The Role of Protein Arginine Methyltransferases in Inflammatory Responses

Discovery of an ApoE4-targeted small-molecule SirT1 enhancer for the treatment of Alzheimer's disease

Decreased expression of sirtuin 1 (SirT1) has been implicated in Alzheimer's disease (AD), and as we previously reported, is related to transcriptional repression by the major risk factor for sporadic AD, apolipoprotein E4 (ApoE4). Herein we describe the discovery of an orally brain-permeable small-molecule, DDL-218, that enhanced SirT1 in ApoE4-expressing neuronal cells and a murine AD model. DDL-218 increased the transcription factor NFYb resulting in upregulation of PRMT5. Mechanistic and modeling studies show that binding of ApoE4 to the SirT1 gene promoter can be displaced by PRMT5 leading to increased SirT1 transcription. DDL-218 treatment elicited improvement in memory in the AD model, suggesting that DDL-218 enhancement of neurotrophic SirT1 in the brain has potential to modulate neuronal activity that may clinically provide an improvement in cognitive function and complement the current anti-Aβ antibody monotherapy. Our findings support further development of DDL-218 as a novel ApoE4-targeted therapeutic candidate for AD.

Resolving 3-Dimensional Genomic Landscape of CD4+ T Cells in the Peripheral Blood of Patients with Psoriasis

A precise regulation of gene expression depends on the accuracy of the 3-dimensional (3D) structure of chromatin; however, the effects of the 3D genome on gene expression in psoriasis remain unknown. In this study, we conducted Hi-C and RNA sequencing on CD4+ T cells collected from 5 patients with psoriasis and 3 healthy controls and constructed a comprehensive 3D chromatin interaction map to delineate the genomic hierarchies, including A/B compartments, topologically associated domains, and chromatin loops. Then, the specific superenhancers related to psoriasis were identified by Hi-C and H3K27ac chromatin immunoprecipitation sequencing data. Subsequently, comprehensive analyses were carried out on the differentially expressed genes that are associated with altered topologically associated domains, loops, and superenhancers in psoriasis. Finally, we screened the candidate target genes and examined the potential functional SNP in psoriasis affected by disruptions of the spatial organization. This study provides a comprehensive reference for examining the 3D genome interactions in psoriasis and elucidating the interplay between spatial organization disruption and gene regulation. We hope that our findings can help clarify the mechanisms underlying the pathogenesis of psoriasis and shed light on the role of 3D genomic structure, therefore informing potential therapeutic approaches.

Protein arginine methyltransferases as regulators of cellular stress

Arginine modification can be a "switch" to regulate DNA transcription and a post-translational modification via methylation of a variety of cellular targets involved in signal transduction, gene transcription, DNA repair, and mRNA alterations. This consequently can turn downstream biological effectors "on" and "off". Arginine methylation is catalyzed by protein arginine methyltransferases (PRMTs 1-9) in both the nucleus and cytoplasm, and is thought to be involved in many disease processes. However, PRMTs have not been well-documented in the brain and their function as it relates to metabolism, circulation, functional learning and memory are understudied. In this review, we provide a comprehensive overview of PRMTs relevant to cellular stress, and future directions into PRMTs as therapeutic regulators in brain pathologies.

β-1,3-glucan from Euglena gracilis: a promising epidrug targeting epigenetic regulators PRMTs and SIRTs for therapeutic applications in ovarian cancer

Natural products serve as a valuable resource in drug discovery and the identification of bioactive molecules in the field of epimedicine, which targets epigenetic regulator enzymes through epidrugs. In this study, β-1,3-glucan (BG), a natural storage polysaccharide in Euglena gracilis, a well-known immunostimulatory agent, is propounded as a promising epidrug. To elucidate the therapeutic efficacy of BG against ovarian cancer, the molecular interactions between BG and epigenetic regulators, Protein Arginine Methyltransferases (PRMTs) and Sirtuins (SIRTs) were investigated using computational methods followed by in vitro gene expression studies in SKOV-3 ovarian cancer cell line. The binding energies of PRMT5 and SIRT5 against BG were observed as -65.5 and -68.2 kcal/mol, respectively. The in vitro cytotoxic effects of BG against human ovarian cancer cell line, SKOV-3 showed an IC50 of 150 µg/mL at 48 h. Significant epigenetic modifications were observed to be influenced by BG which increased the gene expression of PRMT5, SIRT5 and Nrf2 to 0.3, 0.5, and 0.7 fold-change respectively, while the Nrf1/2 plasmid showed reduced reporter activity by 29%. Collectively, both in silico and in vitro studies provided valuable insights into the epigenetic regulation of PRMT5 and SIRT5 by BG via Nrf1/2. Nonetheless, further preclinical and clinical investigations are essential to validate the therapeutic properties of BG as an epidrug against ovarian cancer.

The PRMT6/STAT1/ACSL1 axis promotes ferroptosis in diabetic nephropathy

Hyperglycaemia-induced ferroptosis is a significant contributor to kidney dysfunction in diabetic nephropathy (DN) patients. In addition, targeting ferroptosis has clinical implications for the treatment of DN. However, effective therapeutic targets for ferroptosis have not been identified. In this study, we aimed to explore the precise role of protein arginine methyltransferase 6 (PRMT6) in regulating ferroptosis in DN. In the present study, we utilized a mouse DN model consisting of both wild-type and PRMT6-knockout (PRMT6-/-) mice. Transcriptomic and lipidomic analyses, along with various molecular biological methodologies, were used to determine the potential mechanism by which PRMT6 regulates ferroptosis in DN. Our results indicate that PRMT6 downregulation participates in kidney dysfunction and renal cell death via the modulation of ferroptosis in DN. Moreover, PRMT6 reduction induced lipid peroxidation by upregulating acyl-CoA synthetase long-chain family member 1 (ACSL1) expression, ultimately contributing to ferroptosis. Furthermore, we investigated the molecular mechanism by which PRMT6 interacts with signal transducer and activator of transcription 1 (STAT1) to jointly regulate ACSL1 transcription. Additionally, treatment with the STAT1-specific inhibitor fludarabine delayed DN progression. Furthermore, we observed that PRMT6 and STAT1 synergistically regulate ACSL1 transcription to mediate ferroptosis in hyperglycaemic cells. Our study demonstrated that PRMT6 and STAT1 comodulate ACSL1 transcription to induce the production of phospholipid-polyunsaturated fatty acids (PL-PUFAs), thus participating in ferroptosis in DN. These findings suggest that the PRMT6/STAT1/ACSL1 axis is a new therapeutic target for the prevention and treatment of DN.

Role of protein arginine methyltransferase 1 in obesity-related metabolic disorders: Research progress and implications

Obesity has become a major global problem that significantly confers an increased risk of developing life-threatening complications, including type 2 diabetes mellitus, fatty liver disease and cardiovascular diseases. Protein arginine methyltransferases (PRMTs) are enzymes that catalyse the methylation of target proteins. They are ubiquitous in eukaryotes and regulate transcription, splicing, cell metabolism and RNA biology. As a key, epigenetically modified enzyme, protein arginine methyltransferase 1 (PRMT1) is involved in obesity-related metabolic processes, such as lipid metabolism, the insulin signalling pathway, energy balance and inflammation, and plays an important role in the pathology of obesity-related metabolic disorders. This review summarizes recent research on the role of PRMT1 in obesity-related metabolic disorders. The primary objective was to comprehensively elucidate the functional role and regulatory mechanisms of PRMT1. Moreover, this study attempts to review the pathogenesis of PRMT1-mediated obesity-related metabolic disorders, thereby offering pivotal information for further studies and clinical treatment.

