Microglia serve a key role in the regulation of iron homeostasis in the central nervous system (CNS) [56]. Intuitively, iron homeostasis relies on the expression of iron-uptake and iron-release proteins on the cellular membrane. The mechanism of iron uptake in microglia has been uncovered, and microglial iron accumulation occurs in cerebral ischemia. It was found that microglia are able to take up non-transferrin-bound iron (NTBI) via a transferrin-independent mechanism [57, 58]. Moreover, transferrin receptor 1 (TfR1) has been identified in microglia both in vivo and in vitro [59, 60, 61]. It was reported that the expression of TfR1 and intracellular iron are both upregulated in hypoxia-induced microglia [60]. Divalent metal transporter 1 (DMT1), a pivotal protein for both transferrin-dependent and transferrin-independent iron uptake, has been identified in microglia [56, 62, 63, 64]. Hypoxia-inducible factor-1 (HIF-1) is known as a critical regulator, which is responsible for the facilitation, adaptation, and survival of cells from normoxia to hypoxia [65, 66]. Qian et al. [67] demonstrated that DMT1 is a target gene of HIF-1 and that silencing HIF-1 down-regulates DMT1 expression and ferrous uptake. Hence, the identification of TfR1, DMT1, and iron content in hypoxia indicates that microglia might take up transferrin-Fe via NTBI and TfR1/DMT1 pathways and might be regulated in hypoxia. Ferroportin 1 (Fpn1) is currently the only known microglial iron exporter [68]. It was also verified that Hephaestin (Heph), which is a critical ferroxidase, is expressed in microglia [69]. Yang et al. [70] reported that the levels of Fpn1 and Heph proteins were downregulated in MCAO models. Another study found that ischemic onset significantly upregulated the levels of the iron-import proteins TfR1 and DMT1 and decreased the expression of Fpn1 in reactive microglia, also indicating that iron deposition occurred in activated microglia after IS [71]. Thus, Fpn1/Heph may be the pathway of iron efflux in physiological and ischemia-induced microglia. Moreover, accumulated iron in hypoxia-induced microglia can stimulate ROS and modulate inflammatory processes via the generation of pro-inflammatory and anti-inflammatory cytokines [72]. In hypoxic-ischemic conditions, an excessive gliosis process can result in tertiary cerebral injury, and astrocyte cytotoxicity would be induced by microglial signaling, while the regular microglial response promotes the regeneration process. On the other hand, studies suggest that microglia activation prevents excessive iron accumulation in response to hypoxic damage [73, 74]. It was reported that excessively retained microglial iron is a key mediator of oligodendrocyte cytotoxicity in periventricular white matter following hypoxia [74]. Taken together, activated microglia play a crucial role in physiological and cerebral ischemia via regulating iron metabolism, and this has been partially corroborated, implying that a treatment strategy targeting microglial iron metabolism and ferroptosis modulation may have potential therapeutic value in treating IS.

Astrocytes, one of the most important components of the BBB, influence the regulation of iron homeostasis in the cerebral area [75, 76]. Studies have shown that astrocytes are responsible for acquiring nutrients such as iron from the circulating blood [77]. Astrocytes are also able to transport various types of iron, such as Tf-Fe [78], NTBI [79], and heme [80], through coupling with proteins such as ceruloplasmin (CP), which is known as the form of glycosylphosphatidylinositol-anchored proteins in the astrocyte membrane [81, 82, 83]. In addition, astrocytes can take up iron via the TfR1/DMT1 pathway, and it is transferred to proteins, including Fpn1 and CP [84]. Moreover, findings suggest that iron effluxes from astrocytes via the Fpn1/CP pathway [85]. CP is highly expressed in astrocytes and suppresses iron-induced lipid peroxidation [86]. Patients with aceruloplasminemia present serious iron accumulation in astrocytes and iron deposition, which is also observed in the astrocytes of mice consistently lacking CP [87, 88]. Ryan et al. [89] reported that the CP level was significantly upregulated in permanent MCAO models. Conversely, loss of CP dilated the lesion size and aggravated neurological function recovery with a decline in ferroportin and a raise in DMT1 proteins, indicating the neuroprotective effects of CP in IS via iron regulation in astrocytes [89]. In addition, hypoxia can stimulate the expression of HIF-1$\alpha$, as well as TfR1, DMT1, and Fpn1 proteins, thus promoting Tf-Fe and NTBI uptake and iron release in astrocytes and a progressive enhancement in cellular iron content [90]. Therefore, strategies targeting iron metabolism in activated astrocytes might play a role in IS pathogenesis.

