Subject(s)
Gastrins/metabolism , Hypertension , Kidney/physiology , Receptor, Angiotensin, Type 1/genetics , Receptors, Dopamine D1/genetics , Sodium/metabolism , Stomach/physiology , Animals , Blood Pressure/physiology , Humans , Hypertension/genetics , Hypertension/metabolism , Ion Transport/genetics , Salt Tolerance/physiology , Signal Transduction/geneticsABSTRACT
The influence of a single gene on the pathogenesis of essential hypertension may be difficult to ascertain, unless the gene interacts with other genes that are germane to blood pressure regulation. G-protein-coupled receptor kinase type 4 (GRK4) is one such gene. We have reported that the expression of its variant hGRK4γ(142V) in mice results in hypertension because of impaired dopamine D1 receptor. Signaling through dopamine D1 receptor and angiotensin II type I receptor (AT1R) reciprocally modulates renal sodium excretion and blood pressure. Here, we demonstrate the ability of the hGRK4γ(142V) to increase the expression and activity of the AT1R. We show that hGRK4γ(142V) phosphorylates histone deacetylase type 1 and promotes its nuclear export to the cytoplasm, resulting in increased AT1R expression and greater pressor response to angiotensin II. AT1R blockade and the deletion of the Agtr1a gene normalize the hypertension in hGRK4γ(142V) mice. These findings illustrate the unique role of GRK4 by targeting receptors with opposite physiological activity for the same goal of maintaining blood pressure homeostasis, and thus making the GRK4 a relevant therapeutic target to control blood pressure.
Subject(s)
Benzimidazoles/pharmacology , Blood Pressure/physiology , G-Protein-Coupled Receptor Kinase 4/genetics , Gene Expression Regulation , Histone Deacetylase 1/antagonists & inhibitors , Hypertension/genetics , Receptor, Angiotensin, Type 1/genetics , Tetrazoles/pharmacology , Angiotensin II Type 1 Receptor Blockers/pharmacology , Animals , Biphenyl Compounds , Disease Models, Animal , Essential Hypertension , Female , G-Protein-Coupled Receptor Kinase 4/biosynthesis , HEK293 Cells , Histone Deacetylase 1/metabolism , Humans , Hypertension/drug therapy , Hypertension/metabolism , Immunoblotting , Kidney/metabolism , Kidney/pathology , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , RNA/genetics , Real-Time Polymerase Chain Reaction , Receptor, Angiotensin, Type 1/biosynthesis , Receptor, Angiotensin, Type 1/drug effects , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The renin-angiotensin-aldosterone (RAAS) and renal dopaminergic systems interact to maintain sodium balance. High NaCl intake increases renal synthesis of dopamine and dopaminergic receptor activity, decreasing epithelial sodium transport, whereas sodium deficit activates the RAAS, increasing epithelial sodium transport. We tested the hypothesis that attenuation of the natriuretic effect of dopamine D1-like receptors during salt restriction results in part from increased RAAS activity in seven salt-resistant normotensive adults using a double-blind placebo-controlled balanced crossover design. All subjects attained sodium balance on low (50 mmol Na(+)/day) and high (300 mmol Na(+)/day) NaCl diets, administered 4 weeks apart. Sodium, potassium, lithium, para-aminohippurate, and creatinine clearances were measured before, during, and after a 3-hour infusion of fenoldopam, a D1-like receptor agonist, with and without pretreatment with enalapril, an angiotensin converting enzyme inhibitor. On the high NaCl diet, fenoldopam-induced natriuresis was associated with the inhibition of renal proximal and distal tubule sodium transport. On the low NaCl diet, fenoldopam decreased renal distal tubule sodium transport but did not cause natriuresis. The addition of enalapril to fenoldopam restored the natriuretic effect of fenoldopam and its inhibitory effect on proximal tubule sodium transport. Thus, on a high NaCl diet fenoldopam causes natriuresis by inhibiting renal proximal and distal tubule transport, but on a low NaCl diet the increased RAAS activity prevents the D1-like receptor from inhibiting renal proximal tubule sodium transport, neutralizing the natriuretic effect of fenoldopam. These results demonstrate an interaction between the renin-angiotensin and renal dopaminergic systems in humans and highlight the influence of dietary NaCl on these interactions.
