The effects of topical doxepin on responses to histamine, substance P and prostaglandin E2 in human skin

The tricyclic antidepressant, doxepin, is known to have H₁ and H₂ antihistaminic effects. Recently, 5% doxepin cream has been marketed in the U.S.A. for treatment of eczematous dermatoses. We investigated the effects of topical doxepin treatment on histamine-, substance P-and prostaglandin E₂-(PGE₂) induced responses in the skin of normal and atopic subjects. We compared the effects of topical doxepin with those of the oral antihistamine terfenadine. The weal volume and flare area responses to histamine were significantly reduced by treatment with topical doxepin or oral terfenadine in both normal and atopic subjects (P<0·05). The mean ±SEM percentage reduction in flare area for 10μ/site of histamine in non-atopics and atopics was 48±8% and 60±17% with terfenadine, and 54 ± 12% and 81 ± 4% with topical doxepin, respectively. The mean percentage reduction in weal volume for the same dose of histamine in non-atopics and atopics was 70 ± 9% and 63 ± 16% with terfenadine, and 96 ± 2% and 89 ± 6% with topical doxepin, respectively. The flare but not the weal response to substance P was inhibited by both treatments in all subjects (P<0·05). The mean ±SEM percentage reduction in flare area for 200 pmol/site of substance P in non-atopics and atopics was 53 ± 10% and 73 ±4% with terfenadine, and 74 ± 7% and 75 ± 4% with topical doxepin, respectively. The cutaneous responses to PGE₂ were not affected by either drug. The inhibitory effects of doxepin were as great as those of terfenadine, and doxepin had a significantly greater effect than terfenadine in inhibiting the weal response to histamine and flare response to substance P in normal volunteers (P<0·05). There was no significant difference between atopics and non-atopics in the percentage reduction of cutaneous responses by oral terfenadine or topical doxepin. Marked sedation occurred in three of the first 10 subjects treated with topical doxepin, necessitating a reduction in dosage for the remaining six subjects. In summary, topical doxepin was as effective as, and sometimes more effective than, a standard dose of oral terfenadine in the inhibition of histamine-induced and axon-reflex-mediated cutaneous responses. The marked sedative effect may limit its clinical use in some patients.     

Effects of histamine receptor antagonists on histamine-induced responses in human skin.

The effects of intradermally administered histamine H1- and H2-receptor antagonists on the cutaneous responses--redness, weal, flare and itch--induced by intradermal injection of histamine were studied in man. Weal and redness were studied after blockade of the axon reflex by local infiltration with lidocaine. All responses were significantly inhibited by the H1-receptor antagonist mepyramine. The H2-antagonists cimetidine and metiamide reduced flare and itch significantly but not to the same extenet as mepyramine and not in a clearly dose-related manner. The size of weal and redness was not significantly reduced by cimetidine. No further reduction of flare, itch or weal was obtained by adding metiamide or cimetidine to mepyramine. After blockade of the axon reflex with lidocaine the histamine-induced weals turned white at the centre. This blanching was more prominent when histamine was injected in combination with cimetidine. Substituting mepyramine for cimetidine resulted in small weals with an intense red colour. It is concluded that, apart from being engaged in the direct vasodilatory response to histamine, H2-receptors do not seem to be involved in the other cutaneous responses to histamine studied.     

Effects of H1 antagonists on the cutaneous vascular response to histamine and bradykinin: a study using scanning laser Doppler imaging

