Neuroprotective Effects of Selective Inhibition of Histone Deacetylase 3 in Experimental Stroke

The Two Faces of HDAC3: Neuroinflammation in Disease and Neuroprotection in Recovery

Histone deacetylase 3 (HDAC3) is a critical regulator of gene expression, influencing a variety of cellular processes in the central nervous system. As such, dysfunction of this enzyme may serve as a key driver in the pathophysiology of various neuropsychiatric disorders and neurodegenerative diseases. HDAC3 plays a crucial role in regulating neuroinflammation, and is now widely recognized as a major contributor to neurological conditions, as well as in promoting neuroprotective recovery following brain injury, hemorrhage and stroke. Emerging evidence suggests that pharmacological inhibition of HDAC3 can mitigate behavioral and neuroimmune deficits in various brain diseases and disorders, offering a promising therapeutic strategy. Understanding HDAC3 in the healthy brain lays the necessary foundation to define and resolve its dysfunction in a disease state. This review explores the mechanisms of HDAC3 in various cell types and its involvement in disease pathology, emphasizing the potential of HDAC3 inhibition to address neuroimmune, gene expression and behavioral deficits in a range of neurodegenerative and neuropsychiatric conditions.

Unraveling the protein post-translational modification landscape: Neuroinflammation and neuronal death after stroke

The impact of stroke on global health is profound, with both high mortality and morbidity rates. This condition can result from cerebral ischemia, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH). The pathophysiology of stroke involves secondary damage and irreversible loss of neuronal function. Post-translational modifications (PTMs) have been recognized as crucial regulatory mechanisms in ischemic and hemorrhagic stroke-induced brain injury. These PTMs include phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and succinylation. This comprehensive review delves into recent research on the PTMs landscape associated with neuroinflammation and neuronal death specific to cerebral ischemia, ICH, and SAH. This review aims to explain the role of PTMs in regulating pathologic mechanisms and present critical techniques and proteomic strategies for identifying PTMs. This knowledge helps us comprehend the underlying mechanisms of stroke injury and repair processes, leading to the development of innovative treatment strategies. Importantly, this review underscores the significance of exploring PTMs to understand the pathophysiology of stroke.

Arresting the bad seed: HDAC3 regulates proliferation of different microglia after ischemic stroke

The accumulation of self-renewed polarized microglia in the penumbra is a critical neuroinflammatory process after ischemic stroke, leading to secondary demyelination and neuronal loss. Although known to regulate tumor cell proliferation and neuroinflammation, HDAC3's role in microgliosis and microglial polarization remains unclear. We demonstrated that microglial HDAC3 knockout (HDAC3-miKO) ameliorated poststroke long-term functional and histological outcomes. RNA-seq analysis revealed mitosis as the primary process affected in HDAC3-deficent microglia following stroke. Notably, HDAC3-miKO specifically inhibited proliferation of proinflammatory microglia without affecting anti-inflammatory microglia, preventing microglial transition to a proinflammatory state. Moreover, ATAC-seq showed that HDAC3-miKO induced closing of accessible regions enriched with PU.1 motifs. Overexpressing microglial PU.1 via an AAV approach reversed HDAC3-miKO-induced proliferation inhibition and protective effects on ischemic stroke, indicating PU.1 as a downstream molecule that mediates HDAC3's effects on stroke. These findings uncovered that HDAC3/PU.1 axis, which mediated differential proliferation-related reprogramming in different microglia populations, drove poststroke inflammatory state transition, and contributed to pathophysiology of ischemic stroke.

