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

Mosca²,

Lucciarini³

et al. 2008

J Pharmacol Exp Ther

The activity of substance P (SP) in the rat thymus seems to be tightly controlled by its bioavailability. In this study, we provide evidence for the expression of the SP-degrading enzyme, neutral endopeptidase (NEP)/CD10, by rat thymocyte subsets, and we illustrate its involvement in the in vivo SP/neurokinin-1 receptor (NK 1 R)-mediated regulation of thymocyte survival and proliferation. NEP/CD10 was expressed at both mRNA and protein levels on a substantial portion (45.5%) of CD5 ϩ thymocytes, namely on the CD4 ϩ CD8 ϩ (double positive; DP) and CD4 ϩ subsets. Continuous administration of thiorphan, a specific NEP/CD10 inhibitor, by means of miniosmotic pumps, enhanced rat thymocyte preprotachykinin-A (PPT-A) and NK 1 R mRNA expression as well as SP and NK 1 R protein levels in an NK 1 R-dependent manner. Thiorphan increased CD10 ϩ CD4 ϩ and CD10 ϩ DP thymocyte numbers, and an NK 1 R antagonist,, abrogated these stimulatory effects. In addition, the NEP/CD10 inhibitor stimulated interleukin (IL)-2 production, IL-2 receptor ␣ chain expression, and concanavalin A-induced proliferation of CD5 ϩ thymocytes, and it inhibited spontaneous and NK 1 R-dependent thymocyte apoptosis. The thiorphan-protective antiapoptotic and proliferative effects involved the activation of Akt serine-threonine kinase, subsequent up-regulation of survivin mRNA, down-regulation of procaspase-3 mRNA levels, and suppression of caspase-3 activity, which were inhibited by SR140333 and mimicked by exogenous SP administration. Overall, our findings suggest that by controlling SP availability, NEP/CD10 negatively regulates thymocyte homeostasis and development.Development of T lymphocytes is a complex process that depends on both stromal cell interactions and the production of soluble factors such as cytokines, peptide hormones, and neuropeptides locally synthesized or released in the thymic microenvironment (Blalock and Smith, 1985). In the thymus, the concentration of biologically active peptides is maintained by a specialized family of enzymes, the endopeptidases (Naquet and Pierres, 1991).The neutral endopeptidase (NEP)-24.11 (EC 3.4.24.11), also known as enkephalinase, neprilysin, common acute lymphoblastic leukemia antigen, or CD10 (Turner and Tanzawa, 1997), is the prototype of a family of membrane-bound zincdependent endopeptidases that regulate the physiological action of a variety of peptides by lowering their extracellular concentration available for receptor binding. Molecular cloning of NEP/CD10 revealed that it is a type II integral membrane protein consisting of a short NH 2 -terminal cytoplasmic domain and a large extracellular domain that contains the active site of the enzyme. It was first isolated as a major 90 to 100-kDa glycoprotein from the renal brush border membrane of rabbits (Kerr and Kenny, 1974).NEP/CD10 is expressed on early normal T-and B-cell progenitors (Shipp and Look, 1993) and on the majority of acute lymphoblastic leukemias and lymphoid malignancies with immature phenotypes (Ritz et al., 1981). Unfracti...

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 85%

Thiorphan-Induced Survival and Proliferation of Rat Thymocytes by Activation of Akt/Survivin Pathway and Inhibition of Caspase-3 Activity

Mosca²,

Lucciarini³

et al. 2008

J Pharmacol Exp Ther

“…Previous findings using in vitro autoradiography have indicated the presence of SP binding sites in the rat thymus [28], but direct evidence of the expression of NK-1R on thymocytes is still lacking.…”

Section: Expression Of Nk-1r On Rat Thymocytesmentioning

confidence: 96%

“…In addition, SP-immunoreactive fibers have been described in the parenchyma of both the thymus and secondary lymphoid tissues. SP-positive nerve fibers enter the thymic cortex from the septa and are distributed among cortical thymocytes and mastocytes [5,6], and SP-positive fibers and cells are frequently associated with the vasculature [28].…”

Section: Introductionmentioning

confidence: 99%

Expression of Substance P and Its Neurokinin-1 Receptor on Thymocytes: Functional Relevance in the Regulation of Thymocyte Apoptosis and Proliferation

Santoni

Lucciarini

et al. 2002

Neuroimmunomodulation

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.

“…In the thymus microenvironment SP is not only released by the nerve fibers and endothelial cells but can also be synthesized by bone marrow-derived lymphoid cells [41,42]. We recently provided evidence on the expression and function of SP and NK-1R by rat thymocytes, and on the capability of SP administration to rescue thymocytes from spontaneous and NK-1R antagonist (SR140333)-induced apoptosis [40].…”

Section: Introductionmentioning

confidence: 99%

Neonatal Capsaicin Treatment Affects Rat Thymocyte Proliferation and Cell Death by Modulating Substance P and Neurokinin-1 Receptor Expression

Santoni

Lucciarini

et al. 2004

Neuroimmunomodulation

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.