Differential Effects of Cyclosporin A and Tacrolimus on Magnesium Influx in Caco2 Cells

Abstract

PURPOSE: Hypomagnesemia with urinary magnesium (Mg) wasting is a well acknowledged side effect of cyclosporin A (CsA) and tacrolimus (FK506) treatments. TRPM6, TRPM7 and MagT1 are involved in the active transcellular Mg transport processes in intestine and kidney. Since Mg homeostasis is tightly controlled by the dynamic action of intestinal absorption of dietary Mg and renal excretion of Mg, we investigated whether CsA and FK506 in commercially available solutions for clinical use decrease the expression and the function of TRPM6, TRPM7 or MagT1 in the intestinal epithelial cell line Caco2. METHODS: Changes of intracellular free Mg concentrations were measured by Mag-fura-2 imaging in Mg-free medium after the addition of 1 mM MgCl2. TRPM6, TRPM7 and MagT1 were evidenced in cells by immunofluorescence. Proteins and mRNAs were quantified after 18 hours of treatment with CsA or FK506 by western-blot and real-time RT-PCR analyses, respectively. RESULTS: TRPM6 and MagT1 were evidenced on all cell membranes, TRPM7 only on the inner membranes. CsA was responsible for a profound decrease in Mg2+ influx in intestinal epithelial cells, which may result in a decrease of intestinal Mg absorption, whereas FK506 was responsible for a marked increase in Mg2+ influx. Neither CsA nor FK506 altered TRPM6, TRPM7 or MagT1 mRNA levels or MagT1 protein level. CONCLUSIONS: In Caco2 cells, Mg2+ influx was inhibited by CsA solutions whereas enhanced by FK506 solutions, without alteration of MagT1, TRPM6 and TRPM7 expression, leading to the conclusion that CsA and FK506 have opposite effects in the functional activity of the Mg transporters herein examined. In clinical use, FK506 should be preferred for patients at risk for hypomagnesemia.
 
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Trpm7

“…One known side effect of calcineurin inhibitors is hypomagnesemia. Cyclosporin A and FK506 (tacrolimus), important calcineurin inhibitors, affect Mg flux as assessed by MagFura measurements in the intestinal epithelial cell line CaCo (Gouadon et al 2012). While cyclosporin A counteracts Mg accumulation, FK506 increases Mg influx without altering expression levels of TRPM6, TRPM7, or MagT1.…”

Untitled

“…Hypomagnesemia with urinary magnesium excretion is a well-known adverse effect of tacrolimus treatment in solid-organ transplant recipients. 20 Woodside and associates 21 demonstrated that calcineurin inhibitors caused hypomagnesemia in patients with renal transplant. In adult renal transplant recipients, the prevalence of hypomagnesemia was found to range from 10.2% to 43%.…”

Mg2+ homeostasis

“…Furthermore, two recent studies link the cyclosporineinduced hypomagnesemia with hampered EGF signaling toward TRPM6 [77,78 & ]. In addition, Gouadon et al [79] used Caco2 cells to determine differential effects of cyclosporine and tacrolimus on Mg 2þ influx without altering expression of TRPM6 or other Mg 2þ transporters. Fourth, in 1979, hypomagnesemia was established as a serious side-effect in patients receiving cisplatin chemotherapy [6].…”