Gut Microbiota-Derived Trimethylamine Promotes Inflammation with a Potential Impact on Epigenetic and Mitochondrial Homeostasis in Caco-2 Cells

Trimethylamine (TMA), a byproduct of gut microbiota metabolism from dietary precursors, is not only the precursor of trimethylamine-N-oxide (TMAO) but may also affect gut health. An in vitro model of intestinal epithelium of Caco-2 cells was used to evaluate the impact of TMA on inflammation, paracellular permeability, epigenetics and mitochondrial functions. The expression levels of pro-inflammatory cytokines (IL-6, IL-1β) increased significantly after 24 h exposure to TMA 1 mM. TMA exposure was associated with an upregulation of SIRT1 (TMA 1 mM, 400 μM, 10 μM) and DNMT1 (TMA 1 mM, 400 µM) genes, while DNMT3A expression decreased (TMA 1 mM). In a cell-free model, TMA (from 0.1 µM to 1 mM) induced a dose-dependent reduction in Sirtuin enzyme activity. In Caco-2 cells, TMA reduced total ATP levels and significantly downregulated ND6 expression (TMA 1 mM). TMA excess (1 mM) reduced intracellular mitochondrial DNA copy numbers and increased the methylation of the light-strand promoter in the D-loop area of mtDNA. Also, TMA (1 mM, 400 µM, 10 µM) increased the permeability of Caco-2 epithelium, as evidenced by the reduced transepithelial electrical resistance values. Based on our preliminary results, TMA excess might promote inflammation in intestinal cells and disturb epigenetic and mitochondrial homeostasis.

PRMT6 deficiency or inhibition alleviates neuropathic pain by decreasing glycolysis and inflammation in microglia

Microglia induced chronic inflammation is the critical pathology of Neuropathic pain (NP). Metabolic reprogramming of macrophage has been intensively reported in various chronic inflammation diseases. However, the metabolic reprogramming of microglia in chronic pain remains to be elusive. Here, we reported that immuno-metabolic markers (HIF-1α, PKM2, GLUT1 and lactate) were related with increased expression of PRMT6 in the ipsilateral spinal cord dorsal horn of the chronic construction injury (CCI) mice. PRMT6 deficiency or prophylactic and therapeutic intrathecal administration of PRMT6 inhibitor (EPZ020411) ameliorated CCI-induced NP, inflammation and glycolysis in the ipsilateral spinal cord dorsal horn. PRMT6 knockout or knockdown inhibited LPS-induced inflammation, proliferation and glycolysis in microglia cells. While PRMT6 overexpression exacerbated LPS-induced inflammation, proliferation and glycolysis in BV2 cells. Recent research revealed that PRMT6 could interact with and methylate HIF-1α, which increased HIF-1α protein stability. In sum, increased expression of PRMT6 exacerbates NP progress by increasing glycolysis and neuroinflammation through interacting with and stabilizing HIF-1α in a methyltransferase manner, which outlines novel pathological mechanism and drug target for NP.

CRISPR-Cas9-mediated chicken prmt5 gene knockout and its critical role in interferon regulation

Protein arginine methyltransferase 5 (PRMT5), a type II arginine methyltransferase, controls arginine dimethylation of a variety of substrates. While many papers have reported the function of mammalian PRMT5, it remains unclear how PRMT5 functions in chicken cells. In this study, we found that chicken (ch) PRMT5 is widely expressed in a variety of chicken tissues and is distributed in both the cytoplasm and the nucleus. Ectopic expression of chPRMT5 significantly suppresses chIFN-β activation induced by chMDA5. In addition, a prmt5 gene-deficient DF-1 cell line was constructed using CRISPR/Cas9. In comparison with the wild-type cells, the prmt5-/- DF-1 cells displays normal morphology and maintain proliferative capacity. Luciferase reporter assay and overexpression showed that prmt5-/- DF-1 cells had increased IFN-β production. With identified chicken PRMT5 and CRISPR/Cas9 knockout performed in DF-1 cells, we uncovered a functional link of chPRMT5 in suppression of IFN-β production and interferon-stimulated gene expression.

Microproteomic-Based Analysis of the Goat Milk Protein Synthesis Network and Casein Production Evaluation

Goat milk has been consumed by humans since ancient times and is highly nutritious. Its quality is mainly determined by its casein content. Milk protein synthesis is controlled by a complex network with many signal pathways. Therefore, the aim of our study is to clearly depict the signal pathways involved in milk protein synthesis in goat mammary epithelial cells (GMECs) using state-of-the-art microproteomic techniques and to identify the key genes involved in the signal pathway. The microproteomic analysis identified more than 2253 proteins, with 323 pathways annotated from the identified proteins. Knockdown of IRS1 expression significantly influenced goat casein composition (α, β, and κ); therefore, this study also examined the insulin receptor substrate 1 (IRS1) gene more closely. A total of 12 differential expression proteins (DEPs) were characterized as upregulated or downregulated in the IRS1-silenced sample compared to the negative control. The enrichment and signal pathways of these DEPs in GMECs were identified using GO annotation and KEGG, as well as KOG analysis. Our findings expand our understanding of the functional genes involved in milk protein synthesis in goats, paving the way for new approaches for modifying casein content for the dairy goat industry and milk product development.

The role of protein arginine N-methyltransferases in inflammation

Protein arginine methyltransferases (PRMTs) promote the methylation of numerous proteins at their arginine residues. An increasing number of publications have suggested that dysregulation of PRMTs participates in various human diseases, such as cardiovascular diseases, cancer, diabetes and neurodegenerative disorders. Inflammation is one normal response to infection or injury by immune system, which can keep body homeostasis. Emerging data reveal that inflammation is associated with the development of numerous diseases. Moreover, accumulated evidence proves that PRMTs have been characterized to regulate inflammation in various diseases. In this review article, we delineate the function and molecular mechanism of PRMTs in regulation of inflammation in current literature. Moreover, we discuss that targeting PRMTs by its inhibitors and compounds could have therapeutic potential.

Protection of c-Fos from autophagic degradation by PRMT1-mediated methylation fosters gastric tumorigenesis

Both AP-1 and PRMT1 are vital molecules in variety of cellular progresssion, but the interaction between these proteins in the context of cellular functions is less clear. Gastric cancer (GC) is one of the pernicious diseases worldwide. An in-depth understanding of the molecular mode of action underlying gastric tumorigenesis is still elusive. In this study, we found that PRMT1 directly interacts with c-Fos and enhances AP-1 activation. PRMT1-mediated arginine methylation (mono- and dimethylation) of c-Fos synergistically enhances c-Fos-mediated AP-1 liveliness and consequently increases c-Fos protein stabilization. Consistent with this finding, PRMT1 knockdown decreases the protein level of c-Fos. We discovered that the c-Fos protein undergoes autophagic degradation and found that PRMT1-mediated methylation at R287 protects c-Fos from autophagosomal degradation and is linked to clinicopathologic variables as well as prognosis in stomach tumor. Together, our data demonstrate that PRMT1-mediated c-Fos protein stabilization promotes gastric tumorigenesis. We contend that targeting this modification could constitute a new therapeutic strategy in gastric cancer.

Affi-BAMS™: A Robust Targeted Proteomics Microarray Platform to Measure Histone Post-Translational Modifications

For targeted protein panels, the ability to specifically assay post-translational modifications (PTMs) in a quantitative, sensitive, and straightforward manner would substantially advance biological and pharmacological studies. The present study highlights the effectiveness of the Affi-BAMS™ epitope-directed affinity bead capture/MALDI MS platform for quantitatively defining complex PTM marks of H3 and H4 histones. Using H3 and H4 histone peptides and isotopically labelled derivatives, this affinity bead and MALDI MS platform achieves a range of >3 orders of magnitude with a technical precision CV of <5%. Using nuclear cellular lysates, Affi-BAMS PTM-peptide capture resolves heterogeneous histone N-terminal PTMs with as little as 100 µg of starting material. In an HDAC inhibitor and MCF7 cell line model, the ability to monitor dynamic histone H3 acetylation and methylation events is further demonstrated (including SILAC quantification). Affi-BAMS (and its capacity for the multiplexing of samples and target PTM-proteins) thus provides a uniquely efficient and effective approach for analyzing dynamic epigenetic histone marks, which is critical for the regulation of chromatin structure and gene expression.

