MDM2-Mediated Ubiquitination of Angiotensin-Converting Enzyme 2 Contributes to the Development of Pulmonary Arterial Hypertension

UBR1 Promotes Sex-Dependent ACE2 Ubiquitination in Hypertension

BACKGROUND

Ang-II (angiotensin II) impairs the function of the antihypertensive enzyme ACE2 (angiotensin-converting enzyme 2) by promoting its internalization, ubiquitination, and degradation, thus contributing to hypertension. However, few ACE2 ubiquitination partners have been identified, and their role in hypertension remains unknown.

METHODS

Proteomics and bioinformatic analyses were used to identify ACE2 ubiquitination partners in the brain, heart, and kidney of hypertensive C57BL6/J mice of both sexes. The interaction between UBR1 (ubiquitin protein ligase E3 component N-recognin) and ACE2 was validated in cells. Central and peripheral UBR1 knockdown was then performed in male mice to investigate its role in the maintenance of hypertension.

RESULTS

Proteomics analysis of the hypothalamus identified UBR1 as a potential E3 (ubiquitin protein ligase) ligase promoting ACE2 ubiquitination. Enhanced UBR1 expression, associated with ACE2 reduction, was confirmed in various tissues from hypertensive male mice and human samples. Treatment of endothelial and smooth muscle cells with testosterone, but not 17β-estradiol, confirmed a sex-specific regulation of UBR1. In vivo silencing of UBR1 using chronic administration of small interference RNA resulted in the restoration of ACE2 levels in hypertensive male mice. A transient decrease in blood pressure after intracerebroventricular, but not systemic, infusion was also observed. Interestingly, UBR1 knockdown increased brain activation of Nedd4-2 (neural precursor cell expressed developmentally downregulated protein 4), an E3 ligase promoting ACE2 ubiquitination, and reduced expression of serum and glucocorticoid-regulated kinase 1, the kinase that inactivates Nedd4-2.

CONCLUSIONS

These data demonstrate that UBR1 is a novel E3 ubiquitin ligase targeting ACE2 in hypertension. UBR1 and Nedd4-2 appear to work synergistically to ubiquitinate ACE2. Targeting these ubiquitin ligases may represent a novel strategy to restore ACE2 compensatory activity in hypertension.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Evaluation of Angiotensin-Converting Enzyme 2 Expression In Vivo with Novel 68Ga-Labeled Peptides Originated from the Coronavirus Receptor-Binding Domain

Angiotensin-converting enzyme 2 (ACE2) is not only a key to the renin-angiotensin-aldosterone system and related diseases, but also the main entry point on cell surfaces for certain coronaviruses, including severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. By analyzing the different key binding sites from the receptor-binding domain (RBD) of SARS-CoV and SARS-CoV-2, nine new ACE2-targeting peptides (A1 to A9) were designed, synthesized and connected with a chelator, 1,4,7-triazacyclononane-N,N',N''-triacetic acid (NOTA). NOTA-A1, NOTA-A2, NOTA-A4, NOTA-A5, and NOTA-A8 were successfully labeled with [68Ga]Ga3+ and were used for biological evaluation. [68Ga]Ga-NOTA-A2, [68Ga]Ga-NOTA-A5, and [68Ga]Ga-NOTA-A8 showed specific binding to ACE2 via cell assays, and their binding sites and binding capacity were calculated by molecular docking and molecular dynamics simulations. In tumor-bearing mice, A549 tumors were visualized 60 min postinjection of [68Ga]Ga-NOTA-A2, [68Ga]Ga-NOTA-A5, or [68Ga]Ga-NOTA-A8. These peptides also accumulated in the organs with high-level ACE2 expression, confirmed by immunohistochemical stain. Among them, [68Ga]Ga-NOTA-A5 exhibited the highest tumor uptake and tumor/background ratio, and it successfully tracked the increased ACE2 levels in mice tissues after excessive Losartan treatment. In a first-in-human study, the distribution of [68Ga]Ga-NOTA-A5 was evaluated with positron emission tomography/computed tomography (PET/CT) in three participants without adverse events. 68Ga-labeled peptides originated from the coronavirus RBD, with [68Ga]Ga-NOTA-A5 as a typical representative, seem to be safe and effective for the evaluation of ACE2 expression in vivo with PET/CT, facilitating further mechanism investigation and clinical evaluation of ACE2-related diseases.

Przewaquinone A inhibits Angiotensin II-induced endothelial diastolic dysfunction activation of AMPK

BACKGROUND

Endothelial dysfunction (ED), characterized by markedly reduced nitric oxide (NO) bioavailability, vasoconstriction, and a shift toward a proinflammatory and prothrombotic state, is an important contributor to hypertension, atherosclerosis, and other cardiovascular diseases. Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) is widely involved in cardiovascular development. Przewaquinone A (PA), a lipophilic diterpene quinone extracted from Salvia przewalskii Maxim, inhibits vascular contraction.

PURPOSE

Herein, the goal was to explore the protective effect of PA on ED in vivo and in vitro, as well as the underlying mechanisms.

METHODS

A human umbilical vein endothelial cell (HUVEC) model of ED induced by angiotensin II (AngII) was used for in vitro observations. Levels of AMPK, endothelial nitric oxide synthase (eNOS), vascular cell adhesion molecule-1 (VCAM-1), nitric oxide (NO), and endothelin-1 (ET-1) were detected by western blotting and ELISA. A mouse model of hypertension was established by continuous infusion of AngII (1000 ng/kg/min) for 4 weeks using osmotic pumps. Following PA and/or valsartan administration, NO and ET-1 levels were measured. The levels of AMPK signaling-related proteins in the thoracic aorta were evaluated by immunohistochemistry. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were measured using the tail cuff method. Isolated aortic vascular tone measurements were used to evaluate the vasodilatory function in mice. Molecular docking, molecular dynamics, and surface plasmon resonance imaging (SPRi) were used to confirm AMPK and PA interactions.

RESULTS

PA inhibited AngII-induced vasoconstriction and vascular adhesion as well as activated AMPK signaling in a dose-dependent manner. Moreover, PA markedly suppressed blood pressure, activated vasodilation in mice following AngII stimulation, and promoted the activation of AMPK signaling. Furthermore, molecular simulations and SPRi revealed that PA directly targeted AMPK. AMPK inhibition partly abolished the protective effects of PA against endothelial dysfunction.

CONCLUSION

PA activates AMPK and ameliorates endothelial dysfunction during hypertension.

Erythrophagocytosis-induced ferroptosis contributes to pulmonary microvascular thrombosis and thrombotic vascular remodeling in pulmonary arterial hypertension

BACKGROUND

Whether primary or just as a complication from the progression of pulmonary arterial hypertension (PAH), thrombosis seems to be an important player in this condition. The crosstalk between red blood cells (RBCs) and pulmonary microvascular endothelial cells (PMVECs) and their role in PAH remain undefined.

OBJECTIVES

The goals of this study were to assess the role of RBC-PMVEC interaction in microvascular thrombosis and thrombotic vascular remodeling under hypoxic conditions.

METHODS

We established an in vitro hypoxic coincubation model of RBC and PMVEC as well as a hypoxic mouse model. We investigated erythrophagocytosis (EP), ferroptosis, thrombosis tendency, and pulmonary hemodynamics in experimental PAH.

RESULTS

Increased EP in PMVEC triggered ferroptosis, enhanced procoagulant activity, and exacerbated vessel remodeling under hypoxic conditions. In the PAH mouse model induced by chronic hypoxia, EP-induced ferroptosis followed by upregulated TMEM16F led to a high tendency of thrombus formation and thrombotic vascular remodeling. Inhibition of ferroptosis or silencing of TMEM16F could alleviate hypercoagulable phenotype, reverse right ventricular systolic pressure, right ventricular hypertrophy index, and remodeling of pulmonary vessels.

CONCLUSION

These results illustrate the pathogenic RBC-PMVEC interactions in PAH. Inhibition EP, ferroptosis, or TMEM16F could be a novel therapeutic target to prevent PAH development and thrombotic complications.

AMPK Attenuation of β-Adrenergic Receptor-Induced Cardiac Injury via Phosphorylation of β-Arrestin-1-ser330

BACKGROUND

β-adrenergic receptor (β-AR) overactivation is a major pathological cue associated with cardiac injury and diseases. AMPK (AMP-activated protein kinase), a conserved energy sensor, regulates energy metabolism and is cardioprotective. However, whether AMPK exerts cardioprotective effects via regulating the signaling pathway downstream of β-AR remains unclear.

METHODS

Using immunoprecipitation, mass spectrometry, site-specific mutation, in vitro kinase assay, and in vivo animal studies, we determined whether AMPK phosphorylates β-arrestin-1 at serine (Ser) 330. Wild-type mice and mice with site-specific mutagenesis (S330A knock-in [KI]/S330D KI) were subcutaneously injected with the β-AR agonist isoproterenol (5 mg/kg) to evaluate the causality between β-adrenergic insult and β-arrestin-1 Ser330 phosphorylation. Cardiac transcriptomics was used to identify changes in gene expression from β-arrestin-1-S330A/S330D mutation and β-adrenergic insult.

