Induction of ubiquitin-conjugating enzyme by aggregated low density lipoprotein in human macrophages and its implications for atherosclerosis

Targeting protein modifications in metabolic diseases: molecular mechanisms and targeted therapies

The ever-increasing prevalence of noncommunicable diseases (NCDs) represents a major public health burden worldwide. The most common form of NCD is metabolic diseases, which affect people of all ages and usually manifest their pathobiology through life-threatening cardiovascular complications. A comprehensive understanding of the pathobiology of metabolic diseases will generate novel targets for improved therapies across the common metabolic spectrum. Protein posttranslational modification (PTM) is an important term that refers to biochemical modification of specific amino acid residues in target proteins, which immensely increases the functional diversity of the proteome. The range of PTMs includes phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, glycosylation, palmitoylation, myristoylation, prenylation, cholesterylation, glutathionylation, S-nitrosylation, sulfhydration, citrullination, ADP ribosylation, and several novel PTMs. Here, we offer a comprehensive review of PTMs and their roles in common metabolic diseases and pathological consequences, including diabetes, obesity, fatty liver diseases, hyperlipidemia, and atherosclerosis. Building upon this framework, we afford a through description of proteins and pathways involved in metabolic diseases by focusing on PTM-based protein modifications, showcase the pharmaceutical intervention of PTMs in preclinical studies and clinical trials, and offer future perspectives. Fundamental research defining the mechanisms whereby PTMs of proteins regulate metabolic diseases will open new avenues for therapeutic intervention.

Intersection of the Ubiquitin–Proteasome System with Oxidative Stress in Cardiovascular Disease

Cardiovascular diseases (CVDs) present a major social problem worldwide due to their high incidence and mortality rate. Many pathophysiological mechanisms are involved in CVDs, and oxidative stress plays a vital mediating role in most of these mechanisms. The ubiquitin–proteasome system (UPS) is the main machinery responsible for degrading cytosolic proteins in the repair system, which interacts with the mechanisms regulating endoplasmic reticulum homeostasis. Recent evidence also points to the role of UPS dysfunction in the development of CVDs. The UPS has been associated with oxidative stress and regulates reduction–oxidation homeostasis. However, the mechanisms underlying UPS-mediated oxidative stress’s contribution to CVDs are unclear, especially the role of these interactions at different disease stages. This review highlights the recent research progress on the roles of the UPS and oxidative stress, individually and in combination, in CVDs, focusing on the pathophysiology of key CVDs, including atherosclerosis, ischemia–reperfusion injury, cardiomyopathy, and heart failure. This synthesis provides new insight for continued research on the UPS–oxidative stress interaction, in turn suggesting novel targets for the treatment and prevention of CVDs.

Deep Transcriptomic Analysis Reveals the Dynamic Developmental Progression during Early Development of Channel Catfish (Ictalurus punctatus)

The transition from fertilized egg to larva in fish is accompanied with various biological processes. We selected seven early developmental stages in channel catfish, Ictalurus punctatus, for transcriptome analysis, and covered 22,635 genes with 590 million high-quality RNA-sequencing (seq) reads. Differential expression analysis between neighboring developmental timepoints revealed significantly enriched biological categories associated with growth, development and morphogenesis, which was most evident at 2 vs. 5 days post fertilization (dpf) and 5 vs. 6 dpf. A gene co-expression network was constructed using the Weighted Gene Co-expression Network Analysis (WGCNA) approach and four critical modules were identified. Among candidate hub genes, GDF10, FOXA2, HCEA and SYCE3 were involved in head formation, egg development and the transverse central element of synaptonemal complexes. CK1, OAZ2, DARS1 and UBE2V2 were mainly associated with regulation of cell cycle, growth, brain development, differentiation and proliferation of enterocytes. IFI44L and ZIP10 were critical for the regulation of immune activity and ion transport. Additionally, TCK1 and TGFB1 were related to phosphate transport and regulating cell proliferation. All these genes play vital roles in embryogenesis and regulation of early development. These results serve as a rich dataset for functional genomic studies. Our work reveals new insights of the underlying mechanisms in channel catfish early development.

The ubiquitin-conjugating enzyme UBE2K determines neurogenic potential through histone H3 in human embryonic stem cells

Histones modulate gene expression by chromatin compaction, regulating numerous processes such as differentiation. However, the mechanisms underlying histone degradation remain elusive. Human embryonic stem cells (hESCs) have a unique chromatin architecture characterized by low levels of trimethylated histone H3 at lysine 9 (H3K9me3), a heterochromatin-associated modification. Here we assess the link between the intrinsic epigenetic landscape and ubiquitin-proteasome system of hESCs. We find that hESCs exhibit high expression of the ubiquitin-conjugating enzyme UBE2K. Loss of UBE2K upregulates the trimethyltransferase SETDB1, resulting in H3K9 trimethylation and repression of neurogenic genes during differentiation. Besides H3K9 trimethylation, UBE2K binds histone H3 to induce its polyubiquitination and degradation by the proteasome. Notably, ubc-20, the worm orthologue of UBE2K, also regulates histone H3 levels and H3K9 trimethylation in Caenorhabditis elegans germ cells. Thus, our results indicate that UBE2K crosses evolutionary boundaries to promote histone H3 degradation and reduce H3K9me3 repressive marks in immortal cells.

Azra Fatima et al. show that ubiquitin-conjugating enzyme UBE2K regulates neurogenic potential through its target histone H3 in human embryonic stem cells. This study suggests that UBE2K promotes histone H3 degradation, reducing the H3K9me3 repressive marks in immortal cells of both worms and humans.

