sphingosine-kinase and Lymphopenia

FTY720 is a recently approved first line therapy for relapsing forms of multiple sclerosis. In this context, FTY720 is a pro-drug, with its anti-multiple sclerosis, immunosuppressive effects largely elicited following its phosphorylation by sphingosine kinase 2 and subsequent modulation of G protein-coupled sphingosine 1-phosphate (S1P) receptor 1 that induces lymphopenia by altering lymphocyte trafficking. A number of other biological effects of FTY720 have, however, been described, including considerable evidence that this drug also has anti-cancer properties. These other effects of FTY720 are independent of S1P receptors, and appear facilitated by modulation of a range of other recently described protein targets by nonphosphorylated FTY720. Here, we review the direct targets of FTY720 that contribute to its anti-cancer properties. We also discuss other recently described protein effectors that, in combination with S1P receptors, appear to contribute to its immunosuppressive effects.

Topics: Antineoplastic Agents; Apoptosis; Fingolimod Hydrochloride; Humans; Immunosuppressive Agents; Lymphopenia; Lysophospholipids; Multiple Sclerosis; Neoplasms; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Propylene Glycols; Receptors, Lysosphingolipid; Sphingosine

Sphingosine 1-phosphate (S1P) is an important mediator of cancer cell growth and proliferation. Production of S1P is catalyzed by sphingosine kinase 1 (SphK). Safingol, (l-threo-dihydrosphingosine) is a putative inhibitor of SphK. We conducted a phase I trial of safingol (S) alone and in combination with cisplatin (C).. A 3 + 3 dose escalation was used. For safety, S was given alone 1 week before the combination. S + C were then administered every 3 weeks. S was given over 60 to 120 minutes, depending on dose. Sixty minutes later, C was given over 60 minutes. The C dose of 75 mg/m(2) was reduced in cohort 4 to 60 mg/m(2) due to excessive fatigue.. Forty-three patients were treated, 41 were evaluable for toxicity, and 37 for response. The maximum tolerated dose (MTD) was S 840 mg/m(2) over 120 minutes C 60 mg/m(2), every 3 weeks. Dose-limiting toxicity (DLT) attributed to cisplatin included fatigue and hyponatremia. DLT from S was hepatic enzyme elevation. S pharmacokinetic parameters were linear throughout the dose range with no significant interaction with C. Patients treated at or near the MTD achieved S levels of more than 20 μmol/L and maintained levels greater than and equal to 5 μmol/L for 4 hours. The best response was stable disease in 6 patients for on average 3.3 months (range 1.8-7.2 m). One patient with adrenal cortical cancer had significant regression of liver and lung metastases and another had prolonged stable disease. S was associated with a dose-dependent reduction in S1P in plasma.. Safingol, the first putative SphK inhibitor to enter clinical trials, can be safely administered in combination with cisplatin. Reversible dose-dependent hepatic toxicity was seen, as expected from preclinical data. Target inhibition was achieved with downregulation of S1P. The recommended phase II dose is S 840 mg/m(2) and C 60 mg/m(2), every 3 weeks.

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Combined Chemotherapy Protocols; Area Under Curve; Cisplatin; Dose-Response Relationship, Drug; Drug Administration Schedule; Fatigue; Female; Humans; Lymphopenia; Lysophospholipids; Male; Metabolic Clearance Rate; Middle Aged; Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Sphingosine; Treatment Outcome

