Hyperoxia activates ATM independent from mitochondrial ROS and dysfunction.

Area of Science:

• Cell Biology
• Mitochondrial Biology
• Oxidative Stress

Background:

• Hyperoxia, used for respiratory distress, can cause mitochondrial dysfunction and DNA damage via reactive oxygen species (ROS).
• Ataxia telangiectasia mutated (ATM) kinase, activated by nuclear DNA damage, influences cell death pathways.
• The role of ATM in mitochondrial function and its activation by mitochondrial ROS remains unclear.

Purpose of the Study:

• To investigate whether hyperoxia-induced mitochondrial dysfunction and ROS activate ATM kinase.
• To determine if ATM plays a role in regulating mitochondrial homeostasis under hyperoxic conditions.

Main Methods:

• A549 lung epithelial cells were exposed to hyperoxia.
• Mitochondrial respiration, ROS levels, and mitochondrial DNA double-strand breaks were assessed.
• ATM activation and downstream targets (p53) were analyzed under various conditions, including antimycin A treatment and SOD2 depletion.

Main Results:

• Hyperoxia impaired mitochondrial respiration and increased ROS, but did not induce mitochondrial DNA double-strand breaks.
• ATM was not activated by mitochondrial dysfunction or ROS; it did not mediate p53 activation in response to mitochondrial inhibition.
• ATM appeared to dampen mitochondrial ROS accumulation during hyperoxia.

Conclusions:

• Hyperoxia-induced mitochondrial dysfunction and ROS do not activate ATM kinase.
• ATM's primary role in hyperoxia may involve responding to nuclear DNA damage and attenuating mitochondrial ROS.
• ATM may protect against oxygen toxicity by mitigating mitochondrial ROS.