Ascomycete derivative to MS therapeutic: S1P receptor modulator FTY720

Anti-inflammatory Efficacy of Combined Natural Alkaloid Berberine and S1PR Modulator Fingolimod at Low Doses in Ulcerative Colitis Preclinical Models

The natural alkaloid berberine is being studied as a drug candidate for the treatment of ulcerative colitis (UC). Fingolimod is an immunomodulator approved for the treatment of multiple sclerosis. Whether fingolimod use can be extended to UC and how it interacts with berberine remain unclear. In the present study, the anti-inflammatory efficacies of berberine, fingolimod, and a combination of half-doses of them was examined in mice with dextran sulfate sodium-induced colitis. In mice with subchronic colitis, 14-day oral administration of fingolimod had greater efficacy than berberine in ameliorating the disease clinical severity and colon shortening. However, in mice with chronic colitis, 30-day oral administration of berberine was more effective than fingolimod except on splenic swelling. Notably, the combination of half-doses of each drug was equally effective as the superior single drugs for two models and resulted in reduced splenic swelling in the chronic colitis model. The inhibition of cytokine expression and STAT3 activation, as well as binding to the sphingosine 1-phosphate receptor by both drugs, contributed to the combination efficacy. Our findings suggest that fingolimod in combination with berberine at reduced doses represents a novel therapy for UC that attains satisfactory efficacy with reduced potentials for adverse effects.

Molecular Effects of FDA-Approved Multiple Sclerosis Drugs on Glial Cells and Neurons of the Central Nervous System

Multiple sclerosis (MS) is characterized by peripheral and central inflammatory features, as well as demyelination and neurodegeneration. The available Food and Drug Administration (FDA)-approved drugs for MS have been designed to suppress the peripheral immune system. In addition, however, the effects of these drugs may be partially attributed to their influence on glial cells and neurons of the central nervous system (CNS). We here describe the molecular effects of the traditional and more recent FDA-approved MS drugs Fingolimod, Dimethyl Fumarate, Glatiramer Acetate, Interferon-β, Teriflunomide, Laquinimod, Natalizumab, Alemtuzumab and Ocrelizumab on microglia, astrocytes, neurons and oligodendrocytes. Furthermore, we point to a possible common molecular effect of these drugs, namely a key role for NFκB signaling, causing a switch from pro-inflammatory microglia and astrocytes to anti-inflammatory phenotypes of these CNS cell types that recently emerged as central players in MS pathogenesis. This notion argues for the need to further explore the molecular mechanisms underlying MS drug action.

AKP-11 - A Novel S1P1 Agonist with Favorable Safety Profile Attenuates Experimental Autoimmune Encephalomyelitis in Rat Model of Multiple Sclerosis

Sphingosine-1-phosphate receptor 1 (S1P1) mediated regulation of lymphocyte egress from lymphoid organs is recognized as the mechanism of FTY720 (Fingolimod, Gilenya) efficacy in relapsing-remitting forms of multiple sclerosis (RRMS). In this study we describe a novel S1P1 agonist AKP-11, next generation of S1P1 agonist, with immunomodulatory activities in cell culture model and for therapeutic efficacy against an animal model of MS, i.e. experimental autoimmune encephalomyelitis (EAE) but without the adverse effects observed with FTY720. Like FTY720, AKP-11 bound to S1P1 is internalized and activates intracellular AKT and ERKs cellular signaling pathways. In contrast to FTY720, AKP-11 mediated S1P1 downregulation is independent of sphingosine kinase activity indicating it to be a direct agonist of S1P1. The S1P1 loss and inhibition of lymphocyte egress by FTY720 leads to lymphopenia. In comparison with FTY720, oral administration of AKP-11 caused milder and reversible lymphopenia while providing a similar degree of therapeutic efficacy in the EAE animal model. Consistent with the observed reversible lymphopenia with AKP-11, the S1P1 recycled back to cell membrane in AKP-11 treated cells following its withdrawal, but not with withdrawal of FTY720. Accordingly, a smaller degree of ubiquitination and proteolysis of S1P1 was observed in AKP-11 treated cells as compared to FTY720. Consistent with previous observations, FTY720 treatment is associated with adverse effects of bradycardia and lung vascular leaks in rodents, whereas AKP-11 treatment had undetectable effects on bradycardia and reduced lung vascular leaks as compared to FTY720. Taken together, the data documents that AKP-11 treatment cause milder and reversible lymphopenia with milder adverse effects while maintaining therapeutic efficacy similar to that observed with FTY720, thus indicating therapeutic potential of AKP-11 for treatment of MS and related autoimmune disorders.

