Identification and Quantification of Total Coumarins from Urtica dentata Hand and Its Roles in Promoting Immune Tolerance via TLR4-Mediated Dendritic Cell Immaturation

Urtica dentata Hand (UDH) is traditionally used in the Alpine region as a herbal medicine. Immunotherapy using total coumarins (TC) of UDH has been proposed, yet the cellular and molecular mechanisms remain incompletely characterized. Additionally, there is no method available for the quantification of the main coumarins in UDH. We describe maturation-resistant, TC-conditioned dendritic cell (DC), which expressed much lower MHC class II (I-Ak) and CD86, showed reduced capacity to stimulate effector T cell responses and upregulated PD-Ll (programmed death ligand-1). TC-DC-stimulated regulatory cells (Treg) were superior alloantigen-specific suppressor of the T effector response as compared to those stimulated by control (CTR)-DC. Furthermore, TC-conditioned DC increased the levels of Foxp3 and CTLA-4 in the CD25 T cell population. TC-DC downregulated toll like receptor 4 (TLR4) protein expression in response to LPS. This indicates that down-regulation of TLR4 in response to TC on DC is a critical signaling pathway that regulates the phenotype and function of DC. We also established a sensitive and specific high-performance liquid chromatography-diodearray detection-mass spectrometry (HPLC-DAD-MS) method for simultaneous identification of its main coumarins, 6,6',7,7'-tetramethoxyl-8,8'-biscoumarin (1), 7,7'-dihydroxy-6,6'-dimethoxy-8,8'-biscoumarin (2), 7,7'-dimethoxy-6,6'-biscoumarin (3), and scoparone (4). A demonstration of this mechanism and the method for identification and quantification of TC in UDH endorsed their potential as a tolerance-promoting herbal medicine to prevent or treat transplantation rejection and autoimmune diseases.     

Le Infezioni Con “Stubborn” Ottenute per Trauma E Il Grado di Recettività dei Tipi di Grano

Abstract

Dioecy ensures cross pollination but pollen must travel from male to female plants, sometimes covering long distances. The present study concerns the reproductive strategy of two Italian dioecious plants: Mercurialis annua L. and Bryonia dioica L. The former is anemophilous and the latter is entomophilous; the latter has nectar and pollen as rewards. The distribution of pollen grains on the stigma is very different in the two species, reflecting the different types of pollination. In both species there is a number-dependent mechanism of pollen germination on the stigma. This mechanism could enhance male gametophytic competition.     

Inheritance of progeny sex ratio in Urtica dioica

Seed samples collected from female Urtica dioica plants in the field showed considerable inter-family variation in the sex ratio (faction of males). To investigate the inheritance pattern of the sex ratio trait, crosses were performed between individual male and female plants from different sex ratio families. Our results suggest, at least for the families studied here, that maternal parents strongly contribute to the variation in the primary sex ratio. Furthermore, progeny sex ratios from reciprocal crosses were significantly different and resembled the sex ratios produced by their maternal parents. We discuss the possible mechanisms underlying maternal control.     

Direct and ecological costs of resistance and tolerance in the stinging nettle

Plant resistance and tolerance to herbivores, parasites, pathogens, and abiotic factors may involve two types of costs. First, resistance and tolerance may be costly in terms of plant fitness. Second, resistance and tolerance to multiple enemies may involve ecological trade-offs. Our study species, the stinging nettle ( Urtica dioica L.) has significant variation among seed families in resistance and tolerance as well as costs of resistance and tolerance to the holoparasitic plant Cuscuta europaea L. Here we report on variation among seed families (i.e. genetic) in tolerance to nutrient limitation and in resistance to both mammalian herbivores (i.e. number of stinging trichomes) and an invertebrate herbivore (i.e. inverse of the performance of a generalist snail, Arianta arbustorum). Our results indicate direct fitness costs of snail resistance in terms of host reproduction whereas we did not detect fitness costs of mammalian resistance or tolerance to nutrient limitation. We further tested for ecological trade-offs among tolerance or resistance to the parasitic plant, herbivore resistance, and tolerance to nutrient limitation in the stinging nettle. Tolerance of nettles to nutrient limitation and resistance to mammalian herbivores tended to correlate negatively. However, there were no significant correlations among resistance and tolerance to the different natural enemies (i.e. parasitic plants, snails, and mammals). The results of this greenhouse study thus suggest that resistance and tolerance of nettles to diverse enemies are free to evolve independently of each other but not completely without direct costs in terms of plant fitness.     

