Evidence for the involvement of opioid neuropeptides in the adherence and migration of immunocompetent invertebrate hemocytes

Battleground midgut: The cost to the mosquito for hosting the malaria parasite

In eco-evolutionary studies of parasite-host interactions, virulence is defined as a reduction in host fitness as a result of infection relative to an uninfected host. Pathogen virulence may either promote parasite transmission, when correlated with higher parasite replication rate, or decrease the transmission rate if the pathogen quickly kills the host. This evolutionary mechanism, referred to as 'trade-off' theory, proposes that pathogen virulence evolves towards a level that most benefits the transmission. It has been generally predicted that pathogens evolve towards low virulence in their insect vectors, mainly due to the high dependence of parasite transmission on their vector survival. Therefore, the degree of virulence which malaria parasites impose on mosquito vectors may depend on several external and internal factors. Here, we review briefly (i) the role of mosquito in parasite development, with a particular focus on mosquito midgut as the battleground between Plasmodium and the mosquito host. We aim to point out (ii) the histology of the mosquito midgut epithelium and its role in host defence against parasite's countermeasures in the three main battle sites, namely (a) the lumen (microbiota and biochemical environment), (b) the peritrophic membrane (physical barrier) and (c) the tubular epithelium including the basal membrane (physical and biochemical barrier). Lastly, (iii) we describe the impact which malaria parasite and its virulence factors have on mosquito fitness.

Transcriptome analysis of hemocytes from the white shrimp Litopenaeus vannamei with the injection of dopamine

As a crucial neuroendocrine-immune factor, dopamine (DA) could regulate the immune system of Litopenaeus vannamei. To understand the immune mechanisms and regulatory pathways of DA in L. vannamei, the transcriptome analysis of hemocytes of L. vannamei with injection of DA (10^-6 mol/shrimp) at 3 and 12 h were performed in this study. Moreover, quantitative real-time PCR (qPCR) method was applied to validate the accuracy of transcriptome sequencing and analyze the expression pattern of candidate differentially expressed genes (DEGs) at different time points (0, 3, 6, 12, and 24 h) after DA injection. The results showed that a total of 51382 unigenes with a N50 length of 2341 bp were generated. And 1397 and 457 DEGs were obtained by comparative transcriptome at 3 and 12h respectively. Moreover, the results of functional annotation and enriched pathway showed that the DEGs were involved in phagosome (ko04145), lysosome (ko04142), Endocytosis (ko04144), and NOD-like receptor signaling pathway (ko04621). Besides, the Pearson's correlation coefficient (R) between transcriptome sequencing and qPCR was 0.845, which confirmed the reliability of the transcriptome sequencing results and the accuracy of assembly. Furthermore, the expression pattern of 15 candidate DEGs, containing 9 up-regulated and 6 down-regulated DEGs at 3 h, indicated the regulation of DA in physiological functions especially in the immune system. Therefore, these results revealed that DA induced the expressions of membrane receptors or proteins, activated intracellular signaling pathways, regulated cellular and humoral immune systems, controlled antioxidation and apoptosis, and was involved in the regulation of neuroendocrine system. These findings are helpful to promote the understanding on the effects of biogenic amines on physiological functions and regulatory networks of crustacean, and offer a substantial material and foundation for researching the immune response of crustacean.

Effects of a Sudden Drop in Salinity on Immune Response Mechanisms of Anadara kagoshimensis

In this experiment, the effects of a sudden drop of salinity on the immune response mechanisms of the ark shell Anadara kagoshimensis were examined by simulating the sudden drop of salinity that occurs in seawater after a rainstorm. Additionally, the differentially expressed genes (DEGs) were identified using transcriptome sequencing. When the salinity dropped from 30‱ (S30) to 14‱ (S14), the phagocytic activity of blood lymphocytes, the O₂^- levels produced from respiratory burst, the content of reactive oxygen species, and the activities of lysozymes and acid phosphatases increased significantly, whereas the total count of blood lymphocytes did not increase. Total count of blood lymphocytes in 22‱ salinity (S22) was significantly higher than that in any other group. The raw data obtained from sequencing were processed with Trimmomatic (Version 0.36). The expression levels of unigenes were calculated using transcripts per million (TPM) based on the effects of sequencing depth, gene length, and sample on reads. Differential expression analysis was performed using DESeq (Version 1.12.4). Transcriptome sequencing revealed 269 (101 up-regulated, 168 down-regulated), 326 (246 up-regulated, 80 down-regulated), and 185 (132 up-regulated, 53 down-regulated) significant DEGs from comparison of the S14 vs. S22, S22 vs. S30, and S14 vs. S30 groups, respectively. Gene Ontology enrichment analysis of the DEGs in these salinity comparison groups revealed that the cellular amino acid metabolic process, the regulation of protein processing, the regulation of response to stress, and other terms were significantly enriched. Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that nucleotide-binding, oligomerization domain (NOD)-like receptor signaling pathway (ko04621), apoptosis-multiple species (ko04215), Toll and Imd signaling pathway (ko04624), NF-κB signaling pathway (ko04064), apoptosis (ko04210), and focal adhesion (ko04510) were significantly enriched in all salinity comparison groups. qRT-PCR verification of 12 DEGs in the above six pathways was conducted, and the results were consistent with the transcriptome sequencing results in terms of up-regulation and down-regulation, which illustrates that the transcriptome sequencing data are credible. These results were used to preliminarily explore the effects of a sudden drop of salinity on blood physiological and biochemical indexes and immunoregulatory mechanisms of A. kagoshimensis. They also provide a theoretical basis for the selection of bottom areas optimal for release and proliferation of A. kagoshimensis required to restore the declining populations of this species.

