DeSUMOylation of MKK7 kinase by the SUMO2/3 protease SENP3 potentiates lipopolysaccharide-induced inflammatory signaling in macrophages

Analysis of preoperative serum cytokine levels in patients with oral squamous cell carcinoma

This study investigates preoperative serum cytokine levels in patients with oral squamous cell carcinoma (OSCC). The study included 51 patients with OSCC and 42 healthy controls (HCs). Serum samples of 12 cytokines were analyzed using a multiplex bead-based flow cytometry immunoassay. Mann-Whitney U test and binary logistic regression analysis were performed to identify significant indicators of OSCC. Receiver operating characteristic (ROC) curves evaluated the diagnostic performance.Spearman analysis was assessed the correlation between cytokines and tumor-node-metastasis staging of OSCC. Serum levels of interleukin (IL)-2, IL-5, IL-6, IL-8, IL-12P70, IL-17, and interferon gamma (IFN-γ) were significantly higher (P < 0.05) in patients with OSCC than in HCs. IL-5, IL-6, IL-8, IL-12P70, IL-17, IFN-γ, combination 1 (IL-6 and IL-8), and combination 2 (IL-6 and IL-12P70) had area under the curve (AUC) values > 0.7, with combination 2 exhibited the highest AUC of 0.995. Serum cytokine profiles were significantly different (P < 0.05) between the patients with OSCC and HCs. IL-5, IL-6, IL-8, IL-12P70, IL-17, IFN-γ, combination 1, and combination 2 effectively distinguished between HCs and patients with OSCC. Cytokine combinations enhanced OSCC diagnostic accuracy, with significantly elevated IL-6 levels (P < 0.05) in advanced-stage compared to early-stage OSCC, indicating its potential impact on disease progression and prognosis.

SENP3: Cancers and diseases

SUMOylation is a protein modification process that involves the covalent attachment of a small ubiquitin-like modifier (SUMO) to a specific lysine residue on the target protein. This modification can influence the function, localization, stability, and interactions of proteins, thereby regulating various cellular processes. Altering the SUMOylation of certain proteins is expected to be a potential approach for treating specific cancers and diseases. Among these, SENP3 can affect target proteins by regulating the deSUMOylation process, which in turn influences the transcriptional activity of downstream genes, playing a role in either promoting or inhibiting cancer. SENP3 regulates the SUMO status of proteins in numerous signaling pathways, modulating the activity of specific signaling molecules to impact cellular responses and tumor progression. Additionally, SENP3 promotes cell growth and division by deSUMOylating key cyclins. In the context of DNA repair, SENP3 regulates the activity of proteins associated with DNA repair by deSUMOylating repair factors, thereby enhancing DNA repair and maintaining genome stability. Furthermore, SENP3 has specific functions in various other diseases. The complex roles of SENP3 indicate its potential as both a therapeutic target and a biomarker.

SUMO: A new perspective to decipher fibrosis

Fibrosis is characterized by excessive extracellular matrix (ECM) deposition resulting from dysregulated wound healing and connective tissue repair mechanisms. Excessive accumulation of ECM leads to fibrous tissue formation, impairing organ function and driving the progression of various fibrotic diseases. Recently, the role of small ubiquitin-like modifiers (SUMO) in fibrotic diseases has attracted significant attention. SUMO-mediated SUMOylation, a highly conserved posttranslational modification, participates in a variety of biological processes, including nuclear-cytosolic transport, cell cycle progression, DNA damage repair, and cellular metabolism. Conversely, SUMO-specific proteases cleave the isopeptide bond of SUMO conjugates, thereby regulating the deSUMOylation process. Mounting evidence indicates that SUMOylation and deSUMOylation regulate the functions of several proteins, such as Smad3, NF-κB, and promyelocytic leukemia protein, which are implicated in fibrotic diseases like liver fibrosis, myocardial fibrosis, and pulmonary fibrosis. This review summarizes the role of SUMO in fibrosis-related pathways and explores its pathological relevance in various fibrotic diseases. All evidence suggest that the SUMO pathway is important targets for the development of treatments for fibrotic diseases.

SENP1 Promotes Caspase-11 Inflammasome Activation and Aggravates Inflammatory Response in Murine Acute Lung Injury Induced by Lipopolysaccharide

BACKGROUND

Infection is the leading cause of acute lung injury (ALI). Macrophages, which are pivotal innate immune cells, play a critical role in mediating inflammatory processes. Intracellular lipopolysaccharide (LPS) from invasive Gram-negative bacteria can activate the caspase-11 inflammasome, leading to the induction of pyroptosis in macrophages. This process subsequently triggers the release of inflammatory cytokines and damage-associated molecular patterns from pyroptotic macrophages, thereby exacerbating inflammatory progression in ALI. However, the precise regulatory mechanisms governing caspase-11 activation is still unclear. Sentrin-specific proteases (SENPs) have been identified as notable targets for their anti-inflammatory properties. Nevertheless, the specific role of SENPs in macrophage pyroptosis during the pathogenesis of ALI remains unknown.

METHODS

We used LPS as an endotoxin to induce ALI. We analyzed the expression and location of sentrin-specific protease 1 (SENP1), pulmonary impairment, macrophage infiltration, caspase-11 inflammasome expression and activation, caspase-11 SUMOylation, and inflammatory cytokine secretion.

RESULTS

Upregulated expression of SENP1 in lung tissue and macrophages was observed following LPS stimulation. SENP1 mediates de-SUMOylation and activation of caspase-11 inflammasome in macrophages. Moreover, pharmacological inhibition or genetic deficiency of SENP1 in macrophages significantly improved ALI-related histological damage by reducing the secretion of inflammatory cytokines and suppressing caspase-11-dependent pyroptosis.

CONCLUSIONS

Collectively, our findings highlight the involvement of SENP1 in caspase-11 activation and inflammatory progression in macrophages, thereby establishing a scientific foundation for the exploration of novel therapeutic strategies aimed at treating ALI.

SUMO proteases: from cellular functions to disease

Posttranslational modification by small ubiquitin-like modifiers (SUMOs) is critical in regulating diverse cellular processes including gene expression, cell cycle progression, genome integrity, cellular metabolism, and inflammation and immunity. The covalent attachment of SUMOs to target proteins is highly dynamic and reversible through the concerted action of SUMO conjugating and deconjugating enzymes. In mammalian cells, sentrin-specific proteases (SENPs) are the most abundant family of deconjugating enzymes. This review highlights recent advances in our knowledge of the substrates and cellular and physiological processes controlled by SENPs. Notably, SENPs are emerging as significant players in cancer, as well as in other diseases, making them attractive targets for therapeutic intervention. Consequently, a growing amount of effort in the field is being directed towards the development of SENP inhibitors.

