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Dang Z, Su S, Jin G, Nan X, Ma L, Li Z, Lu D, Ge R. Tsantan Sumtang attenuated chronic hypoxia-induced right ventricular structure remodeling and fibrosis by equilibrating local ACE-AngII-AT1R/ACE2-Ang1-7-Mas axis in rat. JOURNAL OF ETHNOPHARMACOLOGY 2020; 250:112470. [PMID: 31862407 DOI: 10.1016/j.jep.2019.112470] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 12/02/2019] [Accepted: 12/09/2019] [Indexed: 06/10/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Tsantan Sumtang, which consists of Choerospondias axillaris (Roxb.) Burtt et Hill, Myristica fragrans Houtt and Santalum album L, is a traditional and common prescription of Tibetan medicine. Tsantan Sumtang originates from Four Tantra with properties of nourishing heart and has been used as a folk medicine for cardiovascular diseases and heart failure in Qinghai, Tibet and Inner Mongolia. Our previous studies found that Tsantan Sumtang showed beneficial effects on right ventricular structure in hypoxia rats, while the underling mechanism remains unclear. AIM OF THE STUDY To elucidate the underlying mechanisms of Tsantan Sumtang attenuated right ventricular (RV) remodeling and fibrosis of chronic hypoxia-induced pulmonary arterial hypertension (HPAH) rats. MATERIALS AND METHODS Fifty male Sprague Dawley (SD) rats (170 ± 20 g) were randomly divided into control group, hypoxia group, and hypoxia + Tsantan Sumtang groups (1.0 g· kg-1·day-1, 1.25 g· kg-1·day-1, 1.5 g ·kg-1·day-1). Rats in the hypoxia group and hypoxia + Tsantan Sumtang groups were maintained in a hypobaric chamber by adjusting the inner pressure and oxygen content to simulate an altitude of 4500 m for 28 days. The mean pulmonary arterial pressure (mPAP), right ventricle hypertrophy index (RVHI), the ratio of RV weight to tibia length (TL) (RV/TL), heart rate (HR) and RV systolic pressure (RVSP) was determined. Histomorphological assay of RV structure was evaluated by hematoxylin and eosin (HE) staining. RV tissue fibrosis was assessed by collagen proportion area (CPA), collagen I, collagen III and hydroxyproline content. CPA was obtained by picro-sirius red staining (PSR). The expression of collagen I and collagen III were detected by immunohistochemistry and western blotting. The hydroxyproline content was detected by alkaline hydrolysis. In addition, the level of angiotensin II (AngII) and angiotensin 1-7 (Ang1-7) in RV tissue was tested by enzyme-linked immune sorbent assay (ELISA). Protein expression of angiotensin-converting enzyme (ACE), AngII, AngII type 1 receptor (AT1R), angiotensin-converting enzyme 2 (ACE2), Mas receptor (Mas) were determined by immunohistochemistry and western blotting. mRNA level of ACE, AT1R, ACE2, Mas were tested by qPCR. The chemical profile of Tsantan Sumtang was revealed by UHPLC-Q-Exactive hybrid quadrupole-orbitrap mass analysis. RESULTS Our results showed that RVHI, RV/TL and RVSP were significantly increased in HPAH rat. Furthermore, levels of collagen I, collagen III and hydroxyproline were up-regulated in RV tissue under hypoxia. We found that RV hypertrophy and fibrosis were associated with increased expression of ACE, AngII, AT1R as well as decreased expression of ACE2, Ang1-7 and Mas. RV remodeling and fibrosis were attenuated after Tsantan Sumtang administration by up-regulating ACE2 and Mas level as well as down-regulating ACE, AngII and AT1R levels in RV tissue. 35 constituents in Tsantan Sumtang were identified. CONCLUSION Tsantan Sumtang attenuated RV remodeling and fibrosis in rat exposed to chronic hypoxia. The pharmacological effect of Tsantan Sumtang was based on equilibrating ACE-AngII-AT1R and ACE2-Ang1-7-Mas axis of RV tissue in HPAH rat.