Met-enkephalin inhibits ROS production through Wnt/β-catenin signaling in the ZF4 cells of zebrafish

Opioid neuropeptides are developed early in the course of a long evolutionary process. As the endogenous messengers of immune system, opioid neuropeptides participate in regulating immune response. In this study, the mechanism that Met-enkephalin (M-ENK) inhibits ROS production through Wnt/β-catenin signaling was investigated in the ZF4 cells of zebrafish. ZF4 cells were exposed to 0, 10, 20, 40, 80, and 160 μM Met-enkephalin (M-ENK) for 24 h, and the cell viability was detected with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. The cell viability was significantly increased by 10, 20, 40, 80, and 160 μM M-ENK. After ZF4 cells were exposed to 0, 20, 40, and 80 μM M-ENK for 24 h, the mRNA expression of Wnt10b, β-catenin, and CCAAT/enhancer binding protein α (C/EBPα) was significantly increased by 40 and 80 μM M-ENK. However, the mRNA and protein expression of GSK-3β was significantly decreased by 40 and 80 μM M-ENK. The protein expression of β-catenin was significantly induced by 40 and 80 μM M-ENK, while the protein expression of p-β-catenin was significantly decreased by 20, 40, and 80 μM M-ENK. In addition, the mRNA expression of CAT, SOD, and GSH-PX was significantly increased by 40 and 80 μM M-ENK. The levels of H₂O₂, ·OH, and O₂^·- were significantly decreased, but the activity of CAT, SOD, and GSH-PX was significantly increased by 40 and 80 μM M-ENK. The fluorescence intensity of reactive oxygen species (ROS) was decreased, and that of mitochondrial membrane potential (MMP) was increased with the increase of M-ENK concentration in ZF4 cells. The results showed that M-ENK could induce Wnt/β-catenin signaling, which further inhibited ROS production through the induction of C/EBPα, MMP, and the activities of antioxidant enzymes.

Immune-Neuroendocrine Interactions: Evolution, Ecology, and Susceptibility to Illness

The integration between immune and neuroendocrine systems is crucial for maintaining homeostasis from invertebrates to humans. In the first, the phagocytic cell, i.e., the immunocyte, is the main actor, while in the latter, the principle player is the lymphocyte. Immunocytes are characterized by the presence of pro-opiomelanocortin (POMC) peptides, CRH, and other molecules that display a significant similarity to their mammalian counterparts regarding their functions, as both are mainly involved in fundamental functions such as immune (chemotaxis, phagocytosis, cytotoxicity, etc.) and neuroendocrine (stress) responses. Furthermore, the immune-neuroendocrine system provides vital answers to ecological and immunological demands in terms of economy and efficiency. Finally, susceptibility to disease emerges as the result of a continuous dynamic interaction between the world within and the world outside. New fields such as ecological immunology study the susceptibility to pathogens in an evolutionary perspective while the field of neuro-endocrine-immunology studies the susceptibility from a more immediate perspective.

Allatotropin: A pleiotropic neuropeptide that elicits mosquito immune responses

Allatotropins (AT) are neuropeptides with pleotropic functions on a variety of insect tissues. They affect processes such as juvenile hormone biosynthesis, cardiac rhythm, oviduct and hindgut contractions, nutrient absorption and circadian cycle. The present work provides experimental evidence that AT elicits immune responses in two important mosquito disease vectors, Anopheles albimanus and Aedes aegypti. Hemocytes and an immune-competent mosquito cell line responded to AT by showing strong morphological changes and increasing bacterial phagocytic activity. Phenoloxidase activity in hemolymph was also increased in Ae. aegypti mosquitoes treated with AT but not in An. albimanus, suggesting differences in the AT-dependent immune activation in the two species. In addition, two important insect immune markers, nitric oxide levels and expression of antimicrobial peptide genes, were increased in An. albimanus guts after AT treatment. AT conjugated to quantum dot nanocrystals (QDots) specifically labeled hemocytes in vivo in both mosquito species, implying molecular interactions between AT and hemocytes. The results of our studies suggest a new role for AT in the modulation of the immune response in mosquitoes.

Circulating phagocytes: the ancient and conserved interface between immune and neuroendocrine function

Immune and neuroendocrine functions display significant overlap in highly divergent and evolutionarily distant models such as molluscs, crustaceans, insects and mammals. Fundamental players in this crosstalk are professional phagocytes: macrophages in vertebrates and immunocytes in invertebrates. Although they have different developmental origins, macrophages and immunocytes possess comparable functions and differentiate under the control of evolutionarily conserved transcription factors. Macrophages and immunocytes share their pools of receptors, signalling molecules and pathways with neural cells and the neuro-endocrine system. In crustaceans, adult transdifferentiation of circulating haemocytes into neural cells has been documented recently. In light of developmental, molecular and functional evidence, we propose that the immune-neuroendocrine role of circulating phagocytes pre-dates the split of protostomian and deuterostomian superphyla and has been conserved during the evolution of the main groups of metazoans.

Mitochondria and chloroplasts shared in animal and plant tissues: significance of communication

Mitochondria have long been recognized as the main source of energy production for the eukaryotic cell. Recent studies have found that the mitochondria have a variety of dynamic functions aside from the production of energy. It communicates bidirectionally with other organelles in order to modulate its energy balance efficiently, as well as maintain homeostasis, ultimately prolonging its own and the cell’s longevity. The mitochondria achieves this level of regulation via specific and common bidirectional chemical messengers, especially involving the endoplasmic/sarcoplasmic reticulum (ER/SR), deoxyribonucleoside triphosphates (dNTP’s), ATP and the generation of reactive oxygen species (ROS). Its communication network is also involved in stress associated events. In this regard, the activation of the Bax family proteins and the release of cytochrome c occurs during cellular stress. The communication can also promote apoptosis of the cell. When mitochondrial abnormalities cannot be dealt with, there is an increased chance that major illnesses like type 2 diabetes, Alzheimer’s disease, and cancer may occur. Importantly, functioning chloroplasts can be found in animals, suggesting conserved chemical messengers during its evolutionary path. The dynamic capacity of mitochondria is also noted by their ability to function anaerobically. Indeed, this latter phenomenon may represent a return to an earlier developmental stage of mitochondria, suggesting certain disorders result from its untimely appearance.