Sepsis mouse models revealed thymus atrophy, characterised by decreased thymus weight and loss of thymocytes due to apoptosis. Mice suffered from lymphopenia, a lack of T cells in the periphery, which attenuates their ability to fight against recurring and secondary infections during sepsis progression. Key players in thymus atrophy are IL-6, which is directly involved in thymus involution, and the sphingosine-1-phosphate - sphingosine-1-phosphate receptor 1 signaling, influencing thymocytes emigration. In healthy individuals a sphingosine-1-phosphate (S1P) gradient from lymphoid organs to the circulatory system serves as signal for mature T cell egress. In the present study we investigated, whether inhibition of S1P generation improves thymus involution. In sepsis, induced by cecal ligation and puncture (CLP), S1P in the thymus increased, while it decreased in serum, thus disrupting the naturally occurring S1P gradient. As a potential source of S1P we identified increased numbers of apoptotic cells in the thymic cortex of septic mice. Pharmacological inhibition of the S1P generating sphingosine kinases, by 4- [[4-(4-Chlorophenyl)-2-thiazolyl]amino]phenol (SK I-II), administered directly following CLP, prevented thymus atrophy. This was reflected by lymphocytosis, diminished apoptosis, decreased IL-6 expression, and an unaltered thymus weight. In addition SK I-II-treatment preserved the S1P balance and prevented S1P-dependent internalization of the sphingosine-1-phosphate receptor 1. Our data suggest that inhibition of sphingosine kinase and thus, S1P generation during sepsis restores thymic T cell egress, which might improve septic outcome.

Topics: Aminophenols; Animals; Apoptosis; Atrophy; Cecum; Disease Models, Animal; Interleukin-6; Lymphocytosis; Lymphopenia; Lysophospholipids; Male; Mice; Mice, Inbred C57BL; Phosphotransferases (Alcohol Group Acceptor); Receptors, Lysosphingolipid; Sepsis; Sphingosine; Thiazoles; Thymocytes; Thymus Gland

Modifying FTY720, an immunosuppressant modulator, led to a new series of well phosphorylated tetralin analogs as potent S1P1 receptor agonists. The stereochemistry effect of tetralin ring was probed, and (-)-(R)-2-amino-2-((S)-6-octyl-1,2,3,4-tetrahydronaphthalen-2-yl)propan-1-ol was identified as a good SphK2 substrate and potent S1P1 agonist with good oral bioavailability.

Topics: Administration, Oral; Animals; Crystallography, X-Ray; Immunosuppressive Agents; Lymphopenia; Mice; Models, Molecular; Multiple Sclerosis; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Prodrugs; Receptors, Lysosphingolipid; Structure-Activity Relationship; Tetrahydronaphthalenes

Sphingosine kinases (SKs) 1 and 2 produce high concentrations of sphingosine 1-phosphate (S1P) in blood and lymph. In contrast, S1P concentrations in lymphoid tissues are kept low by the S1P-degrading activity of the S1P-lyase. These differences in S1P concentrations drive lymphocyte circulation. Inhibition of the S1P-lyase prevents lymphocyte egress and causes lymphopenia because of increased S1P levels in lymphoid tissues. In this study, we investigated the source of this accumulating S1P in lymphoid tissues by using SK2-deficient (SK2(-/-)) mice. In contrast to wild-type mice, SK2(-/-) mice exhibited attenuated lymphopenia after S1P-lyase inhibition by 4-deoxypyridoxine (DOP). Consistently, S1P concentrations were only modestly increased in lymphoid tissues of SK2(-/-) mice compared with a significantly higher increase in wild-type mice after DOP treatment. Low S1P concentrations in lymphoid tissues of DOP-treated SK2(-/-) mice were accompanied by higher S1P concentrations in blood, suggesting that SK2(-/-) mice display defective S1P transport from blood into lymphoid tissues. To investigate this potential new role of SK2, RBCs loaded with traceable C17-S1P were transfused into wild-type and SK2(-/-) mice, resulting in much higher C17-S1P concentrations in blood of SK2(-/-) mice compared with wild-type mice 2 h after transfusion. Moreover, cocultures of RBCs with mouse splenocytes and endothelial cells demonstrated that SK2 regulated cellular uptake of S1P from RBCs. Collectively, our data suggest that S1P in lymphoid tissues derives from blood and point to an essential role of SK2 in S1P transport.