Structural analyses of the Slm1-PH domain demonstrate ligand binding in the non-canonical site

Background

Pleckstrin homology (PH) domains are common membrane-targeting modules and their best characterized ligands are a set of important signaling lipids that include phosphatidylinositol phosphates (PtdInsPs). PH domains recognize PtdInsPs through two distinct mechanisms that use different binding pockets on opposite sides of the β-strands 1 and 2: i) a canonical binding site delimited by the β1-β2 and β3-β4loops and ii) a non-canonical binding site bordered by the β1-β2 and β5-β6loops. The PH domain-containing protein Slm1 from budding yeast Saccharomyces cerevisiae is required for actin cytoskeleton polarization and cell growth. We recently reported that this PH domain binds PtdInsPs and phosphorylated sphingolipids in a cooperative manner.

Principal Findings

To study the structural basis for the Slm1-PH domain (Slm1-PH) specificity, we co-crystallized this domain with different soluble compounds that have structures analogous to anionic lipid head groups of reported Slm1 ligands: inositol 4-phosphate, which mimics phosphatidylinositol-4-phosphate (PtdIns(4)P), and phosphoserine as a surrogate for dihydrosphingosine 1-phosphate (DHS1-P). We found electron densities for the ligands within the so-called non-canonical binding site. An additional positively charged surface that contacts a phosphate group was identified next to the canonical binding site.

Conclusions

Our results suggest that Slm1-PH utilizes a non-canonical binding site to bind PtdInsPs, similar to that described for the PH domains of β-spectrin, Tiam1 and ArhGAP9. Additionally, Slm1-PH may have retained an active canonical site. We propose that the presence of both a canonical and a non-canonical binding pocket in Slm1-PH may account for the cooperative binding to PtdInsPs and DHS-1P.

Recent developments in multiple sclerosis therapeutics

Multiple sclerosis, the most common neurologic disorder of young adults, is traditionally considered to be an inflammatory, autoimmune, demyelinating disease of the central nervous system. Based on this understanding, the initial therapeutic strategies were directed at immune modulation and inflammation control. These approaches, including high-dose corticosteroids for acute relapses and long-term use of parenteral interferon-beta, glatiramer acetate or natalizumab for disease modification, are at best moderately effective. Growing evidence supports that, while an inflammatory pathology characterizes the early relapsing stage of multiple sclerosis, neurodegenerative pathology dominates the later progressive stage of the disease. Multiple sclerosis disease-modifying therapies currently in development attempt to specifically target the underlying pathology at each stage of the disease, while avoiding frequent self-injection. These include a variety of oral medications and monoclonal antibodies to reduce inflammation in relapsing multiple sclerosis and agents intended to promote neuroprotection and neurorepair in progressive multiple sclerosis. Although newer therapies for relapsing MS have the potential to be more effective and easier to administer than current therapies, they also carry greater risks. Effective treatments for progressive multiple sclerosis are still being sought.

Sphingolipids in inflammation: pathological implications and potential therapeutic targets

Sphingolipids are formed via the metabolism of sphingomyelin, a constituent of the plasma membrane, or by de novo synthesis. Enzymatic pathways result in the formation of several different lipid mediators, which are known to have important roles in many cellular processes, including proliferation, apoptosis and migration. Several studies now suggest that these sphingolipid mediators, including ceramide, ceramide 1-phosphate and sphingosine 1-phosphate (S1P), are likely to have an integral role in inflammation. This can involve, for example, activation of pro-inflammatory transcription factors in different cell types and induction of cyclooxygenase-2, leading to production of pro-inflammatory prostaglandins. The mode of action of each sphingolipid is different. Increased ceramide production leads to the formation of ceramide-rich areas of the membrane, which may assemble signalling complexes, whereas S1P acts via high-affinity G-protein-coupled S1P receptors on the plasma membrane. Recent studies have demonstrated that in vitro effects of sphingolipids on inflammation can translate into in vivo models. This review will highlight the areas of research where sphingolipids are involved in inflammation and the mechanisms of action of each mediator. In addition, the therapeutic potential of drugs that alter sphingolipid actions will be examined with reference to disease states, such as asthma and inflammatory bowel disease, which involve important inflammatory components. A significant body of research now indicates that sphingolipids are intimately involved in the inflammatory process and recent studies have demonstrated that these lipids, together with associated enzymes and receptors, can provide effective drug targets for the treatment of pathological inflammation.

