ARTICLE
Vitiligo affects men and women equally and can occur at any age. The
etiology of the disease is still unknown [1]. Besides the most popular
autoimmune theory, several groups have recently shown the involvement
of oxidative stress in the pathophysiology of this disease [2, 3]. The
mechanism by which oral psoralens and UV-A radiation (PUVA) stimulate
melanocyte proliferation in vitiligo and other hipopigmentary diseases
is not known [4]. PUVA is immunosuppressive as a result of its effect
on cytotoxic T lymphocytes. This action of PUVA on T lymphocytes could
also be the explanation for the therapeutic effect of PUVA on vitiligo.
Any theory of therapy must explain not only the action on cytotoxic T
lymphocytes, but also the stimulation of melanocyte proliferation and
the migration of melanocytes to the epidermis from the hair follicle [5].
In vivo exposure of human epidermis to solar-stimulated UV-irradiation
causes changes in the enzymic antioxidant defence system which, in turn,
are accompanied by increased levels of oxidative stress [6]. Photosensitizing
agents are also known to generate reactive oxygen species [7]. These problems
may be prevented by the use of antioxidants.
Material and methods
Patients
Thirty patients with active, extensive, and generalized vitiligo, who
were outpatients, were included in the study (16 females and 14 males)
after informed consent was obtained, ensuring that the procedures of PUVA
and vitamin E therapy had been fully explained. The mean age was 29.92
± 15.70 years (range 14-60). The skin phototypes (Fitzpatrick classification)
were types II (n = 4), III (n = 22), and IV (n = 4). Patients were assigned
to receive either only PUVA (first group) or PUVA and vitamin E (900 IU
daily perorally) (second group) for six months. Table
I shows the number, age, sex, and duration of disease of all patients
with vitiligo who were treated with either PUVA vs vitamin E or
only PUVA for six months.
Therapy
The patients in the first group were irradiated three times weekly with
only psoralen (systemically) plus UVA fluorescent tubes (Dermalight 6000)
with the emission spectrum between 315-400 nm. The patients in the second
group were irradiated three times weekly with psoralen plus UVA and they
took vitamin E (900 IU daily). The ultraviolet dose was increased in 20%
increments until erythema developed and according to the patient's tolerance.
Evaluation of the treatment and antioxidant system
The patients were evaluated after three and six months of treatment.
Total body photographs were taken for each patient, including photographs
of the front and back sides of patients in a standard pose. The results
were scored as bad (no improvement or improvement less than 25%), moderate
(improvement between 25% and 74%), and good (75% or more).
All blood and skin samples obtained in the study were picked up 48 hrs
after the last irradiation. The samples of the skin biopsies were used
for lipid peroxidation determination. Lipid peroxidation was measured
as the level of malonaldehyde (end-product of lipid peroxidation) by the
thiobarbituric acid method [8]. The blood cells (erythrocytes) were used
for the determination of superoxide dismutase activity, glutathione peroxidase
activity and catalase activity. Superoxide dismutase activity was determined
by the method described by Podczsay [9]. Glutathione peroxidase was assayed
using Paglia's method with modifications made by Prohaska [10, 11]. Catalase
activity was determined according to the method of Aebi [12]. The base
levels of vitamin E were not determined in this study.
Ethics
The local ethics committee approved the study, and consent was obtained
from each individual.
Statistics
Fisher's exact test, Mann-Whitney U test, Wilcoxon matched pairs test,
and Kruskall-Wallis test were used in statistical analysis.
Results
Six (40%) patients in the first group had good scores, four (26.66%)
had moderate scores, and five (33.33%) bad scores. Nine (60%) patients
in the second group had good scores, three (20%) patients had moderate
scores, and three (20%) had bad scores. Although the number of good clinical
results was higher in the group treated with vitamin E, there was no significant
difference between two groups (p > 0.05) (Table
II).
Epidermal levels of lipoperoxides were evaluated in the affected epidermis
of the patients in both groups. Before treatment, the mean value of lipoperoxides
in the first group was 1.34 ± 0.50, but 1.19 ± 0.38 in the second
group (p > 0.05). After treatment, the mean value of lipoperoxides
in the first group was 1.79 ± 0.47, and 1.44 ± 0.52 in the second
group (p > 0.05). Statistical analysis revealed a significant difference
between the levels of lipoperoxides before and after treatment in the
first group (p < 0.05), but there was no significant difference between
the levels of lipoperoxides before and after treatment in the second group
(p > 0.05). These results show that there was a significant difference
in the oxidative stress generated from PUVA therapy between two groups
(Table III).
