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Proceedings S.Z.M.C. Vol: 35(3): pp. 6-11, 2021.               PSZMC-801-35-3-2021 
 

Efficacy of Telmisartan in Pristane Induced Arthritis  
Rat Model 
1Quratulain Mehdi, 2Noaman Ishaq, 3Saba Batool, 4Kulsoom Farhat, 5Saman Omer,  
4Arooj Shahid 
1Department of Pharmacology, Quetta Institute of Medical Sciences, Quetta 
2Department of Pharmacology, Bakhtawar Amin Medical and Dental College, Multan 
3Department of Pharmacology, CMH Multan Institute of Medical Sciences, Multan 
4Department of Pharmacology, Army Medical College, Rawalpindi 
5Department of Pharmacology, Mohtarma Benazir Bhutto Shaheed Medical College, Mirpur AJK 

 
ABSTRACT 

Introduction: Rheumatoid arthritis is one of the most common systemic inflammatory diseases characterized by 
progressive damage to the joints. There is rising evidence that Renin Angiotensin Aldosterone System signaling is also 
involved in the inflammatory response in rheumatoid arthritis and its blockers possess anti-arthritic properties. 
Telmisartan is an angiotensin receptor blocker and PPAR-γ agonist and its anti-arthritic effects were evaluated. 
Aims & Objectives: This experimental study was designed to evaluate the anti-arthritic efficacy of telmisartan in 
pristane induced rat model of arthritis in adult female rats. 
Place and duration of study: The study was conducted in the Department of Pharmacology, Army Medical College, 
Rawalpindi, in collaboration with National Institute of Health and Armed Forces Institute of Pathology from July 2020 
to August 2020. 
Material & Methods: Twenty four (24) adult non-pregnant female Sprague Dawley rats were divided in three groups 
(n=8) designated as Group A (normal control), Group B (arthritic control) and Group C (telmisartan group) & 
maintained on standard diet and water adlibitum. Rheumatoid arthritis was induced in each rat of Groups B &C by a 
single intradermal injection of 0.5ml pristane at the base of its tail on day 0 and the disease developed in two weeks. All 
3 groups were given distilled water 2.5 ml/kg from 2-4 weeks and Group C was additionally given dissolved telmisartan 
orally at 2 mg/kg/day. Anti-arthritic efficacy was determined by assessing arthrogram score and total leukocyte count on 
day 0, 14 and 28 along with histological examination done at the end of the study. Data analysis was done using SPSS 
version 25. 
Results: Healthy rats in group A maintained a unremarkable arthogram & histogram score & TLC count of 6675±350/μl 
during the entire study period. Telmisartan administration in Group C for two weeks after pristane induction resulted in 
significant reduction in arthrogram score (AS) 9.5±3.66, total leukocyte count (TLC) 7350±550/μl and histological score 
(HS) to 6.88±1.24 as compared to (AS) 14.50±2.07, WBC 10150±350/μL & (HS) 10.75±2.05 in Group B, left untreated 
with pristane alone. The intergroup comparison showed significant p value < 0.05 respectively. 
Conclusion: Anti-arthritic effect was shown by telmisartan as it was able to ameliorate the changes induced by pristane. 
 
Key words: Anti-arthritic efficacy, Telmisartan, Pristane, Rheumatoid arthritis 
 
 

INTRODUCTION 

Rheumatoid arthritis (RA) is one of the most 
common inflammatory disorders occurring due to 
multiple factors including environmental and 
genetic risk factors.1 Clinical presentation of 
symmetrical joint involvement comprises of 
arthralgia, swelling, redness and limited mobility. 
The risk of development of extra articular 
manifestations such as keratitis, rheumatoid 
nodules, pericarditis and pleuritis is increased with 
poor control or severe disease. It is responsible for 

continuing disability, premature death and increased 
socioeconomic burden.2 
Several strategies are employed in managing the 
disease. Surgical approaches help in improvement 
of functional activity and structural misalignment of 
joints but considered as a last resort. Physical and 
occupational therapy helps in relieving the muscular 
spasm and related joint stiffness.3 Current therapies 
include Non Steroidal Anti-Inflammatory Drugs 
(NSAIDS), Glucocorticoids (GCs) and biological 
agents which improve pain, fatigue and disability 
with more focus on controlling synovitis.4 
Treatment modalities with fewer side effects are 
required for improvement of therapy. 

