Glucocorticoid-mediated alterations in fluidity of rabbit cardiac muscle microvessel endothelial cell membranes: influences on eicosanoid release

Emission Sources of Campylobacter from Agricultural Farms, Impact on Environmental Contamination and Intervention Strategies

Although extensive research has been carried out to describe the transmission pathways of Campylobacter entering livestock farms, the role of livestock farms as source of Campylobacter contamination of the environment is still poorly investigated. It is assumed that Campylobacter-positive livestock farms contribute to an environmental contamination, depending on the animal species on the farm, their Campylobacter status, the housing system, manure management as well as their general farm hygienic and biosecurity management. Different emission sources, like manure, air, water, insects and rodents as well as personnel, including equipment and vehicles, contribute to Campylobacter emission into the environment. Even though Campylobacter are rather fastidious bacteria, they are able to survive in the environment for even a longer period of time, when environmental conditions enable survival in specific niches. We conclude that a significant reduction of Campylobacter emission in the environment can be successfully achieved if various intervention strategies, depending on the farm type, are applied simultaneously, including proper general and personal hygiene, establishing of hygienic barriers, insect controls, manure management and hygienization of stables, barns and exhaust air.

Nongenomic cortisol signaling in fish

Glucocorticoids are critical regulators of the cellular processes that allow animals to cope with stressors. In teleosts, cortisol is the primary circulating glucocorticoid and this hormone mediates a suite of physiological responses, most importantly energy substrate mobilization that is essential for acute stress adaptation. Cortisol signaling has been extensively studied and the majority of work has been on the activation of the glucocorticoid receptor (GR), a ligand-bound transcription factor, and the associated downstream transcriptional and protein responses. Despite the role of this hormone in acute stress adaptation, very few studies have examined the rapid effects of this hormone on cellular function. The nongenomic corticosteroid effects, which are rapid (seconds to minutes) and independent of transcription and translation, involve changes to second-messenger pathways and effector proteins, but the primary receptors involved in this pathway activation remain elusive. In teleosts, a few studies suggested the possibility that GR located on the membrane may be initiating a rapid response based on the abrogation of this effect with RU486, a GR antagonist. However, studies have also proposed other signaling mechanisms, including a putative novel membrane receptor and changes to membrane biophysical properties as initiators of rapid signaling in response to cortisol stimulation. Emerging evidence suggests that cortisol activates multiple signaling pathways in cells to bring about rapid effects, but the underlying physiological implications on acute stress adaptation are far from clear.

Intermittent Glucocorticoid Dosing Improves Muscle Repair and Function in Mice with Limb-Girdle Muscular Dystrophy

The muscular dystrophies are genetically diverse. Shared pathological features among muscular dystrophies include breakdown, or loss of muscle, and accompanying fibrotic replacement. Novel strategies are needed to enhance muscle repair and function and to slow this pathological remodeling. Glucocorticoid steroids, like prednisone, are known to delay loss of ambulation in patients with Duchenne muscular dystrophy but are accompanied by prominent adverse effects. However, less is known about the effects of steroid administration in other types of muscular dystrophies, including limb-girdle muscular dystrophies (LGMDs). LGMD 2B is caused by loss of dysferlin, a membrane repair protein, and LGMD 2C is caused by loss of the dystrophin-associated protein, γ-sarcoglycan. Herein, we assessed the efficacy of steroid dosing on sarcolemmal repair, muscle function, histopathology, and the regenerative capacity of primary muscle cells. We found that in murine models of LGMD 2B and 2C, daily prednisone dosing reduced muscle damage and fibroinflammatory infiltration. However, daily prednisone dosing also correlated with increased muscle adipogenesis and atrophic remodeling. Conversely, intermittent dosing of prednisone, provided once weekly, enhanced muscle repair and did not induce atrophy or adipogenesis, and was associated with improved muscle function. These data indicate that dosing frequency of glucocorticoid steroids affects muscle remodeling in non-Duchenne muscular dystrophies, suggesting a positive outcome associated with intermittent steroid dosing in LGMD 2B and 2C muscle.