RESULTS

Metformin could decrease cAMP/PKA (protein kinase A) signaling induced by isoproterenol. AMPK bound to β-arrestin-1 and phosphorylated Ser330 with the highest phosphorylated mass spectrometry score. AMPK activation promoted β-arrestin-1 Ser330 phosphorylation in vitro and in vivo. Neonatal mouse cardiomyocytes overexpressing β-arrestin-1-S330D (active form) inhibited the β-AR/cAMP/PKA axis by increasing PDE (phosphodiesterase) 4 expression and activity. Cardiac transcriptomics revealed that the differentially expressed genes between isoproterenol-treated S330A KI and S330D KI mice were mainly involved in immune processes and inflammatory response. β-arrestin-1 Ser330 phosphorylation inhibited isoproterenol-induced reactive oxygen species production and NLRP3 (NOD-like receptor protein 3) inflammasome activation in neonatal mouse cardiomyocytes. In S330D KI mice, the β-AR-activated cAMP/PKA pathways were attenuated, leading to repressed inflammasome activation, reduced expression of proinflammatory cytokines, and mitigated macrophage infiltration. Compared with S330A KI mice, S330D KI mice showed diminished cardiac fibrosis and improved cardiac function upon isoproterenol exposure. However, the cardiac protection exerted by AMPK was abolished in S330A KI mice.

CONCLUSIONS

AMPK phosphorylation of β-arrestin-1 Ser330 potentiated PDE4 expression and activity, thereby inhibiting β-AR/cAMP/PKA activation. Subsequently, β-arrestin-1 Ser330 phosphorylation blocks β-AR-induced cardiac inflammasome activation and remodeling.

Fine-tuning AMPK in physiology and disease using point-mutant mouse models

AMP-activated protein kinase (AMPK) is an evolutionarily conserved serine/threonine kinase that monitors the cellular energy status to adapt it to the fluctuating nutritional and environmental conditions in an organism. AMPK plays an integral part in a wide array of physiological processes, such as cell growth, autophagy and mitochondrial function, and is implicated in diverse diseases, including cancer, metabolic disorders, cardiovascular diseases and neurodegenerative diseases. AMPK orchestrates many different physiological outcomes by phosphorylating a broad range of downstream substrates. However, the importance of AMPK-mediated regulation of these substrates in vivo remains an ongoing area of investigation to better understand its precise role in cellular and metabolic homeostasis. Here, we provide a comprehensive overview of our understanding of the kinase function of AMPK in vivo, as uncovered from mouse models that harbor phosphorylation mutations in AMPK substrates. We discuss some of the inherent limitations of these mouse models, highlight the broader implications of these studies for understanding human health and disease, and explore the valuable insights gained that could inform future therapeutic strategies for the treatment of metabolic and non-metabolic disorders.

Multi-Omics Characterization of E3 Regulatory Patterns in Different Cancer Types

Ubiquitination, a post-translational modification, refers to the covalent attachment of ubiquitin molecules to substrates. This modification plays a critical role in diverse cellular processes such as protein degradation. The specificity of ubiquitination for substrates is regulated by E3 ubiquitin ligases. Dysregulation of ubiquitination has been associated with numerous diseases, including cancers. In our study, we first investigated the protein expression patterns of E3 ligases across 12 cancer types. Our findings indicated that E3 ligases tend to be up-regulated and exhibit reduced tissue specificity in tumors. Moreover, the correlation of protein expression between E3 ligases and substrates demonstrated significant changes in cancers, suggesting that E3-substrate specificity alters in tumors compared to normal tissues. By integrating transcriptome, proteome, and ubiquitylome data, we further characterized the E3-substrate regulatory patterns in lung squamous cell carcinoma. Our analysis revealed that the upregulation of the SKP2 E3 ligase leads to excessive degradation of BRCA2, potentially promoting tumor cell proliferation and metastasis. Furthermore, the upregulation of E3 ubiquitin-protein ligase TRIM33 was identified as a biomarker associated with a favorable prognosis by inhibiting the cell cycle. This work exemplifies how leveraging multi-omics data to analyze E3 ligases across various cancers can unveil prognosis biomarkers and facilitate the identification of potential drug targets for cancer therapy.

BRCC3 Regulation of ALK2 in Vascular Smooth Muscle Cells: Implication in Pulmonary Hypertension

BACKGROUND

An imbalance of antiproliferative BMP (bone morphogenetic protein) signaling and proliferative TGF-β (transforming growth factor-β) signaling is implicated in the development of pulmonary arterial hypertension (PAH). The posttranslational modification (eg, phosphorylation and ubiquitination) of TGF-β family receptors, including BMPR2 (bone morphogenetic protein type 2 receptor)/ALK2 (activin receptor-like kinase-2) and TGF-βR2/R1, and receptor-regulated Smads significantly affects their activity and thus regulates the target cell fate. BRCC3 modifies the activity and stability of its substrate proteins through K63-dependent deubiquitination. By modulating the posttranslational modifications of the BMP/TGF-β-PPARγ pathway, BRCC3 may play a role in pulmonary vascular remodeling, hence the pathogenesis of PAH.

METHODS

Bioinformatic analyses were used to explore the mechanism by which BRCC3 deubiquitinates ALK2. Cultured pulmonary artery smooth muscle cells (PASMCs), mouse models, and specimens from patients with idiopathic PAH were used to investigate the rebalance between BMP and TGF-β signaling in regulating ALK2 phosphorylation and ubiquitination in the context of pulmonary hypertension.

RESULTS

BRCC3 was significantly downregulated in PASMCs from patients with PAH and animals with experimental pulmonary hypertension. BRCC3, by de-ubiquitinating ALK2 at Lys-472 and Lys-475, activated receptor-regulated Smad1/5/9, which resulted in transcriptional activation of BMP-regulated PPARγ, p53, and Id1. Overexpression of BRCC3 also attenuated TGF-β signaling by downregulating TGF-β expression and inhibiting phosphorylation of Smad3. Experiments in vitro indicated that overexpression of BRCC3 or the de-ubiquitin-mimetic ALK2-K472/475R attenuated PASMC proliferation and migration and enhanced PASMC apoptosis. In SM22α-BRCC3-Tg mice, pulmonary hypertension was ameliorated because of activation of the ALK2-Smad1/5-PPARγ axis in PASMCs. In contrast, Brcc3-/- mice showed increased susceptibility of experimental pulmonary hypertension because of inhibition of the ALK2-Smad1/5 signaling.

CONCLUSIONS

These results suggest a pivotal role of BRCC3 in sustaining pulmonary vascular homeostasis by maintaining the integrity of the BMP signaling (ie, the ALK2-Smad1/5-PPARγ axis) while suppressing TGF-β signaling in PASMCs. Such rebalance of BMP/TGF-β pathways is translationally important for PAH alleviation.

Angiotensin-Converting Enzyme 2 Posttranslational Modifications and Implications for Hypertension and SARS-CoV-2: 2023 Lewis K. Dahl Memorial Lecture

ACE2 (angiotensin-converting enzyme 2), a multifunctional transmembrane protein, is well recognized as an important member of the (RAS) renin-angiotensin system with important roles in the regulation of cardiovascular function by opposing the harmful effects of Ang-II (angiotensin II) and AT1R (Ang-II type 1 receptor) activation. More recently, ACE2 was found to be the entry point for the SARS-CoV-2 virus into cells, causing COVID-19. This finding has led to an exponential rise in the number of publications focused on ACE2, albeit these studies often have opposite objectives to the preservation of ACE2 in cardiovascular regulation. However, notwithstanding accumulating data of the role of ACE2 in the generation of angiotensin-(1-7) and SARS-CoV-2 internalization, numerous other putative roles of this enzyme remain less investigated and not yet characterized. Currently, no drug modulating ACE2 function or expression is available in the clinic, and the development of new pharmacological tools should attempt targeting each step of the lifespan of the protein from synthesis to degradation. The present review expands on our presentation during the 2023 Lewis K. Dahl Memorial Lecture Sponsored by the American Heart Association Council on Hypertension. We provide a critical summary of the current knowledge of the mechanisms controlling ACE2 internalization and intracellular trafficking, the mutual regulation with GPCRs (G-protein-coupled receptors) and other proteins, and posttranslational modifications. A major focus is on ubiquitination which has become a critical step in the modulation of ACE2 cellular levels.

UBR1 Promotes Sex-Dependent ACE2 Ubiquitination in Hypertension

Background

Angiotensin (Ang)-II impairs the function of the antihypertensive enzyme ACE2 by promoting its internalization, ubiquitination and degradation thus contributing to hypertension. However, few ACE2 ubiquitination partners have been identified and their role in hypertension remains unknown.

Methods

Proteomics and bioinformatic analysis were used to identify ACE2 ubiquitination partners in the brain, heart, and kidney from Ang-II-infused C57BL6/J mice from both sexes and validated the interaction between UBR1 and ACE2 in cells. Central and peripheral UBR1 knockdown was then performed in male mice to investigate its role in the maintenance of hypertension.

Results

Proteomics analysis from hypothalamus identified UBR1 as a potential E3 ligase promoting ACE2 ubiquitination. Enhanced UBR1 expression, associated with ACE2 reduction, was confirmed in various tissues from hypertensive male mice and human samples. Treatment of endothelial and smooth muscle cells with testosterone, but not 17β-estradiol, confirmed a sex-specific regulation of UBR1. In vivo silencing of UBR1 using chronic administration of small interference RNA resulted in the restoration of ACE2 levels in hypertensive males. A transient decrease in blood pressure following intracerebroventricular, but not systemic, infusion was also observed. Interestingly, UBR1 knockdown increased the brain activation of Nedd4-2, an E3 ligase promoting ACE2 ubiquitination and reduced expression of SGK1, the kinase inactivating Nedd4-2. Conclusions: These data demonstrate that UBR1 is a novel ubiquitin ligase targeting ACE2 in hypertension. UBR1 and Nedd4-2 E3 ligases appear to work synergistically to ubiquitinate ACE2. Targeting of these ubiquitin ligases may represent a novel strategy to restore ACE2 compensatory activity in hypertension.

