Iron metabolism is a crucial system in organisms, and it has been shown to be closely associated with ferroptosis (15). Ferroptosis not only influences the organism, but also has an impact on various other physiological processes. The overload of iron ions exacerbates the occurrence of cerebral hemorrhage, inducing the onset of ferroptosis (11). In the event of cerebral hemorrhage, blood vessels rupture, leading to the release of a substantial amount of blood and hemoglobin (43). Subsequently, microglia rapidly engulf the released hemoglobin and metabolize Fe²⁺/Fe³⁺ (30). The accumulation of Fe²⁺ and Fe³⁺ signifies an iron overload due to excessive iron build-up, and this is a key factor in ferroptosis (15). Released Fe³⁺ ions enter cells by binding with transferrin receptors on the cell membrane (44). Once inside the cell, Fe³⁺ can be reduced to Fe²⁺ by ferric reductase, a process that is facilitated by hydroxyl radicals. Accumulated ROS resulting from this process lead to the peroxidization of membrane lipids, subsequently leading to a loss of cellular function and cell death. This phenomenon represents one of the characteristic features of ferroptosis (44). Alternatively, excess Fe³⁺ can enter the unstable iron pool through solute carrier family 39 member 14 (45), further promoting ferroptosis. Excess Fe²⁺ can be re-oxidized to Fe³⁺, which is subsequently moved to the extracellular compartment, contributing to a series of iron metabolism processes associated with ferroptosis. Moreover, the presence of this free iron stimulates the production of lipid ROS via participating in the inflammatory response (46), inducing oxidative stress (47), and the Fenton reaction (22). Consequently, there is an accumulation of lipid ROS in vivo, which leads to DNA (48), protein (49) and lipid damage (50), ultimately resulting in cell death. Studies have also demonstrated that neurons require both the ferroptosis inhibitory factor, GPX4, and genes involved in the GPX4-synthesis pathway to survive under conditions of oxidative stress (21,51,52). GPX4 utilizes GSH to reduce peroxidized lipids, thereby preventing lipoatrophy (53). This suggests that neurons are prone to undergoing ferroptosis when exposed to oxidative stress (54). Additionally, the excess iron ions metabolized by microglia are expelled through the transferrin receptor system, leading to a significant accumulation of iron in neurons (55). Subsequently, the neurons undergo the classical reaction of ferroptosis (the Fenton reaction) (56). This reaction catalyzes the generation of ROS, further promoting lipid peroxidation and leading to lipid peroxide accumulation, ultimately inducing ferroptosis (57) (Fig. 1).

Lipid peroxidation is a process in which lipids lose hydrogen atoms due to the activity of free radicals or lipid peroxidases (58). This leads to oxidation, fragmentation and the shortening of lipid carbon chains, resulting in the generation of lipid free radicals, lipid hydroperoxides and reactive aldehydes (such as malondialdehyde and 4-hydroxynonenal) (59). Ultimately, this process causes the oxidative degradation of lipids, thereby damaging the cells. The end product of the Fenton reaction, -OH, fulfills a crucial role in ferroptosis (60). The increase in -OH radicals induces oxidative damage, leading to ferroptosis, and an exacerbation of the edema response at the site of cerebral hemorrhage (61,62). Building upon this, in the event of a cerebral hemorrhage, ferroptosis occurring in the affected region triggers the release of iron ions from blood cells (63). These iron ions instigate oxidative stress reactions, leading to the production of -OH radicals that subsequently target DNA, proteins, and lipid membranes. The resulting damage to these components often aligns with the manifestation of ferroptosis in the brain. Furthermore, the regions affected by ferroptosis are subjected to significant iron accumulation. This accumulation of iron has two subsequent effects. First, it stimulates microglia to continue engulfing the hemoglobin that is released from blood cells, leading to the secretion of yet more iron ions, creating a positive feedback loop (64). Secondly, the accumulating iron participates in various redox reactions in the brain, resulting in an increase in the production of -OH radicals (65) (Fig. 2). In other words, when cerebral hemorrhage occurs, there can be a positive feedback system loop promoting ferroptosis through Fe/-OH/DNA damage/Fe and Fe/microglia/Fe interactions. Consequently, the brain is subjected to further oxidative damage. This oxidative damage, in the presence of interleukin and nitric oxide, further compromises the integrity of the blood-brain barrier, ultimately leading to the development of cerebral edema at the site of hemorrhage (66).

