• Chorng-Kuang How, Sen-Kuang Hou, Hsin-Chin Shih, Mu-Shun Huang, Shih-Hwa Chiou, Chen-Hsen Lee, and Chi-Chang Juan.
• *Institute of Clinical Medicine, and †Department of Emergency Medicine, School of Medicine, National Yang-Ming University; ‡Emergency Department, Taipei Veterans General Hospital; §Institute of Environmental and Occupational Health Sciences, ∥Institute of Emergency and Critical Care Medicine, and ¶Institute of Pharmacy, School of Medicine, National Yang-Ming University; **Department of Medical Research, Taipei Veterans General Hospital; ††Institute of Physiology, School of Medicine, National Yang-Ming University; and ‡‡Department of Education and Research, Taipei City Hospital, Taipei, Taiwan.
• Shock. 2015 Feb 1; 43 (2): 121-7.

AbstractBacterial lipopolysaccharide (LPS) is an effective trigger of the inflammatory response during infection with gram-negative bacilli (GNB), which implicates the pathogenesis of sepsis and septic shock. MicroRNAs (miRNAs) are shown to have a significant role in the fine-tuning of toll-like receptor (TLR)-mediated inflammatory response. We profiled miRNA expression levels in peripheral leukocytes of GNB urosepsis patients and compared them with those of healthy controls. We further explored the regulatory mechanism of endotoxin-responsive miRNAs in TLR and cytokine signaling by using human monocytic cell line (THP-1 cells) treated with LPS antigen stimulation. The expression of two miRNAs, that is, let-7a (P < 0.001) and miR-150 (P < 0.001), were confirmed to be significantly downregulated in GNB urosepsis patients compared with healthy controls. The expression of let-7a is first to be identified as a biomarker of GNB sepsis. By using an in vitro model with the human monocytic cell line, we demonstrated that LPS stimulation downregulated the THP-1 cell expression of let-7a. The downregulation of let-7a is correlated with the induced expression of cytokine-inducible Src homology 2-containing protein without change in cytokine-inducible Src homology 2-containing protein mRNA levels in THP-1 cells via TLR signaling pathway activation. Moreover, gain of function by overexpression of let-7a revealed that let-7a significantly decreased tumor necrosis factor-α and interleukin-1β production in response to LPS. Reduced let-7a and miR-150 levels in peripheral leukocytes correlate with GNB urosepsis patients. Furthermore, let-7a is relevant to the regulation of TLR-mediated innate immune response.

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