Abstract 084: Growth Stress And Cardiorenal Syndrome: Effect Of Renal Insufficiency On Blood Pressure And Cardiac Remodeling In Juvenile Rats

Pediatric patients living with chronic kidney disease (CKD) can experience many of the comorbidities associated with CKD in adults including hypertension and cardiovascular (CV) pathology, as well as impaired somatic growth. The goal of this study was to understand how CKD impacts blood pressure and cardiac remodeling during a period of rapid somatic growth. We hypothesized that renal insufficiency in juvenile rats would lead to both impaired growth and cardiac hypertrophy, demonstrating that it is an appropriate model for studying mechanisms of cardiorenal syndrome (CRS) in pediatric patients. Young male Sprague Dawley rats (4-5 weeks of age) were weighed and underwent nuclear magnetic resonance imaging to assess body mass and composition and were then randomized to naïve (n=6), Sham (n=9) or 5/6 nephrectomy (5/6Nx; n=11) groups. Rats underwent echocardiography before surgery and at the end of the 4 week study. Anesthetized blood pressure was measured via the carotid artery. Tissues were collected weighed and stored for histological and molecular analysis. Results presented as mean±SEM, one-way ANOVA and p<0.05. There were no differences in body weights or composition between groups at the start of the study. No differences were measured between naïve and sham groups throughout the study. The 5/6Nx rats experienced less somatic growth than sham rats. Final body weight was lower in 5/6Nx rats than sham rats (229.2±4.0 vs. 229.6±17g). Similarly, tibialis length (TL) was smaller in 5/6Nx rats than sham rats (35.97±0.64 vs. 38.32±0.22 mm). The 5/6Nx group experienced a large increase in SBP when compared to sham animals (195.2±6.54 vs. 123.8±4.53 mmHg). Heart weight was higher in 5/6Nx vs. sham rats, despite the smaller body size. This difference was even more apparent when heart weight was normalized to TL (5/6Nx, 0.34± 0.10 vs. sham, 0.27±0.01 g/cm). These studies indicate that 5/6Nx surgery in juvenile SD rats can recapitulate characteristics of pediatric CRS and CKD-related growth impairment. Adult male 5/6Nx SD rats in our prior studies developed cardiac hypertrophy in the absence of hypertension. These results suggest that the added stress of growth during renal insufficiency can drive both hypertension and cardiac hypertrophy in juvenile rats.

Cardiometabolic effects of DOCA-salt in male C57BL/6J mice are variably dependent on sodium and nonsodium components of diet

Hypertension characterized by low circulating renin activity accounts for roughly 25%-30% of primary hypertension in humans and can be modeled experimentally via deoxycorticosterone acetate (DOCA)-salt treatment. In this model, phenotypes develop in progressive phases, although the timelines and relative contributions of various mechanisms to phenotype development can be distinct between laboratories. To explore interactions among environmental influences such as diet formulation and dietary sodium (Na) content on phenotype development in the DOCA-salt paradigm, we examined an array of cardiometabolic endpoints in young adult male C57BL/6J mice during sham or DOCA-salt treatments when mice were maintained on several common, commercially available laboratory rodent "chow" diets including PicoLab 5L0D (0.39% Na), Envigo 7913 (0.31% Na), Envigo 2920x (0.15% Na), or a customized version of Envigo 2920x (0.4% Na). Energy balance (weight gain, food intake, digestive efficiency, and energy efficiency), fluid and electrolyte homeostasis (fluid intake, Na intake, fecal Na content, hydration, and fluid compartmentalization), renal functions (urine production rate, glomerular filtration rate, urine Na excretion, renal expression of renin, vasopressin receptors, aquaporin-2 and relationships among markers of vasopressin release, aquaporin-2 shedding, and urine osmolality), and blood pressure, all exhibited changes that were subject to interactions between diet and DOCA-salt. Interestingly, some of these phenotypes, including blood pressure and hydration, were dependent on nonsodium dietary components, as Na-matched diets resulted in distinct phenotype development. These findings provide a broad and robust illustration of an environment × treatment interaction that impacts the use and interpretation of a common rodent model of low-renin hypertension.