Rapid cortisol signaling in response to acute stress involves changes in plasma membrane order in rainbow trout liver

The activation of genomic signaling in response to stressor-mediated cortisol elevation has been studied extensively in teleosts. However, very little is known about the rapid signaling events elicited by this steroid. We tested the hypothesis that cortisol modulates key stress-related signaling pathways in response to an acute stressor in fish liver. To this end, we investigated the effect of an acute stressor on biophysical properties of plasma membrane and on stressor-related protein phosphorylation in rainbow trout (Oncorhynchus mykiss) liver. A role for cortisol in modulating the acute cellular stress response was ascertained by blocking the stressor-induced elevation of this steroid by metyrapone. The acute stressor exposure increased plasma cortisol levels and liver membrane fluidity (measured by anisotropy of 1,6-diphenyl-1,3,5-hexatriene), but these responses were abolished by metyrapone. Atomic force microscopy further confirmed biophysical alterations in liver plasma membrane in response to stress, including changes in membrane domain topography. The changes in membrane order did not correspond to any changes in membrane fatty acid components after stress, suggesting that changes in membrane structure may be associated with cortisol incorporation into the lipid bilayer. Plasma cortisol elevation poststress correlated positively with activation of intracellular stress signaling pathways, including increased phosphorylation of extracellular signal-related kinases as well as several putative PKA and PKC but not Akt substrate proteins. Together, our results indicate that stressor-induced elevation of plasma cortisol level is associated with alterations in plasma membrane fluidity and rapid activation of stress-related signaling pathways in trout liver.

Novel nongenomic signaling by glucocorticoid may involve changes to liver membrane order in rainbow trout

Stress-induced glucocorticoid elevation is a highly conserved response among vertebrates. This facilitates stress adaptation and the mode of action involves activation of the intracellular glucocorticoid receptor leading to the modulation of target gene expression. However, this genomic effect is slow acting and, therefore, a role for glucocorticoid in the rapid response to stress is unclear. Here we show that stress levels of cortisol, the primary glucocorticoid in teleosts, rapidly fluidizes rainbow trout (Oncorhynchus mykiss) liver plasma membranes in vitro. This involved incorporation of the steroid into the lipid domains, as cortisol coupled to a membrane impermeable peptide moiety, did not affect membrane order. Studies confirmed that cortisol, but not sex steroids, increases liver plasma membrane fluidity. Atomic force microscopy revealed cortisol-mediated changes to membrane surface topography and viscoelasticity confirming changes to membrane order. Treating trout hepatocytes with stress levels of cortisol led to the modulation of cell signaling pathways, including the phosphorylation status of putative PKA, PKC and AKT substrate proteins within 10 minutes. The phosphorylation by protein kinases in the presence of cortisol was consistent with that seen with benzyl alcohol, a known membrane fluidizer. Our results suggest that biophysical changes to plasma membrane properties, triggered by stressor-induced glucocorticoid elevation, act as a nonspecific stress response and may rapidly modulate acute stress-signaling pathways.

Glucocorticoid efficacy in asthma: is improved tissue remodeling upstream of anti-inflammation

Synthetic glucocorticoids (GCs), such as prednisone, are among the most widely prescribed drugs worldwide and are used to treat many acute and chronic inflammatory conditions. The current paradigm of GC efficacy is that they are potent anti-inflammatory agents. Decreased inflammation in many disorders is thought to lead to decreased pathological tissue remodeling. However, this model has never been validated. In particular, improvements in inflammation have not been shown to improve the rate of lung function decline in asthma. Herein, we present an alternative paradigm, where GC efficacy is mediated through more successful tissue remodeling, with reduction in inflammation secondary to successful regeneration.

Proteomic profiling of glucocorticoid-exposed myogenic cells: Time series assessment of protein translocation and transcription of inactive mRNAs

BACKGROUND

Prednisone, one of the most highly prescribed drugs, has well characterized effects on gene transcription mediated by the glucocorticoid receptor. These effects are typically occurring on the scale of hours. Prednisone also has a number of non-transcriptional effects (occurring on minutes scale) on protein signaling, yet these are less well studied. We sought to expand the understanding of acute effects of prednisone action on cell signaling using a combination of SILAC strategy and subcellular fractionations from C2C12 myotubes.

