Dafachronic acid and temperature regulate canonical dauer pathways during Nippostrongylus brasiliensis infectious larvae activation.

BACKGROUND: While immune responses to the murine hookworm Nippostrongylus brasiliensis have been investigated, signaling pathways regulating development of infectious larvae (iL3) are not well understood. We hypothesized that N. brasiliensis would use pathways similar to those controlling dauer development in the free-living nematode Caenorhabditis elegans, which is formally known as the "dauer hypothesis." METHODS: To investigate whether dafachronic acid activates the N. brasiliensis DAF-12 homolog, we utilized an in vitro reporter assay. We then utilized RNA-Seq and subsequent bioinformatic analyses to identify N. brasiliensis dauer pathway homologs and examine regulation of these genes during iL3 activation. RESULTS: In this study, we demonstrated that dafachronic acid activates the N. brasiliensis DAF-12 homolog. We then identified N. brasiliensis homologs for members in each of the four canonical dauer pathways and examined their regulation during iL3 activation by either temperature or dafachronic acid. Similar to C. elegans, we found that transcripts encoding antagonistic insulin-like peptides were significantly downregulated during iL3 activation, and that a transcript encoding a phylogenetic homolog of DAF-9 increased during iL3 activation, suggesting that both increased insulin-like and DAF-12 nuclear hormone receptor signaling accompanies iL3 activation. In contrast to C. elegans, we observed a significant decrease in transcripts encoding the dauer transforming growth factor beta ligand DAF-7 during iL3 activation, suggesting a different role for this pathway in parasitic nematode development. CONCLUSIONS: Our data suggest that canonical dauer pathways indeed regulate iL3 activation in the hookworm N. brasiliensis and that DAF-12 may be a therapeutic target in hookworm infections.

Detection of Succinate by Intestinal Tuft Cells Triggers a Type 2 Innate Immune Circuit.

In the small intestine, type 2 responses are regulated by a signaling circuit that involves tuft cells and group 2 innate lymphoid cells (ILC2s). Here, we identified the microbial metabolite succinate as an activating ligand for small intestinal (SI) tuft cells. Sequencing analyses of tuft cells isolated from the small intestine, gall bladder, colon, thymus, and trachea revealed that expression of tuft cell chemosensory receptors is tissue specific. SI tuft cells expressed the succinate receptor (SUCNR1), and providing succinate in drinking water was sufficient to induce a multifaceted type 2 immune response via the tuft-ILC2 circuit. The helminth Nippostrongylus brasiliensis and a tritrichomonad protist both secreted succinate as a metabolite. In vivo sensing of the tritrichomonad required SUCNR1, whereas N. brasiliensis was SUCNR1 independent. These findings define a paradigm wherein tuft cells monitor microbial metabolites to initiate type 2 immunity and suggest the existence of other sensing pathways triggering the response to helminths.

A novel blood-feeding detoxification pathway in Nippostrongylus brasiliensis L3 reveals a potential checkpoint for arresting hookworm development.

As part of on-going efforts to control hookworm infection, the "human hookworm vaccine initiative" has recognised blood feeding as a feasible therapeutic target for inducing immunity against hookworm infection. To this end, molecular approaches have been used to identify candidate targets, such as Necator americanus (Na) haemoglobinase aspartic protease-1 (APR-1), with immunogenicity profiled in canine and hamster models. We sought to accelerate the immune analysis of these identified therapeutic targets by developing an appropriate mouse model. Here we demonstrate that Nippostrongylus brasiliensis (Nb), a phylogenetically distant strongylid nematode of rodents, begins blood feeding early in its development and that immunisation with Na-APR-1 can block its growth and completion of its life cycle. Furthermore, we identify a new haem detoxification pathway in Nb required for blood feeding that can be blocked by drugs of the quinolone family, reducing both infection burden and the associated anaemia in rodents. Collectively, our findings show that haem metabolism has potential as a checkpoint for interrupting hookworm development in early stages of the hookworm life cycle and that the Nippostrongylus brasiliensis rodent model is relevant for identifying novel therapeutic targets against human hookworm.

