Altered serum uric Acid level in lichen planus patients.

BACKGROUND: Lichen planus (LP) is a common disorder whose etiopathogenesis is not clear. Recently, it has been suggested that increased reactive oxygen species (ROS) play important roles in the underlying mechanism of LP.
OBJECTIVES: The principal aim of this study was to evaluate serum uric acid (UA) levels as a measure of the antioxidant defense status in LP patients.
METHODS: Serum UA levels were determined in 58 LP patients and 61 controls.
RESULTS: Serum UA levels were significantly decreased in patients with respect to controls. Moreover, serum UA level was decreased according to increasing duration of disease.
CONCLUSIONS: The results of our study suggest that LP is associated with decrease of UA levels in serum. UA may be a potential, useful biomarker of antioxidant status in LP for elaboration of treatment strategy and monitoring.

What was known?

Free radicals have an important role in the underlying mechanism of LP.

Introduction

Lichen planus (LP) is a subacute to chronic, inflammatory, papulosquamous disorder characterized by typical lesions. Small, shiny, flat-topped, polygonal, faintly erythematous to violaceous papules that may coalesce into plaques involve the skin, mucous membrane, and nail. LP can clinically present in various forms including classical, hypertrophic, actinic, annular, follicular, eruptive, and linear types. It affects all races and occurs usually from 30 to 70 years of age.[1]

An abnormal immune response is probably the basis of this disease and the pathogenesis includes lymphocytic infiltration and keratinocyte necrosis.[2] Recently, it has been suggested that free radicals have an important involvement in the underlying mechanism of various skin diseases.[3] In LP, the inflammatory cellular infiltrate, which consists mainly of CD4+ lymphocytes, is a well-known source of reactive oxygen species (ROS).[4] In high concentrations ROS damages endothelial cells, and subsequently intercellular adhesion molecule (ICAM) 1 is further upregulated and expressed. T lymphocytes are recruited at the site of inflammation by this expression of ICAM-1. This process may cause perivascular infiltration of T-cells and exocytosis of lymphocytes as observed in LP.[5] Also oxidative stress may activate nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), which is an important transcription factor. NFκB controls transcription of various cytokine genes that include interleukin (IL)-2 and tumor necrosis factor (TNF)-α, and also major histocompatibility complex (MHC) class 1 gene and IL-2 receptor gene. TNF-α may produce H2O2 and superoxide anions in epidermal keratinocytes.[6] Also, oxidative stress is involved in both pro- and antiapoptotic signaling in response to TNF-α.[7] Further, oxidative stress and increased inflammatory mediators release effector molecules including granzyme that can promote local tissue damage.[8]

The primary defense mechanisms against oxidative stress include antioxidants like some enzymes, vitamins, uric acid (UA), etc.[910] UA is one of the important antioxidants in plasma.[11] UA can scavenge ROS and can chelate metal ions.[12] Thus, monitoring UA level in serum as an indicator of the antioxidant defense (oxidative balance) could be important for the clinicians’ treatment strategy.

There is paucity of data available in the literature regarding serum UA levels in LP patients, particularly from our country. There are conflicting reports of association of UA levels among LP patients: Some found decreased levels of UA suggesting oxidative stress, while others failed to find any difference.[1314] So, the present study was designed to determine whether LP was accompanied by change in serum UA levels, and if so, whether there is any correlation between the duration of disease and degree of change in UA levels in serum.

Materials and Methods

This study was a hospital-based, case-control study conducted in the Departments of Dermatology and Biochemistry of Murshidabad Medical College and Hospital, Berhampore, West Bengal. The study was approved by the local ethical committee and all patients and control subjects gave their informed consent to take part in this investigation.