RESULTS

De novo translation of proteins was inhibited in both SILAC labeled and unlabeled C2C12 myotubes. Unlabeled cells were exposed to prednisone while SILAC labeled cells remained untreated. After 0, 5, 15, and 30 minutes of prednisone exposure, labeled and unlabeled cells were mixed at 1:1 ratios and fractionated into cytosolic and nuclear fractions. A total of 534 proteins in the cytosol and 626 proteins in the nucleus were identified and quantitated, using 3 or more peptides per protein with peptide based probability < or = 0.001. We identified significant increases (1.7- to 3.1- fold) in cytoplasmic abundance of 11 ribosomal proteins within 5 minutes of exposure, all of which returned to baseline by 30 min. We hypothesized that these drug-induced acute changes in the subcellular localization of the cell's protein translational machinery could lead to altered translation of quiescent RNAs. To test this, de novo protein synthesis was assayed after 15 minutes of drug exposure. Quantitative fluorography identified 16 2D gel spots showing rapid changes in translation; five of these were identified by MS/MS (pyruvate kinase, annexin A6 isoform A and isoform B, nasopharyngeal epithelium specific protein 1, and isoform 2 of Replication factor C subunit 1), and all showed the 5' terminal oligopyrimidine motifs associated with mRNA sequestration to and from inactive mRNA pools.

CONCLUSION

We describe novel approaches of subcellular proteomic profiling and assessment of acute changes on a minute-based time scale. These data expand the current knowledge of acute, non-transcriptional activities of glucocorticoids, including changes in protein subcellular localization, altered translation of quiescent RNA pools, and PKC-mediated cytoskeleton remodeling.

Effects of glucocorticoids on endogenous and transcellular metabolism of eicosanoids in asthma

BACKGROUND

Human blood polymorphonuclear cells, which biosynthesize eicosanoids from the 5-lipoxygenase (5-LO) pathway, are likely to be involved in asthma, in which glucocorticoids represent the first line of therapy. Their effects on leukotriene release after a short course of treatment, which have been reported in several studies, are controversial.

OBJECTIVE

We sought to investigate whether long-term oral glucocorticoids inhibit lipid mediators from the 5-LO pathway.

METHODS

Twelve normal control subjects, 29 asthmatic subjects, and 50 glucocorticoid-dependent asthmatic subjects were included in the study. Polymorphonuclear cells were studied for endogenous and transcellular metabolism of eicosanoids.

RESULTS

Total leukotriene B(4) production was significantly lower in cells from glucocorticoid-dependent asthmatic subjects (mean +/- SD, 177 +/- 26 ng/10(7) cells) than in control subjects (406 +/- 27), untreated asthmatic subjects (421 +/- 34), and asthmatic subjects treated with inhaled glucocorticoids (290 +/- 56). When incubated with arachidonic acid, these polymorphonuclear cells released very low amounts of 5(S)- and 12(S)-hydroxy-eicosatetraenoic acid (HETE), whereas endogenous 15(S)-HETE was found in substantial amounts. The transformation of exogenous 15(S)-HETE into 5(S),15(S)-diHETE and lipoxins was significantly more important in untreated asthmatic subjects than in control subjects and glucocorticoid-dependent asthmatic subjects.

CONCLUSION

This study showed that long-term oral corticotherapy affects the 5-LO activity and leads to a decrease production of all metabolites in contrast to short-term or inhaled glucocorticoids. This study also questions the site of action of glucocorticoids in regulating the availability of arachidonic acid and potential eicosanoid regulation, as previously held in phospholipase A2 studies.

