Gene silencing by double-stranded RNA, denoted RNA interference, represents a new paradigm for rational drug design1. However, the transformative therapeutic potential of short interfering RNA (siRNA) has been stymied by a key obstacle—safe delivery to specified target cells in vivo2. Macrophages are particularly attractive targets for RNA interference therapy because they promote pathogenic inflammatory responses in diseases such as rheumatoid arthritis, atherosclerosis, inflammatory bowel disease and diabetes3. Here we report the engineering of β1,3-d-glucan-encapsulated siRNA particles (GeRPs) as efficient oral delivery vehicles that potently silence genes in mouse macrophages in vitro and in vivo. Oral gavage of mice with GeRPs containing as little as 20 μg kg-1 siRNA directed against tumour necrosis factor α (Tnf-α) depleted its messenger RNA in macrophages recovered from the peritoneum, spleen, liver and lung, and lowered serum Tnf-α levels. Screening with GeRPs for inflammation genes revealed that the mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) is a previously unknown mediator of cytokine expression. Importantly, silencing Map4k4 in macrophages in vivo protected mice from lipopolysaccharide-induced lethality by inhibiting Tnf-α and interleukin-1β production. This technology defines a new strategy for oral delivery of siRNA to attenuate inflammatory responses in human disease.
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We appreciate critical reading of the manuscript and suggestions by C. Mello, V. Ambros, G. Hannon, S. Corvera and J. Sullivan. We thank P. Zamore for advice on methods. We also appreciate the technical help of P. Furcinitti, A. Burkhart and A. Goller. This work was supported by The University of Massachusetts Diabetes and Endocrinology Center (DK 32520), including its Genomics, Bioinformatics and Imaging Cores, the Diabetes Genome Anatomy Project (DK 60837), Commonwealth Medicine and NIH grant DK 30898.
Author Contributions G.R.O., M.A. and M.P.C. initially conceptualized the study. M.A., G.J.T., M.W., M.C. and S.M.N. performed experiments, and all authors participated in designing experiments, and analysing and interpreting data. M.A. and G.J.T. contributed equally to this work. G.R.O. and E.S. provided the β1,3-d-glucan-shell-encapsulated cationic materials and they with M.A. and G.J.T. developed the GeRP formulations used in these studies. M.A., G.R.O. and M.P.C. wrote the manuscript.
[Competing interests: After the completion of this work and submission of this manuscript, the authors’ institution licensed the reported technology to RXi Pharmaceutials, Inc. M.P.C. served as a member of the Scientific Advisory Board of RXi during the reported work and G.R.O. currently receives funding from the company through a sponsored research agreement to his institution. G.R.O. is also a consultant for Biotech Pharmacon ASA and Eden Research plc.]
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Aouadi, M., Tesz, G., Nicoloro, S. et al. Orally delivered siRNA targeting macrophage Map4k4 suppresses systemic inflammation. Nature 458, 1180–1184 (2009). https://doi.org/10.1038/nature07774
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