PRMT5 inhibition ameliorates inflammation and promotes the osteogenic differentiation of LPS‑induced periodontal stem cells via STAT3/NF‑κB signaling

It has been reported that protein arginine methyltransferase 5 (PRMT5) serves a significant role in osteogenic differentiation and inflammatory response. Nevertheless, its role in periodontitis as well as its underlying mechanism remain to be elucidated. The aim of the present study was to explore the role of PRMT5 in periodontitis and whether PRMT5 could reduce liposaccharide (LPS)-induced inflammation of human periodontal ligament stem cells (hPDLSCs) and promote osteogenic differentiation through STAT3/NF-κB signaling. In the current study, the expression levels of PRMT5 were determined in LPS-induced hPDLSCs by reverse transcription-quantitative PCR and western blot analysis. ELISA and western blot analysis were employed to assess the secretion and expression levels of inflammatory factors, respectively. The osteogenic differentiation and mineralization potential of hPDLSCs were evaluated using alkaline phosphatase (ALP) activity assay, Alizarin red staining and western blot analysis. Additionally, western blot analysis was applied to determine the expression levels of the STAT3/NF-κB signaling pathway-related proteins. The results showed that the expression levels of PRMT5 were significantly enhanced in LPS-induced hPDLSCs. Additionally, PRMT5 knockdown reduced the contents of IL-1β, IL-6, TNF-α, inducible nitric oxide synthase and cyclooxygenase-2. PRMT5 depletion also enhanced ALP activity, improved the mineralization ability and upregulated bone morphogenetic protein 2, osteocalcin and runt-related transcription factor 2 in LPS-induced hPDLSCs. Furthermore, PRMT5 knockdown inhibited inflammation and promoted the osteogenic differentiation of hPDLSCs via blocking the activation of the STAT3/NF-κB signaling pathway. In conclusion, PRMT5 inhibition suppressed LPS-induced inflammation and accelerated osteogenic differentiation in hPDLSCs via regulating STAT3/NF-κB signaling, thus providing a potential targeted therapy for the improvement of periodontitis.

PRMT1 reverts the immune escape of necroptotic colon cancer through RIP3 methylation

Necroptosis plays a double-edged sword role in necroptotic cancer cell death and tumor immune escape. How cancer orchestrates necroptosis with immune escape and tumor progression remains largely unclear. We found that RIP3, the central activator of necroptosis, was methylated by PRMT1 methyltransferase at the amino acid of RIP3 R486 in human and the conserved amino acid R479 in mouse. The methylation of RIP3 by PRMT1 inhibited the interaction of RIP3 with RIP1 to suppress RIP1-RIP3 necrosome complex, thereby blocking RIP3 phosphorylation and necroptosis activation. Moreover, the methylation-deficiency RIP3 mutant promoted necroptosis, immune escape and colon cancer progression due to increasing tumor infiltrated myeloid-derived immune suppressor cells (MDSC), while PRMT1 reverted the immune escape of RIP3 necroptotic colon cancer. Importantly, we generated a RIP3 R486 di-methylation specific antibody (RIP3ADMA). Clinical patient samples analysis revealed that the protein levels of PRMT1 and RIP3ADMA were positively correlated in cancer tissues and both of them predicted the longer patient survival. Our study provides insights into the molecular mechanism of PRMT1-mediated RIP3 methylation in the regulation of necroptosis and colon cancer immunity, as well as reveals PRMT1 and RIP3ADMA as the valuable prognosis markers of colon cancer.

Protein Arginine Methyltransferase 5 (PRMT5) Mutations in Cancer Cells

Arginine methylation is a form of posttranslational modification that regulates many cellular functions such as development, DNA damage repair, inflammatory response, splicing, and signal transduction, among others. Protein arginine methyltransferase 5 (PRMT5) is one of nine identified methyltransferases, and it can methylate both histone and non-histone targets. It has pleiotropic functions, including recruitment of repair machinery to a chromosomal DNA double strand break (DSB) and coordinating the interplay between repair and checkpoint activation. Thus, PRMT5 has been actively studied as a cancer treatment target, and small molecule inhibitors of its enzymatic activity have already been developed. In this report, we analyzed all reported PRMT5 mutations appearing in cancer cells using data from the Catalogue of Somatic Mutations in Cancers (COSMIC). Our goal is to classify mutations as either drivers or passengers to understand which ones are likely to promote cellular transformation. Using gold standard artificial intelligence algorithms, we uncovered several key driver mutations in the active site of the enzyme (D306H, L315P, and N318K). In silico protein modeling shows that these mutations may affect the affinity of PRMT5 for S-adenosylmethionine (SAM), which is required as a methyl donor. Electrostatic analysis of the enzyme active site shows that one of these mutations creates a tunnel in the vicinity of the SAM binding site, which may allow interfering molecules to enter the enzyme active site and decrease its activity. We also identified several non-coding mutations that appear to affect PRMT5 splicing. Our analyses provide insights into the role of PRMT5 mutations in cancer cells. Additionally, since PRMT5 single molecule inhibitors have already been developed, this work may uncover future directions in how mutations can affect targeted inhibition.

Protein arginine methyltransferases in renal development, injury, repair, and fibrosis

Protein arginine methyltransferases (PRMTs) methylate a range of histone and non-histone substrates and participate in multiple biological processes by regulating gene transcription and post-translational modifications. To date, most studies on PRMTs have focused on their roles in tumors and in the physiological and pathological conditions of other organs. Emerging evidence indicates that PRMTs are expressed in the kidney and contribute to renal development, injury, repair, and fibrosis. In this review, we summarize the role and the mechanisms of PRMTs in regulating these renal processes and provide a perspective for future clinical applications.

Discovery of cysteine-targeting covalent histone methyltransferase inhibitors

Post-translational methylation of histone lysine or arginine residues by histone methyltransferases (HMTs) plays crucial roles in gene regulation and diverse physiological processes and is implicated in a plethora of human diseases, especially cancer. Therefore, histone methyltransferases have been increasingly recognized as potential therapeutic targets. Consequently, the discovery and development of histone methyltransferase inhibitors have been pursued with steadily increasing interest over the past decade. However, the disadvantages of limited clinical efficacy, moderate selectivity, and propensity for acquired resistance have hindered the development of HMTs inhibitors. Targeted covalent modification represents a proven strategy for kinase drug development and has gained increasing attention in HMTs drug discovery. In this review, we focus on the discovery, characterization, and biological applications of covalent inhibitors for HMTs with emphasis on advancements in the field. In addition, we identify the challenges and future directions in this fast-growing research area of drug discovery.

PRMT6 functionally associates with PRMT5 to promote colorectal cancer progression through epigenetically repressing the expression of CDKN2B and CCNG1

BACKGROUND

Protein arginine methyltransferase 6 (PRMT6) is a type I arginine methyltransferase that asymmetrically dimethylates histone H3 arginine 2 (H3R2me2a). However, the biological roles and underlying molecular mechanisms of PRMT6 in colorectal cancer (CRC) remain unclear.

METHODS

PRMT6 expression in CRC tissue was examined using immunohistochemistry. The effect of PRMT6 on CRC cells was investigated in vitro and in vivo. Mass spectrometry, co-immunoprecipitation and GST pulldown assays were performed to identify interaction partners of PRMT6. RNA-seq, chromatin immunoprecipitation, Western blot and qRT-PCR assays were used to investigate the mechanism of PRMT6 in gene regulation.

RESULTS

PRMT6 is significantly upregulated in CRC tissues and facilitates cell proliferation of CRC cells in vitro and in vivo. Through RNA-seq analysis, CDKN2B (p15^INK4b) and CCNG1 were identified as new transcriptional targets of PRMT6. PRMT6-dependent H3R2me2a mark was predominantly deposited at the promoters of CDKN2B and CCNG1 in CRC cells. Furthermore, PRMT5 was firstly characterized as an interaction partner of PRMT6. Notably, H3R2me2a coincides with PRMT5-mediated H4R3me2s and H3R8me2s marks at the promoters of CDKN2B and CCNG1 genes, thus leading to transcriptional repression of these genes.

CONCLUSIONS

PRMT6 functionally associates with PRMT5 to promote CRC progression through epigenetically repressing the expression of CDKN2B and CCNG1. These insights raise the possibility that combinational intervention of PRMT6 and PRMT5 may be a promising strategy for CRC therapy.

