Loss of ubiquitin-conjugating enzyme E2 (Ubc9) in macrophages exacerbates multiple low-dose streptozotocin-induced diabetes by attenuating M2 macrophage polarization

PDIA3 orchestrates effector T cell program by serving as a chaperone to facilitate the non-canonical nuclear import of STAT1 and PKM2

Dysregulated T cell activation underpins the immunopathology of rheumatoid arthritis (RA), yet the machineries that orchestrate T cell effector program remain incompletely understood. Herein, we leveraged bulk and single-cell RNA sequencing data from RA patients and validated protein disulfide isomerase family A member 3 (PDIA3) as a potential therapeutic target. PDIA3 is remarkably upregulated in pathogenic CD4 T cells derived from RA patients and positively correlates with C-reactive protein level and disease activity score 28. Pharmacological inhibition or genetic ablation of PDIA3 alleviates RA-associated articular pathology and autoimmune responses. Mechanistically, T cell receptor signaling triggers intracellular calcium flux to activate NFAT1, a process that is further potentiated by Wnt5a under RA settings. Activated NFAT1 then directly binds to the Pdia3 promoter to enhance the expression of PDIA3, which complexes with STAT1 or PKM2 to facilitate their nuclear import for transcribing T helper 1 (Th1) and Th17 lineage-related genes, respectively. This non-canonical regulatory mechanism likely occurs under pathological conditions, as PDIA3 could only be highly induced following aberrant external stimuli. Together, our data support that targeting PDIA3 is a vital strategy to mitigate autoimmune diseases, such as RA, in clinical settings.

Ubiquitin-conjugating enzyme E2 for regulating autophagy in diabetic cardiomyopathy: A mini-review

The prevalence of diabetic cardiomyopathy (DCM) increases year by year with the increase in the prevalence of diabetes mellitus (DM), which is one of the most serious cardiovascular complications of DM and a major cause of death in diabetic patients. Although the pathological molecular features of DCM have not been fully elucidated, increasing evidence suggests that impaired autophagy in cardiomyocytes plays a nonnegligible role in the development of DCM. It has been shown that SUMOylation [SUMO = small ubiquitin-like modifier], a post-translational modification of proteins, and its associated ubiquitin-proteasome system mediates protein quality control in the heart and plays an important role in the proteotoxic environment of the heart. Specifically, the expression of ubiquitin-conjugating enzyme E2 (Ubc9), the only SUMO-E2 enzyme, exerts a positive regulatory effect on autophagy in cardiomyocytes with potential cardioprotective effects. This review focuses on the role that autophagy plays in DCM and the potential for Ubc9-regulated autophagy pathways to ameliorate DCM, highlighting the potential of Ubc9 as an interventional target in DCM and providing new insights into the pathogenesis of the disease.

Effect of macrophage polarization on parasitic protection against type 1 diabetes mellitus

Type 1 diabetes mellitus is a chronic disease caused by the destruction of pancreatic beta cells. Based on the hygiene hypothesis, a growing body of evidence suggests a negative association between parasitic infections and diabetes in humans and animal models. The mechanism of parasite-mediated prevention of type 1 diabetes mellitus may be related to the adaptive and innate immune systems. Macrophage polarization is a new paradigm for the treatment of type 1 diabetes mellitus, and different host macrophage subsets play various roles during parasite infection. Proinflammatory cytokines are released by M1 macrophages, which are important in the development of type 1 diabetes mellitus. Parasite-activated M2 macrophages prevent the development of type 1 diabetes mellitus and can influence the development of adaptive immune responses through several mechanisms, including Th2 cells and regulatory T cells. Here, we review the role and mechanism of macrophage polarization in parasitic protection against type 1 diabetes mellitus.

Ubc9 regulates the expression of MHC II in dendritic cells to enhance DSS-induced colitis by mediating RBPJ SUMOylation

SUMOylation is an evolutionary conserved regulatory mechanism, in which Ubc9 is the only E2 conjugating enzyme. Previous studies demonstrated that SUMOylation is involved in multiple biological processes, but its role in dendritic cells (DCs) remains to be fully addressed. Herein in this report, we found that DCs deficient in Ubc9 protected mice from dextran sulfate sodium (DSS)-induced colitis, as evidenced by the ameliorated weight loss, colon length, and disrupted colon structure. Mechanistically, Ubc9 mediated SUMOylation of RBPJ, by which it stabilized RBPJ from ubiquitin-mediated degradation to enhance its transcriptional activity, while Ciita, a critical transcription factor, is a direct target downstream of RBPJ, which forms an enhanceosome complex to transcribe the expression of MHC II genes. Therefore, loss of Ubc9 abolished RBPJ SUMOylation, which was coupled with reduced Ciita transcription, thereby attenuating the expression of MHC class II genes. As a consequence of defective MHC II expression, Ubc9-/- DCs were featured by the impaired capability to process antigen and to prime effector CD4+ T cells, thereby protecting mice from DSS-induced colitis. Together, our results shed novel insight into the understanding of SUMOylation in the regulation of DC functions in pathological conditions.

FSTL1 Suppresses Triple-Negative Breast Cancer Lung Metastasis by Inhibiting M2-like Tumor-Associated Macrophage Recruitment toward the Lungs

Immune cell infiltration into the tumor microenvironment is associated with cancer prognosis. Tumor-associated macrophages play essential roles in tumor initiation, progression, and metastasis. Follistatin-like protein 1 (FSTL1), a widely expressed glycoprotein in human and mouse tissues, is a tumor suppressor in various cancers and a regulator of macrophage polarization. However, the mechanism by which FSTL1 affects crosstalk between breast cancer cells and macrophages remains unclear. By analyzing public data, we found that FSTL1 expression was significantly low in breast cancer tissues compared to normal breast tissues, and high expression of FSTL1 in patients indicated prolonged survival. Using flow cytometry, we found that total and M2-like macrophages dramatically increased in the metastatic lung tissues during breast cancer lung metastasis in Fstl1^+/- mice. Transwell assay in vitro and q-PCR experimental results showed that FSTL1 inhibited macrophage migration toward 4T1 cells by decreasing CSF1, VEGF-α, and TGF-β secretion in 4T1 cells. We demonstrated that FSTL1 inhibited M2-like tumor-associated macrophage recruitment toward the lungs by suppressing CSF1, VEGF-α, and TGF-β secretion in 4T1 cells. Therefore, we identified a potential therapeutic strategy for triple-negative breast cancer.

