15 research outputs found
Comparison of TNFα to Lipopolysaccharide as an Inflammagen to Characterize the Idiosyncratic Hepatotoxicity Potential of Drugs: Trovafloxacin as an Example
Idiosyncratic drug reactions (IDRs) are poorly understood, unpredictable, and not detected in preclinical studies. Although the cause of these reactions is likely multi-factorial, one hypothesis is that an underlying inflammatory state lowers the tolerance to a xenobiotic. Previously used in an inflammation IDR model, bacterial lipopolysaccharide (LPS) is heterogeneous in nature, making development of standardized testing protocols difficult. Here, the use of rat tumor necrosis factor-α (TNFα) to replace LPS as an inflammatory stimulus was investigated. Sprague-Dawley rats were treated with separate preparations of LPS or TNFα, and hepatic transcriptomic effects were compared. TNFα showed enhanced consistency at the transcriptomic level compared to LPS. TNFα and LPS regulated similar biochemical pathways, although LPS was associated with more robust inflammatory signaling than TNFα. Rats were then codosed with TNFα and trovafloxacin (TVX), an IDR-associated drug, and evaluated by liver histopathology, clinical chemistry, and gene expression analysis. TNFα/TVX induced unique gene expression changes that clustered separately from TNFα/levofloxacin, a drug not associated with IDRs. TNFα/TVX cotreatment led to autoinduction of TNFα resulting in potentiation of underlying gene expression stress signals. Comparison of TNFα/TVX and LPS/TVX gene expression profiles revealed similarities in the regulation of biochemical pathways. In conclusion, TNFα could be used in lieu of LPS as an inflammatory stimulus in this model of IDRs
Coexposure of Mice to Trovafloxacin and Lipopolysaccharide, a Model of Idiosyncratic Hepatotoxicity, Results in a Unique Gene Expression Profile and Interferon Gamma–Dependent Liver Injury
The antibiotic trovafloxacin (TVX) has caused severe idiosyncratic hepatotoxicity in people, whereas levofloxacin (LVX) has not. Mice cotreated with TVX and lipopolysaccharide (LPS), but not with LVX and LPS, develop severe hepatocellular necrosis. Mice were treated with TVX and/or LPS, and hepatic gene expression changes were measured before liver injury using gene array. Hepatic gene expression profiles from mice treated with TVX/LPS clustered differently from those treated with LPS or TVX alone. Several of the probe sets expressed differently in TVX/LPS–treated mice were involved in interferon (IFN) signaling and the janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway. A time course of plasma concentrations of IFN-γ and interleukin (IL)-18, which directly induces IFN-γ production, revealed that both cytokines were selectively increased in TVX/LPS–treated mice. Both IL-18−/− and IFN-γ−/− mice were significantly protected from TVX/LPS–induced liver injury. In addition, IFN-γ−/− mice had decreased plasma concentrations of tumor necrosis factor-α, IL-18, and IL-1β when compared to wild-type mice. In conclusion, the altered expression of genes involved in IFN signaling in TVX/LPS–treated mice led to the finding that IL-18 and IFN-γ play a critical role in TVX/LPS–induced liver injury
Gene Expression Profiles in Livers from Diclofenac-Treated Rats Reveal Intestinal Bacteria-Dependent and -Independent Pathways Associated with Liver Injury
Comparative NMR-Based Metabonomic Investigation of the Metabolic Phenotype Associated with Tienilic Acid and Tienilic Acid Isomer
An NMR-based metabonomic approach was applied to study
the systems
level metabolic effects of two closely related thiophene compounds,
tienilic acid (TA) and tienilic acid isomer (TAI). The metabonomic
data were anchored with traditional clinical chemistry and histopathologic
analyses. TA was removed from the market as a result of suspected
immune-mediated hepatotoxicity, whereas TAI is an intrinsic hepatotoxin.
