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

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.

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.

Mediterranean diet and inflammaging within the hormesis paradigm

A coherent set of epidemiological data shows that the Mediterranean diet has beneficial effects capable of preventing a variety of age-related diseases in which low-grade, chronic inflammation/inflammaging plays a major role, but the underpinning mechanism(s) is/are still unclear. It is suggested here that the Mediterranean diet can be conceptualized as a form of chronic hormetic stress, similar to what has been proposed regarding calorie restriction, the most thoroughly studied nutritional intervention. Data on the presence in key Mediterranean foods of a variety of compounds capable of exerting hormetic effects are summarized, and the mechanistic role of the nuclear factor erythroid 2 pathway is highlighted. Within this conceptual framework, particular attention has been devoted to the neurohormetic and neuroprotective properties of the Mediterranean diet, as well as to its ability to maintain an optimal balance between pro- and anti-inflammaging. Finally, the European Commission-funded project NU-AGE is discussed because it addresses a number of variables not commonly taken into consideration, such as age, sex, and ethnicity/genetics, that can modulate the hormetic effect of the Mediterranean diet.

Thymus: Conservation in evolution

From an evolutionary point of view, the thymus is a new organ observed for the first time in fish concomitantly with the appearance of adaptive clonotypical immunity. Hormone and neuropeptide expression was demonstrated in different species suggesting a conserved role of these molecules. An integrated evolution of immune and neuroendocrine responses appears to have been realized by means of the re-use of ancestral material, such as neuroendocrine cells and mediators, to create a thymic microenvironment for the maturation and differentiation of T cells.

Cross-talk among immune and neuroendocrine systems in molluscs and other invertebrate models

The comparison between immune and neuroendocrine systems in vertebrates and invertebrates suggest an ancient origin and a high degree of conservation for the mechanisms underlying the integration between immune and stress responses. This suggests that in both vertebrates and invertebrates the stress response involves the integrated network of soluble mediators (e.g., neurotransmitters, hormones and cytokines) and cell functions (e.g., chemotaxis and phagocytosis), that interact with a common objective, i.e., the maintenance of body homeostasis. During evolution, several changes observed in the stress response of more complex taxa could be the result of new roles of ancestral molecules, such as ancient immune mediators may have been recruited as neurotransmitters and hormones, or vice versa. We review older and recent evidence suggesting that immune and neuro-endocrine functions during the stress response were deeply intertwined already at the dawn of multicellular organisms. These observations found relevant reflections in the demonstration that immune cells can transdifferentiate in olfactory neurons in crayfish and the recently re-proposed neural transdifferentiation in humans.

The early stress responses in fish larvae

During the life cycle of fish the larval stages are the most interesting and variable. Teleost larvae undergo a daily increase in adaptability and many organs differentiate and become active. These processes are concerted and require an early neuro-immune-endocrine integration. In larvae communication among the nervous, endocrine and immune systems utilizes several known signal molecule families which could be different from those of the adult fish. The immune-neuroendocrine system was studied in several fish species, among which in particular the sea bass (Dicentrarchus labrax), that is a species of great commercial interest, very important in aquaculture and thus highly studied. Indeed the immune system of this species is the best known among marine teleosts. In this review the data on main signal molecules of stress carried out on larvae of fish are considered and discussed. For sea bass active roles in the early immunological responses of some well-known molecules involved in the stress, such as ACTH, nitric oxide, CRF, HSP-70 and cortisol have been proposed. These molecules and/or their receptors are biologically active mainly in the gut before complete differentiation of gut-associated lymphoid tissue (GALT), probably acting in an autocrine/paracrine way. An intriguing idea emerges from all results of these researches; the molecules involved in stress responses, expressed in the adult cells of the hypothalamic-pituitary axis, during the larval life of fish are present in several other localizations, where they perform probably the same role. It may be hypothesized that the functions performed by hypothalamic-pituitary system are particularly important for the survival of the larva and therefore they comprises several other localizations of body. Indeed the larval stages of fish are very crucial phases that include many physiological changes and several possible stress both internal and environmental.

NET amyloidogenic backbone in human activated neutrophils

Activated human neutrophils produce a fibrillar DNA network [neutrophil extracellular traps (NETs)] for entrapping and killing bacteria, fungi, protozoa and viruses. Our results suggest that the neutrophil extracellular traps show a resistant amyloidogenic backbone utilized for addressing reputed proteins and DNA against the non-self. The formation of amyloid fibrils in neutrophils is regulated by the imbalance of reactive oxygen species (ROS) in the cytoplasm. The intensity and source of the ROS signal is determinant for promoting stress-associated responses such as amyloidogenesis and closely related events: autophagy, exosome release, activation of the adrenocorticotrophin hormone/α-melanocyte-stimulating hormone (ACTH/α-MSH) loop and synthesis of specific cytokines. These interconnected responses in human activated neutrophils, that have been evaluated from a morphofunctional and quantitative viewpoint, represent primitive, but potent, innate defence mechanisms. In invertebrates, circulating phagocytic immune cells, when activated, show responses similar to those described previously for activated human neutrophils. Invertebrate cells within endoplasmic reticulum cisternae produce a fibrillar material which is then assembled into an amyloidogenic scaffold utilized to convey melanin close to the invader. These findings, in consideration to the critical role played by NET in the development of several pathologies, could explain the structural resistance of these scaffolds and could provide the basis for developing new diagnostic and therapeutic approaches in immunomediated diseases in which the innate branch of the immune system has a pivotal role.

