The invertebrate phagocytic immunocyte: clues to a common evolution of immune and neuroendocrine systems

Immunology of Aging: the Birth of Inflammaging

The inflammaging concept was introduced in 2000 by Prof. Franceschi. This was an evolutionary or rather a revolutionary conceptualization of the immune changes in response to a lifelong stress. This conceptualization permitted to consider the lifelong proinflammatory process as an adaptation which could eventually lead to either beneficial or detrimental consequences. This dichotomy is influenced by both the genetics and the environment. Depending on which way prevails in an individual, the outcome may be healthy longevity or pathological aging burdened with aging-related diseases. The concept of inflammaging has also revealed the complex, systemic nature of aging. Thus, this conceptualization opens the way to consider age-related processes in their complexity, meaning that not only the process but also all counter-processes should be considered. It has also opened the way to add new concepts to the original one, leading to better understanding of the nature of inflammaging and of aging itself. Finally, it showed the way towards potential multimodal interventions involving a holistic approach to optimize the aging process towards a healthy longevity.

Metal accumulation and morphofunctional damage in coelomocytes of earthworm collected from industrially contaminated soil of Kolkata, India

The current study is aimed to assess the ecotoxicological effects of toxic metals and seasonal shift of the physicochemical characteristics of soil in an endogeic earthworm Metaphire posthuma of industrially contaminated soil of Calcutta leather complex. The accumulation of cadmium, chromium, lead and mercury was quantitated in whole earthworms and coelomocytes. The accumulation of metals was derived to be high in the coelomocytes than whole earthworms. Morphofunctional shift in coelomocytes indicated a high level of metal toxicity in soil inhabitants. The shift in differential coelomocyte count and cellular damage including intense cytoplasmic vacuolation and membrane blebbing of coelomocytes of M. posthuma of contaminated soil were suggestive to a state of immunocompromisation in the same species. Shift in the generation of nitric oxide and activity of inducible nitric oxide synthase indicated a possible immunosuppression in earthworm. Depletion in the acetylcholinesterase activity of coelomocytes indicated neurotoxicity of metals leached from the dumped wastes in Calcutta leather complex. Integrated biomarker response based analysis was carried out to assess the biomarker potential of experimental endpoints of M. posthuma to monitor metal toxicity in soil.

Non-traditional roles of immune cells in regeneration: an evolutionary perspective

Immune cells are known to engage in pathogen defense. However, emerging research has revealed additional roles for immune cells, which are independent of their function in the immune response. Here, we underscore the ability of cells outside of the adaptive immune system to respond to recurring infections through the lens of evolution and cellular memory. With this in mind, we then discuss the bidirectional crosstalk between the immune cells and stem cells and present examples where these interactions regulate tissue repair and regeneration. We conclude by suggesting that comprehensive analyses of the immune system may enable biomedical applications in stem cell biology and regenerative medicine.

Functional analysis of TcCTL12 in innate immunity and development in Tribolium castaneum

C-type lectins (CTLs) play vital roles in invertebrates' innate immunity. Six CTL-X type lectins are identified in Tribolium castaneum. However, their functions and regulating mechanisms remain elusive. Here, TcCTL12, one CTL-X, was identified and cloned from T. castaneum. Spatiotemporal expression profiling revealed that TcCTL12 highly expressed in late pupa and early adult of T. castaneum in comparison with other developmental stages, and exhibited the highest expression level in the haemolymph and central nervous system (CNS). Then, the expression of TcCTL12 was remarkably induced by the stimulation of Escherichia coli and Staphylococcus aureus. Moreover, the recombinant protein TcCTL12 could bind pathogen-associated molecular patterns (PAMPs) including LPS and PGN, and displayed agglutinative activity to both Gram-positive and Gram-negative bacteria in a calcium-dependent manner in vitro. Furthermore, RNAi of TcCTL12 caused T. castaneum pupation and eclosion defected. The abnormal pupa thinned their epidermal, and appeared the abnormal development of muscle cell compared with the control group. Additionally, depletion of TcCTL12 resulted in reducing fertility of offspring and affected their fecundity. In sum, these results indicated that TcCTL12 had extensive functions in the regulation of development in T. castaneum, in addition to the immune response. It further expanded insights into CTL functions in insects.

Early Biological Modulations Resulting from 1-Week Venlafaxine Exposure of Marine Mussels Mytilus galloprovincialis Determined by a Metabolomic Approach

There is growing evidence of the presence of pharmaceuticals in natural waters and their accumulation in aquatic organisms. While their mode of action on non-target organisms is still not clearly understood, their effects warrant assessment. The present study assessed the metabolome of the Mediterranean mussel (Mytilus galloprovincialis) exposed to a 10 µg/L nominal concentration of the antidepressant venlafaxine (VLF) at 3 time-points (1, 3, and 7 days). Over the exposure period, we observed up- or down-modulations of 113 metabolites, belonging to several metabolisms, e.g., amino acids (phenylalanine, tyrosine, tryptophan, etc.), purine and pyrimidine metabolisms (adenosine, cyclic AMP, thymidine, etc.), and several other metabolites involved in diverse functions. Serotonin showed the same time-course modulation pattern in both male and female mussels, which was consistent with its mode of action in humans, i.e., after a slight decrease on the first day of exposure, its levels increased at day 7 in exposed mussels. We found that the modulation pattern of impacted metabolites was not constant over time and it was gender-specific, as male and female mussels responded differently to VLF exposure.