Hypoxia defined as a common culprit/initiation factor in mitochondrial-mediated proinflammatory processes

In mammals and invertebrates, the activities of neuro- and immuno-competent cells, e.g., glia, which are present in nervous tissues, are deemed of critical importance to normative neuronal function. The responsiveness of invertebrate and vertebrate immuno-competent glia to a common set of signal molecules, such as nitric oxide and endogenous morphine, is functionally linked to physiologically driven innate immunological and neuronal activities. Importantly, the presence of a common, evolutionarily conserved, set of signal molecules in comparative animal groups strongly suggests an expansive intermediate metabolic profile dependent on high output mitochondrial ATP production and utilization. Normative bidirectional neural-immune communication across invertebrate and vertebrate species requires common anatomical and biochemical substrates and pathways involved in energy production and mitochondrial integrity. Within this closed-loop system, abnormal perturbation of the respective tissue functions will have profound ramifications in functionally altering associated nervous and vascular systems and it is highly likely that the initial trigger to the induction of a physiologically debilitating pro-inflammatory state is a micro-environmental hypoxic event. This is surmised by the need for an unwavering constant oxygen supply. In this case, temporal perturbations of normative oxygen tension may be tolerated for short, but not extended, periods and ischemic/hypoxic perturbations in oxygen delivery represent significant physiological challenges to overall cellular and multiple organ system viability. Hence, hypoxic triggering of multiple pro-inflammatory events, if not corrected, will promote pathophysiological amplification leading to a deleterious cascade of bio-senescent cellular and molecular signaling pathways, which converge to markedly impair mitochondrial energy utilization and ATP production.

Mytilus galloprovincialis myticin C: a chemotactic molecule with antiviral activity and immunoregulatory properties

Previous research has shown that an antimicrobial peptide (AMP) of the myticin class C (Myt C) is the most abundantly expressed gene in cDNA and suppressive subtractive hybridization (SSH) libraries after immune stimulation of mussel Mytilus galloprovincialis. However, to date, the expression pattern, the antimicrobial activities and the immunomodulatory properties of the Myt C peptide have not been determined. In contrast, it is known that Myt C mRNA presents an unusual and high level of polymorphism of unidentified biological significance. Therefore, to provide a better understanding of the features of this interesting molecule, we have investigated its function using four different cloned and expressed variants of Myt C cDNA and polyclonal anti-Myt C sera. The in vivo results suggest that this AMP, mainly present in hemocytes, could be acting as an immune system modulator molecule because its overexpression was able to alter the expression of mussel immune-related genes (as the antimicrobial peptides Myticin B and Mytilin B, the C1q domain-containing protein MgC1q, and lysozyme). Moreover, the in vitro results indicate that Myt C peptides have antimicrobial and chemotactic properties. Their recombinant expression in a fish cell line conferred protection against two different fish viruses (enveloped and non-enveloped). Cell extracts from Myt C expressing fish cells were also able to attract hemocytes. All together, these results suggest that Myt C should be considered not only as an AMP but also as the first chemokine/cytokine-like molecule identified in bivalves and one of the few examples in all of the invertebrates.

Discrepant effects of mammalian factors on molluscan cell motility, chemotaxis and phagocytosis: divergent evolution or finely tuned contingency?

Cell motility, cell migration and phagocytosis are distinct, though frequently sequential, processes. They are fundamental for the maintenance of homoeostasis in single cells as well as in pluricellular organisms. Like vertebrates, invertebrate immune functions are strictly dependent on cell motility, chemotaxis and phagocytosis. Several comparative immunobiology experiments have tested the effects of mammalian factors on cell migration and phagocytic activity in invertebrate immune-competent cells. The discrepancies that were found suggest various hypotheses, e.g. species-specific reactions to heterologous factors. Here, we reconsider data concerning the effects of POMC (proopiomelanocortin)-derived peptides, cytokines and growth factors on molluscan immunocytes in the light of recent findings that also encompass the effects of experimental conditions.

Opioid peptides and opiate alkaloids in immunoregulatory processes

Among the various non-neuronal cell types known to express and utilize neuropeptides, those of the immune system have received much attention in recent years. In particular, comparative studies in vertebrates and invertebrates have shown that endogenous opioid peptides are engaged in receptor mediated autoregulatory immune and neuroendocrine processes. The majority of these immune processes are stimulatory, as determined by their effects on conformational changes indicative of immunocyte activation, cellular motility, and phagocytosis. Endogenous opioid peptides form an effective network of messenger molecules in cooperation with cytokines, opiate alkaloids, and certain regulatory enzymes (neutral endopeptidase 24.11). Peptide-mediated immunostimulatory effects observed in this system are operationally counteracted by the inhibitory effects of morphine and related opiates. Opioid/opiate signaling processes are mediated by several types of receptors with different degrees of selectivity. Among them the recently identified, opioid insensitive µ(3) receptor deserves attention on account of its specificity for opiate alkaloids.

Characterisation of Mytilus edulis hemocyte subpopulations by single cell time-lapse motility imaging

In bivalve molluscs, defence against pathogens mainly relies on fast tissue infiltration by immunocompetent hemocytes that migrate from circulating hemolymph to sites of infection, in order to deliver, in situ, an effective immune response. In the present work, we have investigated dynamics of hemocyte subpopulations motility by combining flow cytometry coupled to Coulter-type cell volume determination, Hoffman modulation contrast microscopy, time-lapse imaging and off-line analysis of cell shape changes. Our results revealed fast modifications of hemocyte aspect in vitro, with bidirectional transitions from spread outlines to condensed cell body morphologies, in the minute range. Amoeboid or non-amoeboid types of locomotion were observed, depending on the cell shapes and on the cell subtypes, with velocities reaching up to 30 mum min(-1). Correlations between motion profiles, Hemacolor staining and flow cytometry analysis on living cells help to propose a functional mussel hemocyte classification including the motile properties of these cells. In particular, basophils were shown to be involved in dynamic hemocyte-hemocyte interactions and in the constitution of aggregation cores. Physiological implications, in terms of immune response in organisms devoid of endothelium-closed vascular system, and potential applications of hemocyte motility studies for the development and the interpretation of experiments involving hemocytes in the field of marine ecotoxicology are discussed.

Nitric oxide release by hemocytes of the mussel Mytilus galloprovincialis Lmk was provoked by interleukin-2 but not by lipopolysaccharide

As other marine and land mollusks, mussels have special cells in charge of the immune function called hemocytes. The activation of these cells leads to a series of events that end up in phagocytosis and in secretion of digestive enzymes that eliminate the pathogen. The production of nitric oxide is among the early activation processes. Contrary to what happens in cells of vertebrates and of other species of mollusks, in hemocytes of Mytilus galloprovincialis, LPS did not induce secretion of NO to the medium. However, human IL-2 provoked an important increase in NO production. The maximal synthesis of NO was detected after the hemocytes were incubated with the cytokine for 24h. In both stimulated and non-stimulated cells, Western blotting showed the presence of a protein of 130kDa, recognized by anti-mouse iNOS. Therefore, the higher production of NO can only be explained as a direct action of some effector upon the nitric oxide synthetase. NO production decreased by the action of H-89, a powerful inhibitor of the cAMP-dependent protein kinase (PKA). This suggests the involvement of PKA in the pathway of NO synthesis.