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.

Yessotoxin affects fMLP-induced cell shape changes inMytilus galloprovincialisimmunocytes

Using computer-assisted microscopic image analysis, we have found that algal yessotoxin (YTX) affects the immune response of Mytilus galloprovincialis. Indeed, YTX increases immunocyte cell motility through the involvement of both extracellular Ca2+ and cAMP, but not through protein kinase A, protein kinase C or phosphoinositide 3-kinase. Alone, however, the toxin does not induce any effect, as its action on cell motility is observed only after addition of the chemotactic substance N-formyl-Meth-Leu-Phe (fMLP). fMLP is known to induce cellular changes via both the phosphatidylinositol and cAMP pathways and, from this scenario, we can surmise that Ca2+ and cAMP concentrations rise sufficiently in fMLP-activated immunocytes to reveal YTX action. One possible explanation is that the toxin increases fMLP-mediated cell activation by intervening in L-type Ca2+-channel opening through a cAMP-dependent/PKA-independent pathway.

The main actors involved in parasitization of Heliothis virescens larva

At the moment of parasitization by another insect, the host Heliothis larva is able to defend itself by the activation of humoral and cellular defenses characterized by unusual reactions of hemocytes in response to external stimuli. Here, we have combined light and electron microscopy, staining reactions, and immunocytochemical characterization to analyze the activation and deactivation of one of the most important immune responses involved in invertebrates defense, i.e., melanin production and deposition. The insect host/parasitoid system is a good model to study these events. The activated granulocytes of the host insect are a major repository of amyloid fibrils forming a lattice in the cell. Subsequently, the exocytosed amyloid lattice constitutes the template for melanin deposition in the hemocel. Furthermore, cross-talk between immune and neuroendocrine systems mediated by hormones, cytokines, and neuromodulators with the activation of stress-sensoring circuits to produce and release molecules such as adrenocorticotropin hormone, alpha melanocyte-stimulating hormone, and neutral endopeptidase occurs. Thus, parasitization promotes massive morphological and physiological modifications in the host insect hemocytes and mimics general stress conditions in which phenomena such as amyloid fibril formation, melanin polymerization, pro-inflammatory cytokine production, and activation of the adrenocorticotropin hormone system occur. These events observed in invertebrates are also reported in the literature for vertebrates, suggesting that this network of mechanisms and responses is maintained throughout evolution.

The evolution of pro-opiomelanocortin: looking for the invertebrate fingerprints

The presence and role of the pro-opiomelanocortin (POMC) gene and encoded peptides in invertebrates are here summarized and discussed. Some of the POMC-derived peptides show a significant similarity regarding their functions, suggesting their appearance before the split of protostomian-deuterostomian lineages and their maintenance during evolution. The basic mechanisms that govern the exchange of information between cells are usually well conserved, and this could have also been for POMC-derived peptides, that are mainly involved in fundamental functions such as immune and neuroendocrine responses. However, the presence and functions that POMC-derived peptides exhibit in taxonomically distant models, are not always reflected by the expected gene homology, leaving the problem of POMC evolution in invertebrates in need of additional study.

Evolution of immune-neuroendocrine integration from an ecological immunology perspective

Bow tie architecture can support evolutionary integration between the immune and neuroendocrine systems, answering ecological immunology demands in terms of economy and efficiency.

Sleeping to fuel the immune system: mammalian sleep and resistance to parasites

Sleep is an enigma. Why animals forgo eating and reproducing, while potentially increasing their risk of predation remains unknown. Although some may question whether all animals sleep, it is clear that all living organisms possess defenses against attack by pathogens. Immune responses of humans and animals are impaired by sleep loss, and responses to immune challenge include altered sleep. Thus, sleep is hypothesized to be a component of the acute phase response to infection and to function in host defense. Examining phylogenetic relationships among sleep parameters, components of the mammalian immune system and resistance to infection may provide insight into the evolution of sleep and lead to a greater appreciation for the role of sleep in host defense.

Presence of and stress-related changes in urocortin-like molecules in neurons and immune cells from the mussel Mytilus galloprovincialis

The distribution of urocortin (UCN)-like material is investigated in the bivalve mollusc Mytilus galloprovincialis. Immunocytochemical data demonstrate that UCN-like molecules are present in ganglionic neurons, microglial cells and immunocytes. Moreover, a co-localization of UCN- and corticotrophin-releasing hormone (CRH)-like molecules is found in microglial cells and in immunocytes, but not in neurons. Following high salinity-stress experiments, immunoreactivity for UCN and CRH increased in ganglionic neurons and immunocytes. Our findings extend the number of molecules potentially used by molluscan immunocytes to confront stress situations and strengthen the idea of functional conservation of stress-related molecules during evolution.

Comparative psychoneuroimmunology: evidence from the insects

Interactions between immune systems, nervous systems, and behavior are well established in vertebrates. A comparative examination of these interactions in other animals will help us understand their evolution and present adaptive functions. Insects show immune-behavioral interactions similar to those seen in vertebrates, suggesting that many of them may have a highly conserved function. Activation of an immune response in insects results in illness-induced anorexia, behavioral fever, changes in reproductive behavior, and decreased learning ability in a broad range of species. Flight-or-fight behaviors result in a decline in disease resistance. In insects, illness-induced anorexia may enhance immunity. Stress-induced immunosuppression is probably due to physiological conflicts between the immune response and those of other physiological processes. Because insects occupy a wide range of ecological niches, they will be useful in examining how some immune-behavioral interactions are sculpted by an animal's behavioral ecology.

