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Yang J, Villar VAM, Jose PA, Zeng C. Renal Dopamine Receptors and Oxidative Stress: Role in Hypertension. Antioxid Redox Signal 2021; 34:716-735. [PMID: 32349533 PMCID: PMC7910420 DOI: 10.1089/ars.2020.8106] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Significance: The kidney plays an important role in the long-term control of blood pressure. Oxidative stress is one of the fundamental mechanisms responsible for the development of hypertension. Dopamine, via five subtypes of receptors, plays an important role in the control of blood pressure by various mechanisms, including the inhibition of oxidative stress. Recent Advances: Dopamine receptors exert their regulatory function to decrease the oxidative stress in the kidney and ultimately maintain normal sodium balance and blood pressure homeostasis. An aberration of this regulation may be involved in the pathogenesis of hypertension. Critical Issues: Our present article reviews the important role of oxidative stress and intrarenal dopaminergic system in the regulation of blood pressure, summarizes the current knowledge on renal dopamine receptor-mediated antioxidation, including decreasing reactive oxygen species production, inhibiting pro-oxidant enzyme nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and stimulating antioxidative enzymes, and also discusses its underlying mechanisms, including the increased activity of G protein-coupled receptor kinase 4 (GRK4) and abnormal trafficking of renal dopamine receptors in hypertensive status. Future Directions: Identifying the mechanisms of renal dopamine receptors in the regulation of oxidative stress and their contribution to the pathogenesis of hypertension remains an important research focus. Increased understanding of the role of reciprocal regulation between renal dopamine receptors and oxidative stress in the regulation of blood pressure may give us novel insights into the pathogenesis of hypertension and provide a new treatment strategy for hypertension.
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Affiliation(s)
- Jian Yang
- Department of Clinical Nutrition, The Third Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Van Anthony M Villar
- Division of Renal Diseases & Hypertension, Department of Medicine, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
| | - Pedro A Jose
- Division of Renal Diseases & Hypertension, Department of Medicine, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA
| | - Chunyu Zeng
- Department of Cardiology, Fujian Heart Medical Center, Fujian Medical University Union Hospital, Fuzhou, People's Republic of China.,Department of Cardiology, Daping Hospital, The Third Military Medical University, Chongqing, People's Republic of China
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Dopamine Receptors and the Kidney: An Overview of Health- and Pharmacological-Targeted Implications. Biomolecules 2021; 11:biom11020254. [PMID: 33578816 PMCID: PMC7916607 DOI: 10.3390/biom11020254] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 02/05/2021] [Accepted: 02/06/2021] [Indexed: 12/21/2022] Open
Abstract
The dopaminergic system can adapt to the different physiological or pathological situations to which the kidneys are subjected throughout life, maintaining homeostasis of natriuresis, extracellular volume, and blood pressure levels. The role of renal dopamine receptor dysfunction is clearly established in the pathogenesis of essential hypertension. Its associations with other pathological states such as insulin resistance and redox balance have also been associated with dysfunction of the dopaminergic system. The different dopamine receptors (D1-D5) show a protective effect against hypertension and kidney disorders. It is essential to take into account the various interactions of the dopaminergic system with other elements, such as adrenergic receptors. The approach to therapeutic strategies for essential hypertension must go through the blocking of those elements that lead to renal vasoconstriction or the restoration of the normal functioning of dopamine receptors. D1-like receptors are fundamental in this role, and new therapeutic efforts should be directed to the restoration of their functioning in many patients. More studies will be needed to allow the development of drugs that can be targeted to renal dopamine receptors in the treatment of hypertension.
