Principles of hematotoxicology: laboratory assessment and interpretation of data

Opinion on the Optimal Histologic Evaluation of the Bone Marrow in Nonclinical Toxicity Studies

Identification of bone marrow toxicity is an important issue in drug development and toxicologic pathologists play a critical role in that identification. Knowledge of the general components of bone marrow, relevant anatomical and species differences, and the standard approach (routine systematic histological evaluation of the bone marrow in conjunction with analysis of the peripheral complete blood count data) will be reviewed. Specific morphologic features that anatomic pathologists should look for in the various components of bone marrow as well as suggested terminology for bone marrow findings will be discussed. Finally, an opinion on the limitations of the standard approach to bone marrow evaluation will be provided including general recommendations on when additional methods (image analysis of hematoxylin and eosin stained slides, flow cytometry or Sysmex XT 2000iV analysis, cytological evaluation of bone marrow smears, in vitro models, and transmission electron microscopy) might be useful in the detection or further characterization of bone marrow toxicity. [Box: see text].

Toxicological evaluation of a saponin-rich standardized extract of fenugreek seeds (FenuSMART®): Acute, sub-chronic and genotoxicity studies

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Safety evaluation of a standardized extract of fenugreek seeds (FenuSMART).

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Acute and subchronic oral toxicity studies of FenuSMART on Wistar rats.

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Mutagenicity study of FenuSMART.

The present study investigated the safety of a saponin-rich standardized extract of fenugreek seeds (FenuSMART^®; FHE), that has been clinically shown to be effective in ameliorating the postmenopausal discomforts and establishing hormonal balance. The safety was assessed by oral acute (2500 mg/kg b. wt. for 14 days) and subchronic (250, 500 and 1000 mg/kg b. wt. for 90 days) toxicity studies on Wistar rats and mutagenicity studies employing Salmonella typhimurium strains. Administration of FHE did not produce any toxicologically significant changes in clinical/behavioral observations, ophthalmic examinations, body weight, organ weight, feed consumption, urinalysis, hematology and clinical biochemistry parameters when compared to the untreated control group of animals. Highest dose recovery group (1000 mg/kg b. wt.) of animals also showed no mortality or adverse events; with hematological and biochemical parameters at par with those of controls. Terminal autopsy revealed no alterations in relative organ weight or any treatment-related histopathology changes. FHE also showed no mutagenicity upon Ames test employing TA-98, TA-100 and TA-102 Salmonella typhimurium strains with or without metabolic activation. Based on the results of the study, the no observed-adverse-effect level (NOAEL) of FHE was determined as 1000 mg/kg b. wt./day, the highest dose tested.

An In Vitro Model of Hematotoxicity: Differentiation of Bone Marrow-Derived Stem/Progenitor Cells into Hematopoietic Lineages and Evaluation of Lineage-Specific Hematotoxicity

Hematotoxicity is a significant issue for drug safety and can result from direct cytotoxicity toward circulating mature blood cell types as well as targeting of immature blood-forming stem cells/progenitor cells in the bone marrow. In vitro models for understanding and investigating the hematotoxicity potential of new test items/drugs are critical in early preclinical drug development. The traditional method, colony forming unit (CFU) assay, is commonly used and has been validated as a method for hematotoxicity screening. The CFU assay has multiple limitations for its application in investigative work. In this paper, we describe a detailed protocol for a liquid-culture, microplate-based in vitro hematotoxicity assay to evaluate lineage-specific (myeloid, erythroid, and megakaryocytic) hematotoxicity at different stages of differentiation. This assay has multiple advantages over the traditional CFU assay, including being suitable for high-throughput screening and flexible enough to allow inclusion of additional endpoints for mechanistic studies. Therefore, it is an extremely useful tool for scientists in pharmaceutical discovery and development. © 2018 by John Wiley & Sons, Inc.

K. Safety assessment of a standardized polyphenolic extract of clove buds: Subchronic toxicity and mutagenicity studies

Despite the various reports on the toxicity of clove oil and its major component eugenol, systematic evaluations on the safety of polyphenolic extracts of clove buds have not been reported. Considering the health beneficial pharmacological effects and recent use of clove polyphenols as dietary supplements, the present study investigated the safety of a standardized polyphenolic extract of clove buds (Clovinol), as assessed by oral acute (5 g/kg b.wt. for 14 days) and subchronic (0.25, 0.5 and 1 g/kg b.wt. for 90 days) toxicity studies on Wistar rats and mutagenicity studies employing Salmonella typhimurium strains. Administration of Clovinol did not result in any toxicologically significant changes in clinical/behavioural observations, ophthalmic examinations, body weights, organ weights, feed consumption, urinalysis, hematology and clinical biochemistry parameters when compared to the untreated control group of animals, indicating the no observed-adverse-effect level (NOAEL) as 1000 mg/kg b.wt./day; the highest dose tested. Terminal necropsy did not reveal any treatment-related histopathology changes. Clovinol did not show genotoxicity when tested on TA-98, TA-100 and TA-102 with or without metabolic activation; rather exhibited significant antimutagenic potential against the known mutagens, sodium azide, NPD and tobacco as well as against 2-acetamidoflourene, which needed metabolic activation for mutagenicity.

