JNK/p66Shc/ITCH Signaling Pathway Mediates Angiotensin II-induced Ferritin Degradation and Labile Iron Pool Increase

Abstract

Angiotensin II (Ang II) induces deleterious changes in cellular iron metabolism and increases the generation of reactive oxygen species. This leads to an impairment of neuronal and vascular function. However, the mechanism underpinning Ang II-induced changes in iron metabolism is not known. We hypothesized that Ang II-induced ferritin degradation and an increase in the labile iron pool are mediated by the c-Jun N-terminal kinase (JNK)/p66Shc/ITCH signaling pathway. We show that Ang II treatment induced ferritin degradation in an endothelial cell lines derived from the bovine stem pulmonary artery (CPAE), human umbilical vein endothelial cells (HUVEC), and HT22 neuronal cells. Ferritin degradation was accompanied by an increase in the labile iron pool, as determined by changes in calcein fluorescence. The JNK inhibitor SP600125 abolished Ang II-induced ferritin degradation. Furthermore, the effect of Ang II on ferritin levels was completely abolished in cells transfected with vectors encoding catalytically inactive variants of JNK1 or JNK2. CPAE cells expressing inactive ITCHor p66Shc (substrates of JNK kinases) were completely resistant to Ang II-induced ferritin degradation. These observations suggest that Ang II-induced ferritin degradation and, hence, elevation of the levels of highly reactive iron, are mediated by the JNK/p66Shc/ITCH signaling pathway.Nutrients 2020, 12, 668 2 of 12 Vascular diseases are associated with an increase in the production of reactive oxygen species (ROS) in the vessel wall and with endothelial dysfunction. It is generally assumed that increased ROS levels, particularly superoxide (O 2 .-) levels, on the one hand reduce nitric oxide (NO) bioavailability and on the other give rise to deleterious peroxynitrite. Ang II is a well-known inducer of endothelial cell activation and smooth muscle cell proliferation resulting from ROS-induced signal transduction [7,8]. ROS production by nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) and the activation of redox-dependent signaling cascades by Ang II are considered critical processes underlying neuronal-vascular injury and inflammation [9,10]. Further, an increasing number of reports demonstrate that Ang II induces iron accumulation in several tissues, including the aorta and neuronal tissue [11]. This might play a role in the impairment of vascular function and arterial remodeling induced by Ang II, possibly by enhancing iron-dependent oxidative stress [12]. In addition, iron chelation suppresses Ang II-induced upregulation of TGF-β1 in the heart and attenuates vascular dysfunction in the aorta [13,14]. The majority of intracellular iron is stored by ferritin, a protein composed of L and H subunits. Ferritin-stored iron is considered to be safe (inert), as it does not participate in free radical-generating reactions, e.g., the Fenton reaction and others. Hence, the iron-dependent formation of ROS is associated with the levels of free iron bound to low-molecular weight compounds, such as nucleotides and amino acids, etc. Th...

Effect of 8-Day Fasting on Leukocytes Expression of Genes and Proteins Involved in Iron Metabolism in Healthy Men

“…Observed decrease in genes involved in iron storage and export and increase in those responsible for iron import into a cell resemble those data when only iron deficiency was applied. Conversely, we did not observe significant changes in proteins like ferritin H, L and ferroportin after 8 d of fasting what has been shown in iron deficiency state induced e.g., by iron chelator [51]. Certainly, more study is needed to fully understand the effects of fasting on iron metabolism.…”

“…FTL is mainly responsible for iron storage and its synthesis is controlled on both, transcriptional and translational levels. Previously, we have demonstrated that during stress, when stress activated protein kinases are functioning, ferritin undergoes partial degradation and releases iron [ 51 ]. Increase in iron levels affects the activity of iron-responsive proteins (IRP1 and IRP2) and leads to an increased translation of ferritin.…”

Effect of Ischemic Preconditioning on Marathon-Induced Changes in Serum Exerkine Levels and Inflammation

“…Thus, it can be expected that an increased accumulation of stored iron (ferritin iron) may exert an adverse effect during stress, such as exhaustive exercise. For example, while c-jun terminal kinase (JNK) is activated during exercise, it is indispensable for ferritin degradation during stress (Borkowska et al, 2020a). Conversely, adaptation to training leads to a reduction of body iron stores, as athletes and recreationally active people have relatively low serum ferritin levels, as shown in several studies (Constantini et al, 2000;Kortas et al, 2015).…”

“…Iron that is not metabolically active is stored in ferritin so as to protect it from free radical-generating reactions. However, there is some evidence that stored iron can be liberated under stress conditions, when stress-activated protein kinasedependent ferritin degradation takes place (Borkowska et al, 2020a). These findings imply that stored iron is not "safe, " what supports earlier observation (Borkowska et al, 2020b).…”

Homocysteine-induced decrease in HUVEC cells’ resistance to oxidative stress is mediated by Akt-dependent changes in iron metabolism

“…In addition, some reducing agents can liberate iron from ferritin [ 33 ]. In fact, these and many other studies suggest that iron is not safely stored in ferritin [ 10 , 34 ]. In our model, an initial decrease in ferritin protein level was observed at relatively early time points which evidently indicates ferritin degradation.…”