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Biomedical subjects

John X Wilson

Publications and source records attributed to John X Wilson.

At least 19 recordsLinked to original sources
PubMed2006

Ascorbate inhibits NADPH oxidase subunit p47phox expression in microvascular endothelial cells.

The production of reactive oxygen species (ROS) is central to the etiology of endothelial dysfunction in sepsis. Endothelial cells respond to infection by activating NADPH oxidases that are sources of intracellular ROS and potential targets for therapeutic administration of antioxidants. Ascorbate is an antioxidant that accumulates in these cells and improves capillary blood flow, vascular reactivity, arterial blood pressure, and survival in experimental sepsis. Therefore, the present study tested the hypothesis that ascorbate regulates NADPH oxidases in microvascular endothelial cells exposed to septic insult. We observed that incubation with Escherichia coli lipopolysaccharide (LPS) and interferon-gamma (IFNgamma) increased NADPH oxidase activity and expression of the enzyme subunit p47phox in mouse microvascular endothelial cells of skeletal muscle origin. Pretreatment of the cells with ascorbate prevented these increases. Polyethylene glycol-conjugated catalase and selective inhibitors of Jak2 also abrogated induction of p47phox. Exogenous hydrogen peroxide induced p47phox expression that was prevented by pretreatment of the cells with ascorbate. LPS+IFNgamma or hydrogen peroxide activated the Jak2/Stat1/IRF1 pathway and this effect was also inhibited by ascorbate. In conclusion, ascorbate blocks the stimulation by septic insult of redox-sensitive Jak2/Stat1/IRF1 signaling, p47phox expression, and NADPH oxidase activity in microvascular endothelial cells. Because endothelial NADPH oxidases produce ROS that can cause endothelial dysfunction, their inhibition by ascorbate may represent a new strategy for sepsis therapy.

Animals↗
PubMed2006

Hypotonic shock stimulates ascorbate release from coronary artery endothelial cells by a Ca2+ -independent pathway.

In endothelial cells, anion channels open upon osmotic swelling during shear stress and hypotonic shock. Therefore, we examined the effects of hypotonic shock on release of the antioxidant anion ascorbate from pig coronary artery endothelial cells. Hypotonic shock potentiated ascorbate release from freshly isolated or cultured pig coronary artery endothelial cells; subsequently cultured endothelial cells were used. The hypotonic shock-induced increase in Asc release was rapid, depended on the degree of hypotonic shock, and not due to membrane leakiness. Stimulating P2Y2 like receptors in endothelial cells with ATP causes ascorbate release via a Ca2+ -mediated pathway. Hypotonic shock-induced release differed from the Ca2+-mediated Asc release because: (a) the increase in release with hypotonic shock was additive to that with ATP or A23187 (Ca2+ -ionophore), (b) apyrase, suramin or removing extracellular Ca2+ did not affect the hypotonic shock-stimulated release, (c) anion channel blockers inhibited the release by the two pathways differently, and (d) hypotonic shock increased the ascorbate release from endothelial cells and cultured smooth muscle cells whereas the Ca2+ -mediated ascorbate release occurred only in endothelial cells. Accumulation of ascorbate by endothelial cells was examined at extracellular ascorbate concentrations of 10 (Na+ -ascorbate symporter not saturated) and 5000 microM (Na+ -ascorbate symporter saturated). Hypotonic shock and A23187 decreased ascorbate accumulation at 10 microM ascorbate but increased it at 5000 microM. The effects of the two treatments were additive and also differed from each other with substitution of gluconate for extracellular chloride. Thus, ascorbate release from endothelial cells can be potentiated by two distinct pathways - hypotonic shock mediated and ATP/Ca2+ stimulated.

Adenosine Triphosphate↗
PubMed2006

Coenzyme Q(1) depletes NAD(P)H and impairs recycling of ascorbate in astrocytes.

