Activities of enzymes in platelet activating factor biosynthetic pathways in the gerbil model of cerebral ischemia

1996 ◽  
Vol 74 (3) ◽  
pp. 347-354 ◽  
Author(s):  
Andre Siegel ◽  
R. Roy Baker
Keyword(s):  
Cerebral Ischemia ◽  
Enzyme Activities ◽  
De Novo ◽  
Platelet Activating Factor ◽  
Atp Depletion ◽  
In Vitro Assays ◽  
Transferase Activity ◽  
Biosynthetic Pathways ◽  
Bilateral Carotid ◽  
Choline Phosphotransferase

The activities of enzymes in platelet activating factor (PAF) biosynthetic pathways were analyzed in hippocampal and cerebral cortical regions of normal and ischemic gerbil brain to assess changes in enzyme activities and potential modulators that could explain the accentuated production of PAF seen in ischemia. Global forebrain ischemia was produced by bilateral carotid artery ligation, and the effectiveness of the ligation was shown by free fatty acid release and ATP depletion. Specific activities of 1-alkyl-2-acetyl-sn-glycerol (AAG) choline phosphotransferase, 1-alkyl-sn-glycero-3-phosphate (AGP) acetyl transferase, and 1-alkyl-sn-glycero-3-phosphocholine (lyso PAF) acetyl transferase in tissue homogenates were in the ratio 4:1:0.1, respectively. Sham-operated and ischemic or ischemic–reperfused tissues showed similar activities for individual enzymes, indicating that enzyme levels or activation states did not change in ischemic or reperfused tissues. However, small metabolites (relevant to ischemia) added to the in vitro assays did modify enzyme activities. Physiological concentrations of MgATP severely inhibited AGP acetyl transferase activity, and this resulted in the ratio of AGP acyl transferase to AGP acetyl transferase activities changing from 48:1 in the presence of 2.5 mM MgATP to 6:1 in the absence of MgATP. This suggests that falling ATP levels in cerebral ischemia may promote the de novo pathway of PAF biosynthesis by releasing inhibition of AGP acetyl transferase. Lyso PAF acetyl transferase was much less active than AGP acetyl transferase and was also inhibited by MgATP. AAG choline phosphotransferase was not inhibited by MgATP but was inhibited by calcium. However the superior specific activity of the choline phosphotransferase in comparison with the AGP acetyl transferase suggested that the lowered choline phosphotransferase activity in the presence of rising intracellular calcium would not seriously compromise the synthesis of PAF by the de novo route. Both acetyl transferase enzymes were also inhibited by oleoyl CoA.Key words: gerbil, cerebral ischemia, platelet activating factor, enzymes.

scholarly journals Σπειραματικά επίπεδα και προέλευση του παράγοντα ενεργοποίησης των αιμοπεταλίων (PAF) στην πειραματική σπειραματονεφρίτιδα

1990 ◽  
Author(s):  
Αντώνιος Ζάγκλης
Keyword(s):  
De Novo ◽  
Mesangial Cells ◽  
Rat Kidney ◽  
Platelet Activating Factor ◽  
Cell Types ◽  
Transferase Activity ◽  
Polymorphonuclear Leucocytes ◽  
Alkyl Ether ◽  
Nephrotoxic Serum Nephritis ◽  
Dependent Model

The renal glomerulus and its various cell types (i.e. mesangial cells, endothelial cells) have been shown to synthesize compounds with autacoid and proinflammatory effects. [97,98] The spectrum of proinflammatory compounds of glomerular origin has recently expanded to include the alkyl ether glycerophospholipids, including 1-O-alkyl-2- acetyl-sn- glycero-3- phosphorylcholine, which is structurally identical with platelet activating factor (PAF).This compound can induce platelet and neutrophil aggregation and chemokinesis, vasodilation, increased vascular permeability and stimulation of eicosanoid production. We have demonstrated that PAF can be both synthesized and degraded in isolated glomeruli and in mesangial cells, [7,99] the latter being also capable of de novo synthesis of PAF precursors. Recent observations indicate that PAF receptor antagonism ameliorates glomerular inflammation in rabbit nephrotoxic serum nephritis, as well as the glomerular inflammatory injury induced by in situ formation of immune complexes in the rat kidney with experimental passive reverse Arthus reaction. [100,101] The present study was undertaken in order to assess the levels and cellular sources of glomerular PAF in glomeruli isolated from rats with: 1) Nephrotoxic serum nephritis, an infiltrative and complement dependent model of immune injury and 2) passive Heymann nephritis a non- infiltrative but complement dependent model. The role of complement, platelets and polymorphonuclear leucocytes was assessed. The observation that mesangial cells is the main source of PAF production in the rat glomerulus, prompted the assessment of the effect of various inflammatory mediators on the acetyl-transferase activity of the mesangial cells. […]

