Roger Hurst | New Zealand Institute for Plant and Food Research Limited (original) (raw)
Papers by Roger Hurst
Brain research, Jan 5, 1999
Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important ... more Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important role in the pathogenesis of many encephalopathies, including multiple sclerosis (MS) and cerebral malaria (CM). The expression of four surface molecules of relevance to MS and CM on the immortalized human umbilical vein endothelial cell line, ECV304, was investigated using immunofluorescence flow cytometry. We found that ECV304 cells express intercellular adhesion molecule-1 (ICAM-1) and low levels of CD36, but not vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. This expression pattern was unaltered on ECV304 cells which were co-cultured with C6 glioma cells; conditions under which the endothelial cells display enhanced barrier formation. Tumour necrosis factor-alpha (TNF-alpha), which is elevated in MS and CM, decreased the integrity of the barrier in co-cultured endothelial cells and upregulated the expression of ICAM-1 nine-fold. The significance of elevated ICAM-1 expressio...
Neurochemical Research, 1998
We have previously reported that the co-culture of endothelial and glioma cell lines provides an ... more We have previously reported that the co-culture of endothelial and glioma cell lines provides an in vitro model for investigating properties of the blood-brain barrier (BBB). To characterise the model system further we have investigated the effects of vasoactive substances implicated in increases in BBB permeability. Additionally, we have also examined whether activation of cyclic AMP signalling pathways, which elevate cerebral endothelial cell barrier function, similarly modulate our model system. ATP, histamine, bradykinin, and serotonin significantly decreased model BBB transendothelial electrical resistance and manipulations which elevate cyclic AMP enhanced culture resistance. These data indicate that our model BBB system responds in a manner characteristic of cerebral microvascular endothelial cells and the BBB in vivo. These data further emphasize the usefulness of our model system.
Molecular Nutrition & Food Research, 2010
Nitric Oxide, 1997
factor-a; nitric oxide; mitochondria; respiration; cycated in the breakdown of blood-brain barrie... more factor-a; nitric oxide; mitochondria; respiration; cycated in the breakdown of blood-brain barrier tochrome oxidase; ATP. (BBB) function which can occur during various inflammatory conditions. Recent evidence suggests a role for the free radical nitric oxide (NO) in the pro-
Neuroreport, 2001
The suitability of various commercially available endothelial cell lines in studies of astrocytic... more The suitability of various commercially available endothelial cell lines in studies of astrocytic/endothelial cell interactions was assessed. The endothelial-like cell line ECV304 was compared with T24/83, Eahy929, and b.End5 and rat cerebral endothelial cells in their ability, when co-cultured with rat (C6) glioma cells, to form a transendothelial electrical resistance (TEER), an indicator of tight junction formation which is an important property of the blood-brain barrier. As reported previously, the basal TEER of ECV304 cell monolayers was significantly enhanced upon co-culture, an effect reproduced by human 1321N1 astrocytes and primary rat astrocytes. T24/83 cells formed a patchy, gapped monolayer, which produced a poor basal TEER with little in the way of an increase upon co-culture. Similarly, all the other cell monolayers analysed demonstrated poor TEERs that were only moderately increased upon co-culture. These data confirm that while no endothelial cell line with ideal features is available, ECV304 cells remain an appropriate choice especially for studies of astrocyte/endothelial cell interactions.
Neurochemistry International, 1999
Previously we reported that the co-culture of non-brain vascular endothelial cells with glioma ce... more Previously we reported that the co-culture of non-brain vascular endothelial cells with glioma cells leads to the induction of a more differentiated endothelial cell phenotype which exhibits important properties of the blood-brain barrier (BBB). Recognising the potential for improving the model barrier system with agents known to modify the growth and differentiation of cells in culture we examined the effects of four differentiating agents (butyric acid, dexamethasone, retinoic acid, and dimethyl sulfoxide) on barrier function. Of these agents only butyric acid and dexamethasone resulted in an enhancement (depending on the dose used) of transendothelial electrical resistance (barrier function). The greatest effect was observed with butyric acid in a dose-dependent manner and was slow in onset and only occurred in the endothelial/glial cell co-cultures. These data indicate that butyric acid may be a beneficial agent in optimising conditions necessary for induction of BBB properties in in vitro barrier systems.
