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

Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Cell Proliferation ; drug effects ; Cells, Cultured ; Collagen Type I ; biosynthesis ; Hepatocytes ; cytology ; metabolism ; Tetrazoles ; pharmacology ; Valine ; analogs & derivatives ; pharmacology ; Valsartan

OBJECTIVETo explore the role of angiotensin II type 1 (AT1) receptor in activation of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) in lung of mice with LPS-induced acute lung injury (ALI).

METHODSEighty-eight BABL/c mice were divided into control group (n = 8), LPS group (n = 40), and LPS + AT1 receptor antagonist ZD7155 group (n = 40) according to the random number table. Puncture of trachea was done in all mice. Mice in LPS + ZD7155 group were intraperitoneally injected with 10 mg/kg ZD7155. Mice in LPS and control groups were intraperitoneally injected with normal saline in the same volume as that of ZD7155. Thirty minutes later, 1 mg/mL LPS was dripped into trachea of mice in LPS and LPS + ZD7155 groups (2 mg/kg). Normal saline in the same volume as that of LPS was dripped into trachea of mice in control group. Lung tissue samples of mice in LPS and LPS + ZD7155 groups were harvested at post dripping hour (PDH) 1, 3, 6, 12, and 24. Lung tissue sample of mice in control group was harvested at PDH 24. Expression of AT1 receptor was determined with Western blot. AP-1 and NF-kappaB activity in lung tissue was detected with electrophoretic mobility shift assay. Data were processed with one-way analysis of variance.

RESULTSThe relative expression amount of AT1 receptor protein in lung tissue of mice in LPS group at each time point was increased obviously as compared with that of mice in control group (0.69 +/- 0.28, F = 9.356, with P values all below 0.01), and it peaked at PDH 6 (3.44 +/- 0.90), while that of mice in LPS + ZD7155 group was less than that in LPS group at each time point (F = 9.356, with P values all below 0.01). NF-kappaB activity in mice lung was markedly increased in LPS group at each time point as compared with mice in control group (5.47 +/- 0.08, F = 26.443, with P values all below 0.05), and its peak value in LPS group was found at PDH 3 (52.33 +/- 3.25). While NF-kappaB activity in mice of LPS + ZD7155 group was obviously lower than that in LPS group at each time point (F = 26.443, with P values all below 0.05). AP-1 activity in lung was enhanced significantly in LPS group at each time point as compared with that in control group (2.5 +/- 0.4, F = 34.685, with P values all below 0.05), and the activity peaked at PDH 6 (73.3 +/- 9.5) in LPS group. The activity was obviously weaker in mice in LPS + ZD7155 group as compared with that in LPS group at each time point (F = 34.685, with P values all below 0.05).

CONCLUSIONSAT1 receptor contributes to LPS-induced ALI through activating NF-kappaB and AP-1 in lung tissue.

Acute Lung Injury ; metabolism ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Lipopolysaccharides ; pharmacology ; Lung ; pathology ; Male ; Mice ; Mice, Inbred BALB C ; NF-kappa B ; metabolism ; Receptor, Angiotensin, Type 1 ; metabolism ; Transcription Factor AP-1 ; metabolism

OBJECTIVEAngiotensin II is an important pro inflammation factor in the cardiovascular system. This experiment is aimed to study the effects of angiotensin II on inducible nitric oxide synthase expression in human umbilical endothelial cells.

METHODSHuman umbilical endothelial cells were cultured in vitro and treated with angiotensin II alone or in combination with AT1, AT2 and NF-kappaB inhibitors respectively. The inducible nitric oxide synthase expressions at protein and mRNA levels were measured with Western blot and reverse transcription-polymerase chain reaction (RT-PCR), and the activity of NF-kappaB was analyzed with EMSA.

RESULTSAngiotensin II up-regulated inducible nitric oxide synthase expressions at the protein and mRNA levels at 5 h (P < 0.05), the activity of NF-kappaB was enhanced at 2 h (P < 0.05). These effects could be blocked by AT1 and NF-kappaB inhibitors but not by AT2 inhibitor.

