The circadian rhythm: A new target of natural products that can protect against diseases of the metabolic system, cardiovascular system, and nervous system.

BACKGROUND: The treatment of metabolic system, cardiovascular system, and nervous system diseases remains to be explored. In the internal environment of organisms, the metabolism of substances such as carbohydrates, lipids and proteins (including biohormones and enzymes) exhibit a certain circadian rhythm to maintain the energy supply and material cycle needed for the normal activities of organisms. As a key factor for the health of organisms, the circadian rhythm can be disrupted by pathological conditions, and this disruption accelerates the progression of diseases and results in a vicious cycle. The current treatments targeting the circadian rhythm for the treatment of metabolic system, cardiovascular system, and nervous system diseases have certain limitations, and the identification of safer and more effective circadian rhythm regulators is needed. AIM OF THE REVIEW: To systematically assess the possibility of using the biological clock as a natural product target for disease intervention, this work reviews a range of evidence on the potential effectiveness of natural products targeting the circadian rhythm to protect against diseases of the metabolic system, cardiovascular system, and nervous system. This manuscript focuses on how natural products restore normal function by affecting the amplitude of the expression of circadian factors, sleep/wake cycles and the structure of the gut microbiota. KEY SCIENTIFIC CONCEPTS OF THE REVIEW: This work proposes that the circadian rhythm, which is regulated by the amplitude of the expression of circadian rhythm-related factors and the sleep/wake cycle, is crucial for diseases of the metabolic system, cardiovascular system and nervous system and is a new target for slowing the progression of diseases through the use of natural products. This manuscript provides a reference for the molecular modeling of natural products that target the circadian rhythm and provides a new perspective for the time-targeted action of drugs.

Scavenging Glyoxal and Methylglyoxal by Synephrine and Neohesperidin from Flowers of Citrus aurantium L. var. amara Engl. in Mice and Humans.

There is considerable research evidence that α-dicarbonyl compounds, including glyoxal (GO) and methylglyoxal (MGO), are closely related to many chronic diseases. In this work, after comparison of the capture capacity, reaction pathway, and reaction rate of synephrine (SYN) and neohesperidin (NEO) on GO/MGO in vitro, experimental mice were administrated with SYN and NEO alone and in combination. Quantitative data from UHPLC-QQQ-MS/MS revealed that SYN/NEO/HES (hesperetin, the metabolite of NEO) could form the GO/MGO-adducts in mice (except SYN-MGO), and the levels of GO/MGO-adducts in mouse urine and fecal samples were dose-dependent. Moreover, SYN and NEO had a synergistic scavenging effect on GO in vivo by promoting each other to form more GO adducts, while SYN could promote NEO to form more MGO-adducts, although it could not form MGO-adducts. Additionally, human experiments showed that the GO/MGO-adducts of SYN/NEO/HES found in mice were also detected in human urine and fecal samples after drinking flowers of Citrus aurantium L. var. amara Engl. (FCAVA) tea using UHPLC-QTOF-MS/MS. These findings provide a novel strategy to reduce endogenous GO/MGO via the consumption of dietary FCAVA rich in SYN and NEO.

MFG-E8 induces epithelial-mesenchymal transition and anoikis resistance to promote the metastasis of pancreatic cancer cells.

Pancreatic cancer is an extremely malignant tumor, and only a few clinical treatment options exist. MFG-E8 and kindlin-2 all play an important role in cancer progression. However, the specific mechanism occurring between MFG-E8, kindlin-2 and the migration and invasion of pancreatic cancer cells remains unelucidated. To unravel the specific mechanism, this study assessed the potential association between MFG-E8 and kindlin-2 as well as the involvement of MFG-E8 in pancreatic cancer using two pancreatic cancer cell lines (MiaPaCa-2 and PANC-1). Pancreatic cancer cells were treated with 0, 250, and 500 ng/ml MFG-E8, and the effects of MFG-E8 on the migration, invasion, and anoikis of pancreatic cancer cells were observed. To investigate the role of kindlin-2 in pancreatic cancer, kindlin-2-shRNAi was transfected to knock down its expression level in the two pancreatic cancer cell lines. Furthermore, cilengitide, a receptor blocker of MFG-E8, was used to explore the relationship between MFG-E8, kindlin-2, and pancreatic cancer progression. Our findings demonstrated that MFG-E8 promotes the migration and invasion of pancreatic cancer cells and induces cell anoikis resistance in a dose-dependent manner, which was effectively counteracted by cilengitide, a receptor blocker. Additionally, the knockdown of kindlin-2 expression nullified the effect of MFG-E8 on the migration and invasion of pancreatic cancer cells. Consequently, this study provides insights into the specific mechanism underlying the interplay between MFG-E8 and kindlin-2 in the progression of pancreatic cancer cells.

