Cellular and molecular characteristics of stromal Lkb1 deficiency-induced gastrointestinal polyposis based on single-cell RNA sequencing.

Liver kinase B1 (Lkb1), encoded by serine/threonine kinase (Stk11), is a serine/threonine kinase and tumor suppressor that is strongly implicated in Peutz-Jeghers syndrome (PJS). Numerous studies have shown that mesenchymal-specific Lkb1 is sufficient for the development of PJS-like polyps in mice. However, the cellular origin and components of these Lkb1-associated polyps and underlying mechanisms remain elusive. In this study, we generated tamoxifen-inducible Lkb1flox/flox;Myh11-Cre/ERT2 and Lkb1flox/flox;PDGFRα-Cre/ERT2 mice, performed single-cell RNA sequencing (scRNA-seq) and imaging-based lineage tracing, and aimed to investigate the cellular complexity of gastrointestinal polyps associated with PJS. We found that Lkb1flox/+;Myh11-Cre/ERT2 mice developed gastrointestinal polyps starting at 9 months after tamoxifen treatment. scRNA-seq revealed aberrant stem cell-like characteristics of epithelial cells from polyp tissues of Lkb1flox/+;Myh11-Cre/ERT2 mice. The Lkb1-associated polyps were further characterized by a branching smooth muscle core, abundant extracellular matrix deposition, and high immune cell infiltration. In addition, the Spp1-Cd44 or Spp1-Itga8/Itgb1 axes were identified as important interactions among epithelial, mesenchymal, and immune compartments in Lkb1-associated polyps. These characteristics of gastrointestinal polyps were also demonstrated in another mouse model, tamoxifen-inducible Lkb1flox/flox;PDGFRα-Cre/ERT2 mice, which developed obvious gastrointestinal polyps as early as 2-3 months after tamoxifen treatment. Our findings further confirm the critical role of mesenchymal Lkb1/Stk11 in gastrointestinal polyposis and provide novel insight into the cellular complexity of Lkb1-associated polyp biology. © 2024 The Pathological Society of Great Britain and Ireland.

SUMOylation of TEAD1 Modulates the Mechanism of Pathological Cardiac Hypertrophy.

Pathological cardiac hypertrophy is the leading cause of heart failure and has an extremely complicated pathogenesis. TEA domain transcription factor 1 (TEAD1) is recognized as an important transcription factor that plays a key regulatory role in cardiovascular disease. This study aimed to explore the role of TEAD1 in cardiac hypertrophy and to clarify the regulatory role of small ubiquitin-like modifier (SUMO)-mediated modifications. First, the expression level of TEAD1 in patients with heart failure, mice, and cardiomyocytes is investigated. It is discovered that TEAD1 is modified by SUMO1 during cardiac hypertrophy and that the process of deSUMOylation is regulated by SUMO-specific protease 1 (SENP1). Lysine 173 is an essential site for TEAD1 SUMOylation, which affects the protein stability, nuclear localization, and DNA-binding ability of TEAD1 and enhances the interaction between TEAD1 and its transcriptional co-activator yes-associated protein 1 in the Hippo pathway. Finally, adeno-associated virus serotype 9 is used to construct TEAD1 wild-type and KR mutant mice and demonstrated that the deSUMOylation of TEAD1 markedly exacerbated cardiomyocyte enlargement in vitro and in a mouse model of cardiac hypertrophy. The results provide novel evidence that the SUMOylation of TEAD1 is a promising therapeutic strategy for hypertrophy-related heart failure.

Dynamics of Endothelial Cell Generation and Turnover in Arteries During Homeostasis and Diseases.

BACKGROUND: Endothelial cell (EC) generation and turnover by self-proliferation contributes to vascular repair and regeneration. The ability to accurately measure the dynamics of EC generation would advance our understanding of cellular mechanisms of vascular homeostasis and diseases. However, it is currently challenging to evaluate the dynamics of EC generation in large vessels such as arteries because of their infrequent proliferation. METHODS: By using dual recombination systems based on Cre-loxP and Dre-rox, we developed a genetic system for temporally seamless recording of EC proliferation in vivo. We combined genetic recording of EC proliferation with single-cell RNA sequencing and gene knockout to uncover cellular and molecular mechanisms underlying EC generation in arteries during homeostasis and disease. RESULTS: Genetic proliferation tracing reveals that ≈3% of aortic ECs undergo proliferation per month in adult mice during homeostasis. The orientation of aortic EC division is generally parallel to blood flow in the aorta, which is regulated by the mechanosensing protein Piezo1. Single-cell RNA sequencing analysis reveals 4 heterogeneous aortic EC subpopulations with distinct proliferative activity. EC cluster 1 exhibits transit-amplifying cell features with preferential proliferative capacity and enriched expression of stem cell markers such as Sca1 and Sox18. EC proliferation increases in hypertension but decreases in type 2 diabetes, coinciding with changes in the extent of EC cluster 1 proliferation. Combined gene knockout and proliferation tracing reveals that Hippo/vascular endothelial growth factor receptor 2 signaling pathways regulate EC proliferation in large vessels. CONCLUSIONS: Genetic proliferation tracing quantitatively delineates the dynamics of EC generation and turnover, as well as EC division orientation, in large vessels during homeostasis and disease. An EC subpopulation in the aorta exhibits more robust cell proliferation during homeostasis and type 2 diabetes, identifying it as a potential therapeutic target for vascular repair and regeneration.