Subject(s)
Blood Pressure/physiology , Diet, Sodium-Restricted , Receptors, Dopamine/physiology , Renin-Angiotensin System/physiology , Adult , Cross-Over Studies , Double-Blind Method , Female , Humans , Kidney/metabolism , MaleABSTRACT
Extracellular vesicles (EVs) carry signals within or at their limiting membranes, providing a mechanism by which cells can exchange more complex information than what was previously thought. In addition to mRNAs and microRNAs, there are DNA fragments in EVs. Solexa sequencing indicated the presence of at least 16434 genomic DNA (gDNA) fragments in the EVs from human plasma. Immunofluorescence study showed direct evidence that acridine orange-stained EV DNAs could be transferred into the cells and localize to and inside the nuclear membrane. However, whether the transferred EV DNAs are functional or not is not clear. We found that EV gDNAs could be homologously or heterologously transferred from donor cells to recipient cells, and increase gDNA-coding mRNA, protein expression, and function (e.g. AT1 receptor). An endogenous promoter of the AT1 receptor, NF-κB, could be recruited to the transferred DNAs in the nucleus, and increase the transcription of AT1 receptor in the recipient cells. Moreover, the transferred EV gDNAs have pathophysiological significance. BCR/ABL hybrid gene, involved in the pathogenesis of chronic myeloid leukemia, could be transferred from K562 EVs to HEK293 cells or neutrophils. Our present study shows that the gDNAs transferred from EVs to cells have physiological significance, not only to increase the gDNA-coding mRNA and protein levels, but also to influence function in recipient cells.
Subject(s)
Cell Communication/physiology , DNA/metabolism , Transport Vesicles/physiology , Biological Transport , HEK293 Cells , Humans , NF-kappa B/genetics , NeutrophilsABSTRACT
D5 dopamine receptor (D5R) knock-out mice (D5(-/-)) have a higher blood pressure (BP) and higher reactive oxygen species (ROS) production than their D5R wild-type littermates (D5(+/+)). We tested the hypothesis that the high BP and increased ROS production in D5(-/-) mice may be caused by decreased heme oxygenase-1 (HO-1) expression and activity. We found that renal HO-1 protein expression and HO enzyme activity were decreased (65 and 50%, respectively) in D5(-/-) relative to D5(+/+) mice. A 24 h of administration of hemin, an HO-1 inducer, increased HO-1 expression and HO activity (6.8- and 1.9-fold, respectively) and normalized the increased ROS production and BP in D5(-/-) mice. Expression of HO-1 protein and HO activity were increased (2.3- and 1.5-fold, respectively) in HEK cells that heterologously expressed human wild-type D5R (HEK-hD5R), but not the empty vector-transfected HEK-293 cells. Fenoldopam (Fen), a D5R agonist, increased HO activity (3 h), HO-1 protein expression, HO-1 and D5R colocalization and co-immunoprecipitation in HEK-hD5R cells. Cellular NADPH oxidase activity was decreased by 35% in HEK-hD5R that was abrogated with silencing of the heme oxygenase 1 gene (HMOX1). HMOX1 siRNA also impaired the ability of Fen to decrease NADPH oxidase activity in HEK-hD5R cells. In summary, the D5R positively regulates HO-1 through direct protein/protein interaction in the short-term and by increasing HO-1 protein expression in the long-term. The impaired D5R regulation of HO-1 and ROS production contributes to the pathogenesis of hypertension in D5(-/-) mice.
Subject(s)
Blood Pressure/physiology , Heme Oxygenase-1/metabolism , Hypertension/metabolism , NADPH Oxidases/metabolism , Reactive Oxygen Species/metabolism , Receptors, Dopamine D5/metabolism , Animals , Dopamine Agonists/pharmacology , Fenoldopam/pharmacology , HEK293 Cells , Humans , Hypertension/enzymology , Hypertension/genetics , Mice , Mice, Knockout , Receptors, Dopamine D5/genetics , Up-Regulation/drug effectsABSTRACT
Renal dopamine receptors participate in the regulation of blood pressure. Genetic factors, including polymorphisms of the dopamine D(2) receptor gene (DRD2) are associated with essential hypertension, but the mechanisms of their contribution are incompletely understood. Mice lacking Drd2 (D(2)-/-) have elevated blood pressure, increased renal expression of inflammatory factors, and renal injury. We tested the hypothesis that decreased dopamine D(2) receptor (D(2)R) function increases vulnerability to renal inflammation independently of blood pressure, is an immediate cause of renal injury, and contributes to the subsequent development of hypertension. In D(2)-/- mice, treatment with apocynin normalized blood pressure and decreased oxidative stress, but did not affect the expression of inflammatory factors. In mouse RPTCs Drd2 silencing increased the expression of TNFα and MCP-1, while treatment with a D(2)R agonist abolished the angiotensin II-induced increase in TNF-α and MCP-1. In uni-nephrectomized wild-type mice, selective Drd2 silencing by subcapsular infusion of Drd2 siRNA into the remaining kidney produced the same increase in renal cytokines/chemokines that occurs after Drd2 deletion, increased the expression of markers of renal injury, and increased blood pressure. Moreover, in mice with two intact kidneys, short-term Drd2 silencing in one kidney, leaving the other kidney undisturbed, induced inflammatory factors and markers of renal injury in the treated kidney without increasing blood pressure. Our results demonstrate that the impact of decreased D(2)R function on renal inflammation is a primary effect, not necessarily associated with enhanced oxidant activity, or blood pressure; renal damage is the cause, not the result, of hypertension. Deficient renal D(2)R function may be of clinical relevance since common polymorphisms of the human DRD2 gene result in decreased D(2)R expression and function.
