USP25 Deficiency Exacerbates Acute Pancreatitis via Up-Regulating TBK1-NF-κB Signaling in Macrophages

Annexin A1 regulates inflammatory-immune response and reduces pancreatic and extra- pancreatic injury during severe acute pancreatitis

Severe acute pancreatitis (SAP) poses significant challenges due to its complex pathophysiology, which includes inflammatory-immune responses that cause considerable damage to both the pancreas and other tissues. In this study, we explored the role of Annexin A1 (Anxa1), a glucocorticoid-regulated protein recognized for its anti-inflammatory properties, in regulating inflammation during acute pancreatitis. Using flow cytometry, single-cell RNA sequencing, and gene expression analysis, we examined how Anxa1 expression is regulated in myeloid cells throughout acute pancreatitis, employing various animal models to evaluate the consequences of modulating Anxa1 on injuries induced by SAP. Our findings revealed dynamic regulation of Anxa1 expression in myeloid cells, with mice lacking Anxa1 exhibiting worsened pancreatic injury and heightened systemic inflammation, resulting in significant damage to extra-pancreatic organs such as the lungs, liver, and kidneys. In contrast, treatment with Ac2-26, a synthetic peptide derived from Anxa1, effectively mitigated both pancreatic and extra-pancreatic inflammation and tissue damage. Overall, this study highlights the critical role of Anxa1 in modulating inflammatory responses during acute pancreatitis. Targeting Anxa1 presents a promising therapeutic strategy to mitigate pancreatic injury and prevent systemic complications associated with severe acute pancreatitis.

Macrophage-mimicking nanotherapy for attenuation of acute pancreatitis

Acute pancreatitis (AP) is a highly fatal pancreatic inflammation. In recent years, synthetic nanoparticles have been extensively developed as drug carriers to address the challenges of systemic adverse reactions and lack of specificity in drug delivery. However, systemically administered nanoparticle therapy is rapidly cleared from circulation by the mononuclear phagocyte system (MPS), leading to suboptimal drug concentrations in inflamed tissues and suboptimal pharmacokinetics. To address this challenge, we herein demonstrate a surface masking strategy that involves coating the surface of selenylated Poria cocos polysaccharide nanoparticles with a layer of macrophage plasma membrane to circumvent MPS sequestration, thereby enhancing the therapeutic efficacy of selenylated Poria cocos polysaccharide nanoparticles. Nanoparticles encapsulated with macrophage membranes can simulate the active homing efficacy of macrophages to inflamed lesions during AP, resulting in excessive infiltration of macrophages in pancreatic inflammation sites and prolonged tissue retention time. This technique converts non-adhesive lipid nanoparticles into bioadhesive nanoparticles, increasing local tissue accumulation under inflammatory conditions, including the pancreas and vulnerable lungs. The mechanism is related to targeting pro-inflammatory macrophages. In murine models of mild and severe AP, intravenous treatment with macrophage-mimicking nanoparticles effectively reduces systemic inflammation level and diminishes the recruitment of macrophages and neutrophils. Mechanistic studies elucidate that macrophage membrane-biomimetic selenylated Poria cocos polysaccharide nanoparticles primarily mitigate pancreatic inflammation by inhibiting the AKT/mTOR pathway to reverse autophagic flux impairment. This allows us to envision that the developed biomimetic nanotherapy approach could potentially serve as a novel strategy for pancreatic drug therapy.

Ubiquitin-specific protease 25 improves myocardial ischemia-reperfusion injury by deubiquitinating NLRP3 and negatively regulating NLRP3 inflammasome activity in cardiomyocytes

BACKGROUND

Myocardial ischemia/reperfusion injury (MI/RI) restricts the effect of myocardial reperfusion therapy and lacks effective prevention and treatment methods. Deubiquitinating enzymes (DUBs), especially members of the ubiquitin-specific protease (USP) family of DUBs, are key proteins in the ubiquitination modification process and play a vital role in MI/RI. Therefore, we aimed to investigate the role of USP25, as a member of the USP family, in MI/RI and its molecular mechanism.

