Murugavel Ponnusamy

Circular RNA mediates cardiomyocyte death via miRNA-dependent upregulation of MTP18 expression

Circular RNAs (circRNAs) have important roles in several cellular processes. No study has established the pathophysiological role for circRNAs in the heart. Here, we show that a circRNA (mitochondrial fission and apoptosis-related circRNA (MFACR)) regulates mitochondrial fission and apoptosis in the heart by directly targeting and downregulating miR-652-3p; this in turn blocks mitochondrial fission and cardiomyocyte cell death by suppressing MTP18 translation. MTP18 deficiency reduces mitochondrial fission and suppresses cardiomyocyte apoptosis and MI. miR-652-3p directly downregulates MTP18 and attenuates mitochondrial fission, cardiomyocyte apoptosis, and MI in vitro and in vivo. MFACR directly sequesters miR-652-3p in the cytoplasm and inhibits its activity. MFACR knockdown in cardiomyocytes and mice attenuates mitochondrial fission and MI. Our results reveal a crucial role for circRNA in regulating mitochondrial dynamics and apoptosis in the heart; as such, circRNAs may serve as a potential therapeutic avenue for cardiovascular diseases.

Understanding cardiomyocyte proliferation: an insight into cell cycle activity

Cardiomyocyte proliferation and regeneration are key to the functional recovery of myocardial tissue from injury. In the recent years, studies on cardiomyocyte proliferation overturned the traditional belief that adult cardiomyocytes permanently withdraw from the cell cycle activity. Hence, targeting cardiomyocyte proliferation is one of the potential therapeutic strategies for myocardial regeneration and repair. To achieve this, a deep understanding of the fundamental mechanisms involved in cardiomyocyte cell cycle as well as differences between neonatal and adult cardiomyocytes’ cell cycle activity is required. This review focuses on the recent progress in understanding of cardiomyocyte cell cycle activity at different life stages viz., gestation, birth, and adulthood. The temporal expression/activities of major cell cycle activators (cyclins and CDKs), inhibitors (p21, p27, p57, p16, and p18), and cell-cycle-associated proteins (Rb, p107, and p130) in cardiomyocytes during gestation and postnatal life are described in this review. The influence of different transcription factors and microRNAs on the expression of cell cycle proteins is demonstrated. This review also deals major pathways (PI3K/AKT, Wnt/β-catenin, and Hippo-YAP) associated with cardiomyocyte cell cycle progression. Furthermore, the postnatal alterations in structure and cellular events responsible for the loss of cell cycle activity are also illustrated.

LncRNA CAIF inhibits autophagy and attenuates myocardial infarction by blocking p53-mediated myocardin transcription

Increasing evidence suggests that long noncoding RNAs (lncRNAs) play crucial roles in various biological processes. However, little is known about the effects of lncRNAs on autophagy. Here we report that a lncRNA, termed cardiac autophagy inhibitory factor (CAIF), suppresses cardiac autophagy and attenuates myocardial infarction by targeting p53-mediated myocardin transcription. Myocardin expression is upregulated upon H2O2 and ischemia/reperfusion, and knockdown of myocardin inhibits autophagy and attenuates myocardial infarction. p53 regulates cardiomyocytes autophagy and myocardial ischemia/reperfusion injury by regulating myocardin expression. CAIF directly binds to p53 protein and blocks p53-mediated myocardin transcription, which results in the decrease of myocardin expression. Collectively, our data reveal a novel CAIF-p53-myocardin axis as a critical regulator in cardiomyocyte autophagy, which will be potential therapeutic targets in treatment of defective autophagy-associated cardiovascular diseases.Little is known about the role of long lncRNAs in autophagy. The authors identify lncCAIF, and show that it suppresses cardiac autophagy and attenuates myocardial infarction by targeting p53 -mediated transcription of myocardin.

