ABSTRACT
Objective: To investigate the roles of osteopontin (OPN) and nuclear transcription factor in a rat model of chronic cyclosporine A (CsA) nephrotoxicity. Methods: Male Sprague-Dawley rats maintained on a low salt diet were treated daily with vehicle (olive oil, 1 mL • kg-1 • d-1, sc.) and CsA (15 mL • kg-1 • d-1, sc.) for 4 weeks. Renal histopathology was estimated by trichrome staining (tubulointerstitial fibrosis) and immunohistochemistry (ED-1) to assess the degrees of renal tubulointerstitial lesions. In addition, OPN mRNA and protein expression and nuclear transcription factor (NF-κB and AP-1) were studied by northern blotting analysis, immunohistochemistry, electrophoretic mobility shift assay, and immunoblotting analysis. Results: CsA-treated rats displayed significantly striped tubulointerstitial fibrosis ([38. 9 ± 3. 3]%/5 mm2 vs [0± 0]%/5 mm2, P<0. 01) and increased ED-1-positive cells (89±9 vs 7±2, P<0. 01). Compared with VH-treated rats, CsA-treated rats showed significantly upregulated OPN mRNA and protein expression in the proximal tubular cells, mainly localizing at areas of severe injured tissues. CsA-treated group also had significantly increased activities of NF-κB ([218±19]% vs [ 116± 15] %, P<0. 01) and AP-1 ([735±225]% vs[101±4]%, P<0. 01), and significantly decreased expression of ([9 ± 7]% vs [105±7]%, P<0. 01). Correlation analysis revealed that upregulated OPN mRNA was positively correlated with tubulointerstitial fibrosis (r= 0.959, P<0. 001) and activities of NF-κB and AP-1 (NF-κB: r = 0.773, P<0. 01; AP-1: r =0.619, P = 0. 01, respectively). Conclusion: Our findings suggest that OPN, nuclear transcription factor NF-κB and AP-1 are involved in renal tubulointerstitial injury in chronic CsA nephrotoxicity.