Serum cyclin-dependent kinase 9 is a potential biomarker of atherosclerotic inflammation

Proteomic Studies of Blood and Vascular Wall in Atherosclerosis

The review is devoted to the analysis of literature data related to the role of proteomic studies in the study of atherosclerotic cardiovascular diseases. Diagnosis of patients with atherosclerotic plaques before clinical manifestations is an arduous task. The review presents the results of research on the new proteomic potential biomarkers of coronary heart disease, coronary atherosclerosis, acute coronary syndrome, myocardial infarction, carotid artery atherosclerosis. Also, the analysis of literature data on proteomic studies of the vascular wall was carried out. To assess the involvement of proteins in the pathological process of atherosclerosis, it is important to investigate the specific relationships between proteins in the arteries, expression and concentration of proteins. The development of proteomic technologies has made it possible to analyse the number of proteins associated with the development of the disease. Analysis of the proteomic profile of the vascular wall in atherosclerosis can help to detect possible diagnostically significant protein structures or potential biomarkers of the disease and develop novel approaches to the diagnosis of atherosclerosis and its complications.

Advances in Cardiovascular Biomarker Discovery

Cardiovascular diseases are the leading causes of mortality worldwide. Among them, hypertension and its pathological complications pose a major risk for the development of other cardiovascular diseases, including heart failure and stroke. Identifying novel and early stage biomarkers of hypertension and other cardiovascular diseases is of paramount importance in predicting and preventing the major morbidity and mortality associated with these diseases. Biomarkers of such diseases or predisposition to their development are identified by changes in a specific indicator’s expression between healthy individuals and patients. These include changes in protein and microRNA (miRNA) levels. Protein profiling using mass spectrometry and miRNA screening utilizing microarray and sequencing have facilitated the discovery of proteins and miRNA as biomarker candidates. In this review, we summarized some of the different, promising early stage protein and miRNA biomarker candidates as well as the currently used biomarkers for hypertension and other cardiovascular diseases. Although a number of promising markers have been identified, it is unlikely that a single biomarker will unambiguously aid in the classification of these diseases. A multi-marker panel-strategy appears useful and promising for classifying and refining risk stratification among patients with cardiovascular disease.

Transcriptional cyclin-dependent kinases as the mediators of inflammation-a review

Cyclin-dependent kinases (CDKs) belong to the serine/threonine kinase family, and their unique interactions with a variety of cyclin complexes influence its catalytic activity to ensure unimpaired cell cycle progression. In addition to their cell cycle regulatory roles, it is becoming increasingly clear that the CDKs can have multiple functional roles like transcription, epigenetic regulation, metabolism, stem cell self-renewal, neuronal functions, and in spermatogenesis. Further in addition, recent reports suggest that CDKs have a remarkable regulatory role in influencing the pro-inflammatory functions of various cytokines during the clinical inflammatory responses. CDKs initiate the inflammatory responses by triggering the activity of prominent pro-inflammatory transcription factors such as nuclear factor kappa B (NF-kB), signal transducer and activator of transcription 3 (STAT3), and activator protein 1 (AP-1). The transcriptional CDKs (tCDKs) is crucial for organizing various transcription events and associated processes such as RNA capping, splicing, 3' end formation, and chromatin remodeling. Although the in-depth mechanism of certain mammalian CDKs is explored with respect to inflammation, the role of other tCDKs or any synergistic play among the members still remains unexplored. Until today, there is only supportive and palliative care available most of the inflammatory disorders, and thus it is the right time to explore novel pharmacological targets. In this regard, we focus on the pathophysiological role of CDK7, CDK8 and CDK9 and their impact on the development of inflammatory disorders within the mammals. Additionally, we discuss the potential trends of having tCDKs as a therapeutic target for fine-tuning inflammatory disorders.

Long Non-coding RNA PEBP1P2 Suppresses Proliferative VSMCs Phenotypic Switching and Proliferation in Atherosclerosis

Long non-coding RNAs (lncRNAs) play a crucial role in the growth of vascular smooth muscle cells (VSMCs), the dysfunction of which is closely associated with the initiation and progression of cardiovascular diseases (CVDs). Abnormal phenotypic switching and proliferation of VSMCs constitute a significant event in the progression of atherosclerosis. The present study identified a novel lncRNA, PEBP1P2, which serves as a valuable regulator of VSMCs in phenotypic transformation and proliferation. The expression of PEBP1P2 was remarkably decreased in proliferating VSMCs and pathological arteries when using a balloon injury model of rats. Furthermore, we found that PEBP1P2 represses proliferation, migration, and dedifferentiation during phenotype switching in VSMCs induced by platelet-derived growth factor BB (PDGF-BB). Mechanistically, cyclin-dependent kinase 9 (CDK9) was confirmed to be the direct target of PEBP1P2, which was proven to mediate phenotypic switching and proliferation of VSMCs and was rescued by PEBP1P2. Then, we explored the clinical significance, as we observed the decreased expression of PEBP1P2 in the serum of coronary heart disease (CHD) patients and human advanced carotid atherosclerotic plaques. Finally, PEBP1P2 overexpression distinctly suppressed neointima formation and VSMC phenotypic switching in vivo. Taken together, PEBP1P2 inhibits proliferation and migration in VSMCs by directly binding to CDK9, implying that it may be a promising therapeutic target for the treatment of proliferative vascular diseases.