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

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

Allicin promotes functional recovery in ischemic stroke via glutathione peroxidase-1 activation of Src-Akt-Erk.

Allicin exhibits various pharmacological activities and has been suggested to be beneficial in the treatment of stroke. However, the underlying mechanisms are largely unknown. Here, we confirmed that allicin protected the brain from cerebral injury, which could be ascribed to its anti­apoptotic and anti­inflammatory effects, as well as the regulation of lipid metabolism, using proteomics and metabolomics analysis. Our results suggested that allicin could significantly ameliorate behavioral characteristics, cerebral infarct area, cell apoptosis, inflammatory factors, and lipid metabolic-related factors (arachidonic acid, 15-hydroperoxy-eicosatetraenoic acid (15S-HPETE), palmitoylcarnitine, and acylcarnitine) by recalibrating astrocyte homeostasis in mice with photothrombotic stroke (PT). In astrocytes, allicin significantly increased glutathione peroxidase 1 (GPX1) levels and inhibited the arachidonic acid-related pathway, which was also observed in the brains of mice with PT. Allicin was proven to inhibit hypoxia-induced astrocyte apoptosis by increasing GPX1 expression, activating proto-oncogene tyrosine-protein kinase Src (Src)- protein kinase B (AKT)-extracellular signal-regulated kinase (ERK) phosphorylation, and decreasing lipid peroxidation. Thus, we concluded that allicin significantly prevented and ameliorated ischemic stroke by increasing GPX1 levels to complete the complex physiological process.

Transient Receptor Vanilloid Subtype 4-Mediated Ca2+ Influx Promotes Glomerular Endothelial Inflammation in Sepsis-Associated Acute Kidney Injury.

Sepsis-associated acute kidney injury (S-AKI) is a frequent complication in patients who are critically ill, which is often initiated by glomerular endothelial cell dysfunction. Although transient receptor vanilloid subtype 4 (TRPV4) ion channels are known to be permeable to Ca2+ and are widely expressed in the kidneys, the role of TRPV4 on glomerular endothelial inflammation in sepsis remains elusive. In the present study, we found that TRPV4 expression in mouse glomerular endothelial cells (MGECs) increased after lipopolysaccharide (LPS) stimulation or cecal ligation and puncture challenge, which increased intracellular Ca2+ in MGECs. Furthermore, the inhibition or knockdown of TRPV4 suppressed LPS-induced phosphorylation and translocation of inflammatory transcription factors NF-κB and IRF-3 in MGECs. Clamping intracellular Ca2+ mimicked LPS-induced responses observed in the absence of TRPV4. In vivo experiments showed that the pharmacologic blockade or knockdown of TRPV4 reduced glomerular endothelial inflammatory responses, increased survival rate, and improved renal function in cecal ligation and puncture-induced sepsis without altering renal cortical blood perfusion. Taken together, our results suggest that TRPV4 promotes glomerular endothelial inflammation in S-AKI and that its inhibition or knockdown alleviates glomerular endothelial inflammation by reducing Ca2+ overload and NF-κB/IRF-3 activation. These findings provide insights that may aid in the development of novel pharmacologic strategies for the treatment of S-AKI.

L-shaped association of serum 25-hydroxyvitamin D concentrations with cardiovascular and all-cause mortality in individuals with osteoarthritis: results from the NHANES database prospective cohort study.