Oligodendrocytes, a myelin-forming cell type in the cerebral area, have high iron requirements for normal function. Moreover, they require two- to three-fold higher energy levels than other cell types in the CNS during myelination. Oligodendrocytes also synthesize cholesterol, which is a highly metabolically demanding process and makes them vulnerable to hypoperfusion. The white matter, which is comprised of critical axonal projections, is especially vulnerable to ischemia and has attracted attention lately. About 95% of patients with IS suffer from white matter injury, accounting for half of the stroke total mean infarct volume [91]. It has been considered that white matter injury after stroke is highly correlated with axon degeneration, oligodendrocyte damage, and nerve demyelination [92]. A recent study showed that ischemia increases intracellular iron uptake with the upregulation of oligodendrocytes and myelin markers (markers of oligodendrocyte differentiation [MBP], oligodendrocyte-specific protein [OSP], and helix-loop-helix transcription factor) during the recovery phase of IS [93]. Michalski et al. [94] reported that OSP and MBP display early expression after the ischemic onset and promote protective and regenerative reactions in IS pathogenesis. Therefore, oligodendrocytes might have effects on white matter injury, such as myelination, after IS via iron regulation.

Activated microglia are frequently present during oxidative stress and the inflammatory processes of IS [97]. Specifically, they are closely connected to an excessive ROS response in the early stage of IS [98, 99]. NADPH oxidase (NOX), which is known as a primary source of ROS production, has been consistently reported to participate in the pathogenesis of cerebral ischemic injury [100]. Recently, NOX was also identified as a biomarker predicting ferroptosis via GPX4-independent control of the lipid ROS accumulation system [101, 102]. During ischemic conditions, NOX-mediated ROS production is reported to occur in microglia, and targeting NOX-dependent ROS generation suppresses microglial activation and polarization and ferroptosis [103]. Peroxiredoxin-1 (Prdx1) is known as one of the typical antioxidant enzymes, and it can inhibit ROS deposition and keep the reduction-oxidation status in both normal oxidative metabolism and oxidative stress [104, 105]. In a recent study, Kim et al. [106] identified stroke-associated microglia (SAM) and showed that Prdx1 deficiency decreased the extent of SAM in IS and exacerbated cerebral injury, which indicates that SAM might have potential antioxidant effects on stroke-induced microglia. Under neuroinflammatory conditions, reduced ROS levels and fewer apoptotic neurons present in CX3CR1-deficient MCAO mice suppressed the proliferation and regulated the polarization of microglia, which inhibited the process of releasing inflammatory cytokines to improve the ischemic brain injury outcome [107]. Consistently, inhibiting the production of microglial proinflammatory cytokines and lipid peroxidation via silencing acyl-CoA synthetase long-chain family member 4 (ACSL4) in IS has proved to inhibit ferroptosis in neurons [108].

Inhibiting excessive ROS production after IS has been proposed as the most effective strategy to improve the prognosis outcome. Elastin-derived peptides are shown as the scavengers of free radicals via the induced activities of antioxidant enzymes, which are detectable in the cerebrospinal fluid of patients after IS [109, 110]. In mouse astrocytes induced by OGD, the Val-Gly-Val-Ala-Pro-Gly (VGVAPG) peptide upregulated nitric oxide release during ROS accumulation [111]. However, the effects were reversed by decreasing ROS production when knocking down the galactosidase beta 1 gene, which indicates that the VGVAPG peptide has pro-survival effects on activating astrocytes via mediating ROS regulation [111].

The functional impairment of mitochondria, resulting in increased ROS deposition and oxidative stress in cerebral ischemia, has been shown to initiate and enhance the vulnerability of cells to ferroptosis [19, 112]. Some important modulators, such as triiodo-l-thyronine and inositol trisphosphate receptor type 2, which can promote astrocyte mitochondrial adenosine triphosphate (ATP) production and the disruption of astrocytic Ca${}^{2+}$ signaling, respectively, have been proposed to have effects on mitochondrial dysfunction [113, 114].

