Captopril can have nephrotoxic effects, which are largely attributed to accumulated renin and "escaped" angiotensin II (Ang II). Here we test whether angiotensin converting enzyme-1 (ACE1) inhibition damages kidneys via alteration of renal afferent arteriolar responses to Ang II and inflammatory signaling. C57Bl/6 mice were given vehicle or captopril (60 mg/kg per day) for four weeks. Hypertension was obtained by minipump supplying Ang II (400 ng/kg per min) during the second 2 weeks. We assessed kidney histology by periodic acid-Schiff (PAS) and Masson staining, glomerular filtration rate (GFR) by FITC-labeled inulin clearance, and responses to Ang II assessed in afferent arterioles in vitro. Moreover, arteriolar H₂O₂ and catalase, plasma renin were assayed by commercial kits, and mRNAs of renin receptor, transforming growth factor-β (TGF-β) and cyclooxygenase-2 (COX-2) in the renal cortex, mRNAs of angiotensin receptor-1 (AT₁R) and AT₂R in the preglomerular arterioles were detected by RT-qPCR. The results showed that, compared to vehicle, mice given captopril showed lowered blood pressure, reduced GFR, increased plasma renin, renal interstitial fibrosis and tubular epithelial vacuolar degeneration, increased expression of mRNAs of renal TGF-β and COX-2, decreased production of H₂O₂ and increased catalase activity in preglomerular arterioles and enhanced afferent arteriolar Ang II contractions. The latter were blunted by incubation with H₂O₂. The mRNAs of renal microvascular AT₁R and AT₂R remained unaffected by captopril. Ang II-infused mice showed increased blood pressure and reduced afferent arteriolar Ang II responses. Administration of captopril to the Ang II-infused mice normalized blood pressure, but not arteriolar Ang II responses. We conclude that inhibition of ACE1 enhances renal microvascular reactivity to Ang II and may enhance important inflammatory pathways.
Angiotensin II/pharmacology* ; Animals ; Arterioles/metabolism* ; Captopril/pharmacology* ; Hydrogen Peroxide/pharmacology* ; Kidney ; Mice

To investigate the molecular mechanism of angiotensin II (Ang II) receptor activation in adult rat cardiac fibroblasts, the expressions of cell signal transduction-associated genes were studied by using cDNA microarray. Cardiac fibroblasts of adult Sprague-Dawley rats (230~250 g) were isolated and cultured. The cells were divided into 4 groups: Ang II, Ang II + losartan, Ang II + PD123319, Ang II + losartan + PD123319. The expressions of Ang II receptors were studied by immunohistochemical staining. Total RNA was extracted and purified. After cDNA synthesis and biotin-16-dUTP labeling, the probes were denatured and hybridized with GEArray Q Series mouse G Protein-coupled Receptors Signaling Pathway Finder Gene Array (MM-025) containing 96 genes associated with 11 pathways. The arrays were scanned with a Uniscand1000 scanner and further analyzed with GEArray Analyzer software. RT-PCR was used to further confirm the results of gene microarray. The results of immunohistochemical staining showed that the expression of Ang II type 2 (AT2) receptor was evidently induced by Ang II stimulation when Ang II type 1 (AT1) receptor was blocked. The results of gene array indicated that blocking AT1 receptor changed 34 genes (more than 2 folds), 30 were down-regulated and 4 were up-regulated. The maximum change was not beyond 20 folds. The following 9 pathways were activated: cAMP/PKA, Ca2+, PKC, PLC, MAPK, PI-3 kinase, NO-cGMP, Rho, NF-kappaB pathways. Blockade of AT2 receptor caused 64 genes changing more than 2 folds (48 were down-regulated and 16 were up-regulated). Eleven pathways were basically activated. The change of the following 7 genes was over 30 folds: Cyp19a1 (37 folds), Il1r2 (42 folds), Cflar (53 folds), Bcl21 (31 folds), Pik3cg (278 folds), Cdkn1a (90 folds), Agt (162 folds). According to the activated extent, the signal transduction pathways in turn were PI-3 kinase, NF-kappaB and JAK-STAT pathways. Blocking both AT1 and AT2 receptors changed 46 genes more than 2 folds (36 were down-regulated and 10 were up-regulated). Eleven pathways were basically activated. The results of RT-PCR of IL-1beta and TNF-alpha confirmed the observations in gene microarray. Our results show that Ang II can induce a high expression of AT2 receptor in adult rat cardiac fibroblasts when AT1 receptor is blocked, and the signal mechanism of AT2 receptor is clearly different from that of AT1 receptor.
Angiotensin II ; pharmacology ; Angiotensin Receptor Antagonists ; pharmacology ; Animals ; Fibroblasts ; metabolism ; Gene Expression ; Imidazoles ; pharmacology ; Losartan ; pharmacology ; Myocardium ; cytology ; Pyridines ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptor, Angiotensin, Type 1 ; metabolism ; Receptor, Angiotensin, Type 2 ; metabolism ; Signal Transduction

