Arf-like GTPase Arl8b regulates lytic granule polarization and natural killer cell–mediated cytotoxicity

Natural killer (NK) lymphocytes contain lysosome-related organelles (LROs), known as lytic granules, which upon formation of immune synapse with the target cell, polarize toward the immune synapse to deliver their contents to the target cell membrane. Here, we identify a small GTP-binding protein, ADP-ribosylation factor-like 8b (Arl8b), as a critical factor required for NK cell–mediated cytotoxicity. Our findings indicate that Arl8b drives the polarization of lytic granules and microtubule-organizing centers (MTOCs) toward the immune synapse between effector NK lymphocytes and target cells. Using a glutathione S-transferase pull-down approach, we identify kinesin family member 5B (KIF5B; the heavy chain of kinesin-1) as an interaction partner of Arl8b from NK cell lysates. Previous studies showed that interaction between kinesin-1 and Arl8b is mediated by SifA and kinesin-interacting protein (SKIP) and the tripartite complex drives the anterograde movement of lysosomes. Silencing of both KIF5B and SKIP in NK cells, similar to Arl8b, led to failure of MTOC-lytic granule polarization to the immune synapse, suggesting that Arl8b and kinesin-1 together control this critical step in NK cell cytotoxicity.     

A Flow Cytometry-Based Quantitative Drug Sensitivity Assay for All Plasmodium falciparum Gametocyte Stages

Background

Malaria elimination/eradication campaigns emphasize interruption of parasite transmission as a priority strategy. Screening for new drugs and vaccines against gametocytes is therefore urgently needed. However, current methods for sexual stage drug assays, usually performed by counting or via fluorescent markers are either laborious or restricted to a certain stage. Here we describe the use of a transgenic parasite line for assaying drug sensitivity in all gametocyte stages.

Methods

A transgenic parasite line expressing green fluorescence protein (GFP) under the control of the gametocyte-specific gene α-tubulin II promoter was generated. This parasite line expresses GFP in all gametocyte stages. Using this transgenic line, we developed a flow cytometry-based assay to determine drug sensitivity of all gametocyte stages, and tested the gametocytocidal activities of four antimalarial drugs.

Findings

This assay proved to be suitable for determining drug sensitivity of all sexual stages and can be automated. A Z’ factor of 0.79±0.02 indicated that this assay could be further optimized for high-throughput screening. The daily sensitivity of gametocytes to three antimalarial drugs (chloroquine, dihydroartemisinin and pyronaridine) showed a drastic decrease from stage III on, whereas it remained relatively steady for primaquine.

Conclusions

A drug assay was developed to use a single transgenic parasite line for determining drug susceptibility of all gametocyte stages. This assay may be further automated into a high-throughput platform for screening compound libraries against P. falciparum gametocytes.     

Rohitukine inhibits in vitro adipogenesis arresting mitotic clonal expansion and improves dyslipidemia in vivo

We developed a common feature pharmacophore model using known antiadipogenic compounds (CFPMA). We identified rohitukine, a reported chromone anticancer alkaloid as a potential hit through in silico mapping of the in-house natural product library on CFPMA. Studies were designed to assess the antiadipogenic potential of rohitukine. Rohitukine was isolated from Dysoxylum binacteriferum Hook. to ⬧95% purity. As predicted by CFPMA, rohitukine was indeed found to be an antiadipogenic molecule. Rohitukine inhibited lipid accumulation and adipogenic differentiation in a concentration- and exposure-time-dependent manner in 3T3-L1 and C3H10T1/2 cells. Rohitukine downregulated expression of PPARγ, CCAAT/enhancer binding protein α, adipocyte protein 2 (aP2), FAS, and glucose transporter 4. It also suppressed mRNA expression of LPL, sterol-regulatory element binding protein (SREBP) 1c, FAS, and aP2, the downstream targets of PPARγ. Rohitukine arrests cells in S phase during mitotic clonal expansion. Rohitukine was bioavailable, and 25.7% of orally administered compound reached systemic circulation. We evaluated the effect of rohitukine on dyslipidemia induced by high-fat diet in the hamster model. Rohitukine increased hepatic expression of liver X receptor α and decreased expression of SREBP-2 and associated targets. Rohitukine decreased hepatic and gonadal lipid accumulation and ameliorated dyslipidemia significantly. In summary, our strategy to identify a novel antiadipogenic molecule using CFPMA successfully resulted in identification of rohitukine, which confirmed antiadipogenic activity and also exhibited in vivo antidyslipidemic activity.     