Jietacins, azoxy antibiotics with potent nematocidal activity: Design, synthesis, and biological evaluation against parasitic nematodes.

Jietacins, an azoxy antibiotic class of chemicals, were isolated from the culture broth of Streptomyces sp. KP-197. They have a unique structural motif, including a vinyl azoxy group and a long acyclic aliphatic chain, which is usually branched but non-branched in the case of jietacin C. During a drug discovery program, we found that jietacins display potent anthelmintic activity against parasitic nematodes and that jietacin A has a moderate or low acute toxicity (LD50 > 300 mg/kg) and no mutagenic potential in a mini Ames screen. This suggests that jietacins have potential for drug discovery research. In order to create a novel anthelmintic agent, we performed design, synthesis, and biological evaluation of jietacin derivatives against parasitic nematodes. Of these derivatives, we found that a fully synthesized simplified derivative exhibited better anthelmintic activity against three parasitic nematodes than natural jietacins. In addition, it had a better efficacy in vivo through oral administration against a mouse nematode. This indicated that the azoxy motif could prove useful as a template for anthelmintic discovery, possibly creating a class of anthelmintic with novel skeletons, a potential new mode of action, and providing further insight for rational drug design.

IL-4 up-regulates cyclooxygenase-1 expression in macrophages.

Macrophages use various cell-surface receptors to sense their environment and undergo polarized responses. The cytokines, interleukin (IL)-4 and IL-13, released from T-helper type 2 (Th2) cells, drive macrophage polarization toward an alternatively activated phenotype (M2). This phenotype is associated with the expression of potent pro-resolving mediators, such as the prostaglandin (PG) D2-derived cyclopentenone metabolite, 15d-PGJ2, produced by the cyclooxygenase (Ptgs; Cox) pathway. Interestingly, IL-4 treatment of bone marrow-derived macrophages (BMDMs) significantly down-regulates Cox-2 protein expression, whereas Cox-1 levels are significantly increased. This phenomenon not only challenges the dogma that Cox-1 is only developmentally regulated, but also demonstrates a novel mechanism in which IL-4-dependent regulation of Cox-1 involves the activation of the mechanistic target of rapamycin complex (mTORC). Using specific chemical inhibitors, we demonstrate here that IL-4-dependent Cox-1 up-regulation occurs at the post-transcriptional level via the Fes-Akt-mTORC axis. Activation of AMP-activated protein kinase (AMPK) by metformin, inhibition of mTORC by torin 1, or CRISPR/Cas9-mediated genetic knock-out of tuberous sclerosis complex-2 (Tsc2) blocked the IL-4-dependent expression of Cox-1 and the ability of macrophages to polarize to M2. However, use of 15d-PGJ2 partially rescued the effects of AMPK activation, suggesting the importance of Cox-1 in macrophage polarization as also observed in a model of gastrointestinal helminth clearance. In summary, these findings suggest a new paradigm where IL-4-dependent up-regulation of Cox-1 expression may play a key role in tissue homeostasis and wound healing during Th2-mediated immune responses, such as parasitic infections.

In vivo efficacy of PF1022A and nicotinic acetylcholine receptor agonists alone and in combination against Nippostrongylus brasiliensis.

