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Updated: Sep 6, 2025
Improved Rodent Model of Myocardial Ischemia and Reperfusion Injury
Published on: March 7, 2022
Yin and Yang of NADPH Oxidases in Myocardial Ischemia-Reperfusion
Shouji Matsushima1, Junichi Sadoshima2
1Department of Cardiovascular Medicine, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Abstract:
Oxidative stress is critically involved in the pathophysiology of myocardial ischemic-reperfusion (I/R) injury. NADPH oxidase (Nox) 2 and 4, major sources of reactive oxygen species (ROS) in cardiomyocytes, are upregulated in response to I/R. Suppression of Nox-derived ROS prevents mitochondrial dysfunction and endoplasmic reticulum (ER) stress, leading to attenuation of myocardial I/R injury. However, minimal levels of ROS by either Nox2 or Nox4 are required for energy metabolism during I/R in the heart, preserving hypoxia-inducible factor-1α (HIF-1α) and peroxisome proliferator-activated receptor-α (PPARα) levels. Furthermore, extreme suppression of Nox activity induces reductive stress, leading to paradoxical increases in ROS levels. Nox4 has distinct roles in organelles such as mitochondria, ER, and ER-mitochondria contact sites (MAMs). Mitochondrial Nox4 exerts a detrimental effect, causing ROS-induced mitochondrial dysfunction during I/R, whereas Nox4 in the ER and MAMs is potentially protective against I/R injury through regulation of autophagy and MAM function, respectively. Although Nox isoforms are potential therapeutic targets for I/R injury, to maximize the effect of intervention, it is likely important to optimize the ROS level and selectively inhibit Nox4 in mitochondria. Here, we discuss the 'Yin and Yang' functions of Nox isoforms during myocardial I/R.
Insights
NADPH oxidase (Nox) enzymes play a dual role in heart injury after blood flow is restored. Optimizing reactive oxygen species (ROS) levels and targeting specific Nox4 in mitochondria is key for treating myocardial ischemic-reperfusion injury.
Area of Science:
- Cardiovascular Biology
- Oxidative Stress Research
- Cellular Physiology
Background:
- Oxidative stress is central to myocardial ischemic-reperfusion (I/R) injury.
- NADPH oxidase (Nox) 2 and 4 are key producers of reactive oxygen species (ROS) in cardiomyocytes, elevated during I/R.
- While ROS contribute to I/R injury, minimal ROS are essential for cardiac energy metabolism and preserving key regulatory factors.
Purpose of the Study:
- To elucidate the complex roles of Nox isoforms, particularly Nox4, in myocardial I/R injury.
- To investigate the organelle-specific functions of Nox4 in mitochondria, endoplasmic reticulum (ER), and ER-mitochondria contact sites (MAMs).
- To explore therapeutic strategies for I/R injury by modulating ROS levels and Nox activity.
Main Methods:
- Review and discussion of existing literature on Nox isoforms and ROS in myocardial I/R.
- Analysis of the distinct functions of Nox4 in different cellular compartments.
- Exploration of the concept of 'reductive stress' and its implications.
Main Results:
- Nox-derived ROS contribute to I/R injury by causing mitochondrial dysfunction and ER stress.
- Minimal ROS from Nox2 or Nox4 are crucial for maintaining energy metabolism and HIF-1α/PPARα levels during I/R.
- Mitochondrial Nox4 is detrimental, while ER/MAM Nox4 may be protective, influencing autophagy and MAM function.
Conclusions:
- Nox isoforms exhibit 'Yin and Yang' functions in myocardial I/R, with context-dependent effects.
- Selective inhibition of mitochondrial Nox4, alongside ROS level optimization, is a promising therapeutic approach for I/R injury.
- Understanding the compartmentalized roles of Nox4 is critical for developing effective interventions against heart I/R damage.
