The PINK1/Parkin pathway is one of the most important pathways in the mitophagy pathway and most of the mitophagy is mediated by this pathway (Painter et al., 2020). PINK1 is a serine/threonine ubiquitin kinase located primarily in the inner mitochondrial membrane, and its downstream molecule, Parkin, is an E3 ubiquitin ligase (Zhao et al., 2024). Normally, PINK1 is rapidly cleaved and degraded by mitochondrial processing protease (MPP) and proteolytic PINK1 protein [pesenilin-associated rhomboid-like (PARL)], and is therefore extremely low in mitochondria (Geisler et al., 2010; Poole et al., 2010). Under stress, the mitochondrial membrane potential is depolarized and related proteases such as MPP and PARL are inhibited. Originally low levels of PINK1 begin to accumulate and become phosphorylated at the Ser228 and 402 sites, thereby activating PINK1 kinase (Sekine and Youle, 2018). Subsequently, cytoplasmic Parkin translocates to the damaged mitochondrial outer membrane. Mediated by PINK1, Parkin’s Ser 65 site is phosphorylated and initiates its E3 ubiquitin ligase activity, resulting in ubiquitin phosphorylation of mitochondrial outer membrane protein junctions (Harper et al., 2018). Phosphorylated ubiquitin has a high affinity for Parkin, which leads to Parkin recruitment, and newly recruited Parkin will further ubiquitinate mitochondrial outer membrane proteins, thus forming a strong positive feedback loop that amplifies ubiquitin signaling and promotes the aggregation of autophagy receptor 62 (isolation vesicle 1) at the same time (Matsuda and Yamano, 2020). P62 contains an LC3 binding domain (LIR), which helps transport damaged mitochondria to autophagosomes by binding to microtubule-associated protein 1 light chain 3 (LC3) on the autophagosome membrane via LIR. In addition, P62 has a specific ubiquitin-binding domain, UbA (ubiquitin-associated binding domain), a structure that allows P62 to directly recognize and bind to ubiquitinated proteins (Danieli and Martens, 2018). Ubiquitin (Ub) is a small protein that attaches to other proteins by ubiquitination. The process of ubiquitination involves three enzymes: activating enzyme (E1), conjugating enzyme (E2), and ligase (E3), which work in concert to attach ubiquitin molecules to target proteins. During mitophagy, the ubiquitinated protein or organelle is recognized by the p62 autophagy receptor. In conclusion, PINK1 accumulates in mitochondria and phosphorylates at Ser228 and 402 sites, followed by the transfer of Parkin to the OMM and phosphorylates at Ser 65, initiating its E3 ubiquitin ligase activity and phosphorylating the Ub of the mitochondrial outer membrane protein linkage. Then P62 starts to recruit and binds to LC3-II, which sends the damaged mitochondria to autophagosomes and is phagocytosed by autophagosomes. Mature autophagosomes bind to lysosomes to form autophagolytic lysosomes, and eventually the damaged mitochondria are degraded (Lazarou et al., 2015).

FUNDC1, an autophagy receptor protein located in the OMM and containing a transmembrane LIR structural domain, regulates mitochondrial fusion/fission (DRP1 and OPA1) and induces mitophagy under hypoxic conditions (Chen et al., 2016). In the normal state, FUNDC1 is stably present in the OMM and remains highly phosphorylated (Ser13 and Tyr18 sites phosphorylated) (Greene et al., 2012). FUNDC1 activity is regulated by a variety of signaling pathways. Bcl-2 is primarily involved in apoptosis, but it also plays an important role in the regulation of mitophagy (Dikic and Elazar, 2018). Bcl-2 interacts with phosphoglycerate mutase/protein phosphatase (PGAM5), a member of the phosphoglycerate mutase family, and prevents dephosphorylation of the LIR structural domain of FUNDC1, thereby inhibiting FUNDC1-mediated mitophagy (Wu H. et al., 2014). However, under hypoxia, PGAM5 dephosphorylates the LIR structural domain of FUNDC1 and binds to LC3, thereby inducing mitophagy and helping the cell to remove damaged mitochondria and maintain cellular stability (Wu W. et al., 2014; Chen et al., 2016). LC3 is a key protein in the autophagy process, which is involved in the formation and maturation of autophagosomes. In mitophagy, the interaction between LC3 and FUNDC1 is particularly important, and the LIR domain of FUNDC1 directly binds to LC3 to promote autophagosome formation, encapsulation and disassembly of damaged mitochondria (Wu W. et al., 2014). In addition, AMPK also regulates mitophagy. Activated AMPK under normal conditions inhibits mitophagy by activating AKT, which promotes the phosphorylation of FUNDC1. Under energy-deficient conditions, activated AMPK dephosphorylates FUNDC1, thereby activating mitophagy. In conclusion, FUNDC1, Bcl-2, and LC3 interact with each other to form a complex and sophisticated regulatory system. Dephosphorylated FUNDC1 is able to bind to LC3, thus activating mitophagy. At the same time, Bcl-2 in turn can affect the activity of FUNDC1, thereby regulating the process of mitophagy. This ensures that mitophagy is able to regulate mitochondrial mass in a timely and accurate manner under physiological and pathological conditions, which is crucial for the brain with high energy demands.