Scavenging Glyoxal and Methylglyoxal by Synephrine Alone or in Combination with Neohesperidin at High Temperatures.

α-Dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), are a series of chemical hazards that exist in vivo and in vitro, posing a threat to human health. We aimed to explore the scavenging effects on GO/MGO by synephrine (SYN) alone or in combination with neohesperidin (NEO). First, through LC-MS/MS, we confirmed that both SYN and NEO could effectively remove GO and form GO adducts, while NEO could also clear MGO by forming MGO adducts, and its ability to clear MGO was stronger than that of GO. Second, a synergistic inhibitory effect on GO was found when SYN and NEO were used in combination by using the Chou-Talalay method; on the other hand, SYN could promote NEO to clear more MGO, although SYN could not capture MGO. Third, after synthesizing four GO/MGO-adducts (SYN-GO-1, SYN-GO-3, NEO-GO-7, and NEO-MGO-2) and identifying their structure through NMR, strict correlations between the GO/MGO-adducts and the GO/MGO-clearance rate were found when using SYN and NEO alone or in combination. Furthermore, it was inferred that the synergistic effect between SYN and NEO stems from their mutual promotion in capturing more GO by the quantitative analysis of the adducts in the combined model. Finally, a study was conducted on flowers of Citrus aurantium L. var. amara Engl. (FCAVA, an edible tea) rich in SYN and NEO, which could serve as an effective GO and MGO scavenger in the presence of both GO and MGO. Therefore, our study provided well-defined evidence that SYN and NEO, alone or in combination, could efficiently scavenge GO/MGO at high temperatures, whether in the pure form or located in FCAVA.

Blocking CIRP protects against acute pancreatitis by improving mitochondrial function and suppressing pyroptosis in acinar cells.

Acute pancreatitis (AP) continues to pose a major challenge as targeted therapeutic interventions are absent. Mitochondrial dysfunction and inflammasome-dependent pyroptosis are involved in the pathogenic mechanisms of AP. CIRP is a stress-response protein and a damage-associated molecular pattern (DAMP) molecule. In our previous studies, we discovered that excessive CIRP can directly damage pancreatic acinar cells. Nonetheless, the precise involvement of CIRP in AP is still unexplored. The primary aim of this study was to examine the potential involvement of CIRP in the development of pyroptosis and mitochondrial dysfunction in AP. To study this, an L-arginine-induced AP mouse model was used. Our results showed that Caspase-1-mediated pyroptosis and mitochondria-derived reactive oxygen species (ROS) were crucial factors in the occurrence of tissue damage and inflammation in AP. A substantial increase in the CIRP serum levels was observed in AP mice. Blocking CIRP by either CIRP gene knockout or systemic administration of C23, a competing inhibitor of CIRP, reduced ROS accumulation and pyroptosis in AP mice. These effects were associated with attenuated pancreatic injury and inflammation. In addition, CIRP-triggered mitochondrial dysfunction, autophagy impairment, and pyroptosis in pancreatic acinar cells were prevented by TAK242, an inhibitor of CIRP receptor TLR4. In conclusion, CIRP can induce mitochondrial dysfunction and pyroptosis in pancreatic acinar cells, and blocking CIRP may be a valuable approach to treating patients with AP.

Bruceine B Displays Potent Antimyeloma Activity by Inducing the Degradation of the Transcription Factor c-Maf.