Single-cell RNA-seq profiling of individual Biomphalaria glabrata immune cells with a focus on immunologically relevant transcripts

The immune cells of the snail Biomphalaria glabrata are classified into hyalinocyte and granulocyte subtypes. Both subtypes are essential for the proper functioning of the snail immune response, which we understand best within the context of how it responds to challenge with the human parasite Schistosoma mansoni. Granulocytes are adherent phagocytic cells that possess conspicuous granules within the cell cytoplasm. Hyalinocytes, on the other hand, are predominantly non-adherent and are known to produce a handful of anti-S. mansoni immune effectors. While our understanding of these cells has progressed, an in-depth comparison of the functional capabilities of each type of immune cell has yet to be undertaken. Here, we present the results of a single-cell RNA-seq study in which single granulocytes and hyalinocytes from S. mansoni-susceptible M-line B. glabrata and S. mansoni-resistant BS-90 B. glabrata are compared without immune stimulation. This transcriptomic analysis supports a role for the hyalinocytes as producers of immune effectors such as biomphalysin and thioester-containing proteins. It suggests that granulocytes are primarily responsible for producing fibrinogen-related proteins and are armed with various pattern-recognition receptors such as toll-like receptors with a confirmed role in the anti-S. mansoni immune response. This analysis also confirms that the granulocytes and hyalinocytes of BS-90 snails are generally more immunologically prepared than their M-line counterparts. As the first single-cell analysis of the transcriptional profiles of B. glabrata immune cells, this study provides crucial context for understanding the B. glabrata immune response. It sets the stage for future investigations into how each immune cell subtype differs in its response to various immunological threats.

Planarians (Platyhelminthes)-An Emerging Model Organism for Investigating Innate Immune Mechanisms

An organism responds to the invading pathogens such as bacteria, viruses, protozoans, and fungi by engaging innate and adaptive immune system, which functions by activating various signal transduction pathways. As invertebrate organisms (such as sponges, worms, cnidarians, molluscs, crustaceans, insects, and echinoderms) are devoid of an adaptive immune system, and their defense mechanisms solely rely on innate immune system components. Investigating the immune response in such organisms helps to elucidate the immune mechanisms that vertebrates have inherited or evolved from invertebrates. Planarians are non-parasitic invertebrates from the phylum Platyhelminthes and are being investigated for several decades for understanding the whole-body regeneration process. However, recent findings have emerged planarians as a useful model for studying innate immunity as they are resistant to a broad spectrum of bacteria. This review intends to highlight the research findings on various antimicrobial resistance genes, signaling pathways involved in innate immune recognition, immune-related memory and immune cells in planarian flatworms.

Crustacean hyperglycemic hormone (CHH) affects hemocyte intracellular signaling pathways to regulate exocytosis and immune response in white shrimp Litopenaeus vannamei

Recombinant Litopenaeus vannamei CHH (rLvCHH) was obtained from a bacterial expression system and the intracellular signaling pathways involved in exocytosis and immune response after rLvCHH injection (0.2 and 2 μg/shrimp) was investigated in this study. The results showed that CHH contents increased 51.4%-110.2% (0.2 μg/shrimp) and 65.0%-211.3% (2 μg/shrimp) of the control level. And the contents of three biogenic amines in hemolymph presented a similar variation pattern after rLvCHH injection, but reached the highest level at different time points. Furthermore, the mRNA expression levels of membrane-bound guanylyl cyclase (mGC) (1.20-1.93 fold) and biogenic amine receptors, including type 2 dopamine receptor (DA2R) (0.72-0.89 fold), α2 adrenergic receptor (α2-AR) (0.72-0.91 fold) and 5-HT7 receptor (5-HT7R) (1.37-3.49 fold) in hemocytes were changed consistently with their ligands. In addition, the second messenger and protein kinases shared a similar trend and reached the maximum at the same time respectively. The expression levels of nuclear transcription factor (cAMP response element-binding protein, CREB) and exocytosis-related proteins transcripts were basically overexpressed after rLvCHH stimulation, which reached the peaks at 1 h or 3 h. Eventually, the phenoloxidase (PO) activity (37.4%-158.5%) and antibacterial activity (31.8%-122.3%) in hemolymph were dramatically enhanced within 6 h, while the proPO activity in hemocytes significantly decreased (11.2%-62.6%). Collectively, these results indicate that shrimps L. vannamei could carry out a simple but 'smart' NEI regulation by releasing different neuroendocrine factors at different stages after rLvCHH stimulation, which could couple with their receptors and trigger the downstream signaling pathways during the immune responses in hemocytes.

