Portal de Periódicos da CAPES

P75 Plays a Key Role in the Induction of the Sprouting of Sensory Nerve Fibers in Inflamed Skin

2007; Elsevier BV; Volume: 127; Issue: 8 Linguagem: Inglês

10.1038/sj.jid.5700806

1523-1747

Manabu Taniguchi, Shinsuke Matsuzaki, Masaya Tohyama,

Food Allergy and Anaphylaxis Research

nerve growth factor picryl chloride (2,4,6-trinitrochlorobenzene) TO THE EDITOR In hyperkeratosis and acanthosis, peripheral branches of sensory nerves increase remarkably in number, particularly in the epidermis of inflamed skin (Mihm et al., 1976Mihm Jr, M.C. Soter N.A. Dvorak H.F. Austen K.F. The structure of normal skin and the morphology of atopic eczema.J Invest Dermatol. 1976; 67: 305-312Crossref PubMed Scopus (298) Google Scholar; Pincelli et al., 1990Pincelli C. Fantani F. Massimi P. Girolomoni G. Seidenari S. Giannetti A. Neuropeptides in skin from patients with atopic dermatitis : an immunohistochemical study.Br J Dermatol. 1990; 122: 745-750Crossref PubMed Scopus (143) Google Scholar; Tobin et al., 1992Tobin D. Nabarro G. de la Faille H.B. van Vloten W.A. Schuurman H.-J. Increased number of immuno-reactive nerve fibres in atopic dermatitis.J Allergy Clin Immunol. 1992; 90: 613-622Abstract Full Text PDF PubMed Scopus (189) Google Scholar; Ostlere et al., 1995Ostlere L.S. Cowen T. Rustin M.H.A. Neuropeptides in the skin of patients with atopic dermatitis.Clin Exp Dermatol. 1995; 20: 462-467Crossref PubMed Scopus (114) Google Scholar). It has been supposed that nerve growth factor (NGF) secreted from keratinocytes in inflamed skin may induce the sprouting of the neurites of sensory fibers (Dou et al., 2006Dou Y.C. Hagströmer L. Emtestam L. Johansson O. Increased nerve growth factor and its receptors in atopic dermatitis: an immunohistochemical study.Arch Dermatol Res. 2006; 298: 31-37Crossref PubMed Scopus (99) Google Scholar) because of an increase in both NGF expression in the keratinocytes (Kinkelin et al., 2000Kinkelin I. Motzing S. Koltenzenburg M. Brocker E.B. Increase in NGF content and nerve fiber sprouting in human allergic contact eczema.Cell Tissue Res. 2000; 302: 31-37Crossref PubMed Scopus (85) Google Scholar; Takano et al., 2005Takano N. Sakurai T. Kurachi M. Effects of anti-nerve growth factor antibody on symptoms in the NC/Nga mouse, atopic dermatitis model.J Pharmacol Sci. 2005; 99: 277-286Crossref PubMed Scopus (82) Google Scholar; Tanaka and Matsuda, 2005Tanaka A. Matsuda H. Expression of nerve growth factor in itchy skins of atopic NC/NgaTnd mice.J Vet Med Sci. 2005; 67: 915-919Crossref PubMed Scopus (48) Google Scholar) and cutaneous innervation in the epidermis in the inflamed skin (Horiuchi et al., 2005Horiuchi Y. Bae S. Katayama I. Nerve growth factor (NGF) and epidermal nerve fibers in atopic dermatitis model NC/Nga mice.J Dermatol Sci. 2005; 39: 56-58Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar). The NGF effect may occur via low-affinity receptors (p75) and high-affinity receptors (TrkA), although direct evidence for this is lacking. This study clearly demonstrates, by using p75 knockout mice, that sprouting of sensory fibers in the epidermis and hyperkeratosis and acanthosis of the inflamed skin are induced by an NGF–p75 pathway. Five female mice with a C57BL/6j background and p75 gene mutation (Lee et al., 1992Lee K.F. Li E. Huber L.J. Landis S.C. Sharpe A.H. Chao M.V. Jaenisch R. Targeted mutation of the gene encoding the low affinity NGF receptor p75 leads to deficits in the peripheral sensory nervous system.Cell. 1992; 69: 737-749Abstract Full Text PDF PubMed Scopus (801) Google Scholar) (Jackson Laboratory, Maine) were used in this study. The anterior abdominal skin was painted with 100 μl of a 5% picryl chloride (PC) solution (Tokyo Kasei Kogyo, Tokyo, Japan) for the initial sensitization. The cutaneous reaction in the sensitized C57BL/6j and p75 knockout mice was evoked by repeated paintings of both ears with 15 μl of 1% PC solution. Controls received repeated paintings of the ears with 15 μl of solvent without the PC. The PC challenge was repeated once a week for 4 weeks, followed by three times per week, 10 times in total, from 7 days after the