Inhibiting MLL1-WDR5 interaction ameliorates neuropathic allodynia by attenuating histone H3 lysine 4 trimethylation-dependent spinal mGluR5 transcription

The effect of intra spinal administration of cerium oxide nanoparticles on central pain mechanism: An experimental study

This study investigated Cerium oxide nanoparticles (CeONPs) effect on central neuropathic pain (CNP). The compressive method of spinal cord injury (SCI) model was used for pain induction. Three groups were formed by a random allocation of 24 rats. In the treatment group, CeONPs were injected above and below the lesion site immediately after inducing SCI. pain symptoms were evaluated using acetone, Radian Heat, and Von Frey tests weekly for six weeks. Finally, we counted fibroblasts using H&E staining. We evaluated the expression of Cx43, GAD65 and HDAC2 proteins using the western blot method. The analysis of results was done by PRISM software. At the end of the study, we found that CeONPs reduced pain symptoms to levels similar to those observed in normal animals. CeONPs also increased the expression of GAD65 and Cx43 proteins but did not affect HDAC2 inhibition. CeONPs probably have a pain-relieving effect on chronic pain by potentially preserving GAD65 and Cx43 protein expression and hindering fibroblast infiltration.

Protein Arginine Methyltransferase 5 Contributes to Paclitaxel-Induced Neuropathic Pain by Activating Transient Receptor Potential Vanilloid 1 Epigenetic Modification in Dorsal Root Ganglion

BACKGROUND

Paclitaxel (PTX), which is a first-line chemotherapy drug used to treat various types of cancers, exhibits peripheral neuropathy as a common side effect that is difficult to treat. Protein arginine methyltransferase 5 (PRMT 5) is a key regulator of the chemotherapy response, as chemotherapy drugs induce PRMT5 expression. However, little is known about the PRMT5-mediated epigenetic mechanisms involved in PTX-induced neuropathic allodynia.

METHODS

Sprague-Dawley rats were intraperitoneally given PTX to induce neuropathic pain. Biochemical analyses were conducted to measure the protein expression levels in the dorsal root ganglion (DRG) of the animals. The von Frey test and hot plate test were used to evaluate nociceptive behaviors.

RESULTS

PTX increased the PRMT5 (mean difference [MD]: 0.68, 95% confidence interval [CI], 0.88-0.48; P < .001 for vehicle)-mediated deposition of histone H3R2 dimethyl symmetric (H3R2me2s) at the transient receptor potential vanilloid 1 ( Trpv1 ) promoter in the DRG. PRMT5-induced H3R2me2s recruited WD repeat domain 5 (WDR5) to increase trimethylation of lysine 4 on histone H3 (H3K4me3) at Trpv1 promoters, thus resulting in TRPV1 transcriptional activation (MD: 0.65, 95% CI, 0.82-0.49; P < .001 for vehicle) in DRG in PTX-induced neuropathic pain. Moreover, PTX increased the activity of NADPH oxidase 4 (NOX4) (MD: 0.66, 95% CI, 0.81-0.51; P < .001 for vehicle), PRMT5-induced H3R2me2s, and WDR5-mediated H3K4me3 in the DRG in PTX-induced neuropathic pain. Pharmacological antagonism and the selective knockdown of PRMT5 in DRG neurons completely blocked PRMT5-mediated H3R2me2s, WDR5-mediated H3K4me3, or TRPV1 expression and neuropathic pain development after PTX injection. Remarkably, NOX4 inhibition not only attenuated allodynia behavior and reversed the above-mentioned signaling but also reversed NOX4 upregulation via PTX.

CONCLUSIONS

Thus, the NOX4/PRMT5-associated epigenetic mechanism in DRG has a dominant function in the transcriptional activation of TRPV1 in PTX-induced neuropathic pain.

