Effect of atrial natriuretic factor on vasopressin-stimulated cyclic AMP accumulation in papillary collecting tubule.
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Animals↗
Biomedical subjects
M J Dunn
Publications and source records attributed to M J Dunn.
Thrombin induces the preproendothelin-1 gene in endothelial cells by a protein tyrosine kinase-linked mechanism.
Thrombin stimulates synthesis and secretion of endothelin-1 (ET-1), a vasoactive peptide that triggers responses in the vascular endothelium and smooth muscle. We investigated the signal transduction pathways by which thrombin stimulates preproET-1 gene expression and ET-1 peptide secretion in macrovascular cells (human umbilical vein endothelial cells [HUVECs] and bovine pulmonary artery endothelial cells [BPAECs]) and microvascular cells (human microvascular endothelial cell line [HMEC-1]). Thrombin (4 U/mL) stimulated maximal induction of ET-1 peptide secretion and preproET-1 mRNA after 2 hours in HUVECs and BPAECs and after 1 hour in HMEC-1. A synthetic thrombin receptor activator peptide confirmed ligand-specific receptor actions to induce preproET-1 mRNA. Protein kinase C (PKC) activation by phorbol ester transiently induced preproET-1 mRNA but had no effect on ET-1 peptide synthesis. PKC inhibitors sangivamycin and calphostin C and PKC depletion failed to suppress thrombin-stimulated preproET-1 mRNA. Adenylate cyclase and cAMP-dependent protein kinase did not participate in thrombin-induced preproET-1 gene activation. Thrombin stimulated a rapid increase in phosphotyrosine-containing proteins, suggesting a role for tyrosine phosphorylation in thrombin signaling. These data demonstrate that thrombin induces the preproET-1 gene and ET-1 peptide synthesis by a PKC-independent PTK-dependent pathway in macrovascular and microvascular endothelial cells. Protein tyrosine kinase inhibitors herbimycin A and genistein blocked thrombin-stimulated preproET-1 mRNA and peptide secretion, whereas daidzein, which lacks inhibitory activity, did not suppress thrombin-induced ET-1.
Animals↗
Interactions of the vasoconstrictor peptides, angiotensin II and endothelin-1, with vasodilatory prostaglandins.
Vasoconstrictor peptides, such as angiotensin II (Ang II) and endothelin-1 (ET-1), stimulate the synthesis and release of vasodilatory prostaglandins from multiple tissues and diverse cellular types. The synthesis of PGE2 and PGI2 acts as a negative feedback loop to antagonize the contractile actions of Ang II and ET-1. Inhibition of prostaglandin synthesis with nonsteroidal anti-inflammatory drugs (NSAIDs) enhances the constrictor actions of Ang II and ET-1 on the vasculature of the kidney and on the glomerulus. The enhanced production of prostaglandins, in response to constrictor peptides, is both short- and long-term. Prostaglandin synthesis is regulated at multiple steps, including: (1) phospholipase A2, which releases arachidonic acid from membrane phospholipids; (2) PGH synthase (PGHS), which converts arachidonic acid to the endoperoxides PGG2 and PGH2; and (3) PG synthases convert the endoperoxides to PGI2, PGE2, and others. ET-1 acutely activates phospholipase A2 through phosphorylation and acute increases of intracellular calcium. ET-1 also chronically enhances phospholipase A2 activity by transcriptional induction of this enzyme. There are no known acute effects of ET-1 to acutely enhance PGHS activity through posttranslational modification of the molecule. Chronically, however, cellular content of PGHS-2 can be induced through transcriptional induction of the enzyme in response to ET-1. Hence, ET-1 short- and long-term activates a modulatory feedback pathway that depends on upregulation of arachidonic acid release through phospholipase A2 and enhanced synthesis of prostaglandin endoperoxides through PGHS-2.
Angiotensin II↗
Endothelin regulates PGE2 formation in rat mesangial cells through induction of prostaglandin endoperoxide synthase-2.
Endothelin-1 stimulates vascular smooth muscle and mesangial cells to release prostaglandin E2 which attenuates the vasoconstrictor and mitogenic effects of endothelin. The role of endothelin-1 to regulate prostaglandin endoperoxide synthase (PGHS)-1 and -2 gene expression and protein synthesis was evaluated in cultured mesangial cells. Endothelin induced mRNA and protein expression for PGHS-2 but not for PGHS-1. A direct correlation was observed between the mass of immunoprecipitated PGHS protein and PGE2 synthetic enzymatic activity.
