Occupational effects in patients with post-COVID-19 syndrome

BACKGROUND

It is well recognized that some individuals experience persistent symptoms following an initial SARS-CoV-2 infection. Symptoms affect physical, cognitive and mental well-being and can adversely impact activities of daily living, including the ability to work.

AIMS

To examine the impact of post-COVID-19 syndrome with respect to effects on quality of life and impact on work in a cohort of people referred to a 'Long COVID' service.

METHODS

All triaged patients (over 18 years with symptoms more than 12 weeks since the initial infection) completed a symptom assessment questionnaire. Occupation and working status (at work, at work struggling with symptoms and off work) were also recorded. Impact on function and quality of life was assessed using the EQ5D5L questionnaire.

RESULTS

A total of 214 patients (median age 51.0 years, 135 females) were seen from January to September 2021. Analysis of occupational status showed: 18% were working, 40% were working but struggling and 35% had stopped working due to symptoms. Those unable to work reported significantly more fatigue, a greater perception of the need for support and lower quality-of-life scores.

CONCLUSIONS

This study shows the extensive impact of post-COVID-19 syndrome on the ability to return to work. Specific return-to-work guidance is needed to support a large proportion of those struggling with the condition. The involvement of the Occupational Health team should form part of the multidisciplinary, collaborative approach to support rehabilitation and improve long-term outcomes for this condition.

Cell type-specific immune dysregulation in severely ill COVID-19 patients

Coronavirus disease 2019 (COVID-19) has quickly become the most serious pandemic since the 1918 flu pandemic. In extreme situations, patients develop a dysregulated inflammatory lung injury called acute respiratory distress syndrome (ARDS) that causes progressive respiratory failure requiring mechanical ventilatory support. Recent studies have demonstrated immunologic dysfunction in severely ill COVID-19 patients. To further delineate the dysregulated immune response driving more severe clinical course from SARS-CoV-2 infection, we used single-cell RNA sequencing (scRNAseq) to analyze the transcriptome of peripheral blood mononuclear cells (PBMC) from hospitalized COVID-19 patients having mild disease (n = 5), developing ARDS (n = 6), and recovering from ARDS (n = 6). Our data demonstrated an overwhelming inflammatory response with select immunodeficiencies within various immune populations in ARDS patients. Specifically, their monocytes had defects in antigen presentation and deficiencies in interferon responsiveness that contrasted the higher interferon signals in lymphocytes. Furthermore, cytotoxic activity was suppressed in both NK and CD8 lymphocytes whereas B cell activation was deficient, which is consistent with the delayed viral clearance in severely ill COVID-19 patients. Finally, we identified altered signaling pathways in the severe group that suggests immunosenescence and immunometabolic changes could be contributing to the dysfunctional immune response. Our study demonstrates that COVID-19 patients with ARDS have an immunologically distinct response when compared to those with a more innocuous disease course and show a state of immune imbalance in which deficiencies in both the innate and adaptive immune response may be contributing to a more severe disease course in COVID-19.

PiSZ alpha-1 antitrypsin deficiency (AATD): pulmonary phenotype and prognosis relative to PiZZ AATD and PiMM COPD

INTRODUCTION

The PiSZ genotype results in less severe deficiency of alpha-1 antitrypsin (AAT) than PiZZ. Less is known about phenotypic and prognostic features.

METHODS

We studied 699 PiZZ, 126 PiSZ and 316 PiMM patients. All AAT deficiency (AATD) patients were augmentation naive. PiSZ were compared with PiZZ patients for clinical phenotype at baseline including CT findings, smoke exposure, progression of lung disease and survival. Similarly, PiSZ patients diagnosed as a result of investigation for possible lung disease (lung index cases) were compared with PiMM. Multivariable analytical techniques and matching (PiSZ to PiZZ) were employed to account for demographic differences.

