[Association of triglyceride glucose index and risk of incident hypertension: a prospective cohort study].

Objective: To explore the relationship between the triglyceride glucose (TyG) index and the risk of developing hypertension among rural Chinese adults. Methods: A prospective cohort study was conducted from 2007 to 2008, involving 20 194 adults selected through random cluster sampling from a rural community in Luoyang City, Henan Province. Follow-ups were carried out in 2013-2014 and 2018-2020. After excluding participants with hypertension at baseline, those with missing TyG index data, individuals who passed away during follow-up, and those with incomplete hypertension status at the second visit, 9 802 participants were included in the analysis. Baseline and follow-up assessments included questionnaire interviews, physical measurements (including blood pressure), and blood sample collection for fasting lipid and glucose levels. Participants were divided into four groups according to TyG index quartiles, and a modified Poisson regression model was utilized to assess the association between TyG index quartiles and hypertension risk. Results: The study cohort comprised 9 802 participants with a median age of 48 (39, 57) years, including 3 803 males (38.80%). Participants were distributed across TyG index quartiles as follows: TyG<8.2 group (2 224 individuals), TyG 8.2-8.5 group (2 653 individuals), TyG 8.6-8.9 (2 441 individuals), and TyG≥9.0 (2 484 individuals). Over a follow-up period of (11.1±1.3) years, 3 378 subjects developed hypertension, resulting in a cumulative incidence of 34.46% (3 378/9 802). The risk of hypertension increased with higher TyG index quartiles (Ptrend<0.05). Compared to the TyG<8.2, the TyG 8.2-8.5 (RR=1.11, 95%CI 1.01-1.22, P=0.023), TyG 8.6-8.9 (RR=1.16, 95%CI 1.06-1.27, P=0.023), and TyG≥9.0 (RR=1.20, 95%CI 1.10-1.31, P=0.023) exhibited increased hypertension risk after adjusting for age, gender, educational level, and other potential confounders. Subgroup analyses based on gender and age at baseline yielded results consistent with the main analysis. Conclusions: The TyG index is positively correlated with the risk of developing hypertension in the rural adult population.

[Application value of combined deep inhalation and breath-hold technique guided by four-dimensional CT in preoperative localization of solitary pulmonary nodules].

Objective: To explore the clinical value of four dimensional computed tomography (4 D CT) guided combined with deep inhalation and breath hold (DIBH) technique in the preoperative localization of solitary pulmonary nodules. Methods: The data of a total of 106 patients with solitary pulmonary nodules from March 2018 to May 2021 in the Ningbo First Hospital were collected retrospectively. Among them, there were 26 males and 80 females aged from 21 to 83 (47.4±14.2) years. According to different localization methods, 53 cases were divided into the control group, as the pulmonary nodules were located by CT guided injection of indocyanine green under calm breathing and 53 cases were divided into in the experimental group, as those patients were treated with indocyanine green injection under the guidance of 4 D CT combined with DIBH technology to locate pulmonary nodules. The three-dimensional distance deviation between pulmonary nodules and indocyanine green injection points was compared between the two groups to obtain the accuracy of pulmonary nodule localization. The preoperative positioning time of the two groups was compared by timing. Results: Among the 106 patients, there were 46 pure ground glass nodules, 32 sub solid nodules and 28 solid nodules, all of which were successfully localized before operation, with a success rate of 100%. The size of pulmonary nodules in the control group was (9.1±2.3) mm and the three-dimensional deviation[M(Q1, Q3)]between indocyanine green injection site and pulmonary nodules was X axis [7.0 (3.7, 12.6)] mm, Y axis [6.6 (2.9, 11.2)] mm, Z axis [3.0 (2.0, 6.0)]mm, respectively, and the preoperative positioning time was (11.4±3.8) min. The size of pulmonary nodules in the experimental group was (8.9±2.1) mm, and the deviations in 3 D direction were X axis [4.8 (3.0, 7.9)]mm, Y axis [3.8 (1.3, 7.5)]mm, Z axis [4.0 (2.0, 6.0)] mm, respectively. The preoperative positioning time was (9.3±3.0) min. There were statistically significant differences in preoperative positioning time and deviation of X and Y axis between the experimental group and the control group (P<0.05), but no statistically significant differences was found in deviation of Z axis (P>0.05). Conclusion: 4 D CT guided DIBH technology could improve the accuracy of preoperative localization of pulmonary nodules and save operation time, which is worthy of popularization.

