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Satou R, Ye D, Lu HS, Katsurada A, Dugas CM, Daugherty A, Motazedian S, Navar LG. Abstract 044: Stimulation Of Intrarenal Angiotensinogen Expression And The Development Of Hypertension And Kidney Injury In Angiotensin II-infused Hepatic Angiotensinogen Knockout Mice. Hypertension 2022. [DOI: 10.1161/hyp.79.suppl_1.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Regulation of systemic and local angiotensinogen (AGT) levels is a key determinant of tissue angiotensin II (Ang II) levels and inappropriate AGT augmentation promotes the development of hypertension and tissue injury. Kidney and urinary AGT levels are increased in Ang II-mediated hypertension. Recent studies have demonstrated that circulating hepatocyte-derived AGT (hAGT) enters kidneys sustaining kidney and urinary AGT levels. However, roles of hAGT in blood pressure elevation and kidney injury in Ang II-mediated hypertension have not been delineated. This study tested if hAGT contributes to the development of the pathophysiological events in Ang II-infused mice. A low dose of Ang II (400 ng/kg/min) was infused to male wild type (WT) and hAGT gene knockout (KO) mice (N=9 and 13) for 4 weeks. The control group in each genotype received vehicle (Veh) infusion (N=5 and 6). Western blot confirmed non-detectable levels of hAGT in KO mice. hAGT KO markedly decreased plasma AGT levels (WT+Veh:12.2±0.6 vs. hAGT KO+Veh: 0.8±0.1 μg/ml). Ang II infusion did not elevate plasma AGT levels in either WT and hAGT KO mice. Although hAGT KO mice exhibited a lower baseline of systolic blood pressure (SBP) than WT mice, Ang II-mediated increases in SBP was not attenuated in hAGT KO mice (ΔSBP in WT+Ang II: 30.1±4.4 vs. hAGT KO+Ang II: 26.0±4.2 mmHg). Kidney AGT mRNA levels were increased by Ang II infusion to the same extent in both WT and hAGT mice (WT+Ang II: 1.30±0.04 vs. hAGT KO+Ang II: 1.34±0.06, ratio to control). Likewise, Ang II infusion increased IL-6 mRNA to the same magnitude in both WT and hAGT KO mice. Urinary AGT was sustained in hAGT KO+Veh mice (66±9%) compared to WT+Veh mice. Ang II infusion did not alter urinary AGT levels in both groups. Glomerular mesangial expansion and fibrosis by Ang II infusion were not observed. Ang II infusion developed tubulointerstitial fibrosis in renal cortex and medulla. hAGT KO prevented the fibrosis only in the medulla. These outcomes demonstrate that elevation of SBP, augmentation of intrarenal AGT and IL-6 expression, and the development of renal cortical fibrosis in Ang II-mediated hypertension do not require hAGT. In contrast, hAGT contributes to renal medullary fibrosis which may be due to the lower absolute levels of blood pressure.
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Navar LG, Hansen‐Estruch C, Bikhet MH, Javed M, Katsurada A, Satou R, Shao W, Ayares D, Cooper DKC, Judd E. The Renin‐Angiotensin System after Pig Kidney Transplantation in Baboons. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.l7769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Rosivall L, Cypress M, Navar LG. Editorial. Physiol Int 2017; 104:91-96. [PMID: 28665195 DOI: 10.1556/2060.104.2017.2.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Satou R, Franco MG, Katsurada A, Miyata K, Navar LG. Abstract 015: Immunosuppression Attenuates Intrarenal Angiotensinogen Augmentation in Angiotensin II Dependent Hypertension. Hypertension 2016. [DOI: 10.1161/hyp.68.suppl_1.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Augmented intrarenal angiotensinogen (AGT) is a critical contributor to activation of intrarenal renin-angiotensin system (RAS) leading to the development of hypertension and associated kidney injury. It has been shown that treatment with mycophenolate mofetil (MMF), an immunosuppressive drug, mitigates the increased intrarenal angiotensin (Ang) II levels and blood pressure in hypertensive animal models, suggesting that an activated immune system mediates intrarenal RAS activation and consequent hypertension. Associated macrophage (MΦ) infiltration augments pro-inflammatory cytokine levels including interleukin-6 (IL-6), which plays a crucial role in augmentation of AGT expression in cultured renal proximal tubular cells. Accordingly, this study was performed to establish pathophysiological