Lipoxygenases (LOXs), a key component in the process of ferroptosis, have gained significant attention in recent years (67). One study demonstrated that conducting diphenyl-1-pyrenylphosphine experiments using HEK-293 cells revealed the formation of lipid hydroperoxides catalyzed by LOX (68). Based on the findings of this study, it is hypothesized that LOX activity may enhance the accumulation of lipid hydroperoxides within cells, thereby promoting ferroptosis. This may be associated with a specific ferroptotic pathway, such as the hypoxia-inducible factor-prolyl hydroxylase domain pathway (69). Therefore, measuring LOX activity and the levels of lipid hydroperoxides may serve as valuable assays for assessing the occurrence of ferroptosis (70), given that LOX activation may drive this process (71).

It is widely recognized that elevated levels of glutamate can exert neurotoxic effects on the brain during disease conditions (72). In response to this neurotoxic effect, system Xc⁻ fulfills a crucial function. System Xc⁻ is a heterodimeric cystine/glutamate antiporter protein that consists of two core components: Solute carrier family 7 member 11 (SLC7A11), serving as the catalytic subunit, and solute carrier family 3 member 2, which acts as an anchoring protein (73). In the context of stroke and its relevance to ferroptosis, particular attention has been focused on the SLC7A11 gene, which encodes a sodium-independent member of the anionic amino acid transport system (51). Its highly specific role in transporting cysteine (74) and glutamate (75) has been shown to be of great importance. In general, system Xc⁻ facilitates the extracellular transport of high intracellular concentrations of glutamate, whereas the anionic form of cysteine is transported in exchange for glutamate (76). The intracellularly transported cysteine is subsequently utilized for the synthesis of cysteine and GSH (77). GSH, a tripeptide composed of glutamate, cysteine and glycine, fulfills critical roles in various physiological functions, including the scavenging of free radicals, acting as an antioxidant (78) and maintaining cellular redox balance (79). GSH also activates various enzymes that influence cellular metabolic processes, and serves as an essential intracellular antioxidant in brain diseases (such as Parkinson's disease), contributing to the scavenging of free radicals and preserving redox balance both inside and outside of cells (80).

System Xc⁻ functions within the central nervous system, where microglia, the representative immune cells, are activated from a resting state and migrate to the injured brain (81). Activated microglia can exert anti-neuroinflammatory effects (82). However, it will inhibit the release of glutamate (83), which has the consequence of inhibiting the protective effects mediated by GSH in stroke. Following a stroke, two main areas are primarily affected: i) The infarct zone (where cell death occurs due to ischemia) (84); and ii) the surrounding ischemic penumbra (85). Alterations in glutamate are known to induce the occurrence of ferroptosis during a stroke, with a significant increase in extracellular glutamate levels released by neurons in these areas (86). Consequently, the balance between system Xc⁻ and glutamate transport is disrupted, leading to both a reduced intracellular uptake of glutamate and an inhibition of GSH synthesis due to the lack of necessary raw materials (87). Ultimately, this impairment in the cellular antioxidant defense results in an accumulation of lipid ROS, with the subsequent induction of ferroptosis.

GPX4, a downstream target of GSH action, functions as a unique intracellular antioxidant enzyme acting on membrane lipid repair, which is able to directly reduce peroxidized phospholipids produced in cell membranes (88,89), and it converts toxic lipid ROS into non-toxic lipid alcohols with the aid of GSH, which thereby reduces the level of oxidative damage to cells (90). However, the generation of large amounts of lipid ROS during stroke disrupts this oxidative balance, resulting in both a large accumulation of lipid ROS and the development of peroxidation, which is the main feature of ferroptosis (42). In addition, lipid ROS have also been shown to directly react with polyunsaturated fatty acids (PUFAs) on lipid membranes via oxidation, which directly leads to the occurrence of ferroptosis in cells (91).