BRD4 promotes gouty arthritis through MDM2-mediated PPARγ degradation and pyroptosis

BACKGROUND

Gouty arthritis (GA) is characterized by monosodium urate (MSU) crystal accumulation that instigates NLRP3-mediated pyroptosis; however, the underlying regulatory mechanisms have yet to be fully elucidated. The present research endeavors to elucidate the regulatory mechanisms underpinning this MSU-induced pyroptotic cascade in GA.

METHODS

J774 cells were exposed to lipopolysaccharide and MSU crystals to establish in vitro GA models, whereas C57BL/6 J male mice received MSU crystal injections to mimic in vivo GA conditions. Gene and protein expression levels were evaluated using real-time quantitative PCR, Western blotting, and immunohistochemical assays. Inflammatory markers were quantified via enzyme-linked immunosorbent assays. Pyroptosis was evaluated using immunofluorescence staining for caspase-1 and flow cytometry with caspase-1/propidium iodide staining. The interaction between MDM2 and PPARγ was analyzed through co-immunoprecipitation assays, whereas the interaction between BRD4 and the MDM2 promoter was examined using chromatin immunoprecipitation and dual-luciferase reporter assays. Mouse joint tissues were histopathologically evaluated using hematoxylin and eosin staining.

RESULTS

In GA, PPARγ was downregulated, whereas its overexpression mitigated NLRP3 inflammasome activation and pyroptosis. MDM2, which was upregulated in GA, destabilized PPARγ through the ubiquitin-proteasome degradation pathway, whereas its silencing attenuated NLRP3 activation by elevating PPARγ levels. Concurrently, BRD4 was elevated in GA and exacerbated NLRP3 activation and pyroptosis by transcriptionally upregulating MDM2, thereby promoting PPARγ degradation. In vivo experiments showed that BRD4 silencing ameliorated GA through this MDM2-PPARγ-pyroptosis axis.

CONCLUSION

BRD4 promotes inflammation and pyroptosis in GA through MDM2-mediated PPARγ degradation, underscoring the therapeutic potential of targeting this pathway in GA management.

Alternative Renin-Angiotensin System

The renin-angiotensin system is the most important peptide hormone system in the regulation of cardiovascular homeostasis. Its classical arm consists of the enzymes, renin, and angiotensin-converting enzyme, generating angiotensin II from angiotensinogen, which activates its AT1 receptor, thereby increasing blood pressure, retaining salt and water, and inducing cardiovascular hypertrophy and fibrosis. However, angiotensin II can also activate a second receptor, the AT2 receptor. Moreover, the removal of the C-terminal phenylalanine from angiotensin II by ACE2 (angiotensin-converting enzyme 2) yields angiotensin-(1-7), and this peptide interacts with its receptor Mas. When the aminoterminal Asp of angiotensin-(1-7) is decarboxylated, alamandine is generated, which activates the Mas-related G-protein-coupled receptor D, MrgD (Mas-related G-protein-coupled receptor type D). Since Mas, MrgD, and the AT2 receptor have opposing effects to the classical AT1 receptor, they and the enzymes and peptides activating them are called the alternative or protective arm of the renin-angiotensin system. This review will cover the historical aspects and the current standing of this recent addition to the biology of the renin-angiotensin system.

POLE2 promotes osteosarcoma progression by enhancing the stability of CD44

Osteosarcoma (OS) is the most prevalent primary malignancy of bone in children and adolescents. It is extremely urgent to develop a new therapy for OS. In this study, the GSE14359 chip from the GEO database was used to screen differentially expressed genes in OS. DNA polymerase epsilon 2 (POLE2) was confirmed to overexpress in OS tissues and cell lines by immunohistochemical staining, qPCR and Western blot. Knockdown of POLE2 inhibited the proliferation and migration of OS cells in vitro, as well as the growth of tumors in vivo, while the apoptosis rate was increased. Bioinformatics analysis revealed that CD44 and Rac signaling pathway were the downstream molecule and pathway of POLE2, which were inhibited by knockdown of POLE2. POLE2 reduced the ubiquitination degradation of CD44 by acting on MDM2. Moreover, knockdown of CD44 inhibited the tumor-promoting effects of POLE2 overexpression on OS cells. In conclusion, POLE2 augmented the expression of CD44 via inhibiting MDM2-mediated ubiquitination, and then activated Rac signaling pathway to influence the progression of OS, indicating that POLE2/CD44 might be potential targets for OS treatment.

Endothelial H2S-AMPK dysfunction upregulates the angiocrine factor PAI-1 and contributes to lung fibrosis

Dysfunction of the vascular angiocrine system is critically involved in regenerative defects and fibrosis of injured organs. Previous studies have identified various angiocrine factors and found that risk factors such as aging and metabolic disorders can disturb the vascular angiocrine system in fibrotic organs. One existing key gap is what sense the fibrotic risk to modulate the vascular angiocrine system in organ fibrosis. Here, using human and mouse data, we discovered that the metabolic pathway hydrogen sulfide (H2S)-AMP-activated protein kinase (AMPK) is a sensor of fibrotic stress and serves as a key mechanism upregulating the angiocrine factor plasminogen activator inhibitor-1 (PAI-1) in endothelial cells to participate in lung fibrosis. Activation of the metabolic sensor AMPK was inhibited in endothelial cells of fibrotic lungs, and AMPK inactivation was correlated with enriched fibrotic signature and reduced lung functions in humans. The inactivation of endothelial AMPK accelerated lung fibrosis in mice, while the activation of endothelial AMPK with metformin alleviated lung fibrosis. In fibrotic lungs, endothelial AMPK inactivation led to YAP activation and overexpression of the angiocrine factor PAI-1, which was positively correlated with the fibrotic signature in human fibrotic lungs and inhibition of PAI-1 with Tiplaxtinin mitigated lung fibrosis. Further study identified that the deficiency of the antioxidative gas metabolite H2S accounted for the inactivation of AMPK and activation of YAP-PAI-1 signaling in endothelial cells of fibrotic lungs. H2S deficiency was involved in human lung fibrosis and H2S supplement reversed mouse lung fibrosis in an endothelial AMPK-dependent manner. These findings provide new insight into the mechanism underlying the deregulation of the vascular angiocrine system in fibrotic organs.

Environmental dose of 16 priority-controlled PAHs induce endothelial dysfunction: An in vivo and in vitro study

Polycyclic aromatic hydrocarbons (PAHs) exposure is related to the occurrence of cardiovascular diseases (CVDs). Endothelial dysfunction is considered an initial event of CVDs. To confirm the relationship of PAHs exposure with endothelial dysfunction, 8-week-old male SD rats and primary human umbilical vein endothelial cells (HUVECs) were co-treated with environmental doses of 16 priority-controlled PAHs for 90 d and 48 h, respectively. Results showed that 10× PAHs exposure remarkably raised tumor necrosis factor-α and malonaldehyde levels in rat serum (p < 0.05), but had no effects on interleukin-8 levels and superoxide dismutase activity. The expressions of SIRT1 in HUVECs and rat aorta were attenuated after PAHs treatment. Interestingly, PAHs exposure did not activate the expression of total endothelial nitric oxide synthase (eNOS), but 10× PAHs exposure significantly elevated the expression of phosphorylated eNOS (Ser1177) in HUVECs and repressed it in aortas, accompanied with raised nitrite level both in serum and HUVECs by 48.50-253.70 %. PAHs exposure also led to the augment of endothelin-1 (ET-1) levels by 19.76-38.54 %, angiotensin (Ang II) levels by 20.09-39.69 % in HUVECs, but had no effects on ET-1 and Ang II levels in serum. Additionally, PAHs exposure improved endocan levels both in HUVECs and serum by 305.05-620.48 % and stimulated the THP-1 cells adhered to HUVECs (p < 0.05). After PAHs treatment, the smooth muscle alignment was disordered and the vascular smooth muscle locally proliferated in rat aorta. Notably, the systolic blood pressure of rats exposed to 10× PAHs increased significantly compared with the control ones (131.28 ± 5.20 vs 116.75 ± 5.33 mmHg). In summary, environmental chronic PAHs exposure may result in endothelial dysfunction in SD rats and primary HUVECs. Our research can confirm the cardiovascular damage caused by chronic exposure to PAHs and provide ideas for the prevention or intervention of CVDs affected by environmental factors.

Ubiquitin ligase MDM2 mediates endothelial inflammation in Kawasaki disease vasculitis development

Background

Kawasaki disease (KD) often complicates coronary artery lesions (CALs). Despite the established significance of STAT3 signaling during the acute phase of KD and signal transducer and activator of transcription 3 (STAT3) signaling being closely related to CALs, it remains unknown whether and how STAT3 was regulated by ubiquitination during KD pathogenesis.

Methods

Bioinformatics and immunoprecipitation assays were conducted, and an E3 ligase, murine double minute 2 (MDM2) was identified as the ubiquitin ligase of STAT3. The blood samples from KD patients before and after intravenous immunoglobulin (IVIG) treatment were utilized to analyze the expression level of MDM2. Human coronary artery endothelial cells (HCAECs) and a mouse model were used to study the mechanisms of MDM2-STAT3 signaling during KD pathogenesis.