The oncogenic transcription factor c-Maf has been proposed as an ideal therapeutic target for multiple myeloma (MM), a not-yet-curable malignancy of plasma cells. In the present study, we establish a c-Maf-based luciferase screen system and apply it to screen a homemade library composed of natural products from which bruceine B (BB) is identified to display potent antimyeloma activity. BB is a key ingredient isolated from the Chinese traditional medicinal plant Brucea javanica (L.) Merr. (Simaroubaceae). BB inhibits MM cell proliferation and induces MM cell apoptosis in a caspase-3-dependent manner. The mechanism studies showed that BB inhibits c-Maf transcriptional activity and downregulates the expression of CCND2 and ITGB7, the downstream genes typically modulated by c-Maf. Moreover, BB induces c-Maf degradation via proteasomes by inducing c-Maf for K48-linked polyubiquitination in association with downregulated Otub1 and USP5, two proven deubiquitinases of c-Maf. We also found that c-Maf activates STAT3 and BB suppresses the STAT3 signaling. In the in vivo study, BB displays potent antimyeloma activity and almost suppresses the growth of myeloma xenografts in 7 days but shows no overt toxicity to mice. In conclusion, this study identifies BB as a novel inhibitor of c-Maf by promoting its degradation via the ubiquitin-proteasomal pathway. Given the safety and the successful clinical application of bruceine products in traditional medicine, BB is ensured for further investigation for the treatment of patients with MM.

Exploring a novel HE image segmentation technique for glioblastoma: A hybrid slime mould and differential evolution approach.

Glioblastoma is a primary brain tumor with high incidence and mortality rates, posing a significant threat to human health. It is crucial to provide necessary diagnostic assistance for its management. Among them, Multi-threshold Image Segmentation (MIS) is considered the most efficient and intuitive method in image processing. In recent years, many scholars have combined different metaheuristic algorithms with MIS to improve the quality of Image Segmentation (IS). Slime Mould Algorithm (SMA) is a metaheuristic approach inspired by the foraging behavior of slime mould populations in nature. In this investigation, we introduce a hybridized variant named BDSMA, aimed at overcoming the inherent limitations of the original algorithm. These limitations encompass inadequate exploitation capacity and a tendency to converge prematurely towards local optima when dealing with complex multidimensional problems. To bolster the algorithm's optimization prowess, we integrate the original algorithm with a robust exploitative operator called Differential Evolution (DE). Additionally, we introduce a strategy for handling solutions that surpass boundaries. The incorporation of an advanced cooperative mixing model accelerates the convergence of BDSMA, refining its precision and preventing it from becoming trapped in local optima. To substantiate the effectiveness of our proposed approach, we conduct a comprehensive series of comparative experiments involving 30 benchmark functions. The results of these experiments demonstrate the superiority of our method in terms of both convergence speed and precision. Moreover, within this study, we propose a MIS technique. This technique is subsequently employed to conduct experiments on IS at both low and high threshold levels. The effectiveness of the BDSMA-based MIS technique is further showcased through its successful application to the medical image of brain glioblastoma. The evaluation of these experimental outcomes, utilizing image quality metrics, conclusively underscores the exceptional efficacy of the algorithm we have put forth.

Multi-task learning framework to predict the status of central venous catheter based on radiographs.

Hospital patients can have catheters and lines inserted during the course of their admission to give medicines for the treatment of medical issues, especially the central venous catheter (CVC). However, malposition of CVC will lead to many complications, even death. Clinicians always detect the status of the catheter to avoid the above issues via X-ray images. To reduce the workload of clinicians and improve the efficiency of CVC status detection, a multi-task learning framework for catheter status classification based on the convolutional neural network (CNN) is proposed. The proposed framework contains three significant components which are modified HRNet, multi-task supervision including segmentation supervision and heatmap regression supervision as well as classification branch. The modified HRNet maintaining high-resolution features from the start to the end can ensure to generation of high-quality assisted information for classification. The multi-task supervision can assist in alleviating the presence of other line-like structures such as other tubes and anatomical structures shown in the X-ray image. Furthermore, during the inference, this module is also considered as an interpretation interface to show where the framework pays attention to. Eventually, the classification branch is proposed to predict the class of the status of the catheter. A public CVC dataset is utilized to evaluate the performance of the proposed method, which gains 0.823 AUC (Area under the ROC curve) and 82.6% accuracy in the test dataset. Compared with two state-of-the-art methods (ATCM method and EDMC method), the proposed method can perform best.

