Effects of indole-3-carbinol on biotransformation enzymes in the rat: in vivo changes in liver and small intestinal mucosa in comparison with primary hepatocyte cultures

Groups of male Wistar rats were fed semi-synthetic diets containing 0, 200 or 500 mg indole-3-carbinol (13C)/kg for 2, 7, 14 or 28 days. After 2 days, P-450 activities were already induced, but the isoenzyme pattern induced was different in the liver and the small intestine. Hepatic P4501A1, P4501A2 and P4502B1 apoprotein levels were dose-relatedly enhanced, whereas in the small intestine induced levels of P4502B1 and P4501A1 were detected but P4501A2 was not induced. Pentoxy- and ethoxyresorufin dealkylation (PROD and EROD) were dose-relatedly enhanced in the liver (5- and 7-fold, respectively, in the higher dose group) as well as in the small intestine (8- and 13-fold, respectively, at 500 mg 13C/kg diet). Testosterone 16 alpha- and 16 beta-hydroxylation in the small intestine were enhanced (6-9-fold) from day 2 onwards, but in the liver these activities were only slightly enhanced from day 7 onwards. Thus, the major forms induced in the liver appear to be P4501A1, P4501A2, P4502B1 and, to a lesser extent, P4503A, whereas in the small intestine all of the effects that were found are associated with only one cytochrome P-450, P4502B1. After 2 days I3C (500 mg/kg) induced glutathione S-transferase in the liver (1.3-fold) and small intestine (1.5-fold). Hepatic glucuronyl transferase (GT1) was induced (about 1.6-fold) after 7, 14 and 28 days. DT-diaphorase was induced in the liver (2.7-fold) and small intestine (1.5-fold) after 14 days of exposure to 500 mg I3C/kg diet. Treatment of rat hepatocytes with indole-3-acetonitrile and 3,3'-diindolylmethane, but not I3C and indole-3-carboxaldehyde, enhanced EROD activity and halved testosterone 16 alpha- and 2 alpha-hydroxylation. All four indoles slightly induced glutathione S-transferase in cultured hepatocytes. Thus, the in vitro studies suggest that the in vivo effects of I3C have to be attributed to indole-condensation products, such as 3,3'-diindolylmethane, but not to I3C itself.

Effects of various medium formulations and attachment substrata on the performance of cultured ruminant hepatocytes in biotransformation studies

1. A procedure for the isolation and primary culture of hepatocytes from goat and cattle is described. Hepatocyte culture performance was monitored for 51 h by measuring viability, cytochrome P-450 maintenance, dealkylation of scoparone and ethylmorphine, and glucuronidation of phenol red. 2. Culture medium composition is discussed in relation to differences between splanchnic blood composition of ruminant and monogastric animal species. Main differences are in glucose and volatile fatty acid concentrations. Modified Williams' E culture medium did not yield higher culture performance than non-modified Williams' E. 3. Coating of culture dishes with either collagen or fibronectin did not improve culture performance. 4. Williams' E, although developed for rodent cells, proves to be a suitable basal medium for ruminant hepatocytes. In this medium, culture quality is high for at least several days. 5. In cultured goat hepatocytes, biotransformation rate for scoparone amounted to 20 nmol/mg protein per h, for ethylmorphine 96 nmol/mg protein per h and for phenol red 2 nmol/mg protein per h. Biotransformation activity in cow hepatocytes is approximately half that in goat hepatocytes.

Interlaboratory comparison of microsomal ethoxyresorufin and pentoxyresorufin O-dealkylation determinations: standardization of assay conditions