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Asghar M, Lokhandwala MF. Antioxidant Supplementation Normalizes Elevated Protein Kinase C Activity in the Proximal Tubules of Old Rats. Exp Biol Med (Maywood) 2016; 229:270-5. [PMID: 14988520 DOI: 10.1177/153537020422900308] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Aging is associated with increase in oxidative stress. Earlier, we have shown that higher basal protein kinase C (PKC) activity in the proximal tubules (PTs) of old rats contributes to the hyperphosphorylation of Na,K-ATPase and subsequent decrease in basal Na,K-ATPase activity, resulting in diminished natriuretic response to dopamine in these animals. We hypothesized that the increase in PKC activity in PTs of old rats is caused by increased oxidative stress and that antioxidants administration should reduce/normalize the elevated PKC activity in the renal PTs of old rats. We studied the effect of two antioxidants, namely, α-lipoic acid (LA) and tempol, on oxidants level and PKC activity in the PTs of adult (6-month) and old (24-month) Fischer 344 rats. We found that the accumulation of fluorescent dichlorofluorescein (DCF), an indicator of oxidant production, was higher in the PTs of old compared to adult rats. Dietary supplementation with LA for 2 weeks normalized the increased DCF level in old rats. Carboxymethylysine and malondialdehyde, markers of oxidative damage, were elevated in the PTs of old rats, which were normalized to the level of adult rats when tempol was provided in drinking water for 3 weeks. Both LA and tempol treatment also normalized the higher basal PKC activity in the PTs of old rats to the level seen in adult rats. These results suggest that increase in oxidative stress causes an increase in PKC activity, and that antioxidants, while reducing oxidative stress, also normalize PKC activity in the PTs of old rats.
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Affiliation(s)
- Mohammad Asghar
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, Texas 77204, USA
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Choi MR, Kouyoumdzian NM, Rukavina Mikusic NL, Kravetz MC, Rosón MI, Rodríguez Fermepin M, Fernández BE. Renal dopaminergic system: Pathophysiological implications and clinical perspectives. World J Nephrol 2015; 4:196-212. [PMID: 25949933 PMCID: PMC4419129 DOI: 10.5527/wjn.v4.i2.196] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 08/29/2014] [Accepted: 02/09/2015] [Indexed: 02/06/2023] Open
Abstract
Fluid homeostasis, blood pressure and redox balance in the kidney are regulated by an intricate interaction between local and systemic anti-natriuretic and natriuretic systems. Intrarenal dopamine plays a central role on this interactive network. By activating specific receptors, dopamine promotes sodium excretion and stimulates anti-oxidant and anti-inflammatory pathways. Different pathological scenarios where renal sodium excretion is dysregulated, as in nephrotic syndrome, hypertension and renal inflammation, can be associated with impaired action of renal dopamine including alteration in biosynthesis, dopamine receptor expression and signal transduction. Given its properties on the regulation of renal blood flow and sodium excretion, exogenous dopamine has been postulated as a potential therapeutic strategy to prevent renal failure in critically ill patients. The aim of this review is to update and discuss on the most recent findings about renal dopaminergic system and its role in several diseases involving the kidneys and the potential use of dopamine as a nephroprotective agent.
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Pokkunuri I, Chugh G, Rizvi I, Asghar M. Age-related hypertension and salt sensitivity are associated with unique cortico-medullary distribution of D1R, AT1R, and NADPH-oxidase in FBN rats. Clin Exp Hypertens 2015; 37:1-7. [PMID: 25562528 DOI: 10.3109/10641963.2014.977489] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We examined effects of normal (NS) and high salt (HS) on blood pressure (BP) and cortico-medullary distribution of dopamine D1 receptor (D1R), angiotensin AT1 receptor (AT1R), NADPH oxidase-gp(91phox), and sodium transporters (NHE-3, Na, K ATPase) in adult and aged rats. Aged rats fed with NS diet had higher BP, which further increased with HS. HS increased D1R mRNA and protein levels in cortex and medulla of adult rats. NS or HS fed-aged rats had higher AT1R and gp(91phox) mRNA levels in cortex and medulla. Aged rats fed with NS diet had higher gp(91phox) protein levels in cortex. HS diet increased AT1R and gp(91phox) protein levels in medulla of aged rats. Aged rats fed with NS or HS diet had higher NHE-3 protein levels in medulla. HS increased Na, K ATPase protein levels in medulla of aged rats. HS increased urinary kidney injury molecule-1 (KIM-1) but not protein or albumin levels in aged rats. These results suggest that cortical gp(91phox) and medullary NHE-3 contribute to age-related hypertension. Whereas D1R (cortical and medullary) together with medullary AT1R, gp(91phox) and Na, K-ATPase contribute to salt sensitivity in aged rats. And, KIM-1 may be a better marker for kidney damage.