OBJECTIVETo study the effect of angiotensin II on phosphoinositide-3 kinase/Akt cascade in cultured fibroblasts derived from patients with hypertrophic scars.

METHODSThe expression of AT1 and AT2 receptor was detected by immunofluorescence staining. Cultured human skin fibroblasts were treated with Ang II (10(-9) - 10(-7) mol/L), with or without an AT1 receptor blocker, valsartan or an AT2 receptor antagonist, PD123319. The phosphorylation of Akt was detected by western blotting, and PI3K activity was measured by Assay of PI3-K activity.

RESULTSImmunofluorescence staining showed that cultured fibroblasts derived from hypertrophic scars expressed both AT1 and AT2 receptors. Ang II increased Akt phosphorylation and PI3K activity in cultured hypertrophic scar fibroblasts in a dose- and time-dependent manner. Additionally, Ang II-induced Akt phosphorylation was blocked by wortmannin, a PI3-K inhibitor. This Ang II-activated PI3-K/Akt cascade was significantly inhibited by valsartan, an AT1 receptor specific blocker (P<0.05), whereas enhanced by PD123319, an AT2 receptor antagonist (P<0.05).

CONCLUSIONThese results indicate that Ang II receptors regulates PI3-K/Akt cascade of hypertrophic scars fibroblasts via AT1 and AT2.

Angiotensin II ; pharmacology ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Angiotensin II Type 2 Receptor Blockers ; Cells, Cultured ; Cicatrix, Hypertrophic ; metabolism ; pathology ; Fibroblasts ; cytology ; drug effects ; metabolism ; Humans ; Imidazoles ; pharmacology ; Phosphatidylinositol 3-Kinases ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Pyridines ; pharmacology ; Receptor, Angiotensin, Type 1 ; Signal Transduction ; Tetrazoles ; pharmacology ; Valine ; analogs & derivatives ; pharmacology ; Valsartan

OBJECTIVETo investigate the effect of Coriolus versicolor polysaccharide B (CVP-B) on increased membrane glycosaminoglycans (GAG) expression and intracellular glutathione (GSH) of RAW264.7 macrophages exposed to angiotensin II (Ang II).

METHODSThe plasma membrane of RAW264.7 macrophages exposed to Ang II treatment was isolated by ultracentrifugation, and the membrane GAG expression was analyzed using 1, 9-dimethylmethylene blue (DMMB) spectrophotometric assay for sulfated GAG. The intracellular reduced GSH was determined using fluorophotometry.

RESULTSThe GAG content in the macrophage membranes increased by up to 54% following cell exposure to 1.0 micromol/L Ang II, whereas in presence of 1.0 micromol;/L Ang II, CVP-B at 1, 10, and 50 microg/ml decreased the GAG content by 13%, 43% (P<0.01), and 52% (P<0.01), respectively. The macrophage GSH activity decreased by 69% following incubation with 1.0 micromol;/L Ang II for 24 h, and CVP-B treatment at 1, 10, and 50 microg/ml in presence of 1.0 micromol;/L Ang II resulted in significant increment of GSH activity by 31%(P<0.05), 104% (P<0.01), and 168% (P<0.01), respectively.

CONCLUSIONThese data provide the first evidence that CVP-B inhibits elevated GAG expression in RAW264.7 macrophage membrane induced by Ang II.

