CYLD Deubiquitinase Negatively Regulates High Glucose-Induced NF-κB Inflammatory Signaling in Mesangial Cells

USP9X suppresses ferroptosis in diabetic kidney disease by deubiquitinating Nrf2 in vitro

Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates many critical genes associated with iron storage and transportation, the activity of which is influenced by E3 ligase-mediated ubiquitination. We wondered whether there is a deubiquitinase that mediates the deubiquitination of Nrf2 to stabilize Nrf2 expression and further prevent diabetic kidney disease (DKD). High glucose (HG) was applied to induce an in vitro model of DKD. The effects of HG on HK-2 cell viability, apoptosis, Fe2+ level, Nrf2, and ubiquitin-specific protease 9X (USP9X) were assessed by cell counting kit-8 (CCK-8) assay, flow cytometry, iron assay, and Western blot. The direct interaction between Nrf2 and USP9X was analyzed using co-immunoprecipitation and ubiquitination assay. After transfection and ferrostatin-1 (Fer-1) intervention, Nrf2 and USP9X levels, cell viability, apoptosis, and Fe2+ level were tested again. Reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH) contents, and ferroptosis-related markers were assessed by ROS assay kit, ELISA, and Western blot. HG reduced cell viability and levels of USP9X and Nrf2, while elevating apoptosis and Fe2+ level. An interaction between USP9X and Nrf2 has been verified and USP9X deubiquitinated Nrf2. Nrf2 up-regulation augmented the viability, GSH content, and ferroptosis-related protein expressions, while suppressing the apoptosis, Fe2+ level, MDA, and ROS content in HG-mediated HK-2 cells, which was reversed by USP9X silencing. Fer-1 offset the combined modulation of Nrf2 and siUSP9X on HG-induced HK-2 cells. USP9X mediates Nrf2 deubiquitinase to hamper the ferroptosis in DKD in vitro.

The roles of the ubiquitin-proteasome system in renal disease

The ubiquitin-proteasome system (UPS) is a major pathway of specific intracellular protein degradation through proteasome degradation of ubiquitin-labeled substrates. Numerous biological processes, including the cell cycle, transcription, translation, apoptosis, receptor activity, and intracellular signaling, are regulated by UPS. Alterations of the UPS, which render them more or less susceptible to degradation, are responsible for disorders of renal diseases. This review aims to summarize the mechanism of UPS in renal diseases. Besides, this review explores the relationship among UPS, autophagy, and deubiquitination in the development of renal disease. The specific molecular linkages among these systems and pathogenesis, on the other hand, are unknown and controversial. In addition, we briefly describe some anti-renal disease agents targeting UPS components. This review emphasizes UPS as a promising therapeutic modality for the treatment of kidney disease. Our work, though still basic and limited, could provide options to future potential therapeutic targets for renal diseases with a UPS underlying basis.

Qufeng epimedium decoction alleviates rheumatoid arthritis through CYLD-antagonized NF-kB activation by deubiquitinating Sirt1

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disease that markedly limits the patients´ day-to-day functional abilities and life quality. Currently, there is no known cure for RA. Qufeng epimedium decoction, a traditional Chinese medicine, is widely used in China to treat RA. However, its underlying mechanism remains elusive.

METHODS

The RA animal model was established to investigate the anti-RA effect and regulatory effect on fibroblast-like synoviocytes (FLS) pyroptosis, qRT-PCR, Western blot, flow cytometry, histology staining, and ELISA were utilized to confirm the gene and protein expressions. The interactions between Sirt1 and CYLD were validated through Co-immunoprecipitation (Co-IP) and RNA-FISH assay.

RESULTS

Administration with Qufeng epimedium decoction attenuated inflammatory damage, excessive proliferation, and FLSs pyroptosis in an RA rat model. Moreover, treatment of Qufeng epimedium decoction reduced the ubiquitination modification level of Sirt1 in FLSs isolated from an RA rat model. Mechanistically, CYLD, an intermediation for linking Qufeng epimedium decoction and RA, was responsible for Sirt1 deubiquitination to its protein stabilization, thereby deactivating the NF-kB /GSDMD signaling pathway.

CONCLUSION

Our findings indicate that Qufeng epimedium decoction suppresses FLSs pyroptosis and RA progression via CYLD-mediated Sirt1 deubiquitination and deactivation of the NF-kB /GSDMD signaling pathway. This study sheds light on the underlying mechanism of Qufeng epimedium decoction's effectiveness in RA treatment.

