The changes in serum interleukin-6 in patients with rheumatoid arthritis

Objectives: To evaluate serum levels of interleukin (IL)-6 in rheumatoid arthritis (RA) patients and to assess the correlations of this cytokine with clinical and laboratory parameters. Subjects and methods: 86 patients with RA and 30 healthy volunteers were enrolled in the study.

THE CHANGES IN SERUM INTERLEUKIN-6 IN PATIENTS WITH

RHEUMATOID ARTHRITIS

Nguyen Huy Thong*; Doan Van De*; Nguyen Dang Dung** SUMMARY

Objectives: To evaluate serum levels of interleukin (IL)-6 in rheumatoid arthritis (RA) patients

and to assess the correlations of this cytokine with clinical and laboratory parameters Subjects and methods: 86 patients with RA and 30 healthy volunteers were enrolled in the study

Disease activity was determined by disease activity score (DAS28) in patients with RA Patients with RA were categorized as low and moderate (DAS28 ≤ 5.1) and high (5.1 > DAS28) according to DAS28 The serum levels of IL-6 cytokine was measured by Fluorescence Covalent

Microbead Immunosorbent Assay (FCMIA) Results: Serum IL-6 levels was significantly

elevated in RA patients comparing with controls (p = 0.042) Serum IL-6 showed no significant correlations with mesurements of disease activity Conclusions: This study showed that patients with RA had a significantly increased cytokine level for IL-6, but high level of serum IL-6 cytokine was not associated with disease activity measurements However, further follow-up studies involving large samples are required to clarify precise role of this cytokine in development and

progress disease

* Keywords: Rheumatoid arthritis; IL-6; Disease activity

INTRODUCTION

Rheumatoid arthritis is a chronic

inflammatory disease characterized by

joint swelling, joint tenderness, and

destruction of synovial joints, leading to

severe disability and premature mortality [1]

Cytokine networks, including IL-6, are

critical for the initiation and perpetuation

of both systemic and local inflammatory

responses seen in chronic inflammatory

arthritis [2] IL-6 may also be mediating

many of the systematic manifestations of

RA including inducing the acute-phase

reaction [including C-reactive protein (CRP)],

anaemia through hecipidin production,

fatigue via the hypothalmic - pituitary -

adrenal (HPA) axis and osteoporosis from

its effect on osteoclasts [3], thus it may influence on levels of disease activity in

RA patients

Several disease activity indices based

on different clinical, laboratory, and physical measures have been introduced Most of these, including the Disease Activity Score (DAS), the modified DAS in 28 joints (DAS28), the Simplified Disease Activity Index (SDAI), the Clinical Disease Activity Index (CDAI), rely on either quantitative joint counts, patient-reported outcomes or both, and erythrocyte sedimentation rate (ESR) and serum CRP, those have some limitations and can be influenced by aging, sex and conditions other than RA (eg., osteoarthritis, fibromyalgia, anemia) [4, 5]

** 103 Hospital

** Vietnam Military Medical University

Corresponding author: Nguyen Huy Thong (bsthong103@gmail.com)

Date received: 10/07/2017

Date accepted: 08/08/2017

The aim of this study was: To evaluate

serum levels of IL-6 in RA patients and its

role in assessing of disease activity

SUBJECTS AND METHODS

1 Subjects

This study was conducted at Department

of Rheumatology and Endocrinology of 103

Military Hospital between May, 2012 and

June, 2015

Eighty six patients, 75 women and

11 men, with the diagnosis of RA fulfilled

the ACR/EULAR 2010 RA classification

criteria [1] Before entering study, 43 and

4 patients were taking glucocorticoids and

conventional synthetic disease-modifying

antirheumatic drugs (DMARDs), respectively

Patients with other concomitant rheumatic

disease, severe infection, chronic autoimmune

disease, and/or taking bio-DMARDs, which

may affect laboratory and cytokine profile

were excluded from the study

- Healthy subject population: thirty

sex-matched healthy controls (age mean

41.60 ± 4.57; range 35 - 50 years, 26 women

and 4 men) were included in the study

2 Methods

* Clinical assessment:

Disease activity was assessed by the

28-joint disease activity score C-reactive

protein (DAS28 CRP) [6] in RA patients

Based on the DAS28 CRP, the patients

were subdivided into 2 subgroups: low and

moderate group (DAS28 ≤ 5.1), and high

group (DAS28 > 5.1) Patient global

assessment of disease activity and

provider global assessment of disease

activity were evaluated using a 10 cm horizontal visual analog scale (VAS)

We also calculated SDAI (Simplified Disease Activity Index) and CDAI (Clinical Disease Activity Index) Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were recorded

* Laboratory analysis:

Blood samples of patients and controls were collected and put in a sterile plain tube and stored frozen at -80oC until analysis We used commercially available human fluorescence covalent microbead immunosorbent assay (FCMIA) kits for IL-6, IL-17 and TNF-α (R&D systems MN, USA) The procedure for the FCMIA method was performed according to the instructions provided by the manufacturer The levels

of cytokines were recorded as a pg/mL

* Statistical analysis:

All statistical analyses were performed using the statistical package for the social sciences (SPSS), version 18.0, for Windows (SPSS, Chicago, IL, USA) Continuos variables are presented as the mean ± standard deviation or median The normality

of the distribution for all variables was assessed by the Kolmogorov-Smirnov test Intergroup comparisons were made using

the student’s t-test for normally distributed variables and Mann - Whitney U test for

non-parametric variables To assess the correlations between variables, Sperman’s rank or Pearson’s correlation analysis were used according to data distribution Values of p < 0.05 were considered statistically significant

RESULTS

1 Patients and demographic, clinical characteristics

Table 1: Demographic and clinical characteristics of RA patients and control

RA group (n = 86) Control group (n = 30)