Extraction of proteins and preliminary characterization of physicochemical properties in Toona sinensis fruit.

We investigated the extraction of Toona sinensis fruit proteins and preliminarily characterized their physicochemical properties. The results showed that optimal extraction occurred under conditions of pH 10.5, a duration of 40 min, a liquid-to-solid ratio of 25:1, and a temperature of 40°C by an orthogonal design using T. sinensis fruit protein as the index and single factor. The total nitrogen content was 13.8 g/100 g and included 17 different amino acids. The glutamate level was highest at 35.37%, followed by arginine at 15.31%. The isoelectric point of T. sinensis fruit protein was between 6.8 and 10.0 with a typical absorption peak by infrared chromatography. Three protein bands were analyzed using SDS-polyacrylamide gel electrophoresis, with relative molecular weights of 55, 51, and 22 kDa. This study provides a theoretical basis for the comprehensive utilization of T. sinensis fruit by further investigating the biological activity of its proteins.

Acyclovir and transmission of HIV-1 from persons infected with HIV-1 and HSV-2.

BACKGROUND: Most persons who are infected with human immunodeficiency virus type 1 (HIV-1) are also infected with herpes simplex virus type 2 (HSV-2), which is frequently reactivated and is associated with increased plasma and genital levels of HIV-1. Therapy to suppress HSV-2 reduces the frequency of reactivation of HSV-2 as well as HIV-1 levels, suggesting that suppression of HSV-2 may reduce the risk of transmission of HIV-1. METHODS: We conducted a randomized, placebo-controlled trial of suppressive therapy for HSV-2 (acyclovir at a dose of 400 mg orally twice daily) in couples in which only one of the partners was seropositive for HIV-1 (CD4 count, > or = 250 cells per cubic millimeter) and that partner was also infected with HSV-2 and was not taking antiretroviral therapy at the time of enrollment. The primary end point was transmission of HIV-1 to the partner who was not initially infected with HIV-1; linkage of transmissions was assessed by means of genetic sequencing of viruses. RESULTS: A total of 3408 couples were enrolled at 14 sites in Africa. Of the partners who were infected with HIV-1, 68% were women, and the baseline median CD4 count was 462 cells per cubic millimeter. Of 132 HIV-1 seroconversions that occurred after randomization (an incidence of 2.7 per 100 person-years), 84 were linked within couples by viral sequencing: 41 in the acyclovir group and 43 in the placebo group (hazard ratio with acyclovir, 0.92, 95% confidence interval [CI], 0.60 to 1.41; P=0.69). Suppression with acyclovir reduced the mean plasma concentration of HIV-1 by 0.25 log(10) copies per milliliter (95% CI, 0.22 to 0.29; P<0.001) and the occurrence of HSV-2-positive genital ulcers by 73% (risk ratio, 0.27; 95% CI, 0.20 to 0.36; P<0.001). A total of 92% of the partners infected with HIV-1 and 84% of the partners not infected with HIV-1 remained in the study for 24 months. The level of adherence to the dispensed study drug was 96%. No serious adverse events related to acyclovir were observed. CONCLUSIONS: Daily acyclovir therapy did not reduce the risk of transmission of HIV-1, despite a reduction in plasma HIV-1 RNA of 0.25 log(10) copies per milliliter and a 73% reduction in the occurrence of genital ulcers due to HSV-2. (ClinicalTrials.gov number, NCT00194519.)