CONCLUSIONAngiotensin II can upregulate the expression of inducible nitric oxide synthase through NF-kappaB pathway in human umbilical endothelial cells. AT1, other than AT2, play a key role in this process.

Angiotensin II ; pharmacology ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Angiotensin II Type 2 Receptor Blockers ; Cell Line ; Endothelial Cells ; chemistry ; drug effects ; Heart Failure ; metabolism ; Humans ; NF-kappa B ; metabolism ; Nitric Oxide Synthase Type II ; biosynthesis ; Reverse Transcriptase Polymerase Chain Reaction ; Umbilical Veins ; cytology ; Up-Regulation

Our previous studies suggest that the vascular local renin-angiotensin system (L-RAS) plays a pivotal role in the region-specific vascular adaptation due to simulated weightlessness. The present study was designed to determine whether simulated weightlessness still induced adaptive changes in rat vessels when angiotensin II type 1 receptor (AT(1)R) was chronically blocked by the administration of losartan, and whether the expressions of key elements in the L-RAS in the large arteries would change. Tail suspension for 4 weeks was used to simulate the physiological effect of weightlessness. The responses of the basilar, anterior tibial, carotid arteries and abdominal aorta were observed by morphometric technique with light microscopy. The expressions of angiotensinogen (AGT) and AT(1)R in the walls of common carotid artery and abdominal aorta were determined using immunohistochemical technique. The results showed that simulated weightlessness induced hypertrophy of the media of basilar artery and smooth muscle layers of carotid artery, but atrophic change in the anterior tibial artery and abdominal aorta. After 4 weeks of losartan treatment, all these arteries showed significant atrophic changes. However, simulated weightlessness still induced relative hypertrophy of the basilar artery and carotid artery and atrophy of the abdominal aorta when AT(1)R was blocked. After 4 weeks of simulated weightlessness, the expressions of AGT and AT(1)R were upregualted in the wall of carotid artery, but downregulated in the wall of abdominal aorta and perivascular tissues. Losartan decreased AGT and AT(1)R expressions only in the wall of abdominal aorta; whereas simulated weightlessness further decreased AT(1)R expression in the wall of abdominal aorta when AT(1)R was blocked. We conclude that simulated weightlessness for 4 weeks still induces structural changes and upregulates or downregulates the key elements in L-RAS in the large and medium-sized arteries from fore and hind body parts of rats when AT(1)R is blocked. The results suggest that the L-RAS in arterial tissue plays a pivotal role in these differential structural changes. However, there still exist other regulatory pathways to mediate the adaptive regulation of cerebral vessels when AT(1)R is blocked.
Adaptation, Physiological ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Aorta, Abdominal ; drug effects ; physiopathology ; Carotid Arteries ; drug effects ; physiopathology ; Hindlimb Suspension ; Losartan ; pharmacology ; Rats ; Receptor, Angiotensin, Type 1 ; Weightlessness Simulation

Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Cardiovascular Agents ; pharmacology ; Clinical Trials as Topic ; Heart Failure ; drug therapy ; Humans ; Neprilysin ; antagonists & inhibitors

BACKGROUNDIntrarenal activation of the renin angiotensin system (RAS) plays an important role in mediating renal fibrosis. Both angiotensin converting enzyme inhibitors (ACEIs) and angiotensin II (AngII) receptor antagonists have been shown to exert a protective role against diabetic and non-diabetic nephropathy. However, the exact mechanism of how blocking local RAS prevents renal fibrosis is unclear. The present study was to investigate the influence of a new AngII receptor antagonist, irbesartan (Irb), on AngII-induced hypertrophy in human proximal tubular cell line (HK-2).

METHODSThe cell line, HK-2, was grown in Dulbeccos's Modified Eagle's Medium containing 10% heat-inactivated fetal calf serum. After rested in serum-free medium for 24 hours, the effects of Irb on AngII (10(-7) mol/L)-induced [(3)H]-leucine incorporation, total protein content (measured by the Coomassie brilliant blue G250 method), and change in cell size (determined by scanning electron microscopy) were observed. The influence of Irb on the cell cycle was analyzed by fluorescence activated cell sorter (FACS) flow cytometry.

