Subbiah Ramasamy

MiRNAs with apoptosis regulating potential are differentially expressed in chronic exercise-induced physiologically hypertrophied hearts.

Physiological cardiac hypertrophy is an adaptive mechanism, induced during chronic exercise. As it is reversible and not associated with cardiomyocyte death, it is considered as a natural tactic to prevent cardiac dysfunction and failure. Though, different studies revealed the importance of microRNAs (miRNAs) in pathological hypertrophy, their role during physiological hypertrophy is largely unexplored. Hence, this study is aimed at revealing the global expression profile of miRNAs during physiological cardiac hypertrophy. Chronic swimming protocol continuously for eight weeks resulted in induction of physiological hypertrophy in rats and histopathology revealed the absence of tissue damage, apoptosis or fibrosis. Subsequently, the total RNA was isolated and small RNA sequencing was executed. Analysis of small RNA reads revealed the differential expression of a large set of miRNAs during physiological hypertrophy. The expression profile of the significantly differentially expressed miRNAs was validated by qPCR. In silico prediction of target genes by miRanda, miRdB and TargetScan and subsequent qPCR analysis unraveled that miRNAs including miR-99b, miR-100, miR-19b, miR-10, miR-208a, miR-133, miR-191a, miR-22, miR-30e and miR-181a are targeting the genes that primarily regulate cell proliferation and cell death. Gene ontology and pathway mapping showed that the differentially expressed miRNAs and their target genes were mapped to apoptosis and cell death pathways principally via PI3K/Akt/mTOR and MAPK signaling. In summary, our data indicates that regulation of these miRNAs with apoptosis regulating potential can be one of the major key factors in determining pathological or physiological hypertrophy by controlling fibrosis, apoptosis and cell death mechanisms.

Prolonged monocrotophos intake induces cardiac oxidative stress and myocardial damage in rats.

The morbidity and mortality rate of cardiovascular diseases are increasing massively worldwide. The environmental pollutants especially agrochemicals are the most unrecognized cardiovascular risk factors. Monocrotophos (MCP), an organophosphate pesticide with acetylcholine esterase inhibition activity is widely used in India and other parts of the world. The present study investigated the cardiotoxicity of prolonged intake of MCP. Wistar rats were administered 1/50th of LD50 dosage of MCP (0.36mg/kg body weight) orally via gavage daily for three weeks. MCP administered animals exhibited mild-hyperglycemia and dyslipidemia in blood. Cardiac oxidative stress was conferred by accumulation of protein carbonyls, lipid peroxidation and glutathione production. The cardiac markers (cTn-I, CK-MB and LDH) were showed elevated expression in blood plasma, which signals the cardiac tissue damage. The histopathology of the heart tissue authenticated the MCP induced tissue damage by showing signs of nonspecific inflammatory changes and oedema between muscle fibres. Thus the findings of this preliminary study illustrate the cardiotoxic effect of prolonged MCP intake in rats and suggest that MCP can be a possible independent and potent environmental cardiovascular risk factor.

Gut Microbiota, Endocrine-Disrupting Chemicals, and the Diabetes Epidemic

Diabetes is rapidly emerging as one of the biggest health concerns worldwide, with profound implications for disability, mortality, and costs. This suddenly escalating rate of diabetes correlates with global industrialization and the production of plastics, pesticides, synthetic fertilizers, electronic waste, and food additives that release endocrine-disrupting chemicals (EDCs) into the environment and the food chain. Emerging evidence indicates an association between exposure of EDCs and diabetes. In humans, these chemicals are also metabolized by the gut microbiota and thereby their toxicodynamics are altered. In this review we highlight studies that focus on the role of gut microbiota in EDC-induced hyperglycemia and dysregulated glucose homeostasis. We also discuss the translational implications of understanding EDC-microbiota interactions for the diagnosis and treatment of diabetes.

miRNA and piRNA mediated Akt pathway in heart: antisense expands to survive.

The Akt signalling pathway is a crucial network of proteins, which plays a role in neonatal cellular proliferation, hypertrophy and cellular survival mechanism in the heart through a multifaceted system including, small non-coding RNAs (sncRNAs). Despite numerous reports on the distorted expression of these proteins in various cardiovascular diseases, this review focuses on the role of miRNA and piRNA in altering Akt signalling. Nevertheless the role of these sncRNAs in the Akt pathway needs to be studied in detail, there are evidence indicating that they can play a vital function in Akt-mediated cardiac survival. Recent reports indicate that, modification of such miRNA/piRNA causes alteration in the Akt pathway during both physiology and pathology. Therefore, understanding the antisense mediated molecular mechanisms of Akt pathway can devise a new vision towards biomarkers and therapeutic approaches to various cardiovascular diseases.

Cardiac isoform of alpha 2 macroglobulin, an early diagnostic marker for cardiac manifestations in AIDS patients.

This study investigated the possible role of the cardiac isoform of alpha 2-macroglobulin (CA2M) as an early diagnostic marker for HIV-associated cardiovascular manifestations. A total of 349 samples were analysed by Western blot and quantified by sandwich enzyme-linked immunosorbent assay. The levels of CA2M present in sera of HIV-associated cardiac diseases were significantly higher than those of HIV without cardiac involvement and healthy sera. CA2M may act as a novel diagnostic marker to identify cardiac manifestations in HIV/AIDS patients.

