Double Deletion of Angiotensin II Type 2 and Mas Receptors Accelerates Aging-Related Muscle Weakness in Male Mice

Background The activation of AT2 (angiotensin II type 2 receptor ) and Mas receptor by angiotensin II and angiotensin-(1-7), respectively, is the primary process that counteracts activation of the canonical renin-angiotensin system (RAS). Although inhibition of canonical RAS could delay the progression of physiological aging, we recently reported that deletion of Mas had no impact on the aging process in mice. Here, we used male mice with a deletion of only AT2 or a double deletion of AT2 and Mas to clarify whether these receptors contribute to the aging process in a complementary manner, primarily by focusing on aging-related muscle weakness. Methods and Results Serial changes in grip strength of these mice up to 24 months of age showed that AT2/Mas knockout mice, but not AT2 knockout mice, had significantly weaker grip strength than wild-type mice from the age of 18 months. AT2/Mas knockout mice exhibited larger sizes, but smaller numbers and increased frequency of central nucleation (a marker of aged muscle) of single skeletal muscle fibers than AT2 knockout mice. Canonical RAS-associated genes, inflammation-associated genes, and senescence-associated genes were highly expressed in skeletal muscles of AT2/Mas knockout mice. Muscle angiotensin II content increased in AT2/Mas knockout mice. Conclusions Double deletion of AT2 and Mas in mice exaggerated aging-associated muscle weakness, accompanied by signatures of activated RAS, inflammation, and aging in skeletal muscles. Because aging-associated phenotypes were absent in single deletions of the receptors, AT2 and Mas could complement each other in preventing local activation of RAS during aging.

Angiotensin II and Amyloid-β Synergistically Induce Brain Vascular Smooth Muscle Cell Senescence

BACKGROUND

Amyloid-β (Aβ) induces cerebrovascular damage and is reported to stimulate endothelial cell senescence. We previously demonstrated that angiotensin II (Ang II)-promoted vascular senescence. We examined the possible cross-talk between Ang II and Aβ in regulating brain vascular smooth muscle cell (BVSMC) senescence.

METHODS

BVSMCs were prepared from adult male mice and stimulated with Ang II (0, 0.1, 1, 10, and 100 nmol/l) and/or Aβ 1-40 (0, 0.1, 0.3, 0.5, 1, 3, and 5 µmol/l) for the indicated times. Cellular senescence was evaluated by senescence-associated β-galactosidase staining.

RESULTS

Treatment with Ang II (100 nmol/l) or Aβ (1 µmol/l) at a higher dose increased senescent cells compared with control at 6 days. Treatment with Ang II (10 nmol/l) or Aβ (0.5 µmol/l) at a lower dose had no effect on senescence whereas a combined treatment with lower doses of Ang II and Aβ significantly enhanced senescent cells. This senescence enhanced by lower dose combination was markedly blocked by valsartan (Ang II type 1 receptor inhibitor) or TAK-242 (Aβ receptor TLR4 inhibitor) treatment. Moreover, lower dose combination caused increases in superoxide anion levels and p-ERK expression for 2 days, NF-κB activity, p-IκB, p-IKKα/β, p16 and p53 expression for 4 days, and an obvious decrease in pRb expression. These changes by lower dose combination, except in p-IκB expression and NF-κB activity, were significantly inhibited by pretreatment with U0126 (ERK inhibitor).

CONCLUSIONS

Ang II and Aβ synergistically promoted BVSMC senescence at least due to enhancement of the p-ERK-p16-pRb signaling pathway, oxidative stress, and NF-κB/IκB activity.

Deterioration of cognitive function after transient cerebral ischemia with amyloid-β infusion-possible amelioration of cognitive function by AT2 receptor activation

Background

To promote understanding of the pathogenesis of cognitive impairment or dementia, we explored the potential interaction between transient cerebral ischemia and amyloid-β (Aβ) infusion in mediating cognitive decline and examined the possible ameliorative effect of angiotensin II type 2 (AT₂) receptor activation in vascular smooth muscle cells (VSMC) on this cognitive deficit.

Methods

Adult male wild-type mice (WT) and mice with VSMC-specific AT₂ receptor overexpression (smAT₂) were subjected to intracerebroventricular (ICV) injection of Aβ1-40. Transient cerebral ischemia was induced by 15 min of bilateral common carotid artery occlusion (BCCAO) 24 h after Aβ injection.

Results

Aβ injection in WT induced a cognitive decline, whereas BCCAO did not cause a significant cognitive deficit. In contrast, WT with BCCAO following Aβ injection exhibited more marked cognitive decline compared to Aβ injection alone, in concert with increases in superoxide anion production, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and expression of p22phox, p40phox, monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-1β in the hippocampus, and upregulation of RAGE (receptor for advanced glycation end product), an Aβ transporter. BCCAO following Aβ injection further enhanced neuronal pyknosis in the hippocampus, compared with BCCAO or Aβ injection alone. In contrast, smAT₂ did not show a cognitive decline, increase in oxidative stress, inflammation, and RAGE level or neuronal pyknosis, which were induced by BCCAO with/without Aβ injection in WT.

Conclusions

Transient cerebral ischemia might worsen Aβ infusion-mediated cognitive decline and vice versa, with possible involvement of amplified oxidative stress and inflammation and impairment of the RAGE-mediated Aβ clearance system, contributing to exaggerated neuronal degeneration. AT₂ receptor activation in VSMC could play an inhibitory role in this cognitive deficit.

Abstract WP533: Chronic Cerebral Damage Aggravates Vascular Remodeling in Cuff-Induced Vascular Injury Mouse Model

Introduction: Distant organ dysfunction has been highlighted whereby acute or chronic damage in one organ may induce dysfunctions of the other organs such as cardiorenal syndrome. Vascular injury is an important process in various vascular diseases. However, the relationship cerebral ischemic damage and peripheral vascular disorder is still unclear. Therefore, we have investigated the possible pathophysiological interactions between brain ischemia and vascular remodeling.

Methods: Eight-week-old male C57BL/6 mice underwent permanent cerebral brain ischemia by permanent occlusion of the left middle cerebral artery occlusion (MCAO) by electrocoagulation using a subtemporal approach. Four weeks after MCAO, vascular injury was induced by polyethylene cuff placement on the femoral artery. Neointima formation was determined 14 days after cuff placement by evaluating intima/media ratio. Mice were administrated 0.5% tempol, antioxidant agent, in drinking water from after MCAO. Macrophage fractions in spleen two weeks after MCAO were examined and M1 and M2-polarized macrophages were separated by flow cytometry and analyzed.

Results: Cerebral ischemia did not influence the intima/media ratio 6 weeks after MCAO compared with sham-operated mice. Neointima formation in the injured artery was significantly increased 2 weeks after cuff placement. Interestingly, the neointima formation 2 weeks after cuff placement was more marked in MCAO-operated mice compared with sham-operated mice. We observed that treatment with tempol did not improve increased neointima formation in MCAO-operated mice. Next, we examined the macrophage fractions in spleen 2 weeks after MCAO. The macrophage fraction in SVF evaluated by F4/80 staining did not differ between sham- and MCAO-operated mice. There was no significant difference in M1 and M2 fraction with/without MCAO.

Conclusion: These results suggest that cerebral ischemic injury aggravate peripheral vascular disorders, and we are addressing the possible roles of renin-angiotensin system and inflammation etc. involved in these interesting results, which could provide us with the discovery of new pathological mechanisms concerning the distant organ dysfunctions between brain and peripheral vasculature.

Abstract P269: Chronic Cerebral Ischemic Injury Worsens Vascular Dysfunction

Introduction: Distant organ dysfunction has been highlighted whereby acute or chronic damage in one organ may induce acute or chronic dysfunctions of the other organs such as cardiorenal syndrome. Vascular remodeling is an important process in various vascular diseases. However, the relationship cerebral ischemic damage and peripheral vascular disorder is still unclear. Therefore, we have investigated the possible pathophysiological interactions between brain ischemia and vascular remodeling.

Methods: Eight-week-old male C57BL/6 mice underwent permanent cerebral brain ischemia by permanent occlusion of the left middle cerebral artery occlusion (MCAO) by electrocoagulation using a subtemporal approach. Four weeks after MCAO, vascular injury was induced by polyethylene cuff placement on the femoral artery. Neointima formation was determined 14 days after cuff placement by evaluating intima/media ratio. Macrophage fractions in spleen two weeks after MCAO were examined and M1 and M2-polarized macrophages were separated by flow cytometry and analyzed.

