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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that angiotensin II (AII) is a mitogen for neonatal rat cardiac fibroblasts. However, the signaling events that lead to fibroblast cell growth in response to AII remain to be elucidated. Mitogen-activated protein (MAP) kinases are cytosolic serine/threonine kinases which have been shown to be activated in quiescent cells by diverse growth stimuli, thereby being linked to growth regulatory pathways. This study was designed to determine whether MAP-kinase activation occurred in response to AII/receptor coupling in neonatal rat cardiac fibroblasts and the role of MAP-kinase activation in the AII-induced proliferation of these cells. Immunoblot analysis of MAP-kinase isoforms revealed predominantly p44 with less p42 MAP-kinase in rat cardiac fibroblasts. Both isoforms were activated upon stimulation of the cells with AII for 5 min or platelet derived growth factor-BB for 10 min. Angiotensin II stimulated MAP-kinase in a dose-dependent fashion with an EC50 of 2.5 nM. Two minutes following stimulation with 1 microM AII MAP-kinase activity increased from 90 +/- 17.9 to 477.5 +/- 75.9 pmol/min/mg protein, P < 0.05, n = 4. A smaller, sustained, secondary increase in MAP-kinase activity from 37.7 +/- 5.3 to 110.9 +/- 15.3 pmol/min/mg protein, P < 0.05, n = 4, was observed in response to AII between 120-150 minutes following receptor occupancy. The responses to AII were markedly attenuated by the AT1 receptor antagonist EXP3174. Stimulation of the cells with carbachol induced the first but not the second phase of MAP-kinase activity and this compound had no effect on cellular growth. The second phase of MAP-kinase activity 2-2.5 h after AII stimulation, paralleled data demonstrating that a 2-3 h receptor occupancy with AII was necessary to induce DNA synthesis and fibroblast proliferation. These results indicate that AII stimulates a biphasic activation of MAP-kinase by the AT1 receptor and that this pathway may participate in the AII induced mitogenic response in cardiac fibroblasts.
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PMID:Angiotensin II is a potent stimulator of MAP-kinase activity in neonatal rat cardiac fibroblasts. 747 73

Angiotensin-II (AII), which stimulates steroidogenesis in bovine adrenocortical (BAC) cells through the phosphoinositides pathway, activates p42-p44 mitogen-activated protein kinases (MAPKs) after 5 min of treatment (EC50 = 0.1 nM). This activation is 1) completely inhibited by the AII receptor AT1 subtype antagonist Dup 753 (10 microM), but unaffected by the AT2 antagonist PD 123177; 2) not reproduced by the AT2 agonist CGP 42112A; 3) insensitive to pretreatment with pertussis toxin; and 4) abolished by a 48-h preexposure of the cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA; 1 microM), which down-regulates protein kinase-C activity. Fibroblast growth factor-2, a potent mitogen for BAC cells, which acts through its tyrosine kinase receptor, also activates MAPK (EC50 = 0.3 in a TPA-insensitive manner, while exhibiting no detectable effect on BAC cell steroidogenesis. In contrast, ACTH, which stimulates steroidogenesis via cAMP and inhibits BAC cell proliferation, does not stimulate MAPK. Indeed, ACTH completely blocks (IC50 = 0.01 nM) the stimulation of MAPK by AII, fibroblast growth factor-2, or TPA. Therefore, bovine adrenocortical cells provide an example of positive and negative hormonal regulation of MAPK activity through a cross-talk between the inositide-, cAMP-, and growth factor-activated tyrosine kinase pathways.
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PMID:Hormonal regulation of mitogen-activated protein kinase activity in bovine adrenocortical cells: cross-talk between phosphoinositides, adenosine 3',5'-monophosphate, and tyrosine kinase receptor pathways. 786 5