relevance for the effects of stimulated MΦ and IL-6 on intrarenal AGT augmentation in Ang II-dependent hypertension. Ang II (80 ng/min) was infused with/without daily MMF administration (50 ng/kg) to Sprague-Dawley rats for 2 weeks. Mean arterial pressure (MAP) in Ang II infused rats was slightly higher (169.7±6.1 mmHg) than MAP in Ang II+MMF group (154.7±2.0 mmHg) which was not statistically different than in control group. The augmentation of urinary AGT and urinary protein by Ang II infusion was attenuated by MMF treatment (AGT, control: 89.3±25.2, Ang II: 1,194±305.1, and Ang II+MMF: 389±192.0 ng/day). Importantly, the augmentation of urinary AGT by Ang II infusion was observed before the onset of proteinuria. Urinary 8-isoprostane levels were not altered by Ang II and/or MMF during the 2-week treatments. MMF treatment suppressed Ang II-induced renal MΦ infiltration and IL-6 elevation (IL-6 mRNA, Ang II: 32.4±7.5 and Ang II+MMF: 3.6±1.7, ratio to control). qRT-PCR, western blot and immunohistochemistry revealed elevated intrarenal AGT mRNA and protein levels in Ang II infused rats which were normalized by the MMF treatment (AGT mRNA, Ang II: 2.5±0.2 and Ang II+MMF: 1.5±0.1, ratio to control). These results indicate that stimulated IL-6 production in infiltrated MΦ contributes to intrarenal AGT augmentation in early stages of Ang II-dependent hypertension, which contributes to the development of kidney injury.
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Carmines PK, Casellas D, Navar LG. Control of renal hemodynamics by intrarenal mechanisms. CONTRIBUTIONS TO NEPHROLOGY 2015; 41:1-9. [PMID: 6525831 DOI: 10.1159/000429255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Satou R, Hering-Smith KS, Navar LG. Abstract 564: Differential Expression and Regulation of Angiotensinogen in Renal Proximal Tubule Cells From S1, S2 and S3 Segments. Hypertension 2013. [DOI: 10.1161/hyp.62.suppl_1.a564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In angiotensin II (Ang II)-dependent hypertension, intrarenal angiotensinogen (AGT) augmentation induced by Ang II and associated pathogenic factors including interleukin 6 (IL-6) cause further elevation of intratubular Ang II production, leading to the progression of hypertension and kidney injury. Recent studies have suggested that renal proximal straight tubules (S3 segment) are the main source of intrarenal AGT and that S1 and S2 segments do not express AGT mRNA under normal conditions. However, AGT expression and its regulation by Ang II and/or IL-6 in each proximal tubule segment have not been demonstrated an in vitro setting. The availability of specific cell lines derived from mouse S1, S2 and S3 segments provided an opportunity to decisively determine each segments’ capability to express AGT and respond to stimuli. Thus, this study was performed to determine AGT expression and its response to stimulation with Ang II and IL-6 in S1, S2 and S3 cell line. Basal AGT mRNA and protein levels were detected by RT-PCR and western blot analysis. Basal levels of Ang II type 1 receptor (AT1R) and STAT3, which is a transcription factor in IL-6 signaling pathway, were also measured. In addition, the cells were incubated with 100 nM Ang II and/or 400 nM IL-6 for 24 h. Basal AGT levels in S1 and S3 cells were lower than in mouse whole kidney (0.09-fold and 0.33-fold compared with mouse whole kidney). S2 cells exhibited the highest basal AGT levels (4.15-fold) among these cells. In S1 cells, AGT expression was stimulated by IL-6 (1.89 ± 0.32, ratio to control) and co-stimulation with Ang II and IL-6 (1.85 ± 0.28) although Ang II alone did not alter AGT levels. In S2 cells, only the co-stimulation increased AGT expression (1.35 ± 0.01). No changes were observed by similar treatments in S3 cells. Basal AT1R levels were lower in S3 than in S1 and S2 cells (0.97 ± 0.09 in S2, 0.32 ± 0.07 in S3, ratio to S1). S1 cells showed the highest basal levels of STAT3. Basal STAT3 levels in S3 cells were lower than that in S1 and S2 cells. These results indicate that S2 cells are main source of intrarenal AGT which can be augmented by Ang II and IL-6 during the development of Ang II-dependent hypertension. Furthermore, low basal levels of AT1R and STAT3 in S3 cells explain why these cells do not respond to Ang II and IL-6.