Equimolar doses of TA and TAI were administered to Sprague–Dawley
rats, and sampling was conducted at 2, 6, and 24 h post-treatment.
Histopathologic analyses revealed development of a significant hepatic
lesion 24 h post-TAI treatment with a parallel increase in plasma
alanine aminotransferase (ALT) activity. In contrast, TA was not associated
with the development of a hepatic lesion or an increase in plasma
ALT activity. High-resolution NMR spectral metabolic profiles were
generated for liver extracts, plasma, and urine at multiple time points.
Multivariate statistical tools were applied to model the metabolic
profiles and identify discriminatory metabolites that reflected both
the adaptation to TA administration and the onset and progression
of TAI-induced hepatotoxicity. TAI was shown to induce marked metabolic
effects on the metabolome at all time points, with dramatic metabolic
perturbations at 24 h post-treatment correlating with the histopathologic
and clinical chemistry evidence of a hepatic lesion. The TAI-induced
metabolic perturbations provided evidence for the generation of electrophilic
reactive metabolites and a significant impairment of bioenergetic
metabolic pathways. TA induced early metabolic perturbations that
were largely resolved by 24 h post-treatment, suggesting the reestablishment
of metabolic homeostasis and the ability to adapt to the intervention,
with hepatic hypotaurine potentially representing a means of assessment
of hepatic adaptation. This comparative metabonomic approach enabled
the discrimination of metabolic perturbations that were common to
both treatments and were interpreted as nontoxic thiophene-induced
perturbations. Importantly, this approach enabled the identification
of temporal metabolic perturbations that were unique to TAI or TA
treatment and hence were of relevance to the development of toxicity
or the ability to adapt. This approach is applicable to the future
study of pharmacologically and structurally similar compounds and
represents a refined means of identification of biomarkers of toxicity
Modest Inflammation Enhances Diclofenac Hepatotoxicity in Rats: Role of Neutrophils and Bacterial Translocation
A Cytochrome P450–Independent Mechanism of Acetaminophen-Induced Injury in Cultured Mouse Hepatocytes
Effect of allyl alcohol on hepatic transporter expression: Zonal patterns of expression and role of Kupffer cell function
During APAP toxicity, activation of Kupffer cells is critical for protection from hepatotoxicity and up-regulation of multidrug resistance-associated protein 4 (Mrp4) in centrilobular hepatocytes. The present study was performed to determine the expression profile Of Uptake and efflux transporters in mouse liver following treatment with allyl alcohol (AlOH), a periportal hepatotoxicant. This study also investigated the role of Kupffer cells in AlOH hepatotoxicity, and whether changes in transport protein expression by AlOH are dependent on the presence of Kupffer cells. C57BL/6J mice received 0.1 ml chlodronate liposomes to deplete Kupffer cells or empty liposomes 48 h prior to dosing with 60 mg/kg AlOH, i.p. Hepatotoxicity was assessed by plasma ALT and histopathology. Hepatic transporter mRNA and protein expression were determined by branched DNA signal amplification assay and Western blotting, respectively. Depletion of Kupffer cells by liposomal clodronate treatment resulted in heightened susceptibility to AlOH toxicity, Exposure to AlOH increased mRNA levels of several Mrp genes, while decreasing organic anion transporting polypeptides (Oatps) mRNA expression. Protein analysis mirrored many of these mRNA changes. The presence of Kupffer cells was not required for the observed changes in uptake and efflux transporters induced by AlOH. Immunofluorescent analysis revealed enhanced Mrp4 staining exclusively in centrilobular hepatocytes of AlOH treated mice. These findings demonstrate that Kupffer cells are protective from AlOH toxicity and that induction of Mrp4 occurs in liver regions away from areas of AlOH damage independent of Kupffer cell function. These results suggest that Kupffer cell mediators do not play a role in mediating centrilobular Mrp4 induction in response to periportal damage by AlOH. (C) 2009 Elsevier Inc. All rights reserve