WD Repeat Domain 5 Inhibitors for Cancer Therapy: Not What You Think

WDR5 is a conserved nuclear protein that scaffolds the assembly of epigenetic regulatory complexes and moonlights in functions ranging from recruiting MYC oncoproteins to chromatin to facilitating the integrity of mitosis. It is also a high-value target for anti-cancer therapies, with small molecule WDR5 inhibitors and degraders undergoing extensive preclinical assessment. WDR5 inhibitors were originally conceived as epigenetic modulators, proposed to inhibit cancer cells by reversing oncogenic patterns of histone H3 lysine 4 methylation-a notion that persists to this day. This premise, however, does not withstand contemporary inspection and establishes expectations for the mechanisms and utility of WDR5 inhibitors that can likely never be met. Here, we highlight salient misconceptions regarding WDR5 inhibitors as epigenetic modulators and provide a unified model for their action as a ribosome-directed anti-cancer therapy that helps focus understanding of when and how the tumor-inhibiting properties of these agents can best be understood and exploited.

ARID5B-mediated LINC01128 epigenetically activated pyroptosis and apoptosis by promoting the formation of the BTF3/STAT3 complex in β2GPI/anti-β2GPI-treated monocytes

BACKGROUND

Alterations of the trimethylation of histone 3 lysine 4 (H3K4me3) mark in monocytes are implicated in the development of autoimmune diseases. Therefore, the purpose of our study was to elucidate the role of H3K4me3-mediated epigenetics in the pathogenesis of antiphospholipid syndrome (APS).

METHODS

H3K4me3 Cleavage Under Targets and Tagmentation and Assay for Transposase-Accessible Chromatin were performed to determine the epigenetic profiles. Luciferase reporter assay, RNA immunoprecipitation, RNA pull-down, co-immunoprecipitation and chromatin immunoprecipitation were performed for mechanistic studies. Transmission electron microscopy and propidium iodide staining confirmed cell pyroptosis. Primary monocytes from patients with primary APS (PAPS) and healthy donors were utilised to test the levels of key molecules. A mouse model mimicked APS was constructed with beta2-glycoprotein I (β2GPI) injection. Blood velocity was detected using murine Doppler ultrasound.

RESULTS

H3K4me3 signal and open chromatin at the ARID5B promoter were increased in an in vitro model of APS. The epigenetic factor ARID5B directly activated LINC01128 transcription at its promoter. LINC01128 promoted the formation of the BTF3/STAT3 complex to enhance STAT3 phosphorylation. Activated STAT3 interacted with the NLRP3 promoter and subsequently stimulated pyroptosis and apoptosis. ARID5B or BTF3 depletion compensated for LINC01128-induced pyroptosis and apoptosis by inhibiting STAT3 phosphorylation. In mice with APS, β2GPI exposure elevated the levels of key proteins of pyroptosis and apoptosis pathways in bone marrow-derived monocytes, reduced the blood velocity of the ascending aorta, increased the thrombus size of the carotid artery, and promoted the release of interleukin (IL)-18, IL-1β and tissue factor. Patients with PAPS had the high-expressed ARID5B and LINC01128, especially those with triple positivity for antiphospholipid antibodies. Moreover, there was a positive correlation between ARID5B and LINC01128 expression.

CONCLUSION

This study indicated that ARID5B/LINC01128 was synergistically upregulated in APS, and they aggravated disease pathogenesis by enhancing the formation of the BTF3/STAT3 complex and boosting p-STAT3-mediated pyroptosis and apoptosis, thereby providing candidate therapeutic targets for APS.

HIGHLIGHTS

The H3K4me3 mark and chromatin accessibility at the ARID5B promoter are increased in vitro model mimicked APS. ARID5B-mediated LINC01128 induces pyroptosis and apoptosis via p-STAT3 by binding to BTF3. ARID5B is high- expressed in patients with primary APS and positively correlated with LINC01128 expression. OICR-9429 treatment mitigates pyroptosis and related inflammation in vivo and in vitro models mimicked APS.