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Satou R, Hopfer U, Navar LG. Abstract 565: Angiotensin Ii Type 1 Receptor Activation is Required for Angiotensin Ii and Interleukin 6-induced Augmentation of Angiotensinogen Expression in Mouse Renal Proximal Tubular Cells. Hypertension 2013. [DOI: 10.1161/hyp.62.suppl_1.a565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In angiotensin II (AngII) dependent hypertension, an inappropriate elevation of intrarenal Ang II leads to the progression of hypertension and kidney injury. Intrarenal angiotensinogen (AGT), produced mainly by renal proximal tubular cells (PTC), is a crucial factor in regulation of intratubular Ang II. Increases in intrarenal AGT are associated with increases in intrarenal immune cells and interleukin 6 (IL-6) levels which contribute to Ang II-dependent AGT augmentation. These results suggest that Ang II and IL-6 synergize to increase AGT levels during progression of Ang II-dependent hypertension. However, the interactions among Ang II, Ang II type 1 receptors (AT1R) and IL-6 on AGT expression and the mechanisms have not been delineated. In this study, mouse PTC (WT-PTC) and AT1aR knockout strains (AT1aRKO-PTC) were used to test the existence of this synergism between Ang II and IL-6. Basal AGT mRNA expression levels in PTC were determined and compared with that in mouse mesangial cells which is another established AGT-expressing kidney cells. AGT mRNA expression levels were measured by real-time RT-PCR and normalized based on GAPDH levels. WT-PTC had 21.1-fold (± 2.0) higher basal AGT mRNA levels than mesangial cells, indicating markedly high AGT production by the PTC. Further, WT-PTC and AT1aRKO-PTC were incubated with 100 nM Ang II and/or 400 nM IL-6 for 24 h. Stimulation with either Ang II or IL-6 alone did not significantly alter AGT mRNA expression in both WT-PTC and AT1RaKO-PTC. Co-stimulation with Ang II and IL-6 increased AGT mRNA levels (1.59 ± 0.04, ratio to control) in WT-, but not AT1aRKO-PTC. To test for involvement of the NF-κB signaling pathway in the synergism between Ang II and IL-6, activation of NF-κB as an AT1R signaling pathway was evaluated by western blot analysis. Furthermore, WT-PCT were treated with an NF-κB inhibitor during the co-stimulation. In WT-PTC, IκB levels were decreased by the co-stimulation (0.61 ± 0.04, ratio to control) indicating NF-κB activation. Ten μM Parthenolide, an NF-κB inhibitor, attenuated the AGT mRNA increase induced by the co-stimulation. These results suggest that simultaneous AT1R activation acts synergistically with IL-6 to increase AGT expression in mouse PTC and that the signaling pathway involves NF-κB.
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Gonzalez AA, Leach D, Navar LG, Prieto MC. Abstract 401: Prostaglandin E2 Stimulates Renin Synthesis in Mouse Collecting Duct M-1 Cells via Ep1 Receptor Through Pkc/camp/creb Pathway. Hypertension 2012. [DOI: 10.1161/hyp.60.suppl_1.a401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Prostaglandin E2 (PGE2) plays a major role in regulating renin expression and release by the renal juxtaglomerular (JG) cells. Recently it has been demonstrated that PGE2-dependent upregulation of renin in JG cells is mediated by activation of E prostaoind receptor type 4 (EP4) via cAMP accumulation. Renin is also produced by the principal cells of the collecting ducts (CD) and is upregulated during angiotensin II-dependent hypertension. However, the effects of PGE2 on CD renin remain unknown. Four types of receptors have been described in rat and mouse CD, EP1, EP3 and EP4. Here, we tested the hypothesis that renin is upregulated by PGE2 via activation of EP receptors in mouse CD M-1 cells. By immunostaining we confirmed the presence of EP1, EP3 and EP4 receptors, while EP2 was not detected. A dose response treatment with PGE2 showed increased levels of renin mRNA and protein with a maximum response at 1 μmol/L (mRNA: 19.3 ± 3.0; P<0.05; protein: 3.01 ± 0.08 fold change; P<0.05). To assess which EP receptor is involved in the renin upregulation we used specific EP receptor antagonists: ONO-8711 (EP1; 10 nmol/L), L-798106 (EP3; 10 μmol/L) and AH 23848 (EP4; 10 μmol/L). EP1 antagonist suppressed the PGE2-mediated upregulation of collecting duct renin mRNA and protein (mRNA: 1.0 ± 0.2; protein: 0.98 ± 0.13 fold change; P=NS), while EP4 antagonist only partially decreased it (mRNA: 11.2 ± 2.8; P<0.05; protein: 2.81 ± 0.07 fold change; P<0.05). EP3 antagonist exacerbated the PGE2 mediated-upregulation of renin (mRNA: 50.3 ± 6.0; P<0.05; protein: 3.56 ± 0.08; fold change; P<0.05). Because EP1 is a Gq linked receptor that activates PKC, we further assessed the effects of PKC inhibition using calphostin C and a PKCα dominant negative (DN) on renin expression. Calphostin C and PKCα-DN blunted the PGE2-induced renin upregulation. Importantly, the increases in cAMP levels and phosphorylation of the cAMP response element-binding transcription factor (CREB) mediated by PGE2 were also prevented by both treatments. The results indicate that in mouse CD cells, EP1 receptor activation upregulates renin synthesis via PKC/cAMP/CREB, suggesting that the presence of PGE2 in renal medullary tissues may contribute to the stimulation of collecting duct renin.