Agaricales ; chemistry ; Angiotensin II ; pharmacology ; Animals ; Cell Line ; Cell Membrane ; metabolism ; Glutathione ; analysis ; Glycosaminoglycans ; analysis ; Macrophages ; metabolism ; Mice ; Polysaccharides ; pharmacology

The study is to investigate the effect of angiotensin II (Ang II) and its receptor blockers on migration and endothelin-1 (ET-1) expression of rat vascular adventitial fibroblast subpopulations. Vascular adventitial fibroblasts were individually expanded by using cloning rings, and the effects of Ang II on the migration of adventitial fibroblast subpopulations were evaluated by Transwell. Fluorescence quantitative-PCR detected the expression of preproET-1 mRNA induced by Ang II, and its receptor antagonists losartan and PD-123319. The concentration of ET-1 was determined by ELISA. It showed that spindle shaped and epithelioid shaped cells were isolated by using cloning rings, named as spindle cells and round cells. RT-PCR showed that fibroblast subpopulations did not have leukocytes, endothelial cells and smooth muscle cells, namely pure cell lines. Compared with respective control cells, two subpopulations had transferring ability. Ang II significantly improved round cells migration in a concentration-dependent manner, and had no obvious influence on spindle cells migration. Ang II (1 x 10(-8) - 1 x 10(-6) mol x L(-1)) significantly increased the expression of preproET-1 mRNA in round cells (P < 0.01), and had no significant effect on the expression of preproET-1 mRNA in spindle cells. Losartan blocked the expression of preproET-1 mRNA induced by Ang II in round cells, and had no significant effect on the expression of preproET-1 mRNA in spindle cells. The effects of Ang II and ET-1 receptor inhibitors on the release of ET-1 were similar to the expression of preproET-1 mRNA. The results indicate that there are two cell subpopulations: round cells and spindle cells in rat vascular adventitial fibroblasts. Ang II significantly improved cells migration, and increased the expression of ET-1 in round cell subpopulation. It suggested that there may be different migratory mechanisms in two cell subpopulations, and the two subpopulations may play a different role in vascular remodeling and reparative process.
Angiotensin II ; pharmacology ; Angiotensin Receptor Antagonists ; pharmacology ; Animals ; Cell Movement ; drug effects ; Cells, Cultured ; Endothelin-1 ; genetics ; metabolism ; Fibroblasts ; cytology ; metabolism ; Imidazoles ; pharmacology ; Losartan ; pharmacology ; Male ; Pyridines ; pharmacology ; RNA, Messenger ; metabolism ; Rats ; Rats, Sprague-Dawley ; Vasoconstrictor Agents ; pharmacology

AIMThe effects of angiotensin II on the changes of Ca2+ signal in cultured rat neonatal myocytes were investigated in order to reveal the localization and distribution of elementary Ca2+ signaling units.

METHODSThe cultured neonate rat myocytes were treated with angiotensin II, and calcium signal was detected using confocal laser scanning microscopy and fluo-4/AM calcium probe.

RESULTSThe propagation of Ca2+ waves was observed in rest and angiotensin II stimulated cardiac myocytes. Calcium fluorescent intensity oscillated slightly in myocytes and the average intensity was much higher in the nucleus than in the cytosol, all of which could be magnified significantly by AngII (10(-6) mol/L). Ca2+ oscillation induced by Ang II was completely blocked by NO donor sodium nitroprusside. AngII evoked Ca2+ sparks close to the cell surface membrane, and couldn't be abolished by sodium nitroprusside.

CONCLUSIONThere are spatiotemporal dynamics of Ca2+ signaling patterns such as Ca2+ wave, Ca2+ spikes, Ca2+ oscillation and the whole cell Ca2+ transients induced by angiotensin II, which might play very important roles in cellular cardiac function.

Angiotensin II ; pharmacology ; Animals ; Calcium ; metabolism ; Calcium Signaling ; Cells, Cultured ; Microscopy, Confocal ; Myocytes, Cardiac ; drug effects ; metabolism ; Rats

OBJECTIVETo investigate the effect of rosiglitazone on angiotensin II (Ang II)-induced mRNA and protein expressions of toll-like receptor 4 (TLR4) and myeloperoxidase (MPO) activity in RAW264.7 cells to explore its anti- inflammatory and anti-atherosclerotic mechanisms.

