FTY720 reduces extracellular matrix expansion associated with ischemia-reperfusion induced injury

Ischemia-reperfusion (IR) is one of the strongest nonimmune factors associated with the development of chronic allograft nephropathy (CAN). This effect is often exacerbated by immunosuppressive medications, most notably cyclosporine. Although traditionally the macrophage was thought to stimulate fibroblast activity in CAN, recent evidence supports a role for lymphocytes. FTY720 is a new immunosuppressant that promotes lymphocyte sequestration into lymph nodes and Peyer's patches. This study investigated the effect of FTY720 on renal fibrosis in the rat following an IR insult (IRI).

A rat model of IRI was used in which male Sprague-Dawley rats (under isoflurane anaesthesia) underwent bilateral flank incision with removal of the right kidney and clamping of the left renal hilum for 45 minutes. Five groups of animals were studied (n=4): nephrectomy only, IRI only, IRI+FTY720 (1 mg/kg/d), IRI+cyclosporine (15 mg/kg/d), and IRI+FTY 720 (1 mg/kg/d) and cyclosporine (15 mg/kg/d). Animals were humanely killed at 30 days.

Serum creatinine (SCr) level was significantly reduced in the FTY720-treated animals. IRI alone produced a significant increase in SCr level compared with neprectomized animals (138 micromol/L vs 55 micromol/L; P<.05). This effect was potentiated by treatment with cyclosporine (173 micromol/L vs 55 micromol/L; P<.05). Treatment with FTY720 significantly reduced SCr level in rats following IRI alone (81 micromol/L vs 138 micromol/L; P<.01) and in rats following IRI + cyclosporine (98 micromol/L vs 173 micromol/L; P<.014). Parallel changes were seen in the levels of proteinuria. Fibrosis was assessed using Masson's trichrome (MT) staining. IRI alone produced a significant increase in MT staining compared with nephrectomized animals (0.92 vs 0.03; P<.05). This effect was potentiated by treatment with cyclosporine (1.12 vs 0.92; P=.022). Treatment with FTY720 reduced the level of MT staining in rats following IRI alone (0.34 vs 0.92; P<.05) and in rats following IRI+cyclosporine (70.34 vs 1.12; P<.05). Levels of TGF-beta1 were considerably reduced in FTY720-treated animals (compared with cyclosporine+IRI and IRI only), either alone (196+/-31 pg/mL vs 1105+/-59 pg/mL and 611+/-38; P<.05) or in conjunction with cyclosporine (423+/-26 pg/mL vs 1105+/-59 pg/mL and 611+/-38; P<.05).

Our study shows that treatment with FTY720 can reduce renal fibrosis as a result of IRI, both alone and in conjunction with cyclosporine. This provides promising evidence for using FTY720 in a calcineurin-free or reduced-dose immunosuppression protocol in an effort to reduce the incidence of CAN.