Probing the mechanisms of hydrazide-based HDAC inhibitors binding to HDAC3 using Gaussian accelerated molecular dynamics (GaMD) simulations

Histone deacetylases (HDACs) have emerged as promising targets for anticancer drug development. They regulate gene expression by removing acetyl groups from lysine residues on histone tails, leading to chromatin condensation. A hydrazide-based HDAC inhibitor, N-(4-(2-Propylhydrazine-1-carbonyl)benzyl)-1H-indole-2-carboxamide (11h), has been reported to exhibit significant in vivo antitumor activity. In comparison to the lead compound N-(4-(2-Propylhydrazine-1-carbonyl)benzyl)cinnamamide (17), compound 11h demonstrates 2- to 5-fold higher HDAC inhibition and cell-based antitumor activity. However, the inhibitory mechanism of 11h remains insufficiently explored. In this study, we conducted 500 ns Gaussian Accelerated Molecular Dynamics (GaMD) simulations on Histone deacetylase 3 (HDAC3) and two complex systems (HDAC3-17 and HDAC3-11h). Our findings revealed that upon inhibitor binding, the active pocket volume of HDAC3 undergone alterations, and the movement of the L6-loop toward the active site impeded substrate entry. Moreover, we observed a destabilization of the α-helix in the aa75-89 region of HDAC3 compared to the two complex systems, indicating partial unwinding. Notably, 11h exhibited a closer proximity of its carbonyl oxygen to the active pocket's Zn2+ metal compared to 17, increasing the likelihood of coordination with the Zn2+ metal. The analysis of protein-ligand interactions highlighted a greater number of hydrogen bonds and other interactions between 11h and the receptor protein when compared to 17, underscoring the stronger binding of 11h to HDAC3. In conclusion, our study provided theoretical insights into the inhibitory mechanism of hydrazide-based HDAC inhibitors on HDAC3, thereby contributing to the development of improved drug targets for cancer therapy.Communicated by Ramaswamy H. Sarma.

HDAC1 is Involved in Neuroinflammation and Blood-Brain Barrier Damage in Stroke Pathogenesis

Background

Stroke is a common cause of disability and mortality worldwide; however, effective therapy remains limited. In stroke pathogenesis, ischemia/reperfusion injury triggers gliosis and neuroinflammation that further activates matrix metalloproteinases (MMPs), thereby damaging the blood-brain barrier (BBB). Increased BBB permeability promotes macrophage infiltration and brain edema, thereby worsening behavioral outcomes and prognosis. Histone deacetylase 1 (HDAC1) is a repressor of epigenomic gene transcription and participates in DNA damage and cell cycle regulation. Although HDAC1 is deregulated after stroke and is involved in neuronal loss and DNA repair, its role in neuroinflammation and BBB damage remains unknown.

Methods

The rats with cerebral ischemia were evaluated in behavioral outcomes, levels of inflammation in gliosis and cytokines, and BBB damage by using an endothelin-1-induced rat model with cerebral ischemia/reperfusion injury.

Results

The results revealed that HDAC1 dysfunction could promote BBB damage through the destruction of tight junction proteins, such as ZO-1 and occludin, after stroke in rats. HDAC1 inhibition also increased the levels of astrocyte and microglial gliosis, tumor necrosis factor-alpha, interleukin-1 beta, lactate dehydrogenase, and reactive oxygen species, further triggering MMP-2 and MMP-9 activity. Moreover, modified neurological severity scores for the cylinder test revealed that HDAC1 inhibition deteriorated behavioral outcomes in rats with cerebral ischemia.

Discussion

HDAC1 plays a crucial role in ischemia/reperfusion-induced neuroinflammation and BBB damage, thus indicating its potential as a therapeutic target.

RGFP966 exerts neuroprotective effect via HDAC3/Nrf2 pathway after surgical brain injury in rats

Histone deacetylase 3 (HDAC3) restores chromatin nucleosomes to a transcriptional repression state, thereby inhibiting gene expression. Studies have found that HDAC3 expression is upregulated in a variety of pathological states of the central nervous system and related to its neurotoxicity. However, the role of HDAC3 in surgical brain injury (SBI) has not been thoroughly explored.

OBJECTIVE

To observe the role of HDAC3 in SBI and the outcome of SBI after its suppression.