Autophagy related gene (Atg) is an important gene in the autophagy process, and UNC-51-like kinase1 (ULK1) is the only serine/threonine protein kinase among the 38 known autophagy related proteins, which is an indispensable component of autophagic vesicles. The Atg/ULK1 complex is the major molecule that initiates mitophagy. The Atg/ULK1 complex consists of the interaction of ULK1, family interacting protein of 200 kDa (FIP200), Atg13, and Atg101. The PI3K/AKT/mTOR signaling pathway is an important pathway in the regulation of mitophagy. Phosphoinositide 3-kinase (PI3K) consists of different catalytic subunits, each with a different function. The α-catalytic subunit of PI3K inhibits autophagy while the β-catalytic subunit promotes autophagy (Kma and Baruah, 2022). When ROS are over-accumulated, the β-catalytic subunit of PI3K is activated to produce inositol triphosphate diphosphate (PIP3), and accumulation of PIP3 leads to the recruitment and activation of AKT (also known as protein kinase B) (Wang et al., 2020). Activation of AKT inhibits the downstream mTOR. mTOR is a complex of 2 protein kinases, mTOR1 and mTOR2, that is sensitive to cellular nutrient levels and plays a role in the regulation of cell growth and survival through autophagy. mTOR is a key factor in the inhibition of mitophagy as a key factor in the inhibition of mitophagy. When mTORC1 activity is reduced, it promotes the phosphorylation of ULK1 and Atg13, which negatively regulates the ULK1 complex and promotes the formation of autophagic vesicles. With the activation of the ULK1 complex, Atg9 vesicles can only be recruited to the site of autophagosome formation, thus initiating autophagy. It was shown that cognitive deficits in VaD rats could be improved through the PI3K/Akt/mTOR signaling pathway, which may be related to the increase in the level of mitophagy and the inhibition of neuronal apoptosis, which attenuated neuronal damage and mitochondrial dysfunction (Zheng et al., 2021).

FOXOs belong to subgroup O of the forkhead family of proteins, which play important roles in the regulation of cell autophagy, mitochondrial function, proliferation and differentiation, oxidative stress, etc. The FOXOs family contains four members, FOXO1, FOXO3, FOXO4 and FOXO6. Among them, FOXO1 is the only member of the forkhead family of transcription factors with a forkhead structure, and its activity is regulated by PI3K/AKT/mTOR and AMPK signaling pathways (Brunet et al., 1999). The PI3K/AKT/mTOR signaling pathway is associated with cell growth and proliferation. Under physiological conditions, the PI3K/AKT/mTOR signaling pathway is highly active, and activated AKT phosphorylates the Ser25 site of FOXO1, leading to its translocation from the nucleus to the cytoplasm, thus inhibiting its transcriptional activity. Under stress or energy deprivation, AMPK was activated and the above pathway was inhibited. FOXO1 entered the nucleus to activate the expression of LC3 gene and increased the level of mitophagy, thus enabling the cell to maintain energy homeostasis under energy deprivation.

AMPK (adenylate-activated protein kinase) regulates mitophagy by directly phosphorylating ULK1 or indirectly acting on the ULK1 complex (Egan et al., 2011). Under hypoxia, lack of energy, or elevated ROS, the intracellular AMP/ATP ratio is elevated, and AMP binds directly to AMPK, thereby activating AMPK (Herzig and Shaw, 2018; Matzinger et al., 2020). AMPK can directly phosphorylate specific amino acid residues (e.g., Ser317 and Ser777) of the ULK1 protein, thereby enhancing ULK1 activity and initiating autophagy. ULK1 forms a complex with several key proteins, such as ATG13, FIP200 (RB1CC1), and ATG101, which together regulate the initiation of autophagy. AMPK can enhance the interaction between ATG13 and ULK1 by phosphorylating ATG13, thereby promoting the stability and function of the autophagy complex (Herzig and Shaw, 2018; Lin and Hardie, 2018). In addition, AMPK activates ULK1 by inhibiting signaling associated with mTORC1. mTORC1 normally inhibits ULK1 under nutrient-sufficient conditions, thereby inhibiting autophagy. When AMPK is activated, it can derepress ULK1 by inhibiting mTORC1 or phosphorylating proteins that interact with mTORC1. At low energy or activated AMPK can promote FUNDC1 dephosphorylation, which activates mitophagy. Studies have shown that activation of AMPK increases FUNDC1 expression (Cai et al., 2021). In contrast, under normal conditions, activated AMPK inhibits mitophagy by activating AKT and promoting phosphorylation of FUNDC1. Metformin is an adenosine monophosphate-activated protein kinase (AMPK) agonist that crosses the BBB and activates AMPK to exert neuroprotective effects (Kersten et al., 2022; Guo et al., 2023). A recent study has shown that metformin is neuroprotective by activating the AMPK/ULK1/PINK1/Parkin signaling pathway and regulating the levels of apoptosis and mitophagy in a hyperglycemic constructed CI/RI animal model and a cellular model of hyperglycemic incubation oxygen–glucose deprivation/reperfusion (OGD/R) (Guo et al., 2023).

Mitochondrial DNA (mtDNA) is a special kind of DNA that exists in the mitochondria of cells. mtDNA is usually a circular double-stranded, unlike the linear DNA in the nucleus. Due to the insufficient repair system of mtDNA and the lack of protective histones, mtDNA is easily damaged when oxidative stress occurs (Kazak et al., 2012). Damaged mtDNA can lead to dysfunction of the mitochondrial respiratory chain, resulting in elevated levels of ROS, which will further damage mtDNA, it was found that ATAD3B contains a LIR motif, which binds to LC3 and promotes mitophagy in a manner that is independent of the PINK1 signaling pathway, resulting in the clearance of the damaged mtDNA (Shu et al., 2021). Under normal conditions, ATAD3B is heterologously coupled to ATAD3A, thereby promoting the targeting of the C-terminal region of ATAD3B to the mitochondrial membrane gap, whereas OS-induced mtDNA damage reduces the heterogeneous heterodimerization of ATAD3B-ATAD3A, leading to the exposure of the C-terminal end of ATAD3B on the mitochondrial outer membrane, which in turn recruits LC3 to initiate mitophagy (Shu et al., 2021).