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Affiliation(s)
- Indira Pokkunuri
- Department of Pharmacological and Pharmaceutical Sciences, Heart and Kidney Institute, College of Pharmacy, University of Houston , Houston, TX , USA
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Chugh G, Pokkunuri I, Asghar M. Renal dopamine and angiotensin II receptor signaling in age-related hypertension. Am J Physiol Renal Physiol 2012; 304:F1-7. [PMID: 23097467 DOI: 10.1152/ajprenal.00441.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Kidneys play a vital role in long-term regulation of blood pressure. This is achieved by actions of many renal and nonrenal factors acting on the kidney that help maintain the body's water and electrolyte balance and thus control blood pressure. Several endogenously formed or circulating hormones/peptides, by acting within the kidney, regulate fluid and water homeostasis and blood pressure. Dopamine and angiotensin II are the two key renal factors that, via acting on their receptors and counterregulating each other's function, maintain water and sodium balance. In this review, we provide recent advances in the signaling cascades of these renal receptors, especially at the level of their cross talk, and discuss their roles in blood pressure regulation in the aging process.
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Affiliation(s)
- Gaurav Chugh
- Heart and Kidney Institute, College of Pharmacy, Univ. of Houston, Houston, TX 77204, USA
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Chugh G, Lokhandwala MF, Asghar M. Altered functioning of both renal dopamine D1 and angiotensin II type 1 receptors causes hypertension in old rats. Hypertension 2012; 59:1029-36. [PMID: 22411927 DOI: 10.1161/hypertensionaha.112.192302] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Activation of renal dopamine D1 (D1R) and angiotensin II type 1 receptors (AT(1)Rs) influences the activity of proximal tubular sodium transporter Na,K-ATPase and maintains sodium homeostasis and blood pressure. We reported recently that diminished D1R and exaggerated AT(1)R functions are associated with hypertension in old Fischer 344 × Brown Norway F1 (FBN) rats, and oxidative stress plays a central role in this phenomenon. Here we studied the mechanisms of age-associated increase in oxidative stress on diminished D1R and exaggerated AT(1)R functions in the renal proximal tubules of control and antioxidant Tempol-treated adult and old FBN rats. Although D1R numbers and D1R agonist SKF38393-mediated stimulation of [(35)S]-GTPγS binding (index of D1R activation) were lower, G protein-coupled receptor kinase 4 (kinase that uncouples D1R) levels were higher in old FBN rats. Tempol treatment restored D1R numbers and G protein coupling and reduced G protein-coupled receptor kinase 4 levels in old FBN rats. Angiotensin II-mediated stimulation of [(35)S]-GTPγS binding and Na,K-ATPase activity were higher in old FBN rats, which were also restored with Tempol treatment. We also measured renal AT(1)R function in adult and old Fischer 344 (F344) rats, which, despite exhibiting an age-related increase in oxidative stress and diminished renal D1R function, are normotensive. We found that diuretic and natriuretic responses to candesartan (indices of AT(1)R function) were similar in F344 rats, a likely explanation for the absence of age-associated hypertension in these rats. Perhaps, alterations in both D1R (diminished) and AT(1)R (exaggerated) functions are necessary for the development of age-associated hypertension, as seen in old FBN rats.
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Affiliation(s)
- Gaurav Chugh
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204, USA
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Chugh G, Lokhandwala MF, Asghar M. Oxidative stress alters renal D1 and AT1 receptor functions and increases blood pressure in old rats. Am J Physiol Renal Physiol 2010; 300:F133-8. [PMID: 20943769 DOI: 10.1152/ajprenal.00465.2010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Aging is associated with an increase in oxidative stress and blood pressure (BP). Renal dopamine D1 (D1R) and angiotensin II AT1 (AT1R) receptors maintain sodium homeostasis and BP. We hypothesized that age-associated increase in oxidative stress causes altered D1R and AT1R functions and high BP in aging. To test this, adult (3 mo) and old (21 mo) Fischer 344 × Brown Norway F1 rats were supplemented without/with antioxidant tempol followed by determining oxidative stress markers (urinary antioxidant capacity, proximal tubular NADPH-gp91phox, and plasma 8-isoprostane), D1R and AT1R functions, and BP. The D1R and AT1R functions were determined by measuring diuretic and natriuretic responses to D1R agonist (SKF-38393; 1 μg·kg(-1)·min(-1) iv) and AT1R antagonist (candesartan; 10 μg/kg iv), respectively. We found that the total urinary antioxidant capacity was lower in old rats, which increased with tempol treatment. In addition, tempol decreased the elevated NADPH-gp91phox and 8-isoprostane levels in old rats. Systolic, diastolic, and mean arterial BPs were higher in old rats and were reduced by tempol. Although SKF-38393 produced diuresis in both adult and old rats, urinary sodium excretion (UNaV) increased only in adult rats. While candesartan increased diuresis and UNaV in adult and old rats, the magnitude of response was greater in old rats. Tempol treatment in old rats reduced candesartan-induced increase in diuresis and UNaV. Our results demonstrate that diminished renal D1R and exaggerated AT1R functions are associated with high BP in old rats. Furthermore, oxidative stress may cause altered renal D1R and AT1R functions and high BP in old rats.