Subject(s)
Hypertension/physiopathology , Inflammation/etiology , Kidney Diseases/etiology , Receptors, Dopamine D2/physiology , Animals , Down-Regulation , Gene Expression Profiling , Immunohistochemistry , Inflammation/physiopathology , Kidney Diseases/physiopathology , Mice , Mice, Inbred C57BL , Mice, Knockout , Real-Time Polymerase Chain Reaction , Receptors, Dopamine D2/geneticsABSTRACT
OBJECTIVE: Abnormal vascular smooth muscle cell (VSMC) proliferation is involved in the development of vascular diseases. However, the mechanisms by which insulin exerts this effect are not completely known. We hypothesize that microRNAs might be involved in insulin-induced VSMC proliferation. METHODS: VSMC proliferation was determined by [H]-thymidine incorporation; microRNAs were determined by microRNA chips and real-time PCR; and p21expression was determined by immunoblotting. RESULTS: In this study, we found that insulin increased VSMC proliferation and miR-208 expression. Overexpression of miR-208 increased basal and insulin-mediated VSMC proliferation. Although a miR-208 inhibitor, by itself, had no effect on VSMC proliferation, it reduced the insulin-mediated cell proliferation. Moreover, miR-208 increased the transformation of cell cycle from G0/G1 phase to the S phase. Bioinformatics analysis found that p21, a member of the cyclin-dependent kinase (CDK)-inhibitory protein family, may be the target of miR-208. Insulin decreased p21 expression in VSMCs; transfection of miR-208 also decreased p21 protein expression. In the presence of miR-208 inhibitor, the inhibitory effect of insulin on p21 expression in VSMCs was partially blocked. The interaction between miR-208 and p21 was direct. Using a luciferase reporter with entire wild-type p21 3'UTR or a mutant p21 3'UTR in HEK293 cells, we found that miR-208 decreased but neither miR-208 mimic nor the mutant p21 3'UTR had any significant effect on the luciferase activity. CONCLUSION: This study indicates that miRNAs, miR-208, in particular, are involved in the insulin-induced VSMC proliferation via downregulation of its potential target, p21, a key member of CDK-inhibitory protein family.
Subject(s)
Cell Proliferation/drug effects , Cyclin-Dependent Kinase Inhibitor p21/metabolism , Insulin/pharmacology , MicroRNAs/metabolism , Muscle, Smooth, Vascular/cytology , Muscle, Smooth, Vascular/metabolism , Animals , Aorta/cytology , Aorta/metabolism , Cell Cycle/drug effects , Cell Cycle/physiology , Cells, Cultured , Dose-Response Relationship, Drug , Down-Regulation/physiology , Models, Animal , Rats , Rats, Sprague-Dawley , Signal Transduction/drug effects , Signal Transduction/physiologyABSTRACT
BACKGROUND: The relationship between achieving target blood pressures and medication modification among hypertensive patients in Japan is relatively unknown. We examined the incidence of prescription changes and how the prescription changes influence success rates in achieving target blood pressures in a group of patients with uncontrolled hypertension. METHODS: This prospective observational cohort study (July 2006 to May 2007) examined the association between blood pressure control and antihypertensive medication among 2,735 Japanese hypertensive patients who completed four seasonal follow-ups and whose medications were verified. The primary outcome was "therapeutic failure" at the third follow-up survey. Logistic regression analyzed how prescription changes may influence therapeutic failure risk. Common medication changes were estimated using follow-up data. RESULTS: Median ages and proportion of males were 73 years and 43.8% vs. 69 years and 45.6% in those with controlled and those with uncontrolled hypertension at baseline, respectively. At baseline, 1,496 patients were uncontrolled, and 296 (18.0%) changed prescriptions during the follow-up period. Among patients with diabetes mellitus, renal disease, or organ damage and vascular complications, who were uncontrolled at baseline, prescription changes during the year significantly increased therapeutic failures at the third follow-up after adjusting for related variables. About half of the changes at each follow-up visit remained in the same class or combination category. CONCLUSIONS: This study identified infrequent changes in prescription and minor modifications of medication even among uncontrolled hypertension. We highlight the importance of reviewing prescription content to maintain or improve blood pressure levels to achieve recommended treatment goals.
