Excessive weight gain in women with a normal pre-pregnancy BMI is associated with increased neonatal adiposity

BACKGROUND

More than 40% of women with a normal pre-pregnancy body mass index (BMI) exceed the 2009 Institute of Medicine (IOM) guidelines' recommended weight gain of 25-35 lb. Excessive gestational weight gain is one modifiable factor that may be contributing to childhood overweight and obesity.

OBJECTIVE

The objective of this study was to evaluate differences in adiposity from neonates born to mothers with a normal pre-pregnancy BMI who either gained within or above IOM guidelines.

METHODS

Neonatal adiposity was measured within 72 h of birth by the method of air displacement plethysmography.

RESULTS

Compared with mothers who gained within IOM guidelines (N = 27), mothers with excessive gestational weight gain (N = 11) (mean 29.0 vs. 45.2 lb) had neonates with 50% more fat mass (348 vs. 525 g) and 3% greater body fat (10.7 vs. 13.9%).

CONCLUSIONS

Increased adiposity at birth may predispose these children to increased risk of obesity and highlight the importance that women avoid gaining excessive weight in pregnancy.

Effects of rasagiline, its metabolite aminoindan and selegiline on glutamate receptor mediated signalling in the rat hippocampus slice in vitro

BACKGROUND

Rasagiline, a new drug developed to treat Parkinson's disease, is known to inhibit monoamine oxidase B. However, its metabolite R-(-)-aminoindan does not show this kind of activity. The present series of in vitro experiments using the rat hippocampal slice preparation deals with effects of both compounds on the pyramidal cell response after electric stimulation of the Schaffer Collaterals in comparison to selegiline, another MAO B inhibitor.

METHOD

Stimulation of the Schaffer Collaterals by single stimuli (SS) or theta burst stimulation (TBS) resulted in stable responses of pyramidal cells measured as population spike amplitude (about 1 mV under control SS conditions or about 2 mV after TBS).

RESULTS

During the first series, this response was attenuated in the presence of rasagiline and aminoindan-to a lesser degree of selegiline-in a concentration dependent manner (5-50 μM) after single stimuli as well as under TBS. During oxygen/glucose deprivation for 10 min the amplitude of the population spike breaks down by 75%. The presence of rasagiline and aminoindan, but rarely the presence of selegiline, prevented this break down. Following glutamate receptor mediated enhancements of neuronal transmission in a second series of experiments very clear differences could be observed in comparison to the action of selegiline: NMDA receptor, AMPA receptor as well as metabotropic glutamate receptor mediated increases of transmission were concentration dependently (0,3 - 2 μM) antagonized by rasagiline and aminoindan, but not by selegiline. On the opposite, only selegiline attenuated kainate receptor mediated increases of excitability. Thus, both monoamino oxidase (MAO) B inhibitors show attenuation of glutamatergic transmission in the hippocampus but interfere with different receptor mediated excitatory modulations at low concentrations.

CONCLUSIONS

Since aminoindan does not induce MAO B inhibition, these effects must be regarded as being independent from MAO B inhibition. The results provide strong evidence for a neuroprotective activity of rasagiline and aminoindan in concert with an extended clinical indication into the direction of other diseases like Alzheimer's disease or stroke.

Ecdysteroid biosynthesis and embryonic development are disturbed in insects (Locusta migratoria) reared on plant diet (Triticum sativum) with a selectively modified sterol profile

Wheat seedlings germinating in the presence of the systemic fungicide fenpropimorph accumulate 9beta,19-cyclopropylsterols (95% of total sterols) in place of Delta(5)-sterols, which are normally produced in these plants. Adult females of the phytophagous insect Locusta migratoria show a dramatic decrease in their cholesterol content when reared on fenpropimorph-treated wheat. These females lay eggs with the ecdysteroid concentration reduced by up to 80% as compared to controls. Injection of fenpropimorph to the insects or feeding them on wheat coated with the fungicide (normal sterol composition) does not affect their sterol or ecdysteroid profiles; addition of cholesterol to fenpropimorph-treated wheat prior to feeding restores normal ecdysteroid titers in the insects. The severe reduction of the ecdysteroid content in eggs laid by females reared on fenpropimorph-treated wheat is associated with a series of developmental arrests and/or abnormalities. The results show that the dietary 9beta,19-cyclopropylsterols cannot be used by Locusta in place of Delta(5)-sterols for ecdysteroid biosynthesis. They suggest that the selective inhibition of specific enzymes in the sterol biosynthetic pathway of the plants can be used as a strategy to control insect development.

Toll receptors in Drosophila: a family of molecules regulating development and immunity

In recent years, Toll-like receptors (TLRs) have emerged as key receptors which detect microbes and initiate an inflammatory response. The Toll receptor was originally identified and characterized 14 years ago for its role in the embryonic development of the fruit-fly Drosophila melanogaster. Subsequently, it was also shown to be an essential component of the signaling pathway mediating the anti-fungal host defense in this model organism. New factors involved in the activation of the Toll receptor or in intracytoplasmic signaling during the immune response in Drosophila have recently been identified. The existence of significant functional differences between mammalian TLRs and Drosophila Toll receptors is also becoming apparent.

A genome-wide analysis of immune responses in Drosophila

Oligonucleotide DNA microarrays were used for a genome-wide analysis of immune-challenged Drosophila infected with Gram-positive or Gram-negative bacteria, or with fungi. Aside from the expression of an established set of immune defense genes, a significant number of previously unseen immune-induced genes were found. Genes of particular interest include corin- and Stubble-like genes, both of which have a type II transmembrane domain; easter- and snake-like genes, which may fulfil the roles of easter and snake in the Toll pathway; and a masquerade-like gene, potentially involved in enzyme regulation. The microarray data has also helped to greatly reduce the number of target genes in large gene groups, such as the proteases, helping to direct the choices for future mutant studies. Many of the up-regulated genes fit into the current conceptual framework of host defense, whereas others, including the substantial number of genes with unknown functions, offer new avenues for research.