In vitro effects of LPS, IL-2, PDGF and CRF on haemocytes of Mytilus galloprovincialis Lmk

The cells in charge of the innate immune response in the marine mussel Mytilus galloprovincialis Lmk. are the haemocytes. These cells respond in different ways to agents such as lipopolysaccharide (LPS), interleukin-2 (IL-2), platelet-derived growth factor (PDGF) and corticotropin releasing factor (CRF). After stimulation of the haemocytes, the expression of molecules reactive with monoclonal antibodies raised to the alpha chain of the IL-2 receptor, present in their membrane, differed depending on the agent used. The same happened with regard to the levels of dopamine, adrenaline and noradrenaline released to the medium by the haemocytes. It should also be noted that no catecholamine release was detected and the level of expression of IL-2Ralpha showed no significant variation in cultured cells that had not been treated with inducers. These facts would indicate that most haemocytes were in the same starting condition at the moment that the stimulation was performed. Therefore, cultured haemocytes can be a highly reliable model in the study of the innate immune system.

Mussel blood cells, resistant to the cytotoxic effects of okadaic acid, do not express cell membrane p-glycoprotein activity (multixenobiotic resistance)

Okadaic acid (OA) is a dinoflagellate toxin, accumulating in shellfish and causing diarrhetic shellfish poisoning (DSP) in humans. OA is a highly cytotoxic agent in most cell lines because of its inhibiting properties of protein phosphatases. So far, the cytotoxicity of OA in mussels, the main vectors of DSP, has not been investigated. In this paper, the viability of mussel (Mytilus edulis) blood cells incubated in 10 nM-1 microM OA was studied. After 72 h of exposure, viability was reduced to 54% in 1 microM OA compared with 88% in control cells. This yielded a LC50 of >1 microM for OA, which is 30-1000-times higher compared with other cell types. It was hypothesised that P-glycoprotein (p-gp) activity (multixenobiotic resistance, MXR) contributed to the resistance to OA. Vincristine and rhodamine B was used as p-gp substrates and verapamil or staurosporine (ST) as inhibitors of p-gp transport. However, no indications of cell membrane p-gp activity were detected. Instead, experimental observations led to the conclusion that a MXR transport system was present within lysosomal membranes. Various concentrations of OA did not affect the dynamics of vincristine in blood cells. As a positive control for the assay, p-gp activity was measured in mussel gill tissue. The efflux of rhodamine B was reduced by verapamil, which is, considered evidence for cell membrane p-gp activity, thus the accuracy of the method was confirmed. Rhodamine B efflux was also reduced by OA in gill tissue, which suggested that OA is either a competitive substrate or inhibitor of p-gp activity. When the volume of the lysosomal compartment was measured in blood cells pre-exposed to OA, a significant increase was detected compared with control cells. It was proposed that uptake and storage of OA within the lysosomal system might protect mussel blood cells from the cytotoxic effects of this compound.

Identification by subtractive suppression hybridization of bacteria-induced genes expressed in Manduca sexta fat body

Insect immune processes are mediated by programs of differential gene expression. To understand the molecular regulation of the immune response in the tobacco hornworm, Manduca sexta, the relevant subset of differentially expressed genes of interest must be identified, cloned and studied in detail. In this study, suppression subtractive hybridization, a PCR-based method for cDNA subtraction was performed to identify mRNAs from fat body of immunized larvae that are not present (or present at a low level) in control larvae. A subtracted cDNA library enriched in immune-inducible genes was constructed. Northern blot analysis of a sample of clones from our subtracted library indicated that >90% of the clones randomly selected from the subtracted library are immune inducible. Sequence analysis of 238 expressed sequence tags (ESTs) revealed that 120 ESTs, representing 54 distinct genes or gene families, had sequences identical or similar to previously characterized genes, some of which have been confirmed to be involved in innate immunity. These ESTs were categorized into seven groups, including pattern recognition proteins, serine proteinases and their inhibitors, and antimicrobial proteins. 112 ESTs, about 47.5% of the library, showed no significant similarity to any known genes. The sequences identified in this M. sexta library reflect our knowledge of insect immune strategies and may facilitate better understanding of insect immune responses.

Opioid receptors on white blood cells: effect of HIV infection and methadone treatment

Opioid receptors (OR) are involved in many physiological and pathological immune functions. During recent years, the treatment of opiate addiction with methadone in HIV-positive and HIV-negative patients has become widely accepted. However, little is known on the occurrence and course of OR on lymphocytes of these individuals. The objective of the study was to detect and quantify OR on peripheral white blood cells (WBC) by fluorescence-activated cell sorting using polyclonal antibodies and reverse transcriptase polymerase chain reaction, and to assess the influence of HIV infection and methadone treatment. We compared OR levels in 80 HIV-positive homosexuals, 18 HIV-positive intravenous drug users (IVDU) treated with methadone, 18 HIV-negative IVDU receiving methadone and 25 healthy controls. HIV infection was shown to decrease the amount of OR on WBC, especially of the delta-subtype on lymphocytes and granulocytes. The decrease correlated with the duration of HIV-infection (P<0.01), and inversely with the HIV viral load (P<0.01). In contrast, chronic methadone administration led to a significant increase of OR exclusively in HIV-negative IVDU. In particular the delta-OR was increased by 31-, 62- and 42-fold on lymphocytes, monocytes and granulocytes of HIV-negative patients (each P<0.005), respectively, which was not observed in HIV-positive IVDU. Therefore, HIV seems to reduce OR particularly on lymphocytes and granulocytes regardless of the mode of HIV transmission. The quantification of OR on immune cells may help to elucidate the effects of opioid analogues in health and drug addiction.

The endocannabinoid system in invertebrates

What is the role of the cannabinoid system in invertebrates and can it tell us something about the human system? We discuss in this review the possible presence of the cannabinoid system in invertebrates. Endocannabinoid processes, i.e., enzymatic hydrolysis, as well as cannabinoid receptors and endocannabinoids, have been identified in various species of invertebrates. These signal molecules appear to have multiple roles in invertebrates; diminishing sensory input, control of reproduction, feeding behavior, neurotransmission and antiinflammatory actions. We propose that since this system worked so well, it was retained during evolution, and that invertebrates can serve as a model to study endogenous cannabinoid signaling.

