Distribution of substance P positive cells and nerve fibers in the rat thymus

Neuro-immune modulation of the thymus microenvironment (review)

The thymus is the primary site for T-cell lympho-poiesis. Its function includes the maturation and selection of antigen specific T cells and selective release of these cells to the periphery. These highly complex processes require precise parenchymal organization and compartmentation where a plethora of signalling pathways occur, performing strict control on the maturation and selection processes of T lymphocytes. In this review, the main morphological characteristics of the thymus microenvironment, with particular emphasis on nerve fibers and neuropeptides were assessed, as both are responsible for neuro-immune‑modulation functions. Among several neurotransmitters that affect thymus function, we highlight the dopaminergic system as only recently has its importance on thymus function and lymphocyte physiology come to light.

Evidence of conserved neuroendocrine interactions in the thymus: intrathymic expression of neuropeptides in mammalian and non-mammalian vertebrates

The function of lymphoid organs and immune cells is often modulated by hormones, steroids and neuropeptides produced by the neuroendocrine and immune systems. The thymus intrinsically produces these factors and a comparative analysis of the expression of neuropeptides in the thymus of different species would highlight the evolutionary importance of neuroendocrine interaction in T cell development. In this review, we highlight the evidence which describes the intrathymic expression and function of various neuropeptides and their receptors, in particular somatostatin, substance P, vasointestinal polypeptide, calcitonin gene-related peptide and neuropeptide Y, in mammals (human, rodent) and non-mammals (avian, amphibian and teleost), and conclude that neuropeptides play a conserved role in vertebrate thymocyte development.

Pharmacological modulation of wound healing in experimental burns

Factors involved in wound healing and their interdependence are not yet fully understood; nevertheless, new prospects for therapy to favor speedy and optimal healing are emerging. Reports about wound healing modulation by local application of simple and natural agents abound even in the recent literature, however, most are anecdotal and lack solid scientific evidence. We describe the effect of silver sulfadiazine and moist exposed burn ointment (MEBO), a recently described burn ointment of herbal origin, on mast cells and several wound healing cytokines (bFGF, IL-1, TGF-beta, and NGF) in the rabbit experimental burn model. The results demonstrate that various inflammatory cells, growth factors and cytokines present in the wound bed may be modulated by application of local agents with drastic effects on their expression dynamics with characteristic temporal and spatial regulation and changes in the expression pattern. Such data are likely to be important for the development of novel strategies for wound healing since they shed some light on the potential formulations of temporally and combinatory optimized therapeutic regimens.

Neuroimmune link in the mucosa of chronic gastritis with Helicobacter pylori infection

It is suggested that different neuropeptides regulate gastric mucosal integrity and participate in the development of chronic gastritis. The aim of this study was to examine the roles and changes of immunoreactive (IR) nerves and immunocompetent cells in human gastritis. Immunohistochemical, immunocytochemical, and confocal laser microscopic methods were used. All investigated nerve fibers were found in different quantities in the mucosa of both control and gastritis samples. The number of SP, NPY, and VIP IR nerve fibers increased significantly (P < 0.05) in gastritis. No IR immunocompetent cells (lymphocytes, plasma cells, mast cells) were found in the control, however, some showed NPY (16.8%) and SP (9.4%) immunoreactivity in chronic gastritis. The distance between nerve fibers and immunocompetent cells was 200 nm to 1 microm. In conclusion, the increased number of SP, NPY, and VIP IR nerves and IR immunocytes suggests that they participate in development of neurogenic inflammation, repairing processes of chronic gastritis.

Evolutionary conservation of neuropeptide expression in the thymus of different species

Evidence suggests that the immune and neuroendocrine systems cross talk by sharing ligands and receptors. Hormones and neuropeptides produced by the neuroendocrine system often modulate the function of lymphoid organs and immune cells. We have previously reported the intrathymic expression of somatostatin (SOM) in the mouse and that several neuropeptides, most notably calcitonin-gene-related peptide (CGRP), neuropeptide Y (NPY), SOM and substance P (SP), can modulate thymocyte development. However, little is known about the intrathymic expression of these neuropeptides either in the mouse or in other species. Moreover, a comparative analysis of the expression of these molecules would highlight the evolutionary importance of intrathymic neuroendocrine interactions in T-cell development. We have studied the expression of different neuropeptides in the thymus of zebrafish, Xenopus, avians, rodent, porcine, equine and human by immunohistochemistry and reverse transcription-polymerase chain reaction. We found that CGRP, NPY, SOM, SP and vasointestinal polypeptide (VIP) are expressed in the thymus of all species investigated. The thymic location of many of these neuropeptides was conserved and appears to be within the stromal compartments. Interestingly, in the avian thymus the expression of CGRP, SOM and SP appears to change depending on the age of the tissue. These findings suggest that neuropeptides may play an important role in T-cell development and provide further evidence of cross talk between the immune and neuroendocrine systems.