Mass-cytometry-based quantitation of global histone post-translational modifications at single-cell resolution across peripheral immune cells in IBD

BACKGROUND AND AIMS

Current understanding of histone post-translational modifications (histone modifications) across immune cell types in patients with inflammatory bowel disease (IBD) during remission and flare is limited. The study aimed to quantify histone modifications at a single-cell resolution in IBD patients during remission and flare and how they differ compared to healthy controls.

METHODS

We performed a case-control study of 94 subjects (83 IBD patients and 11 healthy controls). IBD patients had either UC (n=38) or CD (n=45) in clinical remission or flare. We used epigenetic profiling by time-of-flight (EpiTOF) to investigate changes in histone modifications within peripheral blood mononuclear cells from IBD patients.

RESULTS

We discovered substantial heterogeneity in histone modifications across multiple immune cell types in IBD patients. They had a higher proportion of less differentiated CD34 + hematopoietic progenitors, and a subset of CD56 bright NK cells and γδ T cells characterized by distinct histone modifications associated with the gene transcription. The subset of CD56 bright NK cells had increased several histone acetylations. An epigenetically defined subset of NK was associated with higher levels of CRP in peripheral blood. CD14+ monocytes from IBD patients had significantly decreased cleaved H3T22, suggesting they were epigenetically primed for macrophage differentiation.

CONCLUSION

We describe the first systems-level quantification of histone modifications across immune cells from IBD patients at a single-cell resolution revealing the increased epigenetic heterogeneity that is not possible with traditional ChIP-seq profiling. Our data open new directions in investigating the association between histone modifications and IBD pathology using other epigenomic tools.

Multi-OMICs analysis reveals metabolic and epigenetic changes associated with macrophage polarization

Macrophages (MФ) are an essential immune cell for defense and repair that travel to different tissues and adapt based on local stimuli. A critical factor that may govern their polarization is the crosstalk between metabolism and epigenetics. However, simultaneous measurements of metabolites, epigenetics, and proteins (phenotype) have been a major technical challenge. To address this, we have developed a novel triomics approach using mass spectrometry to comprehensively analyze metabolites, proteins, and histone modifications in a single sample. To demonstrate this technique, we investigated the metabolic-epigenetic-phenotype axis following polarization of human blood–derived monocytes into either ‘proinflammatory M1-’ or ‘anti-inflammatory M2-’ MФs. We report here a complex relationship between arginine, tryptophan, glucose, and the citric acid cycle metabolism, protein and histone post-translational modifications, and human macrophage polarization that was previously not described. Surprisingly, M1-MФs had globally reduced histone acetylation levels but high levels of acetylated amino acids. This suggests acetyl-CoA was diverted, in part, toward acetylated amino acids. Consistent with this, stable isotope tracing of glucose revealed reduced usage of acetyl-CoA for histone acetylation in M1-MФs. Furthermore, isotope tracing also revealed MФs uncoupled glycolysis from the tricarboxylic acid cycle, as evidenced by poor isotope enrichment of succinate. M2-MФs had high levels of kynurenine and serotonin, which are reported to have immune-suppressive effects. Kynurenine is upstream of de novo NAD⁺ metabolism that is a necessary cofactor for Sirtuin-type histone deacetylases. Taken together, we demonstrate a complex interplay between metabolism and epigenetics that may ultimately influence cell phenotype.

PRMT6/LMNA/CXCL12 signaling pathway regulated the osteo/odontogenic differentiation ability in dental stem cells isolated from apical papilla

Tooth loss and maxillofacial bone defect are common diseases, which seriously affect people's health. Effective tooth and maxillofacial bone tissue regeneration is a key problem that need to be solved. In the present study, we investigate the role of PRMT6 in osteo/odontogenic differentiation and migration capacity by using SCAPs. Our results showed that knockdown of PRMT6 promoted the osteo/odontogenic differentiation compared with the control group, as detected by alkaline phosphatase activity, alizarin red staining, and the indicators of osteo/odontogenic differentiation measured by Western blot. In addition, overexpression of PRMT6 inhibited the osteo/odontogenic differentiation potentials of SCAPs. Then, knockdown of PRMT6 promoted the migration ability and overexpression of PRMT6 inhibited the migration ability in SCAPs. Mechanically, we discovered that the depletion of PRMT6 promoted the expression of CXCL12 by decreasing H3R2 methylation in the promoter region of CXCL12. In addition, PRMT6 formed a protein complex with LMNA, a nuclear structural protein. Depletion of LMNA inhibited the osteo/odontogenic differentiation and CXCL12 expression and increased the intranucleus PRMT6 in SCAPs. To sum up, PRMT6 might inhibit the osteo/odontogenic differentiation and migration ability of SCAPs via inhibiting CXCL12. And LMNA might be a negative regulator of PRMT6. It is suggested that PRMT6 may be a key target for SCAP-mediated bone and tooth tissue regeneration.

Gene expression adjustment of inflammatory mechanisms in dairy cow mammary gland parenchyma during host defense against staphylococci

The aim of the study was to identify differences in the expression of splice variants of the PRMT2, LTF and C4A genes in the mammary glands of healthy dairy cows and those infected with staphylococci. An expression study was conducted on 38 Polish Holstein-Friesian dairy cows who were removed from the herd owing to subclinical and chronic mastitic or reproductive issues. Two days before slaughter, milk samples were taken for microbiological analysis and examined for the presence of bacteria. The mammary gland parenchyma samples with a predominance of secretory tissue were taken; these were divided into three groups according to the health status of the mammary gland: H (without pathogenic bacteria in milk), CoNS (with coagulase-negative staphylococci in milk), and CoPS (with coagulase-positive staphylococci in milk). Two of the investigated genes, LTF and C4A, demonstrated variants unequivocally expressed in infected tissue. Two LTF gene variants were found to be associated with cow health status, and with the type of bacteria causing mastitis (CoPS or CoNS). In addition, the expression of C4A isoforms differed with regard to mastitis etiology groups. The comprehensive evaluation of PRMT2 transcript suggested that the gene may also be involved in course of mastitis: two of four PRMT2 transcripts showed increased expression in the mammary gland of the CoPS group compared to controls. The obtained results are important for the knowledge on the etiology of bovine mastitis. The effects of the identified mastitis-relevant splice variants need to be further explored on the protein level to verify the suitability of splice variants and recognize their contribution towards the disease phenotypes and course.

The Influence of Arginine Methylation in Immunity and Inflammation

Exploration in the field of epigenetics has revealed that protein arginine methyltransferases (PRMTs) contribute to disease, and this has given way to the development of specific small molecule compounds that inhibit arginine methylation. Protein arginine methylation is known to regulate fundamental cellular processes, such as transcription; pre-mRNA splicing and other RNA processing mechanisms; signal transduction, including the anti-viral response; and cellular metabolism. PRMTs are also implicated in the regulation of physiological processes, including embryonic development, myogenesis, and the immune system. Finally, the dysregulation of PRMTs is apparent in cancer, neurodegeneration, muscular disorders, and during inflammation. Herein, we review the functions of PRMTs in immunity and inflammation. We also discuss recent progress with PRMTs regarding the modulation of gene expression related to T and B lymphocyte differentiation, germinal center dynamics, and anti-viral signaling responses, as well as the clinical relevance of using PRMT inhibitors alone or in combination with other drugs to treat cancer, immune, and inflammatory-related diseases.

Evaluation of salivary and serum methylated arginine metabolites and nitric oxide synthase in advanced periodontitis patients

OBJECTIVES

Methylated arginine metabolites and nitric oxide synthase (NOS) play a critical role in regulating endothelial function. The aim of this study was to determine levels of NOS, and methylated arginine metabolites (ADMA, SDMA, homoarginine, arginine, and L-NMMA) and IL-6 in serum and saliva in patients with advanced periodontal diseases and identify their association with clinical parameters.

MATERIALS AND METHODS

The study consisted of two groups: healthy individuals (control: n = 24), and generalized Stage III Grade B periodontitis (P: n = 21). Clinical periodontal parameters (probing pocket depth, bleeding on probing, clinical attachment level) were recorded. IL 6 and NOS levels in saliva and serum were analyzed by enzyme-linked immunosorbent assay (ELISA). ADMA, SDMA, homoArg, arginine, and L-NMMA in saliva and serum were analyzed by liquid chromatography-mass spectrometry (LC MS/MS).

