Postnatal development of neurogenic inflammation in the rat.

We have studied the development in the rat of neurogenic inflammatory mechanisms that mediate cutaneous plasma extravasation. At birth and at postnatal day 10, intradermal injection of substance P, histamine, and bradykinin produced no significant plasma extravasation. At day 13 through adulthood (days 42-49), all test agents produced significant plasma extravasation which increased with increasing age. In the adult rat, pretreatment with 6-hydroxydopamine, to eliminate sympathetic postganglionic nerve terminals, attenuated the plasma extravasation elicited by substance P, histamine and bradykinin. The possible role of the sympathetic postganglionic neuron in the age-dependent changes in neurogenic inflammation is discussed.     

Role of the Na+-K+-2Cl- cotransporter in the development of capsaicin-induced neurogenic inflammation

Recent behavioral and electrophysiological studies have attributed an important role to dorsal root reflexes (DRRs) in the initiation and development of neurogenic inflammation produced by intradermal capsaicin (CAP). The DRRs can occur in peptidergic fibers, resulting in peripheral release of neuromediators that produce vasodilation, plasma extravasation and subsequently hyperalgesia and allodynia. In this study, we have evaluated the effect of spinal administration of bumetanide (a blocker of the Na+-K+-2Cl- cotransporter, NKCC) on DRR activity, changes in cutaneous blood flow (vasodilation), hindpaw edema, mechanical allodynia, and hyperalgesia induced by intradermal injection of 1% CAP in Sprague-Dawley rats. Vasodilation was monitored using laser Doppler flowmetry, neurogenic edema was evaluated by measurements of hindpaw volume, and secondary mechanical allodynia and hyperalesia were tested using von Frey filaments (10 and 200 mN) applied to the plantar surface of the paw. Changes in the blood flow were blocked significantly by intrathecal bumetanide at 10 and 100 microM in both pre- and posttreatment studies. Spinal bumetanide at 10 and 100 microM blocked neurogenic edema when it was administered before CAP injection, but only bumetanide at 100 microM administered after CAP injection reduced the paw edema significantly. Furthermore, the administration of bumetanide onto the spinal cord reduced the increment in DRR activity produced by CAP. Finally, both secondary mechanical allodynia and hyperalesia were reduced by bumetanide at 1, 10, and 100 microM. Taken together these results suggest that NKCC is involved in the increases in DRR activity, neurogenic inflammation and hyperalgesia and allodynia induced by intradermal CAP.     

Alterations in histamine metabolism of rat gastric mucosa following vagotomy

1. In female rats subjected to truncal vagotomy with pyloroplasty, pyloroplasty alone or sham operation, the behaviour of gastric mucosal histamine was investigated combining in vivo and in vitro methods.2. Following truncal vagotomy with pyloroplasty mucosal histamine formation, determined in vitro, increased about fivefold and histamine content was significantly elevated. The heightened histamine formation was reflected in increased excretion of histamine in the urine.3. On pentagastrin infusion, mucosal histamine formation increased about twofold following vagotomy with pyloroplasty and sevenfold in the sham-operated controls. Histamine content concomitantly fell in both groups to about the same level. These alterations were paralleled by increased excretion of histamine in the urine.4. Kinetic studies in which [(14)C]histidine was injected and the resulting urinary [(14)C]histamine determined, indicated that during the first hour of pentagastrin infusion newly formed histamine was more slowly mobilized following vagotomy with pyloroplasty than in the controls.5. In rats subjected to a pyloroplasty alone, the increase in urinary histamine on pentagastrin infusion was significantly larger than in the sham-operated controls. Kinetic studies indicated that this was due to a larger mobilization of preformed histamine.6. The changes in mucosal histamine metabolism are discussed in relation to the pattern of acid secretion following the actual surgical procedures.     

Spinal TRPA1 ion channels contribute to cutaneous neurogenic inflammation in the rat