Collagen Mimetic Peptide with a Coiled Coil Trimerization Domain Forms Fibrils Having D-Period-like Structures.

Fibrillar collagen is the major protein in the extracellular matrix and regulates cell behavior via chemical and mechanical cues. The key structural element of collagen fibrils is the axially repeating D-period, formed by the lateral association of collagen triple helices. We have developed fibril-forming collagen mimetic peptides (FCMPs) with repeated amino acid sequences, which form fibrils having D-period-like structures. Containing over 100 amino acid residues, these peptides are produced by bacterial expression using designed genes. Here, we report the fibrillogenesis of a new FCMP containing an α-helix coiled coil domain. The latest findings highlight the importance of the amino acid sequence periodicity in FCMP fibril formation. Additionally, our results demonstrate the remarkable adaptability of collagen fibrils' molecular packing. Mirroring native collagen fibrils, in both the structure and the fibrillogenesis process, these FCMPs are useful molecular tools for advancing collagen research and developing novel biomaterials.

Serum sirtuin1: a potential blood biomarker for early diagnosis of Alzheimer's disease.

BACKGROUND: Sirtuin 1, a nicotinamide adenine dinucleotide-dependent deacetylase that is highly expressed in the hippocampus and anterior cortex tissues related to Alzheimer's Disease pathology, can cross the blood-brain barrier and is a promising biomarker. METHODS: A 1:1:1 case-control study was conducted and serum fasting blood glucose, triglyceride, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, SIRT1, IL-6, Aß1-42, T-tau and P-tau-181 levels were evaluated in blood samples of 26 patients form the Alzheimer's Disease group, 26 patients form the mild cognitive impairment group, and 26 individuals form the normal control group. Receiver operator characteristic curves were used to evaluate the diagnostic significance. RESULTS: Serum SIRT1 level was significantly down-regulated in the mild cognitive impairment patients and Alzheimer's Disease patients compared with that in the normal control group (P<0.05). ROC curve analysis demonstrated that SIRT1 was a promising biomarker to distinguish Alzheimer's Disease patients from the mild cognitive impairment patients and the normal control group. In addition, SIRT1 was estimated to perform well in the diagnosis of Alzheimer's Disease ([AUC] = 0.742). CONCLUSIONS: In summary, the present study suggested that serum SIRT1 might be an early promising diagnostic biomarker for Alzheimer's Disease.

Long-circulating gambogic acid-loaded nanodiamond composite nanosystem with inhibition of cell migration for tumor therapy.

Herein, ultra dispersed and stably suspended nanodiamonds (NDs) were demonstrated to have a high load capacity, sustained release, and ability to serve as a biocompatible vehicle for delivery anticancer drugs. NDs with size of 50-100 nm exhibited good biocompatibility in normal human liver (L-02) cells. In particular, 50 nm ND not only promoted the noticeable proliferation of the L-02 cells but also can effectively inhibited the migration of human liver carcinoma (HepG2) cells. The gambogic acid-loaded nanodiamond (ND/GA) complex assembled by π-π stacking exhibits ultrasensitive and apparent suppression efficiency on the proliferation of HepG2 cells through high internalization and less efflux compared to free GA. More importantly, the ND/GA system can significantly increase the intracellular reactive oxygen species (ROS) levels in HepG2 cells and thus induce the cell apoptosis. The increase in intracellular ROS levels causes damage to the mitochondrial membrane potential (MMP) and activates cysteinyl aspartate specific proteinase 3 (Caspase-3) and cysteinyl aspartate specific proteinase 9 (Caspase-9), which leads to the occurrence of apoptosis. In vivo experiments also confirmed that the ND/GA complex has a much higher anti-tumor capability than free GA. Thus, the current ND/GA system is promising for cancer therapy.

Inhibition of USP10 induces myeloma cell apoptosis by promoting cyclin D3 degradation.