Results: Body weight after MCAO and cuff placement did not differ among all groups. Cerebral ischemia did not influence the intima/media ratio 6 weeks after MCAO (MCAO-Cuff (-), 0.123) compared with sham-operated mice (sham-Cuff (-), 0.120). Neointima formation in the injured artery was significantly increased 2 weeks after cuff placement (sham-Cuff (+), 0.258). Interestingly, the neointima formation 2 weeks after cuff placement was more marked in MCAO-operated mice (MCAO-Cuff (+), 0.369) compared with sham-Cuff (+). Next, we examined the macrophage fractions in spleen 2 weeks after MCAO. The macrophage fraction in SVF evaluated by F4/80 staining did not differ between sham- (7.5%) and MCAO-operated (7.6%) mice. There was no significant difference in M1 and M2 fraction with/without MCAO.

Conclusion: These results suggest that cerebral ischemic injury aggravate peripheral vascular disorders, and we are addressing the possible roles of renin-angiotensin system and oxidative stress etc. involved in these interesting results, which could provide us with the discovery of new pathological mechanisms concerning the distant organ dysfunctions between brain and peripheral vasculature.

Abstract P332: Hesperidin in Citrus Fruit Juice Plays a Role in Preventing Cognitive Impairment Induced by Ischemic Brain Damage

Recently we reported that drinking Citrus iyo juice (CI) inhibited more effectively vascular remodeling in the inflammation-induced vascular injury mouse model than Citrus unshiu juice (CU). These results led us to explore the possibility that citrus fruits juice drinking could attenuate cognitive decline in transient cerebral ischemia mouse model, focusing on the effects of flavanone, hesperidin, which is more abundantly contained in CI compared with CU and has antioxidant activity. Eight-week-old male C57BL/6 mice were administrated 10 % CI or CU in drinking water or 100 mg/kg/day hesperidin orally by gavage. Two weeks after administration, brain ischemia was induced by bilateral common carotid artery occlusion (BCCAO) for 18 minutes. The Y maze task was performed 2 weeks after BCCAO operation. After cognitive task, cerebral blood flow (CBF) was measured by a laser speckle flowmetry. Morphological changes in the hippocampus were examined. Administration of CI, CU or hesperidin did not influence systolic blood pressure, body weight and brain weight. Cognitive function was significantly impaired (sham, 71% (16 of 23) vs BCCAO, 55% (14 of 27) in Y maze) with the increase in superoxide anion production after BCCAO. The cognitive impairment was more effectively attenuated by the administration of CI than CU (CI, 66% (13 of 23); CU, 61% (17 of 27)) with the significant increase in CBF. Interestingly, we also observed that the treatment with hesperidin significantly prevented cognitive decline (67% (13 of 21)) after BCCAO. The increase in superoxide anion production 24 hours after BCCAO (expressed as fold-increase compared to sham) was attenuated by CI or hesperidin, not by CU (BCCAO, 4.0; CI, 1.2; hesperidin, 1.1; CU, 3.0). The fold-increase in TNF-α mRNA in the hippocampus 24 hours after BCCAO was prevented by hesperidin (BCCAO 5.0; hesperidin, 2.8). Cell number in CA1 region of hippocampus decreased in BCCAO-operated mice. Hesperidin treatment attenuated this decrease (sham, 163±5; BCCAO, 136±4; hesperidin, 154±4). These results suggest that the intake of hesperidin in citrus fruits juice should prevent cognitive decline after brain ischemia at least in part due to reduction of oxidative stress, inflammatory cytokine and an increase in CBF.

Abstract P238: Cerebral Ischemia With Amyloid-Beta Infusion Deteriorates Cognitive Decline ~Possible Amelioration of Cognitive Function by AT 2 Receptor Activation~

Objectives: Amyloid-β (Aβ) deposition in brain and cerebral vessels accelerates the pathogenesis of Alzheimer’s disease and vascular cognitive impairment. We examined possibilities that cerebral ischemia worsens Aβ infusion-mediated cognitive decline, and that angiotensin II type 2 (AT 2 ) receptor stimulation in vascular smooth muscle cells (VSMC) could ameliorate this cognitive impairment induced by cerebral ischemia and Aβ.

Methods: Adult male wild-type mice (WT) and the mice with VSMC-specific AT 2 receptor overexpression (smAT 2 ) were used. Mice were subjected to intracerebroventricular (ICV) injection of Aβ1-40. Cerebral ischemia was induced by 15 minutes of bilateral common carotid artery occlusion (BCCAO) 24 hours after Aβ injection. Cognitive function was evaluated by Morris water maze test 3 weeks after Aβ injection.

Results: ICV injection of Aβ in WT showed impaired cognitive function (arriving time to platform at day 5: control, 26.53±4.46 sec; Aβ, 65.35±7.44 sec), whereas BCCAO did not decline significantly cognitive function. In contrast, BCCAO following Aβ injection exhibited more marked cognitive impairment (84.27±8.00 sec) compared to Aβ injection alone in concert with the increases in superoxide anion production, NADPH oxidase activity, expressions of NADPH oxidase subunit p 22 phox , p 40 phox and inflammatory cytokines such as MCP-1, IL1-β in the hippocampus. BCCAO following Aβ injection significantly enhanced the expression of Aβ clearance factor, RAGE (receptor for advanced glycation end product). Aβ injection did not increase the neuron pyknosis in the hippocampus, whereas the number of neuron pyknosis was increased significantly with BCCAO (control, 6.33±0.88/field; Aβ with BCCAO, 46.33±4.10/field). On the other hand, smAT 2 did not show cognitive impairment, the increases in oxidative stress, inflammation markers and RAGE expression, pyknosis, which were induced by Aβ injection with/without BCCAO in WT.

Conclusion: Cerebral ischemia exaggerated Aβ-induced cognitive decline with possible involvements of enhanced oxidative stress, inflammation, neuronal degeneration, and breakdown of RAGE-mediated Aβ clearance. AT 2 receptor activation in VSMC could play preventive roles in this cognitive decline.

Abstract P254: Synergistic Effect of Angiotensin II and Amyloid-Beta on Brain Vascular Smooth Muscle Cell Senescence

Objectives: Cerebrovascular damage has been known to contribute to cognitive impairment and dementia. Amyloid-β (Aβ) induces cerebrovascular damage and is reported to stimulate endothelial cell senescence. We previously demonstrated that angiotensin II (Ang II) plays an important role in enhancing the vascular senescence. Here, we examined the possible cross-talk between Ang II and Aβ in regulating brain vascular smoot muscle cell (BVSMC) senescence.

Methods: BVSMCs were prepared from adult male C57BL/6 mice by enzymatic digestion method. Cells were stimulated with Ang II with/without Aβ 1-40. Cellular senescence was evaluated by senescence associated β-galactosidase staining. Oxidative stress was determined by measuring superoxide anion production. Signal transduction was examined by Western blotting and luciferase activity assay.

Results: Treatment with Ang II (100nM) or Aβ (1uM) at a relatively higher dose for 6 days significantly increased the percentage of senescent cells (25±1.43, 16±0.53 respectively) compared with control (13±2.22, 11±0.76 respectively). Treatment with Ang II less than 10nM or Aβ less than 0.5uM had no significant effect on cellular senescence. Interestingly, combination treatment of lower doses of Ang II (10nM) and Aβ (0.5uM) for 6 or 8 days markedly increased the percentage of senescent cells compared with control (control, 9±1.11; Ang II+Aβ, 15±0.77 for 6 days, control, 8±0.83; Ang II+Aβ, 15±1.14 for 8 days). Moreover, this lower dose combination of Ang II and Aβ induced significant increases in superoxide anion production, p-IκB, p16 and p53 expression, NF-κB activity for 4 days, p-ERK and p-IKKα/β expression for 2 days, and obvious decrease in pRb expression. These increases in senescent cells, superoxide anion production, expressions of p-ERK, p16, pRb by lower dose combination Ang II and Aβ were significantly inhibited by the treatment with U0126, an ERK inhibitor. However, U0126 had no significant effect on NF-κB activity.

Conclusion: Ang II and Aβ synergistically promoted BVSMC senescence at least due to the enhancement of p-ERK-p16-pRb signaling pathway and oxidative stress, and the increase in NF-κB/IκB activity would be involved in this synergistic effect.