Assay conditions and results of cytochrome P-450 dependent 7-ethoxyresorufin (ER) and 7-pentoxyresorufin (PR) O-dealkylation (OD) by rat liver microsomes were compared by four laboratories in the Netherlands. Microsomal mixtures were prepared from control, 3-methylcholanthrene and phenobarbital pretreated animals, resulting in different levels of cytochrome P-450 isozymes. EROD and PROD activities were determined in each laboratory according to their own protocols. Considerable variability was found both between and within laboratories. Further studies demonstrated that protocol differences are important factors causing this interlaboratory variation. Main factors of influence were buffer type, batch of resorufin used for calibration, substrate solvent and substrate concentration. Based on the results obtained, standardized protocols for optimized measurement of microsomal EROD and PROD activities were developed. Additional experiments demonstrated that the use of these standardized protocols reduced intralaboratory variation in both the EROD and the PROD assay, whereas it also reduced the interlaboratory variability for the PROD determinations. The interlaboratory variation for measurement of microsomal EROD activities was only reduced for the laboratories using a Cobas-Bio analyzer. The results of the present study demonstrate clearly that data obtained with EROD and PROD activity measurements are highly sensitive to factors frequently varying from one laboratory to another. In addition, they demonstrate the necessity to be careful with absolute values presented in the literature for these activities, unless well characterized assay conditions are applied.

Acid reaction products of indole-3-carbinol and their effects on cytochrome P450 and phase II enzymes in rat and monkey hepatocytes

The effects of three acid condensation products of indole-3-carbinol (I3C), i.e. 3,3'-diindolylmethane (DIM), 5,6,11,12,17,18-hexahydrocyclonona[1,2-b:4,5-b':7,8-b"]tri-indole (CTI) and 2,3-bis[3-indolylmethyl]indole (BII), on cytochrome P450 and phase II enzymes were studied in primary cultures of rat and cynomolgus monkey liver cells. In rat hepatocytes all three indole derivatives dose-relatedly induced the ethoxyresorufin O-dealkylation (EROD) activity (to 24-fold) and 7 alpha-hydroxylation of testosterone (to 4-fold), whereas all three decreased the 16 alpha- and 2 alpha-testosterone hydroxylation (DIM to 60%, CTI and BII to a mere 5% of the control cells). Treatment of monkey hepatocytes with DIM and BII enhanced the EROD activity to 6- and 9-fold, respectively. Furthermore, BII decreased the 6 beta-hydroxylation of testosterone (to 60% of the untreated cultures) in monkey cells. Phase II enzymes were also affected. In rat hepatocytes DIM, CTI and BII enhanced DT-diaphorase (DTD) (= NAD(P)H-quinone reductase) activity, and DIM and BII the glucuronidation of 1-naphthol. In monkey cells BII only enhanced DTD, and no changes were observed in the glucuronidation of 1-naphthol after treatment with either DIM or BII. The indole derivatives did not affect glutathione S-transferase activity and sulfation of 1-naphthol in either rat or monkey hepatocytes. These results identify two novel acid condensation products of I3C, CTI and BII, as potent compounds in affecting biotransformation in rat as well as in monkey hepatocytes.

Induction of terminal differentiation in cultured human keratinocytes by polychlorinated aromatic hydrocarbons as measured by cell size analysis

Polychlorinated aromatic hydrocarbons modulate the proliferation and differentiation of human epidermal cells in vivo and in culture. One of the earliest events in the process of terminal differentiation is the increase in cell size. In this report the usefulness of morphometric cell size analysis as a quantifiable marker for chemical-induced differentiation was examined. Concentration-related increases in cell size distribution were induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and 2,3,4,7,8-pentachlorodibenzofuran in normal human keratinocytes and cells from an SV40-transformed keratinocyte cell line (SVK14) whereas the analog 1,2,3,4-tetrachlorodibenzo-p-dioxin did not affect the cell size distribution up to a concentration of 100 nM. The minimal effective concentrations of five 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins/dibenzofurans and a coplanar polychlorbiphenyl necessary to induce an increase in cell size distribution were determined in SVK14 cells. It was found that the potency of these compounds relative to that of 2,3,7,8-TCDD correlated well with the toxicity equivalency factors observed in other test systems. This indicates that the keratinocyte cell assay is a useful method for establishing the relative potency of various "dioxins" and their mixtures.

