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Girardi ACC, Polidoro JZ, Castro PC, Pio-Abreu A, Noronha IL, Drager LF. Mechanisms of heart failure and chronic kidney disease protection by SGLT2 inhibitors in nondiabetic conditions. Am J Physiol Cell Physiol 2024; 327:C525-C544. [PMID: 38881421 DOI: 10.1152/ajpcell.00143.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 06/11/2024] [Accepted: 06/11/2024] [Indexed: 06/18/2024]
Abstract
Sodium-glucose cotransporter 2 inhibitors (SGLT2is), initially developed for type 2 diabetes (T2D) treatment, have demonstrated significant cardiovascular and renal benefits in heart failure (HF) and chronic kidney disease (CKD), irrespective of T2D. This review provides an analysis of the multifaceted mechanisms underlying the cardiorenal benefits of SGLT2i in HF and CKD outside of the T2D context. Eight major aspects of the protective effects of SGLT2i beyond glycemic control are explored: 1) the impact on renal hemodynamics and tubuloglomerular feedback; 2) the natriuretic effects via proximal tubule Na+/H+ exchanger NHE3 inhibition; 3) the modulation of neurohumoral pathways with evidence of attenuated sympathetic activity; 4) the impact on erythropoiesis, not only in the context of local hypoxia but also systemic inflammation and iron regulation; 5) the uricosuria and mitigation of the hyperuricemic environment in cardiorenal syndromes; 6) the multiorgan metabolic reprogramming including the potential induction of a fasting-like state, improvement in glucose and insulin tolerance, and stimulation of lipolysis and ketogenesis; 7) the vascular endothelial growth factor A (VEGF-A) upregulation and angiogenesis, and 8) the direct cardiac effects. The intricate interplay between renal, neurohumoral, metabolic, and cardiac effects underscores the complexity of SGLT2i actions and provides valuable insights into their therapeutic implications for HF and CKD. Furthermore, this review sets the stage for future research to evaluate the individual contributions of these mechanisms in diverse clinical settings.
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Affiliation(s)
- Adriana C C Girardi
- Laboratório de Genética e Cardiologia Molecular, Faculdade de Medicina, Instituto do Coração (InCor), Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
| | - Juliano Z Polidoro
- Laboratório de Genética e Cardiologia Molecular, Faculdade de Medicina, Instituto do Coração (InCor), Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
| | - Paulo C Castro
- Laboratório de Genética e Cardiologia Molecular, Faculdade de Medicina, Instituto do Coração (InCor), Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
| | - Andrea Pio-Abreu
- Disciplina de Nefrologia, Faculdade de Medicina, Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
| | - Irene L Noronha
- Disciplina de Nefrologia, Faculdade de Medicina, Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
| | - Luciano F Drager
- Disciplina de Nefrologia, Faculdade de Medicina, Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
- Unidade de Hipertensão, Faculdade de Medicina, Instituto do Coração (InCor), Hospital das Clínicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil
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Kuang SY, Ahmetaj B, Qu X. Fundamental equations and hypotheses governing glomerular hemodynamics. Front Physiol 2024; 15:1440627. [PMID: 39206387 PMCID: PMC11349631 DOI: 10.3389/fphys.2024.1440627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Accepted: 07/19/2024] [Indexed: 09/04/2024] Open
Abstract
The glomerular filtration rate (GFR) is the outcome of glomerular hemodynamics, influenced by a series of parameters: renal plasma flow, resistances of afferent arterioles and efferent arterioles (EAs), hydrostatic pressures in the glomerular capillary and Bowman's capsule, and plasma colloid osmotic pressure in the glomerular capillary. Although mathematical models have been proposed to predict the GFR at both the single-nephron level and the two-kidney system level using these parameters, mathematical equations governing glomerular filtration have not been well-established because of two major problems. First, the two-kidney system-level models are simply extended from the equations at the single-nephron level, which is inappropriate in epistemology and methodology. Second, the role of EAs in maintaining the normal GFR is underappreciated. In this article, these two problems are concretely elaborated, which collectively shows the need for a shift in epistemology toward a more holistic and evolving way of thinking, as reflected in the concept of the complex adaptive system (CAS). Then, we illustrate eight fundamental mathematical equations and four hypotheses governing glomerular hemodynamics at both the single-nephron and two-kidney levels as the theoretical foundation of glomerular hemodynamics. This illustration takes two steps. The first step is to modify the existing equations in the literature and establish a new equation within the conventional paradigm of epistemology. The second step is to formulate four hypotheses through logical reasoning from the perspective of the CAS (beyond the conventional paradigm). Finally, we apply the new equation and hypotheses to comprehensively analyze glomerular hemodynamics under different conditions and predict the GFR. By doing so, some concrete issues are eliminated. Unresolved issues are discussed from the perspective of the CAS and a desinger's view. In summary, this article advances the theoretical study of glomerular dynamics by 1) clarifying the necessity of shifting to the CAS paradigm; 2) adding new knowledge/insights into the significant role of EAs in maintaining the normal GFR; 3) bridging the significant gap between research findings and physiology education; and 4) establishing a new and advanced foundation for physiology education.
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Affiliation(s)
- Serena Y. Kuang
- Department of Foundational Medical Studies, Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - Besjana Ahmetaj
- Department of Foundational Medical Studies, Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - Xianggui Qu
- Department of Mathematics and Statistics, Oakland University, Rochester, MI, United States
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Higashihara E, Harada T, Fukuhara H. Juxtaglomerular apparatus-mediated homeostatic mechanisms: therapeutic implication for chronic kidney disease. Expert Opin Pharmacother 2024; 25:819-832. [PMID: 38773961 DOI: 10.1080/14656566.2024.2357188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 05/15/2024] [Indexed: 05/24/2024]
Abstract
INTRODUCTION Juxtaglomerular apparatus (JGA)-mediated homeostatic mechanism links to how sodium-glucose cotransporter 2 inhibitors (SGLT2is) slow progression of chronic kidney disease (CKD) and may link to how tolvaptan slows renal function decline in autosomal dominant polycystic kidney disease (ADPKD). AREA COVERED JGA-mediated homeostatic mechanism has been hypothesized based on investigations of tubuloglomerular feedback and renin-angiotensin system. We reviewed clinical trials of SGLT2is and tolvaptan to assess the relationship between this mechanism and these drugs. EXPERT OPINION When sodium load to macula densa (MD) increases, MD increases adenosine production, constricting afferent arteriole (Af-art) and protecting glomeruli. Concurrently, MD signaling suppresses renin secretion, increases urinary sodium excretion, and counterbalances reduced sodium filtration. However, when there is marked increase in sodium load per-nephron, as in advanced CKD, MD adenosine production increases, relaxing Af-art and maintaining sodium homeostasis at the expense of glomeruli. The beneficial effects of tolvaptan on renal function in ADPKD may also depend on the JGA-mediated homeostatic mechanisms since tolvaptan inhibits sodium reabsorption in the thick ascending limb.The JGA-mediated homeostatic mechanism regulates Af-arts, constricting to relaxing according to homeostatic needs. Understanding this mechanism may contribute to the development of pharmacotherapeutic compounds and better care for patients with CKD.
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Affiliation(s)
- Eiji Higashihara
- Department of Urology, Kyorin University School of Medicine, Mitaka, Japan
| | - Takeo Harada
- Department of Renal and Cardiovascular Research, Otsuka Pharmaceutical Co. Ltd, Tokushima, Japan
| | - Hiroshi Fukuhara
- Department of Urology, Kyorin University School of Medicine, Mitaka, Japan
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Dixon AJ, Osei-Owusu P. Elastin haploinsufficiency accelerates age-related structural and functional changes in the renal microvasculature and impairment of renal hemodynamics in female mice. Front Physiol 2023; 14:1141094. [PMID: 37179824 PMCID: PMC10167050 DOI: 10.3389/fphys.2023.1141094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 04/11/2023] [Indexed: 05/15/2023] Open
Abstract
Age-related decline in functional elastin is associated with increased arterial stiffness, a known risk factor for developing cardiovascular disease. While the contribution of elastin insufficiency to the stiffening of conduit arteries is well described, little is known about the impact on the structure and function of the resistance vasculature, which contributes to total peripheral resistance and the regulation of organ perfusion. In this study, we determined how elastin insufficiency impinges on age-related changes in the structure and biomechanical properties of the renal microvasculature, altering renal hemodynamics and the response of the renal vascular bed to changes in renal perfusion pressure (RPP) in female mice. Using Doppler ultrasonography, we found that resistive index and pulsatility index were elevated in young Eln +/- and aged mice. Histological examination showed thinner internal and external elastic laminae, accompanied by increased elastin fragmentation in the medial layer without any calcium deposits in the small intrarenal arteries of kidneys from young Eln +/- and aged mice. Pressure myography of interlobar arteries showed that vessels from young Eln +/- and aged mice had a slight decrease in distensibility during pressure loading but a substantial decline in vascular recoil efficiency upon pressure unloading. To examine whether structural changes in the renal microvasculature influenced renal hemodynamics, we clamped neurohumoral input and increased renal perfusion pressure by simultaneously occluding the superior mesenteric and celiac arteries. Increased renal perfusion pressure caused robust changes in blood pressure in all groups; however, changes in renal vascular resistance and renal blood flow (RBF) were blunted in young Eln +/- and aged mice, accompanied by decreased autoregulatory index, indicating greater impairment of renal autoregulation. Finally, increased pulse pressure in aged Eln +/- mice positively correlated with high renal blood flow. Together, our data show that the loss of elastin negatively affects the structural and functional integrity of the renal microvasculature, ultimately worsening age-related decline in kidney function.
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Affiliation(s)
- Alethia J Dixon
- Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States
| | - Patrick Osei-Owusu
- Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States
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Williams JM, Murphy SR, Wu W, Border JJ, Fan F, Roman RJ. Renoprotective effects of empagliflozin in type 1 and type 2 models of diabetic nephropathy superimposed with hypertension. GeroScience 2022; 44:2845-2861. [PMID: 35767209 PMCID: PMC9768063 DOI: 10.1007/s11357-022-00610-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 06/15/2022] [Indexed: 01/07/2023] Open
Abstract
Diabetes, hypertension, and aging are major contributors to cardiovascular and chronic kidney disease (CKD). Sodium/glucose cotransporter 2 (SGLT2) inhibitors have become a preferred treatment for type II diabetic patients since they have cardiorenal protective effects. However, most elderly diabetic patients also have hypertension, and the effects of SGLT2 inhibitors have not been studied in hypertensive diabetic patients or animal models. The present study examined if controlling hyperglycemia with empagliflozin, or given in combination with lisinopril, slows the progression of renal injury in hypertensive diabetic rats. Studies were performed using hypertensive streptozotocin-induced type 1 diabetic Dahl salt-sensitive (STZ-SS) rats and in deoxycorticosterone-salt hypertensive type 2 diabetic nephropathy (T2DN) rats. Administration of empagliflozin alone or in combination with lisinopril reduced blood glucose, proteinuria, glomerular injury, and renal fibrosis in STZ-SS rats without altering renal blood flow (RBF) or glomerular filtration rate (GFR). Blood pressure and renal hypertrophy were also reduced in rats treated with empagliflozin and lisinopril. Administration of empagliflozin alone or in combination with lisinopril lowered blood glucose, glomerulosclerosis, and renal fibrosis but had no effect on blood pressure, kidney weight, or proteinuria in hypertensive T2DN rats. RBF was not altered in any of the treatment groups, and GFR was elevated in empagliflozin-treated hypertensive T2DN rats. These results indicate that empagliflozin is highly effective in controlling blood glucose levels and slows the progression of renal injury in both hypertensive type 1 and type 2 diabetic rats, especially when given in combination with lisinopril to lower blood pressure.