Topics: Animals; B-Lymphocyte Subsets; Catalysis; Cells, Cultured; Coculture Techniques; Endothelium, Vascular; Humans; Lymphoid Tissue; Lymphopenia; Lysophospholipids; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Protein Transport; Sphingosine; T-Lymphocyte Subsets

Immunotherapeutic drugs that mimic sphingosine 1-phosphate (S1P) disrupt lymphocyte trafficking and cause T helper and T effector cells to be retained in secondary lymphoid tissue and away from sites of inflammation. The prototypical therapeutic agent, 2-alkyl-2-amino-1,3-propanediol (FTY720), stimulates S1P signaling pathways only after it is phosphorylated by one or more unknown kinases. We generated sphingosine kinase 2 (SPHK2) null mice to demonstrate that this kinase is responsible for FTY720 phosphorylation and thereby its subsequent actions on the immune system. Both systemic and lymphocyte-localized sources of SPHK2 contributed to FTY720 induced lymphopenia. Although FTY720 was selectively activated in vivo by SPHK2, other S1P pro-drugs can be phosphorylated to cause lymphopenia through the action of additional sphingosine kinases. Our results emphasize the importance of SPHK2 expression in both lymphocytes and other tissues for immune modulation and drug metabolism.

Topics: Animals; Fingolimod Hydrochloride; Flow Cytometry; Homozygote; Immunosuppressive Agents; Lymphocytes; Lymphopenia; Lysophospholipids; Mice; Mice, Inbred C57BL; Mice, Knockout; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Prodrugs; Propylene Glycols; Reverse Transcriptase Polymerase Chain Reaction; Sphingosine

Sphingosine-1-phosphate (S1P), a lipid signaling molecule that regulates many cellular functions, is synthesized from sphingosine and ATP by the action of sphingosine kinase. Two such kinases have been identified, SPHK1 and SPHK2. To begin to investigate the physiological functions of sphingosine kinase and S1P signaling, we generated mice deficient in SPHK1. Sphk1 null mice were viable, fertile, and without any obvious abnormalities. Total SPHK activity in most Sphk1-/-tissues was substantially, but not completely, reduced indicating the presence of multiple sphingosine kinases. S1P levels in most tissues from the Sphk1-/- mice were not markedly decreased. In serum, however, there was a significant decrease in the S1P level. Although S1P signaling regulates lymphocyte trafficking, lymphocyte distribution was unaffected in lymphoid organs of Sphk1-/- mice. The immunosuppressant FTY720 was phosphorylated and elicited lymphopenia in the Sphk1 null mice showing that SPHK1 is not required for the functional activation of this sphingosine analogue prodrug. The results with these Sphk1 null mice reveal that some key physiologic processes that require S1P receptor signaling, such as vascular development and proper lymphocyte distribution, can occur in the absence of SPHK1.

Topics: Animals; Base Sequence; DNA; Fingolimod Hydrochloride; Immunosuppressive Agents; Lymphocytes; Lymphopenia; Lysophospholipids; Mice; Mice, Knockout; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Prodrugs; Propylene Glycols; Receptors, Lysosphingolipid; Signal Transduction; Sphingosine

Immunosuppressant drugs such as cyclosporin have allowed widespread organ transplantation, but their utility remains limited by toxicities, and they are ineffective in chronic management of autoimmune diseases such as multiple sclerosis. In contrast, the immune modulating drug FTY720 is efficacious in a variety of transplant and autoimmune models without inducing a generalized immunosuppressed state and is effective in human kidney transplantation. FTY720 elicits a lymphopenia resulting from a reversible redistribution of lymphocytes from circulation to secondary lymphoid tissues by unknown mechanisms. Using FTY720 and several analogs, we show now that FTY720 is phosphorylated by sphingosine kinase; the phosphorylated compound is a potent agonist at four sphingosine 1-phosphate receptors and represents the therapeutic principle in a rodent model of multiple sclerosis. Our results suggest that FTY720, after phosphorylation, acts through sphingosine 1-phosphate signaling pathways to modulate chemotactic responses and lymphocyte trafficking.

Topics: Animals; Apoptosis; Cell Line; Cell Membrane; Chemotaxis; Dose-Response Relationship, Drug; Encephalomyelitis, Autoimmune, Experimental; Fingolimod Hydrochloride; Guanosine 5'-O-(3-Thiotriphosphate); Insecta; Kidney; Lipid Metabolism; Lymphocytes; Lymphopenia; Mice; Models, Chemical; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Propylene Glycols; Rats; Rats, Inbred Lew; Rats, Wistar; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Receptors, Lysophospholipid; Recombinant Proteins; Signal Transduction; Sphingosine; Time Factors