Serum level of interleukin-17 and its relation to interleukin-6 and tumor necrosis factor alpha level in patients with rheumatoid arthritis

Journal of military pharmaco-medicine no6-2019

SERUM LEVEL OF INTERLEUKIN-17 AND ITS RELATION TO
INTERLEUKIN-6 AND TUMOR NECROSIS FACTOR ALPHA
LEVEL IN PATIENTS WITH RHEUMATOID ARTHRITIS
Nguyen Huy Thong1; Nguyen Dang Dung2; Quyen Dang Tuyen1
SUMMARY
Objectives: To investigate serum level of interleukin-17 in rheumatoid arthritis patients and to
assess the relationship of this cytokine with serum levels of IL-6 and tumor necrosis factor α.
Subjects and methods: 82 patients with rheumatoid arthritis and 30 healthy volunteers were
enrolled in the study. Disease activity was determined by disease activity score (DAS28) in
patients with rheumatoid arthritis. Serum levels of IL-6, IL-17 and TNF-α were measured by
fluorescence covalent microbead immunosorbent assay. Results: Serum level of IL-17 in
rheumatoid arthritis patients and controls were 0.59 ± 0.92 and 0.62 ± 0.94 pg/mL, respectively.
There was no difference in serum levels of IL-17 in RA patients compared to that in controls
(p > 0.05). Serum IL-17 level, however, seemed to be correlated with changes in serum levels of
IL-6 and TNF-α in rheumatoid arthritis patients: in patients with elevated serum levels of IL-17,
the IL-6 and TNF-α were higher compared to those in patients with normal serum level of IL-17.
Conclusions: Serum level of IL-17 in patients with rheumatoid arthritis did not differ from that in
healthy people. Higher serum level of IL-17 correlated with higher serum levels of of IL-6 and TNF-α.
* Keywords: Rheumatoid arthritis; IL-6; IL-17; TNF-α.

INTRODUCTION
Rheumatoid arthritis (RA) is a chronic
inflammatory disease characterized by joint
swelling, joint tenderness, and destruction
of synovium, leading to severe disability
and premature mortality of patients [1].
Cytokine networks play a fundamental
role in the processes that cause
inflammation, articular destruction of RA

[2]. IL-17 possesses properties of a proinflammatory cytokine, and plays very
important roles in pathogenesis of RA [3].
IL-17 is a cytokine that stimulates the
production of a variety of inflammatory

mediators, and plays a leading role in
regulating the relationship between proinflammatory cytokines. In this role, IL-17
activates not only B cells to produce
antibodies, but also macrophages, synovial
fibroblasts, chondrocytes to secret cytokines,
such as IL-1, IL-6, TNF-α, and matrix
metalloproteinase (MMPs) [4, 5].That is
the reason why serum IL-17 may be related
to serum IL-6 and TNF-α in RA patients.
Thus, the aim of this study was: To
evaluate serum levels of IL-17 and its
relation serum IL-6 and TNF-α levels in
RA patients.

1. 103 Military Hospital
2. Vietnam Military Medical University
Corresponding author: Nguyen Dang Dung ()
Date received: 26/06/2019
Date accepted: 06/08/2019

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Journal of military pharmaco-medicine no6-2019
SUBJECTS AND METHODS

assessment

of

disease

activity

[7].

Erythrocyte Sedimentation Rate (ESR)

1. Subjects.

and C-reactive protein (CRP) were also

* Patients:

recorded.

This study was carried out at Department

* Laboratory analysis:

of Rheumatology and Endocrinology of

Blood samples of patients and controls

103 Military Hospital between May 2012

were collected and put in a sterile plain

and June 2015.
Eighty two patients, 71 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 taken glucocorticoids and
conventional synthetic disease-modifying
anti-rheumatic
respectively.

drugs
Patients

(DMARDs),
with

other

concomitant rheumatic diseases, severe
infections, chronic autoimmune diseases,

and/or taking bio-DMARDs which may
influence laboratory and cytokine profile

tube and stored frozen at -80oC until
analysis. We used commercially available
human Fluorescence covalent microbead
immunesorbent assay (FCMIA) kits for IL6, IL-17 and TNF-α (R&D systems MN,
USA). The assay was performed according
to

the

instructions

provided

by

the

manufacturer. Serum levels of cytokines
were reported as pg/mL.
The cut-off values of serum IL-6, IL-17
and TNF-α were determined by ROC
(Receiver Operating Curve).
* Statistical analysis:

were excluded from the study.
* Healthy subject population: thirty sex-

All statistical analyses were performed

matched healthy controls (mean age

using the Statistical Package for the

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

Social Sciences (SPSS) for Windows,

women and 4 men) were included in the

version 18.0 (SPSS, Chicago, IL, USA).

study.

