Magnesium Deficiency Causes Loss of Response to Intermittent Hypoxia in Paraganglion Cells

Satoru Torii,Kentaro Kobayashi,Masayuki Takahashi,Kasumi Katahira,Kenji Goryo,Natsuki Matsushita,Ken-Ichi Yasumoto,Yoshiaki Fujii-Kuriyama,Kazuhiro Sogawa

doi:10.1074/jbc.m109.004424

Abstract

Magnesium deficiency is suggested to contribute to many age-related diseases. Hypoxia-inducible factor 1alpha (HIF-1alpha) is known to be a master regulator of hypoxic response. Here we show that hypomagnesemia suppresses reactive oxygen species (ROS)-induced HIF-1alpha activity in paraganglion cells of the adrenal medulla and carotid body. In PC12 cells cultured in the low magnesium medium and treated with cobalt chloride (CoCl(2)) or exposed to intermittent hypoxia, ROS-mediated HIF-1alpha activity was suppressed. This suppression was due to up-regulation of inhibitory PAS (Per/Arnt/Sim) domain protein (IPAS) that was caused by NF-kappaB activation, which resulted from ROS and calcium influx mainly through the T-type calcium channels. Induction of tyrosine hydroxylase, a target of HIF-1, by CoCl(2) injection was suppressed in the adrenal medulla of magnesium-deficient mice because of up-regulation of IPAS. Also in the carotid body of magnesium-deficient mice, CoCl(2) and chronic intermittent hypoxia failed to enhance the tyrosine hydroxylase expression. These results demonstrate that serum magnesium levels are a key determinant for ROS-induced hypoxic responses.

Highlights

Hypoxia-inducible factor 1␣ (HIF-1␣)2 and its family members are master regulators of hypoxic response [1,2,3]
Previous studies have shown that HIF-1␣ in normoxia is hydroxylated by prolyl hydroxylases in an O2 and Fe2ϩ-dependent manner and recognized by pVHL, leading to degradation
It is generally accepted that prolyl hydroxylase activity is inhibited by sustained hypoxia and by Co2ϩ that can substitute active-site Fe2ϩ [22]

Summary

EXPERIMENTAL PROCEDURES

Cell Culture, DNA Transfection, and IH Treatment—PC12, Hep3B, C6, and B16-f10 cells were obtained from the Cell Resource Center for Biomedical Research of Tohoku University. PC12 cells were maintained in RPMI 1640 (Wako Pure Chemical Industries) supplemented with 10% fetal bovine serum in collagen IV-coated dishes (BD Biosciences) under 5% CO2 at 37 °C and transferred every 3 days. Transfection was performed using the lipofection reagent (TransFast; Promega)

Magnesium Deficiency Causes Loss of Response to Hypoxia

RESULTS

DISCUSSION