Results

The MDM2 expression level decreased while the STAT3 level and vascular endothelial growth factor A (VEGFA) level increased in KD patients with CALs and the KD mouse model. Mechanistically, MDM2 colocalized with STAT3 in HCAECs and the coronary vessels of the KD mouse model. Knocking down MDM2 caused an increased level of STAT3 protein in HCAECs, whereas MDM2 overexpression upregulated the ubiquitination level of STAT3 protein, hence leading to significantly decreased turnover of STAT3 and VEGFA.

Conclusions

MDM2 functions as a negative regulator of STAT3 signaling by promoting its ubiquitination during KD pathogenesis, thus providing a potential intervention target for KD therapy.

Expression and clinical significance of miR-8078 in patients with congenital heart disease-associated pulmonary arterial hypertension

OBJECTIVES

This study aimed to analyze the plasma levels of miR-8078 in patients with congenital heart disease-associated pulmonary arterial hypertension (CHD-PAH) and to explore the diagnostic value and potential mechanisms of miR-8078 in CHD-PAH.

METHODS

Plasma samples were collected from 110 patients with congenital heart disease. Subsequently, based on the mean pulmonary artery pressure (PAPm) measured via right heart catheterization, the patients were divided into three groups: no-PAH group (Group W, PAPm < 25 mmHg), mild group (Group M, 25 mmHg ≤ PAPm < 35 mmHg), and moderate-to-severe group (Group H, PAPm ≥ 35 mmHg). The study also involved a control group (Group C) comprised of 40 healthy individuals. The miR-8078 expression levels were determined by means of reverse transcription-polymerase chain reaction (RT-PCR). The target genes and biological functions of miR-8078 were predicted using TargetScan, PicTar, and miRDB software. Statistical analysis was performed to evaluate the correlation between miR-8078 and hemodynamic parameters in CHD-PAH, in addition to its diagnostic value.

RESULTS

The plasma miR-8078 expression levels were significantly higher in the moderate-to-severe group when compared with the control group, no-PAH group, and mild group (p < 0.05). Furthermore, the mild group and no-PAH group showed significantly higher miR-8078 expression levels when compared with the control group (p < 0.05). Both results were consistent with the high-throughput sequencing results. KEGG pathway analysis of the miR-8078 target genes revealed associations with morphine addiction, ubiquitin-mediated proteolysis, and parathyroid hormone synthesis and secretion. GO enrichment analysis indicated the involvement of miR-8078 in the regulation of transcription by RNA polymerase II, the positive regulation of stress-activated MAPK cascade, the transmembrane transport of CI- and K+ ions, chromatin organization, and atrioventricular valve morphogenesis. Correlation analysis showed that the miR-8078 expression levels were positively correlated with the pulmonary artery systolic pressure, mean pulmonary artery pressure, and pulmonary vascular resistance (correlation coefficients of 0.404, 0.397, and 0.283, respectively; all p < 0.05). Univariate and multivariate regression analyses revealed plasma miR-8078 (odds ratio: 1.475, 95 % confidence interval: 1.053-2.065, p < 0.05) to be an independent risk factor for CHD-PAH. Receiver operating characteristic curve analysis revealed that the area under the curve (AUC) for miR-8078 alone and for B-type natriuretic peptide alone in diagnosing CHD-PAH was 0.686 and 0.851, respectively, while the AUC for a combined diagnosis was 0.874, which was higher than that associated with the individual diagnoses (p < 0.05).

CONCLUSION

The findings of this study suggest that miR-8078 is upregulated in CHD-PAH, while the results of the bioinformatics analysis indicate its involvement in the pathogenesis of CHD-PAH, suggesting it to be a potential therapeutic target or biomarker.

Interference of MDM2 attenuates vascular endothelial dysfunction in hypertension partly through blocking Notch1/NLRP3 inflammasome pathway

BACKGROUND

Hypertension is a life-threatening disease mainly featured as vascular endothelial dysfunction. This study aims to explore the regulatory role of murine double minute 2 (MDM2) in hypertension and vascular damage.

METHODS

Mice were infused with angiotensin II (AngII) to establish a hypertension mouse model in vivo and AngII-stimulated HUVECs were constructed to simulate the damage of vascular endothelial cells in hypertension in vitro. The plasmids targeting to MDM2 was injected to mice or transfected to HUVECs. qRT-PCR and western blot were performed to detect corresponding gene expression in mice aorta. Blood pressure was measured. H&E and Masson staining were conducted to evaluate histological changes of aorta. Responses to the acetylcholine (ACh) and sodium nitroprusside (SNP) were assessed in aorta. ZO-1 expression and cell apoptosis were detected by immunofluorescence and TUNEL, respectively. Network formation ability was determined employing a tube formation.

RESULTS

MDM2 was upregulated in hypertensive mice. Knockdown of MDM2 inhibited AngII-induced high BP, histological damage, vascular relaxation to Ach, and promoted the levels of p-eNOS and ZO-1 in the aorta in hypertensive mice. MDM2 knockdown inactivated Notch1 signaling and NLRP3 inflammasome, while the inhibitory effect of MDM2 knockdown on NLRP3 inflammasome activation was partly restored by the activation of Notch1. Furthermore, knockdown of MDM2 relieved AngII-induced endothelial dysfunction in HUVECs, as well as suppressing AngII-promoted cell apoptosis. Whereas, the impacts generated by MDM2 knockdown were partly weakened by the activation of Notch1 signaling or NLRP3 inflammasome.

CONCLUSION

In summary, knockdown of MDM2 can attenuate vascular endothelial dysfunction in hypertension, which may be achieved through inhibiting the activation of Notch1 and NLRP3 inflammasome.

The Apelin/APJ System: A Potential Therapeutic Target for Sepsis

Apelin is the native ligand for the G protein-coupled receptor APJ. Numerous studies have demonstrated that the Apelin/APJ system has positive inotropic, anti-inflammatory, and anti-apoptotic effects and regulates fluid homeostasis. The Apelin/APJ system has been demonstrated to play a protective role in sepsis and may serve as a promising therapeutic target for the treatment of sepsis. Better understanding of the mechanisms of the effects of the Apelin/APJ system will aid in the development of novel drugs for the treatment of sepsis. In this review, we provide a brief overview of the physiological role of the Apelin/APJ system and its role in sepsis.

The role and mechanism of AMPK in pulmonary hypertension

Pulmonary hypertension (PH) is a chronic progressive disease with high mortality. There has been more and more research focusing on the role of AMPK in PH. AMPK consists of three subunits-α, β, and γ. The crosstalk among these subunits ultimately leads to a delicate balance to affect PH, which results in conflicting conclusions about the role of AMPK in PH. It is still unclear how these subunits interfere with each other and achieve balance to improve or deteriorate PH. Several signaling pathways are related to AMPK in the treatment of PH, including AMPK/eNOS/NO pathway, Nox4/mTORC2/AMPK pathway, AMPK/BMP/Smad pathway, and SIRT3-AMPK pathway. Among these pathways, the role and mechanism of AMPK/eNOS/NO and Nox4/mTORC2/AMPK pathways are clearer than others, while the SIRT3-AMPK pathway remains still unclear in the treatment of PH. There are drugs targeting AMPK to improve PH, such as metformin (MET), MET combination, and rhodiola extract. In addition, several novel factors target AMPK for improving PH, such as ADAMTS8, TUFM, and Salt-inducible kinases. However, more researches are needed to explore the specific AMPK signaling pathways involved in these novel factors in the future. In conclusion, AMPK plays an important role in PH.

Transcriptional profiles of pulmonary artery endothelial cells in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is characterized by endothelial cell (EC) dysfunction. There are no data from living patients to inform whether differential gene expression of pulmonary artery ECs (PAECs) can discern disease subtypes, progression and pathogenesis. We aimed to further validate our previously described method to propagate ECs from right heart catheter (RHC) balloon tips and to perform additional PAEC phenotyping. We performed bulk RNA sequencing of PAECs from RHC balloons. Using unsupervised dimensionality reduction and clustering we compared transcriptional signatures from PAH to controls and other forms of pulmonary hypertension. Select PAEC samples underwent single cell and population growth characterization and anoikis quantification. Fifty-four specimens were analyzed from 49 subjects. The transcriptome appeared stable over limited passages. Six genes involved in sex steroid signaling, metabolism, and oncogenesis were significantly upregulated in PAH subjects as compared to controls. Genes regulating BMP and Wnt signaling, oxidative stress and cellular metabolism were differentially expressed in PAH subjects. Changes in gene expression tracked with clinical events in PAH subjects with serial samples over time. Functional assays demonstrated enhanced replication competency and anoikis resistance. Our findings recapitulate fundamental biological processes of PAH and provide new evidence of a cancer-like phenotype in ECs from the central vasculature of PAH patients. This "cell biopsy" method may provide insight into patient and lung EC heterogeneity to advance precision medicine approaches in PAH.

Angiotensin-Converting Enzyme 2 (ACE2) Signaling in Pulmonary Arterial Hypertension: Underpinning Mechanisms and Potential Targeting Strategies

Pulmonary arterial hypertension (PAH) is a debilitating progressive disease characterized by excessive pulmonary vasoconstriction and abnormal vascular remodeling processes that lead to right-ventricular heart failure and, ultimately, death. Although our understanding of its pathophysiology has advanced and several treatment modalities are currently available for the management of PAH patients, none are curative and the prognosis remains poor. Therefore, further research is required to decipher the molecular mechanisms associated with PAH. Angiotensin-converting enzyme 2 (ACE2) plays an important role through its vasoprotective functions in cardiopulmonary homeostasis, and accumulating preclinical and clinical evidence shows that the upregulation of the ACE2/Angiotensin-(1-7)/MAS1 proto-oncogene, G protein-coupled receptor (Mas 1 receptor) signaling axis is implicated in the pathophysiology of PAH. Herein, we highlight the molecular mechanisms of ACE2 signaling in PAH and discuss its potential as a therapeutic target.