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Affiliation(s)
- Gaurav Chugh
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204, USA
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George L, Lokhandwala MF, Asghar M. Exercise activates redox-sensitive transcription factors and restores renal D1 receptor function in old rats. Am J Physiol Renal Physiol 2009; 297:F1174-80. [PMID: 19759268 PMCID: PMC2781333 DOI: 10.1152/ajprenal.00397.2009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Accepted: 09/15/2009] [Indexed: 02/06/2023] Open
Abstract
We have previously reported that age-associated oxidative stress via protein kinase C (PKC) increases D1 receptor (D1R) phosphorylation and causes D1R-G protein uncoupling in renal proximal tubules (RPTs) of old Fischer 344 rats. This results in reduced ability of D1R agonist SKF-38393 to inhibit Na+-K+-ATPase in RPTs of old rats. Here, we studied the effect of treadmill exercise on markers of oxidative stress, PKC, D1R phosphorylation, D1R-G protein coupling, and Na+-K+-ATPase activity in RPTs of adult and old rats. We found increased levels of malondialdehyde, a marker of oxidative stress, in RPTs of old rats, which decreased during exercise. Nuclear levels of nuclear erythroid-related factor (Nrf)-2 and nuclear factor (NF)-kappaB in RPTs, transcription factors involved in antioxidant enzyme gene transcription, increased in exercised old rats. This was accompanied by an increase in the activity and expression of antioxidant enzymes, superoxide dismutase and heme oxygenase-1. Age-related decrease in the levels of D1R mRNAs and proteins was attenuated during exercise. Furthermore, exercise in old rats decreased PKC activity and D1R phosphorylation and increased SKF-38393-mediated [35S]guanosine 5'-O-(3-thiotriphosphate) binding (an index of D1R-G protein coupling). SKF-38393 also caused inhibition of Na+-K+-ATPase in these animals. Also, exercise caused a decrease in proteinuria and increase in phosphaturia in old rats. These results suggest beneficial effects of exercise in terms of increasing antioxidant defenses, decreasing oxidative stress, and improving kidney function in general and D1R function in particular in aging. Both Nrf-2 and NF-kappaB seem to play key role in this phenomenon.
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MESH Headings
- Animals
- Male
- Rats
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Aging/physiology
- Dopamine Agonists/pharmacology
- GTP-Binding Proteins/metabolism
- Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology
- Heme Oxygenase-1/metabolism
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/enzymology
- Kidney Tubules, Proximal/metabolism
- Malondialdehyde/metabolism
- NF-kappa B/metabolism
- Oxidation-Reduction
- Phosphates/urine
- Physical Conditioning, Animal/physiology
- Protein Kinase C/metabolism
- Proteinuria/metabolism
- Rats, Inbred F344
- Receptors, Dopamine D1/physiology
- Sodium-Potassium-Exchanging ATPase/antagonists & inhibitors
- Superoxide Dismutase/metabolism
- Transcription Factors/metabolism
- NF-E2-Related Factor 2/metabolism
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Affiliation(s)
- Liza George
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204, USA
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Asghar M, Chillar A, Lokhandwala MF. Renal proximal tubules from old Fischer 344 rats grow into epithelial cells in cultures and exhibit increased oxidative stress and reduced D1 receptor function. Am J Physiol Cell Physiol 2008; 295:C1326-31. [PMID: 18799649 DOI: 10.1152/ajpcell.00367.2008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Earlier we reported defects in D1 receptor function in renal proximal tubules (RPTs) of aged Fischer 344 (F344) and obese Zucker rats. However, the defects in the receptor function in RPTs of obese Zucker rats do not pass onto primary cultures of RPTs from these animals. Here, we determined whether the defects in D1 receptor function in RPTs of aged F344 rats pass onto the primary cultures. RPTs from aged (24-mo) and adult (6-mo) F344 rats were grown into primary cultures. The microscopic studies showed that cells in cultures from adult and old rats were healthy as determined by the shape and size of the cells and nuclei. D1 receptor agonist SKF-38393 produced inhibition of (86)Rb (rubidium) uptake, index of Na-K-ATPase activity, in cells from adult rats, but this was reduced in old rats. Also, SKF-38393 increased the [(35)S]GTPgammaS binding, index of receptor activation, in the membranes of cells from adult rats but to a lesser extent from old rats. Furthermore, there was a downward trend in the levels of D1 receptor numbers and in the receptor proteins in old rats. Interestingly, gp(91phox) subunit of NADPH oxidase and cellular protein carbonyl levels (oxidative stress marker) were higher in cultures from old rats. These results show that RPTs from adult and old F344 rats grow into epithelial cells in cultures. Furthermore, cells in cultures from old rats are at a higher level of oxidative stress, which may be contributing to the reduced D1 receptor function in the cells from old compared with adult rats.
