Chronic Treatment of a Mouse Model of Cerebral Amyloid Angiopathy and Brain AT ₁ Receptor Expression

Figures

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  Figure 1.. Simplified representation of the RAAS activity in the vasculature and in the brain. (A) In the vasculature, the kidneys release the enzyme renin, along with its precursor prorenin. Renin is responsible for cleaving angiotensinogen, giving rise to angiotensin (Ang) I, which is then cleaved by the angiotensin-converting enzyme (ACE), generating Ang II. In turn, Ang II can activate both Ang II type 1 receptors (AT1Rs) and Ang II type 2 receptors (AT2Rs). Additionally, Ang II can be further cleaved by ACE-2, prolylcarboxypeptidase (PRCP), or carboxypeptidase A (CPA) to generate Ang-(1–7), which can activate MasRs and AT2Rs (to a lesser extent), and inhibit AT1Rs, counteracting the effects of Ang II. Alternatively, Ang-(1–7) can also be formed through cleavage of Ang I by different enzymes. (B) In the brain, astroglia produce angiotensinogen128, which can be cleaved by renin, prorenin, or a renin-like enzyme present in neurons129, to give rise to Ang I130, 131. In turn, ACEs, which are expressed on the cell membranes of the brain, cleave Ang I, giving rise to Ang II132. Like in the vasculature, Ang-(1–7) activity in the brain counteracts the effects of Ang II. Created in BioRender.…

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  Figure 2.. Generic timeline of the study for each cohort. Mice started on the drug treatment at approximately 3 months of age, undergoing blood pressure measurements 2 and 4 months into treatment. Euthanasia occurred at approximately 8 months of age, when significant CAA pathology is observed in Tg-SwDI mice, followed by cryostat sectioning of brains and RAR. Created in BioRender. Speth, R. (2025) https://BioRender.com/t7lrdza

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  Figure 3.. RAR experimental design. Four Coplin jars that can hold 10 slides each were filled with AM5 and used to carry out the pre-incubation step. After 10 min in solution, slides were immediately transferred to their respective incubation jars, where they incubated for 60 min at room temperature. Each incubation jar contained 35 mL of a stock solution prepared by mixing assay medium 5 (AM5) solution (150 mM sodium chloride, 5 mM disodium EDTA, 0.1 mM Bacitracin, and 500 mM dibasic sodium phosphate; pH 7.1 – 7.2) and 125I-SI Ang II ligand to achieve a concentration of 255 pM. Additionally, 35 μL of 10 μM losartan were added to half of the Coplin jars. Slides were blotted using a paper towel before the first two water rinses and after the last two water rinses. Each water rinse swirl did not last for more than 1 or 2 seconds. Created in BioRender. Speth, R. (2025) https://BioRender.com/omwatj2

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  Figure 4.. Drug intake and systolic BP. (A) There was no statistically significant difference observed between actual drug intake and the target doses of each drug (red dotted line). In the males, p=0.3333 for telmisartan and p=0.1978 for lisinopril. In the females, p=0.4228 for telmisartan and p=0.7805 for lisinopril. (B) Systolic blood pressure was measured using the tail cuff method at 2-months post-initiation of treatment. There was a main effect of group [F (3, 99) = 16.50, p<0.0001, ηp2=0.3333]; overall, untreated Tg-SwDI (p<0.0001, d=1.187), telmisartan-treated Tg-SwDI (p<0.0001, d=1.474), and lisinopril-treated Tg-SwDI (p<0.0001, d=1.521) all had significantly lower systolic BP compared to WT mice groups. In the males, systolic BP of WTs was significantly higher than that of telmisartan-treated Tg-SwDI mice (p=0.0214, d=1.076). In the females, systolic BP of WTs was significantly higher than that of untreated Tg-SwDI mice (p<0.0001, d=2.148), telmisartan-treated Tg-SwDI mice (p<0.0001, d=1.972), and lisinopril-treated Tg-SwDI mice (p<0.0001, d=3.106). A statistically significant main effect of sex was observed [F (1, 99) = 36.50, p<0.0001, ηp2=0.2694], with multiple comparisons…

