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Clinical application of siRNA-based therapeutics outside of the liver has been hindered by the inefficient delivery of siRNA effector molecules into extra-hepatic organs and cells of interest. To understand the parameters that enable RNAi activity in vivo, it is necessary to develop a systematic approach to identify which cells within a tissue are permissive to oligonucleotide internalization and activity. In the present study, we evaluate the distribution and activity within the lung of chemically stabilized siRNA to characterize cell-type tropism and structure-activity relationship. We demonstrate intratracheal delivery of fully modified siRNA for RNAi-mediated target knockdown in lung CD11c + cells (dendritic cells, alveolar macrophages) and alveolar epithelial cells. Finally, we use an allergen-induced model of lung inflammation to demonstrate the capacity of inhaled siRNA to induce target knockdown in dendritic cells and ameliorate lung pathology., (Copyright © 2019 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.)

In the intestinal epithelium, activation of phosphatidylinositol 3-kinase (PI3-kinase)/AKT pathways, via growth factor-mediated signaling, has been shown to regulate cell proliferation and inhibit apoptosis. An immune-activated receptor critical for Th2 immune responses, IL-4Ralpha can also activate PI3-kinase via insulin receptor substrate (IRS)-dependent signaling. Here, using the intestinal goblet cell-specific gene RELMbeta, we investigated the effect of PI3-kinase activation via Th2 immune responses on the goblet cell phenotype. IL-13 stimulation activated PI3-kinase and AKT signal transduction in LS174T cells. Not only did pharmacological inhibition of PI3-kinase and AKT1/2 inhibit RELMbeta induction by IL-13, but AKT inhibition also significantly reduced constitutive basal expression of RELMbeta, a response reproduced by the simultaneous pharmacological inhibition of both epidermal growth factor receptor and IGF-I receptor signaling. In vivo, the disruption of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), an inhibitor of PI3-kinase activation, led to the activation of RELMbeta expression in the small intestine. Furthermore, induction of an intestinal Th2 immune response by infection with a small intestinal nematode parasite, Heligmosomoides polygyrus, led to enhanced epithelial cell proliferation, activation of AKT as demonstrated by the loss of Foxo1 nuclear localization, and robust induction of RELMbeta expression in wild-type, but not IL-4Ralpha knockout, mice. These results demonstrate that Th2 immune responses can regulate goblet cell responses by activation of PI3-kinase and AKT pathways via IL-4Ralpha.