About this Journal Submit a Manuscript Table of Contents
International Journal of Hypertension
Volume 2012 (2012), Article ID 169649, 7 pages
http://dx.doi.org/10.1155/2012/169649
Review Article

Roles of Brain Angiotensin II in Cognitive Function and Dementia

Department of Molecular Cardiovascular Biology and Pharmacology, Ehime University Graduate School of Medicine, Shitsukawa, Ehime, Tohon 791-0295, Japan

Received 14 September 2012; Revised 14 November 2012; Accepted 20 November 2012

Academic Editor: Marc de Gasparo

Copyright © 2012 Masaki Mogi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The brain renin-angiotensin system (RAS) has been highlighted as having a pathological role in stroke, dementia, and neurodegenerative disease. Particularly, in dementia, epidemiological studies indicate a preventive effect of RAS blockade on cognitive impairment in Alzheimer disease (AD). Moreover, basic experiments suggest a role of brain angiotensin II in neural injury, neuroinflammation, and cognitive function and that RAS blockade attenuates cognitive impairment in rodent dementia models of AD. Therefore, RAS regulation is expected to have therapeutic potential for AD. Here, we discuss the role of angiotensin II in cognitive impairment and AD. Angiotensin II binds to the type 2 receptor (AT2) and works mainly by binding with the type 1 receptor (AT1). AT2 receptor signaling plays a role in protection against multiple-organ damage. A direct AT2 receptor agonist is now available and is expected to reduce inflammation and oxidative stress and enhance cell differentiation. We and other groups reported that AT2 receptor activation enhances neuronal differentiation and neurite outgrowth in the brain. Here, we also review the effect of the AT2 receptor on cognitive function. RAS modulation may be a new therapeutic option for dementia including AD in the future.

1. Introduction

The renin-angiotensin system (RAS) in the brain is well known to be involved in systemic blood pressure control, including the regulation of cerebral blood flow [1]. Angiotensin II, a major player in RAS mainly via the angiotensin type 1 (AT1) receptor, plays an important role in the pathophysiology of tissue dysfunction [2, 3]; therefore, RAS blockade by AT1 receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs), which are widely used as antihypertensive drugs, is expected to prevent multiple-organ damage. Cognitive impairment and dementia are common serious health problems that impair quality of life in the elderly. Previous reports indicate the possibility that treatment with antihypertensive agents prevents the impairment of quality of life including cognitive performance [4, 5]. Possible beneficial effects of RAS blockade on cognitive function are also being highlighted in the clinical field [6, 7]. An epidemiological study by Li et al. recently showed that male subjects treated with ARBs exhibited a significant reduction in the incidence and progression of Alzheimer disease (AD) and dementia compared with those treated with ACEIs and other cardiovascular drugs [8]. Moreover, Davies et al. also reported that patients diagnosed with dementia had fewer prescriptions for ARBs and ACEIs. Interestingly, the inverse associations with AD were stronger for ARBs compared with ACEIs [9]. In contrast, Ohrui et al. demonstrated that long-term use of ACEIs may have a protective role against the development of AD, probably through their direct effects on RAS in the brain [10]. In a subanalysis of the Study on Cognition and Prognosis in the Elderly (SCOPE) trial, hypertensives treated with an ARB, candesartan, showed less decline of specific areas of cognitive function such as attention and episodic memory [11]. However, almost all large clinical intervention trials have shown no significant difference in the incidence of dementia between treatment with ARBs or ACEIs and the placebo group. The Ongoing telmisartan alone and in combination with ramipril global endpoint trial (ONTARGET) and the parallel telmisartan randomized assessment study in ACE intolerant subjects with cardiovascular disease (TRANSCEND) trial showed no clear effects on cognitive outcomes [12]. The reason why RAS blockade failed to prevent dementia may be the short-term observation for the long-term preclinical disease stage of dementia; however, the detailed explanation is not clear. Another reason is the selection of hypertensive patients, who have high cardiovascular disease morbidity, in these trials. A large number of these patients are likely to go on to develop dementia, most likely with strong vascular underpinning. In these trials, vascular dementia and AD are not well distinguished because most studies focused on dementia as subanalysis. As described in the review by Kehoe and Passmore, RAS has multifunctional involvement not only in vascular dementia but also in AD [13]. Therefore, in such specific groups with cardiovascular risk, the distinction of dementia subtype is very important in comparing the incidence of dementia.