Effects of eicosapentaenoic acid and docosahexaenoic acid on plasma membrane fluidity of aortic endothelial cells

We investigated the relative effects of n-3 eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) on the plasma membrane fluidity of endothelial cells (EC) cultured from the thoracic aorta by determining fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its cationic derivative trimethylamino-DPH (TMA-DPH). Fluidity assessed by TMA-DPH demonstrated no significant differences in plasma membranes of vehicle (dimethyl sulfoxide; DMSO)-, EPA-, and DHA-treated EC. Plasma membrane fluidity assessed by DPH polarization, however, was significantly higher in the order of DHA > EPA > DMSO. Total cholesterol content decreased significantly by 28.4 and 15.9% in the plasma membranes of DHA- and EPA-treated cells, respectively. Total phospholipid content remained unaltered in the plasma membranes of the three groups of cells; however, the molar ratio of total cholesterol to phospholipid decreased significantly only in the membranes of DHA-treated EC. The unsaturation index in the plasma membranes of EPA- and DHA-treated cells increased by 35.7 and 64.3%, respectively, compared with that in the plasma membranes of control cells. The activities of catalase and glutathione peroxidase in the whole-cell homogenates, and levels of lipid peroxides in either the whole-cell homogenates or in plasma membrane fractions were not altered in EPA- or DHA-treated EC. These results indicate that the influence of DHA is greater than that of EPA in increasing plasma membrane fluidity of vascular EC. We speculate that the greater effect of DHA compared to EPA is due to its greater ability to decrease membrane cholesterol content or the cholesterol/phospholipid molar ratio, or both, and also to its greater ability in elevating the unsaturation index in the plasma membranes of EC.

Effect of aging on plasma membrane fluidity of rat aortic endothelial cells

To assess age-related changes in the physical properties of vascular endothelial cell (EC) plasma membranes, we measured membrane fluidity with 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene, and 10-(1-pyrene)dodecanoic acid, and investigated the parameters affecting membrane fluidity of endothelial cells (ECs) cultured from the thoracic aortas of young (5-week-old) and aged (100-week-old) rats. Plasma membrane fluidity of aged rat ECs was significantly lower than that of young rat ECs, as assessed by increased 1,6-diphenyl-1,3,5-hexatriene fluorescence polarization and by decreased pyrene excimer formation, although 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene did not demonstrate a change in membrane fluidity with aging. Compared with those in young rat ECs, cholesterol concentrations in aged rat ECs were significantly higher, whereas phospholipid concentrations were unchanged; consequently, the cholesterol/phospholipid molar ratio was significantly higher in aged rat ECs. Lipid peroxide levels measured with thiobarbituric acid reactive substances were significantly higher in EC plasma membranes of aged rats. These results indicate that age-related increases in cholesterol and lipid peroxide in vascular EC plasma membranes reduce membrane fluidity.

Association of age-related decrease in platelet membrane fluidity with platelet lipid peroxide

The influence of age on platelet lipid peroxide (LPO), platelet membrane fluidity and the composition of fatty acid was investigated in female Wistar rats widely ranging in age from 14 to 720 days old. LPO levels were significantly higher (p<0.05) in the platelets of upper age groups than in those of lower age groups, showing a significantly positive correlation with age (r=0.84, p<0.0001). Membrane fluidity, assessed by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization, was significantly reduced with age. The composition of fatty acid demonstrated an age-related elevation (p<0.05) in the unsaturation index. The rises in the LPO levels revealed a significantly positive correlation with DPH-polarization (r=0.73, p<0.0001). Thus our results suggested that the age-related deterioration of platelet membrane fluidity, despite a significant elevation in the unsaturation index, was due to the age-related higher basal levels of LPO in platelets.

Mechanisms of acute vasodilator response to bacterial lipopolysaccharide in the rat coronary microcirculation

