In vitro antiplasmodial activity of some medicinal plants of Burkina Faso

Malaria remains a major public health problem due to the emergence and spread of Plasmodium falciparum drug resistance. There is an urgent need to investigate new sources of antimalarial drugs which are more effective against Plasmodium falciparum. One of the potential sources of antimalarial drugs is traditional medicinal plants. In this work, we studied the in vitro antiplasmodial activity of chloromethylenic, methanolic, and MeOH/H₂O (1/1) crude extracts and decoction obtained from eight medicinal plants collected in Burkina Faso and of total alkaloids for five plants. Extracts were evaluated in vitro for efficacy against Plasmodium falciparum strain K1, which is resistant to chloroquine, pyrimethamine and proguanil using the fluorescence-based SYBR Green I assay. The antiproliferative activity on human-derived hepatoma cell line HepG2 and Chinese hamster ovary (CHO) cells was evaluated using the 3-[4,5-dimethylthyazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test in order to determine the selectivity index. Among the plant extracts tested for in vitro antiplasmodial activity, 16 were considered to be inactive (with IC₅₀?>?10 μg/ml), six showed a moderate activity (5?<?IC₅₀?≤?10 μg/ml), and six were found to have a good in vitro activity with IC₅₀ value?≤?5 μg/ml. The highest antiplasmodial activity was found for extracts from: the alkaloid leaf extract and the chloromethylenic extracts of Combretum fragrans (IC₅₀?=?3 μg/ml, IC₅₀?=?5 μg/ml), the total alkaloids and the chloromethylenic leaf extracts of Combretum collinum (IC₅₀?=?4 μg/ml), the MeOH/H₂O leaf extract of Terminalia avicennioides (IC₅₀?=?3.5 μg/ml), and the alkaloid leaf extract of Pavetta crassipes (IC₅₀?=?5 μg/ml). Three other extracts showed moderate antiplasmodial activity (5?<?IC₅₀?≤?10 μg/ml): Terminalia avicennioides and Combretum fragrans methanolic extracts and Acacia kirkii alkaloid leaf extract (IC₅₀?=?6.5, 9 and 10 μg/ml respectively). The Terminalia avicennioides crude MeOH/H₂O (80:20 v/v) extract of the leaves was submitted to a successive liquid/liquid extraction with ethylacetate and n-butanol respectively. The extracts were investigated for in vitro antiplasmodial activity and antioxidant properties using DPPH^●, ABTS⁺ and FRAP methods. The ethylacetate extract showed the best antiplasmodial activity (7 μg/ml) and the active constituent was isolated as ellagic acid by bioguided fractionation with an IC₅₀?=?0.2 μM on Plasmodium falciparum and SI?=?152. Besides, Terminalia avicennioides leaf extract and ellagic acid showed a good antioxidant activity. Our finding confirms the importance of investigating the antimalarial activity of plant species used in traditional medicine. Overall, two plants belonging to the Combretaceae family, Combretum fragrans and Combretum collinum appeared to be the best candidates and will be further investigated for their antiplasmodial properties, in order to isolate the molecules responsible for the antiplasmodial activity.     

Fluorochrome‐based definition of naturally occurring Foxp3+ regulatory T cells of intra‐ and extrathymic origin

Under physiological conditions, studies on the biology of naturally induced Foxp3⁺ Treg cells of intra‐ and extrathymic origin have been hampered by the lack of unambiguous markers to discriminate the mature progeny of such developmental Treg‐cell sublineages. Here, we report on experiments in double‐transgenic mice, in which red fluorescent protein (RFP) is expressed in all Foxp3⁺ Treg cells, whereas Foxp3‐dependent GFP expression is exclusively confined to intrathymically induced Foxp3⁺ Treg cells. This novel molecular genetic tool enabled us to faithfully track and characterize naturally induced Treg cells of intrathymic (RFP⁺GFP⁺) and extrathymic (RFP⁺GFP^?) origin in otherwise unmanipulated mice. These experiments directly demonstrate that extrathymically induced Treg cells substantially contribute to the overall pool of mature Foxp3⁺ Treg cells residing in peripheral lymphoid tissues of steady‐state mice. Furthermore, we provide evidence that intra‐ and extrathymically induced Foxp3⁺ Treg cells represent distinct phenotypic and functional sublineages.     