METHODS

Rat SBI model was used, and intraperitoneal injection of RGFP966 (HDAC3 specific inhibitor) was used to detect the changes of HDAC3 expression and neuronal apoptosis indexes in the surrounding cortex of SBI rats, and the cerebral edema and neurological outcome of rats were observed.

RESULTS

The expression of HDAC3 in the peripheral cortex of SBI rats was increased, and RGFP966 inhibited the upregulation of HDAC3 and saved the nerve cells around the damaged area. In addition, RGFP966 increased the expression of anti-oxidative stress proteins such as heme oxygenase-1 (HO-1) and superoxide dismutase 2 (SOD2). At the same time, the expression of apoptotic marker protein cleaved-caspase-3 (cle-caspase-3) was decreased, while the expression level of apoptotic protective marker protein B-cell lymphoma 2 (Bcl-2) was increased. In addition, this research demonstrated that in the RGFP966 rat SBI model, the expression level of antioxidant modifier nuclear factor-erythroid 2-related factor 2 (Nrf2) was increased.

CONCLUSION

RGFP966 might activate HDAC3/Nrf2 signaling pathway by inhibiting HDAC3, regulated oxidative stress and nerve cell apoptosis induced by SBI in rat SBI model, reduced brain edema, and had a protective effect on nerve injury. It might be a potential target of SBI pathology.

Tackling the glial scar in spinal cord regeneration: new discoveries and future directions

Axonal regeneration and functional recovery are poor after spinal cord injury (SCI), typified by the formation of an injury scar. While this scar was traditionally believed to be primarily responsible for axonal regeneration failure, current knowledge takes a more holistic approach that considers the intrinsic growth capacity of axons. Targeting the SCI scar has also not reproducibly yielded nearly the same efficacy in animal models compared to these neuron-directed approaches. These results suggest that the major reason behind central nervous system (CNS) regeneration failure is not the injury scar but a failure to stimulate axon growth adequately. These findings raise questions about whether targeting neuroinflammation and glial scarring still constitute viable translational avenues. We provide a comprehensive review of the dual role of neuroinflammation and scarring after SCI and how future research can produce therapeutic strategies targeting the hurdles to axonal regeneration posed by these processes without compromising neuroprotection.

The role of HDAC3 and its inhibitors in regulation of oxidative stress and chronic diseases

HDAC3 is a specific and crucial member of the HDAC family. It is required for embryonic growth, development, and physiological function. The regulation of oxidative stress is an important factor in intracellular homeostasis and signal transduction. Currently, HDAC3 has been found to regulate several oxidative stress-related processes and molecules dependent on its deacetylase and non-enzymatic activities. In this review, we comprehensively summarize the knowledge of the relationship of HDAC3 with mitochondria function and metabolism, ROS-produced enzymes, antioxidant enzymes, and oxidative stress-associated transcription factors. We also discuss the role of HDAC3 and its inhibitors in some chronic cardiovascular, kidney, and neurodegenerative diseases. Due to the simultaneous existence of enzyme activity and non-enzyme activity, HDAC3 and the development of its selective inhibitors still need further exploration in the future.

Histone Deacetylase 3 Inhibition Decreases Cerebral Edema and Protects the Blood–Brain Barrier After Stroke