The effect of angiotensin II on cognition has been examined in basic studies. Although the blood-brain barrier is impermeable for all RAS components, the local brain RAS has possible physiological and pharmacological functions in the neuronal system [14]. Gard reviewed the contradictory role of angiotensin II in memory and learning in animal studies [15]. Angiotensin II enhances memory and learning in rodents [16, 17], but other studies suggest that angiotensin II decreases cognition [18]. To assess the paradoxical effect of angiotensin II on cognitive function, we therefore performed cognitive tests in mice with continuous activation of angiotensin II, using transgenic mice carrying both the human renin and angiotensinogen genes (hRN/hANG-Tg) [19]. Interestingly, the avoidance rate in hRN/hANG-Tg mice did not increase from 14 weeks of age; however, that from 8 to 13 weeks of age tended to be higher than that in wild-type mice. These findings suggest that the acute or subacute effect of angiotensin II may enhance cognitive function, but chronic treatment with angiotensin II may exhaust neural function and result in cognitive impairment. Angiotensin II induces cerebrovascular remodeling, promotes vascular inflammation and oxidative stress, and results in impairment of regulation of cerebral blood flow (CBF) [20, 21]. Moreover, endothelial function in cerebral vessels was impaired in a genetic model of angiotensin-II-dependent hypertension [22, 23]. On the other hand, Lanz et al. showed that angiotensin II induced sustained central nervous system (CNS) inflammation via transforming growth factor- (TGF-)β in an experimental autoimmune encephalomyelitis (EAE) mouse model [24]. Furthermore, angiotensin II induced astrocyte senescence, which is involved in age-associated neurodegenerative disease via superoxide production [25]. In contrast, a centrally active ACE inhibitor, perindopril, was reported to prevent cognitive impairment in chronic central hypoperfusion rats [26] and Alzheimer disease model mice [27]. These reports indicate that continuous angiotensin II stimulation impairs cognitive function via stimulation of the AT1 receptor with “environmental degradation of neurons” such as a decrease in CBF and an increase in oxidative stress, CNS inflammation, and cellular senescence in the brain. Such multiple stimuli by angiotensin II induce cognitive impairment following neuronal degeneration.

2. Effects of Angiotensin II on Amyloid β Metabolism and Cholinergic System

There are two major proposed pathomechanisms of AD; the amyloid cascade hypothesis and the cholinergic hypothesis. Amyloid β (Aβ) is a 39–42 amino acid peptide, produced by cleavage of amyloid precursor protein (APP) [28]. Aβ (1–42) causes the neurodegenerative abnormalities that lead to clinical AD [29]. Although the effect of angiotensin converting enzyme on Aβ metabolism is one of the hot topics in the relation between RAS and AD [30], it seems that angiotensin II does not directly affect Aβ secretion or secretase activity via activation of the AT1 receptor [31]. On the other hand, blockade of RAS may affect Aβ metabolism. For example, an ARB, valsartan, was able to attenuate oligomerization of amyloid β peptides into high molecular weight oligomeric peptides [32]. Moreover, treatment with valsartan also disrupted the development of amyloid β-mediated cognitive impairment in Tg2576 mice, a model of Alzheimer disease; however, it is reported that this beneficial effect is not observed with treatment with other ARBs. We previously reported that Aβ (1–40) concentration in the brain of ddY mice that underwent intracerebroventricular injection of Aβ (1–40) was significantly decreased by treatment with an ARB, telmisartan [33]. Moreover, Danielyan et al. reported that intranasal administration of losartan exerts direct neuroprotective effects via its Aβ-reducing and anti-inflammatory effects in the central nervous system [34]. These results indicate that treatment with ARBs may have a beneficial effect on Aβ-induced brain injury through unknown mechanisms on Aβ metabolism by angiotensin II inhibition. On the other hand, brain-penetrating ACEIs such as perindopril prevent cognitive impairment in mice with intracerebroventricular Aβ (1–40) injection via attenuation of oxidative stress and hippocampal astrocyte activation [35]. ACE activity is increased in the hippocampus of these AD mice and suppressed by perindopril treatment. Although there is concern that ACEIs may enhance brain Aβ (1–42) deposition from basic research [36] because ACE converts Aβ (1–42), which plays a causative role in the development of Alzheimer disease, to Aβ (1–40) [37], recent pilot clinical trials showed that ramipril inhibits cerebrospinal fluid (CSF) ACE activity, but did not influence CSF Aβ (1–42) and cognition [38]. The effects of other RAS components involving angiotensin-II-generating enzymes on cognition have also been discussed. Aβ clearance is induced by many kinds of degrading enzyme such as neprilysin (NEP), insulin-degrading enzyme, and endothelin-converting enzyme. Angiotensin II is also generated by degradation of angiotensinogen and angiotensin I by tonins, cathepsins, and chymases as well as ACE. Gene polymorphism in cathepsin G, one of the angiotensin generating enzymes, showed no significant association with AD [39]. In our knowledge, no report has examined the relation between tonin, chymase, and dementia; however, inhibition of angiotensin generating enzymes may also inhibit Aβ degradation. Therefore, it is difficult to assess the effect on Aβ metabolism of drugs that inhibit angiotensin II based on degrading angiotensinogen. Further investigation is necessary to understand the relation among angiotensin II, ACE, other degrading enzymes, and Aβ metabolism.