The cyclooctadepsipeptide PF1022A and the aminophenylamidines amidantel, deacylated amidantel (dAMD) and tribendimidine were tested as examples for drug classes potentially interesting for development as anthelmintics against human helminthiases. These compounds and levamisole were tested alone and in combination to determine their efficacy against the rat hookworm Nippostrongylus brasiliensis. After three oral treatments, intestinal worms were counted. Drug effects on parasite morphology were studied using scanning electron microscopy (SEM). Plasma pharmacokinetics were determined for tribendimidine and dAMD. All drugs reduced worm burden in a dose-dependent manner, however amidantel was significantly less active than the other aminophenylamidines. Combinations of tribendimidine and dAMD with levamisole or PF1022A at suboptimal doses revealed additive effects. While PF1022A caused virtually no changes in morphology, levamisole, dAMD and tribendimidine caused severe contraction, particularly in the hind body region. Worms exposed to combinations of PF1022A and aminophenylamidines were indistinguishable from worms exposed only to aminophenylamidines. After oral treatment with tribendimidine, only the active metabolite dAMD was detectable in plasma and concentrations were not significantly different for oral treatment with dAMD. The results support further evaluation of cyclooctadepsipeptides alone and in combination with cholinergic drugs to improve efficacy. Combining these with registered drugs may help to prevent development of resistance.

In vitro efficacy of cyclooctadepsipepdtides and aminophenylamidines alone and in combination against third-stage larvae and adult worms of Nippostrongylus brasiliensis and first-stage larvae of Trichinella spiralis.

The present study investigates the in vitro efficacy of derivatives of the cyclooctadepsipeptides and the aminophenylamidines, which are promising candidates for the evaluation of the treatment of human soil-transmitted helminthiases. The effects of emodepside and PF1022A as well as of amidantel, deacylated amidantel and tribendimidine were evaluated in a concentration range between 0.01 and 100 µg/ml against third-stage larvae (L3) and adult worms of Nippostrongylus brasiliensis and first-stage larvae (L1) of Trichinella spiralis. Furthermore, drug combinations of PF1022A plus deacylated amidantel or tribendimidine and of tribendimidine plus levamisole were tested for any potential additive or even synergistic interactions. Emodepside had a significantly lower EC(50) value than PF1022A in the T. spiralis (0.02788 vs. 0.05862 µg/ml) and the N. brasiliensis (0.06188 vs. 0.1485 µg/ml) motility assays but not in the acetylcholine esterase secretion assay with adult N. brasiliensis (0.05650 vs. 0.06886 µg/ml). While amidantel showed only minimal or at best partial inhibition of nematode motility and acetylcholine esterase secretion, tribendimidine was nearly as potent as deacylated amidantel. Whereas deacylated amidantel had a significantly lower EC(50) than tribendimidine in the N. brasiliensis L3 motility assay (0.05492 vs. 0.2080 µg/ml), differences were not significant in the T. spiralis L1 motility assay (0.7766 vs. 1.145 µg/ml). Surprisingly, none of the combinations showed improved efficacy when compared to the individual drugs including levamisole/tribendimidine, which have previously been reported to act synergistically against Ancylostoma ceylanicum.

Unusual terpenylated acylphloroglucinols from Dryopteris wallichiana.

Four unusual terpenylated acylphloroglucinols were isolated from the diethyl ether extract of the scales and rhizomes of the fern Dryopteris wallichiana together with the known compounds albaspidins AA and AB, and filixic acids ABA and ABB. Structures of the isolated compounds were established by extensive spectroscopic analysis and their absolute configuration at C-14″ was determined by comparing their CD spectra with those simulated for the respective isomers. Pure acylphloroglucinols displayed moderate in vitro nematocidal activity against L4 stage larvae of Nippostrongylus brasiliensis (LD50=22-121 µM).

Synthesis and anti-intestinal nematode activity of variously substituted benzonaphthyridine derivatives.

A series of benzonaphthyridine derivatives bearing the C=N linkage moiety were designed and synthesized. The structures of all the newly synthesized compounds were identified by elemental analysis, 1H-NMR, 13C-NMR and MS. Their anti-intestinal nematode activities against Nippostrongylus brazilliensis were evaluated in vivo by an oral route in male rats. Among these compounds, at concentrations of 10 mg/kg of rat, the compound 7-chloro-2-methoxy-10-(4-(4'-(1H-indol-5'-yl)methylene)aminophenyl)-amino-benzo[b][1,5] naphthyridine (4n) produced the highest activity, with 80.2% deparasitization. These compounds may find usefulness in the discovery and development of new anti-intestinal drugs.

