Roles of mast cells and sensory nerves in cutaneous vascular hyperpermeability and scratching behavior induced by poly-L-arginine in rats

Development of mechanisms associated with neurogenic-mediated skin inflammation during the growth of rats

Neurogenic-mediated inflammation may be associated with several inflammatory skin diseases including atopic dermatitis. However, age-dependent differences in neurogenic-mediated skin responses are not fully understood. We compared skin plasma leakage in rats aged 2 and 8 wk, which was induced by topical capsaicin, topical formalin, and intracutaneous substance P, whose effects are mediated via tachykinin NK1 receptors. Evans blue dye extravasation served as an index of the increase in skin vascular permeability. Capsaicin, formalin, and substance P caused a skin response in a dose-dependent manner in both age groups. However, the skin response was much greater in adults than in pups. In addition, the localization of sensory C-fibers and tachykinin NK1 receptors in the skin was investigated by immunofluorescent staining with antisubstance P and antitachykinin NK1 receptor antibodies, respectively. Substance P-immunoreactive nerves were detected throughout the dermis and tachykinin NK1 receptors were mainly detected in blood vessel walls in the dermis in both age groups. However, they were more sparsely distributed in pups. In conclusion, the weak neurogenic-mediated skin inflammation in pups is probably because of immature neural mechanisms associated with skin inflammation such as reduced innervation of sensory C-fibers and low expression of tachykinin NK1 receptors.

A transient unresponsive state of self-scratching behaviour is induced in mice by skin-scratching stimulation

When mice were scratched with brushes on their dorsal skins, they began to scratch themselves with their hind paws. Thus, self-scratching behaviour was induced in mice in response to skin-scratching stimulation. If the second skin-scratching stimulation was given within a few days, the induction of the second self-scratching behaviour was significantly suppressed compared with the first one. Thereafter, mice gradually recovered from this unresponsive state within a week. Thus, a transient unresponsive state of self-scratching behaviour is induced by skin-scratching stimulation. Pretreatment with a tachykinin receptor NK-1R antagonist L-703606 or capsaicin significantly suppressed self-scratching behaviour, while pretreatment with a neutral endopeptidase inhibitor phosphoramidon significantly enhanced it. Pretreatment with a calcitonin gene-related peptide (CGRP) receptor antagonist CGRP(8-37) did not affect the following self-scratching behaviour. From these results, it is suggested that substance P (SP) signalling through its receptor NK-1R at least in part mediates the induction of self-scratching behaviour. After skin-scratching stimulation, immunoreactivity of SP both in the peripheral nerve fibres and in the dorsal root ganglion (DRG) neurons was significantly decreased and was well-correlated with suppression of self-scratching behaviour. From these findings, it is suggested that the induction of unresponsive states of self-scratching behaviour may be at least in part caused by the depleted states of SP in peripheral nerve fibres and/or in DRG neurons. The induction of a transient unresponsive state after skin-scratching may possibly happen also in patients with pruritus. Thus, further studies to elucidate the precise mechanisms are required.

Rapid changes in substance P signaling and neutral endopeptidase induced by skin-scratching stimulation in mice

BACKGROUND

Skin-scratching is a commonly seen behavior in patients with pruritus which sometimes exacerbates original lesions. Substance P (SP) signaling may play a predominant role in the pathophysiology induced by skin-scratching, however, it has not been well-elucidated.

OBJECTIVES

To clarify changes in SP, its receptor NK-1R and a degradating enzyme neutral endopeptidase (NEP) induced by skin-scratching stimulation in mice.

METHODS

After skin-scratching stimulation was given to mice, changes in SP signaling were investigated as follows. Mast cell degranulation was examined with toluidine blue staining. SP-immunoreactive nerve fibers and the expressions of NK-1R and NEP were examined with immunofluorescence. Protein contents of SP and the enzymatic activity of NEP were examined with an ELISA and a colorimetric assay, respectively.

