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Allograft inflammatory factor-1 (AIF-1) is a 17 kDa cytokine-inducible calcium-binding protein that in Vertebrates plays an important role in allografts immune response. Since its expression is mainly limited to the monocyte/macrophage lineage, it was recently suggested that it could play a key role during inflammatory responses, allograft rejection, as well as in the activation of macrophages. To clarify this point we have focused our research on the possible role of AIF-1 during the inflammatory response after injury in the leech Hirudo medicinalis (Annelida, Hirudinea). This invertebrate is an excellent animal model since the responses evoked during inflammation and tissue repair are clear and easily detectable and have a striking similarity with vertebrate responses. Moreover the analysis of an EST library from H. medicinalis CNS, revealed the presence of a gene, named Hmaif-1/alias Hmiba1, showing a high homology with vertebrate aif-1. Our data show that the related protein, named HmAIF-1, is constitutively expressed in unlesioned leeches and that dramatically increases 48 h after wounds and tissue transplants. Immunohistochemistry experiments, using a specific anti HmAIF-1 polyclonal antibody, shows that this factor is present in spread, CD68+ /CD45+ macrophage-like cells. A few days after experimental wounding of the body wall, the amount of these immunopositive cells increases at the lesion site. In conclusion here we propose that in leech HmAIF-1 factor is involved in inflammation events like its vertebrate counterparts.

LPS stimulation provokes serious cellular stress with an increase of cytoplasmic reactive oxygen species (ROS). We have investigated, among the different cellular defenses, amyloidogenesis as common physiological response to attenuate oxidative stress. Optical and electron microscopic observations of the following LPS activated cell lines [insect (larval hemocytes, IPLB-LdFB and Drosophila Schneider’s S2 cells); mouse (NIH3T3 embryonic fibroblasts); Human (Human Umbilical Vein Endothelial Cells (HUVEC), neutrophils, and mesenchymal stem cells] reveal that, all are characterized by irregular profiles, cytoplasmic empty vacuoles or by cisternae containing fibrillar material. The compartmentalized fibrillar material shows staining properties typical of amyloid fibrils. LPS activation leads to ROS generation, resulting in pH acidification. Stimulated cells show pink cytoplasm in May-Grünwald Giemsa differential staining, giving a gross indication of a lower intracellular pH. Moreover the activation of amyloidogenesis is also linked with an extensive production of ACTH and α-MSH in all cultured cell types. We suggest that amyloidogenesis is a common, physiological cellular response to weak ROS, starting when other anti-stress cellular systems failed to restore homeostasis. The morphological evidence and/or functional characterization of synthesized amyloid fibrils could be an early indicator of oxidative stress that may lead to a general inflammatory process.

In some leeches like Hirudo medicinalis, any kind of stimulation (surgical wound or growth factor injection) provokes the botryoidal tissue response. This peculiar tissue, localized in the loose connective tissue between gut and body wall, is formed by granular botryoidal cells and flattened endothelial-like cells. Under stimulation, the botryoidal tissue changes its shape to form new capillaries. In mammals, the molecular regulation of the angiogenic phenotype requires coordinated input from a number of signalling molecules: among them the GTPase Ras is one of the major actor. In our current study, we determine whether Ras activation alone would be sufficient to drive vessels formation from leech botryoidal tissue. Our findings indicate that assembly and disassembly of actin filaments regulated by Ras protein is involved in morphological modification of botryoidal tissue cells during leech angiogenic process.

Protostomes and Deuterostomes show the same nexus between melanin production, and amyloid fibril production, i.e., the presence of melanin is indissolubly linked to amyloid scaffold that, in turn, is conditioned by the redox status/cytoplasmic pH modification, pro-protein cleavage presence, adrenocorticotropin hormone (ACTH), melanocyte-stimulating hormone (α-MSH), and neutral endopeptidase (NEP) overexpressions. These events represent the crucial component of immune response in invertebrates, while in vertebrates these series of occurrences could be interpreted as a modest and very restricted innate immune response. On the whole, it emerges that the mechanisms involving amyloid fibrils/pigment synthesis in phylogenetically distant metazoan (viz, cnidaria, molluscs, annelids, insects, ascidians and vertebrates) are evolutionary conserved. Furthermore, our data show the relationship between immune and neuroendocrine systems in amyloid/melanin synthesis. Indeed the process is closely associated to ACTH-α-MSH production, and their role in stress responses leading to pigment production reflects and confirms again their ancient phylogeny.