Ascorbate is an important antioxidant in the brain. Astrocytes are capable of recycling ascorbate by taking up and then reducing its oxidation product dehydroascorbic acid (DHAA) using reducing equivalents derived from NAD(P)H. Astrocytes also contain NAD(P)H-dependent quinone reductases, such as NAD(P)H:quinone oxidoreductase (NQO1), which are capable of reducing coenzyme Q and its analogs. Short-chain coenzyme Q analogs have been proposed as therapeutic agents for neurodegenerative illnesses, but they may cause oxidative stress by non-enzymatic redox cycling or enzyme-dependent depletion of NAD(P)H. Therefore, we tested the hypothesis that the short-chain coenzyme Q analog coenzyme Q(1) (CoQ(1), ubiquinone-5) decreases intracellular NAD(P)H levels in astrocytes and impairs the ability of these cells to replace extracellular DHAA with ascorbate (i.e., ascorbate recycling). We observed that CoQ(1) inhibited the production of intra- and extracellular ascorbate by primary rat astrocytes incubated with DHAA in glucose-free medium. Reduction of CoQ(1) to CoQ(1)H(2) by astrocytes was partially blocked by the NQO1 inhibitor dicumarol but was not affected by DHAA. The inhibition of ascorbate recycling by CoQ(1) was attenuated by dicumarol and was abolished by glucose. CoQ(1) lowered intracellular levels of reactive oxygen species, as measured by oxidation of 2',7'-dichlorofluorescin but also produced marked decreases in the concentrations of NADH and NADPH. We conclude that in astrocytes CoQ(1) recycling depletes NAD(P)H and inhibits ascorbate recycling when glucose metabolism is limited. Because DHAA can cause cell-lethal oxidative stress in neurons and ascorbate produced by astrocytes may be neuroprotective, coenzyme Q analogs may adversely affect brain function through this novel mechanism.

Animals↗
PubMed2006

Ca2+-mediated ascorbate release from coronary artery endothelial cells.

1.--The addition of Ca(2+) ionophore A23187 or ATP to freshly isolated or cultured pig coronary artery endothelial cells (PCEC) potentiated the release of ascorbate (Asc). Cultured PCEC were used to characterize the Ca(2+)-mediated release. An increase in Ca(2+)-mediated Asc release was observed from PCEC preincubated with Asc, Asc-2-phosphate or dehydroascorbic acid (DHAA). 2.--The effects of various ATP analogs and inhibition by suramin were consistent with the ATP-induced release being mediated by P2Y2-like receptors. 3.--ATP-stimulated Asc release was Ca(2+)-mediated because (a) ATP analogs that increased Asc release also elevated cytosolic [Ca(2+)], (b) Ca(2+) ionophore A23187 and cyclopiazonic acid stimulated the Asc release, (c) removing extracellular Ca(2+) and chelating intracellular Ca(2+)inhibited the ATP-induced release, and (d) inositol-selective phospholipase C inhibitor U73122 also inhibited this release. 4.--Accumulation of Asc by PCEC was examined at Asc concentrations of 10 microM (Na(+)-Asc symporter not saturated) and 5 mM (Na(+)-Asc symporter saturated). At 10 microM Asc, A23187 and ATP caused an inhibition of Asc accumulation but at 5 mM Asc, both the agents caused a stimulation. Substituting gluconate for chloride did not affect the basal Asc uptake but it abolished the effects of A23187. 5.--PCEC but not pig coronary artery smooth muscle cells show a Ca(2+)- mediated Asc release pathway that may be activated by agents such as ATP.

Adenosine Triphosphate↗
PubMed2005

Sepsis inhibits recycling and glutamate-stimulated export of ascorbate by astrocytes.