RESULTS

Pack-years smoked and FEV1 exhibited a negative correlation in PiSZ and ZZ patients (both r=-0.43), with emphysema and COPD occurring more commonly in PiZZ patients at <20 pack-year exposure. In multivariable analyses, PiSZ patients were less likely to have emphysema (p<0.01) and had better survival than PiZZ (p=0.017), but lung function decline did not differ significantly. 42% of PiSZ patients had upper-zone-dominant emphysema on CT scan. Analyses of AAT level confirmed a critical threshold at 11 μM, particularly with regard to phenotypes classical of PiZZ AATD.Significant baseline differences suggested that PiSZ had presented earlier to health services than PiMM. Once this was accounted for, risk of emphysema did not differ between PiSZ and PiMM although survival was lower in PiMM patients (p<0.01).

CONCLUSIONS

PiSZ patients are less susceptible to cigarette smoke than PiZZ. The pattern of emphysema may be similar at diagnosis to usual COPD.

Phytotoxicity of zinc and manganese to seedlings grown in soil contaminated by zinc smelting

Historic emissions from two zinc smelters have injured the forest on Blue Mountain near Palmerton, Pennsylvania, USA. Seedlings of soybeans and five tree species were grown in a greenhouse in a series of mixtures of smelter-contaminated and reference soils and then phytotoxic thresholds were calculated. As little as 10% Palmerton soil mixed with reference soil killed or greatly stunted seedlings of most species. Zinc was the principal cause of the phytotoxicity to the tree seedlings, although Mn and Cd may also have been phytotoxic in the most contaminated soil mixtures. Calcium deficiency seemed to play a role in the observed phytotoxicity. Exposed soybeans showed symptoms of Mn toxicity. A test of the effect of liming on remediation of the Zn and Mn phytotoxicity caused a striking decrease in Sr-nitrate extractable metals in soils and demonstrated that liming was critical to remediation and restoration.

Inheritance and expression of lysine plus threonine resistance selected in maize tissue culture

Selection for resistance to growth inhibition by lysine plus threonine in equimolar concentrations (LT) in tissue cultures of maize yielded a stable resistant line, LT19. Genetic analysis of progeny of plants regenerated from LT19 showed that LT resistance was inherited as a single dominant nuclear gene, temporarily designated Ltr(*)-19. Tissue cultures initiated from resistant embryos required 5-10 times higher levels of LT to inhibit growth than did cultures from LT-sensitive embryos. LT resistance in Ltr(*)-19 was expressed as much reduced inhibition of root and shoot growth in the presence of LT. The free pool of threonine was increased 6 times in cultures initiated from immature embryos of LT-resistant plants, and 75-100 times in kernels homozygous for Ltr(*)-19, as compared to cultures and kernels from LT-sensitive embryos and plants, respectively. Overproduction of free threonine increased the total threonine content in homozygous Ltr(*)-19 kernels by 33-59%. The results demonstrate that LT resistance selected with tissue culture methods is heritable and is expressed in cultures, seedlings, and kernels. Furthermore, they demonstrate a method to obtain amino acid-overproducer mutants in maize, which have the potential to increase substantially specific amino acids in kernels. The capability to increase specifically the nutritionally limiting amino acid(s) could have important nutritional implications for the grain of cereals and other crops.

Inheritance of selected pathotoxin resistance in maize plants regenerated from cell cultures

Texas male-sterile cytoplasm (cms-T) maize is susceptible to Helminthosporium maydis race T and its pathotoxin, whereas nonsterile cytoplasm maize is resistant. Callus cultures initiated from immature embryos of a cms-T genotype, BC(1)A188(T), were susceptible to the toxin and were capable of plant regeneration. Toxin-resistant cell lines were selected by a sublethal enrichment procedure in which cms-T callus was grown for several selection cycles (subculture transfers) in the presence of progressively higher concentrations of toxin. Periodically during the selection process, plants were regenerated from the cms-T cultures to determine their susceptibility or resistance to the toxin. Plants regenerated after four cycles of selection were male-sterile and toxin-susceptible as shown by leaf bioassays. All plants regenerated from cell lines isolated from the fifth selection cycle onward, however, were toxin-resistant and 52 of 65 were fully male-fertile. The remaining 13 "male-sterile" resistant plants did not shed pollen and did not resemble cms-T plants in tassel morphology. Some "male-sterile" plants produced anthers containing a small amount of starch-filled pollen, suggesting that the sterility of these 13 plants was not the result of the cms-T trait. Leaf bioassays on F(1) progeny from regenerated resistant plants indicated that resistance to the toxin was inherited only through the female. The male-fertility trait also was inherited only through the female. After inoculation with H. maydis race T spores, leaf lesion size for progeny from regenerated resistant plants coincided with their reaction to the toxin. This result indicated that plant resistance to the pathogen was closely correlated with the toxin resistance obtained through cell culture selection.

