Leukocyte Populations in Human Preterm and Term Breast Milk Identified by Multicolour Flow Cytometry

Background

Extremely preterm infants are highly susceptible to bacterial infections but breast milk provides some protection. It is unknown if leukocyte numbers and subsets in milk differ between term and preterm breast milk. This study serially characterised leukocyte populations in breast milk of mothers of preterm and term infants using multicolour flow cytometry methods for extended differential leukocyte counts in blood.

Methods

Sixty mothers of extremely preterm (<28 weeks gestational age), very preterm (28–31 wk), and moderately preterm (32–36 wk), as well as term (37–41 wk) infants were recruited. Colostrum (d2–5), transitional (d8–12) and mature milk (d26–30) samples were collected, cells isolated, and leukocyte subsets analysed using flow cytometry.

Results

The major CD45+ leukocyte populations circulating in blood were also detectable in breast milk but at different frequencies. Progression of lactation was associated with decreasing CD45+ leukocyte concentration, as well as increases in the relative frequencies of neutrophils and immature granulocytes, and decreases in the relative frequencies of eosinophils, myeloid and B cell precursors, and CD16- monocytes. No differences were observed between preterm and term breast milk in leukocyte concentration, though minor differences between preterm groups in some leukocyte frequencies were observed.

Conclusions

Flow cytometry is a useful tool to identify and quantify leukocyte subsets in breast milk. The stage of lactation is associated with major changes in milk leukocyte composition in this population. Fresh preterm breast milk is not deficient in leukocytes, but shorter gestation may be associated with minor differences in leukocyte subset frequencies in preterm compared to term breast milk.     

Plant volatiles induced by herbivore eggs prime defences and mediate shifts in the reproductive strategy of receiving plants

Plants can detect cues associated with the risk of future herbivory and modify defence phenotypes accordingly; however, our current understanding is limited both with respect to the range of early warning cues to which plants respond and the nature of the responses. Here we report that exposure to volatile emissions from plant tissues infested with herbivore eggs promotes stronger defence responses to subsequent herbivory in two Brassica species. Furthermore, exposure to these volatile cues elicited an apparent shift from growth to reproduction in Brassica nigra, with exposed plants exhibiting increased flower and seed production, but reduced leaf production, relative to unexposed controls. Our results thus document plant defence priming in response to a novel environmental cue, oviposition‐induced plant volatiles, while also showing that plant responses to early warning cues can include changes in both defence and life‐history traits.     

Truffles Regulate Plant Root Morphogenesis via the Production of Auxin and Ethylene