BACKGROUND: The relationship between vitamin D status and mortality in patients with osteoarthritis (OA) is unknown. This study investigated the associations of serum 25-hydroxyvitamin D [25(OH)D] concentrations with all-cause and cause-specific mortality among American adults with OA. METHODS: This study included 2556 adults with OA from the National Health and Nutrition Examination Survey (2001-2014). Death outcomes were ascertained by linkage to National Death Index (NDI) records through 31 December 2015. Cox proportional hazards model and two-piecewise Cox proportional hazards model were used to elucidate the nonlinear relationship between serum 25(OH)D concentrations and mortality in OA patients, and stratified analyses were performed to identify patients with higher mortality risk. RESULTS: During 16,606 person-years of follow-up, 438 all-cause deaths occurred, including 74 cardiovascular disease (CVD)-related and 78 cancer deaths. After multivariable adjustment, lower serum 25(OH)D levels were significantly and nonlinearly associated with higher risks of all-cause and CVD mortality among participants with OA. Furthermore, we discovered L-shaped associations between serum 25(OH)D levels and all-cause and CVD mortality, with mortality plateauing at 54.40 nmol/L for all-cause mortality and 27.70 nmol/L for CVD mortality. Compared to participants with 25(OH)D levels below the inflection points, those with higher levels had a 2% lower risk for all-cause mortality (hazard ratio [HR] 0.98, 95% confidence interval [CI] 0.96-0.99) and 17% lower risk for CVD mortality (HR 0.83, 95% CI 0.72-0.95). CONCLUSIONS: Nonlinear associations of serum 25(OH)D levels with all-cause and CVD mortality were observed in American patients with OA. The thresholds of 27.70 and 54.40 nmol/L for CVD and all-cause mortality, respectively, may represent intervention targets for lowering the risk of premature death and cardiovascular disease, but this needs to be confirmed in large clinical trials.

Genetic Lineage Tracing of Pericardial Cavity Macrophages in the Injured Heart.

BACKGROUND: Macrophages play an important role in cardiac repair after myocardial infarction (MI). In addition to the resident macrophages and blood-derived monocytes, Gata6+ cavity macrophages located in the pericardial space were recently reported to relocate to the injured myocardium and prevent cardiac fibrosis. However, there is no direct genetic evidence to support it. METHODS: We used dual recombinases (Cre and Dre) to specifically label Gata6+ pericardial macrophages (GPCMs) in vivo. For functional study, we generated genetic systems to specifically ablate GPCMs by induced expression of DTR (diphtheria toxin receptor) or knockout of Gata6 (GATA binding protein 6) gene in GPCMs. We used these genetic systems to study GPCMs in pericardium intact MI model. RESULTS: Dual recombinases-mediated genetic system targeted GPCMs specifically and efficiently. Lineage tracing study revealed accumulation of GPCMs on the surface of MI heart without deep penetration into the myocardium. We did not detect significant change of cardiac fibrosis or function of MI hearts after cell ablation or Gata6 knockout in GPCMs. CONCLUSIONS: GPCMs minimally invade the injured heart after MI. Nor do they prevent cardiac fibrosis and exhibit reparative function on injured heart. This study also underlines the importance of using specific genetic tool for studying in vivo cell fates and functions.

LUBAC and OTULIN regulate autophagy initiation and maturation by mediating the linear ubiquitination and the stabilization of ATG13.