Abstract P249: ICV Infusion Of AgRP Modulates Feeding Behavior And Energy Expenditure In Mice

A subset of Agouti-related protein (AgRP) neurons within the arcuate nucleus express angiotensin type 1a receptors (AT1A), and genetic ablation of AT1A in these cells disinhibits AgRP gene expression and attenuates energy expenditure (EE) in mice. To further understand the role of AgRP in metabolic control, and to establish relevant dosing schedules in this species, here we tested the effect of intracerebroventricular infusion (icv) of recombinant AgRP on metabolic functions in C57BL/6J male mice. First, we examined the effects of AgRP(82-132) (21 days, 1 or 10 nmol/d, icv) or artificial cerebrospinal fluid (aCSF) using metabolic cages. High dose AgRP reduced body mass (aCSF n=12, +0.8±0.6 vs 1 nmol/d n=14, +0.6±0.6 vs 10 nmol/d n=11, -1.5±0.5 p<0.05 g/21d), without affecting food intake (15.1±1.2 vs 14.1±1.1 vs 16.3±1.1 kcal/d) or digestive efficiency (85.2±0.5 vs 84.5±0.7 vs 85.1±0.6 %), but a significant reduction in energy efficiency (+3.8±2.0 vs +2.7±2.8 vs -5.9±2.2 p<0.05 mg/kcal) indicated increased total EE. Next, we examined the effect of AgRP(82-132) (14 days, 1 nmol/d, icv) using a multiplexed system (Promethion, Sable). AgRP had no effect on body mass (25.1±1.2, n=8 vs 26.7±0.5, n=8), overall body composition (by NMR), heat production (Weir, 24h: 0.485±0.015 vs 0.490±0.022 kcal/h), or respiratory exchange ratio (0.88±0.01 vs 0.89±0.01). AgRP increased total food intake (10.1±0.6, n=8 vs 11.9±0.5, n=8, kcal/d, p=0.03) through a synergistic effect on number of meals and median meal mass. We conclude that AgRP (1-10 nmol/d, 2-3 wk, icv) infusion causes subtle changes in feeding behavior without effect on digestive efficiency. In contrast, EE is paradoxically increased by AgRP when infused at a high dose (10 nmol/d). We postulate that these differences may reflect differential accessibility of the peptide to relevant feeding vs autonomic control regions of the hypothalamus when infused into the cerebral ventricles, and/or compensatory increases in EE secondary to changes in feeding behavior. Future studies to deconvolute the role of AgRP in the control of EE in mice will require site-specific delivery of the peptide to relevant target regions or manipulation of its receptor in those regions. Funding: HL134850, HL084207

Pregnancy Protects Hyperandrogenemic Female Rats From Postmenopausal Hypertension

Polycystic ovary syndrome, the most common endocrine disorder in women of reproductive age, is characterized by hyperandrogenemia, obesity, insulin resistance, and elevated blood pressure. However, few studies have focused on the consequences of pregnancy on postmenopausal cardiovascular disease and hypertension in polycystic ovary syndrome women. In hyperandrogenemic female (HAF) rats, the hypothesis was tested that previous pregnancy protects against age-related hypertension. Rats were implanted with dihydrotestosterone (7.5 mg/90 days, beginning at 4 weeks and continued throughout life) or placebo pellets (controls), became pregnant at 10 to 15 weeks, and pups were weaned at postnatal day 21. Dams and virgins were then aged to 10 months (still estrous cycling) or 16 months (postcycling). Although numbers of offspring per litter were similar for HAF and control dams, birth weights were lower in HAF offspring. At 10 months of age, there were no differences in blood pressure, proteinuria, nitrate/nitrite excretion, or body composition in previously pregnant HAF versus virgin HAF. However, by 16 months of age, despite no differences in dihydrotestosterone, fat mass/or lean mass/body weight, previously pregnant HAF had significantly lower blood pressure and proteinuria, higher nitrate/nitrite excretion, with increased intrarenal mRNA expression of endothelin B receptor and eNOS (endothelial nitric oxide synthase), and decreased ACE (angiotensin-converting enzyme), AT1aR (angiotensin 1a receptor), and endothelin A receptor than virgin HAF. Thus, pregnancy protects HAF rats against age-related hypertension, and the mechanism(s) may be due to differential regulation of the nitric oxide, endothelin, and renin-angiotensin systems. These data suggest that polycystic ovary syndrome women who have experienced uncomplicated pregnancy may be protected from postmenopausal hypertension.

Exploration of cardiometabolic and developmental significance of angiotensinogen expression by cells expressing the leptin receptor or agouti-related peptide

