Txnip C247S mutation protects the heart against acute myocardial infarction
Yoshinobu Nakayama1, Nobuhiro Mukai1, Bing F Wang2
1Department of Molecular, Cellular & Biomedical Sciences, City University of New York School of Medicine, City College of New York, NY, New York, United States of America.
Rationale:
Thioredoxin-interacting protein (Txnip) is a novel molecular target with translational potential in diverse human diseases. Txnip has several established cellular actions including binding to thioredoxin, a scavenger of reactive oxygen species (ROS). It has been long recognized from in vitro evidence that Txnip forms a disulfide bridge through cysteine 247 (C247) with reduced thioredoxin to inhibit the anti-oxidative properties of thioredoxin. However, the physiological significance of the Txnip-thioredoxin interaction remains largely undefined in vivo.
Objective:
A single mutation of Txnip, C247S, abolishes the binding of Txnip with thioredoxin. Using a conditional and inducible approach with a mouse model of a mutant Txnip that does not bind thioredoxin, we tested whether the interaction of thioredoxin with Txnip is required for Txnip's pro-oxidative or cytotoxic effects in the heart.
Methods And Results:
Overexpression of Txnip C247S in cells resulted in a reduction in ROS, due to an inability to inhibit thioredoxin. Hypoxia (1% O2, 24 h)-induced killing effects of Txnip were decreased by lower levels of cellular ROS in Txnip C247S-expressing cells compared with wild-type Txnip-expressing cells. Then, myocardial ischemic injuries were assessed in the animal model. Cardiomyocyte-specific Txnip C247S knock-in mice had better survival with smaller infarct size following myocardial infarction (MI) compared to control animals. The absence of Txnip's inhibition of thioredoxin promoted mitochondrial anti-oxidative capacities in cardiomyocytes, thereby protecting the heart from oxidative damage induced by MI. Furthermore, an unbiased RNA sequencing screen identified that hypoxia-inducible factor 1 signaling pathway was involved in Txnip C247S-mediated cardioprotective mechanisms.
Conclusion:
Txnip is a cysteine-containing redox protein that robustly regulates the thioredoxin system via a disulfide bond-switching mechanism in adult cardiomyocytes. Our results provide the direct in vivo evidence that regulation of redox state by Txnip is a crucial component for myocardial homeostasis under ischemic stress.
Insights
Thioredoxin-interacting protein (Txnip) regulates heart cell redox balance. Blocking Txnip binding to thioredoxin protects the heart from oxidative stress and myocardial infarction injury in vivo.
Area of Science:
- Cardiovascular Biology
- Redox Biology
- Molecular Medicine
Background:
- Thioredoxin-interacting protein (Txnip) targets thioredoxin, a reactive oxygen species (ROS) scavenger.
- Txnip inhibits thioredoxin's antioxidant function via disulfide bond formation at cysteine 247 (C247).
- The in vivo significance of Txnip-thioredoxin interaction in cardiovascular disease remains unclear.
Purpose of the Study:
- To investigate the in vivo role of Txnip-thioredoxin interaction in cardiac oxidative stress and injury.
- To determine if Txnip's pro-oxidant effects in the heart are mediated by thioredoxin inhibition.
Main Methods:
- Utilized a conditional, inducible mouse model with a Txnip C247S mutation that prevents thioredoxin binding.
- Assessed ROS levels, cell viability under hypoxia, and myocardial ischemic injury (infarct size, survival) following myocardial infarction (MI).
- Performed RNA sequencing to identify molecular pathways involved in Txnip C247S-mediated cardioprotection.
Main Results:
- Txnip C247S expression reduced cellular ROS and protected cells from hypoxia-induced death.
- Txnip C247S knock-in mice exhibited improved survival and reduced infarct size post-MI.
- Inhibition of Txnip binding to thioredoxin enhanced mitochondrial antioxidant capacity in cardiomyocytes.
- Hypoxia-inducible factor 1 (HIF-1) signaling was implicated in the cardioprotective effects.
Conclusions:
- Txnip regulates myocardial redox state in adult cardiomyocytes through disulfide bond switching with thioredoxin.
- Txnip-thioredoxin interaction is critical for maintaining myocardial homeostasis during ischemic stress.
- Targeting the Txnip-thioredoxin interaction offers a potential therapeutic strategy for heart disease.