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Affiliation(s)
- Zhancui Dang
- Research Center for High Altitude Medicine, Qinghai University, Xining, 810001, China; Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province (Qinghai-Utah Joint Research Key Lab for High Altitude Medicine), Xining, 810001, China; Medical College, Qinghai University, Xining, 810001, China
| | - Shanshan Su
- Technical Center of Xining Customs District, Key Laboratory of Food Safety Research in Qinghai Province, Xining, 810003, China
| | - Guoen Jin
- Research Center for High Altitude Medicine, Qinghai University, Xining, 810001, China; Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province (Qinghai-Utah Joint Research Key Lab for High Altitude Medicine), Xining, 810001, China
| | - Xingmei Nan
- Medical College, Qinghai University, Xining, 810001, China
| | - Lan Ma
- Research Center for High Altitude Medicine, Qinghai University, Xining, 810001, China; Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province (Qinghai-Utah Joint Research Key Lab for High Altitude Medicine), Xining, 810001, China
| | - Zhanqiang Li
- Research Center for High Altitude Medicine, Qinghai University, Xining, 810001, China; Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province (Qinghai-Utah Joint Research Key Lab for High Altitude Medicine), Xining, 810001, China.
| | - Dianxiang Lu
- Research Center for High Altitude Medicine, Qinghai University, Xining, 810001, China; Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province (Qinghai-Utah Joint Research Key Lab for High Altitude Medicine), Xining, 810001, China.
| | - Rili Ge
- Research Center for High Altitude Medicine, Qinghai University, Xining, 810001, China; Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province (Qinghai-Utah Joint Research Key Lab for High Altitude Medicine), Xining, 810001, China.
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Fung ML. The role of local renin-angiotensin system in arterial chemoreceptors in sleep-breathing disorders. Front Physiol 2014; 5:336. [PMID: 25249981 PMCID: PMC4155775 DOI: 10.3389/fphys.2014.00336] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 08/15/2014] [Indexed: 11/23/2022] Open
Abstract
The renin-angiotensin system (RAS) plays pivotal roles in the regulation of cardiovascular and renal functions to maintain the fluid and electrolyte homeostasis. Experimental studies have demonstrated a locally expressed RAS in the carotid body, which is functional significant in the effect of angiotensin peptides on the regulation of the activity of peripheral chemoreceptors and the chemoreflex. The physiological and pathophysiological implications of the RAS in the carotid body have been proposed upon recent studies showing a significant upregulation of the RAS expression under hypoxic conditions relevant to altitude acclimation and sleep apnea and also in animal model of heart failure. Specifically, the increased expression of angiotensinogen, angiotensin-converting enzyme and angiotensin AT1 receptors plays significant roles in the augmented carotid chemoreceptor activity and inflammation of the carotid body. This review aims to summarize these results with highlights on the pathophysiological function of the RAS under hypoxic conditions. It is concluded that the maladaptive changes of the RAS in the carotid body plays a pathogenic role in sleep apnea and heart failure, which could potentially be a therapeutic target for the treatment of the pathophysiological consequence of sleep apnea.
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Affiliation(s)
- Man Lung Fung
- Department of Physiology, University of Hong Kong Pokfulam, Hong Kong
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Current Research of the RAS in Pancreatitis and Pancreatic Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 690:179-99. [DOI: 10.1007/978-90-481-9060-7_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Inhibition of renin-angiotensin system in experimental acute pancreatitis in rats: a new therapeutic target? ACTA ACUST UNITED AC 2009; 62:353-60. [PMID: 19525099 DOI: 10.1016/j.etp.2009.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 04/06/2009] [Accepted: 05/11/2009] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Pancreatic renin-angiotensin system has been implied to play a role in the regulation of pancreatic functions and could be a new therapeutic target in acute pancreatitis. The aim of this study was to evaluate the therapeutic potential of angiotensin-converting-enzyme inhibition by captopril and angiotensin II type 1 receptor inhibition by L-158809 and losartan experimentally in acute pancreatitis. DESIGN Rats were randomly divided into 15 groups. Acute edematous pancreatitis was induced by injection of cerulein 20microg/kg SC four times at hourly intervals. Severe necrotizing pancreatitis was induced by retrograde injection of 3% taurocholate into the biliary-pancreatic duct. INTERVENTIONS Captopril, L-158809 and losartan were given intraperitoneally. Main outcome features: pancreatic pathology, pancreatic myeloperoxidase activity and serum amylase activity were assessed. RESULTS Captopril decreased serum amylase (10,809+/-1867 vs. 4085+/-1028U/L, p<0.01), myeloperoxidase activity (3.5+/-0.5 vs. 1.5+/-0.1, p<0.05) and histopathological score (5.0+/-0.4 vs. 1.1+/-0.5, p<0.01) in acute edematous pancreatitis. In taurocholate induced severe necrotizing pancreatitis captopril ameliorated histopathological score (10.1+/-1.2 vs. 3.4+/-0.5, p<0.01), pancreatic parenchymal necrosis (4.5+/-0.6 vs. 0.0+/-0.0, p<0.001), fatty necrosis (2.8+/-0.9 vs. 0.1+/-0.1, p<0.01) and edema (2.1+/-0.3 vs. 1.4+/-0.3, p<0.05). However, L-158809 did not have similar beneficial effects on acute pancreatitis in rats while losartan decreased pancreatic parenchymal necrosis and neutrophil infiltration. CONCLUSIONS This study not only demonstrated the differential effects of captopril, losartan and L-158809 in acute pancreatitis but also showed that there is still much to investigate about pancreatic renin-angiotensin system. Inhibition of angiotensin-converting enzyme should be evaluated carefully as a potential new therapeutic target in acute pancreatitis.
