The Effect of Angiotensin Receptor Type 2 Inhibition and Estrogen on Experimental Traumatic Brain Injury

Document Type: Original Article


1 Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences

2 Endocrinology and Metabolism Research Center, Institute of Basic and Clinical Physiology Sciences, Kerman University of Medical Sciences

3 Physiology Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran


Background: Estrogen interferes with renin‑angiotensin system (RAS). Increasing evidence suggests that estrogen interferes with the RAS
such as decreasing angiotensin receptor in the brain. Objectives: This study aimed at investigating the mutual interaction between estrogen
and candesartan (an angiotensin receptor blocker) to inhibit or amplify each other’s neuroprotective effects after traumatic brain injury (TBI).
Materials and Methods: Female rats were divided into 11 groups and the ovaries were removed in nine groups. Study groups included sham,
TBI, oil, vehicle (Veh), a low dose (LC) and a high dose (HC) of candesartan, estrogen (E2), Veh + Veh, and a combination of estrogen with
a low dose (E2 + LC) and a high dose (E2 + HC) of candesartan. TBI was induced by the Marmarou’s method. Brain edema and integrity of
blood–brain barrier (BBB) were assayed by calculating brain water content (BWC) and Evans blue content, respectively. The neurological
outcome was evaluated using the veterinary coma scale (VCS). Results: The results showed that the BWC in the E2 group was less than that
of the oil group (P < 0.01) and in the HC group was also less than that of the Veh group (P < 0.05). Posttraumatic Evans blue content in the
TBI, oil, and Veh groups was higher than that in the E2 (P < 0.001) and HC (P < 0.001) groups. Although there was no significant difference in
the above indicators between the LC and Veh groups, both the BWC and Evans blue content in the E2 + LC group were lower compared to the
oil + Veh group (P < 0.001). In addition, the VCS increased in the E2, HC, and combined groups after TBI (P < 0.01). Conclusion: Prescribing
estrogen alone and a high dose of candesartan and a low dose of candesartan with estrogen has a neuroprotective effect on brain edema,
permeability of BBB, and neurological scores. This may suggest that estrogen and candesartan (especially in a low dose) act via similar paths.


1. Maas AI, Stocchetti N, Bullock R. Moderate and severe traumatic brain injury in adults. Lancet Neurol 2008;7:728‑41.

2. Zitnay G. Lessons from National and International TBI Societies and Funds Like NBIRTT. Re‑Engineering of the Damaged Brain and Spinal Cord. Austria: Springer; 2005. p. 131‑3.

3. Bruns J Jr., Hauser WA. The epidemiology of traumatic brain injury: A review. Epilepsia 2003;44:2‑10.

4. Marklund N, Hillered L. Animal modelling of traumatic brain injury in preclinical drug development: Where do we go from here? Br J Pharmacol 2011;164:1207‑29.

5. Fouda AY, Artham S, El‑Remessy AB, Fagan SC. Renin‑angiotensin system as a potential therapeutic target in stroke and retinopathy: Experimental and clinical evidence. Clin Sci (Lond) 2016;130:221‑38.

6. Liu H, Kitazato KT, Uno M, Yagi K, Kanematsu Y, Tamura T, et al. Protective mechanisms of the angiotensin II type 1 receptor blocker candesartan against cerebral ischemia: In vivo and in vitro studies. J Hypertens 2008;26:1435‑45.

7. Tozlu S, Girault I, Vacher S, Vendrell J, Andrieu C, Spyratos F, et al. Identification of novel genes that co‑cluster with estrogen receptor alpha in breast tumor biopsy specimens, using a large‑scale real‑time reverse transcription‑PCR approach. Endocr Relat Cancer 2006;13:1109‑20.

8. Behl C, Skutella T, Lezoualc’h F, Post A, Widmann M, Newton CJ, et al. Neuroprotection against oxidative stress by estrogens: Structure‑activity relationship. Mol Pharmacol 1997;51:535‑41.

9. Maghool F, Khaksari M, Siahposht Khachki A. Differences in brain edema and intracranial pressure following traumatic brain injury across the estrous cycle: Involvement of female sex steroid hormones. Brain Res 2013;1497:61‑72.

10. Naderi V, Khaksari M, Abbasi R, Maghool F. Estrogen provides neuroprotection against brain edema and blood brain barrier disruption through both estrogen receptors α and β following traumatic brain injury. Iran J Basic Med Sci 2015;18:138‑44.

