Open trial of topical tacalcitol [1α24(OH)2 _D3] and solar irradiation for vitiligo vulgaris: upregulation of c

ARTICLE

Auteur(s) : Ichiro KATAYAMA, Miwa ASHIDA, Aki MAEDA, Kumiko EISHI, Hiroyuki MUROTA, Sang Jae BAE

Department of Dermatology, Nagasaki University School of Medicine, 1-7-1, Sakamoto, Nagasaki, Japan

Article accepted on 25/03/2003

Vitiligo vulgaris is a common skin disease. The clinical response to topical steroid ointment or PUVA therapy is usually poor. Such regimens are generally avoided in the treatment of lesions on the face or in pediatric cases because of the undesirable side effects [1]. Skin grafting is an alternate therapy for vitiligo although grafting of the periorbital lesion is relatively difficult [2]. Therefore we applied tacalcitol [1α24(OH)₂D₃] with or without UV light or solar irradiation, which upregulates NGF β, one of the melanocyte growth factor producers, and mRNA expression by human cultured keratinocytes as reported previously for the possible regeneration of melanocytes in vitiligo [3].

Patients and method

Initial patient

A 12-year old girl was seen in our institution with a depigmented lesion around the right eyelid which had not responded to topical corticosteroid treatment of several months’ duration. In August 1997, topical vitamin D₃, tacalcitol [1α24(OH)₂D₃] was started for vitiliginous skin resulting in follicular repigmentation within 4 months. In June 1998, she noticed marked repigmentation of the vitiliginous skin after experiencing a burning sensation and an erythematous response to several days of solar irradiation. Within one month, most of the vitiliginous lesion had been covered with repigmented skin, except for the margin of the eyelid which did not receive solar irradiation (Fig. 1). A patch test and photopatch test with tacalcitol [1α24(OH)₂D₃] on the normal skin both yielded negative results. An open patch test with tacalcitol [1α24(OH)₂D₃] under solar irradiation also gave a negative result.

Study patients

To confirm the excellent response to combination therapy with topical vitamin D3 ointment and solar irradiation for vitiligo achieved in the initial patients, we conducted an open trial in other patients, most of whom had shown poor clinical responses to the prior topical corticosteroid therapy or PUVA therapy. After obtaining verbal informed consent, 15 cases (9 men and 6 women) with vitiligo were enrolled in this study. The clinical profiles are summarized in the Table I.

Table I. A summary of patients profiles and clinical results in this study

Treatment protocol

Each patient was instructed to sunbathe for 30 minutes within 1 hour after topical application of the tacalcitol [1α24(OH)₂D₃] ointment or cream to the skin lesions every day. Repigmentation of the vitiliginous skin was evaluated every 2 weeks. The clinical effect of the therapy was assessed as follows: no response, poor response (less than 30% clearance), fair response (30-70% clearance), and excellent response (more than 70% clearance).

In vitro investigation

To clarify the mechanism of action of vitamin D3, c-Kit (receptor for c-Kit ligand) mRNA expression by human cultured melanocytes was investigated. Melanocytes were purchased from Cell System (Sanko Junyaku Co., LTD. Osaka, Japan) and cultured in the supplied medium. Various doses of tacalcitol [1α24(OH)₂D₃] (Teijin Pharmaceutical. Co. LTD. Tokyo, Japan) were added to the culture with or without UVB (FL20SE.3, Toshiba Medical Supply, emission spectrum of 275-375 nm peaking at 305 nm), UVA (1J/cm2) (light source; FL32S.BL, Toshiba Medical Supply, Tokyo, Japan, emission spectrum of 300-430 nm peaking at 352 nm) or polarized linear infrared (20J/cm2) (light source; superlizer, Tokyo Iken Co. Ltd., Tokyo, Japan, emission spectrum of 600-1600 nm peaking at 1000 nm) irradiation. In the case of solar irradiation, the culture plate was placed under the sunlight for two minutes. mRNA expression of c-Kit by melanocytes was assayed by RT-PCR at various times. after start of the culture. Primers used for c-kit was as follows [4]:
5’:GAT ACT GTT GTT GCT TTC CGT TCA A
3’:TCA ATT TCT CCA CCT GCT TCG TA (GENE BANK:LO4143).