Angiotensin II (ANG II) Agtr1a receptor (AT_1A) is expressed in cells of the arcuate nucleus of the hypothalamus that express the leptin receptor (Lepr) and agouti-related peptide (Agrp). Agtr1a expression in these cells is required to stimulate resting energy expenditure in response to leptin and high-fat diets (HFDs), but the mechanism activating AT_1A signaling by leptin remains unclear. To probe the role of local paracrine/autocrine ANG II generation and signaling in this mechanism, we bred mice harboring a conditional allele for angiotensinogen (Agt, encoding AGT) with mice expressing Cre-recombinase via the Lepr or Agrp promoters to cause cell-specific deletions of Agt (Agt^Lepr-KO and Agt^Agrp-KO mice, respectively). Agt^Lepr-KO mice were phenotypically normal, arguing against a paracrine/autocrine AGT signaling mechanism for metabolic control. In contrast, Agt^Agrp-KO mice exhibited reduced preweaning survival, and surviving adults exhibited altered renal structure and steroid flux, paralleling previous reports of animals with whole body Agt deficiency or Agt disruption in albumin (Alb)-expressing cells (thought to cause liver-specific disruption). Surprisingly, adult Agt^Agrp-KO mice exhibited normal circulating AGT protein and hepatic Agt mRNA expression but reduced Agt mRNA expression in adrenal glands. Reanalysis of RNA-sequencing data sets describing transcriptomes of normal adrenal glands suggests that Agrp and Alb are both expressed in this tissue, and fluorescent reporter gene expression confirms Cre activity in adrenal gland of both Agrp-Cre and Alb-Cre mice. These findings lead to the iconoclastic conclusion that extrahepatic (i.e., adrenal) expression of Agt is critically required for normal renal development and survival.

Consequences of advanced aging on renal function in chronic hyperandrogenemic female rat model: implications for aging women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine and reproductive disorder in premenopausal women, characterized by hyperandrogenemia, metabolic syndrome, and inflammation. Women who had PCOS during their reproductive years remain hyperandrogenemic after menopause. The consequence of chronic hyperandrogenemia with advanced aging has not been studied to our knowledge. We have characterized a model of hyperandrogenemia in female rats and have aged them to 22–25 months to mimic advanced aging in hyperandrogenemic women, and tested the hypothesis that chronic exposure to hyperandrogenemia with aging has a deleterious effect on renal function. Female rats were chronically implanted with dihydrotestosterone pellets (DHT 7.5 mg/90 days) that were changed every 85 days or placebo pellets, and renal function was measured by clearance methods. Aging DHT‐treated females had a threefold higher level of DHT with significantly higher body weight, mean arterial pressure, left kidney weight, proteinuria, and kidney injury molecule‐1 (KIM‐1), than did age‐matched controls. In addition, DHT‐treated‐old females had a 60% reduction in glomerular filtration rate, 40% reduction in renal plasma flow, and significant reduction in urinary nitrate and nitrite excretion (UNOxV), an index of nitric oxide production. Morphological examination of kidneys showed that old DHT‐treated females had significant focal segmental glomerulosclerosis, global sclerosis, and interstitial fibrosis compared to controls. Thus chronic hyperandrogenemia that persists into old age in females is associated with renal injury. These data suggest that women with chronic hyperandrogenemia such as in PCOS may be at increased risk for development of chronic kidney disease with advanced age.

Platelet activation and erythrocyte lysis during brief exposure of blood to pathophysiological shear stress in vitro

BACKGROUND

Interaction of von Willebrand factor (VWF) with circulating platelets is the trigger for thrombosis in a region of arterial stenosis. These events are typically studied in vitro under conditions where platelets adhere to a VWF-coated surface. Our approach assesses platelet responses in the absence of adhesion.

OBJECTIVE

To characterize extent of platelet activation and erythrocyte lysis in an artificial stenosis model.

METHODS

Whole blood is perfused through a length of polyetheretherketone tubing that includes an artificial stenosis, comprising narrow-bore (89-381 μm) tubing. Secretion of [14C] serotonin and hemoglobin release was measured to evaluate platelet activation and hemolysis respectively at various perfusion rates and different stenosis dimensions.

RESULTS

Platelet activation and erythrocyte lysis increased progressively with increasing perfusion rate and decreasing stenosis diameter; the length of the stenosis had negligible influence. Modest platelet activation (5-10% secretion of [14C] serotonin) occurred without significant erythrocyte lysis under a limited range of perfusion conditions (4-6 mL/min flow through a 127 μm stenosis).

CONCLUSIONS

Our experimental approach mimics conditions in severe arterial stenosis or a mechanical heart valve. It could be a valuable aid in the development of novel drugs to treat arterial thrombosis and in the design of heart valves.

Cardiovascular and Metabolic Consequences of Testosterone Supplements in Young and Old Male Spontaneously Hypertensive Rats: Implications for Testosterone Supplements in Men

Background

The safety of testosterone supplements in men remains unclear. In the present study, we tested the hypothesis that in young and old male spontaneously hypertensive rats (SHR), long‐term testosterone supplements increase blood pressure and that the mechanism is mediated in part by activation of the renin‐angiotensin system.

