Relationship between Vitamin D and Psoriasis

Psoriasis is a chronic inflammatory disease with immune involvement and increasing of keratinocytes in skin that manifest as dermatitis. Meanwhile, psoriasis is a systemic disease that affected other organs and can increase risk of metabolic disorders and chronic disease. Although, the etiology of psoriasis is not fully revealed but several factors such as genetic, auto-immunity and spiritual condition can affect presentation and development of disease.

Because vitamin D other than diet, is synthesized in the skin so it is proposed that this vitamin can affect cutaneous immune system. With regard to reports of many studies, vitamin D could have anti-proliferative and anti-inflammatory effects on skin diseases such as psoriasis. In many studies it is surveyed effects of topical therapy of vitamin D as adjunctive treatment in psoriasis and in a few of them performed in related to oral supplementation of this vitamin. Thus, it is necessary to represent effectiveness of vitamin D supplementation (as topical or oral) and reveal involvement mechanisms of this vitamin on psoriasis as a inflammatory skin disease.

Keywords:Auto-immunity, Inflammatory disease, Keratinocytes, Psoriasis, Vitamin D

Psoriasis is a chronic autoimmune and inflammatory disease [1]. That is characterized by hyperproliferation of keratinocytes, dysfunction of epidermal barrier in skin lesions and accumulation of activated inflammatory cells [2]. The primary manifestation of psoriasis is revealed on the skin as dermatitis although inflammatory processes may involve other organs [3]. Also, psoriasis is a systemic disease so that other than skin, can increase risk of metabolic disorders such as obesity [4], cardiovascular diseases [5] and even stroke [6]. Psoriasis involves the innate and acquired immunologic systems [7]. This lead to produce so many T-cells and pro-inflammatory cytokines in circulation. The overload T-cells especially T- helper1 and increasing in proliferation of keratinocytes cause development of psoriasis plaques [8]. The prevalence of psoriasis in adulthood is estimated in range between 0.27 % and 11.4 % that related to age, sex, geography, genetic and environmental factors [9].

Psoriasis presented as many kinds include: Plaque Psoriasis (vulgaris), Guttate Psoriasis, Invers Psoriasis, Pustular Psoriasis, Erythrodermic Psoriasis, Nail Psoriasis and Psoriatic arthritis [10]. The etiology of psoriasis is not fully detected but it is thought that several factors affect its development such as genetic, autoimmunity condition, hormonal status and psychosomatic issues [11]. It is proposed that vitamin D has roles related to psoriasis due to synthesized in skin and action on cutaneous immune system [12]. It is reported that vitamin D might act as a modulator of immune and inflammation mechanisms [13]. Vitamin D has many biological functions such as multiplication and differentiation of keratinocytes [14]. However, most studies focused on topical therapy and only a few studies have revealed the effectiveness of oral vitamin D in treatment of psoriasis [10]. Besides, there is controversy in effectiveness of vitamin D supplementation as adjunctive treatment in this disease [13,15,16]. Thus, it is necessary to survey efficacy of vitamin D in management of psoriasis.

Vitamin D is a fat-soluble hormone- like that available for body from diet and synthesize in the skin by exposure to radiation from sunlight [17]. Vitamin D from two manner as Vitamin D3, is transferred to liver for hydroxylation and change to 25 OH D3. This form of D enter in circulation and currently considered regular biomarker of the serum vitamin D level but is not the most active of vitamin unless it transfer to kidneys and change to 1,25(OH)2 D3 or Calcitriol by further hydroxylation [18]. Other than simple diffusion, absorption of calcium and phosphorus in the intestine perform via active transport that do with inducing and making of transport protein by Calcitriol in mucosa (as the most important role) that enhancing of absorption. Then, these minerals participate in several organs such as bones, muscles, brain, and others [18].

In last decade, it is concentrated to functions of vitamin D other than calcium-phosphorus metabolism in bones. It is demonstrated that vitamin D performs different tasks include role in Excretion of insulin from β -cells of pancreas, modulation of Immune system, barrier integrity and permeability of membrane and regulation of keratinocytes proliferation and differentiation [12].