Independent and simultaneous effect of crustacean hyperglycemic hormone and dopamine on the hemocyte intracellular signaling pathways and immune responses in white shrimp Litopenaeus vannamei

Immune responses and intracellular signaling pathways were examined after hemolymph of Litopenaeus vannamei being incubated in Crustacean hyperglycemic hormone (CHH), dopamine (DA) and DA antagonist (Y). The results showed that the effect CHH and CHH + DA + Y on viability of hemocytes were no significant changes compared to the control group. However, in DA, DA + Y and CHH + DA groups, the viability of hemocytes decreased significantly. The phagocytic activity and the antibacterial activity of CHH group were increased significantly within 12h. Whereas the CHH + DA, DA were significantly lower than the control. PO in haemolymph was up-regulated after CHH and DA incubation. The proPO has the opposite change in all groups. In addition, DA + Y, CHH + DA + Y has a similar trend with the DA and CHH respectively. Furthermore, a significant increase of cAMP, CaM and cGMP were found in treatment groups except for the CaM concentration of the CHH group and the cGMP concentration of DA group. There is no significant change observed in the CHH group about CaM concentration. Whereas the cGMP of DA group decreased within 12h. The results suggest that DA could depress the immune responses by cAMP-, CaM-pathways. However, the CHH is on the contrary, which transduced the signals from cAMP, cGMP to PKA, PKC and PKG to enhance the immune response parameters.

The Neuroendocrine-Immune Regulation in Response to Environmental Stress in Marine Bivalves

Marine bivalves, which include many species worldwide, from intertidal zones to hydrothermal vents and cold seeps, are important components of the ecosystem and biodiversity. In their living habitats, marine bivalves need to cope with a series of harsh environmental stressors, including biotic threats (bacterium, virus, and protozoan) and abiotic threats (temperature, salinity, and pollutants). In order to adapt to these surroundings, marine bivalves have evolved sophisticated stress response mechanisms, in which neuroendocrine regulation plays an important role. The nervous system and hemocyte are pillars of the neuroendocrine system. Various neurotransmitters, hormones, neuropeptides, and cytokines have been also characterized as signal messengers or effectors to regulate humoral and cellular immunity, energy metabolism, shell formation, and larval development in response to a vast array of environmental stressors. In this review substantial consideration will be devoted to outline the vital components of the neuroendocrine system identified in bivalves, as well as its modulation repertoire in response to environmental stressors, thereby illustrating the dramatic adaptation mechanisms of molluscs.

Inflammaging: a new immune-metabolic viewpoint for age-related diseases

Ageing and age-related diseases share some basic mechanistic pillars that largely converge on inflammation. During ageing, chronic, sterile, low-grade inflammation - called inflammaging - develops, which contributes to the pathogenesis of age-related diseases. From an evolutionary perspective, a variety of stimuli sustain inflammaging, including pathogens (non-self), endogenous cell debris and misplaced molecules (self) and nutrients and gut microbiota (quasi-self). A limited number of receptors, whose degeneracy allows them to recognize many signals and to activate the innate immune responses, sense these stimuli. In this situation, metaflammation (the metabolic inflammation accompanying metabolic diseases) is thought to be the form of chronic inflammation that is driven by nutrient excess or overnutrition; metaflammation is characterized by the same mechanisms underpinning inflammaging. The gut microbiota has a central role in both metaflammation and inflammaging owing to its ability to release inflammatory products, contribute to circadian rhythms and crosstalk with other organs and systems. We argue that chronic diseases are not only the result of ageing and inflammaging; these diseases also accelerate the ageing process and can be considered a manifestation of accelerated ageing. Finally, we propose the use of new biomarkers (DNA methylation, glycomics, metabolomics and lipidomics) that are capable of assessing biological versus chronological age in metabolic diseases.

Unbiased classification of mosquito blood cells by single-cell genomics and high-content imaging

Mosquito blood cells are immune cells that help control infection by vector-borne pathogens. Despite their importance, little is known about mosquito blood cell biology beyond morphological and functional criteria used for their classification. Here, we combined the power of single-cell RNA sequencing, high-content imaging flow cytometry, and single-molecule RNA hybridization to analyze a subset of blood cells of the malaria mosquito Anopheles gambiae By demonstrating that blood cells express nearly half of the mosquito transcriptome, our dataset represents an unprecedented view into their transcriptional program. Analyses of differentially expressed genes identified transcriptional signatures of two cell types and provide insights into the current classification of these cells. We further demonstrate the active transfer of a cellular marker between blood cells that may confound their identification. We propose that cell-to-cell exchange may contribute to cellular diversity and functional plasticity seen across biological systems.

