Biomedical subjects

I Langezaal

Publications and source records attributed to I Langezaal.

4 recordsLinked to original sources

PubMedDate not supplied

Whole blood cytokine response as a measure of immunotoxicity.

Immunotoxicity, although increasingly recognized as a potential hazard, still lacks standardized in vivo and in vitro models. The considerable species differences and species-specific effects in immune responses prompt the development of human in vitro test systems. Immunotoxic reactions comprise activation (inflammatory processes, autoaggressive processes, pyrogenicity), sensitization (priming, idiosyncratic reactions) and impairment of immune responses (anergy, immunosuppression). We have previously studied a human whole blood system which allows the study of the release of inflammatory cytokines in response to a variety of stimuli. This model allows the assessment of this basic immune mechanism without preparation artefacts and relatively small interindividual variances. We have used this model previously to assess pyrogens, namely type (1) immunotoxic reactions. The model also proved to be suitable for immunopharmacological studies in vitro as well as ex vivo. Here, we studied the suitability of the test system to study type (3) immunotoxic effects. In order to also allow ex vivo studies, we have transferred the system to murine blood. This report summarizes our own use of this model with special emphasis on immunotoxicological studies. Our own listed bibliography gives access to the variety of applications of the human whole blood model since its introduction in 1982.

Adjuvants, Immunologic↗

PubMedDate not supplied

Activation of the complement system as an indicator of pyrogenic reaction to lipopolysaccharide (LPS).

The generation of biologically active complement split products through the direct reaction of microorganisms with complement proteins is one of the earliest events of the defence reaction in humans. Complement activation develops within minutes, which highly corresponds with the onset of a febrile reaction after exposure to pyrogens. The possibility of the use of complement activation in human plasma as an indicator of pyrogen contamination has been tested. Additionally, the co-stimulatory effect of complement activation on tumor necrosis factor-alpha (TNF-alpha) production by blood-separated macrophages exposed to lipopolysaccharide (LPS) has been demonstrated. As an indicator of complement activation in test samples, the concentration of the iC3b fragment was measured by using an ELISA system based on neoantigen formation. The 3-h exposure time has been identified as optimal for the test. The variability between iC3b concentrations in untreated control samples obtained from seven unrelated healthy donors was less than 10%, while after activation by 100 ng/ml LPS, it increased to 13%. The lower detection limit has been identified as 10 pg/ml LPS. As the complement test is not affected by drug-cell interactions or cell viability, the test can be used in situations where tested formulations contain active substances, which interfere with a cell-based test. We conclude that a test based on the detection of complement activation in human plasma should be considered as a valuable element of an in vitro pyrogenicity testing battery along with a cell-based assay.

Animal Testing Alternatives↗

PubMedDate not supplied

The use of genetically engineered cells for assessing CYP2D6-related polymorphic effects.

As an example of advanced testing in the field of metabolism in an industrial environment, the introduction of some novel approaches, including the use of genetically engineered cell lines for assessing CYP 2D6-related polymorphic effects is illustrated. In this paper, it is demonstrated that novel in vitro test systems can be developed by using these genetically engineered cell lines for evaluating the potential risks associated with proprietary drugs (especially if their metabolism depends to a high extent on CYP 2D6). Moreover, it is demonstrated that, by the use of these in vitro methods, issues such as polymorphism, for which no animal models are available, can be assessed in such a way that predictions can be made on adverse effects which, up to now, could only be detected during clinical trials. Through the use of these new biotechnological in vitro metabolism models, clinically relevant data can be obtained for a scientifically-based human risk assessment, and animal use can be reduced.

Animal Testing Alternatives↗

PubMedDate not supplied

A Genetically engineered cell-based system for detecting metabolism-mediated toxicity.

Xenobiotics undergoing bioactivation by CYP450 enzymes form reactive metabolites that may exert direct metabolism-mediated toxicity. An in vitro model was developed to study the direct toxic effects that follow the metabolic activation of chemicals. The model uses monolayer cultures of genetically engineered NIH-3T3 or V79 cells that express individual human or rat CYP450 isoforms, respectively. Following exposure to 1,3-dichloropropanol or cyclophosphamide, basal cytotoxicity endpoints, including neutral red uptake and Alamar Blue( reduction were used to assess changes in cell number and functional viability resulting from the formation of metabolites. Cell lines that express cytochrome P450 enzymes metabolised the test compounds, leading to increased toxicity compared with that observed in the control cell line. The use of specific inhibitors confirmed that the formation of reactive metabolites was CYP450-isoform dependent. These results indicate that a panel of genetically engineered cell lines expressing various cytochrome P450 enzyme isoforms can be used to reveal measurable metabolising capabilities, and could become a useful tool for the detection and possible determination of CYP450 isoforms in human liver metabolism-mediated toxicity.

3T3 Cells↗