RESULTS

After skin-scratching stimulation, mast cells significantly degranulated within several minutes. SP-immunoreactive nerve fibers disappeared immediately from sensory nerve fibers, indicating the quick secretion and the depletion of SP. Both protein contents of SP and NEP activity in skin decreased dramatically soon after skin-scratching stimulation and thereafter they returned to the basal level within a week. The expression of NK-1R was significantly upregulated in epidermal basal keratinocytes after several days, in which NEP and NK-1R were well-coexpressed. Blocking NK-1R by an NK-1R antagonist suppressed scratching-induced decreases in SP-immunoreactive nerve fibers and in NEP activity.

CONCLUSIONS

The present study clarified changing patterns of factors involved in SP signaling and NEP induced by skin-scratching stimulation. These findings provide basic and useful information to understand the pathophysiology of scratching-associated pruritic skin diseases.

Erratum to “Changes in cutaneous sensory nerve fibers induced by skin-scratching in mice” [J. Dermatol. Sci. 46 (2007) 41–51]

BACKGROUND

Skin-scratching behavior, a common response observed in patients with pruritus, is supposed to promote the sprouting of cutaneous sensory nerve fibers. Thus, it sometimes exacerbates the original lesions. However, the precise changes that develop in cutaneous sensory nerve fibers after skin-scratching have not yet been elucidated.

OBJECTIVE

To investigate how and what kinds of cutaneous sensory nerve fibers increase and how nerve growth factor (NGF) and its receptors change after skin-scratching.

METHODS

After scratching the dorsal skin of anesthetized ICR mice, change in cutaneous nerve fibers was detected by immunofluorescence for protein gene product 9.5 (PGP9.5), substance P (SP) and/or calcitonin gene-related peptide (CGRP). To investigate the involvement of NGF signaling, the production of NGF and the expression of its receptors were examined using ELISA and/or immunofluorescence, respectively.

RESULTS

Skin-scratching dramatically induced the sprouting of cutaneous nerve fibers. Both dermal and epidermal nerve fibers began to increase and reached a peak at days 3-7. At the same time, nerve fibers containing SP or CGRP increased significantly. NGF in the scratched skin increased immediately and reached a peak at days 1-3. The expression of NGF receptors, such as phosphorylated trk A and p75, on nerve fibers was remarkably upregulated within 2 days.

CONCLUSIONS

Skin-scratching induced the sprouting of cutaneous sensory nerve fibers in the skin within several days, thus possibly leading to enhanced neurogenic inflammation. Analysis of the expression of NGF and its receptors suggest that NGF signaling may be, at least in part, involved in these changes.

Intraepidermal nerve fibers increase in dry skin of acetone-treated mice

BACKGROUND

Skin dryness is apparent in several pruritic skin diseases, such as xerosis and atopic dermatitis. Our previous study has demonstrated an increase of nerve fibers in the epidermis of patients with xerosis, suggesting the contribution of nerve fibers to itching.

OBJECTIVE

This study was conducted to reveal a direct linkage between dry skin and intraepidermal nerve growth.

METHODS

ICR mice treated with acetone were used as a dry skin model. Time-dependent measurement of transepidermal water loss (TEWL) and stratum corneum (SC) hydration was performed on the treated areas. Moreover, both the distribution of intraepidermal nerve fibers and the expression of epidermal nerve growth factor (NGF) and amphiregulin (AR) were examined sequentially with immunohistochemistry and quantitative RT-PCR. The same experiments were carried out in control mice treated with sterile water.

RESULTS

Enhanced TEWL and decreased SC hydration were observed in the acetone-treated skins during the first hour after the treatment. These parameters gradually returned to the normal range within 48 h. In the acetone-treated mice, we found that there were many nerve fibers in the epidermis between 16 and 48 h after the treatment. No changes of the parameters for barrier disruption and intraepidermal nerve growth were observed in the control skins. Moreover, the expression of epidermal NGF and AR at the protein and mRNA levels was increased before the penetration of nerve fibers into the epidermis.

CONCLUSIONS

These results suggest that increases of epidermal NGF and AR levels are associated with intraepidermal nerve growth in acetone-treated mice.