Continuous variables are presented as
mean ± standard deviation or median.

2. Methods.

The normality of the distribution for all

* Clinical assessment:

variables was assessed by Kolmogorov-

Disease activity was assessed by the

Smirnov test. Intergroup comparisons

28-joint disease activity score C-reactive

were made using the student’s t-test for

protein (DAS28 CRP) [6] in RA patients.

normally distributed variables and Mann-

Patient global assessment of disease

Whitney

activity and provider global assessment

variables. Difference with p value being

of

less than 0.05 was considered statistically

disease

activity

were

evaluated

using Visual Analog Scale Formats for

U

test

for

non-parametric

significant.
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Journal of military pharmaco-medicine no6-2019
RESULTS
1. Patients and demographic, clinical characteristics.
Table 1: Demographic and clinical characteristics of RA patients and controls.

Mean age ± SD (min - max) (years)
Sex, n (female/male)
Mean disease duration ± SD (years)

RA group
(n = 82)

Control group
(n = 30)

53.44 ± 7.30; 35 - 66

41.60 ± 4.57; 35 - 50

75/11

26/4

4.29 ± 5.34

Mean tender joint count ± SD (range 0 - 28)

14.13 ± 9.08; 13.00

Mean swollen joint count ± SD (range 0 - 28)

10.52 ± 7.38; 9.0

Mean morning stiffness ± SD (minutes)

37.25 ± 33.82; 30.00

Mean patient global assessment of disease
activity ± SD (cm)

7.16 ± 2.25

Mean provider global assessment of disease
activity ± SD (cm)

5.65 ± 1.92

Mean ESR ± SD (mm/h)

79.68 ± 44.37

7.63 ± 3.92

Mean plasma CRP ± SD (mg/L)

68.37 ± 47.24

0.52 ± 0.36

Mean, DAS28 CRP
DAS28 CRP

Pre-study
treatment

6.19 ± 1.36; 2.81 - 8.50

Low or moderate (n, %)

17; 20.5

High (n, %)

66; 79.5

Glucorticoids (n, %)

43 (50.6)

DMARDs (n, %)

4 (4.7)

(DAS28 (CRP) is missing in three patients)
(Anti-CCP: Anti-cyclic citrulinated peptide; CRP: C-reative protein; DAS28: Disease
Activity Score; ESR: Erythrocyte Sedimentation Rate)
Patients and healthy people in the control group did not significantly differ in sex
distribution. The mean age of controls was considerably lower than that in 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). The proportion of patients had low or
moderate and high disease activity based on DAS28 CRP was 20.5% (17/83 patients)
and 79.5% (66/86 patients), respectively.
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Journal of military pharmaco-medicine no6-2019
2. Changes in serum levels of IL-17, IL-6, TNF-α and relations between serum
IL-17 and serum IL-6, TNF-α in RA patients.
Table 2: The comparison of serum IL-6, IL-17 and TNF-α levels of patients and controls.
Serum cytokines

Patients

Controls

(pg/mL)

n = 82

n = 30

X ± SD

19.06 ± 22.94

9.19 ± 8.43

Median

10.49

7.18

IQR

3.69 - 25.55

2.84 - 11.41

X ± SD

0.59 ± 0.92

0.62 ± 0.94

Median

0.30

0.27

IQR

0.00 - 0.07

0.00 - 1.07

X ± SD

2.37 ± 2.69

3.87 ± 2.11

Median

1.68

3.69

IQR

0.48 - 2.82

2.42 - 4.84

IL-6

IL-17

TNF-α

p

< 0.05*

> 0.05

< 0.001*

(*: Test Mann - Whitney, IQR: Interquartile Range)
Statistics shows that the median of serum IL-6 of patients was considerably higher
than that in controls (p < 0.05). There was no significant difference in the median of
serum IL-17 levels between patients and controls. The median of serum TNF-α of
patients was significantly lower than that in controls (p < 0.001).