Nutrient-gene interaction in ageing and successful ageing. A single nutrient (zinc) and some target genes related to inflammatory/immune response

In this paper, we reviewed data regarding to the pivotal role played by the zinc-gene interaction in affecting some relevant cytokines (IL-6 and TNF-alpha) and heat shock proteins (Hsp70-2) in ageing, successful ageing (nonagenarians) and in some age-related diseases (atherosclerosis and infections). The polymorphisms of the genes codifying these proteins are predictive on one hand in longevity, such as IL-6 -174G/C locus, on the other hand 1267 Hsp70-2A/B or TNF-alpha -308G/A polymorphisms are associated to worsening atherosclerosis or severe infections, respectively, rather than longevity. Taking into account that longevity has a strong genetic component but, at the same time, is affected by life style and environmental factors, the analysis of these polymorphisms in association to some immune parameters (NK cell cytotoxicity) and nutritional factors (zinc) is a useful tool to unravel the role played by these genetic factors in longevity and in the appearance of age-related diseases. Indeed, these polymorphisms are associated with chronic inflammation, low zinc ion bioavailability, depressed innate immune response and high gene expression of metallothioneins, which have a limited zinc release for an optimal innate immune response in ageing. Therefore, the nutrient (zinc)-gene (IL-6, TNF-alpha and Hsp70-2) interaction is pivotal to keep under control the inflammatory/immune response with subsequent longevity, indicating these genes as "robust" for "healthy ageing".

Nitric oxide production by hemocytes of larva and pharate prepupa of Galleria mellonella in response to bacterial lipopolysaccharide: Cytoprotective or cytotoxic?

Nitric oxide production by the hemocytes of the last instar larvae and sessile pharate prepupa of Galleria mellonella (Lepidoptera: Pyralidae) was demonstrated in vitro in response to preparations of bacterial lipopolysaccharide (LPS) from Escherichia coli using the Griess reaction. Augmented, dose dependent nitric oxide production was observed in the pharate prepupal hemocytes compared with larval hemocytes. This was partially reversed in a dose dependent manner with S-methyl thiourea (SMT), a specific inhibitor of inducible nitric oxide synthase (iNOS). A decrease in NO production was also observed when non-selective inhibitors such as N(G)-nitro-L-arginine (L-NAME) and N-omega-nitro-L-arginine (L-NNA) were used, albeit the inhibition was not to the extent of SMT. Challenge with the entomopathogenic Gram-negative bacterium Photorhabdus asymbiotica also enhanced NO production by hemocytes of both stages. SMT, alone or in combination with P. asymbiotica significantly decreased levels of NO production. However, it was observed that phenoloxidase activity (a cascade for innate immune responses) was independent of NO production stimulation. NO donors, S-nitroso-N-acetyl-penicillamine (SNAP) and diethylenetriamine NO adduct (DETA/NO) at various concentrations (100-500 microM) resulted in the lysis of hemocytes dose dependently. The nitrite production in these cases was however similar to LPS stimulation (10 microg/mL) and 1.5-3 fold lower than those observed upon P. asymbiotica (2.5 x 10(7) cfu/mL) stimulation. Survival analysis (Kaplan-Meier) following injection of P. asymbiotica alone or in combination with SMT revealed that only 12.5% (median survival 25.5 h) of co-injected larvae of G. mellonella survived in comparison to 28.6% (median survival 29 h) survivors in P. asymbiotica alone-injected groups till the end of the study. In contrast, co-injected pharate prepupa survived longer (median survival 28 h) than the P. asymbiotica alone-injected individuals (median survival 24 h); however, both co-injected and P. asymbiotica-injected groups showed 100% mortality at the end of the study. Based on the above, we propose that although NO production is involved in cellular immune responses of this insect to bacterial infection it does not appear to be a part of the signalling pathway that initiates the prophenoloxidase (PPO) cascade, and the extended NO production/overproduction by pharate prepupal hemocytes could result in cytotoxic rather than cytoprotective effects compared with larval hemocytes.

Evolutionary origins of vertebrate placodes: insights from developmental studies and from comparisons with other deuterostomes

Ectodermal placodes comprise the adenohypophyseal, olfactory, lens, profundal, trigeminal, otic, lateral line, and epibranchial placodes. The first part of this review presents a brief overview of placode development. Placodes give rise to a variety of cell types and contribute to many sensory organs and ganglia of the vertebrate head. While different placodes differ with respect to location and derivative cell types, all appear to originate from a common panplacodal primordium, induced at the anterior neural plate border by a combination of mesodermal and neural signals and defined by the expression of Six1, Six4, and Eya genes. Evidence from mouse and zebrafish mutants suggests that these genes promote generic placodal properties such as cell proliferation, cell shape changes, and specification of neurons. The common developmental origin of placodes suggests that all placodes may have evolved in several steps from a common precursor. The second part of this review summarizes our current knowledge of placode evolution. Although placodes (like neural crest cells) have been proposed to be evolutionary novelties of vertebrates, recent studies in ascidians and amphioxus have proposed that some placodes originated earlier in the chordate lineage. However, while the origin of several cellular and molecular components of placodes (e.g., regionalized expression domains of transcription factors and some neuronal or neurosecretory cell types) clearly predates the origin of vertebrates, there is presently little evidence that these components are integrated into placodes in protochordates. A scenario is presented according to which all placodes evolved from an adenohypophyseal-olfactory protoplacode, which may have originated in the vertebrate ancestor from the anlage of a rostral neurosecretory organ (surviving as Hatschek's pit in present-day amphioxus).