Sepsis causes brain dysfunction. Because neurotransmission requires high ascorbate and low dehydroascorbic acid (DHAA) concentrations in brain extracellular fluid, the effect of septic insult on ascorbate recycling (i.e., uptake and reduction of DHAA) and export was investigated in primary rat and mouse astrocytes. DHAA raised intracellular ascorbate to physiological levels but extracellular ascorbate only slightly. Septic insult by lipopolysaccharide and interferon-gamma increased ascorbate recycling in astrocytes permeabilized with saponin but decreased it in those with intact plasma membrane. The decrease was due to inhibition of the glucose transporter (GLUT1) that translocates DHAA because septic insult slowed uptake of the nonmetabolizable GLUT1 substrate 3-O-methylglucose. Septic insult also abolished stimulation by glutamate of ascorbate export. Specific nitric oxide synthase (NOS) inhibitors and nNOS and iNOS deficiency failed to alter the effects of septic insult. Inhibitors of NADPH oxidase generally did not protect against septic insult, because only one of those tested (diphenylene iodonium) increased GLUT1 activity and ascorbate recycling. We conclude that astrocytes take up DHAA and use it to synthesize ascorbate that is exported in response to glutamate. This mechanism may provide the antioxidant on demand to neurons under normal conditions, but it is attenuated after septic insult.

3-O-Methylglucose↗
PubMed2005

The biosynthesis of ascorbate protects isolated rat hepatocytes from cumene hydroperoxide-mediated oxidative stress.

Most animals synthesize ascorbate. It is an essential enzymatic cofactor for the synthesis of a variety of biological molecules and also a powerful antioxidant. There is, however, little direct evidence supporting an antioxidant role for endogenously produced ascorbate. Recently, we demonstrated that incubation of rat hepatocytes with 1-bromoheptane or phorone simultaneously depleted glutathione (GSH) and triggered rapid ascorbate synthesis. The present study investigates the hypothesis that endogenous ascorbate synthesis can confer protection against oxidative stress. Rat and guinea pig hepatocytes were depleted of GSH with 1-bromoheptane and subsequently treated with the oxidative stressor cumene hydroperoxide (CHP) in the presence or absence of the ascorbate synthesis inhibitor sorbinil. In rat hepatocytes, ascorbate content increased linearly (from 15.1 to 35.8 nmol/10(6) cells) over a 105-min incubation. Prior depletion of GSH increased CHP-induced cellular reactive oxygen species (ROS) production, lipid peroxidation, and cell death in rat and guinea pig hepatocytes. Inhibiting ascorbate synthesis, however, further elevated ROS production (2-fold), lipid peroxidation (1.5-fold), and cell death (2-fold) in rat hepatocytes only. This is the first time that endogenous ascorbate synthesis has been shown to decrease cellular susceptibility to oxidative stress. Protection by endogenously produced ascorbate may therefore need to be addressed when extrapolating data to humans from experiments using rodents capable of synthesizing ascorbate.

Animals↗
PubMed2005

Activation of catechol-O-methyltransferase in astrocytes stimulates homocysteine synthesis and export to neurons.

Elevation of the total homocysteine (tHcy) concentration in plasma has been implicated in neurodegeneration in patients with stroke, dementia, Alzheimer disease, and Parkinson disease. Because the mechanisms controlling brain tHcy are unknown, the present study investigated its synthesis and transport in primary rat brain cell cultures. We found that the catechol-O-methyltransferase (COMT) substrate 3,4-dihydroxybenzoic acid (DHB) increased export of tHcy in astrocytes, but not in neurons. The export mechanism was selective for tHcy over cyst(e)ine, total glutathione (tGSH) or cysteinylglycine (Cys-Gly). tHcy export from astrocytes was also induced by the COMT substrates levodopa (L-DOPA), dopamine and quercetin, and it was blocked by the COMT inhibitors tropolone and entacapone. This export was associated with increased synthesis of tHcy because both intracellular and extracellular tHcy concentrations rose during COMT activation. Incubation in cyst(e)ine-deficient medium inhibited the tHcy export response to COMT activation. Exogenous tHcy (100 muM) was accumulated into neurons, but not into astrocytes. We conclude that activation of COMT causes sustained synthesis of Hcy in astrocytes and transport of this amino acid to neurons.

Amino Acids↗
PubMed2005

Ascorbate uptake in pig coronary artery endothelial cells.