MBD2 facilitates tumor metastasis by mitigating DDB2 expression

Despite past extensive studies, the pathoetiologies underlying tumor metastasis remain poorly understood, which renders its treatment largely unsuccessful. The methyl-CpG-binding domain 2 (MBD2), a "reader" to interpret DNA methylome-encoded information, has been noted to be involved in the development of certain types of tumors, while its exact impact on tumor metastasis remains elusive. Herein we demonstrated that patients with LUAD metastasis were highly correlated with enhanced MBD2 expression. Therefore, knockdown of MBD2 significantly attenuated the migration and invasion of LUAD cells (A549 and H1975 cell lines) coupled with attenuated epithelial-mesenchymal transition (EMT). Moreover, similar results were observed in other types of tumor cells (B16F10). Mechanistically, MBD2 selectively bound to the methylated CpG DNA within the DDB2 promoter, by which MBD2 repressed DDB2 expression to promote tumor metastasis. As a result, administration of MBD2 siRNA-loaded liposomes remarkably suppressed EMT along with attenuated tumor metastasis in the B16F10 tumor-bearing mice. Collectively, our study indicates that MBD2 could be a promising prognostic marker for tumor metastasis, while administration of MBD2 siRNA-loaded liposomes could be a viable therapeutic approach against tumor metastasis in clinical settings.

Adipose Tissue Macrophage-Mediated Inflammation in Obesity: A Link to Posttranslational Modification

Adipose tissue macrophages (ATM) are an essential type of immune cells in adipose tissue. Obesity induces the inflammation of adipose tissues, as expressed by ATM accumulation, that is more likely to become a source of systemic metabolic diseases, including insulin resistance. The process is characterized by the transcriptional regulation of inflammatory pathways by virtue of signaling molecules such as cytokines and free fatty acids. Notably, posttranslational modification (PTM) is a key link for these signaling molecules to trigger the proinflammatory or anti-inflammatory phenotype of ATMs. This review focuses on summarizing the functions and molecular mechanisms of ATMs regulating inflammation in obese adipose tissue. Furthermore, the role of PTM is elaborated, hoping to identify new horizons of treatment and prevention for obesity-mediated metabolic disease.

The indispensability of macrophage adaptor proteins in chronic inflammatory diseases

Adaptor proteins represent key signalling molecules involved in regulating immune responses. The host's innate immune system recognizes pathogens via various surface and intracellular receptors. Adaptor molecules are centrally involved in different receptor-mediated signalling pathways, acting as bridges between the receptors and other molecules. The presence of adaptors in major signalling pathways involved in the pathogenesis of various chronic inflammatory diseases has drawn attention toward the role of these proteins in such diseases. In this review, we summarize the importance and roles of different adaptor molecules in macrophage-mediated signalling in various chronic disease states. We highlight the mechanistic roles of adaptors and how they are involved in protein-protein interactions (PPI) via different domains to carry out signalling. Hence, we also provide insights into how targeting these adaptor proteins can be a good therapeutic strategy against various chronic inflammatory diseases.

Exosomal USP13 derived from microvascular endothelial cells regulates immune microenvironment and improves functional recovery after spinal cord injury by stabilizing IκBα

Spinal cord injury (SCI) can result in irreversible sensory and motor disability with no effective treatment currently. After SCI, infiltrated macrophages accumulate in epicenter through destructed blood-spinal cord barrier (BSCB). Further, great majority of macrophages are preferentially polarized to M1 phenotype, with only a few transient M2 phenotype. The purpose of this study was to explore roles of vascular endothelial cells in microglia/macrophages polarization and the underlying mechanism. Lipopolysaccharide (LPS) was used to pretreat BV2 microglia and RAW264.7 macrophages followed by administration of conditioned medium from microvascular endothelial cell line bEnd.3 cells (ECM). Analyses were then performed to determine the effects of exosomes on microglia/macrophages polarization and mitochondrial function. The findings demonstrated that administration of ECM shifted microglia/macrophages towards M2 polarization, ameliorated mitochondrial impairment, and reduced reactive oxygen species (ROS) production in vitro. Notably, administration of GW4869, an exosomal secretion inhibitor, significantly reversed these observed benefits. Further results revealed that exosomes derived from bEnd.3 cells (Exos) promote motor rehabilitation and M2 polarization of microglia/macrophages in vivo. Ubiquitin-specific protease 13 (USP13) was shown to be significantly enriched in BV2 microglia treated with Exos. USP13 binds to, deubiquitinates and stabilizes the NF-κB inhibitor alpha (IκBα), thus regulating microglia/macrophages polarization. Administration of the selective IκBα inhibitor betulinic acid (BA) inhibited the beneficial effect of Exos in vivo. These findings uncovered the potential mechanism underlying the communications between vascular endothelial cells and microglia/macrophages after SCI. In addition, this study indicates exosomes might be a promising therapeutic strategy for SCI treatment.

