammatory changes, noticeable under brown TUNEL-positive staining in microscopy analysis. In addition, the serum content of asymmetric dimethylarginine (ADMA) increased, whereas nitric oxide (NO) levels decreased. Furthermore, the dimethylarginine dimethylaminohydrolase II (DDAHII) expression and activity, as well as the phosphorylation of endothelial nitric oxide synthase (eNOS) in aortic tissue, were inhibited. Human umbilical vein endothelial cells were treated with 50 μM iron dextran for 48 hours, after which the cell viability, NO content, DDAHII expression and activity, and phosphorylation of eNOS decreased and lactate dehydrogenase and caspase-3 activity, ADMA content, and apoptotic cells significantly increased. After the addition of L-arginine (L-Arg) or pAD/DDAHII, the abovementioned changes were reversed. By dynamically detecting the changes of ROS generation in the cytoplasm and mitochondria and interfering with different aspects of signaling pathways, we have confirmed for the first time that excessive ROS originates from the cytoplasm and activates the ROS-induced ROS release (RIRR) mechanism, leading to mitochondrial dysfunction. Together, our data suggested that excessive free iron ions produced excess ROS in the cytoplasm. Thus, excess ROS create one vicious circle by activating the ADMA/eNOS/DDAHII/NO pathway and another vicious circle by activation of the RIRR mechanism, which, when combined, induce a ROS burst, resulting in mitochondrial dysfunction and damaged VECs.

Double-edged effects and mechanisms of Zn2+ microenvironments on osteogenic activity of BMSCs: osteogenic differentiation or apoptosis

“…18,47 In addition, iron overload damaged the endothelial mitochondria via the ROS/ADMA/DDAHII/eNOS/NO pathway. 48 However, the inuence of excessive Zn 2+ ions on the apoptosis of BMSCs and the involved mechanism still remain obscure. These issues are the crucial factors to explore the negative effects of zinc microenvironments on the growth and osteogenic activity of BMSCs.…”

Current understanding of the metabolism of micronutrients in chronic alcoholic liver disease

“…Ferroptosis is a form of iron-dependent oxidative cell death that is morphologically, biochemically, and genetically different from autophagy and apoptosis. In addition, an excessive iron-induced ROS burst could lead to mitochondrial dysfunction, which is a typical characteristic of ferroptosis[ 37 ]. Inhibition of ferroptosis can relieve ethanol-induced liver injury[ 38 - 40 ].…”

Signalling, Metabolic Pathways and Iron Homeostasis in Endothelial Cells in Health, Atherosclerosis and Alzheimer’s Disease

“…Iron overload in ECs increases the expression of pro-inflammatory markers such as VCAM-1, ICAM-1 and E-selectin [ 270 ] and decreases the activity of eNOS, impairing the endothelial-dependent relaxation of blood vessels [ 271 ]. Consistently with a detrimental effect of excessive iron towards endothelial function, we found that downregulation of the mitochondrial transporter ABCB8 in HUVECs and Human Microvascular ECs induces iron-dependent mitochondrial ROS production resulting in reduced mitochondrial activity and EC senescence [ 135 ].…”