Drosophila Toll is activated by Gram-positive bacteria through a circulating peptidoglycan recognition protein

Microbial infection activates two distinct intracellular signalling cascades in the immune-responsive fat body of Drosophila. Gram-positive bacteria and fungi predominantly induce the Toll signalling pathway, whereas Gram-negative bacteria activate the Imd pathway. Loss-of-function mutants in either pathway reduce the resistance to corresponding infections. Genetic screens have identified a range of genes involved in these intracellular signalling cascades, but how they are activated by microbial infection is largely unknown. Activation of the transmembrane receptor Toll requires a proteolytically cleaved form of an extracellular cytokine-like polypeptide, Spätzle, suggesting that Toll does not itself function as a bona fide recognition receptor of microbial patterns. This is in apparent contrast with the mammalian Toll-like receptors and raises the question of which host molecules actually recognize microbial patterns to activate Toll through Spätzle. Here we present a mutation that blocks Toll activation by Gram-positive bacteria and significantly decreases resistance to this type of infection. The mutation semmelweis (seml) inactivates the gene encoding a peptidoglycan recognition protein (PGRP-SA). Interestingly, seml does not affect Toll activation by fungal infection, indicating the existence of a distinct recognition system for fungi to activate the Toll pathway.

Gambicin: a novel immune responsive antimicrobial peptide from the malaria vector Anopheles gambiae

A novel mosquito antimicrobial peptide, gambicin, and the corresponding gene were isolated in parallel through differential display-PCR, an expressed sequence tag (EST) project, and characterization of an antimicrobial activity in a mosquito cell line by reverse-phase chromatography. The 616-bp gambicin ORF encodes an 81-residue protein that is processed and secreted as a 61-aa mature peptide containing eight cysteines engaged in four disulfide bridges. Gambicin lacks sequence homology with other known proteins. Like other Anopheles gambiae antimicrobial peptide genes, gambicin is induced by natural or experimental infection in the midgut, fatbody, and hemocyte-like cell lines. Within the midgut, gambicin is predominantly expressed in the anterior part. Both local and systemic gambicin expression is induced during early and late stages of natural malaria infection. In vitro experiments showed that the 6.8-kDa mature peptide can kill both Gram-positive and Gram-negative bacteria, has a morphogenic effect on a filamentous fungus, and is marginally lethal to Plasmodium berghei ookinetes. An oxidized form of gambicin isolated from the cell line medium was more active against bacteria than the nonoxidized form from the same medium.

LPS-induced immune response in Drosophila

The study of the regulation of the inducible synthesis of antimicrobial peptides in Drosophila melanogaster has established this insect as a powerful model in which to study innate immunity. In particular, the molecular characterization of the regulatory pathway controlling the antifungal peptide drosomycin has revealed the importance of Toll receptors in innate immunity. We report here that injection of LPS into flies induces an immune response, suggesting that LPS receptors are used in Drosophila to detect Gram-negative bacteria infection. We have identified in the recently sequenced genome of Drosophila eight genes coding for Toll-like receptors in addition to Toll, which may function as LPS receptors. However, overexpression of a selection of these genes in tissue-culture cells does not result in up-regulation of the antibacterial peptide genes. These results are discussed in light of the recent data from genetic screens aimed at identifying the genes controlling the antibacterial response in Drosophila.

Drosophila immune deficiency (IMD) is a death domain protein that activates antibacterial defense and can promote apoptosis

We report the molecular characterization of the immune deficiency (imd) gene, which controls antibacterial defense in Drosophila. imd encodes a protein with a death domain similar to that of mammalian RIP (receptor interacting protein), a protein that plays a role in both NF-kappaB activation and apoptosis. We show that imd functions upstream of the DmIKK signalosome and the caspase DREDD in the control of antibacterial peptide genes. Strikingly, overexpression of imd leads to constitutive transcription of these genes and to apoptosis, and both effects are blocked by coexpression of the caspase inhibitor P35. We also show that imd is involved in the apoptotic response to UV irradiation. These data raise the possibility that antibacterial response and apoptosis share common control elements in Drosophila.

Toll receptors in innate immunity

Innate immunity is the first-line host defense of multicellular organisms that rapidly operates to limit infection upon exposure to infectious agents. In addition, the cells and molecules operating during this early stage of the immune response in vertebrates have a decisive impact on the shaping of the subsequent adaptive response. Genetic studies initially performed in the fruitfly Drosophila and later in mice have revealed the importance of proteins of the Toll family in the innate immune response. We present here our current understanding of the role of this evolutionary ancient family of proteins that are thought to function as cytokine receptors (Toll in Drosophila) or pattern-recognition receptors (TLRs in mammals) and activate similar, albeit non-identical, signal-transduction pathways in flies and mammals.

Toll and Toll-like proteins: an ancient family of receptors signaling infection

Innate immunity is the first-line host defense of multicellular organisms that rapidly operates to limit infection upon exposure to microbes. It involves intracellular signaling pathways in the fruit-fly Drosophila and in mammals that show striking similarities. Recent genetic and biochemical data have revealed, in particular, that proteins of the Toll family play a critical role in the immediate response to infection. We review here the recent developments on the structural and functional characterization of this evolutionary ancient and important family of proteins, which can function as cytokine receptors (Toll in Drosophila) or pattern recognition receptors (TLR4 in mammals) and activate similar, albeit non identical signal transduction pathways, in flies and mammals.