Pharmacokinetics and metabolism of (R,R)-methoxyfenoterol in rat

(R,R)-fenoterol (Fen), a beta(2)-adrenoceptor agonist, is under clinical investigation in the treatment of congestive heart disease. The pharmacokinetics and metabolism of the 4-methoxyphenyl derivative of (R,R)-Fen, (R,R)-MFen, have been determined following intravenous and oral administration to the rat and compared with corresponding results obtained with (R,R)-Fen. Results from the study suggest that (R,R)-MFen can offer pharmacokinetic and metabolic advantages in comparison to an earlier (R,R)-Fen. The oral administration revealed that the net exposure of (R,R)-MFen was about three-fold higher than that of (R,R)-Fen (7.2 versus 2.3 min x nmol ml(-1)), while intravenous administration proved that the clearance was significantly reduced, 48 versus 146 ml min(-1) kg(-1), the T(1/2) was significantly longer, 152.9 versus 108.9 min, and the area under the curve (AUC) was significantly increased, 300 versus 119 min x nmol ml(-1). (R,R)-MFen was primarily cleared by glucuronidation associated with significant presystemic glucuronidation of the compound. After intravenous and oral administration of (R,R)-MFen, (R,R)-Fen and (R,R)-Fen-G were detected in the urine samples indicating that (R,R)-MFen was O-demethylated and subsequently conjugated to (R,R)-Fen-G. The total (R,R)-Fen and (R,R)-Fen-G as a percentage of the dose after intravenous administration was 3.6%, while after oral administration was 0.3%, indicating that only a small fraction of the drug escaped presystemic glucuronidation and was available for O-demethylation. The glucuronidation pattern was confirmed by the results from in vitro studies where incubation of (R,R)-MFen with rat hepatocytes produced (R,R)-MFen-G, (R,R)-Fen and (R,R)-Fen-G, while incubation with rat intestinal microsomes only resulted in the formation of (R,R)-MFen-G.

Evaluation of heterogeneity in pharmacotherapy trials for drug dependence: a Bayesian approach

AIMS

Difficulty identifying effective pharmacotherapies for cocaine dependence has led to suggestions that subgroup differences may account for some of the heterogeneity in treatment response. Well-attested methodological difficulties associated with these analyses recommend the use of Bayesian statistical reasoning for evaluation of salient interaction effects.

METHODS

A secondary data analysis of a previously published, double-blind, randomized controlled trial examines the interaction of decision-making, as measured by the Iowa Gambling Task, and citalopram in increasing longest sustained abstinence from cocaine use.

RESULTS

Bayesian analysis indicated that there was a 99% chance that improved decision-making enhances response to citalopram. Given the strong positive nature of this finding, a formal, quantitative Bayesian approach to evaluate the result from the perspective of a skeptic was applied.

CONCLUSIONS

Bayesian statistical reasoning provides a formal means of weighing evidence for the presence of an interaction in scenarios where conventional, Frequentist analyses may be less informative. [Supplementary materials are available for this article. Go to the publisher's online edition of The American Journal of Drug and Alcohol Abuse for the following free supplemental resource: Appendix 1].