RESULTS

Clinical parameters were significantly higher in the periodontitis group (p < 0.001). In periodontitis group, NOS, ADMA, and arginine levels in saliva were statistically significantly higher than control group (p < 0.05). Serum levels of SDMA were statistically significantly lower, and IL-6 was statistically significantly higher in P group than C group (p < 0.05). ADMA, NOS, and arginine levels were significantly positive correlated with all clinical periodontal parameters (p < 0.05).

CONCLUSIONS

These findings suggest that there is a relationship between severity of periodontal disease and endothelial dysfunction by means of ADMA. Salivary ADMA may be related with periodontal inflammation.

CLINICAL RELEVANCE

ADMA levels in periodontal inflammation are associated with endothelial dysfunction. According to the results of our study, periodontal inflammation is effective on both local and systemic methylated arginine metabolites and nitric oxide synthase levels. This may shed light on the relationship between periodontal disease and systemic status.

CARM1 promotes gastric cancer progression by regulating TFE3 mediated autophagy enhancement through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways

BACKGROUND

The role of CARM1 in tumors is inconsistent. It acts as an oncogene in most cancers but it inhibits the progression of liver and pancreatic cancers. CARM1 has recently been reported to regulate autophagy, but this function is also context-dependent. However, the effect of CARM1 on gastric cancer (GC) has not been studied. We aimed to explore whether CARM1 was involved in the progression of GC by regulating autophagy.

METHODS

The clinical values of CARM1 and autophagy in GC were evaluated by immunohistochemistry and qRT-PCR. Transmission electron microscopy, immunofluorescence and western blotting were employed to identify autophagy. The role of CARM1 in GC was investigated by CCK-8, colony formation and flow cytometry assays in vitro and a xenograft model in vivo. Immunoprecipitation assays were performed to determine the interaction of CARM1 and TFE3.

RESULTS

CARM1 was upregulated in clinical GC tissues and cell lines, and higher CARM1 expression predicted worse prognosis. CARM1 enhanced GC cell proliferation, facilitated G1-S transition and inhibited ER stress-induced apoptosis by regulating autophagy. Importantly, treatment with a CARM1 inhibitor rescued the tumor-promoting effects of CARM1 both in vitro and in vivo. Furthermore, we demonstrated that CARM1 promoted TFE3 nuclear translocation to induce autophagy through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways.

CONCLUSION

CARM1 promoted GC cell proliferation, accelerated G1-S transition and reduced ER stress-induced apoptosis by regulating autophagy. Mechanistically, CARM1 triggered autophagy by facilitating TFE3 nuclear translocation through the AMPK-mTOR and AMPK-CARM1-TFE3 signaling pathways.

The Role of Oxidative Stress in Epigenetic Changes Underlying Autoimmunity

Significance: Epigenetic dysregulation plays an important role in the pathogenesis and development of autoimmune diseases. Oxidative stress is associated with autoimmunity and is also known to alter epigenetic mechanisms. Understanding the interplay between oxidative stress and epigenetics will provide insights into the role of environmental triggers in the development of autoimmunity in genetically susceptible individuals. Recent Advances: Abnormal DNA and histone methylation patterns in genes and pathways involved in interferon and tumor necrosis factor signaling, cellular survival, proliferation, metabolism, organ development, and autoantibody production have been described in autoimmunity. Inhibitors of DNA and histone methyltransferases showed potential therapeutic effects in animal models of autoimmune diseases. Oxidative stress can regulate epigenetic mechanisms via effects on DNA damage repair mechanisms, cellular metabolism and the local redox environment, and redox-sensitive transcription factors and pathways. Critical Issues: Studies looking into oxidative stress and epigenetics in autoimmunity are relatively limited. The number of available longitudinal studies to explore the role of DNA methylation in the development of autoimmune diseases is small. Future Directions: Exploring the relationship between oxidative stress and epigenetics in autoimmunity will provide clues for potential preventative measures and treatment strategies. Inception cohorts with longitudinal follow-up would help to evaluate epigenetic marks as potential biomarkers for disease development, progression, and treatment response in autoimmunity. Antioxid. Redox Signal. 36, 423-440.

Protein arginine N-methyltransferase 1 gene polymorphism is associated with proliferative diabetic retinopathy in a Japanese population

AIMS

To investigate the effects of single-nucleotide polymorphisms (SNPs) around the protein arginine N-methyltransferase 1 (PRMT1) gene on the incidence and severity of diabetic retinopathy (DR).

METHODS

A total of 310 Japanese patients with type 2 diabetes mellitus (T2DM) were investigated. Genotyping of ten tagged SNPs were performed by quantitative real-time polymerase chain reaction (qRT-PCR). The association between each SNP genotype and diabetic microangiopathy was assessed using univariate analysis in a dominant model of the minor alleles followed by multivariate logistic regression analysis with the propensity score matching (PSM) method. The effect of disease-related SNP on PRMT1 and hypoxia-inducible factor-1α (HIF-1α) mRNA levels in vivo was evaluated by qRT-PCR.

RESULTS

In the univariate analysis, the minor A allele at rs374569 and the minor C allele at rs3745468 were associated with DR severity (P = 0.047 and P = 0.003, respectively), but not diabetic nephropathy and peripheral polyneuropathy severity. Multivariate analysis showed that the rs3745468 variant caused an increased incidence of proliferative DR (PDR) (odds ratio 9.37, 95% confidence interval 1.12-78.0, P = 0.039). In the PSM cohort, the patients carrying the rs3745468 variant had lower PRMT1 mRNA levels compared to those without the variant (P = 0.037), and there was an inverse correlation between PRMT1 and HIF-1α mRNA levels (r = -0.233, P = 0.035).

CONCLUSIONS

The rs3745468 variant in the PRMT1 gene was associated with an increased incidence of PDR in Japanese patients with T2DM and might be involved in the HIF-1-dependent hypoxic pathway through altered PRMT1 levels.

Inhibition of PRMT6 reduces neomycin-induced inner ear hair cell injury through the restraint of FoxG1 arginine methylation

OBJECTIVE

Hair cells in the inner ear have been demonstrated to be sensitive to the ototoxicity from some beneficial pharmaceutical drugs. This study aimed to explore the role of protein arginine methyltransferase 6 (PRMT6) in the process of neomycin-induced hearing loss and the underlying mechanism.

METHODS

The neomycin-induced hearing loss mouse model and hair cell injury in vitro model were established. We took advantage of the HEI-OC1 cell line to evaluate PRMT6 expression in neomycin-induced hair cells, and the effect of PRMT6 on mitochondrial function and FoxG1 arginine methylation. Apoptotic cells were assessed and apoptotic marker cleaved caspase-3 level was detected. Reactive oxygen species (ROS) level and mitochondrial membrane potential (MMP) were subsequently measured.

RESULT

The result showed that PRMT6 was significantly upregulated in neomycin-induced HEI-OC-1 cells, and PRMT6 silencing prevented MMP loss, reduced ROS production, as well as decreased cell apoptosis under neomycin treatment. Further results showed that FoxG1 was downregulated in neomycin-induced HEI-OC-1 cells, and PRMT6 promoted the FoxG1-mediated luciferase activity, while PRMT6 silencing reversed this effect. Mechanistic experiments revealed that PRMT6 silencing reduced the arginine methylation level of FoxG1 protein. In vivo, neomycin-induced upregulation of hearing thresholds and increased cell apoptosis, whereas PRMT6 inhibitor partly reversed these effects.

CONCLUSION

Our findings suggested that inhibition of PRMT6 reduced neomycin-induced inner ear hair cell injury through the restraint of FoxG1 arginine methylation.

Alterations of Asymmetric Dimethylarginine (ADMA)-Containing Protein Profiles Associated with Chronic Pancreatitis Pathogenesis

Objective

The pathophysiological mechanisms of chronic pancreatitis (CP) still remain poorly understood. In this study, we aimed to characterize asymmetric dimethylarginine (ADMA)-containing proteins in pancreatic tissues and its relationship with CP pathogenesis.