Immunobiography and the Heterogeneity of Immune Responses in the Elderly: A Focus on Inflammaging and Trained Immunity

Owing to its memory and plasticity, the immune system (IS) is capable of recording all the immunological experiences and stimuli it was exposed to. The combination of type, dose, intensity, and temporal sequence of antigenic stimuli that each individual is exposed to has been named “immunobiography.” This immunological history induces a lifelong continuous adaptation of the IS, which is responsible for the capability to mount strong, weak or no response to specific antigens, thus determining the large heterogeneity of immunological responses. In the last years, it is becoming clear that memory is not solely a feature of adaptive immunity, as it has been observed that also innate immune cells are provided with a sort of memory, dubbed “trained immunity.” In this review, we discuss the main characteristics of trained immunity as a possible contributor to inflammaging within the perspective of immunobiography, with particular attention to the phenotypic changes of the cell populations known to be involved in trained immunity. In conclusion, immunobiography emerges as a pervasive and comprehensive concept that could help in understanding and interpret the individual heterogeneity of immune responses (to infections and vaccinations) that becomes particularly evident at old age and could affect immunosenescence and inflammaging.

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.

Catecholamines are produced by ascidian immune cells: The involvement of PKA and PKC in the adrenergic signaling pathway

The stress response is a complex mechanism, which includes changes in the immune system to enable organisms to maintain homeostasis. The neurohormones dopamine, noradrenaline (NA) and adrenalin are responsible for the physiological modulations that occur during acute stress. In the present study, we analyzed the effects of NA on the immune system specific to nitric-oxide (NO) production by subpopulations of immune cells (hemocytes) of the ascidian Phallusia nigra. We also investigated the capability of immune cells to produce catecholamine (CA). Finally, we tested the involvement of protein kinase A (PKA) and C (PKC) in the NA downstream signaling pathway. The results revealed that NA can reduce NO production by P. nigra hemocytes threefold, and that signet-ring cells, univacuolar refractile granulocytes and morula cells are the cell types most involved in this event. A challenge effected with Zymosan A induced CA production, and co-incubation with both inhibitors of the second messengers PKA and PKC revealed the involvement of these molecules in the adrenergic pathway of P. nigra hemocytes. Taken together, these results suggest that NO production can be down-regulated by NA through α- and β-adrenoceptors via the second messengers PKA and PKC.

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.

Evolutionary Aspects of Macrophages Polarization

Macrophages constitute a heterogeneous population of myeloid cells that are essential for maintaining homeostasis and as a first line of innate responders controlling and organizing host defenses against pathogens. Monocyte-macrophage lineage cells are among the most functionally diverse and plastic cells of the immune system. They undergo specific activation into functionally distinct phenotypes in response to immune signals and microbial products. In mammals, macrophage functional heterogeneity is defined by two activation states, M1 and M2, which represent two polar ends of a continuum exhibiting pro-inflammatory and tissue repair activities, respectively. While the ancient evolutionary origin of macrophages as phagocytic defenders is well established, the evolutionary roots of the specialized division of macrophages into subsets with polarized activation phenotypes is less well defined. Accordingly, this chapter focuses on recent advances in the understanding of the evolution of macrophage polarization and functional heterogeneity with a focus on ectothermic vertebrates.

Cellular Organization of Neuroimmune Interactions in the Gastrointestinal Tract

The gastrointestinal (GI) tract is the largest immune organ; in vertebrates, it is the only organ whose function is controlled by its own intrinsic enteric nervous system (ENS), but it is additionally regulated by extrinsic (sympathetic and parasympathetic) innervation. The GI nervous and immune systems are highly integrated in their common goal, which is to unite digestive functions with protection from ingested environmental threats. This review discusses the physiological relevance of enteric neuroimmune integration by summarizing the current knowledge of evolutionary and developmental pathways, cellular organization, and molecular mechanisms of neuroimmune interactions in health and disease.

Effect of salinity on regulation mechanism of neuroendocrine-immunoregulatory network in Litopenaeus vannamei

The effects of low salinity (transferred from 31‰ to 26‰, 21‰, and 16‰) on the regulation pathways of neuroendocrine-immunoregulatory network were investigated in Litopenaeus vannamei. The results showed that the hormones (corticotrophin-releasing hormone, adrenocorticotropic hormone) and biogenic amines (dopamine, noradrenaline, 5-hydroxytryptamine) concentrations in lower salinity groups increased significantly within 12 h. The gene expression of biogenic amine receptors showed that dopamine receptor D4 and α2 adrenergic receptor in lower salinity groups decreased significantly within 12 h, whereas the 5-HT7 receptor significantly increased within 1d. The second messenger synthetases (adenylyl cyclase, phospholipase C) and the second messengers (cyclic adenosine monophosphate, cyclic guanosine monophosphate) of lower salinity groups shared a similar trend in which adenylyl cyclase and cyclic adenosine monophosphate reached the maximum at 12 h, whereas phospholipase C and cyclic guanosine monophosphate reached the minimum. The immune parameters (total hemocyte count, phenoloxidase activity, phagocytic activity, crustin expression, antibacterial activity, C-type lectin expression, hemagglutinating activity) in lower salinity groups decreased significantly within 12 h. Except for the total hemocyte count, all the parameters recovered to the control levels afterwards. Therefore, it may be concluded that the neuroendocrine-immunoregulatory network plays a principal role in adapting to salinity changes as the main center for sensing the stress and causes immune response in L. vannamei.

