Histone Deacetylation 10 Alleviates Inflammation After Intracerebral Hemorrhage via the PTPN22/NLRP3 Pathway in Rats

Groebke Blackburn Bienaymé-mediated multi-component synthesis of selective HDAC6 inhibitors with anti-inflammatory properties

Histone deacetylases (HDACs) are a class of enzymes that cleave acyl groups from lysine residues of histone and non-histone proteins. There are 18 human HDAC isoforms with different cellular targets and functions. Among them, HDAC6 was found to be overexpressed in different types of cancer. However, when used in monotherapy, HDAC6 inhibition by selective inhibitors fails to show pronounced anti-cancer effects. The HDAC6 enzyme also addresses non-histone proteins like α-tubulin and cortactin, making it important for cell migration and angiogenesis. Recently, the NLRP3 inflammasome was identified as an important regulator of inflammation and immune responses and, importantly, HDAC6 is critically involved the activation of the inflammasome. We herein report the design, synthesis and biological evaluation of a library of selective HDAC6 inhibitors. Starting from the previously published crystal structure of MAIP-032 in complex with CD2 of zHDAC6, we performed docking studies to evaluate additional possible interactions of the cap group with the L1-loop pocket. Based on the results we synthesized 13 novel HDAC6 inhibitors via the Groebke-Blackburn-Bienaymé three component reaction as the key step. Compounds 8k (HDAC1 IC50: 5.87 μM; HDAC6 IC50: 0.024 μM; selectivity factor (SF1/6): 245) and 8m (HDAC1 IC50: 3.07 μM; HDAC6 IC50: 0.026 μM; SF1/6: 118) emerged as the most potent and selective inhibitors of HDAC6 and outperformed the lead structure MAIP-032 (HDAC1 IC50: 2.20 μM; HDAC6 IC50: 0.058 μM; SF1/6: 38) both in terms of inhibitory potency and selectivity. Subsequent immunoblot analysis confirmed the high selectivity of 8k and 8m for HDAC6 in a cellular environment. While neither 8k and 8m nor the selectivity HDAC6 inhibitor tubastatin A showed antiproliferative effects in the U-87 MG glioblastoma cell line, compound 8m attenuated cell migration significantly in wound healing assays in U-87 MG cells. Moreover, in macrophages compounds 8k and 8m demonstrated significant inhibition of LPS-induced IL1B mRNA expression and TNF release. These findings suggest that our imidazo[1,2-a]pyridine-capped HDAC6 inhibitors may serve as promising candidates for the development of drugs to effectively treat NLRP3 inflammasome-driven inflammatory diseases.

Zinc-Dependent Histone Deacetylases in Lung Endothelial Pathobiology

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and, as such, provides a semi-selective barrier between the blood and the interstitial space. Compromise of the lung EC barrier due to inflammatory or toxic events may result in pulmonary edema, which is a cardinal feature of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS). The EC functions are controlled, at least in part, via epigenetic mechanisms mediated by histone deacetylases (HDACs). Zinc-dependent HDACs represent the largest group of HDACs and are activated by Zn2+. Members of this HDAC group are involved in epigenetic regulation primarily by modifying the structure of chromatin upon removal of acetyl groups from histones. In addition, they can deacetylate many non-histone histone proteins, including those located in extranuclear compartments. Recently, the therapeutic potential of inhibiting zinc-dependent HDACs for EC barrier preservation has gained momentum. However, the role of specific HDAC subtypes in EC barrier regulation remains largely unknown. This review aims to provide an update on the role of zinc-dependent HDACs in endothelial dysfunction and its related diseases. We will broadly focus on biological contributions, signaling pathways and transcriptional roles of HDACs in endothelial pathobiology associated mainly with lung diseases, and we will discuss the potential of their inhibitors for lung injury prevention.