Recent Developments in Islet Biology: A Review With Patient Perspectives

Navigating the coronavirus disease-2019 (COVID-19, now COVID) pandemic has required resilience and creativity worldwide. Despite early challenges to productivity, more than 2,000 peer-reviewed articles on islet biology were published in 2021. Herein, we highlight noteworthy advances in islet research between January 2021 and April 2022, focussing on 5 areas. First, we discuss new insights into the role of glucokinase, mitogen-activated protein kinase-kinase/extracellular signal-regulated kinase and mitochondrial function on insulin secretion from the pancreatic β cell, provided by new genetically modified mouse models and live imaging. We then discuss a new connection between lipid handling and improved insulin secretion in the context of glucotoxicity, focussing on fatty acid-binding protein 4 and fetuin-A. Advances in high-throughput "omic" analysis evolved to where one can generate more finely tuned genetic and molecular profiles within broad classifications of type 1 diabetes and type 2 diabetes. Next, we highlight breakthroughs in diabetes treatment using stem cell-derived β cells and innovative strategies to improve islet survival posttransplantation. Last, we update our understanding of the impact of severe acute respiratory syndrome-coronavirus-2 infection on pancreatic islet function and discuss current evidence regarding proposed links between COVID and new-onset diabetes. We address these breakthroughs in 2 settings: one for a scientific audience and the other for the public, particularly those living with or affected by diabetes. Bridging biomedical research in diabetes to the community living with or affected by diabetes, our partners living with type 1 diabetes or type 2 diabetes also provide their perspectives on these latest advances in islet biology.

Dietary selenomethionine attenuates obesity by enhancing beiging process in white adipose tissue

Imbalanced nutrient intake causes abnormal energy metabolism, which results in obesity. There is feasible evidence that selenium-rich (Se-rich) foods may alleviate obesity and enhance general public health, but the underlying mechanisms remain elusive. Herein we examined the effect of Se supplementation on white adipose tissue beiging process. The mice were fed with a normal diet or a Se-deficient high-fat diet (DHFD) until significant differences in terms of body weight, glucose tolerance and insulin sensitivity. Next, mice in the DHFD group were changed to a high-fat diet (HFD) containing specified amounts of selenomethionine (SeMet) (0, 150, 300, and 600 μg/kg) and continued to feed for 14 weeks. Notably, 150 μg/kg SeMet supplement highly protected mice from DHFD-induced obesity, insulin resistance, and lipid deposits in the liver and kidney, and featured by the enhanced beiging process in white adipose tissue and increased energy expenditure. Moreover, upon cold challenge, 150 μg/kg SeMet supplement enhanced cold tolerance in mice by inducing adipose beiging to promote energy expenditure, as evidenced by the increased expression of uncoupling protein-1 (UCP1) in adipocytes. Similarly, SeMet (10 μM) promoted the differentiation of beige adipocytes from the stromal vascular fraction. Collectively, our data support that optimal supplementation of SeMet could enhance the beiging process to attenuate HFD-induced obesity, which provides new insights into the relationship between dietary SeMet and type 2 diabetes.

UBC9 deficiency enhances immunostimulatory macrophage activation and subsequent antitumor T cell response in prostate cancer

The role of tumor-associated macrophages (TAMs), along with the regulatory mechanisms underlying distinct macrophage activation states, remains poorly understood in prostate cancer (PCa). Herein, we report that PCa growth in mice with macrophage-specific Ubc9 deficiency is substantially suppressed compared with that in wild-type littermates, an effect partially ascribed to the augmented CD8+ T cell response. Biochemical and molecular analyses revealed that signal transducer and activator of transcription 4 (STAT4) is a crucial UBC9-mediated SUMOylation target, with lysine residue 350 (K350) as the major modification site. Site-directed mutation of STAT4 (K350R) enhanced its nuclear translocation and stability, thereby facilitating the proinflammatory activation of macrophages. Importantly, administration of the UBC9 inhibitor 2-D08 promoted the antitumor effect of TAMs and increased the expression of PD-1 on CD8+ T cells, supporting a synergistic antitumor efficacy once it combined with the immune checkpoint blockade therapy. Together, our results demonstrate that ablation of UBC9 could reverse the immunosuppressive phenotype of TAMs by promoting STAT4-mediated macrophage activation and macrophage-CD8+ T cell crosstalk, which provides valuable insights to halt the pathogenic process of tumorigenesis.

SUMOylation of ERp44 enhances Ero1α ER retention contributing to the pathogenesis of obesity and insulin resistance

OBJECTIVE

As the only E2 conjugating enzyme for the SUMO system, Ubc9-mediated SUMOylation has been recognized to regulate diverse biological processes, but its impact on adipocytes relevant to obesity and insulin resistance is yet to be elucidated.

METHODS

We established adipocyte-specific Ubc9 deficient mice to explore the effects of Ubc9 on obesity and metabolic disorders induced by high-fat diet (HFD) in adult mice. The molecular targets of SUMOylation were explored by liquid chromatography-mass spectrometry, and the regulatory mechanism of SUMOylation in T2D was analyzed.

RESULTS

Adipocyte-specific depletion of Ubc9 (AdipoQ-Cre-Ubc9^fl/fl, Ubc9^AKO) protected mice from HFD-induced obesity, insulin resistance, and hepatosteatosis. The Ubc9^AKO mice were featured by the reduced HFD-induced endoplasmic reticulum (ER) stress and inflammatory response. Mechanically, over nutrition rendered adipocytes to undergo a SUMOylation turnover characterized by the change of SUMOylation levels and substrates. ERp44 displayed the highest change in terms of SUMOylation levels of substrates involved in ER-related functions. The lack of ERp44 SUMOylation at lysine 76 (K76) located within the thioredoxin (TRX)-like domain by Ubc9 deficiency enhanced its degradation and suppressed its covalent binding to Ero1α, an oxidase that exists in the ER but lacks ER retention motif, thereby alleviating endoplasmic reticulum stress by promoting Ero1α secretion.