Attenuation of stroke damage by angiotensin II type 2 receptor stimulation via peroxisome proliferator-activated receptor-gamma activation

The brain renin-angiotensin system plays a crucial role in ischemic stroke. It is known that stimulation of the angiotensin II type 2 (AT₂) receptor protects against ischemic brain injury. We recently demonstrated that AT₂ receptor stimulation by compound 21 (C21), a direct AT₂ receptor agonist, inhibited vascular intimal proliferation with activation of peroxisome proliferator-activated receptor-gamma (PPAR-γ). However, whether direct AT₂ receptor stimulation protects against ischemic brain injury via PPAR-γ activation is still unknown. 8-week-old male C57BL/6 J mice were subjected to middle cerebral artery (MCA) occlusion. 2 weeks before MCA occlusion, they were administered C21 with or without GW9662, a PPAR-γ antagonist. Neurologic deficit, ischemic size, superoxide anion, superoxide dismutase (SOD) activity, expression of NADPH subunits and blood brain barrier (BBB) stabilization were assessed 24 h after MCA occlusion. Cerebral blood flow (CBF) was measured in the core and periphery of the MCA territory before, immediately after, 1 h and 24 h after MCA occlusion. Treatment with C21 markedly decreased the neurologic deficit and ischemic size with an increase in CBF, SOD activity and BBB stabilization genes compared with the non-treated group. Co-administration of GW9662 partially attenuated this protective effect of C21 on neurologic deficit and ischemic size via an increase in superoxide anion production and a decrease of SOD activity and BBB stabilization genes, while GW9662 treatment alone had no significant effect on neurologic deficit and ischemic size. These results suggest that direct AT₂ receptor stimulation has a preventive effect on stroke-induced brain injury partly due to activation of PPAR-γ.

Predicting outcome of Morris water maze test in vascular dementia mouse model with deep learning

The Morris water maze test (MWM) is one of the most popular and established behavioral tests to evaluate rodents’ spatial learning ability. The conventional training period is around 5 days, but there is no clear evidence or guidelines about the appropriate duration. In many cases, the final outcome of the MWM seems predicable from previous data and their trend. So, we assumed that if we can predict the final result with high accuracy, the experimental period could be shortened and the burden on testers reduced. An artificial neural network (ANN) is a useful modeling method for datasets that enables us to obtain an accurate mathematical model. Therefore, we constructed an ANN system to estimate the final outcome in MWM from the previously obtained 4 days of data in both normal mice and vascular dementia model mice. Ten-week-old male C57B1/6 mice (wild type, WT) were subjected to bilateral common carotid artery stenosis (WT-BCAS) or sham-operation (WT-sham). At 6 weeks after surgery, we evaluated their cognitive function with MWM. Mean escape latency was significantly longer in WT-BCAS than in WT-sham. All data were collected and used as training data and test data for the ANN system. We defined a multiple layer perceptron (MLP) as a prediction model using an open source framework for deep learning, Chainer. After a certain number of updates, we compared the predicted values and actual measured values with test data. A significant correlation coefficient was derived form the updated ANN model in both WT-sham and WT-BCAS. Next, we analyzed the predictive capability of human testers with the same datasets. There was no significant difference in the prediction accuracy between human testers and ANN models in both WT-sham and WT-BCAS. In conclusion, deep learning method with ANN could predict the final outcome in MWM from 4 days of data with high predictive accuracy in a vascular dementia model.

Beneficial Effect of Mas Receptor Deficiency on Vascular Cognitive Impairment in the Presence of Angiotensin II Type 2 Receptor

BACKGROUND

The classical renin-angiotensin system is known as the angiotensin (Ang)-converting enzyme/Ang II/Ang type 1 receptor axis, which induces various organ damage including cognitive decline. The angiotensin-converting enzyme 2/Ang-(1-7)/Mas axis is known to exert antagonistic actions against the classical renin-angiotensin system axis in the cardiovascular system. However, its roles in the brain remain unclear. We examined possible roles of the angiotensin-converting enzyme 2/Ang-(1-7)/Mas axis in cognitive function, employing vascular cognitive impairment model mice.

METHODS AND RESULTS

Male 10-week-old C57BL6 (wild-type mice, Mas1 knockout mice, Ang II type 2 receptor knockout mice, and Ang II type 2 receptor/Mas1 double knockout mice were subjected to bilateral carotid artery stenosis (BCAS) surgery. Six weeks after treatment, they were subjected to cognitive tasks. Brain samples were used for histopathological analysis. Cognitive function was significantly impaired in wild-type and double knockout mice after BCAS. On the other hand, the cognitive function of Mas1 knockout mice was maintained in spite of the reduction of cerebral blood flow with BCAS. Total cell number in the dentate gyrus region was significantly reduced after BCAS in wild-type but not in Mas1 knockout mice. The number of doublecortin-positive cells in the subgranular zone was not significantly different between wild-type and Mas1 knockout mice. Ang-(1-7) administration did not improve cognitive function in all mice after BCAS surgery.

CONCLUSIONS

Lack of the Mas receptor may have a protective effect against chronic brain ischemia when the Ang II type 2 receptor exists.

Abstract WP259: AT2 Receptor-interacting Protein Enhances Protective Effect of AT2 Receptor Stimulation in Ischemic Brain Damage

Objective: Accumulating evidences and previous our research suggest that angiotensin II type 2 (AT 2 ) receptor stimulation could contribute to protection against ischemic brain damage. We have cloned ATIP (AT 2 receptor interacting protein) as a protein interacting specifically with the C-terminal tail of the AT 2 receptor, and reported that ATIP might play key roles in diverse mechanisms of AT 2 receptor signaling. However, the effect of ATIP on ischemic brain damage is still unclear. Therefore, we investigated the effects of the ATIP and compound 21 (C21), a selective non-peptidic AT2 receptor agonist, on focal cerebral ischemia.

Method: Ten-week-old male ATIP-transgenic (ATIP-Tg) and littermate (WT) mice were subjected to middle cerebral artery occlusion (MCAO) with silicon-coated micro-filament. C21 (10 μg/kg/day) was administered 2 weeks before MCAO. Twenty-four hours after MCAO, ischemic area was determined. Cerebral blood flow (CBF) before and after MCAO was measured by laser speckle flowmetry. Collateral circulation was evaluated by the perfusion of India ink. Expression of mRNA was determined by real-time RT-PCR.

Results: There was no significant difference in ischemic size without C21 treatment between two strains. Treatment with C21 decreased ischemic size in both strains. Interestingly, this protective effect of C21 was more marked in ATIP-Tg compared with WT mice. In CBF of core region of ischemic area, there were no significant differences among all groups. However, the reduction of CBF in penumbra region just after MCA occlusion was attenuated in ATIP-Tg mice with C21 administration. Treatment with C21 tended to increase the cerebral collateral number before MCA occlusion in ATIP-Tg mice. Expression of vascular endothelial growth factor (VEGF) mRNA in the cortex before MCA occlusion did not differ among all groups. Expression of methyl methanesulfonate sensitive 2 (MMS2) as a neuroprotective factor increased in ipsilateral hemisphere of ATIP-Tg mice compared with contralateral hemisphere.

Conclusions: These results suggested that ATIP could enhance the cerebral protective effects of AT 2 receptor stimulation at least in part due to the attenuation of CBF reduction and increase of MMS2 expression after ischemia.

Abstract TP423: Hesperidin in Citrus Fruits Juice Improves Brain Ischemia-Induced Cognitive Impairment

Introduction: We recently reported that drinking Citrus iyo juice (CI) inhibited more effectively vascular remodeling in inflammation-induced vascular injury mouse model than Citrus unshiu juice (CU) (PLoS One. 2015). These results led us to explore the possibility that citrus fruits juice drinking could attenuate cognitive decline in transient cerebral ischemia model, focusing on the effects of flavanone, hesperidin, which is more abundantly contained in CI compared with CU and has antioxidant activity.

Methods: Eight-week-old male C57BL/6 mice were administrated 10 % CI or CU in drinking water or 100 mg/kg/day hesperidin orally by gavage. Two weeks after administration, brain ischemia was induced by bilateral common carotid artery occlusion (BCCAO) for 18 minutes. The Y maze task was performed 2 weeks after BCCAO operation. After cognitive task, cerebral blood flow (CBF) was measured by a laser speckle flowmetry. Cerebral superoxide anion production 24 hours after BCCAO was measured by dihydroethidium (DHE) staining. mRNA levels were measured by quantitative real-time RT-PCR.

Results: Administration of CI, CU or hesperidin did not influence systolic blood pressure, bodyweight and brain weight. Cognitive function was impaired with the increase in superoxide anion production after BCCAO. The cognitive impairment was more effectively attenuated by the administration of CI with the significant increase in CBF than sham group. Interestingly, we also observed that the treatment with hesperidin significantly prevented cognitive decline after BCCAO. Superoxide anion production determined by DHE was attenuated by CI or hesperidin, not by CU. The increases in mRNA levels of tumor necrosis factor (TNF)-α in the brain of the brain 24 hours after BCCAO was prevented by hesperidin. Two weeks after BCCAO, expression of mRNA of NADPH oxidase subunits in the brain tended to decrease in treatment with hesperidin. AT1, AT2 and Mas receptor mRNA expression in the brain did not differ among three groups.