USP2 inhibition prevents infection with ACE2-dependent coronaviruses in vitro and is protective against SARS-CoV-2 in mice

Targeting angiotensin-converting enzyme 2 (ACE2) represents a promising and effective approach to combat not only the COVID-19 pandemic but also potential future pandemics arising from coronaviruses that depend on ACE2 for infection. Here, we report ubiquitin specific peptidase 2 (USP2) as a host-directed antiviral target; we further describe the development of MS102, an orally available USP2 inhibitor with viable antiviral activity against ACE2-dependent coronaviruses. Mechanistically, USP2 serves as a physiological deubiquitinase of ACE2, and targeted inhibition with specific small-molecule inhibitor ML364 leads to a marked and reversible reduction in ACE2 protein abundance, thereby blocking various ACE2-dependent coronaviruses tested. Using human ACE2 transgenic mouse models, we further demonstrate that ML364 efficiently controls disease caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as evidenced by reduced viral loads and ameliorated lung inflammation. Furthermore, we improved the in vivo performance of ML364 in terms of both pharmacokinetics and antiviral activity. The resulting lead compound, MS102, holds promise as an oral therapeutic option for treating infections with coronaviruses that are reliant on ACE2.

Pinocembrin attenuates susceptibility to atrial fibrillation in rats with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a disease characterized by pulmonary vascular remodeling that triggers fibrosis and excessive myocardium apoptosis, ultimately facilitating atrial fibrillation (AF). In various rat models, Pinocembrin has anti-fibrotic and anti-apoptotic effects, reducing arrhythmia vulnerability. However, whether pinocembrin alleviates to AF in a PAH model remains unclear. The experiment aims to investigate how pinocembrin affects AF susceptibility in PAH rats and the possible mechanisms involved.

METHODS

The PAH model was induced by monocrotaline (MCT; i. p. 60 mg/kg). Concurrently, rats received pinocembrin (i.p.50 mg/kg) or saline. Hemodynamics parameters, electrocardiogram parameters, lung H.E. staining, atrial electrophysiological parameters, histology, Western blot, and TUNEL assay were detected.

RESULTS

Compared to the control rats, MCT-induced PAH rats possessed prominently enhancive mPAP (mean pulmonary artery pressure), pulmonary vascular remodeling, AF inducibility, HRV, right atrial myocardial fibrosis, apoptosis, atrial ERP, APD, and P-wave duration. Additionally, there were lowered protein levels of Cav1.2, Kv4.2, Kv4.3, and connexin 40 (CX40) in the MCT group in right atrial tissue. However, pinocembrin reversed the above pathologies and alleviated the activity of the Rho A/ROCKs signaling pathway, including the expression of Rho A, ROCK1, ROCK2, and its downstream MYPT-1, LIMK2, BCL-2, BAX, cleaved-caspase3 in right atrial and HL-1 cells.

CONCLUSION

Present data exhibited pinocembrin attenuated atrial electrical, ion-channel, and autonomic remodeling, diminished myocardial fibrosis and apoptosis levels, thereby reducing susceptibility to AF in the MCT-induced PAH rats. Furthermore, we found that pinocembrin exerted inhibitory action on the Rho A/ROCK signaling pathway, which may be potentially associated with its anti-AF effects.

New Approaches Targeting the Renin-Angiotensin System: Inhibition of Brain Aminopeptidase A, ACE2 Ubiquitination, and Angiotensinogen

Despite the availability of various therapeutic classes of antihypertensive drugs, hypertension remains poorly controlled, in part because of poor adherence. Hence, there is a need for the development of antihypertensive drugs acting on new targets to improve control of blood pressure. This review discusses novel insights (including the data of recent clinical trials) with regard to interference with the renin-angiotensin system, focusing on the enzymes aminopeptidase A and angiotensin-converting enzyme 2 (ACE2) in the brain, as well as the substrate of renin- angiotensinogen-in the liver. It raises the possibility that centrally acting amino peptidase A inhibitors (eg, firibastat), preventing the conversion of angiotensin II to angiotensin III in the brain, might be particularly useful in African Americans and patients with obesity. Firibastat additionally upregulates brain ACE2, allowing the conversion of angiotensin II to its protective metabolite angiotensin-(1-7). Furthermore, antisense oligonucleotides or small interfering ribonucleic acids suppress hepatic angiotensinogen for weeks to months after 1 injection and thus could potentially overcome adherence issues. Finally, interference with ACE2 ubiquitination is emerging as a future option for the treatment of neurogenic hypertension, given that ubiquitination resistance might upregulate ACE2 activity.

Posttranslational modifications of ACE2 protein: Implications for SARS-CoV-2 infection and beyond

The present worldwide pandemic of coronavirus disease 2019 (COVID-19) has highlighted the important function of angiotensin-converting enzyme 2 (ACE2) as a receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry. A deeper understanding of ACE2 could offer insights into the mechanisms of SARS-CoV-2 infection. While ACE2 is subject to regulation by various factors in vivo, current research in this area is insufficient to fully elucidate the corresponding pathways of control. Posttranslational modification (PTM) is a powerful tool for broadening the variety of proteins. The PTM study of ACE2 will help us to make up for the deficiency in the regulation of protein synthesis and translation. However, research on PTM-related aspects of ACE2 remains limited, mostly focused on glycosylation. Accordingly, a comprehensive review of ACE2 PTMs could help us better understand the infection process and provide a basis for the treatment of COVID-19 and beyond.

A role of TRIM59 in pulmonary hypertension: modulating the protein ubiquitylation modification

BACKGROUND

Pulmonary hypertension (PH), an infrequent disease, is characterized by excessive pulmonary vascular remodeling and proliferation of pulmonary artery smooth muscle cells (PASMCs). However, its underlying molecular mechanisms remain unclear. Uncovering its molecular mechanisms will be beneficial to the treatment of PH.

METHODS

Differently expressed genes (DEGs) in the lung tissues of PH patients were analyzed with a GEO dataset GSE113439. From these DEGs, we focused on TRIM59 which was highly expressed in PH patients. Subsequently, the expression of TRIM59 in the pulmonary arteries of PH patients, lung tissues of PH rat model and PASMCs cultured in a hypoxic condition was verified by quantitative real-time PCR (qPCR), western blot and immunohistochemistry. Furthermore, the role of TRIM59 in PAMSC proliferation and pathological changes in PH rats was assessed via gain-of-function and loss-of-function experiments. In addition, the transcriptional regulation of YAP1/TEAD4 on TRIM59 was confirmed by qPCR, western blot, luciferase reporter assay, ChIP and DNA pull-down. In order to uncover the underlying mechanisms of TRIM59, a protein ubiquitomics and a CoIP- HPLC-MS/MS were companied to identify the direct targets of TRIM59.

RESULTS

TRIM59 was highly expressed in the pulmonary arteries of PH patients and lung tissues of PH rats. Over-expression of TRIM59 accelerated the proliferation of PASMCs, while TRIM59 silencing resulted in the opposite results. Moreover, TRIM59 silencing mitigated the injuries in heart and lung and attenuated pulmonary vascular remodeling during PH. In addition, its transcription was positively regulated by YAP1/TEAD4. Then we further explored the underlying mechanisms of TRIM59 and found that TRIM59 overexpression resulted in an altered ubiquitylation of proteins. Accompanied with the results of CoIP- HPLC-MS/MS, 34 proteins were identified as the direct targets of TRIM59.

CONCLUSION

TRIM59 was highly expressed in PH patients and promoted the proliferation of PASMCs and pulmonary vascular remodeling, thus contributing to the pathogenesis of PH. It is indicated that TRIM59 may become a potential target for PH treatment.

Nedd4-2 up-regulation is associated with ACE2 ubiquitination in hypertension

AIMS

Angiotensin-converting enzyme 2 (ACE2) is a critical component of the compensatory renin-angiotensin system that is down-regulated during the development of hypertension, possibly via ubiquitination. However, little is known about the mechanisms involved in ACE2 ubiquitination in neurogenic hypertension. This study aimed at identifying ACE2 ubiquitination partners, establishing causal relationships and clinical relevance, and testing a gene therapy strategy to mitigate ACE2 ubiquitination in neurogenic hypertension.

METHODS AND RESULTS

Bioinformatics and proteomics were combined to identify E3 ubiquitin ligases associated with ACE2 ubiquitination in chronically hypertensive mice. In vitro gain/loss of function experiments assessed ACE2 expression and activity to validate the interaction between ACE2 and the identified E3 ligase. Mutation experiments were further used to generate a ubiquitination-resistant ACE2 mutant (ACE2-5R). Optogenetics, blood pressure telemetry, pharmacological blockade of GABAA receptors in mice expressing ACE2-5R in the bed nucleus of the stria terminalis (BNST), and capillary western analysis were used to assess the role of ACE2 ubiquitination in neurogenic hypertension. Ubiquitination was first validated as leading to ACE2 down-regulation, and Neural precursor cell-expressed developmentally down-regulated protein 4-2 (Nedd4-2) was identified as a E3 ligase up-regulated in hypertension and promoting ACE2 ubiquitination. Mutation of lysine residues in the C-terminal of ACE2 was associated with increased activity and resistance to angiotensin (Ang)-II-mediated degradation. Mice transfected with ACE2-5R in the BNST exhibited enhanced GABAergic input to the paraventricular nucleus (PVN) and a reduction in hypertension. ACE2-5R expression was associated with reduced Nedd4-2 levels in the BNST.

