FTY720 blocks allograft rejection by homing of lymphocytes in vivo

Sphingosine 1-phosphate (S1P) induces shape change in rat C6 glioma cells through the S1P2 receptor: development of an agonist for S1P receptors

Treatment with isoprenaline led to a change in the cell morphology of rat C6 glioma cells. This morphological change was reverted by the addition of sphingosine 1-phosphate (S1P). Using this morphological change as a response marker we determined that DS-SG-44 ((2S,3R)-2-amino-3-hydroxy-4-(4-octylphenyl)butyl phosphoric acid) was an agonist of S1P receptors. The DS-SG-44-induced morphological reversion was not observed with such structurally related molecules as DS-SG-45 ((2S,3R)-2-amino-3-hydroxy-4-(3-octylphenyl)butyl phosphoric acid) and DS-SG-12 ((2S,3R)-2-amino-4-(4-octylphenyl)butane-1,3-diol). The S1P- and DS-SG-44-induced shape changes were neither reproduced with the S1P1/S1P3 receptor agonist VPC24191 nor inhibited by the S1P1/S1P3 receptor antagonist, VPC23019. Transfection with small interfering RNA (siRNA) for the S1P2 receptor greatly inhibited the DS-SG-44-induced shape change, and in part an S1P-induced response. In the presence of VPC23019, siRNA transfection for the S1P2 receptor almost completely blocked the S1P- and DS-SG-44-induced shape changes. Our results suggested that DS-SG-44, a newly-synthesized S1P analogue, acted as an S1P receptor agonist and that the S1P-induced shape change in rat C6 glioma cells was mediated mainly through the S1P2 receptor, and cooperatively through the S1P1/S1P3 receptors.

Protective effects of FTY720 on chronic allograft nephropathy by reducing late lymphocytic infiltration

BACKGROUND

Lymphocytic infiltration is obvious throughout early and late stages of chronic allograft nephropathy. Early infiltrating lymphocytes are involved in initial insults to kidney allografts, but the contribution of late infiltration to long-term allograft attrition is still controversial. Early application of FTY720 reduced the number of graft infiltrating lymphocytes, and inhibited acute rejection. The present study investigated the potential of FTY720 to reduce the number of infiltrating lymphocytes even at a late stage, and, thus, slow the pace of chronic allograft nephropathy.

METHODS

Fisher (F344) rat kidneys were orthotopically transplanted into Lewis recipients with an initial 10-day course of cyclosporine A (1.5 mg/kg/day). FTY720, at a dose of 0.5 mg/kg/day, or vehicle was administered to recipients either from weeks 12 to 24 or from 20 to 24 after transplantation. Animals were harvested 24 weeks after transplantation for histologic, immunohistologic, and molecular analysis.

RESULTS

FTY720, either initiated at 12 or 20 weeks after transplantation, reduced urinary protein excretion, and significantly ameliorated glomerulosclerosis, interstitial fibrosis, tubular atrophy, and intimal proliferation of graft arteries at 24 weeks after transplantation. Furthermore FTY720 markedly suppressed lymphocyte infiltration and decreased mRNA levels of interleukin-10 (IL-10), transforming growth factor-beta (TGF-beta), and platelet-derived growth factor-B (PDGF-B) but enhanced the number of apoptotic cells in grafts.

CONCLUSIONS

FTY720 ameliorated chronic allograft nephropathy even at advanced stages. Furthermore, our data suggest that this effect was achieved by a reduction of graft infiltrating lymphocytes.

New immunosuppressive drugs: an update

An increasing number of immunosuppressive drugs became available for clinical use over the past few decades. These include substances with recently recognized immunosuppressive properties, which needed careful evaluation in various trials before they could be approved for use in different diseases. The effectiveness of other agents was already established, but knowledge about their modes of action or the mechanisms that lead to side effects was acquired much later. This understanding also contributed to the development of new drugs that display synergistic effects or lack certain adverse effects. The greater choice afforded by such research endeavours allows us to select the best therapeutic strategy for an individual patient; however, this requires a comprehensive knowledge of the available options. The present review provides an update of current knowledge of the most important substances (including calcineurin and target of rapamycin inhibitors, regulators of gene expression, and inhibitors of purine and pyrimidine synthesis) and surveys some of the novel agents that are expected to play an important role in the future.