Truffles are symbiotic fungi that form ectomycorrhizas with plant roots. Here we present evidence that at an early stage of the interaction, i.e. prior to physical contact, mycelia of the white truffle Tuber borchii and the black truffle Tuber melanopsorum induce alterations in root morphology of the host Cistus incanus and the nonhost Arabidopsis (Arabidopsis thaliana; i.e. primary root shortening, lateral root formation, root hair stimulation). This was most likely due to the production of indole-3-acetic acid (IAA) and ethylene by the mycelium. Application of a mixture of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and IAA fully mimicked the root morphology induced by the mycelium for both host and nonhost plants. Application of the single hormones only partially mimicked it. Furthermore, primary root growth was not inhibited in the Arabidopsis auxin transport mutant aux1-7 by truffle metabolites while root branching was less effected in the ethylene-insensitive mutant ein2-LH. The double mutant aux1-7;ein2-LH displayed reduced sensitivity to fungus-induced primary root shortening and branching. In agreement with the signaling nature of truffle metabolites, increased expression of the auxin response reporter DR5∷GFP in Arabidopsis root meristems subjected to the mycelium could be observed, confirming that truffles modify the endogenous hormonal balance of plants. Last, we demonstrate that truffles synthesize ethylene from l-methionine probably through the α-keto-γ-(methylthio)butyric acid pathway. Taken together, these results establish the central role of IAA and ethylene as signal molecules in truffle/plant interactions.Ectomycorrhizal symbioses are mutualistic interactions between filamentous fungi and plant roots. Truffles, which are ascomycete fungi renown for their aromatic fruiting bodies, form ectomycorrhizas (ECM) in temperate climates predominantly with trees (i.e. hazel [Corylus avellana], oaks [Quercus spp.]).In soil, microorganisms communicate with plants by exchanging chemical signals throughout the rhizosphere. Depending on the nature of the interaction, these molecules can be either volatiles or solutes (dissolved solids). For example, rhizobacteria induce growth promotion in Arabidopsis (Arabidopsis thaliana) through the action of the volatile compound 2,3-butanediol (Ryu et al., 2003). The sesquiterpene volatile (E)-β-caryophyllene is produced by maize (Zea mays) roots fed upon by arthropods, and serves as attractant to natural enemies of the insects (Rasmann et al., 2005). Nonvolatile signal molecules can also dissolve in water and diffuse in the soil. Indeed the nitrogen-fixing bacteria Rhizobium secrete a nodulation factor that induces changes in root morphology of legumes (Dénarié and Cullimore, 1993; Heidstra and Bisseling, 1996). Mycelium branching is induced in the mycorrhizal fungus Gigaspora margarita by 5-deoxy-strigol, a strigolactone exuded from the roots of the legume host Lotus japonicus (Akiyama et al., 2005).Also ectomycorrhizal fungi engage in a molecular dialogue with plants and produce chemical signals that modulate plant root/ECM morphogenesis. The indole alkaloid hypaphorine produced by ectomycorrhizal fungus Pisolithus tinctorius inhibits root hair elongation in the host Eucalyptus globules and the nonhost Arabidopsis (Béguiristain et al.,1995; Reboutier et al., 2002). Hormones, mainly indole-3-acetic acid (IAA), have also been often implicated in symbiotic interactions (Barker and Tagu, 2000; Martin et al., 2001; Sirrenberg et al., 2007; Contreras-Cornejo et al., 2009). Most studies involving hormones have focused at a late stage of interaction, when ECMs were developing or already formed (for review, see Barker and Tagu, 2000). Indeed IAA-overproducing mutants of the ectomycorrhizal fungus Hebeloma cylindrosporum form significantly more mycorrhizas with the host Pinus pinaster than the wild type (Gay et al., 1994). Similarly applying exogenous IAA to the ectomycorrhizal system Piloderma croceum/Quercus robur also resulted in a more intense ECM colonization of the host compared to controls with no additional IAA (Herrmann et al., 2004).Truffles form ECM with a variety of hosts such as oaks, hazels, but also some shrubs (i.e. Cistus). Under laboratory conditions, the establishment of the symbiotic phase takes 2 to 3 months (Sisti et al., 1998; Miozzi et al., 2005). Strains of the same truffle species vary in their capacity to colonize a single host (Giomaro et al., 2000). Volatile organic compounds have been implicated in the signaling between truffle and plants. Splivallo et al. (2007) discussed the phytotoxic activity of fruiting body volatiles and Menotta et al. (2004) highlighted their potential role as mycorrhization signals. Fruiting bodies volatiles shortened primary roots of plants (Splivallo et al., 2007) while the effect of mycelial metabolites has not been addressed.Our aim here was to investigate how truffle mycelia modify plant root architecture. We focus our effort on an early stage of interaction (10 d) to explain changes in root morphology prior to ECM formation and highlight the action of diffusible signals on the host plant Cistus incanus and the nonhost Arabidopsis. Using Arabidopsis mutants, we did not aim to investigate the mechanism behind the IAA/ethylene cross talk but rather to show that the fungal metabolites are perceived in planta through both auxin and ethylene signaling pathways. We illustrate how truffle metabolites modify the auxin response of the root meristem using the auxin reporter line DR5∷GFP. We further demonstrate that both hormones are produced by truffles at concentrations that fully explain the root phenotypic responses of the host and nonhost plants. Last, we elucidate ethylene biosynthesis in truffles.     