Effects of cooked brussels sprouts on cytochrome P-450 profile and phase II enzymes in liver and small intestinal mucosa of the rat

Male Wistar rats were given semi-synthetic diets supplemented with 0, 2.5, 5 and 20% cooked Brussels sprouts for 2, 7, 14 or 28 days. The effects on several cytochrome P-450 enzymes and phase II enzymes (glutathione S-transferase (GST), glucuronyl transferases 1 and 2 (GT1 and GT2) and DT-diaphorase (DTD)) in the liver and small intestinal mucosa were investigated. From 2 days of exposure onwards Brussels sprouts induced P4501A2 and--to a lesser extent--P4501A1 apoprotein levels in the liver, whereas in the small intestine markedly enhanced P4502B apoprotein levels could be detected. No enhanced P4503A apoprotein levels were observed. The 5 and 20% sprouts diets increased the intestinal pentoxyresorufin depentylation (PROD, 4.5-9-fold), and the hydroxylation of testosterone at the 16 alpha- and 16 beta-site (2.6-4.2-fold) after 2 days of exposure. In addition, the 20% sprouts died also enhanced the intestinal ethoxyresorufin deethylation (EROD) activity (c. 5-fold), the hepatic EROD and PROD activities (c. 2-fold) and the formation of 6 beta-hydroxytestosterone (c. 1.6-fold); the formation of 2 alpha-hydroxytestosterone in the liver was decreased (to c. 70% of the control value). GST activity was induced both in the liver (5 and 20% diet) and intestine (20% diet only) throughout the experiment. The 20% sprouts diet enhanced the hepatic DTD and GT1 activities, whereas the GT2 activity was decreased. The induction of DTD in the small intestine after 2 days (2.5-3.2-fold with 5 and 20% sprouts diets, respectively) diminished during the experiment. These results indicate that dietary exposure to cooked Brussels sprouts for only 2 days can change the metabolic activities of several phase II enzymes and cytochrome P-450 enzymes, of which P4502B is the predominant form induced in the small intestine.

Comparison of cytochrome P450 isoenzyme profiles in rat liver and hepatocyte cultures. The effects of model inducers on apoproteins and biotransformation activities

The metabolic profile of seven subfamilies of cytochrome P450 (P450IA, IIA, IIB, IIC, IIE, IIIA, IVA) was studied in rat liver (in vivo) and in primary hepatocyte cultures (in vitro) after treatment with various inducers. The dealkylation of 7-ethoxyresorufin (EROD) and 7-pentoxyresorufin (PROD), aniline 4-hydroxylation and the regio- and stereoselective hydroxylation of testosterone were measured to characterize the isoenzyme pattern in intact hepatocytes and in liver microsomes. Occurrence of isoenzyme apoproteins was determined using Western blotting. Primary cultures of rat hepatocytes retain the capacity to respond to inducers of isoenzymes belonging to six different subfamilies (P450IA, IIA, IIB, IIC, IIIA and IVA). Treatment of cells with beta-naphthoflavone revealed a P450-activity profile similar to in vivo, namely a highly induced EROD (P450IA1), a small enhancement of testosterone 7 alpha-hydroxylation (P450IIA) and a marked reduction in 2 alpha- and 16 alpha-hydroxylation (P450IIC11). Exposure of cultured cells to phenobarbital resulted in a higher testosterone 16 beta-hydroxylation (reflecting P450IIB), though to a lesser extent than in vivo. The induction of P450IIIA due to both phenobarbital and dexamethasone, as mirrored by 6 beta- and 15 beta-hydroxylation of testosterone, was the same in cultured hepatocytes and in vivo. Treatment of cells with clofibric acid resulted in an induction profile similar to the one observed in liver microsomes from clofibrate-treated rats: the apoprotein P450IVA as well as the apoprotein P450IIB1/2 and its associated activities (PROD and testosterone 16 beta-hydroxylation) were induced. Isoniazid, a known in vivo inducer of P450IIE1 and aniline 4-hydroxylation, did not change any of the determined P450-dependent activities in vitro.

Biotransformation of scoparone used to monitor changes in cytochrome P450 activities in primary hepatocyte cultures derived from rats, hamsters and monkeys