E2-25K SUMOylation inhibits proteasome for cell death during cerebral ischemia/reperfusion

Cerebral ischemia/reperfusion (I/R) causes brain damage accompanied by ubiquitin accumulation and impairment of proteasome activity. In this study, we report that E2-25K, an E2-conjugating enzyme, is SUMOylated during oxidative stress and regulates cerebral I/R-induced damage. Knockdown of E2-25K expression protects against oxygen/glucose deprivation and reoxygenation (OGD/R)-induced neuronal cell death, whereas ectopic expression of E2-25K stimulates it. Compared with the control mice, cerebral infarction lesions and behavioral/neurological disorders are ameliorated in E2-25K knockout mice during middle cerebral artery occlusion and reperfusion. In particular, E2-25K is SUMOylated at Lys14 under oxidative stress, OGD/R and I/R to prompt cell death. Further, E2-25K downregulates the proteasome subunit S5a to impair proteasome complex and thus restrain proteasome activity under oxidative stress. This proteasome inhibitory activity of E2-25K is dependent on its SUMOylation. These results suggest that E2-25K has a crucial role in oxidative stress and cerebral I/R-induced damage through inhibiting proteasome via its SUMOylation.

Changes in expression of proteasome in rats at different stages of atherosclerosis

It has been suggested that proteasome system has a role in initiation, progression, and complication stages of atherosclerosis. Although there is still controversy, there has been no research that compares the expression of proteasome in tissue and serum at each of these stages. This study aimed to investigated the expression of proteasome at different stages of atherosclerosis using rat model. We measured the expression of aortic proteasome by immunohistochemical analyses and were then analyzed using ImageJ software for percentage of area and integrated density. We used Photoshop version 3.0 to analyze aortic proteasome expression as a comparison. We measured serum proteasome expression by enzyme linked immunosorbents assays. Kruskal-Wallis test was used to compare mean value of percentage of area and serum proteasome. Analysis of variance test was used to compare mean value of integrated density. Correlation test between vascular proteasome expression and serum proteasome expression was made using Spearman test. A P-value of 0.05 was considered statistically significant. Compared with normal, percentage of area was higher in initiation, progression, and complication. Compared with normal, integrated density was higher in initiation and further higher in progression and complication. Data from Image J is similar with data from Photoshop. Serum proteasome expression was higher in initiation compared with normal, and further higher in progression and complication. It was concluded that there were different vascular proteasome expression and serum proteasome expression at the stages of atherosclerosis. These results may be used in research into new marker and therapeutic target in atherosclerosis.

Metabolomic Quantitative Trait Loci (mQTL) Mapping Implicates the Ubiquitin Proteasome System in Cardiovascular Disease Pathogenesis

Levels of certain circulating short-chain dicarboxylacylcarnitine (SCDA), long-chain dicarboxylacylcarnitine (LCDA) and medium chain acylcarnitine (MCA) metabolites are heritable and predict cardiovascular disease (CVD) events. Little is known about the biological pathways that influence levels of most of these metabolites. Here, we analyzed genetics, epigenetics, and transcriptomics with metabolomics in samples from a large CVD cohort to identify novel genetic markers for CVD and to better understand the role of metabolites in CVD pathogenesis. Using genomewide association in the CATHGEN cohort (N = 1490), we observed associations of several metabolites with genetic loci. Our strongest findings were for SCDA metabolite levels with variants in genes that regulate components of endoplasmic reticulum (ER) stress (USP3, HERC1, STIM1, SEL1L, FBXO25, SUGT1) These findings were validated in a second cohort of CATHGEN subjects (N = 2022, combined p = 8.4x10^-6–2.3x10^-10). Importantly, variants in these genes independently predicted CVD events. Association of genomewide methylation profiles with SCDA metabolites identified two ER stress genes as differentially methylated (BRSK2 and HOOK2). Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm. Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP. Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

Cardiovascular disease is a strongly heritable trait. Despite application of the latest genomic technologies, the genetic architecture of disease risk remains poorly defined, and mechanisms underlying this susceptibility are incompletely understood. In this study, we performed genome-wide mapping of heart disease-related metabolites measured in the blood as the genetic traits of interest (instead of the disease itself), in a large cohort of 3512 patients at risk of heart disease from the CATHGEN study. Our goal was to discover new cardiovascular disease genes and thereby mechanisms of disease pathogenesis by understanding the genes that regulate levels of these metabolites. These analyses identified novel genetic variants associated with metabolite levels and with cardiovascular disease itself. Importantly, by utilizing an unbiased systems-based approach integrating genetics, gene expression, epigenetics and metabolomics, we uncovered a novel pathway of heart disease pathogenesis, that of endoplasmic reticulum (ER) stress, represented by elevated levels of circulating short-chain dicarboxylacylcarnitine (SCDA) metabolites.

Nitric oxide affects UbcH10 levels differently in type 1 and type 2 diabetic rats

BACKGROUND

Nitric oxide (NO) more effectively inhibits neointimal hyperplasia in type 2 diabetic versus nondiabetic and type 1 diabetic rodents. NO also decreases the ubiquitin-conjugating enzyme UbcH10, which is critical to cell-cycle regulation. This study seeks to determine whether UbcH10 levels in the vasculature of diabetic animal models account for the differential efficacy of NO at inhibiting neointimal hyperplasia.

MATERIALS AND METHODS

Vascular smooth muscle cells (VSMCs) harvested from nondiabetic lean Zucker (LZ) and type 2 diabetic Zucker diabetic fatty (ZDF) rats were exposed to high glucose (25 mM) and high insulin (24 nM) conditions to mimic the diabetic environment in vitro. LZ, streptozotocin-injected LZ (STZ, type 1 diabetic), and ZDF rats underwent carotid artery balloon injury (±10 mg PROLI/NO), and vessels were harvested at 3 and 14 d. UbcH10 was assessed by Western blotting and immunofluorescent staining.