The cell cycle regulator cyclin D3 (CCND3) is highly expressed in multiple myeloma (MM) and it promotes MM cell proliferation. After a certain phase of cell cycle, CCND3 is rapidly degraded, which is essential for the strict control of MM cell cycle progress and proliferation. In the present study, we investigated the molecular mechanisms regulating CCND3 degradation in MM cells. By utilizing affinity purification-coupled tandem mass spectrometry, we identified the deubiquitinase USP10 interacting with CCND3 in human MM OPM2 and KMS11 cell lines. Furthermore, USP10 specifically prevented CCND3 from K48-linked polyubiquitination and proteasomal degradation, therefore enhancing its activity. We demonstrated that the N-terminal domain (aa. 1-205) of USP10 was dispensable for binding to and deubiquitinating CCND3. Although Thr283 was important for CCND3 activity, it was dispensable for CCND3 ubiquitination and stability modulated by USP10. By stabilizing CCND3, USP10 activated the CCND3/CDK4/6 signaling pathway, phosphorylated Rb, and upregulated CDK4, CDK6 and E2F-1 in OPM2 and KMS11 cells. Consistent with these findings, inhibition of USP10 by Spautin-1 resulted in accumulation of CCND3 with K48-linked polyubiquitination and degradation that synergized with Palbociclib, a CDK4/6 inhibitor, to induce MM cell apoptosis. In nude mice bearing myeloma xenografts with OPM2 and KMS11 cells, combined administration of Spautin-l and Palbociclib almost suppressed tumor growth within 30 days. This study thus identifies USP10 as the first deubiquitinase of CCND3 and also finds that targeting the USP10/CCND3/CDK4/6 axis may be a novel modality for the treatment of myeloma.

The ubiquitin ligase HERC4 suppresses MafA transcriptional activity triggered by GSK3ß in myeloma by atypical K63-linked polyubiquitination.

MafA and c-Maf are close members of the Maf transcription factor family and indicators of poor prognosis of multiple myeloma (MM). Our previous study finds that the ubiquitin ligase HERC4 induces c-Maf degradation but stabilizes MafA, and the mechanism is elusive. In the present study, we find that HERC4 interacts with MafA and mediates its K63-linked polyubiquitination at K33. Moreover, HERC4 inhibits MafA phosphorylation and its transcriptional activity triggered by glycogen synthase kinase 3ß (GSK3ß). The K33R MafA variant prevents HERC4 from inhibiting MafA phosphorylation and increases MafA transcriptional activity. Further analyses reveal that MafA can also activate the STAT3 signaling, but it is suppressed by HERC4. Lastly, we demonstrate that lithium chloride, a GSK3ß inhibitor, can upregulate HERC4 and synergizes dexamethasone, a typical anti-MM drug, in inhibiting MM cell proliferation and xenograft growth in nude mice. These findings thus highlight a novel regulation of MafA oncogenic activity in MM and provide the rationale by targeting HERC4/GSK3ß/MafA for the treatment of MM.

Rapid and Sensitive Fluorescence Detection of Staphylococcus aureus Based on Polyethyleneimine-Enhanced Boronate Affinity Isolation.

There are increasing demands for fast and simple detection of pathogens in foodstuffs. Fluorescence analysis has demonstrated significant advantages for easy operation and high sensitivity, although it is usually hindered by a complex matrix, low bacterial abundance, and long-term bacterial enrichment. Effective enrichment procedures are required to meet the requirements for food detection. Here, boronate-functionalized cellulose filter paper and specific fluorescent probes were combined. An integrated approach for the enrichment of detection of Staphylococcus aureus was proposed. The modification of polyethyleneimine demonstrated a significant effect in enhancing the bacterial enrichment, and the boronate affinity efficiency of the paper was increased by about 51~132%. With optimized conditions, the adsorption efficiency for S. aureus was evaluated as 1.87 × 108 CFU/cm2, the linear range of the fluorescent analysis was 104 CFU/mL~108 CFU/mL (R2 = 0.9835), and the lowest limit of detection (LOD) was calculated as 2.24 × 102 CFU/mL. Such efficiency was validated with milk and yogurt samples. These results indicated that the material had a high enrichment capacity, simple operation, and high substrate tolerance, which had the promising potential to be the established method for the fast detection of food pathogens.

