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 demonstrated that this drug produces negative side effects in several organs and in particular in the lymphoid organs and in the kidney. It has been suggested that the CsA causes deleterious effects because it increases the oxygen free radical production. Here we wanted to test whether antioxidants protect 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 intraperitoneally injected with MB (1 mg/kg/day) for 21 days; group II animals 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 for the same periods as groups I and II, and group IV animals were injected subcutaneously with olive oil for 21 days as controls. The kidneys and the thymuses were subsequently removed and examined by conventional morphological staining (hematoxylin-eosin and Masson's trichrome) and enzymatic (NADPH-diaphorase, cytochrome, c oxidase, and superoxide anion production) and immunoenzymatic (inducible nitric oxide synthase--iNOS, endothelial nitric oxide synthase--eNOS) techniques. The thymuses were used to check the persistence of CsA-immunosuppressive 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 oxidase showed a strong activity in proximal tubules, a moderate activity in distal tubules, and a weak activity in glomeruli and in the Henle loops. The expression of iNOS was weak in the proximal tubular epithelial cells and negative in the glomeruli, while eNOS was found to be moderately positive in the glomeruli and in the interstitial arteries, but not in the tubules and in the Henle loops. Degenerative changes with tubulointerstitial injury in the cortex of CsA-treated kidneys (group II) and increases of NADPH-diaphorase levels, iNOS activity, and superoxide staining were found in all structures. The expression of eNOS did not change in group I, III and IV animals. MB combined with CsA prevented the degenerative changes caused by CsA, preserving the structural, enzymatic, and immunoenzymatic integrity of the renal parenchyma. The mechanism by which MB exerts its protective action is not yet clear, but it seems to be due to its ability to inhibit xanthine oxidase and to quench nitric oxide production. Moreover, these data have been also supported by the following: (1) the superoxide anion levels were very high after CsA treatment and reduced after CsA-MB treatment, and (2) the iNOS levels increased in CsA-treated rats and showed normal levels after CsA-MB treatment. Moreover we demonstrated that MB administration did no compromise the CsA immunosuppressive effects, since the thymus showed a cytoarchitecture like that observed in CsA-treated rats.