Biomedical subjects

Andreas Billich

Publications and source records attributed to Andreas Billich.

At least 19 recordsLinked to original sources

PubMed2007

Drug evaluation: apilimod, an oral IL-12/IL-23 inhibitor for the treatment of autoimmune diseases and common variable immunodeficiency.

Apilimod is a small molecule that inhibits IL-12 and IL-23 production - cytokines that are involved in autoimmune diseases - through the prevention of nuclear translocation of c-Rel. Synta Pharmaceuticals Corp is developing apilimod for the potential treatment of Crohn's disease (CD) and other autoimmune diseases. Preclinical studies demonstrated the successful inhibition of IL-12 and IL-23 production by the drug. In the clinical setting, apilimod has been generally well tolerated, with mild-to-moderate side effects reported, including headaches and nausea. Patients with CD responded within 14 days of treatment with apilimod and, after 28 days, the drug significantly reduced the Crohn's disease activity index (CDAI). Apilimod is currently in phase II clinical trials for rheumatoid arthritis, common variable immunodeficiency and CD. From the data available to date, apilimod appears to be a promising treatment for CD, and the oral formulation of this compound provides an advantage for apilimod over injectable therapies.

Animals↗

PubMed2006

A critical beta6-beta7 loop in the pleckstrin homology domain of ceramide kinase.

CerK (ceramide kinase) produces ceramide 1-phosphate, a sphingophospholipid with recognized signalling properties. It localizes to the Golgi complex and fractionates essentially between detergent-soluble and -insoluble fractions; however, the determinants are unknown. Here, we made a detailed mutagenesis study of the N-terminal PH domain (pleckstrin homology domain) of CerK, based on modelling, and identified key positively charged amino acid residues within an unusual motif in the loop interconnecting beta-strands 6 and 7. These residues are critical for CerK membrane association and polyphosphoinositide binding and activity. Their mutagenesis results in increased thermolability, sensitivity to proteolysis, reduced apparent molecular mass as well as propensity of the recombinant mutant protein to aggregate, indicating that this loop impacts the overall conformation of the CerK protein. This is in contrast with most PH domains whose function strongly relies on charges located in the beta1-beta2 loop.

Amino Acid Sequence↗

PubMed2006

Constrained azacyclic analogues of the immunomodulatory agent FTY720 as molecular probes for sphingosine 1-phosphate receptors.

Constrained azacyclic analogues of FTY720 were prepared starting with d- and l-pyroglutamic acids. One enantiomer was shown to be a substrate for sphingosine kinase 2, being phosphorylated 4-fold more efficiently than FTY720. Among the corresponding phosphates, two were found to have unusual specificity in binding to S1P receptors: while being inactive on S1P1 and S1P3, they acted as potent agonists on S1P4 and S1P5. The phosphates may be useful to explore the biology and binding site of these receptors.

Animals↗

PubMed2006

Effects of ceramide-1-phosphate on cultured cells: dependence on dodecane in the vehicle.

Ceramide-1-phosphate (C1P), the product of ceramide kinase, is a sphingophospholipid with recently recognized signaling properties. In particular, it was reported to be mitogenic and capable of direct stimulation of cytosolic phospholipase A(2alpha). Much of the present knowledge has relied on the use of C1P of various acyl chain lengths, together with diverse protocols to deliver it to cultured cells. A mixture of ethanol (or methanol) with dodecane, as the vehicle, has become popular. However, the contribution of this solvent to the observed effects of C1P has not been documented. Here, we show that addition of C1P in ethanol-dodecane to culture medium leads to irreversible cytotoxic effects. These culminate in mitochondrial swelling, vacuole formation, and cell death. Not only the toxicity of C1P, but also its ability to trigger prostaglandin E2 release, is fully dependent upon addition of a premade C1P-dodecane mixture. Furthermore, we show that these effects are not restricted to C1P. They result from the capacity of dodecane to interact with phospholipids; hence, they go undetected with a vehicle control. This study should raise awareness about the use of dodecane for phospholipid delivery and, in turn, help in unraveling C1P signaling, which is still poorly understood.

Alkanes↗

PubMed2006

Sphingosine 1-phosphate phosphatase 2 is induced during inflammatory responses.

