Serum Levels of Tumor Necrosis Factor - alpha in Patients With Psoriasis.

Background: Psoriasis can be described as a T-cell-mediated disease, with a complex role for variety of cytokines and other factors. Among the inflammatory molecules influencing the keratinocites, TNF-α appears critical in sustaining most of the clinical manifestations of psoriasis. It is postulated that changes in cytokine production both locally and systemically could be useful in monitoring disease activity. Objective: The aim of the study was to evaluate serum levels of tumor necrosis factor alpha (TNF-α) in patients with psoriasis and the healthy subjects, and also to assess a possible association between TNF-α, clinical type and severity of disease.
Methods: We studied the levels of serum TNF-α in 60 patients with psoriasis and in the serum of helthy 20 controls. According to the clinical type of disease, patients with psoriasis were divided into four groups: chronic plaque psoriasis (CPP), erythrodermic psoriasis (EP), pustular psoriasis (PP) and psoriatic arthritis (PA). Blood samples were collected from all psoriasis patients and from healthy control subjects. Serum level of TNF-α were measured by an enzyme-linked immunosorbent assay (ELISA) technique. The severity of CPP was assessed by Psoriasis Area and Severity Index (PASI).
Results: Serum levels of TNF-α in patients with psoriasis were significialy higher than in the control group (3.25+1.74 pg/mL vs 0.20+0.01pg/mL, respectively). Significantly elevated serum TNF-α was in patients with PP type (7.39+6.92 pg/mL). There was statistically significant difference between the mean level of TNF-ɑ compared to the clinical type of psoriasis (p<0.05). The mean PASI score in patients with CPP was 0.56±12.45. It was not found statistically significant correlation between serum level of TNF-ɑ and PASI score in patients with CPP (p>0,05).
Conclusion: Our results have demonstrated the imortance of determining serum levels of TNF-ɑ in patients with psoriasis. Further investigations are required to clarify the pathogenic role and clinical significance of TNF-ɑ, and these findings may provide important clues to assist in the development of new therapeutic strategies for patients with psoriasis.

BACKGROUND

Psoriasis is a common inflammatory and hyperproliferative skin disease wich affecting approximately 2% to 3% of the world’s population (1). The disease is classified into several clinical types of which the most common is chronic plaque psoriasis and it occurs in 80% to 90% of patients with psoriasis (2). Psoriasis has a multifactorial ethyology, including genetic predisposition, environmental factors, and vascular and immune system disturbances. Although the etiopathogenesis of the disease is still unclear, there is evidence that many of cytokines released by keratinocytes and inflammatory leukocytes may contribute to the induction or persistence of the inflammatory process in psoriasis. It is assumed that the disease starts with the activation of T-lymphocytes under the influence of anknown antigen, which leads to secretion of number of cytokines which are activated by T-lymphocytes, inflammatory cells and keratinocytes. Activated T-lymphocytes release the tumor necrosis factor-α, gamma interferon (IFN-γ) and other cytokines (3). Chemokines, which are produced consequently as a response to IFN-γ, TNF-α and probably other cytokines, also play a role in recruiting leukocytes to areas of inflammation. It is postulated that changes in cytokine production both locally and systemically could be useful in monitoring disease activity.

Tumor necrosis factor-alpha is thought to play a kay role in the pathogenesis of psoriasis on account of its immunomodulatory properties. In psoriasis, TNF-α promotes innate immune cell activation and trafficking to the skin which results in accelerated keratinocyte proliferation (4). TNF-α induces production of intercellular adhesion molecule-1 (ICAM-1) by keratinocytes, as well as IL-8 by keratinocytes, dermal fibroblasts, and endothelial cells (5-7) which is chemotactic for neutrophils and lymphocites. It also increases the rate of secretion of proinflammatory cytokines such as IL-1 and IL-6 by keratinocytes (8-9). Althought it is well known that multiple cytokines simultaneously play a role in psoriasis, many authors have measured only one particular cytokine. Many studies have revealed the elevated concentration of TNF-α in serum of patients with psoriasis, as well as correlation between the levels of serum TNF-α and severity of disease (10-11). TNFα was found to be more useful than the other tested cytokines as a follow–up marker for monitoring disease severity (12).