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Chan H, Leung PS, Tam MSC. Effect of angiotensin AT1 receptor antagonist on D-galactosamine-induced acute liver injury. Clin Exp Pharmacol Physiol 2007; 34:985-91. [PMID: 17714083 DOI: 10.1111/j.1440-1681.2007.04669.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
1. Acute liver injury is a severe disease in which metabolic homeostasis is affected. The presence of liver cell death triggers a cascade of inflammatory responses leading to various degrees of liver damage. The pathophysiology of liver injury is complex, involving an interplay between parenchymal and non-parenchymal cells. 2. There is increasing evidence for a role of the local renin-angiotensin system (RAS) in liver cell death, inflammatory response and liver regeneration. It has been shown that the local RAS plays an important regulatory role in a variety of tissues. In experimental hepatic fibrogenesis, the angiotensin AT(1) receptor (AT(1)R) blocker losartan has been shown to be able to attenuate transforming growth factor-b1 activity and collagen gene expression. 3. In the present study, using a D-galactosamine (GalN)-induced liver failure rat, AT(1)R were localized around the centrilobular region, which was not evident in normal liver. Blood tests showed an elevation of total bilirubin and alanine aminotransferase. Furthermore, there was an increase in tissue-specific inhibitor of metalloproteinase (TIMP)-1 protein in the liver. Losartan treatment was able to reduce all these parameters. Levels of TIMP-1 protein were reduced by 1.5- and 1.56-fold on Days 1 and 3, respectively (both P < 0.05), in the losartan-treated group relative to the GalN-treated group. The survival rate of the losartan-treated group was significantly higher than that of the GalN-treated group (5 day survival 85 vs 42.5%, respectively; P < 0.05). 4. In conclusion, the AT(1)R blocker losartan suppresses GalN-induced liver injury. This may indicate that AT(1)R blockers may have therapeutic potential in the treatment of acute liver injury.
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Affiliation(s)
- Herman Chan
- Department of Physiology, The Chinese University of Hong Kong, Hong Kong SAR, China.
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Fung ML, Lam SY, Wong TP, Tjong YW, Leung PS. Carotid Body AT(4) Receptor Expression and its Upregulation in Chronic Hypoxia. Open Cardiovasc Med J 2007; 1:1-7. [PMID: 18949084 PMCID: PMC2570565 DOI: 10.2174/1874192400701010001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Revised: 05/30/2007] [Accepted: 06/01/2007] [Indexed: 11/22/2022] Open
Abstract
Hypoxia regulates the local expression of angiotensin-generating system in the rat carotid body and the me-tabolite angiotensin IV (Ang IV) may be involved in the modulation of carotid body function. We tested the hypothesis that Ang IV-binding angiotensin AT4 receptors play a role in the adaptive change of the carotid body in hypoxia. The expression and localization of Ang IV-binding sites and AT4 receptors in the rat carotid bodies were studied with histochemistry. Specific fluorescein-labeled Ang IV binding sites and positive staining of AT4 immunoreactivity were mainly found in lobules in the carotid body. Double-labeling study showed the AT4 receptor was localized in glomus cells containing tyrosine hydroxylase, suggesting the expression in the chemosensitive cells. Intriguingly, the Ang IV-binding and AT4 immunoreactivity were more intense in the carotid body of chronically hypoxic (CH) rats (breathing 10% oxygen for 4 weeks) than the normoxic (Nx) control. Also, the protein level of AT4 receptor was doubled in the CH comparing with the Nx group, supporting an upregulation of the expression in hypoxia. To examine if Ang IV induces intracellular Ca2+ response in the carotid body, cytosolic calcium ([Ca2+]i) was measured by spectrofluorimetry in fura-2-loaded glomus cells dissociated from CH and Nx carotid bodies. Exogenous Ang IV elevated [Ca2+]i in the glomus cells and the Ang IV response was significantly greater in the CH than the Nx group. Hence, hypoxia induces an upregulation of the expression of AT4 receptors in the glomus cells of the carotid body with an increase in the Ang IV-induced [Ca2+]i elevation. This may be an additional pathway enhancing the Ang II action for the activation of chemoreflex in the hypoxic response during chronic hypoxia.