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Affiliation(s)
- Mohammad Asghar
- Heart and Kidney Institute, College of Pharmacy, Univ. of Houston, Houston, TX 77204, USA.
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Asghar M, George L, Lokhandwala MF. Exercise decreases oxidative stress and inflammation and restores renal dopamine D1 receptor function in old rats. Am J Physiol Renal Physiol 2007; 293:F914-9. [PMID: 17634393 DOI: 10.1152/ajprenal.00272.2007] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Recently, we reported that oxidative stress decreases D1 receptor numbers and G protein activation in renal proximal tubules (RPT), resulting in diminished natriuretic response to dopamine in old rats. We tested the hypothesis that exercise in old rats will decrease oxidative stress and restore natriuretic response to D1 receptor agonist, SKF 38393. Old (23 mo) rats were subjected to rest (sedentary) or to treadmill exercise followed by measurement of oxidative stress [malondialdehyde (MDA)], inflammation [C-reactive protein (CRP)], anti-inflammation (IL-10), antioxidant enzyme [superoxide dismutase (SOD)], and natriuretic response to SKF 38393. We found that MDA levels decreased and total SOD activity and Cu/ZnSOD protein increased in RPT of exercised rats. Exercise increased the nuclear levels of Nrf2 transcription factor (which binds to anti-oxidant response elements) in RPT. The levels of CRP decreased and IL-10 increased in RPT of exercised rats. Furthermore, exercise increased the basal bindings of [3H]SCH 23390 and [35S]GTPγS (indexes of D1 receptor number and G protein activation, respectively) together with D1 receptor and Gαq proteins in RPT membranes. Moreover, SKF 38393 increased sodium excretion in exercised rats. Also, exercise decreased the levels of proteins in the urine of old rats. These results demonstrate that exercise decreases oxidative stress, inflammation, and proteinuria and increases anti-oxidant defense and D1 receptor function in old rats. Therefore, exercise may prove beneficial in preventing age-associated increases in oxidative stress, inflammation, and preserving kidney function, in general, and renal D1 receptor responsiveness, in particular.
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Affiliation(s)
- Mohammad Asghar
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204, USA.
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Fardoun RZ, Asghar M, Lokhandwala M. Role of nuclear factor kappa B (NF-kappaB) in oxidative stress-induced defective dopamine D1 receptor signaling in the renal proximal tubules of Sprague-Dawley rats. Free Radic Biol Med 2007; 42:756-64. [PMID: 17320758 PMCID: PMC2696818 DOI: 10.1016/j.freeradbiomed.2006.11.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Revised: 11/06/2006] [Accepted: 11/25/2006] [Indexed: 01/11/2023]
Abstract
Dopamine promotes sodium excretion, in part, via activation of D1 receptors in renal proximal tubules (PT) and subsequent inhibition of Na, K-ATPase. Recently, we have reported that oxidative stress causes D1 receptor-G-protein uncoupling via mechanisms involving protein kinase C (PKC) and G-protein-coupled receptor kinase 2 (GRK 2) in the primary cultures of renal PT of Sprague-Dawley (SD) rats. There are reports suggesting that redox-sensitive nuclear transcription factor, NF-kappaB, is activated in conditions associated with oxidative stress. This study was designed to identify the role of NF-kappaB in oxidative stress-induced defective renal D1 receptor-G-protein coupling and function. Treatment of the PT with hydrogen peroxide (H(2)O(2), 50 microM/20 min) induced the nuclear translocation of NF-kappaB, increased PKC activity, and triggered the translocation of GRK 2 to the proximal tubular membranes. This was accompanied by hyperphosphorylation of D1 receptors and defective D1 receptor-G-protein coupling. The functional consequence of these changes was decreased D1 receptor activation-mediated inhibition of Na, K-ATPase activity. Interestingly, pretreatment with pyrrolidine dithiocarbamate (PDTC, 25 microM/10 min), an NF-kappaB inhibitor, blocked the H(2)O(2)-induced nuclear translocation of NF-kappaB, increase in PKC activity, and GRK 2 translocation and hyperphosphorylation of D1 receptors in the proximal tubular membranes. Furthermore, PDTC restored D1 receptor G-protein coupling and D1 receptor agonist-mediated inhibition of the Na, K-ATPase activity. Therefore, we suggest that oxidative stress causes nuclear translocation of NF-kappaB in the renal proximal tubules, which contributes to defective D1 receptor-G-protein coupling and function via mechanisms involving PKC, membranous translocation of GRK 2, and subsequent phosphorylation of dopamine D1 receptors.