ACTH response to LPS in the first stages of development of the fish Dicentrarchus labrax L

ACTH and ACTH receptor-like molecules were found at the examined stages of development (2, 4, 8, 12, 18, and 24 days post-hatching) in yolk sac, pronephros tubules, interrenal tissue, thymus, liver, spleen, cardinal veins, and skin of the teleost fish Dicentrarchus labrax. ACTH and the related receptor-like molecules show a similar distribution. LPS treatment at two different stages (8 and 24 days post-hatching) provoked both a release and an induction of ACTH-like molecules, suggesting an important role of this peptide to control the modifications in body homeostasis during the first period of the sea bass' life, i.e., 30 days post-hatching, before the lymphoid cells have reached complete maturation.

Genes involved in immune response/inflammation, IGF1/insulin pathway and response to oxidative stress play a major role in the genetics of human longevity: the lesson of centenarians

In this paper, we review data of recent literature on the distribution in centenarians of candidate germ-line polymorphisms that likely affect the individual chance to reach the extreme limit of human life. On the basis of previous observations on the immunology, endocrinology and cellular biology of centenarians we focused on genes that regulate immune responses and inflammation (IL-6, IL-1 cluster, IL-10), genes involved in the insulin/IGF-I signalling pathway and genes that counteract oxidative stress (PON1). On the whole, data indicate that polymorphisms of these genes likely contribute to human longevity, in accord with observations emerging from a variety of animal models, and suggest that a common core of master genes and metabolic pathways are responsible for aging and longevity across animal species. Moreover, in the concern of our plan to discover new genetic factors related to longevity, we explored the possibility to by-pass the need of an a-priori choice of candidate genes, extending the search to genes and genomic regions of still unknown function. Alu sequences may be considered as good markers of highly variable and potentially unstable loci in functionally important genomic regions. We extensively screened Alu-rich genomic sites and found a new genomic region associated with longevity.

The stimulatory effect of alpha-melanotropin on progesterone release from rat granulosa cells is inhibited by interleukin-1beta and by tumour necrosis factor-alpha

AIM

Several studies have shown that a variety of peptides and cytokines are involved in ovarian regulatory mechanisms; however, their exact function is still unclear. In this work we study whether the administration of peptide alpha-melanotropin and the cytokines interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) on their own modify the release of progesterone in cultured granulosa cells (GC) from pro-oestrous rats. We also investigate an interaction between these cytokines and alpha-melanotropin in the modulation of progesterone secretion.

METHODS

Granulosa cells were collected from the ovaries of female Wistar rats and cultured for up to 24 h in the presence of different concentrations of alpha-melanotropin, cytokines or a combination of both. Progesterone concentration was measured by radioimmunoassay.

RESULTS

The addition of alpha-melanotropin in a dose of 0.01 and 0.1 mm had no effect on progesterone release, whereas a dose of 1 mm significantly increased progesterone release (P < 0.01) compared with the control culture. Progesterone release was not modified when different concentrations of interleukin-1beta or TNF-alpha were added to the cell cultures. However, when interleukin-1beta or TNF-alpha were added simultaneously with 1 microm alpha-melanotropin, a significant reduction (P < 0.01 for interleukin-1beta and P < 0.05 for TNF-alpha) of the steroid release was found with respect to the alpha-melanotropin-treated group.

CONCLUSIONS

These results lead us to suggest that, although alpha-melanotropin stimulates progesterone release in pre-ovulatory GC, this effect is blocked by the presence of interleukin-1beta or TNF-alpha.

Occurrence of ACTH- and enkephalin-like peptides in the developing gut of Dicentrarchus labrax L

We carried out immunohistochemical tests in the developing gut of the sea bass Dicentrarchus labrax to follow the appearance and distribution of the immunoreactivity (IR) to antibodies against POMC-derived, adrenocorticotropic hormone (ACTH), alpha-melanocyte stimulating hormone (alpha-MSH) and beta-endorphin (beta-End), and against two enkephalins, with the aim to study a possible involvement of these molecules in the early neuro-immune-endocrine integration. Our data show that IR to antibodies against some molecules involved in the stress response, such as ACTH and enkephalins, are present in the sea bass gut from an early larval stage (4 days after hatching), before transition to the exotrophic feeding. Moreover, the present study demonstrates for the first time the presence of ACTH-like immunoreactive material in developing gut of a fish. The possible roles of tested molecules are discussed.

