Sequence-dependent off-target inhibition of TLR7/8 sensing by synthetic microRNA inhibitors.
ABSTRACT: Anti-microRNA (miRNA) oligonucleotides (AMOs) with 2'-O-Methyl (2'OMe) residues are commonly used to study miRNA function and can achieve high potency, with low cytotoxicity. Not withstanding this, we demonstrate the sequence-dependent capacity of 2'OMe AMOs to inhibit Toll-like receptor (TLR) 7 and 8 sensing of immunostimulatory RNA, independent of their miRNA-targeting function. Through a screen of 29 AMOs targeting common miRNAs, we found a subset of sequences highly inhibitory to TLR7 sensing in mouse macrophages. Interspecies conservation of this inhibitory activity was confirmed on TLR7/8 activity in human peripheral blood mononuclear cells. Significantly, we identified a core motif governing the inhibitory activity of these AMOs, which is present in more than 50 AMOs targeted to human miRNAs in miRBaseV20. DNA/locked nucleic acids (LNA) AMOs synthesized with a phosphorothioate backbone also inhibited TLR7 sensing in a sequence-dependent manner, demonstrating that the off-target effects of AMOs are not restricted to 2'OMe modification. Taken together, our work establishes the potential for off-target effects of AMOs on TLR7/8 function, which should be taken into account in their therapeutic development and in vivo application.
Project description:MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression post-transcriptionally. Previous studies, which characterized miRNA function, revealed their involvement in fundamental biological processes. Importantly, miRNA expression is deregulated in many human diseases. Specific inhibition of miRNAs using chemically modified anti-miRNA oligonucleotides (AMOs) can be a potential therapeutic strategy for diseases in which a specific miRNA is overexpressed. 2'-O-Methyl (2'-OMe)-4'-thioRNA is a hybrid type of chemically modified oligonucleotide, exhibiting high binding affinity to complementary RNAs and high resistance to nuclease degradation. Here, we evaluate 2'-OMe-4'-thioribonucleosides for chemical modification on AMOs. Optimization of the modification pattern using a variety of chemically modified AMOs that are perfectly complementary to mature miR-21 revealed that the uniformly 2'-OMe-4'-thioribonucleoside-modified AMO was most potent. Further investigation showed that phosphorothioate modification contributed to long-term miR-122 inhibition by the 2'-OMe-4'-thioribonucleoside-modified AMO. Moreover, systemically administrated AMOs to mouse using a liposomal delivery system, YSK05-MEND, showed delivery to the liver and efficient inhibition of miR-122 activity at a low dose in vivo.
Project description:Anti-microRNA oligonucleotides (AMOs) are steric blocking antisense reagents that inhibit microRNA (miRNA) function by hybridizing and repressing the activity of a mature miRNA. First generation AMOs employed 2'-O-Methyl RNA nucleotides (2'OMe) with phosphorothioate (PS) internucleotide linkages positioned at both ends to block exonuclease attack. Second generation AMOs improved potency through the use of chemical modifications that increase binding affinity to the target, such as locked nucleic acid (LNA) residues. However, this strategy can reduce specificity as high binding affinity compounds can bind to and suppress function of related sequences even if one or more mismatches are present. Further, unnatural modified nucleic acid residues can have toxic side effects. In the present study, a variety of non-nucleotide modifiers were screened for utility in steric blocking antisense applications. A novel compound, N,N-diethyl-4-(4-nitronaphthalen-1-ylazo)-phenylamine ("ZEN"), was discovered that increased binding affinity and blocked exonuclease degradation when placed at or near each end of a single-stranded oligonucleotide. This new modification was combined with the 2'OMe RNA backbone to make ZEN-AMOs. The new ZEN-AMOs have high potency and can effectively inhibit miRNA function in vitro at low nanomolar concentrations, show high specificity, and have low toxicity in cell culture.Molecular Therapy-Nucleic Acids (2013) 2, e117; doi:10.1038/mtna.2013.46; published online 27 August 2013.
Project description:Tissue ischemia, such as transient myocardial ischemia, leads to release of cellular RNA including microRNA(miRNA) into the circulation and extracellular (ex-) space, but the biological function of the ex-RNA is poorly understood. We recently reported that cardiac RNA of both human and rodent origins induced cytokine production and immune cell activation. However, the identity of the ex-RNA responsible for the proinflammatory effect remains unclear. In the current study, using an miRNA array, we profiled the plasma miRNAs 4 h after transient myocardial ischemia (45 min) or sham procedure. Among 38 plasma miRNAs that were elevated following ischemia, eight were tested for their ability to induce cytokine response in macrophages and cardiomyocytes. We found that six miRNA mimics (miR-34a, -122, -133a, -142, -146a, and -208a) induced cytokine production in a dose-dependent manner. The effects of miRNAs (miR-133a, -146a, and -208a) were diminished by uridine?adenosine mutation and by RNase pretreatment. The miRNA-induced cytokine (MIP-2, TNF-?, and IL-6) production was abolished in cells deficient of TLR7 or MyD88, or by a TLR7 antagonist, but remained the same in TLR3- or Trif-deficient cells. In vivo, mice i.p. injected with miR-133a or miR-146a had marked peritoneal neutrophil and monocyte migration, which was significantly attenuated in TLR7-/- mice. Moreover, locked nucleic acid anti-miRNA inhibitors of these six miRNAs markedly reduced cardiac RNA-induced cytokine production. Taken together, these data demonstrate that ex-miRNA mimics (miR-34a, -122, -133a, -142, -146a, and -208a) are potent innate immune activators and that the miRNAs most likely induce cytokine production and leukocyte migration through TLR7 signaling.
