Selenium (Se) is an essential trace element required for maintaining redox homeostasis and cellular antioxidant defenses through its incorporation into selenoproteins such as glutathione peroxidases (GPxs) and thioredoxin reductases [1]. Insufficient Se intake disrupts redox balance, leading to reactive oxygen species (ROS) accumulation and impaired antioxidant defense [2], particularly affecting the cardiovascular system [3]. Indeed, Se deficiency has been strongly linked to ischemia/reperfusion (I/R) injury, in which excessive ROS generation and weakened GPx activity aggravate oxidative damage to the vascular endothelium, impair mitochondrial function, and exacerbate cardiomyocyte death [4]. In addition, in the chicken embryo model, Se deficiency has been shown to induce oxidative stress and endoplasmic reticulum (ER) stress-dependent apoptotic signaling in vascular endothelial cells, ultimately leading to vascular structural disorganization and increased vascular permeability [[5], [6], [7]]. Se deficiency also directly compromises endothelial barrier function. Pan et al. [8] demonstrated that Se deficiency disrupts tight junction integrity in broiler vein endothelial cells. Accumulating evidence indicates that Se deficiency is closely associated with vascular inflammatory injury [9]. Se deficiency decreases selenoprotein expression and antioxidant defenses in chicken arteries, leading to enhanced inflammatory cytokine production [10,11]. In addition, Se deficiency exacerbates endothelial injury and inflammatory responses in chicken veins through excessive ROS production [12]. Despite these advances in avian models, it remains unclear whether Se deficiency induces similar inflammatory injury in venous tissues of large-animal models, particularly in pigs. Moreover, previous studies have predominantly focused on Se deficiency-induced oxidative stress and apoptosis in myocardial or vascular tissues, whereas whether Se deficiency disrupts vascular homeostasis through iron-dependent cell death mechanisms has been rarely explored. Notably, ferroptosis links redox imbalance with dysregulated iron metabolism, providing a mechanistic framework distinct from classical oxidative stress-mediated injury.

Ferroptosis is an iron-dependent cell death modality characterized by excessive lipid peroxidation [13], which has been shown to be closely associated with the development and progression of various cardiovascular diseases [14,15]. In the vascular system, oxidized low-density lipoprotein (ox-LDL) can induce ferroptosis in vascular endothelial cells, thereby disrupting vascular endothelial integrity and function [16]. This makes lipids in the blood more prone to deposit within the vessel wall, promoting the formation of atherosclerotic plaques [17]. Bai et al. [18] further confirmed that in a high-fat diet-induced atherosclerosis model, the ferroptosis inhibitor Fer-1 effectively alleviated vascular endothelial injury and improved vascular function. Emerging evidence indicates that endothelial ferroptosis is closely linked to vascular inflammation. Suppression of ferroptosis alleviates Lipopolysaccharide (LPS)-induced vascular endothelial cell inflammatory responses [19], while in cardiovascular diseases, ferroptotic cell death promotes oxidative stress and inflammation, and its inhibition mitigates vascular injury [20]. Consistently, endothelial cell ferroptosis has been shown to activate the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome, further amplifying vascular inflammation [21]. Accumulating studies emphasize that metabolic homeostasis and nutrient states broadly influence ferroptotic regulation. Peroxisomal lipid metabolism has been shown to modulate ferroptosis susceptibility in metabolic disorders, linking core lipid metabolic pathways to ferroptotic execution [22]. And dietary components and micronutrients have emerged as key modulators of ferroptosis by regulating iron homeostasis, antioxidant defenses, and lipid peroxidation [23]. However, how nutritional factors such as Se deficiency regulate this process remains to be elucidated.

NCOA4 functions as a selective cargo receptor and is a key regulator of ferritinophagy. Mechanistically, NCOA4-mediated ferritinophagy plays an increasingly important role in maintaining intracellular iron homeostasis by facilitating ferritin transport and iron release [[24], [25], [26]]. The Adenosine 5′-monophosphate-activated protein (AMPK)- kinasemammalian target of rapamycin (mTOR) signaling axis has recently emerged as a critical upstream regulator of NCOA4-mediated ferritinophagy. Energy stress or nutrient deprivation activates AMPK, suppresses mTOR activity, and thereby enhances ferritinophagic flux and intracellular iron mobilization [27]. Nevertheless, the dysregulation of NCOA4 activity has been linked to diverse pathological processes [28,29]. NCOA4 promotes the degradation of ferritin to release labile iron, thereby triggering ferroptosis in vascular endothelial cells and driving aortic inflammation and the progression of atherosclerosis [30]. Moreover, certain pathological stimuli, such as high-dose ionizing radiation, can further accelerate vascular injury and plaque formation by activating the p38/NCOA4-ferroptosis axis [31]. There also exists a close link between cytosolic iron overload induced by ferritinophagy and mitochondrial iron overload. This accumulation of iron burden may represent a key mechanism of ferroptosis. Iron ions not only catalyze ROS generation through the Fenton reaction but are also transported into mitochondria by the newly identified mitochondrial iron transporter SFXN1 [32,33]. SFXN1 is predominantly localized to the mitochondrial inner membrane and functions to import cytosolic Fe²⁺ into the mitochondrial matrix. NCOA4-mediated ferritinophagy has been shown to upregulate SFXN1 expression, leading to mitochondrial iron overload and subsequently triggering a series of mitochondrial structural and functional impairments [34,35]. Studies have revealed that targeted reduction of mitochondrial iron (achieved through genetic modulation or permeable chelators) can mitigate myocardial injury and improve cardiac function [36]. Specifically, Li et al. [32] demonstrated that cytosolic iron overload activates SFXN1, a mitochondrial membrane-localized protein, subsequently triggering mitochondrial iron overload and leading to ferroptosis in myocardial injury. However, whether SFXN1 links ferritinophagy-derived cytosolic iron to mitochondrial dysfunction and ferroptosis under Se-deficient conditions is unknown.

Given the close resemblance of porcine cardiovascular anatomy, lipid metabolism, and micronutrient requirements to those of humans, this model provides clinically relevant insights into Se deficiency-associated vascular injury that may not be fully captured in rodent models. Therefore, this study aims to elucidate the specific mechanisms by which Se deficiency induces venous injury in pigs, with a particular focus on the regulatory roles of NCOA4-mediated ferritinophagy and SFXN1-associated mitochondrial iron overload. Our findings provide new mechanistic insights into Se deficiency-induced vascular dysfunction from the perspective of iron metabolism and ferroptosis.