HnRNP K regulates inflammatory gene expression by mediating splicing pattern of transcriptional factors

HnRNP K is a heterogeneous nuclear ribonucleoprotein and has been identified as an oncogene in most solid tumors via regulating gene expression or alternative splicing of genes by binding both DNA and pre-mRNA. However, how hnRNP K affects tumorigenesis and regulates the gene expression in cervical cancer (CESC) remains to be elucidated. In these data, higher expression of hnRNP K was observed in CESC and was negatively correlated with the patient survival time. We then overexpressed hnRNP K (hnRNP K-OE) and found that its overexpression promoted cell proliferation in HeLa cells (P = 0.0052). Next, global transcriptome sequencing (RNA-seq) experiments were conducted to explore gene expression and alternative splicing profiles regulated by hnRNP K. It is shown that upregulated genes by hnRNP K-OE were associated with inflammatory response and an apoptotic process of neuron cells, which involves in cancer. In addition, the alternative splicing of those genes regulated by hnRNP K-OE was associated with transcriptional regulation. Analysis of the binding features of dysregulated transcription factors (TFs) in the promoter region of the inflammatory response genes regulated by hnRNP K revealed that hnRNP K may modulate the expression level of genes related to inflammatory response by influencing the alternative splicing of TFs. Among these hnRNP K-TFs-inflammatory gene regulatory networks, quantitative reverse transcription polymerase chain reaction (RT-qPCR) experiments and gene silencing were conducted to verify the hnRNP K-IRF1-CCL5 axis. In conclusion, the hnRNP K-TFs-inflammatory gene regulatory axis provides a novel molecular mechanism for hnRNP K in promoting CESC and offers a new therapeutic target.

Progress on siRNA-based gene therapy targeting secondary injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a life-threatening condition with a high mortality rate. For survivors, quality of life is determined by primary and secondary phases of injury. The prospects for injury repair and recovery after ICH are highly dependent on the extent of secondary injury. Currently, no effective treatments are available to prevent secondary injury or its long-term effects. One promising strategy that has recently garnered attention is gene therapy, in particular, small interfering RNAs (siRNA), which silence specific genes responsible for destructive effects after hemorrhage. Gene therapy as a potential treatment for ICH is being actively researched in animal studies. However, there are many barriers to the systemic delivery of siRNA-based therapy, as the use of naked siRNA has limitations. Recently, the Food and Drug Administration approved two siRNA-based therapies, and several are undergoing Phase 3 clinical trials. In this review, we describe the advancements in siRNA-based gene therapy for ICH and also summarize its advantages and disadvantages.

Interplay between Gut Microbiota and NLRP3 Inflammasome in Intracerebral Hemorrhage

The pathophysiological process of intracerebral hemorrhage (ICH) is very complex, involving various mechanisms such as apoptosis, oxidative stress and inflammation. As one of the key factors, the inflammatory response is responsible for the pathological process of acute brain injury and is associated with the prognosis of patients. Abnormal or dysregulated inflammatory responses after ICH can aggravate cell damage in the injured brain tissue. The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a multiprotein complex distributed in the cytosol, which can be triggered by multiple signals. The NLRP3 inflammasome is activated after ICH, thus promoting neuroinflammation and aggravating brain edema. In addition, there is evidence that the gut microbiota is crucial in the activation of the NLRP3 inflammasome. The gut microbiota plays a key role in a variety of CNS disorders. Changes in the diversity and species of the gut microbiota affect neuroinflammation through the activation of the NLRP3 inflammasome and the release of inflammatory cytokines. In turn, the gut microbiota composition can be influenced by the activation of the NLRP3 inflammasome. Thereby, the regulation of the microbe-gut-brain axis via the NLRP3 inflammasome may serve as a novel idea for protecting against secondary brain injury (SBI) in ICH patients. Here, we review the recent evidence on the functions of the NLRP3 inflammasome and the gut microbiota in ICH, as well as their interactions, during the pathological process of ICH.