Nuclear factor erythroid 2-related factor 2 (Nrf2) belongs to the leucine zipper family and includes different functional domains such as Neh1 to Neh7 (Kaspar et al., 2009). Nrf2 is a transcription factor that maintains cellular redox homeostasis and is mainly responsible for regulating the expression of a series of antioxidant response genes to prevent cellular damage caused by ROS. When not activated by ROS, Nrf2 mainly exists in the cytoplasm and binds to Kelch-like ECH-associated protein 1 (Keap1) to form a relatively stable complex, and Keap1 restricts the activity of Nrf2 by promoting ubiquitination and subsequent proteasomal degradation of Nrf2 (Sykiotis and Bohmann, 2008). In the case of oxidative stress occurring with excessive accumulation of ROS, this leads to a decrease in the binding capacity of Nrf2, which is therefore no longer ubiquitinated and degraded but accumulates in the cytoplasm (Li et al., 2018). Keap1 dissociates from Nrf2, followed by Nrf2 nuclear translocation into the nucleus and binding to the antioxidant response element (ARE), which activates the expression of a series of antioxidant and cytoprotective genes, such as Heme oxygenase-1 (HO-1), GST, and GSH, thereby protecting the organism from ROS (He et al., 2020; Chen, 2021). HO-1 has anti-oxidative stress and maintenance of homeostasis in the intracellular environment, and its expression is increased under conditions of oxidative stress, inflammation, heavy metal exposure, and hyperthermia. HO-1 catalyzes the breakdown of hemoglobin into CO, Fe²⁺, and bilirubin. This process removes both heme, which is harmful to the body, and produces bilirubin, which has antioxidant properties, and CO, which is anti-inflammatory and vasodilatory, thus helping to reduce oxidative stress and inflammatory responses and preventing cellular damage. When the level of oxidative stress is reduced, the newly synthesized Keap1 promotes ubiquitination and degradation of Nrf2, and the activity of Nrf2 is re-inhibited, returning the organism to its normal state.

Janus Kinase 2 (JAK2) is a tyrosine kinase belonging to the Janus family that has only one catalytic structural domain and no Src homology 2 (SH2) structural domain. Therefore, JAK2 can not only phosphorylate to bind to other cytokine receptors, but also phosphorylate multiple signaling molecules containing SH2 structural domains (Zhong et al., 2021). Signal Transducer and Activator of Transcription3 (STAT3) is a downstream molecule of JAK2 and belongs to the STAT family of transcription factors. STAT3 consists of an N-terminal structural domain, coiled-coil domain, DNA-binding domain, linker domain, SH2 (Src homology region 2) domain and C-terminal activation domain. Domain, DNA binding domain, linker domain, SH2 (Src homology region 2) domain and C-terminal activation domain. When cytokines (e.g., erythropoietin, interferon, interleukin, etc.) bind to its receptor, they cause a conformational change in the receptor, leading to activation of JAK2 phosphorylation. Activated JAK2 promotes the phosphorylation of STAT3, which undergoes a conformational change to form a dimer and translocate to the nucleus, thereby activating the transcription of antioxidant genes. ROS can directly activate the JAK2/STAT3 pathway, which leads to the expression of antioxidant genes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx), to help scavenge ROS and reduce the damage caused by oxidative stress.

AMPK is a serine/threonine protein kinase complex consisting of an alpha catalytic subunit and two regulatory subunits, beta and gamma (Chen et al., 2018). Under hypoxia, lack of energy, or elevated ROS, the intracellular AMP/ATP ratio is elevated, and AMP binds directly to AMPK, thereby activating AMPK (Herzig and Shaw, 2018). Activated AMPK phosphorylates Nrf2 and Keap1, changing their conformation, thereby reducing their binding capacity, promoting the displacement of Nrf2 to the nucleus and binding to the anti-oxidative stress element (ARE), and activating the expression of a series of antioxidant genes. In addition, AMPK maintains mitochondrial quality by promoting mitophagy and neo-mitochondrial production, which reduces ROS production at the source (Wang et al., 2022). Curcumin promotes Parkin-mediated mitophagy and ameliorates mitochondrial damage through the AMPK/TFEB signaling pathway (Cao et al., 2020). Activation of the AMPK/Nrf2/HO-1 pathway reduces ROS and MDA levels as well as increases SOD and GPx activity and ameliorates CI/RI-induced oxidative stress (Huo et al., 2023). In addition to its antioxidant role by interfering with the Nrf2/Keap1 signaling pathway, AMPK can also play a role by activating FOXO and SIRT1. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is another one of the sources of ROS, which produces O²⁻ by catalyzing the oxidation reaction of NADPH. Activated AMPK activates FOXO and SIRT1, which in turn promotes the expression of SOD and glutathione peroxidase, inhibits the activity of NADPH oxidase, and improves cellular antioxidant levels (Tang et al., 2014; Duan et al., 2017; Tang et al., 2021).

FOXO (Forkhead Box O) is a transcription factor that promotes the expression of antioxidant and longevity genes, of which FOXO1, FOXO3, FOXO4, and FOXO6 are involved in the expression of antioxidant genes. AMPK is activated under low energy and hypoxia. Activated AMPK can activate FOXO through phosphorylation, which enhances the transcriptional activity of FOXO and translocates to the nucleus. Promote the expression of antioxidant genes to generate SOD, GPx, glutathione S-transferase (GST), and glutathione synthetase (GCL), which can lighten the cellular damage by oxidative stress (Guo et al., 2017). In addition, AMPK can indirectly regulate the activity of FOXO family proteins through mTOR. As shown previously, mTOR promotes protein synthesis and cell growth mainly through mTORC1 (mTOR complex 1). Under stress, activated AMPK can phosphorylate and activate the activity of TSC2 (Tuberous Sclerosis Complex 2), a component of mTORC1, thus reducing energy consumption. Whereas mTORC1 promotes the activity of AKT kinase, activated AKT phosphorylates FOXO at Ser256, Ser319 and Thr24 sites, which leads to the transfer of FOXO from the nucleus to the cytoplasm, where it binds to phospho-specific proteins and is thus confined to the cytoplasm (Li et al., 2017; Omorou et al., 2023). Since FOXO is required for its initiation of transcription in the nucleus, when FOXO is phosphorylated by AKT it is unable to transcribe antioxidant genes. While AMPK inhibits mTORC1, AKT activity is also inhibited. When AKT activity is low, phosphorylation and extra-nuclear translocation of FOXO protein is reduced, and therefore, FOXO protein can remain in the nucleus to activate the expression of antioxidant genes (Deng et al., 2023).