AMPK has a critical role in ferroptosis following cerebral hemorrhage. AMPK is an energy sensor widely present in various tissues and cells. For instance, when it is present in brain tissue and microglial cells, it can alleviate secondary damage from cerebral haemorrhage (92). It regulates cellular energy metabolism balance (93), and participates in the regulation of multiple biological processes, including glycogen synthesis (94), fatty acid synthesis (95) and mitochondrial biogenesis (96). Studies have found that Spatholobi Caulis (SC) has the ability to activate AMPK (97). Subsequent 2,7-dichlorodihydrofluorescein diacetate experiments using HepG2 cells revealed that the combined effect of arachidonic acid (AA) and iron led to increased intracellular ROS production (97). However, pretreatment with SC suppressed the production of ROS when combined with AA and iron. This suggests that AMPK may possess antioxidant capacity (97). In in vivo experiments, using a mouse liver injury model, it was shown that oral administration of SC (which activates AMPK) could alleviate liver damage mediated by acute acetaminophen (by enhancing oxidative stress and increasing cell injury), exerting antioxidant effects (97). Therefore, both in vivo and in vitro experiments indicate that AMPK can play a role in protecting against oxidative damage, possibly by inhibiting ferroptosis to provide neuroprotection (97). Furthermore, in vitro and in vivo models of intracerebral hemorrhage were created by treating BV2 cells with hemoglobin and intraventricular injection of type IV collagenase into Sprague-Dawley rats, respectively. In vitro experiments showed a phosphorylation reaction of AMPK after initial intervention with AMPK inhibitors in BV2 cells. Subsequently, pharmacological intervention led to upregulation of ROS and lipid peroxidation levels (positive regulators of ferroptosis) in BV2 cells, and silenced GPX4 (a key negative regulator of ferroptosis) levels through the AMPK signaling pathway (92). In in vivo experiments, iron deposition at the site of brain injury was observed through Perl's staining (92). So, both in vitro and in vivo experiments have demonstrated the occurrence of ferroptosis during cerebral hemorrhage. Additionally, the AMPK signaling pathway, targeting GPX4 (a negative regulator of ferroptosis), was found to be involved in neuroprotection (92). Moreover, in the field of tumor research, it has been shown that AMPK can reduce the occurrence of ferroptosis by regulating intracellular lipid synthesis metabolism (98). When ferroptosis occurs, the AMPK-mediated phosphorylation of acetyl-coenzyme A carboxylase is considered to inhibit ferroptosis by limiting the production of PUFAs (99). However, the specific role and mechanism of AMPK in the field of cerebral hemorrhage and ferroptosis have yet to be fully elucidated. When AMPK activation protects neurons from damage caused by cerebral hemorrhage through a series of antioxidant, anti-inflammatory and anti-apoptotic pathways, this may result in a reduction in the occurrence of ferroptosis (98). However, following cerebral hemorrhage, AMPK activation may increase the levels of intracellular free iron ions, which, in turn, may exacerbate oxidative stress and cell damage, potentially contributing to ferroptosis (92). Therefore, the mechanism of action of AMPK in cerebral hemorrhage may potentially exert an impact on ferroptosis. However, the current research findings are both inconsistent and limited. Further research is needed to address this issue.