Microfluorometer assay to measure the expression of beta-galactosidase and green fluorescent protein reporter genes in single Drosophila flies

beta-galactosidase and green fluorescent protein (GFP) are among the most commonly used reporter genes to monitor gene expression in various organisms including Drosophila melanogaster. Their expression is usually detected in a qualitative way by direct microscopic observations of cells, tissues, or whole animals. To measure in vivo the inducibility of two antimicrobial peptide genes expressed during the Drosophila innate immune response, we have adapted two reporter gene systems based on the beta-galactosidase enzymatic activity and GFP. We have designed a 96-well microplate fluorometric assay sensitive enough to quantify the expression of both reporter genes in single flies. The assay has enabled us to process efficiently and rapidly a large number of individual mutant flies generated during an ethylmethane sulfonate saturation mutagenesis of the Drosophila genome. This method may be used in any screen that requires the quantification of reporter gene activity in individual insects.

Insect immunity. Constitutive expression of a cysteine-rich antifungal and a linear antibacterial peptide in a termite insect

Two novel antimicrobial peptides, which we propose to name termicin and spinigerin, have been isolated from the fungus-growing termite Pseudacanthotermes spiniger (heterometabole insect, Isoptera). Termicin is a 36-amino acid residue antifungal peptide, with six cysteines arranged in a disulfide array similar to that of insect defensins. In contrast to most insect defensins, termicin is C-terminally amidated. Spinigerin consists of 25 amino acids and is devoid of cysteines. It is active against bacteria and fungi. Termicin and spinigerin show no obvious sequence similarities with other peptides. Termicin is constitutively present in hemocyte granules and in salivary glands. The presence of termicin and spinigerin in unchallenged termites contrasts with observations in evolutionary recent insects or insects undergoing complete metamorphosis, in which antimicrobial peptides are induced in the fat body and released into the hemolymph after septic injury.

Tissue-specific inducible expression of antimicrobial peptide genes in Drosophila surface epithelia

The production of antimicrobial peptides is an important aspect of host defense in multicellular organisms. In Drosophila, seven antimicrobial peptides with different spectra of activities are synthesized by the fat body during the immune response and secreted into the hemolymph. Using GFP reporter transgenes, we show here that all seven Drosophila antimicrobial peptides can be induced in surface epithelia in a tissue-specific manner. The imd gene plays a critical role in the activation of this local response to infection. In particular, drosomycin expression, which is regulated by the Toll pathway during the systemic response, is regulated by imd in the respiratory tract, thus demonstrating the existence of distinct regulatory mechanisms for local and systemic induction of antimicrobial peptide genes in Drosophila.

Constitutive expression of a complement-like protein in toll and JAK gain-of-function mutants of Drosophila

We show that Drosophila expresses four genes encoding proteins with significant similarities with the thiolester-containing proteins of the complement C3/alpha(2)-macroglobulin superfamily. The genes are transcribed at a low level during all stages of development, and their expression is markedly up-regulated after an immune challenge. For one of these genes, which is predominantly expressed in the larval fat body, we observe a constitutive expression in gain-of-function mutants of the Janus kinase (JAK) hop and a reduced inducibility in loss-of-function hop mutants. We also observe a constitutive expression in gain-of-function Toll mutants. We discuss the possible roles of these novel complement-like proteins in the Drosophila host defense.

Role of Drosophila IKK gamma in a toll-independent antibacterial immune response

We have generated, by ethylmethane sulfonate mutagenesis, loss-of-function mutants in the Drosophila homolog of the mammalian I-kappa B kinase (IKK) complex component IKK gamma (also called NEMO). Our data show that Drosophila IKK gamma is required for the Relish-dependent immune induction of the genes encoding antibacterial peptides and for resistance to infections by Escherichia coli. However, it is not required for the Toll-DIF-dependent antifungal host defense. The results indicate distinct control mechanisms of the Rel-like transactivators DIF and Relish in the Drosophila innate immune response and show that Drosophila Toll does not signal through a IKK gamma-dependent signaling complex. Thus, in contrast to the vertebrate inflammatory response, IKK gamma is required for the activation of only one immune signaling pathway in Drosophila.

Toll-related receptors and the control of antimicrobial peptide expression in Drosophila

Insects defend themselves against infectious microorganisms by synthesizing potent antimicrobial peptides. Drosophila has appeared in recent years as a favorable model to study this innate host defense. A genetic analysis of the regulation of the antifungal peptide drosomycin has demonstrated a key role for the transmembrane receptor Toll, which prompted the search for mammalian homologs. Two of these, Toll-like receptor (TLR)2 and TLR4, recently were shown to play a critical role in innate immunity against bacteria. Here we describe six additional Toll-related genes (Toll-3 to Toll-8) in Drosophila in addition to 18-wheeler. Two of these genes, Toll-3 and Toll-4, are expressed at a low level. Toll-6, -7, and -8, on the other hand, are expressed at high levels during embryogenesis and molting, suggesting that, like Toll and 18w, they perform developmental functions. Finally, Toll-5 is expressed only in larvae and adults. By using chimeric constructs, we have tested the capacity of the signaling Toll/IL-1R homology domains of these receptors to activate antimicrobial peptide promoters and found that only Toll and Toll-5 can activate the drosomycin promoter in transfected cells, thus demonstrating specificity at the level of the Toll/IL-1R homology domain. In contrast, none of these constructs activated antibacterial peptide promoters, suggesting that Toll-related receptors are not involved in the regulation of antibacterial peptide expression. This result was independently confirmed by the demonstration that a dominant-negative version of the kinase Pelle can block induction of drosomycin by the cytokine Spaetzle, but does not affect induction of the antibacterial peptide attacin by lipopolysaccharide.