Neurochemical Research, 2000
Using the in vitro blood-brain barrier (BBB) model ECV304/C6, which consists of cocultures of hum... more Using the in vitro blood-brain barrier (BBB) model ECV304/C6, which consists of cocultures of human umbilical vein endothelial-like cells (ECV304) and rat glioma cells (C6), the role of peroxynitrite (OONO-) in nitric oxide (NO*)-mediated BBB disruption was evaluated. Endothelial cell cultures were exposed to NO* gas, in the presence or absence of the OONO- blocker FeTPPS. Separate exposure to NO* and OONO- resulted in endothelial cell cytotoxicity and a decline in barrier integrity. Unfortunately, FeTPPS induced significant detrimental effects on model BBB integrity at a concentration of 300 microM and above. At 250 microM (the highest concentration usable), FeTPPS displayed a trend toward prevention of NO* elicited perturbation of barrier integrity. Dichlorofluorescein diacetate is oxidized to fluorescent dichlorofluorescein by OONO- but only marginally by NO* or O2*-. We observed large and rapid increases in fluorescence in ECV304 preloaded cells following NO* exposure, which were blocked by FeTPPS. Furthermore, using an antinitrotyrosine antibody we detected the nitration of endothelial cell proteins following NO* exposure and conclude that NO*-mediated BBB dysfunction is predominantly elicited by OONO- and not NO*. Proposed mechanisms of NO*-mediated OONO- elicited barrier dysfunction and damage are discussed.
European Journal of Applied Physiology, 2009
Prolonged oxidative stress is detrimental to health; however, transient oxidative stress may impr... more Prolonged oxidative stress is detrimental to health; however, transient oxidative stress may improve immune capability. We examined whether exercise-induced increases in the plasma oxidative generating capability enhance immune responsiveness to potential pathogens. Twelve individuals underwent a 30-min row and pre and post-exercise bloods were collected for oxidative stress and immune assessment. We found that exercise induced a transient increase in plasma carbonyls (3.2-5.3 nmol/mg protein) and creatine kinase activity (0.5-1.2 absorbance/min/mg protein) and that lipopolysaccharide (LPS) stimulation (0.5-24 h) of pre- and post-exercise blood augmented temporal tumour necrosis factor-alpha (TNFalpha) secretion. Further characterisation of plasma using a modified dihydro-2',7'-dichlorohydrofluorescein (DCF) assay revealed that addition of a sub-threshold of hydrogen peroxide to post-exercise (and not pre-exercise) plasma caused a sixfold increase in the radical oxygen species (ROS) generating capability after 15 min (555 +/- 131 to 3607 +/- 488 change in fluorescent intensity [DeltaFI]), which was inhibited using 60 mM N-acetyl-L: -cysteine (920 +/- 154 DeltaFI). Furthermore, cell experiments revealed that LPS stimulation of either THP-1 cells pre-incubated with post-exercise plasma or peripheral blood mononuclear cells pre-treated with pro-oxidants, modulated the temporal secretion of key cytokines that regulate the initiation, progression and resolution of an inflammatory response. These results indicate that exercise-induced changes in plasma parameters (e.g. oxidative generating capability-dependent or independent of inflammatory mediators) augment the temporal LPS response and support the notion that repeated transient oxidative stress (such as that induced by regular exercise) is important for a "healthy" immune system.
Brain Research, 2001
The process of nitric-oxide (NO)-induced cellular toxicity may involve energy deprivation since t... more The process of nitric-oxide (NO)-induced cellular toxicity may involve energy deprivation since the radical is reported to prevent both mitochondrial oxidative phosphorylation and glycolysis. In order to determine whether these processes are important in NO-induced blood-brain barrier (BBB) dysfunction, we used a cell culture model of the BBB and compared the effects of gaseous NO, potassium cyanide (KCN, a mitochondrial respiratory chain inhibitor) and iodoacetate [IA, an inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH)] on endothelial cell ATP content, GAPDH activity and barrier integrity. NO lead to a rapid breakdown in model barrier integrity and resulted in a reduction in endothelial cell ATP content and GAPDH activity. KCN had no effect on endothelial cell ATP content or barrier integrity, while IA, at a concentration that completely blocked endothelial cell GAPDH activity, resulted in a rapid decline in ATP content but did not lead to a decline in barrier integrity until at least 2 h of exposure. These results indicate that inhibition of endothelial cell GAPDH activity rather than mitochondrial respiration causes an energy deficiency and delayed barrier dysfunction. However, the rapid detrimental effects of gaseous NO on barrier integrity cannot be fully explained by endothelial cell energy depletion and may be related to the actions of the free radical and its products on cellular lipids.