First observation of fluid-like eddy-dominant bursty bulk flow turbulence in the Earth's tail plasma sheet.

Turbulence is a ubiquitous phenomenon in neutral and conductive fluids. According to classical theory, turbulence is a rotating flow containing vortices of different scales. Eddies play a fundamental role in the nonlinear cascade of kinetic energy at different scales in turbulent flow. In conductive fluids, the Alfvénic/kinetic Alfvénic wave (AW/KAW) is the new "cell" of magnetohydrodynamic (MHD) turbulence (frozen-in condition). Wave energy, which has equal kinetic and magnetic energy, is redistributed among multiple-scale Fourier modes and transferred from the large MHD scale to the small kinetic scale through the collision of counter-propagating Alfvénic wave packages propagating along the magnetic field line. Fluid-like eddy-dominant plasma flow turbulence has never been found in space since the launch of the first satellite in 1957. In this paper, we report the first observation of eddy-dominant turbulence within magnetic reconnection-generated fast flow in the Earth's tail plasma sheet by the Magnetospheric Multiscale Spacecraft (MMS). In eddy-dominant turbulent reconnection jet, ions dominate the flow field while electrons dominate current and magnetic fluctuations. Our findings shed new light on the nonlinear kinetic and magnetic energy cascade in MHD turbulence.

Survey on tetracycline resistance and antibiotic-resistant genotype of avian Escherichia coli in North China.

The experiment was performed to investigate the tetracycline resistance and antibiotic-resistant genotype of avian Escherichia coli in North China and to analyze the correlation of genotype and phenotype. The resistance of 164 E. coli isolates (from Beijing, Tianjin, inner Mongolia, Shanxi, and Hebei regions of China) to tetracycline, doxycycline, and minocycline was investigated by using a drug susceptibility test. The results show that the rate of resistance to tetracycline antibiotics was 89.63% (147/164). The higher resistance rate was 84.76% (139/164) to tetracycline and 70.12% (115/164) to doxycycline, and the lowest resistance rate was 4.88% (8/164) to minocycline. The distribution of tetracycline resistance (Tcr) genes (tetA, tetB, tetC, and tetM) in avian E. coli isolates was detected by PCR. Of the isolates, 82.32% (135/164) carried tetracycline resistance genes. The positive rates of tetA, tetB, and tetM were 57.93% (95/164), 38.41% (63/164), and 10.97% (18/164), respectively. No tetC was amplified in avian E. coli isolates. The total positive rate of resistance genes (82.32%) was almost equal to the total rate of resistance to tetracycline antibiotics (89.63%). Thus, the positive rate of genotype was basically in line with that of phenotype for tetracycline resistance. The tetracycline resistance genes are widely distributed in E. coli and their main resistance mechanism to tetracycline is the active efflux effect mediated by tetA and tetB.

Beam particle identification and tagging of incompletely stripped heavy beams with HEIST.

A challenge preventing successful inverse kinematics measurements with heavy nuclei that are not fully stripped is identifying and tagging the beam particles. For this purpose, the HEavy ISotope Tagger (HEIST) has been developed. HEIST utilizes two micro-channel plate timing detectors to measure the time-of-flight, a multi-sampling ion chamber to measure energy loss, and a high-purity germanium detector to identify isomer decays and calibrate the isotope identification system. HEIST has successfully identified 198Pb and other nearby nuclei at energies of about 75 MeV/A. In the experiment discussed, a typical cut containing 89% of all 198Pb80+ in the beam had a purity of 86%. We examine the issues of charge state contamination. The observed charge state populations of these ions are presented and, using an adjusted beam energy, are well described by the charge state model GLOBAL.

Establishing an experimental model of photodynamically induced anterior ischemic optic neuropathy.