 



7

Efficacy of Telmisartan in Pristane Induced Arthritis Rat Model 

 

The Renin Angiotensin Aldosterone System 
(RAAS) is well known for its function as regulator 
of blood pressure but there is accumulating 
validation that its signaling is involved in reaction to 
inflammation identified in various disease states. 
Angiotensin II Type 1 Receptor (AT1R) can be 
presumed as a potential therapeutic target as rodent 
models of arthritis have massively expressed its 
presence in cultured RA-fibroblast like synoviocytes 
(FLS) as well as in hyperplastic synovium. The role 
of Angiotensin Converting Enzyme Inhibitors 
(ACEIs) and Angiotensin Receptor Blockers 
(ARBs) in ameliorating the laboratory and clinical 
parameters has also been documented.5 Telmisartan 
showed betterment in the parameters of arthritis in a 
rat model of RA. It exerts anti-inflammatory actions 
by restraining Tumor Necrosis Factor α (TNF-α) 
production and inhibiting pro-inflammatory 
mediators such as Interleukin-6 (IL-6) and Nuclear 
Factor kappa beta (NF-κβ).6 
Various experiments and studies are being carried 
out to explore the anti-inflammatory properties of 
telmisartan with regards to various conditions. The 
current study is intended to demonstrate the anti-
arthritic effects of telmisartan in rat model of 
pristane induced arthritis (PIA). 
 

MATERIAL AND METHODS 

Study design:  Laboratory based experimental 
study. 
Ethical approval: The Ethics Review Committee of 
“Center for Research in Experimental and Applied 
Medicine (CREAM)”, Army Medical College gave 
the approval for study. 
Setting: It was carried out in department of 
Pharmacology and Therapeutics, Army Medical 
College (AMC), Rawalpindi in collaboration with 
National Institute of Health (NIH), Islamabad and 
Armed Forces Institute of Pathology (AFIP). Study 
was conducted for duration of one month from July 
to August 2020 and the animals were kept in animal 
house of NIH Islamabad. 
Sampling Technique and size: Twenty Four (24) 
adult non-pregnant female Sprague Dawley rats 
weighing 250-300 grams were randomly divided 
into three groups of eight animals each. 
Experimental setup: The rats were acclimatized for 
a week before the start of experiment. They were 
retained in wire topped cages and standard 
environmental conditions were maintained with 
temperature ranging between 25±5˚C and 50±10 % 
humidity. Free excess to clean drinking water and 
standard rodent diet ad libitum was provided during 
the study duration. Twenty four (24) adult non-