Evaluation of epigenetic (HDAC, DNMT) and pain (Gad65, TGF) factors following photobiomodulation therapy in a neuropathic pain model

Photobiomodulation therapy (PBMT) is converted to the most common analgesic treatment before the whole mechanism is yet to be discovered. This study for the first time was designed to investigate alternations of epigenetic factors after pain and PBMT. The CCI model was chosen to induce pain. Pain evaluation tests including plantar, acetone, von Frey, and pinch were done weekly. Then spinal cord tissue was isolated for evaluating mRNA expression of DNMT3a, HDAC1, and NRSF using RT-qPCR method, and protein expression factors of HDAC2 and DNMT3a using western blotting. GAD65 and TGF-β proteins were assessed by the IHC method. PBMT increased the pain threshold up to the point where it roughly met the pain threshold of the control group. After three weeks of treatment, both PBMT protocols demonstrated a reduction in allodynia and hyperalgesia. While some molecules, such as TGF-β and Gad65, increased following PBMT, we observed no inhibition of NRSF, HDAC1, and DNMT3a expression despite implementing two different protocols.

The Epigenetics of Neuropathic Pain: A Systematic Update

Epigenetics deals with alterations to the gene expression that occur without change in the nucleotide sequence in the DNA. Various covalent modifications of the DNA and/or the surrounding histone proteins have been revealed, including DNA methylation, histone acetylation, and methylation, which can either stimulate or inhibit protein expression at the transcriptional level. In the past decade, an exponentially increasing amount of data has been published on the association between epigenetic changes and the pathomechanism of pain, including its most challenging form, neuropathic pain. Epigenetic regulation of the chromatin by writer, reader, and eraser proteins has been revealed for diverse protein targets involved in the pathomechanism of neuropathic pain. They include receptors, ion channels, transporters, enzymes, cytokines, chemokines, growth factors, inflammasome proteins, etc. Most work has been invested in clarifying the epigenetic downregulation of mu opioid receptors and various K+ channels, two types of structures mediating neuronal inhibition. Conversely, epigenetic upregulation has been revealed for glutamate receptors, growth factors, and lymphokines involved in neuronal excitation. All these data cannot only help better understand the development of neuropathic pain but outline epigenetic writers, readers, and erasers whose pharmacological inhibition may represent a novel option in the treatment of pain.

MLL1 inhibits the neurogenic potential of SCAPs by interacting with WDR5 and repressing HES1

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising treatment for spinal cord injury (SCI), but improving the neurogenic potential of MSCs remains a challenge. Mixed lineage leukemia 1 (MLL1), an H3K4me3 methyltransferases, plays a critical role in regulating lineage-specific gene expression and influences neurogenesis. In this study, we investigated the role and mechanism of MLL1 in the neurogenesis of stem cells from apical papilla (SCAPs). We examined the expression of neural markers, and the nerve repair and regeneration ability of SCAPs using dynamic changes in neuron-like cells, immunofluorescence staining, and a SCI model. We employed a coimmunoprecipitation (Co-IP) assay, real-time RT-PCR, microarray analysis, and chromatin immunoprecipitation (ChIP) assay to investigate the molecular mechanism. The results showed that MLL1 knock-down increased the expression of neural markers, including neurogenic differentiation factor (NeuroD), neural cell adhesion molecule (NCAM), tyrosine hydroxylase (TH), βIII-tubulin and Nestin, and promoted neuron-like cell formation in SCAPs. In vivo, a transplantation experiment showed that depletion of MLL 1 in SCAPs can restore motor function in a rat SCI model. MLL1 can combine with WD repeat domain 5 (WDR5) and WDR5 inhibit the expression of neural markers in SCAPs. MLL1 regulates Hairy and enhancer of split 1 (HES1) expression by directly binds to HES1 promoters via regulating H3K4me3 methylation by interacting with WDR5. Additionally, HES1 enhances the expression of neural markers in SCAPs. Our findings demonstrate that MLL1 inhibits the neurogenic potential of SCAPs by interacting with WDR5 and repressing HES1. These results provide a potential therapeutic target for promoting the recovery of motor function in SCI patients.