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  Figure 5.. Specific binding of 125I-SI Ang II in the peri-hypothalamic regions of the brain of Tg-SwDI mice. (A) A medium effect of treatment was observed in the PeVN, although not statistically significant [F (3, 30) = 1.538, p=0.2251, ηp2=0.1333] (N=38; no outliers). Untreated Tg-SwDI mice showed elevated concentration of AT1R compared to WTs in both males (p=0.3966, d=0.8880) and females (p=0.9524, d=0.5083). In the males, telmisartan reduced specific binding in Tg-SwDI mice (p=0.3754, d=0.8593). No main effect of sex was observed [F (1, 30) = 0.799, p=0.379, ηp2=0.026]. (B) No main effect of treatment was observed in the PVN [F (3, 30) = 0.4686, p=0.7064, ηp2=0.0448] (N=38; no outliers). Untreated Tg-SwDI males showed elevated concentration of AT1R compared to WTs (p=0.8405, d=0.5506). In the females, telmisartan reduced specific binding in drug-treated Tg-SwDI mice (p=0.8463, d=0.5086). No main effect of sex was observed [F (1, 30) = 1.40E-04, p=0.991, ηp2=4.67E-06]. (C) A medium effect of treatment was observed in the SFO, although not statistically significant [F (3, 24) = 1.123, p=0.3595, ηp2=0.1231] (N=32; 4 outliers removed). Untreated Tg-SwDI females showed elevated concentration…

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  Figure 6.. Specific binding of 125I-SI Ang II in the striatum of Tg-SwDI mice. (A) A medium effect of treatment was observed in the NAcc, although not statistically significant [F (3, 30) = 0.8254, p=0.4903, ηp2=0.0762] (N=38; no outliers). In the males, telmisartan increased specific binding compared to untreated Tg-SwDI mice (p=0.328, d=1.16). No main effect of sex was observed [F (1, 30) = 0.0040, p=0.9497, ηp2=0.0001). (B) No main effect of treatment was observed in the CPu [F (3, 30) = 0.6130, p=0.6119, ηp2=0.0578] (N=38; no outliers). In the males, telmisartan increased specific binding, compared to untreated Tg-SwDI males (p=0.5748, d=0.7090). No main effect of sex was observed [F (1, 30) = 0.149, p=0.702, ηp2=0.005].

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  Figure 7.. Specific binding of 125I-SI Ang II in the amygdala of Tg-SwDI mice. (A) No main effect of treatment was observed in the MeA [F (3, 29) = 0.4964, p=0.6877, ηp2=0.0488] (N=37; 1 outlier removed). Untreated Tg-SwDI females expressed elevated concentration of AT1Rs, compared to WTs (p=0.4747, d=1.018). No main effect of sex was observed [F (1, 29) = 0.9795, p=0.3305, ηp2=0.0327]. (B) No main effect of treatment was observed in the CeA/BLA [F (3, 30) = 0.2351, p=0.8712, ηp2=0.0230] (N=38; no outliers). Untreated Tg-SwDI females expressed elevated concentration of AT1Rs, compared to WTs (p=0.6727, d=0.9489). No main effect of sex was observed [F (1, 30) = 0.4594, p=0.5031, ηp2=0.0151].

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  Figure 8.. Specific binding of 125I-SI Ang II in the lateral septum of Tg-SwDI mice. A medium effect of treatment was observed in the lateral septum, although not statistically significant [F (3, 29) = 0.7532, p=0.5295, ηp2=0.0723] (N=37; 1 outlier removed). In the males, telmisartan increased specific binding, compared to untreated Tg-SwDI males (p=0.2965, d=1.777). Untreated Tg-SwDI females showed lower concentration of AT1Rs than WTs (p=0.7225, d=0.6548). No main effect of sex was observed [F (1, 29) = 0.0834, p=0.7748, ηp2 =0.0029].

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  Figure 9.. Specific binding of 125I-SI Ang II in the hippocampus of Tg-SwDI mice. A medium effect of treatment was observed in the dHpc, although not statistically significant [F (3, 28) = 1.208, p=0.3252, ηp2=0.1146] (N=36; 2 outliers removed). In the males, telmisartan decreased specific binding compared to untreated Tg-SwDI males (p=0.6194, d=1.081). Untreated Tg-SwDI females expressed slightly elevated concentration of AT1Rs compared to WTs (p=0.8351, d=0.9635). Both drugs decreased specific binding in females, compared to untreated Tg-SwDI females (p=0.5473, d=0.9962 for telmisartan and p=0.5555, d=0.7856 for lisinopril). A medium effect of sex was observed, although not statistically significant [F (1, 28) = 2.881, p=0.1007, ηp2 =0.0933].

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  Figure 10.. Specific binding of 125I-SI Ang II in the sensorimotor cortex of Tg-SwDI mice. A large effect of treatment was observed in the SMC, although not statistically significant [F (3, 23) = 1.768, p=0.1814, ηp2=0.1873] (N=31; 6 outliers removed). In the males, both drugs decreased specific binding, compared to untreated Tg-SwDI males (p=0.5952, d=1.151 for telmisartan and p=0.4333, d=1.766 for lisinopril). Untreated Tg-SwDI females expressed slightly elevated concentration of AT1Rs, compared to WTs (p=0.7629, d=0.9847). Telmisartan decreased specific binding in the females compared to untreated Tg-SwDI females (p=0.3974, d=1.421). No main effect of sex was observed [F (1, 23) = 0.3049, p=0.5862, ηp2=0.0131].