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.

Mutual modulation between norepinephrine and nitric oxide in haemocytes during the mollusc immune response

Nitric oxide (NO) is one of the most important immune molecules in innate immunity of invertebrates, and it can be regulated by norepinephrine in ascidian haemocytes. In the present study, the mutual modulation and underlying mechanism between norepinephrine and NO were explored in haemocytes of the scallop Chlamys farreri. After lipopolysaccharide stimulation, NO production increased to a significant level at 24 h, and norepinephrine concentration rose to remarkable levels at 3 h and 12~48 h. A significant decrease of NO production was observed in the haemocytes concomitantly stimulated with lipopolysaccharide and α-adrenoceptor agonist, while a dramatic increase of NO production was observed in the haemocytes incubated with lipopolysaccharide and β-adrenoceptor agonist. Meanwhile, the concentration of cyclic adenosine monophosphate (cAMP) decreased significantly in the haemocytes treated by lipopolysaccharide and α/β-adrenoceptor agonist, while the content of Ca(2+) was elevated in those triggered by lipopolysaccharide and β-adrenoceptor agonist. When the haemocytes was incubated with NO donor, norepinephrine concentration was significantly enhanced during 1~24 h. Collectively, these results suggested that norepinephrine exerted varied effects on NO production at different immune stages via a novel α/β-adrenoceptor-cAMP/Ca(2+) regulatory pattern, and NO might have a feedback effect on the synthesis of norepinephrine in the scallop haemocytes.

A lipidomic perspective on inflammatory macrophage eicosanoid signaling

Macrophages are central to essential physiological processes including the regulation of innate and adaptive immunity, but they are also central to a number of inflammatory disease states. These immune cells also possess remarkable plasticity and display various shades of functionalities based on changes in the surrounding molecular environment. Macrophage biology has defined various phenotypes and roles in inflammation based primarily on cytokine and chemokine profiles of cells in different activation states. Importantly, macrophages are elite producers of eicosanoids and other related lipid mediators during inflammation, but specific roles of these molecules have not generally been incorporated into the larger context of macrophage biology. In this review, we discuss the current classification of macrophage types and their roles in inflammation and disease, along with the practical challenges of studying biologically relevant phenotypes ex vivo. Using the latest advances in eicosanoid lipidomics, we highlight several key studies from our laboratory that provide a comprehensive understanding of how eicosanoid metabolism differs between macrophage phenotypes, along with how this metabolism is altered by changes in membrane fatty acid distribution and varied durations of Toll-like receptor (TLR) priming. In conclusion, we summarize several examples of the benefit of macrophage plasticity to develop accurate cellular mechanisms of lipid metabolism, and insights from lipidomic analyses about the differences in eicosanoid pathway enzyme activity in vitro vs. in cells ex vivo. Examples of new techniques to further understand the role of macrophage eicosanoid signaling in vivo are also discussed.

Epigenetic modification in neurons of the mollusc Pomacea canaliculata after immune challenge

In human and rodents, the transcriptional response of neurons to stress is related to epigenetic modifications of both DNA and histone proteins. To assess the suitability of simple invertebrate models in studying the basic mechanisms of stress-related epigenetic modifications, we analyzed epigenetic modifications in neurons of the freshwater snail Pomacea canaliculata after the injection of Escherichia coli-derived lipopolysaccharide (LPS). The phospho-acetylation of histone H3, together with the induction of stress-related factors, c-Fos and HSP70, were evaluated in large and small neurons of the pedal ganglia of sham- and LPS-injected snails. Immunocytochemical investigations showed that after LPS injection, the immunopositivity towards phospho (Ser10)-acetyl (Lys14)-histone H3 and c-Fos increases in the nuclei of small gangliar neurons. Western blot analysis confirmed a significant increase of phospho (Ser10)-acetyl (Lys14)-histone H3 in nuclear extracts from 2h LPS-injected animals. c-Fos protein levels were significantly augmented 6h after LPS injection. Immunocytochemistry and western blot indicated that no changes occurred in HSP70 distribution and protein levels. To our knowledge this is the first demonstration of epigenetic changes in molluscan neurons after an immune challenge and indicate the gastropod P. canaliculata as a suitable model for evolutionary and translational studies on stress-related epigenetic modifications.