Angiotensin II (Ang II) is a potent regulator of proximal tubule functions, including transport, metabolism, and cell proliferation. The opossum kidney (OK) cell line is a useful model of renal proximal tubule. Mitogen-activated protein (MAP) kinases are rapidly phosphorylated and activated in response to various agonists. We investigated Ang II effects on serine/threonine kinase cascades in OK cells. The major findings of the present study are that Ang II stimulated MAP kinase kinase (MAPKK), MAP kinase (MAPK), and S6 kinase activities, and that it increased phosphorylation of Raf-1 kinase and p42 MAP kinase in OK cells. These stimulations of kinases were dose-dependent (from 10(-6) to 10(-11) M). The time course of activation was sequential; the peak stimulation was reached at 5 to 10 minutes for Raf-1 kinase, MAPKK and MAPK, and at 20 minutes for S6 kinase. The activation of MAPK was inhibited by approximately 70% with prolonged 24-hour PMA pretreatment or in the presence of calphostin C or H-7. Tyrosine kinase inhibitors (genistein and herbimycin) did not inhibit AngII-induced MAPK activity. This activation of MAPK was also inhibited via AT1 receptor antagonist, Dup753 and pertussis toxin. This evidence suggests that the activation of serine/threonine cascades by Ang II is largely dependent on PMA-sensitive PKC, and is not dependent on tyrosine kinase and pertussis toxin.
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PMID:Sequential activation of MAP kinase cascade by angiotensin II in opossum kidney cells. 858 39

1. Stimulation of the AT1 receptor by angiotensin II (AII) gives a larger mitogenic response in vascular smooth muscle cells from spontaneously hypertensive rats (SHR) compared to those from normotensive (WKY) controls. Here we investigated whether the p42 and p44 mitogen activated protein kinase (MAPK) pathway is differentially regulated in these cells by AT1 receptors. 2. We showed that there is a similar level of p42 and p44 MAPK immunoreactivity in the SHR and WKY derived cells. 3. However, by use of an antiserum specific for the tyrosine phosphorylated form of MAPK, and an assay with a nonapeptide MAPK substrate, we showed that AII (100 nM)-stimulated phosphorylation and activation of p42mapk and p44mapk are enhanced in the SHR derived cells. 4. This increased MAPK activity in SHR derived cells was also seen on protein kinase C activation with 100 nM phorbol myristate acetate (PMA). The size and time course of the response to PMA was the same as that to AII in each cell type. 5. The protein kinase C inhibitor Ro 31-8220 attenuated the early (2 min) phase of AII stimulation of MAPK activity and the entire stimulation caused by PMA. At longer times of AII stimulation both p42mapk and p44mapk were activated by an Ro 31-8220-insensitive mechanism. 6. Agonist or PMA stimulation of MAPK activity was inhibited by the tyrosine kinase inhibitor genistein. AII stimulated tyrosine protein phosphorylation to a greater degree in SHR than WKY cells. 7. These results show that the MAPK response of SHR derived cells is increased over that of WKY cells by mechanisms independent of the enhanced stimulation of phospholipase C; amplification at the level of sequential protein kinase C and tyrosine kinase steps leads to the enhanced responsiveness of MAPK in the SHR derived cells.
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PMID:Angiotensin II responses of vascular smooth muscle cells from hypertensive rats: enhancement at the level of p42 and p44 mitogen activated protein kinase. 931 27

Angiotensin II (Ang II) receptors of the AT1 subtype are coupled to heterotrimeric G nucleotide-binding proteins, G(q/11), to activate phospholipase C-beta isoforms with production of inositol 1,4,5-trisphosphate (InsP3) and diacylglycerol. The resultant release of intracellular Ca2+ and increased Ca2+ influx are major determinants of several acute cellular responses initiated by Ang II, including secretion of aldosterone from the adrenal cortex and smooth muscle contraction. However, cellular events related to more prolonged effects of Ang II, such as hypertrophic and hyperplastic responses, are triggered by intracellular signaling cascades that are less dependent on Ca2+ signals. The Ang II-induced activation of Raf-1 kinase, p42 MAP-kinase and c-fos expression in response to Ang II in adrenal glomerulosa cells does not require Ca2+ influx. Moreover, the dose-response relationships for Raf-1 activation, MAP-kinase activation and mitogenesis show significantly higher sensitivity to Ang II than the InsP3, Ca2+-release and aldosterone secretory responses. The sensitivities of both Raf-1 kinase and MAP-kinase stimulation by Ang II to the inhibitors of phosphoinositide kinases, wortmannin and LY 294002, suggest that inositol phospholipids may play a role in these activation events unrelated to their role in Ca2+ signaling. To investigate the changes of various inositides after stimulation at the single cell level, fluorescent probes were developed in which pleckstrin homology domains with distinct binding specificities to inositol phospholipids were fused to the green fluorescent protein and expressed in NIH 3T3 cells. The use of these probes revealed heterogeneity of the inositol lipid pools and their complex relationship to Ca2+ signals. The use of these tools will help to further clarify the complex role of these lipids in initiating Ca2+-dependent and -independent signaling responses.
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PMID:Signaling events activated by angiotensin II receptors: what goes before and after the calcium signals. 988 5