11. Shahrokhi N, Khaksari M, Soltani Z, Mahmoodi M, Nakhaee N. Effect of sex steroid hormones on brain edema, intracranial pressure, and neurologic outcomes after traumatic brain injury. Can J Physiol Pharmacol 2010;88:414‑21.

12. Brown CM, Suzuki S, Jelks KA, Wise PM. Estradiol is a potent protective, restorative, and trophic factor after brain injury. Semin Reprod Med 2009;27:240‑9.

13. Gallagher PE, Li P, Lenhart JR, Chappell MC, Brosnihan KB. Estrogen regulation of angiotensin‑converting enzyme mRNA. Hypertension 1999;33:323‑8.

14. Shimada K, Kitazato KT, Kinouchi T, Yagi K, Tada Y, Satomi J, et al. Activation of estrogen receptor‑α and of angiotensin‑converting enzyme 2 suppresses ischemic brain damage in oophorectomized rats. Hypertension 2011;57:1161‑6.

15. Dean SA, Tan J, O’Brien ER, Leenen FH. 17beta‑estradiol downregulates tissue angiotensin‑converting enzyme and ANG II type 1 receptor in female rats. Am J Physiol Regul Integr Comp Physiol 2005;288:R759‑66.

16. Khaksari M, Soltani Z, Shahrokhi N, Moshtaghi G, Asadikaram G. The role of estrogen and progesterone, administered alone and in combination, in modulating cytokine concentration following traumatic brain injury. Can J Physiol Pharmacol 2011;89:31‑40.

17. O’Connor CA, Cernak I, Vink R. Both estrogen and progesterone attenuate edema formation following diffuse traumatic brain injury in rats. Brain Res 2005;1062:171‑4.

18. Panahpour H, Bohlooli S, Motavallibashi S. Antioxidant activity‑mediated neuroprotective effects of an antagonist of at1 receptors, candesartan, against cerebral ischemia and edema in rats. Neurophysiology 2013;45:441‑7.

19. Tota S, Kamat PK, Awasthi H, Singh N, Raghubir R, Nath C, et al. Candesartan improves memory decline in mice: Involvement of AT1 receptors in memory deficit induced by intracerebral streptozotocin. Behav Brain Res 2009;199:235‑40.

20. Marmarou A, Foda MA, van den Brink W, Campbell J, Kita H, Demetriadou K, et al. A new model of diffuse brain injury in rats. Part I: Pathophysiology and biomechanics. J Neurosurg 1994;80:291‑300.

21. Cotroneo MS, Fritz WA, Lamartiniere CA. Dynamic profiling of estrogen receptor and epidermal growth factor signaling in the uteri of genistein‑ and estrogen‑treated rats. Food Chem Toxicol 2005;43:637‑45.

22. Soltani Z, Khasksari M, Shahrokhi N, Nakhaei N, Shaibani V. Effect of Combined Administration of Estrogen and Progesterone on Brain Edema and Neurological Outcome after Traumatic Brain Injury in Female Rats. IJEM 2009;10:629-38.

23. SarkakiAR, Khaksari Haddad M, Soltani Z, Shahrokhi N, Mahmoodi M. Time‑ and dose‑dependent neuroprotective effects of sex steroid hormones on inflammatory cytokines after a traumatic brain injury. J Neurotrauma 2013;30:47‑54.

24. Guo Q, Sayeed I, Baronne LM, Hoffman SW, Guennoun R, Stein DG. Progesterone administration modulates AQP4 expression and edema after traumatic brain injury in male rats. Exp Neurol 2006;198:469‑78.

25. Suehiro E, Fujisawa H, Akimura T, Ishihara H, Kajiwara K, Kato S, et al. Increased matrix metalloproteinase‑9 in blood in association with activation of interleukin‑6 after traumatic brain injury: Influence of hypothermic therapy. J Neurotrauma 2004;21:1706‑11.

26. Globus MY, Alonso O, Dietrich WD, Busto R, Ginsberg MD. Glutamate release and free radical production following brain injury: Effects of posttraumatic hypothermia. J Neurochem 1995;65:1704‑11.

27. Soltani Z, Khaksari M, Shahrokhi N, Mohammadi G, Mofid B, Vaziri A, et al. Effect of estrogen and/or progesterone administration on traumatic brain injury‑caused brain edema: The changes of aquaporin‑4 and interleukin‑6. J Physiol Biochem 2016;72:33‑44.