Conclusion: These results suggest that the intake of hesperidin in citrus fruits juice should prevent cognitive decline after brain ischemia at least in part due to reduction of oxidative stress, inflammatory cytokine and an increase in CBF.

Roles of angiotensin II type 2 receptor in mice with fetal growth restriction

Our previous report indicated that vascular injury enhances vascular remodeling in fetal growth restriction (FGR) mice. The angiotensin II type 2 receptor (AT₂R) is relatively highly expressed in fetal mice. Therefore, we investigated the roles of AT₂R in FGR-induced cardiovascular disease using AT₂R knockout (AT₂KO) mice. Dams (wild-type and AT₂KO mice) were fed an isocaloric diet containing 20% protein (NP) or 8% protein (LP) until delivery. Arterial blood pressure, body weight, and histological changes in organs were investigated in offspring. The birth weight of offspring from dams fed an LP diet (LPO) was significantly lower than that of offspring from dams fed an NP diet. The heart/body and kidney/body weight ratios in AT₂KO-LPO at 12 weeks of age were significantly higher than those in the other groups. Greater thickness of the left ventricular wall, larger cardiomyocyte size and enhancement of perivascular fibrosis were observed in AT₂KO-LPO. Interestingly, mRNA expression of collagen I and inflammatory cytokines was markedly higher in the AT₂KO-LPO heart at 6 weeks of age but not at 12 weeks of age. AT₂R signaling may be involved in cardiovascular disorders of adult offspring with FGR. Regulation of AT₂R could contribute to preventing future cardiovascular disease in FGR offspring.

Abstract P450: AT2 Receptor Stimulation Reduces Ischemic Brain Damage Through AT2 Receptor-interacting Protein Signal

Objectives: We reported the preventive effects of angiotensin II type 2 (AT2) receptor stimulation on ischemic brain damage. Moreover, we have cloned ATIP (AT2 receptor interacting protein) as a protein interacting specifically with the C-terminal tail of the AT2 receptor, and suggest that ATIP should play key roles in diverse mechanisms of AT2 receptor actions. However, the effect of ATIP on ischemic brain damage is unclear. Therefore, we investigated the effects of the ATIP and compound 21 (C21), a selective non-peptide AT2 receptor agonist, on focal cerebral ischemia.

Method: Ten-week-old male ATIP-transgenic (ATIP-Tg) and littermate (WT) mice were subjected to middle cerebral artery occlusion (MCAO) with silicon-coated micro-filament. C21 (10 μg/kg/day) was administered 2 weeks before MCAO. Twenty-four hours after MCAO, ischemic volume was determined and depicted as mm 3 . Expression of methyl methanesulfonate sensitive 2 (MMS2) mRNA as a neuroprotective factor was determined by real-time RT-PCR. Cerebral blood flow (CBF) before and after MCA occlusion were measured by laser speckle flowmetry. Collateral circulation was evaluated by the perfusion of India ink.

Results: Systolic blood pressure did not differ among all groups. There was no significant difference in ischemic size without C21 treatment between two strains (WT, 80 mm 3 ; ATIP-Tg, 75 mm 3 ). Treatment with C21 significantly decreased ischemic size in both strains (WT, 66 mm 3 ; ATIP-Tg, 50 mm 3 ). Interestingly, this protective effect of C21 was more marked in ATIP-Tg compared with WT mice (WT, 16% (66 of 80); ATIP-Tg, 27% (50 of 75) reduction, respectively). MMS2 expression increased in ipsilateral hemisphere of ATIP-Tg mice compared with contralateral hemisphere. There were no significant differences in CBF of core region of ischemic area, among all groups. However, the reduction of CBF in penumbra region after MCA occlusion was attenuated in ATIP-Tg mice with C21 administration. Treatment with C21 tended to increase the cerebral collateral number before MCA occlusion in ATIP-Tg mice not in WT.

Conclusions: These results suggested that ATIP could enhance the cerebral protective effects of AT 2 receptor stimulation at least in part due to the increase of CBF and MMS2 expression after ischemia.

Abstract P448: Interaction Between Ischemic Brain Injury and Amyloid-β Deposition in Cognitive Decline; Possible Cognitive Protection by AT 2 Receptor Activation

Objectives: Cerebrovascular damage could breakdown amyloid-β (Aβ) clearance and accelerate Aβ deposition. We examined the interaction between ischemic brain damage and Aβ deposition in cognitive function, focusing on the roles of angiotensin II type 2 (AT 2 ) receptor in vascular smooth muscle cells (VSMC).

Methods: Male wild-type mice (WT) or the mice with VSMC-specific AT 2 receptor overexpression (smAT 2 ) were used. Mice were subjected to ICV injection of Aβ1-40. Ischemic brain injury was induced by bilateral common carotid artery occlusion (BCCAO) 24 hours after Aβ1-40 injection. Three weeks after Aβ1-40 injection, cognitive function was evaluated by the Morris water maze test. Brain samples obtained 8 days after Aβ1-40 injection were used to study the related signals.

Results: ICV injection of Aβ1-40 in WT showed impaired cognitive function (arriving time to platform at day 5: control, 26.53±4.46 sec; Aβ, 65.35±7.44 sec), whereas BCCAO alone did not decline significantly cognitive function. In contrast, BCCAO following Aβ1-40 injection exhibited more marked cognitive impairment (84.27±8.00 sec) compared to Aβ injection alone with the increase in expressions of NADPH oxidase subunits such as p22phox and p67phox in the hippocampus of mice. Aβ1-40 injection with BCCAO tended to increase the mRNA levels of inflammatory cytokines such as MCP-1 and TNFα. BCCAO significantly enhanced the expression of Aβ clearance factor, RAGE (receptor for advanced glycation end product). Aβ1-40 injection did not increase the neuron pyknosis in the hippocampus, whereas the number of neuron pyknosis was increased significantly with BCCAO (control, 6.33±0.88/field; Aβ with BCCAO, 46.33±4.10/field). On the other hand, smAT 2 did not show cognitive impairment, the changes of the expression for NADPH oxidase subunits and inflammatory cytokines, and neuron pyknosis, which were induced by BCCAO with/without Aβ1-40 injection in WT.

Conclusion: Ischemic brain injury could enhance Aβ-induced cognitive impairment with possible involvement of enhanced oxidative stress, neuron degeneration, and breakdown of RAGE-mediated Aβ clearance. AT 2 receptor activation in VSMC could play inhibitory roles in the cognitive decline induced by ischemic brain damage and Aβ deposition.

Abstract P447: Hesperidin, Ingredient of Citrus Fruits Juice, Attenuates Cognitive Impairment Induced by Ischemic Brain Damage

Objectives: We reported that drinking Citrus iyo juice (CI) inhibited more effectively vascular remodeling in inflammation-induced vascular injury mouse model than Citrus unshiu juice (CU) (PLoS One. 2015). We aim to explore the possibility that citrus fruits juice drinking could attenuate cognitive decline in transient cerebral ischemia model, focusing on the effects of flavanone, hesperidin, which is more abundantly contained in CI compared with CU and has antioxidant activity.

Methods: C57BL/6 mice were administrated 10% CI or CU in drinking water or 100 mg/kg/day hesperidin orally by gavage. Two weeks after administration, brain ischemia was induced by bilateral common carotid artery occlusion (BCCAO) for 18 minutes. Cognitive function was determined by Y-maze task 2 weeks after BCCAO (the number of alternations/total arm entry). Cerebral blood flow (CBF) was measured by a laser speckle flowmetry. Cerebral superoxide anion production 24 hours after BCCAO was measured by dihydroethidium staining and depicted as arbitrary unit of intensity vs control. mRNA levels were measured by quantitative real-time RT-PCR.

Results: Cognitive function was impaired with the increase in superoxide anion production after BCCAO (71% (16 of 23) vs 55% (14 of 27) in Y maze). The cognitive impairment was more effectively attenuated by the administration of CI with the significant increase in CBF than CU (CI, 66% (13 of 23); CU, 61% (17 of 27)). Interestingly, we observed that the treatment with hesperidin significantly prevented cognitive decline (67% (13 of 21)) after BCCAO with the increase in CBF. Administration of CI, CU or hesperidin did not influence systolic blood pressure, body and brain weight. Superoxide anion production was attenuated by CI or hesperidin, not by CU (BCCAO, 4.0; CI, 1.2; hesperidin, 1.1; CU, 3.0). The increases in mRNA levels of NADPH oxidase subunit such as p22 and p47, and TNFα in the cortex of the brain after BCCAO seemed to be prevented by hesperidin. AT1, AT2, and Mas receptor mRNA levels in the brain cortex did not differ among these groups.