CONCLUSION

Our data identify Nedd4-2 as the first E3 ubiquitin ligase involved in ACE2 ubiquitination in Ang-II-mediated hypertension. We demonstrate the pivotal role of ACE2 on GABAergic neurons in the maintenance of an inhibitory tone to the PVN and the regulation of pre-sympathetic activity. These findings provide a new working model where Nedd4-2 could contribute to ACE2 ubiquitination, leading to the development of neurogenic hypertension and highlighting potential novel therapeutic strategies.

ACE2 in chronic disease and COVID-19: gene regulation and post-translational modification

Angiotensin-converting enzyme 2 (ACE2), a counter regulator of the renin-angiotensin system, provides protection against several chronic diseases. Besides chronic diseases, ACE2 is the host receptor for SARS-CoV or SARS-CoV-2 virus, mediating the first step of virus infection. ACE2 levels are regulated by transcriptional, post-transcriptional, and post-translational regulation or modification. ACE2 transcription is enhanced by transcription factors including Ikaros, HNFs, GATA6, STAT3 or SIRT1, whereas ACE2 transcription is reduced by the transcription factor Brg1-FoxM1 complex or ERRα. ACE2 levels are also regulated by histone modification or miRNA-induced destabilization. The protein kinase AMPK, CK1α, or MAP4K3 phosphorylates ACE2 protein and induces ACE2 protein levels by decreasing its ubiquitination. The ubiquitination of ACE2 is induced by the E3 ubiquitin ligase MDM2 or UBR4 and decreased by the deubiquitinase UCHL1 or USP50. ACE2 protein levels are also increased by the E3 ligase PIAS4-mediated SUMOylation or the methyltransferase PRMT5-mediated ACE2 methylation, whereas ACE2 protein levels are decreased by AP2-mediated lysosomal degradation. ACE2 is downregulated in several human chronic diseases like diabetes, hypertension, or lung injury. In contrast, SARS-CoV-2 upregulates ACE2 levels, enhancing host cell susceptibility to virus infection. Moreover, soluble ACE2 protein and exosomal ACE2 protein facilitate SARS-CoV-2 infection into host cells. In this review, we summarize the gene regulation and post-translational modification of ACE2 in chronic disease and COVID-19. Understanding the regulation and modification of ACE2 may help to develop prevention or treatment strategies for ACE2-mediated diseases.

MDM2 Influences ACE2 Stability and SARS-CoV-2 Uptake

Angiotensin-converting enzyme 2 (ACE2) is the central entry receptor for SARS-CoV-2. However, surprisingly little is known about the effects of host regulators on ACE2 localization, expression, and the associated influence on SARS-CoV-2 infection. Here we identify that ACE2 expression levels are regulated by the E3 ligase MDM2 and that MDM2 levels indirectly influence infection with SARS-CoV-2. Genetic depletion of MDM2 elevated ACE2 expression levels, which strongly promoted infection with all SARS-CoV-2 isolates tested. SARS-CoV-2 spike-pseudotyped viruses and the uptake of non-replication-competent virus-like particles showed that MDM2 affects the viral uptake process. MDM2 ubiquitinates Lysine 788 of ACE2 to induce proteasomal degradation, and degradation of this residue led to higher ACE2 expression levels and superior virus particle uptake. Our study illustrates that cellular regulators of ACE2 stability, such as MDM2, play an important role in defining the infection capabilities of SARS-CoV-2.

E3 Ubiquitin Ligases in Endothelial Dysfunction and Vascular Diseases: Roles and Potential Therapies

ABSTRACT

Ubiquitin E3 ligases are a structurally conserved family of enzymes that exert a variety of regulatory functions in immunity, cell death, and tumorigenesis through the ubiquitination of target proteins. Emerging evidence has shown that E3 ubiquitin ligases play crucial roles in the pathogenesis of endothelial dysfunction and related vascular diseases. Here, we reviewed the new findings of E3 ubiquitin ligases in regulating endothelial dysfunction, including endothelial junctions and vascular integrity, endothelial activation, and endothelial apoptosis. The critical role and potential mechanism of E3 ubiquitin ligases in vascular diseases, such as atherosclerosis, diabetes, hypertension, pulmonary hypertension, and acute lung injury, were summarized. Finally, the clinical significance and potential therapeutic strategies associated with the regulation of E3 ubiquitin ligases were also proposed.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

CircItgb5 promotes synthetic phenotype of pulmonary artery smooth muscle cells via interacting with miR-96-5p and Uba1 in monocrotaline-induced pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a rare but fatal cardiopulmonary disease mainly characterized by pulmonary vascular remodeling. Aberrant expression of circRNAs has been reported to play a crucial role in pulmonary vascular remodeling. The existing literature predominantly centers on studies that examined the sponge mechanism of circRNAs. However, the mechanism of circRNAs in regulating PAH-related protein remains largely unknown. This study aimed to investigate the effect of circItgb5 on pulmonary vascular remodeling and the underlying functional mechanism.

MATERIALS AND METHODS

High-throughput circRNAs sequencing was used to detect circItgb5 expression in control and PDGF-BB-treated pulmonary arterial smooth muscle cells (PASMCs). Localization of circItgb5 in PASMCs was determined via the fluorescence in situ hybridization assay. Sanger sequencing was applied to analyze the circularization of Itgb5. The identification of proteins interacting with circItgb5 was achieved through a RNA pull-down assay. To assess the impact of circItgb5 on PASMCs proliferation, an EdU assay was employed. Additionally, the cell cycle of PASMCs was examined using a flow cytometry assay. Western blotting was used to detect biomarkers associated with the phenotypic switch of PASMCs. Furthermore, a monocrotaline (MCT)-induced PAH rat model was established to explore the effect of silencing circItgb5 on pulmonary vascular remodeling.

RESULTS

CircItgb5 was significantly upregulated in PDGF-BB-treated PASMCs and was predominately localized in the cytoplasm of PASMCs. In vivo experiments revealed that the knockdown of circItgb5 attenuated MCT-induced pulmonary vascular remodeling and right ventricular hypertrophy. In vitro experiments revealed that circItgb5 promoted the transition of PASMCs to synthetic phenotype. Mechanistically, circItgb5 sponged miR-96-5p to increase mTOR level and interacted with Uba1 protein to activate the Ube2n/Mdm2/ACE2 pathway.

CONCLUSIONS

CircItgb5 promoted the transition of PASMCs to synthetic phenotype by interacting with miR-96-5p and Uba1 protein. Knockdown of circItgb5 mitigated pulmonary arterial pressure, pulmonary vascular remodeling and right ventricular hypertrophy. Overall, circItgb5 has the potential for application as a therapeutic target for PAH.

Inhibiting the Deubiquitinase UCHL1 Reduces SARS-CoV-2 Viral Uptake by ACE2

Coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a significant public health burden with limited treatment options. Many β-coronaviruses, including SARS-CoV-2, gain entry to host cells through the interaction of SARS-CoV-2 spike protein with membrane-bound ACE2 (angiotensin-converting enzyme 2). Given its necessity for SARS-CoV-2 infection, ACE2 represents a potential therapeutic target in COVID-19. However, early attempts focusing on ACE2 in COVID-19 have not validated it as a druggable target nor identified other ACE2-related novel proteins for therapeutic intervention. Here, we identify a mechanism for ACE2 protein modulation by the deubiquitinase (DUB) enzyme UCHL1 (ubiquitin carboxyl-terminal hydrolase isozyme L1). ACE2 is constitutively ubiquitinated and degraded by the proteasome in lung epithelia. SARS-CoV-2 spike protein cellular internalization increased ACE2 protein abundance by decreasing its degradation. Using an siRNA library targeting 96 human DUBs, we identified UCHL1 as a putative regulator of ACE2 function as a viral receptor. Overexpressed UCHL1 preserved ACE2 protein abundance, whereas silencing of the DUB in cells destabilized ACE2 through increased polyubiquitination. A commercially available small molecule inhibitor of UCHL1 DUB activity decreased ACE2 protein concentrations coupled with inhibition of SARS-CoV-2 infection in epithelial cells. These findings describe a unique pathway of ACE2 regulation uncovering UCHL1 as a potential therapeutic target to modulate COVID-19 viral entry as a platform for future small molecule design and testing.

Mean pulmonary artery pressure estimated by echocardiogram rapidly exceeds 20 mmHg from the normal range in patients with connective tissue disease

Earlier intervention for pulmonary hypertension (PH) has been reported to improve the prognosis of patients with connective tissue disease (CTD). However, it is not fully elucidated how rapidly PH develops in patients showing normal mean pulmonary arterial pressure (mPAP) at the index investigation. We evaluated 191 CTD patients with normal mPAP retrospectively. The mPAP was estimated by the formerly defined method employing echocardiography (mPAP^echo). We investigated predictive factors that predict increasing mPAP^echo at follow-up transthoracic echocardiography (TTE) using uni- and multi variable analysis. The mean age was 61.5 years old, and 160 patients were female. The percentage of patients in whom mPAP^echo exceeded 20 mmHg at follow-up TTE was 38%. Multivariable analysis revealed that acceleration time/ejection time (AcT/ET) measured at the right ventricular outflow tract at initial TTE was independently associated with the consequent increase of mPAP^echo at the follow-up TTE. When using 0.43 of best cutoff value in AcT/ET calculated by receiver operating characteristic analysis, the change in mPAP^echo in patients with low AcT/ET was significantly higher than in those with high AcT/ET (3.05 mmHg in patients with AcT/ET < 0.43 and 1.00 mmHg in patients with AcT/ET ≥ 0.43, p < 0.001). Thirty-eight percent of CTD patients who show the normal estimated mPAP by TTE develop gradual elevation of mPAP to the level to consider early intervention within 2 years. AcT/ET at initial TTE can predict increasing mPAP at follow-up TTE.