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Affiliation(s)
- Jan M Williams
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA
| | - Sydney R Murphy
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA
| | - Wenjie Wu
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA
| | - Jane J Border
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA
| | - Fan Fan
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA
| | - Richard J Roman
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216, USA.
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van Ochten M, Westerhof BE, Spaanderman MEA, Antonius TAJ, van Drongelen J. Modeling renal autoregulation in a hemodynamic, first-trimester gestational model. Physiol Rep 2022; 10:e15484. [PMID: 36200318 PMCID: PMC9535437 DOI: 10.14814/phy2.15484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/13/2022] [Accepted: 09/14/2022] [Indexed: 11/06/2022] Open
Abstract
The maternal cardiovascular system, led by renal volume regulatory responses, changes during pregnancy to ensure an adequate circulation for fetal development and growth. Circulatory maladjustment predisposes to hypertensive complications during pregnancy. Mathematical models can be used to gain insight in the gestational cardiovascular physiology. In this study, we developed an accurate, robust, and transparent model for renal autoregulation implemented in an existing circulatory gestational model. This renal autoregulation model aims to maintain steady glomerular pressure by the myogenic response, and glomerular filtration rate by tubuloglomerular feedback, both by inducing a change in the radius, and thus resistance, of the afferent arteriole. The modeled response of renal blood flow and the afferent arteriole following blood pressure increase were compared to published observations in rats. With solely the myogenic response, our model had a maximum deviation of 7% in change in renal blood flow and 7% in renal vascular resistance. When both the myogenic response and tubuloglomerular feedback were concurrently activated, the maximum deviation was 7% in change in renal blood flow and 5% in renal vascular resistance. These results show that our model is able to represent renal autoregulatory behavior comparable to empirical data. Further studies should focus on extending the model with other regulatory mechanisms to understand the hemodynamic changes in healthy and complicated pregnancy.
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Affiliation(s)
- Maaike van Ochten
- Department of Gynecology and ObstetricsRadboud University Medical CenterNijmegenThe Netherlands
- Department of Gynecology and ObstetricsMaastricht University Medical CenterMaastrichtThe Netherlands
- Division of Neonatology, Department of PerinatologyRadboud University Medical Center, Radboud Institute for Health Sciences, Amalia Children's HospitalNijmegenThe Netherlands
| | - Berend E. Westerhof
- Division of Neonatology, Department of PerinatologyRadboud University Medical Center, Radboud Institute for Health Sciences, Amalia Children's HospitalNijmegenThe Netherlands
- Department of Pulmonary MedicineAmsterdam University Medical Centers, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular SciencesAmsterdamThe Netherlands
| | - Marc E. A. Spaanderman
- Department of Gynecology and ObstetricsRadboud University Medical CenterNijmegenThe Netherlands
- Department of Gynecology and ObstetricsMaastricht University Medical CenterMaastrichtThe Netherlands
| | - Tim A. J. Antonius
- Division of Neonatology, Department of PerinatologyRadboud University Medical Center, Radboud Institute for Health Sciences, Amalia Children's HospitalNijmegenThe Netherlands
| | - Joris van Drongelen
- Department of Gynecology and ObstetricsRadboud University Medical CenterNijmegenThe Netherlands
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Abstract
SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes from failing. This includes blood glucose dependent and independent mechanisms. SGLT2 inhibitors lower glomerular pressure and filtration, thereby reducing the physical stress on the filtration barrier and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular glucotoxicity and improved mitochondrial function and autophagy, can reduce proinflammatory and profibrotic signaling and preserve tubular function and GFR in long term. By shifting transport downstream, SGLT2 inhibitors may mimic systemic hypoxia and stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs.
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Affiliation(s)
- Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA, USA; Department of Pharmacology, University of California San Diego, La Jolla, CA, USA; VA San Diego Healthcare System, 3350 La Jolla Village Drive (9151), San Diego, CA 92161, USA.
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8
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Pak ES, Cha JJ, Cha DR, Kanasaki K, Ha H. Adenosine receptors as emerging therapeutic targets for diabetic kidney disease. Kidney Res Clin Pract 2022; 41:S74-S88. [PMID: 36239063 PMCID: PMC9590297 DOI: 10.23876/j.krcp.22.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 04/27/2022] [Accepted: 05/05/2022] [Indexed: 08/07/2023] Open
Abstract
Diabetic kidney disease (DKD) is now a pandemic worldwide, and novel therapeutic options are urgently required. Adenosine, an adenosine triphosphate metabolite, plays a role in kidney homeostasis through interacting with four types of adenosine receptors (ARs): A1AR, A2AAR, A2BAR, and A3AR. Increasing evidence highlights the role of adenosine and ARs in the development and progression of DKD: 1) increased adenosine in the plasma and urine of diabetics with kidney injury, 2) increased expression of each of the ARs in diabetic kidneys, 3) the protective effect of coffee, a commonly ingested nonselective AR antagonist, on DKD, and 4) the protective effect of AR modulators in experimental DKD models. We propose AR modulators as a new therapeutic option to treat DKD. Detailed mechanistic studies on the pharmacology of AR modulators will help us to develop effective first-in-class AR modulators against DKD.
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Affiliation(s)
- Eun Seon Pak
- Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
| | - Jin Joo Cha
- Department of Nephrology, Korea University Ansan Hospital, Ansan, Republic of Korea
| | - Dae Ryong Cha
- Department of Nephrology, Korea University Ansan Hospital, Ansan, Republic of Korea
| | - Keizo Kanasaki
- Department of Internal Medical 1, Shimane University Faculty of Medicine, Izumo, Japan
| | - Hunjoo Ha
- Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
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Monu SR, Wang H, Potter DL, Liao TD, Ortiz PA. Decreased tubuloglomerular feedback response in high-fat diet-induced obesity. Am J Physiol Renal Physiol 2022; 322:F429-F436. [PMID: 35224993 PMCID: PMC9169969 DOI: 10.1152/ajprenal.00307.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 02/07/2022] [Accepted: 02/16/2022] [Indexed: 12/17/2022] Open
Abstract
Obesity increases the risk of renal damage, but the mechanisms are not clear. Normally, kidneys autoregulate to keep the glomerular capillary pressure (PGC), renal blood flow, and glomerular filtration rate in a steady state. However, in obesity, higher PGC, renal blood flow, and glomerular filtration rate are noted. Together, these may lead to glomerular damage. PGC is controlled mainly by afferent arteriole resistance, which, in turn, is regulated by tubuloglomerular feedback (TGF), a vasoconstrictor mechanism. High fat-induced obesity causes renal damage, and this may be related to increased PGC. However, there are no studies as to whether high-fat diet (HFD)-induced obesity affects TGF. We hypothesized that TGF would be attenuated in obesity caused by HFD feeding (60% fat) in Sprague-Dawley rats. Sprague-Dawley rats fed a normal-fat diet (NFD; 12% fat) served as the control. We studied 4 and 16 wk of HFD feeding using in vivo renal micropuncture of individual rat nephrons. We did not observe significant differences in body weight, TGF response, and mean arterial pressure at 4 wk of HFD feeding, but after 16 wk of HFD, rats were heavier and hypertensive. The maximal TGF response was smaller in HFD-fed rats than in NFD-fed rats, indicating an attenuation of TGF in HFD-induced obesity. Baseline PGC was higher in HFD-fed rats than in NFD-fed rats and was associated with higher glomerulosclerosis. We conclude that attenuated TGF and higher PGC along with hypertension in HFD-fed obese Sprague-Dawley rats could explain the higher propensity of glomerular damage observed in obesity.NEW & NOTEWORTHY Reduced tubuloglomerular feedback, higher glomerular capillary pressure, and hypertension in combination may explain the higher glomerular damage observed in high-fat diet-induced obesity.
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Affiliation(s)
- Sumit R Monu
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan
| | - Hong Wang
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan
| | - D'Anna L Potter
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan
| | - Tang-Dong Liao
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan
| | - Pablo A Ortiz
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan
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Thomson SC, Vallon V. Effects of SGLT2 inhibitor and dietary NaCl on glomerular hemodynamics assessed by micropuncture in diabetic rats. Am J Physiol Renal Physiol 2021; 320:F761-F771. [PMID: 33645318 PMCID: PMC8174804 DOI: 10.1152/ajprenal.00552.2020] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 02/09/2021] [Accepted: 02/19/2021] [Indexed: 01/10/2023] Open
Abstract
Inhibitors of the main proximal tubular Na-glucose cotransporter (SGLT2) mitigate diabetic glomerular hyperfiltration and have been approved by the United States Food and Drug Administration for slowing the progression of diabetic kidney disease. It has been proposed that SGLT2 inhibitors improve hard renal outcomes by reducing glomerular capillary pressure (PGC) via a tubuloglomerular feedback (TGF) response to a decrease in proximal reabsorption (Jprox). However, the effect of SGLT2 inhibition on PGC has not been measured. Here, we studied the effects of acute SGLT2 blockade (ertugliflozin) on Jprox and glomerular hemodynamics in two-period micropuncture experiments using streptozotocin-induced diabetic rats fed high- or low-NaCl diets. PGC was measured by direct capillary puncture or computed from tubular stop-flow pressure (PSF). TGF is intact while measuring PGC directly but rendered inoperative when measuring PSF. Acute SGLT2 inhibitor reduced Jprox by ∼30%, reduced PGC by 5-8 mmHg, and reduced glomerular filtration rate (GFR) by ∼25% (all P < 0.0001) but had no effect on PSF. The decrease in PGC was larger with the low-NaCl diet (8 vs. 5 mmHg, P = 0.04) where PGC was higher to begin with (54 vs. 50 mmHg, P = 0.003). Greater decreases in PGC corresponded, unexpectedly, to lesser decreases in GFR (P = 0.04). In conclusion, these results confirm expectations that PGC would decline in response to acute SGLT2 inhibition and that a functioning TGF system is required for this. We infer a contribution of postglomerular vasorelaxation to the TGF responses where decreases in PGC were large and decreases in GFR were small.NEW & NOTEWORTHY It has been theorized that Na-glucose cotransporter (SGLT2) blockade slows progression of diabetic kidney disease by reducing physical strain on the glomerulus. This is the first direct measurement of intraglomerular pressure during SGLT2 blockade. Findings confirmed that SGLT2 blockade does reduce glomerular capillary pressure, that this is mediated through tubuloglomerular feedback, and that the tubuloglomerular feedback response to SGLT2 blockade involves preglomerular vasoconstriction and postglomerular vasorelaxation.
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Affiliation(s)
- Scott Culver Thomson
- Division of Nephrology-Hypertension, Department of Medicine, University of California, San Diego, California; and Veterans Affairs San Diego Healthcare System, La Jolla, California
| | - Volker Vallon
- Division of Nephrology-Hypertension, Department of Medicine, University of California, San Diego, California; and Veterans Affairs San Diego Healthcare System, La Jolla, California
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Abstract
SGLT2 inhibitors are antihyperglycemic drugs that protect kidneys and the heart of patients with or without type 2 diabetes and preserved or reduced kidney function from failing. The involved protective mechanisms include blood glucose-dependent and -independent mechanisms: SGLT2 inhibitors prevent both hyper- and hypoglycemia, with expectedly little net effect on HbA1C. Metabolic adaptations to induced urinary glucose loss include reduced fat mass and more ketone bodies as additional fuel. SGLT2 inhibitors lower glomerular capillary hypertension and hyperfiltration, thereby reducing the physical stress on the filtration barrier, albuminuria, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity, may preserve tubular function and glomerular filtration rate in the long term. SGLT2 inhibitors may mimic systemic hypoxia and stimulate erythropoiesis, which improves organ oxygen delivery. SGLT2 inhibitors are proximal tubule and osmotic diuretics that reduce volume retention and blood pressure and preserve heart function, potentially in part by overcoming the resistance to diuretics and atrial-natriuretic-peptide and inhibiting Na-H exchangers and sympathetic tone.