The role of miR-214 in cardiovascular diseases

Abstract Cardiovascular disease (CVD) is the leading cause of death throughout the world. The increase in new patients every year leads to a demand for the identification of valid and novel prognostic and diagnostic biomarkers for the prevention and treatment of cardiovascular diseases. MicroRNAs (miRNAs) are critical endogenous small noncoding RNAs that negatively modulate gene expression by regulating its translation. miRNAs are implicated in most physiological processes of the heart and in the pathological progression of cardiovascular diseases. miR‐214 is a deregulated miRNA in many pathological conditions, and it contributes to the pathogenesis of multiple human disorders, including cancer and cardiovascular diseases. miR‐214 has dual functions in different cardiac pathological circumstances. However, it is considered as a promising marker in the prognosis, diagnosis and treatment of cardiovascular diseases. In this review, we discuss the role of miR‐214 in various cardiac disease conditions, including ischaemic heart diseases, cardiac hypertrophy, pulmonary arterial hypertension (PAH), angiogenesis following vascular injury and heart failure.

Effects of miRNAs on myocardial apoptosis by modulating mitochondria related proteins

Myocardial apoptosis play a vital role in pathogenesis of cardiovascular diseases. The intrinsic pathway of apoptosis (mitochondrial apoptosis pathway) and abnormal mitochondrial fission and fusion have a detrimental effect on cells under a variety of intracellular stresses including hypoxia, oxidative stress, drug toxicity or DNA damage and contributes to the development of heart failure (HF), myocardial infarction (MI), diabetic cardiomyopathy and ischaemia/reperfusion injury (I/R). MicroRNAs (miRNAs) are endogenous short non‐coding RNAs, which target 3′‐untranslated region of mRNA to switch off gene expression. They play crucial roles in regulating complicated cardiac signalling and transcriptional events during cardiac development as well as in diseased condition. In this review, we summarize the molecular mechanism of mitochondrial apoptosis in cardiac cells and influence of miRNAs on them. MiRNAs regulate cardiac mitochondrial apoptosis by exert their effects on mitochondrial fission and fusion, reactive oxygen species (ROS) generation and Ca2+ homeostasis, Bcl‐2 family members, and other mitochondrial function proteins. This advancement in understanding mechanism of cardiac cells death provides us new therapy targets for cardiovascular diseases associated with mitochondrial dysfunctions.

The Role of MicroRNA and LncRNA-MicroRNA Interactions in Regulating Ischemic Heart Disease

Approximately 2% of the human genome consists of protein-coding regions. Therefore, the majority of transcripts are noncoding RNAs, such as microRNA (miRNA) and long noncoding RNAs (lncRNAs). In ischemic heart disease, the majority of miRNAs are repressors or destabilizers of target messenger RNAs. The lncRNAs are a second class of noncoding RNAs that have recently gained attention for their roles in heart disease and in regulating the functions of miRNA. In this review, we summarize the role of miRNA in pathological cardiac hypertrophy and myocardial infarction. In addition, we discuss the functional interactions of miRNA and lncRNA and its impact on these ischemic heart diseases.

PIWI family emerging as a decisive factor of cell fate: An overview

PIWI proteins and piRNAs primarily functions as a safeguard of germline cells by activating epigenetic regulations, silencing transposons and maintaining chromatin structure. Increasing evidences reveal that PIWI proteins and piRNAs have broader functions in many vital biological processes including cell proliferation, differentiation and survival. They have been recognized as a crucial factor in the cellular events due their role in controlling mRNA expression, turnover and translation. PIWIs, with or without its partner non-coding RNA (piRNA), govern the expression and activity of many transcription factors and signaling molecules by mastering their expression and/or post-translational modifications by directly interacting with them. In this review, we focus on the functional role of PIWI family of proteins and piRNA in physiological and pathological conditions. We compile the current knowledge about the impact of alterations of PIWI and/or piRNA on expression and activities of signaling mediators and transcriptional networks associated with cell differentiation, proliferation and survival.

