Abstract: Background - Cyclosporine is an immunosuppressive agent widely used in dogs. Pharmacodynamic effects on canine hepatic tissue have not been evaluated. Hypothesis/Objectives - Our objective was to evaluate activated interleukin-2 (IL-2) gene expression in canine hepatic tissue after incubation with cyclosporine. Our hypothesis was that IL-2 expression would be inhibited by cyclosporine in a concentration-dependent fashion. Animals - Normal hepatic tissue harvested from four canine cadavers. Methods - Hepatic tissues were harvested, and then homogenized and digested. Lymphocytes were isolated and incubated in 0, 10, 100, 500, and 1000 ng/ml of cyclosporine, in duplicate, for one hour. Subsequently, lymphocytes were activated with phorbol-12-myristate-13-acetate and ionomycin, and incubated for 5 hours. After RNA extraction, IL-2 gene expression was measured by quantitative reverse transcription PCR, and cycle threshold (Ct) values were recorded. One-way ANOVA and polynomial analysis were used for statistical analysis. Results - Ct values for IL-2 expression increased significantly as cyclosporine concentration increased from 10 (P = 0.0019) to 100 ng/ml (P = 0.00167), with no significant differences between concentrations of 0 and 10 ng/ml (P = 0.9999), 100 and 500 ng/ml (P = 0.1670), and 500 and 1000 ng/ml (P = 0.9618). A positive correlation was observed between IL-2 expression Ct value and cyclosporine concentration (P<0.01). Conclusions and Clinical Importance - Cyclosporine significantly inhibited IL-2 gene expression in canine ex-vivo hepatic tissue in a concentration-dependent fashion. Further in-vivo studies are necessary to determine the clinical significance of these findings.