In the cholinergic hypothesis, AD is also characterized by a loss of neurons, especially those expressing nicotinic acetylcholine receptors (nAChR) [40, 41]. To improve the cognitive deficit in AD, one promising drug target currently under investigation is the neuronal nicotinic alpha7 acetylcholine receptor (α7nAChR) [42, 43]. Although there are few reports about the correlation between α7nAChR and angiotensin II, Marrero’s group has demonstrated that angiotensin II blocks nicotine-mediated neuroprotection against Aβ (1–42) via activation of the tyrosine phosphatase, SHP-1 [44]. They also showed that angiotensin II inhibits α7nAChR-induced activation of the JAK2-PI-3 K cascade in PC12 cells through AT2 receptor-induced SHP-1 activation [45]. However, AT2 receptor-induced SHP-1 activation also induces cerebellar development and neural differentiation [46, 47]. Moreover, Aβ triggered AT2 receptor oligomerization in the hippocampus [48] and impaired coupling of the muscarinic acetylcholine receptor (mAChR) to heterotrimeric GTP-binding proteins (Gα q/11) [49]. Therefore, the AT2 receptor may interact with the cholinergic system; however, the actual effect of angiotensin II mediated by AChRs is still an enigma (Figure 1).

169649.fig.001
Figure 1: Possible effect of angiotensin II on neurovascular unit. AT2: angiotensin II type 2 receptor, AchR: acetylcholine receptor, BBB: blood brain barrier, and TGF-β: transforming growth factor β.

3. Effects of Angiotensin II on Neurovascular Unit

Nonneuronal cells such as vascular cells and glia (astrocytes, microglia and oligodendroglia) comprise the “neurovascular unit” and could play important roles in disease pathogenesis [50]. Especially, CBF functions in concert as a part of the neurovascular unit to maintain homeostasis of the cerebral microenvironment [51]. Iadecola and colleagues demonstrated that angiotensin II increases the production of reactive oxygen species (ROS) in cerebral microvessels via gp91phox (nox-2), a subunit of NADPH oxidase [20, 51]. Moreover, recently they also demonstrated that slow infusion of the pressor angiotensin II induces attenuation of the increase in CBF induced by neural activity (whisker stimulation) and by endothelium-dependent vasodilators, without elevation of mean arterial pressure (MAP) [52]. Such an effect of angiotensin II reduces blood supply and contributes to increased susceptibility to dementia. Interestingly, this angiotensin-induced cerebrovascular dysregulation was attenuated in female compared with male mice [53]. This sexual dimorphism of the cerebral blood-vessel response to angiotensin II may be implicated in the sex difference in cognitive impairment reported in epidemiological studies [54]. On the other hand, Takeda et al. demonstrated that the ARB olmesartan ameliorates amyloid β-induced impairment of functional hyperemia evoked by whisker stimulation via a decrease in oxidative stress in brain microvessels [55]. Recently, Zhang et al. reported that angiotensin II increases cerebral microvasculature inflammation via induction of oxidative stress and leads to immune-endothelial interaction, resulting in enhancement of BBB permeability [56]. Therefore, angiotensin-II-induced oxidative stress may have a key role in dysfunction of the neurovascular unit (Figure 1).

On the other hand, several reports indicate the effect of angiotensin II on astrocytes to be neuroinflammation, neuronal damage and astrocyte senescence. For example, Lanz et al. clearly demonstrated that angiotensin II acts as a paracrine mediator, sustaining inflammation in the CNS via TGF-β upregulation in astrocytes [24]. We also reported that aldosterone secretion induced by angiotensin II in astrocytes enhances neuronal damage due to angiotensin II [57]. Moreover, Liu et al. showed that angiotensin II induces astrocyte senescence via superoxide production [25]. These findings of astrocyte dysfunction induced by angiotensin II also explain the crucial role of angiotensin II in dysfunction of the neurovascular unit (Figure 1).

