INTRODUCTION:

The Atherosclerosis is contributed as one of the biggest cause of mortality and morbidity worldwide especially in the developing countries⁽¹⁾. It is the common reason of peripheral artery disorders, strokes in addition to heart attacks. It is a complicated process, also it may be occurred via sedentary lifestyle and high-fat diet⁽²⁾. It is considered as a most vital risk reasons for cardiovascular disorders.

Atherosclerosis is an advance functional and structural vascular disorder which starts cellular and molecular episode activated via endothelial dysfunction, leading to reduced production of nitric oxide, raised production of endothelin-1 and actions of cyclooxgenase and inflammatory processes⁽³⁾. Atherosclerosis prevalence is three–four times larger in diabetics than non-diabetics patients at equivalent plasma total cholesterol levels⁽⁴⁾.

Upon binding of angiotensin II through its receptor, promotes endothelial dysfunction, stimulates inflammation and encourages the oxidation of plasma lipoproteins within atherosclerotic plaques^(5,6). As the dysfunction of endothelium signify the beginning of atherosclerosis, enhanced inflammatory processes supports the growth of weak plaques, and reactive oxygen species exert destructive actions like the instruction of smooth muscle cells and macrophage apoptosis^(7,8).

Atherosclerosis progression may suppress by blockade of the angiotensin II type1 receptor and this lead to stabilization of susceptible plaques⁽⁹⁾. Numerous studies showed that management with drug that block AT1 receptor can satisfy atherosclerotic plaque development and decrease inflammation levels and cytokine expression⁽¹⁰⁾. It has been usually recognized that adhering of monocytes into vascular endothelial cells and converting to macrophage is an important position at the prophase of atherosclerosis⁽¹¹⁾. E-selectin, vascular cellular adhesion molecule-1 and intracellular adhesion molecule-1 play essential roles in this development⁽¹²⁾. In patients with coronary heart disorders, they have been regarded as mediators for the revealing of dysfunction of endotheliam. Thus, it may be an excellent method to inhibit the improvement of atherosclerosis by stopping the expression of vascular cellular adhesion molecule-1, E-selectin and intracellular adhesion molecule-1⁽¹³⁾.

It has been widely established that inflammation have a vital responsibility in atherogenesis and arbitrating all steps of this disorder from beginning to progression and also the through thrombotic obstacles of this disease⁽¹⁴⁾. The formation and development of atherosclerosis contributes by inflammation and the beneficial potential of some anti-inflammatory drugs have been estimated for probable anti-atherosclerotic action. Modern findings propose that the agents with anti-inflammatory actions show to done useful actions on atherosclerosis and their consequent on cardiovascular disorders. In Addition to that, enhanced expression of adhesion substances like ICAM-1 have a significant part in the of atherosclerotic disorders pathogenesis⁽¹⁵⁾. So, the ability drugs to interfering with oxidative parameters and inflammatory pathway is measured as the therapeutic impending for in assessment of their athero-protective actions⁽¹⁶⁾.

Irbesartan, one of the most widely used angiotensin receptor blockers, in addition to its function in the obstruction of the angiotensin 1 receptor it has ability to activate a peroxisome proliferator-activated receptorgamma⁽¹⁸⁾. Activation of peroxisome proliferator-activated receptorgamma also exerts anti-inflammatory actions and decrease the reactive oxygen species production⁽¹⁹⁾, irbesartan may additionally suppress expression of inflammatory chemokine and reduce death of apoptotic cell in the plaque. The antiatherogenic actions of irbesartan, however, have not been totally considered , and the mechanisms underlying its therapeutic actions stay not clear⁽¹⁹⁾.

MATERIALS AND METHODS:

Animals:

In the present study twenty-four male rabbits (weighing 1.2-1.8 kg) were used. The rabbits were located in the animal house of faculty ofPharmacy in Al Kufa-university. The animals were reserved in cages in air conditioned room with60–65% humidity, twenty five °C ±2 temp. and a 12 hour light: twelve hour darkcycle. There was adaptation time of seven days previous to the experiment. This study was mannered in the direction of the national guidelines for the Care and Use of Laboratory Animals. The study procedure was accepted by the High Committeefor Review and Approval of Research Proposals in University of Kufa\Faculty of pharmacy.