Effect of bioactive tannoid principles of Emblica officinalis on ischemia-reperfusion-induced oxidative stress in rat heart.

The tannoid principles of the fruits of Emblica officinalis have been reported to exhibit antioxidant activity in vitro and in vivo. In the present study, an emblicanin-A (37%) and -B (33%) enriched fraction of fresh juice of Emblica fruits (EOT) was investigated for antioxidant activity against ischemia-reperfusion (IRI)-induced oxidative stress in rat heart. Vitamin E (VE) was used as the standard antioxidant agent. IRI was induced in isolated rat heart by perfusing it with modified Kreb-Hensleitt's solution for 5 min, followed by a period of ischemia (stoppage of perfusion) for 10 min and then restoring the perfusion (reperfusion) for 15 min. IRI induced a significant decrease in the activities of cardiac superoxide dismutase, catalase and glutathione peroxidase, with a concomitant increase in lipid peroxidation. These IRI-induced effects were prevented by the administration of EOT (50 and 100 mg/kg body wt.) and VE (200 mg/kg body wt.) given orally twice daily for 14 days prior to the sacrifice of the animals and initiation of the perfusion experiments. The study confirms the antioxidant effect of E. officinalis and indicates that the fruits of the plant may have a cardioprotective effect.     

Effect of Withania somnifera glycowithanolides on a rat model of tardive dyskinesia.

Withania somnifera glycowithanolides (WSG) were investigated for their preventive effect on the animal model of tardive dyskinesia (TD), induced by once daily administration of the neuroleptic, haloperidol (1.5 mg/kg, i.p.), for 28 days. Involuntary orofacial movements (chewing movements, tongue protusion and buccal tremors) were assessed as TD parameters. WSG (100 and 200 mg, p.o.), administered concomitantly with haloperidol for 28 days, inhibited the induction of the neuroleptic TD. Haloperidol-induced TD was also attenuated by the antioxidant, vitamin E (400 and 800 mg/kg, p.o.), but remained unaffected by the GABA-mimetic antiepileptic agent, sodium valproate (200 and 400 mg/kg, p.o.), both agents being administered for 28 days like WSG. The results indicate that the reported antioxidant effect of WSG, rather than its GABA-mimetic action, may be responsible for the prevention of haloperidol-induced TD.     

Bleaching of photosynthetic pigments inChlorella protothecoides grown in the presence of SANDOZ 9785 (4-chloro-5-dimethylamino-2-phenyl-3 (2H) pyridazinone)

The unicellular green algaChlorella protothecoides was grown in the presence of various concentrations (30–300 μM) of the herbicide SANDOZ 9785 (4-chloro-5-(dimethylamino)-2-phenyl-3 (2H) pyridazinone). When the cells were grown autotrophically in the presence of the herbicide, there was a decrease in chlorophylls and carotenoids estimated on culture volume basis compared to the control. The absorption spectra of carotenes and colourless precursors extracted from photosynthetic particles showed that there was a higher carotenoid precursors/carotene ratio in the treated cells. Similarly the carotenoid precursors/xanthophyll ratio was increased by SANDOZ 9785 treatment. Chlorophylla synthesis appeared to be inhibited more than chlorophyllb synthesis in SANDOZ 9785 treated cells resulting in a decrease in the chlorophylla/b ratio.     