METHODS

Transcriptome sequencing was applied to evaluate the differential expression of USP families during hypoxia/reoxygenation (H/R) and validated in human and mouse heart samples and cardiomyocytes by performing quantitative polymerase chain reaction. Wild-type or USP25-/- mice were used to develop the MI/RI model. Co-immunoprecipitation (Co-IP) combined with liquid chromatography-tandem mass spectrometry analysis was used to screen the potential substrate protein of USP25 in H/R-induced cardiomyocyte injury. TUNEL and Hoechst/propidium iodide staining and western blot were used to detect the level of pyroptosis. In addition, cardiomyocyte-specific USP25 overexpression in NLRP3-/- mice with AAV9 vectors was used to validate the biological function of USP25 and NLRP3 interaction.

RESULTS

We found that the expression level of USP25 was significantly decreased in I/R-induced mouse heart tissues and primary cardiomyocytes in a time-dependent manner. USP25 deficiency exacerbated MI/RI and aggravated I/R-induced cardiac remodelling in mice. Mechanistically, USP25 directly binds to NLRP3 protein and K63-linkedly deubiquitinates NLRP3 at residue K243 via its active site C178, thus hindering NLRP3-ASC interaction and ASC oligomerization to inhibit NLRP3 activation and pyroptosis in cardiomyocytes. We further showed that the overexpression of USP25 in cardiomyocytes ameliorated MI/RI in mice, whereas this protective effect disappeared when NLRP3 is knocked out.

CONCLUSIONS

Our study demonstrated that USP25 ameliorates MI/RI by regulating NLRP3 activation and its mediated pyroptosis. This finding extends the protective role of USP25 in cardiovascular disease and provides an experimental basis for future USP25-based drug development for the treatment of MI/RI.

KEY POINTS

The deubiquitinating enzyme USP25 was down-regulated both in myocardial ischemia/reperfusion injury (MI/RI) myocardium tissues. The deficiency of USP25 worsened exacerbated MI/RI in mice, whereas the overexpression of USP25 in cardiomyocytes mitigated this pathological phenotype. USP25 directly interacts with the NLRP3 protein and deubiquitinates it via K63 linkage at residue K243 through its active site C178, thus affecting NLRP3-ASC interaction and ASC oligomerization to inhibit NLRP3 activation and pyroptosis in cardiomyocytes.

Targeting deubiquitinating enzymes (DUBs) and ubiquitin pathway modulators to enhance host defense against bacterial infections

The rise of antibiotic-resistant bacterial pathogens poses a critical global health challenge, necessitating innovative therapeutic approaches. This study explores host-targeted therapies (HTTs) by focusing on deubiquitinating enzymes (DUBs), essential modulators of the ubiquitin-proteasome system (UPS) that regulate host-pathogen interactions during many bacterial infections. Using Salmonella-infected macrophages as a model, we identified UPS modulators that enhance bacterial clearance and observed significant changes in DUB expression, particularly USP25, USP46, and Otud7b. The small-molecule DUB inhibitor AZ-1 significantly reduced intracellular bacterial loads in vitro and mitigated early disease severity in a murine model by decreasing fecal bacterial loads and preserving host weight. However, AZ-1 alone did not achieve complete clearance of Salmonella and required combination with extracellular-targeting antibiotics for optimal efficacy. Notably, AZ-1 demonstrated broad-spectrum activity against multidrug-resistant pathogens, including Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Transcriptomic analyses revealed infection-induced DUB regulation and highlighted pathways modulating immune responses, including TNF-α secretion. These findings highlight the potential of targeting the UPS as a host-directed antimicrobial strategy and provide a foundation for developing innovative therapies to combat antimicrobial resistance.

RNF128 deficiency in macrophages promotes colonic inflammation by suppressing the autophagic degradation of S100A8

Macrophages play important roles in maintaining intestinal homeostasis and in the pathogenesis of inflammatory bowel diseases (IBDs). However, the underlying mechanisms that govern macrophage-mediated inflammation are still largely unknown. In this study, we report that RNF128 is downregulated in proinflammatory macrophages. RNF128 deficiency leads to elevated levels of effector cytokines in vitro and accelerates the progression of IBD in mouse models. Bone marrow transplantation experiments revealed that RNF128 deficiency in bone marrow cells contributes to the worsening of DSS-induced colitis. Mechanistically, RNF128 interacts with and destabilizes S100A8 by promoting its autophagic degradation, which is mediated by the cargo receptor Tollip. Moreover, the administration of an S100A8 neutralizing antibody mitigated the development of colitis and improved survival in DSS-treated Rnf128-/- mice. Overall, our study underscores the anti-inflammatory role of RNF128 in macrophages during the progression of colitis and highlights the potential of targeting the RNF128-Tollip-S100A8 axis to attenuate intestinal inflammation for the treatment of colitis.

