Nitric oxide and peroxynitrite-mediated pulmonary cell death

Area of Science:

• Pulmonary toxicology
• Cellular and molecular biology
• Biochemistry

Background:

• Nitric oxide (NO) is produced in the lung and used therapeutically.
• Peroxynitrite (ONOO-), formed from NO and superoxide, may mediate NO-induced lung injury.
• Investigating NO and ONOO- reactivity is crucial for understanding lung cell responses.

Purpose of the Study:

• To investigate the molecular and cellular reactivities of nitric oxide (NO) and peroxynitrite (ONOO-) in pulmonary cells.
• To compare the injury mechanisms induced by NO and ONOO- in bovine pulmonary artery endothelial cells (BPAEC) and rat type II epithelial cells.
• To determine the role of superoxide and thiols in NO-mediated cellular effects.

Main Methods:

• Exposure of BPAEC and rat type II epithelial cells to NO and ONOO- generated by specific chemical donors.
• Assessment of cellular viability, mitochondrial membrane potential, redox activity, and DNA fragmentation.
• Evaluation of the protective effect of N-acetylcysteine against NO-induced injury.

Main Results:

• Peroxynitrite (ONOO-) exposure caused significant injury and death in both BPAEC and type II epithelial cells.
• NO exposure did not harm BPAEC but induced injury in type II epithelial cells, similar to ONOO-.
• NO-induced injury in type II cells was mitigated by N-acetylcysteine preincubation.
• BPAEC cell death involved mitochondrial depolarization, loss of redox activity, and DNA fragmentation.

Conclusions:

• Peroxynitrite (ONOO-) is a potent cytotoxic agent for pulmonary endothelial and epithelial cells.
• Nitric oxide (NO) exhibits differential toxicity, primarily affecting epithelial cells, potentially through reactions with superoxide.
• Reduced thiols, like N-acetylcysteine, can protect against NO-mediated cellular damage in type II epithelial cells.
• The pathological and physiological impacts of NO are influenced by its interactions with superoxide and cellular thiols.