E3 Ubiquitin Ligases as Immunotherapeutic Target in Atherosclerotic Cardiovascular Disease

CBL-b E3 ligase-mediated neddylation and activation of PARP-1 induce vascular calcification

Vascular calcification (VC) refers to the accumulation of mineral deposits on the walls of arteries and veins, and it is closely associated with increased mortality in cardiovascular disease patients, particularly among high-risk patients with diabetes and chronic kidney disease (CKD). Neuronal precursor cell-expressed developmentally downregulated protein 8 (NEDD8) is a ubiquitin-like protein that plays a pivotal role in various cellular functions, primarily through its conjugation to target proteins and subsequent relay of biological signals. However, the role of NEDDylation in VC has not been investigated. In our study, we observed that MLN4924, an inhibitor of the NEDD8-activating E1 enzyme, effectively impedes the progression of VC. LC‒MS/MS analysis revealed that poly(ADP‒ribose) polymerase 1 (PARP-1) is subjected to NEDD8 conjugation, leading to an increase in PARP-1 activity during VC. We subsequently revealed that PARP-1 NEDDylation is mediated by the E3 ligase CBL proto-oncogene B (CBL-b) and is reversed by NEDD8-specific protease 1 (NEDP-1) during VC. Furthermore, the CBL-b C373 peptide effectively mitigated the inactive form of the E3 ligase activity of CBL-b, ultimately preventing VC. These findings provide compelling evidence that the NEDD8-dependent activation of PARP-1 represents a novel mechanism underlying vascular calcification and suggests a promising new therapeutic target for VC.

Long Non-Coding RNA Nuclear-Enriched Abundant Transcript 1 (NEAT1) Facilitates Foam Cell Formation and Atherosclerosis Progression Through the miR-17-5p/Itchy E3 Ubiquitin Protein Ligase (ITCH)/Liver Kinase B1 (LKB1) Axis

BACKGROUND

Foam cell formation is an important step for atherosclerosis (AS) progression. We investigated the mechanism by which the long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) regulates foam cell formation during AS progression.

METHODS AND RESULTS

An in vivo AS model was created by feeding ApoE-/-mice a high-fat diet. Oxidized low-density lipoprotein (ox-LDL)-stimulated macrophages were used as a cellular AS model. Interactions between NEAT1, miR-17-5p, itchy E3 ubiquitin protein ligase (ITCH) and liver kinase B1 (LKB1) were analyzed. NEAT1 and ITCH were highly expressed in clinical samples collected from 10 AS patients and in ox-LDL-treated macrophages, whereas expression of both miR-17-5p and LKB1 was low. ITCH knockdown inhibited ox-LDL-induced lipid accumulation and LDL uptake in macrophages. Mechanistically speakingly, ITCH promoted LDL uptake and lipid accumulation in macrophages by mediating LKB1 ubiquitination degradation. NEAT1 knockdown reduced LDL uptake and lipid accumulation in macrophages and AS progression in vivo. NEAT1 promoted ITCH expression in macrophages by acting as a sponge for miR-17-5p. Inhibition of miR-17-5p facilitated ox-LDL-induced increase in LDL uptake and lipid accumulation in macrophages, which was reversed by NEAT1/ITCH knockdown.

CONCLUSIONS

NEAT1 accelerated foam cell formation during AS progression through the miR-17-5p/ITCH/LKB1 axis.

An update on the role of TRIM/NLRP3 signaling pathway in atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease of large and medium arteries that includes lipid metabolism disorder and recruitment of immune cells to the artery wall. An increasing number of studies have confirmed that inflammasome over-activation is associated with the onset and progression of atherosclerosis. The NLRP3 inflammasome, in particular, has been proven to increase the incidence rate of cardiovascular diseases (CVD) by promoting pro-inflammatory cytokine release and reducing plaque stability. The strict control of inflammasome and prevention of excessive inflammatory reactions have been the research focus of inflammatory diseases. Tripartite motif (TRIM) is a protein family with a conservative structure and rapid evolution. Several studies have demonstrated the TRIM family's regulatory role in mediating inflammation. This review aims to clarify the relationship between TRIMs and NLRP3 inflammasome and provide insights for future research and treatment discovery.

Transient increase in atherosclerotic plaque macrophage content following Streptococcus pneumoniae pneumonia in ApoE-deficient mice

Introduction

Despite epidemiological associations between community acquired pneumonia (CAP) and myocardial infarction, mechanisms that modify cardiovascular disease during CAP are not well defined. In particular, largely due to a lack of relevant experimental models, the effect of pneumonia on atherosclerotic plaques is unclear. We describe the development of a murine model of the commonest cause of CAP, Streptococcus pneumoniae pneumonia, on a background of established atherosclerosis. We go on to use our model to investigate the effects of pneumococcal pneumonia on atherosclerosis.

Methods

C57BL/6J and ApoE-/- mice were fed a high fat diet to promote atherosclerotic plaque formation. Mice were then infected with a range of S. pneumoniae serotypes (1, 4 or 14) with the aim of establishing a model to study atherosclerotic plaque evolution after pneumonia and bacteremia. Laser capture microdissection of plaque macrophages enabled transcriptomic analysis.

Results

Intratracheal instillation of S. pneumoniae in mice fed a cholate containing diet resulted in low survival rates following infection, suggestive of increased susceptibility to severe infection. Optimization steps resulted in a final model of male ApoE-/- mice fed a Western diet then infected by intranasal instillation of serotype 4 (TIGR4) S. pneumoniae followed by antibiotic administration. This protocol resulted in high rates of bacteremia (88.9%) and survival (88.5%). Pneumonia resulted in increased aortic sinus plaque macrophage content 2 weeks post pneumonia but not at 8 weeks, and no difference in plaque burden or other plaque vulnerability markers were found at either time point. Microarray and qPCR analysis of plaque macrophages identified downregulation of two E3 ubiquitin ligases, Huwe1 and Itch, following pneumonia. Treatment with atorvastatin failed to alter plaque macrophage content or other plaque features.

Discussion

Without antibiotics, ApoE-/- mice fed a high fat diet were highly susceptible to mortality following S. pneumoniae infection. The major infection associated change in plaque morphology was an early increase in plaque macrophages. Our results also hint at a role for the ubiquitin proteasome system in the response to pneumococcal infection in the plaque microenvironment.