Digest: Life history evolution in Darwin's dream ponds*

Can variation in sex‐specific parental investment lead to sexual dimorphism in immune response? Keller et al. (2018) measured immune cell parameters, expression of candidate genes, and composition of buccal microbiota in mouthbrooding cichlid species from Lake Tanganyika that show either maternal or biparental care. They found that maternal mouthbrooding species have increased sexual dimorphism in immune parameters, while biparental mouthbrooders exhibit an upregulated adaptive immune response, suggesting resource allocation shifts between parental investment and the immune system.     

Plant homeodomain (PHD) fingers of CHD4 are histone H3-binding modules with preference for unmodified H3K4 and methylated H3K9

A major challenge in chromatin biology is to understand the mechanisms by which chromatin is remodeled into active or inactive states as required during development and cell differentiation. One complex implicated in these processes is the nucleosome remodeling and histone deacetylase (NuRD) complex, which contains both histone deacetylase and nucleosome remodeling activities and has been implicated in the silencing of subsets of genes involved in various stages of cellular development. Chromodomain-helicase-DNA-binding protein 4 (CHD4) is a core component of the NuRD complex and contains a nucleosome remodeling ATPase domain along with two chromodomains and two plant homeodomain (PHD) fingers. We have previously demonstrated that the second PHD finger of CHD4 binds peptides corresponding to the N terminus of histone H3 methylated at Lys(9). Here, we determine the solution structure of PHD2 in complex with H3K9me3, revealing the molecular basis of histone recognition, including a cation-π recognition mechanism for methylated Lys(9). Additionally, we demonstrate that the first PHD finger also exhibits binding to the N terminus of H3, and we establish the histone-binding surface of this domain. This is the first instance where histone binding ability has been demonstrated for two separate PHD modules within the one protein. These findings suggest that CHD4 could bind to two H3 N-terminal tails on the same nucleosome or on two separate nucleosomes simultaneously, presenting exciting implications for the mechanism by which CHD4 and the NuRD complex could direct chromatin remodeling.     

Endothelial Progenitor Cells in the Pathogenesis of Idiopathic Pulmonary Fibrosis: An Evolving Concept

Background

Idiopathic pulmonary fibrosis (IPF) has been associated with abnormal vascular remodeling. Bone marrow derived endothelial progenitor cells (EPCs) are considered to possess lung tissue repair and vascular remodeling properties.

Objectives

The study aimed to assess early EPCs levels and EPCs endogenous vascular endothelial growth factor (VEGF) expression in IPF. In order to examine alterations in the mobilization of EPCs from the bone marrow we measured plasma VEGF.

Main Results

Twenty-three patients with IPF and fifteen healthy subjects were included. The number of early EPCs colonies was markedly reduced in IPF patients vs controls (6.00±6.49 vs 49.68±16.73, respectively, p<0.001). EPCs were further decreased in patients presenting systolic pulmonary arterial pressure (sPAP)≥35 mmHg. The number of colonies per well correlated negatively with P_(A-a)O₂ (r =  −0.750, p<0.001). Additionally, VEGF mRNA levels were significantly increased in IPF patients. There were no differences observed in VEGF plasma levels in IPF patients when compared to controls.

Conclusions

The current data suggest that inadequate levels of early EPCs may potentially contribute to suppressed repair and recovery of the damaged pulmonary endothelium and thereby may drive the sequence of events in profibrogenic direction. Increased VEGFmRNA levels in the clinical context of IPF may represent a compensatory mechanism to overcome reduced EPCs levels.     

Activin-A causes Hepatic stellate cell activation via the induction of TNFα and TGFβ in Kupffer cells

Background & aims

TGFβ superfamily member Activin-A is a multifunctional hormone/cytokine expressed in multiple tissues and cells, where it regulates cellular differentiation, proliferation, inflammation and tissue architecture. High activin-A levels have been reported in alcoholic cirrhosis and non-alcoholic steatohepatitis (NASH). Our aim was to identify the cell types involved in the fibrotic processes induced by activin-A in liver and verify the liver diseases that this molecule can be found increased.