Zinc Modulates Endotoxin-Induced Human Macrophage Inflammation through ZIP8 Induction and C/EBPβ Inhibition.

Charlie J Pyle,Claire E Dodd,Saife Akhter,Shengying Bao,Daren L Knoell,Larry S Schlesinger,Roland Lang

doi:10.1371/journal.pone.0169531

Abstract

Two vital functions of the innate immune system are to initiate inflammation and redistribute micronutrients in favor of the host. Zinc is an essential micronutrient used in host defense. The zinc importer ZIP8 is uniquely induced through stimulation of the NF-κB pathway by LPS in monocytes and functions to regulate inflammation in a zinc-dependent manner. Herein we determined the impact of zinc metabolism following LPS-induced inflammation in human macrophages. We observed that ZIP8 is constitutively expressed in resting macrophages and strikingly elevated following LPS exposure, a response that is unique compared to the 13 other known zinc import proteins. During LPS exposure, extracellular zinc concentrations within the physiological range markedly reduced IL-10 mRNA expression and protein release but increased mRNA expression of TNFα, IL-8, and IL-6. ZIP8 knockdown inhibited LPS-driven cellular accumulation of zinc and prevented zinc-dependent reduction of IL-10 release. Further, zinc supplementation reduced nuclear localization and activity of C/EBPβ, a transcription factor known to drive IL-10 expression. These studies demonstrate for the first time that zinc regulates LPS-mediated immune activation of human macrophages in a ZIP8-dependent manner, reducing IL-10. Based on these findings we predict that macrophage zinc metabolism is important in host defense against pathogens.

Highlights

Micronutrient metabolism plays a critical role in innate immune defense against microbial infection
We hypothesized that zinc transporter SLC39A8 (ZIP8)-mediated transport of extracellular zinc into human macrophages has the capacity to modulate the balance of pro- and anti-inflammatory cytokines produced in response to LPS
We first examined the capacity of LPS to influence the expression of all ZIPs (1–14) in human macrophages via mRNA expression in monocyte-derived macrophages (MDMs) cultured in RPMI containing 10% autologous serum from individual donors by qRT-PCR

Summary

Introduction

Micronutrient metabolism plays a critical role in innate immune defense against microbial infection. We hypothesized that ZIP8-mediated transport of extracellular zinc into human macrophages has the capacity to modulate the balance of pro- and anti-inflammatory cytokines produced in response to LPS. ZIP8-mediated zinc uptake within hours of LPS stimulation resulted in reduced IL-10 production and an increase in the pro-inflammatory cytokine response.

Results

Conclusion