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Affiliation(s)
- Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA;
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093, USA
- VA San Diego Healthcare System, San Diego, California 92161, USA
| | - Subodh Verma
- Division of Cardiac Surgery, St. Michael's Hospital, University of Toronto, Toronto, Ontario M5B 1W8, Canada;
- Departments of Surgery and Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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12
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Tuttle KR, Brosius FC, Cavender MA, Fioretto P, Fowler KJ, Heerspink HJ, Manley T, McGuire DK, Molitch ME, Mottl AK, Perreault L, Rosas SE, Rossing P, Sola L, Vallon V, Wanner C, Perkovic V. SGLT2 Inhibition for CKD and Cardiovascular Disease in Type 2 Diabetes: Report of a Scientific Workshop Sponsored by the National Kidney Foundation. Am J Kidney Dis 2021; 77:94-109. [DOI: 10.1053/j.ajkd.2020.08.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 08/04/2020] [Indexed: 12/25/2022]
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13
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Tuttle KR, Brosius FC, Cavender MA, Fioretto P, Fowler KJ, Heerspink HJL, Manley T, McGuire DK, Molitch ME, Mottl AK, Perreault L, Rosas SE, Rossing P, Sola L, Vallon V, Wanner C, Perkovic V. SGLT2 Inhibition for CKD and Cardiovascular Disease in Type 2 Diabetes: Report of a Scientific Workshop Sponsored by the National Kidney Foundation. Diabetes 2021; 70:1-16. [PMID: 33106255 PMCID: PMC8162454 DOI: 10.2337/dbi20-0040] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 08/04/2020] [Indexed: 12/24/2022]
Abstract
Diabetes is the most frequent cause of chronic kidney disease (CKD), leading to nearly half of all cases of kidney failure requiring replacement therapy. The principal cause of death among patients with diabetes and CKD is cardiovascular disease (CVD). Sodium/glucose cotransporter 2 (SGLT2) inhibitors were developed to lower blood glucose levels by inhibiting glucose reabsorption in the proximal tubule. In clinical trials designed to demonstrate the CVD safety of SGLT2 inhibitors in type 2 diabetes mellitus (T2DM), consistent reductions in risks for secondary kidney disease end points (albuminuria and a composite of serum creatinine doubling or 40% estimated glomerular filtration rate decline, kidney failure, or death), along with reductions in CVD events, were observed. In patients with CKD, the kidney and CVD benefits of canagliflozin were established by the CREDENCE (Canagliflozin and Renal Events in Diabetes With Established Nephropathy Clinical Evaluation) trial in patients with T2DM, urinary albumin-creatinine ratio >300 mg/g, and estimated glomerular filtration rate of 30 to <90 mL/min/1.73 m2 To clarify and support the role of SGLT2 inhibitors for treatment of T2DM and CKD, the National Kidney Foundation convened a scientific workshop with an international panel of more than 80 experts. They discussed the current state of knowledge and unanswered questions in order to propose therapeutic approaches and delineate future research. SGLT2 inhibitors improve glomerular hemodynamic function and are thought to ameliorate other local and systemic mechanisms involved in the pathogenesis of CKD and CVD. SGLT2 inhibitors should be used when possible by people with T2DM to reduce risks for CKD and CVD in alignment with the clinical trial entry criteria. Important risks of SGLT2 inhibitors include euglycemic ketoacidosis, genital mycotic infections, and volume depletion. Careful consideration should be given to the balance of benefits and harms of SGLT2 inhibitors and risk mitigation strategies. Effective implementation strategies are needed to achieve widespread use of these life-saving medications.
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Affiliation(s)
- Katherine R Tuttle
- Providence Health Care and University of Washington School of Medicine, Spokane, WA
| | | | | | - Paola Fioretto
- Department of Medicine, University of Padua, Padua, Italy
| | | | | | - Tom Manley
- National Kidney Foundation, New York, NY
| | | | - Mark E Molitch
- Division of Endocrinology, Metabolism and Molecular Medicine, Northwestern, University Feinberg School of Medicine, Chicago, IL
| | - Amy K Mottl
- University of North Carolina School of Medicine, Chapel Hill, NC
| | | | - Sylvia E Rosas
- Joslin Diabetes Center and Harvard Medical School, Boston, MA
| | - Peter Rossing
- Steno Diabetes Center Copenhagen, Gentofte, Denmark
- University of Copenhagen, Copenhagen, Denmark
| | - Laura Sola
- University of the Republic, Montevideo, Uruguay
| | | | - Christoph Wanner
- Division of Nephrology, University Hospital Würzburg, Würzburg, Germany
| | - Vlado Perkovic
- George Institute for Global Health, UNSW Sydney, Australia
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14
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León-Jiménez D, López-Mendoza M, Pérez-Temprano R, Górriz JL, Miramontes-González JP. In response to the paper 'High-protein diet: A barrier to the nephroprotective effects of sodium-glucose co-transporter-2 inhibitors?'. Diabetes Obes Metab 2020; 22:1701-1702. [PMID: 32424874 DOI: 10.1111/dom.14087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 05/11/2020] [Indexed: 11/29/2022]
Affiliation(s)
- David León-Jiménez
- Internal Medicine Diabetes, Obesity and Vascular Risk.Virgen del Rocío University Hospital, University of Seville, Seville, Spain
| | | | - Ramón Pérez-Temprano
- Internal Medicine, Risk Vascular Unit, Virgen Macarena University Hospital, Seville, Spain
| | - José Luis Górriz
- Department of Nephrology, Hospital Clínico Universitario, INCLIVA, Universidad de Valencia, Valencia, Spain
| | - José Pablo Miramontes-González
- Internal Medicine Hospital Río Hortega. Instituto de Investigaciones Biomédicas de Salamanca-IBSAL, Universidad Pontificia de Salamanca, Salamanca, Spain
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15
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Razga Z. Functional Relevancies of Trans-Differentiation in the Juxtaglomerular Apparatus of Rat Kidney. Int J Nephrol Renovasc Dis 2020; 13:147-156. [PMID: 32606889 PMCID: PMC7297338 DOI: 10.2147/ijnrd.s246476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/09/2020] [Indexed: 12/17/2022] Open
Abstract
Glomerular filtration rate is controlled by the contractile effect of angiotensin II on afferent and efferent arterioles. The renin positivity of the afferent arterioles depends on tubuloglomerular feedback via the macula densa (MD) and short loop feedback via the afferent arteriolar endothelia. The renin-producing cells are trans-differentiated from smooth muscle cells (SMCs) of mainly the afferent arterioles, the MD cells are trans-differentiated from the neighboring tubular cells, and the high-permeability endothelial cells are trans-differentiated from normal permeability endothelial cells facing the renin-negative part of the afferent arterioles. All of the trans-differentiations depend on the activity of the renin-angiotensin system (RAS). The distribution of AT1 receptors for angiotensin II expresses the contractile effects of angiotensin II on renin-negative SMCs and the negative effect on trans-differentiation of renin-positive SMCs and MD cells. The purpose of this review is to summarize the stereological data of molecules like angiotensin II AT1 receptors, L-type calcium channels, and renin receptors in the juxtaglomerular apparatus of normal and STZ-induced diabetic rat kidneys, thus showing their functional relevancies on trans-differentiation among the juxtaglomerular apparatus’ elements.
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Affiliation(s)
- Zsolt Razga
- Department of Pathology, University of Szeged, Szeged, Hungary
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16
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Romero CA, Carretero OA. Tubule-vascular feedback in renal autoregulation. Am J Physiol Renal Physiol 2019; 316:F1218-F1226. [PMID: 30838873 DOI: 10.1152/ajprenal.00381.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Afferent arteriole (Af-Art) diameter regulates pressure and flow into the glomerulus, which are the main determinants of the glomerular filtration rate. Thus, Af-Art resistance is crucial for Na+ filtration. Af-Arts play a role as integrative centers, where systemic and local systems interact to determine the final degree of resistance. The tubule of a single nephron contacts an Af-Art of the same nephron at two locations: in the transition of the thick ascending limb to the distal tubule (macula densa) and again in the connecting tubule. These two sites are the anatomic basis of two intrinsic feedback mechanisms: tubule-glomerular feedback and connecting tubule-glomerular feedback. The cross communications between the tubules and Af-Arts integrate tubular Na+ and water processing with the hemodynamic conditions of the kidneys. Tubule-glomerular feedback provides negative feedback that tends to avoid salt loss, and connecting tubule-glomerular feedback provides positive feedback that favors salt excretion by modulating tubule-glomerular feedback (resetting it) and increasing glomerular filtration rate. These feedback mechanisms are also exposed to systemic modulators (hormones and the nervous system); however, they can work in isolated kidneys or nephrons. The exaggerated activation or absence of any of these mechanisms may lead to disequilibrium in salt and water homeostasis, especially in extreme conditions (e.g., high-salt diet/low-salt diet) and may be part of the pathogenesis of some diseases. In this review, we focus on molecular signaling, feedback interactions, and the physiological roles of these two feedback mechanisms.
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Affiliation(s)
- Cesar A Romero
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Oscar A Carretero
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
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17
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O'Neill J, Jasionek G, Drummond SE, Brett O, Lucking EF, Abdulla MA, O'Halloran KD. Renal cortical oxygen tension is decreased following exposure to long-term but not short-term intermittent hypoxia in the rat. Am J Physiol Renal Physiol 2019; 316:F635-F645. [PMID: 30648908 DOI: 10.1152/ajprenal.00254.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Chronic kidney disease (CKD) occurs in more than 50% of patients with obstructive sleep apnea (OSA). However, the impact of intermittent hypoxia (IH) on renal function and oxygen homeostasis is unclear. Male Sprague-Dawley rats were exposed to IH (270 s at 21% O2; 90 s hypoxia, 6.5% O2 at nadir) for 4 h [acute IH (AIH)] or to chronic IH (CIH) for 8 h/day for 2 wk. Animals were anesthetized and surgically prepared for the measurement of mean arterial pressure (MAP), and left renal excretory function, renal blood flow (RBF), and renal oxygen tension (Po2). AIH had no effect on MAP (123 ± 14 vs. 129 ± 14 mmHg, means ± SE, sham vs. IH). The CIH group was hypertensive (122 ± 9 vs. 144 ± 15 mmHg, P < 0.05). Glomerular filtration rate (GFR) (0.92 ± 0.27 vs. 1.33 ± 0.33 ml/min), RBF (3.8 ± 1.5 vs. 7.2 ± 2.4 ml/min), and transported sodium (TNa) (132 ± 39 vs. 201 ± 47 μmol/min) were increased in the AIH group (all P < 0.05). In the CIH group, GFR (1.25 ± 0.28 vs. 0.86 ± 0.28 ml/min, P < 0.05) and TNa (160 ± 39 vs. 120 ± 40 μmol/min, P < 0.05) were decreased, while RBF (4.13 ± 1.5 vs. 3.08 ± 1.5 ml/min) was not significantly different. Oxygen consumption (QO2) was increased in the AIH group (6.76 ± 2.60 vs. 13.60 ± 7.77 μmol/min, P < 0.05), but it was not significantly altered in the CIH group (3.97 ± 2.63 vs. 6.82 ± 3.29 μmol/min). Cortical Po2 was not significantly different in the AIH group (46 ± 4 vs. 46 ± 3 mmHg), but it was decreased in the CIH group (44 ± 5 mmHg vs. 38 ± 2 mmHg, P < 0.05). For AIH, renal oxygen homeostasis was preserved through a maintained balance between O2 supply (RBF) and consumption (GFR). For CIH, mismatched TNa and QO2 reflect inefficient O2 utilization and, thereby, sustained decrease in cortical Po2.
