FTY720 treatment prolongs skin graft survival in a completely incompatible strain combination

Fingolimod reduces salivary infiltrates and increases salivary secretion in a murine Sjögren's model

Sjögren's Syndrome (SjS) is a chronic, systemic autoimmune disease causing xerostomia, xerophthalmia, and systemic symptoms. The principal pathological finding in SjS is the accumulation of lymphocytes in exocrine glandular tissue and elsewhere, leading to secretory dysfunction and other abnormalities. A rational therapeutic approach might be to interfere with lymphocyte migration to the periphery from central lymphoid tissues. We thus examined in an animal model of SjS the effects of Fingolimod (FTY720, Gilenya™), which interferes with migration of lymphocytes to peripheral sites. Fingolimod induces sequestration of lymphocytes in lymphoid organs by altering lymphocyte expression of sphingosine-1-phosphate receptors. In the C57Bl/6. NOD.Aec1Aec2 (AEC) model of SjS, Fingolimod reduced circulating T and B cell numbers. Treatment of AEC mice with Fingolimod increased salivary output and decreased the size of salivary gland infiltrates. Oral Fingolimod thus merits further consideration in the management of SjS in humans.

Prolongation of skin graft survival in mice by an azaphenothiazine derivative

Azaphenothiazines are predominantly immunosuppressive compounds. We evaluated the efficacy of an azaphenothiazine derivative, 6-chloroethylureidoethyldiquino[3,2-b;2',3'-e][1,4]thiazine (DQT) in prolongation of survival of skin allografts between BALB/c and C57Bl/6 mice. The mice were treated intraperitoneally (i.p.) with 100 μg of DQT on alternate days, on days 1-13 of the experiment (7 doses). The effect of DQT on a two-way mixed lymphocyte reaction (MLR) in the human model, as well as its effect on production of TNF α and IL-10 in a whole blood cell culture, stimulated by lipopolysaccharide (LPS), were evaluated. In addition, DQT effects were investigated regarding the proportion of T cell subsets in human peripheral blood lymphocytes (PBMC) by flow cytometry. Lastly, the effect of DQT on expression of signaling molecules involved in pro apoptotic pathways was determined by RT PCR. The results showed that DQT significantly extended skin graft survival. The compound also strongly suppressed two-way MLR in the human model at a concentration range of 2.5-5.0 μM. In addition, DQT inhibited LPS-inducible TNF α, but not IL-10 production. The compound preferentially caused a loss of the CD3-CD8+CD11b + PBMC cell subset, and transformed CD3+CD8+^high into CD3+CD8+^low cells. Lastly, we demonstrated significant increases in expression of caspases (in particular caspase 8) and of p53 in a culture of Jurkat T cells. We conclude that the immunosuppressive actions of the compound in allograft rejection may be predominantly associated with induction of cell apoptosis and inhibition of TNF α production. The apoptosis could be predominantly selective for the CD3-CD8+CD11b + cell phenotype.

Skin allograft survival and analysis of renal parameters after FTY720 + tacrolimus treatment in mice

Calcineurin inhibitors such as cyclosporine (CsA) and tacrolimus (FK506) show similar efficacy to prevent rejection within the first year after organ transplantation. However, their use is limited by side effects, such as kidney damage, hypertension, new-onset diabetes, and hyperlipidemia. The consensus opinion suggests that compared with CsA, FK506 has fewer negative effects on blood pressure, serum lipids, and renal function. Nevertheless, FK506 use is associated with a higher incidence of posttransplantation diabetes mellitus. FTY720 is a new compound that has shown beneficial effects in animal models of rejection in transplantation, ischemia/reperfusion injury, autoimmune diseases, and tumor development. Our aim was to investigate whether FTY720 + tacrolimus association could provide additional immunosuppression without causing renal toxicity. FTY720 as a monotherapy or in association with FK506 was administered to C57BL/6 mice for 21 days to prevent skin graft rejection and to evaluate renal function and structure. Increased skin allograft survival in the FTY720 + FK506 group was associated with decreased cell numbers in the spleen, blood, and axillary lymph nodes. Changes in major histocompatibility complex (MHC) class II and intercellular adhesion molecule-1 (ICAM-1) expressions in splenocytes were also found in this group. The major effects already described for FK506 (diabetes) or FTY720 (lymphopenia) were observed after 21 days administration even when the drugs were associated. FTY720 associated with FK506 caused fewer changes in kidney structure, and blood glucose levels were lower than in FK506 monotherapy.

