Low extracellular magnesium ions induce lipid peroxidation and activation of nuclear factor-kappa B in canine cerebral vascular smooth muscle: possible relation to traumatic brain injury and strokes

Abstract

The present study was designed to test the hypothesis that administration of low extracellular levels of magnesium ions ([Mg 2+] o) to primary cultured cerebral vascular smooth muscle cells will cause lipid peroxidation, degradation of IκB-α, and activation of nuclear transcription factor kappa B (NF-κB) in cultured cerebral vascular smooth muscle cells. Low [Mg 2+] o (0, 0.15, 0.3 and 0.48 mM) resulted in concentration-dependent rises in malondialdehyde (MDA) in as little as 3 h after exposure to low [Mg 2+] o, rising to levels 3–12×normal after 18–24 h; the lower the [Mg 2+] o, the higher the MDA level. Using electrophoretic mobility shift assays and specific antibodies, low [Mg 2+] o caused two DNA-binding proteins (p50, p65) to rise in nuclear extracts in a concentration-dependent manner. High [Mg 2+] o (i.e. 4.8 mM) downregulated p50 and p65. Using a rabbit antibody, IκB phosphorylation (and degradation) was stimulated by low [Mg 2+] o (in a concentration-dependent manner) and inhibited by a low concentration of the NF-κB inhibitor, pyrrolidine dithiocarbamate. These new biochemical and molecular data indicate that low [Mg 2+] o, in concentrations found in the blood of patients, after traumatic brain injury (TBI) and diverse types of strokes, can elicit rapid lipid peroxidation and activation of NF-κB in cerebral vascular smooth muscle cells. The present results, when viewed in light of other recently published data, suggest that low [Mg 2+] o-induced lipid peroxidation and activation of NF-κB play important roles in TBI and diverse types of strokes.