Pesticide induced alterations in marrow physiology and depletion of stem and stromal progenitor population: an experimental model to study the toxic effects of pesticide

Long-term exposure of agriculturally used organochloride and organophosphate pesticides have been shown to cause long-lasting hematotoxicity and increased incidence of aplastic anemia in humans. The mechanisms involved in pesticide induced hematotoxicity and the features of toxicity that may play a major role in bone marrow suppression are not known. The aim of the present study was to investigate the hematological consequences of pesticide exposure in swiss albino mice exposed to aqueous mixture of common agriculturally used pesticides for 6 h/day, 5 days/week for 13 weeks. After the end of last exposure, without a recovery period, the strong hematotoxic effect of pesticide was assessed in mice with long-term bone marrow explant culture (LTBMC-Ex) system and cell colony forming assays. Bone marrow explant culture from the pesticide exposed group of mice failed to generate a supportive stromal matrix and did not produce adequate number of hematopoietic cells and found to contain largely the adipogenic precursors. The decreased cell colony numbers in the pesticide exposed group indicated defective maturational and functional status of different marrow cell lineages. As a whole, exposure of mice to the mixture of pesticides reduced the total number of bone marrow cells (granulocytes are the major targets of pesticide toxicity), hematopoietic, and non-hematopoietic progenitor cells and most of the hematological parameters. Replication of primitive stem/progenitor cells in the marrow was decreased following pesticide exposure with G0/G1-phase arrest of most of the cells. The progenitor cells showed decreased percentage of cells in S/G2/M-phase. The increased apoptosis profile of the marrow progenitors (Increased CD95 expression) and primitive stem cells (High Annexin-V positivity on Sca1+ cells) with an elevated intracellular cleaved caspase-3 level on the Sca1+ bone marrow cells provided the base necessary for explaining the deranged bone marrow microenvironmental structure which was evident from scanning electron micrographs. These results clearly indicate a strong, long lasting toxic effect of pesticides on the bone marrow microenvironment and different microenvironmental components which ultimately leads to the formation of a degenerative disease like aplastic anemia.

Comparative in vitro and ex-vivo myelotoxicity of aflatoxins B1 and M1 on haematopoietic progenitors (BFU-E, CFU-E, and CFU-GM): species-related susceptibility

Haemato- and myelotoxicity are adverse effects caused by mycotoxins. Due to the relevance of aflatoxins to human health, the present study, employing CFU-GM-, BFU-E- and CFU-E-clonogenic assays, aimed at (i) comparing, in vitro, the sensitivity of human vs. murine haematopoietic progenitors to AFB1 and AFM1 (0.001-50microg/ml), (ii) assessing whether a single AFB1 in vivo treatment (0.3-3mg/kgb.w.) alters the ability of murine bone marrow cells to form myeloid and erythroid colonies, and (iii) comparing the in vitro with the in vitro ex-vivo data. We demonstrated (i) species-related sensitivity to AFB1, showing higher susceptibility of human myeloid and erythroid progenitors (IC(50) values: about 4 times lower in human than in murine cells), (ii) higher sensitivity of CFU-GM and BFU-E colonies, both more markedly affected, particularly by AFB1 (IC(50): 2.45+/-1.08 and 1.82+/-0.8microM for humans, and 11.08+/-2.92 and 1.81+/-0.20microM for mice, respectively), than the mature CFU-E (AFB1 IC(50): 12.58+/-5.4 and 40.27+/-6.05microM), irrespectively of animal species, (iii) regarding AFM1, a species- and lineage-related susceptibility similar to that observed for AFB1 and (iv) lack of effects after AFB1 in vivo treatment on the proliferation of haematopoietic colonies.