Conclusion: Taken together, these results suggest that the intake of hesperidin in CI should prevent cognitive decline after brain ischemia at least in part due to reduction of oxidative stress and an increase in CBF.

Abstract P233: Mas Receptor Deficiency Does Not Impair Cognitive Funcion of Vascular Dementia Model in the Presence of Angiotensin II Type 2 Receptor

Objective: Angiotensin (Ang) converting enzyme (ACE) 2/ Ang-(1-7)/Mas receptor axis has been considered as protective arm in the renin-angiotensin system and Ang-(1-7) is thought to interact with Ang II type 2 (AT 2 ) receptor according. Mas receptor is expressed highly in hippocampus and blood vessels in brain, but its actual function is still unclear. Thus, we examined the possible roles of Mas receptor in relation to the vascular cognitive impairment focusing on the interaction with AT 2 receptor.

Design and Methods: Male 10-week-old C57BL6 mice (wild-type, WT), Mas1 receptor knockout mice (MasKO) and AT 2 /Mas1 receptor double knockout mice (DKO) were subjected to bilateral carotid artery stenosis (BCAS) surgery. After six weeks from the treatment, we evaluated their cognitive function with Y-maze test and the Morris water maze test.

Results: The cerebral blood flow (CBF) in each BCAS group was significantly reduced compared to its sham-operated counterparts (WT; 31.5±0.6 vs 28.0±0.8, MasKO; 31.7±0.8 vs 27.7±0.8, DKO; 33.0±0.5 vs 29.1±0.7). The alternation behavior (%) was significantly reduced in WT mice with BCAS compared to sham mice (69.6±3.5 vs 57.9±2.1), but there was no significant difference in MasKO and DKO mice (MasKO; 64.1±2.5 vs 63.1±2.5, DKO; 67.6±2.1 vs 61.1±4.0) in Y maze test. In the Morris water maze test, the mean arrival time at platform at day 5 (sec) was significantly higher in WT-BCAS mice than WT-sham mice (Sham; 20.9±4.6 vs BCAS; 47.3±6.5). In contrast to the results in WT, there was no significant difference in MasKO mice (Sham; 32.8±8.5 vs BCAS; 34.5±7.3). DKO-sham mice showed significantly lower spatial learning ability compared with WT-sham mice (DKO; 77.4±11.9 vs WT; 20.9±4.6). The total cell count in dentate gyrus area was significantly lower in WT-BCAS compared to WT-sham (sham; 255.7±7.0 vs BCAS; 209.4±5.4), but there was no significant change in MasKO mice(sham; 256.5±2.5 vs BCAS; 233.2±16.4). We could not see significant difference in the number of DCX-positive cells and the expressions of proinflammatory cytokines such as IL-6, TNF-α and MCP-1in all mouse groups.

Conclusion: Mas receptor deficiency seems to be beneficial in vascular dementia on condition that AT 2 receptor exists.

Evidence for Heterodimerization and Functional Interaction of the Angiotensin Type 2 Receptor and the Receptor MAS

The angiotensin type 2 receptor (AT2R) and the receptor MAS are receptors of the protective arm of the renin-angiotensin system. They mediate strikingly similar actions. Moreover, in various studies, AT2R antagonists blocked the effects of MAS agonists and vice versa. Such cross-inhibition may indicate heterodimerization of these receptors. Therefore, this study investigated the molecular and functional interplay between MAS and the AT2R. Molecular interactions were assessed by fluorescence resonance energy transfer and by cross correlation spectroscopy in human embryonic kidney-293 cells transfected with vectors encoding fluorophore-tagged MAS or AT2R. Functional interaction of AT2R and MAS was studied in astrocytes with CX3C chemokine receptor-1 messenger RNA expression as readout. Coexpression of fluorophore-tagged AT2R and MAS resulted in a fluorescence resonance energy transfer efficiency of 10.8 ± 0.8%, indicating that AT2R and MAS are capable to form heterodimers. Heterodimerization was verified by competition experiments using untagged AT2R and MAS. Specificity of dimerization of AT2R and MAS was supported by lack of dimerization with the transient receptor potential cation channel, subfamily C-member 6. Dimerization of the AT2R was abolished when it was mutated at cysteine residue 35. AT2R and MAS stimulation with the respective agonists, Compound 21 or angiotensin-(1-7), significantly induced CX3C chemokine receptor-1 messenger RNA expression. Effects of each agonist were blocked by an AT2R antagonist (PD123319) and also by a MAS antagonist (A-779). Knockout of a single of these receptors made astrocytes unresponsive for both agonists. Our results suggest that MAS and the AT2R form heterodimers and that-at least in astrocytes-both receptors functionally depend on each other.

Abstract WP289: Interaction Between Stroke and Amyloid-β Deposition in Cognitive Function ~Possible Involvement of Antagonist Effect of AT 2 Receptor Activation~

Background and Aim: Stroke is known to be causally related with Alzheimer’s disease pathology and amyloid-β (Aβ) deposition has been suggested to induce cerebral amyloid angiopathy resulting in stroke-associated cognitive decline. Angiotensin (Ang) type 1 (AT 1 ) receptor activation impairs cognitive performance, whereas Ang II type 2 (AT 2 ) receptor stimulation has been reported to improve cognitive impairment. We examined the interaction between stroke and Aβ deposition in cognitive function, and the possible antagonist effect of AT 2 receptor in vascular smooth muscle cells (VSMC) on this cognitive decline.

Methods: Adult (10-12 weeks old) male wild-type (WT) mice (C57BL/6J mice) or the mice with AT 2 receptor overexpression in VSMC (SMAT2) were used. Mice were subjected to intracerebroventricular (ICV) injection of Aβ1-40 following 15 minutes global brain ischemia operation. Three weeks after Aβ1-40 ICV injection, cognitive function of spatial learning memory was evaluated by the Morris water maze test. Brain samples were obtained after behavioral testing, and the expression of inflammatory cytokines and NADPH oxidase subunits were measured by real-time quantitative RT-PCR.

Results: ICV injection of Aβ1-40 in WT mice showed impaired cognitive function. On the other hand, WT mice with transient global brain ischemia did not decline significantly cognitive function. In contrast, WT mice with Aβ1-40 ICV injection with global brain ischemia exhibited more marked cognitive impairment compared with control mice. These results suggested that transient brain ischemia and amyloid-β deposition exerted at least additive effects on cognitive impairment. This cognitive decline was accompanied with increased expressions of inflammatory cytokines such as monocyte chemoattractant protein-1 and NADPH oxidase subunits including p22 phox . On the other hand, SMAT 2 mice did not show cognitive impairment by global brain ischemia with/without Aβ1-40 ICV injection.

Conclusion: Brain ischemia and amyloid-β deposition induced additive or synergistic effect on cognitive impairment. AT 2 receptor activation in VSMC could play an inhibitory role in the cognitive decline induced by brain ischemia and amyloid-β deposition.

Abstract WP290: AT2 Receptor Stimulation Reduces Stroke Size in Concert With AT2 Receptor-Interacting Protein

Objective: We previously reported that the ischemic brain area was significantly larger in angiotensin II type 2 (AT 2 ) receptor-deficient mice after middle cerebral artery (MCA) occlusion compared to wild-type mice. We have cloned ATIP (AT 2 receptor interacting protein) as a protein interacting specifically with the C-terminal tail of the AT 2 receptor, and suggest that ATIP might play key roles in diverse mechanisms of AT 2 receptor signaling. However, the effect of ATIP on brain damage has not been clarified. We investigated the possibility that ATIP could enhance the protective effects of compound 21 (C21), a selective direct non-peptidic AT 2 receptor agonist, on focal cerebral ischemia.

Method: Ten week-old male ATIP-transgenic (ATIP-Tg) and littermate (WT) mice were subjected to permanent MCA occlusion with silicon-coated micro-filament. C21 (10 μg/kg/day) was administered 2 weeks before MCA occlusion. Twenty-four hours after MCA occlusion, ischemic area and neurological deficit was assessed. Cerebral blood flow (CBF) was measured by laser speckle flowmetry. Expression of methyl methanesulfonate sensitive 2 (MMS2) as a neuroprotective factor were measured by real-time RT-PCR. Collateral circulation was evaluated by the perfusion of India ink.

Results: Systolic blood pressure did not differ between ATIP-Tg and WT mice with or without C21. There was no significant difference in ischemic size without C21 treatment between two strains. Treatment with C21 decreased ischemic size and improved neurological deficit in both strains. These protective effects by C21 were more marked in ATIP-Tg mice compared with WT mice. Treatment of C21 did not affect CBF in the core region of ischemic area after MCA occlusion in both strains; however, the reduction of CBF in penumbra region was markedly attenuated in ATIP-Tg mice treated with C21. MMS2 expression increased in ipsilateral hemisphere of ATIP-Tg mice compared with contralateral hemisphere. C21 treatment tended to increase collateral number in ATIP-Tg mice.