Characterization of ANIT-induced toxicity using precision-cut rat and dog liver slices cultured in a dynamic organ roller system

This article describes the toxicity of alpha-naphthylisothiocyanate (ANIT), a compound known to induce dose-dependent hepatobiliary toxicity in vivo, using the slice model. Liver slices (200 microm thick) from male Sprague-Dawley rats and male beagle dogs were cultured for 7 days while exposed to a range of ANIT concentrations (1- 100 microM for rat and 4-320 microM for dog). Tissues (and medium for dog) were evaluated using a panel of clinically relevant biomarkers for liver and histological endpoints to assess viability and proliferation. ANIT increased slice levels of enzyme biomarkers corresponding to biliary markers. At high concentrations (80-100 microM for rat, 320 microM for dog) a diminution of tissue enzyme levels was observed, corresponding to severe hepatobiliary injury. By days 5 and 7, biochemical markers in the medium of dog slices indicated an elevation of hepatocellular and biliary markers. Histologically for both species, minimal hepatocellular injury was noted, but proliferation of biliary epithelial cells (BEC) was observed using 5-bromo-2-deoxyuridine (BrdU) immunostaining. In rat slices, ANIT increased the expression of inducible nitrous oxide synthase (iNOS) within 12 hrs of exposure. In summary, additional experimentation using slice culture may further demonstrate its value in screening compounds that cause hepatobiliary toxicity.

Comparison of the capacitation-like state of cooled boar spermatozoa with true capacitation

Cryopreserved spermatozoa demonstrate reduced conception rates compared with fresh spermatozoa when used for artificial insemination. The preliminary stage of cryopreservation of spermatozoa involves cooling to 5 degrees C, during which spermatozoa experience a capacitation-like change, which may be partially responsible for the reduced conception rate observed. The aim of this study was to determine the nature of these capacitation-like changes and how much this process resembles true capacitation. Boar spermatozoa, cooled to 5 degrees C and re-warmed to physiological temperatures (39 degrees C), were compared with spermatozoa capacitated in Tyrode's complete medium (TALP) for 2 h at 39 degrees C. Fluorescent probes, and SDS-PAGE and western blotting were used to visualize events known to occur during capacitation in vitro. Chlortetracycline staining of membrane domains and Fluo-3 detection of changes in intracellular free calcium by flow cytometry in cooled and re-warmed spermatozoa showed similarities to those of capacitated spermatozoa. Alterations to lipid bilayer fluidity assessed by merocyanine fluorescence staining and intracellular signalling pathways detected by tyrosine phosphorylation of cooled and re-warmed spermatozoa, did not completely reflect the changes detected during capacitation in vitro. Thus, cooling spermatozoa to 5 degrees C results in a similar endpoint to that observed in capacitated cells in terms of reactive membranes and changes in intracellular ion concentrations, which may account for their comparable functionality. However, these modifications are not completely analogous and should not be considered true capacitation, but rather a by-passing of the capacitation process.

Comparison of the capacitation-like state of cooled boar spermatozoa with true capacitation

Cryopreserved spermatozoa demonstrate reduced conception rates compared with fresh spermatozoa when used for artificial insemination. The preliminary stage of cryopreservation of spermatozoa involves cooling to 5 degrees C, during which spermatozoa experience a capacitation-like change, which may be partially responsible for the reduced conception rate observed. The aim of this study was to determine the nature of these capacitation-like changes and how much this process resembles true capacitation. Boar spermatozoa, cooled to 5 degrees C and re-warmed to physiological temperatures (39 degrees C), were compared with spermatozoa capacitated in Tyrode's complete medium (TALP) for 2 h at 39 degrees C. Fluorescent probes, and SDS-PAGE and western blotting were used to visualize events known to occur during capacitation in vitro. Chlortetracycline staining of membrane domains and Fluo-3 detection of changes in intracellular free calcium by flow cytometry in cooled and re-warmed spermatozoa showed similarities to those of capacitated spermatozoa. Alterations to lipid bilayer fluidity assessed by merocyanine fluorescence staining and intracellular signalling pathways detected by tyrosine phosphorylation of cooled and re-warmed spermatozoa, did not completely reflect the changes detected during capacitation in vitro. Thus, cooling spermatozoa to 5 degrees C results in a similar endpoint to that observed in capacitated cells in terms of reactive membranes and changes in intracellular ion concentrations, which may account for their comparable functionality. However, these modifications are not completely analogous and should not be considered true capacitation, but rather a by-passing of the capacitation process.