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Affiliation(s)
- Man-Lung Fung
- Department of Physiology, University of Hong Kong, Pokfulam, Hong Kong
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de Frutos S, Spangler R, Alò D, Bosc LVG. NFATc3 mediates chronic hypoxia-induced pulmonary arterial remodeling with alpha-actin up-regulation. J Biol Chem 2007; 282:15081-9. [PMID: 17403661 PMCID: PMC2754407 DOI: 10.1074/jbc.m702679200] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Physiological responses to chronic hypoxia include polycythemia, pulmonary arterial remodeling, and vasoconstriction. Chronic hypoxia causes pulmonary arterial hypertension leading to right ventricular hypertrophy and heart failure. During pulmonary hypertension, pulmonary arteries exhibit increased expression of smooth muscle-alpha-actin and -myosin heavy chain. NFATc3 (nuclear factor of activated T cells isoform c3), which is aCa(2+)-dependent transcription factor, has been recently linked to smooth muscle phenotypic maintenance through the regulation of the expression of alpha-actin. The aim of this study was to determine if: (a) NFATc3 is expressed in murine pulmonary arteries, (b) hypoxia induces NFAT activation, (c) NFATc3 mediates the up-regulation of alpha-actin during chronic hypoxia, and (d) NFATc3 is involved in chronic hypoxia-induced pulmonary vascular remodeling. NFATc3 transcript and protein were found in pulmonary arteries. NFAT-luciferase reporter mice were exposed to normoxia (630 torr) or hypoxia (380 torr) for 2, 7, or 21 days. Exposure to hypoxia elicited a significant increase in luciferase activity and pulmonary arterial smooth muscle nuclear NFATc3 localization, demonstrating NFAT activation. Hypoxia induced up-regulation of alpha-actin and was prevented by the calcineurin/NFAT inhibitor, cyclosporin A (25 mg/kg/day s.c.). In addition, NFATc3 knock-out mice did not showed increased alpha-actin levels and arterial wall thickness after hypoxia. These results strongly suggest that NFATc3 plays a role in the chronic hypoxia-induced vascular changes that underlie pulmonary hypertension.
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MESH Headings
- Actins/biosynthesis
- Actins/genetics
- Active Transport, Cell Nucleus/drug effects
- Active Transport, Cell Nucleus/genetics
- Animals
- Calcineurin/metabolism
- Calcineurin Inhibitors
- Cardiomyopathy, Hypertrophic/genetics
- Cardiomyopathy, Hypertrophic/metabolism
- Cardiomyopathy, Hypertrophic/pathology
- Cardiomyopathy, Hypertrophic/physiopathology
- Cell Nucleus/metabolism
- Chronic Disease
- Cyclosporine/pharmacology
- Enzyme Inhibitors/pharmacology
- Hypertension, Pulmonary/genetics
- Hypertension, Pulmonary/metabolism
- Hypertension, Pulmonary/pathology
- Hypertension, Pulmonary/physiopathology
- Hypoxia/genetics
- Hypoxia/metabolism
- Hypoxia/pathology
- Hypoxia/physiopathology
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Knockout
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/pathology
- NFATC Transcription Factors/antagonists & inhibitors
- NFATC Transcription Factors/deficiency
- NFATC Transcription Factors/metabolism
- Polycythemia/genetics
- Polycythemia/metabolism
- Polycythemia/pathology
- Polycythemia/physiopathology
- Pulmonary Artery/metabolism
- Pulmonary Artery/pathology
- Pulmonary Artery/physiopathology
- Up-Regulation/drug effects
- Up-Regulation/genetics
- Vasoconstriction/drug effects
- Vasoconstriction/genetics
- Ventricular Remodeling/drug effects
- Ventricular Remodeling/genetics
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Affiliation(s)
- Sergio de Frutos
- Department of Cell Biology and Physiology, School of Medicine, University of New Mexico, Albuquerque, New Mexico 87131, USA