Methods

Totally 36 patients with CP were enrolled in this study. Seven other cholangiocarcinoma patients without pancreas involvements or patients with benign pancreatic tumors were included as the control group. Total proteins in human pancreatic tissues were digested by trypsin, and ADMA-containing peptides were enriched via immunoaffinity purification. The LC-MS/MS was performed to characterize ADMA-containing peptides and their modification sites in CP tissues. Relative asymmetric arginine dimethylation levels of HNRNPA3 proteins in human pancreatic tissues were detected by the immunoprecipitation combined with Western blot. The serum inflammatory factors were determined via the ELISA method.

Results

A total of 134 ADMA sites in the control group and 137 ADMA sites in CP tissues were characterized by mass spectrometry, which belong to 93 and 94 ADMA-containing proteins in the control group and CP tissues, respectively. Glycine and proline residues were significantly overrepresented in the flanking sequences of ADMA sites. ADMA-containing proteins in the CP tissues were associated with various biological processes, especially the RNA metabolism and splicing pathways. Multiple protein members of the spliceosome pathway such as HNRNPA3 possess ADMA sites in the CP tissues. HNRNPA3 dimethylation levels were greatly increased in CP tissues, which were positively correlated with inflammatory factors.

Conclusion

The pathogenesis of CP is associated with alterations of asymmetric arginine dimethylation in pancreatic tissues.

PRMT1 promotes extracellular matrix degradation and apoptosis of chondrocytes in temporomandibular joint osteoarthritis via the AKT/FOXO1 signaling pathway

Temporomandibular joint osteoarthritis (TMJOA) is a chronic degenerative joint disease characterized by extracellular matrix (ECM) degradation and chondrocyte apoptosis. The aim of this study was to investigate the role of PRMT1 in TMJOA pathogenesis and its underlying molecular mechanism. Compared to the control group, PRMT1 was highly expressed in IL-1β-treated chondrocytes and articular cartilage following MIA injection into rat TMJs. Furthermore, knocking down PRMT1 considerably inhibited ECM degradation and apoptosis induced by IL-1β. Mechanistic analyses further revealed that PRMT1 knockdown activated the PI3K/AKT signaling pathway and prevented FOXO1 from translocating to the nucleus. Moreover, an inhibitor of AKT (LY294002) rescued the effect of PRMT1 knockdown on IL-1β-induced ECM degradation and apoptosis, and AMI-1, a selective inhibitor of PRMT1, inhibited PRMT1 expression and reversed the pathological progress of TMJOA. Thus, our findings suggest that PRMT1 plays an essential role in ECM degradation and chondrocyte apoptosis in TMJOA via the AKT/FOXO1 signaling pathway.

Zebrafish prmt2 Attenuates Antiviral Innate Immunity by Targeting traf6

TNFR-associated factor 6 (TRAF6) not only recruits TBK1/IKKε to MAVS upon virus infection but also catalyzes K63-linked polyubiquitination on substrate or itself, which is critical for NEMO-dependent and -independent TBK1/IKKε activation, leading to the production of type I IFNs. The regulation at the TRAF6 level could affect the activation of antiviral innate immunity. In this study, we demonstrate that zebrafish prmt2, a type I arginine methyltransferase, attenuates traf6-mediated antiviral response. Prmt2 binds to the C terminus of traf6 to catalyze arginine asymmetric dimethylation of traf6 at arginine 100, preventing its K63-linked autoubiquitination, which results in the suppression of traf6 activation. In addition, it seems that the N terminus of prmt2 competes with mavs for traf6 binding and prevents the recruitment of tbk1/ikkε to mavs. By zebrafish model, we show that loss of prmt2 promotes the survival ratio of zebrafish larvae after challenge with spring viremia of carp virus. Therefore, we reveal, to our knowledge, a novel function of prmt2 in the negative regulation of antiviral innate immunity by targeting traf6.

Cellular pathways influenced by protein arginine methylation: Implications for cancer

Arginine methylation is an influential post-translational modification occurring on histones, RNA binding proteins, and many other cellular proteins, affecting their function by altering their protein-protein and protein-nucleic acid interactions. Recently, a wealth of information has been gathered, implicating protein arginine methyltransferases (PRMTs), enzymes that deposit arginine methylation, in transcription, pre-mRNA splicing, DNA damage signaling, and immune signaling with major implications for cancer therapy, especially immunotherapy. This review summarizes this recent progress and the current state of PRMT inhibitors, some in clinical trials, as promising drug targets for cancer.

The Structure and Functions of PRMT5 in Human Diseases

Since the discovery of protein arginine methyltransferase 5 (PRMT5) and the resolution of its structure, an increasing number of papers have investigated and delineated the structural and functional role of PRMT5 in diseased conditions. PRMT5 is a type II arginine methyltransferase that catalyzes symmetric dimethylation marks on histones and non-histone proteins. From gene regulation to human development, PRMT5 is involved in many vital biological functions in humans. The role of PRMT5 in various cancers is particularly well-documented, and investigations into the development of better PRMT5 inhibitors to promote tumor regression are ongoing. Notably, emerging studies have demonstrated the pathological contribution of PRMT5 in the progression of inflammatory diseases, such as diabetes, cardiovascular diseases, and neurodegenerative disorders. However, more research in this direction is needed. Herein, we critically review the position of PRMT5 in current literature, including its structure, mechanism of action, regulation, physiological and pathological relevance, and therapeutic strategies.

Protein arginine methyltransferase 2 (PRMT2) promotes dextran sulfate sodium-induced colitis by inhibiting the SOCS3 promoter via histone H3R8 asymmetric dimethylation

BACKGROUND AND PURPOSE

There is emerging evidence for a critical role for epigenetic modifiers in the development of inflammatory bowel disease (IBD). Protein arginine methyltransferase 2 (PRMT2) is responsible for the methylation of arginine residues on histones and targets transcription factors involved in many cellular processes, including gene transcription, mRNA splicing, cell proliferation, and cell differentiation. In this study, the role and underlying mechanisms of PRMT2 in colitis were studied.

EXPERIMENTAL APPROACH

A mouse dextran sulfate sodium (DSS)-induced experimental colitis model was used to study PRMT2 in colitis. Lentivirus-induced PRMT2 silencing or overexpression in vivo was applied to address the role of PRMT2 in colitis. Detailed western blot and expression analysis were done to understand epigenetic changes induced by PRMT2 in colitis.

KEY RESULTS

PRMT2 is highly expressed in inflammatory bowel disease patients, in inflamed murine colon and in TNF-α stimulated murine gut epithelial cells. PRMT2 overexpression aggravates, while knockdown alleviates DSS-induced colitis, suggesting that PRMT2 is a pivotal mediator of colitis in mice. Mechanistically, PRMT2 mediates colitis by increasing repressive histone mark H3R8 asymmetric methylation (H3R8me2a) at the promoter region of the suppressor of cytokine signalling 3 promoter (SOCS3). Resultant inhibition of SOCS3 expression and inhibition of SOCS3-mediated degradation of TNF receptor associated factor 5 (TRAF5) via ubiquitination led to elevated TRAF5 expression and TRAF5-mediated downstream NF-κB/MAPK activation.

CONCLUSION AND IMPLICATIONS

Our study demonstrates that PRMT2 acts as a transcriptional co-activator for proinflammatory genes during colitis. Hence, targeting PRMT2 may provide a novel therapeutic approach for colitis.

Role of Protein Arginine Methyltransferases and Inflammation in Muscle Pathophysiology

Arginine methylation mediated by protein arginine methyltransferases (PRMTs) is a post-translational modification of both histone and non-histone substrates related to diverse biological processes. PRMTs appear to be critical regulators in skeletal muscle physiology, including regeneration, metabolic homeostasis, and plasticity. Chronic inflammation is commonly associated with the decline of skeletal muscle mass and strength related to aging or chronic diseases, defined as sarcopenia. In turn, declined skeletal muscle mass and strength can exacerbate chronic inflammation. Thus, understanding the molecular regulatory pathway underlying the crosstalk between skeletal muscle function and inflammation might be essential for the intervention of muscle pathophysiology. In this review, we will address the current knowledge on the role of PRMTs in skeletal muscle physiology and pathophysiology with a specific emphasis on its relationship with inflammation.

