Mineralization and residue characteristics of chloramphenicol in aerobic soils: evidence from a carbon-14 study.

Chloramphenicol, a broad-spectrum antibiotic employed for controlling bacterial infections, presents an intriguing aspect in terms of its environmental fate in soils. 14C-labeled chloramphenicol was used to explore its mineralization and residue characteristics in three distinct agricultural soils in China. The findings revealed a nuanced pattern in the fate of 14C-chloramphenicol, with notable variations among the different soils under investigation. The chloramphenicol extract residue exhibited a reduction of 18.04% in sandy clay soil, 23.04% in clay loam soil, and 21.73% in loamy clay soil. Notably, the mineralization rate in sandy clay soil was 25.22% surpassed that in the other two soils, particularly during the initial stages of incubation. Over time, the diminishing extract residue underwent conversion into minerals and bound residue. The formation rate of bound residue was increased from 44.59 to 53.65% after adding 10% manure, suggesting that chloramphenicol easily binds with soils rich in organic matter. The bound residue is predominantly localized in the humin fraction across all soils. Additionally, the sterilized soil experiments indicated the pivotal role of microorganisms in influencing the fate of chloramphenicol under the specified experimental conditions. In conclusion, this study offers valuable insights into the environmental dynamics of chloramphenicol in soils, emphasizing the importance of soil composition, organic matter content, and microbial activity. The findings contribute to a scientific understanding of the environmental safety implications associated with chloramphenicol usage.

Retinoic Acid Signaling Modulates Recipient Gut Barrier Integrity and Microbiota After Allogeneic Hematopoietic Stem Cell Transplantation in Mice.

Graft-versus-host disease (GVHD) remains a major complication after allogeneic hematopoietic stem cell transplantation (HSCT). An impaired intestinal epithelial barrier is an important component of GVHD pathogenesis. However, contributing host factors that modulate mucosal barrier integrity during GVHD are poorly defined. We hypothesized that vitamin A and retinoic acid (RA) exert positive impacts on maintaining intestinal barrier function after HSCT, thus preventing or dampening GVHD severity. Unexpectedly, we found that exogenous RA increased intestinal permeability of recipient mice after allogeneic HSCT. Serum bacterial endotoxin levels were significantly higher in GVHD mice fed a vitamin A-high (VAH) diet compared to those fed a vitamin A-normal (VAN) diet, indicating a more compromised intestinal barrier function. Furthermore, VAH mice showed more severe lung GVHD with increased donor T cell infiltration in this tissue and died significantly faster than VAN recipients. 16S rRNA sequencing of fecal samples revealed significant differences in the diversity and composition of gut microbiota between VAN and VAH transplant recipients. Collectively, we show that retinoic acid signaling may negatively impact intestinal barrier function during GVHD. Mild vitamin A supplementation is associated with increased lung GVHD and more profound gut dysbiosis. Micronutrients such as vitamin A could modulate complications of allogeneic HSCT, which may be mediated by shaping gut microbiota.

Iron overload as a risk factor for poor graft function following allogeneic hematopoietic stem cell transplantation.

Hematological malignancies are increasingly treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT). Unfortunately, iron overload is a frequent adverse effect of allo-HSCT and is associated with poor prognosis. In the present study, we investigated hematopoiesis in iron-overloaded mice and elucidated the effects of iron overload on the bone marrow (BM) microenvironment. Iron-overloaded BALB/C mice were generated by injecting 20 mg/mL saccharated iron oxide intraperitoneally. Hematoxylin-eosin staining was performed to evaluate the effects of an iron overload in mice. BM cells obtained from C57BL/6 mice were transplanted into irradiated BALB/C mice (whole-body irradiation of 4 Gy, twice with a 4-hours interval) by tail vein injection. Two weeks after allo-HSCT, the hematopoietic reconstitution capacity was evaluated in recipients by colony-forming assays. Histopathological examinations showed brown-stained granular deposits, irregularly arranged lymphocytes in the liver tissues, and blue-stained blocks in the BM collected from mice received injections of high-dose saccharated iron oxide (20 mg/mL). Iron-overloaded mice showed more platelets, higher-hemoglobin (HGB) concentration, fewer granulocyte-macrophage colony-forming units (CFU-GM), erythrocyte colony-forming units (CFU-E), and mixed granulocyte/erythrocyte/monocyte/megakaryocyte colony-forming units (CFU-mix) than healthy mice. Iron-overloaded recipients presented with reduced erythrocytes and HGB concentration in peripheral blood, along with decreased marrow stroma cells, CFU-GM, CFU-E, and CFU-mix relative to healthy recipients. Taken together, our findings demonstrate that iron overload might alter the number of red blood cells after transplantation in mice by destroying the BM microenvironment, thereby affecting the recovery of BM hematopoietic function.