Animals↗
Thrombin-mediated ET-1 gene regulation involves CaM kinases and calcineurin in human endothelial cells.
The preproendothelin-1 (preproET-1) gene is induced by thrombin after phosphorylation of nonreceptor protein tyrosine kinase pathways. This study investigated the contribution of Ca2+/calmodulin-dependent intracellular signaling cascades to this pathway and measured ET-1 mRNA levels by Northern blot analysis in human endothelial cells. Increased intracellular Ca2+ levels in response to Ca2+ ionophore or Ca2+ ATPase inhibitors tert-butylhydroquinone and thapsigargin mimicked thrombin actions on ET-1 mRNA induction. Thrombin-mediated activation of ET-1 mRNA was reduced by specific calmodulin antagonists W7 or calmidazolium and after inhibition of CaM kinase II by KN-62. Inhibition of calcium/calmodulin-dependent phosphatase calcineurin by cyclosporin A, however, stimulated ET-1 mRNA in human endothelial cells. Phosphotyrosine immunoblot assays show that calcium/calmodulin-dependent signaling pathways precede thrombin-induced tyrosine phosphorylation, and that the calcium/calmodulin-dependent phosphatase calcineurin also exerts its effects via activation of protein tyrosine kinases. These observations demonstrate that thrombin stimulates the preproET-1 gene in human endothelial cells through calcium-dependent activation of CaM kinase and protein tyrosine kinases, and that calcineurin may also participate in regulation of the prepro ET-1 gene.
Calcineurin↗
ET-1 and PDGF BB induce MEK mRNA and protein expression in mesangial cells.
To evaluate a possible mechanism for the chronic regulation of MAPK/ERK kinase-1 (MEK-1) and p42 mitogen-activated protein kinase (MAPK) we studied the long-term effects of the G-protein-coupled receptor agonist endothelin-1 (ET-1) and the protein tyrosine kinase-coupled receptor agonist platelet-derived growth factor BB (PDGF BB) on MEK-1 and p42 MAPK in glomerular mesangial cells (GMCs). ET-1 and PDGF BB led to a time-dependent increase in MEK-1 mRNA expression without altering p42 MAPK mRNA levels. The effect of ET-1 and PDGF BB on MEK-1 mRNA expression was maximal after 24 h (3.3-fold) or 6 h (2.9-fold). Furthermore, the effect of ET-1 and PDGF BB on MEK-1 mRNA expression was additive (4.2-fold after 6 h) and was inhibited by actinomycin D (5 micrograms/ml). Cycloheximide (10 micrograms/ml) inhibited MEK-1 mRNA induction but stimulated p42 MAPK mRNA expression in both the absence and the presence of ET-1 and/or PDGF BB. The ET-1 and PDGF BB-induced increase in MEK-1 mRNA was accompanied by sustained enhancement of both p45 MEK protein expression after 12 h and by elevation of p42 MAPK activity for up to 24 h. We conclude that, in GMCs, MEK-1 acts like a delayed-early gene, whereas p42 MAPK resembles an immediate-early gene. MEK-1 mRNA and protein levels, as well as p42 MAPK activity, can be chronically regulated by both a seven-transmembrane domain receptor-coupled peptide such as ET-1 and by an agonist binding to a receptor with intrinsic protein tyrosine kinase activity, such as PDGF BB.
Animals↗
Endothelin stimulates prostaglandin endoperoxide synthase-2 mRNA expression and protein synthesis through a tyrosine kinase-signaling pathway in rat mesangial cells.
We evaluated the role of endothelin-1 (ET-1), a vasoconstrictor peptide, to regulate prostaglandin endoperoxide synthase (PGHS)-1 and -2 gene expression and protein synthesis in cultured rat mesangial cells (MC). ET-1 induced mRNA for PGHS-2 but not PGHS-1 and also stimulated protein accumulation of PGHS-2 but not PGHS-1 in MC. ET-1 induction of PGHS-2 protein was accompanied by a sustained enhancement of enzymatic activity assessed by conversion of arachidonic acid to prostaglandin E2. The ET-1-stimulated PGHS-2 expression was reduced with protein tyrosine kinase but not with protein kinase C inhibitors or in protein kinase C-depleted cells. Both dexamethasone and heparin reduced ET-1-activated PGHS-2 mRNA expression and protein formation. We conclude that in MC, ET-1 induces PGHS-2 through a protein tyrosine kinase-dependent pathway.