Numerous methods and drugs have been used to treat anterior ischemic optic neuropathy (AION); however, further investigations to determine the value of treatments for AION have been impeded by the lack of appropriate animal models of AION, significantly impacting on in-depth study of the disease. A rat model of AION was established, and corresponding functional changes of the fundus were observed using fundus fluorescein angiography (FFA), optical coherence tomography (OCT), and flash visual-evoked potential (F-VEP) in order to confirm the reliability of the AION model histopathologically. One day after model establishment, histopathology demonstrated that portions of the optic disc were highly edematous, with edema of nerve fibers and loose tissue, accompanied by displacement of the surrounding retina. At 23 days, the optic disc and surrounding nerve fiber layers had become thinner. None of the above-mentioned changes was observed in the laser, hematoporphyrin derivative (HPD), or naive groups. The results of fundus, FFA, F-VEP, and OCT-within 90 days after model establishment-confirmed that krypton red laser irradiation (647 nm), applied 2 h after HPD injection, can establish an ideal animal model of AION.

Effects of subchronic inhalation exposure to ethyl tertiary butyl ether on splenocytes in mice.

Ethyl tertiary-butyl ether (ETBE) is a motor fuel oxygenate used in reformulated gasoline. The current use of ETBE in gasoline or petrol is modest but increasing. To investigate the effects of ETBE on splenocytes, mice were exposed to 0 (control), 500 ppm, 1750 ppm, or 5000 ppm of ETBE by inhalation for 6 h/day for 5 days/wk over a 6- or 13-week period. Splenocytes were harvested from the control and exposed mice, and the following cell phenotypes were quantified by flow cytometry: (1) B cells (PerCP-Cy5.5-CD45R/B220), (2) T cells (PerCP-Cy5-CD3e), (3) T cell subsets (FITC-CD4 and PE-CD8a), (4) natural killer (NK) cells (PE-NK1.1), and (5) macrophages (FITC-CD11b). Body weight and the weight of the spleen were also examined. ETBE-exposure did not affect the weight of the spleen or body weight, while it transiently increased the number of RBC and the Hb concentration. The numbers of splenic CD3+, CD4+, and CD8+ T cells, the percentage of CD4+ T cells and the CD4+/CD8+ T cell ratio in the ETBE-exposed groups were significantly decreased in a dose-dependent manner. However, ETBE exposure did not affect the numbers of splenic NK cells, B cells, or macrophages or the total number of splenocytes. The above findings indicate that ETBE selectively affects the number of splenic T cells in mice.

New evidence of Yangtze delta recession after closing of the Three Gorges Dam.

Many deltas are likely undergoing net erosion because of rapid decreases in riverine sediment supply and rising global sea levels. However, detecting erosion in subaqueous deltas is usually difficult because of the lack of bathymetric data. In this study, by comparing bathymetric data between 1981 and 2012 and surficial sediment grain sizes from the Yangtze subaqueous delta front over the last three decades, we found severe erosion and significant sediment coarsening in recent years since the construction of Three Gorges Dam (TGD), the largest dam in the world. We attributed these morphological and sedimentary variations mainly to the human-induced drastic decline of river sediment discharge. Combined with previous studies based on bathymetric data from different areas of the same delta, we theorize that the Yangtze subaqueous delta is experiencing overall (net) erosion, although local accumulation was also noted. We expect that the Yangtze sediment discharge will further decrease in the near future because of construction of new dams and delta recession will continue to occur.

Sol-gel fabrication and photoluminescence properties of SiO2 @ Gd2O3:Eu3+ core-shell particles.