P-TEFb as A Promising Therapeutic Target

The positive transcription elongation factor b (P-TEFb) was first identified as a general factor that stimulates transcription elongation by RNA polymerase II (RNAPII), but soon afterwards it turned out to be an essential cellular co-factor of human immunodeficiency virus (HIV) transcription mediated by viral Tat proteins. Studies on the mechanisms of Tat-dependent HIV transcription have led to radical advances in our knowledge regarding the mechanism of eukaryotic transcription, including the discoveries that P-TEFb-mediated elongation control of cellular transcription is a main regulatory step of gene expression in eukaryotes, and deregulation of P-TEFb activity plays critical roles in many human diseases and conditions in addition to HIV/AIDS. P-TEFb is now recognized as an attractive and promising therapeutic target for inflammation/autoimmune diseases, cardiac hypertrophy, cancer, infectious diseases, etc. In this review article, I will summarize our knowledge about basic P-TEFb functions, the regulatory mechanism of P-TEFb-dependent transcription, P-TEFb’s involvement in biological processes and diseases, and current approaches to manipulating P-TEFb functions for the treatment of these diseases.

Role of adipokine zinc-α2-glycoprotein in coronary heart disease

Zinc-α₂-glycoprotein (AZGP1) is a newly identified adipokine that is associated with lipid metabolism and vascular fibrosis. Although adipokines contribute to lipid dysfunction and its related diseases, including stroke and coronary heart disease (CHD), the role of AZGP1 remains unclear. In this study, the role of AZGP1 in atherosclerosis and CHD was investigated. Serum AZGP1 levels from control (n = 84) and CHD (n = 91) patients were examined by ELISA and its relationship with various clinical parameters was analyzed. Immunohistochemistry and immunofluorescence were used to detect the expression of AZGP1 and its receptor in coronary atherosclerotic arteries. THP-1 and human embryonic kidney 293 cells were used to verify its anti-inflammatory role in atherosclerosis. Serum AZGP1 levels in CHD patients were lower than controls (P < 0.01) and independently associated with CHD prevalence (P = 0.021). AZGP1 levels also inversely correlated with the Gensini score. Immunohistochemistry and immunofluorescence showed that AZGP1 and its receptor β₃-adrenoceptor (β₃-AR) colocalized in lipid-rich areas of atherosclerotic plaques, particularly around macrophages. In vitro, AZGP1 had no effect on foam cell formation but showed anti-inflammatory effects through its regulation of JNK/AP-1 signaling. In summary, AZGP1 is an anti-inflammatory agent that can be targeted for CHD treatment.

A Proteomic Study of Atherosclerotic Plaques in Men with Coronary Atherosclerosis

Background: To study the changes in protein composition of atherosclerotic plaques at different stages of their development in coronary atherosclerosis using proteomics. Methods: The object of research consisted of homogenates of atherosclerotic plaques from coronary arteries at different stages of development, obtained from 15 patients. Plaque proteins were separated by two-dimensional electrophoresis. The resultant protein spots were identified by the matrix-assisted laser desorption ionization method with peptide mass mapping. Results: Groups of differentially expressed proteins, in which the amounts of proteins differed more than twofold (p < 0.05), were identified in pools of homogenates of atherosclerotic plaques at three stages of development. The amounts of the following proteins were increased in stable atherosclerotic plaques at the stage of lipidosis and fibrosis: vimentin, tropomyosin β-chain, actin, keratin, tubulin β-chain, microfibril-associated glycoprotein 4, serum amyloid P-component, and annexin 5. In plaques at the stage of fibrosis and calcification, the amounts of mimecan and fibrinogen were increased. In unstable atherosclerotic plaque of the necrotic–dystrophic type, the amounts of human serum albumin, mimecan, fibrinogen, serum amyloid P-component and annexin were increased. Conclusion: This proteomic study identifies the proteins present in atherosclerotic plaques of coronary arteries by comparing their proteomes at three different stages of plaque development during coronary atherosclerosis.

Activation of activator protein 2 alpha by aspirin alleviates atherosclerotic plaque growth and instability in vivo

AIMS

Aspirin has been used for the secondary prevention and treatment of cardiovascular disease for several decades. We investigated the roles of transcriptional factor activator protein 2α (AP-2α) in the beneficial effects of aspirin in the growth and vulnerability of atherosclerotic plaque.