T cell replicative senescence in human aging

The decline of the immune system appears to be an intractable consequence of aging, leading to increased susceptibility to infections, reduced effectiveness of vaccination and higher incidences of many diseases including osteoporosis and cancer in the elderly. These outcomes can be attributed, at least in part, to a phenomenon known as T cell replicative senescence, a terminal state characterized by dysregulated immune function, loss of the CD28 costimulatory molecule, shortened telomeres and elevated production of proinflammatory cytokines. Senescent CD8 T cells, which accumulate in the elderly, have been shown to frequently bear antigen specificity against cytomegalovirus (CMV), suggesting that this common and persistent infection may drive immune senescence and result in functional and phenotypic changes to the T cell repertoire. Senescent T cells have also been identified in patients with certain cancers, autoimmune diseases and chronic infections, such as HIV. This review discusses the in vivo and in vitro evidence for the contribution of CD8 T cell replicative senescence to a plethora of age-related pathologies and a few possible therapeutic avenues to delay or prevent this differentiative end-state in T cells. The age-associated remodeling of the immune system, through accumulation of senescent T cells has farreaching consequences on the individual and society alike, for the current healthcare system needs to meet the urgent demands of the increasing proportions of the elderly in the US and abroad.

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.

T cell replicative senescence in human aging

The decline of the immune system appears to be an intractable consequence of aging, leading to increased susceptibility to infections, reduced effectiveness of vaccination and higher incidences of many diseases including osteoporosis and cancer in the elderly. These outcomes can be attributed, at least in part, to a phenomenon known as T cell replicative senescence, a terminal state characterized by dysregulated immune function, loss of the CD28 costimulatory molecule, shortened telomeres and elevated production of proinflammatory cytokines. Senescent CD8 T cells, which accumulate in the elderly, have been shown to frequently bear antigen specificity against cytomegalovirus (CMV), suggesting that this common and persistent infection may drive immune senescence and result in functional and phenotypic changes to the T cell repertoire. Senescent T cells have also been identified in patients with certain cancers, autoimmune diseases and chronic infections, such as HIV. This review discusses the in vivo and in vitro evidence for the contribution of CD8 T cell replicative senescence to a plethora of age-related pathologies and a few possible therapeutic avenues to delay or prevent this differentiative end-state in T cells. The age-associated remodeling of the immune system, through accumulation of senescent T cells has farreaching consequences on the individual and society alike, for the current healthcare system needs to meet the urgent demands of the increasing proportions of the elderly in the US and abroad.

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.

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.

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.

Why should an immune response activate the stress response? Insights from the insects (the cricket Gryllus texensis)

Mediators of the stress response (e.g. glucocorticoids and norepinephrine) can be immunosuppressive. Nevertheless, immune challenge leads to the release of these compounds in vertebrates. To resolve this paradox, it has been suggested that stress hormones help restore immune homeostasis, preventing self-damage. A comparative approach may provide additional hypotheses as to why an immune challenge induces the release of stress hormones/neurohormones. Octopamine, a neurohormonal mediator of the stress response in the cricket Gryllus texensis, increased in concentration in the hemolymph during an immune challenge. Therefore, the release of stress hormones during an immune response occurs in animals across phyla. Octopamine induced an increase in lipid concentration in the hemolymph. After an acute stress (flying or running) the total number of hemocytes in the hemolymph increased. Injections of octopamine had the same effect, suggesting that it may enhance hemocyte-dependent immune functions. On the other hand, octopamine decreased lysozyme-like activity in vitro, suggesting that it inhibits some immune functions. However, lysozyme-like activity was increased by the presence of heat-killed bacteria in vitro and this increase was significantly augmented by the presence of octopamine. Therefore, the effect of octopamine on immune function differed depending on the presence of pathogens. Stress hormones may help shift immune function into the most optimal configuration depending on the physiological context.

Aging of the immune system as a prognostic factor for human longevity

Accumulating data are documenting an inverse relationship between immune status, response to vaccination, health, and longevity, suggesting that the immune system becomes less effective with advancing age and that this is clinically relevant. The mechanisms and consequences of age-associated immune alterations, designated immunosenescence, are briefly reviewed here.

Potential biomarkers of ageing

Life span in individual humans is very heterogeneous.Thus, the ageing rate, measured as the decline of functional capacity and stress resistance, is different in every individual. There have been attempts made to analyse this individual age, the so-called biological age, in comparison to chronological age. Biomarkers of ageing should help to characterise this biological age and, as age is a major risk factor in many degenerative diseases,could be subsequently used to identify individuals at high risk of developing age-associated diseases or disabilities. Markers based on oxidative stress, protein glycation,inflammation, cellular senescence and hormonal deregulation are discussed.

Inflammaging as a major characteristic of old people: can it be prevented or cured?

Widespread aging at the population level is a recent phenomenon that emerged in affluent societies. Inflammation is necessary to cope with damaging agents and is crucial for survival, particularly to cope with acute inflammation during our reproductive years. But chronic exposure to a variety of antigens, especially to some viruses such as cytomegalovirus, for a period much longer than that predicted by evolution, induces a chronic low-grade inflammatory status that contributes to age-associated morbidity and mortality. This condition carries the proposed name "inflammaging". Centenarians are unique in that, despite high levels of pro-inflammatory markers, they also exhibit anti-inflammatory markers that may delay disease onset. The key to successful aging and longevity is to decrease chronic inflammation without compromising an acute response when exposed to pathogens.