The SIRT2-p53 pathway exerts neuroprotective effects by modulating GPX4 and SCL7A11, inhibiting the occurrence of ferroptosis (100). SIRT2 is a NAD+-dependent deacetylase predominantly localized in the cytoplasm and has been demonstrated to be involved in the mechanisms of neuroinflammation- and neuroimmunology-related diseases (101). Additionally, P53, a tumor suppressor protein, has also been implicated in ferroptosis. In the context of ferroptosis, P53 has been shown to regulate the expression of key genes involved in iron metabolism, lipid peroxidation and antioxidant defense. P53 inhibits cystine uptake and sensitizes cells to ferroptosis by inhibiting the expression of SLC7A11, a key component of cystine/glutamate retrotransporters. Previously, the traumatic brain injury model using the controlled cortical impact (CCI) injury method found that knockdown of P53 could significantly block ferroptosis after CCI. In addition, inhibition of SIRT2 led to upregulation of acetylation and expression of P53, exacerbating ferroptosis after CCI. In other words, P53-mediated ferroptosis is involved in the pathogenesis of TBI, and SIRT2 exerts a neuroprotective effect on TBI by inhibiting P53-mediated ferroptosis (100).

The overall role of NCOA4 in cerebral stroke has been controversial, and its specific effects on ferroptosis, contributing to this process, have yet to be fully elucidated. Currently, studies on NCOA4 have revealed its potential dual role in either promoting (102) or inhibiting ferroptosis (103). Moreover, investigations on ovarian cancer cell models with manipulated NCOA4 expression have implicated NCOA4 in the processes of both formation and degradation of intracellular iron storage autophagosomes (104). Furthermore, in ovarian cancer cells, it has been observed that up-regulation of C-MYC (a gene regulating tumor proliferation) leads to a significant reduction in ROS content (104). On the other hand, overexpression of NCOA4 reverses these changes. These findings suggest that C-MYC may exert an inhibitory effect on ferroptosis in ovarian cancer cells through NCOA4-mediated ferritin autophagy (104). The process of NCOA4-mediated ferritin autophagy appears to play a role in suppressing ferroptosis in ovarian cancer cells (104). Autophagy-associated pathways induce an excessive degradation of ferritin, leading to an increase in the amount of free iron in neurons. Therefore, when cerebral ischemia occurs, NCOA4 may promote the release of iron ions and trigger ferroptosis in cells (105). Due to the large impact of NCOA4 in cerebral ischemia-reperfusion injury, it has been shown that the autophagy-related 5 (ATG5)-ATG7-NCOA4 pathway also has an important role in ferroptosis (106). Notably, NCOA4 is a selective autophagy receptor that is essential for mediating ferritin phagocytosis in certain tissues (for example, brain tissue) and cells (for example, red blood cells) (107,108). However, other studies have found that, under conditions such as hypoxic-ischemic brain injury, NCOA4 may protect cells from excessive damage caused by free iron ions via regulating intracellular iron metabolism. In this case, NCOA4 is considered as a factor that inhibits ferroptosis (109,110).

DFO induces ferroptosis during a stroke; DFO is an iron chelator that is able to reduce the accumulation and precipitation of iron in cells or tissues by binding to ferric (Fe³⁺) ions to form a stable complex, thereby allowing the removal of excess iron from cells (158). In the general field of cancer research, DFO has been shown to have good antioxidant activity (162); it acts as an anti-proliferative agent, and can induce apoptosis in cancer cells (163). At present, extensive research is being performed on the use of DFO in various iron overload-associated brain diseases (representing a class of neurological disorders caused by excessive accumulation of iron ions in the body, such as thalassemia). DFO has been shown to help regulate iron balance in the body, and to reduce neurological damage and functional impairments associated with iron overload (164). Similarly, significant research has also been performed on the role of DFO in neurodegenerative diseases (such as diseases that are characterized by neuronal cell death and functional impairments, including Alzheimer's disease, Parkinson's disease and Huntington's disease, which are associated with oxidative stress, abnormal neurodevelopment and protein aggregation) (153). Upon reviewing the literature, DFO has been shown to reduce the level of cell death through reducing free radicals (165), and to promote wound healing and healing in diabetic patients (166), although due to the potential toxicity of DFO itself (167), the research remains only at an early stage (160). In addition, animal experiments were used to demonstrate that the treatment of mice with DFO, wherein the aging process was simulated, led to a marked alleviation of the occurrence of ferroptosis, with the consequent inhibition of the increase of age spots in mice due to iron overload, thereby achieving the desired protective effect of delaying aging (168). In investigating the neurological and cognitive functions of aged mice in a study focused on the auditory cortex, the effect of alleviating ferroptosis in the brain was achieved by treatment with DFO, suggesting that DFO may be used to treat auditory and cognitive impairment resulting from age-associated problems (169). It is noteworthy that, although DFO primarily functions as an iron chelator in ferroptosis (158), investigations utilizing rodent models propose that DFO could impact stroke through gene-mediated mechanisms (69,170). Therefore, the role of DFO in ferroptosis warrants further investigation.