1. In this study the mechanisms of the acute vasodilator action of bacterial lipopolysaccharide (LPS) were investigated in the rat Langendorff perfused heart. 2. Infusion of LPS (5 microg ml(-1)) caused a rapid and sustained fall in coronary perfusion pressure (PP) of 59 +/- 4 mmHg (n = 12) and a biphasic increase in NO levels determined in the coronary effluent by chemiluminescent detection. Both the fall in PP and the increase in NO release were completely abolished (n = 3) by pretreatment of hearts with the NO synthase inhibitor L-NAME (50 microM). 3. LPS-induced vasodilatation was markedly attenuated to 5 +/- 4 mmHg (n 3) by pretreatment of hearts with the B2 kinin receptor antagonist Hoe-140 (100 nM). 4. Vasodilator responses to LPS were also blocked by brief pretreatment with mepacrine (0.5 microM, n = 3) or nordihydroguaiaretic acid (0.1 microM, n = 4) and markedly attenuated by WEB 2086 (3 microM, n = 4). 5. Thirty minutes pretreatment of hearts with dexamethasone (1 nM), but not progesterone (1 microM), significantly modified responses to LPS. The action of dexamethasone was time-dependent, having no effect when applied either simultaneously with or pre-perfused for 5 min before the administration of LPS but inhibiting the response to LPS by 91 +/- 1% (n = 4) when pre-perfused for 15 min. The inhibition caused by dexamethasone was blocked by 15 min pretreatment with the glucocorticoid receptor antagonist RU-486 (100 nM) or by 2 min pre-perfusion of a 1:200 dilution of LCPS1, a selective antilipocortin 1 (LC1) neutralizing antibody. 6. Treatment with the protein synthesis inhibitor, cycloheximide (10 microM, for 15 min) selectively blunted LPS-induced vasodilatation, reducing the latter to 3 +/- 5 mmHg (n = 3), while having no effect on vasodilator responses to either bradykinin or sodium nitroprusside. 7. These results indicate that LPS-induced vasodilatation in the rat heart is dependent on activation of kinin B2 receptors and synthesis of NO. In addition, phospholipase A2 (PLA2) is activated by LPS resulting in the release of platelet-activating factor (PAF) and lipoxygenase but not cyclo-oxygenase products. These effects are dependent on de novo synthesis of an intermediate protein which remains to be identified.

Lower degree of esterification of serum cholesterol in depression: relevance for depression and suicide research

Previous studies have suggested that depression and suicide are related to alterations in total cholesterol serum concentrations, and that an altered distribution of haptoglobin (Hp) phenotypes in major depression indicates that variation on chromosome 16 may be associated with that illness. Lecithin:cholesterol acyl transferase (LCAT, EC 2.3.1.43), the enzyme that catalyzes the esterifying reaction of cholesterol in serum, is located close to the Hp gene. This study examined the serum concentrations of total and free cholesterol and the esterified cholesterol ratio in 26 healthy controls, 47 unipolar depressed subjects (16 minor, 14 simple major and 17 melancholic depressed subjects) and 12 relatives of melancholic subjects. Depressed subjects (regardless of subtype) and relatives of depressed subjects had a significantly lower esterified cholesterol ratio than normal controls. No significant differences in total or free cholesterol concentrations were found between the above study groups. In depressed subjects, there were no significant relationships between the esterified cholesterol ratio, total or free cholesterol and postdexamethasone adrenocorticotropic or cortisol values, Hp phenotypes, severity of illness or suicidal symptoms. It is hypothesized that lower esterification in serum cholesterol may constitute a vulnerability factor for depression through alterations in cell membrane microviscosity.

Increased lipid fluidity in synaptosomes from brains of hyperosmolal rats

Taurine, a product of sulfur amino acid metabolism, is important in cerebral osmoregulation. To understand the adaptive changes in transport which accompany different hyperosmolal states, we determined lipid composition and fluorescence anisotropy of synaptosomal liposomes from rats with chronic hypernatremic dehydration (CHD), streptozocin-induced (STZ) diabetes, and insulin treated diabetes. Induction of CHD increased serum osmolality, and enhanced in vitro synaptosomal taurine uptake (P < 0.01, n = 3, vs. control). Fluorescence anisotropy studies showed that the fluidity of lipids from CHD synaptosomes was higher than control (P < 0.05, n = 3). STZ-diabetes resulted in hyperglycemia, increased serum osmolality, and stimulated synaptosomal taurine uptake (P < 0.01, n = 3, vs. control). Insulin treatment of diabetic rats restored serum osmolality and taurine transport to control values. The fluidity of diabetic rat brain synaptosomal lipids was significantly higher than control (P < 0.05, n = 3); fluidity was normalized by insulin administration to diabetic rats. Total fatty acid, cholesterol, and cholesterol/phospholipid molar ratio of CHD, STZ, and insulin treated diabetic rats were similar to control. However, the ratio of saturated to unsaturated fatty acids was decreased in hyperosmolal states. This suggests that adaptive increases in cerebral taurine transport during hyperosmolality may result from a direct effect on membrane composition that alters fluidity and permits enhanced transmembrane flux of osmoprotective molecules.

