Does methylene blue protect the kidney tissues from damage induced by ciclosporin A treatment?

Ciclosporin A (CsA) is the first-choice immunosuppressant universally used in allotransplantation and autoimmune diseases. However, it has been demons trated that this drug produces negative side effects in several organs and in particular in the lymphoid organs and in the kidney. It has been suggest ed that the CsA causes deleterious effects because it increases the oxygen free radical production. Here we wanted to test whether antioxidants protec t the kidney parenchyma from the toxicity induced by CsA. We used methylene blue (MB), because it inhibits the formation of oxygen free radicals. The study was carried out in four groups of Wistar rats. Group I animals were i ntraperitoneally injected with MB (1 mg/kg/day) for 21 days; group II anima ls were subcutaneously injected with CsA (15 mg/kg/day) for 21 days; group III animals were treated with CsA combined with MB at the same doses and fo r the same periods as groups I and II, and group IV animals were injected s ubcutaneously with olive oil for 21 days as controls. The kidneys and the t hymuses were subsequently removed and examined by conventional morphologica l staining (hematoxylin-eosin and Masson's trichrome) and enzymatic (NADPH- diaphorase, cytochrome, c oxidase, and superoxide anion production) and imm unoenzymatic (inducible nitric oxide synthase - NOS, endothelial nitric oxi de synthase eNOS) techniques. The thymuses were used to check the persisten ce of CsA-immunsuppressive effects during MB administration. Group I, III, and IV animals showed a normal kidney architecture and low levels of NADPH- diaphorase and of superoxide anion in all structures studied (proximal and distal tubules, glomeruli and the Henle loops). The cytochrome c oxiclase s howed a strong activity in proximal tubules, a moderate activity in distal tubules, and a weak activity in glomeruli and in the Henle loops. The expre ssion of NOS was weak in the proximal tubular epithelial cells and negative in the glomeruli, while eNOS was found to be moderately positive in the gl omeruli and in the interstitial arteries, but not in the tubules and in the Henle loops. Degenerative changes with tubulointerstitial injury in the co rtex of CsA-treated kidneys (group II) and increases of NADPH-diaphorase le vels, NOS activity, and superoxide staining were found in all structures. T he expression of eNOS did not change in group I, III and IV animals. MB com bined with CsA prevented the degenerative changes caused by CsA, preserving the structural, enzymatic, and immunoenzymatic integrity of the renal pare nchyma. The mechanism by which MB exerts its protective action is not yet c lear, but it seems to be due to its ability to inhibit xanthine oxiclase an d to quench nitric oxide production. More-over, these data have been also s upported by the following: (1) the superoxide anion levels were very high a fter CsA treatment and reduced after CsA-MB treatment, and (2) the NOS leve ls increased in CsA-treated rats and showed normal levels after CsA-MB trea tment. Moreover we demonstrated that MB administration did no compromise th e CsA immunosuppressive effects, since the thymus showed a cytoarchitecture like that observed in CsA-treated rats. Copyright (C) 2001 S. Karger AG, B asel.