Ubiquitin-specific protease 22 ameliorates chronic alcohol-associated liver disease by regulating BRD4

USP22 promotes angiotensin II-induced podocyte injury by deubiquitinating and stabilizing HMGB1

BACKGROUND

Chronic kidney disease (CKD) remains a significant global health burden, with hypertensive nephropathy (HN) as one of its primary causes. Podocyte injury is a key factor in the progression of CKD. However, the molecular mechanisms underlying angiotensin II-induced podocyte injury remain incompletely understood. Ubiquitin-specific protease 22 (USP22) has been reported to facilitate a range of cellular processes, including cell proliferation and apoptosis. However, the role of USP22 in HN pathogenesis is unclear.

METHODS

The expression of USP22 was assessed in kidney samples from hypertensive nephropathy patients, angiotensin II-induced hypertensive nephropathy mouse models, and cultured podocytes treated with angiotensin II. Podocyte-specific USP22 knockout mice were used to investigate the effects of USP22 deletion on podocyte injury and inflammation.

RESULTS

USP22 expression was significantly upregulated in kidneys of HN patients, angiotensin II-induced mouse models, and cultured podocytes. Podocyte-specific deletion of USP22 markedly reduced angiotensin II-induced podocyte injury and inflammatory responses. Furthermore, we identified high-mobility group box protein 1 (HMGB1) as a protein that interacts with USP22. USP22 deubiquitinated and stabilized HMGB1 through K48-linked ubiquitination. Downregulation of USP22 expression improved kidney function and pathological changes in HN by promoting HMGB1 degradation.

CONCLUSION

This study identifies USP22 as a key regulator of angiotensin II-induced podocyte injury and inflammation through its interaction with HMGB1. Our findings revealed that following glomerular injury, damage and shedding of tubular cells also occurred. Targeting the USP22-HMGB1 axis offers a promising therapeutic strategy for treating hypertensive nephropathy and other types of CKD.

USP22/BRD4 mediated hedgehog pathway activation contributes to airway remodeling in asthma

Bromodomain-containing protein 4 (BRD4) is recognized as a member of the bromodomain and extraterminal (BET) family that is involved in the airway inflammation and airway remodeling of asthma. However, the underlying mechanisms of BRD4 in airway smooth muscle cells (ASMCs) proliferation and airway remodeling remain unclear. Primary cultured rat ASMCs and ovalbumin (OVA)-induced rat asthma models were applied to address these issues in the present study. We showed that transforming growth factor β1 (TGF-β1) increased the protein expression of ubiquitin specific peptidase 22 (USP22), which deubiquitinated BRD4 therefore increased its expression, and then resulted in the upregulation of glioma-associated oncogene homolog 1 (GLI1) and osteopontin (OPN) leading to ASMCs proliferation. We further confirmed that induction of TGF-β1 sequentially upregulated USP22, BRD4, GLI1 and OPN leading to airway remodeling in OVA-induced rat asthma models, targeting TGF-β1/USP22/BRD4/GLI1/OPN pathway axis effectively attenuated airway remodeling and asthma development. Our study provides novel sights to understand the role of TGF-β1/USP22/BRD4/GLI1/OPN axis in airway remodeling, and targeting this pathway might have potential value for the prevention and treatment of asthma.

Targeted Degradation of Bromodomain-Containing Protein 4 Enabled by Reactive Oxygen Species-Activatable NanoPROTACs as an Efficient Strategy to Reverse Liver Fibrosis in Chronic Liver Injury

Liver fibrosis is an inadequate response to tissue stress, with reactive oxygen species (ROS) overproduction in activated hepatic stellate cells (aHSCs). Bromodomain-containing protein 4 (BRD4) was found to be upregulated in aHSCs and has been identified as an effective target for the treatment of liver fibrosis. However, inhibition of BRD4 with traditional kinase inhibitors achieved only limited success because of its low therapeutic efficiency. Furthermore, the exact mechanism by which BRD4 regulates liver fibrosis remains unclear and needs to be elucidated. In this work, we proposed an efficiency strategy, i.e., targeted degradation of BRD4 by ROS-activatable NanoPROTACs, for the treatment of liver fibrosis, both in vitro and in vivo. More importantly, we clarified the mechanism by which BRD4 regulates liver fibrosis. Thus, this strategy may represent an alternative to previously reported strategies and may be extensively applied to the design of ROS-activatable proteolysis-targeting chimeras for the treatment of other organ fibrosis.