RESULTS

NO more effectively reduced UbcH10 levels in LZ versus ZDF VSMCs; however, addition of insulin and glucose dramatically potentiated the inhibitory effect of NO on UbcH10 in ZDF VSMCs. Three days after balloon injury, Western blotting showed NO decreased free UbcH10 and increased polyubiquitinated UbcH10 levels by 35% in both STZ and ZDF animals. Fourteen days after injury, immunofluorescent staining showed increased UbcH10 levels throughout the arterial wall in all animal models. NO decreased UbcH10 levels in LZ and STZ rats but not in ZDF.

CONCLUSIONS

These data suggest a disconnect between UbcH10 levels and neointimal hyperplasia formation in type 2 diabetic models and contribute valuable insight regarding differential efficacy of NO in these models.

Targeting the ubiquitin-proteasome system in atherosclerosis: status quo, challenges, and perspectives

SIGNIFICANCE

Atherosclerosis is a vascular disease of worldwide significance with fatal complications such as myocardial infarction, stroke, and peripheral artery disease. Atherosclerosis is recognized as a chronic inflammatory disease leading to arterial plaque formation and vessel narrowing in different vascular beds. Besides the strong inflammatory nature of atherosclerosis, it is also characterized by proliferation, apoptosis, and enhanced oxidative stress. The ubiquitin-proteasome system (UPS) is the major intracellular degradation system in eukaryotic cells. Besides its essential role in the degradation of dysfunctional and oxidatively damaged proteins, it is involved in many processes that influence disease progression in atherosclerosis. Hence, it is logical to ask whether targeting the proteasome is a reasonable and feasible option for the treatment of atherosclerosis.

RECENT ADVANCES

Several lines of evidence suggest stage-specific dysfunction of the UPS in atherogenesis. Regulation of key processes by the proteasome in atherosclerosis, as well as the modulation of these processes by proteasome inhibitors in vascular cells, is outlined in this review. The treatment of atherosclerotic animal models with proteasome inhibitors yielded partly opposing results, the potentially underlying reasons of which are discussed here.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Targeting UPS function in atherosclerosis is a promising but challenging option. Limitations of current proteasome inhibitors, dose dependency, and the cell specificity of effects, as well as the potential of future therapeutics are discussed. A stage-specific in-depth exploration of UPS function in atherosclerosis in the future will help identify targets and windows for beneficial intervention.

Hip2 ubiquitin-conjugating enzyme overcomes radiation-induced G2/M arrest

Radiation induces cell cycle arrest and/or cell death in mammalian cells. In the present study, we show that Hip2, a ubiquitin-conjugating enzyme, can overcome radiation-induced G2/M cell cycle arrest and trigger the entry into mitosis. Ionizing radiation increased the levels of Hip2 by preventing its degradation but not its gene transcription. The stability of Hip2 in irradiated cells was further confirmed using live cell fluorescence imaging. Flow cytometric and molecular analyses revealed that Hip2 abrogated radiation-induced G2/M arrest, promoting entry into mitosis. Bimolecular fluorescence complementation assays and co-immunoprecipitation experiments showed that Hip2 interacted with and targeted p53 for degradation via the ubiquitin proteasome system, resulting in the activation of cdc2-cyclin B1 kinase to promote mitotic entry. These results contribute to our understanding of the mechanisms that regulate cell cycle progression and DNA damage-induced G2/M checkpoint cellular responses.

Validation of the association between PSMA6 -8 C/G polymorphism and type 2 diabetes mellitus in Chinese Dongxiang and Han populations

OBJECTIVE

The aim of our study was to validate association between -8 C/G variant of PSMA6 gene and T2DM in Chinese Dongxiang and Han populations.

METHOD

We genotyped PSMA6 gene -8 C/G polymorphism in the control groups and T2DM groups in two populations from China using PCR-RFLP technique. Phenotypes and biochemical indicators were measured by biochemical technique.

RESULT

The frequencies of CG+GG genotype were observably different from CC genotype in the T2DM groups and control groups (for Dongxiang population: OR = 1.341, 95% CI: 1.101-1.632, P = 0.004; for Han population: OR = 1.313, 95% CI: 1.085-1.569, P = 0.006 after adjusting for gender, age, and BMI, respectively). In the Dongxiang population, the FPG, HOMA-IR, SBP and TG levels of CG+GG genotype were markedly higher than those of the CC genotype in control group (all P < 0.05). However, in the Han population, we only found that the FPI level of the CC genotype was significantly higher than that of the CG+GG genotype in control group (P < 0.05).

CONCLUSION

Our investigation suggests that -8 C/G variant of PSMA6 gene may be associated with T2DM and diabetes-related metabolic traits in Chinese Dongxiang and Han populations.

The ubiquitin-proteasome system and cardiovascular disease

Over the past decade, the role of the ubiquitin-proteasome system (UPS) has been the subject of numerous studies to elucidate its role in cardiovascular physiology and pathophysiology. There have been many advances in this field including the use of proteomics to achieve a better understanding of how the cardiac proteasome is regulated. Moreover, improved methods for the assessment of UPS function and the development of genetic models to study the role of the UPS have led to the realization that often the function of this system deviates from the norm in many cardiovascular pathologies. Hence, dysfunction has been described in atherosclerosis, familial cardiac proteinopathies, idiopathic dilated cardiomyopathies, and myocardial ischemia. This has led to numerous studies of the ubiquitin protein (E3) ligases and their roles in cardiac physiology and pathophysiology. This has also led to the controversial proposition of treating atherosclerosis, cardiac hypertrophy, and myocardial ischemia with proteasome inhibitors. Furthering our knowledge of this system may help in the development of new UPS-based therapeutic modalities for mitigation of cardiovascular disease.