Project description:Intracellular microRNAs (miRNAs) are key regulators of gene expression. The role of extracellular miRNAs in neuronal activation and sensory behaviors are unknown. Here we report an unconventional role of extracellular miRNAs for rapid excitation of nociceptor neurons via toll-like receptor-7 (TLR7) and its coupling to TRPA1 ion channel. miRNA-let-7b induces rapid inward currents and action potentials in dorsal root ganglion (DRG) neurons. These responses require the GUUGUGU motif, only occur in neurons coexpressing TLR7 and TRPA1, and are abolished in mice lacking Tlr7 or Trpa1. Furthermore, let-7b induces TLR7/TRPA1-dependent single-channel activities in DRG neurons and HEK293 cells overexpressing TLR7/TRPA1. Intraplantar injection of let-7b elicits rapid spontaneous pain via TLR7 and TRPA1. Finally, let-7b can be released from DRG neurons by neuronal activation, and let-7b inhibitor reduces formalin-induced TRPA1 currents and spontaneous pain. Thus, secreted extracellular miRNAs may serve as novel pain mediators via activating TLR7/TRPA1 in nociceptor neurons.
Project description:Anti-miRNA antisense inhibitors (AMOs) have demonstrated their utility in miRNA research and potential in miRNA therapy. Here we report a modified AMO approach in which multiple antisense units are engineered into a single unit that is able to simultaneously silence multiple-target miRNAs, the multiple-target AMO or MTg-AMO. We validated the technique with two separate MTg-AMOs: anti-miR-21/anti-miR-155/anti-miR-17-5p and anti-miR-1/anti-miR-133. We first verified the ability of the MTg-AMOs to antagonize the repressive actions of their target miRNAs using luciferase reporter activity assays and to specifically knock down the levels of their target miRNAs using real-time RT-PCR methods. We then used the MTg-AMO approach to identify several tumor suppressors-TGFBI, APC and BCL2L11 as the target genes for oncogenic miR-21, miR-155 and miR-17-5p, respectively, and two cardiac ion channel genes HCN2 (encoding a subunit of cardiac pacemaker channel) and CACNA1C (encoding the alpha-subunit of cardiac L-type Ca(2+) channel) for the muscle-specific miR-1 and miR-133. We further demonstrated that the MTg-AMO targeting miR-21, miR-155 and miR-17-5p produced a greater inhibitory effect on cancer cell growth, compared with the regular single-target AMOs. Moreover, while using the regular single-target AMOs excluded HCN2 as a target gene for either miR-1 or miR-133, the MTg-AMO approach is able to reveal HCN2 as the target for both miR-1 and miR-133. Our findings suggest the MTg-AMO as an improved approach for miRNA target finding and for studying function of miRNAs. This approach may find its broad application for exploring biological processes involving multiple miRNAs and multiple genes.
Project description:RNA-specific adenosine deaminase (ADAR)-mediated adenosine-to-inosine (A-to-I) editing is a critical arm of the antiviral response. However, mechanistic insights into how A-to-I RNA editing affects viral infection are lacking. We posited that inosine incorporation into RNA facilitates sensing of nonself RNA by innate immune sensors and accordingly investigated the impact of inosine-modified RNA on Toll-like receptor 7 and 8 (TLR7/8) sensing. Inosine incorporation into synthetic single-stranded RNA (ssRNA) potentiated tumor necrosis factor alpha (TNF-?) or alpha interferon (IFN-?) production in human peripheral blood mononuclear cells (PBMCs) in a sequence-dependent manner, indicative of TLR7/8 recruitment. The effect of inosine incorporation on TLR7/8 sensing was restricted to immunostimulatory ssRNAs and was not seen with inosine-containing short double-stranded RNAs or with a deoxy-inosine-modified ssRNA. Inosine-mediated increase of self-secondary structure of an ssRNA resulted in potentiated IFN-? production in human PBMCs through TLR7 recruitment, as established through the use of a TLR7 antagonist and Tlr7-deficient cells. There was a correlation between hyperediting of influenza A viral ssRNA and its ability to stimulate TNF-?, independent of 5'-triphosphate residues, and involving Adar-1. Furthermore, A-to-I editing of viral ssRNA directly enhanced mouse Tlr7 sensing, when present in proportions reproducing biologically relevant levels of RNA editing. Thus, we demonstrate for the first time that inosine incorporation into immunostimulatory ssRNA can potentiate TLR7/8 activation. Our results suggest a novel function of A-to-I RNA editing, which is to facilitate TLR7/8 sensing of phagocytosed viral RNA.
