Flare and itch induced by substance P in human skin.

Intradermal injection of synthetic substance P (10(-7)--10(-5) M in humans produced flare, wheal and itching. These responses were inhibited by oral pretreatment of the subjects with an antihistaminic drug (chlorcyclizine) or by local pretreatment with Compound 48/80 administered to deplete the local stores of mast-cell bound histamine. The findings indicate that the responses induced by substance P were mainly mediated by histamine released from the dermal mast cells. In contrast to previously studied histamine liberators, substance P was less potent when acting on rat mast cells in vitro than on human skin mast cells in vivo. When incubated with rat peritoneal mast cells, about 100 times higher concentrations (10(-5) M) were required to induce histamine release than in the in vivo studies on humans. It was concluded that substance P is a potent histamine liberator in human skin.     

Potent vasodilator activity of calcitonin gene-related peptide in human skin

We have recently shown that the novel neuropeptide calcitonin gene-related peptide, CGRP, is a potent vasodilator. In this paper we report a detailed study of the effects of CGRP in human skin. CGRP induces a clearly defined, long-lasting erythema. We have measured the effect of CGRP on blood flow in human skin using a laser Doppler technique and have demonstrated increased local blood flow that persists for a number of hours. We compared the response of CGRP with other known vasodilators [histamine, prostaglandin (PG) E2, PGI2, substance P, and vasoactive intestinal peptide (VIP)] in the skin, and in all subjects the erythema induced by CGRP was more persistent than that induced by the other mediators tested. Except at high doses the local vasodilatation induced by CGRP was not associated with a wheal and flare as seen with histamine, substance P, and VIP. CGRP is an extremely potent vasodilator and if released into the circulation, or locally from peripheral nerve endings, it could have a role in the regulation of blood flow in both physiologic and pathologic conditions; CGRP may be the endogenous mediator of the flare in the triple response. A deficiency in CGRP secretion or action could be an important component of peripheral vascular disease. Some flushing reactions (e.g., those associated with medullary thyroid carcinoma) may result from circulating CGRP.     

Inflammatory skin responses induced by icatibant injection are mast cell mediated and attenuated by H(1)-antihistamines

Icatibant, a bradykinin-2 receptor antagonist, is administered by subcutaneous injection for the treatment of attacks of type I and type II hereditary angioedema. Following injection, patients feel transient pain followed by a short-lived wheal and flare response at the injection site. We hypothesized that the icatibant-induced wheal and flare response follows histamine release from activated skin mast cells and would therefore be reduced by an H(1)-antihistamine. Intradermal injection of 100 μl of 100 μg/ml histamine and 10 mg/ml icatibant into the forearms of health volunteers caused wheal and flare responses of a similar magnitude which were reduced by cetirizine pretreatment by 49% and 41% (histamine) and 35% and 41% (icatibant). Studies in vitro showed that icatibant at 1 × 10(-4) and 1 × 10(-5) M caused significant (P < 0.05) histamine release from isolated human cutaneous mast cells. In conclusion, icatibant induces histamine-mediated wheal and flare responses that may be reduced in severity by prophylactic administration of an H(1)-antihistamine.     

Histamine is released following aminolevulinic acid-photodynamic therapy of human skin and mediates an aminolevulinic acid dose-related immediate inflammatory response

Acute skin inflammation occurs following topical aminolevulinic acid-photodynamic therapy (ALA-PDT), but its nature and mediation are ill defined. As we observed an urticarial response, a potential role for histamine was explored. In 13 healthy volunteers, we assessed the time course and dose-response of the acute cutaneous response(s) to ALA-PDT, the impact of H(1) antihistamine blockade, and measured dermal histamine release. An ALA dose series was iontophoresed into ventral forearm skin and exposed to red light. All participants exhibited an immediate urticarial response, both wheal and flare correlating with log ALA dose. Subsequently, a dose-related erythema developed at treatment sites by 3 hours and persisted at 24 hours. H(1) blockade with oral cetirizine doubled the median minimal urticating dose of ALA and reduced the slope of dose-response for wheal and flare, whereas at the highest ALA dose, mean wheal and flare areas reduced by 68 and 60%, respectively. In contrast, cetirizine did not influence the 24 hour minimal phototoxic dose or erythema dose-response. Histamine release after ALA-PDT mirrored the urticarial response, levels peaking within 30 minutes and returning to baseline by 24 hours. Thus, two discrete acute inflammatory responses to topical ALA-PDT occur in human skin; histamine mediates the immediate response, but does not appear involved in the delayed phototoxicity.     

