A permeabilized cell system for studying regulation of aryl hydrocarbon hydroxylase: NADPH as rate limiting factor in benzo(a)pyrene metabolism

Sadowski, Ivan; Wright, James A.; Israels, L. G.

doi:10.1016/0020-711x(85)90250-2

Cited by 17 publications

(2 citation statements)

References 10 publications

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“…The DHEA class of steroids inhibit inflammation through pleiotropic mechanisms distinct from both NSAIDs and glucocorticoids. They may act by inhibiting glucose-6-phosphate dehydrogenase (G6PDH) and suppressing oxygen-free radical formation (Babior, 1982;Imlay, 1988;Sadowski, 1985;Pashko, 1993, 1994). DHEA steroids are also very effective inhibitors of NO production.…”

Section: Discussionmentioning

confidence: 99%

A Novel Dehydroepiandrosterone Analog Improves Functional Recovery in a Rat Traumatic Brain Injury Model

Malik

Narayan²,

Wendling³

et al. 2003

Journal of Neurotrauma

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The purpose of this study was to investigate the efficacy of a novel steroid, fluasterone (DHEF, a dehydroepiandrosterone (DHEA) analog), at improving functional recovery in a rat model of traumatic brain injury (TBI). The lateral cortical impact model was utilized in two studies of efficacy and therapeutic window. DHEF was given (25 mg/kg, intraperitoneally) at the initial time point and once a day for 2 more days. Study A included four groups: sham injury, vehicle treated (n = 22); injured, vehicle treated (n = 30); injured, pretreated (5-10 min prior to injury, n = 24); and injured, posttreated (initial dose 30 min postinjury, n = 15). Study B (therapeutic window) included five groups: sham injury, vehicle treated (n = 17); injured, vehicle treated (n = 26); and three posttreatment groups: initial dose at 30 min (n = 18), 2 h (n = 23), or 12 h (n = 16) postinjury. Three criteria were used to grade functional recovery. In study A, DHEF improved beam walk performance both with pretreatment (79%) and 30-min posttreatment group (54%; p < 0.01, Dunnett vs. injured vehicle). In study B, the 12-h posttreatment group showed a 97% improvement in beam walk performance (p < 0.01, Dunnett). The 30-min and 12-h posttreatment groups showed a decreased incidence of falls from the beam, which reached statistical significance (p < 0.05, Dunnett). Tests of memory (Morris water maze) and neurological reflexes both revealed significant improvements in all DHEF treatment groups. In cultured rat mesangial cells, DHEF (and DHEA) potently inhibited interleukin-1beta-induced cyclooxygenase-2 (COX2) mRNA and prostaglandin (PGE2) production. In contrast, DHEF treatment did not alter injury-induced COX2 mRNA levels in the cortex or hippocampus. However, DHEF (and DHEA) relaxed ex vivo bovine middle cerebral artery preparations by about 30%, with an IC(50) approximately 40 microM. This was a direct effect on the vascular smooth muscle, independent of the endothelial cell layer. Fluasterone (DHEF) treatments improved functional recovery in a rat TBI model. Possible mechanisms of action for this novel DHEA analog are discussed. These findings suggest an exciting potential use for this agent in the clinical treatment of traumatic brain injury.

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Section: Discussionmentioning

confidence: 99%

A Novel Dehydroepiandrosterone Analog Improves Functional Recovery in a Rat Traumatic Brain Injury Model

Malik

Narayan²,

Wendling³

et al. 2003

Journal of Neurotrauma

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“…In agreement with this interpretation it has recently been observed that ethanol infusion into rats, which causes liver NADPH oxidation (Reinke et al, 1980) strongly inhibits phenol production by BaP (Reinke et al, 1982). In addition, recent evidence, obtained from a permeabilized whole-cell system, suggests that NADPH is rate-limiting in the mixed function oxidation of BaP (Sadowski et al, 1985).…”

Section: Discussionmentioning

confidence: 99%

Benzo(a)pyrene metabolism by lymphocytes from normal individuals and individuals carrying the mediterranean variant of glucose‐6‐phosphate dehydrogenase

