RNA interference (RNAi) is a robust gene silencing mechanism that degrades mRNAs complementary to the antisense strands of double-stranded, short interfering RNAs (siRNAs). As a therapeutic strategy, RNAi has an advantage over small-molecule drugs, as virtually all genes are susceptible to targeting by siRNA molecules. This advantage is, however, counterbalanced by the daunting challenge of achieving safe, effective delivery of oligonucleotides to specific tissues in vivo. Lipid-based carriers of siRNA therapeutics can now target the liver in metabolic diseases and are being assessed in clinical trials for the treatment of hypercholesterolemia. For this indication, a chemically modified oligonucleotide that targets endogenous small RNA modulators of gene expression (microRNAs) is also under investigation in clinical trials. Emerging 'self-delivery' siRNAs that are covalently linked to lipophilic moieties show promise for the future development of therapies. Besides the liver, inflammation of the adipose tissue in patients with obesity and type 2 diabetes mellitus may be an attractive target for siRNA therapeutics. Administration of siRNAs encapsulated within glucan microspheres can silence genes in inflammatory phagocytic cells, as can certain lipid-based carriers of siRNA. New technologies that combine siRNA molecules with antibodies or other targeting molecules also appear encouraging. Although still at an early stage, the emergence of RNAi-based therapeutics has the potential to markedly influence our clinical future.
"miRNA inhibitors termed miRNA sponges , antagomirs , locked-nucleic-acid-modified oligonucleotides , and reconstituted high-density lipoprotein nanoparticles  are some of the approaches that have been pursued. Currently recognized delivery barriers, development of novel nanomaterials, nanovector fabrication methods, and delivery approaches have been reviewed [48,49]. In yet another strategy, antibodies against various cell surface receptors were used for delivery; and upon intravenous administration, the complex was taken up by specific cells via receptor-mediated endocytosis . "
[Show abstract][Hide abstract] ABSTRACT: Small noncoding microRNAs (miRNAs) are important regulators of post-transcriptional gene regulation and have altered the prevailing view of a linear relationship between gene and protein expression. Aberrant miRNA expression is an emerging theme for a wide variety of diseases, highlighting the fundamental role played by miRNAs in both physiological and pathological states. The identification of stable miRNAs in bodily fluids paved the way for their use as novel biomarkers amenable to clinical diagnosis in translational medicine. Identification of miRNAs in exosomes that are functional upon delivery to the recipient cells has highlighted a novel method of intercellular communication. Delivery of miRNAs to recipient cells via blood, with functional gene regulatory consequences, opens up novel avenues for target intervention. Exosomes thus offer a novel strategy for delivering drugs or RNA therapeutic agents. Though much work lies ahead, circulating miRNAs are unequivocally ushering in a new era of novel biomarker discovery, intercellular communication mechanisms, and therapeutic intervention strategies.
"In human NAFLD, 23 miRNAs regulating cell proliferation, apoptosis, inflammation, oxidative stress and metabolism were either overexpressed or underexpressed . Changes in miRNAs in the metabolic syndrome that underpin NAFLD and non-alcoholic steatohepatitis (NASH) have recently been reviewed in relevance to potential therapeutic strategies . In alcoholic liver disease, the role of inflammation and Kupffer cells (KCs) activation resulting in increased TNFa production has been long established. "
[Show abstract][Hide abstract] ABSTRACT: In recent years microRNAs have emerged as crucial small non-coding RNA molecules with diverse roles in various diseases including diseases of the liver. In this review, we highlight the latest advances in the field of microRNA biology and their potential as emerging therapeutic targets in liver disease.
Journal of Hepatology 04/2012; 57(2):462-6. DOI:10.1016/j.jhep.2012.01.030 · 11.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human Immunodeficiency Virus-type 1 (HIV-1) binds to CD4 and CCR5 receptors on target cells in the human female reproductive tract. We sought to determine whether reducing levels of messenger RNA (mRNA) transcripts that encode these receptors in female reproductive tract cells could protect mucosal tissue explants from HIV-1 infection. Explants prepared from the endometrium, endocervix, and ectocervix of hysterectomy tissues from HIV-1 sero-negative women were exposed to nanoparticles containing CD4- and CCR5-specific short-interfering RNA (siRNA) sequences. Explants were then exposed two days later to HIV-1, and HIV-1 reverse transcripts were measured five days post-infection. Explants treated with nanoparticles containing CD4- and CCR5-specific siRNA showed reduced levels of CD4 and CCR5 transcripts, and significantly lower levels of HIV-1 reverse transcripts compared to those treated with an irrelevant siRNA. In female reproductive tract explants and in peripheral blood cell cultures, siRNA transfection induced the secretion of IFN-alpha (IFN-α), a potent antiviral cytokine. In female mice, murine-specific Cd4-siRNA nanoparticles instilled within the uterus significantly reduced murine Cd4 transcripts by day 3. Our findings demonstrate that siRNA nanoparticles reduce expression of HIV-1 infectivity receptors in human female reproductive tract tissues and also inhibit HIV-1 infection. Murine studies demonstrate that nanoparticles can penetrate the reproductive tract tissues in vivo and silence gene expression. The induction of IFN-α after siRNA transfection can potentially contribute to the antiviral effect. These findings support the therapeutic development of nanoparticles to deliver siRNA molecules to silence host cell receptors in the female reproductive tract as a novel microbicide to inhibit mucosal HIV-1 transmission.
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