ABSTRACT
Unlike mammals, the CNS of the medicinal leech can regenerate damaged neurites, thus restoring neural functions after lesion. We previously demonstrated that the injured leech nerve cord is able to mount an immune response promoting the regenerative processes. Indeed neurons and microglia express sensing receptors like Hm-TLR1, a leech TLR ortholog, associated with chemokine release in response to a septic challenge or lesion. To gain insights into the TLR signaling pathways involved during these neuroimmune responses, members of the MyD88 family were investigated. In the present study, we report the characterization of Hm-MyD88 and Hm-SARM. The expression of their encoding gene was strongly regulated in leech CNS not only upon immune challenge but also during CNS repair, suggesting their involvement in both processes. This work also showed for the first time that differentiated neurons of the CNS could respond to LPS through a MyD88-dependent signalling pathway, while in mammals, studies describing the direct effect of LPS on neurons and the outcomes of such treatment are scarce and controversial. In the present study, we established that this PAMP induced the relocalization of Hm-MyD88 in isolated neurons.
Subject(s)
Cytoskeletal Proteins/metabolism , Hirudo medicinalis/metabolism , Myeloid Differentiation Factor 88/metabolism , Amino Acid Sequence , Animals , Central Nervous System/metabolism , Cytoskeletal Proteins/classification , Cytoskeletal Proteins/genetics , Humans , Lipopolysaccharides/toxicity , Microglia/metabolism , Molecular Sequence Data , Myeloid Differentiation Factor 88/classification , Myeloid Differentiation Factor 88/genetics , Nerve Regeneration , Neurons/metabolism , Sequence Alignment , Signal Transduction/drug effects , Toll-Like Receptor 1/genetics , Toll-Like Receptor 1/metabolismABSTRACT
Disturbances in mood such as anxiety and depression are often associated with altered hypothalamo-pituitary-adrenal (HPA) axis reactivity, but also with changes in cytokine production, such as interleukin-6 (IL-6), an essential immune factor produced by macrophages and lymphocytes during inflammatory processes. The reciprocal relationship between the HPA axis and the immune system is now well established. In order to understand better the endocrine reactivity of anxious individuals faced with an immune challenge, a model of innate anxiety-related behavior, HAB and LAB rats (HABs, high and LABs, low anxiety-related behavior) was used in this study. We sought to determine whether injection of lipopolysaccharide (LPS) induced a differential HPA axis reactivity and plasma IL-6 release in HABs and LABs. After LPS injection, the plasma adrenal corticotrophic hormone increase did not differ between HABs and LABs, whereas a larger increase in plasma corticosterone levels occurred in HABs than in LABs at 2 h after injection. Moreover, basal IL-6 levels were lower in HABs than in LABs, leading to a higher IL-6 2 h/basal ratio in HABs. In conclusion, we propose for the first time a link between the endocrine and immune systems of HABs and LABs and suggest that IL-6 could be a neuroendocrine correlate of trait anxiety in HABs.
Subject(s)
Anxiety/immunology , Anxiety/metabolism , Corticosterone/blood , Interleukin-6/blood , Adrenocorticotropic Hormone/blood , Analysis of Variance , Animals , Anxiety/pathology , Behavior, Animal , Body Weight/drug effects , Body Weight/physiology , Brain/drug effects , Brain/metabolism , Brain/pathology , Cosyntropin/analogs & derivatives , Cosyntropin/metabolism , Disease Models, Animal , Lipopolysaccharides/administration & dosage , Male , Protein Binding/drug effects , Rats , Receptors, Corticotropin/metabolismABSTRACT
It is widely accepted that all organisms have processes that maintain their state of health. Failure of these processes, such as those involving the naturally occurring antibacterial peptides, may lead to pathological events. Recent results demonstrate that these peptides, such as peptide B, appear in invertebrates and vertebrates (including humans) immediately after tissue trauma, and maintain themselves for long durations (over 4h). Their degradation products lead to other inflammatory peptides, such as Met-enkephalin-Arg-Phe. These newly described antibacterial peptides, which are released and not induced, are present on neuropeptide precursors such as proenkephalin. This is a new field of research, in that the same protein contains proposed neuropeptides, antibacterial peptides, and immune stimulatory peptides. The focus of this review is to describe how the pro-enkephalin derived peptides participate in immune processes.