Lysosomal phospholipase A2: A novel player in host immunity to Mycobacterium tuberculosis

Phospholipases catalyze the cleavage of membrane phospholipids into smaller bioactive molecules. The lysosomal phospholipase A₂ (LPLA₂) is specifically expressed in macrophages. LPLA₂ gene deletion in mice causes lysosomal phospholipid accumulation in tissue macrophages leading to phospholipidosis. This phenotype becomes most prominent in alveolar macrophages where LPLA₂ contributes to surfactant phospholipid degradation. High expression of LPLA₂ in alveolar macrophages prompted us to investigate its role in host immunity against the respiratory pathogen Mycobacterium tuberculosis, the causative agent of tuberculosis. Here we report that adaptive immune responses to M. tuberculosis were impaired in LPLA₂ deficient mice. Upon aerosol infection with M. tuberculosis, LPLA₂ deficient mice showed enhanced mycobacterial counts but less lung immunopathology and pulmonary inflammatory responses. Compromised T‐cell priming in the lymph nodes was associated with impaired pulmonary T‐cell recruitment and activation. Together with reduced Th1 type cytokine production, these results indicate that LPLA₂ is indispensable for the induction of adaptive T‐cell immunity to M. tuberculosis. Taken together, we identified an unexpected and novel function of a lysosomal phospholipid‐degrading enzyme.     

EXPLORING THE VALIDITY AND PREDICTIVE POWER OF AN EXTENDED VOLUNTEER FUNCTIONS INVENTORY WITHIN THE CONTEXT OF EPISODIC SKILLED VOLUNTEERING BY RETIREES

The current study examined the structure of the volunteer functions inventory within a sample of older individuals (N = 187). The career items were replaced with items examining the concept of continuity of work, a potentially more useful and relevant concept for this population. Factor analysis supported a four factor solution, with values, social and continuity emerging as single factors and enhancement and protective items loading together on a single factor. Understanding items did not load highly on any factor. The values and continuity functions were the only dimensions to emerge as predictors of intention to volunteer. This research has important implications for understanding the motivation of older adults to engage in contemporary volunteering settings.     

Retrograde perfusion in isolated perfused mouse lungs—Feasibility and effects on cytokine levels and pulmonary oedema formation

Retrograde lung vascular perfusion can appear in high‐risk surgeries. The present report is the first to study long‐term retrograde perfusion of isolated perfused mouse lungs (IPLs) and to use the tyrosine kinase ephB4 and its ligand ephrinB2 as potential markers for acute lung injury. Mouse lungs were subjected to anterograde or retrograde perfusion with normal‐pressure ventilation (NV) or high‐pressure ventilation (=overventilation, OV) for 4 hours. Outcome parameters were cytokine, ephrinB2 and ephB4 levels in perfusate samples and bronchoalveolar lavage (BAL), and the wet‐to‐dry ratio. Anterograde perfusion was feasible for 4 hours, while lungs receiving retrograde perfusion presented considerable collapse rates. Retrograde perfusion resulted in an increased wet‐to‐dry ratio when combined with high‐pressure ventilation; other physiological parameters were not affected. Cytokine levels in BAL and perfusate, as well as levels of soluble ephB4 in BAL were increased in OV, while soluble ephrinB2 BAL levels were increased in retrograde perfusion. BAL levels of ephrinB2 and ephB4 were also determined in vivo, including mice ventilated for 7 hours with normal‐volume ventilation (NVV) or high‐volume ventilation (HVV) with increased levels of ephB4 in HVV BAL compared to NVV. Retrograde perfusion in IPL is limited as a routine method to investigate effects due to collapse for yet unclear reasons. If successful, retrograde perfusion has an influence on pulmonary oedema formation. In BAL, ephrinB2 seems to be up‐regulated by flow reversal, while ephB4 is a marker for acute lung injury.     

CYLD deletion triggers nuclear factor-κB-signaling and increases cell death resistance in murine hepatocytes