Clinical effects of phospholipase D2 in attenuating acute pancreatitis

BACKGROUND

The objective of the current study was to elucidate the clinical mechanism through which phospholipase D2 (PLD2) exerted a regulatory effect on neutrophil migration, thereby alleviating the progression of acute pancreatitis.

AIM

To elucidate the clinical mechanism through which PLD2 exerted a regulatory effect on neutrophil migration, thereby alleviating the progression of acute pancreatitis.

METHODS

The study involved 90 patients diagnosed with acute pancreatitis, admitted to our hospital between March 2020 and November 2022. A retrospective analysis was conducted, categorizing patients based on Ranson score severity into mild (n = 25), moderate (n = 30), and severe (n = 35) groups. Relevant data was collected for each group. Western blot analysis assessed PLD2 protein expression in patient serum. Real-time reverse transcription polymerase chain reaction was used to evaluate the mRNA expression of chemokine receptors associated with neutrophil migration. Serum levels of inflammatory factors in patients were detected using enzyme-linked immunosorbent assay. Transwell migration tests were conducted to compare migration of neutrophils across groups and analyze the influence of PLD2 on neutrophil migration.

RESULTS

Overall data analysis did not find significant differences between patient groups (P > 0.05). The expression of PLD2 protein in the severe group was lower than that in the moderate and mild groups (P < 0.05). The expression level of PLD2 in the moderate group was also lower than that in the mild group (P < 0.05). The severity of acute pancreatitis is negatively correlated with PLD2 expression (r = -0.75, P = 0.002). The mRNA levels of C-X-C chemokine receptor type 1, C-X-C chemokine receptor type 2, C-C chemokine receptor type 2, and C-C chemokine receptor type 5 in the severe group are significantly higher than those in the moderate and mild groups (P < 0.05), and the expression levels in the moderate group are also higher than those in the mild group (P < 0.05). The levels of C-reactive protein, tumor necrosis factor-α, interleukin-1β, and interleukin-6 in the severe group were higher than those in the moderate and mild groups (P < 0.05), and the levels in the moderate group were also higher than those in the mild group (P < 0.05). The number of migrating neutrophils in the severe group was higher than that in the moderate and mild groups (P < 0.05), and the moderate group was also higher than the mild group (P < 0.05). In addition, the number of migrating neutrophils in the mild group combined with PLD2 inhibitor was higher than that in the mild group (P < 0.05), and the number of migrating neutrophils in the moderate group combined with PLD2 inhibitor was higher than that in the moderate group (P < 0.05). The number of migrating neutrophils in the severe group + PLD2 inhibitor group was significantly higher than that in the severe group (P < 0.05), indicating that PLD2 inhibitors significantly stimulated neutrophil migration.

CONCLUSION

PLD2 exerted a crucial regulatory role in the pathological progression of acute pancreatitis. Its protein expression varied among patients based on the severity of the disease, and a negative correlation existed between PLD2 expression and disease severity. Additionally, PLD2 appeared to impede acute pancreatitis progression by limiting neutrophil migration.

ATP citrate lyase ablation hampers exocrine regeneration via TLR4/NF-kappaB signaling after acute pancreatitis in mice

BACKGROUND

ATP citrate lyase (Acly) is widely expressed in many tissues, has been proved to be involved in the pathogenesis of many inflammatory diseases. So far, the importance of Acly in acute pancreatitis(AP) has not been clearly determined. The purpose of this study is to clarify whether Acly can evoke inflammatory cascades in the progression of AP and hamper the subsequent regeneration process of pancreas.