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Affiliation(s)
- Riham Zein Fardoun
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204, USA
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Fardoun RZ, Asghar M, Lokhandwala M. Role of oxidative stress in defective renal dopamine D1 receptor-G protein coupling and function in old Fischer 344 rats. Am J Physiol Renal Physiol 2006; 291:F945-51. [PMID: 16757732 DOI: 10.1152/ajprenal.00111.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Aging is associated with an increase in oxidative stress. Previously, we have reported that dopamine failed to inhibit proximal tubular Na-K-ATPase and to promote sodium excretion in old rats (Beheray S, Kansra V, Hussain T, and Lokhandwala MF. Kidney Int 58: 712–720, 2000). This was due to uncoupling of dopamine D1 receptors from G proteins resulting from hyperphosphorylation of D1 receptors. The present study was designed to test the role of oxidative stress in the age-related decline in renal dopamine D1 receptor function. We observed that old animals had increased malondialdehyde (MDA) levels, a biomarker of oxidative stress, and decreased D1 receptor number and protein in the proximal tubules (PT) compared with adult rats. In old rats, there was increased G protein-coupled receptor kinase-2 (GRK-2) abundance, increased basal serine phosphorylation of D1 receptors, and defective D1 receptor-G protein coupling in PT membranes. Interestingly, supplementation with an antioxidant, tempol (1 mmol/l in drinking water for 15 days), lowered MDA levels and normalized D1 receptor number and protein in old rats to the level seen in adult rats. Furthermore, tempol decreased GRK-2 abundance and D1 receptor serine phosphorylation and restored D1 receptor-G protein coupling in PT of old rats. The functional consequence of these changes was the restoration of the natriuretic response to D1 receptor activation in tempol-supplemented old rats. Therefore, in old rats, tempol reduces oxidative stress and prevents GRK-2 membranous abundance and hyperphosphorylation of D1 receptors, resulting in restoration of D1 receptor-G protein coupling and the natriuretic response to SKF-38393. Thus tempol, by lowering oxidative stress, normalizes the age-related decline in dopamine receptor function.
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Affiliation(s)
- Riham Zein Fardoun
- Heart and Kidney Institute, College of Pharmacy, Univ. of Houston, Houston, TX 77204-5041, USA
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Carrington JL, Bellino FL. Developing a research agenda in biogerontology: physiological systems. SCIENCE OF AGING KNOWLEDGE ENVIRONMENT : SAGE KE 2006; 2006:pe17. [PMID: 16807481 DOI: 10.1126/sageke.2006.10.pe17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Biology of Aging Program (BAP) at the National Institute on Aging supports research in many areas, including processes of cell senescence and apoptosis, genetic influences on aging, and how aging leads to tissue dysfunction. Several approaches to research on aging physiological systems are described, along with BAP programmatic efforts to enhance and support that research. Understanding the relation between aging and tissue dysfunction has led to new insights into how health can be improved for aged individuals.
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Affiliation(s)
- Jill L Carrington
- Biology of Aging Program, National Institute on Aging, Bethesda, MD 20892, USA.