METHODS AND RESULTS

In mice deficient of apolipoprotein E (Apoe-/-), aspirin (20, 50 mg/kg/day) suppressed the progression of atherosclerosis in aortic roots and increased the plaque stability in carotid atherosclerotic plaques induced by collar-placement. In vivo lentivirus-mediated RNA interference of AP-2α reversed the inhibitory effects of aspirin on atherosclerosis in Apoe-/- mice. Mechanically, aspirin increased AP-2α phosphorylation and its activity, upregulated IkBα mRNA and protein levels, and reduced oxidative stress in cultured vascular smooth muscle cells. Furthermore, deficiency of AP-2α completely abolished aspirin-induced upregulation of IkBα levels and inhibition of oxidative stress in Apoe-/- mice. Clinically, conventional doses of aspirin increased AP-2α phosphorylation and IkBα protein expression in humans subjects.

CONCLUSION

Aspirin activates AP-2α to upregulate IkBα gene expression, resulting in attenuations of plaque development and instability in atherosclerosis.

CDK9: A key player in cancer and other diseases

Cyclin-Dependent Kinase 9 (CDK9) is part of a functional diverse group of enzymes responsible for cell cycle control and progression. It associates mainly with Cyclin T1 and forms the Positive Transcription Elongation Factor b (p-TEFb) complex responsible for regulation of transcription elongation and mRNA maturation. Recent studies have highlighted the importance of CDK9 in many relevant pathologic processes, like cancer, cardiovascular diseases, and viral replication. Herein we provide an overview of the different pathways in which CDK9 is directly and indirectly involved.

Dynamic interplay between tumour, stroma and immune system can drive or prevent tumour progression

In the tumour microenvironment, cancer cells directly interact with both the immune system and the stroma. It is firmly established that the immune system, historically believed to be a major part of the body's defence against tumour progression, can be reprogrammed by tumour cells to be ineffective, inactivated, or even acquire tumour promoting phenotypes. Likewise, stromal cells and extracellular matrix can also have pro-and anti-tumour properties. However, there is strong evidence that the stroma and immune system also directly interact, therefore creating a tripartite interaction that exists between cancer cells, immune cells and tumour stroma. This interaction contributes to the maintenance of a chronically inflamed tumour microenvironment with pro-tumorigenic immune phenotypes and facilitated metastatic dissemination. A comprehensive understanding of cancer in the context of dynamical interactions of the immune system and the tumour stroma is therefore required to truly understand the progression toward and past malignancy.

How to use and integrate bioinformatics tools to compare proteomic data from distinct conditions? A tutorial using the pathological similarities between Aortic Valve Stenosis and Coronary Artery Disease as a case-study

Nowadays we are surrounded by a plethora of bioinformatics tools, powerful enough to deal with the large amounts of data arising from proteomic studies, but whose application is sometimes hard to find. Therefore, we used a specific clinical problem - to discriminate pathophysiology and potential biomarkers between two similar cardiovascular diseases, aortic valve stenosis (AVS) and coronary artery disease (CAD) - to make a step-by-step guide through four bioinformatics tools: STRING, DisGeNET, Cytoscape and ClueGO. Proteome data was collected from articles available on PubMed centered on proteomic studies enrolling subjects with AVS or CAD. Through the analysis of gene ontology provided by STRING and ClueGO we could find specific biological phenomena associated with AVS, such as down-regulation of elastic fiber assembly, and with CAD, such as up-regulation of plasminogen activation. Moreover, through Cytoscape and DisGeNET we could pinpoint surrogate markers either for AVS (e.g. popeye domain containing protein 2 and 28S ribosomal protein S36, mitochondrial) or for CAD (e.g. ankyrin repeat and SOCS box protein 7) which deserve future validation. Data recycling and integration as well as research orientation are among the main advantages of resorting to bioinformatics analysis, hence these tutorials can be of great convenience for proteomics investigators.

BIOLOGICAL SIGNIFICANCE

As we saw for aortic valve stenosis and coronary artery disease, it can be of great relevance to perform preliminary bioinformatics analysis with already published proteomics data. It not only saves us time in the lab (avoiding work duplication) as it points out new hypothesis to explain the phenotypical presentation of the diseases as well as new surrogate markers with clinical relevance, deserving future scrutiny. These essential steps can be easily overcome if one follows the steps proposed in our tutorial for STRING, DisGeNET, Cytoscape and ClueGO utilization.

Potential Use of Flavopiridol in Treatment of Chronic Diseases

This chapter describes the potential use of flavopiridol, a CDK inhibitor with anti-inflammatory and anti-proliferative activities, in the treatment of various chronic diseases. Flavopiridol arrests cell cycle progression in the G1 or G2 phase by inhibiting the kinase activities of CDK1, CDK2, CDK4/6, and CDK7. Additionally, it binds tightly to CDK9, a component of the P-TEFb complex (CDK9/cyclin T), and interferes with RNA polymerase II activation and associated transcription. This in turn inhibits expression of several pro-survival and anti-apoptotic genes, and enhances cytotoxicity in transformed cells or differentiation in growth-arrested cells. Recent studies indicate that flavopiridol elicits anti-inflammatory activity via CDK9 and NFκB-dependent signaling. Overall, these effects of flavopiridol potentiate its ability to overcome aberrant cell cycle activation and/or inflammatory stimuli, which are mediators of various chronic diseases.