Results

Fair to excellent clinical responses were obtained in 6 of the 15 patients (Fig. 2). Those achieving fair to excellent responses generally had had vitiligo for less than 5 years (Fig. 3). Repigmentation was observed within 1 month in 4 patients and 2 months in 2 patients. The other patients did not respond to this regimen up to 6 months after the therapy.
Most of those with a favorable clinical response experienced skin irritation with a moderate erythematous response after exposure to solar irradiation before the onset of repigmentation. The patch test or photopatch test with tacalcitol[1α24(OH)₂D₃] performed on nonlesional skin yielded negative results in most patients.
Interestingly, 5 of the 6 patients who showed improvement had not shown a favorable clinical response to the prior topical corticosteroid therapy (Fig. 4).
Three treatment-naive and 4 patients who had received PUVA with or without topical corticosteroid therapy before vitamin D₃ and solar irradiation showed poor clinical responses to the combination therapy as shown in the Table. The responsive lesions were located on both sun-exposed and sun-protected regions (manuscript in preparation).
The results of the in vitro study revealed that tacalcitol [1α24(OH)₂D₃] clearly upregulated the c-Kit mRNA expression by cultured human melanocyte under linear polarized infrared, UVA and solar irradiation, but not under UVB irradiation at the concentration of 10^-10 M. (Fig. 5). UVB itself showed rather strong c-Kit mRNA expression and tacalcitol downregulated its expression at the same concentration. Combination of tacalcitol [1α24(OH)₂D₃] and UV irradiation did not affect NGF mRNA expression by melanocytes. (Fig. 5).

Discussion

Although the clinical response to tacalcitol [1α24(OH)₂D₃] alone was unfavorable in our experience, the combination of solar irradiation and tacalcitol ointment induced marked repigmentation in 2 patients and favorable response in 4 patients.
Recently Yalcin et al. and others reported that combination therapy with topical calcipotriol and PUVA or calcipotriol alone improved vitiligo that had not responded to previous PUVA therapy [5-7]. Our results were similar to theirs, except that we used solar irradiation instead of PUVA, because solar irradiation is more convenient for patients. In contrast to the previous report by Parsad et al. [6], our patients were asked to take solar irradiation within one hour after tacalcitol[1α24(OH)₂D₃] ointment. Most of our patients who exhibited a fair clinical response to the combination therapy had also been resistant to previous PUVA or topical corticosteroid therapy. The reason for these conflicting results is unexplained at present.
Our preliminary experiment suggests that tacalcitol upregulates c-Kit expression by melanocytes under linear polarized infrared irradiation. The enhanced c-Kit expression was more marked under solar irradiation than under UVA or infrared irradiation. Recent reports suggest that c-Kit expression by lesional melanocytes is downregulated in vitiligo [8].
c-Kit ligand binds to c-Kit on the melanocyte cell membrane resulting in melanogenesis. c-Kit also induces melanocyte migration from the neural crest to the skin in the embryonic stage [9]. Therefore, our combination therapy may improve vitiligo lesions through modulation of c-Kit/c-Kit ligand system. The effect on other melanocyte stimulating agents such as endothelin-1 [10], prostaglandin [11], histamine [12] or growth factors [13] should be clarified in future studies.
Apart from the effect on melanocyte growth, vitamin D₃ has been shown to have immunomodulatory effects on T cells or other immunocommpetent cells [14, 15] such as macrophages or neutrophils. Therefore, vitamin D₃ might inhibit T cell mediated-melanocyte destruction as shown in vitiligo during the immunotherapy for melanoma [16]. In our previous study, we have demonstrated that tacalcitol [1α24(OH)₂D₃] downreglates IL8 and RANTES production and upregulates NGF β production by cultured keratinocytes [17]. RANTES is the chemoattractant for T cells and NGF β inhibits the apoptosis of melanocytes. Modulation of the production of these molecules by vitamin D₃ may contribute the resolution of vitiligo.
Recently Ermis O et al. [18] reported that calcipotriol affects the defective Ca^2 + homeostasis of melanocyte function in vitiligo, however we did not have a chance to see Ca^2 + metabolism in the vitiligo lesion in this study. This important issue should be clarified in future work.
Finally narrow band ultraviolet B has been reported to be a useful and well-tolerated therapy for vitiligo [19]. Although we found limited clinical effect after UVB (not narrow band UVB) therapy in our cases, solar irradiation and vitamin D₃ may have a similar effect to narrow band UVB. As reported by Lebwohl M et al. [20], UVA caused reductions in the concentration of calcipotrien, vitamin D₃ ointment has been recommended to apply after UVA exposure in PUVA therapy or to use in the evening in a simple application. UVB but not narrow band UVB might inactivate tacalcitol[1α24(OH)₂D₃] resulting in limited clinical effects of refractory vitiligo.
In conclusion, a combination of vitamin D₃ ointment and solar irradiation is an alternate therapy for steroid or PUVA resistant vitiligo. Upregulation of c-Kit mRNA expression by melanocytes after infrared and vitamin D₃ might be one candidate for the mechanism of action of this therapy.

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