In 2002, the China Food and Drug Administration granted approval for the use of 3-N-Butylphthalide (NBP) in treating ischemic stroke, which consists of optical isomers l-NBP, dl-NBP, and d-NBP, which is isolated from seeds of Apium graveolens (Chinese celery). The effectiveness of butylphthalide has been validated through various clinical trials and animal experiments in alleviating neuroinflammation, preserving mitochondrial function, mitigating oxidative stress, and ameliorating BBB impairment [32].

Yan et al. [33] found NBP significantly reduced cerebral infarction size, cell apoptosis, BBB damage, and brain edema in mice as a neuroprotective role with I/R injury of MCA occlusion (MCAO) preconditioned. Many researchers have investigated the pathways involved in the neuroprotective effects of NBP. Huang et al. [34] suggested that early application of butylphthalide alleviated cerebral I/R injury by inhibiting mitochondrial high-temperature requirement A2 (HtrA2/Omi)-mediated apoptosis in MCAO rats. Zhan et al. [35] proved that NBP exerted a neuroprotective effect on MCAO mice by up-regulating miR-21 level to inhibit neuronal apoptosis and reactive oxygen species (ROS) production as well as improve cell proliferation activity, which may be associated with the inhibition of Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) pathway. NBP also plays a neuroprotective role in clinical studies, improving functional outcomes in patients with AIS. Wang et al. [36] conducted a randomized controlled clinical trial among patients with AIS receiving intravenous thrombolysis or endovascular therapy. In that study, NBP was associated with a higher percentage of patients with favorable functional outcomes at 90 days compared with placebo. In summary, the neuroprotective effect of NBP on AIS has been extensively confirmed in both animal and human, making it widely used in clinical practice.

Edaravone, a low molecular-weighted free radical scavenger, can readily traverse the BBB and effectively reduce the production of oxygen free radicals while modulating additional deleterious cascades, such as inhibition of lipid oxidation, inhibition of endothelial nitric oxide synthase, and activation of MMP-9 [37, 38]. The neuroprotective effects of edaravone are shown in the meta-analysis of randomized controlled trials and prospective cohorts on edaravone [39]. Nowadays, an edaravone-containing compound drug, edaravone dexborneol, has gained widespread utility in animal and clinical studies. Wu et al. [40] first combined borneol, an anti-inflammatory drug, with edaravone in a rat model of transient cerebral ischemia-reperfusion. They discovered that this combination exhibited a treatment time window of 6 h and significantly improved the damage in a permanent cerebral ischemia-reperfusion model. In terms of the study of molecular pathways, Hu et al. [41] showed that edaravone dexborneol effectively suppressed nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) inflammation-induced activation of microglial pyroptosis in experimental ischemic stroke through NF-κB/NLRP3/gasdermin D (GSDMD) signaling pathway using transient MCAO (tMCAO) mouse model in vivo and oxygen-glucose deprivation (OGD) BV2 cell model in vitro. A multi-center, randomized, double-blind, controlled phase III trial, Thrombus Aspiration in ST-Elevation Myocardial Infarction in Scandinavia (TASTE) trial [42], enrolled 1,165 AIS patients who were randomly assigned to receive either edaravone dexborneol or edaravone. The proportion of patients with good functional outcomes at 90 days was significantly higher in the edaravone dexborneol group than in the edaravone group [mRS score ≤ 1, 67.18% vs. 58.97%; odds ratio (OR): 1.42; 95% confidence interval (CI): 1.12 to 1.81; P = 0.004]. Therefore, the neuroprotective effect of edaravone dexborneol is more worthy of promotion than edaravone in clinical trials. TASTE-III, a randomized, controlled trial has been completed evaluating the efficacy and safety of edaravone dexborneol in patients with AIS undergoing reperfusion therapy, and the results are pending. In addition to edaravone dexborneol, oral administration of edaravone [43] and edaravone ionic liquid [44] have also been proven to have good anti-oxidative free radicals and reduce I/R injury in animal experiments. In conclusion, edaravone dexborneol is a neuroprotective agent with relatively sufficient clinical research data.