Methods and Results

In untreated males, serum testosterone exhibited a sustained decrease after 5 months of age, reaching a nadir by 18 to 22 months of age. The reductions in serum testosterone were accompanied by an increase in body weight until very old age (18 months). Testosterone supplements were given for 6 weeks to young (12 weeks‐YMSHR) and old (21–22 months‐OMSHR) male SHR that increased serum testosterone by 2‐fold in young males and by 4‐fold in old males. Testosterone supplements decreased body weight, fat mass, lean mass, and plasma leptin, and increased plasma estradiol in YMSHR but had no effect in OMSHR. Mean arterial pressure (MAP) was significantly higher in OMSHR than in YMSHR and testosterone supplements decreased MAP in OMSHR, but significantly increased MAP in YMSHR. Enalapril, the angiotensin‐converting enzyme inhibitor, reduced MAP in both control and testosterone‐supplemented YMSHR, but had a greater effect on MAP in testosterone‐treated rats, suggesting the mechanism responsible for the increase in MAP in YMSHR is mediated at least in part by activation of the renin‐angiotensin system.

Conclusions

Taken together with previous studies, these data suggest that testosterone supplements may have differential effects on men depending on age, cardiovascular and metabolic status, and dose and whether given long‐term or short‐term.

Abstract P259: Characterization of Hyperandrogenemic Female Rats With History of Pregnancy

Women with polycystic ovarian syndrome (PCOS) experience hyperandrogenemia, elevated MAP, irregular menses, and difficulty becoming pregnant. As a result many PCOS women undergo assisted fertilization. The long-term cardiovascular consequences of pregnancy in PCOS women are not clear. We tested the hypothesis that a single pregnancy attenuates cardio-renal parameters in hyperandrogenemic female rats, a model of PCOS. Female SD rats were implanted with Dihydrotestosterone (DHT, 7.5mg/90d; replaced every 85 d) or placebo pellets, beginning at 6 wks of age. At 3 months females were paired with SD males. After delivery and lactation, females were divided into placebo (PL) or DHT rats with (P) or without pregnancy (NP) and allowed to age to 10 mos (still estrous cycling) or 16 mos (post cycling) (n=5-8/grp). At 10 mos, body weight (BW), proteinuria (UPrV), and MAP were higher in DHT than PL rats, and pregnancy history had little effect. At 16 mos, BW was higher in DHT than PL rats, and was similar in NP and P groups. UPrV and MAP were also higher in DHT groups than PL, but were significantly attenuated in DHT-P vs DHT-NP. These data suggest that pregnancy in women with PCOS may be cardiovascular protective with aging. The mechanisms remain to be determined.

a, p<0.05 vs PL-NP; b, p<0.05 vs PL-P; c, p<0.05 vs DHT-NP, mean ± SEM, two-way ANOVA.

Supported by NIH-R01HL66072, PO1HL51971 (JFR).

Abstract P167: Aging Exacerbates Increased MAP and Proteinuria in Male Rat Offspring of Hyperandrogenemic Mothers

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting 6-10 % of women, and is associated with hyperandrogenemia, oligo/anovulation and polycystic ovaries. Many women with PCOS have difficulty getting pregnant and, when they do, the infants are predisposed to preterm birth, metabolic disorders during childhood, and potential risk for the daughters to develop PCOS. The mechanisms by which the offspring of women with PCOS develop negative health outcomes are unknown. Our lab has already characterized the phenotype of young PCOS offspring showing an increased MAP and proteinuria in the males. In this study we tested the hypothesis that aging will exacerbate the negative health outcomes observed in the offspring of PCOS dams. Twelve months old female (F) and male (M) offspring of control (C) and PCOS (P) dams (SD; DHT 7.5mg/90d) were divided into 4 groups: F-C, F-P, M-C and M-P. At 12 months old, there is a significant decrease in body weight in F-P and M-P, compared to F-C and M-C, respectively (F-P: 284±4 vs. F-C: 301±5; M-P: 533±8 vs. M-C: 575±8 mg/24h, p<0.001) and the body weight remains lower until 18 months of age. Body composition analysis showed that there is a decrease in lean mass in F-P and M-P, compared to F-C and M-C, respectively (F-P: 284±4 vs. F-C: 301±5; M-P: 533±8 vs. M-C: 575±8 mg/24h, p<0.01). Proteinuria at 12 months, is higher in F-P and M-P, compared to F-C and M-C, respectively (F-P: 18±2 vs. F-C: 9±1; M-P: 169±8 vs. M-C: 108±6 mg/24h, p<0.001). This increased proteinuria is still observed at 15 months (F-P: 33±5 vs. F-C: 5±1; M-P: 143±7 vs. M-C: 103±4 mg/24h, p<0.001). Baseline mean arterial pressure (MAP, telemetry, 17 months old) was similar F-P vs. F-C (F-C: 109±2 mmHg vs. F-P: 107±1 mmHg; p=NS). However, in males, MAP was significantly higher in M-P than M-C (M-C: 114±1 mmHg vs. M-P: 127±1 mmHg; p<0.05). These results showed that aging exacerbates the increased MAP and proteinuria in males. Female offspring do not develop a PCOS phenotype with aging. Future studies will be necessary to determine the exact mechanisms responsible for the increase in blood pressure and renal injury.