SIRT1 (Sirtuin 1) and SIRT13 belong to the same sirtuin family, NAD⁺-dependent deacetylases with regulatory and anti-aging effects on oxidative stress (Singh and Ubaid, 2020). AMPK increases intracellular NAD⁺ levels by promoting metabolic pathways such as fatty acid oxidation and glycolysis. NAD⁺ is an essential substrate for SIRT1, and increasing NAD⁺ levels enhances the deacetylation activity of SIRT1. SIRT1 deacetylates a variety of transcription factors, such as FOXO proteins, p53, and NF-κB. FOXO proteins and the p53 transcription factor have a role in the regulation of oxidative stress. After FOXO acetylation, its ability to bind to DNA is reduced, thereby decreasing its transcriptional activity. FOXO has a role in regulating oxidative stress, and the acetylation of FOXO reduces its ability to bind to DNA, thereby decreasing its transcriptional activity. Activated SIRT1 deacetylates FOXO and enhances the transcriptional activity of FOXO, enabling it to bind to DNA more efficiently and activate its downstream target genes of SOD, catalase, and GPx to improve the cellular antioxidant defense capacity (She et al., 2018). In addition, SIRT1 participates in the regulation of oxidative stress by modulating the activity of Tumor Protein 53 (p53) through deacetylation. p53 is a tumor suppressor protein that is widely present in human cells, and its activity can be modulated by acetylation and deacetylation, which enhances the transcriptional activity of p53 and contributes to the activation of apoptosis and cell cycle arrest (Wu et al., 2022). On the other hand, SIRT1 regulates the activity of p53 through deacetylation, thereby modulating the expression of antioxidant-related genes such as glutathione peroxidase 1 (GPX1), SOD2, TP53-induced glycolysis and Apoptosis regulator (TIGAR), and aldehyde dehydrogenase 4 (ALDH4), and reduces the cellular damage caused by ROS (Liu et al., 2020). In summary, AMPK plays an antioxidant role by activating the Nrf2/HO-1 signaling pathway and regulating FOXO and SIRT1 factors to promote the expression of antioxidant genes. AMPK also maintains the quality of mitochondria by promoting mitophagy and neo-mitochondrial production, which reduces ROS production from the root. Mitochondrial deacetylase Sirtuin-3 (SIRT3) has an antioxidant effect. Cellular experiments have demonstrated that Aβ decreases the level of SIRT3 in neurons, whereas a lack of SIRT3 leads to increased levels of oxidative stress, neuronal hyperexcitability, and a decrease in survival, and that the use of SIRT3 agonists reduces the level of ROS and inhibits neuronal hyperexcitability (Ying et al., 2022). Also, animal experiments showed that inhibition of SIRT3 resulted in elevated neuronal excitability, whereas decreasing ROS levels reversed the neuronal hyperactivity caused by the lack of SIRT3, and these findings suggest that SIRT3 regulates the level of oxidative stress in AD neurons (Ying et al., 2022).

MAPK kinase kinase (MAPKKK), MAPK kinase (MAPK kinase, MAPKK) is the upstream molecule of the MAPK signaling pathway. JNK belongs to the MAP kinase (mitogen-activated protein kinase) family of kinases, which plays an important role in a variety of physiological and pathological processes, such as cell cycle, reproduction, apoptosis and cellular stress. It plays an important role in various physiological and pathological processes including cell cycle, reproduction, apoptosis and cellular stress, especially in the process of oxidative stress (Johnson and Lapadat, 2002). There are three isoforms of the JNK family, including JNK1, JNK2, and JNK3. When oxidative stress occurs, ROS can activate JNK by affecting upstream kinases of JNK, such as MAPKKK and MAPKK. ASK1 (Apoptosis Signal-regulating Kinase 1) belongs to an isoform of MAPKKK, also known as MAPKKK5, and can be activated by ROS, tumor necrosis factor-alpha (TNF-alpha), and lipopolysaccharide, among others. Trx is an ASK1-binding protein, and inhibits the activity of ASK1 through binding to it (Matsuzawa and Ichijo, 2008). Under oxidative stress, the sulfhydryl groups in the two cysteine residues contained in Trx are oxidized to form a disulfide bond, which separates Trx from ASK1 and induces the aggregation and activation of ASK1, which in turn activates downstream JNK (Matsuzawa and Ichijo, 2008; Katagiri et al., 2010). JNK activation phosphorylates a variety of transcription factors and promotes the expression of antioxidant genes, thereby exerting an antioxidant effect. Activation of JNK/SAPK in response to oxidative stress mediates the activation of BACE, which in turn leads to elevated Aβ levels (Tamagno et al., 2005, 2006).

CI/RI is a form of brain tissue damage that occurs as a result of the recirculation of blood in the brain following a period of cerebral ischemia and hypoxia (Salameh and Dhein, 2015; Liu et al., 2023). This leads to a range of cognitive impairments, including reduced learning and memory abilities. The Circle of Willis is a ring of arteries located at the base of the brain, consisting of the anterior cerebral arteries, middle cerebral arteries, posterior cerebral arteries, basilar arteries, and communicating arteries, which equalize and distribute blood flow from the internal carotid arteries and vertebral arteries (Mastorakos and McGavern, 2019). The anterior, middle, and posterior cerebral arteries and their branches form abundant cortical arteries and arterioles on the surface of the brain. Cortical artery branches penetrate deep into the brain parenchyma, giving rise to smaller arterioles, and the perivascular space has become an important site for the removal of unwanted proteins and peptides (e.g., Aβ) (Gorelick et al., 2011; Laman and Weller, 2013). The vascular structure of the brain, especially its “outside-in” blood supply, places the deeper part of the brain at the junction of the two main blood supply areas - the watershed areas - which are most susceptible to ischemic injury in the event of a drop in blood pressure or a decrease in blood flow.