Alteration in the metabolism of free radicals in wheat seedlings grown in the presence of 4-chloro-5-dimethylamino-2-phenyl-3(2H) pyridazinone

When wheat seedlings were grown in the presence of 62.5-500μM 4 chloro-5-dimethylamino-2-phenyl-3(2H) pyridazinone, an inhibitor of photosystem II electron transport, there was a marked inhibition of in vivo photosystem II electron transport as revealed by the analysis of fast chlorophyll a fluorescence transients in intact leaves and by the inhibition (95% at 500μM) of net photosynthesis in intact leaves Accompanying this inhibition of photosystem II electron transport, there was a decrease in the content of photosynthetic pigments. The extent of lipid peroxidation, measured in terms of malondialdehyde content was not increased; rather it was found decreased. An analysis of in vitro lipid peroxidation of the thylakoid membranes of control and 4-chloro-5-dimethylamino-2-phenyl-3(2H) pyridazinone treated plants in the presence of a sensitizer dye (toluidine blue) showed a similar rate both in the control and treated samples suggesting that the availability of unsaturated fatty acids as a substrate for lipid peroxidation was not limiting even though it decreased in the treated plants. On the other hand, it appears that the availability of the free radicals for lipid peroxidation was decreased byenhanced activity of the enzyme systems involved in the metabolism of free radicals. Measurements of the activities of enzymes involved in the metabolism of free radicals showed an increase in the activities of NADPH-glutathione reductase (6–8 fold) and catalase (15–30%) and a decrease in the activity of superoxide dismutase (30–45%) in the treated plants.     

Life Cycle of Tetranychus macfarlanei Baker and Pritchard (Acari: Tetranychidae): A New Pest of Medicinal Plants in West Bengal

The life cycle of Tetranychus macfarlanei Baker and Pritchard was studied on two different medicinal plants, Clitoria ternatea L. and Justicia adhatoda L. Nees, in BOD at 32.5 °C and 75 % RH during April 2007 to May 2007. Observations towards duration of different stages like egg, larva, protonymph, deutonymph, adult, total life cycle, preoviposition, oviposition, postoviposition periods, longevity of female and male, and fecundity, sex ratio were recorded. Total developmental period of T. macfarlanei from egg to adult was 6.4 ± 0.37 (Mean ± SE) and 10.6 ± 0.56 days on C. ternatea and J. adhatoda, respectively. On C. ternatea, the fecundity in case of fertilized and unfertilized female were 91.6 ± 11.61 and 80 ± 21.64 eggs, respectively and longevity of fertilized and unfertilized female was 16.4 ± 1.44 and 8.6 ± 2.32 days, respectively. The corresponding figure on J. adhatoda for fecundity in case of fertilized and unfertilized female were 39 ± 2.85 and 19.8 ± 3.90 eggs, respectively and for longevity was 16 ± 0.37 and 11 ± 086 days, respectively. Among the two hosts, C. ternatea appears to be more preferred to J. adhatoda because life cycle was completed in shorter time and fecundity and female longevity were for longer duration.     

Histone posttranslational modifications and cell fate determination: lens induction requires the lysine acetyltransferases CBP and p300

Lens induction is a classical embryologic model to study cell fate determination. It has been proposed earlier that specific changes in core histone modifications accompany the process of cell fate specification and determination. The lysine acetyltransferases CBP and p300 function as principal enzymes that modify core histones to facilitate specific gene expression. Herein, we performed conditional inactivation of both CBP and p300 in the ectodermal cells that give rise to the lens placode. Inactivation of both CBP and p300 resulted in the dramatic discontinuation of all aspects of lens specification and organogenesis, resulting in aphakia. The CBP/p300^−/− ectodermal cells are viable and not prone to apoptosis. These cells showed reduced expression of Six3 and Sox2, while expression of Pax6 was not upregulated, indicating discontinuation of lens induction. Consequently, expression of αB- and αA-crystallins was not initiated. Mutant ectoderm exhibited markedly reduced levels of histone H3 K18 and K27 acetylation, subtly increased H3 K27me3 and unaltered overall levels of H3 K9ac and H3 K4me3. Our data demonstrate that CBP and p300 are required to establish lens cell-type identity during lens induction, and suggest that posttranslational histone modifications are integral to normal cell fate determination in the mammalian lens.