The coumarin derivative scoparone is regioselectively demethylated yielding isoscopoletin and scopoletin. The ratio of the formation rates of these two metabolites (isoscopoletin/scopoletin; I/S ratio) is reported to mirror the contribution of several cytochrome P450 (P450) isoenzymes to the biotransformation of scoparine. The metabolism of scoparine has been studied in primary liver cell cultures of rats, hamsters, cynomolgus monkeys and in human liver cells. Rat hepatocytes appeared to metabolize scoparone 7 to 10 times slower than those of hamsters and monkeys. In hepatocyte monolayers of all three species the loss of P450 was paralleled by a decrease in total scoparone metabolism. In hamsters but not in rats, a decrease of the I/S ratio was found during primary culture of liver cells. A similar shift in the metabolic pattern of scoparine observed with the monkey hepatocytes was statistically not significant. Most likely, in hamster and possibly in monkey hepatocyte cultures the different P450s involved in scoparone metabolism decrease at unequal rates. In rat liver cells, however, the pattern of these P450 isoenzymes remains more or less unaltered. In contrast to liver cells from the other species, human hepatocytes did not secrete scopoletin in detectable amounts. Scoparone demethylation in humans may be qualitatively different from that in other mammals.

Structure elucidation of acid reaction products of indole-3-carbinol: detection in vivo and enzyme induction in vitro

The potency of indole-3-carbinol (I3C) to form condensation products under acidic aqueous conditions was studied. After identifying a known dimer, 3,3'-diindolylmethane (DIM), we elucidated the structures of two trimers also found in acid reaction mixtures: 5,6,11,12,17,18-hexahydrocyclonona[1,2-b:4,5-b':7,8-b"]tri-indole (CTI), and 2,3-bis[3-indolylmethyl] indole (BII). The formation of these indole oligomers was shown to be pH dependent. The highest amounts of DIM and BII were formed in aqueous solutions having a pH value ranging from 4 to 5. No CTI could be detected at pH values above 4.5. In rats that received an oral dose of I3C we could detect DIM and BII in gastric contents, stomach tissue, small intestine and liver. No CTI could be detected in vivo after oral exposure to I3C. In in vitro experiments, using rat hepatocytes, the cytochrome P-450IA1 apoprotein level, 7-ethoxyresorufin O-deethylation activity (EROD) and DT-diaphorase activity (DTD) were markedly enhanced by DIM and CTI as well as BII.

Immunohistochemical detection of cytochrome P450 isoenzymes in cultured human epidermal cells

We used specific monoclonal antibodies (MAb) to human cytochrome P450 isoenzymes to determine the presence of these proteins in human epidermal cells. Two MAb (P450-5 and P450-8) recognize major forms of hepatic cytochrome P450 involved in biotransformation of xenobiotics. A third MAb, to cytochrome P450-9, is not fully characterized. The proteins were determined by the indirect immunoperoxidase technique after fixation with methanol and acetone. Biopsy materials for cultured keratinocytes, i.e., foreskin and hair follicles, contained the two major forms of cytochrome P450. In cultured keratinocytes derived from hair follicles the proteins were undetectable, whereas the keratinocytes derived from foreskin continued to express the two major forms of hepatic cytochrome P450. Cultured human fibroblasts and a human keratinocyte cell line (SVK14) showed staining similar to that of the foreskin keratinocytes. Cytochrome P450-9 was detectable only in human hepatocytes. The results indicate that, under the culture conditions applied, cultured human foreskin cells and the cell line SVK14 continue to express specific cytochrome P450 isoenzymes in culture, in contrast to hair follicle keratinocytes.

The isoenzyme pattern of cytochrome P450 in rat hepatocytes in primary culture, comparing different enzyme activities in microsomal incubations and in intact monolayers

Changes in the isoenzyme pattern of cytochrome P450 during culture were investigated in primary cultures of rat hepatocytes, measuring specific enzyme activities in microsomes prepared from cultured cells as well as in intact monolayers. Assays of 7-ethoxyresorufin O-deethylation (EROD), 7-pentoxyresorufin O-depentylation (PROD), aniline 4-hydroxylation (AH) and the specific regioselective hydroxylation of testosterone were used as representatives of the activities of seven isoenzymes of cytochrome P450. The isoenzyme profile expressed as catalytic activities was qualitatively and quantitatively similar in microsomes obtained from freshly isolated hepatocytes in comparison with microsomes obtained from whole livers of untreated rats. There was a relatively high activity in EROD, AH and the oxidation of testosterone at the 7 alpha, 2 alpha, 6 beta, 16 alpha and 17 sites (androstenedione). During culture, these microsomal enzyme activities declined at a similar rate to ca. 50% of the activities of microsomes prepared from freshly isolated hepatocytes after 24 hr and to 15% after 96 hr. The overall decline of cytochrome P450-dependent activities during culture was not accompanied with gross changes in catalytic profile. Determining the same drug-metabolizing activities directly in intact hepatocyte monolayers revealed a much higher metabolic rate for all measured P450-dependent activities. The profile of the catalytic activities was essentially the same as measured in microsomes prepared from cultured hepatocytes. The relatively low activity towards the 7 alpha site of testosterone measured in intact hepatocytes, however, remained constant during culture. Determination of enzyme activities directly in intact hepatocytes is a convenient way of studying changes in monooxygenase activities of different P450 isoenzymes in vitro.