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Redding KM, Chen BL, Singh A, Re RN, Navar LG, Seth DM, Sigmund CD, Tang WW, Cook JL. Transgenic mice expressing an intracellular fluorescent fusion of angiotensin II demonstrate renal thrombotic microangiopathy and elevated blood pressure. Am J Physiol Heart Circ Physiol 2010; 298:H1807-18. [PMID: 20363893 PMCID: PMC2886647 DOI: 10.1152/ajpheart.00027.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 03/29/2010] [Indexed: 01/09/2023]
Abstract
We have generated transgenic mice that express angiotensin II (ANG II) fused downstream of enhanced cyan fluorescent protein, expression of which is regulated by the mouse metallothionein promoter. The fusion protein, which lacks a secretory signal, is retained intracellularly. In the present study, RT-PCR, immunoblot analyses, whole-animal fluorescent imaging, and fluorescent microscopy of murine embryonic fibroblasts confirm expression of the fusion protein in vivo and in vitro. The transgene is expressed in all tissues tested (including brain, heart, kidney, liver, lung, and testes), and radioimmunoassay of plasma samples obtained from transgenic mice indicate no increase in circulating ANG II over wild-type levels, consistent with intracellular retention of the transgene product. Kidneys from transgenic and corresponding wild-type littermates were histologically evaluated, and abnormalities in transgenic mice consistent with thrombotic microangiopathy were observed; microthrombosis was frequently observed within the glomerular capillaries and small vessels. In addition, systolic and diastolic blood pressures, measured by telemetry (n = 8 for each group), were significantly higher in transgenic mice compared with wild-type littermates. Blood pressure of line A male transgenic mice was 125 + or - 1.7 over 97 + or - 1.6 compared with 109 + or - 1.7 over 83 + or - 1.4 mmHg in wild-type littermates (systolic over diastolic). In summary, overexpression of an intracellular fluorescent fusion protein of ANG II correlates with elevated blood pressure and kidney pathology. This transgenic model may be useful to further explore the intracellular renin-angiotensin system and its implication in abnormal kidney function and hypertension.
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Peti-Peterdi J, Navar LG, Darwin Bell P, Casellas D, Carmines PK, Inscho EW, Oparil S. A true champion of Hungarian kidney research and nephrology education--tribute to László Rosivall. ACTA PHYSIOLOGICA HUNGARICA 2009; 96:375-382. [PMID: 19706379 DOI: 10.1556/aphysiol.96.2009.3.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This article pays tribute to the tremendous achievements of Dr. László Rosivall in renal (patho)physiology research and nephrology education in Hungary on the occasion of his 60th birthday. For the past several decades Dr. Rosivall has been a charismatic leader of academic institutions, national and international societies, foundations in physiology, nephrology and hypertension, but the most important of his many contributions, is his role as a scientist. He earned his MD with Summa cum Laude at Semmelweis University (1973) and was invited immediately after that to join the laboratory of Hársing. He studied the distribution of intra-renal blood flow employing then state-of-the-art methods as well as developed his own technique at Semmelweis University and at the University of Bergen with Knut Aukland. This led to his PhD thesis and degree in 1980. An important determinant of his early basic scientific training and development was his postdoctoral research fellowship and later many visiting professorships in the Nephrology Research and Training Center (NRTC) at the University of Alabama at Birmingham, Birmingham, AL, USA between 1981 and 1983. Actually, this research fellowship not only impacted his own future career, but it also cleared the path for many other young Hungarian scientists who later trained with Dr. Rosivall and then at UAB. The early 1980s were the years of significant scientific discoveries and the NRTC team at UAB made important contributions by their studies on renal and glomerular hemodynamics, the renin-angiotensin system (12, 19, 22) and by the development of classic experimental techniques like renal micropuncture, microperfusion, and the juxtamedullary nephron preparation (3) that are still being used worldwide. When Dr. Rosivall joined UAB in the 1980s, the team at the NRTC included Drs. Navar, Bell, Inscho, Carmines, Casellas, and Oparil, among many others, who share their fond memories of working with Dr. Rosivall in this article.