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Bouffard L, Papirakis ME, Maheux P. Enalapril increases the local extravasation of macromolecules and nitric oxide synthase in pancreas of the fructose-fed insulin-resistant rat model. Pancreas 2006; 33:418-24. [PMID: 17079949 DOI: 10.1097/01.mpa.0000236729.01123.7d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES Angiotensin-converting enzyme (ACE) inhibitors have been associated with an increased risk of acute pancreatitis. The pathogenesis of this condition remains unclear, but an activation of the kinin system and a resultant localized angioedema have been implicated in the initial step leading to acute pancreatic damage. The goal of the present study was to explore the impact of ACE inhibition on pancreatic microcirculation and capillary permeability in normal and insulin-resistant rats. METHODS Chow- or fructose-fed Sprague-Dawley rats were treated with enalapril (dosage, 10 mg.kg.d) or vehicle for 4 weeks before measuring in vivo the extravasation of Evans blue (EB) dye in pancreas. Unanesthetized animals (n = 10-17 per group) were injected with EB 20 mg.kg in the caudal vein 10 minutes before killing, and EB dye was extracted from each pancreas by using formamide. RESULTS Relative to controls, enalapril-treated animals showed a 5-fold increase in pancreatic extravasation of EB in the fructose-fed rat model (P < 0.001); smaller changes (2-fold) were observed in the chow-fed animals treated with enalapril (P < 0.001). The increase in pancreatic vasopermeability observed with enalapril in the fructose-fed animals was accompanied by a significant increase in total pancreatic nitric oxide synthase (NOS) activity compared to controls (Delta = +128%; P < 0.001). This increase in NOS activity seemed to be solely attributable to an upregulation of the endothelial NOS isoform because only the eNOS immunoreactive mass (as opposed to nNOS) seemed to be increased in the pancreas of these animals. Treatment with enalapril was not associated with any increase in serum amylase concentrations in either animal subgroup. CONCLUSIONS Enalapril increases capillary permeability (extravasation of macromolecules) in the pancreas of the fructose-fed rat model. This suggests that ACE inhibition upregulates the eNOS isoform locally, increases vasopermeability of the pancreas, and can therefore result in local edema in the fructose-fed insulin-resistant rat model.
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Affiliation(s)
- Lucie Bouffard
- Department of Medicine, Division of Endocrinology & Metabolism, Université de Sherbrooke, Quebec, Canada
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Bonfigli A, Colafarina S, Falone S, Di Giulio C, Di Ilio C, Amicarelli F. High levels of antioxidant enzymatic defence assure good protection against hypoxic stress in spontaneously diabetic rats. Int J Biochem Cell Biol 2006; 38:2196-208. [PMID: 16904932 DOI: 10.1016/j.biocel.2006.06.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Revised: 06/20/2006] [Accepted: 06/25/2006] [Indexed: 01/22/2023]
Abstract
Recent data from literature report that reactive oxygen species (ROS) seem to play a crucial role in the etiology of both types I and II diabetes. This may render diabetic individuals more prone to oxidative injury when challenged with hypoxic stress. It is in fact well known that many diabetic complications cause ischaemic episodes, with a consequent reduction in oxygen supply to various tissues and organs. To check this hypothesis, in this work we tested type I diabetic individuals' antioxidant capability towards a hypoxic-mediated oxidative challenge. In particular, spontaneously diabetic and age-matched non-diabetic biobreeding (BB) Wistar rats were submitted to chronic normobaric hypoxia, and the response of antioxidant enzymes, as well as redox-sensitive transcription factor NF-kappaB and p53, were monitored. Results show that diabetic subjects present a dramatic enhancement in the major antioxidant enzymes activities, thus supporting the notion of diabetes-related changes in cellular redox status. This allows diabetic individuals to counteract hypoxia-mediated oxidative challenge better than the non-diabetic counterpart. Also the behaviour of both the redox-sensitive nuclear transcription factor NF-kappaB and p53 protein in response to hypoxic stimulation seems to support the hypothesis of a better ROS scavenging efficiency in diabetics under hypoxic conditions. In conclusion, high levels of antioxidant enzymatic defences in diabetic BB rats reflect a positive adaptive response able to assure an efficient protection not only against chronic, diabetes-mediated reactive oxygen species (ROS) overproduction, but also versus further oxidative damage.