Animals↗
Local production of cytokines in the human cardiac allograft. A sequential study.
The observations of 2 types of CD4+ T cells (Th1 and Th2), which can be distinguished by their different cytokine profiles, has led to the possibility that analysis of cytokine profiles produced locally within transplanted allografts could be predictive of rejection or acceptance of that graft. We have investigated the expression of IL-2 and TNF beta (Th1 type cytokines), IL-4 and IL-10 (Th2 type cytokines), and the proinflammatory cytokines TNF alpha and IL-1 beta in sequential endomyocardial biopsies collected from 12 cardiac transplant recipients during the first 4 months after transplantation, by the analysis of RNA extracted from each biopsy by reverse transcriptase-polymerase chain reaction. The results obtained were compared with histopathological and clinical indicators of rejection. IL-2 was found in all severe (grade 3), in 57% of moderate (grade 2), in 21% of mild (grade 1) rejection, and in only 1 nonrejection (subsequently progressing to grade 3), where rejection was classified by routine histology. IL-4 and IL-10 were absent from grade 3 rejection, but present in 24% (IL-4) and in 17% (IL-10) of mild rejection and in a single nonrejecting biopsy, respectively. IL-4 was found in 2 cases of moderate rejection, and IL-10 in 1 case of moderate rejection. Statistical analysis showed that the presence of IL-2 positively correlated with both mild and moderate rejection, while IL-4 correlated with mild rejection (P < or = 0.05). IL-1 beta, TNF alpha, and TNF beta were found in both rejecting and nonrejecting biopsies, with no significant differences between the histological grades. Our results suggest that in the human situation, IL-2 and IL-4 may indeed be important in the modulation of rejection.
Base Sequence↗
Endothelin-1 stimulates cytosolic phospholipase A2 in Chinese hamster ovary cells stably expressing the human ETA or ETB receptor subtype.
The ability of endothelin-1 (ET-1) to activate cytosolic phospholipase A2 (cPLA2) has been studied in Chinese Hamster ovary (CHO) cells stably expressing either the human ETA (CHO/ETA) or the human ETB (CHO/ETB) receptor subtype. ET-1 dose-dependently increased a dithiothreitol-insensitive cPLA2 activity in both cell types. In CHO/ETA cells, BQ-123, an ETA-selective antagonist, completely blocked ET-1-induced cPLA2 stimulation. In CHO/ETB cells, the ET-1 response was mimicked by 4AlaET-1 which could be blocked partially by PD 145065, a nonselective antagonist of ETA and ETB. As expected, ET-1 stimulated PGE2 synthesis in CHO cells transfected with ET receptors. We conclude that ET-1 can stimulate cPLA2 via both the human ETA and ETB receptor subtype.
Animals↗
The human myocardial two-dimensional gel protein database: update 1994.
An updated human heart protein two-dimensional electrophoresis (2-DE) database is presented. The database, which contains some 1388 protein spots characterised in terms of M(r) and pI, has been analysed further by Western immunoblotting and protein sequencing. From a total of 103 protein spots analysed, 49 have been identified by immunoblotting and 32 have been identified by protein sequencing. A further six proteins have tentatively been assigned by comparison with the human heart 2-DE protein database of Jungblut et al. (Electrophoresis) 1994, 15, 685-607). This database is being used in studies of alterations in protein expression in the diseased and transplanted human heart.
Amino Acid Sequence↗
PGE2 induces c-fos expression by a cAMP-independent mechanism in glomerular mesangial cells.