Using spontaneously hypertensive and aortic banded rats, we have shown that expression of myocardial osteopontin, an extracellular matrix protein, coincides with the development of heart failure and is inhibited by captopril, suggesting a role for angiotensin II (ANG II). This study tested whether ANG II induces osteopontin expression in adult rat ventricular myocytes and cardiac microvascular endothelial cells (CMEC), and if so, whether induction is mediated via activation of mitogen-activated protein kinases (p42/44 MAPK) and involves reactive oxygen species (ROS). ANG II (1 microM, 16 h) increased osteopontin expression (fold increase 3.3+/-0.34, n = 12, P < 0.01) in CMEC as measured by northern analysis, but not in ARVM. ANG II stimulated osteopontin expression in CMEC in a time- (within 4 h) and concentration-dependent manner, which was prevented by the AT1 receptor antagonist, losartan. ANG II elicited robust phosphorylation of p42/44 MAPK as measured using phospho-specific antibodies, and increased superoxide production as measured by cytochrome c reduction and lucigenin chemiluminescence assays. These effects were blocked by diphenylene iodonium (DPI), an inhibitor of the flavoprotein component of NAD(P)H oxidase. PD98059, an inhibitor of p42/44 MAPK pathway, and DPI each inhibited ANG II-stimulated osteopontin expression. Northern blot analysis showed basal expression of p22phox, a critical component of NADH/NADPH oxidase system, which was increased 40-60% by exposure to ANG II. These results suggest that p42/44 MAPK is a critical component of the ROS-sensitive signaling pathways activated by ANG II in CMEC and plays a key role in the regulation of osteopontin gene expression. Published 2001 Wiley-Liss, Inc.
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PMID:Regulation of angiotensin II-stimulated osteopontin expression in cardiac microvascular endothelial cells: role of p42/44 mitogen-activated protein kinase and reactive oxygen species. 1138 29

Expression of glutamine:fructose-6-phosphate amidotransferase (GFAT), the rate-limiting enzyme for glucose entry into the hexosamine pathway, is transcriptionally regulated. Immunohistochemical studies of human kidney biopsies demonstrate increased GFAT expression in diabetic glomeruli, but the mechanism responsible for this overexpression is unknown. Given the role of ANG II in diabetic kidney disease, we chose to study the effect of ANG II on GFAT promoter activity in mesangial cells (MC). Exposure of MC to ANG II (10(-7) M) increased GFAT promoter activity (2.5-fold), mRNA (3-fold), and protein (1.6-fold). ANG II-mediated GFAT promoter activation was inhibited by the ANG II type I receptor antagonist candesartan (10(-8) M) but was unaffected by the ANG II type II receptor antagonist PD-123319 (10(-8) M). The intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (10(-6) M), protein kinase C (PKC) inhibitors bisindoylmaleimide-4 (10(-6) M) and calphostin C (10(-7) M), protein tyrosine kinase (PTK) inhibitor genistein (10(-4) M), Src family kinase inhibitor PP2 (2.5 x 10(-7) M), p42/44 mitogen-activated protein kinase (MAPK) inhibitor PD-98059 (10(-5) M), and the epidermal growth factor (EGF) inhibitor AG-1478 all attenuated GFAT promoter activation by ANG II. We conclude that the GFAT promoter is activated by ANG II via the AT1 receptor. Promoter activation is calcium dependent and PKC dependent but also involves PTK signaling pathways including Src, the EGF receptor, and p42/44 MAPK.
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PMID:Angiotensin II activates the GFAT promoter in mesangial cells. 1139 56