Genetics and Epigenetics of Spontaneous Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a complex and heterogeneous disease, and there is no effective treatment. Spontaneous ICH represents the final manifestation of different types of cerebral small vessel disease, usually categorized as: lobar (mostly related to cerebral amyloid angiopathy) and nonlobar (hypertension-related vasculopathy) ICH. Accurate phenotyping aims to reflect these biological differences in the underlying mechanisms and has been demonstrated to be crucial to the success of genetic studies in this field. This review summarizes how current knowledge on genetics and epigenetics of this devastating stroke subtype are contributing to improve the understanding of ICH pathophysiology and their potential role in developing therapeutic strategies.

Small interfering RNAs based therapies for intracerebral hemorrhage: challenges and progress in drug delivery systems

Intracerebral hemorrhage (ICH) is a subtype of stroke associated with higher rates of mortality. Currently, no effective drug treatment is available for ICH. The molecular pathways following ICH are complicated and diverse. Nucleic acid therapeutics such as gene knockdown by small interfering RNAs (siRNAs) have been developed in recent years to modulate ICH’s destructive pathways and mitigate its outcomes. However, siRNAs delivery to the central nervous system is challenging and faces many roadblocks. Existing barriers to systemic delivery of siRNA limit the use of naked siRNA; therefore, siRNA-vectors developed to protect and deliver these therapies into the specific-target areas of the brain, or cell types seem quite promising. Efficient delivery of siRNA via nanoparticles emerged as a viable and effective alternative therapeutic tool for central nervous system-related diseases. This review discusses the obstacles to siRNA delivery, including the advantages and disadvantages of viral and nonviral vectors. Additionally, we provide a comprehensive overview of recent progress in nanotherapeutics areas, primarily focusing on the delivery system of siRNA for ICH treatment.

Mechanism of Baicalein in Brain Injury After Intracerebral Hemorrhage by Inhibiting the ROS/NLRP3 Inflammasome Pathway

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke with high disability/mortality. Baicalein has strong anti-inflammatory activity. This study aims to explore the mechanism of baicalein on brain injury after ICH. The model of brain injury after ICH was established by collagenase induction, followed by the evaluation of neurological severity, brain water content, the degenerated neurons, neuronal apoptosis, and reactive oxygen species (ROS). The ICH model was treated with baicalein or silencing NLRP3 to detect brain injury. The expression of NLRP3 inflammasome was detected after treatment with ROS scavenger. The expressions of oxidative stress markers and inflammatory factors were detected, and the levels of components in NLRP3 inflammasome were detected. Baicalein reduced the damage of nervous system, lesion surface, brain water content, and apoptosis. Baicalein inhibited malondialdehyde and increased IL-10 by inhibiting ROS in brain tissue after ICH. Baicalein inhibited the high expression of NLRP3 inflammasome in ICH. ROS scavenger inhibited the NLRP3 inflammatory response by inhibiting ROS levels. Silencing NLRP3 alleviated the brain injury after ICH by inhibiting excessive oxidative stress and inflammatory factors. Overall, baicalein alleviated the brain injury after ICH by inhibiting ROS and NLRP3 inflammasome.

Roles of Histone Deacetylases in Acute Myeloid Leukemia With Fusion Proteins

Accurate orchestration of gene expression is critical for the process of normal hematopoiesis, and dysregulation is closely associated with leukemogenesis. Epigenetic aberration is one of the major causes contributing to acute myeloid leukemia (AML), where chromosomal rearrangements are frequently found. Increasing evidences have shown the pivotal roles of histone deacetylases (HDACs) in chromatin remodeling, which are involved in stemness maintenance, cell fate determination, proliferation and differentiation, via mastering the transcriptional switch of key genes. In abnormal, these functions can be bloomed to elicit carcinogenesis. Presently, HDAC family members are appealing targets for drug exploration, many of which have been deployed to the AML treatment. As the majority of AML events are associated with chromosomal translocation resulting in oncogenic fusion proteins, it is valuable to comprehensively understand the mutual interactions between HDACs and oncogenic proteins. Therefore, we reviewed the process of leukemogenesis and roles of HDAC members acting in this progress, providing an insight for the target anchoring, investigation of hyperacetylated-agents, and how the current knowledge could be applied in AML treatment.