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Gonzalez-Villalobos RA, Seth DM, Satou R, Horton H, Ohashi N, Miyata K, Katsurada A, Tran DV, Kobori H, Navar LG. Intrarenal angiotensin II and angiotensinogen augmentation in chronic angiotensin II-infused mice. Am J Physiol Renal Physiol 2008; 295:F772-9. [PMID: 18579707 DOI: 10.1152/ajprenal.00019.2008] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objectives of this study were to determine the effects of chronic angiotensin II (ANG II) infusions on ANG II content and angiotensinogen expression in the mouse kidney and the role of the angiotensin II type 1 receptor (AT(1)R) in mediating these changes. C57BL/6J male mice were subjected to ANG II infusions at doses of 400 or 1,000 ng.kg(-1).min(-1) either alone or with an AT(1)R blocker (olmesartan; 3 mg.kg(-1).day(-1)) for 12 days. Systolic and mean arterial pressures were determined by tail-cuff plethysmography and radiotelemetry. On day 13, blood and kidneys were collected for ANG II determinations by radioimmunoanalysis and intrarenal angiotensinogen expression studies by quantitative RT-PCR, Western blotting, and immunohistochemistry. ANG II infusions at the low dose elicited progressive increases in systolic blood pressure (135 +/- 2.5 mmHg). In contrast, the high dose induced a rapid increase (152 +/- 2.5, P < 0.05 vs. controls, 109 +/- 2.8). Renal ANG II content was increased by ANG II infusions at the low dose (1,203 +/- 253 fmol/g) and the high dose (1,258 +/- 173) vs. controls (499 +/- 40, P < 0.05). Kidney angiotensinogen mRNA and protein were increased only by the low dose to 1.13 +/- 0.02 and 1.26 +/- 0.10, respectively, over controls (1.00, P < 0.05). These effects were not observed in mice infused at the high dose and those receiving olmesartan. The results indicate that chronic ANG II infusions augment mouse intrarenal ANG II content with AT(1)R-dependent uptake occurring at both doses, but only the low dose of infusion, which elicited a slow progressive response, causes an AT(1)R-dependent increase in intrarenal angiotensinogen expression.
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Caplanusi A, Fuller AJ, Gonzalez-Villalobos RA, Hammond TG, Navar LG. Metabolic inhibition-induced transient Ca2+ increase depends on mitochondria in a human proximal renal cell line. Am J Physiol Renal Physiol 2007; 293:F533-40. [PMID: 17522266 DOI: 10.1152/ajprenal.00030.2007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
During ischemia or hypoxia an increase in intracellular cytosolic Ca(2+) induces deleterious events but is also implicated in signaling processes triggered in such conditions. In MDCK cells (distal tubular origin), it was shown that mitochondria confer protection during metabolic inhibition (MI), by buffering the Ca(2+) overload via mitochondrial Na(+)-Ca(2+) exchanger (NCX). To further assess this process in cells of human origin, human cortical renal epithelial cells (proximal tubular origin) were subjected to MI and changes in cytosolic Ca(2+) ([Ca(2+)](i)), Na(+), and ATP concentrations were monitored. MI was accomplished with both antimycin A and 2-deoxyglucose and induced a 3.5-fold increase in [Ca(2+)](i), reaching 136.5 +/- 15.8 nM in the first 3.45 min. Subsequently [Ca(2+)](i) dropped and stabilized to 62.7 +/- 7.3 nM by 30 min. The first phase of the transient increase was La(3+) sensitive, not influenced by diltiazem, and abolished when mitochondria were deenergized with the protonophore carbonylcyanide p-trifluoromethoxyphenylhydrazone. The subsequent recovery phase was impaired in a Na(+)-free medium and weakened when the mitochondrial NCX was blocked with 7-chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one (CGP-37157). Thus Ca(2+) entry is likely mediated by store-operated Ca(2+) channels and depends on energized mitochondria, whereas [Ca(2+)](i) recovery relied partially on the activity of mitochondrial NCX. These results indicate a possible mitochondrial-mediated signaling process triggered by MI, support the hypothesis that mitochondrial NCX has an important role in the Ca(2+) clearance, and overall suggest that mitochondria play a preponderant role in the regulation of responses to MI in human renal epithelial cells.