A uniform nanolayer of europium-doped Gd2O3 was coated on the surface of preformed submicron silica spheres by a Pechini sol-gel process. The resulted SiO2 @ Gd2O3:Eu3+ core-shell structured phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays. The XRD results show that the Gd2O3:Eu3+ layers start to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. The core-shell phosphors possess perfect spherical shape with narrow size distribution (average size: 640 nm) and non-agglomeration. The thickness of the Gd2O3:Eu3+ shells on the SiO2 cores can be adjusted by changing the deposition cycles (70 nm for three deposition cycles). Under short UV excitation, the obtained SiO2@Gd2O3:Eu3+ particles show a strong red emission with 5D0-7F2 (610 nm) of Eu3+ as the most prominent group. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

Septic metastatic lesions of pyogenic liver abscess. Their association with Klebsiella pneumoniae bacteremia in diabetic patients.

Septic metastatic endophthalmitis from Klebsiella pneumoniae liver abscess, first reported in seven cases treated at the Veterans General Hospital, Taipei, Taiwan, between 1981 and 1985, was seen in six similar cases at the same hospital in the subsequent 2 years. We conducted a retrospective search for factors that might be associated with these complications of pyogenic liver abscess. A total of 23 cases with septic metastatic lesions from pyogenic liver abscess were found between 1981 and 1987, and 164 cases of pyogenic liver abscess without septic metastatic lesions were identified as a comparison group. Klebsiella pneumoniae liver abscess, bacteremia, and the underlying diabetes mellitus were significantly more common in the study group than in the comparison group. Of the 23 patients with septic metastatic lesions, there were 14 cases (60.8%) of endophthalmitis or uveitis, 10 cases (43.4%) of pulmonary abscess and/or emboli, six cases (26.0%) of brain abscess and/or purulent meningitis, five cases (21.7%) of bacteriuria and/or prostate abscess, two cases (8.6%) of osteomyelitis and/or pyogenic arthritis, and one case (4.3%) of psoas abscess.

Cytochrome P450-related differences between rats and mice in the metabolism of benzene, toluene and trichloroethylene in liver microsomes.

In evaluating the risks to humans of exposure to chemicals, the results of studies in rodents are sometimes used as a basis for extrapolation. It is therefore important to elucidate differences in metabolism among species. Differences in cytochrome P450-catalysed oxidation of benzene, toluene and trichloroethylene (TRI) between male Wistar rats and male B6C3F1 mice were investigated by immunoblot and immunoinhibition assays using monoclonal antibodies (MAbs) to cytochrome P450 (CYP1A1/2, CYP2B1/2, CYP2E1 and CYP2C11/6). Immunoblot analysis showed that anti-CYP2B1/2 did not detect any protein in either untreated rat or mouse liver microsomes, whereas with anti-CYP2E1 and/or anti-CYP1A1/2 a clear-cut band was seen more in liver microsomes from mice than from rats. Mouse liver microsomes had a greater monooxidation activity for benzene and TRI than rat liver microsomes; mice also had a higher rate of aromatic hydroxylation of toluene at low substrate concentration, but a low rate of side-chain oxidation when a high concentration of toluene was used. The metabolism of benzene was saturated in mice at around 0.23 mM, but the metabolism of the other two solvents was not saturated in either rats or mice at the low concentrations used. Anti-CYP2E1 inhibited the metabolism of benzene, toluene and TRI in microsomes from mice to a greater extent than in rats, while anti-CYP2C11/6 inhibited their metabolism in rats to a greater extent than in mice; anti-CYP1A1/2 inhibited the metabolism of TRI only in microsomes from mice. These results indicate that (i) male B6C3F1 mice have more CYP2E1 and 1A1/2 than male Wistar rats, whereas rats have more CYP2C11/6 than mice; (ii) rats and mice express CYP2B1/2 but they are not immunochemically detectable; (iii) CYP2E1 and 2C11/6 in both species are responsible for the metabolism of benzene, toluene and TRI, whereas CYP1A1/2 in mice catalyses the oxidation of TRI. The differences in the metabolism of benzene, toluene and TRI in rats and in mice may therefore depend, at least in part, on differences in the distribution of P450 isozymes between the two species.

Monoclonal antibody-directed assessment of toluene induction of rat hepatic cytochrome P450 isozymes.