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Affiliation(s)
- Julie O'Neill
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
| | - Greg Jasionek
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
| | - Sarah E Drummond
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
| | - Orla Brett
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
| | - Eric F Lucking
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
| | - Mohammed A Abdulla
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
| | - Ken D O'Halloran
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork , Cork , Ireland
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18
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Monu SR, Maheshwari M, Peterson EL, Carretero OA. Role of connecting tubule glomerular feedback in obesity related renal damage. Am J Physiol Renal Physiol 2018; 315:F1708-F1713. [PMID: 30303713 DOI: 10.1152/ajprenal.00227.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Zucker obese rats (ZOR) have higher glomerular capillary pressure (PGC) that can cause renal damage. PGC is controlled by afferent (Af-Art) and efferent arteriole (Ef-Art) resistance. Af-Art resistance is regulated by factors that regulate other arterioles, such as myogenic response. In addition, it is also regulated by 2 intrinsic feedback mechanisms: 1) tubuloglomerular feedback (TGF) that causes Af-Art constriction in response to increased NaCl in the macula densa and 2) connecting tubule glomerular feedback (CTGF) that causes Af-Art dilatation in response to an increase in NaCl transport in the connecting tubule via the epithelial sodium channel. Since CTGF is an Af-Art dilatory mechanism, we hypothesized that increased CTGF contributes to TGF attenuation, which in turn increases PGC in ZOR. We performed a renal micropuncture experiment and measured stop-flow pressure (PSF), which is an indirect measurement of PGC in ZOR. Maximal TGF response at 40 nl/min was attenuated in ZOR (4.47 ± 0.60 mmHg) in comparison to the Zucker lean rats (ZLR; 8.54 ± 0.73 mmHg, P < 0.05), and CTGF was elevated in ZOR (5.34 ± 0.87 mmHg) compared with ZLR (1.12 ± 1.28 mmHg, P < 0.05). CTGF inhibition with epithelial sodium channel blocker normalized the maximum PSF change in ZOR indicating that CTGF plays a significant role in TGF attenuation (ZOR, 10.67 ± 1.07 mmHg vs. ZLR, 9.5 ± 1.53 mmHg). We conclude that enhanced CTGF contributes to TGF attenuation in ZOR and potentially contribute to progressive renal damage.
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Affiliation(s)
- Sumit R Monu
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Mani Maheshwari
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan.,Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia
| | - Edward L Peterson
- Department of Public Health Sciences, Henry Ford Hospital , Detroit, Michigan
| | - Oscar A Carretero
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
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19
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Zhang J, Jiang S, Wei J, Yip KP, Wang L, Lai EY, Liu R. Glucose dilates renal afferent arterioles via glucose transporter-1. Am J Physiol Renal Physiol 2018; 315:F123-F129. [PMID: 29513069 PMCID: PMC6335005 DOI: 10.1152/ajprenal.00409.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Glomerular hyperfiltration occurs during the early stage of diabetes. An acute glucose infusion increases glomerular filtration rate. The involvement of tubuloglomerular feedback response and direct effect of glucose on the afferent arterioles (Af-Arts) have been suggested. However, the signaling pathways to trigger Af-Art dilatation have not been fully identified. Therefore, in the present study we tested our hypothesis that an increase in glucose concentration enhances endothelial nitric oxide synthesis activity and dilates the Af-Arts via glucose transporter-1 (GLUT1) using isolated mouse Af-Arts with perfusion. We isolated and microperfused the Af-Arts from nondiabetic C57BL/6 mice. The Af-Arts were preconstricted with norepinephrine (1 µM). When we switched the d-glucose concentration from low (5 mM) to high (30 mM) in the perfusate, the preconstricted Af-Arts significantly dilated by 37.8 ± 7.1%, but L-glucose did not trigger the dilation. GLUT1 mRNA was identified in microdisserted Af-Arts measured by RT-PCR. Changes in nitric oxide (NO) production in Af-Art were also measured using fluorescent probe when ambient glucose concentration was increased. When the d-glucose concentration was switched from 5 to 30 mM, NO generation in Af-Art was significantly increased by 19.2 ± 6.2% (84.7 ± 4.1 to 101.0 ± 9.3 U/min). l-Glucose had no effect on the NO generation. The GLUT1-selective antagonist 4-[({[4-(1,1-Dimethylethyl)phenyl]sulfonyl}amino)methyl]- N-3-pyridinylbenzamide and the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester blocked the high glucose-induced NO generation and vasodilation. In conclusion, we demonstrated that an increase in glucose concentration dilates the Af-Art by stimulation of the endothelium-derived NO production mediated by GLUT1.
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Affiliation(s)
- Jie Zhang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine , Tampa, Florida
| | - Shan Jiang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine , Tampa, Florida.,Department of Physiology, Zhejiang University School of Medicine , Zhejiang , China
| | - Jin Wei
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine , Tampa, Florida
| | - Kay-Pong Yip
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine , Tampa, Florida
| | - Lei Wang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine , Tampa, Florida
| | - En Yin Lai
- Department of Physiology, Zhejiang University School of Medicine , Zhejiang , China
| | - Ruisheng Liu
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine , Tampa, Florida
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20
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Lacy ER, Reale E. A unique juxtaglomerular apparatus in the river ray, Potamotrygon humerosa, a freshwater stingray. ZOOMORPHOLOGY 2017. [DOI: 10.1007/s00435-017-0372-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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21
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Wang H, Romero CA, Masjoan Juncos JX, Monu SR, Peterson EL, Carretero OA. Effect of salt intake on afferent arteriolar dilatation: role of connecting tubule glomerular feedback (CTGF). Am J Physiol Renal Physiol 2017; 313:F1209-F1215. [PMID: 28835421 DOI: 10.1152/ajprenal.00320.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 08/10/2017] [Accepted: 08/16/2017] [Indexed: 01/13/2023] Open
Abstract
Afferent arteriole (Af-Art) resistance is modulated by two intrinsic nephron feedbacks: 1) the vasoconstrictor tubuloglomerular feedback (TGF) mediated by Na+-K+-2Cl- cotransporters (NKCC2) in the macula densa and blocked by furosemide and 2) the vasodilator connecting tubule glomerular feedback (CTGF), mediated by epithelial Na+ channels (ENaC) in the connecting tubule and blocked by benzamil. High salt intake reduces Af-Art vasoconstrictor ability in Dahl salt-sensitive rats (Dahl SS). Previously, we measured CTGF indirectly, by differences between TGF responses with and without CTGF inhibition. We recently developed a new method to measure CTGF more directly by simultaneously inhibiting NKCC2 and the Na+/H+ exchanger (NHE). We hypothesize that in vivo during simultaneous inhibition of NKCC2 and NHE, CTGF causes an Af-Art dilatation revealed by an increase in stop-flow pressure (PSF) in Dahl SS and that is enhanced with a high salt intake. In the presence of furosemide alone, increasing nephron perfusion did not change the PSF in either Dahl salt-resistant rats (Dahl SR) or Dahl SS. When furosemide and an NHE inhibitor, dimethylamiloride, were perfused simultaneously, an increase in tubular flow caused Af-Art dilatation that was demonstrated by an increase in PSF. This increase was greater in Dahl SS [4.5 ± 0.4 (SE) mmHg] than in Dahl SR (2.5 ± 0.3 mmHg; P < 0.01). We confirmed that CTGF causes this vasodilation, since benzamil completely blocked this effect. However, a high salt intake did not augment the Af-Art dilatation. We conclude that during simultaneous inhibition of NKCC2 and NHE in the nephron, CTGF induces Af-Art dilatation and a high salt intake failed to enhance this effect.
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Affiliation(s)
- Hong Wang
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and
| | - Cesar A Romero
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and
| | - J X Masjoan Juncos
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and
| | - Sumit R Monu
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and
| | - Edward L Peterson
- Department of Public Health Sciences, Henry Ford Hospital, Detroit, Michigan
| | - Oscar A Carretero
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and
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22
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Silva L, Subiabre M, Araos J, Sáez T, Salsoso R, Pardo F, Leiva A, San Martín R, Toledo F, Sobrevia L. Insulin/adenosine axis linked signalling. Mol Aspects Med 2017; 55:45-61. [DOI: 10.1016/j.mam.2016.11.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 11/16/2016] [Accepted: 11/17/2016] [Indexed: 12/22/2022]
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Monu SR, Ren Y, Masjoan-Juncos JX, Kutskill K, Wang H, Kumar N, Peterson EL, Carretero OA. Connecting tubule glomerular feedback mediates tubuloglomerular feedback resetting after unilateral nephrectomy. Am J Physiol Renal Physiol 2017; 315:F806-F811. [PMID: 28424211 DOI: 10.1152/ajprenal.00619.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Unilaterally nephrectomized rats (UNx) have higher glomerular capillary pressure (PGC) that can cause significant glomerular injury in the remnant kidney. PGC is controlled by the ratio of afferent (Af-Art) and efferent arteriole resistance. Af-Art resistance in turn is regulated by two intrinsic feedback mechanisms: 1) tubuloglomerular feedback (TGF) that causes Af-Art constriction in response to increased NaCl in the macula densa; and 2) connecting tubule glomerular feedback (CTGF) that causes Af-Art dilatation in response to an increase in NaCl transport in the connecting tubule via the epithelial sodium channel (ENaC). Resetting of TGF post-UNx can allow systemic pressure to be transmitted to the glomerulus and cause renal damage, but the mechanism behind this resetting is unclear. Since CTGF is an Af-Art dilatory mechanism, we hypothesized that CTGF is increased after UNx and contributes to TGF resetting. To test this hypothesis, we performed UNx in Sprague-Dawley (8) rats. Twenty-four hours after surgery, we performed micropuncture of individual nephrons and measured stop-flow pressure (PSF). PSF is an indirect measurement of PGC. Maximal TGF response at 40 nl/min was 8.9 ± 1.24 mmHg in sham-UNx rats and 1.39 ± 1.02 mmHg in UNx rats, indicating TGF resetting after UNx. When CTGF was inhibited with the ENaC blocker benzamil (1 μM/l), the TGF response was 12.29 ± 2.01 mmHg in UNx rats and 13.03 ± 1.25 mmHg in sham-UNx rats, indicating restoration of the TGF responses in UNx. We conclude that enhanced CTGF contributes to TGF resetting after UNx.