Quantitative Proteomics-Based Substrate Screening Revealed Cyclophilin Stabilization Regulated by Deubiquitinase Ubp7

Quantitative proteomics has emerged as a crucial approach to identifying ubiquitinated substrates to investigate the functions of ubiquitination in cells. In this regard, although the substrate screening of certain enzymes in the ubiquitin system has been based on proteome or ubiquitinome level measurements, the direct comparison of these two approaches has not been determined to date. To quantitatively compare the efficiency and effectiveness of substrate screening from the entire proteomics to the ubiquitinomics filter, we used yeast deubiquitinating enzyme, Ubp7, as an example to evaluate it in this study. A total of 112 potential ubiquitinated substrates were identified from the ubiquitinomics level, whereas only 27 regulated substrates were identified from the entire proteomic screening, demonstrating the increased efficiency of ubiquitinomics quantitative analysis. Subsequently, we selected cyclophilin A (Cpr1) protein as an example, which was filtered out at the proteomics level but was a promising candidate according to the ubiquitinomics filter. Additional investigations revealed that Cpr1 possessed a K48-linked ubiquitin chain regulated by Ubp7, which may affect its homeostasis and, consequently, sensitivity to the therapeutic drug cyclosporine (CsA).

Down-regulated cylindromatosis enhances NF-κB activation and aggravates inflammation in HBV-ACLF patients

The pathogenesis of liver in patients with hepatitis B virus-associated acute chronic liver failure (HBV-ACLF) remains largely unknown. We aimed to elucidate the molecular mechanism underlying the pathogenesis of liver in HBV-ACLF patients by using multiple approaches including transcriptome analysis. We performed transcriptomic sequencing analysis on the liver of HBV-ACLF patients (n = 6), chronic hepatitis B (n = 6), liver cirrhosis (n = 6) and normal control (n = 5), then explored the potential pathogenesis mechanism in liver specimen from another 48 subjects and further validated the molecular and cellular mechanisms using THP-1 cells. RNA-sequencing data analysis indicated that, among the genes up-regulated in HBV-ACLF, genes related to inflammatory response and chemotaxis accounted for a large proportion of the total DEGs. A number of key chemokines (CCL2, CCL5, CCL20, CXCL5, CXCL6, CXCL8) and NF-ĸB pathway were identified to be robust in the liver samples from HBV-ACLF patients. Interestingly, cylindromatosis (CYLD) was found to be downregulated in the liver of HBV-ACLF patients, in line with the well-established role of CYLD in regulating most of the chemokines and pro-inflammatory cytokines (CCL2, CCL5, CCL20, CXCL5, CXCL6, CXCL8, IL-6, IL-1β) via inhibition of NF-ĸB. Indeed, the knockdown of CYLD resulted in sustained activation of NF-ĸB in macrophages and enhanced chemokines and inflammatory cytokines production, which in turn enhanced chemotactic migration of neutrophil, monocyte, T lymphocytes, and NK cell. In conclusions, down-regulated CYLD aggravated inflammatory cell chemotaxis through enhancing NF-κB activation in HBV-ACLF patients, thereby participating in the pathogenesis of HBV-ACLF injury.

Blockade of the Notch Signaling Pathway Promotes M2 Macrophage Polarization to Suppress Cardiac Fibrosis Remodeling in Mice With Myocardial Infarction

Myocardial infarction (MI) is regarded as a serious ischemic heart disease on a global level. The current study set out to explore the mechanism of the Notch signaling pathway in the regulation of fibrosis remodeling after the occurrence of MI. First, experimental mice were infected with recombination signal binding protein J (RBP-J) shRNA and empty adenovirus vector, followed by the establishment of MI mouse models and detection of cardiac function. After 4 weeks of MI, mice in the sh-RBP-J group were found to exhibit significantly improved cardiac function relative to the sh-NC group. Moreover, knockdown of RBP-J brought about decreased infarct area, promoted cardiac macrophages M2 polarization, reduced cardiac fibrosis, and further decreased transcription and protein expressions of inflammatory factors and fibrosis-related factors. Furthermore, downregulation of cylindromatosis (CYLD) using si-CYLD reversed the results that knockdown of RBP-J inhibited fibrogenesis and the release of inflammatory factors. Altogether, our findings indicated that the blockade of Notch signaling promotes M2 polarization of cardiac macrophages and improves cardiac function by inhibiting the imbalance of fibrotic remodeling after MI.