METHODSMurine RAW264.7 cells were pretreated with rosiglitazone at 2.5, 5, and 10 micromol/L prior to exposure to AngII (0.1 micromol/L). TLR4 mRNA level was analyzed by RT-PCR, and TLR4 protein expression by Western blotting. MPO activity in the cell supernatant was assayed by colorimetry. In another experiment, the cells were pretreated with a neutralizing anti-TLR4 antibody (1 mg/L) for 1 h prior to rosiglitazone (10 micromol/L) treatment for 1 h, and subsequently stimulated with AngII or LPS (100 micromol/L) for 24 h to observe the change of MPO activity.

RESULTSRosiglitazone downregulated AngII-induced mRNA and protein expressions of TLR4, and inhibited MPO activity in RAW264.7 cells in a concentration-dependent manner. The TLR4 blocker partially antagonized the effect of AngII on MPO activity, and the inhibitory effect was markedly enhanced by rosiglitazone. Rosiglitazone significantly inhibited LPS (a specific TLR4 ligand)-induced MPO activity in RAW264.7 cells.

CONCLUSIONRosiglitazone downregulates Ang II-induced TLR4 expression in RAW264.7 cells and inhibits MPO secretion possibly by interfering with TLR4 to relieve the inflammatory reaction, which may be one of its anti-atherosclerotic mechanisms.

Angiotensin II ; pharmacology ; Animals ; Anti-Inflammatory Agents, Non-Steroidal ; pharmacology ; Cell Line ; Macrophages ; cytology ; metabolism ; Mice ; Peroxidase ; metabolism ; Thiazolidinediones ; pharmacology ; Toll-Like Receptor 4 ; genetics ; metabolism

OBJECTIVETo investigate the effects of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand on angiotensin II (AngII)-induced endothelin-1 (ET-1) and NO secretion by endothelial cells in comparison with AngII type I receptor (AT1R) antagonist losartan, so as to reveal the relationship between PPAR gamma and essential hypertension.

METHODSCultured human umbilical vein endothelial cells (HUVECs) were treated with AngII, PPAR gamma ligand troglitazone, AngII plus troglitazone, and AngII plus AT1R antagonist losartan, respectively, and the concentrations of NO and ET-1 in the cell culture supernatant were measured to evaluate the effects of troglitazone and losartan on AngII-induced NO and ET-1 production by human endothelial cells.

RESULTSTreatment of the HUVECs with troglitazone at 10 micromol/L and 50 micromol/L did not produce significant changes in ET-1 concentration in the cell culture supernatants, but significantly increased NO concentration as compared with the control group (P<0.05). Triglitazone at the concentration of 50 micromol/L significantly inhibited AngII (1x10(-6) mol/L)-induced ET-1 production (P<0.05), and at both 10 and 50 micromol/L, troglitazone inhibited the NO release-lowering effect of AngII in the endothelial cells (P<0.05). Both troglitazone and losartan inhibited AngII-induced ET-1 production by the endothelial cells, but losartan showed more potent effect (P<0.05). Similarly, both troglitazone and losartan inhibited decreased NO production in response to AngII treatment, and again losartan showed stronger effect (P<0.05).

CONCLUSIONPPAR gamma ligand troglitazone can inhibit AngII-induced ET-1 production enhancement and decreased NO release by the endothelial cells, but its effect is not so strong as losartan, suggesting that troglitazone modulates blood pressure not solely through AT1R pathway.

Angiotensin II ; metabolism ; pharmacology ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Antihypertensive Agents ; pharmacology ; Cell Line ; Chromans ; pharmacology ; Dose-Response Relationship, Drug ; Endothelial Cells ; drug effects ; metabolism ; secretion ; Endothelin-1 ; secretion ; Gene Expression Regulation ; drug effects ; Humans ; Hypertension ; metabolism ; Immunohistochemistry ; Losartan ; pharmacology ; Nitric Oxide ; secretion ; PPAR gamma ; metabolism ; Receptor, Angiotensin, Type 1 ; metabolism ; Thiazolidinediones ; pharmacology

BACKGROUNDAngiotensin II (Ang II) is a very important vasoactive peptide that acts upon hepatic stellate cells (HSCs), which are major effector cells in hepatic cirrhosis and portal hypertension. The present study was aimed to investigate the effects of Ang II and angiotensin II type 1 receptor antagonist (AT(1)RA) on the proliferation, contraction and collagen synthesis in HSCs.