Subject(s)
Antihypertensive Agents/therapeutic use , Hypertension/drug therapy , Practice Patterns, Physicians' , Aged , Angiotensin Receptor Antagonists/therapeutic use , Calcium Channel Blockers/therapeutic use , Drug Prescriptions , Female , Humans , Japan , Male , Prospective Studies , Treatment OutcomeABSTRACT
D(5) dopamine receptor (D(5)R)-deficient (D(5)(-/-)) mice have hypertension that is aggravated by an increase in sodium intake. The present experiments were designed to test the hypothesis that a dysregulation of renal sodium transporters is related to the salt sensitivity in D(5)(-/-) mice. D(5)R was expressed in the renal proximal tubule, thick ascending limb, distal convoluted tubule, and cortical and outer medullary collecting ducts in D(5)(+/+) mice. On a control Na(+) diet, renal protein expressions of NKCC2 (sodium-potassium-2 chloride cotransporter), sodium chloride cotransporter, and alpha and gamma subunits of the epithelial sodium channel were greater in D(5)(-/-) than in D(5)(+/+) mice. Renal renin abundance and urine aldosterone levels were similar but renal angiotensin II type 1 receptor (AT(1)R) protein expression was increased in D(5)(-/-) mice. An elevated Na(+) diet increased further the elevated blood pressure of D(5)(-/-) mice but did not affect the normal blood pressure of D(5)(+/+) mice. The increased levels of NKCC2, sodium chloride cotransporter, and alpha and gamma subunits of the epithelial sodium channel persisted with the elevated Na(+) diet and unaffected by chronic AT(1)R blockade (losartan) in D(5)(-/-) mice. The expressions of proximal sodium transporters NHE3 (sodium hydrogen exchanger type 3) and NaPi2 (sodium phosphate cotransporter type 2) were increased by the elevated Na(+) diet in D(5)(-/-) mice; the increased expression of NHE3 but not NaPi2 was abolished by AT(1)R blockade. Our findings suggest that the increased protein expression of sodium transporters/channels in distal nephron segments may be the direct consequence of the disruption of D(5)R, independent of the renin-angiotensin aldosterone system.
Subject(s)
Diet, Sodium-Restricted , Hypertension/physiopathology , Receptors, Dopamine D5/deficiency , Receptors, Dopamine D5/genetics , Sodium Chloride Symporters/metabolism , Sodium-Potassium-Chloride Symporters/metabolism , Analysis of Variance , Animals , Disease Models, Animal , Hypertension/genetics , Immunoblotting , Immunohistochemistry , Kidney Cortex/drug effects , Kidney Cortex/metabolism , Kidney Medulla/drug effects , Kidney Medulla/metabolism , Losartan/pharmacology , Mice , Mice, Inbred C57BL , Mice, Knockout , Probability , Random Allocation , Receptors, Dopamine D5/metabolism , Sodium Channels/physiology , Sodium Chloride Symporters/drug effects , Sodium Chloride Symporters/genetics , Sodium-Potassium-Chloride Symporters/drug effects , Sodium-Potassium-Chloride Symporters/genetics , Up-RegulationABSTRACT
Complex interactions between genes and environment result in a sodium-induced elevation in blood pressure (salt sensitivity) and/or hypertension that lead to significant morbidity and mortality affecting up to 25% of the middle-aged adult population worldwide. Determining the etiology of genetic and/or environmentally-induced high blood pressure has been difficult because of the many interacting systems involved. Two main pathways have been implicated as principal determinants of blood pressure since they are located in the kidney (the key organ responsible for blood pressure regulation), and have profound effects on sodium balance: the dopaminergic and renin-angiotensin systems. These systems counteract or modulate each other, in concert with a host of intracellular second messenger pathways to regulate sodium and water balance. In particular, the G protein-coupled receptor kinase type 4 (GRK4) appears to play a key role in regulating dopaminergic-mediated natriuresis. Constitutively activated GRK4 gene variants (R65L, A142V, and A486V), by themselves or by their interaction with other genes involved in blood pressure regulation, are associated with essential hypertension and/or salt-sensitive hypertension in several ethnic groups. GRK4γ ï 142Vï transgenic mice are hypertensive on normal salt intake while GRK4γï 486Vï transgenic mice develop hypertension only with an increase in salt intake. GRK4 gene variants have been shown to hyperphosphorylate, desensitize, and internalize two members of the dopamine receptor family, the D(1) (D(1)R) and D(3) (D(3)R) dopamine receptors, but also increase the expression of a key receptor of the renin-angiotensin system, the angiotensin type 1 receptor (AT(1)R). Knowledge of the numerous blood pressure regulatory pathways involving angiotensin and dopamine may provide new therapeutic approaches to the pharmacological regulation of sodium excretion and ultimately blood pressure control.