Phosphorylated Upstream Frameshift 1-dependent Nonsense-mediated μ-Opioid Receptor mRNA Decay in the Spinal Cord Contributes to the Development of Neuropathic Allodynia-like Behavior in Rats

BACKGROUND

Nonsense-mediated messenger RNA (mRNA) decay increases targeted mRNA degradation and has been implicated in the regulation of gene expression in neurons. The authors hypothesized that nonsense-mediated μ-opioid receptor mRNA decay in the spinal cord is involved in the development of neuropathic allodynia-like behavior in rats.

METHODS

Adult Sprague-Dawley rats of both sexes received spinal nerve ligation to induce neuropathic allodynia-like behavior. The mRNA and protein expression contents in the dorsal horn of animals were measured by biochemical analyses. Nociceptive behaviors were evaluated by the von Frey test and the burrow test.

RESULTS

On Day 7, spinal nerve ligation significantly increased phosphorylated upstream frameshift 1 (UPF1) expression in the dorsal horn (mean ± SD; 0.34 ± 0.19 in the sham ipsilateral group vs. 0.88 ± 0.15 in the nerve ligation ipsilateral group; P < 0.001; data in arbitrary units) and drove allodynia-like behaviors in rats (10.58 ± 1.72 g in the sham ipsilateral group vs. 1.19 ± 0.31 g in the nerve ligation ipsilateral group, P < 0.001). No sex-based differences were found in either Western blotting or behavior tests in rats. Eukaryotic translation initiation factor 4A3 (eIF4A3) triggered SMG1 kinase (0.06 ± 0.02 in the sham group vs. 0.20 ± 0.08 in the nerve ligation group, P = 0.005, data in arbitrary units)-mediated UPF1 phosphorylation, leading to increased nonsense-mediated mRNA decay factor SMG7 binding and µ-opioid receptor mRNA degradation (0.87 ± 0.11-fold in the sham group vs. 0.50 ± 0.11-fold in the nerve ligation group, P = 0.002) in the dorsal horn of the spinal cord after spinal nerve ligation. Pharmacologic or genetic inhibition of this signaling pathway in vivo ameliorated allodynia-like behaviors after spinal nerve ligation.

CONCLUSIONS

This study suggests that phosphorylated UPF1-dependent nonsense-mediated μ-opioid receptor mRNA decay is involved in the pathogenesis of neuropathic pain.

EDITOR’S PERSPECTIVE

The WD repeat-containing protein 5 (WDR5) antagonist WDR5-0103 restores the efficacy of cytotoxic drugs in multidrug-resistant cancer cells overexpressing ABCB1 or ABCG2

The development of multidrug resistance (MDR) is one of the major challenges in the treatment of cancer which is caused by the overexpression of the ATP-binding cassette (ABC) transporters ABCB1 (P-glycoprotein) and/or ABCG2 (BCRP/MXR/ABCP) in cancer cells. These transporters are capable of reducing the efficacy of cytotoxic drugs by actively effluxing them out of cancer cells. Since there is currently no approved treatment for patients with multidrug-resistant tumors, the drug repurposing approach provides an alternative route to identify agents to reverse MDR mediated by ABCB1 and/or ABCG2 in multidrug-resistant cancer cells. WDR5-0103 is a histone H3 lysine 4 (H3K4) methyltransferase inhibitor that disrupts the interaction between the WD repeat-containing protein 5 (WDR5) and mixed-lineage leukemia (MLL) protein. In this study, the effect of WDR5-0103 on MDR mediated by ABCB1 and ABCG2 was determined. We found that in a concentration-dependent manner, WDR5-0103 could sensitize ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to conventional cytotoxic drugs. Our results showed that WDR5-0103 reverses MDR and improves drug-induced apoptosis in multidrug-resistant cancer cells by inhibiting the drug-efflux function of ABCB1 and ABCG2, without altering the protein expression of ABCB1 or ABCG2. The potential sites of interactions of WDR5-0103 with the drug-binding pockets of ABCB1 and ABCG2 were predicted by molecular docking. In conclusion, the MDR reversal activity of WDR5-0103 demonstrated here indicates that it could be used in combination therapy to provide benefits to a subset of patients with tumor expressing high levels of ABCB1 or ABCG2.

