Kandiah Jeyaseelan

Natriuretic peptide receptor 3 (NPR3) is regulated by microRNA-100

Natriuretic peptide receptor 3 (NPR3) is the clearance receptor for the cardiac natriuretic peptides (NPs). By modulating the level of NPs, NPR3 plays an important role in cardiovascular homeostasis. Although the physiological functions of NPR3 have been explored, little is known about its regulation in health or disease. MicroRNAs play an essential role in the post-transcriptional expression of many genes. Our aim was to investigate potential microRNA-based regulation of NPR3 in multiple models. Hypoxic challenge elevated levels of NPPB and ADM mRNA, as well as NT-proBNP and MR-proADM in human left ventricle derived cardiac cells (HCMa), and in the corresponding conditioned medium, as revealed by qRT-PCR and ELISA. NPR3 was decreased while NPR1 was increased by hypoxia at mRNA and protein levels in HCMa. Down-regulation of NPR3 mRNA was also observed in infarct and peri-infarct cardiac tissue from rats undergoing myocardial infarction. From microRNA microarray analyses and microRNA target predictive databases, miR-100 was selected as a candidate regulator of NPR3 expression. Further analyses confirmed up-regulation of miR-100 in hypoxic cells and associated conditioned media. Antagomir-based silencing of miR-100 enhanced NPR3 expression in HCMa. Furthermore, miR-100 levels were markedly up-regulated in rat hearts and in peripheral blood after myocardial infarction and in the blood from heart failure patients. Results from this study point to a role for miR-100 in the regulation of NPR3 expression, and suggest a possible therapeutic target for modulation of NP bioactivity in heart disease.

MicroRNA-31 promotes adverse cardiac remodeling and dysfunction in ischemic heart disease

RATIONALEnMyocardial infarction (MI) triggers a dynamic microRNA response with the potential of yielding therapeutic targets.nnnOBJECTIVEnWe aimed to identify novel aberrantly expressed cardiac microRNAs post-MI with potential roles in adverse remodeling in a rat model, and to provide post-ischemic therapeutic inhibition of a candidate pathological microRNA in vivo.nnnMETHODS AND RESULTSnFollowing microRNA array profiling in rat hearts 2 and 14days post-MI, we identified a time-dependent up-regulation of miR-31 compared to sham-operated rats. A progressive increase of miR-31 (up to 91.4±11.3 fold) was detected in the infarcted myocardium by quantitative real-time PCR. Following target prediction analysis, reporter gene assays confirmed that miR-31 targets the 3´UTR of cardiac troponin-T (Tnnt2), E2F transcription factor 6 (E2f6), mineralocorticoid receptor (Nr3c2) and metalloproteinase inhibitor 4 (Timp4) mRNAs. In vitro, hypoxia and oxidative stress up-regulated miR-31 and suppressed target genes in cardiac cell cultures, whereas LNA-based oligonucleotide inhibition of miR-31 (miR-31i) reversed its repressive effect on target mRNAs. Therapeutic post-ischemic administration of miR-31i in rats silenced cardiac miR-31 and enhanced expression of target genes, while preserving cardiac structure and function at 2 and 4weeks post-MI. Left ventricular ejection fraction (EF) improved by 10% (from day 2 to 30 post-MI) in miR-31i-treated rats, whereas controls receiving scrambled LNA inhibitor or placebo incurred a 17% deterioration in EF. miR-31i decreased end-diastolic pressure and infarct size; attenuated interstitial fibrosis in the remote myocardium and enhanced cardiac output.nnnCONCLUSIONnmiR-31 induction after MI is deleterious to cardiac function while its therapeutic inhibition in vivo ameliorates cardiac dysfunction and prevents the development of post-ischemic adverse remodeling.