There are 8.6 billion neurons and 25–30 billion glial cells in the brain, making the brain the organ that consumes the most oxygen (Huang et al., 2023). Compared with muscle and liver, the brain has relatively insufficient energy reserves, which largely depends on blood supply, and is therefore extremely sensitive to ischemia. When ischemia and hypoxia occur, ATP synthesis in the brain is reduced, neurons are depolarized, excitatory amino acids are released from the presynaptic membrane, excitatory amino acids are reduced from the postsynaptic membrane, and Ca²⁺ is overloaded, which ultimately results in the gradual death of neurons and produces structural damage to the brain tissue. During reperfusion, the above damage is further aggravated, resulting in mitochondrial damage and the production of large amounts of inflammatory factors and ROS (Li et al., 2015). In conclusion, the series of reactions mentioned above (ROS, Ca²⁺ overload and excitatory amino acid damage, etc.) can damage the structure of mitochondria, cause mitochondrial dysfunction and activate intracellular mitophagy. In the acute phase of ischemia, mitochondrial damage was severe but no obvious mitophagy was detected; however, with the prolongation of ischemia over a certain period of time, the degree of mitophagy increased (Orellana-Urzúa et al., 2020). In the early stage of cerebral ischemia–reperfusion injury, damaged mitochondria can be cleared in time by mitophagy, which reduces the production of ROS and thus exerts neuroprotective effects. Under normal conditions, mitophagy helps to maintain the energy metabolism and barrier function of BBB endothelial cells. However, after the occurrence of CI/RI the level of inflammatory factors in the brain increased, and BBB permeability increased (Choi et al., 2014). Microglia are the main immune cells in the nervous system. Microglia are activated in the early stage of CI/RI and play the roles of phagocytosis of damaged and dead cells, release of inflammatory factors and cytokines. Inflammatory factors such as TNF-α, IL-1β, and IL-6 bind to the target cells through specific receptors and activate the downstream inflammatory signaling pathways (e.g., the NF-κB signaling pathway), which further promote inflammatory factors and chemokine expression. Inflammatory factors such as TNF-α, IL-1β and IL-6 bind to target cells through specific receptors and activate downstream inflammatory signaling pathways (e.g., NF-κB signaling pathway), further promoting the expression of inflammatory factors and chemokines, exacerbating inflammatory responses, inducing apoptosis and necrosis, and resulting in brain tissue damage. However, sustained high levels of inflammatory factors induce or exacerbate oxidative stress and mitochondrial dysfunction, inhibit mitophagy, and cause greater tissue damage. In the case of CI/RI, inflammatory factors or ROS cause neuronal death and impairment of the structural integrity of the BBB, leading to easier entry of blood components and inflammatory factors into the brain tissue and exacerbating brain damage (Zhong et al., 2022). In conclusion, in CI/RI, neuroinflammation, mitophagy, and oxidative stress are not isolated from each other; there is a complex interplay between them, and the complex mechanism between them determines the degree of brain tissue damage.

Studies have shown that Jiawei Sijunzi Tang can significantly improve the neurological function, reduce mNSS score, maintain mitochondrial homeostasis, increase the mitochondrial membrane potential level and Ca²⁺-Mg²⁺-ATPase activity, and reduce the O²⁻ content in the CI/RI model rats through the PINK1/Parkin signaling pathway (SONG et al., 2023). When the PINK1/Parkin signaling pathway is activated, it promotes mitochondrial autophagy, inhibits the activation of NLRP3 inflammatory vesicles and reduces the level of inflammation (Fan et al., 2021). Both in vivo and in vitro experiments demonstrated that Ligustilide (Chuanxiong Lactone) promotes mitophagy via PINK1/Parkin, thereby ameliorating neuronal injury in CI/RI. Therefore, neuronal injury can be ameliorated by targeting intervention in the PINK1/Parkin signaling pathway to promote mitophagy (Mao et al., 2022). Therefore, neuronal injury can be ameliorated by targeting intervention in the PINK1/Parkin signaling pathway to promote mitophagy. Electroacupuncture (EA) is a method of preventing and treating diseases by using a combination of acupuncture and electrical stimulation, which has the effect of increasing synaptic plasticity and improving the level of neurotrophic factors, after the needle is inserted into the acupoint to obtain Qi (Lai et al., 2019). EA was found to enhance Pink1/Parkin-mediated mitochondrial autophagic clearance, reduce accumulation of damaged mitochondria, and ameliorate nitro/oxidative stress-induced functional impairment of brain CI/RI mitochondria (Wang et al., 2019). Tissue-type plasminogen activator (tPA), the only FDA-approved clinical thrombolytic agent, exerts neuroprotection by activating AMPK to increase FUNDC1 expression, thereby inhibiting apoptosis and improving mitochondrial function (Cai et al., 2021). Polyrhachis vicina (Roger) increased the level of mitophagy and promoted angiogenesis through activation of the SIRT3-mediated Pink1/Parkin signaling pathway, significantly reduced neurological scores and infarct area, alleviated cortical neuron apoptosis, and increased hippocampal Nissl density in CI/RI rats (Wei et al., 2023).

VaD is a cognitive impairment caused by various cerebrovascular diseases and is one of the most common forms of dementia, accounting for 20% of all cases. As life expectancy increases and the incidence of cardiovascular diseases continues to rise, it is likely that the prevalence of VaD will continue to grow in the coming decades (Wu et al., 2016). The primary clinical manifestations of vascular dementia (VaD) include cognitive impairment and motor abnormalities, which have a significant adverse impact on the quality of life of the patients (Gorelick et al., 2011; O'Brien and Thomas, 2015). There are many causes of VaD, such as insufficient cerebral perfusion, oxidative stress, neuroinflammation, vascular lesions in the brain (atherosclerosis, endothelial dysfunction, and cerebral small-vessel disease, etc.), alterations in the permeability of the blood–brain barrier (BBB), and cholinergic damage (Sharp et al., 2009; Iadecola, 2013; Liu et al., 2017). However, reduced cerebral blood supply due to ischemic or hemorrhagic brain lesions, for example, thus leaving the brain in a state of chronic cerebral hypoperfusion (CCH) is the most common cause of VaD (Wang et al., 2010; Iadecola, 2013). Decreased cerebral blood flow (CBF) can lead to changes in spatial memory (Sigfridsson et al., 2020), CCH can cause some damage to brain tissue, such as lacunar infarcts, brain atrophy, white matter damage, microhemorrhages, and microinfarcts, which can lead to brain dysfunction and cognitive impairment (Alosco et al., 2013). Study shows reduced serum levels of Parkin protein in patients with VaD and AD (Castellazzi et al., 2019). Rapamycin (RAPA) improved cognitive deficits and attenuated neuronal damage and mitochondrial dysfunction in VaD rats by increasing the level of mitophagy and inhibiting neuronal apoptosis via the PI3K/Akt/mTOR signaling pathway (Zheng et al., 2021). ZiShenHuoXue Formula (ZSHXF) is composed of He Shouwu, Chinese wolfberry, mulberry, Schisandra chinensis, Salviae Miltiorrhizae, Puerariae Root, Yizi Ren, Acorus calamus, Ulmus, Preparation of Yuanzhi, Scorpion, Hawthorn, and it is an empirical formula for the treatment of VaD, which was formed under the guidance of the master of national medicine Liu Zuyi, and has exact clinical efficacy (Zhou et al., 2004; Wu et al., 2015). It was also shown that ZSHXD could attenuate neuronal damage through PINK1/Parkin-mediated mitophagy and exert neuroprotective effects in VaD rats (Zhao et al., 2024).