Phorbol esters induce translocation of the nPKC p105 to membrane in mussel hemocytes

Previous works revealed the presence of the nPKC enzyme p105 in hemocytes of M. galloprovincialis Lmk. Specific mussel antibodies were obtained from mouse and used in confocal microscopy and Western blotting. These techniques allowed the observation of p105 cytosol-to-membrane translocation induced by TPA for the first time in hemocytes of molluscs. The incubation of mussel immune cells with TPA for longer than 30 min also triggered a down-regulation process. Mussel hemocytes are an excellent model to study the molecular processes of innate immunity.

Immunohistochemical localization of nNOS in the skin and nerve fibers of the earthworm Lumbricus terrestris L. (Annelida Oligochaeta)

The epidermis of the earthworm Lumbricus terrestris is a multifunctional tissue. It is composed of supporting, mucous, neuroendocrine-like, sensory and basal cells. NO is considered to be a molecule that regulates numerous functional activities (also in non-neuronal cells) in vertebrates. In the earthworm epidermis, we found neuronal NO synthase immunopositivity in orthochromatic and metachromatic mucous cells, neuroendocrine-like cells and in epidermal and subepidermal nerve fibers and striated muscle fibers. It is suggested that NO has a multitude of biological actions, affecting functional activities of the epidermis such as tissue homeostasis, control of secretion, proliferation, respiration, defense, water-salt balance, as well as regulation of tonus in vascular and striated muscles.

Interaction between endocrine and immune systems in fish

Diseases in fish are serious problems for the development of aquaculture. The outbreak of fish disease is largely dependent on environmental and endogenous factors resulting in opportunistic infection. Recent studies, particularly on stress response, have revealed that bidirectional communication between the endocrine and immune systems via hormones and cytokines exists at the level of teleost fish. Recently information on such messengers and receptors has accumulated in fish research particularly at the molecular level. Furthermore, it has become apparent in fish that cells of the immune system produce or express hormones and their receptors and vice versa to exchange information between the two systems. This review summarizes and updates the knowledge on endocrine-immune interactions in fish with special emphasis on the roles of such mediators or receptors for their interactions.

Evidence for a direct link between stress and immunity in the mollusc Haliotis tuberculata

Stress is thought to cause increased disease outbreaks and mortality in a number of invertebrates but currently very little information is available on mechanisms linking physiological states of stress and reduced disease resistance in these organisms. In the present study, we examined the possibility that stress alters immune functions, the principal line of defense against pathogens, in a molluscan model, the abalone Haliotis turbeculata. Immune parameters were investigated in abalones subjected to a 15 min mechanical disturbance which, as indicated by noradrenaline and dopamine hemolymphatic levels, resulted in a transient state of physiological stress. During the application of the stressor, immune parameters such as the number of circulating hemocytes, the migratory activity, the phagocytic capacity and the respiratory burst responses of hemocytes, decreased significantly. All parameters returned to initial values within 15-30 min after the end of the disturbance and a transient period of immunostimulation occurred between 100 and 480 min after the stress for all immune parameters except intracellular superoxide anion production. These results indicate that in the abalone H. tuberculata, as in vertebrates, a link exists between stress and the immune system. This may begin to answer why stress and disease outbreaks are linked in shellfish.

Zinc alpha-2-glycoprotein regulates melanin production by normal and malignant melanocytes

Zinc alpha-2-glycoprotein is secreted by a variety of normal and malignant epithelial cells and overexpression by tumors has been implicated in cancer cachexia. To investigate biologic properties of zinc alpha-2-glycoprotein further, stable transfectants of recombinant human zinc alpha-2-glycoprotein were created in the B16F10 murine melanoma cell line. Both B16-recombinant human zinc alpha-2-glycoprotein clones with strong expression of zinc alpha-2-glycoprotein and vector-transfected B16 cells treated with exogenous zinc alpha-2-glycoprotein had decreased melanin production in vitro. Furthermore, B16-recombinant human zinc alpha-2-glycoprotein clones formed amelanotic tumors in vivo, despite their melanin production in vitro. Although no qualitative differences in tyrosinase mRNA expression could be detected by reverse transcription-polymerase chain reaction, B16-recombinant human zinc alpha-2-glycoprotein tumors had decreased levels of tyrosinase protein and minimal tyrosinase activity. Purified zinc alpha-2-glycoprotein also decreased tyrosinase activity in vector-transfected B16 tumor sections in vitro. Taken together, these studies demonstrate that zinc alpha-2-glycoprotein inhibits melanin production by B16 melanoma cells via post-transcriptional effects on tyrosinase protein. As zinc alpha-2-glycoprotein decreases melanin synthesis more strongly in vivo than in vitro, however, it is likely that zinc alpha-2-glycoprotein affects melanin synthesis through indirect mechanisms as well. Zinc alpha-2-glycoprotein also inhibits melanin production by melan-A primary melanocytes in vitro. As zinc alpha-2-glycoprotein is normally produced by epidermal keratinocytes, these studies raise the possibility that epidermal-derived zinc alpha-2-glycoprotein may play a part in normal regulation of melanin production in vivo, in addition to its previously described role in cancer cachexia.