AJP: Regulatory, Integrative and Comparative Physiology, 2009
Exercise-induced oxidative stress is instrumental in achieving the health benefits from regular e... more Exercise-induced oxidative stress is instrumental in achieving the health benefits from regular exercise. Therefore, inappropriate use of fruit-derived products (commonly applied as prophalytic antioxidants) may counteract the positive effects of exercise. Using human exercise and cellular models we found that 1) blackcurrant supplementation suppressed exercise-induced oxidative stress, e.g., plasma carbonyls (0.9 +/- 0.1 vs. 0.6 +/- 0.1 nmol/mg protein, placebo vs. blackcurrant), and 2) preincubation of THP-1 cells with an anthocyanin-rich blackcurrant extract inhibited LPS-stimulated cytokine secretion [TNF-alpha (16,453 +/- 322 vs. 10,941 +/- 82 pg/ml, control vs. extract, P < 0.05) and IL-6 (476 +/- 14 vs. 326 +/- 32 pg/ml, control vs. extract, P < 0.05)] and NF-kappaB activation. In addition to its antioxidant and anti-inflammatory properties, we found that postexercise plasma collected after blackcurrant supplementation enhanced the differential temporal LPS-stimulated inflammatory response in THP-1 cells, resulting in an early suppression of TNF-alpha (1,741 +/- 32 vs. 1,312 +/- 42 pg/ml, placebo vs. blackcurrant, P < 0.05) and IL-6 (44 +/- 5 vs. 36 +/- 3 pg/ml, placebo vs. blackcurrant, P < 0.05) secretion after 24 h. Furthermore, by using an oxidative stress cell model, we found that preincubation of THP-1 cells with hydrogen peroxide (H(2)O(2)) prior to extract exposure caused a greater suppression of LPS-stimulated cytokine secretion after 24 h, which was not evident when cells were simultaneously incubated with H(2)O(2) and the extract. In summary, our findings support the concept that consumption of blackcurrant anthocyanins alleviate oxidative stress, and may, if given at the appropriate amount and time, complement the ability of exercise to enhance immune responsiveness to potential pathogens.
Basic & Clinical Pharmacology & Toxicology, 2015
Ascorbic acid in combination with aspirin has been used in order to prevent aspirin-induced oxida... more Ascorbic acid in combination with aspirin has been used in order to prevent aspirin-induced oxidative GI damage. We aimed to determine whether ascorbic acid reduces or prevents aspirin-induced changes in intestinal permeability over a 6-hr period using saccharidic probes mannitol and lactulose. The effects of administration of 600 mg aspirin alone, 500 mg ascorbic acid alone and simultaneous dosage of both agents were compared in a cross-over study in twenty-eight healthy female volunteers. These effects were also compared with that of a placebo. The ability of ascorbic acid to mitigate the effects of aspirin when administered either half an hour before or after dosage with aspirin was also assessed in nineteen healthy female volunteers. The excretion of lactulose over the 6-hr period after dosage was augmented, after consumption of either aspirin or ascorbic acid compared with that after consumption of placebo. Dosage with ascorbic acid alone augmented the excretion of lactulose more than did aspirin alone. Simultaneous dosage with both agents augmented the excretion of lactulose in an additive manner. The timing of dosage with ascorbic acid in relation to that with aspirin had no significant effect on the excretion of the two sugars. These findings indicate that ascorbic acid does not prevent aspirin-induced increase in gut permeability rather that both agents augment it to a similar extent. The additive effect on simultaneous dosage with both agents in augmenting the absorption of lactulose suggests that each influences paracellular permeability by different pathways. This article is protected by copyright. All rights reserved.
