Magnesium deficiency promotes secretion of high-mobility group box 1 protein from lipopolysaccharide-activated macrophages in vitro

Background: High-mobility group box 1 (HMGB1) is a critical mediator of sepsis that is closely related to sepsis lethality. Magnesium deficiency predisposes to worse outcomes from endotoxin challenge by promoting the production of cytokines. However, whether magnesium deficiency affects the expression and release of HMGB1 is not currently known. In the present study, we explored the effect of magnesium deficiency on the expression and secretion of HMGB1 in lipopolysaccharide (LPS)-activated RAW264.7 macrophages. Methods: RAW264.7 cells were incubated with LPS in normal magnesium (1 mmol/L magnesium sulfate) or low magnesium (0.1 mmol/L magnesium sulfate) in Roswell Park Memorial Institute 1640 medium. An enzyme-linked immunosorbent assay was used to detect HMGB1 levels in the culture supernatant. Real-time polymerase chain reaction was used to assess the HMGB1 mRNA levels. A nuclear/cytoplasm extraction kit was used to extract the nuclear and cytoplasmic proteins. Western blotting was used to observe the changes in translocation of HMGB1 from the nucleus to the cytoplasm. A nuclear factor kappa-light chain enhancer of activated B cells (NF-kappa B) p50/p65 transcription factor assay kit was used to analyze the NF-kappa B activity in nuclear extracts. Results: Magnesium deficiency promoted translocation of HMGB1 from the nucleus to the cytoplasm and its extracellular secretion in LPS-activated macrophages, while enhancing the expression of HMGB1 mRNA. Furthermore, magnesium deficiency promoted the translocation of NF-kappa B from the cytoplasm to the nucleus in LPS-activated macrophages. Conclusions: Magnesium deficiency promotes the translocation of HMGB1 from the nucleus to the cytoplasm and the expression of HMGB1 mRNA. Magnesium deficiency also activates the NF-kappa B signaling pathway. Crown Copyright (C) 2013 Published by Elsevier Inc. All rights reserved.