The Rel protein DIF mediates the antifungal but not the antibacterial host defense in Drosophila

We have isolated two Drosophila lines that carry point mutations in the gene coding for the NF-KB-like factor DIF. Like mutants of the Toll pathway, Dif mutant flies are susceptible to fungal but not to bacterial infections. Genetic epistasis experiments demonstrate that Dif mediates the Toll-dependent control of the inducibility of the antifungal peptide gene Drosomycin. Strikingly, DIF alone is required for the antifungal response in adults, but is redundant in larvae with Dorsal, another Rel family member. In Drosophila, Dif appears to be dedicated to the antifungal defense elicited by fungi and gram-positive bacteria. We discuss in this light the possibility that NF-KB1/p50 might be required more specifically in the innate immune response against gram-positive bacteria in mammals.

The phytopathogenic bacteria Erwinia carotovora infects Drosophila and activates an immune response

Although Drosophila possesses potent immune responses, little is known about the microbial pathogens that infect Drosophila. We have identified members of the bacterial genus Erwinia that induce the systemic expression of genes encoding antimicrobial peptides in Drosophila larvae after ingestion. These Erwinia strains are phytopathogens and use flies as vectors; our data suggest that these strains have also evolved mechanisms for exploiting their insect vectors as hosts. Erwinia infections induce an antimicrobial response in Drosophila larvae with a preferential expression of antibacterial versus antifungal peptide-encoding genes. Antibacterial peptide gene expression after Erwinia infection is reduced in two Drosophila mutants that have reduced numbers of hemocytes, suggesting that blood cells play a role in regulating Drosophila antimicrobial responses and also illustrating that this Drosophila-Erwinia interaction provides a powerful model for dissecting host-pathogen relationships.

Signaling mechanisms in the antimicrobial host defense of Drosophila

Drosophila has appeared in recent years as a powerful model to study innate immunity. Several papers published in the past year shed light on the role of the three Rel proteins Dorsal, Dif and Relish in the regulation of antimicrobial peptide expression. In addition, the discovery that a blood serine protease inhibitor is involved in the control of the antifungal response indicates that Toll is activated upon triggering of a proteolytic cascade and does not function as a Drosophila pattern recognition receptor.

Androctonin, a hydrophilic disulphide-bridged non-haemolytic anti-microbial peptide: a plausible mode of action

Androctonin is a 25-residue non-haemolytic anti-microbial peptide isolated from the scorpion Androctonus australis and contains two disulphide bridges. Androctonin is different from known native anti-microbial peptides, being a relatively hydrophilic and non-amphipathic molecule. This raises the possibility that the target of androctonin might not be the bacterial membrane, shown to be a target for most amphipathic lytic peptides. To shed light on its mode of action on bacteria and its non-haemolytic activity, we synthesized androctonin, its fluorescent derivatives and its all-D-amino acid enantiomer. The enantiomer preserved high activity, suggesting a lipid-peptide interaction between androctonin and bacterial membranes. In Gram-positive and (at higher concentrations) Gram-negative bacteria, androctonin induced an immediate perturbation of the permeability properties of the cytoplasmic membrane of the bacterial energetic state, concomitant with perturbation of the morphology of the cell envelope as revealed by electron microscopy. Androctonin binds only to negatively charged lipid vesicles and induces the leakage of markers at high concentrations and with a slow kinetics, in contrast with amphipathic alpha-helical anti-microbial peptides that bind and permeate negatively charged vesicles, and to a smaller extent also zwitterionic ones. This might explain the selective lytic activity of androctonin towards bacteria but not red blood cells. Polarized attenuated total reflection-Fourier transform infrared spectroscopy revealed that androctonin adopts a beta-sheet structure in membranes and did not affect the lipid acyl chain order, which supports a detergent-like effect. The small size of androctonin, its hydrophilic character and its physicochemical properties are favourable features for its potential application as a replacement for commercially available antibiotics to which bacteria have developed resistance.

Effect of atenolol and celiprolol on acetylcholine-induced coronary vasomotion in coronary artery disease

Earlier studies have reported on the potentiated muscarinic vasoconstriction of intracoronary acetylcholine after metoprolol application in patients with coronary artery disease. The present study investigated the effect of celiprolol, atenolol, and placebo on acetylcholine-induced vasomotion in patients with coronary artery disease. Furthermore, direct effects on coronary vasomotion and on hemodynamics were evaluated. Acetylcholine (intracoronary concentrations of 6.3x10(-7), 2.0x10(-6), and 6.3x10(-6) M) was given before and after double-blind celiprolol (0.30 mg/kg IV), atenolol (0.15 mg/kg IV), or placebo in 3x12 patients. Vasomotion was investigated by quantitative coronary angiography in proximal and distal segments of epicardial coronary arteries, and by the determination of the coronary resistance index based on Doppler-flow measurements. The investigated drugs had no direct affect on the diameter of the epicardial coronary arteries. However, celiprolol, in contrast to atenolol, significantly reduced systemic vascular resistance (change after atenolol: from 1,855+/-308 to 2,161+/-550 dyne s cm(-5); celiprolol: 1,691+/-435 to 1,411+/-343 dyne s cm(-5); and placebo: 1,722+/-215 to 1,710+/-213 dyne s cm(-5), p<0.001) and the coronary resistance index (change after atenolol: 2.52+/-3.58 to 2.86+/-4.24; celiprolol: 2.70+/-1.55 to 2.49+/-2.26; and placebo: 1.97+/-1.35 to 1.92+/-1.25, p<0.01). Celiprolol, atenolol, and placebo did not have different effects on acetylcholine-induced coronary vasomotion of epicardial conductance vessels (diminution of proximal lumen diameter before/after atenolol: 0.42+/-0.39/0.44+/-0.39 mm; celiprolol: 0.32+/-0.26/0.30+/-0.24 mm; and placebo: 0.36+/-0.29/0.43+/-0.40 mm) and of coronary resistance vessels (reduction of coronary resistance index before/after atenolol: 1.95 +/-4.74/ 1.92+/-3.74; celiprolol: 0.98+/-0.73/1.41+/-1.50; and placebo: 1.16+/-1.29/1.16+/-1.04). In contrast to atenolol, celiprolol possesses vasodilative properties in systemic and coronary resistance vessels. There was no direct effect on the diameter of conductance vessels. Acetylcholine-induced coronary vasomotion both in conductance and resistance vessels was not influenced by the beta blockers that were studied. This suggests that atenolol and celiprolol do not influence endothelium-dependent, nitric oxide related vasomotion.