Carbohydrate mediation of boar sperm binding to oviductal epithelial cells in vitro

After mating, mammalian spermatozoa are transported to the lower oviductal isthmus. Spermatozoa are sequestered at the isthmus by attaching and interacting with oviductal epithelial cells, hence forming a sperm reservoir. In several mammalian species, specific carbohydrates mediate sperm-oviductal epithelial cell binding. A quantitative in vitro free cell bioassay was developed to investigate the involvement of carbohydrate recognition in pig sperm-oviductal epithelial cell interactions. This assay was validated. The sensitivity of the assay was such that it was possible to discriminate between different sperm concentrations and sperm-oviductal epithelial cell co-incubation periods, spermatozoa with damaged plasma membranes and epithelial cells of non-reproductive origin. Optimal conditions were used to incubate spermatozoa and oviductal epithelial cells in the presence of six hexose sugars at concentrations of 0, 2, 10 and 50 mmol l(-1). A significant (P < or = 0.05) reduction in the binding of spermatozoa to the oviductal epithelium was detected with 2, 10 and 50 mmol maltose l(-1), 50 mmol lactose l(-1) and 50 mmol mannose l(-1). These findings support the hypothesis that attachment of pig spermatozoa to oviductal epithelium before fertilization is mediated by carbohydrate recognition.

Analysis of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane in rat plasma. II. Pharmacokinetic profile in male and female Sprague-Dawley rats evaluated by capillary electrophoresis

This paper describes a pharmacokinetic study performed in Sprague-Dawley rats after i.v. administration of a single 6-mg/kg dose of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane (Altropane). Plasma samples were collected from the retro-orbital sinus at times up to 3 h after drug administration, extracted by solid-phase extraction, and the drug levels determined by capillary electrophoresis (CE). Pharmacokinetic parameters were determined by a standard noncompartmental model using WinNonlin version 1.5. The maximum plasma concentrations, clearances of the drug, and areas under the curve for male and female rats were 5.74 and 7.26 microg/ml, 135.7 and 98.5 ml/kg x min, and 44.23 and 60.92 microg x min/ml, respectively. The drug was cleared very rapidly from the systemic circulation, with a terminal t(1/2) of 7 to 10 min and a mean residence time of about 11 min for both sexes. The volume of distribution was approximately 1 l/kg. No metabolites were detected when the samples were analyzed individually. However, after samples were pooled and concentrated, traces of two unknown peaks that may represent metabolites were detected in concentrates from the last two timepoints. Part I of this work [J. Chromatogr. A, 895 (2000) 87] describes validation of CE methods for the analysis of aqueous and plasma samples of Altropane, including its solid-phase extraction from rat plasma.

In vitro/in vivo scaling of alprazolam metabolism by CYP3A4 and CYP3A5 in humans

We attempted to predict the in vivo metabolic clearance of alprazolam from in vitro metabolic studies using human liver microsomes and human CYP recombinants. Good correlations were observed between the intrinsic clearance (CL(int)) for 4-hydroxylation and CYP3A4 content and between the CL(int) for alpha-hydroxylation and CYP3A5 content in ten human liver microsomal samples. Using the recombinant CYP isoforms expressed in insect cells, the CL(int) for CYP3A4 was about 2-fold higher than the CL(int) for CYP3A5 in the case of 4-hydroxylation. However, the CL(int) for CYP3A5 was about 3-fold higher than the CL(int) for CYP3A4 in the case of alpha-hydroxylation. The metabolic rates for 4- and alpha-hydroxylation increased as the added amount of cytochrome b(5) increased, and their maximum values were 3- to 4-fold higher than those without cytochrome b(5). The values of CL(int), in vivo predicted from in vitro studies using human liver microsomes and CYP3A4 and CYP3A5 recombinants were within 2.5 times of the observed value calculated from literature data. The average CL(int) value (sum of 4- and alpha-hydroxylation) obtained using three human liver microsomal samples was 4-fold higher than that obtained using three small intestinal microsomal samples from the same donors, indicating the minor contribution of intestinal metabolism to alprazolam disposition. The area under the plasma concentration-time curve (AUC) of alprazolam is reported to increase following co-administration of ketoconazole and the magnitude of the increase predicted from the in vitro K(i) values and reported pharmacokinetic parameters of ketoconazole was 2.30-2.45, which is close to the value observed in vivo (3.19). A quantitative prediction of the AUC increase by cimetidine was also successful (1.73-1.79 vs 1.58-1.64), considering the active transport of cimetidine into the liver. In conclusion, we have succeeded in carrying out an in vitro/in vivo scaling of alprazolam metabolism using human liver microsomes and human CYP3A4 and CYP3A5 recombinants.