Abstract P134: Hypertension in Postmenopausal Women: Role of Renin-angiotensin System and Eicosanoids

Hyperandrogenemic postmenopausal women have elevated blood pressure (BP) and the mechanisms responsible for it have not been elucidated. We tested the hypothesis that activated renin-angiotensin system (RAS) in combination with cytochrome P450 (CYP 450) arachidonic acid metabolites in renal microvasculature contribute to the elevated BP in post-estrous cycling hyperandrogenemic female (PMHAF) rats. Female SD rats were implanted with DHT (7.5mg/90d) or placebo pellets (n=12/grp) beginning at 6 wks of age; pellets were changed every 85 d. At 14 months of age, baseline mean arterial pressure (MAP, telemetry) was measured in control and PMHAF rats. Each group was then divided into two groups, one group received non-specific CYP 450 inhibitor, 1-aminobenzotriazole (1-ABT; 100mg/kg/day, i.p.), and the other received Losartan (40mg/kg/day, P.O.) for 10 days. For the following 10 days all rats received both drugs. Baseline BP was significantly higher in PMHAF than controls (112±3 vs 126±3 mmHg, p=0.008). 1-ABT alone had no effect on BP in either control or PMHAF rats. Losartan alone reduced MAP in both groups (112±3 vs 97±3 mmHg, p<0.05 in control and 126±3 vs 100±3 mmHg, p<0.05 in PMHAF). In control rats first given 1-ABT, losartan had no effect on BP (112±3 vs 113±2 mmHg, p=NS). In control rats first given losartan, BP continued to decrease over the next 10 days (97±3 vs 87±2 mmHg, p=0.046). Just as in control rats, in PMHAF rats given 1-ABT first, losartan had no further effect on BP (130±2 vs 126±4 mmHg, P=NS). Unlike in control rats, PMHAF rats given 1-ABT after losartan, the BP increased to back to baseline levels (126±3 vs 116±5 mmHg, p=NS). This data suggests that BP in aging female control rats is mediated by the RAS and likely greater vasoconstrictor to vasodilator ratios of eicosanoids. BP control in PMHAF rats is more complex with the RAS playing a major role. Data suggests that vasodilators (EETs) in the renal microvasculature and 20-HETE in the tubules contribute to BP control which would explain the increase in BP back to baseline with 1-ABT + losartan. Future studies will be necessary to determine exact mechanisms responsible for the hypertension in PMHAF rats, and may explain why in hyperandrogenemic women BP is difficult to control to normotensive levels. PO1HL51971.

Abstract P132: Role of NO/NOS System in Blood Pressure Regulation in Postmenopausal Female SHR with Hormone Replacement Therapy

Estradiol (E 2 ) and testosterone (T) stimulate synthesis of nitric oxide (NO). Since the WHI study, postmenopausal women are given E 2 and/or T supplements to alleviate the symptoms of menopause. NO is a key regulator of blood pressure (BP), mediating endothelial and vascular function. Studies from our lab showed that E 2 plays little role in BP control in young female SHR; however, whether E 2 replacement with or without T would reduce BP in postmenopausal female SHR is not known. If E 2 does not reduce BP in old female SHR, it is possible that there is a defect in the NO system that prevents the vasodilatory E 2 effect mediated by NO. The hypothesis tested in this study was that E 2 /T replacement would reduce BP in old female SHR, and if not, the mechanism responsible is a deficient NO system that is incapable of upregulating in response to E 2 . After baseline (B) mean arterial pressure (MAP; telemetry), female SHR (19 mos, n=5) were implanted with 17-β E 2 (0.1 mg/pellet) and T (5mm in silastic tubes) and MAP was measured. After a transient reduction in MAP over 2-3 days (B: 175±5; E 2 +T: 161±4 mm Hg, p<0.05), MAP returned to baseline levels by day 4 (176±5 mm Hg). These data suggest that the acute vasodilatory response to E 2 /T in old female SHR was intact. On day 8 T tubes were removed, and MAP was measured for additional 16 days. Removal of T had no effect on BP (175±5 mm Hg). To evaluate NO system, rats were given: 1) 2% L-Arginine (L-Arg, 21 d); 2) 0.1% sodium nitrite (NaNO 2 , 6 d); 3) nitro-L-arginine methyl ester (L-NAME, 4mg/kg/d, 5 d). L-Arg supplement failed to change MAP (B: 175±5, L-Arg: 176±5 mm Hg, p<NS). In contrast, NaNO 2 did decrease MAP (B: 176±5, NaNO 2 : 161±3 mm Hg, p<0.05), suggesting a deficient endogenous synthesis of NO but the ability of the old female SHR to respond to an NO donor. L-NAME increased MAP (B: 176±5; L-NAME: 189±3 mm Hg, p<0.05). In total, these data suggest that the NO system in old female SHR is capable of responding appropriately to NO donors or complete blockade. However, the lack of response to L-Arg suggests a deficiency in the ability to normally synthesize NO, and thus may in part be responsible for the lack of a depressor response to E 2 , and therefore, may contribute to the elevated BP in old female SHR. Supported by NIH-R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM).