Constitutive activation of toll-mediated antifungal defense in serpin-deficient Drosophila

The antifungal defense of Drosophila is controlled by the spaetzle/Toll/cactus gene cassette. Here, a loss-of-function mutation in the gene encoding a blood serine protease inhibitor, Spn43Ac, was shown to lead to constitutive expression of the antifungal peptide drosomycin, and this effect was mediated by the spaetzle and Toll gene products. Spaetzle was cleaved by proteolytic enzymes to its active ligand form shortly after immune challenge, and cleaved Spaetzle was constitutively present in Spn43Ac-deficient flies. Hence, Spn43Ac negatively regulates the Toll signaling pathway, and Toll does not function as a pattern recognition receptor in the Drosophila host defense.

A mosaic analysis in Drosophila fat body cells of the control of antimicrobial peptide genes by the Rel proteins Dorsal and DIF

Expression of the gene encoding the antifungal peptide Drosomycin in Drosophila adults is controlled by the Toll signaling pathway. The Rel proteins Dorsal and DIF (Dorsal-related immunity factor) are possible candidates for the transactivating protein in the Toll pathway that directly regulates the drosomycin gene. We have examined the requirement of Dorsal and DIF for drosomycin expression in larval fat body cells, the predominant immune-responsive tissue, using the yeast site-specific flp/FRT recombination system to generate cell clones homozygous for a deficiency uncovering both the dorsal and the dif genes. Here we show that in the absence of both genes, the immune-inducibility of drosomycin is lost but can be rescued by overexpression of either dorsal or dif under the control of a heat-shock promoter. This result suggests a functional redundancy between both Rel proteins in the control of drosomycin gene expression in the larvae of Drosophila. Interestingly, the gene encoding the antibacterial peptide Diptericin remains fully inducible in the absence of the dorsal and dif genes. Finally, we have used fat body cell clones homozygous for various mutations to show that a linear activation cascade Spaetzle--> Toll-->Cactus-->Dorsal/DIF leads to the induction of the drosomycin gene in larval fat body cells.

Phylogenetic perspectives in innate immunity

The concept of innate immunity refers to the first-line host defense that serves to limit infection in the early hours after exposure to microorganisms. Recent data have highlighted similarities between pathogen recognition, signaling pathways, and effector mechanisms of innate immunity in Drosophila and mammals, pointing to a common ancestry of these defenses. In addition to its role in the early phase of defense, innate immunity in mammals appears to play a key role in stimulating the subsequent, clonal response of adaptive immunity.

Insect immunity. Isolation from the lepidopteran Heliothis virescens of a novel insect defensin with potent antifungal activity

Lepidoptera have been reported to produce several antibacterial peptides in response to septic injury. However, in marked contrast to other insect groups, no inducible antifungal molecules had been described so far in this insect order. Surprisingly, also cysteine-rich antimicrobial peptides, which predominate in the antimicrobial defense of other insects, had not been discovered in Lepidoptera. Here we report the isolation from the hemolymph of immune induced larvae of the lepidopteran Heliothis virescens of a cysteine-rich molecule with exclusive antifungal activity. We have fully characterized this antifungal molecule, which has significant homology with the insect defensins, a large family of antibacterial peptides directed against Gram-positive strains. Interestingly, the novel peptide shows also similarities with the antifungal peptide drosomycin from Drosophila. Thus, Lepidoptera appear to have built their humoral immune response against bacteria on cecropins and attacins. In addition, we report that Lepidoptera have conferred antifungal properties to the well conserved structure of antibacterial insect defensins through amino acid replacements.

Insect immunity: molecular cloning, expression, and characterization of cDNAs and genomic DNA encoding three isoforms of insect defensin in Aedes aegypti

Aedes aegypti were immune activated by injection with bacteria, and the expression of insect defensins was measured over time. Northern analyses indicated that defensin transcriptional activity continued for at least 21 days after bacterial injection, and up to 10 days after saline inoculation. Mature defensin levels in the haemolymph reached approximately 45 microM at 24 h post inoculation. cDNAs encoding the preprodefensins of three previously described mature Ae. aegypti defensins were amplified by PCR, cloned and sequenced. Genomic clones were amplified using primers designed against the cDNA sequence. Sequence comparison indicates that there is significant inter- and intra-isoform variability in the signal peptide and prodefensin sequences of defensin genes. Preprodefensin sequences of isoforms A and B are very similar, consisting of a signal peptide region of twenty amino acids, a prodefensin region of thirty-eight amino acids and a forty amino acid mature peptide domain. The sequence encoding isoform C is significantly different, comprising a signal peptide region of twenty-three amino acids, a prodefensin region of thirty-six amino acids, and the mature protein domain of forty amino acids. Analysis of the genomic clones of each isoform revealed one intron spatially conserved in the prodefensin region of all sequences. The intron in isoforms A and B is 64 nt long, and except for a 4 nt substitution in one clone, these intron sequences are identical. The intron in isoform C is 76 nt long and does not share significant identity with the intron sequences of isoforms A or B. The defensin gene mapped to chromosome 3, between two known loci, blt and LF168.