Sphingosine 1-phosphate (S1P) levels in cells and, consequently, its bioactivity as a signalling molecule are controlled by the action of enzymes responsible for its synthesis and degradation. In the present report, we examined alterations in expression patterns of enzymes involved in S1P-metabolism (sphingosine kinases including their splice variants, sphingosine 1-phosphate phosphatases, and sphingosine 1-phosphate lyase) under certain inflammatory conditions. We found that sphingosine kinase type 1 (SPHK1) mRNA could be triggered in a cell type-specific manner; individual SPHK1 splice variants were induced with similar kinetics. Remarkably, expression and activity of S1P phosphatase 2 (SPP2) was found to be highly upregulated by inflammatory stimuli in a variety of cells (e.g., neutrophils, endothelial cells). Bandshift analysis using oligonucleotides spanning predicted NFkappaB sites within the SPP2 promoter and silencing of NFkappaB/RelA via RelA-directed siRNA demonstrated that SPP2 is an NFkappaB-dependent gene. Silencing of SPP2 expression in endothelial cells, in turn, led to a marked reduction of TNF-alpha-induced IL-1beta mRNA and protein and to a partial reduction of induced IL-8, suggesting a pro-inflammatory role of SPP2. Notably, up-regulation of SPP2 was detected in samples of lesional skin of patients with psoriasis, an inflammatory skin disease. This study provides detailed insights into the regulation of SPP2 gene expression and suggests that SPP2 might be a novel player in pro-inflammatory signalling.

Binding Sites↗

PubMed2005

NBD-labeled derivatives of the immunomodulatory drug FTY720 as tools for metabolism and mode of action studies.

Fluorescently labeled chiral analogs of the immunomodulatory drug FTY720 and its corresponding phosphates with variable aliphatic spacers between the aromatic ring and the NBD label have been synthesized. Determining the influence of the spacer on the in vitro phosphorylation rate by SPHK1 and 2 resulted in the identification of NBD-(R)-AAL 1c,d which are phosphorylated with an efficiency comparable to that of the unlabeled FTY720 analog (R)-AAL. Furthermore, the NBD-(R)-AAL phosphates 10c,d were proven to be a functional S1P receptor agonist.

Calcium↗

PubMed2005

Sphingosine kinase type 2 is essential for lymphopenia induced by the immunomodulatory drug FTY720.

FTY720, a potent immunomodulatory drug in phase 2/3 clinical trials, induces rapid and reversible sequestration of lymphocytes into secondary lymphoid organs, thereby preventing their migration to sites of inflammation. As prerequisite for its function, phosphorylation of FTY720 to yield a potent agonist of the sphingosine-1-phosphate receptor S1P(1) is required in vivo, catalyzed by an as-yet-unknown kinase. Here, we report on the generation of sphingosine kinase 2 (SPHK2) knockout mice and demonstrate that this enzyme is essential for FTY720 phosphate formation in vivo. Consequently, administration of FTY720 does not induce lymphopenia in SPHK2-deficient mice. After direct dosage of FTY720 phosphate, lymphopenia is only transient in this strain, indicating that SPHK2 is constantly required to maintain FTY720 phosphate levels in vivo.

Animals↗

PubMed2005

Novel cyclosporin derivatives featuring enhanced skin penetration despite increased molecular weight.

Topical cyclosporin A (CsA, 1) is not effective in the treatment of skin diseases, due to its low skin penetration. Following a prodrug strategy, a series of novel derivatives of 1 and of 2-[O-(2-hydroxyethyl)-d-Ser(8)]-CsA (SDZ IMM 125, 5) with potentially enhanced skin penetration properties were synthesized, in order to achieve higher levels of the active parent drugs in the skin. Permeation through skin and prodrug/drug levels in the skin were measured in vitro using rat and human skin. Introduction of a polar side chain, either in the form of a positively charged quaternary amine, a negatively charged phosphate or sulfate, or an amphiphilic phosphocholine moiety, generally increased permeability. Maximal increase in permeability through skin relative to CsA was up to 300-fold with rat skin, and up to 16-fold with human skin. Penetration into skin, as evaluated by measurement of prodrug/drug concentrations in the skin after 48 h, could be enhanced up to 14-fold (rat and human skin). Increases of permeation rates and skin concentrations showed no strict correlation. Using the phosphate 10 as prodrug, a 2.5-fold higher concentration of the active parent compound (5) could be achieved in rat skin as when administering 5 itself. The results demonstrate that in contrast with the '500 Dalton rule', which postulates poor skin penetration of molecules larger than 500 Da, high skin permeation can be achieved also with compounds of a molecular weight in the range between 1200 and 1600 Da. Results also indicate that in principle higher skin levels of active drug can be attained with a prodrug strategy in this class of compounds.