Vitamin C promotes ACE2 degradation and protects against SARS-CoV-2 infection

ACE2 is a major receptor for cellular entry of SARS-CoV-2. Despite advances in targeting ACE2 to inhibit SARS-CoV-2 binding, strategies to flexibly and sufficiently reduce ACE2 levels for the prevention of SARS-CoV-2 infection have not been explored. Here, we reveal vitamin C (VitC) administration as a potent strategy to prevent SARS-CoV-2 infection. VitC reduces ACE2 protein levels in a dose-dependent manner, while even a partial reduction in ACE2 levels can greatly inhibit SARS-CoV-2 infection. Further studies reveal that USP50 is a crucial regulator of ACE2 levels. VitC blocks the USP50-ACE2 interaction, thus promoting K48-linked polyubiquitination of ACE2 at Lys788 and subsequent degradation of ACE2 without affecting its transcriptional expression. Importantly, VitC administration reduces host ACE2 levels and greatly blocks SARS-CoV-2 infection in mice. This study reveals that ACE2 protein levels are down-regulated by an essential nutrient, VitC, thereby enhancing protection against infection of SARS-CoV-2 and its variants.

Angiotensin-converting enzyme 2-at the heart of the COVID-19 pandemic

ACE2 is the indispensable entry receptor for SARS-CoV and SARS-CoV-2. Because of the COVID-19 pandemic, it has become one of the most therapeutically targeted human molecules in biomedicine. ACE2 serves two fundamental physiological roles: as an enzyme, it alters peptide cascade balance; as a chaperone, it controls intestinal amino acid uptake. ACE2's tissue distribution, affected by co-morbidities and sex, explains the broad tropism of coronaviruses and the clinical manifestations of SARS and COVID-19. ACE2-based therapeutics provide a universal strategy to prevent and treat SARS-CoV-2 infections, applicable to all SARS-CoV-2 variants and other emerging zoonotic coronaviruses exploiting ACE2 as their cellular receptor.

CDK4/6 inhibitor palbociclib promotes SARS-CoV-2 cell entry by down-regulating SKP2 dependent ACE2 degradation

Coronavirus disease 2019 (COVID-19) outbreak has become a global pandemic. CDK4/6 inhibitor palbociclib was reported to be one of the top-scored repurposed drugs to treat COVID-19. As the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry, expression level of angiotensin-converting enzyme 2 (ACE2) is closely related to SARS-CoV-2 infection. In this study, we demonstrated that palbociclib and other methods could arrest cells in G0/G1 phase and up-regulate ACE2 mRNA and protein levels without altering its subcellular localization. Palbociclib inhibited ubiquitin-proteasome and lysosomal degradation of ACE2 through down-regulating S-phase kinase-associated protein 2 (SKP2). In addition, increased ACE2 expression induced by palbociclib and other cell cycle arresting compounds facilitated pseudotyped SARS-CoV-2 infection. This study suggested that ACE2 expression was down-regulated in proliferating cells. Cell cycle arresting compounds could increase ACE2 expression and facilitate SARS-CoV-2 cell entry, which may not be suitable therapeutic agents for the treatment of SARS-CoV-2 infection.

USP15 promotes pulmonary vascular remodeling in pulmonary hypertension in a YAP1/TAZ-dependent manner

Pulmonary hypertension (PH) is a life-threatening cardiopulmonary disease characterized by pulmonary vascular remodeling. Excessive growth and migration of pulmonary artery smooth muscle cells (PASMCs) are believed to be major contributors to pulmonary vascular remodeling. Ubiquitin-specific protease 15 (USP15) is a vital deubiquitinase that has been shown to be critically involved in many pathologies. However, the effect of USP15 on PH has not yet been explored. In this study, the upregulation of USP15 was identified in the lungs of PH patients, mice with SU5416/hypoxia (SuHx)-induced PH and rats with monocrotaline (MCT)-induced PH. Moreover, adeno-associated virus-mediated functional loss of USP15 markedly alleviated PH exacerbation in SuHx-induced mice and MCT-induced rats. In addition, the abnormal upregulation and nuclear translocation of YAP1/TAZ was validated after PH modeling. Human pulmonary artery smooth muscle cells (hPASMCs) were exposed to hypoxia to mimic PH in vitro, and USP15 knockdown significantly inhibited cell proliferation, migration, and YAP1/TAZ signaling in hypoxic hPASMCs. Rescue assays further suggested that USP15 promoted hPASMC proliferation and migration in a YAP1/TAZ-dependent manner. Coimmunoprecipitation assays indicated that USP15 could interact with YAP1, while TAZ bound to USP15 after hypoxia treatment. We further determined that USP15 stabilized YAP1 by inhibiting the K48-linked ubiquitination of YAP1. In summary, our findings reveal the regulatory role of USP15 in PH progression and provide novel insights into the pathogenesis of PH.

Potential long-term effects of SARS-CoV-2 infection on the pulmonary vasculature: Multilayered cross-talks in the setting of coinfections and comorbidities

The Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and its sublineages pose a new challenge to healthcare systems worldwide due to its ability to efficiently spread in immunized populations and its resistance to currently available therapies. COVID-19, although targeting primarily the respiratory system, is also now well established that later affects every organ in the body. Most importantly, despite the available therapy and vaccine-elicited protection, the long-term consequences of viral infection in breakthrough and asymptomatic individuals are areas of concern. In the past two years, investigators accumulated evidence on how the virus triggers our immune system and the molecular signals involved in the cross-talk between immune cells and structural cells in the pulmonary vasculature to drive pathological lung complications such as endothelial dysfunction and thrombosis. In the review, we emphasize recent updates on the pathophysiological inflammatory and immune responses associated with SARS-CoV-2 infection and their potential long-term consequences that may consequently lead to the development of pulmonary vascular diseases.

Pathogenic Mechanisms of Pulmonary Arterial Hypertension: Homeostasis Imbalance of Endothelium-Derived Relaxing and Contracting Factors

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease. Sustained pulmonary vasoconstriction and concentric pulmonary vascular remodeling contribute to the elevated pulmonary vascular resistance and pulmonary artery pressure in PAH. Endothelial cells regulate vascular tension by producing endothelium-derived relaxing factors (EDRFs) and endothelium-derived contracting factors (EDCFs). Homeostasis of EDRF and EDCF production has been identified as a marker of the endothelium integrity. Impaired synthesis or release of EDRFs induces persistent vascular contraction and pulmonary artery remodeling, which subsequently leads to the development and progression of PAH. In this review, the authors summarize how EDRFs and EDCFs affect pulmonary vascular homeostasis, with special attention to the recently published novel mechanisms related to endothelial dysfunction in PAH and drugs associated with EDRFs and EDCFs.

Novel hub genes associated with pulmonary artery remodeling in pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening disease with complex pathogenesis. According to etiology, PH is divided into five major groups in clinical classification. However, pulmonary artery (PA) remodeling is their common feature, in addition to bone morphogenetic protein receptor type 2; it is elusive whether there are other novel common genes and similar underlying mechanisms. To identify novel common hub genes involved in PA remodeling at different PH groups, we analyzed mRNA-Seq data located in the general gene expression profile GSE130391 utilizing bioinformatics technology. This database contains PA samples from different PH groups of hospitalized patients with chronic thromboembolic pulmonary hypertension (CTEPH), idiopathic pulmonary artery hypertension (IPAH), and PA samples from organ donors without known pulmonary vascular diseases as control. We screened 22 hub genes that affect PA remodeling, most of which have not been reported in PH. We verified the top 10 common hub genes in hypoxia with Sugen-induced PAH rat models by qRT-PCR. The three upregulated candidate genes are WASF1, ARHGEF1 and RB1 and the seven downregulated candidate genes are IL1R1, RHOB, DAPK1, TNFAIP6, PKN1, PLOD2, and MYOF. WASF1, ARHGEF1, and RB1 were upregulated significantly in hypoxia with Sugen-induced PAH, while IL1R1, DAPK1, and TNFA1P6 were upregulated significantly in hypoxia with Sugen-induced PAH. The DEGs detected by mRNA-Seq in hospitalized patients with PH are different from those in animal models. This study will provide some novel target genes to further study PH mechanisms and treatment.

SARS-CoV-2 down-regulates ACE2 through lysosomal degradation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes its Spike (S) glycoprotein to bind to the angiotensin-converting enzyme 2 (ACE2) receptor for cellular entry. ACE2 is a critical negative regulator of the renin-angiotensin system and plays a protective role in preventing tissue injury. Expression of ACE2 has been shown to decrease upon infection by SARS-CoV. However, whether SARS-CoV-2 down-regulates ACE2 and the underlying mechanism and biological impact of this down-regulation have not been well defined. Here we show that the SARS-CoV-2 infection down-regulates ACE2 in vivo in an animal model, and in cultured cells in vitro, by inducing clathrin- and AP2-dependent endocytosis, leading to its degradation in the lysosome. SARS-CoV-2 S-treated cells and ACE2 knockdown cells exhibit similar alterations in downstream gene expression, with a pattern indicative of activated cytokine signaling that is associated with respiratory distress and inflammatory diseases often observed in COVID-19 patients. Finally, we have identified a soluble ACE2 fragment with a stronger binding to SARS-CoV-2 S that can efficiently block ACE2 down-regulation and viral infection. Thus, our study suggests that ACE2 down-regulation represents an important mechanism underlying SARS-CoV-2-associated pathology, and blocking this process could be a promising therapeutic strategy.