Prostanoids induce expression of several immediate-early genes, but the molecular mechanisms underlying these responses remain poorly characterized. We studied induction of the proto-oncogene c-fos by PGE2 in mesangial cells as a model of gene regulation by prostanoids. PGE2 induced marked and transient accumulation of c-fos mRNA. Addition of exogenous 8-bromo-cAMP or forskolin failed to induce c-fos mRNA, suggesting that activation of an EP2 receptor linked to adenylate cyclase did not account for induction of c-fos by PGE2. These data contrast with previous experiments in NIH 3T3 cells in which PGE2 induced c-fos by a cAMP-dependent mechanism. Depletion of protein kinase C blocked induction of c-fos mRNA by PGE2, whereas a protein tyrosine kinase inhibitor had no effect. We further showed that PGE2 induces the c-fos gene by increasing the transactivating capacity of the serum-response element. Transient transfections with a CAT fusion gene driven by an AP-1 cis-element demonstrated that although PGE2 markedly induced c-fos, PGE2 did not increase AP-1-driven transcriptional responses. Electrophoretic gel mobility shift assays revealed that PGE2 failed to increase binding of AP-1 complexes to a consensus AP-1 DNA sequence. Taken together, these experiments provide evidence for a cAMP-independent, protein kinase C-dependent pathway linking a PGE2 receptor on the plasma membrane to transcriptional activation in the nucleus. Regulation of gene transcription by PGE2 probably involves c-fos induction without concomitant activation of AP-1.
8-Bromo Cyclic Adenosine Monophosphate↗
Induction of heat-shock proteins enhances myocardial and endothelial functional recovery after prolonged cardioplegic arrest.
The aim of this study was to investigate the role of heat-shock proteins after heat-shock stress on the post-ischemic recovery of cardiac mechanical and endothelial function following a prolonged cardiac arrest. Isolated working rat hearts were subjected to a cardioplegic arrest for 4 hours at 4 degrees C. Three groups (n = 8 in each) were studied: (1) control, (2) sham-treated, and (3) heat-shocked rats. Postischemic recovery of cardiac output and endothelial function (as percent of preischemic control values) was 57.8% +/- 2.8% and 20.8% +/- 3.9% in group 1, 50.9% +/- 4.0% and 26.3% +/- 5.9% in group 2, and 74.0% +/- 2.4% and 51.2% +/- 8.0% in group 3, respectively. Both postischemic myocardial and endothelial function were improved by heat stress.
Animals↗
Use of indirect immunofluorescence and western blotting to assess the role of circulating antimyocardial antibodies in dogs with dilated cardiomyopathy.
The presence of circulating anti-heart IgG and IgM autoantibodies was assessed by indirect immunofluorescence and by probing Western blot transfers of normal canine myocardial proteins separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis with samples of sera from dogs with dilated cardiomyopathy (n = 27) and from healthy control dogs (n = 20). No difference was demonstrated between the two groups using either method. Sera taken from the affected dogs at three monthly intervals throughout the course of the disease showed no change at all in the pattern of reactivity. The results of this study suggest that indirect immunofluorescence and the probing of Western blot transfers of a crude preparation of normal canine myocardium with canine sera will demonstrate too many apparent autoantigens for the technique to identify unique, disease-associated autoantibodies.
Animals↗
Characterization of platelet-activating factor synthesis in glomerular endothelial cell lines.
Platelet-activating factor synthesis in two transformed lines of glomerular endothelial cells was characterized and contrasted with platelet-activating factor production in macrovascular-derived endothelial cells as well as with glomerular cells of mesenchymal origin. Platelet-activating factor synthesis was assessed in intact cells and in cell-free preparations. Glomerular endothelial cells constitutively synthesize bio-active alkyl-PAF, and this basal activity can be chronically augmented by various inflammatory and thrombotic agents. In contrast, thrombin-mediated platelet-activating factor formation in bovine pulmonary aortic endothelial cells as well as in glomerular mesangial cells is acute and transient. The potential role of anti-inflammatory prostanoids to function as negative feedback modulators of thrombin- or endothelin-mediated platelet-activating factor synthesis was also investigated, as the synthesis of platelet-activating factor is often associated with the formation of these prostanoids. Indomethacin augmented receptor-mediated platelet-activating factor synthesis while prostanoids of the E and I series reduced agonist-stimulated PAF synthesis. In summary, the unique capacity of glomerular endothelial cells to respond to inflammatory stimuli with sustained platelet-activating factor synthesis is a clear indication of this cell's pivotal role in augmenting the inflammatory response in the limited environment of the glomerulus.