Analysis of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane in rat plasma. I. Method development and validation by capillary electrophoresis

Altropane, 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nor tropane, is an imaging agent that was developed recently for early detection of Parkinson's disease. Its promise as a useful radiopharmaceutical for single-photon emission computed tomography or positron emission tomography imaging of the brain has been well demonstrated, and it is currently undergoing clinical trials. This paper presents methods development and validation of capillary electrophoresis (CE) techniques to analyze Altropane in aqueous environments as well as in rat plasma, using an internal standard, nicotinamide. N-Allylaltropane, 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-allylnortropane, which is a known degradation product of the Altropane precursor (tributyltinaltropane), was used to verify the method's specificity. A solid-phase extraction method for extraction of Altropane from rat plasma is also described. The results presented in this paper demonstrate the applicability of CE methods to study the pharmacokinetic properties of Altropane in animal models. The results of the pharmacokinetic study will be published later, as Part II.

Investigation into the effects of temperature and stirring rate on the solid-phase extraction of diuron from water using a C18 extraction disk

A novel experimental method for determining the equilibrium constant, Keq, and the uptake rate constant, kup, for the solid-phase extraction (SPE) of diuron from water using a C18 Empore extraction disk is reported. Log Keq and log kup are determined at 7.0, 11.0, 18.0 and 23.0 degrees C and for stirring rates of 100, 200 and 400 rpm. From a Van 't Hoff plot of log Keq versus T-1 the enthalpy of sorption, delta H0, is shown to be negative which indicates that the thermodynamic process of uptake is exothermic. The rate of stirring has no effect on log Keq over the temperature range 7.0-23.0 degrees C. The enthalpy of activation, delta H0, calculated from Arrhenius plots of log kup versus T-1 at 100, 200 and 400 rpm show that the kinetic process of uptake is endothermic. At 100 rpm the rate of uptake is limited by the aqueous diffusion of diuron. At 200 rpm or greater the aqueous diffusion layer around the disk is sufficiently small to prevent diffusion from being a limiting factor. The method described in this paper is limited to the analysis of analytes that contain a significant UV chromophore and are relatively soluble in water, but it can also be used to investigate pH and salinity effects on the SPE of diuron from water.

Primary cardiac and pericardial neoplasms: radiologic-pathologic correlation

Primary cardiac and pericardial neoplasms are rare lesions and include both benign and malignant histologic types. Myxoma is the most frequent primary cardiac neoplasm, but other benign tumors include papillary fibroelastoma, rhabdomyoma, fibroma, hemangioma, lipoma, and paraganglioma. Cardiac sarcoma represents the second most common primary cardiac neoplasm. Lymphoma can also affect the heart primarily. Pericardial tumors that affect the heart include benign teratomas and malignant mesotheliomas. Patients affected with cardiac or pericardial neoplasms often present with cardiovascular compromise or embolic phenomena and exhibit cardiomegaly at chest radiography. Benign cardiac tumors typically manifest as intracavitary, mural, or epicardial focal masses, whereas malignant tumors demonstrate invasive features and may involve the heart diffusely. Benign lesions can usually be successfully excised, but patients with malignant lesions have an extremely poor prognosis.