Intravenous morphine reduces plasma endothelin 1 concentration through activation of neutral endopeptidase 24.11 in patients with myocardial infarction

STUDY OBJECTIVE

Morphine has multiple cardiovascular effects, but its action on hydrolysis of endothelin 1 (ET-1) has not been investigated.

METHODS

We measured plasma levels of ET-1, C-terminal degradation products of ET-1, and neutral endopeptidase 24.11 (NEP) in 68 patients with acute Q-wave myocardial infarction and 29 control subjects. All the patients underwent blood sampling at initial presentation and 10 minutes later. Thirty-six of those with Q-wave myocardial infarction intravenously received 3 mg of morphine immediately after the first sampling (group 1), and the other 32 received the same after the second sampling (group 2). Twenty-four of the control subjects (group 3) were randomized to the protocol of group 1, and the remaining 5 subjects (group 4) were randomized to the protocol of group 2.

RESULTS

The plasma ET-1 levels were significantly higher in groups 1 and 2 than in groups 3 and 4 (control groups). In group 1, the ET-1 level decreased significantly at second blood samplings (2.5+/-0.4 pmol/L versus 1.7+/-0.6 pmol/L, P <.001), whereas there were no definite changes of ET-1 levels in group 2 (2.5+/-0.5 pmol/L versus 2.6+/-0.6 pmol/L, P =not significant). However, the C-terminal degradation products increased significantly at second blood samplings in group 1 (0.8+/-0.2 pmol/L versus 1.3+/-0.4 pmol/L, P <.001), whereas there were no definite changes in group 2 (0.9+/-0.3 pmol/L versus 0.9+/-0.4 pmol/L, P =not significant). There was no significant difference in baseline NEP activities between groups 1 and 2 (5.02+/-1.30 nmol/mg protein versus 5.06+/-1.48 nmol/mg protein, P =not significant). However, the NEP activities at second blood samplings declined significantly in group 1 (9.76+/-1.76 nmol/mg protein, P <.001 versus baseline), whereas no definite changes were observed in group 2 (5.09+/-1.62 nmol/mg protein, P =not significant versus baseline).

CONCLUSION

Intravenous morphine may increase NEP activities to accentuate hydrolysis of ET-1.

Invertebrate molecular neuroimmune processes

During the course of evolution, invertebrates and vertebrates have kept in common similar signaling molecules e.g. neuropeptides, opiates etc... Complete hormonal-enzymatic systems such as the opioid-opiate-cannabinoid systems have been found in both nervous central and immune systems of these animals. These signaling molecules can be found free in blood circulation and act as immunomodulators. The present review is focused on peptides derived from the opioid proopiomelanocortin precursor, the opiates and the endocannabinoids, which are very powerful immunosuppressors, and example models of the bidirectional communications between the endocrine and the immune systems. Parasites use these immunosuppressors with magnificence in their crosstalk with their host.

Differential distribution and defence involvement of antimicrobial peptides in mussel

In previous papers, we characterised 3 types of 4-kDa, cysteine-rich, cationic antimicrobial peptides: MGDs (for Mytilus galloprovincialis defensins), mytilins and myticins, which are abundant in the mussel hemocytes. In the present work, we revealed a differential distribution of the cells expressing the different genes. In addition, using confocal and electron microscopy, we confirmed that defensins and mytilins were partially located in different sub-types of circulating hemocytes although the peptides can be located in the same cell, and even in the same granule. We also demonstrated that mytilins exert their microbicidal effect within the cells through the process of phagosome-mytilin granule fusion leading to the co-location of ingested bacteria and mytilins.

Comparative biology of the endocannabinoid system possible role in the immune response

In this review we discuss data showing that the endogenous cannabinoid system, represented by cannabinoid receptors, endogenous cannabinoid receptor ligands and enzymes for the biosynthesis and degradation of these ligands, is conserved throughout evolution from coelenterates to man. This signaling system has been suggested to play several roles in animals, including the regulation of cell development and growth, nervous functions, reproduction and feeding behavior. In this article, however, we shall describe with more detail the possible function of the endogenous cannabinoid system in the modulation of immune response in organisms from the lower to the higher levels of animal evolution.

Morphine-like substance in leech ganglia. Evidence and immune modulation

Binding experiments followed by measurement of nitric oxide release revealed an opiate alkaloid high affinity receptor with no affinity to opioids, representing a new mu-subtype receptor in the brain of the leech Theromyzon tessulatum. In addition, evidence of morphine-like substances was found in immunocytochemical studies and HPLC coupled to electrochemical detection (500 mV and 0.02 Hz). Based on previous evidence of the involvement of morphine as an immune response inhibitor, we demonstrate that in leech ganglia injection of lipopolysaccharide (LPS; a potent immunostimulatory agent derived from bacteria) provoked an increase in the level of ganglionic morphine-like substances after a prolonged latency period of 24 h (from 2.4 +/- 1.1 pmol per ganglion to 78 +/- 12.3 pmol per ganglion; P < 0.005; LPS injected 1 microg x mL-1); this effect is both concentration- and time-dependent. Finally, we have demonstrated that morphine, after binding to its own receptor, inhibits leech immunocyte activation through adenylate cyclase inhibition and nitric oxide release. This report confirms that morphine is an evolutionarily stable potent immunomodulator.