Sent to destroy: the ubiquitin proteasome system regulates cell signaling and protein quality control in cardiovascular development and disease

The ubiquitin proteasome system (UPS) plays a crucial role in biological processes integral to the development of the cardiovascular system and cardiovascular diseases. The UPS prototypically recognizes specific protein substrates and places polyubiquitin chains on them for subsequent destruction by the proteasome. This system is in place to degrade not only misfolded and damaged proteins, but is essential also in regulating a host of cell signaling pathways involved in proliferation, adaptation to stress, regulation of cell size, and cell death. During the development of the cardiovascular system, the UPS regulates cell signaling by modifying transcription factors, receptors, and structural proteins. Later, in the event of cardiovascular diseases as diverse as atherosclerosis, cardiac hypertrophy, and ischemia/reperfusion injury, ubiquitin ligases and the proteasome are implicated in protecting and exacerbating clinical outcomes. However, when misfolded and damaged proteins are ubiquitinated by the UPS, their destruction by the proteasome is not always possible because of their aggregated confirmations. Recent studies have discovered how these ubiquitinated misfolded proteins can be destroyed by alternative "specific" mechanisms. The cytosolic receptors p62, NBR, and histone deacetylase 6 recognize aggregated ubiquitinated proteins and target them for autophagy in the process of "selective autophagy." Even the ubiquitination of multiple proteins within whole organelles that drive the more general macro-autophagy may be due, in part, to similar ubiquitin-driven mechanisms. In summary, the crosstalk between the UPS and autophagy highlight the pivotal and diverse roles the UPS plays in maintaining protein quality control and regulating cardiovascular development and disease.

On to the road to degradation: atherosclerosis and the proteasome

Protein metabolism is a central element of every living cell. The ubiquitin-proteasome system (UPS) is an integral part of the protein metabolism machinery mediating post-transcriptional processing and degradation of the majority of intracellular proteins. Over the past few years, remarkable progress has been made in our understanding of the role of the UPS in vascular biology and pathobiology, particularly atherosclerosis. This review reflects on the recent developments from the effects on endothelial cells and the initial stage of atherosclerosis to the effects on vascular smooth muscle and the progression stage of atherosclerosis and finally to the effects on cell viability and the complication stage of atherosclerosis. It will conclude with the integration of the available information in a synoptic view of the involvement of the UPS in atherosclerosis.

The ubiquitin‐proteasome system—micro target for macro intervention?

The ubiquitin-proteasome system is the two sequential labeling and degradation system that accounts for the degradation of 80-90% of all intracellular proteins. Based on the diversity of its substrates, it is integrated in many different biological processes, especially inflammation and cell proliferation. Given the significance of these two processes for primary atherosclerosis and restenosis, the ubiquitin-proteasome system may be an amendable target in cardiovascular therapy. This review provides background information on the ubiquitin-proteasome system, currently available data on its involvement in cardiovascular diseases, and a future perspective on the targeted use proteasome inhibitors, including drug-eluting stents.

A novel missense mutation of ABCA1 in transmembrane alpha-helix in a Japanese patient with Tangier disease

Tangier disease (TD) is a hereditary disorder characterized by the severe deficiency or absence of high-density lipoprotein cholesterol (HDL-C). TD is caused by mutations in the ATP-binding cassette transporter A1 (ABCA1) gene, most of which are located in the extracellular loops and nucleotide-binding domains. Here we describe the first case of TD carrying a missense mutation in a transmembrane alpha-helix of ABCA1. A 31-year-old Japanese woman had an extremely low level of HDL-C (1mg/dl) and yellowish tonsillar swelling, leading to the diagnosis of TD. The proband was homozygous for a point mutation of T4978C in exon 37, which results in the substitution of cysteine-1660 to arginine (C1660R) in the 8th transmembrane segment of ABCA1. Her parents, grandmother, and brother were found to be heterozygous for the same mutation. Both peripheral blood leukocytes from the patient and HEK293 cells transfected with T4978C-mutated ABCA1 normally expressed ABCA1 on the plasma membrane and had normal apolipoprotein A-I-binding ability. However, apolipoprotein A-I-mediated efflux of cholesterol and phospholipids was markedly diminished in HEK293 cells transfected with T4978C-mutated ABCA1. These results suggest that this mutant is normally translated and exists as a stable product with normal localization, yet is functionally defective. Cysteine-1660 appears to be a critical residue for cholesterol transport of ABCA1.

Expression of ubiquitin in peripheral inflammatory cells from patients with coronary artery disease

In addition to its role in the removal of damaged and unneeded proteins, the ubiquitin-proteasome system (UPS) may play a key role in coronary artery disease (CAD). To investigate the expression of ubiquitin in monocytes and lymphocytes isolated from patients at different stages of CAD, 120 patients with CAD (40 with acute myocardial infarction [AMI], 40 with unstable angina pectoris [UAP] and 40 with stable angina pectoris [SAP]) were selected; 40 patients with normal coronary arteries served as controls. At both the mRNA and protein levels, ubiquitin expression was higher in patients with CAD than in controls, and patients with AMI had a much higher expression of ubiquitin (at both the mRNA and protein levels) than those with SAP and UAP. These data indicate that ubiquitin expression increased with increasing severity of CAD, suggesting that ubiquitin may play a critical role in the development and progression of CAD.

The ubiquitin-proteasome system contributes to the inflammatory injury in ischemic diabetic myocardium: the role of glycemic control

BACKGROUND

Because the ubiquitin-proteasome pathway (UPS) is required for activation of nuclear factor kappa beta (NFkB), a transcription factor that regulates inflammatory genes, we evaluated the UPS activity, NFkB activation, and tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, in ischemic specimens of diabetic myocardium and relate them to the glycemic control (HbA(1c)), oxidative stress (nitrotyrosine, a modified amino acid produced by reactive O(2)), and cardiac outcome (echocardiographic parameters). Moreover, the role of UPS, NFkB, and TNF-alpha in the cardiac tissue injury of acute ischemia/reperfusion (I/R) was evaluated in streptozotocin (STZ)-hyperglycemic rats. Finally, this study aimed to elucidate whether an intervention on UPS with bortezomib, an inhibitor of UPS, may counteract the extensive myocardial infarction and increased inflammatory reaction into the hyperglycemic myocardium.