Effects of cetirizine and epinastine on the skin response to histamine iontophoresis

Epinastine and cetirizine are second-generation, nonsedating and long-lasting antihistamines that are now frequently used for the allergic disorders. We have examined the inhibitory effects of these two drugs on the histamine-induced flare and wheal responses using iontophoresis at 1, 2, 4, 8 and 24 h after the oral administration by a double-blind, cross-over and placebo-controlled study. Both cetirizine and epinastine significantly inhibited the histamine-induced flare and wheal responses at 2 h after the oral administration when compared with placebo. The inhibitory effects of cetirizine and epinastine on the flare response lasted long until at 24 h, however, epinastine was less potent than cetirizine. The inhibitory effects on the wheal response was also clearly and significantly evident at 2-8 h by cetirizine and epinastine. At 24 h cetirizine only showed the significant inhibition on the histamine-induced wheal response. In contrast, epinastine seemed to exhibit the inhibitory capacity earlier than did cetirizine. The inhibitory action of the drugs on the histamine-induced wheal response peaked at 4 h after the oral administration. The histamine-induced itch sensation was also markedly or completely suppressed at 2-8 h by the drugs. Thus, both drugs exhibited the potent and long-lasting antihistamine activity on the skin responses induced by histamine iontophoresis.     

The intradermal effects of the H3 receptor agonist R α methylhistamine in human skin

We have investigated the possible existence of the H₃ histamine receptor in human skin with the highly selective ligands R α methylhistamine (RAMHA) (H₃ agonist) and thioperamide (H₃ antagonist). We compared the intradermal effects of RAMHA with histamine, and studied their potential modulation by the H₁ antagonist terfenadine, and H₂ antagonist cimetidine. The effects of RAMHA and thioperamide on codeine phosphate-, substance P- and histamine-induced weal and flare responses were also studied. RAMHA produced dose-related weal and flare responses that were approximately 10- and fivefold less, respectively, than responses to histamine. Flare responses to RAMHA were significantly inhibited by oral terfenadine ( P  < 0.05). Weal and flare responses to histamine after oral cimetidine showed much intersubject variation, and cimetidine did not significantly alter either RAMHA- or histamine-induced weal and flare responses. Codeine phosphate-, substance P- and histamine-induced responses were not significantly affected by concurrent administration of RAMHA. Thioperamide was not found to influence codeine phosphate-, substance P-, RAMHA- or histamine-induced effects. RAMHA induces vascular (weal and flare) responses in human skin, and these responses are partially inhibited by terfenadine. There is a trend for RAMHA to have an additive effect to the weal induced by substance P and histamine, although our results largely do not reach statistical significance. Thioperamide does not affect the vascular responses to RAMHA, codeine phosphate, histamine or substance P. We cannot conclude that the effects of RAMHA are induced by H₃ receptors on cutaneous endothelial or mast cells.     

SUBSTANCE P PROVOKES CUTANEOUS ERYTHEMA AND EDEMA THROUGH A HISTAMINE-INDEPENDENT PATHWAY

Substance P is a neuropeptide (contained in/and released from the A delta and C nerve fibers of the skin), which provokes erythema, edema, and pruritus after intradermal injection. Local pretreatment with capsaicin produces decreased substance P-dependent erythema, with edema similar to that observed before pretreatment with capsaicin. We injected histamine and in a parallel experiment, substance P in five volunteers before and after local treatment with capsaicin, with 48/80, after 5 days of hydroxyzine. The injection of SP provoked erythema centered by a wheal. After treatment with 48/80, SP provoked increased erythema and a wheal. After hydroxyzine treatment, the injection of histamine produced no erythema or edema in four of the five subjects, while SP provoked erythema in all five subjects and edema similar to that observed before treatment with hydroxyzine. These data support the hypothesis that substance P provokes erythema and edema both with histamine-dependent and histamine-independent pathways.     