Histamine plays an important part in the cutaneous weal and flare response which underlies many allergic skin conditions. It has a direct effect on the local vasculature to promote vasodilatation and increase microvascular permeability and may also initiate the more widely spread neurogenic flare. Quantification of these responses and studies of the mediator mechanisms underlying them have been limited by the lack of appropriate techniques to investigate them. To address this we have used two relatively new techniques, scanning laser Doppler imaging (LDI) and dermal microdialysis to measure changes in skin blood flow and the release of histamine within the weal and flare, following intradermal injection of histamine or bradykinin. These measurements have been made both in the absence and presence of the H₁ receptor blockers cetirizine and loratadine. Scanning LDI of the inflammatory response revealed marked differences in both the development and steady state responses to the intradermal injection of histamine (1–3 μmol/L) and bradykinin (1 μmol/L). The development of the flare and the weal response to both histamine and bradykinin was significantly reduced by cetirizine but not by loratadine. The histamine-induced flare area fell by 57 ± 4% (mean ± SEM, n = 10, P < 0.001) after cetirizine and the area of the weal fell by 73 ± 11% (P < 0.009). Bradykinin-induced inflammatory responses were similarly reduced by cetirizine, the weal by 60 ± 16% (P < 0.02) and the flare by 61 ± 4% (P < 0.005). Measurement of histamine concentration in skin using microdialysis, in six subjects, confirmed that histamine levels rose in the dialysate collected from the weal to 310 ± 16 nmol/L following injection of histamine. Histamine levels also rose following bradykinin injection in some subjects (mean 147 ± 46 nmol/L, range 18–336). Little increase in histamine concentration was seen in the dialysate from the flare following injection of either histamine or bradykinin. The histamine concentration in dialysate from unprovoked skin was 4.19 ± 0.75 nmol/L. These data reveal differences in the dermal responses to different mediators when assessed using scanning LDI. They confirm that histamine is released within the weal but not the flare response to the intradermal injection of both histamine and bradykinin and that its effects on the local vasculature to cause the oedematous weal and the axon reflex-mediated flare are significantly attenuated by the H₁ antagonist cetirizine and to a lesser extent by the H₁ antagonist loratadine.     

The effects of astemizole, cetirizine and loratadine on the time course of weal and flare reactions to histamine, codeine and antigen

An open cross-over study was performed to assess the effects of astemizole, cetirizine and loratadine on weal and flare reactions to intradermal histamine, codeine and house dust mite antigen. Percentage inhibition of weal area, flare area and weal volume was greatest for cetirizine, then astemizole and smallest for loratadine. Wealing due to mast-cell degranulation with either codeine or antigen was less inhibited by all three antihistamines than that due to histamine itself. Time-course studies revealed similarities between wealing provoked by codeine and histamine but different characteristics to that induced by antigen.     

Effects of H1- and H2-antihistamines on platelet-activating factor and bradykinin-induced inflammatory responses in human skin

Previous studies show that oral antihistamines affect the Weal and flare response to intradermal injections of the inflammatory mediators platelet-activating factor (PAF) and bradykinin (BK). The aim of this study was to compare the effects of terfenadine (an H₂-antagonist) and cimetidine (an H₂-antagonist) on weal and Hare responses to PAF and BK in healthy non-atopic human volunteers. The effects of doxepin on PAF responses were investigated, as there is evidence that doxepin may have direct anti-PAF ejects in addition to its known antihisiaminic actions.     

Dose-response relationship between objective measures of histamine-induced weals and dose of terfenadine.

Terfenadine is a safe non-sedative H1-receptor antagonist. This study aimed to quantify the relative reduction in weal and flare area, thickness and erythema at 4, 8, 12 and 24 h following a single but variable oral dose of terfenadine compared with pre-treatment measurements, in order to compare the dose-effect relationship and time course of the different dosages. In a double-blind randomized cross-over study, 12 healthy volunteers were given 60, 120 or 240 mg of terfenadine or placebo. Twenty micrograms of histamine acid phosphate was then injected intradermally at 4, 8, 12 and 24 h. The weal and flare areas were measured by planimetry, the thickness of the weal by an A-scan pulsed ultrasound device and the redness of both the weal and flare by an erythema-meter. A definite dose-response relationship was demonstrated between the weal and flare areas and the three active treatments. For the weal area, there was a significant difference between 60 mg and 240 mg of terfenadine at 4 h (p less than 0.01), at 8 and 12 h (p less than 0.05). For the flare area there was a similar significant difference at 4 h (p less than 0.01) and at 8 h (p less than 0.05). A dose-response relationship was demonstrated between weal erythema and 120 mg or 240 mg and 60 mg of terfenadine (p less than 0.05). There was a correlation between the plasma levels of the major metabolite and the initial dose of terfenadine, demonstrating their expected proportionality. This metabolite was also demonstrated in tissue fluid.     