50 Hz magnetic fields of varying flux intensity affect cell shape changes in invertebrate immunocytes: the role of potassium ion channels

The effect induced by exposure to 50 Hz magnetic fields (MFs) in immunocytes from the mussel Mytilus galloprovincialis is evaluated. The whole animal was exposed for 15 and 30 min to MF intensities ranging from 200 to 1,000 microT. The changes in the cellular shape of immunocytes, expressed as shape factor (SF), were studied at different times after addition of the chemotacting substance N-formyl-Meth-Leu-Phe (fMLP). Results show that MFs provoke differing delays in fMLP-induced cellular shape changes: 200 microT are ineffective, while levels from 300 microT upwards cause a significant increase in immunocyte SF values compared to controls. Reactivation of the cells is possible up to an intensity of 600 microT. The use of PCO 400, an opener of ATP-sensitive K+ channels, shows that potassium channels are involved in the effect of MFs on M. galloprovincialis immunocytes.

Biology of kidney cells: ontogeny-recapitulating phylogeny

Biology of kidney cells can be used as a model for further understanding of ontogeny-recapitulating phylogeny. The common and species-specific structural and functional relationship between blood capillaries and the environment via a filtration barrier of nephrons is a biological phenomenon resulting from renal cell memory acquired through evolution. Genetically programmed development, a subsequent series of gene expression, and inductive interactions played a key role in differentiation and maintenance of specific activities of kidneys in birds and mammals. Various environmental factors may alter kidney development and specific activities at the levels of gene expression, repression, or derepression, and defensive mechanisms involved in reaction to risk factors are developed. Autoimmunity and cancerogenesis are closely dependent on a variety of environmental agents, such as antigens originating from infections with some viruses and toxins, or irradiation, advanced industrialization, and progress of civilization. As a result of gene mutation, delation, rearrangement, and/or susceptibility to different agents, renal cell memory is altered. Instead of cell-specific activities, the abilities for regeneration, and other genetically programmed activities, the genesis of kidney diseases are common. Balkan endemic nephropathy, as regional disease, is an important example of the role, of environmental agents, at the level of genes. Research programs on molecular genetics will contribute to our efforts both to prevent infections and to elucidate the genesis, diagnosis, prognosis, prevention, and therapy of kidney diseases.

Lack of neuronal NOS has consequences for the expression of POMC and POMC-derived peptides in the mouse pituitary

The relevance of NO in neuroendocrine signalling has been investigated by analysis of cellular expression of pro-opiomelanocortin (POMC) and the POMC-derived peptides beta-endorphin, alpha-melanocyte stimulating hormone and adrenocorticotropin. Expression patterns were studied in the pituitary gland of 150-day old wild-type and neuronal-NOS (nNOS) knock-out mice by using immunohistochemistry, in situ hybridization and Northern blot analysis. Remaining NO-generating capacities in the knock-out mice were demonstrated by immunohistochemical localization of inducible, endothelial and neuronal NOS isoforms. Quantitative analysis revealed that cellular expression of POMC mRNA was drastically reduced in the pituitary of knock-out mice in comparison to controls. In situ hybridization studies demonstrated that this reduction was most pronounced in the intermediate lobe, while the anterior lobe was much less affected. Immunostaining for the proteolytic fragments of POMC was significantly reduced in the intermediate lobe cells of knock-out mice. A moderate reduction of immunostaining for these peptides was also observed in adenopituitary cells of nNOS knock-out mice. Our data demonstrate that the lack of nNOS substantially affects cellular levels of pituitary opioid peptides, which may have consequences for the response of these animals to stress and pain.

An immunohistochemical study of adenohypophyseal cells in the viviparous reptile Chalcides chalcides

The morphology of the hypophysis and the immunocharacteristics of the adenohypophyseal cells in the viviparous reptile Chalcides chalcides were studied by light microscopy, using conventional staining methods and an indirect antibody technique (ABC method), respectively. The general morphology of the C. chalcides hypophysis was comparable to that of other reptiles, showing three main regions: the pars distalis, the pars intermedia and the pars nervosa. The gland appeared as an elongated body in a cephalic-caudal direction and was almost completely enclosed in the sella turcica. For this reason, the hypophysis was studied in toto with the brain in decalcified specimens. The pars distalis accounted for most of the whole organ. The pars intermedia surrounded the pars nervosa as a goblet. The pars tuberalis was lacking. The immunohistochemical identification of the adenohypophyseal cells was performed using rabbit antisera against mammalian/synthetic hypophyseal hormones. Prolactin cells were clustered in small cellular cordons in the rostral pars distalis and in the medial pars distalis in both male and female specimens. Somatotropic cells were found in the caudal pars distalis. Corticotropic cells were observed in the medio-rostral pars distalis, as well as in the pars intermedia, where melanotropic cells were also present. Melanotropic cells were confined to the pars intermedia. Gonadotropic cells were mostly distributed in the ventral and lateral portions of the pars distalis, where they were found isolated or in small clusters. Thyrotropic cells were detected in the pars distalis with a distribution similar to that of the gonadotropic cells; however, atypically, they were also found in the pars intermedia. Therefore, the cytological characteristics of the adenohypophyseal cells appeared mostly conserved.