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Affiliation(s)
- A Bonfigli
- Dipartimento di Biologia di Base ed Applicata, Università di L'Aquila, via Vetoio, Coppito, 67100 L'Aquila, Italy
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Kampf C, Lau T, Olsson R, Leung PS, Carlsson PO. Angiotensin II type 1 receptor inhibition markedly improves the blood perfusion, oxygen tension and first phase of glucose-stimulated insulin secretion in revascularised syngeneic mouse islet grafts. Diabetologia 2005; 48:1159-67. [PMID: 15877216 DOI: 10.1007/s00125-005-1761-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2005] [Accepted: 02/05/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS We recently found evidence of an angiotensin-generating system in pancreatic islets. The present study investigated the effect of endogenously produced angiotensin II on microcirculation and function in transplanted islets. MATERIALS AND METHODS Losartan, an angiotensin II type 1 receptor inhibitor, was administered either acute intravenously to mice with 4-week-old islet renal subcapsular transplants, or added to the drinking water for the final 14 days or throughout the 4-week post-transplantation period. The graft-bearing kidney was, in some cases, dissected out and perfused in vitro to evaluate the effect of angiotensin II and losartan on glucose-stimulated insulin release from the grafts. RESULTS Losartan treatment throughout the 4-week post-transplantation period had negative effects on islet revascularisation as well as on islet graft insulin release. However, administration of losartan, either intravenously or orally, after the formation of a new vascular network, improved islet graft blood perfusion. PO2 in the islet transplants was also effectively improved by the losartan treatment. Graft perfusion experiments showed a markedly better first phase of glucose-stimulated insulin release in transplanted islets when exposed to losartan. In contrast, acute administration of angiotensin II decreased islet graft blood flow, PO2 and glucose-stimulated insulin release. CONCLUSIONS/INTERPRETATION This study shows that inhibition of the islet reninangiotensin system may be a feasible strategy to increase the blood perfusion, PO2 and function within islet grafts. Such treatment should not be initiated, however, before the islet vascular system has been formed.
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Affiliation(s)
- C Kampf
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Abstract
Several regulatory systems are implicated in the regulation of islet function and beta cell mass. Of great interest in this context are some endocrine, paracrine/autocrine, and intracrine regulators. These include, to name but a few, the gut peptides, growth factors, prostaglandins, and some vasoactive mediators such as nitric oxide, bradykinins, endothelins, and angiotensins. Apart from its potent vasoconstrictor actions, the renin-angiotensin system (RAS) that generates angiotensin II has several novel functions-stimulation and inhibition of cell proliferation; induction of apoptosis; generation of reactive oxygen species; regulation of hormone secretion; and proinflammatory and profibrogenic actions. In the pancreas, recent evidence supports the presence of an islet RAS, which is subject to activation by islet transplantation and diabetes. Such a local islet RAS, if activated, may drive islet fibrosis and reduce islet blood flow, oxygen tension, and insulin biosynthesis. Moreover, activation of an islet RAS may drive the synthesis of reactive oxygen species, cause oxidative stress-induced beta cell dysfunction and apoptosis, and thus contribute to the islet dysfunction seen in type 2 diabetes and after islet transplantation. Blockade of the RAS could contribute to the development of novel therapeutic strategies in the prevention and treatment of patients with diabetes and in islet transplantation.
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Affiliation(s)
- Po Sing Leung
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
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Uesugi T, Froh M, Gäbele E, Isayama F, Bradford BU, Ikai I, Yamaoka Y, Arteel GE. Contribution of Angiotensin II to Alcohol-Induced Pancreatic Fibrosis in Rats. J Pharmacol Exp Ther 2004; 311:921-8. [PMID: 15316086 DOI: 10.1124/jpet.104.071324] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The mechanisms by which alcohol causes pancreatic fibrosis remain unknown. Recent studies have demonstrated that angiotensin II contributes to the development of fibrosis in liver, kidney, and heart injury. Here, the effects of angiotensin-converting enzyme inhibitor (captopril) and angiotensin II receptor antagonist (losartan) on alcohol-induced pancreatic fibrosis were examined in an intragastric ethanol-feeding model. Male rats were fed a high-fat liquid diet with either ethanol (16-20 g/kg/day) or isocaloric maltose-dextrin (control) for 4 weeks. Subgroups daily received captopril (60 mg/kg/day), losartan (3 mg/kg/day), or no additional agent included in liquid diets. Mean urine alcohol concentrations in all groups fed ethanol were more than 270 mg/dl and not significantly different. Dietary alcohol caused diffuse gland atrophy and interlobular and intralobular fibrosis with mild structural distortion in the pancreas, an effect that was blunted by captopril or losartan treatment. Alcohol also increased the number of alpha-smooth muscle actin-positive cells and transforming growth factor-beta mRNA expression in the pancreas. These increases were blunted significantly by captopril or losartan treatment. These data suggest that angiotensin II contributes to the development of chronic alcohol-induced pancreatic fibrosis through its stimulation of transforming growth factor-beta expression.