Changes in cutaneous sensory nerve fibers induced by skin-scratching in mice

BACKGROUND

Skin-scratching behavior, a common response observed in patients with pruritus, is supposed to promote the sprouting of cutaneous sensory nerve fibers. Thus, it sometimes exacerbates the original lesions. However, the precise changes that develop in cutaneous sensory nerve fibers after skin-scratching have not yet been elucidated.

OBJECTIVE

To investigate how and what kinds of cutaneous sensory nerve fibers increase and how nerve growth factor (NGF) and its receptors change after skin-scratching.

METHODS

After scratching the dorsal skin of anesthetized ICR mice, change in cutaneous nerve fibers was detected by immunofluorescence for protein gene product 9.5 (PGP9.5), substance P (SP) and/or calcitonin gene-related peptide (CGRP). To investigate the involvement of NGF signaling, the production of NGF and the expression of its receptors were examined using ELISA and/or immunofluorescence, respectively.

RESULTS

Skin-scratching dramatically induced the sprouting of cutaneous nerve fibers. Both dermal and epidermal nerve fibers began to increase and reached a peak at days 3-7. At the same time, nerve fibers containing SP or CGRP increased significantly. NGF in the scratched skin increased immediately and reached a peak at days 1-3. The expression of NGF receptors, such as phosphorylated trk A and p75, on nerve fibers was remarkably upregulated within 2 days.

CONCLUSIONS

Skin-scratching induced the sprouting of cutaneous sensory nerve fibers in the skin within several days, thus possibly leading to enhanced neurogenic inflammation. Analyses of the expression of NGF and its receptors suggest that NGF signaling may be, at least in part, involved in these changes.

Neurophysiological, neuroimmunological, and neuroendocrine basis of pruritus

Pruritus (itch) can be defined as an unpleasant cutaneous sensation associated with the immediate desire to scratch. Recent findings have identified potential classes of endogenous "itch mediators" and establish a modern concept for the pathophysiology of pruritus. First, there in no universal peripheral itch mediator, but disease-specific sets of involved mediators. Second, numerous mediators of skin cells can activate and sensitize pruritic nerve endings, and even modulate their growth. Our knowledge of itch processing in the spinal cord and the involved centers in the central nervous system is rapidly growing. This review summarizes the current information about the significance of neuron-skin interactions, ion channels, neuropeptides, proteases, cannabinoids, opioids, kinins, cytokines, biogenic amines, neurotransmitters, and their receptors in the pathobiology of pruritus. A deeper understanding of these circuits is required for the development of novel antipruritic strategies.

A novel acoustic evaluation system of scratching in mouse dermatitis: rapid and specific detection of invisibly rapid scratch in an atopic dermatitis model mouse

Scratching is an essential and a skin specific behavior induced by itching, which is a common symptom of atopic dermatitis (AD) and other types of dermatitis. Itching sensation and scratching are closely associated and thus scratching times are currently used for evaluating itching in animal models. However, objective measuring systems of scratching to assess the grade of dermatitis and the effectiveness of anti-pruritic drugs in animal dermatitis models are lacking. To investigate a quantitative evaluation system for itching, we have developed a novel acoustic scratching counting system and compared its accuracy with time-consuming slow-motion video recording system. We have also objectively evaluated the efficacy of an antihistamine using this novel system. Scratching behavior of an AD model mouse (K14 driven IL-18 transgenic mouse) was recorded visually and acoustically. Specific scratching sound produced by mice was recorded and counted using a software we have developed, and the results obtained using our acoustic system were not statistically different from data obtained using slow motion video system. Surprisingly, mice scratched more than 10 times/second, which was invisibly rapid motion and revealed inaccuracy of conventional hand counting system. Results were identical to that of measured by 10 times time costing slow-motion video analysis. The antihistamine is clearly effective for suppression of scratching as demonstrated using this objective and accurate method. This novel motion analysis system will open a window for physiological and pathological analysis for animal models and development of anti-pruritic drugs.