METHODS

Ventricular biopsy specimens from 16 nondiabetic and 18 type 2 diabetic patients presenting with unstable angina who underwent coronary artery bypass were collected during coronary bypass surgery. Ejection fraction (EF); myocardial performance index (MPI), which measures both systolic and diastolic function, immunostaining, and cardiac levels of nitrotyrosine; UPS activity; NFkB; and TNF-alpha were investigated in both ischemic human myocardium and heart tissue from STZ-hyperglycemic rats subject to a myocardial ischemia/reperfusion procedure.

RESULTS

We found that diabetic patients had higher MPI (P<.041) and reduced EF (P<.008) compared with nondiabetic patients. Diabetic specimens had higher nitrotyrosine, UPS activity, NFkB, and TNF-alpha levels compared with nondiabetic patients (P<.001). This was mirrored by consistently high levels of UPS and inflammatory markers in STZ-infarcted hearts, associated with high myocardial damage. In contrast, lesions from normoglycemic animals as well as from hyperglycemic rats treated with bortezomib showed low levels of ubiquitin-proteasome activity, inflammation, and myocardial damage (P<.01).

CONCLUSIONS

By contributing to the increased inflammation, the UPS overactivity may enhance the risk of complication during myocardial ischemia in diabetic patients.

Expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in peripheral inflammatory cells from patients with coronary heart disease

: The increased expression of heme oxygenase-1 content, a stress-response protein, directly correlates with the incidence of coronary heart disease. Down-regulation of hypoxia inducible factor-1α activity, a major downstream effector of the signaling pathways activated by hypoxia, increases cell survival after hypoxia. The ubiquitin system, a non-lysosomal pathway of protein degradation, is involved in processes of coronary heart disease. The aim of this study was to investigate the expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in both monocytes and lymphocytes isolated from patients at the mRNA and protein levels in different stages of coronary heart disease and their possible correlation.

: A total of 90 patients with coronary heart disease (30 acute myocardial infarction, 30 unstable angina pectoris, and 30 stable angina pectoris) were selected, and 30 cases with normal coronary artery served as controls. The mRNA and protein expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in monocytes and lymphocytes were examined by semi-quantitative reverse transcriptase polymerase chain reaction and Western blotting, respectively.

: The mRNA expression of heme oxygenase-1 and ubiquitin was associated with the severity of coronary heart disease (p<0.05). There was no significant difference in hypoxia inducible factor-1α mRNA expression between the coronary heart disease patients and controls. The protein expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin was significantly stronger in patients with coronary heart disease than in controls, and the expression levels increased with the severity of the disease. There was a positive association between heme oxygenase-1 and hypoxia inducible factor-1α and ubiquitin, antioxidative therapy with adrenergic receptor blocker, angiotensin-converting enzyme inhibitor or statins up-regulated the expression of heme oxygenase-1 and hypoxia inducible factor-1α.

: These data suggest that heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin are involved in the development and progression of coronary heart disease and thus may be useful biomarkers for coronary heart disease.

Clin Chem Lab Med 2009;47:327–33.

The possible role of the ubiquitin proteasome system in the development of atherosclerosis in diabetes

We have reviewed the impact of the ubiquitin proteasome system (UPS) on atherosclerosis progression of diabetic patients. A puzzle of many pieces of evidence suggests that UPS, in addition to its role in the removal of damaged proteins, is involved in a number of biological processes including inflammation, proliferation and apoptosis, all of which constitute important characteristics of atherosclerosis. From what can be gathered from the very few studies on the UPS in diabetic cardiovascular diseases published so far, the system seems to be functionally active to a different extent in the initiation, progression, and complication stage of atherosclerosis in the diabetic people. Further evidence for this theory, however, has to be given, for instance by specifically targeted antagonism of the UPS. Nonetheless, this hypothesis may help us understand why diverse therapeutic interventions, which have in common the ability to reduce ubiquitin-proteasome activity, can impede or delay the onset of diabetes and cardiovascular diseases (CVD).

People with type 2 diabetes are disproportionately affected by CVD, compared with those without diabetes [1]. The prevalence, incidence, and mortality from all forms of CVD (myocardial infarction, cerebro-vascular disease and congestive heart failure) are strikingly increased in persons with diabetes compared with those withoutdiabetes [2]. Furthermore, diabetic patients have not benefited by the advances in the management of obesity, dyslipidemia, and hypertension that have resulted in a decrease in mortality for coronary heart disease (CHD) patients without diabetes [3]. Nevertheless, these risk factors do not fully explain the excess risk for CHD associated with diabetes [4,5]. Thus, the determinants of progression of atherosclerosis in persons with diabetes must be elucidated. Beyond the major risk factors, several studies have demonstrated that such factors, strictly related to diabetes, as insulin-resistance, post-prandial hyperglycemia and chronic hyperglycemia play a role in the atherosclerotic process and may require intervention [6,7]. Moreover, it is important to recognize that these risk factors frequently "cluster" inindividual patients and possibly interact with each other, favouring the atherosclerosis progression toward plaque instability. Thus, a fundamental question is, "which is the common soil hypothesis that may unifying the burden of all these factors on atherosclerosis of diabetic patients? Because evidences suggest that insulin-resistance, diabetes and CHD share in common a deregulation of ubiquitin-proteasome system (UPS), the major pathway for nonlysosomal intracellular protein degradation in eucaryotic cells [8,9], in this review ubiquitin-proteasome deregulation is proposed as the common persistent pathogenic factor mediating the initial stage of the atherosclerosis as well as the progression to complicated plaque in diabetic patients.