Probiotics isolated from the fermented grains of Chinese baijiu alleviate alcohol-induced liver injury by regulating alcohol metabolism and the gut microbiota in mice

Alcoholic liver disease is one of the diseases with a high mortality rate worldwide, resulting from excessive and chronic alcohol consumption. With the rapid rise of intestinal microbial research, more and more researchers have begun to focus on the role of probiotics in preventing, alleviating or treating diseases. In this study, effects of lactic acid bacteria (LAB), a general type of probiotic, isolated from the fermented grains of Chinese baijiu, on alcohol-induced liver injury and alcohol metabolism were investigated, and the results showed that Lactiplantibacillus pentosus LTJ12, Pediococcus acidilactici LTJ28, Lactiplantibacillus plantarum LTJ30, and Pediococcus acidilactici LTJ32 could prevent drunkenness and sober up, and had a good protective effect on alcoholic liver injury. These LAB, especially Lactiplantibacillus, can reduce the drunken rate and mortality of drinking mice, shorten the sobriety time, decrease the content of ethanol in serum, reduce the activity or content of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), triglyceride (TG) and malondialdehyde (MDA), increase the activity or content of superoxide dismutase (SOD), glutathione (GSH) and nitric oxide (NO), and also improve the activity of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) of the liver. The LAB intervention basically reversed the changes in the mRNA levels of genes related to ethanol/drug metabolism (CYP2E1, ADH1 and ALDH2), antioxidant markers (SOD2 and CAT), cellular inflammation, apoptosis and proliferation (SIRT1, SMYD3 and BRD4) and lipid metabolism (SREBP1 and FASn). In addition, we have found that the regulatory effect of these probiotics may be related to the SMYD3/BRD4 pathway, which needs further detailed research. Besides, the probiotics increased the abundance of gut microbes, restored the imbalance of the intestinal flora caused by alcohol consumption, and regulated the changes in the intestinal short-chain fatty acid content caused by chronic alcohol consumption. These results suggested that these baijiu-derived probiotics can effectively prevent drunkenness and chronic alcoholic liver injury. It is of great significance to provide scientific basis for subsequent research and development of new anti-alcoholism health products based on probiotics and the intestinal microecological regulation mechanism.

BRISC inactivation alleviates alcohol-induced liver injury in mice

BRCC3 isopeptidase complex (BRISC) is a JAMM subfamily deubiquitinase that has been revealed to be required for optional activation of NLRP3 inflammasome and TLR4/NF-κB signaling pathway. BRISC plays an important role in lipopolysaccharide (LPS)/D-galactosamine-induced acute liver failure, while its functional contribution to alcoholic liver disease (ALD) is still unclear. In this study, we found that the expression of BRISC components was increased in liver tissues of alcoholic hepatitis (AH) animal models and patients with AH. Mice lacking either the scaffold subunit ABRO1 or the catalytic subunit BRCC3 showed attenuated liver steatosis, inflammation, and liver injury compared to control mice after chronic plus binge ethanol feeding. Moreover, pharmacological inhibition of BRISC activity by a BRISC inhibitor thiolutin potently protected mice from ALD development. Preliminary mechanistical studies showed that BRISC deficiency did not directly affect alcohol-induced hepatocyte injury or the translocation of LPS through the damaged gut mucosa after ethanol feeding, but prevented alcohol-induced NLRP3 inflammasome activation in liver. Collectively, our work revealed a previously unknown role of BRISC in ALD and suggested that BRISC may serve as a promising therapeutic target for ALD treatment.