We have previously shown that selective inhibition of histone deacetylase 3 (HDAC3) decreases infarct volume and improves long-term functional outcomes after stroke. In this study, we examined the effects of HDAC3 inhibition on cerebral edema and blood–brain barrier (BBB) leakage and explored its underlying mechanisms. Adult male Wistar rats were subjected to 2-h middle cerebral artery occlusion (MCAO) and randomly treated i.p. with either vehicle or a selective HDAC3 inhibitor (RGFP966) at 2 and 24 h after stroke. Modified neurological severity scores (mNSS) were calculated at 2 h, 1 day, and 3 days. H&E, Evans blue dye (EBD) assay, and fluorescein isothiocyanate (FITC)-dextran were employed to assess cerebral edema and BBB leakage. Western blot for matrix metalloproteinase-9 (MMP9), MMP-9 zymography, and immunostaining for HDAC3, GFAP, Iba-1, albumin, aquaporin-4, claudin-5, ZO-1, and NF-kB were performed. Early RGFP966 administration decreased cerebral edema (p = 0.002) and BBB leakage, as measured by EBD assay, FITC-dextran, and albumin extravasation (p < 0.01). RGFP966 significantly increased tight junction proteins (claudin-5 and ZO-1) in the peri-infarct area. RGFP966 also significantly decreased HDAC3 in GFAP + astrocytes, which correlated with better mNSS (r = 0.67, p = 0.03) and decreased cerebral edema (r = 0.64, p = 0.04). RGFP966 decreased aquaporin-4 in GFAP + astrocytes (p = 0.002), as well as, the inflammatory markers Iba-1, NF-kB, and MMP9 in the ischemic brain (p < 0.05). Early HDAC3 inhibition decreases cerebral edema and BBB leakage. BBB protection by RGFP966 is mediated in part by the upregulation of tight junction proteins, downregulation of aquaporin-4 and HDAC3 in astrocytes, and decreased neuroinflammation.

Identification of novel leads as potent inhibitors of HDAC3 using ligand-based pharmacophore modeling and MD simulation

In the landscape of epigenetic regulation, histone deacetylase 3 (HDAC3) has emerged as a prominent therapeutic target for the design and development of candidate drugs against various types of cancers and other human disorders. Herein, we have performed ligand-based pharmacophore modeling, virtual screening, molecular docking, and MD simulations to design potent and selective inhibitors against HDAC3. The predicted best pharmacophore model 'Hypo 1' showed excellent correlation (R2 = 0.994), lowest RMSD (0.373), lowest total cost value (102.519), and highest cost difference (124.08). Hypo 1 consists of four salient pharmacophore features viz. one hydrogen bond acceptor (HBA), one ring aromatic (RA), and two hydrophobic (HYP). Hypo 1 was validated by Fischer's randomization with a 95% of confidence level and the external test set of 60 compounds with a good correlation coefficient (R2 = 0.970). The virtual screening of chemical databases, drug-like properties calculations followed by molecular docking resulted in identifying 22 representative hit compounds. Performed 50 ns of MD simulations on top three hits were retained the salient π-stacking, Zn2+ coordination, hydrogen bonding, and hydrophobic interactions with catalytic residues from the active site pocket of HDAC3. Total binding energy calculated by MM-PBSA showed that the Hit 1 and Hit 2 formed stable complexes with HDAC3 as compared to reference TSA. Further, the PLIP analysis showed a close resemblance between the salient pharmacophore features of Hypo 1 and the presence of molecular interactions in co-crystallized FDA-approved drugs. We conclude that the screened hit compounds may act as potent inhibitors of HDAC3 and further preclinical and clinical studies may pave the way for developing them as effective therapeutic agents for the treatment of different cancers and neurodegenerative disorders.

RGFP966 is protective against lipopolysaccharide-induced depressive-like behaviors in mice by inhibiting neuroinflammation and microglial activation