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Affiliation(s)
- Sumit R Monu
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Yilin Ren
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - J X Masjoan-Juncos
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Kristopher Kutskill
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Hong Wang
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Nitin Kumar
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Edward L Peterson
- Department of Public Health Sciences, Henry Ford Hospital , Detroit, Michigan
| | - Oscar A Carretero
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
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24
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Osei-Owusu P, Owens EA, Jie L, Reis JS, Forrester SJ, Kawai T, Eguchi S, Singh H, Blumer KJ. Regulation of Renal Hemodynamics and Function by RGS2. PLoS One 2015; 10:e0132594. [PMID: 26193676 PMCID: PMC4508038 DOI: 10.1371/journal.pone.0132594] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 06/16/2015] [Indexed: 12/16/2022] Open
Abstract
Regulator of G protein signaling 2 (RGS2) controls G protein coupled receptor (GPCR) signaling by acting as a GTPase-activating protein for heterotrimeric G proteins. Certain Rgs2 gene mutations have been linked to human hypertension. Renal RGS2 deficiency is sufficient to cause hypertension in mice; however, the pathological mechanisms are unknown. Here we determined how the loss of RGS2 affects renal function. We examined renal hemodynamics and tubular function by monitoring renal blood flow (RBF), glomerular filtration rate (GFR), epithelial sodium channel (ENaC) expression and localization, and pressure natriuresis in wild type (WT) and RGS2 null (RGS2-/-) mice. Pressure natriuresis was determined by stepwise increases in renal perfusion pressure (RPP) and blood flow, or by systemic blockade of nitric oxide synthase with L-NG-Nitroarginine methyl ester (L-NAME). Baseline GFR was markedly decreased in RGS2-/- mice compared to WT controls (5.0 ± 0.8 vs. 2.5 ± 0.1 μl/min/g body weight, p<0.01). RBF was reduced (35.4 ± 3.6 vs. 29.1 ± 2.1 μl/min/g body weight, p=0.08) while renal vascular resistance (RVR; 2.1 ± 0.2 vs. 3.0 ± 0.2 mmHg/μl/min/g body weight, p<0.01) was elevated in RGS2-/- compared to WT mice. RGS2 deficiency caused decreased sensitivity and magnitude of changes in RVR and RBF after a step increase in RPP. The acute pressure–natriuresis curve was shifted rightward in RGS2-/- relative to WT mice. Sodium excretion rate following increased RPP by L-NAME was markedly decreased in RGS2-/- mice and accompanied by increased translocation of ENaC to the luminal wall. We conclude that RGS2 deficiency impairs renal function and autoregulation by increasing renal vascular resistance and reducing renal blood flow. These changes impair renal sodium handling by favoring sodium retention. The findings provide a new line of evidence for renal dysfunction as a primary cause of hypertension.
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Affiliation(s)
- Patrick Osei-Owusu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, 19102, United States of America
- * E-mail:
| | - Elizabeth A. Owens
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, 19102, United States of America
| | - Li Jie
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, 19102, United States of America
| | - Janaina S. Reis
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, 19102, United States of America
| | - Steven J. Forrester
- Cardiovascular Research Center and Department of Physiology, Temple University, Philadelphia, Pennsylvania, 19140, United States of America
| | - Tatsuo Kawai
- Cardiovascular Research Center and Department of Physiology, Temple University, Philadelphia, Pennsylvania, 19140, United States of America
| | - Satoru Eguchi
- Cardiovascular Research Center and Department of Physiology, Temple University, Philadelphia, Pennsylvania, 19140, United States of America
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, 19102, United States of America
| | - Kendall J. Blumer
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, 63110, United States of America
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Persson P, Hansell P, Palm F. Reduced adenosine A2a receptor–mediated efferent arteriolar vasodilation contributes to diabetes-induced glomerular hyperfiltration. Kidney Int 2015; 87:109-15. [DOI: 10.1038/ki.2014.219] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 04/17/2014] [Accepted: 05/01/2014] [Indexed: 11/09/2022]
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Heterogeneous downregulation of angiotensin II AT1-A and AT1-B receptors in arterioles in STZ-induced diabetic rat kidneys. BIOMED RESEARCH INTERNATIONAL 2014; 2014:947506. [PMID: 24587998 PMCID: PMC3918853 DOI: 10.1155/2014/947506] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 08/01/2013] [Accepted: 10/31/2013] [Indexed: 01/13/2023]
Abstract
INTRODUCTION The renin granulation of kidney arterioles is enhanced in diabetes despite the fact that the level of angiotensin II in the diabetic kidney is elevated. Therefore, the number of angiotensin II AT1-A and AT1-B receptors in afferent and efferent arteriole's renin-positive and renin-negative smooth muscle cells (SMC) was estimated. METHOD Immunohistochemistry at the electron microscopic level was combined with 3D stereological sampling techniques. RESULTS In diabetes the enhanced downregulation of AT1-B receptors in the renin-positive than in the renin-negative SMCs in both arterioles was resulted: the significant difference in the number of AT1 (AT1-A + AT1-B) receptors between the two types of SMCs in the normal rats was further increased in diabetes and in contrast with the significant difference observed between the afferent and efferent arterioles in the normal animals, there was no such difference in diabetes. CONCLUSIONS The enhanced downregulation of the AT1-B receptors in the renin-negative SMCs in the efferent arterioles demonstrates that the regulation of the glomerular filtration rate by the pre- and postglomerular arterioles is changed in diabetes. The enhanced downregulation of the AT1-B receptors in the renin-positive SMCs in the arterioles may result in an enhanced level of renin granulation in the arterioles.
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Abstract
SIGNIFICANCE Renal oxidative stress can be a cause, a consequence, or more often a potentiating factor for hypertension. Increased reactive oxygen species (ROS) in the kidney have been reported in multiple models of hypertension and related to renal vasoconstriction and alterations of renal function. Nicotinamide adenine dinucleotide phosphate oxidase is the central source of ROS in the hypertensive kidney, but a defective antioxidant system also can contribute. RECENT ADVANCES Superoxide has been identified as the principal ROS implicated for vascular and tubular dysfunction, but hydrogen peroxide (H2O2) has been implicated in diminishing preglomerular vascular reactivity, and promoting medullary blood flow and pressure natriuresis in hypertensive animals. CRITICAL ISSUES AND FUTURE DIRECTIONS Increased renal ROS have been implicated in renal vasoconstriction, renin release, activation of renal afferent nerves, augmented contraction, and myogenic responses of afferent arterioles, enhanced tubuloglomerular feedback, dysfunction of glomerular cells, and proteinuria. Inhibition of ROS with antioxidants, superoxide dismutase mimetics, or blockers of the renin-angiotensin-aldosterone system or genetic deletion of one of the components of the signaling cascade often attenuates or delays the onset of hypertension and preserves the renal structure and function. Novel approaches are required to dampen the renal oxidative stress pathways to reduced O2(-•) rather than H2O2 selectivity and/or to enhance the endogenous antioxidant pathways to susceptible subjects to prevent the development and renal-damaging effects of hypertension.
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Affiliation(s)
- Magali Araujo
- Hypertension, Kidney and Vascular Research Center, Georgetown University , Washington, District of Columbia
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Carubelli V, Metra M, Lombardi C, Bettari L, Bugatti S, Lazzarini V, Dei Cas L. Renal dysfunction in acute heart failure: epidemiology, mechanisms and assessment. Heart Fail Rev 2013; 17:271-82. [PMID: 21748453 DOI: 10.1007/s10741-011-9265-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Renal dysfunction is often present and/or worsens in patients with heart failure and this is associated with increased costs of care, complications and mortality. The cardiorenal syndrome can be defined as the presence or development of renal dysfunction in patients with heart failure. Its mechanisms are likely related to low cardiac output, increased venous congestion and renal venous pressure, neurohormonal and inflammatory activation and local changes, such as adenosine release. Many drugs, including loop diuretics, may contribute to worsening renal function through the activation of some of these mechanisms. Renal damage is conventionally defined by the increase in creatinine and blood urea nitrogen blood levels. However, these changes may be not related with renal injury or prognosis. New biomarkers of renal injury seem promising but still need to be validated. Thus, despite the epidemiological evidence, we are still lacking of satisfactory tools to assess renal injury and function and its prognostic significance.
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Affiliation(s)
- Valentina Carubelli
- Cardiology, c/o Spedali Civili di Brescia, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy.
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Li Z, TenHoor C, Marbury T, Swan S, Ticho B, Rogge M, Nestorov I. Clinical Pharmacokinetics of Tonapofylline: Evaluation of Dose Proportionality, Oral Bioavailability, and Gender and Food Effects in Healthy Human Subjects. J Clin Pharmacol 2013; 51:1004-14. [DOI: 10.1177/0091270010377633] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Persson P, Hansell P, Palm F. Adenosine A2 receptor-mediated regulation of renal hemodynamics and glomerular filtration rate is abolished in diabetes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 765:225-230. [PMID: 22879037 DOI: 10.1007/978-1-4614-4989-8_31] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Alterations in glomerular filtration rate (GFR) are one of the earliest indications of altered kidney function in diabetes. Adenosine regulates GFR through tubuloglomerular feedback mechanism acting on adenosine A1 receptor. In addition, adenosine can directly regulate vascular tone by acting on A1 and A2 receptors expressed in afferent and efferent arterioles. Opposite to A1 receptors, A2 receptors mediate vasorelaxation. This study investigates the involvement of adenosine A2 receptors in regulation of renal blood flow (RBF) and GFR in control and diabetic kidneys. GFR was measured by inulin clearance and RBF by a transonic flow probe placed around the renal artery. Measurements were performed in isoflurane-anesthetized normoglycemic and alloxan-diabetic C57BL/6 mice during baseline and after acute administration of 3,7-dimethyl-1-propargylxanthine (DMPX), a selective A2 receptor antagonist. GFR and RBF were lower in diabetic mice compared to control (258 ± 61 vs. 443 ± 33 μl min(-1) and 1,083 ± 51 vs. 1,405 ± 78 μl min(-1)). In control animals, DMPX decreased RBF by -6%, whereas GFR increased +44%. DMPX had no effects on GFR and RBF in diabetic mice. Sodium excretion increased in diabetic mice after A2 receptor blockade (+78%). In conclusion, adenosine acting on A2 receptors mediates an efferent arteriolar dilatation which reduces filtration fraction (FF) and maintains GFR within normal range in normoglycemic mice. However, this regulation is absent in diabetic mice, which may contribute to reduced oxygen availability in the diabetic kidney.
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Affiliation(s)
- Patrik Persson
- Department of Medical Cell Biology, Uppsala University, BMC, 571, 75123, Uppsala, Sweden
| | - Peter Hansell
- Department of Medical Cell Biology, Uppsala University, BMC, 571, 75123, Uppsala, Sweden
| | - Fredrik Palm
- Department of Medical Cell Biology, Uppsala University, BMC, 571, 75123, Uppsala, Sweden. .,Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
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Carlström M, Wilcox CS, Welch WJ. Adenosine A2A receptor activation attenuates tubuloglomerular feedback responses by stimulation of endothelial nitric oxide synthase. Am J Physiol Renal Physiol 2010; 300:F457-64. [PMID: 21106859 DOI: 10.1152/ajprenal.00567.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine A(2) receptors have been suggested to modulate tubuloglomerular feedback (TGF) responses by counteracting adenosine A(1) receptor-mediated vasoconstriction, but the mechanisms are unclear. We tested the hypothesis that A(2A) receptor activation blunts TGF by release of nitric oxide in the juxtaglomerular apparatus (JGA). Maximal TGF responses were measured in male Sprague-Dawley rats as changes in proximal stop-flow pressure (ΔP(SF)) in response to increased perfusion of the loop of Henle (0 to 40 nl/min) with artificial tubular fluid (ATF). The maximal TGF response was studied after 5 min intratubular perfusion (10 nl/min) with ATF or ATF + A(2A) receptor agonist (CGS-21680; 10(-7) mol/l). The interaction with nitric oxide synthase (NOS) isoforms was tested by perfusion with a nonselective NOS inhibitor [N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME); 10(-3) mol/l] or a selective neuronal NOS (nNOS) inhibitor [N(ω)-propyl-L-arginine (L-NPA); 10(-6) mol/l] alone, and with the A(2A) agonist. Blood pressure, urine flow, and P(SF) at 0 nl/min were similar among the groups. The maximal TGF response (ΔP(SF)) with ATF alone (12.3 ± 0.6 mmHg) was attenuated by selective A(2A) stimulation (9.5 ± 0.4 mmHg). L-NAME enhanced maximal TGF responses (18.9 ± 0.4 mmHg) significantly more than L-NPA (15.2 ± 0.7 mmHg). Stimulation of A(2A) receptors did not influence maximal TGF response during nonselective NOS inhibition (19.0 ± 0.4) but attenuated responses during nNOS inhibition (10.3 ± 0.4 mmHg). In conclusion, adenosine A(2A) receptor activation attenuated TGF responses by stimulation of endothelial NOS (eNOS), presumably in the afferent arteriole. Moreover, NO derived from both eNOS and nNOS in the JGA may blunt TGF responses.