7.16 ± 2.25

Mean provider global assessment of disease

5.65 ± 1.92

DAS28 CRP

Pre-study treatment

(DAS28 (CRP) is missing in three patients

Abbreviations: anti-CCP: anti-cyclic citrulinated peptide; CRP: C-reative protein; DAS28: Disease Activity Score; ESR: Erythrocyte Sedimentation Rate)

Patients and controls did not significantly differ in sex The mean age of controls was lower than that of RA patients The mean disease duration in RA patients was 4.29 ± 5.34 years The mean DAS28 CRP was 6.19 ± 1.36 (range 2.81 - 8.50) Seventeen (20.5%) and sixty six (79.5%) patients had low-moderate and high DAS28 CRP, respectively

2 Comparison of laboratory parameters among patients and healthy subjects

The mean and median of serum IL-6 of RA patients and controls was 19.06 ± 22.94;

10.49 and 9.19 ± 8.43; 7.18 (pg/mL), respectively Median of serum IL-6 concentrations

in RA patients was significantly higher than that in controls group (p = 0.042)

Serum IL-6 had a positive correlation with serum TNF-α in RA patients (r = 0.233,

p = 0.035)

3 Correlation between serum IL-6 and clinical, laboratory variables in RA

patients group

Table 2: The comparison of serum IL-6 based on measurements of disease activity

Plasma IL-6 levels (pg/ml)

p

Joint tender count 28

0.974

Joint swollen count 28

0.332

Low and moderate

DAS28 CRP

0.581

(Abbreviations: DAS28 CRP: Disease Activity Score C-Reactive Protein)

Figure 1: The comparision of serum interleukin

(IL)-6 levels between RA patients and controls

(p, test Mann - Whitney)

Figure 2: The correlation of serum interleukin

(IL)-6 levels and serum tumor necrosis factor (TNF)-α levels in rheumatoid arthritis patients (numbers are Spearman correlation coefficients)

Table 3: The correlation of serum IL-6 levels in RA patients with measurements of

disease activity

IL-6

(Abbreviations: TJC: Tender joint count; SJC: Swollen joint count; MS: Morning stiffness;

PtGA: Patient global assessment of disease activity’ PGA: Provider global assessement of disease activity; r: Spearman’s correlation coefficient)

There were no differences according to joint tender count 28, joint swollen count 28 and DAS28 CRP

Table 4: The correlation of serum IL-6 levels with composite indices in RA patients

IL-6

(Abbreviations: DAS28 CRP: Disease Activity Score C-reactive protein; DAS28 ESR: Disease Activity Score erythrocyte sedimentation rate; SDA:, Simplified disease activity index; CDAI: Clinical disease activity index; r: Spearman’s correlation coefficient)

There were no associations between the serum IL-6 levels of RA patients with measurements of disease activity

DISCUSSION

In the present study, we evaluated

serum levels of IL-6 cytokine in patients

with RA, and its associations with clinical

and laboratory parameters

IL-6 is a pleiotropic cytokine with diverse

activities IL-6 plays an important role

in inflammation, bone metabolic,

haematopoiesis, immune regulation [7]

These activities contribute to both systemic

and local symptoms associated with RA

[2] IL-6 is involved in pathology of chronic

inflammation of synovium, joint damage

as well as systemic symptoms such as

anemia [8], fatigue [9], osteoporosis [9]

In accordance with other authors [10,

11, 12], we found that serum IL-6 was significantly increased in RA patients

compared to healthy subjects (figure 1)

In the current study, serum IL-6 had a significantly positive correlation with

serum TNF-α (figure 2) In consistent of

our observation, Manicourt D.H et al (1993) also reported that serum IL-6 had

a positive correlation with serum TNF-α (r = 0.487, p = 0.007) These studies supports the concept that TNF-α played

a key role in pathogenesis of RA by stimulating pro-inflammation cytokines including IL-6

IL-6 is a pleiotropic cytokine and

contributes to both systemic and local

symptoms associated with RA [2], so it

may influence the disease activity of RA

patients We assessed the change of

serum IL-6 according to measurements of

disease activity to value serum IL-6 in

assessing levels of disease activities in

RA patients In the present study, serum

IL-6 median of low and moderate disease

group lower than high group but it was not

significant (p = 0.581) (table 2) Ibrahim

Tekeog˘lu et al (2016) found a significant

difference in serum IL-6 mean between

high disease activity group and low group

(p = 0.046), however there was no difference

between patients had a moderate and low

disease activity

In the present study we also did not

observe the correlation between serum

IL-6 with measurements of disease activity

such as joint tender count 28, joint swollen

count 28, morning stiffness, PtGA, PGA,

ESR, plasma CRP levels as well as

composite index DAS28 CRP, DAS28

ESR, SDAI and CDAI In consistent of our

observation, Soo-Jin Chung et al (2011)

found that serum IL-6 was not associated

with DAS28 ESR [11] However, contrary to

our results, other studies found serum IL-6

had a positive association with DAS28

CRP and DAS28 ESR do Prado et al

found a positive correlation between IL-6

levels and TJC28 (r = 0.39; p < 0.01) [12]

Thus, there are many controversial studies

regarding the relationship between serum

IL-6 as an assessing role of disease

activity and measurements of disease

activity in RA patients, so we need more

studies with larger sample size to

discover this interesting correlation

Our study has some limitations The sample size of patients was relatively small, and the patients were on drug treatment including glucorticoids DMARDs

In fact, our study had a cross-sectional design, and cytokines profile had wide range

CONCLUSION

Our study demonstrated a significant higher increase of serum IL-6 in RA patients compared with healthy controls However, we did not find any associations between serum IL-6 levels and measurements

of disease activity in RA patients

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