Exploring potential targets for natural product therapy of DN: the role of SUMOylation

Diabetic nephropathy (DN) is a common and serious micro-vascular complication of diabetes and a leading cause of end-stage renal disease globally. This disease primarily affects middle-aged and elderly individuals, especially those with a diabetes history of over 10 years and poor long-term blood glucose control. Small ubiquitin-related modifiers (SUMOs) are a group of reversible post-translational modifications of proteins that are widely expressed in eukaryotes. SUMO proteins intervene in the progression of DN by modulating various signaling cascades, such as Nrf2-mediated oxidative stress, NF-κB, TGF-β, and MAPK pathways. Recent advancements indicate that natural products regulating SUMOylation hold promise as targets for intervening in DN. In a previous article published in 2022, we reviewed the mechanisms by which SUMOylation intervenes in renal fibrosis and presented a summary of some natural products with therapeutic potential. Therefore, this paper will focus on DN. The aim of this review is to elucidate the mechanism of action of SUMOylation in DN and related natural products with therapeutic potential, thereby summarising the targets and candidate natural products for the treatment of DN through the modulation of SUMOylation, such as ginkgolic acid, ginkgolide B, resveratrol, astragaloside IV, etc., and highlighting that natural product-mediated modulation of SUMOylation is a potential therapeutic strategy for the treatment of DN as a potential therapeutic strategy.

SENP3 sensitizes macrophages to ferroptosis via de-SUMOylation of FSP1

Ferroptosis, driven by an imbalance in redox homeostasis, has recently been identified to regulate macrophage function and inflammatory responses. SENP3 is a redox-sensitive de-SUMOylation protease that plays an important role in macrophage function. However, doubt remains on whether SENP3 and SUMOylation regulate macrophage ferroptosis. For the first time, the results of our study suggest that SENP3 sensitizes macrophages to RSL3-induced ferroptosis. We showed that SENP3 promotes the ferroptosis of M2 macrophages to decrease M2 macrophage proportion in vivo. Mechanistically, we identified the ferroptosis repressor FSP1 as a substrate for SUMOylation and confirmed that SUMOylation takes place mainly at its K162 site. We found that SENP3 sensitizes macrophages to ferroptosis by interacting with and de-SUMOylating FSP1 at the K162 site. In summary, our study describes a novel type of posttranslational modification for FSP1 and advances our knowledge of the biological functions of SENP3 and SUMOylation in macrophage ferroptosis.

Sumo-regulatory SENP2 controls the homeostatic squamous mitosis-differentiation checkpoint

Squamous or epidermoid cancer arises in stratified epithelia but also is frequent in the non-epidermoid epithelium of the lung by unclear mechanisms. A poorly studied mitotic checkpoint drives epithelial cells bearing irreparable genetic damage into epidermoid differentiation. We performed an RNA-sequencing gene search to target unknown regulators of this response and selected the SUMO regulatory protein SENP2. Alterations of SENP2 expression have been associated with some types of cancer. We found the protein to be strongly localised to mitotic spindles of freshly isolated human epidermal cells. Primary cells rapidly differentiated after silencing SENP2 with specific shRNAs. Loss of SENP2 produced in synchronised epithelial cells delays in mitotic entry and exit and defects in chromosomal alignment. The results altogether strongly argue for an essential role of SENP2 in the mitotic spindle and hence in controlling differentiation. In addition, the expression of SENP2 displayed an inverse correlation with the immuno-checkpoint biomarker PD-L1 in a pilot collection of aggressive lung carcinomas. Consistently, metastatic head and neck cancer cells that do not respond to the mitosis-differentiation checkpoint were resistant to depletion of SENP2. Our results identify SENP2 as a novel regulator of the epithelial mitosis-differentiation checkpoint and a potential biomarker in epithelial cancer.

SENP3-regulated Nodal signaling plays a potential role in cardiac left-right asymmetry development

Congenital heart disease (CHD) is a type of major defect that occurs during embryonic development. Although significant advances have been made in the treatment of CHD, its etiology and molecular mechanism remain unclear. To identify the critical role of SUMOylation in cardiac development, we generated SENP3 knockout mice and showed that SENP3 knockout mice die on embryonic day 8.5 with an open neural tube and reversed left-right cardiac asymmetry. Moreover, SENP3 knockout promoted apoptosis and senescence of H9C2 cells. Further studies showed that Nodal, a critical gene that forms left-right asymmetry, is regulated by SENP3 and that SENP3 regulates cell apoptosis and senescence in a Nodal-dependent manner. Furthermore, Nodal was hyper-SUMOylated after SENP3 knockout, and SUMOylation of Nodal inhibited its ubiquitination and ubiquitin-proteasome degradation pathway. Nodal overexpression enhanced cell apoptosis and senescence; however, the mutation at the SUMOylation site of Nodal reversed its effect on the apoptosis and senescence of H9C2 cells. More importantly, the SENP3-Nodal axis regulates cell senescence by inducing cell autophagy. These results suggest that the SENP3-Nodal signaling axis regulates cardiac senescence-autophagy homeostasis, which in turn affects cardiac development and results in the occurrence of CHD.

The chromatin remodeling factor Arid1a cooperates with Jun/Fos to promote osteoclastogenesis by epigenetically upregulating Siglec15 expression

Osteoporosis is characterized by an imbalance between osteoclast-mediated bone resorption and osteoblast-related bone formation, particularly increased osteoclastogenesis. However, the mechanisms by which epigenetic factors regulate osteoclast precursor differentiation during osteoclastogenesis remain poorly understood. Here, we show that the specific knockout of the chromatin remodeling factor Arid1a in bone marrow-derived macrophages (BMDMs) results in increased bone mass. The loss of Arid1a in BMDM inhibits cell-cell fusion and maturation of osteoclast precursors, thereby suppressing osteoclast differentiation. Mechanistically, Arid1a increases the chromatin access in the gene promoter region of sialic acid-binding Ig-like lectin 15 (Siglec15) by transcription factor Jun/Fos, which results in the upregulation of Siglec15 and promotion of osteoclast differentiation. However, the loss of Arid1a reprograms the chromatin structure to restrict Siglec15 expression in osteoclast precursors, thereby inhibiting BMDM differentiation into mature osteoclasts. Deleting Arid1a after ovariectomy (a model for postmenopausal bone loss) alleviated bone loss and maintained bone mass. In summary, epigenetic reprogramming mediated by Arid1a loss suppresses osteoclast differentiation and may serve as a promising therapeutic strategy for treating bone loss diseases.

The role of SUMO specific peptidase 3 in secondary inflammation of ischemic stroke in mice

Ischemic stroke is the main cause of death and disability, and microglia play a crucial role in the pathophysiology of hypoxic ischemic brain injury. We found that SENP3 is highly expressed in the early stages of ischemic stroke in both in vivo and in vitro mouse models, and may be related to the deSUMOylation of the key kinase MKK7 in the TLR4/p-JNK signaling pathway. Knocking down SENP3 can inhibit the deSUMOylation of MKK7, thereby inhibiting the activation of the TLR4/p-JNK signaling pathway in an in vitro stroke model. Proteomic analysis showed that SENP3 undergoes phosphorylation at the T429 site after ischemic stroke. Computer simulation predictions show a significant enhancement of the interaction between pT429-SENP3 and MKK7, which has been confirmed through experiments on the interaction of biological macromolecules (SPR). The mitochondrial metabolic abnormalities caused by energy abnormalities in the early stages of stroke provide a good explanation for the phosphorylation of SENP3. Therefore, we used the mitochondrial complex inhibitor TTFA to reverse demonstrate that the phosphorylation of SENP3 comes from the large amount of adenosine triphosphate produced by mitochondrial abnormal metabolism caused by early oxygen glucose deficiency. Finally, proteomic analysis indicates that a significant amount of oxidative phosphorylation does occur in the early stages of stroke. In summary, targeted regulation of SENP3 phosphorylation to affect the deSUMOylation of MKK7 may inhibit secondary inflammation in ischemic stroke.