Study design:

The animals were arbitrarily grouped into 3 groups:

1. Control group(n= eight): The rabbits were take normal chow diet and tap water for twelve weeks.

2. Induced untreated group (n= eight ); the rabbits were take high cholesterol diet (a 0.05% cholesterol) and tap water for twelve weeks

3. Irbesartan treated group (n =eight ): All rabbits in this group were take same atherogenic diet (0.05%) in group II plus irbesartan (0.5 mg/kg) once daily at morning for twelve weeks.

Serum and tissue preparations:

The blood samples were analyzed at zero time and in each four weeks after starting of experimental diets for assessment of serum HDL-Cholesterol, triglycerides (TG), totalcholesterol (TC), endothelin-1(ED-1)and intracellular adhesion molecule-1(ICAM-1) level. At the finish of the study, aorta was collected after scarification of animals and use to prepare homogenate of tissue which was made in media of phosphate- buffered (pH 7.4), saline (0.1 M) that contain1% Triton-one hundred and protease inhibitor cocktail via using a high intensity ultrasonic liquid processor. Then homogenates were centrifuged at four C^o and supernatants were used for evaluate the aortic intimal thickness and the levels of aortic Malondialdehyde (MDA) and aortic reduced glutathione (GSH).

Statistical analysis:

Statistical analysis was done by SPSS 21.0 for windows lnc. The data were stated as mean±SEM.; the means at different time for the same group was compared by paired t-test. Analysis of Variance (ANOVA) was used for multiple comparisons among all groups. Level of significance was P< 0.05 for statisticaldecision.

RESULTS:

There was a small not significant decrease in body weight of irbesartan taking group proposed that the consumption of food may be was the same in all the groups and the atherogenic dietor irbesartan had no action on the body weight. In compares with the control group, the levels of total cholesterol, triglyceride, high density lipoprotien, endothelin-1, intracellular adhesion molecule-1, aortic MDA and aortic intimal thickness were significantly enlarged and aortic GSH were significantly diminished in the rabbits with atherogenic diet ( group two)(P < 0.05).

Table 1:alterations in theserum lipid profilelevelsof the study groups. The data was expressed as Mean ±SEM.by paired T-test.

Group

(mg/dl)

TG (mg/dl)

HDL (mg/dl)

1. Controlgroup (n=eight)

Zero time

83±

2.42

36.9±

5.16

12.9±

2.8

12 weeks

88±

3.66

34.9±

3.2

13.5±

3.1

2.Induced untreated

Group(n=eight)

Zero time

92±

3.35

36±5.1

13.2±

1.4

12 weeks

895±

23*

355±

13.3*

35±

4.8*

3.Irbesartan treated

Group(n=eigth)

Zero time

86±

5.4

33.8±5.1

13.4±

3.9

12 weeks

911±

10.22*

322±

12.1*

41.1±

4.9*

*p<0.05

Table 2:alterations in thelevel of serum inflammatory mediators (ED-1 and ICAM- 1) in all study groups. The data wasexpressed as Mean ±SEM .Using paired T-test.

Group		ED-1(pg/ml)	ICAM-1(pg/ml)
1.Controlgroup (n=eight)	Zero time	0.39±0.26	6.9±1.2
1.Controlgroup (n=eight)	12 weeks	0.44±0.15	7.2±0.8
2.Induced Untreated Group(n=eight)	Zero time	0.41±0.32	7.1±0.7
2.Induced Untreated Group(n=eight)	12weeks	1.9±0.59*	24.6±1.9*
3.Irbesarantreated Group (n=eight)	Zero time	0.48±0.17	7.6±0.27
3.Irbesarantreated Group (n=eight)	12weeks	1.1±1.12*	17.3±1.8*

*p<0.05

Table 3: Thelevel of aortic intima thickness and aorticoxidative parameters (MDA and GTH) in all experimental groups after 12 weeks .The data was expressed as Mean ±SEM. Using paired T-test.

Group

Aortic MDA

µmole/gm aorta

Aortic GTH

nmole/mg aorta

Aortic intima

thickness (µm)

1.Controlgroup (n=8)

3.1 ±

0.44

35.9±

2.9

27.4±

2.9

2.Induced untreated

Group(n=8)

9.7 ±

0.71*

17.8±

2.5*

288.2±

22.8*

3.Irbesartantreated

Group (n=8)

4.1±

0.58**

31.3±

2.2**

197.3±

25.9**

*p<0.05 ** p<0.05 as compare to group two

Irbesartan management don’t demonstrate significant action on lipid parameters when compared with group two (P > 0.05). Irbesartan was diminished the increment in endothelin-1, intracellular adhesion molecule-1, aortic MDA and aortic intimal thickness in compare with group two (P < 0.05). Also it restored aortic glutathione level (P < 0.05). as revealed in table (1), table (2) and table (3).