scholarly journals Cerebral Ischemia after Bilateral Carotid Artery Occlusion and Intraluminal Suture Occlusion in Mice: Evaluation of the Patency of the Posterior Communicating Artery

1998 ◽  
Vol 18 (5) ◽  
pp. 570-579 ◽  
Author(s):  
Kazuo Kitagawa ◽  
Masayasu Matsumoto ◽  
Gongming Yang ◽  
Takuma Mabuchi ◽  
Yoshiki Yagita ◽  
...  
Keyword(s):  
Cerebral Ischemia ◽  
Carotid Artery ◽  
Neuronal Death ◽  
Transgenic Animals ◽  
Artery Occlusion ◽  
Atp Depletion ◽  
Mouse Strains ◽  
Doppler Flowmetry ◽  
Bilateral Carotid ◽  
Intracranial Vasculature

Cerebral ischemia models using mice have drawn increasing attention, particularly because of the availability of transgenic animals. However, the variability of intracranial vasculature at the circle of Willis in mice can influence the degree of ischemia in both the bilateral common carotid artery (CCA) occlusion and intraluminal suture occlusion models. We have developed a method to predict the extent of the anastomosis between carotid and vertebrobasilar circulation in three mouse strains (C57BL/6, CBA, and DBA/2) by measuring cortical microperfusion with laser Doppler flowmetry during a 1-minute occlusion of both CCA. When animals showed residual cortical microperfusion of less than 12% during bilateral CCA occlusion, the mice showed absence of functional anastomosis, developed ATP depletion in the frontal cortex during occlusion, and had ischemic neuronal death in the hippocampus and caudoputamen after occlusion for 15 minutes and recirculation for 7 days. Furthermore, those mice exhibited decreased local cerebral blood flow and associated ischemic neuronal death in the hippocampus, within the territory supplied by the posterior cerebral artery, with the intraluminal suture occlusion model. The current study demonstrates the need for assessment of intracranial vasculature in each animal by measuring cortical microperfusion during temporary occlusion of both CCA, no matter whether cerebral ischemia is produced by bilateral CCA occlusion or intraluminal suture occlusion in transgenic mice.

Platelet-activating factor and the kidney

1986 ◽  
Vol 251 (1) ◽  
pp. F1-F11 ◽  
Author(s):  
D. Schlondorff ◽  
R. Neuwirth
Keyword(s):  
De Novo ◽  
Mesangial Cells ◽  
Biological Activities ◽  
Platelet Activating Factor ◽  
Calcium Ionophore ◽  
Initial Step ◽  
Renal Physiology ◽  
Dependent Manner ◽  
Glomerular Mesangial Cells ◽  
Isolated Kidney

