Extracellular ubiquitin levels are increased in coronary heart disease and associated with the severity of the disease

Almost 50 Years of Monomeric Extracellular Ubiquitin (eUb)

Monomeric ubiquitin (Ub) is a 76-amino-acid highly conserved protein found in eukaryotes. The biological activity of Ub first described in the 1970s was extracellular, but it quickly gained relevance due to its intracellular role, i.e., post-translational modification of intracellular proteins (ubiquitination) that regulate numerous eukaryotic cellular processes. In the following years, the extracellular role of Ub was relegated to the background, until a correlation between higher survival rate and increased serum Ub concentrations in patients with sepsis and burns was observed. Although the mechanism of action (MoA) of extracellular ubiquitin (eUb) is not yet well understood, further studies have shown that it may ameliorate the inflammatory response in tissue injury and multiple sclerosis diseases. These observations, compounded with the high stability and low immunogenicity of eUb due to its high conservation in eukaryotes, have made this small protein a relevant candidate for biotherapeutic development. Here, we review the in vitro and in vivo effects of eUb on immunologic, cardiovascular, and nervous systems, and discuss the potential MoAs of eUb as an anti-inflammatory, antimicrobial, and cardio- and brain-protective agent.

Macrophages in the Inflammatory Phase following Myocardial Infarction: Role of Exogenous Ubiquitin

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. One of the most common implications of CVD is myocardial infarction (MI). Following MI, the repair of the infarcted heart occurs through three distinct, yet overlapping phases of inflammation, proliferation, and maturation. Macrophages are essential to the resolution of the inflammatory phase due to their role in phagocytosis and efferocytosis. However, excessive and long-term macrophage accumulation at the area of injury and dysregulated function can induce adverse cardiac remodeling post-MI. Ubiquitin (UB) is a highly evolutionarily conserved small protein and is a normal constituent of plasma. Levels of UB are increased in the plasma during a variety of pathological conditions, including ischemic heart disease. Treatment of mice with UB associates with decreased inflammatory response and improved heart function following ischemia/reperfusion injury. This review summarizes the role of macrophages in the infarct healing process of the heart post-MI, and discusses the role of exogenous UB in myocardial remodeling post-MI and in the modulation of macrophage phenotype and function.

Post-ischemic cardioprotective potential of exogenous ubiquitin in myocardial remodeling late after ischemia/reperfusion injury

AIMS

Pretreatment with ubiquitin (UB) associates with preservation of heart function 3 days post-ischemia/reperfusion (I/R) injury. This study investigated the cardioprotective potential of exogenous UB late after myocardial I/R injury. To enhance the clinical relevance, UB treatment was started at the time of reperfusion and continued for 28 days post-I/R.

MAIN METHODS

Mice underwent ligation of the left anterior descending coronary artery for 45 min. At the time of reperfusion, mice were treated with UB or saline which was continued until 28 days post-I/R. Heart function was measured at 3, 7, 14 and 28 days post-I/R using echocardiography. Biochemical parameters of the heart and serum cytokines/chemokines levels were measured 28 days post-I/R.

KEY FINDINGS

I/R decreased heart function and induced LV dilation at all time points post-I/R. However, I/R + UB exhibited improved heart function throughout the observation period, while LV dilation was lower in I/R + UB group at 3, 14 and 28 days post-I/R. I/R-mediated increase in myocardial fibrosis, hypertrophy and apoptosis were significantly lower in I/R + UB vs. I/R. Collagen-1α1 and MMP-2 expression was lower, while MMP-9 and TIMP-2 expression was higher in I/R + UB vs. I/R. MYH-7B (hypertrophy marker) expression was lower in I/R + UB vs. I/R. GSK3β activation was lower (vs. Sham), while activation of ERK1/2 (vs. I/R) and AKT (vs. Sham) was higher in I/R + UB. Serum levels of IL-6, G-CSF and IL-2 were lower in I/R + UB vs. I/R.

SIGNIFICANCE

Post-ischemic UB treatment improves heart function, and associates with decreased myocardial fibrosis, apoptosis, hypertrophy and serum cytokine/chemokine levels.

Identifying a Serum Exosomal-Associated lncRNA/circRNA-miRNA-mRNA Network in Coronary Heart Disease

Background

Accumulating evidence supports the importance of noncoding RNAs and exosomes in coronary heart disease (CHD). However, exosomal-associated competing endogenous RNA- (ceRNA-) mediated regulatory mechanisms in CHD are largely unexplored. The present study aimed to explore exosomal-associated ceRNA networks in CHD.

Methods

Data from 6 CHD patients and 32 normal controls were downloaded from the ExoRBase database. CHD and normal controls were compared by screening differentially expressed mRNAs (DEMs), lncRNAs (DELs), and circRNAs (DECs) in serum exosomes. MicroRNAs (miRNAs) targeting DEMs were predicted using the Targetscan and miRanda databases, and miRNAs targeted by DELs and DECs were predicted using the miRcode and starBase databases, respectively. The biological functions and related signaling pathways of DEMs were analyzed using the David and KOBAS databases. Subsequently, a protein-protein interaction (PPI) network was established to screen out on which hub genes enrichment analyses should be performed, and a ceRNA network (lncRNA/circRNA-miRNA-mRNA) was constructed to elucidate ceRNA axes in CHD.