Improving COVID-19 CT classification of CNNs by learning parameter-efficient representation.

The COVID-19 pandemic continues to spread rapidly over the world and causes a tremendous crisis in global human health and the economy. Its early detection and diagnosis are crucial for controlling the further spread. Many deep learning-based methods have been proposed to assist clinicians in automatic COVID-19 diagnosis based on computed tomography imaging. However, challenges still remain, including low data diversity in existing datasets, and unsatisfied detection resulting from insufficient accuracy and sensitivity of deep learning models. To enhance the data diversity, we design augmentation techniques of incremental levels and apply them to the largest open-access benchmark dataset, COVIDx CT-2A. Meanwhile, similarity regularization (SR) derived from contrastive learning is proposed in this study to enable CNNs to learn more parameter-efficient representations, thus improve the accuracy and sensitivity of CNNs. The results on seven commonly used CNNs demonstrate that CNN performance can be improved stably through applying the designed augmentation and SR techniques. In particular, DenseNet121 with SR achieves an average test accuracy of 99.44% in three trials for three-category classification, including normal, non-COVID-19 pneumonia, and COVID-19 pneumonia. The achieved precision, sensitivity, and specificity for the COVID-19 pneumonia category are 98.40%, 99.59%, and 99.50%, respectively. These statistics suggest that our method has surpassed the existing state-of-the-art methods on the COVIDx CT-2A dataset. Source code is available at https://github.com/YujiaKCL/COVID-CT-Similarity-Regularization.

Research advances on the contamination of vegetables by Enterohemorrhagic Escherichia coli: pathways, processes and interaction.

Enterohemorrhagic Escherichia coli is considered one of the primary bacterial pathogens that cause foodborne diseases because it can survive in meat, vegetables and so on. Understanding of the effect of vegetable characteristics on the adhesion and proliferation process of EHEC is necessary to develop control measures. In this review, the amount and methods of adhesion, the internalization pathway and proliferation process of EHEC have been described during the vegetable contamination. Types, cultivars, tissue characteristics, leaf age, and damage degree can affect EHEC adhesion on vegetables. EHEC cells contaminate the root surface of vegetables through soil and further internalize. It can also contaminate the stem scar tissue of vegetables by rain or irrigation water and internalize the vertical axis, as well as the stomata, necrotic lesions and damaged tissues of vegetable leaves. After EHEC adhered to the vegetables, they may further proliferate and form biofilms. Leaf and fruit tissues were more sensitive to biofilm formation, and shedding rate of biofilms on epidermis tissue was faster. Insights into the mechanisms of vegetable contamination by EHEC, including the role of exopolysaccharides and proteins responsible for movement, adhesion and oxidative stress response could reveal the molecular mechanism by which EHEC contaminates vegetables.

A case of a pregnant woman with a special splenic artery aneurysm.

Visceral artery aneurysm, especially splenic artery aneurysm, is rare and is usually associated with pregnancy. When such aneurysms rupture, they can be fatal, and they often require emergency surgery. This case report includes a review of the literature and describes a effective multidisciplinary approach to managing this type of aneurysm. We describe the treatment of a ruptured splenic artery aneurysm and the careful coordination of obstetric, vascular surgery, and intensive care teams. The uniqueness of this case arose from the metal embolization coil that was found to have fallen off from a recently embolized ruptured splenic artery aneurysm. The management of this ruptured splenic artery aneurysm and iatrogenic foreign body insult required a combination of multiple specialties to provide life-saving treatment. Such cases should be managed by multidisciplinary teams if institutional resources allow for it.

Segment-Long-Spacing (SLS) and the Polymorphic Structures of Fibrillar Collagen.