Sphingosine-1-phosphate signaling and the skin

Sphingolipids have long been viewed as rather passive structural components of cellular membranes. More recently, it has become evident that metabolism of sphingomyelin yields several lipid mediators that evoke diverse and specific responses in different cell types. One sphingomyelin derivate, sphingosine-1-phosphate (S1P), has attracted particular attention for its effect on epidermal cells, which differs from those on most other cell types. S1P inhibits keratinocyte proliferation and induces keratinocyte differentiation and migration, suggesting a role for S1P in the re-epithelialization of wounds. The migratory response involves the phosphorylation and activation of Smad3. In epithelial tumors, S1P signaling has been linked with potential oncogenic effects, but has also been found to inhibit metastasis in a mouse melanoma model. S1P promotes endothelial cell survival, acts as a chemoattractant for vascular cells, and exerts a protective effect on the endothelial barrier. Conversely, S1P receptor knockout leads to embryonic lethality mainly due to impaired vascular maturation. S1P presumably modulates peripheral T-lymphocyte levels by stimulating their egress from lymphoid organs rather than by promoting T-cell proliferation. The S1P analog FTY720 (fingolimod) acts as a functional antagonist by inhibiting lymphocyte egress, and thus holds great promise as an immunosuppressant drug for the prevention of allograft rejection and treatment of T-lymphocyte-driven inflammatory skin diseases, such as lupus erythematosus, psoriasis, and atopic dermatitis. Topical use of S1P and other sphingosine compounds is also under investigation, particularly for the treatment of acne vulgaris.

The thymus is required for the ability of FTY720 to prolong skin allograft survival across different histocompatibility MHC barriers

The immunosuppressive effect of FTY720 is associated with the reversible sequestration of lymphocytes from the blood and the spleen into secondary lymphoid organs and reduced egress of mature thymocytes from the thymus. This work was designed to dissect the differential effect of FTY720 on CD4 and CD8 T cell-mediated mechanisms of skin graft rejection in the presence (euthymic) or absence (thymectomized) of thymic output. To that end, untreated and FTY720-treated euthymic (Euthy) and thymectomized (ATX) mice received skin allografts across a full, class II or class I major histocompatibility complex (MHC) mismatched (MM) barriers and graft survival was monitored. We demonstrate that a short course of FTY720 treatment significantly augments the survival of full, class I and class II MHC MM skin grafts compared to the nontreated controls. Interestingly, FTY720-treated Euthy recipients showed a significantly prolonged skin allograft survival compared to FTY720-treated ATX mice. These results together show that FTY720 impairs both CD4 and CD8 T cell-mediated mechanisms of rejection and, more importantly, the presence of the thymus is necessary for the ability of FTY720 to modulate skin allograft rejection across different histocompatibility MHC barriers.

Long-term effect of FTY720 on lymphocyte count and islet allograft survival in mice

This study was performed to observe the long-term effect of FTY720 on lymphocyte count change and islet allograft survival. Diabetic C57BL/6 mice were given FTY720 (group 1, 0.5 mg/kg/day; group 2, 1.0 mg/kg/day) or its vehicle (group 3, controls) after transplantation. Median graft survival time was prolonged in a dose-dependent manner (group 1, 84.5 days; group 2, >100 days, and group 3, 10 days, P < 0.01). Peripheral blood lymphocytes in groups 1 and 2 decreased to 23.81% and 12.59% compared with control group after FTY720 treatment. Lymphocytes from mesenteric lymph nodes and axillary nodes in groups 1 and 2 significantly increased on day 5, but decreased on day 14. Lymphocyte infiltration to the graft site was attenuated in groups 1 and 2. In conclusion, continuous FTY720 administration can induce and maintain lymphopenia, and inhibit lymphocytes from infiltrating the graft site so as to prolong islet allograft survival in mice.