Crataegus Special Extract WS 1442 Effects on eNOS and microRNA 155.

Increased expression of microRNA 155 (miR-155) results in a decrease in endothelial nitric oxide synthase (eNOS) expression and impaired endothelial function. Factors that have been shown to increase expression of miR-155 may be mitigated by WS 1442, an extract of hawthorn leaves and flowers (Crataegus special extract) that contains a range of pharmacologically active substances including oligomeric proanthocyanidins and flavonoids. The purpose of this study is to determine the effect of WS 1442 on the expression of miR-155 and eNOS in the presence of tumor necrosis factor (TNF-α). Human umbilical vein endothelial cells (HUVECs) were studied after the exposure to TNF-α, with or without simvastatin (positive control) and WS 1442. The expression levels of eNOS, phosphorylated eNOS, and miR-155 in the different HUVEC treatment groups were determined by western blot and quantitative real-time polymerase chain reaction, respectively. To evaluate the effect of WS 1442 on the eNOS activity, the medium and intracellular nitrate/nitrite (NO) concentrations were also analyzed using a colorimetric Griess assay kit. The results demonstrated that TNF-α upregulated miR-155 expression and decreased eNOS expression and NO concentrations. WS 1442 also increased miR-155 expression and decreased eNOS expression but, unlike TNF-α, increased phosphorylated eNOS expression and NO concentrations. Surprisingly, WS 1442 increased miR-155 expression; however, WS 1442 mitigated the overall negative effect of miR-155 on decreasing eNOS expression by increasing expression of phosphorylated eNOS and resulting in an increase in NO concentrations. In the setting where miR-155 may be expressed, WS 1442 may offer vascular protection by increasing the expression of phosphorylated eNOS.

An ex vivo approach to botanical-drug interactions: a proof of concept study.

ETHNOPHARMACOLOGICAL RELEVANCE: Botanical medicines are frequently used in combination with therapeutic drugs, imposing a risk for harmful botanical-drug interactions (BDIs). Among the existing BDI evaluation methods, clinical studies are the most desirable, but due to their expense and protracted time-line for completion, conventional in vitro methodologies remain the most frequently used BDI assessment tools. However, many predictions generated from in vitro studies are inconsistent with clinical findings. Accordingly, the present study aimed to develop a novel ex vivo approach for BDI assessment and expand the safety evaluation methodology in applied ethnopharmacological research. MATERIALS AND METHODS: This approach differs from conventional in vitro methods in that rather than botanical extracts or individual phytochemicals being prepared in artificial buffers, human plasma/serum collected from a limited number of subjects administered botanical supplements was utilized to assess BDIs. To validate the methodology, human plasma/serum samples collected from healthy subjects administered either milk thistle or goldenseal extracts were utilized in incubation studies to determine their potential inhibitory effects on CYP2C9 and CYP3A4/5, respectively. Silybin A and B, two principal milk thistle phytochemicals, and hydrastine and berberine, the purported active constituents in goldenseal, were evaluated in both phosphate buffer and human plasma based in vitro incubation systems. RESULTS: Ex vivo study results were consistent with formal clinical study findings for the effect of milk thistle on the disposition of tolbutamide, a CYP2C9 substrate, and for goldenseal׳s influence on the pharmacokinetics of midazolam, a widely accepted CYP3A4/5 substrate. Compared to conventional in vitro BDI methodologies of assessment, the introduction of human plasma into the in vitro study model changed the observed inhibitory effect of silybin A, silybin B and hydrastine and berberine on CYP2C9 and CYP3A4/5, respectively, results which more closely mirrored those generated in clinical study. CONCLUSIONS: Data from conventional buffer-based in vitro studies were less predictive than the ex vivo assessments. Thus, this novel ex vivo approach may be more effective at predicting clinically relevant BDIs than conventional in vitro methods.

The effects of milk thistle (Silybum marianum) on human cytochrome P450 activity.