4. Effect of AT2 Receptors on Cognition and Dementia

The major actions of angiotensin II are mediated by the AT1 receptor, whereas the role of a second receptor subtype known as the angiotensin II type 2 (AT2) receptor is suggested to be protecting of the brain [58]. In the brain, AT2 receptors are expressed not only in the vascular wall but also in areas related to learning and control of motor activity [59, 60]. Mice with deletion of the AT2 receptor were reported to exhibit worse cognitive function compared with wild-type mice [60]. Reinecke et al. demonstrated the possibility that stimulation of the AT2 receptor may promote cell differentiation and regeneration in neuronal tissue [61] and that AT2 receptor stimulation supported neuronal survival and neurite outgrowth in response to ischemia-induced neuronal injury [62]. We also demonstrated that AT2 receptor signaling enhanced neural differentiation and the repair of damaged DNA through induction of a neural differentiating factor, methyl methanesulfonate-sensitive 2 (MMS2), which is one of the ubiquitin conjugating enzyme variants [47]. Moreover, Gallo-Payet et al. reported that angiotensin II induces neural differentiation and neurite outgrowth via mitogen-activated protein kinase [63] or nitric oxide [64] through AT2 receptor activation, and is involved in cerebellar development [65]. Therefore, direct AT2 receptor stimulation is expected to have a beneficial effect on cognitive function. We examined the possibility that direct stimulation of the AT2 receptor by a newly generated direct AT2 receptor agonist, Compound 21 (C21), would enhance cognitive function [66]. Daily intraperitoneal injection of C21 for 2 weeks significantly enhanced spatial learning evaluated by the Morris water maze test in C57BL6 mice, but this effect was not observed in AT2 receptor-deficient mice. C21 treatment increased cerebral blood flow assessed by laser speckle flowmetry and hippocampal field-excitatory postsynaptic potential. Moreover, treatment with C21 prevented cognitive decline in an Alzheimer disease mouse model with intracerebroventricular injection of amyloid β (1–40). AT2 receptor activation is reported to stimulate the release of NO/cGMP and may mediate vascular relaxation and blood flow indirectly through modulation of bradykinin release [67]. In our model, C21-induced cognitive enhancement was attenuated by coadministration of icatibant, a bradykinin B2 receptor antagonist. Therefore, direct activation of the AT2 receptor improves spatial learning via an increase in microcirculation, partly through modulation of bradykinin. The preventive effect of AT2 receptor signaling on dementia is summarized in Figure 2. Clinical use of C21 is expected to be a new therapeutic option in patients with dementia.

169649.fig.002
Figure 2: Effect of angiotensin II type 2 receptor signaling on cognitive function. AT2: angiotensin II type 2 receptor, ATIP: AT2 receptor-interacting protein, Id1: inhibitor of DNA binding protein 1, MMS2: methyl methanesulfonate-sensitive 2, NO: nitric oxide, SHP-1: Src homology 2 domain-containing protein-tyrosine phosphatase 1, and Ubc-13: ubiquitin conjugating enzyme 13.

5. Conclusion

Continuous stimulation with angiotensin II may damage neurons via multiple cascades through AT1 receptor stimulation. On the other hand, stimulation of the AT2 receptor is expected to prevent neural damage and cognitive impairment (Figure 3). However, it is difficult to perform clinical intervention studies to confirm the results of animal studies because of the long-term progression of cognitive impairment. Moreover, in clinical practice, it is not possible to exclude the antihypertensive effect of RAS blockade on cognition in patients with hypertension. However, RAS modulation may be a new therapeutic option for dementia including AD in the future. Therefore, the hypothesis that RAS regulation affects future cognitive function should be confirmed with carefully designed clinical studies.

169649.fig.003
Figure 3: Effect of angiotensin II on cognitive function. ACE: angiotensin converting enzyme inhibitor, AT1: angiotensin II type 1 receptor, AT2: angiotensin II type 2 receptor, and ARB: angiotensin II type 1 receptor blocker.

Abbreviations

AD:Alzheimer disease
ARB:Angiotensin II type 1 ( ) receptor blocker
receptor:Angiotensin II type 1 receptor
receptor:Angiotensin II type 2 receptor
ACE:Angiotensin converting enzyme
CBF:Cerebral surface blood flow
hRN/hANG-Tg:Human renin and angiotensinogen genes
RAS:Renin-angiotensin system
si:Small interfering
MMS2:Methyl methanesulfonate-sensitive 2.

Conflict of Interests

The authors declare no conflict of interests.

Acknowledgment

This work was supported by grants from the Ministry of Education, Science, Sports, and Culture of Japan to M. Mogi, J. Iwanami, and M. Horiuchi.

