From Physiological Redox Signalling to Oxidant Stress

Area of Science:

• Cardiovascular Physiology
• Cellular Signaling
• Oxidative Stress Biology

Background:

• Oxidant stress is linked to cardiovascular diseases like pulmonary hypertension, yet antioxidant treatments have failed.
• This failure stems from an incomplete understanding of reactive oxygen species (ROS) in cell signaling and their complex interplay with ROS generators (mitochondria, NADPH oxidases - NOX) and calcium (Ca2+) signaling.

Purpose of the Study:

• To explore the physiological regulation of NOX and mitochondrial ROS production and degradation.
• To examine the interactions between ROS, their generators, and Ca2+ signaling pathways.
• To discuss how disrupted ROS regulation contributes to pulmonary hypertension.

Main Methods:

• Review of existing literature on ROS signaling, mitochondrial function, NOX activity, and Ca2+ dynamics.
• Analysis of the mechanisms underlying ROS-induced ROS release and positive feedback loops.
• Discussion of compartmentalization in cellular ROS signaling.

Main Results:

• At physiological levels, ROS reversibly modulate enzyme and transcription factor activity, primarily through thiol oxidation.
• ROS signaling pathways can activate ROS production by NOX and mitochondria (ROS-induced ROS release), creating positive feedback loops.
• Compartmentalization of ROS signaling, similar to Ca2+, normally prevents uncontrolled ROS production.

Conclusions:

• Dysregulation of ROS signaling in pulmonary hypertension may result from loss of spatiotemporal control and activation of positive feedback mechanisms.
• A deeper understanding of ROS regulation is essential for developing targeted therapies for cardiovascular diseases.