Before, during and after treatment, the levels of superoxide dismutase
SOD, catalase (CAT), and glutathione peroxidase (GSH-Px) activities in
both groups were measured as shown in Table
IV. There was no statistically significant difference between the
two groups (p > 0.05).
The patients in both groups exhibited tolerable adverse effects including
minimal erythema, nausea, and headache.
Discussion
Vitiligo is currently considered a depigmented dermatosis with several
options for treatment [5, 13-16]. Currently best studied and therefore
most applied are oral and topical psoralen plus UV-A (PUVA), phenylalanine
plus UV-A, oral and topical khellin plus UV-A, UV-B narrowband and broadband
therapy, and corticosteroids (oral, topical, and intralesional) [16].
When patients exhibit generalized vitiligo, oral psoralen plus UV-A is
recommended [16, 17].
Photobiological effects of psoralens in humans are numerous. They photosensitize
erythema, hyperpigmentation, and skin aging, and affect the immune system.
Molecular mechanisms of photochemical reactions of psoralens with substrates
are also numerous [18]. A single dose of UV-irradiation was found to result
in a transient reduction in SOD activity and this was followed by increased
amounts of conjugated diene double bonds, an index for oxidative stress.
In vivo exposure of human epidermis to solar-simulated UV-irradiation
causes changes in the enzymic antioxidant defence system which, in turn,
are accompanied by an increased level of oxidative stress [6]. Reactive
oxygen species are capable of bleaching constitutional melanin and causing
membrane lysis through lipid peroxidation reactions [2]. The use of antioxidants
inhibits these effects of UV-irradiation, and antioxidants can be used
as a tool for improvement of psoralene photochemotherapy [18].
In vitiligo patients, the epidermal levels of ubiquinol, vitamin E,
reduced glutathione (GSH), and CAT activity were reduced. An imbalance
of the intracellular redox status and a significant depletion of enzymatic
and non-enzymatic antioxidants are seen in the epidermis of vitiligo patients,
and represent the fingerprint of an abnormal oxidative stress leading
to epidermal cell injury [19]. PUVA treatment leads to depletion of GSH
levels in the skin [20]. A decreased GSH is associated with strong decreases
in tyrosine hydroxylase activity and melanin production in the skin [21].
Both alpha-tocopherol and GSH-deficiency potentiate the susceptibility
of the cells to oxidative membrane injury [22].
However, the blood levels of vitamin E, SOD,
GSH, GSH-Px, lipoperoxides and polyunsaturated fatty acids of phospholipids
in vitiligo patients are not significantly different from those of healthy
age matched controls [23].
In our study, epidermal oxidative stress in the patients in the first
group showed a significantly greater increase than did those of the second
group. The basis of this process is the reaction of psoralen-photosensitized
oxidation of unsaturated lipids and the impairment of barrier functions
of biomembranes [18]. This epidermal oxidative stress may be the cause
of premature melanocyte cell death. In contrast, epidermal oxidative stress
in the patients in the second group did not change significantly. Our
hypothesis is that the oxidative stress caused by the photochemical reaction
in these patients was inhibited by vitamin E as an antioxidant.
An imbalance in the antioxidant system and free radical-mediated damage
are initial pathogenetic events in melanocyte degeneration in vitiligo
[3]. Therefore, to achieve manifest repigmentation and to improve psoralen
photochemotherapy, antioxidants may be kept in mind as an adjuvant in
the treatment of vitiligo patients. Vitamin E may prevent an oxidative
distress resulting from PUVA therapy, and may improve the number of good
responses to PUVA, although this improvement is not significant statistically
and clinically in vitiligo patients in our study.
Article accepted on 25/9/01
CONCLUSION
Acknowledgements
We thank to Cumhuriyet University Research Fund for their financial
support.
REFERENCES
1. Ortonne JP, Bose SK. Vitiligo: where do we stand? Pigment
Cell Res 1993; 8: 61-72.
2. Schallreuter KU, Wood JM, Berger J. Low catalase levels in
the epidermis of patients with vitiligo. J Invest Dermatol 1991;
97: 1081-5.