Developmental changes of renal brushborder membrane ionic permeability

Renal brush-border membrane vesicles (BBMV) show an age-dependent increase in height of the Na(+)-gradient driven overshoot for glucose and proline uptake. Conversely, early uptake of 22Na+ is more rapid in BBMV from kidney of 7-day-old vs. adult rats. To understand the mechanisms responsible for these observations, ionic permeability characteristics of BBMV from different aged animals were determined using an electrical potential sensitive fluorescent dye, diS-C3(5). Absolute and relative ionic permeabilities were determined after a 3-h incubation in 100 mM KCl. Intravesicular K+ ([K+]in), a measure of absolute K+ permeability, was calculated from the extravesicular K+ at which valinomycin produced no potential difference (PD). [K+]in was significantly lower in vesicles from 7-day, compared to adult (P < 0.01). While Cl- permeability, relative to that of K+ was similar, PNa+/PK+ decreased significantly with age (P < 0.05, 7 day vs. adult). In the presence of an inwardly directed NaCl gradient, the lower PNa+ relative to PCl- of the adult vesicles would result in a less positive intravesicular charge, which would therefore augment Na(+)-solute co-transport. Fluorescence polarization studies also show that lipids from BBM vesicles of 7-day-old rats are more fluid than those from adult. These differences are likely due to developmental lipid compositional changes, which influence membrane transport and permeability characteristics. These findings would explain, in part, the age-dependent alterations of renal BBMV solute transport.

On radiation damage to normal tissues and its treatment. II. Anti-inflammatory drugs

In addition to transiently inhibiting cell cycle progression and sterilizing those cells capable of proliferation, irradiation disturbs the homeostasis effected by endogenous mediators of intercellular communication (humoral component of tissue response to radiation). Changes in the mediator levels may modulate radiation effects either by assisting a return to normality (e.g., through a rise in H-type cell lineage-specific growth factors) or by aggravating the damage. The latter mode is illustrated with reports on changes in eicosanoid levels after irradiation and on results of empirical treatment of radiation injuries with anti-inflammatory drugs. Prodromal, acute and chronic effects of radiation are accompanied by excessive production of eicosanoids (prostaglandins, prostacyclin, thromboxanes and leukotrienes). These endogenous mediators of inflammatory reactions may be responsible for the vasodilatation, vasoconstriction, increased microvascular permeability, thrombosis and chemotaxis observed after radiation exposure. Glucocorticoids inhibit eicosanoid synthesis primarily by interfering with phospholipase A2 whilst non-steroidal anti-inflammatory drugs prevent prostaglandin/thromboxane synthesis by inhibiting cyclooxygenase. When administered after irradiation on empirical grounds, drugs belonging to both groups tend to attenuate a range of prodromal, acute and chronic effects of radiation in man and animals. Taken together, these two sets of observations are highly suggestive of a contribution of humoral factors to the adverse responses of normal tissues and organs to radiation. A full account of radiation damage should therefore consist of complementary descriptions of cellular and humoral events. Further studies on anti-inflammatory drug treatment of radiation damage to normal organs are justified and desirable.

Lipid fluidity modulates platelet aggregation and agglutination in vitro

To determine the effect of altered membrane fluidity on platelet aggregation/agglutination, fresh, washed human platelets were treated with A2C, a cyclopropyl fatty acid ester which is known to enhance mobility of intrinsic membrane bilayer constituents and increase membrane fluidity. Fluorescence polarization studies demonstrated A2C incubation time- and concentration-dependent increases in platelet membrane fluidity (decreased fluorescence anisotropy). Preincubation with A2C was associated with diminished collagen, thrombin and ristocetin-induced platelet aggregation/agglutination. Aggregation/agglutination was diminished by 93 +/- 5% for collagen (0.2 mg/ml), 53 +/- 3% for thrombin (1.0 U/ml) and 85 +/- 9% for ristocetin (1.1 mg/ml). These data suggest that membrane fluidity is involved in the regulation of platelet function.