Interleukin-1β contributes via nitric oxide to the upregulation and functional activity of the zinc transporter Zip14 (Slc39a14) in murine hepatocytes

Abstract

Zinc metabolism during chronic disease is dysregulated by inflammatory cytokines. Experiments with IL-6 knockout mice show that LPS regulates expression of the zinc transporter, Zip14, by a mechanism that is partially independent of IL-6. The LPS-induced model of sepsis may occur by a mechanism signaled by nitric oxide (NO) as a secondary messenger. To address the hypothesis that NO can modulate Zip14 expression, we treated primary hepatocytes from wild-type mice with the NO donor S-nitroso N-acetyl penicillamine (SNAP). After treatment with SNAP, steady-state Zip14 mRNA levels displayed a maximal increase after 8 h and a concomitant increase in the transcriptional activity of the gene. Chromatin immunoprecipitation documented the kinetics of activator protein (AP)-1 and RNA polymerase II association with the Zip14 promoter after NO exposure, indicating a role of AP-1 in transcription of Zip14. We then stimulated the primary murine hepatocytes with IL-1β, an LPS-induced proinflammatory cytokine and a potent activator of inducible NO synthase (iNOS) and NO production. In support of our hypothesis, IL-1β treatment led to a threefold increase in Zip14 mRNA and enhanced zinc transport, as measured with a zinc fluorophore, in wild-type but not iNOS−/−hepatocytes. These data suggest that signaling pathways activated by NO are factors in the upregulation of Zip14, which in turn mediates hepatic zinc accumulation and hypozincemia during inflammation and sepsis.