Low-dose testosterone protects against renal ischemia-reperfusion injury by increasing renal IL-10-to-TNF-α ratio and attenuating T-cell infiltration

Renal ischemia-reperfusion (I/R) in male rats causes reductions in plasma testosterone, and infusion of testosterone 3 h postreperfusion is protective. We tested the hypotheses that acute high doses of testosterone promote renal injury after I/R, and that acute low-dose testosterone is protective by the following: 1) increasing renal IL-10 and reducing TNF-α; 2) its effects on nitric oxide; and 3) reducing intrarenal T-cell infiltration. Rats were subjected to renal I/R, followed by intravenous infusion of vehicle or testosterone (20, 50, or 100 μg/kg) 3 h postreperfusion. Low-dose testosterone (20 μg/kg) reduced plasma creatinine, increased nitrate/nitrite excretion, increased intrarenal IL-10, and reduced intrarenal TNF-α, whereas 50 μg/kg testosterone failed to reduce plasma creatinine, increased IL-10, but failed to reduce TNF-α. A higher dose of testosterone (100 mg/kg) not only failed to reduce plasma creatinine, but significantly increased both IL-10 and TNF-α compared with other groups. Low-dose nitro-l-arginine methyl ester (1 mg·kg(-1)·day(-1)), given 2 days before I/R, prevented low-dose testosterone (20 μg/kg) from protecting against I/R injury, and was associated with lack of increase in intrarenal IL-10. Intrarenal CD4(+) and CD8(+) T cells were significantly increased with I/R, but were attenuated with low-dose testosterone, as were effector T helper 17 cells. The present studies suggest that acute, low-dose testosterone is protective against I/R AKI in males due to its effects on inflammation by reducing renal T-cell infiltration and by shifting the balance to favor anti-inflammatory cytokine production rather than proinflammatory cytokines.

Abstract P038: Testosterone Supplements Have Differential Effects on Blood Pressure in Old and Young Male Spontaneously Hypertensive Rats

Testosterone (“T”) supplements are widely used by men to improve their quality of life, libido, and protect against osteoporosis. In clinical studies, both high and low “T” levels were found to be associated with hypertension and cardiovascular risk. Endogenous “T” levels are reduced in obese men and rats. We have shown previously that “T” supplements in middle-aged (6 mos) obese Zucker rats improved symptoms of the metabolic syndrome and caused weight loss, but increased their blood pressure. How “T” supplements affect hypertensive men and rats is unknown. We hypothesized that “T” supplements would further increase blood pressure (BP) in both old and young male spontaneously hypertensive rats (SHR). Old (O=20-22 mos) and young (Y=10 wks) male SHR were treated with “T” (testosterone propionate 8 mg/10 mm silastic pellet; OT and YT, implanted sc) or placebo (empty pellets; OP and YP, sc). Pellets were changed every 3 weeks for 8 weeks. Mean arterial pressure (MAP) was measured by telemetry for 2 weeks. MAP in OP was higher than in YP (OP: 166±7 vs YP: 148±0.5 mmHg, p<0.001). As we predicted, “T” increased MAP in YT (YP: 148±1 vs YT: 157±1 mmHg, p<0.001). In contrast, “T” decreased MAP in OT (OP: 166±1 vs OT: 155±1 mmHg, p<0.001). These data suggest that in younger men, especially men who are already hypertensive, blood pressure should be monitored closely during “T” supplementation in order to prevent further cardiovascular disease. Since “T” reduced MAP in older male SHR, these data suggest that “T” supplements may not be as detrimental in older hypertensive men as in young men. Future studies will need to be done to determine the mechanisms by which “T” increases BP in young males and the mechanisms by which “T” reduces BP in old males. Supported by NIH-R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM), EFF Endocrine Res Grant (LLY).

