A versatile Plasmodium falciparum reporter line expressing NanoLuc enables highly sensitive multi-stage drug assays.

Transgenic luciferase-expressing Plasmodium falciparum parasites have been widely used for the evaluation of anti-malarial compounds. Here, to screen for anti-malarial drugs effective against multiple stages of the parasite, we generate a P. falciparum reporter parasite that constitutively expresses NanoLuciferase (NanoLuc) throughout its whole life cycle. The NanoLuc-expressing P. falciparum reporter parasite shows a quantitative NanoLuc signal in the asexual blood, gametocyte, mosquito, and liver stages. We also establish assay systems to evaluate the anti-malarial activity of compounds at the asexual blood, gametocyte, and liver stages, and then determine the 50% inhibitory concentration (IC50) value of several anti-malarial compounds. Through the development of this robust high-throughput screening system, we identify an anti-malarial compound that kills the asexual blood stage parasites. Our study highlights the utility of the NanoLuc reporter line, which may advance anti-malarial drug development through the improved screening of compounds targeting the human malarial parasite at multiple stages.

Development of Cycloisomerization with Rearrangement of a Tosyl Group Using N-Tosyl-o-allenylaniline.

Sulfonyl indoles were synthesized by migratory cycloisomerization from the allene N-tosyl-o-allenylaniline. 3-Tosyl indoles or 4-tosyl indoles were selectively produced using a Pd catalyst or a Au catalyst, respectively.

Reagent-Controlled Regioselective Intramolecular [2+2] Cycloaddition between Vinylsilanes and Allenes.

This paper provides the first report of the intramolecular [2+2] cycloaddition of vinylsilane. The [2+2] cycloaddition of allenes is a useful reaction that can synthesize cyclobutanes. However, no previous works have attempted to control the regioselectivity between the two double bonds of allenes only by changing the reaction conditions, although there have been some reports of the regioselective [2+2] cycloaddition of allenes by changing the substrate. In this study, we have succeeded in controlling intramolecular [2+2] cycloaddition reactions at the proximal and distal positions of allenes simply by changing the reaction conditions. We found that the atomic radius of silicon is very important for perfect control of the reaction's sites. The structures of all key compounds were determined by the crystal sponge method which could identify the structures of liquid compounds.

Direct synthesis of dialkylarylvinylsilane derivatives: metathesis of dialkylaryl-iso-propenylsilane and its application to tetracyclic silacycle dye synthesis.

The metathesis of dialkylarylvinylsilane, which has not been accomplished to date, is achieved using dialkylaryl-iso-propenylsilane as a substrate. In addition, we discovered that the reason why the metathesis of a ruthenium carbene complex and dialkylarylvinylsilane is difficult is the formation of a carbide complex.

Pd-Catalyzed Migratory Cycloisomerization of N-Allyl- o-allenylaniline Derivatives.

The Pd-catalyzed migratory cycloisomerization of N-allyl- o-allenyl aniline derivatives is first reported to give indoles having a substituent at the 2-position.

Cascade Multiple Diels-Alder Reactions of Styrene Derivatives with Maleimide or Maleic Anhydride.

We developed novel one-pot multiple Diels-Alder reactions, which are frequently used in the construction of six-membered rings in functional molecular synthesis. We report triple and double Diels-Alder reactions with styrene derivatives, where the secondary Diels-Alder reaction takes place at a different position from that of the conventional Wagner-Jauregg reaction.

Palladium-Catalyzed Seven-Membered Silacycle Construction: 1,7-Enyne Hydroxycyclization To Give a Benzosilepine Skeleton.

A palladium-catalyzed hydroxycyclization reaction of 1,7-enynes to afford seven-membered silacycles (1 H-benzo[ b]silepine skeletons) is developed. This is the first example of both seven-membered ring construction from enynes using a palladium catalyst and hydroxycyclization of enynes to give seven-membered silacycles.

One-pot enyne metathesis/Diels-Alder/oxidation to six-membered silacycles with a multi-ring core: discovery of novel fluorophores.

Polycyclic compounds containing a six-membered silacycle are important. However, we have limited knowledge of the nature of these six-membered silacycles because methodologies for their synthesis remain under-developed. Here, we have developed a one-pot enyne metathesis/Diels-Alder/oxidation methodology for the synthesis of six-membered silacycles. Some of these compounds are novel fluorophores.