Subject(s)
Enkephalins/immunology , Protein Precursors/immunology , Animals , Anti-Infective Agents/immunology , Enkephalin, Methionine/immunology , Humans , Inflammation/etiology , Inflammation/immunology , Inflammation Mediators/immunology , Invertebrates/immunology , Vertebrates/immunologyABSTRACT
Antibacterial peptides, found in both invertebrates and vertebrates, represent a potential innate defense mechanism against microbial infections. However, it is unknown whether this process occurs in humans during surgery. We looked for evidence of release of antibacterial peptides during coronary artery bypass grafting (CABG). We used immunological techniques and antibacterial assays combined with high-performance gel-permeation chromatography, reverse-phase HPLC, N-terminal sequencing and comparison with synthetic standards to characterize the peptide B/enkelytin. We show the presence of anionic antibacterial peptide, the peptide B/enkelytin which correspond to the C-terminal part of proenkephalin A, from the plasma of patients undergoing CABG. Our studies show that peptide B/enkelytin is initially present at low levels in plasma and is then released in increased amounts just after skin incision. Antibacterial assays confirmed that the peptides specifically target gram-positive bacteria. We also demonstrate that peptide B/enkelytin is metabolized in vivo to the opioid peptides methionine-enkephalin-Arg-Phe and methionine-enkephalin, peptides that we show have granulocyte chemotactic activity. These findings suggest that in humans, surgical incision leads to the release of antibacterial peptides. Furthermore, these antibacterial peptides can be metabolized into compounds that have immune-activating properties.
Subject(s)
Coronary Artery Bypass , Coronary Disease/immunology , Coronary Disease/microbiology , Enkephalins/blood , Peptide Fragments/blood , Amino Acid Sequence , Coronary Disease/surgery , Enkephalin, Methionine/blood , Enkephalin, Methionine/chemistry , Enkephalin, Methionine/isolation & purification , Enkephalins/chemistry , Enkephalins/isolation & purification , Escherichia coli , Escherichia coli Infections/blood , Escherichia coli Infections/immunology , Female , Gram-Positive Bacterial Infections/blood , Gram-Positive Bacterial Infections/immunology , Humans , Immunoblotting , Male , Micrococcus luteus , Middle Aged , Molecular Sequence Data , Peptide Fragments/chemistry , Peptide Fragments/isolation & purification , Protein Precursors/blood , Protein Precursors/chemistry , Protein Precursors/isolation & purification , Staphylococcal Infections/blood , Staphylococcal Infections/immunology , Staphylococcus aureus/immunologyABSTRACT
Lipopolysaccharides (LPS) injection into the coelomic fluid of the leech Theromyzon tessulatum stimulates release of proenkephalin A (PEA)-derived peptides as determined by immunoprecipitation and Western blot analyses. This release occurs in the first 15 min after LPS exposure and yields a 5.3-kDa peptide fragment corresponding to the C-terminal part of the precursor. This fragment is then cleaved to free an antibacterial peptide related to mammals arginine phenylalanine extended enkelytin: the peptide B. These PEA processing peptides were characterized using a combination of techniques including reversed-phase HPLC, microsequencing and mass spectrometry. The isolated invertebrate peptide B presents a high sequence homology with the bovine's and the same activity against Gram+bacteria. Titrations revealed the simultaneous appearance of Methionine-enkephalin (ME) and peptide B in invertebrates after stimulation by LPS (in a dose-dependent manner), surgical trauma or electrical stimulations to neural tissues of the mussel. Furthermore, peptide B processing in vitro yields Methionine-enkephalin arginine phenylalanine (MERF), which exhibits via the delta receptors, immunocyte excitatory properties, i.e., movement and conformational changes, but no antibacterial activity. We surmise that this unified response to the various stimuli is a survival strategy for organism by providing immediate antibacterial activity and immunocyte stimulation, thereby reducing any immune latency period needed for an adequate immune response.