Oxazolone and diclofenac-induced popliteal lymph node assay reactions are attenuated in mice orally pretreated with the respective compound: potential role for the induction of regulatory mechanisms following enteric administration

Re-evaluation of benzyl alcohol (E 1519) as food additive

The Panel on Food Additives and Flavourings (FAF) provided a scientific opinion re-evaluating the safety of benzyl alcohol (E 1519) when used as a food additive. The Panel considered that adequate exposure and toxicity data were available. Benzyl alcohol (E 1519) is authorised as a food additive in the EU in accordance with Annex III to Regulation (EC) No 1333/2008. The Panel considered benzyl alcohol of low acute toxicity with no concern with respect to genotoxicity and carcinogenicity and established an acceptable daily intake (ADI) of 4 mg/kg body weight (bw) per day based on a no observable adverse effect level (NOAEL) of 400 mg/kg bw per day from the carcinogenicity study in rats. The mean and high exposure estimates in the refined exposure scenarios were maximally 0.27 and 0.81 mg/kg bw per day in toddlers, respectively. The exposure estimates to benzyl alcohol (E 1519) were below the ADI of 4 mg/kg bw per day in all population groups. The Panel noted that also the exposure in the regulatory maximum level exposure assessment scenario is below the ADI in all population groups. The Panel concluded that the exposure to benzyl alcohol (E 1519) does not raise a safety concern at the reported uses and use levels.

Novel gene markers of immunosuppressive chemicals in mouse lymph node assay

The murine local lymph node assay (LLNA) is an immunologically based test of the sensitizing potential of immunotoxicants, but also evaluates immunosuppressive potential with good sensitivity and specificity. We conducted the LLNA with calcineurin inhibitors (tacrolimus and cyclosporin A), antimetabolites (methotrexate and azathioprine), steroids (dexamethasone and prednisolone), and an alkylator (cyclophosphamide). We performed a comprehensive analysis of results of gene expression in lymph nodes obtained in the LLNA using a highly sensitive DNA chip, 3D-Gene™, and the quantitative reverse transcription-polymerase chain reaction (qPCR). Zfp459 expression increased in all animals treated with immunosuppressive chemicals. Ltf, Cbll1 and Lias expression changed specifically in response to the calcineurin inhibitors, Fmo2 and 9630033F20Rik in response to the antimetabolites, Krt8, Gjb1, Hmha1 and Sfrs7 in response to the steroids, and Gbp1 and Mup5 in response to the alkylator. Therefore, these genes were considered novel markers for immunosuppression and their expression could be used to evaluate the mechanism of action of immunosuppressive chemicals.

Inflammatory stress and idiosyncratic hepatotoxicity: hints from animal models

Adverse drug reactions (ADRs) present a serious human health problem. They are major contributors to hospitalization and mortality throughout the world (Lazarou et al., 1998; Pirmohamed et al., 2004). A small fraction (less than 5%) of ADRs can be classified as "idiosyncratic." Idiosyncratic ADRs (IADRs) are caused by drugs with diverse pharmacological effects and occur at various times during drug therapy. Although IADRs affect a number of organs, liver toxicity occurs frequently and is the primary focus of this review. Because of the inconsistency of clinical data and the lack of experimental animal models, how IADRs arise is largely undefined. Generation of toxic drug metabolites and induction of specific immunity are frequently cited as causes of IADRs, but definitive evidence supporting either mechanism is lacking for most drugs. Among the more recent hypotheses for causation of IADRs is that inflammatory stress induced by exogenous or endogenous inflammagens is a susceptibility factor. In this review, we give a brief overview of idiosyncratic hepatotoxicity and the inflammatory response induced by bacterial lipopolysaccharide. We discuss the inflammatory stress hypothesis and use as examples two drugs that have caused IADRs in human patients: ranitidine and diclofenac. The review focuses on experimental animal models that support the inflammatory stress hypothesis and on the mechanisms of hepatotoxic response in these models. The need for design of epidemiological studies and the potential for implementation of inflammation interaction studies in preclinical toxicity screening are also discussed briefly.

Tipping the balance towards tolerance: the basis for therapeutic immune modulation by gold?

Gold salts have long been used in the treatment of rheumatoid arthritis. However, the basis for their therapeutic immune-modulating properties has never been satisfactorily explained. Furthermore, treatments are often marred by the development of adverse immune reactions such as hypersensitivity and even exacerbation of autoimmunity. We would like to propose a hypothesis to explain the basis for both the beneficial and adverse immune-modulating effects of gold in the treatment of rheumatoid arthritis. If accepted, this hypothesis will allow for the development of safer and more effective treatments with gold salts. The principle underlying this hypothesis also has broader implications for how immune hypersensitivity and tolerance are perceived.

Murine models of drug hypersensitivity

PURPOSE OF REVIEW

Drug hypersensitivity reactions are relatively rare but may result in severe morbidity and fatalities. Due to the idiosyncratic nature and multifactorial etiology of these reactions, development of a single animal model to study the immunosensitizing mechanisms of all drugs is impossible. This hampers the development of predictive screening models that are urgently needed to assess the immunostimulating capacity of newly developed drugs. The present review will focus on recent findings on mechanisms of drug hypersensitivity reactions obtained with murine models, and on the use of these models as potential screening tools to assess the immunostimulating capacity of drugs.

RECENT FINDINGS

Mechanisms of drug-induced sensitization versus tolerance appear dependent on generally accepted immunological paradigms. For instance, co-stimulatory signaling by antigen-presenting cells is decisive in drug-induced immunosensitization and both T cells and antigen-presenting cells are important for the induction of tolerance to orally administered drugs. From recent studies it has been hypothesized that expression of stress-associated transcription factors and the expression of costimulatory molecules or cytokine production within hours or days after the initial exposure may be representative of drug-induced hypersensitivity reactions and may thus be used as predictive parameters to screen for immunosensitizing drugs.

SUMMARY

The development of animal models to study mechanisms of drug hypersensitivity reactions is still in its infancy. Much effort has been made, however, to search for early indicators of immunostimulation in murine animal models that may eventually appear useful in a tiered strategy to assess drug-induced sensitization.