Mosquito-Plasmodium interactions in response to immune activation of the vector

During the development of Plasmodium sp. within the mosquito midgut, the parasite undergoes a series of developmental changes. The elongated ookinete migrates through the layers of the midgut where it forms the oocyst under the basal lamina. We demonstrate here that if Aedes aegypti or Anopheles gambiae, normally susceptible to Plasmodium gallinaceum and P. berghei, respectively, are immune activated by the injection of bacteria into the hemocoel, and subsequently are fed on an infectious bloodmeal, there is a significant reduction in the prevalence and mean intensity of infection of oocysts on the midgut. Only those mosquitoes immune activated prior to, or immediately after, parasite ingestion exhibit this reduction in parasite development. Mosquitoes immune activated 2-5 days after bloodfeeding show no differences in parasite burdens compared with naive controls. Northern analyses reveal that transcriptional activity for mosquito defensins is not detected in the whole bodies of Ae. aegypti from 4 h to 10 days after ingesting P. gallinaceum, suggesting that parasite ingestion, passage from the food bolus through the midgut, oocyst formation, and subsequent release of sporozoites into the hemolymph do not induce the production of defensin. However, reverse transcriptase-PCR of RNA isolated solely from the midguts of Ae. aegypti indicates that transcription of mosquito defensins occurs in the midguts of naive mosquitoes and those ingesting an infectious or noninfectious bloodmeal. Bacteria-challenged Ae. aegypti showed high levels of mature defensin in the hemolymph that correlate with a lower prevalence and mean intensity of infection with oocysts. Because few oocysts were found on the midgut of immune-activated mosquitoes, the data suggest that some factor, induced by bacterial challenge, kills the parasite at a preoocyst stage.

Analysis of the Drosophila host defense in domino mutant larvae, which are devoid of hemocytes

We have analyzed the Drosophila immune response in domino mutant larvae, which are devoid of blood cells. The domino mutants have a good larval viability, but they die as prepupae. We show that, on immune challenge, induction of the genes encoding antimicrobial peptides in the fat body is not affected significantly in the mutant larvae, indicating that hemocytes are not essential in this process. The hemocoele of domino larvae contains numerous live microorganisms, the presence of which induces a weak antimicrobial response in the fat body. A full response is observed only after septic injury. We propose that the fat body cells are activated both by the presence of microorganisms and by injury and that injury potentiates the effect of microorganisms. Survival experiments after an immune challenge showed that domino mutants devoid of blood cells maintain a wild-type resistance to septic injury. This resistance was also observed in mutant larvae in which the synthesis of antibacterial peptides is impaired (immune deficiency larvae) and in mutants that are deficient for humoral melanization (Black cells larvae). However, if domino was combined with either the immune deficiency or the Black cell mutation, the resistance to septic injury was reduced severely. These results establish the relevance of the three immune reactions: phagocytosis, synthesis of antibacterial peptides, and melanization. By working in synergy, they provide Drosophila a highly effective defense against injury and/or infection.

Differential display of peptides induced during the immune response of Drosophila: a matrix-assisted laser desorption ionization time-of-flight mass spectrometry study

We have developed an approach based on a differential mass spectrometric analysis to detect molecules induced during the immune response of Drosophila, regardless of their biological activities. For this, we have applied directly matrix-assisted laser desorption/ionization MS to hemolymph samples from individual flies before and after an immune challenge. This method provided precise information on the molecular masses of immune-induced molecules and allowed the detection, in the molecular range of 1.5-11 kDa, of 24 Drosophila immune-induced molecules (DIMs). These molecules are all peptides, and four correspond to already characterized antimicrobial peptides. We have further analyzed the induction of the various peptides by immune challenge in wild-type flies and in mutants with a compromised antimicrobial response. We also describe a methodology combining matrix-assisted laser desorption ionization time-of-flight MS, HPLC, and Edman degradation, which yielded the peptide sequence of three of the DIMs. Finally, molecular cloning and Northern blot analyses revealed that one of the DIMs is produced as a prepropeptide and is inducible on a bacterial challenge.

Plasmodium gallinaceum: differential killing of some mosquito stages of the parasite by insect defensin

We examined several insect antimicrobial peptides to study their effect on Plasmodium gallinaceum zygotes, ookinetes, oocysts, and sporozoites. Only two insect defensins-Aeschna cyanea (dragon fly) and Phormia terranovae (flesh fly)-had a profound toxic effect on the oocysts in Aedes aegypti and on isolated sporozoites. The defensins affected the oocysts in a time-dependent manner. Injecting the peptide into the hemolymph 1 or 2 days after an infectious blood meal had no significant effect on prevalence of infection or relative oocyst density per mosquito. When injected 3 days after parasite ingestion, the relative oocyst density was significantly reduced. Injection on day 4 or later damaged the developing oocysts, although the oocysts density per mosquito was not significantly different when examined on day 8. The oocysts were swollen or had extensive internal vacuolization. The peptides had no detectable effect on the early stages of the parasite: the zygotes and ookinetes tested in vitro. Both the defensins were highly toxic to isolated sporozoites in vitro as indicated by disruption of the membrane permeability barrier, a change in morphology, and loss of motility. In contrast to the toxicity of cecropin and magainin for mosquitoes, defensin, at concentrations that kill parasites, is not toxic to mosquitoes, suggesting that defensin should be studied further as a potential molecule to block sporogonic development of Plasmodium.