OBJECTIVE

The aim of our study was to evaluate serum levels of TNF-α in psoriatic patients and healthy subjects, and also to assess the possible correlation between serum levels of TNF-α, clinical type and severity of psoriasis.

PATIENTS AND METHODS

The study included 60 patients with psoriasis (27 female and 33 males; median age 52.2). The planned research is conducted on the basis of the usual approaches the subject method history and objective medical examination. The patients who had recived any topical or systemic treatment within previous 3 months were excluded from the study, as well as patients with any diseases based on the immune pathomechanism, which could influence serum concentracions of TNF-α. According to the clinical type of psoriasis, patients were divided into four groups: CPP (n=42, 70.0%) patients with chronic plaque psoriasis, EP (n=9, 15.0%) patients with erythrodermic psoriasis, PP (n=6, 10.0%) pustular psoriasis and PA (n=3, 5.0%) psoriatic arthritis. The control group consist of 20 generaly healthy people (13 female and 7 male, median age 47.4). The skin lesion severity of CPP, including erythema, induration, scales, and surface, was assessed with the use of Psoariasis Area and Severity Index (PASI) (13). Serum TNF-α levels were measured by enzyme-linked immunosorbent assay (ELISA) technique, using Quantikinine Human TNF-α Immunoasay (R&D System, Minneapolis, MN, USA). Briefly, this assay empoys the quantitative sandwich enzyme immunoassay technique. Standards and samples are pipetted into the wells and any TNF-α present is bound by the immobilized antibody. After washing away any unbound substances, an enzyme-linked polyclonal antibody specific for TNF-α is added to the wells. Folowing a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of TNF-α bound in the initial step. The color development is stopped and the intensity of the color is measured. The PASI scores of patients with plaque psoriasis and their correlation with serum TNF-α were evaluated. Statistical analysis of the data was perfomed using SPSS Version 17. The data are expressed as mean + standard deviation. The test distribution was done by Kolmogorov-Smirnov test, and copmarations mean values between groups were performed by t-test. Pearson’s correlation coefficient was used in correlation analyses. The data were considered statistically significant if p values were less than 0.05.

All subjects gave their informed consent in accordance with the requirements of the Institutional Ethical Committee. This study was conducted in accordance with the guidelines of the Declaration of Helsinki, with the participant’s rights and safety taking precedence.

RESULTS

The study group comprised of 60 patients (27 female and 33 males; the mean age of the patients was 52.2 years, ranging from 14 to 85 years), and 20 healty controls (13 female and 7 male, the mean age 47.40 years, ranging from 21 to 75 years). There were no significant difference in age and female/male ratio between the patients and controls (p>0.05). In the total of patients with psoriasis there were 42 of them with CPP clinical type, 9 patients with EP, 6 patients had PP and 3 patients had PA. The mean duration of psoriasis was 12.9+11.9 (range 1-516 months). Serum levels of TNF-α in patients with psoriasis were significialy higher than in the control group (3.25+1.74 pg/mL vs 0.20+0.01pg/mL, respectively).

Significantly elevated serum TNF-α was in patients with PP type (7.39+6.92 pg/mL), compared with those suffering from CPP (2.98+1.90 pg/mL), patients with EP (2.88+2.11 pg/mL), and in patients with PA type by which TNF-α was undetectable (.00+.00 pg/mL). There was statistically significant difference between the mean level of TNF-ɑ compared to the clinical type of psoriasis (p<0.05). In the total of 42 patients with CPP type, 36 (85.71%) had mild disease (PASI<50) and 6 (14.29%) patients had severe form of disease (PASI>50). The mean PASI score in patients with CPP was 0.56±12.45. It was not found statistically significant correlation between serum level of TNF-ɑ and PASI score in patients with CPP (p>0,05).

DISCUSSION

Psoriasis can be described as a T-cell mediated disease, with a complex role for variety of cytokines and other factors. It has been hipothesized to be an immune-mediated disorder in which the excessive reproduction of keratinocytes is due to cytokine such as interferon gamma and tumor necrosis factor secreted by infiltrating CD4+ and CD8+ T cells and natural killer cells (14). The serum cytokine concentration are altered by several process like the production, tissue/cellular deposition, degradation, and elimination of these molecules; futhermore other tissue sources of cytokines production might exist beside the circulating T cells. The noted cytokine, chemokine and cellular interactions may contribute to the self-perpetuation of the type 1 pathway, which can in turn be correlated with the chronic nature of psoriasis.