Abstract P040: Role of 20-HETE in Elevated Blood Pressure in Hyperandrogenemic Female Rats, a Model of Polycystic Ovarian Syndrome

Polycystic ovary syndrome (PCOS) is the most common reproductive disorder in premenopausal women, is characterized by hyperandrogenemia, metabolic syndrome and inflammation. They also exhibit elevated blood pressure (BP) but may not be treated since they do not meet the criteria for hypertension (BP>130/90 mm Hg). We have characterized a female rat model of hyperandrogenemia (HAF) using dihydrotestosterone (DHT) that mimics many characteristics of women with PCOS. In the present study we tested the hypothesis that androgen-induced upregulation of the cytochrome P450 4A2 isoform (CYP4A2) and the formation of 20-hydroxyeicosatetraenoic acid (20-HETE) in renal microvasculature contributes to the elevated BP in HAF rats. Female rats of SS.5BN consomic strain (wild type) rats and CYP4A2-/- rats on this same background were implanted with DHT (7.5mg/90d) or placebo pellets (n=5-8/grp) beginning at 6 wks of age; pellets were changed every 85 d. At 14 wks of age, rats were implanted with radiotelemetry transmitters, and mean arterial pressure (MAP) was measured for 10 days. Endogenous 20-HETE levels were measured using LC-MS in renal microvessels isolated using an Evans Blue sieving technique. DHT-treated HAF-SS.5BN rats had significantly higher MAP compared to placebo-SS.5BN (128±6 vs. 104±1 mmHg, p<0.004). In contrast, HAF-CYP4A2-/- rats had no change in MAP compared to placebo-CYP4A2-/- controls (120±4 vs 118±3 mmHg, p=NS). Endogenous 20-HETE levels in renal microvessels of HAF-SS.5BN rats were significantly increased compared to Placebo-SS.5BN (2.27±0.91 vs. 0.32±0.037 pmol/mg, p<0.01). The 20-HETE levels were lower in CYP4A2-/- than SS.5BN but DHT in HAF-CYP4A2-/- had no effect on 20-HETE levels compared to Placebo- CYP4A2-/-. These results suggest that androgen-mediated upregulation of the expression of CYP4A2 and the production of 20-HETE in renal microvessels contribute to elevated BP in HAF rats. These data also suggest that methods to attenuate 20-HETE may provide a novel therapeutic to reduce BP in women with PCOS. Work supported by NIH RO1HL66072 and PO1HL51971.

Abstract P039: Testosterone Increases BP in Male SHR by Activating the Renin-angiotensin System: A Cautionary Tale for “Low T” Supplements

Testosterone supplements are widely prescribed for men in the US to improve overall quality of life by increasing libido and sexual performance and protecting against osteoporosis. Whether testosterone supplements affect CVD either positively or negatively is not clear since study results are controversial. Previously, we showed that chronic testosterone supplements cause hypertension in obese male Zucker rats but improves inflammation and metabolic syndrome symptoms. We also found that testosterone supplements in young male SHR further increase their BP, and that castration attenuates the hypertension. In the present study we followed up on these previous studies and tested the hypothesis that, because the SHR are lean, chronic testosterone supplements will increase lean body mass but increase the BP via a renin angiotensin system (RAS) mechanism. Male SHR were treated with testosterone (8 mg/10 mm silastic pellet implanted sc) or placebo (empty pellets sc), beginning at 12 weeks of age for 8 weeks. Fat mass and lean mass were measured by ECHO MRI. Contrary to our hypothesis, testosterone supplements had no effect on lean mass, but reduced fat mass by 49% (4.9±0.6 vs 2.5±0.4 %BW, p<0.05). Baseline mean arterial pressure (MAP by telemetry) was higher in testosterone supplemented rats than placebo controls (157±0.4 vs. 147±0.7 mmHg, p<0.05). Enalapril (200 mg/L) reduced MAP by 25% in testosterone group (157±0.4 vs 118±6 mmHg, p<0.05) and by 14% placebo rats (148±0.5 vs 127±5 mmHg, p<0.05). MAPs after enalapril were similar between placebo and testosterone-treated rats. These data suggest that the RAS contributes to the elevated BP in testosterone supplemented male SHR. The data also suggest that caution should be taken in prescribing hypertensive men with testosterone supplements. Supported by NIH-R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM), EFF Endocrine Res Grant (LLY).

Abstract P081: Tempol Decreases Blood Pressure in Aged Female SHR When Treated With Acetazolamide