FTY720 inhibits ceramide synthases and up-regulates dihydrosphingosine 1-phosphate formation in human lung endothelial cells

Novel immunomodulatory molecule FTY720 is a synthetic analog of myriocin, but unlike myriocin FTY720 does not inhibit serine palmitoyltransferase. Although many of the effects of FTY720 are ascribed to its phosphorylation and subsequent sphingosine 1-phosphate (S1P)-like action through S1P(1,3-5) receptors, studies on modulation of intracellular balance of signaling sphingolipids by FTY720 are limited. In this study, we used stable isotope pulse labeling of human pulmonary artery endothelial cells with l-[U-(13)C, (15)N]serine as well as in vitro enzymatic assays and liquid chromatography-tandem mass spectrometry methodology to characterize FTY720 interference with sphingolipid de novo biosynthesis. In human pulmonary artery endothelial cells, FTY720 inhibited ceramide synthases, resulting in decreased cellular levels of dihydroceramides, ceramides, sphingosine, and S1P but increased levels of dihydrosphingosine and dihydrosphingosine 1-phosphate (DHS1P). The FTY720-induced modulation of sphingolipid de novo biosynthesis was similar to that of fumonisin B1, a classical inhibitor of ceramide synthases, but differed in the efficiency to inhibit biosynthesis of short-chain versus long-chain ceramides. In vitro kinetic studies revealed that FTY720 is a competitive inhibitor of ceramide synthase 2 toward dihydrosphingosine with an apparent K(i) of 2.15 microm. FTY720-induced up-regulation of DHS1P level was mediated by sphingosine kinase (SphK) 1, but not SphK2, as confirmed by experiments using SphK1/2 silencing with small interfering RNA. Our data demonstrate for the first time the ability of FTY720 to inhibit ceramide synthases and modulate the intracellular balance of signaling sphingolipids. These findings open a novel direction for therapeutic applications of FTY720 that focuses on inhibition of ceramide biosynthesis, ceramide-dependent signaling, and the up-regulation of DHS1P generation in cells.

Full pharmacological efficacy of a novel S1P1 agonist that does not require S1P-like headgroup interactions

Strong evidence exists for interactions of zwitterionic phosphate and amine groups in sphingosine-1 phosphate (S1P) to conserved Arg and Glu residues present at the extracellular face of the third transmembrane domain of S1P receptors. The contribution of Arg(120) and Glu(121) for high-affinity ligand-receptor interactions is essential, because single-point R(120)A or E(121)A S1P(1) mutants neither bind S1P nor transduce S1P function. Because S1P receptors are therapeutically interesting, identifying potent selective agonists with different binding modes and in vivo efficacy is of pharmacological importance. Here we describe a modestly water-soluble highly selective S1P(1) agonist [2-(4-(5-(3,4-diethoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl amino) ethanol (CYM-5442)] that does not require Arg(120) or Glu(121) residues for activating S1P(1)-dependent p42/p44 mitogen-activated protein kinase phosphorylation, which defines a new hydrophobic pocket in S1P(1). CYM-5442 is a full agonist in vitro for S1P(1) internalization, phosphorylation, and ubiquitination. It is noteworthy that CYM-5442 was a full agonist for induction and maintenance of S1P(1)-dependent blood lymphopenia, decreasing B lymphocytes by 65% and T lymphocytes by 85% of vehicle. Induction of CYM-5442 lymphopenia was dose- and time-dependent, requiring serum concentrations in the 50 nM range. In vitro measures of S1P(1) activation by CYM-5442 were noncompetitively inhibited by a specific S1P(1) antagonist [(R)-3-amino-(3-hexylphenylamino)-4-oxobutylphosphonic acid (W146)], competitive for S1P, 2-amino-2-(4-octylphenethyl)propane-1,3-diol (FTY720-P), and 5-[4-phenyl-5-(trifluoromethyl)-2-thienyl]-3-[3-(trifluoromethyl)phenyl]-1,2, 4-oxadiazole (SEW2871). In addition, lymphopenia induced by CYM-5442 was reversed by W146 administration or upon pharmacokinetic agonist clearance. Pharmacokinetics in mice also indicated that CYM-5442 partitions significantly in central nervous tissue. These data show that CYM-5442 activates S1P(1)-dependent pathways in vitro and to levels of full efficacy in vivo through a hydrophobic pocket separate from the orthosteric site of S1P binding that is headgroup-dependent.