pregnant female Sprague Dawley rats were divided 
in three groups (n=8) and were assigned as 
Group A (normal control): Comprised of healthy 
rats. Intradermal injection of 0.1 ml normal saline 
was given at the base of tail at day 0 and rats were 
given distilled water 2.5 ml/kg/day orally from 14 to 
28 days. 
Group B (arthritic control): Rheumatoid arthritis 
was induced with pristane on day 0 and rats were 
given distilled water 2.5 ml/kg/day orally from 14 to 
28 days after induction. 
Group C (telmisartan group): Rheumatoid 
arthritis was induced with pristane on day 0 and rats 
were treated with telmisartan manufactured by 
Pharm Evo (Pvt) Ltd in a dose of 2 mg/kg/day orally 
for two weeks after induction.7 
Induction of rheumatoid arthritis: Induction of 
RA was done by a single intradermal injection of 
0.5 ml of pristane purchased from Martin Dow 
Marker Ltd at the base of tail of each rat in Group B 
and Group C.8 Arthritis developed gradually over a 
period of two weeks. 
Assessment of arthritic progression by 
arthrogram score: The assessment of arthritic 
progression was done by clinical scoring of joint 
inflammation on all four limbs on alternate days 
from week 0 to 4 weeks after pristane injection. It 
ranged from 0-4, where 0=no swelling and redness; 
1=single joint involvement; 2=involvement of two 
joints; 3= involvement of more than two joints; 
4=severe arthritis involving whole paw and digits. 
The collective minimum score for all four limbs 
would be 0 and maximum would be 16.9 The 
arthrogram score at day 0, 14 and 28 were 
statistically analyzed. 
Hematological analysis: Blood was collected from 
the lateral tail vein on day 0, 14 and 28 and was 
stored in Ethylene Diamine Tetra Acetic acid 
(EDTA) tubes for the analysis of Total Leukocyte 
Count (TLC).10 It was done by using Sysmex KX-21 
automated analyzer. 
Joint histopathology: All the rats were euthanized 
by chloroform at the end of the study on day 28. The 
proximal part of tibia was sliced by using 5.5" 
angled bone cutter and right ankle joints were 
removed. Slides were   prepared with Eosin and 
hematoxylin stains. Histological scoring was done 
according to a set criteria as described by Alabarse 
and his colleagues. For synovial inflammation, five 
high‐power magnification fields were scored for the 
percentage of infiltrating mononuclear cells as 
follows: 0, absent; 1, mild (1-10%); 2, moderate 
(11-50%); 3, severe (51-100%); for synovial 
hyperplasia: 0, absent; 1, mild (5-10 layers); 2, 
moderate (11-50 layers); 3, severe (>20 layers); for 



8

Efficacy of Telmisartan in Pristane Induced Arthritis Rat Model 

 

extension of pannus formation: 0, absent; 1, mild; 2, 
moderate; 3, severe; for synovial fibrosis: 0, absent; 
1, mild (1-10%); 2, moderate (11-50%); 3, severe 
(51-100%); for cartilage erosion, that is, the 
percentage of the cartilage surface that was eroded: 
0, absent; 1, mild (1-10%); 2, moderate (11-50%); 3, 
severe (51-100%); and for bone erosion: 0, none; 1, 
minor erosion(s) observed only at high‐power 
magnification fields; 2, moderate erosion(s) 
observed at low magnification; 3, severe 
transcortical erosion(s).11 
 
Statistical analysis: 
The Statistical Package for the Social Sciences 
(SPSS) version 25 was used for data analysis with 
quantitative data expressed as Mean + Standard 
Deviation (SD). One way of analysis of variance 
(ANOVA) was applied to observe the mean 
difference among control and experimental group 
and compared by Post Hoc Tukey’s test. The 
difference between two observations was considered 
significant if the p value was equal to or less than 
0.05 (p ≤0.05). 
 

RESULTS 

The arthrogram score was zero in all the groups at 
day 0. It remained zero in group A throughout the 
study duration whereas in group B it reached a mean 
of 13.5±2.97 by day 14 and reached a mean of 
14.5±2.07 by day 28. Fig-1 shows a rat of group B 
with arthrogram score 12. Arthrogram score of 
group C reached a mean of 12.5±3.96 by day 14 and 
was declined after treatment with telmisartan by day 
28 with a mean of 9.5±3.66. Fig-2 shows a rat of 
group C with arthrogram score 04. 
 

 
Fig-1: Rat of Group B with hind paws showing edema 

and redness 
 

 
Fig-2: Rat of Group C with improved arthrogram score. 
 