1-Alkyl-2-acetylglycerophosphocholine Esterase↗
Renal actions of endothelin: linking cellular signaling pathways to kidney disease.
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Animals↗
Endothelin-1 stimulates cytosolic phospholipase A2 activity and gene expression in rat glomerular mesangial cells.
Endothelin-1 (ET-1) stimulates vascular smooth muscle and mesangial cells to release prostaglandin E2 (PGE2), which can attenuate the vasoconstrictor and mitogenic effects of this peptide. Phospholipase A2 (PLA2)-mediated release of arachidonic acid from the sn-2 position of membrane phospholipids is thought to be one of the rate-limiting steps in prostaglandin (PG) synthesis. We evaluated the role of ET-1 to regulate gene expression, protein synthesis and enzymatic activity of cytosolic PLA2 (cPLA2), an intracellular form of the PLA2 enzyme family, in cultured rat mesangial cells using both acute and chronic incubation protocols. Acute ET-1-induced stimulation of cPLA2 activity was maximal after 10 minutes (181.1 +/- 6.84% of control), persisted for 40 minutes and did not require new protein synthesis. Heparin, a potent inhibitor of intracellular Ca2+ increase as well as mitogen-activated protein (MAP) kinase activation and cell proliferation, did not affect the rapid cPLA2 stimulation by ET-1. Chronic incubation of glomerular mesangial cells with ET-1 (1 to 24 hr) led to time- and dose-dependent increases in cPLA2 mRNA expression which was maximal after six hours, persisted up to 24 hours and which was accompanied by both cPLA2 protein formation, as assessed by Western analysis, as well as by stimulation of enzymatic activity. Inhibition of protein synthesis by cycloheximide increased basal cPLA2 mRNA accumulation in quiescent mesangial cells, and the combination of ET-1 and cycloheximide resulted in a greater induction of cPLA2 gene expression when compared to ET-1 alone. Actinomycin D treatment blocked the effect of ET-1 on cPLA2 mRNA accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Endothelins stimulate mitogen-activated protein kinase cascade through either ETA or ETB.
Endothelin (ET) has been shown to activate mitogen-activated protein kinase (MAPK). However, it has been unclear which of the ET receptors is coupled to MAPK activation. In the present study, we conducted experiments to determine which ET receptor is linked to MAPK activation. We found that both human ETA and ETB were coupled to the MAPK cascade in ETA or ETB cDNA-transfected Chinese hamster ovary cells. ET-1 was more potent than ET-3 in the activation of p42 MAPK, induction of MAPK kinase (MAPKK) gel retardation and uptake of [3H]thymidine in ETA-transfected cells, whereas sarafotoxin (S6c) showed no stimulatory effect on the kinases and [3H]thymidine uptake. ET-1, ET-3, and S6c had approximately the same potency to activate p42 MAPK, MAPKK gel retardation, and [3H]thymidine uptake in ETB-transfected cells. These data suggest that 1) ET isopeptides, through either ETA or ETB receptors, induce the MAPK cascade as well as cell proliferation; and 2) the different potencies of ET isopeptides for activation of the MAPK cascade and induction of cell growth are mainly due to their different affinities toward ETA and ETB.
Animals↗
Causes of admissions of rural African patients to Murchison Hospital, Natal, South Africa.
An analysis has been made of causes of admission of black patients in 1991 to Murchison Hospital, Port Shepstone, Natal. Of 6675 total admissions, 6329 (95%) were classifiable. Of the latter, 1462 (23%) were aged 12 years and-younger, namely, 763 boys and 699 girls. Their chief causes of admission were pneumonia, gastroenteritis, trauma, acute glomerular nephritis, and malnutritional diseases. Of 4867 adults (73%), 1536 were males and 3331 females. Among men, chief causes were tuberculosis, congestive cardiac failure, hypertension and cerebral vascular accidents. Among women, apart from pregnancy, chief causes of admission were disorders of pregnancy, tuberculosis, congestive cardiac failure, pneumonia, diabetes, and hypertension. Of western diseases, 3.9% of adults were admitted for diabetes, and 2.8% for asthma. The general pattern of admissions is similar to that in other rural hospitals. The causes of admissions are discussed, regarding (1) public health improvements occurring, and (2) means of promoting further improvements by (a) community self-help, and (b) help from State health and other services.
Adult↗