Sex ratio of some long-lived dioecious plants in a sand dune area

In dioecious plants the fraction of males among flowering plants in the field (the secondary sex ratio) is the result of the fraction of males in the seeds (the primary sex ratio) and the subsequent survival and age at first reproduction of the two genders. It has been assumed that survival and age at first reproduction are the main determinants of biased secondary sex ratio but, especially for long-lived perennials, few data are available. We address this issue for natural populations of four long-lived perennials in a dune area. In Asparagus officinale and Bryonia dioica, the secondary sex ratio was unbiased. In Salix repens the secondary sex ratio was female-biased (0.337). Hippophae rhamnoides populations were male-biased; the average sex ratio of flowering plants was 0.658, while the fraction of males varied between 0.39 near the sea to 0.84 at the inland side of the dunes. The primary sex ratio was estimated by germinating seeds and growing plants under favourable conditions with minimal mortality. In S. repens the primary sex ratio in seeds was variable among mother plants and was, on average, female-biased (0.289). This is close to the secondary sex ratio, suggesting that the female bias already originates in the seed stage. In Hippophae rhamnoides the primary sex ratio was slightly male-biased (0.564). We argue that in this species, apart from the primary sex ratio, higher mortality and a later age at first reproduction for females contribute to the strong male bias among flowering plants in the field.     

The effects of phosphorus nutrition and soil pH on the growth of some ancient woodland indicator plants and their interaction with competitor species

The forest under-storey herbs Anemone nemorosa, Lamiastrum galeobdolon and Veronica montana are generally considered indicator species of old, broadleaved woodland sites where the soil fertility is often low. In a glasshouse bioassay, however, all three species not only showed large positive growth responses to supplied P concentrations (0–10mgL ^–1) solutions, but also tolerated high P concentrations (20–40mgL ^–1), well above those normally found in their natural habitat. Plants responded by raising the concentrations of P in their shoot and root tissues and increasing their biomass, resulting in an increased P uptake. A shade-tolerant competitor species, Urtica dioica, also grew vigorously across the full range of P concentrations, restricting the growth of the woodland species. This emphasises the difficulty of establishing semi-natural woodland vegetation in the presence of competitor species, for example in situations where new woodlands are planted on fertile ex-agricultural soils containing large residual concentrations of P. The influence of soil pH on the growth and nutrient relations of A. nemorosa, L. galeobdolon, V. montana, Poa trivialisandU. dioicawas determined in a separate experiment using an ex-arable soil as the growing medium with pH levels adjusted from 7.4 to 5.8 and 4.3 respectively. Acidifying the soil enhanced growth, but reduced the concentrations of N, P and K in the leaves of all three woodland species, probably due to dilution of these minerals in the increased dry matter production. The competitor species (P. trivialis and U. dioica) responded in similar manner to the woodland indicator species. These results suggest that manipulating soil pH as a means of facilitating the establishment of woodland indicator species in new farm woods is unlikely, in the short term, to be effective where competitor species are present.     

Distribution of the stands with Urtica dioica L. along the Lužnice River floodplain on the border between Austria and Czechoslovakia and land management

The effects of different management practices (mainly mowing, grazing, nutrient enrichment) on floodplain vegetation were compared between the Austrian and Czech part of the Lunice River floodplain using nitrophilous vegetation with Urtica dioica. The vegetation samples situated on crosswise transects (40 in total) were used for the analysis of vegetation. Correlations between the floodplain width on these transects and the proportions (expressed as percentage of the total floodplain width) of selected characteristics (Urtica dioica and Phalaris arundinacea stands and managed areas) were not statistically significant. Differences in the proportions of selected characteristics between the two parts of the floodplain were not significant either, except differences in the proportion of managed areas and species richness (higher species richness and proportion of managed areas are in the Austrian part of the floodplain). The different environmental variables were used in ordinations (DCA and CCA) of vegetation samples. In the DCA, four groups of samples were interpreted. In the CCA changes the moisture gradient was the most important one. The transect distance (from the first transect in Austria) and the soil moisture had the closest relationship to the species data.     