AD is a neurodegenerative disease that mostly occurs in the elderly population, and its main clinical manifestations are memory loss, cognitive impairment, language impairment and accompanied by depression, apathy and other emotions, which make it difficult to take care of oneself in daily life, and bring a heavy burden to patients and their families. Aging is one of the most important factors in the development of AD. With the aging of the world’s population, the incidence of AD is on the rise year by year, and it is expected that by 2050, there will be as many as 152 million AD patients in the world, and the cost of treating AD will be as high as 1.1 trillion U.S. dollars by then (Orobets and Karamyshev, 2023; Yang et al., 2023b). The main pathologic manifestations of AD are amyloid-β (Aβ) formation of senile plaques, tau protein formation of neurofibrillary tangle (NTF), neuronal damage and synaptic dysfunction (Yeo et al., 2014). Numerous studies have shown that neuroinflammation is another important factor exacerbating AD. Microglia (MG) are important immune cells in the central nervous system, which can recognize and remove pathogens, damaged cells to maintain the role of brain microenvironmental homeostasis. In the early stages of AD, MGs have a role in recognizing and clearing Aβ deposits. However, as AD progresses, MGs are in an over-activated state, releasing pro-inflammatory cytokines and exacerbating the pathologic process of AD. Thus, MG plays a complex role in the pathophysiology of AD, both as a defense mechanism in the early stages of the disease and as a facilitator in the late stages of the disease. Higher levels of inflammatory factors inhibit mitophagy, and in AD, low levels of PINK1 and Parkin lead to impaired mitophagy (Pradeepkiran and Reddy, 2020; Tran and Reddy, 2020; Morton et al., 2021). Increased levels of mitophagy were found to reduce Aβ deposition and NTF in human neuronal cells and improve memory deficits in AD model mice (Fang et al., 2019). Synaptophysin, a membrane glycoprotein mainly found in the synaptic vesicle membrane of neurons, has a role in transmitting neural signals and regulating synaptic plasticity. Treatment with mitophagy enhancers resulted in a significant increase in the cell survival rate of mutant tau-HT22 cells, as well as an increase in the mRNA and protein levels of both synaptophysin and mitophagy genes (Kshirsagar et al., 2021). Studies have shown cerebrovascular dysfunction in patients at risk for AD or in early stages of AD, suggesting that inadequate cerebral perfusion is associated with the development of AD (Iadecola, 2004; Claassen et al., 2009; Sabayan et al., 2012; Gao et al., 2013). In the presence of inadequate cerebral perfusion and hypoxia, β-secretase is activated and tau protein is hyperphosphorylated (Kitaguchi et al., 2009; Koike et al., 2010). By increasing the level of mitophagy, Aβ deposition can be reduced and the phagocytosis and anti-inflammatory effects of microglia can be modulated, which in turn attenuates cognitive deficits in APP/PS1 mice; mitophagy also inhibits the overphosphorylation of tau proteins and ameliorates the memory deficits in the genetically modified nematode Hidradenitis elegans cryptic rod nematode and APP/PS1 mice (Fang et al., 2019). An acetylated derivative of Andrographolide (3,14,19-triacetylandrographolide, ADA) ameliorates cognitive deficits and reduces Aβ deposition and neuronal damage in Apoe4 mice by improving mitochondrial autophagy via the SIRT3/FOXO3a signaling pathway, which in turn inhibits NLRP3 inflammatory vesicles (Zhou et al., 2024). Experiments showed that MCL-1 is a mitophagy receptor that directly binds to LC3A, while UMI-77 is a mitophagy activator that can be targeted to induce mitophagy. UMI-77 effectively induced mitophagy at a sublethal dose and improved the cognitive deficits in APP/PS1 mice, reduced the inflammatory response and the pathologic damages induced by Aβ plaques, and promoted the damaged mitochondria clearance of damaged mitochondria (Cen et al., 2020). The amyloid precursor protein intracellular domain (AICD) is a transcription factor that regulates the transcription of multiple genes, and AICD interacts with FOXO3a in the nucleus to regulate the transcription of the PINK1 promoter (Goiran et al., 2018). Furthermore, modulation of γ-secretase activity or AICD expression affects Pink1-mediated mitophagy (Goiran et al., 2018).