CONCLUSIONS

Our data suggest that modulation of ERp44 SUMOylation in adipocytes could be a feasible strategy against obesity and insulin resistance in clinical settings.

Macrophage: Key player in the pathogenesis of autoimmune diseases

The macrophage is an essential part of the innate immune system and also serves as the bridge between innate immunity and adaptive immune response. As the initiator and executor of the adaptive immune response, macrophage plays an important role in various physiological processes such as immune tolerance, fibrosis, inflammatory response, angiogenesis and phagocytosis of apoptotic cells. Consequently, macrophage dysfunction is a vital cause of the occurrence and development of autoimmune diseases. In this review, we mainly discuss the functions of macrophages in autoimmune diseases, especially in systemic lupus erythematosus (SLE), rheumatic arthritis (RA), systemic sclerosis (SSc) and type 1 diabetes (T1D), providing references for the treatment and prevention of autoimmune diseases.

Phenolipid JE improves metabolic profile and inhibits gluconeogenesis via modulating AKT-mediated insulin signaling in STZ-induced diabetic mice

Phenolipids are characteristic phytochemicals of Syzygium genus. However, the antidiabetic potential and underlying molecular mechanism of these components are not fully elucidated. Herein, we studied the anti-diabetic effects of jambone E (JE), a phenolipid from S. cumini, with in vitro and in vivo models. Data from current study showed that JE enhanced glucose consumption and uptake, promoted glycogen synthesis, and suppressed gluconeogenesis in insulin resistant (IR)-HepG2 cells and primary mouse hepatocytes. JE also attenuated streptozotocin-induced hyperglycemia and hyperlipidemia in type 1 diabetic (T1D) mice. Eleven metabolites (e.g. trimethylamine n-oxide, 4-pyridoxic acid, phosphatidylinositol 39:4, phenaceturic acid, and hippuric acid) were identified as potential serum biomarkers for JE's antidiabetic effects by an untargeted metabolomics approach. The further molecular mechanistic study revealed that JE up-regulated phosphorylation levels of protein kinase B (AKT), glycogen synthase kinase 3 beta, and forkhead box O1 (FoxO1), promoted nuclear exclusion of FoxO1 whilst decreased gene expression levels of peroxisome proliferator-activated receptor gamma coactivator-1 alpha, phosphoenolpyruvate carboxykinase and glucose 6-phosphatase in IR-HepG2 cells and T1D mice. Our data suggested that JE might be a potent activator for AKT-mediated insulin signaling pathway, which was confirmed by the usage of AKT inhibitor and AKT-target siRNA interference, as well as the cellular thermal shift assay. Findings from the current study shed light on the anti-diabetic effects of phenolipids in the Syzygium species, which supports the use of medicinal plants in the Syzygium genus for potential pharmaceutical applications.

Posttranslational modifications in diabetes: Mechanisms and functions

As one of the most widespread chronic diseases, diabetes and its accompanying complications affect approximately one tenth of individuals worldwide and represent a growing cause of morbidity and mortality. Accumulating evidence has proven that the process of diabetes is complex and interactive, involving various cellular responses and signaling cascades by posttranslational modifications (PTMs). Therefore, understanding the mechanisms and functions of PTMs in regulatory networks has fundamental importance for understanding the prediction, onset, diagnosis, progression, and treatment of diabetes. In this review, we offer a holistic summary and illustration of the crosstalk between PTMs and diabetes, including both types 1 and 2. Meanwhile, we discuss the potential use of PTMs in diabetes treatment and provide a prospective direction for deeply understanding the metabolic diseases.

Changes of macrophage and CD4+ T cell in inflammatory response in type 1 diabetic mice

Immune cells play an important role in the development of inflammation in type 1 diabetes mellitus, so we want to explore the changes of CD4+ T cells and macrophages in vivo, which can provide an experimental basis for immunotherapy based on CD4+ T cells and macrophages. The intraperitoneal injection of streptozocin was used to induce a type 1 diabetes mellitus mouse model; the blood glucose, body weight, and the expression of inflammatory factors in the kidney were measured. Immunohistochemistry was applied to determine and analyze the infiltration of CD4+ T cells and macrophages in the spleen, pancreas, and kidney. The subtypes of macrophages in the kidney and CD4+ T cells in the spleen were analyzed by flow cytometry. Our study suggests that CD4+ T cells and macrophages increase, while the inflammatory immune response system is activated in the development of T1DM. CD4+ T cells positively correlated with macrophages in the pancreas and kidney of T1DM. CD4+ T cells turn to pro-inflammatory subtypes in the spleen of T1DM, while macrophages turn to pro-inflammatory subtypes in the kidney of T1DM. Therefore, regulation of CD4+ T cells and macrophages may be a potential target for T1DM and kidney complications.

The interferon regulatory factors, a double-edged sword, in the pathogenesis of type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease resulted from the unrestrained inflammatory attack towards the insulin-producing islet β cells. Although the exact etiology underlying T1D remains elusive, viral infections, especially those specific strains of enterovirus, are acknowledged as a critical environmental cue involved in the early phase of disease initiation. Viral infections could either directly impede β cell function, or elicit pathological autoinflammatory reactions for β cell killing. Autoimmune responses are bolstered by a massive body of virus-derived exogenous pathogen-associated molecular patterns (PAMPs) and the presence of β cell-derived damage-associated molecular patterns (DAMPs). In particular, the nucleic acid components and the downstream nucleic acid sensing pathways serve as the major effector mechanism. The endogenous retroviral RNA, mitochondrial DNA (mtDNA) and genomic fragments generated by stressed or dying β cells induce host responses reminiscent of viral infection, a phenomenon termed as viral mimicry during the early stage of T1D development. Given that the interferon regulatory factors (IRFs) are considered as hub transcription factors to modulate immune responses relevant to viral infection, we thus sought to summarize the critical role of IRFs in T1D pathogenesis. We discuss with focus for the impact of IRFs on the sensitivity of β cells to cytokine stimulation, the vulnerability of β cells to viral infection/mimicry, and the intensity of immune response. Together, targeting certain IRF members, alone or together with other therapeutics, could be a promising strategy against T1D.