Meat Science, 2007
The accumulation of metmyoglobin (MetMb) at the surface of meat during storage contributes signif... more The accumulation of metmyoglobin (MetMb) at the surface of meat during storage contributes significantly to its discolouration. Under appropriate conditions it may be possible to utilise residual meat MetMb reducing activity to maintain fresh colour. Venison meat colour stability is poorer compared with other species. Hence, we evaluated the capacity of completely discoloured venison (n = 12 animals) to reduce MetMb under anaerobic conditions in order to decipher more clearly the role MetMb reducing activity may play. The reducing capacity of venison (1 day, 3, and 6 weeks post-mortem), electrical stimulation, surface location (top and bottom) and rigor temperature (15 and 35°C) on MetMb were evaluated. Surface MetMb decreased (P < 0.001) during storage while deoxymyoglobin increased (P < 0.001) demonstrating MetMb reduction. Metmyoglobin reduction was greater (P < 0.001) in venison which entered rigor at 15°C, the reduction at the bottom surface of the steaks was greater (P < 0.001) compared with the top surface, and electrical stimulation had no affect (P > 0.05). These data demonstrate that metmyoglobin reducing activity occurs anaerobically in completely discoloured venison following storage display. The practical application for this finding needs to be determined.
Kidney and Blood Pressure Research, 1992
Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) c... more Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) contraction which is inhibited by pirenzepine. To identify the cellular signalling mechanism, we analyzed Carb-activated phosphoinositide hydrolysis in myo-[2-3H] inositol preloaded cells of isolated rat glomeruli. Carb evoked a rapid (5 s, 30.4 +/- 8.3% of basal) and sustained (60 s, 157.2 +/- 1.2% of basal) inositol trisphosphate (IP3) response. Acetylcholine 100 microM (Ach) in the presence of eserine also evoked IP3 formation. Mobilization of Ca2+ was monitored by preloading glomerular cells with 45Ca2+ (200 microCi/ml) and analyzing the cellular efflux using a constant perifusion system. Both Carb and Ach induced transient 45Ca2+ efflux, with peak values above baseline of 69.0 +/- 19.9 and 71.5 +/- 7.9%, respectively. Incubation with pirenzepine or prior release of Ca2+ from an IP3-sensitive intracellular pool by Thapsigargin (2 microM) prevented Carb-evoked Ca2+ release (100 and 60%, respectively). Therefore, glomerular cells possess functional cholinergic receptors which stimulate contraction via IP3-mediated intracellular Ca2+ release.
Journal of Cellular Physiology, 1996
... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, Unite... more ... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, United Kingdom. *Correspondence: RD Hurst, Department of Neurochemistry, Institute of Neurology, University of London, Queen Square, London WC1N 3BG, UK. Publication History. ...
Journal of Cellular Physiology, 1996
... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK. *... more ... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK. *Correspondence: RD Hurst, Department of Neurochemistry, Institute of Neurology, University of London, Queen Square, London WC1N 3BG, UK. Publication History. ...
FEBS Letters, 1988
The neuropeptide bombesin provoked a dose-dependent stimulation of 45Ca2+ efflux from pre-loaded ... more The neuropeptide bombesin provoked a dose-dependent stimulation of 45Ca2+ efflux from pre-loaded islets of Langerhans. This response occurred rapidly, was not sustained and did not depend on the presence of extracellular calcium, suggesting that it resulted from the mobilization of intracellular calcium stores. Under conditions when large increases in %aZ+ efflux were observed, bombesin completely failed to stimulate the rate of insulin secretion. Similar results were also obtained with the muscarinic cholinergic agonist, carbachol. The data suggest that the release of calcium from intracellular pools is not sufficient to induce an increase in insulin secretion in normal islet cells.
