Type I Interferon Supports Inducible Nitric Oxide Synthase in Murine Hepatoma Cells and Hepatocytes and during Experimental Acetaminophen-Induced Liver Damage.

Malte Bachmann,Heiko Mühl,Zoe Waibler,Thomas Pleli,Josef Pfeilschifter

doi:10.3389/fimmu.2017.00890

Malte Bachmann, Heiko Mühl + Show 3 more

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https://doi.org/10.3389/fimmu.2017.00890

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Abstract

Cytokine regulation of high-output nitric oxide (NO) derived from inducible NO synthase (iNOS) is critically involved in inflammation biology and host defense. Herein, we set out to characterize the role of type I interferon (IFN) as potential regulator of hepatic iNOS in vitro and in vivo. In this regard, we identified in murine Hepa1-6 hepatoma cells a potent synergism between pro-inflammatory interleukin-β/tumor necrosis factor-α and immunoregulatory IFNβ as detected by analysis of iNOS expression and nitrite release. Upregulation of iNOS by IFNβ coincided with enhanced binding of signal transducer and activator of transcription-1 to a regulatory region at the murine iNOS promoter known to support target gene expression in response to this signaling pathway. Synergistic iNOS induction under the influence of IFNβ was confirmed in alternate murine Hepa56.1D hepatoma cells and primary hepatocytes. To assess iNOS regulation by type I IFN in vivo, murine acetaminophen (APAP)-induced sterile liver inflammation was investigated. In this model of acute liver injury, excessive necroinflammation drives iNOS expression in diverse liver cell types, among others hepatocytes. Herein, we demonstrate impaired iNOS expression in type I IFN receptor-deficient mice which associated with diminished APAP-induced liver damage. Data presented indicate a vital role of type I IFN within the inflamed liver for fine-tuning pathological processes such as overt iNOS expression.

Highlights

High-output nitric oxide (NO) production achieved by inducible NO synthase is key to efficient innate host defense and involved in pathological inflammation at diverse organs including the liver [1,2,3,4]
The combination IL-1β plus TNFα was employed since pilot experiments in Hepa1-6 cells demonstrated that this combination synergizes for induction of the prototypic hepatocyte-derived nuclear factor (NF)-κB-dependent chemokine MIP2 [29]
Detailed analysis revealed that triplet stimulation by IL-1β/ TNFα/IFNβ is superior to that by either IL-1β/IFNβ or TNFα/ IFNβ (Figure 1D) and that potentiation of inducible NO synthase (iNOS) is likewise detectable in the context of IFNβ preincubation (Figure 1E)

Summary

Introduction

High-output nitric oxide (NO) production achieved by inducible NO synthase (iNOS) is key to efficient innate host defense and involved in pathological inflammation at diverse organs including the liver [1,2,3,4]. There, iNOS is detectable in several cell types including Kupffer cells and hepatocytes. Depending on the biochemical and cellular context STAT1 is able to support iNOS expression as STAT1 homodimer or as part of a protein complex together with STAT2 and IRF9 known as interferon (IFN)-stimulated gene factor (ISGF)-3 [1, 2, 6,7,8,9]. We set out to further characterize in vitro and in vivo the role of type I IFN for murine hepatic iNOS regulation by using the cellular model of IFNβ-stimulated hepatoma cells (Hepa, Hepa56.1D) and hepatocytes and by investigating murine acetaminophen (paracetamol, APAP)-induced sterile liver inflammation in the context type I IFN receptor-deficient mice

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