Mast cell activation and degranulation occur early during induction of periosteal bone resorption

We have previously postulated that mast cells participate in the cellular network involved in osteoclastic resorption, probably through histamine release. In this study, we examined mast cell activation and histamine release during origination of resorption. Groups of 10 rats were killed 0, 0.5, 1, 1.5, 3, 6, 9, 12 and 18 h after induction of resorption in a synchronized model of cortical resorption along the mandible. The total number of mast cells was transiently decreased by about one-third at 1 and 9 h. Mast cell activation was monitored by Alcian blue-safranin staining. Early after induction, mast cells started to release their mediator stores; complete release led to the apparent disappearance of the cells with the staining technique used. Histamine immunostaining confirmed the release of histamine and its diffusion in the extracellular environment. Massive degranulation was observed at 1.5 and 9 h with toluidine blue staining. Cell recovery, assessed in terms of histidine decarboxylase expression, occurred gradually. The number of ED1+ osteoclast precursors strongly increased from 12 h up to 18 h. Most parameters had returned to baseline at 18 h, except the ED1+ cells. H2 receptor inhibition with famotidine strongly decreased ED1+ osteoclast precursors at 12 h and subsequently osteoclasts at the peak of resorption. These data support a role of mast cells in resorption origination. They show an early and transient intervention of mast cells in the events regulating the recruitment of circulating osteoclast precursors and ultimately of resorption. Mast cell activation and degranulation induce the release of mediators, particularly histamine acting through its H2 receptors, which are likely involved in these reactions.

[Recent development of new drugs for the treatment of allergic diseases]

Due to the prevalence of allergic diseases such as bronchial asthma, allergic rhinoconjunctivitis and dermallergosis, efforts at the discovery of novel and effective medications for prevention and treatment of these conditions have been reinforced. Recently, it has been recognized that these allergic diseases are a chronic inflammatory disorder of the lower and upper airways and skin. In this article, we reviewed the recent development of the following new antiallergic therapies: anti-Th2 cytokine antibodies, decoy receptors, receptor antibodies, anti-IgE antibodies, anti-cell adhesion molecules antibodies, antisense oligonucleotides, keratinocyte modulators, inhibitors of phosphodiesterase 4, tachykinin receptor antagonists, and anti-histaminic drugs. Most of these new agents are aimed to inhibit various components of allergic inflammation. The future use of allergic disease therapies hold great promise and excitement.

A new analytical system for quantification scratching behaviour in mice

BACKGROUND

Scratching behaviour is an important component of human atopic dermatitis. The duration of scratching determines the extent of skin damage and thus the rash, but quantification of this is difficult. Establishment of a method for measuring the duration of scratching is important in order to make objective assessments of the factors that may cause the itch and also the efficacy of new antipruritic drugs.

OBJECTIVES

A novel method for assessing the duration of scratching in mice was evaluated, based on the time course changes in the distance between the animal's hind limbs and the back of the neck during scratching behaviour.

METHODS

Compound 48/80 was administered intradermally to the back of ICR mice and their scratching behaviour was recorded on digital videotape. The distance between the back and the hind limb was measured continuously using an image analysis system.

RESULTS

Measurement of the frequency and duration when the mouse's hind limb came into contact with the back of the neck provided an accurate method of quantitating scratching behaviour.

CONCLUSIONS

This system provides a new method of quantifying scratching behaviour in a mouse.

Biphasic response of cutaneous blood flow induced by passive cutaneous anaphylaxis in rats

In the immediate phase of passive cutaneous anaphylaxis, sensitized skin mast cells release various mediators when activated by antigen. The present study investigated the effects of the mediators on cutaneous blood flow at the antigen-antibody reaction site. Induction of passive cutaneous anaphylaxis produced a biphasic response consisting of an initial decrease, followed by a sustained increase, in the cutaneous blood flow. The initial phase was almost eliminated by the 5-hydroxytryptamine receptor antagonist methysergide, whereas the second phase was sensitive to the histamine H(2) receptor antagonist ranitidine. The histamine H(1) receptor antagonist chlorpheniramine, the denervation of sensory nerves with capsaicin, the cyclooxygenase inhibitor indomethacin, or the bradykinin B(2) receptor antagonist D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-L-(2alpha,3beta,7abeta)-octahydro-1H-indole-2-carbonyl-L-arginine (HOE140) did not affect the blood-flow changes caused by the anaphylaxis. These results suggest that 5-hydroxytryptamine and histamine H(2) receptors mediate the initial decrease and the subsequent increase in cutaneous blood flow, respectively, induced by passive cutaneous anaphylaxis in rats.