Platelet-activating factor (PAF) represents a group of phospholipids with the basic structure of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine. A number of different cells are capable of producing PAF in response to various stimuli. The initial step of PAF formation is activation of phospholipase A2 in a calcium-dependent manner, yielding lyso-PAF. During this step arachidonic acid is also released and can be converted to its respective cyclooxygenase and lipoxygenase products. The lyso-PAF generated is then acetylated in position 2 of the glycerol backbone by a coenzyme A (CoA)-dependent acetyltransferase. An additional pathway may exist whereby PAF is generated de novo from 1-alkyl-2-acetyl-sn-glycerol by phosphocholine transferase. PAF inactivation in cells and blood is by specific acetylhydrolases. PAF exhibits a variety of biological activities including platelet and leukocyte aggregation and activation, increased vascular permeability, respiratory distress, decreased cardiac output, and hypotension. In the kidney PAF can produce decreases in blood flow, glomerular filtration, and fluid and electrolyte excretion. Intrarenal artery injection of PAF may also result in glomerular accumulation of platelets and leukocytes and mild proteinuria. PAF increases prostaglandin formation in the isolated kidney and in cultured glomerular mesangial cells. PAF also causes contraction of mesangial cells. Upon stimulation with calcium ionophore the isolated kidney, isolated glomeruli and medullary cells, and cultured mesangial cells are capable of producing PAF. The potential role for PAF in renal physiology and pathophysiology requires further investigation that may be complicated by 1) the multiple interactions of PAF, prostaglandins, and leukotrienes and 2) the autocoid nature of PAF, which may restrict its action to its site of generation.

scholarly journals A Model of Global Cerebral Ischemia in C57 BL/6 Mice

2004 ◽  
Vol 24 (2) ◽  
pp. 151-158 ◽  
Author(s):  
Ichiro Yonekura ◽  
Nobutaka Kawahara ◽  
Hirofumi Nakatomi ◽  
Kazuhide Furuya ◽  
Takaaki Kirino
Keyword(s):  
Cerebral Ischemia ◽  
Genetic Background ◽  
Neuronal Degeneration ◽  
Neuronal Damage ◽  
Neuronal Injury ◽  
Genetically Engineered ◽  
Global Cerebral Ischemia ◽  
Vessel Occlusion ◽  
Bilateral Carotid ◽  
The Mean

A reproducible model of global cerebral ischemia in mice is essential for elucidating the molecular mechanism of ischemic neuronal injury. Such a model is particularly important in the mouse because many genetically engineered mutant animals are available. In C57BL/6 and SV129/EMS mice, we evaluated a three-vessel occlusion model. Occlusion of the basilar artery with a miniature clip was followed by bilateral carotid occlusion. The mean cortical cerebral blood flow was reduced to less than 10% of the preischemic value, and the mean anoxic depolarization was attained within 1 minute. In C57BL/6 mice, there was CA1 hippocampal neuronal degeneration 4 days after ischemia. Neuronal damage depended upon ischemic duration: the surviving neuronal count was 78.5 ± 8.5% after 8-minute ischemia and 8.4 ± 12.7% after 14-minute ischemia. In SV129/EMS mice, similar neuronal degeneration was not observed after 14-minute ischemia. The global ischemia model in C57BL/6 mice showed high reproducibility and consistent neuronal injury in the CA1 sector, indicating that comparison of ischemic outcome between wild-type and mutant mice could provide meaningful data using the C57BL/6 genetic background. Strain differences in this study highlight the need for consideration of genetic background when evaluating ischemia experiments in mice.

scholarly journals Elucidating genes involved in sesquiterpenoid and flavonoid biosynthetic pathways in Saussurea lappa by de novo leaf transcriptome analysis

Genomics ◽  
2019 ◽  
Vol 111 (6) ◽  
pp. 1474-1482 ◽  
Author(s):  
Savita Bains ◽  
Vasundhara Thakur ◽  
Jagdeep Kaur ◽  
Kashmir Singh ◽  
Ravneet Kaur
Keyword(s):  
Transcriptome Analysis ◽  
De Novo ◽  
Biosynthetic Pathways ◽  
Saussurea Lappa ◽  
Leaf Transcriptome

scholarly journals ATP-dependent release of glucocorticoid receptors from the nuclear matrix.