Subject(s)
Blood Pressure , Dopamine/metabolism , G-Protein-Coupled Receptor Kinase 4/metabolism , Hypertension/metabolism , Kidney/metabolism , Adult , Amino Acid Substitution , Animals , Dopamine/genetics , Female , G-Protein-Coupled Receptor Kinase 4/genetics , Humans , Hypertension/drug therapy , Hypertension/genetics , Male , Mice , Mice, Transgenic , Middle Aged , Mutation, Missense , Phosphorylation , Receptor, Angiotensin, Type 1/genetics , Receptor, Angiotensin, Type 1/metabolism , Receptors, Dopamine D1/genetics , Receptors, Dopamine D1/metabolism , Receptors, Dopamine D3/genetics , Receptors, Dopamine D3/metabolism , Renin-Angiotensin System/geneticsABSTRACT
BACKGROUND: The dopaminergic and endothelin systems, by regulating sodium transport in the renal proximal tubule (RPT), participate in the control of blood pressure. The D(3) and ETB receptors are expressed in RPTs, and D(3) receptor function in RPTs is impaired in spontaneously hypertensive rats (SHRs). Therefore, we tested the hypothesis that D(3) receptors can regulate ETB receptors, and that D(3) receptor regulation of ETB receptors in RPTs is impaired in SHRs. METHODS: ETB receptor expression in RPT cells was measured by immunoblotting and reverse transcriptase-PCR and ETB receptor function by measuring Na(+)-K(+) ATPase activity. D(3)/ETB receptor interaction was studied by co-immunoprecipitation. RESULTS: In Wistar-Kyoto (WKY) RPT cells, the D(3) receptor agonist, PD128907, increased ETB receptor protein expression, effects that were blocked by removal of calcium in the culture medium. The stimulatory effect of D(3) on ETB receptor mRNA and protein expression was also blocked by nicardipine. In contrast, in SHR RPT cells, PD128907 decreased ETB receptor expression. Basal D(3)/ETB receptor co-immunoprecipitation was three times greater in WKY than in SHRs. The absolute amount of D(3)/ETB receptor co-immunoprecipitation induced by a D(3) receptor agonist was also greater in WKY than in SHRs. Stimulation of ETB receptors decreased Na(+)-K(+) ATPase activity in WKY but not in SHR cells. Pretreatment with PD128907 augmented the inhibitory effect of BQ3020 on Na(+)-K(+) ATPase activity in WKY but not in SHR cells. CONCLUSIONS: D(3) receptors regulate ETB receptors by physical receptor interaction and govern receptor expression and function. D(3) receptor regulation of ETB receptors is aberrant in RPT cells from SHRs.