SENP3 mediates the activation of the Wnt/β-catenin signaling pathway to accelerate the growth and metastasis of oesophagal squamous cell carcinoma in mice

As a common malignant tumor, esophageal squamous cell carcinoma (ESCC) is occasionally seen in clinical practice. This type of disease has low incidence rate and mortality. The post-translational modification of small ubiquitin like modifiers (SUMO) can play a crucial role in regulating protein function, and can significantly impact the occurrence and development of diseases. SUMO-specific peptidase (SENP) affects cell activity by regulating the biological function of SUMO. SENP3 belongs to the SENP family, and available data indicate that many malignancies are associated with SENPs, it is currently unclear its role in ESCC. This study indicates that there is a high level of SENP3 expression in ESCC tumor cells. If the expression level of this gene is high, it can have a significant impact on ESCC cell lines and affect physiological activities such as invasion of KYSE170 cells. If the gene is knocked out, this situation will not occur. There is also research data indicating that this gene can effectively activate related signaling pathways, thereby promoting the physiological activities of malignant tumor cells. In a nude mouse xenograft tumor model, KYSE170 cells with SENP3 expression knockdown induced a smaller volume and weight of tumor tissue. Therefore, it can be clearly stated that SENP3 can enable Wnt/ β- The catenin signaling pathway is stimulated, which in turn affects the physiological activities of ESCC cells, including the invasion process. The results of this article lay the foundation for clinical staff to carry out clinical management.

Impaired bisecting GlcNAc reprogrammed M1 polarization of macrophage

The functions of macrophages are governed by distinct polarization phenotypes, which can be categorized as either anti-tumor/M1 type or pro-tumor/M2 type. Glycosylation is known to play a crucial role in various cellular processes, but its influence on macrophage polarization is not well-studied. In this study, we observed a significant decrease in bisecting GlcNAc during M0-M1 polarization, and impaired bisecting GlcNAc was found to drive M0-M1 polarization. Using a glycoproteomics strategy, we identified Lgals3bp as a specific glycoprotein carrying bisecting GlcNAc. A high level of bisecting GlcNAc modification facilitated the degradation of Lgals3bp, while a low level of bisecting GlcNAc stabilized Lgals3bp. Elevated levels of Lgals3bp promoted M1 polarization through the activation of the NF-кB pathway. Conversely, the activated NF-кB pathway significantly repressed the transcription of MGAT3, leading to reduced levels of bisecting GlcNAc modification on Lgals3bp. Overall, our study highlights the impact of glycosylation on macrophage polarization and suggests the potential of engineered macrophages via glycosylated modification. Video Abstract.

Porcine β-Defensin 114: Creating a Dichotomous Response to Inflammation

The immunity-related functions of defensins seem to be dependent on environmental stimuli, the cell type, and the concentration of peptides. However, the function and mechanism of porcine β-defensin 114 (pBD114) in regulating the inflammatory response to macrophages are unclear. Therefore, the modulatory effects of porcine pBD114 on the inflammatory response were investigated by treating the mouse monocyte macrophage cell line RAW264.7 with different concentrations of pBD114 with or without lipopolysaccharide (LPS). RNA-seq analysis was performed to investigate the mechanisms underlying pBD114's regulation of inflammatory responses in macrophages. In addition, the inflammatory response-modulating effects of pBD114 were also further verified with a mouse assay. The results showed that 100 μg/mL of pBD114 significantly promoted the secretion of TNF-α and IL-10 in RAW264.7. However, the LPS-induced increase in TNFα in the RAW264.7 cell cultures was significantly decreased with 10 μg/mL of pBD114. These results suggest that pBD114 can exhibit pro-inflammatory activities under normal physiological conditions with 100 μg/mL of pBD114, and anti-inflammatory activities during an excessive inflammatory response with 10 μg/mL of pBD114. RNA-seq analysis was performed to gain further insights into the effects of pBD114 on the inflammatory response. Among the pBD114-promoting RAW264.7 pro-inflammatory responses, pBD114 significantly up-regulated 1170 genes and down-regulated 724 genes. KEGG enrichment showed that the differentially expressed genes (DEGs) were significantly enriched in the immune- and signal-transduction-related signaling pathways. Protein-Protein Interaction (PPI) and key driver analysis (KDA) analyses revealed that Bcl10 and Bcl3 were the key genes. In addition, pBD114 significantly up-regulated 12 genes and down-regulated 38 genes in the anti-inflammatory response. KEGG enrichment analysis revealed that the DEGs were mainly enriched in the "Cytokine-cytokine receptor interaction" signaling pathway, and PPI and KDA analyses showed that Stat1 and Csf2 were the key genes. The results of qRT-PCR verified those of RNA-seq. In vivo mouse tests also confirmed the pro- or anti-inflammatory activities of pBD114. Although the inflammatory response is a rapid and complex physiological reaction to noxious stimuli, this study found that pBD114 plays an essential role mainly by acting on the genes related to immunity, signal transduction, signaling molecules, and interactions. In conclusion, this study provides a certain theoretical basis for the research and application of defensins.

Myeloid SENP3 deficiency protects mice from diet and age-induced obesity via regulation of YAP1 SUMOylation

Obesity is characterized by chronic low-grade inflammation, which is driven by macrophage infiltration in adipose tissue and leads to elevated cytokines such as interleukin-1β (IL-1β) in the circulation and tissues. Previous studies demonstrate that SENP3, a redox-sensitive SUMO2/3-specific protease, is strongly implicated in the development and progression of cancer and cardiovascular diseases. However, the role of SENP3 in obesity-associated inflammation remains largely unknown. To better understand the effects of SENP3 on adipose tissue macrophage (ATM) activation and function within the context of obesity, we generated mice with myeloid-specific deletion of SENP3 (Senp3flox/flox;Lyz2-Cre mice). We found that the expression of SENP3 is dramatically increased in ATMs during high-fat diet (HFD)-induced obesity in mice. Senp3flox/flox;Lyz2-Cre mice show lower body weight gain and reduced adiposity and adipocyte size after challenged with HFD and during aging. Myeloid-specific SENP3 deletion attenuates macrophage infiltration in adipose tissue and reduces serum levels of inflammatory factors during diet and age-induced obesity. Furthermore, we found that SENP3 knockout markedly inhibits cytokine release from macrophage after lipopolysaccharide and palmitic acid treatment in vitro. Mechanistically, in cultured peritoneal macrophages, SENP3 protein level is enhanced by IL-1β, in parallel with the upregulation of Yes-associated protein 1 (YAP1). Moreover, we demonstrated that SENP3 modulates de-SUMO modification of YAP1 and SENP3 deletion abolishes the upregulation of YAP1 induced by IL-1β. Most importantly, SENP3 deficiency reduces YAP1 protein level in adipose tissue during obesity. Our results highlight the important role of SENP3 in ATM inflammation and diet and age-induced obesity.

