Losartan attenuates sex-dependent hypertension, neuroinflammation, and cognitive impairment in the aging male sprague–dawley rat

Figures

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  Fig. 1. Male, but not female, Sprague-Dawley rats develop age-dependent hypertension and sympathoexcitation. (A) Mean arterial pressure (MAP; mmHg) measured via acute instrumentation in conscious 3, 8, and 16 month old (MO) male rats (n = 5–6/group). (B) Peak change in MAP to ganglionic blockade with hexamethonium (30 mg/kg I.V.) in male rats (n = 6/group). (C) Plasma norepinephrine (NE) content (nmol/L) in male rats (n = 6/group). (D) MAP measured via acute instrumentation in conscious 3, 8 and 16 month old female rats (n = 6/group). (E) Peak change in MAP to ganglionic blockade with hexamethonium in female rats (n = 6/group). (F) Plasma NE content (nmol/L) in female rats (n = 6/group). Statistical significance was determined using one-way ANOVA with a post-hoc Tukey test, **p < 0.01, ***p < 0.005, ****p < 0.0001

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  Fig. 2. Male, but not female, Sprague–Dawley rats develop BBB disruption and neuroinflammation in the PVN with age. A Representative photomicrographs (captured at 10 × magnification) from level 2 of the PVN (bregma − 1.72 to − 2.04 mm) of FITC extravasation as a measure of BBB disruption in male rats at 3, 8, and 16 months old; scale bar = 200 μm. B FITC extravasation in level 2 of the PVN in aging male rats (n = 6/group). C Representative photomicrographs (captured at 10X magnification) from level 2 of the PVN (bregma − 1.72 to − 2.04) of FITC extravasation as a measure of blood brain barrier disruption in female rats at 3, 8, and 16 months old; Scale bar shown in A. D FITC extravasation in level 2 of the PVN in aging female rats (n = 6/group). E Representative photomicrographs (captured at 10X magnification with 40X magnification inset) from level 2 of the PVN (bregma − 1.72 to − 2.04 mm) of microglia (stained using OX-42/CD11b/c) in male rats at 3, 8, and 16 months old; scale bar (10X) = 200 μm; scale bar (40X) = 50 μm. F Number of active microglia per 80,000 μm2 in level 2 of the PVN in aging male rats (n = 6/group). G Total number of microglia per 80,000 μm2 in level 2 of the PVN in…

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  Fig. 3. Male, but not female, Sprague–Dawley rats exhibit increased proinflammatory cytokine expression in the PVN with age. A Representative photomicrographs of interleukin-6 (IL-6) expression in level 2 of the PVN (bregma − 1.72to − 2.04 mm) of male rats at 3, 8, and 16 months old. B IL-6 expression as percent area of the PVN in male Sprague–Dawley rats (N = 5–6/group). C Representative photomicrographs of IL-6 expression in level 2 of the PVN (bregma − 1.72 to − 2.04 mm) of female rats at 3, 8, and 16 months old. D IL-6 expression as percent area of the PVN in female Sprague–Dawley rats (N = 5–6/group). E Representative photomicrographs of tumor necrosis factor-⍺ (TNF-⍺) expression in level 2 of the PVN (bregma − 1.72 to − 2.04 mm) of male rats at 3, 8, and 16 months old. F TNF-⍺ expression as percent area of the PVN in male Sprague–Dawley rats (N = 5–6/group). G Representative photomicrographs of TNF-⍺ expression in level 2 of the PVN (bregma − 1.72 to − 2.04 mm) of female rats at 3, 8, and 16 months old. H TNF-⍺ expression as percent area of the PVN in female Sprague–Dawley rats (N = 5–6/group). Scale bar = 200 μm. Statistical significance was determined using one-way ANOVA with a…