Effects of acrivastine, loratadine and cetirizine on histamine-induced wheal and flare responses

It is accepted that studies evaluating histamine-induced wheal and flare reactions in the skin represent a simple and reliable method for demonstrating pharmacodynamic activity and pharmacokinetics of the H1-receptor antagonists. In this study, the effects of single oral doses of acrivastine (8 mg), loratadine (10 mg) and cetirizine (10 mg) on the histamine-induced wheal and flare reactions were compared in 60 healthy volunteers. The wheal and flare responses were produced by prick test using 1% histamine solution. Measurements were performed before the ingestion of antihistamines (baseline values) and afterwards at 15, 30, 90, 240, 360 min and 24 h. The values obtained for each antihistamine were compared with each other and with baseline values. Cetirizine was found to be superior to acrivastine and loratadine for the suppression of wheal and flare responses at 240, 360 min and 24 h (P < 0.05) and acrivastine was superior to the other two antihistamines for the suppression of flare response at 30 min (P < 0.05). Our results indicate that a single dose of cetirizine provides a more effective and long acting suppression on wheal and flare reactions in urticaria when compared to acrivastine and loratadine.     

Skin reactivity to neuropeptides in atopic dermatitis

Adults with atopic dermatitis (AD), with respiratory atopy only and healthy non-atopic controls were given intradermal injections of substance P (SP), neurokinin A (NKA), neurotensin (NT), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and histamine into the normal-appearing skin on the back. The weal and flare responses were evaluated after 3, 5 and 15 min and the areas calculated using an automatic image analyser. With the three different concentrations used (1, 3 and 30 pmols) a statistically significant (P less than 0.05) reduction in both the weal and flare response to SP, NKA, NT and histamine and a reduced flare to CGRP was observed only in AD patients. Among those with AD there was no uniformity of response to the individual neuropeptide and in general the more severely affected showed a lower reactivity. Dose-response relationships were evaluated for SP and NT (10-320 pmols) in AD and healthy controls. In AD dose-response curves and time-course relationships were similar to controls, but at significantly reduced levels. The itch response to the neuropeptides and histamine was not different in atopics and controls. We suggest that this hyporesponsiveness in AD is the result of natural tachyphylaxis of the target structures (mast cells and blood vessels) and possibly due to a higher availability of neuropeptides in the skin or to a primary abnormal sensitivity of the blood vessels and mast cells to these peptides.     

Rapid effects of olopatadine hydrochloride on the histamine-induced skin responses

Olopatadine hydrochloride is one of the second-generation nonsedating antihistamines that are used for treating allergic disorders such as urticaria, rhinitis, and atopic dermatitis. We examined the inhibitory effects of this drug on the flare and wheal responses induced by histamine iontophoresis at 30, 60, and 90 min after oral administration in a double-blind, cross-over, and placebo-controlled study. Olopatadine hydrochloride significantly inhibited the histamine-induced flare and wheal responses as early as 60 min after oral administration when compared with placebo. Significant inihibitory effects of olopatadine hydrochloride on the itch responses were seen at 90 min after administration. Thus, olopatadine hydrochloride exhibited a very rapid and potent antihistamine effect on the histamine-induced skin responses.     

Regulation of wheal and flare by tea tree oil: complementary human and rodent studies