RESULTSAngII induced cell hypertrophy in a time and dose dependent manner. Stimulation of cells with AngII for 48 hours resulted in a increase in [(3)H]-leucine incorporation [0 hour: (5584 +/- 1016) cpm/10(5) cells vs 48 hours: (10741 +/- 802) cpm/10(5) cells, P < 0.05], which was significantly attenuated by treatment with Irb. AngII significantly increased the total protein content in HK-2 cells [control: (0.169 +/- 0.011) mg/10(5) cells vs AngII group: (0.202 +/- 0.010) mg/10(5) cells, P < 0.05], which was also markedly inhibited by cotreatment with Irb (P < 0.01). Scanning electron microscopy showed that AngII induced an increase in average physical cell size, which was significantly inhibited by Irb [control: (11.92 +/- 1.62) microm; AngII group: (20.63 +/- 3.83) micro m; AngII + Irb group: (13.59 +/- 3.15) micro m; P < 0.01 vs control, respectively]. Furthermore, flow cytometry revealed that AngII arrested cells in the G(0)-G(1) phase, which was significantly reversed by treatment with Irb [G(0)-G(1) cells in AngII group: (76.09 +/- 1.82)%, in AngII + Irb group: (67.00 +/- 2.52)%, P < 0.05].

CONCLUSIONIrb can inhibit AngII-induced hypertrophy in HK-2 cells.

Angiotensin II ; pharmacology ; Angiotensin II Type 1 Receptor Blockers ; Biphenyl Compounds ; pharmacology ; Cell Cycle ; drug effects ; Cells, Cultured ; Humans ; Hypertrophy ; Kidney Tubules, Proximal ; drug effects ; pathology ; ultrastructure ; Protein Biosynthesis ; Tetrazoles ; pharmacology

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

To test the hypothesis that exogenous purified angiotensin II (ANG) might cause apoptosis of alveolar epithelial cells (AECs) and acute lung injury, male Wistar rats were intratracheally instilled with purified ANG (10 mumol/L), ANG plus the caspase inhibitor ZVAD-fmk (60 mumol/L), ANG plus the ANG receptor AT1 antagonist losartan (LOS, 100 mumol/L) or sterile phosphate-buffered saline (PBS) vehicle alone. Six or 20 h later, the lungs were lavaged in situ for determination of bronchoalveolar lavage (BAL) fluid content of hemoglobin (Hb) and fluorescent (BODIPY)-albumin, a bolus of which was injected intravenously 15 min prior to BAL. Terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) revealed that instillation of ANG, but not PBS alone, increased labeling of fragmented DNA in bronchiolar epithelial cells and in AECs (P<0.05) at 6 h post-ANG. Increased TUNEL was abrogated by concurrent instillation of ZVAD-fmk or LOS. Significant increased numbers of caspase-positive cells were observed by anti-caspase 3 immunolabeling after instillation of ANG (P<0.01); the same doses of LOS or ZVAD-fmk that blocked TUNEL also blocked the activation of caspase 3 (P<0.01). Intratracheal instillation of ANG also remarkably increased BAL BODIPY-albumin (P< 0.01) and Hb (P<0.05), both of which were eliminated by ZVAD-fmk or LOS. These data indicate that exposure of AECs to ANG in vivo is sufficient to induce apoptosis and alveolar epithelial barrier injury mediated by ANG receptor AT1.
Amino Acid Chloromethyl Ketones ; pharmacology ; Angiotensin II ; adverse effects ; Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Apoptosis ; Caspase 3 ; metabolism ; Caspase Inhibitors ; pharmacology ; Epithelial Cells ; pathology ; Losartan ; pharmacology ; Lung Injury ; chemically induced ; pathology ; Male ; Rats ; Rats, Wistar ; Receptor, Angiotensin, Type 1 ; metabolism