Antibodies specific for a segment of human membrane IgE deplete IgE-producing B cells in humanized mice.

IgE-mediated hypersensitivity is central to the pathogenesis of asthma and other allergic diseases. Although neutralization of serum IgE with IgE-specific antibodies is in general an efficacious treatment for allergic asthma, one limitation of this approach is its lack of effect on IgE production. Here, we have developed a strategy to disrupt IgE production by generating monoclonal antibodies that target a segment of membrane IgE on human IgE-switched B cells that is not present in serum IgE. This segment is known as the M1' domain, and using genetically modified mice that contain the human M1' domain inserted into the mouse IgE locus, we demonstrated that M1'-specific antibodies reduced serum IgE and IgE-producing plasma cells in vivo, without affecting other immunoglobulin isotypes. M1'-specific antibodies were effective when delivered prophylactically and therapeutically in mouse models of immunization, allergic asthma, and Nippostrongylus brasiliensis infection, likely by inducing apoptosis of IgE-producing B cells. In addition, we generated a humanized M1'-specific antibody that was active on primary human cells in vivo, as determined by its reduction of serum IgE levels and IgE plasma cell numbers in a human PBMC-SCID mouse model. Thus, targeting of human IgE-producing B cells with apoptosis-inducing M1'-specific antibodies may be a novel treatment for asthma and allergy.

Bisabolanes from the red alga Laurencia scoparia.

Three novel halogenated beta-bisabolene sesquiterpenoids (1-3), together with two know triquinane alcohol sesquiterpenes (6 and 7), were isolated from the red alga Laurencia scoparia and their structures elucidated by spectroscopic methods. Single-crystal X-ray crystallography allowed us to confirm the structure of 1 as well as to determine the absolute configuration of all stereocenters. To the best of our knowledge, the isolation of beta-bisabolenes from the genus Laurencia has no precedent in the literature. Compound 1 showed weak in vitro anthelmintic activity against parasitant stage (L4) Nippostrongilus brasiliensis.

Synthesis and biological evaluation of simplified mycothiazole analogues.

Thiazoline and oxazoline analogues of the natural product mycothiazole were synthesized from a common intermediate and evaluated in vitro against HCT-15 colon cancer cells and L(4) larvae of nematode Nippostrongylus brasiliensis. The nature of the heterocyclic moiety seems to modulate the cytotoxic or anthelmintic activity.

[Activity of the anthelmintic agent trichlorophen on the models of human helminthiasis]. / Aktivnost' otechestvennogo antigel'mintika trikhlofena na modeliakh gel'mintozov cheloveka.

Trials of trichlorophen have shown its high efficacy on models of cestode infections: hymenolepiasis (at the adult and cysticercoid stages of development on three types of animals: outbred albino mice, albino rats and golden hamsters), preimaginal echinococciasis alveolaris, larval alveolar echinococciasis (at the early stage of development of the parasite in experiments on cotton rats). The high nematodical activity of trichlorophen was first found on models of trichocephaliasis in DBA/2y mice, nippostrongyloidiasis (in in vitro experiments), and aspiculuriasis in outbred mice. The agent proved to be ineffective at the tissue developmental stage of Hymenolepsis nana (H. nana), the dwarf tapeworm, in albino mice, during experimental opisthorchiasis in golden hamsters. It showed a low efficacy in treating trichinosis in outbred albino mice. Unlike carbamatebenzimidazoles, trichlorophen was inactive at the tissue stage of H. nana; it exerted no effects on the eggs of a dwarf tapeworm in trichinosis. Trichlorophen was also inactive in treating experimental opisthorchiasis in golden hamsters.

Synthesis of anthelmintically active N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A.