NF-κB-inducing kinase (NIK) is activated in pancreatic β-cells but does not contribute to the development of diabetes

The transcription factor nuclear factor-κB (NF-κB) has a key role in the pathogenesis of diabetes and its complications. Although activation of the canonical NF-κB pathway in β-cells is generally deleterious, little is known about the role of the non-canonical NF-κB signalling and its main regulator, the NF-κB-inducing kinase (NIK), on pancreatic β-cell survival and function. Previous studies based on models of NIK overexpression in pancreatic islet cells showed that NIK induced either spontaneous β-cell death due to islet inflammation or glucose intolerance during diet-induced obesity (DIO) in mice. Therefore, NIK has been proposed as a potential target for diabetes therapy. However, no clear studies showed whether inhibition of NIK improves diabetes development. Here we show that genetic silencing of NIK in pancreatic β-cells neither modifies diabetes incidence nor inflammatory responses in a mouse model of immune-mediated diabetes. Moreover, NIK silencing in DIO mice did not influence body weight gain, nor glucose metabolism. In vitro studies corroborated the in vivo findings in terms of β-cell survival, function, and downstream gene regulation. Taken together, our data suggest that NIK activation is dispensable for the development of diabetes.

Role of Polyamines and Hypusine in β Cells and Diabetes Pathogenesis

The polyamines—putrescine, spermidine, and spermine—are polycationic, low molecular weight amines with cellular functions primarily related to mRNA translation and cell proliferation. Polyamines partly exert their effects via the hypusine pathway, wherein the polyamine spermidine provides the aminobutyl moiety to allow posttranslational modification of the translation factor eIF5A with the rare amino acid hypusine (hydroxy putrescine lysine). The “hypusinated” eIF5A (eIF5A^hyp) is considered to be the active form of the translation factor necessary for the translation of mRNAs associated with stress and inflammation. Recently, it has been demonstrated that activity of the polyamines-hypusine circuit in insulin-producing islet β cells contributes to diabetes pathogenesis under conditions of inflammation. Elevated levels of polyamines are reported in both exocrine and endocrine cells of the pancreas, which may contribute to endoplasmic reticulum stress, oxidative stress, inflammatory response, and autophagy. In this review, we have summarized the existing research on polyamine-hypusine metabolism in the context of β-cell function and diabetes pathogenesis.

Regulation of Glucose, Fatty Acid and Amino Acid Metabolism by Ubiquitination and SUMOylation for Cancer Progression

Ubiquitination and SUMOylation, which are posttranslational modifications, play prominent roles in regulating both protein expression and function in cells, as well as various cellular signal transduction pathways. Metabolic reprogramming often occurs in various diseases, especially cancer, which has become a new entry point for understanding cancer mechanisms and developing treatment methods. Ubiquitination or SUMOylation of protein substrates determines the fate of modified proteins. Through accurate and timely degradation and stabilization of the substrate, ubiquitination and SUMOylation widely control various crucial pathways and different proteins involved in cancer metabolic reprogramming. An understanding of the regulatory mechanisms of ubiquitination and SUMOylation of cell proteins may help us elucidate the molecular mechanism underlying cancer development and provide an important theory for new treatments. In this review, we summarize the processes of ubiquitination and SUMOylation and discuss how ubiquitination and SUMOylation affect cancer metabolism by regulating the key enzymes in the metabolic pathway, including glucose, lipid and amino acid metabolism, to finally reshape cancer metabolism.

Circular RNA Cdyl promotes abdominal aortic aneurysm formation by inducing M1 macrophage polarization and M1-type inflammation

Macrophage polarization plays a crucial role in regulating abdominal aortic aneurysm (AAA) formation. Circular RNAs (circRNAs) are important regulators of macrophage polarization during the development of cardiovascular diseases. How-ever, the roles of circRNAs in regulating AAA formation through modulation of macrophage polarization remain unknown. In the present study, we compared circRNA microarray data under two distinct polarizing conditions (M1 and M2 macrophages) and identified an M1-enriched circRNA, circCdyl. Loss- and gain-of-function assay results demonstrated that circCdyl overexpression accelerated angiotensin II (Ang II)- and calcium chloride (CaCl₂)-induced AAA formation by promoting M1 polarization and M1-type inflammation, while circCdyl deficiency showed the opposite effects. RNA pulldown, mass spectrometry analysis, and RNA immunoprecipitation (RIP) assays were conducted to elucidate the underlying mechanisms by which circCdyl regulates AAA formation and showed that circCdyl promotes vascular inflammation and M1 polarization by inhibiting interferon regulatory factor 4 (IRF4) entry into the nucleus, significantly inducing AAA formation. In addition, circCdyl was shown to act as a let-7c sponge, promoting C/EBP-δ expression in macrophages to induce M1 polarization. Our results indicate an important role for circCdyl-mediated macrophage polarization in AAA formation and provide a potent therapeutic target for AAA treatment.