An improved method for measuring vascular permeability in rat and mouse skin

INTRODUCTION

We have improved a rodent vascular permeability measurement method employing fluorescent dye-labeled bovine serum albumin.

METHODS

The incubation duration for direct fluorescent detection of skin injected with an inflammatory agent was decided based on regression curve parameters with the correlation coefficient obtained from the least squares method.

RESULTS

A suitable incubation time was determined to be 2-6 h. The recovery of FITC-BSA from the skin sample was very good, and the correlation coefficient of the linear regression curve was .99. The linear relation between the previous dye extraction method using brilliant blue 6B and the new and improved fluorescence method was very high. In mice, histamine-induced serum exudation in the back skin increased from 0.31 to 1.25 microg/site in a dose-dependent manner and reached a plateau at 1.25-2.5 microg/site. The serum exudation caused by histamine increased to 10 microg/site and almost reached a plateau at 10-40 microg/site in rats. The time required for the measurement of fluorescence intensity was very short because a microplate reader was used as the measurement apparatus.

CONCLUSION

The improved method is easy to use and sensitive and does not necessitate extraction of dye from the skin.

Pharmacological, pharmacokinetic and clinical properties of olopatadine hydrochloride, a new antiallergic drug

Olopatadine hydrochloride (olopatadine, 11-[(Z)-3-(dimethylamino)propylidene]-6,11-dihydrodibenz[b,e]oxepin-2-acetic acid monohydrochloride) is a novel antiallergic/histamine H1-receptor antagonistic drug that was synthesized and evaluated in our laboratories. Oral administration of olopatadine at doses of 0.03 mg/kg or higher inhibited the symptoms of experimental allergic skin responses, rhinoconjunctivitis and bronchial asthma in sensitized guinea pigs and rats. Olopatadine is a selective histamine H1-receptor antagonist possessing inhibitory effects on the release of inflammatory lipid mediators such as leukotriene and thromboxane from human polymorphonuclear leukocytes and eosinophils. Olopatadine also inhibited the tachykininergic contraction in the guinea pig bronchi by prejunctional inhibition of peripheral sensory nerves. Olopatadine exerted no significant effects on action potential duration in isolated guinea pig ventricular myocytes, myocardium and human ether-a-go-go-related gene channel. Olopatadine was highly and rapidly absorbed in healthy human volunteers. The urinary excretion of olopatadine accounted for not less than 58% and the contribution of metabolism was considerably low in the clearance of olopatadine in humans. Olopatadine is one of the few renal clearance drugs in antiallergic drugs. Olopatadine was shown to be useful for the treatment of allergic rhinitis and chronic urticaria in double-blind clinical trials. Olopatadine was approved in Japan for the treatment of allergic rhinitis, chronic urticaria, eczema dermatitis, prurigo, pruritus cutaneous, psoriasis vulgaris and erythema exsudativum multiforme in December, 2000. Ophthalmic solution of olopatadine was also approved in the United States for the treatment of seasonal allergic conjunctivitis in December, 1996 (Appendix: also in the European Union, it was approved in February 2002).

Effects of olopatadine hydrochloride on the cutaneous vascular hyperpermeability and the scratching behavior induced by poly-L-arginine in rats

Intradermal injections of poly-L-arginine induce cutaneous vascular hyperpermeability and scratching behavior in rats. Recently, we elucidated that the plasma extravasation involved both histamine and substance P, while the scratching behavior involved substance P, but not histamine. This study examined the effects of olopatadine hydrochloride (olopatadine), an antiallergic drug with histamine H1-antagonistic action, on the poly-L-arginine-induced responses. Olopatadine (1 mg/kg, p.o.) significantly inhibited both the plasma extravasation and the scratching behavior, suggesting that its inhibitory effects are mediated by the suppression of neuropeptidergic action as well as histaminic action. Olopatadine seems to be a novel-type drug for the treatment of dermatitis.