Retrotransposons and piRNA: the missing link in central nervous system.

From times when the whole genome were not available to the present explosion of genome knowledge, the biology of non-coding RNA molecules are an unknown ocean of gems. One among them are PIWI-interacting RNAs (piRNAs) that restrict the mobility of various retrotransposons. PIWI proteins and piRNAs once thought to be germline specific was now explored to be expressed in different somatic cells. Emerging proofs of piRNAs from central nervous system has raised serious questions regarding the role of retrotransposons and its silencing mechanism. In this review, we have focused on the existing knowledge of retrotransposons and piRNAs in the central nervous system and have provided future insights. Meta-analysis of retrotransposons in various mammalian genomes and piRNA targets showcased the abundance of LINE transposon and the possibility of piRNA mediated retrotransposon expression. Thus, understanding the retrotransposons-piRNA pathway will provide a new vision for the study of development, physiology and pathology of the central nervous system.

Abundant and Altered Expression of PIWI-Interacting RNAs during Cardiac Hypertrophy

BACKGROUND The discovery of PIWI-interacting RNAs (piRNAs) has fundamentally changed our understanding of post transcriptional regulation of transposons and other genes. Unlike miRNA and siRNA, the piRNAs are the most abundant but least studied RNA species in mammals. Although the expression of PIWI proteins and piRNAs has long been regarded as germline specific, increasing evidences suggest the expression of piRNAs in somatic cells. METHODS In this study, the small RNA sequencing executed during induction of cardiac hypertrophy in both in vivo and in vitro conditions were annotated for the expression of piRNAs. The expression of piRNAs was validated by qPCR and RNA immunoprecipitation. In addition, the presence of piRNAs in circulation of myocardial infarction patients was studied by qPCR. RESULTS We identified an abundant and altered expression of piRNAs during cardiac hypertrophy. The differentially expressed piRNAs was validated by qPCR and RNA immunoprecipitation. The significantly and differentially expressed piRNAs were predicted to target different retrotransposons and mRNAs in the rat genome. The detection of specific piRNA in serum of myocardial infarction patients suggests the potential of piRNA for diagnosis. CONCLUSION Overall this study is the first to provide a whole-genome analysis of the large repertoire of piRNAs in the cardiac system and this would pave a new path to understanding the molecular aetiology of piRNA and retrotransposons in the physiology and pathology of the cardiac system.

Egr-1 mediated cardiac miR-99 family expression diverges physiological hypertrophy from pathological hypertrophy

Abstract The physiological cardiac hypertrophy is an adaptive condition without myocyte cell death, while pathological hypertrophy is a maladaptive condition associated with myocyte cell death. This study explores the miRNome of &agr;‐2M‐induced physiologically hypertrophied cardiomyocytes and the role of miRNA‐99 family during cardiac hypertrophy. Physiological and pathological cardiac hypertrophy was induced in H9c2 cardiomyoblast cell lines using &agr;‐2M and isoproterenol respectively. Total RNA isolation and small RNA sequencing were executed for physiological hypertrophy model. The differentially expressed miRNAs and its target mRNAs were validated in animal models. Transcription factor binding sites were predicted in the promoter of specific miRNAs and validated by ChIP‐PCR. Subsequently, the selected miRNA was functionally characterized by overexpression and silencing. The effects of silencing of upstream regulator and downstream target gene were studied. Analysis of small RNA reads revealed the differential expression of a large set of miRNAs during hypertrophy, of which miR‐99 family was highly downregulated upon &agr;‐2M treatment. However, this miR‐99 family expression was upregulated during pathological hypertrophy and confirmed in animal models. ChIP‐PCR confirms the binding of Egr‐1 transcription factor to the miR‐99 promoter. Further, silencing of Egr‐1 decreased the expression of miR‐99. The overexpression or silencing of miR‐99 diverges the physiological hypertrophy to pathological hypertrophy and vice versa by regulating Akt‐1 pathway. Silencing of Akt‐1 replicates the effect of overexpression of miR‐99. Conclusion The results proved Egr‐1 mediated regulation of miR‐99 family that plays a key role in determining the fate of cardiac hypertrophy by regulating Akt‐1 signaling. Graphical abstract Schematic representation of determination of cardiac hypertrophy by Egr‐1‐mediated regulation of microRNA‐99. Figure. No Caption available.

Emerging cardiac non-coding landscape: The importance of meta-analysis

The invention of transcriptome-wide deep sequencing technology has fundamentally changed our understanding of the complex networks that mediate cardiac functions. Since its inception, researchers have uncovered various novel pathways and transcripts that could be one day used for therapeutics and diagnostics. The characterization of various non-protein coding RNAs (ncRNAs) has aided the study of cardiac manifestation in more detail. Although numerous studies have unearthed the importance of miRNA and lncRNA, the existence and importance of other ncRNAs have been neglected due to their unusual behaviors and outdated ideologies. Recent studies focused on these neglected molecules have proven that these molecules are functional and of great potential. This review brings into focus some of those ncRNAs that were once thought to be futile and not expressed in the heart with an emphasis on the use of meta-data.