Depression is a prevalent mental disorder. However, its pathophysiological mechanism has still remained elusive, and a limited number of effective treatments have been presented. Recent studies have shown that neuroinflammation and microglial activation are involved in the pathogenesis of depression. Histone deacetylase 3 (HDAC3) has neurotoxic effects on several neuropathological conditions. The inhibition of HDAC3 has been reported to induce anti-inflammatory and antioxidant effects. RGFP966 is a highly selective inhibitor of HDAC3. This study aimed to investigate the antidepressant effect of RGFP966 on lipopolysaccharide (LPS)-induced depressive-like behaviors in mice and to explore its possible mechanism. Adult male C57BL/6J mice were utilized in this study. The LPS and RGFP966 were injected intraperitoneally daily for 5 days. The behavior tests were performed to elucidate the depression-like behaviors. Western blot, ELISA and immunofluorescence staining were used to study the HDAC3/TLR4/NLRP3 pathway-related proteins. The results of behavioral tests showed that RGFP966 could improve the LPS-induced depressive-like behaviors in mice. The results of Western blotting showed that RGFP966 treatment downregulated the expression levels of toll-like receptor 4 (TLR4), nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3), caspase-1, and interleukin-1β (IL-1β) (P < 0.05). Furthermore, the results of immunofluorescence staining showed that RGFP966 treatment inhibited microglial activation in the hippocampus of mice (P < 0.01). These findings suggested that RGFP966 could effectively ameliorate LPS-induced depressive-like behaviors in mice by inhibiting neuroinflammation and microglial activation. The anti-inflammatory mechanism of RGFP966 might be related to the inhibition of the HDAC3/TLR4/NLRP3 signaling pathway. Therefore, inhibition of HDAC3 using RGFP966 could serve as a potential treatment strategy for depression.

Inhibited HDAC3 or Elevated MicroRNA-494-3p Plays a Protective Role in Myocardial Ischemia-Reperfusion Injury via Suppression of BRD4

Increased histone deacetylase 3 (HDAC3) has been demonstrated to contribute to the pathogenesis of myocardial ischemia-reperfusion injury (MI/RI). Therefore, the goal of this study was to investigate how HDAC3 regulated MI/RI by mediating microRNA (miR)-494-3p/dromodomain-containing protein 4 (BRD4) axis. The MI/RI model was established by ligating the right anterior descending coronary artery. Cardiomyocytes from newborn mice were treated with hypoxia/reoxygenation (H/R). Gain-of-function and loss-of-function approaches were implemented to figure out the roles of miR-494-3p and HDAC3 in MI/RI. miR-494-3p, HDAC3, and BRD4 in myocardial tissues of mice with MI/RI and H/R-treated cardiomyocytes were detected. The relationships between miR-494-3p and HDAC3 and BRD4 were identified. Reduced miR-494-3p and upregulated HDAC3 and BRD4 exhibited in myocardial tissues of mice with MI/RI and H/R-treated cardiomyocytes. Inhibited HDAC3 or elevated miR-494-3p repressed the inflammation and apoptosis, improved cardiac function, and ameliorated myocardial injury in myocardial tissues of mice with MI/RI. Suppression of HDAC3 or elevation of miR-494-3p depressed inflammation and apoptosis and promoted cell viability of primary cardiomyocytes. miR-494-3p targeted BRD4. The study concludes that suppressed HDAC3 plays a protective role in MI/RI by upregulation of miR-494-3p and inhibition of BRD4, which could be helpful for MI/RI therapy.

Impaired Cognitive Flexibility Induced by Chronic Cerebral Hypoperfusion in the 5XFAD Transgenic Mouse Model of Mixed Dementia

Cerebrovascular lesions are widely prevalent in patients with Alzheimer’s disease (AD), but their relationship to the pathophysiology of AD remains poorly understood. An improved understanding of the interaction of cerebrovascular damage with AD is crucial for the development of therapeutic approaches. Herein, we investigated the effects of chronic cerebral hypoperfusion (CCH) in a 5XFAD transgenic (Tg) mouse model of AD. We established CCH conditions in both Tg and non-Tg mice by inducing unilateral common carotid artery occlusion (UCCAO). Cognitive performance in mice was evaluated, and their brain tissue was examined for amyloid-beta (Aβ) pathology to elucidate possible mechanisms. We found that UCCAO-operated Tg mice showed impaired cognitive flexibility in the reversal phase of the hidden-platform water maze task compared to sham-operated Tg mice. Interestingly, UCCAO-operated Tg mice used fewer spatial cognitive strategies than sham-operated Tg mice during reversal learning. These cognitive deficits were accompanied by increased Aβ plaque burden and Aβ42 levels in the hippocampus and prefrontal cortex, 2 regions that play essential roles in the regulation of cognitive flexibility. Furthermore, changes in cognitive flexibility are strongly correlated with the expression levels of enzymes related to Aβ clearance, such as neprilysin and insulin-degrading enzymes. These findings suggest that, in 5XFAD mice, impaired cognitive flexibility is related to CCH, and that Aβ clearance might be involved in this process.