Subject(s)
Kidney Tubules, Proximal/physiology , Receptor, Endothelin B/physiology , Receptors, Dopamine D3/physiology , Animals , Benzopyrans/pharmacology , Blotting, Western , Calcium Channel Blockers/pharmacology , Cells, Cultured , Dopamine Agonists/pharmacology , Dopamine Antagonists/pharmacology , GTP-Binding Proteins/physiology , Immunoprecipitation , Indans/pharmacology , Kidney Tubules, Proximal/cytology , Nicardipine/pharmacology , Oxazines/pharmacology , Rats , Rats, Inbred SHR , Rats, Inbred WKY , Receptor, Endothelin B/genetics , Receptors, Dopamine D3/agonists , Receptors, Dopamine D3/antagonists & inhibitors , Reverse Transcriptase Polymerase Chain Reaction , Second Messenger Systems/physiology , Sodium-Potassium-Exchanging ATPase/metabolism , Species SpecificityABSTRACT
Aging is a major risk factor for hypertension and cardiovascular disease. Accumulating evidence suggests that telomere length is a marker for biological aging of the cardiovascular system. Telomere length is determined by genetic and environmental factors. Studies in different racial populations are required to determine the prognostic value of telomere length in hypertension and cardiovascular diseases. The main objective of this study was to investigate the association between leukocyte telomere length and the risk and prognosis of hypertension in a Chinese population. The relative telomere length of leukocytes was determined by a quantitative PCR-based method in 767 subjects: 379 healthy controls and 388 hypertensive patients, ages 30 to 80 years. The median telomere length ratio, 0.57 (interquartile range: 0.48 to 0.72), was shorter in hypertensive than in healthy normotensive subjects (0.67; interquartile range: 0.53 to 0.93; P<0.001). After 5 years of follow-up, subjects with shorter telomeres were at a higher risk of developing coronary artery disease than individuals with longer telomeres (odds ratio: 3.315; 95% CI: 1.662 to 6.609; P<0.001). Multivariate analysis showed that short telomere length and hypertension were independent risk factors for developing coronary artery disease. Our data suggest that mean leukocyte telomere length is a potential predictor of coronary artery disease and support the hypothesis that differences in biological aging can contribute to the risk and variability of developing hypertension and cardiovascular diseases.
Subject(s)
Asian People/statistics & numerical data , Hypertension/ethnology , Hypertension/genetics , Telomere/genetics , Telomere/pathology , Adult , Aged , Aged, 80 and over , Aging , Coronary Artery Disease/ethnology , Coronary Artery Disease/genetics , Female , Follow-Up Studies , Humans , Leukocytes/immunology , Leukocytes/pathology , Male , Middle Aged , Polymerase Chain Reaction , Predictive Value of Tests , Prognosis , Risk Factors , Telomere/immunologyABSTRACT
Dopamine is important in the pathogenesis of hypertension because of abnormalities in receptor-mediated regulation of renal sodium transport. Dopamine receptors are classified into D(1)-like (D(1), D(5)) and D(2)-like (D(2), D(3), D(4)) subtypes, all of which are expressed in the kidney. Mice deficient in specific dopamine receptors have been generated to provide holistic assessment on the varying physiological roles of each receptor subtype. This review examines recent studies on these mutant mouse models and evaluates the impact of individual dopamine receptor subtypes on blood pressure regulation.
Subject(s)
Hypertension/metabolism , Kidney/metabolism , Mice, Knockout , Receptors, Dopamine/genetics , Animals , Disease Models, Animal , Dopamine/metabolism , Hypertension/genetics , Mice , Receptors, Dopamine/metabolism , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolism , Sodium/metabolismABSTRACT
Dopaminergic and endothelin systems participate in the control blood pressure by regulating sodium transport in the renal proximal tubule. Disruption of either the endothelin B receptor (ETB) or D(3) dopamine receptor gene in mice produces hypertension. To examine whether these two receptors interact we studied the Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats by selectively infusing reagents into the right kidney of anesthetized rats. The D(3) receptor agonist (PD128907) caused natriuresis in WKY rats which was partially blocked by the ETB receptor antagonist. In contrast, PD128907 blunted sodium excretion in the SHRs. We found using laser confocal microscopy that the ETB receptor was mainly located in the cell membrane in control WKY cells. Treatment with the D(3) receptor antagonist caused its internalization into intracellular compartments that contained the D(3) receptors. Combined use of D(3) and ETB antagonists failed to internalize ETB receptors in cells from WKY rats. In contrast in SHR cells, ETB receptors were found mainly in internal compartments under basal condition and thus were likely prevented from interacting with the agonist-stimulated, membrane-bound D(3) receptors. Our studies suggest that D(3) receptors physically interact with proximal tubule ETB receptors and that the blunted natriuretic effect of dopamine in SHRs may be explained, in part, by abnormal D(3)/ETB receptor interactions.