Cytochrome P450 isozymes induced in rat liver by a range of concentrations of toluene were studied with monoclonal antibodies (MAbs) to specific P450 isozymes and by enzyme assays. Nitrosodimethylamine demethylase activity was significantly increased in microsomes from rats exposed to more than 1000 ppm of toluene, an increase that was dose-dependent. Anti-CYP2E1 significantly inhibited the metabolism of toluene to benzyl alcohol (BA) by about 50%, in microsomes from 1000 to 4000 ppm toluene-exposed rats, at low substrate concentration (0.2 mM). With anti-CYP2B1/2, the rate of BA formation was decreased by 15-17% in microsomes from rats of 2000 and 4000 ppm toluene exposures at high substrate concentration (5.0 mM). On the other hand, anti-CYP2C11/6 inhibited the rate of formation of BA in all of the microsomes, but the extent of inhibition was progressively decreased from 55% in control to 33% in 4000 ppm exposure. Immunoblot analysis with anti-CYP2E1 and anti-CYP2B1/2 revealed stronger immunoreactive bands in microsomes from rats exposed to more than 1000 and 2000 ppm of toluene, respectively. Stronger bands were also observed in microsomes from rats of 2000-4000 ppm toluene exposures with anti-CYP3A1/2, but no immunoreactivity appeared with anti-CYP1A1/2. These results suggest that toluene induces CYP2E1, CYP2B1/2 and CYP3A1/2, but reduces CYP2C11/6, and has no effect on CYP1A1/2.

Enhancement of ethanol-induced lipid peroxidation in rat liver by lowered carbohydrate intake.

In order to investigate the effect of carbohydrate intake on ethanol-induced lipid peroxidation and cytotoxicity, rats were maintained on four different test diets, a medium-carbohydrate (carbohydrate intake, 8.4 g/day/rat on average), a low-carbohydrate (carbohydrate intake, 2.8 g/day/rat on average), an ethanol-containing medium-carbohydrate (carbohydrate and an ethanol intake, 8.4 and 2.9 g/day/rat on average, respectively), and an ethanol-containing low-carbohydrate diet (2.8 and 2.9 g/day/rat on average, respectively). Ethanol and the low-carbohydrate diet each increased the liver malondialdehyde content, but the combined effect of both (ethanol-containing low-carbohydrate diet) was much more prominent than either alone. The degree of increase in malondialdehyde content almost paralleled the activity of the microsomal ethanol oxidizing system. Both the low-carbohydrate and the ethanol-containing low-carbohydrate diets decreased the liver glutathione content, but ethanol combined with the medium-carbohydrate diet had no effect on the content. Ethanol treatment increased the liver triglyceride content only when combined with the low-carbohydrate diet. The rate of NADPH-dependent microsomal malondialdehyde formation was much higher in microsomes from rats maintained on the ethanol-containing low-carbohydrate diet than in those from rats on the ethanol-containing medium-carbohydrate diet, indicating that lowered carbohydrate intake augments ethanol-induced malondialdehyde accumulation in the liver by enhancing the rate of lipid peroxidation. In addition, when incubated with red blood cells in the presence of NADPH, microsomes from rats fed the ethanol-containing low-carbohydrate diet caused marked hemolysis, which was prevented by the addition of 5 mM glutathione to the incubation system. Furthermore, addition of 50 mM ethanol to the reaction system greatly accentuated the hemolysis. These results suggest that lowered carbohydrate intake at the time of ethanol consumption potentiates ethanol cytotoxicity by enhancing ethanol-induced lipid peroxidation.

A comparative study on the contribution of cytochrome P450 isozymes to metabolism of benzene, toluene and trichloroethylene in rat liver.

