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Updated: Jul 5, 2026
Human Liver Microphysiological System for Assessing Drug-Induced Liver Toxicity In Vitro
Published on: January 31, 2022
Troglitazone-induced hepatic mitochondrial proteome expression dynamics in heterozygous Sod2(+/-) mice: two-stage
Yie Hou Lee1, Maxey C M Chung, Qingsong Lin
1Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597.
Abstract:
The determinants of susceptibility to troglitazone-induced idiosyncratic liver injury have not yet been determined; however, troglitazone has been shown to target mitochondria and induce mitochondria-mediated hepatocellular injury in vitro. The aim of this study was to use a systems approach to analyze the dynamics of mitochondrial changes at the proteome level and more clearly define the mechanisms and time course of troglitazone hepatotoxicity by using a previously characterized mouse model that is highly sensitized to troglitazone hepatotoxicity. Mice heterozygous in mitochondrial superoxide dismutase-2 (Sod2(+/-)) were injected intraperitoneally with troglitazone (30 mg/kg/day) or vehicle daily for 2 or 4 weeks. Hepatic mitochondria were isolated, purified, and subjected to two-dimensional difference gel electrophoresis (2D-DIGE). We found that among the ~1500 resolved hepatic mitochondrial proteins, 70 exhibited significantly altered abundance after troglitazone treatment. MALDI-TOF/TOF MS/MS analysis revealed that early changes (2 weeks) included increased levels of heat shock protein family members (mortalin, HSP7C), Lon protease, and catalase, indicating induction of a mitochondrial stress response. In contrast, after 4 weeks, a number of critical proteins including ATP synthase beta-subunit, aconitase-2, and catalase exhibited decreased abundance, and total protein carbonyls were significantly increased, suggesting uncompensated oxidative damage. Aconitase-2 (ACO2) was decreased at both time points, making this protein a potential sensitive and early biomarker for mitochondrial oxidant stress. These results show that, in this murine model of underlying clinically silent mitochondrial stress, superimposed troglitazone induces a two-stage response: an initial adaptive response, followed by a toxic response involving oxidant injury to mitochondrial proteins.
Insights
Troglitazone causes liver injury by targeting mitochondria. This study reveals a two-stage mitochondrial response in mice, starting with stress adaptation and progressing to oxidative damage, identifying aconitase-2 as an early biomarker.
Area of Science:
- Biochemistry
- Toxicology
- Mitochondrial Biology
Background:
- Troglitazone-induced liver injury mechanisms remain unclear.
- Troglitazone is known to target mitochondria and cause hepatocellular injury.
- Mice heterozygous for mitochondrial superoxide dismutase-2 (Sod2(+/-)) are sensitized to troglitazone hepatotoxicity.
Purpose of the Study:
- To analyze mitochondrial proteome dynamics in response to troglitazone.
- To define the mechanisms and time course of troglitazone-induced hepatotoxicity.
- To identify early biomarkers of mitochondrial oxidant stress.
Main Methods:
- Mice (Sod2(+/-)) were treated with troglitazone or vehicle for 2 or 4 weeks.
- Hepatic mitochondria were isolated and analyzed using 2D-DIGE.
- Protein identification was performed using MALDI-TOF/TOF MS/MS.
Main Results:
- Troglitazone altered the abundance of 70 out of ~1500 hepatic mitochondrial proteins.
- Early changes (2 weeks) indicated a mitochondrial stress response (e.g., increased HSPs, catalase).
- Later changes (4 weeks) showed decreased critical proteins (e.g., ATP synthase, aconitase-2) and increased oxidative damage.
Conclusions:
- Troglitazone induces a two-stage mitochondrial response: adaptive stress followed by oxidant injury.
- Aconitase-2 (ACO2) is a potential early and sensitive biomarker for mitochondrial oxidant stress.
- This study elucidates mechanisms of troglitazone hepatotoxicity in a susceptible mouse model.