Cell Calcium, 1993
The presence of L-type calcium (Ca2p-channels and the effects of &+-channel antagonists on ceils ... more The presence of L-type calcium (Ca2p-channels and the effects of &+-channel antagonists on ceils of rat gfomeruli were investfgated. Gfomerufi were isolated by graded sieving and after preincubatfon (10 min) in zero Ca2+, the uptake of &Ca2' by gfomerufar ceils was measured. Degfarfftfon wfth KCI (50 mM) or the dihydropyrfdine agonist Bay K 8644 (10 PM) stfmufated Ca uptake by 13% and 24%, respectively, above control (lOO%), which was inhibited by nffedipine (Nif, 10 f&l), P < 0.05, and by both S and R isomers of verapamif (Ver, 10 separate experimental preparation, isolated gfomeruli were preioaded (46 in the absence of &Ca2
Brain research, Jan 5, 1999
Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important ... more Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important role in the pathogenesis of many encephalopathies, including multiple sclerosis (MS) and cerebral malaria (CM). The expression of four surface molecules of relevance to MS and CM on the immortalized human umbilical vein endothelial cell line, ECV304, was investigated using immunofluorescence flow cytometry. We found that ECV304 cells express intercellular adhesion molecule-1 (ICAM-1) and low levels of CD36, but not vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. This expression pattern was unaltered on ECV304 cells which were co-cultured with C6 glioma cells; conditions under which the endothelial cells display enhanced barrier formation. Tumour necrosis factor-alpha (TNF-alpha), which is elevated in MS and CM, decreased the integrity of the barrier in co-cultured endothelial cells and upregulated the expression of ICAM-1 nine-fold. The significance of elevated ICAM-1 expressio...
Neurochemical Research, 1998
We have previously reported that the co-culture of endothelial and glioma cell lines provides an ... more We have previously reported that the co-culture of endothelial and glioma cell lines provides an in vitro model for investigating properties of the blood-brain barrier (BBB). To characterise the model system further we have investigated the effects of vasoactive substances implicated in increases in BBB permeability. Additionally, we have also examined whether activation of cyclic AMP signalling pathways, which elevate cerebral endothelial cell barrier function, similarly modulate our model system. ATP, histamine, bradykinin, and serotonin significantly decreased model BBB transendothelial electrical resistance and manipulations which elevate cyclic AMP enhanced culture resistance. These data indicate that our model BBB system responds in a manner characteristic of cerebral microvascular endothelial cells and the BBB in vivo. These data further emphasize the usefulness of our model system.
Molecular Nutrition & Food Research, 2010
Nitric Oxide, 1997
factor-a; nitric oxide; mitochondria; respiration; cycated in the breakdown of blood-brain barrie... more factor-a; nitric oxide; mitochondria; respiration; cycated in the breakdown of blood-brain barrier tochrome oxidase; ATP. (BBB) function which can occur during various inflammatory conditions. Recent evidence suggests a role for the free radical nitric oxide (NO) in the pro-
Neuroreport, 2001
The suitability of various commercially available endothelial cell lines in studies of astrocytic... more The suitability of various commercially available endothelial cell lines in studies of astrocytic/endothelial cell interactions was assessed. The endothelial-like cell line ECV304 was compared with T24/83, Eahy929, and b.End5 and rat cerebral endothelial cells in their ability, when co-cultured with rat (C6) glioma cells, to form a transendothelial electrical resistance (TEER), an indicator of tight junction formation which is an important property of the blood-brain barrier. As reported previously, the basal TEER of ECV304 cell monolayers was significantly enhanced upon co-culture, an effect reproduced by human 1321N1 astrocytes and primary rat astrocytes. T24/83 cells formed a patchy, gapped monolayer, which produced a poor basal TEER with little in the way of an increase upon co-culture. Similarly, all the other cell monolayers analysed demonstrated poor TEERs that were only moderately increased upon co-culture. These data confirm that while no endothelial cell line with ideal features is available, ECV304 cells remain an appropriate choice especially for studies of astrocyte/endothelial cell interactions.
Neurochemistry International, 1999
Previously we reported that the co-culture of non-brain vascular endothelial cells with glioma ce... more Previously we reported that the co-culture of non-brain vascular endothelial cells with glioma cells leads to the induction of a more differentiated endothelial cell phenotype which exhibits important properties of the blood-brain barrier (BBB). Recognising the potential for improving the model barrier system with agents known to modify the growth and differentiation of cells in culture we examined the effects of four differentiating agents (butyric acid, dexamethasone, retinoic acid, and dimethyl sulfoxide) on barrier function. Of these agents only butyric acid and dexamethasone resulted in an enhancement (depending on the dose used) of transendothelial electrical resistance (barrier function). The greatest effect was observed with butyric acid in a dose-dependent manner and was slow in onset and only occurred in the endothelial/glial cell co-cultures. These data indicate that butyric acid may be a beneficial agent in optimising conditions necessary for induction of BBB properties in in vitro barrier systems.