The duration of the present study was 3 months and included 61 LP patients attending the Dermatology outpatient department (OPD), duration ranging from 1 month to 12 months. In addition, 61 patients who were age- and sex-matched with the subjects served as controls. The controls had attended the OPD with minor ailments like scabies, minor pyoderma, tinea, etc., Complete history and physical examination of all cases and controls were undertaken, and wherever necessary, skin biopsy was taken to confirm the diagnosis. Exclusion criteria included subjects who had received any systemic steroid or other immunosuppressive drugs and nonsteroidal anti-inflammatory drugs (NSAIDs) within the last 4 weeks and topical medications within the last 2 weeks. Other exclusion criteria included smokers, patients with history of trauma or any surgery within 1 month prior to sampling, and those suffering from systemic or other dermatologic diseases affecting immune system or any malignancy. Lastly, subjects having febrile illness, gout, pregnancy, kidney and liver dysfunction, obesity, ketosis, familial hyperuricemia, and blood dyscrasias were excluded.

Five milliliter of venous blood sample was collected from each case and control after 12 h of fasting. All samples were coded and assayed in a blind fashion by an investigator who was unaware of the subjects’ clinical status.

Serum UA was assayed using Siemens, Mumbai, India and Coralab 3000 semiautoanalyser, by uricase method.[15]

Statistical analysis of the data was performed by using Statistical Package for Social Sciences (SPSS version 16) and inferences were drawn. P < 0.05 was considered to be significant.

Results

Blood was drawn from 30 male patients and 28 female patients because three patients dropped out from the study. The age of patients ranged from 27 to 65 years.

No significant correlation was found between the patients’ age and serum UA levels.

There was no significant difference in UA levels between male and female patients.

Mean duration of disease in patients (including recurrences and remissions) was 15 months (ranging from 1 month to 3 years and 11 months).

The different types of LP among the study group were as follows: Classical (58%), hypertrophic (19%), eruptive (10%), linear (8%), actinic (2%), annular (2%), and follicular (1%).

The differences of UA levels between the different subsets of LP were not statistically tested because of the low number of patients in the individual subsets.

Mean serum UA levels in patients and controls were 3.6033 and 3.9484 mg%, respectively and the difference was found to be significant (P < 0.001) [Table 1]. Similarly, analysis of the duration of the disease and the level of UA estimated at different periods of suffering showed that there was significant lowering of UA level with increasing duration of the disease [Tables 2 and 3]. Again, analysis of age of patients with UA levels elicited no difference (P = 0.3), but analysis of duration of disease and UA levels elicited significant difference (P < 0.001) [Table 4].

Table 1

Paired sample test of uric acid (UA) levels of patients’ and controls’ serum explaining the significance in difference

Table 2

Paired sample test table showing correlation between duration of disease and serum uric acid (UA) levels

Table 3

One-way ANOVA table showing correlation between duration of disease and serum UA levels

Table 4

Correlations table showing correlation between duration of disease and serum UA levels

Mean serum UA levels in patients and in controls were 3.60 and 3.94 mg/dl, respectively and the difference between the mean of the two groups was 0.34 mg/dl. This difference is highly significant.

The comparison of paired data of duration of LP and serum UA level for each patient shows significant decrease (difference) in UA levels with increasing duration of the disease.

One-way analysis of variance (ANOVA) table showing correlation between duration of disease and serum UA levels, showing similar change as in Table 2.

Correlations table showing correlation between duration of disease and serum uric acid (UA) levels

This shows that there is much less correlation between age and UA levels (correlation coeffiecient −0.07); whereas, there is high correlation between UA levels and duration of the disease (coefficient −0.525).