3. Maresca V, Roccella M, Roccella F, Camera E, Del Porto G,
Passi S, Grammatico P, Picardo M. Increased sensitivity to peroxidative
agents as a possible pathogenetic factor of melanocyte damage in vitiligo.
J Invest Dermatol 1997; 109: 310-3.
4. Hoenigsman H, Fitzpatrick TB, Pathak MA. Oral photochemotherapy
with psoralens and UVA (PUVA): principles and practice. In: Fitzpatrick
TB, Eisen AZ, Wolff K, Freedberg IM, Austen KF, eds. Dermatology in
General Medicine. New York: McGraw Hill Book Co, 1993: 1743-4.
5. Fitzpatrick TB. Mechanisms of phototherapy of vitiligo. Arch
Dermatol 1997; 133: 1591-2.
6. Punnonen K, Autio P, Kiistala U, Ahotupo M. In vivo
effects of solar-stimulated ultraviolet irradiation on antioxidant enzymes
and lipid peroxidation in human epidermis. Br J Dermatol 1991;
125: 18-20.
7. Dalle Carbonare M, Pathak MA. Skin photosensitizing agents
and the role of reactive oxygen species in photoaging. J Photochem
Photobiol B 1992; 14: 105-24.
8. Buege JA, Aust SD. Microsomal lipid peroxidation. Methods
Enzymol 1978; 52: 302-10.
9. Podczasy JS, Wei R. Reduction of iodonitrotetrazolium violet
by superoxide radicals. Biochem Biophys Res Comm 1988; 150: 1294-301.
10. Paglia DE, Valentine WN. Studies on the quantitative and
qualitative chracterization of erythrocyte glutathione peroxidase. J
Lab Clin Med 1967; 70: 158-69.
11. Prohaska JR, Oh SH, Hoekstra WG, Ganther HE. Glutathione
peroxidase: inhibition by cyanide and release of selenium. Biochem
Biophys Res Comm 1977; 74: 64-71.
12. Aebi H. Catalase in vitro. Methods in Enzymology
1984; 105: 121-6.
13. Camacho F, Mazuecos J. Treatment of vitiligo oral end topical
phenylalanine: 6 years of experience. Arch Dermatol 1999; 135:
216-7.
14. Westerhof W, Nieuweboer-Krobotova L. Treatment of vitiligo
with UV-B radiation vs topical psoralen plus UV-A. Arch Dermatol
1997; 133: 1525-8.
15. Skouge J, Warwick L, Morison L. Vitiligo treatment with a
combination of PUVA therapy and epidermal autografts. Arch Dermatol
1995; 131: 1257-8.
16. Njoo MD, Spuls PI, Bos JD, Westerhof W, Bossuyf FM. Nonsurgical
repigmentation therapies in vitiligo. Arch Dermatol 1998; 134:
1532-40.
17. Hann SK, Cho MY, Im S, Park YK. Treatment of vitiligo with
oral 5-methoxypsoralen. J Dermatol 1991; 18: 324-9.
18. Potapenko AY, Kyagova AA. The application of antioxidants
in investigations and optimization of photochemotherapy. Membr Cell
Biol 1998; 12: 269-78.
19. Passi S, Grandinetti M, Maggio F, Stancato A, De Luca C.
Epidermal oxidative stress in vitiligo. Pigment Cell Res 1998;
11: 81-5.
20. Wheeler LA, Aswad A, Connor MJ, Lowe N. Depletion of cutaneous
glutathione and the induction of inflammation by 8-methoxypsoralene plus
UVA radiation. J Invest Dermatol 1986; 87: 658-62.
21. Benathan M, Virador V, Furumura M, Kobyashi N, Panizzon RG,
Hearing VJ. Co-regulation of melanin precursors and tyrosinase in human
pigment cells: roles of cysteine and glutathione. Cell Mol Biol
1999; 45: 981-90.
22. Bekyarova G, Yankova T. Alpha-tocopherol and reduced glutathione
deficiency and decreased deformability of erythrocytes after thermal skin
injury. Acta Physiol Pharmacol Bulg 1998; 23: 55-9.
23. Picardo M, Passi S, Morrone A, Grandinetti M, Di Carlo A,
Ippolito F. Antioxidant status in the blood of patients with active vitiligo.
Pigment Cell Res 1994; 7: 110-5.
|
Printable version