Expression of the onconeural CV2/CRMP5 antigen in thymus and thymoma

Anti-CV2 antibodies (AB) react with the developmentally regulated neural proteins CRMPs and particularly with CRMP5. They occur with small cell lung cancer (SCLC) and thymoma. SCLCs universally express CRMP5. We investigated the expression of CRMPs in thymoma and thymus. In thymoma, none of the CRMPs were detected by immunohistochemistry in tumorous epithelial cells with specific antibodies including CRMP5 but an antibody reacting with a peptide common to the CRMPs labeled a 66-kDa protein in Western blot of rat brain, thymus, and thymoma extracts. Thus, the normal CRMP5 is probably not expressed by tumorous epithelial cells. These results indicate that the mechanisms leading to CRMP5 autoimmunization are different in SCLC and thymoma.

Autonomic innervation of immune organs and neuroimmune modulation

1. Increasing evidence indicates the occurrence of functional interconnections between immune and nervous systems, although data available on the mechanisms of this bi-directional cross-talking are frequently incomplete and not always focussed on their relevance for neuroimmune modulation. 2. Primary (bone marrow and thymus) and secondary (spleen and lymph nodes) lymphoid organs are supplied with an autonomic (mainly sympathetic) efferent innervation and with an afferent sensory innervation. Anatomical studies have revealed origin, pattern of distribution and targets of nerve fibre populations supplying lymphoid organs. 3. Classic (catecholamines and acetylcholine) and peptide transmitters of neural and non-neural origin are released in the lymphoid microenvironment and contribute to neuroimmune modulation. Neuropeptide Y, substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide represent the neuropeptides most involved in neuroimmune modulation. 4. Immune cells and immune organs express specific receptors for (neuro)transmitters. These receptors have been shown to respond in vivo and/or in vitro to the neural substances and their manipulation can alter immune responses. Changes in immune function can also influence the distribution of nerves and the expression of neural receptors in lymphoid organs. 5. Data on different populations of nerve fibres supplying immune organs and their role in providing a link between nervous and immune systems are reviewed. Anatomical connections between nervous and immune systems represent the structural support of the complex network of immune responses. A detailed knowledge of interactions between nervous and immune systems may represent an important basis for the development of strategies for treating pathologies in which altered neuroimmune cross-talking may be involved.

Neonatal capsaicin treatment affects rat thymocyte proliferation and cell death by modulating substance P and neurokinin-1 receptor expression

Herein we provide evidence that substance P (SP) and its neurokinin-1 receptor (NK-1R) expressed on thymocytes counteract thymus depletion induced by neonatal capsaicin (CPS) treatment by affecting thymocyte proliferation and apoptotic death. SP administration reversed the CPS-mediated inhibitory effects on the total thymocyte number and subset distribution, namely CD4+ and CD4- CD8- cells, through its interaction with NK-1R as shown by concomitant NK-1R (SR140333) antagonist administration. SP-induced enhancement of thymus cellularity parallels its ability of inhibiting the thymocyte apoptotic program. Indeed, exogenously administered SP completely nullified CPS-induced apoptosis, and SR140333 abrogated the SP-mediated protective effect. SP administration also stimulated concanavalin A (Con A)-induced thymocyte proliferation of CPS-treated rats, completely reversing the CPS-induced inhibition. The SP-mediated stimulation of Con A-induced thymocyte proliferation was NK-1R dependent as shown by concomitant administration of SP and SR140333 to CPS-treated rats. Our results also demonstrate that CPS treatment induces a marked decrease of thymocyte PPT-A mRNA level and endogenous SP content as evaluated by quantitative RT-PCR, in situ hybridization and cytofluorimetric analysis. By contrast, NK-1R mRNA levels were increased in thymocytes from CPS-treated rats. Exogenous SP administration augmented PPT-A, SP and NK-1R thymocyte expression in CPS-treated rats, and this enhancement was antagonized by SR140333 administration. Overall, our results strongly suggest that the immunomodulatory effects of neonatal CPS treatment on rat thymocyte functions are dependent on vanilloid-mediated regulation of SP and NK-1R functional expression by neuronal and immune cells.

Expression of substance P and its neurokinin-1 receptor on thymocytes: functional relevance in the regulation of thymocyte apoptosis and proliferation

Herein, we provide evidence of the expression and function of substance P (SP) and neurokinin-1 receptor (NK-1R) in the rat thymus. In situ hybridization evidenced NK-1R mRNA mainly in the thymic medulla, and Northern blot analysis of mRNA from FACS-sorted thymocytes identified NK-1R on CD4+, CD8+ and double-positive subpopulations. With flow cytometry, it could be seen that NK-1R was expressed on the majority of CD5+ thymocytes, and it was identified by Western blot analysis as two bands migrating at 44 and 54 kD. SP administration rescues thymocytes from spontaneous and NK-1R antagonist (SR140333)-induced apoptosis and stimulates concanavalin A (ConA)-induced thymocyte proliferation, CD25 expression and IL-2 production, whereas SR140333 exerts inhibitory effects on these functions. We also demonstrated the expression of mRNA for the SP precursor preprotachykinin-A in the thymic medulla and purified CD5+ thymocytes. SP protein was detected on 40% of CD5+ thymocytes and identified as a band of 1.3 kD by Western blot analysis. Finally, thymocytes spontaneously released SP, which was increased upon ConA or CD3 stimulation.