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Affiliation(s)
- Mattias Carlström
- Division of Nephrology and Hypertension, and Hypertension, Kidney & Vascular Research Center, Georgetown University, Washington, DC 20057, USA
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Carlström M, Wilcox CS, Welch WJ. Adenosine A(2) receptors modulate tubuloglomerular feedback. Am J Physiol Renal Physiol 2010; 299:F412-7. [PMID: 20519378 DOI: 10.1152/ajprenal.00211.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine can mediate the tubuloglomerular (TGF) response via activation of A(1) receptors on the afferent arteriole, but both adenosine A(1) and A(2) receptors can regulate preglomerular resistance. We tested the hypothesis that adenosine A(2) receptors offset the effect of A(1) receptors and modulate the TGF. Maximal TGF responses were measured in male Sprague-Dawley rats as changes in proximal stop-flow pressure (DeltaP(SF)) in response to increased perfusion of the loop of Henle (0 to 40 nl/min) with artificial tubular fluid (ATF). The maximal TGF response was studied after 5 min of intratubular perfusion (10 nl/min) with ATF alone, or with ATF plus the A(2A) receptor antagonist (ZM-241385; 10(-7) or 10(-5) mol/l), A(1) receptor antagonist (PSB-36; 10(-8) mol/l), or with a combination of A(1) (PSB-36; 10(-8) mol/l) and A(2A) (ZM-241385; 10(-7) mol/l) antagonists. The maximal TGF response (DeltaP(SF)) with ATF alone was 11.7 +/- 1.0 mmHg. Specific A(2) inhibition (low dose) enhanced the maximal TGF response (15.7 +/- 0.8 mmHg; P < 0.01), whereas a high dose (unspecific inhibition) attenuated the response (5.0 +/- 0.4 mmHg; P < 0.001). A(1) inhibition alone led to a paradoxical TGF response, with an increase in P(SF) of 3.1 +/- 0.5 mmHg (P < 0.05). Simultaneous application of A(1) and A(2) antagonists abolished the TGF response (DeltaP(SF): 0.4 +/- 0.3 mmHg). In conclusion, adenosine A(2) receptors modulate the TGF response by counteracting the effects of adenosine A(1) receptors.
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Affiliation(s)
- Mattias Carlström
- Department of Medicine, Georgetown University Medical Center, Washington, District of Columbia, USA
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Abstract
PURPOSE OF REVIEW We review some basic homeostatic principles that are frequently disregarded to provide boundary conditions to test any new theory containing new details. Homeostasis as applied to total body salt is discussed with a linear model for salt homeostasis that is extraordinarily simple wherein total body salt drives the salt excretion. The basics of tubuloglomerular feedback (TGF) and its implications for salt homeostasis are then reviewed. RECENT FINDINGS Advances in the field discussed include new details on the apical and basolateral transport of sodium chloride (NaCl) in the macula densa cells during TGF response, direct evidence of contribution of TGF to renal autoregulation and the description of vasodilatory adenosine A2b receptors in the 'efferent' TGF response. Finally, recent information about the role of proximal tubular microvilli as mechanosensors in the flow-dependent tubular reabsorption as a mechanism to explain glomerulotubular balance is reviewed. SUMMARY Notwithstanding the complexity of salt balance at a molecular level, the overall salt homeostasis is simple. Various natritropic nerves and hormones stabilize any disturbance in salt balance. A change in glomerular filtration rate (GFR) brought about by these natritropes will be partially counteracted by the impact of TGF on nephron function. Thus, by stabilizing GFR, TGF reduces the usefulness of GFR as an instrument of salt balance, and lessens the efficiency of salt homeostasis.
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Mitrovic V, Seferovic P, Dodic S, Krotin M, Neskovic A, Dickstein K, de Voogd H, Böcker C, Ziegler D, Godes M, Nakov R, Essers H, Verboom C, Hocher B. Cardio-renal effects of the A1 adenosine receptor antagonist SLV320 in patients with heart failure. Circ Heart Fail 2009; 2:523-31. [PMID: 19919976 DOI: 10.1161/circheartfailure.108.798389] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Blocking the tubuloglomerular feedback mechanism with adenosine A1 receptor antagonists seems to improve diuresis and sodium excretion without compromising the glomerular filtration rate in patients with heart failure. However, the direct cardiac effects of this compound class have not been investigated to date. METHODS AND RESULTS In total, 111 patients (109 men and 2 women) received a 1-hour infusion of 5, 10, and 15 mg SLV320, an adenosine A1 receptor antagonist, placebo, or 40 mg furosemide. Mean age was 57.9 years, mean ejection fraction was 28.1%, 82 patients were of New York Heart Association class II, and 29 patients were of New York Heart Association class III. Hemodynamic parameters (heart rate, blood pressure, pulmonary capillary wedge pressure, mean pulmonary arterial pressure, systemic vascular resistance, right atrial pressure, and cardiac output) were determined. Kidney function was assessed by cystatin C measurements and by analysis of urine output and urine electrolytes. In addition, pharmacokinetics of SLV320 and ex vivo inhibition of adenosine A1 receptor activity were performed. SLV320 was well tolerated, and no serious adverse events were observed. Heart rate, blood pressure, pulmonary capillary wedge pressure, mean pulmonary arterial pressure, right atrial pressure, and cardiac output were not altered by any dose of SLV320. Pulmonary capillary wedge pressure was significantly (P=0.04) decreased by furosemide (-6.2+/-5.9 mm Hg). Systemic vascular resistance was significantly (P=0.04) increased in the furosemide group (+166.70+/-261.87 dynes . s(-1) . cm(-5)), whereas all SLV320 groups showed no significant alterations of systemic vascular resistance. Changes from baseline cystatin C plasma concentrations decreased after 10 mg SLV320 (-0.093+/-0.137 mg/L, P=0.046), whereas furosemide resulted in a significant (P=0.03) increase of cystatin C (+0.052+/-0.065 mg/L) versus baseline. All values represent mean changes+/-SD from baseline at 3 hours postdosing: SLV320 (10 and 15 mg) increased significantly sodium excretion and diuresis compared with placebo during the 0- to 6-hour collection period postdosing. CONCLUSIONS SLV320 infusion shows no immediate effects on cardiac hemodynamics. SLV320 might improve glomerular filtration rate while simultaneously promoting natriuresis and diuresis. Clinical Trial Registration- clinicaltrials.gov Indentifier: NCT00160134.
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Affiliation(s)
- Veselin Mitrovic
- Kerckhoff-Klinik, Department of Cardiology and Cardiosurgery, Bad Nauheim, Germany
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Oppermann M, Qin Y, Lai EY, Eisner C, Li L, Huang Y, Mizel D, Fryc J, Wilcox CS, Briggs J, Schnermann J, Castrop H. Enhanced tubuloglomerular feedback in mice with vascular overexpression of A1 adenosine receptors. Am J Physiol Renal Physiol 2009; 297:F1256-64. [PMID: 19741017 DOI: 10.1152/ajprenal.00264.2009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine 1 receptors (A1AR) in the kidney are expressed in the vasculature and the tubular system. Pharmacological inhibition or global genetic deletion of A1AR causes marked reductions or abolishment of tubuloglomerular feedback (TGF) responses. To assess the function of vascular A1AR in TGF, we generated transgenic mouse lines in which A1AR expression in smooth muscle was augmented by placing A1AR under the control of a 5.38-kb fragment of the rat smooth muscle alpha-actin promoter and first intron (12). Two founder lines with highest expression in the kidney [353 +/- 42 and 575 +/- 43% compared with the wild type (WT)] were used in the experiments. Enhanced expression of A1AR at the expected site in these lines was confirmed by augmented constrictor responses of isolated afferent arterioles to administration of the A1AR agonist N6-cyclohexyladenosine. Maximum TGF responses (0-30 nl/min flow step) were increased from 8.4 +/- 0.9 mmHg in WT (n = 21) to 14.2 +/- 0.7 mmHg in A1AR-transgene (tg) 4 (n = 22; P < 0.0001), and to 12.6 +/- 1.2 mmHg in A1AR-tg7 (n = 12; P < 0.02). Stepwise changes in perfusion flow caused greater numerical TGF responses in A1AR-tg than WT in all flow ranges with differences reaching levels of significance in the intermediate flow ranges of 7.5-10 and 10-15 nl/min. Proximal-distal single-nephron glomerular filtration rate (SNGFR) differences (free-flow micropuncture) were also increased in A1AR-tg, averaging 6.25 +/- 1.5 nl/min compared with 2.6 +/- 0.51 nl/min in WT (P = 0.034). Basal plasma renin concentrations as well as the suppression of renin secretion after volume expansion were similar in A1AR-tg and WT mice, suggesting lack of transgene expression in juxtaglomerular cells. These data indicate that A1AR expression in vascular smooth muscle cells is a critical component for TGF signaling and that changes in renal vascular A1AR expression may determine the magnitude of TGF responses.
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Affiliation(s)
- Mona Oppermann
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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Bell TD, Welch WJ. Regulation of renal arteriolar tone by adenosine: novel role for type 2 receptors. Kidney Int 2009; 75:769-71. [PMID: 19337216 DOI: 10.1038/ki.2009.18] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Tubuloglomerular feedback regulation of glomerular filtration rate (GFR) is mediated by adenosine, which acts on type 1 receptors in the afferent arteriole to increase resistance. However, new findings in isolated mouse tissue suggest that adenosine also dilates the efferent arteriole, which would reinforce the ability of adenosine to reduce GFR. This new information extends the concept that adenosine acts as a paracrine agent on both afferent and efferent arterioles.