Valproic acid mitigates spinal nerve ligation-induced neuropathic pain in rats by modulating microglial function and inhibiting neuroinflammatory response

Spinal inflammation is a pathophysiological state of neuropathic pain (NP). The subsequent microglial activation and neuroinflammatory response are contributing factors for long-lasting behavioral hypersensitivity. Valproic acid (VPA), a histone deacetylase inhibitor, has promising anti-inflammatory and neuroprotective properties for clinical use in the treatment of neurological disorders. However, the underlying mechanisms of its effects on NP have not been determined. This study aimed to clarify the possible mechanisms by which VPA alleviates NP in rat models induced by spinal nerve ligation (SNL). Intraperitoneal injection of VPA (300 mg/kg) efficiently attenuated mechanical allodynia in rats with NP. VPA exerted anti-inflammatory effects by downregulating proinflammatory cytokines (tumor necrosis factor-α, cytokines interleukin-1β, cytokines interleukin-6; TNF-α, IL-1β, and IL-6) and upregulating anti-inflammatory cytokines (transforming growth factor-β, cytokines interleukin-10, cytokines interleukin-4; TGF-β, IL-10 and IL-4). Additionally, VPA suppressed spinal microgliosis and promoted the polarization of microglia towards the M2 phenotype to further ameliorate spinal neuroinflammation. VPA also exerted neuroprotective effects by decreasing spinal cell apoptosis. The anti-inflammatory and neuroprotective effects may have depended on changes in nuclear histone deacetylase 3 (HDAC3) expression following VPA treatment. Moreover, VPA treatment inhibited nuclear factor-κB (NF-κB) p65 nuclear expression and upregulated acetylated the signal transducer and activator of transcription 1 (STAT1). In addition, VPA suppressed SNL-induced phosphorylation of Janus Kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). Taken together, our results demonstrate that VPA is a promising anti-inflammatory agent suitable for NP therapy that regulates microglial function and suppresses spinal neuroinflammation via the STAT1/NF-κB and JAK2/STAT3 signaling pathways.

Comparative Proteomics Unveils LRRFIP1 as a New Player in the DAPK1 Interactome of Neurons Exposed to Oxygen and Glucose Deprivation

Death-associated protein kinase 1 (DAPK1) is a pleiotropic hub of a number of networked distributed intracellular processes. Among them, DAPK1 is known to interact with the excitotoxicity driver NMDA receptor (NMDAR), and in sudden pathophysiological conditions of the brain, e.g., stroke, several lines of evidence link DAPK1 with the transduction of glutamate-induced events that determine neuronal fate. In turn, DAPK1 expression and activity are known to be affected by the redox status of the cell. To delineate specific and differential neuronal DAPK1 interactors in stroke-like conditions in vitro, we exposed primary cultures of rat cortical neurons to oxygen/glucose deprivation (OGD), a condition that increases reactive oxygen species (ROS) and lipid peroxides. OGD or control samples were co-immunoprecipitated separately, trypsin-digested, and proteins in the interactome identified by high-resolution LC-MS/MS. Data were processed and curated using bioinformatics tools. OGD increased total DAPK1 protein levels, cleavage into shorter isoforms, and dephosphorylation to render the active DAPK1 form. The DAPK1 interactome comprises some 600 proteins, mostly involving binding, catalytic and structural molecular functions. OGD up-regulated 190 and down-regulated 192 candidate DAPK1-interacting proteins. Some differentially up-regulated interactors related to NMDAR were validated by WB. In addition, a novel differential DAPK1 partner, LRRFIP1, was further confirmed by reverse Co-IP. Furthermore, LRRFIP1 levels were increased by pro-oxidant conditions such as ODG or the ferroptosis inducer erastin. The present study identifies novel partners of DAPK1, such as LRRFIP1, which are suitable as targets for neuroprotection.

Interactive Effects of a Combination of the HDAC3 and HDAC9 Genes with Diabetes Mellitus on the Risk of Ischemic Stroke

BACKGROUND AND AIM

 Previous studies indicated that the HDAC3 and HDAC9 genes play critical roles in atherosclerosis and ischemic stroke (IS). The purpose of this study was to investigate the association of combined single-nucleotide polymorphisms in the HDAC3 and HDAC9 genes with the susceptibility to IS.

METHODS

 A case-control study was conducted including 863 IS patients and 863 age- and gender-matched healthy participants. A polygenic score was developed to estimate the contribution of a combination of the HDAC3 and HDAC9 genes to the risk of IS. The interactive effects of traditional risk factors of stroke and the polygenic score on the risk of IS were explored. Additionally, the association between the polygenic score and the progression of atherosclerosis, a potential risk factor of IS, was examined in our healthy controls.

RESULTS

 Subjects with a higher polygenic score had an increased risk of IS (odds ratio: 1.83; 95% confidence interval: 1.38-2.43) after adjusting for covariates compared with individuals with a lower polygenic score. An interactive effect of diabetes mellitus and the polygenic score on the risk of IS was observed. A significant positive correlation between the polygenic score and a change in the plaque score (standardized β = 0.42, p = 0.0235) in healthy controls with diabetes mellitus was found.

CONCLUSION

 Our results suggested that the combination of the HDAC3 and HDAC9 genes with a history of diabetes mellitus could exacerbate the deterioration of atherosclerosis, thereby increasing the risk of IS. Further studies are warranted to explore our results in other populations.

Galectin-9 Promotes Neuronal Restoration via Binding TLR-4 in a Rat Intracerebral Hemorrhage Model

Intracerebral hemorrhage (ICH) is a devastating disease with high rates of mortality and morbidity. Galactose lectin-9 (Gal-9) belongs to the family of β-galactoside-binding lectins, which has been shown to play a vital role in immune tolerance and inflammation. However, the function of Gal-9 in ICH has not been fully studied in details. Several experiments were carried out to explore the role of Gal-9 in the late period of ICH. Primarily, ICH models were established in male adult Sprague Dawley (SD) rats. Next, the relative protein levels of Gal-9 at different time points after ICH were examined and the result showed that the level of Gal-9 increased and peaked at the 7th day after ICH. Then we found that when the content of Gal-9 increased, both the number of M2-type microglia and the corresponding anti-inflammatory factors also increased. Through co-immunoprecipitation (CO-IP) analysis, it was found that Gal-9 combines with Toll-like receptor-4 (TLR-4) during the period of the recovery after ICH. TUNEL staining and Fluoro-Jade B staining (FJB) proved that the amount of cell death decreased with the increase of Gal-9 content. Additionally, several behavioral experiments also demonstrated that when the level of Gal-9 increased, the motor, sensory, learning, and memory abilities of the rats recovered better compared to the ICH group. In short, this study illustrated that Gal-9 takes a crucial role after ICH. Enhancing Gal-9 could alleviate brain injury and promote the recovery of ICH-induced injury, so that Gal-9 may exploit a new pathway for clinical treatment of ICH.