Reduced oxygen supply to brain tissue after ischemia, altered mitochondrial membrane potential, and affected oxidative phosphorylation result in reduced ATP production, leading to the production of reactive oxygen species such as superoxide anion (O²⁻), hydroxyl radical (·OH), reactive nitrogen species (RNS), and nitric oxide (NO), which promotes inflammation, damages proteins, cell membranes, and the DAN, and causes damage to the organism (Kong et al., 2020; Trujillo-Rangel et al., 2022). Pnn is a serine- and arginine-rich protein that plays multiple roles in regulating cell differentiation, proliferation, and migration (Joo et al., 2014). Studies have shown that Pnn deficiency exacerbates oxidative stress in neurons and exacerbates brain CI/RI in mice (Hsu et al., 2022). Nitric oxide synthase (NOS) is responsible for the production of nitric oxide (NO). NOS can be classified into three main categories: endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) (Pradhan et al., 2018). NOX located in the cell membrane is another source of ROS during the reperfusion phase. The NOX enzyme uses oxygen as the final electron acceptor via NADPH and immediately produces O²⁻. O²⁻ crosses the membrane via the anion channel pore, resulting in the degradation of NO, the formation of peroxynitrite, and the nitration of protein tyrosine (Wu et al., 2018). Melatonin attenuates cerebral CI/RI damage in mice by upregulating SIRT3 expression and activating SIRT3 signaling after middle cerebral artery occlusion (Liu et al., 2019). Diosgenin increases protein expression of SIRT2, T-Nrf2, N-Nrf1, NQO1 and HO-527 in vivo and in vitro, and activates the SIRT2/Nrf2 signaling pathway to inhibit oxidative stress to attenuate brain CI/RI injury (Lee et al., 2012). Sanggenon C (SC), a flavonoid present in Cortex Mori, inhibits RhoA-ROCK signaling, reduces inflammation and oxidative stress levels in middle cerebral artery occlusion (MCAO) reperfused rats, and reduces post-CI/RI is injury (Zhao and Xu, 2020). Parthenolide (PN) is a sesquiterpene lactone extracted from Tanacetum parthenium, which can alleviate OGD/R-induced oxidative stress and neuroinflammatory injury through activation of the Akt/GSK-3β signaling pathway, and exert a protective effect on PC12 cells. Puerarin (PUE) is one of the main components of the traditional Chinese medicine Puerariae Lobatae Radix. A recent study showed that PUE activated the PI3K/Akt/Nrf2 signaling pathway, induced dissociation of the Nrf2-Keap1 complex and accelerated nuclear translocation of Nrf2, thereby intervening in oxidative stress and protecting neuronal cells in both the middle cerebral artery occlusion/reperfusion (MCAO/R) model rat and the oxygen–glucose deprivation/reperfusion (OGD/R) cell model (Zhang et al., 2023). Sodium butyrate (NaB) Significantly increased the protein expression levels of Jak2, STAT3 and SOD activity, and decreased MDA activity and IL-1β, TNF-α, IL-8 levels in CI/RI mice. Meanwhile, the positive neurons of TUNEL staining were significantly reduced, i.e., NaB prevented oxidative stress, inflammatory response and neuronal apoptosis by inhibiting the JNK/STAT pathway and reduced neuronal injury after CI/RI (Wang et al., 2019).

Micro RNA (miRNA) is a non-coding small RNA molecule with about 18–25 nucleotides, which has the role of regulating gene expression, participating in cell growth and differentiation, regulating stress and immunity, etc. miRNAs have been associated with many diseases, such as cancer, cardiovascular diseases, and neurodegenerative diseases, etc. In the central nervous system (CNS), 15 miRNAs were found to be up-regulated and 44 miRNAs were found to be up-regulated in the presence of CI/RI. In the central nervous system, miRNAs are involved in synapses, myelin sheaths and cerebral angiogenesis. Fifteen miRNAs were found to be up-regulated and 44 miRNAs were found to be down-regulated under CI/RI conditions (Min et al., 2015). It was shown that miR-489-3p was up-regulated and SIRT1 was down-regulated in the brain tissues of rats with transient middle cerebral artery occlusion (tMCAO) model, whereas down-regulation of miR-489-3p or up-regulation of SIRT1 ameliorated behavioral dysfunctions, lowered the level of oxidative stress, and reduced neuronal damage and apoptosis in rats (Song L. et al., 2022). lncRNA 22 prime to Xist (FTX) inhibits apoptosis and oxidative stress through the miR-186-5p/MDM4 pathway, thereby attenuating CI/RI (Xiao et al., 2022). In the rat CI/RI model and SH-SY5Y cells using the hypoxia/reoxygenation (H/R) model, NOX2 expression was significantly increased, whereas the expression level of miR-652, a potential target of NOX2, was significantly decreased in brain tissue and plasma (Zuo et al., 2020). In contrast, miR-652 significantly reduced NOX2 expression and ROS generation, as well as tissue damage in brain tissues of CI/RI rats (Zuo et al., 2020). Lignans, a major component of Syringa pinnatifolia Hemsl, activated the Nrf2/HO-1 signaling pathway, increased SOD and GPx activities, decreased MDA levels, and inhibited the expression of NOX2 and NOX4, which significantly ameliorated the neurological function of brain tissues and pathological injuries, and it alleviated the CI/RI and OS, and reduced the volume of cerebral infarction (Hao et al., 2023). Modeling using the middle cerebral artery occlusion (MCAO) method showed a significant increase in the levels of phosphorylated JNK, p38, and ERK in rats of the model group, and intervention with fucoidan resulted in a decrease in the levels of phosphorylated JNK, p38, and ERK, as well as an increase in the activity of SOD, a decrease in the levels of MDA, and a decrease in the damage caused by CI/RI in the rats, which might be related to the fact that Fucoidan inhibits the MAPK pathway (Che et al., 2017).