The effect of beclobric acid and clofibric acid on peroxisomal beta-oxidation and peroxisome proliferation in primary cultures of rat, monkey and human hepatocytes

The peroxisome-proliferating effects of clofibric acid and beclobric acid were studied in primary cultures of hepatocytes derived from rat, monkey (Macaca fascicularis) and human liver. Determination of peroxisomal fatty acid beta-oxidation and morphometrical analysis of the peroxisomal compartment were performed after incubation of 1-day-old hepatocyte cultures for 3 days with either compound. In rat liver cell cultures both compounds gave a 10-fold increase in peroxisomal beta-oxidation, a 3-fold increase in the relative number of peroxisomes and a 1.5-fold increase in the mean size of peroxisomes. Beclobric acid gave its maximal effect at a concentration of 10 microM, which is at least one order of magnitude lower than the maximum-effect concentration of clofibric acid. At concentrations greater than 300 microM beclobric acid was cytotoxic. No stimulation of peroxisomal fatty acid beta-oxidation was found in either monkey or human hepatocyte cultures. Morphometrical analysis also showed no increase in the peroxisomal compartment in cultures derived from these species, as indicated by the lack of increase in both relative number and size of peroxisomes. In all three species tested beclobric acid was equally cytotoxic for hepatocytes in vitro. These results are of relevance for the interpretation of the peroxisome-proliferating effects of clofibrate and similar compounds in rats. Since peroxisome proliferation may be correlated to increased hepatic tumour incidences in the rat, the absence of peroxisome proliferation in primates suggests the absence of tumourogenic activity by hypolipidemic compounds in these species.

Effects of sulphydryl reagents on the formation of the aniline metabolite 4-aminophenol and its sulphate and glucuronide conjugates in primary cultures of rat hepatocytes

1. The effects of various sulphydryl-blocking reagents on aniline biotransformation and cytochrome P-450 levels were studied in cultured rat hepatocytes. 2. Exposure of aniline-metabolizing hepatocytes to p-chloro-mercuribenzoate (PCMB) or p-chloromercuribenzenesulphonic acid (PCMBS) resulted in decreased levels of cytochrome P-450, decreased glucuronidation of 4-aminophenol and increased levels of free 4-aminophenol. 3. Incubation of aniline-metabolizing hepatocytes with disulfiram resulted in decreased formation of 4-aminophenol, but this was not associated with impaired glucuronidation or cytochrome P-450 levels. 4. Exposure of aniline-metabolizing hepatocytes to mersalyl, 2,2'-dithiodipyridine (DTP), 6,6'-carboxydipyridine disulphide (CPDS) or N-ethylmaleimide did not affect the biotransformation of aniline or cytochrome P-450 levels. 5. Metyrapone prevented degradation of cytochrome P-450. Exposure of cells to SKF-525 A inhibited aniline biotransformation without altering cytochrome P-450 levels. 6. PCMB and PCMBS inhibited aniline metabolism, probably by binding to a cysteinyl-SH residue in cytochrome P-450 apoenzyme and 'active sites' of UDP-glucuronyl transferases. Disulfiram inhibited aniline biotransformation, probably indirectly by diminishing NADPH.

Rapid method for the determination and quantification of bromosulphophthalein and metabolites in cultured hepatocytes, culture media and bile by high-performance liquid chromatography

An ion-pair high-performance liquid chromatographic method for the rapid, selective and sensitive analysis of samples containing bromosulphophthalein (BSP) and its conjugates is presented. The method is useful for analysis in bile, culture media and cultured hepatocytes. Two sample preparation methods are described. Even though BSP recovery from albumin binding is complete, only a small percentage of free BSP can be detected in cells, possibly owing to a conjugation-related pool of BSP in cells. As BSP-glutathione recovery is complete, the method offers a useful tool to investigate impairment of glutathione conjugation.