Administration, Topical↗

PubMed2005

Characterization of a ceramide kinase-like protein.

Ceramide is a key player governing cell fate, and its conversion to ceramide-1-phosphate by ceramide kinase (CERK) is emerging as an important mean to regulate apoptosis and inflammatory processes. We identified a new ceramide kinase homolog, designated CERK-like protein (CERKL) and we compared it to the known CERK. Real time-PCR analysis of human tissues revealed a restricted pattern of expression for CERKL mRNA. Surprisingly, various ceramides, known substrates for CERK, were not phosphorylated by CERKL in vitro. Upon 32P(i)-pulse labeling of COS-1 cells transiently expressing CERKL, or incubation with NBD-C6-ceramide, ceramide-1-phosphate was not detected. After recombinant expression in COS-1 cells, CERKL was partially recovered in the soluble fraction, as a phosphorylated protein. Live cell imaging indicated localization of GFP-tagged CERKL to many cell compartments, including specific association with nucleoli. Two splice variants of CERKL did not localize to nucleoli nor did a CERKL variant with a point mutation in the putative ATP binding site. We also studied a naturally occurring CERKL mutant (R257X), recently linked to the pathology of retinitis pigmentosa. It accumulated in the nucleus but was not associated with nucleoli. Treatment with the calcium ionophore A23187 led to clearing of CERKL from nucleoli, but had no effect on the R257X CERKL mutant. Collectively, although kinase activity of CERKL remains to be proven, these findings suggest a functional link between CERKL and its nucleolar localization. Furthermore, we propose that the cause for retinitis pigmentosa in patients bearing the CERKL R257X mutation might be the accumulation of a truncated CERKL protein in the nucleus.

Amino Acid Sequence↗

PubMed2005

N-Acyl arylsulfonamides as novel, reversible inhibitors of human steroid sulfatase.

Steroid sulfatase (STS) is an attractive target for a range of oestrogen- and androgen-dependent diseases. In search of novel chemotypes of STS inhibitors, we had previously identified nortropinyl-arylsulfonylureas 1; however, while these compounds were good inhibitors of purified STS (lowest K(i)=76 nM), they showed only weak inhibition of STS activity in cells (lowest IC(50) around 2 microM). Extended structure-activity relationship studies involving modification of the phenylacetyl side chain and replacement of the nortropine element by simpler scaffolds led to the discovery of N-acyl arylsulfonamides, more specifically N-(Boc-piperidine-4-carbonyl)-benzenesulfonamides, as STS inhibitors, some of which exhibit improved cellular potency (best IC(50)=270 nM).

Animals↗

PubMed2005

The role of sphingosine and ceramide kinases in inflammatory responses.

The 1-phosphates of sphingosine and ceramide (S1P and C1P) have emerged as key representatives of a new group of lipid signalling molecules. S1P is known to act both as an extracellular mediator and as an intracellular 'second messenger,' while C1P currently is only known for its intracellular actions. Therefore, sphingosine and ceramide kinases, the enzymes involved in the generation of these lipid mediators, are now in the spotlight. This review summarizes current information on structure, localization, substrate specificity, activation, and binding partners of these kinases, and then focuses on discoveries in relation to immune cell regulation and inflammation, addressing in particular mast cell activation and degranulation, IL-12 signalling, prostaglandin biosynthesis, monocyte activation, and neutrophil priming.

Animals↗

PubMed2005

Basal and induced sphingosine kinase 1 activity in A549 carcinoma cells: function in cell survival and IL-1beta and TNF-alpha induced production of inflammatory mediators.