Deubiquitinating enzymes (DUBs): Regulation, homeostasis, and oxidative stress response

Ubiquitin signaling is a conserved, widespread, and dynamic process in which protein substrates are rapidly modified by ubiquitin to impact protein activity, localization, or stability. To regulate this process, deubiquitinating enzymes (DUBs) counter the signal induced by ubiquitin conjugases and ligases by removing ubiquitin from these substrates. Many DUBs selectively regulate physiological pathways employing conserved mechanisms of ubiquitin bond cleavage. DUB activity is highly regulated in dynamic environments through protein-protein interaction, posttranslational modification, and relocalization. The largest family of DUBs, cysteine proteases, are also sensitive to regulation by oxidative stress, as reactive oxygen species (ROS) directly modify the catalytic cysteine required for their enzymatic activity. Current research has implicated DUB activity in human diseases, including various cancers and neurodegenerative disorders. Due to their selectivity and functional roles, DUBs have become important targets for therapeutic development to treat these conditions. This review will discuss the main classes of DUBs and their regulatory mechanisms with a particular focus on DUB redox regulation and its physiological impact during oxidative stress.

Beneficial effects of chlorogenic acid treatment on neuroinflammation after deep hypothermic circulatory arrest may be mediated through CYLD/NF-κB signaling

Deep hypothermic circulatory arrest (DHCA) during heart surgery may induce neuroinflammation leading to neurocognitive dysfunction. Chlorogenic acid (CA) is a common phytochemical, which can attenuate neuroinflammation. Nevertheless, the underlying mechanism involved in the anti-inflammatory effect of CA after DHCA is unknown. The present study therefore characterized the anti-inflammatory functions of CA after DHCA using in vivo and in vitro DHCA models. The activation of microglia, inflammatory cytokine levels, and the NF-κB pathway were measured. The results showed that CA treatment ameliorated neurocognitive function and reduced the inflammatory cytokine levels in the brain and circulation. Furthermore, the microglial and NF-κB activations were suppressed after DHCA. CA exerted the same anti-inflammatory effect in hypothermia OGD microglial cells as the in vivo study. Additional studies indicated that the regulation of ubiquitin ligase activity of TRAF6 and RIP1 by CYLD was related to the mechanism involving inhibition of CA in the NF-κB pathway. Together, the results showed that CA may attenuate neuroinflammation after DHCA by modulating the signaling of CYLD/NF-κB.

Downregulation of miR‑181b inhibits human colon cancer cell proliferation by targeting CYLD and inhibiting the NF‑κB signaling pathway

It has been reported that microRNA (miRNA/miR)-181b plays an important role in regulating cellular proliferation, invasion and apoptosis in various tumors. However, the role of miR-181b and its molecular mechanisms in colon cancer cells have not yet been elucidated. The present study thus aimed to investigate the mechanisms of miR-181b targeting cylindromatosis (CYLD) to regulate the nuclear factor-κB (NF-κB) signaling pathway, and to determine its role in colon cancer cell proliferation and apoptosis. For this purpose, miR-181b was overexpressed and silenced in the SW480 cell line. The cell proliferation and apoptotic rates were determined using a Cell Counting kit and colony formation assays, and Annexin V-FITC staining, respectively. The expression levels of proteins associated with the NF-κB signaling pathway and apoptosis were detected by western blot analysis. Furthermore, a dual luciferase assay was applied to confirm the interaction between miR-181b and CYLD. CYLD was also overexpressed and silenced in the SW480 cell line using a CYLD overexpression plasmid and siRNA technology, respectively. Transfected cells were used for subsequent experiments. In addition, a nude mouse model was established to measure tumor volume and weight. Immunohistochemistry and a TUNEL assay were performed to detect the Ki67 levels and the cell apoptotic rate, respectively. Compared with the control group, miR-181 silencing or CYLD overexpression significantly attenuated cell proliferation, invasion and migration, and notably increased the proportion of apoptotic cells. Furthermore, the expression levels of Bax and cleaved caspase-3 were markedly increased, whereas those of Bcl-2 were significantly decresaed (P<0.05). In addition, the protein expression levels of p-p65/p65 and p-IκBα/IκBα were significantly down-regulated and upregulated, respectively (P<0.05). Consistent with the results obtained in vitro, in vivo experiments using a nude mouse model yielded similar findings. The aforementioned results indicated that miR-181b down-regulation inhibited human colon cancer cell proliferation by targeting CYLD to attenuate the activity of the NF-κB signaling pathway.