Effects Of FTY720 On Renal Interstitial Fibrosis Of Unilateral Ureteral Obstructic Rats And Study Of Its Mechanism

【Objective】FTY720 is a novel immune modulating drug which obtained through structural modification of ISP-1, an immunosuppressive substance newly purified from Cordyceps sinensis , a Chinese herb traditionally used in the treatment of renal diseases. In recent years, the role of FTY720 in the immune mediated glomerulonephritis has been demonstrated, but its effects on renal interstitial fibrosis, a major determinant for prognosis, remain uncertain.. The present study is aimed to examine the inhibitory effect of FTY720 on renal interstitial fibrosis and peritubular cappilary loss in unilateral ureteral obstructic rats and to study the underlying mechanism .【Methods】Fouty-five males SD rats were randomly divided into sham-operated(SHAM) , unilateral ureteral obstruction (UUO) and UUO treated with FTY720 (UUO+FTY720) group . 0.5mg.kg-1.d-1 of FTY720 or vehicle was administrated through daily gavage and begun from three days before the operation till being sacrificed. 5 rats in each groups were sacrificed at day 7, day 14 and day 21 afte UUO or Sham-operation. In order to document if renal fibrosis closely correlates with renal insufficiency, 24-hour urine protein, blood urea nitrogen (BUN) and plasma creatinine were determined .Tubulointerstitial injury and interstitial fibrosis were examined by morphological analysis, apoptosis of tubular epithelial cells was examined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling , the expression of CD3,ED1 ,α-SMA ,COL-Ⅲ,CD141and VEGF was detected by immunohistochemical nethod and scored semi-quantitively. The number of CD141 positive PTC was quantitated in an area of 100 renal tubules.【Results】The amount of 24 hours urine protein was ((9.7±1.74)mg·d-1 at 14d after operation in FTY720 treated group, much lower than that in UUO group, which was (15.48±1.52 )mg·d-1 at same time .(P<0.05). Serum creatinine were (123±15.76)μmol·L-1,(65.88±6.08)μmol·L-1(,51.38±6.9)μmol·L-1 in UUO groups respectively at 7,14,21d, and (41.76±4.51)μmol·L-1,(39.54±7.94)μmol·L-1,(38.5±4.52)μmol·L-1 in FTY720 treated group at 7,14,21d, the levels in FTY720 treated group were significantly lower than those in UUO group. The Blood urea nitrogen was (16.14±3.21)mmol·L-1(,10.7±1.66)mmol·L-1 in UUO group and (8.08±0.96 )mmol·L-1(,6.98±0.80)mmol·L-1 in FTY720 treated group at 7,14d respectively, the levels were significantly lower in FTY720 group than that in UUO group (P<0.05). The renal pathological evaluation indicated that the scores of renal interstitial fibrosis were lower in FTY720 group than that in UUO group. Obvious lymphocyte and macrophage infiltration were found in tubular interstitial area in UUO group but significantly less in FTY720 treated group (P<0.01). Immunohistochemistry study revealed thatα-SMA expression was limited to vessels in SHAM group, but extended to renal tubule and interstitium in UUO and FTY720 treated group, while relatively weaker expression was observed in FTY720 group than in UUO group . Some collagenⅢexpression was found in SHAM group, which was much enhanced in UUO group at 7,14,21d and mainly distributed in renal interstitium, the expression in FTY720 group was also increased compared to SHAM group, but much lower than that in UUO group. In the SHAM group , there were no significant injury in peritubular capillary, and the numbers of CD141 positive PTC were 158.6±8.29, 155.2±5.89, 157±4.47 at 7, 14, 21 day. In the UUO group, peritubular capillary injuried severely ,and peritubular capillary density decreased markedly, the numbers of CD141 positive PTC were 116.8±8.92, 98.8±3.96, 62.2±7.01 at the 7th,14th,21st day. FTY720 could relieve the impairment and loss of peritubular capillary, as demonstrated in FTY720 treated group,the numbers of CD141 positive PTC were 132.5±8.32, 119.4±12.21, 85±2.59 at the 7th,14th,21st day ,significantly higher than those in UUO group(P<0.01)., No tubular epithelial cells apoptosis was observed in SHAM group, apoptosis was found in UUO group at day 7 after operation but was decreased in FTY720 treated group (P<0.01). The immunohistochemistry study revealed that the expression of VEGF protein was higher in FTY720 treated group than in UUO group(P<0.01),but still lower than in SHAM group(P<0.05).【Conclusions】Novel immunomodulator FTY720 can obviously inhibite lymphocyte and macrophage infiltration, renal tubule cell transdifferentiation, extracellular matrix accumulation and inhibit the tubular epithelial cell apoptosis, increase the expression of VEGF protein ,and prevent the loss of peritubular capillary interstitial fibrosis, thus ameliorate renal interstitial fibrosis and prevent renal disease progression.