Sphingosine-1-phosphate, a lipid mediator produced by sphingosine kinases, regulates diverse cellular processes, ranging from cell growth and survival to effector functions, such as proinflammatory mediator synthesis. Using human A549 epithelial lung carcinoma cells as a model system, we observed transient upregulation of sphingosine kinase type 1 (SPHK1) enzyme activity upon stimulation with both TNF-alpha or IL-1beta. This transient activation of SPHK1 was found to be required for cytokine-induced COX-2 transcription and PGE2 production, since not only specific siRNA (abolishing both basal and induced SPHK1 enzyme activity), but also a dominant-negative SPHK1 mutant (suppressing induced SPHK1 activity only) both reduced COX-2 and PGE2. Furthermore, TNF-alpha- or IL-1beta-induced transcription of selected cytokines, chemokines, and adhesion molecules (IL-6, RANTES, MCP-1, and VCAM-1) was found to require SPHK1 activation. Suppression of SPHK1 activation led to reduction of cytokine-induced IkappaBalpha phosphorylation and consequently diminished NFkappaB activity due to reduced nuclear translocation of RelA (p65), explaining the dependence of inflammatory mediator production on SPHK1 activation. Inhibition of basal SPHK1 activity by N,N-dimethylsphingosine or by downregulation of its expression using siRNA induced spontaneous apoptosis in A549 cells, an effect that can be explained through interference with constitutive NFkappaB activity in this cell type. In contrast, expression of the dominant-negative mutant did not induce apoptosis. Taken together, these findings demonstrate a role of SPHK1 activation in proinflammatory signalling and of SPHK1 basal activity in survival of A549 lung carcinoma cells.

Apoptosis↗

PubMed2005

Pimecrolimus permeates less than tacrolimus through normal, inflamed, or corticosteroid-pretreated skin.

The permeabilities of normal human and normal, inflamed, or corticosteroid (CS) pretreated skin of young domestic pigs for pimecrolimus and tacrolimus were compared in vitro, using Franz-type diffusion cells. The test articles were either used as 1.0% solutions or as the marketed formulations (Elidel 1% cream, Protopic 0.1%, and 0.03% ointment). In normal human skin, the permeation rate of pimecrolimus from the 1% cream was about sixfold lower than that of tacrolimus from 0.1% ointment and by a factor of 4.3 lower compared with tacrolimus from Protopic 0.03%. In pigs, sodium laurylsulfate-induced irritant contact dermatitis resulted in significantly faster skin permeation of both drugs from applied solutions. The permeation rate for pimecrolimus was lower than that for tacrolimus. Thus, at 24 h, pimecrolimus concentrations in the receptor fluid were 2.8-fold lower than the tacrolimus levels. Compared with normal porcine skin, permeation of drugs through hydrocortisone (1.0%)-, mometasone (0.1%)-, or clobetasol-17-butyrate (0.05%)-pretreated skin was increased by factors of 3.6 (pimecrolimus, applied as 1% cream) and 1.7 (tacrolimus, applied as 0.1% ointment). In normal pig skin, the permeation rate of tacrolimus was found to be 11.2 times higher than that of pimecrolimus and 3.5- to 7.1-fold higher in CS-pretreated skin, independent of the potency of the CSs. The present in vitro data suggest that in patients with acute skin inflammation or after therapy with topical CSs, percutaneous absorption and, as a consequence, systemic drug exposure will be lower with Elidel 1% cream as compared with Protopic 0.1% and 0.03% ointment.

Adrenal Cortex Hormones↗

PubMed2005

Steroid sulfatase inhibitors: their potential in the therapy of breast cancer.

