Magnesium supplementation prevents experimental chronic cyclosporine a nephrotoxicity via renin-angiotensin system independent mechanism.
BACKGROUND
We have previously shown that correction of hypomagnesemia by magnesium (Mg) supplementation ameliorates chronic cyclosporine A (CsA) nephropathy via inhibiting gene expression of fibrogenic molecules. Experiments were conducted to further elucidate upstream mechanism of the beneficial effects upon CsA nephrotoxicity.


METHODS
CsA (15 mg/kg/day, subcutaneous [SC]) was administered daily to rats maintained on low sodium diet for 7, 14, and 28 days. Because blockade of renin-angiotensin system improves chronic CsA nephropathy, the effects of Mg supplementation and those of angiotensin-converting enzyme inhibitor (ACEI) were compared on renal function, renal histology, mononuclear cell infiltration, and gene expression profile.


RESULTS
CsA induced a decline in glomerular filtration and developed characteristic striped fibrosis that were mostly evident at day 28. Mg attenuated CsA-induced impaired renal function, whereas ACEI did not. Interstitial inflammation as evidenced by monocyte/macrophage infiltration preceded the renal fibrosis and increased progressively with the CsA treatment period. Concomitantly, CsA markedly up-regulated expression of chemoattractant proteins, osteopontin, and monocyte chemoattractant protein-1. These changes were abolished by Mg but were only partially affected with ACEI. CsA promoted renal mRNA expression of fibrogenic molecules and extracellular matrices that were almost completely abolished by Mg but partially suppressed by ACEI. Similarly, CsA-induced chronic fibrotic lesion was markedly attenuated by Mg supplementation but was partially attenuated by ACEI.


CONCLUSIONS
Mg supplementation abolished CsA-induced precedent interstitial inflammation possibly via inhibition of chemoattractants expression and consequently attenuated tubulointerstitial fibrosis. In this protective mechanism, factors independent of the renin-angiotensin system appears to be mainly involved.
D000818:Animals; D015152:Blotting, Northern; D018932:Chemokine CCL2 / Q000235:genetics; D002908:Chronic Disease; D003094:Collagen / Q000235:genetics; D016572:Cyclosporine / Q000633:toxicity*; D019332:Endothelin-1 / Q000235:genetics; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000633:toxicity*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008274:Magnesium / Q000627:therapeutic use*; D008297:Male; D053495:Osteopontin; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012084:Renin-Angiotensin System / Q000187:drug effects* / Q000502:physiology; D012795:Sialoglycoproteins / Q000032:analysis / Q000235:genetics; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics
D018932:Chemokine CCL2; D019332:Endothelin-1; D007166:Immunosuppressive Agents; D012333:RNA, Messenger; D012795:Sialoglycoproteins; C506897:Spp1 protein, rat; D019715:Tissue Inhibitor of Metalloproteinase-1; D053495:Osteopontin; D016572:Cyclosporine; D003094:Collagen; D008274:Magnesium