1996 ◽  
Vol 16 (5) ◽  
pp. 1989-2001 ◽  
Author(s):  
Y Tang ◽  
D B DeFranco
Keyword(s):  
Nuclear Receptors ◽  
Nuclear Matrix ◽  
Nuclear Export ◽  
Glucocorticoid Receptors ◽  
De Novo ◽  
Steroid Receptors ◽  
Simian Virus 40 ◽  
Atp Depletion ◽  
Nuclear Proteins ◽  
The Matrix

Glucocorticoid receptors (GRs) have the capacity to shuttle between the nuclear and cytoplasmic compartments, sharing that trait with other steroid receptors and unrelated nuclear proteins of diverse function. Although nuclear import of steroid receptors, like that of nearly all other karyophilic proteins examined to date, requires ATP, there appear to be different energetic requirements for export of proteins, including steroid receptors, from nuclei. In an attempt to reveal which steps, if any, in the nuclear export pathway utilized by steroid receptors require ATP, we have used indirect immunofluorescence to visualize GRs within cells subjected to a reversible ATP depletion. Under conditions which lead to >95% depletion of cellular ATP levels within 90 min, GRs remain localized within nuclei and do not efflux into the cytoplasm. Under analogous conditions of ATP depletion, transfected progesterone receptors are also retained within nuclei. Importantly, GRs which accumulate within nuclei of ATP-depleted cells are distinguished from nuclear receptors in metabolically active cells by their resistance to in situ extraction with a hypotonic, detergent-containing buffer. GRs in ATP-depleted cells are not permanently trapped in this nuclear compartment, as nuclear receptors rapidly regain their capacity to be extracted upon restoration of cellular ATP, even in the absence of de novo protein synthesis. More extensive extraction of cells with high salt and detergent, coupled with DNase I digestion, established that a significant fraction of GRs in ATP-depleted cells are associated with an RNA-containing nuclear matrix. Quantitative Western blot (immunoblot) analysis confirmed the dramatic increase in GR binding to the nuclear matrix of ATP-depleted cells, while confocal microscopy revealed that GRs are bound to the matrix throughout all planes of the nucleus. ATP depletion does not lead to wholesale collapse of nuclear proteins onto the matrix, as the interaction of a subpopulation of simian virus 40 large tumor antigen with the nuclear matrix is not quantitatively altered in ATP-depleted Cos-1 cells. Nuclear GRs which are not bound to the nuclear matrix of metabolically active cells (i.e., a DNA-binding domain deletion mutant and a beta-galactosidase chimera possessing the GR nuclear localization signal sequence) are not recruited to the matrix upon depletion of cellular ATP. Thus, it appears that ATP depletion does not expose the GR to nuclear matrix interactions which are not normally encountered in cells but merely alters the dynamics of such interactions. The dynamic association of steroid receptors with the nuclear matrix may provide a mechanism which is utilized by these regulable transcription factors to facilitate their efficient scanning of the genome.

scholarly journals Trehalose recycling promotes energy-efficient mycomembrane reorganization in nutrient-limited mycobacteria

2019 ◽  
Author(s):  
Amol Arunrao Pohane ◽  
Caleb R. Carr ◽  
Jaishree Garhyan ◽  
Benjamin M. Swarts ◽  
M. Sloan Siegrist
Keyword(s):  
Energy Efficient ◽  
De Novo ◽  
Cell Envelope ◽  
Bacterial Pathogens ◽  
Atp Depletion ◽  
Redox Stress ◽  
Mycobacterial Cell ◽  
Resource Limited ◽  
Trehalose Synthesis ◽  
Long Chain

AbstractThe mycomembrane layer of the mycobacterial cell envelope is a barrier to environmental, immune and antibiotic insults. We find that there is mycomembrane remodeling along the periphery of nutrient-starved, non-replicating mycobacterial cells. Remodeling is supported by recycling of trehalose, a non-mammalian disaccharide that shuttles long-chain mycolate lipids to the mycomembrane. In the absence of trehalose recycling, mycomembrane synthesis continues but mycobacteria experience ATP depletion, enhanced respiration and redox stress. Redox stress from depletion of the trehalose pool is suppressed in a mutant that lacks the OtsAB de novo trehalose synthesis pathway. Our data suggest that trehalose recycling alleviates the energetic burden of mycomembrane remodeling. Loss of trehalose salvage is known to attenuate M. tuberculosis during infection and render the bacterium more susceptible to a variety of drugs. Recycling pathways are emerging targets for sensitizing resource-limited bacterial pathogens to host and antibiotic stress.

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