TNF-α is a multifunctional proinflammatory cytokine which has been implicated in the pathogenesis of several chronic inflammatory disorders with an autoimmune component. Among the inflammatory molecules influencing the keratinocites, TNF-α appears critical in sustaining most of the clinical manifestations of psoriasis, at both the joint and skin localizations (15). However, this cytokine not only acts as mediator of immunity and inflammation, but also affects not-immune responses within tissues such as cell proliferation and differentiation (16).

TNF-α is produced in the skin by keratinocytes, melanocytes, Langerhans cells, activated T cells, NK cells, and mast cells. A metalloproteinase known as TACE (TNF-α converting enzyme) is necessary for the release of TNF-α from the T cells. TNF-α acts autocrine, stimulating its own production, as well as paracrine, inducing the formation of numerous cytokines and other proinflammatory mediators in neighboring cells (17). It is considered that TNF-α contributes to the pathogenesis of psoriasis through its ability to promote immune cells on skin and in the same time provokes the proliferation of keratinocytes (18). In the involved skin of psoriasis TNF-α, TNF-receptor 1,- receptor 2 are upregulated in dermal blood vessels (19). In addition, increased serum levels of TNF-α in patients with psoriasis compared with normal controls has been reported, thereby confirming the pathogenic role of this cytokine in psoriasis (20).

The results presented in our study demonstrate that the mean serum levels of TNF-α were significantly elevated in psoriatic patients in comparison with healthy subjects. Our results are consistent with the findings of Verghese et al. (21) who found highly significant difference in TNF-α level between patients with psoriasis and controls (21). When it comes to the study of Kyriakou at al. (22), they found that serum levels of TNF-α in psoriatic patients were significantly higher compared to healthy controls, and they also concluded that levels of TNF-α were higher in patients with psoriatic changes both on skin and nails, than by those which had only skin changes (22). Abdel-Hamid et al. (23) reported the significantly elevated serum levels of TNF-α in patients with chronic plaque psoriasis and active skin lesions, as well as the correlation between serum TNF-α levels and severity of disease according to the PASI test (23). Our study also found increased serum TNF-α in patients with CPP, but without statistically significant correlation between mean serum levels of TNF-ɑ and PASI score (p>0.05). Also, similarly to our results, Ozer et al. (24) demonstrated that the levels of TNF-α, IFN–γ, IL-6, IL-8, IL-12, and IL-18 in serum are significantly elevated in patients with active psoriatic lesions than by healthy control. Furthermore, high levels of these cytokines are in correlation with clinical severity of psoriasis and they concluded that the measuring serum levels of these cytokines can be objective parameter for disease severity (24).

However, serum cytokine levels do not necessarily reflect local regional activity and the measurement should be performed repeatedly during the disease course.

CONCLUSION

The curent study underscores the imortant role of TNF-α in the development of psoriasis and it suggests that TNF-α might be a useful for clinical evaluation of psoriasis severity. Further investigations are required to clarify the pathogenic role and clinical significance of TNF-α, and these findings may provide important clues to assist in the development of new therapeutic strategies for patients with psoriasis.

Table 1.

Value of serum TNF-alpha with regards to study groups

Study Groups	N	X (pg/ml)	SD	SEM	Minimum (pg/ml)	Maximum (pg/ml)
Psoriasis	60	3.25	1.74	1.12	0.01	43.99
Control	20	0.20	0.01	0.003	0.16	0.24
F=1.100; p=0.013

Table 2.

The mean value of serum TNF-alpha compared with clinical type of psoriasis

Psoriasis		N	X (pg/ml)	SD	SEM	Minimum(pg/ml)	Maximum(pg/ml)
Clinical type of psoriasis	Chronic plaque p.	42	2.98	1.90	1.21	.00	39.80
	P. erythrodermica	9	2.88	2.11	1.70	.00	15.39
	P. pustulosa	6	7.39	6.92	1.31	.00	43.99
	P. arthropatica	3	.00	.00	.00	.00	.00
	F=1.209; p=0.016