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Botros FT, Olszanecki R, Prieto-Carrasquero MC, Goodman AI, Navar LG, Abraham NG. Induction of heme oxygenase-1 in renovascular hypertension is associated with inhibition of apoptosis. Cell Mol Biol (Noisy-le-grand) 2007; 53:51-60. [PMID: 17531161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Accepted: 06/14/2006] [Indexed: 05/15/2023]
Abstract
The goal of this study was to characterize the impact of induction or inhibition of the heme-HO system on renal apoptosis in clipped and non-clipped kidneys from 2K1C hypertensive rats. Male Sprague-Dawley rats had a 0.25 mm silver clip placed around the left renal artery. Four groups of rats were studied: sham operated animals, 2K1C control rats, 2K1C rats received weekly injections of CoPP (5 mg/100 g body wt, administered subcutaneously), and 2K1C rats pretreated with SnMP (5 mg/ 100g body wt, administered intraperitoneally three times a week). The animals were sacrificed three weeks after surgery. We measured systolic blood pressure, plasma renin activity, non-clipped and clipped kidney HO-1 and HO-2 protein expression, HO activity, heme content, nitrotyrosine levels, and activation of selected pro- and anti-apoptotic proteins. Systolic blood pressure and plasma renin activity were significantly higher in 2K1C rats compared to sham rats. Compared to kidneys from sham animals, clipped kidneys from 2K1C rats showed a significant increase in HO-1 expression with increases in HO activity (26%), heme content (47%) and nitrotyrosine levels (49%), accompanied by an increase in caspase-3 and caspase-9 activity. In contrast, non-clipped kidneys from 2K1C rats showed no differences in HO-1 expression, HO activity, heme content, nitrotyrosine levels and caspase activity compared to sham rats. In clipped kidneys from 2K1C rats, inhibition of HO activity by SnMP augmented caspase-3 and caspase-9 activity and decreased expression of the anti-apoptotic Bcl-2 protein, while induction of HO-1 with CoPP strongly inhibited the activity of both caspases and increased the induction of Bcl-2 and Bcl-xl proteins. These findings demonstrate that the clipped kidneys responded to decreased renal perfusion pressure and increased oxidative stress by activation of the heme-HO system, which exerts antiapoptotic action via mechanisms involving decreased caspase-3 and caspase-9 activity, and increased expression of antiapoptotic molecules.
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Mitchell KD, Botros FT, Navar LG. Intrarenal renin-angiotensin system and counteracting protective mechanisms in angiotensin II-dependent hypertension. ACTA ACUST UNITED AC 2007; 94:31-48. [PMID: 17444274 DOI: 10.1556/aphysiol.94.2007.1-2.5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It is now well accepted that alterations in kidney function, due either to primary renal disease or to inappropriate hormonal influences on the kidney, are a cardinal characteristic in all forms of hypertension, and lead to a reduced ability of the kidneys to excrete sodium and the consequent development of elevated arterial pressures. However, it is also apparent that many extrarenal factors are important contributors to altered kidney function and hypertension. Central to many hypertensinogenic processes is the inappropriate activation of the renin-angiotensin system (RAS) and its downstream consequences by various pathophysiologic mechanisms. There may also be derangements in arachidonic acid metabolites, endothelium derived factors such as nitric oxide and carbon monoxide, and various paracrine and neural systems that normally interact with or provide a counteracting balance to the actions of the RAS. Thus, when the capacity of the kidneys to maintain sodium balance and extracellular fluid volume within appropriate ranges is compromised, increases in arterial pressure become necessary to re-establish normal balance.