Understanding the role of histone deacetylase and their inhibitors in neurodegenerative disorders: Current targets and future perspective

Neurodegenerative diseases are a group of pathological conditions that cause motor inc-ordination (jerking movements), cognitive and memory impairments result from degeneration of neurons in a specific area of the brain. Oxidative stress, mitochondrial dysfunction, excitotoxicity, neuroinflammation, neurochemical imbalance and histone deacetylase enzymes (HDAC) are known to play a crucial role in neurodegeneration. HDAC is classified into four categories (class I, II, III and class IV) depending upon their location and functions. HDAC1 and 2 are involved in neurodegeneration, while HDAC3-11 and class III HDACs are beneficial as neuroprotective. HDACs are localized in different parts of the brain- HDAC1 (hippocampus and cortex), HDAC2 (nucleus), HDAC3, 4, 5, 7 and 9 (nucleus and cytoplasm), HDAC6 & HDAC7 (cytoplasm) and HDAC11 (Nucleus, cornus ammonis 1 and spinal cord). In pathological conditions, HDAC up-regulates glutamate, phosphorylation of tau, and glial fibrillary acidic proteins while down-regulating BDNF, Heat shock protein 70 and Gelsolin. Class III HDACs are divided into seven sub-classes (SIRT1-SIRT7). Sirtuins are localized in the different parts of the brain and neuron -Sirt1 (nucleus), Sirt2 (cortex, striatum, hippocampus and spinal cord), Sirt3 (mitochondria and cytoplasm), Sirt4, Sirt5 & Sirt6 (mitochondria), Sirt7 (nucleus) and Sirt8 (nucleolus). SIRTs (1, 3, 4, and 6) are involved in neuronal survival, proliferation and modulating stress response, and SIRT2 is associated with Parkinsonism, Huntington’s disease and Alzheimer’s disease, whereas SIRT6 is only associated with Alzheimer’s disease. In this critical review, we have discussed the mechanisms and therapeutic targets of HDACs that would be beneficial for the management of neurodegenerative disorders.

Histone deacetylase 10, a potential epigenetic target for therapy

Histone deacetylase (HDAC) 10, a class II family, has been implicated in various tumors and non-tumor diseases, which makes the discovery of biological functions and novel inhibitors a fundamental endeavor. In cancers, HDAC10 plays crucial roles in regulating various cellular processes through its epigenetic functions or targeting some decisive molecular or signaling pathways. It also has potential clinical utility for targeting tumors and non-tumor diseases, such as renal cell carcinoma, prostate cancer, immunoglobulin A nephropathy (IgAN), intracerebral hemorrhage, human immunodeficiency virus (HIV) infection and schizophrenia. To date, relatively few studies have investigated HDAC10-specific inhibitors. Therefore, it is important to study the biological functions of HDAC10 for the future development of specific HDAC10 inhibitors. In this review, we analyzed the biological functions, mechanisms and inhibitors of HDAC10, which makes HDAC10 an appealing therapeutic target.

Fiber Derived Microbial Metabolites Prevent Acute Kidney Injury Through G-Protein Coupled Receptors and HDAC Inhibition