SENP3-mediated deSUMOylation of c-Jun facilitates microglia-induced neuroinflammation after cerebral ischemia and reperfusion injury

Recent evidences have implicated that SENP3 is a deSUMOylase which possesses neuronal damage effects in cerebral ischemia. However, its role in microglia remains poorly understood. Here, we found that SENP3 was upregulated in the peri-infarct areas of mice following ischemic stroke. Furthermore, knockdown of SENP3 significantly inhibits the expression of proinflammatory cytokines and chemokines in microglial cells. Mechanistically, SENP3 can bind and then mediated the deSUMOylation of c-Jun, which activated its transcriptional activity, ultimately followed by the activation of MAPK/AP-1 signaling pathway. In addition, microglia-specific SENP3 knockdown alleviated ischemia-induced neuronal damage, and markedly diminished infract volume, ameliorated sensorimotor and cognitive function in animals subjected to ischemic stroke. These results indicated SENP3 functions as a novel regulator of microglia-induced neuroinflammation by activating the MAPK/AP-1 signaling pathway via mediating the deSUMOylation of c-Jun. Interventions of SENP3 expression or its interaction with c-Jun would be a new and promising therapeutic strategy for ischemic stroke.

The effect of ROS-YAP crosstalk on osteoimmune response orchestrating osteogenesis

Bone defect repair is a common medical concern. In spite of various existing treatments, its management still requires improvement. Here we show that YAP, a downstream signaling of Hippo pathway, might interplay with redox oxygen species (ROS) and modulate osteoimmunology, which refers to the interaction between immune and skeletal system during bone defect repair. We modulated the ROS level of RAW264.7 cells and found YAP level was reversely regulated. Meanwhile, we detected the feedback of YAP on oxidation level. The results demonstrated that the antioxidant enzyme expression was in proportion to the YAP level of RAW264.7 cells. Additionally, indirect coculture system was applied and it indicated that RAW264.7 cells under oxidative stress could impede proliferation and migration ability of MC3T3-E1 pre-osteoblasts. Consistently, in vivo experiment verified high oxidant level slowed down mice osteogenesis during bone defect repair, while antioxidant and upregulation of YAP accelerated this process. Additionally, we established a mouse model with YAP conditional knockout in macrophages. The results identified that deficiency of YAP in macrophages negatively affected bone defect repair in vivo. In summary, our study indicated that ROS and YAP could jointly modulate osteogenesis via their effect on osteoimmunology.ABBREVIATIONS: GPX4, glutathione peroxidase 4; NAC, N-Acetyl-L-cysteine; qRT-PCR, real-time quantitative PCR; ROS, reactive oxygen species; Tb.N, trabecular number; Tb.Sp, trabecular separation.

SENP3 deletion promotes M2 macrophage polarization and accelerates wound healing through smad6/IκB/p65 signaling pathway

Macrophages preferentially polarize to the anti-inflammatory M2 subtype in response to alterations in the wound microenvironment. SUMO-specific protease 3 (SENP3), a SUMO-specific protease, has been proven to regulate inflammation in macrophages by deSUMOylating substrate proteins, but its contribution to wound healing is poorly defined. Here, we report that SENP3 deletion promotes M2 macrophage polarization and accelerates wound healing in macrophage-specific SENP3 knockout mice. Notably, it affects wound healing through the suppression of inflammation and promotion of angiogenesis and collagen remodeling. Mechanistically, we identified that SENP3 knockout facilitates M2 polarization through the Smad6/IκB/p65 signaling pathway. SENP3 knockout elevated the expression of Smad6 and IκB. Moreover, Smad6 silencing enhanced the expression of p-p65 and proinflammatory cytokines while inhibiting the level of IκB. Our study revealed the essential role of SENP3 in M2 polarization and wound healing, which offers a theoretical basis for further research and a therapeutic strategy for wound healing.

Loss of SENP3 mediated the formation of nasal polyps in nasal mucosal inflammation by increasing alternative activated macrophage

BACKGROUND AND AIM

Small ubiquitin-like modifier (SUMO)-specific protease (SENP)3 is a protease molecule that responds to reactive oxygen species (ROS) with high sensitivity. However, the role of ROS and SENP3 in the formation of nasal polyps (NPs) remains unclear. This study aimed to explore how SENP3 influenced the outcome of chronic rhinosinusitis (CRS) by altering macrophage function, that is, the formation of NPs.

METHODS

The alternative activation of macrophage (M2) was detected with CD68+ CD206+ in humans and CD206+ in mice. The nasal mucosa of patients with CRS was tested using flow cytometry (CD68, CD80, and CD206) and triple-color immunofluorescence staining (CD68, CD206, and SENP3). The bone marrow-derived macrophages from SENP3 knockout and control mice were stimulated with interleukin (IL)-4 and IL-13 to analyze alternative macrophage polarization in vitro. An animal model of allergic rhinitis was constructed using SENP3 knockout mice. CD206 was detected by immunofluorescence staining. The thickening of eosinophil-infiltrated mucosa was detected by Luna staining.

RESULTS

The number of CD68+ CD206+ M2 increased in the nasal mucosa of patients with CRS with NP (CRSwNP) compared with patients with CRS without NP (CRSsNP), but with no significant difference between the groups. SENP3 knockout increased the polarization of F4/80+ CD206+ M2. Meanwhile, the number of CD206+ M2 significantly increased in the allergic rhinitis model constructed using SENP3 knockout mice and controls, with a more obvious proliferation of the nasal mucosa.

CONCLUSION

Downregulation of SENP3 promotes the formation of nasal polyps mediated by increasing alternative activated macrophage in nasal mucosal inflammation.

SENP3 Aggravates Renal Tubular Epithelial Cell Apoptosis in Lipopolysaccharide-Induced Acute Kidney Injury via deSUMOylation of Drp1

BACKGROUND

Sepsis causes acute kidney injury (AKI) in critically ill patients, although the mechanisms underlying the pathophysiology are not fully understood. SUMO-specific proteases 3 (SENP3), a member of the deSUMOylating enzyme family, is known as a redox sensor and could regulate multiple cellular signaling pathways. However, the role of SENP3 in septic AKI remains unclear.

OBJECTIVES

The purpose of this study was to investigate the role of SENP3 in lipopolysaccharide (LPS)-induced AKI model.

METHODS

C57BL/6 mice were given intraperitoneal injection of LPS (10 mg/kg). NRK-52E cells were treated with LPS in vitro. The SENP3 protein expression was analyzed by Western blotting. The levels of reactive oxygen species (ROS) in cells were measured using DCFH-DA. SENP3-siRNA or SENP3-plasmid was, respectively, transfected into NRK-52E cells to knock down or overexpress the SENP3 expression. Western blotting was performed to analyze the protein expression of cleaved caspase 3, cytochrome c, and dynamin-related protein 1 (Drp1). The mitochondrial membrane potential was measured using JC-1 assay kit. Co-immunoprecipitation was used to determine the interaction of Drp1 and SMUO2/3.

