Possible mechanisms of the concentration-dependent action of substance P to induce histamine release from rat peritoneal mast cells and the effect of extracellular calcium on mast-cell activation

Changes in Tissue Substance P Levels in Patients With Carpal Tunnel Syndrome

BACKGROUND:

Although carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in adults, its etiology is not completely known. Chronic inflammation, fibrosis of the transverse carpal ligament (TCL), and altered sensory response contribute to the symptoms.

OBJECTIVE:

Because substance P (SP) is known to be involved in neuropathic pain, chronic inflammation, and fibrosis, the present study evaluated changes in SP levels in patients with CTS.

METHODS:

TCL, median nerve adventitia, and synovial connective tissue of the middle flexor digitorum superficialis tendon samples from patients (n = 42) with CTS and healthy control subjects (n = 13) who were operated on for hand wounds were obtained at surgery. A group of these patients with CTS (n = 9) had received meloxicam treatment for 10 days before surgery. A 2-step acetic acid extraction was used to determine changes in SP levels in free nerve endings (neuronal) and in nonneuronal cells.

RESULTS:

Changes in SP levels were observed in both neuronal and nonneuronal tissues. SP levels increased in extracts of the TCL and synovial connective tissue of the middle flexor digitorum superficialis tendon but not in the median nerve adventitia of patients with CTS. Meloxicam pretreatment increased SP levels in nonneuronal components of the TCL.

CONCLUSION:

These findings suggest that SP contributes to the pain and inflammation associated with CTS. Further studies are required to evaluate the therapeutic potentials of SP receptor (NK1R) antagonists in CTS.

The effect of extremely low-frequency electromagnetic fields on skin and thyroid amine- and peptide-containing cells in rats: an immunohistochemical and morphometrical study

The aim of this study was to investigate the influence of extremely low-frequency electromagnetic fields (ELF-EMFs) on mast cells (MCs), parafollicular cells, and nerve fibers in rat skin and thyroid gland. The experiment was performed on 24 2-month-old Wistar male rats exposed for 4h a day, 7 days a week for 1 month to EMFs (50 Hz, 100-300 microT, 54-160 V/m). After sacrifice, samples of skin and thyroid were processed for indirect immunohistochemistry or toluidine blue staining and then were analyzed using the methods of stereology. The antibody markers to serotonin, substance P, calcitonin gene-related peptide (CGRP), and protein gene product 9.5 (PGP) were applied to skin sections and PGP, CGRP, and neuropeptide Y (NPY) markers to the thyroid. A significantly increased number of serotonin-positive MCs in the skin and NPY-containing nerve fibers in the thyroid of rats exposed to ELF-EMF was found compared to controls, indicating a possible EMF effect on skin and thyroid vasculature.

Evidence for a restricted rather than generalized stimulatory response of skin-derived human mast cells to substance P

To resolve the controversy regarding substance P (SP) mediated stimulation of mast cells (MC), we demonstrate that SP triggers histamine release from purified human skin MC (sMC), but contrast to stimulation via FcepsilonRI, does not effect the production of TNF-alpha or IL-8. Conversely, both anti-IgE and SP are suppressive in terms of IL-6. By quantitative RT-PCR, the amount of templates at baseline (per 25 ng total RNA) is 2178 (IL-6), 2,665 (IL-8) and 94 (TNF-alpha), and remains unaltered by SP. Contrast to sMC, LAD2 MC respond to SP with stronger histamine release and robust TNF-alpha production in an only partially neurokinin-1R mediated manner, while histamine release of sMC is chiefly mediated by this receptor. We conclude that human sMC are responsive to SP in a selective manner by eliciting degranulation without the induction of cytokines and that SP-triggered cytokine production varies among MC subtypes, likely through differences in signaling mechanisms.

Liver fluke (Fasciola hepatica)-derived peptides activate rat peritoneal mast cells

Short peptides with sequences derived from those found in the tegumental antigen of Fasciola hepatica have been synthesised. Incubation of some of these peptides with rat peritoneal mast cells resulted in the degranulation of the cells as measured by a histamine release assay. This activity was shown to be associated with the proline-lysine-proline motif, which is responsible for the induction of mast cell degranulation by the mammalian bioactive peptide substance P. Studies on the mode of action of the fluke-derived peptide indicated that it was operating through the same biochemical pathways as substance P. The implications of these findings for the development of immune responses during parasite infections are discussed.