Neurochemical Research, 2000
Using the in vitro blood-brain barrier (BBB) model ECV304/C6, which consists of cocultures of hum... more Using the in vitro blood-brain barrier (BBB) model ECV304/C6, which consists of cocultures of human umbilical vein endothelial-like cells (ECV304) and rat glioma cells (C6), the role of peroxynitrite (OONO-) in nitric oxide (NO*)-mediated BBB disruption was evaluated. Endothelial cell cultures were exposed to NO* gas, in the presence or absence of the OONO- blocker FeTPPS. Separate exposure to NO* and OONO- resulted in endothelial cell cytotoxicity and a decline in barrier integrity. Unfortunately, FeTPPS induced significant detrimental effects on model BBB integrity at a concentration of 300 microM and above. At 250 microM (the highest concentration usable), FeTPPS displayed a trend toward prevention of NO* elicited perturbation of barrier integrity. Dichlorofluorescein diacetate is oxidized to fluorescent dichlorofluorescein by OONO- but only marginally by NO* or O2*-. We observed large and rapid increases in fluorescence in ECV304 preloaded cells following NO* exposure, which were blocked by FeTPPS. Furthermore, using an antinitrotyrosine antibody we detected the nitration of endothelial cell proteins following NO* exposure and conclude that NO*-mediated BBB dysfunction is predominantly elicited by OONO- and not NO*. Proposed mechanisms of NO*-mediated OONO- elicited barrier dysfunction and damage are discussed.
European Journal of Applied Physiology, 2009
Prolonged oxidative stress is detrimental to health; however, transient oxidative stress may impr... more Prolonged oxidative stress is detrimental to health; however, transient oxidative stress may improve immune capability. We examined whether exercise-induced increases in the plasma oxidative generating capability enhance immune responsiveness to potential pathogens. Twelve individuals underwent a 30-min row and pre and post-exercise bloods were collected for oxidative stress and immune assessment. We found that exercise induced a transient increase in plasma carbonyls (3.2-5.3 nmol/mg protein) and creatine kinase activity (0.5-1.2 absorbance/min/mg protein) and that lipopolysaccharide (LPS) stimulation (0.5-24 h) of pre- and post-exercise blood augmented temporal tumour necrosis factor-alpha (TNFalpha) secretion. Further characterisation of plasma using a modified dihydro-2',7'-dichlorohydrofluorescein (DCF) assay revealed that addition of a sub-threshold of hydrogen peroxide to post-exercise (and not pre-exercise) plasma caused a sixfold increase in the radical oxygen species (ROS) generating capability after 15 min (555 +/- 131 to 3607 +/- 488 change in fluorescent intensity [DeltaFI]), which was inhibited using 60 mM N-acetyl-L: -cysteine (920 +/- 154 DeltaFI). Furthermore, cell experiments revealed that LPS stimulation of either THP-1 cells pre-incubated with post-exercise plasma or peripheral blood mononuclear cells pre-treated with pro-oxidants, modulated the temporal secretion of key cytokines that regulate the initiation, progression and resolution of an inflammatory response. These results indicate that exercise-induced changes in plasma parameters (e.g. oxidative generating capability-dependent or independent of inflammatory mediators) augment the temporal LPS response and support the notion that repeated transient oxidative stress (such as that induced by regular exercise) is important for a "healthy" immune system.
Brain Research, 2001
The process of nitric-oxide (NO)-induced cellular toxicity may involve energy deprivation since t... more The process of nitric-oxide (NO)-induced cellular toxicity may involve energy deprivation since the radical is reported to prevent both mitochondrial oxidative phosphorylation and glycolysis. In order to determine whether these processes are important in NO-induced blood-brain barrier (BBB) dysfunction, we used a cell culture model of the BBB and compared the effects of gaseous NO, potassium cyanide (KCN, a mitochondrial respiratory chain inhibitor) and iodoacetate [IA, an inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH)] on endothelial cell ATP content, GAPDH activity and barrier integrity. NO lead to a rapid breakdown in model barrier integrity and resulted in a reduction in endothelial cell ATP content and GAPDH activity. KCN had no effect on endothelial cell ATP content or barrier integrity, while IA, at a concentration that completely blocked endothelial cell GAPDH activity, resulted in a rapid decline in ATP content but did not lead to a decline in barrier integrity until at least 2 h of exposure. These results indicate that inhibition of endothelial cell GAPDH activity rather than mitochondrial respiration causes an energy deficiency and delayed barrier dysfunction. However, the rapid detrimental effects of gaseous NO on barrier integrity cannot be fully explained by endothelial cell energy depletion and may be related to the actions of the free radical and its products on cellular lipids.