Macroautophagy/autophagy is a membrane-mediated intracellular degradation pathway, through which bulky cytoplasmic content is digested in lysosomes. How the autophagy initiation and maturation steps are regulated is not clear. In this study, we found an E3 ubiquitin ligase complex, linear ubiquitin chain assembly complex (LUBAC) and a deubiquitinating enzyme (DUB) OTULIN localize to the phagophore area to control autophagy initiation and maturation. LUBAC key component RNF31/HOIP translocates to the LC3 puncta area when autophagy is induced. RNF31 knockdown inhibits autophagy initiation, and cells are more sensitive to bacterial infection. OTULIN knockdown, however, promotes autophagy initiation but blocks autophagy maturation. In OTULIN knockdown cells, excessive ubiquitinated ATG13 protein was recruited to the phagophore for prolonged expansion, and therefore inhibits autophagosome maturation. Together, our study provides evidence that LUBAC and OTULIN cooperatively regulate autophagy initiation and autophagosome maturation by mediating the linear ubiquitination and the stabilization of ATG13.Abbreviations: ATG: autophagy-related; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CQ: chloroquine; CUL1-FBXL20: cullin 1-F-box and leucine rich repeat protein 20; CUL3-KLHL20: cullin 3-kelch like family member 20; CUL4-AMBRA1: cullin 4-autophagy and beclin 1 regulator 1; CYLD: CYLD lysine 63 deubiquitinase; DAPI: 4',6-diamidino-2-phenylindole; DUB: deubiquitinating enzyme; EBSS: Earle's Balanced Salt Solution; GFP: green fluorescent protein; GST: glutathione S-transferase; IKBKG/NEMO: inhibitor of nuclear factor kappa B kinase regulatory subunit gamma; LUBAC: linear ubiquitin chain assembly complex; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3B; MIM: MIT-interacting motif; mRFP: monomeric red fluorescent protein; NEDD4: NEDD4 E3 ubiquitin protein ligase; NFKB: NF-kappaB complex; OPTN: optineurin; OTULIN: OTU deubiquitinase with linear linkage specificity; PIK3C3/Vps34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns: phosphatidylinositol; PtdIns3K: class III phosphatidylinositol 3-kinase complex; PtdIns3P: phosphatidylinositol 3-phosphate; RBCK1/HOIL1: RANBP2-type and C3HC4-type zinc finger containing 1; RB1CC1/FIP200: RB1-inducible coiled-coil 1; RIPK1: receptor interacting serine/threonine kinase 1; RNF216: ring finger protein 216; RNF31/HOIP: ring finger protein 31; RT-PCR: reverse transcriptase polymerase chain reaction; S. Typhimurium: Salmonella enterica serovar Typhimurium; SHARPIN: SHANK associated RH domain interactor; SMURF1: SMAD specific E3 ubiquitin protein ligase 1; SQSTM1: sequestosome 1; STING: stimulator of interferon response cGAMP interactor 1; STUB1/CHIP: STIP1 homology and U-box containing protein 1; TNF/TNF-alpha: tumor necrosis factor; TNFAIP3/A20: TNF alpha induced protein 3; TRAF6: TNF receptor associated factor 6; TRIM32: tripartite motif containing 32; UBAN: ubiquitin binding in TNIP/ABIN and IKBKG/NEMO proteins; ULK1/2: unc-51 like autophagy activating kinase 1/2; USP: ubiquitin specific peptidase; UVRAG: UV radiation resistance associated; VCPIP1: valosin containing protein interacting protein 1; WIPI2: WD repeat domain, phosphoinositide interacting protein 2; ZBTB16-CUL3-RBX1: zinc finger and BTB domain containing protein 16-cullin 3-ring-box 1; ZRANB1: zinc finger RANBP2-type containing 1.

Lunapark Is a Component of a Ubiquitin Ligase Complex Localized to the Endoplasmic Reticulum Three-way Junctions.

The endoplasmic reticulum (ER) network comprises sheets and tubules that are connected by dynamic three-way junctions. Lunapark (Lnp) localizes to and stabilizes ER three-way junctions by antagonizing the small GTPase Atlastin, but how Lnp shapes the ER network is unclear. Here, we used an affinity purification approach and mass spectrometry to identify Lnp as an interacting partner of the ER protein quality control ubiquitin ligase gp78. Accordingly, Lnp purified from mammalian cells has a ubiquitin ligase activity in vitro Intriguingly, biochemical analyses show that this activity can be attributed not only to associated ubiquitin ligase, but also to an intrinsic ubiquitin ligase activity borne by Lnp itself. This activity is contained in the N-terminal 45 amino acids of Lnp although this segment does not share homology to any known ubiquitin ligase motifs. Despite its interaction with gp78, Lnp does not seem to have a broad function in degradation of misfolded ER proteins. On the other hand, the N-terminal ubiquitin ligase-bearing motif is required for the ER three-way junction localization of Lnp. Our study identifies a new type of ubiquitin ligase and reveals a potential link between ubiquitin and ER morphology regulation.

Effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus).

Nitrite (NO2(-)) is commonly present as contaminant in aquatic environment and toxic to aquatic organisms. In the present study, we investigated the effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus). Fish were exposed to various concentrations of nitrite (0, 0.02, 0.08, 0.4 and 0.8mM) for 96 h. Fish blood and gills were collected to assay haematological parameters, oxidative stress and expression of genes after 0, 24, 48 and 96 h of exposure. In blood, the data showed that the levels of methemoglobin (MetHb), triglyceride (TG), potassium (K(+)), cortisol, heat shock protein 70 (HSP70) and glucose significantly increased in treatments with higher concentrations of nitrite (0.4 and/or 0.8mM) after 48 and 96 h, while the levels of haemoglobin (Hb) and sodium (Na(+)) significantly decreased in these treatments. In gills, nitrite (0.4 and/or 0.8mM) apparently reduced the levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH), increased the formation of malondialdehyde (MDA), up-regulated the mRNA levels of c-jun amino-terminal kinase (JUK1), p53, caspase-3, caspase-7 and caspase-9 after 48 and 96 h of exposure. The results suggested caspase-dependent and JUK signaling pathways played important roles in nitrite-induced apoptosis in fish. Further, this study provides new insights into how nitrite affects the physiological responses and apoptosis in a marine fish.