In the tentacle of Sepia officinalis, smooth-like, helical and cross-striated fibres deriving from different populations of myoblasts are present. Myoblasts appear at different times during the development and express two muscle-specific transcription factors: Myf5-like and MyoD-like factors. Myoblasts expressing Myf5 give rise to slow fibres, whereas fast fibres derive from MyoD+ myoblasts. We found that a Hedgehog (Hh)-like signal was present in the central nerve cord of the tentacle from the early stages of development and in a specific population of myoblasts which are the precursors of slow muscle fibres. The model showed interesting similarities with vertebrates, in which Sonic hedgehog is a protein secreted by axial structures (the notochord and neurotube) and is involved in slow muscle differentiation and in survival of muscle precursors.

Allograft inflammatory factor-1 (AIF-1) is a 17 kDa cytokine-inducible calcium-binding protein that in Vertebrates plays an important role in allografts immune response. Since its expression is mainly limited to the monocyte/macrophage lineage, it was recently suggested that it could play a key role during inflammatory responses, allograft rejection, as well as in the activation of macrophages. To clarify this point we have focused our research on the possible role of AIF-1 during the inflammatory response after injury in the leech Hirudo medicinalis (Annelida, Hirudinea). This invertebrate is an excellent animal model since the responses evoked during inflammation and tissue repair are clear and easily detectable and have a striking similarity with vertebrate responses. Moreover the analysis of an EST library from H. medicinalis CNS, revealed the presence of a gene, named Hmaif-1/alias Hmiba1, showing a high homology with vertebrate aif-1. Our data show that the related protein, named HmAIF-1, is constitutively expressed in unlesioned leeches and that dramatically increases 48 h after wounds and tissue transplants. Immunohistochemistry experiments, using a specific anti HmAIF-1 polyclonal antibody, shows that this factor is present in spread, CD68+ /CD45+ macrophage-like cells. A few days after experimental wounding of the body wall, the amount of these immunopositive cells increases at the lesion site. In conclusion here we propose that in leech HmAIF-1 factor is involved in inflammation events like its vertebrate counterparts.

Toxoneuron nigriceps is an endophagous parasitoid of larval stages of the noctuid moth Heliothisvirescens. As all parasitoids, this wasp avoid host immune reaction by a combination of several passiveand active mechanisms. Secretions injected by ovipositing females, which contain venom, calyx fluid andpolydnaviruses, are the most probably factors actively disrupting Heliothis virescens immune system. Thispaper describes the main alterations of the host immune response observed shortly after oviposition by T.nigriceps. A transient block of prophenoloxidase activity is registered along with changes in hemocytenumber, adhesion and structure, which suggest the occurrence of apoptosis. In contrast, the hostplasmatocytes appear structurally unaltered, but unable to produce a capsule in vitro.

The wound healing process in leeches involves different types of cells like macrophages, NK-likecells and granulocytes. These cells that are involved in immune defence, can co-operate to attackand/or isolate the non self (de Eguileor et al., 1999; de Eguileor et al., 2000a; de Eguileor et al.,2000b). In addition other types of cells, like fibroblasts and endothelial cells, are involved in theformation of new vessels. To exert their functional role, all these cells must infiltrate and migratethrough extracellular matrix (de Eguileor et al., 2001a; de Eguileor et al., 2003).Here we show, by histochemical and biochemical methods, that the cathepsin B peptidase ispresent and active in all migrating cells, involved in immune responses of leeches subjected todifferent stimuli. Interstingly the cellular function of cathepsin B in invertebrates appear to beequivalent to that of vertebrates, where the secreted enzyme plays a role in basement membrane andmatrix disruption operated by cells involved in angiogenesis, wound repair and immune defence.

LPS stimulation provokes serious cellular stress with an increase of cytoplasmic reactive oxygen species (ROS). We have investigated, among the different cellular defenses, amyloidogenesis as common physiological response to attenuate oxidative stress. Optical and electron microscopic observations of the following LPS activated cell lines [insect (larval hemocytes, IPLB-LdFB and Drosophila Schneider’s S2 cells); mouse (NIH3T3 embryonic fibroblasts); Human (Human Umbilical Vein Endothelial Cells (HUVEC), neutrophils, and mesenchymal stem cells] reveal that, all are characterized by irregular profiles, cytoplasmic empty vacuoles or by cisternae containing fibrillar material. The compartmentalized fibrillar material shows staining properties typical of amyloid fibrils. LPS activation leads to ROS generation, resulting in pH acidification. Stimulated cells show pink cytoplasm in May-Grünwald Giemsa differential staining, giving a gross indication of a lower intracellular pH. Moreover the activation of amyloidogenesis is also linked with an extensive production of ACTH and α-MSH in all cultured cell types. We suggest that amyloidogenesis is a common, physiological cellular response to weak ROS, starting when other anti-stress cellular systems failed to restore homeostasis. The morphological evidence and/or functional characterization of synthesized amyloid fibrils could be an early indicator of oxidative stress that may lead to a general inflammatory process.

