Lipocalin 2 Upregulation Protects Hepatocytes from IL1-β-Induced Stress

Abstract

Background: Lipocalin 2 (LCN2), a protein primarily produced by hepatocytes, is highly upregulated under various conditions that induce cellular stress, such as intoxication, infection or inflammation. However, the precise biological functions and underlying mechanisms of LCN2 in hepatocytes remains unknown. Methods: Hepatocyte stress was successfully induced by treating Huh7 cells with interleukin-1β (IL-1β). Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α) and LCN2 levels were measured in IL-1β treated Huh7 cells and supernatant. Additionally, microarray analysis was conducted to identify genes differentially expressed in LCN2-silenced and control Huh7 cells. Results: TNF-α, IL-6 and LCN2 were significantly elevated in Huh7 cells after IL-1β) treatment. In LCN2-silenced Huh7 cells, expression of IL-6 and TNF-α was significantly increased when compared with the expression levels of control Huh7 cells. Furthermore, differentially expressed genes were observed between the LCN2-silenced and control cells. Microarray analysis indicated that LCN2 acted by influencing genes involved in protein metabolism, stress response, cell cycle and proliferation. Conclusions: Our results suggest that LCN2 upregulation protects hepatocytes from IL-1β-induced stress. Additionally, our microarray analysis of LCN2-silenced and control cells provides a better understanding of the mechanisms that may be influenced by LCN2 induction.

Inflammatory Cytokine TNFα Promotes the Long-Term Expansion of Primary Hepatocytes in 3D Culture

“…3D hepatocyte colonies derived in our culture media were morphologically distinct from liver organoids previously derived from BECs (Huch et al, 2013; 2015). In our hepatocyte colonies, polygonal cells were tightly packed in compact 3D structures, with larger colonies organized with pseudo-glandular rosettes with occasional lumen-like structures (Figure 2A, S2A).…”

“…Acute phase proteins are usually expressed during inflammation to promote clearance of pathogens, and to limit excessive inflammatory responses (Robinson et al, 2016). For instance, Lcn2 has been shown to exert protective effect against cytokine-induced stress during acute liver injury (Borkham-Kamphorst et al, 2013; Hu et al, 2015). Further, cytokines and chemokines ( Ccl20, Cxcl1, Cxcl5, Ccl2 ), many of which are induced by TNFα or interleukins, were highly expressed in culture but notably absent in primary hepatocytes (Figure 5B).…”

Interleukin-1β (IL-1β) transcriptionally activates hepcidin by inducing CCAAT enhancer-binding protein δ (C/EBPδ) expression in hepatocytes

“…A previous study revealed that IL-1␤ stimulates hepcidin expression by inducing BMP2 expression in Huh7 cells, a human liver-derived cell line (20). In addition, IL-1␤ up-regulated IL-6 expression in various cell lines, including Huh7 cells (21). Thus, it is possible that BMP2 and/or IL-6 are produced in response to IL-1␤ treatment in hepatocytes and that these molecules induce hepcidin expression in an autocrine manner.…”

Involvement of Interleukin 6 in Hepatitis B Viral Infection

“…In the human IL-6 gene 5′-flanking region, functional cis-regulatory elements consist of binding sites for NF-кB and nuclear factor IL6 (NF-IL6) [27]. Many factors such as IL-1 and tumor necrosis factor (TNF) can activate cis-regulatory elements, which results in the activation of the IL-6 promoter [25,28]. HBx enhances IL-6 gene transcription by increasing NF-кB and/or NF-IL6 DNA binding activity [26].…”