When applied 20 min after injection of histamine into human forearm skin, tea tree oil (TTO) reduces the developing cutaneous vascular response. In this study, the effect of TTO on inflammatory microvascular changes was dissected at the base of an experimental blister on rat skin. 1,8-Cineole, representing 2% of TTO, reduced vascular changes induced by sensory neuropeptides released when the distal portion of a cut sciatic nerve was electrically stimulated. The pre-terminal modulatory effect of 1,8-Cineole was confirmed in tests in sensory-denervated rats. Terpinen-4-ol (approximately 40% TTO) reduced substance P-induced microvascular changes and protein extravasation by a direct nitric oxide-mediated effect on the microvasculature, without sensory nerve involvement. alpha-Terpineol (3% of TTO) regulated both pre- and post-sensory nerve terminals. In human skin, terpinen-4-ol applied 10 min after histamine injection, but not alpha-terpineol or 1,8-cineole, regulated the developing wheal and flare suggesting that the histamine-induced responses in humans (at the dose used in this study, 50 microL of 330 microM histamine) are in large part determined by histamine directly affecting the vasculature via post-terminal-mediated events. The underlying strength of these studies is the use of a well-established rat physiologic model to differentiate the mechanism of regulation of microvascular changes by modulatory agents.     

Acute effects of substance P and calcitonin gene-related peptide in human skin--a microdialysis study

Upon activation nociceptors release neuropeptides in the skin provoking vasodilation and plasma protein extravasation in rodents, but only vasodilation in humans. Pivotal peptides in the induction of neurogenic inflammation comprise calcitonin gene-related peptide and substance P, the latter being suggested to act partly via degranulation of mast cells. In this study substance P and calcitonin gene-related peptide-induced vasodilation, protein extravasation, histamine release, and sensory effects were investigated simultaneously in human skin by dermal microdialysis. The vasodilatory prostaglandin E(2) and the mast cell activator codeine served as positive controls. Substance P and calcitonin gene-related peptide applied intradermally via large cut-off plasmapheresis capillaries induced dose-dependent local vasodilation, but only SP provoked protein extravasation in concentrations greater than 10(-9) M. Substance P-induced (10(-8)-10(-6) M) protein extravasation was not accompanied by histamine release and was unaffected by cetirizine (histamine H1 blocker, 200 microg per ml). Only the highest concentration of substance P (10(-5) M) induced significant histamine release. Neither neuropeptide caused any axon reflex erythema or any itch or pain sensation, whereas mast cell degranulation by codeine dose dependently provoked itch, flare, protein extravasation, and histamine release. In human skin calcitonin gene-related peptide and substance P induce vasodilation by a mechanism not involving histamine. No evidence for neuropeptide-induced activation of nociceptors was obtained. Our results suggest that endogenous calcitonin gene-related peptide and substance P have no acute sensory function in human skin. The lack of neurogenic protein extravasation in humans can most probably be attributed to low local concentrations of this neuropeptide still sufficient to exert trophic and immunomodulatory effects (10(-11) M), but too low to induce protein extravasation (10(-8) M) or even mast cell degranulation (10(-5) M). J Invest Dermatol 115:1015-1020 2000     

The effect of capsaicin on some experimental inflammations in human skin

Topical application of capsaicin is thought to deplete substance P from local sensory nerve terminals. In experiments on human skin inflammation was induced by injection of substance P (SP) or histamine intradermally, UV irradiation, non-immunologic contact urticaria, tuberculin reaction, contact allergens and benzalkonium chloride with or without capsaicin pretreatment. The flare response to SP and histamine was suppressed by capsaicin pretreatment whereas the wheal was enlarged. Interestingly, capsaicin pretreatment enhanced the responses to all other inflammatory agents.     

Effects of capsaicin, bradykinin and prostaglandin E2 in the human skin

The actions and interactions of putative mediators of inflammation, such as substance P (SP), histamine, bradykinin and prostaglandins (PGE2) were studied in human skin. In addition, the effects of capsaicin were examined as it is known to release (and to deplete) SP and calcitonin gene-related peptide from C-fibres. The flare evoked by bradykinin was abolished by pretreatment with lignocaine (local anesthetic), compound 48/80 (mast-cell histamine liberator), mepyramine (H1-receptor antagonist) and indomethacin (cyclo-oxygenase inhibitor) but was unaffected by atropine and ketanserin (serotonin antagonist). The weal response was not reduced by any of the drugs. The flare evoked by capsaicin was abolished by lignocaine and indomethacin but was unaffected by compound 48/80, mepyramine, atropine and ketanserin. The weal response was reduced by indomethacin. The flare response to bradykinin seems to reflect the activation of C-fibres and associated mast cells, while the flare response to capsaicin seems to reflect the activation of C-fibres only. Repeated injections of capsaicin and bradykinin produced tachyphylaxis (and cross-tachyphylaxis) and greatly reduced the SP-evoked flare. Capsaicin produced tachyphylaxis also after treatment of the skin with a local anaesthetic, suggesting that it develops independently of C-fibre impulse flow. The tachyphylaxis produced by bradykinin and capsaicin seems to reflect the depletion of messenger peptides from the C-fibres. The flare response to SP following capsaicin- or bradykinin-induced desensitization gradually returned to normal after 5-8 weeks. The erythema evoked by PGE2 was reduced by 30% following pretreatment with lignocaine, mepyramine or compound 48/80.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reactions to intradermally injected substance P and topically applied mustard oil in atopic dermatitis patients.