Evaluation of the effects of peptide antibiotics human beta-defensins-1/-2 and LL-37 on histamine release and prostaglandin D(2) production from mast cells

Antimicrobial peptides, human beta-defensins (hBD-1/-2), and LL-37 (a peptide of human cathelicidin CAP18) are predominately expressed at epithelial tissues, where they participate in the innate host defense by killing invading microorganisms. In this study, to investigate the interactions between epithelial cell-derived antimicrobial peptides and mast cells, we evaluated the effects of hBD-1/-2 and LL-37 on mast cell functions using rat peritoneal mast cells. hBD-2 and LL-37 but not hBD-1 induced histamine release and intracellular Ca(2+) mobilization, and hBD-2 was more potent than LL-37. Interestingly, histamine release and intracellular Ca(2+) mobilization elicited by hBD-2 and LL-37 were markedly suppressed by BAPTA-AM (an intracellular Ca(2+) chelating agent), pertussis toxin and U-73122 (a phospholipase C inhibitor). In addition, among the peptides examined, only hBD-2 significantly induced PGD(2) production, which was abolished by indomethacin (cyclooxygenase-1/-2 inhibitor) but not NS-398 (cyclooxygenase-2 inhibitor), suggesting that hBD-2-induced PGD(2) production is mediated by cyclooxygenase-1. Likewise, the PGD(2) production was suppressed by pertussis toxin and U-73122. These observations suggest that hBD-2 and LL-37 stimulate mast cells to mobilize intracellular Ca(2+) and release histamine or generate PGD(2) in a G protein-phospholipase C-dependent manner. Thus, hBD-2 and LL-37 may have modulatory effects on inflammatory reactions.

Immunologically induced histamine release from rat peritoneal mast cells is enhanced by low levels of substance P

Although direct activation of mast cells by high concentrations (>10(-6) M) of substance P is well established, the effect of sub-micromolar concentrations of the neuropeptide on mast cell activation has not been reported. We hence investigated if substance P would modulate immunologic activation of mast cells by studying the effect of the neuropeptide on anti-rat immunologlobulin E antibody (anti-IgE)-induced histamine release from purified rat peritoneal mast cells. We observed that substance P could dose-dependently potentiate anti-IgE-induced histamine release from rat peritoneal mast cells at concentrations (3x10(-9) M to 3x10(-7) M) which alone induced insignificant or low level of histamine release. While the potentiating effect of substance P was not suppressed by any of the non-peptide tachykinin receptor antagonists CP99994 ((2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine), SR48968 ((S)-N-methyl-N-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) butyl-benzamide) and SR142801 ((S)-(N)-(1-[3-(1-benzoyl-3(3,4-dichlorophenyl)piperidine-3-yl)propyl]-4-phenylpiperidin-4-yl)-N-methyl-acetamide), it was mimicked by compound 48/80 and suppressed by benzalkonium chloride. Hence, substance P enhanced anti-IgE-induced histamine release through a similar receptor-independent mechanism as the direct mast cell activating action of polybasic compounds. Since high concentrations of substance P required for directly activating mast cells may not be achievable physiologically, the enhancing actions of the neuropeptide on the immunologic activation of mast cells may be more clinically relevant in the pathogenesis of various inflammatory conditions.

Process extension and intracellular Ca2+ in cultured murine oligodendrocytes

Previous investigations have shown that phorbol esters stimulate process extension in oligodendrocytes (OL), likely by the activation of protein kinase C (PKC). In this report, we demonstrate that treatment of OL with 4beta-phorbol-12, 13-dibutyrate (PDB; 0.1-1 microM) resulted in an increase in intracellular Ca2+ concentration ([Ca2+]i) from 94+/-2 nM (mean+/-S.E.M.) to 244+/-10 nM. This increase was produced by Ca2+ influx through a La3+-insensitive pathway. Changes in [Ca2+]i were also produced by modifying the extracellular Ca2+ concentration ([Ca2+]o) where [Ca2+]i was increased by elevations in [Ca2+]o. In parallel experiments we found that increased [Ca2+]o alone, without concurrent phorbol ester application, resulted in increased OL process extension as determined by the percent of OL with long processes (greater than 3 times the cell body diameter). These results demonstrate that increasing [Ca2+]o stimulates OL process outgrowth. Furthermore, both elevations in [Ca2+]o and PDB exposure increase [Ca2+]i, suggesting that some of the effects of phorbol esters on OL process extension are likely mediated by changes in [Ca2+]i.

Mast cells in clinical dermatology

Recent advances in cutaneous mast cell biology are briefly reviewed with special reference to our own studies on cultured human mast cells. Of note are the heterogeneity of mastocytosis, the important participation of mast cells in allergic inflammation by releasing cytokines and the inhibitory effect of histamine release from mast cells by phototherapy. It is also stressed that mast cells play a major role in tissue remodelling. These novel findings suggest that mast cells can no longer be regarded simply as cells that initiate immediate allergic reactions, but that they are responsible for various chronic inflammatory or immunological events through cytokine-dependent leucocyte recruitment. The regulation of mast cell activation should be a critical issue and, thus, a promising therapeutic approach in clinical dermatology.