Combined Deficiency in Glutathione Peroxidase 4 and Vitamin E Causes Multiorgan Thrombus Formation and Early Death in Mice

Abstract

Rationale: Growing evidence indicates that oxidative stress contributes markedly to endothelial dysfunction. The selenoenzyme glutathione peroxidase 4 (Gpx4) is an intracellular antioxidant enzyme important for the protection of membranes by its unique activity to reduce complex hydroperoxides in membrane bilayers and lipoprotein particles. Yet a role of Gpx4 in endothelial cell function has remained enigmatic. Objective: To investigate the role of Gpx4 ablation and subsequent lipid peroxidation in the vascular compartment in vivo. Methods and Results: Endothelium-specific deletion of Gpx4 had no obvious impact on normal vascular homeostasis, nor did it impair tumor-derived angiogenesis in mice maintained on a normal diet. In stark contrast, aortic explants from endothelium-specific Gpx4 knockout mice showed a markedly reduced number of endothelial branches in sprouting assays. To shed light onto this apparent discrepancy between the in vivo and ex vivo results, we depleted mice of a second antioxidant, vitamin E, which is normally absent under ex vivo conditions. Therefore, mice were fed a vitamin E–depleted diet for 6 weeks before endothelial deletion of Gpx4 was induced by 4-hydroxytamoxifen. Surprisingly, ≈80% of the knockout mice died. Histopathological analysis revealed detachment of endothelial cells from the basement membrane and endothelial cell death in multiple organs, which triggered thrombus formation. Thromboembolic events were the likely cause of various clinical pathologies, including heart failure, renal and splenic microinfarctions, and paraplegia. Conclusions: Here, we show for the first time that in the absence of Gpx4, sufficient vitamin E supplementation is crucial for endothelial viability.

An Overview of Pathways of Regulated Necrosis in Acute Kidney Injury

“…They reported their findings on endothelial-specific conditional Gpx4 floxed mice, a model in which endothelial ferroptosis is induced by tamoxifen administration. 119 Under homeostatic conditions, these mice did not show apparent abnormalities. When these mice were fed vitamin E-depleted chow before endothelial ablation of GPX-4, detachment of endothelium with massive thrombotic microangiopathy and renal failure occurred and subsequently all mice rapidly died of multi-organ failure.…”

“…118 It remains unclear if ferroptosis plays a role in endotoxic shock-associated renal failure because the later-generation ferrostatins (or conditional ablation of Gpx4) were not tested in this model. A study by Wortmann et al 119 highlighted that besides RN in tubular epithelial cells, other parenchymal cells also are of importance in renal homeostasis. They reported their findings on endothelial-specific conditional Gpx4 floxed mice, a model in which endothelial ferroptosis is induced by tamoxifen administration.…”

Glutathione peroxidase 4 prevents necroptosis in mouse erythroid precursors

“…Thus, vitamin E acts as the compensating ROS scavenger and provides a back-up system for Gpx4 in vivo, as it has recently been suggested in endothelial cells. 33 hemolytic anemia, but rather are characterized by insufficient erythropoiesis. Lipid peroxidation, ROS formation, and induction of necrosis have been linked by several groups [39][40][41][42] to an increase in redox-active iron, the so-called intracellular labile iron pool, and to an increase in lysosomal iron.…”

“…33 To examine whether this was also the case during reticulocyte maturation, and to restrict Gpx4 deletion to the hematopoietic system, we performed adoptive transfer experiments using bone marrow derived from Gpx4 F/F or Gpx4 D mice.…”

Role of Glutathione Peroxidase 4 in Glutamate-Induced Oxytosis in the Retina

“…We have elucidated the roles of GPx4 in photoreceptors [18], retinal pigment epithelium [19], and conjunctival cells [20]. Systemic abrogation of GPx4 leads to lethality on embryonic day 7 [21], and studies have identified drastic disease phenotypes of photoreceptors [18], cerebral neurons [22], vascular endothelium [23], and spermatocytes in conditional knockout mice [24]. …”