Skin reactions and itch or burning pain sensations following intradermal injection of the neuropeptide substance P and topical application of the substance P releasing agent mustard oil were studied in 20 atopic dermatitis patients and 20 healthy controls. Changes in skin blood flow were measured with a Laser Doppler flowmeter. Areas of wheal and flare reactions were evaluated planimetrically. Simultaneous with Laser Doppler flowmeter measurements, subjective itch and burning pain ratings were verbally reported on a category partitioning scale at 10-second intervals. Substance P evoked dose-dependent wheal, flare, and itch reactions in both patients and controls. However, substance P doses of 10(-9) -10(-11) mol elicited smaller flares in patients than in the controls whereas the wheal sizes were similar in both groups. Substance P-induced itch ratings were lower in patients at a dose of 10(-10) mol, and the onset of itching was delayed at all substance P levels applied. Mustard oil elicited similar neurogenic inflammatory reactions in both groups, although pain sensations were significantly delayed in atopic dermatitis patients at two mustard oil concentrations, which is further indication of a desensitization of afferent nerve endings contributing to the neurogenic inflammatory reactions in the skin of these patients.     

The inhibition spectrum of solar urticaria suppresses the wheal-flare response following intradermal injection with photo-activated autologous serum but not with compound 48/80

BACKGROUND: The inhibition spectrum (IS) in solar urticaria was identified mainly in Japanese patients with solar urticaria, although the mechanism of action of the IS has not been elucidated. METHODS: Because an intradermal injection of action spectrum (AS)-irradiated serum in a case of solar urticaria induced a wheal response, we studied the responsiveness of the intradermal injection after an IS irradiation. RESULTS: An AS in this patient was composed of visible light shorter than 500 nm, while an IS was composed of visible light longer than 530 nm. When the IS was exposed immediately after the AS irradiation, the wheal response was inhibited. However, when the IS was exposed before the AS irradiation, the wheal response was not inhibited. An intradermal injection of her serum produced no reaction, whereas an intradermal injection of her serum pre-irradiated with visible light induced a wheal flare response. Further examination revealed that the in vivo wheal-inducing activity of her serum irradiated with visible light could be attenuated by post-IS irradiation at the injection site, while the wheal-inducing activity of her visible light-irradiated serum was not inhibited by irradiation of the activated serum with the IS. The wheal-flare response induced by compound 48/80 and histamine was not altered by IS irradiation at the site of skin tests. CONCLUSION: These findings indicate that photoallergens in the patient's serum that are activated by visible light irradiation are responsible for the development of her symptoms and that the IS may suppress the wheal response by inhibiting the binding of the photoallergens to mast cells, not by inactivating the photoallergens and stabilizing mast cells.     