The N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A represent novel derivatives with activity against Trichinella spiralis Owen and Nippostrongylus brasiliensis Lane in vitro and against parasitic nematodes in mice and sheep. Some of them show better activity against Hymenolepis nana Siebold, Heterakis spumosa Schneider and Heligmosomoides polygyrus Dujardin in mice than the natural product PF1022A. In particular an improved efficacy against Haemonchus contortus Rudolphi and Trichostrongylus colubriformis Giles in sheep compared to the potent cyclic octadepsipeptide PF1022A and its mono-thionated derivative has been observed. Here we report on a specific modification at the N-methyl amide linkage by using the mono-thionated PF1022A, resulting in novel anthelmintically active backbone analogues of PF 1022A.

Resistance of cotton rats, Sigmodon hispidus, to primary infection by Nippostrongylus brasiliensis.

The resistance of cotton rats, Sigmodon hispidus to Nippostrongylus brasiliensis infection was examined and compared the response to that of the susceptible Indian soft-furred rat, Millardia meltada. After a primary infection with infective third-stage N. brasiliensis larvae (L3), the number of eggs in feces and adult worm recovery rates from the small intestine of cotton rats were significantly lower than in the controls. To determine whether cotton rat resistance was observed during the migratory phase or the intestinal phase, cotton rats and control animals were challenged subcutaneously with L3 or intraduodenally with adult worms, and larval recovery from lungs and adult worm burden were evaluated. The recovery rate of larvae from the lungs of cotton rats was about five-fold lower than from controls. Adult worm recovery from the small intestine of cotton rats was also lower than that from the controls, but the difference (two-fold lower) was smaller than that observed for lung recovery. Carbon treatment at a dose of 250-500 mg/kg effectively increased larval worm recovery from the lungs of cotton rats. However, this treatment had no effect on worm recovery from the intestine after intraduodenal implantation of adult N. brasiliensis. These results suggest that macrophage function have important role in the expression of strong resistance during the migratory phase of N. brasiliensis infection in cotton rats.

Activity of the cyclic depsipeptide emodepside (BAY 44-4400) against larval and adult stages of nematodes in rodents and the influence on worm survival.

The present investigations deal with the activity of the cyclic depsipeptide emodepside (BAY 44-4400) against larval and adult stages of three rodent nematodes. While emodepside acts strongly against the adult stages of the rat nematodes Nippostrongylus brasiliensis and Strongyloides ratti, as well as against the mouse nematode Heligmosomoides polygyrus, its actions against the larval stages of these nematodes vary according to the species. Thus, emodepside is highly effective against the lung and intestine larval stages of N. brasiliensis and S. ratti. By contrast. the larval stages of H. polygyrus in the intestine are only partly affected by higher emodepside dosages.

Nematocidal activity of natural polyphenols from bryophytes and their derivatives.

The nematocidal in vitro activity of three natural perotetins (phenolic bisbibenzyiethers) and eleven diphenyl ethers used as synthetic precursors has been assayed using two different experimental models, Caenorhabditis elegans and Nippostrongylus brasiliensis. Nine compounds showed some activity against C. elegans and nine against N. brasiliensis. For the former model, three compounds displayed an activity similar to that of the standards, whereas for N. brasiliensis none of the tested compounds was as active as the standards. From the in vitro results, five compounds (3, 4, 8, 9, 13) could be selected as lead compounds to continue the search for improved activity.

New sesquiterpene derivatives from the red alga Laurencia scoparia. Isolation, structure determination, and anthelmintic activity.

Eleven sesquiterpenes (1-11) and one long chain aldehyde (12) have been isolated from the dichloromethane extract of the red alga Laurencia scoparia. Four of them are new natural products. Scopariol (1) is a new natural product with an unusual rearranged chamigrane-type structure. The other three are beta-chamigrenes: isorigidol (2), (+)-3-(Z)-bromomethylidene-10 beta-bromo-beta-chamigrene (3), and (-)-3-(E)-bromomethylidene-10 beta-bromo-beta-chamigrene (4). The in vitro activity of compounds 1-12 against the parasitant stage of Nippostrongylus brasiliensis (L4) has been studied.