Prostaglandin E2 and muscle proteolysis: effect of burn injury and cycloheximide

Rats were subjected to a single hindlimb scald, and 3 days later soleus muscles from the burned and contralateral unburned hindlimbs were studied in vitro. Burned limb muscle released 354% more prostaglandin E2 (PGE2) and 119% more tyrosine than the contralateral uninjured counterpart. Neither the rate of net proteolysis in the uninjured muscle nor the stimulated net proteolysis in the burned limb muscle could be reduced by 90% inhibition of PGE2 production with aspirin or indomethacin. Inhibition of tissue protein synthesis with 5 X 10(-5) M cycloheximide stimulated tyrosine release by soleus muscles of both hindlimbs, but the increment in the burned limb muscle was 167% greater than in the contralateral uninjured counterpart. Concomitantly, cycloheximide decreased PGE2 releases by injured and uninjured muscles 90 and 73%, respectively. This previously unrecognized action of cycloheximide was investigated in soleus muscles of normal uninjured rats. It was found that 1 X 10(-6) M cycloheximide produces a 70% inhibition of muscle PGE2 release and increasing the concentration of inhibitor up to 500-fold does not further decrease PGE2 production. Cycloheximide acts by reducing the availability of endogenous arachidonic acid for PGE2 synthesis.

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Phospholipids, prostaglandin E2, and proteolysis in denervated muscle

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.251.1.r165 ◽

1986 ◽

Vol 251 (1) ◽

pp. R165-R173 ◽

Cited By ~ 1

Author(s):

J. Turinsky

Keyword(s):

Protein Synthesis ◽

Prostaglandin E2 ◽

Pge2 Production ◽

Nerve Transection ◽

Denervated Muscle ◽

Sciatic Nerve Transection ◽

Tissue Protein ◽

Pge2 Release ◽

Denervated Muscles

Soleus muscles of rats were studied up to 16 days after sciatic nerve transection. At the end of this period the denervated soleus muscles exhibited decreased content of diphosphatidylglycerol (-44%), normal level of phosphatidylethanolamine, and increased contents of phosphatidylcholine (+24%), sphingomyelin (+48%), lysophosphatidylcholine (+110%), phosphatidylinositol (+37%), and phosphatidylserine (+40%) per milligram of tissue protein. In studies in vitro, prostaglandin E2 (PGE2) release and tyrosine release by denervated soleus muscles were 319 and 141%, respectively, greater than those of sham muscles. An almost complete inhibition of PGE2 release with 5 X 10(-4) M aspirin or 2.8 X 10(-6) M indomethacin had no effect on tyrosine release of sham muscles or the stimulated tyrosine release of the denervated muscles. Addition of 5 X 10(-5) M cycloheximide in the medium resulted in 63% inhibition of PGE2 release by both groups of muscles; concomitant absolute increments in tyrosine releases by denervated and sham muscles did not statistically differ. In the presence of both 5 X 10(-5) M cycloheximide and 5 X 10(-4) M aspirin in the medium, PGE2 production by denervated and sham muscles was inhibited 87% while tyrosine release of denervated muscles was 108% higher than that of sham animals. It is concluded that 1) atrophy of denervated soleus muscle is associated with stimulated activity of tissue phospholipase A2, increased production of prostaglandin E2, increased total proteolytic rate, and unchanged rate of protein synthesis; 2) acute inhibition of PGE2 production does not inhibit the stimulated proteolysis in denervated muscle; and 3) cycloheximide inhibits PGE2 production by muscle.

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Effects of atrial natriuretic peptide on renal medullary prostaglandin E2 production

AJP Renal Physiology ◽

10.1152/ajprenal.1989.257.3.f336 ◽

1989 ◽

Vol 257 (3) ◽

pp. F336-F340

Author(s):

R. J. Bolterman ◽

M. D. Bentley ◽

S. M. Sandberg ◽

M. J. Fiksen-Olsen ◽

J. C. Romero

Keyword(s):

Arachidonic Acid ◽

Atrial Natriuretic Peptide ◽

Prostaglandin E2 ◽

Natriuretic Peptide ◽

Inhibitory Effect ◽

Pge2 Production ◽

In Vitro Effects ◽

Different Doses ◽

Atrial Natriuretic

Like arachidonic acid (AA) and bradykinin (BK), the intrarenal administration of atrial natriuretic peptide (ANP) has been shown to increase the urinary excretion of prostaglandin E2 (PGE2). In the present study, the direct in vitro effects of ANP on PGE2 production were compared with those of AA and BK. Canine renal inner medullary slices were preincubated for 30 min and washed in aerated Krebs-Ringer buffer (37 degrees C). During the final incubation period, with the use of varied concentrations of AA, BK, or ANP in Krebs-Ringer buffer, samples were obtained at 0 and 30 min to be used for radioimmunoassay of PGE2. Although the rate of PGE2 production was significantly increased 11-fold with AA and threefold with BK, it was unaffected by four different doses of ANP (10(-5) to 10(-11) M). Furthermore, the production of PGE2 during basal and stimulated (BK or AA) conditions was significantly blocked by indomethacin but not by ANP. These results indicate that ANP had no direct stimulatory or inhibitory effect on the medullary production of PGE2.