AJP: Regulatory, Integrative and Comparative Physiology, 2009
Exercise-induced oxidative stress is instrumental in achieving the health benefits from regular e... more Exercise-induced oxidative stress is instrumental in achieving the health benefits from regular exercise. Therefore, inappropriate use of fruit-derived products (commonly applied as prophalytic antioxidants) may counteract the positive effects of exercise. Using human exercise and cellular models we found that 1) blackcurrant supplementation suppressed exercise-induced oxidative stress, e.g., plasma carbonyls (0.9 +/- 0.1 vs. 0.6 +/- 0.1 nmol/mg protein, placebo vs. blackcurrant), and 2) preincubation of THP-1 cells with an anthocyanin-rich blackcurrant extract inhibited LPS-stimulated cytokine secretion [TNF-alpha (16,453 +/- 322 vs. 10,941 +/- 82 pg/ml, control vs. extract, P < 0.05) and IL-6 (476 +/- 14 vs. 326 +/- 32 pg/ml, control vs. extract, P < 0.05)] and NF-kappaB activation. In addition to its antioxidant and anti-inflammatory properties, we found that postexercise plasma collected after blackcurrant supplementation enhanced the differential temporal LPS-stimulated inflammatory response in THP-1 cells, resulting in an early suppression of TNF-alpha (1,741 +/- 32 vs. 1,312 +/- 42 pg/ml, placebo vs. blackcurrant, P < 0.05) and IL-6 (44 +/- 5 vs. 36 +/- 3 pg/ml, placebo vs. blackcurrant, P < 0.05) secretion after 24 h. Furthermore, by using an oxidative stress cell model, we found that preincubation of THP-1 cells with hydrogen peroxide (H(2)O(2)) prior to extract exposure caused a greater suppression of LPS-stimulated cytokine secretion after 24 h, which was not evident when cells were simultaneously incubated with H(2)O(2) and the extract. In summary, our findings support the concept that consumption of blackcurrant anthocyanins alleviate oxidative stress, and may, if given at the appropriate amount and time, complement the ability of exercise to enhance immune responsiveness to potential pathogens.
Basic & Clinical Pharmacology & Toxicology, 2015
Ascorbic acid in combination with aspirin has been used in order to prevent aspirin-induced oxida... more Ascorbic acid in combination with aspirin has been used in order to prevent aspirin-induced oxidative GI damage. We aimed to determine whether ascorbic acid reduces or prevents aspirin-induced changes in intestinal permeability over a 6-hr period using saccharidic probes mannitol and lactulose. The effects of administration of 600 mg aspirin alone, 500 mg ascorbic acid alone and simultaneous dosage of both agents were compared in a cross-over study in twenty-eight healthy female volunteers. These effects were also compared with that of a placebo. The ability of ascorbic acid to mitigate the effects of aspirin when administered either half an hour before or after dosage with aspirin was also assessed in nineteen healthy female volunteers. The excretion of lactulose over the 6-hr period after dosage was augmented, after consumption of either aspirin or ascorbic acid compared with that after consumption of placebo. Dosage with ascorbic acid alone augmented the excretion of lactulose more than did aspirin alone. Simultaneous dosage with both agents augmented the excretion of lactulose in an additive manner. The timing of dosage with ascorbic acid in relation to that with aspirin had no significant effect on the excretion of the two sugars. These findings indicate that ascorbic acid does not prevent aspirin-induced increase in gut permeability rather that both agents augment it to a similar extent. The additive effect on simultaneous dosage with both agents in augmenting the absorption of lactulose suggests that each influences paracellular permeability by different pathways. This article is protected by copyright. All rights reserved.