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Gonzalez‐Villalobos RA, Satou R, Katsurada A, Kobori H, Hammond TG, Navar LG. Megalin mediates the uptake of angiotensin II in proximal tubule cells. FASEB J 2007. [DOI: 10.1096/fasebj.21.6.a1245-c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Gonzalez-Villalobos R, Klassen RB, Allen PL, Johanson K, Baker CB, Kobori H, Navar LG, Hammond TG. Megalin binds and internalizes angiotensin-(1-7). Am J Physiol Renal Physiol 2005; 290:F1270-5. [PMID: 16380466 PMCID: PMC2040263 DOI: 10.1152/ajprenal.00164.2005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Megalin is a multiligand receptor heavily involved in protein endocytosis. We recently demonstrated that megalin binds and mediates internalization of ANG II. Although there is a strong structural resemblance between ANG II and ANG-(1-7), their physiological actions and their affinity for the angiotensin type 1 receptor (AT(1)R) are dissimilar. Therefore, the hypothesis of the present work was to test whether megalin binds and internalizes ANG-(1-7). The uptake of ANG-(1-7) was determined by exposure of confluent monolayers of BN/MSV cells (a model representative of the yolk sac epithelium) to fluorescently labeled ANG-(1-7) (100 nM) and measurement of the amount of cell-associated fluorescence after 4 h by flow cytometry. Anti-megalin antisera and an AT(1)R blocker (olmesartan) were used to interfere with uptake via megalin and the AT(1)R, respectively. ANG-(1-7) uptake was prevented by anti-megalin antisera (63%) to a higher degree than olmesartan (13%) (P < 0.001). In analysis by flow cytometry of binding experiments performed in brush-border membrane vesicles isolated from kidneys of CD-1 mice, anti-megalin antisera interfered with ANG-(1-7) binding more strongly than olmesartan (P < 0.05 against positive control). Interactions of megalin with ANG-(1-7) at a molecular level were studied by surface plasmon resonance, demonstrating that ANG-(1-7) binds megalin dose and time dependently and with an affinity similar to ANG II. These results show that the scavenger receptor megalin binds and internalizes ANG-(1-7).
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Cohen EP, Kobori H, Moulder JE, Fish BL, Navar LG. 200 INTRARENAL ANGIOTENSINOGEN IN RADIATION NEPHROPATHY. J Investig Med 2005. [DOI: 10.2310/6650.2005.00006.199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Green T, Rodriguez J, Navar LG. 335 RENAL HEMODYNAMIC RESPONSES TO CYCLOOXYGENASE-2 INHIBITION IN RATS DURING ACUTE AND CHRONIC ANGIOTENSIN-CONVERTING ENZYME INHIBITION. J Investig Med 2005. [DOI: 10.2310/6650.2005.00006.334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Navar LG. The legacy of Homer W. Smith: mechanistic insights into renal physiology. J Clin Invest 2004. [DOI: 10.1172/jci200423150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Gonzalez-Villalobos R, Klassen RB, Allen PL, Navar LG, Hammond TG. Megalin binds and internalizes angiotensin II. Am J Physiol Renal Physiol 2004; 288:F420-7. [PMID: 15467006 DOI: 10.1152/ajprenal.00243.2004] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Megalin is an abundant membrane protein heavily involved in receptor-mediated endocytosis. The major functions of megalin in vivo remain incompletely defined as megalin typically faces specialized milieus such as glomerular filtrate, airways, epididymal fluid, thyroid colloid, and yolk sac fluid, which lack many of its known ligands. In the course of studies on ANG II internalization, we were surprised when only part of the uptake of labeled ANG II into immortalized yolk sac cells (BN-16 cells) was blocked by specific peptide inhibitors and direct competitors of the angiotensin type 1 receptor. This led us to test if megalin was a receptor for ANG II. Four lines of direct evidence demonstrate that megalin and, to a lesser extent, its chaperone protein cubilin are receptors for ANG II. First, in BN-16 cells anti-megalin and anti-cubilin antisera interfere with ANG II uptake. Second, also in BN-16 cells, pure ANG II competes for uptake of a known megalin ligand. Third, in proximal tubule cell brush-border membrane vesicles extracted from mice, anti-megalin antisera interfere with ANG II binding. Fourth, purified megalin binds ANG II directly in surface plasmon resonance experiments. The finding that megalin is a receptor for ANG II suggests a major new function for the megalin pathway in vivo. These results also indicate that ANG II internalization in some tissues is megalin dependent and that megalin may play a role in regulating proximal tubule ANG II levels.