In vivo regulation of the IkappaB homologue cactus during the immune response of Drosophila

The dorsoventral regulatory gene pathway (spätzle/Toll/cactus) controls the expression of several antimicrobial genes during the immune response of Drosophila. This regulatory cascade shows striking similarities with the cytokine-induced activation cascade of NF-kappaB during the inflammatory response in mammals. Here, we have studied the regulation of the IkappaB homologue Cactus in the fat body during the immune response. We observe that the cactus gene is up-regulated in response to immune challenge. Interestingly, the expression of the cactus gene is controlled by the spätzle/Toll/cactus gene pathway, indicating that the cactus gene is autoregulated. We also show that two Cactus isoforms are expressed in the cytoplasm of fat body cells and that they are rapidly degraded and resynthesized after immune challenge. This degradation is also dependent on the Toll signaling pathway. Altogether, our results underline the striking similarities between the regulation of IkappaB and cactus during the immune response.

A novel insect defensin from the ant Formica rufa

By combination of size exclusion and reversed-phase chromatography, we have isolated a novel member of insect defensin-type antimicrobial peptides from the entire bodies of bacteria-challenged Formica rufa (hymenoptera, formicidae). The molecular mass of the purified peptide was estimated to be 4120.42 by matrix-assisted laser desorption/ionization-time of flight/mass spectrometry. Sequence analysis revealed that this peptide consisted of 40 amino acid residues with six cysteines engaged in the formation of three intramolecular disulfide bridges. This peptide is unique among the arthropod defensins in terms of the presence of asparatic acid and alanine at position 33 and as C-terminal residue, respectively. In addition, this novel defensin from Formica rufa has the particularity to have no C-terminal extension in contrast to those reported for other hymenoptera defensins.

A drosomycin-GFP reporter transgene reveals a local immune response in Drosophila that is not dependent on the Toll pathway

A hallmark of the systemic antimicrobial response of Drosophila is the synthesis by the fat body of several antimicrobial peptides which are released into the hemolymph in response to a septic injury. One of these peptides, drosomycin, is active primarily against fungi. Using a drosomycin-green fluorescent protein (GFP) reporter gene, we now show that in addition to the fat body, a variety of epithelial tissues that are in direct contact with the external environment, including those of the respiratory, digestive and reproductive tracts, can express the antifungal peptide, suggesting a local response to infections affecting these barrier tissues. As is the case for vertebrate epithelia, insect epithelia appear to be more than passive physical barriers and are likely to constitute an active component of innate immunity. We also show that, in contrast to the systemic antifungal response, this local immune response is independent of the Toll pathway.

Drosophila host defense: differential induction of antimicrobial peptide genes after infection by various classes of microorganisms

Insects respond to microbial infection by the rapid and transient expression of several genes encoding potent antimicrobial peptides. Herein we demonstrate that this antimicrobial response of Drosophila is not aspecific but can discriminate between various classes of microorganisms. We first observe that the genes encoding antibacterial and antifungal peptides are differentially expressed after injection of distinct microorganisms. More strikingly, Drosophila that are naturally infected by entomopathogenic fungi exhibit an adapted response by producing only peptides with antifungal activities. This response is mediated through the selective activation of the Toll pathway.

Antimicrobial peptide defense in Drosophila

Drosophila responds to a septic injury by the rapid synthesis of antimicrobial peptides. These molecules are predominantly produced by the fat body, a functional equivalent of mammalian liver, and are secreted into the hemolymph where their concentrations can reach up to 100 microM. Six distinct antibacterial peptides (plus isoforms) and one antifungal peptide have been characterized in Drosophila and their genes cloned. The induction of the gene encoding the antifungal peptide relies on the spätzle/Toll/cactus gene cassette, which is involved in the control of dorsoventral patterning in the embryo, and shows interesting structural and functional similarities with cytokine-induced activation of NF-kappa B in mammalian cells. An additional pathway, dependent on the as yet unidentified imd (for immune-deficiency) gene, is required for the full induction of the antibacterial peptide genes. Mutants deficient for the Toll and imd pathways exhibit a severely reduced survival to fungal and bacterial infections, respectively. Recent data on the molecular mechanisms underlying recognition of non-self are also discussed in this review.

Treatment of l(2)mbn Drosophila tumorous blood cells with the steroid hormone ecdysone amplifies the inducibility of antimicrobial peptide gene expression

Insects rely on both humoral and cellular mechanisms to defend themselves against microbial infections. The humoral response involves synthesis of a battery of potent antimicrobial peptides by the fat body and, to a lesser extent, by blood cells. The cellular response on the other hand consists of phagocytosis of small microorganisms and melanization and encapsulation of larger parasites. The l(2)mbn cell line, established from tumorous larval hemocytes, represents a system of choice to dissect the molecular events controlling cellular immunity. We report here that l(2)mbn cells can be efficiently induced to differentiate in adherent, macrophage-like cells by treatment with 20-hydroxyecdysone. Ecdysone treatment increases both the phagocytic capacity of l(2)mbn cells and their competence to express antimicrobial genes in response to immune challenge. We also report that expression of several regulatory molecules thought to be involved in the immune response is up-regulated by ecdysone in l(2)mbn cells.