Although smooth muscle and endothelial cells in pig coronary artery are morphologically and functionally distinct, ascorbate uptake has been characterized only in smooth muscle cells. Ascorbate transporters in kidney and intestinal epithelial cells differ from those in smooth muscle. We examined ascorbate transport and mRNA expression of sodium-dependent vitamin C transporters (SVCT) by RT-PCR in the pig coronary artery endothelial cell cultures. When 14C-ascorbate uptake in endothelial cells was examined as 14C or by HPLC, the two values did not differ from each other. 14C-ascorbate uptake was Na(+)-dependent, stereoselective for L-ascorbate and inhibited by sulfinpyrazone. The kinetic characteristics of the uptake were: Km = 27 +/- 3 microM (Hill coefficient = 1) for ascorbate and Km = 73 +/- 14 mM (Hill coefficient = 2) for Na+. Surprisingly, endothelial cells had similar kinetic parameters as smooth muscle cells, except for a slightly lower uptake velocity in endothelial cells. Comparison with the smooth muscle showed that both tissue types expressed mRNA for SVCT2. Endothelial cells differ from epithelial cells which express mainly SVCT1 but resemble smooth muscle cells in this respect.

Animals↗
PubMed2005

Endotoxin increases ascorbate recycling and concentration in mouse liver.

Sublethal exposure to Escherichia coli endotoxin [lipopolysaccharide (LPS)] attenuates the lethal effects of subsequent insults associated with oxidative stress, such as higher LPS dose, septic peritonitis, and ischemia. Because administration of the antioxidant ascorbate protects against these same insults and injection of dehydroascorbic acid (DHAA) protects against ischemia, the hypothesis that sublethal LPS increases endogenous ascorbate concentration and recycling (i.e., synthesis from DHAA) was tested. Injection of LPS [5 x 10(6) endotoxin units/kg body weight, i.p.] in mice caused a temporary inhibition of food intake, which was significant by 20 h and recovered within 3 d. LPS increased ascorbate concentration in adrenal gland, heart, kidney, and liver. LPS had similar effects in wild-type and Slc23a2+/- mice despite the latter's deficiency in the ascorbate transporter SVCT2. In liver, the ascorbate response to LPS was not accompanied by change in glutathione concentration. LPS decreased gulonolactone oxidase activity, which is rate-limiting for de novo synthesis of ascorbate from glucose, but increased the rate of DHAA reduction to ascorbate. In conclusion, sublethal endotoxin increases ascorbate recycling in liver and ascorbate concentration in liver, adrenal gland, heart, and kidney. The enhanced rate of ascorbate production from DHAA may protect these organs against the reactive oxygen species produced by subsequent, potentially lethal challenges.

Adrenal Glands↗
PubMed2005

Delayed ascorbate bolus protects against maldistribution of microvascular blood flow in septic rat skeletal muscle.

OBJECTIVE: Although early administration of ascorbate has been shown to protect against the microvascular dysfunction in sepsis, it is not clear if a delayed introduction of ascorbate also yields beneficial effects. The main objective was to determine the therapeutic window for treatment of an animal model of sepsis with bolus injection of ascorbate. We also determined if sepsis per se affects urinary excretion of ascorbate. DESIGN: Prospective, controlled laboratory study. SETTING: Animal laboratory in a university-affiliated research institute. SUBJECTS: Male Sprague-Dawley rats, 300-400 g of body weight. INTERVENTIONS: Rats were made septic by cecal ligation and perforation (CLP) and volume resuscitated by continuous saline infusion. Ascorbate bolus (7.6 mg/100 g of body weight) or saline vehicle was injected intravenously at 1, 6, or 24 hrs after CLP. MEASUREMENTS AND MAIN RESULTS: At 24 hrs post-CLP, sepsis caused antidiuresis and decreased plasma ascorbate concentration, but it did not affect urinary excretion of ascorbate in rats that received only saline. Sepsis also caused maldistribution of capillary blood flow in skeletal muscle. This maldistribution of flow was prevented by ascorbate injected at 6 hrs post-CLP. At 48 hrs post-CLP, in addition to the flow maldistribution, sepsis caused systemic arterial hypotension and fever that were prevented by both immediate (1 hr post-CLP) and delayed injections of ascorbate (24 hrs post-CLP). CONCLUSION: Despite volume resuscitation, the present model of sepsis resulted in maldistribution of capillary blood flow within 24 hrs and hypotension within 48 hrs. Our finding that intravenous bolus of ascorbate can protect against these deficits even if delayed 6-24 hrs after the septic insult shows, for the first time, that ascorbate can reverse microcirculatory dysfunction after the onset of sepsis.