Glucagon-like peptide-1 (GLP-1) is a multifunctional polypeptide that activates GLP-1 receptor (GLP-1R), playing a crucial role in neuroprotection [45]. Numerous animal studies have confirmed the significance of GLP-1/GLP-1R as key molecules for neuroprotection, particularly beneficial for AIS patients with diabetes. The neuroprotective effects of GLP-1/GLP-1R primarily involve reducing neuroinflammation, and MMP-9 to reduce BBB damage, oxidative stress, cell excitability, cell apoptosis, and pyroptosis [46–48].

Insulin-like growth factor-1 (IGF-1) induces various neuroprotective activities through the activation of phosphoinositide 3-kinases/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) and mitogen-activated protein kinase (MAPK) pathways [49, 50]. MicroRNA (miRNA) analysis conducted by Bake et al. [51] revealed that IGF-1 significantly downregulated the PI3K/Akt signaling pathway, cell adhesion/endothelial stromal cell receptor pathway, T and B cell signaling pathway, and cytokines storm and inflammatory factors. This implies that IGF-1 exerts neuroprotective effects mainly by protecting the BBB and inhibiting neuroinflammation. The above are neuroprotective drugs related to glucose metabolism.

The two categories of medications are extensively utilized in clinical practice, particularly for individuals diagnosed with diabetes. Although no randomized clinical controlled trials investigating the aforementioned drugs’ neuroprotective effects have been officially published yet, we anticipate their promising prospects for AIS patients in future research.

Traditional Chinese medicine (TCM), derived from natural extracts and analogs of herbs, is now widely employed in animal studies, clinical research, and clinical practice of AIS due to its multi-target, multi-pathway, and wide range of effects containing anti-oxidative, anti-apoptotic, anti-neuroinflammatory, and neuromodulatory effects [10, 52]. A review conducted in 2022 on the neuroprotective effects of TCM [53] classified the natural compounds of TCM into glycosides (astragaloside IV, gastrodin, ginsenoside Rg1, and salidroside), flavonoids (baicalin, icariin, puerarin, and breviscapine), phenols (resveratrol, curcumin, and salvianolic acid B), and terpenes (ginkgolide B and catalpol). The targets of TCM are numerous and not fully elucidated. In preclinical studies, a natural compound can exert its neuroprotective effects through different mechanisms. For instance, astragaloside IV, a natural compound extracted from Astragalus, showed neuroprotective effects through calcium-sensing-receptor-mediated apoptosis. Apart from these natural compounds, we can also see the neuroprotective effects of many TCM prescriptions, such as Tongxinluo [54], XingNaoJing [55], Gualou Guizhi decoction [56], Tao Hong Si Wu decoction [57], etc. in those preclinical studies. In clinical trials, Zhang et al. [58] conducted a randomized clinical trial to validate the efficacy and safety of ginkgo diterpene lactone. In conclusion, TCM still has great therapeutic potential. Further exploration regarding their molecular mechanisms is challenging.

Nerinetide (NA-1) is a polypeptide that interferes with postsynaptic density protein 95 (PSD-95) and reduces the interaction between PSD-95 and neuronal nitric oxide synthase, thereby reducing nitric oxide radical production and its mediated cell death [59]. In the preclinical model of ischemic stroke, it has shown promise in reducing infarct size during cerebral ischemia-reperfusion and improving functional prognosis [60]. However, in a large randomized controlled trial (ESCAPE-NA1) [61] published in 2020, the rate of favorable functional outcome at 90 days in patients undergoing endovascular thrombectomy was not significantly different with NA-1 compared with the control group, which represented a failure of clinical translation. In the case of utilizing experimental models similar to humans in preclinical research, the failure of clinical translation not only indicates that we need to find a preclinical model that is more suitable for humans but also motivates us to look for multi-target and multi-pathway neuroprotective drugs. Previous observational studies have demonstrated a positive association between NA-1 and favorable patient outcomes in those not receiving recombinant tissue-type plasminogen activator (rt-PA) [61], thus highlighting the need for further clinical investigations on NA-1.

