Zinc signals in neutrophil granulocytes are required for the formation of neutrophil extracellular traps

Abstract

Zinc signals, i.e. changes in the free intracellular Zn(2+)concentration, are an integral component of signal transduction in several immune cells. The aim of the present study was to investigate if this is also the case in neutrophil granulocytes. One neutrophil function is NETosis, the release of a matrix composed of DNA, chromatin and granule proteins to capture extracellular bacteria within so-called neutrophil extracellular traps (NET). NETosis can be induced by the protein kinase C (PKC) activator 12-myristate 13-acetate (PMA). PMA treatment led to a zinc signal in neutrophil granulocytes. NETosis was inhibited when the zinc signal was sequestered by the membrane permeable high affinity chelator N,N,N',N',-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN). PKC-mediated NET formation depends on the production of reactive oxygen species (ROS) by NADPH oxidase. Inhibition of NADPH oxidase with diphenyleneiodonium chloride blocked ROS formation and NETosis, as well as the zinc signal. TPEN, however, had no effect on PKC activity and ROS production, indicating that Zn(2+) is not required for activation of PKC, but for signals downstream of ROS production. In conclusion, zinc signals are an essential component of the ROS-dependent signal transduction leading to NETosis.

Ion Channels in Innate and Adaptive Immunity

“…For example, Zn 2+ supplementation enhances phagocytosis of Escherichia coli and S. aureus by peritoneal macrophages and killing of Trypanosoma cruzi (325, 326). Zn 2+ deficiency results in reduced neutrophil and macrophage chemotaxis, phagocytosis, production of ROS, and netosis by neutrophils (327). Zn 2+ is also important for the production of proinflammatory cytokines by macrophages (328, 329) and for the recognition and killing of target cells by NK cells.…”

Intracellular zinc in insulin secretion and action: a determinant of diabetes risk?

“…In some cell types, levels of free Zn 2+ increase in response to stimuli (9) , to 1 nM or above (10,11) ; at the site of release from intracellular stores, free zinc concentrations might be higher. However, with some exceptions (12,13) , changes in cytosolic zinc are slower and smaller than those seen e.g. for calcium ions where a signalling role is very clearly defined (14) .…”

Immunological orchestration of zinc homeostasis: The battle between host mechanisms and pathogen defenses

“…Activation of neutrophils with the protein kinase C activator, phorbol 12-myristate 13-acetate results in an ROS-dependent increase in intracellular Zn that is required for NET formation. Chelation of Zn with a membrane permeable Zn chelator blocks NETosis without impacting ROS production, suggesting a role for Zn downstream of NADPH oxidase function in neutrophils [70]. This finding appears contrary to the idea that calprotectin mediated sequestration of Zn potentially augments NADPH oxidase activity.…”

“…This finding appears contrary to the idea that calprotectin mediated sequestration of Zn potentially augments NADPH oxidase activity. But, a rise in intracellular Zn may be required to support very early stages of NET formation, as chelation of the metal an hour post neutrophil activation fails to inhibit NETosis [70]. The duration for which neutrophils experience an intracellular elevation in free Zn is unknown, but it can be proposed this pool is eventually sequestered to sustain ROS production by NADPH oxidase.…”