FTY720 rescue therapy in the dark agouti rat model of experimental autoimmune encephalomyelitis: expression of central nervous system genes and reversal of blood-brain-barrier damage

FTY720 (fingolimod) is an oral sphingosine-1 phosphate (S1P) receptor modulator in phase III development for the treatment of multiple sclerosis. To further investigate its mode of action, we analyzed gene expression in the central nervous system (CNS) during experimental autoimmune encephalomyelitis (EAE). FTY720 downregulated inflammatory genes in addition to vascular adhesion molecules. It decreased the matrix metalloproteinase gene MMP-9 and increased its counterregulator--tissue inhibitor of metalloproteinase, TIMP-1--resulting in a proteolytic balance that favors preservation of blood-brain-barrier (BBB) integrity. Furthermore, FTY720 reduced S1P lyase that increases the S1P concentration in the brain, in line with a marked reversal of neurological deficits and raising the possibility for enhanced triggering of S1P receptors on resident brain cells. This is accompanied by an increase in S1P(1) and S1P(5) in contrast with the attenuation of S1P(3) and S1P(4). Late-stage rescue therapy with FTY720, even up to 1 month after EAE onset, reversed BBB leakiness and reduced demyelination, along with normalization of neurologic function. Our results indicate rapid blockade of ongoing disease processes by FTY720, and structural restoration of the CNS parenchyma, which is likely caused by the inhibition of autoimmune T cell infiltration and direct modulation of microvascular and/or glial cells.

Biodiversity of sphingoid bases ("sphingosines") and related amino alcohols

"Sphingosin" was first described by J. L. W. Thudichum in 1884 and structurally characterized as 2S,3R,4E-2-aminooctadec-4-ene-1,3-diol in 1947 by Herb Carter, who also proposed the designation of "lipides derived from sphingosine as sphingolipides." This category of amino alcohols is now known to encompass hundreds of compounds that are referred to as sphingoid bases and sphingoid base-like compounds, which vary in chain length, number, position, and stereochemistry of double bonds, hydroxyl groups, and other functionalities. Some have especially intriguing features, such as the tail-to-tail combination of two sphingoid bases in the alpha,omega-sphingoids produced by sponges. Most of these compounds participate in cell structure and regulation, and some (such as the fumonisins) disrupt normal sphingolipid metabolism and cause plant and animal disease. Many of the naturally occurring and synthetic sphingoid bases are cytotoxic for cancer cells and pathogenic microorganisms or have other potentially useful bioactivities; hence, they offer promise as pharmaceutical leads. This thematic review gives an overview of the biodiversity of the backbones of sphingolipids and the broader field of naturally occurring and synthetic sphingoid base-like compounds.

FTY720 sustains and restores neuronal function in the DA rat model of MOG-induced experimental autoimmune encephalomyelitis

FTY720 (fingolimod) is an oral sphingosine 1-phosphate (S1P) receptor modulator under development for the treatment of multiple sclerosis (MS). To elucidate its effects in the central nervous system (CNS), we compared functional parameters of nerve conductance in the DA rat model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) after preventive and therapeutic treatment. We demonstrate that prophylactic therapy protected against the emergence of EAE symptoms, neuropathology, and disturbances to visual and somatosensory evoked potentials (VEP, SEP). Moreover, therapeutic treatment from day 25 to 45 markedly reversed paralysis in established EAE and normalized the electrophysiological responses, correlating with decreased demyelination in the brain and spinal cord. The effectiveness of FTY720 in this model is likely due to several contributing factors. Evidence thus far supports its role in the reduction of inflammation and preservation of blood-brain-barrier integrity. FTY720 may also act via S1P receptors in glial cells to promote endogenous repair mechanisms that complement its immunomodulatory action.