Oxidative stress contributes to the development and maintenance of hypertension in male rodents, but studies in females have rarely shown a reduction in blood pressure (BP) with antioxidants. Tempol, a superoxide dismutase mimetic, decreases BP in young male SHR, but fails to reduce BP in either young or old female SHR, despite the fact that females have similar or higher levels of oxidative stress markers. The reason for the sex difference in the response to tempol remains unclear. Acetazolamide inhibits carbonic anhydrase in the proximal tubule thus increasing sodium delivery to the distal nephron, and thereby should increase distal oxidative stress. Acetazolamide was used to test the hypothesis that with increased sodium delivery to the distal nephron, tempol would reduce the BP in aging female SHR. Female SHR, 20-22 mos old, were divided into three groups (n=4-6/grp): Control (C), Acetazolamide (A), and Acetazolamide+Tempol (A+T). After baseline mean arterial pressure (MAP; telemetry), rats received vehicle (C) or acetazolamide (A and A+T). On day 8, rats in C and A+T groups were given tempol (30 mg/kg) for 11 days. Baseline MAP was similar (C: 170±7; A: 182±4; A+T: 172±6 mm Hg, p=NS). Tempol had no effect on MAP in C+T, but reduced MAP in A+T group (C+T: 169±1; A: 171±1; A+T: 151±5 mm Hg; p<0.005 A+T vs A, C+T). Basal renal oxidative stress measured by lucigenin chemiluminescence was not different in the groups; NADPH-stimulated oxidative stress was decreased in A+T compared to A and C+T (C+T: 641.8±72.2; A: 499.3±18.3; A+T: 406.2±56.3 RLU/mg/min; p<0.05, A+T vs A, C+T). Plasma total antioxidant capacity was increased by tempol only in A+T rats (C+T: 59.07±9.67; A: 69.01±4.66; A+T: 118.24±18.38 nmol/μl; p<0.05, A+T vs A, C+T). Thus tempol is capable of modestly reducing MAP in aging female SHR when proximal sodium reabsorption is blocked. The data suggest that oxidative stress-mediated BP control is dependent on increased sodium delivery to the distal nephron. Because hypertension in male SHR is attenuated with tempol alone, but not in females, taken together, the data suggest sex differences in sodium handling and thus localization of oxidative stress production in the kidneys of SHR. Supported by NIH-R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM).

Abstract 246: Role Of Cytochrome P450 4a2 In Mediating The Elevated Blood Pressure In A Rat Model Of Polycystic Ovary Syndrome

Women with polycystic ovary syndrome (PCOS) often have elevated blood pressure (BP). PCOS is characterized in part by increases in androgens, and androgens can increase cytochrome P450 (CYP) 4A isoforms and 20-HETE synthesis. We have found that CYP4A2 expression is increased in renal vasculature of hyperandrogenemic female rats, a model of PCOS. In the present study we tested the hypothesis that androgen increase would not cause elevated BP in CYP4A2 -/- rats compared with wild type SS.Bn5 rats. CYP4A2 -/- and SS.Bn5 rats (n=6-8/grp) were treated from 4 wks of age with dihydrotestosterone pellets (DHT 7.5 mg/90 d) or placebo pellets until 14 wks, and then telemetry transmitters were implanted. After 2 wks, mean arterial pressure (MAP) was measured for 10 days. DHT increased MAP and decreased HR in SS.Bn5 compared with placebo controls (placebo: 104±2 vs. DHT: 126±6 mmHg, p<0.001). In contrast, while placebo-treated CYP4A2 -/- rats had higher MAP than WT, DHT did not increase BP in CYP4A2 -/- rats (Placebo: 120±1 vs. DHT: 118±1 mmHg, p=NS). These data suggest that CYP4A2 may be necessary for DHT to increase BP in our model of PCOS. However, by what mechanism(s) CYP4A2 -/- rats have higher MAP than SS.Bn5 WT remains to be determined. Supported by NIH R01HL66072, P01HL05971 and AHA 14POST18640015.

Identification of a redox-sensitive switch within the JAK2 catalytic domain

Four cysteine residues (Cys866, Cys917, Cys1094, and Cys1105) have direct roles in cooperatively regulating Janus kinase 2 (JAK2) catalytic activity. Additional site-directed mutagenesis experiments now provide evidence that two of these residues (Cys866 and Cys917) act together as a redox-sensitive switch, allowing JAK2's catalytic activity to be directly regulated by the redox state of the cell. We created several variants of the truncated JAK2 (GST/(NΔ661)rJAK2), which incorporated cysteine-to-serine or cysteine-to-alanine mutations. The catalytic activities of these mutant enzymes were evaluated by in vitro autokinase assays and by in situ autophosphorylation and transphosphorylation assays. Cysteine-to-alanine mutagenesis revealed that the mechanistic role of Cys866 and Cys917 is functionally distinct from that of Cys1094 and Cys1105. Most notable is the observation that the robust activity of the CC866,917AA mutant is unaltered by pretreatment with dithiothreitol or o-iodosobenzoate, unlike all other JAK2 variants previously examined. This work provides the first direct evidence for a cysteine-based redox-sensitive switch that regulates JAK2 catalytic activity. The presence of this redox-sensitive switch predicts that reactive oxygen species can impair the cell's response to JAK-coupled cytokines under conditions of oxidative stress, which we confirm in a murine pancreatic β-islet cell line.