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is the primary initiator of pulmonary inflammation following liver injury in mice
1 Surgery, Washington University School of Medicine, st louis, Missouri, United States
2 Medicine, Vanderbilt University, Nashville, Tennessee, United States
3 Immunology, Washington University School of Medicine, St. Louis, Missouri, United States; Surgery, Washington University School of Medicine, st louis, Missouri, United States
* To whom correspondence should be addressed. E-mail: chapmanw{at}wudosis.wustl.edu.
Hepatic injury can lead to systemic and pulmonary inflammation through activation of NF-
B-dependent pathways and production of various pro-inflammatory cytokines. The exact mechanism remains unknown, although prior research suggests interleukin-1
(IL-1
) plays an integral role. Cultured murine alveolar macrophages were used to identify an optimized IL-1
-specific siRNA sequence, which then was encapsulated in liposomes and administered intraperitoneally to transgenic HLL mice (5 HIV-LTR-Luciferase). A 35% hepatic mass cryoablation in HLL and IL-1 receptor 1 knockout mice (IL1R1KO) was performed as a model for liver-induced pulmonary inflammation. IL-1
siRNA pretreatment effectively and significantly reduced circulating IL-1
levels at 4 hours post-hepatic injury. IL-6 also was suppressed in mice with impaired IL-1 signaling pathways. NF-
B activation in the non-injured liver of HLL reporter mice pretreated with IL-1
siRNA was found to be reduced compared to controls. Pulmonary NF-
B activity in this group also was diminished relative to controls. C-X-C chemokine levels in the lung remained significantly lower in IL-1-pathway-deficient mice. Similarly, lung myeloperoxidase content was unchanged from baseline at 24 hours post-liver injury in IL-1
siRNA treated animals, whereas all other control groups demonstrated marked pulmonary neutrophilic infiltration. In conclusion, liver injury-induced lung inflammation in this model is mediated predominantly by IL-1
. Knockdown of IL-1
expression prior to hepatic injury led to significant reductions in both cytokine production and NF-
B activation. This translated to reduced pulmonary neutrophil accumulation. Pretreatment with IL-1
siRNA may represent a novel intervention for preventing liver-mediated pulmonary inflammation.
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