Proinflammatory Role for let-7 MicroRNAS in Experimental Asthma

Abstract

MicroRNAs (miRNAs) are short, non-coding RNAs that target and silence protein coding genes through 3-UTR elements. Evidence increasingly assigns an immunosuppressive role for miRNAs in immunity, but relatively few miRNAs have been studied, and an overall understanding of the importance of these regulatory transcripts in complex in vivo systems is lacking.Here we have applied multiple technologies to globally analyze miRNA expression and function in allergic lung disease, an experimental model of asthma. Deep sequencing and microarray analyses of the mouse lung short RNAome revealed numerous extant and novel miRNAs and other transcript classes. Similar to mRNAs, lung miRNA expression changed dynamically during the transition from the naive to the allergic state, suggesting numerous functional relationships. A possible role for miRNA editing in altering the lung mRNA target repertoire was also identified. Multiple members of the highly conserved let-7 miRNA family were the most abundant lung miRNAs, and we confirmed in vitro that interleukin 13 (IL-13), a cytokine essential for expression for allergic lung disease, is regulated by mmulet-7a. However, inhibition of let-7 miRNAs in vivo using a locked nucleic acid profoundly inhibited production of allergic cytokines and the disease phenotype. Our findings thus reveal unexpected complexity in the miRNAome underlying allergic lung disease and demonstrate a proinflammatory role for let-7 miRNAs. MicroRNAs (miRNAs)3 are short regulatory RNAs with the potential to target and suppress multiple genes across diverse signaling pathways comprising biologically meaningful networks. Consequently, miRNAs that are inappropriately expressed in the context of specific diseases are of particular interest as therapeutic targets if they can be shown to coordinate such networks. Initially transcribed as relatively long primary transcripts, pri-miRNAs are subsequently modified by the nuclear RNAses Drosha and Pasha to yield precursor miRNAs (pre-miRNAs) that are further processed by the cytoplasmic RNase III Dicer to form short double-stranded miR-miR* duplexes, one strand of which (miR) is then integrated into the RNA-induced silencing complex that includes the enzymes Dicer and Argonaute (Ago). The mature miRNAs (ϳ17-24 nt) direct the RNA-induced silencing complex to specific target sites located within the 3Ј-UTR of target genes. Once bound to target sites, miRNAs repress translation through mRNA decay, translational inhibition, and/or sequestration into processing bodies (1-3).Recent estimates indicate that over 60% of protein-coding genes carry 3Ј-UTR miRNA target sites, suggesting a role for miRNAs in the control of gene expression in diverse processes (4). Indeed, miRNAs have now been firmly linked to the regulation of early development (5), cell proliferation, and cell death (6); apoptosis and fat metabolism (7); and cell differentiation (8). In addition, studies of miRNA expression in chronic lymphocytic leukemia (9), colonic adenocarcinoma (10), Burkitt lymphoma, and cardiac ...

MicroRNA-26a/-26b-COX-2-MIP-2 Loop Regulates Allergic Inflammation and Allergic Inflammation-promoted Enhanced Tumorigenic and Metastatic Potential of Cancer Cells

“…Cultures were maintained in 5% CO 2 at 37°C. Bone marrow-derived mouse mast cells were isolated and cultured according to standard procedures (24). B16F1 and B16F10 melanoma cells were cultured in Dulbecco's modified minimal essential medium (DMEM; Gibco) supplemented with heat-inactivated 10% fetal bovine serum (FBS; Gibco) and antibiotics at 37°C in a humidified incubator with a mixture of 95% air and 5% CO 2 .…”

“…The inhibition of miR-145 inhibits eosinophilic inflammation, mucus hypersecretion, T(H)2 cytokine production, and airway hyperresponsiveness (23). Let-7 miRNA mediates allergic lung disease by regulating the production of proinflammatory cytokines (24). Selective blockade of miR-126 suppresses the asthmatic phenotype, resulting in diminished T(H)2 responses, inflammation, airway hyperresponsiveness, eosinophil recruitment, and mucus hypersecretion (25).…”

Subtypes of Asthma Defined by Epithelial Cell Expression of Messenger RNA and MicroRNA

“…miR-375 was found to be down-regulated in IL-13 transgenic mice and repressed in human bronchial (and esophageal) epithelial cells by IL-13 (47). let-7 has a complicated but proinflammatory role in a murine model of asthma (48). Finally, broad-based miRNA profiling has been performed in murine models of acute and chronic asthma, identifying additional possible biomarkers (49).…”

Differential Expression of MicroRNAs in Chronic Obstructive Pulmonary Disease

“…miR-21 shows abnormal expression for vascular diseases in pulmonary [13]. It was revealed that miRNA-26 behaved as a regulatory factor in smooth muscle hypertrophy (enlargement) and let-7 miRNA increased the inflammatory related to asthma [14]. It is believed that miR-17-92 cluster (take part in 13q31.3) expressions of pulmonary to be high during embryonic development and low in adulthood, has a role in the regulation of pulmonary development [11,15].…”