METHODSHSC-T6 rat hepatic stellate cell line was studied. The proliferation of the HSC cells was evaluated by MTT colorimetric assay while HSC DNA synthesis was measured by (3)H-thymidine incorporation. The effects of angiotensin II and AT(1)RA on HSCs contraction were studied by analysis of the contraction of the collagen lattice. Cell culture media were analyzed by RT-PCR to detect secretion of collagen I (Col I), collagen III (Col III) and transforming growth factor beta1 (TGF-beta1) by enzyme linked immunosorbent assay. HSC was harvested to measure collagen I, collagen III and tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA expression.

RESULTSAng II ((1 x 10(-10) - 1 x 10(-4)) mol/L) stimulated DNA synthesis and proliferation in HSCs compared with untreated control cells. AT(1)RA inhibited angiotensin II induced proliferation of HSCs. A linear increase in the contractive area of collagen lattice correlated with the concentration of angiotensin II (1 x 10(-9) - 1 x 10(-5) mol/L) and with time over 48 hours. AT(1)RA blocks angiotensin II induced contraction of collagen lattice. Col I, Col III and TGF-beta1 levels of the Ang II group were higher than those of control group and this increase was downregulated by AT(1)RA. The mRNA expressions of Col I, Col III and TIMP-1 were higher in HSCs from the Ang II group than the control group and downregulated by AT(1)RA.

CONCLUSIONSAngiotensin II increased DNA synthesis and proliferation of HSCs in a dose-dependent manner, stimulated the contraction of HSCs dose- and time-dependently. Angiotensin also promoted excretion of Col I, Col III and TGF-beta1 levels and stimulated Col I, Col III and TIMP-1 expression in HSCs. Angiotensin acts via the angiotensin II receptor because all of these effects are blocked by angiotensin II type 1 receptor antagonist.

Angiotensin II ; pharmacology ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Calcium ; metabolism ; Cell Proliferation ; drug effects ; Cells, Cultured ; Collagen ; biosynthesis ; Dose-Response Relationship, Drug ; Liver ; cytology ; drug effects ; metabolism ; Rats ; Transforming Growth Factor beta1 ; biosynthesis

OBJECTIVETo investigate the effect of angiotensin (Ang)II and its Janns-activated kinase-2 (JAK2) signal pathway in transdifferentiation of renal tubular cells under the challenge of acute ischemic reperfusion injury.

METHODSModels of acute ischemic reperfusion injury were established and the level of local AngII, a key element of renin-angiotensin system (RAS), in kidney was measured using radioimmunity technique. The expression of alpha-smooth muscle actin (alpha-SMA), a phenotype of mesenchymal cells, was detected by RT-PCR and immunohistochemistry methods. Renal tubule cells (NRK-52E) were cultured with various concentration of AngII, followed by blocking of PD123319, AngII receptor 2 antagonist, and AG490, an inhibitor of JAK2 signal pathway.

RESULTSAngII of kidney tissue increased immediately after acute ischemic-reperfusion injury, in time dependent fashion. Expression of alpha-SMA in renal tubule cells was found at 48 hours after ischemic-reperfusion injury and in NRK-52E cells treated by high concentration of AngII and was dose and time dependent. The peak of alpha-SMA expression was seen after 30 minute treatment at the dose of 10(-9) mol/L, which was interrupted by both of PD123319 and AG490.

CONCLUSIONSTransdifferentiation of renal tubular epithelial cells occurs under acute ischemic-reperfusion injury. Local renin-angiotensin system may play a role in the transdifferentiation of TEC through AT2 receptor and its JAK2 signal pathway.

Actins ; genetics ; metabolism ; Angiotensin II ; administration & dosage ; metabolism ; pharmacology ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Cell Differentiation ; drug effects ; Cell Line ; Dose-Response Relationship, Drug ; Imidazoles ; pharmacology ; Janus Kinase 2 ; antagonists & inhibitors ; Kidney Tubules ; cytology ; metabolism ; Male ; Pyridines ; pharmacology ; RNA, Messenger ; metabolism ; Rats ; Rats, Wistar ; Renin-Angiotensin System ; Reperfusion Injury ; metabolism ; pathology ; Signal Transduction ; drug effects ; Tyrphostins ; pharmacology