Involvement of BRD4 in Alcoholic Liver Injury: Autophagy Modulation via Regulation of the SIRT1/Beclin1 Axis

Alcoholic liver disease (ALD) caused by chronic alcohol abuse involves complex processes from steatosis to fibrosis, cirrhosis, and hepatocellular carcinoma, posing a global health issue. Bromodomain protein 4 (BRD4) typically serves as a "reader" modulating the functions of transcription factors involved in various biological processes and disease progression. However, the specific mechanisms underlying alcoholic liver injury remain unclear. In this study, we detected aberrant BRD4 expression in the alcohol-induced ALD mouse model of chronic and binge ethanol feeding developed by the National Institute on Alcohol Abuse and Alcoholism, consistent with the in vitro results in Aml-12 mouse hepatocytes. Blocking and inhibiting BRD4 restored the impaired autophagic flux and lysosomal functions in alcohol-treated Aml-12 cells, whereas BRD4 overexpression reduced the expression levels of autophagy marker and lysosomal genes. Furthermore, mouse BRD4 knockdown, mediated by a short hairpin RNA carried by the adeno-associated virus serotype 8, significantly attenuated the alcohol-induced hepatocyte damage, including lipid deposition and inflammatory cell infiltration. Mechanistically, BRD4 overexpression in alcoholic liver injury inhibited the expression of sirtuin (SIRT)1 in Aml-12 cells. Chromatin immunoprecipitation and dual-luciferase reporter assays revealed that BRD4 functions as a transcription factor and suppressor, actively binding to the SIRT1 promoter region and inhibiting its transcription. SIRT1 activated autophagy, which was suppressed in alcoholic liver injury via Beclin1 deacetylation. In conclusion, our study revealed that BRD4 negatively regulated the SIRT1/Beclin1 axis and that its deficiency alleviated alcohol-induced liver injury in mice, thus providing a new strategy for ALD treatment.

BRD4: an effective target for organ fibrosis

Fibrosis is an excessive wound-healing response induced by repeated or chronic external stimuli to tissues, significantly impacting quality of life and primarily contributing to organ failure. Organ fibrosis is reported to cause 45% of all-cause mortality worldwide. Despite extensive efforts to develop new antifibrotic drugs, drug discovery has not kept pace with the clinical demand. Currently, only pirfenidone and nintedanib are approved by the FDA to treat pulmonary fibrotic illness, whereas there are currently no available antifibrotic drugs for hepatic, cardiac or renal fibrosis. The development of fibrosis is closely related to epigenetic alterations. The field of epigenetics primarily studies biological processes, including chromatin modifications, epigenetic readers, DNA transcription and RNA translation. The bromodomain and extra-terminal structural domain (BET) family, a class of epigenetic readers, specifically recognizes acetylated histone lysine residues and promotes the formation of transcriptional complexes. Bromodomain-containing protein 4 (BRD4) is one of the most well-researched proteins in the BET family. BRD4 is implicated in the expression of genes related to inflammation and pro-fibrosis during fibrosis. Inhibition of BRD4 has shown promising anti-fibrotic effects in preclinical studies; however, no BRD4 inhibitor has been approved for clinical use. This review introduces the structure and function of BET proteins, the research progress on BRD4 in organ fibrosis, and the inhibitors of BRD4 utilized in fibrosis. We emphasize the feasibility of targeting BRD4 as an anti-fibrotic strategy and discuss the therapeutic potential and challenges associated with BRD4 inhibitors in treating fibrotic diseases.