METHODS

Experimental pancreatitis in mice with a specific deficiency of Acly in the pancreas and in control mice through repetitive cerulein injections in vivo. The pancreas pathological grading, cell proliferative potential and the formation of acinar-to-ductal metaplasia (ADM) were evaluated. The levels of inflammatory cytokines in plasma were qualified by enzyme-linked immuno sorbent assay (ELISA). Pancreatic malondialdehyde (MDA), superoxide dismutase (SOD) activity and reduced glutathione (GSH) contents were measured for oxidative stress. The infiltration of macrophages and neutrophils, the expression of Toll like receptor 4 (TLR4), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and the activation of nuclear factor kappaB (NF-κB) and cleaved Caspase-3, were measured using immunostaining. The mRNA transcription levels of TLR4, TNF-α, and IL-1β in pancreatic tissues were detected by quantitative real-time PCR as well. Additionally, inhibition of TLR4 signaling by TAK-242 in AP mice with a pancreas-specific deletion of Acly was conducted in vivo.

RESULTS

The results demonstrated that the elimination of pancreatic Acly not only exacerbated the severity of pancreatitis in mice during the initial inflammatory phase, as evidenced by more severe pathological damage, but also impeded the healing process of the exocrine pancreas by enhancing the formation of ADM and decreasing the ability of acinar cells to proliferate. In addition, deficiency of Acly increased the circulating TNF-α, IL-1β and IL-6, the infiltration of macrophages and neutrophils, agumented the activation of nuclear factor kappaB (NF-κB) p65, the expression of TLR4, TNF-α, IL-1β and cleaved Caspase-3, and exacerbated excessive oxidative stress in the pancreas at specific time points of AP mice. However, TLR4 inhibition significantly attenuated the structural and functional damage of the pancreas induced by AP in mice with a pancreas-specific deletion of Acly, as indicated by improvement of the above indexes.

CONCLUSIONS

The present study demonstrated that ablation of pancreatic Acly intensified inflammatory reaction and cell death, and dampened exocrine regeneration following AP, due to the positive regulation of TLR4/NF-κB signaling activation.

Micheliolide ameliorates severe acute pancreatitis in mice through potentiating Nrf2-mediated anti-inflammation and anti-oxidation effects

Severe acute pancreatitis (SAP) is an acute inflammatory injury disease with significant mortality rate and currently without effective strategy being available. Inflammation and oxidative stress play central roles in the etiology of SAP. Micheliolide (MCL), an active monomeric component isolated from Michelia champaca, has been proved its multiple therapeutic properties including anti-inflammatory, antioxidant and anti-cancer. Nevertheless, the therapeutic effect and underlying mechanism of MCL in SAP still remain unclear. Here, we found that caerulein with lipopolysaccharide (LPS)-induced SAP murine models exhibited severe pancreatic injury, including necrosis, edema, and vacuolation of acinar cells in the pancreas, elevated serum levels of amylase and lipase, and reduced number of the exocrine cells. As expected, MCL treatment alleviated these side effects. Mechanistically, MCL triggered nuclear factor erythroid 2-related factor 2 (Nrf2) activation, thereby activating Nrf2-regulated antioxidative pathways and inhibiting nuclear factor kappa B p65 (NF-κB p65)-mediated inflammatory response, resulting in protection against pancreatic injury in SAP mice. In addition, Nrf2 gene deficiency abolished the beneficial effects of MCL on SAP-induced pancreatic inflammation and oxidative stress and blocked the ability of MCL to alleviate the pancreatic injury in SAP mice. Collectively, these findings indicated that the suppression of SAP-induced pancreatic injury by MCL was at least in part due to Nrf2-mediated anti-oxidation effect and inhibition of inflammation.

Identifying the ceRNA Regulatory Network in Early-Stage Acute Pancreatitis and Investigating the Therapeutic Potential of NEAT1 in Mouse Models

Purpose

Acute pancreatitis (AP) is a common digestive disorder characterized by high morbidity and mortality. This study aims to uncover differentially expressed long noncoding RNAs (lncRNAs) and mRNAs, as well as related pathways, in the early stage of acute pancreatitis (AP), with a focus on the role of Neat1 in AP and severe acute pancreatitis (SAP).