Psoriasis is a inflammatory skin disease with involving of immune system. Dysfunction of immunity in organ lead to activation of lymphocytes T (T-cells) particularly T-helper 1 that produce many cytokines such as interleukin 2, interleukin 6, tumor necrosis factor alpha (TNF-α) and interferon gama (IFN-). These disturbances of immune function make tissue changes and inflammatory skin [19]. One of the most important task of vitamin D is modulation and regulation of cutaneous immune system as inhibition of T cell proliferation [12]. This vitamin inhibits the expression of pro-inflammatory cytokines produced by T lymphocytes [19]. Vitamin D helps to synthesis of glycosylceramides in the skin and via regulate barrier integrity and permeability in this organ that lead to improve of injured tissue [16]. This action due to role of vitamin D in regulation of level of calcium in cell and effect on calcium receptor and activity of phospholipase C enzymes [20]. It is showed that alterations in level of calcitriol and polymorphisms of the vitamin D receptor gene could lead to several disorders and autoimmune diseases, including psoriasis [21,22]. It is reported that level of serum calcitriol [1,25 (OH)2 D3] in psoriasis patients is lower than healthy subjects [23] specially in psoriatic arthritis [24]. Also, It is revealed that serum vitamin D was lower in women than men [25]. In addition, expression of vitamin D receptor decreased in skin of psoriasis patients that lead to lower expression of tight junction proteins [26]. Therefore, low level of vitamin D is inversely associated with predisposing of inflammatory condition [23].

Use of vitamin D in treatment of psoriasis

Attention to vitamin D in treatment of psoriasis have been known since 1985 and effectiveness of this vitamin reported in several studies [25,27]. Thenceforward, physician applied topical form of vitamin D for cure of psoriasis plaque as the first-line medication singly or in combination with topical corticosteroids [28-31]. Also, topical treatment with vitamin D have not any serious side effects in comparison to corticosteroids [13,32]. The therapeutic function of vitamin D as topical perform via mechanism related to its receptors that lead to inhibition of proliferation and differentiation of keratinocyte by increasing intracellular calcium [33]. Also, topical vitamin D may inhibit cytokines such as IL-2, IL-6, and interferon-gamma and via suppress inflammation [34].

Most performed studies in related to effects of vitamin D on psoriasis were in form topical [10]. However, use of oral administration of vitamin D in treatment of psoriasis come back to many years ago. But it is deposited due to probably side effect as hypercalcemia [35]. Indeed, from1985 to the present, only a few research have evaluated the effectiveness of oral vitamin D in treatment of psoriasis and results were controversy so that degree of efficacy of supplementation was not significant in some of them [10]. It was not investigated the optimal dose of oral vitamin D in any study. However, most studies reported that oral vitamin D in within range 0.25 – 2 μg (10 – 80 IU) per day have not obvious side effect. [10]. Of course, it is not reported side effects of vitamin D as oral (systemic) administration with higher doses such as 40000 IU per day [36]. However, no evidence has been reported about the efficacy of the highest doses of oral vitamin D in treatment of psoriasis [10].

Furthermore, Vitamin D treatment is not effective for all patients with psoriasis [35,37,38]. The reviews of studies in use of oral vitamin D in psoriasis were inconclusive and controversial. Thus, it is necessary that more large studies performed to show the efficacy, optimal dose, and side effects of oral vitamin D in patients with psoriasis [10]. Now, topical vitamin D or its analogs such as Calcipotriol apply effectively and safe in treatment of psoriasis without systemic side effects [35,37].

Psoriasis as a inflammatory disease accompany with immune system disturbance and it is presented several kinds. Vitamin D could affect this dysfunction due to its task in immune modulation. Among several kinds of vitamin D supplementary, topical D is more effectiveness than oral form and today it is considered as one of the medications for treatment of psoriasis. However, there is a challenge in apply administration of vitamin D and need to more research for confirming of this effect on psoriasis.

The author has declared no conflict of interest.

It is appreciating the personnel of School of Medical Science, Azad University of Chalus, Iran for their great collaboration and corporation in performing of this study.