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Updated: Aug 21, 2026
Human Liver Microphysiological System for Assessing Drug-Induced Liver Toxicity In Vitro
Published on: January 31, 2022
Chaperone proteins involved in troglitazone-induced toxicity in human hepatoma cell lines
Rawiwan Maniratanachote1, Keiichi Minami, Miki Katoh
1Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Abstract:
Troglitazone (TRO), an effective thiazolidinedione antidiabetic agent, was reported to produce idiosyncratic hepatotoxic effects in some individuals. In contrast, rosiglitazone (RSG), in the same group of agents, has no significant toxic effects and now is widely used. In this study, human hepatoma (HepG2) cell lines were exposed to various doses of TRO as well as RSG (0, 25, 50, and 75 microM) for 48 h. Cell lysates were separated by two-dimensional electrophoresis, and the gels were stained with coomassie brilliant blue to compare the spot profiles. The greatest protein expression at a MW of 75 kDa and isoelectric point of 5 was specifically increased with TRO treatments of 50 and 75 microM. The spot was identified as a mixture of immunoglobulin heavy chain binding protein (BiP) and, to a lesser extent, protein disulfide isomerase-related protein (PDIrp). Immunoblot analyses showed that the BiP protein was dose-dependently increased by TRO treatment and, to a lower degree, by RSG. These effects were also correlated with the high induction of BiP mRNA by TRO (50 and 75 microM) and the lower induction by RSG. However, both treatments showed no significant effects on PDIrp expression. The toxic effects of TRO in relation to the overexpression of BiP were also demonstrated in HLE cells, another human hepatoma cell line. In HLE cells, the inhibition of BiP expression by small interference RNA rendered cells more susceptible to the toxic effects of TRO. These results suggest that the overexpression of BiP is a defense mechanism of the endoplasmic reticulum in response to TRO-induced toxicity.
Insights
Troglitazone (TRO) increases immunoglobulin heavy chain binding protein (BiP) expression, a potential defense mechanism against its liver toxicity. Rosiglitazone (RSG) showed less effect, highlighting differing cellular responses to antidiabetic agents.
Area of Science:
- Hepatology
- Molecular Biology
- Pharmacology
Background:
- Troglitazone (TRO), a thiazolidinedione antidiabetic, causes idiosyncratic hepatotoxicity.
- Rosiglitazone (RSG), a similar agent, lacks significant toxic effects and is widely used.
- Understanding the molecular mechanisms behind TRO-induced liver injury is crucial.
Purpose of the Study:
- To investigate the differential protein expression in human hepatoma cells exposed to TRO and RSG.
- To identify proteins involved in TRO-induced hepatotoxicity.
- To elucidate the role of endoplasmic reticulum stress response in TRO toxicity.
Main Methods:
- Human hepatoma cell lines (HepG2, HLE) treated with varying doses of TRO and RSG.
- Proteomic analysis using two-dimensional electrophoresis and immunoblotting.
- Gene expression analysis of BiP and PDIrp via mRNA levels.
- RNA interference to inhibit BiP expression in HLE cells.
Main Results:
- TRO treatment significantly increased the expression of immunoglobulin heavy chain binding protein (BiP) and protein disulfide isomerase-related protein (PDIrp) in HepG2 cells.
- BiP protein and mRNA levels were dose-dependently upregulated by TRO, with a lesser effect observed for RSG.
- Inhibition of BiP expression in HLE cells increased susceptibility to TRO-induced toxicity.
- PDIrp expression was not significantly affected by either drug.
Conclusions:
- Overexpression of BiP serves as an endoplasmic reticulum defense mechanism against TRO-induced cellular damage.
- Differential regulation of BiP expression may contribute to the distinct safety profiles of TRO and RSG.
- Targeting ER stress pathways could offer therapeutic strategies for managing drug-induced liver injury.