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Kawada H, Yasuoka Y, Fukuda H, Kawahara K. Low [NaCl]-induced neuronal nitric oxide synthase (nNOS) expression and NO generation are regulated by intracellular pH in a mouse macula densa cell line (NE-MD). J Physiol Sci 2009; 59:165-73. [PMID: 19340543 PMCID: PMC10716943 DOI: 10.1007/s12576-009-0022-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 01/14/2009] [Indexed: 10/20/2022]
Abstract
Changes in the luminal NaCl concentration ([NaCl]) at the macula densa (MD) modulate the tubuloglomerular feedback (TGF) responses via an affect on the release of nitric oxide (NO). This study was performed in a newly established mouse macula densa cell line (NE-MD) to investigate the effects of lowering [NaCl] on the neuronal NO synthase (nNOS) protein expression and L-arginine (Arg)-induced NO release. Expression of nNOS protein and release of NO were evaluated by Western blot analysis and an NO-sensitive electrode, respectively. Intracellular pH (pH(i)) was monitored by the BCECF assay. Although there was weak staining of the nNOS protein expression, L-Arg-induced NO generation was negligible in normal (140 mM NaCl) solution. Both were significantly (P < 0.05) increased either in the presence of furosemide (12 microM), an inhibitor of the Na(+)-K(+)-2Cl(-) cotransporter, or in a low (23 mM) Cl(-) solution. Furosemide- and low Cl(-)-induced NO generation was completely inhibited by 50 microM 7-nitroindasole (7-NI), a nNOS inhibitor. Moreover, these increases were significantly (P < 0.05) inhibited by the addition of 100 microM amiloride, an inhibitor of the Na(+)/H(+) exchanger, or by its analogue 5-(N)-ethyl-N-isopropyl amiloride (EIPA), and also at a lower pH of 7.1. Furthermore, nNOS expression and NO release were not stimulated in as low as 19 mM Na(+) solution. In conclusion, low [Cl(-)], but not low [Na(+)] in the lumen at the MD, increased nNOS protein expression and NO generation. Changes in the luminal [NaCl] may modulate the TGF system via an effect on the NO generation from the MD.
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Affiliation(s)
- Hideaki Kawada
- Department of Cellular and Molecular Physiology, Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan
| | - Yukiko Yasuoka
- Department of Cellular and Molecular Physiology, Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan
- Department of Physiology, Kitasato University School of Medicine, Kitasato 1-15-1, Sagamihara, 228-8555 Japan
| | - Hidekazu Fukuda
- Department of Physiology, Kitasato University School of Medicine, Kitasato 1-15-1, Sagamihara, 228-8555 Japan
| | - Katsumasa Kawahara
- Department of Cellular and Molecular Physiology, Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan
- Department of Physiology, Kitasato University School of Medicine, Kitasato 1-15-1, Sagamihara, 228-8555 Japan
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Komlosi P, Bell PD, Zhang ZR. Tubuloglomerular feedback mechanisms in nephron segments beyond the macula densa. Curr Opin Nephrol Hypertens 2009; 18:57-62. [PMID: 19077690 DOI: 10.1097/mnh.0b013e32831daf54] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW To summarize recent evidence regarding the role of distal nephron segments other than the macula densa in sensing the tubular environment and transmitting this signal to the adjacent vasculature. RECENT FINDINGS In addition to the classical contact site between the macula densa plaque and the afferent arteriole, there is accumulating evidence suggesting a functional association between the distal nephron and the vasculature at three distinct additional sites: at the terminal cortical thick ascending limb, at the early distal tubule and also at the connecting tubule segment. The epithelial cells around the macula densa also sense and respond to changes in tubular flow and salt content and may transmit this signal to the adjacent afferent arteriole. SUMMARY There are multiple sites of anatomical and functional contact between the distal nephron and the vasculature supplying the glomerulus, and these may contribute to the regulation of glomerular filtration rate and renal hemodynamics.
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Affiliation(s)
- Peter Komlosi
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, USA.
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Singh P, Deng A, Blantz RC, Thomson SC. Unexpected effect of angiotensin AT1 receptor blockade on tubuloglomerular feedback in early subtotal nephrectomy. Am J Physiol Renal Physiol 2009; 296:F1158-65. [PMID: 19211684 DOI: 10.1152/ajprenal.90722.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
After subtotal nephrectomy (STN), the remaining nephrons engage in hyperfiltration, which may be facilitated by a reduced sensitivity of the tubuloglomerular feedback (TGF) response to increased distal delivery. However, a muted TGF response would contradict the notion of remnant kidney as a prototype of angiotensin II (ANG II) excess, since ANG II normally sensitizes the TGF response and stimulates proximal reabsorption. We examined the role of ANG II as a modulator of TGF and proximal reabsorption in 7 days after STN in male rats. Single-nephron glomerular filtration rate (SNGFR) and proximal reabsorption (J(prox)) were measured in late proximal collections while perfusing Henle's loop for minimal and maximal TGF stimulation in rats treated with the angiotensin type 1 (AT(1)) receptor blocker losartan or placebo in drinking water for 7 days. Perfusion of Henle's loop yielded a robust TGF response in sham-operated rats. In STN, the feedback responses were highly variable and nil, on average. Paradoxical TGF responses to augmented late proximal flow were confirmed in SNGFR measurements from the early distal nephron. Chronic losartan treatment normalized the average TGF response without reducing the variability. J(prox) was subtly affected by chronic losartan in sham surgery or STN, after controlling for differences in SNGFR. However, when administered acutely into the early S1 segment, losartan potently suppressed J(prox) in STN and sham-operated rats alike. Chronic losartan stabilizes the TGF system in remnant kidneys. This cannot be explained by currently known actions of AT(1) receptors but is commensurate with a salutary effect of an intact TGF system on dynamic autoregulation of intraglomerular flow and pressure.
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Affiliation(s)
- Prabhleen Singh
- Division of Nephrology-Hypertension, Department of Veterans Affairs San Diego Healthcare System and University of California, San Diego School of Medicine, La Jolla, California, USA
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Activation of A(2) adenosine receptors dilates cortical efferent arterioles in mouse. Kidney Int 2009; 75:793-9. [PMID: 19165174 DOI: 10.1038/ki.2008.684] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Adenosine can induce vasodilatation and vasoconstriction of the renal afferent arteriole of the mouse. We determined here its direct effect on efferent arterioles of mouse kidneys. Using isolated-perfused cortical efferent arterioles, we measured changes in luminal diameter in response to adenosine. Extraluminal application of adenosine and cyclohexyladenosine had no effect on the luminal diameter. When the vessels were constricted by the thromboxane mimetic U46619, application of adenosine and 5'-N-ethylcarboxamido-adenosine dilated the efferent arterioles in a dose-dependent manner. We also found that the adenosine-induced vasodilatation was inhibited by the A(2)-specific receptor blocker 3,7-dimethyl-1-propargylxanthine. In the presence of this inhibitor, adenosine failed to alter the basal vessel diameter of quiescent efferent arterioles. Using primer-specific polymerase chain reaction we found that the adenosine A(1), A(2a), A(2b), and A(3) receptors were expressed in microdissected mouse efferent arterioles. We conclude that adenosine dilates the efferent arteriole using the A(2) receptor subtype at concentrations compatible with activation of the A(2b) receptor.
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Cross-talk between arterioles and tubules in the kidney. Pediatr Nephrol 2009; 24:31-5. [PMID: 18488254 PMCID: PMC2697568 DOI: 10.1007/s00467-008-0852-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 03/03/2008] [Accepted: 03/06/2008] [Indexed: 10/22/2022]
Abstract
In hypertension the pressure natriuresis set point is shifted to a higher pressure due to an increase in both renal vascular resistance and sodium (Na) reabsorption. The afferent arterioles (Af-Arts) and efferent arterioles (Ef-Arts) account for most renal vascular resistance; they control glomerular filtration rate (GFR) and peritubular pressure, and, consequently, renal function. Af-Art and Ef-Art resistance is regulated by factors similar to those in other arterioles and also by tubuloglomerular feedback (TGF). TGF operates via the macula densa, which senses increases in sodium chloride (NaCl) and sends a signal that constricts the Af-Art and dilates the Ef-Art. In the outer renal cortex, the connecting tubule (CNT) returns to the glomerular hilus and contacts the Af-Art. This morphology is compatible with cross-talk between the CNT and Af-Art, so-called connecting tubule glomerular feedback (CTGF). Our studies show that increasing NaCl delivery to the CNT results in Af-Art dilatation that can be blocked by inhibitors of Na transport. We believe cross-talk between the CNT and Af-Art is a novel mechanism that may contribute to regulation of renal blood flow and GFR.
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Navar LG, Arendshorst WJ, Pallone TL, Inscho EW, Imig JD, Bell PD. The Renal Microcirculation. Compr Physiol 2008. [DOI: 10.1002/cphy.cp020413] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Razga Z, Nyengaard JR. Up- and down-regulation of angiotensin II AT1-A and AT1-B receptors in afferent and efferent rat kidney arterioles. J Renin Angiotensin Aldosterone Syst 2008; 9:196-201. [DOI: 10.1177/1470320308098592] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Introduction. The contractile effect of angiotensin II via AT1 receptors on the kidney arterioles is a crucial element in the kidney microcirculation.Angiotensin II also plays a role as an inhibitor via the AT1 receptors in the renin granulation of the arterioles.We have previously demonstrated that the AT1 receptors are downregulated in the renin-positive smooth muscle cells (SMCs) in contrast to renin-negative SMCs. In this study, we estimated the numbers of the AT1 receptor sub-types separately in the afferent and efferent arterioles and the renin-positive and renin-negative SMCs. Methods. The immunohistochemical signals of theAT1-A and AT1-B receptors were counted by stereological methods.1 Results. The number of AT1-B receptors in the efferent arterioles (expressed in signals/µm 3; mean (CV): 0.32 (0.33)) was significantly higher (78%; p<0.05) as compared with the number in the afferent arterioles (0.18 (0.11)). No differences were found in the AT1-A receptors. In a number ofAT 1-A receptors, significant differences (p<0.01) were detected between the afferent arteriolar renin-positive SMCs (0.13 (0.36)) and the number in renin-negative SMCs (0.25 (0.34)).The AT1-B receptors did not display any differences. Conclusions. These results indicate that the AT1 receptor sub-types are regulated independently in the SMCs of the normal kidney arterioles.
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Affiliation(s)
- Zsolt Razga
- Department of Pathology, University of Szeged, Hungary, . u-szeged.hu
| | - Jens Randel Nyengaard
- Stereology and Electron Microscopy Research Laboratory and MIND Centre, University of Aarhus, Denmark
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Navar LG, Arendshorst WJ, Pallone TL, Inscho EW, Imig JD, Bell PD. The Renal Microcirculation. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00015-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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Stegbauer J, Kuczka Y, Vonend O, Quack I, Sellin L, Patzak A, Steege A, Langnaese K, Rump LC. Endothelial nitric oxide synthase is predominantly involved in angiotensin II modulation of renal vascular resistance and norepinephrine release. Am J Physiol Regul Integr Comp Physiol 2007; 294:R421-8. [PMID: 18046021 DOI: 10.1152/ajpregu.00481.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric oxide (NO) is mainly generated by endothelial NO synthase (eNOS) or neuronal NOS (nNOS). Recent studies indicate that angiotensin II generates NO release, which modulates renal vascular resistance and sympathetic neurotransmission. Experiments in wild-type [eNOS(+/+) and nNOS(+/+)], eNOS-deficient [eNOS(-/-)], and nNOS-deficient [nNOS(-/-)] mice were performed to determine which NOS isoform is involved. Isolated mice kidneys were perfused with Krebs-Henseleit solution. Endogenous norepinephrine release was measured by HPLC. Angiotensin II dose dependently increased renal vascular resistance in all mice species. EC(50) and maximal pressor responses to angiotensin II were greater in eNOS(-/-) than in nNOS(-/-) and smaller in wild-type mice. The nonselective NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 0.3 mM) enhanced angiotensin II-induced pressor responses in nNOS(-/-) and wild-type mice but not in eNOS(-/-) mice. In nNOS(+/+) mice, 7-nitroindazole monosodium salt (7-NINA; 0.3 mM), a selective nNOS inhibitor, enhanced angiotensin II-induced pressor responses slightly. Angiotensin II-enhanced renal nerve stimulation induced norepinephrine release in all species. L-NAME (0.3 mM) reduced angiotensin II-mediated facilitation of norepinephrine release in nNOS(-/-) and wild-type mice but not in eNOS(-/-) mice. 7-NINA failed to modulate norepinephrine release in nNOS(+/+) mice. (4-Chlorophrnylthio)guanosine-3', 5'-cyclic monophosphate (0.1 nM) increased norepinephrine release. mRNA expression of eNOS, nNOS, and inducible NOS did not differ between mice strains. In conclusion, angiotensin II-mediated effects on renal vascular resistance and sympathetic neurotransmission are modulated by NO in mice. These effects are mediated by eNOS and nNOS, but NO derived from eNOS dominates. Only NO derived from eNOS seems to modulate angiotensin II-mediated renal norepinephrine release.