In the spinal dorsal horn, TRPA1 ion channels on central terminals of peptidergic primary afferent nerve fibers regulate transmission to glutamatergic and GABAergic interneurons. Here we determine the cutaneous anti-inflammatory effect of a spinally administered TRPA1 channel antagonist to test the hypothesis that spinal TRPA1 channels contribute to cutaneous neurogenic inflammation induced by sustained noxious stimulation. According to the hypothesis, spinal TRPA1 channels facilitate transmission of injury discharge to GABAergic interneurons that induce a dorsal root reflex, which results in increased release of proinflammatory compounds in the skin. Intraplantar capsaicin, a TRPV1 channel agonist, was used to induce neurogenic inflammation in anesthetized rats that were pretreated intrathecally (i.t.), intraplantarly (i.pl.) or intraperitoneally (i.p.) with vehicle or Chembridge-5861526 (CHEM, a TRPA1 channel antagonist). For assessment of neurogenic inflammation, the capsaicin-induced increase of cutaneous blood flow was determined adjacent to the capsaicin-treated skin site with a laser Doppler flowmeter. Capsaicin-induced a marked increase in cutaneous blood flow. The capsaicin-induced blood flow increase was attenuated in a dose-related fashion by i.t. pretreatment with CHEM (3-10 μg). Pretreatment with CHEM at a dose of 3 mg/kg i.p. or 20 μg i.pl. failed to attenuate the capsaicin-induced increase of blood flow. The results indicate that spinal TRPA1 channels contribute to cutaneous neurogenic inflammation adjacent to the injury site, probably by facilitating a dorsal root reflex in peptidergic primary afferent nerve fibers.     

Mechanisms mediating Porphyromonas gingivalis gingipain RgpA-induced oral mucosa inflammation in vivo

Suffusion of gingipain RgpA (GRgpA) elicited a significant concentration-dependent increase in the clearance of macromolecules from in situ hamster cheek pouch which was attenuated by NPC 17647, a selective bradykinin B(2) receptor antagonist. Leupeptin and a mixture of proteinase inhibitors also attenuated GRgpA-induced responses. These data indicate that GRgpA elicits plasma exudation from in situ oral mucosa in a catalytic site-dependent fashion by elaborating bradykinin.     

Role of histamine in a rat model of colitis

We examined the possible involvement of mast cells in a rat model of colitis, by monitoring levels of histamine at various times after inducing inflammation with intrarectal trinitrobenzene sulfonic acid in 50% ethanol. The ability of a histamine H₁ antagonist, diphenhydramine, to modify colitis was also assessed. As expected, trinitrobenzene sulfonic acid in 50% ethanol induced a sustained colitis. Myeloperoxidase levels in macroscopically damaged tissue peaked at one week, and declined thereafter. In contrast, tissue histamine levels were normal at one week, then increased in damaged tissue to approximately four times normal levels at four weeks. Indices of inflammation were markedly suppressed at one week by diphenhydramine, while tissue histamine levels were unaffected. Chronic colitis in rats is thus apparently accompanied by a local mast cell hyperplasia or influx. Moreover, antagonism of a major mast cell mediator, histamine, significantly reduces the severity of inflammation in this model.Abbreviations MPO myeloperoxidas - SCF stem cell factor - TNB trinitrobenzene sulfonic acid     

Up-regulation of histamine H1 receptors in an allergic rat nasal mucosa model

Inflammation Research -     

Effect of GABA-ergic agents on development of neurogenic lesions in the rat stomach

Laboratory of Pharmacotherapy, Department of Pharmacology, Research Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR A. V. Val'dman.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 110, No. 11, pp. 504–506, November, 1990.     

Neuropeptides and inflammation: presumed mechanisms in neurogenic inflammation]

Neuropeptides, among which substance P, VIP (Vasoactive intestinal peptide), somatostatin, neurotensin, dynorphin and enkephalins, are able to modulate inflammatory processes. Increasing interest is now devoted to these peptides in different inflammatory diseases, concerning skin, lung and joins. The effect of substance P can be dependent on its C-terminal moiety implicating by this way an interaction with specific neurokinin receptors or can be dependent on its N-terminal moiety which does not involve a specific membrane receptor. Such diversity of the action mechanisms of peptides should influence the evolution of the anti-inflammatory therapeutic.     

Dynamic changes of the neurogenic potential in the rat cochlear nucleus during post-natal development

Neuronal stem cells have been described in the post-natal cochlear nucleus recently. The aim of the study was to analyse the neurogenic potential in the cochlear nucleus from the early post-natal days until adulthood. Cochlear nuclei from Sprague–Dawley rats from post-natal day P3 up to P40 were examined. Neurosphere assays showed persistent neurosphere formation from the early post-natal days until adulthood. The numbers of generated neurospheres were fewer in older ages. Neurospheres were smaller, but displayed the same pattern of neuronal stem cell markers. The markers GFAP, MBP and ß-III Tubulin showed differentiation of dissociated cells from the neurospheres in all cells of the neuronal lineage. BrdU incorporation could be detected, in an age-dependent decrease, in whole-mount experiments of the cochlear nucleus on all examined days. BrdU co-labelled with Atoh1 and ß-III Tubulin. In addition, gene expression and cellular distribution studies of the neuronal stem cell markers displayed an age-dependent reduction in both quantity and numbers. The presented results display a possible neurogenic potential until adulthood in the cochlear nucleus by in vitro and in vivo experiments. The fact that this potential is highest at a critical period of development reveals possible functional importance for the development of the cochlear nucleus and the auditory function. The persistent neurogenic potential displayed until adulthood could be a neurogenic niche in the adult cochlear nucleus, which might be used for potential therapeutic strategies.     