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Synthesis of prostaglandin E2 in different segments of isolated collecting tubules from adult and neonatal rabbits

AJP Renal Physiology ◽

10.1152/ajprenal.1985.248.1.f134 ◽

1985 ◽

Vol 248 (1) ◽

pp. F134-F144 ◽

Cited By ~ 3

Author(s):

D. Schlondorff ◽

J. A. Satriano ◽

G. J. Schwartz

Keyword(s):

Arachidonic Acid ◽

Prostaglandin E2 ◽

Feedback Loop ◽

Pge2 Production ◽

Large Variability ◽

Pge2 Synthesis ◽

Collecting Tubule ◽

Concentrate Urine ◽

Collecting Tubules

Prostaglandin E2 (PGE2) inhibits the action of the antidiuretic hormone (ADH) in isolated collecting tubules. A negative feedback loop has been postulated whereby ADH stimulates PGE2 synthesis. Furthermore, lysyl-bradykinin (LBK) inhibits the antidiuretic effect of ADH, probably via PGE2. Enhanced PGE2 synthesis has also been implicated as contributing to the inability to maximally concentrate urine during the neonatal period. We investigated PGE2 synthesis in microdissected cortical (CCT), medullary (MCT), and branched cortical (BCT) collecting tubules from adult and in corticomedullary collecting tubules (CT) from newborn rabbits. Isolated BCT produced significantly less PGE2 (12 +/- 2 pg X mm-1 X 20 min-1) than CCT (65 +/- 9) or MCT (76 +/- 8) from kidneys of adult rabbits. CT from newborn rabbits produced only 19 +/- 3 pg/mm, significantly less than either CCT or MCT from adults. A large variability in basal PGE2 production and hormonal response was observed from tubule to tubule. Under either basal conditions or in the presence of 2 microM arachidonic acid, LBK enhanced PGE2 synthesis in CCT and MCT from adults. ADH enhanced PGE2 production in MCT under basal conditions and in CCT in the presence of arachidonic acid. Neither LBK nor ADH stimulated PGE2 synthesis in neonatal CT. A23187 consistently stimulated PGE2 synthesis in CCT and MCT from adults and, to a lesser extent, in CT from newborn rabbits. Our results support the hypothesis that ADH and LBK enhance PGE2 synthesis in the collecting tubule. This response is, however, subject to large variations from tubule to tubule and depends on the in vitro incubation conditions.

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Cyclic Mechanical Stretching Induces Autophagic Cell Death in Tenofibroblasts Through Activation of Prostaglandin E2 Production

Cellular Physiology and Biochemistry ◽

10.1159/000374050 ◽

2015 ◽

Vol 36 (1) ◽

pp. 24-33 ◽

Cited By ~ 15

Author(s):

Hua Chen ◽

Liyang Chen ◽

Biao Cheng ◽

Chaoyin Jiang

Keyword(s):

Cell Death ◽

Prostaglandin E2 ◽

Underlying Mechanism ◽

Autophagic Cell Death ◽

Pge2 Production ◽

Dependent Manner ◽

Small Interfering Rnas ◽

Pge2 Release ◽

Mechanical Stretching

Background/Aims: Autophagic cell death has recently been implicated in the pathophysiology of tendinopathy. Prostaglandin E2 (PGE2), a known inflammatory mediator of tendinitis, inhibits tenofibroblast proliferation in vitro; however, the underlying mechanism is unclear. The present study investigated the relationship between PGE2 production and autophagic cell death in mechanically loaded human patellar tendon fibroblasts (HPTFs) in vitro. Methods: Cultured HPTFs were subjected to exogenous PGE2 treatment or repetitive cyclic mechanical stretching. Cell death was determined by flow cytometry with acridine orange/ethidium bromide staining. Induction of autophagy was assessed by autophagy markers including the formation of autophagosomes and autolysosomes (by electron microscopy, AO staining, and formation of GPF-LC3-labeled vacuoles) and the expression of LC3-II and BECN1 (by western blot). Stretching-induced PGE2 release was determined by ELISA. Results: Exogenous PGE2 significantly induced cell death and autophagy in HPTFs in a dose-dependent manner. Blocking autophagy using inhibitors 3-methyladenine and chloroquine, or small interfering RNAs against autophagy genes Becn-1 and Atg-5 prevented PGE2-induced cell death. Cyclic mechanical stretching at 8% and 12% magnitudes for 24 h significantly stimulated PGE2 release by HPTFs in a magnitude-dependent manner. In addition, mechanical stretching induced autophagy and cell death. Blocking PGE2 production using COX inhibitors indomethacin and celecoxib significantly reduced stretching-induced autophagy and cell death. Conclusion: Taken together, cyclic mechanical stretching induces autophagic cell death in tenofibroblasts through activation of PGE2 production.