After the Prestige oil spill modifications in NO production and other parameters related to the immune response were detected in hemocytes of Mytilus galloprovincialis

In marine mollusks, many physiologic functions are regulated seasonally depending on such factors as the reproductive cycle or the presence of food. The synthesis of nitric oxide by hemocytes of Mytilus galloprovincialis is among the multiple physiologic actions in the immune response, and it is also affected by season. The maximal basal production of NO by hemocytes of M. galloprovincialis was detected in summer, whereas the minimum values were detected in winter. In winter, the presence of IL-2 induced an increase in NO production that was not detected in summer. Three months after the Prestige oil spill (November 2002), basal NO production by the hemocytes of mussels in the Galician coast showed a progressive decrease and stopping, both in summer and in winter. The characteristic increase of NO synthesis induced by IL-2 in winter also disappeared all through 2003 and 2004. The two different nitric oxide synthases previously identified by immunoblotting between 1999 and 2002 were undetectable in both 2003 and 2004. When comparing the data obtained during 2003 and 2004 to those obtained in previous years, an increase in the proportion of SH cells was detected. Also, these cells showed a higher sensitivity to apoptosis- and necrosis-inducing agents than in earlier years.

Urochordate whole body regeneration inaugurates a diverse innate immune signaling profile

The phenomenon of whole body regeneration (WBR) from minute soma fragments is a rare event in chordates, confined to the subfamily of botryllid ascidians and is poorly understood on the cellular and molecular levels. We assembled a list of 1326 ESTs from subtracted mRNA, at early stages of Botrylloides leachi WBR, and classified them into functional categories. Sixty-seven (15%) ESTs with roles in innate immunity signaling were classified into a broad functional group, a result supported by domain search and RT-PCR reactions. Gene ontology analysis for human homologous to the immune gene category, identified 22 significant entries, of which "peptidase activity" and "protease inhibitor activity", stood out as functioning during WBR. Analyzing expressions of serine protease Bl-TrSP, a representative candidate gene from the "peptidase activity" subgroup, revealed low transcript levels in naïve vasculature with upregulated expression during WBR. This was confirmed by in situ hybridization that further elucidated staining restricted to a circulating population of macrophage cells. Furthermore, Bl-TrSP was localized in regeneration niches within vasculature, in regenerating buds, and in buds, during blastogenesis. Functional inhibition of serine protease activity disrupts early remodeling processes of the vasculature microenvironment and hinders WBR. Comparison of genome-wide transcription of WBR with five other developmental processes in ascidians (including metamorphosis, budding and blastogenesis), revealed a broad conservation of immune signaling expressions, suggesting a ubiquitous route of harnessing immune-related genes within a broader range of tunicate developmental context. This, in turn, may have enabled the high diversity of life history traits represented by urochordate ascidians.

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.

The immune system in extreme longevity

Recent observations indicate that immunosenescence is not accompanied by an unavoidable and progressive deterioration of the immune function, but is rather the result of a remodeling where some functions are reduced, others remain unchanged or even increased. In addition, it appears that the ancestral/innate compartment of the immune system is relatively preserved during aging in comparison to the more recent and sophisticated adaptive compartment that exhibit more profound modifications. The T-cell branch displays an age-dependent decline of the absolute number of total T-cells (CD3+), involving both CD4+ and CD8+ subsets, accompanied by an increase of NK cells with well-preserved cytotoxic function and by a reduction of B-cells. One of the main characteristics of the immune system during aging is a progressive, age-dependent decline of the virgin T-cells (CD95-), which is particularly profound at the level of the CD8+ subpopulation of the oldest old subjects. The progressive exhaustion of this important T-cell subpopulation dedicated primarily to the defense against new antigenic challenges (viral, neoplastic, bacterial ones), could be a consequence of both the thymic involution and the lifelong chronic antigenic stimulation. The immune function of the elderly, is therefore weakened by the exhaustion of CD95- virgin cells that are replaced by large clonal expansions of CD28- T-cells. The origin of CD28- cells has not been completely clarified yet, but it is assumed that they represent cells in the phase of replicative senescence characterized by shortening telomers and reduced proliferative capacity. A major characteristic of the immune system during aging is the up-regulation of the inflammatory responses which appears to be detrimental for longevity. In this regard, we have recently observed a progressive age-dependent increase of type 1(IL-2, IFN-gamma, TNF-alpha) and type 2 (IL-4, IL-6, IL-10) positive CD8+ T-cells; in particular, type 1 cytokine-positive cells significantly increased, with age, in all CD8+ subsets particularly among effector/cytotoxic and memory cells. A major force able to drive a chronic pro-inflammatory state during aging may be represented by persistent viral infections by EBV and CMV. Therefore, we have determined the frequency and the absolute number of viral antigen-specific CD8+ T-cells in subjects older than 85 years, who were serologically positive for CMV or EBV. In the majority of these subjects we detected the presence of T lymphocytes positive for epitopes of CMV or EBV. In all subjects the absolute number of CMV-positive CD8+ cells outnumbered that of EBV-positive ones. In addition, the majority of CMV+ T cells were included within the CD28- subpopulation, while EBV+ T cells belonged mainly to the CD28+ subset. These data indicate that the chronic antigenic stimulation induced by persistent viral infections during aging bring about important modifications among CD8+ subsets, which are particularly evident in the presence of CMV persistence. The age-dependent expansions of CD8+CD28- T-cells, mostly positive for pro-inflammatory cytokines and including the majority of CMV-epitope-specific cells, underlines the importance of chronic antigenic stimulation in the pathogenesis of the main immunological alterations of aging and may favour the appearance of several pathologies (arteriosclerosis, dementia, osteoporosis, cancer) all of which share an inflammatory pathogenesis.