MBD2 acts as a repressor to maintain the homeostasis of the Th1 program in type 1 diabetes by regulating the STAT1-IFN-γ axis

The methyl-CpG-binding domain 2 (MBD2) interprets DNA methylome-encoded information through binding to the methylated CpG DNA, by which it regulates target gene expression at the transcriptional level. Although derailed DNA methylation has long been recognized to trigger or promote autoimmune responses in type 1 diabetes (T1D), the exact role of MBD2 in T1D pathogenesis, however, remains poorly defined. Herein, we generated an Mbd2 knockout model in the NOD background and found that Mbd2 deficiency exacerbated the development of spontaneous T1D in NOD mice. Adoptive transfer of Mbd2^-/- CD4 T cells into NOD.scid mice further confirmed the observation. Mechanistically, Th1 stimulation rendered the Stat1 promoter to undergo a DNA methylation turnover featured by the changes of DNA methylation levels or patterns along with the induction of MBD2 expression, which then bound to the methylated CpG DNA within the Stat1 promoter, by which MBD2 maintains the homeostasis of Th1 program to prevent autoimmunity. As a result, ectopic MBD2 expression alleviated CD4 T cell diabetogenicity following their adoptive transfer into NOD.scid mice. Collectively, our data suggest that MBD2 could be a viable target to develop epigenetic-based therapeutics against T1D in clinical settings.

Aloperine protects beta-cells against streptozocin-induced injury to attenuate diabetes by targeting NOS1

Type 1 diabetes (T1D) is a metabolic dysfunction characterized by the selective destruction of islet β-cells, with oxidative stress playing an essential role in the manifestation of this disease state. Aloperine (ALO) represents the main active alkaloid extracted from the traditional Chinese herbal Sophora alopecuroidesL. and features outstanding antioxidative properties. In this study, T1D was induced by a single high dose streptozotocin (STZ, 150 mg/kg, intraperitoneal) in mice. Diabetic animals were intragastrically administered ALO at a dose of 50 mg/kg/day. Notably, treatment of ALO (50 mg/kg/day) for seven consecutive days could observably reverse the onset of diabetes induced by STZ accompanied by weight gain, lower blood glucose levels, and relief of β-cells damage. Our in vitro study further demonstrated that ALO protected β-cells from STZ/hydrogen peroxide-induced oxidative damage as manifested by increased expression of MnSOD and CAT. Furthermore, a network pharmacology study revealed that NOS1 represented the main target of ALO. Mechanistic studies subsequently showed that treatment of ALO increased the expression of NOS1, whereas NOS2 was decreased. Moreover, a docking study carried out suggested that ALO could fit into the binding pocket of human NOS1 and molecular dynamics simulation further validated this docking event. Collectively, the administration of ALO prior to diabetes could be a viable approach to the prevention of β-cell injury. This study may offer a novel potential herbal medicine against T1D and may further help improve the understanding of the underlying molecular mechanisms of ALO-mediated protection against oxidative stress.

Extracellular vesicles derived from melatonin-preconditioned mesenchymal stem cells containing USP29 repair traumatic spinal cord injury by stabilizing NRF2

Spinal cord injury (SCI) is a devastating trauma that leads to irreversible motor and sensory dysfunction and is, so far, without effective treatment. Recently, however, nano-sized extracellular vesicles derived from preconditioned mesenchymal stem cells (MSCs) have shown great promise in treating various diseases, including SCI. In this study, we investigated whether extracellular vesicles (MEVs) derived from MSCs pretreated with melatonin (MT), which is well recognized to be useful in treating diseases, including Alzheimer's disease, non-small cell lung cancer, acute ischemia-reperfusion liver injury, chronic kidney disease, and SCI, are better able to promote functional recovery in mice after SCI than extracellular vesicles derived from MSCs without preconditioning (EVs). MEVs were found to facilitate motor behavioral recovery more than EVs and to increase microglia/macrophages polarization from M1-like to M2-like in mice. Experiments in BV2 microglia and RAW264.7 macrophages confirmed that MEVs facilitate M2-like polarization and also showed that they reduce the production of reactive oxygen species (ROS) and regulate mitochondrial function. Proteomics analysis revealed that ubiquitin-specific protease 29 (USP29) was markedly increased in MEVs, and knockdown of USP29 in MEVs (shUSP29-MEVs) abolished MEVs-mediated benefits in vitro and in vivo. We then showed that USP29 interacts with, deubiquitinates and therefore stabilizes nuclear factor-like 2 (NRF2), thereby regulating microglia/macrophages polarization. In NRF2 knockout mice, MEVs failed to promote functional recovery and M2-like microglia/macrophages polarization. We also showed that MT reduced global N6-methyladenosine (m⁶ A) modification and levels of the m⁶ A "writer" methyltransferase-like 3 (METTL3). The stability of USP29 mRNA in MSCs was enhanced by treatment with MT, but inhibited by overexpression of METTL3. This study describes a very promising extracellular vesicle-based approach for treating SCI.

The Role of Protein SUMOylation in Human Hepatocellular Carcinoma: A Potential Target of New Drug Discovery and Development

Simple Summary

The small ubiquitin-like modifier is a highly conserved post-translational modification protein, mainly found in eukaryotes. Recently, studies have shown that SUMOylation promotes the development of liver cancer. This article summarises the recent literature on SUMOylation and Hepatocellular carcinoma (HCC). The mechanism of SUMOs in liver cancer cells was described. It also shows the potential of SUMO as a therapeutic target for liver cancer. At the same time, this article also enumerates the practical application in clinical, developing progress and future direction of HCC in clinical practice.

Abstract

Small ubiquitin-like modifier (SUMO) is a highly conserved post-translational modification protein, mainly found in eukaryotes. They are widely expressed in different tissues, including the liver. As an essential post-translational modification, SUMOylation is involved in many necessary regulations in cells. It plays a vital role in DNA repair, transcription regulation, protein stability and cell cycle progression. Increasing shreds of evidence show that SUMOylation is closely related to Hepatocellular carcinoma (HCC). The high expression of SUMOs in the inflammatory hepatic tissue may lead to the carcinogenesis of HCC. At the same time, SUMOs will upregulate the proliferation and survival of HCC, migration, invasion and metastasis of HCC, tumour microenvironment as well as drug resistance. This study reviewed the role of SUMOylation in liver cancer. In addition, it also discussed natural compounds that modulate SUMO and target SUMO drugs in clinical trials. Considering the critical role of SUMO protein in the occurrence of HCC, the drug regulation of SUMOylation may become a potential target for treatment, prognostic monitoring and adjuvant chemotherapy of HCC.