Prediction of in vivo interaction between triazolam and erythromycin based on in vitro studies using human liver microsomes and recombinant human CYP3A4

PURPOSE

To quantitatively predict the in vivo interaction between triazolam and erythromycin, which involves mechanism-based inhibition of CYP3A4, from in vitro studies using human liver microsomes (HLM) and recombinant human CYP3A4 (REC).

METHODS

HLM or REC was preincubated with erythromycin in the presence of NADPH and then triazolam was added. alpha- and 4-hydroxy (OH) triazolam were quantified after a 3 min incubation and the kinetic parameters for enzyme inactivation (k(inact) and K('app)) were obtained. Drug-drug interaction in vivo was predicted based on a physiologically-based pharmacokinetic (PBPK) model, using triazolam and erythromycin pharmacokinetic parameters obtained from the literature and kinetic parameters for the enzyme inactivation obtained in the in vitro studies.

RESULTS

Whichever enzyme was used, triazolam metabolism was not inhibited without preincubation, even if the erythromycin concentration was increased. The degree of inhibition depended on preincubation time and erythromycin concentration. The values obtained for k(inact) and K('app) were 0.062 min(-1) and 15.9 microM (alpha-OH, HLM), 0.055 min(-1) and 17.4 microM (4-OH, HLM), 0.173 min(-1) and 19.1 microM (alpha-OH, REC), and 0.097 min(-1) and 18.9 microM (4-OH, REC). Based on the kinetic parameters obtained using HLM and REC, the AUCpo of triazolam was predicted to increase 2.0- and 2.6-fold, respectively, following oral administration of erythromycin (333 mg t.i.d. for 3 days), which agreed well with the reported data.

CONCLUSIONS

In vivo interaction between triazolam and erythromycin was successfully predicted from in vitro data based on a PBPK model involving a mechanism-based inhibition of CYP3A4.

Prediction of in vivo drug-drug interactions between tolbutamide and various sulfonamides in humans based on in vitro experiments

Drug-drug interactions between tolbutamide and sulfonamides have extensively been reported. We attempted to predict the in vivo interaction between tolbutamide and sulfonamides from the in vitro metabolic inhibition studies. The inhibition constant (K(i)) was derived from the inhibitory effects of eight sulfonamides (sulfaphenazole, sulfadiazine, sulfamethizole, sulfisoxazole, sulfamethoxazole, sulfapyridine, sulfadimethoxine, and sulfamonomethoxine) on tolbutamide metabolism. We found that the inhibitory effect of sulfaphenazole was greatest among the eight sulfonamides examined. Furthermore, the contribution of each P450 enzyme to tolbutamide metabolism was investigated by using recombinant P450 enzymes. Although cytochrome P450 (CYP) 2C8, 2C9, and 2C19 metabolized tolbutamide, the main enzyme involved was CYP2C9. The K(i) values of several sulfonamides were comparable between human liver microsomes and recombinant CYP2C9. The maximum unbound plasma concentration of sulfonamides in the portal vein was calculated from literature data on the pharmacokinetics of sulfonamides. Using the K(i) values obtained from in vitro inhibition studies, the degree of increase in tolbutamide area under the plasma concentration-time curve (AUC) was predicted. About 4.8- and 1.6-fold increases in tolbutamide AUC were predicted by coadministration of sulfaphenazole and sulfamethizole, respectively, which agreed well with the reported increases in humans. Furthermore, the increase in tolbutamide AUC by coadministration of sulfadiazine, sulfisoxazole, and sulfamethizole was predicted to be 1.5- to 2. 6-fold, although the corresponding in vivo effects have not been reported. It is concluded that some of these sulfonamides have to be carefully coadministered with CYP2C9 substrates such as tolbutamide although coadministration of sulfaphenazole needs the greatest care.

