title: TLR2 activation causes no morbidity or cardiovascular failure, despite excessive systemic nitric oxide production.
abstract: OBJECTIVE
  Septic shock is the leading cause of death in intensive care units worldwide, resulting from a progressive systemic inflammatory reaction causing cardiovascular and organ failure. Nitric oxide (NO) is a potent vasodilator and inhibition of NO synthases (NOS) can increase blood pressure in septic shock. However, NOS inhibition does not improve outcome, on the contrary, and certain NO donors may even provide protection. In addition, NOS produce superoxide in case of substrate or cofactor deficiency or oxidation. We hypothesized that excessive systemic iNOS-derived NO production is insufficient to trigger cardiovascular failure and shock.
  
  
  RESULTS
  We found that the systemic injection with various synthetic Toll-like receptor-2 (TLR2), TLR3, or TLR9 agonists triggered systemic NO production identical to that of lipopolysaccharide (LPS) or tumour necrosis factor. In contrast to the latter, however, these agonists did not cause hypothermia or any other signs of discomfort or morbidity, and inflammatory cytokine production was low. TLR2 stimulation with the triacylated lipopeptide Pam3CSK4 not only caused identical NO levels in circulation, but also identical iNOS expression patterns as LPS. Nevertheless, Pam3CSK4 did not cause hypotension, bradycardia, reduced blood flow, or inadequate tissue perfusion in the kidney or the liver.
  
  
  CONCLUSIONS
  We demonstrate that excessive iNOS-derived NO in circulation is not necessarily linked to concomitant cardiovascular collapse, morbidity, or mortality. As such, our data indicate that the central role of iNOS-derived NO in inflammation-associated cardiovascular failure may be overestimated.
authors.affiliation: Department for Molecular Biomedical Research, VIB, Technologiepark 927, Ghent B-9052, Belgium.
authors.forename: Anje
authors.initials: A
authors.lastname: Cauwels
authors.forename: Benjamin
authors.initials: B
authors.lastname: Vandendriessche
authors.forename: Jennyfer
authors.initials: J
authors.lastname: Bultinck
authors.forename: Benedicte
authors.initials: B
authors.lastname: Descamps
authors.forename: Elke
authors.initials: E
authors.lastname: Rogge
authors.forename: Tom
authors.initials: T
authors.lastname: Van Nieuwenhuysen
authors.forename: Magdalena
authors.initials: M
authors.lastname: Sips
authors.forename: Christian
authors.initials: C
authors.lastname: Vanhove
authors.forename: Peter
authors.initials: P
authors.lastname: Brouckaert
mesh_terms: D000818:Animals; D016207:Cytokines / Q000502:physiology; D005260:Female; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009017:Morbidity; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000502:physiology; D012772:Shock, Septic / Q000209:etiology*; D018746:Systemic Inflammatory Response Syndrome / Q000209:etiology; D051195:Toll-Like Receptor 2 / Q000502:physiology*
chemical_list: D016207:Cytokines; D008070:Lipopolysaccharides; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase
keywords: Hypotension; LPS; NOS; Shock; TLR2