The mean TLC of group A, B and C was 
6600±300/μL, 6562±450/μL and 6488±360/μL 
respectively on day 0.  It remained almost constant 
in group A on day 14 and day 28 with a mean of 
6600±310/μL and 6675±380/μL. TLC was 
increased on day 14 in the other two groups with 
mean of 9988±510/μL and 9987±710/μL. Group B 
was left untreated and its mean TLC on day 28 was 
10150±350/μL whereas a dosing schedule of 2 
mg/kg/day of telmisartan led to a decrease in levels 
of TLC to 7350±550/μL. 
The histological examination of group A revealed 
minimum score as it was disease free and did not 
show any microscopic changes. The synovium 
lining was smooth with no penetration of infiltrating 
cells. Maximum score was seen in the rats of group 
B which ranged from 8-13. Marked percentage of 
infiltrating mononuclear cells was seen in four out 
of six slides while rest showed moderate infiltration. 
Two slides showed severe synovial hyperplasia but 
was moderate in other slides. The extension of 
pannus formation was maximum in two slides while 
the others showed mild to moderate pannus 
formation. Six out of eight slides showed moderate 
synovial hyperplasia. All the slides showed cartilage 
erosion. Mild to moderate presence of bone erosion 
was seen in all slides except one. Mean score of this 
group was 10.75±2.05. Fig-3 shows a slide of Group 
B with a score of 10 showing bone erosion and 
inflammation with infiltrating cells. Slides of group 
C showed improvement. The score ranged from 5-9. 
Two slides showed moderate infiltrating 
mononuclear cells, two showed no infiltration while 
four showed mild infiltration of mononuclear cells. 
Mild to moderate synovial hyperplasia was present 
in all the slides. Mild pannus formation and synovial 
fibrosis was a feature of all the groups. Five slides 
showed mild cartilage erosion, whereas the 
remaining slides showed moderate erosion. Mild 
bone erosion was seen in five slides and moderate in 
two slides. The mean score of this group was 
6.88±1.24. Fig-4 shows a score of 07 with surface 
corrugation. 



9

Efficacy of Telmisartan in Pristane Induced Arthritis Rat Model 

 

 
Fig-3: Photomicrograph of ankle joint of Group B 
 

 
Fig-4: Photomicrograph of ankle joint of a rat of Group C 
 
Treatment with telmisartan for two weeks decreased 
the arthrogram score, TLC and also showed 
improvement on histological examination. The 
intergroup comparison of the three groups of all the 
parameters depicted a statistically significant p 
value ˂ 0.001 as shown in Table-1. 
 

Parameter 
Group A 

(n=8) 
Group B 

(n=8) 
Group C 

(n=8) 
p value 

ANOVA
Mean±SD Mean±SD Mean±SD 

Arthrogram 
score 0 

14.50±2.07 9.5±3.66 ˂ 0.001* 

Total 
Leukocyte 

count (per μL)
6675±380 10150±350 7350±550 

 
˂ 0.001* 

Histopathology 
score 0 10.75±2.05 6.88±1.24 ˂ 0.001* 

* significant  p value  ≤0.05 
Table-1: Intergroup comparison of arthrogram score, 

total leukocyte count and histopathology score 
on day 28. 

 
DISCUSSION 

RA is one of the common types of arthritis in the 
elderly population affecting the quality of life. The 
main pathological characters include persistent 
chronic synovitis, dysplasia of synovial membrane 
and pannus formation eventually causing cartilage 
and joint obliteration.12 
PIA is one of the extensively used models for 
research purpose due to appreciative resemblance to 
the chemical characteristics of RA.13 It is similar to 
the condition seen in humans due to the presence of 