Conclusions: These results suggested that ATIP could enhance the cerebral protective effects of AT 2 receptor stimulation at least in part due to the improvement of CBF and increase of MMS2 expression.

Abstract WP106: Attenuation of Stroke Damage by Angiotensin II Type 2 Receptor Stimulation via Peroxisome Proliferator-Activated Receptor-gamma Activation

Introduction and hypothesis: Brain renin–angiotensin system plays a role in ischemic brain damage after stroke. It is known that stimulation of angiotensin II type 2 (AT 2 ) receptor has a protective role in ischemic brain injury. We demonstrated that AT 2 receptor stimulation by compound 21 (C21), direct AT 2 receptor agonist, inhibited vascular intimal proliferation with activation of peroxisome proliferator-activated receptor-gamma (PPAR-γ). Agents with PPAR-γ agonistic effect have been demonstrated to be neuroprotective in brain ischemia. However, whether direct AT 2 receptor stimulation has a protective effect on ischemic brain injury via PPAR-γ activation is still unknown. Thus, we investigated the beneficial effect of C21 on ischemic brain damage by AT 2 receptor stimulation via PPAR-γ activation.

Methods: Eight-week-old male C57BL/6J and human renin and human angiotensinogen double-transgenic (hRN/hANG-Tg) mice were subjected to middle cerebral artery (MCA) occlusion. Before MCA occlusion, they were administered C21 with or without GW9662, a PPAR-γ antagonist, for 2 weeks. Ischemic size, inflammation and oxidative stress were assessed 24 hours after MCA occlusion. Cerebral blood flow was measured in the core and periphery of the MCA territory before, immediately after, 1 hour and 24 hours after MCA occlusion.

Results: Administration of C21 with or without GW9662 had no significant effect on blood pressure. Ischemic brain area at 24 hours after MCA occlusion was significantly enlarged in hRN/hANG-Tg mice, compared with C57BL/6J mice. Treatment with C21 decreased the ischemic area compared with the no-treatment group, with an increase in cerebral blood flow, both in C57BL/6J and hRN/hANG-Tg mice. Co-administration of GW9662 partially attenuated the protective effect of C21 on ischemic size, via an increment in the expression of inflammatory cytokines and superoxide production, although GW9662 treatment alone had no significant effect on ischemic size.

Conclusions: These results suggest that direct AT 2 receptor stimulation has a beneficial effect on stroke partly due to activation of PPAR-γ.

Deficiency of angiotensin-converting enzyme 2 causes deterioration of cognitive function

The classical renin–angiotensin system (RAS), known as the angiotensin (Ang)-converting enzyme (ACE)/Ang II/Ang II type 1 (AT1) receptor axis, induces various organ damages including cognitive decline. On the other hand, the ACE2/Ang-(1–7)/Mas receptor axis has been highlighted as exerting antagonistic actions against the classical RAS axis in the cardiovascular system. However, the roles of the ACE2/Ang-(1–7)/Mas axis in cognitive function largely remain to be elucidated, and we therefore examined possible roles of ACE2 in cognitive function. Male, 10-week-old C57BL6 (wild type, WT) mice and ACE2 knockout (KO) mice were subjected to the Morris water maze task and Y maze test to evaluate cognitive function. ACE2KO mice exhibited significant impairment of cognitive function, compared with that in WT mice. Superoxide anion production increased in ACE2KO mice, with increased mRNA levels of NADPH oxidase subunit, p22^phox, p40^phox, p67^phox, and gp91^phox in the hippocampus of ACE2KO mice compared with WT mice. The protein level of SOD3 decreased in ACE2KO mice compared with WT mice. The AT1 receptor mRNA level in the hippocampus was higher in ACE2KO mice compared with WT mice. In contrast, the AT2 receptor mRNA level in the hippocampus did not differ between the two strains. Mas receptor mRNA was highly expressed in the hippocampus compared with the cortex. Brain-derived neurotrophic factor (BDNF) mRNA and protein levels were lower in the hippocampus in ACE2KO mice compared with WT mice. Taken together, ACE2 deficiency resulted in impaired cognitive function, probably at least in part because of enhanced oxidative stress and a decrease in BDNF.

[The Protective Arm of Renin Angiotensin System; Recent Research Progress and Expectation for New Therapeutic Approach]

The renin-angiotensin system (RAS) plays a role in the cardiovascular system including blood pressure regulation. Angiotensin II binds two major receptors, angiotensin II type 1(AT1) receptor and angiotensin II type 2(AT2) receptor. The majority of well-known angiotensin II actions are mediated via AT1 receptor stimulation; however, there is recent accumulating evidence suggesting that the AT2 receptor not only opposes the AT1 receptor, but also has unique effects beyond interaction with AT1 receptor signaling. Moreover, novel pathways beyond the classical actions of RAS, the angiotensin converting enzyme(ACE)/ angiotensin II/AT1 receptor axis, have been highlighted: the ACE2/angiotensin-(1-7)/ Mas receptor axis including AT2 receptor as a new opposing axis, So-called 'Protective Arm of RAS' against the ACE/angiotensin II/AT1 receptor axis.

Platelet-endothelial cell interaction in brain microvessels of angiotensin II type-2 receptor knockout mice following transient bilateral common carotid artery occlusion

The purpose of this study was to investigate the behavior of platelets (rolling and adhesion) in cerebral microvessels of angiotensin II type-2 receptor-knockout (AT2RKO) mice after transient bilateral carotid artery occlusion using intravital fluorescence microscopy. Twenty AT2RKO mice, consisting of 11 mice in the sham group and 9 mice in the ischemia reperfusion group (reperfusion after 15 min of bilateral, total carotid artery occlusion) were used in this study. The hole traversed the bone and dura mater, but arachnoid, pia mater, and cerebral parenchyma were preserved. Platelets were harvested from donor mice and stained using carboxyfluorescein diacetate succinimidyl ester. The number of platelets showing rolling and adhesion to pial vessels in AT2 deficient mice at 3 and 6 h after cerebral ischemia reperfusion was significantly higher than that in the sham group (P < 0.05). In addition, AT2 receptor has an inhibitory role in platelet rolling and adhesion after cerebral ischemia reperfusion.

Identification of the Mtus1 Splice Variant as a Novel Inhibitory Factor Against Cardiac Hypertrophy

Background

In cardiac hypertrophy and failure, there is a widespread alteration in mRNA splicing, but the role of splice variants in cardiac hypertrophy has not yet been fully elucidated. In this study, we used an exon array to identify novel splice variants associated with cardiac hypertrophy.

Methods and Results

We performed genome‐wide exon array analysis and developed a splicing profile in murine hearts with hypertrophy induced by transverse aortic constriction for 8 weeks. Following global analysis of splice variants using the Mouse Exon 1.0 ST Array, we identified 46 spliced genes and narrowed our focus to 1 gene, mitochondrial tumor suppressor 1 (Mtus1), whose splice variants were registered in the NCBI RefSeq database. Notably, one of the splice variants Mtus1A was specifically upregulated, although the total expression of the Mtus1 gene remained unchanged. We showed that Mtus1A was localized in the mitochondria, and its expression level increased with the degree of cardiac hypertrophy. In cultured cardiomyocytes, Mtus1A overexpression reduced phenylephrine‐induced reactive oxygen species production and consequent ERK phosphorylation, resulting in a decrease in both cell size and protein synthesis. In vivo, cardiac‐specific Mtus1A transgenic mice showed left ventricle wall thinning and a reduced hypertrophic response to pressure overload and phenylephrine treatment.

Conclusions

We found that Mtus1 is specifically spliced in hypertrophic hearts and that the Mtus1A variant has an inhibitory effect on cardiac hypertrophy. Mtus1A is, therefore, a possible diagnostic and therapeutic target for cardiac hypertrophy and failure.

Angiotensin II Type 2 Receptor Inhibits Vascular Intimal Proliferation With Activation of PPARγ

BACKGROUND

Angiotensin II type 2 (AT2) receptor stimulation could exert beneficial effects on vascular remodeling. Previously, we reported that AT2 receptor stimulation ameliorated insulin resistance in diabetic mice accompanied by PPARγ activation which also plays a variety of crucial roles in the vasculature. Therefore, this study aimed to investigate the vascular protective effect of the AT2 receptor with activation of PPARγ involving AT2 receptor-interacting protein (ATIP).

