J Infect Dis. 2016 Mar 16. pii: jiw109. [Epub ahead of print]

microRNAs constitute a negative feedback loop in Streptococcus pneumoniae induced macrophage activation.

Griss K1, Bertrams W2, Sittka-Stark A2, Seidel K2, Stielow C2, Hippenstiel S3, Suttorp N3, Eberhardt M4, Wilhelm J5, Vera J4, Schmeck B6.

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Streptococcus pneumoniae causes high mortality as a major pneumonia-inducing pathogen. In pneumonia, control of innate immunity is necessary to prevent organ damage. We assessed the role of microRNAs as regulators in pneumococcus infection of human macrophages.Exposure of primary blood-derived human macrophages with pneumococci resulted in transcriptional changes in several gene clusters and a significant deregulation of 10 microRNAs. Computational network analysis retrieved miRNA-146a as one putatively important regulator of pneumococci-induced host cell activation. Its induction partly depended on bacterial viability and was completely inhibited by blocking toll-like receptor 2 (TLR-2) or depleting its mediator MyD88. Furthermore, miRNA-146a induction did not require the autocrine feedback of IL-1β and TNF-α released from infected macrophages, and repressed the TLR-2 downstream mediators IRAK-1 and TRAF-6 as well as the inflammatory factors cyclooxygenase 2 and IL-1β. In summary, pneumococci recognition induces a negative feedback loop, preventing excessive inflammation via miR-146a and potentially other miRNAs.

© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

PMID: 26984146 [PubMed - as supplied by publisher]