References

  1. M. de Gasparo, K. J. Catt, T. Inagami, J. W. Wright, and T. Unger, “International union of pharmacology. XXIII. The angiotensin II receptors,” Pharmacological Reviews, vol. 52, no. 3, pp. 415–472, 2000. View at Scopus
  2. R. E. Schmieder, K. F. Hilgers, M. P. Schlaich, and B. M. Schmidt, “Renin-angiotensin system and cardiovascular risk,” The Lancet, vol. 369, no. 9568, pp. 1208–1219, 2007. View at Publisher · View at Google Scholar · View at Scopus
  3. J. Iwanami, M. Mogi, M. Iwai, and M. Horiuchi, “Inhibition of the renin-angiotensin system and target organ protection,” Hypertension Research, vol. 32, no. 4, pp. 229–237, 2009. View at Publisher · View at Google Scholar · View at Scopus
  4. R. Fogari and A. Zoppi, “Effect of antihypertensive agents on quality of life in the elderly,” Drugs and Aging, vol. 21, no. 6, pp. 377–393, 2004. View at Publisher · View at Google Scholar · View at Scopus
  5. A. Fletcher, “Quality of life in the management of hypertension,” Clinical and Experimental Hypertension, vol. 21, no. 5-6, pp. 961–972, 1999. View at Scopus
  6. J. W. Wright and J. W. Harding, “The brain RAS and Alzheimer's disease,” Experimental Neurology, vol. 223, no. 2, pp. 326–333, 2010. View at Publisher · View at Google Scholar · View at Scopus
  7. M. Mogi and M. Horiuchi, “Effects of angiotensin II receptor blockers on dementia,” Hypertension Research, vol. 32, no. 9, pp. 738–740, 2009. View at Publisher · View at Google Scholar · View at Scopus
  8. N. C. Li, A. Lee, R. A. Whitmer et al., “Use of angiotensin receptor blockers and risk of dementia in a predominantly male population: prospective cohort analysis,” British Medical Journal, vol. 340, p. b5465, 2010. View at Publisher · View at Google Scholar · View at Scopus
  9. N. M. Davies, P. G. Kehoe, Y. Ben-Shlomo, and R. M. Martin, “Associations of anti-hypertensive treatments with Alzheimer's disease, vascular dementia, and other dementias,” Journal of Alzheimer's Disease, vol. 26, no. 4, pp. 699–708, 2011.
  10. T. Ohrui, T. Matsui, M. Yamaya et al., “Angiotensin-converting enzyme inhibitors and incidence of Alzheimer's disease in Japan [7],” Journal of the American Geriatrics Society, vol. 52, no. 4, pp. 649–650, 2004. View at Publisher · View at Google Scholar · View at Scopus
  11. B. K. Saxby, F. Harrington, K. A. Wesnes, I. G. McKeith, and G. A. Ford, “Candesartan and cognitive decline in older patients with hypertension: a substudy of the SCOPE trial,” Neurology, vol. 70, no. 19, pp. 1858–1866, 2008. View at Publisher · View at Google Scholar · View at Scopus
  12. C. Anderson, K. Teo, P. Gao et al., “Renin-angiotensin system blockade and cognitive function in patients at high risk of cardiovascular disease: analysis of data from the ONTARGET and TRANSCEND studies,” The Lancet Neurology, vol. 10, no. 1, pp. 43–53, 2011. View at Publisher · View at Google Scholar · View at Scopus
  13. P. G. Kehoe and P. A. Passmore, “The renin-angiotensin system and antihypertensive drugs in Alzheimer's disease: current standing of the angiotensin hypothesis?” Journal of Alzheimer's Disease, vol. 30, supplement 2, pp. S251–S268, 2012.
  14. J. W. Wright and J. W. Harding, “Brain renin-angiotensin-A new look at an old system,” Progress in Neurobiology, vol. 95, no. 1, pp. 49–67, 2011. View at Publisher · View at Google Scholar · View at Scopus
  15. P. R. Gard, “The role of angiotensin II in cognition and behaviour,” European Journal of Pharmacology, vol. 438, no. 1-2, pp. 1–14, 2002. View at Publisher · View at Google Scholar · View at Scopus
  16. V. Georgiev and D. Yonkov, “Participation of angiotensin II in learning and memory. I. Interaction of angiotensin II with saralasin,” Methods and Findings in Experimental and Clinical Pharmacology, vol. 7, no. 8, pp. 415–418, 1985. View at Scopus
  17. A. Kułakowska, W. Karwowska, K. Wiśniewski, and J. J. Braszko, “Losartan influences behavioural effects of angiotensin II in rats,” Pharmacological Research, vol. 34, no. 3-4, pp. 109–115, 1996. View at Publisher · View at Google Scholar · View at Scopus
  18. V. Raghavendra, K. Chopra, and S. K. Kulkarni, “Involvement of cholinergic system in losartan-induced facilitation of spatial and short-term working memory,” Neuropeptides, vol. 32, no. 5, pp. 417–421, 1998. View at Publisher · View at Google Scholar · View at Scopus
  19. S. Inaba, M. Iwai, M. Furuno et al., “Continuous activation of renin-angiotensin system impairs cognitive function in renin/angiotensinogen transgenic mice,” Hypertension, vol. 53, no. 2, pp. 356–362, 2009. View at Publisher · View at Google Scholar · View at Scopus