Milk thistle (Silybum marianum) extracts are widely used as a complementary and alternative treatment of various hepatic conditions and a host of other diseases/disorders. The active constituents of milk thistle supplements are believed to be the flavonolignans contained within the extracts. In vitro studies have suggested that some milk thistle components may significantly inhibit specific cytochrome P450 (P450) enzymes. However, determining the potential for clinically significant drug interactions with milk thistle products has been complicated by inconsistencies between in vitro and in vivo study results. The aim of the present study was to determine the effect of a standardized milk thistle supplement on major P450 drug-metabolizing enzymes after a 14-day exposure period. CYP1A2, CYP2C9, CYP2D6, and CYP3A4/5 activities were measured by simultaneously administering the four probe drugs, caffeine, tolbutamide, dextromethorphan, and midazolam, to nine healthy volunteers before and after exposure to a standardized milk thistle extract given thrice daily for 14 days. The three most abundant falvonolignans found in plasma, following exposure to milk thistle extracts, were silybin A, silybin B, and isosilybin B. The concentrations of these three major constituents were individually measured in study subjects as potential perpetrators. The peak concentrations and areas under the time-concentration curves of the four probe drugs were determined with the milk thistle administration. Exposure to milk thistle extract produced no significant influence on CYP1A2, CYP2C9, CYP2D6, or CYP3A4/5 activities.

An assessment of pharmacokinetics and antioxidant activity of free silymarin flavonolignans in healthy volunteers: a dose escalation study.

Milk thistle (Silybum marianum) extracts, one of the most widely used dietary supplements, contain a mixture of six major flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B, silychristin, and silydianin) and other components. However, the pharmacokinetics of the free individual flavonolignans have been only partially investigated in humans. Furthermore, antioxidant effects of the extract, which may underlie the basis of many therapeutic effects, have not been thoroughly assessed. The present study evaluated the pharmacokinetics of the six major flavonolignans in healthy volunteers receiving single doses of either one (175 mg), two (350 mg), or three (525 mg) milk thistle capsule(s) on three separate study visits. Additionally, the steady-state pharmacokinetic parameters were determined after the subjects were administered one capsule three times daily for 28 consecutive days. Our results demonstrated that all six flavonolignans were rapidly absorbed and eliminated. In order of abundance, the exposure to free flavonolignans was greatest for silybin A followed by silybin B, isosilybin B, isosilybin A, silychristin, and silydianin. The systemic exposure to these compounds appeared linear and dose proportional. The disposition of flavonolignans was stereoselective, as evidenced by the apparent clearance of silybin B, which was significantly greater than silybin A, whereas the apparent clearance of isosilybin B was significantly lower than isosilybin A. The concentrations of urinary 8-epi-prostaglandin F2α, a commonly used biomarker of oxidative status in humans, were considerably decreased in study subjects after a 28-day exposure to the extract (1.3 ± 0.9 versus 0.8 ± 0.9 ng/mg creatinine) but failed to reach statistical significance (P = 0.076).

A sensitive LC-MS/MS assay for the simultaneous analysis of the major active components of silymarin in human plasma.

Silymarin, an extract of crushed achenes of the milk thistle plant Silybum marianum is a multi-constituent mixture, 70-80% of which consists of a complex assortment containing the flavonolignans silybin A and B, isosilybin A and B, silydianin, and silychristin, and the flavonoid taxifolin. To date, numerous pharmacological actions of the silymarin extract have been documented in the biomedical literature, including hepatoprotective, anti-inflammatory, anti-tumor, and anti-fibrotic activities. The present study describes a novel liquid chromatographic-tandem mass spectrometric method for simultaneous analysis of silychristin, silydianin, silybin A and silybin B, isosilybin A and isosilybin B, and taxifolin in human plasma employing liquid-liquid extraction. This assay provides excellent resolution of the individual silymarin constituents via utilization of a 100 A 250 mm × 2 mm, 5 µm C(18) column with the mobile phase consisting of 51% methanol, 0.1% formic acid, and 10mM ammonium acetate. The lower limit of quantification was 2 ng/ml for each constituent. Calibration curves were linear over the range from 2 ng/ml to 100 ng/ml for all analytes (r(2)>0.99). The intra- and inter-day accuracies were 91-106.5% and 95.1-111.9%, respectively. The intra- and inter-day precision was within 10.5%. Additionally, recovery, stability, and matrix effects were fully validated as well. This method was successfully applied to human plasma samples from subjects treated with the milk thistle extract Legalon(®).

Limitations of in vitro assessments of the drug interaction potential of botanical supplements.

