Tachykinin-related peptides (TRPs) are one of the most prominent families of neuropeptides in the animal kingdom. Insect TRPs display strong structural and functional homology to vertebrate ...tachykinins (TKs). To study functional homologies between these two neuropeptide families, the influence of human substance P (SP, one of the essential vertebrate TKs) on the immune system of the mealworm beetle, Tenebrio molitor L., was analysed.
Human SP influences the phagocytic abilities of T. molitor haemocytes. Peptide injection leads to an increase in the number of haemocytes participating in the phagocytosis of latex beads. In contrast, incubation of haemocytes from non-injected beetles in a solution of physiological saline and SP causes a decrease in phagocytic activity. Treatment with human SP also led to increased adhesion of haemocytes, but no changes in the arrangement of the F-actin cytoskeleton were observed. Interestingly, 6 h after human SP injection, increased DNA integrity in T. molitor haemocytes was reported. The opposite effects were observed 24 h after SP injection.
Human SP caused the upregulation of humoral immune responses, such as phenoloxidase (PO) activity in the T. molitor haemolymph, and the downregulation of immune-related genes encoding coleoptericin A, tenecin 3 and Toll receptor. However, genes encoding attacin 2 and cecropin were upregulated. Despite these differences, the antimicrobial activity of T. molitor haemolymph was significantly lower in beetles injected with SP than in control beetles. Moreover, an analysis of the direct influence of SP on lysozyme activity was performed. Our results suggest that SP at a concentration of 10−6 M can directly inhibit lysozyme activity. However, an opposite effect was reported after the application of SP at a concentration of 10−4 M.
The presented results suggest structural and functional homology between TK signalling in vertebrates and insects. Primarily, this was visible in the context of the humoral response and general antimicrobial activity of T. molitor haemolymph. However, some of the results related to haemocyte function may also indicate the importance of the TK and TRP sequences for evoking immunological effects.
•Human substance P influence insect cellular and humoral response.•Human substance P can directly affect lysozyme activity.•Results suggest homology between TK signalling in vertebrates and insects.
Tachykinin-related peptides (TRPs) are important neuropeptides. Here we show that they affect the insect immune system, especially the cellular response. We also identify and predict the sequence and ...structure of the tachykinin-related peptide receptor (TRPR) and confirm the presence of expression of gene encoding TRPR on Tenebrio molitor haemocytes.
After application of the Tenmo-TRP-7 in T. molitor the number of circulating haemocytes increased and the number of haemocytes participating in phagocytosis of latex beads decreased in a dose- and time-dependent fashion. Also, Tenmo-TRP-7 affects the adhesion ability of haemocytes. Six hours after injection of Tenmo-TRP-7, a decrease of haemocyte surface area was observed under both tested Tenmo-TRP-7 concentrations (10−7 and 10−5 M). The opposite effect was reported 24 h after injection, which indicates that the influence of Tenmo-TRP-7 on modulation of haemocyte behaviour differs at different stages of stress response. Tenmo-TRP-7 application also resulted in increased phenoloxidase activity 6 and 24 h after injection.
The assessment of DNA integrity of haemocytes showed that the injection of Tenmo-TRP-7 at 10−7 M led to a decrease in DNA damage compared to control individuals. This effect was only visible 6 h after Tenmo-TRP-7 application. After 24 h, Tenmo-TRP-7 injection increased DNA damage.
We also confirmed the expression of immune-related genes in nervous tissue of T. molitor. Transcripts for genes encoding receptors participating in pathogen recognition processes and antimicrobial peptides were detected in T. molitor brain, retrocerebral complex and ventral nerve cord. These results may indicate a role of the insect nervous system in pathogen recognition and modulation of immune response similar to vertebrates.
Taken together, our results support the notion that tachykinin-related peptides probably play an important role in the regulation of the insect immune system. Moreover, some resemblances with action of tachykinin-related peptides and substance P showed that insects can be potential model organisms for analysis of hormonal regulation of conserved innate immune mechanisms.
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•Insect tachykinin-related peptides possess immunomodulatory properties.•Tachykinin-related peptides influence haemocytes activity.•Tachykinin-related peptides application increase activity of phenoloxidase.•Tachykinin-related peptides can reduce DNA damages in haemocytes.•Immune-related genes are present in the Tenebrio nervous system.
The characteristics of binding of tuftsin (Thr-Lys-Pro-Arg) and several of its synthetic analogues, to specific membrane receptors on rabbit polymorphonuclear granulocytes, were compared with the ...binding characteristics of rabbit specific antibody to tuftsin. 3H-Arg4-tuftsin was used as the principal ligand. Six analogues were studied. Two of these, Thr-Lys-Pro and Ala-Lys-tuftsin-Glu-Ala3, showed no binding affinity either to receptor or antibody. Ala-Lys-tuftsin showed less binding than tuftsin to both acceptors. Three showed stronger binding than tuftsin. The order of binding among these was tuftsin ( Glu2-tuftsin ( Pro-Pro3-tuftsin (tuftsinyltuftsin. This same order of binding was found with both receptor and antibody.
We report 104 analogues of the potent antiovulatory antagonist of LHRH, N-Ac-D-Nal-D-Cpa-D-Pal-Ser-Lys(Nic)-D-Lys(Nic)-Leu-Ilys-Pro-D-Ala- NH2, Antide. We replaced the Nic group in Antide with other ...acyl substituents to modulate size, hydrophilicity or basicity of the molecule, we also replaced the Lys residues with shorter basic amino acids, and made cyclic 5/6 analogues as well as position 5 or 6 dimers. We substituted Ilys8 with other alkyl groups and acyl derivatives. When injected in 0.1% DMSO in water in a typical antiovulatory (AO) assay. Antide gives six rats ovulating out of eight (6/8) at 2 micrograms, 4/8 at 4 micrograms, and in the histamine release assay (HRA). ED50 is > 300 micrograms/ml; Lys(N-Isobutyl)8Antide gave 2/8 at 2 micrograms/rat; Lys (8-Qis)5Antide gave 1/8 at 1 microgram, and 0/8 at 2 micrograms, and in the HRA ED50. 22 micrograms/ml; D-Lys(8-Qis)5Antide gave 4/8 at 1 microgram and 0/8 at 2 micrograms, and in the HRA, ED50 was 27 micrograms/ml; Lys(8-Qic)8 gave 5/8 at 1 microgram 1/8 at 2 micrograms/ Lys(2-Pyc)6Antide gave 3/8 at 1 microgram, and 0/8 at 2 micrograms, and in the HRA ED50 was 116 micrograms/ml; D-Lys (2-Pyc)5Antide gave 5/8 at 1 microgram and in the HRA, ED50 was 100- > 300 micrograms/ml; Lys(2-Pyc)5.D-Lys(2-Pyc)6Antide gave 2/8 at 1 microgram. The substitutions of the Nic groups of Antide at Lys5 or D-Lys6 with 8-Qis or with 2-Pyc groups seem to give highly potent antiovulatory antagonists of LHRH and constitute significant new leads to generate potent antiovulatory compounds endowed with moderate or low histamine release.
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