Subject(s)
Kidney/metabolism , Natriuresis , Receptor, Endothelin B/metabolism , Receptors, Dopamine D3/agonists , Receptors, Dopamine D3/metabolism , Animals , Cell Membrane/chemistry , Endocytosis , Endothelin B Receptor Antagonists , Kidney Tubules, Proximal/chemistry , Natriuresis/drug effects , Protein Binding , Rats , Rats, Inbred SHR , Rats, Inbred WKY , Receptor, Endothelin B/analysis , Receptors, Dopamine D3/antagonists & inhibitorsABSTRACT
Hypertension is a multigenic disorder in which abnormal counterregulation between dopamine and Ang II plays a role. Recent studies suggest that this counterregulation results, at least in part, from regulation of the expression of both the antihypertensive dopamine 5 receptor (D5R) and the prohypertensive Ang II type 1 receptor (AT1R). In this report, we investigated the in vivo and in vitro interaction between these GPCRs. Disruption of the gene encoding D5R in mice increased both blood pressure and AT1R protein expression, and the increase in blood pressure was reversed by AT1R blockade. Activation of D5R increased the degradation of glycosylated AT1R in proteasomes in HEK cells and human renal proximal tubule cells heterologously and endogenously expressing human AT1R and D5R. Confocal microscopy, Förster/fluorescence resonance energy transfer microscopy, and fluorescence lifetime imaging microscopy revealed that activation of D5R initiated ubiquitination of the glycosylated AT1R at the plasma membrane. The regulated degradation of AT1R via a ubiquitin/proteasome pathway by activation of D5R provides what we believe to be a novel mechanism whereby blood pressure can be regulated by the interaction of 2 counterregulatory GPCRs. Our results therefore suggest that treatments for hypertension might be optimized by designing compounds that can target the AT1R and the D5R.
Subject(s)
Gene Expression Regulation , Proteasome Endopeptidase Complex/metabolism , Receptors, Angiotensin/metabolism , Receptors, Dopamine D5/physiology , Ubiquitin/metabolism , Animals , Blood Pressure , Cell Line , Cell Membrane/metabolism , Glycosylation , Humans , Kidney Tubules/metabolism , Mice , Models, Biological , Receptors, Dopamine D5/geneticsABSTRACT
Dopamine plays an important role in the pathogenesis of hypertension by regulating epithelial sodium transport and by interacting with vasoactive hormones/humoral factors, such as aldosterone, angiotensin, catecholamines, endothelin, oxytocin, prolactin pro-opiomelancortin, reactive oxygen species, renin, and vasopressin. Dopamine receptors are classified into D(1)-like (D(1) and D(5)) and D(2)-like (D(2), D(3), and D(4)) subtypes based on their structure and pharmacology. In recent years, mice deficient in one or more of the five dopamine receptor subtypes have been generated, leading to a better understanding of the physiological role of each of the dopamine receptor subtypes. This review summarizes the results from studies of various dopamine receptor mutant mice on the role of individual dopamine receptor subtypes and their interactions with other G protein-coupled receptors in the regulation of blood pressure.
Subject(s)
Dopamine/physiology , Hypertension/genetics , Hypertension/physiopathology , Receptors, Dopamine/genetics , Receptors, Dopamine/physiology , Animals , Blood Pressure/genetics , Blood Pressure/physiology , Mice , Mice, Knockout , Receptors, Dopamine D1/genetics , Receptors, Dopamine D1/physiology , Receptors, Dopamine D2/genetics , Receptors, Dopamine D2/physiology , Receptors, Dopamine D3/genetics , Receptors, Dopamine D3/physiology , Receptors, Dopamine D4/genetics , Receptors, Dopamine D4/physiology , Receptors, Dopamine D5/genetics , Receptors, Dopamine D5/physiologyABSTRACT
BACKGROUND: Urinary albumin excretion frequently persists in diabetic patients who are treated with angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB). Sulodexide, a glycosaminoglycan mixture of 80% heparan sulfate and 20% dermatan sulfate, has been hypothesized to reduce persistent albuminuria. We have conducted a multi-center randomized double-blind pilot study in order to determine the effect of 6 months' therapy with sulodexide on urinary albumin excretion and to address logistical issues for a full-scale trial. METHODS: A total of 149 patients with type 2 diabetes and an albumin:creatinine ratio (ACR) between 20 and 300 mg/g were randomized with equal allocation to either placebo, 200 mg of sulodexide or 400 mg of sulodexide. The primary endpoint was the achievement, at 6 months, of either 3(1) return to normoalbuminuria (ACR < 20 mg/g with a decrease of at least 25%) or (2) a decrease in ACR of at least 50% from the baseline value. All patients used a maximum tolerated recommended FDA approved dose of an ACEI or ARB for at least 60 days and had stable blood pressure prior to randomization. RESULTS: The primary efficacy endpoint was achieved in 25.3% of the patients in the two sulodexide groups combined versus 15.4% of the placebo-treated patients (P = 0.26). The primary endpoint was achieved in 33.3% (P = 0.075 for the comparison to placebo) in the sulodexide 200 mg group and 18.4% (P = 0.781) in the sulodexide 400 mg group. (No consistent patterns of side effects were observed. CONCLUSION: Based on the experience gained in this pilot study, one full-scale trial is currently being conducted to evaluate the effects of sulodexide on change in ACR in patients with persistent microalbuminuria, and a longer-term trial is underway to evaluate the effects of sulodexide on long-term renal disease progression in patients with overt proteinuria.