Although there are inherent and recognized limitations of in vitro screening methodologies to assess conventional drug-drug interactions (DDIs) per industry guidelines and those adopted by independent laboratories, further limitations are being appreciated which are unique to the evaluation of botanical products and potential DDIs in which they may participate. Among the larger issues faced are the uncertainty in assigning hepatic concentrations of multiple constituents and their potential metabolites, accounting for oral bioavailability, distribution, first-pass metabolism and active metabolites. Furthermore, the wide variability in the chemical composition of commercially available botanical supplement formulations continues to be a major concern, and manufacturing standards or enforcement thereof is essentially nonexistent in most countries. Differing formulations, unspecified product excipients, administration and absorption of the therapeutic ingredient(s) of a standardized dosage form, the very presence and/or concentration of one or more phytoconstituents within a supplement are typically unknown and nontarget entities. A further issue is the absence of authentic analytical standards, and the inability to accurately screen the entities as mixtures to even approximate typical scenarios, which may occur following the ingestion of dietary supplements, adds additional layers of complexity to experimental design and difficulty in interpreting experimental results. Multiple challenges exist in experimental methodologies employed in performing in vitro research with conventional pharmaceuticals and those unique to botanical extracts. These obstacles prevent the investigators from effectively utilizing high-throughput models to accomplish more than essentially "flag" suspected sources of drug interactions which must be further evaluated in vivo, at present, in order to confirm clinical significance. This review is intended to discuss the problems and challenges in evaluating botanical-drug interactions using in vitro methodologies.

Identification of selected therapeutic agents as inhibitors of carboxylesterase 1: potential sources of metabolic drug interactions.

A series of studies were designed and carried out in order to explore the potential for the major human hepatic hydrolase, carboxylesterase 1 (hCES1), to serve as a target of metabolic inhibition by a variety of medications. The risk of adverse drug-drug interaction(s) is present when metabolic inhibitors are combined with known or suspected substrates of a given enzyme. In the present report the abundantly expressed hepatic enzyme, hCES1, was examined as a potential target of metabolic inhibition by a number of routinely prescribed medications. hCES1 has been seldom assessed in this regard despite its role in the metabolism and detoxification of many compounds. The psychostimulant methylphenidate (MPH) was chosen as an hCES1 selective substrate. In vitro studies were performed using previously developed cell lines which overexpress hCES1 with both p-nitrophenyl acetate and d-MPH serving as known substrates. Aripiprazole, perphenazine, thioridazine, and fluoxetine were determined to be the potent hCES1 inhibitors. A complementary animal study followed in vitro screening studies to further evaluate the inhibitory effect of aripiprazole on CES1 activity in FVB mice. The results suggest that the concurrent administration of racemic (i.e. dl-) MPH with aripiprazole significantly increased the plasma concentrations of both total MPH as well as the less active l-isomer. The ratio of d-MPH and l-MPH plasma concentrations was significantly decreased in the mice treated with aripiprazole compared to the control animals, indicating an overall decrease of CES1 catalytic activity in aripiprazole treated animals. Additionally, a quantitative structure-activity relationship based analysis identified a number of structural similarities of CES1 inhibitors. In conclusion, drug-drug interactions with MPH are likely mediated via CES1 inhibition as a result of concomitant drug therapies. CES1 inhibition represents an overlooked and little studied source of variability in MPH disposition, tolerability, and response.

Evaluation of antipsychotic drugs as inhibitors of multidrug resistance transporter P-glycoprotein.

RATIONALE: The multidrug resistance transporter, P-glycoprotein (P-gp), is involved in efflux transport of several antipsychotics in the blood-brain barrier (BBB). OBJECTIVES: In the present study, we evaluated the inhibitory effect of the antipsychotics, i.e., risperidone, olanzapine, quetiapine, clozapine, haloperidol, chlorpromazine, a major metabolite of risperidone, 9-OH-risperidone, and a positive control inhibitor, PSC833, on the cellular uptake of a prototypic substrate of P-gp, rhodamine (Rhd) 123, in LLC-PK1 and L-MDR1 cells. MATERIALS AND METHODS: After incubation of the antipsychotics (1-100 microM) and the positive (10 microM PSC833) or negative (1% dimethyl sulfoxide) controls with 5 microM Rhd 123 for 1 h, the effects of the antipsychotics on the intracellular accumulation of Rhd 123 were examined using a flow cytometric method. RESULTS: All the antipsychotics showed various degrees of inhibitory effects on P-gp activity. The rank order of the concentration of inhibitor to cause 50% of the maximal increment of intracellular Rhd 123 fluorescence (EC(50)) was: PSC833 (0.5 microM) < olanzapine (3.9 microM) < chlorpromazine (5.8 microM) < risperidone (6.6 microM) < haloperidol (9.1 microM) < quetiapine (9.8 microM) < 9-OH-risperidone (12.5 microM) < clozapine (30 microM). Considering that the antipsychotics' plasma concentrations are generally lower than 1 microM, the present results suggest that olanzapine and risperidone are the only agents that may inhibit P-gp activity in the BBB. However, most of the antipsychotics are extensively accumulated in tissues. In addition, when given orally, the drug concentrations in the gastrointestinal tract are likely to be high. CONCLUSIONS: Pharmacokinetic interactions due to inhibition of P-gp activity by the antipsychotics appear possible and warrant further investigation.