Type I nitroreductases in soil enterobacteria reduce TNT (2,4,6,-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine)

Many enteric bacteria express a type I oxygen-insensitive nitroreductase, which reduces nitro groups on many different nitroaromatic compounds under aerobic conditions. Enzymatic reduction of nitramines was also documented in enteric bacteria under anaerobic conditions. This study indicates that nitramine reduction in enteric bacteria is carried out by the type I, or oxygen-insensitive nitroreductase, rather than a type II enzyme. The enteric bacterium Morganella morganii strain B2 with documented hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) nitroreductase activity, and Enterobacter cloacae strain 96-3 with documented 2,4,6-trinitrotoluene (TNT) nitroreductase activity, were used here to show that the explosives TNT and RDX were both reduced by a type I nitroreductase. Morganella morganii and E. cloacae exhibited RDX and TNT nitroreductase activities in whole cell assays. Type I nitroreductase, purified from E. cloacae, oxidized NADPH with TNT or RDX as substrate. When expression of the E. cloacae type I nitroreductase gene was induced in an Escherichia coli strain carrying a plasmid, a simultaneous increase in TNT and RDX nitroreductase activities was observed. In addition, neither TNT nor RDX nitroreductase activity was detected in nitrofurazone-resistant mutants of M. morganii. We conclude that a type I nitroreductase present in these two enteric bacteria was responsible for the nitroreduction of both types of explosive.

Variation of hepatic methotrexate 7-hydroxylase activity in animals and humans

This study deals with individual and species variations in the converting activity of methotrexate (MTX) to 7-hydroxymethotrexate in animals and humans. When MTX 7-hydroxylase was assayed in six human liver cytosols, a 48-fold range of intersubject variation of the activity was observed. The variations were correlated to the concentrations of aldehyde oxidase activity in human subjects assayed with benzaldehyde as a substrate. Species differences of liver MTX 7-hydroxylase activity were also observed. The activity was highest in rabbits, followed by rats, hamsters, and monkeys but was undetectable in dogs. Strain differences of MTX 7-hydroxylase activity based on aldehyde oxidase activity were also observed in rats and mice. The results suggest that aldehyde oxidase functions as MTX 7-hydroxylase in livers of animals and humans, and the observed differences of MTX 7-hydroxylase activity are due to variations in the amount of aldehyde oxidase present.

Primary active transport of organic anions on bile canalicular membrane in humans

Biliary excretion of several anionic compounds was examined by assessing their ATP-dependent uptake in bile canalicular membrane vesicles (CMV) prepared from six human liver samples. 2, 4-Dinitrophenyl-S-glutathione (DNP-SG), leukotriene C4 (LTC4), sulfobromophthalein glutathione (BSP-SG), E3040 glucuronide (E-glu), beta-estradiol 17-(beta-D-glucuronide) (E2-17G), grepafloxacin glucuronide (GPFXG), pravastatin, BQ-123, and methotrexate, which are known to be substrates for the rat canalicular multispecific organic anion transporter, and taurocholic acid (TCA), a substrate for the bile acid transporter, were used as substrates. ATP-dependent and saturable uptake of TCA, DNP-SG, LTC4, E-glu, E2-17G, and GPFXG was observed in all human CMV preparations examined, suggesting that these compounds are excreted in the bile via a primary active transport system in humans. Primary active transport of the other substrates was also seen in some of CMV preparations but was negligible in the others. The ATP-dependent uptake of all the compounds exhibited a large inter-CMV variation, and there was a significant correlation between the uptake of glutathione conjugates (DNP-SG, LTC4, and BSP-SG) and glucuronides (E-glu, E2-17G, and GPFXG). However, there was no significant correlation between TCA and the other organic anions, implying that the transporters for TCA and for organic anions are different also in humans. When the average value for the ATP-dependent uptake by each preparation of human CMVs was compared with that of rat CMVs, the uptake of glutathione conjugates and nonconjugated anions (pravastatin, BQ-123, and methotrexate) in humans was approximately 3- to 76-fold lower than that in rats, whereas the uptake of glucuronides was similar in the two species. Thus there is a species difference in the primary active transport of organic anions across the bile canalicular membrane that is less marked for glucuronides.