A snapshot of protein trafficking in SARS-CoV-2 infection

SARS-CoV-2 is a human pathogenic virus responsible for the COVID-19 (coronavirus disease 2019) pandemic. The infection cycle of SARS-CoV-2 involves several related steps, including virus entry, gene expression, RNA replication, assembly of infectious virions and their egress. For all of these steps, the virus relies on and exploits host cell factors, cellular organelles, and processes such as endocytosis, nuclear transport, protein secretion, metabolite transport at membrane contact sites (MSC) and exocytotic pathways. To do this, SARS-CoV-2 has evolved multifunctional viral proteins that hijack cellular factors and modulate their function by unique strategies. In this Review, we highlight cellular trafficking factors, processes, and organelles of relevance to the SARS-CoV-2 infection cycle and how viral proteins make use of and perturb cellular transport during the viral infection cycle.

MIR99AHG inhibits EMT in pulmonary fibrosis via the miR-136-5p/USP4/ACE2 axis

Background

Long non-coding RNAs (lncRNAs) are closely related to the occurrence and development of cancer. Abnormally expressed lncRNA can be used as a diagnostic marker for cancer. In this study, we aim to investigate the clinical significance of MIR99AHG expression in lung adenocarcinoma (LUAD), and its biological roles in LUAD progression.

Methods

The relative expression of MIR99AHG in LUAD tissues and cell lines was analyzed using public databases and RT-qPCR. The biological functions of MIR99AHG were investigated using a loss-of-function approach. The effect of MIR99AHG on lung fibrosis was assessed by scratch assay, invasion assay and lung fibrosis rat model. FISH, luciferase reporter assay and immunofluorescence were performed to elucidate the underlying molecular mechanisms.

Results

LncRNA MIR99AHG expression level was downregulated in LUAD tissues and cell lines. Low MIR99AHG levels were associated with poorer patient overall survival. Functional analysis showed that MIR99AHG is associated with the LUAD malignant phenotype in vitro and in vivo. Further mechanistic studies showed that, MIR99AHG functions as a competitive endogenous RNA (ceRNA) to antagonize miR-136-5p-mediated ubiquitin specific protease 4 (USP4) degradation, thereby unregulated the expression of angiotensin-converting enzyme 2 (ACE2), a downstream target gene of USP4, which in turn affected alveolar type II epithelial cell fibrosis and epithelial–mesenchymal transition (EMT). In summary, the MIR99AHG/miR-136-5p/USP4/ACE2 signalling axis regulates lung fibrosis and EMT, thus inhibiting LUAD progression.

Conclusion

This study showed that downregulated MIR99AHG leads to the development of pulmonary fibrosis. Therefore, overexpression of MIR99AHG may provide a new approach to preventing LUAD progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03633-y.

Identification of Signal Pathways and Hub Genes of Pulmonary Arterial Hypertension by Bioinformatic Analysis

Pulmonary arterial hypertension (PAH) is a progressive and complex pulmonary vascular disease with poor prognosis. The aim of this study was to provide a new understanding of the pathogenesis of disease and potential treatment targets for patients with PAH based on multiple-microarray analysis.Two microarray datasets (GSE53408 and GSE113439) downloaded from the Gene Expression Omnibus (GEO) database were analysed. All the raw data were processed by R, and differentially expressed genes (DEGs) were screened out by the “limma” package. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed and visualized by R and Cytoscape software. Protein-protein interactions (PPI) of DEGs were analysed based on the NetworkAnalyst online tool. A total of 442 upregulated DEGs and 84 downregulated DEGs were identified. GO enrichment analysis showed that these DEGs were mainly enriched in mitotic nuclear division, organelle fission, chromosome segregation, nuclear division, and sister chromatid segregation. Significant KEGG pathway enrichment included ribosome biogenesis in eukaryotes, RNA transport, proteoglycans in cancer, dilated cardiomyopathy, rheumatoid arthritis, vascular smooth muscle contraction, focal adhesion, regulation of the actin cytoskeleton, and hypertrophic cardiomyopathy. The PPI network identified 10 hub genes including HSP90AA1, CDC5L, MDM2, LRRK2, CFTR, IQGAP1, CAND1, TOP2A, DDX21, and HIF1A. We elucidated potential biomarkers and therapeutic targets for PAH by bioinformatic analysis, which provides a theoretical basis for future study.

Corosolic acid sensitizes ferroptosis by upregulating HERPUD1 in liver cancer cells

Primary liver cancer is the third leading cause of cancer death in the world, and the lack of effective treatments is the main reason for the high mortality. Corosolic acid (CA) has been proved to have antitumor activity. In this study, we found that CA can sensitize liver cancer cells to ferroptosis, which is a regulated form of cell death characterized by iron-dependent lipid peroxides reaching lethal levels. Here, we revealed that CA can inhibit glutathione (GSH) synthesis via HERPUD1, decreasing the cellular GSH level and causing liver cancer cells to become more sensitive to ferroptosis. Mechanistically, further studies found that HERPUD1 reduced the ubiquitination of the GSS-associated E3 ubiquitin ligase MDM2, which promoted ubiquitination of GSS, thereby inhibiting GSH synthesis to increase ferroptosis susceptibility. Importantly, a mouse xenograft model also demonstrated that CA inhibits tumor growth via HERPUD1. Collectively, our findings suggesting that CA is a candidate component for the development of treatments against liver cancer.

GMI, a protein from Ganoderma microsporum, induces ACE2 degradation to alleviate infection of SARS-CoV-2 Spike-pseudotyped virus

BACKGROUND

Severe Acute Respiratory Syndrome Coronavirus Type 2 (SARS-CoV-2) induces a global serious pandemic and is responsible for over 4 million human deaths. Currently, although various vaccines have been developed, humans can still get SARS-CoV-2 infection after being vaccinated. Therefore, the blocking of SARS-CoV-2 infection may be potential therapeutic strategies. Ganoderma microsporum immunomodulatory protein (GMI), a small fungal protein, is cloned from Ganoderma microsporum. It exhibits anti-cancer and immunomodulatory functions. Currently, it is still unclear whether GMI involves in interfering with viral infection.

PURPOSE

This study aimed to examine the potential functions and mechanisms of GMI on inhibiting SARS-CoV-2 pseudovirus infection.

METHODS

The effects of GMI were examined in vitro on ACE2 overexpressing HEK293T (HEK293T/ACE2) cells exposed to SARS-CoV-2 Spike lentiviral pseudovirus encoding a green fluorescent protein (GFP) gene. The infection efficacy was determined using fluorescence microscopy and flow cytometry. The protein level of ACE2 was verified by Western blot. The effects of GMI on cell viability of HEK293T/ACE2 and lung epithelial WI38-2RA cells were determined by MTT assay. Mice received GMI via nebulizer.

RESULTS

GMI did not affect the cell viability of HEK293T/ACE2, WI38-2RA and macrophages. Functional studies showed that GMI inhibited GFP expressing SARS-CoV-2 pseudovirus from infecting HEK293T/ACE2 cells. GMI slightly interfered the interaction between ACE2 and Spike protein. GMI interacted with S2 domain of Spike protein. Specifically, GMI dramatically reduced ACE2 expression in HEK293T/ACE2 and WI38-2RA cells. Mechanistically, GMI induced ACE2 degradation via activating protein degradation system, including proteasome and lysosome. Abolishing proteasome and lysosome by MG132 and bafilomycin A1, respectively, rescued GMI-reduced ACE2 levels. In addition, GMI triggered dynamin and lipid raft-mediated ACE2 endocytosis. ACE2 levels were downregulated in the lung tissue after the mice inhaling GMI.

CONCLUSIONS

GMI prevents SARS-CoV-2 pseudovirus infection via induction of ACE2 degradation in host cells. Our findings suggest that GMI will be a potential prevention agent to alleviate SARS-CoV-2 infection.

Tripartite motif 25 ameliorates doxorubicin-induced cardiotoxicity by degrading p85α

Doxorubicin (DOX)-based chemotherapy is widely used to treat malignant tumors; however, the cardiotoxicity induced by DOX restricts its clinical usage. A therapeutic dose of DOX can activate ubiquitin-proteasome system. However, whether and how ubiquitin-proteasome system brings out DOX-induced cardiotoxicity remains to be investigated. Here we conducted a proteomics analysis of a DOX-induced cardiotoxicity model to screen the potentially ubiquitination-related molecules. Dysregulated TRIM25 was found to contribute to the cardiotoxicity. In vivo and in vitro cardiotoxicity experiments revealed that TRIM25 ameliorated DOX-induced cardiotoxicity. Electron microscopy and endoplasmic reticulum stress markers revealed that TRIM25 mitigated endoplasmic reticulum stress and apoptosis in DOX-induced cardiomyocytes. Mechanistically, the Co-immunoprecipitation assays and CHX pulse-chase experiment determined that TRIM25 affected p85α stability and promoted its ubiquitination and degradation. This leads to increase of nuclear translocation of XBP-1s, which mitigates endoplasmic reticulum stress. These findings reveal that TRIM25 may have a therapeutic role for DOX-induced cardiotoxicity.