28. Khaksari M, Abbasloo E, Dehghan F, Soltani Z, Asadikaram G. The brain cytokine levels are modulated by estrogen following traumatic brain injury: Which estrogen receptor serves as modulator? Int Immunopharmacol 2015;28:279‑87.

29. Hurn PD, Littleton‑Kearney MT, Kirsch JR, Dharmarajan AM, Traystman RJ. Postischemic cerebral blood flow recovery in the female: Effect of 17 beta‑estradiol. J Cereb Blood Flow Metab 1995;15:666‑72.

30. Walf AA, Koonce CJ, Frye CA. Estradiol or diarylpropionitrile administration to wild type, but not estrogen receptor beta knockout, mice enhances performance in the object recognition and object placement tasks. Neurobiol Learn Mem 2008;89:513‑21.

31. Khaksari M, Soltani Z, Shahrokhi N. Effects of female sex steroids administration on pathophysiologic mechanisms in traumatic brain injury. Transl Stroke Res 2018;9:393‑416.

32. Carswell HV, Bingham D, Wallace K, Nilsen M, Graham DI, Dominiczak AF, et al. Differential effects of 17beta‑estradiol upon stroke damage in stroke prone and normotensive rats. J Cereb Blood Flow Metab 2004;24:298‑304.

33. Bingham D, Macrae IM, Carswell HV. Detrimental effects of 17beta‑oestradiol after permanent middle cerebral artery occlusion. J Cereb Blood Flow Metab 2005;25:414‑20.

34. Vergouwen MD, Anderson RE, Meyer FB. Gender differences and the effects of synthetic exogenous and non‑synthetic estrogens in focal cerebral ischemia. Brain Res 2000;878:88‑97.

35. Soltani Z, Shahrokhi N, Karamouzian S, Khaksari M, Mofid B, Nakhaee N, et al. Does progesterone improve outcome in diffuse axonal injury? Brain Inj 2017;31:16‑23.

36. Villapol S, Yaszemski AK, Logan TT, Sánchez‑Lemus E, Saavedra JM, Symes AJ. Candesartan, an angiotensin II AT1‑receptor blocker and PPAR‑γ agonist, reduces lesion volume and improves motor and memory function after traumatic brain injury in mice. Neuropsychopharmacology 2012;37:2817.

37. Hinoi T, Tomohiro Y, Kajiwara S, Matsuo S, Fujimoto Y, Yamamoto S, et al. Telmisartan, an angiotensin II type 1 receptor blocker, improves coronary microcirculation and insulin resistance among essential hypertensive patients without left ventricular hypertrophy. Hypertens Res 2008;31:615‑22.

38. Benigni A, Cassis P, Remuzzi G. Angiotensin II revisited: New roles in inflammation, immunology and aging. EMBO Mol Med 2010;2:247‑57.

39. Dohi Y, Ohashi M, Sugiyama M, Takase H, Sato K, Ueda R, et al. Candesartan reduces oxidative stress and inflammation in patients with essential hypertension. Hypertens Res 2003;26:691‑7.

40. Quan N, Banks WA. Brain‑immune communication pathways. Brain Behav Immun 2007;21:727‑35.

41. Zhou J, Pavel J, Macova M, Yu ZX, Imboden H, Ge L, et al. AT1 receptor blockade regulates the local angiotensin II system in cerebral microvessels from spontaneously hypertensive rats. Stroke 2006;37:1271‑6.

42. Brdon J, Kaiser S, Hagemann F, Zhao Y, Culman J, Gohlke P, et al. Comparison between early and delayed systemic treatment with candesartan of rats after ischaemic stroke. J Hypertens 2007;25:187‑96.

43. Ciriello J, Roder S. 17β‑estradiol alters the response of subfornical organ neurons that project to supraoptic nucleus to plasma angiotensin II and hypernatremia. Brain Res 2013;1526:54‑64.

44. Ji H, Menini S, Zheng W, Pesce C, Wu X, Sandberg K, et al. Role of angiotensin‑converting enzyme 2 and angiotensin (1‑7) in 17beta‑oestradiol regulation of renal pathology in renal wrap hypertension in rats. Exp Physiol 2008;93:648‑57.

45. Cheng Y, Li Q, Zhang Y, Wen Q, Zhao J. Effects of female sex hormones on expression of the ang‑(1‑7)/Mas‑R/nNOS pathways in rat brain. Can J Physiol Pharmacol 2015;93:993‑8.