Development of a novel sulfonate ester-based prodrug strategy.

A self-immolative γ-aminopropylsulfonate linker was investigated for use in the development of prodrugs that are reactive to various chemical or biological stimuli. To demonstrate their utility, a leucine-conjugated prodrug of 5-chloroquinolin-8-ol (5-Cl-8-HQ), which is a potent inhibitor against aminopeptidase from Aeromonas proteolytica (AAP), was synthesized. The sulfonate prodrug was considerably stable under physiological conditions, with only enzyme-mediated hydrolysis of leucine triggering the subsequent intramolecular cyclization to simultaneously release 5-Cl-8-HQ and form γ-sultam. It was also confirmed that this γ-aminopropylsulfonate linker was applicable for prodrugs of not only 8-HQ derivatives but also other drugs bearing a phenolic hydroxy group.

Development of an Enyne Metathesis/Isomerization/Diels-Alder One-Pot Reaction for the Synthesis of a Novel Near-Infrared (NIR) Dye Core.

N-Alkyl-N-allyl-2-alkynylaniline derivatives undergo a tandem ring-closing enyne metathesis/isomerization/Diels-Alder cycloaddition sequence in the presence of a second-generation Grubbs catalyst and dienophiles. In practice, the acyclic enyne in the presence of the ruthenium alkylidene first undergoes ring-closing metathesis to generate cyclic 4-vinyl-1,2-dihydroquinolines; following diene isomerization and then the addition of a dienophile, these ring-closing metathesis products are selectively converted into a 7-methyl-4H-naphtho[3,2,1-de]quinoline-8,11-dione core. Overall, the reaction sequence converts simple aniline derivatives into π-conjugated small molecules, which have characteristic absorption in the near-infrared region, in a single operation through three unique ruthenium-catalyzed transformations.

Nitrogen-containing bisphosphonate, YM529/ONO-5920 (a novel minodronic acid), inhibits RANKL expression in a cultured bone marrow stromal cell line ST2.

Increase in bone resorption by osteoclasts can cause metabolic bone diseases, such as osteoporosis. Recent attention has been paid to the receptor activator of the NF-kappaB ligand (RANKL), an accelerator of osteoclast differentiation. RANKL is expressed on the bone marrow-derived stromal cell membrane and induces the differentiation of osteoclasts by binding to RANK expressed on the osteoclast precursor cell membrane. Since the inhibition of RANKL expression can lead to the inhibition of osteoclastic bone resorption, the clinical application of RANKL inhibition could be expected to have a major effect on metabolic bone disease therapy. In this study, we investigated whether or not YM529/ONO-5920, a nitrogen-containing bisphosphonate (a novel minodronic acid), inhibits RANKL expression in a bone marrow-derived stromal cell line (ST2 cells). Reverse transcription-polymerase chain reaction revealed that the administration of YM529/ONO-5920 to ST2 cells inhibited RANKL mRNA expression and reduced RANKL proteins as assessed by Western blot analysis. The inhibition of RANKL mRNA expression was reversed when geranylgeranyl pyrophosphate (GGPP), an intermediate in the mevalonate pathway, was used in combination. Furthermore, YM529/ONO-5920 reduced phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2), and similarly, U0126, a mitogen-activated protein kinase kinase 1/2 inhibitor, inhibited RANKL expression. Pretreatment with GGPP reversed the YM529/ONO-5920-induced decrease in phosphorylation of ERK. Furthermore, YM529/ONO-5920 decreased TRAP-positive cells in co-culture of ST2 cells and an osteoclast cell line, C7 cells, and this decrease was inhibited by pretreatment with GGPP. This indicates that YM529/ONO-5920 inhibits GGPP biosynthesis in the mevalonate pathway and then signal transduction in the Ras-mitogen-activated protein kinase pathway, thereby inhibiting RANKL expression on ST2 cells. These results suggest a newly elucidated action of bisphosphonates in the inhibition of bone resorption.

Pretreatment with PKC inhibitor triggers TNF-alpha induced apoptosis in TNF-alpha-resistant B16 melanoma BL6 cells.