Feo

Ruggiu

Lenzerini

et al. 1987

Intl Journal of Cancer

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In vitro growing human lymphocytes (HL) and fibroblasts, isolated from glucose-6-phosphate dehydrogenase (G6PD)-deficient subjects (Mediterranean variant), show a sharp decrease in this enzymatic activity and in NADPH:NADP+ ratio. These cells are less able than controls to hydroxylate benzo(a)pyrene (BaP) when tested in the absence of an exogenous NADPH-generating system. They exhibit great resistance to the toxic effect of BaP. G6PD-deficient fibroblasts are less prone than controls to in vitro transformation by BaP. To investigate whether this depends on a decreased production of active BaP metabolites and BaP:DNA adducts by G6PD-deficient cells, BaP metabolism was studied in G6PD-deficient HL cultured in vitro in the presence of mitogens and treated with BaP for 24 hr. HPLC profiles of organo- and water-soluble metabolites revealed that both types of benzo(a)anthracene (BaA)-induced HL produced: 4,5-, 7,8-, 9,10-diols, 1,3-, 3,6-quinones, 3-, 9-hydroxy and 2 peaks of more polar metabolites. There was a 25-76% decrease of organo- and water-soluble metabolites in the G6PD-deficient cells. When HL were incubated with 7,8-diol, the formation of metabolites mutagenic for Salmonella typhimurium (His-) was very low in G6PD-deficient cells. BaP:deoxyadenosine (dAde) and BaP:deoxyguanosine (dGua) adducts were identified after incubation of both types of HL with BaP. There was a 31-79% fall in adduct formation by G6PD-deficient cells. Our results indicate that G6PD-deficient human lymphocytes are less able to metabolize BaP than normal lymphocytes. We suggest that the NADPH pool is inadequate, in deficient cells, for active BaP metabolism.

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Cytochrome P450‐dependent alkoxyphenoxazone dealkylase activity in rat alveolar type II cells: Effect of pretreatment with β‐naphthoflavone

Rabovsky

Judy

Sapola

et al. 1989

Cell Biochemistry & Function

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Cytochrome P450-dependent alkoxyphenoxazone dealkylase activity was measured in alveolar type II cells from control and beta-naphthoflavone (ip) treated-rats. Type II cells were isolated from collagenase/elastase-digested lung tissue and purified by centrifugal elutriation. The specificity of the cytochrome P450-dependent activity towards four alkoxyphenoxazones (methoxy-, ethoxy-, pentoxy-, and benzyloxyphenoxazone) was measured under conditions that minimized interference by cytosolic conjugating- and NADPH-dependent quinone reductase activities. Ethoxyphenoxazone dealkylase activity was induced 17-fold following beta-naphthoflavone treatment and was further characterized by its kinetic parameters and sensitivities toward in vitro inhibitors (Km(app) = 0.20 microM, Vmax = 1.74 pmoles resorufin min-1 (10(6) cells)-1 10(6) cells; I50 (alpha-naphthoflavone) = 0.025 microM, and I50 (metyrapone) = 72 microM). beta-Naphthoflavone pretreatment of the rats did not result in statistically significant changes in methoxy-, pentoxy-, or benzyloxyphenoxazone dealkylase activity of alveolar type II cells, although, a trend towards decrease activity was observed for benzyloxyphenoxazone. beta-Naphthoflavone pretreatment had no effect on oxygen consumption or trypan blue exclusion in alveolar type II cells and macrophage ethoxyphenoxazone dealkylase and benzyloxphenoxazone dealkylase activities were not affected by the beta-naththoflavone pretreatment. The results show that exposure to beta-naphthoflavone resulted in an increase in type II cell cytochrome P450-dependent ethoxyphenoxazone dealkylase activity but not in other alveolar type II cell or macrophage alkoxyphenoxazone dealkylase activities or in parameters that monitor viability and cell wall integrity.

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A permeabilized cell system for studying regulation of aryl hydrocarbon hydroxylase: NADPH as rate limiting factor in benzo(a)pyrene metabolism

Cited by 17 publications

References 10 publications

A Novel Dehydroepiandrosterone Analog Improves Functional Recovery in a Rat Traumatic Brain Injury Model

A Novel Dehydroepiandrosterone Analog Improves Functional Recovery in a Rat Traumatic Brain Injury Model

Benzo(a)pyrene metabolism by lymphocytes from normal individuals and individuals carrying the mediterranean variant of glucose‐6‐phosphate dehydrogenase

Cytochrome P450‐dependent alkoxyphenoxazone dealkylase activity in rat alveolar type II cells: Effect of pretreatment with β‐naphthoflavone

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