Modifications in the B10 and B26-30 regions of the B chain of human insulin alter affinity for the human IGF-I receptor more than for the insulin receptor

Inversion of the natural sequence of the B chain of human insulin (HI) from ProB28LysB29 to LysB28ProB29 generates an insulin analogue with reduced tendency to self-associate. Since this substitution increases the homology of insulin to insulin-like growth factor-I (IGF-I), we have examined the affinity of a series of insulin analogues with the general modified structure XaaB28ProB29 HI for binding to both human placental insulin and IGF-I receptors. The XaaB28ProB29 HI series is approximately equipotent to HI in binding to the insulin receptor with the exception of when Xaa = Phe, Trp, Leu, Ile, and Gly (40-60% relative to HI). Substitution with basic residues in the B28 position increased the relative affinity to the IGF-I receptor approximately 1.5-2-fold (ArgB28ProB29 > OrnB28ProB29 = LysB28ProB29). Substitution with acidic residues reduced relative affinity for the IGF-I receptor approximately 2-fold (CyaB28ProB29 = GluB28ProB29 > AspB28ProB29). Combination of AspB10 substitution in conjunction with a modification in the B28-29 position (e.g. AspB10LysB28ProB29 HI) showed an additional 2-fold selective increase in affinity for the IGF-I receptor, suggesting that these two effects are additive. Addition of Arg residues at B31-32, on the backbone of either HI or AspB10 HI, increased affinity for the IGF-I receptor 10 and 28 fold, respectively, compared to HI, confirming the significance of enhanced positive charge at the C-terminal end of the insulin B-chain in increasing selectivity for the IGF-I receptor. This relative increase in IGF-I receptor affinity correlated largely, but not completely, with enhanced growth promoting activity in human mammary epithelial cells. In the case of LysB28ProB29 HI, growth activity correlated with dissociation kinetics from the insulin receptor which were shown to be identical with those of human insulin.

Characterization of novel cysteine-rich antimicrobial peptides from scorpion blood

We have isolated, from the hemolymph of unchallenged scorpions of the species Androctonus australis, three distinct antimicrobial peptides, which we have fully characterized by Edman degradation, electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization mass spectrometry. Two are novel molecules: (i) androctonin, a 25-residue peptide with two disulfide bridges, active against both bacteria (Gram-positive and Gram-negative) and fungi and showing marked sequence homology to tachyplesins and polyphemusins from horseshoe crabs; and (ii) buthinin, a 34-residue antibacterial (Gram-positive and Gram-negative) peptide with three disulfide bridges. The third peptide contains 37 residues and three disulfide bridges and clearly belongs to the family of anti-Gram-positive insect defensins. We have synthesized androctonin and explored its activity spectrum and mode of action.

Pancreatic polypeptide administration improves abnormal glucose metabolism in patients with chronic pancreatitis

Chronic pancreatitis (CP) is associated with lowered plasma levels and a blunted nutrient-induced release of pancreatic polypeptide (PP). To investigate the possible role of PP on glucose metabolism, we studied male patients with documented CP (n = 5) and obesity-matched control subjects (NL) (n = 6). Hepatic glucose production (HGP) and overall glucose disposal rates were determined by [3-3H]glucose infusion during a hyperinsulinemic-euglycemic clamp during three separate admissions. Basal rates of HGP were higher in CP patients. In response to an infusion of insulin (60 pmol.m-2.min-1), HGP fell 91 +/- 5% in NL subjects but only 68 +/- 8% in CP subjects (P < 0.05). One month later, the clamp was repeated during the final 2 h of an 8-h infusion of bovine PP (2 pmol.kg-1.min-1). HGP before the insulin infusion and its subsequent suppression (NL: 83 +/- 5%; CP: 86 +/- 15%) were nearly identical between groups. In follow-up studies 1 month after the PP infusion, HGP both basally and in response to insulin alone were similar to the first study. During oral glucose tolerance tests (OGTT) performed 18 h after the PP infusion, subjects with normal (n = 7) baseline OGTT responses showed no effect. All patients with diabetic (n = 3) or nondiagnostic (n = 1) OGTT responses, however, demonstrated lowered mean plasma glucose levels (approximately -2.3 mmol/L; range: -0.6 to -7.2 mmol/L). OGTTs repeated 1 month after the PP treatment showed a return to pretreatment responses. We conclude that chronic pancreatitis accompanied by PP deficiency is associated with partial hepatic resistance both in the basal state and in response to hyperinsulinemia. This impairment is reversed after iv PP administration. PP deficiency may therefore play a role in the development of pancreatogenic diabetes caused by pancreatic injury.

The dorsoventral regulatory gene cassette spätzle/Toll/cactus controls the potent antifungal response in Drosophila adults

The cytokine-induced activation cascade of NF-kappaB in mammals and the activation of the morphogen dorsal in Drosophila embryos show striking structural and functional similarities (Toll/IL-1, Cactus/I-kappaB, and dorsal/NF-kappaB). Here we demonstrate that these parallels extend to the immune response of Drosophila. In particular, the intracellular components of the dorsoventral signaling pathway (except for dorsal) and the extracellular Toll ligand, spätzle, control expression of the antifungal peptide gene drosomycin in adults. We also show that mutations in the Toll signaling pathway dramatically reduce survival after fungal infection. Antibacterial genes are induced either by a distinct pathway involving the immune deficiency gene (imd) or by combined activation of both imd and dorsoventral pathways.

Innate immunity. Isolation of several cysteine-rich antimicrobial peptides from the blood of a mollusc, Mytilus edulis

We have isolated from the blood of immune-challenged and untreated mussels (Mytilus edulis) antibacterial and antifungal peptides. We have characterized two isoforms of a novel 34-residue, cysteine-rich, peptide with potent bactericidal activity and partially characterized a novel 6.2-kDa antifungal peptide containing 12 cysteines. We report the presence of two members of the insect defensin family of antibacterial peptides and provide a phylogenetic analysis that indicates that mollusc and arthropod defensins have a common ancestry. Our data argue that circulating antimicrobial peptides represent an ancient host defense mechanism that predated the separation between molluscs and arthropods at the root of the Cambrian, about 545 million years ago.