Effects of 1,2-dibromoethane on isolated hepatocytes: functional alterations and induction of lipid peroxidation

1. Isolated rat hepatocytes were exposed to the fumigant 1,2-dibromoethane (DBE) and cytotoxicity was evaluated by studying parameters of cellular function and lipid peroxidation. 2. DBE caused plasma membrane damage, as determined by leakage of lactate dehydrogenase, and was more severe in shaken suspensions than stationary suspensions, suggesting that cells were more fragile after DBE exposure. 3. DBE decreased hepatocyte glycogen content and stimulated albumin synthesis in hepatocyte suspensions. 4. Lipid peroxidation resulted from DBE exposure and was greater in cells isolated from phenobarbital-pretreated rats. Shaking the suspensions enhanced lipid peroxidation. Ethane production did not parallel formation of thiobarbituric acid reactants, suggesting that these parameters of lipid peroxidation reflect different mechanisms of molecular interaction of DBE.

Interlaboratory comparison of total cytochrome P-450 and protein determinations in rat liver microsomes. Reinvestigation of assay conditions

Assay conditions in determining total cytochrome P-450 in four laboratories were compared. Although the determination was derived from the original Omura and Sato method in each laboratory, the four standard protocols differed slightly, resulting in considerable differences in the results. Since the cytochrome P-450 content is usually expressed per mg protein, the protein assay conditions were evaluated as well. Furthermore, we compared the cytochrome P-450 values obtained by the CO- and the dithionite (DT)-difference methods. The effect of a number of variables in the assay was investigated. The influence of the storage temperature of the microsomes was ascertained as well as effects of the gassing time with CO and the time between addition of dithionite, CO-gassing and the recording of the difference spectra. After evaluating these variables a standard operation procedure was established. Using this procedure the interlaboratory coefficient of variation for total cytochrome P-450 was 4.8%, a value which was comparable to the intralaboratory coefficients of variation. The final results also show that the millimolar extinction coefficient for the DT-difference method is higher than for the CO-difference method.

NADH-ferrihemoglobin reductase in avian erythrocytes

The assay for NADH-ferrihemoglobin reductase (NADH-FR) was optimized for avian blood samples. In this assay the pH optimum for Japanese quail red cell NADH-FR was 5.5, which was close to the enzyme's pI. Enzyme kinetic parameters were determined for quail, chicken and turkey NADH-FR. Preparation of erythrocyte ghost-cells and subsequent fractionation showed that the enzyme was present in the plasma membrane as well as in the nuclear membrane, while Triton X-100 treatment gave a release of enzyme activity from the membrane. In the cytosolar fraction of avian red cells no NADH-FR could be detected.

Kinetics of the formation and secretion of the aniline metabolite 4-aminophenol and its conjugates by isolated rat hepatocytes

The rates of secretion of 4-aminophenol and its sulphate and glucuronide conjugate were determined in cultures of rat hepatocytes with aniline and 4-aminophenol as substrates. When 4-aminophenol (300 microM) was used as substrate, 4-aminophenol disappeared from the medium within 30 min. Secretion of conjugates continued for more than 60 min, when 70% of the 4-aminophenol had been secreted as conjugates. At a low concn. of 4-aminophenol, the sulphate ester was the main metabolite, while secretion of the glucuronide showed a more than proportional rise ('lag phase') with increasing substrate concn. At higher concn. (greater than 300 microM) about equal amounts of both conjugates were formed. Without inorganic sulphate, sulphation of 4-aminophenol was greatly diminished and the lag phase in glucuronide secretion was not found. With 1 mM aniline as substrate up to 300 microM of conjugated 4-aminophenol was secreted with a linear time-dependence for at least two hours. With aniline as substrate the sulphate ester was the most important conjugate and lag phases in the secretion of both conjugates were minimal. Phenobarbitone pretreatment in vivo stimulated the secretion of conjugated products after incubation with aniline. No dramatic changes in the profile of the lag phases were seen. The differences in the conjugation profiles of both substrates can be explained by taking into consideration the differences in the expected intracellular concentrations.