Methods

In this study, we performed high-throughput RNA sequencing on pancreatic tissue samples from three normal mice and three mice with cerulein-induced AP to describe and analyze the expression profiles of long non-coding RNAs (lncRNAs) and mRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted on the differentially expressed mRNAs to identify enriched pathways and biological processes. An lncRNA-miRNA-mRNA interaction network was constructed to elucidate potential regulatory mechanisms. Furthermore, we utilized Neat1 knockout mice to investigate the role of Neat1 in the pathogenesis of cerulein-AP and L-arginine-severe acute pancreatitis (SAP).

Results

Our results revealed that 261 lncRNAs and 1522 mRNAs were differentially expressed in the cerulein-AP group compared to the control group. GO and KEGG analyses of the differentially expressed mRNAs indicated that the functions of the corresponding genes are enriched in cellular metabolism, intercellular structure, and positive regulation of inflammation, which are closely related to the central events in the pathogenesis of AP. A ceRNA network involving 5 lncRNAs, 226 mRNAs, and 61 miRNAs were constructed. Neat1 was identified to have the potential therapeutic effects in AP. Neat1 knockout in mice inhibited pyroptosis in both the AP/SAP mouse models.

Conclusion

We found that lncRNAs, particularly Neat1, play a significant role in the pathogenesis of AP. This finding may provide new insights into further exploring the pathogenesis of SAP and could lead to the identification of new targets for the treatment of AP and SAP.

Structural basis for the bi-specificity of USP25 and USP28 inhibitors

The development of cancer therapeutics is often hindered by the fact that specific oncogenes cannot be directly pharmaceutically addressed. Targeting deubiquitylases that stabilize these oncogenes provides a promising alternative. USP28 and USP25 have been identified as such target deubiquitylases, and several small-molecule inhibitors indiscriminately inhibiting both enzymes have been developed. To obtain insights into their mode of inhibition, we structurally and functionally characterized USP28 in the presence of the three different inhibitors AZ1, Vismodegib and FT206. The compounds bind into a common pocket acting as a molecular sink. Our analysis provides an explanation why the two enzymes are inhibited with similar potency while other deubiquitylases are not affected. Furthermore, a key glutamate residue at position 366/373 in USP28/USP25 plays a central structural role for pocket stability and thereby for inhibition and activity. Obstructing the inhibitor-binding pocket by mutation of this glutamate may provide a tool to accelerate future drug development efforts for selective inhibitors of either USP28 or USP25 targeting distinct binding pockets.

The role of mitochondrial damage-associated molecular patterns in acute pancreatitis

Acute pancreatitis (AP) is one of the most common gastrointestinal tract diseases with significant morbidity and mortality. Current treatments remain unspecific and supportive due to the severity and clinical course of AP, which can fluctuate rapidly and unpredictably. Mitochondria, cellular power plant to produce energy, are involved in a variety of physiological or pathological activities in human body. There is a growing evidence indicating that mitochondria damage-associated molecular patterns (mtDAMPs) play an important role in pathogenesis and progression of AP. With the pro-inflammatory properties, released mtDAMPs may damage pancreatic cells by binding with receptors, activating downstream molecules and releasing inflammatory factors. This review focuses on the possible interaction between AP and mtDAMPs, which include cytochrome c (Cyt c), mitochondrial transcription factor A (TFAM), mitochondrial DNA (mtDNA), cardiolipin (CL), adenosine triphosphate (ATP) and succinate, with focus on experimental research and potential therapeutic targets in clinical practice. Preventing or diminishing the release of mtDAMPs or targeting the mtDAMPs receptors might have a role in AP progression.