Analysis of Variance↗
PubMed2005

Regulation of vitamin C transport.

Ascorbic acid and dehydroascorbic acid (DHAA, oxidized vitamin C) are dietary sources of vitamin C in humans. Both nutrients are absorbed from the lumen of the intestine and renal tubules by, respectively, enterocytes and renal epithelial cells. Subsequently vitamin C circulates in the blood and enters all of the other cells of the body. Concerning flux across the plasma membrane, simple diffusion of ascorbic acid plays only a small or negligible role. More important are specific mechanisms of transport and metabolism that concentrate vitamin C intracellularly to enhance its function as an enzyme cofactor and antioxidant. The known transport mechanisms are facilitated diffusion of DHAA through glucose-sensitive and -insensitive transporters, facilitated diffusion of ascorbate through channels, exocytosis of ascorbate in secretory vesicles, and secondary active transport of ascorbate through the sodium-dependent vitamin C transporters SVCT1 and SVCT2 proteins that are encoded by the genes Slc23a1 and Slc23a2, respectively. Evidence is reviewed indicating that these transport pathways are regulated under physiological conditions and altered by aging and disease.

Animals↗
PubMed2004

Ascorbate protects against impaired arteriolar constriction in sepsis by inhibiting inducible nitric oxide synthase expression.

Compromised microvascular responsiveness is one of the key factors associated with mortality of septic patients. The present study addresses the mechanism of protection by ascorbate against impaired vasoconstriction in septic mice. Sepsis (i.e., cecal ligation and puncture (CLP) model) elevated both plasma protein carbonyl (i.e., an index of oxidative stress) and plasma nitrite/nitrate (NOx) levels, reduced baseline mean arterial blood pressure (MABP), and inhibited the MABP pressor response to angiotensin II (Ang II) at 6 h post-CLP. At the microvascular level, sepsis increased the inducible nitric oxide synthase (iNOS) mRNA level in cremaster muscle arterioles (18-25 microm diameter) at 3 h post-CLP, and impaired vasoconstriction to Ang II in these arterioles at 6 h post-CLP. At 24 h post-CLP, sepsis resulted in 9% survival. An intravenous bolus of ascorbate (200 mg/kg body wt) given 30 min prior to CLP prevented the protein carbonyl and NOx increases, partially restored the baseline arterial pressure, and completely protected against all arteriolar iNOS mRNA increases, arteriolar constriction hyporesponsiveness, and pressor response impairment. Survival increased to 65%. In septic mice, iNOS gene knockout resulted in protection of arteriolar constriction and pressor responses identical to that provided by ascorbate. Ascorbate bolus given 3 h post-CLP protected against the increase in plasma NOx concentration and against the pressor response impairment. We conclude that ascorbate may protect arteriolar vasoconstrictor responsiveness in sepsis by inhibiting excessive NO production.

Angiotensin II↗
PubMed2004

Antioxidant protection from HIV-1 gp120-induced neuroglial toxicity.