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Marwaha A, Lokhandwala MF. Tempol reduces oxidative stress and restores renal dopamine D1-like receptor- G protein coupling and function in hyperglycemic rats. Am J Physiol Renal Physiol 2006; 291:F58-66. [PMID: 16478977 DOI: 10.1152/ajprenal.00362.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dopamine via activation of renal D1-like receptors inhibits the activities of Na-K-ATPase and Na/H exchanger and subsequently increases sodium excretion. Decreased renal dopamine production and sodium excretion are associated with hyperglycemic conditions. We have earlier reported D1-like receptor-G protein uncoupling and reduced response to D1-like receptor activation in streptozotocin (STZ)-treated hyperglycemic rats (Marwaha A, Banday AA, and Lokhandwala MF. Am J Physiol Renal Physiol 286: F451-F457, 2004). The present study was designed to test the hypothesis that oxidative stress associated with hyperglycemia increases basal D1-like receptor serine phosphorylation via activation of the PKC-G protein receptor kinase (GRK) pathway, resulting in loss of D1-like receptor-G protein coupling and function. We observed that STZ-treated rats exhibited oxidative stress as evidenced by increased lipid peroxidation. Furthermore, PKC activity and expression of PKC-betaI- and -delta-isoforms were increased in STZ-treated rats. In addition, in STZ-treated rats there was increased GRK2 translocation to proximal tubular membrane and increased basal serine D1-like receptor phosphorylation. Supplementation with the antioxidant tempol lowered oxidative stress in STZ-treated rats, led to normalization of PKC activity, and prevented GRK2 translocation. Furthermore, tempol supplementation in STZ-treated rats restored D1-like receptor-G protein coupling and inhibition of Na-K-ATPase activity on D1-like receptor agonist stimulation. The functional consequence was the restoration of the natriuretic response to D1-like receptor activation. We conclude that oxidative stress associated with hyperglycemia causes an increase in activity and expression of PKC. This leads to translocation of GRK2, subsequent phosphorylation of the D1-like receptor, its uncoupling from G proteins and loss of responsiveness to agonist stimulation.
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Affiliation(s)
- Aditi Marwaha
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204-5041, USA
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Abstract
Dopamine has been recognized as an important modulator of central as well as peripheral physiologic functions in both humans and animals. Dopamine receptors have been identified in a number of organs and tissues, which include several regions within the central nervous system, sympathetic ganglia and postganglionic nerve terminals, various vascular beds, the heart, the gastrointestinal tract, and the kidney. The peripheral dopamine receptors influence cardiovascular and renal function by decreasing afterload and vascular resistance and promoting sodium excretion. Within the kidney, dopamine receptors are present along the nephron, with highest density on proximal tubule epithelial cells. It has been reported that there is a defective dopamine receptor, especially D(1) receptor function, in the proximal tubule of various animal models of hypertension as well as in humans with essential hypertension. Recent reports have revealed the site of and the molecular mechanisms responsible for the defect in D(1) receptors in hypertension. Moreover, recent studies have also demonstrated that the disruption of various dopamine receptor subtypes and their function produces hypertension in rodents. In this review, we present evidence that dopamine and dopamine receptors play an important role in regulating renal sodium excretion and that defective renal dopamine production and/or dopamine receptor function may contribute to the development of various forms of hypertension.
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Affiliation(s)
- Tahir Hussain
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, Texas 77204, USA
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Asghar M, Hussain T, Lokhandwala MF. Higher basal serine phosphorylation of D1A receptors in proximal tubules of old Fischer 344 rats. Am J Physiol Renal Physiol 2002; 283:F350-5. [PMID: 12110520 DOI: 10.1152/ajprenal.00361.2001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Dopamine (DA) and D1-like receptor agonists promote an increase in Na excretion by means of activation of the D1-like receptor signaling cascade and subsequent inhibition of the Na/H exchanger and Na-K-ATPase in renal proximal tubules. Recently, our laboratory reported that DA and the D1-like receptor agonist failed to inhibit Na-K-ATPase activity in old Fischer 344 rats because of uncoupling of D1A receptors from G proteins and that this abnormality led to a diminished natriuretic response to DA in old Fischer 344 rats. In this study, we have tested the hypothesis that the mechanism of this uncoupling may be an altered phosphorylation of D1A receptors in old rats. In experiments performed in renal cortical slices, both DA and SKF-38393, a D1-like receptor agonist, increased the serine phosphorylation of D1A receptors in adult (6 mo) but not old (24 mo) rats. Interestingly, the basal serine phosphorylation of D1A receptors was higher in old than in adult rats. Competition ligand binding ([3H]SCH-23390) experiments on the D1-like receptor in adult and old rats with fenoldopam, a D1-like receptor agonist, revealed the presence of two affinity states of the receptors. There was a rightward shift in the agonist displacement of the ligand in old compared with adult rats, as reflected in the IC50 values (adult vs. old, 7.46 x 10(-9) +/- 2.26 vs. 7.93 x 10(-7) +/- 1.33 M). Also, there was a reduction in agonist affinity in the low-affinity receptors in old compared with adult rats (IC50, adult vs. old, 5.67 x 10(-5) +/- 1.33 vs. 12.60 x 10(-5) +/- 6.50 M). Moreover, the abundance of D1A receptor proteins was approximately 47% lower in the membranes of old compared with adult rats. We speculate that higher basal serine phosphorylation of D1A receptors may have rendered the D1A receptor uncoupled from G protein, leading to a reduced agonist affinity state and thus diminished natriuretic response to DA in old rats.