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Affiliation(s)
- Takehiko Uesugi
- Department of Pharmacology and Toxicology, 1307 Research Tower, HSC, University of Louisville School of Medicine, Louisville, KY 40292, USA
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Lau T, Carlsson PO, Leung PS. Evidence for a local angiotensin-generating system and dose-dependent inhibition of glucose-stimulated insulin release by angiotensin II in isolated pancreatic islets. Diabetologia 2004; 47:240-8. [PMID: 14722647 DOI: 10.1007/s00125-003-1295-1] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2003] [Revised: 11/06/2003] [Indexed: 01/13/2023]
Abstract
AIMS/HYPOTHESIS A local angiotensin-generating system has been found in the exocrine pancreas. This study aimed, primarily, to investigate the existence of a local angiotensin-generating system in the pancreatic islets and, secondly, to elucidate its role in regulating insulin secretion. METHODS Real-time RT-PCR and western blot were used to investigate if angiotensin-generating components are present in the mouse pancreatic islets, which are subject to regulation by islet transplantation. The localisation of AT1-receptors in islets was investigated by immunohistochemistry. Batch-type incubations of isolated islets were applied for studying the influence of angiotensin II on the glucose-stimulated insulin release, glucose oxidation and (pro)insulin, and total protein biosynthesis. RESULTS Major components, namely angiotensinogen, ACE, AT1- and AT2-receptors, were expressed in endogenous islets. AT1-receptors were localised to pancreatic beta cells. Exposure of the isolated islets to angiotensin II induced a dose-dependent inhibition of glucose-stimulated insulin release and inhibited (pro)insulin biosynthesis. This inhibitory action was fully preventable by pretreatment of the islets with losartan, an AT1-receptor antagonist. We also investigated if the expression of these components was changed after islet transplantation. Notably, a markedly increased expression of mRNA for the AT1-receptor was observed in islets retrieved from 4-week-old syngeneic islet transplants, a finding that was confirmed at the protein level. CONCLUSION/INTERPRETATION These data indicate the existence of an islet angiotensin-generating system of potential importance in the physiological regulation of glucose-induced insulin secretion, thus diabetes mellitus. The increased expression of the AT1-receptor in islet transplants could have relevance to islet-graft function.
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MESH Headings
- Angiotensin II/pharmacology
- Angiotensin II Type 1 Receptor Blockers
- Angiotensin II Type 2 Receptor Blockers
- Angiotensinogen/genetics
- Animals
- Blotting, Western
- Dose-Response Relationship, Drug
- Gene Expression/drug effects
- Glucose/metabolism
- Glucose/pharmacology
- Imidazoles/pharmacology
- Immunohistochemistry
- In Vitro Techniques
- Insulin/metabolism
- Insulin Secretion
- Islets of Langerhans/drug effects
- Islets of Langerhans/metabolism
- Islets of Langerhans/physiology
- Islets of Langerhans Transplantation/methods
- Losartan/pharmacology
- Male
- Mice
- Mice, Inbred C57BL
- Oxidation-Reduction/drug effects
- Peptidyl-Dipeptidase A/genetics
- Proinsulin/biosynthesis
- Protein Biosynthesis
- Pyridines/pharmacology
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/metabolism
- Renin-Angiotensin System/genetics
- Renin-Angiotensin System/physiology
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- T Lau
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong
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Benöhr P, Harsch S, Proksch B, Gleiter CH. Does angiotensin II modulate erythropoietin production in HepG2 cells? NEPHRON. EXPERIMENTAL NEPHROLOGY 2004; 98:e124-31. [PMID: 15627795 DOI: 10.1159/000081556] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 07/14/2004] [Indexed: 11/19/2022]
Abstract
BACKGROUND In humans, infusion of angiotensin II increases erythropoietin (EPO) serum levels in a dose-dependent manner. However, it is not known whether angiotensin II stimulates EPO-producing renal fibroblasts directly via a receptor or by alteration of renal hemodynamics with a consecutive decrease of renal blood flow. The purpose of this study was to investigate EPO secretion and gene expression under direct angiotensin II stimulation in a cell model thereby excluding hemodynamic effects. METHODS In an established EPO-secreting cell line (HepG2), EPO concentrations were measured under various conditions (normoxia and hypoxia) and different angiotensin II concentrations. mRNA levels of EPO were analyzed by LightCycler quantitative PCR after reverse transcription normalized to the housekeeping gene cyclophilin. RESULTS Angiotensin II did not affect EPO production in any concentration (1 nM or 100 microM) under conditions of normoxia. Reduced oxygen tension (1% O2) led to the expected increase of EPO and EPO gene expression. EPO secretion stimulated by hypoxia is not significantly changed by any concentration of angiotensin II. CONCLUSION In summary, this study shows that angiotensin II does not alter EPO production in HepG2 cell culture under normoxic or hypoxic conditions. This might point towards the hypothesis that in vivo renal cortical blood flow and consecutively the decrease of oxygen tension may lead to an increase of EPO secretion.
