Tier 2 — strong

Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology (Nobel Lecture)

Ignarro LJ
Angewandte Chemie International Edition 1999 Volume 38, Issue 13-14, pages 1882-1892

Bibliography

PubMed
PMID 34182699
DOI
10.1002/(SICI)1521-3773(19990712)38:13/14<1882::AID-ANIE1882>3.0.CO;2-V
Funding
Work in the author's laboratory was supported by grants from the National Institutes of Health, the American Heart Association, the American Cancer Society, and the Laubisch Fund at the University of California, Los Angeles.

Study snapshot

DesignNarrative review / Nobel lecture
ModelHuman vasculature, isolated animal (rabbit, bovine, rat) arteries and platelets, cell culture
SampleN/A (narrative synthesis, not a single study)
InterventionN/A (review of NO donors, EDRF, and acetylcholine-induced relaxation across cited studies)
DurationN/A (synthesizes research spanning approximately 1977-1999)
EndpointsChemical identity of endothelium-derived relaxing factor (EDRF) as nitric oxide; Mechanism of NO-mediated vascular smooth muscle relaxation via soluble guanylate cyclase and cyclic GMP; Physiological roles of endogenous NO in regulating vascular tone and inhibiting platelet aggregation; NO as a non-adrenergic, non-cholinergic (NANC) neurotransmitter mediating penile erection

What the study showed, in plain terms

This is Louis Ignarro's Nobel Prize lecture, delivered after he shared the 1998 Nobel Prize in Physiology or Medicine with Robert Furchgott and Ferid Murad for discovering that nitric oxide (NO) acts as a signaling molecule in the cardiovascular system. In it, Ignarro recounts the scientific journey from the identification of an unknown "endothelium-derived relaxing factor" (EDRF) released by blood vessel lining cells, through his own laboratory's experiments proving that EDRF and nitric oxide are chemically and pharmacologically identical.

The lecture explains how NO, once inside vascular smooth muscle cells, activates an enzyme called soluble guanylate cyclase, raising levels of a molecule called cyclic GMP that causes blood vessels to relax and widen, lowering blood pressure and increasing blood flow. It also describes how the same signaling pathway explains how nitroglycerin and related drugs have treated angina (chest pain from restricted blood flow to the heart) for over a century, and how NO helps prevent blood clots by keeping platelets from clumping together.

Finally, Ignarro describes NO's broader biological roles beyond the blood vessels, including its function as a neurotransmitter in the brain and peripheral nerves, and its specific role in mediating penile erection, which led directly to the development of drugs like sildenafil (Viagra).

Key findings

  • Endothelium-derived relaxing factor (EDRF), discovered by Furchgott in 1980, and nitric oxide were shown by Ignarro's lab to be chemically and pharmacologically indistinguishable, resolving a major controversy in vascular biology.
  • NO activates soluble guanylate cyclase in vascular smooth muscle by binding its heme iron center, raising cGMP and producing relaxation and vasodilation.
  • Organic nitrates such as nitroglycerin act as exogenous NO donors, explaining a century of empirical use in treating angina before the underlying mechanism was known.
  • Endogenous NO tonically inhibits platelet aggregation and adhesion, contributing to vascular antithrombotic homeostasis.
  • NO is released by non-adrenergic, non-cholinergic (NANC) nerves and mediates penile erection, providing the mechanistic basis for phosphodiesterase-5 inhibitor drugs such as sildenafil.

What this study can and cannot tell us

As a Nobel lecture, this is a first-person retrospective and celebratory narrative rather than a systematic review, so it emphasizes the author's own contributions and lacks independent quantitative synthesis of the broader literature.

No explicit competing-interest disclosure was present in the source article, though a general funding acknowledgment was provided.

Related papers in the corpus

Tier 3
The nature of endothelium-derived vascular relaxant factor
Griffith TM et al. · Nature · 1984
Tier 3
Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor
Palmer RM et al. · Nature · 1987
Tier 3
Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide
Ignarro LJ et al. · Proceedings of the National Academy of Sciences of the USA · 1987
Tier 2
Nitric oxide as a unique signaling molecule in the vascular system: a historical overview
Ignarro LJ et al. · Journal of Physiology and Pharmacology · 2002

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability