Abstract
Increased focus has been placed on the role of histone deacetylase inhibitors as crucial players in subarachnoid hemorrhage (SAH) progression. Therefore, this study was designed to expand the understanding of SAH by exploring the downstream mechanism of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in SAH. The expression of TDP-43 in patients with SAH and rat models of SAH was measured. Then, western blot analysis, immunofluorescence staining, and transmission electron microscope were used to investigate the in vitro effect of TDP-43 on a neuronal cell model of SAH established by oxyhemoglobin treatment. Immunofluorescence staining and coimmunoprecipitation assays were conducted to explore the relationship among histone deacetylase 1 (HDAC1), heat shock protein 70 (HSP70), and TDP-43. Furthermore, the in vivo effect of HDAC1 on SAH was investigated in rat models of SAH established by endovascular perforation. High expression of TDP-43 in the cerebrospinal fluid of patients with SAH and brain tissues of rat models of SAH was observed, and TDP-43 accumulation in the cytoplasm and the formation of inclusion bodies were responsible for axonal damage, abnormal nuclear membrane morphology, and apoptosis in neurons. TDP-43 degradation was promoted by the HDAC1 inhibitor SAHA via the acetylation of HSP70, alleviating SAH, and this effect was verified in vivo in rat models. In conclusion, SAHA relieved axonal damage and neurological dysfunction after SAH via the HSP70 acetylation-induced degradation of TDP-43, highlighting a novel therapeutic target for SAH.
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Introduction
Subarachnoid hemorrhage (SAH) is a lethal and devastating intracranial hemorrhage that is frequently misdiagnosed in the initial stage and increases the risk of mortality and disability1,2. SAH, which is mainly induced by aneurysmal rupture and peri-mesencephalic bleeding, is a dangerous disease that is commonly characterized by acute headache, nausea/vomiting and neck pain, with a mortality rate within 24 h of 25% and an overall mortality rate of 50%3. Accumulating evidence has suggested that SAH-induced early brain injury is a key factor that affects the prognosis of SAH patients4. Although great achievements have been made in understanding the pathogenesis and pathophysiology of SAH, as well as in the treatment and management of SAH, its underlying molecular, cellular, and circulatory dynamics remain largely unclear, and its prognosis is still not satisfactory5,6. Thus, in-depth exploration of SAH is needed to improve management.
Suberoylanilide hydroxamic acid (SAHA), also called vorinostat, belongs to the hydroxamic acid class of histone deacetylase (HDAC) inhibitors7,8. It was shown that SAHA exerted great clinical utility as a therapeutic intervention after intracerebral hemorrhage9. Moreover, HDACs are potent enzymes that posttranslationally modify both histone and nonhistone acetylation sites, thereby affecting many cellular processes, such as the cell cycle and apoptosis10. Notably, the exacerbating effects of HDAC4 on SAH can be inhibited by SAHA11. HDAC1 inactivation was shown to protect against neuronal death and brain injury12. Moreover, it was identified that heat shock protein 70 (HSP70) was a cytosolic substrate of HDAC5 and could be hyperacetylated by HDAC5, which was further associated with the proliferation of hypoxic tumor cells13. HSP70 is a well-known therapeutic target for SAH14. In addition, HSP70 was shown to inhibit the cytoplasmic accumulation of TDP-43, which is responsible for the formation of insoluble inclusion bodies and is a hallmark of neurodegenerative diseases15,16. Moreover, TDP-43 was identified as a prognostic biomarker for SAH17. Herein, SAHA is hypothesized to be involved in the development of SAH by interacting with the HDAC1/HSP70/TDP-43 axis.
Materials and methods
Ethics statement
The current study was approved by the IRB of The Third ** solution (NCI4106, Pierce, Rockford, IL, USA) was used for development. ImageJ 1.48 u software (Bio-Rad, Hercules, CA, USA) was used to perform quantitative protein analysis (internal reference: GAPDH).
Reverse transcription–quantitative polymerase chain reaction (RT–qPCR)
Cells were lysed using a TRIzol kit (Invitrogen, Carlsbad, CA, USA), and total RNA was extracted from cell and tissue samples. RNA quality and concentration were measured by UV–Vis spectrophotometry (ND-1000, Thermo Fisher Scientific). For mRNA analysis, an RT kit (RR047A, Takara, Tokyo, Japan) was used to perform RT to obtain cDNA. Subsequently, cDNA was used as a template, and the SYBR® Premix Ex TaqTM II kit (Perfect Real Time, DRR081, Takara) was used to perform fluorescent qPCR. The samples were subjected to RT–qPCR in a real-time fluorescent qPCR instrument (ABI 7500, ABI, Foster City, CA, USA). The 2−ΔΔCT method was used to quantify expression, and GAPDH was used as the internal reference. The primers are shown in Supplementary Table 1.
Nuclear and cytoplasmic separation experiment
A NE-PER™ Nuclear and Cytoplasm Extraction Kit (78833, Thermo Fisher Scientific, https://www.thermofisher.cn/) was used to separate the nucleus and cytoplasm in each group of cells, as well as to separate nuclear and cytoplasmic proteins. Then, western blot analysis was performed to measure the expression of TDP-43 (ab109535, 1:1000, Abcam). GAPDH (ab8245, 1:1000, Abcam) was used as the internal reference for cytoplasmic proteins, and Lamin A (ab133256, 1:1000, Abcam) was used for nucleoproteins. The ratio of the gray value of TDP-43 to the gray value of each control protein was used for quantitative analysis by ImageJ 1.48 u software (Bio-Rad, Hercules, CA, USA).
Determination of malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity
After 72 h, the brain was perfused with PBS, and then the ipsilateral cortex was homogenized to measure MDA levels and the activity of SOD. The MDA level was measured by reacting MDA and thiobarbituric acid under acidic conditions (high temperature). SOD activity was measured by the WST-1 method.
Fluoro-Jade C (FJC) staining
Brain sections were deparaffinized, dehydrated, incubated in a 0.06% potassium permanganate solution (Sigma–Aldrich) for 10 min, and reacted in FJC working solution (0.1% acetic acid) for 20 min. A fluorescence microscope (Olympus) was used to observe FJC-positive cells, and the number was counted by technicians who were blinded to experimental conditions.
Dihydroethidium (DHE) staining
DHE staining was carried out to measure superoxide anions, which indicate the level of oxidative stress in tissues23. The ventral side of the left hemisphere was examined with the help of a laser scanning confocal microscope (A1 Si, Nikon, Tokyo, Japan). The representative image was obtained from a Section 2 mm posterior to the bregma.
Coimmunoprecipitation (Co-IP) assay
Equal amounts of cell lysates (1500 µg) were immunoprecipitated with 1 μg of HSP70, HDAC1, TDP-43, or acetyl-K antibodies and 50 μL protein A/G agarose. The immunoprecipitate was washed twice with 10 mM HEPES (pH 7.9), 1 mM EDTA, 150 mM NaCl, and 1% Nonidet P-40 and boiled for 10 min. Then, the precipitated proteins were eluted with 30 μL of sodium dodecyl sulfate (SDS)–PAGE buffer. The eluted proteins were separated by 8% SDS–PAGE, transferred to a nitrocellulose membrane, and examined with the corresponding antibodies.
Flow cytometry
After 48 h of transfection, the cells were detached with EDTA-free 0.25% trypsin (YB15050057, YuBo Biotech Co., Ltd., Shanghai, China), collected in a flow tube, and centrifuged, and the supernatant was discarded. According to the directions of the Annexin-V-fluorescein isothiocyanate (Annexin-V-FITC) cell apoptosis detection kit (K201-100, BioVision, Milpitas, CA, USA), the Annexin-V-FITC/PI dye solution was prepared. Then, 1 × 106 cells were resuspended in 100 μL of dye solution, incubated at room temperature for 15 min, and 1 mL HEPES buffer solution was added (PB180325, Procell, Wuhan, Hubei, China), followed by cell apoptosis detection.
Measurement of neurite length
ImageJ software was used to quantify neurite length. Images of cells labeled with anti-GFP and anti-neurofilament antibodies were captured by an Axiovert camera (images were processed using Volocity software). The Neuron J ImageJ plug-in was used to measure the lengths of neurites. Approximately 150 cells under each experimental condition were analyzed by three independent researchers.
Transmission electron microscopy (TEM)
The grid was checked at 80 KV on a Philips CM120 electron microscope with a low-magnification image (X4, X800 or X7000) of the white matter area containing the axon tract, as well as a high-magnification image (X15000 or X20000) of axons and other subcellular elements that were captured. From the examined samples, axons with myelin sheaths and axon organelles conformed to the ultrastructural standards. TEM images were captured with a charge-coupled device camera (Gatan, Pleasanton, CA, USA) and processed with Digital Micrograph software (Gatan).
Statistical analysis
SPSS 21.0 statistical software (IBM Corp., Armonk, NY, USA) was used for statistical analysis. Measurement data are displayed as the mean ± standard deviation. First, the normality and homogeneity of variance were tested. Data with a normal distribution and even variance between two groups were analyzed by unpaired t tests, while data comparisons among multiple groups were performed using one-way analysis of variance (ANOVA). Comparisons among data at different time points were performed by repeated-measures ANOVA with Tukey’s post-hoc test. A value of P < 0.05 was considered statistically significant.
Results
TDP-43 was elevated in SAH patients and a rat model of SAH
To explore the mechanism of TDP-43 in SAH, cerebrospinal fluid was collected from 10 non-SAH patients and 15 patients with aneurysmal SAH. We found that the expression of TDP-43 in the cerebrospinal fluid of SAH patients was much higher than that in the CSF of non-SAH patients (Fig. 1a, b).
Then, a rat model of SAH were constructed by the endovascular puncture. In model rats, we found severe cerebral hemorrhage, increased brain water content (Supplementary Fig. 1a), severe neurological damage (Supplementary Fig. 1b), impaired motor function (Supplementary Fig. 1c), and learning and memory impairment (Supplementary Fig. 1d). The number of DHE-positive cells increased dramatically, SOD activity decreased, and MDA levels increased in rats with SAH (Supplementary Fig. 1e, f). TUNEL and FJC staining demonstrated that the number of apoptotic neuronal cells and neuronal cell degeneration notably increased in rats with SAH (Supplementary Fig. 1g, h). IHC staining of APP showed that there was a large number of positive local accumulations in the white matter area of rats with SAH (Supplementary Fig. 1i). TEM revealed that there were a variety of ultrastructural features of myelinated and unmyelinated axonal damage at the cerebral infarcts and hairy infarcts of rats with SAH, including axon enlargement, nerve fiber compaction, and organelle aggregation (Supplementary Fig. 1j). Therefore, the rat model of SAH was successfully constructed and featured cognitive impairment and axonal injury.
The expression of TDP-43 in the brain tissues of SAH rats at 3 h, 6 h, 24 h, 72 h, 7 d, and 14 d after SAH modeling was examined, and the results showed that TDP-43 increased notably after SAH modeling, and the highest expression was observed at 72 h (Fig. 1c). Immunofluorescence analysis revealed that the fluorescence intensity of TDP-43 in neurons was much higher than that in microglia or astrocytes (Fig. 1d). In summary, TDP-43 was mainly located in neurons and was highly expressed in the cerebrospinal fluid of SAH patients and a rat model of SAH.
TDP-43 overexpression promoted cognitive impairment and axonal damage in rats with SAH
The lateral ventricle was injected with TDP-43-overexpressing lentivirus to determine the mechanism by which TDP-43 regulated cognitive impairment in SAH. The level of TDP-43 mRNA in the brain tissues of rats 72 h after SAH modeling was determined by RT–qPCR. The results demonstrated that the expression of TDP-43 in rats with SAH that were infected with oe-TDP-43 was sharply increased compared with that in rats with SAH that were injected with oe-NC (Fig. 2a). Three rats were randomly selected, and the level of TDP-43 protein in brain tissues was analyzed by western blotting. The expression of TDP-43 in rats after infection with oe-TDP-43 was notably increased (Fig. 2b). Cognitive tests revealed that oe-TDP-43 increased nerve function damage, reduced exercise capacity, impaired memory function, and increased total travel distance in the water maze in rats with SAH (Fig. 2c–e). Rats that were treated with oe-TDP-43 exhibited an increased number of FJC-positive cells and NeuN+TUNEL+ cells (Fig. 2f, g), indicating that neuronal injury was intensified. In addition, the number of APP-positive cells in rats infected with oe-TDP-43 was elevated (Fig. 2h). Compared with that in rats infected with oe-NC, the number of swollen and dystrophic axons in rats infected with oe-TDP-43 increased dramatically (Fig. 2i), indicating that axon damage was enhanced. In summary, TDP-43 overexpression further deteriorated cognitive dysfunction and axonal damage in rats with SAH.
OxyHb-induced axonal damage by promoting TDP-43 accumulation in the cytoplasm
To explore the underlying mechanism by which TDP-43 affects axonal damage, neurons were treated with 20 μM OxyHb for 6, 12, and 24 h. We showed that the expression of TDP-43 increased during the treatment time (Fig. 3a). The expression of axon damage marker proteins, including dynactin, neurofilament light (NFL) and apolipoprotein E (ApoE), was then measured, the protein expression of dynactin and NFL increased, while the level of ApoE decreased increasing OxyHb treatment time (Fig. 3a), indicating that OxyHb induced axonal damage. The position of TDP-43 in OxyHb-treated neurons was further observed by immunofluorescence staining, and the results showed that the localization of TDP-43 in the cytoplasm was notably increased (Fig. 3b). Nuclear and cytoplasmic separation experiments showed that the expression of TDP-43 in the cytoplasm increased notably (Fig. 3c). The length of neurofilament-associated antigen (NAA) antibody-labeled neurites and enhanced green fluorescent protein (EGFP)-labeled neurites was measured by immunofluorescence staining, and the results demonstrated that OxyHb decreased total neurite length in neurons, while TDP-43 silencing reversed this outcome (Fig. 3d). In addition, OxyHb treatment induced irregular nuclear morphology and invaginations of the nuclear membrane, which was reversed by TDP-43 silencing (Fig. 3e). Flow cytometry showed that neuronal apoptosis was increased with OxyHb treatment time, and TDP-43 silencing inhibited OxyHb-induced neuronal apoptosis (Fig. 3f). In summary, OxyHb induced cytoplasmic accumulation of TDP-43 and resulted in axonal damage and abnormal nuclear membrane morphology, and further promoted neuronal apoptosis. TDP-43 silencing alleviated axonal damage and abnormal nuclear membrane morphology and inhibited neuronal apoptosis.
HDAC1/HSP70/TDP-43 triple complexes promoted cytoplasmic accumulation of TDP-43
The STRING website predicted that HDAC1-HSP70 (Hspa1b)-TARDBP (TDP-43) was a regulatory pathway (Fig. 4a). The colocalization of HDAC1 and HSP70 with TDP-43 was examined, and the results demonstrated that the positive rate of HDAC1, HSP70, and TDP-43 in the brain tissues of rats with SAH increased notably compared with that in sham-operated rats, and the pathological colocalization resulted in the formation of point aggregates (Fig. 4b). Then, 293T cells were transfected with HDAC1 or HSP70. the Co-IP results showed that acetyl-K levels were sharply reduced (Supplementary Fig. 2a), indicating that HDAC1 mediated the deacetylation of HSP70. In addition, HDAC1 silencing notably enhanced HSP70 acetylation (Supplementary Fig. 2b). The expression of TDP-43 in the cytoplasm gradually increased with increasing HDAC1 concentrations, while TDP-43 expression in the nucleus remained unchanged (Fig. 4c). sh-HDAC1-treated neurons were treated with 50 μg/mL cycloheximide (CHX) for 0 h, 2 h, 4 h, and 8 h. TDP-43 protein levels gradually decreased with prolonged CHX treatment time (Fig. 4d). sh-HDAC1-treated neurons were treated with 5 μM of the proteasome inhibitor MG132. Western blot analysis revealed that MG132 inhibited the degradation of TDP-43 compared with that in neurons that were not treated with MG132 (Fig. 4e), indicating that HDAC1 silencing promoted TDP-43 degradation through the proteasome pathway. 293 T cells were transfected with Flag-HDAC1, HA-TDP-43, and Myc-HDAC1, and the Co-IP results revealed that these factors could bind with each other (Fig. 4f). In summary, HDAC1 could bind to HSP70 and TDP-43, promote HSP70 deacetylation and enhance TDP-43 accumulation in the cytoplasm while inhibiting protein degradation. In contrast, HDAC1 silencing promoted proteasomal degradation of TDP-43.
HDAC1 silencing inhibited TDP-43 expression to reduce OxyHb-induced axonal damage
The SAH-related microarray GSE54083 was obtained from the GEO database and further analyzed, and the results revealed that HDAC1 was highly expressed in SAH (Fig. 5a). KEGG enrichment analysis showed that HDAC1-related genes were mainly enriched in pathways such as “Metabolic pathways”, “Neuroactive ligand–receptor interaction”, “Cytokine–cytokine receptor interaction”, “Herpes simplex virus 1 infection” and “Huntington disease” (Fig. 5b). RT–qPCR showed that OxyHb notably elevated the expression of HDAC1 in neurons, and sh-HDAC1 reduced the mRNA levels of HDAC1 in OxyHb-treated neurons (Fig. 5c). Based on the western blot results, OxyHb treatment promoted the expression of HDAC1 and TDP-43 in neurons and inhibited the level of acetyl-K, while sh-HDAC1 treatment reduced the levels of HDAC1 and TDP-43 but increased the acetyl-K level in OxyHb-treated neurons (Fig. 5d). Immunofluorescence staining indicated that OxyHb increased the level of TDP-43 in the cytoplasm, while sh-HDAC1 resulted in decreased TDP-43 in the cytoplasm (Fig. 5e). Moreover, we found reduced expression of TDP-43 in the cytoplasm but increased neurite length in neurons that were treated with OxyHb + sh-HDAC1 compared with those treated with OxyHb + sh-NC (Fig. 5f, g). TEM revealed that compared with that of neurons treated with OxyHb + sh-NC, the morphology of neurons treated with OxyHb + sh-HDAC1 was round and regular, and nuclear membrane morphology was normal (Fig. 5h). Flow cytometry showed that compared with neurons treated with OxyHb + sh-NC, neurons treated with OxyHb + sh-HDAC1 exhibited reduced apoptosis (Fig. 5i). In summary, HDAC1 silencing inhibited TDP-43 expression and alleviated OxyHb-induced axonal damage.
SAHA alleviated neuronal damage by promoting TDP-43 degradation by maintaining the acetylation level of HDAC1/HSP70 complexes
Neurons were treated with the HDAC1 inhibitor SAHA (1 μM) for 30 min, and the acetylation level of HSP70 was measured. SAHA treatment notably promoted HSP70 acetylation in 293T cells (Supplementary Fig. 3a). According to the IP results, a notable increase in HSP70 levels was observed (Supplementary Fig. 3b). SAHA-treated 293 T cells were further transfected with Flag-HDAC1, Myc-HSP70, and HA-TDP-43. The Co-IP results showed that the level of TDP-43 that immunoprecipitated with HDAC1 was markedly reduced (Fig. 6a), and the same results were observed in SAHA-treated neurons (Fig. 6a). CHX-treated neurons were further treated with SAHA, and the results showed that SAHA treatment markedly promoted the protein degradation of TDP-43 in neurons that were treated with CHX (Fig. 6b). The colocalization of TDP-43 and HDAC1 was examined by immunofluorescence staining, and the results showed that the accumulation of TDP-43 in the cytoplasm of neurons induced by OxyHb was reduced by SAHA treatment, and the ratio of nuclear-to-cytoplasmic TDP-43 was reduced (Fig. 6c). In addition, compared with that of neurons treated with OxyHb + DMSO, neurite length was increased by TDP-43 (Fig. 6d). Flow cytometry showed that compared with neurons treated with OxyHb + DMSO, neurons treated with OxyHb + SAHA had notably reduced levels of apoptosis (Fig. 6e). Overall, SAHA, which is an HDAC1 inhibitor, promoted the degradation of the TDP-43 protein by maintaining the acetylation of HSP70 and inhibiting the accumulation of TDP in the cytoplasm, ultimately alleviating neurite damage.
SAHA relieved axonal damage and neurological dysfunction after SAH by inhibiting the HDAC1/HSP70/TDP-43 axis
To further explore whether the deacetylase inhibitor SAHA is involved in the regulation of nerve damage in SAH by mediating the HDAC1/HSP70/TDP-43 axis, SAH model rats were injected with lentivirus-mediated sh-HDAC1 and SAHA in the lateral ventricle. RT–qPCR analysis showed that the level of HDAC1 in rats with SAH that were injected with sh-NC was notably increased relative to that in sham-operated rats. The level of HDAC1 was notably decreased in rats with SAH that were injected with sh-HDAC1 compared with that of rats with SAH that were injected with sh-NC. Compared with that of rats with SAH that were treated with DMSO, the level of HDAC1 showed no obvious change in rats with SAH that were treated with SAHA (Fig. 7a). In addition, the levels of HDAC1 and TDP-43 in rats with SAH that were injected with sh-HDAC1 were reduced, the level of acetyl-K was elevated, and the level of HSP70 remained unchanged relative to the effect of sh-NC treatment. Compared with rats with SAH that were treated with DMSO, acetyl-K levels increased markedly, HDAC1 and HSP70 levels remained unchanged, and TDP-43 levels decreased notably in rats with SAH that were treated with SAHA (Fig. 7b). Cognitive tests showed that compared with that of rats with SAH that were injected with sh-NC, the neurological damage score was reduced, and the exercise capacity and memory level were increased in rats with SAH that were injected with sh-HDAC1; the same behavioral phenotype was observed after SAHA treatment (Fig. 7c–e). Then, FJC and TUNEL staining demonstrated that in comparison to that of rats with SAH that were injected with sh-NC, the number of FJC-positive cells and the number of NeuN+TUNEL+ cells in rats with SAH that were injected with sh-HDAC1 were reduced, and the same trend was observed after SAHA treatment (Fig. 7f, g), indicating that neuronal damage was reduced. APP expression was then examined by IHC staining, and the results demonstrated that the number of APP-positive cells in rats with SAH that were injected with sh-HDAC1 was largely decreased compared with that of rats with SAH that were injected with sh-NC, and SAHA treatment inhibited the positive rate of APP in brain tissues (Fig. 7h). The number of swollen and dystrophic axons in rats with SAH that were injected with sh-NC was notably reduced compared with that in rats with SAH that were injected with sh-HDAC1, and SAHA treatment alleviated axonal damage (Fig. 7i). In conclusion, SAHA alleviated axonal damage and cognitive impairment by mediating the degradation of TDP-43 through the acetylation of HSP70 and the inhibition of HDAC1.
Discussion
The average SAH patient is 55 years old, and this condition commonly leads to cognitive impairments in survivors because of axonal damage and white matter injury24,25. Much attention has been given to the function of various HDAC inhibitors in the progression of intracerebral hemorrhage, including SAH26,27. Here, we attempted to clarify the mechanisms of the HDAC inhibitor SAHA in SAH, and our results revealed that SAHA relieved neuronal and axonal damage by promoting TDP-43 degradation by enhancing the acetylation of HSP70 through HDAC1 inhibition, thereby attenuating the development of SAH.
We discovered that TDP-43 was highly expressed in the cerebrospinal fluid of SAH patients and in the brain tissues of a rat model of SAH. Consistent with our findings, a previous study also showed upregulated expression of TDP-43 in the cerebrospinal fluid of patients with aneurysmal SAH and the brain tissues of a rat model of SAH17. Furthermore, our study revealed that TDP-43 overexpression enhanced cognitive impairment in rats with SAH in vivo and that TDP-43 accumulation in the cytoplasm in a neuronal cell model of SAH worsened axonal damage in vitro. Cytoplasmic mislocalization is a characteristic of TDP-43 pathology and is further recognized as a hallmark of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), Parkinson’s disease and Huntington’s disease28,29,30. Specifically, TDP-43 acetylation increased the accumulation of insoluble and hyperphosphorylated TDP-43 inclusions, which contributed to the pathogenesis of ALS and FTLD31. Another study showed that TDP-43 promoted Alzheimer’s disease development32. In summary, these lines of evidence validated the exacerbating role of TDP-43 in SAH progression.
Then, TDP-43 protein degradation was inhibited by HSP70 deacetylation, which induced cytoplasmic aggregation and further promoted inclusion body formation. Similar to our findings, another study showed that the pathological accumulation of insoluble TDP-43 could be reduced by HSPs and attenuate amyotrophic lateral sclerosis33. Moreover, the deacetylation of HSP70 was promoted by HDAC1, and HDAC1 silencing promoted TDP-43 degradation, thereby alleviating neuronal and axonal damage, abnormal nuclear membrane morphology, and apoptosis in a neuronal cell model of SAH. A prior study showed that protein deacetylation, which is the reverse process of acetylation (a posttranslational modification), was mediated by deacetylases34. Moreover, the inhibition of HDACs was reported to exert a protective effect against acute lung injury by acetylating and suppressing HSP90 activity35. Moreover, HDAC silencing was shown to reduce white matter damage after intracerebral hemorrhage36. Furthermore, this study showed that the HDAC inhibitor SAHA alleviated axonal injury and cognitive impairment in rats with SAH by elevating TDP-43 degradation by enhancing the acetylation of HSP70 by inhibiting HDAC1 enzymatic activity. SAHA is a well-recognized HDAC inhibitor that has also been confirmed to alleviate intracerebral hemorrhage9 In addition, a recent study revealed that SAHA attenuated hemorrhagic shock and resuscitation-induced lung injury by repressing histone acetylation37. Hence, these findings support the role of SAHA in ameliorating SAH development by regulating the HDAC1/HSP70/TDP-43 axis.
Taken together, the findings of this study confirmed that SAHA plays an inhibitory role in SAH progression by promoting the degradation of TDP-43 by enhancing the acetylation of HSP through the suppression of HDAC1 activity (Fig. 8). However, the efficacy of HDAC inhibitors in SAH is a novel research focus that needs further investigation.
Change history
04 July 2022
A Correction to this paper has been published: https://doi.org/10.1038/s12276-022-00783-3
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Acknowledgements
This study was supported by the National Natural Science Foundation of China (81870944), the National Natural Science Foundation of China (81771233), the Specific Research Projects for Capital Health Development (2018-2-2041), the Bei**g Science and Technology Planning Project (Z181100009618035), the Bei**g Municipal Administration of Hospitals’ Ascent Plan (DFL20190501) and the Research and Promotion Program of Appropriate Techniques for Intervention of Chinese High-risk Stroke People (GN-2020R0007).
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K.L., Z.W., F.L., and A.L. designed the study. K.L., K.Z., and S.Y. collated the data, performed data analyses, and produced the initial draft of the manuscript. K.L., Z.W., K.Z., S.Y., F.L., and A.L. contributed to drafting the manuscript. All authors have read and approved the final submitted manuscript.
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Luo, K., Wang, Z., Zhuang, K. et al. Suberoylanilide hydroxamic acid suppresses axonal damage and neurological dysfunction after subarachnoid hemorrhage via the HDAC1/HSP70/TDP-43 axis. Exp Mol Med 54, 1423–1433 (2022). https://doi.org/10.1038/s12276-022-00761-9
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DOI: https://doi.org/10.1038/s12276-022-00761-9
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