METHODS AND RESULTS

Vascular injury was induced by polyethylene-cuff placement around the femoral artery in C57BL/6J mice. Treatment with compound 21 (C21), an AT2 receptor agonist, decreased neointimal formation, cell proliferation, and the mRNA levels of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor (TNF)-α, and interleukin-1β, and phosphorylation of nuclear factor-kappa B, and increased PPARγ DNA-binding activity in the injured artery, whereas these inhibitory effects of C21 were attenuated by co-treatment with a PPARγ antagonist, GW9662. Treatment of vascular smooth muscle cells (VSMC) with C21 prepared from smAT2 transgenic mice, which highly express the AT2 receptor in VSMC, increased both PPARγ activity and its DNA-binding activity determined by dual-luciferase assay and electrophoresis mobility shift assay (EMSA), respectively. We observed that ATIP was involved in PPARγ complex formation, and that transfection of siRNA of ATIP1 attenuated the AT2 receptor-mediated increase in PPARγ activity in VSMC. In response to AT2 receptor stimulation, ATIP was translocated from the plasma membrane to the nucleus.

CONCLUSIONS

Our results suggest a new mechanism by which AT2 receptor stimulation activates PPARγ, thereby resulting in amelioration of vascular intimal proliferation, and that ATIP plays an important role in AT2 receptor-mediated PPARγ activation.

Synergistic Inhibitory Effect of Rosuvastatin and Angiotensin II Type 2 Receptor Agonist on Vascular Remodeling

We investigated the possibility that coadministration of rosuvastatin and compound 21 (C21), a selective angiotensin II type 2 (AT2) receptor agonist, could exert synergistic preventive effects on vascular injury. Vascular injury was induced by polyethylene cuff placement on the femoral artery in 9-week-old male C57BL/6J mice. Mice were treated with rosuvastatin and/or with C21 after cuff placement. Neointima formation was determined 14 days after the operation and cell proliferation, and superoxide anion production and expression of inflammatory cytokines were examined 7 days after cuff placement. Neointima formation was significantly attenuated by the treatment of rosuvastatin (5 mg kg(-1) day(-1)) or C21 (10 μg kg(-1) day(-1)), associated with the decreases in proliferating cell nuclear antigen (PCNA) labeling index, oxidative stress, and the expression of inflammatory markers. Treatment with a noneffective dose of rosuvastatin (0.5 mg kg(-1) day(-1)) plus a low dose of C21 (1 μg kg(-1) day(-1)) inhibited the PCNA labeling index, superoxide anion production, mRNA expressions of NAD(P)H subunits, and mRNA and protein expressions of inflammatory markers associated with marked inhibition of neointima formation. Angiotensin II type 1 (AT1) receptor mRNA expression did not differ the groups. By contrast, AT2 receptor mRNA expression was increased by administration of C21 at the dose of 10 μg kg(-1) day(-1) but not by C21 at the dose of 1 μg kg(-1) day(-1) or rosuvastatin. The combination of rosuvastatin and AT2 receptor agonist exerted synergistic preventive effects on vascular remodeling associated with the decreases in cell proliferation, oxidative stress, and inflammatory reaction. That could be a powerful approach to vascular disease prevention.

The results of a survey of physicians about the Japanese Society of Hypertension Guidelines for the Management of Hypertension 2014 and its clinical use

The current study investigated physicians' awareness and use of the Japanese Society of Hypertension Guidelines for the Management of Hypertension 2014 (JSH2014) and is based on the results of a survey performed by the Publicity and Advertisement Committee of JSH. A questionnaire was used to survey physicians' awareness of the JSH2014, their recommended target blood pressure for hypertensive patients with complications and their use of antihypertensive drugs. Physicians who downloaded a PDF version of JSH2014 during the 6 months after its publication (April-September 2014) were asked to complete an online questionnaire. Of the 7872 respondents, 91% were aware of the JSH and complied partially, mostly or completely with it in their practice. With reference to hypertensive patients, ∼70% of physicians who completed the questionnaire recommended a target blood pressure (BP) of 140/90 mm Hg for an office BP value, and 40% recommended 135/85 mm Hg for a home BP value. Physicians recommended target BP levels of 130/80 mm Hg for patients with diabetes or chronic kidney disease (50-63% of physician surveyed) and for elderly patients with diabetes or kidney disease (45-55% of respondents), whereas they recommended 140/90 mm Hg for elderly patients with low cardiovascular disease risk (56-60% of physician surveyed) and for patients with chronic-phase stroke (40-47% of respondents). The most commonly prescribed combination of antihypertensive drugs was angiotensin receptor blocker (ARB) with calcium channel blocker. In addition, physicians' first choice of drug for patients with diabetes or chronic kidney disease was most often ARB. Overall, the survey results showed that the new recommendations from the JSH2014 accurately reflect daily clinical practices for hypertension management used by Japanese physicians.

Diabetic mice exhibited a peculiar alteration in body composition with exaggerated ectopic fat deposition after muscle injury due to anomalous cell differentiation

BACKGROUND

Sarcopenic obesity, age-related muscle loss, which is compensated by an increase in fat mass, impairs quality of life in elderly people. Although the increase in intramuscular fat is associated with decreased insulin sensitivity and increased metabolic risk factors, the origin of diabetes-associated intramuscular fat has not been elucidated. Here, we investigated intramuscular fat deposition using a muscle injury model in type 2 diabetic mice.

METHODS

Male 8-week-old C57BL/6 and 8-week-old and 26-week-old KKAy underwent intramuscular injection of cardiotoxin (Ctx) (100 μL/10 μM) into the tibialis anterior (TA) muscles. After 2 weeks, the muscles were removed and evaluated.

RESULTS

KKAy exhibited impaired muscle regeneration and ectopic fat deposition. Such impairment was more marked in older KKAy. These changes were also observed in another diabetic mouse model, db/db and diet-induced obese mice but not in streptozocin-induced diabetic mice. Deposited fat was platelet-derived growth factor (PDGF) receptor alpha positive and its cytoskeleton was stained with Masson's trichrome, indicating it to be of fibro-adipocyte progenitor cell origin. Expression of a myogenic marker, myoD, was lower and that of PDGF receptor alpha and CCAAT/enhancer binding protein (CEBP) alpha was higher in Ctx-injured TA of KKAy compared with that of C57BL/6. Peroxisome proliferator-activated receptor γ (PPARγ) was highly expressed in fat-forming lesions in older KKAy. Treatment with all-trans retinoic acid prevented the formation of intramuscular fat; however, treatment with GW9662, a PPARγ antagonist, increased the fibrotic change in muscle.

CONCLUSIONS

Diabetic mice showed impaired muscle regeneration with fat deposition, suggesting that diabetes may enhance sarcopenic obesity through a mechanism involving anomalous fibro-adipocyte progenitor cell differentiation.

Angiotensin AT2-receptor stimulation improves survival and neurological outcome after experimental stroke in mice

This study investigated the effect of post-stroke, direct AT2-receptor (AT2R) stimulation with the non-peptide AT2R-agonist compound 21 (C21) on infarct size, survival and neurological outcome after middle cerebral artery occlusion (MCAO) in mice and looked for potential underlying mechanisms. C57/BL6J or AT2R-knockout mice (AT2-KO) underwent MCAO for 30 min followed by reperfusion. Starting 45 min after MCAO, mice were treated once daily for 4 days with either vehicle or C21 (0.03 mg/kg ip). Neurological deficits were scored daily. Infarct volumes were measured 96 h post-stroke by MRI. C21 significantly improved survival after MCAO when compared to vehicle-treated mice. C21 treatment had no impact on infarct size, but significantly attenuated neurological deficits. Expression of brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB) (receptor for BDNF) and growth-associated protein 43 (GAP-43) were significantly increased in the peri-infarct cortex of C21-treated mice when compared to vehicle-treated mice. Furthermore, the number of apoptotic neurons was significantly decreased in the peri-infarct cortex in mice treated with C21 compared to controls. There were no effects of C21 on neurological outcome, infarct size and expression of BDNF or GAP-43 in AT2-KO mice. From these data, it can be concluded that AT2R stimulation attenuates early mortality and neurological deficits after experimental stroke through neuroprotective mechanisms in an AT2R-specific way. Key message • AT2R stimulation after MCAO in mice reduces mortality and neurological deficits.• AT2R stimulation increases BDNF synthesis and protects neurons from apoptosis.• The AT2R-agonist C21 acts protectively when applied post-stroke and peripherally.