Targeted Inhibition of FTO Demethylase Protects Mice Against LPS-Induced Septic Shock by Suppressing NLRP3 Inflammasome

Sepsis refers to the systemic inflammatory response syndrome caused by infection. It is a major clinical problem and cause of death for patients in intensive care units worldwide. The Fat mass and obesity-related protein (FTO) is the primary N⁶-methyladenosine demethylase. However, the role of FTO in the pathogenesis of inflammatory diseases remains unclear. We herein show that nanoparticle-mediated Fto-siRNA delivery or FTO inhibitor entacapone administration dramatically inhibited macrophage activation, reduced the tissue damage and improved survival in a mouse model of LPS-induced endotoxic shock. Importantly, ablation of FTO could inhibit NLRP3 inflammasome through FoxO1/NF-κB signaling in macrophages. In conclusion, FTO is involved in inflammatory response of LPS-induced septic shock and inhibition of FTO is promising for the treatment of septic shock.

The Molecular Basis of Ubiquitin-Conjugating Enzymes (E2s) as a Potential Target for Cancer Therapy

Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

SUMOylation Connects Cell Stress Responses and Inflammatory Control: Lessons From the Gut as a Model Organ

Conjugation with the small ubiquitin-like modifier (SUMO) constitutes a key post-translational modification regulating the stability, activity, and subcellular localization of its target proteins. However, the vast numbers of identified SUMO substrates obscure a clear view on the function of SUMOylation in health and disease. This article presents a comprehensive review on the physiological relevance of SUMOylation by discussing how global SUMOylation levels—rather than specific protein SUMOylation—shapes the immune response. In particular, we highlight the growing body of work on SUMOylation in intestinal pathologies, because of the unique metabolic, infectious, and inflammatory challenges of this organ. Recent studies show that global SUMOylation can help restrain detrimental inflammation while maintaining immune defenses and tissue integrity. These results warrant further efforts to develop new therapeutic tools and strategies to control SUMOylation in infectious and inflammatory disorders.

MBD2 serves as a viable target against pulmonary fibrosis by inhibiting macrophage M2 program

Despite past extensive studies, the mechanisms underlying pulmonary fibrosis (PF) still remain poorly understood. Here, we demonstrated that lungs originating from different types of patients with PF, including coronavirus disease 2019, systemic sclerosis-associated interstitial lung disease, and idiopathic PF, and from mice following bleomycin (BLM)-induced PF are characterized by the altered methyl-CpG-binding domain 2 (MBD2) expression in macrophages. Depletion of Mbd2 in macrophages protected mice against BLM-induced PF. Mbd2 deficiency significantly attenuated transforming growth factor-β1 (TGF-β1) production and reduced M2 macrophage accumulation in the lung following BLM induction. Mechanistically, Mbd2 selectively bound to the Ship promoter in macrophages, by which it repressed Ship expression and enhanced PI3K/Akt signaling to promote the macrophage M2 program. Therefore, intratracheal administration of liposomes loaded with Mbd2 siRNA protected mice from BLM-induced lung injuries and fibrosis. Together, our data support the possibility that MBD2 could be a viable target against PF in clinical settings.

Chrysophanol protects human bronchial epithelial cells from cigarette smoke extract (CSE)-induced apoptosis

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease characterized by the persistent airflow obstruction. Chrysophanol, an anthraquinone derivative isolated from the rhizomes of Rheum palmatum, has been reported to be protective for some inflammatory diseases. The present report aimed to dissect its effect on cigarette smoke extract (CSE)-induced apoptosis in 16HBECs, a human bronchial epithelial cell line.

METHODS

CCK8 cell viability assay was conducted to evaluate the protective effect of chrysophanol on 16HBECs after CSE induction. Western blot analysis, Annexin V/PI staining and TUNEL assay were conducted to test the effect of chrysophanol on 16HBECs apoptosis induced by CSE. Then the western blot assay measured associated molecular pathways to dissect the mechanisms underlying protective effect of chrysophanol on 16HBECs.

RESULTS

Chrysophanol protects 16HBECs against CSE-induced apoptosis in a dose dependent manner. Specifically, pre-treatment of 16HBECs with 20 mmol/l of chrysophanol, reduced CSE-induced apoptosis by almost 10%. Mechanistically, chrysophanol manifested high potency to attenuate CSE-induced expression of apoptotic markers, Bax and cleaved caspase 3. In particular, chrysophanol not only represses CSE-induced oxidative stress by inhibiting CYP1A1 expression, but also suppresses CSE-induced ER stress by inhibiting pPERK, ATF4 and ATF6 expression.

CONCLUSION

Chrysophanol showed protective effect on CSE-induced epithelial injuries in cell line 16HBECs. And our data support that chrysophanol could be employed to reduce the toxicity of cigarette smoke in bronchial epithelial cells, which may have the potential to decrease the risk for developing COPD in smoking subjects.