Biological and immunological characterization of multiple GnRH in an opisthobranch mollusk, Aplysia californica

Gonadotropin-releasing hormone (GnRH) is a neurohormone central to the regulation of reproductive functions in vertebrates. Recently, several studies have reported the presence of GnRH immunoreactivity (IR) in a number of mollusks, suggesting that the distribution of GnRH may not be restricted to Phylum Chordata. In the present study, we extend our investigations to an opisthobranch mollusk, Aplysia californica, to characterize the source, chemical nature, and biological activity of molluscan GnRH-related molecules. Specific radioimmunoassays (RIAs) of various tissue extracts of Aplysia revealed that only ovotestis, hemocytes, and hemolymph contained significant amounts of GnRH that crossreacts with antisera raised against tunicate-I (tI) and mammalian (m) GnRH. Further RIAs and extractions revealed that the GnRH-IR in the hemolymph is biochemically and immunologically distinct from the GnRH-IR in the hemocytes and ovotestis. Using reverse-phase high-performance liquid chromatography coupled with RIAs, the GnRH-IR in the hemolymph was resolved into two major peaks. The first peak eluted earlier than most known forms of vertebrate GnRH, and the later peak coeluted with m, lamprey I, chicken II, and tI-GnRH. However, both peaks were broad and may contain a heterogeneous mixture of GnRH-IR. Immunocytochemical study showed that tI-GnRH-IR was present in the connective sheath surrounding the central nervous system, with a strong presence in what appeared to be vascular space, again suggesting the close association between Aplysia GnRH-IR and circulation. Finally, treatment of the neuroendocrine bag cells with chicken II GnRH significantly decreased the duration of the afterdischarge (AD, a characteristic pattern of electrical firing in bag cell neurons) and the number of action potentials fired during an AD, indicating the presence of a corresponding GnRH receptor in the Aplysia central nervous system. Overall, the results demonstrated the presence of multiple forms of GnRH-IR that crossreact with tI- and mGnRH antisera in A. californica and the ability of a vertebrate GnRH to alter Aplysia neural activity. Together, these data suggest that GnRH may be a factor released by the ovotestis and hemocytes into the circulation to alter neural functions. GnRH-IR produced by the latter may serve as a novel mediator of the neural and immune functions in Aplysia.

Basal nitric oxide limits immune, nervous and cardiovascular excitation: human endothelia express a mu opiate receptor

Nitric oxide (NO) is a major signaling molecule in the immune, cardiovascular and nervous systems. The synthesizing enzyme, nitric oxide synthase (NOS) occurs in three forms: endothelial (e), neuronal (n) and inducible (i) NOS. The first two are constitutively expressed. We surmise that in many tissues there is a basal level of NO and that the actions of several signaling molecules initiate increases in cNOS-derived NO to enhance momentary basal levels that exerts inhibitory cellular actions, via cellular conformational changes. It is our contention that much of the literature concerning the actions of NO really deal with i-NOS-derived NO. We make the case that cNOS is responsible for a basal or 'tonal' level of NO; that this NO keeps particular types of cells in a state of inhibition and that activation of these cells occurs through disinhibition. Furthermore, naturally occurring signaling molecules such as morphine, anandamide, interleukin-10 and 17-beta-estradiol appear to exert, in part, their beneficial physiological actions, i.e., immune and endothelial down regulation by the stimulation of cNOS. In regard to opiates, we demonstrate the presence of a human endothelial mu opiate receptor by RT-PCR and sequence determination, further substantiating the role of opiates in vascular coupling to NO release. Taken together, cNOS derived NO enhances basal NO actions, i.e., cellular activation state, and these actions are further enhanced by iNOS derived NO.

Changes in the behavioral and immunological parameters of the mollusk Biomphalaria tenagophila induced by disruption of the circadian cycle as a consequence of continuous illumination

In the present investigation we studied some behavioral and immunological parameters of adult gastropod mollusk, Biomphalaria tenagophila, which have been reproducing for several generations under laboratory conditions. One group of gastropods was kept on a 14-h light/10-h dark cycle, corresponding to a regular circadian cycle, and another group was exposed to continuous light for 48 h. Animals were studied along (behavioral groups) or immediately after (immunological groups) 48 h of regular circadian cycle or continuous light conditions. Stopping/floating, dragging and sliding were the behavioral aspects considered (N = 20 for regular cycle; N = 20 for continuous illumination) and number of hemocytes/microl hemolymph was the immunological parameter studied (N = 15 for regular cycle, N = 14 for continuous illumination). Animals under continuous illumination were more active (sliding = 33 episodes, dragging = 48 episodes) and displayed a lower number of hemocytes (78.0 +/- 24. 27/microl) when compared with mollusks kept on a regular circadian cycle (sliding = 18 episodes, dragging = 27 episodes; hemocytes = 157.6 +/- 53.27/microl). The data are discussed in terms of neural circuits and neuroimmunological relations with the possible stressful effect of continuous illumination.

Invertebrate opioid precursors: evolutionary conservation and the significance of enzymatic processing

Invertebrate tissues contain mammalian-like proenkephalin, prodynorphin, and proopiomelanocortin. Amino acid sequence determination of these opioid gene products reveals the presence of various opioid peptides exhibiting high sequence identity with their mammalian counterparts. These associated peptides are flanked by dibasic amino acid residues, indicating cleavage sites. Together with the presence of various processing enzymes, i.e., neutral endopeptidase 24.11 and angiotensin-converting enzymes, this suggests that opioid precursor processing is also similar to that described in mammals. It is noted that the levels and/or activity of invertebrate neutral endopeptidase 24.11 can be upregulated by signaling molecules shown to perform the same function in mammals, i.e., morphine. Critical to opioid precursor processing are immunocytes that contain the precursors and transport processing enzymes to sites of inflammation, in part, to cleave these peptide precursors, thus liberating immune-stimulating molecules. Furthermore, in response to lipopolysaccharides, Met-enkephalin levels peak immediately and hours after the exposure, revealing a release and induction process. It appears that the opioid precursors and their processing enzymes first evolved in "simple" animals and the have been maintained and embellished during the course of evolution guided by conformational matching.

Chemotactic responses of tunicate (Urochordata, Ascidiacea) hemocytes in vitro

A number of molecules were found to alter the motility of tunicate hemocytes. Bacterial lipopolysaccharide (LPS) significantly enhanced cell mobility relative to non-stimulated controls. Responses to LPS were not directional and so represented chemokinesis. In contrast, checkerboard analyses indicated that two tunicate hemolymph proteins, tunIL1-alpha and -beta, stimulated truly directional chemotaxis by hemocytes. The data suggest that tunIL1 proteins may contribute to defense by altering the localization of immunocompetent cells.