Results

A total of 312 DEMs, 43 DELs, and 85 DECs were identified between CHD patients and normal controls. Functional enrichment analysis showed that DEMs were significantly enriched in “chromatin silencing at rDNA,” “telomere organization,” and “negative regulation of gene expression, epigenetic.” PPI network analysis showed that 25 hub DEMs were closely related to CHD, of which ubiquitin C (UBC) was the most important. Hub genes were mainly enriched in “cellular protein metabolic process” functions. The exosomal-associated ceRNA regulatory network incorporated 48 DEMs, 73 predicted miRNAs, 10 DELs, and 15 DECs. The LncRNA/circRNA-miRNA-mRNA interaction axes (RPL7AP11/hsa-miR-17-5p/UBC and RPL7AP11/hsa-miR-20b-5p/UBC) were obtained from the network.

Conclusions

Our findings provide a novel perspective on the potential role of exosomal-associated ceRNA network regulation of the pathogenesis of CHD.

Experimental evidence and network pharmacology-based analysis reveal the molecular mechanism of Tongxinluo capsule administered in coronary heart diseases

BACKGROUND

Tongxinluo (TXL) capsule, a polypharmacy derived from traditional Chinese medicine (TCM), has been widely used in coronary heart disease (CHD), while the underlying mechanism of TXL capsule is still unclear. The present study aimed at investigating the underlying mechanism of TXL acting on CHD patients and providing substantial evidence in molecular evidence by means of a network pharmacological analysis.

METHOD

Active compounds and targeted genes of TXL were retrieved from TCM systems pharmacology (TCMSP) and TCM integrative database (TCMID). CHD and coronary artery disease were treated as search queries in GeneCards and Online Mendelian Inheritance in Man (OMIM) databases to obtain disease-related genes. Visualization of disease-targets network was performed under administration of Cytoscape software. Besides, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were administered. H9c2 cells were used to validate the predicted results in cardiomyocytes/reoxygenation model, and anti-inflammatory ability was examined.

RESULTS

A network of a total of 212 nodes and 1016 edges was obtained. Peptide and ubiquitin-like protein ligase binding occupied a leading position of GO enrichment. For KEGG analysis, fluid shear stress and atherosclerosis, as well as inflammation-related pathways were enriched. Cellular validation revealed the anti-inflammatory effect of β-sitosterol, eriodictyol, odoricarpin, and tirucallol as active compounds of TXL.

CONCLUSION

Our study provided substantial molecular evidence that TXL capsule possessed the characteristics of multitargets with safe profile, and the main component is capable of regulating cytokine level in CHD patients.

Extracellular ubiquitin protects cardiomyocytes during ischemia/hypoxia by inhibiting mitochondrial apoptosis pathway through CXCR4

AIM

Acute myocardial infarction (AMI) is one of the deadliest diseases worldwide. The search for countermeasures to reduce cardiomyocytes death in the infarcted area has always been the focus of research. Ubiquitin (UB) is a small polypeptide mainly involved in proteasome-mediated protein degradation in cells, whereas extracellular UB in body fluids can also function through its receptor CXC chemokine receptor type 4 (CXCR4). This study aimed to explore the functional roles of extracellular UB in cardiomyocytes during ischemia/hypoxia (I/H).

METHODS

H9C2 cells were subjected to I/H treatment and cell injury was evaluated by cell viability, morphology changes and apoptosis rate. UB expression and levels of ubiquitinated proteins after I/H injury were measured. The effects of extracellular UB on I/H-induced cardiomyocytes apoptosis and the possible underlying mechanisms were studied.

RESULTS

I/H injury induced the decrease of cell viability as well as enhanced impaired cell morphology and apoptosis rate in H9C2 cells. Levels of UB mRNA and ubiquitinated proteins were significantly up-regulated after I/H treatment, whereas the concentration of extracellular UB in the conditioned media did not show significant change and the intracellular mono-UB levels in cells were down-regulated. Extracellular UB treatment protected cardiomyocytes from I/H injury by inhibiting the overactivation of mitochondria-dependent apoptosis pathway and up-regulating autophagy level. Inhibition of CXCR4 receptor using AMD3100 abolished cardioprotective effects of extracellular UB.

CONCLUSION

The up-regulation of UB was suggested to be an adaptive response to resist I/H-induced cardiomyocytes apoptosis, and additional extracellular UB treatment might serve as a new potential therapeutic drug for AMI.

Cardioprotective Potential of Exogenous Ubiquitin

Ischemic heart disease (IHD) accounts for the majority of heart disease-related deaths worldwide. Ubiquitin (UB), found in all eukaryotic cells, is a highly conserved low molecular weight (~8.5 kDa) protein. A well-known intracellular function of UB is to regulate protein turnover via the UB-proteasome system. UB is a normal constituent of plasma, and elevated levels of UB are observed in the serum of patients under a variety of pathological conditions. Recent studies provide evidence for cardioprotective potential of exogenous UB in the remodeling process of the heart in IHD, including effects on cardiac myocyte apoptosis, inflammatory response, and reorganization of the vasculature and extracellular matrix. This review summarizes functions of UB with an emphasis on the role of exogenous UB in myocardial remodeling in IHD.