Pyrazole derivative Z10 ameliorates acute pancreatitis by inhibiting the ERK/Ddt pathway

Acute pancreatitis (AP) can lead to death; however, there is no specific treatment for AP. Screening of drugs for AP treatment is rarely performed. Compounds were screened in a primary pancreatic acinar cell and peritoneal macrophage coculture system. Compounds were used in vitro and in vivo. Compound targets were predicted and validated. Among the 18 nitrogen-containing heterocycles, Z10 was shown to decrease the cerulein plus lipopolysaccharide (CL)-induced secretion of both acinar digestive enzymes and macrophage cytokines. Z10 was also shown to ameliorate CL-induced or sodium taurocholate-induced AP in mice. Proteomics analysis and enzyme linked immunosorbent assay (ELISA) revealed that Z10 decreased the levels of D-dopachrome tautomerase (Ddt) within macrophages and those in the extracellular milieu under CL treatment. Z10 also decreased Ddt expression in AP mice. Moreover, exogenous Ddt induced cytokine and digestive enzyme secretion, which could be inhibited by Z10. Ddt knockdown inhibited CL-induced cytokine secretion. Medium from CL-treated macrophages induced the release of amylase by acinar cells, and Ddt knockdown medium decreased amylase secretion. The target of Z10 was predicted to be ERK2. Z10 increased the thermostability of ERK1/2 but not ERK1 K72A/ERK2 K52A. The docking poses of ERK1 and ERK2 with Z10 were similar. Z10 inhibited ERK1/2 phosphorylation, and Ddt levels and cytokines were regulated by ERK1/2 during AP. Additionally, Z10 could not further inhibit cytokines under ERK1/2 knockdown with CL. Thus, this study revealed that Z10-mediated ERK1/2 inhibition decreased Ddt expression and secretion by macrophages. Ddt inhibition decreased cytokine release and digestive enzyme secretion.

Long non-coding RNA MM2P suppresses M1-polarized macrophages-mediated excessive inflammation to prevent sodium taurocholate-induced acute pancreatitis by blocking SHP2-mediated STAT3 dephosphorylation

M1 macrophage-mediated excessive inflammatory response plays a key role in the onset and progression of acute pancreatitis (AP), and this study aimed to investigate the role and underlying mechanisms by which the macrophage polarization-related long noncoding RNA (lncRNA) MM2P participated in the regulation of AP progression. By performing quantitative reverse-transcription PCR (qRT-PCR) assay, lncRNA MM2P was found to be downregulated in both sodium taurocholate-induced AP model mice tissues and lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and gain-of-function experiments confirmed that overexpression of lncRNA MM2P counteracted inflammatory responses, reduced macrophage infiltration and facilitated M1-to-M2 transformation of macrophages to ameliorate AP development in vitro and in vivo. Further mechanical experiments revealed that lncRNA MM2P inhibited Src homology 2 containing protein tyrosine phosphatase 2 (SHP2)-mediated signal transducer and activator of transcription 3 (STAT3) dephosphorylation to activate the STAT3 signaling, and silencing of SHP2 suppressed M1 type skewing in LPS-induced RAW264.7 cells. Interestingly, our rescuing experiments verified that lncRNA MM2P-induced suppressing effects on M1-polarization of LPS-treated RAW264.7 cells were abrogated by co-treating cells with STAT3 inhibitor stattic. Collectively, our data for the first time revealed that lncRNA MM2P suppressed M1-polarized macrophages to attenuate the progression of sodium taurocholate-induced AP, and lncRNA MM2P might be an ideal biomarker for AP diagnosis and treatment.

USP25 Inhibits Neuroinflammatory Responses After Cerebral Ischemic Stroke by Deubiquitinating TAB2

Cerebral ischemic stroke is a leading cause of morbidity and mortality globally. However, the mechanisms underlying ischemic stroke injury remain poorly understood. Here, it is found that deficiency of the ubiquitin-specific protease USP25 significantly aggravate ischemic stroke injury in mice. USP25 has no impact on neuronal death under hypoxic conditions, but reduced ischemic stroke-induced neuronal loss and neurological deficits by inhibiting microglia-mediated neuroinflammation. Mechanistically, USP25 restricts the activation of NF-κB and MAPK signaling by regulating TAB2. As a deubiquitinating enzyme, USP25 removeds K63-specific polyubiquitin chains from TAB2. AAV9-mediated TAB2 knockdown ameliorates ischemic stroke injury and abolishes the effect of USP25 deletion. In both mouse and human brains, USP25 is markedly upregulated in microglia in the ischemic penumbra, implying a clinical relevance of USP25 in ischemic stroke. Collectively, USP25 is identified as a critical inhibitor of ischemic stroke injury and this data suggest USP25 may serve as a therapeutic target for ischemic stroke.