Cardiovascular disease could be contained based on currently available data!

Largely due to better control of infectious diseases and significant advances in biomedical research, life expectancy worldwide has increased dramatically in the last three decades. However, as the average age of the population has risen, the incidence of chronic age-related diseases such as arthritis, Alzheimer's, Parkinson's, cardiovascular disease, cancer, osteoporosis, benign prostatic hyperplasia, and late-onset diabetes have increased and have become serious public health problem, as well. The etiology of these disorders is still incompletely understood, therefore, neither preventive strategies nor long-term effective treatment modalities are available for these disorders. In keeping with the aforementioned, the ultimate goal in cardiovascular research is to prevent the onset of cardiovascular episodes and thereby allow successful ageing without morbidity and cognitive decline. Herein, I argue that cardiovascular episodes could be contained with relatively simple approaches. Cardiovascular disorder is characterized by cellular and molecular changes that are commonplace in age-related diseases in other organ system, such alterations include increased level of oxidative stress, perturbed energy metabolism, and "horror autotoxicus" largely brought about by the perturbation of ubiquitin -proteasome system, and excessive oxidative stress damage to the cardiac muscle cells and tissues, and cross-reactions of specific antibodies against human heat shock protein 60 with that of mycobacterial heat shock protein 65. "Horror autotoxicus", a Latin expression, is a term coined by Paul Ehrlich at the turn of the last century to describe autoimmunity to self, or the attack of "self" by immune system, which ultimately results to autoimmune condition. Based on the currently available data, the risk of cardiovascular episodes and several other age-related disorders, including cancer, Alzheimer's disease and diabetes, is known to be influenced by the nature and level of food intake. Now, a wealth of scientific data from studies of rodents and monkeys has documented the significant beneficial effects of calorie restriction (CR) or dietary restriction (DR), and multiple antioxidant agents in extending life span and reducing the incidence of progeroid-related diseases. Reduced levels of cellular oxidative stress, protection of genome from deleterious damage, detoxification of toxic molecules, and enhancement of energy homeostasis, contribute to the beneficial effects of dietary restriction and multiple antioxidant agents. Recent findings suggest that employment of DR and multiple antioxidant agents (including, catalase, glutathione peroxidase, CuZn superoxide dismutase, and Mn superoxide dismutase = enzymes forming the primary defense against oxygen toxicity), and ozone therapy may mount an effective resistance to pathogenic factors relevant to the pathogenesis of cardiovascular episodes. Hence, while further studies will be needed to establish the extent to which CR and multiple antioxidant agents will reduce incidence of cardiovascular episodes in humans, it would seem prudent to recommend CR and multiple antioxidant agents as widely applicable preventive approach for cardiovascular disorders and other progeroid-related disorders.

Inhibitory Effects of Procyanidin B2 Dimer on Lipid-laden Macrophage Formation

A proteomic analysis of procyanidin B(2) isolated from cocoa against oxidized low-density lipoprotein-induced lipid-laden macrophage formation was performed. Of approximately 400 detected proteins, 12 were differentially expressed as a result of B(2) treatment. They were subsequently identified by liquid chromatography-electrospray ionization-tandem mass spectrometry and the SWISS-PROT database. Further reverse transcriptase-polymerase chain reaction and Western blot analysis revealed that B(2) strongly inhibited arachidonic acid inflammatory reactions, apoptosis, and their coupled mitogen-activated protein kinase and NF-kappaB pathways. To highlight proteins or genes with similar expressed patterns and similarly biological function induced by B(2) in lipid-laden macrophages, a cluster and Kyoto Encyclopedia of Genes and Genomes pathway analysis were performed. The data were mapped to multiple pathways. Further validation of the bioinformatic results revealed that activation of Wnt signaling may contribute to the cardioprotection of B(2). The differentially expressed genes and proteins mentioned above induced by B(2) are through regulating nuclear transcription factors, activating peroxisome proliferator-activated receptor-gamma and inhibiting AP-1 mRNA expressions. These in vitro data help to interpret the beneficial effects of B(2) in reducing the risk of atherosclerosis after consumption of flavonoid-rich foods. Many differentially expressed genes induced by B(2) help to uncover novel targets and may help to target disease interactions in atherosclerosis in the future.

Increased activity of the ubiquitin-proteasome system in patients with symptomatic carotid disease is associated with enhanced inflammation and may destabilize the atherosclerotic plaque: effects of rosiglitazone treatment

OBJECTIVES

We evaluated ubiquitin-proteasome activity in carotid plaques of asymptomatic and symptomatic patients and the effect of rosiglitazone, a peroxisome proliferator-activated receptor-gamma activator, in symptomatic plaques.

BACKGROUND

The role of the ubiquitin-proteasome system, the major pathway for non-lysosomal intracellular protein degradation in eucaryotic cells, in the progression of atherosclerotic plaque to instability is unclear.

METHODS

Plaques were obtained from 40 symptomatic and 38 asymptomatic patients undergoing carotid endarterectomy. Symptomatic patients received 8 mg rosiglitazone (n = 20) or placebo (n = 20) for 4 months before scheduled endarterectomy. Plaques were analyzed for macrophages (CD68), T-lymphocytes (CD3), inflammatory cells (HLA-DR), ubiquitin-proteasome activity, nuclear factor kappa B (NFkB), inhibitory kappa B (IkB)-beta, nitrotyrosine, matrix metalloproteinase (MMP)-9, and collagen content (immunohistochemistry and enzyme-linked immunosorbent assay).