Formation and disposition of N-hydroxylated metabolites of aniline and nitrobenzene by isolated rat hepatocytes

The formation and secretion of phenylhydroxylamine plus nitrosobenzene was studied in cultures of isolated rat hepatocytes after addition of aniline or nitrobenzene. With aniline concn. up to 10 mM, N-oxygenated metabolites were secreted linearly with time over 2 h. Phenobarbitone pretreatment in vivo for c. 5 d increased aniline N-hydroxylation by a factor of 2.8. Nitrobenzene reduction by isolated rat hepatocytes, yielding phenylhydroxylamine plus nitrosobenzene in the medium, was stimulated 1.9-fold and 4.3-fold after phenobarbitone pretreatment in vivo for 5 and 10 d, respectively. After reduction of nitrobenzene by isolated hepatocytes, the secretion of N-oxygenated products into the medium was non-linear with time for substrate concn. higher than 2.5 mM, probably due to the formation of cytotoxic concn. of nitrosobenzene. Isolated rat hepatocytes reduced phenylhydroxylamine to aniline. Results indicate that isolated rat hepatocytes are a reliable and sensitive system to demonstrate N-oxygenated metabolites of aromatic amino- and reduction of nitrocompounds.

Reversed phase high-performance liquid chromatography of heterocyclic aromatic N-oxides: application to measurement of N-oxidation by microsomes and rat hepatocytes in primary culture

1. The rates of N-oxide formation from pyridine, nicotinamide and isonicotinamide by rat liver microsomes and by cultured rat hepatocytes have been quantified using a simple h.p.l.c. system. 2. Hepatocytes produce hetero-aromatic N-oxides for at least 5 h, making them a useful system to study the N-oxidation of pyridines.

Effects of phenylhydroxylamine and aminophenols in Japanese quail in vivo

1. The effects of phenylhydroxylamine, and o- and p-aminophenol were studied in the Japanese quail. 2. Symptoms normally observed in aniline-treated birds were seen in quail after phenylhydroxylamine dosage at > 10 mg/kg. Aminophenols (up to 50 mg/kg) did not give these symptoms. 3. Injection of phenylhydroxylamine (50 mg/kg) resulted in formation of 70% ferrihaemoglobin after 5 min, following which a rapid reduction of ferrihaemoglobin was observed. 4. Phenylhydroxylamine reached highest blood concn. of 0.2 mumol/ml after 5 min. Phenylhydroxylamine was reduced to aniline within 5 min. 5. The effects of aniline in vivo are most probably due to O2 shortage caused by ferrihaemoglobin formation.

Biochemical processes involved in ferrihemoglobin formation by monohydroxyaniline derivatives in erythrocytes of birds and mammals

Background

Major depressive disorder (MDD) is the leading cause of global disability; however, the existing treatments do not always address cognitive dysfunction—a core feature of MDD. Immersive virtual reality (VR) has emerged as a promising modality to enhance the real-world effectiveness of cognitive remediation.

Objective

This study aimed to develop the first prototype VR cognitive remediation program for MDD (“bWell-D”). This study gathered qualitative data from end users early in the design process to enhance its efficacy and feasibility in clinical settings.

Methods

Semistructured end-user interviews were conducted remotely (n=15 patients and n=12 clinicians), assessing the participants’ perceptions and goals for a VR cognitive remediation program. Video samples of bWell-D were also shared to obtain feedback regarding the program. The interviews were transcribed, coded, and analyzed via thematic analysis.

Results

End users showed an optimistic outlook toward VR as a treatment modality, and perceived it as a novel approach with the potential of having multiple applications. The participants expressed a need for an engaging VR treatment that included realistic and multisensorial settings and activities, as well as customizable features. Some skepticism regarding its effectiveness was also reported, especially when the real-world applications of the practiced skills were not made explicit, as well as some concerns regarding equipment accessibility. A home-based or hybrid (ie, home and clinic) treatment modality was preferred.

Conclusions

Patients and clinicians considered bWell-D interesting, acceptable, and potentially feasible, and provided suggestions to enhance its real-world applicability. The inclusion of end-user feedback is encouraged when developing future VR programs for clinical purposes.