Epigenetics-mediated pathological alternations and their potential in antiphospholipid syndrome diagnosis and therapy

APS (antiphospholipid syndrome) is a systematic autoimmune disease accompanied with venous or arterial thrombosis and poor pregnant manifestations, partly attributing to the successive elevated aPL (antiphospholipid antibodies) and provoked prothrombotic and proinflammatory molecules production. Nowadays, most researches focus on the laboratory detection and clinic features of APS, but its precise etiology remains to be deeply explored. As we all know, the dysfunction of ECs (endothelial cells), monocytes, platelets, trophoblasts and neutrophils are key contributors to APS progression. Especially, their epigenetic variations, mainly including the promoter CpGs methylation, histone PTMs (post-translational modifications) and ncRNAs (noncoding RNAs), result in genes expression or silence engaged in inflammation initiation, thrombosis formation, autoimmune activation and APOs (adverse pregnancy outcomes) in APS. Given the potential of epigenetic markers serving as diagnostic biomarkers or therapeutic targets of APS, and the encouraging advancements in epigenetic drugs are being made. In this review, we would systematically introduce the epigenetic underlying mechanisms for APS progression, comprehensively elucidate the functional mechanisms of epigenetics in boosting ECs, monocytes, platelets, trophoblasts and neutrophils. Lastly, the application of epigenetic alterations for probing novel diagnostic, specific therapeutic and prognostic strategies would be proposed.

Epigenetic Mechanisms of Neural Plasticity in Chronic Neuropathic Pain

Neuropathic pain is a challenging clinical problem and remains difficult to treat. Altered gene expression in peripheral sensory nerves and neurons due to nerve injury is well documented and contributes critically to the synaptic plasticity in the spinal cord and the initiation and maintenance of chronic pain. However, our understanding of the epigenetic mechanisms regulating the transcription of pro-nociceptive (e.g., NMDA receptors and α2δ-1) and antinociceptive (e.g., potassium channels and opioid and cannabinoid receptors) genes are still limited. In this review, we summarize recent studies determining the roles of histone modifications (including methylation, acetylation, and ubiquitination), DNA methylation, and noncoding RNAs in neuropathic pain development. We review the epigenetic writer, reader, and eraser proteins that participate in the transcriptional control of the expression of key ion channels and neurotransmitter receptors in the dorsal root ganglion after traumatic nerve injury, which is commonly used as a preclinical model of neuropathic pain. A better understanding of epigenetic reprogramming involved in the transition from acute to chronic pain could lead to the development of new treatments for neuropathic pain.

WIN site inhibition disrupts a subset of WDR5 function

WDR5 nucleates the assembly of histone-modifying complexes and acts outside this context in a range of chromatin-centric processes. WDR5 is also a prominent target for pharmacological inhibition in cancer. Small-molecule degraders of WDR5 have been described, but most drug discovery efforts center on blocking the WIN site of WDR5, an arginine binding cavity that engages MLL/SET enzymes that deposit histone H3 lysine 4 methylation (H3K4me). Therapeutic application of WIN site inhibitors is complicated by the disparate functions of WDR5, but is generally guided by two assumptions-that WIN site inhibitors disable all functions of WDR5, and that changes in H3K4me drive the transcriptional response of cancer cells to WIN site blockade. Here, we test these assumptions by comparing the impact of WIN site inhibition versus WDR5 degradation on H3K4me and transcriptional processes. We show that WIN site inhibition disables only a specific subset of WDR5 activity, and that H3K4me changes induced by WDR5 depletion do not explain accompanying transcriptional responses. These data recast WIN site inhibitors as selective loss-of-function agents, contradict H3K4me as a relevant mechanism of action for WDR5 inhibitors, and indicate distinct clinical applications of WIN site inhibitors and WDR5 degraders.