AIM:To analyze the role of CYLD for receptor-mediated cell death of murine hepatocytes in acute liver injury models.METHODS:Hepatocyte cell death in CYLD knockout mice(CYLD-/-)was analyzed by application of liver injury models for CD95-(Jo2)and tumor necrosis factor(TNF)-α-[D-Gal N/lipopolysaccharide(LPS)]induced apoptosis.Liver injury was assessed by measurement of serum transaminases and histological analysis.Apoptosis induction was quantified by cleaved PARP staining and Western blotting of activated caspases.Nuclear factor(NF)-κB,ERK,Akt and jun amino-terminal kinases signaling were assessed.Primary Hepatocytes were isolated by two step-collagenase perfusion and treated with recombinant TNF-αand with the CD95-ligand Jo2.Cell viability was analyzed by MTT-assay.RESULTS:Livers of CYLD-/-mice showed increased anti-apoptotic NF-κB signaling.In both applied liver injury models CYLD-/-mice showed a significantly reduced apoptosis sensitivity.After D-Gal N/LPS treatment CYLD-/-mice exhibited significantly lower levels of alanine aminotransferase(ALT)(295 U/L vs 859 U/L,P<0.05)and aspartate aminotransferase(AST)(560 U/L vs 1025 U/L,P<0.01).After Jo injection CYLD-/-mice showed 2-fold lower ALT(50 U/L vs 110 U/L,P<0.01)and lower AST(250 U/L vs 435 U/L,P<0.01)serumlevels compared to WT mice.In addition,isolated CYLD-/-primary murine hepatocytes(PMH)were less sensitive towards death receptor-mediated apoptosis and showed increased levels of Bcl-2,XIAP,c IAP1/2,survivin and c-FLIP expression upon TNF-and CD95-receptor triggering,respectively.Inhibition of NF-κB activation by the inhibitor of NF-κB phosphorylation inhibitor BAY 11-7085 inhibited the expression of antiapoptotic proteins and re-sensitized CYLD-/-PMH towards TNF-and CD95-receptor mediated cell death.CONCLUSION:CYLD is a central regulator of apoptotic cell death in murine hepatocytes by controlling NF-κB dependent anti-apoptotic signaling.     

Channelrhodopsin-2–XXL,a powerful optogenetic tool for low-light applications

Channelrhodopsin-2 (ChR2) has provided a breakthrough for the optogenetic control of neuronal activity. In adult Drosophila melanogaster, however, its applications are severely constrained. This limitation in a powerful model system has curtailed unfolding the full potential of ChR2 for behavioral neuroscience. Here, we describe the D156C mutant, termed ChR2-XXL (extra high expression and long open state), which displays increased expression, improved subcellular localization, elevated retinal affinity, an extended open-state lifetime, and photocurrent amplitudes greatly exceeding those of all heretofore published ChR variants. As a result, neuronal activity could be efficiently evoked with ambient light and even without retinal supplementation. We validated the benefits of the variant in intact flies by eliciting simple and complex behaviors. We demonstrate efficient and prolonged photostimulation of monosynaptic transmission at the neuromuscular junction and reliable activation of a gustatory reflex pathway. Innate male courtship was triggered in male and female flies, and olfactory memories were written through light-induced associative training.Identifying causal relationships between neuronal activity and animal behavior is a fundamental goal of neuroscience. Crucially, this task requires testing whether defined neuronal populations are sufficient for eliciting behavioral modules. The development of light-gated ion channels that can be genetically targeted to specific cells has provided a unique solution to this challenge. In pioneering work, such optogenetic effectors or actuators were originally used as multicomponent approaches (1–3). The introduction of Channelrhodopsin-1 (ChR1) (4) and especially ChR2 as a light-sensitive cation channel (5) dramatically advanced the field by providing an efficient and straightforward single-component strategy for stimulating neuronal activity (6, 7).Besides cell-specific targeting of appropriate effector elements, precise neuronal control by optogenetics demands efficient light delivery to the neurons of interest. For behavioral studies, photostimulation is ideally accomplished in intact, freely moving organisms and accompanied by functional readouts. The combination of a rich, well-characterized behavioral repertoire and elegant molecular genetics has contributed to Drosophila’s strong impact on behavioral neurogenetics (8, 9). However, low light transmission through the pigmented cuticle presupposes high light intensities for using ChR2 in flies. This obstacle greatly complicates the experimental setup for freely moving animals, and the required light energies can cause heat damage when stimulation is applied over extended time periods. Moreover, limited cellular availability of all-trans-retinal (hereafter retinal for short) demands adding high retinal concentrations as a dietary supplement. If optical access to target cells is not provided by a translucent body wall (e.g., as in nematodes, zebrafish, and Drosophila larvae), an alternative solution is the implantation of an optical fiber directly into the brain. Although this approach has been used successfully in mammals (10), such an invasive procedure is infeasible for the study of intact small organisms.Due to these restrictions in Drosophila, ChR2 has not reached the popularity attained in other organisms, and instead the field has turned mainly to thermogenetic neuronal stimulation (11–13). As with all techniques, there are also drawbacks to using temperature as a stimulus, such as undesired background activity and a multitude of temperature-sensitive cellular processes and behavioral responses. Photo-liberation of caged ATP, combined with genetic targeting of ATP-gated ion channels, has been introduced as a different optogenetic technique in Drosophila (3, 14). However, its applications are constrained by invasive, time-consuming procedures for injection of caged ATP and a limited experimental time window.Here, we introduce improved ChR2 variants as an alternative approach to address these shortcomings in Drosophila. Compared with wild-type ChR2 (ChR2-wt), expression of these mutants in target cells led to strongly enhanced photocurrents. We provide the first report, to our knowledge, of ChR2-T159C (15, 16) in flies and describe a ChR2 variant, ChR2-XXL (extra high expression and long open state), that is characterized by an extended open-state lifetime, elevated cellular expression, enhanced axonal localization, and reduced dependence on retinal addition. As a consequence, this mutant does not require dietary retinal supplementation to depolarize cells, evoke synaptic transmission, and activate neuronal networks at very low irradiance. These features enabled behavioral photostimulation in freely moving flies using diffuse low-intensity light.     