Cloning, molecular characterization, and distribution of a gene homologous to delta opioid receptor from zebrafish (Danio rerio)

A full-length cDNA, ZFOR1, has been isolated from the teleost zebrafish (Danio rerio) using a probe from rat mu opioid receptor. ZFOR1 encodes a 373 amino acid protein with seven potential transmembrane domains that shows a high degree of homology to mammalian delta opioid receptor. We have also isolated a genomic clone which contains two exons of ZFOR1, homologous to exons 2 and 3 in mouse and human delta opioid receptor. Expression of ZFOR1 appears to be restricted to nervous tissue as assessed by Northern blot. In situ hybridization in zebrafish brain with specific probes revealed several discrete areas of ZFOR1 expression; higher levels are detected in dorsal telencephalic areas, the periventricular layer of the optic tectum, and the granular layer of the cerebellum. This is the first molecular evidence of the presence of the delta opioid receptor in a non-mammalian species and suggests that it has been highly conserved throughout vertebrate evolution.

Attenuation of neutrophil and endothelial activation by intravenous morphine in patients with acute myocardial infarction

To investigate the effects of morphine on neutrophil and endothelial activation, we measured serum levels of intercellular adhesion molecule-1 (ICAM-1), L-selectin, and neutrophil endopeptidase 24.11 (NEP) in 38 patients with acute myocardial infarction (group 1) and 16 control subjects (group 2). In group 1, all the patients underwent blood sampling at initial presentation and 10 minutes later. Twenty of them had 3 mg of morphine administered intravenously immediately after the first sampling (group 1A) and the other 18 after a second sampling (group 1B). The serum levels of ICAM-1 and L-selectin were both significantly higher in groups 1A and 1B than in group 2. In group 1A, the ICAM-1 decreased significantly at second blood samplings (310 +/- 28 vs 368 +/- 30 ng/ml; p <0.001), whereas in group 1B there was no significant change in ICAM-1 (357 +/- 33 vs 359 +/- 26 ng/ml; p = NS). In group 1A, the L-selectin decreased significantly at second blood samplings (2.3 +/- 1.2 mg/L, p <0.001 vs baseline), whereas in group 1B there was no significant change in L-selectin (3.9 +/- 1.0 mg/L, p = NS vs baseline). There was no significant difference in baseline NEP activities between groups 1A and 1B (4.89 +/- 1.22 vs 5.14 +/- 1.57 nmol/mg protein; p = NS). However, the NEP activities at second blood samplings decreased significantly in group 1A (9.88 +/- 1.86 nmol/mg protein, p <0.001 vs baseline), whereas no significant changes were observed in group 1B (5.09 +/- 1.62 nmol/mg protein, p = NS vs baseline). In conclusion, morphine increased NEP activities and thus attenuated shedding of L-selectin and ICAM-1.

Invertebrate proenkephalin: delta opioid binding sites in leech ganglia and immunocytes

The leech Theromyzon tessulatum and the marine mussel Mytilus edulis immunocytes contain a mammalian-like proenkephalin molecule. The opioid precursor was purified by gel permeation chromatography, anti-Met- and Leu-enkephalin-affinity column separation and then by reversed-phase HPLC. The amino acid sequence analysis, determined by Edman degradation, enzymatic treatments and matrix assisted laser desorption time of flight. The structure of the leech proenkephalin material demonstrates considerable amino acid sequence similarity with amphibian proenkephalin (e.g. 25.4% with Xenopus laevis) but it is smaller, 15 kDa vs. 30 kDa. In contrast, Mytilus proenkephalin is not only larger (26 kDa) but it exhibits a higher sequence identity with guinea pig proenkephalin (50%). Both of the invertebrate materials possess Met-enkephalin and Leu-enkephalin in a ratio of 3:1 for Mytilus and 1:2 in the leech. They also contain Met-enkephalin-Arg-Gly-Leu and Met-enkephalin-Arg-Phe sequences that are flanked by dibasic amino acid residues, demonstrating cleavage sites. Furthermore, using sequence comparison with bovine proenkephalin A (209-237), enkelytin (FAEPLPSEEEGESYSKEVPEMEKRYGGFM), an antibacterial peptide is found in the proenkephalin of both animals and it exhibits a 98% sequence identity with mammalian material. Finally, opioid binding experiments demonstrate the presence in leech ganglia and immunocytes of delta1 and delta2 opioid receptor subtypes as also found human and Mytilus immune cells. This report constitutes the first complete biochemical characterization of mammalian proenkephalin in invertebrates, demonstrating its origin in simpler animals.

Pro-opiomelanocortin-derived peptides, cytokines, and nitric oxide in immune responses and stress: an evolutionary approach

In vertebrates, including man, the study of stress has contributed substantially to unravelling the complex relationship between immune-neuroendocrine interactions and the systems involved. On the basis of data on the presence and distribution of the main actors (POMC products, cytokines, biogenic amines, and steroid hormones) in different species and taxa from invertebrates to vertebrates, we argue that these responses have been deeply connected and interrelated since the beginning of life. Moreover, the study of nitric oxide suggests that the inflammatory reaction is located precisely between the immune and stress responses, sharing the same fundamental evolutionary roots. The major argument in favor of this hypothesis is that the immune, stress, and inflammation responses appear to be mediated by a common pool of molecules that have been conserved throughout evolution and that from a network of adaptive mechanisms. One cell type, the macrophage, appears to emerge as that most capable of supporting this network critical for survival; it was probably a major target of selective pressure. All these data fit the unitarian hypothesis we propose, by which evolution favors what has been conserved, rather than what has changed, as far as both molecules and functions are concerned.

Purification, sequence analysis, and cellular localization of a prodynorphin-derived peptide related to the alpha-neo-endorphin in the rhynchobdellid leech Theromyzon tessulatum

Cells immunoreactive to an antiserum specifically directed against vertebrate alpha-Neo-endorphin (alpha-NE) were detected in the internal wall of anterior and posterior suckers of the rhynchobdellid leech Theromyzon tessulatum. These cells have morphological and ultrastructural characteristics close to the "releasing gland cells" of adhesive organs. The epitope recognized by anti-alpha-NE was contained in granules having a diameter of 0.2-0.3 microm. Previous works involving the brain of this leech demonstrate the existence of approximately 14 neurons immunoreactive to the anti-alpha-NE. Following an extensive purification including high pressure gel permeation and reversed-phase high performance liquid chromatography, epitopes contained in both suckers and central nervous system were isolated. Purity of the isolated peptides was controlled by capillary electrophoresis. Their sequences were determined by a combination of automated Edman degradation, electrospray mass spectrometry measurement, and coelution experiments in reversed-phase high performance liquid chromatography with synthetic alpha-NE. The results demonstrate that epitopes recognized by the anti-alpha-NE in the suckers and the central nervous system are identical to vertebrate alpha-NE (YGGFLRKYPK). This finding constitutes the first biochemical characterization of a prodynorphin-derived peptide in invertebrates. Moreover the isolation of this peptide in the annelida establishes the very ancient phylogenetic origin of alpha-NE as well as its conservation in evolution.