Steroid sulfatase (STS) is the only well characterized enzyme in human cells that is capable to desulfate estrone 3-sulfate (E1S) and dehydroepiandrosterone sulfate (DHEAS) as a first step in the conversion of these precursors to active hormones. STS has been found to be highly expressed in estrogen-dependent breast tumors in post-menopausal women and is regarded as a crucial component of the local estrogen production that is required for tumor growth and survival. Inhibitors of STS are expected to block the intra-tumoral estrogen synthesis and, therefore, are considered as potential new therapeutic agents for the treatment of estrogen-dependent cancers of the breast and the endometrium. In this review, we give an overview on the current status in the field of medicinal chemistry of STS inhibitors. Newer developments comprise potent aryl sulfamate-based irreversible inhibitors, and several types of reversible inhibitors. Other directions include compounds with dual mode of action, such as compounds that block both STS and aromatase, or act as STS inhibitors and antiproliferative or antiangiogenic agents at the same time. In particular, these agents featuring an extended mode of action hold promise to be included in the armamentarium to fight endocrine-dependent cancer.

Animals↗

PubMed2004

Ceramide kinase targeting and activity determined by its N-terminal pleckstrin homology domain.

The N-terminus of ceramide kinase (CERK) is thought to be myristoylated and to contain a pleckstrin homology (PH) domain. We found that deletion of this region (DeltaPH-CERK) ablates activity. This is not due to prevention of N-terminal myristoylation since a G2A CERK mutant, which cannot be myristoylated, was active. CERK was able to bind liposomes, as well as the isolated unmyristoylated PH domain; DeltaPH-CERK was not. Upon analysis of EGFP-tagged proteins, CERK was found associated with the Golgi complex. Osmotic cell swelling induced translocation of CERK to the plasma membrane and formation of large vesicles displaying bound CERK. None of these features occurred with DeltaPH-CERK, which remained disseminated throughout the cytoplasm. These findings show that the PH domain of CERK is essential for localization, translocation, and activity of this lipid kinase.

Animals↗

PubMed2004

Estrone formate: a novel type of irreversible inhibitor of human steroid sulfatase.

A series of estrone conjugates of the type estrone-3-O-C(O,S)-X have been prepared and evaluated for inhibition of human steroid sulfatase (STS). Among the carbamate (6), thiocarbamate (8), cyanate (7), formate (9), and acetate (10) analogs of estrone, only 9 was found to inhibit STS in a time- and concentration-dependent manner. With an IC(50) of 0.42 microM 9 is the first potent inactivator of STS which does not feature the sulfamate group. Furthermore a formate-type inhibitor featuring a benzoxazole moiety in place of the steroid skeleton (14) was prepared, suggesting a general principle of inactivation by the formate group. As the mode of action we propose an immediate transfer of the formyl moiety to a nucleophilic residue in the active site of STS.

Binding Sites↗

PubMed2004

2-(1-adamantyl)-4-(thio)chromenone-6-carboxylic acids: potent reversible inhibitors of human steroid sulfatase.

Steroid sulfatase (STS) is an attractive target for the potential therapy of a number of estrogen- and androgen-dependent disorders. Most potent STS inhibitors known so far act as irreversible enzyme blockers and feature an aryl sulfamate moiety; even minor modifications at the sulfamate group result in drastically decreased activity. On the basis of a recently reported subclass of highly potent STS inhibitors, i.e., chromenone sulfamates, we now extended the investigation of structure-activity relationships to hitherto unstudied sulfamate replacements. Thereby, we discovered 2-(1-adamantyl)-4-(thio)chromenone-6-carboxylic acids (5d and 5j) as potent, reversible inhibitors of STS. In a cell-free system using purified human STS, both new inhibitors show similar Ki values (0.50 microM and 0.53 microM, respectively). However, the thio analogue 5j is superior to 5d (IC50 = 0.18 microM versus 9.4 microM) in a cellular assay system using CHO cells overexpressing STS. Compound 5j is an example of a reversible STS inhibitor with potent activity toward the target enzyme in a cellular test system. Moreover, 5d,j are stable and have no estrogenic potential.

Adamantane↗

PubMed2004

Fluorescence-labeled sphingosines as substrates of sphingosine kinases 1 and 2.

Fluorescently labeled d-erythro-sphingosines have been successfully synthesized in 9 and 12 steps starting from commercially available Garner aldehyde. Determining the influence of the nature, position and linkage of the label on the in vitro phosphorylation rate by sphingosine kinases 1 and 2 resulted in the identification of a pyrene- and a NBD-labeled sphingosine which are both phosphorylated with efficiency comparable to the natural substrate.

Cell Line↗