Tier 3 — preclinical

Nitric Oxide and Endothelial Dysfunction

Cyr AR, Huckaby LV, Shiva SS, Zuckerbraun BS
Critical Care Clinics 2020 36(2):307-321

Bibliography

PubMed
PMID 32172815
PubMed Central
PMC9015729
DOI
10.1016/j.ccc.2019.12.009
Competing interests
Not stated in the source article (institutional book-chapter format; no explicit conflict-of-interest disclosure provided)

Study snapshot

DesignNarrative clinical review (not a primary study)
ModelN/A - review of critical illness/sepsis endothelial dysfunction
SampleN/A - review
InterventionN/A - review
DurationN/A - review
EndpointsEndothelial NO synthase activity and eNOS uncoupling; Microvascular permeability and vascular tone in sepsis/critical illness

What the study showed, in plain terms

The endothelium - the thin layer of cells lining our blood vessels - relies on nitric oxide (NO) to keep vessels relaxed, blood flowing smoothly, and clotting in check. This chapter, from a critical care medicine textbook, explains what goes wrong with NO signaling when patients become critically ill, and how doctors might intervene.

In conditions like sepsis and ARDS, the enzyme that makes NO (eNOS) can become dysfunctional and start producing damaging free radicals instead - a state called "eNOS uncoupling." This flips the endothelium from a protective, blood-flow-friendly surface into one that promotes inflammation, leaky vessels, and clot formation. The authors review how this happens and discuss therapies, including inhaled NO and NO-donor drugs, aimed at restoring healthy vascular signaling in critically ill patients.

Key findings

  • Healthy endothelium constitutively produces NO via eNOS to maintain vasodilation, inhibit platelet aggregation and leukocyte adhesion, and preserve vascular barrier integrity
  • In critical illness (sepsis, ischemia-reperfusion, ARDS), eNOS becomes "uncoupled" - producing superoxide instead of NO - which drives a pro-inflammatory, pro-thrombotic, and hyperpermeable endothelial phenotype
  • Tetrahydrobiopterin (BH4) depletion is a key driver of eNOS uncoupling, making BH4 supplementation and antioxidant strategies potential therapeutic targets
  • Exogenous NO delivery strategies (inhaled NO, NO donors) are discussed as approaches to restore endothelial function in critically ill patients, though clinical benefit remains an active area of investigation

What this study can and cannot tell us

As a book-chapter-style narrative review, this article does not perform its own systematic literature search or formally grade the quality of the studies it cites. Much of the mechanistic evidence on eNOS uncoupling comes from animal and cell-culture models; translating NO-based interventions into consistent clinical benefit in heterogeneous critically ill patient populations remains unresolved.

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