Chart 1: The distributions of RA according to serum IL-17 levels.
The percentage of patients with elevated serum cytokine levels (elevated serum
levels of 1, 2 or 3 cytokines) was 73.20%, among which the percentage of patients with
elevated serum IL-17 (either single elevation of IL-17 level, or elevated IL-17 in
combination with IL-6 and/or serum TNF-α) was 56.10%; meanwhile, only 17.10% of
RA patients had elevated IL-6 and/or TNF-α level.
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Journal of military pharmaco-medicine no6-2019
Table 3: The comparison of serum IL-6 and serum TNF-α based on serum IL-17 groups.
Normal

Elevated

n = 36

n = 46

X ± SD

16.70 ± 23.19

20.68 ± 22.86

Median

6.81

12.87

IQR

2.94 - 20.19

6.30 - 26.28

X ± SD

1.81 ± 2.53

2.81 ± 2.76

Median

1.06

2.24

IQR

0.48 - 2.24

0.89 - 3.50

Serum IL-17

Serum IL-6 (pg/mL)

Serum TNF-α (pg/mL)

p

0.068*

< 0.05*

(*: Test Mann - Whitney; IQR: Interquartile Range)
Assessing the change of serum IL-6, TNF-α according to serum IL-17 groups of RA
patients, the results showed that the median of serum TNF-α of patient group with
elevated serum IL-17 was higher than that of healthy group (p < 0.05). The median
serum IL-6 had an increased trend in patients with elevated serum IL-17 compared to

healthy group (p = 0.068).
DISCUSSION
In the present study, serum levels of
IL-17 as well as IL-6 and TNF-α cytokine
were evaluated in patients with RA.
Additionally, the relationships between
serum IL-17 and serum IL-6, TNF-α were
also assessed.
Our results showed that there was no
significant difference in median value of
serum IL-17 level of the patients compared
to that of the controls (p = 0.879, by
Mann-Whitney test) (table 2). However,
the percentage of RA patients having
elevated serum IL-17 level was 56.10%,
which was higher than that of IL-6 and
TNF-α (chart 1).
In contrast, it was reported that in RA
patients, serum level of IL-17 was
significantly higher than that in healthy
people [8, 9, 10], as well as that of
patients with osteoarthritis [11]. IL-17 level
158

was not only elevated in serum, but also
in synovial fluid of RA patients at early
stage of the disease without treatment,
and the level of IL-17 in synovial fluid was
proportionally correlated with that in serum
[9, 12].

The results of current study showed
that serum IL-17 levels in RA patients
were not elevated compared to that in
healthy people. This was probably
because in RA patients at the clinical
period of the disease, serum IL-17 level
might be lower than that before the
disease onset, which was in accordance
with remarks by Kokkonen H et al (2010),
in which the authors found that median
value of serum IL-17 levels of RA patients
before disease onset was 28.7 pg/mL and
then it decreased to 6.0 pg/mL during the
illness period of the disease, which was
lower than that in healthy people at the
same age and gender distribution (being


Journal of military pharmaco-medicine no6-2019
21.1 pg/mL). The difference in serum IL17 level of the RA patients and of the
controls was significant with p value being
6.1 x 10-5 [13].
Additionally, it was reported that the
production and secretion of most of Th1
cytokines (IL-1β, IL-2, IL-3, IL-6, TNF,
interferon-γ) and Th17 cytokines (IL-17,
GM-CSF) were down-regulated by
corticoids [14]. In this study, 50.6% of RA
patients were treated by corticoids before
having serum cytokines testing (table 1),

and it might be one possible cause of the
low level of serum IL-17 we have observed.
However, when analyzing data, the results
of this study indicated that there was no
significant difference between median
values of serum IL-17 levels of the RA
patients who underwent corticoid treatment
compared to that of treatment-naïve ones.
Furthermore, in this study, the change
in serum IL-17 level seemed to influence
the change in serum IL-6 and TNF-α
levels. The results of chart 1 and table 3
indicated that serum IL-17 levels of RA
patients were increased along with elevation
of serum IL-6 and TNF-α levels. These
findings were in accordance with a report
by Miossec P (2007), in that IL-17 seemed
to play a central role in pathogenesis of
RA by stimulating synovial macrophages,
fibroblasts and dendritic cells to produce
and secrete pro-inflammatory cytokines,
including IL-6 and TNF-α [4], and in the
meantime, IL-17 was the "conductor" that
regulated the interaction between cytokines
[5].
Our study has some limitations. The
sample size of patients was relatively
small, many patients were on medication
treatment, including glucocorticoids as

well as DMARDs, before enrolment in this
research. Treatment regimens might
influence the serum levels of cytokines.
On the other hand, this study was
designed as a cross-sectional one, and
cytokines profile was not evaluated in
comparison with that in treatment-naive
RA patients. Furthermore, patients of this
study were mainly in an established
period of RA disease.
CONCLUSION
This study demonstrated that there
was no difference in serum IL-17 between
RA patients and healthy people. Serum
IL-17 seemed to influence the changes in
serum IL-6 and TNF-α in RA patients.
However, further follow-up research
involving large samples are required to
clarify the precise role of IL-17 in
relationships with IL-6 and TNF-α in the
development of RA disease.
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