Characterization and immunocytochemical localization of actin and fibronectin in haemocytes of the mussel Mytilus galloprovincialis

Cell-extracellular matrix interactions are recognized to be important for human leucocyte functions, including chemotaxis and phagocytosis. These activities depend on a reorganization of the microfilament actin (F-actin) promoted by fibronectin, one of the major components of extracellular matrices. Although invertebrate haemocytes are, in many aspects, similar to the human granulocyte-monocyte-macrophage cell lineage, actin and fibronectin have not been well studied in these cells. Consequently, the characterization and structural organization of actin and fibronectin in mussel (Mytilus galloprovincialis) haemocytes was investigated using Western blotting analysis, indirect immunofluorescence and immunoelectron microscopy. Actin was immunocharacterized by an anti-total actin monoclonal antibody. Fibronectin was immunocharacterized by an autologous polyclonal antiserum directed against the protein of mussel haemolymph. Actin was mainly localized along the peripheral cytoplasm of the haemocyte. The distribution of the F-actin microfilaments was assayed with Rhodamine-labelled phalloidin. F-actin was associated mainly with stress-fibres of spreading haemocytes and with microspikes at the adhesion sites. The labelling by the anti-fibronectin antiserum of the haemocyte rough endoplasmic reticulum vesicles, revealed by immunoelectron microscopy, suggests that these cells are involved in fibronectin biosynthesis. Gold particles were also present along the outer surfaces of the cell plasma membrane and its protrusions. Mussel fibronectin was localized immunohistochemically at the adhesion sites and in the extracellular matrix fibrils. The relationships between fibronectin and the actin cytoskeleton in Mytilus galloprovincialis haemocytes are discussed.

How schistosomes profit from the stress responses they elicit in their hosts

Results obtained with the model Trichobilharzia ocellata-Lymnaea stagnalis have confirmed the hypothesis that the physiological effects evoked by schistosomes in their snail host--castration and giant growth--are brought about by them interfering with the neuroendocrine systems (NES) regulating the physiological processes concerned. As soon as differentiating cercariae are present in the daughter sporocysts a factor can be detected in the haemolymph of the snail host, called schistosomin, which acts both at the central and the peripheral parts of the NES involved in regulation of reproduction and growth. Schistosomin appears to be a host-derived factor, which is probably released by cells of the internal defence system, the haemocytes, and by connective tissue cells, the telo-glial cells. It meets the criteria of having a cytokine-like function although its molecular structure does not show sequence homology with any of the vertebrate-type cytokines identified to date. Its cytokine nature explains why schistosomin can interfere with different neuroendocrine regulatory systems both at the central and peripheral--target--level, namely after binding to its own receptor. Schistosomin is probably not only responsible for the effects exerted by the parasite on female reproduction but also for those on male reproduction and on growth so that energy and space become available for the continuous production of cercariae. The nature of the humoral cercarial factor, which induces schistosomin release, is as yet unknown. Based on its hydrophobic character and on the fact that it can pass through the wall of the daughter sporocyst, it is supposed to be a diffusible molecule or a protonephridial excretion product. It does not seem to be a vertebrate-type steroid, an ecdysteroid or an eicosanoid. Results obtained in vitro have indicated that schistosomin might have a suppressive effect on haemocyte activity. Plasma from snails 5-6 weeks post-exposure showed a tendency to inhibit phagocytic activity of haemocytes from non-infected snails, that is preparatory to the escape and migration of cercariae. Once shedding has started this effect of schistosomin is overrruled by a strong activation of haemocyte activity coinciding with the tissue damage that the cercariae cause in the host. The cercariae escape from being attacked by masking their surface coat with host molecules. As the physiological effects caused by schistosomes resemble those observed during stress in mammals, experiments were carried out to find out whether schistosomin is also released in non-parasitized snails during stress resulting in an inhibiting effect on reproduction.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoendocrine reshaping with age

The interaction of the endocrine, immune, and nervous systems in modulating each other's activity opens the track for a new way of looking to the effects ongoing on each of the three systems. This new approach finds it bases in old times, since evolution shows how we missed for many years a relation between the three systems that was clearly manifested in lower species. In this chapter, the effects of aging on the immune, endocrine and nervous systems are proposed as the consequence of the influences of each system on the others.

Microglia in invertebrate ganglia

The results of this study lend strong support to the concept of the existence in insects and molluscs of a distinctive class of neuroglial cells comparable to vertebrate microglia. The evidence presented is as valid as that used in reference to the separate status of vertebrate microglia--i.e., the demonstration of a close structural and functional relationship of these cells with cells of the immune system. As in vertebrates, the excision of ganglia from three invertebrate species (the molluscs Planorbarius corneus and Mytilus edulis and the insect Leucophaea maderae) and their maintenance in incubation media led to an exodus of small cells and their accumulation in the culture dish. During this process, they underwent conformational changes from stellate to rounded, and then to more or less ameboid, comparable to those indicative of the process of activation in the animals' immunocytes. Functional characteristics which these translocated microglia-like cells share with immunocytes are motility, phagocytotic activity, and adherence to the culture dish. Furthermore, the two cells have certain biochemical features in common--e.g., the presence of certain cytokines and (at least in Planorbarius) that of corticotropin. An additional phenomenon of particular interest for the classification of microglial elements is their response to morphine. At 10(-6) M, this drug decreases not only the number of cells emerging from the excised ganglia but also the degree of their transformation to the "active" ameboid form. This dose-dependent and naloxone-sensitive effect of morphine on microglial cells parallels that on activated immunocytes of the same species. Corresponding results demonstrating an inhibitory effect of morphine on mobilized microglial cells of the frog Rana pipiens indicate that this relationship between the two cell types under consideration also exists in vertebrates. Binding and displacement experiments with membrane homogenates of microglial cells as well as immunocytes of Mytilus have shown that the effects of morphine on both cell types are mediated by the same special opiate receptor (mu 3).