Abstract WP264: Possible Epigenetic Modulation of Cerebral Angiotensin Type 2 Receptor in the Cognitive Function in Vascular Dementia

Introduction: It is well known that activation of angiotensin type 1 (AT1) receptor results in cognitive impairment. In contrast, accumulating evidences suggest that angiotensin II type 2 (AT2) receptor stimulation might prevent cognitive impairment in mice. We recently reported that administration of compound 21, newly developed direct AT2 receptor agonist, improved cognitive decline in the mouse model of vascular dementia induced by bilateral common carotid artery stenosis (BCAS). Cerebral histone deacetylase (HDAC) 2 has been highlighted in terms of epigenetic modulation of cognitive function. These results led us to examine the effects of HDAC on AT2 receptor-mediated improvement of cognitive decline.

Methods: Ten-week-old male wild type (WT) (C57BL/6) or AT2 receptor knockout (AT2KO) mice were subjected to BCAS. HDAC inhibitor (SAHA; 25 mg/kg/day) was administrated from 4 weeks after BCAS operation. The Morris water maze task was performed 6 weeks after BCAS operation. HDAC2 and inflammatory cytokine levels in the hippocampus were determined. Cerebral blood flow (CBF) were assessed by laser speckle flowmetry.

Results: HDAC2 protein level in the hippocampus did not differ between WT and AT2KO mice at 10 weeks of age, whereas HDAC2 of AT2KO mice at 20 weeks of age was higher compared with that of WT mice. Cognitive impairment after BCAS was more marked in AT2KO mice. Treatment with SAHA attenuated BCAS-induced prolongation of escape latency in the Morris water maze test both in WT and AT2KO mice; however this effect of SAHA was more marked in AT2KO mice. Decrease in CBF after BCAS was not affected by SAHA treatment. Expression of inflammatory cytokine mRNA was increased by BCAS and this increase was attenuated by SAHA treatment.

Conclusions: We speculate that modulation of cerebral AT2 receptor could be new therapeutic tool to prevent cognitive impairment via epigenetic abnormalities.

Abstract WP266: Deficiency of Angiotensin Converting Enzyme 2 Causes Deterioration of Cognitive Function

Introduction: The classical renin-angiotensin system (RAS), known as the angiotensin (Ang) converting enzyme (ACE)/Ang II/Ang II type 1 (AT1) receptor axis, induces various organ damage including cognitive decline. On the other hand, the ACE2/Ang-(1-7)/Mas receptor axis has been highlighted as exerting antagonistic actions against the classical RAS axis in the cardiovascular system. However, the roles of the ACE2/Ang-(1-7)/Mas axis in cognitive function largely remain to be elucidated, and we therefore examined possible roles of ACE2 in cognitive function.

Methods: Male 10-week-old C57BL6 (wild-type: WT) mice and ACE2 knockout (KO) mice were subjected to the Morris water maze task to evaluate spatial cognitive function. Vascular dementia model were induced by bilateral common carotid artery stenosis (BCAS). The Morris water maze task was performed 6 weeks after BCAS operation.

Results: ACE2KO mice exhibited significant impairment of spatial cognitive function, compared with that in WT mice, without significant difference in cerebral blood flow determined by laser speckle flowmetry and morphological changes in the hippocampus between both strains. Superoxide anion production in the hippocampus tended to be increased in ACE2KO mice, with increased mRNA levels of NADPH oxidase subunit in the hippocampus of ACE2KO compared with WT mice. Protein level of superoxide dismutase (SOD) 3 tended to be decreased in ACE2KO mice compared with WT mice. AT1 receptor mRNA level in the hippocampus was higher in ACE2KO mice compared with WT mice. In contrast, AT2 receptor mRNA level in the hippocampus did not differ between the two strains. Mas receptor mRNA was highly expressed in the hippocampus compared with the cortex, with no significant difference between ACE2KO and WT mice. Brain-derived neurotrophic factor (BDNF) mRNA was lower in the hippocampus in ACE2KO mice compared with WT mice. Escape latency after BCAS was prolonged in WT mice compared with sham operated mice, whereas impaired cognitive function in ACE2 KO mice was not further exaggerated after BCAS.

Conclusion: Taken together ACE2 deficiency resulted in impaired cognitive function probably due to enhanced oxidative stress and a decrease in BDNF.

Low-Protein Diet-Induced Fetal Growth Restriction Leads to Exaggerated Proliferative Response to Vascular Injury in Postnatal Life

BACKGROUND

We investigated the effects of fetal growth restriction (FGR) induced by maternal protein restriction on inflammatory vascular remodeling using a cuff-induced vascular injury mouse model.

METHODS

Dams (C57BL/6J strain mice) were fed an isocaloric diet containing 20% protein (normal protein; NP) or 8% protein (low protein; LP) from 10 weeks of age until delivery. On the day of delivery, all dams were returned to the NP diet. After weaning, offspring were fed the NP diet. When offspring were 10 weeks of age, vascular injury was induced by polyethylene cuff placement around the femoral artery.

RESULTS

Birth weight in offspring from dams fed LP until delivery (LPO) was significantly lower, but body weight was the same at 2 weeks after birth compared with that in NP offspring (NPO). Arterial blood pressure at 12 weeks of age did not differ between LPO and NPO. Neointima formation was exaggerated in LPO compared with NPO and associated with an increase in cell proliferation assessed by proliferating cell nuclear antigen (PCNA) staining index. Moreover, LPO showed enhanced expression of monocyte chemotactic protein-1, interleukin (IL)-6, IL-1β, tumor necrosis factor-α, and production of superoxide anion in the injured artery. Moreover, mRNA expression of isoforms of NAD(P)H oxidase subunits such as p22phox, p40phox, p47phox, p67phox, gp91phpx, and Rac1 in the injured arteries were enhanced in LPO. Furthermore, HIF-1α expression was increased in LPO compared with that in NPO.

CONCLUSIONS

These results suggest that maternal low-protein diet-induced FGR increases susceptibility of the vasculature to postnatal injury.

Role of the renal sympathetic nerve in renal glucose metabolism during the development of type 2 diabetes in rats

AIMS/HYPOTHESIS

Recent clinical studies have shown that renal sympathetic denervation (RDX) improves glucose metabolism in patients with resistant hypertension. We aimed to elucidate the potential contribution of the renal sympathetic nervous system to glucose metabolism during the development of type 2 diabetes.

METHODS

Uninephrectomised diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats underwent RDX at 25 weeks of age and were followed up to 46 weeks of age.

RESULTS

RDX decreased plasma and renal tissue noradrenaline (norepinephrine) levels and BP. RDX also improved glucose metabolism and insulin sensitivity, which was associated with increased in vivo glucose uptake by peripheral tissues. Furthermore, RDX suppressed overexpression of sodium-glucose cotransporter 2 (Sglt2 [also known as Slc5a2]) in renal tissues, which was followed by an augmentation of glycosuria in type 2 diabetic OLETF rats. Similar improvements in glucose metabolism after RDX were observed in young OLETF rats at the prediabetic stage (21 weeks of age) without changing BP.

CONCLUSIONS/INTERPRETATION

Here, we propose the new concept of a connection between renal glucose metabolism and the renal sympathetic nervous system during the development of type 2 diabetes. Our data demonstrate that RDX exerts beneficial effects on glucose metabolism by an increase in tissue glucose uptake and glycosuria induced by Sglt2 suppression. These data have provided a new insight not only into the treatment of hypertensive type 2 diabetic patients, but also the pathophysiology of insulin resistance manifested by sympathetic hyperactivity.

Angiotensin II type 2 receptor signaling affects dopamine levels in the brain and prevents binge eating disorder

INTRODUCTION

Binge eating disorder (BED) is associated with dopaminergic activation as food reward, resulting in metabolism-related disorders. Stimulation of angiotensin type 2 (AT2) receptor is reported to inhibit dopamine synthesis. We investigated the possible roles of AT2 receptor-mediated dopamine regulation in the pathogenesis of BED.

MATERIALS AND METHODS

Male C57BL/6 mice, type 2 diabetic (KKAy) mice and AT2 receptor-null (AT2KO) mice at eight weeks old were treated with AT2 receptor agonist, compound 21 (C21) or saline for two weeks. Mice were subjected to fasting for two days followed by re-feeding for seven days.

RESULTS

Treatment with C21 attenuated the rebound proportion of body weight, food intake and water intake in KKAy mice, but not in C57BL/6 and AT2KO mice. Dopamine concentration in the striatum was further increased by fasting in KKAy and AT2KO mice. Administration of C21 significantly attenuated this fasting-induced increase in dopamine level only in KKAy mice. Dopamine receptor D1, D2 expression in the substantia nigra were markedly lower in KKAy mice compared with C57BL/6 mice, while administration of C21 increased their expression in KKAy mice.

CONCLUSIONS

Our study suggests that AT2 receptor stimulation may be a new therapeutic approach to improve eating disorder associated with dopamine resistance.