Meat Science, 2007
The accumulation of metmyoglobin (MetMb) at the surface of meat during storage contributes signif... more The accumulation of metmyoglobin (MetMb) at the surface of meat during storage contributes significantly to its discolouration. Under appropriate conditions it may be possible to utilise residual meat MetMb reducing activity to maintain fresh colour. Venison meat colour stability is poorer compared with other species. Hence, we evaluated the capacity of completely discoloured venison (n = 12 animals) to reduce MetMb under anaerobic conditions in order to decipher more clearly the role MetMb reducing activity may play. The reducing capacity of venison (1 day, 3, and 6 weeks post-mortem), electrical stimulation, surface location (top and bottom) and rigor temperature (15 and 35°C) on MetMb were evaluated. Surface MetMb decreased (P < 0.001) during storage while deoxymyoglobin increased (P < 0.001) demonstrating MetMb reduction. Metmyoglobin reduction was greater (P < 0.001) in venison which entered rigor at 15°C, the reduction at the bottom surface of the steaks was greater (P < 0.001) compared with the top surface, and electrical stimulation had no affect (P > 0.05). These data demonstrate that metmyoglobin reducing activity occurs anaerobically in completely discoloured venison following storage display. The practical application for this finding needs to be determined.
Kidney and Blood Pressure Research, 1992
Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) c... more Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) contraction which is inhibited by pirenzepine. To identify the cellular signalling mechanism, we analyzed Carb-activated phosphoinositide hydrolysis in myo-[2-3H] inositol preloaded cells of isolated rat glomeruli. Carb evoked a rapid (5 s, 30.4 +/- 8.3% of basal) and sustained (60 s, 157.2 +/- 1.2% of basal) inositol trisphosphate (IP3) response. Acetylcholine 100 microM (Ach) in the presence of eserine also evoked IP3 formation. Mobilization of Ca2+ was monitored by preloading glomerular cells with 45Ca2+ (200 microCi/ml) and analyzing the cellular efflux using a constant perifusion system. Both Carb and Ach induced transient 45Ca2+ efflux, with peak values above baseline of 69.0 +/- 19.9 and 71.5 +/- 7.9%, respectively. Incubation with pirenzepine or prior release of Ca2+ from an IP3-sensitive intracellular pool by Thapsigargin (2 microM) prevented Carb-evoked Ca2+ release (100 and 60%, respectively). Therefore, glomerular cells possess functional cholinergic receptors which stimulate contraction via IP3-mediated intracellular Ca2+ release.
Journal of Cellular Physiology, 1996
... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, Unite... more ... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, United Kingdom. *Correspondence: RD Hurst, Department of Neurochemistry, Institute of Neurology, University of London, Queen Square, London WC1N 3BG, UK. Publication History. ...
Journal of Cellular Physiology, 1996
... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK. *... more ... Department of Cellular Physiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK. *Correspondence: RD Hurst, Department of Neurochemistry, Institute of Neurology, University of London, Queen Square, London WC1N 3BG, UK. Publication History. ...
FEBS Letters, 1988
The neuropeptide bombesin provoked a dose-dependent stimulation of 45Ca2+ efflux from pre-loaded ... more The neuropeptide bombesin provoked a dose-dependent stimulation of 45Ca2+ efflux from pre-loaded islets of Langerhans. This response occurred rapidly, was not sustained and did not depend on the presence of extracellular calcium, suggesting that it resulted from the mobilization of intracellular calcium stores. Under conditions when large increases in %aZ+ efflux were observed, bombesin completely failed to stimulate the rate of insulin secretion. Similar results were also obtained with the muscarinic cholinergic agonist, carbachol. The data suggest that the release of calcium from intracellular pools is not sufficient to induce an increase in insulin secretion in normal islet cells.
Cell Calcium, 1993
The presence of L-type calcium (Ca2p-channels and the effects of &+-channel antagonists on ceils ... more The presence of L-type calcium (Ca2p-channels and the effects of &+-channel antagonists on ceils of rat gfomeruli were investfgated. Gfomerufi were isolated by graded sieving and after preincubatfon (10 min) in zero Ca2+, the uptake of &Ca2' by gfomerufar ceils was measured. Degfarfftfon wfth KCI (50 mM) or the dihydropyrfdine agonist Bay K 8644 (10 PM) stfmufated Ca uptake by 13% and 24%, respectively, above control (lOO%), which was inhibited by nffedipine (Nif, 10 f&l), P < 0.05, and by both S and R isomers of verapamif (Ver, 10 separate experimental preparation, isolated gfomeruli were preioaded (46 in the absence of &Ca2