microRNA expression in blood of dengue patients

Background Dengue is the most common arboviral illness worldwide. While most infected patients recover, a proportion of them develop severe complications or fatality. Nevertheless, the pathophysiological mechanisms which distinguish the disease severity and associated complications are not clearly understood. We studied blood profiles of dengue patients in order to identify microRNAs that could play a role in these pathophysiological mechanisms. Methods Blood samples from 26 dengue-infected patients were collected within 0–14 days of infection. Together with samples obtained from six healthy individuals, microRNA profiles were generated to identify significantly altered microRNAs upon dengue infection. Profiles of patients with influenza were also used to determine the disease specificity of these altered microRNAs. Their discriminative power to distinguish dengue from influenza was then tested statistically. Results Several significantly altered microRNAs were identified in patients with dengue. Twelve microRNAs were specifically altered upon acute dengue whereas 14 microRNAs exhibited similar expression between dengue and influenza. Seventeen microRNAs which could potentially distinguish dengue-related complications were also identified. Expression of miR-24-1-5p, miR-512-5p and miR-4640-3p distinguished mild dengue from those exhibiting liver complications whereas miR-383 was significantly upregulated in mild dengue compared to those diagnosed as severe dengue with fluid accumulation. Conclusions We identified two panels of microRNAs – one specific for dengue and the other common to dengue and influenza. We also report on the differentially expressed microRNAs in patients with mild versus severe dengue, which could be the basis for the complications seen in them.

Era of the tiny titans: microRNAs

The discovery of non-coding RNAs demonstrating regulatory control over gene expression has contravened the central dogma theory. Once considered as junk, these RNAs are now an area of active research. The 22 nucleotides long microRNAs (miRNAs), a subset of short non-coding RNAs, were the first to be considered attractive, and over the past decade they have been aggressively studied for roles in disease pathology as well as their relevance in therapeutics. As appropriate expression of miRNAs is critical for normal development, it is understandable that their dysregulation may be the cause or effect of a pathological condition. Madathil et al. [1] highlighted that: Although the change in miRNA expression in response to brain injury indicates their crucial roles and makes them ideal for therapeutic interventions, their precise function is still elusive. To date, there are still limitations regarding a targeted therapeutic intervention, given the ‘one miRNA and multiple targets’ phenomenon. Yet this very characteristic of miRNAs is also believed to be its forte, as it allows coordinated control of the many but related targets to bring about the desired outcomes. Although a miRNA-based targeted therapeutic intervention for central nervous system (CNS) injuries remains to be investigated, research into areas such as viral infection, heart disease and cancer have far advanced their discoveries into clinical trials, thus signifying the immense potential that these tiny oligonucleotides hold. Nonetheless, as emphasized by Madathil et al. [1], it is inevitable that a single alteration in miRNA expression will induce a cascade of changes in protein expression which will eventually impact on multiple signaling pathways. This was reinforced in our recent study where anti-miR-320a mediated recovery from acute stroke was evident with connotations in multiple crucial pathways [2]. Although the study proved that brain water channels, aquaporins 1 and 4, were direct targets of miR-320 and suppressing its expression would have implications in edema accumulation, it also identified a plethora of other potential targets with relevance to processes such as survival, proliferation, cell communication, transcriptional regulation and anti-inflammation. The radical reduction of ischemic damage seen by regulating miR-320 expression proposes it to be a potential therapeutic target for stroke. Nevertheless, due to the complexity imposed by the very promiscuous nature of miRNAs, it is critical to carefully access their clinical potential. More recently, miR-137, -181c, -9 and -29a/b have been identified as non-invasive biomarkers of Alzheimer’s disease where the expression of circulating miR181c was reduced in serum samples of Alzheimer’s patients [3]. Yet another report pronounced that expression of miR-181 cluster is down regulated in the penumbra upon ischemic brain injury [4]. These studies corroborate Madathil et al.’s hypothesis that alterations in miRNAs, upon any form of acute CNS injury, may contribute to the subsequent development of chronic brain diseases. Thus therapeutic strategies aimed at regulating crucial ‘acute injury response’ miRNAs may be able to halt the advancement of acute injury pathology into the development of chronic brain diseases. While the predisposition to age-related neurodegenerative diseases as a consequence of acute brain injury has been implicated previously, a more exhaustive study showed that upsurge in neuro-inflammation and subdual of neurogenesis, were the fundamental causes for progressive deterioration of the injured brain [5]. Thus focusing on the associated signaling pathways and relating them to subsequent processes could enable elucidation of important miRNAs in CNS injury.