Subject(s)
Albuminuria/drug therapy , Diabetes Mellitus, Type 2/drug therapy , Glycosaminoglycans/administration & dosage , Hypoglycemic Agents/administration & dosage , Aged , Albuminuria/etiology , Analysis of Variance , Angiotensin-Converting Enzyme Inhibitors/administration & dosage , Angiotensin-Converting Enzyme Inhibitors/adverse effects , Chronic Disease , Confidence Intervals , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/diagnosis , Dose-Response Relationship, Drug , Double-Blind Method , Drug Administration Schedule , Female , Follow-Up Studies , Humans , Male , Middle Aged , Pilot Projects , Probability , Reference Values , Severity of Illness Index , Treatment Outcome , UrinalysisABSTRACT
Dopamine plays an important role in the pathogenesis of hypertension by regulating epithelial sodium transport, vascular smooth muscle contractility and production of reactive oxygen species and by interacting with the renin-angiotensin and sympathetic nervous systems. Dopamine receptors are classified into D(1)-like (D(1) and D(5)) and D(2)-like (D(2), D(3) and D(4)) subtypes based on their structure and pharmacology. Each of the dopamine receptor subtypes participates in the regulation of blood pressure by mechanisms specific for the subtype. Some receptors regulate blood pressure by influencing the central and/or peripheral nervous system; others influence epithelial transport and regulate the secretion and receptors of several humoral agents. This review summarizes the physiology of the different dopamine receptors in the regulation of blood pressure, and the relationship between dopamine receptor subtypes and hypertension.
Subject(s)
Hypertension/physiopathology , Receptors, Dopamine/physiology , Blood Pressure/physiology , Dopamine/metabolism , Gastrointestinal Tract/metabolism , Gastrointestinal Tract/physiopathology , Humans , Hypertension/metabolism , Kidney/metabolism , Kidney/physiopathology , Muscle, Smooth, Vascular/metabolism , Muscle, Smooth, Vascular/physiopathology , Receptors, Dopamine/metabolism , Receptors, Dopamine D1/metabolism , Receptors, Dopamine D1/physiology , Receptors, Dopamine D2/metabolism , Receptors, Dopamine D2/physiology , Receptors, Dopamine D3/metabolism , Receptors, Dopamine D3/physiology , Receptors, Dopamine D4/metabolism , Receptors, Dopamine D4/physiology , Receptors, Dopamine D5/metabolism , Receptors, Dopamine D5/physiologyABSTRACT
G protein-coupled receptor (GPCR) kinases (GRKs) regulate the sensitivity of GPCRs, including dopamine receptors. The GRK4 locus is linked to, and some of its polymorphisms are associated with, human essential hypertension. Transgenic mice overexpressing human (h) GRK4gamma A142V on a mixed genetic background (C57BL/6J and SJL/J) have impaired renal D(1)-dopamine receptor (D(1)R) function and increased blood pressure. We now report that hGRK4gamma A142V transgenic mice, in C57BL/6J background, are hypertensive and have higher blood pressures than hGRK4gamma wild-type transgenic and nontransgenic mice. The hypertensive phenotype is stable because blood pressures in transgenic founders and F6 offspring are similarly increased. To determine whether the hypertension is associated with increased production of reactive oxygen species (ROS), we measured renal NADPH oxidase (Nox2 and Nox4) and heme oxygenase (HO-1 and HO-2) protein expressions and urinary excretion of 8-isoprostane and compared the effect of Tempol on blood pressure in hGRK4gamma A142V transgenic mice and D(5)R knockout (D(5)(-/-)) mice in which hypertension is mediated by increased ROS. The expressions of Nox isoforms and HO-2 and the urinary excretion of 8-isoprostane were similar in hGRK4gamma A142V transgenic mice and their controls. HO-1 expression was increased in hGRK4gamma A142V relative to hGRK4gamma wild-type transgenic mice. In contrast with the hypotensive effect of Tempol in D(5)(-/-) mice, it had no effect in hGRK4gamma A142V transgenic mice. We conclude that the elevated blood pressure of hGRK4gamma A142V transgenic mice is due mainly to the effect of hGRK4gamma A142V transgene acting via D(1)R and increased ROS production is not a contributor.