The development of VaD is inextricably linked to oxidative stress. The excessive accumulation of ROS oxidises unsaturated fatty acids on neuronal cell membranes, thereby causing cellular damage, triggering an inflammatory response, and resulting in vascular damage and dysfunction. This ultimately leads to a significant loss of neurons and inadequate blood supply to the brain, which in turn gives rise to VaD (Li Z. et al., 2011). Oxidative stress induced by the overactivation of NADPH oxidase plays an important role in the pathology of VaD. Studies have shown that the expression of NADPH oxidase is increased in the brain tissues of VaD rats, and cognitive deficits in VaD rats can be attenuated by inhibiting the activity of NADPH oxidase, suggesting that NADPH oxidase plays an important role in the pathogenesis of VaD (Choi et al., 2014). It was found that Puerarin could significantly reduce MDA levels and increase GSH-Px levels in the hippocampus and frontal cortex of VaD model rats, and improve the ability of rats to learn to improve memory. The study also used Puerarin to treat H₂O₂-stimulated SH-SY5Y cells, and the results showed that Puerarin could up-regulate key genes related to the expression of antioxidant proteins, such as Nrf2, FOXO1, FOXO3, and FOXO4, and alleviate oxidative stress damage (Zhang et al., 2015). It was found that resveratrol shortened the escape latency and distance of VaD model rats in the Morris water maze experiment, and extended the percentage of time spent in the target quadrant and the percentage of distance swum during the orientation voyage, suggesting that resveratrol improves the learning and memory abilities of VaD rats (Ma et al., 2013). Further experiments revealed that resveratrol decreased MOD levels in the hippocampus and cerebral cortex and increased SOD and GSH levels in VaD model rats (Ma et al., 2013). It was found that Artemisia annua Linn’e could reduce the level of oxidative stress and neuroinflammation, protect neurons, and attenuate cortical microvascular and BBB injury after chronic cerebral hypoperfusion (CCH) by activating the Nrf2/Keap1/ARE signaling pathway, which could protect the Neurovascular unit (NVU) integrity, thereby improving cognitive function in VaD model animals with bilateral common carotid artery occlusion (BCCAO) (Kim et al., 2023). Ligusticum chuanxiong lactone (LIG) is one of the main active ingredients of Angelica sinensis, and the results of Morris water maze showed that LIG effectively improved the learning and memory deficits in VaD rats, which may be related to the activation of the AMPK/SIRT signaling pathway by LIG to reduce oxidative stress damage and anti-apoptosis (Peng et al., 2022). Amorphous selenium nanodots (A SeNDs) inhibited oxidative stress damage in vascular dementia rat neurons by activating the NMDAR pathway (Zhu et al., 2023). Glycyrrhizic acid (GA) exerted antioxidant effects by restoring mitochondrial complexes I and IV, enzymatic and non-enzymatic antioxidant activities, and reducing ROS production through modulation of the GSK3β/Nrf2 signaling pathway, and exerted a protective effect against chronic cerebral hypoperfusion in VaD rats (Sathyamoorthy et al., 2020). Another study showed that GA improved learning memory ability, attenuated cellular damage, decreased MDA levels, and increased SOD activity in VaD model rats, which may be related to the inhibition of oxidative stress and the reduction of the current intensity of voltage-gated sodium channels (VGSC) in pyramidal neurons of the hippocampal CA1 region (Guo et al., 2016).

The pathogenesis of AD is a complex process, with a number of well-known mechanisms involved, including Aβ deposition, tau protein hyperphosphorylation, oxidative stress, neuroinflammation, cholinergic damage and metal ion disorders. The formation of senile plaques by Aβ deposition and the formation of neurofibrillary tangles by tau protein hyperphosphorylation represent the two most significant pathological manifestations of AD. Furthermore, the interaction between Aβ and ROS serves to exacerbate the pathological process of AD (Tamagno et al., 2021). Aβ is a polypeptide cleaved by Amyloid precursor protein (APP). APP is cleaved by α-secretase (ADAM10) or β-secretase (BACE1) to form an intracellular structural domain, which is further cleaved by γ-secretase. APP is cleaved by α-secretase and γ-secretase to produce P3 fragments. This pathway is designated the non-amyloid pathway, whereas the amyloid pathway entails the proteolytic processing of APP by β-secretase and γ-secretase, ultimately resulting in the generation of the Aβ fragment (Tarasoff-Conway et al., 2015; Koelsch, 2017). A competitive relationship exists between α-secretase and β-secretase. Studies have demonstrated that β-secretase levels and activity are markedly elevated in the brains of patients diagnosed with AD (Koelsch, 2017). ROS promote Aβ production by affecting the activity of β-secretase and γ-secretase (amyloid pathway). In turn, Aβ can bind directly to mitochondria, impairing mitochondrial function, affecting the electron transport chain, and increasing ROS production (Mehrabadi and Sadr, 2020). Aβ deposition can also lead to peroxidation of membrane lipids, which not only damages the integrity of cell membranes, but also further promotes the production of ROS. At the same time, Aβ deposition affects the expression and activity of antioxidants such as SOD and glutathione peroxidase, reducing the body’s antioxidant capacity (Athari Nik Azm et al., 2018). In conclusion, ROS and Aβ interact with each other, thereby exacerbating AD pathology. Magnoflorine, a quaternary salt porphyrin alkaloid, was found to reduce Aβ-induced apoptosis and decrease ROS levels through the JNK signaling pathway and improve learning memory in AD mice (Zhong et al., 2023). Ginsenoside Rk3 inhibited apoptosis and glial cell activation by activating the AMPK/Nrf2 signaling pathway, increasing the levels of glutathione reductase (GSH) and superoxide dismutase (SOD), and decreasing the levels of malondialdehyde (MDA), thereby improving the learning and memory abilities of APP/PS1 mice (She et al., 2023). BisdemethoxyCurcumin (BDMC) is a classical derivative of curcumin with neuroprotective effects. After intervention with BDMC, APP/PS1 mice showed improved cognitive function, decreased Aβ deposition, reduced oxidative stress levels, increased neuron numbers, and elevated SIRT1 expression levels. However, after intervention with an inhibitor of SIRT1, it was found that the above results were inextricably linked to the upregulation of SIRT1, i.e., BDMC could alleviate cognitive deficits in APP/PS1 mice by upregulating SIRT1 to achieve an anti-oxidative stress effect (Xu et al., 2020). Sesamin and sesamol reduced the level of oxidative stress in H₂O₂-induced human neuroblastoma (SH-SY5Y) through the SIRT1-SIRT3-FOXO3a signaling pathway. Imperatorin, a major constituent of Prehistoria, has the ability to promote Nrf2 nuclear translocation and increase the expression levels of Nrf2, NQO-1, and HO-1, thereby reducing oxidative stress, lowering mitochondrial membrane potential, and ameliorating cobalt chloride-induced apoptosis (Liao et al., 2023).