In some leeches like Hirudo medicinalis, any kind of stimulation (surgical wound or growth factor injection) provokes the botryoidal tissue response. This peculiar tissue, localized in the loose connective tissue between gut and body wall, is formed by granular botryoidal cells and flattened endothelial-like cells. Under stimulation, the botryoidal tissue changes its shape to form new capillaries. In mammals, the molecular regulation of the angiogenic phenotype requires coordinated input from a number of signalling molecules: among them the GTPase Ras is one of the major actor. In our current study, we determine whether Ras activation alone would be sufficient to drive vessels formation from leech botryoidal tissue. Our findings indicate that assembly and disassembly of actin filaments regulated by Ras protein is involved in morphological modification of botryoidal tissue cells during leech angiogenic process.

Protostomes and Deuterostomes show the same nexus between melanin production, and amyloid fibril production, i.e., the presence of melanin is indissolubly linked to amyloid scaffold that, in turn, is conditioned by the redox status/cytoplasmic pH modification, pro-protein cleavage presence, adrenocorticotropin hormone (ACTH), melanocyte-stimulating hormone (α-MSH), and neutral endopeptidase (NEP) overexpressions. These events represent the crucial component of immune response in invertebrates, while in vertebrates these series of occurrences could be interpreted as a modest and very restricted innate immune response. On the whole, it emerges that the mechanisms involving amyloid fibrils/pigment synthesis in phylogenetically distant metazoan (viz, cnidaria, molluscs, annelids, insects, ascidians and vertebrates) are evolutionary conserved. Furthermore, our data show the relationship between immune and neuroendocrine systems in amyloid/melanin synthesis. Indeed the process is closely associated to ACTH-α-MSH production, and their role in stress responses leading to pigment production reflects and confirms again their ancient phylogeny.

In the tentacle of Sepia officinalis, smooth-like, helical and cross-striated fibres deriving from different populations of myoblasts are present. Myoblasts appear at different times during the development and express two muscle-specific transcription factors: Myf5-like and MyoD-like factors. Myoblasts expressing Myf5 give rise to slow fibres, whereas fast fibres derive from MyoD+ myoblasts. We found that a Hedgehog (Hh)-like signal was present in the central nerve cord of the tentacle from the early stages of development and in a specific population of myoblasts which are the precursors of slow muscle fibres. The model showed interesting similarities with vertebrates, in which Sonic hedgehog is a protein secreted by axial structures (the notochord and neurotube) and is involved in slow muscle differentiation and in survival of muscle precursors.

Toxoneuron nigriceps is an endophagous parasitoid of larval stages of the noctuid moth Heliothis virescens. As all parasitoids, this wasp avoid host immune reaction by a combination of several passive and active mechanisms. Secretions injected by ovipositing females, which contain venom, calyx fluid and polydnaviruses, are the most probably factors actively disrupting Heliothis virescens immune system. This paper describes the main alterations of the host immune response observed shortly after oviposition by T. nigriceps. A transient block of prophenoloxidase activity is registered along with changes in hemocyte number, adhesion and structure, which suggest the occurrence of apoptosis. In contrast, the host plasmatocytes appear structurally unaltered, but unable to produce a capsule in vitro.

The wound healing process in leeches involves different types of cells like macrophages, NK-like cells and granulocytes. These cells that are involved in immune defence, can co-operate to attack and/or isolate the non self (de Eguileor et al., 1999; de Eguileor et al., 2000a; de Eguileor et al., 2000b). In addition other types of cells, like fibroblasts and endothelial cells, are involved in the formation of new vessels. To exert their functional role, all these cells must infiltrate and migrate through extracellular matrix (de Eguileor et al., 2001a; de Eguileor et al., 2003). Here we show, by histochemical and biochemical methods, that the cathepsin B peptidase is present and active in all migrating cells, involved in immune responses of leeches subjected to different stimuli. Interstingly the cellular function of cathepsin B in invertebrates appear to be equivalent to that of vertebrates, where the secreted enzyme plays a role in basement membrane and matrix disruption operated by cells involved in angiogenesis, wound repair and immune defence.