The contribution of P450IIE1, P450IIC11/6, P450IIB1/2 and P450IA1/2 to the formation of chloral hydrate (CH) from trichloroethylene (TRI) was investigated in microsomes from control, ethanol-, phenobarbital (PB)- and 3-methylcholanthrene (MC)-treated rats using monoclonal antibodies (MAbs) to the respective P450 isozymes, and compared with their roles in benzene and toluene metabolism. Anti-P450IIE1 inhibited the formation of CH from TRI more strongly in microsomes from ethanol-treated rats than in microsomes from control rats at low concentration of TRI when net inhibition was compared. Anti-P450IIC11/6 inhibited CH formation in microsomes from control and PB-treated rats at high, not low, concentration of TRI, but the net inhibition in control microsomes was less than that due to anti-P450IIE1. Anti-P450IIB1/2 and anti-P450IA1/2 also inhibited CH formation from TRI in microsomes from PB- and MC-treated rats, respectively, stronger at high substrate concentration than at low concentration. These results indicate that P450IIE1, P450IIC11/6, P450IIB1/2 and P450IA1/2 are involved in the metabolic step from TRI to CH, and the first isozyme may be a low-Km TRI oxidase and the others high-Km one. Comparing the contributions of four isozymes to benzene, toluene and TRI metabolism, all four acted in the metabolism of these compounds, but P450IIE1 did not catalyse o-cresol formation nor P450IA1/2 benzyl alcohol formation from toluene, suggesting regioselectivity of toluene metabolism in the action of these two isozymes. The contribution of P450IIE1 in benzene and TRI oxidation was greater than that of P450IIC11/6, but the reverse was seen with respect to benzyl alcohol formation from toluene, indicating that P450IIC11/6 is relatively inactive towards benzene and TRI oxidation, but is primarily involved in toluene metabolism. P450IIB1/2 and P450IIC11/6 attacked all the metabolic positions studied, but only in the side-chain metabolism of toluene was their contribution significant, suggesting that these two isozymes are quite similar in function.

Monoclonal antibody-directed characterization of cytochrome P450 isozymes responsible for toluene metabolism in rat liver.

Monoclonal antibodies (MAbs) were used to study the contribution of cytochromes P450IA1/IA2, P450IIB1/IIB2, P450IIC11/IIC6 and P450IIE1 to toluene side-chain (benzyl alcohol, BA, formation) and ring (o- and p-cresol formation) oxidation in liver microsomes from fed, one-day fasted, and phenobarbital (PB)-, 3-methylcholanthrene (MC)- and ethanol-treated rats. All rats were fed synthetic liquid diets. MAb 1-7-1 against P450IA1/IA2 inhibited markedly o-cresol formation and slightly p-cresol formation but not BA formation only in microsomes from MC-treated rats. MAbs 2-66-3, 4-7-1 and 4-29-5 against P450IIB1/IIB2 strongly inhibited BA, o-cresol and p-cresol formation only in PB-induced microsomes. MAb 1-68-11 against P450IIC11/IIC6 inhibited BA formation at high toluene concentration in the following order: fed greater than fasted greater than ethanol = MC greater than PB, and ethanol greater than or equal to fed = fasted greater than MC greater than PB on the basis of the percentage and net amount inhibition, respectively. MAb 1-91-3 against P450IIE1 inhibited BA formation at low toluene concentration, but not at high concentration, in the following order: ethanol greater than fasted = fed greater than MC, and ethanol greater than fasted greater than fed greater than MC on the basis of percentage and net inhibition, respectively. MAbs 1-68-11 and 1-91-3 also inhibited p-cresol formation at high and low toluene concentrations, respectively. These results indicate that (i) both P450IIE1 and P450IIC11/IIC6 are constitutive isozymes mainly responsible for the formation of BA and p-cresol from toluene as low- and high-Km isozymes, respectively; (ii) P450IIE1, but not P450IIC11/IIC6, is induced by one-day fasting and ethanol treatment; (iii) both P450IIE1 and P450IIC11/IIC6 are decreased by PB and MC treatments; (iv) P450IIE1 is inhibited by high concentration of toluene; (v) P450IIB1/IIB2 can contribute to the formation of BA, o- and p-cresol from toluene, while P450IAI/IA2 preferentially contributes to the formation of o-cresol.

