Altered Expression of Alpha2beta1 Integrin in Kidney Fibroblasts: A Potential Mechanism for CsA-induced Nephrotoxicity

Nephrotoxicity is considered a significant cause of patient morbidity following chronic Cyclosporine A (CsA) treatment. The exact mechanism of CsA-induced nephrotoxicity remains to be fully clarified. Tubulointerstitial fibrosis is widely regarded as a major pathway of CsA toxicity; therefore, the role of integrins as regulators of collagen in the extra-cellular matrix can be deemed pivotal. The objective of the present study was to observe the expression levels of alpha2beta1 integrin following CsA treatment +/- antioxidants. Adhesion assay, immunofluorescent and flow cytometric analyses were performed on kidney fibroblasts obtained from rats after administration of CsA (25 mg/kg/day) +/- Vitamin E (vit. E) and Quercetin (Q) for 4 weeks. Total RNA was collected from the aforementioned fibroblasts for semi-quantitative reverse transcriptase-polymerase chain reaction analysis of α2 and β1 integrins. We found that α2 and β1 integrins were both markedly reduced following treatment with CsA, i.e., 25% and 13%, respectively, but were normal following subsequent consumption of the antioxidants vit. E and Q. Attachment and spreading of the CsA-treated fibroblasts declined from 82% to 50%; however, this effect was partially reversed to 70% following antioxidant treatment. Similar results were observed in the spreading assay in which the level of spreading decreased from 73% to 21% and was subsequently restored to 46%. We conclude that cell adhesion, mediated by binding of integrin to collagen, which is a prerequisite of normal cell viability and collagen regulation, may be a novel pathway further explaining the nephrotoxic effects of CsA.