miRNAs as potential therapeutic targets and diagnostic biomarkers for cardiovascular disease with a particular focus on WO2010091204

ABSTRACT Introduction: A number of miRNAs have been reported to be critically involved in the regulation of cardiovascular disease (CVDs). Therefore, the development of potent analogues/inhibitors for miRNAs have thus become a key focus in the present drug discovery. In this review, we discuss the basic research and clinical use of miRNAs as the early diagnosis and therapeutic targets for CVD. We have also focused on the efficiency of therapeutically targeting miR-499, which is considered as one of the most promising molecules for treating CVDs. Areas covered: In this review, we have discussed the patents and patent applications related to miRNAs detected in CVD patients published in recent years. This review also covers the expression pattern of miR-499, as well as it highlights functions of its inhibitors in CVD. We used Google and Pubmed search engines to find relevant patents. Expert opinion: Although a massive number of miRNAs are patented as CVD biomarkers, further work is absolutely required to evaluate the reliable diagnostic values and therapeutic potential of these candidates. Overall, targeting miRNAs is definitely a promising strategy to be investigated for diagnosis and treatment of CVDs in future, however, the delivery system and off-targets effects are still a difficult challenge need to be elucidated.

The role of ubiquitin proteasomal system and autophagy-lysosome pathway in Alzheimer’s disease

Abstract Alzheimer’s disease (AD) is the most common neurodegenerative disorder leading to dementia in the elderly population. AD is associated with the buildup of β-amyloid and tau, which aggregate into extracellular plaques and neurofibrillary tangles. Although the exact mechanism of pathological process of AD is unclear, the dysfunction of protein degradation mechanisms has been proposed to play an important role in AD. The cellular degradation of abnormal or misfolded proteins consists of three different mechanisms: the ubiquitin proteasomal system (UPS), autophagy-lysosomal pathway (ALP), and interaction of molecular chaperones with UPS or ALP. Any disturbance to these systems causes proteins to accumulate, resulting in pathological process of AD. In this review, we summarize the knowledge of protein degradation pathways in the pathogenesis of AD in light of the current literature. In the future, the regulation UPS or ALP machineries could be the cornerstones of the treatment of AD.

MiR-485-5p modulates mitochondrial fission through targeting mitochondrial anchored protein ligase in cardiac hypertrophy

The pathogenesis of cardiac hypertrophy is tightly associated with mitochondrial dysfunction. Disequilibrium of mitochondrial dynamic is one of the main drivers in the pathological processes during development of various cardiac diseases. However, the effect of mitochondrial dynamics on cardiac hypertrophy remains largely unclear. MicroRNAs (miRNAs) are small noncoding RNAs that can switch off expression of many genes. Mitochondrial anchored protein ligase (MAPL) is a small ubiquitin-like modifier (SUMO) E3 ligase, which is an important contributor in mitochondrial fission process. In this study, we found that hypertrophic agonist phenylephrine (PE) enhanced the expression of MAPL and promoted mitochondrial fission, while it decreased the expression of mitochondrial fusion protein2 (Mfn2) in hypertrophic cardiomyocytes. Silencing expression of MAPL by siRNA attenuated PE-induced depletion of Mfn2 and increase of mitochondrial fission as well as hypertrophic response in cultured primary cardiomyocytes. MiR-485-5p is screened as a candidate inhibitor of MAPL. Overexpression of miR-485-5p blocked mitochondrial fission and hypertrophy induced by PE through inhibiting MAPL expression and increasing the level of Mfn2 in cultured primary cardiomyocytes. In mice model of cardiac hypertrophy induced by PE, the administration of miR-485-5p agomir significantly decreased the PE induced increase in the expression of MAPL and hypertrophic markers (ANP and β-MHC) along with protection of cardiac structure and function. Together, this study exhibits a novel signaling axis composed of miR-485-5p/MAPL/Mfn2, which regulates mitochondrial machinery and cardiac hypertrophy.