Toluene metabolism by cDNA-expressed human hepatic cytochrome P450.

The metabolism of toluene in human liver microsomes and by cDNA-expressed human cytochrome P450s (CYPs) was investigated. Toluene was metabolized mainly to benzyl alcohol and slightly to o- and p-cresol by human liver microsomes. Formation of o-cresol was elevated in microsomes from human livers derived from cigarette smokers, but the induced CYP isoforms were not clear. Of the eleven human CYP forms studied, CYP2E1 was the most active in forming benzyl alcohol, followed by CYP2B6, CYP2C8, CYP1A2, and CYP1A1, in that order. The activities of CYP2A6, CYP2C9, CYP2D6, CYP3A3, CYP3A4, and CYP3A5 were negligible. In addition, CYP2B6 and CYP2E1 catalyzed the formation of p-cresol (11-12% of total metabolites), and CYP1A2 catalyzed the formation of both o-(22%) and p-cresol (35%). The relationship between the amino acid sequence of rat CYP2B1 cDNA and the activity for toluene metabolism was investigated using variants, because of great differences in the forming of toluene ring products between CYP2B1 and CYP2B6. These results suggest that the structure of CYP2B1 at the site of Leu 58 rather than Ile-114 and Glu-282 plays an important role in the formation of toluene ring products, whereas in CYP2B1 Ile-114 plays an important role in the formation of benzyl alcohol. These results may explain, in part, the lower activity of CYP2B6, which has Phe at position 58 of the protein, for toluene ring oxidations than that of CYP2B1.

CYP2C11 and CYP2B1 are major cytochrome P450 forms involved in styrene oxidation in liver and lung microsomes from untreated rats, respectively.

The contribution of cytochrome P450s (P450s) to the formation of styrene glycol from styrene in rat liver microsomes was investigated using monoclonal antibodies to P450s. Anti-CYP2E1 inhibited the formation to a similar extent in ethanol-treated microsomes and in control microsomes in terms of percentage inhibition, whereas to a greater extent in the former than the latter in terms of net inhibition, and only at low substrate concentration. Anti-CYP2C11/6 also inhibited the formation in control and in ethanol-treated microsomes at both low and high concentrations of styrene, and the net degree of inhibition was greater than that obtained with anti-CYP2E1, even in ethanol-treated microsomes where CYP2E1 was induced. Anti-CYP2B1/2 and anti-CYP1A1/2 inhibited the formation only in phenobarbital (PB)- and 3-methylcholanthrene (MC)-induced microsomes, respectively. These results suggest that (1) at least four P450s, CYP2C11/6, CYP2E1, CYP2B1/2 and CYP1A1/2, contribute to the metabolism of styrene, (2) CYP2C11/6, which probably corresponds to CYP2C11, is the major form of P450 responsible for the metabolism in untreated rat liver microsomes, and also in those treated with ethanol. Anti-CYP2E1 inhibited styrene oxidation more prominently in microsomes from styrene-treated rats than in those from control rats at a low substrate concentration. Although styrene treatment did not influence the total metabolism of styrene in liver microsomes at a high substrate concentration, inhibition of the metabolism by anti-CYP2C11/6 decreased with increasing styrene dose, whereas that by anti-CYP2B1/2 increased, suggesting that styrene treatment increases CYP2B1/2 but decreases CYP2C11/6 in rat liver, and the major form of P450 which mediates styrene oxidation is CYP2B1/2 after the treatment. Only anti-CYP2B1/2, which probably corresponds to CYP2B1, inhibited styrene oxidation in lung microsomes from untreated and even styrene-treated rats. Thus, the major form of P450 responsible for the metabolism of styrene is different in each tissue.