BACKGROUND: The pathogenesis of HIV-1 glycoprotein 120 (gp120) associated neuroglial toxicity remains unresolved, but oxidative injury has been widely implicated as a contributing factor. In previous studies, exposure of primary human central nervous system tissue cultures to gp120 led to a simplification of neuronal dendritic elements as well as astrocytic hypertrophy and hyperplasia; neuropathological features of HIV-1-associated dementia. Gp120 and proinflammatory cytokines upregulate inducible nitric oxide synthase (iNOS), an important source of nitric oxide (NO) and nitrosative stress. Because ascorbate scavenges reactive nitrogen and oxygen species, we studied the effect of ascorbate supplementation on iNOS expression as well as the neuronal and glial structural changes associated with gp120 exposure. METHODS: Human CNS cultures were derived from 16-18 week gestation post-mortem fetal brain. Cultures were incubated with 400 microM ascorbate-2-O-phosphate (Asc-p) or vehicle for 18 hours then exposed to 1 nM gp120 for 24 hours. The expression of iNOS and neuronal (MAP2) and astrocytic (GFAP) structural proteins was examined by immunohistochemistry and immunofluorescence using confocal scanning laser microscopy (CSLM). RESULTS: Following gp120 exposure iNOS was markedly upregulated from undetectable levels at baseline. Double label CSLM studies revealed astrocytes to be the prime source of iNOS with rare neurons expressing iNOS. This upregulation was attenuated by the preincubation with Asc-p, which raised the intracellular concentration of ascorbate. Astrocytic hypertrophy and neuronal injury caused by gp120 were also prevented by preincubation with ascorbate. CONCLUSIONS: Ascorbate supplementation prevents the deleterious upregulation of iNOS and associated neuronal and astrocytic protein expression and structural changes caused by gp120 in human brain cell cultures.

Journal Article↗
PubMed2004

Glycogenolysis is directed towards ascorbate synthesis by glutathione conjugation.

Using isolated rat hepatocytes we have shown that glutathione (GSH) depletion by glutathione-S-transferase (GST)-catalyzed conjugation with 1-bromoheptane or phorone was accompanied by a significant elevation in ascorbate synthesis. Glycogenolysis was also stimulated without a significant rise in glucose synthesis. Furthermore, when glycogenolysis was stimulated in control hepatocytes by increasing intracellular cAMP levels (with glucagon or dibutyryl cAMP), cellular glucose levels, but not ascorbate levels, increased. These data suggest that GSH depletion can stimulate ascorbate synthesis independently of glucose synthesis and that hepatocytes can direct glycogenolysis towards ascorbate synthesis during GSH conjugation.

Animals↗
PubMed2004

Activation of P2 nucleotide receptors stimulates acid efflux from astrocytes.

Acidification of the extracellular fluid modulates neurotransmission and ischemic injury in brain. The purpose of the present study was to investigate the effects of purine and pyrimidine transmitters on acid efflux from brain astrocytes. Using RT-PCR, we detected transcripts for the following nucleotide receptors in rat primary astrocyte cultures: P2X1, P2X2, P2X3, P2X4, P2X6, P2X7, P2Y1, P2Y2, P2Y4, and P2Y6. Adenosine 5'-triphosphate (ATP) was found to rapidly induce a biphasic increase in acid efflux, monitored by microphysiometry, consisting of an initial transient and a sustained plateau. Compared with ATP, the P2Y agonist uridine 5'-triphosphate (UTP) induced a much smaller initial response but an equal plateau. The poorly hydrolyzable ATP analogue ATPgammaS caused the same initial response as did ATP, but a much smaller plateau, suggesting that the latter phase was due to extracellular degradation of nucleotides. The P2 receptor antagonist, suramin, blocked stimulation of acid efflux by ATP. Removal of extracellular glucose or elevation of extracellular K+ decreased the basal rate of acid efflux but not the stimulation induced by ATP. Inhibition of Na+/H+ exchange by cariporide suppressed the initial phase of ATP-stimulated acid efflux. The intracellular Ca2+ chelator bisaminophenoxyethane- tetraacetic acid (BAPTA) lowered basal acid efflux and abolished the initial phase of the response to ATP. In conclusion, ATP acts through P2 nucleotide receptors on astrocytes to stimulate the Ca2+ -dependent efflux of protons, mediated in part by activation of Na+/H+ exchange. The resulting acidification of the extracellular fluid may serve as an intercellular signal in brain.