Fer-1 has been shown to inhibit ferroptosis during stroke (161). Traditionally, the most direct way to inhibit ferroptosis has been to utilize appropriate ferroptosis inhibitors. In the field of stroke-related research, the most commonly used ferroptosis inhibitor is Fer-1, whose main effects are to scavenge ROS and to inhibit erastin, the aforementioned class I inducer of ferroptosis (113,171). The effect of Fer-1 was verified with experimentally administered ventricular Fer-1 in experiments with rats, where it was found to inhibit erastin-induced accumulation of ROS in the cytoplasm and lipids, resulting in a decrease in ROS and lower levels of ferroptosis, demonstrating that Fer-1 could appreciably slow down the onset of ferroptosis in the brain (171). Notably, when Fer-1 intervention was present in the ventricles, the levels of iron deposition and neuronal degeneration were both significantly reduced, reducing the level of cellular damage, while also improving long-term motor and cognitive function (172). After a stroke, iron tends to accumulate in the damaged area, where it participates in oxidative stress reactions, leading to more cell damage and inflammatory responses (173). In addition, free iron is able to promote abnormal protein aggregation and neurodevelopmental abnormalities (174). The inhibitor Fer-1 may reduce oxidative stress reactions by reducing levels of free iron ions, thereby reducing cell damage and inflammatory responses following a stroke (166). Furthermore, inhibiting ferroptosis may also lead to the aggregation of abnormal proteins and abnormalities in neurodevelopment (175). Fer-1 exerts protective effects on cerebral ischemia-reperfusion injury by activating the Akt/GSK-3β pathway, indicating that ferroptosis may become a novel target in the treatment of ischemic stroke in the future (176). However, at present, few studies have reported on the specific effects and associated pathways of Fer-1 following a stroke, and therefore our knowledge is currently relatively limited; further experimental and clinical studies are required to explore its underlying mechanisms of action, and the potential therapeutic effects.

Through clinical trial studies, TCM combined with the influencing factors associated with ferroptosis has been shown to be more effective than single-drug treatment for stroke (177,178). It is well established that TCM herbs have antioxidant, anti-inflammatory and blood-brain barrier-protective effects, and that they can prevent stroke in advance by various means (179–181). For example, Danhong injection, a standardized injection comprising danshen (Salvia miltiorrhiza) and saffron, has been shown in studies to improve ferroptosis in ischemic stroke (182,183). In addition, moxibustion (a form of therapy that entails the burning of mugwort leaves), as one of the more frequently used treatments, has an important role in the treatment of cerebral infarction. It has been found that moxibustion can reduce neurological damage and neuronal death, reduce the accumulation of ROS and inhibit ferroptosis (184). In conclusion, the effects of certain Chinese medicines and their active ingredients on stroke both involve multiple pathways and are multi-targeted. In addition, the intervention of Chinese medicines on ferroptosis has been shown to be more stable and safer to use compared with small-molecule inducers or inhibitors of ferroptosis (185). For example, astragaloside IV can alleviate brain injury by inhibiting the ferroptosis-associated sequestosome-1/kelch-like ECH associated protein 1/nuclear factor erythroid 2-related factor 2 pathway (177,186). In addition, there are studies reporting that TCM treatment can reduce the side effects of drug toxicity in patients via targeting ferroptosis, leading to significant improvements in patient safety and quality of life (187,188). The impact that specific Chinese medicines and their active constituents have on stroke involves multiple pathways and targets, and these are summarized in Table IV (125,182,189–191).