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Jackson KE, Moehlen MW, Johnson FK, Navar LG, Johnson RA. 244 CARBON MONOXIDE ACUTELY ALTERS WATER/SODIUM EXCRETION IN L-NAME TREATED RATS. J Investig Med 2004. [DOI: 10.1136/jim-52-suppl1-797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Nishiyama A, Navar LG. Response to J. Schnermann: Adenosine mediates tubuloglomerular feedback. Am J Physiol Regul Integr Comp Physiol 2002. [DOI: 10.1152/ajpregu.2002.283.1.ra278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Navar LG, Nishiyama A. Intrarenal formation of angiotensin II. CONTRIBUTIONS TO NEPHROLOGY 2002:1-15. [PMID: 11705276 DOI: 10.1159/000060154] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Shi SJ, Nguyen HT, Sharma GD, Navar LG, Pandey KN. Genetic disruption of atrial natriuretic peptide receptor-A alters renin and angiotensin II levels. Am J Physiol Renal Physiol 2001; 281:F665-73. [PMID: 11553513 DOI: 10.1152/ajprenal.2001.281.4.f665] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We have studied cardiovascular and renal phenotypes in Npr1 (genetic determinant of natriuretic peptide receptor-A; NPRA) gene-disrupted mutant mouse model. The baseline systolic arterial pressure (SAP) in 0-copy mutant (-/-) mice (143 +/- 2 mmHg) was significantly higher than in 2-copy wild-type (+/+) animals (104 +/- 2 mmHg); however, the SAP in 1-copy heterozygotes (+/-) was at an intermediate value (120 +/- 4 mmHg). To determine whether Npr1 gene function affects the renin-angiotensin-aldosterone system (RAAS), we measured the components of RAAS in plasma, kidney, and adrenal gland of 0-copy, 1-copy, and 2-copy male mice. Newborn (2 days after the birth) 0-copy pups showed 2.5-fold higher intrarenal renin contents compared with 2-copy wild-type counterparts (0-copy 72 +/- 12 vs. 2-copy 30 +/- 7 microg ANG I. mg protein(-1). h(-1), respectively). The intrarenal ANG II level in 0-copy pups was also higher than in 2-copy controls (0-copy 33 +/- 5 vs. 2-copy 20 +/- 2 pg/mg protein, respectively). However, both young (3 wk) and adult (16 wk) 0-copy mutant mice showed a dramatic 50-80% reduction in plasma renin concentrations (PRCs) and in expression of renal renin message compared with 2-copy control animals. In contrast, the adrenal renin content and mRNA expression levels were 1.5- to 2-fold higher in 0-copy adult mice than in 2-copy animals. The results suggest that inhibition of renal and systemic RAAS is a compensatory response that prevents greater increases in elevated arterial pressures in adult NPRA null mutant mice. However, the greater renin and ANG II levels seen in 0-copy newborn pups provide evidence that the direct effect of NPRA activation on renin is an inhibitory response.
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Kobori H, Harrison-Bernard LM, Navar LG. Enhancement of angiotensinogen expression in angiotensin II-dependent hypertension. Hypertension 2001; 37:1329-35. [PMID: 11358949 PMCID: PMC2575649 DOI: 10.1161/01.hyp.37.5.1329] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chronic infusion of angiotensin (Ang) II leads to the development of hypertension and enhances intrarenal Ang II content to levels greater than can be explained from the circulating concentrations of the peptide. We previously reported that renal angiotensinogen (Ao) mRNA is enhanced in Ang II-dependent hypertension and may contribute to augmented intrarenal Ang II levels, but the Ao protein levels were not significantly increased. Because a high-salt diet (H/S) has been shown to suppress renal expression of Ao mRNA, we examined the effects of chronic Ang II infusion on kidney and liver Ao mRNA and protein levels in male Sprague-Dawley rats (n=12) maintained on an 8% salt diet. Ang II was administered via osmotic minipumps (40 ng/min) to 1 group (n=6) while the remaining rats were sham-operated. A H/S diet alone did not alter systolic blood pressure in sham animals (109+/-6 mm Hg at day 12); however, Ang II infusions to the H/S rats significantly increased systolic blood pressure (167+/-7 at day 12) and intrarenal Ang II content (459+/-107 fmol/g versus 270+/-42) despite a marked suppression of plasma renin activity (0.9+/-0.2 ng Ang I. mL(-1). h(-1) versus 2.8+/-1.3). Ang II infusions significantly increased kidney Ao mRNA compared with the H/S diet alone by 1.9+/-0.1-fold. Western blot analysis of kidney protein extracts showed that the Ang II-infused rats had increased kidney Ao protein levels compared with the H/S diet alone (1.9+/-0.1-fold). Liver Ao mRNA and protein and plasma Ao protein were also significantly increased by Ang II infusions. These data demonstrate the effects of Ang II infusion to stimulate Ao mRNA and protein. Thus, the augmented intrarenal Ang II in Ang II-dependent hypertension may result, in part, by a positive amplification mechanism to activate renal expression of AO:
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