Acids↗
PubMed2004

Gender and sodium-ascorbate transporter isoforms determine ascorbate concentrations in mice.

We evaluated the hypothesis that sodium-dependent vitamin C (ascorbate) transporters SVCT1 and SVCT2 (encoded by genes Slc23a1 and Slc23a2) regulate ascorbate concentrations in tissues of adult mice. Slc23a2+/- and Slc23a2+/+ mice were fed an ascorbate-free diet for 10-12 wk, and then segregated according to gender and genome, and were placed in groups of 3-4 in metabolic cages for 24-h urine collection. RT-PCR analysis showed that liver and kidney expressed mainly SVCT1, and brain, skeletal muscle, and spleen expressed predominantly SVCT2. Slc23a2+/- mice had low SVCT2 but normal SVCT1 messenger RNA (mRNA) levels, which did not differ between genders. Ascorbate concentrations were lower in Slc23a2+/- than Slc23a2+/+ mice in tissues where SVCT2 was the main isoform. Compared with males, females had lower ascorbate excretion and ascorbate:creatinine ratio in urine and had higher ascorbate concentrations in plasma and SVCT1-predominant tissues. SVCT2 contributed to a gender effect in spleen because males had higher spleen ascorbate concentration than females in wild-type but not in Slc23a2+/- mice. Hepatic gulonolactone oxidase mRNA and activity levels did not differ with genotype or gender, indicating no differences in ascorbate synthesis. We concluded that SVCT2 is a major determinant of ascorbate accumulation in tissues lacking SVCT1. The SVCT isoforms appear to function independently of one another because SVCT1 expression and ascorbate concentrations in SVCT1-predominant organs were not affected by SVCT2 deficiency. Additionally, lower ascorbate excretion in females may elevate the vitamin's concentrations in plasma and tissues expressing SVCT1 that, unlike SVCT2, is not saturated by plasma ascorbate concentrations.

Animals↗
PubMed2004

Propofol neuroprotection in cerebral ischemia and its effects on low-molecular-weight antioxidants and skilled motor tasks.

BACKGROUND: Propofol is neuroprotective when administered immediately after stroke. The therapeutic window, duration of administration, and antioxidant mechanisms of propofol in neuroprotection are not known. The effects of propofol after stroke were examined in the conscious animal. The authors have previously shown that light propofol anesthesia (25 mg x kg(-1) x h(-1)) for a period of 4 h, even if delayed 1 h after the onset of ischemia, decreases infarct volume 3 days after the stroke. METHODS: Cerebral ischemia was induced in awake Wistar rats by a local intracerebral injection of the potent vasoconstrictor, endothelin (6 pmol in 3 microl) into the striatum. Propofol treatment after ischemia was delayed up to 4 h, and the infusion period shortened from 4 h to 1 h. Infarct volume was assessed 3 or 21 days after the stroke. Neurologic outcome was evaluated on days 14-21 after ischemia. Tissue ascorbate and glutathione concentrations were evaluated at 4 h and 3 days after ischemia. RESULTS: Infarct volumes were reduced 3 days after ischemia when propofol treatment (25 mg x kg(-1) x h(-1)) was delayed for 2 h (0.5+/-0.3 mm3) but not 4 h (2.0+/-0.9 mm3), compared with intralipid controls (2.4 +/- 0.7 mm3). The propofol infusion period of 3 h but not 1 h reduced infarct volume. Propofol treatment did not reduce infarct volume 21 days after the stroke, although motor function improvements (Montoya staircase test) were observed 14-21 days after the stroke. Propofol neuroprotection was independent of tissue ascorbate and glutathione concentrations. CONCLUSIONS: Concurrent or delayed administration of propofol is neuroprotective 3 days after ischemia. Although there were no differences in infarct volume 21 days after ischemia, propofol-treated animals had functional improvements at this time.

Animals↗