  20. K. Kazama, J. Anrather, P. Zhou et al., “Angiotensin II impairs neurovascular coupling in neocortex through NADPH oxidase-derived radicals,” Circulation Research, vol. 95, no. 10, pp. 1019–1026, 2004. View at Publisher · View at Google Scholar · View at Scopus
  21. Y. Wei, A. T. Whaley-Connell, K. Chen et al., “NADPH oxidase contributes to vascular inflammation, insulin resistance, and remodeling in the transgenic (mRen2) rat,” Hypertension, vol. 50, no. 2, pp. 384–391, 2007. View at Publisher · View at Google Scholar · View at Scopus
  22. S. P. Didion, C. D. Sigmund, and F. M. Faraci, “Impaired endothelial function in transgenic mice expressing both human renin and human angiotensinogen,” Stroke, vol. 31, no. 3, pp. 760–765, 2000. View at Scopus
  23. F. M. Faraci, K. G. Lamping, M. L. Modrick, M. J. Ryan, C. D. Sigmund, and S. P. Didion, “Cerebral vascular effects of angiotensin II: new insights from genetic models,” Journal of Cerebral Blood Flow and Metabolism, vol. 26, no. 4, pp. 449–455, 2006. View at Publisher · View at Google Scholar · View at Scopus
  24. T. V. Lanz, Z. Ding, P. P. Ho et al., “Angiotensin II sustains brain inflammation in mice via TGF-β,” Journal of Clinical Investigation, vol. 120, no. 8, pp. 2782–2794, 2010. View at Publisher · View at Google Scholar · View at Scopus
  25. G. Liu, N. Hosomi, H. Hitomi et al., “Angiotensin II induces human astrocyte senescence through reactive oxygen species production,” Hypertension Research, vol. 34, no. 4, pp. 479–483, 2011. View at Publisher · View at Google Scholar · View at Scopus
  26. K. Yamada, T. Horita, M. Takayama, et al., “Effect of a centrally active angiotensin converting enzyme inhibitor, perindopril, on cognitive performance in chronic cerebral hypo-perfusion rats,” Brain Research, vol. 1421, no. 1, pp. 10–120, 2011.
  27. K. Yamada, S. Uchida, S. Takahashi et al., “Effect of a centrally active angiotensin-converting enzyme inhibitor, perindopril, on cognitive performance in a mouse model of Alzheimer's disease,” Brain Research C, vol. 1352, pp. 176–186, 2010. View at Publisher · View at Google Scholar · View at Scopus
  28. W. E. Van Nostrand, J. Davis-Salinas, and S. M. Saporito-Irwin, “Amyloid β-protein induces the cerebrovascular cellular pathology of Alzheimer's disease and related disorders,” Annals of the New York Academy of Sciences, vol. 777, pp. 297–302, 1996. View at Scopus
  29. J. Hardy and D. J. Selkoe, “The amyloid hypothesis of Alzheimer's disease: progress and problems on the road to therapeutics,” Science, vol. 297, no. 5580, pp. 353–356, 2002. View at Publisher · View at Google Scholar · View at Scopus
  30. K. Zou and M. Michikawa, “Angiotensin-converting enzyme as a potential target for treatment of Alzheimer's disease: inhibition or activation?” Reviews in the Neurosciences, vol. 19, no. 4-5, pp. 203–212, 2008. View at Scopus
  31. B. R. Wang, J. Q. Shi, Y. D. Zhang, D. L. Zhu, and J. P. Shi, “Angiotensin II does not directly affect Aβ secretion or β-/γ-secretase activity via activation of angiotensin II type 1 receptor,” Neuroscience Letters, vol. 500, no. 2, pp. 103–107, 2011. View at Publisher · View at Google Scholar · View at Scopus
  32. J. Wang, L. Ho, L. Chen et al., “Valsartan lowers brain β-amyloid protein levels and improves spatial learning in a mouse model of Alzheimer disease,” Journal of Clinical Investigation, vol. 117, no. 11, pp. 3393–3402, 2007. View at Publisher · View at Google Scholar · View at Scopus
  33. K. Tsukuda, M. Mogi, J. Iwanami et al., “Cognitive deficit in amyloid-β-injected mice was improved by pretreatment with a low dose of telmisartan partly because of peroxisome proliferator-activated receptor-γ activation,” Hypertension, vol. 54, no. 4, pp. 782–787, 2009. View at Publisher · View at Google Scholar · View at Scopus
  34. L. Danielyan, R. Klein, L. R. Hanson et al., “Protective effects of intranasal losartan in the APP/PS1 transgenic mouse model of Alzheimer disease,” Rejuvenation Research, vol. 13, no. 2-3, pp. 195–201, 2010. View at Publisher · View at Google Scholar · View at Scopus
  35. Y. F. Dong, K. Kataoka, Y. Tokutomi, et al., “Perindopril, a centrally active angiotensin-converting enzyme inhibitor, prevents cognitive impairment in mouse models of Alzheimer's disease,” FASEB Journal, vol. 25, no. 9, pp. 2911–2920, 2011. View at Publisher · View at Google Scholar
