The Molecular Mechanisms of HDACi in Regulating Ischemic Stroke

Ischemic stroke (IS) accounts for approximately 80% of all stroke cases and is a leading cause of death and long-term disability worldwide. Its core pathological mechanism involves the interruption of cerebral blood flow, leading to neuronal cell death and ischemic tissue necrosis in the brain, which is associated with multiple molecular processes including apoptosis, inflammation, and oxidative stress. This review systematically discusses the classification of HDACs, the mechanisms of action of HDAC inhibitors, and their multiple effects in inhibiting cell apoptosis, regulating neuroinflammation, repairing the blood-brain barrier, and improving cognitive function following IS. HDACs function by removing acetyl groups from histone lysine residues, leading to chromatin condensation and gene silencing. The HDAC family is classified into four classes: class I (HDAC1, 2, 3, 8), class IIa (HDAC4, 5, 7, 9), class IIb (HDAC6, 10), and class IV (HDAC11), with class III being the NAD+-dependent sirtuins. Histone deacetylase inhibitors (HDACi) exert significant neuroprotective effects following ischemic stroke through a multi-target, multi-pathway synergistic mechanism. The core mechanisms include inhibition of neuronal apoptosis, regulation of neuroinflammation, protection of the blood-brain barrier (BBB), and improvement of cognitive impairments (PSCI). HDACi regulate gene expression epigenetically by upregulating genes such as p21/CIP1, leading to cell cycle arrest, while also modulating apoptosis-related proteins by inhibiting pro-apoptotic signaling pathways, thereby reducing neuronal cell death. In terms of neuroinflammation, HDACi suppress NF‑κB and activate Nrf2 pathways, decreasing the release of pro-inflammatory cytokines and preventing the pro-inflammatory polarization of microglia and macrophages, thus modulating the inflammatory response. Regarding BBB protection, HDACi regulate the expression and restoration of tight junction proteins such as occludin and claudin-5, while inhibiting the release of destructive factors like MMP-9, alleviating vasogenic edema, and maintaining BBB integrity. Furthermore, HDACi promote the transcription of neurotrophic factors and synaptic-associated genes, enhancing neuroplasticity and repairing neuronal networks, ultimately improving cognitive functions. Therefore, HDACi demonstrate great potential as a multifaceted therapeutic strategy for ischemic stroke. HDACis represent a powerful multi-target therapeutic approach that transcends the limitations of traditional thrombolytic therapies. HDACis represent a powerful multi-target therapeutic approach that transcends the limitations of traditional thrombolytic therapies, which are hampered by a narrow time window and risks of reperfusion injury. Histone acetylation is increased by HDACis, which relaxes chromatin and reactivates protective gene transcription. Their selectivity and chemical structure are used to classify them. Trichostatin A (TSA) and sodium butyrate (SB), a short-chain fatty acid, are examples of broad-spectrum inhibitors that are effective in lowering infarct volume and reducing neuroinflammation. More selective inhibitors, including Tubastatin A (HDAC6-selective) and Entinostat (class I-selective), may have fewer adverse effects while increasing efficacy. By suppressing apoptosis by modifying the p53, Bcl-2, and JNK pathways, reducing neuroinflammation by blocking NF-κB and NLRP3 activation, preserving the integrity of the blood-brain barrier by strengthening tight junction proteins, and promoting synaptic plasticity, neurogenesis, and the expression of neurotrophic factors like BDNF, these inhibitors provide neuroprotection through a variety of interrelated mechanisms.Despite their great potential, HDACis’ clinical translation is fraught with difficulties, mostly because of non-selective inhibition-related adverse effects such as hepatotoxicity and gastrointestinal problems with valproic acid (VPA). In order to accomplish targeted delivery to the brain, future research is consequently shifting toward the development of highly selective inhibitors, refining dosing regimes, and utilizing cutting-edge drug delivery technologies like nanoparticles. In summary, the development of effective neuroprotective and neurorestorative treatments for IS may be greatly aided by a nuanced, spatiotemporally accurate understanding of HDAC activities and the judicious use of subtype-selective HDACis.