Functional Interplay between Methyltransferases and Inflammasomes in Inflammatory Responses and Diseases

An inflammasome is an intracellular protein complex that is activated in response to a pathogenic infection and cellular damage. It triggers inflammatory responses by promoting inflammatory cell death (called pyroptosis) and the secretion of pro-inflammatory cytokines, interleukin (IL)-1β and IL-18. Many types of inflammasomes have been identified and demonstrated to play a central role in inducing inflammatory responses, leading to the onset and progression of numerous inflammatory diseases. Methylation is a biological process by which methyl groups are transferred from methyl donors to proteins, nucleic acids, and other cellular molecules. Methylation plays critical roles in various biological functions by modulating gene expression, protein activity, protein localization, and molecular stability, and aberrant regulation of methylation causes deleterious outcomes in various human diseases. Methylation is a key determinant of inflammatory responses and diseases. This review highlights the current understanding of the functional relationship between inflammasome regulation and methylation of cellular molecules in inflammatory responses and diseases.

Protein arginine methylation: from enigmatic functions to therapeutic targeting

Protein arginine methyltransferases (PRMTs) are emerging as attractive therapeutic targets. PRMTs regulate transcription, splicing, RNA biology, the DNA damage response and cell metabolism; these fundamental processes are altered in many diseases. Mechanistically understanding how these enzymes fuel and sustain cancer cells, especially in specific metabolic contexts or in the presence of certain mutations, has provided the rationale for targeting them in oncology. Ongoing inhibitor development, facilitated by structural biology, has generated tool compounds for the majority of PRMTs and enabled clinical programmes for the most advanced oncology targets, PRMT1 and PRMT5. In-depth mechanistic investigations using genetic and chemical tools continue to delineate the roles of PRMTs in regulating immune cells and cancer cells, and cardiovascular and neuronal function, and determine which pathways involving PRMTs could be synergistically targeted in combination therapies for cancer. This research is enhancing our knowledge of the complex functions of arginine methylation, will guide future clinical development and could identify new clinical indications.

PRMT5 inhibition modulates murine dendritic cells activation by inhibiting the metabolism switch: a new therapeutic target in periodontitis

Background

Protein arginine methyltransferase 5 (PRMT5) catalyzes the methylation of arginine residues in multiple proteins. Recent reports have highlighted the anti-inflammatory role of PRMT5. Dendritic cells (DCs) are well-known professional antigen-presenting cells that are crucial for immune response initiation. However, whether PRMT5 participates in DC immunity processes is unknown.

Methods

In an in vitro experiment, a PRMT5 inhibitor (EPZ015666) was used to inhibit PRMT5 expression, and lipopolysaccharide (LPS) stimulation was applied to mimic the inflammation context. Proinflammatory cytokine production, interferon-stimulated genes (ISGs), costimulatory molecules, major histocompatibility complex (MHC) expression and DC metabolism were measured following PRMT5 inhibition and LPS stimulation. In an in vivo study, we first tested PRMT5 mRNA and protein expression in a BALB/c mouse ligature-induced periodontitis model. Then, we evaluated changes in periodontal tissue and DC migration to cervical lymph nodes after local treatment with the PRMT5 inhibitor.

Results

The in vitro results revealed that PRMT5 inhibition attenuated DC activation and maturation by inhibiting the expression of proinflammatory cytokines, ISGs, costimulatory molecules, and MHC induced by LPS stimulation. We also found that inhibition of PRMT5 blocked the DC metabolic switch to glycolysis. In the in vivo study, we found that PRMT5 inhibition reversed the severity of the lesions and slowed the migration of DCs to cervical lymph nodes.

Conclusions

The results show a critical role of PRMT5 in the control of DC activation through inhibition of the metabolic switch and indicate that PRMT5 is a promising therapeutic target in periodontitis.

DNA or Protein Methylation-Dependent Regulation of Activator Protein-1 Function

Epigenetic regulation and modification govern the transcriptional mechanisms that promote disease initiation and progression, but can also control the oncogenic processes, cell signaling networks, immunogenicity, and immune cells involved in anti-inflammatory and anti-tumor responses. The study of epigenetic mechanisms could have important implications for the development of potential anti-inflammatory treatments and anti-cancer immunotherapies. In this review, we have described the key role of epigenetic progression: DNA methylation, histone methylation or modification, and protein methylation, with an emphasis on the activator protein-1 (AP-1) signaling pathway. Transcription factor AP-1 regulates multiple genes and is involved in diverse cellular processes, including survival, differentiation, apoptosis, and development. Here, the AP-1 regulatory mechanism by DNA, histone, or protein methylation was also reviewed. Various methyltransferases activate or suppress AP-1 activities in diverse ways. We summarize the current studies on epigenetic alterations, which regulate AP-1 signaling during inflammation, cancer, and autoimmune diseases, and discuss the epigenetic mechanisms involved in the regulation of AP-1 signaling.

Palmitic acid methyl ester inhibits cardiac arrest-induced neuroinflammation and mitochondrial dysfunction

We previously discovered that palmitic acid methyl ester (PAME) is a potent vasodilator released from the sympathetic ganglion with vasoactive properties. Post-treatment with PAME can enhance cortical cerebral blood flow and functional learning and memory, while inhibiting neuronal cell death in the CA1 region of the hippocampus under pathological conditions (i.e. cerebral ischemia). Since mechanisms underlying PAME-mediated neuroprotection remain unclear, we investigated the possible neuroprotective mechanisms of PAME after 6 min of asphyxial cardiac arrest (ACA, an animal model of global cerebral ischemia). Our results from capillary-based immunoassay (for the detection of proteins) and cytokine array suggest that PAME (0.02 mg/kg) can decrease neuroinflammatory markers, such as ionized calcium binding adaptor molecule 1 (Iba1, a specific marker for microglia/macrophage activation) and inflammatory cytokines after cardiopulmonary resuscitation. Additionally, the mitochondrial oxygen consumption rate (OCR) and respiratory function in the hippocampal slices were restored following ACA (via Seahorse XF24 Extracellular Flux Analyzer) suggesting that PAME can ameliorate mitochondrial dysfunction. Finally, hippocampal protein arginine methyltransferase 1 (PRMT1) and PRMT8 are enhanced in the presence of PAME to suggest a possible pathway of methylated fatty acids to modulate arginine-based enzymatic methylation. Altogether, our findings suggest that PAME can provide neuroprotection in the presence of ACA to alleviate neuroinflammation and ameliorate mitochondrial dysfunction.

The Landscape of AhR Regulators and Coregulators to Fine-Tune AhR Functions

The aryl-hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates numerous cellular responses. Originally investigated in toxicology because of its ability to bind environmental contaminants, AhR has attracted enormous attention in the field of immunology in the last 20 years. In addition, the discovery of endogenous and plant-derived ligands points to AhR also having a crucial role in normal cell physiology. Thus, AhR is emerging as a promiscuous receptor that can mediate either toxic or physiologic effects upon sensing multiple exogenous and endogenous molecules. Within this scenario, several factors appear to contribute to the outcome of gene transcriptional regulation by AhR, including the nature of the ligand as such and its further metabolism by AhR-induced enzymes, the local tissue microenvironment, and the presence of coregulators or specific transcription factors in the cell. Here, we review the current knowledge on the array of transcription factors and coregulators that, by interacting with AhR, tune its transcriptional activity in response to endogenous and exogenous ligands.

Arginine Methylation in Brain Tumors: Tumor Biology and Therapeutic Strategies

Protein arginine methylation is a common post-translational modification that plays a pivotal role in cellular regulation. Protein arginine methyltransferases (PRMTs) catalyze the modification of target proteins by adding methyl groups to the guanidino nitrogen atoms of arginine residues. Protein arginine methylation takes part in epigenetic and cellular regulation and has been linked to neurodegenerative diseases, metabolic diseases, and tumor progression. Aberrant expression of PRMTs is associated with the development of brain tumors such as glioblastoma and medulloblastoma. Identifying PRMTs as plausible contributors to tumorigenesis has led to preclinical and clinical investigations of PRMT inhibitors for glioblastoma and medulloblastoma therapy. In this review, we discuss the role of arginine methylation in cancer biology and provide an update on the use of small molecule inhibitors of PRMTs to treat glioblastoma, medulloblastoma, and other cancers.