Histamine H4 receptor antagonism reduces hapten-induced scratching behaviour but not inflammation

Abstract:  Effects of the histamine H₄ receptor antagonist JNJ 7777120 (1-[(5-chloro-1 H -indol-2-yl)carbonyl]-4-methylpiperazine) were tested in two models of allergic contact dermatitis. Dermatitis was induced by 2,4-dinitrochlorobenzene and toluene-2,4-diisocyanate, which differ in their Th1–Th2 profile in that way that 2,4-dinitrochlorobenzene is a classical contact allergen with a pronounced Th1-mediated inflammation, while the respiratory chemical allergen toluene-2,4-diisocyanate induces a Th2-dominated inflammation. JNJ 7777120 (15 mg/kg) administered 2 h and 30 min before and 1 h after challenge did not reduce the hapten-induced ear swelling determined 24 h after challenge. This was confirmed by histological evaluation of the ear skin. A repeated administration of the haptens to the rostral part of the back of sensitized animals resulted in a frequent scratching behaviour. An administration of JNJ 7777120 (15 mg/kg) 30 min before challenge reduced this hapten-induced scratching significantly. The H₁ receptor antagonist cetirizine also reduced the scratching bouts in sensitized mice. A combination of H₁ and H₄ receptor antagonists resulted in the strongest inhibition of scratching behaviour associated with allergic dermatitis. These results indicate that H₄ receptor antagonism fails to reduce the allergic inflammatory response but strongly inhibits allergen-induced itch. Thus, a combination of H₄ and H₁ receptor antagonism might be a new strategy to treat pruritus related to allergic diseases like atopic dermatitis.     

Assessment of the duration of action of terfenadine on histamine induced weals

In this study we aimed to quantify the reduction in area, perimeter and thickness of histamine induced weals 12, 18 and 24 h after a single oral dose of 120 mg terfenadine. Ten healthy volunteers were given 120 mg of terfenadine or placebo in a double-blind randomized two-period cross-over study. Twenty micrograms of histamine were then injected intradermally at 12, 18, and 24 h. The thickness of the resulting weal was measured by an A-scan pulsed ultrasound device. The area and perimeter of the resulting weal and flare were measured by tracing onto acetate sheets and using a digitizing tablet linked to a microcomputer. Just before each dose of histamine was injected, blood was taken to measure the level of the major metabolite of terfenadine. There was a significant difference between terfenadine 120 mg and placebo in the area and perimeter of the weal and the area and perimeter of the weal and flare at 12, 18 and 24 h, but no significant difference in weal thickness. Thus, terfenadine suppresses the wealing response caused by intradermally injected histamine over a 24 h period. It may be possible, therefore, to use a once daily dose of terfenadine.     

Cutaneous reactions to substance P and histamine in atopic dermatitis

The flare and weal reactions to intradermal injections of histamine and the peptide substance P were measured in a group of patients with atopic dermatitis and compared to reactions in a non-atopic control group. There was no significant difference in the flare areas between the controls and atopics with either reagent. The weal volumes after injection of substance P and histamine were significantly larger in the atopic group. As substance P causes mast cell histamine release, the increased weal volumes produced by substance P in the atopics may be entirely due to the exaggerated atopic weal reaction to histamine.     

