Inducible Nitric Oxide Synthase (iNOS)

Inducible nitric oxide synthase (iNOS) is an enzyme that immune cells produce when they are activated by infection, injury, or inflammation. It generates large bursts of nitric oxide, a small reactive molecule that helps fight invaders but can also damage nearby cells and DNA when it is produced for long periods.

Origin

The enzyme was identified in the late 1980s and early 1990s, after researchers discovered that macrophages stimulated by bacterial toxins released nitric oxide. It is also called NOS2, distinguishing it from the constantly active forms (nNOS/NOS1 and eNOS/NOS3) found in nerves and blood vessels.

Significance in Asbestos Context

When asbestos fibers lodge in lung or pleural tissue, immune cells called macrophages try to engulf them but cannot break them down. These frustrated macrophages stay switched on for years, producing iNOS and releasing nitric oxide along with other reactive molecules. Over time this chronic chemical assault damages the DNA of nearby mesothelial and lung cells and is one of the biological pathways that helps explain how asbestos exposure decades earlier can lead to mesothelioma, lung cancer, and asbestosis. Patients will rarely see iNOS named in their own medical records, but it often appears in expert reports and scientific literature used to explain the mechanism of asbestos-related disease in court.

Example Sentence

The plaintiff's expert explained that iNOS-driven inflammation from retained asbestos fibers produces the kind of long-term DNA damage that eventually gave rise to her pleural mesothelioma.

Related Terms

Chronic Inflammation, Reactive Oxygen Species, Macrophage, Frustrated Phagocytosis, HMGB1, Oxidative Stress

Notes

• If your case involves a mechanism-of-disease expert, ask whether their report discusses iNOS, reactive nitrogen species, and chronic inflammation as part of the biological link between fiber exposure and your specific diagnosis.
• Preserve any pathology slides and tissue blocks from biopsies or surgeries; researchers can stain these for inflammatory markers if mechanism becomes an issue in your case.
• Ask your oncologist whether ongoing inflammation is being monitored (for example, through CRP or other inflammatory markers) and whether it has any bearing on treatment choices such as immunotherapy.
• Be aware that defense experts may argue iNOS-related inflammation has many causes (smoking, infections, other dusts); a detailed occupational and medical history helps your team rebut that argument.