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Affiliation(s)
- Johannes Stegbauer
- Klinik für Nephrologie der Universitätsklinik Düsseldorf, Heinrich-Heine-Universität Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany
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Patzak A, Steege A, Lai EY, Brinkmann JO, Kupsch E, Spielmann N, Gericke A, Skalweit A, Stegbauer J, Persson PB, Seeliger E. Angiotensin II response in afferent arterioles of mice lacking either the endothelial or neuronal isoform of nitric oxide synthase. Am J Physiol Regul Integr Comp Physiol 2007; 294:R429-37. [PMID: 17959704 DOI: 10.1152/ajpregu.00482.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The aim of the study is to evaluate the impact of nitric oxide (NO) produced by endothelial NO synthase (eNOS) and neuronal NOS (nNOS) on the angiotensin II response in afferent arterioles (Af). Dose responses were assessed for angiotensin II in microperfused Af of mice homozygous for disruption of the eNOS gene [eNOS(-/-)], or nNOS gene [nNOS(-/-)], and their wild-type controls, eNOS(+/+) and nNOS(+/+). Angiotensin II at 10(-8) and 10(-6) mol/l reduced the lumen to 69% and 68% in eNOS(+/+), and to 59% and 50% in nNOS(+/+). N(G)-nitro-L-arginine methyl ester (L-NAME) did not change basal arteriolar diameters, but augmented angiotensin II contraction, reducing diameters to 23% and 13% in eNOS(+/+), and 7% and 10% in nNOS(+/+) at 10(-8) and 10(-6) mol/l. The response to angiotensin II was enhanced in nNOS(-/-) mice (41% and 25% at 10(-8) and 10(-6) mol/l) and even more enhanced in eNOS(-/-) mice (12% and 9%) compared with nNOS(+/+) and eNOS(+/+). L-NAME led to complete constriction of Af in these groups. Media-to-lumen ratios of Af did not differ between controls and gene-deficient mice. mRNA expression of angiotensin II receptor types 1A and 1B and type 2 also did not differ. The results reveal that angiotensin II-induced release of NO from both eNOS and nNOS significantly contributes to the control of Af. Results also suggest that eNOS-derived NO is of greater importance than nNOS-derived NO in this isolated arteriolar preparation.
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Affiliation(s)
- Andreas Patzak
- Institut für Vegetative Physiologie, Humboldt-Universität zu Berlin, Universitätsklinikum Charité, Tucholskystrasse 2, 10117 Berlin.
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Kalk P, Eggert B, Relle K, Godes M, Heiden S, Sharkovska Y, Fischer Y, Ziegler D, Bielenberg GW, Hocher B. The adenosine A1 receptor antagonist SLV320 reduces myocardial fibrosis in rats with 5/6 nephrectomy without affecting blood pressure. Br J Pharmacol 2007; 151:1025-32. [PMID: 17558436 PMCID: PMC2042943 DOI: 10.1038/sj.bjp.0707319] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Myocardial fibrosis is an unwanted effect associated with chronic renal failure. The adenosine system is involved in cardiac and renal function. Therefore, we investigated the novel selective adenosine A(1) receptor antagonist SLV320 focusing on its potential in preventing cardiomyopathy in rats with 5/6 nephrectomy. EXPERIMENTAL APPROACH Male Sprague-Dawley rats were allocated to 4 groups of 12 rats each: 5/6 nephrectomy (5/6 NX), 5/6 NX plus SLV320 (10 mg kg(-1) d(-1) mixed with food), sham and sham plus SLV320. Study duration was 12 weeks, blood pressure was assessed repeatedly. At study end kidney function was assessed, blood samples and hearts were taken for histology/immunohistochemistry. Pharmacological properties of SLV320 were assessed using receptor binding and enzyme assays and in vivo. KEY RESULTS SLV320 is a selective and potent adenosine A(1) antagonist in vitro (Ki=1 nM) with a selectivity factor of at least 200 versus other adenosine receptor subtypes. Functional A(1) antagonism was demonstrated in vivo. In rats with 5/6 NX SLV320 significantly decreased albuminuria by about 50%, but did not alter glomerular filtration rate (GFR). SLV320 normalized cardiac collagen I+III contents in 5/6 NX rats. SLV320 prevented nephrectomy-dependent rise in plasma levels of creatinine kinase (CK), ALT and AST. Blood pressure did not differ between study groups. CONCLUSION SLV320 suppresses cardiac fibrosis and attenuates albuminuria without affecting blood pressure in rats with 5/6 nephrectomy, indicating that selective A(1) receptor antagonists may be beneficial in uraemic cardiomyopathy.
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Affiliation(s)
- P Kalk
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
- Institute of Vegetative Physiology, Charite Campus Mitte, Berlin
| | - B Eggert
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
| | - K Relle
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
- Institute of Vegetative Physiology, Charite Campus Mitte, Berlin
| | - M Godes
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
- Institute of Vegetative Physiology, Charite Campus Mitte, Berlin
| | - S Heiden
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
| | - Y Sharkovska
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
| | - Y Fischer
- Solvay Pharmaceuticals Research Laboratories Hannover, Germany
| | - D Ziegler
- Solvay Pharmaceuticals Research Laboratories Hannover, Germany
| | - G-W Bielenberg
- Solvay Pharmaceuticals Research Laboratories Hannover, Germany
| | - B Hocher
- Department of Pharmacology and Toxicology, Center for Cardiovascular Research, Charite, Campus Mitte Berlin, Germany
- Solvay Pharmaceuticals Research Laboratories Hannover, Germany
- Author for correspondence:
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Ren Y, Garvin JL, Liu R, Carretero OA. Possible mechanism of efferent arteriole (Ef-Art) tubuloglomerular feedback. Kidney Int 2007; 71:861-6. [PMID: 17342182 DOI: 10.1038/sj.ki.5002161] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Adenosine triphosphate (ATP) is liberated from macula densa cells in response to increased tubular NaCl delivery. However, it is not known whether ATP from the macula densa is broken down to adenosine, or whether this adenosine mediates efferent arteriole (Ef-Art) tubuloglomerular feedback (TGF). We hypothesized that increased macula densa Ca(2+), release of ATP and degradation of ATP to adenosine are necessary for Ef-Art TGF. Rabbit Ef-Arts and adherent tubular segments (with the macula densa) were simultaneously microperfused in vitro while changing the NaCl concentration at the macula densa. The Ef-Art was perfused orthograde through the end of the afferent arteriole (Af-Art). In Ef-Arts preconstricted with norepinephrine (NE), increasing NaCl concentration from 10 to 80 mM at the macula densa dilated Ef-Arts from 7.5+/-0.7 to 11.1+/-0.3 microm. Buffering increases in macula densa Ca(2+) with the cell-permeant Ca(2+) chelator BAPTA-AM diminished Ef-Art TGF from 3.1+/-0.3 to 0.1+/-0.2 microm. Blocking adenosine formation by adding alpha-beta-methyleneadenosine 5'-diphosphate (MADP) blocked Ef-Art TGF from 2.9+/-0.5 to 0.1+/-0.2 microm. Increasing luminal NaCl at the macula densa from 10 to 45 mM caused a moderate Ef-Art TGF response, 1.3+/-0.1 microm. It was potentiated to 4.0+/-0.3 microm by adding hexokinase, which enhances conversion of ATP into adenosine. Our data show that in vitro changes in macula densa Ca(2+) and ATP release are necessary for Ef-Art TGF. ATP is broken down to form adenosine, which mediates signal transmission of Ef-Art TGF.
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Affiliation(s)
- Y Ren
- Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, Michigan 48202, USA.
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Abstract
The kidney displays highly efficient autoregulation so that under steady-state conditions renal blood flow (RBF) is independent of blood pressure over a wide range of pressure. Autoregulation occurs in the preglomerular microcirculation and is mediated by two, perhaps three, mechanisms. The faster myogenic mechanism and the slower tubuloglomerular feedback contribute both directly and interactively to autoregulation of RBF and of glomerular capillary pressure. Multiple experiments have been used to study autoregulation and can be considered as variants of two basic designs. The first measures RBF after multiple stepwise changes in renal perfusion pressure to assess how a biological condition or experimental maneuver affects the overall pressure-flow relationship. The second uses time-series analysis to better understand the operation of multiple controllers operating in parallel on the same vascular smooth muscle. There are conceptual and experimental limitations to all current experimental designs so that no one design adequately describes autoregulation. In particular, it is clear that the efficiency of autoregulation varies with time and that most current techniques do not adequately address this issue. Also, the time-varying and nonadditive interaction between the myogenic mechanism and tubuloglomerular feedback underscores the difficulty of dissecting their contributions to autoregulation. We consider the modulation of autoregulation by nitric oxide and use it to illustrate the necessity for multiple experimental designs, often applied iteratively.
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Affiliation(s)
- William A Cupples
- Centre for Biomedical Research and Dept. of Biology, Univ. of Victoria, PO Box 3020, STN CSC, Victoria, BC, Canada.
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Abstract
ATP release from macula densa (MD) cells into the interstitium of the juxtaglomerular (JG) apparatus (JGA) is an integral component of the tubuloglomerular feedback (TGF) mechanism that controls the glomerular filtration rate. Because the cells of the JGA express a number of calcium-coupled purinergic receptors, these studies tested the hypothesis that TGF activation triggers a calcium wave that spreads from the MD toward distant cells of the JGA and glomerulus. Ratiometric calcium imaging of in vitro microperfused isolated JGA-glomerulus complex dissected from rabbits was performed with fluo-4/fura red and confocal fluorescence microscopy. Activation of TGF by increasing tubular flow rate at the MD rapidly produced a significant elevation in intracellular Ca(2+) concentration ([Ca(2+)](i)) in extraglomerular mesangial cells (by 187.6 +/- 45.1 nM) and JG renin granular cells (by 281.4 +/- 66.6 nM). Subsequently, cell-to-cell propagation of the calcium signal at a rate of 12.6 +/- 1.1 microm/s was observed upstream toward proximal segments of the afferent arteriole and adjacent glomeruli, as well as toward intraglomerular elements including the most distant podocytes (5.9 +/- 0.4 microm/s). The same calcium wave was observed in nonperfusing glomeruli, causing vasoconstriction and contractions of the glomerular tuft. Gap junction uncoupling, an ATP scavenger enzyme cocktail, and pharmacological inhibition of P(2) purinergic receptors, but not adenosine A(1) receptor blockade, abolished the changes in [Ca(2+)](i) and propagation of the calcium wave. These studies provided evidence that both gap junctional communication and extracellular ATP are integral components of the TGF calcium wave.
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Affiliation(s)
- János Peti-Peterdi
- Department of Physiology and Biophysics, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, USA.
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