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  Fig. 4. Male, but not female, Sprague–Dawley rats develop cognitive impairment. A Representative schematic of the novel object recognition task—a measure of recognition memory. B Representative schematic of the object location task—a measure of spatial memory. C Discrimination index of novel object in 3, 8 and 16 month old male rats (N = 5–6/group). D Discrimination index of novel object in 3, 8 and 16 month old female rats (N = 5–6/group). E Discrimination index of novel location in 3, 8 and 16 month old male rats (N = 5–6/group). F Discrimination index of novel location in 3, 8 and 16 month old female rats (N = 5–6/group). G Time spent at novel object (expressed as percent of total time) in 3, 8 and 16 month old male rats (N = 5–6/group). H Time spent at novel object (expressed as percent of total time) in 3, 8 and 16 month old female rats (N = 5–6/group). I Time spent at novel location (expressed as percent of total time) in 3, 8 and 16 month old male rats (N = 5–6/group). J Time spent at novel location (expressed as percent of total time) in 3, 8 and 16 month old female rats (N = 5–6/group). Statistical significance was determined using one-way ANOVA with a post-hoc Tukey test of…

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  Fig. 5. Losartan improves recognition memory in 16 month old male Sprague–Dawley rats with established hypertension. A Mean arterial pressure (MAP; mmHg) measured via acute instrumentation in male rats at 16 month old (MO) with no treatment, with losartan (LOS; 3 mg/kg/day s.c., 21-days), or with hydrochlorothiazide (HCTZ; 4 mg/kg/day s.c., 14-days); (n = 5–6/group), Data used for 16 month old male is also used in Fig. 1A. B Discrimination index of novel object recognition task performance in losartan treated rats before (PreTx) and after treatment (n = 6/group). C Percent of time spent at novel object in losartan treated rats before (PreTx) and after treatment (n = 6/group). D Discrimination index of novel object recognition task performance in hydrochlorothiazide treated rats before (PreTx) and after treatment (n = 6/group). E Percent of time spent at novel object in hydrochlorothiazide treated rats before (PreTx) and after treatment (n = 6/group). F Discrimination index of object location task performance in losartan treated rats before (PreTx) and after treatment (n = 6/group). G Percent of time spent at novel location in losartan treated rats before (PreTx) and after treatment (n =…

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  Fig. 6. Losartan improves BBB disruption and neuroinflammation in the PVN of 16 month old male Sprague–Dawley rats with established hypertension. A Representative photomicrographs (captured at 10X magnification) from level 2 of the PVN (bregma − 1.72 mm to − 2.04 mm) of FITC extravasation as a measure of BBB disruption in male rats at 16-months-old (MO) with no treatment, with losartan (LOS; 3 mg/kg/day s.c., 21 days), or with hydrochlorothiazide (HCTZ; 4 mg/kg/day s.c., 14 days); Scale bar = 200 μm. Representative image for 16 month old male is also used in Fig. 2A. B FITC extravasation in level 2 of the PVN in male rats at 16 months old with no treatment, with losartan, or with hydrochlorothiazide (n = 5–6/group). Data used for 16 month old male is also used in Fig. 2B. C Representative photomicrographs (captured at 10X magnification with 40X magnification inset) from level 2 of the PVN (bregma − 1.72 to − 2.04 mm) of microglia (stained using OX-42/CD11b/c) in male rats at 16 months old with no treatment, with losartan, or with hydrochlorothiazide; scale bar (10X) = 200 μm; scale bar (40X) = 50 μm. Representative image for 16 month old male is also used in Fig. 2E. D Number of active…

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  Fig. 7. Schematic of proposed hypothesis. BBB disruption and neuroinflammation in the paraventricular nucleus (PVN) contributes to increased sympathetic outflow and hypertension in aged male Sprague–Dawley rats. Age-dependent hypertension is associated with increased cognitive impairment. While hydrochlorothiazide, an NCC antagonist, only lowers blood pressure, losartan, an AT1R lowers blood pressure, attenuates PVN neuroinflammation and improves cognitive function in aged male rats