Stress and immune responses in abalone: limitations in current knowledge and investigative methods based on other models

Increasing mariculture of abalone focuses attention on their immune and stress responses. For abalone, as well as many invertebrates, the function and relationship of these systems and how in vitro tests relate to them are not fully understood. This review focuses on research into the immune system and stress response conducted on abalone and on aspects that can be monitored in vitro. To fill the considerable knowledge gaps, we discuss work on other invertebrate taxa, concentrating on those closest to abalone, and making explicit the phylogenetic relations involved. The stress response appears to be very similar to that in vertebrates, but interpreting most immune responses remains problematic. Phylogeny must be considered: immune function tests derived from research into vertebrates or distantly related invertebrates should not be used in abalone until they have been validated in abalone by studies of susceptibility to pathogens. We suggest phagocytic activity of haemocytes and their efficiency in clearing bacteria are reliable parameters to measure, because they have been directly related to immune competency and are consistently depressed by stress. Carefully designed assays of antimicrobial activity may also be useful. Important aims of future research will be to investigate the relationship between growth, stress and robust immunity, and to develop tests that can be run on production animals, which accurately depict immune status.

Inflammaging and anti-inflammaging: a systemic perspective on aging and longevity emerged from studies in humans

A large part of the aging phenotype, including immunosenescence, is explained by an imbalance between inflammatory and anti-inflammatory networks, which results in the low grade chronic pro-inflammatory status we proposed to call inflammaging. Within this perspective, healthy aging and longevity are likely the result not only of a lower propensity to mount inflammatory responses but also of efficient anti-inflammatory networks, which in normal aging fail to fully neutralize the inflammatory processes consequent to the lifelong antigenic burden and exposure to damaging agents. Such a global imbalance can be a major driving force for frailty and common age-related pathologies, and should be addressed and studied within an evolutionary-based systems biology perspective. Evidence in favor of this conceptualization largely derives from studies in humans. We thus propose that inflammaging can be flanked by anti-inflammaging as major determinants not only of immunosenescence but eventually of global aging and longevity.

Norman Cousins Lecture. The uses and abuses of psychoneuroimmunology: a global overview

Studies of interactions between the nervous and immune systems that effect immunological and behavioral changes are relevant to our understanding biological issues pertinent to evolution, ethology, ecology, and aging, in addition to our understanding the immune and nervous systems per se. Psychoneuroimmunology also relates to homeland security, science education, and the practice of conventional as well as complementary and alternative medicine. This paper will highlight just some of these global implications of psychoneuroimmunology.

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.

Anticipating innate immunity without a Toll

Earthworm innate immunity depends upon small and large leukocytes (coelomocytes) that synthesize and secrete humoral antimicrobial molecules (e.g. lysenin, fetidin, eiseniapore, coelomic cytolytic factor [CCF]; Lumbricin I). Small coelomocytes (cytotoxic) are positive (CD11a, CD45RA, CD45RO, CDw49b, CD54, beta(2)-m and Thy-1 [CD90]; CD24; TNF-alpha) but negative using other mammalian markers. Large coelomocytes (phagocytic) are uniformly negative. Specific earthworm anti-EFCC 1, 2, 3, 4 mAbs are negative for Drosophila melanogaster hemocytes and mammalian cells but positive those of earthworms. Coelomocytes contain several lysosomal enzymes involved in phagocytosis and a pattern recognition molecule (CCF) that may trigger the prophenoloxidase cascade a crucial innate immune response. Earthworms and other invertebrates possess natural, non-specific, non-clonal, and non-anticipatory immune response governed by germ line genes. Toll and Toll-like receptor signaling is essential for phagocytosis and antimicrobial peptide synthesis and secretion in insects and vertebrates but has not yet been shown to be essential in earthworm innate responses.