The diverse and complex functions of collagen during the development of an organism are closely related to the polymorphism of its supramolecular structures in the extracellular matrix. SLS (segment-long-spacing) is one of the best understood alternative structures of collagen. SLS played an instrumental role in the original studies of collagen more than half a century ago that laid the foundation of nearly everything we know about collagen today. Despite being used mostly under in vitro conditions, the natural occurrence of SLS in tissues has also been reported. Here we will provide a brief overview of the major findings of the SLS and other structures of collagen based on a wealth of work published starting from the 1940s. We will discuss the factors that determine the stability and the structural specificity of the different molecular assemblies of collagen in light of the new studies using designed fibril forming collagen peptides. At the end of the chapter, we will summarize some recent discoveries of the alternative structures of collagen in tissues, especially those involved in pathogenic states. A revisit of SLS will likely inspire new understandings concerning the range of critical roles of fibrillar collagen in terms of its organizational diversity in the extracellular matrix.

Induction of zinc finger protein RNF6 auto-ubiquitination for the treatment of myeloma and chronic myeloid leukemia.

The zinc finger ubiquitin ligase RNF6 has been proposed as a potential therapeutic target in several cancers, but understanding its molecular mechanism of degradation has been elusive. In the present study, we find that RNF6 is degraded via auto-ubiquitination in a manner dependent on its Really Interesting New Gene (RING) domain. We determine that when the RING domain is deleted (ΔRING) or the core cysteine residues in the zinc finger are mutated (C632S/C635S), the WT protein, but not the ΔRING or mutant RNF6 protein, undergoes polyubiquitination. We also identify USP7 as a deubiquitinase of RNF6 by tandem mass spectrometry. We show that USP7 interacts with RNF6 and abolishes its K48-linked polyubiquitination, thereby preventing its degradation. In contrast, we found a USP7-specific inhibitor promotes RNF6 polyubiquitination, degradation, and cell death. Furthermore, we demonstrate the anti-leukemic drug Nilotinib and anti-myeloma drug Panobinostat (LBH589) induce RNF6 K48-linked polyubiquitination and degradation in both multiple myeloma (MM) and leukemia cells. In agreement with our hypothesis on the mode of RNF6 degradation, we show these drugs promote RNF6 auto-ubiquitination in an in vitro ubiquitination system without other E3 ligases. Consistently, reexpression of RNF6 ablates drug-induced MM and leukemia cell apoptosis. Therefore, our results reveal that RNF6 is a RING E3 ligase that undergoes auto-ubiquitination, which could be abolished by USP7 and induced by anti-cancer drugs. We propose that chemical induction of RNF6 auto-ubiquitination and degradation could be a novel strategy for the treatment of hematological malignancies including MM and leukemia.

Antagonistic activity of selenium-enriched Bifidobacterium breve against Clostridioides difficile.

Probiotics have the potential to be used in the prevention of Clostridioides difficile infection (CDI). In this study, selenium (Se)-enriched Bifidobacterium breve YH68-Se was obtained under optimal culture conditions with single-factor and response surface optimization. The overall environmental resistance of YH68-Se was superior to that of the parental strain YH68, mainly reflected in the substantial improvement of antioxidant activity and gastrointestinal tolerance. YH68-Se dramatically inhibited C. difficile growth, spore, biofilm, toxin production, and virulence gene expression, rapidly disrupted C. difficile cell membrane permeability and integrity, and altered the membrane proton motive force (PMF), induced a large outflow of intracellular substances and eventually caused bacterial death. The main factor inducing this process originated from the lactic acid (LD) in YH68-Se. In addition, the LD production of YH68 increased with increasing selenite concentration and was accompanied by enhanced activities of thioredoxin reductase (TrxR), glutathione peroxidase (GSH-Px), and increased concentration of autoinducer-2 (AI-2), which may be the crucial factors contributing to the outstanding probiotic properties of YH68-Se and their potent antagonism of C. difficile. KEY POINTS: • Compared with the parental strain B. breve YH68, the environmental resistance of YH68-Se was improved. • YH68-Se was able to produce more lactic acid, which suppressed the important physiological activities of C. difficile and rapidly disrupted their cell membrane structures. • Sodium selenite in the suitable concentration range gradually increases the yield of lactic acid and phenylacetic acid, increased the concentration of autoinducer-2, and enhanced the activities of antioxidant enzymes TrxR and GSH-Px in YH68.