Bi-mode electrolyte-gated synaptic transistor via additional ion doping and its application to artificial nociceptors

Multiple types of synaptic transistors that are capable of processing electrical signals similar to the biological neural system hold enormous potential for application in parallel computing, logic circuits and peripheral detection. However, most of these presented synaptic transistors are confined to a single mode of synaptic plasticity under an electrical stimulus, which tremendously limits efficient memory formation and the multifunctional integration of synaptic transistors. Here, we proposed a bi-mode electrolyte-gated synaptic transistor (BEST) with two dynamic processes, the formation of an electrical double layer (EDL) and electrochemical doping (ECD) by tuning the applied voltages, thereby allowing volatile and non-volatile behavior, which is associated with additional ion doping and nanoscale ionic transport. Benefiting from two controllable dynamic processes, we surprisingly found a third state in the transfer curves besides the "off" and "on" states. Moreover, utilizing this unique property, an artificial nociceptor with multilevel modulation of sensitivity was realized based on our bi-mode device. Finally, a haptic sensory system was constructed to exhibit robotic motion that revealed a unique threshold switching behavior, indicating the applicability to peripheral sensing circuits. Hence, the presented bi-mode synaptic transistor provides promising prospects in achieving multiple-mode integrated devices and simplifying neural circuits, which shows great potential in the development of artificial intelligence.

MMP24 Contributes to Neuropathic Pain in an FTO-Dependent Manner in the Spinal Cord Neurons

Nerve injury-induced gene expression change in the spinal cord is critical for neuropathic pain genesis. RNA N⁶-methyladenosine (m⁶A) modification represents an additional layer of gene regulation. We showed that spinal nerve ligation (SNL) upregulated the expression of matrix metallopeptidase 24 (MMP24) protein, but not Mmp24 mRNA, in the spinal cord neurons. Blocking the SNL-induced upregulation of spinal MMP24 attenuated local neuron sensitization, neuropathic pain development and maintenance. Conversely, mimicking MMP24 increase promoted the spinal ERK activation and produced evoked nociceptive hypersensitivity. Methylated RNA Immunoprecipitation Sequencing (MeRIP-seq) and RNA Immunoprecipitation (RIP) assay indicated the decreased m⁶A enrichment in the Mmp24 mRNA under neuropathic pain condition. Moreover, fat-mass and obesity-associated protein (FTO) was colocalized with MMP24 in spinal neurons and shown increased binding to the Mmp24 mRNA in the spinal cord after SNL. Overexpression or suppression of FTO correlates with promotion or inhibition of MMP24 expression in cultured spinal cord neurons. In conclusion, SNL promoted the m⁶A eraser FTO binding to the Mmp24 mRNA, which subsequently facilitated the translation of MMP24 in the spinal cord, and ultimately contributed to neuropathic pain genesis.

Blocking the Spinal Fbxo3/CARM1/K+ Channel Epigenetic Silencing Pathway as a Strategy for Neuropathic Pain Relief

Many epigenetic regulators are involved in pain-associated spinal plasticity. Coactivator-associated arginine methyltransferase 1 (CARM1), an epigenetic regulator of histone arginine methylation, is a highly interesting target in neuroplasticity. However, its potential contribution to spinal plasticity-associated neuropathic pain development remains poorly explored. Here, we report that nerve injury decreased the expression of spinal CARM1 and induced allodynia. Moreover, decreasing spinal CARM1 expression by Fbxo3-mediated CARM1 ubiquitination promoted H3R17me2 decrement at the K+ channel promoter, thereby causing K+ channel epigenetic silencing and the development of neuropathic pain. Remarkably, in naïve rats, decreasing spinal CARM1 using CARM1 siRNA or a CARM1 inhibitor resulted in similar epigenetic signaling and allodynia. Furthermore, intrathecal administration of BC-1215 (a novel Fbxo3 inhibitor) prevented CARM1 ubiquitination to block K+ channel gene silencing and ameliorate allodynia after nerve injury. Collectively, the results reveal that this newly identified spinal Fbxo3-CARM1-K+ channel gene functional axis promotes neuropathic pain. These findings provide essential insights that will aid in the development of more efficient and specific therapies against neuropathic pain.