Integrative Physiology
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/32551
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Browsing Integrative Physiology by Author "Jones, Kylie"
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Item Elevated Renal Oxidative Stress and Na+ Transporters are Associated with Hypertension in Postpartum Preeclamptic Rats(2024-03-21) Smith, Savanna; Castillo, Angie; Jones, Kylie; Smith, Jonna; Hart, Savannah; Powell, Madison; Cunningham, MarkApproximately 5-10% of US pregnancies result in preeclampsia (PE). PE is characterized by new onset hypertension (HTN) during pregnancy and is usually accompanied by end-organ damage, especially in the kidneys. Postpartum (PP) women and dams that had PE have an increased risk of developing HTN and chronic kidney disease (CKD) later in life. However, mechanisms linking PE to the long-term development of HTN and CKD are unknown. One aspect that may contribute to renal injury in PP PE women and dams is oxidative stress. Elevated concentrations of oxidative stress have been shown to augment the abundance and activity of renal transporters to increase sodium (Na+) reabsorption and blood volume. These alterations in renal transporters can consequently facilitate HTN. We hypothesize that at 6 weeks PP (~3 human years), PE dams will display oxidative stress, renal Na+ transporter abundance, and elevated blood pressure (BP). Pregnant Sprague Dawley rats were assigned to two groups: normal (CON) and PE dams. On gestational day 14, the reduced uterine perfusion pressure surgery was performed to generate a model of PE. Dams gave birth naturally and weaned for 3 weeks. After 6 weeks PP, BP was measured via carotid catheterization, and kidneys were removed and sectioned. Western blots were used to quantify renal Na+ transporters: Na+ K+ 2Cl-transporter (NKCC2) in the kidney medulla (KM) and epithelial Na+ channel (ENaC) in both the kidney cortex (KC) and KM. Oxidative stress was evaluated by heat shock protein 1 (HSP-1), copper zinc superoxide dismutase (CuZnSOD), and manganese superoxide dismutase (MnSOD) via Western blots. Hydrogen peroxide (H2O2) and antioxidant capacity concentrations were assessed via colorimetric assays. PP PE dams had increased BP (126.3±6.18vs105.7±3.74 mmHg, p<0.05) at 6 weeks after birth. KC HSP- 1, H2O2, MnSOD, and antioxidant capacity were unchanged between groups. However, KC CuZnSOD protein abundance was decreased in PP PE dams (69.51±11.64vs100±5.73 IU/Protein/Control%, p<0.05). In the KM, HSP-1 abundance (113.7±3.3vs100±5.07 IU/Protein/Control%, p=0.06) and H2O2 concentrations (1.97±0.11vs1.31± 0.38 nM H2O2/mg Protein, p=0.08) were elevated in PP PE dams. MnSOD, CuZnSOD, and antioxidant capacity were unchanged between groups in the KM. No changes occurred in KC and KM ENaC protein abundance. However, NKCC2 protein abundance was elevated by ~50% in PP PE dams (151.71±22.17vs100±5.59 IU/Protein/Control%, p=0.06). In summary, BP, oxidative stress, and NKCC2 were elevated in PP PE dams at 6 weeks. The presence of oxidative stress in the KM may lead to increased NKCC2 abundance. However, more studies are warranted to make this conclusion. NKCC2 elevation may result in increased Na+ and water reabsorption, leading to an increase in BP. Future studies will assess renal oxidative stress regulation of Na+ transporters in PP PE dams and determine the timeline PP in which changes in oxidative stress, Na+ transporters, and BP occur. This study is clinically relevant, because it indicates oxidative stress and NKCC2 in the KM, separately or together, may have a formative role in the pathogenesis of HTN and CKD in PP PE women later in life.Item Renal Oxidative Stress May Explain Sex Differences in Blood Pressure in Adult Offspring Exposed to an Impoverished Environment(2024-03-21) Castillo, Angie; Smith, Savanna; Smith, Jonna; Jones, Kylie; Powell, MadisonNearly 40 million people experience poverty in the U.S. Poverty is linked to adverse childhood experiences (ACEs) which affects ~64% of adults in the U.S. Previous studies indicate that those who experience ACEs are at a higher risk of developing hypertension (HTN) and cardiovascular diseases (CVDs) later in life, with a greater severity and earlier onset in males. The mechanisms behind the ACEs-attributed development of sex differences in HTN later in life is unknown. One plausible mechanism for this sex difference is increased oxidative stress. One rodent model to mimic poverty as an ACE is the limited bed and nesting (LBN) model. This model simulates an impoverished and low resource environment, as observed in poverty, in which the nesting material during weaning is reduced. We hypothesize that male offspring exposed to LBN will have elevated blood pressure and oxidative stress, while females will have no change in blood pressure and reduced oxidative stress. Pregnant Sprague Dawley rats gave birth naturally and weaned their offspring for 3 weeks. During the weaning period, on Days 2-9, the dams and their respective pups were divided into 2 groups: LBN and control (CON). After LBN treatment, all rats received normal bedding. After weaning, offspring were divided by sex and experimental status: LBN male (n=5), LBN female (n=5), CON male (n=6), and CON female (n=6). At 16-17 weeks, mean arterial pressure (MAP) was measured via carotid catheterization and the kidneys, brain, heart, and plasma were collected to measure antioxidant capacity (AC) via colorimetric biochemical assays. LBN males had a significant increase (18 mmHg) in MAP compared to CON males (128.17±3.93 vs 110.72± 3.93 mmHg, P>0.001), while female LBN and CON rodents displayed no differences. In males, there were no changes in antioxidant capacity in the brain, heart, and plasma. However, there was a significant 2-fold decrease in renal antioxidant capacity (233±14.0 vs 442±12.3 mM Trolox/mg protein, p>0.0001). In females, there were no changes in the kidneys, heart, and brain antioxidant capacity. Conversely, LBN females showed a trending increase in plasma antioxidant capacity compared to CON (3.33±0.16 vs 2.53±0.35 mM Trolox/mg protein, p=0.053). Males exposed to an impoverished environment during weaning have elevated blood pressure, while females do not. This difference in blood pressure may be explained by decreases in renal AC in males only. On the other hand, females may be protected from elevated blood pressure because they experience a slight increase in systemic AC. Future studies will examine the role of antioxidants in blood pressure regulation in the kidneys. This is clinically relevant because ACEs affect a large percentage of the American population with ~17% of adults experiencing 4 or more ACEs, with minorities at a greater risk. Understanding the mechanisms on how ACEs contribute to HTN may alleviate some of the racial and ethnic disparities for people with HTN and CVDs. Perhaps, organ and sex-specific antioxidant therapies may prevent or reduce the development of HTN in adults that were exposed to ACEs, like poverty during childhood.