Discussion

UA being a powerful free radical scavenger as well as being able to act as a chelator of metal ions such as iron and copper by converting them to poorly reactive forms which are unable to catalyze free-radical reactions, is one of the important antioxidants in human biological fluids.[1617] Though the primary defense mechanisms against oxidative stress include antioxidants like some enzymes, vitamins, etc., it is thought that UA contributes to >50% of the antioxidant capacity of blood.[9101618] UA prevents peroxynitrite formation by neutralizing cellular superoxide and preventing its (superoxide) reaction with nitric oxide.[19] It is a scavenger of free radicals, such as NO2, which is formed from the breakdown of peroxynitrite,[20] and may assist in the removal of superoxide by preventing the degradation of superoxide dismutase, the enzyme that is responsible for clearing superoxide from the cell. UA is also very effective at preventing peroxynitrite from nitrating the tyrosine residues of proteins; thereby, preventing the inactivation of cellular enzymes and modification of the cytoskeleton.[19] Some studies have revealed the antioxidant role of UA in other conditions.[2122]

In our study, serum UA levels were significantly decreased in patients with respect to controls [Table 1]. Mean serum UA levels in patients and controls were 3.6 and 3.94 mg/dl, respectively. The difference of means is 0.34 mg/dl. These results point towards a pathological relation of decreased UA levels with LP and its duration, which is further explained in Tables 2 and 4.

(Paired sample test, as shown in Table 2, is applied to paired data of independent observations. Here duration of LP disease and serum UA are paired data. It was analyzed to study the role of duration of the disease on oxidative defense systems of the cases. If the two-tailed significance is more than 0.05, the difference observed has no significance, because such a difference can occur commonly due to chance. Thus, the factor under study may have no influence on the variable. But if the two-tailed significance is less than 0.05, the difference observed is significant, because such a difference is less likely to occur by chance. Influence of the factor to which the sample is exposed may be accepted as an alternative to null hypothesis). Moreover, Tables 2 and 3 show significant correlation between the serum UA levels and duration of disease. A significant decrease of UA levels was also observed in study of LP patients from Italy.[14] On the contrary, a report from Israel found higher prevalence of hyperuricemia than that of general population, though LP was not considered as a cause of overproduction of uric acid.[23]

Lastly, Table 4 shows that serum UA levels were decreased with increasing duration of disease, particularly when the duration exceeded 6 months. (When associated variables of serum UA, i.e., age and duration of disease, are normally distributed, the correlation coefficient calculated is called Pearson's correlation coefficient though it is meant for larger sample size. From the table above it is evident that ‘r’ between UA and duration is −0.525; whereas, it is only −0.07 between UA and age.) So, duration of the disease may have greater impact on oxidative damage in comparison to age of the patients.

Thus, our results point towards a pathological relation of decreased UA levels with LP and its duration.

Indirect evidence of increased oxidative stress in LP is strengthened from the fact that saliva UA is decreased in oral LP patients.[24] Also, vitamin E and C levels are decreased in LP, and supplementation of these may have a role in the management of LP.[25]

As free radical-induced damage is thought to be one of the important factors in the etiopathogenesis of LP, in our opinion, treatment guidelines should include optimal strengthening of antioxidant defense. Serum UA is a potent free radical scavenger, and it has been demonstrated, using two methodologically distinct assays, that systemic administration of UA increases ex vivo serum free radical scavenging capacity to a significantly greater extent than vitamin C, another important aqueous physiologic antioxidant.[26] Also, antioxidant administration increases UA levels.[27]

This study has limitations that must be considered. To assess UA, uricase method was used. UA can be estimated by various methods, but the present method was employed as it is the most commonly used, time tested and standard method. Also, number of patients in the study groups was not large. Thus, care must be taken in extrapolating the present findings to other populations. Patients were taking a number of medications (other than steroids, immunosuppressive drugs, and NSAIDs) to control LP. However, these treatments are characteristic of patients with LP and do not affect serum UA levels. Despite these limitations, we believe that our study points towards using it as an important, promising antioxidant marker for LP. As our findings point to a decrease in the antioxidant UA, the problem of oxidative stress in LP should also be further investigated in a larger number of patients, and other markers of oxidative stress and antioxidants should be assessed.

The results of our study suggest that LP may be related to depletion of UA levels in serum. UA may be considered as a useful biomarker of antioxidant status in LP for elaboration of treatment strategy and monitoring.

What is new?

LP is associated with decrease of UA levels in serum suggesting increased oxidative stress, which may be addressed in treatment schedule.