RESULTS

Compared with asymptomatic plaques, symptomatic plaques had more macrophages, T-lymphocytes, and HLA-DR+ cells (p < 0.001); more ubiquitin-proteasome activity and NFkB (p < 0.001); and more markers of oxidative stress (nitrotyrosine and O2- production) and MMP-9 (p < 0.01) along with a lesser collagen content and IkB-beta levels (p < 0.001). Compared with placebo-treated plaques, rosiglitazone-treated symptomatic plaques presented fewer inflammatory cells (p < 0.01); less ubiquitin, proteasome 20S, and NFkB (p < 0.01); less nitrotyrosine and O2- production (p<0.01); and greater collagen content (p<0.01), indicating a more stable plaque phenotype.

CONCLUSIONS

Ubiquitin-proteasome overactivity is associated with enhanced inflammatory reaction in symptomatic plaques. The inhibition of ubiquitin-proteasome activity in lesions of symptomatic patients by rosiglitazone is associated with plaque stabilization, possibly by down-regulating NFkB-mediated inflammatory pathways.

The ubiquitin-proteasome system and inflammatory activity in diabetic atherosclerotic plaques: effects of rosiglitazone treatment

The role of ubiquitin-proteasome system in the accelerated atherosclerotic progression of diabetic patients is unclear. We evaluated ubiquitin-proteasome activity in carotid plaques of asymptomatic diabetic and nondiabetic patients, as well as the effect of rosiglitazone, a peroxisome proliferator-activated receptor (PPAR)-gamma activator, in diabetic plaques. Plaques were obtained from 46 type 2 diabetic and 30 nondiabetic patients undergoing carotid endarterectomy. Diabetic patients received 8 mg rosiglitazone (n = 23) or placebo (n = 23) for 4 months before scheduled endarterectomy. Plaques were analyzed for macrophages (CD68), T-cells (CD3), inflammatory cells (HLA-DR), ubiquitin, proteasome 20S activity, nuclear factor (NF)-kappaB, inhibitor of kappaB (IkappaB)-beta, tumor necrosis factor (TNF)-alpha, nitrotyrosine, matrix metalloproteinase (MMP)-9, and collagen content (immunohistochemistry and enzyme-linked immunosorbent assay). Compared with nondiabetic plaques, diabetic plaques had more macrophages, T-cells, and HLA-DR+ cells (P < 0.001); more ubiquitin, proteasome 20S activity (TNF-alpha), and NF-kappaB (P < 0.001); and more markers of oxidative stress (nitrotyrosine and O2(-) production) and MMP-9 (P < 0.01), along with a lesser collagen content and IkappaB-beta levels (P < 0.001). Compared with placebo-treated plaques, rosiglitazone-treated diabetic plaques presented less inflammatory cells (P < 0.01); less ubiquitin, proteasome 20S, TNF-alpha, and NF-kappaB (P < 0.01); less nitrotyrosine and superoxide anion production (P < 0.01); and greater collagen content (P < 0.01), indicating a more stable plaque phenotype. Similar findings were obtained in circulating monocytes obtained from the two groups of diabetic patients and cultured in the presence or absence of rosiglitazone (7.0 micromol/l). Ubiquitin-proteasome over-activity is associated with enhanced inflammatory reaction and NF-kappaB expression in diabetic plaques. The inhibition of ubiquitin-proteasome activity in atherosclerotic lesions of diabetic patients by rosiglitazone is associated with morphological and compositional characteristics of a potential stable plaque phenotype, possibly by downregulating NF-kappaB-mediated inflammatory pathways.

Regulation of p53 by the ubiquitin-conjugating enzymes UbcH5B/C in vivo

p53 levels are regulated by ubiquitination and 26 S proteasome-mediated degradation. p53 is a substrate for the E3 ligase Mdm2, however, the ubiquitin-conjugating enzymes (E2s) involved in p53 ubiquitination in intact cells have not been defined previously. To investigate the E2 specificity of Mdm2 we carried out an in vitro screen using a panel of ubiquitin E2s. Of the E2s tested only UbcH5A, -B, and -C and E2-25K support Mdm2-mediated ubiquitination of p53. The same E2s also support Mdm2 auto-ubiquitination. Small interfering RNA-mediated knockdown of UbcH5B/C causes accumulation of Mdm2 and p53 in unstressed cells. We show that suppression of UbcH5B/C inhibits p53 ubiquitination and degradation. Despite up-regulating the level of nuclear p53, UbcH5B/C knockdown does not on its own result in an increase in p53 transcriptional activity or sensitize p53 to activation by the therapeutic drugs doxorubicin and actinomycin D. We provide evidence that Mdm2 is responsible, at least in part, for repression of the transcriptional activity of the accumulated p53. In MCF7 cells levels of UbcH5B/C are reduced by doxorubicin and actinomycin D. This observation and the sensitivity of p53 expression to levels of UbcH5B/C raise the possibility that E2 regulation could be involved in signaling pathways that control the stability of p53. Our data indicate that UbcH5B/C are physiological E2s for Mdm2, which make a significant contribution to the maintenance of low levels of p53 and Mdm2 in unstressed cells and that inhibition of p53 ubiquitination and degradation by targeting UbcH5B/C is not sufficient to up-regulate p53 transcriptional activity.

Oxidative stress-related increase in ubiquitination in early coronary atherogenesis

The ubiquitin-proteasome system (UPS) is involved in the removal of damaged proteins and the activation of transcription factors, such as nuclear-factor-kappaB. Recent reports, however, questioned the functional activity of the UPS under conditions of increased oxidative stress, such as experimental hypercholesterolemia, which was the objective of our study. Pigs were placed on a normal chow diet (N) or on a hypercholesterolemic diet without (HC) or with vitamin C and E supplementation (HC+VIT) for 12 weeks. Compared with N, plasma concentration of total cholesterol increased in both HC and HC+VIT [76 +/- 21 vs. 400 +/- 148 (P<0.05) and 329 +/- 102 (P<0.05) mg/dL], whereas increase in lipid peroxidation, as assessed by LDL-malondialdehyde plasma concentration, was found in HC but not in HC+VIT [6.6 +/- 0.7 vs. 8.5 +/- 0.3 (P<0.05) and 6.8 +/- 0.7 nmol/mg protein]. In comparison with N, the level of ubiquitin conjugates in the coronary artery, as assessed by immunoblotting, increased by 42% in HC but not in HC+VIT and was localized predominantly to media vascular smooth muscle cells by immunostaining. There was no difference in proteasome proteolytic activity among the study groups. These results demonstrate that the UPS is functionally active in early atherogenesis despite increase in oxidative stress with important repercussions in the pathophysiology and therapy of cardiovascular diseases.