Project description:Osteoarthritis (OA) is the most prevalent joint disorder associated with severe chronic pain. Although synovial inflammation is well correlated with pain severity, the molecular mechanism responsible for OA pain remains unclear. Here, we show that extracellular miR-21 released from synovial tissue mediates knee OA pain in surgical OA model rats. miR-21 was the most abundant among increased microRNAs (miRNAs) in the synovial tissue. miR-21 was released into extracellular space from the synovial tissue and increased in the synovial fluid. A single intra-articular injection of miR-21 inhibitor exerted long-term analgesia of knee OA pain, whereas miR-21 injection in naive rats caused knee joint pain. miR-21 mutant, which lacks the Toll-like receptor (TLR) binding motif, but not in the seed sequence, did not cause joint pain, suggesting a non-canonical mode of action different from translational repression. Consistent with this, the algesic effect of miR-21 was blocked by antagonizing TLR7. The TLR7 antagonist also exerted a long-lasting analgesic effect on knee OA pain. Therefore, extracellular miR-21 released from synovial tissue mediates knee OA pain through TLR7 activation in surgical OA model rats. Extracellular miRNA in the joint may be a plausible target for pain therapy, providing a novel analgesic strategy for OA.
Project description:: Muscle wasting is a feature of the cachexia syndrome, which contributes significantly to the mortality of patients with cancer. We have previously demonstrated that miR-21 is secreted through extracellular vesicles (EV) by lung and pancreatic cancer cells and promotes JNK-dependent cell death through its binding to the TLR7 receptor in murine myoblasts. Here, we evaluate the ability of IMO-8503, a TLR7, 8, and 9 antagonist, to inhibit cancer-induced cachexia. Using EVs isolated from lung and pancreatic cancer cells and from patient plasma samples, we demonstrate that IMO-8503 inhibits cell death induced by circulating miRNAs with no significant toxicity. Intraperitoneal administration of the antagonist in a murine model for Lewis lung carcinoma (LLC-induced cachexia) strongly impaired several cachexia-related features, such as the expression of Pax7 as well as caspase-3 and PARP cleavage in skeletal muscles, and significantly prevented the loss of lean mass in tumor-bearing mice. IMO-8503 also impaired circulating miRNA-induced cell death in human primary myoblasts. Taken together, our findings strongly indicate that IMO-8503 serves as a potential therapy for the treatment of cancer cachexia. SIGNIFICANCE: Cancer-associated cachexia is a significant problem for patients with cancer that remain poorly understood, understudied, and inadequately treated; these findings report a potential new therapeutic for the treatment of TLR7-mediated cancer cachexia.
Project description:MicroRNA (miRNA)-guided argonaute (Ago) controls gene expression upon binding to the 3' UTR of mRNA. The miRNA function can be competitively inhibited by single-stranded anti-miRNA oligonucleotides (AMOs). In this study, we constructed a novel type of AMO flanked by interstrand cross-linked 2'-O-methylated RNA duplexes (CLs) that confer a stable helical conformation. Compared with other structured AMOs, AMO flanked by CLs at the 5' and 3' termini exhibited much higher inhibitory activity in cells. Anti-miRNA activity, nuclease resistance, and miRNA modification pattern distinctly differed according to the CL-connected positions in AMOs. Moreover, we found that the 3'-side CL improves nuclease resistance, whereas the 5'-side CL contributes to stable binding with miRNA in Ago upon interaction with the 3' part of miRNA. These structure-function relationship analyses of AMOs provide important insights into the function control of Ago-miRNA complexes, which will be useful for basic miRNA research as well as for determining therapeutic applications of AMO.
Project description:Desmoplastic and hypoxic pancreatic cancer microenvironment induces aberrant expression of miRNAs and hypoxia-inducible factor-1? (HIF-1?) responsible for gemcitabine (GEM) resistance. We demonstrated that miR-519c was down-regulated in pancreatic cancer and transfection of miR-519c in GEM-resistant pancreatic cancer cells inhibited HIF-1? level under hypoxia. We synthesized redox-sensitive mPEG-co-P(Asp)-g-DC-g-S-S-GEM polymer, with GEM payload of 14% (w/w) and 90% GEM release upon incubation with l-glutathione. We synthesized mPEG-co-P(Asp)-g-TEPA-g-DC for complex formation with miRNA. Chemical modification of miR-519c with 2'-O-methyl phosphorothioate (OMe-PS) at 3' end enhanced its stability and activity without being immunogenic. Epidermal growth factor receptor targeting peptide GE11 decoration increased tumor accumulation of micelles after systemic administration and significantly inhibited orthotopic desmoplastic pancreatic cancer growth in NSG mice by down-regulating HIF-1? and genes responsible for glucose uptake and cancer cell metabolism. Our multifunctional nanomedicine of GEM and OMe-PS-miR-519c offers a novel therapeutic strategy to treat desmoplasia and hypoxia-induced chemoresistance in pancreatic cancer.