Zinc-aggravated M1 microglia regulate astrocytic engulfment via P2×7 receptors

Tomoya Hamada; Takaaki Aratake; Youichirou Higashi; Yusuke Ueba; Takahiro Shimizu; Shogo Shimizu; Toshio Yawata; Tetsuya Ueba; Rina Nakamura; Toshifumi Akizawa; Mikiya Fujieda; Motoaki Saito

doi:10.1016/j.jtemb.2020.126518

Zinc-aggravated M1 microglia regulate astrocytic engulfment via P2×7 receptors

J Trace Elem Med Biol. 2020 Apr 11:61:126518. doi: 10.1016/j.jtemb.2020.126518. Online ahead of print.

Authors

Affiliations

¹ Department of Pediatrics, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan; Department of Pharmacology, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan.
² Department of Pharmacology, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan; Research Fellow of Japan Society for the Promotion of Science, Japan.
³ Department of Pharmacology, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan. Electronic address: higasi@kochi-u.ac.jp.
⁴ Department of Neurosurgery, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan.
⁵ Department of Pharmacology, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan.
⁶ Department of Pediatrics, Kochi Medical School, Kochi University, Kohasu, Okoh-cho, Nankoku 783-8505, Japan.

PMID: 32353820
DOI: 10.1016/j.jtemb.2020.126518

Abstract

Background: Glial cells such as astrocytes and microglia play an important role in the central nervous system via communication between these glial cells. Activated microglia can exhibit either the inflammatory M1 phenotype or the anti-inflammatory M2 phenotype, which influences astrocytic neuroprotective functions, including engulfment of cell debris. Recently, extracellular zinc has been shown to promote the inflammatory M1 phenotype in microglia through intracellular zinc accumulation and reactive oxygen species (ROS) generation.

Purpose: Here, we investigated whether the zinc-enhanced inflammatory M1 phenotype of microglia affects the astrocytic engulfing activity.

Methods: Engulfing activity was assessed in astrocytes treated with microglial-conditioned medium (MCM) from lipopolysaccharide (LPS)-activated or from ZnCl₂-pretreated LPS-activated M1 microglia. The effect of zinc on microglia phenotype was also validated using the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and the ROS scavenger Trolox.

Results: Although treatment of astrocytes with LPS showed no significant effect on the engulfing activity, MCM from LPS-induced M1 microglia increased the beads uptake by astrocytes. This increased uptake activity was suppressed when MCM from LPS-induced M1 microglia pretreated with ZnCl₂ was applied to astrocytes, which was further abolished by the intracellular zinc chelator TPEN and the ROS scavenger Trolox. In addition, expression of P2×7 receptors (P2×7R) was increased in astrocytes treated with MCM derived from M1 microglia but not in the M1 microglia pretreated with ZnCl₂.

Conclusion: These findings suggest that zinc pre-treatment abolishes the ability of LPS-induced M1 microglia to increase the engulfing activity in astrocytes via alteration of astrocytic P2×7R.

Keywords: Astrocyte; Engulfing activity; Microglia; Zinc.