Platelet-derived growth factor and transforming growth factor-beta in invertebrate immune and neuroendocrine interactions: another sign of conservation in evolution

Growth factor-like molecules have been found in various invertebrate species. In particular, we have reported the presence of platelet-derived growth factor (PDGF)-AB and transforming growth factor-beta (TGF-beta)1 immunoreactive molecules in molluscs, insects and annelids. Moreover, PDGF-AB and TGF-beta1 affect the main immune functions, such as phagocytosis, chemotaxis and cell motility. Changes in cell shape are induced via interactions of growth factors with their respective specific receptors. The extracellular signals are transduced by the activation of classical signal transduction pathways, such as those involving PKA and PKC, and pivotal transcription regulators, i.e. the Fos, Jun and SMAD proteins. The two growth factors intervene in stress responses by activating the CRH-ACTH-biogenic amine axis. Exogenous administration of PDGF-AB and TGF-beta1 in a molluscan wound provokes an accelerated migration of immunocytes and fibroblasts to the injured area, stimulating granulation tissue formation and wound re-epithelialization. These findings suggest that these molecules are ancestral and that their function is well conserved and crucial in the maintenance of invertebrate homeostasis.

Neuroinflammation and the genetics of Alzheimer's disease: the search for a pro-inflammatory phenotype

The role of interleukin 1 (IL-1) and interleukin 6 (IL-6) in the pathogenesis of Alzheimer's disease (AD) is reviewed within the framework of "inflamm-aging", i.e., the characteristic chronic pro-inflammatory status which develops in old age, and neuroinflammation, i.e., the peculiar inflammatory process which is present in the brain of AD patients. In particular, the data suggesting that several IL-1 and IL-6 gene polymorphisms can contribute to the risk of developing AD are reviewed. The possibility as well as the difficulty in identifying a pro-inflammatory phenotype, and its importance for the prevention, diagnosis and therapy of AD and other age-related pathologies are discussed.

Nitric oxide induces apoptosis in the fat body cell line IPLB-LdFB from the insect Lymantria dispar

The presence of immunoreactive inducible nitric oxide synthase molecules (ir-iNOS) is demonstrated in the Lymantria dispar IPLB-LdFB cell line. The maximum ir-iNOS inducibility is observed 18 h after incubation with sodium nitroprusside (SNP). The increase in NO provoked by SNP in turn induces apoptosis. However, this phenomenon is observed only after 48 h. The NOS-inhibitors N(omega)-nitro-L-arginine methyl ester (L-NAME) and N-[3-(aminomethyl)-benzyl]acetamide (1400W) were both unable to block the SNP-induced apoptosis at all the concentrations used. Incubation with SNP plus N-acetyl-L-cysteine (NAC) further augmented the percentage of cell death with respect to SNP used alone, and this process is seen earlier, i.e. after 24 h. Moreover, the induction of apoptosis in the presence of NAC is time- and concentration-dependent. The high percentage of cell death with SNP+NAC suggests that NAC forms S-nitrosothiols with NO, resulting in an increase in the bioavailability of NO. In conclusion, these findings show the existence of a close relationship between mammalian and invertebrate cells with regards to SNP and NAC induction and the related NO response.

The network and the remodeling theories of aging: historical background and new perspectives

Two general theories, i.e. "the network theory of aging" (1989) and "the remodeling theory of aging" (1995), as well as their implications, new developments, and perspectives are reviewed and discussed. Particular attention has been paid to illustrate: (i) how the network theory of aging fits with recent data on aging and longevity in unicellular organisms (yeast), multicellular organisms (worms), and mammals (mice and humans); (ii) the evolutionary and experimental basis of the remodeling theory of aging (immunological, genetic, and metabolic data in healthy centenarians, and studies on the evolution of the immune response, stress and inflammation) and its recent development (the concepts of "immunological space" and "inflamm-aging"); (iii) the profound relationship between these two theories and the data which suggest that aging and longevity are related, in a complex way, to the capability to cope with a variety of stressors.

Inflamm-aging. An evolutionary perspective on immunosenescence

In this paper we extend the "network theory of aging," and we argue that a global reduction in the capacity to cope with a variety of stressors and a concomitant progressive increase in proinflammatory status are major characteristics of the aging process. This phenomenon, which we will refer to as "inflamm-aging," is provoked by a continuous antigenic load and stress. On the basis of evolutionary studies, we also argue that the immune and the stress responses are equivalent and that antigens are nothing other than particular types of stressors. We also propose to return macrophage to its rightful place as central actor not only in the inflammatory response and immunity, but also in the stress response. The rate of reaching the threshold of proinflammatory status over which diseases/disabilities ensue and the individual capacity to cope with and adapt to stressors are assumed to be complex traits with a genetic component. Finally, we argue that the persistence of inflammatory stimuli over time represents the biologic background (first hit) favoring the susceptibility to age-related diseases/disabilities. A second hit (absence of robust gene variants and/or presence of frail gene variants) is likely necessary to develop overt organ-specific age-related diseases having an inflammatory pathogenesis, such as atherosclerosis, Alzheimer's disease, osteoporosis, and diabetes. Following this perspective, several paradoxes of healthy centenarians (increase of plasma levels of inflammatory cytokines, acute phase proteins, and coagulation factors) are illustrated and explained. In conclusion, the beneficial effects of inflammation devoted to the neutralization of dangerous/harmful agents early in life and in adulthood become detrimental late in life in a period largely not foreseen by evolution, according to the antagonistic pleiotropy theory of aging.