initial sensitization. Histochemistry for substance P, protein gene product 9.5, NGF, and p75 was then performed. The specificity of the immunoreaction for substance P and NGF was confirmed by the absorption test. Specificity for p75 immunoreaction was checked in p75 knockout mice (Figures 1g, h and 2h, i). As a preliminary experiment, PC treatment was found to cause inflammation of the skin of two male NC/Nga Tnd Cr1j mice. All animal experiments were carried out in accordance with a protocol approved by the institutional Animal Care and Use Committee of Osaka University.Figure 2The histological analysis of the epidermis in p75 knockout mice following PC treatment. (a and b) The histological change of the epidermis (auricle) of p75 knockout mice (a) without PC treatment and (b) with PC treatment, stained by hematoxylin. (c) A marked hyperkeratosis and acanthosis was identified in the epidermis of C57BL/6 mice with the PC treatment. (b) However, in the p75 knockout mice with PC treatment, hyperkeratosis and acanthosis was remarkably inhibited. Bar=50 μm. Changes in the immunoreactivity for (d and e) substance P, (f and g) NGF, and (h and i) p75 in the epidermis (auricle) of the p75 knockout mice (d, f, and h) without PC treatment and (e, g, and i) with PC treatment are shown. (d and e) No substance P fibers were found in either the epidermis or dermis of either PC-treated or non-treated mice. In the epidermis of p75 knockout mice, immunoreactivity for NGF was seen in the keratinocytes of the epidermis (f) without PC treatment and (g) with PC treatment. Expression of NGF in the epidermis was stronger in the PC-treated mice than in non-PC-treated mice. Similarly, in the p75 knockout mice, no immunoreactivity for p75 was seen in the keratinocytes or sensory nerve fibers (h) without PC treatment or (i) with PC treatment. Bar=20 μm.View Large Image Figure ViewerDownload (PPT) PC treatment on the C57BL/6 mouse skin resulted in a remarkable hyperkeratosis and acanthosis (Figure 1). Figure 1a–d shows the changes of the localization of substance P fibers and protein gene product 9.5 fibers in the epidermis of C57BL/6 mice after PC treatment, which caused sprouting of sensory fibers in the epidermis of the inflamed skin (Figure 1b and d). Figure 1e–h shows the alteration of NGF and p75-like immunoreactivity in the PC treatment C57BL/6 mice. NGF was weakly expressed in the keratinocytes of C57BL/6 mice without the PC treatment (Figure 1e). In the PC-treatment mice, immunoreactivity in the keratinocytes increased in number in the epidermis (Figure 1f). No NGF-positive fibers were seen in the normal or inflamed skin. The alteration of p75 expression in the keratinocytes was similar to that found with NGF (Figure 1g and h). The most remarkable change found in the expression of p75 in the inflamed skin was the presence of a number of p75-positive fibers in the epidermis (Figure 1h), where no p75-labeled fibers were seen in the normal epidermis (Figure 1g inset). In contrast to C57BL/6 mice, in the p75 knockout mice, hyperkeratosis and acanthosis were inhibited remarkably after PC treatment (Figure 2a–c). In addition, no sprouting of substance P fibers was identified in the epidermis in p75 knockout mice, both with and without PC treatment (Figure 2d and e). PC treatment of p75 knockout mice failed to increase the number of NGF-expressing keratinocytes compared with the PC-treated wild-type mice (Figure 2f and g). In the epidermis of p75 knockout mice with and without PC treatment, p75 expression was not seen in the skin, including the keratinocytes and sensory fibers (Figure 2h and i). Inflammation causes hyperkeratosis, acanthosis, and sprouting of sensory nerve fibers. This study revealed the upregulation of NGF and p75 in the keratinocytes and the existence of p75-positive sprouting nerve fibers in the epidermis of the inflamed skin. These findings strongly suggest that hyperkeratosis, acanthosis, and sprouting of the sensory fibers in the epidermis are attributable to the NGF-p75 pathway. In fact, we demonstrated that in the p75 knockout mice, even under the PC treatment, sprouting of sensory fibers could not be identified