PRMT5 Prevents Cardiomyocyte Hypertrophy via Symmetric Dimethylating HoxA9 and Repressing HoxA9 Expression

The present study reveals a link between protein arginine methyltransferase 5 (PRMT5) and Homebox A9 (HoxA9) in the regulation of cardiomyocyte hypertrophy. In cardiomyocyte hypertrophy induced by β-adrenergic receptor agonist isoprenaline (ISO), PRMT5 expression was decreased while HoxA9 was upregulated. Silencing of PRMT5 or inhibition of PRMT5 by its pharmacological inhibitor EPZ augmented the expressions of cardiomyocyte hypertrophic genes brain natriuretic peptide (BNP) and β-Myosin Heavy Chain (β-MHC), whereas overexpression of PRMT5 inhibited ISO-induced cardiomyocyte hypertrophy, suggesting that PRMT5 ameliorates cardiomyocyte hypertrophy. On the contrary, HoxA9 promoted cardiomyocyte hypertrophy, as implied by the gain-of-function and loss-of-function experiments. HoxA9 was involved in the regulation of PRMT5 in cardiomyocyte hypertrophy, since HoxA9 knockdown prevented si-RPMT5-induced cardiomyocyte hypertrophy, and HoxA9 expression impaired the anti-hypertrophic effect of PRMT5. Co-immunoprecipitation experiments revealed that there were physical interactions between PRMT5 and HoxA9. The symmetric dimethylation level of HoxA9 was decreased by ISO or EPZ treatment, suggesting that HoxA9 is methylated by PRMT5. Additionally, PRMT5 repressed the expression of HoxA9. Chromatin immunoprecipitation (ChIP) assay demonstrated that HoxA9 could bind to the promoter of BNP, and that this binding affinity was further enhanced by ISO or EPZ. In conclusion, this study suggests that PRMT5 symmetric dimethylates HoxA9 and represses HoxA9 expression, thus impairing its binding to BNP promoter and ultimately protecting against cardiomyocyte hypertrophy. These findings provide a novel insight of the mechanism underlying the cardiac protective effect of PRMT5, and suggest potential therapeutic strategies of PRMT5 activation or HoxA9 inhibition in treatment of cardiac hypertrophy.

Inhibition of osteoblast proliferation and migration by exogenous and endogenous formaldehyde

Exogenous and endogenous formaldehyde (FA) both play an important role in cell growth and migration; however, their potential role in osteoblasts remains largely unclear. Cell counting kit-8 (CCK-8) and wound-healing assays revealed that FA exposure at naturally occurring concentrations inhibited the proliferation and migration of mouse preosteoblast MC3T3-E1 cells. Moreover, RNA sequencing (RNA-seq) analysis revealed that FoxO1 signaling pathway components displayed distinct expression patterns upon FA exposure, reflected through significant enrichment of cell migration. In particular, FoxO1-, Sirt1-, and FA-induced protein expression, which was closely associated with cell proliferation and migration, was confirmed by western blotting. The results obtained indicated that the FoxO1 pathway is involved in FA-induced inhibition of cell growth and migration.

Perinatal inflammation alters histone 3 and histone 4 methylation patterns: Effects of MiR-29b supplementation

Preterm birth is still a major health problem and maternal inflammation has been shown to play a role. The combination of maternal inflammation and neonatal hyperoxia contributes to epigenetic changes that influence gene expression and the development of bronchopulmonary dysplasia (BPD). We have previously demonstrated suppression of miR-29b and increases in DNA methylation in infants with severe BPD and in our mouse model of maternal inflammation and neonatal hyperoxia exposure. The present studies further explored epigenetic changes in the murine model to include histone methylation. We identified a global suppression of histone methylation in exposed mice and validated decreases in expression in well-defined histone modifications, specifically H3K4me3, H3K27me3, H3K36me2, H3K79me2, and H4K20me3. We further tested the hypothesis that restoration of miR-29b expression would restore the histone methylation marks. Using lipid nanoparticle delivery of miR-29b, partial to full methylation was reestablished for H3K4me3, H3K27me3, and H4K20me3; all tri-methylation marks. To identify the causes of decreased methylation in exposed mice, we measured commonly identified methylases and demethylases. We found a decreased expression of SUV40H2, a methylase primarily associated with H4K20me3. Further studies are needed to identify the causes for the decreased global histone methylation and potential therapeutic opportunities.

SARS-CoV-2 multifaceted interaction with the human host. Part II: Innate immunity response, immunopathology, and epigenetics

The SARS-CoV-2 makes its way into the cell via the ACE2 receptor and the proteolytic action of TMPRSS2. In response to the SARS-CoV-2 infection, the innate immune response is the first line of defense, triggering multiple signaling pathways to produce interferons, pro-inflammatory cytokines and chemokines, and initiating the adaptive immune response against the virus. Unsurprisingly, the virus has developed strategies to evade detection, which can result in delayed, excessive activation of the innate immune system. The response elicited by the host depends on multiple factors, including health status, age, and sex. An overactive innate immune response can lead to a cytokine storm, inflammation, and vascular disruption, leading to the vast array of symptoms exhibited by COVID-19 patients. What is known about the expression and epigenetic regulation of the ACE2 gene and the various players in the host response are explored in this review.

Transcriptional regulation by methyltransferases and their role in the heart: highlighting novel emerging functionality

Methyltransferases are a superfamily of enzymes that transfer methyl groups to proteins, nucleic acids, and small molecules. Traditionally, these enzymes have been shown to carry out a specific modification (mono-, di-, or trimethylation) on a single, or limited number of, amino acid(s). The largest subgroup of this family, protein methyltransferases, target arginine and lysine side chains of histone molecules to regulate gene expression. Although there is a large number of functional studies that have been performed on individual methyltransferases describing their methylation targets and effects on biological processes, no analyses exist describing the spatial distribution across tissues or their differential expression in the diseased heart. For this review, we performed tissue profiling in protein databases of 199 confirmed or putative methyltransferases to demonstrate the unique tissue-specific expression of these individual proteins. In addition, we examined transcript data sets from human heart failure patients and murine models of heart disease to identify 40 methyltransferases in humans and 15 in mice, which are differentially regulated in the heart, although many have never been functionally interrogated. Lastly, we focused our analysis on the largest subgroup, that of protein methyltransferases, and present a newly emerging phenomenon in which 16 of these enzymes have been shown to play dual roles in regulating transcription by maintaining the ability to both activate and repress transcription through methyltransferase-dependent or -independent mechanisms. Overall, this review highlights a novel paradigm shift in our understanding of the function of histone methyltransferases and correlates their expression in heart disease.

Zebrafish prmt3 negatively regulates antiviral responses

Arginine methylation catalyzed by protein arginine methyltransferases (PRMT) is a common post-translational modification in histone and nonhistone proteins, which regulates many cellular functions. Protein arginine methyltransferase 3 (prmt3), a type I arginine methyltransferase, has been shown to carry out the formation of stable monomethylarginine as an intermediate before the establishment of asymmetric dimethylarginine. To date, however, the role of PRMT3 in antiviral innate immunity has not been elucidated. This study showed that zebrafish prmt3 was upregulated by virus infection and that the overexpression of prmt3 suppressed cellular antiviral response. The PRMT3 inhibitor, SGC707, enhanced antiviral capability. Consistently, prmt3-null zebrafish were more resistant to Spring Viremia of Carp Virus (SVCV) and Grass Carp Reovirus (GCRV) infection. Further assays showed that the overexpression of prmt3 diminished the phosphorylation of irf3 and prmt3 interacted with rig-i. In addition, both zinc-finger domain and catalytic domain of prmt3 were required for the suppressive function of prmt3 on IFN activation. Our findings suggested that zebrafish prmt3 negatively regulated the antiviral responses, implicating the vital role of prmt3-or even arginine methylation-in antiviral innate immunity.