As mentioned above, MMPs are a class of molecules associated with BBB damage. Consequently, anti-MMP molecules have emerged as an important therapeutic strategy for combating hemorrhagic retransformation in AIS. Ji et al. [62] explored the therapeutic potential of an immunoglobulin G (IgG) monoclonal antibody with neutralizing specificity for MMP-9, which significantly attenuated BBB disruption in the stroke model.

Osteopontin is another molecule that has been identified in NVU studies. Spitzer et al. [63] established an NVU transcript database and found that osteopontin was highly upregulated in all NVU cell types at 24 h after ischemic stroke. Targeted therapy with subcutaneous injection of anti-osteopontin antibody could neutralize the expression of osteopontin in NVU cells after ischemic stroke in mice, thereby ensuring the integrity of the NVU and reducing the risk of hemorrhagic retransformation. The aforementioned two agents are currently undergoing preclinical investigations exclusively, with a specific focus on the NVU, exhibiting substantial therapeutic potential as neuroprotective agents.

Ferroptosis has recently been increasingly recognized as an important mechanism of pathological cell death during stroke. Ferrostatin-1 [64] and its analog, Srs11-92 [65], can improve oxidative stress and neuroinflammation following cerebral I/R injury, potentially serving as novel targets for neuroprotection.

Sevoflurane, one of the most commonly used anesthetics, exerts a protective effect on cerebral I/R injury [66]. Currently, the research on sevoflurane is mainly reflected in the control of neuroinflammation and the inhibition of apoptosis. Yang et al. [67] demonstrated that sevoflurane can reduce neuronal apoptosis by mediating the E2F transcription factor 1/enhancer of zeste homolog 2/tissue inhibitor of metalloproteinases 2 (E2F1/EZH2/TIMP2) regulation axis, thereby protecting rats from brain I/R injury. Lyu et al. [66] found that sevoflurane could inhibit ferroptosis of cells through the specificity protein 1/acyl-CoA synthetase long chain family member 4 (SP1/ACSL4)-pathway.

Clomethiazole, derived from thiazole moiety of thiamine, exerts its neuroprotective effects by activating gamma-aminobutyric acid (GABA) receptors [68]. In the clomethiazole acute stroke study (CLASS), a randomized, controlled trial of clomethiazole in 1,360 acute stroke patients, its efficacy was not significantly different from that of the placebo group [69]. Nevertheless, in the subgroup analysis of large stroke, a treatment effect was observed with clomethiazole, as reflected in an increase of Barthel index in proportion to 40.8%, with a relative benefit of 37% compared with placebo [70]. And it shows good safety in clinical application [71].

Substance P, a neuropeptide consisting of 11 amino acids, has been demonstrated to promote the peripheral mobilization of bone marrow mesenchymal stem cells (MSCs) and monocyte/macrophage polarization in various acute and chronic tissue injuries. This peptide has exhibited promising neuroprotective effects in animal studies. Using a rat model of AIS induced by tMCAO, our research team observed that rats treated with substance P exhibited a 3-fold reduction in mortality rates and a 40% decrease in cerebral infarct volumes compared to those administered saline. Furthermore, substance P augmented the expression of neuroprotective and anti-inflammatory genes in the ischemic brain, and induced neuronal survival in the brain penumbra. This led to the preservation of the BBB in ischemic brain tissue [72]. More clinical studies are needed to further explore the neuroprotective effect of substance P.