Deubiquitinase OTUD6A in macrophages promotes intestinal inflammation and colitis via deubiquitination of NLRP3

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract, which has been shown to increase the incidence of colorectal cancer. Recent studies have highlighted the role of ubiquitination, a post-translational modification, in the occurrence and development of colonic inflammation. Ovarian tumor deubiquitinase 6 A (OTUD6A) is a deubiquitinating enzyme, which regulates cell proliferation and tumorigenesis. In this study, we investigated the expression and role of OTUD6A in IBD. Wide-type or Otud6a-/- mice were used to develop dextran sodium sulfate (DSS)- or 2,6,4-trinitrobenzene sulfonic acid (TNBS)-induced colitis model, as well as azoxymethane (AOM)/DSS-induced colitis-associated cancer model. Bone marrow-derived macrophages (BMDMs) were isolated from wild-type and Otud6a-/- mice to dissect molecular mechanisms. Our data show that OTUD6A deficiency attenuated DSS or TNBS-induced colitis, as well as AOM/DSS-induced colitis-related colon cancer in vivo. Bone marrow transplantation experiments further revealed that OTUD6A in myeloid cells was responsible for exacerbation of DSS-induced colitis. Mechanistically, OTUD6A directly bound to NACHT domain of NLRP3 inflammasome and selectively cleaved K48-linked polyubiquitin chains from NLRP3 at K430 and K689 to enhance the stability of NLRP3, leading to increased IL-1β level and inflammation. Taken together, our research identifies a new function of OTUD6A in the pathogenesis of colitis by promoting NLRP3 inflammasome activation, suggesting that OTUD6A could be a potential target for the treatment of IBD.

USP25 Ameliorates Pathological Cardiac Hypertrophy by Stabilizing SERCA2a in Cardiomyocytes

BACKGROUND

Pathological cardiac hypertrophy can lead to heart failure and is one of the leading causes of death globally. Understanding the molecular mechanism of pathological cardiac hypertrophy will contribute to the treatment of heart failure. DUBs (deubiquitinating enzymes) are essential to cardiac pathophysiology by precisely controlling protein function, localization, and degradation. This study set out to investigate the role and molecular mechanism of a DUB, USP25 (ubiquitin-specific peptidase 25), in pathological cardiac hypertrophy.

METHODS

The role of USP25 in myocardial hypertrophy was evaluated in murine cardiomyocytes in response to Ang II (angiotensin II) and transverse aortic constriction stimulation and in hypertrophic myocardium tissues of heart failure patients. Liquid chromotography with mass spectrometry/mass spectrometry analysis combined with Co-IP was used to identify SERCA2a (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2A), an antihypertrophy protein, as an interacting protein of USP25. To clarify the molecular mechanism of USP25 in the regulation of SERCA2a, we constructed a series of mutant plasmids of USP25. In addition, we overexpressed USP25 and SERCA2a in the heart with adenoassociated virus serotype 9 vectors to validate the biological function of USP25 and SERCA2a interaction.

RESULTS

We revealed increased protein level of USP25 in murine cardiomyocytes subject to Ang II and transverse aortic constriction stimulation and in hypertrophic myocardium tissues of patients with heart failure. USP25 deficiency aggravated cardiac hypertrophy and cardiac dysfunction under Ang II and transverse aortic constriction treatment. Mechanistically, USP25 bound to SERCA2a directly via its USP (ubiquitin-specific protease) domain and cysteine at position 178 of USP25 exerts deubiquitination to maintain the stability of the SERCA2a protein by removing the K48 ubiquitin chain and preventing proteasomal pathway degradation, thereby maintaining calcium handling in cardiomyocytes. Moreover, restoration of USP25 expression via adenoassociated virus serotype 9 vectors in USP25^-/- mice attenuated Ang II-induced cardiac hypertrophy and cardiac dysfunction, whereas myocardial overexpression of SERCA2a could mimic the effect of USP25.

CONCLUSIONS

We confirmed that USP25 inhibited cardiac hypertrophy by deubiquitinating and stabilizing SERCA2a.