Tumor necrosis factor alpha (TNF-alpha) modulates various events through several different pathways. Many tumor cells are resistant to this cytokine. Pretreatment of these cells with actinomycin D enhances TNF-alpha-induced apoptosis. In the present study, we investigated the mechanism of this enhancement and whether or not the apoptosis of TNF-alpha-resistant cancer cells can be induced by the inhibition of Protein kinase C (PKC). When TNF-alpha was added after inhibition of PKC by H7, apoptosis was observed, and companied with the activation of nuclear factor kappa B (NF-kappaB). After the inhibition of protein kinase B (Akt) by LY294002 or p38 mitogen-activated protein kinase (p38MAPK) by SB203580, the addition of TNF-alpha did not cause apoptosis. However, after the inhibition of MAPK/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) with U0126, apoptosis was observed when TNF-alpha was added. In the Western blotting analysis, phosphorylation of MEK1/2 occurred at 60 minutes after the addition of TNF-alpha. However, it was noted that after pretreatment with H7, a significant decrease in phosphorylated MEK1/2 was observed. The present findings suggest that MEK1/2 plays an important role in TNF-alpha-resistance in TNF-alpha-resistant B16 melanoma BL6 cells. Furthermore, it was found that MEK1/2 is more important than NF-kappaB, Akt, and p38MAPK in anti-apoptotic PKC signaling and that TNF-alpha-resistance can be overcome by inhibiting MEK1/2. These results suggest the possibility of development of a new anticancer drug treatment.

A new bisphosphonate, YM529 induces apoptosis in HL60 cells by decreasing phosphorylation of single survival signal ERK.

It is believed that bisphosphonates (BPs) induce apoptosis in cells such as myeloma cells, as they inhibit prenylation of G-proteins. However, the details of the apoptosis-inducing mechanism remain obscure. In the present study, we attempted to clarify the mechanism by which YM529, a new bisphosphonate, induces apoptosis. YM529 induced cell deaths in HL60 cells in a concentration-dependent manner. At that time, we observed an increase in Caspase-3 activity and morphological fragmentation of the nuclei. We could confirm that these cell deaths were evidence of apoptosis. The apoptosis induced by YM529 was not inhibited by the addition of farnesyl pyrophosphate (FPP), but was by the addition of geranylgeranyl pyrophosphate (GGPP). When we examined the survival signals at the time of apoptotic induction, we also observed that the administration of YM529 caused a remarkable decrease in the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). However, other survival signals such as nuclear factor kappa B (NF-kappaB), protein kinase B (Akt), and p38 mitogen-activated protein kinase (p38) exhibited no change. In addition, no quantitative change was observed in Bcl-2, which is an anti-apoptosis protein. It was also observed that apoptosis was induced when U0126, an MEK inhibitor, was added to the cells to inhibit ERK. These results suggest that YM529, the new bisphosphonate, induced apoptosis when inhibit GGPP synthase and consequently decreased the levels of phosphorylated ERK, which is a survival signal; moreover, during this process, there is no influence on NF-kappaB, Akt, p38, and Bcl-2. The results of this study also suggest that YM529 can be used as an anticancer agent, in addition to its use as a therapeutic agent to treat osteoporosis.

Apoptosis-inducing effect of a new bisphosphonate, YM529, on various hematopoietic tumor cell lines.

In recent years, it has been reported that bisphosphonates inhibited the cell cycle of myeloma cells to inhibit cell proliferation directly, and it was also reported that bisphosphonates induced apoptosis of myeloma cells in vitro. Recently, YM529 was developed as a new third-generation bisphosphonate. In our experiment, we investigated whether YM529 showed an antitumor effect on hematopoietic tumor cell lines other than myeloma, and we compared YM529 with YM175, which had a relatively more potent antitumor effect than that of existing bisphosphonates. We found that YM529 inhibited cell proliferation in various hematopoietic tumor cell lines (acute promyelocytic leukemia cell line HL-60, chronic myeloid leukemia cell line K562, histiocytic lymphoma cell line U937, lymphoblastic leukemia T cell line Jurkat, acute lymphoblastic leukemia T cell line MOLT-4, lymphoblastic leukemia B cell line CCRF-SB) including myeloma (myeloma cell line HS-Sultan) dose-dependently and time-dependently to a degree equivalent or superior to that in myeloma, and induced apoptosis at a lower concentration as compared with YM175. We confirmed many dead cells as well as apoptosis based on the detection of the nuclei with separate globular structure, the activation of caspase-3, and the decrease in mitochondrial transmembrane potential. Therefore, it is concluded that further utilization of YM529 can be expected against hematopoietic tumor cells in the future.