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)     

Irritant susceptibility and weal and flare reactions to bioactive agents in atopic dermatitis. I. Influence of disease severity

The two main pathogenetic characteristics of atopic dermatitis (AD) are: (i) antigen-dependent ‘specific’ reactivity, and (ii) altered non-immimological ‘non-specific’ reactivity. Our understanding of the role of non-specific reactivity is hampered by the fact that methods available for its quantification are limited. The aim of the present study was to assess the usefulness of two parameters as quantitative measures of non-specific skin reactivity in AD: (i) susceptibility to repeated epicutaneous exposure to an irritant (sodium lauryl sulphate, SLS), assessed by visual scoring and transepidermal water loss(TEWL) measurement, and (ii) reactivity to intracutaneously injected bioactive agents (codeine, FMLP, histamine, methacholine, substance P, trypsin), assessed by measurement of weal and flare size. These two parameters were tested in a group of AD patients, subdivided according to the severity of their dermatitis, and a control group. The visual score and TEWL after SLS exposure tended to be higher in the AD group than in the control group. Furthermore, visual score and post-exposure TEWL were positively correlated with the dermatitis severity score. Weal size following injection of codeine, histamine and substance P, and flare size following injection of all agents, except methacholine, were significantly lower in the AD group than in the control group. Negative correlations were found between weal and flare sizes and the dermatitis severity score. These findings can be explained by down-regulation of structures involved in weal and flare reactions. In conclusion, we propose that epicutaneous irritant susceptibility and reactivity to intracutaneous bioactive agents may be useful indicators of non-specific skin reactivity in AD.     

Effects of local corticosteroids on acute experimental urticaria

Corticosteroids are often used in the treatment of acute or chronic urticaria. However, their effects on mastocyte activation as well as on the histamine-induced dermal oedema remain poorly investigated. The aim of the present study was to investigate the effects of corticosteroids (CS) on the development of acute experimental urticaria induced by prick-tests with histamine and codeine. This experimental model corresponds to the common form of urticaria. CS were administered at the site of the histamine and codeine prick tests in order to test for a direct effect on the development of acute urticaria. Two types of experiments were performed: 1) after a 48-hour period of topical CS application on the forearm, 7 healthy volunteers were skin prick-tested with histamine and codeine simultaneously in duplicate, one series in the pretreated area and the other in a non-treated area. 2) six other volunteers were prick-tested with histamine and codeine on their forearm, in duplicate. Immediately after testing, intradermal methyprednisolone was injected at the site of the prick-tests in the last series. Skin wheal and flare responses were measured after 20 mns and statistically compared with and without CS treatment. Whereas short-term CS topical application did not appear to modify cutaneous reactivity to histamine and codeine, local CS injection was associated with a significant increase in the flare induced by histamine and codeine (respectively + 18 +/- 3% and + 38 +/- 3%; P = 0.05). The wheal tended to be increased after injected CS. In conclusion, these results show that CS are neither able to prevent nor to improve experimental urticaria, i.e. wheal and flare, and even increase the histamine and codeine-induced erythema. That a similar result could apply to patients with chronic urticaria and with systemic CS remains to be studied.     

Aberrant cutaneous weal and flare responses in chronic urticaria.

This study examined cutaneous mast cell behaviour in 14 patients with chronic urticaria but no dermographism and 11 healthy controls, by measuring cutaneous weal and flare reactions evoked in response to intradermal challenge injections of 0.1 ml isotonic saline, histamine (20 micrograms), codeine phosphate (10 micrograms) and compound 48/80 (10 micrograms). Five minutes after each injection, the area of the resulting weal and flare was calculated by computer-aided planimetry. The process was repeated at 15, 30 and 45 min following the injection. In patients, saline flares were significantly larger than those of the volunteers at 15, 30 and 45 min (p < 0.05). However, histamine and codeine flare areas were significantly smaller in the patients when compared to the controls at 15, 30 and 45 min (p < 0.05). Compound 48/80 produced smaller reactions in the patients without reaching statistical significance.     