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Affiliation(s)
- Peter Benöhr
- Abteilung Pharmakologie und Experimentelle Therapie, Institut fur Pharmakologie und Toxikologie, Universitatsklinikum Tubingen, Tubingen, Germany
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15
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Lam SY, Fung ML, Leung PS. Regulation of the angiotensin-converting enzyme activity by a time-course hypoxia in the carotid body. J Appl Physiol (1985) 2003; 96:809-13. [PMID: 14527966 DOI: 10.1152/japplphysiol.00684.2003] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic hypoxia activates a local angiotensin-generating system in the carotid body. Here, we test the hypothesis that the activity of the critical enzyme for this system, angiotensin-converting enzyme (ACE), in the carotid body is subject to regulation by a time-course hypoxia. Results from the carotid body assays showed that ACE activity was markedly increased under the hypoxic stress of 7-, 14-, 21-, and 28-day exposures. The changes in ACE activity of 7-day (15.00 vs. 30.95 x 10(-5) nmol.microg(-1).min(-1)), 14-day (8.73 vs. 30.25 x 10(-5) nmol.microg(-1).min(-1)), and 21-day (11.41 vs. 31.83 x 10(-5) nmol.microg(-1).min(-1)) hypoxia treatments were enhanced significantly. However, ACE activity in 28-day (13.18 vs. 24.53 x 10(-5) nmol.microg(-1).min(-1)) hypoxia treatment was observed to increase insignificantly when compared with results in the respective control groups. Captopril inhibited all rises in ACE activity in both the control and experimental groups. Results clearly indicate an activation of the enzymatic activity of ACE, the critical enzyme for determining the conversion of angiotensin I into the physiologically active angiotensin II, by chronic hypoxia in the carotid body. An increase in the ACE activity may increase the local production of angiotensin II in the carotid body and thus its agonist action at the AT1 receptor. This may be important in the modulation of cardiopulmonary adaptation in the hypoxic ventilatory response as well as for electrolyte and water homeostasis during chronic hypoxia.
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Affiliation(s)
- Siu Yin Lam
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong
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Leung PS, Chappell MC. A local pancreatic renin-angiotensin system: endocrine and exocrine roles. Int J Biochem Cell Biol 2003; 35:838-46. [PMID: 12676170 DOI: 10.1016/s1357-2725(02)00179-6] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The renin-angiotensin system (RAS) is classically characterized as a circulating hormonal system primarily through the production of the physiologically active product angiotensin II (Ang II) that plays a crucial role in the regulation of blood pressure, fluid and electrolyte homeostasis. In addition to this circulating RAS, numerous tissues and organs have been recently demonstrated to exhibit their own RAS products and activities. Such an intrinsic RAS can modulate the specific local functions of their respective tissues and organs, frequently in a paracrine and autocrine manner. Recent findings from our laboratories and others have made a significant contribution on the expression, localization, regulation, and potential role of a local RAS in the pancreas. Although, it is quite intriguing that components of the local pancreatic RAS are responsive to various physiological and pathophysiological conditions, the crucial role of this system in regulating the exocrine and endocrine functions and ultimately the clinical relevance to pancreatic disease is still largely equivocal. Of particular interest in this context are the actions of pancreatic RAS on the growth, anti-proliferation and free radical generation in the pancreas. The aims of the current article focus on the emerging data on the local pancreatic RAS; its involvement in exocrine acinar and endocrine islet aspects, and the clinical significance in the pancreas are particularly addressed. The target for the local pancreatic RAS may provide a new insight into future management of various clinical conditions including islet transplants, diabetes mellitus, pancreatic cancer, pancreatitis and cystic fibrosis.
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Affiliation(s)
- Po Sing Leung
- Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, N. T., Hong Kong, PR China.
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