Endothelin ETA receptor/lipid peroxides/ COX-2/ TGF-β1 signalling underlies aggravated nephrotoxicity caused by cyclosporine plus indomethacin in rats.

Background and Purpose Cyclosporine ( CSA) and non-steroidal anti-inflammatory drugs ( NSAIDs) are co-prescribed for some arthritic conditions. We tested the hypothesis that this combined regimen elicits exaggerated nephrotoxicity in rats via the up-regulation of endothelin ( ET) receptor signalling. Experimental Approach The effects of a 10 day treatment with CSA (20 mg·kg⁻¹·day⁻¹), indomethacin (5 mg·kg⁻¹·day⁻¹) or their combination on renal biochemical, inflammatory, oxidative and structural profiles were assessed. The roles of ET_A receptor and COX-2 pathways in the interaction were evaluated. Key Results Oral treatment with CSA or indomethacin elevated serum urea and creatinine, caused renal tubular atrophy and interstitial fibrosis, increased renal TGF-β1, and reduced immunohistochemical expressions of ET_A receptors and COX-2. CSA, but not indomethacin, increased renal ET-1, the lipid peroxidation product malondialdehyde ( MDA) and GSH activity. Compared with individual treatments, simultaneous CSA/indomethacin exposure caused: (i) greater elevations in serum creatinine and renal MDA; (ii) loss of the compensatory increase in GSH; (iii) renal infiltration of inflammatory cells and worsening of fibrotic and necrotic profiles; and (iv) increased renal ET-1 and decreased ET_A receptor and COX-2 expressions. Blockade of ET_A receptors by atrasentan ameliorated the biochemical, structural, inflammatory and oxidative abnormalities caused by the CSA/indomethacin regimen. Furthermore, atrasentan partly reversed the CSA/indomethacin-evoked reductions in the expression of ET_A receptor and COX-2 protein. Conclusions and Implications The exaggerated oxidative insult and associated dysregulation of the ET_A receptor/ COX-2/ TGF-β1 signalling might account for the aggravated nephrotoxicity caused by the CSA/indomethacin regimen. The potential renoprotective effect of ET_A receptor antagonism might be exploited therapeutically. [ABSTRACT FROM AUTHOR]