Tea tree oil reduces histamine-induced skin inflammation

BACKGROUND: Tea tree oil is the essential oil steam-distilled from Melaleuca alternifolia, an Australian native plant. In recent years it has become increasingly popular as an antimicrobial for the treatment of conditions such as tinea pedis and acne. OBJECTIVES: To investigate the anti-inflammatory properties of tea tree oil on histamine-induced weal and flare. METHODS: Twenty-seven volunteers were injected intradermally in each forearm (study and control assigned on an alternating basis) with histamine diphosphate (5 microg in 50 microL). Flare and weal diameters and double skin thickness were measured every 10 min for 1 h to calculate flare area and weal volume. At 20 min, 25 microL of 100% tea tree oil was applied topically to the study forearm of 21 volunteers. For six volunteers, 25 microL paraffin oil was applied instead of tea tree oil. RESULTS: Application of liquid paraffin had no significant effect on histamine-induced weal and flare. There was also no difference in mean flare area between control arms and those on which tea tree oil was applied. However, mean weal volume significantly decreased after tea tree oil application (10 min after tea tree oil application, P = 0.0004, Mann-Whitney U-test). CONCLUSIONS: This is the first study to show experimentally that tea tree oil can reduce histamine-induced skin inflammation.     

Shock in an Infant with Bullous Mastocytosis

Abstract: A 6-month-old infant had bullous lesions on his posterior neck, upper trunk, and extremities for two months prior to admission for fever and shock. He had an elevated white blood cell count with left shift and normal platelet count, but abnormal coagulation studies. He was treated with intravenous antibiotics, crystalloids, fresh-frozen plasma, and pressor agents. A histamine H₂ receptor antagonist was started for guaiac-positive nesogastric tube drainage. The patient recovered after four days of treatment. A skin biopsy confirmed mastocytosis. A week iater the child passed grossly bloody stools with blood clots. No source of gastrointestinal bleeding was identified by extensive work-up. Blood histamine level measured one day before gastrointestinal bleeding was 16,400 pg/ml (normal 263±202 pg/ml). The bleeding resolved spontaneously. The patient was maintained on cimetidine. Results of a subsequent bone scan were normal. Shock or gastrointestinal bleeding associated with unusual skin lesions should alert the pediatrician to the possibility of mastocytosis.     

Histamine-induced IL-6 and IL-8 production are differentially modulated by IFN-gamma and IL-4 in human keratinocytes

It is known that large amounts of histamine are stored in mast cells located in the superficial dermis of the skin and can be released upon appropriate stimulation. However, the effects of histamine on keratinocyte function have not been well characterized. We therefore examined the capacity of histamine to modulate the production of interleukin (IL)-6 and IL-8 by keratinocytes. We found that histamine significantly augmented the production of IL-6 and IL-8 in a dose- and time-dependent manner. The enhancing effects of histamine were completely inhibited by a potent H1 receptor (H1R) antagonist, emedastine difumarate. Pyrilamine (a much weaker H1R antagonist) and cimetidine (an H2R antagonist) only partially inhibited the enhancing effects of histamine. The histamine-induced up-regulation of IL-6 and IL-8 production, however, was completely abrogated by a combination of pyrilamine and cimetidine. The IL-6 production was significantly enhanced by interferon (IFN)-gamma. Interestingly, IFN-gamma and IL-4 both significantly augmented the histamine-induced IL-6 production. On the other hand, the production of IL-8 was inhibited by IFN-gamma, and IFN-gamma and IL-4 both completely abrogated the histamine-induced IL-8 production. These results suggest that the histamine-induced IL-6 production and IL-8 production are differentially regulated by IFN-gamma and IL-4. Histamine may be an important modulator of cytokine production in epidermal milieu.     

