Short-term magnesium deficiency upregulates sphingomyelin synthase and p53 in cardiovascular tissues and cells: relevance to the de novo synthesis of ceramide

Abstract

The present study tested the hypotheses that 1) short-term dietary deficiency of magnesium (21 days) in rats would result in the upregulation of sphingomyelin synthase (SMS) and p53 in cardiac and vascular (aortic) smooth muscles, 2) low levels of Mg(2+) added to drinking water would either prevent or greatly reduce the upregulation of both SMS and p53, 3) exposure of primary cultured vascular smooth muscle cells (VSMCs) to low extracellular Mg(2+) concentration ([Mg(2)](o)) would lead to the de novo synthesis of ceramide, 4) inhibition of either SMS or p53 in primary culture VSMCs exposed to low [Mg(2+)](o) would lead to reductions in the levels of de novo ceramide synthesis, and 5) inhibition of sphingomyelin palmitoyl-CoA transferase (SPT) or ceramide synthase (CS) in primary cultured VSMCs exposed to low [Mg(2+)](o) would lead to a reduction in the levels of de novo ceramide synthesis. The data indicated that short-term magnesium deficiency (10% normal dietary intake) resulted in the upregulation of SMS and p53 in both ventricular and aortic smooth muscles; even very low levels of water-borne Mg(2+) (e.g., 15 mg·l(-1)·day(-1)) either prevented or ameliorated the upregulation in SMS and p53. Our experiments also showed that VSMCs exposed to low [Mg(2+)](o) resulted in the de novo synthesis of ceramide; the lower the [Mg(2+)](o), the greater the synthesis of ceramide. In addition, the data indicated that inhibition of either SMS, p53, SPT, or CS in VSMCs exposed to low [Mg(2+)](o) resulted in marked reductions in the de novo synthesis of ceramide.

Short-term magnesium deficiency upregulates ceramide synthase in cardiovascular tissues and cells: cross-talk among cytokines, Mg2+, NF-κB, and de novo ceramide

“…Control (600 ppm Mg) and MgD (60 ppm Mg) pellet diets were obtained from DYETS (AIN-93 G diets; Bethlehem, PA). All animals were given their respective diets for 21 days as previously described (14,16). MgD animals were allowed to drink triply distilled water (Mg 2ϩ Ͻ 10 Ϫ6 M) containing one of four different levels of Mg aspartate-HCl (0, 15, 40, or 100 mg/l Mg; Verla Pharm, Tutzing, Germany).…”

“…]o with or without 75 uM scyphostatin (SigmaAldrich) for 18 h. We extracted the lipids in the cells as we have detailed elsewhere (54,55). The ceramide was next converted into ceramide-1-[ 32 P]phosphate by Escherichia coli DAG kinase, and the lipids were separated on high-performance TLC plates as described elsewhere (16,58). After autoradiography, spots corresponding to ceramide-1-phosphate were carefully scraped into vials, and the radioactivity was counted in a scintillation counter (LS-6500; Beckman).…”

“…Very recently, using a short-term (21 days) rat model of dietary MgD, we noted decreased levels of serum SM, lipid peroxidation, and fragmentation of DNA coupled with generation of the tumor suppressor-transcription factor p53 in the left ventricular (LV) and right ventricular (RV) muscles as well as in atrial muscle and vascular smooth muscle (14,16). These alterations (including the change in serum SM) were highly correlated (P Ͻ 0.01) with the levels of serum ionized Mg levels (14,16,68).The de novo synthesis of SM is brought about via the action of serine palmitoyl-CoA transferase (SPT), 3-ketosphinganine Address for reprint requests and other correspondence: B. M. …”

“…Such paradigms, using variations in Mg 2ϩ , also cause membrane oxidation, truncation of membrane fatty acids, and the activation of apoptotic pathways (i.e., caspase-3, apoptotic protease activation factor-1, and release of mitochondrial cytochrome c) concomitant with the significant activation of neutral sphingomyelinase (N-SMase) and alterations in membrane sphingomyelin (SM), leading to the release of ceramides in cultured VSMCs (14 -16, 68). Very recently, using a short-term (21 days) rat model of dietary MgD, we noted decreased levels of serum SM, lipid peroxidation, and fragmentation of DNA coupled with generation of the tumor suppressor-transcription factor p53 in the left ventricular (LV) and right ventricular (RV) muscles as well as in atrial muscle and vascular smooth muscle (14,16). These alterations (including the change in serum SM) were highly correlated (P Ͻ 0.01) with the levels of serum ionized Mg levels (14,16,68).…”

“…We designed experiments with primary culture of VSMCs to determine whether upregulation of CS (and de novo synthesis of ceramide; e.g., Ref. 16) and activation of N-SMase and generation/release of ceramide (14 -16), induced by low [Mg 2ϩ ] o , are associated with activation of NF-B and release/generation of cytokines and/or chemokines in the vascular cells.…”