Nitric oxide (NO)—not to be confused with nitrous oxide (“laughing gas”)—is a signaling molecule involved in the health of the cardiovascular system, joints, lungs, nervous system, and immune system, and it also plays a role in erectile function. The body synthesizes nitric oxide from the amino acid L-arginine through enzymes called nitric oxide synthases.

Nitric Oxide and Joint Health

A review in Arthritis & Rheumatism (August 1993;36(8):1036–1044) highlighted the role nitric oxide plays in the joints. Chondrocytes—the cells that produce cartilage—express a form of nitric oxide synthase that converts L-arginine into nitric oxide. This process appears to influence inflammation and cartilage metabolism.

Cardiovascular Benefits of Nitric Oxide

The vascular endothelium (the lining of blood vessels) produces nitric oxide to help blood vessels relax and maintain healthy circulation. Nitric oxide also influences the autonomic nervous system and plays a protective role in early cardiovascular disease:

  • It suppresses the formation of early atherosclerotic lesions

  • It inhibits platelet adhesion and aggregation, reducing the likelihood of thrombosis

These effects were summarized in a New England Journal of Medicine article (July 27, 1995;333(4):251–253).

A Lancet article (Sept 27, 1997;350:901–902) reported that L-arginine supplementation improved endothelial function in patients with high cholesterol. The same report noted that nitric oxide is a powerful vasodilator and may inhibit plaque formation.

Nitric Oxide and Lung Health

Another New England Journal of Medicine study (July 27, 1995;333(4):214–221) examined nitric oxide synthase in lung tissue. Researchers evaluated:

  • 22 patients with plexogenic pulmonary arteriopathy

  • 24 patients with secondary pulmonary hypertension

  • 22 control subjects

They found that pulmonary hypertension was associated with low nitric oxide synthase activity in the lung endothelium.

Earlier animal studies, also referenced in this issue, showed that L-arginine supplementation improved vasodilation in models of pulmonary hypertension. Human studies have reported that L-arginine may help reduce pulmonary artery pressure, likely by supporting nitric oxide production.

Educational only — not medical advice.