流式细胞仪测量组胺对人角质形成细胞内游离Ca~(2+)的影响

目的探讨组胺对人角质形成细胞(HKC)胞内游离Ca2+浓度的影响。方法利用流式细胞仪(FCM)结合Fluo3染色技术,半定量检测组胺及H2组胺受体拮抗剂西咪替丁对体外培养HKC胞内Ca2+浓度的影响。结果组胺以剂量依赖方式引起HKC胞内Ca2+浓度上升,西咪替丁则完全阻断组胺该作用。结论组胺通过H2组胺受体激活HKC相关信号传导系统,从而引起细胞内Ca2+浓度增加。     

Responses of human dermal microvascular endothelial cells to histamine and their modulation by interleukin 1 and substance P.

The action of histamine on human dermal microvascular endothelial cells and modulation of its effects by the cytokine interleukin-1 and the vasoactive neuropeptide substance P have been investigated. Histamine (10(-6)-10(-3) M) induces release of prostaglandin E2 in a concentration- and time-dependent manner. Prostaglandin E2 release is facilitated principally by histamine H1 receptors as the H1 receptor antagonist pyrilamine attenuates prostaglandin E2 release whereas the H2 receptor antagonist cimetidine only slightly reduces release. In contrast to other cells, the histamine/receptor interaction is not associated with increased intracellular accumulation of the cyclic nucleotides, cyclic AMP, or cyclic GMP. Interleukin-1 induces a concentration-dependent release of prostaglandin E2 following 24 h incubation. However, substance P does not increase release of prostaglandin E2 above baseline. In cells incubated with 1 U/ml human recombinant interleukin 1 alpha for 24 h prior to stimulation with histamine (10(-5)-10(-3) M) for 30 min, there is a significant potentiation of histamine-induced release of prostaglandin E2 (p less than 0.05). Using a solubilized cell sonicate prepared from human dermal microvascular endothelial cells incubated with 1 U/ml human recombinant interleukin 1 alpha for 24 h, conversion of exogenous arachidonic acid into prostaglandin E2 increased by 60.19 +/- 18.28%. Cycloheximide partially reduces the increased conversion but completely blocks interleukin-1-induced release of prostaglandin E2 from intact cells. Substance P does not potentiate histamine-induced release of prostaglandin E2 or increase arachidonic acid conversion. These results demonstrate that human dermal microvascular endothelial cells are responsive to histamine and that interleukin-1, but not substance P, can potentiate histamine-induced release of prostaglandin E2. Interleukin-1 appears to act, at least in part, by regulating the availability of free arachidonic acid. Interactions between histamine and interleukin-1 may be important in the modulation of inflammatory reactions in skin.     

Agonist-antagonist interactions in the skin: comparison of effects of loratadine and cetirizine on skin vascular responses to prick tests with histamine and substance P.

The skin vascular responses (weal, flare, blood flow measurements) elicited by intradermal administration by pricking of histamine (HS) and substance P (SP) were evaluated 6 h after a single intake of anti-H1 agents displaying different activity profile on skin tests at currently recommended dosages (loratadine 10 mg, cetirizine 10 mg) as compared to placebo (P). The weal and flare response and the increases of blood flow occurring in the usual flare area after HS and SP were almost completely abolished by cetirizine. Inhibition of HS- and SP-induced weal and flare reactions was less marked after loratadine and blood flow in the expanding flare after HS and SP showed significant fluctuations over time. In view of the present results and of data obtained in previous experiments with intradermal injection of agonists, we hypothesize that mode of administration of agonists significantly influences the size of the residual weal after anti-H1 agents. We demonstrate that SP weals induced by pricking are largely inhibited by a potent H1 blockade which supports the view that this phenomenon, as well as the SP-flare, is due to SP-induced histamine liberation. We also, for the first time, report on fluctuations recorded at the edge of the developing flare with laser Doppler flowmetry early after prick testing with a weak H1 blockade. This opens up new avenues in dynamically testing H1-receptor occupancy in vivo and in situ in human skin.