Oligodendrocytes and myelin damage cause the functional impairment in IS. Glutamate, which has been recently proposed to promote ferroptosis [115], also contributes to oligodendrocyte excitotoxicity and axonal dysfunction during IS onset [116, 117]. In addition, oligodendrocytes are known to express purinergic receptors, and ATP release and P2X7 receptor activation result in white matter injury in ischemia [118, 119]. Ca${}^{2+}$ influx is the core event in glutamate and ATP excitotoxicity, which further contributes to increased ROS production [118, 120, 121]. It has been reported that ferroptosis contributes to spinal cord injury-induced white matter damage, and ferrostatin-1, a potent inhibitor of ferroptosis, was demonstrated to inhibit excessive ROS deposition and reduce the expression of ferroptosis-related genes and their products. The products of these genes are iron-responsive element binding protein 2 and prostaglandin endoperoxide synthase 2, which can further suppress ferroptosis in oligodendrocytes, thus alleviating white matter injury and promoting functional reinstitution. Plenty of research indicates that oligodendrocytes might be involved in IS via ROS-induced ferroptosis, but further investigations are needed.

Evidence has suggested that fatty acids (FAs) have a close relationship with microglia [125]. Basically, FAs are present in high amounts in the cellular membranes of microglia, which can further be metabolized into bioactive derivatives to mediate the localization and function of proteins and downstream signaling pathways [126]. Microglia can also express various lipid-sensitive receptors, including toll-like receptors, triggering receptors expressed on myeloid cells 2 and receptors for FA derivatives [127]. In addition, it has been shown that FAs can be stored within lipid droplets (LDs) in microglia to regulate the neuroinflammatory response [128]. Saturated, monounsaturated, and polyunsaturated fatty acids (PUFA) are the three main families of FAs, all of which have shown strong effects on microglial cells. Microglia-activated phorbol myristate acetate treatment induces iron accumulation and leads to iron-dependent lipid peroxidation [129]. Moreover, inducible nitric oxide synthase is greatly increased to inhibit ferroptosis by decreasing arachidinate 15-lipoxygenase activity in microglia [130]. These studies indicate that microglia activation may be involved in ferroptosis via inducing lipid peroxidation.

ACSL4 is an important isozyme for the metabolism of PUFA, which results in ferroptosis-mediated cerebral damage at ischemia onset when activated [25, 131]. Cui et al. [25] reported that the ACSL4 level is inhibited in the early phase of IS through hypoxia-inducible factor 1 alpha. They demonstrated that ACSL4 aggravated neuronal death by exacerbating lipid peroxidation-derived ferroptosis and promoting inflammatory cytokine production in microglia simultaneously [25]. Hence, inhibiting microglial lipid peroxidation and inflammatory-induced ferroptosis may be therapeutic targets in treating IS.

Lipids play a fundamental role in astrocyte function, such as energy generation, membrane fluidity, and cell-to-cell signaling [132]. It has been reported that reactive astrocytes drive the death of neurons via lipoparticle secretion [133]. Acrolein, a neurotoxin that is endogenously produced by lipid peroxidation during ischemic onset, induces astrocytic inflammation through the NLR family pyrin domain-containing protein 3 inflammasome [134, 135], suggesting that astrocytes might have neurotoxic effects on neurons via lipid peroxidation during IS.

However, studies have illustrated that the crosstalk between astrocytes and neurons might protect neurons from lipid peroxidation at ischemia onset. LDs are one of the fundamental components of lipid metabolism in astrocytes, thus playing a critical role in maintaining astrocyte–neuron homeostasis [136]. Lipid particle-mediated FA transfer is involved in the deposition of astrocytic LDs after acute stroke and protects neurons from lipid peroxidation [137]. In the acute IS model, omega-3 PUFA present a high neuroprotective and anti-inflammatory potential via targeting the function of astrocytes to alleviate neuronal injury [138]. This indicates that neuron–astrocyte metabolic coupling might suppress ferroptosis via inhibiting lipid peroxidation. Therefore, the dual role of astrocytes in lipid metabolism during IS pathogenesis needs to be investigated.

Oligodendrocytes enwrap CNS axons with myelin, which has an extremely high lipid content and a peculiar lipid composition with a ratio of 2:2:1 cholesterol:phospholipid:glycolipid. As previously mentioned, oligodendrocytes and myelin injuries underlie the neurological damage in the ischemic cerebrum [139, 140]. ATP-binding cassette transporter A1 (ABCA1) has been shown to be one of the representative genes that play a key role in lipid metabolism when treated with the ferroptosis inducer [141]. Li et al. [142] reported that ABCA1 deficiency decreases myelination and oligodendrogenesis and deteriorates the prognosis after IS, indicating that oligodendrocytes might be involved in ferroptosis via lipid metabolism at ischemia onset, but further investigation is needed.