Increased ubiquitin immunoreactivity in unstable atherosclerotic plaques associated with acute coronary syndromes

OBJECTIVES

The current study was designed to examine whether ubiquitin expression is higher in unstable than in stable lesions of patients with acute coronary syndrome (ACS).

BACKGROUND

The ubiquitin system has been identified as the nonlysosomal pathway of protein degradation; it is involved in a number of biologic processes crucial to cell and tissue integrity and therefore, might be potentially involved in the rupture of unstable coronary plaques.

METHODS

We conducted an autopsy-based study of 25 consecutive patients with fatal ACS. Lesions of both infarct-related and noninfarct-related segments from the same patients were examined for the expression and localization of ubiquitin by use of immunohistochemistry and a semiquantitative grading scale.

RESULTS

Ubiquitin immunoreactivity was higher in infarct-related than in noninfarct-related lesions (1.4 +/- 0.5 vs. 1.1 +/- 0.6, p = 0.03). Compared with areas adjacent to the plaque (0.6 +/- 0.7), ubiquitin immunoreactivity was higher in areas around the lipid core (2.5 +/- 0.8, p < 0.001), plaque shoulders (1.6 +/- 1.1, p < 0.001), and fibrous cap regions (1.6 +/- 1.1, p < 0.001). Within the plaque area, co-localization of ubiquitin immunoreactivity with T cells and macrophages was found. In areas adjacent to the plaque, ubiquitin immunoreactivity co-localized with neointima cells and media smooth muscle cells.

CONCLUSIONS

In patients with ACS, ubiquitin immunoreactivity is enhanced in unstable, infarct-related lesions, predominantly in plaque regions of tissue degradation. Based on these findings, this study suggests a role for the ubiquitin system in the destabilization and rupture of coronary atherosclerotic plaques in humans.

The ubiquitin-proteasome pathway in thymocyte apoptosis: caspase-dependent processing of the deubiquitinating enzyme USP7 (HAUSP)

Programmed cell death (apoptosis) is crucial for thymocyte development. We analyzed the role of the ubiquitin (Ub)-proteasome pathway in dexamethasone-triggered and TCR-mediated apoptosis in fetal thymic organ culture (FTOC). Proteasome activity was increased in apoptotic thymocytes, as visualized by active-site labeling of proteasomal beta subunits. The activity of deubiquitinating enzymes in murine apoptotic thymocytes was likewise examined by active-site labeling. We show that the deubiquitinating enzyme USP7 (HAUSP) is proteolytically processed upon dexamethasone-, gamma-irradiation-, and antigen-induced cell death. Such processing of HAUSP does not occur in caspase 3-/- thymocytes, or upon pretreatment of wild type thymocytes with the general caspase inhibitor ZVAD-fmk. Thus, our results suggest that thymocyte apoptosis leads to modification of deubiquitinating enzymes by caspase activity and may provide an additional link between the ubiquitin-proteasome pathway and the caspase cascade during programmed cell death.

Apoptosis in atherosclerosis: focus on oxidized lipids and inflammation

An increasing body of evidence from both animal models and human specimens suggests that apoptosis or programmed cell death is a major event in the pathophysiology of atherosclerosis. Although the significance of apoptosis in atherosclerosis remains unclear, it has been proposed that apoptotic cell death contributes to plaque instability, rupture and thrombus formation. Biochemical and genetic analyses of apoptosis provide an increasingly detailed picture of the intracellular signaling pathways involved. Nevertheless, it remains to be determined whether apoptosis can become a clinically important approach to modulate plaque progression. In this review, we have outlined some of the most recent results concerning apoptosis in atherosclerosis with a special focus on oxidized lipids, inflammation and therapeutic regulation of the apoptotic cell death process.

Induction of apoptosis and inhibition of migration of inflammatory and vascular wall cells by cerivastatin

Statins are thought to play a role in directly affecting immune and mesenchymal cells. Since cerivastatin's pleiotropic effects are poorly investigated, we were interested to find out whether this drug can modulate leukocyte and vessel wall cell functions. Leukocyte migration was tested in modified Boyden microchemotaxis chambers and oxygen radical production was measured fluorometrically. Transendothelial migration experiments were performed with human umbilical vein endothelial cells and neutrophils. Neutrophil, monocyte, and vascular smooth muscle cell caspase-3 activity and annexin-V binding were quantified by FIENA and FACS, respectively. Cerivastatin [10 pM to 100 microM] decreased leukocyte chemotaxis towards interleukin-8 or RANTES. Migration of cells was completely restored by addition of mevalonic acid. In neutrophils, cerivastatin [100 microM] reduced transendothelial migration, whereas treatment of endothelial cells failed to affect transmigration. Neutrophil respiratory burst activity was unaffected by cerivastatin. At concentrations of 10 nM or higher, cerivastatin increased the rate of apoptosis in phagocytes and smooth muscle cells. Results show that cerivastatin is able to inhibit leukocyte chemotaxis, and that cerivastatin induces neutrophil, monocyte, and smooth muscle cell apoptosis. The drug's impact on transendothelial migration is due to its effects on neutrophils. In addition to its lipid-lowering effects, pharmacological properties of cerivastatin may include modulatory actions in leukocytes and mesenchymal cells.