RESULTS

SENP3 protein expression was obviously increased in renal tissues from the mouse model of LPS-induced AKI. Accordingly, SENP3 expression was upregulated in NRK-52E cells treated with LPS in a ROS-dependent manner in vitro. Knockdown of SENP3 dramatically ameliorated LPS-induced apoptosis of NRK-52E cells, whereas overexpression of SENP3 further aggravated LPS-induced apoptosis of NRK-52E cells. Mechanistically, SENP3 triggered Drp1 recruitment to mitochondria by increasing the deSUMOylation of Drp1.

CONCLUSION

SENP3 aggravated renal tubular epithelial cell apoptosis in LPS-induced AKI via Drp1 deSUMOylation manner.

SENP3 affects the expression of PYCR1 to promote bladder cancer proliferation and EMT transformation by deSUMOylation of STAT3

Abnormal activation of signal transducer and activator of transcription 3 (STAT3) has been found in various types of human cancers, including bladder cancer (BC). In our study, we examined the regulation of STAT3 post-translational modifications (PTMs) and found that SENP3 is high in bladder cancer. Sentrin/SUMO-specific protease3 (SENP3) and STAT3 were highly expressed in BC tissues when compared with tissue adjacent to carcinoma. SENP3 induced STAT3 protein level and p-STAT3 translocating into nuclear through deSUMOylation of STAT3. Further, nuclear STAT3, as a transcriptional activity factor, promoted pyrroline-5-carboxylate reductase 1 PYCR1 gene and protein level by interacting with the promoter of (PYCR1). Next, we found that knockdown of PYCR1 inhibited Epithelial to mesenchymal transition of bladder cancer, and simultaneously mitigated the carcinogenic effects of STAT3. In vitro, STAT3 knockdown in bladder cancer cells inhibited cell proliferation, migration, and invasion. In contrast, SENP3 overexpression reversed these effects. In all, results lend novel insights into the regulation of STAT3, which has key roles in bladder cancer progression.

Natural Products Against Renal Fibrosis via Modulation of SUMOylation

Renal fibrosis is the common and final pathological process of kidney diseases. As a dynamic and reversible post-translational modification, SUMOylation and deSUMOylation of transcriptional factors and key mediators significantly affect the development of renal fibrosis. Recent advances suggest that SUMOylation functions as the promising intervening target against renal fibrosis, and natural products prevent renal fibrosis via modulating SUMOylation. Here, we introduce the mechanism of SUMOylation in renal fibrosis and therapeutic effects of natural products. This process starts by summarizing the key mediators and enzymes during SUMOylation and deSUMOylation and its regulation role in transcriptional factors and key mediators in renal fibrosis, then linking the mechanism findings of SUMOylation and natural products to develop novel therapeutic candidates for treating renal fibrosis, and concludes by commenting on promising therapeutic targets and candidate natural products in renal fibrosis via modulating SUMOylation, which highlights modulating SUMOylation as a promising strategy for natural products against renal fibrosis.

SUMO-specific Isopeptidases Tuning Cardiac SUMOylation in Health and Disease

SUMOylation is a transient posttranslational modification with small-ubiquitin like modifiers (SUMO1, SUMO2 and SUMO3) covalently attached to their target-proteins via a multi-step enzymatic cascade. SUMOylation modifies protein-protein interactions, enzymatic-activity or chromatin binding in a multitude of key cellular processes, acting as a highly dynamic molecular switch. To guarantee the rapid kinetics, SUMO target-proteins are kept in a tightly controlled equilibrium of SUMOylation and deSUMOylation. DeSUMOylation is maintained by the SUMO-specific proteases, predominantly of the SENP family. SENP1 and SENP2 represent family members tuning SUMOylation status of all three SUMO isoforms, while SENP3 and SENP5 are dedicated to detach mainly SUMO2/3 from its substrates. SENP6 and SENP7 cleave polySUMO2/3 chains thereby countering the SUMO-targeted-Ubiquitin-Ligase (StUbL) pathway. Several biochemical studies pinpoint towards the SENPs as critical enzymes to control balanced SUMOylation/deSUMOylation in cardiovascular health and disease. This study aims to review the current knowledge about the SUMO-specific proteases in the heart and provides an integrated view of cardiac functions of the deSUMOylating enzymes under physiological and pathological conditions.

Assessment of SENP3-interacting proteins in hepatocytes treated with diethylnitrosamine by BioID assay

SUMOylation of proteins regulates cell behaviors and is reversibly removed by small ubiquitin-like modifier (SUMO)-specific proteases (SENPs). The SENP family member SENP3 is involved in SUMO2/3 deconjugation and has been reported to sense cell stress and accumulate in several human cancer cells and macrophages. We previously reported that Senp3-knockout heterozygous mice showed smaller liver, but the pertinent mechanisms of SENP3 and SUMOylated substrates remain unclear. Thus, in this study, we investigated the interacting proteins with SENP3 and the alteration in hepatocytes treated with the xenobiotic diethylnitrosamine (DEN), which is specifically transformed in the liver and induces DNA double-strand breaks. Our data revealed that a certain amount of SENP3 was present in normal, untreated hepatocytes; however, DEN treatment promoted rapid SENP3 accumulation. SENP3 was mainly localized in the nuclei, and its level was significantly increased in the cytoplasm after 2 h of DEN treatment. The application of the recent proximity-dependent biotinylation (BioID) method led to the identification of 310 SENP3-interacting proteins that were involved in not only gene transcription but also RNA splicing, protein folding, and metabolism. Furthermore, after DEN exposure for a short duration, ribosomal proteins as well as proteins associated with mitochondrial ATP synthesis, membrane transport, and bile acid synthesis, rather than DNA repair proteins, were identified. This study provides insights into the diverse regulatory roles of SENP3, and the BioID method seems to be efficient for identifying physiologically relevant insoluble proteins.

Therapeutic Potential of Targeting the SUMO Pathway in Cancer

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer. The delicate balance between SUMOylation and deSUMOylation is regulated by SENP enzymes possessing SUMO-deconjugation activity. Dysregulation of SUMO machinery components can disrupt the balance of SUMOylation, contributing to the tumorigenesis and drug resistance of various cancers in a context-dependent manner. Many molecular mechanisms relevant to the pathogenesis of specific cancers involve SUMO, highlighting the potential relevance of SUMO machinery components as therapeutic targets. Recent advances in the development of inhibitors targeting SUMOylation and deSUMOylation permit evaluation of the therapeutic potential of targeting the SUMO pathway in cancer. Finally, the first drug inhibiting SUMO pathway, TAK-981, is currently also being evaluated in clinical trials in cancer patients. Intriguingly, the inhibition of SUMOylation may also have the potential to activate the anti-tumor immune response. Here, we comprehensively and systematically review the recent developments in understanding the role of SUMOylation in cancer and specifically focus on elaborating the scientific rationale of targeting the SUMO pathway in different cancers.