Laminar hydathodes inUrticaceae: Survey of tribes and anatomical observations onPilea pumila andUrtica dioica

Laminar hydathodes are known from only three dicot families. InUrticaceae they are associated with minor vein junctions in all five tribes, as surveyed from cleared leaves of 43 species in 30 genera. Only one species lacked hydathodes. Exclusively adaxial hydathodes were found in 28 genera. In tribeElatostemeae, laminar hydathodes inPilea andPellionia species are abaxial, adaxial, or on both surfaces. Guttation was observed in four species.Urtica dioica (adaxial) andPilea pumila (abaxial) were studied anatomically in detail. Hydathodes in the former have normal bundle structure but xylem gaps sometimes occur. In the latter, phloem is displaced in three previously undescribed ways: 1) ends abruptly near hydathode, 2) curves into connecting vein at adjacent junction, or 3) departs xylem, skirts hydathode independently, and rejoins adjacent xylem strand. Laminar hydathodes are a unifying character of theUrticaceae, and they also strengthen its close relationship to theMoraceae.     

Growth responses of Urtica dioica L. to different water table depth

The study has examined the effect of water table depth (WTD) on production, biomass allocation, allometric relationships and transpiration rate in Urtica dioica. The essential importance of WTD for occurence and spread of Urtica has been documented. Water table depths were: 60, 50, 40, 30, 20, and 10 cm below the soil surface. Thirty individuals of Urtica for each WTD, established from apical parts of young rhizomes, has been planted in containers and placed at WTD from the 8th May to the 24th July. The height of all individuals and the length and width of the largest leaf blade of each individual were measured after 42, 55 and 83 days. Transpiration rate was measured after 53 and 82 days. Above-ground biomass of all individuals was harvested on 24 of July and was separated into individual organs. Various biometric parameters were measured. Results showed that biomass, plant height, branching of stems and rhizomes and rhizomes length decreased in containers with a more shallow WTD. Particularly, allometric relationships between plant height and other characteristics such as basal diameter, length of longest branch and rhizome were affected by the water level. The biometric parameters were highly dependent on plant height. Transpiration strongly decreased with decreasing WTD. Therefore, the high water level in the soil suppresses growth of particular organs and water regime of Urtica plants/. Generally, long-term high water content in the soils of floodplains, particularly during floods, limits rapidly, particularly vegetative spread of Urtica in the wetland habitats.     

Different antimetabolic effects of related lectins towards nymphal stages ofNilaparvata lugens

Insect feeding trials were carried out to determine the effects of a range of mannose-specific lectins on third instar nymphs of the rice brown planthopper (BPH), Nilaparvata lugens. Stål. Dose response curves show that Galanthus nivalis agglutinin (GNA) has the strongest toxic effect of the lectins tested, and is effective at concentrations considerably lower than those previously reported. Narcissus pseudonarcissus agglutinin (NPA) and Allium sativum agglutinin (ASA) exhibit a significant antimetabolic effect towards the insect but were less effective (on a molar basis) than GNA. LC₅₀ values for GNA, NPA and ASA are approximately 4 μM, 11 μM and >40 μM respectively. These mannose-specific lectins are serologically identical, but differ in the number of subunits per protein molecule; ASA is a dimer, NPA is a trimer and GNA is a tetramer. The results obtained support the hypothesis, that the effectiveness of the mannose-binding lectins as antimetabolites is determined by the number of subunits per molecule. Two N-acetylglucosamine binding lectins, the dimeric Oryza sativa agglutinin (OSA) and the monomeric Urtica dioica agglutinin (UDA), were also tested but at a concentration of 0.1% w/v exhibited no significant antimetabolic effect towards BPH, although the related lectin wheatgerm agglutinin (WGA) has previously been demonstrated to be toxic towards the insect.