Limiting glutamate transmission in a Vglut2-expressing subpopulation of the subthalamic nucleus is sufficient to cause hyperlocomotion

The subthalamic nucleus (STN) is a key area of the basal ganglia circuitry regulating movement. We identified a subpopulation of neurons within this structure that coexpresses Vglut2 and Pitx2, and by conditional targeting of this subpopulation we reduced Vglut2 expression levels in the STN by 40%, leaving Pitx2 expression intact. This reduction diminished, yet did not eliminate, glutamatergic transmission in the substantia nigra pars reticulata and entopeduncular nucleus, two major targets of the STN. The knockout mice displayed hyperlocomotion and decreased latency in the initiation of movement while preserving normal gait and balance. Spatial cognition, social function, and level of impulsive choice also remained undisturbed. Furthermore, these mice showed reduced dopamine transporter binding and slower dopamine clearance in vivo, suggesting that Vglut2-expressing cells in the STN regulate dopaminergic transmission. Our results demonstrate that altering the contribution of a limited population within the STN is sufficient to achieve results similar to STN lesions and high-frequency stimulation, but with fewer side effects.The subthalamic nucleus (STN) has long been a structure of interest for researchers and clinicians alike. There is ample evidence that high-frequency stimulation of the STN improves symptoms such as tremor, rigidity, and slowness of movement, so called bradykinesia, in patients with Parkinson disease (see ref. 1 for review), but the mechanism through which this is achieved is still unknown. Some studies suggest that electrical stimulation causes a hyperexcitation of this structure (2), whereas others find evidence that the opposite is true (3–5). Other possible interpretations include the activation of the zona incerta, a neighboring white-matter structure (6) or of fibers coming from the motor cortex (7). Bilateral lesions of the STN improve locomotion (8), a result that is consistent with the inactivation hypothesis. However, previous studies have also found cognitive side effects when using high-frequency stimulation of the STN (9), findings supported by lesion studies in experimental animals, which led to abnormalities in operant tasks involving attention and impulsivity (10, 11). The projections of the STN to other regions help explain the multiple roles of this structure: It sends projections to other targets in the basal ganglia, such as the internal segment of the globus pallidus [also termed the entopeduncular nucleus (EP) in rodents] and the substantia nigra pars reticulata (SNr) (12, 13). The STN is also part of a circuit that includes the prefrontal cortex and the nucleus accumbens (14). It is currently unknown, however, whether these different roles reflect a heterogeneous population of cells, characterized by distinct gene expression. If that is the case, it would allow direct control over each cell population, facilitating the investigation of their respective roles. In rodents, the STN is believed to be composed solely of glutamatergic neurons, characterized by expression of the subtype 2 Vesicular glutamate transporter (Vglut2), whereas the other two subtypes (Vglut1 and Vglut3) have not been detected (15, 16). Selective targeted deletion of Vglut2 expression in this nucleus would therefore provide a specific loss-of-function model that would bypass a common problem presented by traditional lesions with pharmacological agents, which have patterns of diffusion that likely affect surrounding structures (17). It is known, however, that Vglut2 is expressed in many other parts of the brain (18), and a complete knockout in the mouse is not viable (19, 20). There is also evidence that the promoter driving expression of the Paired-like homeodomain 2 (Pitx2) gene is strong in the mouse STN (21) but is also not specific to this structure and a full knockout of Pitx2 expression results in premature death (22). To achieve the desired level of specificity, using a conditional knockout technique previously used to eliminate glutamatergic transmission in other cell types (23), we crossed Pitx2-Cre and Vglut2-lox mice, producing Vglut2^{f/f;Pitx2-Cre} conditional knockout (cKO) mice in which Vglut2 expression in the STN was strongly reduced in comparison with expression levels in littermate control mice. To understand the physiological contribution of the selected subpopulation of STN cells, we characterized these cKO mice with regard to anatomical, electrophysiological, and molecular properties, as well as their performance in a range of behavioral tasks.