Short-chain fatty acids (SCFA) derived from gut microbial fermentation of fiber have been shown to exert anti-inflammatory and immune-modulatory properties in acute kidney injury (AKI). However the direct mechanistic link between SCFAs, diet and the gut microbiome is yet to be established. Using the murine model of folic-acid nephropathy (FAN), we examined the effect of dietary fiber on development of AKI (day 2) and subsequent chronic kidney disease (CKD) (day 28). FAN was induced in wild-type and knockout mice lacking G protein–coupled receptors GPR41, GPR43, or GPR109A. Mice were randomized to high-fiber or normal-chow diets, or SCFAs in drinking water. We used 16S rRNA sequencing to assess the gut microbiome and ¹H-NMR spectroscopy for metabolic profiles. Mice fed high-fiber were partially protected against development of AKI and subsequent CKD, exhibiting better kidney function throughout, less tubular injury at day 2 and less interstitial fibrosis and chronic inflammation at day 28 vs controls. Fiber modified the gut microbiome and alleviated dysbiosis induced by AKI, promoting expansion of SCFA-producing bacteria Bifidobacterium and Prevotella, which increased fecal and serum SCFA concentrations. SCFA treatment achieved similar protection, but not in the absence of GPR41 or GPR109A. Histone deacetylase activity (HDAC) was inhibited in kidneys of high-fiber fed mice. We conclude that dietary manipulation of the gut microbiome protects against AKI and subsequent CKD, mediated by HDAC inhibition and activation of GPR41 and GPR109A by SCFAs. This study highlights the potential of the gut microbiome as a modifiable target in the prevention of AKI.

MicroNAR-194-5p hinders the activation of NLRP3 inflammasomes and alleviates neuroinflammation during intracerebral hemorrhage by blocking the interaction between TRAF6 and NLRP3

The possible role of miR-194-5p in brain and neurodegenerative diseases has been reported, but its role in intracerebral hemorrhage (ICH) has not been studied. This study estimated the mechanism of miR-194-5p in ICH. ICH rat model was established by injecting collagenase type VII. miR-194-5p expression in brain tissue of ICH rats was overexpressed by injection of miR-194-5p agomir. Then neurological function score and brain water content were measured. The morphological changes of brain tissue and neuronal apoptosis were evaluated by histological staining. Levels of NLRP3 inflammasomes, IL-1β and IL-18 were measured. The target relation between miR-194-5p and TRAF6 was verified and the binding of TRAF6 to NLRP3 was explored. miR-194-5p was decreased in ICH rats. After overexpression of miR-194-5p, the neuropathological injury in ICH rats was significantly reduced, and NLRP3-mediated inflammatory injury was inhibited. miR-194-5p targeted TRAF6. TRAF6 interacted with NLRP3 to promote the activation of NLRP3 inflammasomes. Overexpression of miR-194-5p reduced the interaction between TRAF6 and NLRP3, thereby alleviating the neuroinflammation. Collectively, overexpression of miR-194-5p reduced the TRAF6/NLRP3 interaction, thus inhibiting the activation of NLRP3 inflammasomes and reducing neuroinflammation during ICH. This study may shed new light on ICH treatment.

Mild hypothermia improves brain injury in rats with intracerebral hemorrhage by inhibiting IRAK2/NF-κB signaling pathway

OBJECTIVE

To explore the effect of mild hypothermia on nerve injury by establishing a rat model of intracerebral hemorrhage (ICH), and to clarify the specific molecular mechanism of mild hypothermia in improving brain injury in ICH rats.

METHODS

The rat model of ICH was established by collagenase injection. The neurological deficit score (NDS), brain tissue water detection, and Nissl staining were applied to detect the degree of brain injury. ELISA was used to analyze the expression of proinflammatory cytokines and serum nerve injury indexes. Flow cytometry and Western Blot were used to detect neuronal apoptosis.

RESULTS

Mild hypothermia treatment significantly improved the brain injury of the ICH rats and down-regulated the inflammatory response and oxidative stress in the brain tissue. Moreover, mild hypothermia also effectively inhibited IRAK2/NF-κB signaling pathway and thus affect neuronal apoptosis.

CONCLUSION

Mild hypothermia alleviates inflammatory response and neuronal apoptosis by inhibiting IRAK2/NF-κB signaling pathway in the ICH rats thus improving brain injury.