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Affiliation(s)
- Mohammad Asghar
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas 77204, USA
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Hussain T, Becker M, Beheray S, Lokhandwala MF. Dopamine fails to inhibit Na,H-exchanger in proximal tubules of obese Zucker rats. Clin Exp Hypertens 2001; 23:591-601. [PMID: 11728004 DOI: 10.1081/ceh-100107389] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Dopamine via the activation of D1-like receptors inhibits Na,K-ATPase and Na,H-exchanger and subsequently increases sodium excretion. We have previously reported that dopamine failed to inhibit Na,K-ATPase in the proximal tubules (PTs) of obese Zucker rats. The present study was designed to determine the effect of dopamine on Na,H-exchanger in PTs of lean and obese Zucker rats, and examine D1-like receptor-coupled signal transduction pathway mediating the inhibition of Na,H-exchanger. We found that dopamine inhibited Na,H-exchanger in the PTs of lean rats but this response was absent in obese rats. In brush border membranes, [3H]SCH 23390 binding revealed a approximately 45% reduction in D1-like receptor binding sites in obese compared to lean rats. Dopamine stimulated cAMP accumulation in PTs of lean but not in obese rats. Forskolin-mediated stimulation of cAMP was similar in lean and obese rats. Dopamine as well as forskolin and dibutyryl cAMP-mediated stimulation of protein kinase A (PKA) was reduced in PTs of obese compared to lean rats. The data suggest that reduction in D1-like receptor binding sites, defective coupling with signaling pathway and inability of PKA activation may be responsible for the failure of dopamine to inhibit Na,H-exchanger in PTs of obese rats. This phenomenon may contribute to an increase in sodium reabsorption and development of hypertension in obese Zucker rats.
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Affiliation(s)
- T Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, TX 77204, USA
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Asghar M, Kansra V, Hussain T, Lokhandwala MF. Hyperphosphorylation of Na-pump contributes to defective renal dopamine response in old rats. J Am Soc Nephrol 2001; 12:226-232. [PMID: 11158212 DOI: 10.1681/asn.v122226] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Dopamine D1-like receptor activation causes phosphorylation and inhibition of Na,K-ATPase (Na-pump) activity in the proximal tubules, which is associated with an increase in sodium excretion. It has been shown that dopamine and SKF 38393, a D1-like receptor agonist, caused inhibition of Na,K-ATPase activity in the proximal tubules of adult (6 mo) but not of old (24 mo) Fischer 344 rats. The present study demonstrated that SKF 38393 and PDBu, a phorbol ester and protein kinase C (PKC) activator, increased phosphorylation of the alpha(1)-subunit of Na,K-ATPase in adult but not in old rats. In adult rats, SKF 38393-mediated phosphorylation was antagonized by SCH 23390, a D1-like receptor antagonist. Similarly, Na,K-ATPase activity was inhibited by SKF 38393 and PDBu in adult but not in old rats. The basal activity of Na,K-ATPase was decreased and the basal phosphorylation state of the enzyme was increased in old compared with adult rats. Basal activity of PKC was higher in old compared with adult rats, and SKF 38393 and PDBu stimulated PKC activity in adult but not in old rats. The conclusion is that the failure of D1-like receptor agonist and phorbol ester to stimulate PKC and inhibit Na,K-ATPase activity in old rats is due, at least in part, to the higher basal PKC activity and Na,K-ATPase phosphorylation in old compared with adult rats.
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Affiliation(s)
- Mohammad Asghar
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
| | - Vikram Kansra
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
| | - Tahir Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
| | - Mustafa F Lokhandwala
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
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