The mRNA expression and promoter methylation status of the p16 gene in colony-forming cells with high proliferative potential in patients with psoriasis

BACKGROUND

Psoriasis is a chronic and relapsing inflammatory disease of the skin associated with various immune abnormalities. It is tempting to speculate that the dysfunctional immunity may influence the haematopoietic microenvironment or haematopoiesis in psoriasis. However, direct evidence of involvement of bone-marrow haematopoietic cells in the pathogenesis of psoriasis is lacking.

AIM

To investigate the proliferative activity of haematopoietic cells of patients with psoriasis and a link between the promoter methylation status and transcriptional activity of the p16 gene and the colony-forming ability of high proliferative potential colony-forming cells (HPP-CFCs).

METHODS

Marrow mononuclear cells were isolated from the bone marrow of patients with psoriasis and normal controls by density gradient centrifugation. A comparison of HPP-CFC colony formation counts between patients with psoriasis and normal controls was carried out by colony-forming assays of HPP-CFCs in methylcellulose semisolid culture medium in vitro. Subsequently, genomic DNA and RNA in HPP-CFCs were isolated, and mRNA expression and p16 promoter methylation status were studied by reverse transcriptase PCR and methylation-specific PCR (MSP), respectively.

RESULTS

In comparison with normal controls, patients with psoriasis showed less HPP-CFC colony formation in the methycellulose semisolid culture system, and showed upregulated mRNA transcriptional level and downregulated promoter methylation of p16.

CONCLUSIONS

Our data demonstrate for the first time the abnormal proliferative activity of haematopoietic cells in patients with psoriasis and a profound link between the promoter methylation status and transcriptional activity of p16 and the colony-forming ability of HPP-CFCs, suggesting that haematopoietic cells are involved in psoriasis.

High-throughputinvitroprofiling assays: lessons learnt from experiences at Novartis

This article reviews the use of a selection of in vitro assays implemented at Novartis and intends to address exposure and safety in early drug discovery. The authors' own experience, based on a large number of 'real' drug discovery compounds, is described to reflect on what has worked, where improvement is needed and how to best use the data for decision making. Possible strategies are discussed, and guidelines are provided on how to organise assays, extract value and contribute knowledge from the data.

BLOOD COAGULATION TESTS IN TOXICOLOGICAL STUDIES-REVIEW OF METHODS AND THEIR SIGNIFICANCE FOR DRUG SAFETY ASSESSMENT-

In general toxicological studies, prothrombin time and activated partial thromboplastin time are routinely measured to assess blood coagulation. Special (problem-driven) tests for blood coagulation are of significance to detect abnormalities and investigate the mechanism of toxicity in detail. In this review, we compiled widely scattered information on blood coagulation testing from different fields in the biological area, and reviewed the methods available and their significance in toxicological studies. The relevant literature cited here reports large species differences in platelet aggregation, coagulation factors or fibrinolysis, and technical limitations. However, the following tests are basically applicable to laboratory animals; (1) assays for individual coagulation factors and protein induced by vitamin K absence or antagonists (PIVKA) to investigate coagulation factor abnormalities; (2) platelet aggregation-, platelet adhesion-, platelet release-tests and von Willebrand factor assay to screen and/or investigate platelet dysfunction; (3) fibrin/fibrinogen degradation products (FDP), D-dimer and thromboelastogram to detect fibrinolitic abnormalities, and assays for plasminogen, plasmin and their activator/inhibitor to investigate fibrinolysis in detail; and (4) bleeding-time to grossly evaluate blood coagulation capability in vivo. An appropriate battery of these tests provides significant information for risk assessment of drugs.

Hematologic reference ranges in a population of patients with schizophrenia

The potential hematotoxic effects of antipsychotic drugs are well known and may limit the use of some effective therapies. Although some previous studies have suggested that patients with schizophrenia may have altered "normal" values, only limited data were available. It is now believed that biological values do not usually follow a normal distribution; therefore, reference ranges are frequently used when interpreting laboratory tests in clinical practice and in research. However, it may be important to use disease-specific hematologic reference ranges when evaluating laboratory test results for patients with schizophrenia. In this study, data taken from patients with schizophrenia prior to treatment in previous phase II and phase III pharmaceutical studies were analyzed to produce reference ranges for a variety of hematologic parameters. An increased variability was shown in the reference ranges for all white blood cell indices between patients with schizophrenia and the population without schizophrenia. Certain reference values also showed heterogeneity for gender, age, and racial descent. This study suggests that abnormal hematologic findings in patients with schizophrenia should be assessed in the context of a valid reference range. This information will be of value to psychiatrists, laboratory scientists, and other physicians who encounter hematologic problems in patients with schizophrenia, as well as in the assessment of the adverse effects of new therapeutic agents.