and hyperkeratosis and acanthosis were inhibited remarkably. These findings indicate that hyperkeratosis, acanthosis, and sprouting of the sensory fibers in the epidermis in the inflamed skin are induced mainly by the NGF-p75 pathway in the epidermis. In inflamed skin, both NGF and TrkA are expressed in the increased keratinocytes (Dou et al., 2006Dou Y.C. Hagströmer L. Emtestam L. Johansson O. Increased nerve growth factor and its receptors in atopic dermatitis: an immunohistochemical study.Arch Dermatol Res. 2006; 298: 31-37Crossref PubMed Scopus (99) Google Scholar). In addition, a significant increase of keratinocytes was seen in the p75 knockout mice (Figure 2a and b). Accordingly, it is possible that the NGF-TrkA pathway is partly involved in hyperkeratosis and acanthosis in the inflamed skin (Raychaudhuri et al., 2004Raychaudhuri S.P. Mrinmoy S. Helena W. Smriti K.-R. K252a, a high-affinity nerve growth factor receptor blocker, improves psoriasis: an in vivo study using the severe combined immunodeficient mouse-human skin model.J Invest Dermatol. 2004; 122: 812-819Crossref PubMed Scopus (75) Google Scholar). In any case, TrkA knockout mice may help to resolve this problem. The findings concerning the expression of p75 in epidermis, not only in normal skin but also in skin with cutaneous inflammation, are controversial. Previous studies reported that basal keratinocytes are immunoreactive for p75 in normal human skin, decreasing the expression under inflammation (Johansson et al., 2002Johansson O. Liang Y. Emtestam L. Increased nerve growth factor and tyrosine kinase A-like immunoreactivities in prurigo nodularis skin – an exploration of the cause of neurohyperplasia.Arch Dermatol Res. 2002; 293: 614-619Crossref PubMed Scopus (76) Google Scholar; Dou et al., 2006Dou Y.C. Hagströmer L. Emtestam L. Johansson O. Increased nerve growth factor and its receptors in atopic dermatitis: an immunohistochemical study.Arch Dermatol Res. 2006; 298: 31-37Crossref PubMed Scopus (99) Google Scholar). However, this study showed that the p75 expression in keratinocytes increased after PC treatment (Figure 1g and h). On the other hand, as to sensory fibers, Dou et al., 2006Dou Y.C. Hagströmer L. Emtestam L. Johansson O. Increased nerve growth factor and its receptors in atopic dermatitis: an immunohistochemical study.Arch Dermatol Res. 2006; 298: 31-37Crossref PubMed Scopus (99) Google Scholar and Johansson et al., 2002Johansson O. Liang Y. Emtestam L. Increased nerve growth factor and tyrosine kinase A-like immunoreactivities in prurigo nodularis skin – an exploration of the cause of neurohyperplasia.Arch Dermatol Res. 2002; 293: 614-619Crossref PubMed Scopus (76) Google Scholar found an increase of p75 fibers in the dermis but failed to demonstrate them in the epidermis, although other authors confirmed the presence of sprouting sensory fibers in the epidermis (Ostlere et al., 1995Ostlere L.S. Cowen T. Rustin M.H.A. Neuropeptides in the skin of patients with atopic dermatitis.Clin Exp Dermatol. 1995; 20: 462-467Crossref PubMed Scopus (114) Google Scholar; Chan et al., 1997Chan J. Smoller B.R. Raychauduri S.P. Jiang W.Y. Farber E.M. Intraepidermal nerve fiber expression of calcitonin gene-related peptide, vasoactive intestinal peptide and substance P in psoriasis.Arch Dermatol Res. 1997; 289: 611-616Crossref PubMed Scopus (76) Google Scholar). In contrast, Bull et al., 1998Bull H.A. Leslie T.A. Chopra S. Dowd P.M. Expression of nerve growth factor receptors in cutaneous inflammation.Br J Dermatol. 1998; 139: 776-783Crossref PubMed Scopus (45) Google Scholar described a decrease of p75 fibers in the inflamed dermis. We have detected the sprouting of p75 fibers in the epidermis together with an increase in the number of p75 fibers in the dermis during inflammation. The discrepancy among these studies might be attributed to the different species or fixation methods used. The authors state no conflict of interest. We thank A. Arakawa, Y. Ohashi, and E. Moriya for technical assistance. This work was supported by the 21st Century COE project and Health Science Research Grants from the Ministry of Health, Welfare and Labour of Japan.