Hypoxic neonatal pulmonary arterial myocytes are sensitized to ROS-generated 8-isoprostane

Area of Science:

• Cardiovascular Research
• Neonatal Physiology
• Oxidative Stress Mechanisms

Background:

• Neonatal pulmonary hypertension is linked to 8-isoprostane, a prostanoid acting via the thromboxane receptor (TP).
• Reactive oxygen species (ROS) play a role in vascular dysfunction.
• The specific impact of hypoxia on vascular smooth muscle ROS, 8-isoprostane, and TP binding in neonates is not fully understood.

Purpose of the Study:

• To investigate the effects of hypoxia on ROS generation in pulmonary artery myocytes.
• To examine hypoxia-induced changes in 8-isoprostane activity and TP binding.
• To elucidate the signaling pathways involved in hypoxia-mediated vasoconstriction.

Main Methods:

• Primary neonatal porcine pulmonary artery myocytes were exposed to normoxic (21% O2) or hypoxic (10% O2) conditions for 72 hours.
• ROS, superoxide, and 8-isoprostane generation were measured.
• Activities of superoxide dismutase (SOD) enzymes (SOD1, SOD2, SOD3) were assessed. TP binding, internalization, and calcium release were analyzed.

Main Results:

• Hypoxia significantly increased ROS, superoxide, and 8-isoprostane generation in myocytes.
• Mitochondrial complex III inhibition ablated ROS generation; SOD2 activity decreased, while SOD1 and SOD3 activities increased under hypoxia.
• Hypoxia enhanced 8-isoprostane affinity for TP receptors, leading to TP internalization and calcium release, which was normalized by adenylyl cyclase activation.

Conclusions:

• Hypoxia induces superoxide accumulation in pulmonary artery myocytes, partly via decreased mitochondrial SOD2 activity.
• This leads to peroxynitrite-driven 8-isoprostane generation, which sensitizes TP receptors.
• The 8-isoprostane/TP pathway contributes to pulmonary vasoconstriction in hypoxic neonates, suggesting a potential therapeutic target.