Stem cells possess the ability to regenerate into new cells and differentiate into different cells. In neuroprotective therapy, they not only have the potential to replace damaged cells and tissues but also create a supportive microenvironment for neurogenesis, release of neurotrophic factors, and restoration of mitochondrial function [73]. Recent studies have focused on different types of stem cells including MSCs, neural stem cells (NSCs), and hair follicle stem cells. Among these, MSCs have been extensively investigated in preclinical and clinical research due to their capacity to mitigate oxidative stress, produce cytokines and extracellular vesicles that inhibit proinflammatory cytokines and inflammatory cell activation, suppress pyroptosis, as well as reduce BBB permeability [74]. Ha et al. [75] verified that adult human NSCs can significantly reduce tissue and neural function loss, which is mediated through its paracrine neuroprotective and proangiogenic activities through the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway. In a 2023 preclinical study, Tang et al. [76] verified for the first time that hepatocyte growth factor-modified hair follicle stem cells could alleviate I/R injury and promote neurological function recovery by inhibiting inflammatory response, protecting the BBB, and promoting angiogenesis. At present, the sample size of patients in the clinical research of stem cells is small, and the clinical evidence is insufficient. For MSCs, there is a randomized controlled trial including twenty patients presenting AIS, which suggested fewer neurological complications, including cerebral edema and hemorrhagic retransformation [77]. For NSCs, an open-label, single-center, dose-escalation study was conducted and eleven men with chronic ischemia stroke were included, in which NSCs were found to cause no adverse events and were associated with improvement in neurological function [78]. Moreover, further investigation is required regarding immune responses induced by stem cell transplantation as well as optimal delivery methods for effective application [73, 79, 80]. Nonetheless, stem cell therapy holds promise as a potential future direction for neuroprotective treatment in AIS.

miRNA is a class of small non-coding RNA molecules, ranging in length from 19 to 24 nucleotides, which plays a key role in biological processes by regulating the expression of messenger RNA. Numerous studies have demonstrated alterations in miRNA expression following AIS, suggesting their potential involvement in the pathophysiologic mechanisms underlying this condition. Modulating miRNA regulation may offer protective effects on the BBB and mitigate I/R injury [81].

The present study, as depicted in Table 1, provides a comprehensive overview of miRNA investigations conducted within the past three years. Notably, all these studies are preclinical and involve experimental animal models, encompassing diverse pathways and targets. However, as their role in the psychopathology of AIS is uncertain, the development of neuroprotective agents against them is currently not a priority. Further exploration through both preclinical and clinical trials is needed to fully elucidate the potential of miRNA as a neuroprotective therapeutic strategy.

In addition to neuroprotective drugs and molecules, many physical therapies have shown neuroprotective effects in AIS patients through preclinical and clinical studies.

Transient ischemic attack (TIA), a transient impairment of brain or retinal nerve function resulting from localized ischemia, manifests as corresponding symptoms and signs at the site of ischemia. Some animal and clinical investigations imply that individuals with a history of TIA tend to exhibit superior functional outcomes post-stroke in comparison to those without any prior history of TIA. Tsai et al. [104] successfully developed a TIA mouse model and corroborated that the occurrence of TIA within 24 h was positively correlated with neurological recovery in rats. In a prospective study of 1,269 patients with nonlacunar stroke, 21.7% of those with a history of TIA had a favorable outcome, compared with 15% of those without a history of TIA [105]. The difference was statistically significant. The findings of this study imply that TIA might possess neuroprotective properties by eliciting ischemic tolerance. In another clinical study involving 887 AIS patients treated with endovascular thrombectomy, TIA occurring within 96 h before symptom onset was independently associated with 3-month functional outcomes but not with a reduction of severity of stroke [106]. In light of this, several researchers have endeavored to investigate the neuroprotective properties of ischemic preconditioning. Remote ischemic conditioning (RIC) refers to restricting blood flow into the limb and then releasing blood into the ischemic site to promote neuroprotection. The neuroprotective impact of RIC on stroke remains inconclusive in clinical practice [107]. To further explore this phenomenon, investigation into additional mechanisms and treatment methods is needed.