SUMO proteases SENP3 and SENP5 spatiotemporally regulate the kinase activity of Aurora A

Precise chromosome segregation is mediated by a well-assembled mitotic spindle, which requires balance of the kinase activity of Aurora A (AurA, also known as AURKA). However, how this kinase activity is regulated remains largely unclear. Here, using in vivo and in vitro assays, we report that conjugation of SUMO2 with AurA at K258 in early mitosis promotes the kinase activity of AurA and facilitates the binding with its activator Bora. Knockdown of the SUMO proteases SENP3 and SENP5 disrupts the deSUMOylation of AurA, leading to increased kinase activity and abnormalities in spindle assembly and chromosome segregation, which could be rescued by suppressing the kinase activity of AurA. Collectively, these results demonstrate that SENP3 and SENP5 deSUMOylate AurA to render spatiotemporal control on its kinase activity in mitosis. This article has an associated First Person interview with the first author of the paper.

SENP3-Mediated PPARγ2 DeSUMOylation in BM-MSCs Potentiates Glucocorticoid-Induced Osteoporosis by Promoting Adipogenesis and Weakening Osteogenesis

Glucocorticoid-induced osteoporosis (GIOP) is the most common secondary osteoporosis and reduced bone formation was the main pathological change in GIOP. Our previous studies have shown that there was an imbalance between adipogenic and osteogenic differentiation in GIOP BM-MSCs and peroxisome proliferator-activated receptor γ2 (PPARγ2) played a vital role in this disorders. Here, we reported that there was an increase in ROS level and SENP3 expression in Dex-induced osteoporotic BM-MSCs, and enhanced adipogenesis and weakened osteogenesis in osteoporotic BM-MSCs might be caused by upregulated SENP3. Then we found that SENP3 de-SUMOylated PPARγ2 on K107 site to potentiate adipogenesis and weaken osteogenesis. These results may provide new strategy and target in the clinical diagnosis and treatment of GIOP.

Redox-sensitive enzyme SENP3 mediates vascular remodeling via de-SUMOylation of β-catenin and regulation of its stability

Background

Oxidative stress plays critical pathophysiological roles in vascular remodeling-related cardiovascular diseases, including hypertension, atherosclerosis, and restenosis. Previous studies demonstrate that SENP3, a redox-sensitive SUMO2/3-specific protease, is strongly implicated in cancer development and progression. However, the role of SENP3 in vascular remodeling remains unknown.

Methods

We generated three mouse models of vascular remodeling due to low shear stress, hypertension, and atherosclerosis. The expression of SENP3 was determined by western blotting and/or immunofluorescence staining in cultured vascular smooth muscle cells (VSMCs), animal models, and human samples. The biological function of SENP3 in proliferation and migration of VSMC and vascular remodeling was further investigated in vitro and in vivo models.

Findings

SENP3 was highly expressed in VSMCs of remodeled arteries, accompanied by elevated reactive oxygen species (ROS) levels. In cultured VSMCs, SENP3 protein levels were enhanced by oxidized low-density lipoprotein and Angiotensin II in a ROS-dependent manner. SENP3 overexpression significantly promoted and sh-RNA-mediated knockdown markedly inhibited VSMCs proliferation and migration. Immunofluorescence staining showed that SENP3 expression was correlated with intimal area in remodeled arteries. Furthermore, we demonstrated that SENP3 interacted with β-catenin and inhibited its proteasome-dependent degradation via de-SUMOylation of β-catenin. Most importantly, SENP3^+/− mice exhibited alleviated vascular remodeling.

Interpretation

Our results highlight the important function of SENP3 as a redox sensor and mediator in vascular remodeling.

SENP3 loss promotes M2 macrophage polarization and breast cancer progression

Tumor‐associated macrophages (TAM) play a crucial role in promoting cancer progression. Upon cytokine stimulation, TAM preferentially polarize to the anti‐inflammatory and pro‐tumor M2 subtype. The mechanism underlying such preferential polarization remains elusive. Here, we report that macrophage‐specific deletion of the SUMO‐specific protease Sentrin/SUMO‐specific protease 3 promotes macrophage polarization towards M2 in bone marrow‐derived macrophage (BMDM) induced by interleukin 4 (IL‐4)/IL‐13 and in an ex vivo model (murine Py8119 cell line), as well as in a mouse orthotopic tumor model. Notably, Sentrin/SUMO‐specific protease 3 (SENP3) loss in macrophages accelerated breast cancer malignancy in ex vivo and in vivo models. Mechanistically, we identified Akt Serine/threonine kinase 1 (Akt1) as the substrate of SENP3 and found that the enhanced Akt1 SUMOylation upon SENP3 loss resulted in Akt1 hyper‐phosphorylation and activation, which facilitates M2 polarization. Analysis of clinical data showed that a lower level of SENP3 in TAM has a strong negative correlation with the level of the M2 marker CD206, as well as with a worse clinical outcome. Thus, increased Akt1 SUMOylation as a result of SENP3 deficiency modulates polarization of macrophages to the M2 subtype within a breast cancer microenvironment, which in turn promotes tumor progression.

Stability of Smyd1 in endothelial cells is controlled by PML-dependent SUMOylation upon cytokine stimulation

Smyd1 is an epigenetic modulator of gene expression that has been well-characterized in muscle cells. It was recently reported that Smyd1 levels are modulated by inflammatory processes. Since inflammation affects the vascular endothelium, this study aimed to characterize Smyd1 expression in endothelial cells. We detected Smyd1 in human endothelial cells (HUVEC and EA.hy926 cells), where the protein was largely localized in PML nuclear bodies (PML-NBs). By transfection of EA.hy926 cells with expression vectors encoding Smyd1, PML, SUMO1, active or mutant forms of the SUMO protease SuPr1 and/or the SUMO-conjugation enzyme UBC9, as well as Smyd1- or PML-specific siRNAs, in the presence or absence of the translation blocker cycloheximide or the proteasome-inhibitor MG132, and supported by computational modeling, we show that Smyd1 is SUMOylated in a PML-dependent manner and thereby addressed for degradation in proteasomes. Furthermore, transfection with Smyd1-encoding vectors led to PML up-regulation at the mRNA level, while PML transfection lowered Smyd1 protein stability. Incubation of EA.hy926 cells with the pro-inflammatory cytokine TNF-α resulted in a constant increase in Smyd1 mRNA and protein over 24 h, while incubation with IFN-γ induced a transient increase in Smyd1 expression, which peaked at 6 h and decreased to control values within 24 h. The IFN-γ-induced increase in Smyd1 was accompanied by more Smyd1 SUMOylation and more/larger PML-NBs. In conclusion, our data indicate that in endothelial cells, Smyd1 levels are regulated through a negative feedback mechanism based on SUMOylation and PML availability. This molecular control loop is stimulated by various cytokines.