DISCUSSION:

In the current study, taking of a cholesterol rich diet to animals for twelve weeks caused in noticeable elevation in lipid parameters as compared to zero time and the control group. significantly, this study established that irbesartan management was significantly reduced total cholesterol and triglyceride while augmented HDL-Cholesterol serum level when compared with group two. Also, the results of present study demonstrated that atherogenic diet stimulate inflammation that described via important altitude in the serum level of intracellular adhesion molecule-1 and endotheline-1 in comparison with that of group one. This is in conformity with that (Zhang et al., 2006) who designated that hypercholesterolemia may cause elevation of CRP secretions by decreasing expressions of PPAR [gamma] in adipocytes. Moreover, (Bohm F., et al 2002) showed that atherosclerosis cause reduction in nitric oxide production and elevation in endothelin-1 production, cyclooxgenase activity and inflammation^(20,21).

These inflammatory responses provoked by atherogenic diet repressed by irbesartan management to remarkable level as revealed by reducing serum level of ICAM-1 and ED-1 than that in group two. This is in agreement with (Y. Jiang et al 2015) who showed that irbesartan satisfy TNFα-induced intracellular adhesion molecule-1 and vascular adhesion molecule-1 expression via the reduction of NF-κB pathways. This finding suggested that irbesartan may has large assistance to stoppage the progression of inflammatory disorders, like atherosclerosis. Angiotensin II (which blocked by irbesartan) plays an vital role in the cardiovascular disorders like myocardial infarction and atherosclerosis⁽²²⁾. It causes the pro-atheroscleroticaction. Reviewing modern studies, they have recommended that angiotensin II enhances intracellular adhesion molecul-1 and vascular adhesion molecule-1expression through NF-κBpathways⁽²³⁾.

In addition to that, the consequences of present study illustratedthat diet rich with cholesterol lead to augmentation in lipid peroxidation and oxidative insult, which was marked viadistinct elevations in the level of aortic MDA and remarkable decline in the level of aortic GSH. These actions were predictable since the prior studies in animals have verified that atherogenic diet associated with enhancement of lipid peroxidation and reduction of antioxidant substances^(24,25). In this study irbesartan was significantly inhibited the increase of aortic MDA level induced in induced untreated group suggesting decrease in reactive oxygen species and consequent lipid peroxidation. In addition to that irbesartan significantly elevateaortic GSH level and that lead to prevented GSH reduction in rabbits with hypercholesterolemea, so, this will preserved antioxidant reserve which is important for vascular defense against lipid peroxide. Therefore, irbesartan has protective activity in cardiovascular and cerebro-vascular disorders associated with elevation of free radical production. Oxidative stress engages in many processes of atherogenesis, like LDL oxidation, endothelial cellinjury and adhesion molecules expression⁽²⁶⁾. In addition to that, inflammation plays anessential role in atherogenesis and arbitrating all levels of this disorder from initiation to progression and the thrombotic complications of atherosclerosis⁽¹¹⁾.

The current study established that irbesartan management extensively reduce the elevation in intimal thickness induced via atherogenic diet in rabbitsas compared with group two.

Collectively, In this study we establish that irbesartan treatment exert anti inflammatory action by reducing (ED-1 and ICAM-1) and antioxidant action via decreasing lipid peroxide (MDA) and enhancing GSH. So these findings may give mechanistic answers how irbesartan decrease aortic intima thickness via number of pathways, including the inhibition of systemic inflammatory response and oxidative stress.

CONCLUSIONS:

Irbesartan treatment effectively prevents atherosclerosis progression through interfering with inflammation pathways and oxidative stress.

ACKNOWLEDGEMENTS:

The authors would like to thank Faculty of Pharmacy, Kufa University for providing all the facilities required to done this study.

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Received on 05.02.2018 Modified on 11.04.2018

Research J. Pharm. and Tech 2018; 11(10): 4324-4328.

DOI: 10.5958/0974-360X.2018.00791.6