Cytotoxicity and cytotoxic molecules in invertebrates

Although lacking the components that characterize the acquired immunity systems of vertebrates, invertebrates nevertheless possess effective general innate immune mechanisms which exhibit striking parallels with those of vertebrates. These innate immune systems include both cellular and humoral elements. Invertebrate phagocytes synthesize both oxygen-dependent and oxygen-independent molecules to combat infectious agents. Cytotoxic substances employed by invertebrates include reactive intermediates of oxygen and nitrogen, antimicrobial peptides, lectins, cytokine- and complement-like molecules, and quinoid intermediates of melanin. The signal transduction pathways that are involved in mediating the production of these substances appear to be very similar among animal species, suggesting a common ancestral origin for the innate immune systems.

Detection of casein fragments in an invertebrate and in a vertebrate using in situ hybridization

Using a non-radioactive in situ hybridization procedure it has been demonstrated that both invertebrates such as the mollusc Mytilus galloprovincialis and lower vertebrates such as the fish Cyprinus carpio express bovine alphaS1- and kappa-casein homologous mRNAs. In particular, positive results were found in molluscan immunocytes, and in cells located in different fish tissues: intestine, endocrine pancreas and kidney. These findings suggest that the casein genes are highly conserved throughout evolution.

PP/PYY cells from endocrine pancreas of the scincid lizard Eumeces inexpectatus synthesize ACTH- and alpha-MSH-like molecules

The endocrine pancreas of the scincid lizard Eumeces inexpectatus secretes four major hormones, insulin, glucagon, somatostatin, and pancreatic polypeptide (PP); in addition, other peptides and neuropeptides, often colocalized in one of the principal cell types (A, B, D, and PP), were detected by light and ultrastructural immunocytochemistry. In particular, the pancreas is rich in peptide tyrosine tyrosine (PYY), ACTH, and alpha-MSH immunoreactivity. When single- and double-immunolabeled serial sections were compared for immunostaining for PP, PYY, ACTH, and alpha-MSH, there was broad coincidence with PP, termed PP/PYY, cells in view of the extensive colocalization of these two peptides. Furthermore, ultrastructural morphometric studies revealed similar secretory granules for PP immunoreactive (ir) and ACTH ir cells, while the endocrine cells express pro-opiomelanocortin (POMC) mRNA, indicating an active, extrapituitary synthesis of the POMC-derived peptides in these cells. In conclusion, the presence of POMC-derived peptides in the endocrine pancreatic cells suggests that they may regulate insulin secretion.

POMC-derived peptides and their biological action

It has long been known that a large number of POMC-related peptides are found in skin. In this introduction I describe the formation of POMC-derived peptides in various tissues to indicate that processing is largely tissue-dependent. I focus on the peptides from the N-terminal fragment, such as gamma-MSH, ACTH and alpha-MSH, and beta-lipopropin as well as beta-endorphin. I touch on the factors that control the synthesis of the various peptides, which are now numerous and varied, and again are tissue specific. The biologic activity of the peptides generated from POMC are described in relation to their possible action in skin. In addition, I describe a new class of peptides induced in skin following injury and which are of great interest.

Immunoreactive POMC-derived peptides and cytokines in the chicken thymus and bursa of Fabricius microenvironments: age-related changes

Changes from hatching to the involutive stage in the thymus and bursa of Fabricius of Gallus domesticus were studied. Pro-opiomelanocortin (POMC)-derived peptides and cytokines were also tested by immunocytochemical procedures. Thymic histological modifications appeared at 3 months and involved an increase in connectival argyrophilic reticular fibres, a proliferation of non-epithelial cells in the reticulum network, the presence of mucous cells and small mucous cysts, and an increase in the number of eosinophilic and myoid cells. A clear distinction between the cortex and the medulla was lost. Immunoreactive POMC-related molecules and cytokines were demonstrated in thymic cells from 4-day-old chicken, and their number increased with ageing. These molecules were expressed in a few single epithelial cells and in interdigitating cells. With ageing, the number of immunoreactive interdigitating cells also increased, and these appeared in an activated phase. Histological modifications in the bursa of Fabricius appeared at 2 months and concerned a folding of the interfollicular surface epithelium covering the bursal plicae and a reduction in lymphoid follicle-associated epithelium. Fibrous tissue gradually increased, and large mucoid cysts were evident. The expression of POMC-derived peptide-and cytokine-like molecules differed during the development and involution phases of the organ. Cells of follicle associated epithelium and dendritic reticular cells of lymphoid follicles were immunoreactive to beta-endorphin between 4 days and 2 months, while ACTH-, alpha-MSH- and cytokine-like molecules were observed in follicles after 2 months. The findings indicate a physiological role of these molecules during the growth and involution of the two organs.

Presence of IL-1- and TNF-like molecules in Galleria mellonella (Lepidoptera) haemocytes and in an insect cell line Fromestigmene acraea (Lepidoptera)

In this study the authors give immunocytochemical evidence for the presence of interleukin (IL)-1alpha- and tumour necrosis factor (TNF) alpha-like molecules in the haemocytes of last instar larvae from the greater wax moth Galleria mellonella. Similar results are demonstrated in a continuous haemocyte line (BTI-EA-1174-A) from the salt marsh caterpillar Estigmene acraea. In Galleria mellonella larvae granular cells show a strong positive reaction with both primary antibodies, whereas plasmatocytes are stained to a lesser extent. Cell line haemocytes also react positively with both antibodies. After activating the cells with lipopolysaccharide (LPS) staining of Estigmene acraea cells is decreased, whereas Galleria mellonella haemocytes show no visible reaction in comparison to non-activated cells.