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Modulation of prostaglandin E2 synthesis in rat skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.262.4.e476 ◽

1992 ◽

Vol 262 (4) ◽

pp. E476-E482 ◽

Cited By ~ 1

Author(s):

J. Turinsky ◽

D. M. O'Sullivan ◽

B. P. Bayly

Keyword(s):

Protein Synthesis ◽

Prostaglandin E2 ◽

Muscle Denervation ◽

Protein Synthesis Inhibitors ◽

Rat Skeletal Muscle ◽

Sham Control ◽

Pge2 Release ◽

Rat Soleus Muscle ◽

Denervated Muscles

The effect of muscle denervation, inhibitors of protein synthesis, G proteins, and sphingolipids on prostaglandin E2 (PGE2) release by rat soleus muscle in vitro was investigated. To assess the effect of muscle denervation, the sciatic nerve in one hindlimb of rats was interrupted, and soleus muscles from the denervated hindlimb and the contralateral sham (control) hindlimb were excised 1-5 days after surgery. Compared with corresponding sham muscles, PGE2 release by denervated muscles was increased 56, 230, and 435% at 1, 3, and 5 days after denervation, respectively. Protein synthesis inhibitors cycloheximide (10 microM) and puromycin (10 microM) lowered PGE2 release by sham and denervated muscles 62-80%. The release of PGE2 by sham and denervated muscles was not altered by pertussis toxin (1 microgram/ml) but was inhibited 30-51% by AlF4-. Addition of 100 microM guanosine 5'-O-(3-thiotriphosphate) to saponin-permeabilized sham and denervated muscles had only a moderate, if any, stimulatory effect on PGE2 release. This effect was not counteracted by 1 mM guanosine 5'-O-(2-thiodiphosphate). Increasing muscle ceramide concentration by incubation with sphingomyelinase (100 mU/ml) increased PGE2 release by sham and denervated muscles 43 and 157%, respectively. Because degradation of ceramides yields sphingosine, the effect of sphingosine was also tested. Sphingosine (25 microM) increased PGE2 release by sham and denervated muscles 139 and 187%, respectively, without affecting muscle viability, as assessed by the release of lactate dehydrogenase. The data indicate that muscle denervation, treatment with sphingomyelinase, and sphingosine stimulate, whereas inhibitors of protein synthesis inhibit PGE2 synthesis by muscle.

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Ornithine alpha-ketoglutarate modulates tissue protein metabolism in burn-injured rats.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1997.273.3.e557 ◽

1997 ◽

Vol 273 (3) ◽

pp. E557 ◽

Cited By ~ 3

Author(s):

J Le Boucher ◽

C Obled ◽

M C Farges ◽

L Cynober

Keyword(s):

Protein Synthesis ◽

Burn Injury ◽

Tissue Level ◽

Whole Body ◽

Synthesis Rate ◽

Total Protein Content ◽

Tissue Protein ◽

Male Wistar Rats ◽

Ad Libitum

Enterally administered ornithine alpha-ketoglutarate (OKG) displays whole body anabolic and anticatabolic properties in trauma situations, especially after burn injury. The aim of this study was to get information about the anabolic effect of OKG at tissue level. Thirty-six male Wistar rats (95 +/- 7 g) were allocated to four groups. Eighteen rats were burned by water (20% body surface area). After a 24-h fast (day 0-day 1), rats were enterally refed for 48 h (day 1-day 3) by use of Osmolite as a low-calorie, low-nitrogen regimen supplemented with either 5 g OKG.kg-1.day-1 (B-OKG) or an equivalent amount of nitrogen in the form of glycine (B-Gly). Nonburned pair-fed controls treated with glycine (C-Gly) and healthy rats fed ad libitum were also studied. On day 3, protein synthesis rates (large dose method), free glutamine concentrations, and total protein content were assessed in tissues. Myofibrillar degradation was assessed by measuring urinary 3-methylhistidine excretion daily from day 0 to day 3. With regard to tissue protein synthesis rates, we demonstrate for the first time that OKG displays anabolic properties in the jejunum [fractional synthesis rate (FSR) in %/day, ad libitum = 101.9 +/- 4.0; C-Gly = 84.7 +/- 3.1, P < 0.01 vs. ad libitum; B-Gly = 84.5 +/- 1.6, P < 0.01 vs. ad libitum; B-OKG = 97.5 +/- 3.2, P < 0.05 vs. C-Gly and B-Gly] as well as in the liver (FSR in %/day, ad libitum = 75.9 +/- 3.7; C-Gly = 53.2 +/- 3.8, P < 0.01 vs. ad libitum; B-Gly = 70.2 +/- 2.0, P < 0.01 vs. C-Gly; B-OKG = 98.7 +/- 4.6, P < 0.01 vs. ad libitum, C-Gly and B-Gly), the latter having previously been observed in vitro. Furthermore, we confirm that OKG inhibits myofibrillar degradation, counteracts the trauma-induced fall of muscle glutamine pool, and induces an increase in glutamine concentration in the jejunum.

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