SENP3 Suppresses Osteoclastogenesis by De-conjugating SUMO2/3 from IRF8 in Bone Marrow-Derived Monocytes

Bone metabolism depends on the balance between osteoclast-driven bone resorption and osteoblast-mediated bone formation. Diseases like osteoporosis are characterized by increased bone destruction due to partially enhanced osteoclastogenesis. Here, we report that the post-translational SUMO modification is critical for regulating osteoclastogenesis. The expression of the SUMO-specific protease SENP3 is downregulated in osteoclast precursors during osteoclast differentiation. Mice with SENP3 deficiency in bone marrow-derived monocytes (BMDMs) exhibit more severe bone loss due to over-activation of osteoclasts after ovariectomy. Deleting SENP3 in BMDMs promotes osteoclast differentiation. Mechanistically, loss of SENP3 increases interferon regulatory factor 8 (IRF8) SUMO3 modification at the K310 amino acid site, which upregulates expression of the nuclear factor of activated T cell c1 (NFATc1) and osteoclastogenesis. In summary, IRF8 de-SUMO modification mediated by SENP3 suppresses osteoclast differentiation and suggests strategies to treat bone loss diseases.

Annexin-A1 SUMOylation regulates microglial polarization after cerebral ischemia by modulating IKKα stability via selective autophagy

Annexin-A1 (ANXA1) has recently been proposed to play a role in microglial activation after brain ischemia, but the underlying mechanism remains poorly understood. Here, we demonstrated that ANXA1 is modified by SUMOylation, and SUMOylated ANXA1 could promote the beneficial phenotype polarization of microglia. Mechanistically, SUMOylated ANXA1 suppressed nuclear factor κB activation and the production of proinflammatory mediators. Further study revealed that SUMOylated ANXA1 targeted the IκB kinase (IKK) complex and selectively enhanced IKKα degradation. Simultaneously, we detected that SUMOylated ANXA1 facilitated the interaction between IKKα and NBR1 to promote IKKα degradation through selective autophagy. Further work revealed that the overexpression of SUMOylated ANXA1 in microglia/macrophages resulted in marked improvement in neurological function in a mouse model of cerebral ischemia. Collectively, our study demonstrates a previously unidentified mechanism whereby SUMOylated ANXA1 regulates microglial polarization and strongly indicates that up-regulation of ANXA1 SUMOylation in microglia may provide therapeutic benefits for cerebral ischemia.

The Critical Roles of the SUMO-Specific Protease SENP3 in Human Diseases and Clinical Implications

Post-translational modification by SUMO (small ubiquitin-like modifier) proteins has been shown to regulate a variety of functions of proteins, including protein stability, chromatin organization, transcription, DNA repair, subcellular localization, protein–protein interactions, and protein homeostasis. SENP (sentrin/SUMO-specific protease) regulates precursor processing and deconjugation of SUMO to control cellular mechanisms. SENP3, which is one of the SENP family members, deconjugates target proteins to alter protein modification. The effect of modification via SUMO and SENP3 is crucial to maintain the balance of SUMOylation and guarantee normal protein function and cellular activities. SENP3 acts as an oxidative stress-responsive molecule under physiological conditions. Under pathological conditions, if the SUMOylation process of proteins is affected by variations in SENP3 levels, it will cause a cellular reaction and ultimately lead to abnormal cellular activities and the occurrence and development of human diseases, including cardiovascular diseases, neurological diseases, and various cancers. In this review, we summarized the most recent advances concerning the critical roles of SENP3 in normal physiological and pathological conditions as well as the potential clinical implications in various diseases. Targeting SENP3 alone or in combination with current therapies might provide powerful targeted therapeutic strategies for the treatment of these diseases.

High SENP3 Expression Promotes Cell Migration, Invasion, and Proliferation by Modulating DNA Methylation of E-Cadherin in Osteosarcoma

SENP3, a sentrin/SUMO2/3-specific protease, is recognized as a transcriptional factor that accumulates under cellular oxidative stress and plays a significant role in the removal of SUMO2/3 modification. In our study, we examined a TCGA dataset and found that the transcripts per million (TPM) value of SENP3 is high in sarcoma, including osteosarcoma (OS). We found that SENP3 was highly expressed in OS cancer tissues when compared with osteofibrous dysplasia tissues. The survival data of SENP3 in TCGA showed that the sarcoma patients with higher SENP3 expression levels showed poor prognosis. In vitro, SENP3 knockdown in OS cancer cells inhibited cell proliferation, migration, and invasion and induced apoptosis. In contrast, SENP3 overexpression reversed these effects. Next, we found that SENP3 inhibited the expression of E-cadherin (E-Cad) by increasing methylation of the E-Cad promoter. Finally, E-Cad expression was increased in the OS cell line MG63 following methylation, and the cell proliferation, migration, and invasion capacity were decreased. In summary, SENP3 played a significant role in OS carcinogenesis and may act as a potential biomarker in the diagnosis and treatment of OS.

Wogonoside inhibits inflammatory cytokine production in lipopolysaccharide-stimulated macrophage by suppressing the activation of the JNK/c-Jun signaling pathway

Background

Mediated by innate immune cells, inflammation is an underlying presence in the pathogenesis of numerous pulmonary diseases. Macrophages play a critical role in mediating the initial response to infection in the lungs. When there is excessive activation of macrophages, hyper-production of inflammatory factors occurs, with inflammation as the ultimate result. Wogonoside, a bioactive flavonoid glycoside, has been reported to alleviate pulmonary inflammation. However, the mechanism underlying the anti-inflammatory effect of wogonoside has not yet been clarified.

Methods

The productions of nitric oxide (NO) and reactive oxygen species (ROS) were determined using a Griess reagent kit and a DAF-FM DA fluorescent probe, respectively. Moreover, the mRNA levels of inflammatory factors were quantified by qPCR, and the binding ability of c-Jun to promoters of inflammatory factors was performed by ChIP assay. Western blot was employed to detect the protein expression of inflammatory factors and signaling pathway.

Results

In this study, we found that pre-treatment with wogonoside dramatically suppressed lipopolysaccharide (LPS)-induced increase in the protein and mRNA levels of inflammatory factors in macrophages, such as cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6. Furthermore, wogonoside profoundly reduced the increase in NO and ROS production and significantly blocked phosphorylation of JNK in LPS-stimulated macrophages. As revealed by Western blot and qPCR analysis, wogonoside mediated the JNK-dependent inhibitory effect. Compared with wogonoside alone, a combination of wogonoside and JNK inhibitor SP600125 provided no extra benefit in suppressing the protein expression and mRNA levels of inflammatory factors in LPS-stimulated macrophages. Additionally, ChIP analysis demonstrated wogonoside to remarkably reduce c-Jun enrichment in COX-2, iNOS, IL-1β, TNF-α, and IL-6 promoters.

Conclusions

Collectively, our findings showed that wogonoside notably suppresses LPS-stimulated production of inflammatory factors by repressing the activation of the JNK/c-Jun signaling pathway in macrophages. This suggests that wogonoside could serve as a promising therapeutic agent for pulmonary diseases related to macrophage inflammation.