  36. M. L. Hemming and D. J. Selkoe, “Amyloid β-protein is degraded by cellular angiotensin-converting enzyme (ACE) and elevated by an ACE inhibitor,” Journal of Biological Chemistry, vol. 280, no. 45, pp. 37644–37650, 2005. View at Publisher · View at Google Scholar · View at Scopus
  37. K. Zou, T. Maeda, A. Watanabe et al., “Aβ42-to-Aβ40- and angiotensin-converting activities in different domains of angiotensin-converting enzyme,” Journal of Biological Chemistry, vol. 284, no. 46, pp. 31914–31920, 2009. View at Publisher · View at Google Scholar · View at Scopus
  38. W. Wharton, J. H. Stein, C. Korcarz, et al., “The effects of ramipril in individuals at risk for Alzheimer's disease: results of a pilot clinical trial,” Journal of Alzheimer's Disease, vol. 32, no. 1, pp. 147–156, 2012.
  39. T. J. Bhojak, S. T. DeKosky, M. Ganguli, and M. I. Kamboh, “Genetic polymorphism in the cathepsin G gene and the risk of Alzheimer's disease,” Neuroscience Letters, vol. 309, no. 2, pp. 138–140, 2001. View at Publisher · View at Google Scholar · View at Scopus
  40. A. Kadir, O. Almkvist, A. Wall, B. Långström, and A. Nordberg, “PET imaging of cortical 11C-nicotine binding correlates with the cognitive function of attention in Alzheimer's disease,” Psychopharmacology, vol. 188, no. 4, pp. 509–520, 2006. View at Publisher · View at Google Scholar · View at Scopus
  41. S. D. Buckingham, A. K. Jones, L. A. Brown, and D. B. Sattelle, “Nicotinic acetylcholine receptor signalling: roles in alzheimer's disease and amyloid neuroprotection,” Pharmacological Reviews, vol. 61, no. 1, pp. 39–61, 2009. View at Publisher · View at Google Scholar · View at Scopus
  42. H. Y. Wang, D. H. S. Lee, M. R. D'Andrea, P. A. Peterson, R. P. Shank, and A. B. Reitz, “β-Amyloid1-42 binds to α7 nicotinic acetylcholine receptor with high affinity. Implications for Alzheimer's disease pathology,” Journal of Biological Chemistry, vol. 275, no. 8, pp. 5626–5632, 2000. View at Publisher · View at Google Scholar · View at Scopus
  43. H. R. Parri, C. M. Hernandez, and K. T. Dineley, “Research update: alpha7 nicotinic acetylcholine receptor mechanisms in Alzheimer's disease,” Biochemical Pharmacology, vol. 82, no. 8, pp. 931–942, 2011. View at Publisher · View at Google Scholar · View at Scopus
  44. S. Shaw, M. Bencherif, and M. B. Marrero, “Angiotensin II blocks nicotine-mediated neuroprotection against β-amyloid (1–42) via activation of the tyrosine phosphatase SHP-1,” Journal of Neuroscience, vol. 23, no. 35, pp. 11224–11228, 2003. View at Scopus
  45. M. B. Marrero and M. Bencherif, “Convergence of alpha 7 nicotinic acetylcholine receptor-activated pathways for anti-apoptosis and anti-inflammation: central role for JAK2 activation of STAT3 and NF-κB,” Brain Research C, vol. 1256, pp. 1–7, 2009. View at Publisher · View at Google Scholar · View at Scopus
  46. L. R. Seguin, R. S. Villarreal, and G. M. Ciuffo, “AT2 receptors recruit c-Src, SHP-1 and FAK upon activation by ang II in PND15 rat hindbrain,” Neurochemistry International, vol. 60, no. 2, pp. 199–207, 2012. View at Publisher · View at Google Scholar
  47. J. M. Li, M. Mogi, K. Tsukuda et al., “Angiotensin II-induced neural differentiation via angiotensin II type 2 (AT2) receptor-MMS2 cascade involving interaction between AT 2 receptor-interacting protein and Src homology 2 domain-containing protein-tyrosine phosphatase 1,” Molecular Endocrinology, vol. 21, no. 2, pp. 499–511, 2007. View at Publisher · View at Google Scholar · View at Scopus
  48. S. AbdAlla, H. Lother, A. El Missiry et al., “Angiotensin II AT2 receptor oligomers mediate G-protein dysfunction in an animal model of Alzheimer disease,” Journal of Biological Chemistry, vol. 284, no. 10, pp. 6554–6565, 2009. View at Publisher · View at Google Scholar · View at Scopus
  49. P. J. Tienari, B. De Strooper, E. Ikonen et al., “The β-amyloid domain is essential for axonal sorting of amyloid precursor protein,” EMBO Journal, vol. 15, no. 19, pp. 5218–5229, 1996. View at Scopus
  50. C. Iadecola, “The overlap between neurodegenerative and vascular factors in the pathogenesis of dementia,” Acta Neuropathologica, vol. 120, no. 3, pp. 287–296, 2010. View at Publisher · View at Google Scholar · View at Scopus
  51. H. Girouard, L. Park, J. Anrather, P. Zhou, and C. Iadecola, “Angiotensin II attenuates endothelium-dependent responses in the cerebral microcirculation through nox-2-derived radicals,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 26, no. 4, pp. 826–832, 2006. View at Publisher · View at Google Scholar · View at Scopus