Antagonistic effects of IL-17 and Astragaloside IV on cortical neurogenesis and cognitive behavior after stroke in adult mice through Akt/GSK-3β pathway

We aimed to investigate the exact effect of IL-17 on regulating neural stem cells (NSCs) stemness and adult neurogenesis in ischemic cortex after stroke, how Astragaloside IV(As-IV) regulated IL-17 expression and the underlying mechanism. Photochemical brain ischemia model was established and IL-17 protein expression was observed at different time after stroke in WT mice. At 3 days after stroke, when IL-17 expression peaked, IL-17 knock out (KO) mice were used to observe cell proliferation and neurogenesis in ischemic cortex. Then, As-IV was administered intravenously to assess cell apoptosis, proliferation, neurogenesis, and cognitive deficits by immunochemistry staining, western blots, and animal behavior tests in WT mice. Furthermore, IL-17 KO mice and As-IV were used simultaneously to evaluate the mechanism of cell apoptosis and proliferation after stroke in vivo. Besides, in vitro, As-IV and recombinant mouse IL-17A was administered, respectively, into NSCs culture, and then their diameters, viable cell proliferation and pathway relevant protein was assessed. The results showed knocking out IL-17 contributed to regulating PI3K/Akt pathway, promoting NSCs proliferation, and neurogenesis after ischemic stroke. Moreover, As-IV treatment helped inhibit neural apoptosis, promote the neurogenesis and eventually relieve mice anxiety after stroke. Unsurprisingly, IL-17 protein expression could be downregulated by As-IV in vivo and in vitro and they exerted antagonistic effect on neurogenesis by regulating Akt/GSK-3β pathway, with significant regulation for apoptosis. In conclusion, IL-17 exerts negative effect on promoting NSCs proliferation, neurogenesis and cognitive deficits after ischemic stroke, which could be reversed by As-IV.

Histone deacetylase-3: Friend and foe of the brain

IMPACT STATEMENT

Brain development and degeneration are highly complex processes that are regulated by a large number of molecules and signaling pathways the identities of which are being unraveled. Accumulating evidence points to histone deacetylases and epigenetic mechanisms as being important regulators of these processes. In this review, we describe that histone deacetylase-3 (HDAC3) is a particularly crucial regulator of both neurodevelopment and neurodegeneration. In addition, HDAC3 regulates memory formation, synaptic plasticity, and the cognitive impairment associated with normal aging. Understanding how HDAC3 functions contributes to the normal development and functioning of the brain while also promoting neurodegeneration could lead to the development of therapeutic approaches for neurodevelopmental, neuropsychiatric, and neurodegenerative disorders.

Parecoxib exhibits anti-inflammatory and neuroprotective effects in a rat model of transient global cerebral ischemia

Transient global cerebral ischemia (tGCI) induces inflammation leading to secondary brain injury. Data suggested that cyclooxygenase-2 (COX-2) is involved in the occurrence and development of inflammatory reaction after reperfusion; however, the effectiveness of a highly selective COX-2 inhibitor, parecoxib, to counteract tGCI remains to be determined. Thus, the aim of this study was to investigate the potential protective actions of parecoxib in a rat model of tGCI and the role inflammation plays in this disorder. Adult male Sprague-Dawley rats were administered parecoxib 10 or 20 mg/kg intraperitoneally (ip) at 5 min, 24 or 48 hr after tGCI. Control rats received an equal volume of 0.9% saline. The rat model of tGCI was established using the method of bilateral common carotid artery occlusion combined with arterial hypotension. The following parameters were measured: Neurological Severity Score, morphological changes in the hippocampal CA1 region, Evans blue (EB) extravasation, brain water content, levels of matrix metalloproteinase-9 (MMP-9), zonula occludens-1 (ZO-1), neuronal apoptosis, the protein expression of Bcl-2, Bax, COX-2, prostaglandin E2 (PGE₂), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α). Parecoxib treatment significantly improved neurological function and morphological defects in the hippocampal CA1 region, reduced levels of COX-2, PGE₂, IL-1β, and TNF-α. In addition, parecoxib attenuated brain edema and BBB destruction as evidenced by increased ZO-1 expression and decreased MMP-9 expression. Further, parecoxib reduced neuronal apoptosis via diminished protein expression of Bax and enhanced expression of Bcl-2.