FTY720 in combination with cyclosporine--an analysis of skin allograft survival and renal function

Acute and chronic nephrotoxicity caused by CsA continuous administration impair kidney allograft survival. Several clinical and experimental protocols have shown benefits to the kidney after decreasing CsA dose, withdrawing the drug or delaying its introduction after transplantation. FTY720 is a new compound that has immunosuppressive characteristics and increase allograft survival in animal models without causing the side effects of calcineurin inhibitors (CNIs). FTY720 described mechanism of action that consists to alter the lymphocyte migration pattern without impairment of the immune system response against pathogens. In our mice model, FTY720 administered alone or in combination with CsA during 21 days increased skin allograft survival in a fully mismatched strain combination and did not cause significant changes in renal function. Moreover, renal structure was normal in all groups suggesting that at low doses (10 mg/kg/day) CsA can be associated during short-term period to other immunosuppressive drugs, i.e. FTY720 without affecting the kidney. Combination of immunosuppressive compounds with FTY720 and/or delayed introduction of low cyclosporine dose could prevent graft rejection and avoid nephrotoxicity.

Inhibition of inducible nitric oxide synthase and cyclooxygenase-2 expression by flavonoids isolated from Tanacetum microphyllum

Plant flavonoids show anti-inflammatory activity both in vitro and in vivo. Some flavonoids have been reported previously to inhibit nitric oxide (NO) and prostaglandin E2 (PGE2) production by suppressing inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. The present study focuses on the effect of various naturally occurring flavonoids (santin, ermanin, centaureidin and 5,3'-dihydroxy-4'-methoxy-7-methoxycarbonylflavonol) on modulation of lipopolysaccharide (LPS)-induced iNOS and COX-2 expression in RAW 264.7 cells. Western blotting showed that all flavonoids suppressed the induction of both iNOS and COX-2. Ermanin and 5,3'-dihydroxy-4'-methoxy-7-methoxycarbonylflavonol were the most potent inhibitors. This study suggests that inhibition of iNOS and COX-2 expression by flavonoids may be one of the mechanisms responsible for their anti-inflammatory effects, and that they may be potential agents for use in the treatment of inflammatory diseases.

FTY720 prevents renal T-cell infiltration after ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury, a common early feature in renal transplantation, results from both free radical species generation and local inflammatory responses that attract different types of cells. The interaction with infiltrating leukocytes could promote damage and death of resident renal cells contributing to worsening of renal function. It has been shown that depletion of host T cells protects against kidney damage after I/R injury, although the mechanism is not fully understood. FTY720, a synthetic analog of a natural product extracted from Isaria sincclairii has shown modulatory properties in experimental models of autoimmune disease, transplantation, and I/R injury. FTY720 alters lymphocyte responses to chemokine homing signals, thereby decreasing the number of lymphocytes in inflammatory sites. We evaluated renal function in mice at 3, 5, and 7 days after I/R injury in the presence or absence of FTY720 treatment. FTY720 treatment promoted earlier recovery of renal function associated with a lower number of renal-infiltrating lymphocytes. These findings confirm previous results showing a protective effect of FTY720 in I/R injury models.

Prolonged administration of FTY720 does not cause renal toxicity in mice

Prevention of allograft rejection without renal toxicity caused by calcineurin-inhibitor immunosuppression is a major goal for transplantation. FTY720 is a synthetic drug that modulates immune responses of transplantation in many animal models. FTY720 modulating mechanisms relate to lymphocyte migration to peripheral lymph nodes instead of inflammatory sites. The drug has no effect on T-cell proliferation or cytokine production, and therefore prevents generalized immunosuppression. However, it is still to be confirmed that FTY720 has no nephrotoxic effects when administered continuously. In the present study FTY720 was administered orally for 21 days to C57BL/6 mice that underwent weekly evaluations. FTY720 (1 mg/kg per day) impaired body weight gain, but had no significant effect on either renal function or structure. Our findings suggest that FTY720 may provide a reasonable add-on therapy in calcineurin-inhibitor-treated transplant recipients.