symmetrical joint involvement, presence of 
rheumatoid factor, bone and cartilage destruction as 
well as dependence of specific immunity seen in 
such models.14 
In the present study the results indicated that the 
development of arthritis correlated with the increase 
in arthrogram score, TLC and histological score in 
Group B as compared to the Group A (normal 
control) till day 14. These findings are backed up by 
a number of studies conducted by researchers. Chen 
and his fellows in 2019 also observed the signs of 
severe arthritis spreading to ankle joints two weeks 
after injecting pristane.15 Regarding TLC, tissue 
homeostasis is maintained by the monitored 
movement of leukocytes between lymphoid and 
peripheral tissue through various stromal 
compartments. This trafficking is disturbed in RA.16 
Feng and Qiu in 2018 successfully created a model 
of RA by subcutaneous injection of emulsion. The 
results indicated higher leukocyte count as well as 
damaged cartilage and considerable infiltration of 
inflammatory cells.17 We followed a therapeutic 
model by commencing the treatment with 
telmisartan on day 14. It significantly lowered the 
aforementioned parameters when compared with the 
Group B (arthritic control). 
Group C (telmisartan group) displayed the absence 
of swelling, redness and an overall decrease in the 
mean arthritic score. These findings were in 
accordance with the work of Hasanin and Mohamed 
who studied the anti-inflammatory effects of 
telmisartan in a rat model and saw a significant 
decrease in arthritic parameters.6 Two weeks 
treatment with telmisartan also displayed a decrease 
in TLC and histological score. Angiotensin II (Ang 
II) has a central role in leukocyte migration and 
infiltration at molecular and cellular level at the sites 
of inflammation.18 It is accountable for regulating 
proliferation of cells and apoptosis by binding to 
AT1R. Ang II exhibited from synovial tissue 
regulates synovial perfusion and growth by its 
actions on synovial AT1R.19 Thus the decrease in 
TLC can be justified by its AT1R blocking 
potential. Other than this, olmesartan, an ARB like 
telmisartan was used orally in a model of zymosan 
induced RA. It decreased the TLC with specific 
reduction in neutrophil count as well as showed 
improvement in histological score.20 This signifies 
that our experimental drug telmisartan may also 
have anti-arthritic effect against RA. 
 
Limitations of study: 
This study has also some limitations. Although the 
study showed that telmisartan has anti-arthritic 
properties, the preventive role of telmisartan should 



10

Efficacy of Telmisartan in Pristane Induced Arthritis Rat Model 

 

also be evaluated in such a model. More over future 
studies should also be conducted using this drug 
focusing on adverse effects. 
 

CONCLUSION 

Oral administration of 2 mg/kg/day of telmisartan 
for two weeks significantly lowered the mean 
arthrogram score, total leukocyte count and 
histological score in a rat model of rheumatoid 
arthritis. Therefore, it can be concluded that 
telmisartan has anti-arthritic effects. 
 
Acknowledgement: 
Authors are thankful to Dr. Hussain Ali, Head of 
Research Animal Facility, National Institute of 
Health, Islamabad for his supervision regarding 
induction of Rheumatoid arthritis. A special thanks 
to Army Medical College, Rawalpindi for 
facilitating us to conduct this project. 
 

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Efficacy of Telmisartan in Pristane Induced Arthritis Rat Model 

 

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The Authors: 
Dr. Quratulain Mehdi 
Demonstrator, 
Department of Pharmacology, 
Quetta Institute of Medical Sciences, Quetta. 
 
Dr. Noaman Ishaq  
Assistant Professor, 
Department of Pharmacology, 
Bakhtawar Amin Medical and Dental College, 
Multan. 
 
Dr. Saba Batool  
Assistant Professor, 
Department of Pharmacology, 
CMH Multan Institute of Medical Sciences, Multan. 
 

Dr. Kulsoom Farhat  
Associate Professor, 
Head, Department & Pharmacology, 
Army Medical College, Rawalpindi. 
 
Dr. Saman Omer  
Demonstrator, 
Department of Pharmacology, 
Mohtarma Benazir Bhutto Shaheed Medical 
College, Mirpur AJK. 
 
Dr. Arooj Shahid  
Demonstrator, 
Department of Pharmacology, 
Army Medical College, Rawalpindi. 
 
Corresponding Author: 
Dr. Quratulain Mehdi 
Demonstrator, 
Department of Pharmacology, 
Quetta Institute of Medical Sciences, Quetta. 
E-mail: qurat.mehdi84@gmail.com