Mast cell tryptase in dermal neurogenic inflammation

BACKGROUND AND AIMS: Eosinophils, mast cells and T lymphocytes are important cells in the allergic inflammatory process. These cells produce and are regulated by cytokines such as interleukin-3 (IL-3), interleukin-5 (IL-5) and granulocyte macrophage-colony stimulating factor (GM-CSF). We initiated this study to evaluate pathological abnormalities and to detect IL-5 in the duodenal mucosa from patients with food allergy. METHODS: Endoscopy duodenal biopsy specimens were obtained from seven food-allergic patients, six atopic healthy controls and six nonatopic healthy controls. IL-5 protein was evaluated by immunohistochemistry. Electron microscopy as well as double immunofluorescent staining were used to identify the labelled cells and to localize IL-5. IL-5 mRNA expression was evaluated by qualitative polymerase chain reaction. RESULTS: A significantly increased number of lymphocytes, mast cells and eosinophils was detected in the lamina propria in food-allergic patients and, in lower number, in atopic controls. Immunostaining for IL-5 was markedly positive in food-allergic patients, slightly increased in atopic controls and negative in nonatopic controls. Ultrastructurally, in food-allergic patients and in atopic controls, IL-5 was localized in eosinophil granules, in the matrix of intact granules and at the periphery of altered granules. Double immunofluorescent staining was performed in food-allergic patients and showed that 86.7% of IL-5+ cells were eosinophils, and that IL-5 was expressed by 24% of eosinophils. IL-5 mRNA was expressed in food-allergic patients but was not detected in atopic and nonatopic controls. CONCLUSION: Activated eosinophils are involved in gut atopic reactions occurring in food allergy and are probably in part upregulated by their own local production of IL-5.     

The effect of histamine on the development of adjuvant arthritis in the rat

Histamine, injected subcutaneously (0.3–10 mg/kg), produced a dose-related inhibition of the primary and secondary inflammation, and the development of the secondary lesions of rat adjuvant arthritis. Histamine was effective when given for short periods around the time of adjuvant administration and could also delay and possibly reverse an established arthritic response. The histamine H₁-agonist, 2-(2-pyridyl)-ethylamine, inhibited rat adjuvant arthritis, whereas the histamine H₂-agonists, impromidine and dimaprit, failed to affect the response. Metiamide, a histamine H₂-antagonist (5 mg/kg), reduced the inflammation in the uninjected hind-paw and the development of secondary lesions.Histamine may have two effects on rat adjuvant arthritis, inhibiting the response via stimulation of H₁-receptors and augmenting the response via stimulation of H₂-receptors. Since histamine is known to bind to and to alter the reactivity of cells which are involved in the regulation of immune responsiveness, it is suggested that interactions with these cells are responsible for the observed effects of histamine.     

Role of intracellular calcium in histamine release from rat mast cells

An aqueous extract of Panax Ginseng C.A. Meyer (G.S.) was prepared by boiling crushed G.S. roots in water. The extract obtained was adjusted to 125 mg G.S. per ml and was administered orally to mice for 5 to 6 days at the daily dose of 10, 50 and 250 mg G.S. per kg or was added to cultures of mouse spleen cells at concentrations varying between 0.25 and 8 mg G.S. per ml. The average total ginsenoside content of the G.S. roots used was determined by HPLC analysis and found to be 0.58%(w/w).Treated mice responded with enhanced antibody formation to either a primary or a secondary challenge with sheep red cells. The effects were dose-dependent. At the highest dose regimen, the primary IgM response was increased by 50% and the secondary IgG and IgM responses were increased by 50 and 100%, respectively. An even more pronounced effect was obtained with natural killer cell activity which was enhanced between 44 and 150% depending on the effector-to-target cell ratios used in the assay. In vitro, G.S. showed two main effects, an inhibition of stimulated and spontaneous lymphocyte proliferation at high, but not cytotoxic concentrations and an enhancement of interferon production particularly in non-stimulated spleen cells.The immunostimulating effects obtainedin vivo are in agreement with the stimulation of interferon production observedin vitro. The inhibition of lymphocyte proliferation, however, cannot be reconciled with the immunostimulatory action of G.S. observedin vivo.