Further studies on the actions of endothelin-1 on blood flow in human skin

When injected into human skin, endothelin-1 produces intense vasoconstriction localized to the site of the injection, but this area of vasoconstriction is surrounded by vasodilatation which spreads several centimetres from the injection site. The vasodilatation induced by intradermal injection of endothelin-1 (63 pmol) into human skin is prevented by local anaesthetic. Pretreatment of human skin with capsaicin also inhibits this response. Pretreatment of subjects with the selective histamine H1-receptor antagonist cetirizine, 10 mg orally 4 h before intradermal injections, inhibited vasodilatation caused by the intradermal injection of histamine (750 pmol), endothelin-1 (63 pmol), and carbachol (750 pmol). Endothelin-1 (0.3-10 microM) and carbachol (1-30 microM) failed to induce histamine release from rat peritoneal mast cells. We conclude that the vasodilatation caused by intradermal injection of endothelin-1 into human skin is neurogenic and is probably mediated by neuropeptide-containing primary afferent neurones. Because neither carbachol nor endothelin-1 cause histamine release from mast cells, our data suggest that histamine release from mast cells at the effector end of the axon reflex is responsible for the carbachol- and endothelin-induced vasodilatation in human skin.     

Skin reactions and itch sensation induced by epicutaneous histamine application in atopic dermatitis and controls

Itch sensations and skin reactions induced by histamine iontophoresis at six different current intensities were studied in 27 atopic dermatitis (AD) patients and 20 healthy controls. Subjective itch ratings were assessed on a visual analogue scale (VAS) for 8-min periods after 10-sec histamine application, while changes of skin blood flow were simultaneously measured using two Laser Doppler flowmeters. Ten minutes after each histamine application, the areas of wheal and flare reactions were planimetrically evaluated. When no or weak current was applied, AD patients revealed stronger wheal and flare reactions than controls, possibly due to disturbed skin barrier function. Higher histamine doses, however, produced weaker subjective and vascular reactions in AD patients. In contrast to the controls, AD patients were unable to distinguish between weak and strong histamine stimulation, as shown by their VAS ratings. These results imply that AD patients have an altered histamine response. In particular, their afferent cutaneous nerve fibers show a decreased ability to signal itching to the central nervous system and to release vasoactive neuropeptides upon histamine stimulation.     

Anti-inflammatory effect of FK-506 on human skin mast cells.

FK-506 and the structurally related macrolide rapamycin are high-affinity ligands for a specific binding protein (FK-506 binding protein). We examined the effects of FK-506 and rapamycin on the release of pre-formed (histamine) and de novo synthesized inflammatory mediators (prostaglandin D2) from mast cells isolated from human skin tissue. FK-506 (0.1 to 100 nM) concentration-dependently inhibited (5 to 65%) histamine release from skin mast cells activated by anti-IgE. FK-506 was more potent in skin mast cells than in basophils (IC40 = 2.15 +/- 0.78 nM versus 5.12 +/- 1.34 nM; p < 0.001), whereas the maximal inhibitory effect was higher in basophils than in skin mast cells (88.77 +/- 2.44% versus 67.30 +/- 3.98%; p < 0.01). FK-506 had little or no inhibitory effect on histamine release from skin mast cells challenged with compound A23187 and substance P, respectively, whereas it completely suppressed A23187-induced histamine release from basophils. FK-506 (0.1 to 100 nM) also inhibited (up to 65%) the de novo synthesis of prostaglandin D2 from skin mast cells challenged with anti-IgE. Despite its structural similarity to FK-506, rapamycin (10 to 300 nM) had little or no effect on the release of histamine from skin mast cells induced by anti-IgE, A23187, and substance P. However, rapamycin competitively antagonized the inhibitory effect of FK-506 on anti-IgE-induced histamine release from skin mast cells with a dissociation constant of about 14 nM. These data indicate that FK-506, but not rapamycin, is a potent anti-inflammatory agent acting on skin mast cells presumably by binding to the FK-506 binding protein. It thus appears that binding to the FK-506 binding protein is necessary, but not sufficient, to deliver an inhibitory signal to skin mast cells.     

Effect of antianaphylactic agents on substance-P induced histamine release from rat peritoneal mast cells

Summary Substance P is known to be a potent histamine liberator for mast cells. The influence of antianaphylactic agents, disodium cromoglycate (DSCG), ketotifen, and tranilast was studied on substance-P and compound 48/80-induced histamine release from rat peritoneal mast cells. Substance-P induced histamine release was inhibited by these agents, while compound 48/80-induced histamine release was not inhibited by tranilast. Our findings suggest that these antianaphylactic agents are assumed to be effective for cutaneous diseases which might be concerned with substance P and histamine.