The P53-P21-RB1 pathway promotes BRD4 degradation in liver cancer through USP1

Liver cancer is notoriously refractory to conventional therapeutics. Tumor progression is governed by the interplay between tumor-promoting genes and tumor-suppressor genes. BRD4, an acetyl lysine-binding protein, is overexpressed in many cancer types, which promotes activation of a pro-tumor gene network. But the underlying mechanism for BRD4 overexpression remains incompletely understood. In addition, understanding the regulatory mechanism of BRD4 protein level will shed insight into BRD4-targeting therapeutics. In this study, we investigated the potential relation between BRD4 protein level and P53, the most frequently dysregulated tumor suppressor. By analyzing the TCGA datasets, we first identify a strong negative correlation between protein levels of P53 and BRD4 in liver cancer. Further investigation shows that P53 promotes BRD4 protein degradation. Mechanistically, P53 indirectly represses the transcription of USP1, a deubiquitinase, through the P21-RB1 axis. USP1 itself is also overexpressed in liver cancer and we show USP1 deubiquitinates BRD4 in vivo and in vitro, which increases BRD4 stability. With cell proliferation assays and xenograft model, we show the pro-tumor role of USP1 is partially mediated by BRD4. With functional transcriptomic analysis, we find the USP1-BRD4 axis upholds expression of a group of cancer-related genes. In summary, we identify a functional P53-P21-RB1-USP1-BRD4 axis in liver cancer.

FXR overexpression prevents hepatic steatosis through inhibiting AIM2 inflammasome activation in alcoholic liver disease

BACKGROUND AND PURPOSE

Alcoholic liver disease (ALD), a metabolic liver disease caused by excessive alcohol consumption, has attracted increasing attention due to its high prevalence and mortality. Up to date, there is no effective and feasible treatment method for ALD. This study was to investigate whether Farnesoid X receptor (FXR, NR1H4) can alleviate ALD and whether this effect is mediated by inhibiting absent in melanoma 2 (AIM2) inflammasome activation.

METHODS

The difference in FXR expression between normal subjects and ALD patients was analyzed using the Gene Expression Omnibus (GEO) database. Lieber-DeCarli liquid diet with 5% ethanol (v/v) (EtOH) was adopted to establish the mouse ALD model. Liver histopathological changes and the accumulation of lipid droplets were assessed by H&E and Oil Red O staining. Quantitative real-time PCR, Western blotting analysis and immunofluorescence staining were utilized to evaluate the expression levels of related genes and proteins. DCFH-DA staining was adopted to visualize reactive oxidative species (ROS).

RESULTS

FXR was distinctly downregulated in liver tissues of patients with steatosis compared to normal livers using the GEO database, and in ethanol-induced AML-12 cellular steatosis model. FXR overexpression ameliorated hepatic lipid metabolism disorder and steatosis induced by ethanol by inhibiting the expression of genes involved in lipid synthesis and inducing the expression of genes responsible for lipid metabolism. Besides, FXR overexpression inhibited ethanol-induced AIM2 inflammasome activation and alleviated oxidative stress and ROS production during ethanol-induced hepatic steatosis. However, when FXR was knocked down, the results were completely opposite.

CONCLUSIONS

FXR attenuated lipid metabolism disorders and lipid degeneration in alcohol-caused liver injury and alleviated oxidative stress and inflammation by inhibiting AIM2 inflammasome activation.

Targeted therapy based on ubiquitin-specific proteases, signalling pathways and E3 ligases in non-small-cell lung cancer

Lung cancer is one of the most common malignant tumours worldwide, with the highest mortality rate. Approximately 1.6 million deaths owing to lung cancer are reported annually; of which, 85% of deaths occur owing to non-small-cell lung cancer (NSCLC). At present, the conventional treatment methods for NSCLC include radiotherapy, chemotherapy, targeted therapy and surgery. However, drug resistance and tumour invasion or metastasis often lead to treatment failure. The ubiquitin–proteasome pathway (UPP) plays an important role in the occurrence and development of tumours. Upregulation or inhibition of proteins or enzymes involved in UPP can promote or inhibit the occurrence and development of tumours, respectively. As regulators of UPP, ubiquitin-specific proteases (USPs) primarily inhibit the degradation of target proteins by proteasomes through deubiquitination and hence play a carcinogenic or anticancer role. This review focuses on the role of USPs in the occurrence and development of NSCLC and the potential of corresponding targeted drugs, PROTACs and small-molecule inhibitors in the treatment of NSCLC.