  52. C. Capone, G. Faraco, L. Park, X. Cao, R. L. Davisson, and C. Iadecola, “The cerebrovascular dysfunction induced by slow pressor doses of angiotensin II precedes the development of hypertension,” American Journal of Physiology-Heart and Circulatory Physiology, vol. 300, no. 1, pp. H397–H407, 2011. View at Publisher · View at Google Scholar · View at Scopus
  53. H. Girouard, A. Lessard, C. Capone, T. A. Milner, and C. Iadecola, “The neurovascular dysfunction induced by angiotensin II in the mouse neocortex is sexually dimorphic,” American Journal of Physiology-Heart and Circulatory Physiology, vol. 294, no. 1, pp. H156–H163, 2008. View at Publisher · View at Google Scholar · View at Scopus
  54. G. A. Laughlin, L. K. McEvoy, D. von Muhlen, et al., “Sex differences in the association of Framingham cardiac risk score with cognitive decline in community-dwelling elders without clinical heart disease,” Psychosomatic Medicine, vol. 73, no. 8, pp. 683–689, 2011. View at Publisher · View at Google Scholar
  55. S. Takeda, N. Sato, D. Takeuchi et al., “Angiotensin receptor blocker prevented β-amyloid-induced cognitive impairment associated with recovery of neurovascular coupling,” Hypertension, vol. 54, no. 6, pp. 1345–1352, 2009. View at Publisher · View at Google Scholar · View at Scopus
  56. M. Zhang, Y. Mao, S. H. Ramirez, R. F. Tuma, and T. Chabrashvili, “Angiotensin II induced cerebral microvascular inflammation and increased blood-brain barrier permeability via oxidative stress,” Neuroscience, vol. 171, no. 3, pp. 852–858, 2010. View at Publisher · View at Google Scholar · View at Scopus
  57. L. J. Min, M. Mogi, J. Iwanami et al., “Angiotensin II and aldosterone-induced neuronal damage in neurons through an astrocyte-dependent mechanism,” Hypertension Research, vol. 34, no. 6, pp. 773–778, 2011. View at Publisher · View at Google Scholar · View at Scopus
  58. M. Horiuchi, M. Mogi, and M. Iwai, “The angiotensin II type 2 receptor in the brain,” Journal of the Renin-Angiotensin-Aldosterone System, vol. 11, no. 1, pp. 1–6, 2010. View at Publisher · View at Google Scholar · View at Scopus
  59. M. Iwai, H. W. Liu, R. Chen et al., “Possible inhibition of focal cerebral ischemia by angiotensin II type 2 receptor stimulation,” Circulation, vol. 110, no. 7, pp. 843–848, 2004. View at Publisher · View at Google Scholar · View at Scopus
  60. M. Mogi, J. M. Li, J. Iwanami et al., “Angiotensin II type-2 receptor stimulation prevents neural damage by transcriptional activation of methyl methanesulfonate sensitive 2,” Hypertension, vol. 48, no. 1, pp. 141–148, 2006. View at Publisher · View at Google Scholar · View at Scopus
  61. K. Reinecke, R. Lucius, A. Reinecke, U. Rickert, T. Herdegen, and T. Unger, “Angiotensin II accelerates functional recovery in the rat sciatic nerve in vivo: role of the AT2 receptor and the transcription factor NF-kappaB,” FASEB Journal, vol. 17, no. 14, pp. 2094–2096, 2003. View at Scopus
  62. J. Li, J. Culman, H. Hörtnagl et al., “Angiotensin AT2 receptor protects against cerebral ischemia-induced neuronal injury,” FASEB Journal, vol. 19, no. 6, pp. 617–619, 2005. View at Publisher · View at Google Scholar · View at Scopus
  63. L. Gendron, L. Laflamme, N. Rivard, C. Asselin, M. D. Payet, and N. Gallo-Payet, “Signals from the AT2 (angiotensin type 2) receptor of angiotensin II inhibit p21(ras) and activate MAPK (mitogen-activated protein kinase) to induce morphological neuronal differentiation in NG108-15 cells,” Molecular Endocrinology, vol. 13, no. 9, pp. 1615–1626, 1999. View at Scopus
  64. F. Cote, L. Laflamme, M. D. Payet, and N. Gallo-Payet, “Nitric oxide, a new second messenger involved in the action of angiotensin II on neuronal differentiation of NG108-15 cells,” Endocrine Research, vol. 24, no. 3-4, pp. 403–407, 1998. View at Scopus
  65. F. Côté, T. H. Do, L. Laflamme, J. M. Gallo, and N. Gallo-Payet, “Activation of the AT2 receptor of angiotensin II induces neurite outgrowth and cell migration in microexplant cultures of the cerebellum,” Journal of Biological Chemistry, vol. 274, no. 44, pp. 31686–31692, 1999. View at Publisher · View at Google Scholar · View at Scopus
  66. F. Jing, M. Mogi, A. Sakata, et al., “Direct stimulation of angiotensin II type 2 receptor enhances spatial memory,” Journal of Cerebral Blood Flow and Metabolism, vol. 32, no. 2, pp. 248–255, 2011.
  67. O. Jöhren, A. Dendorfer, and P. Dominiak, “Cardiovascular and renal function of angiotensin II type-2 receptors,” Cardiovascular Research, vol. 62, no. 3, pp. 460–467, 2004. View at Publisher · View at Google Scholar · View at Scopus