Hypoxia induces an increase in intracellular magnesium via transient receptor potential melastatin 7 (TRPM7) channels in rat hippocampal neurons in vitro

J Biol Chem. 2011 Jun 10;286(23):20194-207. doi: 10.1074/jbc.M110.148494. Epub 2011 Apr 12.

Abstract

TRPM7, a divalent cation channel, plays an important role in neurons damaged from cerebral ischemia due to permitting intracellular calcium overload. This study aimed to explore whether magnesium was transported via a TRPM7 channel into the intracellular space of rat hippocampal neurons after 1 h of oxygen-glucose deprivation (OGD) and acute chemical ischemia (CI) by using methods of the Mg(2+) fluorescent probe Mag-Fura-2 to detect intracellular magnesium concentration ([Mg(2+)](i)) and flame atomic absorption spectrometry to measure extracellular magnesium concentration ([Mg(2+)](o)). The results showed that the neuronal [Mg(2+)](i) was 1.51-fold higher after 1 h of OGD at a basal level, and the increase of neuronal [Mg(2+)](i) reached a peak after 1 h of OGD and was kept for 60 min with re-oxygenation. Meanwhile, the [Mg(2+)](o) decreased after 1 h of OGD and recovered to the pre-ischemic level within 15 min after re-oxygenation. In the case of CI, the [Mg(2+)](i) peak immediately appeared in hippocampal neurons. This increase of [Mg(2+)](i) declined by removing extracellular magnesium in OGD or CI. Furthermore, by using Gd(3+) or 2-aminoethoxydiphenyl borate to inhibit TRPM7 channels, the [Mg(2+)](i) increase, which was induced by OGD or CI, was attenuated without altering the basal level of [Mg(2+)](i). By silencing TRPM7 with shRNA in hippocampal neurons, it was found that not only was the increase of [Mg(2+)](i) induced by OGD or CI but also the basal levels of [Mg(2+)](i) were attenuated. In contrast, overexpression of TRPM7 in HEK293 cells exaggerated both the basal levels and increased [Mg(2+)](i) after 1 h of OGD/CI. These results suggest that anoxia induced the increase of [Mg(2+)](i) via TRPM7 channels in rat hippocampal neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Hypoxia / drug effects
  • Cell Hypoxia / physiology
  • Gene Silencing
  • Glucose / pharmacology
  • HEK293 Cells
  • Hippocampus / cytology
  • Hippocampus / metabolism*
  • Humans
  • Ion Transport / drug effects
  • Ion Transport / physiology
  • Magnesium / metabolism*
  • Neurons / cytology
  • Neurons / metabolism*
  • Protein-Serine-Threonine Kinases
  • Rats
  • Sweetening Agents
  • TRPM Cation Channels / biosynthesis*
  • TRPM Cation Channels / genetics

Substances

  • Sweetening Agents
  • TRPM Cation Channels
  • Protein-Serine-Threonine Kinases
  • TRPM7 protein, human
  • Trpm7 protein, rat
  • Magnesium
  • Glucose