SUMOylation of Pdia3 exacerbates proinsulin misfolding and ER stress in pancreatic beta cells

SUMOylation has long been recognized to regulate multiple biological processes in pancreatic beta cells, but its impact on proinsulin disulfide maturation and endoplasmic reticulum (ER) stress remains elusive. Herein, we conducted comparative proteomic analyses of SUMOylated proteins in primary mouse/human islets following proinflammatory cytokine stimulation. Cytokine challenge rendered beta cells to undergo a SUMOylation turnover manifested by the changes of SUMOylation substrates and SUMOylation levels for multiple substrates. Our data support that SUMOylation may play a crucial role to regulate proinsulin misfolding and ER stress at least by targeting Protein Disulfide Isomerase a3 (Pdia3). SUMOylation regulates Pdia3 enzymatic activity, subcellular localization, and protein binding ability. Furthermore, SUMOylation of Pdia3 exacerbated proinsulin misfolding and ER stress, and repressed Stat3 activation. In contrast, disruption of Pdia3 SUMOylation markedly rescued the outcomes. Collectively, our study expands the understanding how SUMOylation regulates ER stress in beta cells, which shed light on developing potential strategies against beta cell dysfunction.

Integrative Analyses of Genes Associated with Fulminant Type 1 Diabetes

Objective

Fulminant type 1 diabetes (FT1D) is a type of type 1 diabetes, which is characterized by rapid onset of disease and severe metabolic disorders. We intend to screen for crucial genes and potential molecular mechanisms in FT1D in this study.

Method

We downloaded GSE44314, which includes six healthy controls and five patients with FT1D, from the GEO database. Identification of differentially expressed genes (DEGs) was performed by NetworkAnalyst. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of DEGs were screened by an online tool-Database for Annotation, Visualization, and Integration Discovery (DAVID). Protein-protein interaction (PPI) network and hub genes among DEGs were analyzed by NetworkAnalyst. And we also use NetworkAnalyst to find out the microRNAs (miRNAs) and transcription factors (TFs) which regulate the expression of DEGs.

Result

We identified 130 DEGs (60 upregulated and 70 downregulated DEGs) between healthy controls and FT1D patients. GO analysis results revealed that DEGs were mostly enriched in generation of precursor metabolites and energy, neurohypophyseal hormone activity, and mitochondrial inner membrane. KEGG pathway analysis demonstrated that DEGs were mostly involved in nonalcoholic fatty liver disease. Results indicated that NCOA1, SRF, ERBB3, EST1, TOP1, UBE2S, INO80, COX7C, ITGAV, and COX6C were the top hub genes in the PPI network. Furthermore, we recognized that LDLR, POTEM, IFNAR2, BAZ2A, and SRF were the top hub genes in the miRNA-target gene network, and SRF, TSPAN4, CD59, ETS1, and SLC25A25 were the top hub genes in the TF-target gene network.

Conclusion

Our study pinpoints key genes and pathways associated with FT1D by a sequence of bioinformatics analysis on DEGs. These identified genes and pathways provide more detailed molecular mechanisms of FT1D and may provide novel therapeutic targets.

Circular RNA circPPM1F modulates M1 macrophage activation and pancreatic islet inflammation in type 1 diabetes mellitus

Rationale: Macrophages play critical roles in the pathogenesis of type 1 diabetes mellitus (T1DM). Circular RNAs (circRNAs) are a novel class of endogenous RNAs with covalently closed loop structures, implicated in various disease processes. However, their impact on macrophage activation and T1DM pathogenesis remains elusive. Methods: circRNA expression profiles of peripheral blood mononuclear cells (PBMCs) from T1DM children were determined by whole transcriptome microarray. Bioinformatics, quantitative real-time PCR, Western blot, RNA immunoprecipitation (RIP), cell co-culture, cell proliferation, and cell apoptosis assays were performed to investigate the expression, function, and regulatory mechanisms of circPPM1F in vitro. The regulatory role of circPPM1F in vivo was evaluated in the streptozocin-induced diabetic mouse model. Results: We identified 27 upregulated and 31 downregulated differentially expressed circRNAs in T1DM patients. circPPM1F, a circRNA with unknown function, was dominantly expressed in monocytes and significantly upregulated in T1DM patients. Functionally, circPPM1F promoted lipopolysaccharide (LPS)-induced M1 macrophage activation via enhancement of the NF-κB signaling pathway. Mechanistically, circPPM1F competitively interacted with HuR to impair the translation of protein phosphatase, Mg²⁺/Mn²⁺ dependent 1F (PPM1F), thus alleviating the inhibitory effect of PPM1F on the NF-κB pathway. Moreover, eukaryotic initiation factor 4A-III (EIF4A3) and fused in sarcoma (FUS) coordinately regulated circPPM1F expression during M1 macrophage activation. In addition, circPPM1F could exacerbate pancreas injury in the streptozocin-induced diabetic mice by activation of M1 macrophages in vivo. Conclusions: circPPM1F is a novel positive regulator of M1 macrophage activation through the circPPM1F-HuR-PPM1F-NF-κB axis. Overexpression of circPPM1F could promote pancreatic islet injury by enhancing M1 macrophage activation and circPPM1F may serve as a novel potential therapeutic target for T1DM in children.

Blocking protein phosphatase 2A with a peptide protects mice against bleomycin-induced pulmonary fibrosis

Emerging data indicate that endothelial-mesenchymal transition (EndMT) is involved in the pathogenesis of idiopathic pulmonary fibrosis (IPF). A previous study noted that blocking the activity of protein phosphatase 2 A (PP2A) could attenuate EndMT. However, the treatment effects of PP2A inhibitors in pulmonary fibrosis remain not investigated. In the present study, we used a PP2A inhibitor, a newly designed peptide named TAT-Y127WT, to determine the role of PP2A in pulmonary fibrosis. Herein, we showed that TAT-Y127WT protected mice against BLM-induced pulmonary fibrosis by attenuating lung injury and fibrosis. Furthermore, a mechanistic study indicated that TAT-Y127WT could alleviate EndMT in the lungs following BLM induction. Overall, our data showed that PP2A might participate in pulmonary fibrogenesis by promoting EndMT, and TAT-Y127WT could be a potential candidate for new anti-fibrotic therapies for IPF patients.