We demonstrate that human umbilical vein endothelial cells (HUVEC) grown in co-culture (CC) with U87 glioblastoma cells transfected with green fluorescent protein (GFP-U87) exhibit resistance to radiation-mediated apoptosis. cDNA macroarray analysis reveals increases in the accumulation of RNAs for HUVEC genes encoding cell adhesion molecules, growth factor-related proteins, and cell cycle regulatory/DNA repair proteins. An increase in protein expression of integrin alphav, integrin beta1, MAPK(p42), Rad51, DNA-PK(CS), and ataxia telangiectasia gene (ATM) was detected in HUVEC grown in CC with GFP-U87 cells compared with HUVEC grown in mono-culture. Treatment with anti-VEGF antibody decreases the expression of integrin alphav, integrin beta1, DNA-PK(CS) and ATM with a corresponding increase in ionizing radiation (IR)-induced apoptosis. These data support the concept that endothelial cells growing in the tumor microenvironment may develop resistance to cytotoxic therapies due to the up-regulation by tumor cells of endothelial cells genes associated with survival.
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PMID:Glioblastoma cells block radiation-induced programmed cell death of endothelial cells. 1513 73

Autocrine stimulation and paracrine interaction between coronary smooth muscle cells (cSMC) and endothelial cells (EC) act as regulators of the vascular angiogenesis. Basic fibroblast growth factor (bFGF), its receptor FGF-R1, and coreceptor heparansulfate proteoglycan (HSPG) are important components involved in this angiogenic process. We investigated the influence of angiotensin (Ang) II on this trimolecular bFGF complex, the underlying signaling and the proliferative process in human cSMC. Ang II induces an AT1 receptor-dependent expression of bFGF and also upregulates the FGF-R1 and HSPG expression which is suppressed by losartan, the AT1 receptor blocker. AT1 receptor signaling which is characterized by phosphorylation of p42-mitogen-activated protein kinase (MAPK) is involved in Ang II-induced bFGF, FGF-R1 and HSPG upregulation and DNA synthesis in human cSMC. In contrast, inhibition of the AT2 receptor by PD123,319 has no influence on these Ang II-stimulated and via the MAPK cascade-mediated proangiogenic effects. Finally, our data show that the Ang II-induced DNA synthesis in cSMC is mediated via the bFGF expression. In conclusion, our results suggest that the Ang II-induced angiogenic effects in the vessel wall are supported by the AT1 receptor-stimulated and MAPK pathway-mediated upregulation of the autocrine/paracrine trimolecular bFGF complex in cSMC.
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PMID:Angiotensin AT1 receptor upregulates expression of basic fibroblast growth factor, basic fibroblast growth factor receptor and coreceptor in human coronary smooth muscle cells. 1522 45

Current evidence points to renin-angiotensin system as a key mediator in ischemia-reperfusion injury. Rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand, has recently been shown to confer cardioprotection against ischemia-reperfusion in animal models. We sought to examine the expression of ANG II receptors during PPAR-gamma-mediated cardioprotection. Male Sprague-Dawley rats (nondiabetic) were fed either regular rat chow (control diet group, n = 9) or rosiglitazone-rich diet (rosiglitazone-rich diet group, n = 9) and were subjected to 1 h of myocardial ischemia followed by 1 h of reperfusion. A third group of rats had only thoracotomy and pericardiotomy and served as a sham control group (n = 9). Hemodynamics, infarct size, and expression of ANG II type 1 and type 2 receptors (AT1 and AT2) were measured in all groups. There was a 58% reduction of infarct size in the rosiglitazone-rich diet group (P < 0.01 vs. control diet group). Increased myocardial expression of AT(1) receptors in the ischemic-reperfused myocardium was attenuated in the rosiglitazone-rich diet group (P < 0.05 vs. control diet group). Importantly, myocardial AT2 mRNA and protein expression were significantly increased (by >100-fold) in the rosiglitazone-rich diet group (P < 0.05). These changes were accompanied by inhibition of p42/44 MAPK in the rosiglitazone-rich diet group, while the Akt1 expression, believed to mediate insulin sensitization, remained similar in all three groups. The cardioprotective effects of rosiglitazone against myocardial ischemia-reperfusion injury are independent of its insulin-sensitizing properties and are associated with significant overexpression of AT2 receptors along with inhibition of p42/44 MAPK.
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PMID:Cardioprotective effects of rosiglitazone are associated with selective overexpression of type 2 angiotensin receptors and inhibition of p42/44 MAPK. 1658 19


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