SENP3 in monocytes/macrophages up-regulates tissue factor and mediates lipopolysaccharide-induced acute lung injury by enhancing JNK phosphorylation

The mechanisms underlying coagulation abnormalities in sepsis and septic acute lung injury remain unclear. Tissue factor (TF) initiates coagulation; its production can be regulated by reactive oxygen species (ROS); and monocytes/macrophages produce pathological TF during sepsis. The SUMO2/3 protease SENP3 is redox‐sensitive, and SENP3 accumulation in lipopolysaccharide (LPS)‐activated macrophages is ROS‐dependent. To explore whether SENP3 contributes to LPS‐activated coagulation, we used mice with Senp3 conditional knockout (cKO) in myeloid cells. In the model of LPS‐induced sepsis, SENP3 cKO mice exhibited less severe acute lung injury than SENP3 ^fl/fl mice. SENP3 cKO mice exhibited decreased TF expression in monocytes and alveolar macrophages, with consequently compromised coagulation in their blood and lungs. In vitro results showed that ROS‐induced SENP3 accumulation contributed to LPS‐induced TF expression, which was reduced by JNK inhibitor SP600125. Furthermore, mice injected with LPS following SP600125 (75 mg/kg) treatment showed decreased monocytes/macrophages TF production and alleviated coagulation activation, with less severe lung injury and higher survival rates. Collectively, the results suggest that SENP3 mediates LPS‐induced coagulation activation by up‐regulating monocyte/macrophage TF production in a JNK‐dependent manner. This work provides new insights into ROS regulation of LPS‐activated coagulation and reveals a link between SUMOylation and coagulation.

Reformulating Pro-Oxidant Microglia in Neurodegeneration

In neurodegenerative diseases, microglia-mediated neuroinflammation and oxidative stress are central events. Recent genome-wide transcriptomic analyses of microglial cells under different disease conditions have uncovered a new subpopulation named disease-associated microglia (DAM). These studies have challenged the classical view of the microglia polarization state's proinflammatory M1 (classical activation) and immunosuppressive M2 (alternative activation). Molecular signatures of DAM and proinflammatory microglia (highly pro-oxidant) have shown clear differences, yet a partial overlapping gene profile is evident between both phenotypes. The switch activation of homeostatic microglia into reactive microglia relies on the selective activation of key surface receptors involved in the maintenance of brain homeostasis (a.k.a. pattern recognition receptors, PRRs). Two relevant PRRs are toll-like receptors (TLRs) and triggering receptors expressed on myeloid cells-2 (TREM2), whose selective activation is believed to generate either a proinflammatory or a DAM phenotype, respectively. However, the recent identification of endogenous disease-related ligands, which bind to and activate both TLRs and TREM2, anticipates the existence of rather complex microglia responses. Examples of potential endogenous dual ligands include amyloid β, galectin-3, and apolipoprotein E. These pleiotropic ligands induce a microglia polarization that is more complicated than initially expected, suggesting the possibility that different microglia subtypes may coexist. This review highlights the main microglia polarization states under disease conditions and their leading role orchestrating oxidative stress.

A fine-tuning mechanism underlying self-control for autophagy: deSUMOylation of BECN1 by SENP3

The roles of SUMOylation and the related enzymes in autophagic regulation are unclear. Based on our previous studies that identified the SUMO2/3-specific peptidase SENP3 as an oxidative stress-responsive molecule, we investigated the correlation between SUMOylation and macroautophagy/autophagy. We found that Senp3^± mice showed increased autophagy in the liver under basal and fasting conditions, compared to Senp3^+/+ mice. We constructed a liver-specific senp3 knockout mouse; these Senp3-deficient liver tissues showed increased autophagy as well. Autophagic flux was accelerated in hepatic and other cell lines following knockdown of SENP3, both before and after the cells underwent starvation in the form of the serum and amino acid deprivation. We demonstrated that BECN1/beclin 1, the core molecule of the BECN1-PIK3C3 complex, could be SUMO3-conjugated by PIAS3 predominantly at K380 and deSUMOylated by SENP3. The basal SUMOylation of BECN1 was increased upon cellular starvation, which enhanced autophagosome formation by facilitating BECN1 interaction with other complex components UVRAG, PIK3C3 and ATG14, thus promoting PIK3C3 activity. In contrast, SENP3 deSUMOylated BECN1, which impaired BECN1-PIK3C3 complex formation or stability to suppress the PIK3C3 activity. DeSUMOylation of BECN1 restrained autophagy induction under basal conditions and especially upon starvation when SENP3 had accumulated in response to the increased generation of reactive oxygen species. Thus, while reversible SUMOylation regulated the degree of autophagy, SENP3 provided an intrinsic overflow valve for fine-tuning autophagy induction.

ABBREVIATIONS

AL: autolysosome; AP: autophagosome; ATG: autophagy related; ATG14: autophagy related 14; BECN1: beclin 1, autophagy related; cKO: conditional knockout; co-IP: co-immunoprecipitation; CQ: chloroquine; EBSS: Earle's balanced salt solution; GFP: green fluorescent protein; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; NAC: N-acetyl-L-cysteine; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PTM: post-translational modification; RFP: red fluorescent protein; ROS: reactive oxygen species; RUBCN/rubicon: RUN domain and cysteine-rich domain containing, BECN1-interacting protein; SENP3: SUMO specific peptidase 3; shRNA: small hairpin RNA; siRNA: small interfering RNA; SQSTM1: sequestosome 1; SUMO: small ubiquitin-like modifier; UVRAG: UV radiation resistance associated gene.

Unique Polypharmacology Nuclear Receptor Modulator Blocks Inflammatory Signaling Pathways

Obesity and rheumatic disease are mechanistically linked via chronic inflammation. The orphan receptor TREM-1 (triggering receptor expressed on myeloid cells-1) is a potent amplifier of proinflammatory and noninfectious immune responses. Here, we show that the pan modulator SR1903 effectively blocks TREM-1 activation. SR1903 emerged from a chemical series of potent RORγ inverse agonists, although unlike close structural analogues, it has modest agonist activity on LXR and weak repressive activity (inverse agonism) of PPARγ, three receptors that play essential roles in inflammation and metabolism. The anti-inflammatory and antidiabetic efficacy of this unique modulator in collagen-induced arthritis and diet-induced obesity mouse models is demonstrated. Interestingly, in the context of obesity, SR1903 aided in the maintenance of the thymic homeostasis unlike selective RORγ inverse agonists. SR1903 was well-tolerated following chronic administration, and combined, these data suggest that it may represent a viable strategy for treatment of both metabolic and inflammatory disease. More importantly, the ability of SR1903 to block LPS signaling suggests the potential utility of this unique polypharmacological modulator for treatment of innate immune response disorders.

Phase separated microenvironments inside the cell nucleus are linked to disease and regulate epigenetic state, transcription and RNA processing

Proteins and RNAs inside the cell nucleus are organized into distinct phases, also known as liquid-liquid phase separated (LLPS) droplet organelles or nuclear bodies. These regions exist within the spaces between chromatin-rich regions but their function is tightly linked to gene activity. They include major microscopically-observable structures such as the nucleolus, paraspeckle and Cajal body. The biochemical and assembly factors enriched inside these microenvironments regulate chromatin structure, transcription, and RNA processing, and other important cellular functions. Here, we describe published evidence that suggests nuclear bodies are bona fide LLPS droplet organelles and major regulators of the processes listed above. We also outline an updated "Supply or Sequester" model to describe nuclear body function, in which proteins or RNAs are supplied to surrounding genomic regions or sequestered away from their sites of activity. Finally, we describe recent evidence that suggests these microenvironments are both reflective and drivers of diverse pathophysiological states.