A mouse model of overexpression of human IL-6 by tissue-resident macrophages in the context of LPS-induced inflammation

Abstract

Chronic inflammation caused by overexpression of IL-6 underlies a number of pathological conditions Mouse models of systemic chronic inflammation with overexpression of human IL-6 (hIL-6) are in demand not only in the context of studying the molecular mechanisms of inflammation, but also in assessing the effectiveness of clinically approved or newly developed IL-6 inhibitors. One experimental approach in addressing such models in mice relies on the induction of systemic acute inflammation in response to lipopolysaccharide (LPS) administration. This work describes mice with tamoxifen-dependent overexpression of human IL-6 in CX3CR1+ myeloid cells in the context of systemic inflammation induced by LPS administration. Our study demonstrates that the highest expression of the transgene carrying IL6 was observed in the heart, while high production of this cytokine was detected in the blood serum. In response to LPS administration, the production of hIL-6 in the blood increased in transgenic mice, while the production of mIL-6 also increased and was comparable to that in wild-type mice. The consequences of high systemic production of hIL-6, which in our model originates from CX3CR1+ tissue-resident macrophages, were noticeable even in the organs in which these cells are not present. Thus, significant amounts of hIL-6 were detected in tissue lysates of the lungs of transgenic mice after LPS administration. Evaluation of the expression of genes encoding cytokines and markers of tissue remodeling upon injury using quantitative real-time PCR showed significant changes in their expression in the context of LPS-induced systemic inflammation. Thus, this work demonstrates the feasibility of using a mouse model with tamoxifen-dependent transgene activation in CX3CR1+ tissue-resident macrophages to study the effects of systemic overexpression of IL-6 and pharmacological blockade of this cytokine with clinically approved or newly developed inhibitors in the context of experimentally induced diseases.

Keywords

• preclinical models of inflammation
• cytokines
• fibrosis
• il-6