Session Type: Poster Session (Sunday)
Session Time: 9:00AM-11:00AM
Background/Purpose: Fos-like 2 (Fosl-2) is a transcription factor belonging to the Fos family of proteins which is part of the AP-1 transcription complex. The Fosl-2 transgenic (tg) mouse model has been shown to develop a similar phenotype to patients with SSc, such as vascular changes, dysregulation of innate and adaptive immunity, and fibrosis of the skin and visceral organs. Although the etiology is yet to be found, various studies have indicated immune cells, such as macrophages, to be important contributors to the pathogenesis of SSc. In this study, we aimed to determine the role of Fosl-2 expression in macrophages.
Methods: Bone marrow from Fosl-2 tg and wild type (wt) mice was isolated and differentiated into macrophages by stimulation with recombinant mouse macrophage colony stimulating factor (M-CSF) (20 ng/ml) for 7 days. The bone marrow-derived macrophages (BMDM) were stimulated with LPS (10 ng/ml) or IL-4 (10 ng/ml) for various time points. Expression of Fosl-2 and cJun was checked by Western blot. Levels of inflammatory cytokines IFN-g (wt n=12, tg n=15), TNF-α (wt n=9, tg n=11), IL-1β (wt n=8, tg n=9), IL-6 (n=7), and anti-inflammatory markers MRC1 (wt n=9, tg n=11) and CCL22 (n=8) were determined by qPCR and ELISA. To assess the production of nitric oxide, BMDM were stimulated with LPS (10 ng/ml) (n=17) or LPS + IFN-g (10 ng/ml) (n=9) and a Griess assay was performed. An arginase assay was conducted to evaluate urea concentration post stimulation (wt n=7, tg n=3).
Results: We observed induction of Fosl-2 after LPS and IL-4 stimulation in wt and Fosl-2 tg BMDM, with the peak of expression at 4 to 6 hours in wt mice. Tg mice show a higher induction of Fosl-2 after LPS stimulation than wt mice. After LPS stimulation, Fosl-2 tg BMDM showed a decreased mRNA expression of IFN-g (p< 0.0001), TNF-α (p=0.0036), as well as a tendency towards decreased expression of IL-1β. Protein levels of IL-6 and TNF-α appeared to peak around 6h post LPS stimulation and were decreased in tg BMDM compared to wt BMDM (p=0.0044 and p=0.02555). Fosl-2 tg BMDM were characterized by lower concentrations of NO after LPS stimulation (p=0.0061) and further decreased after co-stimulation with IFN-g (p=0.0118), in comparison to wt mice. After stimulation with IL-4, when comparing wt to tg BMDM, MRC1 (p=0.0007) was downregulated and CCL22 (p=0.0361) upregulated.
Conclusion: Our data indicates the involvement of Fosl-2 in the regulation of the inflammatory response of macrophages. Decreased levels of inflammatory cytokines suggest a possible alternative activating phenotype-promoting role of Fosl-2. Alternative activation of macrophages induces fibrosis, thus bringing Fosl-2 and macrophages into the spotlight regarding the development of fibrosis in SSc.
To cite this abstract in AMA style:Rufer C, Rudnik M, Uhtjärv S, Stellato M, Renoux F, Distler O, Kania G. Altered Inflammatory Response of Macrophages in the Fosl-2 Transgenic Mouse Model of Systemic Sclerosis [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/altered-inflammatory-response-of-macrophages-in-the-fosl-2-transgenic-mouse-model-of-systemic-sclerosis/. Accessed October 22, 2020.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/altered-inflammatory-response-of-macrophages-in-the-fosl-2-transgenic-mouse-model-of-systemic-sclerosis/